WORKING MACHINE

A working machine includes: at least one support member connectable to a work attachment to do work by making contact with an object to be contacted; at least one hydraulic cylinder to move the work attachment connected to the at least one support member, a rod-side pressure detector to detect a rod-side hydraulic pressure of hydraulic fluid in communication with a rod-side fluid chamber of the at least one hydraulic cylinder; a bottom-side pressure detector to detect a bottom-side hydraulic pressure of hydraulic fluid in communication with a bottom-side fluid chamber of the at least one hydraulic cylinder; and a controller to calculate a relationship in pressure between the rod-side hydraulic pressure and the bottom-side hydraulic pressure and evaluate, based on the calculated relationship in pressure, a contact state which is a state of contact of the work attachment with the object.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to working machines such as loaders including a skid-steer loader and a compact track loader.

2. Description of the Related Art

For example, a working vehicle as disclosed in JP2021-24383A (wheel loader) includes a fluid pressure detector to detect the pressure of hydraulic fluid in hydraulic cylinder(s) to support and actuate a work attachment (bucket). Such a working vehicle is capable of calculating the weight of a load on the work attachment (such as earth and sand on the bucket lifted above the ground) based on the result of detection by the fluid pressure detector.

There are cases in which a working machine such as a loader having a bucket (work attachment) attached to its arm(s) performs land leveling (leveling of ground) by bringing the bucket into contact with the ground surface. For such land leveling work, the bucket should be maintained in a suitable attitude while in contact with the ground surface to a suitable degree (at a suitable pressure). The way of keeping the bucket in contact with the ground surface in such a manner for land leveling work relies on worker's experience in operation. Note that the same applies when leveling of ground is performed with a dozer blade attached to the arm(s) of the loader instead of the bucket.

In addition to the above cases of the land leveling work using a bucket or a dozer blade, there are also many cases where the work attachment attached to the arm(s) of a working machine such as a loader is required to be in contact with an object such as a to-be-excavated object including ground surface, soil, plants, bedrock, and buildings to a suitable degree (at a suitable pressure).

For example, in cases where a hydraulic breaker attached to the distal end of lift arm(s) of a loader is used to crush a to-be-crushed object such as a concrete wall of an old building, the breaker should be driven after the breaker is brought into contact with the to-be-crushed object. The breaker may otherwise be damaged from idle strokes.

Furthermore, in cases where a sweeper attached to the distal end of lift arm(s) of a loader is used to clean the ground surface (such as a road surface), the rotary brush of the sweeper should not only be merely in contact with the ground surface (road surface) but also be in contact with the ground by a suitable pressure. For example, when the pressure of contact of the rotary brush with the ground is less than a suitable pressure, i.e., when the sweeper is located higher than a position that achieves a suitable contact with the ground surface, the sweeper cannot sweep dust or the like on the ground surface sufficiently, resulting in a reduction in efficiency of cleaning. On the contrary, when the pressure of contact of the rotary brush with the ground is greater than the suitable pressure and the sweeper is strongly pressed against the ground surface, the rotary brush pressed against the ground surface does not rotate well, also resulting in a reduction in efficiency of cleaning.

The same applies to cases in which a brush cutter attached to the distal end of lift arm(s) of a loader is used to mow grass in the bush. It is required that the shoe (sled) on the body cover that supports the rotary blade of the brush cutter be in contact with the ground at a suitable angle (that is, the shoe be parallel to the ground surface and in contact with the ground surface) at a suitable pressure. If the pressure to press the shoe against the ground surface is too large or the angle of the shoe to the ground surface deviates from the suitable angle, the ground may be dug and desired mowing may not be performed.

Thus, many of the work attachments attachable to the working machine such as a loader (to the arm(s) of the working machine) are strictly required to be checked as to whether they are in contact with a contact object (such as earth and sand, plants, concrete, bedrock) to a suitable (predetermined) degree (at a suitable (predetermined) pressure), but such checking whether the work attachment is in contact with the contact object in an appropriate attitude to an appropriate degree relies on the worker's experience.

Also in cases where an earth auger attached to the distal end of the lift arm(s) of the loader is used to make a hole in the ground or a trencher attached to the distal end of the lift arm(s) of the loader is used to dig a trench, it is required that the depth of the hole or the trench be equal to the target depth: in this regard, making such a hole or trench having an accurate depth also relies on the worker's experience.

Working machines according to preferred embodiments of the present invention are each configured to allow a worker to easily know the state of contact between the work attachment and a contact object.

SUMMARY OF THE INVENTION

In a first aspect, a working machine includes: a machine body: at least one support member supported on the machine body and connectable to a work attachment to do work by making contact with an object to be contacted; at least one hydraulic cylinder extendable and retractable to move the work attachment connected to the at least one support member, the at least one hydraulic cylinder including a rod-side fluid chamber and a bottom-side fluid chamber separated by a piston: a rod-side pressure detector to detect a rod-side hydraulic pressure which is a pressure of hydraulic fluid in communication with the rod-side fluid chamber of the at least one hydraulic cylinder; a bottom-side pressure detector to detect a bottom-side hydraulic pressure which is a pressure of hydraulic fluid in communication with the bottom-side fluid chamber of the at least one hydraulic cylinder; and a controller to calculate a relationship in pressure between the rod-side hydraulic pressure detected by the rod-side pressure detector and the bottom-side hydraulic pressure detected by the bottom-side pressure detector and evaluate, based on the calculated relationship in pressure, a contact state which is a state of contact of the work attachment with the object.

The working machine may further include a memory to store a predetermined contact degree, the predetermined contact degree being a degree to which the work attachment is in contact with the object when the work attachment is in a predetermined contact state. The controller may be configured or programmed to: calculate, based on the calculated relationship in pressure, a current contact degree which is a degree to which the work attachment is currently in contact with the object; compare the current contact degree with the stored predetermined contact degree; and determine whether or not the work attachment is in the predetermined contact state.

The working machine may further include an attitude detector to detect an attitude of the work attachment and/or the at least one support member. The controller may be configured or programmed to: if the controller compares the calculated contact degree with the predetermined contact degree and determines that the work attachment is in the predetermined contact state, recognize, as a reference attitude, the attitude detected by the attitude detector at a point in time at which the controller determined that the work attachment was in the predetermined contact state; and based on a change in the attitude detected by the attitude detector from the reference attitude, measure a degree of work done represented as a change in position of the work attachment relative to the object.

The working machine may further include a display to display the degree of work done measured by the controller.

The controller may be configured or programmed to cause the display to display a guidance indication regarding an operation of the at least one hydraulic cylinder to change the attitude to cause the degree of work done to reach a target degree.

The controller may be configured or programmed to, if the controller determines that the degree of work done has reached a target degree based on a result of detection by the attitude detector, cause the display to display an indication that the degree of work done has reached the target degree.

The controller may be configured or programmed to control extension and retraction of the at least one hydraulic cylinder to control the attitude such that the degree of work done reaches a target degree.

The controller may be configured or programmed to, if the controller determines that the work attachment is not in the predetermined contact state, control extension and retraction of the at least one hydraulic cylinder such that the calculated current contact degree reaches the predetermined contact degree.

The working machine may further include a display. The controller may be configured or programmed to, if the controller determines that the work attachment is not in the predetermined contact state, cause the display to display a guidance indication regarding an operation of the at least one hydraulic cylinder to cause the calculated current contact degree to reach the predetermined contact degree.

The controller may be configured or programmed to, if the controller determines that the work attachment is not in the predetermined contact state, prohibit driving of the work attachment.

The memory may store a plurality of the predetermined contact degrees corresponding to a respective plurality of the work attachments. The controller may be configured or programmed to: select one of the plurality of predetermined contact degrees that corresponds to the work attachment connected to the at least one support member; and compare the selected one of the plurality of predetermined contact degrees with the calculated current contact degree.

The working machine may further include an attitude detector to detect an attitude of the work attachment. The controller may be configured or programmed to, if the controller determines that the work attachment is in the predetermined contact state, determine, as the attitude of the work attachment in the predetermined contact state, the attitude detected by the attitude detector at a point in time at which the controller determined that the work attachment was in the predetermined contact state.

The memory may store a proper attitude of the work attachment in the predetermined contact state. The controller may be configured or programmed to, if the controller determines that the work attachment is in the predetermined contact state and the attitude of the work attachment detected by the attitude detector differs from the proper attitude, control extension and retraction of the at least one hydraulic cylinder such that the attitude of the work attachment reaches the proper attitude.

The working machine may further include a display. The memory may store a proper attitude of the work attachment in the predetermined contact state. The controller may be configured or programmed to, if the controller determines that the work attachment is in the predetermined contact state and the attitude of the work attachment detected by the attitude detector differs from the proper attitude, cause the display to display a guidance indication regarding an operation of the at least one hydraulic cylinder to cause the attitude of the work attachment to reach the proper attitude.

The working machine may further include a display. The memory may store a proper attitude of the work attachment in the predetermined contact state. The controller may be configured or programmed to, if the controller determines that the work attachment is in the predetermined contact state and the attitude of the work attachment detected by the attitude detector is equal to the proper attitude, cause the display to display an indication that the work attachment is in the proper attitude and in the predetermined contact state.

The working machine may further include a manual operator to be operated to cause the at least one hydraulic cylinder to extend or retract. The controller may be configured or programmed to, when the manual operator is operated to cause the at least one hydraulic cylinder to extend or retract, calculate a corrected version of the relationship in pressure using a correction value set according to frictional resistance caused by operation of the manual operator on the piston of the at least one hydraulic cylinder.

The correction value may be changed according to a temperature of hydraulic fluid and/or an ambient temperature.

The correction value may be set to differ between when the at least one hydraulic cylinder is not moving and when the at least one hydraulic cylinder is moving.

The correction value may be set to differ between when the manual operator is operated to cause the at least one hydraulic cylinder to extend and when the manual operator is operated to cause the at least one hydraulic cylinder to retract.

The correction value may be set to differ between when the at least one hydraulic cylinder is extending and when the at least one hydraulic cylinder is retracting.

The controller may be configured or programmed to: when the manual operator is operated to cause the at least one hydraulic cylinder to extend, correct the detected bottom-side hydraulic pressure to reduce the detected bottom-side hydraulic pressure; and when the manual operator is operated to cause the at least one hydraulic cylinder to retract, correct the detected rod-side hydraulic pressure to reduce the detected rod-side hydraulic pressure.

In a second aspect, a working machine includes: a machine body: a support member supported on the machine body and connectable to a work attachment to do work by making contact with an object to be contacted: a first hydraulic cylinder extendable and retractable to move the support member relative to the machine body, the first hydraulic cylinder including a rod-side fluid chamber and a bottom-side fluid chamber separated by a piston: a first rod-side pressure detector to detect a first rod-side hydraulic pressure which is a pressure of hydraulic fluid in communication with the rod-side fluid chamber of the first hydraulic cylinder: a first bottom-side pressure detector to detect a first bottom-side hydraulic pressure which is a pressure of hydraulic fluid in communication with the bottom-side fluid chamber of the first hydraulic cylinder: a second hydraulic cylinder extendable and retractable to move the work attachment connected to the support member relative to the support member, the second hydraulic cylinder including a rod-side fluid chamber and a bottom-side fluid chamber separated by a piston: a second rod-side pressure detector to detect a second rod-side hydraulic pressure which is a pressure of hydraulic fluid in communication with the rod-side fluid chamber of the second hydraulic cylinder: a second bottom-side pressure detector to detect a second bottom-side hydraulic pressure which is a pressure of hydraulic fluid in communication with the bottom-side fluid chamber of the second hydraulic cylinder; and a controller to calculate a relationship in pressure between the detected first rod-side hydraulic pressure and the detected first bottom-side hydraulic pressure and a relationship in pressure between the detected second rod-side hydraulic pressure and the detected second bottom-side hydraulic pressure, and evaluate, based on the calculated relationships in pressure, a contact state which is a state of contact of the work attachment with the object.

The working machine may further include a memory to store a predetermined contact degree, the predetermined contact degree being a degree to which the work attachment is in contact with the object when the work attachment is in a predetermined contact state. The controller may be configured or programmed to: calculate, based on the calculated relationships in pressure, a current contact degree which is a degree to which the work attachment is currently in contact with the object; compare the current contact degree with the stored predetermined contact degree; and determine whether or not the work attachment is in the predetermined contact state.

The working machine may further include an attitude detector to detect an attitude of the work attachment and/or the support member. The controller may be configured or programmed to: if the controller compares the calculated contact degree with the predetermined contact degree and determines that the work attachment is in the predetermined contact state, recognize, as a reference attitude, the attitude detected by the attitude detector at a point in time at which the controller determined that the work attachment was in the predetermined contact state; and based on a change in the attitude detected by the attitude detector from the reference attitude, measure a degree of work done represented as a change in position of the work attachment relative to the object.

The controller may be configured or programmed to, if the controller determines that the work attachment is in the predetermined contact state, evaluate the attitude of the work attachment in the predetermined contact state based on a relationship between (i) a relationship in pressure between the first rod-side hydraulic pressure and the first bottom-side hydraulic pressure detected at a point in time at which the controller determined that the work attachment was in the predetermined contact state, and (ii) a relationship in pressure between the second rod-side hydraulic pressure and the second bottom-side hydraulic pressure detected at a point in time at which the controller determined that the work attachment was in the predetermined contact state.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description discusses an overall configuration of working machines1with reference toFIGS.1and2. The working machine1includes a machine body2, a cabin3, a working device4and a traveling device5. The cabin3, the working device4, and the traveling device5are provided on the machine body2. The “forward direction” in the following description refers to the direction indicated by arrow F inFIGS.1and2, and the “rearward direction” in the following description refers to the direction opposite to the direction indicated by arrow F. The “right” in the following description refers to the right of the working machine1when the operator (user) of the working machine1is facing in the forward direction (direction indicated by arrow F). The “left” in the following description refers to the left of the working machine1when the operator (user) of the working machine1is facing in the forward direction (direction indicated by arrow F).

The working machine1inFIG.1is a skid steer loader1A whose traveling device is a wheeled traveling device5A including a pair of left and right front wheels5AF and a pair of left and right rear wheels5AR. The working machine1inFIG.2is a compact track loader1B whose traveling device5is a crawler traveling device5B.

A prime mover6is mounted on the portion of the machine body2that is located rearward of the cabin3. The prime mover6is an internal combustion engine such as a diesel engine or a gasoline engine. Alternatively, the prime mover6may include an internal combustion engine and/or an electric motor, for example. The prime mover6drives hydraulic pumps32L and32R in a travel hydraulic system30ofFIG.5and hydraulic pumps41and42in a work hydraulic system40ofFIGS.6A and6B.

An operator's seat7is mounted on the machine body2. The cabin3is mounted on the machine body2to enclose the operator's seat7. The cabin3is a kind of protector to protect an operator seated on the operator's seat7, meters and manual operators such as levers and switches arranged in the vicinity of the operator's seat7, and/or the like. Another protector having such a function, such as a canopy or a rollover protective structure (ROPS), may be mounted on the machine body2.

Referring toFIGS.1and2, the manual operators to be manually operated by an operator seated on the operator's seat7in the cabin3include a lever (such as a joystick)8(hereinafter referred to as “travel operation lever8”) operable to change the traveling direction and travel speed of the traveling device5, and a lever (such as a joystick)9(hereinafter referred to as “work operation lever9”) operable to swing (move) lift arms10(first support members) of the working device4up and down (raise and lower the lift arms10) and/or swing a work attachment16attached to the working device4up and down (raise and lower the work attachment16). The travel operation lever8and the work operation lever9are located on the left and right sides of a front portion of the operator's seat7.

The manual operators in the cabin3also include a speed change switch23, an attachment driving switch (AUX switch)18and a brake pedal19. Referring toFIG.5, the speed change switch17, operable to change the traveling speed stage of the traveling device5between high and low speed stages, is located in the vicinity of the operator's seat7(for example, on the travel operation lever8).

Referring toFIG.6, the attachment driving switch (AUX switch)18, operable to control fluid supply to a hydraulic actuator when a work attachment including the hydraulic actuator is attached to the working device4, is located in the vicinity of the operator's seat7(for example, on the work operation lever9). Referring toFIG.5, the brake pedal19is located at a position at which a foot of an operator seated on the operator's seat7is to be placed in the cabin3.

The working device4includes a pair of the left and right lift right arms10(support members) attached to the machine body2swingably up and down with respect to the machine body2. The left lift arm10of the pair of left and right lift arms10is on the left side of the cabin3. The right lift arm10is on the right side of the cabin3. Each left arm extends lengthwise in the fore-and-aft direction of the working machine1.

Front portions of the left and right lift arms10are connected to each other via a connection member (not illustrated) in front of the cabin3. Rear portions of the left and right lift arms10are connected to each other via a connection member (not illustrated) behind the cabin3. An assembly of left right and the lift arms10and the front and rear connection members (not illustrated) assembled in this way, defining and functioning as a main body4aof the working device4, is attached to the machine body2swingably up and down with respect to the machine body2.

The manner in which the left and right lift arms10are connected to each other is not limited to using the front and rear connection members as described above. The left and right lift arms10may be connected to each other in any manner, provided that the left and right lift arms10are swingable together up and down with respect to the machine body2.

The working device4includes a pair of left and right lift links12and a pair of left and right control links13to support the left and right lift arms10at a rear portion of the main body2. The working device4includes a pair of left and right lift arm cylinders14as hydraulic actuators to swing the left and right lift arms10up and down with respect to the machine body2.

FIGS.1and2, each of which is a left side view of the working machine1, illustrate the left lift arm10, the left lift link12, the left control link13, and the left lift arm cylinder14which are located leftward of the cabin3. The right lift arm10, the right lift link12, the right control link13, and the right lift arm cylinder14are located rightward of the cabin3in a similar manner.

Note that, inFIGS.1and2, the left and right lift arms10movable (swingable) up and down with respect to the machine body2(the main body4aof the working device4that includes the left and right lift arms10) are in the lowered state such that the work attachment16attached at the distal ends thereof makes contact with the ground. In the following description, the positions, orientations/directions, and the like of the elements of the working device4are discussed on the assumption that the left and right lift arms10are in such a lowered state.

Each of the lift links12extends substantially vertically, is pivotally connected at a top end thereof to a rear end of a corresponding lift arm10via a corresponding pivot12aextending laterally, and is pivotally connected at a bottom end thereof to an upper rear portion of the machine body2via a corresponding pivot12bextending laterally. At a position forward of the lift link12, a head of a piston rod of a corresponding lift arm cylinder14is pivotally connected to the lift arm10via a corresponding pivot14aextending laterally. The bottom end (cylinder bottom) of the lift arm cylinder14is pivotally connected to a lower rear portion of the main body2via a corresponding pivot14bextending laterally.

Each of the lift arm cylinders14includes a piston. The piston is moved by hydraulic pressure to extend or retract the piston rod. In each ofFIGS.1and2, the lift arm cylinders14have the piston rod in their fully or almost fully retracted position. In other words, the lift arms10are lowered when the piston rods of the lift arm cylinders14are retracted.

Each of the lift arms10is provided with a downwardly projecting bracket10athat is located between, in the fore-and-aft direction, the rear end (pivot12a) of the lift arm10and the portion (pivot14a) of the lift arm10that pivotally supports the piston rod of a corresponding lift arm cylinder14. Each of the control links13extends substantially in the fore-and-aft direction, is pivotally connected at a front end thereof to an upper rear portion of the main body2via a corresponding pivot13aextending laterally, and is pivotally connected at a rear end thereof to a corresponding bracket10aof the lift arm10via a corresponding pivot13bextending laterally, when the lift arms10are in the lowered position as illustrated inFIGS.1and2.

The lift arms10each include a bent portion10blocated forward of the cabin3, and extend forward from their rear ends pivotally connected to the lift links12to the bent portions10b. The lift arms10each include a distal end portion10cextending downward from its corresponding bent portion10b. The distal end portions10cof the left and right lift arms10are configured to have the work attachment16pivotally attached thereto.

The working device4includes a pair of left and right attachment cylinders15. The left and right attachment cylinders15are hydraulic actuators to support the work attachment16attached to the distal end portions10cof the left and right lift arms10and swing the work attachment16up and down with respect to the lift arms10via pivots16aeach extending laterally.

Each of the attachment cylinders15is pivotally connected to the bent portion10bof a corresponding lift arm10at a cylinder bottom thereof (an upper end thereof). Each of the pair of left and right attachment cylinders15is pivotally connected at the distal end of the piston rod thereof (at a lower end thereof) to the work attachment16attached to the distal end portions10cof the lift arms10.

The attachment16is pivotally connected at a rear portion thereof to the distal end portions10cof the left and right lift arms10and to the distal ends of the piston rods of the attachment cylinders15in this way, so that the work attachment16is attached to the working device4(to the main body4aof the working device4) swingably up and down with respect to the working device4(lift arms10).

The working device4(lift arms10(support members) is configured to have various kinds of work attachments16attached thereto in this way. Examples of the various kinds of work attachments16include backets, dozer blades, brushcutters, tree-pullers, hydraulic crushers, hydraulic breakers, angle brooms, earth augers, pallet forks, sweepers, mowers, snowblowers and so on.

FIGS.1to4illustrate some types of work attachments16each attached to the working device4of the working machine1, as examples of the work attachment16attached to the working device4. The work attachment16illustrated inFIG.1is a bucket16A. The work attachment16illustrated inFIG.2is a sweeper16B. The work attachment16illustrated inFIG.3is a hydraulic breaker16C. The work attachment16illustrated inFIG.4is an earth auger16D.

Note that it is possible to selectively attach various types of work attachments16to the working device4of the working machine1(to the distal end portions10cof the lift arms10), and also possible to selectively attach work attachments16of the same type having different sizes and/or different specifications to the working device4of the working machine1(to the distal end portions10cof the lift arms10).

Some types of work attachment16such as the sweeper16B inFIG.2, the hydraulic breaker16C inFIG.3, and the earth auger16D inFIG.4include its own hydraulic actuator(s) such as hydraulic motor(s). For the purpose of supplying hydraulic fluid from the working machine1to the hydraulic actuator(s) of such a work attachment16, one of the pair of left and right lift arms10(in the present preferred embodiment, the left lift arm10) has, on the bent portion10bthereof, a pair of AUX ports (hydraulic fluid ports)11.

The AUX ports11are couplers and project from the corresponding lift arm10. The AUX ports (couplers)11can have connected thereto fluid pipes such as hoses, which are connectable at their ends to hydraulic actuator(s) (AUX actuator(s)) of the attachment16attached to the front ends of the left and right lift arms10.

Note that some types of work attachments16such as the bucket16A inFIG.1does not include its own hydraulic actuators, and it is not necessary to supply hydraulic fluid from the working machine1via the AUX ports11. When such a type of work attachment16is attached to the working device4, the AUX ports11are closed.

The following description discusses up-and-down movement (raising and lowering movements) of the lift arms10(the main body4aof the working device4). Upon upward extension of the piston rods of the left and right lift arm cylinders14from the state inFIGS.1and2in which the left and right lift arms10are in the lowered position, the piston rods raise the lift arms10, so that, eventually, the lift arms10(the main body4aof the working device4) swing such that the angle between the lift arms10and the lift arms12increases. Accordingly, the control links13swing diagonally forward and upward and front portions (the bent portions10band the distal end portions10c) of the lift arms10move upward.

When the ends of the control links13pivotally connected to the brackets10aof the lift arms10are moved by swinging the control links13diagonally forward and upward and reach their highest position in the range of the up-and-down movement, the left and right lift arms10(the main body4aof the working device4) can no longer be raised upward. In other words, when the ends of the control links13pivotally connected to the lift arms10reach this position, the left and right lift arms10(the main body4aof the working device4) reach their fully raised position (i.e., the arm height reaches the maximum), and the lift arm cylinders14are in their fully extended position.

The following description discusses the swinging of the work attachment16attached to the working device4relative to the lift arms10. As the piston rods of the left and right attachment cylinders15located between the work attachment16and the left and right lift arms10extend, the work attachment16swings diagonally rearward and downward with respect to the lift arms10(in the anticlockwise direction in a left side view of the working machine1as illustrated inFIGS.1and2). As the piston rods of the left and right attachment cylinders15retract, the work attachment16swings diagonally forward and upward with respect to the lift arms10(in the clockwise direction in a left side view of the working machine1as illustrated inFIGS.1and2.)

Thus, the degree of extension of the piston rods of the attachment cylinders15determines the angle of the work attachment16to the lift arm10. More specifically, the degree of extension of the piston rods of the lift arm cylinders14(such a degree may be hereinafter referred to as “the degree of extension of the lift arm cylinders14” for short) and the degree of extension of the piston rods of the attachment cylinders15(such a degree may be hereinafter referred to as “the degree of extension of the attachment cylinders15” for short) determine the attitude (upward or downward tilting in the fore-and-aft direction) and the position of the work attachment16relative to the machine body2.

Referring toFIGS.1,2,6A, and6B, the working machine1includes an attitude detector62to detect the attitude (position relative to the machine body2) of the work attachment16and the lift arms (support members)10. For the foregoing reasons, the attitude detector62may be a combination of a detector to detect the degree of extension of the lift arm cylinders14and a detector to detect the degree of extension of the attachment cylinders15.

In the present embodiment, the attitude detector62is a combination of an angle detector (angle sensor)62ato detect the angle of rotation of the lift arm(s)10(main body4aof the working device4) relative to the machine body2and an angle detector (angle sensor)62bto detect the angle of rotation of the work attachment16relative to the lift arms10.

Note that, in the working machine1illustrated inFIGS.1and2, the angle detector62ais provided in the vicinity of the pivots14avia which the top ends (heads of the piston rods) of the lift arm cylinders14are pivoted on the lift arms10, and detects changes in the angle between the lift arm cylinders14and the lift arms10which pivot about the pivots14a.

The angle detector62ato detect the angle of the lift arms10(the main body4aof the working device4) relative to the machine body2may be positioned to additionally or alternatively detect the angle between the lift link(s)12and the lift arm(s)10which pivot about the pivot(s)12aor the angle between the machine body2and the control link(s)13which pivot about the pivot(s)13a.

The angle detector62bmay be provided in the vicinity of the pivot(s)16ato detect the angle between the distal end portion(s)10cof the lift arm(s)10and the work attachment16.

The attitude detector62may be an angle detector to detect the angle between the lift arm(s)10and the machine body2and/or the angle between the lift arm(s)10and the work attachment16. Alternatively or additionally, the attitude detector62may be a cylinder length detector to detect the degree of extension of the piston rod(s) of the lift arm cylinder(s)14and/or the degree of extension of the piston rod(s) of the attachment cylinder(s)15.

Alternatively, the attitude detector62may be a combination of detector(s) for the degree of extension of the piston rods of cylinders as described above and detector(s) to detect the angle of rotation of the lift arms10and/or the like as described above.

The working machine1includes a controller20and a display22(seeFIGS.6A and6B). The controller20is capable of, based on the result of detection by the attitude detector62, controlling the lift arm cylinder(s)14and/or the attachment cylinder(s)15such that the attitude of the work attachment16reaches a desired attitude and/or causing the display22to display a guidance indication regarding control of the lift arm cylinder(s)14and/or the attachment cylinder(s)15such that the attitude of the work attachment16reaches a desired attitude. These will be described later in detail.

The working machine1includes a travel hydraulic system30illustrated inFIG.5and a work hydraulic system40illustrated inFIGS.6A and6B. The following discusses these systems.

The following description first discusses the travel hydraulic system30to control drive of the traveling device5with reference to the hydraulic circuit diagram inFIG.5. It is assumed here that the traveling device5(including the traveling devices5A and5B and the like) includes a left traveling device5L on the left portion of the machine body2and a right traveling device5R on the right portion of the machine body2, which can be driven independently of each other.

The travel hydraulic system30includes hydrostatic stepless transmissions (HSTs)31L and31R provided on the machine body2. The HST31L includes a hydraulic pump32L, a hydraulic motor33L, and a pair of fluid passages34La and34Lb between the hydraulic pump32L and the hydraulic motor33L. The HST31R includes a hydraulic pump32R, a hydraulic motor33R, and a pair of fluid passages34Ra and34Rb between the hydraulic pump32R and the hydraulic motor33R.

The hydraulic pumps32L and32R are drivingly connected to an output shaft6aof the prime mover6to be rotated together synchronously with the output rotation of the prime mover6. The hydraulic motor33L is drivingly connected to the left traveling device5L. The hydraulic motor33R is drivingly connected to the right traveling device5R.

The hydraulic pumps32L and32R are variable displacement hydraulic pumps including respective movable swash plates32a. Each of the hydraulic pumps32L and32R includes a pair of pressure receivers32band32c. The tilt direction and angle of the movable swash plate32ais controlled by applying pilot fluid pressure to the pressure receivers32band32c.

Hydraulic pumps41and42are drivingly connected to the output shaft6aof the prime mover6. The hydraulic pump42is driven by the prime mover6to suck fluid from a reservoir tank29and deliver the fluid. A portion of fluid delivered by the hydraulic pump42is supplied to the HSTs31L and31R.

Another portion of the fluid delivered from the hydraulic pump42may flow through pump control valves35operably connected to the travel operation lever8and through shuttle valves36to be applied as pilot pressure fluid to the pressure receivers32band32cof the hydraulic pumps32L and32R to control the movable swash plates32a.

When the travel operation lever8is in a neutral position (N), the movable swash plates32aof the hydraulic pumps32L and32R are in their neutral position and therefore neither the hydraulic pump32L nor the hydraulic pump32R delivers fluid, rotating neither the hydraulic motor33L nor the hydraulic motor33R. Therefore, the left and right traveling devices5L and5R are in their stopped state and therefore the working machine1(the machine body2) is in its stopped state.

The travel operation lever8can be pivoted from the neutral position (N) in all directions including forward (F), rearward (B), leftward (L), and rightward (R) directions. The direction in which the travel operation lever8is pivoted from the neutral position (N) and the angle at which the travel operation lever8is pivoted (the degree of pivoting of the travel operation lever8) determine the direction in which the movable swash plates32aof the hydraulic pumps32L and32R are titled and the angle at which the movable swash plates32aare tilted, respectively. This stops or drives the hydraulic motors33L and33R (left traveling device5L and the right traveling device5R) and determines the direction of driving/rotation and the speed of driving/rotation of the hydraulic motors33L and33R (left traveling device5L and the right traveling device5R). Thus, the direction of travel (turn) and travel speed of the working machine1(machine body2) are controlled according to how the travel operation lever8is operated (the direction in which and the degree to which the travel operation lever8is pivoted).

The hydraulic motors33L and33R are variable displacement hydraulic motors including respective movable swash plates33a. Each of the movable swash plates33ais shiftable between a tilt position for high speed travel (hereinafter referred to as “high-speed tilt position”) (a small angled position, or a position for small displacement) and a tilt position for low speed travel (hereinafter referred to as “low-speed tilt position”) (a large angled position, or a position for large displacement).

Each of the hydraulic motors33L and33R includes a swash plate control actuator33boperably connected to a corresponding movable swash plate33a. The swash plate control actuator33bof the hydraulic motor33L is fluidly connected to a switching valve37L. The swash plate control actuator33bof the hydraulic motor33R is fluidly connected to a switching valve37R.

Each of the switching valves37L and37R is shiftable between a fluid supply position37ato allow fluid to be supplied to a corresponding swash plate control actuator33band a fluid discharge position37bto allow fluid to be discharged from the corresponding swash plate control actuator33b. The switching of each of the switching valves37L and37R between two positions switches the position of a corresponding movable swash plate33abetween two positions.

Each of the switching valves37L and37R is in the fluid supply position37awhen receiving the pilot fluid pressure, and returns to the fluid discharge position37bwhen the pilot fluid pressure is removed. The fluid delivered by the hydraulic pump42can be supplied as pilot pressure fluid to the switching valves37L and37R via a speed-shift solenoid switching valve38.

The speed-shift solenoid switching valve38is shiftable between two positions: an open position38a; and a closed position38b, and is biased to the closed position38b. The speed-shift solenoid switching valve38, when in the closed position38b, isolates the fluid delivered by the hydraulic pump42from the pressure receivers of the switching valves37L and37R, bringing the switching valves37L and37R into their fluid discharge position37b.

The travel hydraulic system30includes a controller20to positionally control the speed-shift solenoid switching valve38and a brake solenoid switching valve39(which is described later). The controller20includes, for example, electric/electronic circuit(s) including a central processing unit (CPU), a microprocessor unit (MPU), a memory, and/or the like.

In the present preferred embodiment, the controller20is used to control the travel hydraulic system30ofFIG.5and the work hydraulic system40ofFIGS.6A and6B. Note, however, that the systems may be controlled by their respective corresponding controllers and the controllers may communicate with each other.

The speed-shift solenoid switching valve38is electrically connected to the controller20. When the speed-shift solenoid switching valve38receives a control signal from the controller20, a solenoid of the speed-shift solenoid switching valve38is energized, so that the speed-shift solenoid switching valve38is shifted to the open position38a, allowing the fluid delivered by the hydraulic pump42to flow therefrom to the switching valves37L and37R as pilot pressure fluid. This brings the switching valves37L and37R into their fluid supply position37a.

The speed change switch23is electrically connected to the controller20. The speed change switch23is shiftable between a high-speed position and a low-speed position. When the speed change switch23is in the high-speed position, the controller20places the speed-shift solenoid switching valve38in the closed position38b, so that the switching valves37L and37R are placed in the fluid supply position37b, the movable swash plates33aof the hydraulic motors33L and33R are placed in the high-speed tilt position, and the hydraulic motors33L and33R rotate in the high-speed stage.

When the speed change switch23is in the low-speed position, the controller20places the speed-shift solenoid switching valve38in the open position38a, so that the switching valves37L and37R are placed in the fluid supply position37a, the movable swash plates33aof the hydraulic motors33L and33R are placed in the low-speed tilt positions, and the hydraulic motors33L and33R rotate in the low-speed stage.

Each of the hydraulic motors33L and33R includes a brake actuator33cdefining and functioning as a hydraulic actuator. The brake actuator33c, when supplied with fluid, brakes a corresponding hydraulic motor33R or33L. The fluid delivered from the hydraulic pump42can be supplied to the brake actuators33cof the hydraulic motors33L and33R via the brake solenoid switching valve39.

The brake solenoid switching valve39is shiftable between two positions: an open position39a; and a closed position39b, and is biased to the closed position39b. The brake solenoid switching valve39, when in the closed position39b, isolates the fluid delivered by the hydraulic pump42from the brake actuators33cof the hydraulic motors33L and33R.

The brake solenoid switching valve39is electrically connected to the controller20. When the brake solenoid switching valve39receives a control signal from the controller20, a solenoid of the brake solenoid switching valve39is energized, so that the brake solenoid switching valve39is shifted to the open position39a, allowing the fluid delivered from the hydraulic pump42to flow therefrom to the brake actuators33c. This brakes the hydraulic motors33L and33R.

The brake pedal19is electrically connected to the controller20. When the brake pedal19is not depressed, the controller20maintains the brake solenoid switching valve39in the closed position39b, and therefore the hydraulic motors33L and33R are not braked. When the brake pedal19is depressed to a brake position, the controller20places the brake solenoid switching valve39in in the open position39a, and the hydraulic motors33L and33R are braked.

FIG.6Aillustrates a work hydraulic system40A which is a first embodiment of the work hydraulic system40, andFIG.6Billustrates a work hydraulic system40B which is a second embodiment of the work hydraulic system40. The following description discusses a configuration of the work hydraulic system40with reference to the hydraulic circuit diagrams inFIGS.6A and6B, based on the assumption that the configuration of the work hydraulic system40is the same between the work hydraulic system40A and the work hydraulic system40B.

The work hydraulic system40includes the hydraulic pumps41and42. The hydraulic pumps41and42are driven together by power from the prime mover6to suck fluid from the common reservoir tank29and deliver fluid from delivery ports thereof.

The hydraulic pump41delivers hydraulic fluid to the hydraulic actuators (i.e., a pair of left and right lift arm cylinders14and a pair of left and right attachment cylinders15) of the working device4of the working machine1and the hydraulic actuator of the attachment16(such as a hydraulic motor16Bc of a sweeper16B (seeFIG.2) to drive a rotary brush16Bb) attached to the working device4.

The machine body2is provided with a lift arm control valve44to control a flow of hydraulic fluid supplied to the left and right lift arm cylinders14, an attachment control valve45to control a flow of hydraulic fluid supplied to the left and right attachment cylinder(s)15, and an AUX control valve46to control a flow of hydraulic fluid supplied to the AUX ports11.

A delivery fluid passage43extends from a delivery port of the hydraulic pump41. Supply fluid passages43a,43band43c, which are parallel to each other and branch from the delivery fluid passage43, are connected to pump ports of the lift arm control valve44, the attachment control valve45, and the AUX control valve46, respectively.

The flow rate of hydraulic fluid in the delivery fluid passage43is adjusted by a flow adjusting valve50in a bleed-off fluid passage49branching from the delivery fluid passage43on the upstream side of the supply fluid passages32a,43band43cand extending to the reservoir tank29. Drain fluid passages49a,49band49cextending from tank ports of the lift arm control valve44, the attachment control valve45and the AUX control valve46are connected to the bleed-off fluid passage49on the downstream side of the flow adjusting valve50.

The hydraulic pump41is a variable displacement hydraulic pump capable of changing the flow rate of fluid delivered therefrom. The work hydraulic system40includes a load sensing (LS) system61defining and functioning as a pump controller to control the flow rate of fluid delivered from the hydraulic pump41according to the type of work done by the working machine1. Specifically, the LS system61has a predetermined load sensing (LS) differential pressure and controls the flow rate of fluid delivered from the hydraulic pump41so that the pressure of fluid delivered from the hydraulic pump41is higher than the maximum of the load pressure(s) of the working hydraulic actuator(s) by the LS differential pressure.

Each of the lift arm cylinders14is a double-acting hydraulic cylinder whose inner space is divided by a piston into a rod-side (upper) fluid chamber14aand a bottom-side (lower) fluid chamber14b. A pair of fluid supply/discharge passages55and56extend from the lift arm control valve44. The fluid supply/discharge passage55is in communication with the rod-side fluid chambers14aof the left and right lift arm cylinders14. The fluid supply/discharge passage56is in communication with the bottom-side fluid chambers14bof the left and right lift arm cylinders14.

The work hydraulic system40includes a lift arm cylinder fluid pressure detector63. The lift arm cylinder fluid pressure detector63includes a rod-side pressure detector63ato detect the pressure of hydraulic fluid in the rod-side fluid chambers14aof the lift arm cylinders14, and a bottom-side pressure detector63bto detect the pressure of hydraulic fluid in the bottom-side fluid chambers14bof the lift arm cylinders14.

The rod-side pressure detector63aand the bottom-side pressure detector63bof the lift arm cylinder fluid pressure detector63are electrically connected to input interface(s) of the controller20, and the controller20receives (i) a detection signal indicative of a rod-side hydraulic pressure P1r which is the pressure of hydraulic fluid in the rod-side fluid chambers14aof the lift arm cylinders14detected by the rod-side pressure detector63aand (ii) a detection signal indicative of a bottom-side hydraulic pressure P1b which is the pressure of hydraulic fluid in the bottom-side fluid chambers14bof the lift arm cylinders14detected by the bottom-side pressure detector63b.

The controller20is capable of calculating a value indicating the relationship (relationship in pressure) between the rod-side hydraulic pressure Pla and the bottom-side hydraulic pressure P1b based on the detection signals received from the lift arm cylinder fluid pressure detector63and, based on the calculated relationship in pressure, evaluating the state of contact between the work attachment16attached to the working device4and a contact object (an object to be contacted)17such as soil.

Note that, since the pressure of hydraulic fluid is constant throughout the range from the port of the lift arm control valve44connected to the fluid supply/discharge passage55through the fluid supply/discharge passage55to the rod-side fluid chambers14aof the lift arm cylinders14, the rod-side pressure detector63ais capable of detecting the pressure of hydraulic fluid in the rod-side fluid chambers14aby detecting hydraulic pressure at a position within the above range. Furthermore, since the pressure of hydraulic fluid is constant throughout the range from the port of the lift arm control valve44connected to the fluid supply/discharge passage56through the fluid supply/discharge passage56to the bottom-side fluid chambers14bof the lift arm cylinders14, the bottom-side pressure detector63bis capable of detecting the pressure of hydraulic fluid in the bottom-side fluid chambers14bby detecting hydraulic pressure at a position within the above range.

Each of the attachment cylinders15is a double-acting hydraulic cylinder whose inner space is separated by a piston into a rod-side (lower) fluid chamber15aand a bottom-side (upper) fluid chamber15b. A pair of fluid supply/discharge passages57and58extend from the attachment control valve45. The fluid supply/discharge passage57is in communication with the bottom-side fluid chambers15bof the left and right attachment cylinders15. The fluid supply/discharge passage58is in communication with the rod-side fluid chambers15aof the left and right attachment cylinders15.

The work hydraulic system40includes an attachment cylinder fluid pressure detector64. The attachment cylinder fluid pressure detector64includes a rod-side pressure detector64ato detect the pressure of hydraulic fluid in the rod-side fluid chambers15aof the attachment cylinders15, and a bottom-side pressure detector64bto detect the pressure of hydraulic fluid in the bottom-side fluid chambers15bof the attachment cylinders15.

The rod-side pressure detector64aand the bottom-side pressure detector64bof the attachment cylinder fluid pressure detector64are electrically connected to input interface(s) of the controller20, and the controller20receives (i) a detection signal indicative of a rod-side hydraulic pressure P2r which is the pressure of hydraulic fluid in the rod-side fluid chambers15aof the attachment cylinders15detected by the rod-side pressure detector64aand (ii) a detection signal indicative of a bottom-side hydraulic pressure P2b which is the pressure of hydraulic fluid in the bottom-side fluid chambers15bof the attachment cylinders detected by the bottom-side pressure detector64b.

The controller20is capable of calculating a value indicating the relationship (relationship in pressure) between the rod-side hydraulic pressure P2r and the bottom-side hydraulic pressure P2b based on the detection signals received from the attachment cylinder fluid pressure detector64and, based on the calculated relationship in pressure, determining the state of contact between the work attachment16attached to the working device4and a contact object17such as soil.

Note that, since the pressure of hydraulic fluid is constant throughout the range from the port of the attachment control valve45connected to the fluid supply/discharge passage58through the fluid supply/discharge passage58to the rod-side fluid chambers15aof the attachment cylinders15, the rod-side pressure detector64ais capable of detecting the pressure of hydraulic fluid in the rod-side fluid chambers15aby detecting hydraulic pressure at a position within the above range. Furthermore, since the pressure of hydraulic fluid is constant throughout the range from the port of the attachment control valve45connected to the fluid supply/discharge passage57through the fluid supply/discharge passage57to the bottom-side fluid chambers15bof the attachment cylinders15, the bottom-side pressure detector64bis capable of detecting the pressure of hydraulic fluid in the bottom-side fluid chambers15bby detecting hydraulic pressure at a position within the above range.

Steps performed by the controller20using the cylinder fluid pressure detectors63and64to evaluate the state of contact between the work attachment16the contact object17, and steps performed by the controller20based on the evaluation, will be described later in detail.

A pair of fluid supply/discharge passages59and60extend from the AUX control valve46and are connected to corresponding ones of the AUX ports11. When the attachment16including hydraulic actuator(s) is attached to the distal ends of the pair of left and right lift arms10, the hydraulic actuator is fluidly connected to the AUX ports11.

Each of the control valves44,45and46is a pilot-operated directional switching valve including a spool and pressure receivers provided on opposite sides of the spool to receive pilot fluid pressure. The hydraulic pump42is a pilot pump to supply pilot pressure fluid to the control valves44and45and/or the like.

As discussed earlier with reference toFIG.5, the hydraulic pump42is a charge pump to deliver hydraulic fluid to the HSTs31L and31R in the travel hydraulic system30, and also defines and functions as a pilot pump to supply pilot pressure fluid to control the movable swash plates32aof the hydraulic pumps32L and32R.

The work operation lever9is manually operated by an operator seated on the operator's seat7. By pivoting the work operation lever9forward or rearward, the lift arm control valve44is actuated and switches positions to cause the lift arm cylinders14to extend or retract, and the lift arms10are swung (moved) up or down with respect to the machine body2. By pivoting the work operation lever9rightward or leftward, the attachment control valve45is actuated and switches positions to cause the attachment cylinder15to extend or retract, and the work attachment16is swung up or down with respect to the lift arms10.

The link structure between (i) the work operation lever9and (ii) the lift arm control valve44and the attachment control valve45differs between the work hydraulic system40A inFIG.6Aand the work hydraulic system40B inFIG.6B. The link structure between the work operation lever9and the cylinder control valves44and45specific to the work hydraulic system40A inFIG.6Aand that specific to the work hydraulic system40B inFIG.6Bwill be described later in detail.

As discussed earlier, when a work attachment16such as the sweeper16B as illustrated inFIG.2, the hydraulic breaker16C as illustrated inFIG.3, or the earth auger16D as illustrated inFIG.4is attached to the working device4, the hydraulic actuator(s) (AUX actuator(s)) of the work attachment16is fluidly connected to the AUX ports11as the couplers via fluid pipes and/or the like to be driven by hydraulic fluid supplied from the AUX control valve46via the AUX ports11.

The work hydraulic system40includes solenoid valves47and48to positionally control the AUX control valve46. The controller20controls the solenoid valves47and48based on operation of the AUX switch18.

The AUX switch18may be a swingable seesaw switch, a slidable switch or a push switch, for example. The AUX switch18is electrically connected to the input interface of the controller20.

When the AUX switch18is operated, an input signal which is an electric signal corresponding to the operation direction and operation amount of the AUX switch18is outputted from the AUX switch18and is inputted to the controller20. The solenoid valves47and48are electrically connected to output interface(s) of the controller20. The controller20outputs current as a control signal to the solenoid valves47and48according to the input signal from the AUX switch18.

For example, hydraulic fluid delivered from the hydraulic pump41via the delivery fluid passage43is supplied to the solenoid valves47and48as pilot pressure fluid whose pressure is to be applied to the AUX control valve46. A source of fluid supplied to the solenoid valves47and48and to be supplied as pilot pressure fluid to the AUX control valve46is omitted inFIG.6A or6B.

When the solenoid valve47receives a control signal from the controller20and its solenoid is energized, the solenoid valve47supplies pilot pressure fluid to the upper pressure receiver of the AUX control valve46inFIGS.6A and6B, so that the spool of the AUX control valve46shifts downward inFIGS.6A and6B. Accordingly, hydraulic fluid is supplied from the AUX control valve46to the hydraulic actuator of the attachment16via the fluid supply/discharge passage59and the AUX ports11(i.e., corresponding one(s) of the AUX ports11) and hydraulic fluid is returned from the hydraulic actuator to the AUX control valve46via the AUX ports11and the fluid supply/discharge passage60.

When the solenoid valve48receives a control signal from the controller20and its solenoid is energized, the solenoid valve48supplies pilot pressure fluid to the lower pressure receiver of the AUX control valve46inFIGS.6A and6B, so that the spool of the AUX control valve46shifts upward inFIGS.6A and6B. Accordingly, hydraulic fluid is supplied from the AUX control valve46to the hydraulic actuator of the attachment16via the fluid supply/discharge passage60and the AUX ports11and hydraulic fluid is returned from the hydraulic actuator to the AUX control valve46via the AUX ports11and the fluid supply/discharge passage59.

The following discusses the link structure between (i) the work operation lever9and (ii) the lift arm control valve44and the attachment cylinder15specific to the work hydraulic system40A inFIG.6A.

In the working machine1, operation valves51,52,53and54are arranged around the base of the work operation lever9. By pivoting the work operation lever9in one direction, one or more of the operation valves51,52,53and54that correspond to that direction are actuated to deliver, as pilot pressure fluid, fluid supplied from the hydraulic pump42.

When the work operation lever9is pivoted forward (see “F” inFIG.6A) from a neutral position (N), the corresponding operation valve51delivers pilot pressure fluid at a flow rate corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) and the pressure of the pilot pressure fluid is applied to the upper pressure receiver of the lift arm control valve44inFIG.6Avia a pilot pressure fluid passage71, so that the spool of the lift arm control valve44shifts downward inFIG.6A. Accordingly, hydraulic fluid is supplied from the lift arm control valve44to the rod-side fluid chambers14aof the lift arm cylinders14via the fluid supply/discharge passage55and hydraulic fluid is discharged from the bottom-side fluid chambers14bof the lift arm cylinders14to the lift arm control valve44via the fluid supply/discharge passage56, causing the piston rods of the lift arm cylinders14to retract to lower the lift arms10.

When the work operation lever9is pivoted rearward (backward) (B) from the neutral position (N), the corresponding operation valve52delivers pilot pressure fluid at a flow rate corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) and the pressure of the pilot pressure fluid is applied to the lower pressure receiver of the lift arm control valve44inFIG.6Avia a pilot pressure fluid passage72, so that the spool of the lift arm control valve44shifts upward inFIG.6A. Accordingly, hydraulic fluid is supplied from the lift arm control valve44to the bottom-side fluid chambers14bof the lift arm cylinders14via the fluid supply/discharge passage56and hydraulic fluid is discharged from the rod-side fluid chambers14aof the lift arm cylinders14to the lift arm control valve44via the fluid supply/discharge passage55, causing the piston rods of the lift arm cylinders14to extend to raise the lift arms10.

When the work operation lever9is pivoted leftward (L) from the neutral position (N), the corresponding operation valve53delivers pilot pressure fluid at a flow rate corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) and the pressure of the pilot pressure fluid is applied to the upper pressure receiver of the attachment control valve45inFIG.6Avia a pilot pressure fluid passage73, so that the spool of the attachment control valve45shifts downward inFIG.6A. Accordingly, hydraulic fluid is supplied from the attachment control valve45to the bottom-side fluid chambers15bof the attachment cylinders15via the fluid supply/discharge passage57and hydraulic fluid is discharged from the rod-side fluid chambers15aof the attachment cylinders15to the attachment control valve45via the fluid supply/discharge passage58, causing the piston rods of the attachment cylinders15to extend to swing the work attachment16downward (in the anticlockwise direction inFIGS.1and2) with respect to the left and right lift arms10.

When the work operation lever9is pivoted rightward (R) from the neutral position (N), the corresponding operation valve54delivers pilot pressure fluid at a flow rate corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) and the pressure of the pilot pressure fluid is applied to the lower pressure receiver of the attachment control valve45inFIG.6Avia a pilot pressure fluid passage74, so that the spool of the attachment control valve45shifts upward inFIG.6A. Accordingly, hydraulic fluid is supplied from the attachment control valve45to the rod-side fluid chambers15aof the attachment cylinders15via the fluid supply/discharge passage58and hydraulic fluid is discharged from the bottom-side fluid chambers15bof the attachment cylinders15to the attachment control valve45via the fluid supply/discharge passage57, causing the piston rods of the attachment cylinders15to retract to swing the attachment16upward (in the clockwise direction inFIGS.1and2) with respect to the left and right lift arms10.

The work operation lever9may be pivotable in four diagonal directions from the neutral position, and both the raising or lowering of the left and right lift arms10and the upward or downward swinging movement of the work attachment16may be achieved by pivoting the work operation lever9in one of the diagonal directions.

In such a case, the following configuration may be used. Pivoting the work operation lever9diagonally forward and leftward from the neutral position (N) lowers the lift arms10while swinging the attachment16downward. Pivoting the work operation lever9diagonally forward and rightward from the neutral position (N) lowers the lift arms10while swinging the attachment16upward. Pivoting the work operation lever9diagonally backward and leftward from the neutral position (N) raises the lift arms10while swinging the attachment16downward. Pivoting the work operation lever9diagonally backward and rightward from the neutral position (N) raises the lift arms10while swinging the attachment16upward.

The work hydraulic system40A is provided with fluid pressure detectors81,82,83, and84to detect hydraulic pressures in the respective pilot pressure fluid passages71,72,73, and74. The fluid pressure detectors81,82,83, and84are electrically connected to the controller20, and the controller20receives signals representative of the hydraulic pressures detected by the fluid pressure detectors81,82,83, and84.

The controller20is capable of determining, based on the signals received from the fluid pressure detectors81,82,83, and84, whether or not the lift arm control valve44or the attachment control valve45is in operation to cause the lift arm cylinder14or the attachment cylinder15to extend or retract. In other words, the controller20is capable of determining whether or not the work operation lever9is operated to actuate the lift arms10or the work attachment16(whether the work operation lever9is pivoted from the neutral position). The controller20is further capable of, based on the signals, recognizing the position of the lift arm control valve44or the attachment control valve45, i.e., the direction of operation and operation amount of the work operation lever9(the direction in which the work operation lever9is pivoted from the neutral position and the angle at which the work operation lever9is pivoted from the neutral position).

The following discusses the link structure between (i) the work operation lever9and (ii) the lift arm control valve44and the attachment cylinder15specific to the work hydraulic system40B inFIG.6B.

The working machine1is provided, at the base of the work operation lever9, with a lever position detector9ato detect the direction of operation and operation amount of the work operation lever9(the direction in which the work operation lever9is pivoted from the neutral position and the angle at which the work operation lever9is pivoted from the neutral position). The lever position detector90is a gyroscope sensor, an angle sensor, a potentiometer, and/or the like. The lever position detector9ais electrically connected to the controller20, and the controller20receives signal(s) representative of the operation direction and operation amount of the work operation lever9detected by the lever position detector9a.

The work hydraulic system40B includes solenoid valves67and68to positionally control the lift arm control valve44, and solenoid valves69and70to positionally control the attachment control valve45. The solenoid valves67,68,69, and70are controlled by the controller20based on the direction of operation and operation amount of the work operation lever9(the direction in which the work operation lever9is pivoted from the neutral position and the angle at which the work operation lever9is pivoted from the neutral position) detected by the lever position detector9a.

When the work operation lever9is pivoted forward (see “F” inFIG.6A) from a neutral position (N) (seeFIG.6A), the controller20applies a control signal (electric current) corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) to the solenoid of the solenoid valve67to energize the solenoid, the solenoid valve67delivers pilot pressure fluid, and the pilot pressure fluid is supplied to the upper pressure receiver of the lift arm control valve44inFIG.6B, so that the spool of the lift arm control valve44shifts downward inFIG.6B. Accordingly, hydraulic fluid is supplied from the lift arm control valve44to the rod-side fluid chambers14aof the lift arm cylinders14via the fluid supply/discharge passage55and hydraulic fluid is discharged from the bottom-side fluid chambers14bof the lift arm cylinders14to the lift arm control valve44via the fluid supply/discharge passage56, causing the piston rods of the lift arm cylinders14to retract to lower the lift arms10.

When the work operation lever9is pivoted rearward (backward) (B) (seeFIG.6A) from the neutral position (N), the controller20applies a control signal (electric current) corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) to the solenoid of the solenoid valve68to energize the solenoid, the solenoid valve68delivers pilot pressure fluid, and the pilot pressure fluid is supplied to the lower pressure receiver of the lift arm control valve44inFIG.6B, so that the spool of the lift arm control valve44shifts upward inFIG.6B. Accordingly, hydraulic fluid is supplied from the lift arm control valve44to the bottom-side fluid chambers14bof the lift arm cylinders14via the fluid supply/discharge passage56and hydraulic fluid is discharged from the rod-side fluid chambers14aof the lift arm cylinders14to the lift arm control valve44via the fluid supply/discharge passage55, causing the piston rods of the lift arm cylinders14to extend to raise the lift arms10.

When the work operation lever9is pivoted leftward (L) (seeFIG.6A) from the neutral position (N) the controller20applies a control signal (electric current) corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) to the solenoid of the solenoid valve69to energize the solenoid, the solenoid valve69delivers pilot pressure fluid, and the pilot pressure fluid is supplied to the upper pressure receiver of the attachment control valve45inFIG.6B, so that the spool of the attachment control valve45shifts downward inFIG.6B. Accordingly, hydraulic fluid is supplied from the attachment control valve45to the bottom-side fluid chambers15bof the attachment cylinder15via the fluid supply/discharge passage57and hydraulic fluid is discharged from the rod-side fluid chambers15aof the attachment cylinders15to the attachment control valve45via the fluid supply/discharge passage58, causing the piston rods of the attachment cylinders15to extend to swing the work attachment16downward (in the anticlockwise direction inFIGS.1and2) with respect to the left and right lift arms10.

When the work operation lever9is pivoted rightward (R) (seeFIG.6A) from the neutral position (N), the controller20applies a control signal (electric current) corresponding to the angle at which the work operation lever9is pivoted from the neutral position (N) (operation amount) to the solenoid of the solenoid valve70to energize the solenoid, the solenoid valve70delivers pilot pressure fluid, and the pilot pressure fluid is supplied to the lower pressure receiver of the attachment control valve45inFIG.6B, so that the spool of the attachment control valve45shifts upward inFIG.6B. Accordingly, hydraulic fluid is supplied from the attachment control valve45to the bottom-side fluid chambers15bof the attachment cylinders15via the fluid supply/discharge passage58and hydraulic fluid is discharged from the bottom-side fluid chambers15bof the attachment cylinders15to the attachment control valve45via the fluid supply/discharge passage57, causing the piston rods of the attachment cylinders15to retract to swing the work attachment16upward (in the clockwise direction inFIGS.1and2) with respect to the left and right lift arms10.

The work operation lever9linked to the work hydraulic system40B inFIG.6Bmay be pivotable in four diagonal directions from the neutral position, and both the raising or lowering of the left and right lift arms10and the upward or downward swinging movement of the work attachment16may be achieved by pivoting the work operation lever9in one of the diagonal directions, similarly to the work operation lever9linked to the work hydraulic system40A inFIG.6A.

In the work hydraulic system40(the work hydraulic system40A inFIG.6Aand the work hydraulic system40B inFIG.6B), the input interface(s) of the controller20has/have electrically connected thereto the rod-side pressure detector63aand the bottom-side pressure detector63bof the lift arm cylinder fluid pressure detector63and have electrically connected thereto the rod-side pressure detector64aand the bottom-side pressure detector64bof the attachment cylinder fluid pressure detector64. The controller20is capable of evaluating the state of contact between the work attachment16and the contact object17based on the result of detection by the lift arm cylinder fluid pressure detector63and/or the attachment cylinder fluid pressure detector64(hereinafter may be referred to as “cylinder fluid pressure detector(s)63and/or64”).

The following description discusses steps performed by the controller20to evaluate the state of contact between the work attachment16and the contact object17based on the result of detection by the cylinder fluid pressure detector(s)63and/or64.

First, major examples of the state of contact between the work attachment16and the contact object17(may be referred to also as “contact state”) are the following three states: a predetermined contact state in which the work attachment16is in contact with the contact object17and apples a predetermined (target, desired) contact pressure on the contact object17; an “insufficient contact state” in which the work attachment16does not apply a sufficient contact pressure on the contact object17because, for example, the work attachment16is spaced from the contact object17; and an “excessive contact state” in which the work attachment16applies an excessive contact pressure on the contact object17, such as, for example, a state in which the work attachment16is digging into the contact object17such as soil.

The “predetermined contact state” may have different meanings depending on the type of work attachment16, the content of work done using the work attachment16, and/or the like. For example, in the case of leveling of soil (earth)17A (leveling of ground) using the bucket16A as illustrated inFIG.1, cleaning of a road surface17B using the sweeper16B as illustrated inFIG.2, or the like, the “predetermined contact state” refers to the state in which the work attachment16is in an optimal (suitable) attitude and in contact with the contact object17A or17B, and this contact state (contact pressure between the work attachment16and the contact object17A or17B which are in this contact state) is required to be maintained during work/travel of the working machine1.

In the case of crushing of a to-be-crushed object17C such as a concrete block using the hydraulic breaker16C as illustrated inFIG.3, the “predetermined contact state” refers to the state in which the hydraulic breaker16C applies a pressing force equal to or greater than a predetermined minimum required pressing force and is in contact with the to-be-crushed object17C.

The hydraulic breaker16C receives hydraulic pressure from the AUX ports11to cause a crushing chisel16Cb in the form of rod to make reciprocating movements. If the chisel16Cb is driven by hydraulic pressure from the AUX ports11while the hydraulic breaker16C is in “the insufficient contact state”, i.e., if the chisel16Cb is driven by hydraulic pressure from the AUX ports11when the hydraulic breaker16C is spaced from the to-be-crushed object17C or when the hydraulic breaker16C is in contact with the to-be-crushed object17C but only applies a pressure less than the minimum required pressure to the to-be-crushed object17C, the chisel16Cb makes idle strokes (idles) and directly receives a very strong hydraulic pressure, and may be damaged.

That is, the “predetermined contact state” for the hydraulic breaker16C refers to the state (contact degree) in which the hydraulic breaker16C is in contact with the to-be-crushed object17C and applies a minimum required pressure (used as a criterion for making a judgment to avoid the insufficient contact state) to the to-be-crushed object17C, instead of an optimal contact state to be maintained during work.

In the case of digging into soil (earth)17D (making a hole) using the earth auger16D as illustrated inFIG.4, it is first necessary to define the state in which the earth auger16D is in contact with the soil17D at a depth-of-excavation of 0, before excavating (digging into) the soil17D while checking the current depth of excavation in order to form a pile hole or the like having a target depth. Therefore, the “predetermined contact state” for excavation using the earth auger16D refers to the state in which the earth auger16D is in contact with the soil17D at a depth-of-excavation of 0.

As has been discussed, the meaning of the “predetermined contact state” differs depending on the type of work attachment16and the content of work as illustrated inFIGS.1to4, and such a state may be required to be maintained as an optimal state or may be required to be achieved temporarily. In any case, the work attachment16is required to be in contact with the contact object17and in the “predetermined contact state” either always or temporarily.

Checking the state of contact between the work attachment16and the contact object17(i.e., checking whether or not the work attachment16is in the predetermined contact state) has depended on the worker's vision and experience in operation of the work operation lever9and/or the like.

In the working machine1according to the present application, the controller20is configured or programmed to (i) refer to the relationship in hydraulic pressure regarding the lift arm cylinder(s)14(relationship between the rod-side hydraulic pressure P1r and the bottom-side hydraulic pressure P1b) calculated based on the results of detection by the lift arm cylinder fluid pressure detector63and/or the relationship in hydraulic pressure regarding the attachment cylinder(s)15(relationship between the rod-side hydraulic pressure P2a and the bottom-side hydraulic pressure P2r) calculated based on the results of detection by the attachment cylinder fluid pressure detector64and (ii) determine whether the state of contact between the work attachment16and the contact object17is the predetermined contact state, the insufficient contact state, the excessive contact state, or the like.

The controller20is capable of calculating a value representing the relationship in hydraulic pressure regarding the lift arm cylinder(s)14and the relationship in hydraulic pressure regarding the attachment cylinder(s)15. There are various possible arithmetic expressions to calculate such a value. In the present embodiment, the value is a cylinder thrust force Fc that is generated depending on the balance between (i) the pressing force between the work attachment16and the contact object17and (ii) the gravity acting on the piston.

The cylinder thrust force Fc is calculated using the following expression.

In the above expression, G represents gravitational acceleration. Pr represents the rod-side hydraulic pressure of a hydraulic cylinder14or15, Aa represents the area on which pressure is acting (hereinafter “pressure area”) of the rod-side fluid chamber of the hydraulic cylinder14or15, Pb represents the bottom-side hydraulic pressure of the hydraulic cylinder14or15, and Ab represents the pressure area of the bottom-side fluid chamber of the hydraulic cylinder14or15. The cylinder thrust force Fc calculated using the above expression is greater when the rod-side hydraulic pressure Pr is greater (when the bottom-side hydraulic pressure Pb is smaller). That is, the cylinder thrust force Fc calculated using the above expression is a force in the direction of retraction of a piston rod. In other words, the cylinder thrust force Fc has a positive value when the direction of the cylinder thrust force Fc is the direction of retraction of a piston rod, whereas the cylinder thrust force Fc has a negative value when the direction of the cylinder thrust force Fc is the direction of extension of the piston rod.

The cylinder thrust force Fc of the lift arm cylinder14is calculated by substituting the pressure area of the rod-side fluid chamber14ainto Aa of the above expression, substituting the pressure area of the bottom-side fluid chamber14binto Ab of the above expression, substituting the rod-side hydraulic pressure P1r detected by the rod-side pressure detector63ainto Pr of the above expression, and substituting the bottom-side hydraulic pressure P1b detected by the bottom-side pressure detector63binto Pb of the above expression.

The cylinder thrust force Fc of the attachment cylinder15is calculated by substituting the pressure area of the rod-side fluid chamber15ainto Aa of the above expression, substituting the pressure area of the bottom-side fluid chamber15binto Ab of the above expression, substituting the rod-side hydraulic pressure P2r detected by the rod-side pressure detector64ainto Pr of the above expression, and substituting the bottom-side hydraulic pressure P2b detected by the bottom-side pressure detector64binto Pb of the above expression.

Note that, when the operator operates the work operation lever9in order to swing the lift arms10upward or downward (cause the lift arm cylinders14to extend or retract) or to swing the work attachment16upward or downward (cause the attachment cylinders15to extend or retract), a thrust force is produced on the piston and therefore a frictional resistance is generated between the piston and the main body of the cylinder.

In the case where the work operation lever9is operated in order to cause the hydraulic cylinders14and/or15to extend or retract (hereinafter may be referred to as “when the work operation lever9is in operation”), the controller20calculates a corrected version of the cylinder thrust force Fc using a correction value set according to the frictional resistance resulting from the operation of the work operation lever9(for example, the controller20corrects the detected rod-side hydraulic pressure Pr or the bottom-side hydraulic pressure Pb and then calculates the cylinder thrust force Fc).

Examples of the correction value include: a correction value Kp set according to static friction generated in the hydraulic cylinders14and/or15when the work operation lever9is in operation but the hydraulic cylinders14and/or15are not moving (stationary); and a correction value Kv set according to kinetic friction generated in the hydraulic cylinders14and/or15when the work operation lever9is in operation and the hydraulic cylinders14and/or15are moving.

The foregoing static friction (frictional force) is a force that keeps the piston at rest against the pressure applied on the piston in the direction of extension or retraction of the piston rod. The foregoing kinetic friction (frictional force) is a force to reduce the movement of the piston which is sliding in the direction of extension or retraction of the piston rod. The correction value Kp and the correction value Kv are different values corresponding to the static frictional force and the kinetic frictional force differing from each other as discussed above. Specifically, the static frictional force is greater than the kinetic frictional force, and therefore the correction value Kp is greater than the correction value Kv.

When the work operation lever9is operated in order to cause the hydraulic cylinders14and/or15to extend (hereinafter referred to as “when the work operation lever9is operated to cause cylinders to extend”), the controller20corrects the detected bottom-side hydraulic pressure Pb to reduce the detected bottom-side hydraulic pressure Pb. When the work operation lever9is operated in order to cause the hydraulic cylinders14and/or15to retract (hereinafter referred to as “when the work operation lever9is operated to cause cylinders to retract”), the controller20corrects the detected rod-side hydraulic pressure Pr to reduce the detected rod-side hydraulic pressure Pr.

Specifically, the controller20calculates the cylinder thrust force Fc using any of the following equations according to the situation.

First, when the work operation lever9is operated to cause cylinders to extend but the hydraulic cylinders14and/or15are not moving (stationary) (pressure in the direction of extension of the piston rod is applied on the piston), the cylinder thrust force Fc is calculated using the following equation using the correction value Kp.

When the work operation lever9is operated to cause cylinders to retract but the hydraulic cylinders14and/or15are not moving (stationary) (pressure in the direction of retraction of the piston rod is applied on the piston), the cylinder thrust force Fc is calculated using the following equation using the correction value Kp.

One way to more accurately calculate the cylinder thrust force Fc would be to set different correction values Kp for when the work operation lever9is operated to cause cylinders to extend and for when the work operation lever9is operated to cause cylinders to retract. Assuming that the correction value Kp for when the work operation lever9is operated to cause cylinders to extend is Kpr and the correction value Kp for when the work operation lever9is operated to cause cylinders to retract is Kpb (#Kpr), the cylinder thrust force Fc is calculated using any of the following equations according to the situation.

Specifically, when the work operation lever9is operated to cause cylinders to extend but the hydraulic cylinders14and/or15are not moving (stationary), the cylinder thrust force Fc is calculated using the following equation using the correction value Kpr.

When the work operation lever9is operated to cause cylinders to retract but the hydraulic cylinders14and/or15are not moving (stationary), the cylinder thrust force Fc is calculated using the following equation using the correction value Kpb.

Next, when the work operation lever9is operated to cause cylinders to extend and the hydraulic cylinders14and/or15are actually extending (hereinafter referred to as “when cylinders are extending”), the cylinder thrust force Fc is calculated using the following equation using the correction value Kv.

When the work operation lever9is operated to cause cylinders to retract and the hydraulic cylinders14and/or15are actually retracting (hereinafter referred to as “when cylinders are retracting”), the cylinder thrust force Fc is calculated using the following equation using the correction value Kv.

One way to more accurately calculate the cylinder thrust force Fc would be to set different correction values Kv for when cylinders are extending and for when cylinders are retracting. Assuming that the correction value Kv for when cylinders are extending is Kvr and the correction value Kv for when cylinders are retracting is Kvb (Kvr), the cylinder thrust force Fc is calculated using any of the following equations according to the situation.

Specifically, when cylinders are extending, the cylinder thrust force Fc is calculated using the following equation using the correction value Kvr.

When cylinders are retracting, the cylinder thrust force Fc is calculated using the following equation using the correction value Kvb.

In order to determine which of the above equations to use to calculate the cylinder thrust force Fc, it is necessary to determine whether or not the work operation lever9is currently in operation and, if the work operation lever9is in operation, to determine whether the work operation lever9is operated to cause cylinders to extend or the work operation lever9is operated to cause cylinders to retract.

In the case where the working machine1includes the work hydraulic system40A ofFIG.6A, the controller20determines whether or not pilot fluid pressure is applied on any of the pilot pressure fluid passages71,72,73, and74and which of the pilot pressure fluid passages71,72,73, and74is/are receiving the pilot fluid pressure based on the results of detection by the fluid pressure detectors81,82,83, and84, thus performing the above-described determination.

On the contrary, in the case where the working machine1includes the work hydraulic system40B ofFIG.6B, the controller20checks the direction in which the work operation lever9is pivoted from the neutral position and the angle at which the work operation lever9is pivoted from the neutral position based on the results of detection by the lever position detector9a, thus performing the above-described determination.

Furthermore, in the case where hydraulic cylinders14and/or15are not moving when the work operation lever9is operated to cause cylinders to extend or when the work operation lever9is operated to cause cylinders to retract, the corresponding rod-side hydraulic pressure Pr or bottom-side hydraulic pressure Pb increases as the operation amount of the work operation lever9(the angle at which the work operation lever9is pivoted from the neutral position) increases; in this regard, the static frictional force would also change as the operation amount changes.

In view of the above, the controller20may change the correction value Kp (Kpr, Kpb) according to the operation amount of the work operation lever9, and calculate the cylinder thrust force Fc using the thus-changed correction value Kp (Kpr, Kpb).

In the case where the working machine1includes the work hydraulic system40B ofFIG.6B, the controller20is capable of checking the operation amount of the work operation lever9(the angle at which the work operation lever9is pivoted from the neutral position) based on a signal received from the lever position detector9a. On the contrary, in the case where the working machine1includes the work hydraulic system40A ofFIG.6A, the controller20is capable of checking the pilot fluid pressure applied on the cylinder control valve(s)44and/or45instead of the operation amount of the work operation lever9based on the results of detection by the fluid pressure detectors81,82,83, and84.

Note that the frictional forces (static frictional force and kinetic frictional force) against hydraulic pressure may change under the influence of ambient temperature changes depending on the material for the hydraulic cylinders14and/or15. Also note that the frictional forces (static frictional force and kinetic frictional force) on the hydraulic cylinders14and/or15may also change under the influence of, for example, changes in viscosity of hydraulic fluid that would result from changes in temperature of the hydraulic fluid.

In view of the above, the correction value Kp (Kpr, Kpb) and/or the correction value Kv (Kvr, Kvb) set according to the frictional forces (static frictional force and kinetic frictional force) may be changed according to the temperature of hydraulic fluid and/or the ambient temperature.

Note that each of the cylinder thrust forces Fc calculated using the above-described equations is an example of a value representative of the relationship in hydraulic pressure between the rod-side hydraulic pressure Pr and the bottom-side hydraulic pressure Pb, and that the value may be corrected depending on the situation by any of various other methods.

Furthermore, it is assumed that the state of contact between the work attachment16and the contact object17is represented by a value of “contact degree C.” when the state of contact is evaluated. In the present embodiment, the contact degree C. is the percentage (%) of the cylinder thrust force Fc calculated as described above based on the results of detection by the cylinder fluid pressure detector(s)63and/or64to the maximum cylinder thrust force Fcm. Specifically, the contact degree C. (unit: %) is calculated using the following equation.

The memory21stores a predetermined contact degree Cp which is an indicator of the predetermined contact state for each work attachment16. Specifically, the state of the work attachment16in which the work attachment16is in contact with the contact object17to a predetermined contact degree Cp is defined as the “predetermined contact state”, and information about each work attachment16stored in the memory21includes the predetermined contact degree Cp of that work attachment16. Note that the foregoing relationship in hydraulic pressure such as a cylinder thrust force corresponding to the predetermined contact degree Cp may be stored instead of or in addition to the predetermined contact degree Cp. The memory21may be contained in the controller20and may be provided external to the controller20and electrically connected to the controller20.

If the current contact degree(s) C. determined based on the cylinder thrust force(s) Fc of the hydraulic cylinder(s)14and/or15calculated based on the results of detection by the cylinder fluid pressure detector(s)63and/or64is the predetermined contact degree Cp (C=Cp), the controller20determines that the current state of contact between the work attachment16and the contact object17is the predetermined contact state.

In cases where the contact degree C. is calculated based on the results of detection by the lift arm cylinder fluid pressure detector63, if the current contact degree C. is less than the predetermined contact degree Cp (C<Cp), the controller20determines that the current state of contact between the work attachment16and the contact object17is the insufficient contact state. In contrast, if the current contact degree C. is greater than the predetermined contact degree Cp (C>Cp), the controller20determines that the current state of contact between the work attachment16and the contact object17is the excessive contact state.

In cases where the contact degree C. is calculated based on the results of detection by the attachment cylinder fluid pressure detector64, if the current contact degree C. is less than the predetermined contact degree Cp (C<Cp), the controller20determines that the current state of contact between the work attachment16and the contact object17is the excessive contact state. In contrast, if the current contact degree C. is greater than the predetermined contact degree Cp (C>Cp), the controller20determines that the current state of contact between the work attachment16and the contact object17is the insufficient contact state.

Note that, as discussed earlier, the cylinder thrust force Fc is an example of an indicator of the relationship in hydraulic pressure between the rod-side hydraulic pressure Pr and the bottom-side hydraulic pressure Pb of a hydraulic cylinder (lift arm cylinder14or attachment cylinder15). The indicator of the relationship in hydraulic pressure is not limited as such.

For example, the foregoing expression is for use when the relationship in hydraulic pressure is represented by the cylinder thrust force Fc in the direction of retraction of a piston rod. The expression may be replaced with another expression for use when the relationship in hydraulic pressure is represented by a cylinder thrust force in the direction of extension of the piston rod. In other words, the cylinder thrust force in the direction of extension of the piston rod may have a positive value and the cylinder thrust force in the direction of retraction of the piston rod may have a negative value.

The indicator does not need to be a value calculated based on the difference between the rod-side hydraulic pressure Pr and the bottom-side hydraulic pressure Pb such as the cylinder thrust force Fc. The indicator of the relationship in hydraulic pressure may be, for example, a value calculated based on the ratio between the rod-side hydraulic pressure Pr and the bottom-side hydraulic pressure Pb.

The contact degree C. and the predetermined contact degree Cp may be any values and not limited to those determined using the foregoing equations, provided that the contact degree C. and the predetermined contact degree Cp are indicators of the state of contact between the work attachment16and the contact object17and are calculated based on the relationship in hydraulic pressure (for example, cylinder thrust force Fc) between the rod-side hydraulic pressure Pr and the bottom-side hydraulic pressure Pb of hydraulic cylinder(s) (lift arm cylinder(s)14and/or attachment cylinder(s)15).

For example, the following arrangement may be used: a value indicating the relationship in hydraulic pressure between the rod-side hydraulic pressure Pr and the bottom-side hydraulic pressure Pb (such as the cylinder thrust force Fc) is used as-is to represent the contact degree: the value is compared with a value representative of the relationship in hydraulic pressure corresponding to the predetermined contact state stored in the memory21; and whether the work attachment16and the contact object17are in the predetermined contact state or not is determined.

The controller20is capable of performing various steps corresponding to the state of contact between the work attachment16and the contact object17(contact degree C.) determined based on the relationship in hydraulic pressure (cylinder thrust force Fc) calculated using the results of detection by the cylinder fluid pressure detector(s)63and/or64.

For example, if the controller20determines that the state of contact of the work attachment16including a hydraulic actuator (AUX actuator) supplied with hydraulic fluid from the AUX port(s)11with the contact object17is the insufficient contact state (C<Cp), the controller20controls the solenoid valve(s)47and/or48to place the AUX control valve46in the position in which hydraulic fluid is not sent to the AUX port(s)11, thus stopping the driving of the hydraulic actuator (AUX actuator) of the work attachment16.

The controller20has a display22electrically connected thereto. The controller may cause the display22to display the relationship in hydraulic pressure (cylinder thrust force Fc) calculated based on the results of detection by the cylinder fluid pressure detector(s)63and/or64and/or the current state of contact (contact degree C.) between the work attachment16and the contact object17determined based on the calculated relationship in hydraulic pressure. Additionally or alternatively, the controller20may cause the display22to display the difference (Cp-C) between the current contact state (contact degree C.) and the predetermined contact state (predetermined contact degree Cp).

Additionally or alternatively, the controller20may, in the case where the work attachment16is not in the predetermined contact state (C≠Cp), issue an alert to an operator by, for example, causing the display22to display an indication that the work attachment16is not in the predetermined contact state. Additionally or alternatively, the controller20may cause the display22to display a guidance indication indicating a manner in which the work operation lever9should be operated to bring the contact state (contact degree C.) into the predetermined contact state (predetermined contact degree Cp). The guidance indication is, for example, the message “Raise lift arms”, “Lower work attachment”, and/or the like.

Additionally or alternatively, the controller20may transmit the foregoing alert, guidance, and/or the like to the operator via sound.

Additionally or alternatively, the controller20may control the lift arm cylinder(s)14and/or attachment cylinder(s)15to bring the current state of contact (contact degree C.) between the work attachment16and the contact object17determined based on the results of detection by the cylinder fluid pressure detector(s)63and/or64into the predetermined contact state (predetermined contact degree Cp).

The lift arm control valve44and/or the attachment control valve45, which are pilot-control proportional valves which change positions in response to pilot pressure inFIGS.6A and6B, may be replaced by proportional solenoid valve(s).

In cases where the control valves44and45are proportional solenoid valves, the work operation lever9may be replaced by the one that includes a lever position detector9ato detect the direction of operation and operation amount of the work operation lever9as illustrated inFIG.9B, and the lever position detector9amay be electrically connected to the/an input interface of the controller20.

In such a case, the controller20may control the energization and deenergization of the solenoid(s) of the lift arm control valve44and/or attachment control valve45based on signal(s) indicating the position and the amount of pivoting of the work operation lever9received from the lever position detector9a.

Alternatively, the lift arm control valve44and the attachment control valve45may stay the same as those illustrated inFIG.6A, i.e., the lift arm control valve44and the attachment control valve45may be pilot-control valves and the pilot pressure fluid to the control valves44and45may be controlled by operating the work operation lever9as illustrated inFIG.6, whereas the work operation lever9may be operable in accordance with an operation signal from the controller20without the operator's operation.

In such a case, the controller20may control the work operation lever9to control the positions of the control valves44and45to ensure that the work attachment16and the contact object17are in the predetermined contact state (predetermined contact degree Cp), according to the contact state (contact degree C.) determined based on the relationship in hydraulic pressure (cylinder thrust force Fc) calculated based on the results of detection by the cylinder fluid pressure detector(s)63and/or64.

As discussed earlier, the following vary depending on the type of work attachment16, the type of content of work, and the like: the predetermined contact state (predetermined contact degree Cp) of the work attachment16and the contact object17; which of the result of detection by the cylinder fluid pressure detector63and the result of detection by the cylinder fluid pressure detector64should be used (or should mainly be used) to evaluate the contact state: which part of the working machine1is to be controlled and how the working machine1is to be controlled based on the determined contact state; and the like.

In this regard, the memory21stores pieces of information relating to the predetermined contact state (predetermined contact degree Cp) of the work attachment16and the contact object17, which of the result of detection by the cylinder fluid pressure detector63and the result of detection by the cylinder fluid pressure detector64should be used (or should mainly be used) to determine the state of contact, which part of the working machine1is to be controlled and how the working machine1is to be controlled based on the determined contact state, and the like, for respective types of work attachment16and/or for respective types of work.

In view of the above, in order for the controller20to select and acquire desired piece(s) of information from the pieces of information stored in the memory21, for example, the display22may display an attachment list65as illustrated inFIG.7before the working machine1does work using the work attachment16. The attachment list65is a list of arranged icons66each including a pictogram of a corresponding work attachment16.

The attachment list65may be displayed in a touch sensitive form. In such a case, it is possible, by pressing with a finger one of the icons66displayed on the display22that includes a pictogram corresponding to the work attachment16attached to the working device4(lift arm10), to cause the controller20to select and acquire a piece of information relating to the work attachment16corresponding to the icon66from the pieces of information stored in the memory21.

For example, the icons66of the attachment list65inFIG.7include an icon66aincluding a pictogram of a bucket16A, an icon66bincluding a pictogram of a sweeper16B, an icon66cincluding a pictogram of a hydraulic breaker16C, and an icon66dincluding a pictogram of an earth auger16D.

It is possible to cause the controller20to acquire a piece of information Ia relating to the bucket16A from the memory21by touching the icon66ain the attachment list65displayed in a touch sensitive form. It is possible to cause the controller20to acquire a piece of information Ib relating to the sweeper16B from the memory21by touching the icon66bin the attachment list65. It is possible to cause the controller20to acquire a piece of information Ic relating to the hydraulic breaker16C from the memory21by touching the icon66cin the attachment list65. It is possible to cause the controller20to acquire a piece of information Id relating to the earth auger16D from the memory21by touching the icon66din the attachment list65.

Note that any structure may be used, provided that a piece of information relating to the work attachment16attached to the working device4can be selected and acquired from the pieces of information stored in the memory21. For example, the icons66of the attachment list65may be replaced by corresponding push buttons provided on, for example, an instrument panel in front of the operator's seat7of the working machine1.

Additionally or alternatively, each work attachment16may include a storage unit such as a microchip storing a piece of information including a desired predetermined contact degree Cp of the work attachment16, which of the relationship in hydraulic pressure (cylinder thrust force Fc) of the lift arm cylinder(s)14and that of the attachment cylinder(s)15should be used (or should mainly be used), and/or the like, and the controller20may be configured or programmed to read the piece of information from the storage unit of the work attachment16attached to the working device4and control the work attachment16and/or the like.

The controller20may be configured or programmed to control the work attachment16and/or the like based on the information acquired from the work attachment16in priority to the information stored in the memory21of the working machine1.

In cases where the work attachment16is an attachment to form, by work such as excavation or boring, a work product such as a hole or a trench in the contact object17in contact with the work attachment16in the predetermined contact state, the controller20may display the degree of work done represented as, for example, the depth of the hole, the depth of trench, or the like. In this regard, the controller20may cause the display22to display a degree-of-work-done gauge WG.

For example, in the case where the earth auger16D is attached to the working device4(lift arm(s)10) as illustrated inFIG.4(that is, in the case of an embodiment in which the foregoing attachment list65is displayed, the earth auger16D is selected from the attachment list65displayed on the display22and the piece of information Id relating to the earth auger16D is selected and acquired), the controller20causes the display22to display a depth-of-excavation gauge67as illustrated inFIG.8, which is an example of the degree-of-work-done gauge WG.

In such a case, the controller20causes the display22to display, as a reference position DO which is a depth-of-excavation of 0 on the depth-of-excavation gauge67, the position of the distal end of the earth auger16D in contact with the soil17D (contact object17) and in the predetermined contact state. The controller20further causes the display22to display, as the depth-of-excavation D, the position of the distal end of the earth auger16D which changes as the excavation proceeds from the reference position DO.

Note that the controller20may acquire the attitude of the working device4when the earth auger16D is at the reference position DO based on the result of detection by the foregoing attitude detector62, and cause the memory21to store the attitude. The controller may, as the earth auger16D proceeds with excavation on the soil17D, further read a change in attitude of the working device4resulting from the progress of the excavation by acquiring the results of detection by the attitude detector62, determine the depth-of-excavation D based on the change, and indicate the determined depth-of-excavation D on the depth-of-excavation gauge67.

The following description discusses control flows inFIGS.9to12corresponding to pieces of work using the respective work attachments16illustrated inFIGS.1to4, based on the assumption that the controller20controls the actions of the working device4(for example, control the lift arm control valve44and/or attachment control valve45which are proportional solenoid valves) until the work attachment16makes contact with the contact object17in a predetermined contact state.

FIG.1illustrates a working machine1performing leveling of soil (earth)17A which is a contact object17(performing leveling of ground) by traveling with the bucket16A in contact with the ground. Note that the bucket16A illustrated inFIG.1does not include its own hydraulic actuators, and the AUX ports11of the working machine1do not need to be fluidly connected to the bucket16A. Therefore, the AUX ports11of the working machine1are closed.

In order to achieve reliable and accurate leveling of the soil17A, it is required that the bucket16A continue being in an optimal attitude and continue applying an optimal contact pressure on the soil17A during the travel/work of the working machine1. That is, it is required that a predetermined (optimal) state of contact between the bucket16A (work attachment16) and the soil17A (contact object17) be maintained.

One example of the predetermined (optimal) contact state of the bucket16A during the land leveling would be, in the case where, for example, the surface of the soil is a horizontal surface, a state in which the bottom surface of the bucket16A is in contact with the surface of the soil such that the bottom surface of the bucket16A is a horizontal surface parallel to the surface of the soil.

If the bucket16A is in contact with the surface of the soil17A such that the bucket16A is tilted downward and forward, the sharp distal end portion of the bucket16A is pressed against the soil17A (and further digs into the soil17A). Such a state is an excessive contact state for the bucket16A which is about to perform land leveling (leveling of ground). If the working machine1travels with the bucket16A in the excessive contact state, the distal end portion of the bucket16A may gouge the soil17A, resulting in a loss of the effect of land leveling (leveling of ground).

In contrast, if the bucket16A is spaced above from the surface of the soil17A and a contact pressure applied by the bucket16A to the soil17A is not large enough, such a state is an insufficient contact state for the bucket16A which is about to perform land leveling (leveling of ground). If the working machine1travels to perform land leveling (leveling of ground) with the bucket16A in the insufficient contact state, a desired effect of land leveling (leveling of ground) may not be obtained, and many stones and rocks and the like would be left on the surface of the soil17A after the land leveling (leveling of ground).

Because the state of contact between the soil17A and the bucket16A which is about to perform land leveling (leveling of ground) (i.e., the attitude of the bucket16A) is evaluated by checking the degree of tilting of the bucket16A in the fore-and-aft direction and/or the like, the state of contact should in fact be evaluated based on the relationship in hydraulic pressure regarding the lift arm cylinder(s)14(relationship between the rod-side hydraulic pressure P1r and the bottom-side hydraulic pressure P1b) and the relationship in hydraulic pressure regarding the attachment cylinder(s)15(relationship between the rod-side hydraulic pressure P2r and the bottom-side hydraulic pressure P2b).

It is assumed here that, however, for ease of description, the contact state of the bucket16A (contact degree C.) is determined based on the relationship in hydraulic pressure (cylinder thrust force Fc) regarding the attachment cylinder(s)15, based on the assumption that the lift arm(s)10has already been placed by the extension/retraction of the lift arm cylinder(s)14in an optimal position for the land leveling (leveling of ground) using the bucket16A, before the bucket16A is brought into contact with the soil17A by the extension/retraction of the attachment cylinder(s)15.

Assume that the predetermined contact state is a state in which the bottom surface of the bucket16A is in full-surface contact with the soil17A such that the bottom surface of the bucket16A is parallel to the surface of the soil17A, as discussed earlier. The predetermined contact degree Cp required for the bucket16A which is about to perform land leveling (leveling of ground) is about 0% to about 1%. That is, such a state is a state in which the bucket16A is in contact with the soil17A without digging into the soil17A and therefore the cylinder thrust force Fc of the attachment cylinder(s)15resulting from the weight of the bucket16A is substantially stable. The predetermined contact degree Cp of the bucket16A in such an orientation, i.e., a predetermined contact degree Cpa, is included in a piece of information Ia relating to the bucket16A stored in the memory21of the working machine1or the storage unit (such as a microchip) of the bucket16A.

The following description discusses a control flow for leveling of soil17A (leveling of ground) using the bucket16A, with reference toFIG.9.

First, the controller20acquires a piece of information Ia relating to the bucket16A in response to selection of a corresponding icon101in the attachment list65displayed on the display22and/or by receiving a signal issued by the work attachment16actually attached to the working device4, for example (step S01). The piece of information Ia includes the predetermined contact degree Cpa (which is about 0% to about 1%) which is the predetermined contact degree Cp required for the bucket16A, and/or the like.

Before the land leveling (leveling of ground) is started, the attachment cylinder(s) is/are operated to bring the bucket16A into contact with the soil17A (step S02), during which the attachment cylinder fluid pressure detector64detects the rod-side hydraulic pressure Pr (P2r) and the bottom-side hydraulic pressure Pb (P2b) (step S03). The controller calculates the cylinder thrust force Fc which is the relationship in hydraulic pressure between the detected rod-side hydraulic pressure Pr (P2r) and the detected bottom-side hydraulic pressure Pb (P2b) and the contact degree C. based on the cylinder thrust force Fc (step S04).

The controller20may cause the display22to display the calculated contact degree C. and/or the like. Note that the detection of the hydraulic pressures may be performed while the piston rod(s) of the attachment cylinder(s)15is/are moving or not moving. If the hydraulic pressures are detected while the piston rod(s) of the attachment cylinder(s)15is/are in action, the cylinder thrust force Fc is calculated via correction in consideration of the sliding resistance of the cylinder(s), as discussed earlier.

The controller20compares the calculated contact degree C. with the selected and acquired predetermined contact degree Cpa (steps S05and S06). If the contact degree C. is greater than the predetermined contact degree Cpa (about 0% to about 1%) (NO in step S05, YES in step S06), the controller20determines that the bucket16A is currently in contact with the soil17A and in the “insufficient contact state” (or the bucket16A is currently not in contact with the soil17A) (step S07), and causes the piston rod(s) of the attachment cylinder(s)15to extend to lower the bucket16A (lower the front portion of the bucket16A) (step S08). The bucket16A continues to be lowered until the contact degree C. calculated based on the results of detection by the attachment cylinder fluid pressure detector64becomes the predetermined contact degree Cpa (about 0% to about 1%) (YES in step S05).

If the contact degree C. is less than the predetermined contact degree Cpa (about 0% to about 1%) (NO in step S05, NO in step S06), the controller20determines that the bucket16A is currently in contact with the soil17A in the “excessive contact state” (the bucket16A is strongly pressed against the soil17A or the bucket16A is stuck in the soil17A) (step S09), and causes the piston rod(s) of the attachment cylinder(s)15to retract to raise the bucket16A (raise the front portion of the bucket16A) (step $10). The bucket16A continues to be raised until the contact degree C. calculated based on the results of detection by the attachment cylinder fluid pressure detector64becomes the predetermined contact degree Cpa (about 0% to about 1%) (YES in step S05).

Note that, in cases where the bucket16A is not in the predetermined contact state (in the insufficient contact state or in the excessive contact state), the controller20may cause the display22to issue an alert or a guidance indication as discussed earlier to prompt the worker to operate the working device4(attachment cylinder(s)15and/or the like) to bring the bucket16A into the predetermined contact state, instead of or in addition to the automatic operation of the working device4(attachment cylinder(s)15and/or the like) as indicated in steps S08and S10.

If the contact degree C. is the predetermined contact degree Cpa (about 0% to about 1%) (YES in step S05), the controller20determines that the bucket16A is currently in contact with the soil17A and in the “predetermined (optimal) contact state” (step S11), and causes the display22to display a message and/or the like indicating that the bucket16A is in the predetermined (optimal) contact state (step S12). Furthermore, the controller20controls, for example, the position of the attachment control valve45(which is a proportional solenoid valve) and/or the like so that the attitude X of the working device4(and the bucket16A) detected by the attitude detector62when the bucket16A is in the predetermined (optimal) contact state, i.e., a proper attitude Xo, is maintained also during the subsequent travel of the working machine1for land leveling (leveling of ground) (step S13).

The steps performed by the controller20as described above are based on the piece of information Ia including the predetermined contact degree Cpa (=about 0% to about 1%) for the bucket16A for land leveling (leveling of ground) and the like. Examples of the type of work attachment16and content of work that can be achieved by performing substantially the same steps as those shown inFIG.9based on the same information as the information Ia include land leveling (leveling of ground) using a dozer blade, snow shoveling using a dozer blade, and the like.

FIG.2illustrates a working machine1which is cleaning a road surface17B (contact object17) by traveling with the sweeper16B in contact with the road surface17B. The sweeper16B includes a main body cover16Ba, a rotary brush16Bb located in a front portion of the main body cover16Ba and having a rotary shaft extending horizontally left to right, and a hydraulic motor16Bc to drive the rotary shaft of the rotary brush16Bb.

The space in a rear portion of the main body cover16Ba that is located rearward of the rotary brush16Bb is to accommodate dust scraped into the space by the rotary brush16Bb. The rear end of the main body cover16Ba is pivotally connected to the distal end portions10cof the left and right lift arms10and the heads of the piston rods of the left and right attachment cylinders15. The hydraulic motor16Bc is connected to the AUX ports11via fluid pipes16Bd.

When the sweeper16B maintains an optimal attitude and causes the rotary brush16Bb to make contact with the road surface17B at a suitable contact pressure (i.e., when the state of contact between the bottom end of the rotary brush16Bb and the road surface17B is a predetermined (optimal) contact state), a preferred cleaning effect is achieved.

Note that, also with regard to evaluating the attitude of the sweeper16B when the sweeper16B is brought into contact with the road surface17B, it is in fact necessary to calculate both the relationship in hydraulic pressure regarding the lift arm cylinder(s)14(relationship between the rod-side hydraulic pressure P1r and the bottom-side hydraulic pressure P1b) and the relationship in hydraulic pressure regarding the attachment cylinder(s) (relationship between the rod-side hydraulic pressure P2r and the bottom-side hydraulic pressure P2b). It is assumed also here that, however, for ease of description, the contact state of the sweeper16B (contact degree C.) is determined based on the relationship in hydraulic pressure (cylinder thrust force Fc) regarding the attachment cylinder(s)15, based on the assumption that the lift arms10have already been placed by the extension/retraction of the lift arm cylinders14in an optimal position.

The predetermined (optimal) state of contact between the sweeper16B and the road surface17B is preferably a state in which the main body cover16Ba is spaced above from the road surface17B to some extent and only the bottom end of the rotary brush16Bb is in contact with the road surface17B. In such a state, the weight of the sweeper16B is applied on the pistons of the attachment cylinders15, and the cylinder thrust force Fc is acting in the direction of retraction of the piston rods. That is, the predetermined contact degree Cp required for the sweeper16B is greater than the predetermined contact degree Cpa of the bucket16A that is set on the assumption that the bottom surface of the bucket16A is in surface contact with the surface of the soil17A.

While the rotary brush16Bb is rotating, the cylinder thrust force Fc acting on the attachment cylinders15in the direction of retraction of the piston rods is greater than while the rotary brush16Bb is in the stopped state, because of the “jacking up” force acting on the sweeper16B (or because a force that raises the sweeper16B is generated). Therefore, it is preferable that there are two different predetermined contact degrees Cp for the sweeper16B in the stopped state and for the sweeper16B in the rotating state.

Thus, the following predetermined contact degrees Cp are set for the sweeper16B: a predetermined contact degree Cpb1 for the rotary brush16Bb in the stopped state (hereinafter referred to as “predetermined contact degree Cpb1 for stopped state” for short); and a predetermined contact degree Cpb2 for the rotary brush16Bb in the rotating state (hereinafter referred to as “predetermined contact degree Cpb2 for driven state” for short). The predetermined contact degree Cpb1 for stopped state may be, for example, about 6% to about 7%. The predetermined contact degree Cpb2 for driven state may be, for example, about 10% to about 11%. These are included in the piece of information Ib relating to the sweeper16B stored in the memory21of the working machine1or a storage unit (such as a microchip) of the sweeper16B.

The following description discusses a control flow for cleaning the road surface17B using the sweeper16B, with reference toFIGS.10A and10B.

First, the controller20acquires a piece of information Ib relating to the sweeper16B in response to selection of a corresponding icon101in the attachment list65and/or by receiving a signal from the sweeper16B actually attached to the working device4as discussed earlier, for example (step S21). The piece of information Ib includes the predetermined contact degree Cpb1 for stopped state which is one of the predetermined contact degrees Cp required for the sweeper16B (about 6% to about 7%), the predetermined contact degree Cpb2 for driven state which is the other of the predetermined contact degrees Cp required for the sweeper16B (about 10% to about 11%), and/or the like.

Before the cleaning is started, the attachment cylinders15are operated to bring the sweeper16B (the rotary brush16Bb of the sweeper16B) into contact with the road surface17B (step S22), during which the attachment cylinder fluid pressure detector64detects the rod-side hydraulic pressure Pr (P2r) and the bottom-side hydraulic pressure Pb (P2b) (step S23). The controller20calculates the cylinder thrust force Fc which is the relationship in hydraulic pressure between the detected rod-side hydraulic pressure Pr (P2r) and the detected bottom-side hydraulic pressure Pb (P2b) and the contact degree C. based on the cylinder thrust force Fc (step S24).

The controller20may cause the display22to display the calculated contact degree C. and/or the like. Note that the detection of the hydraulic pressures may be performed while the piston rods of the attachment cylinders15are moving or not moving. If the hydraulic pressures are detected while the piston rods of the attachment cylinders15are in action, the cylinder thrust force Fc is calculated via correction in consideration of the sliding resistance of the cylinders, as discussed earlier.

Before the controller20determines whether or not the sweeper16B is in the predetermined contact state, the controller20first determines whether the sweeper16B is being driven (i.e., whether the rotary brush16Bb is rotating) or in the stopped state (i.e., whether the rotary brush16Bb is in the stopped state) (step S25).

If the sweeper16B is in the stopped state (No in step S25), the controller20compares the calculated contact degree C. with the predetermined contact degree Cpb1 for stopped state included in the acquired piece of information Ib (steps S26, S27). If the contact degree C. is greater than the predetermined contact degree Cpb1 for stopped state (about 6% to about 7%) (NO in step S26, YES in step S27), the controller20determines that the sweeper16B is currently in contact with the road surface17B and in the “insufficient contact state” (the rotary brush16Bb is spaced from the road surface17B or the rotary brush16Bb only applies a weak pressing force on the road surface17B and therefore dust etc. on the road surface17B would not be sufficiently scraped into the sweeper16B even if the rotary brush16Bb starts being driven now, for example) (step S28), and causes the piston rods of the attachment cylinders15to extend to press down the sweeper16B (front portion of the sweeper16B) (step S29). The sweeper16B continues to be lowered until the contact degree C. calculated based on the results of detection by the attachment cylinder fluid pressure detector64becomes the predetermined contact degree Cpb1 for stopped state (about 6% to about 7%) (YES in step S26).

If the contact degree C. is less than the predetermined contact degree Cpb1 for stopped state (about 6% to about 7%) (NO in step S26, NO in step S27), the controller20determines that the sweeper16B is currently in contact with the road surface17B and in the “excessive contact state” (the rotary brush16Bb applies too great a pressing force on the road surface17B and the rotary brush16Bb would not rotate well and reduce the cleaning efficiency even if the hydraulic motor16Bc starts being driven now, and/or the main body cover16Ba is in contact with the road surface17B) (step S30), and causes the piston rods of the attachment cylinders15to retract to raise the sweeper16B (raise the front portion of the sweeper16B (step S31). The sweeper16B continues to be raised until the contact degree C. calculated based on the results of detection by the attachment cylinder fluid pressure detector64becomes the predetermined contact degree Cpb1 for stopped state (about 6% to about 7%) (YES in step S26).

If the contact degree C. is the predetermined contact degree Cpb1 for stopped state (about 6% to about 7%) (YES in step S26), the controller20determines that the sweeper16B is currently in contact with the road surface17B and in the “predetermined (optimal) contact state” and the rotary brush16Bb is in the stopped state (step S32), and causes the display22to display a message and/or the like to indicate that the sweeper16B is in the predetermined (optimal) contact state (step S33).

When the operator here turns ON the foregoing AUX switch18(YES in step S34), the controller20controls the solenoid valve(s)47and/or48to switch the position of the AUX control valve46to drive the hydraulic motor16Bc of the sweeper16B, thus rotating the rotary brush16Bb (step S35).

After that, the controller20determines that the sweeper16B is being driven (i.e., the rotary brush16Bb is rotating) (YES in step S25), and compares the contact degree C. calculated based on the results of detection by the attachment cylinder fluid pressure detector64with the predetermined contact degree Cpb2 for driven state (about 10% to about 11%) included in the acquired piece of information Ib (steps S36, S37).

Note that the predetermined contact degree Cpb2 for driven state is set in consideration of how the cylinder thrust force Fc of the attachment cylinders15would change when the rotary brush16Bb of the sweeper16B, which is in the predetermined contact state while in the stopped state, is rotated/driven. Therefore, merely bringing the sweeper16B (rotary brush16Bb) from the stopped state into the driven state (turning the AUX switch18from OFF to ON) should basically suffice to change the contact degree C. from the value equivalent to the predetermined contact degree Cpb1 for stopped state (about 6% to about 7%) to a value equivalent to the predetermined contact degree Cpb2 for driven state (about 10% to about 11%) (YES in step S36), without having to perform an operation to change the attitude of the sweeper16B such as an operation to cause the piston rods of the attachment cylinders15to extend or retract.

While the sweeper16B is being driven (while the rotary brush16Bb is rotating), if the contact degree C. is not the predetermined contact degree Cpb2 for driven state (NO in S36), the controller20causes, for example, the piston rods of the attachment cylinders15to extend or retract to bring the sweeper16B into the predetermined contact state, similarly to the case where the sweeper16B (rotary brush16Bb) is in the stopped state.

Specifically, if the contact degree C. is greater than the predetermined contact degree Cpb2 for driven state (about 10% to about 11%) (NO in step S36, YES in step S37), the controller20determines that the sweeper16B is currently in contact with the road surface17B in the “insufficient contact state” and the rotary brush16Bb is currently rotating (step S38), and causes the piston rods of the attachment cylinders15to extend to press down the sweeper16B (front portion of the sweeper16B) (step S39). The sweeper16B continues to be lowered until the contact degree C. calculated based on the results of detection by the attachment cylinder fluid pressure detector64becomes the predetermined contact degree Cpb2 for driven state (about 10% to about 11%) (YES in step S36).

If the contact degree C. is less than the predetermined contact degree Cpb2 for driven state (about 10% to about 11%) (NO in step S36, NO in step S37), the controller20determines that the sweeper16B is currently in contact with the road surface17B and in the “excessive contact state” and the rotary brush16Bb is currently rotating (step S40), and causes the piston rods of the attachment cylinders15to retract to raise the sweeper16B (front portion of the sweeper16B) (step S41). The sweeper16B continues to be raised until the contact degree C. calculated based on the results of detection by the attachment cylinder fluid pressure detector64becomes the predetermined contact degree Cpb2 for driven state (about 10% to about 11%) (YES in step S36).

If the contact degree C. is the predetermined contact degree Cpb2 for driven state (about 10% to about 11%) (YES in step S36), the controller20determines that the sweeper16B is currently in contact with the road surface17B and in the “predetermined (optimal) contact state” and the rotary brush16Bb is currently rotating (step S42), and causes the display22to display a message and/or the like to indicate that the sweeper16B is in the predetermined (optimal) contact state (step S43). Furthermore, the controller20controls, for example, the positions of the lift arm control valve44and the attachment control valve45(which are proportional solenoid valves) so that the attitude X of the working device4(and the sweeper16B) detected by the attitude detector62when the sweeper16B is in the predetermined (optimal) contact state, i.e., a proper attitude Xo, is maintained also during the subsequent travel of the working machine1for cleaning (step S44).

Note that, in cases where the sweeper16B is not in the predetermined contact state (in the insufficient contact state or in the excessive contact state) regardless of whether the rotary brush16Bb is rotating or in the stopped state, the controller20may cause the display22to issue an alert or a guidance indication as discussed earlier to prompt the worker to operate the working device4(attachment cylinders15and the like) to bring the sweeper16B into the predetermined contact state, instead of or in addition to the automatic operation of the working device4(attachment cylinders15and the like) as indicated in steps S29, S31, S39, and S41.

Examples of the work attachment16including a main body which has a driven member to be driven by hydraulic fluid from the AUX ports11and which should be instructed to be spaced above from the ground surface, such as the sweeper16B as illustrated inFIG.2, include an angle broom including a brush having a similar horizontal rotation shaft, a snow blower including an auger having a horizontal shaft, and a brush cutter and a mower which include a rotary blade having a vertical rotation shaft. Also in cases of these work attachments16, the controller20may evaluate the contact state of the work attachment16, bring the contact state into a predetermined (optimal) contact state, and maintain the predetermined (optimal) contact state during work/travel of the working machine1with reference to the control flow shown inFIGS.10A and10B.

FIG.3illustrates a working machine1performing crushing of a to-be-crushed object17C which is a contact object17by bringing a hydraulic breaker16C into contact with the to-be-crushed object17C such as a concrete block. The hydraulic breaker16C includes a main body16Ca and a chisel16Cb in the form of a rod projecting from the main body16Ca.

The main body16Ca contains therein a piston to be driven by hydraulic pressure. The movement of the piston is transmitted to the chisel16Cb, and the to-be-crushed object17C in contact with the chisel16Cb is crushed. Hydraulic fluid to apply hydraulic pressure to drive the piston in the main body16Ca is supplied from the AUX ports11of the working machine1into the main body16Ca via fluid pipes16Cc.

The hydraulic breaker16C is attached to the working device4such that the hydraulic breaker16C is fixed non-rotatably to the distal end portions10cof the left and right lift arms10. That is, the piston rods of the attachment cylinders15usually do not extend or retract to move the hydraulic breaker16C, and the hydraulic breaker16C is moved only by the up and down movements of the lift arms10caused by the extension and retraction of the piston rods of the lift arm cylinders14.

Therefore, the state of contact between the hydraulic breaker16C and the to-be-crushed object17C (contact degree C.) is evaluated based on the relationship in hydraulic pressure regarding the lift arm cylinders14(cylinder thrust force Fc) calculated based on the results of detection by the lift arm cylinder fluid pressure detector63.

It follows that the cylinder thrust force Fc obtained by substituting the rod-side hydraulic pressure P1r and the bottom-side hydraulic pressure P1b detected by the lift arm cylinder fluid pressure detector63into the foregoing expression is a force acting in the direction of retraction of the piston rods, i.e., a force acting in the direction in which the lift arms10are lowered.

The predetermined contact state (predetermined contact degree Cp) for the state of contact between the hydraulic breaker16C (chisel16Cb of the hydraulic breaker16C) and the to-be-crushed object17C is a criterion for making a judgment to avoid the “insufficient contact state” in which the hydraulic breaker16C is likely to be damaged, as discussed earlier. Assuming that the predetermined contact degree Cp for the hydraulic breaker16C is a predetermined contact degree Cpc, the predetermined contact degree Cpc may be, for example, about 10%. The predetermined contact degree Cpc is included in the piece of information Ic relating to the hydraulic breaker16C stored in the memory21of the working machine1or the storage unit (such as a microchip) of the sweeper16B.

The following description discusses a control flow for crushing of the to-be-crushed object17C (such as a concrete block) using the hydraulic breaker16C, with reference toFIG.11.

First, the controller20acquires a piece of information Ic relating to the hydraulic breaker16C in response to selection of a corresponding icon101in the attachment list65and/or by receiving a signal from the hydraulic breaker16C actually attached to the working device4as discussed earlier, for example (step S51). The piece of information Ic includes the predetermined contact degree Cpc (=about 10%) required for the hydraulic breaker16C and/or the like, as described earlier.

Before crushing is started, the controller20first locks the AUX switch18in an OFF position (step S52). That is, the AUX switch18is prevented from being switched to an ON state even if the operator operates the AUX switch18. This prohibits the driving of the hydraulic breaker16C.

While the AUX switch18is kept in the OFF position, the lift arm cylinders14(piston rods of the lift arm cylinders14) extend or retract to raise or lower the lift arms10(step S53) to bring the hydraulic breaker16C close to the to-be-crushed object17C and into contact with the to-be-crushed object17C. Such extension or retraction of the lift arm cylinders14may be achieved by the operator operating the work operation lever9or the controller20controlling the working device4in response to the operator's operation of a switch and/or the like.

While the lift arms10are in operation, the lift arm cylinder fluid pressure detector63detects the rod-side hydraulic pressure Pr (P1r) and the bottom-side hydraulic pressure Pb (P1b) (step S54). The controller20calculates the cylinder thrust force Fc which is the relationship in hydraulic pressure between the detected rod-side hydraulic pressure Pr and the detected bottom-side hydraulic pressure Pb and the contact degree C. based on the cylinder thrust force Fc (step S55).

The controller20may cause the display22to display the calculated contact degree C. and/or the like. Note that the detection of the hydraulic pressures may be performed while the lift arms10in operation are moving or not moving. If the hydraulic pressures are detected while the lift arms10are moving, the cylinder thrust force Fc is calculated via correction in consideration of the sliding resistance of the cylinders, as discussed earlier.

The controller20compares the calculated contact degree C. withe the predetermined contact degree Cpc (about 10%) included in the acquired piece of information Ic (step S56). If the contact degree C. is greater than the predetermined contact degree Cpc (about 10%) (YES in step S56), the controller20determines that the hydraulic breaker16C is currently in contact with the to-be-crushed object17C and in the “predetermined contact state” (step S57), and causes the display22to display a message and/or the like to notify the worker of such (step S58) and unlocks the AUX switch18(step S59). That is, the controller allows driving of the hydraulic breaker16C.

If the contact degree C. is less than the predetermined contact degree Cpc (about 10%) (NO in step S56), the controller20determines that the hydraulic breaker16C is currently in contact with the to-be-crushed object17C in the “insufficient contact state” (the chisel16Cb is spaced above from the to-be-crushed object17C, or the chisel16Cb for example applies only a weak pressing force on the to-be-crushed object17C and the hydraulic breaker16C would be easily damaged if the chisel16Cb starts being driven now) (step S60), and causes the display22to display a message indicating such (step S61).

The controller20determines whether or not the AUX switch18here is in the ON position (whether or not the hydraulic breaker16C is in the driven state) (step S62). If the AUX switch18is in the ON position (YES in step S62), the controller20brings the AUX switch18into the OFF position and locks the AUX switch18in the OFF position (step S63).

After that, the controller20causes the piston rods of the lift arm cylinders14to retract to lower the lift arms10, to increase the cylinder thrust force Fc of the lift arm cylinders14(step S64). The lift arms10continue to be lowered until the contact degree C. calculated based on the results of detection by the lift arm cylinder fluid pressure detector63becomes the predetermined contact degree Cpc (about 10%) (YES in step S56).

Note that, in cases where the hydraulic breaker16C is in the insufficient contact state, the controller20may cause the display22to issue an alert or a guidance indication as discussed earlier to prompt the worker to operate the working device4(lift arm cylinders14and the like) to bring the hydraulic breaker16C into the predetermined contact state, instead of or in addition to the automatic operation of the working device4(lift arm cylinders14and the like) as indicated in step S64.

The steps performed by the controller20as discussed above are based on the piece of information Ic including, for example, the predetermined contact degree Cpc (=about 10%) for the hydraulic breaker16C for when performing crushing and determination of whether or not to allow the operation to turn ON the AUX switch18. In cases of work attachments16which need to be in contact with a contact object while applying a predetermined pressing force or greater force on the contact object similarly to the hydraulic breaker16C, a desired effect of the work would be achieved by performing substantially the same steps as those shown inFIG.11based on information similar to the information Ic.

FIG.4illustrates a working machine1performing work to dig into soil17D (make a hole in the soil17D) by starting driving and rotating the earth auger16D in contact with the soil17D. The earth auger16D includes a fixed plate16Da fixed non-rotatably to the distal end portions10cof the left and right lift arms10, a motor housing 16 Db pivotally supported on the widthwise center of the fixed plate16Da via a universal joint, and an auger shaft16Dc projecting downward from the motor housing 16 Db. The motor housing 16 Db contains therein a hydraulic motor which is a hydraulic actuator to rotate and drive the auger shaft16Dc. The hydraulic motor is connected to the AUX ports11via fluid pipes16Dd.

The position of the distal end of the auger shaft16Dc when the distal end of the auger shaft16Dc of the earth auger16D is in contact with the surface of the soil17D and in the predetermined contact state is defined as the position at a depth-of-excavation of 0 (zero). The distance of the distal end of the auger shaft16Dc which is caused to move downward from the depth-of-excavation D of 0 in the soil17D by driving the earth auger16D, from the position at a depth-of-excavation of 0 is the depth-of-excavation D which is the depth of the hole formed by the excavation. That is, because the position of the earth auger16D at a depth-of-excavation of 0 is defined, the error between the depth of the hole formed and the depth-of-excavation D of the earth auger16D is eliminated, making it possible to accurately make a hole having a desired depth.

Also in the case of the earth auger16D, the state of contact of the earth auger16D with the soil17D (contact degree C.) is evaluated based on the relationship in hydraulic pressure (cylinder thrust force Fc) regarding the lift arm cylinders14calculated based on the results of detection by the lift arm cylinder fluid pressure detector63. Note that the cylinder thrust force Fc calculated in such a case is also a force acting in the direction in which the lift arms10are lowered, i.e., a force acting in the direction of retraction of the lift arm cylinders14.

The predetermined contact state (predetermined contact degree Cp) of the earth auger16D (auger shaft16Dc of the earth auger16D) and the soil17D preferably has a value corresponding to the position of the distal end of the auger shaft16Dc at the point in time at which a depth-of-excavation of 0 is defined. Assuming that the predetermined contact degree Cp for the earth auger16D is a predetermined contact degree Cpd, the predetermined contact degree Cpd may be, for example, about 3%. Such a predetermined contact degree Cpd is included in the piece of information Id relating to the earth auger16D stored in the memory21of the working machine1or a storage unit (such as a microchip) of the earth auger16D.

In the present example, the display22displays a depth-of-excavation gauge67as illustrated inFIG.8, and the current depth-of-excavation D, which is the position of the distal end of the auger shaft16Dc with respect to the soil17D, is indicated such that, for example, the current depth-of-excavation D matches a mark indicative of the corresponding depth on the depth-of-excavation gauge67. Furthermore, the display22is configured to receive input of a target depth Dt. The inputted target depth Dt is indicated such that, for example, the target depth Dt matches a mark indicating the corresponding depth on the depth-of-excavation gauge67.

The following description discusses a control flow for digging into the soil17D (making a hole in the soil17D) using the earth auger16D, with reference toFIG.12.

First, the controller20acquires a piece of information Id relating to the earth auger16D in response to selection of a corresponding icon101in the attachment list65and/or by receiving a signal from the earth auger16D actually attached to the working device4as discussed earlier, for example (step S71). The piece of information Id includes the predetermined contact degree Cpd (=about 3%) required for the earth auger16D and/or the like, as described earlier.

The piece of information Id relating to the earth auger16D also includes a signal indicating a command to display the depth-of-excavation gauge67as illustrated inFIG.8. The controller20, upon acquisition of the information Id, causes the display22to display the depth-of-excavation gauge67(step S72).

The display22is configured to receive input of the target depth Dt, as described earlier. The controller20causes the inputted target depth Dt to be displayed on the depth-of-excavation gauge67such that, for example, the corresponding mark on the depth-of-excavation gauge67is indicated in a marked manner (step S73, seeFIG.8).

Before the excavation (drilling, making a hole) is started, the lift arm cylinders14(piston rods of the lift arm cylinders14) extend or retract to raise or lower the lift arms10(step S74) to bring the earth auger16D close to the soil17D and into contact with the soil17D. Such extension or retraction of the lift arm cylinders14may be achieved by the operator operating the work operation lever9or the controller20controlling the working device4in response to the operator's operation of a switch and/or the like.

While the lift arms10are in operation, the lift arm cylinder fluid pressure detector63detects the rod-side hydraulic pressure Pr (P1r) and the bottom-side hydraulic pressure Pb (P1b) (step S75). The controller20calculates the cylinder thrust force Fc which is the relationship in hydraulic pressure between the detected rod-side hydraulic pressure Pr and the detected bottom-side hydraulic pressure Pb and the contact degree C. based on the cylinder thrust force Fc (step S76).

The controller20may cause the display22to display the calculated contact degree C. and/or the like. Note that the detection of the hydraulic pressures may be performed while the lift arms10in operation are moving or not moving. If the hydraulic pressures are detected while the lift arms10are moving, the cylinder thrust force Fc is calculated via correction in consideration of the sliding resistance of the cylinders, as discussed earlier.

Note that the controller20may keep the AUX switch18locked in the OFF position until the state of contact between the earth auger16D and the soil17D becomes the predetermined contact state. This makes it possible to eliminate or reduce the likelihood that the distal end of the rotating auger shaft16Dc will drill the soil17D upon contact with the soil17D and the position of the distal end will not accurately define a depth-of-excavation 0.

The controller20compares the calculated contact degree C. with the predetermined contact degree Cpd (about 3%) included in the acquired piece of information Id (steps S77, S78). If the contact degree C. is less than the predetermined contact degree Cpd (about 3%) (No in step S77, NO in step S78), the controller20determines that the earth auger16D is currently in contact with the soil17D and in the “insufficient contact state” (the auger shaft16Dc is spaced from the soil17D or the auger shaft16Dc applies only a weak pressing force on the soil17D, for example) (step S79), and causes the piston rods of the lift arm cylinders14to retract to lower the lift arms10to press down the earth auger16D (step S80). The earth auger16D continues to be lowered until the contact degree C. calculated based on the results of detection by the lift arm cylinder fluid pressure detector63becomes the predetermined contact degree Cpd (about 3%) (YES in step S77).

If the contact degree C. is greater than the predetermined contact degree Cpd (about 3%) (No in step S77, YES in step S78), the controller20determines that the earth auger16D is currently in contact with the soil17D and in the “excessive contact state” (the distal end of the auger shaft16Dc may be stuck in the soil17D and the position of the distal end does not accurately define a depth-of-excavation of 0) (step S81), and causes the piston rods of the lift arm cylinders14to extend to raise the lift arms10to raise the earth auger16D (step S82). The earth auger16D continues to be raised until the contact degree C. calculated based on the results of detection by the lift arm cylinder fluid pressure detector63becomes the predetermined contact degree Cpd (about 3%) (YES in step S77).

Note that, in cases where the earth auger16D is not in the predetermined contact state (in the insufficient contact state or excessive contact state), the controller20may cause the display22to issue an alert or a guidance indication as discussed earlier to prompt the worker to operate the working device4(lift arm cylinders14and the like) to bring the earth auger16D into the predetermined contact state, instead of or in addition to the automatic operation of the working device4(lift arm cylinders14and the like) as indicated in steps S80and S82.

If the contact degree C. is the predetermined contact degree Cpd (about 3%) (YES in step S77), the controller20confirms that the earth auger16D is currently in contact with the soil17A and in the “predetermined contact state” (step S83), defines the current position of the distal end (lower end) of the auger shaft16Dc of the earth auger16D in the predetermined contact state as a depth-of-excavation 0, and causes the position to be displayed such that, for example, the corresponding mark on the depth-of-excavation gauge67displayed on the display22is shown in a marked manner (step S84, seeFIG.8).

After confirming that the earth auger16D is in the predetermined contact state and defining the position of the earth auger16D as a depth-of-excavation of 0, assuming that the attitude X of the working device4(lift arms10) obtained here is a reference attitude Xs, the controller20acquires the reference attitude Xs of the working device4(lift arms10) based on the results of detection by the attitude detector62(such as the angle of the lift arms10to the machine body2and/or the degree of extension of the lift arm cylinders14) obtained here, and causes the memory21to store the reference attitude Xs (step S85).

Upon confirmation that the earth auger16D is in the predetermined contact state, the controller20automatically rotates the auger shaft16Dc or the operator turns ON the AUX switch18(step S86) to rotate the auger shaft16Dc. After that, the operator operates the work operation lever9to cause the lift arm cylinders14to retract to lower the lift arms10, thus causing the auger shaft16Dc to dig into the soil17D. While the lift arms10are lowered as such, the controller20receives a signal indicating the attitude X (such as the angle of the lift arms10to the machine body2and/or the degree of extension of the lift arm cylinders14) of the working device4detected by the attitude detector62(step S87).

The controller20recognizes the current attitude X of the working device4based on the result of detection by the attitude detector62, calculates the amount of change in the position of the earth auger16D in the vertical direction based on a difference of the current attitude X from the reference attitude Xs (the attitude X of the working device4with its earth auger16D in the predetermined contact state) stored in the memory21, and causes the display22to display the depth-of-excavation D corresponding to the amount of change using the depth-of-excavation gauge67(step S88, seeFIG.8).

The operator can recognize the difference between the depth-of-excavation D and the target depth Dt which are displayed on the depth-of-excavation gauge67, and therefore the operator can operate the work operation lever9based on the recognition to bring the depth-of-excavation D close to the target depth Dt, eventually making it possible to make a hole having the target depth Dt in the soil17D.

Note that the controller20is capable of calculating the attitude of the working device4having its earth auger16D positioned at the inputted target depth Dt. Therefore, the following arrangement may be used: the controller20automatically lowers the lift arms10to bring the attitude of the working device4, corresponding to the depth-of-excavation D recognized based on the result of detection by the attitude detector62, close to the attitude of the working device4corresponding to the target depth Dt to automatically make a hole having the target depth Dt.

Examples of the work attachment16such as the earth auger16D as illustrated inFIG.4, for which it is confirmed that the state of contact between the earth auger16D and the contact object17(soil17D) is the predetermined contact state and then a work product such as a drilled hole is formed in the contact object17and the work product is completed by causing the degree of work done such as the depth-of-excavation D to reach the target value, include a trencher which is a machine to dig a trench in soil, in addition to the earth auger16D.

Also in cases of a trencher, the controller20may evaluate the contact state of the work attachment16, define the position of the working attachment16as a depth-of-excavation of 0 based on the contact state defined as the predetermined contact state, and cause the trencher to dig a trench in the soil such that the actual depth-of-excavation reaches the target depth, with reference to the control flow inFIG.12.

A working machine1includes: a machine body2: at least one support member (lift arm10) supported on the machine body2and connectable to a work attachment16to do work by making contact with an object17to be contacted; at least one hydraulic cylinder14(or15) extendable and retractable to move the work attachment16connected to the at least one support member (lift arm10), the at least one hydraulic cylinder14(or15) including a rod-side fluid chamber14a(or15a) and a bottom-side fluid chamber14b(or15b) separated by a piston; a rod-side pressure detector63a(or64a) to detect a rod-side hydraulic pressure Pr (P1r or P2r) which is a pressure of hydraulic fluid in communication with the rod-side fluid chamber14a(or15a) of the at least one hydraulic cylinder14(or15): a bottom-side pressure detector63b(or64b) to detect a bottom-side hydraulic pressure Pb (P1b or P2b) which is a pressure of hydraulic fluid in communication with the bottom-side fluid chamber14b(or15b) of the at least one hydraulic cylinder14(or15); and a controller20to calculate a relationship in pressure (cylinder thrust force Fc) between the rod-side hydraulic pressure Pr (P1r or P2r) detected by the rod-side pressure detector63a(or64a) and the bottom-side hydraulic pressure Pb (P1b or P2b) detected by the bottom-side pressure detector63b(or64b) and evaluate, based on the calculated relationship in pressure (cylinder thrust force Fc), a contact state which is a state of contact of the work attachment16with the object17.

The state of contact between the work attachment16and the object17is accurately determined as such. This makes it possible, for example, to eliminate or reduce the likelihood that an unintended or inaccurate work product will result from an inappropriate contact state, and hydraulic actuator(s) and/or the like of the work attachment16will be damaged because of the inappropriate contact state, making it possible for unskilled operators to easily achieve suitable work products using the work attachment16. Furthermore, the state of contact is evaluated based on the detection of the rod-side hydraulic pressure Pr by the rod-side pressure detector63a(or64a) and the detection of the bottom-side hydraulic pressure Pb by the bottom-side pressure detector63b(64b). This eliminates the need for special, complex, and costly devices and thus makes it possible to provide a working machine1suitable also economically.

The working machine1may further include a memory21to store a predetermined contact degree Cp, the predetermined contact degree Cp being a degree to which the work attachment16is in contact with the object17when the work attachment16is in a predetermined contact state. The controller20may be configured or programmed to: calculate, based on the calculated relationship in pressure (cylinder thrust force Fc), a current contact degree C. which is a degree to which the work attachment16is currently in contact with the object17; compare the current contact degree C. with the stored predetermined contact degree Cp; and determine whether or not the work attachment16is in the predetermined contact state.

By comparing the predetermined contact degree Cp and the contact degree C. calculated based on the relationship in hydraulic pressure (cylinder thrust force Fc) which can be easily calculated as described above, it is possible to easily obtain the result of determination of whether the work attachment16is in the predetermined contact state.

The working machine1may further include an attitude detector62to detect an attitude X of the work attachment16and/or the at least one support member (lift arm10). The controller20may be configured or programmed to: if the controller20compares the calculated contact degree C. with the predetermined contact degree Cp and determines that the work attachment16is in the predetermined contact state, recognize, as a reference attitude Xs, the attitude X detected by the attitude detector62at a point in time at which the controller determined that the work attachment16was in the predetermined contact state; and based on a change in the attitude X detected by the attitude detector62from the reference attitude Xs, measure a degree of work done (depth-of-excavation D) represented as a change in position of the work attachment16relative to the object17.

A change in attitude X of the work attachment16and/or the support member (lift arm10) from the reference attitude Xs is used to calculate the degree of work done (depth-of-excavation D). With the above configuration, because the predetermined state of contact (predetermined contact state in which the contact degree C. is the predetermined contact degree Cp) between the work attachment16and the object17corresponding to the reference attitude Xs is accurately defined, the calculated degree of work done (depth-of-excavation D) is also accurate. This makes it possible to make a hole, trench, and/or the like (work product) having a dimension corresponding to the target degree (having a target depth, width, and/or the like) in the soil or the like (object).

The working machine1may further include a display22to display the degree of work done (depth-of-excavation D) measured by the controller20.

The display22allows the operator to easily know the degree of work done (depth-of-excavation D) which is a current work product produced using the work attachment16, and to also know the difference between the target degree (target depth Dt) and the current degree of work done (depth-of-excavation D) and/or the like.

The controller20may be configured or programmed to cause the display22to display a guidance indication regarding an operation of the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) to change the attitude X to cause the degree of work done (depth-of-excavation D) to reach a target degree (target depth Dt).

The guidance indication allows the operator to know what operation they should perform to obtain a target work product, and makes it possible to easily achieve the target work product.

The controller20may be configured or programmed to, if the controller20determines that the degree of work done (depth-of-excavation D) has reached a target degree (target depth Dt) based on a result of detection by the attitude detector62, cause the display22to display an indication that the degree of work done (depth-of-excavation D) has reached the target degree (target depth Dt).

The indication allows the operator to know that the target degree (target depth Dt) has been reached, and the operator therefore stops operating the hydraulic cylinder(s) not to increase the degree of work done (depth-of-excavation D) any further. This makes it possible to obtain an intended work product (such as a hole or a trench having a depth D equal to the target depth Dt).

The controller20may be configured or programmed to control extension and retraction of the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) to control the attitude X such that the degree of work done (depth-of-excavation D) reaches a target degree (target depth Dt).

Since the controller20controls the extension and retraction of the hydraulic cylinder(s) as described above, the degree of work done (depth-of-excavation D) automatically reaches the target degree (target depth Dt) without operation errors or the like that would otherwise be caused by the operator, making it possible to reliably obtain an intended work product (such as a hole or a trench having a depth D equal to the target depth Dt).

The controller20may be configured or programmed to, if the controller20determines that the work attachment16is not in the predetermined contact state, control extension and retraction of the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) such that the calculated current contact degree C. reaches the predetermined contact degree Cp.

Since the controller20controls the extension and retraction of the hydraulic cylinder(s) as described above, the contact degree C. automatically reaches the predetermined contact degree Cp without operation errors or the like that would otherwise be caused by the operator, making it possible to reliably achieve the predetermined state of contact (predetermined contact state) between the work attachment16and the object17.

The working machine1may further include a display22. The controller20may be configured or programmed to, if the controller20determines that the work attachment16is not in the predetermined contact state, cause the display22to display a guidance indication regarding an operation of the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) to cause the calculated current contact degree C. to reach the predetermined contact degree Cp.

The guidance indication allows the operator to know what operation they should perform to achieve the predetermined state of contact (predetermined contact state) between the work attachment16and the object17, making it possible to easily achieve the predetermined contact state which is to be achieved.

The controller20may be configured or programmed to, if the controller20determines that the work attachment16is not in the predetermined contact state, prohibit driving of the work attachment16.

With this, for example, with regard to a work attachment16(such as a hydraulic breaker16C) which is likely to be damaged if the work attachment16is driven when the state of contact between the work attachment16and the object17is not the predetermined contact state, it is possible to prevent or reduce damage to the work attachment16that would otherwise result if the work attachment16is driven while not in the predetermined contact state, and possible to improve durability of the work attachment16.

The memory21may store a plurality of the predetermined contact degrees Cp (Cp1, Cpb1, Cpb2, Cpc, Cpd) corresponding to a respective plurality of the work attachments16. The controller20may be configured or programmed to: select one of the plurality of predetermined contact degrees Cp (Cp1, Cpb1, Cpb2, Cpc, Cpd) that corresponds to the work attachment16connected to the at least one support member (lift arm10); and compare the selected one of the plurality of predetermined contact degrees Cp (Cp1, Cpb1, Cpb2, Cpc, Cpd) with the calculated current contact degree C.

With this, when a work attachment16is actually connected to the support member (lift arm10), the predetermined contact degree Cp corresponding to the work attachment16is selected reliably, contributing to accurately determining whether or not the state of contact between the work attachment16and the object17is the predetermined contact state.

The working machine1may further include an attitude detector62to detect an attitude X of the work attachment16. The controller20may be configured or programmed to, if the controller20determines that the work attachment16is in the predetermined contact state, determine, as the attitude X of the work attachment16(e.g., a bucket16A about to perform leveling of soil17A (leveling of ground) or a sweeper16B about to perform cleaning of a road surface17B) in the predetermined contact state, the attitude X detected by the attitude detector62at a point in time at which the controller20determined that the work attachment16was in the predetermined contact state.

Since it is possible to evaluate the attitude X of the work attachment16in contact with the object17in the predetermined contact state, it is possible to prevent or reduce the loss of the work product (for example, the tilted work attachment16such as the bucket16A scratches the soil) that would otherwise result from an inappropriate attitude X despite that the contact degree C. is the predetermined contact degree Cp, making it possible to more reliably obtain a suitable work product.

The memory21may store a proper attitude Xo of the work attachment16(e.g., a bucket16A about to perform leveling of soil17A (leveling of ground) or a sweeper16B about to perform cleaning of a road surface17B) in the predetermined contact state. The controller may be configured or programmed to, if the controller20determines that the work attachment16is in the predetermined contact state and the attitude X of the work attachment16detected by the attitude detector62differs from the proper attitude Xo, control extension and retraction of the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) such that the attitude X of the work attachment16reaches the proper attitude Xo.

Since the controller20controls the extension and retraction of the hydraulic cylinder(s) as described above, the attitude X of the work attachment16which is in contact with the object17in the predetermined contact state (the state in which the contact degree C. is the predetermined contact degree Cp) automatically reaches the proper attitude Xo without operation errors or the like that would otherwise be caused by the operator, making it possible to reliably obtain a work product that is achievable by the work attachment16in the proper attitude Xo.

The working machine1may further include a display22. The memory21may store a proper attitude Xo of the work attachment16(e.g., a bucket16A about to perform leveling of soil17A (leveling of ground) or a sweeper16B about to perform cleaning of a road surface17B) in the predetermined contact state. The controller20may be configured or programmed to, if the controller20determines that the work attachment16is in the predetermined contact state and the attitude X of the work attachment16detected by the attitude detector62differs from the proper attitude Xo, cause the display22to display a guidance indication regarding an operation of the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) to cause the attitude X of the work attachment16to reach the proper attitude Xo.

The guidance indication allows the operator to know what operation they should perform to cause the attitude X of the work attachment16which is in contact with the object17in the predetermined contact state to reach the proper attitude Xo, and makes it possible to easily achieve the proper attitude Xo which is to be achieved.

The working machine1may further include a display22. The memory21may store a proper attitude Xo of the work attachment16(e.g., a bucket16A about to perform leveling of soil17A (leveling of ground) or a sweeper16B about to perform cleaning of a road surface17B) in the predetermined contact state. The controller20may be configured or programmed to, if the controller20determines that the work attachment16is in the predetermined contact state and the attitude X of the work attachment16detected by the attitude detector62is equal to the proper attitude Xo, cause the display22to display an indication that the work attachment16is in the proper attitude Xo and in the predetermined contact state.

The indication allows the operator to know that the work attachment16is in the proper attitude Xo and in the predetermined contact state, and the operator therefore stops operating the hydraulic cylinder(s) not to change the attitude X to reach the proper attitude Xo any further. This makes it possible to obtain an intended work product (a product achievable by the work attachment16which does work in this state).

The working machine1may include a work operation lever9as a manual operator to be operated to cause the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) to extend or retract. The controller20may be configured or programmed to, if the work operation lever9is operated to cause the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) to extend or retract, calculate a corrected version of the relationship in pressure (cylinder thrust force Fc) using correction value(s) Kp and/or Kv set according to frictional resistance caused by operation of the work operation lever9on the piston of the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15).

With this, the relationship in pressure (cylinder thrust force Fc) is accurately calculated in consideration of variation in hydraulic pressure caused by frictional resistance generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15).

The correction value(s) Kp and/or Kv may be changed according to a temperature of hydraulic fluid and/or an ambient temperature.

With this, the relationship in pressure (cylinder thrust force Fc) is accurately calculated in consideration of frictional resistance generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) that varies with the temperature of hydraulic fluid and/or the ambient temperature.

The correction value may be set to differ between when the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) is not moving (the correction value set for such a case is “correction value Kp”) and when the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) is moving (the correction value set for such a case is “correction value Kv”).

With this, the relationship in pressure (cylinder thrust force Fc) is accurately calculated in consideration of a difference between the static frictional resistance that would be generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) when the hydraulic cylinder is not moving and the kinetic frictional resistance that would be generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) when the hydraulic cylinder is moving.

The correction value may be set to differ between when the work operation lever9is operated to cause the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) to extend (the correction value set for such a case is “correction value Kpr”) and when the work operation lever9is operated to cause the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) to retract (the correction value set for such a case is “correction value Kpb”).

With this, the relationship in pressure (cylinder thrust force Fc) is accurately calculated in consideration of a difference between the frictional resistance that would be generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) while the hydraulic cylinder is extending or receiving a load from the work operation lever9operated to extend the hydraulic cylinder and the frictional resistance that would be generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) while the hydraulic cylinder is retracting or receiving a load from the work operation lever9operated to retract the hydraulic cylinder.

The correction value may be set to differ between when the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) is extending (the correction value set for such a case is “correction value Kvr”) and when the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) is retracting (the correction value set for such a case is “correction value Kvb”).

With this, the relationship in pressure (cylinder thrust force Fc) is accurately calculated in consideration of a difference between the kinetic frictional resistance that would be generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) while the hydraulic cylinder is extending and the kinetic frictional resistance that would be generated in the at least one hydraulic cylinder (the lift arm cylinder(s)14and/or the attachment cylinder(s)15) while the hydraulic cylinder is retracting.

The controller20may be configured or programmed to: if the work operation lever9is operated to cause the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) to extend, correct the detected bottom-side hydraulic pressure Pb to reduce the detected bottom-side hydraulic pressure Pb; and if the work operation lever9is operated to cause the at least one hydraulic cylinder (lift arm cylinder(s)14and/or attachment cylinder(s)15) to retract, correct the detected rod-side hydraulic pressure Pr to reduce the detected rod-side hydraulic pressure Pr.

With this, the detected hydraulic pressures are corrected differently depending on when the hydraulic cylinder is extending and when the hydraulic cylinder is retracting, and the relationship in pressure regarding the hydraulic cylinder is calculated in an appropriate manner corresponding to the case of extension or the case of retraction.

A working machine1includes: a machine body2: a support member (lift arm10) supported on the machine body2and connectable to a work attachment16to do work by making contact with an object17to be contacted: lift arm cylinder(s)14which is a first hydraulic cylinder extendable and retractable to move the support member (lift arm10) relative to the machine body2, the first hydraulic cylinder including a rod-side fluid chamber14aand a bottom-side fluid chamber14bseparated by a piston: a first rod-side pressure detector63ato detect a first rod-side hydraulic pressure P1r which is a pressure of hydraulic fluid in communication with the rod-side fluid chamber14aof the lift arm cylinder(s)14: a first bottom-side pressure detector63bto detect a first bottom-side hydraulic pressure P1b which is a pressure of hydraulic fluid in communication with the bottom-side fluid chamber14bof the lift arm cylinder(s)14: attachment cylinder(s)15which is a second hydraulic cylinder extendable and retractable to move the work attachment16connected to the support member (lift arm10) relative to the support member (lift arm10), the second hydraulic cylinder including a rod-side fluid chamber15aand a bottom-side fluid chamber15bseparated by a piston: a second rod-side pressure detector64ato detect a second rod-side hydraulic pressure P2r which is a pressure of hydraulic fluid in communication with the rod-side fluid chamber15aof the attachment cylinder(s)15: a second bottom-side pressure detector64bto detect a second bottom-side hydraulic pressure P2b which is a pressure of hydraulic fluid in communication with the bottom-side fluid chamber15bof the attachment cylinder(s)15; and a controller20to calculate a relationship in pressure (cylinder thrust force Fc) between the detected first rod-side hydraulic pressure P1r and the detected first bottom-side hydraulic pressure P1b and a relationship in pressure between the detected second rod-side hydraulic pressure P2r and the detected second bottom-side hydraulic pressure P2b, and evaluate, based on the calculated relationships in pressure (cylinder thrust force Fc), a contact state which is a state of contact of the work attachment16with the object17.

The state of contact between the work attachment16and the object17is accurately determined as such. This makes it possible, for example, to eliminate or reduce the likelihood that an unintended or inaccurate work product will result from an inappropriate contact state and hydraulic actuator(s) and/or the like of the work attachment16will be damaged because of the inappropriate contact state, making it possible for unskilled operators to easily obtain suitable work products using the work attachment16. Furthermore, the state of contact is determined based on the detection of the rod-side hydraulic pressures Pr (P1r and P2r) by the rod-side pressure detectors63aand64aand the detection of the bottom-side hydraulic pressures Pb (P1b and P2b) by the bottom-side pressure detectors63band64b. This eliminates the need for special, complex, and costly devices and thus makes it possible to provide a working machine1suitable also economically. Furthermore, since the relationship in hydraulic pressure regarding the lift arm cylinder(s)14and the relationship in hydraulic pressure of the attachment cylinder(s)15which are two types of cylinders are used, it is possible to accurately evaluate the state of contact of the work attachment16with the object17including the attitude of the work attachment16relative to the object17.

The working machine1may further include a memory21to store a predetermined contact degree Cp, the predetermined contact degree Cp being a degree to which the work attachment16is in contact with the object17when the work attachment16is in a predetermined contact state. The controller20may be configured or programmed to: calculate, based on the calculated relationships in pressure, a current contact degree C. which is a degree to which the work attachment16is currently in contact with the object17; compare the current contact degree C. with the stored predetermined contact degree Cp; and determine whether or not the work attachment16is in the predetermined contact state.

By comparing the predetermined contact degree Cp and the contact degree C. which based on the relationship in hydraulic pressure that can be easily calculated as described above, it is possible to easily obtain the result of determination of whether the work attachment16is in the predetermined contact state. Furthermore, since the relationship in hydraulic pressure regarding the lift arm cylinder(s)14and the relationship in hydraulic pressure regarding the attachment cylinder(s)15which are two types of cylinders are used, it is possible to more accurately calculate a contact degree C. that agrees with the actual state of contact of the work attachment16.

The working machine1may further include an attitude detector62to detect an attitude X of the work attachment16and/or the support member (lift arm10). The controller20may be configured or programmed to: if the controller20compares the calculated contact degree C. with the predetermined contact degree Cp and determines that the work attachment16is in the predetermined contact state, recognize, as a reference attitude Xs, the attitude X detected by the attitude detector62at a point in time at which the controller determined that the work attachment16was in the predetermined contact state; and based on a change in the attitude X detected by the attitude detector62from the reference attitude Xs, measure a degree of work done (depth-of-excavation D) represented as a change in position of the work attachment16relative to the object17.

A change in attitude X of the work attachment16and/or the support member (lift arm10) from the reference attitude Xs is used to calculate the degree of work done (depth-of-excavation D). With the above configuration, because the predetermined state of contact (predetermined contact state in which the contact degree C. is the predetermined contact degree Cp) between the work attachment16and the object17corresponding to the reference attitude Xs is accurately defined, the calculated degree of work done (depth-of-excavation D) is also accurate. This makes it possible to make a hole, trench, and/or the like (work product) having a dimension corresponding to the target degree (having a target depth, width, and/or the like) in the soil or the like (object). Furthermore, since the predetermined state of contact (predetermined contact state) between the work attachment16and the object17is evaluated based on the contact degree C. calculated based on the relationship in hydraulic pressure regarding the lift arm cylinder(s)14and the relationship in hydraulic pressure regarding the attachment cylinder(s)15which are two types of cylinders, it is possible to more accurately define the reference attitude Xs, and the degree of work done (depth-of-excavation D) based on a change in attitude X from the reference attitude Xs is also more accurate.

The controller20may be configured or programmed to, if the controller20determines that the work attachment16is in the predetermined contact state, evaluate the attitude X of the work attachment16in the predetermined contact state based on a relationship between (i) a relationship in pressure (cylinder thrust force Fc) between the first rod-side hydraulic pressure P1r and the first bottom-side hydraulic pressure P1b detected at a point in time at which the controller20determined that the work attachment16was in the predetermined contact state, and (ii) a relationship in pressure (cylinder thrust force Fc) between the second rod-side hydraulic pressure P2r and the second bottom-side hydraulic pressure P2b detected at a point in time at which the controller20determined that the work attachment16was in the predetermined contact state.

The attitude X of the work attachment16in the predetermined contact state can be evaluated using as-is the relationships in hydraulic pressure regarding the two types of hydraulic cylinders (lift arm cylinder(s)14and attachment cylinder(s)15) for use in determining whether or not the state of contact between the work attachment16and the object17is the predetermined contact state, without having to use an apparatus such as the attitude detector62, e.g., an angle sensor or a cylinder length detector to detect the attitude of the work attachment16and/or the support member (lift arm10). This makes it possible, at low cost, to prevent or reduce the loss of the work product (for example, the tilted work attachment16such as the bucket16A scratches the soil) that would otherwise result from an inappropriate attitude X despite that the contact degree C. is the predetermined contact degree Cp, making it possible to more reliably achieve a suitable work product.