Hydraulic system for working machine

A hydraulic system for a working machine includes a hydraulic pump to output a hydraulic fluid, an operation device operable to supply a pilot fluid in accordance with an amount by which the operation device is operated, a hydraulic actuator to be operated by the hydraulic fluid, a pilot fluid passage connected to the operation device, a first control valve connected to the pilot fluid passage and to be operated by the pilot fluid to control a flow of the hydraulic fluid, a second control valve to be operated by the pilot fluid to control a flow of the hydraulic fluid, a proportional valve to change a pressure of the pilot fluid to operate the second control valve, a pressure detector provided in the pilot fluid passage to detect a pressure in the pilot fluid passage, and a controller to control the proportional valve based on the pressure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Japanese Patent Application No. 2021-146278 filed on Sep. 8, 2021. The entire contents of this application are hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic system for a working machine, such as a skid-steer loader, a compact track loader, or a backhoe.

2. Description of the Related Art

Japanese Unexamined Patent Application Publication No. 2020-26819 discloses a hydraulic system that increases the flow rate of a hydraulic fluid to be supplied to a hydraulic actuator in a working machine. The hydraulic system disclosed in Japanese Unexamined Patent Application Publication No. 2020-26819 includes a first hydraulic pump and a second hydraulic pump each of which is a fixed displacement pump and outputs a hydraulic fluid, a hydraulic actuator, a first fluid passage that connects the first hydraulic pump and the hydraulic actuator, a second fluid passage that connects the second hydraulic pump and the first fluid passage, a first control valve, a second control valve, and a controller.

The first control valve includes a spool movable between a first supply position at which a hydraulic fluid output from the first hydraulic pump to the first fluid passage is supplied to the hydraulic actuator and a first stop position at which the hydraulic fluid output to the first fluid passage is not supplied to the hydraulic actuator, and is capable of changing, by movement of the spool, the flow rate of the hydraulic fluid to be supplied to the first fluid passage. The second control valve is switchable between a second supply position at which a hydraulic fluid output from the second hydraulic pump to the second fluid passage is supplied to the first fluid passage and a second stop position at which the hydraulic fluid output to the second fluid passage is not supplied to the first fluid passage. A moving speed at which the spool moves from the first supply position to the first stop position when the second control valve is at the second supply position is defined as a first moving speed, and a moving speed at which the spool moves from the first supply position to the first stop position when the second control valve is at the second stop position is defined as a second moving speed. In this case, the controller causes the first moving speed to be lower than the second moving speed.

SUMMARY OF THE INVENTION

In the hydraulic system for the working machine disclosed in Japanese Unexamined Patent Application Publication No. 2020-26819, the control valves are switched using a hydraulic pilot method. That is, the hydraulic-pilot-operated hydraulic system includes a dedicated hydraulic circuit to control the flow of a pilot fluid for operating the control valves. The hydraulic circuit includes an operation device including an operation lever or the like to control the flow of a pilot fluid. The hydraulic circuit is configured to operate the control valves by controlling the flow of a pilot fluid through operation of the operation device, such as operation of an operation lever. However, the operation device in the hydraulic system for the working machine according to Japanese Unexamined Patent Application Publication No. 2020-26819 is provided exclusively for operating the control valves, and has only a single operation pattern for operating the control valves. In other words, the operation device in the hydraulic system for the working machine according to Japanese Unexamined Patent Application Publication No. 2020-26819 has an issue of being unusable for operating other valves of the hydraulic system, such as a switching valve and a proportional valve, that is, the operation device is incapable of changing the operation pattern.

Preferred embodiments of the present invention provide hydraulic systems for working machines, each capable of changing the operation pattern of an operation device (for example, an operation lever) in a working machine adopting a hydraulic pilot method.

Preferred embodiments of the present invention will be described in the following.

A hydraulic system for a working machine according to a first aspect of a preferred embodiment of the present invention includes a hydraulic pump to output a hydraulic fluid, an operation device operable to supply a pilot fluid in accordance with an amount by which the operation device is operated, a hydraulic actuator to be operated by the hydraulic fluid, a pilot fluid passage connected to the operation device, a first control valve connected to the pilot fluid passage to be operated by the pilot fluid to control a flow of the hydraulic fluid to be supplied to the hydraulic actuator, a second control valve to be operated by the pilot fluid to control a flow of the hydraulic fluid, a proportional valve to change, to operate the second control valve, a pressure of the pilot fluid to be supplied to the second control valve, a pressure detector provided in the pilot fluid passage to detect a pressure in the pilot fluid passage, and a controller configured or programmed to control the proportional valve, based on the pressure detected by the pressure detector.

In the first aspect, the hydraulic system may further include a hydraulic port to supply the hydraulic fluid to an outside, and a blocking switching valve capable of blocking the pilot fluid passage connected to the operation device and the first control valve. The second control valve may control a flow of the hydraulic fluid to be supplied to the hydraulic port. The pressure detector may include a pressure sensor between the operation device and the blocking switching valve. The controller may be configured or programmed to, after causing the blocking switching valve to operate to block the pilot fluid passage, control the proportional valve, based on the pressure detected by the pressure sensor.

A hydraulic system for a working machine according to a second aspect of a preferred embodiment of the present invention includes a hydraulic pump to output a hydraulic fluid, an operation device operable to supply a pilot fluid in accordance with an amount by which the operation device is operated, a hydraulic actuator to be operated by the hydraulic fluid, a pilot fluid passage connected to the operation device, a first control valve connected to the pilot fluid passage to be operated by the pilot fluid to control a flow of the hydraulic fluid to be supplied to the hydraulic actuator, a second control valve to be operated by the pilot fluid to control a flow of the hydraulic fluid, a proportional valve to change, to operate the second control valve, a pressure of the pilot fluid to be supplied to the second control valve, a blocking switching valve to block the pilot fluid passage connected to the operation device and the first control valve, a pressure sensor provided in the pilot fluid passage to detect a pressure in the pilot fluid passage, the pressure sensor being between the operation device and the blocking switching valve, and a controller configured or programmed to, after causing the blocking switching valve to operate to block the pilot fluid passage, control the proportional valve, based on the pressure detected by the pressure sensor. The proportional valve is operable to change, to operate the second control valve, a pressure of the pilot fluid to be supplied to the second control valve.

In the second aspect, the proportional valve may include a first proportional valve and a second proportional valve. The first proportional valve and the second proportional valve may change, to operate the second control valve, the pressure of the pilot fluid to be supplied to the second control valve.

In the second aspect, the operation device may be operable in a predetermined first direction and a predetermined second direction different from the first direction, and may include a first output port to output the pilot fluid in accordance with an amount by which the operation device is operated in the first direction, and a second output port to output the pilot fluid in accordance with an amount by which the operation device is operated in the second direction. The pilot fluid passage may include a first pilot fluid passage connected to the first output port of the operation device and a second pilot fluid passage connected to the second output port of the operation device. The first control valve may be connected to the first pilot fluid passage and the second pilot fluid passage to be operated by the pilot fluid supplied through the first pilot fluid passage and the second pilot fluid passage. The second control valve may be a switching valve operable in a predetermined third direction and a predetermined fourth direction different from the third direction. The first proportional valve may change, to operate the second control valve in the third direction, the pressure of the pilot fluid to be supplied to the second control valve. The second proportional valve may change, to operate the second control valve in the fourth direction, the pressure of the pilot fluid to be supplied to the second control valve. The blocking switching valve may block the first pilot fluid passage and the second pilot fluid passage. The pressure sensor may include a first pressure sensor provided in the first pilot fluid passage between the operation device and the blocking switching valve to detect a first pressure in the first pilot fluid passage, and a second pressure sensor provided in the second pilot fluid passage between the operation device and the blocking switching valve to detect a second pressure in the second pilot fluid passage. The controller may be configured or programmed to, after causing the blocking switching valve to operate to block the first pilot fluid passage and the second pilot fluid passage, control the first proportional valve and the second proportional valve, based on the first pressure detected by the first pressure sensor and the second pressure detected by the second pressure sensor.

In the second aspect, the controller may be configured or programmed to, after causing the blocking switching valve to operate to block the first pilot fluid passage and the second pilot fluid passage, in response to detection of an increase in pressure by the first pressure sensor, control the first proportional valve in accordance with a magnitude of the detected pressure, and change, to operate the second control valve in the third direction, the pressure of the pilot fluid to be supplied to the second control valve, and in response to detection of an increase in pressure by the second pressure sensor, control the second proportional valve in accordance with a magnitude of the detected pressure, and change, to operate the second control valve in the fourth direction, the pressure of the pilot fluid to be supplied to the second control valve.

In one aspect, the hydraulic system may further include a solenoid switching valve connected to the hydraulic pump via a fluid passage, and the solenoid switching valve may be operable based on a control signal output from the controller, to operate the blocking switching valve.

Furthermore, in one aspect, the hydraulic system may further include an operation pattern switch to output, to the controller, an instruction to operate the solenoid switching valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG.4is a side view illustrating a working machine according to a preferred embodiment of the present invention.FIG.4illustrates a skid-steer loader as an example of the working machine. The working machines according to preferred embodiments of the present invention are not limited to the skid-steer loader, and may be another type of loader working machine, such as a compact track loader. The working machines according to the preferred embodiments of the present invention may be a working machine other than a loader working machine.

As illustrated inFIG.4, a working machine1includes a machine body2, a cabin3, a working device4, and a traveling device5. In the present preferred embodiment of the present invention, a forward direction corresponds to a forward direction of an operator seated on an operator's seat8of the working machine1(the left side inFIG.4), a rearward direction corresponds to a rearward direction of the operator (the right side inFIG.4), a leftward direction corresponds to a leftward direction of the operator, and a rightward direction corresponds to a rightward direction of the operator. A machine-body-width direction corresponds to a horizontal direction that is orthogonal to a forward-rearward direction. A machine-body-outward direction corresponds to a rightward or leftward direction from a central portion of the machine body2. In other words, the machine-body-outward direction is the machine-body-width direction and is a direction away from the machine body2. A machine-body-inward direction corresponds to a direction opposite to the machine-body-outward direction. In other words, the machine-body-inward direction is the machine-body-width direction and is a direction approaching the machine body2.

The cabin3is mounted on the machine body2. The cabin3includes the operator's seat8. The working device4is attached to the machine body2. The traveling device5is provided on an outer side of the machine body2. A prime mover32is mounted in a rear portion of the machine body2inside the machine body2. The prime mover32includes an electric motor, an engine (internal combustion engine), or the like. In the present preferred embodiment, the prime mover32is an engine.

The working device4includes a pair of booms10, a working tool11, a pair of lift links12, a pair of control links13, a pair of boom cylinders14, and a pair of bucket cylinders15. The pair of booms10are provided on the right side and the left side of the cabin3so as to be swingable up and down. The working tool11is, for example, a bucket, and will be hereinafter referred to as a bucket11. The bucket11is provided at distal end portions (front end portions) of the pair of booms10so as to be swingable up and down.

As illustrated inFIG.4, in accordance with the boom10provided on the left side of the cabin3, the lift link12, the control link13, the boom cylinder14, and the bucket cylinder15are provided on the left side of the cabin3. Although not illustrated inFIG.4, in accordance with the boom10provided on the right side of the cabin3, the lift link12, the control link13, the boom cylinder14, and the bucket cylinder15are provided on the right side of the cabin3. Front portions of the right and left booms10are coupled to each other by an odd-shaped coupling pipe. Base portions (rear portions) of the booms10are coupled to each other by a circular coupling pipe.

Hereinafter, a description will be given of the boom10, the lift link12, the control link13, the boom cylinder14, and the bucket cylinder15provided on the left side of the cabin3.

The lift link12and the control link13support the base portion (rear portion) of the boom10such that the boom10is swingable up and down. The boom cylinder14extends or contracts to raise or lower the boom10. The bucket cylinder15extends or contracts to swing the bucket11.

The lift link12is provided upright at a rear portion of the base portion of the boom10. An upper portion (one end) of the lift link12is pivotally supported via a first pivot shaft16so as to be rotatable about a lateral axis defined by the first pivot shaft16, in the rear portion of the base portion of the boom10. A lower portion (the other end) of the lift link12is pivotally supported via a second pivot shaft17so as to be rotatable about a lateral axis defined by the second pivot shaft17, in the rear portion of the machine body2. The second pivot shaft17is provided below the first pivot shaft16.

An upper portion of the boom cylinder14is pivotally supported via a third pivot shaft18so as to be rotatable about a lateral axis defined by the third pivot shaft18. The third pivot shaft18is provided in a front portion of the base portion of the boom10. A lower portion of the boom cylinder14is pivotally supported via a fourth pivot shaft19so as to be rotatable about a lateral axis defined by the fourth pivot shaft19. The fourth pivot shaft19is provided in a lower portion of the rear portion of the machine body2and below the third pivot shaft18.

The control link13is provided in front of the lift link12. One end of the control link13is pivotally supported via a fifth pivot shaft20so as to be rotatable about a lateral axis defined by the fifth pivot shaft20. The fifth pivot shaft20is provided at a position in front of the lift link12in the machine body2. The other end of the control link13is pivotally supported via a sixth pivot shaft21so as to be rotatable about a lateral axis defined by the sixth pivot shaft21. The sixth pivot shaft21is provided in front of and above the second pivot shaft17in the boom10.

Extending and contracting of the boom cylinder14causes the boom10to swing up and down about the first pivot shaft16, and the distal end portion of the boom10to be raised and lowered, while the base portion of the boom10is supported by the lift link12and the control link13. When the boom10swings up and down, the control link13swings up and down about the fifth pivot shaft20. When the control link13swings up and down, the lift link12swings back and forth about the second pivot shaft17. The bucket cylinder15is disposed near the front portion of the boom10. Extending and contracting of the bucket cylinder15causes the bucket11to swing.

The configuration of the boom10, the lift link12, the control link13, the boom cylinder14, and the bucket cylinder15provided on the left side of the cabin3has been described above. The boom10, the lift link12, the control link13, the boom cylinder14, and the bucket cylinder15provided on the right side of the cabin3have a configuration similar to that described above.

In the front portion of the left boom10, a connection member50(seeFIG.1) is provided. The connection member50is connected to a piping material, such as a pipe, connected to an auxiliary actuator equipped in an auxiliary attachment.

A working tool other than the bucket11may be attached to the front portions of the booms10. Examples of the other working tool include attachments (auxiliary attachments), such as a hydraulic crusher, a hydraulic breaker, an angle broom, an earth auger, a pallet fork, a sweeper, a mower, and a snow blower.

In the present preferred embodiment, the traveling device5includes a wheel-type traveling device5A on the left and a wheel-type traveling device5B on the right, each including a front wheel5F and a rear wheel5R. Alternatively, crawler (including semi-crawler) traveling devices may be adopted as the traveling devices5A and5B.

As illustrated inFIG.1, a hydraulic system for a working machine includes a first hydraulic pump P1, a second hydraulic pump P2, and a third hydraulic pump P3.

Each of the first hydraulic pump P1, the second hydraulic pump P2, and the third hydraulic pump P3is a pump driven by the power of the prime mover32and includes a fixed displacement gear pump. The first hydraulic pump P1is capable of outputting a hydraulic fluid stored in a hydraulic fluid tank22. The first hydraulic pump P1outputs a hydraulic fluid for mainly operating a hydraulic actuator. A first fluid passage40is provided at an output port that outputs a hydraulic fluid in the first hydraulic pump P1.

The second hydraulic pump P2is a pump that is capable of outputting a hydraulic fluid stored in the hydraulic fluid tank22and that increases the amount of hydraulic fluid for the hydraulic actuator. A second fluid passage41is provided at an output port that outputs a hydraulic fluid in the second hydraulic pump P2.

The third hydraulic pump P3is capable of outputting a hydraulic fluid stored in the hydraulic fluid tank22. In particular, the third hydraulic pump P3outputs a hydraulic fluid to be mainly used for control. A third fluid passage43is provided at an output port that outputs a hydraulic fluid in the third hydraulic pump P3. For convenience of description, the hydraulic fluid output from the third hydraulic pump P3will be referred to as a pilot fluid, and the pressure of the pilot fluid will be referred to as a pilot pressure.

A boom control valve56A, a bucket control valve (working tool control valve)56B, which is a first control valve, and an auxiliary control valve56C, which is a second control valve, are connected to the first fluid passage40. The boom control valve56A is a valve that controls hydraulic cylinders to control the booms10(boom cylinders14). The bucket control valve56B is a valve that controls hydraulic cylinders to control the bucket11(bucket cylinders15). The auxiliary control valve56C is a valve that controls an auxiliary actuator (hydraulic cylinder, hydraulic motor) equipped in an auxiliary attachment, such as a hydraulic crusher, a hydraulic breaker, an angle broom, an earth auger, a pallet fork, a sweeper, a mower, or a snow blower.

The boom control valve56A and the bucket control valve56B are each a pilot-operated direct-acting spool three-position switching valve. The boom control valve56A and the bucket control valve56B are switched by a pilot pressure to a neutral position, a first position different from the neutral position, or a second position different from the neutral position and the first position.

The boom cylinders14are connected to the boom control valve56A via fluid passages, and the bucket cylinders15are connected to the bucket control valve56B via fluid passages.

The booms10and the bucket11can be operated by an operation lever58, which is an operation device, provided near the operator's seat8. The operation lever58is supported so as to be tiltable in a forward-rearward direction, a rightward-leftward direction, and an oblique direction from a neutral position. A tilting operation of the operation lever58makes it possible to operate a plurality of pilot valves (operation valves)59A,59B,59C, and59D provided below the operation lever58. The pilot valves59A,59B,59C, and59D are connected to the third hydraulic pump P3by the third fluid passage43.

The plurality of pilot valves (operation valves)59A,59B,59C, and59D are connected to the boom control valve56A and the bucket control valve (working tool control valve)56B by a plurality of fluid passages45a,45b,45c, and45d. Specifically, the pilot valve59A is connected to the boom control valve56A via the fluid passage45a. The pilot valve59B is connected to the boom control valve56A via the fluid passage45b. The pilot valve59C is connected to the bucket control valve56B via the fluid passage45c, which is a first pilot fluid passage connected to a first output port of the operation lever58(operation device). The pilot valve59D is connected to the bucket control valve56B via the fluid passage45d, which is a second pilot fluid passage connected to a second output port of the operation lever58(operation device). For each of the pilot valves (operation valves)59A,59B,59C, and59D, the pressure of the hydraulic fluid to be output can be set in accordance with an operation of the operation lever58.

Specifically, upon the operation lever58being tilted forward, the pilot valve (operation valve)59A for lowering is operated, and a pilot pressure to be output from the pilot valve59A for lowering is set. The pilot pressure acts on a pressure receiver of the boom control valve56A to contract the boom cylinders14, and thus the booms10are lowered.

Upon the operation lever58being tilted rearward, the pilot valve (operation valve)59B for raising is operated, and a pilot pressure to be output from the pilot valve59B for raising is set. The pilot pressure acts on the pressure receiver of the boom control valve56A to extend the boom cylinders14, and thus the booms10are raised.

Upon the operation lever58being tilted rightward (in a first direction), the pilot valve (operation valve)59C for bucket dumping is operated, and a pilot pressure to be output from the first output port, which is an output port of the pilot valve59C, is set. The first output port outputs a hydraulic fluid (that is, a pilot pressure) in accordance with an amount of operation of the operation lever58in the first direction. The pilot pressure acts on a pressure receiver of the bucket control valve56B to extend the bucket cylinders15, and thus the bucket11dumps.

Upon the operation lever58being tilted leftward (in a second direction), the pilot valve (operation valve)59D for bucket shoveling is operated, and a pilot pressure to be output from the second output port, which is an output port of the pilot valve59D, is set. The second output port outputs a hydraulic fluid (that is, a pilot pressure) in accordance with an amount of operation of the operation lever58in the second direction. The pilot pressure acts on the pressure receiver of the bucket control valve56B to contract the bucket cylinders15, and thus the bucket11shovels.

The hydraulic system for the working machine according to the present preferred embodiment includes a second control valve that controls the flow rate of a hydraulic fluid to be supplied from the first fluid passage40to the hydraulic actuator of the auxiliary attachment described above (hereinafter referred to as an auxiliary actuator) via the connection member50. In the present preferred embodiment, the second control valve is the auxiliary control valve56C, and the hydraulic actuator is an auxiliary actuator. Hereinafter, a description will be given under the assumption that the second control valve is the auxiliary control valve56C.

The first fluid passage40includes a first section40athat connects the first hydraulic pump P1and the auxiliary control valve56C, and at least two second sections40band40cconnected to the auxiliary control valve56C.

The auxiliary control valve56C includes an input port (first input port)70, an input port (second input port)102, an output port71, a tank port (first tank port)72, and a tank port (second tank port)101. The input port70is a port to which the first section40aof the first fluid passage40is connected and to which the hydraulic fluid output from the first hydraulic pump P1is supplied. Similarly to the input port70, the input port102is a port to which the first section40aof the first fluid passage40is connected and to which the hydraulic fluid output from the first hydraulic pump P1is supplied, and is a port different from the input port70. The output port71is a port to which the second sections40band40cof the first fluid passage40are connected, and is a port that supplies a hydraulic fluid to the auxiliary actuator. The tank port72is a port that discharges a hydraulic fluid, and is a port that discharges a hydraulic fluid returned from the auxiliary actuator to the auxiliary control valve56C. A discharge fluid passage54is connected to the tank port72. The discharge fluid passage54is connected to the hydraulic fluid tank22, and discharges at least the hydraulic fluid discharged from the tank port72of the auxiliary control valve56C to the hydraulic fluid tank22.

The tank port101is a port that discharges a hydraulic fluid, and is a port that discharges at least a portion of the hydraulic fluid introduced from the input port102to the auxiliary control valve56C. The tank port101is connected to the discharge fluid passage54.

The auxiliary control valve56C is a switching valve including a spool, and is, for example, a pilot-operated direct-acting spool three-position switching valve. The spool of the auxiliary control valve56C is moved in, for example, a third direction and a fourth direction different from the third direction by the pilot pressures respectively acting on pressure receivers61aand61b, thereby being movable to first supply positions62aand62bat which a hydraulic fluid is supplied to the auxiliary actuator and a first stop position (neutral position)62cat which supply of the hydraulic fluid to the auxiliary actuator is stopped. A movement of the spool of the auxiliary control valve56C to either the first supply position62aor62benables the auxiliary control valve56C to change the flow rate of the hydraulic fluid to be output from the output port71of the auxiliary control valve56C.

Pilot fluid passages86aand86bare connected to the pressure receivers61aand61bof the auxiliary control valve56C, respectively. A first proportional valve60A, which is a proportional valve, is provided in the pilot fluid passage86a. A second proportional valve60B, which is a proportional valve, is provided in the pilot fluid passage86b. The proportional valves (first proportional valve60A and second proportional valve60B) are solenoid valves whose opening can be changed by energization. The third fluid passage43is connected to the first proportional valve60A and the second proportional valve60B. The first proportional valve60A and the second proportional valve60B are supplied with a pilot fluid from the third hydraulic pump P3. Changing of the openings of the first proportional valve60A and the second proportional valve60B causes a change in the pilot pressure that acts on the pressure receivers61aand61bof the auxiliary control valve56C, and the spool of the auxiliary control valve56C is moved in a certain direction accordingly.

For example, upon the first proportional valve60A being opened, the pilot fluid acts on the pressure receiver61aof the auxiliary control valve56C via the pilot fluid passage86a, and the pilot pressure to be applied to (act on) the pressure receiver61ais determined by the opening of the first proportional valve60A. In response to the pilot pressure applied to the pressure receiver61abecoming a predetermined value or more, the spool of the auxiliary control valve56C moves from the first stop position62ctoward the first supply position62a. Upon the second proportional valve60B being opened, the pilot fluid acts on the pressure receiver61bof the auxiliary control valve56C via the pilot fluid passage86b, and the pilot pressure to be applied to (act on) the pressure receiver61bis determined by the opening of the second proportional valve60B. In response to the pilot pressure applied to the pressure receiver61bbecoming a predetermined value or more, the spool of the auxiliary control valve56C moves from the first stop position62ctoward the first supply position62b.

Energization or the like of the proportional valves60(first proportional valve60A and second proportional valve60B) is performed by a controller90. The controller90includes a central processing unit (CPU) and a memory or the like.

As illustrated inFIG.1, the hydraulic system for the working machine according to the present preferred embodiment includes, as characteristic components, a blocking switching valve100, a solenoid switching valve110to switch the blocking switching valve100, and pressure sensors120aand120b. The pressure sensors120aand120bare pressure detectors that measure the pilot pressure between the blocking switching valve100and the operation lever (operation device)58.

The blocking switching valve100is provided across both the fluid passage (first pilot fluid passage)45cand the fluid passage (second pilot fluid passage)45dthat connect the operation lever58and the bucket control valve56B. The blocking switching valve100is a valve capable of blocking and unblocking the fluid passages45cand45d.

The blocking switching valve100is a two-position switching valve operated by a pilot pressure. The blocking switching valve100is switchable between two switching positions (a blocking position100aand an unblocking position100b) by a pilot pressure. In the blocking position100a, the blocking switching valve100blocks the fluid passages45cand45dand makes the flow rate of the pilot fluid flowing to the bucket control valve56B zero.

In the unblocking position100b, the blocking switching valve100unblocks the fluid passages45cand45dand allows a pilot fluid to be supplied to the bucket control valve56B. In other words, the blocking switching valve100blocks the flow of a hydraulic fluid through the fluid passages45cand45dwhen being in the blocking position100a, and allows a hydraulic fluid to flow through the fluid passages45cand45dwhen being in the unblocking position100b.

Thus, when the blocking switching valve100is in the blocking position100a, the pilot fluid output from the pilot valves59C and59D of the operation lever58is blocked by the blocking switching valve100in the fluid passages45cand45d. Then, upon a pilot fluid being output from the pilot valves59C and59D by an operation of the operation lever58, the hydraulic pressure in the section from the pilot valves59C and59D to the blocking position100aincreases in the fluid passages45cand45d.

The solenoid switching valve110is a solenoid switching valve connected to the third hydraulic pump P3via the third fluid passage43. The solenoid switching valve110operates on the basis of a control signal output from the controller90. The solenoid switching valve110is a valve that operates the blocking switching valve100by switching, and includes a solenoid two-position switching valve. The solenoid switching valve110applies a pilot fluid (that is, a pilot pressure) supplied from the third hydraulic pump P3to the blocking switching valve100to operate the blocking switching valve100. The solenoid switching valve110is switchable between a first position110aand a second position110b. The solenoid switching valve110is connected to the third fluid passage43. When being in the first position110a, the solenoid switching valve110causes a pilot pressure to act on a pressure receiver of the blocking switching valve100, and causes the blocking switching valve100to be in the blocking position100a. When being in the second position110b, the solenoid switching valve110causes a pilot pressure not to act on the pressure receiver of the blocking switching valve100, and causes the blocking switching valve100to be in the unblocking position100b.

Switching between the first position110aand the second position110bof the solenoid switching valve110is performed by the controller90. An operation pattern switch95, such as a switch that can be turned ON or OFF, is connected to the controller90. The operation pattern switch95outputs an instruction to operate the solenoid switching valve110to the controller90. The operation pattern switch95is, for example, a physical switch such as a swingable seesaw switch or a pushable push switch. When the operation pattern switch95is in an OFF state, the controller90deenergizes the solenoid of the solenoid switching valve110. When the operation pattern switch95is in an ON state, the controller90continuously energizes the solenoid of the solenoid switching valve110.

The operation pattern switch95need not necessarily be the above-described physical switch. The operation pattern switch95may be, for example, a soft switch that is configured or programmed by computer software and that is displayed by the controller90on a display device or the like provided in the working machine1. The controller90is capable of displaying the operation pattern switch95on a touch panel (also referred to as a touch screen) or the like of the display device. Even when the operation pattern switch95is a soft switch displayed on the touch panel, the controller90deenergizes or energizes the solenoid of the solenoid switching valve110by turning ON or OFF the operation pattern switch95, as described above.

In response to the solenoid of the solenoid switching valve110being energized, the solenoid switching valve110is switched to the first position110a, and a pilot pressure acts on the pressure receiver of the blocking switching valve100. Accordingly, the blocking switching valve100is switched to the blocking position100a. In response to the solenoid of the solenoid switching valve110being deenergized, the solenoid switching valve110is switched to the second position110b, and a pilot pressure stops acting on the pressure receiver of the blocking switching valve100. Accordingly, the blocking switching valve100is switched to the unblocking position100b.

The pressure sensor120b, which is a first pressure sensor, is a sensor that is provided in the fluid passage45cdefining and functioning as a first pilot fluid passage, that detects a hydraulic pressure in the fluid passage45ccorresponding to a rightward operation of the operation lever58(referred to as a first pressure), and that outputs an electric signal corresponding to the detected hydraulic pressure. The pressure sensor120bis disposed between the operation lever58, which is an operation device, and the blocking switching valve100, and is electrically connected to the controller90. The pressure sensor120boutputs an electric signal corresponding to the detected hydraulic pressure in the fluid passage45cto the controller90.

The pressure sensor120a, which is a second pressure sensor, is a sensor that is provided in the fluid passage45ddefining and functioning as a second pilot fluid passage, that detects a hydraulic pressure in the fluid passage45dcorresponding to a leftward operation of the operation lever58(referred to as a second pressure), and that outputs an electric signal corresponding to the detected hydraulic pressure. The pressure sensor120ais disposed between the operation lever58, which is an operation device, and the blocking switching valve100, and is electrically connected to the controller90. The pressure sensor120aoutputs an electric signal corresponding to the detected hydraulic pressure in the fluid passage45dto the controller90. The controller90calculates hydraulic pressure values in the fluid passages45dand45con the basis of the electric signals received from the pressure sensors120aand120b.

In the hydraulic system including the blocking switching valve100, the solenoid switching valve110, and the pressure sensors120aand120bdescribed above, the controller90changes the operation target (the control valve56A,56B, or56C) of the operation lever58in response to the operation pattern switch95being turned ON. In the present preferred embodiment, the change of the operation target is referred to as a change of the operation pattern of the operation lever58. The change of the operation pattern makes it possible to operate not only the boom control valve56A and the bucket control valve56B but also the auxiliary control valve56C by using the operation lever58.

A change of the operation pattern in the hydraulic system according to the present preferred embodiment will be described with reference toFIG.2.FIG.2is a flowchart illustrating operations of individual portions or elements of the hydraulic system of the working system according to the present preferred embodiment.

In response to the operation pattern switch95being turned ON while the prime mover32is being driven and the working machine1is in a normal operation state (step S1), the controller90starts changing the operation pattern of the operation lever58(step S10).

After step S10, the controller90continuously energizes the solenoid of the solenoid switching valve110to switch the solenoid switching valve110to the first position110a(step S20). In response to the solenoid switching valve110being switched to the first position110a, a pilot pressure acts on the pressure receiver of the blocking switching valve100. Accordingly, the blocking switching valve100is switched to the blocking position100a, and the fluid passages45cand45dare blocked.

After step S20, the controller90activates the pressure sensor120a, which is a second pressure sensor, and the pressure sensor120b, which is a first pressure sensor (step S30). Accordingly, the pressure sensors120aand120bstart measuring the hydraulic pressures in the fluid passages45dand45c, respectively.

After step S30, for example, the controller90detects that the hydraulic pressure in the fluid passage45c(first pressure) detected by the pressure sensor120bhas increased and that the hydraulic pressure in the fluid passage45d(second pressure) detected by the pressure sensor120ahas decreased (Yes in step S40). In this case, the controller90increases the opening of the first proportional valve60A provided in the pilot fluid passage86a, in accordance with the first pressure detected by the pressure sensor120b(step S50). Accordingly, a pilot pressure is applied to the pressure receiver61aof the auxiliary control valve56C, the spool of the auxiliary control valve56C is moved, the auxiliary control valve56C is switched to the first supply position62a, and the auxiliary actuator is operated.

If the controller90detects neither an increase in the hydraulic pressure in the fluid passage45c(first pressure) nor a decrease in the hydraulic pressure in the fluid passage45d(second pressure) (No in step S40), the process proceeds to step S60.

After step S40, for example, the controller90detects that the hydraulic pressure in the fluid passage45c(first pressure) detected by the pressure sensor120bhas decreased and that the hydraulic pressure in the fluid passage45d(second pressure) detected by the pressure sensor120ahas increased (Yes in step S60). In this case, the controller90increases the opening of the second proportional valve60B provided in the pilot fluid passage86b, in accordance with the second pressure detected by the pressure sensor120a(step S70). Accordingly, a pilot pressure is applied to the pressure receiver61bof the auxiliary control valve56C, the spool of the auxiliary control valve56C is moved, the auxiliary control valve56C is switched to the first supply position62b, and the auxiliary actuator is operated.

If the controller90detects neither a decrease in the hydraulic pressure in the fluid passage45c(first pressure) nor an increase in the hydraulic pressure in the fluid passage45d(second pressure) (No in step S60), the process proceeds to step S80.

In response to the operation pattern switch95being turned OFF (Yes in step S80), the controller90ends changing the operation pattern of the operation lever58(step S90). If the operation pattern switch95is not turned OFF (No in step S80), the process returns to step S40, and the controller90continues changing the operation pattern of the operation lever58.

In steps S50and S70, the controller90increases the opening of the first proportional valve60A and the opening of the second proportional valve60B in accordance with the first pressure and the second pressure detected by the pressure sensors120band120a, respectively. At this time, the controller90may make the opening of the first proportional valve60A proportional to the magnitude of the first pressure, may make the opening of the second proportional valve60B proportional to the magnitude of the second pressure, or may perform control in accordance with a predetermined function having the first pressure and/or the second pressure as a variable. The relationship between the first pressure and the opening of the first proportional valve60A and the relationship between the second pressure and the opening of the second proportional valve60B can be determined as appropriate in accordance with characteristics of the working machine1or characteristics of the operation device of the working machine1.

As described above, according to the hydraulic system for the working machine according to the present preferred embodiment, the operation target of the operation lever58can be changed from the boom control valve56A and the bucket control valve56B to the boom control valve56A and the auxiliary control valve56C. This is referred to as a change of an operation pattern, but the change of the operation pattern is not limited to the configuration of the above-described preferred embodiment.

As described in the present preferred embodiment, the technique and idea of blocking a pilot fluid passage with a configuration corresponding to the blocking switching valve100and the solenoid switching valve110and controlling a configuration corresponding to the first proportional valve60A and the second proportional valve60B on the basis of a change in the hydraulic pressure of the pilot fluid passage can be applied to various portions or elements of the hydraulic system for the working machine.

For example, in the present preferred embodiment, the blocking switching valve100is provided across the fluid passages45cand45d. Alternatively, the blocking switching valve100may be provided across the fluid passages45aand45b. Accordingly, the pressure sensors120aand120bmay be provided, in the fluid passages45aand45b, between the operation lever58and the blocking switching valve100. With this configuration, the controller90is capable of controlling the first proportional valve60A and the second proportional valve60B by operating the operation lever58in a forward-rearward direction.

A modification of the present preferred embodiment will be described with reference toFIG.3.FIG.3is a schematic diagram of a hydraulic system for a working machine according to a modification of the present preferred embodiment. The hydraulic system illustrated inFIG.3has a configuration slightly different from the configuration of the hydraulic system illustrated inFIG.1. In the hydraulic system illustrated inFIG.3, a solenoid blocking switching valve130is provided instead of the blocking switching valve100and the solenoid switching valve110illustrated inFIG.1.

Hereinafter, the solenoid blocking switching valve130will be described. The solenoid blocking switching valve130is provided across both the fluid passage (third pilot fluid passage)45aand the fluid passage (fourth pilot fluid passage)45bthat connect the operation lever58and the boom control valve56A, and is provided across both the fluid passage (first pilot fluid passage)45cand the fluid passage (second pilot fluid passage)45dthat connect the operation lever58and the bucket control valve56B. The solenoid blocking switching valve130is a valve capable of blocking and unblocking the fluid passages45a,45b,45c, and45d.

The solenoid blocking switching valve130is a two-position switching valve including a solenoid switching valve. The solenoid blocking switching valve130is switchable between two switching positions (a blocking position130aand an unblocking position130b) as a result of the solenoid being energized or deenergized.

In the blocking position130a, the solenoid blocking switching valve130blocks the fluid passages45cand45dbetween the pilot valves59C and59D and makes the flow rate of the pilot fluid flowing from the pilot valves59C and59D to the bucket control valve56B zero.

In the blocking position130a, the solenoid blocking switching valve130connects the fluid passage45aconnected to the pilot valve59A to the fluid passage (first pilot fluid passage)45c. This makes it possible to supply a pilot fluid from the pilot valve59A to the bucket control valve56B. Furthermore, in the blocking position130a, the solenoid blocking switching valve130connects the fluid passage45bconnected to the pilot valve59B to the fluid passage (second pilot fluid passage)45d. This makes it possible to supply a pilot fluid from the pilot valve59B to the bucket control valve56B.

In the unblocking position130b, the solenoid blocking switching valve130unblocks the fluid passages45aand45bto allow a pilot fluid to be supplied to the boom control valve56A, and unblocks the fluid passages45cand45dto allow a pilot fluid to be supplied to the bucket control valve56B. In other words, the solenoid blocking switching valve130causes portions near the operation lever58of the fluid passages45aand45bto communicate with the fluid passages45cand45dwhen being in the blocking position130a, and causes the fluid passages45a,45b,45c, and45dto communicate with each other when being in the unblocking position130b.

When the solenoid blocking switching valve130is in the blocking position130a, the fluid passages45aand45bconnected to the boom control valve56A communicate with, in the solenoid blocking switching valve130, the hydraulic fluid tank22or suction ports of the first hydraulic pump P1, the second hydraulic pump P2, and the third hydraulic pump P3, and thus the pilot pressure acting on the boom control valve56A becomes zero.

Thus, when the solenoid blocking switching valve130is in the blocking position130a, the pilot fluid output from the pilot valves59C and59D of the operation lever58is blocked by the solenoid blocking switching valve130in the fluid passages45cand45d. Then, upon a pilot fluid being output from the pilot valves59C and59D by an operation of the operation lever58, the hydraulic pressure in the section from the pilot valves59C and59D to the blocking position130aincreases in the fluid passages45cand45d.

Furthermore, when the solenoid blocking switching valve130is in the blocking position130a, a pilot fluid can be supplied from the pilot valve59A to the bucket control valve56B, and a pilot fluid can be supplied from the pilot valve59B to the bucket control valve56B.

Switching between the blocking position130aand the unblocking position130bin the solenoid blocking switching valve130is performed by the controller90. The operation pattern switch95, such as a switch that can be turned ON or OFF, described in the above preferred embodiment is connected to the controller90. The operation pattern switch95outputs an instruction to operate the solenoid blocking switching valve130to the controller90. When the operation pattern switch95is in an OFF state, the controller90deenergizes the solenoid of the solenoid blocking switching valve130. When the operation pattern switch95is in an ON state, the controller90continuously energizes the solenoid of the solenoid blocking switching valve130.

In response to the solenoid of the solenoid blocking switching valve130being energized, the solenoid blocking switching valve130is switched to the blocking position130a. In response to the solenoid of the solenoid blocking switching valve130being deenergized, the solenoid blocking switching valve130is switched to the unblocking position130b.

The configuration and disposition of the pressure sensor120b, which is a first pressure sensor, and the pressure sensor120a, which is a second pressure sensor, are similar to the configuration and disposition described in the above preferred embodiment.

According to the hydraulic system of the above-described modification, when the solenoid blocking switching valve130is in the blocking position130a, the operation target of the operation lever58can be changed from the bucket control valve56B to the auxiliary control valve56C. In addition, when the solenoid blocking switching valve130is in the blocking position130a, a pilot fluid can be supplied from the pilot valve59A to the bucket control valve56B, and a pilot fluid can be supplied from the pilot valve59B to the bucket control valve56B. Thus, the operation target of the operation lever58can be changed from the boom control valve56A to the bucket control valve56B.

The hydraulic system illustrated inFIG.1according to the above-described preferred embodiment and the hydraulic system illustrated inFIG.3according to the modification each include an operation switch96for operating the auxiliary actuator. The operation switch96includes, for example, a swingable seesaw switch, a slidable slide switch, or a pushable push switch. The operation switch96is provided near the operator's seat8and is connected to the controller90.

The connection member50includes an auxiliary power supply port (also referred to as an external power supply port) to supply power to control a switching valve of the auxiliary attachment connected to the connection member50. Illustration of the auxiliary power supply port is omitted.

The auxiliary power supply port is connected to the controller90, and the controller90controls the voltage to be applied to the auxiliary power supply port. In this configuration, in a first operation mode, the first proportional valve60A and the second proportional valve60B are operated by the operation switch96when the solenoid blocking switching valve130is in the unblocking position130b. In response to the operation switch96being operated, the controller90operates the first proportional valve60A and the second proportional valve60B by outputting a voltage in accordance with the direction and amount of the operation of the operation switch96, and switches the auxiliary control valve56C.

At this time, the controller90ignores the output values of the pressure sensor120aand the pressure sensor120b. Alternatively, the controller90may use the output values of the pressure sensor120aand the pressure sensor120bfor control other than control of the first proportional valve60A and the second proportional valve60B.

In a second operation mode, when the solenoid blocking switching valve130is in the blocking position130aand the controller90is not detecting an operation of the operation switch96, the controller90controls the first proportional valve60A and the second proportional valve60B in accordance with the output values of the pressure sensor120aand the pressure sensor120bas described above. At this time, the controller90sets the voltage to be applied to the auxiliary power supply port to zero.

In a third operation mode, when the solenoid blocking switching valve130is in the blocking position130aand the controller90is detecting an operation of the operation switch96, the controller90operates the first proportional valve60A and the second proportional valve60B by outputting a voltage in accordance with the direction and amount of the operation of the operation switch96, and switches the auxiliary control valve56C. In addition, the controller90applies a voltage to the auxiliary power supply port. As a result of applying a voltage to the auxiliary power supply port, a switching valve of the auxiliary attachment is switched, and the actuator connected to the switching valve is operated.

As described above, as a result of making the voltage to be applied to the auxiliary power supply port in the second operation mode different from the voltage to be applied to the auxiliary power supply port in the third operation mode, two hydraulic actuators provided in the auxiliary attachment can be operated by the first proportional valve60A and the second proportional valve60B.

Although it has been described that the controller90sets the voltage to be applied to the auxiliary power supply port to zero in the second operation mode and applies a voltage to the auxiliary power supply port in the third operation mode, the controller90may apply a voltage to the auxiliary power supply port in the second operation mode and set the voltage to be applied to the auxiliary power supply port to zero in the third operation mode. Also with this configuration, the two hydraulic actuators provided in the auxiliary attachment can be operated by the first proportional valve60A and the second proportional valve60B.

However, if the controller90detects an operation of the operation switch96and output values of the pressure sensor120aand the pressure sensor120b, the controller90preferentially executes the second operation mode.

According to the configurations described in the present preferred embodiment and the modification, the controller90is capable of controlling not only solenoid proportional valves exemplified by the first proportional valve60A and the second proportional valve60B but also various components that are electrically controlled, on the basis of a change in the pressures of the pressure sensors120aand120b. Thus, the change of the operation pattern described in the present preferred embodiment can be applied to not only the working-system hydraulic circuit according to the present preferred embodiment but also a traveling-system hydraulic circuit.

In the above-described preferred embodiment, a description has been given of the configuration in which an object other than an object to be originally operated can be moved by changing control in accordance with a change in pilot pressure also in a hydraulic pilot circuit, but the present invention is not limited to the above-described configuration. For example, a pressure switch may be used, instead of a pressure sensor, as a detector for a pilot pressure, to turn ON/OFF an auxiliary control valve. In addition, although pilot fluid passages are blocked by a blocking switching valve in the above-described preferred embodiment, an operation (for example, an operation of applying a current to a proportional valve or the like to operate the auxiliary control valve) may be performed while an object to be originally operated is operated by the operation lever, without blocking the pilot fluid passages.