Patent Description:
Patent Document <NUM> describes a load measuring device for a work machine that is provided with a lifting magnet configured to attract scraps, wherein the load measuring device includes a load measuring means for measuring a load of the scrap. Patent Document <NUM> also describes that, in a case where an actual overturning moment exceeds an overturning moment specified by a rated load curve, further enlargement of a working radius is restricted.

Further work machines with means for load determination are known from Patent Documents <NUM> to <NUM>.

In the work machine provided with the lifting magnet, when a lifting load (transporting object), such as scrap iron or the like, is attracted and lifted by the lifting magnet, vibration may be generated in an attachment (boom) of the work machine. This is because, in the work machine provided with the lifting magnet, the vibration is generated in the attachment (boom) due to a weight of the lifting magnet provided at a tip end of the attachment and a weight of the lifting load that are large. In addition, during a work of the work machine provided with the lifting magnet, the lifting load located at a position away from a slewing upper structure may be lifted and transported. In this case, the vibration is generated in the attachment (boom) because the lifting load is lifted in a state where the attachment is extended. Hence, a boom cylinder pressure vibrates due to the vibration generated in the attachment (boom). For this reason, when the weight of the lifting load is detected based on the boom cylinder pressure, it may not be possible to suitably measure the weight of the lifting load.

In view of the problem described above, it is one object of the present invention to provide a work machine that can accurately calculate a weight of a transporting object.

The problem described above is solved by a work machine according to claim <NUM>.

According to one embodiment of the present invention, there is provided a work machine including a lower structure; a slewing upper structure attached to the lower structure via a slewing mechanism; an attachment, including at least a boom, and attached to the slewing upper structure; a boom cylinder configured to drive the boom; a work tool attached to the attachment; and a controller, wherein the controller includes a weight calculating part configured to measure a weight of a transporting object to be transported by the work tool, based on a boom cylinder pressure of the boom cylinder, and a vibration control part configured to generate a command for reducing vibration of the attachment.

According to one embodiment described above, it is possible to provide a work machine that can accurately calculate the weight of the transporting object.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings.

<FIG> is a side view of a work machine <NUM> according to one embodiment. A slewing upper structure <NUM> is attached to a lower structure <NUM> of the work machine <NUM> via a slewing mechanism <NUM>. A boom <NUM> is attached to the slewing upper structure <NUM>. An arm <NUM> is attached to a tip end of the boom <NUM>, and a lifting magnet <NUM> is attached to a tip end of the arm <NUM>, as an end attachment (work tool). The boom <NUM> and the arm <NUM> form a work attachment which is an example of an attachment. The boom <NUM> is driven by a boom cylinder <NUM>, the arm <NUM> is driven by an arm cylinder <NUM>, and the lifting magnet <NUM> is driven by a lifting magnet cylinder <NUM>. In the present embodiment, the work tool (transport mechanism) attached to the tip of the attachment, usable to transport a transporting object, is the lifting magnet <NUM>. However, other work tools, such as a bucket for excavating and transporting soil or the like, a grapple, a demolition fork, a harvester including a chain saw, or the like may be attached, depending on a type of work.

A boom angle sensor S1 is attached to the boom <NUM>, an arm angle sensor S2 is attached to the arm <NUM>, and a lifting magnet angle sensor S3 is attached to the lifting magnet <NUM>. A controller <NUM>, a display device <NUM>, a space recognition device <NUM>, a body inclination sensor S4, and a swing angular velocity sensor S5 are attached to the slewing upper structure <NUM>.

The boom angle sensor S1 is configured to detect a boom angle, which is a rotation angle of the boom <NUM> with respect to the slewing upper structure <NUM>. The boom angle sensor S1 may be a rotation angle sensor that detects the rotation angle of the boom <NUM> around a boom foot pin, a cylinder stroke sensor that detects an amount of stroke (amount of boom stroke) of the boom cylinder <NUM>, an inclination (acceleration) sensor that detects an inclination angle of the boom <NUM>, a combination of an acceleration sensor and a gyro sensor, or the like, for example. The same applies to the arm angle sensor S2 that detects an arm angle, which is a rotation angle of the arm <NUM> with respect to the boom <NUM>, and the lifting magnet angle sensor S3 that detects a lifting magnet angle, which is a rotation angle of the lifting magnet <NUM> with respect to the arm <NUM>.

The body inclination sensor S4 is configured to detect an inclination (body inclination angle) of the slewing upper structure <NUM> with respect to a horizontal plane. In the present embodiment, the machine body inclination sensor S4 is an acceleration sensor that detects the inclination angle of the slewing upper structure <NUM> around a longitudinal axis and a lateral axis. The longitudinal axis and the lateral axis of the slewing upper structure <NUM> are orthogonal to each other, and pass through a machine center which is a point on a swing axis of the work machine <NUM>.

The swing angular velocity sensor S5 detects a swing angular velocity of the slewing upper structure <NUM>. In the present embodiment, the swing angular velocity sensor S5 is a gyro sensor, but the swing angular velocity sensor S5 may be a resolver, a rotary encoder, or the like.

The space recognition device <NUM> is configured to capture an image of a surrounding of the work machine <NUM>. The space recognition device <NUM> is a monocular camera, a stereo camera, a distance image camera, an infrared camera, a LIDAR, or the like, for example. In the example illustrated in <FIG>, the space recognition device <NUM> includes a front camera 80F attached to a front end of an upper surface of the slewing upper structure <NUM>, a back camera 80B attached to a back end of the upper surface of the slewing upper structure <NUM>, a left camera <NUM> attached to a left end of the upper surface of the slewing upper structure <NUM>, and a right camera 80R (not visible in <FIG>) attached to a right end of the upper surface of the slewing upper structure <NUM>.

The space recognition device <NUM> is a monocular camera including an imaging element, such as a CCD, a CMOS, or the like, for example, and outputs a captured image to the display device <NUM>. In addition, the space recognition device <NUM> may be configured to calculate a distance from the space recognition device <NUM> or the work machine <NUM> to a recognized object. When a millimeter-wave radar, an ultrasonic sensor, a laser radar, an ultrasonic sensor, a laser radar, or the like is utilized as the space recognition device <NUM>, instead of merely utilizing the captured image, a large number of signals (laser beams or the like) can be transmitted to the object and reflected signals from the object can be received, so as to detect the distance and direction to the object from the reflected signals.

The space recognition device <NUM> is configured to detect the object present in the surrounding of the work machine <NUM>. The object is a dump truck, a terrain shape (inclination, hole, or the like), an electric wire, a utility pole, a person, an animal, a vehicle, a construction machine, a building, a wall, a helmet, a safety vest, a work clothing, a predetermined mark on the helmet, or the like, for example. Hence, the space recognition device <NUM> may be configured to be able to identify at least one of a type, a position, a shape, or the like of the object. For example, the space recognition device <NUM> may be configured to be able to distinguish between the person and the object other than the person.

A boom rod pressure sensor S6a, a boom bottom pressure sensor S6b, and a boom cylinder stroke sensor S7 may be attached to the boom cylinder <NUM>, as pressure sensors for the boom cylinder <NUM>. An arm rod pressure sensor S6c, an arm bottom pressure sensor S6d, and an arm cylinder stroke sensor S8 may be attached to the arm cylinder <NUM>, as pressure sensors for the arm cylinder <NUM>. A lifting magnet rod pressure sensor S6e, a lifting magnet bottom pressure sensor S6f, and a lifting magnet cylinder stroke sensor S9 may be attached to the lifting magnet cylinder <NUM>, as pressure sensors for the lifting magnet cylinder <NUM>.

The boom rod pressure sensor S6a detects a pressure inside a rod-side fluid chamber (hereinafter referred to as "a boom rod pressure") of the boom cylinder <NUM>, and the boom bottom pressure sensor S6b detects a pressure inside a bottom-side fluid chamber (hereinafter referred to as "a boom bottom pressure") of the boom cylinder <NUM>. The arm rod pressure sensor S6c detects a pressure inside a rod-side fluid chamber (hereinafter referred to as "an arm rod pressure") of the arm cylinder <NUM>, and the arm bottom pressure sensor S6d detects a pressure inside a bottom-side fluid chamber (hereinafter referred to as "an arm bottom pressure") of the arm cylinder <NUM>. The lifting magnet rod pressure sensor S6e detects a pressure inside a rod-side fluid chamber (hereinafter referred to as "a lifting magnet rod pressure") of the lifting magnet cylinder <NUM>, and the lifting magnet bottom pressure sensor S6f detects a pressure inside a bottom-side fluid chamber (hereinafter referred to as "a lifting magnet bottom pressure") of the lifting magnet cylinder <NUM>.

The slewing upper structure <NUM> is provided with a cab <NUM>, as a driver's cab, and is provided with a power source, such as an engine <NUM> or the like.

Further, a cab <NUM> is provided on the slewing upper structure <NUM>, so that the cab <NUM> can be raised and lowered via a cab elevator device <NUM>. Hereinafter, a cab that can be raised and lowered in this manner may also be referred to as "an elevator cab". <FIG> illustrates a state where the cab <NUM> is raised to a highest position by the cab elevator device <NUM>. In addition, the cab <NUM> is disposed on a side (generally on a left side) of the boom <NUM>.

<FIG> is a diagram illustrating a configuration example of a driving system attached on the work machine <NUM>. In <FIG>, a mechanical power transmission system is indicated by a double line, a working fluid line is indicated by a bold solid line, a pilot line is indicated by a broken line, an electric control system is indicated by a one-dot chain line, and an electric driving system is indicated by a bold dotted line.

The driving system of the work machine <NUM> mainly includes the engine <NUM>, a main pump <NUM>, a hydraulic pump <NUM>, a pilot pump <NUM>, a control valve <NUM>, an operation device <NUM>, a controller <NUM>, and an engine controller <NUM>.

The engine <NUM> is a power source of the work machine <NUM>, and is a diesel engine that operates to maintain a predetermined engine speed, for example. An output shaft of the engine <NUM> is connected to input shafts of an alternator 11a, the main pump <NUM>, the hydraulic pump <NUM>, and the pilot pump <NUM>.

The main pump <NUM> supplies a working fluid to the control valve <NUM> via a working fluid line <NUM>. In the present embodiment, the main pump <NUM> is a swash plate type variable displacement hydraulic pump.

A regulator <NUM> controls a discharge amount of the main pump <NUM>. In the present embodiment, the regulator <NUM> controls the discharge amount of the main pump <NUM> by adjusting a swash plate tilt angle of the main pump <NUM> according to a control signal or the like from the controller <NUM>.

The pilot pump <NUM> supplies the working fluid to various hydraulic control devices including the operation device <NUM>, via a pilot line <NUM>. In the present embodiment, the pilot pump <NUM> is a fixed displacement hydraulic pump.

The control valve <NUM> is a hydraulic control device that controls a hydraulic system in the work machine <NUM>. The control valve <NUM> selectively supplies the working fluid discharged from the main pump <NUM> to one or more elements selected from the boom cylinder <NUM>, the arm cylinder <NUM>, the lifting magnet cylinder <NUM>, a left drive hydraulic motor <NUM>, a right drive hydraulic motor 1R, and a swing hydraulic motor 2A, for example. In the following description, the boom cylinder <NUM>, the arm cylinder <NUM>, the lifting magnet cylinder <NUM>, the left drive hydraulic motor <NUM>, the right drive hydraulic motor 1R, and the swing hydraulic motor 2A are collectively referred to as "hydraulic actuators".

The operation device <NUM> is a device used by an operator to operate the hydraulic actuators. In the present embodiment, the operation device <NUM> generates a pilot pressure by supplying the working fluid from the pilot pump <NUM> to a pilot port of a corresponding flow control valve inside the control valve <NUM>. More particularly, the operation device <NUM> includes a left operating lever for a swing operation and an arm operation, a right operating lever for a boom operation and a lifting magnet operation, a travel pedal, a travel lever (each of the levers and pedal not illustrated), or the like. The pilot pressure varies according to an operation content (including an operation direction and an operation amount, for example) of the operation device <NUM>.

The operation pressure sensor <NUM> detects the pilot pressure generated by the operation device <NUM>. In the present embodiment, the operation pressure sensor <NUM> detects the pilot pressure generated by the operation device <NUM>, and outputs a detected value with respect to the controller <NUM>. The controller <NUM> grasps operation contents of the operation device <NUM>, based on the output of the operation pressure sensor <NUM>.

The controller <NUM> is a control device that executes various calculations. In the present embodiment, the controller <NUM> is a microcomputer including a CPU, a volatile storage device, a nonvolatile storage device, or the like. For example, the controller <NUM> reads programs corresponding to various functions from the nonvolatile storage device, loads the read programs into the volatile storage device, and causes the CPU to execute processes corresponding to the programs, respectively.

The hydraulic pump <NUM> supplies the working fluid to a hydraulic motor <NUM> via a working fluid line 16a. In the present embodiment, the hydraulic pump <NUM> is a fixed displacement hydraulic pump, and supplies the working fluid to the hydraulic motor <NUM> via a directional control valve <NUM>.

The directional control valve <NUM> is configured to switch a flow of the working fluid discharged from the hydraulic pump <NUM>. In the present embodiment, the directional control valve <NUM> is a solenoid valve having valve positions that are switched according to a control command from the controller <NUM>. The directional control valve <NUM> has a first valve position for enabling communication between the hydraulic pump <NUM> and the hydraulic motor <NUM>, and a second valve position for cutting off the communication between the hydraulic pump <NUM> and the hydraulic motor <NUM>.

When a mode selector switch <NUM> is operated to switch an operation mode of the work machine <NUM> to a lifting magnet mode, the controller <NUM> outputs a control signal with respect to the directional control valve <NUM> to switch the directional control valve <NUM> to the first valve position. When the mode selector switch <NUM> is operated to switch the operation mode of the work machine <NUM> to a mode other than the lifting magnet mode, the controller <NUM> outputs a control signal with respect to the directional control valve <NUM> to switch the directional control valve <NUM> to the second valve position. <FIG> illustrates a state where the directional control valve <NUM> is in the second valve position.

The mode selector switch <NUM> is a switch for switching the operation mode of the work machine <NUM>. In the present embodiment, the mode selector switch <NUM> is a rocker switch provided inside the cab <NUM>. The operator operates the mode selector switch <NUM> to select one of a shovel mode and the lifting magnet mode. The shovel mode is an operation mode in which the work machine <NUM> is operated as an excavator (shovel), and is selected when a bucket is attached to the tip end of the arm <NUM> in place of the lifting magnet <NUM>, for example. The lifting magnet mode is a mode in which the work machine <NUM> is operated as a work machine with the lifting magnet, and is selected when the lifting magnet <NUM> is attached to the tip end of the arm <NUM>. The controller <NUM> may automatically switch the operation mode of the work machine <NUM> based on the outputs of the various sensors.

In a case where the lifting magnet mode is selected, the directional control valve <NUM> is set to the first valve position, to cause the working fluid discharged from the hydraulic pump <NUM> to flow into the hydraulic motor <NUM>. On the other hand, in a case where an operation mode other than the lifting magnet mode is selected, the directional control valve <NUM> is set to the second valve position, to cause the working fluid discharged from the hydraulic pump <NUM> to flow out to a working fluid tank without flowing into the hydraulic motor <NUM>.

A rotation shaft of the hydraulic motor <NUM> is mechanically coupled to a rotation shaft of a generator <NUM>. The generator <NUM> generates electric power for exciting the lifting magnet <NUM>. In the present embodiment, the generator <NUM> is an AC generator that operates according to a control command from a power controller <NUM>.

The power controller <NUM> controls supply and cutoff of the electric power for exciting the lifting magnet <NUM>. In the present embodiment, the power controller <NUM> controls a start and a stop of generation of AC electric power by the generator <NUM> according to a power generation start command and a power generation stop command from the controller <NUM>. In addition, the power controller <NUM> converts the AC electric power generated by the generator <NUM> into DC electric power, and supplies the DC electric power to the lifting magnet <NUM>. Further, the power controller <NUM> can control a magnitude of a voltage applied to the lifting magnet <NUM>, and a magnitude of a current flowing through the lifting magnet <NUM>.

When a lifting magnet switch <NUM> is turned on, the controller <NUM> outputs an attraction command to the power controller <NUM>. The power controller <NUM> that receives the attraction command converts the AC electric power generated by the generator <NUM> into DC electric power, and supplies the DC electric power to the lifting magnet <NUM> so as to excite the lifting magnet <NUM>. The excited lifting magnet <NUM> assumes an attracting state capable of attracting an object (magnetic body).

When the lifting magnet switch <NUM> is turned off, the controller <NUM> outputs a release command to the power controller <NUM>. The power controller <NUM> that receives the release command causes the generator <NUM> to stop generating the power, and causes the lifting magnet <NUM> in the attracting state to assume a non-attracting state (released state). The released state of the lifting magnet <NUM> refers to a state where the supply of electric power to the lifting magnet <NUM> is stopped, and an electromagnetic force generated by the lifting magnet <NUM> is lost.

The lifting magnet switch <NUM> is a switch for switching between the attracting and released states of the lifting magnet <NUM>. In the present embodiment, the lifting magnet switch <NUM> includes a weak excitation button 65A and a strong excitation button 65B that are provided as push button switches at a top of the left operating lever <NUM>, and a release button 65C that is provided as a push button switch at a top of the right operating lever 26R.

The weak excitation button 65A is an example of an input device for applying a predetermined voltage to the lifting magnet <NUM> to put the lifting magnet <NUM> into the attracting state (weak attracting state). The predetermined voltage is a voltage set through a magnetic force adjusting dial <NUM>.

The strong excitation button 65B is an example of an input device for applying a tolerable maximum voltage to the lifting magnet <NUM> to put the lifting magnet <NUM> into the attracting state (strong attracting state).

The release button 65C is an example of an input device for putting the lifting magnet <NUM> into the released state.

The magnetic force adjusting dial <NUM> is a dial for adjusting the magnetic force (attraction force) of the lifting magnet <NUM>. In the present embodiment, the magnetic force adjusting dial <NUM> is provided inside the cab <NUM>, and is configured to be able to switch the magnetic force (attraction force) of the lifting magnet <NUM> in four stages when the weak excitation button 65A is pressed. More particularly, the magnetic force adjusting dial <NUM> is configured to be able to switch the magnetic force (attraction force) of the lifting magnet <NUM> in four stages, from a first level to a fourth level. <FIG> illustrates a state where a third level is selected by the magnetic force adjusting dial <NUM>.

The lifting magnet <NUM> is controlled to generate a magnetic force (attraction force) at the level set by the magnetic force adjusting dial <NUM>. The magnetic force adjusting dial <NUM> outputs data indicating the level of the magnetic force (attraction force) with respect to the controller <NUM>.

According to this configuration, the operator can attract and release the object (magnetic body) by the lifting magnet <NUM> with a finger, while operating the left operating lever <NUM> with the left hand and operating the right operating lever 26R with the right hand to operate the work attachment. Typically, the operator presses the weak excitation button 65A in a state where the lifting magnet <NUM> is caused to make contact with the object (for example, scrap iron or the like) to attract the scrap iron onto the lifting magnet <NUM>. Thereafter, the operator gradually raises the boom <NUM> to lift the lifting magnet <NUM> attracting the scrap iron, and then presses the strong excitation button 65B to increase the magnetic force (attraction force) of the lifting magnet <NUM>. This is to prevent the scrap iron from falling from the lifting magnet <NUM> during transport of the scrap iron by an attachment operation (an operation including at least one of a boom operation, an arm operation, and a bucket operation) or a swing operation.

In addition, the operator can sort the objects by adjusting the magnetic force (attraction force) of the lifting magnet <NUM> using the magnetic force adjusting dial <NUM>. The operator can selectively lift and move relatively light objects from a scrap heap using a relatively weak level of the magnetic force (attractive force) to sort the relatively light objects from relatively heavy objects, for example. This is because the operator can be prevented from lifting the relatively heavy objects by using the relatively weak level of the magnetic force (attraction force).

The work machine <NUM> may be configured to automatically switch the operation mode to a speed limit mode when the weak excitation button 65A or the strong excitation button 65B is pressed. The speed limit mode is an operation mode in which a swinging speed and a driving speed of the attachment are limited in the lifting magnet mode, for example.

Further, in a case where a predetermined operation is performed after the weak excitation button 65A is pressed, or in a case where a predetermined state is reached, the work machine <NUM> may automatically switch the state of the lifting magnet <NUM> to the strong attracting state which is the state that occurs when the strong excitation button 65B is pressed. The predetermined operation is a swing operation, for example. The predetermined state is a state where the attachment assumes a predetermined attitude, specifically, a state where the boom angle assumes a predetermined angle, for example. In this case, the work machine <NUM> can automatically switch the state of the lifting magnet <NUM> to the strong attracting state, even if the strong excitation button 65B is not pressed, when the swing operation is performed after the lifting magnet <NUM>, that is in the weak attracting state by the pressing of the weak excitation button 65A, is lifted according to the boom raising operation, for example.

The display device <NUM> is a device that displays various information. In the present embodiment, the display device <NUM> is fixed on a pillar (not illustrated) at a right front portion of the cab <NUM> where a driver's seat is provided. In addition, as illustrated in <FIG>, the display device <NUM> can display information related to the work machine <NUM> on an image display part <NUM> to provide the information to the operator. Moreover, the display device <NUM> includes a switch panel <NUM> as an input device. The operator can input various commands with respect to the controller <NUM>, by utilizing the switch panel <NUM>.

The switch panel <NUM> is a panel including various switches. In the present embodiment, the switch panel <NUM> includes a light switch 42a, a wiper switch 42b, and a window washer switch 42c, as hardware buttons. The light switch 42a is a switch for switching light, attached to the outside of cab <NUM>, on and off. The wiper switch 42b is a switch for switching a windshield piper between operating and stopped states. The window washer switch 42c is a switch for spraying a window washer fluid.

The display device <NUM> operates by receiving power supply from a storage battery <NUM>. The storage battery <NUM> is charged by electric power generated by the alternator 11a. The electric power of the storage battery <NUM> is also supplied to an electrical component <NUM> or the like other than the controller <NUM> and the display device <NUM>. A starter 11b of the engine <NUM> is driven by the electric power from the storage battery <NUM>, and starts the engine <NUM>.

The engine controller <NUM> controls the engine <NUM>. In the present embodiment, the engine controller <NUM> collects various data indicating the state of the engine <NUM>, and transmits the collected data to the controller <NUM>. Although the engine controller <NUM> and the controller <NUM> are configured as separate components, the engine controller <NUM> and the controller <NUM> may be configured integrally. For example, the engine controller <NUM> may be integrated into the controller <NUM>.

An engine speed adjusting dial <NUM> is a dial for adjusting an engine speed. In the present embodiment, the engine speed adjusting dial <NUM> is provided inside the cab <NUM>, and is configured to be able to switch the engine speed in four stages. More particularly, the engine speed adjusting dial <NUM> is configured to be able to switch the engine speed in four stages, including an SP mode, an H mode, an A mode, and an idle mode. <FIG> illustrates a state where the H mode is selected by the engine speed adjusting dial <NUM>.

The SP mode is a rotation speed mode that is selected in a case where priority is to be given to an amount of work performed, and utilizes a highest engine speed. The H mode is a rotation speed mode that is selected in a case where emphasis is to be given to both the amount of work performed and a fuel consumption, and utilizes a second highest engine speed. The A mode is a rotation speed mode that is selected in a case where the work machine is to be operated with low noise while giving priority to the fuel consumption, and utilizes a third highest engine speed. The idle mode is a rotation speed mode that is selected in a case where the engine is to be operated in an idle state, and utilizes a lowest engine speed (idling speed).

The engine <NUM> is controlled so that the engine speed corresponding to the rotation speed mode set by the engine speed adjusting dial <NUM> is maintained. The engine speed adjusting dial <NUM> outputs data indicating a set state of the engine speed to the controller <NUM>.

In addition, the controller <NUM> includes a target weight setting part <NUM>, a weight calculating part <NUM>, an attraction force control part <NUM>, a maximum payload setting part <NUM>, an accumulated weight calculating part <NUM>, a remaining weight calculating part <NUM>, and a vibration control part <NUM>.

The target weight setting part <NUM> acquires a target weight of the object to be attracted by the lifting magnet <NUM>. The target weight may be input by the operator, may be set based on a remaining weight calculated by the remaining weight calculating part <NUM> which will be described later, or may be preset.

The weight calculating part <NUM> calculates the weight (current weight) of the object attracted to the lifting magnet <NUM>. The current weight is calculated from a balance of a torque around a bottom of the boom <NUM>, for example. More particularly, a thrust of the boom cylinder <NUM> increases due to the object attracted to the lifting magnet <NUM>, and the torque around the bottom of the boom <NUM>, that is calculated from the thrust of the boom cylinder <NUM>, also increases. An increment of the torque coincides with the torque calculated from a weight of the object and a center of gravity of the object. Hence, the weight calculating part <NUM> can calculate the weight of the object, based on the thrust of the boom cylinder <NUM> (measured values of the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b) and the center of gravity of the object. The center of gravity of the object can be experimentally obtained in advance and stored in the controller <NUM>, for example. A method of calculating the weight of the object is not limited to the method described above, and various other methods can be used to calculate the weight of the object.

The attraction force control part <NUM> controls the attraction force of the lifting magnet <NUM>, by controlling a current command value of the current supplied to the lifting magnet <NUM>.

The maximum payload setting part <NUM> sets a maximum payload of the dump truck on which the object is loaded. The maximum payload may be input by the operator, for example. Alternatively, a vehicle type (size or the like) of the dump truck may be determined based on a dump truck image captured by the space recognition device <NUM>, and the maximum payload may be set based on the determined vehicle type (size or the like), for example.

The accumulated weight calculating part <NUM> calculates an accumulated weight of the object loaded on a load-carrying platform of the dump truck.

The remaining weight calculating part <NUM> calculates the remaining weight which is a difference between the maximum payload and the accumulated weight.

The vibration control part <NUM> generates and outputs a command for controlling vibration of the attachment.

Hereinafter, an example of the operation of the work machine <NUM> according to the present embodiment will be described.

First, the target weight setting part <NUM> of the controller <NUM> sets the target weight of the object to be attracted by the lifting magnet <NUM>. The maximum payload setting part <NUM> sets the maximum payload of the dump truck on which the object is loaded.

Next, the operator operates the operation device <NUM> to move the lifting magnet <NUM> to a position above the object to be attracted.

Next, the operator operates the weak excitation button 65A, and causes the lifting magnet <NUM> to generate a magnetic force (attraction force). Thus, the object is attracted to the lifting magnet <NUM>. In this state, the attraction force control part <NUM> of the controller <NUM> issues a first current command value, as the current command value. The first current command value is set to a sufficient current value so that the weight of the object attracted to the lifting magnet <NUM> can be greater than or equal to the target weight. The power controller <NUM> controls the current supplied to the lifting magnet <NUM>, based on the current command value.

Next, the operator operates the operation device <NUM> to raise the lifting magnet <NUM> to a predetermined height. Hence, the object attracted to the lifting magnet <NUM> is lifted together with the lifting magnet <NUM>. This operation performed by the operator also serves as a trigger for the controller <NUM> to start a compensation control which will be described later. Whether or not the lifting magnet <NUM> rose to the predetermined height may be determined based on the attitude of the attachment, a position of each connecting pint of the attachment, an elapsed time from a time when the raising of the lifting magnet <NUM> is started, or may be determined based on the posture of the attachment, the position of each connecting pin of the attachment, the elapsed time from the start of raising the lifting magnet <NUM>, an operation state of an attraction switch, or the like.

Next, the weight calculating part <NUM> of the controller <NUM> calculates the weight (current weight) of the object attracted to (lifted by) the lifting magnet <NUM>.

Next, in a case where the current weight is heavier than the target weight, the attraction force control part <NUM> of the controller <NUM> performs the compensation control of the current supplied to the lifting magnet <NUM>. For example, the attraction force control part <NUM> performs an adjustment so as to decrease the current command value. In this case, the magnetic force (attraction force) of the lifting magnet <NUM> decreases, and a portion of the object attracted to the lifting magnet <NUM> falls. That is, the weight of the object attracted to the lifting magnet <NUM> decreases.

Hereinafter, during the compensation control, the controller <NUM> repeats the calculation of the weight (current weight) of the object attracted to the lifting magnet <NUM> and the adjustment (decreasing) of the current command value, until the current weight reaches the target weight. The current command value at a time when the current weight reaches the target weight will be referred to as a second current command value.

Next, the attraction force control part <NUM> of the controller <NUM> sets the current command value to a third current command value. The third current command value is a current command value larger than the second current command value. Thus, the object having the target weight is prevented from falling off from the lifting magnet <NUM>.

Next, the controller <NUM> notifies the operator when the current weight reaches the target weight. A method of notification may display the notification on the display device <NUM>, or output the notification by speech, for example.

Next, the notified operator operates the strong excitation button 65B to put the lifting magnet <NUM> into the attracting state (strong attracting state). Next, the operator operates the operation device <NUM> to move the slewing upper structure <NUM> and the work attachment (the boom <NUM> and the arm <NUM>), and move the lifting magnet <NUM> above the load-carrying platform of the dump truck. Next, the operator operates the release button 65C, and the release button 65C puts the lifting magnet <NUM> into the released state. Thus, the object having the target weight is loaded onto the load-carrying platform of the dump truck.

The accumulated weight calculating part <NUM> adds the current target weight to the accumulated weight accumulated up to a previous target weight, to update the accumulated weight. The remaining weight calculating part <NUM> calculates the remaining weight, based on the updated accumulated weight.

By repeating the operations described above, the object having a desired accumulated weight can be loaded onto the load-carrying platform of the dump truck.

After raising the lifting magnet <NUM> to the predetermined height, the controller <NUM> may prohibit the swing of the slewing upper structure <NUM> or limit the swing of the slewing upper structure <NUM> to within a predetermined angular range, until the current weight reaches the target weight (while the calculation of the current weight and the current adjustment are repeated). In this case, it is possible to prevent scattering of the falling object to the surrounding when the current weight is adjusted to become the target weight.

Although the object is loaded onto the dump truck in the example described above, the present invention is not limited to such, and the present invention may similarly be applied to a case where the object having a desired target weight is unloaded from the dump truck.

Next, the vibration of the attachment will be described with reference to <FIG> is a schematic diagram illustrating a state where the work machine <NUM> according to the present embodiment suspends a lifting load.

When lifting the lifting load by the lifting magnet <NUM>, the attachment lowers the boom <NUM>, opens the arm <NUM>, and lifts the lifting object at an attitude in which the lifting magnet <NUM> is closed. In addition, the attachment is supported by the slewing upper structure <NUM> on the foot pin side of the boom <NUM>. Moreover, a heavy lifting magnet <NUM> is provided on the tip end of the attachment. Due to this heavy lifting magnet <NUM>, vibration is generated in the boom <NUM> when raising the boom.

Further, due to the vibration of the boom <NUM>, vibration is also generated in the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b). For this reason, when the weight calculating part <NUM> detects the weight of the lifting load based on the pressure of the boom cylinder <NUM>, the weight calculating part <NUM> may not be able to suitably calculate the weight of the lifting load.

Next, an operation for reducing the vibration of the boom <NUM> in the work machine <NUM> according to a first exemplary implementation, will be described with reference to <FIG> and <FIG>. In the work machine <NUM> according to the first exemplary implementation, the controller <NUM> controls a working pressure of the boom cylinder <NUM> to reduce the vibration of the boom <NUM>.

<FIG> is a diagram illustrating a hydraulic circuit of the boom cylinder <NUM> in the work machine <NUM> according to the first exemplary implementation.

In this exemplary implementation, it is assumed that the boom <NUM>, that is, the boom cylinder <NUM>, is operated by a boom operating lever 26A. Further, a pilot line for transferring a secondary-side pilot pressure, from the boom operating lever 26A to a port of a boom controlling valve <NUM> that supplies the working fluid to the boom cylinder <NUM> inside the control valve <NUM>, is referred to as a pilot line 27A.

As illustrated in <FIG>, in this exemplary implementation, bypass fluid passages <NUM> and <NUM> which branch from between the boom controlling valve <NUM> in the control valve <NUM> and the rod-side fluid chamber, and between the boom controlling valve <NUM> and the bottom-side fluid chamber of the boom cylinder <NUM>, respectively, and discharge the working fluid to a tank T, are provided.

The bypass fluid passage <NUM> is provided with a solenoid relief valve <NUM> that discharges the working fluid in the rod-side fluid chamber of the boom cylinder <NUM> to the tank T.

The bypass fluid passage <NUM> is provided with a solenoid relief valve <NUM> that discharges the working fluid in the bottom-side fluid chamber of the boom cylinder <NUM> to the tank T.

The bypass fluid passages <NUM> and <NUM> and the solenoid relief valves <NUM> and <NUM> may be provided either inside or outside the control valve <NUM>.

A rod pressure PR of the boom cylinder <NUM>, detected by the boom rod pressure sensor S6a, is input to the controller <NUM>. A bottom pressure PB of the boom cylinder <NUM>, detected by the boom bottom pressure sensor S6b, is input to the controller <NUM>.

The controller <NUM> can monitor the rod pressure PR and the bottom pressure PB, based on the output signals of the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b input to the controller <NUM>. In addition, the controller <NUM> can appropriately output current command values to the solenoid relief valves <NUM> and <NUM>, to forcibly discharge the working fluid in the rod-side fluid chamber or the bottom-side fluid chamber of the boom cylinder <NUM> to the tank T, thereby reducing an excessive pressure inside the boom cylinder <NUM>.

The vibration control part <NUM> of the controller <NUM> detects the generation of the vibration, based on changes in the rod pressure PR and the bottom pressure PB of the boom cylinder <NUM> detected by the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b. Thereafter, the solenoid relief valves <NUM> and <NUM> are controlled, that is, the hydraulic pressure of the boom cylinder <NUM> is controlled, using the detected values of the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b. More particularly, the vibration control part <NUM> of the controller <NUM> controls the solenoid relief valves <NUM> and <NUM>, so as to reduce a sudden pressure change in the boom cylinder <NUM>. Hence, the vibration of the boom <NUM> (refer to <FIG>) can be reduced. In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b). The generation of the vibration may be detected, using an acceleration sensor (such as a body inclination sensor S4 or the like).

The controller <NUM> may control the solenoid relief valves <NUM> and <NUM>, based on the angular velocity of the boom <NUM> detected by the boom angle sensor S1. Thus, the vibration of the boom <NUM> can be reduced.

In addition, by reducing the vibration of the boom <NUM>, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b). The angular velocity of the boom <NUM> may also be detected by the boom cylinder stroke sensor S7.

<FIG> is a diagram for explaining a hydraulic circuit of another boom cylinder <NUM> in the work machine <NUM> according to the first exemplary implementation. Hereinafter, although two boom cylinders <NUM> are illustrated in <FIG>, the hydraulic circuit for one boom cylinder <NUM> (the boom cylinder <NUM> on the right side in <FIG>) will mainly be described, because the control valve <NUM> and a pressure holding circuit <NUM> which will be described later, are interposed between the main pump <NUM> and the boom cylinder <NUM> in a similar manner for each of the two boom cylinders <NUM>.

The solenoid relief valve <NUM> for discharging the working fluid in the rod-side fluid chamber of the boom cylinder <NUM> to the tank T is provided in a fluid passage that branches from between the control valve <NUM> and the rod-side fluid chamber.

As illustrated in <FIG>, the work machine <NUM> according to the present exemplary implementation is provided with a pressure holding circuit <NUM> that holds the working fluid in the bottom-side fluid chamber of the boom cylinder <NUM> so as not to be discharged therefrom, even in a case where the hydraulic hose breaks due to a rupture or the like, for example.

The pressure holding circuit <NUM> is interposed in a fluid passage connecting the control valve <NUM> and the bottom-side fluid chamber of the boom cylinder <NUM>. The pressure holding circuit <NUM> mainly includes a holding valve <NUM> and a spool valve <NUM>.

The holding valve <NUM> supplies the working fluid supplied from the control valve <NUM> to the bottom-side fluid chamber of the boom cylinder <NUM> via a fluid passage <NUM>, regardless of a state of the spool valve <NUM>.

Moreover, in a case where the spool valve <NUM> is in a non-communicating state (spool state at the left end in <FIG>), the holding valve <NUM> holds the working fluid in the bottom-side fluid chamber of the boom cylinder <NUM>, so that the working fluid is not discharged to a downstream side of the pressure holding circuit <NUM>. On the other hand, in a case where the spool valve <NUM> is in a communicating state (spool state at the right end in <FIG>), the holding valve <NUM> can discharge the working fluid in the bottom-side fluid chamber of the boom cylinder <NUM> to the downstream side of the pressure holding circuit <NUM> via a fluid passage <NUM>.

The communicating and non-communicating states of the spool valve <NUM> are controlled according to the pilot pressure input to a port from a boom lowering remote control valve 26Aa, included in the operation device <NUM> for operating the boom cylinder <NUM>, and outputting the pilot pressure corresponding to the lowering operation of the boom <NUM> (boom lowering operation). More particularly, in a case where the pilot pressure indicating that the boom lowering operation is being performed is input from the boom lowering remote control valve 26Aa, the spool valve <NUM> is controlled to the spool state corresponding to the communicating state (the spool state at the right end in <FIG>). On the other hand, in a case where the pilot pressure indicating that the boom lowering operation is not being performed is input from the boom lowering remote control valve 26Aa, the spool valve <NUM> is controlled to the spool state corresponding to the non-communicating state (the spool state at the left end in <FIG>). Thus, even if the break or the like is generated in the hydraulic hose on the downstream side of the pressure holding circuit <NUM> in a state where the boom lowering operation is not being performed, the working fluid (bottom pressure) in the bottom-side fluid chamber of the boom cylinder <NUM> is held, thereby making it possible to prevent the boom <NUM> from falling.

The pressure holding circuit <NUM> also includes a solenoid relief valve <NUM>.

The solenoid relief valve <NUM> is provided in a fluid passage <NUM>, that branches from a fluid passage <NUM> between the holding valve <NUM> in the pressure holding circuit <NUM> and the bottom-side fluid chamber of the boom cylinder <NUM>, and is connected to the tank T. In other words, the solenoid relief valve <NUM> discharges the working fluid to the tank T from the fluid passage <NUM> on the upstream side of the holding valve, that is, on the side close to the boom cylinder <NUM>. Accordingly, the solenoid relief valve <NUM> can discharge the working fluid in the bottom-side fluid chamber of the boom cylinder <NUM> to the tank T, regardless of the operation state of the pressure holding circuit <NUM>, specifically, regardless of whether the spool valve <NUM> is in the communicating state or the non-communicating state. That is, the working fluid in the bottom-side fluid chamber of the boom cylinder <NUM> can be discharged to the tank T regardless of the presence or absence of the boom lowering operation, while preventing the boom <NUM> from falling by the function of the pressure holding circuit <NUM> to hold the working fluid in the bottom-side fluid chamber of the boom cylinder <NUM>, thereby making it possible to reduce an excessive bottom pressure.

The controller <NUM> can monitor the rod pressure PR and the bottom pressure PB, based on the output signals of the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b input to the controller <NUM>. In addition, the controller <NUM> can forcibly discharge the working fluid in the rod-side fluid chamber or the bottom-side fluid chamber of the boom cylinder <NUM> to the tank T, regardless of the presence or absence of the boom lowering operation, by outputting the current command values to the solenoid relief valve <NUM> and <NUM> as appropriate, thereby making it possible to reduce the excessive pressure in the boom cylinder <NUM>.

The vibration control part <NUM> of the controller <NUM> controls the solenoid relief valves <NUM> and <NUM>, based on the rod pressure PR and the bottom pressure PB of the boom cylinder <NUM> detected by the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b, respectively. In other words, the vibration control part <NUM> controls the hydraulic pressure of the boom cylinder <NUM>. More particularly, the vibration control part <NUM> of the controller <NUM> controls the solenoid relief valves <NUM> and <NUM>, so as to reduce a sudden pressure change in the boom cylinder <NUM>. Hence, it is possible to reduce the vibration of the boom <NUM> (refer to <FIG>). In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b).

Moreover, the vibration control part <NUM> of the controller <NUM> may determine the generation of the vibration of the attachment (boom <NUM>). The vibration control part <NUM> may determine that the vibration is generated in the attachment (boom <NUM>) when a ripple in the pressure value of the boom cylinder <NUM> is detected within a predetermined time period, for example. Furthermore, the vibration control part <NUM> may determine that the vibration is generated in the attachment (boom <NUM>) when the pressure value of the boom cylinder <NUM> rapidly increases or decreases within a predetermined time period and an amount of increase or decrease in the pressure value exceeds a predetermined value, for example. The vibration control part <NUM> of the controller <NUM> may determine the generation of the vibration in the manner described above.

The controller <NUM> may control the solenoid relief valves <NUM> and <NUM>, based on the angular velocity of the boom <NUM> detected by the boom angle sensor S1. Thus, it is possible to reduce the vibration of the boom <NUM>. In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b). The angular velocity of the boom <NUM> may also be detected by the boom cylinder stroke sensor S7.

The controller <NUM> may control only the solenoid relief valve <NUM> on the bottom side, or may control both the solenoid relief valve <NUM> on the bottom side and the solenoid relief valve <NUM> on the rod side.

Next, an operation for reducing the vibration of the boom <NUM> in the work machine <NUM> according to a second exemplary implementation, will be described with reference to <FIG>. In the work machine <NUM> according to the second exemplary implementation, the controller <NUM> controls the control valve <NUM> (controlling valve <NUM>) to reduce the vibration of the boom <NUM>.

<FIG> is a diagram for explaining the hydraulic circuit of the boom cylinder <NUM> in the work machine <NUM> according to the second exemplary implementation. In this exemplary implementation, the operating lever of the work machine is a hydraulic operating lever, and the controller <NUM> reduces the vibration of the boom <NUM> by controlling the pilot pressure to the control valve <NUM> (controlling valve <NUM>). In <FIG>, a mechanical power transmission line, the working fluid line, the pilot line, and an electric control line are indicated by a double line, a solid line, a broken line, and a dotted line, respectively.

The hydraulic system circulates the working fluid from a left main pump <NUM> driven by the engine <NUM> to the working fluid tank via a left center bypass pipeline <NUM> or a left parallel pipeline <NUM>, and circulates the working fluid from a right main pump 14R driven by the engine <NUM> to the working fluid tank via a right center bypass pipeline 40R or a right parallel pipeline 42R. The left main pump <NUM> and the right main pump 14R correspond to the main pump <NUM> of <FIG>.

The left center bypass pipeline <NUM> is a working fluid line passing through controlling valves <NUM>, <NUM>, <NUM>, and <NUM> disposed in the control valve <NUM>. The right center bypass pipeline 40R is a working fluid line passing through controlling valves <NUM>, <NUM>, 175R, and 176R disposed in the control valve <NUM>. The controlling valves <NUM> and 175R correspond to the controlling valve <NUM> of <FIG>. The controlling valves <NUM> and 176R correspond to the controlling valve <NUM> of <FIG>.

The controlling valve <NUM> is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the left main pump <NUM> to the left drive hydraulic motor <NUM>, and discharge the working fluid discharged from the left drive hydraulic motor <NUM> to the working fluid tank.

The controlling valve <NUM> is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the right main pump 14R to the right drive hydraulic motor 1R, and discharge the working fluid discharged from the right drive hydraulic motor 1R to the working fluid tank.

The controlling valve <NUM> is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the left main pump <NUM> to the swing hydraulic motor 2A, and discharge the working fluid discharged from the swing hydraulic motor 2A to the working fluid tank.

The controlling valve <NUM> is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the right main pump 14R to the lifting magnet cylinder <NUM>, and discharge the working fluid in the lifting magnet cylinder <NUM> to the working fluid tank.

The controlling valve <NUM> is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the left main pump <NUM> to the boom cylinder <NUM>.

The controlling valve 175R is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the right main pump 14R to the boom cylinder <NUM>, and discharge the working fluid in the boom cylinder <NUM> to the working fluid tank.

The controlling valve <NUM> is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the left main pump <NUM> to the arm cylinder <NUM>, and discharge the working fluid in the arm cylinder <NUM> to the working fluid tank.

The controlling valve 176R is a spool valve that switches the flow of the working fluid, in order to supply the working fluid discharged from the right main pump 14R to the arm cylinder <NUM>, and discharge the working fluid in the arm cylinder <NUM> to the working fluid tank.

The left parallel pipeline <NUM> is a working fluid line parallel to the left center bypass pipeline <NUM>. In a case where the flow of the working fluid passing through the left center bypass pipeline <NUM> is restricted or cut off by one of the controlling valves <NUM>, <NUM>, and <NUM>, the left parallel pipeline <NUM> can supply the working fluid to a control valve that is located further downstream. The right parallel pipeline 42R is a working fluid line parallel to the right center bypass pipeline 40R. In a case where the flow of the working fluid passing through the right center bypass pipeline 40R is restricted or cut off by one of the controlling valves <NUM>, <NUM>, and 175R, the right parallel pipeline 42R can supply the working fluid to a control value that is located further downstream.

A left regulator <NUM> is configured to be able to control the discharge amount of the left main pump <NUM>. In the present embodiment, the left regulator <NUM> controls the discharge amount of the left main pump <NUM> by adjusting the swash plate tilt angle of the left main pump <NUM> according to the discharge pressure of the left main pump <NUM>, for example. A right regulator 13R is configured to be able to control the discharge amount of the right main pump 14R. In the present embodiment, the right regulator 13R controls the discharge amount of the right main pump 14R by adjusting the swash plate tilt angle of the right main pump 14R according to the discharge pressure of the right main pump 14R, for example. The left regulator <NUM> and the right regulator 13R correspond to the regulator <NUM> of <FIG>. The left regulator <NUM> reduces the discharge amount by adjusting the swash plate tilt angle of the left main pump <NUM> according to an increase in the discharge pressure of the left main pump <NUM>, for example. The same applies to the right regulator 13R. This is to prevent an absorption horsepower of the main pump <NUM> represented by a product of the discharge pressure and the discharge amount from exceeding an output horsepower of the engine <NUM>.

A left discharge pressure sensor <NUM> is an example of the discharge pressure sensor <NUM>, and detects the discharge pressure of the left main pump <NUM>, and outputs the detected value of the discharge pressure to the controller <NUM>. The same applies to the right discharge pressure sensor 28R.

A negative control employed in the hydraulic system of <FIG> will now be described.

In the left center bypass pipeline <NUM>, a left throttle <NUM> is disposed between the controlling valve <NUM> located on a most downstream side and the working fluid tank. The flow of the working fluid discharged from the left main pump <NUM> is restricted by the left throttle <NUM>. The left throttle <NUM> generates a control pressure for controlling the left regulator <NUM>. A left control pressure sensor <NUM> is a sensor for detecting the control pressure, and outputs the detected value to the controller <NUM>. In the right center bypass pipeline 40R, a right throttle 18R is disposed between the controlling valve 176R located on a most downstream side and the working fluid tank. The flow of the working fluid discharged from the right main pump 14R is restricted by the right throttle 18R. The right throttle 18R generates a control pressure for controlling the right regulator 13R. A right control pressure sensor 19R is a sensor for detecting the control pressure, and outputs the detected value to the controller <NUM>.

The controller <NUM> controls the discharge amount of the left main pump <NUM>, by adjusting the swash plate tilt angle of the left main pump <NUM> according to the control pressure. The controller <NUM> decreases the discharge amount of the left main pump <NUM> as the control pressure becomes higher, and increases the discharge amount of the left main pump <NUM> as the control pressure becomes lower. The discharge amount of the right main pump 14R is controlled in a similar manner.

More particularly, as illustrated in <FIG>, in a standby state where none of the hydraulic actuators in the work machine <NUM> is operated, the working fluid discharged from the left main pump <NUM> passes through the left center bypass pipeline <NUM> and reaches the left throttle <NUM>. The flow of the working fluid discharged from the left main pump <NUM> increases the control pressure generated on the upstream side of the left throttle <NUM>. As a result, the controller <NUM> reduces the discharge amount of the left main pump <NUM> to a tolerable minimum discharge amount, and reduces a pressure loess (pumping loss) as the discharged working fluid passes through the left center bypass pipeline <NUM>. On the other hand, in a case where one of the hydraulic actuators is operated, the working fluid discharged from the left main pump <NUM> flows into the hydraulic actuator that is an operation target via the control valve corresponding to the hydraulic actuator that is the operation target. Then, the flow of the working fluid discharged from the left main pump <NUM> reduces or eliminates the amount of the working fluid reaching the left throttle <NUM>, thereby reducing the control pressure generated on the upstream side of the left throttle <NUM>. As a result, the controller <NUM> increases the discharge amount of the left main pump <NUM>, to circulate a sufficient amount of the working fluid to the hydraulic actuator that is the operation target, thereby positively driving the hydraulic actuator that is the operation target. The same applies to the working fluid discharged from the right main pump 14R.

According to the configuration described above, the hydraulic system of <FIG> can reduce wasteful energy consumption in the standby state at each of the left main pump <NUM> and the right main pump 14R. The wasteful energy consumption includes the pumping loss generated in the left center bypass pipeline <NUM> by the working fluid discharged from the left main pump <NUM>, and the pumping loss generated in the right center bypass pipeline 40R by the working fluid discharged from the right main pump 14R. In addition, in the case where the hydraulic actuator is operated, the hydraulic system of <FIG> can supply a necessary and sufficient amount of the working fluid from each of the left main pump <NUM> and the right main pump 14R to the hydraulic actuator that is the operation target.

A pilot pressure circuit, connecting the remote control valve 26Aa to the controlling valve <NUM> (<NUM> and 175R), is provided with pressure reducing valves <NUM> and <NUM>.

The work machine <NUM> causes the lifting magnet <NUM> to attract the lifting load (transporting object) by applying a current to the lifting magnet <NUM> based on the operation command, and thereafter performs a boom raising operation. Then, a swing operation and an arm opening operation are performed in order to transport the lifting load to a release position. However, if the vibration of the attachment (boom <NUM>) generated during the attraction or the boom raising operation is large, the vibration continues even during the swing operation, and the weight of the lifting load cannot be measured accurately. For this reason, the vibration control part <NUM> of the controller <NUM> controls the pressure reducing valves <NUM> and <NUM>, based on the rod pressure PR and the bottom pressure PB of the boom cylinder <NUM> detected by the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b. That is, the pilot pressure of the control valve <NUM> (controlling valve <NUM>) is controlled. More particularly, the vibration control part <NUM> of the controller <NUM> controls the pressure reducing valves <NUM> and <NUM>, so as to reduce a sudden pressure change in the boom cylinder <NUM>. Hence, it is possible to reduce the vibration of the boom <NUM> (refer to <FIG>) within a time period from the attraction (gripping by a grapple) to the release. Further, the weight calculating part <NUM> calculates the weight that is calculated in a case where the vibration of the boom <NUM> is less than or equal to the predetermined threshold value, as the weight of the current lifting load. Accordingly, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b).

The controller <NUM> may control the pressure reducing valves <NUM> and <NUM>, based on the angular velocity of the boom <NUM> detected by the boom angle sensor S1. In this case, it is possible to reduce the vibration of the boom <NUM>. In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b). The angular velocity of the boom <NUM> may also be detected by the boom cylinder stroke sensor S7.

<FIG> is a diagram illustrating a configuration example of an electric operation system in the work machine <NUM> according to the second exemplary implementation. In this example, the operating lever of the work machine is a solenoid operating lever, and the controller <NUM> reduces the vibration of the boom <NUM>, by controlling the pilot pressure to the control valve <NUM> (controlling valve <NUM>).

In a case where the electric operation system provided with the electric operating lever is employed, the controller <NUM> can easily execute an autonomous control function, compared to a case where a hydraulic operation system including a hydraulic operating lever is employed. More particularly, the electric operating system illustrated in <FIG> is an example of a boom operating system, and is configured to mainly include a pilot pressure-operated control valve <NUM>, the boom operating lever 26A as the electric operating lever, the controller <NUM>, a solenoid valve <NUM> for boom raising operation, and a solenoid valve <NUM> for boom lowering operation. The electric operating system of <FIG> can also be similarly applied to an arm operating system, a bucket operating system, or the like.

The pilot pressure-operated control valve <NUM> includes the controlling valve <NUM> (refer to <FIG>) related to the boom cylinder <NUM>, the controlling valve <NUM> (refer to <FIG>) related to the arm cylinder <NUM>, the controlling valve <NUM> (refer to <FIG>) related to the lifting magnet cylinder <NUM>, or the like. The solenoid valve <NUM> is configured to be able to adjust a flow path area of a pipeline connecting the pilot pump <NUM> and a raising side pilot port of the controlling valve <NUM>. The solenoid valve <NUM> is configured to be able to adjust a flow path area of a pipeline connecting the pilot pump <NUM> and a lowering side pilot port of the controlling valve <NUM>.

In a case where a manual operation is performed, the controller <NUM> generates a boom raising operation signal (electric signal) or a boom lowering operation signal (electric signal) according to an operation signal (electric signal) output from an operation signal generating part of the boom operating lever 26A. The operation signal output by the operation signal generating part of the boom operating lever 26A is an electric signal that varies according to an operation amount and an operation direction of the boom operating lever 26A.

More particularly, in a case where the boom operating lever 26A is operated in the boom raising direction, the controller <NUM> outputs a boom raising operation signal (electric signal) corresponding to a lever operation amount to the solenoid valve <NUM>. The solenoid valve <NUM> adjusts the flow path area according to the boom raising operation signal (electric signal), and controls the pilot pressure acting on the raising side pilot port of the controlling valve <NUM>, as the boom raising operation signal (pressure signal). Similarly, in a case where the boom operating lever 26A is operated in the boom lowering direction, the controller <NUM> outputs a boom lowering operation signal (electric signal) corresponding to the lever operation amount to the solenoid valve <NUM>. The solenoid valve <NUM> adjusts the flow path area according to the boom lowering operation signal (electric signal), and controls the pilot pressure acting on the lowering side pilot port of the controlling valve <NUM>, as the boom lowering operation signal (pressure signal).

In a case where an autonomous control is executed, the controller <NUM> generates the boom raising operation signal (electric signal) or the boom lowering operation signal (electric signal) according to a correction operation signal (electric signal), in place of the operation signal (electric signal) output by the operation signal generating part of the boom operating lever 26A, for example. The correction operation signal may be an electric signal generated by the controller <NUM>, or may be an electric signal generated by an external controller or the like other than the controller <NUM>.

The vibration control part <NUM> of the controller <NUM> controls the solenoid valves <NUM> and <NUM>, based on the rod pressure PR and the bottom pressure PB of the boom cylinder <NUM> detected by the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b. That is, the pilot pressure of the control valve <NUM> (controlling valve <NUM>) is controlled. More particularly, the vibration control part <NUM> of the controller <NUM> controls the solenoid valves <NUM> and <NUM>, so as to reduce a sudden pressure change of the boom cylinder <NUM>. Thus, it is possible to reduce the vibration of the boom <NUM> (refer to <FIG>). In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b).

The controller <NUM> may control the solenoid valves <NUM> and <NUM>, based on the angular velocity of the boom <NUM> detected by the boom angle sensor S1. In this case, it is possible to reduce the vibration of the boom <NUM>. In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b). The angular velocity of the boom <NUM> may also be detected by the boom cylinder stroke sensor S7.

<FIG> is a diagram illustrating a configuration example of another electric operation system in the work machine <NUM> according to the second exemplary implementation. In this example, the operating lever of the work machine is a solenoid operating lever, the control valve <NUM> (controlling valve <NUM>) is a solenoid valve, and the controller <NUM> reduces the vibration of the boom <NUM> by controlling an electric signal to the control valve <NUM> (controlling valve <NUM>).

The control valve <NUM> is a solenoid valve, and is controlled by an operation signal (electric signal) from the controller <NUM>.

In this case, the vibration control part <NUM> of the controller <NUM> directly controls the control valve <NUM>, based on the rod pressure PR and the bottom pressure PB of the boom cylinder <NUM> detected by the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b. More particularly, the vibration control part <NUM> of the controller <NUM> controls the control valve <NUM>, so as to reduce a sudden pressure change in the boom cylinder <NUM>. Thus, it is possible to reduce the vibration of the boom <NUM> (refer to <FIG>). In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b).

The controller <NUM> may directly control the control valve <NUM>, based on the angular velocity of the boom <NUM> detected by the boom angle sensor S1. In this case, it is possible to reduce the vibration of the boom <NUM>. In addition, the weight calculating part <NUM> can suitably calculate the weight of the lifting load, based on the pressure of the boom cylinder <NUM> (detected values of the sensors S6a and S6b). The angular velocity of the boom <NUM> may also be detected by the boom cylinder stroke sensor S7.

Next, an operation of reducing the vibration of the boom <NUM> in the work machine <NUM> according to a third exemplary implementation will be described, with reference to <FIG>.

<FIG> is a diagram for explaining switching of a supply voltage (attraction force, magnetic force) of the lifting magnet <NUM> in the work machine <NUM> according to the third exemplary implementation. In <FIG>, the abscissa represents an elapsed time, and the ordinate represents a voltage supplied to the lifting magnet <NUM>. Further, the supply voltage according to a reference example is indicated by a broken line, and the supply voltage in the present exemplary implementation is indicated by a solid line.

As illustrated in <FIG>, the supply voltage in the reference example rises stepwise. For this reason, the boom <NUM> may vibrate when the transporting object, such as scrap iron or the like, attracted by the magnetic force, collides with the lifting magnet <NUM>.

In contrast, the supply voltage in the present exemplary implementation rises smoothly. For this reason, it is possible to reduce the vibration of the boom <NUM> that occurs when the transporting object, such as scrap iron or the like, attracted by the magnetic force, collides with the lifting magnet <NUM>.

The controller <NUM> may detect a change in the boom cylinder pressure and a change in the angular velocity (each acceleration) of the boom <NUM>, to control the supply voltage to the lifting magnet <NUM>.

The vibration reduction of the boom <NUM> by controlling the supply voltage to the lifting magnet <NUM> according to the third exemplary implementation may be applied to the work machine <NUM> according to the first and second exemplary implementations.

The embodiment described above reduces the vibration of the attachment (boom <NUM>) by discharging the working fluid of the boom cylinder <NUM> to the working fluid tank T, as illustrated in <FIG>, <FIG>, or the like, but the present invention is not necessarily limited to this embodiment.

For example, the vibration of the attachment (boom <NUM>) generated during the boom operation may be reduced, by supplying the working fluid of the boom cylinder <NUM> to the arm cylinder <NUM>.

A switching valve (not illustrated) may be provided between the boom cylinder <NUM> and the arm cylinder <NUM>, and the vibration control part <NUM> of the controller <NUM> may control the switching valve, based on the rod pressure PR and the bottom pressure PB of the boom cylinder <NUM> detected by the boom rod pressure sensor S6a and the boom bottom pressure sensor S6b. That is, when a combined operation corresponding to the raising operation of the boom <NUM> (boom raising operation) and an opening operation of the arm <NUM> (arm opening operation) or a closing operation of the arm <NUM> (arm closing operation) is performed, the switching valve switches from a cutoff state to a communicating state. More particularly, the switching valve is switched from the cutoff state to the communicating state according to a pilot pressure supplied from a solenoid proportional valve controlled by the controller <NUM>. Thus, the hydraulic controlling valve <NUM> can supply the working fluid discharged from the bottom-side fluid chamber of the boom cylinder <NUM> to the arm cylinder <NUM> via the switching valve.

In addition, a restoration circuit may be formed in the controlling valve <NUM> of the boom cylinder <NUM>, to discharge the working fluid of the boom cylinder <NUM> to the working fluid tank T. In this case, there is no need to provide the switching valve between the boom cylinder <NUM> and the arm cylinder <NUM>.

Moreover, the configuration is not limited to a configuration that supplies the working fluid of the boom cylinder <NUM> to the arm cylinder <NUM>. The working fluid of the boom cylinder <NUM> may be supplied to the swing hydraulic motor 2A, or may be supplied to a hydraulic cylinder (lifting magnet cylinder <NUM>, bucket cylinder, or the like) that drives an end attachment.

Accordingly, the vibration can be reduced by supplying the working fluid to another hydraulic actuator that performs a combined operation with the boom <NUM>.

Although preferred embodiments and exemplary implementations of the work machine according to the present invention are described heretofore, the present invention is not limited to the embodiments or exemplary implementations described above. In other words, various modifications and variations of the present invention can be made within the scope of the appended claims.

Claim 1:
A work machine (<NUM>) comprising:
a lower structure (<NUM>);
a slewing upper structure (<NUM>) attached to the lower structure (<NUM>) via a slewing mechanism (<NUM>);
an attachment (<NUM>, <NUM>), including at least a boom (<NUM>), and attached to the slewing upper structure (<NUM>);
a boom cylinder (<NUM>) configured to drive the boom (<NUM>);
a work tool (<NUM>) attached to the attachment (<NUM>, <NUM>); and
a controller (<NUM>),
wherein the controller (<NUM>) includes
a weight calculating part (<NUM>) configured to measure a weight of a transporting object to be transported by the work tool (<NUM>), based on a boom cylinder pressure of the boom cylinder (<NUM>), and
a vibration control part (<NUM>) configured to generate a command for reducing vibration of the attachment (<NUM>, <NUM>),
wherein the work tool (<NUM>) is a lifting magnet (<NUM>), and
wherein the vibration control part (<NUM>) generates a command for controlling a supply voltage with respect to the lifting magnet (<NUM>).