Patent Description:
A wheel loader as an example of a work implement has a work implement with a bucket at the tip of the boom. A hydraulic cylinder for boom is provided between the vehicle body of the wheel loader and the boom, and the boom rotates in the vertical direction due to expansion and contraction of the hydraulic cylinder.

A bell crank is attached to the boom, and a hydraulic cylinder for a bucket is provided between one end of the bell crank and the vehicle body. The other end of the bell crank is attached to the bucket by a rod. When the hydraulic cylinder for the bucket extends, the bucket rotates in the tilt direction, and when the hydraulic cylinder for the bucket contracts, the bucket rotates in the dump direction (see, for example, <CIT>).

In such a wheel loader, depending on the boom angle, the bucket reaches the tilt end or the dump end due to the configuration of the work implement linkage before the stroke of the cylinder for the bucket reaches the maximum or minimum value, so that, over the entire boom angle, the maximum stroke of the cylinder for the bucket does not corresponds to the tilt end and the minimum stroke of the cylinder for the bucket does not correspond to the dump end.

Therefore, the impact mitigation control at the tilt end or the dump end is performed based on a map in which the stroke end of the cylinder length in consideration of the bucket shape is defined with respect to the boom angle.

However, it is required to perform mitigation control without considering the boom angle.

An object of the present invention is to provide a work machine and a method for controlling a work machine capable of mitigating an impact at a tilt end or a dump end without considering a boom angle.

A work machine of the present invention includes a boom, a work tool, a cylinder, a sub-link, an operating member, a control section and a detection section. The work tool is configured to drive with respect to the boom. The cylinder is configured to drive the work tool. The sub-link is attached to the boom and is configured to transmit the driving force of the cylinder to the work tool. The control section controls the cylinder based on a posture of the sub-link with respect to the boom. The operating member is configured for operating the work tool. The detection section is configured for detecting a stroke of the cylinder. The control section is configured to give a target cylinder drive command based on one of a first cylinder drive command based on difference between the posture of the sub-link and a limit posture of the sub-link and a second cylinder drive command based on difference between the stroke and an end position of the cylinder. The target cylinder drive command includes information on supplied flow rate of hydraulic fluid to the cylinder. Further, each of the first cylinder drive command and the second cylinder drive command includes information on a limit flow rate for supplied flow rate of hydraulic fluid to the cylinder by operating the operating member, and the control section is configured to give the target cylinder drive command using a larger limit flow rate of both the first cylinder drive command and the second cylinder drive command, wherein a larger limit flow rate results in a smaller flow rate of the hydraulic fluid supplied to the cylinder.

Preferred embodiments of the work machine are defined in claims <NUM> to <NUM>.

A method for controlling a work machine of the present invention includes a detection step and a control step. In the detection step a stroke of a cylinder is detected. In the control step, a target cylinder drive command is given based on one of a first cylinder drive command and a second cylinder drive command to control the cylinder, the first cylinder drive command being based on difference between a posture of a sub-link, which is configured to transmit driving force of the cylinder to a work tool configured to drive with respect to the boom, with respect to the boom and a limit posture of the sub-link, the second cylinder drive command being based on difference between the stroke and an end position of the cylinder, wherein the target cylinder drive command includes information on supplied flow rate of hydraulic fluid to the cylinder, each of the first cylinder drive command and the second cylinder drive command includes information on a limit flow rate for supplied flow rate of hydraulic fluid to the cylinder by operating an operating member for operating the work tool, and the control step involves giving the target cylinder drive command using a larger limit flow rate of both the first cylinder drive command and the second cylinder drive command, wherein a larger limit flow rate results in a smaller flow rate of the hydraulic fluid supplied to the cylinder.

According to the present invention, it is possible to provide a work implement machine and a method for controlling a work machine capable of mitigating an impact at a tilt end or a dump end without considering a boom angle.

Hereinafter, the wheel loader <NUM> (an example of a work machine) according to the embodiment of the present invention will be described with reference to the drawings.

<FIG> is a schematic view showing the configuration of the wheel loader <NUM> of the present embodiment.

The wheel loader <NUM> of the present embodiment includes a vehicle body <NUM> (an example of a vehicle body) and work implement <NUM>. The vehicle body <NUM> includes a vehicle body frame <NUM>, a pair of front tires <NUM>, a cab <NUM>, an engine room <NUM>, a pair of rear tires <NUM>, and a control system <NUM> (see <FIG>).

The wheel loader <NUM> uses work implement <NUM> to perform earth and sand loading work and the like.

The vehicle body frame <NUM> is a so-called articulated type, and includes a front frame <NUM>, a rear frame <NUM>, and a connecting shaft part <NUM>. The front frame <NUM> is arranged in front of the rear frame <NUM>. The connecting shaft part <NUM> is provided at the center in the vehicle width direction, and connects the front frame <NUM> and the rear frame <NUM> so as to be swingable to each other.

The cab <NUM> is provided on the rear frame <NUM> and a driver's seat is arranged in the cab <NUM>. The cab <NUM> is provided with an input/output device <NUM>, a boom operating lever <NUM>, a bucket operating lever <NUM>, and the like, which will be described later.

The pair of front tires <NUM> are attached to the left and right sides of the front frame <NUM>. Further, a pair of rear tires <NUM> are attached to the left and right sides of the rear frame <NUM>.

The work implement <NUM> is driven by hydraulic fluid from the work implement pump. <FIG> is an enlarged side view of work implement <NUM>.

The work implement <NUM> includes a boom <NUM>, a bucket <NUM> (an example of a work tool), a boom cylinder <NUM>, a bucket cylinder <NUM> (an example of an actuator), and a bell crank <NUM> (an example of a sub-link).

One attachment part 14a of the boom <NUM> is rotatably attached to the front part of the front frame <NUM>. The other attachment part 14b of the boom <NUM> is rotatably attached to the rear part of the bucket <NUM>. The tip of the cylinder rod 16a of the boom cylinder <NUM> is rotatably attached to the attachment part 14c provided between the attachment part 14a and the attachment part 14b of the boom <NUM>. The cylinder body of the boom cylinder <NUM> is rotatably attached to the front frame <NUM> at the attachment part 16b.

The bell crank <NUM> includes a bell crank body 18e and a rod 18f. The attachment part 18a provided at one end of the bell crank body 18e is rotatably attached to the tip of the cylinder rod 17a of the bucket cylinder <NUM>. One end of the rod 18f is rotatably attached to an attachment part 18b provided at the other end of the bell crank body 18e. The other end of the rod 18f is rotatably attached to the rear part of the bucket <NUM> at the attachment part <NUM>. The bell crank body 18e rotatably supported by a bell crank support 14d near the center of the boom <NUM> at the attachment part 18c (an example of a fourth mounting part) provided between the attachment part 18a (an example of a second mounting part) and the attachment part 18b (an example of a third mounting part). The cylinder body of the bucket cylinder <NUM> is rotatably attached to the front frame <NUM> at the attachment part 17b (an example of the first attachment part). The expansion and contraction force of the bucket cylinder <NUM> is converted into a rotary motion by the bell crank and transmitted to the bucket <NUM>. The sub-link may include a quick coupler or the like in addition to the bell crank <NUM>.

Due to the expansion and contraction of the bucket cylinder <NUM>, the bucket <NUM> rotates with respect to the boom <NUM> to perform a tilt operation (see arrow J) and a dump operation (see arrow K). Here, the tilt operation of the bucket <NUM> is an operation in which the bucket <NUM> tilts by the opening 15b and the claw 15c of the bucket <NUM> rotating toward the cab <NUM>. The dump operation of the bucket <NUM> is the opposite of the tilt operation, and is an operation in which the bucket <NUM> tilts by the opening 15b and the claw 15c of the bucket <NUM> rotating toward so as to move away from the cab <NUM>.

The boom angle sensor <NUM> is provided on the attachment part 14a of the boom <NUM>. The boom angle sensor <NUM> detects the boom angle (indicated by θa in the figure) between the center line L1 of the boom <NUM> and the horizontal line H, and outputs a detection signal. The center line L1 of the boom <NUM> is a line connecting the attachment part 14a and the attachment part 14b of the boom <NUM>. The boom angle has a negative value when the center line L1 is inclined toward the road surface R (see <FIG>) with respect to the horizontal line H.

The bell crank angle sensor <NUM> is provided on the attachment part 18c of the bell crank <NUM>. The bell crank angle sensor <NUM> detects the bell crank angle (indicated by θb in the figure) between the line L2 connecting the attachment part 18a and the attachment part 18c of the bell crank <NUM> and the center line L1 of the boom <NUM>, and outputs the detection signal. The bell crank angle is an example of a posture of the bell crank <NUM>.

<FIG> is a view showing a control system <NUM> controlling operation of the work implement <NUM>.

The control system <NUM> controls the operation of work implement <NUM>. The control system <NUM> includes a work implement hydraulic pump <NUM>, a boom operating valve <NUM>, a bucket operating valve <NUM>, a pilot pump <NUM>, a discharge circuit <NUM>, an electromagnetic proportional control valve <NUM>, a control device <NUM>, and an EG (engine) control device <NUM>.

The work implement hydraulic pump <NUM> is driven by the engine <NUM> mounted in the engine room <NUM>. The engine <NUM> is an internal combustion engine, and for example, a diesel engine is used. The output of the engine <NUM> is input to the PTO (power Take Off) <NUM>, and then output to the work implement hydraulic pump <NUM> and the transmission <NUM>. The work implement hydraulic pump <NUM> is driven by the engine <NUM> via the PTO <NUM> to discharge the hydraulic fluid. The input side of the clutch <NUM> is attached to the engine <NUM>. The output side of the clutch <NUM> is attached to the torque converter (TC) <NUM>. The output of the engine <NUM> is transmitted to the transmission <NUM> via the PTO <NUM>. The transmission <NUM> transmits the output of the engine <NUM> transmitted via the PTO <NUM> to the front tire <NUM> and the rear tire <NUM>, and the front tire <NUM> and the rear tire <NUM> are driven. As the transmission <NUM>, HST (Hydro Static Transmission), electric drive, and the like can be appropriately used.

The discharge circuit <NUM> is an oil passage through which the hydraulic fluid passes, and is attached to a discharge port in which the work implement hydraulic pump <NUM> discharges the hydraulic fluid. The discharge circuit <NUM> is attached to the boom operating valve <NUM> and the bucket operating valve <NUM>. The boom operating valve <NUM> and the bucket operating valve <NUM> are hydraulic pilot type operation valves. The boom operating valve <NUM> and the bucket operating valve <NUM> are attached to the vehicle body <NUM>. The work implement hydraulic pump <NUM>, the boom operating valve <NUM>, the bucket operating valve <NUM>, and the discharge circuit <NUM> form a parallel hydraulic circuit.

The boom operating valve <NUM> is a <NUM>-position switching valve that can be switched between an A position, a B position, a C position, and a D position. The boom <NUM> raises when the boom operating valve <NUM> is in the A position, the boom <NUM> holds the position neutrally when the boom operating valve <NUM> is in the B position, the boom <NUM> lowers when the boom operating valve <NUM> is in the C position, and D position is "floating".

The bucket operating valve <NUM> is a three-position switching valve that can be switched between a E position, a F position, and a G position. The bucket <NUM> tilts (see arrow J in <FIG>) when the bucket operating valve <NUM> is in the E position, the bucket <NUM> holds the position neutrally when the bucket operating valve <NUM> is in the F position, and the bucket <NUM> dumps (see arrow K in <FIG>) when the bucket operating valve <NUM> is in the G position.

The pilot pump <NUM> is attached to pilot pressure receiving parts of the boom operating valve <NUM> and pilot pressure receiving parts of the bucket operating valve <NUM> via the electromagnetic proportional control valve <NUM>. The pilot pump <NUM> is connected to the PTO <NUM> and is driven by the engine <NUM>. The pilot pump <NUM> supplies a hydraulic fluid of pilot pressure to the pilot pressure receiving parts 22R of the boom operating valve <NUM> and the pilot pressure receiving parts 23R of the bucket operating valve <NUM> via the electromagnetic proportional control valve <NUM>.

The electromagnetic proportional control valve <NUM> includes a boom lowering electromagnetic proportional control valve <NUM>, a boom raising electromagnetic proportional control valve <NUM>, a bucket dump electromagnetic proportional control valve <NUM>, and a bucket tilt electromagnetic proportional control valve <NUM>.

The boom lowering electromagnetic proportional control valve <NUM> and the boom raising electromagnetic proportional control valve <NUM> are attached to each pilot pressure receiving parts 22R of the boom operating valve <NUM>. The bucket dump electromagnetic proportional control valve <NUM> and the bucket tilt electromagnetic proportional control valve <NUM> are attached to each pilot pressure receiving parts 23R of the bucket operating valve <NUM>.

A command signal from the control device <NUM> to each solenoid proportional control valve is input to a solenoid command section <NUM> of the boom lowering electromagnetic proportional control valve <NUM>, the solenoid command section <NUM> of the boom raising electromagnetic proportional control valve <NUM>, the solenoid command section <NUM> of the bucket dump electromagnetic proportional control valve <NUM>, and the solenoid command section <NUM> of the bucket tilt electromagnetic proportional control valve <NUM>.

The boom <NUM> is rotated upward or downward by operations of the boom lowering electromagnetic proportional control valve <NUM>, the boom raising electromagnetic proportional control valve <NUM>, the boom operating valve <NUM>, and the boom cylinder <NUM>.

The bucket <NUM> is tilted and dumped by operation of the bucket dump electromagnetic proportional control valve <NUM>, the bucket tilt electromagnetic proportional control valve <NUM>, the bucket operating valve <NUM>, and the bucket cylinder <NUM>.

The control system <NUM> is provided with the boom operating lever <NUM> and the bucket operating lever <NUM> operated by an operator. The boom operating lever <NUM> is a lever for operating the boom <NUM>. A first potentiometer <NUM> for detecting the operation amount of the boom operating lever <NUM> is attached to the boom operating lever <NUM>.

The bucket operating lever <NUM> is a lever for operating the bucket <NUM>. A second potentiometer <NUM> for detecting the operation amount of the bucket operating lever <NUM> is attached to the bucket operating lever <NUM>.

The detection signals of the first potentiometer <NUM> and the second potentiometer <NUM> are input to the input section <NUM> of the control device <NUM>.

The boom operating lever <NUM> and the bucket operating lever <NUM> may be PPC levers that directly drive the operating valve operating the cylinder with pilot pressure.

The control device <NUM> includes, for example, a processing section <NUM> such as a CPU (Central Processing Unit), a storage section <NUM> such as a ROM (Read Only Memory), an input section <NUM>, and an output section <NUM>.

The processing section <NUM> controls operation of the work implement <NUM> by executing a computer program. The processing section <NUM> is electrically connected to the storage section <NUM>, the input section <NUM>, and the output section <NUM>. The processing section <NUM> reads information from the storage section <NUM> and writes information to the storage section <NUM>. The processing section <NUM> receives information from the input section <NUM>. The processing section <NUM> outputs information from the output section <NUM>.

The storage section <NUM> stores a computer program that controls operation of the work implement <NUM> and information used for controlling the work implement <NUM>. The storage section <NUM> stores a computer program to execute a method for controlling the work machine, and the processing section <NUM> reads and executes this program.

The storage section <NUM> stores the maximum and minimum values of the cylinder length (an example of the stroke) of the bucket cylinder <NUM> and the maximum and minimum values of the bell crank angle. The maximum and minimum values of the bell crank angle correspond to an example of limit postures. The maximum and minimum values of the cylinder length correspond to an example of end positions.

In addition, the storage section <NUM> stores four tables. The first table is a table showing the limit flow rate of the hydraulic fluid to the bucket cylinder <NUM> set for the difference between the bell crank angle acquired from the bell crank angle sensor <NUM> and the maximum value of the bell crank angle. The second table is a table showing the limit flow rate of the hydraulic fluid to the bucket cylinder <NUM> set for the difference between the bell crank angle acquired from the bell crank angle sensor <NUM> and the minimum value of the bell crank angle. The third table is a table showing the limit flow rate of the hydraulic fluid to the bucket cylinder <NUM> set for the difference between the maximum value of the cylinder length of the bucket cylinder <NUM> and the cylinder length of the bucket cylinder <NUM> acquired from the boom angle sensor <NUM> and the bell crank angle sensor <NUM>. The fourth table is a table showing the limit flow rate of the hydraulic fluid to the bucket cylinder <NUM> set for the difference between the minimum value of the cylinder length of the bucket cylinder <NUM> and the cylinder length of the bucket cylinder <NUM> acquired from the boom angle sensor <NUM> and the bell crank angle sensor <NUM>.

Detection signals are input to the input section <NUM> from the boom angle sensor <NUM>, the bell crank angle sensor <NUM>, the first potentiometer <NUM>, and the second potentiometer <NUM>. The processing section <NUM> acquires these detection signals and controls the operation of work implement <NUM>.

Further, the cylinder length (indicated by La in <FIG>) of the bucket cylinder <NUM> is obtained from the boom angle detected by the boom angle sensor <NUM> and the bell crank angle detected by the bell crank angle sensor <NUM>.

The control device <NUM> obtains the cylinder length of the boom cylinder <NUM> and the cylinder length of the bucket cylinder <NUM> by using the detected values of at least one of the boom angle sensor <NUM> and the bell crank angle sensor <NUM>, and controls the operations of the boom <NUM> and the bucket <NUM>.

The output section <NUM> outputs drive commands to the solenoid command section <NUM> of the boom lowering electromagnetic proportional control valve <NUM>, the solenoid command section <NUM> of the boom raising electromagnetic proportional control valve <NUM>, the solenoid command section <NUM> of the bucket dump electromagnetic proportional control valve <NUM>, and the solenoid command section <NUM> of the bucket tilt electromagnetic proportional control valve <NUM>, and the input/output device <NUM>.

The processing section <NUM> gives a command value for operating the boom cylinder <NUM> to the solenoid command section <NUM> of the boom lowering electromagnetic proportional control valve <NUM> or the solenoid command section <NUM> of the boom raising electromagnetic proportional control valve <NUM>, expands and contracts the boom cylinder <NUM>, and raises and lowers the boom <NUM>.

The processing section <NUM> gives a command value for operating the bucket cylinder <NUM> to the solenoid command section <NUM> of the bucket dump electromagnetic proportional control valve <NUM> or the solenoid command section <NUM> of the bucket tilt electromagnetic proportional control valve <NUM>, expands and contracts the bucket cylinder <NUM>, and tilts or dumps the bucket <NUM>.

The input/output device <NUM> is provided inside the cab <NUM>. The input/output device <NUM> is connected to both the input section <NUM> and the output section <NUM>. The input/output device <NUM> includes an input device <NUM> and a display device <NUM>. The operator can input a command value from the input device <NUM> to the control device <NUM>. The display device <NUM> displays information on the status or the control of work implement <NUM>. The input device <NUM> can use a touch panel or a push button type switch. As will be described later, by operating the input device <NUM>, it is possible to display a calibration mode for calibrating the maximum value of the bell crank angle at the tilt end.

In the wheel loader <NUM> of the present embodiment, mitigation stop control is performed at the tilt end and the dump end in order to mitigate the impact at the tilt end and the dump end.

The control device <NUM> of the present embodiment performs mitigation stop control based on the bell crank angle and the stroke length of the bucket cylinder <NUM>.

Before explaining the configuration of the processing section <NUM> for performing mitigation stop control, it will be described that reaching the tilt end and the dump end area detected with the bell crank angle and the stroke length of the bucket cylinder <NUM>.

<FIG> is a view showing a change (G1) in the bucket cylinder length at the tilt end with respect to the boom angle and a change (G2) in the bucket cylinder length at the dump end with respect to the boom angle. The vertical axis shows the bucket cylinder length, and the horizontal axis shows the boom angle.

As shown in G1, when the boom angle is from the maximum value to A1 degree, the bucket reaches the tilt end at the maximum value of the cylinder length of the bucket cylinder <NUM>.

<FIG> is a view showing a state in which the bucket reaches the tilt end at the maximum value of the bucket cylinder <NUM>, and is a view showing an example of a work implement state in P1 of <FIG>. <FIG> shows a state in which the boom angle is the maximum value, the bucket cylinder <NUM> is fully extended, and the bucket <NUM> reaches the tilt end.

On the other hand, when the boom angle is from A1 degree to the minimum value, the bucket reaches the tilt end before the cylinder length of the bucket cylinder <NUM> reaches the maximum value.

This is because the link mechanism of work implement <NUM> reaches the mechanism limit before the cylinder length of the bucket cylinder <NUM> reaches the maximum value, and the bucket cylinder <NUM> cannot be extended any more. <FIG> is a view showing an example of work implement <NUM> in P2 of <FIG>. In the state shown in <FIG>, since the bucket <NUM> is in contact with the bell crank <NUM>, the bucket cylinder <NUM> cannot be extended any more. In <FIG>, the contact position is illustrated as C1, but the contact position at the mechanical limit changes depending on the configuration of the link of work implement3.

In this way, the bucket <NUM> reaches the tilt end due to the mechanical limit of the link mechanism of work implement <NUM> from the minimum value to the angle A1, and the bucket <NUM> reaches the tilt end at the maximum value of the cylinder length of the bucket cylinder <NUM> from the angle A1 to the maximum value.

On the other hand, as shown in G2, the bucket reaches the dump end at the minimum value of the bucket cylinder <NUM> when the boom angle is from the minimum value to A2 degrees, but the bucket reaches the dump end before the cylinder length of the bucket cylinder <NUM> reaches the minimum value when the boom angle is from A2 degrees to the maximum value.

This is because the link mechanism of work implement <NUM> reaches the mechanism limit before the cylinder length of the bucket cylinder <NUM> reaches the minimum value, and the bucket cylinder <NUM> cannot be contracted any more. <FIG> is a view showing an example of work implement <NUM> in P3 of <FIG>. In the state shown in <FIG>, since the bell crank <NUM> is in contact with the frame part of the boom <NUM> arranged along the left-right direction, the bucket cylinder <NUM> cannot be contracted any more (see point C2).

In this way, the bucket cylinder <NUM> reaches the tilt end at the minimum value of the cylinder length of the bucket cylinder <NUM> when the boom angle is from the minimum value to A2 degrees, and the bucket <NUM> reaches the dump end due to the mechanical limits of the link mechanism of the work implement <NUM> when the boom angle is from the predetermined value to the maximum value.

As described above, in the region where the bucket reaches the tilt end and the dump end due to the mechanical limit, the stroke length of the bucket cylinder <NUM> depends on the boom angle, but since the link mechanism reaches the mechanical limit, the bell crank angle is constant.

<FIG> is a view in which the minimum value of the bucket cylinder length (G3), the maximum value of the bucket cylinder length (G4), the minimum value of the bell crank angle (G5), and the maximum value of the bell crank angle (G6) are added to the graph of <FIG>. The vertical axis shows the bucket cylinder length and the horizontal axis shows the boom angle.

As shown in G1 of the bucket cylinder length at the tilt end and G4 of the maximum value of the bucket cylinder length, the maximum value G6 of the bell crank angle matches G1 in the region where the stroke length of the bucket cylinder <NUM> does not reach the maximum value.

On the other hand, as shown in G2 of the bucket cylinder length at the dump end and G3 of the minimum value of the bucket cylinder length, the minimum value G5 of the bell crank angle matches G2 in the region where the bucket cylinder length does not reach the minimum value.

<FIG> is a view showing a graph in which the vertical axis of the graph of <FIG> is converted into a bell crank angle. As shown in <FIG>, the graph corresponding to G1 in <FIG> is illustrated as G1', and G1' shows the change in the bell crank angle at the tilt end with respect to the boom angle. Further, the graph corresponding to G2 in <FIG> is illustrated as G2', and G2' shows the change in the bell crank angle at the dump end with respect to the boom angle. Further, the end line G7 when the boom is lowered is drawn at A3 degree, and the end line G8 when the boom is raised is drawn at A4 degree.

As shown in <FIG>, in the region where the stroke length of the bucket cylinder <NUM> does not reach the maximum value at the tilt end, the bucket <NUM> reaches the tilt end at the maximum value G6 of the bell crank angle. Further, in the region where the stroke length of the bucket cylinder does not reach the minimum value at the dump end, the bucket <NUM> reaches the dump end at the minimum value G5 of the bell crank angle.

As illustrated in <FIG> and <FIG>, it is possible to detect that the bucket <NUM> reaches the tilt end by combining the maximum value of the bucket cylinder length and the maximum value of the bell crank angle.

Note that G11 illustrated by a dotted line in <FIG> is a graph showing the bucket cylinder length at the tilt end when the bucket <NUM> is replaced with another one. The graph corresponding to G11 in <FIG> is illustrated as G11' in <FIG>. In G11 and G11', unlike G1 and G1', the bucket reaches the tilt end at the maximum value of the cylinder length of the bucket cylinder <NUM> when the boom angle is from the maximum value to A5 degrees, and the bucket reaches the tilt end before the cylinder length of the bucket cylinder <NUM> reaches the maximum value when the boom angle is from A5 degrees to the minimum value.

The bucket <NUM> may be replaced with one having a different size by the operator. In that case, the mechanical limit also changes and the maximum value of the bell crank angle also changes, but as described above, the bell crank angle at the mechanical limit is constant. Therefore, when the bucket is replaced, it is possible to detect that the bucket <NUM> reaches the tilt end by obtaining the maximum value of the bell crank angle at the mechanical limit with calibration and using the maximum value and the bucket cylinder length. The calibration of the maximum value of the bell crank angle when the bucket is replaced will be described later.

Further, by combining the minimum value of the bucket cylinder length and the minimum value of the bell crank angle, it is possible to detect that the bucket <NUM> reaches the dump end.

In the present embodiment, the dump end is determined by the shapes of the boom <NUM> and the bell crank <NUM> regardless of the bucket <NUM>, so that it is not necessary to perform calibration and the dump end is determined by the design value.

<FIG> is a block diagram showing the configuration of the processing section <NUM> of the present embodiment. The processing section <NUM> includes a drive command creation section <NUM>, a bell crank limit flow rate calculation section <NUM>, a cylinder limit flow rate calculation section <NUM>, a limit flow rate determination section <NUM>, a drive command determination section <NUM>, and a tilt/dump determination section <NUM>.

The drive command creation section <NUM> creates a drive command based on the operation of the boom operating lever <NUM> and the bucket operating lever <NUM> by the operator. When the boom operating lever <NUM> and the bucket operating lever <NUM> are operated by the operator, the drive command creation section <NUM> acquires the operation amount signal of the boom operating lever <NUM> and the bucket operating lever <NUM> from the first potentiometer <NUM> and the second potentiometer <NUM> via the input section <NUM>. Then, the drive command creation section <NUM> creates a drive command (an example of a target cylinder drive command) corresponding to the operation amount signal.

This drive command is a command to drive the boom cylinder <NUM> or the bucket cylinder <NUM> so as to correspond to the operation amount signal, and defines the flow rate of the hydraulic fluid supplied to the boom cylinder <NUM> or the bucket cylinder <NUM>. Specifically, the drive command is a command so that the boom lowering electromagnetic proportional control valve <NUM>, the boom raising electromagnetic proportional control valve <NUM>, the bucket dump electromagnetic proportional control valve <NUM>, or the bucket tilt electromagnetic proportional control valve <NUM> is set to the opening degree such that the hydraulic fluid of the flow rate corresponding to the operation amount flows.

When a drive command is output to the boom lowering electromagnetic proportional control valve <NUM>, the boom raising electromagnetic proportional control valve <NUM>, the bucket dump electromagnetic proportional control valve <NUM>, or the bucket tilt electromagnetic proportional control valve <NUM>, the boom lowering electromagnetic proportional control valve <NUM>, the boom raising electromagnetic proportional control valve <NUM>, the bucket dump electromagnetic proportional control valve <NUM>, or the bucket tilt electromagnetic proportional control valve <NUM> is driven according to the opening degree information of the drive command. As a result, the pilot pressure according to the drive command is output from the boom lowering electromagnetic proportional control valve <NUM>, the boom raising electromagnetic proportional control valve <NUM>, the bucket dump electromagnetic proportional control valve <NUM>, or the bucket tilt electromagnetic proportional control valve <NUM> to the pilot pressure receiving part of the boom operating valve <NUM> or the bucket operating valve <NUM>. Then the boom cylinder <NUM> or the bucket cylinder <NUM> operates in the corresponding directions at a speed corresponding to each pilot oil pressure.

The tilt/dump determination section <NUM> determines whether the bucket <NUM> is operated to the tilt side or the dump side based on the detection signal from the second potentiometer <NUM> that detects the operation amount of the bucket operating lever <NUM>. The tilt/dump determination section <NUM> transmits the determination result to the bell crank limit flow rate calculation section <NUM> and the cylinder limit flow rate calculation section <NUM>.

The bell crank limit flow rate calculation section <NUM> calculates the limit flow rate when driving the bucket cylinder <NUM> based on the bell crank angle acquired from the bell crank angle sensor <NUM> via the input section <NUM>.

The bell crank limit flow rate calculation section <NUM> includes a first tilt side limit flow rate calculation section <NUM> and a first dump side limit flow rate calculation section <NUM>.

When it is determined that the bucket <NUM> is operated toward the tilt side, the first tilt side limit flow rate calculation section <NUM> calculates the difference between the maximum value of the bell crank angle stored in the storage section <NUM> and the bell crank angle acquired by the bell crank angle sensor <NUM>, and acquires the first tilt side limit flow rate (an example of the first cylinder drive command) from the first table stored in the storage section <NUM>. In the first table, the smaller the difference (the closer the bell crank angle is to the maximum value), the larger the limit flow rate of the flow rate of hydraulic fluid supplied to the bucket cylinder <NUM> is set. By increasing the limit flow rate, the moving speed of the cylinder rod 17a of the bucket cylinder <NUM> is limited. That is, by limiting the moving speed of the bell crank <NUM> before reaching the maximum value of the bell crank angle, it is possible to stop gently when reaching the tilt end due to the mechanism limit.

When it is determined that the bucket <NUM> is operated toward the dump side, the first dump side limit flow rate calculation section <NUM> calculates the difference between the minimum value of the bell crank angle stored in the storage section <NUM> and the bell crank angle acquired by the bell crank angle sensor <NUM>, and acquires the first dump side limit flow rate (an example of the first cylinder drive command) from the second table stored in the storage section <NUM>. In the second table, the smaller the difference (the closer the bell crank angle is to the minimum value), the larger the limit flow rate of the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> is set.

The cylinder limit flow rate calculation section <NUM> includes a cylinder length calculation section <NUM>, a second tilt side limit flow rate calculation section <NUM>, and a second dump side limit flow rate calculation section <NUM>.

The cylinder length calculation section <NUM> calculates the cylinder length of the bucket cylinder <NUM> based on the boom angle acquired from the boom angle sensor <NUM> and the bell crank angle acquired from the bell crank angle sensor <NUM>.

When it is determined that the bucket <NUM> is operated to the tilt side, the second tilt side limit flow rate calculation section <NUM> calculates the difference between the maximum value of the bucket cylinder length stored in the storage section <NUM> and the cylinder lengths calculated by the cylinder length calculation section <NUM>, and acquires the second tilt side limit flow rate (an example of a second cylinder drive command) from the third table stored in the storage section <NUM>. In the third table, the smaller the difference (the closer the cylinder length is to the maximum value), the larger the limit flow rate of the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> is set.

When it is determined that the bucket <NUM> is operated to the dump side, the second dump side limit flow rate calculation section <NUM> calculates the difference between the minimum value of the bucket cylinder length stored in the storage section <NUM> and the cylinder lengths calculated by the cylinder length calculation section <NUM>, and acquires the second dump side limit flow rate (an example of the second cylinder drive command) from the fourth table stored in the storage section <NUM>. In the fourth table, the smaller the difference (the closer the cylinder length is to the minimum value), the larger the limit flow rate of the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> is set.

When it is determined that the bucket <NUM> is operated to the tilt side, the limit flow rate determination section <NUM> determines the larger flow rate of the first tilt side limit flow rate and the second tilt side limit flow rate as the limit flow rate for the drive command of the bucket cylinder <NUM>. Further, when it is determined that the bucket <NUM> is operated to the dump side, the limit flow rate determination section <NUM> determines the larger flow rate of the first dump side limit flow rate and the second dump side limit flow rate as the limit flow rate for the drive command of the bucket cylinder <NUM>.

As described above, in the case of the operation of the bucket <NUM> to the tilt side, the limit flow rate for the closer one of the maximum value of the bell crank angle and the maximum value of the bucket cylinder length is adopted. Further, in the case of the operation of the bucket <NUM> to the dump side, the limit flow rate for the closer one of the minimum value of the bell crank angle and the minimum value of the bucket cylinder length is adopted.

The larger limit flow rate means that the limited flow rate is large. For example, when the maximum flow rate is <NUM>% and the limit flow rate is <NUM>%, the hydraulic fluid is supplied to the bucket cylinder <NUM> at a flow rate of <NUM>%. That is, the larger the limit flow rate, the smaller the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM>.

As a result, in the case of operation of the bucket <NUM> to the tilt side, the limit flow rate increases as the bell crank angle approaches the maximum value or the bucket cylinder length approaches the maximum value, so that the moving speed of the bucket <NUM> slows down and it is possible to mitigate the impact at the tilt end. Further, in the case of the operation of the bucket <NUM> to the dump side, the limit flow rate increases as the bell crank angle approaches the minimum value or the bucket cylinder length approaches the minimum value, so that the moving speed of the bucket <NUM> slows down and it is possible to mitigate the impact at the dump end.

When the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> by the drive command created by the drive command creation section <NUM> exceeds the limit flow rate, the drive command determination section <NUM> creates a drive command of the maximum flow rate so as to keep the limit flow rate. That is, the limit flow rate is <NUM>%, the flow rate can be supplied up to <NUM>%, but when the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> of the drive command created by the drive command creation section <NUM> is set to <NUM>%, the drive command determination section <NUM> determines the drive command so that the flow rate is <NUM>%. That is, the limit flow rate is the upper limit value of the flow rate that can be commanded to drive. When the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> with the drive command created by the drive command creation section <NUM> does not exceed the limit flow rate, the drive command determination section <NUM> control the bucket cylinder <NUM> with the created drive command (an example of a cylinder drive command).

The opening degree of the bucket tilt electromagnetic proportional control valve <NUM> is narrowed in order to increase the limit flow rate of the hydraulic fluid when it is determined that the bucket <NUM> is operated to the tilt side. As a result, the pilot pressure can be lowered, so that the flow rate of the hydraulic fluid to the bucket cylinder <NUM> can be limited.

Further, the opening degree of the bucket dump electromagnetic proportional control valve <NUM> is narrowed in order to increase the limit flow rate of the flow rate of the hydraulic fluid when it is determined that the bucket <NUM> is operated to the dump side. As a result, the pilot pressure can be lowered, so that the flow rate of the hydraulic fluid to the bucket cylinder <NUM> can be limited.

Next, the operation of the embodiment according to the present invention will be described.

<FIG> is a flow chart showing a method for controlling the work machine of the present embodiment.

First, in step S10, when the bucket operating lever <NUM> is operated by the operator, the second potentiometer <NUM> detects the operating amount of the bucket operating lever <NUM>, and the detection signal is input to the input section <NUM> of the control device <NUM>.

Next, in step S11, the tilt/dump determination section <NUM> determines whether the bucket <NUM> is operated to the tilt side or the dump side based on the detection signal of the second potentiometer <NUM>.

In the step S11, when it is determined that the operation is on the tilt side, the control proceeds to step S12.

Next, in step S12, the drive command creation section <NUM> creates a drive command for transmitting to the solenoid command section <NUM> of the bucket tilt electromagnetic proportional control valve <NUM> so that the flow rate of the hydraulic fluid based on the detection signal by the second potentiometer <NUM> is supplied to the bucket cylinder <NUM>.

Next, in step S13, the first tilt side limit flow rate calculation section <NUM> calculates the difference between the maximum value of the bell crank angle stored in the storage section <NUM> and the bell crank angle acquired from the bell crank angle sensor <NUM>, and calculates the first tilt side limit flow rate from the first table stored in the storage section <NUM>.

Next, in step S14, the cylinder length calculation section <NUM> calculates the cylinder length of the bucket cylinder <NUM> based on the boom angle acquired from the boom angle sensor <NUM> and the bell crank angle acquired from the bell crank angle sensor <NUM>.

Next, in step S15, the second tilt side limit flow rate calculation section <NUM> calculates the difference between the maximum value of the bucket cylinder length stored in the storage section <NUM> and the cylinder length calculated by the cylinder length calculation section <NUM>, and acquires the second tilt side limit flow rate from the third table.

Next, in step S16, the limit flow rate determination section <NUM> determines the larger limit flow rate of the calculated first tilt side limit flow rate and the calculated second tilt side limit flow rate as the limit flow rate for the drive command to the bucket cylinder <NUM>.

Next, in step S17, the drive command determination section <NUM> determines whether or not the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> by the drive command created by the drive command creation section <NUM> exceeds the limit flow rate.

When it is determined in step S17 that the flow rate of the supplied hydraulic fluid does not exceed the limit flow rate, the control proceeds to step S18, and in step S18, the drive command created in step S12 is output from the output section <NUM> to the solenoid command section <NUM> of the bucket tilt electromagnetic proportional control valve <NUM>.

On the other hand, when it is determined in step S17 that the flow rate of the supplied hydraulic fluid exceeds the limit flow rate, the control proceeds to step S19, and in step S19, the drive command determination section <NUM> change the drive command so as to maximize the flow rate without exceeding the limit flow rate. Subsequently, in step S18, the changed drive command is output from the output section <NUM> to the solenoid command section <NUM> of the bucket tilt electromagnetic proportional control valve <NUM>.

On the other hand, in step S11, when the tilt/dump determination section <NUM> determines that the operation is on the dump side based on the detection signal of the second potentiometer <NUM>, the control proceeds to step S20.

In step S20, the drive command creation section <NUM> creates a drive command for transmitting to the solenoid command section <NUM> of the bucket dump electromagnetic proportional control valve <NUM> so that the flow rate of the hydraulic fluid based on the detection signal by the second potentiometer <NUM> is supplied to the boom cylinder <NUM> and the bucket cylinder <NUM>.

In step S21, the first dump side limit flow rate calculation section <NUM> calculates the difference between the minimum value of the bell crank angle stored in the storage section <NUM> and the bell crank angle acquired from the bell crank angle sensor <NUM>, and acquires the first dump side limit flow rate from the second table stored in the storage section <NUM>.

Next, in step S22, the cylinder length calculation section <NUM> calculates the cylinder length of the bucket cylinder <NUM> based on the boom angle acquired from the boom angle sensor <NUM> and the bell crank angle acquired from the bell crank angle sensor <NUM>.

Next, in step S23, the second dump side limit flow rate calculation section <NUM> calculates the difference between the minimum value of the bucket cylinder length stored in the storage section <NUM> and the cylinder length calculated by the cylinder length calculation section <NUM>, and acquires the second dump side limit flow rate from the fourth table stored in the storage section <NUM>.

Next, in step S24, the limit flow rate determination section <NUM> determines the larger limit flow rate of the calculated first dump side limit flow rate and the calculated second dump side limit flow rate as the limit flow rate for the drive command to the bucket cylinder <NUM>.

Next, in step S25, the drive command determination section <NUM> determines whether or not the flow rate of the hydraulic fluid supplied to the bucket cylinder <NUM> by the drive command created by the drive command creation section <NUM> exceeds the limit flow rate.

When it is determined in step S25 that the flow rate of the supplied hydraulic fluid does not exceed the limit flow rate, the control proceeds to step S26, and in step S26, the drive command created in step S20 is output from the output section <NUM> to the solenoid command section <NUM> of the bucket dump electromagnetic proportional control valve <NUM>.

On the other hand, when it is determined in step S25 that the flow rate of the supplied hydraulic fluid exceeds the limit flow rate, the control proceeds to step S27, and in step S27, the drive command determination section <NUM> change the drive command so as to maximize the flow rate without exceeding the limit flow rate. Subsequently, in step S26, the changed drive command is output from the output section <NUM> to the solenoid command section <NUM> of the bucket dump electromagnetic proportional control valve <NUM>.

Next, a method for calibrating the maximum value of the bell crank angle when the bucket <NUM> is replaced will be described. <FIG> is a flow chart showing a method for calibrating the maximum value of the bell crank angle.

When the bucket <NUM> is replaced, in step S30, the operator operates the input device <NUM> of the input/output device <NUM> to switch to the calibration mode screen of the maximum value of the bell crank angle.

In step S31, according to the instruction displayed on the display device <NUM> of the input/output device <NUM>, the operator operates the bucket <NUM> to the tilt end (the position where the bucket <NUM> abuts on the boom <NUM>) within the range of the mechanism limit where the bucket cylinder length does not reach the maximum value. For example, in the case of the graph of G11 in <FIG>, the boom angle may be set to a value lower than A5 degrees and the bucket <NUM> may be operated to the tilt end. Actually, since the boom angle that reaches the mechanism limit is not known, the bucket <NUM> may be tilted with the boom angle lowered as much as possible.

Next, in step S32, the bell crank angle at the tilt end is stored as the maximum value of the bell crank angle.

The maximum value of the stored bell crank angle is used in the method for controlling described above.

In this way, by setting the limit flow rate based on the maximum value and the minimum value of the bell crank angle, it is possible to perform mitigation control when the bucket <NUM> reaches the tilt end and the dump end due to the mechanism limit of the link mechanism of the work implement <NUM>.

Further, by setting the limit flow rate based on the maximum value and the minimum value of the cylinder length of the bucket cylinder <NUM>, it is possible to perform mitigation control when the bucket <NUM> reaches the tilt end and the dump end due to the cylinder length of work implement <NUM>.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention.

Claim 1:
A work machine (<NUM>) comprising:
a boom (<NUM>);
a work tool (<NUM>) configured to drive with respect to the boom (<NUM>);
a cylinder (<NUM>) configured to drive the work tool (<NUM>);
a sub-link (<NUM>) attached to the boom (<NUM>), the sub-link (<NUM>) being configured to transmit driving force of the cylinder (<NUM>) to the work tool (<NUM>); and
a control section (<NUM>) configured to control the cylinder (<NUM>) based on a posture of the sub-link (<NUM>) with respect to the boom (<NUM>);
an operating member (<NUM>) for operating the work tool (<NUM>);
a detection section (<NUM>, <NUM>) for detecting a stroke of the cylinder,
wherein the control section (<NUM>) is configured to give a target cylinder drive command based on one of a first cylinder drive command based on difference between the posture of the sub-link (<NUM>) and a limit posture of the sub-link (<NUM>) and a second cylinder drive command based on difference between the stroke and an end position of the cylinder, characterized in that
the target cylinder drive command includes information on supplied flow rate of hydraulic fluid to the cylinder,
each of the first cylinder drive command and the second cylinder drive command includes information on a limit flow rate for supplied flow rate of hydraulic fluid to the cylinder by operating the operating member (<NUM>), and
the control section (<NUM>) is configured to give the target cylinder drive command using a larger limit flow rate of both the first cylinder drive command and the second cylinder drive command,
wherein a larger limit flow rate results in a smaller flow rate of the hydraulic fluid supplied to the cylinder (<NUM>).