Patent Description:
A wheel loader as an example of a work machine 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. 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.

In such a wheel loader, the posture of work implement is grasped from the operation table of the bucket with respect to the expansion and contraction of the bucket cylinder in consideration of the bucket shape.

<CIT>, <CIT>. <CIT> discloses the features of the preambles of claims <NUM> and <NUM>.

However, on the premise of bucket replacement, it is required to grasp the bell crank angle that causes the detection error of the posture of work implement.

An object of the present invention is to provide a method for calibrating a work machine, a controller for a work machine, and a work machine capable of calibrating a measurement value of a bell crank angle in an actual operating angle region.

The method for calibrating the work machine according to the invention is a method for calibrating the work machine including a main body, a boom configured to drive with respect to the main body, a work tool connecting to the boom and configured to drive with respect to the boom, an actuator connecting to the main body and the work tool respectively and configured to drive the work tool, and a sub-link configured to transmit drive of the actuator to the work tool. The method includes an output step, a conversion step, and a calibration step. In the output step a detection value for detecting the angle of the sub-link with respect to the boom in a predetermined posture of the boom and a work tool posture, which are specified, is output. In the conversion step the detection value is converted as a measurement angle of the sub-link with respect to the boom based on a converted value. In the calibration step the conversion value is calibrated based on relationship between the measurement angle and an actual angle in the working tool posture which is specified. Further, there are a plurality of work tool postures, in the output step a detection value for detecting the angle of the sub-link with respect to the boom in each of the plurality of work tool postures is output, the plurality of work tool postures include a dump posture and a tilt posture, in the output step a detection value for detecting the angle of the sub-link with respect to the boom in each of the dump posture and the tilt posture is output, and the dump posture and the tilt posture are postures at a mechanism limit due to the sub-link or an operation limit of the actuator.

The controller for the work machine according to the invention is a controller for the work machine including a main body, a boom configured to drive with respect to the main body, a work tool connecting to the boom and configured to drive with respect to the boom, an actuator connecting to the main body and the work tool respectively and configured to drive the work tool, and a sub-link configured to transmit drive of the actuator to the work tool. The controller include an acquisition section, a display section, and a calibration section. The acquisition section acquires a detection value for detecting the angle of the sub-link with respect to the boom. The display section displays information for specifying a predetermined posture of the boom and a work tool posture when calibrating the conversion value for converting the detection value as the measurement angle of the sub-link with respect to the boom. The calibration section calibrates the conversion value by relationship an actual angle in a specified work tool posture and the measurement angle obtained by converting the detection value in a specified predetermined posture of the boom and a specified work tool posture, which are input based on a display on the display section, based on the conversion value. Further, there are a plurality of work tool postures. The acquisition section is configured to acquire a detection value for detecting the angle of the sub-link with respect to the boom in each of the plurality of work tool postures. The plurality of work tool postures include a dump posture and a tilt posture. The acquisition section is configured to acquire a detection value for detecting the angle of the sub-link with respect to the boom in each of the dump posture and the tilt posture, and the dump posture and the tilt posture are postures at a mechanism limit due to the sub-link or an operation limit of the actuator.

The work machine according to the invention is an articulated wheel loader in which a front frame and a rear frame are connected, and includes a controller for the work machine and an angle detection section. The angle detection section transmits a detection value for detecting an angle of a sub-link with respect to a boom to the controller of the wheel loader.

According to the present invention, it is possible to provide a method for calibrating a work machine, a controller for a work machine, and a work machine capable of calibrating a measurement value of a bell crank angle in an actual operating angle region.

Hereinafter, a 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 main 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 a 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 a center in a 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> described later, a boom operating lever <NUM>, a bucket operating lever <NUM>, and the like.

The pair of front tires <NUM> are attached to left and right sides of the front frame <NUM>. Further, a pair of rear tires <NUM> are attached to 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 main body 18e and a rod 18f. The attachment part 18a provided at one end part of the bell crank main 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 main 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 main 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 a 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 bell crank <NUM> corresponds to an example of a sub-link. 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> moving 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 as a voltage value, and outputs the detected detection voltage. 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.

A bell crank angle sensor <NUM> (an example of an angle detection section) 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> as a voltage value, and outputs the detected detection voltage.

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

The control system <NUM> controls operation of the 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 controller <NUM>, and 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 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 operating 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-type 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 a boom operating lever <NUM> and a 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 voltages 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 controller <NUM> includes a control device <NUM> and an input/output device <NUM>. The control device <NUM> controls the drive of work implement <NUM> and the like. The input/output device <NUM> is arranged in the cab <NUM>, an instruction from the operator is input to the input/output device <NUM>, and the input/output device <NUM> outputs an instruction to the operator.

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> (an example of an acquisition section), 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 a bell crank angle conversion table T1 and a boom angle conversion table T2, which will be described later.

The detection voltages 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 operation of the work implement <NUM>.

Further, the cylinder length of the bucket cylinder <NUM> (indicated by La in <FIG>) 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> using a bucket cylinder length table (see <FIG>) described later.

The control device <NUM> obtains the cylinder length of the bucket cylinder <NUM> using the detection voltages of the boom angle sensor <NUM> and the bell crank angle sensor <NUM>, and controls operation of 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>.

Further, the processing section <NUM> calibrates the bell crank angle detected by the bell crank angle sensor <NUM> and calibrates the boom angle detected by the boom angle sensor <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> (an example of a display section). 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 and the control of work implement <NUM> and the calibration.

A touch panel or a push button type switch can be used as the input device <NUM>.

By operating the input device <NUM>, a calibration mode for calibrating the bell crank angle or calibrating the boom angle can be displayed on the display device <NUM>.

In the wheel loader <NUM> of the present embodiment, the bell crank angle is calibrated by acquiring the detection voltages from the bell crank angle sensor <NUM> while the work implement <NUM> is in the first bell crank calibration posture and the second bell crank calibration posture.

Calibrating the bell crank angle in the first bell crank calibration posture and the second bell crank calibration posture will be described.

<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 to the maximum value, 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 implement.

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 tilt end and the dump end are reached 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.

Further, G11 shown 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 tilt end is reached 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 tilt end is reached 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 which case the mechanical limit also changes and the maximum value of the bell crank angle also changes.

In the bell crank angle calibration, for example, the first bell crank calibration posture may be the minimum value of the bell crank angle, and the second bell crank calibration posture may be the maximum value of the bell crank angle. However, as described above, the maximum value of the bell crank angle changes depending on the presence / absence of the bucket <NUM> and size of the bucket <NUM>.

Further, the first bell crank calibration posture and the second bell crank calibration posture are preferably postures that are fixed to one posture without depending on the operator. Therefore, the first bell crank calibration posture is defined as the posture at the position P3, and the second bell crank calibration posture is defined as the posture at the position P1.

As shown in <FIG> and <FIG>, the first bell crank calibration posture of work implement <NUM> at position P3 is a state in which the boom cylinder <NUM> is extended to the maximum value and the bucket cylinder <NUM> is contracted to bring the bell crank <NUM> into contact with the frame part of the boom <NUM> (see point C2) so that the bucket <NUM> reaches the damp end.

As shown in <FIG> and <FIG>, the second bell crank calibration posture of work implement <NUM> at position P1 is a state in which the boom cylinder <NUM> is extended to the maximum value and the bucket cylinder <NUM> is extended to the maximum value so that the bucket <NUM> reaches the tilt end.

In this way, the first bell crank calibration posture can be obtained by extending the boom cylinder <NUM> to the maximum value and contracting the bucket cylinder <NUM> until the bell crank <NUM> contacts the boom <NUM>. Therefore there is no difference in the first bell crank calibration posture depending on the operator and the presence/absence of the bucket <NUM>.

Further, the second bell crank calibration posture can be obtained by extending the boom cylinder <NUM> to the maximum value and extending the bucket cylinder <NUM> to the maximum value. Therefore there is no difference in the second bell crank calibration posture depending on the operator and the presence/absence of the bucket <NUM>.

As described above, the posture of the position P1 and the posture of the position P3 are selected as the calibration postures since the postures are fixed to one regardless of the presence or absence and the size of the bucket <NUM> and regardless of the operator.

Further, the bell crank angle due to the first bell crank calibration posture and the bell crank angle due to the second bell crank calibration posture are stored in advance in the storage section <NUM>.

<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 section <NUM>, a bell crank angle calibration section <NUM> (an example of a calibration section), a boom angle calibration section <NUM>, and a calibration instruction section <NUM>.

The drive command 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 section <NUM> acquires signals of the operation amount 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 section <NUM> creates a 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 bell crank angle calibration section <NUM> calibrates the bell crank angle when the calibration mode execution instruction by the operator using the input/output device <NUM> is input via the input section <NUM>.

The calibration instruction section <NUM> causes the display device <NUM> to display an operation instruction to the operator. Specifically, the calibration instruction section <NUM> instructs to set the work implement <NUM> to the first bell crank calibration posture and input the first bell crank detection voltage by the bell crank angle sensor <NUM>. The calibration instruction section <NUM> instructs to set the work implement <NUM> to the second bell crank calibration posture, and input the second bell crank detection voltage by the bell crank angle sensor <NUM>.

The bell crank angle calibration section <NUM> converts the first bell crank detection voltage (an example of the detection value) and the second bell crank detection voltage (an example of the detection value) to a bell crank angle (an example of a measurement angle) based on the bell crank angle conversion table T1 (an example of the conversion value) and rewrites the bell crank angle conversion table T1 stored in the storage section <NUM> so that the converted bell crank angles match the first bell crank angle (an example of an actual angle) and the second bell crank angle (an example of an actual angle) stored in advance in each calibration posture.

<FIG> is a view showing the bell crank angle conversion table T1. The storage section <NUM> stores a predetermined initial conversion line TL1 as the initial bell crank angle conversion table T1. In the initial conversion line TL1, the detection voltage at the bell crank angle θ1 in the first bell crank calibration posture is set to V1, and the detection voltage at the bell crank angle θ2 in the second bell crank calibration posture is set to V2.

In the calibration mode, the first bell crank detection voltage V1' from the bell crank angle sensor <NUM> is input in the state in which the work implement <NUM> is set to the first bell crank calibration posture by the operator, and the second bell crank detection voltage V2' from the bell crank angle sensor <NUM> is input in the state in which the work implement <NUM> is set to the second bell crank calibration posture by the operator.

Then, the bell crank angle calibration section <NUM> converts the first bell crank detection voltage V1'based on the initial conversion line TL1 to acquire the bell crank angle θ1', and converts the second bell crank detection voltage V2' based on the initial conversion line TL1 to acquire the bell crank angle θ2'. The bell crank angle calibration section <NUM> calibrates the initial conversion line TL1 to create the post-calibration conversion line TL1' so that the bell crank angle θ1' is the bell crank angle θ1 and the bell crank angle θ2' is the bell crank angle θ2, and stores the post-calibration conversion line TL1' in the storage section <NUM>. That is, the bell crank angle calibration section <NUM> calibrates the initial conversion line TL1 to create a post-calibration conversion line TL1' so that the bell crank angle at the first bell crank detection voltage V1' is θ1 and the bell crank angle at the second bell crank detection voltage V2' is θ2.

When driving the bucket cylinder <NUM> after calibration, the detection voltage input from the bell crank angle sensor <NUM> is converted to the bell crank angle based on the post-calibration conversion line TL1'.

Further, the first bell crank detection voltage V1' in the first bell crank calibration posture is the minimum value of the bell crank angle as illustrated at the position P3 in <FIG>, but the detection voltage V2' in the second bell crank calibration posture is not the maximum value of the bell crank angle, as illustrated at position P1 in <FIG>. Therefore, the bell crank angle of the detection voltage V2 or higher is calculated from the extrapolation of a straight line by the post-calibration conversion line TL1'.

The boom angle calibration section <NUM> calibrates the boom angle when the calibration mode execution instruction by the operator using the input/output device <NUM> is input via the input section <NUM>.

The calibration instruction section <NUM> causes the display device <NUM> to display an operation instruction to the operator. Specifically, the calibration instruction section <NUM> instructs to input the first boom detection voltage by the boom angle sensor <NUM> in the state where the work implement <NUM> is in the first boom calibration posture, and instructs to input the second boom detection voltage by the boom angle sensor <NUM> in the state where the work implement <NUM> is in the second boom calibration posture. The first boom calibration posture is a posture in which the boom cylinder <NUM> is set to the minimum value and the boom <NUM> is rotated most downward, and the second boom calibration posture is a posture in which the boom cylinder <NUM> is set to the maximum value and the boom <NUM> is rotated most upward.

The boom angle calibration section <NUM> rewrites the boom angle conversion table T2 stored in the storage section <NUM> based on the first boom detection voltage and the second boom detection voltage.

<FIG> is a view showing the boom angle conversion table T2. The storage section <NUM> stores a predetermined initial conversion line TL2 as the initial boom angle conversion table T2. In the initial conversion line TL2, the boom detection voltage at the boom angle θ3 in the first boom calibration posture is set to V3, and the boom detection voltage at the boom angle θ4 in the second boom calibration posture is set to V4.

In the calibration mode, the first boom detection voltage V3' from the boom angle sensor <NUM> is input in the state in which the work implement <NUM> is set to the first boom calibration posture by the operator, and the second boom detection voltage V4' from the boom angle sensor <NUM> is input in the state in which the work implement <NUM> is set to the second boom calibration posture by the operator.

Then, the boom angle calibration section <NUM> calibrates the initial conversion line TL2 to create a post-calibration conversion line TL2' so that the boom angle at the first boom detection voltage V3' is θ3 and the boom angle at the second boom detection voltage V4' is θ4, and stores the post-calibration conversion line TL2' in the storage section <NUM>.

The storage section <NUM> stores the bucket cylinder length table illustrated in <FIG>. This bucket cylinder length table is obtained in advance by the design value. The bucket cylinder length is calculated from the bucket cylinder length table based on the value of the bell crank angle θb and the value of the boom angle θa. For example, when the boom angle is θ14 and the bell crank angle is θ3, the bucket cylinder length is L33. In addition, the interval between each numerical value is obtained by interpolation calculation.

In the present embodiment, since the bell crank angle is calibrated together with the boom angle calibration, accurate values can be obtained for any of the boom angle, the bell crank angle, and the bucket cylinder length.

Since the posture of work implement <NUM> can be detected as an accurate value, for example, mitigation stop control to mitigate speed and to stop when reaching the dump end and the tilt end can be performed with high accuracy.

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

The method for calibrating the bell crank angle of the wheel loader of the present embodiment will be described below, and an example of the method for calibrating the wheel loader will be described.

<FIG> is a flow chart showing the method for calibrating the bell crank angle of the wheel loader <NUM> of the present embodiment.

First, in step S10, when a calibration mode execution instruction by the operator using the input/output device <NUM> is input to the bell crank angle calibration section <NUM> via the input section <NUM>, the control proceeds to step S11.

In step S11, the calibration instruction section <NUM> causes the display device <NUM> to display an operation instruction for causing the operator to set the work implement <NUM> to the first bell crank calibration posture.

The calibration instruction section <NUM> causes the display device <NUM> to display an instruction such as "Please rotate the boom <NUM> to the uppermost position, set the bucket <NUM> to the full dump state, and then press the input button. " As a result, the work implement <NUM> is set to the first bell crank calibration posture in which the boom cylinder <NUM> is extended to the maximum value and the bucket cylinder <NUM> is contracted to bring the bell crank <NUM> into contact with the frame part of the boom <NUM> (see point C2) so that the bucket <NUM> reaches the damp end.

Next, in step S12 (an example of the first input step), when the operator sets the work implement <NUM> to the first bell crank calibration posture and then inputs using the input device <NUM>, the first bell crank detection voltage V1' by the bell crank angle sensor <NUM> is input to the input section <NUM>.

Next, in step S13, the calibration instruction section <NUM> causes the display device <NUM> to display an operation instruction for causing the operator to set the work implement <NUM> to the second bell crank calibration posture.

The calibration instruction section <NUM> causes the display device <NUM> to display an instruction such as "Please rotate the boom <NUM> to the uppermost position, set the bucket <NUM> in the full tilt state, and then press the input button. " As a result, the work implement <NUM> can be set to the second bell crank calibration posture in which the boom cylinder <NUM> is extended to the maximum value and the bucket cylinder <NUM> is extended to the maximum value so that the bucket <NUM> reaches the tilt end.

Next, in step S14 (an example of the second input step), when the operator sets the work implement <NUM> to the second bell crank calibration posture and then inputs using the input device <NUM>, the bell crank detection voltage V2' by the bell crank angle sensor <NUM> is input to the input section <NUM>.

Next, in step S15 (an example of the conversion step), the bell crank angle calibration section <NUM> converts the first bell crank detection voltage V1' based on the initial conversion line TL1 to acquire the bell crank angle θ1', and converts the second bell crank detection voltage V2' based on the initial conversion line TL1 to acquire the bell crank angle θ2'.

Next, in step S16 (an example of a calibration step), the bell crank angle calibration section <NUM>, as illustrated in <FIG>, calibrates the initial conversion line TL1 to create the post-calibration conversion line TL1' so that the bell crank angle θ1 ' is the bell crank angle θ1 and the bell crank angle θ2 ' is the bell crank angle is θ2 and stores the post-calibration conversion line TL1' in the storage section <NUM>.

<FIG> is a flow chart showing a method for calibrating the boom angle of the wheel loader <NUM> of the present embodiment.

First, in step S20, when the calibration mode execution instruction by the operator using the input/output device <NUM> is input to the boom angle calibration section <NUM> via the input section <NUM>, the control proceeds to step S21.

In step S21, the calibration instruction section <NUM> causes the display device <NUM> to display an operation instruction for causing the operator to set the work implement <NUM> to the first boom calibration posture.

The calibration instruction section <NUM> causes the display device <NUM> to display an instruction such as "Please press the input button after rotating the boom <NUM> to the lowest position". As a result, the work implement <NUM> can be set to the first boom calibration posture in which the boom cylinder <NUM> is contracted to the minimum value so that the boom <NUM> is in the lowest position.

Next, in step S22, when the operator sets the work implement <NUM> to the first boom calibration posture and then inputs using the input device <NUM>, the first boom detection voltage V3' by the boom angle sensor <NUM> is input to the input section <NUM>.

Next, in step S23, the calibration instruction section <NUM> causes the display device <NUM> to display an operation instruction for causing the operator to set the work implement <NUM> to the second boom calibration posture.

The calibration instruction section <NUM> causes the display device <NUM> to display an instruction such as "Please press the input button after rotating the boom <NUM> to the uppermost position". As a result, the work implement <NUM> can be set to the second boom calibration posture in which the boom cylinder <NUM> is extended to the maximum value so that the boom <NUM> is in the highest position.

Next, in step S24, when the operator sets the work implement <NUM> to the second boom calibration posture and then inputs using the input device <NUM>, the second boom detection voltage V4' by the boom angle sensor <NUM> is input to the input section <NUM>.

Next, in step S25, as illustrated in <FIG>, the boom angle calibration section <NUM> calibrates the initial conversion line TL2 of the boom angle conversion table T2 to create the post- calibration conversion line TL2' so that the boom angle at the first boom detection voltage V3 ' is θ3 and the boom angle at the second boom detection voltage V4 ' is θ4, and stores the post- calibration conversion line TL2' in the storage section <NUM>.

In this way, with operating the wheel loader <NUM> actually, it is possible to acquire the actual angle of the bell crank <NUM> with respect to the boom <NUM> in each of the two postures in the operating region.

Therefore, it is possible to calibrate the bell crank angle conversion table that converts the detection voltage for detecting the angle of the bell crank <NUM> with respect to the boom <NUM> into the measurement angle.

(<NUM>)
In the method for calibrating the wheel loader <NUM> (an example of a work machine) of the present embodiment, in step S16, the bell crank angle conversion table T1 (an example of conversion value) is calibrated so that the bell crank angles θ1' and θ2' (an example of the measurement angle) match the bell crank angles θ1 and θ2 (an example of the actual angle).

As a result, the measurement value by the bell crank angle sensor <NUM> can be calibrated so as to correspond to the actual angle.

(<NUM>)
In the method for calibrating the wheel loader <NUM> (an example of a work machine) of the present embodiment, the conversion value is the bell crank angle conversion table T1 for converting the detection voltage (an example of the detection value) into the bell crank angle (measurement angle).

The measurement angle can be calibrated by rewriting the conversion table for converting the detection voltage to the measurement angle. The conversion value is not limited to the conversion table, and may be, for example, a conversion curve.

(<NUM>)
In the method for calibrating the wheel loader <NUM> (an example of a work machine) of the present embodiment, there are a plurality of bucket postures, and in steps S12 and S14, the detection voltages V1' and V2' for detecting the angle of the bell crank <NUM> with respect to the boom <NUM> in each of the plurality of bucket postures are output.

As a result, the bell crank angle conversion table T1 can be calibrated using the detection voltages at a plurality of points.

(<NUM>)
In the method for calibrating the wheel loader <NUM> (an example of a work machine) of the present embodiment, the plurality of bucket postures include the dump posture and the tilt posture. In steps S12 and S14, detection voltages V1' and V2' for detecting the angle of the bell crank <NUM> with respect to the boom <NUM> in each of the dump posture and the tilt posture are output.

Thereby, the bell crank angle conversion table T1 can be calibrated using the detection voltages in the dump posture and the tilt posture. In addition, the calibration standard is clarified, and error factors such as operation dependence can be eliminated from the operator, so that the calibration work can be performed reliably.

(<NUM>)
In the method for calibrating the wheel loader <NUM> (an example of a work machine) of the present embodiment, the dump posture and the tilt posture are the postures at the mechanism limit by the bell crank <NUM> or by the operation limit of the bucket cylinder <NUM>.

In this way, by using the mechanism limit or the cylinder movable limit, the calibration standard is clarified, and error factors such as operation dependence can be eliminated from the operator, so that the calibration work can be performed reliably.

(<NUM>)
In the method for calibrating the wheel loader <NUM> (an example of a work machine) of the present embodiment, the predetermined posture of the boom <NUM> is the posture in which the boom <NUM> is raised.

As a result, the calibration work can be performed using the bucket posture when the boom <NUM> is raised.

(<NUM>)
The controller <NUM> of the wheel loader <NUM> (an example of a work machine) of the present embodiment is a controller of the wheel loader <NUM> including the vehicle body <NUM> (an example of a main body), the boom <NUM> configured to drive with respect to the vehicle body <NUM>, the bucket <NUM> (an example of a work tool) connecting the boom <NUM> and configured to drive with respect to the boom <NUM>, the bucket cylinder <NUM> (an example of an actuator) connecting to the vehicle body <NUM> and the bucket <NUM> respectively and configured to drive the bucket <NUM>, and the bell crank <NUM> (an example of a sub-link) configured to transmit the drive of the bucket cylinder <NUM> to the bucket <NUM>, and includes the input section <NUM> (an example of an acquisition section), the display device <NUM> (an example of a display section), and the bell crank angle calibration section <NUM> (an example of a calibration section). The input section <NUM> acquires a detection voltage (an example of a detection value) for detecting the angle of the bell crank <NUM> with respect to the boom <NUM>. The display device <NUM> displays information for specifying the predetermined posture of the boom <NUM> and the bucket posture when calibrating the bell crank angle conversion table T1 (an example of a conversion value) for converting the detection voltage as the measurement angle of the bell crank <NUM> with respect to the boom <NUM>. The bell crank angle calibration section <NUM> calibrates the bell crank angle conversion table T1 by the relationship between the bell crank angles θ1 and θ2 (an example of the actual angle) in the specified bucket posture and the bell crank angles θ1' and θ2' (an example of the measurement angle) obtained by converting the detection voltages V1 ' and V2 ' in the specified predetermined posture of the boom <NUM> and the specified bucket posture, which are input based on the display of the display device <NUM>, based on the bell crank angle conversion table T1.

Therefore, it is possible to calibrate the bell crank angle conversion table for converting the detection voltage for detecting the angle of the bell crank <NUM> with respect to the boom <NUM> into the measurement angle.

(<NUM>)
The wheel loader <NUM> (an example of a work machine) of the present embodiment is an articulated wheel loader in which the front frame <NUM> and the rear frame <NUM> are connected, and includes the controller <NUM> and the bell crank angle sensor <NUM>. The bell crank angle sensor <NUM> transmits the detection voltage (an example of a detection value) for detecting the angle of the bell crank <NUM> with respect to the boom <NUM> to the controller <NUM> of the wheel loader <NUM>.

It is possible to provide a wheel loader <NUM> capable of calibrating the angle for detecting the angle of the bell crank <NUM> with respect to the boom <NUM>.

Further, in the above embodiment, for example, a potentiometer is used as the bell crank angle sensor <NUM>, but this is not the only option. An IMU (Inertial measurement unit) or the like may be used.

(D) In the above embodiment, the bell crank angle is calibrated in the state in which the bucket <NUM> is attached to the boom <NUM>, but the bucket <NUM> may not be attached.

(E) In the above embodiment, the angle of the bell crank shown in <FIG> is used as an example of the posture of the bell crank <NUM> with respect to the boom <NUM>, but if the posture of the bell crank <NUM> with respect to the boom <NUM> is uniquely determined, it is not limited to θb in <FIG>, and a combination of a plurality of angles may be used.

Claim 1:
A method for calibrating a work machine (<NUM>) comprising a main body (<NUM>), a boom (<NUM>) configured to drive with respect to the main body (<NUM>), a work tool (<NUM>) connecting to the boom (<NUM>), the work tool (<NUM>) being configured to drive with respect to the boom (<NUM>), an actuator (<NUM>) connecting to the main body (<NUM>) and the work tool (<NUM>) respectively, the actuator (<NUM>) being configured to drive the work tool (<NUM>), and a sub-link (<NUM>) configured to transmit drive of the actuator (<NUM>) to the work tool (<NUM>), wherein the method is characterized by:
an output step (S12, S14) of outputting a detection value (V1', V2') for detecting an angle of the sub-link (<NUM>) with respect to the boom (<NUM>) in a predetermined posture of the boom (<NUM>) and a work tool posture which are specified;
a conversion step (S15) of converting the detection value (V1', V2') as a measurement angle (θ1', θ2') of the sub-link (<NUM>) with respect to the boom (<NUM>) based on a conversion value (T1); and
a calibration step (S16) of calibrating the conversion value (T1) based on a relationship between the measurement angle (θ1', θ2') and an actual angle (θ1, θ2) in the work tool posture which is specified, wherein
there are a plurality of work tool postures,
in the output step (S12, S14) a detection value (V1', V2') for detecting the angle of the sub-link (<NUM>) with respect to the boom (<NUM>) in each of the plurality of work tool postures is output,
the plurality of work tool postures include a dump posture and a tilt posture, in the output step (S12, S14) a detection value for detecting the angle of the sub-link (<NUM>) with respect to the boom (<NUM>) in each of the dump posture and the tilt posture is output, and
the dump posture and the tilt posture are postures at a mechanism limit due to the sub-link (<NUM>) or an operation limit of the actuator (<NUM>).