WORKING MACHINE AND CONTROL METHOD FOR WORKING MACHINE

Abstract

A wheel loader (100) includes a traveling body (2) driven by the power of an engine (31), brake circuits (42a, 42b) with a multi-disc wet brake structure that brake the traveling body (2), an EPC valve (46) that controls the operation of the brake circuits (42a, 42b), and a controller (26) that outputs a control current for operating the EPC valve (46). The controller (26) has a calibration mode for outputting a command current and for calibrating the command current. The controller (26) determines whether a vehicle rest state exists and executes the calibration mode when the vehicle rest state exists.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a work machine and a control method for a work machine. STATE OF THE ART

[0002] Conventionally, for a wheel loader, which is an example of a work machine, an automatic stop system has been proposed that detects an obstacle behind the wheel loader and automatically stops the wheel loader (see, for example, Patent Document 1). In particular, a wheel loader or the like uses a hydraulically operated brake to perform braking based on a command from a controller. List of citationsPatent literature

[0003] Patent Document 1: JP 2022-150637 A SUMMARY OF THE INVENTIONTechnical Problem

[0004] In a wet brake with a multi-disc structure, which is commonly used in work machinery such as wheel loaders, a brake disc or the like wears over time, so the time or the like until the brake starts to brake changes. Since the braking characteristics of the brake change over time due to the deterioration of the disc structure, changes in the hydraulic oil due to the environment, and the like, as described above, it is necessary to take simple measures to deal with this change.

[0005] An object of the present disclosure is to solve the above-described problem and to provide a work machine and a control method for a work machine that can easily take measures corresponding to a change in the braking characteristics of a brake having a multi-disc wet brake structure. Solution to the problem

[0006] A work machine according to one aspect of the present disclosure includes: a traveling body configured to travel by power from a drive source; a brake circuit having a multi-disc wet brake structure configured to brake the traveling body; a control valve configured to control operation of the brake circuit; and a controller configured to output a command current for operating the control valve. The controller has a calibration mode for outputting the command current and calibrating the command current. The controller is configured to determine whether the work machine is in a vehicle rest state and to execute the calibration mode when the work machine is in the vehicle rest state.

[0007] A control method for a work machine according to one aspect of the present disclosure includes: a step of determining whether the work machine is in a vehicle rest state; a step of increasing a command current output to a control valve configured to control actuation of a brake circuit having a multi-disc wet brake structure and configured to brake a traveling body when the work machine is in the vehicle rest state; a step of detecting a pressure of hydraulic oil supplied to the brake circuit; a step of determining whether the pressure of the hydraulic oil reaches a predetermined value based on a detection result; and a step of storing the command current when the pressure of the hydraulic oil reaches a predetermined value. Advantageous effects of the invention

[0008] According to the present disclosure, it is possible to realize a work machine and a control method for a work machine that can easily take measures corresponding to a change in braking characteristics of a brake having a multi-disc wet brake structure. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view illustrating a configuration of a wheel loader 100 (an example of a work machine) according to an embodiment of the present disclosure. Fig. 2 is a block diagram showing a braking system for the wheel loader of Fig. 1 illustrates. Fig. 3 is a hydraulic circuit diagram showing a configuration of the braking device of Fig. 2 illustrates. Fig. 4 is a diagram explaining the structure of a brake circuit of Fig. 2. Fig. 5 is a diagram explaining an operation of the brake circuit of Fig. 2. Fig. 6 is a block diagram illustrating a configuration of a controller used in Fig. 2 is illustrated. Fig. 7 is a flowchart illustrating a control operation of the wheel loader 100 according to the embodiment. Fig. 8 is a diagram illustrating a state in which an object M is located behind the wheel loader 100 according to the embodiment. Fig. 9 is a diagram illustrating various types of information in a case where automatic braking is performed according to the embodiment. Fig. 10 is a diagram illustrating a relationship between a command current output to an EPC valve 46 and a pressure of hydraulic oil supplied to a shuttle valve unit 47 according to the embodiment. Fig. 11 is a flowchart of a calibration mode of the wheel loader 100 according to one embodiment. Fig. 12 is a subroutine flowchart of a calibration process by a calibration processing unit 92 according to the embodiment. Fig. 13 is a flowchart of another calibration mode of the wheel loader 100 according to an embodiment. DESCRIPTION OF EMBODIMENTS

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0010] In the specification and the drawings, identical or corresponding components are denoted by the same reference numerals, and redundant descriptions are omitted. In the drawings, the configuration may be omitted or simplified for the sake of simplicity of description. Furthermore, at least some of the embodiments and modifications can be arbitrarily combined with each other. Wheel loader configuration

[0011] A configuration of a wheel loader 100 in the present embodiment will be described with reference to Fig. 1 described.

[0012] Fig. 1 is a side view showing a configuration of the wheel loader 100 (an example of a work machine) according to an embodiment of the present disclosure. As shown in Fig. As illustrated in FIG. 1, the wheel loader 100 in the present embodiment includes a vehicle body 1 and an object sensor 25a. The vehicle body 1 includes a traveling body 2 and a work implement 3. The work implement 3 is mounted on the traveling body 2. The traveling body 2 includes a vehicle body frame 10, a pair of front tires 4, a cab 5, an engine compartment 6, a pair of rear tires 7, and a steering cylinder 9. The wheel loader 100 performs earth and sand loading work or the like using the work implement 3.

[0013] In the following description, “front,” “rear,” “right,” “left,” “up,” and “down” indicate directions based on a state in which an operator sitting on an operator seat 5s in the cab 5 looks forward. In Fig. 1, the forward-backward direction is indicated by Z, the forward direction is indicated by Zf, and the backward direction is indicated by Zb.

[0014] The vehicle body frame 10 is of the so-called articulated type (swing type) and includes a front frame 11, a rear frame 12, and a coupling shaft portion 13. The front frame 11 is arranged in the forward direction Zf of the rear frame 12. The coupling shaft portion 13 is provided at the center of the vehicle body frame 10 in the left-right direction (vehicle width direction) and pivotally couples the front frame 11 and the rear frame 12. The pair of front tires 4 are attached to the left and right of the front frame 11. The pair of rear tires 7 are attached to the left and right of the rear frame 12.

[0015] The working device 3 is driven by hydraulic oil from a working device pump (not illustrated). The working device 3 includes a boom 14, a bucket 15, a lifting cylinder 16, a bucket cylinder 17, and a bell crank 18. The boom 14 is attached to the front frame 11. The bucket 15 is attached to a distal end of the boom 14.

[0016] The lifting cylinder 16 and the bucket cylinder 17 are hydraulic cylinders. One end of the lifting cylinder 16 is attached to the front frame 11, and the other end of the lifting cylinder 16 is attached to the boom 14. The boom 14 swings up and down by extending and retracting the lifting cylinder 16. One end of the bucket cylinder 17 is attached to the front frame 11, and the other end of the bucket cylinder 17 is attached to the bucket 15 via a bell crank 18. When the bucket cylinder 17 extends and retracts, the bucket 15 swings up and down.

[0017] The cabin 5 is placed on the rear frame 12. Inside the cabin 5, the operator's seat 5s, on which the operator can sit, a steering wheel for steering, a lever for operating the working device 3, various switches, a display, and the like are arranged. The engine compartment 6 is arranged on the rear frame 12 in the rearward direction Zb of the cabin 5 and houses an engine 31 ( Fig. 2). Braking system for wheel loader 100

[0018] Next, with reference to Fig. 2 to 6, a braking system for the wheel loader 100 in the present embodiment is described.

[0019] Fig. 2 is a block diagram showing the braking system for the wheel loader of Fig. 1 illustrates. Fig. 3 is a hydraulic circuit diagram showing a configuration of the braking device of Fig. 2 illustrates. Fig. 4 is a diagram explaining the structure of a brake circuit of Fig. 2. Fig. 5 is a diagram explaining the operation of the brake circuit of Fig. 2. Fig. 6 is a block diagram illustrating a configuration of a controller used in Fig. 2 is illustrated.

[0020] As in Fig. 2, the braking system for the wheel loader 100 includes a driving device 21, a braking device 22, an operating device 23, an operating unit 24, a detecting device 25, and a controller 26.

[0021] The drive device 21 drives the wheel loader 100. The braking device 22 brakes the wheel loader 100. The operating device 23 is operated by an operator. The operating unit 24 performs an operation of both the work implement 3 and the steering system. The detection device 25 detects an object (obstacle) or the like around the vehicle body 1. The controller 26 actuates the drive device 21, the braking device 22, and the operating unit 24 based on the operator's operation of the operating device 23 and the detection by the detection device 25. Drive device 21

[0022] As in Fig. 2, the drive device 21 includes an engine 31, an HST 32, a transfer case 33, an axle 34, the front tire 4 and the rear tire 7.

[0023] The engine 31 is, for example, a diesel engine, and a driving force generated by the engine 31 drives a pump 32a of an HST (Hydro Static Transmission) 32.

[0024] The HST 32 includes the pump 32a, a motor 32b, and a hydraulic circuit 32c. The pump 32a, for example, is a variable-displacement swash plate pump, and the angle of the swash plate can be changed by a solenoid valve 32d. The pump 32a is driven by the motor 31 to discharge the hydraulic oil. The discharged hydraulic oil is supplied to the motor 32c through the hydraulic circuit 32b. The motor 32b, for example, is a swash plate pump, and the angle of the swash plate can be changed by a solenoid valve 32e.

[0025] The hydraulic circuit 32c connects the pump 32a and the motor 32b. The hydraulic circuit 32c includes a first drive circuit 32c1 and a second drive circuit 32c2. When hydraulic oil is supplied from the pump 32a to the motor 32b via the first drive circuit 32c1, the motor 32b is driven in one direction (for example, the forward direction). When hydraulic oil is supplied from the pump 32a to the motor 32b via the second drive circuit 32c2, the motor 32b is driven in the other direction (for example, the reverse direction). The discharge direction of the hydraulic oil to the first drive circuit 32c1 or the second drive circuit 32c2 can be changed by the solenoid valve 32d.

[0026] The transfer case 33 distributes the power of the engine 31 to the front and rear axles 34.

[0027] The pair of front tires 4 is connected to the front axle 34 and is rotated by the distributed power of the engine 31. The pair of rear tires 7 is connected to the rear axle 34 and is rotated by the distributed power of the engine 31. Braking device 22

[0028] The braking device 22 includes a brake unit 40 and a cut-off valve 45. The brake unit 40 brakes the vehicle body 1 based on an operation of the brake pedal 54 and performs automatic braking control of the vehicle body 1 based on a command from the controller 26. The cut-off valve 45 places the brake unit 40 in a state where the braking force can be applied or cannot be applied by the automatic braking control.

[0029] The brake unit 40 includes a brake valve unit 41, brake circuits 42a and 42b (an example of a service brake), a parking brake 43, hydraulic oil supply channels 44a and 44b, an EPC (electric proportional valve) 46, a shuttle valve unit 47, and a tank 48.

[0030] Accumulators, pumps, and the like are connected to the hydraulic oil supply channels 44a and 44b, and the hydraulic oil is supplied.

[0031] As in Fig. 3, the brake valve unit 41 is actuated by a brake pedal 54 to be described later. The brake valve unit 41 includes a rear wheel brake valve 41a and a front wheel brake valve 41b. Both the rear wheel brake valve 41a and the front wheel brake valve 41b are three-position, three-port directional control valves.

[0032] The first port of the rear wheel brake valve 41a is connected to the hydraulic oil supply channel 44a via the accumulator 49a. A second port of the rear wheel brake valve 41a is connected to the tank 48. The third port of the rear wheel brake valve 41a is connected to the rear shuttle valve 47a of the shuttle valve unit 47.

[0033] In the first state, the rear brake valve 41a connects the first port to the third port, connects the hydraulic oil supply channel 44a to the rear shuttle valve 47a, and supplies the hydraulic oil to the rear shuttle valve 47a. In the second state, the rear brake valve 41a closes all ports. In the third state, the rear brake valve 41a connects the second port to the third port and drains the hydraulic oil between the rear shuttle valve 47a and the rear brake valve 41a into the tank 48. In the second and third states, the rear brake valve 41a interrupts the hydraulic oil supply to the rear shuttle valve 47a.

[0034] The first port of the front wheel brake valve 41b is connected to the hydraulic oil supply channel 44b via the accumulator 49b. The second port of the front wheel brake valve 41b is connected to the tank 48. The third port of the front wheel brake valve 41b is connected to the front shuttle valve 47b of the shuttle valve unit 47.

[0035] In the first state, the front brake valve 41b connects the first port to the third port, connects the hydraulic oil supply passage 44b to the front shuttle valve 47b, and supplies the hydraulic oil to the front shuttle valve 47b. In the second state, the front brake valve 41b closes all ports. In the third state, the front brake valve 41b connects the second port to the third port and discharges the hydraulic oil between the front shuttle valve 47b and the front brake valve 41b into the tank 48. The front brake valve 41b interrupts the supply of hydraulic oil to the front shuttle valve 47b in the second and third states.

[0036] The opening degrees of the rear brake valve 41a and the front brake valve 41b are adjusted according to the degree of operation of the brake pedal 54, and the amount of hydraulic oil supplied to the shuttle valve unit 47 is changed. For example, when the degree of operation of the brake pedal 54 is large, the amount of hydraulic oil supplied from the rear brake valve 41a and the front brake valve 41b to the shuttle valve unit 47 increases.

[0037] The brake circuit 42a is provided on the rear axle 34 ( Fig. 2). The brake circuit 42a is connected to the rear shuttle valve 47a. The brake circuit 42b is provided on the front axle 34 ( Fig. 2). The brake circuit 42b is connected to the front shuttle valve 47b.

[0038] Brake circuits 42a and 42b are hydraulic brakes. The braking force of brake circuit 42a increases as the amount or pressure of the hydraulic oil supplied by the rear shuttle valve 47a increases. The braking force of brake circuit 42b increases as the amount or pressure of the hydraulic oil supplied by the front shuttle valve 47b increases.

[0039] The shut-off valve 45 is connected to the hydraulic oil supply channel 44b. The shut-off valve 45 is a four-port solenoid valve and has two states: an open state and a closed state. A first port of the shut-off valve 45 is connected to the hydraulic oil supply channel 44b. A second port of the shut-off valve 45 is connected to the tank 48. A third port of the shut-off valve 45 is connected to the EPC valve 46. A fourth port of the shut-off valve 45 allows air to pass through when open and is blocked when closed.

[0040] The shut-off valve 45 is opened and closed upon instruction from the controller 26. Specifically, the shut-off valve 45 transitions to an open state when activated by an open command from the controller 26 and transitions to a closed state when deactivated by a close command from the controller 26.

[0041] In the open state, the shut-off valve 45 connects the first port to the third port and supplies the hydraulic oil from the hydraulic oil supply passage 44b to the EPC valve 46. Furthermore, in the open state, the shut-off valve 45 connects the fourth port, through which air flows, to the second port connected to the tank 48.

[0042] When closed, the shutoff valve 45 connects the second port to the third port and drains the hydraulic oil between the shutoff valve 45 and the EPC valve 46 into the tank 48. When closed, the shutoff valve 45 closes the first port and the fourth port. Thus, when closed, the shutoff valve 45 stops the supply of hydraulic oil from the hydraulic oil supply channel 44b to the EPC valve 46.

[0043] In the present embodiment, the controller 26 brings the shutoff valve 45 into the open state only when the vehicle body 1 is traveling backward, for example. The backward movement of the vehicle body 1 is determined by the controller 26 based on the signal indicating the lever position in a direction changeover device 52 and the opening degree signal indicating the degree of accelerator pedal operation of an accelerator pedal 55.

[0044] The EPC valve 46 is arranged in a flow path connecting the shutoff valve 45 and the shuttle valve unit 47. The EPC valve 46 is a three-port solenoid valve. A first port of the EPC valve 46 is connected to the shutoff valve 45. A second port of the EPC valve 46 is connected to the tank 48. A third port of the EPC valve 46 is connected to the shuttle valve unit 47.

[0045] In the open state, the EPC valve 46 connects the first port to the third port and supplies the hydraulic oil supplied from the shutoff valve 45 to the shuttle valve unit 47. The opening degree of the EPC valve 46 is adjusted based on an instruction from the controller 26. By adjusting the opening degree of the EPC valve 46, the amount of hydraulic oil supplied to the shuttle valve unit 47 is changed.

[0046] When the EPC valve 46 is in the closed state, the first port is closed, the second port and the third port are connected, and the hydraulic oil in the flow path from the EPC valve 46 to the shuttle valve unit 47 is drained into the tank 48. Accordingly, when the EPC valve 46 is closed, it stops the supply of hydraulic oil from the shutoff valve 45 to the shuttle valve unit 47.

[0047] In the present embodiment, the controller 26 controls the EPC valve 46 to the open state when the wheel loader 100 travels in a predetermined direction (for example, the reverse direction Zb) and it is determined that the risk of collision with an object in the traveling direction is high.

[0048] The shuttle valve unit 47 includes the rear shuttle valve 47a and the front shuttle valve 47b. The rear shuttle valve 47a supplies the hydraulic oil to the brake circuit 42a at a higher pressure than the hydraulic oil supplied via the rear wheel brake valve 41a and the hydraulic oil supplied via the EPC valve 46. The front shuttle valve 47b supplies the hydraulic oil to the brake circuit 42b at a higher pressure than the hydraulic oil supplied via the front wheel brake valve 41b and the hydraulic oil supplied via the EPC valve 46.

[0049] With such a configuration, even when the brake pedal 54 is not depressed and no hydraulic oil is supplied from the brake valve unit 41, the hydraulic oil is supplied from the rear shuttle valve 47a and the front shuttle valve 47b to the brake circuits 42a and 42b, and automatic brake control is performed when the cut-off valve 45 and the EPC valve 46 are opened by the instruction from the controller 26. The brake that is switched between the braking state and the non-braking state by the brake circuits 42a and 42b is, for example, a wet all-disk brake.

[0050] As in Fig. 4, in this example, the structure of the rear brake circuit 42a is provided.

[0051] The multi-disc wet brake mainly includes a plurality of discs 89, a plate 85, a piston 83, an end plate 88, and a spring 84. The brake cylinder consists of a differential case 81 and a bearing support 82, in which a piston 83 is integrated. The plate 85 and the end plate 88 are coupled to a spline portion of the axle housing 87.

[0052] Each of the plurality of discs 89 is attached to an output shaft leading to the rear tire 7 via a spline portion. The plates 85 are interleaved with the discs 89 and are non-rotatably secured to the axle housing 87 by spline portions. The piston 83 is actuated by the oil pressure of the hydraulic oil supplied to the brake circuit 42a. Although the structure of the brake circuit 42a provided at the rear has been described, the structure of the multi-disc wet brake is the same as that of the brake circuit 42b provided in the front tire 4.

[0053] As in Fig. As illustrated in Fig. 5(A), when the hydraulic oil is supplied to the brake circuits 42a and 42b and enters the oil passage in the brake cylinder, the piston 83 is actuated toward the disc 89 by the oil pressure P of the hydraulic oil in the brake cylinder, thereby sandwiching the plate 85 between the plurality of discs 89. This places the wet all-disk brake in a braking state.

[0054] As in Fig. As illustrated in Figure 5(B), when the supply of hydraulic oil to the brake circuits 42a and 42b is stopped, the piston 83 returns to the original position by the repulsion force (restoring force) of the spring 84, and the pressure state between the plate 85 and the disc 89 is released. This brings the wet all-disc brake into a non-braking state.

[0055] As in Fig. As illustrated in Figure 2, the parking brake 43 is provided in the transfer case 33. For example, a wet solid disc brake that can switch between a braking state and a non-braking state, a disc brake, or the like can be used as the parking brake 43. Operating device 23

[0056] The operating device 23 is operated by an operator in the cabin 5 ( Fig. 1). The operating device 23 includes an implement operating unit 51, a travel direction switching device 52, a parking switch 53, a brake pedal 54, an accelerator pedal 55, an implement lock switch 56, and a calibration mode switch 57.

[0057] The work tool operating unit 51 is provided in the cab 5. The work tool operating unit 51 operates an operation of the work tool 3 and is, for example, an operation lever operated by an operator. The operation degree of the work tool operating unit 51 is detected, for example, by a potentiometer, a Hall sensor (integrated circuit), or the like. When the work tool operating unit 51 is operated, an operation signal indicating an operation degree of the work tool operating unit 51 is transmitted to the controller 26. The controller 26 transmits the operation signal as an operation command to the EPC valve 62 for the hoist cylinder 16 and the bucket cylinder 17.

[0058] The travel direction switching device 52 is provided in the cab 5. The operator operates the travel direction switching device 52 to adjust the travel direction of the wheel loader 100. The travel direction switching device 52 is, for example, an FNR lever. The FNR lever can assume the lever position of forward (F), neutral (N), or reverse (R). An operation signal indicating the lever position of the FNR lever is transmitted to the controller 26, and the controller 26 switches the travel direction to forward, neutral, or reverse by controlling the solenoid valve 32d.

[0059] A potentiometer can be used as the position detection sensor that detects the lever position of the FNR lever, or a switch can be provided for each of the forward drive position, the reverse drive position, and the neutral position. Furthermore, both the potentiometer and the switch can be configured so that erroneous operation can be detected even if one of the potentiometer and the switch is operated incorrectly.

[0060] The brake pedal 54 is provided in the cab 5. The brake pedal 54 adjusts the opening degree of the rear wheel brake valve 41a and the front wheel brake valve 41b of the brake valve unit 41.

[0061] The accelerator pedal 55 is provided in the cab 5. The operator operates the accelerator pedal 55 to adjust the throttle opening degree. The accelerator pedal 55 generates an opening degree signal indicating the degree of operation of the accelerator pedal and transmits the opening degree signal to the controller 26. The controller 26 controls the speed of the engine 31 based on the transmitted signal.

[0062] The parking switch 53 is provided in the cab 5 and is a switch whose state can be switched between on and off, and which transmits a signal indicating the state to the controller 26. The controller 26 sets the parking brake 43 to a braking state or a non-braking state based on the transmitted signal.

[0063] The work implement lock switch 56 is provided in the cab 5 and is a switch whose state can be switched between on and off, and which transmits a signal indicating the state to the controller 26. The controller 26 invalidates the operation signal for actuating the operation of the work implement 3 based on the transmitted signal. For example, when the work implement lock switch 56 is turned on, the controller 26 issues a closing command to the EPC valve 62 for the hoist cylinder 16 and the bucket cylinder 17. This closes the EPC valve 62, and the work implement 3 cannot be operated.

[0064] The calibration mode switch 57 is provided in the cab 5 and is a switch whose state can be switched between on and off and which transmits a signal indicating the state to the controller 26. Based on the transmitted signal, the controller 26 starts the execution of a manual calibration mode described later. Detection device 25

[0065] The detection device 25 includes an object sensor 25a and a pressure sensor 75.

[0066] The object sensor 25a detects an object (obstacle) in the vicinity of the vehicle body 1. The object sensor 25a detects an object located in the traveling direction of the wheel loader 100. More specifically, the object sensor 25a is a rear detection unit that detects an object requiring braking located in the reverse direction Zb of the vehicle body 1 when the wheel loader 100 travels in the reverse direction Zb. The object sensor 25a is a front detection unit that detects an object in the forward direction Zf of the vehicle body 1 when the wheel loader 100 travels in the forward direction Zf.

[0067] When the object sensor 25a is a rear detection unit, the rear detection unit is mounted, for example, at the rear end of the vehicle body 1 as shown in Fig. 1, but may also be mounted at a position other than the rear end. If the object sensor 25a is the front detection unit, the front detection unit may be mounted, for example, on the cab 5, the front frame 11, or other components.

[0068] The object sensor 25a is, for example, a LiDAR (Light Detection and Ranging) that emits laser light to detect information on an object. The object sensor 25a may be a radar (Radio Detection and Ranging) that detects information on a target object by emitting radio waves. The radar may, for example, be a millimeter-wave radar that uses a receiving antenna to detect a condition in which a radio wave in a millimeter-wave band emitted by a transmitting antenna is reflected from the surface of an object and returns. The object sensor 25a may be a visual sensor including a camera. The object sensor 25a may be an infrared sensor.

[0069] Information detected by the object sensor 25a is transmitted to the controller 26, and the controller 26 determines whether an object is present in the direction of travel of the vehicle body 1. Furthermore, the controller 26 calculates a distance to the detected object. Based on the distance to the detected object, or the like, the controller 26 can determine whether the risk of a collision between the vehicle body 1 and the object is high.

[0070] As in Fig. 3, the pressure sensor 75 detects the hydraulic pressure in the hydraulic circuit between the EPC valve 46 and the shuttle valve unit 47. In this example, the pressure sensor 75 detects the pressure of the hydraulic oil supplied to the shuttle valve unit 47.

[0071] As in Fig. 2, the information detected by the pressure sensor 75 is transmitted to the controller 26, and the controller 26 performs a calibration process based on the information in the calibration mode. Operating Unit 24

[0072] The operating unit 24 includes the lift cylinder 16, the bucket cylinder 17, the EPC valve 62, and the hydraulic pump 61. Part of the driving force of the engine 31 is transmitted to the hydraulic pump 61. The hydraulic pump 61 is driven by the engine and operates the lift cylinder 16 and the bucket cylinder 17 using the discharged hydraulic oil. The hydraulic oil discharged from the hydraulic pump 61 is supplied to the lift cylinder 16 and the bucket cylinder 17 via the EPC valve 62.

[0073] The EPC valve 62 is opened and closed upon command from the controller 26. Specifically, the EPC valve 62 transitions to an open state when activated by an open command from the controller 26 and transitions to a closed state when deactivated by a close command from the controller 26.

[0074] When open, the EPC valve 62 connects the hydraulic pump 61 and the lifting cylinder 16 and bucket cylinder 17, and supplies the hydraulic oil from the hydraulic pump 61 to the lifting cylinder 16 and bucket cylinder 17. When closed, the EPC valve 62 stops the supply of hydraulic oil from the hydraulic pump 61 to the lifting cylinder 16 and bucket cylinder 17. Control 26

[0075] The controller 26 includes a processor, a memory, and storage. The processor is, for example, a CPU (Central Processing Unit). The memory includes, for example, a non-volatile memory such as a ROM (Read Only Memory) and a volatile memory such as a RAM (Random Access Memory).

[0076] Each of the controller 26 and the operating device 23 may be mounted on the wheel loader 100 or may be arranged outside and away from the wheel loader 100. When the controller 26 and the operating device 23 are each arranged outside and away from the wheel loader 100, the controller 26 and the operating device 23 may each be wirelessly connected to the drive device 21, the braking device 22, the operating device 23, the detection device 25, and the like. The controller 26 may be stored in a server that is remote from the wheel loader 100. Furthermore, since the operating device 23 is separate from the wheel loader 100, the operator can operate the wheel loader 100 remotely without having to enter the cab 5 of the wheel loader 100.

[0077] The controller 26 reads a program stored in memory, expands the program in the working memory, and executes a predetermined process according to the program. The controller 26 can be divided into a collision detection controller and an HST controller. The collision detection controller and the HST controller can have different CPUs. Alternatively, the computer program can be distributed to the controller 26 via a network.

[0078] As in Fig. 6, the controller 26 includes, for example, a detection controller 180, a vehicle body controller 90, and an engine controller 74.

[0079] The detection controller 180, the vehicle body controller 90, and the engine controller 74 each include a processor such as a CPU (Central Processing Unit), a main memory including a non-volatile memory such as a ROM (Read Only Memory) and a volatile memory such as a RAM (Random Access Memory), and storage.

[0080] The recognition controller 180, the vehicle body controller 90, and the engine controller 74 read a program stored in the memory, expand the program in the main memory, and execute predetermined processing according to the program. In the embodiment, it is described that the recognition controller 180, the vehicle body controller 90, and the engine controller 74 each have a CPU, but the recognition controller 180, the vehicle body controller 90, and the engine controller 74 may all have a CPU. Furthermore, the program can be distributed to the recognition controller 180, the vehicle body controller 90, and the engine controller 74 via a network.

[0081] The engine control 74 controls the state of the engine 31 ( Fig. 2). Specifically, the rotational speed of the engine 31 is controlled. The engine controller 74 notifies a rest state determination unit 91 of the vehicle body controller 90, which will be described later, of the operating state of the engine 31. For example, the engine controller 74 notifies the rest state determination unit 91 of an operating state in which work is being performed and a rest state in which work is stopped as the operating state of the engine 31.

[0082] The detection controller 180 detects the presence of an object based on the information detected by the object sensor 25a.

[0083] The vehicle body controller 90 controls the automatic brake based on the detection result of the detection controller 180.

[0084] The recognition controller 180 includes an object information acquisition unit 181 and an object determination unit 182.

[0085] The object information acquisition unit 181 acquires information regarding the rear side detected by the object sensor 25a. The object determination unit 182 determines whether an object is present on the rear side based on the acquired information regarding the rear side. The determination result of the object determination unit 182 is transmitted to the EPC valve control unit 94 described later.

[0086] The vehicle body controller 90 includes the rest state determination unit 91, the calibration processing unit 92, and the EPC valve control unit 94.

[0087] In this embodiment, automatic braking control is performed when an object is detected at the rear during reversing. For example, even in a stopped state where the front tire 4 and the rear tire 7 are not rotating, it can be determined that the vehicle body 1 is in the reverse state if the direction changeover device 52 is in the reverse position.

[0088] When it is determined that the vehicle body 1 is moving backward and the object determination unit 182 determines that there is an object behind the vehicle body 1, the EPC valve control unit 94 outputs a command current serving as an opening command to the EPC valve 46. The opening degree of the EPC valve 46 is adjusted by a command current. In this example, it is set in advance to a predetermined value (described later). The adjustment may be performed based on the distance to the detected object. For example, the deceleration at which the vehicle stops before the object may be calculated from the distance to the detected object, and the EPC valve control unit 94 may transmit an opening command (command current) to the EPC valve 46 to achieve an opening degree at which deceleration occurs.

[0089] The solenoid of the EPC valve 46 is opened based on the opening command (command current), and hydraulic oil is supplied from the EPC valve 46 to the rear shuttle valve 47a and the front shuttle valve 47b. In the rear shuttle valve 47a, either the hydraulic oil from the rear brake valve 41a or the hydraulic oil from the EPC valve 46, which has a higher pressure, is supplied to the brake circuit 42a to apply braking force. Furthermore, in the front shuttle valve 47b, either the hydraulic oil from the front brake valve 41b or the hydraulic oil from the EPC valve 46, which has a higher pressure, is supplied to the brake circuit 42a to apply braking force. As a result, automatic braking is performed and braking force is applied even when the brake pedal 54 is not depressed by the driver. As described later, Fig. 7, the vehicle body 1 can stop in front of the object M. The vehicle body 1 in the stopped state is indicated by a dashed two-dot line.

[0090] Even if the braking force is not applied by the automatic brake, the brake circuits 42a and 42b are actuated when the operator depresses the brake pedal 54 and the hydraulic oil is supplied from the brake valve unit 41 to the shuttle valve unit 47.

[0091] The idle state determination unit 91 determines whether the wheel loader 100 is in the vehicle idle state. Specifically, the idle state determination unit 91 determines whether it is the vehicle idle state based on an operating state of the engine from the engine controller 74, the state of the work implement lock switch 56, and the state of the parking switch 53. For example, the idle state determination unit 91 determines that it is the vehicle idle state based on the operating state of the engine from the engine controller 74 being the idle state, the state of the work implement lock switch 56 being the on state, and the state of the parking switch being the on state.

[0092] The calibration processing unit 92 executes the calibration mode when the vehicle is in the rest state based on the determination result of the rest state determination unit 91. The calibration mode is a process of calibrating a command current serving as an opening command for the EPC valve 46 based on the detection result of the pressure sensor 75. The calibration mode in the calibration processing unit 92 will be described later. Operation

[0093] Next, a control operation of the wheel loader 100 according to the embodiment will be described.

[0094] Fig. 7 is a flowchart illustrating a control process of the wheel loader 100 according to the embodiment. As shown in Fig. 6, the object determination unit 182 determines whether an object is present behind the vehicle body 1 (step S2: Fig. 7).

[0095] If the object determination unit 182 determines in step S2 that an object is present behind the vehicle body 1 (YES in step S2), the EPC valve control unit 94 transmits an opening command (command current) to the EPC valve 46 (step S4: Fig. 7). As a result, the solenoid of the EPC valve 46 is actuated to open the EPC valve 46, and the hydraulic oil is supplied from the EPC valve 46 to the brake circuits 42a and 42b via the rear shuttle valve 47a and the front shuttle valve 47b, so that the braking force is applied by the automatic brake.

[0096] Then the process is terminated (END: Fig. 7).

[0097] On the other hand, if the object determination unit 182 determines in step S2 that there is no object behind the vehicle body 1 (NO in step S2), the state of step S2 is maintained.

[0098] Fig. 8 is a diagram illustrating a state in which an object M is located behind the wheel loader 100 according to the embodiment. As shown in Fig. As illustrated in Fig. 8, in a state where the vehicle body 1 is reversing, the vehicle body 1 can be stopped in front of the object M by the automatic brake when the object M is detected at the rear.

[0099] Fig. 9 is a diagram illustrating various types of information in a case where automatic braking is performed according to the embodiment.

[0100] Fig. 9(A) illustrates the detection distances between the object M detected by the object sensor 25a and the vehicle body 1. In this example, braking is started when the distance between the vehicle body 1 and the object M becomes Ds. More specifically, a case is illustrated where the distance between the vehicle body 1 and the object M becomes Ds at a time T1.

[0101] Fig. 9(B) illustrates the command current Is for controlling the EPC valve 46. More specifically, a case is illustrated in which the command current is controlled by feedforward to become Is after the time T1.

[0102] Fig. 9(C) illustrates the pressure of the hydraulic oil supplied to the shuttle valve unit 47. In this example, the hydraulic oil pressure is controlled to Ps with respect to the command current Is. Automatic braking control is performed by the brake circuits 42a and 42b according to the hydraulic oil supplied to the shuttle valve unit 47.

[0103] Fig. 9(D) illustrates the vehicle speed of the vehicle body 1. In this example, a case is illustrated where, in a state where the vehicle body 1 is traveling backward at a vehicle speed Vs, the vehicle speed is gradually reduced by the control of the automatic brake and the vehicle body 1 stops. Calibration mode

[0104] Fig. 10 is a diagram illustrating a relationship between the command current output to the EPC valve 46 and the pressure of the hydraulic oil supplied to the shuttle valve unit 47 according to the embodiment.

[0105] As in Fig. As illustrated in Figure 10, the braking characteristics of the brake change due to the deterioration of the disc structure over time, the change in the hydraulic oil due to the environment, and the like. That is, the pressure of the hydraulic oil fluctuates with respect to a command current value due to the deterioration of the disc structure over time or the like. In particular, in the brake with the Fig. 4 and Fig. In the multi-disk wet brake structure illustrated in Fig. 5, the gap between the plate 85 and the disc 89 increases as the brake disc or the like wears over time.

[0106] For this reason, as in Fig. 10 illustrates, in order to maintain the same hydraulic oil pressure Ps as the initial pressure after deterioration over time, it is necessary to output a command current Im to the EPC valve 46 that is larger than the initial command current Is. Therefore, it is necessary to calibrate the command current so that a measure corresponding to the change in the braking characteristic of the brake having a multi-disc wet brake structure can be easily taken.

[0107] Furthermore, the spring properties of the return spring 46a in the EPC valve 46, which is in Fig. 3, during initial operation (for example, after approximately 100 hours). When the spring characteristic of the return spring 46a changes, the pressure of the hydraulic oil supplied to the brake circuits 42a and 42b via the EPC valve 46 changes. Therefore, it is necessary to calibrate the command current in order to smoothly take appropriate action when the braking characteristic of the brake changes.

[0108] In this regard, in the calibration mode of the embodiment, the command current is increased, and the command current at which the pressure of the hydraulic oil supplied to the shuttle valve unit 47 becomes Ps is detected. By repeatedly executing the calibration mode, it is possible to easily take measures corresponding to a change in the braking performance of the brake with a multi-disk wet brake structure.

[0109] Fig. 11(A) and Fig. 11(B) are flowcharts of the calibration mode of the wheel loader 100 according to the embodiment. Fig. 11(A) illustrates a flowchart of automatic calibration and Fig. Figure 11(B) illustrates a flowchart of manual calibration. Automatic calibration refers to calibration performed based on a calibration work command issued by the controller 26 itself. Manual calibration is calibration performed based on a calibration work command input by an operator.

[0110] As in Fig. 11(A), during automatic calibration, it is determined whether the usage frequency of the work machine is high or low. To determine whether the usage frequency is high or low, it is determined, for example, whether a predetermined time has passed since the previous calibration work (step S10A). The predetermined time may be set to 100 hours, for example. In addition, when determining the usage frequency, it may be determined whether the usage frequency (the number of uses) of the brake is equal to or greater than a predetermined number. The determination of whether the usage frequency is high or low is performed by the calibration processing unit 92 ( Fig. 6). If, in this determination, it is determined that the usage frequency is low (for example, a predetermined time has not passed since the previous calibration or the number of brake uses is less than a predetermined number), the determination of step S10A is repeated. On the other hand, if, in this determination, it is determined that the usage frequency is high (for example, a predetermined time has passed since the last calibration or the number of brake uses is equal to or greater than a predetermined number), the idle state determination unit 91 determines whether the wheel loader 100 is in the vehicle idle state (step S11).The rest state determination unit 91 determines that it is the vehicle rest state based on the operation state of the engine from the engine controller 74 being the working state, the state of the work implement lock switch 56 being the on state, and the state of the parking switch being the on state.

[0111] Next, in step S11, if the idle state determination unit 91 determines that the wheel loader 100 is in the vehicle idle state (YES in step S11), the idle state determination unit 91 instructs the calibration processing unit 92, and the calibration processing unit 92 executes the calibration processing (step S12). Accordingly, the calibration work is automatically performed, for example, in a warm-up state after the engine 31 is started, and the operator is not required to perform the calibration work. Therefore, the braking characteristics of the brake can be ensured without increasing the operator's workload.

[0112] As in Fig. As illustrated in Fig. 11(B), for example, in manual calibration, it is determined whether there is a calibration work command from the operator (step S10B). The operator's calibration work command may be, for example, a case where the operator instructs the calibration work in a service menu of a monitor. In this determination, the determination of step S10A is repeated when there is no calibration work command from the operator. On the other hand, if it is determined in this determination that the operator's calibration work command is present, the idle state determination unit 91 determines whether the wheel loader 100 is in the vehicle idle state (step S11). The subsequent steps of manual calibration are the same as those of automatic calibration, and the description thereof will not be repeated.

[0113] Fig. 12 is a subroutine flowchart of the calibration process by the calibration processing unit 92 according to the embodiment.

[0114] With reference to Fig. 12, the calibration processing unit 92 increases the command current to be output to the EPC valve 46 (step S14).

[0115] Next, the calibration processing unit 92 detects the pressure of the hydraulic oil supplied to the shuttle valve unit 47 from the pressure sensor 75 (step S15).

[0116] Next, the calibration processing unit 92 stops outputting the command current to the EPC valve 46 when the command current value reaches the maximum value (step S16).

[0117] After the output of the command current to the EPC valve 46 is stopped in step S16, the calibration processing unit 92 recognizes the command current after calibration from the relationship between the command current value and the pressure of the hydraulic oil (step S17).

[0118] Next, the calibration processing unit 92 stores the detected command current values ​​after calibration (step S18).

[0119] The calibration process is then terminated (return). This terminates the calibration mode process.

[0120] Through the above calibration process, it is possible to adjust the command current at which the pressure of the hydraulic oil Ps supplied to the shuttle valve unit 47 becomes ( Fig. 10), even if the braking characteristics of the brake change due to deterioration over time or the like.

[0121] In this example, the wheel loader 100 automatically performs the command current calibration process when the wheel loader 100 is in the vehicle idle state. This makes it possible to maintain the accuracy of the braking characteristics of the brake with a multi-disk wet disc structure.

[0122] Furthermore, by setting the vehicle stop conditions of the implement lock and the parking brake engaged as calibration conditions, it is possible to increase the frequency of automatic calibration work based on the controller's determination. This ensures the braking performance without increasing the operator's time and effort.

[0123] Fig. 13 is a flowchart of another calibration mode of the wheel loader 100 according to an embodiment. As shown in Fig. As illustrated in Figure 13, the calibration processing unit 92 determines whether an instruction to execute the calibration mode is present (step S20). When the calibration mode switch 57 is turned on, the calibration processing unit 92 determines that an instruction to execute the calibration mode is present.

[0124] Next, in step S20, the calibration processing unit 92 executes the calibration processing (step S22) if the calibration processing unit 92 determines that there is an instruction to execute the calibration mode (YES in step S20). The details of the calibration process are the same as in the example described with reference to Fig. 12 described process.

[0125] Specifically, the calibration processing unit 92 increases the command current output to the EPC valve 46 and detects the command current at which the pressure of the hydraulic oil supplied to the shuttle valve unit 47 becomes Ps. The detected command current is stored.

[0126] Then the calibration mode process is ended (END)

[0127] Through this process, the wheel loader 100 executes the command current calibration process when the operator operates the calibration mode switch 57 to turn on the calibration mode switch 57. Therefore, the operator can maintain the accuracy of the braking performance of the multi-disc wet brake structure at the provided time. Other embodiments

[0128] In the embodiment described above, an HST32 is used as the drive device 21. Furthermore, not only the HST but also an HMT (hydromechanical transmission) can be used.

[0129] The wheel loader of the above embodiment can be operated by an operator on board or operated unmanned.

[0130] In the above embodiment, the wheel loader was described as an example of the work machine, but the work machine is not limited to the wheel loader and may also be a hydraulic excavator or the like.

[0131] In the embodiment, the case where automatic braking is performed when the presence of an object on the rear is detected by the detection controller 180 at the time of backward movement has been described, but the invention of the present application can also be applied to a configuration in which automatic braking is performed not only at the time of backward movement but also at the time of forward movement. Attachments

[0132] The embodiments described above include the following technical ideas. Appendix 1

[0133] Work machine that includes: a traveling body (2) configured to travel with the power of a drive source (31); Brake circuits (42a, 42b) having a multi-disc wet brake structure configured to brake the vehicle body; a control valve (46a) configured to control operation of the brake circuit; and a controller (26) configured to output a command current for operating the control valve, wherein the controller has a calibration mode for outputting the command current and for calibrating the command current, and the control is configured to Determine whether the work machine is in a vehicle idle state and execute calibration mode if the work machine is in the vehicle idle state. Appendix 2

[0134] The working machine according to Annex 1, which includes: a parking brake (43); and a work implement lock switch (56) configured to invalidate an operation signal of a work implement, wherein The controller determines whether the work machine is in the vehicle idle state based on an operating state of the power source, a state of the parking brake, and a state of the work device lock switch. Appendix 3

[0135] The working machine according to Annex 1 or 2, where the controller has a manual calibration mode in which an operating instruction is received, the command stream is output, and the command stream is calibrated. Appendix 4

[0136] The work machine according to any one of Appendices 1 to 3, further including a sensor (75) configured to measure a hydraulic pressure when hydraulic oil is supplied to the brake circuit, wherein the controller increases a value of the command current and stores a current value when the hydraulic pressure of the sensor reaches a predetermined value. Appendix 5

[0137] The work machine according to any one of Annexes 1 to 4, further including an object sensor (25a) configured to detect an object around the traveling body, wherein the controller outputs the command stream based on a detection result of the object detection sensor in a case other than the calibration mode. Appendix 6

[0138] The working machine according to one of Annexes 1 to 5, where the controller determines whether the work machine is in the vehicle idle state based on a calibration work command issued by the controller or a calibration work command entered by an operator. Appendix 7

[0139] The working machine according to Annex 6, wherein the controller issues the calibration work command based on a determination result of whether a use frequency of the working machine is high or low. Appendix 8

[0140] A control method for a work machine, including a step of determining (S10) whether the work machine is in a vehicle rest state; a step of increasing (S14) a command current output to a control valve (43) configured to control actuation of the brake circuit (42a, 42b) having a multi-disc wet brake structure configured to brake a traveling body (2) when the work machine is in the vehicle rest state; a step of detecting (S15) a pressure of a hydraulic oil supplied to the brake circuit; a step of determining (S16) whether the pressure of the hydraulic oil reaches a predetermined value based on a detection result; and a step of storing (S18) the command current when the pressure of the hydraulic oil reaches a predetermined value. Although certain embodiments have been described, these are merely examples and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims and is intended to include any modifications within the meaning and scope of the claims. List of reference symbols

[0141] 1 Vehicle body, 2 Traveling body, 3 Working device, 4 Front tire, 5 Cabin, 5s Operator's seat, 6 Engine compartment, 7 Rear tire, 9 Steering cylinder, 10 Vehicle body frame, 11 Front frame, 12 Rear frame, 13 Coupling shaft section, 14 Boom, 15 Bucket, 16 Lift cylinder, 17 Bucket cylinder, 18 Bellows, 21 Drive device, 22 Brake device, 23 Operating device, 24 Operating unit, 25 Detection device, 25a Object sensor, 26 Controller, 31 Motor, 40 Brake unit, 41 Brake valve unit, 41a Rear wheel brake valve, 41b Front wheel brake valve, 42a, 42b Brake circuit, 43 Parking brake, 44a, 44b Hydraulic oil supply passage, 45 Shut-off valve, 46, 62 EPC valve, 46a Return spring, 47 Shuttle valve unit, 47a Rear shuttle valve, 47b Front shuttle valve, 48 Tank, 49a, 49b Accumulator, 51 Implement control unit, 52 Travel direction changeover device, 53 Parking switch, 54 Brake pedal, 55 Accelerator pedal, 56 Implement lock switch, 57 Calibration mode switch, 61 Hydraulic pump,74 Engine control, 75 Pressure sensor, 90 Vehicle body control, 91 Rest state determination unit, 92 Calibration processing unit, 94 EPC valve control unit, 100 Wheel loader, 180 Detection control, 181 Object information acquisition unit, 182 Object determination unit., QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2022-150637 A

[0003]

Claims

[1] Work machine, comprising: a traveling body configured to travel by power from a power source; a brake circuit having a multi-disc wet brake structure configured to brake the traveling body; a control valve configured to control operation of the brake circuit; and a controller configured to output a command current for operating the control valve, wherein the controller has a calibration mode for outputting the command current and for calibrating the command current, and the control is configured to Determine whether the work machine is in a vehicle rest state and Execute calibration mode when the work machine is in the vehicle idle state. [2] Working machine according to claim 1, comprising: a parking brake; and a work tool lock switch configured to invalidate an operation signal of a work tool, wherein the controller determines whether the work machine is in the vehicle idle state based on an operating state of the power source, a state of the parking brake, and a state of the work implement lock switch. [3] Working machine according to claim 1, wherein the controller has a manual calibration mode in which an operating instruction is received, the command stream is output, and the command stream is calibrated. [4] The work machine according to claim 1, further comprising a sensor configured to measure a hydraulic pressure when hydraulic oil is supplied to the brake circuit, wherein the controller increases a value of the command current and stores a current value when the hydraulic pressure of the sensor reaches a predetermined value. [5] The work machine according to claim 1, further comprising an object sensor configured to detect an object around the traveling body, wherein the controller outputs the command stream based on a detection result of the object sensor in a case other than the calibration mode. [6] Working machine according to claim 1, wherein the controller determines whether the work machine is in the vehicle idle state based on a calibration work command issued by the controller or a calibration work command input by an operator. [7] Working machine according to claim 6, wherein the controller issues the calibration work command based on a determination result of whether a usage frequency in the working machine is high or low. [8] Control method for a work machine, comprising Determine whether the work machine is in a vehicle idle state; Increasing a command current output to a control valve configured to control operation of a brake circuit having a multi-disc wet brake structure configured to brake a traveling body when the work machine is in the vehicle rest state; Detecting a pressure of a hydraulic oil supplied to the brake circuit; determining whether the pressure of the hydraulic oil reaches a predetermined value based on a detection result; and Storing the command current when the hydraulic oil pressure reaches a predetermined value.

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