Work machine, system for work machine, and method for controlling work machine

Abstract

A vehicle body (1) can travel. A vehicle speed sensor (24) detects the vehicle speed of the vehicle body (1). A braking operation device (51A) outputs a braking signal for the vehicle body by being operated by an operator. An object sensor (25) detects an object behind the vehicle body (1). An automatic brake device (45) applies brakes on the vehicle body (1) by means of an automatic brake on the basis of the detection result of the object sensor (25). A controller (26) outputs an automatic braking instruction for applying brakes on the vehicle body (1) by the operation of the automatic brake device (45), and then cancels the operation of the automatic brake device (45) on the basis of the vehicle speed and the braking signal.

Description

Work machine, work machine system, and work machine control method

[0001] The present disclosure relates to a work machine, a system for a work machine, and a method for controlling a work machine.

[0002] Conventionally, automatic braking systems have been proposed for wheel loaders, which are an example of construction machines, that detect obstacles behind the loader and automatically stop the machine. For example, Japanese Patent Application Laid-Open No. 2019-31823 (Patent Document 1) discloses a technology in which, even if the construction machine automatically stops in such an automatic braking system, the automatic stop can be released by operating an emergency brake release switch, allowing the machine to move again.

[0003] JP 2019-31823 A

[0004] However, when releasing the emergency brake release switch as in Patent Document 1, it is difficult to respond when the operator makes an unintended action, such as the work machine starting to move the moment the automatic braking control is released.

[0005] One object of the present disclosure is to provide a work machine, a work machine system, and a work machine control method that can easily take appropriate action even when the work machine performs an operation unintended by the operator in relation to automatic braking control.

[0006] Furthermore, in Patent Document 1, no consideration is given to the possibility of erroneous detection of an object (obstacle) when the work machine is traveling at high speed during automatic braking control.

[0007] Another object of the present disclosure is to provide a work machine, a work machine system, and a work machine control method that can easily and appropriately respond to erroneous object detection when traveling at high speeds during automatic braking control.

[0008] A work machine and a work machine system according to the present disclosure each include a vehicle body, a vehicle speed sensor, a brake operation device, an object sensor, an automatic braking device, and a controller. The vehicle body is capable of traveling. The vehicle speed sensor detects the speed of the vehicle body. The brake operation device outputs a braking signal for the vehicle body when operated by an operator. The object sensor detects objects behind the vehicle body. The automatic braking device brakes the vehicle body by automatic braking based on the detection result of the object sensor. The controller outputs an automatic braking command to brake the vehicle body by activating the automatic braking device, and then releases activation of the automatic braking device based on the vehicle speed and the braking signal.

[0009] One control method for a work machine disclosed herein is a control method for a work machine having a drivable vehicle body, a brake operating device that outputs a braking signal for the vehicle body when operated by an operator, and an automatic braking device that automatically brakes the vehicle body based on the detection result of an object behind the vehicle body, and includes the following steps.

[0010] An automatic braking command is output to brake the vehicle body by operating the automatic braking device. After the automatic braking command is output, the operation of the automatic braking device is released based on the vehicle speed and the braking signal of the vehicle body.

[0011] Each of the other work machines and work machine systems disclosed herein includes a vehicle body, a vehicle speed sensor, a forward / reverse switching device, an object sensor, an automatic braking device, a release device, and a controller. The vehicle body is capable of traveling. The vehicle speed sensor detects the vehicle speed of the vehicle body. The forward / reverse switching device switches the traveling direction of the vehicle body. The object sensor detects objects behind the vehicle body. The automatic braking device brakes the vehicle body by automatic braking based on the detection result of the object sensor. The release device outputs a release signal that is operated by an operator to temporarily disable operation of the automatic braking device. When the automatic braking device is activated while the vehicle body is traveling, the controller releases operation of the automatic braking device based on an operation signal indicating reverse from the forward / reverse switching device, the vehicle speed detected by the vehicle speed sensor, and the release signal output from the release device.

[0012] Another control method for a work machine disclosed herein is a control method for a work machine having a drivable body and an automatic braking device that automatically brakes the body based on the detection result of an object behind the body, and includes the following steps.

[0013] The automatic braking device is activated while the vehicle is traveling, and is deactivated based on an operation signal indicating that the vehicle is traveling in reverse, the vehicle speed, and a deactivation signal that temporarily disables the activation of the automatic braking device by the operator.

[0014] According to one aspect of the present disclosure, it is possible to realize a work machine, a work machine system, and a work machine control method that can easily take appropriate action even when the work machine performs an operation unintended by the operator in relation to automatic braking control.

[0015] According to another aspect of the present disclosure, it is possible to realize a work machine, a work machine system, and a work machine control method that can easily and appropriately respond to erroneous object detection when traveling at high speeds during automatic braking control.

[0016] Fig. 2 is a side view showing the configuration of a wheel loader according to an embodiment of the present disclosure. Fig. 3 is a block diagram showing a braking system of the wheel loader of Fig. 1. Fig. 4 is a hydraulic circuit diagram showing the configuration of the braking device of Fig. 2. Fig. 5 is a diagram showing the arrangement positions of a forward / reverse switching device, a release device, an accelerator, and a brake pedal. Fig. 6 is a flow chart showing a control method for a wheel loader according to an embodiment of the present disclosure.

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the specification and drawings, identical or corresponding components are designated by the same reference numerals, and redundant explanations will not be repeated. In addition, in the drawings, configurations may be omitted or simplified for the sake of convenience.

[0018] <Configuration of Wheel Loader 100> The configuration of a wheel loader 100 in this embodiment will be described with reference to FIG.

[0019] FIG. 1 is a side view showing the configuration of a wheel loader 100 (an example of a work machine) according to an embodiment of the present disclosure. As shown in FIG. 1, the wheel loader 100 according to this embodiment has a vehicle body (car body) 1 and an object sensor 25. The vehicle body 1 is capable of traveling. The vehicle body 1 has a traveling body 2 and a work implement 3. The work implement 3 is disposed on the traveling body 2. The traveling body 2 has a 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 work such as loading earth and sand using the work implement 3.

[0020] In the following description, the terms "front," "rear," "right," "left," "up," and "down" refer to directions based on the state seen from the operator seated in the driver's seat 5s in the cab 5. In Fig. 1, the fore-and-aft direction is indicated by Z, with Zf indicating the front direction and Zb indicating the rear direction.

[0021] The body frame 10 is of a so-called articulated type and includes a front frame 11, a rear frame 12, and a connecting shaft 13. The front frame 11 is disposed in the forward direction Zf of the rear frame 12. The connecting shaft 13 is provided in the center of the body frame 10 in the left-right direction (vehicle width direction), and connects the front frame 11 and the rear frame 12 to each other so that they can rotate. A pair of front tires 4 are attached to the left and right of the front frame 11. Furthermore, a pair of rear tires 7 are attached to the left and right of the rear frame 12.

[0022] The work implement 3 is driven by hydraulic oil from a work implement pump (not shown). The work implement 3 has a boom 14, a bucket 15, a lift 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 the tip of the boom 14.

[0023] The lift cylinder 16 and the bucket cylinder 17 are hydraulic cylinders. One end of the lift cylinder 16 is attached to the front frame 11, and the other end of the lift cylinder 16 is attached to the boom 14. The boom 14 rotates up and down as the lift cylinder 16 extends and retracts. 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. The bucket 15 rotates up and down as the bucket cylinder 17 extends and retracts.

[0024] The cab 5 is mounted on the rear frame 12. Inside the cab 5, there are arranged a driver's seat 5s for an operator to sit in, a handle for steering, levers for operating the work implement 3, various switches, display devices, etc. The engine room 6 is arranged on the rear frame 12 in the rear direction Zb of the cab 5, and houses an engine 31.

[0025] <Brake System of Wheel Loader 100> Next, the brake system of the wheel loader 100 in this embodiment will be described with reference to Figs. 2 to 4.

[0026] Fig. 2 is a block diagram showing the braking system of the wheel loader of Fig. 1. Fig. 3 is a hydraulic circuit diagram showing the configuration of the braking device of Fig. 2. Fig. 4 is a diagram showing the positions of the forward / reverse switching device, the release device, the accelerator pedal, and the brake pedal.

[0027] As shown in FIG. 2 , the braking system of the wheel loader 100 has a drive device 21 , a brake device 22 , an operation device 23 , a vehicle speed sensor 24 , an object sensor 25 , and a controller 26 .

[0028] The drive device 21 drives the wheel loader 100. The brake device 22 brakes the vehicle body 1. The operation device 23 is operated by an operator. The vehicle speed sensor 24 detects the vehicle speed (traveling speed) of the vehicle body 1. The object sensor 25 detects objects (obstacles) around the vehicle body 1. The controller 26 operates the drive device 21 and the brake device 22 based on the operator's operation of the operation device 23 and detections by the vehicle speed sensor 24 and the object sensor 25.

[0029] (Drive Device 21) As shown in FIG. 2, the drive device 21 has an engine 31, an HST 32, a transfer case 33, an axle 34, front tires 4, and rear tires 7.

[0030] The engine 31 is, for example, a diesel engine, and the driving force generated by the engine 31 drives a pump 32 a of an HST (Hydro Static Transmission) 32 .

[0031] The HST 32 has a pump 32a, a motor 32b, and a hydraulic circuit 32c. The pump 32a is, for example, a swash plate type variable displacement pump, and the angle of the swash plate can be changed by a solenoid 32d. The pump 32a is driven by the engine 31 to discharge hydraulic oil. The discharged hydraulic oil is sent to the motor 32b through the hydraulic circuit 32c. The motor 32b is, for example, a swash plate type pump, and the angle of the swash plate can be changed by a solenoid 32e.

[0032] The hydraulic circuit 32c connects the pump 32a and the motor 32b. The hydraulic circuit 32c has a first drive circuit 32c1 and a second drive circuit 32c2. Hydraulic oil is supplied from the pump 32a to the motor 32b via the first drive circuit 32c1, thereby driving the motor 32b in one direction (for example, the forward direction). Hydraulic oil is supplied from the pump 32a to the motor 32b via the second drive circuit 32c2, thereby driving the motor 32b in the other direction (for example, the reverse direction). The direction of hydraulic oil discharge to the first drive circuit 32c1 or the second drive circuit 32c2 can be changed by the solenoid 32d.

[0033] The transfer 33 distributes the output from the engine 31 to the front and rear axles 34. The driving force generated by the engine 31 may be distributed to the front and rear axles 34 via a torque converter and a transmission.

[0034] A pair of front tires 4 are connected to the front axle 34 and rotate with the distributed power from the engine 31. A pair of rear tires 7 are connected to the rear axle 34 and rotate with the distributed power from the engine 31.

[0035] (Brake Device 22) As shown in FIG. 2, the brake device 22 brakes the vehicle body 1 based on the operation of the brake pedal 51 and performs automatic braking control of the vehicle body 1 based on a command from the controller 26.

[0036] The braking device 22 has a brake valve unit 41, brake circuits 42a, 42b (an example of a service brake), a parking brake 43, hydraulic oil supply passages 44a, 44b, an EPC (Electric Proportional Valve) valve 46, a shuttle valve unit 47, and a tank 48.

[0037] An accumulator, a pump, etc. are connected to the hydraulic oil supply passages 44a, 44b, and hydraulic oil is supplied thereto.

[0038] 3, the brake valve unit 41 is operated by a brake pedal 51 (described later). The brake valve unit 41 has a rear brake valve 41 a and a front brake valve 41 b. Each of the rear brake valve 41 a and the front brake valve 41 b is a three-position selector valve having three ports.

[0039] A first port of the rear brake valve 41 a is connected to a hydraulic oil supply passage 44 a via an accumulator 49 a. A second port of the rear brake valve 41 a is connected to a tank 48. A third port of the rear brake valve 41 a is connected to a rear shuttle valve 47 a of a shuttle valve unit 47.

[0040] In the first state, the rear brake valve 41a connects the first port to the third port, connects the hydraulic oil supply path 44a to the rear shuttle valve 47a, and supplies 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 discharges hydraulic oil between the rear shuttle valve 47a and the rear brake valve 41a to the tank 48. In the second and third states, the rear brake valve 41a stops the supply of hydraulic oil to the rear shuttle valve 47a.

[0041] A first port of the front brake valve 41b is connected to a hydraulic oil supply passage 44b via an accumulator 49b. A second port of the front brake valve 41b is connected to a tank 48. A third port of the front brake valve 41b is connected to a front shuttle valve 47b of the shuttle valve unit 47.

[0042] In the first state, the front brake valve 41b connects the first port to the third port, connects the hydraulic oil supply path 44b to the front shuttle valve 47b, and supplies 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 hydraulic oil between the front shuttle valve 47b and the front brake valve 41b to the tank 48. In the second and third states, the front brake valve 41b stops the supply of hydraulic oil to the front shuttle valve 47b.

[0043] The opening degrees of the rear brake valves 41 a and the front brake valves 41 b are adjusted in accordance with the amount of operation of the brake pedal 51, and the amount of hydraulic oil supplied to the shuttle valve unit 47 is changed. For example, when the amount of operation of the brake pedal 51 is large, the amount of hydraulic oil supplied from the rear brake valves 41 a and the front brake valves 41 b to the shuttle valve unit 47 increases.

[0044] The brake circuit 42a is provided on the rear axle 34 (FIG. 2) and is connected to the rear shuttle valve 47a. The brake circuit 42b is provided on the front axle 34 (FIG. 2) and is connected to the front shuttle valve 47b.

[0045] The brake circuits 42a and 42b are hydraulic brakes. The braking force of the brake circuit 42a increases as the amount or pressure of hydraulic oil supplied from the rear shuttle valve 47a increases. The braking force of the brake circuit 42b increases as the amount or pressure of hydraulic oil supplied from the front shuttle valve 47b increases.

[0046] The EPC valve 46 is connected to the hydraulic oil supply line 44b. The EPC valve 46 is a solenoid valve having three ports. A first port of the EPC valve 46 is connected to the hydraulic oil supply line 44b. A second port of the EPC valve 46 is connected to a tank 48. A third port of the EPC valve 46 is connected to a shuttle valve unit 47.

[0047] In the open state, the EPC valve 46 connects the first port and the third port, and supplies hydraulic oil supplied from the hydraulic oil supply passage 44b to the shuttle valve unit 47. The opening degree of the EPC valve 46 is adjusted based on an instruction from the controller 26, thereby changing the amount of hydraulic oil supplied to the shuttle valve unit 47.

[0048] In the closed state, the EPC valve 46 closes the first port, connects the second port and the third port, and discharges the hydraulic oil in the flow path from the EPC valve 46 to the shuttle valve unit 47 to the tank 48. As a result, in the closed state, the EPC valve 46 stops the supply of hydraulic oil from the hydraulic oil supply path 44b to the shuttle valve unit 47.

[0049] In this embodiment, the controller 26 controls the EPC valve 46 to an open state when it is determined that the wheel loader 100 is traveling in a predetermined direction (for example, the backward direction Zb) and there is a high risk of interference with an object in the traveling direction.

[0050] The shuttle valve unit 47 has a rear shuttle valve 47a and a front shuttle valve 47b. The rear shuttle valve 47a supplies the hydraulic oil having a higher pressure, either the hydraulic oil supplied via the rear brake valve 41a or the hydraulic oil supplied via the EPC valve 46, to the brake circuit 42a. The front shuttle valve 47b supplies the hydraulic oil having a higher pressure, either the hydraulic oil supplied via the front brake valve 41b or the hydraulic oil supplied via the EPC valve 46, to the brake circuit 42b.

[0051] With this configuration, even if the brake pedal 51 is not operated and hydraulic oil is not supplied from the brake valve unit 41, when the EPC valve 46 is opened by instruction from the controller 26, hydraulic oil is supplied to the brake circuits 42a, 42b from the rear shuttle valve 47a and the front shuttle valve 47b, and automatic braking control is performed.

[0052] The brakes that can be switched between a braking state and a non-braking state by the brake circuits 42a, 42b are, for example, wet multi-disc brakes. A wet multi-disc brake primarily comprises multiple discs, plates, pistons, and springs. Each of the multiple discs is integrated with an output shaft for the front tire 4 or rear tire 7. The plates are arranged alternately with the discs, attached to a fixed member, and do not rotate. The pistons are actuated by the hydraulic pressure of hydraulic oil supplied to the brake circuits 42a, 42b. When the pistons are actuated, the plates are sandwiched and pressed between the multiple discs. This activates the wet multi-disc brake and puts it into a braking state. Furthermore, when the supply of hydraulic oil to the brake circuits 42a, 42b is stopped, the pistons return to their original positions due to the repulsive force (restoring force) of the springs, releasing the pressure between the plates and discs. This puts the wet multi-disc brake into a non-braking state.

[0053] The EPC valve 46 , the shuttle valve unit 47 and the brake circuits 42 a and 42 b correspond to an example of an automatic braking device 45 that applies automatic braking to the vehicle body 1 based on the detection result of the object sensor 25 .

[0054] 2, the parking brake 43 is provided on the transfer 33. As the parking brake 43, for example, a wet multi-stage brake or a disc brake that can be switched between a braking state and a non-braking state can be used.

[0055] 2, the operating device 23 is operated by an operator seated in the cab 5 (FIG. 1). The operating device 23 has a brake pedal 51, a release device 52, a forward / reverse switching device 53, and an accelerator 54.

[0056] As shown in FIG. 4 , the brake pedal 51 is provided inside the cab 5, in front of the driver's seat 5s. The brake pedal 51 adjusts the opening degree of the rear brake valve 41 a and the front brake valve 41 b of the brake valve unit 41 depending on the amount of operation of the brake pedal 51. The amount of operation of the brake pedal 51 is detected by, for example, a brake pressure sensor, a pedal stroke sensor, etc. A signal indicating the amount of operation of the brake pedal 51 detected by the brake pressure sensor, the pedal stroke sensor, etc. is transmitted to the controller 26. The brake pedal 51 and the brake operation amount detection sensors (brake pressure sensor, pedal stroke sensor, etc.) correspond to an example of a brake operation device 51A that outputs a braking signal for the vehicle body 1 when operated by an operator.

[0057] The release device 52 is a device that outputs a release signal to temporarily disable the operation of the automatic braking device 45, and is a switch, button, or the like. The release device 52 may be an automatic braking control cancel switch. Note that the temporary disabling of the automatic braking by the automatic braking control cancel switch is different from the release of the automatic braking in the present disclosure, because the automatic braking is reactivated when the switch operation is completed. The release device 52 is provided inside the cab 5. The release device 52 may be provided on a console 61 located to the side of the driver's seat 5s as shown in FIG. 4. For example, any one of a plurality of switches 63 located on the console 61 may be set to the release device 52. An armrest 62 may be provided between the driver's seat 5s and the console 61.

[0058] 2 , the operator operates the release device 52 to temporarily release (disable) the operation of the automatic braking device 45. The operator's operation causes the release device 52 to send a release signal to the controller 26. Upon receiving the release signal, the controller 26 closes the EPC valve 46 to temporarily release the operation of the automatic braking device 45.

[0059] The forward / reverse switching device 53 is provided inside the cab 5. The forward / reverse switching device 53 may be a lever 64 that protrudes from the steering column, as shown in FIG. 4 , or may be a lever that protrudes from the floor of the cab 5.

[0060] 2, the operator switches and sets the traveling direction of the vehicle body 1 by operating the forward / reverse switching device 53. The forward / reverse switching device 53 is, for example, an FNR lever. The FNR lever 53 can be positioned in forward (F), neutral (N), or reverse (R). An operation signal indicating the lever position of the FNR lever 53 is sent to the controller 26, and the controller 26 switches the traveling direction to forward, neutral, or reverse by controlling the solenoid 32d.

[0061] A potentiometer may be used as a position detection sensor that detects the lever position of the FNR lever 53, or switches may be provided for the forward position, reverse position, and neutral position. Also, both the potentiometer and the switch may be provided so that erroneous operation of either one can be detected.

[0062] As shown in FIG. 4 , the accelerator 54 is located inside the cab 5, in front of the driver's seat 5s. The operator sets the throttle opening by operating the accelerator 54. The accelerator 54 generates an opening signal indicating the accelerator operation amount and transmits it to the controller 26. The controller 26 controls the rotation speed of the engine 31 based on the transmitted signal.

[0063] An initiating device for initiating automatic braking control is also provided inside the cab 5. The initiating device is, for example, a key switch. The operator can switch the key switch from an OFF state to an ON state by inserting a key into the key switch, for example. This causes the key switch to send an operation signal indicating the ON state or OFF state to the controller 26. When the controller 26 receives an ON state operation signal, it controls the engine 31 to start and initiates automatic braking control. When the controller 26 receives an OFF state operation signal, it stops the engine 31.

[0064] 2, the vehicle speed sensor 24 detects the speed of the vehicle body 1. The vehicle speed sensor 24 detects the speed of the vehicle body 1, for example, by detecting the rotational speed of the output shaft of the transmission, and generates a signal of the detected vehicle speed. The vehicle speed sensor 24 transmits the vehicle speed signal to the controller 26.

[0065] The vehicle speed sensor 24 may detect the vehicle speed of the vehicle body 1 by detecting, for example, the rotational speed of the front tires 4 or the rear tires 7. The vehicle speed sensor 24 may also be, for example, an IMU (Inertial Measurement Unit) that detects the acceleration of the traveling vehicle body 1. In this case, the vehicle speed is calculated from the product of the acceleration of the vehicle body 1 detected by the IMU.

[0066] (Object sensor 25) As shown in Figure 2, the object sensor 25 detects objects around the vehicle body 1. The object sensor 25 detects objects located in the traveling direction of the wheel loader 100. Specifically, the object sensor 25 is a rear detection unit that detects objects in the rear direction Zb of the vehicle body 1 when the wheel loader 100 travels in the rear direction Zb.

[0067] When the object sensor 25 is a rear detection unit, the rear detection unit 25 is attached to the rear end of the vehicle body 1 as shown in FIG. 1, for example, but may be attached to a location other than the rear end.

[0068] The object sensor 25 may be, for example, a LiDAR (Light Detection and Ranging) that emits laser light to acquire information about an object. The object sensor 25 may also be a Radar (Radio Detection and Ranging) that emits radio waves to acquire information about an object. The Radar may be, for example, a millimeter-wave radar that uses a receiving antenna to detect how millimeter-wave band radio waves emitted from a transmitting antenna are reflected off the surface of an object and returned. The object sensor 25 may also be a visual sensor including a camera. The object sensor 25 may also be an infrared sensor.

[0069] Information detected by the object sensor 25 is transmitted to the controller 26, which determines whether or not an object is present in the traveling direction of the vehicle body 1. The controller 26 also calculates the distance to the detected object. The controller 26 may determine whether or not there is a high risk that the vehicle body 1 will interfere with the object based on the distance to the detected object, etc.

[0070] 2 includes a processor, a main memory, and a storage. The processor is, for example, a central processing unit (CPU). The main memory includes, for example, a non-volatile memory such as a read-only memory (ROM) and a volatile memory such as a random access memory (RAM).

[0071] The controller 26 and the operation device 23 may each be mounted on the wheel loader 100, or may be located remotely outside the wheel loader 100. When the controller 26 and the operation device 23 are each located remotely outside the wheel loader 100, the controller 26 and the operation device 23 may each be connected wirelessly to the drive device 21, the braking device 22, the vehicle speed sensor 24, the object sensor 25, etc. The controller 26 may be stored in a server remote from the wheel loader 100. Furthermore, since the operation device 23 is located remote from the wheel loader 100, the operator may remotely operate the wheel loader 100 from a remote location remote from the wheel loader 100 without boarding the cab 5 of the wheel loader 100.

[0072] The controller 26 reads the program stored in the storage, loads it into the main memory, and executes predetermined processing in accordance with the program. The controller 26 may be divided into a collision detection controller and an HST controller. The collision detection controller and the HST controller may have separate CPUs. The program may also be distributed to the controller 26 via a network.

[0073] <Control Method of Wheel Loader 100> Next, a control method of the wheel loader 100 in this embodiment will be described mainly with reference to FIG.

[0074] 5 is a flow diagram showing a control method for a wheel loader according to one embodiment of the present disclosure. As shown in FIG. 5, automatic braking control is initiated in step S1. The automatic braking control is initiated, for example, by turning on the above-mentioned initiation device.

[0075] The controller 26 starts the automatic braking control when it receives an operation signal indicating the ON state from the initiation device. The state in which the automatic braking control is started (ON state) means a state in which the controller 26 can automatically control the opening and closing operation of the EPC valve 46 based on the detection results of the forward / reverse switching device 53 and the detection results of the object sensor 25.

[0076] In step S2, while automatic braking control is being executed, the controller 26 acquires information about the traveling direction of the wheel loader 100 and information about objects (obstacles). The controller 26 acquires information about the traveling direction of the wheel loader 100 from the forward / reverse switching device 53. The forward / reverse switching device 53 is, for example, an FNR lever, and the controller 26 acquires a signal indicating the lever position of the FNR lever - forward, neutral, or reverse. The controller 26 acquires information from the object sensor 25 as to whether or not an object is present in the traveling direction (rearward direction Zb) of the vehicle body 1.

[0077] In step S3, the controller 26 determines whether there is a high risk of the vehicle body 1 interfering with an object in the traveling direction (rearward direction Zb) of the vehicle body 1. The controller 26 makes this determination based on information on the traveling direction of the vehicle body 1 and information on the object.

[0078] If the controller 26 determines that there is not a high risk of the wheel loader 100 interfering with an object in the traveling direction, the controller 26 repeats the steps of obtaining traveling direction information and object information (step S2) and determining whether there will be interference with an object (step S3). On the other hand, if the controller 26 determines that there is a high risk of the vehicle body 1 interfering with an object in the traveling direction, the controller 26 outputs an automatic braking command to brake the vehicle body 1. Specifically, the controller 26 outputs a command to open the EPC valve 46 as the automatic braking command.

[0079] In step S4, the EPC valve 46 is controlled to be in an open state, thereby activating the automatic braking device 45. Specifically, when the EPC valve 46 is in an open state, hydraulic oil is supplied from the rear shuttle valve 47 a and the front shuttle valve 47 b to the brake circuits 42 a, 42 b, and braking operations are performed.

[0080] The state in which the automatic braking device 45 is operating means that braking force is being applied by the brake circuits 42 a and 42 b. For example, when the automatic braking device 45 is a wet multi-disc brake, the plate is sandwiched and pressed between multiple discs, thereby braking the vehicle body 1.

[0081] The opening degree of the EPC valve 46 is adjusted by a command current output from the controller 26 to the EPC valve 46. In this example, the command current is set to a predetermined value in advance. The command current may also be adjusted based on the distance to the detected object. For example, the controller 26 may calculate the deceleration required to stop the vehicle in front of the detected object based on the distance to the object, and transmit an open command (command current) to the EPC valve 46 so that the opening degree is such that the deceleration is achieved.

[0082] In this way, the controller 26 executes automatic braking control to automatically brake the vehicle's traveling based on the detection result of an object in the traveling direction. In the automatic braking control, the controller 26 automatically controls the traveling by the braking device 22 based on the detection result of an object by the object sensor 25. As a result, even if the operator does not operate the brake pedal 51, the automatic braking control is executed and braking force is exerted, enabling the vehicle body 1 to stop before the object.

[0083] (One Example of Deactivating the Automatic Brake Device) When the automatic brake device 45 is activated by the automatic braking control as described above, the operator may wish to deactivate the automatic brake device 45 in order to carry out normal use or to approach an object further. If a predetermined deactivation condition is met, the operation of the automatic brake device 45 is deactivated. Note that normal use refers to use in a state in which the automatic braking control is deactivated.

[0084] In this embodiment, after the automatic braking device 45 has been activated, in step S5 the controller 26 determines whether or not the release conditions for deactivating the automatic braking device 45 are met. When the operator wishes to use the wheel loader 100 normally, these release conditions are met, for example, when the three conditions of the wheel loader 100 being stopped, the operator operating the brake pedal 51, and the forward / reverse switching device 53 being in a state other than reverse (i.e., forward or neutral) are met. When the operator wishes to move the wheel loader 100 closer to an object, the release conditions are met, for example, when the three conditions of the wheel loader 100 being stopped, the operator operating the brake pedal 51, and the release device 52 being pressed and held down are met.

[0085] The controller 26 determines whether or not the wheel loader 100 is stopped based on the detection result of the vehicle speed sensor 24. The controller 26 determines that the wheel loader 100 is stopped when the vehicle speed of the wheel loader 100 detected by the vehicle speed sensor 24 remains at or below a predetermined speed for a predetermined period of time or longer, for example.

[0086] The controller 26 determines whether or not the operator is operating the brake pedal 51 based on the detection results of, for example, a brake pressure sensor, a pedal stroke sensor, etc. The controller 26 determines that the brake pedal 51 is being operated when, for example, the brake pressure detected by the brake pressure sensor is equal to or greater than a predetermined pressure and continues for a predetermined period of time or longer.

[0087] The controller 26 determines whether the forward / reverse switching device 53 is in a state other than reverse based on an operation signal output from the forward / reverse switching device 53. When the controller 26 receives a forward or neutral operation signal from the forward / reverse switching device 53, it determines that the forward / reverse switching device 53 is in a state other than reverse.

[0088] The controller 26 determines whether the release device 52 has been pressed and held down based on the release signal output from the release device 52. When the controller 26 continuously receives the release signal from the release device 52 for a predetermined period of time or more, the controller 26 determines that the release device 52 has been pressed and held down.

[0089] As described above, when the operator wishes to use the wheel loader 100 normally, the controller 26 releases the operation of the automatic brake device 45, for example, based on the vehicle speed of the vehicle body 1 detected by the vehicle speed sensor 24, the braking signal output from the brake operation device 51A, and the operation signal of the forward / reverse switch device 53. Also, when the operator wishes to bring the wheel loader 100 closer to an object, the controller 26 releases the operation of the automatic brake device 45, for example, based on the vehicle speed of the vehicle body 1 detected by the vehicle speed sensor 24, the braking signal output from the brake operation device 51A, and the release signal output from the release device 52.

[0090] If the controller 26 determines that the release condition is not satisfied, it repeats the determination in step S5 while maintaining the operation of the automatic braking device 45. On the other hand, if the controller 26 determines that the release condition is satisfied, it controls the EPC valve 46 to be in a closed state.

[0091] In step S6, the EPC valve 46 is controlled to the closed state as described above, thereby deactivating the automatic braking device 45. Specifically, when the EPC valve 46 is closed, the supply of hydraulic oil to the brake circuits 42a, 42b is cut off, and the automatic braking device 45 is deactivated.

[0092] The state in which the automatic braking device 45 is deactivated means that no braking force is being applied by the brake circuits 42 a and 42 b. In the case where the brake is a wet multi-disc brake, an example of the state in which the automatic braking device 45 is deactivated means that the plate is not pressed between the multiple discs.

[0093] In this way, the controller 26 releases the operation of the automatic brake device 45 when the release conditions are met. This allows the vehicle body 1 to travel in order to use the wheel loader 100 normally or to approach an object that could become an obstacle.

[0094] (Another Example of Deactivating the Automatic Brake Device) In the above-described automatic braking control, the automatic brake device 45 may be activated based on an erroneous detection of an object in the traveling direction of the vehicle body 1. In such a case, the operator may wish to deactivate the automatic brake device 45 and continue traveling at his / her own will. Therefore, when a predetermined deactivation condition is satisfied, the operation of the automatic brake device 45 is deactivated.

[0095] In this embodiment, after the automatic braking device 45 is activated, in step S5, the controller 26 determines whether or not a release condition is met for deactivating the automatic braking device 45. If the automatic braking device 45 is activated due to the above-mentioned erroneous detection while the vehicle body 1 is traveling at high speed, this release condition will be met when the following three conditions are met: the vehicle body 1 is traveling at high speed, the forward / reverse switching device 53 is in the reverse state (i.e., the traveling direction is backward), and the release device 52 is short-pushed.

[0096] The controller 26 determines whether or not the wheel loader 100 is traveling at high speed based on the detection result of the vehicle speed sensor 24. The controller 26 determines that the vehicle body 1 is traveling at high speed when the vehicle speed of the vehicle body 1 detected by the vehicle speed sensor 24 is equal to or greater than a predetermined threshold value (for example, 10 km / h). The vehicle speed used for the above determination is, for example, the vehicle speed at the time the release device 52 is pressed.

[0097] The controller 26 determines whether the forward / reverse switching device 53 is in a reverse state based on an operation signal output from the forward / reverse switching device 53. When the controller 26 receives a reverse operation signal from the forward / reverse switching device 53, it determines that the forward / reverse switching device 53 is in a reverse state and that the vehicle is traveling in the reverse direction.

[0098] The controller 26 determines whether the release device 52 has been pressed based on the release signal output from the release device 52. The controller 26 determines that the release device 52 has been pressed briefly based on a change in the waveform of the release signal output from the release device 52. The controller 26 determines that the release device 52 has been pressed briefly, for example, based on obtaining a rising edge (or a falling edge) of the waveform of the release signal when the release signal switches from OFF to ON.

[0099] Based on the above, when it is desired to deactivate the automatic braking device 45 that has been activated due to the above-mentioned erroneous detection, the controller 26 deactivates the operation of the automatic braking device 45 based on, for example, the vehicle speed of the vehicle body 1 detected by the vehicle speed sensor 24, an operation signal indicating reverse movement from the forward / reverse switching device 53, and a release signal output from the release device 52.

[0100] If the controller 26 determines that the release condition is not satisfied, it repeats the determination in step S5 while maintaining the operation of the automatic braking device 45. On the other hand, if the controller 26 determines that the release condition is satisfied, it controls the EPC valve 46 to be in a closed state.

[0101] In step S6, the EPC valve 46 is controlled to the closed state as described above, thereby deactivating the automatic braking device 45. Specifically, when the EPC valve 46 is closed, the supply of hydraulic oil to the brake circuits 42a, 42b is cut off, and the automatic braking device 45 is deactivated.

[0102] The state in which the automatic braking device 45 is deactivated means that no braking force is being applied by the brake circuits 42 a and 42 b. In the case where the brake is a wet multi-disc brake, an example of the state in which the automatic braking device 45 is deactivated means that the plate is not pressed between the multiple discs.

[0103] In this way, when the release condition is satisfied, the controller 26 releases the operation of the automatic braking device 45. Therefore, the operation of the automatic braking device 45 based on the erroneous detection of an object can be released at the operator's discretion, allowing the vehicle body 1 to continue traveling.

[0104] <Effects> Next, the effects of this embodiment will be described.

[0105] When the wheel loader 100 has stopped due to the execution of automatic braking control, there are cases where it is desired to deactivate the automatic braking device 45 by automatic braking control in order to use the wheel loader 100 normally or to allow the wheel loader 100 to approach an object (obstacle) further. However, immediately after the automatic braking is released, the wheel loader 100 may move in an unintended manner by creeping, sliding down, or the like. Furthermore, if the operation of the automatic braking device 45 is deactivated unintentionally due to a malfunction of a sensor or the like, the operator may not be able to apply the brakes in time. There is also a demand for the ability to easily deactivate the automatic braking device 45 when it is desired to allow the wheel loader 100 to approach an object further, for example.

[0106] 2, in this embodiment, the controller 26 outputs an automatic braking command to activate the automatic braking device 45 to brake the vehicle body 1 (step S4), and then releases the operation of the automatic braking device 45 based on the vehicle speed and braking signal of the vehicle body 1 (step S6). As a result, after the automatic braking command to brake the vehicle body 1 has been output, the vehicle body 1 can be driven for normal use of the wheel loader 100 or to approach an object that is an obstacle.

[0107] Furthermore, the release conditions for releasing the operation of the automatic braking device 45 include the operator operating the brake operating device 51A. Therefore, even if an unintended movement such as creeping or sliding occurs the moment the operation of the automatic braking device 45 is released, the operator can immediately operate the brake operating device 51A to apply the brakes. Therefore, even if the wheel loader 100 moves in an unintended manner by the operator in relation to automatic braking control, an appropriate response can be easily taken.

[0108] Furthermore, the conditions for canceling the operation of the automatic braking device 45 are the vehicle speed of the wheel loader 100 and the operation of the brake operating device 51A by the operator. Therefore, the operation of the automatic braking device 45 can be canceled by the simple operation of operating the brake operating device 51A.

[0109] 2, in this embodiment, the controller 26 deactivates the automatic braking device 45 based on the vehicle speed, the braking signal, and the operation signal of the forward / reverse switching device 53. This makes it possible to deactivate the automatic braking device 45 taking into account the traveling direction of the wheel loader 100 after activation of the automatic braking device 45 has been deactivated.

[0110] 2, in this embodiment, the controller 26 releases the operation of the automatic braking device 45 based on the vehicle speed, the braking signal, and the operation signal of the forward / reverse switching device 53. In this way, the automatic braking release conditions are multiplexed (duplicated), so that even if a failure occurs in one sensor, the automatic braking device 45 will not be released unintentionally.

[0111] 2, in this embodiment, when the forward / reverse switching device 53 selects a mode other than reverse, the controller 26 deactivates the automatic braking device 45. As a result, after the automatic braking device 45 is deactivated, the wheel loader 100 can be used normally while avoiding interference with objects behind.

[0112] 2, in this embodiment, the controller 26 releases the operation of the automatic braking device 45 based on a release signal output from the release device 52. This temporarily disables the operation of the automatic braking device 45, making it possible to move the wheel loader 100 closer to the object.

[0113] 2, in this embodiment, the controller 26 releases the operation of the automatic braking device 45 when it receives a release signal output from the release device 52 continuously for a predetermined time or longer. This prevents the automatic braking device 45 from being released by an operator's mistaken operation.

[0114] 2, in this embodiment, when the controller 26 detects that the vehicle speed is equal to or less than a predetermined speed for a predetermined period of time or more, the controller 26 cancels the operation of the automatic braking device 45. This makes it possible to cancel the operation of the automatic braking device 45 only when the vehicle speed is reliably equal to or less than the predetermined speed.

[0115] 2, in this embodiment, when the controller 26 receives a braking signal continuously for a predetermined period of time or more, it deactivates the automatic braking device 45. This makes it possible to prevent the automatic braking device 45 from being deactivated due to an erroneous operation of the brake operating device 51A.

[0116] 2, in this embodiment, the controller 26 outputs an automatic braking command to activate the automatic braking device 45 to brake the vehicle body 1 (step S4), and then, if a release condition is met (step S5), the controller 26 releases the operation of the automatic braking device 45 (step S6). As a result, even if the automatic braking device 45 is activated based on an erroneous detection of an object in the traveling direction of the vehicle body 1, the operation of the automatic braking device 45 can be released and the vehicle body 1 can continue traveling.

[0117] Furthermore, the release condition for releasing the operation of the automatic braking device 45 includes the operator operating the release device 52. This allows the operator to release the operation of the automatic braking device 45 at will and continue traveling of the vehicle body 1. This makes it easy to take appropriate measures against erroneous detection of an object during high-speed traveling under automatic braking control.

[0118] In this embodiment, when the vehicle body 1 is moving backward at a speed equal to or greater than a predetermined threshold, the controller 26 releases the operation of the automatic brake device 45 based on the release signal. This allows the vehicle body 1 to continue moving backward without stopping, thereby improving work efficiency.

[0119] In this embodiment, the controller 26 releases the operation of the automatic braking device 45 based on a change in the waveform of the release signal. This makes it possible to release the operation of the automatic braking device 45 by a short push of the release device 52.

[0120] <Additional Notes> The above description includes the following additional features.

[0121] (Supplementary Note 1) A work machine comprising: a vehicle body capable of travelling; a vehicle speed sensor that detects the vehicle speed of the vehicle body; a brake operation device that is operated by an operator to output a braking signal for the vehicle body; an object sensor that detects an object behind the vehicle body; an automatic braking device that applies automatic brakes to the vehicle body based on the detection result of the object sensor; and a controller that outputs an automatic braking command to brake the vehicle body by operating the automatic braking device, and then releases operation of the automatic braking device based on the vehicle speed and the braking signal.

[0122] (Supplementary Note 2) The working machine according to Supplementary Note 1, further comprising a forward / reverse switching device that switches the traveling direction of the vehicle body, wherein the controller releases the operation of the automatic brake device based on the vehicle speed, the braking signal, and an operation signal of the forward / reverse switching device.

[0123] (Supplementary Note 3) The work machine according to Supplementary Note 2, wherein the controller deactivates the automatic brake device based on the vehicle speed and the braking signal and when the forward / reverse switching device selects a mode other than reverse.

[0124] (Supplementary Note 4) The working machine according to Supplementary Note 1, further comprising a release device that outputs a release signal to temporarily disable operation of the automatic braking device, wherein the controller releases operation of the automatic braking device based on the vehicle speed, the braking signal, and the release signal.

[0125] (Supplementary Note 5) The work machine according to Supplementary Note 4, wherein the controller releases the operation of the automatic brake device based on the vehicle speed and the braking signal and when the release signal is continuously acquired for a predetermined time or more.

[0126] (Supplementary Note 6) The work machine according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the controller deactivates the automatic brake device when the vehicle speed remains at or below a predetermined speed for a predetermined time or more.

[0127] (Supplementary Note 7) The work machine according to any one of Supplementary Note 1 to Supplementary Note 6, wherein, in a case where the braking signal is a brake pressure, the controller deactivates the automatic brake device if the brake pressure continues to be at a predetermined pressure for a predetermined time or more.

[0128] (Supplementary Note 8) A work machine system comprising: a vehicle body capable of travelling; a vehicle speed sensor for detecting the vehicle speed of the vehicle body; a brake operation device for outputting a braking signal for the vehicle body when operated by an operator; an object sensor for detecting an object behind the vehicle body; an automatic braking device for applying automatic brakes to the vehicle body based on the detection results of the object sensor; and a controller for outputting an automatic braking command for braking the vehicle body by operating the automatic braking device, and then releasing the operation of the automatic braking device based on the vehicle speed and the braking signal.

[0129] (Supplementary Note 9) A control method for a work machine having a vehicle body capable of traveling, a brake operating device that outputs a braking signal for the vehicle body when operated by an operator, and an automatic braking device that brakes the vehicle body with automatic brakes based on the detection results of an object behind the vehicle body, the control method for a work machine comprising: a step of outputting an automatic braking command that brakes the vehicle body by operating the automatic braking device; and a step of releasing the operation of the automatic braking device based on the vehicle speed of the vehicle body and the braking signal after outputting the automatic braking command.

[0130] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0131] REFERENCE SIGNS LIST 1 vehicle body, 2 travelling body, 3 work equipment, 4 front tire, 5 cab, 5s driver's seat, 6 engine room, 7 rear tire, 9 steering cylinder, 10 vehicle frame, 11 front frame, 12 rear frame, 13 connecting shaft portion, 14 boom, 15 bucket, 16 lift cylinder, 17 bucket cylinder, 18 bell crank, 21 drive device, 22 braking device, 23 operation device, 24 vehicle speed sensor, 25 object sensor, 26 controller, 31 engine, 32a pump, 32b motor, 32c hydraulic circuit, 32c1 first drive circuit, 32c2 second drive circuit, 32d, 32e solenoid, 33 transfer, 34 axle, 41 brake valve unit, 41a rear brake valve, 41b front brake valve, 42a, 42b brake circuit, 43 Parking brake, 44a, 44b hydraulic oil supply line, 45 automatic braking device, 46 EPC valve, 47 shuttle valve unit, 47a rear shuttle valve, 47b front shuttle valve, 48 tank, 49a, 49b accumulator, 51 brake pedal, 51A brake operation device, 52 release device, 53 forward / reverse switching device, 54 accelerator, 61 console, 62 armrest, 63 switch, 100 wheel loader.

Claims

1. A work machine comprising: a vehicle body capable of travelling; a vehicle speed sensor that detects the vehicle speed of the vehicle body; a brake operation device that outputs a braking signal for the vehicle body when operated by an operator; an object sensor that detects objects behind the vehicle body; an automatic braking device that applies automatic brakes to the vehicle body based on the detection results of the object sensor; and a controller that outputs an automatic braking command to brake the vehicle body by operating the automatic braking device, and then releases operation of the automatic braking device based on the vehicle speed and the braking signal.

2. A work machine as described in claim 1, further comprising a forward / reverse switching device that switches the traveling direction of the vehicle body, and the controller deactivates the automatic brake device based on the vehicle speed, the braking signal, and an operation signal from the forward / reverse switching device.

3. A work machine as described in claim 2, wherein the controller deactivates the automatic brake device based on the vehicle speed and the braking signal when the forward / reverse switching device selects a mode other than reverse.

4. A work machine as described in claim 1, further comprising a release device that outputs a release signal to temporarily disable operation of the automatic braking device, and the controller releases operation of the automatic braking device based on the vehicle speed, the braking signal, and the release signal.

5. A work machine as described in claim 4, wherein the controller releases the operation of the automatic brake device based on the vehicle speed and the braking signal and when the release signal is continuously received for a predetermined period of time or more.

6. A work machine as set forth in claim 1, wherein the controller deactivates the automatic brake device when the vehicle speed remains below a predetermined speed for a predetermined period of time or more.

7. A work machine according to claim 1, wherein, when the braking signal is a brake pressure, the controller deactivates the automatic brake device if the brake pressure continues at a predetermined pressure for a predetermined time or longer.

8. A work machine system comprising: a vehicle body capable of travelling; a vehicle speed sensor that detects the vehicle body's speed; a brake operation device that outputs a braking signal for the vehicle body when operated by an operator; an object sensor that detects objects behind the vehicle body; an automatic braking device that applies automatic brakes to the vehicle body based on the detection results of the object sensor; and a controller that outputs an automatic braking command to brake the vehicle body by operating the automatic braking device, and then releases operation of the automatic braking device based on the vehicle speed and the braking signal.

9. A control method for a work machine having a drivable vehicle body, a brake operating device that outputs a braking signal for the vehicle body when operated by an operator, and an automatic braking device that brakes the vehicle body with automatic brakes based on the detection results of an object behind the vehicle body, comprising: a step of outputting an automatic braking command that brakes the vehicle body by operating the automatic braking device; and a step of deactivating the automatic braking device based on the vehicle speed of the vehicle body and the braking signal after outputting the automatic braking command.

10. A work machine comprising: a vehicle body capable of travelling; a vehicle speed sensor that detects the vehicle speed of the vehicle body; a forward / reverse switching device that switches the direction of travel of the vehicle body; an object sensor that detects objects behind the vehicle body; an automatic braking device that applies automatic brakes to the vehicle body based on the detection results of the object sensor; a release device that outputs a release signal that is operated by an operator to temporarily disable operation of the automatic braking device; and a controller that, when the automatic braking device is activated while the vehicle body is travelling, releases operation of the automatic braking device based on an operation signal indicating reverse movement of the forward / reverse switching device, the vehicle speed detected by the vehicle speed sensor, and the release signal output from the release device.

11. A work machine according to claim 10, wherein the controller releases the operation of the automatic brake device based on the release signal when the vehicle body is moving backward at a vehicle speed equal to or greater than a predetermined threshold.

12. The work machine according to claim 11, wherein the controller deactivates the automatic brake device based on a change in the waveform of the release signal.

13. A work machine system comprising: a vehicle body capable of travelling; a vehicle speed sensor that detects the vehicle speed of the vehicle body; a forward / reverse switching device that switches the direction of travel of the vehicle body; an object sensor that detects objects behind the vehicle body; an automatic braking device that applies automatic brakes to the vehicle body based on the detection results of the object sensor; a release device that outputs a release signal that is operated by an operator to temporarily disable operation of the automatic braking device; and a controller that, when the automatic braking device is activated while the vehicle body is travelling, releases operation of the automatic braking device based on an operation signal indicating reverse movement of the forward / reverse switching device, the vehicle speed detected by the vehicle speed sensor, and the release signal output from the release device.

14. A control method for a work machine having a vehicle body capable of traveling and an automatic braking device that applies automatic brakes to the vehicle body based on the detection of an object behind the vehicle body, the control method for a work machine comprising the steps of: activating the automatic braking device while the vehicle body is traveling; and deactivating the operation of the automatic braking device based on an operation signal indicating that the vehicle body is traveling in reverse, the vehicle speed of the vehicle body, and a release signal that temporarily disables the operation of the automatic braking device by operation by an operator.

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