Work vehicle

Abstract

Provided is a work vehicle capable of diagnosing malfunctions of an automatic braking device in advance.　This work vehicle comprises a vehicle body, a travel device, a brake device, an automatic braking device including an electromagnetic proportional valve and an electromagnetic switching valve for controlling a supply of hydraulic oil to the brake device, a pressure sensor for detecting a control pressure of the automatic braking device, an obstacle detection sensor, and a controller for controlling the opening and closing operations of the electromagnetic proportional valve and the electromagnetic switching valve on the basis of a detection signal from the obstacle detection sensor, wherein the controller executes a malfunction diagnosis mode on the basis of fulfillment of a predetermined condition, and when the failure diagnosis mode is executed, the controller opens / closes the electromagnetic proportional valve and the electromagnetic switching valve, compares the control pressure detected by the pressure sensor with a preset threshold, and determines that the automatic brake device is in a malfunction state if the control pressure detected by the pressure sensor is not within the range of the threshold.

Description

Work vehicles

[0001] The present invention relates to work vehicles such as wheel loaders, and more particularly to work vehicles equipped with an automatic braking system.

[0002] As background technology for this field, for example, Patent Document 1 discloses a wheel loader (work vehicle) that activates an automatic braking system to decelerate the vehicle body when an obstacle detection sensor mounted on the vehicle body detects an obstacle.

[0003] The automatic braking system is equipped with an electromagnetic proportional valve that controls the hydraulic pressure output to the disc brakes at an opening degree corresponding to the control current. When the obstacle detection sensor detects an obstacle, the electromagnetic proportional valve is switched, and pressurized oil is applied to activate the disc brakes, causing the vehicle to decelerate.

[0004] Patent No. 7002634

[0005] In the prior art described in Patent Document 1, the electromagnetic proportional valve operates only when it detects an obstacle. Therefore, if no obstacle is detected for a long period of time, or if the vehicle is out of service, oil will not flow for an extended period. In such a state, if contaminants accumulate around the spool of the electromagnetic proportional valve, the operation of the electromagnetic proportional valve will be hindered, making it impossible to properly control the hydraulic pressure output to the disc brake. Therefore, it is necessary to diagnose and understand such a state in advance. However, Patent Document 1 does not allow for the prior diagnosis of automatic braking system failures.

[0006] Therefore, the present invention aims to provide a work vehicle capable of diagnosing malfunctions of automatic braking systems in advance.

[0007] To achieve the above objective, one aspect of the present invention provides a work vehicle comprising: a vehicle body; a running gear for moving the vehicle body; a braking device for braking the running gear with supplied pressurized oil; an automatic braking device including an electromagnetic proportional valve and an electromagnetic switching valve for controlling the supply of pressurized oil to the braking device; a pressure sensor for detecting the control pressure of the automatic braking device; an obstacle detection sensor for detecting obstacles present around the vehicle body; and a controller for controlling the opening and closing operations of the electromagnetic proportional valve and the electromagnetic switching valve based on detection signals from the obstacle detection sensor, wherein the controller executes a fault diagnosis mode based on the fulfillment of predetermined conditions, and when the fault diagnosis mode is executed, the controller opens and closes the electromagnetic proportional valve and the electromagnetic switching valve, compares the control pressure detected by the pressure sensor with a pre-set threshold, and determines that the automatic braking device is in a faulty state when the control pressure detected by the pressure sensor is not within the range of the threshold.

[0008] According to the present invention, it is possible to provide a work vehicle that can diagnose malfunctions of the automatic braking system in advance. Other problems, configurations, and effects will be clarified by the following description of the embodiments.

[0009] This is a side view of a wheel loader according to an embodiment of the present invention. This is a configuration diagram showing the hydraulic and electrical circuits of the wheel loader. This is a block diagram of the brake controller. This is a flowchart showing the processing procedure for the automatic brake test. This is a flowchart showing the processing procedure for the brake controller. This is a flowchart showing the processing procedure for the brake controller.

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] Figure 1 is a side view of a wheel loader 100, which is an example of a work vehicle according to an embodiment of the present invention. The wheel loader 100 comprises a vehicle body composed of a front frame 110 and a rear frame 120, and a front work implement 101 provided at the front of the vehicle body. The front frame 110 and the rear frame 120 are rotatably connected to each other by a center pin 102, and the front frame 110 bends left and right relative to the rear frame 120 by the extension and retraction of a steering cylinder (not shown).

[0012] The front frame 110 is equipped with a pair of left and right tires 6F and a front work implement 101. The rear frame 120 is equipped with a pair of left and right tires 6B, a driver's cab 121 where the operator sits, an engine room 122 which houses the engine 1 (see Figure 1) described later, and a counterweight 124 for maintaining the balance of the vehicle body. The front work implement 101 comprises a lift arm 111 and a bucket 112. The lift arm 111 rotates vertically (tilts and drops) driven by a lift arm cylinder 115, and the bucket 112 rotates vertically (clouds or dumps) driven by a bucket cylinder 116.

[0013] Figure 2 is a diagram showing the hydraulic and electrical circuits of the wheel loader 100 according to this embodiment. The driving force of the engine 1 mounted on the wheel loader 100 is reduced by the transmission 2 and transmitted to the front and rear axles 4 via the propeller shaft 3. The driving force transmitted to the axles 4 is transmitted to the left and right tires 6 (6F, 6B), which are the running gear, via a differential device and final reduction gear (not shown) within the axles 4, causing the wheel loader 100 to move.

[0014] Furthermore, the wheel loader 100 is equipped with a hydraulic pump 31 driven by the engine 1 to supply hydraulic fluid, and a hydraulic fluid tank 33 for storing the hydraulic fluid. The pressurized oil supplied from the hydraulic pump 31 operates the front work implement 101 and a switching spool (not shown) in the control valve 32. The control valve 32 switches the oil passages to the lift arm cylinder 115 and bucket cylinder 116 in response to operation signals from the arm operation lever 34 and bucket operation lever 35 located in the driver's cab 121 of the wheel loader 100, thereby extending and retracting the lift arm cylinder 115 and bucket cylinder 116 according to the operator's instructions.

[0015] Furthermore, the wheel loader 100 brakes the tires 6 with a wet disc brake 5 (braking device). The disc brake 5 is housed in an integrated case of the axle 4 together with a differential device (not shown). When hydraulic fluid is supplied to the disc brake 5 via the brake valve 20, the disc brake 5 generates a braking force corresponding to the pressure of the hydraulic fluid. The wheel loader 100 is equipped with a hydraulic power source 21 that supplies pressurized oil to the disc brake 5. The hydraulic power source 21 is a pressure source with a pressure lower than the discharge pressure of the hydraulic pump 31, and is composed of, for example, an accumulator that stores pressurized oil reduced in pressure from the hydraulic pump 31.

[0016] The brake valve 20 is a pressure reducing valve that reduces the pressure of the pressurized oil supplied from the hydraulic power source 21 to a pressure corresponding to the compression force of the spring. When the brake pedal 22 located in the driver's cab 121 is pressed by the operator, the brake valve 20 reduces the pressure of the pressurized oil supplied from the hydraulic power source 21 to a pressure corresponding to the pressing force (amount of pressing) of the brake pedal 22. The brake valve 20 reduces the pressure of the hydraulic fluid so that a higher pressure hydraulic fluid is supplied to the disc brake 5 as the compression force of the spring increases, that is, as the pressing force of the brake pedal 22 increases.

[0017] In this embodiment, the brake valve 20 can be operated not only by the operation of the brake pedal 22 but also by pilot pressure. Specifically, the brake valve 20 is also operated by pilot pressure regulated by an automatic braking device, which will be described later. The brake valve 20 reduces the pressure of the hydraulic fluid so that as the pressure in the pipeline 23c increases, it supplies hydraulic fluid at a higher pressure to the disc brake 5.

[0018] Furthermore, the wheel loader 100 is equipped with a dry or wet parking brake device 7 (auxiliary brake device) on the propeller shaft 3. The parking brake device 7 is released by a parking brake release switch 8, and when not released, it brakes the propeller shaft 3 with a spring (not shown) and a parking brake disc.

[0019] The conduit 23c includes an electromagnetic switching valve 24 that constitutes an automatic braking system, and an electromagnetic proportional valve 25 provided upstream of the electromagnetic switching valve 24. The conduit 23a connected to the output port of the electromagnetic proportional valve 25 branches into a conduit 23b connected to the input port of the electromagnetic switching valve 24, and a conduit 23d (hereinafter referred to as the bleed-off circuit) that connects to the hydraulic fluid tank 33 via a throttle 26 that constitutes an automatic braking system.

[0020] The electromagnetic switching valve 24 is switched between two positions, on and off, by a switching signal from the brake controller 40, and controls the flow of pressurized oil (pilot pressure) to the brake valve 20. The electromagnetic proportional valve 25 opens and closes with an opening degree corresponding to the control current, which is a command signal from the brake controller 40, and continuously controls the flow rate of pressurized oil flowing through the pipeline 23a according to the current value of the braking current. The control of the electromagnetic switching valve 24 and the electromagnetic proportional valve 25 by the brake controller 40 will be explained in detail later. The throttle 26 is a fixed throttle such as an orifice, and pressurized oil flows through it at a flow rate corresponding to the pressure difference between the pipeline 23a and the hydraulic oil tank 33. An automatic brake pressure sensor 28 that detects the pressure (pilot pressure) of the pressurized oil in the pipeline is provided in the pipeline 23c. The electromagnetic switching valve 24 and the electromagnetic proportional valve 25 may use either a characteristic of opening when energized or a characteristic of opening when de-energized. In the former case, the valves are opened by outputting an excitation signal from the brake controller 40 to the electromagnetic switching valve 24 and the electromagnetic proportional valve 25, while in the latter case, the valves are opened by the brake controller 40 stopping the output of the excitation signal.

[0021] The brake controller 40 controls the operation of the electromagnetic switching valve 24 and the electromagnetic proportional valve 25. An automatic brake changeover switch 41 is connected to the brake controller 40. When the operator moves the automatic brake changeover switch 41 to the ON position, the brake controller 40 switches the automatic brake system (electromagnetic switching valve 24 and electromagnetic proportional valve 25) from the stopped state to the operating state.

[0022] Furthermore, an obstacle detection sensor 42 is connected to the brake controller 40. The obstacle detection sensor 42 detects the presence or absence of obstacles behind the vehicle. Here, obstacles include other work vehicles, workers and personnel entering and exiting work vehicles, structures at the work site, etc.

[0023] The obstacle detection sensor 42 is a laser rangefinder installed at a predetermined location on the rear of the vehicle, for example, near the counterweight 124. Of course, instead of a laser rangefinder, a stereo camera, monocular camera, or millimeter-wave radar can also be used as the obstacle detection sensor 42.

[0024] Furthermore, the brake controller 40 is connected to an automatic brake test switch 43, which performs fault diagnosis control for the automatic braking system, as described later. The automatic brake test switch 43 is, for example, an electrical switch. Of course, instead of an electrical switch, a programmatic switch executed using a liquid crystal display and its operating device may be used.

[0025] In this embodiment, a display device 44 is connected to the brake controller 40. The display device 44 is located in the driver's cab 121 of the wheel loader 100. The display device 44 is, for example, a liquid crystal display or a lamp, and notifies the operator of vehicle information through images or illumination status.

[0026] Next, the functions of the brake controller 40 will be described. The brake controller 40 has a configuration in which the CPU, RAM, ROM, HDD, input I / F, and output I / F are connected to each other via a bus. In this hardware configuration, the CPU reads the arithmetic program (software) stored in a recording medium such as ROM, HDD, or optical disc, expands it onto RAM, and executes the expanded arithmetic program. The arithmetic program and the hardware work together to realize the functions of the brake controller 40.

[0027] Figure 3 is a block diagram showing the configuration of the brake controller 40 and the equipment related to the automatic braking system. As shown in Figure 3, the brake controller 40 includes a storage unit 47, a determination unit 48, a command signal output unit 45, and a fault determination unit 46.

[0028] The memory unit 47 contains the engine start determination threshold r, which will be described later. ＥｎｇＳｔａｒｔ The automatic brake standby pressure P1 and the automatic brake braking pressure P2, and the upper limit pressure P1 when the automatic brake is in standby mode. ｍａｘ and the lower limit pressure P1 when automatic brake is in standby mode ｍｉｎ And, the upper limit pressure P2 during automatic braking. ｍａｘ and the lower limit pressure P2 during automatic braking. ｍｉｎ, an upper limit pressure P3 when the automatic brake is not activated, an automatic brake standby pressure test time t1, and an automatic brake braking pressure test time t2 are stored.

[0029] The determination unit 48 acquires the operating state of the automatic brake changeover switch 41, data (detection signal) relating to the distance between the vehicle body and an obstacle output from the obstacle detection sensor 42, the operating state of the automatic brake test switch 43, the operating state of the parking brake release switch 8, and the engine rotation speed r output from the engine control unit 1a Ｅｎｇ and data relating to the foregoing, respectively.

[0030] The determination unit 48 is configured such that when an automatic brake test completion flag described later is off, and the engine rotation speed r Ｅｎｇ is equal to or greater than the engine start determination threshold r ＥｎｇＳｔａｒｔ or more, and the parking brake release switch 8 is off, outputs an automatic brake test command signal.

[0031] Further, the determination unit 48 is configured such that when the engine rotation speed r Ｅｎｇ is equal to or greater than the engine start determination threshold r ＥｎｇＳｔａｒｔ or more, the parking brake release switch 8 is off, and the automatic brake test switch 43 is turned on, also outputs the automatic brake test command signal.

[0032] Further, when the operating state of the automatic brake changeover switch 41 is off or there is no obstacle, the determination unit 48 outputs an automatic brake standby command signal.

[0033] Further, when the operating state of the automatic brake changeover switch 41 is on and an obstacle is present, the determination unit 48 outputs an automatic brake braking command signal.

[0034] When the determination unit 48 outputs the automatic brake standby command signal, the command signal output unit 45 switches the electromagnetic changeover valve 24 to the closed position, and outputs a control signal corresponding to the automatic brake standby pressure P1 to the electromagnetic proportional valve 25. The automatic brake standby pressure P1 is a pressure preset for adjusting the flow rate of pressure oil flowing through the bleed-off circuit (the pipe line 23d).

[0035] Further, when the determination unit 48 is outputting an automatic brake braking command signal, the command signal output unit 45 switches the electromagnetic switching valve 24 to the open position, and outputs a control signal corresponding to the automatic brake braking pressure P2 to the electromagnetic proportional valve 25. The automatic brake braking pressure P2 is a pressure that generates a preset braking force to prevent the brake valve 20 from colliding with an obstacle when the automatic brake is activated.

[0036] Further, when an automatic brake device failure determination flag described later is on, the command signal output unit 45 switches the electromagnetic switching valve 24 to the closed position, outputs a control signal such that the output pressure of the electromagnetic proportional valve 25 becomes zero, and further causes the display device 44 to output a display indicating a failure state of the automatic brake device.

[0037] The failure determination unit 46 acquires the command signal output from the determination unit 48 and the automatic brake pressure Pp output from the automatic brake pressure sensor 28 respectively, and performs failure determination by comparing them with a threshold value recorded in the storage unit 47.

[0038] The failure determination unit 46 turns on an automatic brake device failure determination flag (the initial value is off) when the determination unit 48 outputs an automatic brake standby command signal and the automatic brake pressure Pp is larger than the upper limit pressure P3 when the automatic brake is not activated.

[0039] When the determination unit 48 outputs an automatic brake test command signal, the command signal output unit 45 and the failure determination unit 46 execute automatic brake test control (failure diagnosis mode) described below.

[0040] FIG. 4 is a flowchart showing control processing of the command signal output unit 45 and the failure determination unit 46 when automatic brake test control is executed. As shown in FIG. 4, when the processing is started, the command signal output unit 45 switches the electromagnetic switching valve 24 to an open state (step S1). Next, the command signal output unit 45 outputs a control signal corresponding to the automatic brake standby pressure P1 to the electromagnetic proportional valve 25 (step S2 / first state). After t1 seconds have elapsed since output of the control signal (step S3), the failure determination unit 46 acquires the automatic brake pressure Pp and sets it as Pp1 (step S4).

[0041] Next, the command signal output unit 45 outputs a control signal corresponding to the automatic brake braking pressure P2 to the electromagnetic proportional valve 25 (step S5 / second state). After t2 seconds have elapsed since the output of the control signal (step S6), the fault determination unit 46 obtains the automatic brake pressure Pp and sets it to Pp2 (step S7). The fault determination unit 46 determines that Pp1 is P1 ｍｉｎ When Pp1 is less than P1 ｍａｘ When it is greater than (Step S8, Yes), or when Pp2 is greater than P2 ｍｉｎ When Pp2 is less than or Pp2 ｍａｘ If it is greater than (Step S9, Yes), the automatic braking system malfunction detection flag is turned on (Step S10).

[0042] Next, the command signal output unit 45 turns on the automatic brake test completion flag (the initial value is off) (step S11). In the wheel loader 100 according to this embodiment, this automatic brake test control makes it possible to determine whether an appropriate control pressure can be obtained for the automatic brake device when the brake controller 40 operates the electromagnetic switching valve 24 and the electromagnetic proportional valve 25.

[0043] Next, the control process of the automatic braking system by the brake controller 40 will be described. Figures 5A and 5B are flowcharts showing the control procedure of the automatic braking system. The processes shown in S1 to S23 of Figure 5 are started, for example, when the key switch of the engine 1 is turned on, and are repeated at a predetermined interval (for example, every 0.1 seconds) until the key switch of the engine 1 is turned off.

[0044] As shown in Figure 5, when processing begins, the determination unit 48 receives the engine speed r from the engine control unit 1a. Ｅｎｇ The data obtained is the state of the output signal from the parking brake release switch 8 and the state of the output signal from the automatic brake test switch 43 (step S1). Engine speed r Ｅｎｇ The engine start determination threshold r ＥｎｇＳｔａｒｔ If the value is greater than (Step S2, Yes), the process proceeds to determining the parking brake operation status (Step S3). If the process proceeds to Step S3, the determination unit 48 determines whether or not the parking brake device 7 has been released.

[0045] If the parking brake device 7 is released (step S3, No), the automatic brake test completion flag is turned on (step S4), and the process proceeds to step S8. Therefore, if the parking brake device 7 is released before the automatic brake test execution determination (before the fault diagnosis mode is executed), the automatic brake test completion flag is turned on, and the automatic brake test control is not executed afterward. On the other hand, if the parking brake device 7 is not released (step S3, Yes), the process proceeds to the automatic brake test execution determination.

[0046] First, if the automatic brake test completion flag (initial value is off) is off (step S5, Yes), the process proceeds to step S7, where the command signal output unit 45 and the fault determination unit 46 execute the automatic brake test control process. Also, if the automatic brake test completion flag is on (step S5, No), and the automatic brake test switch 43 is on (step S6, Yes), the process proceeds to step S7, where the automatic brake test control is executed. If the automatic brake test switch 43 is off in step S6, the process proceeds to step S8.

[0047] Furthermore, if the parking brake device 7 is released using the parking brake release switch 8 in step S7, the system determines that the operator is attempting to move the vehicle, interrupts the automatic brake test process, proceeds to step S4, and turns on the automatic brake test completion flag.

[0048] When the system proceeds to step S8, the fault determination unit 46 determines whether the automatic brake fault determination flag is on or off. If the fault determination flag is on (step S8, Yes), the automatic brake system is set to fault determination mode (step S9). When the system is set to fault determination mode, the command signal output unit 45 switches the electromagnetic switching valve 24 to the closed state (step S10) and stops the control signal to set the control pressure of the electromagnetic proportional valve 25 to zero (step S11). In other words, the electromagnetic switching valve 24 and the electromagnetic proportional valve 25 are closed. The system also outputs an automatic brake system fault detection signal to the display device 44, and the display device 44 displays an automatic brake fault notification.

[0049] If the fault detection flag is off (step S8, No), the determination unit 48 obtains data on the output signal of the automatic braking device from the automatic brake selector switch 41 and data on the presence or absence of obstacles behind the wheel loader 100 from the obstacle detection sensor 42 (step S13), and determines the operating mode of the automatic braking device. The determination unit 48 determines whether or not "on" is selected based on the output signal from the automatic brake selector switch 41 (step S14). If "on" is selected in the automatic brake selector switch 41 (step S14, Yes), the process proceeds to determining the presence or absence of obstacles (step S15). On the other hand, if the automatic brake selector switch 41 is off (step S14, No), the automatic braking device is set to standby mode (step S19). The processing in standby mode will be explained later.

[0050] If the process proceeds to step S15, the determination unit 48 determines whether or not there is an obstacle behind the wheel loader 100 based on the data acquired from the obstacle detection sensor 42. If the obstacle detection sensor 42 detects an obstacle in step S3 (step S15, Yes), the automatic braking device is set to automatic braking mode (step S16). The processing in automatic braking mode will be explained later. On the other hand, if the obstacle detection sensor 42 does not detect an obstacle (step S15, No), the automatic braking device is set to standby mode (step S19).

[0051] Next, the processing when the system switches to each mode of the automatic braking device will be explained. When the system switches to the automatic braking mode (step S16), the command signal output unit 45 switches the electromagnetic switching valve 24 to the open position (step S17). Then, proceeding to step S18, the command signal output unit 45 operates the electromagnetic proportional valve 25 with characteristics corresponding to the automatic braking pressure P2.

[0052] When the system enters standby mode (step S19), the command signal output unit 45 switches the electromagnetic switching valve 24 to the closed position (step S20). Next, the process proceeds to step S21, where the command signal output unit 45 operates the electromagnetic proportional valve 25 with characteristics corresponding to the automatic brake standby pressure P1. Then, the fault determination unit 46 acquires data on the automatic brake pressure Pp from the automatic brake pressure sensor 28 (step S22) and compares it with the upper limit pressure P3 when the automatic brake is not activated (step S23). If the automatic brake pressure Pp is greater than the upper limit pressure P3 when the automatic brake is not activated (step S23, No), the fault determination unit 46 turns on the automatic brake device fault determination flag (step S24).

[0053] In the wheel loader 100 according to the embodiment described above, it is possible to determine whether or not there is a malfunction in the electromagnetic switching valve 24 and the electromagnetic proportional valve 25 that constitute the automatic braking system when the engine is started or when requested by the operator (when the automatic brake test switch 43 is turned ON). Furthermore, since the test operation is performed every time the engine is started, it is possible to prevent malfunction of the electromagnetic valve (especially the electromagnetic proportional valve 25) due to the accumulation of contaminants. In addition, if an unintended pressure is applied to the pipeline 23c due to a malfunction of the electromagnetic switching valve 24, it is possible to stop the operation of the electromagnetic proportional valve 25, thereby preventing the disc brake 5 from remaining under load.

[0054] Furthermore, by executing the fault diagnosis mode for each of the following states, the presence or absence of a malfunction in the automatic braking system can be accurately determined: the first state in which the electromagnetic switching valve 24 is open and the output of the electromagnetic proportional valve 25 is controlled to the automatic brake standby pressure P1, and the second state in which the electromagnetic switching valve 24 is open and the output of the electromagnetic proportional valve 25 is controlled to the automatic brake braking pressure P2. In addition, when the parking brake system 7 is released by operating the parking brake release switch 8, the automatic brake test completion flag is turned on (step S4) and the fault diagnosis mode is not executed, so it does not interfere with the movement of the wheel loader 100 and is easy to use.

[0055] The embodiments described above are illustrative for explaining the present invention and are not intended to limit the scope of the present invention to those embodiments only. The parties may implement the present invention in various other ways without departing from the spirit of the invention.

[0056] Furthermore, in the above embodiment, an obstacle detection sensor 42 installed facing the rear of the vehicle body (rear frame 120) is configured to sense obstacles. However, the direction in which obstacle sensing is performed is not limited to the rear of the vehicle body. For example, sensing may be performed only in front of the vehicle body (front frame 110) or both in the front and rear directions. In addition, although a wheel loader 100 was used as an example to describe the embodiment of the present invention, it goes without saying that the present invention can be applied to any work vehicle, such as a wheeled hydraulic excavator.

[0057] 1: Engine 5: Disc brake (braking device) 6: Tires 7: Parking brake (auxiliary brake device) 8: Parking brake release switch 20: Brake valve 21: Hydraulic source 22: Brake pedal 23a, 23b, 23c, 23d: Piping 24: Solenoid switching valve (automatic braking device) 25: Solenoid proportional valve (automatic braking device) 26: Throttle (automatic braking device) 28: Automatic brake pressure sensor (pressure sensor) 31: Hydraulic pump 40: Brake controller (controller) 41: Automatic brake switching switch 42: Obstacle detection sensor 43: Automatic brake test switch 44: Display device 100: Wheel loader (work vehicle) 101: Front work equipment 110: Front frame (vehicle body) 120: Rear frame (vehicle body)

Claims

1. A work vehicle comprising: a vehicle body; a running gear for moving the vehicle body; a braking device for braking the running gear with supplied pressurized oil; an automatic braking device including an electromagnetic proportional valve and an electromagnetic switching valve for controlling the supply of pressurized oil to the braking device; a pressure sensor for detecting the control pressure of the automatic braking device; an obstacle detection sensor for detecting obstacles present around the vehicle body; and a controller for controlling the opening and closing operations of the electromagnetic proportional valve and the electromagnetic switching valve based on detection signals from the obstacle detection sensor, wherein the controller executes a fault diagnosis mode based on the fulfillment of predetermined conditions; when the fault diagnosis mode is executed, the controller opens and closes the electromagnetic proportional valve and the electromagnetic switching valve, compares the control pressure detected by the pressure sensor with a pre-set threshold, and determines that the automatic braking device is in a faulty state when the control pressure detected by the pressure sensor is not within the range of the threshold.

2. A work vehicle according to claim 1, wherein the automatic braking device is configured to activate the braking device by opening the electromagnetic proportional valve and the electromagnetic switching valve, and the controller controls the electromagnetic proportional valve and the electromagnetic switching valve to close when it determines that the automatic braking device is in a malfunction state.

3. A work vehicle according to claim 1, wherein the controller, in the fault diagnosis mode, opens the electromagnetic switching valve and switches the opening and closing operation of the electromagnetic proportional valve between a first state and a second state, and determines a fault in the automatic braking device for each state.

4. A work vehicle according to claim 1, wherein the vehicle body further comprises an auxiliary brake device operated independently of the brake device, and the controller interrupts the execution of the fault diagnosis mode if the auxiliary brake device is released while the fault diagnosis mode is being executed.

5. A work vehicle according to claim 1, further comprising an engine as a drive source for the running gear and an automatic brake test switch for executing the fault diagnosis mode, wherein the controller executes the fault diagnosis mode based on at least the starting of the engine or the turning on of the automatic brake test switch as the predetermined conditions.

6. A work vehicle according to claim 1, wherein the vehicle body further comprises an auxiliary brake device operated independently of the brake device, and the controller controls the system so as not to transition to the fault diagnosis mode if the auxiliary brake device is released before the fault diagnosis mode is executed.

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