Brake system

Abstract

To provide a brake system in which brake operation at manual operation can be compatible with brake control at automatic operation at low cost.SOLUTION: A brake system 1 comprises: a solenoid valve 9 which has a first open position 9a which communicates between a hydraulic fluid channel 21 where hydraulic fluid flows between a brake booster 6 and the solenoid valve 9 and a hydraulic fluid channel 23 where hydraulic fluid flows between the solenoid valve 9 and a brake wheel cylinder 4, and a second open position 9b which communicates between a hydraulic fluid channel 22 where hydraulic fluid flows to the solenoid valve 9 without passing through the brake booster 6 and the hydraulic fluid channel 23; and a brake control part 41 which controls, when braking a fork lift 2 during automatic operation of the fork lift 2, a solenoid operation part 24 of the solenoid valve 9 to switch a position of the solenoid valve 9 from the first open position 9a to the second open position 9b.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a braking system.

Background Art

[0002] As a braking system used in industrial vehicles and the like, for example, the technology described in Patent Document 1 is known. The braking system described in Patent Document 1 includes a brake pedal, a vacuum booster and a master cylinder connected to the brake pedal via a rod, a first hydraulic cylinder having a piston disposed between the brake pedal and the vacuum booster and connected to the rod, a second hydraulic cylinder connected to the first hydraulic cylinder via a hydraulic pipe, a movable member that pushes the piston of the second hydraulic cylinder, and a motor that drives the movable member. When the motor is rotationally driven while the driver is not stepping on the brake pedal, the movable member advances together with the piston of the second hydraulic cylinder, and hydraulic pressure is generated inside the second hydraulic cylinder, the hydraulic pipe, and the first hydraulic cylinder. For this reason, the piston of the first hydraulic cylinder advances and pushes the rod, thereby operating the vacuum booster and generating brake hydraulic pressure in the master cylinder.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above prior art, in order to brake an industrial vehicle during automatic driving of the industrial vehicle, it is necessary to add a dedicated first hydraulic cylinder, a second hydraulic cylinder, a movable member, and a motor between the brake pedal and the vacuum booster. For this reason, the device for automatically braking the industrial vehicle becomes complicated, and the number of newly designed and manufactured products increases. Therefore, the cost for achieving compatibility between the brake operation during manual driving and the brake control during automatic driving increases.

[0005] An object of the present invention is to provide a brake system capable of achieving compatibility between the brake operation during manual driving and the brake control during automatic driving at low cost.

Means for Solving the Problems

[0006] One aspect of the present invention is a brake system for braking an industrial vehicle capable of automatic driving, including a brake pedal operated by a driver of the industrial vehicle, a hydraulic brake device that applies a braking force to the wheels of the industrial vehicle, an oil pump that supplies hydraulic oil to the hydraulic brake device, a booster device disposed between the oil pump and the hydraulic brake device to assist the force of the driver operating the brake pedal, a solenoid valve disposed between the booster device and the hydraulic brake device, a first hydraulic oil flow path through which hydraulic oil flows between the booster device and the solenoid valve, a second hydraulic oil flow path through which hydraulic oil that does not pass through the booster device flows toward the solenoid valve, a third hydraulic oil flow path through which hydraulic oil flows between the solenoid valve and the hydraulic brake device, and a brake control unit that controls the solenoid valve when braking the industrial vehicle during automatic driving of the industrial vehicle. The solenoid valve has a first open position that connects the first hydraulic oil flow path and the third hydraulic oil flow path and blocks the second hydraulic oil flow path and the third hydraulic oil flow path, and a second open position that connects the second hydraulic oil flow path and the third hydraulic oil flow path and blocks the first hydraulic oil flow path and the third hydraulic oil flow path. The brake control unit controls the solenoid operation unit of the solenoid valve so that the position of the solenoid valve switches from the first open position to the second open position when braking the industrial vehicle during automatic driving of the industrial vehicle.

[0007] In such a braking system, usually the solenoid valve is in the first open position, and the manual operation of the industrial vehicle is carried out. During the manual operation of the industrial vehicle, when the brake pedal is operated by the driver, the hydraulic oil from the booster device flows through the first hydraulic oil flow path, the solenoid valve and the third hydraulic oil flow path and is supplied to the hydraulic braking device, so that the hydraulic braking device applies braking force to the wheels. On the other hand, when braking the industrial vehicle during automatic driving of the industrial vehicle, the solenoid operation part of the solenoid valve is controlled so that the position of the solenoid valve is switched from the first open position to the second open position. For this reason, the hydraulic oil that does not pass through the booster device flows through the second hydraulic oil flow path, the solenoid valve and the third hydraulic oil flow path and is supplied to the hydraulic braking device, so that the hydraulic braking device applies braking force to the wheels. Here, as the solenoid valve, an existing electromagnetic switching valve can be used. Therefore, it is not necessary to newly design and manufacture a device for automatically braking the industrial vehicle. Thereby, the compatibility between the brake operation during manual operation and the brake control during automatic operation can be realized at low cost.

[0008] The braking system further includes a brake pressure detection unit that detects the pressure of the hydraulic oil supplied to the hydraulic braking device. When braking the industrial vehicle during automatic driving of the industrial vehicle, the braking control unit may control the solenoid operation part so that the position of the solenoid valve is switched from the first position to the second position and the pressure of the hydraulic oil supplied to the hydraulic braking device is adjusted to the set pressure.

[0009] In such a configuration, when braking the industrial vehicle during automatic driving of the industrial vehicle, the pressure of the hydraulic oil supplied to the hydraulic braking device is adjusted to the set pressure. Therefore, the braking force applied to the wheels of the industrial vehicle can be easily adjusted.

[0010] The braking system further includes an accumulator that accumulates the hydraulic oil discharged from the oil pump, and a charge valve that is disposed between the oil pump, the booster device, and the accumulator and switches an oil passage through which the hydraulic oil from the oil pump is supplied to the accumulator and an oil passage through which the hydraulic oil from the oil pump is supplied to the booster device according to the pressure of the accumulator. The second hydraulic oil passage may be a passage through which the hydraulic oil flows from the accumulator to the solenoid valve.

[0011] In such a configuration, when braking the industrial vehicle during automatic driving of the industrial vehicle, the hydraulic oil accumulated in the accumulator flows through the second hydraulic oil passage, the solenoid valve, and the third hydraulic oil passage and is supplied to the hydraulic brake device, so that the hydraulic brake device applies a braking force to the wheels. Therefore, during the automatic driving of the industrial vehicle, the industrial vehicle can be effectively braked with a simple configuration.

[0012] The braking system further includes an accumulator pressure detection unit that detects the pressure of the accumulator, and a pump control unit that controls a drive source that rotationally drives the oil pump based on the pressure of the accumulator during automatic driving of the industrial vehicle. The pump control unit may control the drive source so as to stop the rotation of the oil pump or decrease the rotation speed of the oil pump when the pressure of the accumulator is equal to or higher than a specified pressure.

[0013] In such a configuration, when the pressure of the accumulator is equal to or higher than the specified pressure, the rotation of the oil pump stops or the rotation speed of the oil pump decreases. When braking the industrial vehicle during automatic driving of the industrial vehicle, since the hydraulic oil is supplied from the accumulator to the hydraulic brake device, it is not necessary to always operate the oil pump. Therefore, by stopping the rotation of the oil pump or decreasing the rotation speed of the oil pump, the energy consumption of the oil pump is reduced. Therefore, the fuel efficiency of the industrial vehicle is improved, and the operation time of the industrial vehicle can be extended.

[0014] The braking system may further include a detection unit that detects whether the brake pedal has been operated during the automatic driving of the industrial vehicle, and an automatic driving stop control unit that controls the solenoid operation unit so that when the detection unit detects that the brake pedal has been operated during the automatic driving of the industrial vehicle with the solenoid valve in the second open position, the position of the solenoid valve switches from the second open position to the first open position.

[0015] In such a configuration, when the industrial vehicle brakes during automatic driving, if the brake pedal is operated by the driver with the solenoid valve in the second open position, the position of the solenoid valve switches from the second open position to the first open position, and the braking of the industrial vehicle by automatic driving is forcibly stopped. For this reason, when hydraulic oil is supplied from the booster device to the hydraulic braking device, braking force is applied to the wheels. Thus, when the brake pedal is operated during the automatic driving of the industrial vehicle, the driving mode switches from automatic driving to manual driving. Therefore, it is possible to prevent brake control from being performed against the driver's intention.

Effect of the Invention

[0016] According to the present invention, it is possible to inexpensively achieve compatibility between the brake operation during manual driving and the brake control during automatic driving.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0019] FIG. 1 is a configuration diagram showing a brake system according to an embodiment of the present invention. In FIG. 1, the brake system 1 of the present embodiment is mounted on a forklift 2 which is one of industrial vehicles. The forklift 2 is an electric forklift capable of autonomous driving.

[0020] The brake system 1 is a system for braking the forklift 2. The brake system 1 includes a brake pedal 3, a brake wheel cylinder 4, an oil pump 5, a brake booster 6, an accumulator 7, a charge valve 8, and a solenoid valve 9.

[0021] The brake pedal 3 is an operation pedal that is stepped on and operated by the driver of the forklift 2 with the foot.

[0022] The brake wheel cylinder 4 is a hydraulic brake device that applies a braking force to the wheels 10 of the forklift 2 using hydraulic oil. The brake wheel cylinder 4 has, for example, a brake disc or a brake drum.

[0023] The oil pump 5 is rotationally driven by a pump motor 11. The pump motor 11 is a drive source that rotationally drives the oil pump 5. The oil pump 5 sucks up the hydraulic oil stored in the oil tank 12 and supplies it to the brake booster 6 and the brake wheel cylinder 4.

[0024] A suction filter 13 for preventing dust from entering the oil pump 5 is disposed in the oil tank 12. The suction filter 13 is connected to the oil pump 5 via an oil flow path 14. The oil flow path 14 is a path through which the hydraulic oil flows from the suction filter 13 to the oil pump 5.

[0025] The brake booster 6 is connected to the brake pedal 3 and is disposed between the oil pump 5 and the brake wheel cylinder 4. The brake booster 6 is a force - multiplying device that assists the force with which the driver operates the brake pedal 3.

[0026] The brake booster 6 is connected to the oil tank 12 via oil flow paths 15, 16. The oil flow paths 15, 16 are paths through which the hydraulic oil flows from the brake booster 6 to the oil tank 12. A cooler 17 for cooling the hydraulic oil returning to the oil tank 12 is provided in the oil flow path 16.

[0027] The accumulator 7 accumulates the hydraulic oil discharged from the discharge port 5a of the oil pump 5. The accumulator 7 is filled with a pressurized gas such as nitrogen gas. The hydraulic oil from the oil pump 5 is confined by a valve in the accumulator 7 and accumulated. When the valve is opened in that state, the hydraulic oil in the accumulator 7 is pushed out and discharged by the force of the expansion of the pressurized gas.

[0028] The charge valve 8 is disposed between the oil pump 5, the brake booster 6, and the accumulator 7. The charge valve 8 switches an oil passage through which hydraulic oil from the oil pump 5 is supplied to the brake booster 6 and an oil passage through which hydraulic oil from the oil pump 5 is supplied to the accumulator 7 according to the pressure of the accumulator 7.

[0029] The charge valve 8 is connected to the discharge port 5a of the oil pump 5 via the hydraulic oil passage 18. The hydraulic oil passage 18 is a passage through which hydraulic oil flows from the oil pump 5 to the charge valve 8.

[0030] Also, the charge valve 8 is connected to the brake booster 6 via the hydraulic oil passage 19. The hydraulic oil passage 19 is a passage through which hydraulic oil flows from the charge valve 8 to the brake booster 6.

[0031] Also, the charge valve 8 is connected to the accumulator 7 via the hydraulic oil passage 20. The hydraulic oil passage 20 is a passage through which hydraulic oil flows from the charge valve 8 to the accumulator 7.

[0032] The charge valve 8 switches an oil passage that connects the hydraulic oil passage 18 and the hydraulic oil passage 19 and an oil passage that connects the hydraulic oil passage 18 and the hydraulic oil passages 19 and 20.

[0033] Specifically, until the pressure of the accumulator 7 reaches the set pressure, the charge valve 8 supplies the hydraulic oil from the oil pump 5 to the accumulator 7 preferentially by connecting the hydraulic oil passage 18 and the hydraulic oil passages 19 and 20. When the pressure of the accumulator 7 reaches the set pressure, the charge valve 8 supplies the hydraulic oil from the oil pump 5 to the brake booster 6 by connecting the hydraulic oil passage 18 and the hydraulic oil passage 19 and blocking the hydraulic oil passage 18 and the hydraulic oil passage 20. Note that the set pressure of the charge valve 8 can be adjusted manually.

[0034] The solenoid valve 9 is disposed between the brake booster 6 and the accumulator 7 and the brake wheel cylinder 4. The solenoid valve 9 is an electromagnetic proportional switching valve that switches the flow of hydraulic oil between the brake booster 6 and the accumulator 7 and the brake wheel cylinder 4.

[0035] The solenoid valve 9 is connected to the brake booster 6 via the hydraulic oil flow path 21. The hydraulic oil flow path 21 is a first hydraulic oil flow path through which hydraulic oil flows bidirectionally between the brake booster 6 and the solenoid valve 9.

[0036] Also, the solenoid valve 9 is connected to the accumulator 7 via the hydraulic oil flow path 22. The hydraulic oil flow path 22 is a second hydraulic oil flow path through which hydraulic oil flows from the accumulator 7 to the solenoid valve 9. The hydraulic oil flow path 22 is a flow path through which hydraulic oil that does not pass through the brake booster 6 flows toward the solenoid valve 9.

[0037] Also, the solenoid valve 9 is connected to the brake wheel cylinder 4 via the hydraulic oil flow path 23. The hydraulic oil flow path 23 is a third hydraulic oil flow path through which hydraulic oil flows bidirectionally between the solenoid valve 9 and the brake wheel cylinder 4.

[0038] As shown in FIG. 2, the solenoid valve 9 has a first open position 9a that communicates the hydraulic oil flow path 21 and the hydraulic oil flow path 23 and blocks the hydraulic oil flow path 22 and the hydraulic oil flow path 23, a second open position 9b that communicates the hydraulic oil flow path 22 and the hydraulic oil flow path 23 and blocks the hydraulic oil flow path 21 and the hydraulic oil flow path 23, and a closed position 9c that is disposed between the first open position 9a and the second open position 9b and blocks the hydraulic oil flow paths 21, 22 and the hydraulic oil flow path 23.

[0039] The solenoid valve 9 is provided with a solenoid operating unit 24 to which an electric signal is input. When the solenoid valve 9 is in the first open position 9a, the opening degree of the solenoid valve 9 is constant. When the solenoid valve 9 is in the second open position 9b, the opening degree of the solenoid valve 9 changes according to the value of the electric signal (for example, current value) input to the solenoid operating unit 24. Specifically, the larger the value of the electric signal input to the solenoid operating unit 24, the larger the opening degree of the solenoid valve 9.

[0040] In a normal state where no electric signal is supplied to the solenoid operating unit 24, the solenoid valve 9 is in the first open position 9a (shown in the figure) by the spring 25. When an electric signal is supplied to the solenoid operating unit 24 and the solenoid operating unit 24 is energized, the solenoid valve 9 switches from the first open position 9a to the second open position 9b.

[0041] Also, as shown in FIGS. 1 and 2, the braking system 1 includes an automatic operation switch 30, a pressure sensor 31, a potentiometer 32, an alarm 33, a brake controller 34, a pressure sensor 35, and a pump controller 36.

[0042] The automatic operation switch 30 is an instruction operation unit for the driver to instruct the automatic operation of the forklift 2. When the automatic operation switch 30 is OFF, the operation mode of the forklift 2 is the manual operation mode. The manual operation mode is a mode in which the forklift 2 is run by manual operation by the driver. When the automatic operation switch 30 is ON, the operation mode of the forklift 2 is the automatic operation mode. The automatic operation mode is a mode in which the forklift 2 is automatically controlled to run by the automatic operation controller 37.

[0043] When the automatic driving switch 30 is turned ON and the automatic driving of the forklift 2 is instructed, the automatic driving controller 37 controls the drive unit 38 based on the detection values of various sensors so that the forklift 2 automatically travels. The drive unit 38 includes a traveling motor that rotates the wheels 10 of the forklift 2 and a steering motor that steers the wheels 10.

[0044] The pressure sensor 31 is connected to the hydraulic oil flow path 23. The pressure sensor 31 constitutes a brake pressure detection unit that detects the pressure of the hydraulic oil supplied to the brake wheel cylinder 4 as the brake pressure.

[0045] The potentiometer 32 detects the depression amount (operation amount) of the brake pedal 3. The potentiometer 32 constitutes a detection unit that detects whether the brake pedal 3 has been operated during the automatic driving of the forklift 2.

[0046] When it is detected that the brake pedal 3 has been operated during the automatic driving of the forklift 2, the alarm 33 gives an alarm sound or an alarm display to the driver.

[0047] The brake controller 34 is composed of a CPU, a RAM, a ROM, an input / output interface, etc. The brake controller 34 has a braking control unit 41 and an automatic driving stop control unit 42.

[0048] When braking the forklift 2 during the automatic driving of the forklift 2, the braking control unit 41 controls the solenoid valve 9. When braking the forklift 2 during the automatic driving of the forklift 2, the braking control unit 41 controls the solenoid operation unit 24 of the solenoid valve 9 so that the position of the solenoid valve 9 switches from the first open position 9a to the second open position 9b and the pressure of the hydraulic oil supplied to the brake wheel cylinder 4 is adjusted to the set pressure.

[0049] FIG. 3 is a flowchart showing the procedure of the braking control process executed by the braking control unit 41. This process is executed when the automatic driving switch 30 is turned on. Before the execution of this process, the solenoid valve 9 is in the first open position 9a.

[0050] In FIG. 3, the braking control unit 41 first acquires the control command signal of the automatic driving controller 37 (step S101). Then, the braking control unit 41 determines whether it is the braking start timing of the forklift 2 based on the control command signal of the automatic driving controller 37 (step S102). When the braking control unit 41 determines that it is not the braking start timing of the forklift 2, it executes the above step S101 again.

[0051] When the braking control unit 41 determines that it is the braking start timing of the forklift 2, it outputs a control signal for switching the position of the solenoid valve 9 from the first open position 9a to the second open position 9b to the solenoid operation unit 24 of the solenoid valve 9 (step S103). As a result, since the hydraulic oil flow path 22 and the hydraulic oil flow path 23 communicate with each other, hydraulic oil is supplied from the accumulator 7 to the brake wheel cylinder 4, and a braking force is applied to the wheels 10.

[0052] Subsequently, the braking control unit 41 acquires the detection value of the pressure sensor 31 (step S104). Then, the braking control unit 41 outputs a control signal for adjusting the pressure of the hydraulic oil (brake pressure) supplied to the brake wheel cylinder 4 to the set pressure based on the detection value of the pressure sensor 31 to the solenoid operation unit 24 (step S105). The information on the set pressure is included in the control command signal of the automatic driving controller 37. As a result, the solenoid valve 9 is adjusted to open at an opening degree corresponding to the set pressure in the second open position 9b.

[0053] Subsequently, the braking control unit 41 acquires the control command signal of the automatic driving controller 37 (step S106). Then, the braking control unit 41 determines whether it is the braking end timing of the forklift 2 based on the control command signal of the automatic driving controller 37 (step S107). When the braking control unit 41 determines that it is not the braking end timing of the forklift 2, it executes the above step S106 again.

[0054] When the braking control unit 41 determines that it is the braking end timing of the forklift 2, it outputs a control signal for switching the position of the solenoid valve 9 from the second open position 9b to the first open position 9a to the solenoid operation unit 24 of the solenoid valve 9 (step S108), and executes the above step S101 again. As a result, since the hydraulic oil flow path 22 and the hydraulic oil flow path 23 are blocked, the supply of hydraulic oil from the accumulator 7 to the brake wheel cylinder 4 stops, and the application of braking force to the wheels 10 is released.

[0055] Returning to FIG. 2, when the automatic driving stop control unit 42 detects that the brake pedal 3 has been operated during the automatic driving of the forklift by the potentiometer 32 while the solenoid valve 9 is in the second open position 9b, it controls the solenoid operation unit 24 of the solenoid valve 9 so that the position of the solenoid valve 9 switches from the second open position 9b to the first open position 9a.

[0056] FIG. 4 is a flowchart showing the procedure of the automatic driving stop control process executed by the automatic driving stop control unit 42. This process is also executed when the automatic driving switch 30 is turned on.

[0057] In FIG. 4, the automatic driving stop control unit 42 determines whether the current position of the solenoid valve 9 is the second open position 9b (step S111). The determination of whether the current position of the solenoid valve 9 is the second open position 9b is made based on, for example, the control signal output from the braking control unit 41 to the solenoid operation unit 24 of the solenoid valve 9.

[0058] When the automatic driving stop control unit 42 determines that the current position of the solenoid valve 9 is the second open position 9b, it acquires the detected value of the potentiometer 32 (step S112). Then, the automatic driving stop control unit 42 determines whether the brake pedal 3 has been operated based on the detected value of the potentiometer 32 (step S113). When the automatic driving stop control unit 42 determines that the brake pedal 3 has not been operated, it executes the above step S111 again.

[0059] When the automatic driving stop control unit 42 determines that the brake pedal 3 has been operated, it outputs a control signal for switching the position of the solenoid valve 9 from the second open position 9b to the first open position 9a to the solenoid operation unit 24 of the solenoid valve 9 (step S114). As a result, since the hydraulic oil flow path 22 and the hydraulic oil flow path 23 are blocked, the brake control by the automatic driving of the forklift 2 is forcibly stopped.

[0060] Then, the automatic driving stop control unit 42 outputs an alarm signal to the alarm 33 (step S115) and executes the above step S111 again. Thereby, an alarm indicating that the brake control by the automatic driving of the forklift 2 has been forcibly stopped is given to the driver by the alarm 33.

[0061] Returning to FIG. 2, the pressure sensor 35 is connected to the hydraulic oil flow path 20. The pressure sensor 35 constitutes an accumulator pressure detection unit that detects the pressure of the accumulator 7.

[0062] The pump controller 36 is composed of a CPU, a RAM, a ROM, an input / output interface, etc. The pump controller 36 constitutes a pump control unit that controls the pump motor 11 based on the pressure of the accumulator 7 during the automatic driving of the forklift 2. When the pressure of the accumulator 7 is equal to or higher than the specified pressure, the pump controller 36 controls the pump motor 11 to stop the rotation of the oil pump 5.

[0063] FIG. 5 is a flowchart showing the procedure of the oil pump control process executed by the pump controller 36. This process is executed when the ignition switch (not shown) of the forklift 2 is turned ON.

[0064] In FIG. 5, the pump controller 36 first acquires the operation signal of the automatic operation switch 30 (step S121). Then, the pump controller 36 determines whether the operation signal of the automatic operation switch 30 is an ON signal (step S122).

[0065] When the pump controller 36 determines that the operation signal of the automatic operation switch 30 is not an ON signal, it determines that the operation mode of the forklift 2 is the manual operation mode, and outputs a control signal for rotating the pump motor 11 at a specified rotational speed to the pump motor 11 (step S123), and executes the above step S121 again. Thereby, the oil pump 5 rotates at the specified rotational speed.

[0066] When the pump controller 36 determines that the operation signal of the automatic operation switch 30 is an ON signal, it determines that the operation mode of the forklift 2 is the automatic operation mode, and acquires the detection value of the pressure sensor 35 (step S124). Then, the pump controller 36 determines whether the pressure of the accumulator 7 is equal to or higher than the specified pressure based on the detection value of the pressure sensor 35 (step S125). The specified pressure is the pressure at which the accumulator 7 is maintained in the pressure accumulation state.

[0067] When the pump controller 36 determines that the pressure of the accumulator 7 is lower than the specified pressure, it outputs a control signal for rotating the pump motor 11 at a specified rotational speed to the pump motor 11 (step S123), and executes the above step S121 again. Thereby, the oil pump 5 rotates at the specified rotational speed.

[0068] When the pump controller 36 determines that the pressure of the accumulator 7 is equal to or higher than the specified pressure, it outputs a control signal for stopping the rotation of the pump motor 11 to the pump motor 11 (step S126), and executes the above-described step S121 again. As a result, the rotation of the oil pump 5 stops.

[0069] In the braking system 1 as described above, in the manual operation mode in which the automatic operation switch 30 is not turned on, the solenoid valve 9 is in the first open position 9a. In this case, when the driver operates the brake pedal 3, the hydraulic oil in the brake booster 6 flows through the hydraulic oil flow path 21, the solenoid valve 9, and the hydraulic oil flow path 23 and is supplied to the brake wheel cylinder 4. As a result, the brake wheel cylinder 4 operates, and braking force is applied to the wheel 10.

[0070] When the driver turns on the automatic operation switch 30, the operation mode of the forklift 2 switches from the manual operation mode to the automatic operation mode, and the drive unit 38 is controlled by the automatic operation controller 37 so that the forklift 2 travels automatically.

[0071] When the forklift 2 stops or decelerates during the automatic travel of the forklift 2, the position of the solenoid valve 9 is switched from the first open position 9a to the second open position 9b by the control signal from the brake controller 34, and the hydraulic oil flow path 22 and the hydraulic oil flow path 23 are communicated with each other. However, while the position of the solenoid valve 9 is being switched, the position of the solenoid valve 9 temporarily becomes the closed position 9c, so that the backflow of the hydraulic oil from the brake wheel cylinder 4 to the accumulator 7 is prevented.

[0072] Then, the hydraulic oil accumulated in the accumulator 7 flows through the hydraulic oil flow path 22, the solenoid valve 9, and the hydraulic oil flow path 23 and is supplied to the brake wheel cylinder 4. As a result, the brake wheel cylinder 4 operates, and braking force is applied to the wheel 10.

[0073] When the pressure of the accumulator 7 decreases and the pressure accumulation state of the accumulator 7 cannot be maintained, the hydraulic oil is supplied from the oil pump 5 to the accumulator 7 by the charge valve 8, so that the accumulator 7 enters the pressure accumulation state.

[0074] As described above, in this embodiment, normally the solenoid valve 9 is in the first open position 9a, and the manual operation of the forklift 2 is carried out. When the brake pedal 3 is operated by the driver during the manual operation of the forklift 2, the hydraulic oil from the brake booster 6 flows through the hydraulic oil flow path 21, the solenoid valve 9 and the hydraulic oil flow path 23 and is supplied to the brake wheel cylinder 4, so that the brake wheel cylinder 4 applies a braking force to the wheel 10. On the other hand, when braking the forklift 2 during the automatic operation of the forklift 2, the solenoid operation portion 24 of the solenoid valve 9 is controlled so that the solenoid valve 9 switches from the first open position 9a to the second open position 9b. For this reason, the hydraulic oil that does not pass through the brake booster 6 flows through the hydraulic oil flow path 22, the solenoid valve 9 and the hydraulic oil flow path 23 and is supplied to the brake wheel cylinder 4, so that the brake wheel cylinder 4 applies a braking force to the wheel 10. Here, as the solenoid valve 9, an existing electromagnetic proportional switching valve can be used. Therefore, it is not necessary to newly design and manufacture a device for automatically braking the forklift 2. Thereby, it is possible to achieve both the brake operation during manual operation and the brake control during automatic operation at low cost.

[0075] Also, during the automatic operation of the forklift 2, since the hydraulic oil is supplied to the brake wheel cylinder 4 without automatically operating the brake pedal 3, the variation in the braking force applied to the wheel 10 is suppressed, and the time lag generated when the braking force is applied to the wheel 10 is reduced.

[0076] Also, in this embodiment, when braking the forklift 2 during automatic driving, the solenoid operation unit 24 of the solenoid valve 9 is controlled so that the pressure of the hydraulic oil supplied to the brake wheel cylinder 4 is not adjusted to the set pressure. Therefore, the braking force applied to the wheels 10 of the forklift 2 can be easily adjusted.

[0077] Also, in this embodiment, when braking the forklift 2 during automatic driving, the hydraulic oil accumulated in the accumulator 7 flows through the hydraulic oil flow path 22, the solenoid valve 9, and the hydraulic oil flow path 23 and is supplied to the brake wheel cylinder 4, whereby the brake wheel cylinder 4 applies a braking force to the wheels 10. Therefore, during the automatic driving of the forklift 2, the forklift 2 can be effectively braked with a simple configuration. Also, as the accumulator 7 and the charge valve 8, existing products can be used.

[0078] Also, in this embodiment, when the pressure of the accumulator 7 is equal to or higher than the specified pressure, the rotation of the oil pump 5 stops. When braking the forklift 2 during automatic driving, since the hydraulic oil is supplied from the accumulator 7 to the brake wheel cylinder 4, it is not necessary to always operate the oil pump 5. Therefore, by stopping the rotation of the oil pump 5, the energy consumption of the oil pump 5 is reduced. Therefore, the fuel efficiency of the forklift 2 is improved, and the operating time of the forklift 2 can be extended.

[0079] In addition, in the present embodiment, when the forklift 2 is braked during automatic driving of the forklift 2, and the brake pedal 3 is operated by the driver while the solenoid valve 9 is in the second open position 9b, the position of the solenoid valve 9 switches from the second open position 9b to the first open position 9a, and the braking of the forklift 2 by automatic driving is forcibly stopped. Therefore, the working oil is supplied from the brake booster 6 to the brake wheel cylinder 4, and braking force is applied to the wheels 10. When the brake pedal 3 is operated during the automatic driving of the forklift 2 in this way, the operation switches from automatic driving to manual driving. Accordingly, it is possible to prevent the brake control from being performed against the intention of the driver.

[0080] FIG. 6 is a flowchart showing a modification of the procedure of the oil pump control process executed by the pump controller 36, and corresponds to FIG. 5.

[0081] In FIG. 6, the pump controller 36 executes the above-described steps S121, S122, S124, and S125. Then, when the pump controller 36 determines in step S125 that the pressure of the accumulator 7 is equal to or higher than the specified pressure, the pump controller 36 outputs a control signal for reducing the rotational speed of the pump motor 11 to be lower than the specified rotational speed to the pump motor 11 (step S126A). As a result, the rotational speed of the oil pump 5 decreases below the specified rotational speed.

[0082] In such a modification, by reducing the rotational speed of the oil pump 5, the energy consumption of the oil pump 5 is reduced. Therefore, as in the above embodiment, the fuel efficiency of the forklift 2 can be improved, and the operating time of the forklift 2 can be extended.

[0083] Note that the present invention is not limited to the above embodiment. For example, in the above embodiment, the solenoid valve 9 is an electromagnetic proportional switching valve whose opening degree is variable in the second open position 9b, but the solenoid valve 9 is not particularly limited to an electromagnetic proportional switching valve, and an electromagnetic switching valve or the like whose opening degree is constant in the second open position 9b may be used.

[0084] Further, in the above embodiment, the brake controller 34 and the pump controller 36 are provided, but the form is not particularly limited thereto, and the brake controller 34 and the pump controller 36 may be configured by one controller. In this case, one controller will have the above-described braking control unit 41 and automatic operation stop control unit 42, and the pump control unit which is the function of the pump controller 36.

[0085] Further, in the above embodiment, the oil pump 5 is driven by the pump motor 11, but the drive source for driving the oil pump 5 is not particularly limited to the pump motor 11, and it may be an engine 50 as shown in FIG. 7.

[0086] When the drive source is the engine 50, since control of the rotation speed of the oil pump 5 becomes unnecessary, the above-described pressure sensor 35 and pump controller 36 may be omitted. Further, when the drive source is the engine 50, the forklift 2 may be provided with an inching pedal. In this case, even when the inching pedal is operated by the driver, since the hydraulic oil is supplied from the brake booster 6 to the brake wheel cylinder 4, a braking force is applied to the wheels 10.

[0087] Further, in the above embodiment, the brake booster 6 is disposed between the oil pump 5 and the brake wheel cylinder 4, but the force multiplying device for assisting the force with which the driver operates the brake pedal 3 is not particularly limited to the brake booster 6, and for example, a brake valve, a master cylinder, or the like may be used.

[0088] Further, in the above embodiment, by detecting the operation amount of the brake pedal 3 by the potentiometer 32, it is detected whether the brake pedal 3 has been operated during the automatic operation of the forklift 2, but the form is not particularly limited thereto. For example, it may be detected whether the brake pedal 3 has been operated during the automatic operation of the forklift 2 by using a contact switch or the like that detects whether the brake pedal 3 has come into contact.

[0089] Furthermore, although the brake system 1 of the above embodiment is mounted on the forklift 2, the present invention is applicable to industrial vehicles other than forklifts (for example, towing tractors, etc.) as long as they are equipped with a brake pedal.

Explanation of Signs

[0090] 1... Brake system, 2... Forklift (industrial vehicle), 3... Brake pedal, 4... Brake wheel cylinder (hydraulic brake device), 5... Oil pump, 6... Brake booster (doubling device), 7... Accumulator, 8... Charge valve, 9... Solenoid valve, 9a... First open position, 9b... Second open position, 10... Wheel, 21... Working oil flow path (first working oil flow path), 22... Working oil flow path (second working oil flow path), 23... Working oil flow path (third working oil flow path), 31... Pressure sensor (brake pressure detection unit), 32... Potentiometer (detection unit), 35... Pressure sensor (accumulator pressure detection unit), 36... Pump controller (pump control unit), 41... Brake control unit, 42... Automatic operation stop control unit.

Claims

1. In a braking system for braking an automatically drivable industrial vehicle, a brake pedal operated by a driver of the industrial vehicle, a hydraulic brake device that applies braking force to wheels of the industrial vehicle, an oil pump that supplies hydraulic oil to the hydraulic brake device, a force multiplying device that is disposed between the oil pump and the hydraulic brake device and assists the force of the driver operating the brake pedal, an accumulator that accumulates the hydraulic oil discharged from the oil pump, a charge valve that is disposed between the oil pump, the force multiplying device, and the accumulator and switches an oil passage through which the hydraulic oil from the oil pump is supplied to the accumulator and an oil passage through which the hydraulic oil from the oil pump is supplied to the force multiplying device according to the pressure of the accumulator, a solenoid valve disposed between the force multiplying device and the hydraulic brake device, a first hydraulic oil flow path through which hydraulic oil flows between the force multiplying device and the solenoid valve, a second hydraulic oil flow path through which hydraulic oil that does not pass through the force multiplying device flows toward the solenoid valve, a third hydraulic oil flow path through which hydraulic oil flows between the solenoid valve and the hydraulic brake device, and a braking control unit that controls the solenoid valve when braking the industrial vehicle during automatic driving of the industrial vehicle, wherein the second hydraulic oil flow path is a flow path through which hydraulic oil flows from the accumulator to the solenoid valve, the solenoid valve has a first open position in which the first hydraulic oil flow path and the third hydraulic oil flow path are communicated with each other and the second hydraulic oil flow path and the third hydraulic oil flow path are blocked, and a second open position in which the second hydraulic oil flow path and the third hydraulic oil flow path are communicated with each other and the first hydraulic oil flow path and the third hydraulic oil flow path are blocked, and the braking control unit controls a solenoid operation unit of the solenoid valve so that the position of the solenoid valve is switched from the first open position to the second open position when braking the industrial vehicle during automatic driving of the industrial vehicle.

2. The braking system further includes a brake pressure detection unit that detects the pressure of the hydraulic oil supplied to the hydraulic brake device. When braking the industrial vehicle during automatic driving of the industrial vehicle, the brake control unit controls the solenoid operation unit so that the position of the solenoid valve switches from the first open position to the second open position and the pressure of the hydraulic oil supplied to the hydraulic brake device is adjusted to a set pressure. The brake system according to claim 1.

3. An accumulator pressure detection unit that detects the pressure of the accumulator, During automatic driving of the industrial vehicle, further comprising a pump control unit that controls a drive source for rotationally driving the oil pump based on the pressure of the accumulator, When the pressure of the accumulator is equal to or higher than a specified pressure, the pump control unit controls the drive source so as to stop the rotation of the oil pump or reduce the rotational speed of the oil pump. The brake system according to claim 1 or 2.

4. A detection unit that detects whether the brake pedal has been operated during automatic driving of the industrial vehicle, When the detection unit detects that the brake pedal has been operated during automatic driving of the industrial vehicle in a state where the solenoid valve is in the second open position, an automatic driving stop control unit that controls the solenoid operation unit so that the position of the solenoid valve switches from the second open position to the first open position. The brake system according to any one of claims 1 to 3.

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