JP2021008167A - Brake system of vehicle - Google Patents

Abstract

To provide a brake system of a vehicle which can quickly supply a necessary flow rate of hydraulic oil to a brake unit while reducing a capacity of a hydraulic pump.SOLUTION: A brake system 12 includes a wet type brake unit 15 driven by hydraulic oil discharged from a hydraulic pump 14, an accumulator 16 for accumulating hydraulic oil discharged from the hydraulic pump 14, an electromagnetic switch valve 17 for switching a brake position and an accumulation position, and a brake valve 19 arranged among the electromagnetic switch valve 17, the accumulator 16 and the wet type brake unit 15, in which the brake valve 19 permits supply of the hydraulic oil to the wet type brake unit 15 from the hydraulic pump 14 and the accumulator 16 when the brake pedal 13 is operated, and blocks supply of the hydraulic oil to the wet type brake unit 15 from the hydraulic pump 14 and the accumulator 16 when the operation of the brake pedal 13 is released.SELECTED DRAWING: Figure 1

Description

The present invention relates to a vehicle braking system.

As a vehicle braking system, for example, the technique described in Patent Document 1 is known. The braking system described in Patent Document 1 is mounted on a reach type forklift provided with a lift cylinder and a tilt cylinder driven by hydraulic oil discharged from a hydraulic pump. The brake system consists of a front wheel brake that brakes a pair of left and right front wheels, a rear wheel brake that brakes the drive wheels (rear wheels), a brake passage that connects the brake cylinder of the front wheel brake and the bottom chamber of the lift cylinder, and this. It is equipped with an electromagnetic switching valve arranged in the brake passage. When the brake pedal is not depressed, the electromagnetic switching valve is in the brake position, so that the bottom pressure of the lift cylinder is supplied to the brake cylinder via the brake passage, and the front wheels are braked by the brake cylinder.

Japanese Unexamined Patent Publication No. 2003-81588

In the brake system as described above, it takes time for the required flow rate of hydraulic oil to be supplied to the brake cylinder of the brake unit. In order to quickly supply the required flow rate of hydraulic oil to the brake cylinder, it is necessary to increase the discharge flow rate of the hydraulic pump by increasing the capacity of the hydraulic pump. However, if the capacity of the hydraulic pump is increased, the work load of the hydraulic pump increases, which leads to deterioration of fuel efficiency. In addition, since the physique of the hydraulic pump becomes large, layout restrictions are imposed.

An object of the present invention is to provide a vehicle braking system capable of rapidly supplying a required flow rate of hydraulic oil to a brake unit while reducing the capacity of a hydraulic pump.

The vehicle brake system according to one aspect of the present invention includes a brake operating unit operated by an operator, a hydraulic pump for discharging hydraulic oil, a brake unit driven by hydraulic oil discharged from the hydraulic pump, and hydraulic pressure. An accumulator that accumulates the hydraulic oil discharged from the pump, a first position that allows the hydraulic oil to be supplied from the hydraulic pump to the brake unit, and a second position that allows the hydraulic oil to be supplied from the hydraulic pump to the accumulator. It is equipped with a switching valve for switching, a switching valve, and a brake valve arranged between the accumulator and the brake unit. The brake valve is used to supply hydraulic oil from the hydraulic pump and accumulator to the brake unit when the brake operation unit is operated. When the supply is allowed and the operation of the brake operating unit is released, the supply of hydraulic oil from the hydraulic pump and accumulator to the brake unit is cut off.

In such a braking system, the brake valve allows the supply of hydraulic oil from the hydraulic pump and accumulator to the brake unit when the brake operating section is operated. Therefore, when the brake operation unit is operated while the switching valve is in the first position, the hydraulic oil discharged from the hydraulic pump is supplied to the brake unit through the switching valve and the brake valve, and also to the accumulator. The accumulated hydraulic oil is supplied to the brake unit through the brake valve. In this way, hydraulic oil is simultaneously supplied to the brake unit from the hydraulic pump and accumulator. As a result, the required flow rate of hydraulic oil can be quickly supplied to the brake unit while reducing the capacity of the hydraulic pump.

The brake system switches the switching valve from the first position to the second position when the operation detection unit that detects the operation state of the brake operation unit and the operation detection unit detects that the operation of the brake operation unit is released. A control unit for controlling the vehicle may be further provided. In such a configuration, when the operation of the brake operating unit is released, the switching valve is switched from the first position to the second position, so that hydraulic oil is supplied from the hydraulic pump to the accumulator. Therefore, even after the hydraulic oil is supplied from the accumulator to the brake unit, the hydraulic oil is supplied to the accumulator, so that the accumulator is secured in the accumulator state.

The control unit may control the switching valve to switch from the second position to the first position after a predetermined time has elapsed after controlling the switching valve to switch to the second position. In such a configuration, since the switching valve is switched from the second position to the first position after a lapse of a predetermined time, it is not necessary to waste the hydraulic oil discharged from the hydraulic pump to the accumulator side.

The brake system further includes a pressure detection unit that detects the pressure of the hydraulic oil accumulated in the accumulator, and the control unit detects that the accumulator has been accumulated to a preset specified pressure by the pressure detection unit. The switching valve may be controlled to switch from the second position to the first position. In such a configuration, when the accumulator is accumulating to a specified pressure, the switching valve is switched from the second position to the first position. Therefore, the time for the hydraulic oil discharged from the hydraulic pump to be accumulated in the accumulator is shortened. As a result, the fuel efficiency of the vehicle can be improved.

The brake system may further include a relief valve that is located between the switching valve and the accumulator and opens when the pressure of the hydraulic oil stored in the accumulator exceeds a predetermined pressure. In such a configuration, when the pressure of the accumulator exceeds a predetermined pressure, the relief valve opens and the hydraulic oil discharged from the hydraulic pump is released, so that excessive hydraulic oil is prevented from being accumulated in the accumulator. ..

The brake system may be further provided with a check valve located between the brake valve and the brake unit to prevent backflow of hydraulic oil from the brake unit side to the accumulator side. In such a configuration, when the pressure of the brake unit becomes higher than the pressure of the accumulator, the check valve closes, so that the hydraulic oil supplied from the hydraulic pump to the brake piston is prevented from flowing to the accumulator.

According to the present invention, it is possible to quickly supply the required flow rate of hydraulic oil to the brake unit while reducing the capacity of the hydraulic pump.

It is a schematic block diagram which shows the hydraulic system provided with the brake system of the vehicle which concerns on 1st Embodiment of this invention. It is a hydraulic circuit diagram which shows the structure of the electromagnetic switching valve shown in FIG. It is a hydraulic circuit diagram which shows the structure of the brake valve shown in FIG. It is a flowchart which shows the procedure of the control processing executed by the controller shown in FIG. FIG. 5 is a schematic configuration diagram showing an initial state in which the brake pedal is not depressed in the brake system shown in FIG. 1. FIG. 5 is a schematic configuration diagram showing a state in which the brake pedal is depressed from the initial state shown in FIG. It is a schematic block diagram which shows the state which the check valve is closed from the state shown in FIG. It is a schematic block diagram which shows the state which the brake pedal returned from the state shown in FIG. 7. It is a schematic block diagram which shows the state which the relief valve is opened from the state shown in FIG. It is a schematic block diagram which shows the hydraulic system provided with the brake system of the vehicle which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the procedure of the control processing executed by the controller shown in FIG.

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 designated by the same reference numerals, and duplicate description will be omitted.

FIG. 1 is a schematic configuration diagram showing a hydraulic system including a vehicle braking system according to the first embodiment of the present invention. In FIG. 1, the hydraulic system 1 is mounted on a forklift 2 which is an industrial vehicle. The forklift 2 includes an engine 3 and a torque converter 4 attached to an output shaft of the engine 3.

The hydraulic system 1 includes a tank 5, a hydraulic pump 6 for cargo handling and steering, a lift cylinder 7, a tilt cylinder 8, a rear cylinder 9, a control valve 10, and a steering valve 11.

The tank 5 stores hydraulic oil. The hydraulic pump 6 is driven by the engine 3 via the torque converter 4. The hydraulic pump 6 sucks in and discharges the hydraulic oil stored in the tank 5.

The lift cylinder 7, tilt cylinder 8, and rear cylinder 9 are driven by hydraulic oil discharged from the hydraulic pump 6. The lift cylinder 7 is a hydraulic cylinder attached to a mast (not shown) to raise and lower a fork (not shown). The tilt cylinder 8 is a hydraulic cylinder that tilts the mast. The rear cylinder 9 is a hydraulic cylinder that steers the steering wheels (not shown).

The control valve 10 is arranged between the hydraulic pump 6, the lift cylinder 7, the tilt cylinder 8, and the rear cylinder 9. The control valve 10 controls the flow of hydraulic oil between the hydraulic pump 6 and the lift cylinder 7 in response to the operation of the lift operation lever (not shown), and also responds to the operation of the tilt operation lever (not shown). Controls the flow of hydraulic oil between the hydraulic pump 6 and the tilt cylinder 8.

The steering valve 11 is arranged between the control valve 10 and the rear cylinder 9. The steering valve 11 controls the flow of hydraulic oil between the hydraulic pump 6 and the rear cylinder 9 in response to the operation of the steering wheel (not shown).

The brake system 12 of this embodiment constitutes a part of the hydraulic system 1. The brake system 12 includes a brake pedal 13, a hydraulic pump 14 for braking, a wet brake unit 15, an accumulator 16, an electromagnetic switching valve 17, a hydraulic oil cooler 18, a brake valve 19, and a check valve 20. It is equipped with a relief valve 21.

The brake pedal 13 is a brake operation unit operated by an operator. The hydraulic pump 14 is driven by the engine 3 via the torque converter 4. The hydraulic pump 14 is arranged coaxially with the hydraulic pump 6. The hydraulic pump 14 sucks in and discharges the hydraulic oil stored in the tank 5. An oil passage 22 between the tank 5 and the hydraulic pump 6 is provided with a suction filter 23 for preventing dust and the like from entering the hydraulic pumps 6 and 14.

The wet brake unit 15 has a wet brake disc 24 that brakes the drive wheels (not shown) of the forklift 2, and a brake piston 25 that operates the wet brake disc 24. The brake piston 25 is driven by the hydraulic oil discharged from the hydraulic pump 14.

The accumulator 16 accumulates hydraulic oil discharged from the hydraulic pump 14. At this time, the accumulator 16 is stored so as to have a pressure (specified pressure) required to move the brake piston 25. The specified pressure of the accumulator 16 is preset.

The electromagnetic switching valve 17 is arranged between the hydraulic pump 14, the brake valve 19, and the accumulator 16. The hydraulic pump 14 and the electromagnetic switching valve 17 are connected via an oil passage 26. The electromagnetic switching valve 17 and the brake valve 19 are connected via an oil passage 27. The electromagnetic switching valve 17 and the accumulator 16 are connected via an oil passage 28.

FIG. 2 is a hydraulic circuit diagram showing the configuration of the electromagnetic switching valve 17. In FIG. 2, the electromagnetic switching valve 17 has a spool 30, a spring 31 provided on one end side of the spool 30, and a solenoid operating portion 32 provided on the other end side of the spool 30. The spool 30 is switched to the braking position 30a (first position) or the accumulator position 30b (second position) according to the electric signal (current) input to the solenoid operating unit 32. That is, the electromagnetic switching valve 17 is a switching valve that switches between the braking position 30a and the accumulator position 30b.

The braking position 30a is a position where the oil passages 26 and 27 communicate with each other and the oil passages 26 and 28 are blocked. That is, the braking position 30a is a position that allows the supply of hydraulic oil from the hydraulic pump 14 to the brake piston 25 and shuts off the supply of hydraulic oil from the hydraulic pump 14 to the accumulator 16. The pressure accumulation position 30b is a position where the oil passages 26 and 28 communicate with each other and the oil passages 26 and 27 are cut off. That is, the pressure accumulator position 30b is a position that allows the supply of hydraulic oil from the hydraulic pump 14 to the accumulator 16 and shuts off the supply of hydraulic oil from the hydraulic pump 14 to the brake piston 25.

Returning to FIG. 1, the hydraulic oil cooler 18 cools the hydraulic oil discharged from the hydraulic pump 14. A cooling oil passage 33 is connected to the hydraulic oil cooler 18. The cooling oil passage 33 is an oil passage that cools the wet brake disc 24 by supplying the hydraulic oil cooled by the hydraulic oil cooler 18 to the wet brake unit 15. The cooling oil passage 33 connects the hydraulic oil cooler 18 and the tank 5 via the wet brake unit 15. The hydraulic oil after cooling the wet brake disc 24 returns to the tank 5.

A return filter 34 is arranged between the wet brake unit 15 and the tank 5 in the cooling oil passage 33. A check valve 36 is provided in the oil passage 35 between the hydraulic oil cooler 18 and the tank 5.

The brake valve 19 is arranged between the hydraulic pump 14, the accumulator 16, the brake piston 25, the hydraulic oil cooler 18, and the tank 5. The brake valve 19 switches the flow of hydraulic oil between the hydraulic pump 14, the accumulator 16, the brake piston 25, the hydraulic oil cooler 18, and the tank 5 in response to the operation of the brake pedal 13.

The brake valve 19 and the accumulator 16 are connected via an oil passage 37. The brake valve 19 and the brake piston 25 are connected to each other via oil passages 38 and 39. The oil passage 39 is branched and connected to the oil passage 38. The brake valve 19 and the hydraulic oil cooler 18 are connected to each other via an oil passage 40. The brake valve 19 and the tank 5 are connected via an oil passage 41. A check valve 43 is provided in the oil passage 42 between the oil passage 40 and the tank 5.

FIG. 3 is a hydraulic circuit diagram showing the configuration of the brake valve 19. In FIG. 3, the brake valve 19 has a spool 44, a spring 45 provided on one end side of the spool 44, and a spring 46 provided on the other end side of the spool 44. The urging force of the spring 45 is stronger than the urging force of the spring 46.

The brake pedal 13 is arranged on the other end side (spring 46 side) of the spool 44. The brake pedal 13 is connected to the spool 44 via a spring 46. The spool 44 is switched to the normal position 44a or the braking position 44b according to the operation of the brake pedal 13. That is, the brake valve 19 is a switching valve that switches between the normal position 44a and the braking position 44b.

The normal position 44a is a position where the oil passages 27 and 40 communicate with each other, the oil passages 38 and 41 communicate with each other, and the oil passages 37 and 39 are blocked. That is, the normal position 44a cuts off the supply of hydraulic oil from the hydraulic pump 14 to the brake piston 25, cuts off the supply of hydraulic oil from the accumulator 16 to the brake piston 25, and cuts off the supply of hydraulic oil from the hydraulic pump 14 to the hydraulic oil cooler 18. It is a position that allows the supply of hydraulic oil and allows the communication between the brake piston 25 and the tank 5.

The braking position 44b is a position where the oil passages 27 and 38 communicate with each other, the oil passages 27 and 40 communicate with each other, the oil passages 37 and 39 communicate with each other, and the oil passages 38 and 41 are blocked. That is, the braking position 44b allows the supply of hydraulic oil from the hydraulic pump 14 to the brake piston 25, allows the supply of hydraulic oil from the accumulator 16 to the brake piston 25, and allows the hydraulic pump 14 to supply the hydraulic oil cooler 18. It is a position that allows the supply of hydraulic oil and cuts off the communication between the brake piston 25 and the tank 5. The brake valve 19 is provided with a variable diaphragm 47. When the brake valve 19 is at the braking position 44b, the hydraulic oil from the hydraulic pump 14 is supplied to the hydraulic oil cooler 18 through the variable throttle 47.

When the brake pedal 13 is stepped on, that is, when the brake pedal 13 is operated, the spool 44 is pushed toward the spring 45 by the brake pedal 13, so that the brake valve 19 switches from the normal position 44a to the braking position 44b. When the brake pedal 13 is returned, that is, when the operation of the brake pedal 13 is released, the force of the spring 45 overcomes the force of the spring 46, so that the brake valve 19 switches from the braking position 44b to the normal position 44a.

Therefore, the brake valve 19 allows the hydraulic oil to be supplied from the hydraulic pump 14 and the accumulator 16 to the brake piston 25 when the brake pedal 13 is operated, and the hydraulic pump 14 when the operation of the brake pedal 13 is released. And the supply of hydraulic oil from the accumulator 16 to the brake piston 25 is cut off.

Returning to FIG. 1, the check valve 20 is arranged between the brake valve 19 and the brake piston 25. Specifically, the check valve 20 is arranged in an oil passage 39 through which hydraulic oil from the accumulator 16 flows. The check valve 20 is a valve that prevents backflow of hydraulic oil from the brake piston 25 side to the accumulator 16 side.

The relief valve 21 is arranged between the electromagnetic switching valve 17 and the accumulator 16. Specifically, the relief valve 21 is arranged in an oil passage 28 through which hydraulic oil accumulated in the accumulator 16 flows. The relief valve 21 is a valve that opens when the pressure in the oil passage 28, that is, the pressure of the hydraulic oil accumulated in the accumulator 16 becomes equal to or higher than a preset relief pressure (predetermined pressure). The relief pressure of the relief valve 21 is equal to the specified pressure of the accumulator 16. The relief pressure of the relief valve 21 may be higher than the specified pressure of the accumulator 16. When the relief valve 21 is opened, the hydraulic oil discharged from the hydraulic pump 14 returns to the tank 5 through the oil passage 48.

Further, the brake system 12 includes a stroke sensor 49 and a controller 50. The stroke sensor 49 detects whether or not the brake pedal 13 is depressed. That is, the stroke sensor 49 constitutes an operation detection unit that detects the operation state of the brake pedal 13.

The controller 50 is composed of a CPU, RAM, ROM, an input / output interface, and the like. The controller 50 constitutes a control unit that controls the electromagnetic switching valve 17 based on the detection signal of the stroke sensor 49.

FIG. 4 is a flowchart showing a procedure of control processing executed by the controller 50. Before the execution of this process is started, the electromagnetic switching valve 17 is at the braking position 30a.

In FIG. 4, the controller 50 first acquires the detection signal of the stroke sensor 49 (procedure S101). Then, the controller 50 determines whether or not the brake pedal 13 is depressed based on the detection signal of the stroke sensor 49 (procedure S102). When the controller 50 determines that the brake pedal 13 has not been depressed, the controller 50 executes the procedure S101 again.

When the controller 50 determines that the brake pedal 13 has been depressed, the controller 50 acquires the detection signal of the stroke sensor 49 (procedure S103). Then, the controller 50 determines whether or not the brake pedal 13 has returned based on the detection signal of the stroke sensor 49 (procedure S104). When the controller 50 determines that the brake pedal 13 has not returned, the controller 50 executes the procedure S103 again.

When the controller 50 determines that the brake pedal 13 has returned, it outputs a pressure accumulator control signal for switching the electromagnetic switching valve 17 to the accumulator position 30b to the solenoid operation unit 32 of the electromagnetic switching valve 17 (procedure S105). As a result, the electromagnetic switching valve 17 is switched from the braking position 30a to the accumulator position 30b.

Subsequently, the controller 50 determines whether or not a predetermined time (for example, several seconds) has elapsed since the accumulator control signal was output to the solenoid operation unit 32 (procedure S106). When the controller 50 determines that the predetermined time has elapsed, it outputs a braking control signal for switching the electromagnetic switching valve 17 to the braking position 30a to the solenoid operating unit 32 of the electromagnetic switching valve 17 (procedure S107), and the controller 50 outputs the braking control signal to the solenoid operating unit 32 of the electromagnetic switching valve 17 (procedure S107). Is executed again. As a result, the electromagnetic switching valve 17 is switched from the accumulator position 30b to the braking position 30a.

The operation of the brake system 12 configured as described above will be described. In the initial state before the brake pedal 13 is depressed, the electromagnetic switching valve 17 is in the braking position 30a, and the brake valve 19 is in the normal position 44a. Therefore, in the electromagnetic switching valve 17, the oil passages 26 and 27 are communicated with each other, and the oil passages 26 and 28 are shut off. Further, in the brake valve 19, the oil passages 27 and 40 are communicated with each other, the oil passages 27 and 38 are cut off, and the oil passages 37 and 39 are cut off.

In such an initial state, as shown in FIG. 5, the hydraulic oil discharged from the hydraulic pump 14 flows through the oil passage 26, the electromagnetic switching valve 17, the oil passage 27, the brake valve 19, and the oil passage 40, and the hydraulic oil. It is supplied to the cooler 18. Then, the hydraulic oil cooled by the hydraulic oil cooler 18 flows through the cooling oil passage 33 and is supplied to the wet brake unit 15, so that the wet brake disc 24 is cooled.

When the operator depresses the brake pedal 13, the brake valve 19 switches from the normal position 44a to the braking position 44b. Then, in the brake valve 19, the oil passages 27 and 38 are communicated, the oil passages 37 and 39 are communicated, and the oil passages 27 and 40 are shut off.

Therefore, as shown in FIG. 6, the hydraulic oil from the hydraulic pump 14 flows through the oil passage 26, the electromagnetic switching valve 17, the oil passage 27, the brake valve 19, and the oil passage 38, and is supplied to the brake piston 25. Further, the hydraulic oil from the accumulator 16 flows through the oil passage 37, the brake valve 19 and the oil passages 39 and 38, and is supplied to the brake piston 25. As a result, the brake piston 25 is driven, so that the drive wheels (not shown) of the forklift 2 are braked by the wet brake disc 24.

When hydraulic oil is supplied to the brake piston 25 from the hydraulic pump 14 and the accumulator 16, the pressure in the oil passage 38, that is, the pressure in the brake piston 25 gradually increases. Then, when the pressure of the brake piston 25 becomes higher than the pressure of the accumulator 16, the check valve 20 is closed as shown in FIG. 7, so that the hydraulic oil from the accumulator 16 is not supplied to the brake piston 25. If the brake pedal 13 is further depressed in this state, the brake piston 25 is further boosted, so that a sufficient braking force is generated on the wet brake disc 24.

After that, when the operator returns the brake pedal 13, the brake valve 19 switches from the braking position 44b to the normal position 44a. Then, in the brake valve 19, the oil passages 27 and 40 are communicated, the oil passages 27 and 38 are cut off, and the oil passages 37 and 39 are cut off. Further, since the stroke sensor 49 detects that the brake pedal 13 has returned, the electromagnetic switching valve 17 is switched from the braking position 30a to the pressure accumulation position 30b by the pressure accumulation control signal from the controller 50. Therefore, in the electromagnetic switching valve 17, the oil passages 26 and 28 are communicated with each other, and the oil passages 26 and 27 are shut off.

Therefore, as shown in FIG. 8, the hydraulic oil from the hydraulic pump 14 flows through the oil passage 26, the electromagnetic switching valve 17, and the oil passage 28 and is supplied to the accumulator 16, thereby accumulating the accumulator 16.

Then, when the accumulator 16 is accumulated to a specified pressure, the relief valve 21 opens. Therefore, as shown in FIG. 9, the hydraulic oil from the hydraulic pump 14 flows through the oil passage 48 and is opened to the tank 5. As a result, the pressure of the accumulator 16 is maintained at the specified pressure.

After that, the electromagnetic switching valve 17 is switched from the accumulator position 30b to the braking position 30a by the braking control signal from the controller 50. Therefore, the initial state as shown in FIG. 5 is returned, and the hydraulic oil from the hydraulic pump 14 is supplied to the hydraulic oil cooler 18.

As described above, in the present embodiment, the brake valve 19 allows the hydraulic oil to be supplied from the hydraulic pump 14 and the accumulator 16 to the brake piston 25 when the brake pedal 13 is operated. Therefore, when the brake pedal 13 is operated while the electromagnetic switching valve 17 is in the braking position 30a, the hydraulic oil discharged from the hydraulic pump 14 passes through the electromagnetic switching valve 17 and the brake valve 19 to the brake piston 25. At the same time, the hydraulic oil accumulated in the accumulator 16 is supplied to the brake piston 25 through the brake valve 19. In this way, hydraulic oil is simultaneously supplied from the hydraulic pump 14 and the accumulator 16 to the brake piston 25. As a result, the required flow rate of hydraulic oil can be quickly supplied to the brake piston 25 while reducing the capacity of the hydraulic pump 14. When the capacity of the hydraulic pump 14 is reduced, the work load of the hydraulic pump 14 is reduced, so that the fuel consumption of the forklift 2 is improved. Further, when the capacity of the hydraulic pump 14 is reduced, the physique of the hydraulic pump 14 becomes smaller, so that the layout is not restricted.

Further, in the present embodiment, when the operation of the brake pedal 13 is released, the electromagnetic switching valve 17 is switched from the braking position 30a to the accumulator position 30b, so that hydraulic oil is supplied from the hydraulic pump 14 to the accumulator 16. Therefore, even after the hydraulic oil is supplied from the accumulator 16 to the brake piston 25, the hydraulic oil is supplied to the accumulator 16, so that the accumulator 16 is secured in the accumulator state.

Further, in the present embodiment, the electromagnetic switching valve 17 is switched from the accumulator position 30b to the braking position 30a after a lapse of a predetermined time after the electromagnetic switching valve 17 is controlled to be switched to the accumulator position 30b, so that the hydraulic pump 14 It is not necessary to waste the hydraulic oil discharged from the accumulator 16 side.

Further, in the present embodiment, when the pressure of the accumulator 16 becomes equal to or higher than a predetermined pressure, the relief valve 21 opens and the hydraulic oil discharged from the hydraulic pump 14 is released, so that excess hydraulic oil is accumulated in the accumulator 16. Is prevented.

Further, in the present embodiment, when the pressure of the brake piston 25 becomes higher than the pressure of the accumulator 16, the check valve 20 closes, so that the hydraulic oil supplied from the hydraulic pump 14 to the brake piston 25 is prevented from flowing to the accumulator 16. Will be done.

FIG. 10 is a schematic configuration diagram showing a hydraulic system including a vehicle braking system according to a second embodiment of the present invention. In FIG. 10, the brake system 12 of the present embodiment includes a pressure sensor 51 in addition to the configuration of the first embodiment described above. The pressure sensor 51 detects the pressure in the oil passage 28 through which the hydraulic oil accumulated in the accumulator 16 flows. The pressure sensor 51 constitutes a pressure detection unit that detects the pressure of the hydraulic oil accumulated in the accumulator 16.

Further, the brake system 12 includes a controller 50A instead of the controller 50 in the first embodiment described above. The controller 50A constitutes a control unit that controls the electromagnetic switching valve 17 based on the detection signals of the stroke sensor 49 and the pressure sensor 51.

FIG. 11 is a flowchart showing a procedure of control processing executed by the controller 50A. In FIG. 11, the controller 50A executes steps S101 to S105 in the same manner as the flowchart shown in FIG. After executing the procedure S105, the controller 50A acquires the detection signal of the pressure sensor 51 (procedure S111).

Then, the controller 50A determines whether or not the accumulator 16 has accumulated a specified pressure based on the detection signal of the pressure sensor 51 (procedure S112). When the controller 50A determines that the accumulator 16 is not accumulating to the specified pressure, the controller 50A executes the procedure S111 again.

When the controller 50A determines that the accumulator 16 has accumulated a specified pressure, it outputs a braking control signal for switching the electromagnetic switching valve 17 to the braking position 30a to the solenoid operating unit 32 of the electromagnetic switching valve 17 (procedure S107). ..

As described above, in the present embodiment, when the accumulator 16 is accumulating to the specified pressure, the electromagnetic switching valve 17 is switched from the accumulator position 30b to the braking position 30a. Therefore, the time for the hydraulic oil discharged from the hydraulic pump 14 to be accumulated in the accumulator 16 is shortened. As a result, the fuel efficiency of the forklift 2 can be further improved.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the brake valve 19 is composed of one switching valve, but the present invention is not particularly limited to that, and the brake valve 19 may be composed of a plurality of valves.

Further, in the above embodiment, the electromagnetic switching valve 17 is arranged between the hydraulic pump 14, the wet brake unit 15, and the accumulator 16, but the embodiment is not particularly limited, and the hydraulic pump 14, the wet brake unit 15, and the wet brake unit 15 and The switching valve arranged between the accumulator 16 and the accumulator 16 may be, for example, a pilot type switching valve or the like.

Further, the brake system 12 of the above embodiment includes a hydraulic oil cooler 18 for cooling the hydraulic oil, and the hydraulic oil cooled by the hydraulic oil cooler 18 is used to cool the wet brake disc 24. Is also applicable to braking systems that do not have such a hydraulic oil cooler 18.

Further, although the brake system 12 of the above embodiment is mounted on the forklift 2, the present invention can be applied to a vehicle other than an industrial vehicle such as a forklift.

2 ... Forklift (vehicle), 12 ... Brake system, 13 ... Brake pedal (brake operation unit), 14 ... Hydraulic pump, 15 ... Wet brake unit (brake unit), 16 ... Accumulator, 17 ... Electromagnetic switching valve (switching valve) , 19 ... Brake valve, 20 ... Check valve, 21 ... Relief valve, 30a ... Braking position (first position), 30b ... Accumulation position (second position), 49 ... Stroke sensor (operation detection unit), 50, 50A ... Controller (control unit), 51 ... Pressure sensor (pressure detection unit).

Claims (6)

The brake operation unit operated by the operator and
A hydraulic pump that discharges hydraulic oil and
A brake unit driven by hydraulic oil discharged from the hydraulic pump and
An accumulator that accumulates hydraulic oil discharged from the hydraulic pump and
A switching valve that switches between a first position that allows the supply of hydraulic oil from the hydraulic pump to the brake unit and a second position that allows the supply of hydraulic oil from the hydraulic pump to the accumulator.
The switching valve and the brake valve arranged between the accumulator and the brake unit are provided.
The brake valve allows the supply of hydraulic oil from the hydraulic pump and the accumulator to the brake unit when the brake operation unit is operated, and when the operation of the brake operation unit is released, the hydraulic pump And a vehicle brake system that shuts off the supply of hydraulic oil from the accumulator to the brake unit. An operation detection unit that detects the operation state of the brake operation unit,
Claim 1 further includes a control unit that controls the switching valve to switch from the first position to the second position when the operation detection unit detects that the operation of the brake operation unit has been released. The vehicle braking system described. 2. The second aspect of the present invention, wherein the control unit controls the switching valve to switch from the second position to the first position when a predetermined time elapses after controlling the switching valve to switch to the second position. Vehicle braking system. A pressure detection unit for detecting the pressure of the hydraulic oil accumulated in the accumulator is further provided.
A claim that the control unit controls the switching valve to switch from the second position to the first position when the pressure detecting unit detects that the accumulator has accumulated a predetermined pressure set in advance. Item 2. The vehicle braking system according to item 2. The vehicle brake according to any one of claims 1 to 4, further comprising a relief valve arranged between the switching valve and the accumulator and opened when the pressure of the hydraulic oil accumulated in the accumulator exceeds a predetermined pressure. system. The vehicle according to any one of claims 1 to 5, further comprising a check valve arranged between the brake valve and the brake unit to prevent backflow of hydraulic oil from the brake unit side to the accumulator side. Brake system.

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