JPH0549536U - Vehicle parking brake device - Google Patents

Abstract

(57) [Summary] [Purpose] To improve the performance of the parking brake system. [Structure] A brake unit 3 provided on the rear wheel 9,
A vehicle including a hydraulic cylinder 5 for operating the brake unit 3 with a cable 23, an oil pump 7 capable of supplying working oil to the pressure chamber 15 of the hydraulic cylinder 5, a switching valve 33 interposed in an oil passage 28, and the like. The parking brake device 1. When braking, switch valve 3
3 is switched to the illustrated first position 33A. This allows
The working oil in the pressure chamber 15 is discharged to the oil tank 38, and the return spring 18 exerts a large force on each cable 2
3 is pulled, and each brake unit 3 strongly locks each rear wheel 9. On the other hand, when releasing the brake, the switching valve 33 is switched to the second position 33B. This allows
The working oil flows into the pressure chamber 15, the spring 18 is contracted, the pulling operation of each cable 23 is released, and each rear wheel 9 is unlocked.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a parking brake device for a vehicle.

[0002]

[Prior Art]

 Conventionally, a parking brake device for a vehicle includes a brake lever arranged in a driver's seat, a cable extending from the brake lever to each of the left and right rear wheels, a brake unit provided on each of the rear wheels, and operated by the cable. It is equipped with. When the driver operates the brake lever and pulls each cable after the vehicle is stopped, each brake unit is activated, each rear wheel is locked, and the parking brake is applied.

[0003]

[Problems to be solved by the device]

 However, in the above-described conventional parking brake device for a vehicle, the driver pulls each cable via the brake lever, so that each cable cannot be pulled with a large force. Therefore, there is a problem that it is difficult to operate the brake unit with a large operation force, and this problem becomes more serious especially in a vehicle with a large total weight.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a parking brake device for a vehicle capable of increasing the brake operating force.

[0005]

[Means for Solving the Problems]

 In order to achieve the above object, according to the present invention, a brake unit provided on a wheel, a hydraulic cylinder in which a piston rod is connected to a brake unit via an operation cable, and a piston in the hydraulic cylinder are provided. A pressure chamber and a spring chamber, a compression spring that is housed in the spring chamber and operates the brake unit by constantly pressing the piston rod to one side, a pressure source that can supply hydraulic fluid to the pressure chamber, and a pressure source. A passage communicating with the pressure chamber is provided in the middle of the passage, and the driver can switch the pressure chamber. In the first position, the pressure chamber is connected to the low pressure side, and in the second position, the pressure source communicates with the pressure chamber. And a switching valve for controlling the parking brake device of the vehicle.

[0006]

[Action]

 When the parking brake device is activated after the vehicle is stopped, the driver switches the switching valve to the first position. When the switching valve is switched to the first position, the pressure chamber of the hydraulic cylinder is connected to the low pressure side, so the compression spring in the spring chamber presses the piston to one side while discharging the hydraulic fluid in the pressure chamber to the low pressure side. To do. Therefore, the piston rod operates the operation cable with a large force, and the brake unit strongly locks the wheel.

On the other hand, when releasing the parking brake device, the driver switches the switching valve from the first position to the second position. When the switching valve is switched to the second position, the hydraulic fluid is supplied from the pressure source into the pressure chamber of the hydraulic cylinder, and the piston moves the piston rod to the other while compressing the compression spring. Therefore, the piston rod releases the operation of the operating cable and the brake unit unlocks the wheels.

[0008]

【Example】

 Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an embodiment of a parking brake device for a vehicle to which the present invention is applied. The parking brake device is provided, for example, on a truck in addition to a service brake. The parking brake device 1 is composed of a brake unit 3, a hydraulic cylinder 5, an oil pump 7, and the like.

The brake unit 3 is provided on each of the left and right rear wheels 9, for example. The brake unit 3 is a leading trailing type drum brake unit, and when the lever 11 is rotated to one side, each brake shoe 12 frictionally engages with a brake drum (not shown) and rear wheels. Lock 9 The hydraulic cylinder 5 is a single acting cylinder. Inside the cylinder 5, a piston 14 defines a pressure chamber 15 and a spring chamber 16, and a piston rod 17 extends rearward of the cylinder 5 from the spring chamber 16 side. The extending portion of the piston rod 17 is covered with a dustproof bellows (not shown).

A return spring 18 is housed in the spring chamber 16. The return spring 18 can generate a larger cable operating force than the cable operating force exerted by the driver operating the brake lever in the conventional parking brake device, and this operating force causes the piston to operate. Degenerate the rod 17.

The tip of the piston rod 17 is connected to the connecting member 21. Both ends of the connecting member 21 are connected to the lever 11 of the brake unit 3 via a cable 23, respectively. Each cable 23 is protected by a tube 24 and moves inside the tube 24. Therefore, when the piston rod 17 is retracted, the connecting member 21 pulls each cable 23 to rotate the lever 11 in one direction.

The oil pump 7 is driven by the electric motor 26, sucks the working oil from the oil tank 38 through the oil passage 39, and pumps the working oil toward the pressure chamber 15 of the hydraulic cylinder 5 through the oil passage 28. To do. For example, the electric motor 26 drives the oil pump 7 when the pressure in the accumulator 31 described below becomes lower than a predetermined value, and stops the oil pump 7 when the pressure in the accumulator 31 becomes higher than a predetermined value.

Further, an accumulator 31 is provided in the middle of an oil passage 28 that connects the oil pump 7 and the hydraulic cylinder 5, and a switching valve 33 is provided between the accumulator 31 and the hydraulic cylinder 5. There is. The accumulator 31 is a spring type pressure accumulator tank and is set to have a predetermined volume. Therefore, the working oil can be supplied to the pressure chamber 15 of the hydraulic cylinder 5 even when the oil pump 7 is stopped. The inside of the accumulator 31 is constantly set within a predetermined pressure range by the electric motor 26 and the oil pump 7.

The switching valve 33 is a 3-port, 2-position switching valve, and is arranged, for example, near the driver's seat. The first port 33c of the switching valve 33 communicates with the accumulator 31, the second port 33d communicates with the pressure chamber 15 of the hydraulic cylinder 5, and the third port 33e communicates with the oil tank 38 via the oil passage 37. ing. In the illustrated first position 33A, the switching valve 33 closes the first port 33c and connects the second port 33d and the third port 33e. In the second position 33B, the first port 33c and the second port 33d are communicated with each other, and the third port 33e is closed.

The switching valve 33 is directly switched by a brake lever 35 arranged in the driver's seat. The brake lever 35 is operated by the driver. Next, the operation of the parking brake device 1 will be described. When the parking brake device 1 is operated after the vehicle is stopped, the driver switches the switching valve 33 to the first position 33A. When the switching valve 33 is switched to the first position 33A, the working oil in the pressure chamber 15 of the hydraulic cylinder 5 is discharged from the second port 33d of the switching valve 33 to the oil tank 38 via the third port 33e. It Therefore, the return spring 18 in the spring chamber 16 pushes the piston 14 to one side and retracts the piston rod 17.

As described above, the return spring 18 retracts the piston rod 17 with a larger operating force than the cable operating force exerted by the driver in the conventional parking brake device. When the piston rod 17 retracts, the connecting member 21 pulls each cable 23 with a large force, and the lever 11 of the brake unit 3 is rotated to one side. Therefore, each brake shoe 12 is strongly pressed against the brake drum, and the rear wheel 9 is strongly locked.

On the other hand, when releasing the parking brake device 1, the driver switches the switching valve 33 from the first position 33A to the second position 33B. When the switching valve 33 is switched to the second position 33B, the pressure chamber 15 of the hydraulic cylinder 5 is connected to the accumulator 31 and the oil pump 7 from the second port 33d of the switching valve 33 via the first port 33c. Therefore, the working oil flows into the pressure chamber 15 to increase the pressure, and in response to this increase, the piston 14 compresses the return spring 18 and the piston rod 17 extends.

When the piston rod 17 extends, the connecting member 21 releases the pulling operation of the cable 23. Therefore, the lever 11 of the brake unit 3 is rotated to the other side, the brake shoe 12 is separated from the brake drum, and the rear wheel 9 is unlocked. The vehicle runs in this state. Since the oil pump 7 is driven by the electric motor 26, the degree of freedom of these mounting positions is great and it is not necessary to provide a special pump mounting means on the vehicle engine side.

Further, since the cylinder 5 is of a hydraulic type, the cylinder 5 itself can be downsized, and the parking brake device 1 can be downsized. Although the oil pump 7 is driven by the electric motor 26 in the present embodiment, the present invention is not limited to this, and may be driven by the vehicle engine.

Further, in this embodiment, the switching valve 33 is arranged near the driver's seat and is directly switched by the brake lever 35, but the invention is not limited to this. For example, the switching valve 33 may be arranged at a position where the oil passage 28 that connects the oil pump 7 and the hydraulic cylinder 5 can be shortened. In this case, it is desirable to connect the switching valve 33 and the brake lever 35 arranged in the driver's seat via an operation force transmission mechanism such as a control cable. By shortening the oil passage 28, the time lag required for the working oil to flow is reduced, and the responsiveness of the parking brake device is improved.

[0021]

[Effect of the device]

 As described above, according to the present invention, a brake unit provided on a wheel, a hydraulic cylinder in which a piston rod is connected to the brake unit through an operation cable, and a piston in a hydraulic cylinder are defined. Pressure chamber and spring chamber, a compression spring that is housed in the spring chamber and operates the brake unit by constantly pressing the piston rod to one side, a pressure source that can supply hydraulic fluid to the pressure chamber, a pressure source and a pressure chamber. A passage that connects the pressure chamber to the low pressure side in the first position and a passage that connects the pressure chamber and the pressure chamber in the second position. Since the parking brake device of the vehicle is configured to include the valve, the force for operating the operation cable, that is, the brake unit can be increased. As a result, there is an excellent effect that the performance of the parking brake device can be improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a vehicle parking brake device to which the present invention is applied.

[Explanation of reference numerals] 1 parking brake device 3 brake unit 5 hydraulic cylinder 7 oil pump 9 rear wheel 14 piston 15 pressure chamber 16 spring chamber 17 piston rod 18 return spring 23 cable 28 oil passage 33 switching valve 33A first position 33B second Position 38 Oil tank

Claims (1)

[Scope of utility model registration request] 1. A brake unit provided on a wheel,
A hydraulic cylinder in which a piston rod is in communication with the brake unit via an operation cable, a pressure chamber and a spring chamber defined by the piston in the hydraulic cylinder, and a spring chamber that are housed in the spring chamber to constantly push the piston rod to one side. A compression spring that operates the brake unit, a pressure source that can supply hydraulic fluid to the pressure chamber, a passage that connects the pressure source and the pressure chamber, and a passage in the middle of the passage. A parking brake device for a vehicle, which is capable of connecting a pressure chamber to a low pressure side at a first position, and includes a switching valve which connects a pressure source and the pressure chamber at a second position.