KR850000091B1 - Wheel cylinder of drum brake - Google Patents

Abstract

This invention concerns the wheel cylinder of a drum brake, and does not necessarily regulate the valve separately. A cylinder body(12) has an internal part(14). A working piston(16) contacts the pressure- chamber(20), and acts to push the first sue(22) of the drum brake. A compressed fluid is passed to the pressurechamber(20) through the supply pathway(30,32,34,36). A wheel cylinder(10), which is involved in the valve(50), regulates the internal pressure of the pressure chamber.

Description

Wheel cylinder of drum brake

1 is a longitudinal sectional view of a preferred embodiment of a wheel cylinder according to the present invention.

2 is a longitudinal sectional view of another embodiment of the wheel cylinder of FIG.

* Explanation of symbols for main parts of the drawings

10 wheel cylinder 12 cylinder body

14: inner diameter 16, 18: working piston

20: pressure chamber 22, 24: brake shoe

26, 28: annular seal 30: inlet orifice

32: annular groove 34: clogged inner neck

36: radial passage 50: brake adjustment valve

52: differential piston 54: annular chamber

56, 71: axial passage 58: ball valve

60: valve seat 62, 66, 74: spring

69: second orifice 70: discharge valve

72: bowl

The present invention relates to a wheel cylinder.

The brake system of a motor vehicle generally controls the pressure of the hydraulic oil in the brake motor connected to the rear wheel of the automobile by using a brake control valve between the oil pressure source and the brake motor.

This necessitates two relationships: contacting the pressure source and the inlet orifice of the control valve and contacting the outlet orifice of the control valve and the brake motor.

Such a structure has a disadvantage in that it is complicated and has a high risk of damage compared to a brake system without a control valve because a plurality of hydraulic connections are required between the pressure oil source and the control valve and between the control valve and the brake motor.

In the case of a brake system equipped with a conventional method of connecting a control valve to a corresponding brake motor by a flexible coupling, a considerable energy absorption occurs between the brake and the flexible coupling, thus delaying the operation of the control valve. Therefore, the response time of the brake system is slowed down.

The brake system equipped with a control valve according to the conventional method may cause an air bubble to be enclosed into the valve during the discharge operation of the brake motor during the discharge operation, which results in a long period of reciprocation of the lung moon when the brake is actually applied. This occurs.

To eliminate this drawback, the valve must be tilted at an angle when fitted to the vehicle.

On cold days, the hydraulic fluid flowing through the control valve located under the vehicle body becomes more viscous and the flow of the hydraulic fluid becomes worse. Therefore, failure to reheat the hydraulic fluid during brake operation adversely affects the response time of the brake system.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device for improving the response time of a brake system equipped with one or more control valves.

The wheel cylinder to be provided by the present invention includes a cylinder body having an inner diameter portion therein, and at least one working piston housed therein so as to be able to act on the inner diameter portion thereof and in contact with a pressure chamber therein. In order to push the first shoe of the drum brake, it is able to move to the outside of the inner diameter part, and the electric cylinder has a supply passage for supplying the oil from the oil source to the electric pressure chamber, and the pressure is supplied according to the pressure supplied from the oil source. The valve to be used to adjust the pressure in the room is caught by a wheel cylinder woven into the electric cylinder, and the electric supply passage is an annular groove made in the electrically operated piston to receive the hydraulic pressure from the electric pressure oil source, and one side leads to the electric pressure chamber and the other. Shaft is shaft made in electric working piston leading to electric annular groove And has a part including a sealed inner diameter portion and the direction, the valve is characterized in that is housed in a blind bore portion in the axial direction of the working piston.

In the following description of the invention, other advantages will be apparent from the following description made with reference to the accompanying drawings.

In FIG. 1, reference numeral 10 denotes a wheel cylinder including a body 12 made of the inner diameter portion 14.

The first actuating piston 16 and the second actuating piston 18 are housed to be able to act in the inner diameter portion 14 and a pressure chamber 20 is formed therebetween. The pistons 16 and 18 are actuated by the pressure in the pressure chamber 20 and used to push the drum brake shoes 22 and 24 (indicated in part), respectively.

Each piston 16, 18 has annular seals 26, 28, and cooperates with the inner diameter portion 14 to seal the pressure chamber 20. The hydraulic chamber is supplied with pressure oil from a pressure source (not shown) via a supply passage.

The supply passage includes an inlet orifice 30 provided in the main body 12 and an annular groove 32 formed in the piston 16 and a pressure chamber (1) opened in the cylindrical wall of the inner diameter portion 14. 20) and a second portion including a closed inner diameter portion 34 and a radial communication passage. At any position in the axial direction, the annular groove communicates with the inlet orifice 30 and thus communicates with the pressure oil source. The closed inner diameter portion 34 is layered so that its bottom portion forms a small diameter portion 40 and its open end forms a large diameter portion 38. A brake adjustment valve (indicated by reference numeral 50) is disposed in the inner diameter portion 34.

The valve 50 is a fixed brake compensation device in this embodiment, the main feature of which is described in French Patent No. 2,248,182 except that the compensation device incorporated in the wheel cylinder is not a load control but a fixed compensation device. As known in the brake compensator.

The valve 50 includes a differential piston 52 sealed in a layered inner diameter 34 of the piston 16 and slidably attached thereto. The large cross section of the differential piston 52 slides in the large diameter portion 38 of the inner diameter portion, and the cross section is adjacent to the pressure chamber 20.

The small cross-sectional portion of the piston 52 is under pressure in the annular chamber 54 communicating with the radial passage 36, that is, the supply pressure. The passage 56 extends through the differential piston 52 and consists of an axial portion that communicates the radial portion and the annular chamber 54 to the pressure chamber 20. In this passage, the valve seat 60, which is provided on the differential piston 52, by the spring 62 having a weak valve 58, is pressed. The actuating piston 16 has a fixed side wall portion 64 and the side wall portion because the piston 52 is generally pressed to the left side (in FIG. 1) by a spring action supported by the bottom of the closed inner diameter portion 34. 64 lifts the bowl valve 58 out of the valve seat 60. In FIG. 1, the differential piston 52 indicates the position when the bowl valve 58 is in the restricted closing position.

The main body 12 of the wheel cylinder 10 also has a second orifice 69 open to the pressure chamber 20 which is used to simultaneously discharge pressure oil of the wheel cylinder and the brake adjustment valve.

Next, the operation of the wheel cylinder will be described.

During the first brake stage, the differential piston 52 is pushed to the left of FIG. 1 by the force of the spring 66 so that the valve seat 60 and the bowl valve 58 are separated from each other to form a gap. . As a result, through this interval, the pressure chamber 20 receives the pressure oil from the pressure oil source (not shown) without any limitation.

The pressure of the supply fluid increases while the fluid pressure in the annular chamber 54 and the passage 56 remains the same as the pressure in the pressure chamber 20. In this step, the force acting on the differential piston 52 is roughly shown. The force of the force by the spring 66 and the small effective cross-sectional area of the right side of the differential piston 52 multiplied by the pressure of the supply fluid is equal to the differential. This is a force to move the piston 52 to the left of FIG. On the other hand, the force of the magnitude obtained by multiplying the pressure in the pressure chamber 20 by the large effective cross-sectional area of the left side of the differential piston 52 becomes a force for moving the differential piston 52 to the right.

Therefore, during the first brake stage, the pressure of the supply fluid is equal to the pressure in the pressure chamber 20, and the differential piston 52 generated by the same pressure acts on the difference in the effective cross-sectional area of both ends of the differential piston 52. The force to move to the right of one degree is smaller than the force to which the spring 66 moves the differential piston 52 to the left.

In this state, the supply pressure is continuously increased so that a predetermined limit value, that is, a pressure value at which the force of the magnitude multiplied by the predetermined pressure multiplied by the difference in the effective cross-sectional area at both ends of the differential piston 52 is equal to the force generated by the spring 66. At this point, the differential piston 52 starts to move to the right of FIG. 1 so that the ball valve 58 comes into contact with the valve seat 60 in a state of preventing fluid leakage, and a second brake step is started.

If the supply pressure continues to increase while the valve valve 58 is closed, the pressure in the pressure chamber 20 adjacent to the large effective cross-sectional area of the differential piston 52 becomes smaller than the increased supply pressure of the small effective cross-sectional area. The differential piston 52 again moves to the left side, and the valve valve 58 is separated from the valve seat 60 so that the pressure chamber 20 and the pressure oil source communicate with each other again. As described above, in the second brake stage, the bowl valve 58 sequentially performs the opening and closing movement as the supply pressure increases. During this brake step, the speed at which the pressure in the pressure chamber 20 increases decreases in proportion to the ratio of the effective cross-sectional areas at both ends of the differential piston 52 as in the conventional case. A more detailed description of this and the operation and features of the ball valve 50 as a brake compensator according to the movement of the differential piston 52 are well shown in the aforementioned French Patent No. 2,248,182.

In the case of a brake system in which each rear wheel brake is equipped with a wheel cylinder, the lateral stability of the vehicle is still maintained by an adjustment valve that will be fitted to the grooved wheel cylinder.

2 shows another embodiment which is almost identical to the wheel cylinder of FIG.

The same components as those in FIG. 1 are designated by the same reference numerals.

The wheel cylinder of FIG. 2 is provided in the axial passage 71 of the piston 16 and has a discharge valve 70 which communicates with the radial passage 36 and the pressure chamber 20.

The bowl 72 of the valve 70 is pressed by the spring 74 against the valve seat 76 against the pressure in the radial passage 36.

The wheel cylinder of FIG. 2 operates in the first stage as in the case of FIG. That is, the pressure increases without any limitation at first, and in the subsequent second stage, the pressure increase in the pressure chamber 20 is limited by the action of the compensator.

When the pressure difference between the passage 36 and the pressure chamber 20 reaches a predetermined value and the bowl 72 is lifted from the valve seat 76 against the force of the spring, the third step is started, and the passage ( The pressure rises back to normal since any pressure increase in 36 is transmitted to the pressure chamber 20 as it is. Therefore, when the pressure from the oil pressure source is high, the vehicle can be braked more efficiently than using the brake cylinder with the adjustment means as shown in FIG. 1 by using the valve 70.

The wheel cylinder described for the structure and operation has the following advantages. The flow of hydraulic oil between the hydraulic oil source and the wheel cylinders is ensured in a single line, such as used in brake systems without brake control valves, including drum brakes.

As a result, there is no need to change the hydraulic piping when changing from a vehicle equipped with a wheel cylinder without a built-in adjusting device to a vehicle equipped with a wheel cylinder with an adjustment valve.

In addition, when the control valve according to the structure of the present invention is located between the wheel cylinder and the main cylinder, the response time of the brake system is greatly prevented from absorbing energy by the flexible coupling interposed between the control valve and the wheel cylinder. Can be greatly reduced.

Moreover, in the structure according to the present invention, since the control valve is disposed near the drum brake shoe, i.e., near the friction surface, the heat generated during the first application of the brake will reduce the viscosity of the hydraulic oil in the control valve. This has the advantage of shortening the response time, especially on cold days.

In addition, as described above, the wheel cylinder according to the present invention can be used to simultaneously discharge pressure oil of the control valve and the wheel cylinder.

Furthermore, since the regulating valve disposed in the wheel cylinder is protected from dust and dirt, its reliability is further improved.

The wheel cylinder described is equally applicable to a wheel cylinder with a closed inner diameter to receive a single piston having two actuating pistons in its inner diameter.

Claims (1)

A cylinder body 12 having an inner diameter portion 14 formed therein and at least one working piston 16 which is housed so as to be able to act in the inner diameter portion 14 at one end thereof and in contact with the pressure chamber 20 therein is provided. And the piston 16 is moved outwardly of the inner diameter portion 14 to push the first shoe 22 of the drum brake and is supplied for supplying pressure fluid from the pressure fluid source to the pressure chamber 20. In a wheel cylinder in which there are passages 30, 32, 36, 34, and in which a valve 50 is used to adjust the pressure in the pressure chamber 20 in accordance with the pressure supplied from the pressure fluid source. An annular groove 32 made in the working piston 16 to receive the pressure fluid from the pressure fluid source, and one side passes through the pressure chamber 20 and the other side passes through the annular groove 32. Axially blocked inner diameter made in said actuating piston 16 34 is located in the supply passage portion is included, the valve 50 to the wheel cylinders (10), characterized in that it is accommodated in a blind inner diameter portion 34 in the axial direction of the working piston (16).

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