JPH0516793A - Booster device - Google Patents

Abstract

PURPOSE:To insure large hysteresis without increasing hardness of rubber of a reaction disc by providing a resistance member to make larger sliding resistance of a valve plunger at retreating than that at advancing, extending over the valve plunger and the through hole of a valve body. CONSTITUTION:A valve body 2 is slidably provided in a shell 1, a stepped hole 2A in the axial direction is drillingly provided in the shaft part. A valve plunger 4 is slidably fitted in a small diameter hole 2a on the right side of the stepped hole 2A, and its right end is connected to an input shaft 5. The whole step part of the stepped hole 2A is formed into an annular projection 2b extending leftwards, the recessed hollow part 6a formed on the base part of a signal shaft 6 is slidably fitted thereto. Further, a reaction disc 7 made of rubber is received in the recessed hollow part 6a. An annular groove 4a is formed on the outer circumferential part on the left side of the valve plunger 4, and a ring-like seal member 8 made of rubber is mounted therein. A right inclined lip part 8a is provided on the outer circumferential edge of the seal member 8, and closely contacted with the inner circumferential face of the small diameter hole 2a.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a booster, and more particularly to a booster capable of obtaining a large hysteresis.

2. Description of the Related Art Conventionally, as a booster, a valve body slidably provided in a shell, an axial through hole provided in the valve body, and a through hole of the valve body are slidably fitted therein. A valve plunger that is engaged with and interlocks with the input shaft; an output shaft that slidably fits the base portion of the valve body and faces the valve plunger; and an interposition between the base portion of the output shaft and the valve plunger. A reaction disk for transmitting a reaction force of the output acting on the output shaft to the input shaft via the valve plunger is known. In such a conventional booster, when the booster with the input shaft moved forward is operated, the reaction disk and the valve plunger come into contact with each other, whereby an output having a predetermined servo ratio can be obtained from the output shaft. Then, when the valve plunger and the reaction disc come into contact with each other, the output sharply rises, and the sharp output rise is generally called jumping. By the way, in the conventional booster having the above-described configuration, the driver is given a good brake feeling by increasing the hysteresis which is the difference between the input when the brake pedal is depressed and the input when the brake pedal is released. It has been known that this can be achieved, and there has been an idea to secure a large hysteresis by increasing the hardness of the rubber used for the reaction disc.

However, if the hardness of the rubber of the reaction disk is increased in order to secure a large hysteresis, the jumping amount will vary. Not only that, but when the booster is used at low temperature, the hardness of the reaction disc becomes higher than that at room temperature, so the jumping amount at low temperature becomes larger than that at room temperature, which However, there is a drawback that the driver's brake feeling is hindered.

In view of the above-mentioned circumstances, the present invention provides a valve body slidably provided in a shell,
An axial through hole provided in the valve body, a valve plunger slidably fitted in the through hole of the valve body and interlocking with the input shaft, and a base portion slidably fitted in the valve body. Output shaft facing the above valve plunger,
Interposed between the base of this output shaft and the valve plunger,
In a booster equipped with a reaction disc that transmits the reaction force of the output acting on the output shaft to the input shaft via the valve plunger, a comparison is made when the valve plunger is advanced across the valve plunger and the through hole of the valve body. And a resistance member for increasing sliding resistance when the valve plunger retracts.

According to this structure, the sliding resistance when the valve plunger is retracted is greater than when the valve plunger is moved forward. Therefore, the flow path switching operation by the valve mechanism interlocking with the input shaft is performed by the input shaft. When the input shaft moves backward, it becomes slower than when the input shaft moves forward. Therefore, a large hysteresis can be secured without increasing the hardness of the rubber used for the reaction disc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 shows a main part in a shell 1 of a negative pressure type brake booster. In FIG. 1, a valve body 2 is slidably provided in a shell 1, and a valve mechanism 3 having a conventionally known structure is housed in the valve body 2. The valve mechanism 3 switches the communication state of the fluid passage formed in the valve body 2. The shaft portion of the valve body 2 is provided with a stepped hole 2A in the axial direction, and the small diameter hole 2 located on the right side of the stepped hole 2A.
A valve plunger 4 forming a part of the valve mechanism 3 is slidably fitted to a. An input shaft 5 is connected to an end portion of the valve plunger 4 on the right side, and the valve mechanism 3 is operated as the input shaft 5 is advanced and retracted. Stepped hole 2A in the valve body 2
The entire stepped portion is an annular protrusion 2b extending toward the left side, and a recessed portion 6a formed in the base portion of the output shaft 6 is slidably fitted to the annular protrusion 2b. A disk-shaped reaction disk 7 made of rubber is housed in the recess 6a of the output shaft 6, and the outer peripheral side of the right end surface 7a of the reaction disk 7 is the end surface of the annular projection 2b of the valve body 2. Abutting against. Therefore, the reaction disc 7 is sandwiched between the recessed portion 6a of the output shaft 6 and the end surface of the annular protrusion 2b, and when the brake booster shown in FIG. A required gap is formed between the end surface 7a and the end surface of the valve plunger 4. The configuration described above and the operation based on it are the same as those of the conventionally known negative pressure type brake booster, and when the brake pedal is depressed from the non-operation state shown in the figure, the input shaft 5 is moved forward (leftward). The valve mechanism 3 is operated to switch the flow path. As a result, a pressure difference is generated across the power piston (not shown) provided in the valve body 2,
The entire valve body 2 is moved to the left. Further, the right end surface 7a of the reaction disk 7 compressed in the axial direction comes into contact with the end surface of the valve plunger 4, and the output of the output shaft 6 with a predetermined servo ratio can be obtained. At that time, the reaction force of the output acting on the output shaft 6 is transmitted to the input shaft 5 via the reaction disk 7 and the valve plunger 4. When the right end surface 7a of the reaction disk 7 and the valve plunger 4 come into contact with each other, the output sharply rises, and the sharp output rise is generally called jumping. Therefore, in this embodiment, an annular groove 4a is formed in the outer peripheral portion on the left side of the valve plunger 4, and a rubber ring-shaped seal member 8 is attached to the annular groove 4a. The outer peripheral edge of the seal member 8 is a lip portion 8a inclined to the right side, and this lip portion 8a is brought into close contact with the inner peripheral surface of the small diameter hole 2a of the valve body 2. Therefore, the lip portion 8a slides on the inner peripheral surface of the small diameter hole 2a as the valve plunger 4 advances and retracts while maintaining the airtightness of the space before and after the lip portion 8a. As described above, in the present embodiment, the provision of the seal member 8 makes it possible to increase the sliding resistance when the valve plunger 4 is retracted as compared with when the valve plunger 4 is advanced. That is, when the valve plunger 4 is advanced (leftward), the diameter of the lip portion 8a is reduced, so that the sliding resistance of the valve plunger 4 is small, while the valve plunger 4 is retracted (rightward). When this is done, the lip portion 8a is expanded in diameter, so that the sliding resistance of the valve plunger 4 is increased. Therefore,
The switching operation of the flow path by the valve mechanism 3 interlocked with the input shaft 5 is slower when the input shaft 5 moves backward than when the input shaft 5 moves forward, whereby a large hysteresis can be secured. Further, in this embodiment, since it is not necessary to increase the hardness of the reaction disc 7 itself,
The jumping amount does not vary. Further, unlike the case where the hardness of the reaction disk 7 is increased to increase the hysteresis, the jumping amount at the low temperature does not become extremely larger than the jumping amount at the normal temperature. FIG. 2 shows a second embodiment of the present invention. In the second embodiment, the outer peripheral portion on the left side of the valve plunger 104 has a smaller diameter than that of the first embodiment, and the disc-shaped member 111 is integrally connected to the left end of the outer peripheral portion having the reduced diameter. is doing. The outer peripheral portion of the member 111, which is substantially the left end, is slidably fitted in the small diameter hole 102a of the valve body 102. An annular bulge 102c that bulges radially inward is provided at the right end of the small diameter hole 102a of the valve body 102. The annular bulge 102c and the valve plunger 104 are provided.
Of the coiled compression spring 112
Is provided. When the compression spring 112 is in the natural state, the tip of the member 111 of the valve plunger 104 is located at the inoperative position in the drawing, and the member 1 of the valve plunger 104 is in the non-operating position.
A required gap is maintained between 11 and the reaction disk 107 as in the first embodiment. The other structure is the same as that of the first embodiment, and the members corresponding to the first embodiment have the member numbers added with 100. In the second embodiment, the compression spring 112 is used in place of the seal member 8 in the first embodiment. Even with such a configuration, the valve plunger 104 is compared with that when the valve plunger 104 is advanced. When the plunger 104 is retracted, the substantial sliding resistance of the valve plunger 104 can be increased. Therefore, it is possible to obtain the same effect as that of the first embodiment.

As described above, according to the present invention, it is possible to obtain a large hysteresis without increasing the hardness of the rubber used for the reaction disk.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

2 Valve body 4 Valve plunger 5 Input shaft 6 Output shaft 7 Reaction disk 8 Seal member (resistive member)

Claims (1)

Claim: What is claimed is: 1. A valve body slidably provided in a shell, an axial through hole provided in the valve body, and a slidably fitted into the through hole of the valve body. And a valve plunger that interlocks with the input shaft, an output shaft that slidably fits the base portion of the valve body to face the valve plunger, and is interposed between the base portion of the output shaft and the valve plunger. And a reaction disk that transmits a reaction force of the output force acting on the output shaft to the input shaft via the valve plunger, the valve plunger and the through hole of the valve body across the valve plunger when the valve plunger moves forward. A booster characterized by comprising a resistance member for increasing sliding resistance when the valve plunger retracts in comparison.