JPH05185926A - Reaction force transmitting mechanism of booster - Google Patents

Abstract

PURPOSE:To provide a large hysteresis by a simple constitution by making the inner circumferential edge of the edge surface of a valve body which is brought into contact with a reaction disk to be a tapered surface where the front side is radially expanding. CONSTITUTION:From the servo-balanced condition where a breather valve provided with a valve mechanism and a vacuum valve are closed, a valve plunger 2 advances, and the position of the tip surface 2a of the valve plunger 2 is on the upper side when the breather valve is opened. From the servo- balanced condition, the valve plunger 2 sets back, and the position of the tip surface 2a of the valve plunger 2 is on the lower side when the vacuum valve is opened. A tapered surface 1d is formed so as to include the position of the tip surface 2a of the valve plunger 2 when the breather valve is opened and the position of the tip surface 2a of the valve plunger 2 when the vacuum valve is opened. In the servo-balanced region after a brake booster is started to operate, the servo-ratio can be changed when the brake pedal is operated, and when the brake is released, obtaining a large hysteresis.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a reaction force transmission mechanism of a booster.

2. Description of the Related Art Conventionally, a valve body slidably provided in a shell, a valve plunger slidably fitted in a through hole formed in the valve body and interlocking with an input shaft, and the valve body A reaction disc that is interposed between an output shaft having a base portion slidably fitted therein and an end surface of the valve body in which the output hole has a through hole and that faces the tip end surface of the valve plunger. With and
A booster configured to transmit the reaction force of the output acting on the output shaft to the input shaft via a reaction disk and a valve plunger is well known. On the basis of such a configuration, there is also known a technique of increasing the hysteresis by making the servo ratio different between when the brake pedal is depressed and when the brake pedal is released (for example, the actual fairness 3 -3095). That is, actual fairness 3-30
In the booster of Japanese Patent Publication No. 95, a collar member is interposed between the reaction disc and the valve plunger, and in the servo balance region after the start of operation of the booster, an atmospheric valve and a vacuum valve of a valve mechanism are provided. When the brake pedal is depressed from the servo-balanced state where both are closed, the atmospheric valve is opened. At this time, the reaction disc comes into contact with both the collar member and the valve plunger, so that the output increases with a small servo ratio. On the other hand, when the brake pedal is released from the servo-balanced state, the vacuum valve is opened, so the atmosphere inside the variable pressure chamber escapes to the constant pressure chamber side and the output drops, and in that case, the reaction disc is only the valve plunger. , The output decreases with a large servo ratio. As described above, in the booster disclosed in Japanese Utility Model Publication No. 3-3095, a large hysteresis is obtained by increasing the servo ratio when the brake pedal is released rather than the servo ratio when the brake pedal is depressed. It was

However, in the booster disclosed in Japanese Utility Model Publication No. 3-3095, the collar member is interposed between the reaction disc and the valve plunger. However, there is a drawback that the number of parts is increased and the structure becomes complicated.

In view of the above-mentioned circumstances, the present invention provides a valve body slidably provided in a shell,
A valve plunger slidably fitted in a through hole formed in the valve body and interlocking with an input shaft, an output shaft having a base portion slidably fitted in the valve body, and a base portion of the output shaft. And a reaction disc facing the end face of the valve plunger and interposed between the end face of the valve body and the end face of the valve body where the through hole opens, and the reaction disc and the valve plunger act as a reaction force of the output acting on the output shaft. In the reaction force transmission mechanism of the booster configured to transmit to the input shaft via the input shaft, the inner peripheral edge of the end surface of the valve body that abuts against the reaction disk is a tapered surface whose front side increases in diameter.

According to such a structure, in the servo balance region after the operation of the booster is started, the brake pedal is depressed from the servo balance state in which both the atmospheric valve and the vacuum valve of the valve mechanism are closed to depress the atmospheric pressure. The position of the valve plunger with respect to the valve body when the valve is opened is earlier than the position of the valve plunger with respect to the valve body when the brake pedal is released from the servo balance state and the vacuum valve is opened. In this way, when the position of the valve plunger with respect to the valve body comes earlier when the brake pedal is depressed than when the brake pedal is released, the reaction disk is pushed forward by that amount. Therefore, when the brake pedal is depressed, the contact area of the reaction disc that contacts the tapered surface is smaller than when the brake pedal is released, and the servo ratio is also smaller. As a result, the hysteresis, which is the difference between the inputs when the brake pedal is released and when the brake pedal is depressed, can be increased. Therefore, compared to the above-mentioned conventional technique, a large hysteresis can be obtained with a simple structure.

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 of a negative pressure type brake booster basically having a conventionally known structure. In FIG. 1, reference numeral 1 denotes a valve body slidably provided in a shell (not shown), and a shaft portion of the valve body 1 has a stepped hole 1A having a large diameter on the front side. A small-diameter portion 1a on the rear side of the stepped hole 1A is slidably fitted with a valve plunger 2 forming a part of a valve mechanism, and an input is made to a rear-side end portion of the valve plunger 2 not shown. The axes are connected. The stepped portion of the stepped hole 1A in the valve body 1 is an annular protrusion 1b extending toward the front side, and a concave portion 3a formed at the base of the output shaft 3 is slidable on the outer peripheral surface of the annular protrusion 1b. It is fitted. A disk-shaped reaction disk 4 made of rubber is housed in the recess 3a of the output shaft 3. The right end surface 4a and the left end surface 4b of the reaction disk 4 are flat over the entire area, and the outer peripheral side of the right end surface 4a is brought into contact with the end surface 1c of the annular projection 1b of the valve body 1 while the right end surface is formed. The shaft side of 4a faces the tip surface 2a of the valve plunger 2. Although not shown, in the non-actuated state of the brake booster, a required gap is formed between the right end face 4a of the reaction disc 4 and the front end face 2a of the valve plunger 2. Then, when the brake booster is actuated by depressing the brake pedal from the inoperative state, the input shaft and the valve plunger 2 are moved forward (to the left), so that a valve mechanism (not shown) is activated.
That is, since the vacuum valve of the valve mechanism is closed and the atmosphere valve is opened, the atmosphere is introduced into the variable pressure chamber (not shown). This causes a pressure difference between the constant pressure chamber and the variable pressure chamber to move the valve body 1 forward, and the shaft portion of the right end surface 4a of the reaction disc 4 bulges toward the rear side. Is eliminated and the right end face 4a of the reaction disc 4 and the tip end face 2a of the valve plunger 2 come into contact with each other. Therefore, from this time point to the full load point, the output increases at a predetermined servo ratio determined by the area of the tip surface 2a of the valve plunger 2 and the area of the end surface 1c of the annular protrusion 1b of the valve body 1. At the same time, the reaction force of the output acting on the output shaft 3 is transmitted to the input shaft (not shown) via the reaction disc 4 and the valve plunger 2. The above-described structure and the operation based on it are the same as those of the conventionally known negative pressure type brake booster. Therefore, in the present invention, the tapered surface 1d whose diameter is increased on the front side is formed on the inner peripheral edge of the end surface 1c of the annular projection 1b. In this embodiment, the tapered surface 1d is set as follows. That is, the position of the tip end surface 2a of the valve plunger 2 when the valve plunger 2 is moved forward and the atmospheric valve is opened from the servo balance state in which both the atmospheric valve and the vacuum valve included in the valve mechanism (not shown) are closed is illustrated. 1 is shown above the center line of FIG. 1, and the position of the tip end surface 2a of the valve plunger 2 when the valve plunger 2 is retracted from the servo balance state and the vacuum valve is opened is shown in FIG. It is shown on the lower side. The tapered surface 1d is formed so as to include the position of the tip surface 2a of the valve plunger 2 when the atmospheric valve is opened and the position of the tip surface 2a of the valve plunger 2 when the vacuum valve is opened. ing. According to the configuration of the present embodiment, it is possible to change the servo ratio between when the brake pedal is depressed and when the brake pedal is released, in the servo balance region after the operation of the brake booster is started. Hysteresis can be obtained. That is, from the servo balance state in which both the atmospheric valve and the vacuum valve of the valve mechanism are closed, the valve plunger 2 when the atmospheric pressure valve is opened by depressing the brake pedal shown above the center line in FIG. The position of the front end face 2a of the valve plunger 2 is located before the position of the front end face 2a of the valve plunger 2 when the brake pedal is released and the vacuum valve is opened from the servo balance state shown below the center line in FIG. Become. Thus, when the position of the front end surface 2a of the valve plunger 2 relative to the valve body 1 is more forward when the brake pedal is depressed than when the brake pedal is released, the reaction disc is moved by the front end surface 2a of the valve plunger 2 accordingly. 4 will be pushed forward. for that reason,
The contact area of the reaction disc 4 contacting the tapered surface 1d becomes smaller when the brake pedal is depressed than when the brake pedal is released. Therefore, as shown in FIG. 3, the servo ratio when the brake pedal is released (straight line B) is larger than the servo ratio when the brake pedal is depressed (straight line A), and the servo balance in a small input area is large. Compared to the state, a larger amount of hysteresis can be obtained in the servo balance state in a large input area. As described above, in the present embodiment, it is possible to reduce the cost of the booster because a large hysteresis can be obtained with a simple structure without increasing the number of parts, assuming a conventionally known structure. .. (Second Embodiment) FIG. 2 shows a second embodiment of the present invention. The second embodiment is based on the structure of the first embodiment shown in FIG.
The outer peripheral edge of the tip end surface 102a of No. 2 is chamfered largely, and the part is made into the taper surface 102b. 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. According to such a configuration of the second embodiment, the contact area of the reaction disc 4 can be changed also by the tapered surface 102b of the valve plunger 102, so that a larger hysteresis can be obtained.

As described above, according to the present invention, it is possible to obtain an effect that a large hysteresis can be obtained with a simpler structure than the conventional one.

[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.

FIG. 3 is a characteristic diagram showing a relationship between input and output according to an embodiment of the present invention.

[Explanation of symbols]

 1 Valve body 1a Small diameter part (hole) 1c End surface 1d Tapered surface 2 Valve plunger 2a Tip surface 3 Output shaft 3a Recessed part (base part) 4 Reaction disk

Claims (1)

[Claims] 1. A valve body slidably provided in a shell, a valve plunger slidably fitted in a through hole formed in the valve body and interlocking with an input shaft, and a base portion of the valve body. And a reaction disc that is interposed between the base of the output shaft and the end surface of the valve body where the through hole opens and that faces the tip surface of the valve plunger. In the reaction force transmission mechanism of the booster, which is configured to transmit the output reaction force acting on the output shaft to the input shaft through the reaction disc and the valve plunger, the end face of the valve body that abuts the reaction disc is A reaction force transmission mechanism for a booster, wherein an inner peripheral edge is a tapered surface whose front side is expanded in diameter.