JPH0141538B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brake booster, and more particularly to a brake booster that reduces the invalid stroke of an input shaft at the start of operation.

In general, a brake booster advances a valve plunger linked to the advancement of an input shaft, first cutting off communication between a negative pressure chamber and an atmospheric pressure chamber, and then communicating the atmospheric pressure chamber with the atmosphere. The resulting pressure difference between the negative pressure chamber and the atmospheric pressure chamber operates the power piston to obtain a boosting effect. When the brake booster returns,
By retracting the valve plunger, the atmospheric pressure chamber is cut off from the atmosphere, and the negative pressure chamber and the atmospheric pressure chamber are communicated, eliminating the pressure difference between the two chambers and returning the power piston to its original non-operating position by the return spring. I'm trying to get it back.

However, during the return operation, in order to quickly return the power piston, it is necessary to increase the flow area between the negative pressure chamber and the atmospheric pressure chamber to quickly eliminate the pressure difference between the two chambers. Yes, but
For this reason, if the stroke amount of the valve plunger is set large, the negative pressure chamber and the atmospheric pressure chamber cannot be isolated unless the valve plunger and input shaft are advanced by that stroke amount at the start of the next operation, and as a result, The invalid stroke of the input shaft was increasing.

In order to improve these shortcomings, conventionally, a key member that prevents the valve plunger from coming out of the valve body is used to ensure a large flow path area when the power piston returns, and when the power piston is not in operation, the flow path is closed. A brake booster has been proposed that has a smaller area and can reduce the invalid stroke at the start of the next operation. This brake booster is provided with the key member slidable relative to the valve body in its operating direction, and when the power piston returns, the key member is set on the backward side relative to the valve body to ensure the large flow path area. ,
When the key member is in a non-operating state, the key member is brought into contact with the inner surface of the shell to stop the key member and the valve plunger from retracting, and a little later than the valve plunger is stopped, the valve body is moved by the key member or the back of the power piston. is stopped by bringing the diaphragm into contact with the inner surface of the shell,
As a result, the invalid stroke is reduced by placing both valve plungers in a non-operating state while moving the valve plunger forward relative to the valve body.

However, in a brake booster with such a structure, abnormal noise is likely to occur due to collision between the shell and the key member, which are usually made of metal, and even if one side is made of synthetic resin or an elastic body such as rubber is provided, Because the collision point is on the inner surface of the shell close to the outside and the contact area cannot be very large, it has not always been sufficient to suppress the generation of abnormal noise.

In view of these circumstances, the present invention has been developed by bringing the valve body into contact with the inner surface of the shell during non-operation to restrict its retreat, and by interlocking a power piston and a valve plunger that are slidably provided on the valve body. During operation, the valve plunger is moved forward relative to the valve body to reduce the invalid stroke, and this configuration allows a larger contact area compared to the key member to be secured, thereby suppressing the generation of abnormal noise. The present invention provides a brake booster.

The present invention will be described below with reference to the illustrated embodiments.
In FIG. 1, 1 is a front shell, 2 is a rear shell, 3 is a valve body, and 4 is a power piston attached to the outer circumference of the valve body 3 so as to be slidable along its operating direction. The inner circumferential portion 5a of the diaphragm 5 is fitted onto the outer circumference of the cylindrical portion 4a formed in the cylindrical portion 4a, and the outer circumferential portion 5b of the diaphragm 5 is sandwiched between the front shell 1 and the rear shell 2, and the inside thereof is formed into a negative pressure chamber 6. It is divided into an atmospheric pressure chamber 7. The cylindrical portion 4a of the power piston 4 is slidably fitted to the outer circumference of the valve body 3, and the bent portion of the cylindrical portion 4a is brought into contact with the end surface of the large diameter portion 3a of the valve body 3. When atmospheric pressure is introduced into the atmospheric pressure chamber 7 and an acting force due to a pressure difference acts on the power piston 4, the acting force can be transmitted to the valve body 3 via the end face of the large diameter portion 3a. In addition, the inner circumferential surface of the cylindrical portion 4a and the valve body 3
A seal member 8 is provided between the outer peripheral surface of the negative pressure chamber 6 and the atmospheric pressure chamber 7 to maintain airtightness between the negative pressure chamber 6 and the atmospheric pressure chamber 7.

The unend cylindrical portion 3b of the valve body 3 protrudes from the opening 2a of the rear shell 2 to the outside while being kept airtight by a seal member 9, and a valve mechanism 10 is provided within the cylindrical portion 3b. This valve mechanism 10 is equipped with a valve plunger 11 and an input shaft 12 as well as conventionally known ones, and when in the non-operating state, the valve mechanism 10 is constantly introduced into the negative pressure chamber 6 via the negative pressure introduction pipe 13 of the front shell 1. An axial passage 14 formed in the valve body 3, a gap between the valve body 15 and the valve seat 3c of the valve body 3, and a radial passage 16
The valve body 3, power piston 4, etc. are held in a non-operating position by a return spring 17.

The key member 20 that prevents the valve plunger 11 from coming out of the valve body 3 has an engaging portion 20a that is inserted into the valve body 3 and engages with the intermediate small diameter portion of the valve plunger 11, as shown in FIG.
and an interlocking portion 20b that protrudes outside the valve body 3 and interlocks with the power piston 4.
The tip of the cylindrical portion 4a of the power piston 4 is
As shown in FIGS. 1 and 2, this portion is bent inward to form a contact portion 4b with the interlocking portion 20b of the key member 20, and the support plate 21 is fixed to the outer periphery of the cylindrical portion 4a. , the key member 20 on its inner surface
is supported so that it does not fall out from the valve body 3. The key member 20 is inserted into the valve body 3 so as to be able to swing freely.
A fulcrum portion 3 that serves as a fulcrum for the key member 20 is provided on the inner surface of the hole 3d through which the
It forms e. In Fig. 1, 22 is a reaction disk, 23 is a push rod, and 24 is a reaction disk.
is a return spring for the input shaft 12.

In the above configuration, in the non-operating state shown in FIG. 1, the input shaft 12 and the valve plunger 11 are already in a position where they are advanced by a required amount with respect to the valve body 3, and the valve body 15 and The gap between the valve seat 3c and the valve seat 3c is very small. When the valve plunger 11 is further advanced from this state via the input shaft 12, the valve body 15 seats on the valve seat 3c, cutting off communication between the negative pressure chamber 6 and the atmospheric pressure chamber 7, and the subsequent valve plunger 11 advances, the valve plunger 11
The end of the valve body 15 is separated from the valve body 15 to introduce atmospheric pressure into the atmospheric pressure chamber 7. Then, the power piston 4 is moved forward against the return spring 17, and when the power piston 4 comes into contact with the large diameter portion 3a of the valve body 3 and both move forward together, the braking action is performed as in the conventional case. It is done.

After this, when the forward force of the input shaft 12 is released,
As shown in FIG. 3, the return spring 24 of the input shaft 12
As a result, the input shaft 12 and the valve plunger 11 are retracted with respect to the valve body 3, whereby the key member 20 is rotated clockwise about the fulcrum portion 3e. At this time, the power piston 4 is located at the forward end with respect to the valve body 3 due to the pressure difference between the negative pressure chamber 6 and the atmospheric pressure chamber 7, and the connecting portion 20b of the key member 20 is the abutting portion of the power piston 4. When the valve plunger 11 and the input shaft 12 come into contact with the valve body 3 and their clockwise rotation is restricted, the valve plunger 11 and the input shaft 12 are also stopped from retreating relative to the valve body 3. In this state, the valve body 15 is largely separated from the valve seat 3c, allowing the negative pressure chamber 6 and the atmospheric pressure chamber 7 to communicate with each other with a large flow area.

Valve body 3 while maintaining the state shown in Figure 3.
etc. are retracted by the return spring 17 to near the non-operating position, first the valve body 3
comes into contact with the inner surface of the rear shell 2, and its backward movement is stopped. On the other hand, the power piston 4 that receives the biasing force of the return spring 17 continues to move backward, and when the power piston 4 is moved backward with respect to the valve body 3, the return spring 24 of the input shaft 12 causes the elastic force of the return spring 17 to be applied to the power piston 4. Since the key member 20 is larger, the key member 20 is rotated counterclockwise about the fulcrum portion 3e to advance the valve plunger 11 and the input shaft 12 with respect to the valve body 3. When the counterclockwise rotation of the key member 20 is restricted by coming into contact with the inner surface of the hole 3d, the forward movement of the valve plunger 11 is also stopped, but in this state, the gap between the valve body 15 and the valve seat 3c is becomes very small, making the invalid stroke at the start of the next operation very small.

FIG. 4 shows another embodiment of the present invention, in which a key member 2 is provided instead of forming a fulcrum 3e on the valve body 3.
A fulcrum portion 20c is formed at 0. The rest of the structure is the same as that of the above-described embodiment, and the same parts are designated by the same reference numerals.

In the above embodiment, the return spring 17 is used as a biasing means for biasing the power piston 4 in the backward direction with respect to the valve body 3, but as shown in FIG. 1 and the valve body 3 to prevent its repulsive force from being transmitted to the power piston 4, and a disc spring 25 is installed between the large diameter portion 3a of the valve body 3 and the valve body 4.
may be provided and used as the energizing means. In this case, the elastic force of the disc spring is smaller than the elastic force of the return spring 17, and the elastic force of the return spring 24 is
It should be larger than that of . Further, in the above embodiment, the key member 20 is used as a link member for interlocking the valve plunger 11 and the power piston 4, but the link member and the key member may be provided independently. Furthermore, an elastic body such as rubber may be provided on the contact surface between the valve body 3 and the rear shell 2.

As described above, in the present invention, since the valve body and the shell are brought into contact with each other, the contact area between them can be increased, and the generation of abnormal noise can be effectively suppressed. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of the present invention, and FIG.
The figure is a sectional view taken along the - line in Fig. 1, Fig. 3 is a sectional view of the main part showing a state different from Fig. 1, and Fig. 4.
FIG. 5 is a sectional view of essential parts showing other embodiments of the present invention. 1...Front shell, 2...Rear shell, 3
... Valve body, 4 ... Power piston, 10
... Valve mechanism, 11 ... Valve plunger, 17 ... Return spring, 20 ... Key member.

Claims (1)

[Claims] 1. A valve body that accommodates a valve mechanism that controls the switching of a pressure fluid flow path, and that is in contact with the inner surface of the shell to restrict retraction when not in operation, and a valve body that is provided so as to be slidable along the direction of operation of the valve body. a power piston, a biasing means for biasing the power piston in a backward direction with respect to the valve body, and a valve plunger constituting the valve mechanism and the power piston are interlocked, and when the power piston retreats with respect to the valve body, the power piston is biased in the backward direction. A brake booster comprising: a link member for advancing a plunger relative to a valve body.