JPS6311008Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a brake booster for an automobile.

[Conventional technology]

A conventional booster of this kind has a key that is engaged with a recess of the piston and a recess of the air valve to define the retracted position of the air valve, and the outer end of the key is attached to the inner wall of the housing. A contact type type is known.

[Problem that the invention attempts to solve]

However, in the above-mentioned conventional booster, the point where the key contacts the piston and the contact area are small, so the movement of the piston becomes unstable when the piston returns (during rest), and the operating function of the booster becomes unstable. However, it had the disadvantage of poor reliability.

In view of the above drawbacks, the present invention aims to improve the stability of the piston by increasing the area of contact between the key and the piston.

[Means for solving problems]

The brake booster of the present invention includes a piston with a diaphragm that divides the inside of the housing into a front chamber and a rear chamber, a control valve installed in the piston, and a push rod inside the piston that moves in conjunction with the brake pedal. an air valve that is slidably built in and controls a pressure difference between a front chamber and a rear chamber of the piston in the housing in cooperation with the control valve and a seat formed in the piston; A part is inserted into the central part, and a claw part at the tip of the central part engages with an annular recess of the air valve to regulate the retracted position of the air valve, and has arm parts that hold the outer circumferential surface of the piston from both sides; A brake booster comprising a substantially W-shaped key, the arm portion of which comes into contact with the inner wall of the housing when the brake booster is at rest to restrict the retreating position of the piston,
A stepped portion is provided in a portion of the piston adjacent to the recessed portion, and the arm portion of the key is configured to abut against the stepped portion of the stepped portion and the inner wall of the housing when the piston returns.

[Effect of idea]

According to the present invention, when the piston returns, the contact area and the contact area between the piston and the key are increased, which makes it possible to ensure the stability of the piston operation, improve the sealing performance of the sliding part of the piston, and improve the bearings. reliability, such as performance, is improved. In addition, compared to conventional keys, the key of the present invention has a structure in which the piston does not come into contact with only the body of the key, but also with the body and the inner circumference of the arm, so there is less deflection in the key, and when the key is at rest, The gap between the control valve and the seat can be reliably maintained at the set value, contributing to improved braking response.

〔Example〕

Hereinafter, embodiments of the present invention will be described based on the accompanying drawings. In FIG. 1, a housing 11 of a booster 10 has a front portion 11a and a rear portion 11b.
(Hereinafter, the left side in FIG. 1 will be referred to as the front, and the right side will be referred to as the rear.) and a rear chamber 15. power piston 12
is formed by integrally joining a central portion 12a molded from a resin material and a disk portion 12b made of a metal plate. The outer circumferential beat portion of the diaphragm 13 is airtightly held between the housing 11 and a bent portion 11b' fixed to the inner wall of the housing 11, and the diaphragm 1
The inner circumferential beat portion 3 is airtightly held between the inner circumferential edge of the disk portion 12b and the center portion 12a. The front chamber 14 is connected to the intake manifold (not shown) of the engine via a check valve (not shown) from a port 17 provided in the housing 11, and is configured to be constantly supplied with negative pressure while the engine is operating. has been done.

The center portion 12a of the power piston 12 has a cylindrical portion 12c extending rearward, and this cylindrical portion 12c protrudes rearward outside the housing from a center hole in the rear portion 11b of the housing 11. Said rear part 1
A seal member 19 that is integrally assembled with the bearing member 18 is installed inside the center hole of 1b. The center part 12a of the power piston 12 is hollow,
A well-known control valve mechanism 20 including a control valve 21 and an air valve 22 is installed in this hollow space. Control valve 21 is attached to power piston 12 by a retainer 23 at its rear end. The control valve 21 is cylindrical, flexible, movable in the axial direction, and is urged forward by a spring 24.

On the other hand, the air valve 22 is integrally connected to the tip of a push rod 25, which is connected to a brake pedal (not shown), by caulking or the like. An annular recess 22b is formed in a portion adjacent to the front end 22a of the air valve 22, and a key 26 fitted into the recess 12d of the piston 12 is inserted into the recess 22b.
The upper claw portion 26a (FIG. 2) of the body portion 26A is engaged. This engagement restricts movement of the air valve 22 in the axial direction.

A valve seat 27 is formed on the inner circumference of the piston 12 and controls the pressure difference between the front chamber 14 and the rear chamber 15 by coming into contact with the front end surface of the control valve 21 . In the state shown in FIG. 1, there is a gap between the front end surface of the control valve 21 and the seat 27, and in this state, the chamber 28 in the piston 12 communicates with the through holes 29 and 30. Since the through hole 30 is always in communication with the annular chamber 31 outside the piston 12, the front chamber 14 and the rear chamber 15 are in communication with each other.

On the front end surface of the center portion 12a of the piston 12,
An output rod retainer 33 supporting one end of the return spring 32 is attached. The retainer 33 is attached to the disk portion 12 of the piston 12.
The lower end portions of the outer circumferential ends 33a at three locations are similarly fixed to the inner sides of the claw members 34 at three locations on the circumference that are welded to b by rotating and engaging them. That is, as shown in FIG.
3a, bend the tip end radially outward to the claw member 3.
It is engaged by slipping into the inside of the claw 34a of No. 4. In this case, it is fixed by caulking the end portion 34b of the claw after it has been inserted, but this fixing method is not limited to this. For example, a small protrusion may be formed on the inside of the claw 34a. It may be provided that the corrugated portion 33b is locked by passing over the small protrusion at the end of the sinking stroke. here,
Flange portion 12 that is the outer peripheral end of the center portion 12a
a' is a recess 12a into which the outer peripheral end 33a fits;
is formed. With this fitting, the retainer 3
3 is prevented from rotating around the operating axis with respect to the piston 12. The other end of the return spring 32 is
The spring 32 is supported by a receiving member 35 that is welded to the inside of the housing front portion 11a, so that the spring 32 constantly urges the piston 12 rearward in the axial direction.

An output member 36 is disposed at the center of the return spring 32. The output member 36 consists of a rod 37 that passes through the front wall of the housing 11 in an airtight and slidable manner, and a cylindrical body 38 that is integrally connected to the rear end of the rod 37. Cylindrical body 38
is slidably attached to a large diameter hole 39 bored in the center portion 12a. The large diameter hole 39 is the small diameter hole 4
0, and a reaction disk 41 made of rubber is installed on the side of the large diameter hole 39 adjacent to the small diameter hole 40.

The cylindrical portion 12c of the power piston 12 is covered with a rubber boot 42, the front end of which is fixed to the rear end of the housing rear portion 11b, and the rear end of the boot 42 is secured to the outer periphery of the push rod 25. It is locked. The boot 42 expands and contracts in the axial direction when the push rod 25 or the piston 12 moves in the axial direction. Two types of filters 43 and 44 are attached to the open rear end of the circumferential portion 12a.
A receiving member 46 for receiving a spring 45 is disposed on the front end face of the filter 43 located at the front. Since the inner circumference of the receiving member 46 is always in contact with the shoulder of the push rod 25,
The push rod 25 is biased rearward in the axial direction by a spring 45 via the receiving member 46.

A chamber 47 for housing the spring 24 is formed inside the control valve 21, and mounting bolts 48 and 49 for fixing the booster 10 are provided in the housing front part 11a and the rear part 11b. It is being

Next, the shape of the key 26 and the piston 12 that engages with the key 26 will be explained in detail. The key 26 is formed into a substantially W-shape when viewed in the cross-sectional view of FIG. 2, and a U-shaped groove 26b is formed by the two claw portions 26a. The tip of the claw portion 26a can come into contact with the inner wall shoulder of the piston center portion 12a as shown in FIG. In addition, the arm portion 26 of the key 26
A convex portion 26d is provided at c, and another convex portion 26d' is formed below. Further, a small hole 26f is formed in the convex portion 26e provided above the arm portion 26c.
is drilled. Both end bent portions 50a of a metal linear retainer 50 having a circular cross section are engaged with the small hole 26f. The retainer 50 is suspended to prevent the key 26 from falling by itself, and has an inner center portion 50b that elastically contacts the outer surface of the piston 12 and a protrusion 121 ( (see FIG. 1) prevents the retainer 50 from moving in the direction of the operating axis.
The cross-sectional shape of the retainer 50 is not limited to a circular shape, but may be rectangular or other shapes. It is sufficient that the cross-sectional width is at least smaller than the width of the key and that it has elasticity in the direction of the piston after assembly.

The end surface of the key 26 can come into contact with the end surface of the piston 12, and this contact is possible because the piston 12 is formed with a stepped portion 122 having a width e (see FIG. 2). The stepped portion 12
2 and the inner peripheral portion of the key 26 (and the left side surface in FIG. 1) abut against each other with a width of e.

Note that the arc 111 shown in two-dot chain line in FIG. 2 indicates the inner wall edge of the housing rear portion 11b, and
When the outer peripheral end of the housing contacts the inner wall of the housing rear portion 11b, the contact is made with a width f (FIG. 2). Furthermore, although the retainer 50 is shown in FIGS. 1 and 2 as being located above, the positional relationship between the retainer 50 and the key 26 is not necessarily limited to that shown in the drawings. 50 may be located on the left side of FIG. 2, and the key 26 may be located on the right side. In this case, it goes without saying that the concave portion 12d of the piston 12 and the stepped portion 12
It is also necessary to match the position of the key 26 with the position of the key 26.

Next, the operation will be explained. FIG. 1 shows the booster 10 in a rest state, where the piston 12 receives the urging force of the return spring 32 and the lower end of the key 26 is in contact with the inner circumferential surface of the housing rear portion 11b. . In this state, no leftward (forward) force in the axial direction is acting on the push rod 25, and a gap a exists between the left end surface of the control valve 21 and the seat 27.
As a result, the chamber 14 communicating with the negative pressure source communicates with the chamber 15 via the through hole 29, then through this open seat 27 and the control valve 21, the chamber 28, and further through the through hole 30. . Further, the control valve 21 is in contact with the right end surface of the air valve 22 as shown in the figure, so that the control valve 21 is in a closed state. Therefore, the air release circuit via the chamber 47 in the control valve 21, the chamber 45a housing the spring 45, and the filters 43 and 44 is cut off. In this state, the right end surface of the key 26 has a gap b at the center 1.
2a is left between the hole wall and the hole wall.

Next, when the brake pedal is depressed and the push rod 25 is pushed forward, that is, to the left in FIG. With the stroke, the user immediately sits on the seat 27 and closes the valve, first cutting off the communication between the two chambers 14 and 15. Further, by the subsequent depression of the pedal, the air valve 22 and control valve 21 are changed from closed to open. This valve opening degree can be obtained by setting the axial length of the annular recess 22b, so that
The atmospheric pressure that has reached the hollow interior of the control valve 21 quickly enters the rear chamber 15 through the gap between the center of the control valve 21 and the push rod 25. At that time, the route is from the open air valve 22 via the chamber 47 to the chamber 28,
This is a route leading to the rear chamber 15 via the through hole 30. On the other hand, since the front chamber 14 is always under negative pressure, the piston 1
A differential pressure is generated between both sides of the piston 12, and the piston 12 is pushed to the left in the drawing by this differential pressure. piston 1
The leftward movement of the cylinder 2 is transmitted through the reaction disk 41, the cylinder 38, and the output rod 37 to a pressurizing piston (not shown) of the master cylinder for braking. During this time, the brake pedal depression force is transmitted from the push rod 25 to the reaction disc 41 via the air valve 22. The brake reaction force at this time is
This signal is transmitted to both the piston 12 and the air valve 22, and is felt by the driver's foot stepping on the brake pedal via the push rod 25, thereby controlling the braking.

Next, when the brake pedal depression force is released, the air valve 22 is initially moved back to the right relative to the piston 12 via the push rod 25 due to the force of the spring 45. Initially, the retracted position is such that the left side of the key 26 is in contact with the vertical wall of the annular recess 22b as shown in the figure, and the key 26 moves to the right together with the air valve 22, so that the key 26 is inside the piston 12 with the gap b becoming zero. The retracted position of the air valve 22 at is the maximum. When the air valve 22 retreats in this way (the lower right end surface of the key 26 is not yet in contact with the inner wall of the housing rear part 11b), the right end surface of the air valve 22 and the control valve 21
The valve action due to this becomes a closed state and the rear chamber 15
is cut off from the atmosphere. Immediately after that, the contact between the seat 27 and the control valve 21 is released and the valve changes to an open state. This valve open state is the maximum opening degree (a+
b) is maintained. Therefore, the residual atmospheric pressure in the rear chamber 15 is quickly absorbed by the negative pressure source through the other chamber 14 and disappears. The sooner this disappears, the more booster 1
0 to the rest position, and the booster 10
This will improve responsiveness.

In this way, the piston 12 moves further to the right while maintaining the state in which the gap b is zero and the gap between the seat 27 and the control valve 21 is (a+b). Then, the right side surface of the lower end of the key 26 in FIG. 1 comes into contact with the inner wall of the housing rear portion 11b, and a gap b is created as shown in the figure, and the gap (a+b) becomes a gap a, resulting in a rest state. Since the vehicle is in a rest state in which such a gap is formed, the next time the brake pedal is depressed, the negative pressure to the rear chamber 15 is quickly shut off and the brake operation is performed with good responsiveness. In addition, when entering the rest state, the key 26 receives an impact force from the inner wall of the housing rear portion 11b and the stepped portion 122 (FIG. 2) of the piston 12, and when maintaining the rest state, the key 26 The pressing force of the spring 32 is transmitted to the housing via the body and arm of the key, so that it can sufficiently withstand the impact upon return. Note that the shape of the key is not limited to the shape of the above embodiment as long as the arm of the key comes into contact with the stepped portion of the piston and the inner wall of the housing when the key returns.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the booster according to the present invention, FIG. 2 is a cross-sectional view taken along the - line in FIG. 1, and FIG. FIG. 3 is a perspective view showing a state of coupling. 11...Housing, 12...Piston, 14
...Front side chamber, 15 ... Rear side chamber, 21 ... Control valve, 22 ... Air valve, 25 ... Push rod, 26 ... Key, 27 ... Seat, 2
6c...Arm.

Claims (1)

[Claims for Utility Model Registration] A piston with a diaphragm that divides the inside of the housing into a front chamber and a rear chamber, a control valve installed in the piston, and a push rod in the piston that slides by movement in conjunction with a brake pedal. an air valve that is movably built in and controls a pressure difference between a front chamber and a rear chamber of the piston in a housing in cooperation with the control valve and a seat formed on the piston; is inserted, and the claw portion at the tip of the central portion engages with the annular recess of the air valve to restrict the retracted position of the air valve, and
A substantially W-shaped key having arm portions that hold the outer circumferential surface of the piston from both sides, the arm portions coming into contact with the inner wall of the housing when the brake booster is at rest, and regulating the retreating position of the piston. In the brake booster, a stepped portion is provided in a portion of the piston adjacent to the recessed portion, and the arm portion of the key is configured to abut against the stepped portion of the stepped portion and the inner wall of the housing when the piston is at rest. A brake booster that is characterized by: