JPH0411900Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a power piston assembly for a brake booster, and more particularly to a connection structure between a valve body and a power piston.

``Prior Art'' Generally, a valve body and a power piston in a brake booster are constructed separately and integrally connected to each other by a suitable connection structure. Conventionally, the connection structure used was a screw or bayonet structure (Utility Model Application No. 56-3056).
Various configurations are known.

``Problems that the invention aims to solve'' However, in general, conventional connection structures have poor assembly workability, such as those using screws,
Since the bayonet structure is complicated and expensive, a structure that is easy to assemble and is inexpensive is desired.

"Means for Solving the Problem" In view of such circumstances, the present invention forms a stepped portion on the outer periphery of the valve body, and also forms an annular groove on the rear side of the stepped portion, and at least a circular groove is formed in the annular groove. A ring-shaped member having a part cut in the circumferential direction is incorporated, the ring-shaped member is positioned in the axial direction by the annular groove, and the front side of the ring-shaped member is made to protrude outward in the radial direction, so that the ring-shaped member can be elastically deformed. An engaging piece is formed in a protruding manner, and the inner periphery of the hole drilled in the shaft portion of the power piston is fitted onto the outer periphery of the ring-shaped member to prevent the ring-shaped member from expanding from the cut portion. , a power piston is held between the stepped portion and the engaging piece.

"Operation" According to such a configuration, it is only necessary to form a stepped part and a cylindrical part in the valve body, and to prepare a ring-shaped member with an engaging piece formed thereon, so it is extremely inexpensive, similar to the one using screws. It can be configured as follows.

Moreover, when connecting the valve body and the power piston, the ring-shaped member is fitted into the annular hole of the valve body, and in this state, the inner circumference of the hole bored in the shaft of the power piston is connected to the rear of the engagement piece. It is passed from the side while being elastically deformed inward in the radial direction and brought into contact with the end face of the stepped portion, and the elasticity of the engaging piece causes the engaging piece to protrude outward in the radial direction, thereby causing the engaging piece to contact the stepped portion. Since it is only necessary to sandwich the power piston between the two, assembly workability can be made extremely easy.

In this state, the power piston can be sandwiched between the engagement piece of the ring-shaped member and the stepped portion to integrally connect the valve body and the power piston, and the ring-shaped It is possible to prevent the member from expanding from the cut portion and falling off from the annular groove.

``Example'' An example in which the present invention is applied to a tandem brake booster will be described below. In FIG. 3: front and rear front chambers 4 and rear chambers 5
A roughly cylindrical valve body 6 made of synthetic resin is slidably secured to the shaft portions of the rear shell 2 and center plate 3 while keeping airtight with seal members 7 and 8, respectively. It penetrates.

A front power piston 9 and a rear power piston 10 housed in the front chamber 4 and rear chamber 5 are respectively connected to the valve body 6, and a front diaphragm 11 and a rear diaphragm are connected to the back of each power piston 9, 10. 12, respectively, and the front chamber 4 and rear chamber 5 are separated by the diaphragms 11 and 12.
and are divided into two rooms each, making a total of four rooms A,
B, C, and D are formed.

The valve mechanism 15 housed within the valve body 6 is equipped with a valve plunger 16 that is slidably fitted within the valve body 6, and the end of the valve plunger 16 is connected to an input shaft 17 that is linked to a brake pedal (not shown). are doing. Also, valve plunger 1
The tip of the push rod 18 faces the end surface of a reaction disk 19 provided in the large diameter portion at the right end of the push rod 18, and the tip of the push rod 18 is slidably protruded from the shaft portion of the front shell 1 via a seal member 20. The piston is interlocked with the piston of a master cylinder (not shown).

The above power pistons 9, 10 and valve body 6
The valve plunger 16 is normally held in the non-operating position shown in the figure by a return spring 21, and in this non-operating state, the valve plunger 16 is connected to the valve body 6.
The key member 22 that prevents the valve plunger 16 from moving freely to the right comes into contact with the inner surface of the rear shell 2 and restricts the free movement of the valve plunger 16 to the right relative to the valve body 6. This allows the valve mechanism 15 to immediately switch the fluid circuit.

Next, the aforementioned chamber A is a constant pressure chamber into which negative pressure is constantly introduced, and communicates with an intake manifold (not shown) via a negative pressure introducing pipe 25 attached to the front shell 1. Also, this constant pressure chamber A
is an axial passage 2 formed in the valve body 6.
6 and a constant pressure chamber C via the radial passage 27
is connected to.

Further, when the brake booster is not in operation, these constant pressure chambers A and C are connected to the axial passage 26, the gap between the valve element 28 and the valve seat 29 of the valve mechanism 15, and the radial passage 30 formed in the valve body 6. It communicates with the variable pressure chamber D via the valve body 6, and further communicates with the variable pressure chamber B via an axial passage 31 formed in the valve body 6.

In this state, negative pressure is introduced into each of the constant pressure chambers A, C and variable pressure chambers B, D, and the pressure becomes equal, and there is no pressure difference between the front and back of each diaphragm 4, 5, so that the return spring 21
is held in the non-operating position shown.

As shown in an enlarged view in FIG. 2, a flange portion 6a is formed on the outer peripheral surface of the valve body 6 at the front end position in the operating direction, and an annular groove 35 is formed on the rear side of the flange portion 6a. , a ring-shaped member 36 is assembled within this annular groove 35. This ring-shaped member 36 has an inner diameter and a width that substantially match the outer diameter and width of the annular groove 35, and a portion 36a thereof in the circumferential direction is cut off as shown in FIG. By expanding the diameter of the ring-shaped member 36 from the cut portion 36a, the ring-shaped member 36 can be easily assembled into the annular groove 35.

The above-mentioned axial passage 31 is formed to open on the inner circumferential surface of the annular groove 35 and communicate with the inside of the chamber A. In order to ensure the communication, a notch 36b is provided in the ring-shaped member 36. and by forming engaging claws 36c on both sides of the notch 36b and positioning them within the axial passage 31, the notch 36b reliably aligns with the opening of the axial passage 31. That's what I do.

Further, the ring-shaped member 36 is formed with a plurality of engagement pieces 36d whose front sides protrude outward in the radial direction.
A cylindrical portion 9 is formed in the shaft portion of the front power piston 9 so that the distance between the front end portion of each engaging piece 36d and the step end surface 6b of the flange portion 6a when assembled in the cylindrical portion 9 is
The length in the axial direction is made to match that of a.

At this time, the front end of each engagement piece 36d is formed at a position recessed by a required amount from the front end surface of the ring-shaped member 36, so that the cylindrical portion 9a is It is arranged so that it can be positioned on the outer circumferential surface of the ring-shaped member 36 at a position forward of the front end.

The front power piston 9 has the cylindrical portion 9
Step end surface 6b of the flange portion 6a from the left side of a
The outer end thereof is bent forward to form a cylindrical portion 9b surrounding the outer peripheral surface of the flange portion 6a. A seal member 37 is provided inside the bent portion, and the seal member 37 maintains airtightness between the valve body 6 and the front power piston 9.

Further, the left side of the cylindrical portion 9b of the front power piston 9 is folded radially outward to have a U-shaped cross section, and an annular recess 38 with an open right side is formed inside the annular recess 38. It has been expanded to. The annular recess 38 accommodates the inner peripheral bead portion 11a of the front diaphragm 11 disposed on the back surface of the front power piston 9, and is held inside by a retainer 39 fitted around the outer periphery of the cylindrical portion 9b. This prevents the circumferential bead portion 11a from falling out of the annular recess 38.

In this embodiment having the above configuration, when assembling the front power piston 9 to the valve body 6, first the ring-shaped member 39 is attached to the cut portion 36a.
The diameter of the engaging claw 36c is expanded from the axial direction passage 3.
1, the ring-shaped member 36 is assembled into the annular groove 35. By locating the engaging pawl 36c within the axial passage 31 in this way, the notch 36b can be reliably aligned with the opening of the axial passage 31 to ensure communication between the axial passage 31 and the chamber A. can.

Next, with the seal member 37 attached to the outer periphery of the flange portion 6a, the valve body 6 is fitted into the hole 40 in the cylindrical portion 9a of the front power piston 9, and the cylindrical portion 9a is The piece 36d is passed from the rear side while being elastically deformed inward in the radial direction.

When the cylindrical portion 9a passes through the engagement piece 36d,
The inner periphery of the hole 40 comes into contact with the stepped end surface 6b of the flange portion 6a from the rear side in the operating direction, and when a pressure difference occurs between the chambers A and B, pressure is applied to the front power piston 9. The forward force can now be transmitted to the valve body 6.

Further, when the cylindrical portion 9a passes through the engagement piece 36d, the engagement piece 36d returns to the position protruding outward in the radial direction due to its own elasticity, and this engagement piece 3
6d and the step end surface 6b of the flange portion 6a sandwich the cylindrical portion 9a of the front power piston 9, so that the valve body 6 and the front power piston 9 are integrally connected to each other.

At the same time, the front power piston 9
Since the cylindrical portion 9a is located on the ring-shaped member 36, the ring-shaped member 36 is prevented from expanding from the cutting portion 36a and falling off from the annular groove 35.

In this way, the ring-shaped member 36 is inserted into the annular groove 3.
5 and fitting the valve body 6 into the hole 40 of the front power piston 9, the valve body 6 and the front power piston 9 can be integrally connected very easily.

It is clear that the present invention can be applied to a single brake booster.

"Effects of the invention" As described above, according to the invention, the valve body and the power piston can be integrally connected with an extremely inexpensive structure, and the assembly work can be made extremely easy. It will be done.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing one embodiment of the present invention;
The figure is an enlarged sectional view of the main part of FIG. 1, and FIG. 3 is a perspective view of the main part of the ring-shaped member 36. 1...Front shell, 2...Rear shell, 6
...Valve body, 6a...Flange part, 9...
Front power piston, 6b...stepped end surface, 9
a, 9b...cylindrical part, 35... annular groove, 36...
Ring-shaped member, 36a...cutting portion, 36d...engaging piece, 40...hole.

Claims (1)

[Scope of utility model registration request] A stepped portion is formed on the outer periphery of the valve body, and an annular groove is formed on the rear side of the stepped portion, and a ring-shaped member with at least a portion cut in the circumferential direction is incorporated into the annular groove. The member is positioned in the axial direction, and an elastically deformable engagement piece whose front side protrudes outward in the radial direction is formed protrudingly on the ring-shaped member, and the engagement piece is inserted into the hole bored in the shaft of the power piston. A peripheral portion is fitted onto the outer periphery of the ring-shaped member to prevent the ring-shaped member from expanding from the cutting portion, and the power piston is held between the stepped portion and the engagement piece. Power piston assembly for brake booster.