JPH04130578U - negative pressure booster - Google Patents

Abstract

(57) [Summary] [Purpose] A booster piston is housed in a booster shell so as to be able to move back and forth, and a reaction piston connected to an input rod is slidably fitted into a piston boss connected to the booster piston. A small diameter cylinder hole is coaxially provided with a small diameter cylinder hole that is larger in diameter than the small diameter cylinder hole and opens at the front surface of the piston boss, and the large diameter cylinder hole has an elastic cylinder facing the reaction piston. To improve the durability of an elastic piston in a negative pressure booster in which a piston and an output piston having an output rod are slidably fitted in contact with each other. [Structure] A recess 26 having a diameter D _{1 larger than the inner diameter D 2} of the small diameter cylinder hole ₁₈ is provided in a portion of the elastic piston 20 facing the reaction piston 19 .

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

In this invention, the booster piston is housed inside the booster shell so that it can move back and forth. , the piston boss connected to the booster piston has a reaction force piston connected to the input rod. A small-diameter cylinder hole into which the cylinder is slidably fitted, and a cylinder hole with a larger diameter than the small-diameter cylinder hole. The large-diameter cylinder hole that opens at the front of the piston boss is coaxial with the large-diameter cylinder hole. The cylinder hole has an elastic piston facing the reaction piston and an output rod having an output rod. The present invention relates to a negative pressure booster in which a force piston and a force piston are slidably fitted in contact with each other.

0002

[Conventional technology]

Conventionally, such a negative pressure booster has been disclosed, for example, in Japanese Utility Model Publication No. 58-45971. is known.

0003

[Problem that the idea aims to solve]

By the way, the elastic piston transmits the reaction force of the output rod to the input rod. However, in the conventional type described above, the elastic piston partially protrudes into the small diameter cylinder hole. It bulges and deforms so that a part of the operating reaction force is transmitted to the input rod via the reaction force piston. It is now possible to However, when the small diameter cylinder bulges and deforms into the small diameter cylinder hole, the small diameter cylinder The opening edge of the cylinder hole toward the large diameter cylinder hole bites into the elastic piston, causing the Since the load acts intensively on the elastic piston, the above-mentioned bulging deformation may occur repeatedly. As a result, cracks may occur in the elastic piston at areas where concentrated stress is applied, resulting in problems with durability. There is a problem.

0004 The present invention was developed in view of these circumstances, and it avoids stress concentration and improves elasticity. The purpose of the present invention is to provide a negative pressure booster with improved piston durability.

[0005]

[Means to solve the problem]

In order to achieve the above object, the present invention provides a reaction piston of an elastic piston. A recess with a diameter larger than the inner diameter of the small diameter cylinder hole is provided in the opposing part. It will be done.

[0006]

【Example】

An embodiment of the present invention will be described below with reference to the drawings.

[0007] 1 and 2 show an embodiment of the present invention. First, in FIG. The front wall of the booster shell 1 in the pressure booster B has a The master cylinder M is installed.

[0008] The booster shell 1 is composed of a pair of front and rear shell halves 1a and 1b whose opposite ends are connected to each other, and a booster piston 2 is housed within the booster shell 1 so as to be able to reciprocate back and forth. A diaphragm 3 whose outer periphery is sandwiched between the abutting portions of the two shell halves 1a and 1b is superimposed on the rear surface of the booster piston 2. 5. Moreover, the inside of the booster shell 1 is divided by the booster piston 2 and the diaphragm 3 into a negative pressure chamber _RA on the front side facing the front surface of the booster piston 2 and a working chamber R _B on the rear side facing the rear surface of the diaphragm 3. Ru.

[0009] A valve cylinder 5a is integrally protruded from the rear end of the piston boss 5. , is provided protruding from the center of the rear wall of the booster shell 1 to cover the valve cylinder 5a, and is also provided at the rear end. is connected to a rear extension tube 8 having an air inlet 7 via a bush 9 and a seal member 10. and is slidably supported.

[0010] A negative pressure introduction pipe 11 is connected to the front wall of the booster shell 1, and the negative pressure chamber R _A is connected to the intake manifold of the internal combustion engine (Fig. (not shown).

An input rod 13 is connected to the brake pedal 12 , and a valve piston 14 swingably connected to the input rod 13 is slidably fitted into the piston boss 5 . The control valve 15, which is switched and operated in response to the relative movement of the valve piston 14 with the piston boss 5 due to the forward and backward movement of the input rod 13 in response to the operation of the brake pedal 12, is connected to the working chamber _RB and the negative pressure chamber. It is interposed between R _A and the atmosphere inlet 7 .

The control valve 15 is conventionally known and includes the valve piston 14 and a rubber valve body 16 sandwiched between the inner wall of the piston boss 5, and when the brake pedal 12 is not operated, the negative pressure chamber is closed. Communication between R _A and working chamber R _B is cut off, and communication with the atmosphere inlet 7 of both chambers R _A and R _B is also cut off. Further, when the valve piston 14 moves forward relative to the piston boss 5 by operating the brake pedal 12, the control valve 15 communicates the working chamber R _B with the atmosphere inlet 7, and the valve piston 14 moves forward relative to the piston boss 5. Then, the control valve 15 communicates the negative pressure chamber _RA with the working chamber _RB .

[0013] The piston boss 5 has a large diameter cylinder hole 17 that opens at the center of its front surface, and a large diameter cylinder hole 17 that opens at the center of the front surface. A small diameter cylinder hole 18 is provided coaxially with the rear of the cylinder hole 17, The small-diameter cylinder hole 18 is formed integrally with the valve piston 14 or with a front surface of the valve piston 14. A reaction piston 19 that comes into contact with is slidably fitted into the large diameter cylinder hole 17. An elastic piston 20 made of rubber or the like and an output piston 21 slide in contact with each other. Can be fitted freely. An output rod 22 is protruded from the front surface of the output piston 21, and the output The rod 22 is connected to a working piston 23 of a master cylinder M.

A synthetic resin retainer 24 is fitted and abutted on the front surface of the piston boss 5 in order to prevent the output piston 21 from falling out of the large diameter cylinder hole 17, and the retainer 24 and the booster shell 1 The booster piston 2 is always urged in the backward direction, that is, toward the working chamber R _B by the return spring 25 compressed between the front wall of the booster piston 2 and the rear wall of the diaphragm 3. The formed protrusion 3a abuts against the inner surface of the rear wall of the booster shell 1, thereby being regulated.

Referring also to FIG. 2, a circular recess 26 is provided in a portion of the elastic piston 20 that faces the reaction piston 19, and an opening edge 26a of the recess 26 faces the reaction piston 19. It is formed into a spherical shape whose diameter increases toward the end. The diameter D ₁ of the recess 26 is set larger than the inner diameter D ₂ of the small diameter cylinder hole 18 into which the reaction piston 19 is fitted, and the closed end of the recess 26 is provided with an iron plate or hardness H. A reinforcing plate 27 made of rubber with an angle of _S 80° or more and formed into a disc shape with a diameter corresponding to the recess 26 is attached. Therefore, the front end surface of the reaction piston 19 comes into contact with the elastic piston 20 via the reinforcing plate 27, and in the normal state when the brake pedal 12 is not operated, the front end of the reaction piston 19 and the reinforcing plate 27 are spaced L apart. facing each other with a gap between them. Therefore, the distance L is such that when the valve piston 14, that is, the reaction piston 19, moves forward from the backward limit position with respect to the piston boss 5, the control valve 15 introduces the working chamber R _B into the atmosphere. The reaction piston 19 is set not to come into contact with the reinforcing plate 27 until it is brought into communication with the opening 7.

Next, the operation of this embodiment will be explained. In response to the forward movement of the input rod 13 in response to the operation of the brake pedal 12, the control valve 15 communicates the working chamber R _B with the atmospheric air inlet 7. Atmospheric pressure acts on the working chamber R _B , and the booster piston 2 moves forward due to the large pressure difference created between the negative pressure chamber R _A and the working chamber R _B , and the working piston 23 of the master cylinder M is moved through the output rod 22. Can be operated with boost. Furthermore, when the input rod 13 is operated backward by releasing the operating force acting on it, the control valve 15 cuts off the communication between the working chamber R _B and the atmosphere inlet 7 and communicates it with the negative pressure chamber R _A. Therefore, the pressure difference between the working chamber _RB and the negative pressure chamber _RA is reduced, and the force of the return spring 25 causes the booster piston 2 to move backward.

By the way, at the initial stage of the depression operation of the brake pedal 12, due to the setting of the interval L, the reaction piston is not activated by the depression operation of the brake pedal 12 until the control valve 15 communicates the working chamber R _B with the atmosphere inlet 7. 19 does not come into contact with the reinforcing plate 27 and the valve piston 14 moves forward by a certain stroke, the control valve 15 communicates the working chamber R _B with the atmosphere inlet 7, and the booster piston 2 moves forward to move the master cylinder forward. Braking pressure is output from the cylinder M, and the play to the brake terminal is removed as the braking pressure increases.After that, the reaction piston 19 comes into contact with the reinforcing plate 27, and the output of the output rod 22 increases. When the reaction force increases, the actuation reaction force acts on the elastic piston 20 via the output piston 21, the elastic piston 20 bulges toward the small diameter cylinder hole 18, and the reinforcing plate 27 comes into contact with the front end surface of the reaction piston 19. is transmitted to the brake pedal 12 via the input rod 13. At this time, when the cross-sectional area of the output piston 21 is A ₁ , the area of the reinforcing plate 27 is A ₂ , and the output of the output rod 22 is P, the operating reaction force transmitted to the input rod 13 side is P×(A ₂ /A ₁ ).

[0018] In such a negative pressure booster B, the reaction force piston 19 of the elastic piston 20 A recess 26 having a larger diameter than the small diameter cylinder hole 18 is provided in the opposing portion. Since the reinforcing plate 27 is provided at the closed end of the recess 26, the elastic piston 20 is small. The elastic piston 20 is prevented from entering the diameter cylinder hole 18, and the small diameter hole 18 is formed in the elastic piston 20. The opening edge on the large diameter cylinder hole 17 side is prevented from digging into the elastic piston 20. The load does not concentrate on one part, so the elastic piston 20 has a long lifespan. performance is improved.

The present invention not only provides a negative pressure booster B in which a negative pressure chamber R _A and a working chamber R _B are formed on both sides of a single diaphragm 3 as in the above embodiment, but also includes a negative pressure chamber and a working chamber. It is also applicable to tandem type negative pressure boosters provided in pairs.

[0020]

[Effect of the idea]

As described above, according to the present invention, the part of the elastic piston facing the reaction piston is provided with a recess having a diameter larger than the inner diameter of the small-diameter cylinder hole. Concentrates on the elastic piston at the part corresponding to the opening edge on the large diameter cylinder hole side. This is to avoid the application of heavy loads and thereby improve the durability of the elastic piston. I can do that.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view of a negative pressure booster according to an embodiment of the present invention.

FIG. 2 is an enlarged view of the main part of FIG. 1;

[Explanation of symbols]

1 Booster shell 2 Booster piston 5 Piston boss 13 Input rod 17 Large diameter cylinder hole 18 Small diameter cylinder hole 19 Reaction force piston 20 Elastic piston 21 Output piston 22 Output rod 26 Recess B Negative pressure booster D ₁ Diameter of recess D ₂ Small cylinder hole inner diameter of

Claims (1)

[Scope of utility model registration request] Claim 1: A booster piston (2) is housed in a booster shell (1) so as to be able to reciprocate back and forth, and a piston boss (5) connected to the booster piston (2) has an input rod (13). A small diameter cylinder hole (18) into which a series of reaction force pistons (19) are slidably fitted, and a large diameter cylinder that is larger in diameter than the small diameter cylinder hole (18) and opens at the front of the piston boss (5). The large-diameter cylinder hole (17) has an elastic piston (20) facing the reaction piston (19), and an output piston (21) having an output rod (22). In a negative pressure booster in which the elastic pistons (20) are slidably fitted in contact with each other, the inner diameter (D ₂ ) Negative pressure booster, characterized in that a recess (26) is provided with a diameter (D ₁ ) larger than the diameter (D 1 ).