JPS63270275A - Tandem negative pressure booster - Google Patents

Abstract

PURPOSE:To improve response of an output rod with respect to an input rod by balancing the differential force between driving force of a front booster piston and repelling force of a return spring with driving force of a rear booster piston through a reaction mechanism. CONSTITUTION:A return spring 46 for repelling an output rod 43 in retreating direction is contained in second negative pressure chamber 2a, while a stopper means comprising an end wall 11a and a stopper board 36 is arranged between an input rod 25 and a booster shell 1 so as to limit retrieval of the input rod 25. Even when a negative pressure booster B is stopped, i.e. when the input rod 25 is held at limit retrieval position through the stopper means, a slightly higher pressure than that in both negative pressure chambers 2a., 3a is led into respective working chambers 2b, 3b so as to balance the differential force between driving force of a front booster piston 4 and repelling force of the return spring 46 with driving force of a rear booster piston 6 thus loading a reaction mechanism 44 with a portion of repelling force of the return spring 46. Consequently, clearance of mechanism is eliminated and response of the output rod with respect to operation of the input rod can be improved.

Description

Detailed Description of the Invention A1 Objective of the Invention (1) Industrial Field of Application The present invention provides a booster shell with a partition plate that partitions the inside of the booster shell into a front shell chamber and a rear shell chamber. A rear booster piston that divides the rear shell chamber into a first negative pressure chamber on the front side and a first working chamber on the rear side is fixed to the valve cylinder supported on the rear wall so as to be slidable back and forth, and a reaction force mechanism is provided. A front booster piston that divides the front shell chamber into a second negative pressure chamber on the front side and a second working chamber on the rear side is connected to the output rod, and both booster pistons is relatively movable in the axial direction, a negative pressure source is connected to both negative pressure chambers, and the valve cylinder has an input rod that can move forward and backward, and both working chambers are connected to the atmosphere according to the forward and backward movement of this input rod. The present invention relates to a tandem negative pressure booster that is provided with a control valve that switches communication between both negative pressure chambers.

(2) Conventional technology The negative pressure booster is, for example, disclosed in U.S. Pat.
This is already known as described in the publication No.

(3) Problems to be solved by the invention In the conventional tandem type negative pressure booster, the retraction limit of the front boost piston or the rear booster piston is restricted by the booster shell, and the front booster piston is forced to move in the backward direction. Since a biasing return spring is installed, the reaction force mechanism is in an unloaded state when at rest, and play occurs in the mechanism, so there is some delay in the operation of the output rod at the beginning of the operation of the input rod.

The present invention has been made in view of the above circumstances, and provides the tandem negative pressure booster, which applies an appropriate load to the reaction force mechanism even when at rest, and has a good responsiveness of the output rod to the operation of the input rod. The purpose is to provide.

B0 Structure of the Invention (1) Means for Solving Problems In order to achieve the above object, the present invention accommodates a return spring that springs the output rod in the backward direction in the second negative pressure chamber, and A stopper means for regulating the retraction limit of the input rod is provided between the booster shells, and when the retraction limit of the input rod is restricted by this stopper means, the pressure difference between the second negative pressure chamber and the second working chamber is reduced. The force of the difference between the forward force of the front booster piston and the elastic force of the return spring due to The control valve was configured to maintain the control valve in a neutral state in which both working chambers were not communicated with either the negative pressure chambers or the atmosphere while introducing pressure slightly higher than both negative pressure chambers into both working chambers in order to achieve equilibrium between the two working chambers. It is characterized by

(2) Effect According to the above configuration, even when the negative pressure booster is at rest, that is, when the input rod is held at the retraction limit by the stopper means, a slightly higher pressure than both negative pressure chambers is introduced into both working chambers. , the force of the difference between the forward force of the front booster piston and the elastic force of the return spring due to the pressure difference between the second negative pressure chamber and the second working chamber, and the pressure between the first negative pressure chamber and the second working chamber. Since the forward force of the rear booster piston due to the difference is maintained in equilibrium via the reaction force mechanism, a part of the elastic force of the return spring is applied as a load to the reaction force mechanism.

(3) Implementation □Example An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, a brake mask cylinder M operated by the booster B is attached to the front surface of a booster shell 1 of a tandem negative pressure booster B. As shown in FIG.

The booster shell 1 includes a pair of front and rear shell halves 1a, lb whose opposite ends are connected to each other, and a pair of front and rear shell halves 1a, lb which are sandwiched between the two shell halves 1a, lb so that the interior of the booster shell 1 is divided into a front shell chamber 2 and a rear shell chamber. It is composed of a bulkhead plate IC that partitions into 3 and
The rear shell half 1b is supported by a vehicle body (not shown).

The front shell chamber 2 has a front booster piston 4 accommodated therein so as to be able to reciprocate back and forth, and a front booster piston 4 which is superimposed and bonded to the rear surface and sandwiched between the front shell half 1a and the partition plate IC. The rear shell chamber 3 is divided into a front negative pressure chamber 2a and a rear working chamber 2b by a diaphragm 5.
A rear booster piston 6 is housed in the rear booster piston 6 so as to be able to reciprocate back and forth, and a rear diaphragm 7 is bonded to the rear surface thereof and fixed between the shell halves 1a and lb together with the partition wall plate IC, thereby creating a negative pressure on the front side. Chamber 3a and rear working chamber 3b
It is divided into

A valve cylinder 8 made of synthetic resin is fixed to the center of the rear booster piston 6, and this valve cylinder 8 is slidably supported on the bulkhead plate IC via a bushing 9 and a seal member 10, and is also supported on the rear shell half. In the rear extension tube 11 of the body 1b,
It is slidably supported via a bush 12 and a seal member 13.

The front booster piston 4 is equipped with a cylinder shaft 14 whose tip extends rearward, and this cylinder shaft 14 can be slid relative to the valve cylinder 8 through a small gap in a guide hole 15 that opens on the front end surface of the valve cylinder 8. inserted into.

The outer circumferential surface of the cylinder shaft 14 is provided with an annular groove 17 into which the seal member 16 is mounted, and a pair of raised protrusions 1B, 1B sandwiching the annular groove 17 therebetween. The protrusion 18 is slidably fitted into the inner peripheral surface of the guide hole 15. Therefore, the cylinder shaft 14 can slide and swing while maintaining airtightness with the guide hole 15, thereby preventing the generation of prying force caused by mutual tilting of the front booster piston 4 and the valve cylinder 8. It can be prevented.

The front negative pressure chamber 2a is connected to a negative pressure source (not shown) (for example, the inside of an intake manifold of an internal combustion engine) via a negative pressure introduction pipe 19, and is connected to a rear negative pressure source via a crotch boat 20 of the valve cylinder 8. It communicates with the pressure chamber 3a. Also, both front and rear working chambers 2b
, 3b are communicated with each other via a second bifurcated boat 21 of the valve cylinder 8, and are connected to the front and rear negative pressure chambers 2a by a control valve 22.
, 3a and an atmosphere inlet 23 opened in the end wall 11a of the rear extension tube 11.

Inside the valve cylinder 8 is an input rod 25 connected to the brake pedal 24.
The control valve 22 controlled thereby is provided as follows. That is, the partition wall 8 formed in the middle part of the valve cylinder 8
A is provided with a small cylinder hole 26 opening at the center of the rear surface, into which a valve piston 28 is slidably fitted. This valve piston 28 has a flange 28a formed on the outer periphery of the intermediate portion thereof, which faces a step portion 29 connected to the open end of the small cylinder hole 26. This valve piston 28 has the air inlet 23
The front end of the input rod 25 passing through the input rod 25 is coupled to the input rod 25 so as to be swingable.

A first annular valve seat 301 is formed on the rear surface of the partition wall 8a, and a second annular valve seat 30t surrounded by the annular first valve seat 301 is formed on the rear end surface of the valve piston 28. ．． 30□
A valve body 31 cooperating with the valve body 8 is arranged in the valve barrel 8 . Valve body 31
is made of rubber and has a cylindrical shape with both front and rear ends open, and the rear end, that is, the base end 31a, is secured to the inner periphery of the valve cylinder 8 by a holding cylinder 32 fitted to the inner peripheral surface of the valve cylinder 8. It is held in close contact with the surface. The valve body 31 includes a thin flexible portion 31b bent radially inward from the base end 31a, and a thick valve portion 31c continuous to the front end of the flexible portion 31b. 31C is the first and second valve seat 30. ．．
It is placed facing 30□.

The valve portion 31C can be moved back and forth by deforming the flexible portion 31b, and when moving forward, the first and second valve seats 30.
．． 30□, and is received by the front end of the holding cylinder 32 when retracting.

An annular reinforcing plate 33 is embedded in the valve part 31c, and between this and the input rod 25, the valve part 31C is connected to both valve seats 30+, 30.
A valve spring 34 that urges toward □ is contracted.

On the inner surface of the valve cylinder 8, one end of the first crotch boat 20 opens on the outside of the first valve seat 301, and one end of the second bifurcated port 21 opens on the inside of the same valve seat 301.

Further, the inside of the second valve seat 30□ communicates with the atmosphere inlet 23 through the hollow portion of the valve body 31 and the holding cylinder 32.

Thus, the control valve 22 is constituted by the valve body 31, the valve spring 34, the first valve seat 301, and the second valve seat 30□.

A return spring 35 is compressed between the input rod 25 and the holding cylinder 32 and urges the input rod 25 toward its retraction limit.

The backward limit of the input rod 25 is regulated by a stopper plate 36 that is screwed into the input rod 25 so as to be adjustable in forward and backward movement and comes into contact with the inner surface of the end wall 11a of the rear extension tube 11. Therefore, by rotating the stopper plate 36, the screwing position between the stopper plate 36 and the input rod 25 changes, so that the retraction limit of the input rod 25 can be adjusted back and forth. The stopper plate 36 is fixed after the adjustment of the tension by tightening a lock nut 37 which is also threaded onto the input rod 25. A vent hole 38 is bored in the stopper plate 36 so that the stopper plate 36 does not block the air inlet 23.

An air filter 39 is attached to the valve cylinder 8 so as to surround the input rod 25 for filtering the air taken into the valve cylinder 8 from the atmosphere inlet 23 . This air filter 39 is connected to the input rod 25.
It has appropriate flexibility so as not to hinder relative displacement between the valve cylinder 8 and the valve cylinder 8.

The partition wall 8a of the valve cylinder 8 is provided with a large cylinder hole 27 that opens at the center of its front surface. It has a depth that can be understood. A rubber elastic piston 40 whose rear end face faces the valve piston 28 is tightly fitted into the large cylinder hole 27, and an output piston 41 that comes into contact with the front surface of the elastic piston 40 is loosely fitted.
An output rod 43 connected to the piston 42 of the brake mask cylinder M is positively connected to the front end of the output piston 41. The output rod 43 can swing relative to the valve cylinder 8 by loosely fitting the output piston 41 into the large cylinder hole 27. Thus, the valve piston 28 and the elastic piston 40
A reaction force mechanism 44 is constituted by the output piston 41 and the output piston 41 .

A retainer 45 protruding toward the cylinder shaft 14 is sandwiched between the output rod 43 and the output piston 41, and an inward flange 14a that abuts the rear surface of the retainer 45 in a separable manner is attached to the rear end of the cylinder shaft 14. They are connected together. A return spring 46 is compressed between the retainer 45 and the front wall of the booster shell 1 so as to spring the output rod 43 in the backward direction.

The return spring 46 applies a retraction force to the front booster piston 4 via the retainer 45, and also applies a retraction force to the rear booster piston 6 via the retainer 45, the reaction force mechanism 44, and the valve cylinder 8.

The retraction limit of the rear booster piston 6 is regulated by a large number of protrusions 7a on the rear surface of the rear diaphragm 7 coming into contact with the rear wall of the booster shell 1, but the front diaphragm 5 does not touch the bulkhead plate IC even when retracting. Do not touch.

Next, the operation of this embodiment will be explained. First, negative pressure booster B
In the rest state, as shown in FIG. 1, the input rod 25 is located at the retraction limit, and the control valve 22 moves the valve portion 31c between the first and second valve seats 30. ．． Both front and rear working chambers 2 when seated at 30□
b, 3b are in a neutral state in which they are disconnected from both the negative pressure chambers 2a, 3a and the atmospheric air inlet 23, and by such a control valve 22, the negative pressure inlet pipe 19 is connected to both the negative pressure chambers 2a, 3a.
Negative pressure from a negative pressure source supplied through is stored, and negative pressure appropriately diluted with the atmosphere is maintained in both working chambers 2b and 3b. In this way, the front and rear booster pistons 4.6 have a front negative pressure chamber 2a and a working chamber. b, Rear negative pressure chamber 3a
A slight forward force is given by the pressure difference generated between the front booster piston 4 and the working chamber 3b, but the forward force of the front booster piston 4 and
The force difference between the larger elastic force of the return spring 46 and the forward force of the rear booster piston 6 are balanced via the reaction force mechanism 44, and both boost pistons 4 and 6 are slightly moved from the backward limit. It stopped when it moved forward. In this way,
A part of the elastic force of the return spring 46 is applied as a load to the reaction force mechanism 44, so that the end wall of the large cylinder hole 27, the elastic piston 40, and the output piston 41 are connected to each other without placing a large burden on each part. play can be eliminated.

Now, step on the brake pedal 24 to brake the vehicle,
If the input rod 25 and the valve piston 28 are moved forward, initially,
Since the valve cylinder 8 is immovable, the second valve seat 30□ is the valve part 31c.
Immediately move away from the air intake port 23 and connect both working chambers 2b and 3b to the atmosphere inlet 23.
communicate with. As a result, the atmosphere flows from the atmosphere inlet 23 through the second valve seat 30□ and the second bifurcated boat 21 into both working chambers 2b.

3b, and the liquid chambers 2b and 3b are quickly introduced into the negative pressure chamber 2a.
, 3a, a large forward force is obtained based on the pressure difference between them, and both booster pistons 4.6 move forward against the force of the return spring 46.

The forward force of the front booster piston 4 is controlled by the retainer 45.
The forward force of the rear booster piston 6 is transmitted to the output rod 43 through the reaction force mechanism 44, but since the play in the reaction force mechanism 44 has already been eliminated as described above, the rear booster piston The forward force is quickly transmitted from the output rod 43 to the output rod 43. Therefore, the output rod 43
operates forward with good response and drives the piston 42 of the brake mask cylinder M forward. In this way, the brake mask cylinder M can be activated without delay when the brake pedal 24 is depressed, and the vehicle can be braked.

During braking, the valve piston 28 along with the input rod 25
However, the elastic piston 40 bulges and deforms toward the small cylinder hole 26 side due to the reaction force of the rear booster piston 6, and the valve piston 2
Since a part of the reaction force is applied to the brake pedal 8, the force is fed back to the brake pedal 24 side via the valve piston 28 and the input rod 25. Due to the action of the reaction force mechanism 44, the driver can sense the output of the output rod 43, that is, the magnitude of the braking force.

In this case, the reaction force mechanism 44 does not receive the operational reaction force of the booster piston 4, but only receives the operational reaction force of the rear booster piston 6, so that the valve piston 28 and the elastic piston 4
It is possible to obtain a large boost ratio without increasing the cross-sectional area ratio of the small cylinder hole 26 and the large cylinder hole 27 into which the cylinders 0 are fitted, respectively, thereby reducing the load on the reaction force mechanism 44 and improving its durability. can be increased.

When the output of the output rod 43 exceeds the boosting limit point due to an increase in the pedal force applied to the brake pedal 24, that is, the input to the input rod 25, the valve piston 2 brings its tip into contact with the elastic piston 40.
8 also brings the intermediate flange 28a into contact with the stepped portion 29 of the valve cylinder 8, so that the entire input is applied to the valve piston 28 and the valve cylinder 8.
, is transmitted to the output rod 43 via the elastic piston 40 and the output piston 41, and in the end, the sum of the forward force due to the pressure difference of each booster piston 4.6 and the forward force due to the input is output from the output rod 43. Ru.

Next, when the pressure on the brake pedal 24 is released,
First, the input rod 25 retreats together with the valve piston 28 due to the elastic force of the return spring 35, seats the second valve seat 30□ on the valve portion 31c of the valve body 31, and moves the valve portion 31c to the first valve portion 30i.
Since the working chambers 2b and 3b communicate with both the negative pressure chambers 2a and 3a, the pressure difference between the front and rear of each booster piston 4.6 is immediately eliminated, and therefore both the booster pistons 4 and 6 are separated from each other by the return spring 46. Retreating with resiliency,
The operation of the brake mask cylinder M is released. Then, the input rod 25 moves the stopper plate 36 to the partition wall 1 of the extension tube 11.
1a, the rear booster piston 6 returns to the retraction limit where the protrusion 7a of the rear diaphragm 7 contacts the rear wall of the booster shell 1, as shown in FIG. First valve seat 30. is seated on the valve portion 31c, and the valve portion 31c is slightly separated from the second valve seat 30□, so that the atmosphere is again introduced into both the working chambers 2b, 3b, but due to the resulting pressure difference, both booster pistons 4 , 6 move forward a little, they move forward so as to eliminate the small gap between the second valve seat 30□ and the valve part 31c, and the control valve 2
2 to its initial neutral state. In this way both working chambers 2b, 3
A negative pressure diluted with the atmosphere is maintained at point b, and the negative pressure booster B enters the rest state as shown in FIG.

C1 Effects of the Invention As described above, according to the present invention, the return spring that springs the output rod in the backward direction is housed in the second negative pressure chamber, and the limit of the backward movement of the input rod is restricted between the input rod and the booster shell. The stopper means is provided with a stopper means that, when the input rod is restricted to the backward limit, prevents the forward force of the front booster piston due to the pressure difference between the second negative pressure chamber and the second working chamber and the elasticity of the return spring. In order to balance the force difference between the generated force and the forward force of the rear booster piston due to the pressure difference between the first negative pressure chamber and the first working chamber through the reaction force mechanism, the pressure chamber is slightly higher than both negative pressure chambers. Since the control valve is configured to maintain the control valve in a neutral state in which the two working chambers are not communicated with either the negative pressure chambers or the atmosphere while atmospheric pressure is introduced into both working chambers, the elastic force of the return spring is reduced even in the rest state. can be applied to the reaction force mechanism as a load,
Therefore, play can be eliminated from the mechanism, and since the load is relatively small, it does not place a large burden on the reaction force mechanism and does not impair its durability.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; Fig. 1 is a cross-sectional side view of a tandem negative pressure booster in a resting state, and Fig. 2 is a state immediately before the booster returns to its resting position after it has finished operating. FIG. B...Negative pressure booster, M...Mask cylinder...
Booster shell, IC...bulkhead plate, 2.3...front,
Rear shell chamber, 2a...second negative pressure chamber, 3a...first
Negative pressure chamber, 2b...second working chamber, 3b...first working chamber, 4.6...front and rear booster pistons, 8...valve cylinder, 11a, 36...stopper means Constituent end wall and stopper plate, 22... control valve, 25... input rod,
43... Output rod, 44... Reaction force mechanism, 46... Return spring, 47... Rear abutting plate

Claims (1)

[Claims] The booster shell is provided with a partition plate that partitions its interior into a front shell chamber and a rear shell chamber, and the rear shell chamber is connected to a valve cylinder that is slidably supported on the rear wall of the booster shell. A rear booster piston is fixedly installed that partitions the negative pressure chamber into a first working chamber on the rear side, and an output rod is connected via a reaction force mechanism, and the front shell chamber is connected to the second working chamber on the front side. A front booster piston that is divided into a negative pressure chamber and a rear second working chamber is connected, both booster pistons are movable relative to each other in the axial direction, a negative pressure source is connected to both negative pressure chambers, and a valve is connected. In a tandem negative pressure booster, the cylinder is equipped with an input rod that can move forward and backward, and a control valve that switches both working chambers to communicate with the atmosphere and both negative pressure chambers according to the forward and backward movement of the input rod. , a return spring that springs the output rod in the backward direction is housed in the second negative pressure chamber, and a stopper means for regulating the retraction limit of the input rod is provided between the input rod and the booster shell, and the stopper means thereby When the input rod retraction limit is regulated, the second
The force of the difference between the forward force of the front booster piston and the elastic force of the return spring due to the pressure difference between the negative pressure chamber and the second working chamber;
In order to balance the forward force of the rear booster piston due to the pressure difference between the negative pressure chamber and the first working chamber through the reaction force mechanism, a pressure slightly higher than that of both negative pressure chambers is introduced into both working chambers. A tandem negative pressure booster, characterized in that the control valve is maintained in a neutral state in which the working chamber is not communicated with either the negative pressure chambers or the atmosphere.