JPH0510263B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a negative pressure operated brake power booster equipped with a master cylinder.

[Problems with the prior art] In this type of brake unit, when the brake power booster of the negative pressure operating type fails and the brake is activated, the valve of the valve mechanism in the control element housing is damaged by the piston rod pivotally supported by the brake pedal. By pushing the piston against the reaction device and this reaction device acting together with the control element housing and the movable wall against the push rod which acts together with the push rod piston, brake pressure is created in the pressure chamber of the master cylinder. It will occur. However, in such a typical configuration, if a failure occurs in the negative pressure operated brake power booster, it is necessary to press the brake pedal relatively hard before brake pressure is built up, and the piston in the master cylinder must be depressed. While the effective cross-sectional area of remains large,
Moreover, since the piston must be moved only by the depression force without obtaining an external auxiliary force, there is a problem that the depression force becomes relatively large.

Furthermore, a tandem master cylinder for a hydraulic brake system (West German Published Patent Application No. 246529) is known, and the first piston of this tandem master cylinder can be actuated by an output member of a pedal-operated brake power booster. ing. The brake power booster has a movable wall that creates a fluid pressure difference, and the brake power booster is equipped with a device for reducing the required pedal depression force when the brake power booster loses its operating pressure.

For that purpose, the device has a valve which is biased toward the open position and which is switched to the closed position by the actuation pressure of the brake power booster, which valve is located between the reservoir and the pressure chamber. It controls the connection. For this purpose, brake units of this type are equipped with an auxiliary piston, which has a larger diameter than the first piston. The auxiliary piston is arranged between the output member of the brake power booster and the first piston of the master cylinder, and the pressure chamber is a control pressure chamber located between the auxiliary piston and the first piston, i.e.
It is formed by a chamber separated from the first pressure chamber and the second pressure chamber of the master cylinder. However, this conventional tandem master cylinder has
When the negative pressure is removed, the pedal droops relatively far and the first piston and the auxiliary piston abut each other, so that the first piston and the auxiliary piston move together as a common mechanical unit. It has this problem.

[Objective of the Invention] The object of the present invention is to eliminate the disadvantages of the known brake power booster with a master cylinder, and to reduce the amount of pedal depression as much as possible when the operating pressure of the booster is available. To provide a negative pressure operated brake power booster with a master cylinder which can change the pressure transmission ratio by switching to a piston with a smaller effective area when the piston is not available.

[Structure and operation of the invention] In the negative pressure operated brake power booster with master cylinder of the present invention, the push rod passes through an opening provided at the bottom of the cap fixed to the control element housing, and the push rod passes through the opening provided at the bottom of the cap fixed to the control element housing. An axial play is engaged in the housing and provided between the cap and the push rod, which play allows the push rod to move longitudinally relative to the control element housing, and allows the push rod to move in the longitudinal direction relative to the control element housing. A sleeve is provided surrounding the stem, the end of the sleeve on the brake pedal side is brought into contact with the cap, and an annular chamber is provided behind the large-diameter stepped portion of the push rod piston to initiate braking operation. and after the push rod has moved relative to the control element housing,
A sleeve moving with the cap operates a first valve and a second valve, the first valve having a first flow path connecting the annular chamber and the pressure chamber of the brake circuit through the inner bore of the push rod piston. is opened, and the second valve closes a second passage connecting the annular chamber and the socket pipe of the reservoir via the inlet port of the master cylinder.

For the purpose mentioned above, preferably the backup plate is formed with a central opening and is provided with a radially extending stud;
This stud is engaged in a cutout in the sleeve surrounding the stem of the push rod piston. The cutout allows the back-up plate to move longitudinally a predetermined distance relative to the sleeve and is sized such that the pedal-side end of the sleeve abuts against the cap of the control element housing. . The sleeve, which moves coaxially with the stem of the push rod piston, is preferably provided with a slidable friction ring at its end facing the master cylinder, and this friction ring is connected to the annular second valve. works with. This second valve controls a pressure fluid passage from the reservoir through an inlet port to an annular chamber located behind the push rod piston. The annular chamber is connected via an inlet passage to a pressure chamber which is partially located in front of the pushrod piston, and which inlet passage is provided in the housing of the master cylinder. The pressure fluid introduced through this inlet passage is controlled by a first sliding valve consisting of a piston cap during brake application.

In a preferred embodiment, the stem of the pushrod piston is formed with an internal bore that is connected to the pressure chamber. The outlet of the inner bore in the outer surface of the stem is closed in the brake release position by the master cylinder end of the sleeve surrounding the stem, and in the brake application position it is closed by the sleeve in the event of a booster failure. Ru.

Preferably, the back-up plate is supported by the head member of the master cylinder via a spring, and the spring supports a sleeve surrounding the stem of the push rod piston, which surrounds the reaction device via the back-up plate. It is energized against the cap.

In an embodiment of the invention, the push rod acting on the push rod piston passes through an opening in the bottom of the cap, and the push rod is provided with a push plate at its pedal end. This push plate operates in conjunction with a reaction device held on the cylindrical inner surface of the cap.

In addition, in order to ensure normal opening and closing operations of the control slide valve, play is provided between the master cylinder side surface of the push plate and the bottom inner surface of the cap when the brake is released. corresponds to the opening stroke of the first valve, which is comprised of at least the inner hole of the stem and the master cylinder side end of the sleeve.

In a particularly preferred embodiment from a production technology point of view, the cap is provided with a radially outwardly bent rim which supports a spring device on the side of the control element housing and which acts together with the sleeve. The backup plate is generally cup-shaped, and a spring is interposed between the bottom of the backup plate and a retaining ring attached to the end of the sleeve on the control element housing side. The back-up plate that operates with the sleeve is preferably provided with an opening in its center, through which the sleeve passes, and the back-up plate is connected to the stem end of the push rod piston on the side of the control element housing. The retaining ring operates in conjunction with a retaining ring located on the sleeve which will pull the back up plate when the push rod piston moves relative to the sleeve.

[Embodiment of the Invention] An embodiment of the invention will be described below with reference to FIGS. 1 to 3.

1 in FIG. 1 indicates a booster housing of a brake power booster. This booster housing 1 consists of two housing shells 15 and 16, and these housing shells 15 and 16 are
They are connected to each other at a connecting portion 14. The internal space of the booster housing 1 is divided into a negative pressure chamber 2 and a power chamber 3 by a diaphragm holder 5. Negative pressure chamber 2 is connected to negative pressure reduction via a connection boat. The diaphragm holder 5 includes
A rolling diaphragm 4 is glued and a control element housing 7 is provided. This control element housing 7 has a cylindrical shape and is connected to the diaphragm holder 5 and the rolling diaphragm 4. The outer circumferential edge of the rolling diaphragm 4 is inserted in a gas-tight manner into the connection part 14, and its inner circumferential edge surrounds the neck part 17 of the diaphragm holder 5 and is connected to the control element housing 7. 17
is tightened. The cylindrical part 7' of the control element housing 7 projects from the booster housing 1 and holds the power chamber 3 airtight to the outside via a sliding guide ring 18.

A control rod is arranged in the control element housing 7 in an axially slidable manner. This control rod consists of a piston rod 11 and a valve piston 9, and is connected to the brake pedal of the motor vehicle via a clevis (not shown). Furthermore, valve mechanisms 8, 13, 19 are accommodated in the control element housing 7. The valve mechanism 8, 13, 19 is actuated by a valve piston 9 and thereby controls the differential pressure created between the negative pressure chamber 2 and the power chamber 3 via the passages 19, 20.

A cap 21 is provided in the region of the control element housing 7 located in the negative pressure chamber 2, in which the reaction force device 10 is held. The reaction device 10 has a reaction lever or a reaction disk made of an elastic material such as rubber.
Furthermore, the cap 21 is connected to the push rod 1.
This push rod 12 operates the brake master cylinder 23. This master cylinder 2
3 is fixed to the front end surface of a housing shell 16 that constitutes a part of the booster housing 1.

Diaphragm holder 5 with diaphragm 4
as well as for the return of the control element housing 7.
A spring device 6 is arranged between the cap 21 of the control element housing 7 and the housing shell 16 of the booster housing 1.

A floating piston 24 and a push rod piston 25 are arranged within the master cylinder 23. The pushrod piston 25 is designed as a stepped piston. The push rod piston 25 is inserted into a sleeve 27, and the sleeve 27 has a control slide, which is a first valve, disposed slidably in the longitudinal direction with respect to the stem 26 of the push rod piston 25. Functions as a valve train. An annular chamber 28 located behind the stepped portion of the push rod piston 25 is connected to a reservoir (not shown) via an inlet port 31 and a socket pipe 30, which can be closed by a ring-shaped second valve 32. . On the end face of the second valve 32 facing the control element housing 7 there is a locking spring 33.
One end of this lock spring 33 is supported by a head member 34. This head member 34 is connected to the master cylinder 23 on the booster side.
The ends of the sleeve 27 are closed, and an opening for inserting the sleeve 27 is formed in the center thereof. At the master cylinder side end of the sleeve 27,
A slidable friction ring 35 is provided. This friction ring 35 is connected to the push rod piston 2.
5 is in the initial position, provision is made to maintain the second valve 32 in the open position shown in FIGS. 1 and 2. The annular chamber 28 is connected to the filling chamber 3 via the inner hole 36.
It is connected to 7. Furthermore, the entrance passages 45, 4
5' indicates the annular chamber 28 and the push rod piston 2.
The pressure chamber 5 is connected to a first pressure chamber 40 located in front of the pressure chamber 5.

In the illustrated rest state of the master cylinder 23, the first sliding valve 39 as well as the second sliding valve 39
8 and the second valve 32 are open, and fluid communication is established from the socket pipe 30 to the first pressure chamber 40 and the filling chamber 37, and from the socket pipe 41 to the second pressure chamber 42. ing. When the brake operation is started (when the brake booster is in the second state), the piston rod 11 moves immediately, so that the push rod 1
2 and sleeve 27 move to the left almost simultaneously.
The valve mechanism 8, 13, 19 allows air to flow into the power chamber 3, whereby the movable wall 46 consisting of the diaphragm 4 and the diaphragm holder 5 is moved together with the control element housing 7 and the cap 21 in the operating direction. Push rod piston 25 and sleeve 27 are moved simultaneously as described above, and first and second sliding valves 38, 39 are connected to inlet port 4 leading to socket pipes 30 and 41, respectively.
5, 45', and 47, so the first and second
Brake pressure is built up in pressure chambers 40 and 42 of. Since there is no relative movement between the push rod piston 25 and the sleeve 27, the inner hole 3
The first valve communicating with 6, 36' also remains closed, so that the entire cross-sectional area of the push rod piston 25 is utilized.

In the event of a fault in the booster, the control element housing 7 is initially held in the rest position when the brake pedal is depressed, i.e. when the piston rod 11 is moved, but when the push rod 12
is moved in the actuation direction, ie to the left. 1st and 2nd
During the initial phase when the brake pressure is built up in the pressure chambers 40, 42 of
6, 36' to the filling chamber 37 (this filling chamber 37
is in communication with the first pressure chamber 40 via the groove 48. ) will be opened.

As the piston rod 11 is further moved in the direction of arrow A (left) (beyond the play b between the push plate 22 and the cap 21), the movable wall 46
At the same time, the control element housing 7 is moved against the force of the spring device 6. When the play b between the backup plate 49 and the sleeve 27 is eliminated, the sleeve 27 together with the push rod piston 25 is again moved in the direction indicated by arrow A. In such a phase of operation, due to the movement of the sleeve 27, the locking spring 33 is released by the friction ring 35 connected to the sleeve, allowing the second valve 32 to move to the left; This second valve 32 is connected to the inlet port 31
is closed, and the second flow path connecting the annular chamber 28 and the socket pipe 30 communicating with a reservoir (not shown) is blocked.

In the direction of arrow A, the piston rod 11 and the valve mechanism 1
3. As the push rod 12 and sleeve 27 move further, the push rod piston 25
will in this case function as a plunger piston with an effective cross-sectional area denoted by c,
A relatively high hydraulic pressure (corresponding to the applied pedal force) is then built up in the brake circuit. The pressures before and after the large-diameter stepped portion 29 of the push rod piston 25 become equal during this phase of brake operation. During this period, the piston cap 50 of the first sliding valve 38 does not function. When the pedal is released, i.e. piston rod 1
1 moves in the opposite direction to the direction indicated by arrow A, the annular chamber 2 located at the rear of the large-diameter stepped portion 29
8 through the piston cap 50 into the first pressure chamber 40 and is returned to the reservoir via the inlet passages 45, 45' and the socket pipe 30. In the brake release position, the second valve 32 is open again and the first valve, consisting of the sleeve 27, stem 26 and bore 36', is closed.

In a typical booster, the diameter of the tandem master cylinder is set in consideration of power booster failure. In this invention, when the system is normal, the cross-sectional area of the sleeve 27 is simply set by the depression pressure, and the cross-sectional area of the push rod piston 25 is increased relative to the sleeve 27 to increase the amount of pedal depression. The diameter of the sleeve 27 is determined to be as small as possible.

In the booster of the invention, a reduction in the pedal depression pressure and amount and an increase in the braking effect are obtained by the feature that when the booster fails, the effective cross-sectional area of the piston is reduced from a to the cross-sectional area of the sleeve 27. I can do it.

Furthermore, the booster of the present invention can be installed in place of a conventional booster without requiring any changes to either the brake system or the vehicle.

FIG. 4 shows a modification of the invention. In this variant, the floating piston 24' is centered by a spring pot 60 with a screw 59 and a spring 61, and the floating piston 24' is aligned with the master cylinder 23 shown in FIG. The floating piston 24 is provided as an alternative to the floating piston 24 connected to the plunger 24 of the push rod piston 25 in FIG. According to this modification, the pressure fluid in the annular chamber 28 circulates smoothly during the return stroke, and the pressure difference not only in the filling chamber 37' but also in the first and second pressure chambers 40' and 42' is simultaneously reduced. Moreover, it can be easily balanced.

[Effects of the Invention] As explained above, according to the brake power booster of the present invention, when the booster fails and operating pressure cannot be used, the piston with a small effective area operates and the pressure transmission ratio changes. The braking effect can be enhanced even with relatively small pedal depression pressure and amount.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a sectional view of a negative pressure operated brake power booster equipped with a tandem master cylinder, and FIG.
The figure is an enlarged sectional view of the second valve part shown in Fig. 1, Fig. 3 is an enlarged sectional view of the backup plate of Fig. 1 together with the sleeve, and Fig. 4 is a modification of the present invention. FIG. 3 is a partial cross-sectional view of the tandem master cylinder shown in FIG. 1... Booster housing, 6... Spring device, 7... Control element housing, 8, 13, 1
9... Valve mechanism, 9... Valve piston, 10... Reaction force device, 11... Piston rod, 12... Push rod, 15, 16... Housing shell, 2
1... Cap, 22... Push plate, 2
3...Master cylinder, 25...Push rod piston, 26...Stem, 27...Sleeve,
28...Annular chamber, 29...Large diameter stepped portion, 30...Socket pipe, 31...Inlet port, 32...Second valve, 34...Head member, 35...Friction ring, 36, 36'... Inner hole, 38...first sliding valve,
39...Second sliding valve, 40...Pressure chamber, 45,4
5'...Inlet passage, 46...Movable wall, 49...Backup plate, 50...Piston cap, 51...Notch, 52...Spring, 5
4...Rim, 55, 57...Retaining ring, 56...
...Stud, x...play.

Claims (1)

[Scope of Claims] 1. A master cylinder connected to one housing shell constituting a booster housing, a movable wall provided within the booster housing and sealed with respect to the booster housing, and this movable wall. a control element housing which operates together and houses a valve mechanism therein; a piston rod inserted into the control element housing; a valve piston slidable by the piston rod; and the master cylinder side of the valve piston. Depending on the end,
A negative pressure actuated brake power booster with a master cylinder comprising a push rod actuated via a reaction force device and actuating a stepped push rod piston in the master cylinder, the push rod being connected to the control element housing. It passes through an opening in the bottom of a fixed cap and is engaged by this cap in the control element housing, providing axial play between the cap and the push rod, the play being The push rod is thus longitudinally movable relative to the control element housing, and a sleeve is provided surrounding the stem of the push rod piston, the end of the sleeve on the brake pedal side abutting the cap. and an annular chamber is provided behind the large-diameter stepped portion of the push rod piston, the push rod moving with the cap after initiation of a braking operation and movement of the push rod relative to the control element housing. The sleeve operates a first valve and a second valve, the first valve having a first flow path connecting the annular chamber and the pressure chamber of the brake circuit through the inner bore of the push rod piston. open and said second
A negative pressure operated brake power booster with a master cylinder, wherein a valve closes a second flow path connecting the annular chamber and a socket pipe of a reservoir via an inlet port of the master cylinder. 2. A backup plate having an opening in the center and a stud extending in the radial direction, the stud being engaged with a notch formed in the sleeve, and the notch in the sleeve being connected to the backup plate. 2. A vacuum-operated brake power booster with a master cylinder according to claim 1, wherein the plate is sized to be movable longitudinally by a distance b relative to the sleeve. 3. the sleeve, movable coaxially with the stem of the pushrod piston, is provided with a friction ring slidable at the end facing the master cylinder and operative with the annular second valve; The annular chamber is connected to the pressure chamber located in front of the push rod piston via an inlet passage located in the housing of the master cylinder, and during brake operation, the inlet passage connects to the piston cap. A negative pressure operated brake power booster with a master cylinder according to claim 1 or 2, characterized in that the brake power booster is controlled by a first sliding valve provided with a master cylinder. 4 The stem of the push rod piston is provided with an inner hole that communicates with the pressure chamber, and the outlet of the inner hole on the outer surface of the stem is connected to the master cylinder side end of the sleeve that surrounds the stem at the stage of releasing the brake. Claims 1 to 3, characterized in that the sleeve is closed by the sleeve, and is released by the sleeve in the event of a failure of the booster at the beginning of the braking operation. Negative pressure operated brake power booster with master cylinder described in . 5. The backup plate is supported by a head member located on the brake pedal side of the master cylinder via a spring, and the spring biases the sleeve against the cap via the backup plate. A negative pressure operated brake power booster with a master cylinder according to any one of claims 2 to 4. 6. Claims characterized in that a push plate is provided at the brake pedal side end of the push rod, and the push plate operates together with the reaction force device held by the cylindrical inner surface of the cap. A negative pressure operated brake power booster with a master cylinder according to any one of items 1 to 5. 7. The play is formed between the master cylinder side surface of the push plate and the inner surface of the bottom of the cap in the brake release position, and the play corresponds at least to the opening stroke of the first valve. A negative pressure operated brake power booster with a master cylinder according to claim 6, characterized in that: 8. The cap is formed with a radially outwardly curved rim, which rim supports the control element housing side end of the spring device. A negative pressure operated brake power booster with a master cylinder according to any one of the items. 9. The backup plate that operates together with the sleeve has a substantially cup shape, and a spring is interposed between the bottom of the backup plate and a retaining ring disposed at the end of the sleeve on the brake pedal side. A negative pressure operated brake power booster with a master cylinder according to any one of claims 2 to 8. 10 When the push rod piston is moved in the actuating direction relative to the sleeve, the stud of the back up plate operates in conjunction with a retaining ring provided at the end of the push rod piston on the brake pedal side; A negative pressure operated brake power booster with a master cylinder according to any one of claims 2 to 9, wherein the retaining ring pulls the backup plate.