GB2114693A - Vehicle deceleration responsive hydraulic brake regulator - Google Patents

Abstract

A brake pressure regulator consists of a housing (20) which encloses a cavity (32) and which is provided with an inlet port (26) for connection to the master cylinder (10) and an outlet port (28) for connection to the rear brakes (14). The lower part of the cavity forms a ramp (34) on which a spherical mass (36) rolls. Under the effect of inertia forces, this mass (36) moves so as to position itself over a valve seat (38) provided at the exit of the outlet port (28). According to the invention, the seat (38) is situated along the ramp (34). <IMAGE>

Description

SPECIFICATION Braking corrector controlled by deceleration The invention relates to braking correctors and concerns more particularly a corrector controlled by the deceleration of the vehicle.

A corrector is known, for example from U.S.

Patent 2,242,297, of the type consisting of a housing which encloses a cavity, the housing being provided with an inlet port for connection to the master cylinder and an outlet port for connection to at least one rear brake, these two ports emerging into said cavity, the lower part of said cavity forming an inclined ramp rising towards the front of the vehicle, a spherical mass being mounted iri said cavity, a valve seat being provided at the exit of said outlet port, said mass being able to move under the effect ofinertia forces so as to position itself over said valve seat.

In the case of the above patent, the valve seat is situated on the front wall of the cavity. Taking this configuration into account, the outlet port is therefore also necessarily situated at the front of the housing. As a result, it is necessary to form an appropriate elbow at the end of the pipe connecting this outlet port to the rear brakes.

In the same way, although in theory it is possible to locate the entry port on the side of the housing, it is usually situated, for convenience of manufacture, at the rear end of the housing. In either case, it is also necessary to form an appropriate elbow at the end of the pipe coming from the master cylinder.

With the aim of alleviating these disadvantages, the invention proposes a corrector of the type specified above, characterised in that said valve seat is situated along said ramp.

In this way, it is possible to situate the entry port at the front of the housing, which makes it possible to reduce to a minimum the elbow to be formed at the end of the pipe coming from the master cylinder.

Moreover, in a preferred embodiment of the invention, the cavity is formed inside an insert mounted in the housing, the outlet port is situated at the rear of the housing and the communication between the outlet port and the valve seat is established via passages formed between the housing and the insert.

In this case, the elbow to be formed at the end of the pipe leading to the rear brakes is also reduced to a minimum.

It will be noticed that the invention also enables the developed length of the above pipes to be reduced, thereby resulting in a weight saving, which although modest, nevertheless contributes to the lightening of the vehicle.

The invention will be described below with reference to the accompanying-drawings, in which: Figure 1 is a diagram of a braking circuit incorporating a corrector according to the invention, which is shown in longitudinal section; and Figure 2 is a longitudinal section of a second embodiment of a corrector according to the invention.

The braking system in Figure 1 is essentially made up of a master cylinder 10, front brakes 1 2 and rear brakes 14. In the line 16a, 16b serving the rear brakes, a corrector 18 is interposed, whose housing 20 is fixed to the chassis of the vehicle, by means not shown, in such a way that the longitudinal axis of the housing makes an angle a with the horizontal.

The housing 20 is provided with a blind bore 22 closed at its rear end by a plug 24.

An inlet port 26 is provided at the front end of the housing and an outlet port 28 is provided in the plug 24, that is to say at the rear end of the housing.

Inside the bore 22 is mounted a cup-shaped insert 30 in which a cavity 32 is arranged; in direct communication with the entry port, whose lower part forms an inclined ramp 34 on which a spherical mass or ball 36, contained in the cavity 32, is able to roll.

Along this ramp an annular valve seat 38 is positioned, at the exit of a radial passage 40 provided in the insert 30 and connecting the cavity 32 to an axial passage 42 created between the insert 30 and the bore 22 as far as the outlet port 28.

When at rest. the ball 36 is brought into contact by its own weight against the bottom of the insert 30, in which position the valve seat 38 is open. In this way there is free communication between the master cylinder and the rear brakes via the inlet port 26, the cavity 32, the passages 40 and 42 and the outlet port 28.

In operation, with the vehicle moving in the direction of the arrow F, when the master cylinder 10 is operated, the brake fluid is transmitted freely at first, not only to the front brakes 1 2 but also to the rear brakes 14.

When the deceleration resulting from braking exceeds a predetermined value which is a function of the angle a, the ball 36 moves along the ramp 34 and positions itself over the seat 38.

The communication between the master cylinder and the rear brakes being interrupted, any subsequent increase in the braking pressure is only transmitted to the front brakes, the pressure prevailing in the rear brakes remaining equal to the pressure which was prevailing at the moment of closure of the seat 38, so as to avoid locking the rear wheels.

It will be noticed that this closure of the seat 38 is assured for as long as the pressure in the front brakes exceeds that which prevails in the rear brakes.

As illustrated, the plug 24 ensures that the insert 30 is locked inside the housing. Moreover, the insert 30 and the housing 20 are provided with positioning means in the form of an eccentric peg 44 projecting axially from the insert, and a corresponding hole 46 in the housing.

This makes it possible to ensure that the seat 38 is correctly positioned at the lower part of the cavity 32, not only during the assembly of the device but also during its installation on the vehicle chassis.

As explained above, the construction just described permits particularly simple connection to the connecting pipes 1 6a and 16b, minimising the bending operations on those pipes and reducing their developed length.

Figure 2 shows a second embodiment of a braking corrector according to the invention and includes a certain number of elements similar to those of the embodiment shown in Figure 1, to which the same reference numbers will be applied.

In the case of this devIce, the bore 22 carries an extension 23 of reduced diameter, on the same side as the inlet port 26, and the insert 30 carries an extension 31 contained in the bore extension 23. Thus the insert and its extension constitute a stepped piston.

In addition, the insert 30--31 is mounted in and is able to slide in the bore 22-23 and forms three chambers inside the housing: an inlet chamber 48 on the same side as the entry port 26, an outlet chamber 50 on the same side as the outlet port 28, and an intermediate atmospheric chamber 52, the latter being situated between two seals 54 and 56 mounted on the insert 30 and its extension 31 respectively.

As illustrated, the passages 40 and 42 emerge into the outlet chamber 50 beyond the seal 54.

At rest, the ball 36 does not cover the seat 38 and there is free communication between the entry port 26 and the outlet port 28.

In operation, with the vehicle moving in the direction of the arrow F, when the master cylinder is operated, the brake fluid is transmitted at first not only to the front brakes 1 2 but also to the rear brakes 14.

When the deceleration resulting from braking exceeds a predetermined value which is a function of the angle a, the ball 36 moves along the ramp 34 and positions itself over the seat 38.

It will be noticed that in this embodiment the edge of the seat 38 is used to form a ramp element 34 for the bail 36.

The communication between the master cylinder 10 and the rear brakes 1 4 being interrupted, the pressure change in the rear brakes 14 is modified as follows: during an intermediate phase, this pressure remains equal to that prevailing in the outlet chamber 50 at the moment of closure of the ball 36 on the seat 38, the stepped piston 30-31 remaining steady and in end contact with the housing, such that the ratio of the pressure delivered by the master cylinder 10 to the pressure prevailing in the outlet chamber remains less than the ratio of the crosssections of the insert 30 and its extension 31..

During the final phase, the piston 30--31 moves towards the outlet chamber 50 under the effect of the increase in pressure in the entry chamber 48, the ratio of the outlet pressure to the entry pressure remaining equal to the ratio (less than 1) of the cross-sections of the extension 31 and the insert 30.

It will be noticed that, if for various reasons the piston 30-31 is not in end contact with the housing before braking commences, as soon as the pressure starts to rise the piston will be brought into the end contact position as shown in the figure.

Claims (7)

1. Braking corrector controlled by the deceleration of a vehicle, which comprises a housing (20) enclosing a cavity (32), the housing being provided with an inlet port (26) for connection to a master cylinder (10) and an outlet port (28) for connection to at least one rear brake (14), these two ports emerging into said cavity (32), the lower part of said cavity forming an inclined ramp (34) rising towards the front of the vehicle, a spherical mass (36) being mounted in said cavity, a valve seat (38) being provided at the exit of said outlet port, said mass being able to move under the effect of inertia forces so as to position itself over said valve seat (38), characterised in that said valve seat (38) is situated along said ramp (34).

2. Braking corrector according to Claim 1, characterised in that said inlet port (26) is situated at the front end of the said housing.

3. Braking corrector according to either Claim 1 or Claim 2, characterised in that said cavity (32) is formed in an insert (30) mounted in said housing, and in that said outlet port (28) is situated at the rear of said housing, communication between said outlet port (28) and said valve seat (38) being established via passages (40, 42) created between said housing (20) and said insert (30).

4. Braking corrector according to Claim 3, characterised in that said insert (30) and said housing (20) are provided with means (44, 46) for positioning the former relative to the latter.

5. Braking corrector according to Claim 4, characterised in that said positioning means (44, 46) consist of an eccentric peg (44) projecting axially from said insert (30), and a corresponding hole (46) in said housing (20).

6. Braking corrector according to any one of Claims 1 to 5, characterised in that said insert (30) constitutes a stepped piston (30, 31) mounted in ana' able to slide in said housing (20).

7. A braking corrector substantially as described and as shown in the accompanying drawings.