JPS5855020B2 - tandem master cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mask cylinder for a hydraulic brake system,
In particular, the hole has a closed front end, in which the first and second pistons slide, and a first pressure chamber is defined between the pistons, and the closed front end of the hole. A cylinder in which a second pressure chamber is defined between the second piston and the second piston.
- a cylinder, wherein the second piston is in permanent communication between a port opening into the second pressure chamber and a reservoir connection of a cylinder bouncing that is connected to a hydraulic fluid reservoir; A compensation valve member having a compensation passage and controlling fluid flow through the port is provided, the compensation valve member being adapted to close the port when the second piston is advanced from the retracted position. This relates to the type of tandem master cylinder.

Providing a compensating passage in the second piston of the tandem master cylinder may include providing two spaced seals in the second piston to define an annular chamber between the emitters and connecting to the reservoir connection. This is necessary if you want to limit it.

Conventionally, the seal between the first and second pressure chambers of a tandem master cylinder is typically provided by a single annular seal carried by the second piston.

However, this arrangement has the disadvantage that damage to the encapsulant is difficult to detect.

Failure of the seal and subsequent damage to either brake circuit will cause the other circuit to fail due to communication through the damaged seal of the second piston.

For this reason, the use of a single encapsulant has become legally prohibited in some countries.

If the second piston is provided with two sealing parts spaced apart from each other, if one of the sealing members breaks, communication between the two pressure chambers will not occur, and one pressure chamber will open. All that is required is a slide between the tank and the storage tank.

In known mask cylinders of the above-mentioned type, the compensating valve member is positioned by a caged spring in a predetermined position relative to the closed end of the cylinder bore, and the retracted position of the second piston is controlled by a stop for the first piston. and another spring acting between both pistons.

A significant drawback of the above-mentioned known mask cylinders is that controlling the spacing between the compensating valve member and the port is extremely difficult when taking into account the dimensional tolerances of both pistons and of the cage arranged between them. There is a drawback.

Excessive dimensional tolerance between the compensating valve member and the port will result in
Both pistons must be advanced by a correspondingly large amount before the compensation valve closes and pressurization in the second pressure chamber begins.

Therefore, in the case of mass production, there is a disadvantage that, due to dimensional tolerances of various parts, an excessive movement of the piston is required before pressurization is started.

The present invention provides a tandem master cylinder of the type described above, in which a control valve assembly having a compensating valve member is disposed in the second pressure chamber, the control valve assembly being engaged by the front end face of the second piston. an abutment member that is mating and movable in the axial direction relative to the compensation valve member, a stop provided on the abutment member, and the second piston when the second piston assumes a retracted position;
Biasing the compensating valve member forwardly relative to the abutment member to engage the compensating valve member with the stop, thereby determining the relative position of the compensating valve member with respect to the abutment member, and thus the compensating valve member. a resilient device regulating the spacing between the member and the port, and when the second piston is advanced from the retracted position, the compensating valve member moves rearward relative to the abutting member and the port It is characterized by being made to close.

Therefore, the spacing between the compensating valve member and the port is determined substantially by the tolerances of the control valve assembly and not by the sum of the tolerances of other various components.

It is desirable that the retracted position of the second piston is limited to the engagement position with the abutting member.

The second piston may be urged forward into engagement with the abutment member by a second elastic device, preferably in the form of a compression spring, acting between both pistons.

Preferably, the first elastic device acts rearwardly on the abutment member and forwardly on another member engaging directly or indirectly with the housing, the valve member acting on the other member directly or indirectly. Assume that movement backward relative to is restricted.

Preferably, the first resilient device is a caged spring assembly, the assembly comprising a spring restrained between two spring retainers, the rear spring retainer forming an abutment member and the front spring retainer constituting the other member. The valve member is carried by the rear head of an axially elongated double-headed member which limits the movement of the spring retainers in the direction of separation.

The front portion of the cage is secured to the housing so that it cannot move rearward within the bore during use, or
In use, the second pressure chamber is exposed to fluid pressure and is attached to a pressure responsive member whose effective area is equal to or equal to the effective area of the valve member.

In some cases, residual pressure may exist in the second pressure chamber as the second piston approaches its normal retracted position.

Therefore, unless the cage is held in some way, the valve member will not separate from the piston and will pull the cage rearward, causing the cage to move out of its predetermined position.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention will now be described in detail with reference to the accompanying drawings, in which embodiments of the invention are shown.

In FIG. 1, a first and a second piston 1.sub.2 slide within a bore 3 of a cylinder housing 4. In FIG.

The first and second pressure chambers 5, 6 are respectively connected to separate hydraulic circuits through ports (not shown) provided in the wall of the cylinder 4.

The first pressure chamber 5 is connected to one chamber 7 of the reservoir 8 via the tilt valve assembly 9, the annular chamber 10 and the radial port 11 of the first piston 1 when the first piston 1 is in the fully retracted position shown.
The retracted position of the first piston 1 is limited by its engagement with the lower end of the tilt valve assembly 9.

The second piston 2 is a compression spring or a second elastic device 1
2 from the first piston, and the spring 12 acts as a return spring for the first piston.

The rear end of the second piston is provided with a cylindrical projection 13 for positioning a spring 12 which enters into a hole 14 provided at the front end of the first piston 1 when the two pistons are brought into close proximity.

Therefore, it is possible to shorten the overall length of the cylinder compared to the movement stroke of the first piston, and the protruding portion 13 is connected to the spring 12.
gives effective positioning.

The protrusion 13 prevents air from remaining around the hole 14 or the spring 12, and thus serves as a plunger which provides an effective air removal operation.

The second piston 2 has an axially spaced seal 1
5, 16 and between both seals an annular chamber 1T is defined by an annular outer surface recess of the piston 2 and a chamber 17 is located between the two seals.
A hole (not shown) in the wall of the housing adjacent to 9
via which it freely communicates with the second chamber 18 of the reservoir 8 .

The pin 19 acts as a safety stop to prevent the second piston 2 from retreating if the second pressure chamber 6 is excessively pressurized during brake air bleeding or the like.

Compensating passages for the second pressure chamber 6 are provided by axial and radial holes 20.21 provided in the piston 2;
These holes provide communication between the annular chamber 17 and the port 22 opening into the second pressure chamber 6.

A control valve assembly 36 that controls liquid through port 22 includes:
Cage assembly 250 Annular seal 23 held within an annular groove 23' in one head 29 of double-ended rod 24
and a compensating valve member of the type.

The cage assembly 25 defines the mounting length of the compression spring 26, ie, the first elastic device, and is connected to the rod 24 and the rod 24
The maximum separation distance between the two spring retainers 27 and 2B is defined as the position where they engage with the heads 29 and 30 at both ends of the long 1240, respectively. .

A weak spring washer or third elastic device 31 is attached to the head 29 of the rod 24 and the base 32 of the spring retainer 27 as shown in FIG.
The rod 24 and the sealing material 23 are pressed rearward relative to the spring retainer 27.

The spring retainer 28 is fixed in the position shown with respect to the boss 33 by pushing the integral tongue 28 into a recess provided in the outer surface of the tubular boss 23, and the boss 33 has a screw thread that engages with an annular groove in the outer surface thereof. It is fixed to the closed end of the hole 3 by a pin 35 with a dowel.

The compression spring 26 of the cage assembly 25 is stronger than the compression spring 12 acting between the pistons, so that when the pedal force applied to the first piston 1 is released, the cage assembly 25 is fully extended and the second piston 2 takes the retreat position.

In this retracted position, the spring retainer 27 acting as an abutting member
It is regulated by engaging with the front end surface 37 which is the bottom of the hole 34.

The axial position of the sealing material 23 relative to the spring retainer 27 is the second
As shown in the figure, the position is determined by the position where the head 29 of the rod 24 comes into contact with a stop portion (surface) 38 formed on the spring retainer 27.

The axial thickness of the annular sealing material 23 is the same as that of the cage assembly 2.
the desired axial direction necessary to provide fluid communication between the second pressure chamber 6 and the port 22 between the radial sealing surface of the damping member 23 and the end face 37 in the fully extended position of 5; Define so that a gap exists.

This gap is determined by the dimensions of the spring retainer 27, the head 29 of the rod 24 and the seal 23.

When the second piston 2 moves forward in response to the forward movement of the first piston, the rear spring retainer 27 also moves forward together with the second piston, and the spring 26 is compressed.

The head 29 of the rod 24 is released from the force of the spring 26 and, under the force of the spring 31, assumes the position shown in FIG. Close port 22 of piston 2.

When the second piston moves further forward, the spring retainer 2
7 and the head 29 move forward together with the piston 2 in this state.

The hole 34 in the second piston allows a substantial portion of the axial length of the cage assembly 25 to be placed within the second piston, which has the effect of shortening the overall length of the mask cylinder.

Together with the provision of the spring 12 within the bore 14 of the first piston as previously described, the above arrangement achieves a significantly shorter tandem master cylinder.

If the sealing material 16 of the second piston 2 is damaged, the annular chamber 17 that communicates with the storage tank 18 and the first pressure chamber 5 will communicate with each other, but since communication between both pressure chambers 5 and 6 will not occur, the second pressure chamber The brake can be activated by a circuit connected to the pressure chamber.

Similarly, even if the sealing part 15 is damaged, only the second pressure chamber 6 and the annular chamber 17 are communicated with each other, and the first pressure chamber 5 and its associated brake circuit are not affected.

Damage to either of the seals 15, 16 can be detected by providing a differential pressure alarm device between both brake circuits.

If the second piston of the prior art has a single sealing portion that seals between both pressure chambers, damage to the sealing portion cannot be detected by the differential pressure alarm device.

A cage assembly 2 with a compensation port for the second pressure chamber in the second piston and held at the closed end of the cylinder bore 3
The fact that the former has a compensation valve member on the second piston and a compensation port on the closed end of the cylinder hole is different from the conventional type in which a compensation valve member is provided on the second piston and a compensation port is provided on the closed end of the cylinder hole. Whereas it is sufficient to create simple holes by machining,
The latter has the disadvantage that the second piston must be provided with a cylindrical slot for receiving and retaining a fixed valve member retainer for retaining the valve member.

The stroke of both pistons can be adjusted by changing the length of the cage assembly 25.

Although the first piston is shown as being operated by a foot pedal, it could also be operated by a fluid.

In the variant of FIG. 4, the spring retainer 28 is secured to a sleeve 39 integral with the threaded plug 33 by means of a folded tongue 28' (not shown) similar to that of FIG.

The sleeve 39 constitutes a support for holding the spring.

Plug 33' closes a hole 40 in the end wall of the cylinder, which connects cage assembly 25 and sleeve 33.
The plug 33' is of sufficient size to permit passage therethrough, and is adapted to permit assembly of the plug 33' into the housing with the cage assembly attached.

An annular seal 41 is provided for the plug 33'.

In the modification shown in FIG. 5, the spring retainer 28 is not mechanically fixed to the cylinder housing, but the piston 4
2 is held in place by fluid pressure in pressure chamber 6 acting on it.

The spring retainer 28 is secured to the hestone 42 by a bent tongue (not shown).

The piston 42 is cup-shaped and is sealed at the narrow diameter end of the cylinder hole 3 by a sealing material 44 provided in an annular groove on the outer surface of the piston 42 .

There is a vent hole 45 in the end wall of the cylinder housing that communicates with the atmosphere, creating a pressure difference before and after the piston 420 when the second pressure chamber 6 is pressurized, and preventing damage to the sealing material 44 due to liquid leakage. Instruct.

The cross-sectional area of the piston 42 is smaller than the cross-sectional area of a compensating seal (not shown) carried on the rear end of the rod 24.

Therefore, when the second piston approaches its normal retracted position, the force acting on the piston 42 due to the fluid pressure remaining in the second pressure chamber 6 overcomes the force due to the fluid pressure acting on the compensating valve member and is transferred through the rod 24. act to pull the valve member away from the valve seat on the second piston.

[Brief explanation of the drawing]

FIG. 1 shows a side view of an embodiment of a tandem master cylinder according to the invention, with the upper half shown in cross-section and the first and second pistons shown in the retracted position. FIG. 2 is an enlarged detailed view of a portion of the mask cylinder of FIG. 1; FIG. 3 is a view similar to FIG. 2, but with the valve head in a retracted position relative to the rear spring retainer and the spring washer in an extended position; FIG. 4 is a partially enlarged view showing a modification of the front portion of the cage assembly in FIG. 1; FIG. 5 is a diagram similar to FIG. 4, but shows yet another modification. 1...First piston, 2...Second piston, 3...Bore, 4...Cylinder housing, 5...... First pressure chamber, 6...
...Second pressure chamber, 8...Storage tank, T, 18...
...Storage tank chamber, 9...Inclination valve, 10...
... Annular chamber, 11 ... Radial port, 1
2... Compression spring (second elastic device), 13...
...Protrusion, 14... Hole, 15, 16...
... Sealing part, 17 ... Annular chamber, 22 ...
... Port, 36 ... Control valve assembly, 23.
... Compensation valve member, 25 ... Cage assembly, 24 ... Double-ended rod, 26 ...
Compression spring (first elastic device), 2T...spring retainer (impingement member), 29.30...head of rod,
37... End face, 38... Stopping surface (stopping portion).

Claims (1)

[Claims] 1. A device having a hole whose front end is closed, in which first and second pistons slide, a first pressure chamber is defined between the two pistons, and a first pressure chamber is defined between the two pistons; a cylinder housing defining a second pressure chamber between a closed front end of the cylinder and the second piston, the second piston having a port opening into the second pressure chamber; A compensation valve member is provided having a compensation passageway in permanent communication between the port and a cylinder-cylinder reservoir connection connected to a hydraulic fluid reservoir, the compensation valve member controlling fluid flow through the port; The compensation valve member is adapted to close the port when the second piston is advanced from a retracted position, in which the control valve assembly 36 with the compensation valve member 23 is adapted to close the port when the second piston is advanced from a retracted position. placed in the pressure chamber 6,
The control valve assembly is connected to the front end surface 3T of the second piston.
an abutting member 27 that engages with the compensating valve member 23 and is movable in the axial direction relative to the compensating valve member 23, a stop portion 38 provided on the abutting member, and the second piston in the retracted position. when the compensating valve member is biased forwardly relative to the abutting member to cause the compensating valve member to engage the stop, the relative position of the compensating valve member relative to the abutting member, and thus a resilient device 26 regulating the spacing between the compensating valve member and the port 22, the compensating valve member relative to the abutment member when the second piston is advanced from the retracted position; A tandem mask 1 non-tie, characterized in that it moves rearward to close the port. 2. In the tandem master cylinder according to claim 1, the second elastic device 12 biases the second piston forward, and the retracted position of the second piston engages the abutment member. Tandem master cylinder regulated by. 3. In the tandem master cylinder according to claim 1, the elastic device 26 biases the abutment member 27 rearward, and the compensation valve member 23 limits rearward movement relative to the cylinder housing 4. Tandem master cylinder.