WO1992015474A1 - A hydraulic master cylinder - Google Patents

A hydraulic master cylinder Download PDF

Info

Publication number
WO1992015474A1
WO1992015474A1 PCT/GB1992/000252 GB9200252W WO9215474A1 WO 1992015474 A1 WO1992015474 A1 WO 1992015474A1 GB 9200252 W GB9200252 W GB 9200252W WO 9215474 A1 WO9215474 A1 WO 9215474A1
Authority
WO
WIPO (PCT)
Prior art keywords
seal
piston
master cylinder
bore
base portion
Prior art date
Application number
PCT/GB1992/000252
Other languages
French (fr)
Inventor
Maurice John Wimbush
Original Assignee
Automotive Products Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Automotive Products Plc filed Critical Automotive Products Plc
Publication of WO1992015474A1 publication Critical patent/WO1992015474A1/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16J—PISTONS; CYLINDERS; SEALINGS
    • F16J15/00—Sealings
    • F16J15/16—Sealings between relatively-moving surfaces
    • F16J15/166—Sealings between relatively-moving surfaces with means to prevent the extrusion of the packing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60T—VEHICLE BRAKE CONTROL SYSTEMS OR PARTS THEREOF; BRAKE CONTROL SYSTEMS OR PARTS THEREOF, IN GENERAL; ARRANGEMENT OF BRAKING ELEMENTS ON VEHICLES IN GENERAL; PORTABLE DEVICES FOR PREVENTING UNWANTED MOVEMENT OF VEHICLES; VEHICLE MODIFICATIONS TO FACILITATE COOLING OF BRAKES
    • B60T11/00—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
    • B60T11/10—Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant transmitting by fluid means, e.g. hydraulic
    • B60T11/16—Master control, e.g. master cylinders
    • B60T11/236—Piston sealing arrangements

Definitions

  • This invention relates to a hydraulic master cylinder and particularly to a master cylinder for braking systems of motor vehicles.
  • the master cylinder bore is connected to a fluid reservoir by an inlet port that passes through the wall of the master cylinder body.
  • the inlet port is closed by the primary ring-cup seal as the piston is pushed into the master cylinder bore past the inlet port, on application of the brakes, so completely closing communication between the reservoir and the pressurised brake system.
  • the pressurised system expands to reduce the braking pressure and pushes the master cylinder piston and seal back towards its at-rest position. Tills causes the loaded seal to move back past the inlet port so that the pressurised seal is extruded into the inlet port causing damage over a prolonged time period.
  • the present invention provides a hydraulic master cylinder having a piston seal which will be compatible with anti lock braking systems.
  • hydraulic master cylinder having a master cylinder bore and a piston sealingly slidcable in the bore, the bore being supplied by hydraulic fluid through an inlet port which is closed by movement of the piston during a pressure application condition of the piston, wherein the piston seal comprises a seal assembly which scats against a first piston surface and comprises a circular elastomeric seal having a base portion which is
  • a plastics material seal cup having an annular flange which extends axially along the radially outer surface of the seal and a base portion which lies adjacent a radially outer portion of the base portion of the seal, so that a radially inner portion of the base portion of the seal seats on the piston.
  • the inlet port extends through the wall of the master cylinder body to connect a fluid supply to the master cylinder bore at a
  • Fig 1 is a radial cross section through a seal
  • Fig 2 is a part section master cylinder showing a piston and seal assembly in situ.
  • Fig 3 is an elevation of a piston seal assembly of the type used in a tandem master cylinder for a vehicle brake system.
  • the seal assembly 10 for use in a motor vehicle hydraulic brake master cylinder.
  • the seal assembly 10 comprises an elastomer seal 11 and a plastics material seal cup 21.
  • the seal 10 is an annular ring seal which has a cup shaped radial cross section with a base portion 12 with a bottom surface 15 that in use lies adjacent a shoulder 32 of the piston, a radially outer sealing lip 13 that in use seals against a cylinder bore 41, and a radially inner lip 14 that lies against a cylindrical portion 33 of the piston 31.
  • the two sealing lips 13 and 14 extend axially away from the base portion 12 for the similar distances, preferably the same distances.
  • the seal cup 21 surrounds the base portion 12 of the seal 11 and is formed from a plastics material such as nylon, or PTFE (Polythene fluro ethylene) and has an 'L' shaped radial cross section comprising a base portion 22 and an outer annular flange 23.
  • the annular flange 23 extends axially around the outer surface of the seal for up to half the axial length of the seal, preferably to the base of the outer seal lip 13.
  • the base portion 22 extends axially inwardly so that it covers only a radially outer portion 12A of the bottom surface 15 of the seal.
  • the base portion 22 extends radially inwardly to radially align within the inner sur f ace o f t he radi a l l y i nne r seal l ip 1 4 .
  • the base portion 12 of the seal 11 is formed with an 'L' shaped recess 16 at its radially outer surface and bottom surface 15 to receive the 'L' shaped seal cup 21, with the radially inner portion 12B of the base portion of the seal seating on the shoulder 32 of the piston 31.
  • Fig 3 shows a typical master cylinder piston and seal assembly for a brake system tandem master cylinder.
  • the piston 31 is a spool piston with a secondary seal 35 at one end, with the seal assembly 10 forming a primary seal 10 at the other end thereof.
  • the piston 31 has a spring 36 secured to the end face 34 of its end portion 33 with the primary seal 10 thereon.
  • the spring 30 is located between two spring retainers 37, and 37a interconnected by a pin 38 screwed into the end 34 of the piston 31 to preset the length of the spring 36.
  • the seal assembly 10 has its base portion 12 seating against a shoulder 32 formed on the piston and its inner lip 14 sealing against the cylindrical end portion 33 of the piston.
  • An annular array of axially extending feed holes 39 extend through the shoulder 32 to allow fluid to flow to the bottom surface 15 of the seal assembly.
  • the base portion 22 of the cup seal align.s with the holes 39 and prevents extrusion of the seal 11 under load into the holes 39.
  • FIG. 1 there is illustrated a schematic drawing of a brake master cylinder having a master cylinder body 40 with a cylindrical bore 41 therein.
  • the bore 41 is connected to a fluid reservoir (not shown) by an inlet port 42 which is located in front of the piston seal assembly 10 in the
  • the annular seal cup 21 is dimensioned so that there is an annular gap 'S' between the flange 23 and the bore 41.
  • the gap is approxi matel y 0.1 mm nominal clearance for a nominal 24 mm diameter bore.
  • the cross sectional area of the annular gap 'S' is greater than the total cross-sectional area of the feed holes 39 so that the flow of fluid from a unpressurised side of the piston to a pressurised side of the piston is not choked.
  • the seal 21 may be moved past the inlet port 42 during the brake

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Transportation (AREA)
  • Transmission Of Braking Force In Braking Systems (AREA)

Abstract

A hydraulic master cylinder having a master cylinder bore (41) and a piston (31) sealingly slideable therein, the bore having an inlet port (42) which is closed by movement of the piston during a pressure application condition of the piston. The piston (31) has a seal assembly (10) which seats against a first piston surface (32) and comprises an elastomeric seal (11) and a plastics material seal cup (21) which surrounds a radially outer portion of the elastomeric seal (11) so that a radially inner portion of the base portion (15) of the seal (11) seats in contact with the piston, and the seal cup (21) is spaced by a distance 'S' from the bore of the master cylinder.

Description

A HYDRAULIC MASTER CYLINDER
This invention relates to a hydraulic master cylinder and particularly to a master cylinder for braking systems of motor vehicles.
In the conventional brake hydraulic master cylinder, the master cylinder bore is connected to a fluid reservoir by an inlet port that passes through the wall of the master cylinder body. The inlet port is closed by the primary ring-cup seal as the piston is pushed into the master cylinder bore past the inlet port, on application of the brakes, so completely closing communication between the reservoir and the pressurised brake system.
In anti-lock braking systems, the pressurised system expands to reduce the braking pressure and pushes the master cylinder piston and seal back towards its at-rest position. Tills causes the loaded seal to move back past the inlet port so that the pressurised seal is extruded into the inlet port causing damage over a prolonged time period. The present invention provides a hydraulic master cylinder having a piston seal which will be compatible with anti lock braking systems.
According to the invention there is provided a
hydraulic master cylinder having a master cylinder bore and a piston sealingly slidcable in the bore, the bore being supplied by hydraulic fluid through an inlet port which is closed by movement of the piston during a pressure application condition of the piston, wherein the piston seal comprises a seal assembly which scats against a first piston surface and comprises a circular elastomeric seal having a base portion which is
adjacent the first piston surface and has a radially outer annular seal lip extending axially away from said base portion and which in use seals against the bore to generate pressure, and a plastics material seal cup having an annular flange which extends axially along the radially outer surface of the seal and a base portion which lies adjacent a radially outer portion of the base portion of the seal, so that a radially inner portion of the base portion of the seal seats on the piston.
In such a master cylinder, the inlet port extends through the wall of the master cylinder body to connect a fluid supply to the master cylinder bore at a
location in front of the master cylinder primary seal when in its "at-rest" condition, and when the piston is in under load the annular flange of the seal cup prevents extrusion into the inlet port when it is in axial alignment with the inlet port.
The invention will be described by way of example and with reference to the accompanying drawings in which:-
Fig 1 is a radial cross section through a seal
assembly used in a master cylinder according to the invention showing the centre line of the section.
Fig 2 is a part section master cylinder showing a piston and seal assembly in situ.
Fig 3 is an elevation of a piston seal assembly of the type used in a tandem master cylinder for a vehicle brake system.
With reference to Fig 1 there is illustrated a seal assembly 10 for use in a motor vehicle hydraulic brake master cylinder. The seal assembly 10 comprises an elastomer seal 11 and a plastics material seal cup 21. In use the seal assembly 10 sits on a piston 31 (See Fig 3) and is the primary seal for the brake system and should withstand pressures of up to 140 bar. The seal 10 is an annular ring seal which has a cup shaped radial cross section with a base portion 12 with a bottom surface 15 that in use lies adjacent a shoulder 32 of the piston, a radially outer sealing lip 13 that in use seals against a cylinder bore 41, and a radially inner lip 14 that lies against a cylindrical portion 33 of the piston 31. The two sealing lips 13 and 14 extend axially away from the base portion 12 for the similar distances, preferably the same distances.
The seal cup 21 surrounds the base portion 12 of the seal 11 and is formed from a plastics material such as nylon, or PTFE (Polythene fluro ethylene) and has an 'L' shaped radial cross section comprising a base portion 22 and an outer annular flange 23. The annular flange 23 extends axially around the outer surface of the seal for up to half the axial length of the seal, preferably to the base of the outer seal lip 13. The base portion 22 extends axially inwardly so that it covers only a radially outer portion 12A of the bottom surface 15 of the seal. Preferably the base portion 22 extends radially inwardly to radially align within the inner sur f ace o f t he radi a l l y i nne r seal l ip 1 4 .
The base portion 12 of the seal 11 is formed with an 'L' shaped recess 16 at its radially outer surface and bottom surface 15 to receive the 'L' shaped seal cup 21, with the radially inner portion 12B of the base portion of the seal seating on the shoulder 32 of the piston 31.
In use the seal assembly 10 is seated on a piston 31. Fig 3 shows a typical master cylinder piston and seal assembly for a brake system tandem master cylinder.
The piston 31 is a spool piston with a secondary seal 35 at one end, with the seal assembly 10 forming a primary seal 10 at the other end thereof. The piston 31 has a spring 36 secured to the end face 34 of its end portion 33 with the primary seal 10 thereon. The spring 30 is located between two spring retainers 37, and 37a interconnected by a pin 38 screwed into the end 34 of the piston 31 to preset the length of the spring 36.
The seal assembly 10 has its base portion 12 seating against a shoulder 32 formed on the piston and its inner lip 14 sealing against the cylindrical end portion 33 of the piston. An annular array of axially extending feed holes 39 extend through the shoulder 32 to allow fluid to flow to the bottom surface 15 of the seal assembly. The base portion 22 of the cup seal align.s with the holes 39 and prevents extrusion of the seal 11 under load into the holes 39.
With reference now to Fig 2, there is illustrated a schematic drawing of a brake master cylinder having a master cylinder body 40 with a cylindrical bore 41 therein. The bore 41 is connected to a fluid reservoir (not shown) by an inlet port 42 which is located in front of the piston seal assembly 10 in the
conventional manner. When the brakes are applied the piston 31 moves rightwards to a position 10A shown in dotted outline to pressurise the brake system and the seal 11 isolates the inlet port 42 from the pressurised brake system.
The annular seal cup 21 is dimensioned so that there is an annular gap 'S' between the flange 23 and the bore 41. The gap is approxi matel y 0.1 mm nominal clearance for a nominal 24 mm diameter bore. The cross sectional area of the annular gap 'S' is greater than the total cross-sectional area of the feed holes 39 so that the flow of fluid from a unpressurised side of the piston to a pressurised side of the piston is not choked.
In use when the brakes are applied the seal 21 may be moved past the inlet port 42 during the brake
application. When the brake system under pressure expands during an antilock operation the piston and seal may be pushed back into alignment with the inlet port. When in this condition under the load exerted by the fluid in the pressurised braking system, the annular flange 23. of the seal cup 21 extends a
sufficient axial distance along the seal to prevent the heel o f the seal being extruded into the inlet port 42.
When the braking system is released and the piston returns; it will be necessary to feed fluid into the brake system. This is achieved by fluid flowing from reverse side of the piston 31, through the holes
39 and then through the annular gap 'S' and past the oute r seal li p 1 3 i nto the braki ng system

Claims

CLAIMS 1. A hydraulic master cylinder having a master
cylinder bore and a piston sealingly slidable in the bore, the bore being supplied by hydraulic fluid through an inlet port which is closed by movement of the piston during a pressure
application condition of the piston, wherein the piston seal comprises a seal assembly which seats against a first piston surface and comprises a circular elastomeric seal having a base portion which is adjacent the first piston surface and has a radially outer annular seal lip extending axially away from said base portion and which in use seals against the bore to generate pressure, and a plastics material seal cup having an annular flange which extends axially along the radially outer surface of the seal and a base portion which lies adjacent a radially outer portion of the base portion of the seal, so that a radially inner portion of the base portion of the seal seats on the piston.
2. A master cylinder as claimed in Claim 1, wherein the annular flange of the seal cup is spaced from the bore of the master cylinder.
3. A master cylinder as claimed in Claim 1 wherein the seal cup is formed from a plastics material.
4. A master cylinder as claimed in any one of claims 1 to 3 wherein the elastomeric seal is an annular sealing ring of cup shaped radial cross section and includes a radially inner sealing lip in use for sealing against a second surface on said piston, the annular flange on the seal cup extends axially along the seal to substantially the base of the outer annular lip.
5- A master cylinder as claimed in Claim 4 wherein the seal cup has a substantially 'L' radial cross section with its base portion extending radially inwardly as far as the radially inner seal lip.
6. A master cylinder as claimed in any one of claims 1 to 5 wherein the seal assembly seats against an axially directed first surface on the piston, and the adjacent base surface of the seal is connected to a fluid supply side of the piston by axial feed holes passing through the piston, and the base portion of the seal cup is located axially between the feed holes and the elastomeric seal. A master cylinder as claimed in Claim 2, and any one of claims 3 to 6 when dependant upon Claim 2, wherein the seal assembly locates against an axially directed first surface on the piston and the adjacent base surface of seal is connected to a fluid supply side of the piston by axial feed holes passing through the piston, and the cross sectional area of fthe annular space between the flange of the seal cup and the master cylinder bore is greater than the total cross sectional area of the feed holes through the piston.
PCT/GB1992/000252 1991-03-07 1992-02-12 A hydraulic master cylinder WO1992015474A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9104874.4 1991-03-07
GB919104874A GB9104874D0 (en) 1991-03-07 1991-03-07 A seal assembly and piston and cylinder

Publications (1)

Publication Number Publication Date
WO1992015474A1 true WO1992015474A1 (en) 1992-09-17

Family

ID=10691191

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1992/000252 WO1992015474A1 (en) 1991-03-07 1992-02-12 A hydraulic master cylinder

Country Status (2)

Country Link
GB (1) GB9104874D0 (en)
WO (1) WO1992015474A1 (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0894687A1 (en) * 1994-03-16 1999-02-03 Automotive Products France S.A. Hydraulic actuating system
WO1999035401A1 (en) * 1998-01-09 1999-07-15 Robert Bosch Gmbh Reciprocating pump
CN103738329A (en) * 2013-12-24 2014-04-23 日照市北业制动泵有限公司 Automobile hydraulic brake braking main cylinder
TWI552906B (en) * 2010-10-12 2016-10-11 Ｈｂ執行系統股份有限公司 Hydraulic master cylinder and brake master cylinder assembly
CN108547950A (en) * 2018-01-01 2018-09-18 保集团有限公司 The bar of triangular loop seals
US11084475B2 (en) * 2016-11-30 2021-08-10 Robert Bosch Gmbh Master brake cylinder, braking system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1065234A (en) * 1964-05-04 1967-04-12 Mission Mfg Co Improvements in or relating to slush pumps and pistons thereof
DE1530530A1 (en) * 1964-01-08 1970-02-26 Dunlop Rubber Co Control cylinder structure
DE1650075A1 (en) * 1967-12-12 1970-08-06 Knorr Bremse Gmbh Cup collar for hydraulic pistons
DE2246390A1 (en) * 1972-09-21 1974-03-28 Teves Gmbh Alfred Piston and cylinder lip seal - with a film of carbon, graphite or bronze filled PTFE vulcanised onto it

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1530530A1 (en) * 1964-01-08 1970-02-26 Dunlop Rubber Co Control cylinder structure
GB1065234A (en) * 1964-05-04 1967-04-12 Mission Mfg Co Improvements in or relating to slush pumps and pistons thereof
DE1650075A1 (en) * 1967-12-12 1970-08-06 Knorr Bremse Gmbh Cup collar for hydraulic pistons
DE2246390A1 (en) * 1972-09-21 1974-03-28 Teves Gmbh Alfred Piston and cylinder lip seal - with a film of carbon, graphite or bronze filled PTFE vulcanised onto it

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0894687A1 (en) * 1994-03-16 1999-02-03 Automotive Products France S.A. Hydraulic actuating system
WO1999035401A1 (en) * 1998-01-09 1999-07-15 Robert Bosch Gmbh Reciprocating pump
TWI552906B (en) * 2010-10-12 2016-10-11 Ｈｂ執行系統股份有限公司 Hydraulic master cylinder and brake master cylinder assembly
US9731691B2 (en) 2010-10-12 2017-08-15 Hb Performance Systems, Inc. Hydraulic master cylinder with back-up ring
TWI628100B (en) * 2010-10-12 2018-07-01 Ｈｂ執行系統股份有限公司 Method of operating a brake master cylinder
CN103738329A (en) * 2013-12-24 2014-04-23 日照市北业制动泵有限公司 Automobile hydraulic brake braking main cylinder
CN103738329B (en) * 2013-12-24 2016-03-02 日照市北业制动泵有限公司 Brake master cylinder of car hydraulic brake
US11084475B2 (en) * 2016-11-30 2021-08-10 Robert Bosch Gmbh Master brake cylinder, braking system
CN108547950A (en) * 2018-01-01 2018-09-18 保集团有限公司 The bar of triangular loop seals
CN108547950B (en) * 2018-01-01 2024-10-11 保一集团有限公司 Rod seal for triangular ring

Also Published As

Publication number Publication date
GB9104874D0 (en) 1991-04-17

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