WO2011006305A1 - Piston for tandem master cylinder - Google Patents

Piston for tandem master cylinder Download PDF

Info

Publication number
WO2011006305A1
WO2011006305A1 PCT/CN2009/072812 CN2009072812W WO2011006305A1 WO 2011006305 A1 WO2011006305 A1 WO 2011006305A1 CN 2009072812 W CN2009072812 W CN 2009072812W WO 2011006305 A1 WO2011006305 A1 WO 2011006305A1
Authority
WO
WIPO (PCT)
Prior art keywords
piston
master cylinder
tandem master
cylindrical body
primary
Prior art date
Application number
PCT/CN2009/072812
Other languages
French (fr)
Inventor
Omar Brahmi
Stone Sun
Boris Zheng
Original Assignee
Bosch Automotive Products (Suzhou) Co., Ltd.
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 Bosch Automotive Products (Suzhou) Co., Ltd. filed Critical Bosch Automotive Products (Suzhou) Co., Ltd.
Priority to PCT/CN2009/072812 priority Critical patent/WO2011006305A1/en
Publication of WO2011006305A1 publication Critical patent/WO2011006305A1/en

Links

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60TVEHICLE 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
    • B60T11/00Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
    • B60T11/10Transmitting 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
    • B60T11/16Master control, e.g. master cylinders
    • B60T11/20Tandem, side-by-side, or other multiple master cylinder units
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60TVEHICLE 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
    • B60T11/00Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
    • B60T11/10Transmitting 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
    • B60T11/16Master control, e.g. master cylinders
    • B60T11/232Recuperation valves
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60TVEHICLE 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
    • B60T11/00Transmitting braking action from initiating means to ultimate brake actuator without power assistance or drive or where such assistance or drive is irrelevant
    • B60T11/10Transmitting 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
    • B60T11/16Master control, e.g. master cylinders
    • B60T11/236Piston sealing arrangements

Definitions

  • US2005/0060997A1 discloses such a tandem master cylinder in which the secondary piston is molded from plastic.
  • the plastic piston disclosed in US2005/0060997A1 has a complicated structure and is difficult to be manufactured by molding process. Furthermore, the number of parts in the assembled tandem master cylinder is so many that it is not easy to assemble the tandem master cylinder.

Landscapes

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

Abstract

A piston (21) for a tandem master cylinder (41) is provided. The piston (21) comprises a cylindrical body (23) within which a hollow chamber (25) is formed. The hollow chamber (25) is blocked off by a partitioning portion (27) adjacent to one end of the cylindrical body (23) and open at the other end (28). At least one slot (33) is formed in an outer wall of the cylindrical body (23) at the open end (28) of the hollow chamber (25). A tandem master cylinder (41) comprising the piston (21) is also provided. The piston (21) may be manufactured by molding process without requiring complicated molds. Furthermore, the process for molding the piston (21) is relatively simple. The tandem master cylinder (41) has a simple structure and the reduced number of parts, thereby being capable of being manufactured in a low-cost manner.

Description

Piston for tandem master cylinder
FIELD OF THE INVENTION
The present invention relates to a tandem master cylinder for a vacuum brake booster assembly in automotive vehicles, and in particularly to a piston for the tandem master cylinder.
BACKGROUND OF THE INVENTION
The tandem master cylinder for a vacuum brake booster assembly in automotive vehicles generally comprises a master cylinder body enclosing a bore in which a primary piston and a secondary piston are slidably disposed respectively. The primary piston and the secondary piston define with the bore a respective compressible chamber which is associated with a respective vehicle braking circuit. Generally, the primary piston and the secondary piston are made from metal such as aluminum alloy. To reduce weight and cost of the tandem master cylinder, it was proposed that at least the secondary piston of the primary piston and the secondary piston be molded from plastic.
US2005/0060997A1 discloses such a tandem master cylinder in which the secondary piston is molded from plastic. However, the plastic piston disclosed in US2005/0060997A1 has a complicated structure and is difficult to be manufactured by molding process. Furthermore, the number of parts in the assembled tandem master cylinder is so many that it is not easy to assemble the tandem master cylinder.
To overcome the deficiency caused by the complicated structure of the secondary piston, a piston as shown FIGS 1 and 2 was proposed. The piston 1 as shown FIGS 1 and 2 comprises a cylindrical body 3 within which a hollow chamber 5 is formed. The hollow chamber 5 is blacked off by a partitioning portion 7 adjacent one end of the cylindrical body 3 and is open at an opposite end. A projection 9 for mounting a secondary return spring is formed on a side of the partitioning portion 7 facing the open end of the hollow chamber 5 and a recess 11 for receiving a primary pin is formed on an opposite side of the partitioning portion 7. To re-feed a compressible chamber of the secondary piston with the brake fluid, a plurality of holes 13 are formed in the cylindrical body 3. However, to form a plurality of holes in the cylindrical body by molding process, the molds for molding the piston are complicated in structure and the process for molding the piston is troublesome. SUMMARY OF THE INVENTION
It is an object of the present invention to provide a piston for the tandem master cylinder which is capable of be manufactured by molding process without requiring complicated molds. Furthermore, the process for molding the piston is relatively simple.
It is another object of the present invention to provide a tandem master cylinder which has a simple structure and the reduced number of parts, thereby being capable of being manufactured in a low-cost manner.
According to a first aspect of the present invention, there is provided a piston for a tandem master cylinder comprising:
a cylindrical body within which a hollow chamber is formed, the hollow chamber being blacked off by a partitioning portion adjacent one end of the cylindrical body and open at an opposite end; and
at least one slot formed in an outer wall of the cylindrical body at the open end of the hollow chamber.
According to a second aspect of the present invention, there is provided a tandem master cylinder for a vacuum brake booster assembly in automotive vehicles, comprising at least one piston as mentioned in the first aspect of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
For a clear understanding of the present invention, a preferred, non-limiting embodiment of a piston for a tandem master cylinder and a tandem master cylinder comprising such a piston will be described by way of example with reference to the accompanying drawings, in which some parts are removed for clarity.
In the drawings:
FIG. 1 is a perspective view showing a piston for the tandem master cylinder in the prior art;
FIG. 2 is a sectional view of the piston as shown in FIG. 1;
FIG. 3 is a perspective view showing a piston for a tandem master cylinder according to the present invention; FIG. 4 is a sectional view of the piston as shown in FIG. 3; and
FIG. 5 is a schematically sectional view of the tandem master cylinder according to the present invention, showing the tandem master cylinder in a rest position. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS 3 and 4 show a piston 21 for a tandem master cylinder according to the present invention. The piston 21 according to the present invention comprises a cylindrical body 23 within which a hollow chamber 25 is formed. The hollow chamber 25 is blacked off by a partitioning portion 27 adjacent one end of the cylindrical body 23 and is open at an opposite end 28. A projection 29 for mounting a return spring is formed on a side of the partitioning portion 27 facing the open end 28 of the hollow chamber 25 and a recess 31 for receiving a pin is formed on an opposite side of the partitioning portion 27.
Unlike the prior piston 1, at least one slot 33 is formed in an outer wall of the cylindrical body 23 at the open end 28 of the hollow chamber 25. Preferably, as shown in FIGS 3 and 4, two slots 33 are formed diametrically opposite to each other in the outer wall. It should be understood that the number of the slots 33 may be more than two. When there are a plurality of slots 33, the plurality of slots 33 are preferably distributed uniformly in the outer wall of the cylindrical body 23. By replacing the holes passing through the cylindrical body of the prior piston with the slots formed in the outer wall of the cylindrical body, the piston according to the present invention is capable of be manufactured by molding process without requiring complicated molds. Furthermore, the process for molding the piston is relatively simple. The piston 21 according to the present invention may be molded from plastic or metal such as aluminum alloy by molding process. When the piston 21 according to the present invention is molded from plastic by molding process, PPA with 45%-50% glass fibre may be used. It should be understood that it is possible to use PPS with 45% glass fibre. Preferably, the end portion 24 of the cylindrical body 23 in which the slots 33 are formed has an outer diameter slightly less than that of the other portion of the cylindrical body 23. Of course, the end portion 24 of the cylindrical body 23 in which the slots 33 are formed may have the same outer diameter as that of the other portion of the cylindrical body 23. In this manner, the outer surface of the cylindrical body 23 of the piston 21 manufactured by molding process hardly has any parting line or burr. To enhance the strength of the piston 21, a plurality of reinforcing ribs 35 extending from the partitioning portion 27 to an inner surface of the cylindrical body 23 are provided around the recess 31. FIG. 5 is a schematically sectional view of the tandem master cylinder according to the present invention, showing the tandem master cylinder in a rest position. The tandem master cylinder 41 according to the present invention generally comprises a master cylinder body 43 enclosing a bore 45. The bore 45 is blocked off at one end by an end wall 47. A primary piston and a secondary piston are slidably disposed in the bore 45. Since the plastic 21 according to the present invention is preferably used as the secondary piston in the tandem master cylinder 41, only the secondary piston is shown and the primary piston is not shown in Fig 5. However, it goes without saying that the plastic 21 according to the present invention may be used as the primary piston in the tandem master cylinder 41. A secondary return spring 49 is interposed between the end wall 47 of the bore 45 and the partitioning portion 27 of the secondary piston 21. Preferably, a telescopic rod 51 passes through the secondary return spring 49 so that one end of the telescopic rod 51 bears against the end wall 47 of the bore 45 and the other end of the telescopic rod 51 engages with the projection 29. The telescopic rod 51 helps to hold the secondary return spring 49 in position. A primary return spring 53 is interposed between the partitioning portion 27 of the secondary piston 21 and the primary piston (not shown).
The secondary piston 21, the master cylinder body 43 and the end wall 47 of the bore 45 define a secondary compressible chamber 55 which is associated with a secondary vehicle braking circuit by a hole 57 formed in the master cylinder body 43. The primary piston, the master cylinder body 43 and the secondary piston 21 define a primary compressible chamber 59 which is associated with a primary vehicle braking circuit. The secondary vehicle braking circuit and the primary vehicle braking circuit are connected to a braking assembly arranged at the wheels of the vehicle respectively. Further, a secondary supply chamber 61 is defined between the secondary piston 21 and the master cylinder body 43. The secondary supply chamber 61 communicates with a brake fluid reservoir 63 via a passage 65. Of course, a primary supply chamber (not shown) may be formed similarly.
A first lip seal 67 is disposed between an outer surface of the secondary piston 21 and an inner surface of the bore 45 to isolate the secondary supply chamber 61 and the secondary compressible chamber 55 from the primary compressible chamber 59. A second lip seal 69 is disposed between the outer surface of the secondary piston 21 and the inner surface of the bore 45 and adjacent the slots 33 formed in the outer wall of the cylindrical body 23 of the secondary piston 21 so that the brake fluid may flow from the secondary supply chamber 61 to the secondary compressible chamber 55 when the tandem master cylinder is in the rest position as shown in FIG 5 and no brake fluid flows from the secondary supply chamber 61 to the secondary compressible chamber 55 when the tandem master cylinder is actuated during braking action.
It was well known that a vacuum brake booster assembly in automotive vehicles generally comprises a brake booster and a tandem master cylinder. The tandem master cylinder is controlled by a brake pedal actuated by a driver in a passenger compartment of an automotive vehicle by way of a control rod. A brake booster is commonly interposed between the brake pedal and the tandem master cylinder and transmits the braking effort and boost force to the primary piston by a push rod which connects to a rear end of the primary piston.
During braking action, the primary piston slides in the bore 45 towards the secondary piston 21 under the braking effort and boost force, causing the secondary piston 21 to slide towards the end wall 47 of the bore 45. With the sliding of the secondary piston 21 towards the end wall 47, the second lip seal 69 forms a close contact with the outer surface of the secondary piston 21 to isolate the secondary supply chamber 61 from the secondary compressible chamber 55 so that no brake fluid flows from the secondary supply chamber 61 to the secondary compressible chamber 55. With the further sliding of the secondary piston 21 towards the end wall 47, the fluid pressure in the secondary compressible chamber 55 and therefore in the secondary vehicle braking circuit increases, causing the braking assembly to brake the wheels of the vehicle. The braking level increases with the displacement of the primary and secondary pistons in the master cylinder body. When the braking action is released, the secondary piston 21 and the primary piston go back to the rest position as shown in FIG 5 under the action of secondary return spring 49 and the primary return spring 53 respectively. If necessary, the brake fluid from the brake fluid reservoir 63 may flow towards the secondary compressible chamber 55 via the passage 65, the secondary supply chamber 61, a gap between the second lip seal 69 and the end portion 24 of the secondary piston 21 as well as the slots 33 formed in the outer wall of the cylindrical body 23 of the secondary piston 21 to supply the secondary compressible chamber 55 with the brake fluid. Although the preferred embodiments of the invention were described in detail taken in conjunction of the accompanying drawings in a non-limiting sense, it should be understood that various changes and modifications could be made without departing from the scope defined by accompanying claims of the invention.

Claims

What is claimed is:
1. A piston for a tandem master cylinder, comprising:
a cylindrical body within which a hollow chamber is formed, the hollow chamber being blacked off by a partitioning portion adjacent one end of the cylindrical body and open at an opposite end; and
at least one slot formed in an outer wall of the cylindrical body at the open end of the hollow chamber.
2. The piston for a tandem master cylinder as claimed in claim 1, wherein two slots are formed diametrically opposite to each other in the outer wall of the cylindrical body.
3. The piston for a tandem master cylinder as claimed in claim 1, wherein a plurality of slots are distributed uniformly in the outer wall of the cylindrical body.
4. The piston for a tandem master cylinder as claimed in claim 1, wherein an end portion of the cylindrical body in which the slot is formed has an outer diameter less than that of the other portion of the cylindrical body.
5. The piston for a tandem master cylinder as claimed in claim 1, wherein an end portion of the cylindrical body in which the slot is formed has the same outer diameter as that of the other portion of the cylindrical body.
6. The piston for a tandem master cylinder as claimed in claim 1, wherein a projection is formed on a side of the partitioning portion.
7. The piston for a tandem master cylinder as claimed in claim 6, wherein a recess is formed on an opposite side of the partitioning portion.
8. The piston for a tandem master cylinder as claimed in claim 7, wherein a plurality of reinforcing ribs extending from the partitioning portion to an inner surface of the cylindrical body are provided around the recess.
9. The piston for a tandem master cylinder as claimed in claim 1, wherein the piston is molded from plastic by molding process.
10. The piston for a tandem master cylinder as claimed in claim 9, wherein the plastic is PPA with 45%-50% glass fibre or PPS with 45% glass fibre.
11. The piston for a tandem master cylinder as claimed in claim 1, wherein the piston is molded from metal by molding process.
12. A tandem master cylinder for a vacuum brake booster assembly in automotive vehicles comprising at least one piston as claimed in any one of claims 1-11.
13. The tandem master cylinder as claimed in claim 12, comprising:
a master cylinder body enclosing a bore, the bore being blocked off at one end by an end wall;
a primary piston and a secondary piston slidably disposed in the bore;
a secondary return spring interposed between the end wall of the bore and the secondary piston;
a primary return spring interposed between the secondary piston and the primary piston; a secondary compressible chamber defined by the secondary piston, the master cylinder body and the end wall of the bore and associated with a secondary vehicle braking circuit; a primary compressible chamber defined by the primary piston, the master cylinder body and the secondary piston and associated with a primary vehicle braking circuit;
a secondary supply chamber defined between the secondary piston and the master cylinder body and communicating with a secondary brake fluid reservoir;
a primary supply chamber defined between the primary piston and the master cylinder body and communicating with a primary brake fluid reservoir; and
seals disposed between an outer surface of the secondary piston and an inner surface of the bore and between an outer surface of the primary piston and the inner surface of the bore; wherein, the secondary piston is a piston as claimed in any one of claims 1-10.
14. The tandem master cylinder as claimed in claim 13, wherein said seals comprise:
a first lip seal disposed between the outer surface of the secondary piston and the inner surface of the bore to isolate the secondary supply chamber and the secondary compressible chamber from the primary compressible chamber; and
a second lip seal disposed between the outer surface of the secondary piston and the inner surface of the bore and adjacent the slots formed in the outer wall of the cylindrical body of the secondary piston so that the brake fluid flows from the secondary supply chamber to the secondary compressible chamber when the tandem master cylinder is in the rest position and no brake fluid flows from the secondary supply chamber to the secondary compressible chamber during braking action.
PCT/CN2009/072812 2009-07-17 2009-07-17 Piston for tandem master cylinder WO2011006305A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/CN2009/072812 WO2011006305A1 (en) 2009-07-17 2009-07-17 Piston for tandem master cylinder

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2009/072812 WO2011006305A1 (en) 2009-07-17 2009-07-17 Piston for tandem master cylinder

Publications (1)

Publication Number Publication Date
WO2011006305A1 true WO2011006305A1 (en) 2011-01-20

Family

ID=43448880

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2009/072812 WO2011006305A1 (en) 2009-07-17 2009-07-17 Piston for tandem master cylinder

Country Status (1)

Country Link
WO (1) WO2011006305A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011075358A1 (en) * 2011-05-05 2012-11-08 Continental Teves Ag & Co. Ohg Master cylinder, in particular for a regulated braking system
DE102011114708A1 (en) * 2011-09-30 2013-04-04 Lucas Automotive Gmbh Master brake cylinder with improved pressure reduction behavior
DE102012014321A1 (en) * 2012-07-19 2014-01-23 Lucas Automotive Gmbh Master brake cylinder for a motor vehicle brake system with profiled pressure piston
JP2014513007A (en) * 2011-05-05 2014-05-29 コンチネンタル・テベス・アーゲー・ウント・コンパニー・オーハーゲー In particular, a master cylinder for controlled brake devices
WO2015086010A1 (en) * 2013-12-09 2015-06-18 Schaeffler Technologies AG & Co. KG Master cylinder

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003194100A (en) * 2001-12-25 2003-07-09 Aisin Seiki Co Ltd Pressure generating device
US20050060997A1 (en) * 2003-09-23 2005-03-24 Herve Pujol Master cylinder with increased safety and piston for such a master cylinder
EP1889767A1 (en) * 2005-05-27 2008-02-20 Bosch Corporation Master cylinder
WO2008050633A1 (en) * 2006-10-23 2008-05-02 Bosch Corporation Cup seal and master cylinder using the same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2003194100A (en) * 2001-12-25 2003-07-09 Aisin Seiki Co Ltd Pressure generating device
US20050060997A1 (en) * 2003-09-23 2005-03-24 Herve Pujol Master cylinder with increased safety and piston for such a master cylinder
EP1889767A1 (en) * 2005-05-27 2008-02-20 Bosch Corporation Master cylinder
WO2008050633A1 (en) * 2006-10-23 2008-05-02 Bosch Corporation Cup seal and master cylinder using the same

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102011075358A1 (en) * 2011-05-05 2012-11-08 Continental Teves Ag & Co. Ohg Master cylinder, in particular for a regulated braking system
WO2012150345A1 (en) * 2011-05-05 2012-11-08 Continental Teves Ag & Co. Ohg Master cylinder, in particular for a controlled brake system
JP2014513007A (en) * 2011-05-05 2014-05-29 コンチネンタル・テベス・アーゲー・ウント・コンパニー・オーハーゲー In particular, a master cylinder for controlled brake devices
DE102011075358B4 (en) 2011-05-05 2024-01-11 Continental Automotive Technologies GmbH Master cylinder, especially for a regulated braking system
DE102011114708A1 (en) * 2011-09-30 2013-04-04 Lucas Automotive Gmbh Master brake cylinder with improved pressure reduction behavior
DE102012014321A1 (en) * 2012-07-19 2014-01-23 Lucas Automotive Gmbh Master brake cylinder for a motor vehicle brake system with profiled pressure piston
US9925966B2 (en) 2012-07-19 2018-03-27 Lucas Automotive Gmbh Brake master cylinder for a motor vehicle brake system with profiled pressure piston
WO2015086010A1 (en) * 2013-12-09 2015-06-18 Schaeffler Technologies AG & Co. KG Master cylinder
CN105814330A (en) * 2013-12-09 2016-07-27 舍弗勒技术股份两合公司 Master cylinder
CN105814330B (en) * 2013-12-09 2018-06-19 舍弗勒技术股份两合公司 Active cylinder

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