WO1999044873A1

WO1999044873A1 - Hydraulic control unit for an anti-lock brake system having a pump for performing pressure dump function

Info

Publication number: WO1999044873A1
Application number: PCT/US1999/004668
Authority: WO
Inventors: Blaise J. Ganzel
Original assignee: Kelsey-Hayes Company
Priority date: 1998-03-05
Filing date: 1999-03-04
Publication date: 1999-09-10
Also published as: AU2980499A

Abstract

The invention relates to a hydraulic control unit (18, 118) for use in a vehicular anti-lock braking system (10, 110) comprising at least a piston pump and control valves (20, 120). The invention is characterized by the pump having a third pump chamber (28, 128) located around at least one of the pump pistons (56, 16) delimiting at its first end (54) a first pump chamber (24, 124) wherein the pump chambers (24, 28, 124, 128) are in fluid communication with the control valves (20, 120) and adapted to be connected in fluid communication with the wheel brakes (16, 116) for transferring hydraulic fluid from the corresponding wheel brake (16, 116) to the corresponding control valve (20, 120).

Description

TITLE

HYDRAULIC CONTROL UNIT FOR AN ANTI-LOCK BRAKE SYSTEM

HAVING A PUMP FOR PERFORMING PRESSURE DUMP FUNCTION

CROS S REFERENCE TO RELATED APPLICATION

This claims the benefit of U.S. provisional patent application identified as Application Number 60/076,902, filed March 5, 1998.

BACKGROUND OF THE INVENTION This invention relates in general to vehicular brake systems. More specifically, this invention relates to a hydraulic control unit for use in a vehicular anti-lock brake system.

Typical hydraulic control units used in vehicular anti-lock brake systems include a housing having a plurality of fluid control valves or isolation valves for modulating the flow of hydraulic fluid to corresponding wheel brakes during an anti-lock braking event. The housing further includes multiple fluid control valves or dump valves for modulating hydraulic flow from the wheel brakes during the anti-lock braking event. A pump disposed in the housing transfers hydraulic fluid from the dump valves to the isolation valves during the anti-lock braking event. The pump includes a pair of opposing pistons and cylinders each of which define a single pump chamber. Each pump chamber is dedicated to at least one of the isolation valves and to at least one of the dump valves. During the dump mode of an anti-lock braking event, the isolation valve corresponding to the wheel brake associated with the anti-lock braking event momentarily closes, thereby interrupting the flow of fluid to the corresponding wheel brake. At the same time, the dump valve corresponding to the wheel brake associated with the anti-lock braking event opens allowing the pump to draw fluid from the wheel brake.

It is desirable to reduce the cost of the hydraulic control unit by reducing the number of required components and by reducing the required manufacturing operations in producing a housing which can accommodate the required components. It is also desirable to reduce to package size and weight of the hydraulic control unit by reducing the number of required components.

SUMMARY OF THE INVENTION

This invention relates to a hydraulic control unit for use in a vehicular anti-lock brake system. The hydraulic control unit includes a plurality of control valves mounted on a housing. Each of the control valves modulates the flow of hydraulic fluid to at least one of a plurality of wheel brakes during an anti-lock event. An eccentric drive means presenting a drive axis is movably disposed in a cavity of the housing. First and second cylinders extend from the cavity opposite each other and substantially perpendicular to u e drive axis. First ends of first and second pistons are slidably disposed in the first and second cylinders, respectively. Second ends of the pistons extend from the corresponding cylinders and engage the drive means whereby die drive means alternatively moves the pistons in opposite directions with respect to the drive axis during an anti-lock event.

A first pump chamber is formed between the first piston and the first cylinder adjacent to the first end of the first piston. A second pump chamber is formed between the second piston and the second cylinder adjacent to the first end of the second piston. A third pump chamber is formed between the first piston and the first cylinder and between the first and second ends of the first piston. Each of the pump chambers is in fluid communication with at least one of the control valves and is adapted to be connected in fluid communication with at least one of the wheel brakes. In response to the rotation of the drive means, the pistons pump hydraulic fluid into each of the pump chambers from the corresponding wheel brakes and out of each of the pump chambers to the corresponding control valves.

This invention eliminates dump valves commonly associated with typical hydraulic control units used in anti-lock brake systems. Consequently, the component and manufacturing costs and the package size and weight of the hydraulic control unit are reduced. Accordingly, this invention provides a hydraulic control unit for use in a vehicular anti-lock brake system that is relatively inexpensive, compact, and lighter.

Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRA INGS FIG. 1 is a schematic circuit diagram of a vehicular anti-lock brake system according to a first embodiment of this invention.

FIG. 2 is sectional view of a portion of the hydraulic control unit illustrating pistons and drive means according to the invention as shown in FIG. 1. FIG. 3 is sectional view taken along the line 3-3 of FIG. 2. FIG. 4 is a schematic circuit diagram of a vehicular anti-lock brake system according to a second embodiment of this invention.

FIG. 5 is a sectional view of a portion of the hydraulic control unit illustrating pistons and drive means according to the invention as shown in FIG. 4, FIG. 6 is sectional view taken along the line 6-6 of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicular anti-lock brake system according to a first embodiment of this invention is illustrated generally at 10 in FIG. 1. The system 10 comprises a brake pedal 12 connected to a master cylinder 14 for providing pressurized fluid to a plurality of wheel brakes 16. The wheel brakes 16 are shown as a disc brake but may be of any well-known type.

A hydraulic control unit (HCU) 18 is connected in fluid communication with the master cylinder 14 and each of the wheel brakes 1 for controlling the flow hydraulic fluid to and from the wheel brakes 16 during an anti-lock braking event. The HCU 18 includes α plurality of control valves 20. The control valves 20 are normally open solenoid valves of a well know type. Each of the control valves 20 modulates the flow of hydraulic fluid to at least one of the wheel brakes 16. The preferred embodiment as illustrated in FIG. 1 shows three control valves 20. Two of the control valves 20 independently control fluid flow to a separate wheel brake 16, while the remaining control valve 20 controls fluid flow to a pair of different wheel brakes 16.

The HCU 18 further includes first, second and third pump chambers 24, 26 and 28, respectively, for transferring fluid from corresponding wheel brakes 16 to corresponding control valves 20 during an anti-lock brake event. As shown in FIG. 1 , each of the first and third pump chambers 24 and 28 arc each in fluid communication wim independent wheel brakes 1 . Each of the first and third pump chambers 24 and 28 are also in fluid communication with a common pair of control valves 20. The second pump chamber 26 is in fluid communication with a pair of wheel brakes 16 independent from the wheel brakes 16 corresponding to the first and third pump chambers 24 and 28. The second pump chamber 26 is also in fluid communication with a control valve 20 separate from the control valves 20 corresponding to the first and third pump chambers 24 and 28.

As illustrated in FIGS. 2 and 3, the HCU 18 further includes a housing 30 having a cavity 32. An eccentric drive means, indicated generally at 34, is movably disposed in the cavity 32. The drive means 34 includes a drive shaft 36 presenting a drive axis A and rotatably driven by a motor 38. The drive shaft 36 is fixedly disposed in an eccentric bearing 40. The eccentric bearing 40 is rotatably disposed in a load-bearing ring 42. The load-bearing ring 42 is movably disposed in the cavity 32. The load-bearing ring 42 includes a pair of opposing curved inner surfaces 44 huving a radius slightly greater than the radius of the eccentric bearing 40. The curved inner surfaces 44 are connected by a pair of opposing and substantially flat inner surfaces 46 whereby the eccentric bearing 40 alternatively rollably engages the flat inner surfaces 46. The load-bearing ring 42 further includes a pair of opposing and substantially flat outer surfaces 48.

A first cylinder 50 and a second cylinder 52 extend from the cavity 32 opposite one another and substantially perpendicular to the drive axis A. A first end 54 of a First piston 56 and first end 58 of a second piston 60 are slidably disposed in receiving bores formed in the first and second cylinders 50 and 52, respectively. A second end 62 of the first piston 56 and a second end 64 of the second piston 60 extend from the first and second cylinders 50 and 52, respectively, and engage the flat outer surfaces 48 of the load-bearing ring 42, whereby the load-bearing ring 42 alternatively moves the pistons 56 and 60 in opposite directions with respect to the drive axis A during an anti-lock event.

The first pump chamber 24 is formed in the unoccupied space between the first piston 56 and the first cylinder 50 adjacent the first end 54 of the first piston 56. The second pump chamber 26 is formed in the unoccupied space between the second piston 60 and the second cylinder 52 adjacent to the first end 58 of the second piston 60. The third pump chamber 28 is formed in the unoccupied space between the first piston 56 and the first cylinder 50 along a mid-portion of the first piston 56 between its first and second ends 54 and 62. A plurality of seal members 66 such as O-rings are disposed about the pistons 56 and 60 for sealing the pump chambers 24, 26, and 28. A biasing spring 68 is disposed each of the receiving bores of the cylinders

50 and 52 for maintaining engagement between the pistons 56 and 60 and the load- bearing ring 42. One end of the biasing spring 68 engages a spring collar 70 formed on the corresponding piston 56, 60, and the other end of the biasing spring 68 engages a spring seat 72 formed in the corresponding cylinder 50, 52. As illustrated in FIG. 3, the HCU 18 further includes a plurality of inlet and outlet check valves, 74 and 76, respectively. One of each the inlet 74 and outlet 76 check valves are connected in fluid communication with one of each of the pump chambers 24, 26 and 28. The inlet check valves 74 prevent the transfer of hydraulic fluid from the pump chambers 24, 26 and 28 to the corresponding wheel brakes 16. The outlet check valves 76 prevent d e transfer of hydraulic fluid to the pump chambers 24, 26 and 28 from the corresponding control valves 20.

In operation, during an anti-lock event, the motor 38 rotates the drive shaft 36, which rotates the eccentric bearing 40. In turn, the eccentric bearing 40 forces the load-bearing ring 42 to move along the longitudinal axis of the pistons 56 and 60 in a back and forth manner. The load-bearing ring 42 alternatively forces one the pistons 56, 60 to slide in a direction away from the drive axis A compressing a corresponding biasing spring 68. At the same time, the biasing spring 68 of the opposite piston 56, 60 forces the corresponding piston 56, 60 to slide toward the drive axis A. The movement of the pistons 56 and 60 produces a pumping action in the corresponding pump chambers 24, 26 and 28 which causes fluid to be drawn from the corresponding wheel brakes 16 and supplied to the corresponding control valves 20. The control valve 20 corresponding to a particular wheel brake 16 experiencing the anti-lock event is switched to a closed position, thereby interrupting the flow of fluid to the particular wheel brake 16. The pistons 56 and 60 continue to pump fluid from each of the corresponding wheel brakes 16 reducing the fluid pressure in the particular wheel brake. A particular control valve 20 may be switched between the open and closed positions several times before the pressure in a corresponding wheel brake 16 is corrected to a pressure that would eliminate the anti-lock event. Once the anti-lock event, has ended, the motor 38 is turned off and a given control valve 20 is switched back to the open position.

A vehicular anti-lock brake system according to u second embodiment of this invention is generally shown at 100 in FIG. 4. The system 100 is similar to the system 10 with a principle difference being that the system 100 comprises a HCU 1 18 including a fourth pump chamber 178 for transferring fluid from an independent wheel brake 116 to a corresponding pair of control valves 120. The HCU 1 18 further includes a second pump chamber 126 in fluid communication with an independent wheel brake 1 16, and in fluid communication with the pair of control valves 120 corresponding to the fourth pump chamber 178. Each of the first and third pump chambers 124 and 128 arc in fluid communication with independent wheel brakes 1 16 and are in fluid communication with control valves 120 separate from the control valves 120 corresponding to the second and fourth pump chambers 126 and 178. As illustrated in FIGS. 5 and 6, the fourth pump chamber 178 is formed in the unoccupied space between the second piston 160 and the second cylinder 152 along a mid-portion of the second piston 169 between its first and second ends 158 and 164. O-rings 166 are disposed about each of the pistons 156 and 160 for sealing the pump chambers 124, 126, 128 and 178. A biasing spring 168 is disposed about each of the pistons 156 and 160 for maintaining engagement between the pistons 156 and 160 and the driving means 134.

As shown in FIG. 6, an inlet check valve 174 is in fluid communication with each of the pump chambers 124, 126, 128 and 178 for preventing the transfer of hydraulic fluid from the pump chambers 124, 126, 128 and 178 to the corresponding wheel brakes 116. An outlet check valve 176 is in fluid communication with each of the pump chambers 124, 126, 128 and 178 for preventing the transfer of hydraulic fluid from the pump chambers 124, 126, 128 and 178 to the corresponding control valves 120.

The HCU 118 operates in a like manner to the HCU 18 as described, except that the second and fourth pump chambers 126 and 178 draw fluid from separate wheel brakes 116 and supply fluid to a common pair of control valves 120 during an anti-lock event.

The drive means 34 as described provides the function of eliminating the sliding contact between the pistons and the eccentric drive shaft typical of a prior art hydraulic control unit in which a load-bearing ring is absent. Accordingly, the described drive means 34 is not limited to the disclosed HCU's 18 and 118, but can be used in combination with otiier prior art types of hydraulic control units for use in anti-lock brake systems. In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.

Claims

WHAT IS CLAIMED IS: 1 . A hydraulic control unit for use in a vehicular anti-lock braking system comprising: a housing having a cavity; a plurality of control valves mounted on the housing so that each of the control valves modulates the flow of hydraulic fluid to at least one of a plurality of wheel brakes during an anti-lock event; an eccentric drive means presenting a drive axis rotatably disposed in the cavity; a first cylinder and a second cylinder, said cylinders extending from the cavity opposite each other and substantially perpendicular to the drive axis; a first piston and a second piston, each of the pistons having a first end and a second end, the first ends of the first and second pistons slidably disposed in the first and second cylinders, respectively, the second ends of said pistons extending from said corresponding cylinders and engaging the drive means so that the drive means alternatively moves the pistons in opposite directions with respect to the drive axis; a first pump chamber formed between the first piston and the first cylinder adjacent the first end of the first piston, the first pump chamber being in fluid communication with at least one of the control valves and adapted to be connected in fluid communication with at least one of the wheel brakes for transferring hydraulic fluid from the corresponding wheel brake to the corresponding control valve; a second pump chamber formed between die second piston and the second cylinder adjacent the first end of said second piston, the second pump chamber being in fluid communication with at least one of the control valves and adapted to be connected in fluid communication with at least one of the wheel brakes for transferring hydraulic fluid from the corresponding wheel brake to the corresponding control valve; and a third pump chamber formed between the first piston and the first cylinder between the first and second ends of the first piston, the third pump chamber being in fluid communication with at least one of the control valves and adapted to be connected in fluid communication with at least one of the wheel brakes for transferring hydraulic fluid from the corresponding wheel brake to the corresponding control valve.

2. The hydraulic control unit according to claim 1 wherein the drive means includes a load-bearing ring and an eccentric drive shaft rotatably disposed in the ring, the ring engaging each of the second ends of the pistons for sliding the pistons.

3. The hydraulic control unit according to claim 2 wherein the ring includes a pair of opposing curved inner surfaces having a radius slightly greater than the radius of the eccentric drive shaft, the curved surfaces being connected by a pair of opposing and substantially flat inner surfaces whereby the eccentric drive shaft alternatively r╧àllably engages the flat inner surfaces.

4. The hydraulic control unit as set fourth in claim 3 wherein the ring includes a pair of opposing and substantially flat outer surfaces, each of the flat outer surfaces engaging one of the second ends of the pistons.

5. The hydraulic control unit according to claim 1 including a biasing spring disposed in each of the cylinders for maintaining engagement between the pistons and the drive means.

6. The hydraulic control unit according to claim 1 including at least one seal member disposed about the pistons for sealing the chambers.

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7. The hydraulic control unit according to claim 1 including a plurality of inlet check valves and a plurality of outlet check values, each the inlet and outlet check valves being in fluid communication with one of each of the pump chambers for preventing the transfer of hydraulic fluid from the pump chambers to the corresponding wheel brakes and for preventing the transfer of hydraulic fluid to the pump chambers from the corresponding control valves, respectively.

8. The hydraulic control unit as set fourth in claim 1 wherein the control valves are normally open solenoid valves,

9. The hydraulic control unit as set fourth in claim 1 including a fourth pump chamber formed between the second piston and the second cylinder between the first and second ends of the second piston, the fourth pump chamber being in fluid communication with at least one of the control valves and adapted to be connected in fluid communication with at least one of the wheel brakes for transferring hydraulic fluid from the corresponding wheel brake to the corresponding control valve.

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