WO2005030543A1

WO2005030543A1 - Hydraulic brake system micro-regulator

Info

Publication number: WO2005030543A1
Application number: PCT/AU2004/001347
Authority: WO
Inventors: John Curtis; Harry Van Hees
Original assignee: The Innovation Network Pty Ltd
Priority date: 2003-10-02
Filing date: 2004-09-30
Publication date: 2005-04-07

Abstract

A hydraulic brake system micro-regulator characterized in that it includes a housing; said housing having therein a fluid inlet and a fluid outlet connected by a through passage extending therebetween, said through passage providing for passage of hydraulic fluid under pressure therethrough; - a fluid receiving cavity located within said housing, said cavity communicating with said through passage and further communicating with a bleed passage intersecting said through passage, said cavity housing a hollow resilient bulb means positioned in said cavity, said bulb extending only partially into cavity and leaving an expansion space between a base of bulb and a base of said cavity; and a compressible member located in said expansion space below said hollow resilient bulb means, wherein said compressible member serves to resist expansion of said bulb under pressure.

Description

Hydraulic Brake System Micro-regulator

FIELD OF THE INVENTION

The present invention relates to a hydraulic brake system pressurised micro-regulator, modulator or accumulator. The micro-regulator of the invention finds application in motor vehicle hydraulic braking systems.

BACKGROUND OF THE INVENTION

During a braking operation in a vehicle depression of the foot pedal exerts pressure on hydraulic fluid in the braking system. In turn the non-compressible hydraulic fluid transmits the pressure to thereby move the brake callipers or shoes. Dimensional factors at the friction surface, for example, variations in thickness of the discs results in high or low spots at the disc surface, or eccentricities in the brake drums, produce undesirable momentary increases or decreases in hydraulic pressure.

The sudden variation in the hydraulic pressure in the braking system causes inter alia heat build up, excessive wear and tear on the brake system in general and a reduction in braking efficiency. Importantly, brake fade increases and premature wheel lock-up may occur. Overall the potential life of the brakes is substantially reduced.

The hydraulic fluid in the system transmits the pressure variations that then oscillate through the system as secondary pressure spikes.

Attempts to resolve the dilemma of secondary pressure spikes have been put forward. In general, these devices are not satisfactory as they result in a longer brake pedal stroke. An increase in the brake pedal stroke required to produce a significant braking effect is potentially dangerous as the speed with which a braking operation comes into effect may be reduced thereby altering the responsiveness of the braking action. Such devices also significantly alter the feel of the pedal for the driver introducing 'sponginess' into the brake that is generally undesirable.

It is to this situation that the present invention is addressed. The invention provides an alternative to currently available hydraulic brake system regulators. SUMMARY OF THE INVENTION

Therefore according to a first aspect of the present invention there is provided a hydraulic brake system micro-regulator including a housing - said housing having therein a fluid inlet and a fluid outlet connected by a through passage extending therebetween, said through passage providing for passage of hydraulic fluid under pressure therethrough; - - a fluid receiving cavity located within said housing, said cavity communicating with said through passage and further communicating with a bleed passage intersecting said through passage, said cavity housing a hollow resilient bulb means positioned in said cavity, said bulb extending only partially into cavity and leaving an expansion space between a base of bulb and a base of said cavity; and - a compressible member located in said expansion space below said hollow resilient bulb means, wherein said compressible member serves to resist expansion of said bulb under pressure.

Preferably, the compressible member is a closed cell foam pad. The micro-regulator 10 responds to pressure in the system by compressing the compressible member and the compressed air retained therein in an axial direction and thus reaches a position of equilibrium. The compressible rubber bulb absorbs secondary pressure spikes in the system.

Preferably, the rubber bulb, once lubricated is a close radial interference fit in the cavity and any expansion of the bulb is thus permitted only in the axial direction, radial expansion being prevented by the close fit of the bulb in the cavity. A consequence of the limitation of the bulb to axial expansion and movement is the ability of the bulb to act as a piston within the cavity moving under the influence of pressure in the micro- regulator, said movement being modified by the compressible member with its retained compressed air. It can also be observed that the close fit between the extended bulb and an inner wall of the cavity ensures that during assembly of the micro-regulator air in the cavity is trapped below the bulb and enters the compressible member, thus providing for pressurisation.

The compressible member is thus at overpressure and able to more easily maintain equilibrium in the system. In a further form of the invention there is provided a hydraulic brake system pressurised micro-regulator including a housing, - said housing having therein a fluid inlet and a fluid outlet connected by a through passage extending therebetween, said through passage providing for passage of hydraulic fluid under pressure therethrough; - a fluid receiving cavity located within said housing, said cavity communicating with said through passage and further communicating with a bleed passage intersecting said through passage, said cavity housing a hollow resilient bulb means positioned in said cavity, said bulb having a non-uniform linear outer side wall surface to facilitate the retention of a silicon lubricant, said bulb being axially extended with a compressible member adhered thereto, said compressible member having a cylindrical cavity in its centre to serve as a compressed air chamber. - said compressible member and the retained compressed air serve to resist axial expansion of said bulb under pressure.

In a preferred form of the invention the bulb has an uppermost radially extending flange, said flange serving to position the bulb with respect to the cavity. The flange neatly is captured between two halves of the housing thereby restraining the extent of the axial movement of the bulb.

In a particularly preferred form of the invention the flange is pinched and compressed between upper and lower housing portions forming a pressure tight seal.

DESCRIPTION OF DRAWINGS

The following detailed description of the invention refers to the accompanying drawings. Although the description includes exemplary embodiments, other embodiments are possible, and changes may be made to the embodiments described without departing from the spirit and scope of the invention. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts.

Figure 1 illustrates in perspective view a hydraulic brake system pressurised micro-regulator in accordance with a first aspect of the present invention;

Figure 2 shows the micro regulator of figure 1 in cross-sectional view; Figure 3 illustrates the micro regulator of figure 1 in exploded perspective view;

Figure 4 shows the micro regulator of figure 1 in exploded cross-sectional view

Figure 5 illustrates a micro regulator in accordance with a second embodiment of the present invention in exploded perspective view; and

Figure 6 shows the micro regulator of figure 5 in exploded cross-sectional view;

Figure 7 illustrates a micro regulator in accordance with a third embodiment of the present invention in cross sectional assembled view; and

Figure 8 shows the micro regulator of figure 6 in exploded cross-sectional view

DESCRIPTION OF THE PREFERRED EMBODIMENT

Shown in the figures 1-4 is a hydraulic brake system pressurised micro regulator 10 formed in accordance with the present invention.

The micro-regulator 10 includes a housing comprised of an upper housing portion 12 and a lower housing portion 14. The upper and lower housing portions are connectable to one another by means of a threaded connection 16. The upper and lower housing portions 12, 14 are formed of aluminium although a variety of alternative materials are suitable for the construction of the device. When assembled the device 10, as shown in figure 1 is generally cylindrical.

The upper housing portion 12 includes an inlet member 18 and an outlet member 20. The inlet member 18 and outlet member 20 serve to connect the micro-regulator 10 into a normal hydraulic brake system. The inlet 18 and outlet 20 extend radially into the upper portion of the housing 12. Typically, the micro-regulator 10 would be connected to the output of the brake master cylinder of a motor vehicle braking system. The inlet 18 leads to the master cylinder discharge. A through passage 22 in the upper housing 12 carries hydraulic fluid (not shown) through the device 10 from the inlet 18 to the outlet 20. As can be seen in figure 2 the through passage 22 has a narrowed central section 24. A bleed valve 26 suitable for connection to a discharge tube is threadedly connected to the upper portion of the housing 12 through a bleed passage 28 therein. The bleed passage 28 extends downwardly from an upper surface of the upper housing portion 12 and extends orthogonally through the housing to the through passage 22 and intersects the through passage 22 at the narrowed central portion 24. The bleed valve 26 operates in known manner.

The passage 28 extends downwardly beyond the through passage 22 and opens into a cavity 30. The cavity 30 is bound by inner walls 32 and 34 of the upper and lower body portions respectively. The cavity 30 is thus in fluid communication with the passage 28 and also with the through passage 22. Accordingly, hydraulic pressure in the fluid in tfcie system will be reflected in the cavity 30.

Positioned in the cavity is a rubber bulb 36. The bulb 36 is formed of a synthetic rubber material, for example, ethylene propylene diene monomer with a durometer hardness in the range of 70-80. The bulb 36 is a close fit against the sidewalls of the cavity 30. Indeed, the bulb 36 requires lubrication and careful positioning in order to be assembled as shown. It can also be seen that the bulb 36 does not occupy the entire space of the cavity 30 and that expansion are located both above the cavity as seen at 38 and below the cavity as seen at 40.

The lower expansion space 40 is occupied by a closed cell foam compressible member 42. The member 42 is significantly less dense than the bulb 36 having durometer hardness in the range 20-45. In the embodiment under consideration closed cell foam is used to occupy the expansion space 40. It is possible to use other air entrapping materials such as open cell foam in alternative embodiments. However, it is the view of the inventor that closed cell foam with its ability to retain air provides a more beneficial outcome. Nevertheless the invention is not to be taken as being limited to these features.

The bulb 36 is generally cylindrical in shape and at its lower end includes square corners 44 leading to a flat base 46. The corners 44 allow air in the cavity to be sealed therein straight underneath the bulb and prevent it from escaping and forcing the air into the foam pad 42. Because of the close fit between the bulb and the inner sidewalls of the cavity 30 the bulb 36 is lubricated with a silicone lubricant to facilitate insertion. As the bulb 36 is inserted into the cavity 30 the air in the cavity is trapped. Trapping the air in a relatively confined space in this manner pressurizes the expansion space 40 below the bulb and thus provides a positive pressure acting on the bulb 36 biasing the bulb upwardly.

The bulb 36 is supported within the cavity 30 by an uppermost flange 48 extending around the edge of the bulb. The flange 48 rests on an upwardly extending and rounded rim 50 of the lower housing portion 14. Upper housing portion 12 includes a downwardly extending and rounded rim 52 spaced within its inner wall 32 and when the micro-regulator is assembled, rims 50 and 52 are axially aligned. As the micro- regulator is assembled rims 50 and 52 pinch the flange 48 thereby locking the bulb 36 into its designated operating position as shown in figure 2. This locking mechanism causes the uppermost exposed surface 54 of bulb 36 to expand and become slightly _<_ rounded within the cavity 30. This can be seen to advantage by a comparison of the appearance of the bulb 36 in figures 2 and 4. The flange 48 is, in practice, of the order of 4.5mm thickness. In the operative position the flange is compressed to a thickness of approximately 2mm.

When fluid (not shown) is introduced into the cavity 30 and subjected to hydraulic pressure, it spreads out over the surface 54. This action assists the operation of the micro-regulator 10. When a secondary pressure spike occurs the excess fluid spreads over the surface 54 and then only a small piston like movement of the rubber bulb is required to absorb the excess pressure. The trapped air underneath the bulb 36 in the compressed member 42 further assists the process. As the surface area underneath the bulb 36 is smaller than the combined surface area of the bulb in contact with the fluid the regulating device 10 can be achieved by only a minimal movement of the bulb. The effect of a pressure spike is thereby minimised without unduly affecting the operation or feel of the brake pedal stroke by the user.

Illustrated in figures 5 and 6 is a micro-regulator 60 in accordance with a second embodiment of the present invention. The micro-regulator 60 is, in many respects similar to the micro-regulator 10 described hereinabove. For simplicity the same reference numbers will be used throughout the drawings to refer to like parts. The micro-regulator 60 thus includes an upper housing portion 12 and a lower housing portion 14 formed in the manner previously described. Importantly, the upper housing portion 12 includes the passages 22 and 28 and a bleed valve 26.

However, positioned in the cavity 30 of the microregulator 60 is a rubber bulb 62. The bulb 62 is formed of a synthetic rubber material, for example, ethylene propylene diene monomer with a durometer hardness in the range of 70-80. The bulb 62 has a ridged outer side wall 64 to facilitate the retention of a non compressible lubricating gel and is a close fit against the sidewalls of the cavity 30, once lubricated.

The lower expansion space 40 is occupied by a closed cell foam compressible member 76. The compressible member 66 includes a central expansion aperture 68. The member 66 is significantly less dense than the bulb 62 having durometer hardness in the range 20-45. It is possible to use other air entrapping materials such as open cell foam in alternative embodiments. However, it is the view of the inventor that closed cell foam with its ability to retain air provides a more beneficial outcome. Nevertheless the invention is not to be taken as being limited to these features.

The responsiveness of the micro-regulator of the invention may be modified by varying the density of the compressible member 42. For example, in larger vehicles where the master cylinder piston diameter is larger a lower density foam is preferred. By contrast in smaller vehicles a higher density foam may be preferred.

Illustrated in figures 7 and 8 is a micro-regulator 70 in accordance with a second embodiment of the present invention. The micro-regulator 70 is, in many respects similar to the micro-regulator 10 described hereinabove. For simplicity the same reference numbers will be used throughout the drawings to refer to like parts. The micro-regulator 70 thus includes an upper housing portion 12 and a lower housing portion 14 formed in the manner previously described. Importantly, the upper housing portion 12 includes the passages 22;and 28 and a bleed valve 26. In addition the housings 12 and 14 includes the cavities 30 and 40 as in the device shown in figures 1- 4.

However, positioned in the cavity 30 of the microregulator 70 is a rubber bulb 72. The bulb 72 is formed of a synthetic rubber material, for example, ethylene propylene diene monomer with a durometer hardness in the range of 70-80. The bulb 72 has a ridged outer side wall 74 to facilitate the retention of a non compressible lubricating gel and is a close fit against the sidewalls of the cavity 30, once lubricated. The bulb 72 further includes a circumferential groove 76 cut into a lower surface thereof and an uppermost dimple 78 on an uppermost surface thereof.

The micro-regulators 60 and 70 are used and functions in the same manner as the micro-regulator 10 Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus.

In any claims that follow and in the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.

Claims

1. A hydraulic brake system micro-regulator characterized in that it includes a housing; said housing having therein a fluid inlet and a fluid outlet connected by a through passage extending therebetween, said through passage providing for passage of hydraulic fluid under pressure therethrough; - a fluid receiving cavity located within said housing, said cavity communicating with said through passage and further communicating with a bleed passage intersecting said through passage, said cavity housing a hollow resilient bulb means positioned in said cavity, said bulb extending only partially into cavity and leaving an expansion space between a base of bulb and a base of said cavity; and a compressible member located in said expansion space below said hollow resilient bulb means, wherein said compressible member serves to resist expansion of said bulb under pressure.

2. A hydraulic brake system micro-regulator according to claim 1 , characterized in that the compressible member is a closed cell foam pad.

3. A hydraulic brake system micro-regulator according to claim 1 , characterized in that the hollow resilient bulb means is a compressible rubber bulb.

4. A hydraulic brake system micro-regulator according to claim 2, characterized in that the micro-regulator responds to pressure in the system by compressing the compressible member and the compressed air retained therein in an axial direction and thus reaches a position of equilibrium.

5. A hydraulic brake system micro-regulator according to claim 2, characterized in that the hollow resilient bulb means absorbs secondary pressure spikes in the system.

6. A hydraulic brake system micro-regulator according to claim 1 , characterized in that the hollow resilient bulb means is a close radial interference fit in the cavity and any expansion of the bulb is permitted only in the axial direction, radial expansion being prevented by the close fit of the bulb in the cavity.

7. A hydraulic brake system micro-regulator according to claim 1 , characterized in that the hollow resilient bulb means has a non-uniform linear outer side wall surface to facilitate the retention of a silicon lubricant, said bulb being axially extended with a compressible member adhered thereto, said compressible member having a cylindrical cavity in its centre to serve as a compressed air chamber; said compressible member and the retained compressed air serve to resist axial expansion of said bulb under pressure.

8. A hydraulic brake system micro-regulator according to claim 1 , characterized in that the hollow resilient bulb means has an uppermost radially extending flange, said flange serving to position the bulb with respect to the cavity.

9. A hydraulic brake system micro-regulator according to claim 9, characterized in that the hollow resilient bulb means the flange is pinched and compressed between upper and lower housing portions forming a pressure tight seal.