GB1568269A - Hydraulic brake booster fluid pressure accumulator - Google Patents

Description

(54) HYDRAULIC BRAKE BOOSTER FLUID PRESSURE ACCUMULATOR (71) We, THE BENDIX CORPORATION.

a corporation organised and existing under the laws of the State of Delaware, United States of America, of Bendix Center, Southfield, Michigan 48075, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a hydraulic brake booster.

It is known to couple a hydraulic brake booster with a fluid pressure accumulator, so that, when the power source of the hydraulic brake booster circuit fails, stored pressurized fluid in the accumulator is available to provide an assistance in braking. For example, if the fan belt on a motor vehicle breaks, the power steering pump is disabled so that no source of fluid pressure is available to provide assistance to braking unless a secondary pressure source is provided, In this event, the accumulator is communicated with the brake booster pressure chamber.

However, the arrangement of such prior art hydraulic brake boosters coupled with their accumulators, is rather bulky and requires a substantial amount of space in the engine compartment. Due to the tendency of the vehicle manufacturers to reduce the size of most motor vehicles, the space available in the engine compartment is also reduced.

Therefore, the prior art brake booster arrangements can hardly be fitted in the engine compartment, which involves great difficulties as regards the installation and maintenance of the booster.

Therefore, the object of the present invention is to provide a compact hydraulic brake booster which includes a secondary pressure source for assisting brake application when the main pressure source is rendercd inoperative, so as to overcome the above mentioned drawbacks.

In accordance with the invention there is provided a hydraulic brake booster comprising a housing in which is defined a pressure chamber, spool valve means slidably disposed in said housing and cooperating with the latter to respectively communicate said pressure chamber with a low-pressure source when the spool valve means is in an idle first position and with a high-pressure source when the spool valve means is in an operating second position, a piston slidably mounted in said housing and responsive to pressure within said pressure chamber to move relative to the housing to create a brake actuating pressure, characterized in that it comprises a storage chamber defined within said piston, check valve means communicating the pressure chamber and the storage chamber when the pressure in the pressure chamber is greater than that in the storage chamber, operator-operated actuating means engaging the spool valve means to move the same from said first position to said second position, said operator-operated actuating means being adapted to control closure of communication between the high pressure source and the pressure chamber when the spool valve means is in its second position, said actuating means being also adapted to control opening of fluid communication between the storage chamber and the pressure chamber after said spool valve means has been moved to its second position and communication between the high pressure source and the pressure chamber has been closed upon actuation of said operator-operated actuating means.

A hydraulic brake booster in accordance with the invention will now be described by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a schematic illustration of a vehicle hydraulic system with a hydraulic brake booster of the present invention, shown in cross section.

Figure 2 is an enlarged fragmentary crosssectional view of the piston used in the hydraulic brake booster illustrated in Figure 1.

Referring now to the drawings, the brake booster generally indicated by the numeral 10 includes a housing 12 having an inlet port 14, an outlet port 16, and a return or exhaust port 18. The inlet port 14 is com municated to the outlet or high pressure side of the vehicle power steering pump 20, and the outlet port 16 is communicated to the inlet of the vehicle power steering gear 22. The exhaust port 18 and the outlet of the gear 22 are each connected to a reservoir (not shown) at the inlet or low pressure side of the pump 20.

The housing 12 defines first and second bores 24 and 26 therewithin. A piston 28 is slidably mounted in the bore 24 and is provided with a connecting rod 30 which transmits movement of the piston 28 to a conventional automotive master cylinder (not shown) which is mounted just to the left of the housing 12, viewing Figure 1. Of courses movement of the piston 28 to the left generates pressure in the aforementioned master cylinder in the conventional manner. One end of another rod 32 is slidably received in a bore 34 in the piston 28, and the opposite end of the rod 32 is connected to a conventional brake pedal (not shown) mounted in the vehicle operator's compartment.

A spring 40 on rod 32 urges a stop ring 38 against a bracket 36, the rod being slidably mounted in a slot in the bracket. A pivot 48 connects the bracket 36 with the intermediate portion of a lever means 44, one end of which is connected by a further pivot 42 to a bracket 46 which is integral with piston 28.

A spool valve generally indicated by the numeral 50 is slidably mounted in the bore 26 and is adapted to control fluid communication into the booster pressure chamber 52. A secondary valve 54 is slidably mounted on the end of the spool valve 50 extending into the pressure chamber 52 and a third pivot 56 connects the lever means 44 with the secondary valve 54. A spring 58 yieldably urges the secondary valve 54 away from openings 60 in the body of the spool valve 50. Another spring 62 yieldably urges the spool valve 50 into a first or brakereleased position defined by the engagement of a stop 64 carried on the spool valve 50 with a shoulder 66 provided on the wall of the bore 26. The second or brake fully applied position of the spool valve 50 is defined by the engagement of the left hand end of the spool valve 50 with a plug 68 which closes the bore 26.

The spool valve 50 and housing bore 26 include cooperating lands and grooves such that in the first position, illustrated in Figure 1, the pressure chamber 52 is vented via openings 60, passage 88 and openings 80 to the exhaust port 18. As the spool valve 50 moves to the second position with the left end of spool valve 50 abutting plug 68, the pressure chamber 52 is communicated via openings 60, passage 88 and openings 80 to the inlet port 14.

The piston 28, as illustrated more clearly in Figure 2, includes a plug 90 threadably engaging an open end of the piston. The plug and piston cooperate to form a storage chamber 92 located internally of the piston.

A diaphragm 94 slidingly engages the inner wall of the storage chamber 92, and is biased to the right viewing the Figures by a comprehensible gas medium on the left side of the diaphragm, to pressurize the fluid content of the storage chamber.

The plug 90 defines the bore 34 which slidingly receives the rod 32. The rod 32 is slotted at 114 to allow fluid communication between the rod 32 and bore 34. A check valve 96 is centrally disposed in the plug and cooperates with bore 34 to define a passage communicating the storage chamber 92 with the pressure chamber 52 when the pressure in the pressure chamber is larger than the pressure in the pressure chamber is larger than the pressure in the storage chamber. A boss 112 on the inside of plug 90 is staked at its opening to retain the ball check valve 96 within the plug. The plug 90 also carries a pressure relief valve 98 opening communication between the storage chamber and the pressure chamber when the pressure in the storage chamber is above a predetermined value.This relief valve prevents build-up of fluid pressure in the storage chamber above that which is suitable for actuating braking. Communication between the storage and pressure chambers is also established, when the pressure in the pressure chamber is below that in the storage chamber during a brake actuation, by means of a projection 100 on the rod 32, which projection engages the check valve to unseat the ball of the check valve 96.

Seal means 102 and 104 are carried within recesses on the plug and diaphragm, re respectively to seal the plug and piston and to slidingly seal the diaphragm to the inner wall of the storage chamber.

A snap ring 106 retains the diaphragm within the storage chamber and is mounted in a recess on the inner wall of the storage chamber.

The hydraulic brake booster which has been described operates as follows: When the operator presses on the brake pedal, the rod 32 moves to the left viewing Figure 1 and 2, thereby pivoting lever 44 about pivot 42 to move the spool valve 50 to the left in the second position. In this position the spool valve 50 communicates the inlet port 14 with the pressure chamber 52. Increasing pressures in the pressure chamber from the inlet port communicate with the storage chamber 92 via bore 34 and check valve 96, while also urging the piston 28 to the left to engage the connecting rod with a master cylinder for actuating braking.

If the pressure source 20 is disconnected from the hydraulic brake booster 10 or disable, no pressure is communicated to the pressure chamber 52. Moreover, no pressure is communicated to the pressure chamber 52 when the spool valve sticks. Consequently, when the operator steps on the brake pedal to shift the spool valve to the second position no movement of the piston occurs. In accordance with the invention, further movement of the rod 32 pivots the lever 44 to move the valve 54 to the left on the spool valve 50 to close openings 60, whereupon projection 100 on the rod 32 engages check valve 96 to communicate the storage chamber 92 on the right side of diaphragm 94 with the pressure chamber 52. This communication increases the pressure in the pressure chamber 52 to urge piston 28 to the left thereby actuating braking.

With the pressure source disabled or disconnected from the hydraulic brake booster, several brake applications by the operator will exhaust the pressurized fluid contained in the storage chamber. Thereafter, brake actuation proceeds as follows. Stepping on the brake pedal moves the rod 32 to the left to engage projection 100 with check valve 96.

Because the pressurized fluid is spent in preceding brake applications, no increasing pressures are communicated to the pressure chamber. Consequently, further rod movement is required to actuate braking. Such further movement pivots lever 44 about pivot 56 of spool valve 50 to move bracket 46 to the left. Since bracket 46 is integral with piston 28, movement of the bracket moves the piston to operate the master cylinder for actuating braking.

The last-mentioned braking application, which proceeds without a pressure source or a stored pressurized fluid in the storage chamber, results in a manual brake application as the rod 32 mechanically urges the rod 30 in a direction actuating the master cylinder.

Thus it is apparent from the aforemenioned description that the present invention provides a compact hydraulic brake booster with a piston defining an accumulator which permits at least one safety braking application after a pressure source for the booster has been disconnected. Thereafter, with the pressure source disconnected, the operator manually actuates braking.

WHAT WE CLAIM IS:- 1. A hydraulic brake booster comprising a housing in which is defined a pressure chamber, spool valve means slidably disposed in said housing and cooperating with the latter to respectively communicate said pressure chamber with a low-pressure source when the spool valve means is in an idle first position and with a high-pressure source when the spool valve means is in an operating second position, a piston slidably mounted in said housing and responsive to pressure within said pressure chamber to move relative to the housing to create a brake actuating pressure, said booster comprising a storage chamber defined within said piston, check valve means communicating the pressure chamber and the storage chamber when the pressure in the pressure chamber is greater than that in the storage chamber, operator-operated actuating means engaging the spool valve means to move the same from said first position to said second position, said operator-operated actuating means being adapted to control closure of communication between the high pressure source and the pressure chamber when the spool valve means is in its second position, said actuating means being also adapted to control opening of fluid communication between the storage chamber and the pressure chamber after said spool valve means has been moved to its second position and communication between the high pressure source and the pressure chamber has been closed upon actuation of said operator-operated actuating means.

2. A hydraulic brake booster as claimed in claim 1, wherein said check valve means is responsive to actuation of said actuating means for permitting said opening of fluid communication between the storage chamber and the pressure chamber.

3. A hydraulic brake booster as claimed in claim 1 or claim 2, wherein said piston carries a relief valve responsive to pressure within the storage chamber when the pressure within the storage chamber is above a predetermined value.

4. A hydraulic brake booster as claimed in anyone of the preceding claims, wherein said storage chamber defined within the piston is closed by a plug.

5. A hydraulic brake booster as claimed in claim 4, wherein a passage is defined in said plug for communicating the pressure chamber with the storage chamber, said check valve means being disposed in said passage.

6. A hydraulic brake booster as claimed in claim 4 combined with claim 3, wherein said relief valve is disposed in said plug.

7. A hydraulic brake booster as claimed in claim 5, wherein said operator-operated actuating means includes a rod portion which extends into said passage, said rod portion comprising an extension which is engageable with said check valve means, said rod portion including slots cooperating with the passage to communicate the pressure chamber to the storage chamber.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. If the pressure source 20 is disconnected from the hydraulic brake booster 10 or disable, no pressure is communicated to the pressure chamber 52. Moreover, no pressure is communicated to the pressure chamber 52 when the spool valve sticks. Consequently, when the operator steps on the brake pedal to shift the spool valve to the second position no movement of the piston occurs. In accordance with the invention, further movement of the rod 32 pivots the lever 44 to move the valve 54 to the left on the spool valve 50 to close openings 60, whereupon projection 100 on the rod 32 engages check valve 96 to communicate the storage chamber 92 on the right side of diaphragm 94 with the pressure chamber 52. This communication increases the pressure in the pressure chamber 52 to urge piston 28 to the left thereby actuating braking. With the pressure source disabled or disconnected from the hydraulic brake booster, several brake applications by the operator will exhaust the pressurized fluid contained in the storage chamber. Thereafter, brake actuation proceeds as follows. Stepping on the brake pedal moves the rod 32 to the left to engage projection 100 with check valve 96. Because the pressurized fluid is spent in preceding brake applications, no increasing pressures are communicated to the pressure chamber. Consequently, further rod movement is required to actuate braking. Such further movement pivots lever 44 about pivot 56 of spool valve 50 to move bracket 46 to the left. Since bracket 46 is integral with piston 28, movement of the bracket moves the piston to operate the master cylinder for actuating braking. The last-mentioned braking application, which proceeds without a pressure source or a stored pressurized fluid in the storage chamber, results in a manual brake application as the rod 32 mechanically urges the rod 30 in a direction actuating the master cylinder. Thus it is apparent from the aforemenioned description that the present invention provides a compact hydraulic brake booster with a piston defining an accumulator which permits at least one safety braking application after a pressure source for the booster has been disconnected. Thereafter, with the pressure source disconnected, the operator manually actuates braking. WHAT WE CLAIM IS:-

1. A hydraulic brake booster comprising a housing in which is defined a pressure chamber, spool valve means slidably disposed in said housing and cooperating with the latter to respectively communicate said pressure chamber with a low-pressure source when the spool valve means is in an idle first position and with a high-pressure source when the spool valve means is in an operating second position, a piston slidably mounted in said housing and responsive to pressure within said pressure chamber to move relative to the housing to create a brake actuating pressure, said booster comprising a storage chamber defined within said piston, check valve means communicating the pressure chamber and the storage chamber when the pressure in the pressure chamber is greater than that in the storage chamber, operator-operated actuating means engaging the spool valve means to move the same from said first position to said second position, said operator-operated actuating means being adapted to control closure of communication between the high pressure source and the pressure chamber when the spool valve means is in its second position, said actuating means being also adapted to control opening of fluid communication between the storage chamber and the pressure chamber after said spool valve means has been moved to its second position and communication between the high pressure source and the pressure chamber has been closed upon actuation of said operator-operated actuating means.

2. A hydraulic brake booster as claimed in claim 1, wherein said check valve means is responsive to actuation of said actuating means for permitting said opening of fluid communication between the storage chamber and the pressure chamber.

3. A hydraulic brake booster as claimed in claim 1 or claim 2, wherein said piston carries a relief valve responsive to pressure within the storage chamber when the pressure within the storage chamber is above a predetermined value.

4. A hydraulic brake booster as claimed in anyone of the preceding claims, wherein said storage chamber defined within the piston is closed by a plug.

5. A hydraulic brake booster as claimed in claim 4, wherein a passage is defined in said plug for communicating the pressure chamber with the storage chamber, said check valve means being disposed in said passage.

6. A hydraulic brake booster as claimed in claim 4 combined with claim 3, wherein said relief valve is disposed in said plug.

7. A hydraulic brake booster as claimed in claim 5, wherein said operator-operated actuating means includes a rod portion which extends into said passage, said rod portion comprising an extension which is engageable with said check valve means, said rod portion including slots cooperating with the passage to communicate the pressure chamber to the storage chamber.

8. A hydraulic brake booster as claimed

in anyone of the preceding claims, wherein a diaphragm is disposed within said storage chamber, said diaphragm being biased to pressurize the storage chamber.

9. A hydraulic brake booster substantially as hereinabove described and as shown with reference to the accompanying drawings.