Claims:We Claim:

1. A valve (103) to prevent passage of fluid, said valve comprising :
- a housing (200)
- a first port (202) disposed in said housing
- a second port (204) disposed in said housing
- a membrane (206) separating the said first port (202) from said second port (204)
- a sealing member (208) disposed close to said membrane (206), said sealing member (208) and said membrane (206) controlling passage of fluid from said first port (202) to said second port (204)
said valve (103) characterized by
- a magnetic washer 206b embedded along the circumference of said membrane (206)
- a metal insert as part of sealing member (208)

2. A vacuum check valve (103) wherein said membrane (206) with magnetic washer 206b is movably disposed close to sealing element (208), with a pre-tension
3. A vacuum check valve (103) wherein when the engine is not running, said membrane (206) with magnetic washer (206b) and said sealing element (208) with said metal insert attract to each other to seal the passage of fluid from said first port (202) to said second port (204)
4. A vacuum check valve (103) wherein when the engine is not running, said membrane (206) with magnetic washer (206b) moves towards the sealing element (208) because of pre-tension
5. A vacuum check valve (103) wherein when the engine is running, said membrane (206) with magnetic washer (206b) moves away from sealing element (208) because of pressure difference on the two sides of the membrane (206)
6. A vacuum check valve (103) wherein said magnetic washer (206b) is covered with rubber (206a) on both sides
7. A vacuum check valve (103) wherein said membrane (206b) is made of resilient material like rubber
8. A vacuum check valve (103) wherein said membrane (206) expands when force is applied on one side
9. A vacuum check valve (103) wherein said membrane (206) is embedded with a metal washer
10. A vacuum check valve (103) wherein a magnetic insert forms part of said sealing element (208)

11. A vacuum brake booster (102) for a braking system, said vacuum booster comprising:
- A first chamber (102a)
- A second chamber (102b), said first chamber and second chamber separated by a valve
- A membrane 105 separating said first and second chambers (102a, 102b)
- A push rod (114) coupled to said membrane (105)
- A vacuum check valve (103) said check valve (103) comprising
- a housing (200)
- a first port (202) disposed in said housing
- a second port (204) disposed in said housing
- a membrane (206) separating the said first port (202) from said second port (204)
- a sealing member (208) disposed close to said membrane (206), said sealing member (208) and said membrane (206) controlling passage of fluid from said first port (202) to said second port (204);
said valve (103) characterized by
- a magnetic washer (206b) embedded along the circumference of said
membrane (206)
- a metal insert as part of sealing member (208)
, Description: Complete Specification:

The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed.
Field of the invention
[001] This invention relates to the field of brake vacuum boosters for vehicles. The invention in particular relates to a valve to prevent leakage of vacuum or entry of atmospheric pressure in a vacuum brake booster.

Background of the invention

[002] Now days, the vehicles use vacuum booster for braking the vehicle. The vacuum booster is used to reduce the manual force required for press the brake pedal to brake the vehicle. The Vacuum brake boosters make use of vacuum generated by the engine to amplify the force applied by foot on the brake pedal. Thus with little force applied at the brake pedal, the force is amplified by the brake booster and larger force is transferred to the pistons to generate appropriate hydraulic force. The vacuum booster needs vacuum in one chamber to generate the force. This vacuum is generated when the engine is running. When the engine is switched off, the vacuum in the chamber slowly starts leaking to the atmosphere.

[003] Some prior arts try to reduce the leakage of the vacuum by modifying the diaphragm or mounting of the diaphragm. One prior art KR19980060726U discloses a brake booster, the diaphragm has a plurality of mounting holes in the circumferential direction with constant annular spacing. The mounting holes are through formed. The prior art US2009071147A discloses a control system and a method to detect leakage of vacuum in a brake booster. The system includes an engine evaluation module that detects an engine off condition. A pressure evaluation module, during the engine off condition, monitors hydraulic brake line pressure, detects a change in brake booster pressure, and determines a brake booster vacuum decay rate based on the change in brake booster pressure. A fault reporting module detects a brake booster system fault based on the brake line pressure and the brake booster vacuum decay rate.

Brief description of the accompanying drawing

[004] Different modes of the invention are disclosed in detail in the description and illustrated in the accompanying drawing:

[005] Fig. 1 illustrates a braking system for a vehicle
Fig. 2 and 3 illustrate a valve with a magnetic sealing.

Detailed description of the embodiments

[006] FIG. 1 illustrates a typical braking system 100 for a vehicle. The braking system may be a completely mechanical and hydraulic system or a combination of mechanical, hydraulic and electronics system. The braking system 100 typically comprises a vacuum brake booster 102, a tandem master cylinder 104, a brake oil reservoir 106, a hydraulic circuit 108, a brake caliper 110, a brake pedal 112 and a brake push rod 114. The brake pedal 112 is mechanically coupled to the brake push rod 114. The brake booster 102 comprises of two chambers 102a and 102b with a membrane 105 separating the two chambers. The chamber 102a is referred as working chamber and chamber 102b is referred as vacuum chamber. The membrane 105 is made of elastomeric material. The push rod comprises 114 comprises 3 parts, 114a, 114b and 114c. A spring 116 maintains the push rod at a predefined position when there is no force on the brake pedal. The hydraulic circuit 108 is coupled to a brake caliper 110. The brake caliper applies force on the brake disc 111 to reduce the speed of the vehicle whenever brake pedal is pressed by the user. The vacuum chamber 102b is connected to a vacuum source through a vacuum check valve 103.

[007] There is a first valve connecting the working chamber 102a to the atmosphere whenever brake pedal is pressed. There is a second valve connecting the working chamber 102a to the vacuum chamber 102b. The first and second valves are not shown in fig. 1.

[008] In this document the terms “vacuum brake booster”, “brake booster”, “vacuum booster”, “booster” are used interchangeably.

The working of the brake system is explained below.

[009] Assume that the vehicle is moving at a certain speed and there is no force applied on the brake pedal. In this scenario, the first valve is closed thereby cutting the atmospheric air entering into the chamber 102a.The second valve is open connecting both the chambers. Both the chambers are filled with vacuum and are under equilibrium position. The membrane 105 is also under equilibrium position.

[010] When the driver presses the brake pedal to reduce the speed of the vehicle, a force is applied on the brake push rod. The brake push rod moves in the direction of the brake booster. The first valve opens and the second valve closes. The opening of the first valve allows atmospheric air to enter into the chamber 102a. As chamber 102a is at atmospheric pressure and other chamber 102b is filled with vacuum, one side of the membrane 105 experiences atmospheric pressure and the others side of the membrane experiences vacuum. The membrane 105 expands and moves into the chamber 102b, thereby pushing the brake push rod 104c towards the tandem master cylinder with a bigger force. The force applied at the brake pedal is amplified and applied to the brake push rod 104c. The brake push rod 104 pushes the piston in the tandem master cylinder. The force on the pistons in the tandem master cylinder is transferred to the brake oil in the hydraulic circuit 108. Finally the pressure (generated due to force on piston) in the hydraulic circuit causes the calipers 110 to move closer and apply force on the brake disc 111, thereby reducing the speed of the wheels.

[011] When the driver removes the force from the brake pedal, the brake push rod moves towards left (with reference to direction as shown in fig. 1). The first valve closes and the second valve opens. The closing of the first valve cuts off the atmospheric air entering into the chamber 102a. As second valve is open, the chambers 102a and 102b are filled with vacuum. The spring 116 brings the membrane 105 to its original equilibrium position. This results in removal of force on the pistons of the tandem master cylinder resulting in removal of pressure on the calipers and the brake disc.

[012] Vacuum plays an important role in the brake booster based braking systems. Typically the vacuum source is the engine. The engine generates vacuum during the suction stroke and the same is used for brake booster.

[013] The chamber 102b is connected to a vacuum source through the vacuum check valve 103. As long as the engine is running, the vacuum is created and filled in the brake booster chamber 102a and 102b.

[014] When the engine is switched off the engine stops running. There is no generation of vacuum. In the prior arts, the vacuum check valve comprised only one first membrane. This first membrane allows vacuum to flow from vacuum source into the chamber when the engine is running. The function of the membrane inside the vacuum check valve 103 is to prevent leakage of the atmosphere in to vacuum chamber 102b when the engine is not running. When the engine is not running, as the sealing of the membrane in the vacuum check valve 103 is not completely perfect, slowly the atmospheric air starts leaking inside vacuum chamber 102b through the sealing of the membrane. If the engine remains off for a certain time, the entire vacuum leaks into the atmosphere and the chamber 102b is filled with atmospheric air. On certain vehicles, engine will start only when brake pedal is pressed. When the atmospheric air enters into vacuum chamber 102b because of the leakage in sealing element, when the user tries to start the engine, the brakes will not operate or the user has to apply much higher force on the brake pedal as the vacuum booster is not functional because of non-availability of vacuum in chamber 102b.

[015] The invention proposes a new vacuum check valve 103 to prevent the leakage of the atmospheric air into the vacuum chamber 102b when the engine remains off for a prolonged time.

[016] Shown in fig. 2 is a schematic of the vacuum check valve 103 according to one embodiment of the invention. The vacuum check valve 103 comprises a housing 200, a first port 202, a second port 204, a membrane 206, a sealing element 208. The first port 202 is connected to a vacuum source from the engine. The second port 204 is connected to the vacuum chamber 102b of the vacuum booster 100.

[017] Shown in fig. 3 is a blown up view of the membrane 206 and the sealing element 208. The membrane 206 is made of an elastomeric material 206a and a washer 206b. A magnetic washer 206b or a metallic washer 206b is embedded in the membrane 206. The sealing element 208 comprises either a magnetic insert or a metal insert. If the membrane 206 contains a magnetic washer 206b, then the sealing element 208 contains a metallic insert. If the membrane contains a metallic washer 206b, then the sealing element 208 contains a magnetic insert. The objective here is to make the membrane 206 magnetically attract toward the sealing element 208 and seal completely the flow of fluid from first port 202 to second port 204 or vice versa, when the engine is not running.

[018] The membrane 206 is movably placed close to the sealing element 208, with a pre-tension. When the engine is not running, the pre-tension is acting on the membrane 206 and the membrane moves towards the sealing element 208 to seal the flow of fluid. The magnetic washer 208 (or metallic washer 208) and the metallic insert (or magnetic insert) give additional attracting force to seal the flow of fluid.

[019] When the engine starts running, vacuum is created by the engine and the vacuum flows into first port 202. Because of the pressure difference on two sides of the membrane 206, the membrane 206 overcomes the pre-tension and moves away from the sealing element 208 thereby causing a gap between the membrane 206 and the sealing element 208. The vacuum flows from first port 200 towards the second port 202 and then into the vacuum chamber 102b making the brake booster functional. Here the flow of vacuum in one direction represents flow of atmospheric air in opposite direction.

[020] When the engine stops running, vacuum generation stops. The moment vacuum generation stops, a pressure difference is created on two sides of the membrane 206. This causes the membrane 206 to move towards the sealing element 208 because of the pre-tension. This results in closure of the passage between the membrane 206 and the sealing element 208. The vacuum which was trapped in the vacuum chamber 102b remains there as the membrane 206 prevents the flow of fluid from vacuum chamber to atmosphere or entry of atmospheric air into vacuum chamber 102b.

[021] In the prior-arts, only elastomeric membrane is used to prevent the flow of fluid. Because of the tolerances in manufacturing, the sealing was never complete between the membrane 206 and the sealing element 208, and the atmospheric air slowly leaked into vacuum chamber 102b thereby stopping the function of the brake when the engine was started.

[022] The invention proposes additional re-enforcement of the sealing through the magnetic ring/metal ring 206b and the metal/magnetic insert 208. As the membrane 206 has a magnetic washer (or a metal washer) 206b and the sealing element 208 has a metal insert (or a magnetic insert), the sealing of the passage is improved to much higher level. Because of the magnetic attraction between the sealing element 208 and the membrane 206, the membrane 206 seals the passage between the membrane 206 and the sealing element 208 completely thereby preventing the entry of atmospheric air into the vacuum chamber 102b. The vacuum in the vacuum chamber 102b is retained for much longer duration. This increases the safety factor for the user as the brake will be functional before the starting of the engine.

[023] Fig. 3 represents the check valve 103 when the membrane 206 is in open position. This is the case when the engine is running. The passage is shown as arrows between the membrane 206 and the sealing element 208. Fig 4 represents the check valve 103 when the membrane 206 is in closed position. This is the case when engine is not running.

[024] According to the invention, the availability of the vacuum is ensured for a longer duration when the engine remains switched off for prolonged duration. This requirement is also to meet safety guidelines for starting the engine after a certain duration of being in off state and brake booster working normally.

[025] Thus the invention proposes a simple vacuum check valve 103 which can retain the vacuum in the brake booster 102 for a prolonged time to meet the safety guideline. Because the vacuum is already available, the brake booster works normally, even before the engine is started. The user can press the brake and start the engine safely