System, method and device for implementing a dual air supply for a brake system

Abstract

A brake system (10) for an air-braked vehicle includes a working pressure source (12) and a vacuum pressure source (20). The system comprises at least one brake actuator (30) having: a first chamber (32) for receiving a working pressure; a second chamber (34) for receiving vacuum pressure; and a push rod (26) that moves linearly in response to pressure in the first chamber and the second chamber. A brake assembly (28) is mechanically connected to the push rod to apply friction to a wheel end of the vehicle in response to linear movement of the push rod.

Description

Technical Field

[0001] This application relates to a system, method, and apparatus for providing enhanced braking by using dual air supplies. Background Art

[0002] In commercial vehicle applications, air brakes are used to stop the vehicle. Brake actuators are placed at each wheel end to receive service air in response to a signal indicating that the driver desires to apply the service brakes. The brake actuator is divided into two chambers by a diaphragm. Service air enters the first chamber of the brake actuator through an inlet port. The service air acts on the diaphragm and, on the opposite side of the diaphragm, acts against the atmospheric pressure in the second chamber. The movement of the diaphragm causes the push rod assembly to move. The push rod assembly moves an S-cam to actuate a drum brake. In a disc brake, the push rod moves an actuator device. The service air works against the atmospheric pressure that consistently exists in the second chamber. The greater the air pressure permitted to enter the first chamber of the brake actuator, the greater the force applied to the brake assembly. When the air pressure is released from the first chamber, the push rod return spring returns the diaphragm to its released position.

[0003] There is an interest in improving the structure and operation of brake actuators and brake systems, which will assist commercial vehicles in achieving shorter stopping distances. Summary of the Invention

[0004] According to one embodiment, a brake actuator includes: a housing having two chambers; an inlet at the first chamber for receiving a service pressure; an inlet at the second chamber for receiving a vacuum pressure; and a diaphragm separating the first chamber from the second chamber. The push rod moves to a brake-actuating position in response to the service pressure being greater than the vacuum pressure.

[0005] According to another embodiment, a brake system for an air-braked vehicle includes a service pressure source and a vacuum pressure source. The system includes at least one brake actuator having: a first chamber for receiving a service pressure; a second chamber for receiving a vacuum pressure; and a push rod that moves linearly in response to the pressures in the first and second chambers. A brake assembly is mechanically connected to the push rod to apply friction to the wheel end of the vehicle in response to the linear movement of the push rod.

[0006] According to another embodiment, a method for controlling an actuator of an air brake system includes: providing compressed air to a brake controller; transmitting a service brake request signal to the brake controller and a vacuum controller; in response to the service brake request signal, providing a working pressure to a first chamber of the brake actuator; and in response to the service brake request signal, providing a vacuum pressure to a second chamber of the brake actuator. The method causes a push rod to move in response to the working pressure to actuate a brake assembly connected to the brake actuator. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 is a representation of a brake system having a brake actuator according to the present invention.

[0008] Figure 2 is a close-up view of a brake actuator according to the present invention.

[0009] Figure 3 is a flow chart of the operation of a brake system of the present invention. DETAILED DESCRIPTION

[0010] Reference Figure 1 , depicts a brake system 10 having an improved air brake actuator 30.

[0011] An air compressor 12 provides a source of compressed air for the brake system. When air is compressed, it is stored in a first reservoir 14.

[0012] When a driver desires to apply the service brakes of the vehicle, she actuates a foot brake valve 18. The foot brake valve 18 communicates pneumatically with a brake controller 16 using pressure from the first reservoir 14 and / or communicates electrically via a pressure sensor 17. The brake controller 16 includes control logic, pneumatic valves, and electro-pneumatic valves to act in accordance with an indication from the driver that she desires to apply the service brakes.

[0013] In response to the driver's desire to apply the service brakes, the brake controller 16 provides working air to a first side 32 of at least one brake actuator 30, the first side being configured to receive air at a relatively high pressure. Typical commercial vehicles (such as tractors) have brake actuators at each wheel end. Thus, the brake controller 16 will communicate with at least four and up to fourteen brake actuators on a multi-axle heavy vehicle. The brake controller 16 will also communicate electrically with a vacuum controller 24 via a communication bus 25.

[0014] Meanwhile, the vacuum pump 20 supplies vacuum pressure air to the second reservoir 22. When the vacuum controller 24 receives a signal indicating that the driver desires to brake the vehicle, the vacuum controller 24 opens a path for creating a vacuum in the second side 34 of the at least one brake actuator 30. In this manner, the first side 32 has a smaller force to overcome to move the push rod 26 in order to actuate the brake assembly. This feature results in a faster application time for the at least one brake actuator 30. In a type having a clearance adjuster 28, the drum brake is actuated. The system 10 can also be used to actuate a disc brake.

[0015] When the driver removes her foot from the foot brake valve 18, the working pressure is released from the first side 32 of the at least one brake actuator 30 by the brake controller 16 and discharged to the atmosphere. Vacuum can also be released from the second side 34 of the at least one brake actuator 30, or the vacuum can be retained to prepare for the next brake application.

[0016] In another embodiment of the system 10, an air compressor 12 of a different construction can be used to generate both compressed air and vacuum air. In one example, the compression stroke of the compressor 12 will generate compressed air, and the return stroke will generate vacuum. The compressor 12 will be divided into different chambers to capture air from different sources and transfer it to the first reservoir 14 or the second reservoir 22. A separate vacuum pump 20 will not be used.

[0017] In another embodiment of the system 10, the brake controller 16 and the vacuum controller 24 will be combined into a single controller that performs both functions. The single controller will include an input for a brake signal from the foot brake valve 18 via a sensor 17 or via a direct pneumatic connection to the foot brake valve 18. The pneumatic portion of the single controller will have two supply ports (one for receiving working pressure from the first reservoir 14 and one for receiving vacuum pressure from the second reservoir 22), a control port connected to the foot brake valve 18, and two delivery ports (one for delivering working pressure to the first side 32 and one for delivering vacuum air to the second side 34).

[0018] Accordingly, a braking system for an air-braked vehicle includes a source of working pressure and a source of vacuum pressure. The system includes at least one brake actuator having: a first chamber for receiving working pressure; a second chamber for receiving vacuum pressure; and a push rod that moves linearly in response to the pressures in the first and second chambers. A brake assembly is mechanically connected to the push rod to apply friction to the vehicle's wheel end in response to the linear movement of the push rod.

[0019] Figure 2 A close-up view of the brake actuator 30 is shown.

[0020] The brake actuator 30 can be a diaphragm brake actuator. The diaphragm actuator converts the energy of air pressure into mechanical force. The brake actuator 30 is divided into two chambers (a first side 32 and a second side 34) by a diaphragm 36. The two chambers and the separating diaphragm 36 can be clamped together by an external clamping ring 46 or otherwise fastened together.

[0021] The first side 32 includes an input port 40. The input port 40 is connected to a source of compressed air, such as the operating pressure from the brake controller 16. Instead of a vent to the atmosphere as in a typical diaphragm actuator, there is an input port 42 in the second side 34. The input port 42 is connected to a source of vacuum air, such as the vacuum air that will be provided by the vacuum controller 24. A return spring 38 is disposed on the second side 34 to assist in returning the brake actuator 30 to the released position when the operating pressure is removed from the first side 32.

[0022] The push rod plate 44 abuts the diaphragm 36 and is connected to the push rod 26. When the diaphragm 36 moves in response to a difference between the operating pressure and the vacuum pressure, the push rod plate 44 moves the push rod 26. When the push rod 26 moves linearly, if the clearance adjuster 28 is attached to the drum brake assembly, the clearance adjuster moves. If it is a disc brake assembly, the push rod 26 acts directly on the actuator of the disc brake.

[0023] The amount of force necessary to move the push rod 26 depends on the effective area of the diaphragm 26 and the amount of operating pressure applied. In this brake actuator 30, since the pressure in the first side 32 acts on a vacuum rather than on atmospheric air pressure, the amount of force required is diminished. The presence of the vacuum pressure in the second side 34 assists the diaphragm 36 in moving toward the second side 34. The second side 34 can be restored to atmospheric pressure through a vent in the vacuum controller 24 to assist the brake actuator in returning to the released position. The return spring 38 also assists in returning the push rod to the released position.

[0024] Due to the reduction in the force necessary to move the push rod 26, the overall size of the brake actuator 30 can be reduced when vacuum is used. Additionally, the operating pressure of the compressed air portion of the system can be reduced by the value of atmospheric pressure. For example, 150 psi can be the normal operating pressure of the system without vacuum. With vacuum as in the brake system 10, the upper limit pressure at which the compressor operates can be reduced to approximately 135 psi.

[0025] Thus, a brake actuator includes: a housing having two chambers; an inlet at the first chamber for receiving operating pressure; an inlet at the second chamber for receiving vacuum pressure; and a diaphragm separating the first chamber from the second chamber. The push rod moves to the brake actuated position in response to the operating pressure being greater than the vacuum pressure.

[0026] Figure 3 A method 50 for controlling a brake actuator is shown. In step 52, a brake controller 16 monitors a driver's request to apply a service brake by looking for an operating pressure signal or an electrical signal from a pressure sensor 17 associated with a foot brake valve 18, the operating pressure signal or electrical signal indicating that the driver has applied the foot brake valve 18. If there is no signal, the method 50 is idle.

[0027] If a signal is received in step 52, the brake demand pressure is compared with a predetermined pressure. If the brake demand pressure is less than or equal to the predetermined pressure, the vacuum air path is inactive and only the compressed air path is active. The method 50 continues to compare the brake demand with the predetermined pressure. In one example, the predetermined pressure is about fifteen (15) psi.

[0028] When the brake demand is higher than the predetermined pressure, both vacuum air and compressed air will act simultaneously. The method 50 proceeds to step 54.

[0029] The brake controller 16 supplies an operating air pressure to the brake actuator 30. The operating air pressure can be a pneumatic signal received from the foot brake valve 18 or can be representative of the pressure value of the foot brake valve 18. Additionally, if certain functions are active, such as stability control or collision mitigation, the brake controller 16 can automatically supply the operating pressure. In another example, a request to actuate the service brake can be made by an autonomous driving system in communication with or integrated into the brake controller 16.

[0030] In step 56, the brake controller 16 sends a signal that the operating pressure has been applied to a vacuum controller 24. The vacuum controller 24 will respond by supplying vacuum pressure from a second reservoir 22 to the brake actuator 30. In a configuration with a single controller, the operating air and the vacuum pressure will be supplied simultaneously.

[0031] In step 58, the method 50 monitors the release of the foot brake valve 18 or the termination of an automatic brake intervention. As long as the service brake is still requested, the method 50 returns to step 54. If the driver or the automatic brake requests the release of the service brake, the method 50 proceeds to step 60.

[0032] In step 60, the brake controller 16 discharges pressurized air from the brake actuator 30. In step 62, the vacuum controller 24 discontinues the supply of vacuum air to the brake actuator 30, and the second side 34 of the brake actuator 30 is returned to the atmosphere through the vent in the vacuum controller 24. In an alternative embodiment, the vacuum air remains in the brake actuator as long as the vehicle is in operation. In a configuration with a single controller, the release of service air and vacuum air can occur in parallel. The return spring 38 still returns the push rod to the brake released state. At step 64, the method 50 ends.

[0033] Accordingly, a method for controlling an actuator of an air brake system includes: providing compressed air to a brake controller; transmitting a service brake request signal to the brake controller and a vacuum controller; providing a service pressure to a first chamber of the brake actuator in response to the service brake request signal; and providing a vacuum pressure to a second chamber of the brake actuator in response to the service brake request signal. The method causes the push rod to move in response to the service pressure to actuate a brake assembly coupled to the brake actuator.

[0034] In the event that the brake system 10 loses compressed air, which could occur, for example, due to a leak elsewhere in the brake system, the vacuum air can still provide some emergency braking action. The air pressure differential between the first side 32 and the second side 34 can cause the push rod 26 to move towards the second side 34. In the event of a loss of vacuum air, the brake system 10 will still provide full braking action, but the actuation time will be slower than when vacuum air is present.

[0035] While the invention has been illustrated by the description of example processes and system components, and while the various processes and components have been described in detail, the applicant does not intend to limit or in any way restrict the scope of the appended claims to such details. Additional modifications will also be readily apparent to those skilled in the art. Accordingly, the invention in its broadest aspects is not limited to the specific details, embodiments or illustrative examples shown and described. Thus, such details may be modified without departing from the spirit or scope of the applicant's general inventive concept.

Claims

1. A brake actuator, which comprises: a housing having two chambers; an inlet at the first chamber, the first chamber being for receiving working pressure; an inlet at the second chamber, the second chamber being for receiving vacuum pressure; a diaphragm separating the first chamber from the second chamber; and a push rod that moves to a brake-actuated position in response to the working pressure being greater than the vacuum pressure.

2. The brake actuator according to claim 1, further comprising a return spring in the second chamber for returning the push rod to a brake-released position when the working pressure is removed from the first chamber.

3. A braking system for an air-braked vehicle, the braking system comprises: a working pressure source; a vacuum pressure source; at least one brake actuator having: a first chamber for receiving the working pressure; a second chamber for receiving the vacuum pressure; and a push rod that moves linearly in response to the pressures in the first and second chambers; a braking assembly mechanically connected to the push rod to apply friction to a wheel end of the vehicle in response to the linear movement of the push rod.

4. The braking system according to claim 3, wherein, the working pressure source is compressed air from an air compressor transmitted in response to movement of a brake pedal.

5. The braking system according to claim 3, wherein, the vacuum pressure source is a vacuum pump.

6. The braking system according to claim 3, further comprising a brake controller for receiving the working pressure from the brake pedal and transmitting the working pressure to the at least one brake actuator.

7. The braking system according to claim 6, wherein, the brake controller also transmits a signal to a vacuum controller in response to transmitting the working pressure.

8. The braking system according to claim 7, further comprising the vacuum controller for transmitting the vacuum pressure to the at least one brake actuator in response to the signal that the working pressure is transmitted to the brake actuator.

9. The braking system according to claim 6, wherein, the brake controller also transmits the vacuum pressure to the at least one brake actuator.

10. A method for controlling an actuator of an air braking system, the method comprises: providing compressed air to a brake controller; transmitting a service brake request signal to the brake controller and a vacuum controller; providing working pressure to a first chamber of a brake actuator in response to the service brake request signal; providing vacuum pressure to a second chamber of the brake actuator in response to the service brake request signal; and moving a push rod in response to the working pressure to actuate a braking assembly connected to the brake actuator.

11. The method according to claim 10, wherein, the push rod moves faster when there is vacuum pressure in the second chamber than when there is no vacuum pressure in the second chamber.

12. The method according to claim 10, wherein, The braking controller and the vacuum controller are a single controller.

13. The method according to claim 10, wherein, the service brake request signal is compared with a predetermined pressure, and the vacuum pressure is provided only when the service brake request signal is greater than the predetermined pressure.

14. The method according to claim 10, wherein, the predetermined pressure is approximately fifteen (15) psi.

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