Vehicle condition dependent supplemental parking brake system with protection against an unwanted application

A vehicle brake system for a vehicle comprises at least one source of pressurized air for pressurizing the vehicle brake system, and a brake actuator configured to receive air from the source of pressurized air. A control is operatively associated with the source of pressurized air for selective application of the brake actuator. A supplemental parking brake control system is in communication with the control and the brake actuator. The control system is responsive to data indicative of gradient and speed vehicle conditions. The control system is configured to send a signal to the brake actuator to allow gradient and speed dependent supplemental parking. The control system is configured to prevent application of the brake actuator.

BACKGROUND

The present disclosure generally relates to vehicle braking systems, and more particularly, to a supplemental parking brake system, the actuation of the brake system being dependent on predetermined vehicle conditions.

Heavy duty vehicles, such as military vehicles, must sometimes park on gradients of up to 60%. Parking on such gradients is almost impossible without parking brakes being applied on the front axle. An unwanted application of the front (e.g., spring applied) parking brakes can cause an undesirable effect on the vehicle dynamically.

To protect against unwanted front brake application and the concern normally associated with a spring applied parking brake on the front axle, the present disclosure provides a vehicle condition dependent supplemental parking system.

BRIEF DESCRIPTION

According to one aspect of the present disclosure, a vehicle brake system for a vehicle comprises at least one source of pressurized air for pressurizing the vehicle brake system, and a brake actuator configured to receive air from the source of pressurized air. A control is operatively associated with the source of pressurized air for selective application of the brake actuator. A supplemental parking brake control system is in communication with the control and the brake actuator. The control system is responsive to data indicative of gradient and speed vehicle conditions. The control system is configured to send a signal to the brake actuator to allow gradient and speed dependent supplemental parking. The control system is configured to prevent application of the brake actuator.

According to another aspect of the present disclosure, a supplemental brake control system for a front pneumatic brake circuit of a vehicle is provided. The front pneumatic brake circuit includes a source of pressurized air for pressurizing the brake circuit. A front pneumatic brake actuator is configured to receive air from the source of pressurized air. A control is in communication with the source of pressurized air and is configured to send a pneumatic signal to the front pneumatic brake actuator to exhaust pressurized air to atmosphere to actuate the front pneumatic brake actuator. The brake control system comprises a valve and a plurality of switches. The valve is in communication with the control and the front pneumatic brake actuator. The valve has a normally open state for preventing actuation of the front pneumatic brake actuator and a closed state to actuate the front pneumatic brake actuator. The plurality of switches is in communication with the control and the valve. Individual switches are responsive to data indicative of a vehicle condition. Each switch is actuated once its respective vehicle condition is met. The valve is in the open state and the front pneumatic brake actuator remains released when all switches are not actuated and all vehicle conditions are not met. Actuation of each switch sends a signal to the valve to move to the closed state and actuate the front pneumatic brake actuator.

According to yet another aspect of the present disclosure, a method of providing supplemental front parking for a vehicle is provided. Air pressure is provided to a front parking brake actuator. The front parking brake actuator is activated as a function of vehicle gradient and vehicle speed conditions.

DETAILED DESCRIPTION

It should, of course, be understood that the description and drawings herein are merely illustrative and that various modifications and changes can be made to the pneumatic brake system or park system disclosed without departing from the scope of the present disclosure. It will also be appreciated that the various identified components of the pneumatic brake system disclosed herein are merely terms of art that may vary from one manufacturer to another and should not be deemed to limit the present disclosure. Further, details of the identified components of the pneumatic brake system disclosed herein are well known and are commercially available from the assignee of the subject invention so that only selected details will be described herein for purposes of brevity.

Referring now to the drawings, wherein like numerals refer to like parts throughout the several views,FIG. 1partially schematically illustrates a pneumatic vehicle brake system according to one aspect of the present disclosure, which is generally indicated by reference numeral10. The brake system generally is for use in a heavy duty vehicle (not shown), such as a military vehicle; although, this is not required. The brake system10has at least one source of pressurized air (not shown), for example, in the form of a fluid pressure reservoir, for pressurizing the brake system. The reservoir can be charged with fluid pressure by a conventional air compressor (not shown) operated by the engine of the vehicle on which the brake system10is implemented.

A brake actuator20for, for example, a front axle of a vehicle is configured to receive air from the source of pressurized air. In the depicted embodiment, the brake actuator20is spring actuator which converts the energy of air pressure into mechanical force. The brake actuator20generally includes a service chamber30, a push rod32and a tandemly mounted spring brake chamber36to and from which fluid pressure is admitted and exhausted by way of a conduit40to control the spring brake. The reduction or absence of air pressure in the spring brake chamber36actuates the brake actuator.

An antilock brake system (ABS) modulator50and a service relay valve52are operatively associated with the service chamber30of the brake actuator20via conduit54. The ABS modulator is configured to modulate the brake actuator20associated with the front axle in a manner known in the art. Upon signal pressure from the ABS modulator, the service relay valve is configured to graduate, hold or release air pressure from the service chamber30to which it is connected. The service relay valve52provides anti-compounding so that if an operator makes a service brake application, that same pressure goes into the spring brake chamber36so that there is no overstress of the mechanical components of the brake actuator20. In other words, the service relay valve52prevents simultaneous application of the service brake and the spring brake.

A control60is operatively associated with the source of pressurized air for selectively activating the brake actuator20. As depicted, the control60is a push-pull manually operable on-off air control valve with an exhaust function, which is typically mounted on the dash of a heavy duty vehicle. The control typically includes at least two ports, a source or supply port where air enters the control and an outlet or delivery port which supplies air pressure therefrom. The control60is pressure sensitive in that it can automatically move from the applied to the exhaust position if total brake system pressure drops below a predetermined trip brake system pressure. Also, manually pulling a button62of the control60will send a pneumatic signal to the brake actuator20for application of the brake actuator. The control receives pressurized air from the source and when the button60is pushed in, the control delivers air to the spring brake chamber36by way of delivery conduit66. A single check valve70fluidly connects the conduit66to the spring brake chamber and allows air flow only in one direction into the spring brake chamber. The air releases the spring brake actuator for normal vehicle operation. As indicated previously, to apply the brake actuator, the button60is pulled out. This exhausts the control delivery and releases air from the spring brake chamber36by way of conduit40. The structure and operation of the disclosed valves and brake actuator of the brake circuit10described to this point is generally conventional so that further discussion herein is deemed unnecessary to a full and complete understanding of the present disclosure.

The supplemental brake control system100for the pneumatic brake circuit10controls the actuation of the brake actuator20. The control system is in communication with the control60and the brake actuator and is responsive to data indicative of at least gradient and speed vehicle conditions. The control system100is configured to send a signal to the brake actuator20to allow gradient and speed dependent supplemental front axle parking. The control system is also configured to prevent application of the brake actuator. As shown, the supplemental brake control system100comprises a valve102and a plurality of inputs104, individual inputs indicative of a predetermined vehicle condition.

The valve102is operatively associated with the control system and is in communication with the control60and the brake actuator20. In the depicted embodiment, the valve is an electro-pneumatic solenoid which is operatively associated with the spring brake chamber36and the single check valve70. The solenoid valve102has a normally open state to prevent application of the brake actuator20and a closed state to activate the brake actuator. Particularly, the solenoid valve has to be flipped to the closed state to exhaust the air and apply the brake actuator20.

The plurality of inputs104is in communication with the control60and the valve102. In the exemplary embodiment, the plurality of inputs comprises a plurality of switches including a parking indicator switch110, an incline indicator switch112, a speed enable switch114and a vehicle ignition switch116. The individual switches110,112,114,116are responsive to data indicative of a vehicle condition, which at least partially include (i) a parking condition of the vehicle, (ii) a gradient of a road on which the vehicle is to be held stationary, (iii) a speed of the vehicle and (iv) a state of a vehicle ignition. Each switch is actuated once its respective vehicle condition is met. The valve102is in the open state and the brake actuator20remains released when all switches are not actuated and all vehicle conditions are not met. Actuation of each switch sends a signal to the valve102to move to the closed state and activate the brake actuator. Thus, the valve102is responsive to the signal from the plurality of inputs104to prevent activation of the brake actuator by the control60if all vehicle conditions are not met.

The parking indicator switch110is in communication with the control60and is responsive to data indicative of the control being actuated for a front vehicle park condition. In this embodiment, the parking indicator switch is a normally closed switch that can be selectively actuated when a pressure of the brake system10is reduced to a predetermined trip brake system pressure. In the depicted embodiment, a conduit120connects the parking indicator switch110to conduit66. This allows for monitoring of air pressure by the parking indicator switch110. Any reduction in air pressure, for example by the pulling of the button62of the control60, will actuate the parking indicator switch110. Alternatively, it should be appreciated that the parking indicator switch110can be configured to monitor the state of the control60such that the parking indicator switch is actuated by the pulling of the button62.

The incline indicator switch112is responsive to data indicative of a gradient of a surface on which the vehicle is to be held stationary and is only actuated when a grade or hill is detected beneath the vehicle and the gradient is greater than a threshold gradient. In this embodiment, the incline indicator switch is a normally open switch that is selectively actuated on gradients greater than about twenty percent (20%); although, other gradients are contemplated. In one embodiment, to determine gradient, a grade sensor can be provided on the vehicle, the sensor being monitored by an electronic control unit (ECU) to determine if the vehicle is on a level surface. If a gradient greater than the threshold gradient is detected, the incline indicator switch will be actuated. The control system100further includes an override switch124that is configured to override the incline indicator switch112for verification of parking brake operation, particularly that the brake actuator20is functioning/operational on the axle of the vehicle. The override switch can be a push and hold type switch and is mainly used to service/test the vehicle brake actuator so that the vehicle does not have to be on an incline (i.e., a gradient greater than the threshold gradient) to actuate the incline indicator switch112.

The speed enable switch114is responsive to data indicative of vehicle speed and is selectively actuated at vehicle speeds less than a threshold vehicle speed. In this embodiment, the speed enable switch114is a normally closed switch that is selectively actuated at vehicle speeds less than about three (3) mph; although, other vehicle speeds are contemplated. Existing ABS modulator wheel speed sensors or other suitable means can be utilized to detect vehicle speed. Finally, the vehicle ignition switch116is responsive to data indicative of a state of the vehicle ignition. Particularly, the vehicle ignition switch116is actuated when the vehicle ignition is on.

As indicated above, there are many ways to provide vehicle information to the plurality of switches110,112,114,116. For example, vehicle information provided from the ABS modulator, transmission, the dash (i.e., anywhere that information can be accessed from a conventional communication bus) can be transmitted to the switches for actuating each switch if its respective vehicle condition is met. For example, an ECU can be connected to a sensor group and arranged to receive input of the above mentioned vehicle conditions. In this example, the sensor group includes a gradient sensor, speed sensor and an ignition sensor. Signals from the sensors are transmitted to the ECU which differentiates the signals and emits energizing currents for controlling operation of the switches. It should also be appreciated alternative manners for providing gradient and speed dependent supplemental parking instead of the switches are contemplated. For example, the above described sensors for monitoring the vehicle conditions can transport signals to the ECU. The ECU can then emit an energizing current directly to the solenoid valve102to actuate the valve and move the valve to the closed state to actuate the brake actuator20.

In operation, rear parking brake is normal under the full manual operational control of the operator. The control60is supplied with air pressure from the source of pressurized air to pressurize the spring brake chamber36. The brake actuator20is sustained by the single check valve70and the solenoid valve102. The parking brake control system100is in communication with the control60and the brake actuator20. The control system is responsive to data indicative the vehicle conditions. The brake actuator is held off unless those vehicle conditions are met. As indicated above, the vehicle conditions are ignition switch being on, vehicle speed being below a predetermined threshold speed (for example about 3 mph), gradient of the vehicle exceeding a threshold gradient, and a park condition (i.e., the pulling of the control60).

To actuate the brake actuator20, the control button62can be pulled. As indicated previously, the control is pressure sensitive so that it can automatically move from an applied position to an exhaust position. In the applied position, the spring brake chamber36is pressurized and the spring brake is not activated. As brake supply pressure is reduced to the predetermined low trip pressure, the control60moves to the exhaust position, whereby the brake actuator is applied. The parking indicator switch110senses that the button of the control was pulled and/or is responsive to the reduction of brake system pressure (i.e., the pneumatic signal to the brake actuator via the control). If the incline indicator switch112is closed (the gradient was greater that what can be actually sustained with rear brake parking of the rear axle), the vehicle is below a certain speed (to close the speed enable switch114) and the vehicle ignition switch is closed (the vehicle ignition is on), the control system100is configured to send a signal to the brake actuator to allow gradient and speed dependent supplemental front axle parking. Particularly, the control system100sends an energizing signal to the solenoid valve102. In response to the signal, the solenoid valve will flip to the closed state to exhaust the spring brake chamber36through relay valve52. To prevent application of the brake actuator20, each of the vehicle conditions must be met in order for the brake actuator to be actuated or applied. If any one vehicle condition is not met, even though there may be a failure in the park circuit, the brake actuator will not be applied to the front axle. It should be appreciated that the brake system10can have alarms/diagnostics which will notify the operator that each of the switches has changed state. The speed and the gradient threshold values can be preset by the manufacturer of the vehicle to which the system100is implemented.

With reference toFIG. 2, a partial schematic diagram of a pneumatic vehicle brake system, which is generally indicated by reference numeral200, according to another aspect of the present disclosure is illustrated. Reference numerals with a primed suffix (′) refer to like components (e.g., control60is referred to by reference numeral60′), and new numerals identify new components of the brake system200.

The pneumatic brake system200has at least one source of pressurized air, for example, in the form of a fluid pressure reservoir202for pressurizing the brake system. A brake actuator210is configured to receive air from the source of pressurized air. In the depicted embodiment, the brake actuator210is a dual diaphragm/lock type actuator having a lock port220, an auxiliary/emergency port222, a service port224and a mechanical push shaft226. The actuator provides braking for service, emergency and parking. The actuator is adapted to effect a brake application when fluid pressure is communicated to either the service port224or the auxiliary port222. If fluid pressure is also communicated to the lock port220, the brake actuator is released in the normal manner when the fluid pressure level at the service port224or at the auxiliary port222is exhausted. However, if the pressure at the lock port220is vented (i.e., when the brake application is effected), the brake application will be “locked-on”, thereby providing a parking brake capability. An antilock brake system (ABS) modulator50′ and a first service relay valve52′ (which may be of any conventional design known to those skilled in the art) are operatively associated with the service port224of the brake actuator210by way of conduit230.

The first relay valve is fluidly connected to a foot control valve240via conduit244. The foot control valve240is provided with two separate supply and delivery circuits for service (primary) and secondary braking, and includes a foot pedal/treadle246adapted to be selectively actuated by a vehicle operator. A primary or first supply is delivered by the foot control valve to a first supply port of a first double check valve250by way of conduit252. A secondary supply is delivered by the foot control valve to both the first relay valve via conduit244and to a second supply port of the first double check valve250by way of conduit254, which is connected to conduit244. As is well known, the double check valve is configured to select the higher of the fluid pressure levels at the supply ports and direct the flow of pressurized air into its delivery port. When a brake application is effected by the operation of the foot pedal246on the foot control valve240by the vehicle operator, pressurized air is selectively delivered from the secondary supply to a control port C of the first relay valve52′. As indicated previously with respect to the first embodiment, the first relay valve is provided with a supply port and a delivery port. The delivery port D is in communication with the ABS modulator. The first relay valve is responsive to the operation of the foot control valve240to communicate fluid pressure to the service port224of the brake actuator210for application of the service brake.

As shown inFIG. 2, a delivery port of a first double check valve250is connected to a first supply port of a second double check valve260. A second supply port of the second double check valve260is operatively associated with the rear parking brake control by way of conduit262. The delivery port of the second double check valve is connected to a control port of a sequence valve270. The sequence valve270includes at least three ports, the control port, a supply port and a delivery port. As is well know, a source of pressure acting on the control port prevents the sequence valve260from receiving pressurized air into its supply port. A delivery port of the control60′ is fluidly connected to the supply port of the sequence valve260by way of conduit272. The delivery port of the sequence valve delivers pressurized air to a first supply port of a third double check valve280by way of conduit284, which is connected to conduit262. A delivery port of the third double check valve280is in communication with a control port of a second sequence valve290. The supply port of the second sequence valve290is connected to the fluid pressure reservoir202. A delivery port of the second sequence valve is operatively associated with the brake actuator210and a second supply port of the third double check valve280.

The pneumatic brake system200is provided with fail safe features which automatically divert to park brake application should a loss of brake system air pressure occur. Specifically, a first inversion valve300monitors brake system pressure being delivered to the brake actuator210. The first inversion valve300is a normally open pilot-operated, inverting, on-off, two way valve. The first inversion valve includes a control port, a supply port and a delivery port which are labeled C, S and D, respectively. The control port C is in fluid communication with a first supply port of a fourth double check valve310. A second supply port of the fourth double check valve is connected to the first relay valve52′. A delivery port of the fourth double check valve310is fluidly connected to a supply port of a pressure protection valve320, which is a normally closed, pressure control valve. A delivery port of the pressure protection valve320is operatively associated with the lock port220of the brake actuator210. The supply port S of the first inversion valve300is fluidly connected to the fluid pressure reservoir202. The delivery port D of the first inversion valve is connected to a supply port of a second inversion valve330. A delivery port of the second inversion valve is connected to a control port C of a second relay valve52″ by way of conduit332. The second relay valve52″ is in fluid communication with the auxiliary port222of the brake actuator via conduit334for actuation of the brake actuator. A supply port of the second relay valve52″ is fluidly connected to the fluid pressure reservoir202via conduit340.

In a normal operating position, air pressure is applied to a lock port220of the brake actuator210. This allows the push shaft226to freely move back and forth with the application and release of service air pressure. The brake actuator is actuated by releasing the air pressure from the lock port220and applying air pressure to the auxiliary port222. The shaft226will push out and will not retract unless pressure is applied to the lock port. With the sustaining pressure applied to the actuator210, an application of the brake actuator can be avoided. The piggybacking of the first and second inversion valves300and330, respectively, pulses the brake actuator210. In other words, when you park with the dual diaphragm/lock type actuator210, pressure is removed from the lock port220and, at the same time, the auxiliary port222will be ramped to a predetermined pressure. The illustrated valve network provides the ramping (for example, up to about 80 psi and released) so that the brake actuator210is parked with locked force as opposed to pneumatic pressure. Thus, it is necessary to pulse a diaphragm of the brake actuator210to cause application of the brake actuator. Again, the structure and operation of the disclosed valves and brake actuator of brake circuit200described to this point is generally conventional so that further description herein is deemed unnecessary.

Similar to the previous embodiment, a supplemental brake control system100′ for the front pneumatic brake circuit200controls the actuation of the brake actuator210. The control system is in communication with the control60′ and the brake actuator and is responsive to data indicative of gradient and speed vehicle conditions. The control system is configured to send a signal to the brake actuator to allow gradient and speed dependent supplemental front axle parking and prevent application of the brake actuator. As shown, the supplemental brake control system100′ comprises a valve102′ and a plurality of inputs104′. The valve102′ is an electro-pneumatic solenoid having a normally open state for preventing activation of the brake actuator210and a closed state for activating the brake actuator.

The plurality of inputs is in communication with the control and the valve. Similar to the previous embodiment, the plurality of inputs comprises a plurality of switches including a parking indicator switch110′, an incline indicator switch112′, a speed enable switch114′ and a vehicle ignition switch116′. The individual switches110′,112′,114′,116′ are responsive to data indicative of a vehicle condition, which include (i) a parking condition of the vehicle, (ii) a gradient of a road on which the vehicle is to be held stationary, (iii) a speed of the vehicle and (iv) a state of a vehicle ignition. Each switch is actuated once its respective vehicle condition is met. The valve102′ is in the open state and the brake actuator210remains released when all switches are not actuated and all vehicle conditions are not met. Actuation of each switch sends a signal to the valve to move to the closed state and activate the brake actuator210. Thus, the solenoid valve is responsive to the signal from the plurality of switches104′ to prevent activation of the brake actuator210by the control60′ if all vehicle conditions are not met.

As is evident from the foregoing, a method of providing supplemental front parking for a vehicle is provided. Air pressure is provided to a brake actuator. The brake actuator is activated as a function of vehicle gradient and vehicle speed conditions. Accordingly to one exemplary embodiment, the brake actuator is activated if the gradient is greater than about 20% and the vehicle speed is less than about 3 mph. In addition to gradient and speed vehicle conditions, to activate the brake actuator, the vehicle ignition has to be on and a vehicle park condition has to be met. A valve is in communication with the brake actuator and is selectively actuated to activate the brake actuator if all the above vehicle conditions are met.

By using the brake actuator20or the dual diaphragm/lock type actuator210in combination with isolating the pneumatic circuit from failure and requiring certain vehicle conditions to be met, an unwanted parking application can be prevented thus minimizing the potential for the parking brake to impact the dynamic stability of the vehicle. The system also eliminates the potential of the parking brake application on the vehicle axle unless all vehicle conditions are met.