Abstract: When detecting a maladjusted brake component on a commercial vehicle, wheel end temperature is determined as a function of resistance measured by a wheel speed sensor at a wheel end. The measured temperature is compared to low and high temperature thresholds defined by a thermal model, as well as to one or more other wheel speed sensor temperatures. If the measured temperature is below the low temperature threshold and substantially different than the one or more other wheel speed sensors, the brake is determined to be under-adjusted and brake force at the under-adjusted brake is increased. If the measured temperature is above the high temperature threshold and substantially different than the one or more other wheel speed sensors, then the brake is determined to be over-adjusted, and brake force is reduced or modulated at the over-adjusted brake to prevent overheating.

Abstract: When detecting a maladjusted brake component on a commercial vehicle, wheel end temperature is determined as a function of resistance measured by a wheel speed sensor at a wheel end. The measured temperature is compared to low and high temperature thresholds defined by a thermal model, as well as to one or more other wheel speed sensor temperatures. If the measured temperature is below the low temperature threshold and substantially different than the one or more other wheel speed sensors, the brake is determined to be under-adjusted and brake force at the under-adjusted brake is increased. If the measured temperature is above the high temperature threshold and substantially different than the one or more other wheel speed sensors, then the brake is determined to be over-adjusted, and brake force is reduced or modulated at the over-adjusted brake to prevent overheating.

Abstract: A drum brake assembly includes a brake spider having a central aperture configured to receive an axle extending therethrough and first and second brake shoes. Each of the first and second brakes shoes has a first end pivotally coupled to the brake spider. First and second cam followers are disposed at corresponding second ends of the first and second brake shoes. A camshaft has a shaft extending through a camshaft aperture in the brake spider and disposed along a rotational axis and a cam disposed at a first end of the shaft and in engagement with the first and second cam followers. An electric motor has an output shaft coupled to the camshaft. A controller is configured to drive the electric motor to cause rotation of the camshaft and move the first and second brake shoes between positions of engagement and disengagement with an associated braking surface.

Abstract: A drum brake assembly includes a brake spider having a central aperture configured to receive an axle extending therethrough and first and second brake shoes. Each of the first and second brakes shoes has a first end pivotally coupled to the brake spider. First and second cam followers are disposed at corresponding second ends of the first and second brake shoes. A camshaft has a shaft extending through a camshaft aperture in the brake spider and disposed along a rotational axis and a cam disposed at a first end of the shaft and in engagement with the first and second cam followers. An electric motor has an output shaft coupled to the camshaft. A controller is configured to drive the electric motor to cause rotation of the camshaft and move the first and second brake shoes between positions of engagement and disengagement with an associated braking surface.

Abstract: An apparatus and method for preventing parking brake-caused disabling of a vehicle is provided. In at least one of the vehicle's parking brake release actuators' supply lines there is provided a flow arrangement which allows parking brake release fluid to flow to and from the release actuator when its supply line is undamaged, and restricts flow from the release pressure source when the line between the flow arrangement and the actuator is damaged. The flow arrangement may be a pilot-operated, non-graduated control valve, a combination of a pressure protection valve and a check valve arranged in parallel, a velocity-sensing check valve, or any other device or combination of devices which provide the damaged line shutoff or metering functionality. Such an arrangement prevents automatic application of the parking brake by releasing pressure from all of the vehicle's parking brake actuators, thereby precluding automatic vehicle immobilization following damage at one wheel end.

Abstract: An apparatus and method for preventing parking brake-caused disabling of a vehicle is provided. In at least one of the vehicle's parking brake release actuators' supply lines there is provided a flow arrangement which allows parking brake release fluid to flow to and from the release actuator when its supply line is undamaged, and restricts flow from the release pressure source when the line between the flow arrangement and the actuator is damaged. The flow arrangement may be a pilot-operated, non-graduated control valve, a combination of a pressure protection valve and a check valve arranged in parallel, a velocity-sensing check valve, or any other device or combination of devices which provide the damaged line shutoff or metering functionality. Such an arrangement prevents automatic application of the parking brake by releasing pressure from all of the vehicle's parking brake actuators, thereby precluding automatic vehicle immobilization following damage at one wheel end.

Abstract: A proportioning control valve for a fluid pressure braking system for a tractor-trailer combination vehicle permits unproportioned communication of control pressure when the tractor is pulling a trailer but proportions communication of control pressure when the tractor is operated without a trailer to establish a proportionally lower pressure level at the outlet of the valve. When the pressure level at the control port exceeds a predetermined level established by a spring, the control valve proportions at a rate which increases the pressure level at the outlet at a rate greater than the rate of increase of control pressure until the unproportioned pressure level is attained.

Abstract: A proportioning control valve for a fluid pressure braking system for a tractor-trailer combination vehicle permits unproportioned communication of control pressure when the tractor is pulling a trailer but proportions communication of control pressure when the tractor is operated without a trailer to establish a proportonally lower pressure level at the outlet of the valve. The control valve, when operating in the proportioning mode, is also responsive to pressure in the brake reservoir. When pressure in the reservoir drops below a predetermined level, the control valve proportions at a rate which increases the pressure level at the outlet at a rate greater than the rate of increase of control pressure until the unproportioned pressure level is attained.

Abstract: A compressed air system includes an air compressor the inlet of which is communicated to the vehicle engine turbocharger. The outlet of the air compressor is communicated through an air dryer to a storage reservoir. A governor is responsive to the pressure level in the reservoir to generate an unloading signal unloading the air compressor when the pressure in the reservoir attains a predetermined value. The unloading signal is also communicated through a control valve to purge the air dryer during compressor unloading. The control valve closes communication between the governor and the air dryer to trap a predetermined pressure level in the purge volume of the air dryer to prevent the air dryer from purging to atmospheric pressure. Accordingly, a predetermined air pressure level is maintained in the purge volume, so that the outlet of the turbocharger can never be communicated to atmospheric pressure.