Modulator mis-wire test

Details Modulator mis-wire test Modulator mis-wire test

1999-04-15

2001-05-29

McCall, Eric S. (Department: 2855)

Measuring and testing

Brake testing

Vehicle installation

Reexamination Certificate

active

06237401

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to monitoring and testing of a vehicle braking system, and more particularly to monitoring and testing an electronically controlled braking system for an automotive vehicle equipped with pneumatically actuated brakes to determine if there is a mis-wired brake system modulator. Although the present invention may be used with adaptive braking systems, it is also intended for use with other electronically controlled braking systems, such as electropneumatic braking systems.
Generally, it is necessary for a driver to be sure that a vehicle braking system is working properly at all times. Accordingly, it is common to provide a series of checks upon starting the vehicle to assure that the electronically controlled braking system is operating properly. one check relates to the solenoids associated with a brake pressure modulator and the associated electrical circuits which operate the valves and selectively control communication with the vehicle brakes. For example, it is important to discern whether the solenoids are either electrically open or shorted. if it is determined that an electrically open or shorted condition exists in the solenoid circuit, the braking system is shut down and the vehicle driver is provided a suitable warning signal.
Typically, the brake pressure modulator includes an inlet or hold valve, which controls communication with a pressure source, and an exhaust valve which is selectively actuated to exhaust braking pressure to atmosphere. If the exhaust valve is actuated, the inlet or hold valve must also be actuated to preclude dumping the air supplied to the modulator from the pressure source to atmosphere.
The braking system further includes an electronic control unit (ECU), which receives inputs from speed sensors which measure speeds of the vehicle wheels. The ECU processes these wheel speed signals to determine if one or more of the vehicle wheels is about to lock up. If an incipient lock-up condition is sensed, the ECU actuates the inlet or hold solenoid valve, which blocks communication between the pressure source and the brake actuator to thereby hold the pressure level then existing in the actuator. Pressure in the brake actuator is dumped to atmosphere by simultaneously actuating both the hold and exhaust valves.
Three wires connect the ECU with each modulator. One wire is a source wire that supplies power to both solenoids. A second wire provides a ground to the inlet or hold valve if a hold function is desired. Finally, a third wire supplies a ground to the exhaust valve if an exhaust function is desired. On occasion the hold and exhaust wires are reversed. Since the resistance of both of the solenoids is the same, the ECU cannot easily detect the reversed condition of the wires.
In U.S. Pat. No. 5,327,781 miswiring is detected based on the difference in the exhaust sound generated by a correctly wired modulator versus an incorrectly wired modulator. Particularly, when properly wired, the hold solenoid is actuated for ten milliseconds compared to an incorrectly wired modulator which provides an exhaust pulse on the order of thirty milliseconds. This time difference or difference in exhaust sound is not sufficient to consistently identify an incorrectly wired modulator during testing.
When modulators have been incorrectly wired by the original equipment manufacturers or by a mechanic, extended stopping distances of vehicles may be encountered or excessive system pressure may be exhausted during a traction control or ABS event.
The present invention contemplates a new and improved apparatus and method which overcomes the above referenced problems and others and provides a consistent and efficient detection method to determine if a modulator has been miswired.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided an improved apparatus and method for testing an electronically controlled braking system. According to another aspect of the invention, the apparatus and method includes determining if exhaust and hold solenoid valves in a modulator controlling a brake sub-system of at least one wheel on a vehicle are properly wired. First, a brake pedal in a vehicle is depressed. Then, an ignition of the vehicle is turned on to power the vehicle and ECU. The system uses the ECU to determine if at least one of the exhaust and the hold solenoid valves is open or short circuited. If the determination is positive, present information of the vehicle is stored in a storage device in the ECU and testing is aborted. If the determination is negative, the test apparatus and method pauses for a predetermined period of time. As an example, the system then energizes a first one of the hold solenoid valves at least twice, and then energizes one of the exhaust solenoid valves once. Finally, the system determines whether there are two or more signals generated from the energizing step. If there are two or more signals, e.g. audible signals, the solenoid valves are mis-wired.
According to another limited aspect of the present invention, the system serially performs the pausing and valve energizing for the modulator for a plurality of the wheels.
An advantage of this invention is that the miswiring of solenoid valves in a modulator can be more consistently detected.
Another advantage of the invention is that the prospects for miswiring solenoids is reduced.
Still other benefits and advantages of the invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiment.


REFERENCES:
patent: 5327781 (1994-07-01), Moran
patent: 5782541 (1998-07-01), Schappler
patent: 6097998 (2000-08-01), Lancki

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