Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Reexamination Certificate
1998-12-18
2001-09-18
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
C303S122080, C303S015000, C303S071000, C188S170000
Reexamination Certificate
active
06290309
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a control for actuating the spring brake of an electronically controlled braking system if there is an electrical failure.
Braking systems for heavy vehicles typically rely upon pneumatic air for actuation and control of actuation. Traditionally, when an operator steps on the vehicle pedal, a hydraulic or mechanical control supplies air to a service brake chamber of a two-chamber brake actuator. The air actuates a rod to set the brake.
Certain of the brake actuators are provided with a second spring brake chamber having a heavy spring which sets the brake under two conditions. This type of brake is known as an emergency brake, parking brake or simply a spring brake. In a non-actuated mode, air is supplied to a chamber beneath the spring to hold the spring at a non-actuated position. When an operator wishes to move the brake actuator to a parking brake position, the air is relieved and the spring sets the brake. Similarly, should there be a failure in the air system, the air will no longer hold the spring at its non-actuated position, and the spring sets the brake. This is the emergency brake function.
Recently, electronically controlled braking systems have been designed. In these braking systems, an operator's foot movement on the brake pedal creates an electrical signal that causes air flow to the service chamber which applies the brake. Typically, an electrical signal is sent to an air valve to allow air to pass into the service brake chamber.
Electronically controlled brakes are still provided with a spring brake chamber actuated upon parking or failure of air, to set the brake.
No acceptable solutions have been provided, however, for adapting to the problem of an electrical failure. That is, since the controls are electrical, if there is a failure in the power or control line or in the functioning of the associated electronic controls, then the brakes would no longer be functioning.
In the past, it has been proposed to supply redundant pneumatic controls to replace the electric controls in this event of system failure. This is complex and expensive.
SUMMARY OF THE INVENTION
In a disclosed embodiment of this invention, a valve supplying air to the spring brake chamber is controlled electrically. In the event that there is a failure in the electrical system, the valve is moved to a position relieving air flow from the chamber. In that position, air pressure leaves the chamber beneath the spring and the spring moves to its actuated position. The term “electrical failure” may include a loss of power or the signal from the electronic control unit. Also, the electronic controls can have a diagnostic function for self-checking its operation. If the control detects an internal problem, it can signal a failure to set the spring brake. This diagnostic checking is also part of the term “electrical failure” as used in this application.
In a preferred embodiment, the valve is typically maintained in a position allowing air to flow into the spring brake chamber as long as there is electrical power, and no system fault. Upon an electrical failure, then the valve moves to a position blocking air flow into the chamber. At the same time, the valve exhausts the air in the spring brake chamber to allow the spring to expand.
These and other features of the present invention may be best understood from the following specification and drawings, the following of which is a brief description.
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Carlson & Gaskey & Olds
Meritor Wabco Vehicle Control Systems
Oberleitner Robert J.
Williams Thomas J.
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