Fluid-pressure and analogous brake systems – Multiple fluid-receiving devices – Multiple motors
Reexamination Certificate
1998-04-24
2001-01-30
Schwartz, Chris (Department: 3613)
Fluid-pressure and analogous brake systems
Multiple fluid-receiving devices
Multiple motors
C188S00300R, C303S020000
Reexamination Certificate
active
06179390
ABSTRACT:
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
The present invention relates to an electronic brake controller for a towing vehicle for controlling electric brakes of a towed vehicle, such as a trailer, with braking force feedback provided by a force sensor associated with the brake pedal of the towing vehicle.
BACKGROUND OF THE INVENTION
Recreational and utility trailers often are towed by automobiles, pick-up trucks, and other vehicles, such as recreational vehicles. The trailers are provided with an electric braking system that includes a pair of brake shoes (for a two wheeled trailer) which are actuated by a well known electromagnet-actuated lever device to apply a braking force to the drums of the trailer wheels. Generally, the braking force applied by the brake shoes against the wheel drums is proportional to the electric current supplied to the wire coils of the electromagnets.
Electronic brake controllers are available which include a sensing device that generates a brake control signal corresponding to the desired magnitude of braking force to be applied to the towed vehicle. For example, a pendulum is used in some electronic brake controllers to sense deceleration of the towing vehicle upon braking and generate a brake control signal proportional to movement of the pendulum, for example, as described in U.S. Pat. No. 4,721,344.
Such electronic brake controllers usually include an analog pulse width modulator which receives the brake control signal from the sensing device. The pulse width modulator is responsive to the brake control signal to generate an output signal that has constant frequency pulse train with the duty cycle of the pulse train varied in proportion to the magnitude of the brake control signal from the sensing device. An output stage of the controller is electrically connected to the output of the pulse width modulator. The output stage can have multiple power transistors which are connected between the towing vehicle power supply and the towed vehicle brake electromagnets and which function as an electronic switch for supplying electric current to the coils of the electromagnets. The output is responsive to the pulse width modulator output signal to switch the power transistors between conducting and nonconducting “on”/“off” states. As the transistors are so switched, the brake current is divided into a series of pulses. The power supplied to the towed vehicle electromagnets and the resulting magnitude of braking are directly proportional to the duty cycle of the output signal of the pulse width modulator.
An object of the present invention is to provide an electronic brake controller for controlling electric brakes of a towed vehicle in a manner to provide the driver of the towing vehicle with improved control over braking force applied to the wheels of the towed vehicle.
Another object of the present invention is to provide an electronic brake controller for controlling electric brakes of a towed vehicle in a manner to provide a braking force to the wheels of the towed vehicle that is proportional to the braking force applied by the driver to the brake pedal of the towing vehicle.
Still another object of the present invention is to provide an electronic brake controller for controlling electric actuated brakes of a towed vehicle with braking force to the trailer brakes controlled in response to feedback provided by a resistive brake pedal pad sensor that senses the braking force applied by the driver of the towing vehicle.
A further object of the present invention is to provide an electronic brake controller having a main electronic control unit hard wired to the vehicle electrical system and a remote driver-operable manual control unit tethered to the main electronic control unit and positioned at a desired driver-selected location in the towing vehicle to facilitate actuation by the driver of the towing vehicle.
SUMMARY OF THE INVENTION
The present invention provides in one embodiment an electronic brake controller for controlling electric brakes of a towed vehicle, such as a trailer, wherein the electronic brake controller includes a force sensor at the brake pedal of the towing vehicle that senses the braking force applied by the driver of the towing vehicle to the braking pedal by virtue of changes in electrical conductance (or resistance) thereof in dependence on the applied braking force. The force sensor provides an electrical signal proportional to the braking force applied to the brake pedal to an electronic control microprocessor.
The microprocessor receives an initial signal representative of initial electrical conductance (or resistance) of the sensor when the brakes of the towing vehicle are not actuated and a subsequent braking force signal representative of subsequent electrical conductance (or resistance) thereof when the brake pedal is pressed by the driver of the towing vehicle. The microprocessor converts the force sensor signals to corresponding braking output signals and controls braking force applied to the trailer brakes in proportion to the force applied by the driver of the towing vehicle to the brake pedal.
In an illustrative embodiment of the invention, the electronic brake controller is operable to control the towed vehicle electric brakes when the microprocessor detects the towing vehicle brake light “on” condition and the presence of the brake pedal force sensor. During operation, the microprocessor samples the brake pedal force sensor. The microprocessor compares an initial sensor signal (representative of initial sensor conductance) measured when the towing vehicle brake lights are “off” and stored in the microprocessor as a reference sensor conductance value and a subsequent braking signal from the force sensor (representative of subsequent sensor conductance) measured when the towing vehicle brake lights are “on”. From the comparison, the microprocessor provides an output signal to the electric brakes of the towed vehicle that is proportional to the braking force applied by the driver to the towing vehicle brake pedal. In a preferred embodiment of the invention, the microprocessor reads an ambient temperature compensated, amplified braking force signal to provide a temperature-compensated output signal representative of brake force to be applied to the towed vehicle electric brakes.
In one embodiment of the invention, the microprocessor initially reads the force sensor and stores this number or value as an initial reference signal. Thereafter, when the force sensor is activated by the driver's pressing on the brake pedal (brake light “on”), the microprocessor reads the force sensor, determines a higher number or value resulting from pressure on the brake pedal, and subtracts the initial number or value from the subsequent measured number or value and provides an output signal to the electric brakes of the towed vehicle that is proportional to the braking force applied by the driver to the towing vehicle brake pedal (i.e. the difference between the aforementioned initial and subsequent number or value).
When the towing vehicle brakes are not actuated by the driver (brake light is “off”), the microprocessor assumes a sleep mode with periodic wake ups to initially read the brake pedal force sensor signal. If the force sensor is not installed or becomes inoperative (e.g. by becoming disconnected), then the microprocessor will operate in a non-sensor mode where the output signal to the towed vehicle brakes will ramp up with time upon actuation of the brakes pursuant to a preset output setting (braking force) and ramp setting (rate of application of braking force) of the controller. The electronic brake controller also is operable in a manual mode controlled directly by the dri
Guzorek Richard J.
Hallenbeck Ray M.
Kovitz John T.
Verburg Ralph E.
Saturn Electronics & Engineering, Inc.
Schwartz Chris
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