Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
2003-02-14
2004-12-21
Thompson, Gregory D (Department: 2835)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C165S080300, C165S185000, C257S707000, C257S712000, C257S722000, C361S704000, C361S715000
Reexamination Certificate
active
06833990
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an electronic controller module formed of a heat-resistant material, such as a polyamide homopolymer or copolymer, for providing control of electric motors, and an article including such modules. Specifically, the present invention is directed to a module including a nylon-polypropylene, glass-filled material, particularly for use in automotive applications.
BACKGROUND OF THE INVENTION
The electrical systems for which many electronic controllers are presently designed are typically, such as in automobiles, 12 V or 24 V systems. The controllers are typically attached to the car dashboard, seat bottom, or the like by being screwed into place.
Control of present-day electric motors, such as those used in the heating ventilating and air conditioning (HVAC) systems of automobiles, has mainly been achieved using switch-mode technology, in which a fixed power supply is turned on or off as needed to control the speed of the electric motor. In the United States, this technology has been implemented primarily by use of a resistive divider or by pulse width modulation (PWM). A resistive divider operates by modulating the power provided to the electric motor by a constant or adjustable amount, resulting in a choppy or stepwise level of control.
PWM works by modulating the timing of the lead and trail edges of the power signal to the electric motor. PWM results in a relatively inaccurate control of an electric motor, and may also introduce a choppy quality of control.
Alternatively, some use has been made in Europe of a type of linear motor controller. A linear electric motor controller generally works by directly controlling the motor speed by setting the voltage of the power supplied to the electric motor. The speed of the electric motor has a linear relationship with the voltage of the power supplied to the motor, hence the term “linear.” These systems are characterized by an undesirably large latency period, i.e., between detection and correction of the desired motor speed.
Also, some use has been made of analog variable-direct current (DC) voltage for control of variable speed electric motors, with a method that involves using a low-pass filter to generate the DC voltage. The low-pass filter used to generate the DC voltage to the motor introduces a stepwise/choppy quality to the control of the motor voltage, similar to the use of a resistive divider.
The widespread use of linear controllers for control of present-day variable speed electric motors, however, has been frustrated largely due to the large amount of heat generated by such controllers, and the difficulty thus encountered in practice when using such controllers. As an example, linear controllers may require heat dissipation ratings of 90-95 watts. Linear controllers used previously were designed so that the controller was remotely located from heat-sensitive structures, which tended to result in increased size of the controller module. The difficulty in cooling such linear controllers, thermal melting and breakdown of the material enclosing linear controller units, and a need for placement of the controller within a cooling air stream has limited the use of such controllers in practical applications.
On the other hand, PWM-type controllers require a heat dissipation rating of only 6-10 watts, which advantageously allows for the controller to be located adjacent to heat-sensitive components such as plastics. The housing of contemporary electric motor controller units, however, is typically made of standard injection-molded polypropylene plastics, which can handle close contact with 6-10 watts of heat dissipation as with a PWM-type controller, but not the 90-95 watts involved with linear controllers. Thus, switch-mode or PWM-type controllers tend to be highly desired for commercial production applications.
It would be desirable to overcome the various problems and disadvantages of both the heat-issues of linear control systems and the crude control of PWM-type controllers in the prior art to satisfy the design requirements for current electrical systems, in particular automotive systems.
SUMMARY OF THE INVENTION
The present invention now provides an electric motor controller that can be both smaller and lighter in weight than a switch-mode controller of the prior art. This can help increase fuel economy, decrease vehicle size, or increase the space available within the vehicle for other uses, as well as combinations thereof, all of which are highly desirable achievements. The invention also optionally, but preferably, packages the circuitry of the controller into an integrated circuit to further reduce the weight and size of the controller.
The controller includes an internal feedback mechanism to minimize control and monitoring latency, which provides for a more accurate control of the electric motor speed. This mechanism optionally, but preferably, incorporates a digital conversion to generate the motor voltage and current, thereby allowing for further increased accuracy compared to conventional low-pass filters.
The linear motor controller can also include a suitable heat sink, capable of conducting heat from the controller, wherein the heat sink is made of a material and designed so as to maximize the dissipation of heat from the controller. This enables the controller to be located in closer proximity to plastic components and/or a plastic housing, which also then allows for the controller module to be designed smaller if desired. The controller housing and plastic components are designed to be more capable of withstanding the increased wattage of heat dissipated by the controller, thereby also allowing for the controller to be placed in closer proximity to the plastic components and/or housing, thereby also contributing to reduction in size of the controller module. Additionally, the placement of the controller is preferably optimized within a cooling airflow so as to facilitate heat dissipation from the controller through the heat sink.
The invention relates to an automotive electric motor linear speed controller that includes a digital to analog converter means for converting an 8 bit digital signal to analog voltage for setting voltage across the electric motor, a digital state machine means for converting the duty cycle of an input signal for output to the digital to analog converter means, and a closed loop feedback loop means for monitoring and setting the voltage across the automotive motor. It is also advantageous to include an over-current sense circuit for monitoring the current across the electric motor, an over/under voltage sense circuit for monitoring a supply voltage to the electric controller, or both, although neither is strictly required.
Another embodiment of the invention relates to a circuit arrangement in a variable speed automotive electric motor controller. The circuit arrangement includes a controller logic circuit for operating a controller logic finite state machine, in which the state machine sets the voltage supplied to an electric motor. It can also include a closed loop feedback for generating a signal indicating the voltage across the electric motor, which can then be input to the state machine for monitoring thereof.
In another embodiment, the invention includes a system incorporating at least the above-described automotive electric motor linear speed control. In another embodiment, the invention includes a system for controlling the speed of an automotive electric motor, in which the voltage across the electric motor determines the speed of the electric motor. This system can include a digital to analog converter means for converting a digital signal to analog voltage for setting voltage across the electric motor, a microprocessor and associated digital memory for generating the digital signal, where the microprocessor is configured to instantiate and operate a digital state machine for converting the duty cycle of an input signal generated by an associated closed loop feedback means, and a closed loop feedback loop means for monitoring th
Beaumont Marcus
LaCroix Michael Charles
Carter Group, Inc.
Thompson Gregory D
Winston & Strawn LLP
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