Motor vehicle heated seat control

• US 5,229,579 A
• Filed: 03/02/1990
• Issued: 07/20/1993
• Est. Priority Date: 05/13/1987
• Status: Expired due to Fees

• Current Assignee: Nartron Corporation
• Original Assignee: Nartron Corporation
• Inventors: Wilhelm, Daniel D., Ingraham, Ronald D.
• Primary Examiner(s): Paschal, Mark H.
• Application Number:
  US07/488,671
• Time in Patent Office: 1,236 Days
• Field of Search: 219/202, 219/203, 219/491, 219/494, 219/497, 219/499, 219/501, 219/505, 219/481
• US Class Current: 219/202
• CPC Class Codes: B60H 1/2218 controlling the operation of electric heaters
• CPC Class Codes: G05D 23/2401 using a heating element as a sensing element
• CPC Class Codes: H02H 3/087 for dc applications
• CPC Class Codes: H02H 3/12 responsive to underload or no-load for motors H02H7/0827

Abstract

A control for a resistive heating element embedded within a motor vehicle seat is disclosed. In one embodiment, a transistor is biased into conduction to energize the heating element when the temperature of the element is below a threshold that is adjusted by the vehicle operator. A fault sensing system monitors operation of the control unit and de-energizes the heating element if a fault is sensed. Sensed faults include both short circuits and undesirable open circuits. Power application to the resistive heating unit can be either pulsed or continuous. In one embodiment, once a fault is detected, the heating system cannot be re-energized until the vehicle ignition switch is turned off and then returned to its on position.

Claims

1. A method for energizing a resistive heating element of a motor vehicle seat, by use of direct current, said method comprising the steps of:

a) closing a user actuated switch to apply a direct current, vehicle battery energization voltage to an energization switch coupled across a seat heating circuit including the resistive heating element and a DC controlled semi-conductor switching device for controlling direct current flow through the resistive heating element;

b) sensing the temperature of the resistive heating element by the use of a temperature sensor and generating a sensed signal related to the sensed temperature of the resistive heating element;

c) producing a control signal related to a user control input corresponding to a desired vehicle seat temperature;

d) comparing the control signal with the sensed signal by use of DC based circuitry and, if the comparison indicates that the temperature of the resistive heating element should be increased to cause the seat to reach the desired temperature, applying direct current continuously through the heating element by activating the switching device to cause direct current flow through the resistive heating element until the temperature of the motor vehicle seat reaches the desired temperature as indicated by the sensed signal;

e) producing and monitoring by use of DC based circuitry a fault signal indicating one of a heating element short circuit or an undesirable open circuit, and

f) if the fault signal indicates a short circuit across the resistive heating element, or an undesirable open circuit, removing the direct current application from the resistive heating element.

2. A system for controllably heating a vehicle seat, by use of direct current, said system comprising:

a) a resistive heating element adapted for inclusion in the vehicle seat;

b) a seat heater control unit comprising DC based circuitry for controlling application to the resistive heating element of a substantially direct current which is applied to said seat heater control unit;

c) circuitry for selectively applying said direct current to said control unit by means of a switch of the vehicle;

d) a user actuated temperature select device for producing a reference electrical signal representing a desired vehicle seat temperature;

e) said control unit comprising;

i) a DC controlled semi-conductor switching device in series with said resistive heating element;

ii) a temperature sensor separate from said resistive heating element;

iii) a DC based comparator for comparing the reference signal with the sensed temperature for actuating said switching device to provide a continuous application of direct current flow to said resistive heating element in response to said comparison indicating that the sensed temperature is less than the temperature represented by the reference signal.

3. The apparatus of claim 2, wherein:

said temperature sensor comprises a thermistor.

4. The apparatus of claim 2, further comprising:

a) DC based circuitry for sensing excessive current flow through said resistive heating element, and

b) DC based circuitry for interrupting application of electrical power to said resistive heating element in response to sensing of said excessive current flow.

5. The apparatus of claim 4, wherein:

said circuitry for sensing excessive current flow comprises a foil resistor.

6. The apparatus of claim 2, further comprising:

a) DC based circuitry for detecting an undesirable open circuit within said seat heater control unit, and

b) circuitry for interrupting application of electric power to said resistive heating element in response to sensing of said undesirable open circuit.

7. The apparatus of claim 2, further comprising:

a) DC based circuitry for detecting a malfunction in said seat heater control unit, including a malfunction associated with said switching device, and

b) circuitry responsive to detection of a malfunction for disabling further operation of said seat heater control unit, and for re-enabling said operation only after said power switch is turned off and then on again.

8. A vehicle seat heater comprising:

a) a resistive heating element adapted for placement in a vehicle seat;

b) circuitry for controlling application of DC electric power to said resistive heating element;

c) DC based circuitry for detecting a short circuit in said control circuitry;

d) DC based circuitry for detecting an undesirable open circuit in said control circuitry;

e) circuitry responsive to detection of a short circuit for interrupting application of electric power to said resistive heating element, and

f) circuitry responsive to the detection of an undesirable open circuit for interrupting application of electrical power to said resistive heating element.

9. The heater of claim 8, wherein said circuitry for detecting a short circuit includes a foil resistor.

10. Circuitry for controlling application of DC electric power to a resistive heating element for a vehicle seat, said circuitry comprising:

a) ignition control circuitry associated with an ignition circuit of the vehicle for producing an enabling signal when the power is turned on;

b) a seat heater control unit including circuitry responsive to the enabling signal for continuously applying DC electrical power to the resistive heating element, said control unit including temperature responsive feedback circuitry for sensing resistive heating element temperature and regulating the application of DC electric power to the resistive heating element in response to the sensed temperature;

c) circuitry for detecting a malfunction in the control unit by the use of DC, and

d) circuitry for interrupting electrical power application to the resistive heating element in response to said malfunction detection, and for reapplying electrical power to the resistive heating element only after turning off said ignition circuit and then returning the ignition circuit to its on condition.