Electronic controller for predetermined temperature coefficient heater

• US 4,694,145 A
• Filed: 02/15/1985
• Issued: 09/15/1987
• Est. Priority Date: 02/15/1985
• Status: Expired due to Fees

• Current Assignee: Siemens-Bendix Automotive Electronics LP
• Original Assignee: Allied Corp. (Honeywell International Inc.)
• Inventors: Seitz, William R., Romstadt, Douglas J.
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US06/701,907
• Time in Patent Office: 942 Days
• Field of Search: 219/494, 219/205, 219/202, 219/203, 219/497, 219/499, 219/501, 219/483, 219/507, 219/508, 219/505, 123/179 H, 123/179 B
• US Class Current: 219/497
• CPC Class Codes: F02P 19/025 with means for determining glow plug temperature or glow plug resistance

Abstract

An electronic controller for a predetermined temperature coefficient heater provides solid state control of the application of power to the heater. In particular, a positive temperature coefficient glow plug wherein the heater is plated on a ceramic substrate glow plug is controlled by contactless solid state controller. The temperature of the glow plug is sampled by a clock signal and compared with a predetermined temperature value. Pulsed power is supplied to elevate and maintain the temperature of the heater to the predetermined value. In a complete motor vehicle engine wherein one glow plug is used in each cylinder, one glow plug is sampled and controls the remainder of the plugs.

Claims

1. In a diesel engine a system for controlling positive temperature coefficient glow plugs comprising:

at least one positive temperature coefficient glow plug in each cylinder of a diesel engine;

clock means for generating clock signals having a sample period and an activation period;

contactless means for applying activating current to each of said glow plugs;

means for sensing an amount of sensing current to only one of said glow plugs during said sample period of said clock means and generating a first electrical signal proportional to the amount of sensed current, said sensing current being less than said activating current and said sensing means not responsive to said activating current to said glow plugs;

means for generating a second electrical signal proportional to the actual temperature of the diesel engine;

means for generating a third electrical signal representing a predetermined glow plug temperature;

means for generating a fourth electrical signal representing a predetermined operating temperature of said engine;

means responsive to said first and third electrical signals during said activation period of said clock means for activating said contactless means for applying activating current to each of said glow plugs when said actual temperature is less than said predetermined operating temperature; and

means responsive to said second and fourth electrical signals for inhibiting said contactless means for applying activating current to each of said glow plugs when said temperature of said engine is equal to said predetermined operating temperature.

2. A contactless electronic controller for heating a single glow plug comprising:

a glow plug;

clock means for generating clock signals having a sample period and an activation period;

a constant voltage means activated by said sample period of said clock means;

a sensing resistor electrically connected in series between said constant voltage means and said glow plug, said resistor responsive to the voltage drop across said glow plug due to a sensing current flowing therethrough for generating a voltage signal representing the temperature of said glow plug;

means for generating a voltage signal representing the desired operating temperature of said glow plug;

comparison means responsive to said voltage signals representing the desired operating temperature and said temperature of said glow plug for generating a comparison signal when the temperature of said glow plug is less than the desired operating temperature;

latch circuit means responsive to said activation period and said comparison signal for generating a power applying control signal; and

contactless power driver circuit means electrically connected series with said glow plug and in electrical parallel with said constant voltage means and said sensing resistor and responsive to said power applying signal for supplying activating current to said glow plug for raising its temperature to the desired operating temperature.