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Control system

  • US 7,269,492 B2
  • Filed: 06/02/2004
  • Issued: 09/11/2007
  • Est. Priority Date: 06/03/2003
  • Status: Active Grant
First Claim
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1. A control unit built in a casing of a vehicle automatic transmission, said control unit comprising:

  • a CPU which outputs a drive signal according to signals from at least one sensor for sensing vehicle operating parameters;

    a load drive element which supplies a drive current to a load according to the drive signal;

    a temperature sensor which detects a temperature of the control unit;

    a monitor circuit which is connected to receive a periodic signal that is output from the CPU whenever the temperature detected by the temperature sensor is below a specified value and the CPU is in normal operation; and

    a compulsory turn-off circuit which is connected between a control input terminal of the load drive element and ground potential;

    wherein,the monitor circuit outputs a first reset signal to a reset terminal of the CPU when the CPU fails to output the periodic signal;

    the monitor circuit outputs a second reset signal to the compulsory turn-off circuit when the number of the outputs of the first reset signal has reached a specified number;

    upon receipt of the second reset signal, the compulsory turn-off circuit turns off the load drive element and stops the supply of drive current to the load, even if the CPU thereafter outputs said periodic signal; and

    the number of the outputs of the first reset signals is cleared to zero when a key of a vehicle is turned on.

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