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Electronic control system for powershift transmission

  • US 4,855,913 A
  • Filed: 05/29/1987
  • Issued: 08/08/1989
  • Est. Priority Date: 05/29/1987
  • Status: Expired due to Term
First Claim
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1. An electronic control system for a powershift transmission having a plurality of hydraulically-actuated clutches and a plurality of electrically-operated hydraulic valves for selecting the clutch for engagement, each such valve being provided with electrical coil means for operating the valve, the control system comprising:

  • first electrical switching means for providing a first electrical signal to a first electrical coil means associated with a first hydraulic valve for selecting a first clutch of the transmission for engagement;

    second electrical switching means for providing a second electrical signal which is proportional signal to a second electrical coil means associated with a second hydraulic valve for adjusting the hydraulic pressure applied to the first clutch during engagement thereof;

    microprocessor means for operating the powershift transmission in accordance with operating parameters stored within the microprocessor means, the operating parameters including a first parameter corresponding to a reduced hydraulic pressure to be applied to the first clutch during initial engagement thereof,the microprocessor means including first output means for controlling the first electrical switching means, second output means for controlling the second electrical switching means, and means for causing the second electrical signal to command the second hydraulic valve to adjust the hydraulic pressure applied to the first clutch during the initial engagement thereof in accordance with a stored value of the first parameter;

    wherein the second electrical signal is a pulse width modulated (PWM) signal;

    wherein the first signal electrical coil means are solenoid coils, and wherein the first and second electrical switching means are substantially identical in construction;

    means for providing a predetermined time delay between the application of the first electrical signal to the first electrical coil means and the application of the second electrical signal to the second electrical coil means; and

    wherein the operating parameters stored within the microprocessor means includes a second parameter corresponding to the rate at which hydraulic pressure applied to the first clutch during engagement thereof is to be increased from the reduced pressure applied during the initial engagement of the first clutch, and a third parameter corresponding to the maximum length of time reduced hydraulic pressure is to be applied to the first clutch during engagement thereof, andthe microprocessor means includes means for causing the second electrical signal to command the second hydraulic valve to increase the hydraulic pressure applied to the first clutch during engagement thereof from the reduced pressure applied during the initial engagement thereof in accordance with a stored value of the second parameter, and means for causing the second electrical signal to command the second hydraulic valve to apply reduced hydraulic pressure to the first clutch during engagement thereof in accordance with a stored value of the third paramenter.

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