Engine coastdown control system
First Claim
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1. A method of controlling the rate of airflow into an engine of a vehicle during vehicle coastdown, the vehicle having wheels driven by the engine through an automatic transmission, the method comprising the steps of:
- measuring a slip value of the automatic transmission;
sensing a coastdown condition of the vehicle;
comparing the measured slip value to a reference slip value; and
adjusting the rate of airflow into the engine during the sensed coastdown condition in a direction restoring the slip value of the automatic transmission to the reference slip value.
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Abstract
When the throttle of a vehicle engine is released by the vehicle operator of a vehicle having an automatic transmission, the slip of the automatic transmission is measured and the airflow of the engine is trimmed as a function of the measured slip to establish a desired drive-on feel of the vehicle during coastdown.
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Citations
7 Claims
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1. A method of controlling the rate of airflow into an engine of a vehicle during vehicle coastdown, the vehicle having wheels driven by the engine through an automatic transmission, the method comprising the steps of:
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measuring a slip value of the automatic transmission; sensing a coastdown condition of the vehicle; comparing the measured slip value to a reference slip value; and adjusting the rate of airflow into the engine during the sensed coastdown condition in a direction restoring the slip value of the automatic transmission to the reference slip value. - View Dependent Claims (2, 3)
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4. A method of controlling the rate of airflow into an engine of a vehicle during vehicle coastdown, the vehicle having wheels driven by the engine through an automatic transmission, the method comprising the steps of:
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measuring a slip value of the automatic transmission; sensing a coastdown condition of the vehicle; comparing the measured slip value to a reference slip value; controlling the rate of airflow into the engine to a desired coastdown base airflow rate value that is a function of predetermined engine and vehicle parameters; and adjusting the controlled rate of airflow into the engine during the sensed coastdown condition in a direction restoring the slip value of the automatic transmission to the reference slip value.
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5. A method of controlling the rate of airflow into an engine of a vehicle during vehicle coastdown, the vehicle having wheels driven by the engine through an automatic transmission and the engine having fuel delivery that is disabled in response to predetermined vehicle deceleration conditions, the method comprising the steps of:
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measuring a slip value of the automatic transmission; sensing a coastdown condition of the vehicle; controlling the rate of airflow into the engine to a desired coastdown base airflow rate value that is a function of predetermined engine and vehicle parameters; determining an airflow slip correction amount; and when the fuel delivery is disabled during the sensed coastdown condition, adjusting the controlled rate of airflow into the engine by an amount equal to the airflow slip correction amount and in a direction restoring the slip value to the reference slip value. - View Dependent Claims (6)
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7. A system for controlling the rate of airflow into an engine of a vehicle during vehicle coastdown, the vehicle having wheels driven by the engine through an automatic transmission, the system comprising in combination:
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an engine speed sensors sensing a speed of rotation of the engine; a transmission speed sensor sensing a speed of rotation of the transmission output; means for measuring a slip value of the automatic transmission in accord with the difference of the sensed speeds of rotation of the engine and the transmission output; means for determining a coastdown condition of the vehicle; an airflow control valve for controlling a rate of airflow into the engine; means for comparing the measured slip value to a reference slip value; and means for controlling the airflow control valve during the determined coastdown condition to adjust the controlled rate of airflow into the engine in a direction restoring the slip value to the reference slip value.
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Specification