Importance

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Abstract

A traction control system provides coordinated use of axle torque management via engine spark, engine fuel, and transmission gear ratio. Primary torque management is provided by retarding the ignition timing to reduce engine torque. When the spark retard reaches a determined limit value, the vehicle automatic transmission is upshifted which reduces axle torque and engine speed, thus reducing the amount of spark retard required to control a slip condition, thereby increasing the authority of the spark retard system. The limit spark retard threshold is established as a function of the temperature of the catalytic converter so as to prevent an overtemperature condition. Further, fuel control is ultimately used if control of ignition timing is incapable of bringing the acceleration slip under control. This condition may exist, for example, when the spark system authority of control is insufficient due to limitations placed upon its authority in response to a sensed hot catalytic converter condition.

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First Claim