Cruise control overspeed reduction with automatic transmission

A method of controlling speed of a vehicle equipped with an automatic transmission and cruise speed control so as to maintain a driver selected setpoint speed by causing engine braking for an overspeed condition, said method comprising the steps of:

• storing a setpoint speed associated with the cruise speed control;
• detecting speed of the vehicle;
• comparing the detected speed of the vehicle with the setpoint speed;
• determining when the detected vehicle speed exceeds the setpoint speed by an predetermined overspeed value;
• monitoring throttle position of the vehicle and determining if a substantially closed throttle condition exists which is indicative of an attempt to reduce vehicle speed;
• and
• causing a transmission downshift in the automatic transmission when the vehicle speed exceeds the setpoint speed by said overspeed amount while the throttle position is substantially closed so as to brake the vehicle in an attempt to overcome the overspeed condition.

A system for controlling speed of a vehicle equipped with an automatic transmission and cruise speed control to reduce overspeed conditions, said system comprising:

• sensing means for sensing vehicle speed;
• throttle position sensing means for monitoring position of a throttle;
• a cruise speed controller having a user selectable input for receiving a setpoint speed, said cruise speed controller comparing the vehicle speed with the setpoint speed and controlling the throttle position so as to attempt to maintain the vehicle speed within an acceptable range of the setpoint speed;
• and
• an automatic transmission controller for controlling the shifting of the automatic transmission among various gears, said automatic transmission controller determining engagement and disengagement of the various gears based on a stored shift schedule, said automatic transmission controller further providing a downshift to a lower gear during an overspeed condition when the throttle position is substantially closed.