Method of controlling an automatic transmission

• US 6,871,130 B2
• Filed: 09/23/2003
• Issued: 03/22/2005
• Est. Priority Date: 09/30/2002
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Nanri, Takehiko
• Primary Examiner(s): Camby, Richard M.
• Application Number:
  US10/668,613
• Publication Number:
  US 20040098183A1
• Time in Patent Office: 546 Days
• Field of Search: 701/51, 701/53, 701/55, 701/56, 701/82, 701/90, 180/197, 477/34, 477/78, 477/99
• US Class Current: 701/51
• CPC Class Codes: F16H 2059/506 Wheel slip
• CPC Class Codes: F16H 2061/163 Holding the gear for delaying gear shifts under unfavorable conditions, e.g. during cornering
• CPC Class Codes: F16H 59/58 dependent on signals from the steering
• CPC Class Codes: F16H 61/16 Inhibiting or initiating shift during unfavourable conditions, e.g. preventing forward reverse shift at high vehicle speed, preventing engine over speed unintentional control input F16H61/18

Abstract

A downshift control method for an automatic transmission, which transmission is normally downshifted, to increase a gear ratio, when a vehicle throttle is opened more than a preset value. The method includes a step of selecting a slip-determining threshold on the basis of an instantaneous steering angle of a vehicle. The method also includes steps of detecting a perceived rear wheel speed V_s, and averaging a number of rear wheel speeds V_s to derive an average vehicle speed V_a. The normal downshift procedure is overridden, and the automatic transmission is prevented from downshifting, if a difference between the perceived rear wheel speed and the average vehicle speed exceeds the slip-determining threshold T, and the rear wheels are determined to be slipping.

Claims

1. A method of controlling an automatic transmission which is adapted to normally downshift to increase a gear ratio when a vehicle throttle is opened more than a preset amount, the method comprising the steps of:

a) selecting a slip-determining threshold based on an instantaneous steering angle of a vehicle;

b) detecting a perceived rear wheel speed of the vehicle;

c) averaging a number of recorded rear wheel speeds to derive an average vehicle speed; and

d) prohibiting downshifting of the automatic transmission if a difference between the perceived rear wheel speed and the average vehicle speed exceeds the selected slip-determining threshold.

2. The method of claim 1, wherein the selected slip-determining threshold is based on a stored relationship between steering angles and potential slip-determining thresholds.

3. The method of claim 1, wherein the steering angle is decided on the basis of the forward direction of the vehicle.

4. The method of claim 1, wherein the average vehicle speed is derived by averaging a plurality of periodically and recently detected wheel speeds.

5. The method of claim 1, wherein the method is performed by an engine control unit for the vehicle.

6. A method of controlling a downshift function of an automatic transmission in a vehicle having a powertrain, comprising the steps of:

a) monitoring a plurality of signals from a plurality of sensors associated with the powertrain, said sensors comprising a vehicle speed sensor, a throttle position sensor and a steering angle sensor;

b) selecting a slip-determining threshold based on an instantaneous steering angle determined by said steering angle sensor;

c) detecting a perceived rear wheel speed;

d) averaging a plurality of rear wheel speeds and deriving an average vehicle speed; and

e) overriding a normal downshift sequence and prohibiting downshifting of the automatic transmission if a difference between the perceived rear wheel speed and the average vehicle speed exceeds the selected slip-determining threshold.

7. The method of claim 6, wherein the selected slip-determining threshold is based on a stored relationship between steering angles and potential slip-determining thresholds.

8. The method of claim 6, wherein the steering angle is decided on the basis of the forward direction of the vehicle.

9. The method of claim 6, wherein the average vehicle speed is derived by averaging a plurality of periodically and recently detected wheel speeds.

10. The method of claim 6, wherein the method is performed by an engine control unit for the vehicle.