Gear shift control device of automatic transmission with estimation of tire grip limit

• US 5,839,083 A
• Filed: 03/31/1997
• Issued: 11/17/1998
• Est. Priority Date: 05/10/1996
• Status: Expired due to Fees

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Sugiyama, Mizuho
• Primary Examiner(s): Louis Jacques, Jacques H.
• Application Number:
  US08/825,621
• Time in Patent Office: 596 Days
• Field of Search: 701/69, 701/70, 701/71, 701/72, 701/76, 701/82, 701/84, 701/90, 701/92, 701/95, 701/97, 701/51, 701/53, 701/54, 701/62, 701/64, 701/65, 701/74, 180/197, 180/412, 180/446, 180/282, 303/145, 303/146, 303/140, 477/49, 477/156, 477/44, 477/115, 477/125, 477/78, 477/143, 477/154
• US Class Current: 701/62
• CPC Class Codes: B60K 28/165 acting on elements of the vehicle drive train other than the propulsion unit and brakes, e.g. transmission, clutch, differential acting on brakes B60T8/17
• CPC Class Codes: F16H 2059/506 Wheel slip
• 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 gear shift control device of an automatic transmission of a vehicle, including: a means for estimating a target shift stage for harmonizing rotation speed and power output of engine of the vehicle; a means for estimating slip angle of at least one of the pair of drive wheels; a means for estimating slip ratio of the at least one drive wheel which would be caused thereon by the automatic transmission being shifted to the target shift stage; a means for estimating tire grip of the at least one drive wheel based upon the estimated slip angle and the estimated slip ratio; a means for judging if the estimated tire grip of the at least one drive wheel is in a grip range predetermined therefor; and a means for executing gear shift of the automatic transmission when the target shift stage is different from a current shift stage with the estimated tire grip being within the predetermined grip range.

Claims

1. A gear shift control device of an automatic transmission of a vehicle having an engine, a pair of drive wheels and a pair of driven wheels, comprising:

a means for estimating a target shift stage for harmonizing rotation speed and power output of the engine;

a means for estimating slip angle of at least one of the pair of drive wheels;

a means for estimating slip ratio of said at least one drive wheel which would be caused thereon by the automatic transmission being shifted to said target shift stage;

a means for estimating tire grip of said at least one drive wheel based upon said estimated slip angle and said estimated slip ratio;

a means for judging if said estimated tire grip of said at least one drive wheel is in a grip range predetermined therefor; and

a means for executing gear shift of the automatic transmission when said target shift stage is different from a current shift stage with said estimated tire grip being within said predetermined grip range.

2. A gear shift control device according to claim 1, wherein said predetermined grip range is an area defined inside of an ellipse in a coordinate system of abscissa and ordinate providing a coordination of slip angle and slip ratio of said at least one drive wheel, said ellipse having a first radius along one of the abscissa and the ordinate and a second radius along the other of the abscissa and the ordinate, said first radius being such a value of slip angle considered to be a maximum allowable for said at least one drive wheel when the slip ratio thereof is zero, said second radius being such a value of slip ratio considered to be a maximum allowable for said at least one drive wheel when the slip angle thereof is zero.

3. A gear shift control device according to claim 1, wherein the vehicle comprises a means for selectively prohibiting gear shift of the automatic transmission for the purpose of running stability control of the vehicle, said gear shift control device further comprising a means for canceling gear shift prohibition by said gear shift prohibition means when said target shift stage is different from a current shift stage with said estimated tire grip being within said predetermined grip range.