Method and apparatus for downshifting an automatic vehicle transmission

Patent metadata

Field	Value
Publication number	US-2016201797-A1
Application number	US-201414912301-A
Country	US
Kind code	A1
Filing date	Aug 7, 2014
Priority date	Aug 19, 2013
Publication date	Jul 14, 2016
Grant date	—

Abstract

A multi-speed automatic vehicle transmission has an electronic control unit which permits multiple downshifts if certain conditions are satisfied. Such downshifts are direct and omit engagement and disengagement of one or more intermediate speed ratios. Multiple downshifting may allow the actual speed ratio to better match the ideal speed ratio, for example under heavy braking.

First claim

1 - 20 . (canceled)

21 . A method of downshifting in a multi-speed automatic transmission of a vehicle, the method comprising:
commanding a multiple downshift if permitted by a pre-determined control condition, wherein said pre-determined control condition is selected from one or more of: accelerator pedal position being below a position threshold; vehicle brakes being activated; and vehicle brake pressure being above a brake pressure threshold.

22 . A method according to claim 21 where said multiple downshift is a double downshift.

23 . A method according to claim 21 , including the further step of inhibiting temporarily an upshift after said multiple downshift.

24 . A method according to claim 21 , wherein two or more of said control conditions must be satisfied to permit a multiple downshift.

25 . A method according to claim 21 , comprising inhibiting a commanded multiple downshift if prevented by an inhibit condition, and allowing immediately an upshift.

26 . A method according to claim 25 , wherein said inhibit condition is selected from:
detection of a vehicle mode change; accelerator pedal position being above a position threshold; manual downshifting being commanded; road speed exceeding a road speed threshold; road gradient exceeding a gradient threshold; rate of change of vehicle speed is less than a low rate threshold; rate of change of vehicle speed is less than a high rate threshold, and lateral acceleration exceeding a lateral acceleration threshold.

27 . A method according to claim 26 , wherein the vehicle mode change is between one and another of:
highway driving; sand driving; mud driving; snow driving; grass driving; gravel driving; and ice driving.

28 . A method according to claim 26 , wherein the vehicle mode change is between comfort mode and sport mode.

29 . A method according to claim 26 , wherein said inhibit condition requires road speed to exceed said road speed threshold, and road gradient to exceed said road gradient threshold.

30 . A method according to claim 26 , wherein said road gradient threshold comprises thresholds for positive and negative gradient.

31 . A method according to claim 27 , wherein said positive threshold gradient is different from said negative threshold gradient.

32 . A method according to claim 21 , wherein said transmission comprises five or more forward speed ratios, the method including the preliminary step of applying a mask to inhibit a multiple downshift from one or more of said speed ratios.

33 . A method according to claim 21 , wherein said transmission comprises five or more forward speed ratios, the method including the preliminary step of applying a mask to allow a multiple downshift from one or more of said speed ratios.

34 . An electronic control unit of an automatic transmission of a vehicle, said control unit being programmed to implement the method of claim 21 .

35 . A vehicle transmission having five or more individually selectable forward speed ratios, and an electronic control unit according to claim 34 for determining selection of said speed ratios.

36 . A vehicle incorporating the transmission of claim 35 .

Assignees

• Jaguar Land Rover Ltd

Inventors

• Lowndes Andi
• Sahlberg Emil

Classifications

• F16H61/04 Primary

  Smoothing ratio shift · CPC title

• F16H2306/14

  Skipping gear shift · CPC title

• F16H2061/0444

  during fast shifting over two gearsteps, e.g. jumping from fourth to second gear · CPC title

• F16H61/16 Primary

  Inhibiting  {or initiating}  shift during unfavourable conditions  {, e.g. preventing forward-reverse shift at high vehicle speed, preventing engine overspeed}   (F16H61/18 takes precedence) · CPC title

• B60W30/19

  Improvement of gear change, e.g. by synchronisation or smoothing gear shift · CPC title