Transmission shuttle shift deceleration method

• US 5,353,662 A
• Filed: 01/29/1993
• Issued: 10/11/1994
• Est. Priority Date: 01/29/1993
• Status: Expired due to Term

• Current Assignee: Deere & Company
• Original Assignee: Deere & Company
• Inventors: Vaughters, Kevin L.
• Primary Examiner(s): Wright, Dirk
• Assistant Examiner(s): TA, KHOI QUANG
• Application Number:
  US08/010,942
• Time in Patent Office: 620 Days
• Field of Search: 74/335, 74/336 R, 192/0.032, 364/424.1
• US Class Current: 74/336.00R
• CPC Class Codes: F16H 2059/088 Fast forward-reverse-sequence mode
• CPC Class Codes: F16H 2061/0258 Proportional solenoid valve
• CPC Class Codes: F16H 61/0059 Braking of gear output shaft using simultaneous engagement of friction devices applied for different gear ratios
• CPC Class Codes: F16H 61/0246 characterised by initiating reverse gearshift
• CPC Class Codes: F16H 61/684 without interruption of drive
• CPC Class Codes: F16H 61/70 specially adapted for change-speed gearing in group arrangement, i.e. with separate change-speed gear trains arranged in series, e.g. range or overdrive-type gearing arrangements
• CPC Class Codes: Y10T 74/19251 Control mechanism
• CPC Class Codes: Y10T 74/1926 Speed responsive

Abstract

A powershift transmission includes a plurality of clutches, including a final or directional set of clutches. The clutches are controlled by electro-hydraulic direct acting valves and two electro-hydraulic proportional or pressure modulating valves. The pressure modulating valves modulate the pressure supplied to the direct acting valves associated with the three directional clutches. Vehicle deceleration during a shuttle shift is achieved by releasing (unpressurizing) all clutches, then gradually pressurizing only two clutches in the final or directional set.

Claims

1. A method of decelerating an output shaft of a vehicle powershift transmission during a shuttle shift whereby rotation of the output shaft is reversed from a first direction to a second direction, the transmission having a plurality of hydraulic pressure operated clutch elements for shifting the transmission, including a set of directional clutches, the method comprising the following steps:

disengaging all the clutch elements, including all the directional clutches;

applying pressurized fluid to only to both a first directional clutch and to a second directional clutch to lock up the transmission;

when the output shaft speed is less than a threshold value, applying pressurized fluid to at least one selected clutch other than a directional clutch to engage a desired gear and to cause the output shaft to rotate in the second direction; and

releasing pressure from at least the first directional clutch.

2. The method of claim 1, wherein:

the pressure applied to the first and second directional clutches is gradually increased to gradually decelerate the output shaft in.

3. The method of claim 1, further comprising:

gradually increasing the pressure applied to a directional clutch to gradually accelerate the output shaft in the second direction.