Direct drive autoshift transmission control

• US 5,636,120 A
• Filed: 08/09/1996
• Issued: 06/03/1997
• Est. Priority Date: 07/15/1994
• Status: Expired due to Term

• Current Assignee: Caterpillar Incorporated
• Original Assignee: Caterpillar Incorporated
• Inventors: Yesel, Leon P., Kitzerow, John P.
• Primary Examiner(s): PARK, COLLIN
• Application Number:
  US08/696,019
• Time in Patent Office: 298 Days
• Field of Search: 364/424.1, 74/335, 74/336 R, 74/473 R, 477/81, 477/34, 477/115, 477/165
• US Class Current: 701/51
• CPC Class Codes: F16H 2059/006 Overriding automatic control
• CPC Class Codes: F16H 59/42 Input shaft speed
• CPC Class Codes: F16H 61/0248 Control units where shifting is directly initiated by the driver, e.g. semi-automatic transmissions generation of movements for final actuating mechanisms F16H61/28
• CPC Class Codes: Y10T 74/19251 Control mechanism

Abstract

An electronic autoshift control is provided for a transmission and engine to help reduce demands on the operator. Part of the autoshift feature is an auto/manual switch which is a two-position rocker switch controlled by the operator. The switch determines whether the transmission is being operated in the manual or the automatic mode. In the manual mode, all shifting is performed by the operator by moving the shift lever. Once in the automatic mode, the transmission controller takes over with the autoshift feature. When switched to the automatic mode, an auto/manual lamp is lit indicating the transmission'"'"'s automatic mode of operation. The rocker switch also functions as a hold switch. If traction conditions are poor and the operator wants to stay in the present gear, the rocker switch can be toggled to the manual mode. This locks the transmission in its present gear and causes the auto/manual lamp to flash if the shift lever selection and the present transmission selection do not coincide. Once the operator is out of the poor conditions, the switch can be returned to auto thus resuming the autoshift functions.

Claims

1. A method for controlling shifting of an electronic transmission having an output shaft, a plurality of forward and reverse gears to rotate said output shaft in forward and reverse directions, a neutral gear and an operator controlled shift lever for requesting a gear from said forward, neutral and reverse gears, said method comprising the steps of:

monitoring transmission output shaft speed;

operating an auto/manual switch to

respective auto and manual positions to select a corresponding one of auto and manual modes of operation for an electronic shift control of the transmission;

operating said shift lever to request a gear from said forward, reverse and neutral gears;

shifting said transmission to said requested gear when said transmission shift control is operating in said manual mode and automatically selecting a present gear on the basis of said transmission shaft output speed when said shift control is operating in said auto mode;

setting the transmission shift control to the manual mode when the requested gear coincides with the present gear and said auto/manual switch is moved to the manual position; and

automatically holding said transmission in the present gear, when the auto/manual switch is moved from the auto position to the manual position, until the requested gear coincides with the present gear.

2. A method, as set forth in claim 1, including turning an auto/manual lamp off after setting the transmission shift control to the manual mode when the requested gear coincides with the present gear.

3. A method, as set forth in claim 1, including continuously blinking an auto/manual lamp while holding said transmission in the present gear when the requested gear does not coincide with the present gear.

4. A method, as set forth in claim 1, including shifting said transmission to neutral gear when the auto/manual switch is in the auto position and the shift lever has been moved from one of said forward and reverse gears to the neutral gear.

5. A method for controlling shifting of an electronic transmission, as set forth in claim 1, further comprising:

comparing said monitored speed to a directional shift inhibit speed in response to a directional shift request in said automatic mode; and

shifting said transmission to a lowest gear allowed in a current direction of movement when said monitored speed exceeds said directional shift inhibit speed, and otherwise shifting said transmission to a lowest gear allowed in a direction corresponding to said requested gear.

6. A method for controlling shifting of an electronically controlled transmission, said transmission having an output shaft and being electronically shiftable by an electronic shift control between forward and reverse gears to rotate said output shaft in forward and reverse directions and a neutral gear, said transmission having an operator controlled shift lever for requesting a gear from said forward, neutral and reverse gears, said method comprising the steps of:

determining upshift and downshift shift points as functions of the transmission shaft output speed and storing said shift points in a memory;

monitoring transmission output shaft speed;

switching an auto/manual switch to an auto position to operate said shift control in an auto mode;

moving said shift lever from neutral to request a gear from said forward and reverse gears while operating in said auto mode;

determining an appropriate gear using monitored transmission shaft output speed; and

automatically shifting said transmission in said auto mode directly from neutral to the requested gear when said shift lever is moved from neutral to request one of second and third gears; and

the appropriate gear is lower than the requested gear.

7. A method for controlling shifting of an electronically controlled transmission, as set forth in claim 6, further including:

moving said switch from the auto position to the manual position; and

automatically holding said transmission in the present gear in response to the auto/manual switch being moved to the manual position until the requested gear coincides with the present gear.

8. An electronic autoshift control for a transmission having an output shaft and being electronically shiftable between forward and reverse gear to rotate said output shaft in forward and reverse directions and a neutral gear, said electronic autoshift control comprising:

electronic shift control means operable in a manual mode for shifting said transmission between said forward, reverse and neutral gears responsive to operator shift requests, and operable in an automatic mode for shifting said transmission responsive to stored transmission speed shift points;

an operator actuated gear shift lever operable to request a gear from said forward reverse and neutral gears; and

a switch operable between a manual position and an automatic position, for selecting between said automatic and said manual modes, said shift control means holding said transmission in the present gear until the gear requested by said shift lever coincides with the present gear when said switch is moved from the automatic position to the manual position and thereafter shifting said transmission responsive to operator shift requests.

9. An autoshift control, as set forth in claim 8, further including:

means for monitoring the speed of said output shaft, said shift control means responding in said automatic mode to a starting gear shift request out of neutral gear to 2^nd or 3^rd gear when the monitored output shaft speed does not exceed a forced downshift setpoint, by immediately shifting the requested starting gear.

10. An autoshift control, as set forth in claim 9, wherein said shift control means maintains said requested starting gear until a lower gear is requested or said monitored speed exceeds a predetermined value corresponding to said starting gear.

11. An autoshift control, as set forth in claim 8, further including means for monitoring the speed of said output shaft, said shift control means determining an appropriate gear according to said monitored speed and responding to a starting gear shift request out of neutral gear by immediately shifting to the requested starting gear when said starting gear is not greater than the appropriate gear, and otherwise by immediately shifting to the lowest gear not exceeding a forced downshift setpoint.

12. An autoshift control as set forth in claim 8, further including means for monitoring the speed of said output shaft, said shift control means comparing said monitored speed to a directional shift inhibit speed and responsively shifting said transmission in response to a directional shift request in said automatic mode.