Method and apparatus for providing synchronization of low to high shifts in a transfer case

• US 6,579,208 B2
• Filed: 04/02/2001
• Issued: 06/17/2003
• Est. Priority Date: 01/18/2000
• Status: Expired due to Fees

• Current Assignee: BorgWarner Incorporated
• Original Assignee: BorgWarner Incorporated
• Inventors: Oliveira, Gary A., Ficht, John R., Fosmoe, Richard Thomas
• Primary Examiner(s): Estremsky, Sherry
• Assistant Examiner(s): PANG, ROGER L
• Application Number:
  US09/824,608
• Publication Number:
  US 20010029221A1
• Time in Patent Office: 806 Days
• Field of Search: 477/124, 477/109, 477/110, 475/303, 475/153, 475/293, 743/39
• US Class Current: 477/124
• CPC Class Codes: B60K 17/3467 combined with a change speed gearing, e.g. range gear
• CPC Class Codes: B60W 10/02 including control of driveline clutches
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/10 including control of change-speed gearings
• CPC Class Codes: B60W 10/115 with planetary gears
• CPC Class Codes: B60W 10/14 Central differentials for dividing torque between front and rear axles
• CPC Class Codes: B60W 2510/0216 Clutch engagement rate
• CPC Class Codes: B60W 2510/1015 Input shaft speed, e.g. turbine speed
• CPC Class Codes: B60W 2510/104 Output speed
• CPC Class Codes: B60W 30/18 Propelling the vehicle
• CPC Class Codes: B60W 30/1819 Propulsion control with control means using analogue circuits, relays or mechanical links
• CPC Class Codes: F16D 28/00 Electrically-actuated clutches arrangements for synchronisation F16D23/02; clutches actuated directly by means of an electromagnet F16D27/00; automatic clutches F16D43/00 - F16D45/00; external control F16D48/00
• CPC Class Codes: F16H 2059/462 Detecting synchronisation, i.e. speed difference is approaching zero
• CPC Class Codes: F16H 2061/2823 Controlling actuator force way characteristic, i.e. controlling force or movement depending on the actuator position, e.g. for adapting force to synchronisation and engagement of gear clutch
• CPC Class Codes: F16H 2063/3056 using cam or crank gearing
• CPC Class Codes: F16H 2063/3066 using worm gears
• CPC Class Codes: F16H 59/46 dependent on a comparison between speeds
• CPC Class Codes: F16H 61/0403 Synchronisation before shifting
• CPC Class Codes: F16H 61/0437 by using electrical signals F16H61/0403 and F16H61/061 take precedence
• CPC Class Codes: F16H 61/2807 using electric control signals for shift actuators, e.g. electro-hydraulic control therefor F16H61/30, F16H61/32 take precedence; methods for generating shift signals F16H61/0213
• CPC Class Codes: F16H 61/32 : Electric motors actuators or related electrical control means therefor
• CPC Class Codes: F16H 61/702 : using electric or electrohydraulic control means
• CPC Class Codes: F16H 63/304 : the final output mechanisms comprising elements moved by electrical or magnetic force band brake actuating mechanisms F16H63/3003
• CPC Class Codes: F16H 63/46 : Signals to a clutch outside the gearbox

Abstract

The present invention is directed toward a method to digitally control a transfer case through a digital data bus to provide synchronized low to high shift capabilities in vehicles that employ a controller area network (CAN) system. In addition, a transfer case that can be digitally controlled in a vehicle with a controller area network (CAN) system to provide synchronized low to high shifts is also disclosed.

Claims

1. A method of synchronizing low to high shifts in a transfer case used in an automotive vehicle having a controller area network, which passes digital data signals over a digital data bus to a transfer case control unit, said method comprising:

initiating an actuator to move a clutch from engagement with a gear set to a predetermined neutral synchronization point;

sensing the speed of the actuator and routing the signal to the control unit;

determining the time for the clutch to reach the predetermined neutral synchronization point as a function of the sensed speed of the actuator and the known rotational distance through which the actuator must move for the clutch to reach the predetermined neutral synchronization point;

maintaining the actuation of the clutch until it has reached the predetermined neutral synchronization point;

commanding the actuator to stop when the calculated time has elapsed for the clutch to reach the predetermined neutral synchronization point;

sensing the rotational speed of the transfer case input and output shafts;

comparing the input and output shaft rotational speed signals and determining a difference value;

commanding changes in engine RPM and automatic transmission gear settings through the control area network to bring the difference value within a predetermined range; and

,

completing the shift from low to high by commanding further actuation of the clutch from the predetermined neutral synchronization point to a direct torque engagement of the input and output shafts when the calculated difference in the rotational speeds of the input and output shafts is determined to fall within a set predetermined range, indicating synchronization of the shafts.

2. A method as set forth in claim 1 wherein the step of shifting is initiated by actuating a shift change selector that sends control signals through the controller area network to the transfer case control unit.

3. A method as set forth in claim 2 further including the step of providing feedback that a shift is in progress from the transfer case control unit through the controller area network.

4. A method as set forth in claim 3 further including the step of determining whether the transfer case shift is to be made from low to high speed or high to low speed in response to actuation of the shift change selector.

5. A method as set forth in claim 4 further including the steps of determining whether the speed of the vehicle is less than 35 kilometers per hour, and clearing and starting a shift timer before initiating the actuator to move the clutch from engagement with the gear set to the neutral position.

6. A method as set forth in claim 1 further including the step of completing the shift when the difference in the rotational speeds of the input and output shafts is less than 100 RPM.

7. A method as set forth in claim 1 further including the step of completing the shift from low to high if the difference in the rotational speeds of the input and output shafts is greater than a predetermined value for a predetermined time.

8. A method as set forth in claim 7 further including the step of completing the shift from low to high if the difference in the rotational speeds of the input and output shafts is greater than 100 RPM for a predetermined portion of the elapsed time from the initiation of the shift.

9. A method as set forth in claim 8 further including the step of completing the shift from low to high if the difference in the rotational speeds of the input and output shafts is greater than 100 RPM for a 20% of the elapsed time from the initiation of the shift.

10. A method as set forth in claim 1 further including the step of shifting the vehicle transmission into neutral before initiating the shift from low to high in the transfer case.

11. A transfer case having a synchronized low to high shift used in an automotive vehicle having a controller area network which passes digital data signals over a digital data bus, said transfer case comprising:

an input shaft, an output shaft, and a gear set selectively operable to translate torque between said input and output shafts at reduced speeds;

a clutch operable to translate torque between said input and said output shafts either directly or through said gear set, an actuator having a rotational output which is operatively coupled to said clutch for moving said clutch between predetermined positions;

a control unit which calculates the speed of said actuator as it moves said clutch to a neutral position, said control unit further determining the additional time until said clutch will reach a predetermined neutral synchronization point using the speed of said actuator and the remaining rotational distance through which said actuator must move for said clutch to reach said predetermined neutral synchronization point, said control unit further operable to stop said actuator when said clutch has reached said neutral synchronization point for no longer than a predetermined time, said control unit further sensing and comparing the rotational speeds of said input and output shafts and signaling said actuator to complete the shift from low to high by moving said clutch to provide direct torque translation between said input and output shafts when the difference in the rotational speeds of said input and output shafts is less than a predetermined value; and

,

said controller area network including a digital data interface to allow the transfer of digital data between said control unit and other vehicle systems.

12. A transfer case as set forth in claim 11 further including a first speed sensor for providing an input shaft speed signal to said control unit.

13. A transfer case as set forth in claim 12 further including a second speed sensor for providing an output shaft speed signal to said control unit.

14. A transfer case as set forth in claim 11 wherein said clutch is a dog clutch mounted upon said output shaft and rotatable therewith, said clutch being translatable axially along said output shaft between a first position wherein said clutch engages said gear set and translates torque between said input and output shafts at reduced speeds, a neutral position wherein no torque is translated between said input and output shafts and a second position wherein torque is directly translated between said input and output shafts through said clutch.

15. A transfer case as set forth in claim 14 wherein said clutch includes a synchronization point located between said neutral position and said second position.

16. A transfer case as set forth is claim 11 wherein said control unit determines when said clutch has reached said predetermined neutral synchronization point and sends a signal to said controller area network through said digital interface indicating said transfer case is in neutral.

17. A transfer case as set forth in claim 11 wherein said control unit commands the actuator to move said clutch to complete the shift from low to high when the difference in the rotational speeds of said input and output shafts is less than 100 RPM.

18. A transfer case as set forth in claim 11 wherein said control unit commands said actuator to move said clutch to complete the shift from low to high when the difference in the rotational speeds of said input and output shafts is greater than a predetermined value for a predetermined time.

19. A transfer case as set forth in claim 18 wherein said control unit commands said actuator to move said clutch to complete the shift from low to high when the difference in the rotational speeds of said input and output shafts is greater than 100 RPM for a predetermined portion of the elapsed time from the initiation of the shift.

20. A transfer case as set forth in claim 19 wherein said control unit commands said actuator to move said clutch to complete the shift when the difference in the rotational speeds of said input and output shafts is greater than 100 RPM for at lease 20 percent of the elapsed time from the initiation of the shift.