Adjusting Motor Torque to Compensate for Uphill and Downhill Demands During Cruise Control in Hybrid Vehicle

• US 20130296105A1
• Filed: 05/07/2012
• Published: 11/07/2013
• Est. Priority Date: 05/07/2012
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Grutter, Peter John, Huffmaster, Roger Lyle
• Granted Patent: US 8,740,744 B2
• Time in Patent Office: Days
• US Class Current: 477/5
• CPC Class Codes: B60K 2006/4825 Electric machine connected or connectable to gearbox input shaft
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/11 Stepped gearings
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 2710/083 Torque
• CPC Class Codes: B60W 2720/10 Longitudinal speed
• CPC Class Codes: B60W 30/143 Speed control B60W30/16 takes precedence
• CPC Class Codes: B60W 30/18127 Regenerative braking
• CPC Class Codes: B60W 30/18136 Engine braking
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A system and method for controlling a hybrid vehicle having an engine, a battery powered traction motor, and an automatic step-ratio transmission selectively coupled in series by a clutch include engaging the clutch to couple the engine and the motor and controlling motor torque to provide braking torque through the transmission to substantially maintain a cruise control speed. In one embodiment, a hybrid electric vehicle includes a battery powered traction motor connected to a transmission, an engine selectively coupled in series with the motor by a clutch, and a controller communicating with the traction motor and the engine and configured to control the motor to provide braking torque when the clutch is engaged and engine braking torque is insufficient to maintain cruise control speed of the vehicle as the vehicle travels downhill.

Claims

1. A method for controlling a hybrid vehicle having an engine, a traction motor, and an automatic step-ratio transmission selectively coupled in series by a clutch, comprising:

engaging the clutch to couple the engine and the motor; and

controlling motor torque to provide braking torque through the transmission to substantially maintain a cruise control speed.

2. The method of claim 1 further comprising:

inhibiting transmission shifting based on a sum of engine braking torque and motor torque.

3. The method of claim 1 wherein:

the motor torque is a negative motor torque to maintain the cruise control speed of the vehicle as the vehicle travels downhill.

4. The method of claim 1 further comprising:

controlling the motor torque while maintaining a currently selected transmission ratio to provide a positive motor torque through the transmission to substantially maintain the cruise control speed of the vehicle as the vehicle travels uphill.

5. The method of claim 1 further comprising:

controlling engine braking torque to supplement the motor braking torque to attempt to maintain the cruise control speed as the vehicle travels downhill.

6. The method of claim 5 wherein controlling comprises:

controlling the motor to provide an initial motor braking torque when the sum of motor braking torque and engine braking torque is sufficient to maintain the cruise control speed without downshifting the transmission; and

controlling the motor to provide an additional motor braking torque in conjunction with the engine braking torque to maintain the cruise control speed when a transmission downshift is commanded.

7. The method of claim 1 further comprising:

controlling the engine torque to attempt to maintain the cruise control speed of the vehicle as the vehicle travels uphill; and

controlling the motor torque to maintain the cruise control speed without downshifting the transmission.

8. The method of claim 7 wherein the motor torque includes two components:

an initial motor torque associated with no transmission downshift; and

an additional motor torque associated with a commanded transmission downshift.

9. A system for controlling a hybrid vehicle having an engine selectively coupled in series with a traction motor and automatic step-ratio transmission by a clutch, comprising:

a controller configured to increase motor braking torque to the transmission when the clutch is engaged to maintain cruise control speed of the vehicle as the vehicle travels downhill.

10. The system of claim 9 wherein:

the controller is further configured to maintain a current transmission gear ratio until vehicle speed increases after applying a maximum available engine braking torque and motor braking torque.

11. The system of claim 9 wherein:

the controller operates the motor in a generator mode to store power in an associated battery and produce a negative motor torque to maintain the cruise control speed.

12. The system of claim 9 wherein:

the controller controls the motor torque to provide a positive motor torque to maintain the cruise control speed of the vehicle as the vehicle travels uphill.

13. The system of claim 9 wherein:

the controller is further configured to apply engine braking torque to maintain the cruise control speed as the vehicle travels downhill.

14. The system of claim 13 wherein the controller is configured to downshift the transmission when available engine braking torque and motor braking torque are insufficient to maintain the cruise control speed.

15. A hybrid electric vehicle comprising:

a battery power traction motor connected to a transmission;

an engine selectively coupled in series with the motor by a clutch; and

a controller communicating with the traction motor and the engine and configured to control the motor to provide braking torque when the clutch is engaged and engine braking torque is insufficient to maintain cruise control speed of the vehicle as the vehicle travels downhill.

16. The vehicle of claim 15 wherein the controller inhibits shifting of the transmission until available motor torque is insufficient to maintain the cruise control speed.

17. The vehicle of claim 15 wherein the controller is configured to sequentially apply engine braking torque and increasing motor braking torque before commanding a transmission downshift.

18. The vehicle of claim 15 wherein the controller is configured to operate the motor as a generator to store power in the battery to provide motor braking torque.

19. The vehicle of claim 15 wherein the controller is configured to downshift the transmission when the motor braking torque and engine braking torque is insufficient to maintain the cruise control speed.

20. The vehicle of claim 15 wherein the controller is configured to increase motor braking torque to a maximum available braking torque before downshifting the transmission.