METHODS AND SYSTEMS FOR STARTING AN ENGINE

• US 20160046281A1
• Filed: 08/18/2014
• Published: 02/18/2016
• Est. Priority Date: 08/18/2014
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Nedorezov, Felix, Gibson, Alexander O'Connor, Oshinsky, David, Jiang, Hong
• Granted Patent: US 10,183,663 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B60K 2006/268 Electric drive motor starts the engine, i.e. used as starter motor
• CPC Class Codes: B60K 2006/4825 Electric machine connected or connectable to gearbox input shaft
• CPC Class Codes: B60K 6/387 Actuated clutches, i.e. clutches engaged or disengaged by electric, hydraulic or mechanical actuating means
• CPC Class Codes: B60K 6/48 Parallel type
• 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 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 20/40 Controlling the engagement or disengagement of prime movers, e.g. for transition between prime movers power-up or power-down of the driveline B60W30/192
• CPC Class Codes: B60W 2510/06 Combustion engines, Gas turbines
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/0652 Speed change rate
• CPC Class Codes: B60W 2510/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2530/13 Mileage
• CPC Class Codes: B60W 2555/20 Ambient conditions, e.g. wind or rain
• CPC Class Codes: B60W 2710/021 Clutch engagement state
• CPC Class Codes: B60W 2710/025 Clutch slip, i.e. difference between input and output speeds
• CPC Class Codes: B60W 2710/0661 Speed change rate
• CPC Class Codes: B60W 2710/081 Speed
• CPC Class Codes: F02N 11/04 the motors being associated with current generators
• CPC Class Codes: F02N 11/0851 characterised by means for controlling the engagement or disengagement between engine and starter, e.g. meshing of pinion and engine gear
• CPC Class Codes: F02N 15/022 : the starter comprising an intermediate clutch
• CPC Class Codes: F02N 2200/022 : Engine speed
• CPC Class Codes: F02N 5/04 : of inertia type
• CPC Class Codes: F16F 15/131 : the rotating system comprising two or more gyratory masses
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y10S 903/93 : Conjoint control of different elements

Abstract

Methods and systems are provided for improving engine restart operations in a hybrid vehicle. While an engine is cranked via motor torque, engine fueling is delayed until the engine speed is sufficiently high and the engine has been rotating in a forward direction continuously for a threshold duration. A disconnect clutch between the engine and motor is slipped while the engine cranks, the clutch engaged only after the engine has run up to the motor speed.

Claims

1. A method for a hybrid vehicle, comprising:

during an engine restart,

cranking an engine via a motor with a disconnect clutch between the engine and the motor at least partially disengaged while delaying fueling of the engine until only after an engine speed is above a threshold speed and a direction of engine rotation is positive for greater than a threshold duration.

2. The method of claim 1, wherein the direction of engine rotation being positive is based on engine restart crankshaft acceleration.

3. The method of claim 1, wherein the direction of engine rotation being positive is based on a series of engine speed readings over the threshold duration having a progressively larger speed value.

4. The method of claim 1, wherein the disconnect clutch being at least partially disengaged includes the disconnect clutch being slipped.

5. The method of claim 4, wherein a degree of slippage of the disconnect clutch is adjusted based on engine acceleration.

6. The method of claim 1, further comprising, after the engine speed is above the threshold speed and the direction of engine rotation is positive for greater than a threshold duration, fueling the engine.

7. The method of claim 6, further comprising, after resuming fueling of the engine, engaging the disconnect clutch when the engine speed is at or within a threshold of an expected motor speed.

8. The method of claim 7, wherein the expected motor speed is predicted based on an expected transmission gear selection during the engine restart.

9. The method of claim 7, wherein the expected motor speed is predicted based on a derivative of the motor speed after resuming fueling of the engine.

10. The method of claim 9, further comprising, adjusting fueling and/or spark to the engine based on a difference between the engine speed and the motor speed, and further based on a derivative of the engine speed and the derivative of the motor speed after resuming the fueling.

11. The method of claim 10, wherein the adjusting includes increasing fueling and/or retarding spark timing to reduce the difference between the engine speed and the expected motor speed.

12. A method for a hybrid vehicle, comprising:

during an engine restart,

slipping a disconnect clutch between an engine and a motor while cranking the engine unfueled via the motor;

resuming fueling of the engine only after an engine speed is above a threshold speed and engine acceleration is indicative of positive engine rotation; and

adjusting engine torque responsive to a predicted motor synchronous speed.

13. The method of claim 12, wherein adjusting engine torque includes adjusting one or more of engine fuel, air, and spark to increase engine acceleration if the predicted motor synchronous speed is higher than current motor speed, and decrease engine acceleration if the predicted motor synchronous speed is lower than the current motor speed.

14. The method of claim 13, further comprising, engaging the disconnect clutch only after the engine speed of the fueled engine matches the predicted motor synchronous speed.

15. The method of claim 12, wherein a degree of slipping of the disconnect clutch is adjusted based on a difference between the engine speed and a motor speed during the cranking, and further based on a compression torque of the engine.

16. The method of claim 13, wherein the engine acceleration indicative of positive engine rotation includes the engine acceleration being higher than a threshold acceleration for greater than a threshold duration.

17. The method of claim 14, further comprising, learning the slipping of the disconnect clutch at the engine restart as a function of one or more of engine age, ambient temperature, ambient humidity, and hydraulic fluid temperature.

18. A vehicle system, comprising:

an electric motor;

an engine;

a disconnect clutch coupled in a driveline between the engine and the motor;

vehicle wheels configured to receive propulsion power from one or more of the engine electric motor and the engine via the driveline; and

a controller including non-transitory executable instructions for;

receiving an engine restart request; and

in response to the restart request, cranking the engine via the motor with the disconnect clutch at least partially disengaged while delaying fueling of the engine until each of an engine speed is above a first threshold speed and a direction of engine rotation is positive for greater than a threshold duration.

19. The system of claim 18, wherein the controller includes further instructions for, while maintaining the disconnect clutch at least partially disengaged, adjusting a clutch torque capacity of the disconnect clutch based on engine speed during the cranking, the clutch torque capacity increased when the engine speed is lower, the clutch torque capacity decreased when the engine speed is higher.

20. The system of claim 19, wherein the controller includes further instructions for,

after fueling the engine, fully engaging the disconnect clutch when the engine speed is above a second threshold speed, the second threshold speed based on an expected motor speed.