Vehicle And Method For Controlling Engine Start In A Vehicle

• US 20110118915A1
• Filed: 11/13/2009
• Published: 05/19/2011
• Est. Priority Date: 11/13/2009
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Baldwin, Reid Alan, Ortmann, Walter Joseph, Silveri, Andrew John, Kraska, Marvin Paul, Colvin, Daniel Scott, Masterson, Brandon R., Connolly, Francis T.
• Granted Patent: US 8,565,990 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• 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 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 30/19 Improvement of gear change, e.g. by synchronisation or smoothing gear shift
• CPC Class Codes: B60W 30/192 Mitigating problems related to power-up or power-down of the driveline, e.g. start-up of a cold engine
• CPC Class Codes: F02D 41/023 in relation with the gear ratio shifting conjoint control for improving gear change B60W30/19
• CPC Class Codes: F02D 41/062 for starting F02D41/061 takes precedence
• CPC Class Codes: F02N 11/006 using a plurality of electric motors
• CPC Class Codes: F02N 11/08 Circuits or control means specially adapted for starting of engines
• CPC Class Codes: F02N 11/0844 with means for restarting the engine directly after an engine stop request, e.g. caused by change of driver mind
• CPC Class Codes: F02N 11/0848 with means for detecting successful engine start, e.g. to stop starter actuation
• CPC Class Codes: F02N 15/022 the starter comprising an intermediate clutch
• CPC Class Codes: F02N 2300/102 Control of the starter motor speed; Control of the engine speed during cranking
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A vehicle includes a motor/generator, a starter motor, a disconnect clutch disposed between the engine and the motor/generator, and at least one clutch disposed between the motor/generator and the vehicle drive wheels. When an engine start is requested, various parameters are controlled to ensure a smooth engine start wherein driveline torque disturbances are minimized. The starter motor is used to crank the engine upon an engine start request, thereby eliminating the need to transfer torque from the motor/generator to the engine. This helps to further reduce torque disturbances in the driveline when the engine is started.

Claims

1. A method for starting an engine in a vehicle, comprising:

requesting an engine start when the engine is shutdown and the first clutch is open;

initiating operation of a starter motor such that torque is transferred from the starter motor to the engine;

raising the pressure in a first clutch disposed between the engine and an electric machine to a first level substantially simultaneously with the initiating operation of the starter motor, the first level providing for subsequent rapid engagement of the first clutch while allowing the first clutch to slip such that less than an engine turnover torque is transferred from the electric machine to the engine;

operating the electric machine according to a driver demand for torque;

reducing the pressure of the first clutch to a second level while the starter motor is operating;

detecting engine start;

stopping the starter motor; and

fully engaging the first clutch.

2. The method of claim 1, wherein engine start is detected when the engine outputs positive torque.

3. The method of claim 1, the vehicle further having at least one other clutch disposed between the electric machine and vehicle drive wheels, the at least one other clutch being selectively engageable for facilitating torque transfer between the electric machine and the vehicle drive wheels, the at least one other clutch including a plurality of transmission clutches, and at least a portion of an engine start sequence occurs during a transmission downshift, the method further comprising:

controlling oncoming and offgoing transmission clutches during a downshift according to a predetermined shift schedule, thereby effecting slip between the electric machine and the vehicle drive wheels; and

controlling the engine using speed control based on a speed profile determined from a difference between the engine speed and the speed of the electric machine.

4. The method of claim 3, wherein the step of fully engaging the first clutch is performed after the speed of the engine is within a calibratable level of the speed of the electric machine.

5. The method of claim 1, the vehicle further having at least one other clutch disposed between the electric machine and vehicle drive wheels, the at least one other clutch being selectively engageable for facilitating torque transfer between the electric machine and the vehicle drive wheels, the method further comprising:

requesting an engine start after an engine shutdown is initiated and the engine is still operating;

initiating slip in at least one of the at least one other clutch; and

raising the pressure of the first clutch to a third level to facilitate torque transfer from the electric machine to the engine when the slip in the at least one of the at least one other clutch has reached a predetermined level.

6. The method of claim 5, further comprising:

operating the electric machine using torque control according to driver demand;

controlling the slip in the launch clutch around a target slip; and

increasing torque output of the electric machine when a detectable drop in the launch clutch slip occurs.

7. The method of claim 6, further comprising controlling the pressure in the first clutch according to a closed loop pressure control to maintain a slip profile based on the engine speed.

8. A method for starting an engine in a vehicle, comprising:

requesting an engine start when the engine is shutdown and the first clutch is open;

operating an electric machine;

initiating operation of the starter motor such that torque is transferred from the starter motor to the engine;

raising the pressure in a first clutch disposed between the engine and the electric machine to a first level substantially simultaneously with the initiating operation of the starter motor, the first level providing for subsequent rapid engagement of the first clutch while allowing the first clutch to slip such that less than an engine turnover torque is transferred from the electric machine to the engine;

reducing the pressure of the first clutch to a second level while the starter motor is operating;

stopping the starter motor; and

fully engaging the first clutch.

9. The method of claim 8, wherein the step of operating the electric machine is performed such that the electric machine is operated using torque control according to a driver demand for torque.

10. The method of claim 8, wherein the electric machine is not operating when the engine start is requested, and the step of operating the electric machine is performed such that the electric machine is operated in speed control to control the speed of the electric machine within a calibratable level below a desired engine idle speed.

11. The method of claim 8, the vehicle further having at least one other clutch disposed between the electric machine and vehicle drive wheels, the at least one other clutch being selectively engageable for facilitating torque transfer between the electric machine and the vehicle drive wheels, the at least one other clutch including a plurality of transmission clutches, the method further comprising:

controlling oncoming and offgoing transmission clutches during a downshift according to a predetermined shift schedule, thereby effecting slip between the electric machine and the vehicle drive wheels;

determining an amount of slip between the electric machine and the vehicle drive wheels;

continuing to control the on-going and offgoing clutches according to the predetermined shift schedule if the determined slip is above a target slip; and

controlling the on-going and offgoing clutches through a closed loop control around the target slip if the determined slip is not above the target slip.

12. The method of claim 8, the vehicle further having at least one other clutch disposed between the electric machine and vehicle drive wheels, the at least one other clutch being selectively engageable for facilitating torque transfer between the electric machine and the vehicle drive wheels, one of the at least one other clutch being a launch clutch, the method further comprising:

requesting an engine start after an engine shutdown is initiated and the engine is still operating;

initiating slip in the launch clutch; and

raising the pressure of the first clutch to a third level to facilitate torque transfer from the electric machine to the engine when the slip in the launch clutch has reached a predetermined level.

13. The method of claim 12, further comprising:

operating the electric machine using torque control according to driver demand;

controlling the slip in the launch clutch around a target slip; and

increasing torque output of the electric machine when a detectable drop in the launch clutch slip occurs.

14. The method of claim 13, further comprising controlling the pressure in the first clutch according to a closed loop pressure control to maintain a slip profile based on the engine speed.

15. A vehicle including vehicle drive wheels, the vehicle comprising:

an engine;

a starter motor for rotating the engine to facilitate an engine start;

an electric machine operable to propel the vehicle and to rotate the engine;

a first clutch disposed between the engine and the electric machine for selectively connecting the engine to the electric machine; and

a control system including at least one controller, the control system being configured to;

request an engine start when the engine is shutdown and the first clutch is open;

operate the electric machine;

initiate operation of the starter motor such that torque is transferred from the starter motor to the engine;

raise the pressure in the first clutch to a first level substantially simultaneously with the initiating operation of the starter motor, the first level providing for subsequent rapid engagement of the first clutch while allowing the first clutch to slip such that less than an engine turnover torque is transferred from the electric machine to the engine;

reduce the pressure of the first clutch to a second level while the starter motor is operating;

fuel the engine, thereby facilitating torque production by the engine;

stop the starter motor; and

fully engage the first clutch.

16. The vehicle of claim 15, wherein the control system is further configured to operate the electric machine using torque control according to a driver demand for torque.

17. The vehicle of claim 15, wherein the electric machine is shutdown when the engine start is requested, and the control system is further configured to operate the electric machine in speed control to control the speed of the electric machine within a calibratable level below a desired engine idle speed.

18. The vehicle of claim 15, further comprising a plurality of transmission clutches, the control system being further configured to:

control oncoming and offgoing transmission clutches during a downshift according to a predetermined shift schedule to effect slip between the electric machine and the vehicle drive wheels;

determine an amount of slip between the electric machine and the vehicle drive wheels;

continue to control the on-going and offgoing clutches according to the predetermined shift schedule if the determined slip is above a target slip; and

control the on-going and offgoing clutches through a closed loop control around the target slip if the determined slip is not above the target slip.

19. The vehicle of claim 15, further comprising a launch clutch, the control system being further configured to:

request an engine start after an engine shutdown is initiated and the engine is still operating;

initiate slip in the launch clutch; and

raise the pressure of the first clutch to a third level to facilitate torque transfer from the electric machine to the engine when the slip in the launch clutch has reached a predetermined level.

20. The vehicle of claim 19, wherein the control system is further configured to:

operate the electric machine using torque control according to driver demand;

control the slip in the launch clutch around a target slip; and

increase torque output of the electric machine when a detectable drop in the launch clutch slip occurs.