초록 ▼

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

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 at the lowest engine speeds when the engine-required torque is the highest. This reduces the amount of torque necessary to be supplied from the motor/generator, and further helps to reduce torque disturbances in the driveline. If the motor/generator is producing torque to propel the vehicle at the time the engine start is requested, a launch clutch or one or more transmission clutches can be controlled to provide slip between the motor/generator and the vehicle drive wheels to further reduce torque disturbances in the driveline.

대표청구항 ▼

1. A method for starting an engine in a hybrid vehicle being driven by an electric machine, comprising: operating a starter motor;reducing a launch clutch pressure command to cause slip;raising a pressure command to a first clutch transferring torque to the engine when launch clutch slip has reached

1. A method for starting an engine in a hybrid vehicle being driven by an electric machine, comprising: operating a starter motor;reducing a launch clutch pressure command to cause slip;raising a pressure command to a first clutch transferring torque to the engine when launch clutch slip has reached a predetermined level;turning off the starter motor;fueling the engine; andfully engaging the launch clutch after desired engine torque is achieved. 2. The method of claim 1, wherein the hybrid vehicle has at least one other clutch, disposed between the electric machine and vehicle drive wheels, selectively engageable to transfer torque between the electric machine and the drive wheels, the method further comprising facilitating slip in of the at least one other clutch during engagement of the first clutch when no downshift occurs during the engine start. 3. The method of claim 2, wherein the at least one other clutch includes a launch clutch and a plurality of transmission clutches, the method further comprising maintaining engagement of the launch clutch when the electric machine is supplying torque to move the vehicle and at least a portion of a downshift occurs during the engine start, thereby allowing a control of oncoming and offgoing transmission clutches during the downshift to effect slip between the electric machine and the vehicle drive wheels. 4. The method of claim 1, further comprising operating the electric machine using torque control when the electric machine is supplying torque to move the vehicle when the engine start is requested. 5. The method of claim 4, further comprising operating the electric machine using speed control after the starter motor is turned off. 6. The method of claim 1, wherein the step of operating the electric machine includes operating the electric machine using speed control when the electric machine is not supplying torque to move the vehicle when the engine start is requested. 7. The method of claim 1 further comprising fully engaging the first clutch when the speed of the engine approaches the speed of the electric machine. 8. The method of claim 1, wherein engine start is detected when engine speed exceeds starter motor speed by a given amount. 9. A method for starting an engine in a hybrid vehicle, comprising: requesting an engine start when a first clutch disposed between the engine and an electric machine is at least substantially disengaged;operating the electric machine;initiating operation of a starter motor substantially simultaneously withraising the pressure of the first clutch such that torque is transferred from the electric machine to the engine while the starter motor is still operating;turning off the starter motor; andfully engaging the first clutch. 10. The method of claim 9, the hybrid 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: facilitating slip in one of the at least one other clutch; andreducing the pressure of the first clutch from the first level to a stroke pressure before it is raised to the third level, the pressure of the first clutch being raised to the third level by raising the pressure from the stroke pressure by a first calibratable amount when a predetermined slip speed of the one of the at least one other clutch is detected. 11. The method of claim 10, wherein one of the at least one other clutch is a launch clutch, the method further comprising facilitating slip in the launch clutch during the engagement of the first clutch when the electric machine is supplying torque to move the vehicle and no downshift occurs during the engine start. 12. The method of claim 11, wherein the step of operating the electric machine includes operating the electric machine using torque control when the electric machine is supplying torque to move the vehicle when the engine start is requested, the method further comprising increasing torque output of the electric machine by a calibratable amount when a predetermined reduction in a slip speed of the launch clutch occurs. 13. The method of claim 9, the hybrid vehicle further having at least one other clutch disposed between the electric machine and vehicle drive wheels, the at least one other clutch including a plurality of transmission clutches selectively engageable for facilitating torque transfer between the electric machine and the vehicle drive wheels, the method further comprising controlling 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 when at least a portion of the downshift occurs during the engine start. 14. The method of claim 13, further comprising: 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 predetermined target slip; andcontrolling the on-going and offgoing clutches through a closed loop control around the target slip if the determined slip is not above the predetermined target slip. 15. The method of claim 9, wherein the step of turning off the starter motor includes turning off the starter motor when a speed of the engine is a predetermined speed above a speed of the starter motor. 16. The method of claim 9, wherein the step of operating the electric machine includes operating the electric machine using torque control when the electric machine is supplying torque to move the vehicle when the engine start is requested. 17. The method of claim 9, wherein the step of operating the electric machine includes operating the electric machine using speed control when the electric machine is not supplying torque to move the vehicle when the engine start is requested. 18. A hybrid 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 and selectively connecting the engine to the electric machine; anda control system including at least one controller, the control system being configured to: request an engine start when the first clutch is at least substantially disengaged,operate the electric machine,initiate operation of the starter motor substantially simultaneously with the engagement of the first clutch, such that torque is transferred from the starter motor to the engine and required torque transfer from the electric machine to start the engine is reduced,raise the pressure of the first clutch to transfer torque from the electric machine to the engine while the starter motor is still operating;turn off the starter motor,fuel the engine, andfully engage the first clutch. 19. The hybrid vehicle of claim 18, further comprising a plurality of transmission clutches disposed between the electric machine and the vehicle drive wheels, 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 when at least a portion of the downshift occurs during the engine start. 20. The vehicle of claim 19, wherein the control system is further configured to: control the on-going and offgoing clutches according to the predetermined shift schedule if the slip between the electric machine and the vehicle drive wheels is above a predetermined target slip, andcontrol the on-going and offgoing clutches through a closed loop control around the target slip if the slip between the electric machine and the vehicle drive wheels is not above the predetermined target slip.