Hybrid Electric Vehicle Powertrain with Engine Start and Transmission Shift Arbitration

• US 20080119975A1
• Filed: 11/16/2006
• Published: 05/22/2008
• Est. Priority Date: 11/16/2006
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Kraska, Marvin, Bailey, Kathleen, Yamazaki, Mark, Sureshbabu, Natarajan
• Granted Patent: US 7,967,091 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60K 2006/268 Electric drive motor starts the engine, i.e. used as starter motor
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60W 10/06 including control of combustion engines
• 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 20/11 using model predictive control [MPC] strategies, i.e. control methods based on models predicting performance utilising navigation and traffic information in the control strategy B60W20/12
• CPC Class Codes: B60W 2050/006 Interpolation; Extrapolation
• CPC Class Codes: B60W 50/0097 Predicting future conditions
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles

Abstract

A control method and control system for a hybrid electric vehicle powertrain with a multiple-ratio transmission is disclosed in which engine start events are separated in time from transmission ratio shift events to effect a smooth transition from an electric drive state with the engine off to a drive state in which the engine delivers driving power.

Claims

1. A method for controlling a hybrid electric vehicle powertrain having an engine, at least one motor-generator, a multiple-ratio transmission defining parallel power flow paths to vehicle traction wheels and a controller for effecting a transition from motor-generator drive operation to engine drive operation, the method comprising the steps of:

determining whether the powertrain is operating in motor-generator drive operation with the engine off;

determining whether a desired power is less than a calibrated engine-on power threshold value;

calculating a predicted time to start the engine in advance of a transmission ratio shift;

calculating a predicted time to shift the transmission from one ratio to another ratio;

comparing the predicted time to shift the transmission to the predicted time to start the engine; and

starting the engine if the predicted time to shift the transmission is greater than the predicted time to start the engine, whereby a smooth transition from motor-generator drive operation to engine drive operation is achieved.

4. The method set forth in claim 1 wherein the step of calculating a predicted time to shift the transmission from one ratio to another is a function of at least a filtered first derivative of vehicle speed.

5. The method set forth in claim 1 wherein the step of calculating a predicted time to shift the transmission from one ratio to another is a function of at least vehicle acceleration.

2. A method for controlling a hybrid electric vehicle powertrain having an engine, at least one motor-generator, a multiple-ratio transmission defining parallel power flow paths to vehicle traction wheels and a controller for effecting a transition from motor-generator drive operation to engine drive operation, the method comprising:

determining whether the powertrain is operating with the engine off;

calculating a desired rate of increase in desired transmission input power;

determining whether the desired transmission input power is less than a pre-calibrated engine-on power threshold;

determining a desired transmission input power;

calculating a predicted time to start the engine in advance of a transmission ratio shift as a function of at least the desired rate of increase in transmission input power;

measuring vehicle speed;

calculating a predicted time to shift the transmission from one ratio to another ratio as a function of at least vehicle acceleration;

comparing the predicted time to shift the transmission to the predicted time to start the engine; and

starting the engine if the predicted time to shift the transmission is greater than the predicted time to start the engine whereby an engine start is separated in time from a transmission shift to improve smoothness in a transition from motor-generator drive operation to engine drive operation.

3. The method set forth in claim 2 wherein a shift of the transmission in the step of calculating a predicted time to shift the transmission is an upshift from one speed ratio to a higher speed ratio.

6. The method set forth in claim 2 wherein the step of calculating a predicted time to start the engine is determined by computing a difference between an engine-on power threshold and the desired transmission input power and dividing that difference by the desired rate of increase in desired transmission input power.

7. The method set forth in claim 2 wherein the step of calculating a predicted time to shift is determined by computing a difference between vehicle speed before a transmission ratio shift and vehicle speed after the transmission shift divided by an estimated vehicle acceleration.

8. The method set forth in claim 6 wherein the step of calculating a predicted time to shift is determined by computing a difference between vehicle speed before a transmission ratio shift and vehicle speed after the transmission shift divided by an estimated vehicle acceleration.

9. The method set forth in claim 2 wherein the step of starting the engine is executed regardless of the predicted time to shift the transmission if the predicted time to start the engine is less than a calibrated value.

10. The method set forth in claim 8 wherein acceleration is determined as a function of a filtered first derivative of vehicle speed.

11. A method for controlling a hybrid electric vehicle powertrain having an engine, at least one motor-generator, a multiple-ratio transmission defining parallel power flow paths to vehicle traction wheels and a controller for effecting a transition from motor-generator drive operation to engine drive operation, the method comprising:

determining whether the powertrain is operating with the engine off;

calculating a desired rate of increase in desired transmission input power;

determining a desired transmission input power;

determining whether the desired transmission input power is less than a pre-calibrated engine-on power threshold;

calculating a predicted time to start the engine in advance of a transmission ratio shift as a function of at least the desired rate of increase in transmission input power;

measuring vehicle speed;

calculating a predicted time to shift the transmission from one ratio to another ratio as a function of at least vehicle acceleration;

comparing the predicted time to shift the transmission to the predicted time to start the engine;

starting the engine if the predicted time to shift the transmission is greater than the predicted time to start the engine whereby an engine start is separated in time from a transmission shift to improve smoothness in a transition from motor-generator drive operation to engine drive operation; and

establishing an engine start priority over a transmission shift event if the calculated time to start the engine is shorter than a calibrated time to start the engine regardless of the calculated predicted time to shift the transmission.

12. The method set forth in claim 11 wherein acceleration is determined as a function of a filtered first derivative of vehicle speed.

13. A control system for controlling a hybrid electric vehicle powertrain having an engine, at least one motor-generator, a battery, a multiple-ratio transmission defining parallel power flow paths to vehicle traction wheels, a powertrain controller network including a vehicle system controller for establishing and disestablishing each of a plurality of powertrain operating states including an engine-only operating state, an operating state in which both the engine and the motor-generator are active and a motor-generator drive state in which the engine is inactive;

a transmission controller in communication with the vehicle system controller in the powertrain controller network for effecting ratio shifts in the transmission in response to driver and powertrain operating input variables; and

an engine controller in communication with the vehicle system controller in the powertrain controller network for establishing an engine-on state and an engine-off state in response to commands from the vehicle system controller;

the powertrain controller network being configured to predict a time to start the engine following operation of the powertrain in the motor-generator drive state with the engine off and to predict a time to shift the transmission ratio;

the powertrain controller network being configured further to start the engine when the predicted time to shift is greater than the predicted time to start the engine whereby an engine start event and a transmission ratio shift event are separated in time to effect a smooth transition from a motor-generator drive state to an engine drive state.

14. The control system set forth in claim 13 wherein the powertrain controller network is configured further to give immediate priority to an engine start event if the predicted time to start the engine is less than a calibrated value regardless of whether the predicted time to start the engine is less than the predicted time to shift the transmission ratio.