Control system for a hybrid electric vehicle to anticipate the need for a mode change

• US 20030006076A1
• Filed: 08/29/2002
• Published: 01/09/2003
• Est. Priority Date: 10/11/2000
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Tamor, Michael Alan
• Granted Patent: US 7,021,409 B2
• Time in Patent Office: Days
• US Class Current: 180/65.2
• 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 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/10 Controlling the power contribution of each of the prime movers to meet required power demand
• CPC Class Codes: B60W 2050/0031 Mathematical model of the vehicle
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2530/10 Weight
• CPC Class Codes: B60W 2540/10 Accelerator pedal position
• CPC Class Codes: B60W 2540/106 Rate of change
• CPC Class Codes: B60W 2540/12 Brake pedal position
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: Y02T 10/40 Engine management systems
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y10S 903/903 having energy storing means, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/947 Characterized by control of braking, e.g. blending of regeneration, friction braking

Abstract

A parallel hybrid electric vehicle method and system including an internal combustion engine (ICE), an electric traction motor/generator, and a controller. A control strategy is provided to prevent unpredicted or undesired engine starts by anticipating the need for the vehicle engine, while avoiding “false starting” the engine or allowing an annoying lag in performance that will occur if the engine is not started in advance of an actual requirement. The invention anticipates the need for engine starts by monitoring vehicle speed and driver demand and their rates of change. The invention allows consistent performance and operates in a manner pleasing to the customer because a substantially constant drive force is maintained.

Claims

1. A control system for a hybrid electric vehicle powertrain having a throttle-controlled internal combustion engine, an electric motor/generator drive unit and a disconnect clutch between the engine and the drive unit, a power transmission between the drive unit and vehicle traction wheels, and a battery electrically connected to the drive unit for powering the same, the control system comprising:

an electronic controller including an engine speed and torque control and a drive unit speed and torque control whereby engine torque and engine on and off states are controlled;

the drive unit having a speed and torque first operating zone characterized by high efficiency drive unit torque delivery to the transmission with the engine turned off, the engine having a speed and torque second operating zone characterized by high efficiency engine torque delivery with the drive unit turned off; and

means for anticipating an instant when a limit of the speed and torque first operating zone for the drive unit is reached whereby the engine is started at a pre-calculated time before the second operating zone is entered, thereby effecting smooth power transmission from the first operating zone to the second operating zone.

2. The control system set forth in claim 1 wherein the control system includes accelerator pedal and brake pedal driver inputs, the control system including means for responding to the rate of change of accelerator pedal position whereby the engine is started at a calibrated time before a limit for the first operating zone is reached.

3. A control system for a hybrid electric vehicle powertrain having a throttle-controlled internal combustion engine, an electric motor/generator drive unit and a disconnect clutch between the engine and the drive unit, a power transmission between the drive unit and vehicle traction wheels and a battery electrically connected to the drive unit for powering the same, the control system comprising:

an electronic controller including an engine speed and torque control and a drive unit speed and torque control whereby engine torque and engine on and off states and drive unit torque and drive unit on and off states are controlled;

the drive unit having a speed and torque first operating zone characterized by high efficiency drive unit torque delivery to the transmission with the engine turned off, the engine having a speed and torque second operating zone characterized by high efficiency engine torque delivery with the drive unit turned off, and means for anticipating an instant when a limit of one speed and torque operating zone is reached as the other operating zone is entered whereby a smooth power transition is made between the operating zones.

4. The control system set forth in claim 3 wherein the control system includes a throttle actuating accelerator pedal driver input and brake pedal driver inputs, the control system responding to a rate of change of brake pedal force whereby the engine is started at a calibrated time before a limit of the first operating is reached with the powertrain operating in the first operating zone and whereby the drive unit is started at a calibrated time before a limit of the second operating zone is reached with the powertrain operating in the second operating zone.

5. The control system set forth in claim 3 wherein the engine has an accelerator pedal controlled throttle and the electronic controller responds to powertrain operating variables including rate of change of accelerator pedal position.

6. A method for controlling a hybrid electric vehicle powertrain having a throttle-controlled internal combustion engine, an electric motor/generator drive unit and a disconnect clutch between the engine and the drive unit, a power transmission between the drive unit and vehicle traction wheels and a battery electrically connected to the drive unit for powering the same, the method comprising the steps of:

controlling engine speed and torque and drive unit speed and torque in response to changes in engine throttle position whereby the speed and torque values for the drive unit are within a first operating zone corresponding to high efficiency of the drive unit and whereby the speed and torque values for the engine are within a second operating zone corresponding to high efficiency of the engine;

operating the drive unit in the first operating zone with the engine off;

operating the engine in the second operating zone with the drive unit off;

adjusting the speed and torque values in each operating zone by varying engine throttle position;

anticipating, upon changes in speed and torque, the limit of the first operating zone and starting the engine at a pre-calibrated time before the powertrain operates in the second operating zone whereby a smooth transition is made between the operating zones.

7. A method for controlling a hybrid electric vehicle powertrain having a throttle-controlled internal combustion engine, an electric motor/generator drive unit and a disconnect clutch between the engine and the drive unit, a power transmission between the drive unit and vehicle traction wheels, a driver operated brake pedal for controlling regenerative drive unit braking and a battery electrically connected to the drive unit for powering the same, the method comprising the steps of:

controlling engine speed and torque and drive unit speed and torque in response to engine throttle position whereby the speed and torque values for the drive unit are within a first operating zone corresponding to high efficiency of the drive unit and the speed and torque values for the engine are within a second operating zone corresponding to high efficiency of the engine;

operating the drive unit in the first operating zone with the engine off;

operating the engine in the second operating zone with the drive unit off;

establishing regenerative drive unit braking in a regenerative braking operating zone in response to driver operated brake pedal force;

anticipating, upon changes in speed and torque, as brake pedal force changes, a limit of the regenerative braking operating zone whereby the engine is conditioned for developing braking torque a pre-calibrated time before the regenerative braking torque limit is achieved.