Hybrid vehicle capable of reducing NOx emissions and method of operating same

• US 6,595,307 B2
• Filed: 09/27/2001
• Issued: 07/22/2003
• Est. Priority Date: 10/25/2000
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Suzuki, Naoto
• Primary Examiner(s): Johnson, Brian L.
• Assistant Examiner(s): Campbell, Kelly E
• Application Number:
  US09/963,458
• Publication Number:
  US 20020049115A1
• Time in Patent Office: 663 Days
• Field of Search: 180/65.2, 180/65.3, 180/65.4, 180/309, 602/74, 602/84, 602/85, 602/86, 602/99, 603/00, 603/01, 603/02, 603/03
• US Class Current: 180/65.235
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60L 2240/441 Speed
• CPC Class Codes: B60L 2240/445 Temperature
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 2050/0011 Proportional Integral Differential [PID] controller
• CPC Class Codes: B60W 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/068 Engine exhaust temperature
• CPC Class Codes: F01N 3/20 specially adapted for catalytic conversion F01N3/22 takes precedence; Methods of operation or control of catalytic converters
• CPC Class Codes: F02D 41/0235 in relation with the state of the exhaust gas treating apparatus control of exhaust gas treating apparatus per se F01N
• CPC Class Codes: F02D 41/042 for stopping the engine
• CPC Class Codes: F02N 11/04 the motors being associated with current generators
• CPC Class Codes: F02N 11/0818 Conditions for starting or stopping the engine or for deactivating the idle-start-stop mode
• CPC Class Codes: F02N 15/003 Starters comprising a brake mechanism
• CPC Class Codes: F02N 2200/026 Catalyst temperature
• CPC Class Codes: F02N 2300/104 Control of the starter motor torque
• CPC Class Codes: Y02A 50/20 Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• 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 903/917 with transmission for changing gear ratio

Abstract

In a hybrid vehicle including an internal combustion engine, an electric motor, a generator, a battery, and a catalytic converter disposed in an exhaust system of the engine, a determination is made as to whether a condition for stopping the engine is established, based on an operating state of the vehicle. Then, the fuel supply to the engine is cut off when the condition for stopping the engine is established, and a load (for example, a load of the generator) is applied to the engine so as to restrict rotation of the engine.

Claims

1. A hybrid vehicle comprising:

a power train including an internal combustion engine, an electric motor, and a generator, which are operatively connected to each other, at least one of an output of the engine and an output of the electric motor being utilized for running the hybrid vehicle;

a battery electrically connected to the electric motor and to the generator, the electric motor using the battery as an electric power supply, at least one of the output of the engine and inertia of the running hybrid vehicle being utilized for driving the generator so as to charge the battery;

a catalytic converter disposed in an exhaust system of the engine so as to purify an exhaust gas emitted from the engine; and

a controller that;

determines whether a condition for stopping the engine is established, based on an operating state of the vehicle;

cuts off fuel supply to the engine when the condition for stopping the engine is established; and

applies a load of the generator to the engine upon the cutting off of the fuel supply to the engine, wherein the controller determines a temperature of the catalytic converter, and keeps the engine rotating irrespective of establishment of the condition for stopping the engine if the determined temperature of the catalytic converter is higher than a predetermined threshold level.

2. A hybrid vehicle according to claim 1, wherein the electric motor and the generator are integrated as a motor/generator that selectively functions as the motor or as the generator.

3. A hybrid vehicle according to claim 1, wherein the condition for stopping the engine is established when the vehicle is stopped for a predetermined period of time or longer.

4. A hybrid vehicle according to claim 1, wherein the load of the generator is applied to the engine until a speed of the engine becomes less than a threshold speed.

5. A hybrid vehicle comprising:

a power train including an internal combustion engine, an electric motor, and a generator, which are operatively connected to each other, at least one of an output of the engine and an output of the electric motor being utilized for running the hybrid vehicle;

a battery electrically connected to the electric motor and to the generator, the electric motor using the battery as an electric power supply, at least one of the output of the engine and inertia of the running hybrid vehicle being utilized for driving the generator so as to charge the battery;

a catalytic converter disposed in an exhaust system of the engine so as to purify an exhaust gas emitted from the engine; and

a controller that;

determines whether a condition for stopping the engine is established, based on an operating state of the vehicle;

cuts off fuel supply to the engine when the condition for stopping the engine is established; and

applies a load of the generator to the engine upon the cutting off of the fuel supply to the engine; and

a shut-off valve disposed upstream of the catalytic converter in the exhaust system of the engine, wherein the controller closes the shut-off valve upon the cutting off of the fuel supply to the engine.

6. A hybrid vehicle according to claim 5, wherein the electric motor and the generator are integrated as a motor/generator that selectively functions as the motor or as the generator.

7. A hybrid vehicle according to claim 5, wherein the condition for stopping the engine is established when the vehicle is stopped for a predetermined period of time or longer.

8. A hybrid vehicle according to claim 5, wherein the load of the generator is applied to the engine until a speed of the engine becomes less than a threshold speed.

9. A hybrid vehicle, comprising:

a power train including an internal combustion engine, an electric motor, and a generator, which are operatively connected to each other, at least one of an output of the engine and an output of the electric motor being utilized for running the hybrid vehicle;

a battery electrically connected to the electric motor and to the generator, the electric motor using the battery as an electric power supply, at least one of the output of the engine and inertia of the running hybrid vehicle being utilized for driving the generator so as to charge the battery;

a catalytic converter disposed in an exhaust system of the engine so as to purify an exhaust gas emitted from the engine; and

a controller that;

determines whether a condition for stopping the engine is established, based on an operating state of the vehicle;

cuts off fuel supply to the engine when the condition for stopping the engine is established; and

applies a load of the generator to the engine upon the cutting off of the fuel supply to the engine, wherein the load of the generator applied to the engine is controlled in a first manner until a speed of the engine is reduced to a first threshold value, and is then controlled in a second manner when the speed of the engine is reduced from the first threshold value to a second threshold value that is lower than the first threshold value.

10. A hybrid vehicle according to claim 9, wherein the load of the generator applied to the engine is subjected to Proportional-Integral-Differential control when the speed of the engine is reduced from the first threshold value to the second threshold value.

11. A method of controlling a hybrid vehicle that includes:

(a) a power train including an internal combustion engine, an electric motor, and a generator, which are operatively connected to each other, at least one of an output of the engine and an output of the electric motor being utilized for running the hybrid vehicle, (b) a battery electrically connected to the electric motor and to the generator, the electric motor using the battery as an electric power supply, at least one of the output of the engine and inertia of the running hybrid vehicle being utilized for driving the generator so as to charge the battery, and (c) a catalytic converter disposed in an exhaust system of the engine so as to purify an exhaust gas emitted from the engine, the method comprising the steps of;

determining whether a condition for stopping the engine is established, based on an operating state of the vehicle;

cutting off fuel supply to the engine when the condition for stopping the engine is established;

applying a load of the generator to the engine upon the cutting off of the fuel supply to the engine;

determining a temperature of the catalytic converter; and

keeping the engine rotating irrespective of establishment of the condition for stopping the engine if the determined temperature of the catalytic converter is higher than a predetermined threshold level.

12. A method according to claim 11, wherein the electric motor and the generator are integrated as a motor/generator that selectively functions as the motor or as the generator.

13. A method according to claim 11, wherein the condition for stopping the engine is established when the vehicle is stopped for a predetermined period of time or longer.

14. A method according to claim 11, wherein the load of the generator is applied to the engine until a speed of the engine becomes less than a threshold speed.

15. A method, of controlling a hybrid vehicle that includes:

(a) a power train including an internal combustion engine, an electric motor, and a generator, which are operatively connected to each other, at least one of an output of the engine and an output of the electric motor being utilized for running the hybrid vehicle, (b) a battery electrically connected to the electric motor and to the generator, the electric motor using the battery as an electric power supply, at least one of the output of the engine and inertia of the running hybrid vehicle being utilized for driving the generator so as to charge the battery, and (c) a catalytic converter disposed in an exhaust system of the engine so as to purify an exhaust gas emitted from the engine, the method comprising the steps of;

determining whether a condition for stopping the engine is established, based on an operating state of the vehicle;

cutting off fuel supply to the engine when the condition for stopping the engine is established;

applying a load of the generator to the engine upon the cutting off of the fuel supply to the engine; and

closing the shut-off valve upon the cutting off of the fuel supply to the engine;

wherein the vehicle further includes a shut-off valve disposed upstream of the catalytic converter in the exhaust system of the engine.

16. A method according to claim 15, wherein the electric motor and the generator are integrated as a motor/generator that selectively functions as the motor or as the generator.

17. A method according to claim 15, wherein the condition for stopping the engine is established when the vehicle is stopped for a predetermined period of time or longer.

18. A method according to claim 15, wherein the load of the generator applied to the engine is controlled in a first manner until a speed of the engine is reduced to a first threshold value, and is then controlled in a second manner when the speed of the engine is reduced from the first threshold value to a second threshold value that is lower than the first threshold value.

19. A method of controlling a hybrid vehicle that includes:

(a) a power train including an internal combustion engine, an electric motor, and a generator, which are operatively connected to each other, at least one of an output of the engine and an output of the electric motor being utilized for running the hybrid vehicle, (b) a battery electrically connected to the electric motor and to the generator, the electric motor using the battery as an electric power supply, at least one of the output of the engine and inertia of the running hybrid vehicle being utilized for driving the generator so as to charge the battery, and (c) a catalytic converter disposed in an exhaust system of the engine so as to purify an exhaust gas emitted from the engine, the method comprising the steps of;

determining whether a condition for stopping the engine is established, based on an operating state of the vehicle;

cutting off fuel supply to the engine when the condition for stopping the engine is established; and

applying a load of the generator to the engine upon the cutting off of the fuel supply to the engine, wherein the load of the generator applied to the engine is controlled in a first manner until a speed of the engine is reduced to a first threshold value, and is then controlled in a second manner when the speed of the engine is reduced from the first threshold value to a second threshold value that is lower than the first threshold value.

20. A method according to claim 19, wherein the load of the generator applied to the engine is subjected to Proportional-Integral-Differential control when the speed of the engine is reduced from the first threshold value to the second threshold value.