Hybrid vehicle and control method of hybrid vehicle

• US 10,279,798 B2
• Filed: 06/02/2017
• Issued: 05/07/2019
• Est. Priority Date: 06/07/2016
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Kato, Shunya, Ando, Ikuo
• Primary Examiner(s): Hutchinson, Alan D
• Application Number:
  US15/612,377
• Publication Number:
  US 20170349160A1
• Time in Patent Office: 704 Days
• CPC Class Codes: B60K 6/365 with the gears having orbital motion
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/547 the transmission being a stepped gearing
• 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 10/10 including control of change-speed gearings
• CPC Class Codes: B60W 10/115 with planetary gears
• CPC Class Codes: B60W 10/18 including control of braking systems
• 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 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 2510/0638 Engine speed
• CPC Class Codes: B60W 2510/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2510/182 Brake pressure, e.g. of fluid or between pad and disc
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• 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: B60W 2710/0644 Engine speed
• CPC Class Codes: B60W 2710/08 Electric propulsion units
• CPC Class Codes: B60W 2710/1005 Transmission ratio engaged
• CPC Class Codes: B60W 2710/182 : Brake pressure, e.g. of fluid or between pad and disc
• CPC Class Codes: B60W 30/18109 : Braking
• CPC Class Codes: B60W 30/18127 : Regenerative braking
• CPC Class Codes: B60Y 2200/92 : Hybrid vehicles
• CPC Class Codes: B60Y 2300/181 : Hill climbing or descending
• CPC Class Codes: B60Y 2300/18108 : Braking
• CPC Class Codes: B60Y 2300/43 : Control of engines
• CPC Class Codes: B60Y 2300/60 : Control of electric machines, e.g. problems related to electric motors or generators
• CPC Class Codes: B60Y 2400/73 : Planetary gearings
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y10S 903/919 : Stepped shift
• CPC Class Codes: Y10S 903/93 : Conjoint control of different elements

Abstract

When a brake is turned on during travel of a hybrid vehicle, a required braking force required for a drive shaft is set based on a brake depression amount, a base rotation speed of an engine is set based on the required braking force, a shift stage is set based on the base rotation speed and a vehicle speed, a target rotation speed of the engine is set based on the shift stage and the vehicle speed, and the engine, the first motor, and the second motor are controlled such that the engine operates at the target rotation speed and the required braking force acts on the drive shaft.

Claims

1. A hybrid vehicle comprising

an engine,

a first motor,

a planetary gear mechanism including three rotary elements, the three rotary elements being connected to three shafts respectively, the three shaft being an output shaft of the engine, a rotary shaft of the first motor, and a drive shaft connected to an axle,

a second motor configured to input and output a power to and from the drive shaft,

a battery configured to exchange electric power with the first motor and the second motor, and

as a result of an electronic control unit determining that a brake of the hybrid vehicle is turned on during travel of the hybrid vehicle, the electronic control unit configured to:

set a required braking force required for the drive shaft based on a brake depression amount;

set a base rotation speed of the engine based on the required braking force;

set a shift stage based on the base rotation speed and a vehicle speed;

set a target rotation speed of the engine based on the shift stage and the vehicle speed; and

control the engine, the first motor, and the second motor such that the engine operates at the target rotation speed and the required braking force acts on the drive shaft.

2. The hybrid vehicle according to claim 1, wherein

as a result of the electronic control unit determining that the brake is turned on, the electronic control unit is configured to:

set a braking level based on the required braking force; and

set the base rotation speed such that the base rotation speed when the braking level is high is higher than the base rotation speed when the braking level is low.

3. The hybrid vehicle according to claim 2, wherein

as a result of the electronic control unit determining that:

(i) the braking level is a first level, which occurs when the brake is turned on; and

(ii) the required braking force is equal to or greater than a first braking force for a first predetermined time or longer,

the electronic control unit is configured to switch the braking level to a second level higher than a first level, and

as a result of the electronic control unit determining that;

(iii) the braking level is the second level, which occurs when the brake is turned on; and

(iv) the required braking force is less than a second braking force for a second predetermined time or longer, the second braking force is equal to or less than the first braking force,

the electronic control unit is configured to switch the braking level to the first level.

4. The hybrid vehicle according to claim 3, wherein the first braking force is set to decrease as a road surface gradient increases on an uphill road.

5. The hybrid vehicle according to claim 3, wherein

as a result of the electronic control unit determining that:

(i) the braking level is one of the first level and the second level, which occurs when the brake is turned on; and

(ii) the required braking force is equal to or greater than a third braking force, the third braking force is equal to or greater than the second braking force; and

(iii) an increase in the required braking force is equal to or greater than a predetermined increase,

the electronic control unit is configured to switch the braking level to a third level, and

as a result of the electronic control unit determining that;

(iv) the braking level is the third level, which occurs when the brake is turned on; and

(v) the required braking force is less than the second braking force for the second predetermined time or longer,

the electronic control unit is configured to switch the braking level to the first level.

6. The hybrid vehicle according to claim 1, wherein

as a result of the electronic control unit determining that the brake is turned on, the electronic control unit is configured to:

set a temporary shift stage based on the vehicle speed;

set a post-downshift rotation speed based on the vehicle speed, the post-downshift rotation speed is the rotation speed of the engine at a shift stage one step lower than a current shift stage;

set the current shift stage as an upper-limit shift stage when the post-downshift rotation speed is higher than the base rotation speed;

set a shift stage one step lower than the current shift stage as the upper-limit shift stage when the post-downshift rotation speed is equal to or lower than the base rotation speed; and

set the smaller of the temporary shift stage and the upper-limit shift stage as the shift stage.

7. The hybrid vehicle according to claim 6, wherein

as a result of the electronic control unit determining that:

(i) the post-downshift rotation speed is equal to or lower than the base rotation speed when the electronic control unit determines that the brake is turned on; and

(ii) a duration of the current shift stage is less than a third predetermined time,

the electronic control unit is configured to set the current shift stage as the upper-limit shift stage.

8. The hybrid vehicle according to claim 1, wherein, as a result of the electronic control unit determining that the brake is turned on, the electronic control unit is configured to set the base rotation speed such that the base rotation speed when the vehicle speed is low is less than the base rotation speed when the vehicle speed is high.

9. The hybrid vehicle according to claim 1, wherein,

as a result of the electronic control unit determining that an accelerator of the hybrid vehicle is turned on, the electronic control unit is configured to:

set a required driving force required for the drive shaft based on an accelerator depression amount;

set the shift stage based on the accelerator depression amount and the vehicle speed;

set the target rotation speed based on the vehicle speed and the shift stage;

set an upper-limit driving force, the upper-limit driving force being a driving force when an upper-limit power which is output from the engine when the engine rotates at the target rotation speed is output to the drive shaft; and

control the engine, the first motor, and the second motor such that the smaller driving force of the upper-limit driving force and the required driving force is output to the drive shaft and the engine rotates at the target rotation speed.

10. The hybrid vehicle according to claim 1, wherein the shift stage is a virtual shift stage.

11. The hybrid vehicle according to claim 1, further comprising a stepped gearshift attached between the drive shaft and the planetary gear mechanism,

wherein the shift stage is a shift stage of the stepped gearshift or a shift stage obtained by adding a virtual shift stage to the shift stage of the stepped gearshift.

12. A control method of a hybrid vehicle, the hybrid vehicle including an engine, a first motor, a planetary gear mechanism including three rotary elements, a second motor, a battery, and an electronic control unit,

the three rotary elements being connected to three shafts respectively, the three shafts being an output shaft of the engine, a rotary shaft of the first motor, and a drive shaft connected to an axle,

the second motor being configured to input and output a power to and from the drive shaft,

the battery being configured to exchange electric power with the first motor and the second motor,

the control method comprising

determining, by the electronic control unit, whether or not a brake of the hybrid vehicle is turned on during travel of the hybrid vehicle, as a result of the electronic control unit determining that the brake is turned on, the control method further comprising:

setting, by the electronic control unit, a required braking force required for the drive shaft based on a brake depression amount;

setting, by the electronic control unit, a base rotation speed of the engine based on the required braking force;

setting, by the electronic control unit, a shift stage based on the base rotation speed and a vehicle speed;

setting, by the electronic control unit, a target rotation speed of the engine based on the shift stage and the vehicle speed; and

controlling, by the electronic control unit, the engine, the first motor, and the second motor such that the engine operates at the target rotation speed and the required braking force acts on the drive shaft.