Hybrid Vehicle and Control Method Thereof

• US 20090024262A1
• Filed: 12/21/2006
• Published: 01/22/2009
• Est. Priority Date: 12/26/2005
• Status: Active Grant

• Current Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Amamiya, Sumiko
• Granted Patent: US 8,068,946 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60K 1/02 comprising more than one electric motor
• CPC Class Codes: B60K 6/445 Differential gearing distribution type
• CPC Class Codes: B60K 6/52 Driving a plurality of drive axles, e.g. four-wheel drive
• CPC Class Codes: B60L 15/2045 for optimising the use of energy
• CPC Class Codes: B60L 2260/26 Transition between different drive modes
• CPC Class Codes: B60L 2260/28 Four wheel or all wheel drive
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 50/62 charged by low-power generators primarily intended to support the batteries, e.g. range extenders
• 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 2520/26 Wheel slip
• CPC Class Codes: B60W 2520/263 Slip values between front and rear axle
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 2540/215 Selection or confirmation of options
• CPC Class Codes: B60W 2552/15 Road slope, i.e. the inclination of a road segment in the longitudinal direction
• CPC Class Codes: B60W 50/082 Selecting or switching between different modes of propelling
• CPC Class Codes: B60W 50/085 Changing the parameters of the control units, e.g. changing limit values, working points by control input
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y02T 10/84 : Data processing systems or methods, management, administration
• CPC Class Codes: Y02T 10/92 : Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles

Abstract

A hybrid vehicle is provided with means for setting a four-wheel drive condition which is a condition for switching from two-wheel drive to four-wheel drive, and an EV switch which, when turned on by an occupant of the vehicle, places the vehicle in an EV driving mode in which only an electric motor is used as the power source. The four-wheel drive condition setting means changes the four-wheel drive condition to reduce a region in which the vehicle operates in four-wheel drive when the EV switch is on as compared to when the EV switch is off. As a result, the vehicle operates in two-wheel drive more frequently, thus reducing power consumption.

Claims

1. A hybrid vehicle comprising:

an internal combustion engine as a first power source;

an electric motor as a second power source which drives front wheels and rear wheels independently from each other;

an EV switch which, when turned on by an occupant of the vehicle, places the vehicle in an EV driving mode in which only the electric motor is used as the power source; and

a four-wheel drive condition setting device which sets a four-wheel drive condition, which is a condition for switching from two-wheel drive in which one set of wheels, from among the front wheels and the rear wheels, is driven to four-wheel drive in which both the front wheels and the rear wheels are driven, to reduce a region in which the vehicle operates in four-wheel drive when the EV switch is on as compared to when the EV switch is off.

2. The hybrid vehicle according to claim 1, wherein the four-wheel drive condition includes a condition that a slip ratio calculated by the difference in rotation speeds between the front wheels and the rear wheels be equal to or greater than a determining slip ratio which is a predetermined threshold value;

and the four-wheel drive condition setting device sets the determining slip ratio to a higher value when the EV switch is on than when the EV switch is off.

3. The hybrid vehicle according to claim 1, wherein the four-wheel drive condition includes a condition that, when the vehicle is taking off from a standstill, a road gradient at that time be equal to or greater than a determining road gradient which is a predetermined threshold value, and a condition that a speed of the vehicle be equal to or less than a determining vehicle speed which is a predetermined threshold value;

and the four-wheel drive condition setting device sets the determining road gradient to a higher value and sets the determining vehicle speed to a lower value when the EV switch is on than when the EV switch is off.

4. The hybrid vehicle according to claim 1, wherein the four-wheel drive condition setting device has condition change determining device that determines whether the four-wheel drive condition when the EV switch is off should be changed to the four-wheel drive condition when the EV switch is on;

and the condition change determining device prohibits the four-wheel drive condition from being changed when the slip ratio is equal to or greater than the predetermined threshold value or when the road gradient is equal to or greater than the predetermined threshold value.

5. A control method of a hybrid vehicle which is provided with an internal combustion engine and an electric motor as power sources and in which front wheels and rear wheels are driven independently from each other by the electric motor, characterised by comprising the steps of:

determining whether an EV switch which, when turned on by an occupant of the vehicle, places the vehicle in an EV driving mode in which only the electric motor is used as the power source, is turned on; and

changing a four-wheel drive condition, which is a condition for switching from two-wheel drive in which one set of wheels, from among the front wheels and the rear wheels, is driven to four-wheel drive in which both the front wheels and the rear wheels are driven, to reduce a region in which the vehicle operates in four-wheel drive when the EV switch is on as compared to when the EV switch is off.

6. (canceled)