Vehicle drive system

Abstract

According to one embodiment, a vehicle drive system includes a left-wheel drive unit having a first motor and a first transmission and a right-wheel drive unit having a second motor and a second transmission. When a left and right opposite torque control in which a first motor and a second motor produce torque in opposite directions is executed by controlling one motor of the first motor and the second motor to produce forward torque or backward torque and the other motor to produce backward torque or forward torque that is opposite to the torque produced by the one motor, the motor control unit controls the one motor based on a target revolution state quantity of the one motor, while the motor control unit controls the other motor based on a target torque state quantity of the other motor.

1 . A vehicle drive system, including:
 a left-wheel drive unit having
 a first motor for driving a left wheel of a vehicle and 
 a first transmission that is provided on a power transmission line between the first motor and the left wheel; 
   a right-wheel drive unit having
 a second motor for driving a right wheel of the vehicle and 
 a second transmission that is provided on a power transmission line between the second motor and the right wheel; and 
 a motor control unit for controlling the first motor and the second motor, 
   wherein the first and second transmissions each have a first to third rotational elements,   wherein the first motor is connected to the first rotational element of the first transmission,   wherein the second motor is connected to the first rotational element of the second transmission,   wherein the left wheel is connected to the second rotational element of the first transmission,   wherein the right wheel is connected to the second rotational element of the second transmission,   wherein the third rotational element of the first transmission and the third rotational element of the second transmission are coupled to each other, and   wherein, when a left and right opposite torque control in which the first motor and the second motor produce torque in opposite directions is executed by controlling one motor of the first motor and the second motor to produce forward torque or backward torque and the other motor to produce backward torque or forward torque that is opposite to the torque produced by the one motor, the motor control unit controls the one motor based on a target revolution state quantity of the one motor, while the motor control unit controls the other motor based on a target torque state quantity of the other motor.   
     
     
         2 . A vehicle drive system, including:
 a left-wheel drive unit having
 a first motor for driving a left wheel of a vehicle and 
 a first transmission that is provided on a power transmission line between the first motor and the left wheel; 
   a light-wheel drive unit having
 a second motor for driving a right wheel of the vehicle and 
 a second transmission that is provided on a power transmission line between the second motor and the right wheel; and 
   a motor control unit for controlling the first motor and the second motor,   wherein the first and second transmissions each have a first to third rotational elements,   wherein the first motor is connected to the first rotational element of the first transmission,   wherein the second motor is connected to the first rotational element of the second transmission,   wherein the left wheel is connected to the second rotational element of the first transmission,   wherein the right wheel is connected to the second rotational element of the second transmission,   wherein the third rotational element of the first transmission and the third rotational element of the second transmission are coupled to each other, and   wherein, when a left and right opposite torque control in which the first motor and the second motor produce torque in opposite directions is executed by controlling one motor of the first motor and the second motor to produce forward torque or backward torque and the other motor to produce backward torque or forward torque that is opposite to the torque produced by the one motor, the motor control unit controls both the motors of the first motor and the second motor based on target revolution state quantities of both the motors, while the motor control unit adds only to the one motor a correction torque to cause the one motor to attain its target revolution state quantity.   
     
     
         3 . The system of  claim 1 ,
 wherein the target revolution state quantity of the one motor is obtained based on at least one of an efficiency of the one motor and an efficiency of an electric power supply unit that supplies electric power to the one motor.   
     
     
         4 . The system of  claim 3 ,
 wherein the target revolution state quantity of the one motor is obtained based on at least one of the efficiency of the one motor and an efficiency of an electric power converter that is included in the electric power supply unit.   
     
     
         5 . The system of  claim 3 ,
 wherein the target revolution state quantity of the one motor is obtained based on the efficiency of the one motor only.   
     
     
         6 . The system of  claim 1 ,
 wherein the target revolution state quantity of the one motor is obtained based on a target rotation state quantity of the coupled third rotational elements.   
     
     
         7 . The system of  claim 6 ,
 wherein a connection/disconnection unit that can be released or applied and which slows the rotation of the third rotational elements by being applied.   
     
     
         8 . The system of  claim 7 ,
 wherein, when the connection/disconnection unit is released, the target rotation state quantity of the third rotational elements is set so that the third rotational elements are put in a substantially zero rotation state, and   wherein the connection/disconnection unit is applied when the third rotational elements are put in the substantially zero rotation state.   
     
     
         9 . The system of  claim 6 ,
 wherein a rotational-direction restriction unit that permits a rotation of the third rotational elements in one direction based on backward torque of the first and second motors when disengaged and which restricts a rotation of the third rotational elements in the other direction based on forward torque of the first and second motors when engaged.   
     
     
         10 . The system of  claim 9 ,
 wherein, when the rotational-direction restriction unit is disengaged, the target rotation state quantity of the third rotational elements is set so that the third rotational elements rotate in the one direction and are put in the substantially zero rotation state.   
     
     
         11 . The system of  claim 9 ,
 wherein, when the rotational-direction restriction unit is disengaged, the target rotation state quantity of the third rotational elements is set so that the rotational-direction restriction unit is not engaged.   
     
     
         12 . The system of  claim 6 ,
 wherein the target revolution state quantity of the one motor is obtained based on rotation state quantities of the second rotational elements or a rotation state quantity of the left wheel or the right wheel in addition to the target rotation state quantity of the coupled third rotational elements.   
     
     
         13 . The system of  claim 1 ,
 wherein the target torque state quantity is obtained based on a target turning state quantity of the vehicle.   
     
     
         14 . The system of  claim 13 ,
 wherein a target torque difference between the first motor and the second motor based on the target turning state quantity of the vehicle, and   wherein the target torque state quantity is made to be torque half the target torque difference.   
     
     
         15 . The system of  claim 1 ,
 wherein an absolute value of torque produced from the one motor is controlled to be larger than an absolute value of torque produced from the other motor.   
     
     
         16 . The system of  claim 1 ,
 wherein, when the target revolution state quantity of the one motor is higher than an actual revolution state quantity thereof, the correction torque is added to the motor of the first and second motors that is producing the forward torque.   
     
     
         17 . The system of  claim 1 ,
 wherein the first and second transmissions are supported so as to revolve around by the second rotational elements and have fourth rotational elements that mesh with the first rotational elements and the third rotational elements, and   wherein the target revolution state quantity of the one motor is obtained based on target rotation state quantities of the fourth rotational elements.   
     
     
         18 . The system of  claim 17 ,
 wherein the target rotation state quantities of the fourth rotational elements are set so that the rotational directions of the fourth rotational elements that are rotating in one direction or the other direction are not reversed.   
     
     
         19 . The system of  claim 18 ,
 wherein the target revolution state quantity of the one motor obtained based on the target rotation state quantities of the fourth rotational elements is referred to as a first target revolution state quantity,   wherein the target revolution state quantity of the one motor is obtained based on at least one of an efficiency of the one motor and an efficiency of an electric power supply unit that supplies electric power to the one motor and is then referred to as a second target revolution state quantity, and   wherein, when the first target revolution state quantity and the second target revolution state quantity are not satisfied at the same time, the one motor is controlled based on the first target revolution state quantity.   
     
     
         20 . The system of  claim 18 ,
 wherein a connection/disconnection unit that can be released or applied and which slows the rotation of the third rotational elements by being applied,   wherein the target revolution state quantity of the one motor obtained based on the target rotation state quantities of the fourth rotational elements is referred to as a first target revolution state quantity,   wherein the target revolution state quantity of the one motor is obtained based on the target rotation state quantity of the coupled third rotational elements and is then referred to as a third target revolution state quantity, and   wherein, when the first target revolution state quantity and the third target revolution state quantity are not satisfied at the same time, the one motor is controlled based on the third target revolution state quantity.   
     
     
         21 . The system of  claim 1 ,
 wherein the first and second transmissions are planetary gear mechanisms, and   wherein the first rotational elements are sun gears, the second rotational elements are carriers and the third rotational elements are ring gears.