Driving-torque distribution control apparatus of four-wheel drive vehicle
A controller to control a driving-torque distribution to a front wheel and a rear wheel comprises an obtainment portion to obtain a vehicle's lateral acceleration, an engine's output torque, and a vehicle's turning radius during turning of a vehicle, a determination portion to determine a rear-wheel driving-torque distribution rate denoting a rate of the driving torque to be transmitted to the rear wheel relative to the driving torque corresponding to the engine's output torque based on the obtained vehicle's lateral acceleration, engine's output torque, and vehicle's turning radius, and a control-signal output portion to output a control signal to a driving-torque transmission device to adjust the driving torque transmitted to the rear wheel such that the driving torque to be distributed to the rear wheel is controlled according to the determined rear-wheel driving-torque distribution rate.
1. A driving-torque distribution control apparatus of a four-wheel drive vehicle, which comprises a controller and a driving-torque transmission device to adjust a driving torque transmitted to a rear wheel according to a control signal of the controller, thereby controlling a driving-torque distribution of front and rear wheels of the vehicle,
wherein said controller is configured to:
obtain a lateral acceleration generated at the vehicle, an engine's output torque, and a vehicle's turning radius during turning of the vehicle;
determine a rear-wheel driving-torque distribution rate which denotes a rate of the driving torque to be transmitted to the rear wheel relative to the driving torque corresponding to the engine's output torque based on said obtained vehicle's lateral acceleration, engine's output torque, and vehicle's turning radius; and
output the control signal to said driving-torque transmission device such that the driving torque to be distributed to the rear wheel is controlled according to said determined rear-wheel driving-torque distribution rate.
2. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said controller determines the rear-wheel driving-torque distribution rate based on the obtained vehicle's lateral acceleration, engine's output torque, and vehicle's turning radius such that the total sum of loss energy of the sum of tire-loss energy of the front and rear wheels and mechanism-loss energy caused by driving of the rear wheel becomes the minimum.
3. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said controller determines the rear-wheel driving-torque distribution rate such that the greater said obtained vehicle's lateral acceleration is, the larger the rear-wheel driving-torque distribution rate is.
4. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said controller determines the rear-wheel driving-torque distribution rate such that the greater said obtained engine's output torque is, the larger the rear-wheel driving-torque distribution rate is.
5. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said controller determines the rear-wheel driving-torque distribution rate such that the greater said obtained vehicle's turning radius is, the smaller the rear-wheel driving-torque distribution rate is.
6. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said controller determines the rear-wheel driving-torque distribution rate such that the greater said obtained vehicle's lateral acceleration is, the larger the rear-wheel driving-torque distribution rate is, and/or the greater said obtained engine's output torque is, the larger the rear-wheel driving-torque distribution rate is, and/or the greater said obtained vehicle's turning radius is, the smaller the rear-wheel driving-torque distribution rate is.
7. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said controller determines the rear-wheel driving-torque distribution rate based on a map which previously associates the rear-wheel driving-torque distribution rate to be set with a value which is calculated by multiplying the lateral acceleration, the engine's output torque, and the reciprocal of the vehicle's turning radius, the rear-wheel driving-torque distribution rate determined by the controller being configured to correspond to the value calculated by multiplying the obtained lateral acceleration, the obtained engine's output torque, and the reciprocal of the obtained vehicle's turning radius.
8. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said controller determines the rear-wheel driving-torque distribution rate based on a map which previously associates the rear-wheel driving-torque distribution rate to be set with a combination of the lateral acceleration, the engine's output torque, and the vehicle's turning radius, the rear-wheel driving-torque distribution rate determined by the controller being configured to correspond to the combination of the obtained lateral acceleration, the obtained engine's output torque, and the obtained vehicle's turning radius.
9. The driving-torque distribution control apparatus of the four-wheel drive vehicle of claim 1 , wherein said driving-torque transmission device is configured to vary a maximum transmission driving torque which is the maximum of the driving torque transmitted to the rear wheel, and said controller obtains said maximum transmission driving torque based on said rear-wheel driving-torque distribution rate and sets the obtained maximum transmission driving torque for the driving-torque transmission device.