Traction control system for a four-wheel drive motor vehicle

Claim 2

In a power transmitting system for a four-wheel drive vehicle having a central differential for splitting torque of an engine at a predetermined ratio, power trains for transmitting the split torques from output members of the central differential to front and rear wheels respectively of the vehicle, a throttle actuator for changing opening degree of a throttle valve of the engine, and a torque split control device including a clutch provided between the output members of the central differential for changing torque distribution ratio of the torques transmitted to the front and rear wheels, the improvement in the system comprising: front-wheel speed sensors for detecting right and left front-wheel speeds and for producing right and left front-wheel sped signals; rear-wheel speed sensors for detecting right and left rear-wheel speeds and for producing right and left rear-wheel speed signals; first calculator means responsive to the right and left front-wheel and rear-wheel speed signals for producing a front-axle speed signal and a rear-axle speed signal; two-wheel slip detecting means responsive to the front-axle speed signal and the rear-axle speed signal for producing a two-wheel slip signal when the front wheels are slipping with respect to the rear wheels or the rear wheels are slipping with respect to the front wheels; four-wheel slip detecting means responsive to the front-axle and rear-axle speed signals and a vehicle body acceleration signal only at non-existence of the two-wheel slip signal for producing a four-wheel slip signal; actuator means responsive to the two-wheel slip signal for controlling engaging of the clutch controlling the torque distribution ratio so as to reduce the torque to the slipping wheels; and actuating means being responsive to the four-wheel slip signal for actuating the throttle actuator so as to reduce the opening degree of the throttle valve.

Claim 3

The system according to claim 1, wherein the clutch is an oil hydraulic clutch having opposite disks and operates to transmit torque from disks of higher speed to disks of lower speed and by pressure supplied to the clutch.

Claim 4

The system according to claim 1 wherein the central differential is a planetary gear.

Claim 5

The system according to claim 1, further comprising a vehicle body acceleration sensor for producing said vehicle body acceleration signal.

Claim 6

The system according to claim 4, wherein the four-wheel slip detecting means produces the four-wheel slip signal in dependency on the difference between the vehicle body acceleration signal and another acceleration signal representing acceleration of the vehicle wheels calculated based on the front-axle and rear-axle speed signals.

Claim 7

The system according to claim 5, wherein said another acceleration signal represents the derivative of an average of the front-axle and rear-axle speed signals.

Claim 8

The system according to claim 4, wherein the four-wheel slip detecting means produces the four-wheel slip signal in dependency on the difference between a vehicle wheel speed signal based on the front-axle and rear-axle speed signals and a vehicle body speed signal calculated as an integral of the vehicle body acceleration signal.

Claim 9

The system according to claim 7, wherein the vehicle wheel speed signal is an average of the front-axle and rear-axle speed signals.

Claim 10

The system according to claim 1, further comprising a steering angle sensor for producing a steering angle signal corresponding to steering angle; and means responsive to said steering angle signal for producing a reference value corresponding to said steering angle signal, said reference value being a function of the steering angle; said two-wheel slip detecting means is responsive to said reference value for producing said two-wheel slip signal when the difference between said front-axle and rear-axle speeds is greater or less than said reference value.

Claim 11

In a power transmitting system for a four-wheel drive vehicle having a central differential for splitting torque of an engine at a predetermined ratio, power trains for transmitting the split torques from output members of said central differential to front and rear wheels respectively of said vehicle, a throttle actuator for changing an opening degree of a throttle valve of said engine, and a torque split control device including a clutch provided between said output members of said central differential for changing torque distribution ratio of the torques transmitted to said front and rear wheels, the improvement in the system comprising: front-wheel speed sensors for detecting right and left front-wheel speeds and for producing right and left front-wheel speed signals; rear-wheel speed sensors for detecting right and left rear-wheel speeds and for producing right and left rear-wheel speed signals; first calculator means responsive to the right and left front-wheel speed signals and the right and left rear-wheel speed signals for producing a front-axle speed signal and a rear-axle speed signal; two-wheel slip detecting means responsive to said front-axle speed signal and said rear-axle speed signal for producing a two-wheel slip signal when the front wheels are slipping with respect to said rear wheels or when the rear wheels are slipping with respect to the front wheels; four-wheel slip detecting means responsive to said front-axle speed signal, said rear-axle speed signal and a vehicle body acceleration signal for producing a four-wheel slip signal only at non-existence of the two-wheel slip signal; actuator means responsive to said two-wheel slip signal for controlling said torque distribution ratio by controlling engagement of said clutch so as to reduce the torque to the slipping wheels; actuating means responsive to the four-wheel slip signal for actuating said throttle actuator so as to reduce the opening degree of the throttle valve; a vehicle body acceleration sensor for producing said vehicle body acceleration signal; and said vehicle body acceleration sensor comprises a rotational speed sensor of an output shaft of a transmission of said vehicle, said transmission being connected between said engine and an input member of said central differential.

Claim 12

In a power transmitting system for a four-wheel drive vehicle having a central differential for splitting torque of an engine at a predetermined ratio, power trains for transmitting the split torques from output members of said central differential to front and rear wheels respectively of said vehicle, a throttle actuator for changing an opening degree of a throttle valve of said engine, and a torque split control device including a clutch provided between said output members of said central differential for changing torque distribution ratio of the torques transmitted to said front and rear wheels, the improvement in the system comprising: front-wheel speed sensors for detecting right and left front-wheel speeds and for producing right and left front-wheel speed signals; rear-wheel speed sensors for detecting right and left rear-wheel speeds and for producing right and left rear-wheel speed signals; first calculator means responsive to the right and left front-wheel speed signals and the right and left rear-wheel speed signals for producing a front-axle speed signal and a rear-axle speed signal; two-wheel slip detecting means responsive to said front-axle speed signal and said rear-axle speed signal for producing a two-wheel slip signal when the front wheels are slipping with respect to said rear wheels or when the rear wheels are slipping with respect to the front wheels; four-wheel slip detecting means responsive to said front-axle speed signal, said rear-axle speed signal and a vehicle body acceleration signal for producing a four-wheel slip signal only at non-existence of the two-wheel slip signal; actuator means responsive to said two-wheel slip signal for controlling said torque distribution ratio by controlling engagement of said clutch so as to reduce the torque to the slipping wheels; actuating means responsive to the four-wheel slip signal for actuating said throttle actuator so as to reduce the opening degree of the throttle valve; a vehicle body acceleration sensor for producing said vehicle body acceleration signal; and said vehicle body acceleration sensor comprises a rotational speed sensor of an output shaft of a transmission of said vehicle, said transmission being connected between said engine and an input member of said central differential.