Traction control system for four-wheel drive vehicle

• US 5,168,955 A
• Filed: 10/09/1990
• Issued: 12/08/1992
• Est. Priority Date: 10/09/1989
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Naito, Genpei
• Primary Examiner(s): Focarino, Margaret A.
• Assistant Examiner(s): BOEHLER, ANNE MARIE M
• Application Number:
  US07/594,154
• Time in Patent Office: 791 Days
• Field of Search: 180/197, 180/248, 180/233, 180/244, 180/247, 180/249, 364/424.05, 364/426.01, 364/426.03
• US Class Current: 180/197
• CPC Class Codes: B60K 23/0808 for varying torque distribution between driven axles, e.g. by transfer clutch
• CPC Class Codes: B60K 28/165 acting on elements of the vehicle drive train other than the propulsion unit and brakes, e.g. transmission, clutch, differential acting on brakes B60T8/17
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2520/125 Lateral acceleration

Abstract

A traction control system is provided which is applicable to a four-wheel drive vehicle in which a torque split system is incorporated. The torque split system is operable to distribute engine torque to front and rear wheels by an engine torque distribution ratio of front to rear wheels variable based on a difference in rotational speeds between the front and rear wheels. The traction control system is responsive to a slippage ratio of the rotational speeds of the wheels to a vehicle speed greater than a preselected threshold to reduce engine torque to control the traction of the wheels. Therefore, the traction control is effectively carried out while ensuring yaw control of a vehicle body by means of the torque split control.

Claims

1. A combination of a torque split system and a traction control system for an automotive vehicles, said vehicle including pairs of front and rear wheels, one of said pair being a primary driven wheel pair and the other being an auxiliary driven wheel pair, comprising:

rotational speed difference means for determining a rotational speed difference between said primary and auxiliary driven wheel pairs to provide a signal indicative thereof;

torque split means responsive to the signal from said rotational speed difference determining means for distributing an engine torque to wheels of said primary and auxiliary driven wheel pairs by an engine torque distribution ratio variably based on a degree of the rotational speed difference determined by said rotational speed difference determining means;

slippage determining means for determining slippage of said auxiliary driven wheels, to which said engine torque is distributed by said torque split means, relative to a vehicle speed to provide a signal indicative of a degree of slippage; and

traction control means responsive to the signal from said slippage determining means which is greater than a preselected slippage threshold for performing traction control,

wherein said slippage determining means is selectively responsive to (i) a rotational speed of a faster one of said auxiliary wheels, (ii) a rotational speed of a slower one of said auxiliary wheels and (iii) an averaged rotational speed of said auxiliary wheels to provide said signal indicative of a degree of slippage.

2. A combination of a torque split system and a traction control system for an automotive vehicles, said vehicle including pairs of front and rear wheels, one of said pair being a primary driven wheel pair and the other being an auxiliary driven wheel pair, comprising:

rotational speed difference means for determining a rotational speed difference between said primary and auxiliary driven wheel pairs to provide a signal indicative thereof;

torque split means responsive to the signal from said rotational speed difference determining means for distributing an engine torque to wheels of said primary and auxiliary driven wheel pairs by an engine torque distribution ratio variably based on a degree of the rotational speed difference determined by said rotational speed difference determining means;

slippage determining means for determining slippage of said auxiliary driven wheels, to which said engine torque is distributed by said torque split means, relative to a vehicle speed to provide a signal indicative of a degree of slippage;

traction control means responsive to the signal from said slippage determining means which is greater than a preselected slippage threshold for performing traction control,

said rotational speed difference determining means including speed sensor means for monitoring rotational speeds of the primary and auxiliary driven wheel pairs respectively to determine the rotational speed difference between the primary and auxiliary driven wheel pairs, said torque split means bringing the engine torque distribution ratio of the primary to auxiliary wheel pairs toward 1;

1 according to increase in the rotational speed difference between the primary and auxiliary wheel pairs,

said torque split means including clutch means disposed between the auxiliary driven wheel pair and an engine, said torque split means controlling engagement of the clutch means to transmit engine torque to the auxiliary wheel pair according to the engine torque distribution ratio;

vehicle speed sensor means for monitoring a vehicle speed to provide a signal indicative thereof, said slippage determining means being responsive to the signals from said speed sensor means of said slippage sensor means and said vehicle speed sensor means to provide a slippage ratio defined by the rotational speed of the auxiliary driven wheel pair relative to the vehicle speed and providing the signal indicative of the slippage ratio, said traction control means being responsive to the signal from said slippage determining means which represents a slippage ratio greater than the preselected slippage threshold, to reduce engine torque to control traction of the wheels, said vehicle speed sensor further including a longitudinal acceleration sensor which monitors longitudinal acceleration acting on a vehicle body and mathematically integrates the longitudinal acceleration to determine the vehicle speed; and

means for selectively providing to said slippage determining means (i) a rotational speed of a faster one of said auxiliary wheels, (ii) a rotational speed of a slower one of said auxiliary wheels and (iii) an averaged rotational speed of said auxiliary wheels as said rotational speed of said auxiliary wheels.

3. A combination of a torque split system and a traction control system for an automotive vehicle, said vehicle including pairs of front and rear wheels, one of said pair being a primary driven wheel pair and the other being an auxiliary driven wheel pair, comprising:

wheel speed sensor means for monitoring rotational speeds of said primary and auxiliary driven wheels to provide signals indicative thereof;

torque split means including clutch means disposed between the auxiliary driven wheels and an engine responsive to the signals from said wheel speed sensor means for distributing an engine torque to the auxiliary driven wheels by an engine torque distribution ratio of primary to auxiliary driven wheels variably based on a difference in the rotational speeds between the primary and auxiliary driven wheels which is determined based on the signals from said wheel speed sensor means;

slippage sensor means for monitoring slippage of the auxiliary driven wheels relative to a vehicle speed to provide a signal indicative thereof; and

traction control means responsive to the signal from said slippage sensor means being greater than a slippage threshold to control traction of the wheels based on said degree of slippage,

wherein said slippage sensor means is selectively responsive to (i) a rotational speed of a faster one of said auxiliary wheels, (ii) a rotational speed of a slower one of said auxiliary wheels and (iii) an averaged rotational speed of said auxiliary wheels to provide said signal indicative of slippage of said auxiliary wheels.

4. A combination of a torque split system and a traction control system for an automotive vehicle, said vehicle including pairs of front and rear wheels, one of said pair being a primary driven wheel pair and the other being an auxiliary driven wheel pair, comprising:

wheel speed sensor means for monitoring rotational speeds of said primary and auxiliary driven wheels to provide signals indicative thereof;

torque split means including clutch means disposed between the auxiliary driven wheels and an engine responsive to the signals from said wheel speed sensor means for distributing an engine torque to the auxiliary driven wheels by an engine torque distribution ratio of primary to auxiliary driven wheels variably based on a difference in the rotational speeds between the primary and auxiliary driven wheels which is determined based on the signals from said wheel speed sensor means;

slippage sensor means for monitoring slippage of the auxiliary driven wheels relative to a vehicle speed to provide a signal indicative thereof; and

traction control means responsive to the signal from said slippage sensor means being greater than a slippage threshold to control traction of the wheels based on said degree of slippage, wherein said slippage sensor means includes vehicle speed sensor means for monitoring vehicle speed to determine the slippage of said auxiliary driven wheels based on a difference in the rotational speed of said auxiliary driven wheels and the vehicle speed and providing a signal indicative thereof,

said slippage sensor means including vehicle speed sensor means for monitoring vehicle speed to determine the slippage of said auxiliary driven wheels based on a difference in the rotational speed of said auxiliary driven wheels and the vehicle speed and providing a signal indicative thereof,

wherein said slippage determining means is selectively responsive (i) a rotational speed of a faster one of said auxiliary wheels, (ii) a rotational speed of a slower one of said auxiliary wheels and (iii) an averaged rotational speed of said auxiliary wheels to provide said signal indicative of slippage of said auxiliary wheels.