Front/rear wheel torque distribution control apparatus for four wheel drive vehicle

• US 6,497,301 B2
• Filed: 09/18/2001
• Issued: 12/24/2002
• Est. Priority Date: 09/19/2000
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Fukuda, Yoshiyuki, Kusukawa, Hirotaka, Iida, Norio, Gotou, Atsuhiko, Mizuya, Satoshi
• Primary Examiner(s): LERNER, AVRAHAM H
• Application Number:
  US09/954,048
• Publication Number:
  US 20020033291A1
• Time in Patent Office: 462 Days
• Field of Search: 180/233, 180/248, 180/249, 180/250, 180/197, 701/69, 701/88, 701/89, 701/74, 701/87
• US Class Current: 180/249
• CPC Class Codes: B60K 17/3505 with self-actuated means, e.g. by difference of speed
• CPC Class Codes: B60K 23/0808 for varying torque distribution between driven axles, e.g. by transfer clutch
• CPC Class Codes: B60W 2050/0022 Gains, weighting coefficients or weighting functions
• CPC Class Codes: B60W 2050/143 Alarm means
• CPC Class Codes: B60W 2510/0291 Clutch temperature
• CPC Class Codes: B60W 2520/10 Longitudinal speed
• CPC Class Codes: B60W 2530/20 Tyre data
• CPC Class Codes: B60W 2710/105 Output torque

Abstract

To achieve a first object of the present invention, a starting time limit vehicle speed which preferentially permits a torque distribution to front and rear wheels at the time of starting of a vehicle is switched in accordance with a degree of a diameter difference. To achieve a second object of the present invention, when the vehicle makes a normal running with different-diameter tires mounted thereon, a front/rear wheel distribution torque caused by a front/rear wheel rotation speed difference owing to the different-diameter tires is limited by switching a torque gain depending on a degree of a diameter difference.

Claims

1. A front/rear wheel torque distribution control apparatus of a four-wheel drive vehicle having an electronic control clutch for controlling a torque distribution to front and rear wheels, in which one of the front and rear wheels is a main drive wheel and the other is a subsidiary drive wheel, said front/rear wheel torque distribution control apparatus comprising:

a tire diameter difference degree detector for detecting a degree of a diameter difference between a different-diameter tire and a normal-diameter tire when any of the front and rear wheels mounts the different-diameter tires;

a driver request torque calculator for calculating a driver request torque transmitted from the main drive wheel to the subsidiary drive wheel via said electronic control clutch in response to an operation of a driver;

a vehicle speed detector for detecting a vehicle speed;

a starting time limit speed determiner for making a starting time limit speed in which a torque at the time of starting of the vehicle is limited by a vehicle speed lower as the degree of the diameter difference detected by said tire diameter difference degree detector is larger; and

a starting time torque distribution controller for outputting an instruction to obtain the driver request torque calculated by said driver request torque calculator to the electronic control clutch until the vehicle speed becomes equal to a starting time limit vehicle speed determined by said starting time limit vehicle speed determiner when the vehicle mounts the different-diameter tires.

2. The front/rear wheel torque distribution control apparatus according to claim 1, said front/rear wheel torque distribution control apparatus further comprising:

a starting time limit torque determiner for determining a starting time limit torque to be a smaller value as the degree of the tire diameter difference is larger, when the degree of the detected tire diameter difference is larger than a setting value,

wherein when the driver request torque exceeds the starting time limit torque, said starting time torque distribution controller outputs an instruction to obtain the starting time limit torque to said electronic control clutch.

3. The front/rear wheel torque distribution control apparatus according to claim 1, said front/rear wheel torque distribution control apparatus further comprising:

a front/rear wheel rotation speed difference detector for detecting a front/rear wheel rotation speed difference; and

a front/rear wheel distribution torque corresponding value detector for detecting a front/rear wheel distribution torque corresponding value transmitted via said electronic control clutch,

wherein said different-diameter tire detector detects the degree of the diameter difference based on a front/rear wheel rotation speed difference detected, when conditions that the vehicle speed detected by said vehicle speed detector is equal to a setting vehicle speed or more and the front/rear wheel distribution torque corresponding value is equal to a setting value or less are established.

4. The front/rear wheel torque distribution control apparatus according to claim 3, wherein when different-diameter tires of the maximum degree of the diameter difference within an assured range of the degree of the diameter difference are used, said different-diameter tire detector previously measures a time at which a clutch temperature reaches at which a clutch temperature becomes a limit to use the clutch by a tightening torque generated by the front/rear wheel rotation speed difference, and a longest possible time before the clutch temperature becomes the limit is set to a different-diameter tire detection time.

5. A front/rear wheel torque distribution control apparatus of a four-wheel drive vehicle having an electronic control clutch for controlling a torque distribution to front and rear wheels, said front/rear wheel torque distribution control apparatus comprising:

a tire diameter difference degree detector for detecting a degree of a diameter difference when any of front and rear wheels mounts different-diameter tires;

a normal running time detector for detecting a normal running time of the vehicle;

a normal running torque gain determiner for determining a normal running torque gain to be a torque gain smaller than a torque gain at the time when normal-diameter tires are mounted as the degree of the diameter difference detected by the tire diameter difference degree detector is larger, when any of the front and rear wheels mounts the different-diameter tires;

a normal running torque calculator for calculating a normal running torque by multiplying a front/rear wheel rotation speed difference by the torque gain determined by the normal running torque gain determiner; and

a normal running time torque distribution controller for outputting an instruction to obtain the normal running torque calculated by said normal running torque calculator to said electronic control clutch, when the vehicle makes normal running with the different-diameter tires mounted on any of the front and rear wheels thereof.

6. The front/rear wheel torque distribution control apparatus according to claim 5, said front/rear wheel torque distribution control apparatus further comprising:

a driver request torque calculator for calculating a driver request torque in accordance with an operation of a driver, the driver request torque being transmitted via said electronic control clutch,

wherein when the normal running torque is equal to the driver request torque or more, which is calculated by said driver request calculator, said normal running time torque distribution controller outputs an instruction to obtain the driver request torque to said electronic control clutch, when the normal running torque is not more than the driver request torque, said normal running time torque distribution controller outputs an instruction to obtain the normal running torque to said electronic control clutch.

7. A front/rear wheel torque distribution control apparatus of a four-wheel drive vehicle having an electronic control clutch for controlling a torque distribution to front and rear wheels, in which one of the front and rear wheels is a main drive wheel and the other is a subsidiary drive wheel, said front/rear wheel torque distribution control apparatus comprising:

different diameter degree detection means for detecting a degree of a diameter difference between a different-diameter tire and a normal-diameter tire when any of the front and rear wheels mounts the different-diameter tires;

driver request torque calculation means for calculating a driver request torque transmitted from the main drive wheel to the subsidiary drive wheel via said electronic control clutch in response to an operation of a driver;

vehicle speed detection means for detecting a vehicle speed;

starting time limit speed determination means for making a limit speed in which a torque at the time of starting the vehicle is limited by a vehicle speed lower as the degree of the diameter difference detected by said different diameter degree detection means is larger; and

a starting time torque distribution control means for outputting an instruction to obtain the driver request torque calculated by said driver request torque calculation means to the electronic control clutch until the vehicle speed becomes equal to a starting time limit vehicle speed determined by said starting time limit speed determination means when the vehicle mounts the different-diameter tires.