Four-wheel drive system

• US 7,392,875 B2
• Filed: 12/22/2004
• Issued: 07/01/2008
• Est. Priority Date: 12/25/2003
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Matsuzaki, Norikazu
• Primary Examiner(s): Winner; Tony
• Assistant Examiner(s): ARCE, MARLON ALEXANDER
• Application Number:
  US11/017,724
• Publication Number:
  US 20050150702A1
• Time in Patent Office: 1,287 Days
• Field of Search: 180/247, 180/248, 701/89, 701/72, 701/90
• US Class Current: 180/247
• CPC Class Codes: B60K 6/52 Driving a plurality of drive axles, e.g. four-wheel drive
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 2520/26 Wheel slip
• CPC Class Codes: B60W 2520/28 Wheel speed
• CPC Class Codes: B60W 30/18172 Preventing, or responsive to skidding of wheels
• CPC Class Codes: Y02T 10/62 Hybrid vehicles
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

To provide a four-wheel drive system which improves running performance of an automotive vehicle by inhibiting a driving torque from becoming insufficient upon occurrence of a slip.

An R slip sensing means of a DC motor torque calculating means senses a slip due to a spin of rear wheels. When the rear wheel slip is sensed, an R slip DC-motor-torque correcting means corrects a torque of the rear wheels so that a driving force of the rear wheels is reduced and then increased. The R slip DC-motor-torque correcting means reduces a driving torque of the rear wheels to eliminate the slip and holds the reduced driving torque until the slip is eliminated, and then increases the driving torque to a value lower than a value which the driving torque has taken at the time of occurrence of the slip. The driving torque is increased to a predetermined limit value depending on the number of slips.

Claims

1. A four-wheel drive system for controlling driving of four wheels of a four-wheel drive vehicle where torque is distributable to front wheels and rear wheels, the system comprising:

a slip sensing means for sensing a slip of rear wheels due to a spin thereof, and

a torque correcting means for correcting a torque on the rear wheels so that a driving force of the rear wheels whose slip is sensed by the slip sensing means is reduced and then increased,

wherein the torque correcting means operates to reduce the driving torque of the rear wheels until the driving torque reaches to a lower level where the slip is eliminated when the slip of the rear wheels is sensed,

wherein the torque correcting means operates to keep the reduced driving torque until the slip is eliminated and then to increase the driving torque when the slip of the rear wheels is sensed, and

wherein the torque correcting means, after eliminating the slip, operates to increase the driving torque lower than a value which the driving torque has taken at the time of occurrence of the slip.

2. A four-wheel drive system for controlling driving of four wheels of a four-wheel drive vehicle where torque is distributable to front wheels and rear wheels, the system comprising:

a slip sensing means for sensing a slip of rear wheels due to a spin thereof, and

a torque correcting means for correcting a torque on the rear wheels so that a driving force of the rear wheels whose slip is sensed by the slip sensing means is reduced and then increased,

wherein the torque correcting means operates to reduce the driving torque of the rear wheels until the driving torque reaches to a lower level where the slip is eliminated when the slip of the rear wheels is sensed,

wherein the torque correcting means operates, when the slip of any of the rear wheels is sensed, to keep the driving torque as reduced for a predetermined time period and then to increase the driving torque, and

wherein the torque correcting means, after eliminating the slip, operates to increase the driving torque lower than a value which the driving torque has taken at the time of occurrence of the slip.

3. A four-wheel drive system for controlling driving of four wheels of a four-wheel drive vehicle where torque is distributable to front wheels and rear wheels, the system comprising:

a slip sensing means for sensing a slip of rear wheels due to a spin thereof, and

a torque correcting means for correcting a torque on the rear wheels so that a driving force of the rear wheels whose slip is sensed by the slip sensing means is reduced and then increased,

wherein the torque correcting means operates to reduce the driving torque of the rear wheels until the driving torque reaches to a lower level where the slip is eliminated when the slip of the rear wheels is sensed,

wherein the torque correcting means operates to keep the reduced driving torque until the slip is eliminated and then to increase the driving torque when the slip of the rear wheels is sensed, and

wherein the torque correcting means, at the increasing process of the driving torque, operates to increase that up to a predetermined limit value depending on the number of spinning rotations of the rear wheels and to allow repetition of the slip due to the spin and a grip so that a continuous slip is inhibited.

4. A four-wheel drive system for controlling driving of four wheels of a four-wheel drive vehicle where torque is distributable to front wheels and rear wheels, the system comprising:

a slip sensing means for sensing a slip of rear wheels due to a spin thereof, and

a torque correcting means for correcting a torque on the rear wheels so that a driving force of the rear wheels whose slip is sensed by the slip sensing means is reduced and then increased,

wherein the torque correcting means operates to reduce the driving torque of the rear wheels until the driving torque reaches to a lower level where the slip is eliminated when the slip of the rear wheels is sensed,

wherein the torque correcting means operates, when the slip of any of the rear wheels is sensed, to keep the driving torque as reduced for a predetermined time period and then to increase the driving torque, and

wherein the torque correcting means, at the increasing process of the driving torque, operates to increase that up to a predetermined limit value depending on the number of spinning rotations of the rear wheels and to allow repetition of the slip due to the spin and a grip so that a continuous slip is inhibited.

5. A drive system for a four-wheel drive vehicle in which one of front wheels and rear wheels is driven by an internal combustion engine, and the other of the front wheels and rear wheels is driven by an electric motor, comprising:

a slip sensing means for sensing a slip of motor-driven wheels, and

a torque correcting means for correcting a driving torque supplied from the electric motor to the motor-driven wheels,

wherein the torque correcting means is configured to correct the driving torque so as to repeat actions of reducing the driving torque and then increasing the driving torque under a state of a road surface where the slip is sensed repeatedly until the slip is eliminated.

6. The drive system according to claim 5, wherein the torque correcting means is configured to repeat actions of reducing the driving torque, keeping the reduced driving torque for a predetermined time period, and then increasing the driving torque again, under the state of the road surface where the slip is sensed.

7. The drive system according to claim 5, wherein the torque correcting means is configured, when increasing the driving torque after reducing the driving torque under the state of the road surface where the slip is sensed, to increase the driving torque at a level lower than that before being reduced.

8. The drive system according to claim 5, wherein the torque correcting means is configured, when reducing the driving torque under the state of the road surface where the slip is sensed, to reduce the driving torque up to 0 Nm.

9. The drive system according to claim 5, wherein the torque correcting means is configured to set predetermined droving torque-limit values in accordance with the number of slips and increase the driving torque up to a predetermined limit value depending on the number of slips when increasing the driving torque after reducing the driving torque under the state of the road surface where the slip is sensed.