Motor vehicles – Having four wheels driven – With manually operated means for disengaging drive to one or...
Reexamination Certificate
1997-06-20
2001-02-20
Mai, Lanna (Department: 3619)
Motor vehicles
Having four wheels driven
With manually operated means for disengaging drive to one or...
C180S249000
Reexamination Certificate
active
06189642
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to distribution control in a torque distributor mechanism which distributes an engine drive torque between main drive wheels and extra drive wheels according to driving conditions.
BACKGROUND OF THE INVENTION
A device which varies the distribution ratio of a drive torque between the main drive wheels and extra drive wheels of a four-wheel drive vehicle is disclosed for example in Tokkai Hei 2-270641 published in 1990 by Japanese Patent Office.
In this device, the main drive wheels are directly driven, while the extra drive wheels and engine drive shaft are connected via a wet type multi-plate friction clutch.
The torque distribution ratio to the extra drive wheels is varied by varying the grip force of the clutch according to a control signal. The grip force of the clutch is increased the larger the difference between the rotation speeds of the front and rear wheels, i.e. the larger the slip of the rear wheels which are the main drive wheels. As a result, the distribution ratio of the drive force to the front wheels, which are the extra drive wheels, is increased, and the slip of the rear wheels is promptly terminated.
In such a four-wheel drive vehicle, when the vehicle makes a turn during four-wheel drive, the difference in the rotation radius of the front and rear wheels causes a torsion in the suspension, tires and vehicle body.
If the driver stops the vehicle in the turn and turns off the engine, the grip force of the clutch falls to zero because the clutch grip force comes from an oil pump driven by the engine, and as the front wheels suddenly become free, the torsion in the suspension, tyres and vehicle body is immediately released. The release of this torsion causes the vehicle body to vibrate and oscillate in a top/bottom and front/back direction, and this gives an uncomfortable feeling to the driver and passengers of the vehicle.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to prevent a vehicle body from vibrating and oscillating when an engine stopped while the vehicle is making a turn.
In order to achieve the above object, this invention provides a drive torque distribution control system for distributing engine power between a main drive wheel and an extra drive wheel of a vehicle. The system comprises a torque distribution mechanism for transmitting an engine torque to the extra drive wheel at a predetermined distribution ratio, a mechanism for detecting a vehicle speed, a mechanism for setting a first value to the predetermined ratio at a high vehicle speed, and setting a second value higher than the first value to the predetermined ratio at a low vehicle speed, a mechanism for detecting a specific operation by a driver that is performed preceding to turn off the engine, and a mechanism for setting a third value less than the second value to the predetermined ratio when the operation is detected.
It is preferable that the third value is set larger than the first value.
It is also preferable that the vehicle speed detecting mechanism comprises a mechanism for detecting a rotation speed of the extra drive wheel.
It is also preferable that the specific operation detecting mechanism comprises a mechanism for detecting an operation of a parking brake with which the vehicle is provided.
This invention also provides a drive torque distribution control system for a vehicle which is provided with an automatic transmission. This system comprises a torque distribution mechanism for transmitting an output torque of the transmission to the extra drive wheel at a predetermined distribution ratio, a mechanism for detecting a vehicle speed, a mechanism for setting a first value to the predetermined ratio at a high vehicle speed, and setting a second value higher than the first value to the predetermined ratio at a low vehicle speed, a mechanism for detecting that the automatic transmission is in a speed change position corresponding to the stopping of the vehicle, and a mechanism for setting a third value less than the second value to the predetermined ratio when the automatic transmission is changed over to a speed change position corresponding to the stopping of the vehicle.
In this system it is preferable that the mechanism for detecting that the automatic transmission is in a speed change position corresponding to the stopping of the vehicle comprises an inhibitor switch for generating a signal according to a position of a shift lever of the transmission.
It is also preferable that the third value is set larger than the first value.
This invention also provides a vehicle drive torque distribution control system comprising a torque distribution mechanism for transmitting an engine torque to the extra drive wheel at a predetermined distribution ratio, a vehicle speed detector, a detector for detecting that the vehicle has stopped, and a microprocessor programmed to set a first value to the predetermined ratio at a high vehicle speed, set a second value higher than the first value to the predetermined ratio at a low vehicle speed, and set a third value less than the second value to the predetermined ratio when a specific operation is performed by a driver preceding to turn off the engine.
The specific operation may comprises an operation of a parking brake with which the vehicle is provided.
This invention also provides a drive torque distribution control system for a vehicle which is provided with an automatic transmission. The system comprises a torque distribution mechanism for transmitting an engine torque to the extra drive wheel at a predetermined distribution ratio, a vehicle speed detector, a detector for detecting that the vehicle has stopped, and a microprocessor programmed to set a first value to the predetermined ratio at a high vehicle speed, set a second value higher than the first value to the predetermined ratio at a low vehicle speed, and set a third value less than the second value to the predetermined ratio when the automatic transmission is changed over to a speed change position corresponding to the stopping of the vehicle.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
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Fischer Andrew J.
Foley & Lardner
Mai Lanna
Nissan Motor Co,. Ltd.
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