Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
1998-04-28
2001-03-06
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S084000, C701S090000, C701S095000, C701S053000, C701S054000, C477S043000, C477S046000, C477S048000, C180S197000, C303S140000, C303S146000
Reexamination Certificate
active
06199005
ABSTRACT:
The contents of Tokugan Hei 9-111093 and 9-111094, with a filing date of Apr. 28, 1997 in Japan, are hereby incorporated by reference.
FIELD OF THE INVENTION
This invention relates to a drive force controller for preventing slipping of a drive wheel of a vehicle comprising a continuously variable transmission.
BACKGROUND OF THE INVENTION
A drive force control system or traction control system which prevents a drive wheel from slipping during acceleration of a vehicle and prevents the decline of acceleration performance, suppresses wheel slip for example by decreasing an engine output according to the slip of the drive wheels.
The decrease of engine output may be realized for example by closing a second throttle which is provided in parallel with an intake throttle, by stopping fuel injection to a specific cylinder of the engine, or by retarding the fuel ignition timing of the engine.
Tokkai Hei 4-50440 published by the Japanese Patent Office in 1992 discloses the application of a drive force controller which cuts fuel supply to some cylinders of the engine when drive wheels are slipping, to a vehicle comprising a continuously variable transmission (CVT).
In the CVT, a real speed change ratio is found for example from the ratio of the output shaft rotation speed and the input shaft rotation speed of CVT, and speed change control is performed so that the real speed change ratio coincides with a target speed change ratio which is set according to a running state.
However, since the CVT attempts to decrease the speed change ratio when the engine output torque is decreased due to fuel cut, but the response of the CVT is somewhat slower than that of drive force reduction by fuel cut, a hunting, i.e., fluctuation, of the speed change ratio is apt to occur, and the torque transmitted to the drive wheels may also fluctuate. This torque fluctuation causes vibration of the vehicle body.
For example, during acceleration after vehicle startup, the rotation speed of the drive wheels increases suddenly if the drive wheels slip. The output of the engine is therefore correspondingly reduced by performing fuel cut, the drive wheel speed decreases, and the slip converges. The target speed change ratio of the CVT also varies largely relative to the sudden change of drive wheel speed during this time, but as the response of the CVT is lower than that of the engine output variation due to fuel cut, hunting easily occurs while the drive wheel speed is rapidly varying.
Further, although drive force control due to fuel cut is highly responsive, the control resolution is low, and in an engine with a small number of cylinders, the engine output largely varies due to the fuel cut in one cylinder. Therefore, a variation of drive force easily becomes excessive due to fuel cut operation.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to suppress fluctuation of speed change ratio when a CVT is associated with a fuel cut system of a drive force controller.
In order to achieve the above object, this invention provides a vehicle drive force controller for suppressing a slip of a drive wheel of a vehicle driven by a multi-cylinder engine via a continuously variable transmission. The controller comprises a sensor for detecting a slip of the drive wheel, a drive force reducing mechanism for reducing a drive force of the drive wheel, a sensor for detecting a running state of the vehicle, a sensor for detecting a load of the engine, and a microprocessor.
The microprocessor is programmed to calculate a target speed change ratio according to the running state, output to the transmission, a speed change ratio command signal to control a speed change ratio of the transmission to the target speed change ratio, control the drive force reducing mechanism so as to reduce the drive force of the drive wheel when the slip of the drive wheel was detected, control the drive force reducing mechanism so as to further reduce the drive force of the drive wheel when the slip of the drive wheel was detected, when the engine load is larger than a predetermined load than when the engine load is equal to or less than the predetermined load, and modify the speed change ratio command signal so as to reduce a torque transmitted by the transmission is reduced when the engine load is equal to or less than the predetermined load than when the engine load is larger than the predetermined value.
It is preferable that the microprocessor is further programmed to modify the speed change ratio command signal so as to reduce the torque by increasing a response of the transmission.
It is also preferable that the microprocessor is further programmed to control the drive force reducing mechanism so as to further reduce the drive force by decreasing an output of the engine.
It is also preferable that the load detecting sensor detects a rotation speed of the engine when the slip of the drive wheel has been detected.
It is also preferable that the microprocessor is further programmed to prevent the drive force reducing mechanism from reducing the drive force when the engine load is equal to or less than the predetermined load.
It is also preferable that the drive force reducing mechanism comprises fuel injection valves respectively injecting fuel to cylinders of the engine, and the microprocessor is further programmed to control the drive force reducing mechanism so as to reduce the drive force by stopping fuel injection by one of the fuel injection valves.
This invention also provides a vehicle drive force controller comprising a sensor for detecting a slip of the drive wheel, a drive force reducing mechanism for reducing a drive force of the drive wheel, a sensor or detecting a running state of the vehicle, a sensor for detecting a rotation speed of the engine and a microprocessor programmed to calculate a target speed change ratio according to the running state, output to the transmission a speed change ratio command signal to control a speed change ratio of the transmission to the target speed change ratio, control the drive force reducing mechanism so as to reduce the drive force of the drive wheel when the slip of the drive wheel was detected, set the command signal such that a response of the transmission is delayed with respect to a variation of the running state, determine whether or not a rotation speed of the engine is equal to or less than a predetermined value, and modify the command signal such that the response of the transmission when the rotation speed is equal to or less than the predetermined value, is higher than when the rotation speed is larger than the predetermined value.
It is preferable that the drive force reducing mechanism comprises fuel injection valves respectively injecting fuel to cylinders of the engine, and the microprocessor is further programmed to stop fuel injection by one of the fuel injection valves when the slip of the drive wheel is detected.
It is further preferable that the microprocessor is further programmed to set a maximum number of fuel injection valves to be prevented from injecting fuel when the rotation speed of the engine exceeds the predetermined value, to be larger than the maximum number of fuel injection valves to be prevented from injecting fuel when the rotation speed of the engine is equal to or less than the predetermined value.
It is still further preferable that the microprocessor is further programmed to control the fuel injection valves such that a predetermined number of the fuel injection valves is not prevented from injecting fuel when the rotation speed of the engine is equal to or less than a predetermined value.
It is also preferable that the microprocessor is further programmed to determine the target speed change ratio based on the running state of the vehicle, calculate the speed change ratio command value such that the speed change ratio of the transmission follows the target speed change ratio with a predetermined time-constant, and increase the response of the transmission by reducing the time-constant when the rotation speed of the engine is equal to or le
Foley & Lardner
Louis-Jacques Jacques H.
Nissan Motor Co,. Ltd.
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