Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2000-04-25
2001-11-13
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S066000, C701S067000, C701S070000, C701S078000, C701S079000, C477S125000, C477S175000, C477S080000, C477S109000, C477S093000, C477S114000, C477S901000, C477S116000, C477S117000, C477S176000, C477S155000, C477S180000
Reexamination Certificate
active
06317671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a control apparatus for an automatic transmission installed in a vehicle and, more particularly, to a control apparatus for an automatic transmission capable of performing neutral control.
2. Description of Related Art
In some known automatic transmissions for a vehicle, if the vehicle stops in a forward drive range, the control for releasing an input clutch (hereinafter referred to as “neutral control”) is performed for the purpose of improving fuel consumption.
According to the related art, the clutch is released after the lapse of a predetermined length of time from a time when a vehicle speed detected by a vehicle speed sensor becomes zero, by estimating a time when the vehicle is definitely stopped.
However, during the aforementioned control, while the pressure of hydraulic fluid in a hydraulic servo of the input clutch needs to be reduced drastically from a normal line pressure to a release pressure, the hydraulic pressure needs to be released gently to prevent a shock from being caused when releasing the clutch. Therefore, it takes a long time until the operation is completed, and a time lag is generated from the stop of the vehicle to the actual release of the input clutch. As a result, the effect of the neutral control is lessened.
SUMMARY OF THE INVENTION
In consideration of the aforementioned circumstances, the invention aims at providing a control apparatus for an automatic transmission capable of sufficiently producing the effect of neutral control by reducing a period of time from stop of a vehicle to the release of an input clutch.
According to a first aspect of the invention, there is provided a control apparatus for an automatic transmission performing neutral control in which an input clutch for on-off controlling transmission of an engine driving force is released when a vehicle is stopped in a drive range, comprising a vehicle speed sensor for detecting a vehicle speed, vehicle stop prediction means for predicting immediate stop of the vehicle from the vehicle speed detected by the vehicle speed sensor, and input clutch control means for reducing a hydraulic pressure in a hydraulic servo of the input clutch from a hydraulic pressure in a normal engagement state to a predetermined waiting pressure capable of maintaining the engagement state of the input clutch, wherein an operation of releasing the input clutch concurrent with the neutral control is started from a state of the waiting pressure.
If the vehicle speed sensor detects that the vehicle speed has become equal to or lower than a predetermined speed, the vehicle stop prediction means predicts that the vehicle will stop soon. Based on the prediction of the stop of the vehicle, the input clutch control means reduces a hydraulic pressure in the hydraulic servo of the input clutch from a hydraulic pressure (a line pressure or the like) in a normal engagement state to a predetermined waiting pressure (Pwait) capable of maintaining the engagement state of the input clutch. The operation of releasing the input clutch concurrent with the neutral control is started from a state of the waiting pressure (Pwait), whereby the input clutch is released in a short period of time.
In the first aspect of the invention, because the operation of releasing the input clutch (the C
1
clutch) concurrent with the neutral control can be started from the waiting pressure (Pwait) which is lower than the hydraulic pressure in the normal engagement state, the input clutch can be released in a short period of time. Thus, the period during which the engine driving force is not transmitted to the speed-change mechanism portion with the input clutch being released can be prolonged accordingly. As a result, fuel consumption improves, and it becomes possible to produce the effect of the neutral control.
The control apparatus may comprise a brake sensor for detecting the presence or absence of depression of a brake and may be structured such that the vehicle stop prediction means predicts stop of the vehicle from the presence or absence of depression of the brake detected by the brake sensor in addition to the vehicle speed detected by the vehicle speed sensor.
In this structure, the stop of the vehicle can be predicted in consideration of the depression of the brake detected by the brake sensor as well as the vehicle speed detected by the vehicle speed sensor. Thus, the stop of the vehicle can be predicted with high reliability.
The control apparatus may comprise a throttle opening degree sensor for detecting an opening degree of a throttle and may be structured such that the vehicle stop prediction means predicts stop of the vehicle from the opening degree of the throttle detected by the throttle opening degree sensor in addition to the vehicle speed detected by the vehicle speed sensor.
In this structure, the stop of the vehicle can be predicted in consideration of the throttle opening degree detected by the throttle opening degree sensor as well as the vehicle speed detected by the vehicle speed sensor. Thus, the stop of the vehicle can be predicted with high reliability.
The control apparatus may be structured such that the input clutch control means reduces a hydraulic pressure in the hydraulic servo of the input clutch from a line pressure to a predetermined waiting pressure capable of maintaining an engagement state of the input clutch.
In this structure, the hydraulic pressure in the input clutch is drastically reduced from the line pressure to the waiting pressure (Pwait), and the following operation of releasing the input clutch (the C
1
clutch) can be smoothly performed in a short period of time.
The control apparatus may be structured such that the input clutch control means reduces a hydraulic pressure in the hydraulic servo of the input clutch from a hydraulic pressure in a normal engagement state to a predetermined waiting pressure based on a stall torque calculated from an engine at that moment.
In this structure, the hydraulic servo of the input clutch can be kept at the lowest hydraulic pressure capable of maintaining the engagement of the input clutch. Therefore, the following operation of releasing the input clutch (the C
1
clutch) can be smoothly performed in a short period of time.
The control apparatus may comprise vehicle stop determination means and may be structured such that when the vehicle stop determination means determines that the vehicle has stopped, the operation of releasing the input clutch concurrent with the neutral control is started from a state of the waiting pressure.
In this structure, if the vehicle stop determination means determines that the vehicle has stopped, the input clutch is released from the waiting pressure. Thus, the neutral control can be entered in a short period of time.
The control apparatus may comprise a running state detection sensor capable of detecting a signal corresponding to a plurality of stop-degree estimating elements for estimating a stop-degree of the vehicle, stop-degree estimating parameter calculation means for calculating a corresponding stop-degree estimating element from the signal detected by the running state detection sensor and calculating stop-degree estimating parameters corresponding to the respective stop-degree estimating elements, and vehicle stop-degree calculation means for calculating a stop-degree of the vehicle from the stop-degree estimating parameters calculated by the stop-degree estimating parameter calculation means, and may be structured such that the vehicle stop determination means determines whether the vehicle has stopped, based on the stop-degree of the vehicle calculated by the vehicle stop-degree calculation means.
In this structure, a corresponding stop-degree estimating element is calculated from the signal detected by the running state detection sensor, and a stop-degree estimating parameter is calculated from the calculated stop-degree estimating element. In addition, the stop-degree of the vehicle is calculated from the stop-degree estimating param
Saitou Nobutada
Tsutsui Hiroshi
Aisin Aw Co. Ltd.
Cuchlinski Jr. William A.
Mancho Ronnie
Oliff & Berridg,e PLC
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