Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
1998-04-10
2001-04-10
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S062000, C701S064000, C477S109000, C477S125000, C477S148000, C477S904000
Reexamination Certificate
active
06216073
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to an apparatus and a method for controlling a speed change of an automatic transmission of an automobile, and more particularly, to a technique of carrying out a down-shift on the basis of a vehicle running resistance and a drive force.
(2) Related Art of the Invention
Conventionally, in order to speedily carry out a down-shift with respect to an increase of a running resistance such as an incline resistance, there has been proposed a speed change control apparatus for an automatic transmission (see Japanese Unexamined Patent Publication No. 7-239021), which is constructed in a manner of making a comparison between the running resistance and a drive force, and forcibly carrying out a down-shift when the drive force is less than the running resistance.
As described above, with the construction of carrying out a forced down-shift on the basis of the comparison between the running resistance and the drive force, for example, when an uphill incline changes from +4% to +8%, an increase in the uphill incline is made a trigger, a forced down-shift is carried out.
The insufficient drive force is speedily compensated according to the aforesaid forced down-shift; however, the forced down-shift is carried out regardless of a driving operation of a driver. Therefore, there has arisen a problem that the driver feels the aforesaid down-shift like a sudden speed change.
SUMMARY OF THE INVENTION
The present invention has been made taking the aforesaid problem in the prior art into consideration. It is, therefore, an object of the present invention to secure a drive force with respect to a change in a running resistance, and to carry out a down-shift for securing the drive force so as to meet a driver's intention.
To achieve the above object, with the present invention which provides an apparatus and a method for controlling a speed change of an automatic transmission, a driver's down-shift intention is detected, and a down-shift requirement is carried out on the basis of a vehicle running resistance and a drive force only when the driver intends to carry out the down-shift.
With the construction of the present invention, even in the case where a down-shift requirement is output on the basis of the vehicle running resistance and the drive force, when the driver does not intend to carry out the down-shift, the down-shift is not carried out, and only when the driver intends to carry out the down-shift, the down-shift is carried out. Therefore, it is possible to prevent the driver from feeling the down-shift on the basis of the running resistance and the drive force like a sudden speed change.
In this case, when a summed value of the maximum drive force at a current speed change step and a threshold value is smaller than a running resistance, a down-shift requirement may be output.
With the above construction of the present invention, when a drive force for securing a margin of traction is secured with respect to the running resistance, the down-shift requirement is not output; on the other hand, when the margin of traction is not secured, the down-shift requirement is output.
Further, when an engine load is equal to or more than a threshold value, a judgment may be made such that the driver has a down-shift intention.
With the above construction of the present invention, when the engine load is equal to or more than the threshold value, it is estimated that the driver feels an insufficient drive force and has made an operation for increasing the engine load; therefore, it is judged that there is a down-shift intention.
The threshold value of the engine load may be changed in accordance with vehicle operating conditions.
With the above construction of the present invention, even in the same engine load, the down-shift intention is detected or not detected depending upon vehicle operating conditions. Thus, it is possible to accurately judge the down-shift intention regardless of a change in vehicle operating conditions.
The vehicle operating conditions include at least one of a vehicle speed or a speed change step.
With the above construction of the present invention, an engine load level for detecting the down-shift intention changes depending upon vehicle running speed and/or speed change step. In a general automatic speed change control, the down-shift is carried out in a higher engine load state on high vehicle speed side. Therefore, in order to judge the driver's down-shift intention in an engine load state greater than on a low vehicle speed side, a threshold value of the engine load is preferably set to a greater value on the high vehicle speed side. Further, when a speed change step is situated on the low speed side, the down-shift is carried out in a higher engine load state; therefore, the threshold value of the engine load is preferably set to a greater value on the low speed step side.
The threshold value of the engine load may be changed in accordance with vehicle running environment.
With the above construction of the present invention, even in the same engine load, the down-shift intention is detected or not detected depending upon vehicle running environment. Thus, it is possible to accurately judge the down-shift intention regardless of a change in vehicle running environment.
The vehicle running environment may include an incline of a running road surface.
With the above construction of the present invention, an engine load level for detecting the down-shift intention changes depending upon an incline of a road surface where the vehicle is running. In general, when the uphill incline is steep, a driver, who intends to carry out the down-shift, greatly steps on an accelerator pedal. Thus, the threshold value of the engine load is preferably set to a greater value when the uphill incline is steep.
The engine load may be detected on the basis of an accelerator opening operated by the driver.
With the above construction of the present invention, the engine load is representative of an accelerator opening, and when the accelerator opening is equal to or more than the threshold value, the driver's down-shift intention is detected. In place of directly detecting the accelerator opening, it is possible to detect an opening of a throttle vale opening and closing in synchronous with the accelerator pedal.
In order to detect the driver's down-shift intention, when the actual accelerator opening is equal to or more than a threshold value set in accordance with a vehicle running speed, an incline resistance of a running road surface and a speed change step, the driver's down-shift intention may be detected.
With the above construction of the present invention, the driver's down-shift intention is detected according to the result whether or not the accelerator opening corresponding substantially to the engine load is equal to or more than a threshold value set in accordance with a vehicle running speed, an incline resistance of a running road surface and a speed change step.
The other objects and features of the present invention will be apparent from an embodiment set forth below, with reference to the accompanying drawings.
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Horiguchi Masanobu
Ikeda Akira
Louis-Jacques Jacques H.
McDermott & Will & Emery
Unisia Jecs Corporation
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