Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
1998-06-01
2001-01-23
Marmor, Charles A. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S154000, C477S158000
Reexamination Certificate
active
06176812
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a speed change transition control apparatus for an automatic transmission, and more particularly to a speed change transition control apparatus for an automatic transmission that controls fluid pressure which is supplied to the friction engaging element of the speed change mechanism in the automatic transmission during speed changes.
DESCRIPTION OF THE RELATED ART
Generally, in commonly used automatic transmissions for vehicles, the rotational speed of the engine is input via the torque converter. The input rotational speed is changed by a speed change mechanism consisting of a plurality of planetary gear units and is output to the propeller shaft (axle shaft side).
The speed change mechanism in this kind of automatic transmission is usually equipped with a plurality of oil pressure actuated friction engaging elements such as clutches and brakes in order to transmit to a specific gear or carrier constituting the planetary gear unit the rotation of the input shaft transmitted from the torque converter and transmit the rotation of a specific gear or carrier to the output shaft suitably in correspondence to the position of the shift lever, or in order to restrict the rotation of a specific gear or carrier suitably.
If the solenoid valve incorporated in the oil pressure control circuit is controlled, the aforementioned friction engaging elements will be locked or released, and speed changes will be made. In this case, when the friction engaging elements are switched from a released state to a locked state or from a locked state to a released state, if a change in the locking force is not appropriately made, there will be a problem that an excessive torque shock will occur.
For example, when shifting up, the load of the friction engaging element on the release side is reduced to zero and the first stage (so-called torque phase) of a speed change ends, and at the second stage (so-called inertia phase) after the time that an execution gear ratio begins to change, there is a need to increase the locking capacity (i.e., supplied oil pressure) of the friction engaging element on the locking side appropriately at a rate of increase corresponding to the opening angle of the throttle valve to change the rotational speed of the input shaft of the speed change mechanism at an appropriate rate of change.
The reason is that if the above-mentioned locking capacity is too large, the rotational speed of the aforementioned input shaft will reduce rapidly and the speed change time required to shift up will be short, but the torque of the output shaft will increase temporarily and a great shock during a speed change will occur. On the other hand, if the above-mentioned locking capacity is too small, the speed change time will be excessive, resulting in a feeling in speed changes where disengagement between teeth is poor.
Hence, various kinds of techniques which attempt to change the rotational speed of the input shaft of the speed change mechanism more ideally by controlling oil pressure which is supplied to the above-mentioned friction engaging element during speed changes have been proposed.
For instance, in the control technique disclosed in Japanese Laid-Open Patent Publication No. HEI 1-199050, in the inertia phase during a speed change, on the basis of the quantity of change between the rotational speeds of the aforementioned input shaft before and after a speed change and the speed change time previously set in correspondence to the opening angle of the throttle valve, the target rotational speed change rate in the rotational speed of the aforementioned input shaft is calculated. From the calculated target rotational speed change rate, the target rotational speed of the aforementioned input shaft is calculated for each control cycle. With this target rotational speed as a control target value and also with the detected value of the rotational speed of the aforementioned input shaft as a feedback value, the feedback control for the aforementioned supplied oil pressure is performed in real time.
However, in the control technique disclosed in the above-mentioned publication, as shown for example in FIG.
2
(
a
), between a predetermined target rotational speed Nt set at ideal timing and an ideal rate of change against the time axis (horizontal direction in the figure) and an actual rotational speed Ni of the input shaft, a large deviation occurs particularly at a control start point and immediately after the control start point. For this reason, a quantity of control in the feedback control becomes great immediately after the control start point, and a great hunting phenomenon is caused. As shown in FIG.
2
(
a
), since the actual rotational speed Ni and output shaft torque Tp fluctuate considerably, there is a problem that a speed change shock is increased.
On the other hand, there is another conventional control method which changes the rotational speed of the input shaft of the speed change mechanism at a constant rate of change by feeding back oil pressure which is supplied during speed changes.
However, the above-mentioned conventional control method has the following disadvantage, because in the case of an identical speed change, the target change rate in the rotational speed of the input shaft is always constant.
That is, as shown by a solid line in
FIG. 11
, if an actual rotational speed Nt of the input shaft at inertia phase start point X
0
matches with the target change characteristic of a previously set input shaft rotation speed Nt, the input shaft rotation speed Nt during a speed change, together with oil pressure P and output shaft torque Tp, will change nearly as set, and the speed change time will be nearly equal to a previously set time T.
However, actually the actual input shaft rotation speed Nt at inertia phase start point X
0
changes by major factors such as a fluctuation in vehicle speed and a fluctuation in an input torque. For instance, as shown by a dotted line in
FIG. 11
, there are cases where the input shaft rotation speed Nt exceeds a set value. Conventionally, even in such a case, since a feedback control for oil pressure P is performed while a target change rate remains constant, the speed change end point changes from X
1
to X
2
, as shown in FIG.
11
. Also, the actual speed change time T
1
considerably exceeds a set speed change time T
0
, and the output shaft torque Tp during a speed change increases by the amount of inertia force absorption, as shown by the dotted line. For this reason, the time during which the friction engaging elements of the speed change mechanism are slipping while transmitting a torque becomes extended by that amount, and the increased time constitutes an obstacle to an enhancement in the durability of the transmission. Furthermore, since the output shaft torque Tp increases in a time-axis direction, as shown by a dotted line in
FIG. 11
, there is another problem that a feeling in speed changes becomes poor.
SUMMARY OF THE INVENTION
It is an object of the prevent invention to provide a speed change transition control apparatus for an automatic transmission where an increase in the above-mentioned speed change shock is suppressed to obtain a satisfactory feeling in speed changes.
Another object of the present invention is to provide a speed change transition control apparatus for an automatic transmission where, even in the case of the high rotational speed of the transmission during a speed change, the speed change is ended within a predetermined time and therefore enhancements in durability and a feeling in speed changes are achieved.
To achieve the foregoing objects and in accordance with one important aspect of the present invention, there is provided a speed change transition control apparatus for an automatic transmission which has a speed change mechanism for performing speed changes by locking or releasing a plurality of friction engaging elements and also which is equipped with a fluid pressure control element for controlling engagement pressure which is supplied to
Iizuka Naonori
Taki Masaharu
Blank Rome Comisky & McCauley
Ho Ha
Jatco Corporation
Marmor Charles A.
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