Interrelated power delivery controls – including engine control – Transmission control – Including fluid drive
Reexamination Certificate
2001-10-26
2003-11-25
Lorence, Richard M. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Including fluid drive
C701S060000, C192S003300, C477S168000, C477S176000
Reexamination Certificate
active
06652415
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a slip control system that brings relative rotation, i.e., slip rotation between input and output elements of a torque converter used in an automatic transmission closer to a desired value, and particularly to techniques for slip control during a transition from a non-slip-control area to a slip-control area.
BACKGROUND ART
In recent years, there have been proposed and developed various slip control systems that perform slip control for a torque converter lock-up clutch. A pre-compensator equipped slip control system has been disclosed in Japanese Patent Provisional Publication No. 2000-145948 (hereinafter is referred to as “JP2000-145948”). In the slip control system disclosed in JP2000-145948, instead of directly using a value of target slip rotation (hereinafter is referred to as a “target slip rotation &ohgr;
SLPT
” indicated in terms of an angular velocity), a compensated value of target slip rotation (hereinafter is referred to as a “compensated target slip rotation &ohgr;
SLPTC
”) produced by passing target slip rotation &ohgr;
SLPT
through the pre-compensator is used for slip control. The pre-compensator functions to determine the transient response of the slip control system singly. Slip control is executed so that a value of actual slip rotation (hereinafter is referred to as an “actual slip rotation &ohgr;
SLPR
”) is brought closer to the compensated target slip rotation &ohgr;
SLPTC
filtered or compensated for by means of the pre-compensator. In the system of JP2000-145948, when the torque converter is shifted from the non-slip-control area to the slip-control area, target slip rotation &ohgr;
SLPT
is switched from actual slip rotation &ohgr;
SLPR
to a value of required slip rotation (hereinafter is referred to as a “required slip rotation &ohgr;
SLPT0
”) based on both a rotational speed of a turbine runner and a throttle opening, and the required slip rotation &ohgr;
SLPT0
passes through the pre-compensator to produce compensated target slip rotation &ohgr;
SLPTC
, and thus actual slip rotation &ohgr;
SLPR
is feedback-controlled closer to compensated target slip rotation &ohgr;
SLPTC
based on required slip rotation &ohgr;
SLPT0
. Therefore, even when shifting from the non-slip-control area to the slip-control area, it is possible to provide a designated transient-response characteristic determined by the pre-compensator, thereby reducing shocks during engagement of the torque converter lock-up clutch.
SUMMARY OF THE INVENTION
In the system of JP2000-145948, arithmetic calculation for compensated target slip rotation &ohgr;
SLPTC
(corresponding to the transient response), is executed by the pre-compensator immediately when shifting from the non-slip-control area to the slip-control area. On the other hand, an engagement pressure of the lock-up clutch tends to rise with a delay in the response from the time when shifting to the slip-control area. During a period of time that the engagement pressure of the lock-up clutch is still low and thus it is impossible to satisfactorily engage the lock-up clutch, the actual slip rotation cannot be changed. As a result, actual slip rotation &ohgr;
SLPR
tends to decrease with a response delay from the time when shifting to the slip-control area. During such a time period, compensated target slip rotation &ohgr;
SLPTC
(corresponding to the transient response) is gradually decreasing, and therefore a deviation or a difference between actual slip rotation &ohgr;
SLPR
and compensated target slip rotation
SLPTC
tends to increase. That is, the follow-up performance of actual slip rotation &ohgr;
SLPR
toward compensated target slip rotation &ohgr;
SLPTC
is deteriorated. Control constants for the pre-compensator are preset or preprogrammed so that the transient response is optimized when target slip rotation &ohgr;
SLPT
is changing in the slip-control area. However, the value of actual slip rotation &ohgr;
SLPR
occurring at the beginning of shifting to the slip-control area tends to be considerably higher than the value of target slip rotation &ohgr;
SLPT
computed in the slip-control area. In other words, there is a great deviation between actual slip rotation &ohgr;
SLPR
occurring at the beginning of shifting to the slip-control area and target slip rotation &ohgr;
SLPT
computed in the slip-control area. Thus, it is difficult to provide an optimal transient performance by computing the transient response (compensated target slip rotation &ohgr;
SLPTC
) by means of the pre-compensator during shifting to the slip-control area (including initial stages of shifting to the slip-control area) from the transient response characteristic preprogrammed to be suitable to the time when target slip rotation &ohgr;
SLPT
is changing in the slip-control area. In a similar manner, in a feed-back control system arranged at the back of the pre-compensator, assuming that control constants or control gains for the feed-back control system are preset or preprogrammed to be suitable to the time when target slip rotation &ohgr;
SLPT
is changing in the slip-control area, there is a possibility that an optimal response of the feed-back control system cannot be obtained during shifting to the slip-control area. In case of the slip control for the torque converter, the system control responsiveness obtained during a period of time in which actual slip rotation &ohgr;
SLPR
is converging to target slip rotation &ohgr;
SLPT
, exerts a great influence upon the driver's feeling. In particular, if the slip rotation becomes excessively small and thus the torque converter lock-up clutch temporarily shifts to its fully engaged state, undesirable shocks occur. To enhance the transient performance during the transition from the non-slip-control area to the slip-control area, a pre-compensator suitable to the transient response during the transition from the non-slip-control area to the slip-control area can be further added, or control constants suitable for during the transition from the non-slip-control area to the slip-control area can be preprogrammed in addition to the control constants suitable for the time when target slip rotation &ohgr;
SLPT
is changing in the slip-control area. In such a case, the control logic of the control system is very troublesome.
Accordingly, it is an object of the invention to provide a pre-compensator equipped slip control system for a torque converter, which avoids the aforementioned disadvantages.
It is another object of the invention to provide a pre-compensator equipped slip control system for a torque converter which is capable of improving the follow-up performance of actual slip rotation &ohgr;
SLPR
toward compensated target slip rotation &ohgr;
SLPTC
filtered or compensated for by means of the pre-compensator without complicating the control logic.
In order to accomplish the aforementioned and other objects of the present invention, a slip control system for a torque converter employing a lock-up clutch, comprises a pre-compensator that determines a follow-up characteristic of an actual value of a controlled quantity to a desired value of slip rotation between input and output elements of the torque converter and makes a filtering process to a target slip rotation corresponding to the desired value of slip rotation to produce a compensated target slip rotation, a feedforward control section that determines a lock-up clutch engagement pressure by way of feedforward control during a period of time from a time when the torque converter is shifted from a torque-converter action area to a slip-control area to a time when an actual slip rotation corresponding to the actual value of the controlled quantity becomes less than a predetermined slip-rotation threshold value, a feedback control section that controls the lock-up clutch engagement pressure by way of feedback control from the time when the actual slip rotation becomes less than the predetermined slip-rotation threshold value after shifting to the slip-control area, so that the actual slip rotation is
Adachi Kazutaka
Segawa Satoshi
Foley & Lardner
Le David D.
Lorence Richard M.
Nissan Motor Co,. Ltd.
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