Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Preselected indexed position
Patent
1988-02-22
1989-08-22
Diehl, Dwight G.
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Preselected indexed position
192 331, 74733, B60K 4106
Patent
active
048584991
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to an automatic transmission with a lock-up clutch in which the lock-up clutch is released during a shifting operation in order to improve the feeling of the shifting operation.
2. Background Art
In a system having a lock-up clutch arranged within a torque converter connected between an engine and an automatic transmission for transmitting the power of the engine directly to the transmission under predetermined conditions, the lock-up clutch generally is engaged or disengaged based on a shift pattern set for each range of gear positions. More specifically, in order to improve fuel economy, control is exercised in such a manner that the lock-up clutch is released to transmit engine power to the transmission via the torque converter if throttle opening and vehicle velocity are in a torque conversion region of a shift pattern, and in such a manner that the lock-up clutch is engaged to transmit motor power directly to the transmission if throttle opening and vehicle velocity are in a lock-up region of the shift pattern.
However, in a shift pattern set for each range of gear position, lock-up regions adjoin about shift points at the boundaries. Therefore, when the accelerator pedal is depressed by a great amount so that the automatic transmission is operating under a large throttle opening, gears are shifted while the locked up state remains in effect. As a result, a large speed-change shock is produced.
Conventionally, the system shown in FIG. 8 is employed in order to eliminate speed-change shock. Specifically, in an electronic control unit of the automatic transmission, a shift is determined at time t.sub.1 and, after an elapsed time of T.sub.1, a shift signal is delivered to a shift solenoid at a time t.sub.2. However, owing to a response delay in the hydraulic system, the actual shift starts upon passage of a time T.sub.2. Accordingly, the time period T.sub.2 is preset, the lock-up clutch is released at a time t.sub.3 to prevent the occurrence of speed-change shock, and the lock-up clutch is re-engaged at a time t.sub.4, at which the shift ends, upon elapse of a time period T.sub.3. The time periods T.sub.1, T.sub.2, T.sub.3 involving the shift signal and the signals for engaging and disengaged the lock-up clutch are stored in advance by a timer within a computer, and control of the gear shift and lock-up clutch timing is performing based on the timer.
As indicated in Japanese Patent Application Laid-Open No. 61-27365, a system has been disclosed in which engine rotational speed following issuance of a shift command is monitored and the start of a shift is determined when the rate of change in rotational speed surpasses a set value. In other words, the amount of engine racing at the time of a gear shift is fed back and the lock-up clutch is released when the integrated value of the feedback exceeds a set value. In other words, as shown in FIG. 9, at the moment t.sub.2 a rate of change-dN.sub.E /dt in engine rotational speed surpasses a set value .sub..DELTA. N following an instant t.sub.1 at which a shift command is issued, lock-up is suspended by an output duty of 0% and the suspension continues for a set time period T1. If the lock-up region still prevails after this time, the output duty D is abruptly made D.sub.A % and is then gradually raised to 100% at a slope .alpha./T2, so that the torque converter can be returned to the lock-up state. By deciding the set value .sub..DELTA. N of the rate of change in engine rotational speed on the basis of the rate of change in engine rotational speed after issuance of the shift command, namely by setting .sub..DELTA. N to a value obtained by multiplying the maximum value thereof by a safety factor .beta., speed-change shock due to suspension of lock-up is prevented.
Further, as illustrated in Japanese Patent Application Laid-Open No. 61-27364, a system is disclosed in which the lock-up clutch is released upon discriminating the degree to which a shift has progressed after issuance of a shift command using the
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Ito Yasunobu
Suzuki Kenji
Aisin-Warner Kabushiki Kaisha
Diehl Dwight G.
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