Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2000-02-22
2001-07-24
Marmor, Charles A (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S065000
Reexamination Certificate
active
06264581
ABSTRACT:
This application is related to Japanese Patent Application No. Hei 8-270906, incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a controller of an automatic transmission having a lockup clutch whose closing force is controllable and a control method of such an automatic transmission.
2. Description of Related Art
For a conventional automatic transmission provided with a torque converter which connects an output shaft of an engine and an input shaft of a speed change mechanism through fluid, an automatic transmission provided with the torque converter and a lockup clutch in parallel to transmit force in the driving system efficiently has been disclosed. The lockup clutch is a friction clutch capable of transmitting mechanical force between the output and the input shafts.
Recently, by controlling engagement force (closing force) of the lockup clutch, a control of the lockup clutch controlling a transmitting state of the force at the torque converter, that is, a slip control of the lockup clutch (hereinafter referred to slip control) is carried out.
The slip control is carried out for reducing the slip quantity of the torque converter, reducing the transmission loss of the driving force and reducing fuel consumption.
On the other hand, when the slip quantity of the torque converter is too small, torque vibration generated by an engine is transmitted to the output shaft or torque amplification of the torque converter is not operated, so that the driver feels uncomfortable.
Therefore, in the slip control, the slip quantity between the input shaft and the output shaft of the torque converter is controlled by controlling the closing force of the lockup clutch so that the fuel consumption is reduced and deterioration of the driver can be prevented from feeling uncomfortable.
Further, in the slip control, depending on the driving state, there are two different cases where reduction of the fuel consumption takes precedence over the driver's feelings or where the driver's feelings take precedence over the reduction of the fuel consumption. Therefore, the slip quantity of the torque converter needs to be determined properly at each driving state.
For example, the torque amplification operation of the torque converter is not required in a traveling state with a constant throttle opening, so that reduction of the fuel consumption takes precedence over the driver's feelings and a very small slip quantity is appropriate. On the other hand, when the driver depresses the accelerator, a larger slip quantity is preferable to improve the torque amplification operation of the torque converter.
In Japanese Examined Patent Publication No. Sho 63-13060, for example, target slip quantity is determined in a range to be less than the slip quantity when the driving force is transmitted only by the torque converter and to reduce or stop the transmission of torsional vibration. Further, the closing force of the lockup clutch is controlled to make the difference between the real slip quantity and the target slip quantity smaller.
When the real slip quantity comes close to the target slip quantity, only the engine rotational speed changes and turbine rotational speed which is the output shaft rotational speed of the torque converter does not change. This is because when the vehicle is driven by the engine output, that is, when the engine output is connected to the output shaft of the vehicle, inertia of the input side of the torque converter is smaller than inertia of the output side thereof. Therefore, only the rotational speed in the input side which has the smaller inertia is changed.
Therefore, the target slip quantity is determined and the real slip quantity comes close thereto, that is, the engine rotational speed is determined to be larger than the turbine rotational speed by the target slip quantity with the turbine rotational speed as a reference.
When the speed change is in a transitional period, the change in the turbine rotational speed is not always guaranteed to be constant due to the change in engine torque and the state of the speed change clutch. For example, when the speed change is completed much faster than when it was designed and the adjusting control of the target slip quantity is carried out, the sudden change in the engine rotational speed is required, so that the torque shocks are generated.
In a transmission for separately hydraulic-controlling clutches in the closing side and the opening side, when timings of closing and opening of the clutch do not match, the turbine rotational speed is suddenly increased or decreased, and the transmission moves differently compared with its normal movement at the speed change. In this case, when the adjusting control to the target slip quantity is carried out, an abnormal change in the turbine rotational speed superimposes onto the engine rotational speed, which results in changes in engine sound, vibrations in the tachometer, torque shocks and the like. Thus, the driver feels uncomfortable.
Especially, when the abnormal change in the engine rotational speed occurs before a gear ratio change, the tachometer suddenly moves up or down during the constant traveling of the vehicle, so that the driver feels uncomfortable due to abnormal changes of the throttle operation and the tachometer. On the other hand, when the abnormal change in the engine rotational speed occurs while the gear ratios are changing, that is, during an inertia phase, the tachometer goes up and down although the values are usually reduced together with the gear ratio change, so that the driver feels uncomfortable.
SUMMARY OF THE INVENTION
In view of the above problems of the prior art, it is a primary object of the present invention to provide a controller of an automatic transmission having a lockup clutch and a control method of the automatic transmission. When slip control of the lockup clutch is carried out, the controller prevents changes in engine rotational speed although turbine rotational speed changes with the speed change and slip control is carried out without making a driver feel uncomfortable.
The above object is achieved according to a first aspect of the present invention by regulating engaging force using an engaging force regulating device so that slip quantity is controlled to target slip quantity, that is, in a control device for carrying out a slip control of a lockup clutch, a target engine rotational speed control for controlling the engine rotational speed to the target engine rotational speed is carried out instead of the slip control during speed change of the automatic transmission.
In other words, in the present invention, real slip quantity of a torque converter is not controlled to the target slip quantity, but the real engine rotational speed is controlled to come close to the target engine rotational speed. Therefore, unnecessary change in the output shaft rotational speed (turbine rotational speed) of the torque converter does not superimpose onto the engine rotational speed. Therefore, because the engine rotational speed does not change abnormally, change in the engine sound due to abnormal change in the engine rotational speed, vibrations in the tachometer, torque shock and the like are not generated.
The speed change period is a speed change transitional period (inertia phase period) in which speed change ratios change; however, the target engine rotational speed control can be carried out during a period before and after the inertia phase.
For example, the target engine rotational control can be carried out not only during the inertia phase but also during a period (that is, a replenish period) from the generation of the speed change switch command to the start of the inertia phase. If the target engine rotational speed control is carried out during the replenish period, transfer from the target slip quantity control started before the target engine rotational speed control is smooth without shocks and the like. In the transmission in which clutches in the cl
Fujitsuna Masami
Kozaki Tetsuji
Tashiro Tsutomu
Denso Corporation
Marmor Charles A
Pang Roger
Pillsbury & Winthrop LLP
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