Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2000-08-25
2002-02-12
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S144000, C477S148000, C477S175000
Reexamination Certificate
active
06346063
ABSTRACT:
This application is based on Japanese Patent Application No. 11-241789 filed Aug. 27, 1999, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a control apparatus for an automatic transmission of an automotive vehicle, and more particularly to a downshift of the automatic transmission which is initiated when the input speed of the transmission is lower than the synchronizing speed of an operating position to which the transmission is shifted down.
2. Discussion of the Related Art
There is widely known a power transmitting system for an automotive vehicle, which includes (a) an automatic transmission which is shifted to a selected one of a plurality of operating positions by engaging and releasing actions of a plurality of frictional coupling devices by respective hydraulic cylinders, and (b) a hydraulic control device for supplying a pressurized fluid to one of the hydraulic cylinders to effect an engaging action of a corresponding one of the frictional coupling device, the hydraulic control device including a pressure regulating device for controlling the pressure of the pressurized fluid applied to the above-indicated one hydraulic cylinder. JP-A-5-312261 discloses an example of such a power transmitting system, which is adapted to shift down the automatic transmission from a high-gear position to a low-gear position by releasing a frictional coupling device which has been engaged to establish the high-gear position, while at the same time engaging a frictional coupling device for establishing the low-gear position, that is, adapted to effect a so-called “clutch-to-clutch shifting action” wherein the hydraulic pressure of the frictional coupling device which has been engaged to establish the high-gear position is feedback-controlled such that the input speed of the automatic transmission changes at a predetermined rate while the hydraulic pressure of the frictional coupling device for establishing the low-gear position is held at a standby level, and such that the frictional coupling device for the high-gear position is fully released while the frictional coupling device for the low-gear position is fully engaged, after the input speed has substantially reached the synchronizing speed of the low-gear position.
In the conventional clutch-to-clutch shifting action described above, the hydraulic pressures of the two frictional coupling devices must be concurrently controlled, requiring a difficult control of the hydraulic control device. Where a downshift command to shift down the automatic transmission to the low-gear position is generated a comparatively short time after the generation of an upshift command to shift up the automatic transmission to the high-gear position, the clutch-to-clutch downshift cannot be achieved in an adequate manner unless the piston of the hydraulic cylinder (piston of an accumulator communicating with the hydraulic cylinder, if the accumulator is provided) has already reached the stroke end on the engaging side. In this case, therefore, the downshift to the low-gear position must be initiated only after the high-gear position has been once established. This arrangement requires a relatively long time to complete the downshift of the automatic transmission.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a control apparatus for an automatic transmission of an automotive vehicle, which is adapted to initiate a downshift of the automatic transmission from a high-gear position to a low-gear position while the input speed of the automatic transmission is lower than the synchronizing speed of the low-gear position, and which permits the downshift to be smoothly effected, by controlling an engaging action of only a frictional coupling device for establishing the low-gear position.
The above object may be achieved according to the principle of the present invention, which provides an apparatus for controlling an automatic transmission of an automotive vehicle, which is shifted to a selected one of a plurality of operating positions by an engaging action of a frictional coupling device, the apparatus comprising an overshoot engagement control device which is operated to shift the automatic transmission to the selected one operating position such that a shifting action of the automatic transmission is initiated while an input speed of the automatic transmission is lower than a synchronizing speed of the selected one operating position. The overshoot engagement control device controls an engaging force of the frictional coupling device such that the input speed is first raised above the synchronizing speed and is then lowered down toward the synchronizing speed.
In the vehicle transmission control apparatus of the present invention constructed as described above, the shifting action of the automatic transmission to a selected one of the operating positions is initiated while the input speed of the automatic transmission is lower than the synchronizing speed of the selected operating position. To shift the automatic transmission to the selected operating position, the engaging force of the frictional coupling device is controlled such that the input speed is first raised above the synchronizing speed and is then lowered down at a low rate toward the synchronizing speed. In this control arrangement, the engaging force of the frictional coupling device while the input shaft speed is higher than the synchronizing speed can be controlled in a manner similar to that used for controlling the frictional coupling device to shift up the automatic transmission to the selected operating position.
Thus, the automatic transmission can be shifted down to the selected operating position by controlling the engaging action of the single frictional coupling device, so that when the automatic transmission is commanded to be shifted down to the selected operating position a comparatively short time after the automatic transmission was commanded to be shifted up to the operating position one step higher than the selected operating position, the automatic transmission can be immediately shifted down to the selected operating position, without once establishing the higher operating position.
The automatic transmission to which the control apparatus of the present invention is applicable may include a plurality of planetary gear sets, and a plurality of hydraulically operated frictional coupling devices such as clutches and brakes for connecting rotary elements of the planetary gear sets to each other or fixing those rotary elements to the housing of the automatic transmission. In this case, the selected one of the operating positions of the automatic transmission which have respective different speed ratios is established by engaging and releasing actions of the appropriate frictional coupling devices. The automatic transmission may be automatically shifted down or up in response to a shifting command which is generated on the basis of the vehicle running speed and the operating amount of the accelerator pedal. Alternatively, the automatic transmission is commanded to be shifted in response to an operation of a shift lever or switch by the vehicle operator.
The automotive vehicle equipped with the present transmission control apparatus may use a drive power source selected from among various drive power sources such as an engine operated by combustion of a fuel, and an electric motor operated with an electric energy. The output of the drive power source may be electrically controlled depending upon the operating amount of the accelerator pedal or other accelerating member provided for accelerating the vehicle, or the drive power source may be mechanically connected to the accelerating member so that the output of the drive power source is directly controlled by the accelerating member.
The shifting action of the automatic transmission initiated while the input speed is lower than the synchronizing speed of the selected operating positi
Kondo Masami
Nakamura Yasunari
Estremsky Sherry
Lewis Tisha D.
Toyota Jidosha & Kabushiki Kaisha
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