Interrelated power delivery controls – including engine control – Transmission control – Engine controlled by transmission
Reexamination Certificate
2002-07-26
2004-06-15
Pang, Roger (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Engine controlled by transmission
Reexamination Certificate
active
06749534
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an apparatus for controlling a drive system for an automotive vehicle, which drive system includes a drive power source and an automatic transmission. More particularly, the invention relates to improvements in techniques for increasing an output of the drive power source so as to prevent a shifting shock of the automatic transmission, upon a shift-down action of the automatic transmission while the vehicle is in a coasting run without a drive force being transmitted from the drive power source to vehicle drive wheels.
2. Discussion of Related Art
There is widely known an automotive vehicle provided with a drive system including a drive power source such as an internal combustion engine, a fluid-operated power transmitting device connected to the drive power source, and an automatic transmission arranged to transmit a rotary motion of the fluid-operated power transmitting device to drive wheels such that a ratio of the input speed of the automatic transmission to its output speed is variable. An example of such a vehicle is disclosed in JP-A-7-139382 wherein a torque converter provided as the fluid-operated power transmitting device is connected to an automatic transmission such as a planetary gear type transmission. The automatic transmission has a plurality of operating positions which have respective different speed ratios and which are selectively established by respective combinations of engaging and releasing actions of a plurality of frictional coupling devices. In such a vehicle, the automatic transmission is shifted down to increase its speed ratio during a coasting run of the vehicle without a drive force being transmitted from the drive power source to the vehicle drive wheels, with an accelerator pedal being held in its non-operated position, for example. An increase in the speed ratio causes an increase in the operating speeds of the fluid-operated power transmitting device and the drive power source. If this increase in the operating speeds takes place in a so-called “reverse power transfer state” while the speed of the drive power source is lower than the output speed of the fluid-operated power transmitting device (which is the input speed of the automatic transmission), there arise a relatively large amount of variation in the drive force due to an inertia of the drive power source, and application of a relatively large load to the frictional coupling devices and other elements of the automatic transmission. In view of these drawbacks, it is considered to positively increase the output and operating speed of the drive power source upon a shift-down action of the automatic transmission. It is also considered to hold the operating speed of the drive power source during the coasting run of the vehicle higher than the output speed of the fluid-operated power transmitting device (the input speed of the automatic transmission), so that the vehicle is driven with a high response to a subsequent operation of the accelerator pedal which takes place at the end of the coasting run. If the speed of the drive power source is increased in the reverse power transfer state while the speed of the drive power source is lower than the output speed of the by fluid-operated power transmitting device, the direction in which a torque is transmitted through the fluid-operated power transmitting device is reversed, so that the fluid-operated power transmitting device is likely to suffer from a shock. To avoid this drawback, it is desirable to positively increase the operating speed of the drive power source upon a shift-down action of the automatic transmission during the coasting run of the vehicle.
If the output of the drive power source is increased to positively increase its operating speed in the reverse power transfer state while the speed of the drive power source is lower than the output speed of the fluid-operated power transmitting device, the speed of the drive power source is abruptly raised due to a comparatively small load acting on the drive power source, so that the direction in which the torque is transmitted through the fluid-operated power transmitting device is suddenly reversed, giving rise to a risk of generation of noise and shock. The vehicle drive system may be placed in the reverse power transfer state, when a fuel-cut control to cut a fuel supply to the drive power source is effected under a predetermined condition, to improve the fuel economy of the vehicle or to apply a drive-power-source brake such as an engine brake to the vehicle, and when any device (e.g., an air conditioning system) operable by the drive power source is activated.
SUMMARY OF THE INVENTION
The present invention was made in the light of the background art discussed above. It is therefore an object of the present invention to provide an apparatus for controlling a vehicle drive system including a drive power source, a fluid-operated power transmitting device and an automatic transmission, which apparatus is capable of reducing operating noise and shock that may be generated due to a change in the direction of transmission of a torque through the fluid-operated power transmitting device, when the output of the drive power source is increased to increase its operating speed upon a shift-down action of the automatic transmission during a coasting run of the vehicle in which the speed of the drive power source is lower than the output speed of the fluid-operated power transmitting device,
The object indicated above may be achieved according to the principle of the present invention, which provides an apparatus for controlling a drive system of an automotive vehicle including a drive power source, a fluid-operated power transmitting device connected to the drive power source, and an automatic transmission arranged to transmit a rotary motion of the fluid-operated power transmitting device to drive wheels of the vehicle such that a speed ratio which is a ratio of an input speed of the automatic transmission to an output speed thereof is variable, the apparatus being arranged to increase an output of the drive power source for increasing an operating speed of the drive power source upon a shift-down action of the automatic transmission so as to increase the speed ratio during a coasting run of the vehicle in which the output of the drive power source is not transmitted to the drive wheels, the apparatus comprising: an output controlling element operable to control the output of the drive power source; and gradually output increasing means operable upon the shift-down action of the automatic transmission during the coasting run of the vehicle, for controlling the output controlling element so as to gradually increase the operating speed of the drive power source at a predetermined rate.
In this vehicle drive system control apparatus, the output controlling element is controlled by the gradually output increasing means, to gradually increase the operating speed of the drive power source at the predetermined rate, so that a shock to be generated upon the shift-down action of the automatic transmission can be effectively reduced. Where the gradually output increasing means is operated in a reverse power transfer state of the vehicle drive system in which the speed of the drive power source is lower than the output speed of the fluid-operated power transmitting device, the gradual increase of the speed of the drive power source permits a gradual or slow reversal of the direction in which a torque is transmitted through the fluid-operated power transmitting device, so that the amounts of noise and shock due to the reversal of the torque transmitting direction are effectively reduced.
As the drive power source, an internal combustion engine such as a gasoline engine and a diesel engine may be suitably used. However, a drive power source of any other type may be used. As the fluid-operated power transmitting device, a torque converter and a fluid coupling may be suitably used. The automatic transmission m
Ayabe Atsushi
Kimura Hiromichi
Nakamura Mitsuhiro
Ogasawara Hideaki
Sakamoto Naoyuki
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pang Roger
Toyota Jidosha & Kabushiki Kaisha
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