Anti torque shock control device and method engaging torque transmitting clutch between vehicle wheels when transmission is shifted from non drive range to drive range

#The present invention relates to an anti torque shock control method and device for a power transmission system for a vehicle, and more particularly relates to such an anti torque shock control method and device, particularly applicable to a vehicle power transmission system in which a clutch is provided for selectively engaging two of the vehicle wheels together at least partially.

#The present invention has been described in Japanese Patent Applications Ser. Nos. Showa 60-194634 (1985) and Showa 61-176468 (1986), both of which were filed by an applicant the same as the entity assigned or owed duty of assignment of the present patent application; and the present patent application hereby incorporates into itself by reference the text of said Japanese Patent Applications and the claims and the drawings thereof; copies are appended to the present application.

#Nowadays a greatly increasing number of automotive vehicles are being constructed with four wheel drive transmission systems, because such four wheel drive operation, in which all four wheels of the vehicle are powered from its engine via its transmission, is very suitable for driving on poor or slippery road surfaces such as in mud or over bad ground, or upon roads covered with mud, snow, ice, or rain. One type of such transmission system is the so called part time four wheel drive system, in which a 2WD/4WD control clutch is included which can switch the transmission operational mode between a two wheel drive operational mode and a four wheel drive operational mode, i.e. typically which can selectively power the front wheels of the vehicle from the engine while the rear wheels of the vehicle are always being powered from said engine.

#The present invention will now be described with respect to the preferred embodiments of the device and of the method thereof, and with reference to the illustrative drawings appended hereto, which however are provided for the purposes of explanation and exemplification only, and are not intended to be limitative of the scope of the present invention in any way, since this scope is to be delimited solely by the accompanying claims. With relation to the figures, spatial terms are to be understood as referring only to the orientation on the drawing paper of the illustrations of the relevant parts, unless otherwise specified; like reference numerals, unless otherwise so specified, denote the same parts and gaps and spaces and flow chart steps and so on in the various figures relating to one preferred embodiment, and like parts and gaps and spaces and flow chart steps and so on in figures relating to different preferred embodiments; and:

#FIG. 1 is a schematic longitudinal skeleton view of a vehicle power train and of a control system therefor which incorporates the first preferred embodiment of the anti torque shock control device of the present invention, for practicing the first preferred method embodiment;

#FIG. 2 is a schematic partial sectional view of a control system for a clutch of a four wheel drive power transfer device included in the FIG. 1 power train;

#The present invention will now be described with reference to the preferred embodiments of the method and of the device thereof, and with reference to the figures.

#FIG. 1 is a schematic longitudinal skeleton view of a vehicle power train which incorporates the preferred embodiment of the anti torque shock control device of the present invention, said device performing a corresponding method embodiment. In this figure, the reference numeral 1 denotes an internal combustion engine of said vehicle, which is mounted, in this first exemplary case, longitudinally in the front engine room (not particularly shown) of said vehicle. And the reference numeral 2 denotes an automatic speed change device (automatic transmission) of a per se known type, while 3 denotes a four wheel drive power transfer device of a so called part time four wheel drive type, which is selectably operable either in four wheel drive mode or in two wheel drive mode, so as selectably either to drive both the rear pair of wheels of the vehicle and also the front pair of wheels of the vehicle or alternatively to drive only said rear pair of wheels of said vehicle but not said front pair of wheels of said vehicle, as will be explained in detail hereinafter, said four wheel drive power transfer device 3 not having any capability of providing any particular front/rear differential action.

#In more detail, the automatic speed change device 2 incorporates a fluid torque converter 5 of a per se known construction, and the power input shaft of this fluid torque converter 5 is connected to and receives rotational power from a crank shaft of the internal combustion engine 1. And the fluid torque converter 5 is housed within a torque converter housing 4 fitted against and secured to the main body of the internal combustion engine 1, while the automatic speed change device 2 comprises a gear transmission mechanism 7, which is likewise housed within a speed change device housing fitted against and secured to the torque converter housing 4. And the input shaft of the gear transmission mechanism 7 is connected to and receives rotational power from the power output shaft of the fluid torque converter 5; and thereby the gear transmission mechanism 7 receives rotational power from the internal combustion engine 1, with a certain degree of slippage and also torque amplification being provided for said rotational power by the fluid torque converter 5 (unless a lock up clutch thereof, if provided thereto, is activated) as is per se conventional. This gear transmission mechanism 7 may for the purposes of this specification be of a per se known type incorporating various planetary gear mechanisms and friction engaging mechanisms such as clutches and brakes, and, according to selective actuation of said friction engaging mechanisms provided by an electrically controlled electric/hydraulic control mechanism 9 of a per se known sort including various speed change solenoids and so on, provides any one of a plurality of speed reduction stages between its said power input shaft and its power output shaft, its said power output shaft driving the four wheel drive power transfer device 3. Particularly according to the appropriate setting for the present invention, the combination of this automatic speed change device 2 and this electric/hydraulic control mechanism 9 is so constituted as to be capable of operating in various transmission operational ranges, including one or more drive ranges such as "D" range, "S" range, "L" range, and "R" range, and one or more non drive ranges such as "P" range and "N" range, according to the behest of the driver of the vehicle, who typically sets such an automatic transmission operational range upon a manual range setting device, not particularly shown in the figures, such as a shift lever or transmission push buttons or the like.