Importance

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Abstract

A viscous shear coupling for distributing torque between front and rear axles of an all-wheel drive vehicle is provided which comprises a housing, a set of inner blades interdigitating with a set of outer blades, the inner and outer blades being axially spaced apart from each other and axially slidably mounted within the housing, a viscous liquid located within the housing, an adjusting piston within the housing which is axially displaceable so as to adjust the axial distance between adjacent inner and outer blades. The viscous shear coupling further includes a control pressure circuit for delivery of a control pressure fluid to the adjusting piston, a control valve for regulating the delivery of the control pressure fluid to the adjusting piston, and a control device (e.g., a microprocessor) which calculates a desired adjusting piston speed based on driving conditions and adjusts a valve current delivered to the control valve in order to obtain the desired adjusting piston speed. A process for controlling the viscous shear coupling includes acquiring a set of signals indicative of driving conditions and converting them to a set of input parameters, converting the input parameters to a set of basic parameters, ascertaining a set of control deviations from the basic parameters and the input parameters, calculating the desired adjusting piston speed from the control deviations, and adjusting the valve current delivered to the control valve in order to obtain the desired adjusting piston speed.

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First Claim