Importance

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Abstract

A CVT combined with a gearshift mechanism to permit shifting of power flow under conditions of zero load and synchronous speed. The CVT can adjust the output speed within a gear ratio without resetting of the CVT ratio during a shift. The full speed range of the CVT is matched by two planetary drivetrains having normal and inverted characteristics and driven by two shifting gearboxes. Input power is divided into three paths to drive a central CVT and the two shifting gearboxes. The output of one of the gear-boxes is clutched to the normal input of a compound planetary drivetrain and the output of the other gearbox is clutched to the inverted input of the compound planetary. The CVT is coupled to the sun gear input of the compound planetary with the output of the compound planetary providing the output of the gear-assisted CVT. Operation occurs with either of the two clutches engaged to a respective input but not both, so that each gearbox may be shifted when its output is disengaged. Continuous operation from full forward through zero to full reverse is achieved. A control mechanism is provided to attain the necessary synchronization of clutches and gearshifts for proper operation. The gearbox reduces the capacity requirements and energy losses of the CVT for a given overall output. The result is a transmission that utilizes the benefits of the CVT over the full speed range in which losses are reduced and capacity increased by the number of gear steps.

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First Claim