Vehicle drive-train including a clutchless transmission, and method of operation

A method, comprising:

• drawing power from a power storage device to apply torque to an output shaft of a hydraulic drive-motor of a vehicle;
• removing torque from the output shaft of the hydraulic drive-motor;
• shifting a transmission of the vehicle from a first forward gear ratio to a second forward gear ratio;
• and
• during the shifting step, bringing first and second friction surfaces in the transmission into contact, thereby synchronizing rotation of the output shaft of the drive-motor with an output shaft of the transmission, according to the second forward gear ratio.

A vehicle, comprising:

• a hydraulic drive-motor including an output shaft;
• a power output device:
• means for storing power from the power output device;
• and
• a transmission having an output shaft, and an input shaft uninterruptedly coupled to the output shaft of the drive-motor, the transmission having a plurality of gear elements that provide the transmission with a plurality of forward gear ratios, and a synchronizer that selectively and mechanically engages a selected one of the plurality of gear elements for operation of the vehicle at a corresponding one of the plurality of forward gear ratios.

A vehicle drive-train, comprising:

• a hydraulic drive-motor capable of having all motive force removed from an output shaft thereof during normal operation of the drive-train;
• a high-pressure accumulator configured to store power in the form of pressurized hydraulic fluid;
• a transmission having a plurality of forward gear ratios;
• and
• synchronizing means for frictionally synchronizing the output shaft of the drive-motor with an output shaft of the transmission while shifting from a first one of the plurality of forward gear ratios to a second one of the plurality of forward gear ratios.

A drive-train, comprising:

• a hydraulic motor having an output shaft and having an output inertia approximately equal to, or less than, an output inertia generated by a clutch plate of a clutch having a sufficient size to function in a vehicle employing an internal combustion engine with a maximum torque capacity substantially equal to that of the motor;
• a power storage device configured to store power generated by a power output device and provide power to the motor;
• and
• a transmission having an input shaft uninterruptedly coupled to the output shaft of the motor, the transmission further including an output shaft, a plurality of selectable forward gear ratios, and a synchronizer for each of the plurality of gear ratios.