Abstract: A hydraulic system for a mobile work vehicle is configurable in a hybrid mode and a hydrostatic mode. The hydraulic system includes a pump/motor, a propel circuit, a pump, a hydraulic accumulator, and an accessory circuit. The pump/motor is adapted to exchange power with a drive train of the mobile work vehicle. The propel circuit is adapted to exchange hydraulic fluid power with the pump/motor. The pump is adapted to transfer power from a prime mover of the mobile work vehicle to the propel circuit. The hydraulic accumulator is adapted to exchange hydraulic fluid power via an accumulator isolation valve with the propel circuit when the hydraulic system is configured in the hybrid mode. The accessory circuit is adapted to receive hydraulic fluid power from the hydraulic accumulator, at least when the hydraulic system is configured in the hydrostatic mode and the accumulator isolation valve is closed.

Abstract: A method of propelling a vehicle with a hybrid mode and a hydrostatic mode includes determining if a current propulsion mode is hybrid and if a selected mode is hydrostatic. A first transition mode is entered if the selected mode is hydrostatic and the current mode is hybrid. An engine-pump displacement target is set in the first transition mode. The method may include determining if the current mode is hybrid, hydrostatic, or a no-propulsion mode and if the selected mode is hybrid, hydrostatic, or no-propulsion. The engine-pump displacement target may be matched to a system consumption and an accumulator isolation valve closed when an engine-pump output matches the system consumption in the first transition mode. The method may include entering a second transition mode if the selected mode is hybrid and the current mode is hydrostatic.

Abstract: A hydraulic system for a mobile work vehicle is configurable in a hybrid mode and a hydrostatic mode. The hydraulic system includes a pump/motor, a propel circuit, a pump, a hydraulic accumulator, and an accessory circuit. The pump/motor is adapted to exchange power with a drive train of the mobile work vehicle. The propel circuit is adapted to exchange hydraulic fluid power with the pump/motor. The pump is adapted to transfer power from a prime mover of the mobile work vehicle to the propel circuit. The hydraulic accumulator is adapted to exchange hydraulic fluid power via an accumulator isolation valve with the propel circuit when the hydraulic system is configured in the hybrid mode. The accessory circuit is adapted to receive hydraulic fluid power from the hydraulic accumulator, at least when the hydraulic system is configured in the hydrostatic mode and the accumulator isolation valve is closed.

Abstract: A method of propelling a vehicle with a hybrid mode and a hydrostatic mode includes determining if a current propulsion mode is hybrid and if a selected mode is hydrostatic. A first transition mode is entered if the selected mode is hydrostatic and the current mode is hybrid. An engine-pump displacement target is set in the first transition mode. The method may include determining if the current mode is hybrid, hydrostatic, or a no-propulsion mode and if the selected mode is hybrid, hydrostatic, or no-propulsion. The engine-pump displacement target may be matched to a system consumption and an accumulator isolation valve closed when an engine-pump output matches the system consumption in the first transition mode. The method may include entering a second transition mode if the selected mode is hybrid and the current mode is hydrostatic.

Abstract: A hydraulic pump radiant noise reduction method for a forklift or other work machine is disclosed. The method includes initiating a noise control algorithm that is enabled during periods when the displacement of the hydraulic pump remains in the zero displacement position and an operator is not demanding flow from any of the hydraulic branch circuits. When the noise control algorithm is enabled, the control valve assembly associated with the hydraulic branch circuit having the lowest hydraulic fluid pressure in relation to the hydraulic fluid pressures of all other hydraulic branch circuits is opened while the remaining control valve assemblies are in held or placed in a closed position. In an alternative embodiment, a drain valve assembly is provided that is opened when the noise control algorithm is activated.

Abstract: A hybrid hydraulic drivetrain is configured to propel a vehicle and regenerate propulsion energy. The drivetrain includes a prime mover, an accumulator, an axle, a first rotating group, a second rotating group, and a hydraulic transformer. The first rotating group is configured to receive shaft energy from the prime mover, receive shaft energy from the drive axle, send shaft energy to the drive axle, receive hydraulic energy from the hydraulic accumulator, and send hydraulic energy to the accumulator. The second rotating group is configured to receive shaft energy from the prime mover. The hydraulic transformer is configured to charge the accumulator with hydraulic energy received from the second rotating group. The hydraulic transformer may be remotely mounted from the second rotating group. The second rotating group may supply hydraulic energy to an auxiliary circuit of the vehicle. The auxiliary circuit may operate with the prime mover shut down.

Abstract: A hybrid hydraulic drivetrain is configured to propel a vehicle and regenerate propulsion energy. The drivetrain includes a prime mover, an accumulator, an axle, a first rotating group, a second rotating group, and a hydraulic transformer. The first rotating group is configured to receive shaft energy from the prime mover, receive shaft energy from the drive axle, send shaft energy to the drive axle, receive hydraulic energy from the hydraulic accumulator, and send hydraulic energy to the accumulator. The second rotating group is configured to receive shaft energy from the prime mover. The hydraulic transformer is configured to charge the accumulator with hydraulic energy received from the second rotating group. The hydraulic transformer may be remotely mounted from the second rotating group. The second rotating group may supply hydraulic energy to an auxiliary circuit of the vehicle. The auxiliary circuit may operate with the prime mover shut down.