Hydraulic hybrid swing drive system for excavators

1. A swing drive system of a vehicle comprising:

a prime mover mechanically connected to a first hydraulic pump/motor;

a second hydraulic pump/motor mechanically connected to a swing mechanism;

a hydraulic circuit connecting a hydraulic fluid reservoir, a hydraulic accumulator, the first hydraulic pump/motor, and the second hydraulic pump/motor;

wherein the system is operable in a first mode where the second hydraulic pump/motor acts as a pump to retard movement of the swing mechanism and pressurized hydraulic fluid from the second hydraulic pump/motor is pumped into the hydraulic accumulator; and

wherein the system is operable in a second mode wherein the second hydraulic pump/motor acts as a motor to provide supplementary power to the swing mechanism using pressurized fluid from the hydraulic accumulator;

wherein the prime mover is also mechanically connected to a hydraulic pump which is hydraulically connected to a plurality of hydraulic power consumers; and

the swing drive system further comprising a hydraulic accumulator fluidly connected between the hydraulic pump and the plurality of hydraulic power consumers.

2. A swing drive system of a vehicle comprising:

a prime mover mechanically connected to a first hydraulic pump/motor;

a second hydraulic pump/motor mechanically connected to a swing mechanism;

a hydraulic circuit connecting a hydraulic fluid reservoir, a hydraulic accumulator, the first hydraulic pump/motor, and the second hydraulic pump/motor;

wherein the system is operable in a first mode where the second hydraulic pump/motor acts as a pump to retard movement of the swing mechanism and pressurized hydraulic fluid from the second hydraulic pump/motor is pumped into the hydraulic accumulator; and

wherein the system is operable in a second mode wherein the second hydraulic pump/motor acts as a motor to provide supplementary power to the swing mechanism using pressurized fluid from the hydraulic accumulator; and

the swing drive system further comprising

a transmission gear set,

the transmission gear set mechanically connected between the engine and the first hydraulic pump/motor; and

the transmission gear set mechanically connected between the swing mechanism and the second hydraulic pump/motor.

3. The swing drive system according to claim 2 wherein the transmission gear set includes a reverse gear.

4. A swing drive system of a vehicle comprising:

an excavator swing mechanism;

a prime mover mechanically connected to a first hydraulic pump/motor;

a second hydraulic pump/motor mechanically connected to the excavator swing mechanism;

a hydraulic circuit connecting the first hydraulic pump/motor, the second hydraulic pump/motor, a hydraulic accumulator, and a hydraulic reservoir;

an isolation valve associated with the hydraulic accumulator which selectively disconnects the hydraulic accumulator from the rest of the hydraulic circuit;

wherein the system is operable in a first mode where the second hydraulic pump/motor acts as a pump to retard movement of the excavator swing mechanism, the pressurized hydraulic fluid from the second hydraulic pump/motor is pumped into the hydraulic accumulator when the isolation valve is open; and

wherein the system is operable in a second mode wherein the second hydraulic pump/motor provides a supplementary power to the excavator swing mechanism using pressurized fluid from the hydraulic accumulator when the isolation valve is open; and

wherein the system is operable is a third mode where the second hydraulic pump/motor acts as a pump to retard movement of the excavator swing mechanism, the pressurized hydraulic fluid from the second hydraulic pump/motor rotates the first hydraulic pump/motor as a motor which provides supplemental power to the prime mover when the isolation valve is closed; and

further comprising

a transmission gear set,

the transmission gear set mechanically connected between the engine and the first hydraulic pump/motor;

the transmission gear set mechanically connected between the excavator swing mechanism and the second hydraulic pump/motor.

5. The swing drive system of claim 4 further comprising a directional valve positioned within the hydraulic circuit selectively reversing the flow of fluid through the hydraulic circuit and providing a fluid path to the hydraulic accumulator.

6. A swing drive system of a vehicle comprising:

an excavator swing mechanism;

a prime mover mechanically connected to a first hydraulic pump/motor;

a second hydraulic pump/motor mechanically connected to the excavator swing mechanism;

a hydraulic circuit connecting the first hydraulic pump/motor, the second hydraulic pump/motor, a hydraulic accumulator, and a hydraulic reservoir;

an isolation valve associated with the hydraulic accumulator which selectively disconnects the hydraulic accumulator from the rest of the hydraulic circuit;

wherein the system is operable in a first mode where the second hydraulic pump/motor acts as a pump to retard movement of the excavator swing mechanism, the pressurized hydraulic fluid from the second hydraulic pump/motor is pumped into the hydraulic accumulator when the isolation valve is open; and

wherein the system is operable in a second mode wherein the second hydraulic pump/motor provides a supplementary power to the excavator swing mechanism using pressurized fluid from the hydraulic accumulator when the isolation valve is open; and

wherein the system is operable is a third mode where the second hydraulic pump/motor acts as a pump to retard movement of the excavator swing mechanism, the pressurized hydraulic fluid from the second hydraulic pump/motor rotates the first hydraulic pump/motor as a motor which provides supplemental power to the prime mover when the isolation valve is closed; and

further comprising

a transmission gear set,

the transmission gear set mechanically connected between the engine and the first hydraulic pump/motor;

the transmission gear set mechanically connected between the excavator swing mechanism and the second hydraulic pump/motor; and

wherein the transmission gear set includes a reverse gear.

7. A swing drive system of a vehicle comprising:

a prime mover mechanically connected to a first hydraulic pump/motor through a mechanical gearset;

a second hydraulic pump/motor mechanically connected to a swing mechanism through the mechanical gear set;

wherein the mechanical gear set includes a reverse gear;

a hydraulic circuit connecting the first hydraulic pump/motor, the second hydraulic pump/motor, a hydraulic accumulator, and a hydraulic reservoir;

an isolation valve associated with the hydraulic accumulator which selectively disconnects the hydraulic accumulator from the rest of the hydraulic circuit;

wherein the system is operable in a first mode where the second hydraulic pump/motor acts as a pump to retard movement of the swing mechanism, the pressurized hydraulic fluid from the second hydraulic pump/motor is pumped into the hydraulic accumulator when the isolation valve is open; and

wherein the system is operable in a second mode wherein the second hydraulic pump/motor provides a supplementary power to the swing mechanism using pressurized fluid from the hydraulic accumulator when the isolation valve is open; and

wherein the system is operable is a third mode where the second hydraulic pump/motor acts as a pump to retard movement of the swing mechanism, the pressurized hydraulic fluid from the second hydraulic pump/motor rotates the first hydraulic pump/motor as a motor which provides supplemental power to the prime mover when the isolation valve is closed.

8. The swing drive system of claim 7 wherein the mechanical gear set is operable to selectively connect the prime mover to the first hydraulic pump/motor or to connect the prime mover directly to the swing mechanism.

9. The swing drive system according to claim 8 further comprising:

a hydraulic pump driven by the prime mover, the hydraulic pump being fluidly connected to a plurality of hydraulic power consumers; and

a hydraulic accumulator fluidly connected between the hydraulic pump and the plurality of hydraulic power consumers.

10. A swing drive system of a vehicle comprising:

a swing mechanism for the vehicle;

a prime mover mechanically connected to a first hydraulic pump/motor;

a second hydraulic pump/motor mechanically connected to the swing mechanism;

a hydraulic circuit connecting a hydraulic fluid reservoir, a hydraulic accumulator, the first hydraulic pump/motor, and the second hydraulic pump/motor;

wherein the system is operable in a first mode where the second hydraulic pump/motor acts as a pump to retard movement of the swing mechanism and pressurized hydraulic fluid from the second hydraulic pump/motor is pumped into the hydraulic accumulator;

wherein the system is operable in a second mode wherein the second hydraulic pump/motor acts as a motor to provide supplementary power to the swing mechanism using pressurized fluid from the hydraulic accumulator; and

further comprising a directional valve positioned within the hydraulic circuit for selectively reversing the flow of fluid through the hydraulic circuit and providing a fluid path to the hydraulic accumulator that does not pass through the reservoir, the directional valve connecting the accumulator and reservoir to high and low pressure lines respectively during swing operation in both directions.