Energy efficient electric vehicle control system
An electric vehicle comprises an electrical system and a hydraulic system. The electrical system comprises an electric power supply and an electric motor-generator connected to the drive train of the vehicle. The hydraulic system includes a pump, and a hydraulic actuator. At least one of the electrical system and the hydraulic system includes energy recovery means arranged to convert kinetic energy from the drive train to electrical energy or to convert kinetic energy from the hydraulic actuator into hydraulic pressure respectively. The electrical and hydraulic systems are connected such that the recovered energy may be converted from electrical to hydraulic energy and/or vice versa. The hydraulic system may further include a hydraulic accumulator.
1. A lift truck comprising:
an electrical system comprising an electric power supply and an electric motor-generator connected to a drive train of the lift truck; and
a hydraulic system for causing lifting of and additional auxiliary movements of a lift of the lift truck, the hydraulic system including a hydraulic pump/motor, a main hydraulic actuator configured to raise and lower the lift, and one or more auxiliary hydraulic actuators configured to cause the additional auxiliary movements of the lift;
wherein the hydraulic system is configured to selectively redirect hydraulic power from the main hydraulic actuator to hydraulically power the one or more auxiliary actuators without redirection of said hydraulic power first to the hydraulic pump/motor.
2. The lift truck of claim 1 , wherein the hydraulic system further includes a hydraulic accumulator.
3. The lift truck of claim 2 , wherein the hydraulic system includes another motor-generator connected to the hydraulic pump/motor and arranged such that hydraulic power stored in the hydraulic accumulator may be converted to electrical energy.
4. The lift truck of claim 3 , wherein the electrical energy generated from the hydraulic accumulator may be selectively directed to the electric motor-generator of the electrical system to provide motion to the drive train and/or to charge the battery.
5. The lift truck of claim 1 , wherein the electric motor-generator is configured to convert kinetic energy from the drive train to electrical energy and is connected to the hydraulic system such that said electrical energy may be converted to hydraulic power via the hydraulic pump/motor.
6. The lift truck of claim 5 , wherein the electrical power supply is a battery and said electrical energy converted from the drive train may be selectively used to charge the battery.
7. The lift truck of claim 1 , wherein the hydraulic system includes another motor-generator connected to the hydraulic pump/motor and an inverter drive connected to the another motor-generator of the hydraulic system.
8. The lift truck of claim 1 , further comprising an inverter drive connected to the electric motor-generator of the electrical system.
9. The lift truck of claim 1 , wherein the electric motor-generator of the electrical system is connected to a traction drive, and is configured to apply a braking force to the lift truck and to convert the kinetic energy generated during said braking to electrical energy.
10. A lift truck comprising:
a battery;
an inverter drive electrically connected to the battery and connected to a first motor/generator, a traction drive/brake coupled to the first motor/generator;
a second inverter drive electrically connected to the battery and connected to a second motor/generator; and
a hydraulic pump/motor coupled to the second motor/generator and hydraulically connected to a hydraulic lift circuit for causing lifting of and additional auxiliary movements of a lift of the lift truck, the hydraulic lift circuit including a main hydraulic actuator configured to raise and lower the lift, and one or more auxiliary hydraulic actuators configured to cause the additional auxiliary movements of the lift;
wherein hydraulic power from actuation of the main hydraulic actuator is selectively redirected to hydraulically power the one or more auxiliary actuators without redirection of said hydraulic power first to the hydraulic pump/motor.
11. The lift truck of claim 10 , wherein hydraulic power from actuation of the main hydraulic actuator is alternatively selectively converted into electrical power and stored in the battery or converted into torque to move the lift truck.
12. The lift truck of claim 10 , wherein kinetic power from the traction drive/brake is converted to electrical energy and is selectively stored in the battery or further converted to hydraulic power and used to actuate the main hydraulic actuator.
13. The lift truck of claim 12 , wherein the hydraulic lift circuit further includes a hydraulic accumulator, and wherein electrical power converted from the traction drive/brake is alternatively selectively converted into hydraulic power and stored in the accumulator.
14. The lift truck of claim 10 , wherein the hydraulic lift circuit further includes a hydraulic accumulator, and wherein hydraulic power from actuation of the main hydraulic actuator is alternatively selectively stored in the accumulator.