Power system and work machine using same

• US 20050103007A1
• Filed: 11/14/2003
• Published: 05/19/2005
• Est. Priority Date: 11/14/2003
• Status: Active Grant

• Current Assignee: Caterpillar Sarl (Caterpillar Incorporated)
• Original Assignee: Caterpillar Incorporated, Shin Caterpillar Mitsubishi Ltd. (Caterpillar Incorporated)
• Inventors: Yoshino, Kazunori
• Granted Patent: US 6,945,039 B2
• Time in Patent Office: Days
• US Class Current: 60/414
• CPC Class Codes: E02F 9/2091 Control of energy storage means for electrical energy, e.g. battery or capacitors energy recovery arrangements in hydraulic or pneumatic drives E02F9/2217
• CPC Class Codes: E02F 9/2095 Control of electric, electro-mechanical or mechanical equipment not otherwise provided for, e.g. ventilators, electro-driven fans control of hydraulic driven equipment E02F9/22
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: F15B 11/024 by means of differential connection of the servomotor lines, e.g. regenerative circuits
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20515 Electric motor
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/214 the pressure sources being hydrotransformers
• CPC Class Codes: F15B 2211/30575 in a Wheatstone Bridge arrangement (also half bridges)
• CPC Class Codes: F15B 2211/31576 having a single pressure source and a single output member
• CPC Class Codes: F15B 2211/327 electrically or electronically
• CPC Class Codes: F15B 2211/35 Directional control combined with flow control
• CPC Class Codes: F15B 2211/40515 with variable throttles or orifices
• CPC Class Codes: F15B 2211/41563 being connected to a pressure source and a return line
• CPC Class Codes: F15B 2211/426 electrically or electronically
• CPC Class Codes: F15B 2211/45 Control of bleed-off flow, e.g. control of bypass flow to the return line
• CPC Class Codes: F15B 2211/6303 using input signals
• CPC Class Codes: F15B 2211/6346 representing a state of input means, e.g. joystick position
• CPC Class Codes: F15B 2211/6652 Control of the pressure source, e.g. control of the swash plate angle
• CPC Class Codes: F15B 2211/6654 Flow rate control
• CPC Class Codes: F15B 2211/7053 : Double-acting output members
• CPC Class Codes: F15B 2211/7058 : Rotary output members
• CPC Class Codes: F15B 2211/88 : Control measures for saving energy

Abstract

In the present invention, a power system includes at least one hydraulic cylinder that defines a first fluid volume and a second fluid volume separated from one another via a moveable plunger. Hydraulic power created within the hydraulic cylinder is converted to mechanical power by a fluid driven rotating device that is fluidly connected to at least the first fluid volume. A generator is attached to the fluid-driven rotating device, and produces electrical power that is stored in a power storage system including at least one of a battery and a capacitor. The stored electrical power can be supplied to an electric motor that is operable to power a hydraulic pump. The hydraulic pump supplies hydraulic fluid to the hydraulic cylinder. The power system of the present invention is a relatively inexpensive and efficient alternative to a power system including a diesel engine that can be a source of undesirable emissions, noise and vibrations.

Claims

1. A power system comprising:

an electric motor being operable to power a hydraulic pump;

at least one hydraulic cylinder being fluidly connected to the hydraulic pump and defining a first fluid volume and a second fluid volume separated from one another via a moveable plunger;

a fluid driven rotating device being fluidly connected to at least the first fluid volume defined by the hydraulic cylinder and being operable to power a generator; and

a power storage system including at least one of a battery and a capacitor being in electrical communication with the generator and the electric motor.

2. The power system of claim 1 including an inverter being positioned between the electric motor and at least one of the capacitor and battery.

3. The power system of claim 1 wherein the fluid driven rotating device includes a variable displacement hydraulic motor.

4. The power system of claim 3 including an inverter being positioned between the electric motor and at least one of the capacitor and the battery.

5. A work machine comprising a work machine body;

and

the power system of claim 1 being attached to the work machine body.

6. The work machine of claim 5 including an implement attached to the work machine body;

and

the at least one hydraulic cylinder being operably coupled to move the implement.

7. A power system, comprising:

means for converting hydraulic power produced within at least one hydraulic cylinder to mechanical power;

means for converting the mechanical power to electrical power;

means for storing the electrical power in at least one of a battery and a capacitor;

means for supplying an electric motor coupled to the hydraulic pump with the electrical power from at least one of the battery and the capacitor; and

means for supplying hydraulic fluid, via the hydraulic pump, to the at least one hydraulic cylinder.

8. The power system of claim 7 wherein the means for converting hydraulic power to mechanical power includes a variable displacement hydraulic motor.

9. The power system of claim 7 wherein means for supplying the electrical power includes an inverter.

10. The power system of claim 7 wherein the at least one hydraulic cylinder being operably coupled to move a work machine implement.

11. A method of operating an electrical power system, comprising the steps of:

powering a generator, at least in part, by converting hydraulic power created within a hydraulic cylinder to mechanical power;

storing electrical power created by the generator in at least one of a battery and a capacitor;

powering a hydraulic pump, at least in part, by supplying electrical power from at least one of the battery and capacitor to an electric motor coupled to the hydraulic pump; and

supplying hydraulic fluid to the hydraulic cylinder, at least in part, by operating the hydraulic pump.

12. The method of claim 11 wherein the step of powering the generator includes a step of attaching a variable displacement hydraulic motor to the generator.

13. The method of claim 11 wherein the step of powering the generator includes a step of producing hydraulic power by retracting a plunger within a hydraulic cylinder.

14. The method of claim 13 wherein the step of producing hydraulic power includes a step of controlling a speed of the retracting plunger, at least in part, by varying the displacement of the motor.

15. The method of claim 11 wherein the step of powering a hydraulic pump includes a step of inverting electrical current being supplied from at least one of the capacitor and the battery to the electric motor.

16. A power system comprising:

at least one of a battery and a capacitor being configured to supply stored electrical power to an electric motor;

a hydraulic pump being configured to be powered by the electric motor;

a hydraulic cylinder being configured to receive hydraulic fluid from the hydraulic pump;

a fluid driven rotating device being configured to be powered by hydraulic power produced within the hydraulic cylinder; and

a generator being configured to be powered by the fluid driven rotating device and to supply electrical power to at least one of the battery and the capacitor.

17. The power system of claim 16 including an inverter configured to invert the electrical power being supplied from the at least one battery and capacitor to the electric motor.

18. The power system of claim 16 wherein the fluid driven rotating device includes a variable displacement hydraulic motor.