HYDRAULIC CIRCUIT, ENERGY RECOVERY DEVICE, AND HYDRAULIC CIRCUIT FOR WORK MACHINE

• US 20090288408A1
• Filed: 02/27/2006
• Published: 11/26/2009
• Est. Priority Date: 06/06/2005
• Status: Abandoned Application

• Current Assignee: Caterpillar Sarl (Caterpillar Incorporated)
• Original Assignee: Shin Caterpillar Mitsubishi Ltd. (Caterpillar Incorporated)
• Inventors: Tozawa, Shoji, Binnaka, Madoka, Furuta, Hideto
• Application Number:
  US11/912,060
• Publication Number:
  US 20090288408A1
• Time in Patent Office: Days
• US Class Current: 60/435
• CPC Class Codes: E02F 9/2075 of the hybrid type for vehicles in general B60W20/00
• CPC Class Codes: E02F 9/2217 with energy recovery arrangements, e.g. using accumulators, flywheels
• CPC Class Codes: E02F 9/2225 using pressure-compensating valves
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• CPC Class Codes: E02F 9/2246 Control of prime movers, e.g. depending on the hydraulic load of work tools
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: E02F 9/2296 Systems with a variable displacement pump
• CPC Class Codes: F15B 11/024 by means of differential connection of the servomotor lines, e.g. regenerative circuits
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 21/14 Energy-recuperation means
• CPC Class Codes: F15B 2211/20515 Electric motor
• CPC Class Codes: F15B 2211/20523 Internal combustion engine
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/265 Control of multiple pressure sources
• 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

A hydraulic circuit that enables smooth absorption of the energy of a return fluid from a hydraulic actuator by means of an energy recovery motor. A return fluid passage to which the fluid discharged from a boom cylinder is branched is provided at the tank passage side of a solenoid valve of a boom control circuit. The return fluid passage comprises two return passages, which are provided with a flow rate ratio control valve for controlling a ratio of fluid that branches off into the return passages. The flow rate ratio control valve is comprised of a solenoid valve disposed in the return passage, which is provided with an energy recovery motor, and a solenoid valve disposed in the return passage, which branches off the upstream side of the solenoid valve.

Claims

1. A hydraulic circuit comprising:

a first return passage through which return fluid discharged from a hydraulic actuator flows;

an energy recovery motor provided in the return passage and adapted to be driven by energy contained in the return fluid;

a second return passage that branches off the first return passage at a location upstream of the energy recovery motor; and

a flow rate ratio control valve for controlling a flow rate ratio of a flow rate of the return fluid in the first return passage and a flow rate of the return fluid in the second return passage.

2. A hydraulic circuit as claimed in claim 1, wherein the flow rate ratio control valve comprises:

a solenoid valve for controlling a flow rate of the return fluid in the first return passage; and

another solenoid valve for controlling a flow rate of the return fluid in the second return passage.

3. A hydraulic circuit as claimed in claim 1, wherein:

the hydraulic actuator is a boom cylinder for vertically pivoting a boom of a work equipment that is attached to a machine body of a work machine; and

the energy recovery motor is disposed in a return passage provided for hydraulic fluid from the boom cylinder.

4. An energy recovery device comprising:

a hydraulic actuator adapted to be driven by hydraulic fluid supplied from a pump;

an energy recovery motor adapted to be driven by energy contained in return fluid discharged from the hydraulic actuator;

a motor generator adapted to be driven by the energy recovery motor so as to function as a generator for feeding electric power to an electric power storage device as well as be driven by electric power fed from the electric power storage device so as to function as an electric motor; and

a clutch that serves to transmit power from the motor generator to the pump when the motor generator is functioning as an electric motor, and disengage the motor generator from the pump when the motor generator is functioning as a generator.

5. An energy recovery device as claimed in claim 4, wherein:

the hydraulic actuator is a boom cylinder for vertically pivoting a boom of a work equipment that is attached to a machine body of a work machine; and

the energy recovery motor is disposed in a return passage provided for hydraulic fluid from the boom cylinder.

6. A hydraulic circuit for a work machine provided with a work equipment comprising a boom, a stick, and a bucket sequentially connected to one another;

the boom being adapted to be pivoted by a boom cylinder, which is adapted to receive hydraulic fluid from a plurality of main pumps comprising a first main pump and a second main pump;

the stick adapted to be pivoted by a stick cylinder; and

the bucket adapted to be pivoted by a bucket cylinder;

wherein the hydraulic circuit comprises;

a boom cylinder hydraulic fluid feeding passage for feeding hydraulic fluid from the first main pump to the boom cylinder;

a bucket cylinder hydraulic fluid feeding passage that branches off the boom cylinder hydraulic fluid feeding passage and serves to feed hydraulic fluid to the bucket cylinder;

a stick cylinder hydraulic fluid feeding passage for feeding hydraulic fluid from the second main pump to the stick cylinder;

a boom assist pump that, together with the first main pump, serves to feed hydraulic fluid to the boom cylinder hydraulic fluid feeding passage;

a solenoid valve between bucket and boom disposed in the boom cylinder hydraulic fluid feeding passage, at a location between a point at which the bucket cylinder hydraulic fluid feeding passage branches off and a point at which a passage from the boom assist pump joins the boom cylinder hydraulic fluid feeding passage, the solenoid valve between bucket and boom being adapted to shift between a position for enabling the hydraulic fluid that would otherwise be fed to the bucket cylinder to be fed to the boom cylinder in a one-way direction and a position for interrupting the flow of fluid;

a circuit-to-circuit communicating passage between stick and boom for providing fluid communication from the stick cylinder hydraulic fluid feeding passage to a head-side of the boom cylinder; and

a solenoid valve between stick and boom that is disposed in the circuit-to-circuit communicating passage between stick and boom and adapted to shift between a position for enabling the hydraulic fluid that would otherwise be fed to the stick cylinder to be fed to the head-side of the boom cylinder in a one-way direction and a position for interrupting the flow of fluid.

8. A hydraulic circuit for a work machine as claimed in claim 6, wherein the hydraulic circuit further includes:

an energy recovery motor adapted to be driven by energy contained in return fluid discharged from the boom cylinder;

a motor generator adapted to be driven by the energy recovery motor so as to function as a generator for feeding electric power to an electric power storage device as well as be driven by electric power fed from the electric power storage device so as to function as an electric motor; and

a clutch that serves to transmit power from the motor generator to the boom assist pump when the motor generator is functioning as an electric motor and disengage the motor generator from the boom assist pump when the motor generator is functioning as a generator.

7. A hydraulic circuit for a work machine provided with a work equipment having a boom to be pivoted by a boom cylinder, which is adapted to receive hydraulic fluid from a plurality of main pumps comprising a first main pump and a second main pump, wherein the hydraulic circuit comprises:

a boom cylinder hydraulic fluid feeding passage for feeding hydraulic fluid from the first main pump to the boom cylinder;

a boom assist pump that, together with the first main pump, serves to feed hydraulic fluid to the boom cylinder hydraulic fluid feeding passage;

a solenoid valve adapted to shift between a communicating position for enabling hydraulic fluid discharged from the boom assist pump to merge with hydraulic fluid discharged from the first main pump, and a position for interrupting the flow of fluid;

another solenoid valve adapted to shift between a communicating position for enabling hydraulic fluid discharged from the first main pump to merge with hydraulic fluid discharged from the second main pump, and a position for interrupting the flow of fluid;

a pair of travel motors for traveling; and

a straight travel valve disposed in a passage that enables the first and second main pumps to communicate with the pair of travel motors, the straight travel valve being adapted to shift between;

a high-speed travel position for enabling, when the solenoid valves are at their respective communicating positions, supplementary fluid received from the boom assist pump through the solenoid valves to merge with hydraulic fluid fed from the first main pump and the second main pump to the pair of travel motors, and

a straight travel position for feeding equally divided volume of hydraulic fluid from either the first main pump or the second main pump to the pair of travel motors.

9. A hydraulic circuit for a work machine as claimed in claim 7, wherein the hydraulic circuit further includes:

an energy recovery motor adapted to be driven by energy contained in return fluid discharged from the boom cylinder;

a motor generator adapted to be driven by the energy recovery motor so as to function as a generator for feeding electric power to an electric power storage device as well as be driven by electric power fed from the electric power storage device so as to function as an electric motor; and

a clutch that serves to transmit power from the motor generator to the boom assist pump when the motor generator is functioning as an electric motor and disengage the motor generator from the boom assist pump when the motor generator is functioning as a generator.