SYSTEM FOR DRIVING A BOOM OF A HYBRID EXCAVATOR AND A CONTROL METHOD THEREOF

• US 20120324877A1
• Filed: 12/23/2010
• Published: 12/27/2012
• Est. Priority Date: 12/23/2009
• Status: Active Grant

• Current Assignee: HD Hyundai Infracore Co., Ltd.
• Original Assignee: Doosan Infracore Company Limited
• Inventors: Kang, Byung Il
• Granted Patent: US 9,260,835 B2
• Time in Patent Office: Days
• US Class Current: 60/327
• CPC Class Codes: E02F 3/435 for dipper-arms, backhoes or the like
• 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 9/2235 including an electronic controller
• CPC Class Codes: E02F 9/2242 including an electronic controller
• CPC Class Codes: E02F 9/2282 Systems using center bypass type changeover valves
• 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 11/17 using two or more pumps
• CPC Class Codes: F15B 13/044 operated by electrically-controlled means, e.g. solenoids, torque-motors
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/3053 In combination with a pressure compensating valve
• CPC Class Codes: F15B 2211/327 electrically or electronically
• CPC Class Codes: F15B 2211/7128 the chambers being connected in parallel
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups

Abstract

Disclosed are a system for driving a boom of a hybrid excavator, and a method for controlling same. The disclosed system comprises: an electric motor operating by means of a motor or generator; a capacitor for storing electricity generated by the electric motor; a hydraulic pump motor driven by the electric motor to supply working oil to a boom; a boom control valve having a closed circuit for selectively connecting/disconnecting a discharge line and an inlet line of the hydraulic pump motor to/from a head or a load of the boom; a main pump driven by a driving source arranged separately from the motor so as to supply working oil to a bucket, driving motor, or arm; a boom-assisting valve, which connects a discharge line of the main pump to the discharge line of the hydraulic pump motor, such that working oil discharged from the main pump and the hydraulic pump motor can be combined; and a control unit for controlling the electric motor, the hydraulic pump motor, and the boom control valve. The system of the present disclosure minimizes the loss of energy during excavation, which is the main use of an excavator, while using the electric motor, ensures the operating performance of the boom, and recovers regenerative energy from the boom.

Claims

1. A system for driving a boom of a hybrid excavator, comprising:

an electric motor that operates as a motor or an electricity generator;

a capacitor that stores electricity generated by the electric motor;

a hydraulic pump motor that is driven by the electric motor and supplies working fluid to a boom;

a boom control valve that constitutes a closed circuit selectively connecting/disconnecting a discharge line and an intake line of the hydraulic pump motor to/from a head or a rod of the boom;

a main pump that is driven by a driving source disposed separately from the electric motor and supplies the working fluid to a bucket, a traveling motor, or an arm;

a boom-assistant valve that allows the working fluid discharged from the main pump and the hydraulic pump motor to meet each other by connecting the discharge line of the main pump to the discharge line of the hydraulic pump motor; and

a control unit that controls the electric motor, the hydraulic pump motor, and the boom control valve.

2. The system of claim 1, further comprising:

a first control valve that connects an intake line, which connects the hydraulic pump motor with the boom control valve, with a tank for the working fluid; and

a second control valve that connects a discharge line, which connects the hydraulic pump motor with the boom control valve, with a tank for the working fluid,

wherein the control unit controls the first control valve and the second control valve.

3. The system of claim 2, wherein the first control valve is selectively switched when the boom is lifted, and is disconnected when the boom is descended, and the second control valve is disconnected when the boom is lifted, and is selectively switched when the boom is descended.

4. The system of claim 2, wherein the boom-assistant valve is switched such that the flow rate of the main pump is supplied to the boom cylinder, when the control signal of a boom joystick increases and a flow rate over the flow rate supplied from the hydraulic pump motor or the capacity of the electric motor is necessary.

5. The system of claim 2, wherein the first control valve is connected and drains the flow rate flowing into the hydraulic pump motor from the boom cylinder to the tank, when the flow rate flowing into the hydraulic pump motor from the boom cylinder when the boom is descended exceeds the available capacity of the hydraulic pump motor or the capacity of the electric motor.

6. A method of controlling a system for driving a boom of a hybrid excavator, the method comprising:

(a) detecting the amount of operation of a boom joystick;

(b) determining lifting or descending of a boom due to the operation of the boom joystick;

(c) opening a first control valve when the boom is lifted;

(d) comparing the driving power of the boom according to the amount of operation of the boom joystick with the maximum supply power of an electric motor when the boom is lifted;

(e) comparing the consumed flow rate of a boom cylinder with the maximum flow rate of a hydraulic pump motor when the driving power of the boom is smaller than the maximum supply power of the electric motor;

(f) disconnecting the boom-assistant valve, when the consumed flow rate of the boom cylinder is smaller than the maximum flow rate of the hydraulic pump motor;

(g) connecting the boom-assistant valve when the driving power of the boom is larger than the maximum supply power of the electric motor;

(h) opening the second control valve when the boom is descended;

(i) comparing the recovery power of the boom with the maximum recoverable power of the electric motor;

(j) comparing the recovery flow rate of the boom cylinder with the available flow rate of the hydraulic pump motor, when the recovery power of the boom is smaller the maximum recoverable power of the electric motor;

(k) disconnecting the first control valve, when the recovery flow rate of the boom cylinder is smaller than the available flow rate of the hydraulic pump motor;

(l) connecting the first control valve, when the recovery flow rate of the boom cylinder is larger than the available flow rate of the hydraulic pump motor; and

(m) connecting the first control valve, when the recovery power of the boom is larger than the maximum recoverable power of the electric motor.