Drive System for Construction Machine

• US 20200131736A1
• Filed: 04/06/2018
• Published: 04/30/2020
• Est. Priority Date: 09/14/2017
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: SHIMIZU, Juri, HIRAKU, Kenji, TAKAHASHI, Hiromasa, SUGIKI, Shohei
• Granted Patent: US 10,889,964 B2
• Time in Patent Office: Days
• CPC Class Codes: E02F 3/32 working downwardly and towards the machine, e.g. with backhoes
• CPC Class Codes: E02F 3/40 Dippers; Buckets ; Grab devices, e.g. manufacturing processes for buckets, form, geometry or material of buckets devices to connect tools to arms or booms E02F3/3604; teeth therefor E02F9/28
• CPC Class Codes: E02F 3/435 for dipper-arms, backhoes or the like
• CPC Class Codes: E02F 9/22 Hydraulic or pneumatic drives for dipper or bucket arm position control E02F3/43, for blade position control for graders E02F3/844; for turntables E02F9/121; for fork-lift trucks B66F9/22
• CPC Class Codes: E02F 9/2235 including an electronic controller
• CPC Class Codes: E02F 9/2242 including an electronic controller
• CPC Class Codes: E02F 9/2267 Valves or distributors position of valves arrangements on upper-structures E02F9/0875
• CPC Class Codes: E02F 9/2289 Closed circuit
• 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 15/02 Mechanical layout characterised by the means for converting the movement of the fluid-actuated element into movement of the finally-operated member
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/27 Directional control by means of the pressure source
• CPC Class Codes: F15B 2211/30565 having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
• CPC Class Codes: F15B 2211/3058 having additional valves for interconnecting the fluid chambers of a double-acting actuator, e.g. for regeneration mode or for floating mode
• CPC Class Codes: F15B 2211/31558 having a single output member
• CPC Class Codes: F15B 2211/327 electrically or electronically
• CPC Class Codes: F15B 2211/5159 being connected to an output member and a return line
• CPC Class Codes: F15B 2211/526 : electrically or electronically
• CPC Class Codes: F15B 2211/6313 : the pressure being a load pressure
• CPC Class Codes: F15B 2211/665 : Methods of control using electronic components
• CPC Class Codes: F15B 2211/6653 : Pressure control
• CPC Class Codes: F15B 2211/6658 : Control using different modes, e.g. four-quadrant-operation, working mode and transportation mode
• CPC Class Codes: F15B 2211/7053 : Double-acting output members
• CPC Class Codes: F15B 2211/7733 : providing vibrating movement, e.g. dither control for emptying a bucket
• CPC Class Codes: F15B 9/04 : controlled by varying the output of a pump with variable capacity

Abstract

Provided is a work machine that can selectively establish a closed circuit connection between a single rod-type hydraulic cylinder and a plurality of bidirectional-type hydraulic pumps, the work machine being capable of enhancing responsiveness of the single rod-type hydraulic cylinder when a high-speed lever switching operation is conducted in a state in which a rod pressure of the single rod-type hydraulic cylinder is higher than a bottom pressure. When a bucket lever (70a) is operated to a side of extending the bucket cylinder in a state in which a pressure in a rod chamber (5b) of the bucket cylinder (5) is higher than a pressure in a bottom chamber (5a), a controller (50) opens a rod-side proportional valve (45) and discharges a working fluid in the rod chamber to a working fluid tank (25) such that a differential pressure between the pressure in the rod chamber and the pressure in the bottom chamber is reduced below a switching pressure (Psw) of a flushing valve (33).

Claims

1. A work machine comprising:

a work device including a plurality of work members;

a single rod-type hydraulic cylinder that drives one of the plurality of work members;

a bottom-side line connected to a bottom chamber of the single rod-type hydraulic cylinder;

a rod-side line connected to a rod chamber of the single rod-type hydraulic cylinder;

a bidirectional-type first hydraulic pump of which a delivery port on one side is connected to the bottom-side line through a first control valve and a delivery port on another side is connected to the rod-side line through the first control valve;

a bidirectional-type second hydraulic pump of which a delivery port on one side is connected to the bottom-side line through a second control valve and a delivery port on another side is connected to the rod-side line through the second control valve;

an operation lever device having an operation lever for operating the single rod-type hydraulic cylinder to extend and contract;

a working fluid tank;

a flushing valve that is connected to the rod-side line and the rod-side line, and that discharges a surplus flow rate of a lower-pressure side one of the bottom-side line and the rod-side line into the working fluid tank when a differential pressure between the bottom-side line and the rod-side line exceeds a predetermined pressure; and

a controller that controls opening/closing of the first and second control valves and controls tilting amounts of the first and second hydraulic pumps, wherein

the work machine further includes

a bottom pressure sensor that detects a pressure in the bottom chamber;

a rod pressure sensor that detects a pressure in the rod chamber;

a rod-side discharge line that connects the rod-side line and the working fluid tank; and

a rod-side proportional valve provided in the rod-side discharge line, and

the controller is configured to, when the operation lever is operated to a side of extending the single rod-type hydraulic cylinder in a state in which the pressure in the rod chamber is higher than the pressure in the bottom chamber, open the rod-side proportional valve to discharge a working fluid in the rod chamber into the working fluid tank such that a differential pressure between the pressure in the rod chamber and the pressure in the bottom chamber is reduced below the predetermined pressure.

2. The work machine according to claim 1, further comprising:

a bottom-side discharge line that connects the bottom-side line and the working fluid tank; and

a bottom-side proportional valve provided in the bottom-side discharge line, wherein

the controller is configured to, when the operation lever is operated to a side of contracting the single rod-type hydraulic cylinder in a state in which the pressure in the bottom chamber is higher than the pressure in the rod chamber, open the bottom-side proportional valve to discharge the working fluid in the bottom chamber into the working fluid tank such that a differential pressure between the bottom chamber and the rod chamber is reduced below the predetermined pressure.

3. The work machine according to claim 2, further comprising:

a third control valve provided in a portion of the rod-side discharge line that connects the rod-side line and the rod-side proportional valve;

a single tilting-type third hydraulic pump having a delivery port connected to a portion of the rod-side discharge line that connects the third control valve and the rod-side proportional valve, and having a suction port connected to the working fluid tank;

a fourth control valve provided in a portion of the bottom-side discharge line that connects the bottom-side line and the bottom-side proportional valve; and

a single tilting-type fourth hydraulic pump having a delivery port connected to a portion of the bottom-side discharge line that connects the fourth control valve and the bottom-side proportional valve, and having a suction port connected to the working fluid tank.

4. The work machine according to claim 1, wherein

the controller is configured to control tilting of the first hydraulic pump such that the working fluid is supplied from the first hydraulic pump to the bottom chamber and control tilting of the second hydraulic pump such that the working fluid is supplied from the second hydraulic pump to the rod chamber when a switching period of the operation lever is equal to or less than a predetermined period,

open the first control valve and close the second control valve when the operation lever is operated to the side of extending the single rod-type hydraulic cylinder, and

close the first control valve and open the second control valve when the operation lever is operated to aside of contracting the single rod-type hydraulic cylinder.