Working machine

• US 10,184,225 B2
• Filed: 12/22/2015
• Issued: 01/22/2019
• Est. Priority Date: 12/23/2014
• Status: Active Grant

• Current Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Original Assignee: Hitachi Construction Machinery Company Limited (Hitachi, Ltd.)
• Inventors: Hiraku, Kenji, Saitoh, Teppei
• Primary Examiner(s): Kraft, Logan
• Application Number:
  US14/978,702
• Publication Number:
  US 20160177539A1
• Time in Patent Office: 1,127 Days
• CPC Class Codes: E02F 3/425 Drive systems for dipper-arms, backhoes or the like
• CPC Class Codes: E02F 3/435 for dipper-arms, backhoes or the like
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• CPC Class Codes: E02F 9/2242 including an electronic controller
• 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 11/10 in which the servomotor position is a function of the pressure also pressure regulators as operating means for such systems, the device itself may be a position indicating system
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/20569 capable of working as pump and motor
• 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 2211/30595 with additional valves between the groups of valves for multiple output members
• CPC Class Codes: F15B 2211/31535 having multiple pressure sources and a single output member
• CPC Class Codes: F15B 2211/31547 having multiple pressure sources and multiple output members
• CPC Class Codes: F15B 2211/50536 using unloading valves controlling the supply pressure by diverting fluid to the return line
• CPC Class Codes: F15B 2211/526 electrically or electronically
• CPC Class Codes: F15B 2211/56 Control of an upstream pressure
• CPC Class Codes: F15B 2211/613 Feeding circuits
• 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 2211/6653 : Pressure control
• CPC Class Codes: F15B 2211/7053 : Double-acting output members
• CPC Class Codes: F15B 2211/7135 : Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
• CPC Class Codes: F15B 2211/7142 : the output members being arranged in multiple groups
• CPC Class Codes: F15B 2211/785 : Compensation of the difference in flow rate in closed fluid circuits using differential actuators
• CPC Class Codes: F15B 7/006 : Rotary pump input
• CPC Class Codes: Y02P 80/10 : Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

Closed circuit lines (33, 43, 53, 63) for connecting hydraulic cylinders (17, 18, 19) and closed circuit pumps (31, 41, 51, 61) are provided with a charge pressure adjustment apparatus (75) via a charge line (72) to variably adjust the pressure in the charge line (72). An operating device (12) for operating the hydraulic cylinders (17, 18, 19) and the charge pressure adjustment apparatus (75) are connected to a control device (81). In the case of extending the hydraulic cylinders (17, 18, 19), the control device (81) increases a set pressure of the charge pressure adjustment apparatus (75) to be high to increase the pressure in the bottom side of the hydraulic cylinders (17, 18, 19) in accordance with an operating amount of the operating device (12).

Claims

1. A working machine comprising:

at least one hydraulic cylinder in which a bottom side oil chamber and a rod side oil chamber are defined by a piston to which one end of a rod is fixed, and that extends or retracts based upon supply/discharge of hydraulic oil;

at least one closed circuit pump that is connected to the bottom side oil chamber and the rod side oil chamber in the hydraulic cylinder via a closed circuit line configuring a closed circuit;

at least one open circuit pump that is connected to the bottom side oil chamber in the hydraulic cylinder via an open circuit line configuring an open circuit;

a charge pump that is connected to the closed circuit line via a charge line and a check valve to supplement the hydraulic oil to the closed circuit line;

an operating device for operating the hydraulic cylinder; and

a control device that controls the closed circuit pump and the open circuit pump in accordance with an operating amount of the operating device;

wherein

in case of increasing the operating amount of the operating device extending the hydraulic cylinder, the control device controls of the closed circuit pump and the open circuit pump in such a manner as to make a ratio of a supply amount of the hydraulic oil to the bottom side oil chamber in the hydraulic cylinder to a discharge amount of the hydraulic oil from the rod side oil chamber in the hydraulic cylinder larger than a ratio of a pressure-receiving area of the bottom side oil chamber in the hydraulic cylinder to a pressure-receiving area of the rod side oil chamber in the hydraulic cylinder.

2. The working machine according to claim 1, wherein

the charge line is provided with a charge pressure adjustment apparatus that is controlled by the control device and variably adjusts the pressure in the charge line, and

the control device increases a set pressure of the charge pressure adjustment apparatus in accordance with increasing the operating amount of the operating device.