Hydraulic circuit for construction equipment

• US 20080236154A1
• Filed: 03/19/2008
• Published: 10/02/2008
• Est. Priority Date: 03/30/2007
• Status: Active Grant

• Current Assignee: Volvo Construction Equipment AB (AB Volvo)
• Original Assignee: Volvo Construction Equipment Holding Sweden AB
• Inventors: Koo, Bon Seok
• Granted Patent: US 7,841,175 B2
• Time in Patent Office: Days
• US Class Current: 60/421
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• CPC Class Codes: E02F 9/2282 Systems using center bypass type changeover valves
• CPC Class Codes: E02F 9/2285 Pilot-operated systems
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps
• CPC Class Codes: F15B 11/16 with two or more servomotors
• CPC Class Codes: F15B 11/17 using two or more pumps
• CPC Class Codes: F15B 2211/20523 Internal combustion engine
• CPC Class Codes: F15B 2211/20576 with multiple pumps
• CPC Class Codes: F15B 2211/265 Control of multiple pressure sources
• CPC Class Codes: F15B 2211/30505 Non-return valves, i.e. check valves
• CPC Class Codes: F15B 2211/30595 with additional valves between the groups of valves for multiple output members
• CPC Class Codes: F15B 2211/3116 the pump port being open in the centre position, e.g. so-called open centre
• CPC Class Codes: F15B 2211/329 actuated by fluid pressure
• CPC Class Codes: F15B 2211/50518 using pressure relief valves
• CPC Class Codes: F15B 2211/5151 being connected to a pressure source and a directional control valve
• CPC Class Codes: F15B 2211/7142 the output members being arranged in multiple groups

Abstract

A hydraulic circuit for construction equipment is disclosed, which can prevent an abrupt rotation of a swing device when a switching valve for the swing device is shifted in a state that switching valves for a traveling device and a working device have been shifted. The hydraulic circuit includes first to fourth hydraulic pumps; first to fourth switching valves installed in the first to fourth hydraulic pumps, respectively, and shifted to control hydraulic fluid fed to working devices or traveling devices; a confluence switching valve installed in the third hydraulic pump and shifted to supply the hydraulic fluid to the working devices on the first and second hydraulic pump sides; signal lines for the traveling devices and the working devices; a first valve connected between the signal line for the traveling device and an intersection between the signal line for the confluence switching valve and a tank line; and a second valve installed in a flow path between the first valve and the tank line, shifted to discharge pressure in the signal line for the confluence switching valve to the tank line or to block the flow path to form the signal pressure in the signal line for the confluence, in response to a supply of the signal pressure.

Claims

1. A hydraulic circuit for construction equipment comprising:

first to fourth hydraulic pumps;

first switching valves composed of valves installed in a flow path of the first hydraulic pump and shifted to control hydraulic fluid fed to working devices;

second switching valves composed of valves installed in a flow path of the second hydraulic pump and shifted to control hydraulic fluid fed to the working devices;

third switching valves composed of valves installed in a flow path of the third hydraulic pump and shifted to control hydraulic fluid fed to working devices;

fourth switching valves composed of valves installed on upstream sides of the flow paths of the first and second hydraulic pumps, respectively, and shifted to control the hydraulic fluid fed to left and right traveling devices;

a confluence switching valve installed on a downstream side of the flow path of the third hydraulic pump and shifted to supply the hydraulic fluid from the third hydraulic pump to the working devices on the first hydraulic pump side and to the working devices on the second hydraulic pump side, in response to a pilot signal pressure formed in a signal line connected to the fourth hydraulic pump;

a signal line for the traveling devices which is connected to the signal line for the confluence switching valve and in which a signal pressure is formed when the fourth switching valves for the traveling devices are shifted;

signal lines for the working devices which are connected to the signal line for the confluence switching valve and in which a signal pressure is formed when the first and second switching valves for the working devices are shifted;

a first valve having one end connected to the signal line for the traveling device and the other hand connected to an intersection between the signal line for the confluence switching valve and a tank line; and

a second valve installed in a flow path between the first valve and the tank line, shifted to open the flow path to discharge pressure formed in the signal line for the confluence switching valve to the tank line, in response to a supply of the signal pressure, and shifted to block the flow path to form the signal pressure in the signal line for the confluence switching valve when the signal pressure is not supplied thereto.

2. The hydraulic circuit of claim 1, wherein a first throttling part is installed on an upstream side of the signal line for the traveling devices connected to the signal line for the confluence switching valve, and the signal line for the working devices is connected to a downstream side of a second throttling part installed in the signal line for the confluence switching valve.

3. The hydraulic circuit of claim 1, wherein the second valve further comprises an orifice formed in a spool in a position where the flow path is open when the second valve is shifted in response to the supply of the signal pressure thereto.

4. The hydraulic circuit of claim 1, wherein the working device connected to the third switching valve is a swing device or an option device.

5. A hydraulic circuit for construction equipment comprising:

first to fourth hydraulic pumps;

first switching valves composed of valves installed in a flow path of the first hydraulic pump and shifted to control hydraulic fluid fed to working devices;

second switching valves composed of valves installed in a flow path of the second hydraulic pump and shifted to control hydraulic fluid fed to the working devices;

third switching valves composed of valves installed in a flow path of the third hydraulic pump and shifted to control hydraulic fluid fed to working devices;

fourth switching valves composed of valves installed on upstream sides of the flow paths of the first and second hydraulic pumps, respectively, and shifted to control the hydraulic fluid fed to left and right traveling devices;

a confluence switching valve installed on a downstream side of the flow path of the third hydraulic pump, connected to the fourth hydraulic pump, and shifted to supply the hydraulic fluid from the third hydraulic pump to the working devices on the first hydraulic pump side and to the working devices on the second hydraulic pump side, in response to a pilot signal pressure formed in a signal line in which a third throttling part is installed;

a signal line for the traveling devices which is connected to a downstream side of the third throttling part installed in the signal line for the confluence switching valve and in which a signal pressure is formed when the fourth switching valves for the traveling devices are shifted;

signal lines for the working devices which are connected to the signal line for the confluence switching valve and in which a signal pressure is formed when the first and second switching valves for the working devices are shifted; and

a second valve installed to open/close a flow path between the signal line for the confluence switching valve and a tank line, shifted to open the flow path to discharge pressure formed in the signal line for the confluence switching valve to the tank line, in response to a supply of the signal pressure, and shifted to block the flow path to form the signal pressure in the signal line for the confluence switching valve when the signal pressure is not supplied thereto.