Hydraulic circuit

• US 20030089106A1
• Filed: 11/06/2002
• Published: 05/15/2003
• Est. Priority Date: 11/09/2001
• Status: Active Grant

• Current Assignee: Nabco Ltd. (Nabtesco Corporation)
• Original Assignee: Nabco Ltd. (Nabtesco Corporation)
• Inventors: Segawa, Hitoshi, Ioku, Kensuke
• Granted Patent: US 6,799,424 B2
• Time in Patent Office: Days
• US Class Current: 60/328
• CPC Class Codes: E02F 9/2239 using two or more pumps with cross-assistance
• CPC Class Codes: E02F 9/2292 Systems with two or more pumps

Abstract

A hydraulic circuit comprises a first and a second merging line capable of supplying pressure oil from a third pump for a third circuit to directional control valves in a first and a second circuit, respectively, and a merging valve for selectively communicating or cutting off the first and the second merging line with or from the third pump. The merging valve has a first shift position at which the third pump is connected to the second merging line, and a second shift position at which the third pump is connected to the first and the second merging line. The merging valve is shifted continuously between the shift positions. The hydraulic circuit can efficiently distribute pressure oil supplied from the third pump to the first and/or second circuit as well, and can prevent lowering of the operability of each of actuators connected to the first or second circuit.

Claims

1. A hydraulic circuit for driving actuators by pressure oil supplied from a first pump, a second pump and a third pump and returned to a tank, the hydraulic circuit comprising:

a first circuit including a directional control valve supplied with the pressure oil from said first pump, the directional control valve in said first circuit controlling connection between said first pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a second circuit including a directional control valve supplied with the pressure oil from said second pump, the directional control valve in said second circuit controlling connection between said second pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a third circuit including a directional control valve supplied with the pressure oil from said third pump, the directional control valve in said third circuit controlling connection between said third pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a first merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said first circuit;

a second merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said second circuit; and

a merging valve for selectively communicating or cutting off said first merging line and said second merging line with or from said third pump, said merging valve having a first shift position at which said third pump is connected to said second merging line, and a second shift position at which said third pump is connected to said first merging line and said second merging line,

said merging valve being continuously shifted between said first shift position and the second shift position depending on a state of said first circuit or said second circuit.

2. The hydraulic circuit according to claim 1, wherein when the directional control valve in said first circuit is not operated, said merging valve is shifted to said first shift position, and when the directional control valve in said first circuit is operated, said merging valve is shifted toward said second shift position depending on a state of operation of the directional control valve in said first circuit.

3. The hydraulic circuit according to claim 1, wherein said merging valve is continuously shifted between said first shift position and said second shift position depending on a flow rate of the pressure oil required by the directional control valve in said first circuit or said second circuit so that the pressure oil from said third pump is distributed and sent to said first circuit or said second circuit under a pressurized state.

4. A hydraulic circuit for driving actuators by pressure oil supplied from one pump and the other pump and returned to a tank, the hydraulic circuit comprising:

one circuit including a directional control valve supplied with the pressure oil from said one pump, the directional control valve in said one circuit controlling connection between said one pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

the other circuit including a directional control valve supplied with the pressure oil from said other pump, the directional control valve in said other circuit controlling connection between said other pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a merging line disposed to be capable of supplying the pressure oil sent from said other pump under a pressurized state to the directional control valve in said one circuit; and

a merging valve for selectively communicating or cutting off said merging line with or from said other pump,

said merging valve being capable of sending the pressure oil from said other pump under a pressurized state to said one circuit and reducing an opening degree of a throttle disposed between said other pump and said tank depending on a flow rate of the pressure oil required by the directional control valve in said one circuit, thereby increasing a flow rate of the pressure oil sent to said one circuit under the pressurized state.

5. A hydraulic circuit for driving actuators by pressure oil supplied from a first pump, a second pump and a third pump and returned to a tank, the hydraulic circuit comprising:

a first circuit including a directional control valve supplied with the pressure oil from said first pump, the directional control valve in said first circuit controlling connection between said first pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a second circuit including a directional control valve supplied with-the pressure oil from said second pump, the directional control valve in said second circuit controlling connection between said second pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a third circuit including a directional control valve supplied with the pressure oil from said third pump, the directional control valve in said third circuit controlling connection between said third pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a first merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said first circuit;

a second merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said second circuit; and

a merging valve for selectively communicating or cutting off said first merging line and said second merging line with or from said third pump,

said merging valve being capable of sending the pressure oil from said third pump under a pressurized state to said first circuit and said second circuit and reducing an opening degree of a throttle disposed between said third pump and said tank depending on flow rates of the pressure oil required by the directional control valves in said first circuit and said second circuit, thereby increasing flow rates of the pressure oil sent to said first circuit and said second circuit under the pressurized state.

6. A hydraulic circuit for driving actuators by pressure oil supplied from one pump and the other pump and returned to a tank, the hydraulic circuit comprising:

one circuit including a directional control valve supplied with the pressure oil from said one pump, the directional control valve in said one circuit controlling connection between said one pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

the other circuit including a directional control valve supplied with the pressure oil from said other pump, the directional control valve in said other circuit controlling connection between said other pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a merging line disposed to be capable of supplying the pressure oil sent from said other pump under a pressurized state to the directional control valve in said one circuit; and

a merging valve for selectively communicating or cutting off said merging line with or from said other pump,

said merging valve having a shift position at which the side upstream of the directional control valve in said other circuit is connected to said one circuit through a throttle and the side downstream of the directional control valve in said other circuit is also connected to said one circuit.

7. A hydraulic circuit for driving actuators by pressure oil supplied from a first pump, a second pump and a third pump and returned to a tank, the hydraulic circuit comprising:

a first circuit including a directional control valve supplied with the pressure oil from said first pump, the directional control valve in said first circuit controlling connection between said first pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a second circuit including a directional control valve supplied with the pressure oil from said second pump, the directional control valve in said second circuit controlling connection between said second pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a third circuit including a directional control valve supplied with the pressure oil from said third pump, the directional control valve in said third circuit controlling connection between said third pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a first merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said first circuit;

a second merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said second circuit; and

a merging valve for selectively communicating or cutting off said first merging line and said second merging line with or from said third pump,

said merging valve having a shift position at which the side upstream of the directional control valve in said third circuit is connected to said first circuit and said second circuit through a throttle and the side downstream of the directional control valve in said third circuit is also connected to said first circuit and said second circuit.

8. A hydraulic circuit for driving actuators by pressure oil supplied from a first pump, a second pump and a third pump and returned to a tank, the hydraulic circuit comprising:

a first circuit including a directional control valve supplied with the pressure oil from said first pump, the directional control valve in said first circuit controlling connection between said first pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a second circuit including a directional control valve supplied with the pressure oil from said second pump, the directional control valve in said second circuit controlling connection between said second pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a third circuit including a directional control valve supplied with the pressure oil from said third pump, the directional control valve in said third circuit controlling connection between said third pump or said tank and at least one of said actuators and a flow rate of the pressure oil therebetween;

a first merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said first circuit;

a second merging line disposed to be capable of supplying the pressure oil sent from said third pump under a pressurized state to the directional control valve in said second circuit; and

a merging valve for selectively communicating or cutting off said first merging line and said second merging line with or from said third pump,

said merging valve having a shift position at which said third pump is connected to said first merging line and said second merging line,

said shift position establishing a state that the side upstream of the directional control valve in said third circuit is connected to said first circuit through a first throttle, the side upstream of the directional control valve in said third circuit is connected to said second circuit through a second throttle, and the side downstream of the directional control valve in said third circuit is connected to said first circuit.

9. The hydraulic circuit according to claim 8, further comprising sub-valves operating in interlock with the directional control valves in said first circuit and said second circuit, said sub-valves generating a pilot pressure for shifting said merging valve to said shift position.

10. The hydraulic circuit according to claim 9, further comprising detecting means disposed in a line for said pilot pressure, said detecting means detecting a state of operation of the corresponding actuator.

11. A hydraulic circuit for use in a traveling construction machine including actuators driven by pressure oil supplied from a hydraulic pump under a pressurized state and returned to a tank, and provided with a safety device for informing surroundings of the fact the construction machine is traveling, the hydraulic circuit comprising:

a travel control valve for controlling connection between said hydraulic pump or said tank and a travel actuator of said actuators and a flow rate of the pressure oil therebetween; and

a travel signal hydraulic line for generating a travel signal upon operation of said travel control valve,

said safety device being operated in accordance with a state of said travel signal hydraulic line.

12. A hydraulic circuit for use in a construction machine having an auto-idle function of controlling a rotational speed of a driving source for a hydraulic pump depending on a state of operation of each of actuators driven by pressure oil supplied from said hydraulic pump under a pressurized state and returned to a tank, the hydraulic circuit comprising:

a travel control valve for controlling connection between said hydraulic pump or said tank and a travel actuator of said actuators and a flow rate of the pressure oil therebetween;

another control valve for controlling connection between said hydraulic pump or said tank and other one of said actuators than said travel actuator and a flow rate of the pressure oil therebetween;

a travel signal hydraulic line for generating a travel signal upon operation of said travel control valve; and

an auto-idle signal hydraulic line for generating an auto-idle signal upon operation of said other control valve,

the rotational speed of said driving source being controlled in accordance with a state of said travel signal hydraulic line and a state of said auto-idle signal hydraulic line.