JP2002089511A - Hydraulic circuit for construction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent extreme speed down of a main body side actuator by supplying sufficient hydraulic fluid flow amount to the main body actuator even when a pressure of an attachment circuit of a hydraulic excavator gets close to a relief pressure. SOLUTION: In an interlocking operation of an attachment of a hydraulic excavator and other main body side actuator, when pressure of an independent attachment circuit 37 controlling an attachment gets close to a relief pressure, a controller 71 detecting pressure increase condition thereof by a pressure sensor 66 switches an electromagnetic selector valve 68 to a passage connection condition and prioritized flow amount dividing from a pressure correction type flow divider valve 38 to an external passage 67 flows out to a tank 39 via the electromagnetic selector valve 68. A pump 33 increases discharge flow amount in proportion as discharge pressure decreases, much fluid flow is supplied to the main body side actuator main circuit 36 from an independent attachment circuit 37 to prevent an extreme delay of speed of main body side actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a construction machine having a pressure-compensating flow dividing valve.

[0002]

2. Description of the Related Art As shown in FIG. 3, a hydraulic circuit of a construction machine disclosed in Japanese Patent Application Laid-Open No. 2000-73409 has a first pump 2 and a second pump 2 driven by an engine 1 mounted on a hydraulic shovel. Two pumps 3 and a left running circuit 5,
Between the right traveling circuit 6 and the independent attachment circuit 7, a pressure-compensated flow dividing valve 8 is provided.

The left traveling circuit 5 includes a left traveling control spool 11a of a main control valve 11 for controlling hydraulic oil supplied from the first pump 2, and the right traveling circuit 6
Includes a right traveling control spool 12a of a main control valve 12 for controlling the hydraulic oil supplied from the second pump 3, and a left and right crawler type traveling system provided on the hydraulic excavator by the controlled hydraulic oil. Hydraulic motor (not shown)
Drive.

The independent attachment circuit 7 includes an attachment control valve (not shown) for controlling hydraulic oil supplied from the first pump 2 and the second pump 3.
The hydraulic oil controlled by the control valve drives an attachment such as a hydraulic breaker or a crusher attached to the tip of the front working machine of the hydraulic shovel instead of a bucket.

The pressure compensating type flow dividing valve 8 pressure-compensates the flow rate of the hydraulic oil diverted from the first pump 2 to the left traveling circuit 5 and the independent attachment circuit 7 during the interlocking operation of the attachment and traveling, and performs the second operation. Pressure compensating for the flow rate of the hydraulic oil diverted from the pump 3 to the right traveling circuit 6 and the independent attachment circuit 7,
13 and the B1 port and A of the split control spool valve 13.
One pressure compensating valve 14 for keeping the differential pressure (PB1-PA1) at one port at a constant value, the other pressure compensating valve 15 for keeping the differential pressure (PB2-PA2) at the B2 port and the A2 port at a constant value, Non-return valves 16 and 17 provided in the output circuit from the pressure compensating valves 14 and 15 to the independent attachment circuit 7 are built in.

[0006] The diversion control spool valve 13 is connected to the first pump 2.
And internal oil passages 21 and 22 having opening characteristics in which the flow rate of hydraulic oil diverted from the second pump 3 to the right travel circuit 6 is equal to the flow rate of hydraulic oil diverted from the second pump 3 to the right travel circuit 6. The internal oil passages 23 and 24 have opening characteristics in which the flow rate of hydraulic oil shunted from the first pump 2 to the independent attachment circuit 7 and the flow rate of hydraulic oil shunted simultaneously from the second pump 3 to the independent attachment circuit 7 are equal.

As a result, the pressure-compensating type flow dividing valve 8 is operated by the flow dividing control spool valve 13 when the attachment and the traveling are interlocked.
Can be supplied equally to the left traveling circuit 5 and the right traveling circuit 6 at any position, and the traveling bend can be prevented.

[0008]

Generally, a hydraulic pump mounted on a hydraulic excavator has a pump discharge flow rate and a discharge pressure limit diagram (hereinafter a PQ diagram and a PQ diagram) determined by the engine horsepower as shown in FIG. This is set so that the discharge flow rate decreases as the pressure increases.

In the independent attachment circuit 7 in the prior art shown in FIG. 3, the operation of the pressure compensating valves 14 and 15 allows the flow control spool valve 13 to be operated independently of the circuit pressure.
Since the flow rate according to the opening amounts of the internal oil passages 23 and 24 is supplied to the independent attachment circuit 7, the attachment circuit pressure becomes a high pressure near the relief pressure, and the pump discharge flow rate is reduced according to the PQ diagram of FIG. When the opening amount of the internal oil passages 23 and 24 of the diversion control spool valve 13 is considerably open when
Almost all of the pump discharge flow rate flows to the independent attachment circuit 7, and the hydraulic oil does not flow to the main body side actuator such as the traveling hydraulic motor.

For this reason, in the interlocking operation between the attachment and the main body side actuator such as a traveling hydraulic motor, the speed of the main body side actuator becomes extremely slow as soon as the attachment circuit pressure becomes close to the relief pressure. There's a problem.

The present invention has been made in view of the above points, and in a hydraulic circuit of a construction machine having a pressure-compensation type flow dividing valve, when an attachment and a main body side actuator are operated in conjunction with each other, the attachment circuit pressure is reduced. It is an object of the present invention to supply a sufficient hydraulic oil flow rate to the main body-side actuator even when the pressure becomes close to the relief pressure, thereby preventing an extremely low speed of the main body-side actuator.

[0012]

According to the first aspect of the present invention, a hydraulic oil pumped from a tank by a pump mounted on a construction machine is controlled and supplied to a main body-side actuator provided on the construction machine. A main circuit, an attachment circuit that controls the hydraulic oil pumped from the tank by the pump and supplies it to an attachment provided on the construction machine, and a pressure that pressure-compensates the hydraulic oil flow divided from the pump to the main circuit and the attachment circuit. A compensating type flow dividing valve, an external passage for returning hydraulic oil supplied from the pressure compensating type flow dividing valve to the attachment circuit to the tank, and an attachment circuit pressure interposed in the external passage and relief of the attachment circuit pressure during an interlocking operation between the attachment and the main body side actuator. A switching valve that switches from the passage blocking position to the passage communication position when the pressure rises to near the pressure. It is a hydraulic circuit of the setting machine.

In the interlocking operation of the attachment and the main body side actuator, when the attachment circuit pressure becomes close to the relief pressure, the priority flow branched from the pressure compensating type flow dividing valve to the external passage flows to the tank via the switching valve. As a result, the discharge flow rate of the pump increases, and a large flow rate is supplied to the main body side actuator.In the interlocking operation between the attachment and the main body side actuator, as soon as the attachment circuit pressure becomes close to the relief pressure, the main body The speed of the side actuator does not become extremely slow.

According to a second aspect of the present invention, a pump in a hydraulic circuit of a construction machine according to the first aspect includes a first pump and a second pump, and the main circuit includes a hydraulic pressure for the left running of the body. A first main circuit including a left traveling control spool for controlling a motor and a second main circuit including a right traveling control spool for controlling a right traveling hydraulic motor of the fuselage; The hydraulic oil flow supplied from the first pump to the first main circuit and the attachment circuit and the hydraulic oil flow supplied from the second pump to the second main circuit and the attachment circuit during the interlocking operation of the attachment and the traveling Includes a single split control spool valve that is equally controlled.

Since the flow rate of the hydraulic oil supplied to the first main circuit and the second main circuit by the pressure-compensating flow dividing valve at the time of the interlocking operation of the attachment and the traveling is always the same, the left of the first main circuit is The hydraulic oil flow supplied from the traveling control spool to the left traveling hydraulic motor is always the same as the hydraulic oil flow supplied from the right traveling control spool of the second main circuit to the right traveling hydraulic motor. The bending of the machine can be prevented.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an example of a hydraulic circuit, in which a first pump 32 and a second pump 33 driven by an engine 31 mounted on a hydraulic shovel as a construction machine,
A pressure-compensation-type flow dividing valve 38 is provided between the main circuit 35, the second main circuit 36, and an independent attachment circuit 37 as an attachment circuit provided independently of these. First pump 32 and second pump 33
Uses the hydraulic oil pumped from the tank 39 as a pressure compensation type
It is supplied to each circuit 35, 36, 37 via 38.

The first main circuit 35 includes a first pump
A main control valve 41 for controlling the hydraulic oil supplied from the second main circuit 32;
A main control valve 42 for controlling the hydraulic oil supplied from 33 is included.

These main control valves 41 and 42 are
The hydraulic oil supplied from the pumps 32 and 33 via the pressure-compensation type flow dividing valve 38 is subjected to directional control and flow control to be supplied to a main body-side actuator provided in the hydraulic shovel.

The main body side actuator includes a left traveling hydraulic motor for driving the left crawler belt provided on the lower traveling body, a right traveling hydraulic motor for driving the right crawler belt,
A hydraulic motor for turning for rotating the upper revolving structure relative to the lower traveling structure, a boom for a front work machine installed on the upper revolving structure, a hydraulic cylinder for boom for driving an arm and a bucket, a hydraulic cylinder for arm, and This is a bucket hydraulic cylinder.

The main control valve 41 of the first main circuit 35 includes a left running control spool for controlling the left running hydraulic motor of the machine, and the main control valve 42 of the second main circuit 36 is And a main control valve 41, 42 for controlling a turning hydraulic motor and a boom hydraulic cylinder. It includes a boom control spool, an arm control spool that controls an arm hydraulic cylinder, and a bucket control spool that controls a bucket hydraulic cylinder.

The independent attachment circuit 37 includes an attachment control valve (not shown) for controlling hydraulic oil supplied from the first pump 32 and the second pump 33.
The hydraulic oil controlled by the spool of the attachment control valve drives an attachment such as a hydraulic breaker or a crusher mounted in place of a bucket at the tip of a front working machine of a hydraulic shovel.

The pressure-compensating type flow dividing valve 38 pressure-compensates the hydraulic oil flow divided from the first pump 32 to the first main circuit 35 and the independent attachment circuit 37 during the interlocking operation between the attachment and the traveling. The second main circuit 36 and the independent attachment circuit 37 from the second pump 33
And pressure compensation of the flow rate of the hydraulic oil diverted to the diverter control spool valve 43, and the differential pressure (PB1-PA) at the B1 port and the A1 port of the diverter control spool valve 43.
1), a pressure compensating valve 44 for keeping the differential pressure (PB2-PA2) at the B2 port and A2 port at a constant value, and a pressure compensating valve 45 for keeping the differential pressure (PB2-PA2) at a constant value.
And check valves 46 and 47 provided in an output circuit to an independent attachment circuit 37 from the control circuit.

The single flow dividing control spool valve 43 built in the pressure compensating type flow dividing valve 38 has an internal oil passage 51 for hydraulic oil diverted from the first pump 32 to the first main circuit 35, and The internal oil passage 52 of the hydraulic oil diverted to the independent attachment circuit 37, the operation diverted to the internal oil passage 53 of the hydraulic oil diverted from the second pump 33 to the second main circuit 36, and the independent attachment circuit 37 An internal oil passage 54 for oil is formed.

The internal oil passages 51,
The opening characteristic 53 is such that the flow rate of hydraulic oil diverted from the first pump 32 to the first main circuit 35 is equal to the flow rate of hydraulic oil diverted from the second pump 33 to the second main circuit 36 at the same time. And the internal oil passages 52 and 54 are connected to the first pump 32
The opening characteristic is such that the flow rate of the hydraulic oil diverted from the second pump 33 to the independent attachment circuit 37 is equal to the flow rate of the hydraulic oil diverted from the second pump 33 to the independent attachment circuit 37 at the same time.

That is, the split control spool valve 43 is
Control of the flow rate of hydraulic oil supplied from the pump 32 to the first main circuit 35 and the attachment circuit 37 and the flow rate of hydraulic oil supplied to the second main circuit 36 and the attachment circuit 37 from the second pump 33 Is what you do.

In the internal oil passages 52 and 54 for the hydraulic oil diverted to the independent attachment circuit 37, there are provided variable throttle portions 55 and 56 which change according to the spool stroke.

The diversion control spool valve 43 receives the biasing force of the spring 57 on one side, receives the pilot pressure introduced from the Pi port via the pilot pressure introduction path 58 on the other side, and applies a pressing force by the pilot pressure. The spool stroke is controlled at the equilibrium point between the spring stroke and the repulsive force of the spring 57.

That is, the smaller the pilot pressure of the Pi port is, the more the diversion control spool valve 43 is closer to the position 61,
As the pilot pressure at the Pi port increases, the diversion control spool valve 43 shifts to the position 63 via the position 62, and
It changes so that the opening degree of 55 and 56 becomes large. The drain oil passage 64 drawn from the flow dividing control spool valve 43 is communicated with the tank 39.

A pressure sensor 66 is attached to an independent attachment passage 65 for supplying hydraulic oil to the independent attachment circuit 37, and a pressure sensor 66 between the pressure compensating valve 45 and the check valve 47 in the pressure compensating type flow dividing valve 38. The outside passage 67 is branched out from the priority passage.

An electromagnetic switching valve 68 as a switching valve is interposed in the external passage 67, and is connected to the tank 39 via the electromagnetic switching valve 68.

When the circuit pressure of the independent attachment circuit 37, that is, the attachment circuit pressure rises to near the relief pressure during the interlocking operation between the attachment and the main body side actuator, the electromagnetic switching valve 68 is shut off by a solenoid that is energized. This is a switching valve that switches from the position to the passage communication position.

When the electromagnetic switching valve 68 switches to the passage communicating position, the external passage 67 can return the hydraulic oil supplied from the pressure compensation type flow dividing valve 38 to the independent attachment circuit 37 to the tank 39.

The pressure sensor 66 is connected to an input terminal of a controller 71, and the electromagnetic switching valve 68 is connected to an output terminal of the controller 71.

The controller 71 outputs an independent attachment circuit based on an output signal corresponding to a lever signal input from an attachment operating device 72 such as an electric joystick.
The main control valves 41 and 42 for controlling the displacement of the spool of the control valve 37 and controlling the main body actuator by an output signal corresponding to a lever signal input from a main body actuator actuator 73 such as an electric joystick. Displacement control of various spools.

The controller 71 simultaneously operates the attachment operating device 72 and the main body actuator operating device 73 so that these electric signals enter the controller 71 at the same time, and the independent attachment passage 65 has a pressure close to the relief pressure. When the controller 71 sends a switching electric signal to the solenoid of the electromagnetic switching valve 68 only when a signal is input from the pressure sensor 66 to the controller 71, the electromagnetic switching valve 68 is switched to the passage communication state. The flow diverted from the pump 33 to the passage 76 flows out to the tank 39 through the external passage 67.

A bypass passage 74 is provided between the left main control valve 41 and the right main control valve 42, and a bypass valve 75 is provided in the bypass passage 74. The bypass valve 75 simultaneously operates the attachment operation device 72 and the main body-side actuator operation device 73, and outputs the electric signal output from the controller 71 only when a pressure close to the relief pressure is established in the independent attachment passage 65. The signal is received by the solenoid to switch from the passage blocking state to the passage communicating state, and the bypass passage 74 is communicated.

Next, the operation and effect of the embodiment shown in FIG. 1 will be described with reference to FIG.

Whatever external force acts on the diversion control spool valve 43 to affect its movement, the opening characteristic communicating from the P1 port to the A1 port via the internal oil passage 52,
Since the opening characteristics communicating from the 2 port to the A2 port via the internal oil passage 54 are always the same, the hydraulic oil flow divided equally is always equal to the A11 port and A22 of the pressure compensating valves 44 and 45.
Supplied to port.

The flow rate is always equally divided from the first pump 32 and the second pump 33 to the independent attachment circuit 37 by the pressure-compensating flow dividing valve 38 during the interlocking operation of the attachment and the traveling. Since the hydraulic oil flow supplied to the first main circuit 35 and the second main circuit 36 is always the same, for example, the first main control valve
The hydraulic oil flow supplied from the left travel control spool 41 to the left travel hydraulic motor and the second main control valve 42
, The flow rate of the hydraulic oil supplied from the right travel control spool to the right travel hydraulic motor is always the same, so that traveling bending can be prevented.

When the independent attachment operation device 72 and the main body actuator 73 are simultaneously operated to operate the attachment and the main body actuator in an interlocked manner, the circuit pressure of the independent attachment circuit 37 becomes lower than the relief pressure. When approaching, the pressure sensor 66 detects the pressure increase state and inputs the detected pressure increase state to the controller 71.

At this time, the controller 71 operates as an electromagnetic switching valve.
An operation signal is output to the solenoid valve 68, and the electromagnetic switching valve 68 is
67 is switched to a passage communication state communicating with the tank 39. As a result, the priority flow branched from the priority passage on the second pump 33 side of the pressure-compensation type flow dividing valve 38 to the external passage 67 is changed by the electromagnetic switching valve.
By flowing to tank 39 via 68, the second pump
Since the pump discharge pressure of the pump 33 decreases and the point of the second pump 33 on the PQ diagram in FIG. 2 moves from the point Pa to the point Pb, the discharge flow rate from the second pump 33 increases.

At the same time, due to the pressure drop in the passage 76, the pressure compensating valve 45 is displaced to the right in FIG. 1 to reduce the distribution flow rate to the independent attachment circuit 37 and to reduce the flow rate of the main circuit 36.
Main control valve 42 to increase the
The main body actuator has been supplied with a much higher flow rate than the conventional technology, and the circuit pressure of the independent attachment circuit 37 has become close to the relief pressure in the interlocking operation of the attachment and the main body actuator. Suddenly, the speed of the main body side actuator does not become extremely low.

The fact that the attachment circuit pressure is close to the relief pressure means that the attachment is close to the stall state. It is sufficient if there is sufficient oil to maintain the circuit pressure. Even if the flow rate flows to the tank 39, there is no practical problem, and it can be said that the present invention makes sense.

In FIG. 1, when the attachment circuit pressure becomes close to the relief pressure, the flow rate of the actuator on the main body side to the main control valve 42 side dramatically increases as compared with the prior art. Flow rate remains low as in the prior art, and a flow rate difference occurs as it is.

Therefore, the actuator speed on the side of the main control valve 42 increases, but the main control valve 41
The side actuator speed remains slow. At this time,
For example, when the main control valves 41 and 42 are each provided with a traveling spool, a flow difference occurs between the left and right sides, and the traveling bend occurs.

The bypass valve 75 supplies the oil on the right traveling spool side of the main control valve 42 to the left traveling spool side of the main control valve 41 to balance the flow rate, thereby preventing traveling bending. it can. Further, the flow rate of the main control valve 42 is also supplied to the other actuators of the main control valve 41 via the bypass valve 75, so that the speed can be increased as compared with the related art.

In the above description, the case where the external passage 67 is drawn out from the priority passage on the side of the second pump 33 has been described as an example. Similarly, the pressure compensation valve 44 on the side of the first pump 32 is An external passage may be drawn out from the priority passage between the check valve 46 and connected to the electromagnetic switching valve 68.

[0049]

According to the first aspect of the present invention, in the interlocking operation of the attachment and the main body side actuator,
When the attachment circuit pressure approaches the relief pressure,
The priority flow branched from the pressure-compensation type flow dividing valve to the external passage flows to the tank via the switching valve, so that the discharge flow rate of the pump increases and a large amount of flow is supplied to the main body side actuator. In the interlocking operation with the side actuator, the problem that the speed of the main body side actuator becomes extremely low as soon as the attachment circuit pressure becomes close to the relief pressure can be solved, and the workability can be improved.

According to the second aspect of the present invention, the pressure compensation type flow dividing valve is used for the first operation during the interlocking operation between the attachment and the traveling.
Since the flow rate of hydraulic oil supplied to the main circuit and the second main circuit is always the same, the flow rate of hydraulic oil supplied to the left travel hydraulic motor from the left travel control spool of the first main circuit The flow rate of the hydraulic oil supplied from the right travel control spool of the second main circuit to the right travel hydraulic motor is always the same, and the travel of the construction machine can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a hydraulic circuit of a construction machine according to the present invention.

FIG. 2 is a PQ diagram showing pump discharge pressure-discharge flow characteristics.

FIG. 3 is a circuit diagram showing a hydraulic circuit of a conventional construction machine.

[Explanation of symbols]

32 First Pump 33 Second Pump 35 First Main Circuit 36 Second Main Circuit 37 Independent Attachment Circuit as Attachment Circuit 38 Pressure Compensated Dividing Valve 39 Tank 43 Dividing Control Spool Valve 67 External Passage 68 As Switching Valve Solenoid switching valve

Claims (2)

[Claims] 1. A main circuit for controlling hydraulic oil pumped from a tank by a pump mounted on a construction machine to supply the main body actuator provided on the construction machine with hydraulic oil pumped from the tank by the pump. Attachment circuit that controls and supplies to the attachments provided on the construction machine, pressure-compensated flow-dividing valve that pressure-compensates the hydraulic oil flow diverted from the pump to the main circuit and attachment circuit, and pressure-compensated flow-dividing valve to the attachment circuit An external passage that returns the hydraulic oil supplied to the tank to the tank, and a passage communication from the passage blocking position when the attachment circuit pressure rises to near the relief pressure during the interlocking operation between the attachment and the main body side actuator that is interposed in the external passage. A hydraulic circuit for a construction machine, comprising: a switching valve that switches to a position. The pump has a first pump and a second pump, and the main circuit includes a first main circuit including a left traveling control spool for controlling a left traveling hydraulic motor of the aircraft, and a main circuit of the aircraft. A second main circuit including a right traveling control spool for controlling the right traveling hydraulic motor, wherein the pressure-compensated flow dividing valve is connected to the first pump by the first main circuit and the attachment when the attachment and traveling are interlocked. A single diversion control spool valve for equalizing the hydraulic oil flow supplied to the circuit and the hydraulic oil flow supplied from the second pump to the second main circuit and the attachment circuit. 2. A hydraulic circuit for a construction machine according to 1.