JP2000073409A - Hydraulic circuit for construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent running bend caused by variations in motion of a divided flow control spool valve inside a pressure compensation type flow dividing valve in a construction machine. SOLUTION: A pressure compensation type flow dividing valve 33 is provided between first pump 2, second pump 3 and left traveling circuit 31, right traveling circuit 32, independent attachment circuit 7. Then, a divided flow control spool valve 34 built in the pressure compensation type valve 33 is constituted of inside oil paths 36 and 38 with an opening characteristic equivalent to the flow rate of hydraulic fluid diverging to the independent attachment circuit 7 from the first pump 2 and the flow rate of hydraulic fluid simultaneously diverging to the independent attachment circuit 7 from the second pump 3, and it is constituted of inside oil lines 35 and 37 with an opening characteristic equivalent to the flow rate of hydraulic fluid diverging to the left traveling circuit 31 from the first pump 2 and the flow rate of hydraulic fluid simultaneously diverging to the right traveling circuit 32 from the second pump 3.

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 such as a hydraulic shovel.

[0002]

2. Description of the Related Art FIG. 2 shows an example of an independent attachment circuit using a pressure-compensating type flow dividing valve in a conventional two-pump hydraulic excavator.

Each of the discharge oils discharged from the first pump 2 and the second pump 3 driven by the vehicle-mounted engine 1 is supplied to a pressure-compensation-type flow dividing valve (hereinafter, this pressure-compensation-type flow dividing valve is simply referred to as a "flow dividing valve"). 4, it is divided and supplied to two main control valves 5 and 6 and an independent attachment circuit 7.

The main control valves 5 and 6 are provided with various types of spools for controlling hydraulic motors or hydraulic cylinders of a traveling system, a turning system and a working machine system of a hydraulic shovel. The main control valve 6 includes a right traveling spool 6a that controls the right traveling motor that drives the right crawler belt.

A hydraulic circuit for controlling the left traveling motor by the left traveling spool 5a and controlling the right traveling motor by the right traveling spool 6a is referred to as a traveling circuit.

On the other hand, the independent attachment circuit 7 is a hydraulic circuit for controlling hydraulic oil supplied to an attachment such as a hydraulic breaker or a crusher mounted in place of a bucket at the tip of the working machine system. Including valve.

The pressure compensating type flow dividing valve 4 includes two flow dividing control spool valves, that is, a flow dividing control spool valve 8 for a first pump and a flow dividing control spool valve 9 for a second pump, and two pressure compensating valves, that is, a first pressure compensating valve. It comprises a pressure compensating valve 11 for the pump and a pressure compensating valve 12 for the second pump. The hydraulic oil discharged from each of the pumps 2 and 3 is diverted by the diversion control spool valves 8 and 9, , 12 and check valve 13,
After joining through 14, it is supplied to the independent attachment circuit 7.

For example, one of the split control spool valves 8 is
Spool spring 15 by pilot pressure from Pi port
3. The hydraulic oil flow from the P1 port connected to the first pump 2 to the A1 port is freely controlled by the opening characteristics of the spool stroke and the opening area as shown in FIG. .

When no pilot pressure is applied to the Pi port, the entire flow flows from the P1 port to the B1 port.

Next, in the pressure compensating valve 11, oil pressures from the A1 port and the B1 port are introduced into both ends of the spool urged by the spring 16 through oil passages 17 and 18, respectively. A1 'port and B1' port, while compensating the hydraulic pressure supplied from port B1 and port B1.
That is, it is supplied to the independent attachment circuit 7 and the left traveling main control valve 5.

Now, assume that the oil pressures of the A1 port and the B1 port are PA1 and PB1, respectively, the opening degree of the variable throttle portion 19 of the diversion control spool valve 8 (FIG. 3) is Ax, and the hydraulic oil flow from the P1 port to the A1 port. Is QA1, the following equation (1) holds.

QA1 = K · Ax · (PB1−PA1) ^1/2 (1) (where K is a constant) By the way, when the differential pressure (PB1−PA1) becomes a constant differential pressure ΔP Is switched from the position 21 to the position 22 against the urging force of the spring 16, and the position is switched to the position 23 when the differential pressure is further increased.
Is in the position 24, (PB1-PA1) >>. DELTA.P, the pressure compensating valve 11 is in the position 23, and the entire flow rate flows to the PB1 'port side.

On the other hand, when the flow control spool valve 8 is at the position 25 or the position 26, if the pressure PB1 'at the port B1'> the pressure PA1 'at the port A1', a large amount of oil tends to flow to the port A1 '. However, at this time, if the differential pressure (PB1-PA1) becomes larger than ΔP, the pressure compensating valve 11 shifts to the position 23,
That is, the hydraulic fluid is shifted in the direction of restricting the flow rate of the hydraulic oil to the port A1 '.

Conversely, when PB1 '<PA1', a large amount of oil tends to flow to the port B1 ', but at this time, the differential pressure (PB1
When −PA1) becomes smaller than ΔP, the pressure compensating valve 11 shifts toward the position 21 by the urging force of the spring 16, that is, B1 ′.
Shift in the direction to regulate the hydraulic oil flow to the port side.

That is, the pressure compensating valve 11 is connected to the differential pressure (PB1−
PA1) is maintained at a constant value (ΔP).

Therefore, regardless of the pressure PA1 'at the A1' port and the pressure PB1 'at the B1' port, the differential pressure (PB1
−PA1) is constant, so from equation (1), the variable aperture
The flow rate QA1 corresponding to the opening degree Ax of 19 is supplied to the A1 'port, that is, the independent attachment circuit 7.

Since the operating principle of the right-flow split flow control spool valve 9 and the pressure compensating valve 12 is the same as that of the left running split flow control spool valve 8 and the pressure compensating valve 11, P1
Port is P2 port, A1 port is A2 port, B
By replacing 1 port with B2 port, A1 'port with A2' port, and B1 'port with B2' port,
The description is omitted.

In FIG. 2, the flow control spool valves 8, 9
Have the same design with the same opening characteristics shown in FIG. 3 and are controlled by the same pilot pressure at the Pi port, so that the same hydraulic fluid flow rate is always equal to that of each of the first pump 2 and the second pump 3. The flow is divided so as to prevent the traveling bend caused by the difference in the amount of oil supplied to the left and right traveling spools 5a and 6a due to the difference in the divided flow from the pumps 2 and 3.

[0019]

However, the same pilot pressure supplied from the Pi port is applied to both of the flow dividing control spool valves 8 and 9 due to the external force acting on the flow dividing control spool valves 8 and 9, ie, the influence of sliding resistance and fluid force. , 9 may be moved differently even if they are simultaneously loaded on the left and right spools.
There is a possibility that a difference occurs in the flow rate of the working oil supplied to the 5a and the right traveling spool 6a, and the traveling may be bent.

Further, since there are two flow dividing control spool valves 8 and 9, there is also a problem that the flow dividing valve 4 becomes large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a pressure circuit in a construction machine in which first and second pumps and a travel circuit and an attachment circuit are connected via a pressure-compensation type flow dividing valve. It is an object of the present invention to prevent running bending due to variation in the movement of a conventional separately provided flow dividing control spool valve in a compensation type flow dividing valve, and to make the pressure compensated flow dividing valve compact.

[0022]

According to the present invention, a first pump and a second pump mounted on a construction machine and a hydraulic oil supplied from the first pump and the second pump are controlled to be provided on the construction machine. A left traveling circuit and a right traveling circuit for driving the left and right traveling systems, an attachment circuit for controlling hydraulic oil supplied from the first pump and the second pump to drive an attachment provided on the construction machine, A pressure-compensation-type flow-dividing valve for pressure-compensating the hydraulic oil flow divided from the pump to the left traveling circuit and the attachment circuit and the hydraulic oil flow to the right traveling circuit and the attachment circuit from the second pump, respectively; An opening in which the flow rate of hydraulic oil incorporated in the valve and diverted from the first pump to the left traveling circuit and the flow rate of hydraulic oil simultaneously diverted from the second pump to the right traveling circuit are equal. A hydraulic circuit for a construction machine equipped with a with a shunt control spool valve formed with internal oil passage characteristics.

Thus, even if any external force is applied to the flow dividing control spool valve, the same flow of hydraulic oil is always supplied to the left running circuit and the right running circuit from the split flow controlling spool valve. There is no running bending due to variations in the movement of the vehicle. In addition, the pressure-compensating flow dividing valve is made compact by combining the flow dividing control spool valves from the conventional two into one.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in FIG. The same parts as those in the conventional example shown in FIG. 2 are denoted by the same reference numerals, and the description thereof may be omitted.

In FIG. 1, a first pump 2 driven by an engine 1 mounted on a hydraulic excavator as a construction machine
A pressure-compensated flow dividing valve 33 is provided between the second pump 3 and the left traveling circuit 31, the right traveling circuit 32, and the independent attachment circuit 7.

The left traveling circuit 31 includes a left traveling spool 5a of the main control valve 5 for controlling the hydraulic oil supplied from the first pump 2, and the right traveling circuit 32 is supplied from the second pump 3. It includes a right traveling spool 6a of a main control valve 6 for controlling hydraulic oil, and drives hydraulic motors (not shown) of left and right crawler type traveling systems provided on a hydraulic excavator by these controlled hydraulic oils.

The independent attachment circuit 7 includes an attachment control valve (not shown) for controlling the hydraulic oil supplied from the first pump 2 and the second pump 3, and is controlled by the hydraulic oil controlled by the control valve. In addition, an attachment such as a hydraulic breaker or a crusher mounted in place of a bucket at the tip of the front working machine of the hydraulic shovel is driven.

The pressure compensating type flow dividing valve 33 is connected to the first pump 2
From the second pump 3 to the right traveling circuit 32 and the independent attachment circuit 7 while compensating the hydraulic oil flow diverted from the second pump 3 to the left traveling circuit 31 and the independent attachment circuit 7.
And pressure compensation for the flow rate of the hydraulic oil diverted to the diverter control spool valve 34, and the differential pressure (PB1-PA) at the B1 port and the A1 port of the diverter control spool valve 34.
1), a pressure compensating valve 11 for keeping a constant value, a pressure compensating valve 12 for keeping a differential pressure (PB2-PA2) at a B2 port and an A2 port at a constant value, and a pressure compensating valve 11,
Non-return valves 13 and 14 provided in an output circuit from 12 to the independent attachment circuit 7 are incorporated.

The one diversion control spool valve 34 incorporated in the pressure compensation type diversion valve 33 has an internal oil passage 35 for hydraulic oil diverted from the first pump 2 to the left traveling circuit 31 and an independent attachment circuit 7. An internal oil passage 36 for the diverted hydraulic oil,
An internal oil passage 37 for the hydraulic oil diverted from the second pump 3 to the right traveling circuit 32 and an internal oil passage 38 for the hydraulic oil diverted to the independent attachment circuit 7 are formed.

The internal oil passage 36 of the split control spool valve 34
Reference numeral 38 designates an opening characteristic in which the flow rate of the hydraulic oil shunted from the first pump 2 to the independent attachment circuit 7 and the flow rate of the hydraulic oil shunted simultaneously from the second pump 3 to the independent attachment circuit 7 are equalized. The passages 35 and 37 have an opening characteristic in which the flow rate of hydraulic oil diverted from the first pump 2 to the left traveling circuit 31 is equal to the flow rate of hydraulic oil diverted from the second pump 3 to the right traveling circuit 32 at the same time.

As shown in FIG. 3, variable throttle portions 39 and 40 which change according to the spool stroke are provided in the internal oil passages 36 and 38 of the hydraulic oil diverted to the independent attachment circuit 7.

The diversion control spool valve 34 receives the biasing force of the spring 41 on one side, receives the pilot pressure introduced from the Pi port via the pilot pressure introduction passage 42 on the other side, and applies a pressing force by this pilot pressure. The spool stroke is controlled at the equilibrium point between the spring stroke and the repulsive force of the spring 41.

That is, the smaller the pilot pressure of the Pi port is, the more the diversion control spool valve 34 is closer to the position 43,
As the pilot pressure at the Pi port increases, the diversion control spool valve 34 shifts to the position 45 via the position 44, and
39, 40 opening changes. FIG. 1 also shows that the drain oil passage 46 drawn from the control spool valve 34 is communicated with the tank 47.

In short, the feature of the hydraulic circuit shown in FIG. 1 is that the conventional two flow dividing control spool valves 8 and 9 shown in FIG. The function of the diversion control spool valve 34 is the same as that of the conventional diversion control spool valves 8 and 9.

Next, the operation of the embodiment shown in FIG. 1 will be described.

The integrated diversion control spool valve 34 allows two diversion control spool valves 8, 9 in the prior art.
The vehicle does not bend due to the difference in movement due to the external force acting on the vehicle.

That is, no matter what external force acts on the diversion control spool valve 34 to affect its movement, P1
Since the opening characteristic communicating from the port to the A1 port via the internal oil passage 36 and the opening characteristic communicating from the P2 port to the A2 port via the internal oil passage 38 are always the same, the operating principle described in the description of the prior art is used. As a result, the equally divided hydraulic oil flow is always supplied to the A1 'port and the A2' port, and at the same time, the equally divided hydraulic oil flow is also supplied to the B1 'and B2' ports. For this reason, the left traveling spool 5a
Since the flow rate of the hydraulic oil supplied to the right traveling spool 6a is always the same, the flow rate of the hydraulic oil supplied to the left traveling motor and the right traveling motor is always the same, so that no traveling bending occurs.

Further, since the two flow dividing control spool valves 8 and 9 in the prior art are one divided flow controlling spool valve 34, space can be saved, and the size of the pressure-compensation type flow dividing valve 33 is made smaller than in the prior art. be able to.

As described above, the right and left traveling circuits 31, 32 are provided by using the pressure-compensating flow dividing valve 33 in the two-pump hydraulic excavator.
And in a hydraulic circuit for supplying hydraulic oil to the independent attachment circuit 7, by means of a diversion control spool valve 34 in which a conventional diversion control spool valve 8 for the first pump and a diversion control spool valve 9 for the second pump are integrated. , It is possible to prevent running bending due to variation in the movement of the split control spool valves 8 and 9,
In addition, the pressure-compensating flow dividing valve 33 can be made compact.

[0040]

According to the present invention, the same hydraulic oil flow rate can always be supplied to the left traveling circuit and the right traveling circuit regardless of any external force applied to the flow dividing control spool valve. In addition to preventing running bending due to movement variation, the size of the pressure compensation type flow dividing valve can be made compact by changing the flow dividing control spool valve from the conventional two to one.

[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 circuit diagram showing a hydraulic circuit of a conventional construction machine.

FIG. 3 is a characteristic diagram showing an opening characteristic of a spool stroke and an opening area of a flow dividing control spool valve in the hydraulic circuit.

[Explanation of symbols]

 2 1st pump 3 2nd pump 7 Attachment circuit 31 Left traveling circuit 32 Right traveling circuit 33 Pressure compensation type diversion valve 34 Diversion control spool valve 35,36 Internal oil passage 37,38 Internal oil passage

Claims (1)

[Claims] 1. A first pump and a second pump mounted on a construction machine, and a hydraulic oil supplied from the first pump and the second pump are controlled to drive left and right traveling systems provided on the construction machine. A left traveling circuit and a right traveling circuit, an attachment circuit for controlling hydraulic oil supplied from the first pump and the second pump to drive an attachment provided on the construction machine, and a left traveling circuit and an attachment circuit from the first pump. Compensating type flow dividing valve for pressure-compensating the hydraulic oil flow divided into the hydraulic pump and the hydraulic oil flow divided from the second pump to the right traveling circuit and the attachment circuit, respectively; An internal oil passage having an opening characteristic is formed in which the flow rate of hydraulic oil diverted to the left traveling circuit and the flow rate of hydraulic oil simultaneously diverted from the second pump to the right traveling circuit are equal. A hydraulic circuit for a construction machine, comprising: a single flow control spool valve.