JP2009179983A - Hydraulic control circuit of working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control circuit of a working machine capable of supplying a flow rate of hydraulic fluid required by an attachment accurately and improving the interlocking relationship with the other hydraulic actuator by a simple configuration. <P>SOLUTION: In this hydraulic control circuit of the working machine provided with a first hydraulic circuit L1 connected with a hydraulic motor 26a for rotary grinding and a second hydraulic circuit L2 connected with the other hydraulic actuator 23a, a variable throttle valve 1 capable of changing opening by controlling pilot pressure is provided in the first hydraulic circuit L1, and a pressure compensation valve 2 having a pressure compensation spool for ensuring fixed flow rate of hydraulic fluid to be supplied into the hydraulic motor 26a for rotary grinding is provided between the first hydraulic circuit L1 and the second hydraulic circuit L2. A relief valve 19c for negative control is provided on a center bypass L8 on a first hydraulic circuit L1 side. This hydraulic control circuit is also provided with a fifth hydraulic circuit L5 connecting the upstream side of the relief valve 19c for negative control with a pilot port of the variable throttle valve 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic control circuit for controlling a hydraulic excavator equipped with an attachment such as a twin header or a breaker.

  Conventionally, rotary attachments such as end mills and twin headers are known as attachments attached to the front working portion of a hydraulic excavator. These rotary cutting attachments have a built-in hydraulic motor and are driven to rotate by hydraulic oil supplied from a hydraulic pump provided in the body of the hydraulic excavator. On the other hand, the front working unit such as a boom or an arm to which the rotary cutting attachment is attached also uses the same hydraulic pump as a drive source. Therefore, when the rotary cutting attachment is driven while moving the front working part, there is a bias in the distribution of the hydraulic oil supplied from the hydraulic pump, and there is a case where good interlocking cannot be obtained. In particular, in the case of a rotary cutting attachment, since the rotational speed and rotational torque required for the hydraulic motor are relatively large, a decrease in the hydraulic oil flow rate tends to directly lead to a decrease in work efficiency.

Thus, for example, as shown in Patent Document 1, a technique has been proposed in which an electromagnetic proportional priority valve is provided on a hydraulic circuit to control flow distribution. In this technique, when the rotary cutting attachment is operated, the opening degree of the priority valve is controlled so that the flow rate of hydraulic oil supplied to the rotary cutting attachment side always becomes a predetermined priority flow rate. With such a configuration, the rotary cutting attachment can be stably driven, and the working efficiency can be improved.
JP 2006-257714 A

  However, the electromagnetic proportional type priority valve has a problem that the device configuration is complicated and the cost increases. For example, in the technique disclosed in Patent Document 1, not only a variable throttle valve that adjusts a priority flow rate to the rotary cutting attachment side and a solenoid proportional valve for a priority valve that outputs a control pressure introduced to the variable throttle valve, but also a priority valve A controller that outputs a control command to the electromagnetic proportional valve is also required, and the software configuration for control is complicated.

In the technique described in Patent Document 1, there is one hydraulic motor provided on the rotary cutting supply line side, and hydraulic oil having a predetermined discharge flow rate suitable for the hydraulic motor is supplied when the rotary cutting attachment is driven alone. Control is being implemented. Such control ensures a necessary and sufficient hydraulic fluid flow rate for the rotary cutting hydraulic motor.
However, this control cannot cope with a hydraulic circuit in which a plurality of actuators are provided on the rotary cutting supply line side. That is, if there are actuators other than the hydraulic motor on the rotary cutting supply line, the flow rate required by all of them must be secured, and cannot be covered by setting a single discharge flow rate.

  The present invention has been made in view of such problems, and with a simple configuration, can accurately supply the hydraulic oil flow rate required for the attachment and improve the interlocking with other hydraulic actuators. An object of the present invention is to provide a hydraulic control circuit for a work machine.

  In order to achieve the above object, a hydraulic control circuit for a work machine according to a first aspect of the present invention includes a hydraulic motor for driving an attachment, a hydraulic actuator other than the hydraulic motor, the hydraulic motor, and the other hydraulic pressure. In a hydraulic control circuit of a work machine including a hydraulic pump that is a hydraulic drive source of an actuator, a first hydraulic circuit that connects the hydraulic motor and the hydraulic pump, and is interposed on the first hydraulic circuit, A variable throttle valve formed so that the opening degree can be changed by pilot pressure control, a second hydraulic circuit that connects the upstream side of the variable throttle valve and the other hydraulic actuator in the first hydraulic circuit, and the first hydraulic circuit Pressure compensation is provided in both the hydraulic circuit and the second hydraulic circuit, and maintains a differential pressure between the first hydraulic circuit and the second hydraulic circuit to ensure a constant flow rate of hydraulic fluid supplied to the hydraulic motor. A pressure compensation valve having a spool, and a downstream side of the variable throttle valve in the first hydraulic circuit and one end side of the pressure compensation spool are connected to increase the flow rate of hydraulic oil to the first hydraulic circuit. A third hydraulic circuit for driving the pressure compensation spool; and an upstream side of the variable throttle valve in the second hydraulic circuit and the other end side of the pressure compensation spool to connect the hydraulic oil to the second hydraulic circuit. A fourth hydraulic circuit that drives the pressure compensation spool in a direction to increase the flow rate, and a hydraulic oil flow rate and flow that is interposed downstream of the pressure compensation valve on the first hydraulic circuit and supplied to the hydraulic motor A first control valve for controlling the direction, a relief valve for negative control interposed on the center bypass of the first control valve, a center bypass between the first control valve and the relief valve for negative control, and the variable Aperture Of connecting the pilot port, is characterized in that the hydraulic pressure of the center bypass and a fifth hydraulic circuit for introducing a pilot pressure to the variable throttle valve.

According to a second aspect of the present invention, there is provided a hydraulic control circuit for a work machine according to the present invention, in addition to the configuration according to the first aspect, wherein the variable throttle valve reduces the opening degree as the pilot pressure increases, The opening degree is increased as the hydraulic pressure is lower.
A hydraulic control circuit for a work machine according to a third aspect of the present invention includes, in addition to the configuration according to the first or second aspect, a sixth hydraulic circuit that connects the third hydraulic circuit and the hydraulic oil tank, And an electromagnetic switching valve interposed on the sixth hydraulic circuit.

  According to a fourth aspect of the present invention, there is provided a hydraulic control circuit for a work machine according to the present invention, in addition to the configuration according to the third aspect, the hydraulic oil interposed on the second hydraulic circuit and supplied to the other hydraulic actuators. A second control valve for controlling a flow rate and a flow direction, a negative control circuit for guiding the hydraulic pressure downstream of the second control valve to the hydraulic pump, a second electromagnetic switching valve interposed in the negative control circuit, and the hydraulic pressure And a negative control pressure changing means for arbitrarily changing the negative control pressure introduced into the pump.

  According to a fifth aspect of the present invention, there is provided a hydraulic control circuit for a work machine according to the present invention, in addition to the configuration of the fourth aspect, a first operation detecting means for detecting an operation of the hydraulic motor by an operator, and an operator A second operation detecting means for detecting an operation to the other hydraulic actuator; a detection result of the first operation detecting means and the second operation detecting means; the electromagnetic switching valve; the second electromagnetic switching valve; And a control means for controlling the negative control pressure changing means.

  A hydraulic control circuit for a work machine according to a sixth aspect of the present invention is a hydraulic motor that drives an attachment, a hydraulic actuator other than the hydraulic motor, and a hydraulic drive source for the hydraulic motor and the other hydraulic actuator. In a hydraulic control circuit of a work machine comprising a hydraulic pump, a first hydraulic circuit that connects the hydraulic motor and the hydraulic pump, and an interposition on the first hydraulic circuit, the opening degree is controlled by pilot pressure control A variable throttle valve formed to be changeable, a second hydraulic circuit connecting the upstream side of the variable throttle valve in the first hydraulic circuit and the other hydraulic actuator, and the variable throttle on the first hydraulic circuit A first control valve interposed downstream from the valve for controlling the flow rate and flow direction of hydraulic oil supplied to the hydraulic motor, and on the center bypass of the first control valve A negative control relief valve, a center bypass between the first control valve and the negative control relief valve, and a pilot port of the variable throttle valve are connected, and the hydraulic pressure of the center bypass is changed to the variable throttle valve And a fifth hydraulic circuit to be introduced as a pilot pressure.

  According to the hydraulic control circuit for a working machine of the present invention (Claim 1), by introducing the working oil pressure of the center bypass between the first control valve and the relief valve for negative control as a pilot pressure to the variable throttle valve, The hydraulic fluid flow rate required for the first hydraulic circuit side can be accurately supplied according to the driving state of the hydraulic motor. In particular, since the hydraulic fluid flow distributed to the first hydraulic circuit increases as the hydraulic pressure of the center bypass on the first hydraulic circuit side decreases, the hydraulic circuit is provided with a plurality of actuators in the first hydraulic circuit. However, a necessary and sufficient amount of hydraulic fluid flow can be secured.

In addition, by providing the pressure compensation valve, it is possible to ensure sufficient hydraulic oil necessary for driving the rotary cutting motor, and to enhance the interlocking between the rotary cutting motor and other hydraulic actuators. Furthermore, the system configuration is simple and the cost can be reduced.
Further, according to the hydraulic control circuit for a working machine of the present invention (Claim 2), the opening of the variable throttle valve increases as the operating hydraulic pressure of the center bypass on the first hydraulic circuit side becomes lower. As the supplied hydraulic fluid flow rate increases, the hydraulic fluid flow rate distributed to the first hydraulic circuit side can be increased, and the hydraulic fluid flow rate required by the hydraulic motor can be ensured.

Further, according to the hydraulic control circuit for a working machine of the present invention (Claim 3), it is possible to reduce the flow rate of hydraulic fluid to the rotary cutting hydraulic motor by opening the electromagnetic switching valve. Thereby, the working efficiency at the time of operation | movement of only another actuator can be improved. Further, the pump flow rate can be effectively utilized, and waste of hydraulic energy can be suppressed.
Further, according to the hydraulic control circuit for a work machine of the present invention (Claim 4), when only the other actuator is operated, the negative control pressure is introduced into the hydraulic pump to ensure a sufficient hydraulic oil flow rate necessary for the operation of the actuator. can do. In addition, when the rotary cutting hydraulic motor is single-acting, it is possible to arbitrarily set a flow rate of hydraulic oil necessary and sufficient for the operation of the motor, thereby improving workability.

In addition, according to the hydraulic control circuit for a working machine of the present invention (Claim 5), it can be realized at low cost by using an existing system such as a pressure switch of a control lever or a controller.
According to the hydraulic control circuit for a working machine of the present invention (Claim 6), the hydraulic fluid flow rate required for the first hydraulic circuit side is accurately supplied with a simple configuration in accordance with the driving state of the hydraulic motor. be able to.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 4 are diagrams for explaining a hydraulic control circuit according to an embodiment of the present invention. FIG. 1 is a control block and hydraulic circuit diagram showing the overall configuration of the hydraulic control circuit. FIG. FIG. 3 is a hydraulic circuit diagram showing an overall configuration of a hydraulic control circuit according to a modification, and FIG. 4 is a side view of a work machine to which the hydraulic control circuit is applied. FIG.

[1. Hydraulic excavator configuration]
The hydraulic control circuit of this embodiment is applied as a hydraulic circuit of the hydraulic excavator 20 shown in FIG. The hydraulic excavator 20 includes a lower traveling body 22 equipped with a crawler type hydraulic traveling apparatus, and an upper revolving body 21 that is rotatably mounted on the lower traveling body 22 via a revolving device. . A boom 23 and an arm 24 as a front working portion are pivotally supported at the front end portion of the upper swing body 21, and a twin header (attachment) 26 is attached to the tip thereof.

  A hydraulically driven boom cylinder (one of hydraulic actuators) 23 a that swings the boom 23 in the vertical direction is interposed between the frame of the upper swing body 21 and the boom 23. The boom 23 is provided so as to be raised and lowered with respect to the upper swing body 21 by expansion and contraction of the boom cylinder 23a. Similarly, the arm cylinder 24a and the bucket cylinder 25a shown in FIG. 4 are hydraulic actuators for moving the posture of the arm 24 and the twin header 26, respectively.

A hydraulic motor 26 a is built in the base of the twin header 26. The hydraulic motor 26a is a drive source that drives the twin header 26, and is capable of cutting the earth and sand wall surface by rotating a pick at the tip. The hydraulic control circuit according to the present invention is a hydraulic circuit for driving the hydraulic actuators 23a, 24a, 25a and the hydraulic motor 26a.
Further, on the left side of the vehicle body of these front working sections, a cab 27 on which an operator gets on is provided. Inside the cab 27, hydraulic actuators 23a, 24a, 25a and a hydraulic motor 26a, as well as operation levers and various operation switches of various devices such as a traveling device and a turning device of the hydraulic excavator 20 are arranged.

[2. Hydraulic circuit configuration]
FIG. 1 schematically shows a hydraulic circuit to which the hydraulic control circuit is applied. FIG. 1 shows a schematic configuration of a hydraulic circuit for driving the boom 23 and the twin header 26. This hydraulic circuit mainly includes a first hydraulic circuit L1, a second hydraulic circuit L2, a priority circuit 30 for distributing the amount of hydraulic oil supplied to these two hydraulic circuits, and a negative control circuit L7. The

The first hydraulic circuit L1 is a circuit that connects a hydraulic oil flow path from the hydraulic pump 11 to the hydraulic motor 26a. As shown in FIG. 1, between the hydraulic pump 11 and the hydraulic motor 26a on the first hydraulic circuit L1, a control valve (first valve) that adjusts the flow direction and flow rate of the hydraulic oil that has passed through the first hydraulic circuit L1. One control valve) 6a is interposed.
This control valve 6a is configured as a control valve capable of variably controlling the flow direction and flow rate of the hydraulic oil by switching the position of the stem (flow rate control spool) to a plurality of positions. The spool position of the control valve 6a is controlled in accordance with the operation amount of the twin header operation lever.

Further, on a circuit branched from the circuit between the hydraulic pump 11 and the control valve 6a is a relief valve 19a for setting the upper limit value P ₃ of the hydraulic pressure of the first hydraulic circuit L1 is interposed.
When the twin header operation lever is not operated (no load), the spool position of the control valve 6a is controlled to the neutral position. At this time, the circuit is formed so that the hydraulic oil in the first hydraulic circuit L1 flows back to the tank (hydraulic oil tank) 15 through the center bypass L8.

A negative control relief valve 19c is interposed on the center bypass L8. The negative control relief valve 19c is a relief valve for maintaining a certain level of hydraulic pressure in the center bypass L8 even when there is no load. Relief pressure of the negative control relief valve 19c is set to P _2. Hereinafter, the hydraulic pressure in the center bypass L8, also referred to as a negative control relief pressure P _C. Negative control relief pressure P _C, the upper limit value P ₂ becomes at no load, the amount of hydraulic oil supplied to the hydraulic motor 26a from the control valve 6a is reduced As the increase. That is, the relief pressure P _C for negative control is the upper limit value P ₂ when the twin header operation lever is not operated, decreases as lever operation amount increases.

On the other hand, the second hydraulic circuit L2 is a circuit that connects the hydraulic oil flow path from the hydraulic pump 11 to the boom cylinder 23a. Similar to the first hydraulic circuit L1, a control valve (second control valve) 6b is interposed on the second hydraulic circuit L2, and the flow rate and flow direction of hydraulic oil supplied to the boom cylinder 23a are determined here. It has come to be adjusted. The spool position of the control valve 6b is controlled according to the operation amount of the boom operation lever. Further, on the circuit connecting the control valve 6b and the tank 15, a relief valve 19b for setting the upper limit value P ₄ of the working oil pressure of the second hydraulic circuit L2 is interposed.

As shown in FIG. 1, a first pressure sensor (first operation detection means) 9a and a second pressure sensor (second operation detection means) 9b are provided on the twin header operation lever and the boom operation lever, respectively. Thus, the presence or absence of an operation on the hydraulic motor 26a and the boom cylinder 23a by the operator is detected. The presence / absence of the detected operation is input to a controller (control means) 10 described later.
The hydraulic pump 11 is a variable displacement pump provided with a regulator 12 and is driven by an engine 13.

[3. Structure of negative control circuit]
The negative control circuit L7 is a circuit branched from between the control valve 6b and the relief valve 19b on the second hydraulic circuit L2, and is a circuit for negative control in the regulator 12 of the hydraulic pump 11. In the negative control, the discharge flow rate in the hydraulic pump 11 is decreased or increased so as to correspond to the level of the operating hydraulic pressure of the negative control circuit L7, and the output of the hydraulic pump 11 is kept constant. Hereinafter, the hydraulic pressure introduced to the regulator 12 via the negative control circuit L7 is also referred to as negative control pressure.

  On the negative control circuit L7, an electromagnetic switching valve (second electromagnetic switching valve) 7, an electromagnetic proportional pressure reducing valve 18, and a shuttle valve 17 are provided. The electromagnetic switching valve 7 is a two-position switching valve that is controlled by a controller 10 to be described later, and is responsible for introducing and shutting off the operating hydraulic pressure on the second hydraulic circuit L2 side. On the other hand, the electromagnetic proportional pressure reducing valve 18 is a proportional pressure reducing valve controlled by the controller 10, and forcibly changes the negative control pressure by introducing hydraulic oil supplied from the pilot pump 14 to the negative control circuit L7. It is.

  When the electromagnetic proportional pressure reducing valve 18 is turned on (excited state), the hydraulic oil supplied from the pilot pump 14 flows downstream. Further, the electromagnetic proportional pressure reducing valve 18 can arbitrarily set the working hydraulic pressure on the downstream side by adjusting the opening degree. As shown in FIG. 1, the electromagnetic proportional pressure reducing valve 18 is also connected to the tank 15, and its secondary pressure is set to the lowest pressure (tank pressure) when it is off (non-excited state). ing.

In the present embodiment, as in the downstream side hydraulic pressure of the magnitude of the electromagnetic proportional pressure reducing valve 18 becomes the predetermined pressure P _N, defined by the characteristics of the hydraulic motor 26a, the opening degree is set in advance. That is, in this embodiment, the electromagnetic proportional pressure reducing valve 18 is also controlled to be turned on / off by the controller 10 in the same manner as the electromagnetic switching valve 7.
The shuttle valve 17 is a selection valve interposed in a connection portion between the circuit from the second hydraulic circuit L2 side and the circuit from the pilot pump 14 side. Of these circuits, the high pressure side is automatically selected by the shuttle valve 17 and connected to the regulator 12 of the hydraulic pump 11.

For example, as shown in FIG. 1, when the electromagnetic switching valve 7 is in an off state, the operating hydraulic pressure on the second hydraulic circuit L2 side becomes the negative control pressure of the regulator 12, and when the electromagnetic switching valve 7 is in an on state, The working oil pressure set by the electromagnetic proportional pressure reducing valve 18 becomes the negative control pressure. That is, when the electromagnetic switching valve 7 is on and the electromagnetic proportional pressure reducing valve 18 is on, the predetermined pressure _PN is a negative control pressure, and when the electromagnetic switching valve 7 is on and the electromagnetic proportional pressure reducing valve 18 is off. The tank pressure becomes the negative control pressure.

  The pilot pump 14, shuttle valve 17, and electromagnetic proportional pressure reducing valve 18 function as negative control pressure changing means 8 that arbitrarily changes the negative control pressure introduced into the hydraulic pump 11. Note that the regulator 12 is a known pump capacity varying means, and the swash plate control is performed so that the discharge flow rate of the hydraulic pump 11 decreases as the negative control pressure increases, and the discharge flow rate increases as the negative control pressure decreases. Is to implement.

[4. Configuration of priority circuit]
Next, the configuration of the priority circuit 30 will be described in detail. The priority circuit 30 is a circuit for distributing the flow rate of hydraulic fluid supplied from the hydraulic pump 11 to the first hydraulic circuit L1 and the second hydraulic circuit L2. As shown in FIG. 1, the hydraulic oil supply line led from the hydraulic pump 11 is branched into a first hydraulic circuit L <b> 1 and a second hydraulic circuit L <b> 2 inside the priority circuit 30.

The priority circuit 30 includes a variable throttle valve 1, a pressure compensation valve 2, and an electromagnetic switching valve 5. Note that the priority circuit 30 may be formed as a valve unit in which a plurality of types of valves are integrally combined.
As shown in FIG. 1, the variable throttle valve 1 is a flow rate adjusting valve interposed on the first hydraulic circuit L1, and the size (opening) of the throttle can be arbitrarily changed by pilot pressure control. ing. The pilot port 1a of the variable throttle valve 1 is connected to a fifth hydraulic circuit L5 that guides the hydraulic pressure of the center bypass L8. Thus, throttle opening degree of the variable throttle valve 1 is adapted to be controllably increased or reduced in accordance with the magnitude of the negative control relief pressure P _C of the center bypass L8. Between the upstream and downstream sides of the variable throttle valve 1 will produce the differential pressure corresponding to the magnitude of the negative control relief pressure P _C.

The variable throttle valve 1 is provided with an opening characteristic shown in FIG. 2, negative control relief pressure P _C is squeezed the higher opening, the opening is increased the lower the negative control relief pressure P _C It is like that. For example, gradually decreases the opening area of the A ₂ when the opening area when the negative control relief pressure P _C is P ₁ below the maximum value A _2, and the negative control relief pressure P _C is greater than P _1, relief negative control pressure _{P C} is the opening area becomes the minimum value _{a 1} with _{P 2} or more states.

In the present embodiment, the above P ₁ which is one of the threshold of the opening characteristic of the variable throttle valve 1 is set to a lower pressure than a predetermined pressure value P _5. The predetermined pressure value P _5, which is the maximum pressure that can be a hydraulic pump 11 discharges hydraulic oil flow Q _2. Further, the flow rate Q ₂ is the maximum hydraulic oil flow variable throttle valve 1 throttle opening is allocated to the first hydraulic circuit L1 side in the case of A _2.

In the present embodiment, the above P ₂ which is one of the threshold of the opening characteristic of the variable throttle valve 1, has the same value as the upper limit value P ₂ that is set in the negative control relief valve 19c. That is, the time of no load when not operating the twin header control lever is opening A ₁ of the variable throttle valve 1, gradually becomes large opening degree in accordance with the operation amount, up to increase to A ₂ It has become.
The second hydraulic circuit L2 is branched upstream of the variable throttle valve 1 in the first hydraulic circuit L1. On the upstream side of the variable throttle valve 1, the discharge pressure of the hydraulic oil by the hydraulic pump 11 acts as it is. On the other hand, a pressure compensation valve 2 is connected downstream of the variable throttle valve 1.

  The pressure compensation valve 2 is a valve interposed between the first hydraulic circuit L1 and the second hydraulic circuit L2, and controls the hydraulic oil flow rates of both circuits simultaneously. As shown in FIG. 1, the pressure compensation valve 2 has two channels, a first channel 2a and a second channel 2b, and each channel opening has a single spool ( The pressure compensation spool) is simultaneously changed by the movement of the pressure compensation spool. Here, the first flow path 2a is interposed on the first hydraulic circuit L1, and the second flow path 2b is interposed on the second hydraulic circuit L2.

  Two pilot circuits for driving the spool of the pressure compensation valve 2 are prepared. A third hydraulic circuit L3 and a fourth hydraulic circuit L4. First, among the spools of the pressure compensation valve 2, a third hydraulic circuit L3 that guides hydraulic oil downstream of the variable throttle valve 1 is connected to one end of the spool in the sliding direction of the first flow path 2a. Has been. As shown in FIG. 1, an orifice 16 is interposed on the third hydraulic circuit L3. On the other hand, a fourth hydraulic circuit L4 that guides the hydraulic fluid upstream of the variable throttle valve 1 is connected to the other end of the spool (one end on the side where the second flow path 2b is formed in the sliding direction of the spool). Yes.

  By providing two pilot circuits in this way, the spool of the pressure compensation valve 2 is controlled to a position where the differential pressure between the upstream side and the downstream side of the first flow path 2a is kept constant. Therefore, the flow rate on the first flow path 2a side is controlled to be constant regardless of the discharge pressure of the hydraulic pump 11, and the remaining flow rate flows to the second flow path 2b side. That is, it can be said that the pressure compensation valve 2 has a pressure compensation spool that ensures a constant flow rate of hydraulic fluid supplied to the hydraulic motor 26a.

  The hydraulic oil in the third hydraulic circuit L3 acts to move the spool in a direction to decrease the hydraulic oil flow rate on the second flow path 2b side while increasing the hydraulic oil flow rate on the first flow path 2a side. ing. Further, the hydraulic oil in the fourth hydraulic circuit L4 acts to move the spool in a direction to decrease the hydraulic oil flow rate on the first flow path 2a side while increasing the hydraulic oil flow rate on the second flow path 2b side. Yes. For example, when the discharge pressure of the hydraulic pump 11 increases, the flow speed of the hydraulic oil in the first flow path 2a increases, but the spool is pushed by the hydraulic pressure in the fourth hydraulic circuit L4 that rises accordingly. Since it moves to the left in FIG. 1 and the valve opening is reduced, the hydraulic oil flow rate downstream of the first flow path 2a does not change.

Further, a sixth hydraulic circuit L6 connected to the tank 15 is provided on the downstream side of the orifice 16 in the third hydraulic circuit L3. An electromagnetic switching valve 5 is interposed on the sixth hydraulic circuit L6.
The electromagnetic switching valve 5 is a two-position switching valve controlled by the controller 10. Since the sixth hydraulic circuit L6 is shut off when the electromagnetic switching valve 5 is on, the operating hydraulic pressure downstream of the variable throttle valve 1 is connected to one end of the spool of the pressure compensation valve 2 via the third hydraulic circuit L3 as described above. Works. On the other hand, when the electromagnetic switching valve 5 is turned off, the sixth hydraulic circuit L6 is opened (relieved) to the tank 15, and the working hydraulic pressure in the third hydraulic circuit L3 is reduced to the tank pressure.

  That is, when the electromagnetic switching valve 5 is turned off, the spool of the pressure compensation valve 2 moves to the left in FIG. 1 regardless of the state of the throttle opening of the variable throttle valve 1, and the first flow path 2a is completely closed. In addition, the second flow path 2b is completely opened. The electromagnetic switching valve 5 functions to forcibly stop the pressure compensation control in the pressure compensation valve 2. Further, the flow rate adjustment by the variable throttle valve 1 works only when the electromagnetic switching valve 5 is on.

[5. Control configuration]
The controller 10 is an electronic control unit constituted by a microcomputer, and is provided as an LSI device in which a known microprocessor, ROM, RAM, and the like are integrated. In this controller 10, the valve opening degrees of the electromagnetic switching valves 5, 7 and the electromagnetic proportional pressure reducing valve 18 are on / off controlled. As shown in FIG. 1, the controller 10 performs the following control according to detection information by the first pressure sensor 9 a and the second pressure sensor 9 b.

[5-1. Control of electromagnetic switching valve 5]
The controller 10 controls the electromagnetic switching valve 5 to be turned on (cut off) when the first pressure sensor 9a is turned on. That is, pressure compensation on the first hydraulic circuit L1 side is performed by the pressure compensation valve 2 only when the twin header 26 is actually operating.
On the other hand, when the first pressure sensor 9a is off, the electromagnetic switching valve 5 is controlled to be off (circulate). As a result, when the boom 23 is single-acting, the flow of hydraulic oil in the first flow path 2a interposed on the first hydraulic circuit L1 side is interrupted. When the twin header 26 is not operating, the first hydraulic circuit L1 is always shut off.

[5-2. Control of electromagnetic switching valve 7]
Further, the controller 10 controls the electromagnetic switching valve 7 to be turned on (cut off) when the first pressure sensor 9a is turned on. On the other hand, when the first pressure sensor 9a is off, the electromagnetic switching valve 7 is controlled to be off (circulation). That is, only when the boom 23 is single-acting, the hydraulic pressure of the second hydraulic circuit L2 related to normal negative control is introduced into the negative control circuit L7. Further, when the twin header 26 is operated, the operating hydraulic pressure from the second hydraulic circuit L2 side is cut off, so that the negative control pressure of the negative control circuit L7 is forcibly changed according to the control of the electromagnetic proportional pressure reducing valve 18 described below. Will be.

[5-3. Control of electromagnetic proportional pressure reducing valve 18]
Furthermore, the controller 10 controls the electromagnetic proportional pressure reducing valve 18 to be on when the second pressure switch 9b is off. On the other hand, when the second pressure switch 9b is on, the electromagnetic proportional valve 18 is controlled to be off.
That has become a secondary pressure of the electromagnetic proportional pressure reducing valve 18 only when single-acting twin header 26 to be controlled to a predetermined pressure P _N. When the boom 23 is single-acting or when the boom 23 and the twin header 26 are linked, the secondary pressure of the electromagnetic proportional pressure reducing valve 18 is controlled to the lowest pressure (tank pressure).

  The control contents in the controller 10 according to the present invention are summarized as follows.

[6. Action]
With this configuration, the hydraulic control circuit operates as follows.
[6-1. During single-action operation of the boom]
When the boom 23 is operated in a single action, the first pressure sensor 9a is turned off and the second pressure sensor 9b is turned on. Thus, the electromagnetic switching valve 5 is controlled to be turned off, and the sixth hydraulic circuit L6 and the third hydraulic circuit L3 are opened to the tank 15. Therefore, the spool of the pressure compensation valve 2 moves to the left in FIG. 1, and the first flow path 2a is completely closed. That is, the hydraulic fluid flow rate on the first flow path 2a side becomes zero, and the entire flow rate of the hydraulic pump 11 is supplied to the second hydraulic circuit L2 side. Therefore, all the outputs of the hydraulic pump 11 can be assigned to drive the boom cylinder 23a.

Further, since the electromagnetic proportional valve 7 is controlled to be turned off by the controller 10, the working hydraulic pressure of the second hydraulic circuit L2 is guided to the negative control circuit L7. On the other hand, since the electromagnetic proportional pressure reducing valve 18 is also controlled to be turned off, the secondary pressure of the electromagnetic proportional pressure reducing valve 18 becomes the tank pressure. Therefore, in the shuttle valve 17, the operating oil pressure of the second hydraulic circuit L2 is selected as the negative control pressure, and normal negative control can be performed.
It should be noted that in this case, since the first flow path 2a of the pressure compensating valve 2 is closed, negative control relief pressure P _C in the first hydraulic circuit L1 side of the center bypass L8 is held.

[6-2. During single-action operation of twin headers]
During the single-action operation of the twin header 26, the first pressure sensor 9a is turned on and the second hydraulic pressure sensor 9b is turned off. As a result, the electromagnetic proportional valve 5 is controlled to be turned on and the sixth hydraulic circuit L6 is shut off, so that the third hydraulic circuit L3 functions as one pilot circuit of the pressure compensation valve 2. Note that the operating hydraulic pressure of the third hydraulic circuit L3 is a pressure introduced through the orifice 16, and thus is smaller than the discharge pressure of the hydraulic pump 11. On the other hand, the discharge pressure of the hydraulic pump 11 is introduced into the other pilot pressure of the pressure compensation valve 2 via the fourth hydraulic circuit L4.

Thereby, since the differential pressure | voltage between the upstream of the 1st flow path 2a and a downstream is kept constant, the fixed hydraulic fluid flow supplied to the hydraulic motor 26a is securable. For example, the flow rate of hydraulic oil supplied to the hydraulic motor 26 a of the twin header 26 becomes a constant amount with respect to fluctuations in the discharge pressure of the hydraulic pump 11.
On the other hand, when the spool position of the control valve 6a by the operation of the twin header control lever is moved, hydraulic fluid pressure is reduced in the center bypass L8, also decreases the negative control relief pressure P _C which is introduced into the fifth hydraulic circuit L5. Therefore, the opening degree of the variable throttle valve 1 increases, and the flow rate of hydraulic fluid distributed to the first hydraulic circuit L1 side increases. As a result, the hydraulic fluid flow supplied to the first hydraulic circuit L1 is automatically controlled according to the operation amount of the twin header operation lever, and the hydraulic fluid flow increases as the operation amount increases. Thus, the rotation speed of the hydraulic motor 26a can be increased.

At this time, the remaining flow rate out of the total flow rate from the hydraulic pump 11 is supplied to the second flow path 2b side. However, since the proportional solenoid valve 7 and the solenoid proportional pressure reducing valve 18 is controlled to be on by the controller 10, the operating oil pressure in the negative control circuit L7 (negative control pressure) becomes the predetermined pressure P _N which corresponds to the hydraulic motor 26a. That is, the discharge flow rate of the hydraulic pump 11 is controlled by the regulator 12 to an appropriate amount necessary and sufficient for driving the hydraulic motor 26a. Therefore, the hydraulic fluid flow rate on the second flow path 2b side can be reduced, and energy loss can be suppressed.

[6-3. During interlocking operation of boom and twin header]
During the interlock operation of the boom 23 and the twin header 26, both the first pressure sensor 9a and the second pressure sensor 9b are turned on. As a result, the electromagnetic switching valve 5 is controlled to be turned on, the sixth hydraulic circuit L6 is shut off, a constant hydraulic fluid flow rate is secured on the first flow path 2a side of the pressure compensation valve 2, and the remaining hydraulic fluid is It is supplied to the two flow paths 2b side.

  On the other hand, since the electromagnetic switching valve 7 is controlled to be on and the electromagnetic proportional pressure reducing valve 18 is controlled to be off, the tank pressure is selected as the negative control pressure in the shuttle valve 17 of the negative control circuit L7. Thereby, in the regulator 12, the discharge flow rate of the hydraulic pump 11 is set to the maximum amount, a constant hydraulic fluid flow rate can be secured on the first flow path 2a side of the pressure compensation valve 2, and the remaining amount The hydraulic fluid can be supplied to the second flow path 2b side. Therefore, the linkage between the boom 23 and the twin header 23 can be improved.

[7. effect]
According to this hydraulic control circuit, by providing the pressure compensation valve 2, the remaining hydraulic oil is supplied to the second hydraulic circuit L2 side while ensuring the hydraulic oil flow rate distributed to the first hydraulic circuit L1 side. Thus, the linkage between the hydraulic motor 26a and the boom cylinder 23a can be enhanced. For example, there is no problem that the twin header 26 repeats rotating and stopping.

  In addition, by controlling on / off of the electromagnetic switching valve 5 according to the detection information of the first pressure sensor 9a and the second pressure sensor 9b, the pressure compensation spool of the pressure compensation valve 2 is driven to distribute the hydraulic oil. Can be controlled. That is, by closing the electromagnetic switching valve 5, the hydraulic oil flow rate to the hydraulic motor 26 a can be secured, or by opening the electromagnetic switching valve 5, the hydraulic oil supply can be shut off. For example, at the time of single-action operation of the boom, the flow of hydraulic oil to the hydraulic motor 26a side can be interrupted, and the pump flow rate can be effectively utilized.

Thus, energy loss can be suppressed by supply control according to the operating state of the hydraulic device, which can contribute to reduction in fuel consumption. In addition, hydraulic oil can be distributed with a simple configuration, and costs can be reduced.
Also, causing negative control relief pressure P _C provided negative control relief valve 19c on the center bypass L8, by utilizing this negative control relief pressure P _C as a pilot pressure for flow rate control in the variable throttle valve 1, Twin The flow rate of hydraulic oil supplied to the hydraulic motor 26a can be increased or decreased according to the operation amount of the header operation lever. Thereby, the hydraulic fluid flow rate required for the first hydraulic circuit L1 can be accurately supplied according to the driving state of the hydraulic motor 26a. Further, proportional control of the flow rate can be performed without using an electromagnetic proportional valve that requires expensive and complicated control.

[8. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the hydraulic circuit relating to the driving of the boom 23 and the twin header 26 is illustrated, but the hydraulic control circuit of the present invention can be widely applied to a hydraulic circuit including an attachment and other hydraulic actuators. It is. That is, the present invention may be applied to a hydraulic circuit including a hydraulic circuit that drives actuators such as the hydraulic cylinders 24a and 25a other than the boom cylinder 23a, the swing device of the upper swing body 21, and the travel device of the lower travel body 22. Further, it can be applied not only to the twin header 26 but also to a hydraulic circuit provided with various hydraulic devices driven by a hydraulic motor such as a breaker and a magnet as an attachment.

In the above-described embodiment, the hydraulic circuit with one main pump (hydraulic pump 11) is shown, but the number of main pumps is not limited to this and may be two or more. Similarly, the number of control valves interposed on the first hydraulic circuit L1 and the second hydraulic circuit L2 may be a plurality of control valves.
FIG. 3 shows an example of a hydraulic circuit that includes two control valves 6a and 6a ′ on the first hydraulic circuit L1 and controls two hydraulic motors 26a and 26a ′. In such a configuration, if one of the hydraulic motors 26a, 26a 'connected to the first hydraulic circuit L1 operates, the operating oil pressure of the center bypass L8 decreases. By introducing the pressure, it is possible to supply the hydraulic oil flow rate required on the first hydraulic circuit L1 side.

  In the above-described embodiment, the output control of the hydraulic pump 11 using the negative control pressure introduced from the negative control circuit L7 is performed, but the configuration related to the negative control circuit L7 can be omitted. Similarly, regarding the control of the electromagnetic switching valves 5 and 7 and the electromagnetic proportional pressure reducing valve 18, in the above-described embodiment, the control is performed via the controller 10. It is also conceivable to have a mechanism provided with a mechanism for opening and closing the switching valves 5 and 7 and the electromagnetic proportional pressure reducing valve 18. It is sufficient that at least each valve is opened / closed in a correspondence relationship as described in Table 1 above.

  In the above-described embodiment, the present invention is applied to the hydraulic circuit of the excavator 20. However, the application target of the present invention is not limited to this, and various operations such as a bulldozer, a wheel loader, and a hydraulic crane are performed. It can be applied to the hydraulic circuit of a machine.

1 is a control block and hydraulic circuit diagram showing an overall configuration of a hydraulic control circuit according to an embodiment of the present invention. It is an opening characteristic figure of the variable throttle valve interposed in the hydraulic control circuit concerning one embodiment of the present invention. It is a hydraulic circuit diagram which shows the whole structure of the hydraulic control circuit which concerns on the modification of this invention. 1 is a side view of a work machine to which a hydraulic control circuit according to an embodiment of the present invention is applied.

Explanation of symbols

1 Variable throttle valve 2 Pressure compensation valve 5 Electromagnetic switching valve 6a Control valve (first control valve)
6b Control valve (second control valve)
7 Electromagnetic switching valve (second electromagnetic switching valve)
8 Negative control pressure changing means 9a First pressure sensor (first operation detecting means)
9b Second pressure sensor (second operation detecting means)
10 Controller (control means)
11 Hydraulic pump 12 Regulator 15 Tank (hydraulic oil tank)
16 Orifice 17 Shuttle valve 18 Proportional pressure reducing valve 19a, 19b Relief valve 19c Relief valve for negative control 20 Hydraulic excavator (work machine)
23 Boom 23a Boom cylinder (other hydraulic actuator)
26 Twin header (attachment)
26a Hydraulic motor 30 Priority circuit L1 First hydraulic circuit L2 Second hydraulic circuit L3 Third hydraulic circuit L4 Fourth hydraulic circuit L5 Fifth hydraulic circuit L6 Sixth hydraulic circuit L7 Negative control circuit L8 Center bypass

Claims (6)

In a hydraulic control circuit for a work machine comprising a hydraulic motor that drives an attachment, a hydraulic actuator other than the hydraulic motor, and a hydraulic pump that serves as a hydraulic drive source for the hydraulic motor and the other hydraulic actuator,
A first hydraulic circuit connecting the hydraulic motor and the hydraulic pump;
A variable throttle valve interposed on the first hydraulic circuit and configured to change the opening degree by pilot pressure control;
A second hydraulic circuit connecting the upstream side of the variable throttle valve and the other hydraulic actuator in the first hydraulic circuit;
A constant hydraulic oil flow rate supplied to the hydraulic motor is secured by holding the differential pressure between the first hydraulic circuit and the second hydraulic circuit, and being interposed in both the first hydraulic circuit and the second hydraulic circuit. A pressure compensation valve having a pressure compensation spool to perform,
The first hydraulic circuit is connected to the downstream side of the variable throttle valve and one end side of the pressure compensation spool, and the pressure compensation spool is driven in a direction to increase the flow rate of hydraulic fluid to the first hydraulic circuit. Three hydraulic circuits,
The upstream side of the variable throttle valve in the second hydraulic circuit is connected to the other end side of the pressure compensation spool, and the pressure compensation spool is driven in a direction to increase the flow rate of hydraulic oil to the second hydraulic circuit. A fourth hydraulic circuit;
A first control valve interposed on the downstream side of the pressure compensation valve on the first hydraulic circuit and controlling the flow rate and flow direction of hydraulic oil supplied to the hydraulic motor;
A relief valve for a negative control interposed on the center bypass of the first control valve;
A fifth point of connecting a center bypass between the first control valve and the relief valve for negative control and a pilot port of the variable throttle valve, and introducing an operating hydraulic pressure of the center bypass as a pilot pressure to the variable throttle valve. A hydraulic control circuit for a work machine, comprising: a hydraulic circuit. 2. The hydraulic control for a work machine according to claim 1, wherein the variable throttle valve throttles the opening degree as the pilot pressure is higher, and increases the opening degree as the operating hydraulic pressure is lower. circuit. A sixth hydraulic circuit connecting the third hydraulic circuit and the hydraulic oil tank;
The hydraulic control circuit for a work machine according to claim 1, further comprising: an electromagnetic switching valve interposed on the sixth hydraulic circuit. A second control valve interposed on the second hydraulic circuit and controlling the flow rate and flow direction of hydraulic fluid supplied to the other hydraulic actuator;
A negative control circuit for guiding the hydraulic pressure downstream of the second control valve to the hydraulic pump;
A second electromagnetic switching valve interposed in the negative control circuit;
4. The hydraulic control circuit for a work machine according to claim 3, further comprising negative control pressure changing means for arbitrarily changing the negative control pressure introduced into the hydraulic pump. First operation detecting means for detecting an operation on the hydraulic motor by an operator;
Second operation detecting means for detecting an operation to the other hydraulic actuator by an operator;
And a control means for controlling the electromagnetic switching valve, the second electromagnetic switching valve and the negative control pressure changing means based on the detection results of the first operation detecting means and the second operation detecting means. The hydraulic control circuit for a work machine according to claim 4. In a hydraulic control circuit for a work machine comprising a hydraulic motor that drives an attachment, a hydraulic actuator other than the hydraulic motor, and a hydraulic pump that serves as a hydraulic drive source for the hydraulic motor and the other hydraulic actuator,
A first hydraulic circuit connecting the hydraulic motor and the hydraulic pump;
A variable throttle valve interposed on the first hydraulic circuit and configured to change the opening degree by pilot pressure control;
A second hydraulic circuit connecting the upstream side of the variable throttle valve and the other hydraulic actuator in the first hydraulic circuit;
A first control valve interposed downstream of the variable throttle valve on the first hydraulic circuit and controlling the flow rate and flow direction of hydraulic oil supplied to the hydraulic motor;
A relief valve for a negative control interposed on the center bypass of the first control valve;
A fifth point of connecting a center bypass between the first control valve and the relief valve for negative control and a pilot port of the variable throttle valve, and introducing an operating hydraulic pressure of the center bypass as a pilot pressure to the variable throttle valve. A hydraulic control circuit for a work machine, comprising: a hydraulic circuit.

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