JP2009167657A - Hydraulic control circuit of utility machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control circuit of a utility machine, which has a simple constitution, and which enhances the property of interlocking a rotary cutting attachment with a hydraulic actuator except the rotary cutting attachment. <P>SOLUTION: This hydraulic control circuit of the utility machine comprises a first hydraulic circuit L1 which is connected to a hydraulic motor 26a for rotary cutting, and a second hydraulic circuit L2 which is connected to another hydraulic actuator 23a. A throttle valve 1 is provided on the first hydraulic circuit L1, and a pressure compensation valve 2 with a pressure compensation spool for securing a fixed flow rate of a hydraulic fluid for the hydraulic motor 26a is interposed between the first and second hydraulic circuits L1 and L2. Additionally, fifth and sixth hydraulic circuits L5 and L6 communicating with a hydraulic fluid tank 15 are provided in such a manner as to be juxtaposed with respect to a pilot circuit L3 which connects the downstream side of the throttle valve 1 and the one-end side of the pressure compensation spool together; a relief valve 3 is interposed the fifth hydraulic circuit L5; and a solenoid changeover valve 5 is interposed on the sixth hydraulic circuit L6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydraulic control circuit for controlling a hydraulic excavator provided with a rotary cutting attachment.

  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.

  The present invention has been made in view of such a problem, and has a simple configuration, and can improve the interlocking between the rotary cutting attachment and the other hydraulic actuators. The purpose is to provide.

  In order to achieve the above object, a hydraulic control circuit for a working machine according to claim 1 of the present invention includes: a rotary cutting hydraulic motor that drives a rotary cutting attachment; and a hydraulic actuator other than the rotary cutting hydraulic motor; In a hydraulic control circuit of a work machine comprising a hydraulic pump that is a hydraulic drive source of the rotary cutting hydraulic motor and the other hydraulic actuator, a first hydraulic pressure that connects the rotary cutting hydraulic motor and the hydraulic pump A circuit, a throttle valve interposed in the first hydraulic circuit, a second hydraulic circuit connecting the upstream side of the throttle valve and the other hydraulic actuator in the first hydraulic circuit, and the first hydraulic circuit And a pressure that is interposed in both of 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 rotary cutting hydraulic motor. Supplement A pressure compensating valve having a spool, and a downstream side of the throttle valve in the first hydraulic circuit and one end side of the pressure compensating 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 throttle valve in the second hydraulic circuit and the other end side of the pressure compensation spool are connected, and the hydraulic oil flow rate to the second hydraulic circuit is reduced. A fourth hydraulic circuit for driving the pressure compensation spool in the increasing direction, a fifth hydraulic circuit for connecting the third hydraulic circuit and the hydraulic oil tank, and a relief valve interposed on the fifth hydraulic circuit; It is characterized by having.

A hydraulic control circuit for a work machine according to a second aspect of the present invention includes the third hydraulic circuit and the hydraulic oil so as to be in parallel with the fifth hydraulic circuit in addition to the configuration according to the first aspect. A sixth hydraulic circuit connecting the tank and an electromagnetic switching valve interposed on the sixth hydraulic circuit are further provided.
According to a third 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 second aspect, the hydraulic oil interposed on the second hydraulic circuit and supplied to the other hydraulic actuators. A control valve for controlling the flow rate and the flow direction, a negative control circuit for guiding the hydraulic pressure downstream of the control valve to the hydraulic pump, a second electromagnetic switching valve interposed in the negative control circuit, and the hydraulic pump And negative control pressure changing means for arbitrarily changing the negative control pressure.

  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, comprising: a first operation detecting means for detecting an operation of the rotary cutting hydraulic motor by an operator; Control the electromagnetic switching valve, the second electromagnetic switching valve, and the negative control pressure changing means based on detection results of the second operation detecting means for detecting the operation and the first operation detecting means and the second operation detecting means. And a control means.

  According to the hydraulic control circuit for a working machine of the present invention (Claim 1), since the pressure compensation valve is provided, it is possible to secure sufficient hydraulic oil necessary for driving the rotary cutting motor, and the rotary cutting motor. In addition, the linkage of other hydraulic actuators can be enhanced. In addition, since the relief valve is interposed in the fifth hydraulic circuit, the pressure compensation spool is driven when the operating hydraulic pressure of the third hydraulic circuit exceeds the set pressure of the relief valve, and the first hydraulic circuit and the second hydraulic circuit are driven. The distribution of the hydraulic oil flow supplied to the circuit can be switched. Furthermore, proportional control of the flow rate can be performed without using an electromagnetic proportional valve that requires expensive and complicated control, 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), it is possible to reduce the flow rate of hydraulic oil 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 3), when only the other actuator is operated, the negative control pressure is introduced into the hydraulic pump to ensure a sufficient hydraulic fluid 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.

  Further, according to the hydraulic control circuit for a working machine of the present invention (Claim 4), it can be realized at low cost by using an existing system such as a pressure switch or a controller of an operation lever.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 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. PQ characteristic diagram in hydraulic control circuit according to one embodiment of the invention (thick solid line is PQ characteristic of hydraulic pump provided in the hydraulic control circuit, thin solid line is P- of hydraulic fluid distributed to hydraulic motor) FIG. 3 is a side view of a work machine to which the hydraulic control circuit is applied.

[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 (rotary cutting 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. 3 are hydraulic actuators for moving the postures of the arm 24 and the twin header 26, respectively.

  A hydraulic motor (rotary cutting 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, there is a control valve 6a that adjusts the flow direction and flow rate of hydraulic fluid that has passed through the first hydraulic circuit L1. It is intervened.
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 ₁ of the hydraulic pressure of the first hydraulic circuit L1 is interposed.
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. A control valve 6b is interposed on the second hydraulic circuit L2 in the same manner as the first hydraulic circuit L1, and the flow rate and flow direction of hydraulic oil supplied to the boom cylinder 23a are adjusted here. ing. The spool position of the control valve 6b is controlled according to the operation amount of the boom operation lever. In addition, a relief valve 19b for setting the upper limit value P ₃ (P ₃ > P ₁ ) of the hydraulic pressure of the second hydraulic circuit L2 is provided on a circuit connecting the control valve 6b and the tank (hydraulic oil tank) 15. Has been.

  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. The relationship between the discharge flow rate and the discharge pressure by the hydraulic pump 11 is shown by a thick solid line in FIG. A ABC line shows the PQ characteristic at the time of the maximum output of the hydraulic pump 11 (for example, when the boom operation lever is fully operated).

[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 (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 adjustment valve interposed on the first hydraulic circuit L1 and can set the throttle opening arbitrarily in advance. Thereby, a differential pressure corresponding to the set throttle opening is generated between the upstream side and the downstream side of the variable throttle valve 1. The second hydraulic circuit L2 is branched upstream of the variable throttle valve 1 in the first hydraulic circuit L1. Note that the discharge pressure of the hydraulic oil from the hydraulic pump 11 acts on the upstream side of the variable throttle valve 1 as it is. On the other hand, the pressure compensation valve 2 is connected downstream of the variable throttle valve.

  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 fifth hydraulic circuit L5 and a sixth hydraulic circuit L6 connected to the tank 15 are provided on the downstream side of the orifice 16 in the third hydraulic circuit L3. The fifth hydraulic circuit L5 and the sixth hydraulic circuit L6 are connected in parallel to the tank 15 and in parallel to the third hydraulic circuit L3. The relief valve 3 is interposed on the fifth hydraulic circuit L5, while the electromagnetic switching valve 5 is interposed on the sixth hydraulic circuit L6.

The relief valve 3 sets an upper limit value P ₀ of the operating hydraulic pressure in the third hydraulic circuit L3. Here, the valve is kept closed when the hydraulic pressure is P ₀ or less, and is opened at an opening degree proportional to the excess pressure when the hydraulic pressure exceeds P ₀ . When the relief valve 3 is opened, the hydraulic pressure in the third hydraulic circuit L3 decreases, so the spool of the pressure compensation valve 2 moves to the left in FIG. 1 and the hydraulic oil flow rate on the first flow path 2a side decreases. It will be. The upper limit value P ₀ is set lower than the maximum discharge pressure P _{5 at} which the hydraulic pump 11 can discharge the flow rate Q ₂ .

  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 open / closed state of the relief valve 3, and the first flow path 2a is completely closed and the second The 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. In addition, the relief action of the relief valve 3 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 hydraulic pressure from the second hydraulic circuit L2 side is cut off, so that the negative control pressure is forcibly changed according to the control of the electromagnetic proportional pressure reducing valve 18 described below. Become.

[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. In this case, the flow rate of the hydraulic oil supplied to the boom cylinder 23a varies within the range indicated by the line ABC in FIG. 2 with respect to the variation in the discharge pressure of the hydraulic pump 11.

[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, as shown as D-E line in FIG. 2, the hydraulic oil flow supplied to the hydraulic motor 26a of the twin header 26 is a constant predetermined amount Q ₂ to variations in discharge pressure of the hydraulic pump 11 .
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.

Further, when the driving load of the twin header 26 increases to increase the operating hydraulic pressure in the first hydraulic circuit L1, and the pressure on the downstream side of the orifice 16 in the third hydraulic circuit L3 exceeds the upper limit value P ₀ , the relief valve 3 Opens and the hydraulic pressure in the third hydraulic circuit L3 decreases. As a result, the spool of the pressure compensation valve 2 moves to the left in FIG. 1, and the hydraulic oil flow rate on the first flow path 2a side decreases.
Further, the higher the hydraulic pressure that is relieved by the relief valve 3, the smaller the hydraulic oil flow rate on the first flow path 2 a side in the pressure compensation valve 2. Therefore, as shown by the line E-F in FIG. 2, the flow rate of the hydraulic oil supplied to the hydraulic motor 26 a of the twin header 26 decreases in a region where the relief valve 3 has a set pressure P ₀ or more. Note that the pressure value P ₂ in FIG. 2 corresponds to the discharge pressure of the hydraulic pump 11 that generates a pressure large enough to open the relief valve 3 downstream of the orifice 16. This value is determined according to the pressure loss characteristics of the valve 1 and the orifice 16.

In the present embodiment, the upper limit value P ₁ of the working hydraulic pressure in the first hydraulic circuit L1 is set by the relief valve 19a. That is, for example, when the upper limit value P ₁ is less than the pressure value P ₂ , as shown in FIG. 2, the flow rate of hydraulic oil supplied to the hydraulic motor 26a of the twin header 26 is D-E- in FIG. It will fluctuate in the range shown as G line. Therefore, it is possible to ensure a hydraulic fluid flow rate of at least the predetermined amount Q _{1 with} respect to at least the hydraulic motor 26a. When the hydraulic motor 26a requires a predetermined hydraulic fluid flow rate due to its characteristics, a pressure at which the hydraulic oil flow rate can be obtained may be set to a set pressure at which the relief valve 19a opens.

[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. Therefore, in the regulator 12, the discharge flow rate of the hydraulic pump 11 is set to the maximum amount, and a constant hydraulic fluid flow rate is ensured on the first flow path 2a side of the pressure compensation valve 2, and the remaining hydraulic fluid flows. It is supplied to the second flow path 2b side.

For example, as shown in FIG. 2, when the discharge pressure of the hydraulic pump 11 is P ₄ and the discharge flow rate is Q ₃ , Q _{2 in} the range below the line D-E is the operation of the first flow path 2a. The oil flow rate is obtained, and Q ₃ -Q ₂ in the range surrounded by the AB line and the DE line is the hydraulic oil flow rate of the second flow path 2b.
Thereafter, when the working hydraulic pressure in the first hydraulic circuit L1 rises due to an increase in the work load and the pressure on the downstream side of the orifice 16 in the third hydraulic circuit L3 exceeds the upper limit value P ₀ , the single header operation of the twin header 26 is performed. Since the relief valve 3 is opened in the same manner as described above, the hydraulic oil flow rate on the first flow path 2a side in the pressure compensation valve 2 is reduced. Therefore, the flow rate of the hydraulic fluid supplied to the hydraulic motor 26a decreases in a region where the relief valve 3 is at or above the set pressure P ₀ as shown by the line E-F in FIG.

[7. effect]
According to the hydraulic control circuit, the pressure compensation valve 2 is provided, so that a hydraulic oil flow rate Q ₂ necessary and sufficient for driving the hydraulic motor 26 a of the twin header 26 can be secured, and the hydraulic motor 26 a and the boom cylinder 23 a. Can be enhanced.
Further, by controlling on / off of the electromagnetic switching valve 5 according to the discharge pressure P of the hydraulic pump 11, the pressure compensation spool of the pressure compensation valve 2 can be driven to control the distribution of the hydraulic oil. 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.
Further, when the relief valve 3 is interposed on the fifth hydraulic circuit L5, the pilot pressure introduced to the pressure compensation valve 2 via the third hydraulic circuit L3 exceeds the upper limit pressure P ₀ of the relief valve 3 In addition, the priority flow rate of hydraulic oil to the hydraulic motor 26a can be automatically reduced. As a result, even if the work load increases and the hydraulic pressure in the circuit becomes high, the output of the twin header 26 can be temporarily suppressed until the work load decreases. Further, the proportional control of the flow rate can be carried out without using an electromagnetic proportional valve that requires expensive and complicated control, and for example, the characteristics shown by the EF line in FIG. 2 can be given.

  It should be noted that surplus hydraulic oil is directed to the boom cylinder 23a, and the hydraulic oil flow rate in the range surrounded by the EF line and the BC line is supplied to the boom cylinder 23a. The boom 23 can be moved while maintaining the output of the twin header 26. For example, there is no problem that the twin header 26 repeats rotation and stop, and the operation can be stabilized. Therefore, when the boom 23 and the twin header 26 are interlocked, the remaining hydraulic oil can be supplied to the boom 23 after securing the hydraulic oil flow rate necessary for driving the twin header 26, and the interlocking is improved. Can do.

  Also, by controlling the negative control pressure, it is possible to ensure a necessary and sufficient hydraulic fluid flow for the operation of the boom cylinder 23a when the boom 23 is operated in a single operation, and for the operation of the hydraulic motor 26a when the twin header 26 is operated only. Can ensure a sufficient flow rate of hydraulic fluid. Furthermore, when the boom 23 and the twin header 26 are linked, the output of the hydraulic pump 11 can be set to the maximum to increase the work efficiency.

[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 related to the driving of the boom 23 and the twin header 26 is illustrated, but the hydraulic control circuit of the present invention is a hydraulic circuit including a rotary cutting attachment and other hydraulic actuators. Widely applicable to. 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, in the above-described embodiment, the control using the negative control pressure is used for the output control of the hydraulic pump 11, 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 a PQ characteristic diagram in the hydraulic control circuit according to an embodiment of the present invention, the thick solid line is the PQ characteristic of the hydraulic pump provided in the hydraulic control circuit, the thin solid line is the hydraulic oil distributed to the hydraulic motor The PQ characteristics of 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 (throttle valve)
2 Pressure compensation valve 3 Relief valve 5 Electromagnetic switching valve 6a, 6b Control valve (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 20 Hydraulic excavator (work machine)
23 Boom 23a Boom cylinder (other hydraulic actuator)
26 Twin header (rotary cutting attachment)
26a Hydraulic motor (rotary cutting 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

Claims (4)

A rotary cutting hydraulic motor for driving the rotary cutting attachment; a hydraulic actuator other than the rotary cutting hydraulic motor; and a hydraulic pump serving as a hydraulic drive source for the rotary cutting hydraulic motor and the other hydraulic actuator. In the hydraulic control circuit of the work machine
A first hydraulic circuit connecting the rotary cutting hydraulic motor and the hydraulic pump;
A throttle valve interposed in the first hydraulic circuit;
A second hydraulic circuit that connects the upstream side of the throttle valve and the other hydraulic actuator in the first hydraulic circuit;
A constant hydraulic oil that is interposed in both the first hydraulic circuit and the second hydraulic circuit and that supplies the rotary cutting hydraulic motor while maintaining a differential pressure between the first hydraulic circuit and the second hydraulic circuit. A pressure compensation valve having a pressure compensation spool for securing a flow rate;
A third side for connecting the downstream side of the throttle valve and one end side of the pressure compensation spool in the first hydraulic circuit to drive the pressure compensation spool in a direction to increase the flow rate of hydraulic oil to the first hydraulic circuit. A hydraulic circuit;
The second hydraulic circuit is connected to the upstream side of the throttle valve and the other end of the pressure compensation spool to drive the pressure compensation spool in a direction to increase the flow rate of hydraulic oil to the second hydraulic circuit. Four hydraulic circuits,
A fifth hydraulic circuit connecting the third hydraulic circuit and the hydraulic oil tank;
A hydraulic control circuit for a work machine, comprising: a relief valve interposed on the fifth hydraulic circuit. A sixth hydraulic circuit for connecting the third hydraulic circuit and the hydraulic oil tank so as to be in parallel with the fifth hydraulic circuit;
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 control valve which is interposed on the second hydraulic circuit and which controls the flow rate and flow direction of hydraulic oil supplied to the other hydraulic actuators;
A negative control circuit for guiding the hydraulic pressure downstream of the control valve to the hydraulic pump;
A second electromagnetic switching valve interposed in the negative control circuit;
The hydraulic control circuit for a work machine according to claim 2, 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 of the rotary cutting 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 3.

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