JP2006342663A - Hydraulic control circuit of hydraulic backhoe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable continuous operation by a simple and inexpensive structure without changing the speed of an optional device largely when an optional actuator and a main actuator are operated in combination. <P>SOLUTION: A hydraulic control circuit of a hydraulic excavator comprises an exclusive oil passage L50 which can supply pressure oil from hydraulic pumps 2, 3 to an optional control valve 10 from the position on the upstream side of main control valves 5-9, 11, a switch-over valve 50 for opening up the exclusive oil passage L50 upon optional operation, and a flow-rate control valve 51 provided on the upstream side of the main control valves and on the downstream side of the switch-over valve 50 to secure a flow-rate of the pressure oil supplied to the oil passage 50L by controlling the flow-rate of the pressure oil passing through the main control valves 5-9, 11 upon the optional operation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hydraulic control circuit for a hydraulic excavator to which an optional device such as a crusher can be attached.

  Most of the hydraulic circuit of a hydraulic excavator is a two-pump system having two hydraulic pumps. This hydraulic pump distributes and supplies pressure oil to main actuators such as a swing motor, a left and right traveling motor, a boom cylinder, an arm cylinder, and a bucket cylinder, and an option actuator such as an option cylinder.

  Incidentally, in recent years, hydraulic excavators have come to be used for dismantling work such as buildings, foundations and automobiles in addition to conventional excavation work. In this dismantling, an optional device called a crusher that can open and close a bifurcated tip is used instead of the bucket. In that case, a bucket cylinder is used for the forward and backward movement of the crusher, a turning motor is used for the turning operation, and an optional cylinder is used for the opening and closing operation of the crusher. It becomes a composite operation that is operated simultaneously when used. Furthermore, it may be combined with other actuators such as left and right traveling motors.

  However, hydraulic pumps distribute and supply pressure oil to main actuators such as bucket cylinders and swing motors and option actuators such as option cylinders, so the amount of oil supplied to the main actuator is large. In this case, the amount of oil supplied to the optional actuator may decrease, and the reduction may slow down the opening and closing speed of the crusher, which may hinder work efficiency.

  On the other hand, the speed of opening and closing of the crusher is said to determine the work efficiency, so quick movement is desired. The operator does not have to move the excavator body so fast, but only the crusher speed is reduced. There was a strong request not to want.

  Therefore, a new switching circuit has been incorporated into the hydraulic circuit including the control valve, and during the combined operation of the crusher and arm, this switching circuit is operated so that the amount of oil supplied to the actuator for opening and closing the crusher is relatively However, in any case, the hydraulic circuit is complicated, and it is difficult to reduce the cost by using the existing one. In particular, when an existing control valve cannot be used, the cost of the hydraulic excavator is increased. In addition, since the hydraulic circuit is greatly changed depending on the presence or absence of the optional device, it is difficult to reduce the cost by standardization.

  The present invention has been made in consideration of the problems in the hydraulic control circuit of the conventional hydraulic excavator as described above, and has a simple and inexpensive configuration, and the speed of the optional device can be increased during combined operation of the optional actuator and the main actuator. It is an object of the present invention to provide a hydraulic control circuit for a hydraulic excavator that can continue the operation without changing the pressure.

  As means for solving the above problems, the present invention provides a hydraulic control circuit for a hydraulic excavator, a plurality of main actuators for performing traveling, turning and excavating operations, optional actuators provided as options, A main control valve block provided with a plurality of main control valves for individually controlling the operation of the main actuator, an option control valve for controlling the operation of the option actuator, a main operation means for operating the main actuator, and the option Optional operating means for operating an actuator, and the main actuator and a plurality of hydraulic pumps as hydraulic sources of the optional actuator, and discharge oil of these hydraulic pumps to the main actuator The control actuator is configured to be distributed and supplied to the option actuator, and the detection means for detecting that the option operation means is operated, and the pressure oil from at least one of the hydraulic pumps. A dedicated oil passage that can be supplied to the option control valve from a position upstream from each main control valve, and when the option operating means is operated, the dedicated oil passage is opened based on a signal from the detecting means. A switching valve to be opened, and a flow rate of the discharge oil that is provided on the upstream side of the main control valve and passes through the main control valve based on a signal from the detection means when the optional operation means is operated Restricting the flow rate to ensure the flow rate of the discharged oil supplied to the dedicated oil passage. It is obtained by a valve.

  According to the above configuration, when the optional operation means is operated, the switching valve opens the dedicated oil passage based on a signal from the detection means, and is located upstream of the main control valve and the switching A flow rate limiting valve provided on the downstream side of the valve limits the flow rate of the discharged oil passing through the main control valve based on a signal from the detecting means, whereby the discharged oil is supplied to the dedicated oil passage. Secure the flow rate. Therefore, for example, when the crusher is used as an optional device, the dismantling operation is continued without changing the crusher speed even if the arm or the like is operated. Moreover, since the standard main control valve block can be used regardless of whether or not the optional device is installed, a simple and inexpensive configuration can be realized.

  Further, the main actuator includes left and right traveling hydraulic motors, and the switching valve serves as the switching valve for discharging the discharge oil of at least one hydraulic pump to the both traveling hydraulic motors during combined operation of the both traveling hydraulic motors and other actuators. In the case where the straight traveling valve for sorting is provided, and the dedicated oil passage is provided in the straight traveling valve, the circuit configuration is further simplified.

  Further, when the main actuator is not in operation, if the entire flow rate of the hydraulic pump is joined and supplied to the dedicated oil passage, a sufficient pressure oil supply amount from the dedicated oil passage to the optional actuator is secured. .

  According to the present invention, for example, when a crusher is used as an optional device, the dismantling operation is continued without much changing the speed of the crusher even if the arm or the like is operated. In addition, in this case, since the existing main control valve block can be used, a simple and inexpensive configuration is realized. In addition, in this case, since the existing main control valve block can be used, a simple and inexpensive configuration is realized.

  First, a reference example different from the present invention will be described.

  FIG. 1 shows a hydraulic control circuit diagram of the hydraulic excavator according to the reference example. In FIG. 1, the first hydraulic pump 2, the second hydraulic pump 3, and the pilot pump 4 that generates the operating hydraulic pressure Pa are operated by driving the engine 1. The first and second hydraulic pumps 2 and 3 are variable displacement hydraulic pumps, and are constituted by swash plate type axial piston pumps in which the discharge flow rate changes based on the tilt angle displacement of the swash plate.

  The pressure oil discharged from the first and second hydraulic pumps 2 and 3 is a pilot type control valve arranged in the center bypass line LCB on the left side in the drawing, specifically, for driving the right traveling motor 5a. The right travel motor control valve 5, the bucket cylinder control valve 6 for extending and retracting the bucket cylinder 6a, and the boom cylinder control valve 7 for extending and retracting the boom cylinder 7a are supplied to the center on the right side in the figure. A pilot control valve disposed on the bypass line RCB, specifically, a left travel motor control valve 8 for causing the left travel motor 8a to travel, and a swing motor control valve for causing the swing motor 9a to swing. 9. Option cylinder control valve 10 for extending and retracting the option cylinder 10a, arm cylinder It is supplied to the arm cylinder control valve 11 for extending and retracting the 11a.

  The right traveling motor 5a, the bucket cylinder 6a, the boom cylinder 7a, the left traveling motor 8a, the turning motor 9a, and the arm cylinder 11a correspond to the main actuator, and the control valves 5 to 9, 11 correspond to the main control valve. The option cylinder 10a corresponds to an option actuator, and the control valve 10 corresponds to an option control valve. Further, the control valves 5 to 11 are integrally assembled to constitute the main control valve block VB. The main control valve block VB does not necessarily mean physical integration, but includes a case where the main control valve block VB is arranged in a substantially united manner within the compartment.

  The option cylinder 10a has a first position, a position, a second position, a third position, and a third position, and is normally held in the first position. In this reference example, the option cylinder 10a is attached to an optional device called a crusher having a bifurcated tip so as to perform opening / closing operation thereof. Further, since the bucket is removed when the crusher is installed, the crusher is moved back and forth by the bucket cylinder 6a, and the crusher is turned by the turning motor 9a.

  A straight travel valve 12 is interposed in the upstream oil passage L1 of the right travel motor control valve 5. The travel straight valve 12 has a first position and a second position, and is normally held at the first position.

  At this position, the pressure oil discharged from the first hydraulic pump 2 is supplied to the left center bypass line LCB side through the oil passage L1, while the pressure oil discharged from the second hydraulic pump 3 is supplied to the right through the oil passage L2. It is supplied to the center bypass line RCB side. Accordingly, pressure oil is supplied to the right travel motor control valve 5 and the left travel motor control valve 8 independently from the first hydraulic pump 2 and the second hydraulic pump 3, respectively.

  In addition, when the left and right travel levers (not shown) are operated at the same position and the operation valves 31 and 32 as main operation means are operated by the lever, the operation signal enters the controller 24. Whether or not an operation is being performed can be determined from the presence or absence of the operation signal. Then, the controller 24 gives a command signal to the electromagnetic proportional valve 22 based on this determination, and the operation of the electromagnetic proportional valve 22 causes the traveling straight valve 12 to switch from the position to the key position. By switching the traveling straight valve 12, the pressure oil discharged from the first hydraulic pump 2 is distributed and supplied to the swing motor control valve 9, the option cylinder control valve 10, and the arm cylinder control valve 11 through the oil passage L3. Become so.

  At this time, the pressure oil discharged from the second hydraulic pump 3 flows in parallel in the oil passages L1 and L2, and is supplied to the left and right traveling motor control valves 8 and 5. Thereby, for example, even when performing a complex operation that raises and lowers the boom while driving the traveling motors 8a and 5a, the pressure oil discharged from the second hydraulic pump 3 is equal to the left and right traveling motors 8a and 5a. Supplied and can keep running straight.

  A left cut valve 13 is provided downstream of the boom cylinder control valve 7 in the left center bypass line LCB, while a right cut valve is provided downstream of the arm cylinder control valve 11 on the right center bypass line RCB. 14 is provided.

  The left cut valve 13 closes when the control valve on the right center bypass line RCB side is operated, while the right cut valve 14 operates to close when the control valve on the left center bypass line LCB side is operated. . That is, when the traveling straight valve 12 is switched to the key position, the pressure oil discharged from the second hydraulic pump 3 is diverted to the oil passages L1 and L2, so that either control on the right center bypass line RCB side is performed. This is because when the valve is operated, the pump pressure cannot be established unless the left cut valve 13 on the left center bypass line LCB side is closed. On the other hand, one of the control valves on the left center bypass line LCB side is operated. This is because the pump pressure cannot be established unless the right cut valve 14 on the right center bypass line RCB side is closed.

  The oil passage L3 is connected to a joining oil passage L4 branched from the downstream side of the left travel motor control valve 8 in the right center bypass line RCB at a joining point P, and the oil extending from the joining point P Pressure oil is supplied to the option cylinder control valve 10 through the path L5, and pressure oil is supplied to the arm cylinder control valve 11 through oil paths L6 and L7 extending from the junction P.

  The option cylinder control valve 10 can perform a spool switching operation by operating a pedal 30 as an option operating means. That is, when the pedal 30 is not operated, the option cylinder control valve 10 is in the A position and is not connected to the option cylinder 10a. However, when the pedal 30 is operated in the direction A in FIG. Switch to position. Then, the pressure oil discharged from one of the first and second hydraulic pumps 2 and 3 is supplied to the head side oil chamber of the option cylinder 10a and extends the rod, so that the tip of the crusher is opened. be able to. On the other hand, when the pedal 30 is operated in the direction B in FIG. 1, the optional cylinder control valve 10 is switched to the C position. Then, the pressure oil discharged from one of the first and second hydraulic pumps 2 and 3 is supplied to the rod-side oil chamber of the option cylinder 10a and contracts the rod, so that the tip of the crusher is closed. be able to. Thus, in this reference example, the crusher can be opened and closed simply by operating the pedal 30.

  In addition, 15, 16, 26 and 27 in the oil passages L3 to L7 are check valves. In FIG. 1, 17 is an arm push / merge valve for accelerating the arm push, and 18 is a boom raise / merge valve for accelerating the boom raising. The outlet lines L8 and L9 of the left and right cut valves 13 and 14 merge with return lines L10 and L11, respectively, and are connected to the tank 20 via an oil cooler 19. In FIG. 1, 21 is a check valve with a spring in which an opening pressure is set according to the maximum hydraulic pressure of this circuit. Similarly, 23 and 25 are electromagnetic proportional valves controlled by a command signal from the controller 24.

  In the present reference example, pressure sensors P1 and P2 as detection means for detecting the presence or absence of the crusher operation by the pedal 30, and the crusher operation by the detected pressures of the pressure sensors P1 and P2 (hereinafter referred to as crusher operation pressure). Is detected, the bucket cylinder control valve 6, the boom cylinder control valve 7, the swing motor control valve 9, and the arm cylinder control are used in connection with the operation of the option cylinder control valve 10. Throttle means for restricting at least one of the meter-in opening and the meter-out opening of the valve 11 is provided. Note that the option cylinder control valve 10 and the left and right traveling motors 8 and 5 that are often used without being related to the operation of the option cylinder control valve 10 are excluded from the object of the throttle means here. It may be the target of the aperture means.

  This throttle means includes electromagnetic proportional valves 311 to 314 for reducing the secondary pressure of the operation valve 31 for operating the bucket cylinder control valve 6 and the boom cylinder control valve 7 when the crusher operation is performed, Primary pressure control of electromagnetic proportional valves 321 to 324 for reducing the secondary pressure of the operation valve 32 for operating the motor control valve 9 and the arm cylinder control valve 11 when the crusher operation is performed, and the operation valve 31 Therefore, pressure sensors P311 to P314 for detecting the secondary pressure and pressure sensors P321 to P324 for detecting the secondary pressure for primary pressure control of the operation valve 32 are provided. The electromagnetic proportional valves 311 to 314 and 321 to 324 can individually set the secondary pressure according to the forward / backward movement of the boom, arm, and crusher. The electromagnetic proportional valves 311 to 314 and 321 to 324 are not clearly shown in the figure, but are configured by an integrally structured block to achieve compactness.

  Further, as shown in FIG. 2, a pressure reducing valve 41 and a lever lock solenoid valve 42 are provided for reducing the primary pressure of the operation valves 31 and 32 when the crusher operation is performed. In the combination of the pressure reducing valve 41 and the lever lock electromagnetic valve 42, an oil passage as shown in FIG. 2 is normally formed, and the operation valves 31 and 32 are not under primary pressure.

  The primary pressure by adjusting the opening degree of the pressure reducing valve 41, that is, the pressure reducing amount of the primary pressure of the operation valves 31 and 32 is 50% in the case of a combined operation of crusher and boom raising, for example, in a combined operation of crusher and boom lowering. If there is no decompression, the pressure is reduced to 60% for the combined operation of the crusher and the arm pull, 40% for the combined operation of the crusher and the arm push, and 30% for the combined operation of the crusher and the arm. Thus, it is preset individually according to the type of work.

  When detection signals from the pressure sensors P1 and P2 indicating the operation of the pedal 30 are taken into the controller 24, a command signal is issued from the controller 24 to the lever lock solenoid valve 42, and the shut-off lever is operated by this command signal. As a result, the port of the lever lock solenoid valve 42 is switched. Then, the pilot pressure Pa is reduced to the predetermined primary pressure by the pressure reducing valve 41 and taken into the operation valves 31 and 32, and further individually reduced on the secondary pressure lines of the operation valves 31 and 32 to the respective control valves. Comes to work. Since the pressure sensors P 311 to P 314 and P 321 to P 324 are installed on the secondary pressure lines of the operation valves 31 and 32 as described above, the detection signals are also taken into the controller 24. The controller 24 gives a command signal proportional to the signal level to the pressure reducing valve 41 so that the pressure reducing valve 41 is feedback-controlled.

  As described above, when the optional cylinder 10a is used to open and close the crusher and the boom cylinder 6a and the swing motor 9a are used to perform the forward and backward movement and the swing operation of the crusher, according to this reference example, When the crusher operation is detected, at least one of the meter-in opening such as the bucket cylinder control valve 6 and the swing motor control valve 9 and the meter-out opening is throttled. Although the amount of pressure oil supplied to the bucket cylinder 6a, the swing motor 9a, etc. is reduced by the amount, the pressure oil supply amount to the option cylinder 10a is hardly reduced because the option cylinder control valve 10 side cannot be throttled. Therefore, when the crusher is used, even if the excavator body is operated, the dismantling operation is continued without changing the crusher speed so much. Therefore, the work efficiency is improved than the work can be performed comfortably and quickly. In addition, in this case, since the existing main control valve block VB can be used, a simple and inexpensive configuration is realized.

  Next, a first embodiment of the present invention will be described.

  FIG. 3 shows a hydraulic control circuit of the hydraulic excavator according to the first embodiment of the present invention. In addition, the same number is attached | subjected to the element which is common in the said reference example, and the duplication description is abbreviate | omitted.

  This hydraulic control circuit controls at least one discharge oil of pressure lines L51, L52 and first and second hydraulic pumps 2, 3 as detection means for detecting whether or not the crusher as an optional actuator is operated. A dedicated oil passage L50 that can be supplied from the upstream side of the valve block VBY to the optional cylinder control valve 10 and a switching valve 50 that opens and closes the dedicated oil passage L50 depending on whether or not the operation of the crusher is detected are provided. .

  In the first embodiment, the switching valve 50 and the option cylinder control valve 10 are included in the option control valve block VBX, and the block VBX is composed of the other control valves 5 to 9, 11 and the like. A so-called ADD-ON system that can be appropriately mounted on the block VBY is employed.

  The switching valve 50 has a first position as a first position and a second position as a second position, and is normally in the second position. When the crusher is operated, the pressure line L51, The switching valve 50 is switched to the S position by the pilot pressure from L52.

  However, when the actuators 5a to 9a and 11a of the excavator body are not operated at the same time, the total flow rates of the first and second hydraulic pumps 2 and 3 are joined and supplied to the dedicated oil passage L50 of the switching valve 50, Pressure oil is supplied from the dedicated oil passage L50 to the option cylinder 10a via the option cylinder control valve 10.

  On the other hand, when operating the actuators 5a to 9a and 11a of the excavator body, the supply flow rate to the control valves 5 to 9 and 11 is limited, and surplus oil is joined to the dedicated oil passage L50 of the switching valve 50. In this manner, pressure oil is supplied from the dedicated oil passage L50 to the option cylinder 10a via the option cylinder control valve 10. Therefore, a flow controller 51 that is a flow rate limiting valve that adjusts the flow rate according to the operation pressure of the throttle valve 52 and the pedal 30 at a position downstream of the switching valve 50 and upstream of the main control valve block VBX. And are provided. However, the flow controller 51 can be omitted by using a throttle valve with a flow rate adjusting function.

  In the first embodiment, the presence or absence of the crusher operation is detected, and at least one discharge oil of the first and second hydraulic pumps 2 and 3 can be supplied to the option cylinder 10a according to the presence or absence of the operation. The dedicated oil passage L50 of the switching valve 50 is opened and closed. Specifically, when the crusher is operated, in addition to the oil passage distributed and supplied from the hydraulic pump, the dedicated oil passage L50 is opened, and when the actuators 5a to 9a, 11a are operated, the control valve The supply flow rate to 5 to 9 and 11 is limited, and thereby the pressure oil supply amount to the optional cylinder control valve 10 is secured. Therefore, when the crusher is used, even if the excavator body is operated, the dismantling operation is continued without changing the crusher speed so much. Accordingly, work efficiency can be improved because work can be performed comfortably and quickly. In addition, in this case, the main control valve block VBY can be a standard one regardless of whether or not the optional device is installed, so that a simple and inexpensive configuration is realized.

  FIG. 4 shows a hydraulic control circuit of a hydraulic excavator according to the second embodiment of the present invention. In addition, the same number is attached | subjected to the element which is common in the said Embodiment 1, 2, and the duplication description is abbreviate | omitted.

  In the second embodiment, as shown in FIG. 4, the dedicated oil passage L60 is incorporated in the traveling straight valve 60 disposed in the main control valve block VBZ, and therefore, as in the first embodiment. An optional control valve block VBX having a single switching valve 50 is not provided.

  The straight travel valve 60 has a hook position as a third position in addition to a vertical position as a first position and a hound position as a second position, and is normally at the vertical position. When the controller 24 determines that the crusher operation is performed from the crusher operation pressure, the controller 24 gives a command signal to the electromagnetic proportional valve 61, operates the electromagnetic proportional valve 61 by this command signal, and sets the travel straight-advancing valve 60 to the H position. By switching to the heel position, the predetermined flow rate control as described in the second embodiment is performed.

  That is, when operating the crusher, the travel straight-advancing valve 60 is switched to the heel position by operating the pedal 30, but at the same time when the actuators 5a to 9a, 11a of the excavator body are not operated, the first and second hydraulic pumps 2 are operated. , 3 are combined and supplied to the dedicated oil passage L60 of the straight traveling valve 60, and pressure oil is supplied from the dedicated oil passage L60 to the option cylinder 10a via the option cylinder control valve 10. Will come to be.

  On the other hand, when operating the actuators 5a to 9a and 11a of the excavator body, the supply flow rate to the control valves 5 to 9 and 11 is limited, and surplus oil is joined to the dedicated oil passage L60 of the traveling straight valve 60. In this way, pressure oil is supplied from the dedicated oil passage L60 to the option cylinder 10a via the option cylinder control valve 10. For this purpose, a throttle valve 62 and a flow controller 63, which is a flow rate limiting valve that adjusts the flow rate according to the operating pressure of the pedal 30, are provided on the downstream side of the straight travel valve 60.

  However, the flow controller 63 detects the operation pressure of the pedal 30 with the pressure sensor 64, operates the electromagnetic proportional valve 65 in accordance with a command signal from the controller 24 corresponding to the detected pressure, and is set by the restriction flow controller 66. The flow rate is adjusted within the range.

  In the second embodiment, in addition to the same effects as those of the first embodiment, a single switching valve like the switching valve 50 of the second embodiment is not required, so that the circuit configuration is simplified. There is a merit that Therefore, the circuit configuration in a particularly small construction machine becomes easy.

It is a hydraulic circuit diagram of a hydraulic excavator according to a reference example. It is explanatory drawing which shows the example of control by the side of the primary pressure of the operation valve in the said reference example. 1 is a hydraulic circuit diagram of a hydraulic excavator according to a first embodiment of the present invention. FIG. 3 is a hydraulic circuit diagram of a hydraulic excavator according to a second embodiment of the present invention.

Explanation of symbols

2 First hydraulic pump 3 Second hydraulic pump 5 Right travel motor control valve (main control valve)
5a Right travel motor (main actuator)
6 Bucket cylinder control valve (main control valve)
6a Bucket cylinder (main actuator)
7 Boom cylinder control valve (main control valve)
7a Boom cylinder (main actuator)
8 Control valve for left travel motor (main control valve)
8a Left travel motor (main actuator)
9 Control valve for swing motor (main control valve)
9a Swing motor (main actuator)
10 Control valve for optional cylinder (optional control valve)
10a Optional cylinder (optional actuator)
11 Control valve for arm cylinder (main control valve)
11a Arm cylinder (main actuator)
12 Traveling straight valve 24 Controller (throttle means)
30 pedal (option operation means)
31, 32 Operation valve (main operation means)
50 Switching valve 51 Flow controller (Flow limiting valve)
52 Throttle valve 60 Traveling straight valve 61 Proportional solenoid valve 62 Throttle valve 63 Flow controller (flow control valve)
P1, P2 Pressure sensor (detection means)
L50, L60 Exclusive oil passage VB, VBY, VBZ Main control valve block VBX Option control valve block

Claims (3)

A hydraulic control circuit for a hydraulic excavator,
A plurality of main actuators for running, turning and excavating operations;
An optional actuator provided as an option;
A main control valve block provided with a plurality of main control valves for individually controlling the operations of the main actuators;
An optional control valve for controlling the operation of the optional actuator;
Main operating means for operating the main actuator;
Optional operation means for operating the optional actuator;
A plurality of hydraulic pumps as hydraulic sources of the main actuator and the optional actuator, and configured to distribute and supply discharge oil of these hydraulic pumps to the main actuator and the optional actuator;
Detecting means for detecting that the option operating means has been operated;
A dedicated oil passage capable of supplying pressure oil from at least one of the hydraulic pumps to the option control valve from a position upstream of the main control valves;
A switching valve that opens the dedicated oil passage based on a signal from the detection means when the optional operation means is operated;
By providing the upstream side of the main control valve and limiting the flow rate of the discharged oil passing through the main control valve based on a signal from the detection means when the optional operation means is operated. A hydraulic control circuit for a hydraulic excavator, comprising: a flow restriction valve that secures a flow rate of the discharged oil supplied to the dedicated oil passage. In the hydraulic control circuit of the hydraulic excavator according to claim 1,
The main actuator includes left and right traveling hydraulic motors,
The switching valve is a traveling straight valve that distributes the discharge oil of at least one hydraulic pump to the both traveling hydraulic motors during combined operation of the both traveling hydraulic motors and other actuators,
A hydraulic control circuit for a hydraulic excavator, characterized in that the dedicated oil passage is provided in the straight traveling valve. In the hydraulic control circuit of the hydraulic excavator according to claim 1 or 2,
A hydraulic control circuit for a hydraulic excavator, wherein the entire flow rate of the hydraulic pump is joined and supplied to the dedicated oil passage when the main actuator is not operated.

Images