JP6145386B2 - Fluid pressure control device for construction machinery - Google Patents

Description

  The present invention relates to a fluid pressure control device for a construction machine.

  Patent Document 1 discloses a hydraulic control device for a power shovel. The hydraulic control device includes a first circuit system connected to the first pump and a second circuit system connected to the second pump. A traveling control valve, a backup control valve, a turning control valve, a boom 2 control valve, and an arm 1 control valve are connected to the first circuit system in order from the upstream side. To the second circuit system, a travel straight control valve, a travel control valve, a bucket control valve, a boom 1 control valve, and an arm 2 control valve are connected in order from the upstream side.

  The working fluid discharged from the first pump is supplied to each control valve via a neutral passage, and is also supplied to each control valve via a parallel passage provided in parallel with the neutral passage. The working fluid discharged from the second pump is supplied to each control valve through a neutral passage, and is also supplied to each control valve through a parallel passage provided in parallel with the neutral passage.

JP 2009-41616 A

  In a power shovel such as Patent Document 1, when the straight traveling control valve is set to the neutral position, each actuator connected to the control valve of the first circuit system is driven by the discharge fluid of the first pump, Each actuator connected to the control valve of the two-circuit system is driven by the discharge fluid of the second pump.

  At this time, since the boom control valve and the arm control valve are respectively provided in the first circuit system and the second circuit system, the working fluid is supplied from the two pumps of the first pump and the second pump. Can be sufficiently secured.

  However, for example, since the bucket control valve is provided only in the second circuit system, the bucket is driven only by the working fluid from the second pump. That is, since the flow rate of the working fluid that can be supplied to the bucket is limited, there is a possibility that the speed cannot be sufficiently increased when the speed of the bucket is increased.

  The present invention has been made in view of such a technical problem, and provides a fluid pressure control device for a construction machine capable of increasing the flow rate of a working fluid with respect to a control valve provided in a second circuit system. For the purpose.

  The present invention is a fluid pressure control device for a construction machine including a control valve that supplies and discharges working fluid supplied from a first pump and a second pump to each actuator, and is connected to the first pump and is used for the first traveling. When the first control valve group composed of the control valve and the first work control valve arranged downstream from the first travel control valve, and all the control valves of the first control valve group are in the neutral position A first circuit system having a first neutral passage for returning the working fluid of the first pump to the tank and a first parallel passage connected in parallel to the first control valve group, and connected to the second pump A second control valve group comprising a second travel control valve and a second work control valve disposed downstream of the second travel control valve, and all control valves of the second control valve group The second neutral passage for returning the working fluid of the second pump to the tank when is in the neutral position And a second parallel passage connected in parallel to the second control valve group, and connected to the first parallel passage and the second neutral passage on the upstream side of the second control valve group A normal position for supplying the working fluid of the first pump to the first traveling control valve and supplying the working fluid of the second pump to the second traveling control valve; and the working fluid of the first pump for the first traveling A straight traveling position that supplies the control fluid to the control valve and the second travel control valve and supplies the working fluid of the second pump to the first parallel passage and the second parallel passage, and the working fluid of the first parallel passage to the second neutral passage A switching valve having a merging position for merging, and an opening / closing mechanism for opening and closing the first neutral passage, wherein at least one control valve of a control valve to be merged with a control valve downstream of the second traveling control valve is Other than neutral position The first neutral passage is closed by the opening and closing mechanism and the switching valve is switched to the merging position to merge the working fluid of the first pump with the working fluid of the second pump. .

  According to the present invention, when at least one control valve of the control valve to be joined by the control valve downstream of the second traveling control valve is switched to a position other than the neutral position, the first neutral passage is closed by the opening / closing mechanism. At the same time, the working fluid of the first pump is joined to the working fluid of the second pump by switching the switching valve to the joining position. Therefore, since the working fluid is supplied from the two pumps of the first pump and the second pump to the switched control valve, it is possible to sufficiently ensure the speed of the actuator to which the working fluid is supplied from the control valve. it can.

It is a circuit diagram showing a hydraulic control device of a construction machine concerning an embodiment of the present invention. It is sectional drawing which shows a cross section in case the control valve for driving | running | working straight advance is a neutral position. It is sectional drawing which shows a cross section when the control valve for driving | running | working straight advance is a merge position.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a circuit diagram showing a hydraulic control device 100 for a construction machine according to this embodiment.

  The construction machine is, for example, a power shovel, and the first pump P1 and the second pump P2 that discharge the working oil as the working fluid, and the working oil supplied from the first pump P1 and the second pump P2 is used as a traveling motor, A hydraulic control device 100 that feeds and discharges an actuator that drives a boom, an arm, and the like, and a tank T through which hydraulic oil flows back from the hydraulic control device 100 are provided.

  The hydraulic control device 100 includes a first circuit system 10 connected to the first pump P1 and a second circuit system 20 connected to the second pump P2.

  The first circuit system 10 includes a first neutral passage 11 that guides hydraulic oil supplied from the first pump P1 to the tank T, a first control valve group 12 that is connected in series to the first neutral passage 11, and a first control valve group 12. And a first parallel passage 13 branched from the first neutral passage 11 on the upstream side of the one control valve group 12. The first control valve group 12 is connected by a first neutral passage 11 and a first parallel passage 13. The first parallel passage 13 has a branching portion 13a and a first parallel passage portion 13b.

  The first control valve group 12 includes a travel control valve 121 as a first travel control valve, a reserve control valve 122 as a first work control valve, a turning control valve 123 as a first work control valve, The boom 2 control valve 124 as the first work control valve and the arm 1 control valve 125 as the first work control valve are arranged in this order from the upstream. The traveling control valve 121 switches supply and discharge of hydraulic oil to and from a traveling motor provided on the left side of the body of the power shovel. The spare control valve 122 switches supply / discharge of hydraulic oil to / from an actuator that drives an attachment such as a breaker or a crusher attached instead of a bucket described later. The turning control valve 123 switches the supply and discharge of the hydraulic oil to and from the turning motor for turning the turning body arranged at the upper part of the vehicle body. The boom 2 control valve 124 switches supply and discharge of hydraulic oil to and from an actuator that drives the boom. The arm 1 control valve 125 switches supply / discharge of hydraulic oil to / from an actuator that drives the arm.

  When all the control valves 121 to 125 of the first control valve group 12 are in the neutral position, the first neutral passage 11 guides the hydraulic oil supplied from the first pump P1 to the tank T, and at least one control valve 121 is provided. When .about.125 is switched to the operating position, the communication between the hydraulic oil and the tank T is cut off.

  The first parallel passage 13 is provided with a first pump when any one of the control valves 121 to 125 of the first control valve group 12 is switched to the operating position and the communication between the first neutral passage 11 and the tank T is cut off. The hydraulic oil supplied from P1 can be supplied to the control valves 121-125.

  The first circuit system 10 further includes a neutral cut valve 14 as an opening / closing mechanism connected to the first neutral passage 11 downstream of the first control valve group 12. The neutral cut valve 14 opens the first neutral passage 11 when in the illustrated normal position, and closes the first neutral passage 11 when switched to the closed position.

  On the other hand, the second circuit system 20 includes a second neutral passage 21 that guides hydraulic oil supplied from the second pump P2 to the tank T, and a second control valve group 22 that is connected in series to the second neutral passage 21 in series. And a second parallel passage 23 branched from the second neutral passage 21 on the upstream side of the second control valve group 22. The second control valve group 22 is connected by a second neutral passage 21 and a second parallel passage 23.

  The second control valve group 22 includes a travel control valve 221 as a second travel control valve, a bucket control valve 222 as a second work control valve, and a boom 1 control valve 223 as a second work control valve. The arm 2 control valve 224 as the second work control valve is arranged from the upstream in this order. The traveling control valve 221 switches between supply and discharge of hydraulic oil to and from a traveling motor provided on the right side of the vehicle body of the power shovel. Bucket control valve 222 switches supply and discharge of hydraulic oil to and from an actuator that drives the bucket. The boom 1 control valve 223 switches between supplying and discharging hydraulic oil to and from an actuator that drives the boom. The arm 2 control valve 224 switches between supply and discharge of the hydraulic oil to the actuator that drives the arm.

  When all the control valves 221 to 224 of the second control valve group 22 are in the neutral position, the second neutral passage 21 guides hydraulic oil supplied from the second pump P2 to the tank T, and at least one control valve 221 is provided. When .about.224 is switched to the operating position, the communication between the hydraulic oil and the tank T is cut off.

  The second parallel passage 23 is connected to the second pump when the control valve 221 to 224 of the second control valve group 22 is switched to the operating position and the communication between the second neutral passage 21 and the tank T is cut off. The hydraulic oil supplied from P2 can be supplied to the control valves 221 to 224.

  The second circuit system 20 includes a neutral cut valve 24 connected to the second neutral passage 21 downstream from the second control valve group 22, and a second parallel passage 23 upstream from the second control valve group 22. And a straight traveling control valve 25 as a switching valve connected to the second neutral passage 21 downstream from the bifurcation point.

  The neutral cut valve 24 opens the second neutral passage 21 when in the normal position, and closes the second neutral passage 21 when switched to the closed position. Note that other control valve groups (not shown) can be controlled from the branch passage 61 provided upstream of the neutral cut valve 24.

  The straight travel control valve 25 is interposed between the branch portion 13a of the first parallel passage 13 and the first parallel passage portion 13b and connected to the second neutral passage 21, and the normal position A shown in FIG. Can be switched to three positions: a straight traveling position B shown on the left side of FIG. 1 and a merging position C shown on the right side of FIG. The positions A, B, and C of the straight travel control valve 25 change according to the pilot pressure acting on the pilot chambers 25a and 25b provided at both ends of the straight travel control valve 25. When the pilot pressure does not act on any of the pilot chambers 25a and 25b, the straight travel control valve 25 is in the normal position A.

  At the normal position A, the branch portion 13 a is connected to the first parallel passage portion 13 b, and the second neutral passage 21 upstream from the traveling straight travel control valve 25 is connected to the second parallel passage 23. Thus, the hydraulic oil of the first pump P1 is supplied to the control valves 122 to 125 of the first control valve group 12 via the first neutral passage 11 and the first parallel passage 13, and the operation of the second pump P2 is performed. Oil is supplied to the second control valve group 22 via the second parallel passage 23. That is, the hydraulic oil of the first pump P1 is supplied to the travel control valve 121 of the first circuit system 10, and the hydraulic oil of the second pump P2 is supplied to the travel control valve 221 of the second circuit system 20.

  In the straight travel position B, the branching portion 13a is connected to the second neutral passage 21 downstream from the straight travel control valve 25, and the second neutral passage 21 upstream from the straight travel control valve 25 is the first parallel. Connected to the passage portion 13b. Thereby, the hydraulic oil of the first pump P1 is supplied to the traveling control valve 121 of the first circuit system 10 and the traveling control valve 221 of the second circuit system 20, and the hydraulic oil of the second pump P2 is supplied to the first control valve. The control valves 122 to 125 of the group 12 and the control valves 222 to 224 of the second control valve group 22 are supplied. That is, since the circuit for traveling and the circuit other than traveling are independent, the traveling straightness of the vehicle body is ensured.

  At the merge position C, the second neutral passage 21 on the upstream side of the straight travel control valve 25 is connected to the second neutral passage 21 on the downstream side, and the branch portion 13a is formed inside the straight travel control valve 25. The second neutral passage 21 is connected to the second neutral passage 21 through a merging passage 26. As a result, the hydraulic oil of the first pump P1 and the hydraulic oil of the second pump P2 merge and are supplied to the second control valve group 22, and more to the actuator connected to the control valve of the second control valve group 22. The hydraulic oil can be supplied.

  In the merging passage 26 formed inside the straight running control valve 25, a check valve 27 that allows only the flow from the branch portion 13a to the second neutral passage 21 and the flow of hydraulic oil in the merging passage 26 are provided. A restrictor 28 for restricting is provided in this order from the upstream side.

  As a result, the hydraulic oil of the second pump P2 can be prevented from flowing to the branching portion 13a side, and the hydraulic oil of the branching portion 13a can be reduced to reduce the hydraulic oil during the combined operation of the first control valve group 12 and the second control valve group 22. The combined flow rate from the first pump P1 to the second pump P2 can be adjusted and merged into the second neutral passage 21.

  Next, the structure of the straight travel control valve 25 will be described with reference to FIGS. FIG. 2 is a cross-sectional view showing a cross section when the straight traveling control valve 25 is in the normal position A. FIG. FIG. 3 is a cross-sectional view showing a cross section when the straight traveling control valve 25 is at the merging position C. FIG.

  As shown in FIG. 2, the straight travel control valve 25 includes a valve block 30 having a cylindrical hole 30a, and a spool 40 that is inserted into the hole 30a and is slidable in the axial direction (left-right direction in FIG. 2). And comprising. In the following description, one end side of the valve block 30 indicates the left end side in FIG. 2, and the other end side of the valve block 30 indicates the right end side in FIG.

  On the inner peripheral surface of the valve block 30, a first annular groove 31 communicating with the branch portion 13 a, a second annular groove 32 communicating with the second neutral passage 21 downstream from the valve block 30, and upstream of the valve block 30. A third annular groove 33 communicating with the second neutral passage 21 on the side, a fourth annular groove 34 communicating with the first parallel passage portion 13b, and a fifth annular groove communicating with the first annular groove 31 via the supply passage 36. A groove 35 is formed in this order from one end side.

  On the outer peripheral surface of the spool 40, a first annular recess 41 provided at a position facing the first annular groove 31 and a second position provided at a position facing the second annular groove 32 to the third annular groove 33. An annular recess 42 and a third annular recess 43 provided at positions facing each other from the fourth annular groove 34 to the fifth annular groove 35 are formed in this order from one end side.

  A confluence passage 26 extending in the axial direction is formed in the spool 40. The merge passage 26 includes a first opening 51 as a throttle 28 that opens to the second annular recess 42, and a second opening 52. Further, a check valve 27 is interposed between the merging passage 26 and the second opening 52. The check valve 27 is always urged to one end side by the spring 29 so as to allow only the flow of hydraulic oil from the second opening 52 toward the first opening 51.

  Further, at one end of the valve block 30, a spring 25c that biases the spool 40 in the axial direction and a first pilot chamber 25a into which a pilot pressure that biases the spool 40 toward the other end is guided are provided. The other end of the valve block 30 is provided with a second pilot chamber 25b into which a pilot pressure that biases the spool 40 toward one end is guided.

  When the pilot pressure is not guided to either the first pilot chamber 25a or the second pilot chamber 25b, the spool 40 is held at the position shown in FIG. When the pilot pressure is supplied to the first pilot chamber 25a, the spool 40 slides against the urging force of the spring 25c, and when the pilot pressure is supplied to the second pilot chamber 25b, the spring 25c. The spool 40 slides to one end side against the urging force and is held at the position shown in FIG.

  As shown in FIG. 2, when the pilot pressure is not guided to either the first pilot chamber 25a or the second pilot chamber 25b, the straight travel control valve 25 is in the normal position A, and the operation is guided from the branch portion 13a. The oil is supplied to the fifth annular groove 35 via the first annular groove 31 and the supply passage 36, and further supplied to the first parallel passage portion 13b via the third annular recess 43 and the fourth annular groove 34. Further, the hydraulic oil guided from the second neutral passage 21 upstream from the travel straight travel control valve 25 passes through the third annular groove 33, the second annular recess 42, and the second annular groove 32, and the travel straight travel control valve 25. It is supplied to the neutral flow path 21 on the downstream side.

  As shown in FIG. 3, when pilot pressure is supplied to the second pilot chamber 25 b, the straight travel control valve 25 becomes the merge position C, and the second annular groove 32 and the third annular groove 33 formed by the second annular recess 42. However, the communication between the fourth annular groove 34 and the fifth annular groove 35 by the third annular recess 43 is blocked. As a result, the hydraulic fluid guided from the branch portion 13a is supplied to the fifth annular groove 35 via the first annular groove 31 and the supply passage 36, and further, the second opening 52, the check valve 27, and the first opening. 51, supplied to the second neutral passage 21 via the second annular recess 42.

  Further, the second neutral passage 21 upstream of the straight travel control valve 25 and the second parallel passage 23 connected to the second neutral passage 21 communicate with each other on the upstream side of the third annular groove 33. That is, at the merge position C, the hydraulic oil of the first pump P1 supplied from the branch portion 13a merges with the hydraulic oil of the second pump P2 in the second neutral passage 21, and is supplied to the second parallel passage 23.

  Returning to FIG. 1, the case where the straight traveling control valve 25 is switched from the normal position A to the merge position C will be described.

  When the straight traveling control valve 25 is in the normal position A, the hydraulic oil of the second pump P2 is supplied to the second control valve group 22 via the second neutral passage 21 and the second parallel passage 23. In order to operate the bucket at a normal speed, the bucket control valve 222 is switched to a position other than the neutral position, and the hydraulic oil of the second pump P2 is supplied to the actuator that drives the bucket.

  Here, when the bucket is operated at a higher speed than usual, the first neutral passage 11 is closed by the neutral cut valve 14 of the first circuit system 10, and the straight traveling control valve 25 is switched to the merge position C. Then, the bucket control valve 222 is switched to the operating position. As a result, the communication between the first neutral passage 11 and the tank T is cut off, so that the hydraulic oil of the first pump P1 flows preferentially to the branching portion 13a and enters the second neutral passage 21 in the straight travel control valve 25. Join. The joined hydraulic oil is supplied to the bucket control valve 222 via the second parallel passage 23. Therefore, more hydraulic oil is supplied to the actuator that drives the bucket.

  According to the above embodiment, there exist the effects shown below.

  When the bucket control valve 222 is switched to a position other than the neutral position, the first neutral passage 11 is closed by the neutral cut valve 14 of the first circuit system 10 and the straight travel control valve 25 is switched to the merge position C. Thus, the hydraulic oil of the first pump P1 is merged with the hydraulic oil of the second pump P2. Therefore, since the hydraulic oil is supplied to the bucket control valve 222 from the two pumps of the first pump P1 and the second pump P2, more hydraulic oil can be supplied to the actuator that drives the bucket. Therefore, the bucket can be operated at a higher speed by the amount of the increased flow rate.

  Furthermore, by providing the merging position C in the straight traveling control valve 25, the hydraulic oil of the first pump P1 and the hydraulic oil of the second pump P2 are merged in the straight traveling control valve 25. It is not necessary to add extra external piping or the like to the hydraulic control device 100. As a result, the hydraulic oil of the first pump P1 and the hydraulic oil of the second pump P2 can be merged simply by replacing the straight running control valve 25 of the existing hydraulic control apparatus 100. And cost increase can be suppressed.

  Further, since the straight traveling control valve 25 has the check valve 27 that allows only the flow of the working fluid from the branching portion 13a to the second neutral passage 21 when in the merge position C, the operation in the branching portion 13a is performed. When the pressure of the oil is lower than the pressure of the hydraulic oil in the second neutral passage 21, the hydraulic oil flows backward from the second neutral passage 21 to the branch portion 13a, and the pressure of the hydraulic oil in the second neutral passage 21 decreases. Can be prevented.

  Further, since the straight travel control valve 25 has the throttle 28 that restricts the flow of hydraulic oil from the branching portion 13a to the second neutral passage 21 when it is at the merge position C, the hydraulic oil pressure of the branching portion 13a is throttled. Thus, the combined flow rate from the first pump P1 to the second pump P2 can be adjusted and combined with the second neutral passage 21 during the combined operation of the first control valve group 12 and the second control valve group 22.

  Further, a confluence passage 26 extending in the axial direction is formed inside the spool 40 constituting the straight travel control valve 25. When the confluence position C is reached, the confluence passage 26 communicates with the branch portion 13a. The fifth annular groove 35 and the second annular groove 32 communicating with the second parallel passage 23 are communicated with each other. Thereby, since it is not necessary to newly provide the junction passage 26 as external piping, the enlargement of the hydraulic control apparatus 100 can be suppressed.

  Further, since the neutral cut valve 14 of the first circuit system 10 that closes the first neutral passage 11 when the straight traveling control valve 25 is switched to the merge position C is provided on the downstream side of the first control valve group 12, Even when the hydraulic oil of the first pump P1 is merged with the hydraulic oil of the second pump P2, the hydraulic oil of the first pump P1 is supplied to the control valves 121 to 125 of the first control valve group 12. be able to. Thereby, even if the straight traveling control valve 25 is switched to the merging position C for the bucket operation, the actuator connected to each control valve 121 to 125 of the first control valve group 12 is driven, for example, a turning operation is performed. Etc. can be performed. Further, since the throttle 28 is provided, the first control valve group 12 is not excessively joined to the second neutral passage 21 even when the control valve of the second control valve group 22 having a light load is operated. Can be operated.

  The embodiment of the present invention has been described above. However, the above embodiment is merely one example of application of the present invention, and the technical scope of the present invention is limited to the specific configuration of the above embodiment. Absent.

  For example, in the above-described embodiment, when the bucket control valve 222 is switched to a position other than the neutral position, the straight travel control valve 25 is switched to the merging position C, but is provided downstream of the travel control valve 221. If it is a control valve, the straight travel control valve 25 may be switched to the merging position C in accordance with switching of control valves other than the bucket control valve 222.

  Further, in the above embodiment, the check valve 27 is provided in the merge passage 26. However, when it is not necessary to prevent the backflow of the hydraulic oil from the second neutral passage 21 to the branch portion 13a, the check valve 27 is provided. May not be provided.

  Further, in the above embodiment, the throttle 28 is provided in the merging passage 26, but the first control valve group 12 and the second control valve group 22 are combined during the combined operation by reducing the pressure of the hydraulic oil in the branch portion 13a. If it is not necessary to adjust the combined flow rate from the first pump P1 to the second pump P2, the throttle 28 may not be provided.

  Further, in the above embodiment, when the straight traveling control valve 25 is switched to the merge position C, the first neutral passage 11 is closed by the neutral cut valve 14 of the first circuit system 10, but the bucket, boom, If it is not necessary to perform this combined operation, the first neutral passage 11 may be closed by switching the boom 2 control valve 124 instead of the neutral cut valve 14, or other control valves may be switched. The first neutral passage 11 may be closed.

DESCRIPTION OF SYMBOLS 10 1st circuit system 11 1st neutral channel | path 12 1st control valve group 13 1st parallel channel | path 13a Branch part (1st parallel channel | path)
13b 1st parallel path part (1st parallel path)
14 Neutral cut valve (open / close mechanism)
20 Second circuit system 21 Second neutral passage 22 Second control valve group 23 Second parallel passage 25 Control valve for straight travel (switching valve)
26 Confluence passage 27 Check valve 28 Restriction 30 Valve block 30a Hole 40 Spool 100 Fluid pressure control device 121 Travel control valve (first travel control valve)
122 Preliminary control valve (first operation control valve)
123 Control valve for turning (first operation control valve)
124 Control valve for boom 2 (first operation control valve)
125 Control valve for arm 1 (first operation control valve)
221 Travel control valve (second travel control valve)
222 Bucket control valve (second control valve)
223 Boom 1 control valve (second operation control valve)
224 Arm 2 control valve (second operation control valve)
P1 1st pump P2 2nd pump T tank

Claims (5)

A fluid pressure control device for a construction machine comprising a control valve for supplying and discharging working fluid supplied from a first pump and a second pump to each actuator,
A first control valve group connected to the first pump and configured by a first travel control valve and a first work control valve disposed downstream of the first travel control valve; and A first neutral passage for returning the working fluid of the first pump to the tank when all the control valves of the control valve group are in a neutral position, and a first parallel connected in parallel to the first control valve group A first circuit system having a passage;
A second control valve group connected to the second pump and configured by a second travel control valve and a second work control valve disposed downstream of the second travel control valve; A second neutral passage for returning the working fluid of the second pump to the tank when all the control valves of the control valve group are in a neutral position, and a second connected in parallel to the second control valve group A second circuit system having a parallel path;
Connected to the first parallel passage and the second neutral passage on the upstream side of the second control valve group, the working fluid of the first pump is supplied to the first travel control valve and the second pump A normal position for supplying the working fluid to the second traveling control valve, and supplying the working fluid of the first pump to the first traveling control valve and the second traveling control valve and operating the second pump A switching valve having a straight traveling position for supplying fluid to the first parallel passage and the second parallel passage, and a joining position for joining the working fluid of the first parallel passage to the second neutral passage;
An opening and closing mechanism for opening and closing the first neutral passage;
With
When at least one control valve of a control valve to be joined by a control valve downstream of the second travel control valve is switched to a position other than the neutral position, the first neutral passage is closed by the opening / closing mechanism. The working fluid of the first pump is joined to the working fluid of the second pump by switching the switching valve to the joining position.
A fluid pressure control device for a construction machine. The switching valve has a check valve that allows only a flow of working fluid from the first parallel passage to the second neutral passage when the switching valve is in the joining position.
The fluid pressure control device for a construction machine according to claim 1. The switching valve has a throttle that restricts the flow of the working fluid from the first parallel passage to the second neutral passage when the switching valve is in the joining position.
The fluid pressure control device for a construction machine according to claim 1, wherein the fluid pressure control device is for a construction machine. The switching valve has a valve block having a cylindrical hole, and a spool that is inserted into the hole and slides to switch between the normal position, the straight traveling position, and the joining position.
A joining passage for joining the working fluid of the first parallel passage to the second neutral passage is formed inside the spool;
The fluid pressure control device for a construction machine according to any one of claims 1 to 3, wherein The open / close mechanism opens and closes the first neutral passage on the downstream side of the first control valve group;
The fluid pressure control device for a construction machine according to any one of claims 1 to 4, characterized in that:

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