JP2017159983A - Hydraulic circuit of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit of a construction machine in which two winch drums of one-axis one-motor method can be operated by an operating system of a one-axis two drum method.SOLUTION: The hydraulic circuit of a construction machine comprises: a first hydraulic motor 25 that drives a first drum 22 via a first clutch 24; a second hydraulic motor 27 that drives a second drum 23 via a second clutch 26; a first clutch pilot valve 28 that operates the first clutch; a second clutch pilot valve 29 that operates the second clutch; a first rotating direction setting valve 31 that sets a rotating direction of the first hydraulic motor; a second rotating direction setting valve 32 that sets a rotating direction of the second hydraulic motor; a rotating direction setting pilot valve 33 for setting a rotating direction which activates the first rotating direction setting valve and the second rotating direction setting valve; and a first rotating direction-relaying pilot valve 34, a second rotating direction-relaying pilot valve 35 and a pilot pressure-blocking passage 36 which are activated in response to operation of the first clutch pilot valve and the second clutch pilot valve.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic circuit of a construction machine, and more particularly to a hydraulic circuit provided in a construction machine having a plurality of winch drums.

  In construction machines such as cranes and pile driving machines equipped with a plurality of winch drums, a single-shaft one-motor system in which one drum is arranged in one motor is usually employed. In this case, the operating system has one rotating lever of the motor and one clutch lever. Therefore, in the case where two winch drums are mounted, there are two rotation levers and two clutch levers (see, for example, Patent Document 1). On the other hand, there are cases where two drums are arranged on the same axis and two drums are driven by a single motor due to restrictions on the installation space of the machine and the hydraulic system. In the case of this one-shaft two-drum system, there is one rotating lever and two clutch levers.

JP 2012-166888 A

  In the 1-axis 2-drum system, the drum width per one is narrow and the length of the wire rope wound around the drum is limited. Therefore, when trying to lengthen the wire rope to be used, the 1-axis 1-motor system It is conceivable to remodel. However, when two winch drums of 1 axis 1 motor system are installed, the number of operation levers is larger than that of 1 axis 2 drum system, and it is necessary to change the link relation directly connected to the operation lever. The remodeling was so big that it could not be changed easily.

  Therefore, the present invention can operate two winch drums of 1 axis 1 motor system with a 1 axis 2 drum system operation system, and the construction machine adopting 1 axis 2 drum system is changed to 1 axis 1 motor system. It is an object of the present invention to provide a hydraulic circuit of a construction machine that can easily cope with remodeling.

  To achieve the above object, a hydraulic circuit for a construction machine according to the present invention includes a first hydraulic motor that drives a first drum via a first clutch, and a second hydraulic pressure that drives a second drum via a second clutch. A motor, a first clutch pilot valve that operates the first clutch by turning on and off the first clutch pilot pressure supplied to the first clutch, and a second clutch pilot pressure that is supplied to the second clutch and turned on and off. A second clutch pilot valve that operates the second clutch, a first rotation direction setting valve that sets a rotation direction of the first hydraulic motor by switching a path of hydraulic oil supplied from the hydraulic pump to the first hydraulic motor, A second rotational direction setting valve that sets a rotational direction of the second hydraulic motor by switching a path of hydraulic fluid supplied from the hydraulic pump to the second hydraulic motor; A rotation direction setting pilot valve for setting a rotation direction of the first hydraulic motor and the second hydraulic motor by switching a rotation direction setting pilot pressure supplied to the one rotation direction setting valve and the second rotation direction setting valve; The forward rotation pilot pressure path and the reverse rotation pilot pressure path from the rotation direction setting pilot valve include the forward rotation when the first clutch pilot valve and the second clutch pilot valve are both in the clutch disengagement position. When the pilot pressure path and the counter-rotating pilot pressure path are communicated with the first rotation direction setting valve and the second rotation direction setting valve, respectively, when only the first clutch pilot valve is in the on position, the first The path of the forward rotation pilot pressure and the path of the reverse rotation pilot pressure by the pilot pressure from the clutch pilot valve The first rotation direction setting valve communicates with the forward rotation side path and the reverse rotation side path, and the pilot pressure path to the second rotation direction setting valve is shut off, so that only the second clutch pilot valve is in the on position. In this case, the forward rotation pilot pressure path and the reverse rotation pilot pressure path communicate with the forward rotation side path and the reverse rotation side path of the second rotation direction setting valve by the pilot pressure from the second clutch pilot valve, respectively. And a pair of first rotation direction relay pilot valves and a second rotation direction relay pilot valve that block a pilot pressure path to the first rotation direction setting valve, and further, the first clutch pilot valve and the When the second clutch pilot valve is in the joint position, the first clutch pilot valve and the second clutch valve A pilot pressure that blocks a pilot pressure path from the first clutch pilot valve and the second clutch pilot valve to the first rotation direction relay pilot valve and the second rotation direction relay pilot valve by the pilot pressure from the pilot valve. It is characterized by having a blocking path.

  Furthermore, in the hydraulic circuit for the construction machine according to the present invention, when the second rotation direction setting valve is in the neutral position, the hydraulic oil from the hydraulic pump is supplied to the first rotation direction setting valve. At the second hydraulic motor operating position where the pilot pressure is applied to the path or the reverse rotation side path, the hydraulic oil from the hydraulic pump is supplied to the second hydraulic motor, and the hydraulic oil after driving the second hydraulic motor is supplied to the second hydraulic motor. It is characterized by being in a state of being supplied to the one-rotation direction setting valve.

  The pilot pressure shut-off path includes a first pilot pressure switching valve for switching a path on which the pilot pressure from the first clutch pilot valve acts by a pilot pressure from the second clutch pilot valve, and the first pilot pressure switching valve. The first pilot pressure shut-off valve that shuts off the path for operating the rotational relay pilot valve from the first clutch pilot valve and the rotational relay pilot valve from the second clutch pilot valve are operated by the pilot pressure of the path switched by And a second pilot pressure shut-off valve that shuts off the path to be turned on.

  According to the hydraulic circuit of the construction machine of the present invention, the rotation directions of the first hydraulic motor and the second hydraulic motor are set by operating one rotation direction setting pilot valve, and the two first clutch pilot valves and the second clutch are set. By turning the clutch on and off with the pilot valve, the desired drum can be rotated and the hydraulic motor of the drum not in use can be stopped. Accordingly, it is possible to operate two winch drums of one-shaft / one-motor system with a single-shaft / two-drum system operating system having one rotary lever and two clutch levers. Thereby, remodeling when changing a construction machine adopting the single-shaft two-drum system to the single-shaft single-motor system can be easily performed without modifying the operation system.

It is a hydraulic circuit diagram which shows one example of the hydraulic circuit of the construction machine of this invention. Similarly, it is a hydraulic circuit diagram which shows the state which operated the rotation direction of the 1st hydraulic motor and the 2nd hydraulic motor to the positive direction, and cut | disconnected both the 1st clutch and the 2nd clutch. Similarly, it is a hydraulic circuit diagram which shows the state which operated the rotation direction of the 1st hydraulic motor and the 2nd hydraulic motor to the positive direction, put the 1st clutch, and cut | disconnected the 2nd clutch. Similarly, it is a hydraulic circuit diagram which shows the state which operated the rotation direction of the 1st hydraulic motor and the 2nd hydraulic motor to the positive direction, disconnected the 2nd clutch, and put the 2nd clutch. Similarly, it is a hydraulic circuit diagram which shows the state which operated the rotation direction of the 1st hydraulic motor and the 2nd hydraulic motor to the positive direction, and put together the 1st clutch and the 2nd clutch. It is a side view showing an example of a construction machine carrying a plurality of winch drums.

  FIG. 6 is a side view showing a crawler crane which is one of construction machines to which the hydraulic circuit of the construction machine of the present invention can be applied. The crawler crane 11 includes a lower traveling body 12 and an upper revolving body 13 that is turnably provided on the upper portion of the lower traveling body 12. A device room 13a provided with a pump and the like, and a plurality of winches each wound with a main winding rope 14a, an auxiliary winding rope 14b, and a hoisting rope 14c are provided, and a boom 15 that can tilt in the front-rear direction is provided at the front portion. A driver's seat 13b is provided. In the driver's seat 13b, there are provided a plurality of operating devices such as a plurality of winches, crawlers, and a plurality of operating levers, operation pedals, push button switches, and the like, and in the equipment room 13a, An engine and a hydraulic circuit controlled by these operating devices are provided.

  The hydraulic circuit of the present invention is basically similar to the known hydraulic circuit, by switching the path of the hydraulic fluid for power supplied from the hydraulic pump for power by using a plurality of control valves, for example, Controls forward and reverse rotation of the hydraulic motor, and controls expansion and contraction of the cylinder. Switching of the control valve switches the path of pilot oil supplied from a pilot hydraulic pump (not shown) such as an operation lever. The operation is performed by opening and closing or switching the pilot valve by an operating device.

  FIGS. 1 to 5 show an example of a hydraulic circuit of the present invention formed so that two winch drums of a single-shaft single-motor system can be operated by a single-shaft dual-drum operation system.

  That is, the hydraulic circuit 21 shown in the present embodiment includes a first drum 22 wound with the main winding rope 14a, a second drum 23 wound with the auxiliary winding rope 14b, and the first drum 22 as the first drum. A first hydraulic motor 25 that is driven via the clutch 24, a second hydraulic motor 27 that drives the second drum 23 via the second clutch 26, and a first clutch pilot pressure that is supplied to the first clutch 24 The first clutch pilot valve 28 for operating the first clutch 24 by turning on and off, and the second clutch pilot for operating the second clutch 26 by turning on and off the second clutch pilot pressure supplied to the second clutch 26. The rotation direction of the first hydraulic motor 25 is set by switching the path of the hydraulic oil supplied from the valve 29 and the hydraulic pump 30 to the first hydraulic motor 25. A first rotation direction setting valve 31, a second rotation direction setting valve 32 for setting the rotation direction of the second hydraulic motor by switching the path of hydraulic oil supplied from the hydraulic pump 30 to the second hydraulic motor 27, The rotation direction setting pilot pressure supplied to the first rotation direction setting valve 31 and the second rotation direction setting valve 32 is switched between the forward rotation side pilot valve 33a and the reverse rotation side pilot valve 33b to switch the first hydraulic motor 25 and the A rotation direction setting pilot valve 33 that sets the rotation direction of the second hydraulic motor 27 and a pair of first rotation direction relay pilot valves 34 that operate according to the states of the first clutch pilot valve 28 and the second clutch pilot valve 29. And the second rotational direction relay pilot valve 35 and, similarly, the operating conditions of the first clutch pilot valve 28 and the second clutch pilot valve 29. And a pilot pressure cutoff path 36 that operates in response to the first pilot pressure switching valve 37, the first pilot pressure cutoff valve 38, and the second pilot pressure cutoff valve 39 provided in the pilot pressure cutoff path 36. It has been. The first clutch pilot valve 28, the second clutch pilot valve 29, and the rotation direction setting pilot valve 33 can be operated by known operation devices such as operation buttons and operation levers.

  The valve unit provided with the first rotation direction setting valve 31 is provided with various control valves for traveling, etc., and the control operation part provided with the rotation direction setting pilot valve 33 is provided with a boom raising / lowering. The operation lever is provided, and a plurality of check valves are provided in the hydraulic circuit. These are the same as those provided in the normal hydraulic circuit. A description of those not related to the operation of the drum 22 and the second drum 23 will be omitted.

  The operation of the hydraulic circuit shown in this embodiment will be described below with reference to FIGS. In the description of each figure, only the path through which the hydraulic oil flows and the operating path where the pilot pressure is applied are denoted by reference numerals, and the reference numerals for the non-operating paths are omitted.

  First, FIG. 1 shows a state in which the rotation direction setting pilot valve 33 is in the neutral position and the first clutch pilot valve 28 and the second clutch pilot valve 29 are both in the disengaged position (clutch disconnected state). At this time, since the clutch pilot pressure is cut off by the first clutch pilot valve 28 and the second clutch pilot valve 29, both the first clutch 24 and the second clutch 26 are in the disengaged state, and the first drum 22 And the 2nd drum 23 has stopped. Further, the first rotation direction relay pilot valve 34 and the second rotation direction relay pilot valve 35 are also in the neutral position, and the first pilot pressure switching valve 37, the first pilot pressure cutoff valve 38, and the second pilot pressure cutoff valve 39 are Inactive position.

  On the other hand, the hydraulic oil sucked into the hydraulic pump 30 from the tank 50 via the path 51 and boosted to a predetermined pressure passes through the path 52 and passes through the second rotation direction setting valve 32 in which the spool is in the neutral position. 53, the spool passes through the first rotation direction setting valve 31 in the neutral position, and is returned to the tank 50 from the path 54. Therefore, the first hydraulic motor 25 and the second hydraulic motor 27 are also stopped.

  FIG. 2 shows a state where the rotation direction setting pilot valve 33 is operated to the forward rotation side, for example, the winding side. By operating the rotation direction setting pilot valve 33 to the forward rotation side, the forward rotation side pilot valve 33a is in a communicating state, and the pilot pressure from the forward rotation side pilot valve 33a is in a neutral state in the first rotation direction relay. The pilot pressure is divided into two directions in the pilot valve 34, and one pilot pressure pushes the spool of the first rotation direction setting valve 31 to the forward rotation side through the path 71. The other pilot pressure pushes the spool of the second rotation direction setting valve 32 to the forward rotation side through the path 72.

  As a result, the hydraulic oil whose pressure has been increased by the hydraulic pump 30 flows from the second rotation direction setting valve 32 toward the path 55, rotates the second hydraulic motor 27 in the forward direction, and then passes through the path 56 to the second. Return to the rotation direction setting valve 32. The hydraulic oil that has flowed out of the second rotation direction setting valve 32 into the path 53 flows out of the first rotation direction setting valve 31 into the path 57, and rotates the first hydraulic motor 25 in the forward direction. The hydraulic oil from the first hydraulic motor 25 returns to the tank 50 through the path 58, the first rotation direction setting valve 31, the path 59, and the path 54.

  As described above, since the first clutch 24 and the second clutch 26 are both disengaged when the rotation direction setting pilot valve 33 is merely operated to the forward rotation side, the first drum 22 and the second drum Reference numeral 23 denotes a stopped state, and the first hydraulic motor 25 and the second hydraulic motor 27 are idle.

  FIG. 3 shows a state in which the first clutch pilot valve 28 is operated to the engaged position while the rotation direction setting pilot valve 33 is operated to the forward rotation side. By operating the first clutch pilot valve 28 to the engaged position, the pilot pressure from the first clutch pilot valve 28 is transmitted to the first clutch 24 through the path 73, and the first clutch 24 is brought into the engaged state for the first. The hydraulic motor 25 and the first drum 22 are connected.

  Further, the pilot pressure in the path 74 branched from the path 73 is further branched into a path 75 and a path 76, and the pilot pressure in the path 75 is shut off by the first pilot pressure switching valve 37 at a fixed position. The pilot pressure of the path 76 passes through the first pilot pressure shut-off valve 38 at a fixed position, and is divided into a path 77a and a path 77b from the path 77. The pilot pressure in the path 77a and the path 77b pushes the spools of the first rotation direction relay pilot valve 34 and the second rotation direction relay pilot valve 35 to the first rotation position.

  As a result, the pilot pressure from the forward rotation-side pilot valve 33a is transmitted only from the first rotation direction relay pilot valve 34 to the path 71, and similarly, the spool of the first rotation direction setting valve 31 is set to the forward rotation side. Push. Further, the path 72 connected to the second rotation direction setting valve 32 is in communication with the path 79 via the path 78 from the first rotation direction relay pilot valve 34, and the pilot pressure of the second rotation direction setting valve 32 is reduced to the tank. 50, and the spool of the second rotation direction setting valve 32 returns to the neutral position by the action of the spring.

  As described above, when the rotation direction setting pilot valve 33 is operated to the forward rotation side and the first clutch pilot valve 28 is operated to the engaged position, the hydraulic oil boosted by the hydraulic pump 30 is supplied to the second rotation direction setting valve 32. From the first rotational direction setting valve 31 through the path 57, and the first hydraulic motor 25 is rotated in the forward direction.

  The hydraulic oil from the first hydraulic motor 25 returns to the tank 50 through the path 58, the first rotation direction setting valve 31, the path 59, and the path 54, as described above. On the other hand, since the hydraulic oil is not supplied to the second hydraulic motor 27, the second hydraulic motor 27 stops. Therefore, only the first drum 22 can be rotated in the rotation direction set by the rotation direction setting pilot valve 33.

  FIG. 4 shows a state in which the second clutch pilot valve 29 is operated to the on position while the rotation direction setting pilot valve 33 is operated to the forward rotation side. By operating the second clutch pilot valve 29 to the engaged position, the pilot pressure from the second clutch pilot valve 29 is transmitted to the second clutch 26 through the path 80, and the second clutch 26 is brought into the engaged state. The hydraulic motor 27 and the second drum 23 are connected.

  A part of the pilot pressure of the path 81 branched from the path 80 is used for pushing the spool of the first pilot pressure switching valve 37 to the operating position, and the remaining part is the second pilot pressure cutoff at the fixed position. After passing through the valve 39, it is branched into a path 82 and a path 83, and the pilot pressures of the paths 82 and 83 are respectively set to the second spools of the first rotation direction relay pilot valve 34 and the second rotation direction relay pilot valve 35. Push to the rotational position. Further, the path 71 connected to the first rotation direction setting valve 31 is in a state of communicating with the path 79 via the path 78 from the first rotation direction relay pilot valve 34, and the pilot pressure of the first rotation direction setting valve 31 is reduced to the tank. The spool of the first rotation direction setting valve 31 is returned to the neutral position by the action of the spring.

  In this way, when the rotation direction setting pilot valve 33 is operated to the forward rotation side and the second clutch pilot valve 29 is operated to the engaged position, the hydraulic oil boosted by the hydraulic pump 30 is supplied to the second rotation direction setting valve 32. Then, the second hydraulic motor 27 is rotated in the forward direction through the path 55. The hydraulic oil from the second hydraulic motor 27 returns to the second rotational direction setting valve 32 through the path 56 and passes through the path 53 from the second rotational direction setting valve 32 and is in the neutral position as described above. It passes through the direction setting valve 31 and returns to the tank 50 through the path 54. On the other hand, since the hydraulic oil is not supplied to the first hydraulic motor 25, the first hydraulic motor 25 stops. Therefore, only the second drum 23 can be rotated in the rotation direction set by the rotation direction setting pilot valve 33.

  FIG. 5 shows a state in which the first clutch 24 and the second clutch 26 are in the joint position with the rotation direction setting pilot valve 33 operated to the forward rotation side. By operating the first clutch pilot valve 28 to the engaged position, the pilot pressure from the first clutch pilot valve 28 passes the path 73 to bring the first clutch 24 into the engaged state, as in the state shown in FIG. .

  Further, the pilot pressure of the path 74 branched from the path 73 is further branched into a path 75 and a path 76. On the other hand, by operating the second clutch pilot valve 29 to the on position, the pilot pressure from the second clutch pilot valve 29 enters the second clutch 26 through the path 80 and is branched from the path 80. With the pilot pressure of 81, the spool of the first pilot pressure switching valve 37 is pushed to the operating position. As a result, the pilot pressure in the path 75 passes through the first pilot pressure switching valve 37 and is transmitted to the path 84, and the spool of the first pilot pressure cutoff valve 38 is moved to the operating position by the pilot pressure in the path 84a branched from the path 84. While pushing to a certain shut-off position, the spool of the second pilot pressure shut-off valve 39 is pushed to the shut-off position which is the operating position by the pilot pressure branched to the path 84b.

  Thereby, since the pilot pressure acting on the first rotation direction relay pilot valve 34 is cut off, the first rotation direction relay pilot valve 34 has the spool in the neutral position as in the state shown in FIG. The pilot pressure from the forward rotation-side pilot valve 33a is divided into two directions in the first rotation direction relay pilot valve 34, and one pilot pressure passes through the path 71 and passes through the spool of the first rotation direction setting valve 31. The other pilot pressure pushes the spool of the second rotation direction setting valve 32 to the forward rotation side through the path 72.

  The hydraulic oil boosted by the hydraulic pump 30 flows from the second rotation direction setting valve 32 toward the path 55, rotates the second hydraulic motor 27 in the forward direction, and then passes through the path 56 to set the second rotation direction. Returning to the valve 32, the second rotation direction setting valve 32 passes through the path 53 and flows out from the first rotation direction setting valve 31 to the path 57, and the first hydraulic motor 25 is rotated in the forward direction. It returns to the tank 50 through the one rotation direction setting valve 31, the path 59, and the path 54.

  Thus, if necessary, the first clutch 24 and the second clutch 26 are jointly operated and moved to the position so that the first drum 22 and the second drum 23 are rotated in the rotation direction set by the rotation direction setting pilot valve 33. Can be rotated simultaneously.

  As described with reference to FIGS. 3 and 4, when only the first drum 22 or only the second drum 23 is rotated, the hydraulic motor that rotates the other drums can be stopped. The burden can be reduced and the life of the hydraulic motor can be extended. In addition, as explained in FIG. 2, both hydraulic motors can be idled simultaneously, and as explained in FIG. 5, both drums can also be idled. Can be easily performed. Furthermore, the scooping operation can be easily performed by appropriately turning on and off the clutch pilot valve.

  In particular, since it can be configured with only a hydraulic circuit, electrical control is not required, and it is possible to easily and inexpensively modify a construction machine that adopts a single-shaft two-drum system to a single-shaft one-motor system. In addition, it is possible to operate two winch drums of a single shaft / single motor type with a single shaft / two drum type operation system.

  When rotating the drum in the reverse direction, the rotation direction setting pilot valve 33 is operated in the reverse direction, and the pilot pressure is supplied from the reverse direction pilot valve 33b of the rotation direction setting pilot valve 33 to the second rotation direction relay pilot valve 35. The first rotation direction setting valve 31 and the second rotation direction setting valve 32 are transmitted to the first rotation direction setting valve 32 and the spools of both rotation direction setting valves 31, 32 are pushed to the reverse rotation side in the same manner as described above. By operating the clutch pilot valve 28 and the second clutch pilot valve 29, the drums 22 and 23 can be rotated in the reverse direction.

  The construction machine is not limited to a crawler crane, and the present invention can be applied to various construction machines equipped with a plurality of winch drums, such as a pile driver and an earth drill.

DESCRIPTION OF SYMBOLS 11 ... Crawler crane, 12 ... Lower traveling body, 13 ... Upper turning body, 13a ... Equipment room, 13b ... Driver's seat, 14a ... Main winding rope, 14b ... Supplementary winding rope, 14c ... Rising rope, 15 ... Boom, 21 ... Hydraulic circuit, 22 ... first drum, 23 ... second drum, 24 ... first clutch, 25 ... first hydraulic motor, 26 ... second clutch, 27 ... second hydraulic motor, 28 ... first clutch pilot valve, 29 2nd clutch pilot valve, 30 hydraulic pump, 31 first rotation direction setting valve, 32 second rotation direction setting valve, 33 rotational direction setting pilot valve, 33a forward rotation side pilot valve, 33b reverse rotation Side pilot valve 34 ... first rotational direction relay pilot valve 35 ... second rotational direction relay pilot valve 36 ... pilot pressure cutoff path 37 ... first pilot pressure switching valve 38 ... first Pilots pressure shut-off valve, 39 ... second pilot pressure shut-off valve

Claims (3)

A first hydraulic motor for driving the first drum via the first clutch;
A second hydraulic motor for driving the second drum via the second clutch;
A first clutch pilot valve that operates the first clutch by turning on and off a first clutch pilot pressure supplied to the first clutch;
A second clutch pilot valve for operating the second clutch by turning on and off a second clutch pilot pressure supplied to the second clutch;
A first rotation direction setting valve that switches a path of hydraulic oil supplied from the hydraulic pump to the first hydraulic motor and sets a rotation direction of the first hydraulic motor;
A second rotation direction setting valve that sets a rotation direction of the second hydraulic motor by switching a path of hydraulic oil supplied from the hydraulic pump to the second hydraulic motor;
Rotation direction setting pilot valve for setting the rotation direction of the first hydraulic motor and the second hydraulic motor by switching the rotation direction setting pilot pressure supplied to the first rotation direction setting valve and the second rotation direction setting valve And
When the first clutch pilot valve and the second clutch pilot valve are both in the clutch disengaged position, the forward rotation pilot pressure path and the reverse rotation pilot pressure path from the rotation direction setting pilot valve are the forward rotation pilot pressure. When the first rotation direction setting valve and the second rotation direction setting valve are respectively connected to the first rotation direction setting valve and the second rotation direction setting valve. The path of the forward rotation pilot pressure and the path of the reverse rotation pilot pressure are communicated with the forward rotation side path and the reverse rotation side path of the first rotation direction setting valve by the pilot pressure from the valve, respectively, and the second rotation direction setting valve When the pilot pressure path to is cut off and only the second clutch pilot valve is in the on position The forward rotation pilot pressure path and the reverse rotation pilot pressure path are connected to the forward rotation side path and the reverse rotation side path of the second rotation direction setting valve, respectively, by the pilot pressure from the second clutch pilot valve. And a pair of first rotational direction relay pilot valves and a second rotational direction relay pilot valve that block a path of pilot pressure to the first rotational direction setting valve,
Further, when the first clutch pilot valve and the second clutch pilot valve are in the joint position, the first clutch pilot valve is driven by the pilot pressure from the first clutch pilot valve and the second clutch pilot valve. And a pilot pressure cut-off path for blocking a pilot pressure path from the second clutch pilot valve to the first rotation direction relay pilot valve and the second rotation direction relay pilot valve. Hydraulic circuit.   In the neutral position, the second rotation direction setting valve is in a state of supplying hydraulic oil from the hydraulic pump to the first rotation direction setting valve, and pilot pressure is applied to the forward rotation side path or the reverse rotation side path. In the second hydraulic motor operating position, the hydraulic oil from the hydraulic pump is supplied to the second hydraulic motor, and the hydraulic oil after driving the second hydraulic motor is supplied to the first rotation direction setting valve. The hydraulic circuit for a construction machine according to claim 1.   The pilot pressure cutoff path is switched by a first pilot pressure switching valve that switches a path on which the pilot pressure from the first clutch pilot valve acts by a pilot pressure from the second clutch pilot valve, and the first pilot pressure switching valve. A first pilot pressure shut-off valve that shuts off a path for operating the rotational relay pilot valve from the first clutch pilot valve by a pilot pressure of a predetermined path, and a path for operating the rotational relay pilot valve from the second clutch pilot valve The hydraulic circuit for a construction machine according to claim 1, further comprising a second pilot pressure shut-off valve that shuts off the pressure.

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