JP5203131B2 - Hydraulic circuit for construction machinery - Google Patents

Description

  The present invention relates to a hanging work tool that may be used in a suspended manner, such as a lifting magnet, a grapple bucket, a hawk bucket, etc. The present invention relates to a hydraulic circuit of a construction machine to which a rotary work tool that needs to be moved can be exchanged.

  In a construction machine, when attaching a backhoe bucket (a work tool that needs to be rotated during operation like a backhoe bucket) to the tip of a multi-joint work arm. A hydraulic cylinder is attached to the tip arm of the arm, and the piston rod of the hydraulic cylinder is connected to the backhoe bucket via a link mechanism for increasing the rotation angle of the working tool. The link mechanism includes a link (hereinafter referred to as an arm link) pivotally attached to a work tip arm, one end connected to the piston rod to the arm link and the hydraulic cylinder, and the other end connected to a work tool. A link (hereinafter referred to as a work tool link).

  When working with a grapple bucket attached to a long tip arm like a material handling machine, if the grapple bucket is tilted, the tip arm is long and the burden on the tip arm is Therefore, conventionally, the operation is generally performed by operating the hydraulic cylinder so that the grapple bucket is in a vertical posture. However, in consideration of the posture of the grapple bucket, if the operation is performed while operating the hydraulic cylinder, the burden on the operator increases. Therefore, the operation should be performed in a state in which the connection between the hydraulic cylinder and the work tool via the link mechanism is released. (Hereinafter, a working tool that hangs down and performs work is referred to as a hanging work tool.).

  However, when the suspension of the hanging work tool and the hydraulic cylinder via the link mechanism is released and the hanging work tool is suspended and attached to the tip arm, the working tool side end of the work tool link is the hanging work tool. As the working arm is actuated, the work tool link swings and collides with the tip arm, damaging the tip arm.

  In order to prevent the swing of the work tool link when using this hanging work tool, in Patent Document 1, a fixing member is provided on the tip arm, and the end of the work tool link is pinned and fixed to the fixing member. A work tool link anti-sway device has been proposed. In addition, when the structure that fixes the work tool link to the tip arm is adopted, the hydraulic cylinder extends due to the leak of pressure oil from the control valve to the hydraulic cylinder, and therefore, an unreasonable force is exerted on the fixing member via the work tool link. The fixing member may be deformed or damaged. Therefore, in the invention described in Patent Document 1, in order to prevent deformation and damage due to extension of the hydraulic cylinder of the fixing member of the working tool link, a state in which the hanging tool is used and the working tool link is fixed to the tip arm. Has proposed a hydraulic circuit to which means for preventing the extension of the hydraulic cylinder by blocking the pipe line between the control valve and the hydraulic cylinder has been proposed.

  On the other hand, in construction machines, instead of directly attaching the work tool to the tip arm, as described in Patent Document 2 and Patent Document 3, an adapter that can easily attach and detach the work tool is attached to the tip arm. It is connected to the hydraulic cylinder via a link mechanism, and various working tools are exchangeably attached to the adapter. If such an adapter is used, it becomes possible to easily and quickly exchange work tools that differ depending on the type of work.

Japanese Patent No. 3767399 JP-A-9-209391 JP-A-11-107307

  As described in Patent Documents 2 and 3, in a construction machine in which a hanging work tool such as a clamshell bucket and a rotating work tool such as a backhoe bucket are attached in a replaceable manner as described in Patent Document 1, If it is assumed that an adapter is always attached to the tip arm and various work tools are exchangeably attached to the adapter, the work tools can be easily and quickly replaced.

  However, as shown in Patent Document 1, the structure in which the work tool link is fixed to the tip arm when a hanging work tool is used is that the work tool link is always connected to the adapter as described in Patent Documents 2 and 3. It is not possible to adopt it when adopting the configuration to keep. For this reason, there is a problem that the time and labor required for exchanging work tools cannot be reduced.

  In view of the above-described problems, the present invention is a construction machine in which an adapter is attached to a work arm and the adapter is rotatably connected by a hydraulic cylinder via a link mechanism. A hydraulic circuit for construction machinery that eliminates the problem of swinging of the work tool link when using a hanging work tool and reduces the time and labor required to replace the work tool. The purpose is to do.

The hydraulic circuit of the construction machine according to claim 1, wherein the work tool mounting adapter is rotatably attached to the tip arm of the work arm,
A hydraulic cylinder that rotates the adapter via a link mechanism is attached to the tip arm,
As the work tool, a rotary work tool that is rotated by the operation of the hydraulic cylinder at the time of work, and is used by being suspended from the tip arm in a vertical posture regardless of a change in the inclination angle of the tip arm at the time of work. In a hydraulic circuit of a construction machine in which a hanging work tool that is sometimes attached to the adapter is replaceable,
A variable relief valve for setting a maximum hydraulic pressure of each pipe line between a bottom chamber of the hydraulic cylinder, a rod chamber and a control valve of the hydraulic cylinder;
A check valve connected in parallel to each variable relief valve;
The set pressure of the variable relief valve is a high-pressure relief pressure that is a relief pressure that allows the rotary work tool to be turned by supplying pressure oil to the pipe line, and work when the hanging work tool is mounted. Relief pressure switching means capable of selectively switching to a low-pressure side relief pressure that allows the work tool to be rotated from an inclined posture to a vertical posture by the tool's own weight and to suppress shaking of the work tool. And

The hydraulic circuit for a construction machine according to claim 2 is the hydraulic circuit for a construction machine according to claim 1,
An electromagnetic valve for switching the relief pressure of the relief valve;
And a switch for switching the solenoid valve, provided in a cab of the construction machine.

  According to the first aspect of the present invention, when the rotary work tool is used, the rotary work tool is rotated by the hydraulic cylinder by setting the relief pressure of the variable relief valve to the high pressure side relief pressure. Work. On the other hand, when a drooping type work tool is used, the relief pressure of the variable relief valve is set to the low pressure relief pressure. In this case, the inclination angle of the tip arm with respect to the vertical line is changed by the operation of the working arm. Along with this, the inclination angle of the drooping work tool with respect to the vertical line also changes, and hydraulic pressure is generated in the bottom chamber (or rod chamber) of the hydraulic cylinder according to the inclination angle by the weight of the drooping work tool. And, by the hydraulic pressure generated in the bottom chamber (rod chamber), a conduit connected to the bottom chamber (rod chamber), a variable relief valve for the conduit, and a check valve connected to the rod chamber (bottom chamber) side conduit After that, the working oil returns to the rod chamber (bottom chamber), the drooping work tool is returned to the vertical posture, and the work can always be performed in the vertical posture. For this reason, the operator does not need a complicated operation for making the hanging work tool vertical, so that the operation becomes easy and the workability is improved.

  Further, when exchanging the work tool, by setting the relief pressure of the variable relief valve to the high-pressure relief pressure, the adapter for the replacement can be rotated, which is necessary for exchanging the work tool. Time and labor can be reduced.

  Also, when using a hanging work tool, the work tool link is constrained while being connected to the adapter, so the work tool link does not swing with the change in the tilt angle of the tip arm during work, The tip arm is prevented from being damaged by the swing and collision of the work tool link.

  In addition, when working with a hanging work tool, the work tool is always connected to the hydraulic cylinder via the link mechanism, so that the upper swivel body starts turning and depends on the inertia of the work tool when it stops. The swinging of the drooping work implement can be suppressed by the resistance of the hydraulic fluid flow in the hydraulic cylinder, which eliminates the need for an operator operation to prevent this swinging. The burden can be reduced and workability can be improved. In particular, if the low-pressure relief pressure at the time of using the hanging work tool is set to a relief pressure that is slightly higher than the tank pressure, the effect of suppressing the shaking is enhanced. Further, since the swing of the work tool is suppressed, the work tool can be easily positioned.

  Even when working with a hanging work tool, if the work tool needs to be tilted due to special work requirements, the relief valve relief pressure is set to the high pressure relief pressure. Then, it becomes possible to work by inclining the work tool, and the applicability to the work site is improved.

  According to the invention of claim 2, since the switch for switching the solenoid valve for switching the relief pressure is provided in the cab of the construction machine, the relief pressure can be easily and quickly switched.

  FIG. 1 is a side view showing an example of the construction machine of the present invention. Reference numeral 1 denotes a construction machine that performs a cargo handling operation on the ground 3 in the vicinity of the quay 2, and loads and unloads loads to be loaded on the ship 4. Reference numeral 5 denotes a self-propelled lower traveling body. In this example, the lower traveling body 5 is a crawler traveling body, but a wheel-type traveling body or one having an iron wheel that rolls on a rail is applied. There is also a case.

  The tower 6 is installed on the traveling body frame of the lower traveling body 5, and the upper swing body 8 is installed on the top of the tower 6 via the swing device 7. A hydraulic power unit 10, an operator cab 11, a counterweight 12, and the like are mounted on the upper swing body 8. A landing 13 for maintenance and inspection such as a hydraulic power unit 10 mounted on the upper swing body 8 is provided on the lower surface of the upper swing body 8 in the middle of the tower 6. The landing 13 is at a height at which the mounted equipment can be inspected from the lower surface of the upper swing body 8, and has a front-rear width close to the front-rear width of the upper swing body 8. Reference numeral 14 denotes a ladder attached to the landing 13 so that operators, workers, and the like can move up and down on the landing 13 from the ground. A handrail 15 for safety is provided around the landing 13. The upper swing body 8 is also provided with a lifting ladder 16 for the operator or the like to move up and down between the upper swing body 8 and the landing 13. A landing 17 and a handrail 18 are also installed on the upper swing body 8.

  Reference numeral 20 denotes a multi-joint structure working arm attached to the upper swing body 8. The work arm 20 includes a first arm 22 attached to the upper swing body 8 by a hydraulic cylinder 21 so as to be raised and lowered. A second arm (hereinafter referred to as a tip arm) 24 is attached to the tip of the first arm 22 so as to be pivotable in the vertical direction by a hydraulic cylinder 23. The working arm 20 may be configured with a multi-joint structure of three or more arms.

  A drooping work tool is attached to the tip of the tip arm 24 via an adapter 25. In this embodiment, the case where the drooping work tool is a grapple bucket 26 is shown. A hydraulic cylinder 28 is attached to the distal arm 24 and rotates the work tool together with the adapter 25 via the link mechanism 29.

  FIG. 2 is an enlarged view showing the mounting structure of the grapple bucket 26 and the structure of the grapple bucket 26. The adapter 25 is pivotally attached to the tip of the tip arm 24 by a pin 30. As shown in FIG. 1, one end (tube 28 a) of the hydraulic cylinder 28 is attached to a bracket 31 provided on the upper surface of the distal arm 24 by a pin 32. The link constituting the link mechanism 29 has an arm link 34 having one end pivotally attached to the tip arm 24 by a pin 33, and a work tool link 36 having one end pivotally attached to the adapter 25 by a pin 35. The other end (piston rod 28b) is connected to the tip of these links 34, 36 by a pin 37.

  The grapple bucket 26 has a bracket 42 for attaching to the adapter 25 at the top thereof. The bracket 42 is composed of two parallel plates, and is detachably connected to the adapter 25 by pins 40 and 41 with the lower end portion of the adapter 25 interposed therebetween. A frame 43 is provided below the bracket 42, and a plurality of gripping claws 45 are attached to the frame 43 via pivoting shafts 44 so as to be opened and closed. A hydraulic cylinder 46 for opening and closing the claw is attached between the frame 43 and each gripping claw 45.

  FIG. 3 is a side view showing the structure of the adapter 25. As shown in FIG. 3, the adapter 25 is provided with an attachment portion (boss) 47 connected to the tip arm 24 by a pin 30 and an attachment portion (boss) 48 connected to the work tool link 36 by a pin 35. . At the end of the lower frame 50 of the adapter 25, a fixing hook 51 for fitting the pin 40 for connecting the grapple bucket 26 is provided. Reference numeral 52 denotes a movable hook that holds the pin 40 so as not to come out from the fixed hook 51. The movable hook 52 is attached so as to be rotatable about a shaft 53 provided on the lower frame 50.

  Reference numeral 54 denotes a movable arm that is rotatably attached around a pin 35 that connects the adapter 25 to the work tool link 36. The movable arm 54 is provided with a concave fitting portion 55 for fitting and fixing the pin 41 connecting the grapple bucket 26. Reference numeral 56 denotes a hydraulic cylinder for attaching / detaching a work tool to / from the adapter 25. One end of the hydraulic cylinder 56 is connected to the movable hook 52 by a pin 57 and the other end is connected to the movable arm 54 by a pin 58. Reference numeral 59 denotes a pin hole provided in the lower frame 50, into which a lock pin 60 (see FIG. 4D) for locking the movable hook 52 is inserted.

  FIG. 4 shows a procedure for mounting the grapple bucket 26 placed on the adapter 25 on the ground. First, as shown in FIG. 4A, the hydraulic cylinder 56 is contracted to bring the movable arm 54 close to the lower frame 50, and the movable hook 52 is separated from the fixed hook 51 to be in an open state. Then, the adapter 25 is lowered by lowering the first arm 22 shown in FIG. 1, and the fixing hook 51 is fitted to one pin 40 previously attached to the grapple bucket 26 as shown in FIG. 4 (B). To do.

  Next, while slightly lifting the first arm 22 shown in FIG. 1, as shown in FIG. 4C, the hydraulic cylinder 28 attached to the tip arm 24 is extended to rotate the adapter 25 toward the cab 11 side. Then, by lifting the rear side of the adapter 25, the fixing hook 51 faces upward and the pin 40 is prevented from coming off. At the same time, the fitting portion 55 of the movable arm 54 is brought into contact with and brought into contact with the other pin 41 that is previously attached to the adapter 25.

  Next, as shown in FIG. 4D, the hydraulic cylinder 56 is extended and the movable arm 54 is rotated to fit the fitting portion 55 to the pin 41 attached to the grapple bucket 26. At the same time, the movable hook 52 is hooked on the pin 40 and the pin 40 is gripped between the movable hook 52 and the fixed hook 51. Next, the lock pin 60 is inserted into a hole 59 provided in advance in the lower frame 50 to prevent the movable hook 52 from moving, and the movable hook 52 is locked.

  When the grapple bucket 26 is removed from the adapter 25, the grapple bucket 26 is placed on the ground, the lock pin 60 is removed from the lower frame 50, the hydraulic cylinder 56 is contracted to release the movable hook 52 from the pin 40, and at the same time the movable arm 54 is rotated to remove the fitting portion 55 from the pin 41, the hydraulic cylinder 28 is contracted, and the first arm 22 is slightly lifted to remove the grapple bucket 26 from the adapter 25.

  FIG. 5 shows a state in which a backhoe bucket 61, which is an example of a rotating work tool, is attached to the tip arm 24 via an adapter 25. FIG. 6 shows an example in which a lifting magnet 62, which is another example of a hanging work tool, is attached to the tip arm 24 via an adapter 25. In addition, the grapple bucket 26 and the lifting magnet 62 as a hanging type work tool may be used in a rotating manner. In addition, for example, a hawk bucket or the like may be used in either a rotating type or a hanging type.

  FIG. 7 is a hydraulic circuit diagram showing an embodiment of the hydraulic circuit of the present invention. 63 is a main pump included in the hydraulic power unit 10, and 64 and 65 are a pilot pump and an oil tank, respectively. Reference numeral 66 denotes a control valve provided in a hydraulic circuit between the main pump 63 and the hydraulic cylinder 28. 67 is a pilot valve of the control valve 66.

  In the pilot valve 67, when the operation lever 68 is operated in the direction of the arrow 69, the pilot pressure oil from the pilot pump 64 is supplied to the operation chamber 66a of the control valve 66 through the pipe 70, the valve 71, and the pipe 72. The control valve 66 is switched to the upper position. As a result, the pressure oil from the main pump 63 enters the bottom chamber 28c of the hydraulic cylinder 28 through the ports 66c and 66d of the control valve 66 and the pipe line 75, and the hydraulic oil in the rod chamber 28d passes through the pipe 76 and the port of the control valve 66. 66e, 66f and the pipe line 77 are returned to the oil tank 65, and the hydraulic cylinder 28 extends.

  On the contrary, when the operation lever 68 is operated in the direction of the arrow 78, the pilot pressure oil from the pilot pump 64 is supplied to the operation chamber 66b of the control valve 66 through the pipe 70, the valve 79, and the pipe 80, 66 switches to the lower position. As a result, the pressure oil from the main pump 63 enters the rod chamber 28d of the hydraulic cylinder 28 through the ports 66c and 66e of the control valve 66 and the conduit 76, and the hydraulic oil in the bottom chamber 28c becomes the port 75 and the port of the control valve 66. 66d, 66f and the pipe line 77 are returned to the oil tank 65, and the hydraulic cylinder 28 contracts.

  82 and 83 are variable relief valves inserted between the oil tank 65 and pipe lines 75 and 76 between the control valve 66 and the bottom chamber 28c and rod chamber 28d, respectively. Reference numerals 93 and 94 are check valves provided in parallel with these variable relief valves 82 and 83, respectively. The variable relief valves 82 and 83 have operation chambers 82a and 83a. When pilot pressure oil is supplied to these operation chambers 82a and 83a, the relief pressure of the variable relief valves 82 and 83 is high (for example, 17.6 MPa). Set to The high-pressure relief pressure is a hydraulic pressure that is required when working by rotating the backhoe bucket 61 or the like that is a rotating work tool as shown in FIG. On the contrary, in the state where pilot pressure oil is not supplied to the operation chambers 82a and 83a, the relief pressure of the variable relief valves 82 and 83 is set to a low pressure (for example, 3.9 MPa). This low-pressure relief pressure is a hydraulic pressure that enables the drooping work tool to be rotated to a vertical posture by its own weight such as the grapple bucket 26 that is a drooping work tool as shown in FIGS. .

  84 is an electromagnetic valve provided for switching the relief pressure of the variable relief valves 82 and 83. Reference numeral 85 denotes a power source mounted on the upper swing body 8, and 86 denotes a solenoid valve switching switch (see FIG. 8) attached to the cab 11. When using a rotary work tool such as the backhoe bucket 61, the switch 86 is turned off (opened). At this time, since the solenoid 84a of the electromagnetic valve 84 is not energized, the electromagnetic valve 84 is in the lower position in the figure. For this reason, pilot pressure oil from the pilot pump 64 is supplied to the operation chambers 82a and 83a of the variable relief valves 82 and 83 via the pipe line 87, the electromagnetic valve 84, the pipe line 88, and the pipe lines 89 and 90, and the variable relief valve is provided. The relief pressure of the valves 82 and 83 is set to a high pressure. For this reason, when the hydraulic cylinder 28 is expanded or contracted by switching to the upper or lower position of the control valve 66, the hydraulic pressure in the pipes 75 and 76 is set to be higher than the high-pressure relief pressure. The tool can be rotated.

  On the other hand, when the hanging type work tool is used in a state of hanging from the tip arm 24, the switch 86 is turned on (closed). Thereby, the solenoid 85a of the electromagnetic valve 84 is energized by the power supply 85, and the electromagnetic valve 84 is switched to the upper position. For this reason, the secondary side pipe line 88 of the electromagnetic valve 84 communicates with the pipe line 91 connected to the oil tank 65 via the electromagnetic valve 84. For this reason, the hydraulic pressure of the operation chambers 82a and 83a becomes the tank pressure, and the relief pressure of the variable relief valves 82 and 83 becomes the low pressure.

  Thus, when the relief pressure of the variable relief valves 82 and 83 is set to a low pressure, the center of gravity G of the grapple bucket 26 is pin 30 in the state where the grapple bucket 26 is attached via the adapter 25 as shown in FIG. When it is further forward (opposite to the upper swing body 8), rotational force is generated in the direction indicated by the arrow 92 around the pin 30 due to its own weight F of the grapple bucket 26.

In this case, a hydraulic pressure is generated in the rod chamber 28d of the hydraulic cylinder 28 due to this weight. Due to this self-weight, when the inclination angle formed with respect to the vertical line of the line connecting the center of gravity G and the pin 30 is not less than an angle that can be grasped as being substantially vertical, the low-pressure relief pressure is 3.9 MPa or more. If the rod chamber 28d is configured to generate hydraulic pressure , the grapple bucket 26 rotates due to its own weight even though the control valve 66 is in the neutral position shown in the figure. That is, the hydraulic oil in the rod chamber 28 d enters the bottom chamber 28 c through the conduit 76, the variable relief valve 83, the check valve 93, and the conduit 75. At this time, due to the difference in cross-sectional area between the rod chamber 28d and the bottom chamber 28c, the bottom chamber 28c is replenished with hydraulic oil from the oil tank 65 through the conduit 77, the check valve 93, and the conduit 75.

  When the center of gravity G is behind the pin 30, hydraulic pressure due to the weight of the work tool is generated in the bottom chamber 28c. If the hydraulic pressure is equal to or higher than the low pressure relief pressure, the hydraulic oil in the bottom chamber 28c is supplied to the pipe 75, the variable relief valve 82, the check valve 94, the pipe, even though the control valve 66 is in the neutral position. 76 enters the rod chamber 28d. At this time, due to the difference in cross-sectional area between the rod chamber 28 d and the bottom chamber 28 c, part of the hydraulic oil that has exited from the bottom chamber 28 c flows out from the conduit 77 to the oil tank 75.

  As described above, when hydraulic pressure is generated in the bottom chamber 28c due to the weight of the work tool, that is, when the work tool is inclined toward the rear side, due to the difference in cross-sectional area between the rod chamber 28d and the bottom chamber 28c, Compared to the case where the bottom chamber 28c is inclined, the hydraulic pressure generated by its own weight in the bottom chamber 28c is lower, and if the low pressure side relief pressure of the variable relief valves 82 and 83 is the same, the minimum inclination angle that can be rotated by its own weight is It becomes slightly larger when the work tool is inclined toward the rear side. The minimum tiltable angle of rotation can be reduced as the low-pressure side relief pressure is lowered. Therefore, the low-pressure side relief pressure may be set according to the weight of the work tool, the type of work tool, and the like. The minimum inclination angle that can be grasped as the vertical posture is preferably 10 degrees or less from the viewpoint of work efficiency. Further, in order to make the minimum inclination angle forward and rearward of the grapple bucket 26 equal, the low pressure side relief pressure of the variable relief valve 82 on the bottom chamber 82c side with the larger cross sectional area in the hydraulic cylinder 28 is set to the side with the smaller cross sectional area. It may be set lower than the rod chamber 28d.

  As described above, according to this embodiment, the variable relief valves 82 and 83 for setting the hydraulic pressures of the pipe lines 75 and 76 connected to the hydraulic cylinder 28 are provided, and a drooping work tool such as the grapple bucket 26 is used. Since the relief pressure of the variable relief valves 82 and 83 is set to the low-pressure side relief pressure, the hanging work tool such as the grapple bucket 26 is brought into the vertical posture by its own weight regardless of the angle of the tip arm 24. Thus, the operator can work in a suspended state, and the operator does not need to operate the complicated hydraulic cylinder 28 to bring the hanging work tool into a vertical posture. , Workability is improved. Further, when exchanging the work tool, the adapter 25 for replacement can be rotated by setting the relief pressure of the variable relief valves 82 and 83 to the high-pressure relief pressure.

  Therefore, in any case where the rotary work tool or the hanging work tool is attached to the tip arm 24 via the adapter 25, the work can be performed in the rotation mode or the hanging mode of the original work tool. You can also change tools. When the hanging work tool is attached, the work tool link 36 is restrained while being connected to the adapter 25, so that the work tool link 36 does not swing with the operation of the work arm 20, The tip arm 24 is prevented from being damaged by the swing and collision of the work tool link 36.

Further, also when using hanging type work tools such as the grapple bucket 26 and the lifting magnet 62, these work tools are always connected to the hydraulic cylinder 28 via the link mechanism 29, so that the upper swing body 8 starts turning. The vibration due to the inertia of the work tools 26 and 62 at the time of stopping is suppressed by the resistance of the flow of hydraulic oil between the bottom chamber 28c and the rod chamber 28d of the hydraulic cylinder 28 and between the chambers 28c and 28d and the oil tank 65. Is done. For this reason, an operation for preventing shaking by the operator is unnecessary, and in this sense, the burden on the operator can be reduced and workability can be improved. Further, since the swing of the work tool is suppressed, the work tool can be easily positioned. Further, by setting a slightly higher relief pressure than the tank pressure to the low pressure side relief pressure when using hanging type working implement, it is possible to enhance the shake suppressing effect.

  Further, when a hanging work tool such as the grapple bucket 26 is used, for example, when there is an object to be gripped under a certain structure, the relief pressure of the variable relief valves 82 and 83 is changed to the high pressure side relief pressure. If set, the grapple bucket 26 can be held sideways and the object can be gripped. For this reason, the operation | work aspect at the time of using a drooping type working tool can be expanded.

  Further, in the above embodiment, as shown in the plan view of FIG. 8, the switch 86 for switching the relief pressure of the switching circuit of the variable relief valves 82 and 83 is provided in the cab 11 of the construction machine. Can be switched easily and quickly.

  In the above embodiment, the relief pressures of the variable relief valves 82 and 83 are switched by switching the electromagnetic valve 84 with the switch 86. However, as shown in FIG. 9, manual operation means 82b and 83b are used. It is also possible to adopt a configuration that switches the relief pressure.

  In addition to the above-described embodiment, the present invention can also be used for other construction machines that attach a work tool that may be used as a hanging work tool to a work arm.

It is a side view which shows an example of the construction machine to which the hydraulic circuit by this invention is applied. It is an enlarged view which shows the structure and attachment structure of the working tool of FIG. It is a side view which shows an example of the adapter used in this invention. It is a figure which shows the attachment procedure of the working tool by the adapter of this example. It is a side view which shows the state which attached the backhoe bucket which is an example of the rotation type working tool used in the construction machine of this invention to the arm. It is a side view which shows the state which attached the lifting magnet which is an example of the drooping type working tool used in the construction machine of this invention to the arm. 1 is a hydraulic circuit diagram showing an embodiment of a hydraulic circuit of a construction machine according to the present invention. It is a top view which shows arrangement | positioning of the switch for relief pressure switching in this embodiment. It is a hydraulic circuit diagram which shows other embodiment of the hydraulic circuit of the construction machine of this invention.

Explanation of symbols

1: construction machine, 2: quay, 3: ground, 4: ship, 5: lower traveling body, 6: tower, 7: turning device, 8: upper turning body, 10: hydraulic power unit, 11: cab, 12: Counterweight, 13: landing, 14: ladder, 15: handrail, 16: ladder, 17: landing, 18: handrail, 20: working arm, 21: hydraulic cylinder, 22: first arm, 23: hydraulic cylinder, 24: tip arm, 25: adapter, 26: grapple bucket, 28: hydraulic cylinder, 28c: bottom chamber, 28d: rod chamber, 29: link mechanism, 30, 32, 33, 35, 37: pin, 31: bracket, 34: Arm link, 36: Work tool link, 40, 41: Pin, 42: Bracket, 43: Frame, 44: Pivoting shaft, 45: Holding claw, 46: Hydraulic cylinder, 47, 48: Boss 50: lower frame, 51: fixed hook, 52: movable hook, 53: shaft, 54: movable arm, 55: fitting part, 56: hydraulic cylinder, 57, 58: pin, 59: pin hole, 60: lock pin 61: Backhoe bucket, 62: Lifting magnet, 63: Main pump, 64: Pilot pump, 65: Oil tank, 66: Control valve, 67: Pilot valve, 68: Operation lever, 82, 83: Relief valve, 82a, 83a: operation chamber, 82b, 83b: manual operation means, 84: solenoid valve, 85: power supply, 86: switch, 93, 94: check valve

Claims (2)

A work tool mounting adapter is pivotally attached to the tip arm of the work arm,
A hydraulic cylinder that rotates the adapter via a link mechanism is attached to the tip arm,
As the work tool, a rotary work tool that is rotated by the operation of the hydraulic cylinder at the time of work, and is used by being suspended from the tip arm in a vertical posture regardless of a change in the inclination angle of the tip arm at the time of work. In a hydraulic circuit of a construction machine in which a hanging work tool that is sometimes attached to the adapter is replaceable,
A variable relief valve for setting a maximum hydraulic pressure of each pipe line between a bottom chamber of the hydraulic cylinder, a rod chamber and a control valve of the hydraulic cylinder;
A check valve connected in parallel to each variable relief valve;
The set pressure of the variable relief valve is a high-pressure relief pressure that is a relief pressure that allows the rotary work tool to be turned by supplying pressure oil to the pipe line, and work when the hanging work tool is mounted. Relief pressure switching means capable of selectively switching to a low-pressure side relief pressure that allows the work tool to be rotated from an inclined posture to a vertical posture by the tool's own weight and to suppress shaking of the work tool. And the hydraulic circuit of construction machinery. In the hydraulic circuit of the construction machine according to claim 1,
An electromagnetic valve for switching the relief pressure of the relief valve;
A hydraulic circuit for a construction machine, comprising a switch that is provided in a cab of the construction machine and that switches the solenoid valve.

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