JP7165155B2 - working machine - Google Patents

Description

The present invention relates to work machines equipped with suspended hydraulic drive attachments such as processors and harvesters.

2. Description of the Related Art As a type of working machine having a hydraulic excavator as a base machine, there is known one that can perform crane work with a hook provided on a bucket link (see Patent Document 1). In the working machine of the same document, the crane work mode and the excavation work mode can be selected alternatively, and during the selection of the crane work mode, the suction and discharge of the pressure oil to the attachment cylinder (bucket cylinder) is blocked by the electromagnetic valve. It is The solenoid valve is controlled to open and close by the controller according to the selection of the work mode.

JP 2017-150284 A

Attachments to be mounted on working machines include suspension-type attachments. Typical examples of hanging attachments are, for example, forestry processors and harvesters. Hanging attachments include those that are hung via an extension arm from the tip of a working arm consisting of a boom and an arm. The extension arm, like the bucket, is driven by the attachment cylinder and pivots relative to the arm. When working with a work machine using this type of attachment, it may be necessary to hold the extension arm fully deployed in the dumping direction. This is to prevent the attachment from shaking and interfering with the boom and arm during work.

On the other hand, when transporting the working machine with the hanging attachment on a trailer or the like, the working arm including the extension arm may be held in a posture. Therefore, although it is not necessary to drive the extension arm during operation, it is not desirable to omit the function of rotating the extension arm by the attachment cylinder. On the other hand, when a mechanism for locking the operation of the attachment cylinder with an electromagnetic valve is adopted as in Patent Document 1, the operation of the extension arm can be prohibited during work, but allowed during transportation setup. .

However, even if a locking mechanism for the attachment cylinder is provided as in Patent Document 1, there is a possibility that the attachment cylinder may be forgotten to have a predetermined stroke (for example, the most retracted) when locking. You may forget to lock it. If the operator does not realize this and starts work with the extension arm not extended, the special lock mechanism will not function effectively, allowing the attachment to interfere with the boom, etc., which should have been prevented. there is a possibility.

In addition, it is necessary to positively allow the operation of the attachment cylinder in a work machine equipped with a processor or the like only when the work machine is transported, and even if the lock mechanism of Patent Document 1 is adopted, there are few opportunities to use it. quite restrictive. In order to adopt the lock mechanism of the same document, although there are not many opportunities to use it, it is necessary to add a dedicated solenoid valve, its wiring, and a control function for the solenoid valve by a controller. The cost of parts has risen, the number of man-hours for manufacturing has increased due to the complexity of the structure, and the actual situation is that the cost-effectiveness is not justified.

SUMMARY OF THE INVENTION An object of the present invention is to provide a working machine which has a simple structure and which allows free expansion and contraction of an attachment cylinder during transportation, while allowing an extension arm to be naturally extended during work using the attachment. to do.

To achieve the above object, the present invention provides a vehicle body, a boom connected to the vehicle body, an arm connected to the tip of the boom, an extension arm connected to the tip of the arm, a hydraulic actuator, and A suspended hydraulically driven attachment that includes a control valve for the hydraulic actuator and is suspended from the tip of the extension arm, an attachment cylinder that is connected at both ends to the arm and the extension arm, and pressurized oil. A working machine comprising a hydraulic pump for discharging and an on-vehicle control valve unit for controlling supply of pressure oil from the hydraulic pump to the hydraulically driven attachment and the attachment cylinder, wherein the rod port and the bottom port of the attachment cylinder Among them, a first pipe connecting a port through which pressure oil is supplied to the attachment cylinder during a dump operation of the extension arm and the in-vehicle control valve unit, and a second pipe connecting the in-vehicle control valve unit and the hydraulic actuator. and a connecting pipe that connects the first pipe and the second pipe, and a connecting pipe that is provided in the connecting pipe and allows pressure oil to flow from the second pipe to the first pipe while allowing pressure oil to flow from the first pipe and a check valve for prohibiting the flow of pressure oil to the second pipe.

According to the present invention, with a simple structure, the attachment cylinder can be freely expanded and contracted during transportation, while the extension arm can be naturally expanded during work using the attachment.

1 is a side view showing a working posture of a working machine according to a first embodiment of the present invention; FIG. FIG. 2 is a side view showing the transportation posture of the work machine according to the first embodiment of the present invention; 1 is a circuit diagram of a main part of a hydraulic system provided in a working machine according to a first embodiment of the present invention; FIG. A circuit diagram of a main part of a hydraulic system provided in a working machine according to a second embodiment of the present invention.

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

(First embodiment)
－Working machine－
FIG. 1 is a side view showing the working posture of the working machine according to the first embodiment of the present invention, and FIG. 2 is a side view showing the transporting posture of the working machine. Hereinafter, the front of the revolving body 12 is defined as the direction facing the operator sitting in the driver's seat (the left direction in FIG. 1). The working machine shown in FIG. 1 uses a hydraulic excavator as a base machine, and includes a vehicle body 10 and a front working machine 20 attached to the vehicle body 10 . The vehicle body 10 includes a traveling body 11 and a revolving body 12, but may have a configuration in which the traveling body 11 and the revolving body 12 are not separated.

The traveling body 11 constitutes the base structure of the working machine, and is a crawler-type traveling body having left and right crawler belts 13 . The left and right crawler belts 13 are driven by left and right traveling drive devices 14, respectively. The traveling drive device 14 consists of a hydraulic motor and a speed reducer. A revolving body 12 is provided above the running body 11 via a revolving wheel 15. By driving the revolving wheel 15 with a revolving motor (not shown), the running body 11 is rotated about a vertically extending axis. The revolving body 12 revolves. The swing motor is a hydraulic motor, but in addition to using an electric motor, there are cases where both a hydraulic motor and an electric motor are used. In the present embodiment, the working machine including the crawler-type traveling body 11 is illustrated, but the traveling body 11 may be of a wheel type.

The revolving body 12 includes a revolving frame 16, an operator's cab 17, a machine room 18, a counterweight 19, and the like. The revolving frame 16 is a base frame of the revolving body 12 and supports each device mounted on the revolving body 12 . The driver's cab 17 is mounted on one side (the left side in this embodiment) in the left-right direction of the front portion of the revolving frame 16 . Inside the operator's cab 17, there are arranged a driver's seat (not shown) in which an operator sits, an operating device operated by the operator, and the like. The machine room 18 is arranged behind the operator's cab 17 in the revolving frame 16 . Although not shown in FIGS. 1 and 2, the machine room 18 contains a prime mover, which is an engine (internal combustion engine), a hydraulic pump 31 (FIG. 3) driven by the prime mover, and hydraulic fluid that drives each hydraulic actuator. An in-vehicle control valve unit 33 (FIG. 3), heat exchangers, etc. are accommodated. An electric motor may be used as the prime mover. Tanks are arranged on the opposite side of the operator's cab 17 with the front work machine 20 interposed therebetween in the front portion of the revolving frame 16 . Tanks include fuel tanks, hydraulic oil tanks, and the like. The counterweight 19 is a weight that balances the front work machine 20 and is supported at the rear end of the revolving frame 16 .

－Front work machine－
The front work machine 20 is a multi-joint work device and includes a work arm 21 and a hydraulic drive attachment 22 . The working arm 21 includes a boom 23 , an arm 24 , a boom cylinder 25 , an arm cylinder 26 and an attachment cylinder 27 . The boom cylinder 25, the arm cylinder 26 and the attachment cylinder 27 are all double-acting hydraulic cylinders. The boom cylinder 25 is arranged on the ventral side of the boom 23 , the arm cylinder 26 is arranged on the dorsal side of the boom 23 , and the attachment cylinder 27 is arranged on the dorsal side of the arm 24 . The ventral side is the lower side of the working arm 21 with the tip of the arm 24 directed forward, and the dorsal side is the upper side of the working arm 21 in the same posture.

The boom 23 is connected to the vehicle body 10 (specifically, the front portion of the base frame (revolving frame 16) of the revolving body 12) so as to be vertically rotatable via a foot pin (not shown) extending laterally. The boom 23 of this embodiment is L-shaped in side view, and the tip side is inclined forward with respect to the base side. The arm 24 is rotatably connected to the tip of the boom 23 via a pin P2 extending laterally. An extension arm 28 is connected to the tip of the arm 24 via a pin P3 extending in the left and right direction. The extension arm 28 is an arm bent in an L-shape, and the portion on the base side from the pin P3 is bent and extended to the back side of the arm 24 with respect to the portion on the tip side from the pin P3.

The boom cylinder 25 is connected at its proximal end to the vehicle body 10 (the revolving frame 16 of the revolving body 12) via a laterally extending pin (not shown), and is attached to the belly of the boom 23 via a laterally extending pin P5. The tip is connected to the side. The arm cylinder 26 has a base end connected to the dorsal surface of the boom 23 via a pin P6 extending in the left and right direction, and a tip end connected to the base end of the arm 24 via a pin P7 extending in the left and right direction. ing. The attachment cylinder 27 has a base end connected to the back surface of the arm 24 via a pin P8 extending in the left and right direction, and a tip end connected to the base end of the extension arm 28 via a pin P9 extending in the left and right direction. This attachment cylinder 27 is generally called a bucket cylinder in a hydraulic excavator, which is a base machine.

－Hydraulic drive attachment－
The hydraulic drive attachment 22 is a processor in this example, and is swingably suspended from the tip of the extension arm 28 via a pin P10. Processors are used in forestry to cut and transport wood. The work of cutting and transporting trees includes the steps of felling standing trees, trimming the felled timber, measuring the timber, cutting the timber, and loading the cut timber onto the transporter. are used for processes other than felling. The hydraulically driven attachment 22, which is a processor, includes a grapple (gripping mechanism) for gripping wood, a feeding mechanism for feeding the wood gripped by the grapple, and a chainsaw for cutting the gripped wood. The configuration of the processor is described, for example, in Japanese Unexamined Patent Application Publication No. 2012-19702.

FIG. 3 is a circuit diagram of the essential parts of the hydraulic system provided in the working machine according to the first embodiment of the present invention. The hydraulic system shown in FIG. 1 is a representation of the circuit of the hydraulically driven attachment 22 and the attachment cylinder 27 extracted.

The hydraulic drive attachment 22 has a plurality of hydraulic actuators including a grapple open/close cylinder A1 for opening and closing the grapple. Hydraulic actuators mounted on the hydraulic drive attachment 22 other than the grapple opening/closing cylinder A1 include, for example, a feed motor A2 that drives a feed mechanism and a saw motor A3 that drives a chain saw. In this embodiment, the grapple opening/closing cylinder A1 is a double-acting cylinder, the feed motor A2 is a two-way motor, and the saw motor A3 is a one-way motor.

The hydraulically driven attachment 22 also has an attachment control valve unit VU, an inlet port IP and an outlet port OP. The attachment control valve unit VU is composed of a plurality of control valves corresponding to a plurality of hydraulic actuators mounted on the hydraulically driven attachment 22, respectively. This attachment control valve unit VU controls the supply of pressure oil from the hydraulic pump 31 to a plurality of hydraulic actuators mounted on the hydraulic drive attachment 22 . The hydraulic drive attachment 22 incorporates a hydraulic circuit that drives a plurality of hydraulic actuators including the grapple opening/closing cylinder A1, and the inlet port IP and the outlet port OP serve as inlets and outlets of pressure oil to the hydraulic circuit. An in-vehicle control valve unit 33 (described later) is connected to the inlet port IP via a pipe L3, and the pressurized oil (original pressure) supplied via the pipe L3 and the inlet port IP is branched to the attachment control valve unit. It is supplied to each control valve that constitutes the VU. An oil tank 32 is connected to the outlet port OP via a pipe L10.

A control valve corresponding to the grapple opening/closing cylinder A1 is connected to the rod port RP of the grapple opening/closing cylinder A1 via a pipe L4, and is connected to the bottom port BP of the grapple opening/closing cylinder A1 via a pipe L5. This control valve is, for example, a three-position switching valve. When the inlet port IP is connected to the pipe L4 according to the operator's operation, the grapple opening/closing cylinder A1 contracts, and when the inlet port IP is connected to the pipe L5, the grapple opening/closing cylinder A1 extends. do. When the operation is stopped, the control valve switches to the neutral position, for example, the inlet port IP is connected to the outlet port OP and the grapple opening/closing cylinder A1 is held.

A control valve corresponding to the feed motor A2 is connected to the first port of the feed motor A2 via the pipe L6, and is connected to the second port of the feed motor A2 via the pipe L7. This control valve is also, for example, a three-position switching valve. When the inlet port IP is connected to the pipe L6 according to the operator's operation, the feed motor A2 rotates forward, and when the inlet port IP is connected to the pipe L7, the feed motor A2 rotates in the reverse direction. do. Stopping operation switches the control valve to a neutral position, for example connecting the inlet port IP to the outlet port OP and holding the feed motor A2.

A control valve corresponding to saw motor A3 is connected to the first port of saw motor A3 via pipe L8 and to the second port of saw motor A3 via pipe L9. When the control valve connects the inlet port IP to the pipe L8, the saw motor A3 rotates. When the operation is stopped, the control valve is switched to the neutral position, for example, the inlet port IP is connected to the outlet port OP and the saw motor A3 is stopped.

The hydraulically driven attachment 22 is operated by controlling the pressure oil supplied to each hydraulic actuator by the corresponding control valve. The pressure oil that has not been supplied to the hydraulic actuator or the pressure oil that has driven the hydraulic actuator is discharged from the hydraulic drive actuator via the outlet port OP and returns to the oil tank 32 .

－Hydraulic system－
The hydraulic system shown in FIG. 3 includes a hydraulic pump 31, an oil tank 32, an in-vehicle control valve unit 33, a connecting pipe 34, and a check valve 35.

The hydraulic pump 31 sucks hydraulic oil from the oil tank 32 and discharges pressure oil for driving the hydraulic drive attachment 22, the attachment cylinder 27, and the like. Although the hydraulic drive attachment 22 and the attachment cylinder 27 may be configured to have different hydraulic pumps, in this embodiment, the hydraulic pump 31 is used as a common pump.

The in-vehicle control valve unit 33 is composed of a plurality of control valves respectively corresponding to the hydraulically driven attachment 22, the attachment cylinder 27, and the like. The vehicle-mounted control valve unit 33 controls the supply of pressure oil from the hydraulic pump 31 to the hydraulically driven attachment 22 and the attachment cylinder 27 .

A control valve corresponding to the attachment cylinder 27 is connected to the rod port 27a of the attachment cylinder 27 via the pipe L1, and is connected to the bottom port 27b of the attachment cylinder 27 via the pipe L2. This control valve is, for example, a three-position switching valve, and is driven according to an operator's operation. When the discharge pipe 31a of the hydraulic pump 31 is connected to the pipe L1 by the control valve, the attachment cylinder 27 is contracted and the extension arm 28 is rotated and deployed in the dumping direction (FIG. 1). When the discharge pipe 31a is connected to the pipe L2 by the control valve, the attachment cylinder 27 is extended and the extension arm 28 is rotated in the cloud direction and held (FIG. 2). When the operation is stopped, the control valve switches to the neutral position, for example, the discharge pipe 31a is connected to the oil tank 32, and the attachment cylinder 27 is held.

A control valve corresponding to the hydraulically driven attachment 22 in the in-vehicle control valve unit 33 is connected to the inlet port IP of the hydraulically driven attachment 22 via the pipe L3. If the hydraulically driven attachment 22 is operated, the discharge pipe 31a of the hydraulic pump 31 is connected to the pipe L3 to supply pressure oil to the hydraulically driven attachment 22. If the hydraulically driven attachment 22 is not operated, the discharge pipe 31a is connected to the oil tank 32. When the operator operates the hydraulically driven attachment 22, the discharge oil of the hydraulic pump 31 is supplied via the vehicle-mounted control valve unit 33, and at the same time, the hydraulic circuit in the hydraulically driven attachment 22 operates as described above, and the corresponding hydraulic actuator operates. It is designed to

The communication pipe 34 connects the first pipe connecting the attachment cylinder 27 and the vehicle-mounted control valve unit 33 and the second pipe connecting the vehicle-mounted control valve unit 33 and the hydraulic actuator of the hydraulic drive attachment 22 .

The first pipe is a pipe that connects the rod port 27a and the bottom port 27b of the attachment cylinder 27 to which the pressure oil is supplied to the attachment cylinder 27 when the extension arm 28 dumps, and the in-vehicle control valve unit 33. . In this embodiment, the pipe L1 corresponds to the first pipe. If the attachment cylinder 27 is arranged on the ventral side of the arm 24, the pipe L2 corresponds to the first pipe.

The second pipe is a pipe that connects the hydraulic actuator of the hydraulic drive attachment 22 and the vehicle-mounted control valve unit 33, and may correspond to the pipes L3 to L9, but in this embodiment, only the pipe L3 corresponds to the second pipe. . A pipe L3 is a single pipe that connects the in-vehicle control valve unit 33 and the inlet port IP of the hydraulically driven attachment 22. In this embodiment, the pipes L1 and L3 are connected via a single connecting pipe 34. . The term "one" means one path, and includes not only a truly single pipe, but also an apparent single pipe formed by connecting a plurality of pipes in series.

None of the pipes L4 to L9 are connected to the pipe L1. Of course, there is no communication relationship between the pipes L2, L10 and the pipe L1.

Only one check valve 35 is provided in the communication pipe 34 . This check valve 35 allows the flow of pressure oil from the second pipe (pipe L3) to the first pipe (pipe L1), while allowing the pressure oil to flow from the first pipe (pipe L1) to the second pipe (pipe L3). pressure oil flow is prohibited.

-motion-
In this embodiment, when the hydraulically driven attachment 22 is operated, the hydraulic pump 31 and the rod port 27a of the attachment cylinder 27 are connected via the vehicle-mounted control valve unit 33 and the connecting pipe 34 . That is, while the hydraulically driven attachment 22 is performing some operation, the rod port 27a is always pressurized by the pressurized oil supplied to the hydraulically driven attachment 22, and the attachment cylinder 27 is contracted. Therefore, during work using the hydraulically driven attachment 22, the extension arm 28 is automatically deployed in the dumping direction as shown in FIG.

On the other hand, when the hydraulically driven attachment 22 is stopped, pressure oil does not flow through the pipe L3, so the attachment cylinder 27 can be freely operated by a corresponding operating device. The attachment cylinder 27 can be extended by supplying pressure oil to the bottom port 27b. Therefore, for example, when the work machine is transported by a trailer, the extension arm 28 can be held in the cloud direction as shown in FIG.

-effect-
(1) According to this embodiment, as described above, the attachment cylinder 27 can be allowed to expand and contract freely during transportation when the hydraulically driven attachment 22 is not used, and the transportation attitude shown in FIG. 2 can be transferred without any problem. can do. On the other hand, the attachment cylinder 27 can be automatically retracted during work using the hydraulically driven attachment 22, for example. As a result, the hydraulically driven attachment 22 can be used with the extension arm 28 naturally deployed, and interference of the hydraulically driven attachment 22 with the boom 23 and the like during work can be suppressed. Even if the attachment cylinder 27 is forgotten to be contracted, the extension arm 28 is naturally deployed in conjunction with the operation of the hydraulically driven attachment 22. - 特許庁Moreover, it is a simple structure in which the pipes L1 and L3 are connected by the connecting pipe 34 with the check valve 35, and can be easily applied to existing working machines.

(2) The hydraulically driven attachment 22 is a processor. Therefore, although it is necessary to freely allow or restrict the operation of the attachment cylinder 27 depending on the situation, the frequency of switching is low due to the nature of the work. If it costs a lot to allow free movement of the attachment cylinder 27 while restricting the movement of the attachment cylinder 27 during work, it is difficult to implement the function from the viewpoint of cost effectiveness. On the other hand, since the configuration of this embodiment is very simple as described above, it can be easily mounted on an actual machine.

(3) By connecting the pipe L3 that connects the in-vehicle control valve unit 33 and the inlet port IP of the hydraulic drive attachment 22 to the pipe L1, only one set of the connecting pipe 34 and the check valve 35 is required. Pressure oil flows through the pipe L3 only when the hydraulically driven attachment 22 is operated by the in-vehicle control valve unit 33 . Therefore, when the hydraulically driven attachment 22 is operated in some way, the original pressure supplied to the hydraulically driven attachment 22 acts on the rod port 27 a of the attachment cylinder 27 . This mechanism can be realized with an extremely simple configuration in which only one connecting pipe 34 with a check valve connects the pipes L1 and L3.

(Second embodiment)
FIG. 4 is a circuit diagram of a main part of a hydraulic system provided in a working machine according to a second embodiment of the invention, and corresponds to FIG. 3 of the first embodiment. The difference of this embodiment from the first embodiment is that the operation of the attachment cylinder 27 is not interlocked with the operation of the grapple opening/closing cylinder A1.

In this embodiment, the piping connecting the actuators of the hydraulically driven attachment 22 excluding the grapple opening/closing cylinder A1 and the attachment control valve unit VU corresponds to the above-described second piping. Specifically, pipes L6 and L7 supply pressure oil from the corresponding control valves to the feed motor A2 of the two-way rotation type, and pressure oil from the control valves corresponding to the saw motor A3 of the one-way rotation type. The supply pipe L8 constitutes the second pipe. None of the pipes L3 to L5 and L9 are connected to the pipe L1. Of course, there is no communication relationship between the pipes L2, L10 and the pipe L1.

Pipes L6 to L8 constituting the second pipe communicate with the pipe L1 via connecting pipes 34a to 34d. One ends of connecting pipes 34a to 34c are connected to the pipes L6 to L8, respectively, and one end of the connecting pipe 34d is connected to the pipe L1. The other ends of the connecting pipes 34a to 34c are connected to the connecting pipe 34d to merge, thereby connecting the pipes L6 to L8 to the pipe L1.

Check valves 35a to 35d are provided on the connecting pipes 34a to 34d, respectively. Each of the check valves 35a to 35d allows the flow of pressure oil from the second pipe (pipe L6 to L8) to the first pipe (pipe L1), while allowing the pressure oil to flow from the first pipe (pipe L1) to the second pipe ( It is installed in a direction that prohibits the flow of pressure oil to the pipes (L6 to L8).

Other configurations are the same as those of the first embodiment. Note that the check valve 35d can be omitted. Further, although FIG. 4 exemplifies a configuration in which the connecting pipes 34a to 34c are connected to the pipe L1 via the connecting pipe 34d, it is also possible to adopt a structure in which the connecting pipes 34a to 34c are directly connected to the pipe L1.

Also in this embodiment, when the feed motor A2 or the saw motor A3 of the hydraulically driven attachment 22 is driven, the attachment cylinder 27 is automatically contracted, and the extension arm 28 can be naturally deployed for work. The attachment cylinder 27 can be operated without restriction when the hydraulically driven attachment 22 is not used. However, in this embodiment, even if the grapple opening/closing cylinder A1 is driven, the attachment cylinder 27 is not interlocked.

In a narrow space between forests, for example, when picking up chopped lumber with a grapple and loading it into a transporter, it is sometimes desired to adopt a posture in which the extension arm 28 is held in the cloud direction. In this regard, in the first embodiment, the extension arm 28 is automatically deployed when the grapple opening/closing cylinder A1 is driven. On the other hand, in the present embodiment, the attachment cylinder 27 does not interlock when only the grapple function of the hydraulically driven attachment 22 is used.

(Modification)
Although the processor has been described above as an example of the hydraulically driven attachment 22 , the hydraulically driven attachment 22 may be of a hanging type, and a harvester can also be used as the hydraulically driven attachment 22 . Harvesters are also attachments used in forestry like processors, but in addition to the functions provided by processors, harvesters can also be used in the felling process of standing trees. The present invention can also be applied to attachments other than processors and harvesters (for example, the hook device disclosed in Japanese Unexamined Patent Application Publication No. 2019-120020) as long as they are suspension-type hydraulically driven attachments. The present invention is not limited to processors and harvesters that have a plurality of sets of hydraulic actuators and their control valves, but can also be applied to suspension-type hydraulically driven attachments that have at least one set of hydraulic actuators and their control valves.

DESCRIPTION OF SYMBOLS 10... Vehicle body, 22... Hydraulic drive attachment, 23... Boom, 24... Arm, 27... Attachment cylinder, 28... Extension arm, 31... Hydraulic pump, 33... On-vehicle control valve unit, 34, 34a to 34d... Communication pipe, 35 , 35a to 35d... Check valve, A1... Grapple opening/closing cylinder (hydraulic actuator), A2... Feed motor (hydraulic actuator), A3... Saw motor (hydraulic actuator), IP... Inlet port, L1... First pipe, L3... Second Piping, L6 to L8...Second piping, VU...Attachment control valve unit

Claims (4)

a vehicle body;
a boom connected to the vehicle body;
an arm connected to the tip of the boom;
an extension arm connected to the tip of the arm;
a suspension-type hydraulic drive attachment that includes a hydraulic actuator and a control valve for the hydraulic actuator, and is suspended from the tip of the extension arm;
an attachment cylinder having both ends connected to the arm and the extension arm;
a hydraulic pump that discharges pressure oil;
A working machine comprising the hydraulically driven attachment and an on-vehicle control valve unit that controls supply of pressure oil from the hydraulic pump to the attachment cylinder,
a first pipe that connects a port of a rod port and a bottom port of the attachment cylinder to which pressure oil is supplied to the attachment cylinder during a dumping operation of the extension arm and the in-vehicle control valve unit;
a second pipe connecting the in-vehicle control valve unit and the hydraulic actuator;
a connecting pipe that connects the first pipe and the second pipe;
a check valve provided in the connecting pipe for allowing pressure oil to flow from the second pipe to the first pipe while inhibiting pressure oil from flowing from the first pipe to the second pipe; A work machine characterized by: The work machine according to claim 1,
The hydraulic drive attachment is a harvester or a processor, and includes a plurality of hydraulic actuators including grapple open/close cylinders, an attachment control valve unit that controls the supply of pressurized oil from the hydraulic pump to the plurality of hydraulic actuators, and an inlet. and a port, and is configured to divert pressurized oil supplied through the inlet port and supply it from the attachment control valve unit to the plurality of hydraulic actuators. In the work machine according to claim 2,
The working machine, wherein the second pipe is a pipe that connects the vehicle-mounted control valve unit and the inlet port. In the work machine according to claim 2,
The working machine, wherein the second pipe is a pipe for supplying pressure oil from the attachment control valve unit to actuators other than the grapple opening/closing cylinder among the plurality of hydraulic actuators.

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