WO2023188593A1

WO2023188593A1 - Construction machine

Info

Publication number: WO2023188593A1
Application number: PCT/JP2022/046416
Authority: WO
Inventors: 大輔岡; 究高橋; 圭文竹林
Original assignee: 株式会社日立建機ティエラ
Priority date: 2022-03-31
Filing date: 2022-12-16
Publication date: 2023-10-05
Also published as: JPWO2023188593A1; CN117916427A; EP4382675A1; KR20240042053A

Abstract

Provided is a construction machine equipped with a front working device to which an attachment is attached via a quick hitch, a directional control valve that controls the pressure oil discharged from a hydraulic pump and drives the actuator of the front working device, and an operating lever for operating the directional control valve, the construction machine comprising: a lock port connected to the lock-side oil chamber of the lock cylinder of the quick hitch; an unlock port connected to the unlock-side oil chamber of the lock cylinder; a switching valve that switches the connection destination of the lock port and the unlock port to either the hydraulic pump or a tank; a switch for operating the switching valve; a pilot-driven relief valve installed in an oil passage that connects the hydraulic pump and the switching valve; and a relief pilot pipe that connects a hydraulic pipe, which is pressurized in accordance with the operation of the operating lever, to the pressure-receiving chamber of the relief valve.

Description

construction machinery

The present invention relates to construction machines such as hydraulic excavators.

For construction machinery with a front working machine such as a hydraulic excavator, the attachment attached to the front working machine is replaced as necessary. As a device that contributes to facilitating the attachment replacement work, a hydraulic device for attaching and removing attachments called a quick hitch, which is used by being attached to the tip of a front working machine, is known (see Patent Document 1, etc.). A quick hitch can grip (lock) or release (unlock) an attachment by expanding and contracting a lock cylinder.

Japanese Patent Application Publication No. 2015-200104

Generally, the lock cylinder of a quick hitch is connected to the hydraulic pump of the construction machine via a switching valve, and when the unlock operation is performed with a special switch, the oil chamber on the unlock side of the lock cylinder is opened via the switching valve. Connects to hydraulic pump and unlocks.

At this time, it is desired that the quick hitch requires a two-step operation to perform the unlocking operation. Therefore, the quick hitch drive circuit may be configured such that the lock cylinder is unlocked by operating an operating lever for operating an actuator of the construction machine after performing an unlocking operation using a switch. For example, by operating a switch to connect the oil chamber on the unlock side of the lock cylinder to the hydraulic pump, and then operating the operating lever to increase the pressure in the discharge piping of the hydraulic pump, you can connect the oil chamber on the unlock side of the lock cylinder to the hydraulic pump. One example is a configuration in which the oil chamber is pressurized to drive the lock cylinder.

By the way, the lock cylinder mounted on a quick hitch generally has a small capacity because it is placed at the tip of the front work equipment, and depending on the conditions, even if the pump pressure is applied to the oil chamber when the operating lever is not operated, It might work. In this case, even though the operating lever is not operated, the lock cylinder may operate against the operator's intention when the switch is operated.

In contrast, in the hydraulic circuit described in Patent Document 1, the lock cylinder of the quick hitch and the hydraulic pump of the construction machine are connected via two switching valves. In this hydraulic circuit, the oil chamber on the unlocking side of the lock cylinder is connected to the hydraulic pump only after the first switching valve is driven by a switch operation and the second switching valve is driven by a lever operation. rises and the lock cylinder unlocks. In other words, at the stage when the switch is operated, the oil passage between the oil chamber on the unlock side of the lock cylinder and the hydraulic pump is kept blocked by the second switching valve, and the lock is locked before the lever is intentionally operated. The cylinder is configured so that it does not operate.

However, in the hydraulic circuit described in Patent Document 1, the operating pressure of the lever operation and the circuit pressure of the actuator are sensed by a pressure sensor, and the control device determines the lever operation based on the output of the pressure sensor, and the second switching valve A configuration is adopted to control the In this case, if an abnormality occurs in the electrical system such as the pressure sensor or its wiring, it becomes impossible to operate the quick hitch.

An object of the present invention is to provide a construction machine that can stably drive a quick hitch in a two-step operation without using a sensor.

In order to achieve the above object, the present invention provides a front working machine to which an attachment is attached via a quick hitch, an actuator for driving the front working machine, a tank for storing hydraulic oil, and a tank for storing hydraulic fluid. A construction machine comprising: a hydraulic pump that discharges hydraulic oil; a directional control valve that controls the pressure oil discharged from the hydraulic pump to drive the actuator; and an operating lever that operates the directional control valve. A lock port that guides pressure oil from the hydraulic pump to a lock-side oil chamber of the lock cylinder when the attachment is gripped by the operation of the lock cylinder of the quick hitch; When releasing the state, an unlock port that guides pressure oil from the hydraulic pump to the unlock side oil chamber of the lock cylinder, and a connection destination of the lock port and the unlock port to either the hydraulic pump or the tank. a switch for operating the switching valve; a pilot-driven relief valve provided in an oil passage connecting the hydraulic pump and the switching valve; and a pressure receiving chamber of the relief valve that includes the operating lever. To provide a construction machine equipped with a relief pilot pipe to which a hydraulic pipe whose pressure increases with the operation of the construction machine is connected.

According to the present invention, the quick hitch can be stably driven in a two-step operation without using a sensor.

Side view of the construction machine according to the first embodiment of the present invention Side view of the quick hitch attached to the construction machine shown in Figure 1 Circuit diagram of the hydraulic system installed in the construction machine shown in Figure 1 A circuit diagram of a hydraulic system provided in a construction machine according to a second embodiment of the present invention

Embodiments of the present invention will be described below using the drawings.

(First embodiment)
-Construction machinery-
FIG. 1 is a side view of a construction machine according to a first embodiment of the present invention. Hereinafter, the left direction in FIG. 1 will be defined as the front of the rotating structure 3. In this embodiment, a hydraulic excavator with a bucket attached as an attachment (work tool) AT to the tip of the front work machine will be exemplified and explained, but the attachment AT can be of any type depending on the work, such as a grapple, breaker, chisel, etc. will be replaced as appropriate. Further, the present invention can be applied to any construction machine that can attach an attachment to a front working machine via a quick hitch, and the present invention is also applicable to construction machines other than hydraulic excavators, such as wheel loaders.

The hydraulic excavator 1 shown in the figure is configured to include an articulated front working machine 1A and a vehicle body 1B. The vehicle body 1B includes a running body 2 that is driven by left and right running motors (not shown), and a revolving body 3 that is attached to the upper part of the running body 2. The revolving body 3 turns with respect to the traveling body 2 by a turning motor (not shown). The center axis of rotation of the revolving structure 3 is vertical when the hydraulic excavator 1 is stopped on a level ground. The revolving body 3 is provided with a driver's cab 4.

The front working machine 1A is configured by connecting a plurality of driven members (boom 5 and arm 6) that each rotate in a vertical plane. The base end of the boom 5 is rotatably connected to the front part of the revolving body 3. An arm 6 is rotatably connected to the tip of the boom 5. An attachment AT is rotatably connected to the tip of the arm 6 via a quick hitch Q (described later). The boom 5 is driven by a boom cylinder 7 (raises and lowers). The arm 6 is driven by an arm cylinder 8 (cloud operation and dump operation). Attachment AT is driven together with quick hitch Q by attachment cylinder 9 (cloud operation and dump operation). In the hydraulic excavator 1 shown in FIG. 1, the boom cylinder 7, arm cylinder 8, and attachment cylinder 9 constitute an actuator that drives the front working machine 1A.

As mentioned above, the attachment AT can be attached to the front working machine 1A via the quick hitch Q. The quick hitch Q is a hydraulically driven joint device that detachably connects the attachment AT to the front working machine 1A. This quick hitch Q is attached to the tip of the front working machine 1A (the tip of the arm 6) via pins P1 and P2.

-Connection unit-
FIG. 2 is a side view of the quick hitch Q. The quick hitch Q includes a main body frame B, recesses R1 and R2, a hook F, and a lock cylinder C, as shown in FIG.

The main body frame B includes left and right vertical plates B1 and a horizontal plate B2 that connects the left and right vertical plates B1. In FIG. 2, the quick hitch Q is shown viewed from the left, so the left and right vertical plates B1 overlap, and only the left vertical plate B1 is visible. As mentioned above, the quick hitch Q is attached to the tip of the working machine 20 via pins P1 and P2. Specifically, the main body frame B and the attachment link 10 are rotatably connected through a pin P1, and the main body frame B and the tip of the arm 6 are rotatably connected through a pin P2. The attachment link 10 is an element of a link mechanism that connects the attachment cylinder 9 and the arm 6. Bosses B3 and B4 are provided on the left and right vertical plates B1 of the main body frame B on the side closer to the working machine 20 (the right side in FIG. 2). The pin P1 is passed through the attachment link 10 via the boss B3, and the pin P2 is passed through the arm 6 via the boss B4. In this way, the quick hitch Q is attached to the tip of the front working machine 1A, and the attachment link 10 and arm 6 of the front working machine 1A are connected via the quick hitch Q.

The recess R2 is a U-shaped groove located at the lower part of the left and right vertical plates B1 of the main body frame B in the attitude shown in FIG. The recess R2 opens downward (toward the arm cloud) and covers and engages with the pin P4 attached to the attachment AT.

The recess R1 is also a groove provided in the left and right vertical plates B1 of the main body frame B, and is located above the recess R2 in the attitude shown in FIG. The recess R1 opens toward the attachment AT, covers the pin P3 attached to the attachment AT, and engages with the pin P3. When attaching the attachment AT to the quick hitch Q, when the quick hitch Q is rotated counterclockwise in the figure using the pin P4 as a fulcrum with the recess R2 and the pin P4 engaged, the recess R1 is attached to the pin P3. is covered. Therefore, the opening of the recess R1 is set wider than the diameter of the pin P3.

The hook F is a metal fitting that holds and holds the pin P3 that has entered the recess R1, and in this embodiment, is interposed between the left and right vertical plates B1. The hook F is rotatably connected to the left and right vertical plates B1 of the main body frame B via a pin F1, and is attached to the main body frame B with the hook facing the opposite side from the recess R2. .

The lock cylinder C is a hydraulic actuator that rotates the hook F, and like the hook F, it is interposed between the left and right vertical plates B1. One end of the lock cylinder C is rotatably connected to the left and right vertical plates B1 of the main body frame B via a pin C1, and the other end is rotatably connected to the hook F via a pin C2. has been done.

The lock cylinder C is driven by pressure oil discharged from the hydraulic pump 22 (FIG. 3), and when the lock cylinder C extends, the hook F closes, and when the lock cylinder C contracts, the hook F opens. With the pins P3 and P4 in the recesses R1 and R2, the lock cylinder C expands, and the hook F rotates in the direction away from the recess R2 (clockwise in FIG. 2), holds the pin P3, and closes the recess. Pin P3 is restrained (locked) within R1. On the other hand, when the lock cylinder C contracts, the hook F rotates in the direction approaching the recess R2 (counterclockwise in FIG. 2), opens the recess R1, and the pin P3 is released (unlocked). ). In this way, the attachment AT is attached to and detached from the quick hitch Q.

-Hydraulic system-
FIG. 3 is a circuit diagram of a hydraulic system included in the hydraulic excavator shown in FIG. 1. The hydraulic circuit shown in FIG. 3 is an extracted circuit for driving the attachment cylinder 9 and the lock cylinder C. As representative components, a tank 21, a hydraulic pump 22, a pilot pump 23, a directional control valve 24, an electromagnetic switching valve unit 25, etc. are extracted and shown in the figure.

The tank 21 is a container that stores hydraulic oil, and is mounted on the revolving structure 3.

The hydraulic pump 22 is a variable displacement pump that pressurizes hydraulic oil sucked from the tank 21 and discharges pressure oil that drives a hydraulic actuator such as the attachment cylinder 9. This hydraulic pump 22 is driven by a prime mover (engine (internal combustion engine) or motor) mounted on the revolving structure 3. The capacity of the hydraulic pump 22 is controlled by a regulator (not shown). The regulator operates according to pilot pressure from a pilot valve 26 (described later) or the like, or a differential pressure across the hydraulic pump 22, and controls the capacity of the hydraulic pump 22. Note that the hydraulic pump 22 may also be of a fixed capacity type.

The pilot pump 23 is a fixed capacity pump (such as a gear pump) that pressurizes the hydraulic oil sucked from the tank 21 and discharges the pilot oil. The pilot oil serves as a power source for hydraulically driven circuit elements such as the directional control valve 24 .

The directional control valve 24 is a valve that controls the pressure oil discharged from the hydraulic pump 22 to drive the attachment cylinder 9, and controls starting/stopping of the attachment cylinder 9, switching of the expansion/contraction direction, etc. In this embodiment, the directional control valve 24 is a three-position switching valve in which a center bypass line 24a connecting the hydraulic pump 22 to the tank 21 is provided at a central switching position.

Note that the directional control valve 24 is one of a plurality of directional control valves that constitute the directional control valve group 24U. Although circuits for driving the boom cylinder 7, arm cylinder 8, swing motor, and travel motor are not shown in FIG. 3, the direction control valve group 24U includes the boom cylinder 7, arm cylinder 8, swing motor, Directional control valves are included to drive each motor. The circuit that drives the boom cylinder 7, arm cylinder 8, swing motor, and travel motor has the same configuration as the circuit that drives the attachment cylinder 9.

The pilot valve (pressure reducing valve) 26 reduces the pressure of the pilot oil discharged by the pilot pump 23 according to the operation, and generates and outputs pilot pressure that drives the direction control valve 24 and the like. This pilot valve 26 is connected to pressure receiving chambers arranged on both sides of the spool of the directional control valve 24 via

pilot pipes

26a and 26b, and thereby the pilot pump 23 is connected to the pressure receiving chamber of the directional control valve 24. . The pilot valve 26 is operated by an operating lever 26l. The operating lever 26l is arranged inside the driver's cab 4 next to the driver's seat (not shown). As described above, since the directional control valve 24 is driven by the pilot pressure output by the pilot valve 26, the directional control valve 24 is operated by the operating lever 26l that operates the pilot valve 26.

For example, when the operating lever 26l is tilted to one side, pilot pressure is generated in the pilot valve 26 using the pressure of pilot oil discharged by the pilot pump 23 as the source pressure. This pilot pressure is output to the pilot pipe 26a and acts on the pressure receiving chamber on the left side in FIG. 3 of the directional control valve 24. As a result, the spool of the directional control valve 24 moves to the right in the figure (switches to the left switching position), the oil discharged from the hydraulic pump 22 is supplied to the bottom port of the attachment cylinder 9, and the attachment cylinder 9 is extended. Attachment AT rotates toward the cloud.

Conversely, when the operating lever 26l is tilted to the other side, the pilot pressure generated by the pilot valve 26 based on the pilot oil discharged by the pilot pump 23 is transferred to the right side of the direction control valve 24 in FIG. 3 via the pilot piping 26b. acts on the pressure receiving chamber. As a result, the spool of the directional control valve 24 moves to the left in the figure (switches to the right switching position), the oil discharged from the hydraulic pump 22 is supplied to the rod port of the attachment cylinder 9, and the attachment cylinder 9 contracts. Attachment AT rotates in the dumping direction.

When the operating lever 26l is returned to the neutral position, the action of pilot pressure on the directional control valve 24 is stopped, and the spool of the directional control valve 24 returns to the neutral position (center switching position) by the restoring force of the spring 24s. As a result, the attachment cylinder 9 is disconnected from the hydraulic pump 22 and the tank 21 in terms of the circuit, and the attachment cylinder 9 becomes stationary due to the holding pressure. When the spool of the directional control valve 24 is in the neutral position, the pressure oil supplied from the hydraulic pump 22 returns to the tank 21 through the center bypass line 24a.

The electromagnetic switching valve unit 25 is a valve unit that controls the lock cylinder C to control the attachment and detachment of the attachment AT by the quick hitch Q, and includes a switching valve 27, a relief valve 28, and a check valve 29. The lock port 31 and unlock port 32 of the hydraulic circuit shown in FIG. 3 are connected to the hydraulic pump 22 and the tank 21 via this electromagnetic switching valve unit 25. The lock port 31 is connected to the lock side oil chamber C3, and guides pressure oil from the hydraulic pump 22 to the lock side oil chamber C3. The lock-side oil chamber C3 is an oil chamber of the lock cylinder C (in this embodiment, a bottom-side oil chamber) that receives pressure when the quick hitch Q grips the attachment AT due to the operation of the lock cylinder C. The unlock port 32 is connected to the unlock side oil chamber C4, and guides pressure oil from the hydraulic pump 22 to the unlock side oil chamber C4. The unlock side oil chamber C4 is an oil chamber of the lock cylinder C (rod side oil chamber in this embodiment) that receives pressure when the quick hitch Q releases the gripping state of the attachment AT by the operation of the lock cylinder C.

The switching valve 27 is a valve that switches the connection destination of the lock port 31 and the unlock port 32 to either the hydraulic pump 22 or the tank 21. This switching valve 27 is connected to a discharge pipe 22a of the hydraulic pump 22 that connects the hydraulic pump 22 and the direction control valve 24, and is connected to the discharge pipe 22a in parallel with the direction control valve 24. The switching valve 27 of this embodiment is a solenoid valve. A switch 33 for operating the switching valve 27 is provided in the driver's cab 4. A command signal is output from a controller (control device) 34 in response to an operation signal output from the switch 33, and the solenoid is energized or demagnetized by the command signal from the controller 34, and the switching valve 27 is operated.

However, the switching valve 27 may be mechanically linked to the switch 33 so that the switching valve 27 operates in conjunction with the operation of the switch 33 without using the controller 34. In addition, a hydraulically driven valve is adopted as the switching valve 27, and a pilot valve operated by a switch 33 is incorporated into the circuit, so that the switching valve 27 is operated by pilot pressure output from the pilot valve in response to switch operation. It's good as well.

In this embodiment, when the switch 33 is turned on, the solenoid of the switching valve 27 is energized by a command signal from the controller 34, and the spool of the switching valve 27 moves to the left in FIG. position). Thereby, the discharge pipe 22a of the hydraulic pump 22 is connected to the unlock port 32, and at the same time, the tank 21 is connected to the lock port 31.

Conversely, when the switch 33 is off, the command signal from the controller 34 is not output, the solenoid of the switching valve 27 is demagnetized, and the spool of the switching valve 27 is pushed to the right in FIG. switch position). Thereby, the discharge pipe 22a of the hydraulic pump 22 is connected to the lock port 31, and at the same time, the tank 21 is connected to the unlock port 32.

The relief valve 28 is a pilot-driven relief valve provided in an oil path connecting the hydraulic pump 22 and the switching valve 27. More specifically, the relief valve 28 is provided at a position between the switching valve 27 and a branching portion 22b of the discharge pipe 22a of the hydraulic pump 22 to a drive circuit for another actuator. The pressure receiving chamber (pilot chamber) of the relief valve 28 is connected to a hydraulic pipe whose pressure increases as the operating lever 26l is operated, via a relief pilot pipe 28a. In this embodiment, the hydraulic pipe connected to the pressure receiving chamber of the relief valve 28 via the relief pilot pipe 28a is the discharge pipe 22a of the hydraulic pump 22. That is, when the pressure in the discharge pipe 22a exceeds the set pressure defined by the spring 28s of the relief valve 28, the relief valve 28 opens. When the pressure in the discharge pipe 22a falls below the set pressure, the relief valve 28 closes. In FIG. 3, a variable type relief valve is illustrated as the relief valve 28, but the relief valve 28 may be a fixed type relief valve, and is not limited to the illustrated configuration; for example, a non-leak type relief valve may be used. You can also do it.

The check valve 29 prevents pressure oil from flowing out from the lock side oil chamber C3 of the lock cylinder C when the lock port 31 and the hydraulic pump 22 are in a connected state (that is, a state in which the attachment AT is gripped) via the switching valve 27. This is a valve that prevents This check valve 29 is provided between the hydraulic pump 22 and the switching valve 27 (specifically, at a position between the branch portion 22b of the discharge pipe 22a of the hydraulic pump 22 and the switching valve 27). In this embodiment, the check valve 29 is provided between the relief valve 28 and the switching valve 27. In FIG. 3, a spring type check valve is illustrated as the check valve 29, but the check valve 29 may be a swing type or other type of check valve, and is not limited to the configuration shown. Alternatively, for example, an operated check valve may be used.

-motion-
(1) Attachment of Attachment A typical procedure for attaching the attachment AT to the front working machine 1A via the quick hitch Q will be explained.

First, attach the quick hitch Q to the front working machine 1A in advance, and attach the traveling body 2, the swing body 3, the front Operate the work machine 1A as appropriate. When the recess R2 covers the pin P4, turn on the switch 33, extend the attachment cylinder 9 with the hydraulic pump 22 connected to the unlock port 32, and rotate the quick hitch Q in the cloud direction around the pin P4. . During this time, the center bypass line 24a of the directional control valve 24 is throttled (or the pump capacity is controlled by the regulator), the pressure in the discharge pipe 22a of the hydraulic pump 22 increases, the relief valve 28 opens, and the discharge of the hydraulic pump 22 is increased. Oil is led to unlock port 32. As a result, the quick hitch Q rotates with the lock cylinder C contracted and the hook F released, and the recess R1 of the quick hitch Q covers the pin P3 of the attachment AT.

Once the pins P3 and P4 of the attachment AT enter the recesses R1 and R2 of the quick hitch Q, turn off the switch 33 to connect the hydraulic pump 22 to the lock port 31 and move the actuator of the hydraulic excavator 1. The operation at that time is preferably an operation of extending the attachment cylinder 9 (attachment cloud operation). This is because the relative postures of the attachment AT and the front working machine 1A do not change. By driving the actuator of the hydraulic excavator 1 in this manner, the pressure in the discharge pipe 22a of the hydraulic pump 22 is increased again, the relief valve 28 is opened, and the discharge oil of the hydraulic pump 22 is guided to the lock port 31. As a result, the lock cylinder C is extended, the hook F is closed, the attachment AT is gripped by the quick hitch Q, and the attachment AT is securely attached to the front working machine 1A.

Once the attachment AT is attached to the front working machine 1A, the hydraulic excavator 1 is operated by operating each hydraulic actuator with the switch 33 turned off. During this time, every time the hydraulic actuator of the hydraulic excavator 1 is driven, the lock-side oil chamber C3 of the lock cylinder C of the quick hitch Q is pressurized, and a force for gripping the attachment AT is applied. On the other hand, the lock side oil chamber C3 of the lock cylinder C is sealed by the check valve 29, so even when the lock side oil chamber C3 is not pressurized, pressure oil is prevented from flowing out from the lock side oil chamber C3. , the state in which the quick hitch Q firmly grips the attachment AT is maintained.

(2) Attachment Removal A typical procedure for removing attachment AT from quick hitch Q will be explained.

First, the traveling body 2, the revolving body 3, and the front working machine 1A are operated as appropriate so that the attachment AT touches the ground at a predetermined location. After the attachment AT is grounded in a stable posture, the switch 33 is turned on to connect the hydraulic pump 22 to the unlock port 32.

Next, move the actuator of the hydraulic excavator 1. The operation at that time is preferably an operation of contracting the attachment cylinder 9 (attachment dump operation). This is because the relative positional change between the attachment AT and the front working machine 1A is small. By driving the actuator of the hydraulic excavator 1 in this manner, the pressure in the discharge pipe 22a of the hydraulic pump 22 is increased, the relief valve 28 is opened, and the discharge oil of the hydraulic pump 22 is guided to the unlock port 32. As a result, the lock cylinder C contracts, the hook F opens, and the gripping state of the attachment AT by the quick hitch Q is released.

When the hook F is opened, the attachment cylinder 9 is further retracted, and the quick hitch Q is rotated in the dumping direction around the pin P4 of the attachment AT, thereby separating the recess R1 of the quick hitch Q from the pin P3 of the attachment AT. Further, for example, by performing a boom raising operation or the like, the recess R2 of the quick hitch Q is separated from the pin P4 of the attachment AT, and the quick hitch Q is lifted. As a result, the attachment AT is removed from the front working machine 1A.

-effect-
(1) By providing the relief valve 28 between the hydraulic pump 22 and the unlock port 32, the release operation of the gripping state of the attachment AT by the quick hitch Q can be controlled by the operation of the switch 33 and the actuator operation of the hydraulic excavator 1. It can be operated stably in two stages.

For example, even when the hydraulic actuator of the hydraulic excavator 1 is not operated, the pressure in the discharge pipe 22a of the hydraulic pump 22 may not be stable due to multiple factors such as the properties of the hydraulic oil. Therefore, in the hydraulic circuit of FIG. 3, if the relief valve 28 is omitted, there is a possibility that the lock cylinder C will contract when the switch 33 is turned on and the switching valve 27 is driven.

In contrast, in this embodiment, since the relief valve 28 is provided between the hydraulic pump 22 and the unlock port 32, the lock cylinder C does not shrink. Therefore, the lock cylinder C does not contract simply by operating the switch 33, and only after operating the switch 33 and intentionally operating the actuator of the hydraulic excavator 1 to increase the pressure in the discharge pipe 22a, does the lock cylinder C contract. can be contracted.

At this time, if the lock cylinder C is simply to be contracted by a two-step operation, an electromagnetically driven on-off valve is provided in place of the relief valve 28, the attachment operation of the hydraulic excavator 1 is detected by a sensor, and the controller 34 detects the attachment operation of the hydraulic excavator 1. The opening/closing valve may be opened by a signal from the controller. However, in this case, if an abnormality were to occur in the sensor or its electrical system, the lock cylinder C would not be able to be operated, which would hinder attachment and detachment of the attachment AT.

In contrast, in this embodiment, a hydraulically driven relief valve 28 is used, and the pressure in the hydraulic piping (in this example, the discharge piping 22a), which increases in pressure as the actuator is operated, is used as the pilot pressure for the relief valve 28. By doing so, it will not be affected by abnormalities such as sensors.

As described above, according to this embodiment, the quick hitch Q can be stably driven in a two-step operation without using a sensor.

(2) Also, the size and hydraulic circuit of the lock cylinder mounted on the quick hitch vary depending on the manufacturer. For this reason, conventionally, when a switch is operated, the pressure applied to the oil chamber of the lock cylinder is adjusted according to the capacity of the lock cylinder while taking into account the margin. I needed to tune in. In contrast, this embodiment has a great advantage in that it does not require tuning according to the quick hitch Q, and high versatility is ensured.

(3) While working with the attachment AT attached to the front work equipment 1A, every time the hydraulic actuator of the hydraulic excavator 1 is driven, the lock-side oil chamber C3 of the lock cylinder C is pressurized, and the quick hitch Q is attached to the attachment. A force is applied to grip the AT. On the other hand, since the lock side oil chamber C3 of the lock cylinder C is sealed by the check valve 29, pressure oil is prevented from leaking from the lock side oil chamber C3 even when the lock side oil chamber C3 is not pressurized. The state in which the quick hitch Q firmly grips the attachment AT is maintained.

(Second embodiment)
FIG. 4 is a circuit diagram of a hydraulic system included in a construction machine according to a second embodiment of the present invention. In FIG. 4, elements that are the same as or correspond to those in the first embodiment are given the same reference numerals as those in the previous drawings, and the description thereof will be omitted.

This embodiment is different from the first embodiment in that the hydraulic piping connected to the pressure receiving chamber of the relief valve 28 via the relief pilot piping 28a connects the pilot valve 26 (FIG. 3) to the pressure receiving chamber of the direction control valve 24. The point is that the

pilot pipes

26a and 26b are connected to. The other configurations of this embodiment are the same as those of the first embodiment, and the operations when attaching and detaching the attachment AT are also the same as those of the first embodiment.

In this embodiment, when attaching the attachment AT, when the switch 33 is turned off and the attachment cylinder 9 is moved (for example, extended), the pilot pressure output from the pilot valve 26 is applied to the relief valve 28 via the relief pilot piping 28a. Acts on the pressure receiving chamber. As a result, as in the first embodiment, the relief valve 28 opens, the lock cylinder C extends, and the quick hitch Q grips the attachment AT. When removing the attachment AT, the switch 33 is turned on and the attachment cylinder 9 is moved (for example, contracted). As a result, the pilot pressure output from the pilot valve 26 acts on the pressure receiving chamber of the relief valve 28, the relief valve 28 opens, the lock cylinder C contracts, the hook F opens, and the gripping state of the attachment AT by the quick hitch Q is released. be done.

Similarly to the first embodiment, in this embodiment, the quick hitch Q can be stably driven in a two-step operation without using a sensor.

Furthermore, since the relief valve 28 is driven by the pilot pressure related to the operation of the attachment cylinder 9, the second stage operation of the quick hitch Q can be limited to the operation of the attachment cylinder 9. Since the second stage operation of the quick hitch Q is limited to the operation of the attachment cylinder 9, changes in the positional relationship between the front working machine 1A and the attachment AT when attaching and detaching the attachment AT are inevitably suppressed, and the attachment AT The installation and removal work is facilitated.

Note that in this embodiment, a configuration has been described in which the

pilot pipes

26a, 26b of the pilot valve 26 are connected to the pressure receiving chamber of the relief valve 28 via the relief pilot pipe 28a, but the configuration is not necessarily limited to this. When the actuator operation when attaching and detaching the attachment AT is limited to either the extension operation or the contraction operation of the attachment cylinder 9, either one of the

pilot pipes

26a and 26b is connected to the pressure receiving chamber of the relief valve 28. be able to. Further, if the lock cylinder C is operated by an operation other than the attachment cylinder 9 as necessary, the connection source of the pressure receiving chamber of the relief valve 28 may be changed to a pilot pipe related to another hydraulic actuator.

DESCRIPTION OF SYMBOLS 1... Hydraulic excavator (construction machine), 1A... Front work equipment, 7... Boom cylinder (actuator), 8... Arm cylinder (actuator), 9... Attachment cylinder (actuator), 21... Tank, 22... Hydraulic pump, 22a... Discharge piping (hydraulic piping), 23...Pilot pump, 24...Direction control valve, 26...Pilot valve, 26a, 26b...Pilot piping (hydraulic piping), 26l...Operation lever, 27...Switching valve, 28...Relief valve, 28a ...Relief pilot piping, 29...Check valve, 31...Lock port, 32...Unlock port, 33...Switch, AT...Attachment, C...Lock cylinder, C3...Lock side oil chamber, C4...Unlock side oil chamber, Q...Quick hitch

Claims

a front working machine to which an attachment is attached via a quick hitch;
an actuator that drives the front work machine;
A tank for storing hydraulic oil,
a hydraulic pump that discharges hydraulic oil sucked from the tank;
a directional control valve that controls pressure oil discharged from the hydraulic pump to drive the actuator;
A construction machine comprising an operating lever for operating the directional control valve,
a lock port that guides pressure oil from the hydraulic pump to a lock side oil chamber of the lock cylinder when the attachment is gripped by the operation of the lock cylinder of the quick hitch;
an unlock port that guides pressure oil from the hydraulic pump to an unlock side oil chamber of the lock cylinder when the gripping state of the attachment is released by the operation of the lock cylinder of the quick hitch;
a switching valve that switches the connection destination of the lock port and the unlock port to either the hydraulic pump or the tank;
a switch that operates the switching valve;
a pilot-driven relief valve provided in an oil passage connecting the hydraulic pump and the switching valve;
A construction machine comprising: a relief pilot pipe that connects a pressure receiving chamber of the relief valve with a hydraulic pipe that increases the pressure as the operating lever is operated.
The construction machine according to claim 1,
The switching valve is connected to a discharge pipe of the hydraulic pump that connects the hydraulic pump and the directional control valve,
A construction machine, wherein the hydraulic pipe is a discharge pipe of the hydraulic pump.
The construction machine according to claim 1,
A pilot pump that discharges pilot oil;
a pilot valve that is operated by the operating lever to reduce the pressure of the pilot oil and output pilot pressure that drives the directional control valve;
The construction machine is characterized in that the hydraulic piping is a pilot piping that connects the pilot valve to a pressure receiving chamber of the directional control valve.
The construction machine according to claim 1,
a check valve that is provided between the hydraulic pump and the switching valve and prevents pressure oil from flowing out from the lock-side oil chamber when the lock port and the hydraulic pump are in a connected state via the switching valve; A construction machine characterized by being equipped with.