JP2022168505A - work vehicle - Google Patents

Abstract

To provide a work vehicle capable of preventing a connection device detachably connecting two members provided in a vehicle body from unintentionally coming into a lock release state.SOLUTION: A wheel loader 1 comprises: a quick coupler 26 detachably connecting a lift arm 21 with a bucket 23 by a telescopic motion of a coupler cylinder 27; a first hydraulic pump 30 applying hydraulic oil to quick coupler driving circuits 26C1 and 26C2; a direction control valve 32 provided between the first hydraulic pump 30 and the coupler cylinder 27; and a second hydraulic pump 50 supplying hydraulic oil to a travel driving circuit 7C different from the quick coupler driving circuits 26C1 and 26C2. A bottom chamber 27B is connected to the second hydraulic pump 50 in parallel with the travel driving circuit 7C. When the direction control valve 32 is in a neutral position 32N, a part of the hydraulic oil discharged from the second hydraulic pump 50 is supplied to the bottom chamber 27B.SELECTED DRAWING: Figure 4

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work vehicle equipped with a hydraulically driven connecting device for detachably connecting two members provided on a vehicle body.

2. Description of the Related Art Some work vehicles such as wheel loaders and hydraulic excavators are equipped with a coupling device that easily detachably couples two members with a coupling pin driven by a hydraulic cylinder. For example, Patent Literature 1 discloses a crawler hydraulic excavator provided with a pin connecting device for connecting and disconnecting a crawler frame and a car body. This pin connecting device has a pin hole formed in the crawler frame, and a connecting pin and an attachment/detachment cylinder provided in the car body. As a result, the crawler frame and the car body are connected, and the connection pin is released from the pin hole by contraction of the attachment/detachment cylinder, and the crawler frame and the car body are separated by releasing the lock.

Japanese Patent No. 6361475

However, in the pin coupling device described in Patent Document 1, when the control valve for controlling the detachment cylinder is in a neutral state and the hydraulic oil discharged from the hydraulic pump is not supplied to the detachment cylinder, the detachment cylinder does not operate. , the rod is held by the residual pressure remaining in the desorption cylinder. Therefore, if the amount of hydraulic oil leaking from the bottom chamber side of the detachable cylinder is greater than that from the rod chamber side, or if an external force acts on the detachable cylinder in a direction that causes the rod to contract, The attachment/detachment cylinder is operated in the contracting direction, the connecting pin is released from the pin hole, and the crawler frame and the car body are unintentionally separated.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a work vehicle capable of suppressing an unintentional unlocking state of a coupling device that detachably couples two members provided on a vehicle body.

In order to achieve the above object, the present invention provides a vehicle body, first and second members provided on the vehicle body, and attached to the first member, and the first and second members are mounted on the first member by extending and retracting a rod of a hydraulic cylinder. A connecting device that detachably connects a member and the second member, a first hydraulic pump that supplies hydraulic oil to a first hydraulic circuit including the hydraulic cylinder, and between the first hydraulic pump and the hydraulic cylinder. a first directional control valve provided in the first hydraulic pressure a second switching position for communicating the connection between the pump and the bottom chamber of the hydraulic cylinder; and a neutral position for disconnecting the connection between the first hydraulic pump and the rod chamber and the connection between the first hydraulic pump and the bottom chamber. and, when the valve position of the first directional control valve is the second switching position, the coupling device supplies the hydraulic oil discharged from the first hydraulic pump to the bottom chamber and the When the rod is extended to engage with the second member and the valve position of the first directional control valve is the first switching position, the hydraulic oil discharged from the first hydraulic pump flows into the rod chamber. , wherein the work vehicle is provided with a second hydraulic pump that supplies hydraulic oil to a second hydraulic circuit different from the first hydraulic circuit, wherein the bottom chamber is connected to the second hydraulic pump in parallel with the second hydraulic circuit, and when the valve position of the first directional control valve is the neutral position, part of the hydraulic oil discharged from the second hydraulic pump is supplied to the bottom chamber.

ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the coupling device which detachably couples the two members provided in the vehicle body will be in an unlocked state unintentionally. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

1 is an external side view showing one configuration example of a wheel loader according to each embodiment of the present invention; FIG. FIG. 4 is a plan view showing the rear side of the bucket when the quick coupler is in a locked state; FIG. 10 is a plan view showing the rear side of the bucket when the quick coupler is in an unlocked state; 1 is a circuit configuration diagram showing one configuration example of a quick coupler drive circuit according to a first embodiment; FIG. FIG. 11 is a circuit configuration diagram showing one configuration example of a quick coupler drive circuit according to a second embodiment;

Hereinafter, as one aspect of the work vehicle according to each embodiment of the present invention, a wheel loader that performs cargo handling work of excavating work objects such as earth and sand and minerals and loading them onto a loading destination such as a dump truck will be described.

<Configuration of Wheel Loader 1>
First, the configuration of the wheel loader 1 will be described with reference to FIGS. 1 to 3. FIG.

FIG. 1 is an external side view showing one configuration example of a wheel loader 1 according to each embodiment of the present invention.

The wheel loader 1 is an articulated work vehicle that is steered by bending the vehicle body near the center. Specifically, a front frame 1A, which is the front part of the vehicle body, and a rear frame 1B, which is the rear part of the vehicle body, are connected by a center joint 10 so as to be freely rotatable in the left-right direction, and the front frame 1A is connected to the rear frame 1B. It bends in the left and right direction.

The vehicle body is provided with four wheels 11. Two wheels 11 are provided as front wheels 11A on both left and right sides of the front frame 1A, and the remaining two wheels 11 are provided as rear wheels 11B on both left and right sides of the rear frame 1B. ing. Of the four wheels 11, only the front wheel 11A and rear wheel 11B provided on the left side are shown in FIG. Moreover, there is no particular limitation on the specific number of the plurality of wheels 11 provided on the vehicle body.

A hydraulically driven working device 2 for carrying out cargo handling work is attached to the front portion of the front frame 1A. The rear frame 1B includes a driver's cab 12 in which an operator rides, a machine room 13 in which various devices necessary for driving the wheel loader 1 are accommodated, and a work device 2 for keeping the balance so that the vehicle body does not tilt. A counterweight 14 of is provided. In the rear frame 1B, the operator's cab 12 is arranged at the front, the counterweight 14 is arranged at the rear, and the machine room 13 is arranged between the operator's cab 12 and the counterweight 14, respectively.

The working device 2 includes a lift arm 21 attached to the front frame 1A so as to be rotatable in the vertical direction, two lift arm cylinders 22 as hydraulic cylinders for driving the lift arm 21, and a vertical a bucket 23 mounted to be rotatable in the direction, a bucket cylinder 24 as a hydraulic cylinder that drives the bucket 23, and a link mechanism between the bucket 23 and the bucket cylinder 24 that is rotatably connected to the lift arm 21. and a bell crank 25 that Although the two lift arm cylinders 22 are arranged side by side in the lateral direction of the vehicle body, only the lift arm cylinder 22 arranged on the left side is indicated by a broken line in FIG.

When hydraulic oil is supplied to the bottom chambers of the two lift arm cylinders 22 and the rods 220 extend, the lift arms 21 rotate upward with respect to the front frame 1A. On the other hand, when hydraulic oil is supplied to the rod chambers of the two lift arm cylinders 22 and the rods 220 contract, the lift arms 21 rotate downward with respect to the front frame 1A.

The bucket 23 rotates upward with respect to the lift arm 21 (tilting operation) when hydraulic oil is supplied to the bottom chamber of the bucket cylinder 24 and the rod 240 extends. On the other hand, when hydraulic oil is supplied to the rod chamber of the bucket cylinder 24 and the rod 240 contracts, the bucket 23 rotates downward with respect to the lift arm 21 (dump operation). As a result, the bucket 23 can scoop and discharge (discharge) work objects such as sand and minerals.

The bucket 23 can be replaced with various attachments such as blades, and the wheel loader 1 can perform various types of work such as dozing work and snow removal work in addition to cargo handling work using the bucket 23. is also possible. In the wheel loader 1 , a quick coupler 26 is attached to the tip of the lift arm 21 so that the bucket 23 and various attachments can be easily attached and detached from the lift arm 21 .

The configuration and operation of the quick coupler 26 will now be described with reference to FIGS. 2 and 3. FIG.

FIG. 2 is a plan view showing the rear side of the bucket 23 when the quick coupler 26 is locked. FIG. 3 is a plan view showing the rear side of the bucket 23 when the quick coupler 26 is in the unlocked state.

The quick coupler 26 includes a quick coupler main body 260A attached to the tip of the lift arm 21 and arranged to face the rear surface of the bucket 23, and an engaging member provided on the quick coupler main body 260 and engaged with the bucket 23. 260B and a coupler cylinder 27 as a hydraulic cylinder that drives the engaging member 260B.

The engaging member 260B includes a pair of pin portions 261 and 262 inserted into and removed from a pair of pin holes 231 and 232 formed in the rear portion of the bucket 23, a connecting portion 263 connecting the pair of pin portions 261 and 262, is composed of In this embodiment, one of the pair of pin holes 231 and 232 is formed at the left end of the rear surface of the bucket 23, and the other pin hole 232 is formed at the right end of the rear surface of the bucket 23. ing. Therefore, the pair of pin portions 261 and 262 are arranged side by side with a predetermined interval in the left-right direction on the rear surface portion of the bucket 23, that is, the quick coupler main body 260A.

In the following description, of the pair of pin holes 231 and 232, one of the pin holes 231 formed at the left end of the rear surface of the bucket 23 is referred to as a "first pin hole 231". The other pin hole 232 formed at the right end is called "second pin hole 232". Further, of the pair of pin portions 261 and 262, the one corresponding to the first pin hole 231 is called the "first pin portion 261", and the one corresponding to the second pin hole 230R is called the "second pin portion 262". .

The connection portion 263 includes a first fixed piece 263L fixed to the left end portion serving as the base end portion of the first pin portion 261, and a second fixed piece 263L fixed to the left end portion serving as the base end portion of the second pin portion 262. 263R and a connection bar 263C extending in the left-right direction and connecting the first fixing piece 263L and the second fixing piece 263R. In this embodiment, the connection bar 263C connects the first fixed piece 263L and the second fixed piece 263R at positions above the positions of the first pin portion 261 and the second pin portion 262. However, the connection is not limited to this, and the first fixed piece 263L and the second fixed piece 263R may be connected at a position lower than the positions of the first pin portion 261 and the second pin portion 262 .

The coupler cylinder 27 is arranged so that its axial direction extends along the lateral direction of the bucket 23 between the first pin portion 261 and the second pin portion 262, that is, in the central region of the quick coupler main body 260A. The coupler cylinder 27 has a cylindrical cylinder tube 270A through which hydraulic oil flows and a rod 270 that extends and contracts in the axial direction with respect to the cylinder tube 270A. One end side of the rod 270 is fitted into the cylinder tube 270A, and the other end side (tip side) protrudes from the cylinder tube 270A and is attached to the second fixed piece 263R.

As a result, the expansion and contraction of the rod 270 of the coupler cylinder 27 is applied to the second pin portion 262 via the second fixing piece 263R, and to the first pin portion 262 via the second fixing piece 263R, the connection bar 263C, and the first fixing piece 263L. The first pin portion 261 and the second pin portion 262 operate by being transmitted to the pin portion 261 respectively.

First, as shown in FIG. 2, when the rod 270 of the coupler cylinder 27 extends, the second fixed piece 263R moves rightward, so the second pin portion 262 fixed to the second fixed piece 263R also moves rightward. Moving. As a result, the second pin portion 262 is inserted into the second pin hole 232 . Further, when the rod 270 of the coupler cylinder 27 extends, the connecting bar 263C and the first fixing piece 263L move rightward together with the second fixing piece 263R. As a result, the first pin portion 261 fixed to the first fixing piece 263L is also moved rightward and inserted into the first pin hole 231 .

In this manner, the quick coupler 26 has the first pin portion 261 and the second pin portion 262 in the first pin hole 231 of the bucket 23 and the second pin portion 262 in the bucket 23, respectively, by the extension operation of the coupler cylinder 27. A locked state is established by being inserted and engaged. By locking the quick coupler 26, the bucket 23 is connected to the lift arm 21 via the quick coupler 26 (connected state).

On the other hand, as shown in FIG. 3, when the rod 270 of the coupler cylinder 27 contracts, the second fixed piece 263R moves leftward, so the second pin portion 262 fixed to the second fixed piece 263R also moves leftward. Moving. As a result, the second pin portion 262 is removed from the second pin hole 232 . Further, when the rod 270 of the coupler cylinder 27 contracts, the connecting bar 263C and the first fixing piece 263L move leftward together with the second fixing piece 263R. As a result, the first pin portion 261 fixed to the first fixing piece 263</b>L also moves leftward and is removed from the first pin hole 231 .

In this manner, the quick coupler 26 moves from the first pin hole 231 of the bucket 23 to the first pin portion 261 and from the second pin hole 232 of the bucket 23 to the second pin portion 262 by contracting the coupler cylinder 27, respectively. By pulling out and leaving, it becomes an unlocked state (unlocked state). When the quick coupler 26 is unlocked, the bucket 23 is removed from the lift arm 21 (disconnected state).

That is, the quick coupler 26 is such that the first pin portion 261 and the second pin portion 262 are inserted into and removed from the first pin hole 231 and the second pin hole 232 of the bucket 23 as the rod 270 of the coupler cylinder 27 expands and contracts. It is a connecting pin device that detachably connects the bucket 23 to the lift arm 21 by means of.

2 and 3, the quick coupler 26 is configured such that the first pin portion 261 and the second pin portion 262 move in the same direction as the extension and contraction direction of the rod 270 of the coupler cylinder 27, but this is not the only option. For example, the first pin portion 261 is connected to the bottom portion of the cylinder tube 270A of the coupler cylinder 27 (the left end portion of the coupler cylinder 27), moves in the direction opposite to the expansion and contraction direction of the rod 270, and is inserted into and removed from the first pin hole 231. It may be configured to be

The lift arm 21 is one aspect of the first member provided on the vehicle body, and the bucket 23 is one aspect of the second member provided on the vehicle body. The quick coupler 26 is one aspect of a connecting device that is attached to the first member and detachably connects the first member and the second member by extending and retracting the rod of the hydraulic cylinder (coupler cylinder 27).

Next, the quick coupler drive circuit of the wheel loader 1 will be described for each embodiment.

<First embodiment>
A quick coupler drive circuit 26C1 according to the first embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a circuit configuration diagram showing one configuration example of the quick coupler drive circuit 26C1 according to the first embodiment.

A quick coupler drive circuit 26C1 for driving the quick coupler 26 is provided between the coupler cylinder 27, the first hydraulic pump 30 that supplies operating oil to the coupler cylinder 27, and the first hydraulic pump 30 and the coupler cylinder 27. and a directional control device 31. This quick coupler drive circuit 26C1 corresponds to a first hydraulic circuit including the coupler cylinder 27. As shown in FIG.

The directional control device 31 includes a coupler cylinder directional control valve 32 (hereinafter simply referred to as "directional control valve 32") as a first directional control valve provided between the first hydraulic pump 30 and the coupler cylinder 27. , and three relief valves 33A, 33B, 33C that discharge hydraulic fluid to the hydraulic fluid tank 40 when a preset relief pressure is reached. Three relief valves 33A, 33B, 33C are provided corresponding to the discharge line 300, the first line 301, and the second line 302, respectively.

A discharge line 300 connected to the discharge side of the first hydraulic pump 30 and a discharge line 303 connected to the hydraulic oil tank 40 are connected to one side of the directional control valve 32 . A first line 301 connected to the rod chamber 27A of the coupler cylinder 27 and a second line 302 connected to the bottom chamber 27B of the coupler cylinder 27 are connected to the other side of the direction control valve 32 .

The directional control valve 32 has three valve positions, a first switching position 32A, a second switching position 32B, and a neutral position 32N. The directional control valve 32 controls the flow (direction and flow rate) of hydraulic oil discharged from the first hydraulic pump 30 by switching between these three valve positions 32A, 32B, and 32N.

In the first switching position 32A, the discharge line 300 and the first line 301 are communicated (that is, the connection between the first hydraulic pump 30 and the rod chamber 27A of the coupler cylinder 27 is communicated), and the second line 302 and the discharge line 302 are connected. Communicates with line 303 . The second switching position 32B communicates the discharge line 300 and the second line 302 (that is, communicates the connection between the first hydraulic pump 30 and the bottom chamber 27B of the coupler cylinder 27), and the first line 301 and the exhaust line. Communicates with line 303 . At the neutral position 32N, the discharge line 300 and the discharge line 303 are communicated to block the connection between the first hydraulic pump 30 and the rod chamber 27A and the connection between the first hydraulic pump 30 and the bottom chamber 27B.

When the directional control valve 32 is switched to the first switching position 32A, hydraulic fluid discharged from the first hydraulic pump 30 flows into the rod chamber 27A of the coupler cylinder 27 through the discharge line 300 and the first line 301, Hydraulic oil discharged from the bottom chamber 27B of the coupler cylinder 27 flows out to the hydraulic oil tank 40 via the second line 302 and the discharge line 303 . As a result, the rod 270 of the coupler cylinder 27 is contracted, and the quick coupler 26 is separated from the bucket 23 to be unlocked.

On the other hand, when the directional control valve 32 is switched to the second switching position 32B, hydraulic oil discharged from the first hydraulic pump 30 flows into the bottom chamber 27B of the coupler cylinder 27 via the discharge line 300 and the second line 302. At the same time, the hydraulic fluid discharged from the rod chamber 27A of the coupler cylinder 27 flows out to the hydraulic fluid tank 40 via the first line 301 and the discharge line 303. As a result, the rod 270 of the coupler cylinder 27 is extended, and the quick coupler 26 is engaged with the bucket 23 to be locked.

Further, when the direction control valve 32 is switched to the neutral position 32N, the hydraulic oil discharged from the first hydraulic pump 30 returns to the hydraulic oil tank 40 via the discharge line 300 and the discharge line 303 as it is. In this case, since hydraulic oil is not supplied to the rod chamber 27A and the bottom chamber 27B of the coupler cylinder 27, the rod 270 is held by the residual pressure remaining in the coupler cylinder 27.

Mutual switching (valve position switching) between the first switching position 32A, the second switching position 32B, and the neutral position 32N in the direction control valve 32 is performed by a pair of oil chambers 32L and 32R provided in the direction control valve 32. is supplied with pilot pressure oil (pilot pressure acts) to move the internal spool.

Assuming that the pair of oil chambers 32L and 32R are the first oil chamber 32L and the second oil chamber 32R, the directional control valve 32 is arranged such that the pilot pressure acting on the first oil chamber 32L is higher than the pilot pressure acting on the second oil chamber 32R. When the pilot pressure acting on the second oil chamber 32R is greater than the pilot pressure acting on the first oil chamber 32L, the first oil chamber 32L and the second oil chamber 32L are moved to the second switching position 32B. When the pilot pressure of the same magnitude acts on the two oil chambers 32R, they are switched to the neutral position 32N.

A pilot circuit for controlling the directional control valve 32 is provided between a second hydraulic pump 50 as a pilot pump that supplies pilot pressure oil to the directional control valve 32, and between the second hydraulic pump 50 and the first oil chamber 32L. A first electromagnetic control valve 51 for controlling the flow of pilot pressure oil discharged from the second hydraulic pump 50 and supplied to the first oil chamber 32L, and between the second hydraulic pump 50 and the second oil chamber 32R. A second electromagnetic control valve 52 provided to control the flow of pilot pressure oil discharged from the second hydraulic pump 50 and supplied to the second oil chamber 32R, and a discharge connected to the discharge side of the second hydraulic pump 50 and a pilot relief valve 53 that discharges the pilot pressure oil to the hydraulic oil tank 40 when the circuit pressure of the line 500 becomes equal to or higher than a preset relief pressure.

The second hydraulic pump 50 is a hydraulic pump that supplies hydraulic fluid to a second hydraulic circuit (in this embodiment, the traveling drive circuit 7C of the wheel loader 1) different from the quick coupler drive circuit 26C1, which is the first hydraulic circuit. be done. That is, the second hydraulic pump 50 supplies part of the discharged hydraulic fluid to the travel drive circuit 7C, and supplies the other part of the discharged hydraulic fluid to the directional control valve 32 as pilot pressure fluid.

One side of the first electromagnetic control valve 51 is connected to a discharge pilot line 503 connected to the discharge line 500 and the hydraulic oil tank 40 . A first pilot line 501 connected to the first oil chamber 32</b>L of the directional control valve 32 is connected to the other side of the first electromagnetic control valve 51 .

The first electromagnetic control valve 51 connects the discharge line 500 and the first pilot line 501 to guide the pilot pressure oil discharged from the second hydraulic pump 50 to the first oil chamber 32L. 1 pilot line 501 and discharge pilot line 503 are communicated to guide pilot pressure oil discharged from first oil chamber 32</b>L to hydraulic oil tank 40 .

Similarly, a discharge line 500 and a discharge pilot line 503 are connected to one side of the second electromagnetic control valve 52 . A second pilot line 502 connected to the second oil chamber 32R of the directional control valve 32 is connected to the other side of the second electromagnetic control valve 52 . The second electromagnetic control valve 52 has a first control position 52A that communicates the discharge line 500 and the second pilot line 502 to guide the pilot pressure oil discharged from the second hydraulic pump 50 to the second oil chamber 32R, and a second control position 52A. 2 and a second control position 52</b>B that communicates the pilot line 502 and the discharge pilot line 503 to guide the pilot pressure oil discharged from the second oil chamber 32</b>R to the hydraulic oil tank 40 .

Both switching between the first control position 51A and the second control position 51B in the first electromagnetic control valve 51 and switching between the first control position 52A and the second control position 52B in the second electromagnetic control valve 52 are performed by the controller 6. done by A selector switch 120 is connected to the controller 6 as a switching device for switching the state of the quick coupler 26 between a locked state and an unlocked state. Note that the switching device does not necessarily have to be a switch, and may be, for example, a switching lever.

The change-over switch 120 is provided in the operator's cab 12. When the operator operates the change-over switch 120 to lock it, the change-over switch 120 outputs a lock operation signal to the controller 6, and the operator moves the change-over switch 120 to the unlocked state. When the switch 120 is operated to , an unlocking operation signal is output to the controller 6 .

The controller 6 outputs a lock switching signal to the second electromagnetic control valve 52 upon acquiring the lock operation signal. As a result, the second electromagnetic control valve 52 is switched to the first control position 52A and the pilot pressure acts on the second oil chamber 32R of the directional control valve 32, so that the directional control valve 32 is switched to the second switching position 32B. The quick coupler 26 is locked.

On the other hand, upon receiving the unlocking operation signal, it outputs an unlocking switching signal to the first electromagnetic control valve 51 . As a result, the first electromagnetic control valve 51 is switched to the first control position 51A and the pilot pressure acts on the first oil chamber 32L of the directional control valve 32, so that the directional control valve 32 is switched to the first switching position 32A. The quick coupler 26 is unlocked.

When the changeover switch 120 is not operated, that is, in a neutral state, no operation signal is output from the changeover switch 120 to the controller 6. Therefore, the first electromagnetic control valve 51 and the second electromagnetic control valve 52 are both , remains switched to the second control positions 51B and 52B. Therefore, the pilot pressure does not act on the first oil chamber 32L and the second oil chamber 32R of the directional control valve 32. pressure and the residual pressure in the second pilot line 502), the directional control valve 32 switches to the neutral position 32N.

In this case, as described above, the rod 270 is held by the residual pressure remaining inside the coupler cylinder 27 . Here, if an external force is applied to the coupler cylinder 27 in the direction in which the rod 270 contracts, or if hydraulic oil leaks from the bottom chamber 27B side of the coupler cylinder 27 more than from the rod chamber 27A side. , the rod 270 may contract and the quick coupler 26 may become unlocked.

Therefore, the quick coupler drive circuit 26C1 has a branch line 504 branched from the discharge line 500 and connected to the second line 302. As shown in FIG. That is, the bottom chamber 27B of the coupler cylinder 27 is connected to the second hydraulic pump 50 in parallel with the traveling drive circuit 7C. As a result, part of the hydraulic fluid discharged from the second hydraulic pump 50 is supplied to the bottom chamber 27B of the coupler cylinder 27 via the branch line 504 and the second line 302.

Therefore, the discharge line 500 is branched into three lines, ie, a line to the traveling drive circuit 7C, a line to the pilot circuit, and a line to the quick coupler drive circuit 26C1, and the second hydraulic pump 50 discharges. Hydraulic oil is distributed and supplied to each of the traveling drive circuit 7C, the pilot circuit, and the quick coupler drive circuit 26C1.

In this way, part of the hydraulic fluid discharged from the second hydraulic pump 50 is always supplied to the bottom chamber 27B of the coupler cylinder 27, so that the direction control valve 32 is switched to the neutral position 32N. Also, part of the hydraulic fluid discharged from the second hydraulic pump 50 is supplied to the bottom chamber 27B of the coupler cylinder 27, and the rod 270 of the coupler cylinder 27 moves in the extending direction. By holding the coupler 26 in the locked state, it is possible to prevent the unlocked state from occurring unintentionally.

In this embodiment, between the second hydraulic pump 50 and the bottom chamber 27B of the coupler cylinder 27, that is, on the branch line 504, the second hydraulic pump 50 and the coupler cylinder 27 are arranged according to the valve position of the direction control valve 32. A pilot check valve 54 is provided as a second direction control valve for switching between communication and disconnection of the connection with the bottom chamber 27B. Specifically, the pilot check valve 54 allows hydraulic fluid to flow from the second hydraulic pump 50 into the bottom chamber 27B and prevents hydraulic fluid from flowing into the second hydraulic pump 50 from the bottom chamber 27B.

A first pilot branch line 301A branched from the first line 301 is connected to the pilot check valve 54 . That is, the pilot check valve 54 is connected to the first hydraulic pump 30 in parallel with the rod chamber 27A of the coupler cylinder 27 .

When the directional control valve 32 is in the first switching position 32A, the pilot check valve 54 receives the hydraulic pressure acting on the rod chamber 27A of the coupler cylinder 27, that is, the control pressure that controls the rod 270 in the contraction direction. It acts on the pilot check valve 54 via the pilot branch line 301A.

When the operator operates the change-over switch 120 to the unlocked state and the hydraulic oil discharged from the first hydraulic pump 30 is supplied to the rod chamber 27A and the rod 270 contracts, the pilot check valve 54 is shifted upstream ( Since a higher pressure than the second hydraulic pump 50 side) acts, the pilot check valve 54 prevents the hydraulic oil from flowing from the second hydraulic pump 50 to the bottom chamber 27B. That is, when the directional control valve 32 is in the first switching position 32A, the pilot check valve 54 is supplied with control pressure oil that prevents hydraulic oil from flowing into the bottom chamber 27B of the coupler cylinder 27 from the second hydraulic pump 50. be done.

Thus, when the operator intends to unlock the quick coupler 26, the pilot check valve 54 prevents hydraulic fluid from flowing from the second hydraulic pump 50 into the bottom chamber 27B. It is possible to prevent the hydraulic pump 50 from discharging more hydraulic oil than necessary.

In this embodiment, the pilot check valve 54 is used as the second directional control valve, but the present invention is not limited to this. A switching valve capable of switching between communication and disconnection of the connection with the chamber 27B may be used.

Further, in the present embodiment, the pressure of the hydraulic oil supplied from the second hydraulic pump 50 to the bottom chamber 27B is applied to the upstream side of the pilot check valve 54, that is, between the second hydraulic pump 50 and the pilot check valve 54. A pressure reducing valve 55 is provided to reduce the pressure to a predetermined pressure. The "predetermined pressure" set in the pressure reducing valve 55 corresponds to an appropriate operating oil pressure that should act on the bottom chamber 27B.

In this way, by providing the pressure reducing valve 55 between the second hydraulic pump 50 and the bottom chamber 27B, the discharge pressure of the second hydraulic pump 50 does not directly act on the bottom chamber 27B, and the required hydraulic pressure is reduced. It is possible to allow only a minute to act on the bottom chamber 27B.

Further, the pressure reducing valve 55 has a relief function of discharging hydraulic oil flowing backward from the bottom chamber 27</b>B side toward the second hydraulic pump 50 to the hydraulic oil tank 40 . As a result, high pressure can be prevented from being applied to the upstream side of the pressure reducing valve 55, and a relatively low pressure line (for example, a pilot line, a return line, etc.) can be used as the branch line 504.

Furthermore, in the present embodiment, flow rate control for reducing the flow rate of hydraulic oil supplied from the second hydraulic pump 50 to the bottom chamber 27B is provided downstream of the pilot check valve 54, that is, between the pilot check valve 54 and the bottom chamber 27B. A diaphragm 56 is provided as a device. Thus, by providing the throttle 56 between the second hydraulic pump 50 and the bottom chamber 27B, it is possible to suppress the sudden flow of hydraulic oil into the bottom chamber 27B, and the coupler cylinder 27 can be operated slowly and smoothly. It is possible to Note that the flow controller does not necessarily have to be the throttle 56, and may be, for example, a flow control valve.

<Second embodiment>
Next, a quick coupler drive circuit 26C2 according to a second embodiment of the invention will be described with reference to FIG. Note that, in FIG. 5, the same reference numerals are assigned to the components common to those described for the quick coupler drive circuit 26C1 according to the first embodiment, and the description thereof will be omitted.

FIG. 5 is a circuit configuration diagram showing a configuration example of a quick coupler drive circuit 26C2 according to the second embodiment.

In this embodiment, the pressure source of the control pressure oil supplied to the pilot check valve 54 is different from the pressure source in the first embodiment. As shown in FIG. 5, the pilot check valve 54 is connected to a second pilot branch line 501A branched from the first pilot line 501, and the pilot pressure acting on the first oil chamber 32L of the directional control valve 32 is acts through the second pilot branch line 501A.

The pilot pressure acting on the first oil chamber 32L of the directional control valve 32 is a pressure that controls the directional control valve 32 in the direction in which the hydraulic oil discharged from the first hydraulic pump 30 is supplied to the rod chamber 27A. 270 corresponds to the control pressure that controls the contraction direction. In other words, the control pressure oil supplied to the pilot check valve 54 is the pilot pressure oil that switches the valve position of the directional control valve 32 to the second switching position 32B.

Therefore, in this embodiment, as in the first embodiment, when the operator intends to bring the quick coupler 26 into the unlocked state, the pilot check valve 54 allows the second hydraulic pump 50 to flow into the bottom chamber 27B. The inflow of hydraulic oil is blocked, so that the second hydraulic pump 50 can be prevented from discharging more than necessary hydraulic oil.

Each embodiment of the present invention has been described above. In addition, the present invention is not limited to each embodiment described above, and includes various modifications. For example, each of the above-described embodiments has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. Further, part of the configuration of each embodiment described above can be replaced with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of each embodiment described above. . Furthermore, it is possible to add, delete, or replace a part of the configuration of each embodiment described above with another configuration.

For example, in each of the above-described embodiments, the wheel loader 1 is described as one aspect of the work vehicle, but the present invention is not limited to this, and other work vehicles such as a hydraulic excavator may be used.

Further, in each of the above-described embodiments, the rod of the coupler cylinder 27 is used as one aspect of the coupling device that detachably couples two members (the first member and the second member) provided on the vehicle body by extending and retracting the rod of the hydraulic cylinder. Although the quick coupler 26 that detachably connects the lift arm 21 and the bucket 23 by the expansion and contraction of the arm 270 has been described as an example, the quick coupler 26 is attached to the first member, which is one of the two members, and is attached to the rod of the hydraulic cylinder. There is no particular limitation as long as it detachably connects the first member and the second member, which is the other of the two members, by an expansion and contraction operation. For example, a device for connecting a crawler frame and a car body in a hydraulic excavator may be

1: Wheel loader (working vehicle)
7C: travel drive circuit (second hydraulic circuit)
21: Lift arm (first member)
23: Bucket (second member)
26: Quick coupler (connecting device)
26C1, 26C2: quick coupler drive circuit (first hydraulic circuit)
27: coupler cylinder (hydraulic cylinder)
27A: Rod chamber 27B: Bottom chamber 30: First hydraulic pump 32: Direction control valve for coupler cylinder (first direction control valve)
32A: First switching position 32B: Second switching position 32N: Neutral position 50: Second hydraulic pump 54: Pilot check valve (second directional control valve)
55: pressure reducing valve 56: throttle (flow controller)

Claims (8)

a vehicle body;
a first member and a second member provided on the vehicle body;
a connecting device that is attached to the first member and detachably connects the first member and the second member by extension and contraction of a rod of a hydraulic cylinder;
a first hydraulic pump that supplies hydraulic oil to a first hydraulic circuit that includes the hydraulic cylinder;
a first directional control valve provided between the first hydraulic pump and the hydraulic cylinder;
The first directional control valve is
a first switching position communicating the connection between the first hydraulic pump and the rod chamber of the hydraulic cylinder;
a second switching position communicating the connection between the first hydraulic pump and the bottom chamber of the hydraulic cylinder;
a neutral position for disconnecting the connection between the first hydraulic pump and the rod chamber and the connection between the first hydraulic pump and the bottom chamber;
The connecting device is
When the valve position of the first directional control valve is the second switching position, the hydraulic oil discharged from the first hydraulic pump is supplied to the bottom chamber, and the rod extends to extend the second member. engage,
When the valve position of the first directional control valve is the first switching position, hydraulic oil discharged from the first hydraulic pump is supplied to the rod chamber and the rod contracts to contract the second member. In the work vehicle leaving from
A second hydraulic pump that supplies hydraulic oil to a second hydraulic circuit different from the first hydraulic circuit,
The bottom chamber is connected to the second hydraulic pump in parallel with the second hydraulic circuit,
A work vehicle according to claim 1, wherein a portion of hydraulic oil discharged from the second hydraulic pump is supplied to the bottom chamber when the valve position of the first directional control valve is the neutral position. In the work vehicle according to claim 1,
Provided between the second hydraulic pump and the bottom chamber of the hydraulic cylinder, the connection between the second hydraulic pump and the bottom chamber is communicated or interrupted according to the valve position of the first directional control valve. A work vehicle characterized by comprising a second directional control valve for switching between and. In the work vehicle according to claim 2,
The second directional control valve is
A pilot check valve that allows hydraulic fluid to flow from the second hydraulic pump into the bottom chamber of the hydraulic cylinder and prevents hydraulic fluid from flowing from the bottom chamber to the second hydraulic pump,
The pilot check valve has
A work vehicle, wherein when the first directional control valve is in the first switching position, control pressure oil is supplied from the second hydraulic pump to prevent hydraulic oil from flowing into the bottom chamber. In the work vehicle according to claim 3,
The pilot check valve is
connected to the first hydraulic pump in parallel with the rod chamber of the hydraulic cylinder;
The control pressure oil supplied to the pilot check valve is
A working vehicle, wherein the hydraulic oil is supplied from the first hydraulic pump to the rod chamber. In the work vehicle according to claim 3,
The second hydraulic pump is
a pilot pump that supplies pilot pressure oil for switching the valve position of the first directional control valve to the first directional control valve;
The control pressure oil supplied to the pilot check valve is
A work vehicle, wherein the pilot pressure oil switches the valve position of the first directional control valve to the second switching position. In the work vehicle according to claim 1,
A pressure reducing valve is provided between the second hydraulic pump and the bottom chamber of the hydraulic cylinder and reduces pressure of hydraulic oil supplied from the second hydraulic pump to the bottom chamber of the hydraulic cylinder. A work vehicle characterized by: In the work vehicle according to claim 6,
The pressure reducing valve is
A work vehicle having a relief function for discharging hydraulic oil flowing backward from the bottom chamber side of the hydraulic cylinder toward the second hydraulic pump to a hydraulic oil tank. In the work vehicle according to claim 1,
A flow controller is provided between the second hydraulic pump and the bottom chamber of the hydraulic cylinder to reduce the flow rate of hydraulic oil supplied from the second hydraulic pump to the bottom chamber of the hydraulic cylinder. A work vehicle characterized by:

Images