JP5885787B2 - Hydraulic control device - Google Patents

Description

The present invention relates to a hydraulic control device used in a work machine in which various attachments such as a bucket and a pile driving device are detachably attached to an arm provided on a vehicle body.

As such a working machine, an excavator loader or a backhoe used for excavating the ground or moving excavated earth and sand is widely known. Such work machines are configured so that various attachments such as buckets, blades, chip breakers, auger devices and the like can be attached to and detached from the tip of an arm that can swing up and down on the vehicle body. Accordingly, the single work machine can be used for multiple purposes and multiple functions by performing detachment and replacement accordingly (see, for example, Patent Document 1).

In such a work machine, in order to replace the attachment, it is necessary to insert and remove the pin that connects the arm and the attachment and to fix the attachment. An attachment is generally a heavy object, and if this is done manually, a lot of labor is required. Therefore, a hydraulically operated quick hitch mechanism that attaches and detaches the attachment at the tip of the arm is provided, and the supply of pressure oil supplied to the quick hitch cylinder that operates this mechanism is switched by the direction switching valve,
A work machine configured to switch an attachment between a locked state and a released state has been put into practical use. As long as the attachment is locked to the arm, the pressure oil supplied to the quick hitch cylinder can be kept low. For this reason, the supply oil path to the quick hitch cylinder is generally provided by branching from the signal pressure supply oil path that supplies the signal pressure to the hydraulic control device of each part of the vehicle body (see, for example, Patent Document 2).

JP 2005-336767 A JP 2004-036635 A

However, in the work machine as described above, the connecting mechanism part between the arm and the attachment may become stuck due to clogging or the like, and the cylinder thrust is insufficient even when the pressure oil supply direction to the quick hitch mechanism is switched. Thus, it may not be switched to the released state. Here, it is conceivable to increase the set pressure of the signal pressure supply oil passage including the supply oil passage of the quick hitch cylinder. However, such a setting is not preferable because it increases the load on the engine, motor, and the like that drive the hydraulic pump.

On the other hand, work machines use hydraulic actuators that drive work devices such as arm cylinders that swing the arm up and down, turning motors that turn the workbench, and travel motors that run the vehicle. The hydraulic actuator is connected to a control valve provided in a high pressure hydraulic circuit different from the signal pressure circuit, and its operation is controlled. Therefore, a direction switching valve is provided in one of the other hydraulic actuators, for example, the supply oil passage to the arm cylinder, and when the attachment is removed, high pressure oil is supplied from this supply oil passage to the quick hitch cylinder to switch to the release state. Configuration is conceivable. However, in such a configuration, it is necessary to provide a direction switching valve for the signal pressure supply oil passage for locking and holding the attachment and a direction switching valve for switching the supply oil passage for the arm cylinder to the supply oil passage for the quick hitch cylinder. In addition, it is necessary to control the control valve for controlling the operation of the arm cylinder in an interlocked manner, and the configuration of the hydraulic circuit and the control circuit becomes complicated. Since the supply oil passage to the arm cylinder has a high pressure and a large flow rate, the direction switching valve provided in the supply oil passage becomes large, and both the arrangement space and the cost increase. Furthermore, when the direction switching valve provided in the supply oil passage of the arm cylinder is switched, there is a problem that the operability is lowered, for example, the supply pressure to the arm cylinder fluctuates and the arm moves momentarily.

An object of the present invention is to provide a hydraulic control device that can reliably detect whether or not the direction switching valve has been switched in accordance with a switching instruction when the direction switching valve is operated .

In order to achieve the above object, the present invention provides an operating mechanism, a hydraulic cylinder that operates the operating mechanism, a switching valve that controls supply of pressure oil to the hydraulic cylinder, and a switching operation of the switching valve. In the hydraulic control apparatus configured to include a first hydraulic source that supplies a signal pressure of 2 and a second hydraulic source that supplies a line pressure higher than the signal pressure for operating the hydraulic cylinder, the switching valve includes: A valve body having a spool hole, a spool member disposed in the spool hole so as to be axially slidable, and provided on the valve body so as to face one end side of the spool member. An urging means for urging the other end side is provided, and a hydraulic oil chamber for receiving a signal pressure from the first hydraulic pressure source is provided in the valve body so as to face the other end side of the spool member. The spool member is configured to be biased toward the one end side by the signal pressure of the hydraulic oil chamber, and the biasing force that biases the spool member toward the other end side by the biasing means is reduced or released. and, wherein the spool member or by moving the spool member by the signal pressure acting on the hydraulic fluid chamber on the one end side by the urging force for urging the spool member by said biasing means to said other end and or move the other end, it is configured to perform control for supplying and discharging line pressure from the second hydraulic pressure source to the hydraulic cylinder by the switching valve. Further, wherein the spool member extends through the opening to pre Symbol spool member axially at the end of the one end side of the signal pressure from the first hydraulic pressure source is applied, extending in the intermediate portion in the radial direction outer circumference An oil passage in the spool that is open to the surface is formed, and when the spool member moves to the one end side by the signal pressure acting on the hydraulic oil chamber, the valve body has an oil passage in the spool. A signal pressure transmission oil passage is formed in which communication with the opening to the outer peripheral surface of the spool member is switched , and the signal pressure transmitted from the oil passage in the spool via the signal pressure transmission oil passage is detected. It can be detected by guiding it into the oil discharge passage.

In the above hydraulic control device, the detection oil passage is provided with a signal pressure detection means, and the signal pressure detection means detects whether the signal pressure is guided to the detection oil passage, Preferably, the spool member is configured to detect whether or not the spool member has moved to the other end side.

Further, in the above hydraulic control device, the operating mechanism is configured by a quick hitch mechanism that causes the attachment configured to be detachable to the vehicle body to be locked and held on the vehicle body or to release the locked holding state. You may comprise so that the said hydraulic cylinder may be comprised from the quick hitch cylinder which receives the hydraulic pressure supply and act | operates the said quick hitch mechanism.

In the hydraulic control device of the present invention, the spool member moves to the other end side by urging by the urging means on one end side, or receives the signal pressure in the hydraulic oil chamber on the other end side, and The spool member is formed with an oil passage in the spool that extends from one end side where the signal pressure acts and opens to the inner peripheral surface, and the valve body is positioned at the position of the spool member. Accordingly, a signal pressure transmission oil passage is formed in which communication with the oil passage in the spool is switched, and the signal pressure transmitted from the oil passage in the spool via the signal pressure transmission oil passage is entered into the detection oil passage. since lead and it is detectable by the from the change of the signal pressure for switching the movement of the spool member so as to detect the movement of the spool member, associated with the operation of the hydraulic cylinder line pressure supplied and drained The movement of the serial spool member can be reliably detected.

It is the (a) top view and (b) side view of the shovel loader shown as an example of the working machine to which the present invention is applied. It is a front view of the said shovel loader. FIG. 3 is a block diagram of a control circuit mainly including a loader device and a quick hitch mechanism in the shovel loader. It is a side view of the state which attached the pile driving device to the said shovel loader. It is the rear view of the quick hitch mechanism seen in the VV arrow direction in FIG.1 (b). It is a hydraulic circuit diagram of a quick hitch mechanism. It is sectional drawing of the quick hitch control valve in a control valve.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. 1 to 4 show an excavator loader 1 as an example of a working machine using a hydraulic control device according to the present invention. First, the schematic configuration of the excavator loader 1 will be described with reference to this figure.

The shovel loader 1 includes a vehicle body 10 configured to be able to travel and a loader device 20 provided on the vehicle body 10, and an attachment (working device) such as a bucket 22 or a pile driving device 27 at the tip of an arm in the loader device 20. ) Is detachably provided.

The vehicle body 10 includes a vehicle body frame 11 that forms a housing of the excavator loader 1, and the vehicle body frame 1.
1 includes an operator cabin 12 provided at an upper portion of the vehicle 1 and a traveling device 15 including a pair of crawler mechanisms provided on the left and right sides of the vehicle body frame 11.

The vehicle body frame 11 includes left and right side frames 11a protruding upward at the rear of the vehicle body,
An upper frame 11b that connects the side frames 11a, a rear frame 11c that forms a rear end surface of the vehicle body 10, and the like. Inside the vehicle body frame 11 surrounded by these, an engine that is a power source, an engine drive A hydraulic pump, a control valve, etc. are provided.

The operator cabin 12 is formed in a rectangular box-like frame shape that is located at the center in the front-rear direction of the vehicle body 10 and protrudes upward from the vehicle body frame 11. In this configuration mode, a configuration example of a mode in which the front of the vehicle is opened and the left and right sides are protected by side plates formed with a large number of rectangular holes is shown.

The traveling device 15 includes a pair of crawler mechanisms 16 provided on the left and right sides of the vehicle body 10. The idler 16b and the track crawler 16c supported freely, and the track belt (crawler belt) 16d spanned between the sprocket 16a and the idler 16b are configured.

The loader device 20 is mainly composed of a pair of left and right arms 21 provided on the side frame 11a so as to be able to swing up and down, and an arm cylinder 51 for moving the arms 21 up and down. The arm 21 includes a base arm portion 21a whose base end side is pivotally connected to the upper portion of the side frame 11a and extending forward of the vehicle body, and a bent arm portion 21b which is connected to the distal end side of the base arm portion 21a and bends obliquely downward. The tube side end portion of the arm cylinder 51 is pivotally connected to the side frame 11a, and the rod side end portion is pivotally connected to the proximal end side of the bending arm portion 21b. For this reason, the arm 21 can be swung up and down (raised) by operating the arm cylinder 51 to extend and contract.

The front ends of the left and right arms 21 and 21 extend forward of the vehicle body frame 11, and the pivot pin 2 is connected to the front end.
3, the back plate 24 is pivotably pivoted up and down.
The bucket 22 is attached via a quick hitch mechanism 60 described later. A bucket cylinder 52 is straddled between the tip of the arm 21 and the back plate 24, and the bucket 22 is swung up and down with respect to the arm 21 by operating the bucket cylinder 52 to expand and contract. .

An operator seat 13 is provided inside the operator cabin 12 so that an operator can be seated facing the front of the vehicle, and an operation for operating the traveling device 15, the loader device 20, an attachment, and the like around the operator seat 13. A device 30 is provided. Operating device 30
Auxiliary operation for operating the auger motor 53 and the like of the pile driving device 27 in addition to the first operation lever 31 that performs the traveling operation of the vehicle, the second operation lever 32 that performs the swing operation of the arm 21 and the bucket 22 (attachment). The operation lever 33 and the quick hitch operation switch 35 (see FIG. 3) for operating the quick hitch mechanism 60 are configured.

Inside the vehicle body frame 11 is provided a hydraulic control circuit that receives an operation signal output from the operation device 30 (31, 32, 33... 35, etc.) and activates a hydraulic actuator provided in each part of the vehicle body. . FIG. 3 shows a block diagram of a hydraulic control circuit mainly including the loader device 20 and the quick hitch mechanism 60. In FIG. 3, the description of the control system related to the traveling device 15 is omitted.

In the hydraulic control circuit, a multi-manifold type (operating signal is input from the operating device 30)
A laminated type) control valve 40 is provided. The control valve 40 is
Each hydraulic actuator 51, 52, 5 provided in the loader device 20 and the attachment
3 ... a plurality of control valves 41, 42, 43 ... corresponding to the pressurized oil at the line pressure of the attachment drive supplied from the first hydraulic pump P ₁ of the engine-driven, the operating lever 32, 33
Supply / exhaust control is performed on each hydraulic actuator based on the operation signal input from. That is,
The control valve is configured by stacking and connecting an arm control valve 41 corresponding to the arm cylinder 51, a bucket control valve 42 corresponding to the bucket cylinder 52, an auxiliary control valve 43 corresponding to auxiliary equipment such as an auger motor 53, and the like.

The second operating lever 32 of the operating device 30 includes an arm operating valve 32a and a bucket operating valve 32b.
And the hydraulic oil of the signal pressure for controlling the hydraulic equipment supplied from the engine-driven second hydraulic pump P ₂ according to the tilting direction and the tilting angle position from the neutral position of the second operating lever 32. The operation signal is output to the arm control valve 41 and the bucket control valve 42.

As for the operation mode of the second operation lever 32, the arm operation is performed in the front-rear direction, the bucket operation is performed in the left-right direction, and the arm lowering /
When the arm is lifted and tilted left / right from the neutral position, it is set like bucket scooping / bucket dumping. For example, when the second operation lever 32 is tilted backward by a predetermined angle from the neutral position, an “arm lift” operation signal corresponding to the tilt direction and angle position is input from the arm operation valve 32a to the arm control valve 41, The control valve 41 is operated in the spool movement direction and the valve opening degree according to the operation signal, the line cylinder pressure oil is supplied to the arm cylinder 51 in the supply direction and supply amount of the arm raising, and the arm 21 is tilted at the angular position. Is swung upward at a speed corresponding to

The same applies to the bucket scooping / bucket dumping in which the second operation lever 32 is tilted to the left and right from the neutral position. For example, when the second operation lever 32 is tilted to the left by a predetermined angle from the neutral position, the tilt direction and the angular position In response to the operation signal, “bucket scooping” is input from the bucket operation valve 32 b to the bucket control valve 42, and the bucket control valve 42 is operated with the spool moving direction and the valve opening degree corresponding to the operation signal.
Is supplied with the pressure oil of the line pressure in the supply direction and supply amount of the bucket scooping up.
2 is swung upward at a speed corresponding to the tilt angle position.

An auxiliary operation valve 33 a is connected to the auxiliary operation lever 33. As the auxiliary operation valve 33a, an electromagnetic proportional valve is used, and an operation signal corresponding to the tilt direction and tilt angle position of the auxiliary operation lever 33 is output to the auxiliary control valve 43. A quick hitch operation valve 35a is connected to the quick hitch operation switch 35, and the quick hitch operation valve 35a is switched between a non-excitation state and an excitation state. Specifically, when the quick hitch operation switch 35 is in the locking position, the quick hitch operation valve 35a is in a non-excited state, and when the quick hitch operation switch 35 is in the release position, the quick hitch operation valve 35a is in an excited state and is released. The operation signal (referred to as a release signal) is output to the quick hitch control valve 45. The quick hitch hydraulic control circuit will be described in detail later.

The auxiliary control valve 43 extends forward along the arm 21 and has a quick coupling 4 at the front end.
An oil passage provided with 9 is connected. In addition, by using the quick hitch mechanism 60, various attachments such as a pile driving device (auger device) 27, a mixer, and a drop hammer illustrated in FIG. It has become.
For this reason, the pile driving device 2 is mounted by replacing the bucket with the quick hitch mechanism and the hydraulic hose on the pile driving device side is connected to the quick coupling 49.
7 can be supplied with pressure oil.

The pile driving device 27 includes an auger motor 53 that is rotated by receiving pressure oil supplied from the auxiliary control valve 43 via a quick coupling 49, and an auger speed reducer 28 connected to the auger motor 53, and projects downward. The pile member PIL is detachably connected to the drive shaft of the auger speed reducer 28. As described above, an electromagnetic proportional valve is used as the auxiliary operation valve 33a. When the auxiliary operation lever 33 is operated, an operation signal corresponding to the tilt direction and the tilt angle position of the auxiliary operation lever 33 from the auxiliary operation valve 33a. Is input to the auxiliary control valve 43, pressure oil is supplied from the auxiliary control valve 43 to the auger motor 53 in the supply direction and supply amount corresponding to the operation signal, and the auger motor 53 is rotated in the forward and reverse directions. Thereby, the pile member PIL is rotated clockwise or counterclockwise in plan view via the auger reduction gear 28.

In the shovel loader 1 having the outline as described above, a quick hitch mechanism 60 is provided on a back plate 24 attached to the arm 21 so that attachments such as a bucket 22 and a pile driving device 27 can be attached and detached. Yes. Hereinafter, the quick hitch mechanism 60 will be described in detail with reference to the rear view of the quick hitch mechanism 60 shown in FIG. 5 and the hydraulic circuit diagram of the quick hitch mechanism 60 shown in FIG. Here, the bucket 22 is illustrated as an attachment, and for convenience of explanation, the left-right direction in the rear view shown in FIG.

The quick hitch mechanism 60 is disposed so as to be vertically movable right and left of the quick hitch cylinder 55 and the back plate 24 provided on the upper portion of the back plate 24, and is connected to and disengages from the bucket 22 according to the expansion and contraction of the quick hitch cylinder 55 The shaft 65 is mainly used.

The quick hitch cylinder 55 is disposed on the upper portion of the back plate 24 via the link arms 62a and 62b. That is, the quick hitch cylinder 55 has one end connected to the pivot pin 6.
1a is pivoted to the upper left part of the back plate 24, the other end is pivoted to the tube end clevis by the pivot pin 63a, and one end is pivoted to the upper right part of the back plate 24 by the pivot pin 61b. The other end of the back plate 24 is attached to the upper part of the back plate 24 via a link arm 62b pivotally connected to a clevis at the rod end by a pivot pin 63b.

FIG. 5 shows an extended state in which the quick hitch cylinder 55 is extended and the link arms 62a and 62b are in contact with a stopper (not shown). When the quick hitch cylinder 55 is retracted from this extended state, the link arm 62a rotates counterclockwise around the pivot pin 61a, and the link arm 62b pivots clockwise around the pivot pin 61b. Then, the quick hitch cylinder 55 moves upward so as to swing while maintaining a substantially horizontal posture.

In the extended state, the connection shafts 65 and 65 are disposed so as to be vertically movable, located below the tube end and rod end of the quick hitch cylinder 55. Connecting shaft 6
5 has a stepped rod shape composed of a large-diameter connecting rod portion 65a having a tapered connecting portion 65t formed at the lower end, and a small-diameter operating rod portion 65b connected to the connecting flange portion 65a and extending upward. . A collar 66 with a hook is slidably inserted into the operating collar 65b and is positioned between the lower surface of the cam flange 68 fixed to the upper end of the operating collar 65b and the upper surface of the collar 66. A coil spring 67 is supported on the outer peripheral portion of the operating collar 65b.

The back plate 24 is formed with a housing portion 25 having a connecting rod guide hole 25h through which the connecting rod portion 65a is inserted vertically. The connecting rod portion 65a is inserted into the connecting rod guide hole 25h, and the upper portion of the housing portion is inserted. By fixing the collar 66 with the collar to the collar fixing portion, the connecting shaft 65 is attached to the back plate 24 so as to be vertically movable. The connection position of the connecting shaft 65 is such that the quick hitch cylinder 55 is in an extended state, and the link arm 62a,
It is set below the pivot pins 63a and 63b when 62b is at an angular position somewhat exceeding the dead point.

Here, the connecting shaft 65 is biased upward by the spring force of the coil spring 67 mounted between the collar 66 with the hook and the cam flange 68, and in a state where no pressing force is applied to the cam flange 68. The connecting shaft 65 is located above and the connecting portion 65t at the lower end of the connecting collar portion.
Is held in the accommodated state accommodated in the housing portion 25.

When the quick hitch cylinder 55 is extended, the link arm 62a rotates clockwise, the link arm 62b rotates counterclockwise, and the lower surfaces of the link arms 62a and 62b abut against the cam flange 68 of each connecting shaft 65, The connecting shaft 6 against the biasing force of the coil spring 67
Press 5 down. For this reason, the left and right connecting shafts 65 move downward, and the lower end connecting portion 65t protrudes downward from the housing portion 25, and the connecting shaft receiving hole 22t formed in the bucket 22
And the bucket 22 is connected and fixed to the back plate 24.

From this state, when the quick hitch cylinder 55 is contracted, the link arms 62a,
The link arms 62 a and 62 b that have been rotating counterclockwise and clockwise respectively and pressing the connecting shaft 65 downward move away from the cam flange 68 and move upward. For this reason, the connecting shaft 65 is moved upward by the urging force of the coil spring 67, the connecting portion 65t is accommodated in the housing portion 25, and the connection between the back plate 24 and the bucket 22 is released.

The control circuit of the quick hitch mechanism 60 configured as described above will be described in detail with reference to a hydraulic circuit diagram of the quick hitch mechanism 60 shown in FIG. 6 and a sectional view of the spool section of the quick hitch control valve 45 shown in FIG. Explained.

As described above, the control valve 40 is a laminated type composite valve, and the first hydraulic pump P ₁ is connected to the pump port 40 p of the control valve via the oil passage 71. In the control valve 40, the line pressure oil passages such as the arm control valve 41, the bucket control valve 42, and the auxiliary control valve 43 and the line pressure oil passage 451 of the quick hitch control valve 45 communicate with each other and are connected to the pump port 40p. A line pressure oil passage is formed. A relief valve 73 is provided in the oil passage 71a branched from the oil passage 71 and returning to the oil tank T.
By adjusting 3, the maximum pressure of the hydraulic oil supplied to the line pressure oil passage 451 is set to a predetermined line pressure PL of about 21 [MPa], for example.

Similar to the line pressure oil passage, a tank oil passage is formed in the control valve 40 to connect the tank oil passage of each control valve to the tank port 40t. The quick hitch control valve 4
No. 5 tank oil passage 454 is connected to the oil tank T through the oil passage 78 from the tank port 40t.

Each operating valve 32a of the operating device 30, 32 b, branches from the second oil passage 72 of the hydraulic pump P ₂ for supplying a signal pressure for controlling the 33a or the like, the first branch oil passage 72a, the second branch oil passage 72b And the first branch oil passage 72a is a first pilot port 45s ₁ of the quick hitch control valve 45.
Is connected to the second branch oil passage 72b is connected to the second pilot port 45s ₂ via the quick hitch operating valve 35a. Oil passage 7 that branches off from the oil passage 72 and returns to the oil tank T
2c is provided with a relief valve 74. By adjusting the relief valve 74, the pressure of the hydraulic oil supplied to each operation valve and the first and second pilot ports of the quick hitch control valve 45 is, for example, 3. The predetermined signal pressure PS is set to about 5 [MPa].

The quick hitch control valve 45 includes a block-shaped valve body 450, a valve spool 460 slidably fitted to the spool housing of the valve body 450 in the left-right direction in FIG. 7 (hereinafter the same), and a first pilot port 45s. _{A first} spring 471 that is held in the housing on the ₁ side and urges the valve spool 460 to the right, and a piston 475 that is slidable left and right in the housing (hydraulic oil chamber) on the side of the second pilot port 45s _2. And a second spring 472 for preventing backlash that urges the piston 475 to the right.

The valve body 450 includes a line pressure oil passage 451 located on the left and right of the central portion and extending in the front-rear direction and connected to the pump port 40p. Oil passage 454, A port 45 provided on the upper left
A oil passage 452 connected to a, B oil passage 453 connected to B port 45b provided on the upper right side,
An annular signal pressure transmission oil passage for transmitting signal pressure regardless of the movement positions of the internal oil passages 455 and 458, the pressure compensation valve 456, the load check valve 457, and the valve spool 460 formed in the valve body 450. 462 and the like are provided. The signal pressure transmission oil passage 462
Other control valves (for example, arm control valve 4) stacked and connected together with the quick hitch control valve 45
1, a bucket control valve 42, etc.) is connected in the valve housing to a valve position detection oil passage for detecting the spool position.

The bottom side oil chamber 55a of the quick hitch cylinder 55 is connected to the A port 45a via an oil passage 75a, and the quick hitch cylinder 5 is connected to the B port 45b via an oil passage 75b.
5 rod side oil chambers 55b are connected. The tank oil passage 454 that communicates with the front and rear is formed to extend left and right inside the valve and is omitted in FIG.
An overload relief valve 483 (see FIG. 6) is attached to the end of 54b, and the end of the tank oil passage 454a extending to the left is closed with a plug.

The valve spool 460, the axial oil passage 461a extending to the right along the central axis from the axial end of the first pilot port 45s ₁ side, intersects with the axial oil passage 461a is opened to the peripheral surface of the land portion An in-spool oil passage 461 is formed by a first radial oil passage 461b and a second radial oil passage 461c.

In the state where the signal pressure PS does not act on the second pilot port 45s ₂ , the quick hitch control valve 45 urges the valve spool 460 to the right by the spring force of the first spring 471, and the quick hitch control valve 45 shown in FIGS. It is arranged at the normal position shown. In this normal position, the opening of the first radial oil passage 461b formed in the valve spool 460 is the A oil passage 452.
The A port 45 a and the first pilot port 45 s ₁ are connected to each other via the spool internal oil passage 461 and the A oil passage 452. Also, the B oil passage 453 and the tank oil passage 454 are in communication with each other through a notch formed in the land portion on the right end side of the valve spool.
The B port 45b and the tank port 40t are connected. At this time, the line pressure oil passage 451 and the internal oil passage 455 are blocked by the land portion of the valve spool 460.

Therefore, the normal operation in which the quick hitch operation switch 35 is in the locking position (the quick hitch operation valve 35a is in a non-excited state) and the signal pressure PS does not act on the second pilot port 45s ₂ from the quick hitch operation valve 35a. in the position, the oil from the 1 branch oil passage 72a pressurized oil of the signal pressure PS supplied to the first pilot port 45s ₁ is spool oil passage 461 (461a, 461b) ~A oil passage 452 through the a port 45a It is supplied to the bottom side oil chamber 55a of the quick hitch cylinder 55 via the path 75a, and presses the piston rod in the extending direction. For this reason, the quick hitch cylinder 55 is held by a relatively low signal pressure (holding pressure) in the extended state, and the bucket 22 is held in the locked state. At this time, the signal pressure PS acts on the signal pressure transmission oil passage 462 through the second diameter oil passage 461c having a small diameter (orifice shape), and the valve position detection connected to the signal pressure transmission oil passage 462 is detected. by sensing the pressure of the oil passage, and it is capable of detecting the spool position. The hydraulic oil discharged from the rod side oil chamber 55b of the quick hitch cylinder passes through the B port 45b through the B oil passage 453 to the land portion notch to the tank oil passage 454b, and then passes through the oil passage 78 from the tank port 40t. Drained into the tank T.

When the quick hitch operation switch 35 is switched to the release position, the quick hitch operation valve 35a is in an excited state, and the second pilot port 45 extends from the quick hitch operation valve 35a.
signal pressure PS is applied to s _2. The second pilot port 45s ₂ of the housing the piston 4
75 is disposed, and the pressure receiving area of the piston 475 is larger than the pressure receiving area of the shaft end of the valve spool 460, and the piston thrust is set larger than the urging force of the first spring 471. For this reason, when the signal pressure PS acts on the second pilot port 45s ₂ , the valve spool 460 is moved to the left against the spring force of the first spring 471 and is disposed at the operation position.

In the operation position, the opening of the first radial oil passage 461b formed in the valve spool 460 is located between the A oil passage 452 and the left tank oil passage 454a, and the land support portion of the valve body 450 On the other hand, the A oil passage 452 and the tank oil passage 454a communicate with each other through a notch formed in the land portion at the left end. As the valve spool 460 moves to the left, the line pressure oil passage 451 and the internal oil passage 455 communicate with each other via a notch, and the internal oil passage 458 and the B oil passage 453 communicate with each other via a rod portion. , communication between the tank fluid passage 454b of the B fluid passage 453 and the rightward Ru is blocked by the right end of the land portion.

As a result, the A port 45 from the first pilot port 45s ₁ via the oil passage in the spool.
The signal pressure PS supplied to a is cut off, and the A port 45a is connected to the tank port 40t via the A oil passage 452 and the tank oil passage 454. Further, when the line pressure oil passage 451 and the internal oil passage 455 communicate with each other, the line pressure passes through the pressure compensation valve 456 and the load check valve 45.
7, the pump port 40 p and the B port 45 b are connected via the internal oil passage 458 and the B oil passage 453.

Therefore, quick hitch operation switch 35 is switched to the release position, the operating position where the second pilot port 45s ₂ to the signal pressure PS acts from the quick hitch operation valve 35a, is supplied from the pump port 40p in the line pressure oil passage 451 The pressure oil of the line pressure PL is from the internal oil passage 455 to the pressure compensation valve 456 to the load check valve 457 to the internal oil passage 458 to the B oil passage 45.
3 is supplied from the B port 45b to the rod-side oil chamber 55b of the quick hitch cylinder 55 through the oil passage 75b, and presses the piston rod in the reduction direction.

At this time, the pressure acting on the rod side oil chamber 55b of the quick hitch cylinder 55 is a line pressure PL of about 21 [MPa] higher than the signal pressure PS. Therefore, the quick hitch cylinder 55 generates a large cylinder thrust, and even if the link arms 62a and 62b are stuck due to mud clogging etc., the quick hitch cylinder 55 is shortened by crushing dry stuck mud etc. Operate. As a result, the connecting shaft 65 moves upward, the bucket 22 is reliably released from being fixed, and the bucket 22 is unlocked. The hydraulic oil held in the bottom side oil chamber 55a of the quick hitch cylinder is discharged from the bottom side oil chamber 55a as the cylinder contracts and moves from the A port 45a to the A oil passage 452 to the land portion notch. Oil tank T passes through tank oil passage 454a and from tank port 40t through oil passage 78.
To be drained.

Therefore, according to the shovel loader 1 configured as described above, the quick hitch control valve 45 that switches the supply direction of the pressure oil to the quick hitch cylinder 55 changes the signal pressure supplied from the second hydraulic pump P ₂ to the quick hitch. a forward feed which fixes and holds the bucket 22 is supplied to the bottom-side oil chamber 55a of the cylinder, a fixed high pressure line pressure supplied from the first hydraulic pump P ₁ is supplied to the rod side oil chamber 55b bucket 22 for reverse feed and the switching arrangement for releasing the one of at concise structure comprising directional control valve, Ru can provide reliably feasible work machine attachment and detachment of the attachment.

In the embodiment described above, a linear motion cylinder is used as a hydraulic actuator for attaching and detaching the attachment such as the bucket 22 and the connecting shaft is moved via the link arms 62a and 62b. The fixed release may be performed directly by a direct acting cylinder without going through a shaft, or the actuator may be configured using a hydraulic actuator of another operation form such as a swing motor. Furthermore, although the shovel loader is shown as an example of the work machine to which the present invention is applied, the present invention is not limited to the shovel loader, and the same effect can be obtained by similarly applying to a bulldozer, a backhoe and the like. .

P ₁ first hydraulic pump (second hydraulic source)
P ₂ second hydraulic pump (first hydraulic source)
1 Excavator loader (work machine)
DESCRIPTION OF SYMBOLS 10 Car body 15 Traveling apparatus 20 Loader apparatus 21 Arm 22 Bucket (attachment)
27 Pile driver (attachment)
30 Operating device 32 Second operating lever 33 Auxiliary operating lever 35 Quick hitch operating switch 35a Quick hitch operating valve 40 Control valve (40p: pump port, 40t: tank port)
41 Arm control valve (Direction switching valve)
42 Bucket control valve (direction switching valve)
45 Quick hitch control valve (detachable switching valve)
(45a: A port, 45b: B port, 45s ₁ : first pilot port, 45s ₂ : second pilot port)
51 Arm cylinder (hydraulic actuator for working equipment)
52 Bucket cylinder (hydraulic actuator for working equipment)
55 Quick hitch cylinder (Quick hitch actuator)
60 Quick hitch mechanism 450 Valve body 460 Valve spool 461 Oil path in spool (internal oil path)
471 First spring (spring)

Claims (3)

An operating mechanism, a hydraulic cylinder that operates the operating mechanism, a switching valve that controls supply of pressure oil to the hydraulic cylinder, and a first hydraulic source that supplies a signal pressure for performing switching operation of the switching valve A hydraulic control device comprising a second hydraulic power source for supplying a line pressure higher than the signal pressure for operating the hydraulic cylinder;
The switching valve is provided on the valve body so as to face a one end side of the spool member, a valve body having a spool hole, a spool member disposed in the spool hole so as to be slidable in an axial direction. A biasing means for biasing the spool member toward the other end;
A hydraulic oil chamber that receives a signal pressure from the first hydraulic pressure source is provided in the valve body so as to face the other end side of the spool member, and the spool member is moved by the signal pressure of the hydraulic oil chamber. It is configured to bias to one end side,
The biasing force that biases the spool member to the other end side by the biasing means is reduced or released, and the spool member is moved to the one end side by the signal pressure acting on the hydraulic oil chamber, The spool member is moved to the other end side by a biasing force that biases the spool member to the other end side by the biasing means, and the hydraulic pressure is applied to the line pressure from the second hydraulic source by the switching valve. It is configured to perform supply and discharge control to the
It said spool member, the said one end opening to pre Symbol spool member at the end of the signal pressure from the first hydraulic pressure source is applied extending in the axial direction, on an outer peripheral surface extending in the radial direction at an intermediate portion An open oil path in the spool is formed,
Said valve body when said spool member by the signal pressure acting on the hydraulic oil chamber is moved to the one end, it communicates with the opening to the outer peripheral surface of the spool member of the spool in the oil passage are cut switched signal pressure transmission oil passage formed, it has become possible to detect the signal pressure transmitted from the signal pressure transmission oil path said spool oil passage through being led into the test Deaburaro Hydraulic control device characterized by.   A signal pressure detecting means is provided in the detection oil passage, and it is detected whether or not the signal pressure is guided to the detection oil passage by the signal pressure detecting means, and the spool member moves to the other end side. The hydraulic control device according to claim 1, wherein the hydraulic control device is configured to detect whether or not a failure has occurred. The actuating mechanism is constituted by a quick hitch mechanism that causes the attachment configured to be detachable to the vehicle body to be latched and held on the vehicle body or to release the latched holding state.
3. The hydraulic control device according to claim 1, wherein the hydraulic cylinder includes a quick hitch cylinder that receives hydraulic pressure to operate the quick hitch mechanism. 4.

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