JPH0526325Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention, in combination with a hydraulic directional valve,
The present invention relates to a selection valve that selectively operates two or more systems of hydraulic cylinders, and more specifically, to a selection valve that has a function of bringing one of the hydraulic cylinders into a floating state.

[Conventional technology]

In general, a front loader working machine that is driven by hydraulic pressure from a tractor has a rear end of a lift arm 2 pivotally attached to a main body 1 of the tractor, etc., as shown in FIG. A bucket 4 for equipment, etc. is attached, and a lift hydraulic cylinder 5 for raising and lowering the lift arm 2 and a dump hydraulic cylinder 6 for dumping and scooping the bucket 4 are connected to a selection valve 7 and 4 ports as shown in FIG. It is operated by a three-position hydraulic directional valve 8.

The above conventional selection valve 7 has a solenoid 9 on one side.
It is a 6-port, 2-position switching valve equipped with a spring 10 on the other side, and has first to seventh annular grooves 12, 13 on the inner circumferential surface 11, as shown in FIGS. ,14,15,16,17,18
a sleeve 20 having a spool insertion hole 19 formed in parallel, and a spool that is slidably inserted in the insertion hole 19 of the sleeve 20 in the axial direction and has land portions 21 and 22 formed at a predetermined interval. 2
3. The pump side of the sleeve 20 is formed with two ports a and b connected to the hydraulic directional valve 8 via hydraulics 24 and 25, and the port a is branched into first and seventh annular recesses. The grooves 12 and 18 are opened, and the port b is opened to the fourth annular groove 15. Also, sleeve 20
The second, third, fifth and sixth cylinders are on the cylinder side.
4 opened in the annular grooves 13, 14, 16, 17 of
ports c, d, e, f are formed, and ports c,
Ports d are connected to the front and rear chambers 5a and 5b of the lift hydraulic cylinder 5 through oil passages 26 and 27, and ports e and f are connected to the front and rear chambers 6a of the dump hydraulic cylinder 6 through oil passages 28 and 29, respectively. , 6b, respectively. 30 is a hydraulic pump, and 31 is an oil tank.

When the lift arm 2 is to be moved up and down, the solenoid 9 of the selection valve 7 is turned OFF and held in the right position, and the directional control valve 8 is turned OFF.
from the neutral position to the left or right position. Then, the hydraulic oil from the hydraulic pump 30 is fed under pressure to the lift hydraulic cylinder 5 via the selection valve 9 and the oil passages 25, 27 or 24, 26, and causes the lift arm 2 to move up and down. When the bucket 4 is to be operated in a dumping operation or a scooping operation, the solenoid 9 from the selection valve 7 is turned on and switched to the left position, and the directional switching valve 8 is switched from the neutral position to the left or right position.
Then, the hydraulic oil from the hydraulic pump 30 is sent under pressure to the dumping hydraulic cylinder 6 via the selection valve 9 and the oil passages 25, 29 or 24, 28, and causes the bucket 4 to perform a dumping operation and a scooping operation.

By the way, according to the above-mentioned working machine, for example, for loading and unloading work objects such as earth and sand, operation, etc.
While the tractor body 1 is running, the bucket 4 is placed on the ground 32.
Since it was not possible to carry out so-called floating work, in which the bucket cart 4 is moved along the surface of the ground 32, if the ground 32 is uneven, the bucket cart 4 may collide with the uneven surface of the ground 32, damaging the bucket cart 4, and the loading operation may be delayed. cannot be carried out smoothly.

Therefore, conventionally, an electromagnetic stop valve has been inserted between the oil passages 26 and 27 communicating with the lift hydraulic cylinder 5 in order to maintain the lift hydraulic cylinder 5 in a floating state.

[The problem that the idea attempts to solve]

Conventionally, an electromagnetic stop valve 32 has been installed between the oil passages 26 and 27 in order to bring the lift hydraulic cylinder 5 into a floating state. There were problems in that it was difficult, the piping was complicated, and the cost was high.

The present invention, in combination with a hydraulic directional valve,
It is an object of the present invention to provide a selection valve that can maintain one of the hydraulic cylinders in a floating state when selectively operating two or more systems of hydraulic cylinders.

[Means to solve the problem]

The present invention has been proposed to achieve the above object, and includes a selection valve disposed in a hydraulic circuit between first and second hydraulic cylinders and a hydraulic directional valve. , has a spool insertion hole in which first to seventh annular grooves are formed in parallel on the inner circumferential surface, and second, third, and
A port was formed that opened to the fifth and sixth annular grooves, and a port that opened to the fourth annular groove and a port that branched to the first and seventh annular grooves were formed on the pump side. A sleeve, inserted into the spool insertion hole of the sleeve so that the operating position can be changed to three positions, and forming a plurality of lands,
A spool having a bypass passage that opens on the outer peripheral surface of the land between the first and second lands, and in the neutral position, the bypass passage is closed and the third land is closed.
and the fourth annular groove and the sixth and seventh annular grooves are in communication with each other, and at either the left or right position, the third annular groove is connected to the fourth annular groove and the bypass passage. communicates with the first annular groove, and the sixth
and the seventh annular groove communicate with each other, and the first annular groove communicates with the seventh annular groove at the other position.
The second annular groove and the fourth and fifth annular grooves are configured to communicate with each other.

[Effect]

In the neutral position, one of the first and second hydraulic cylinders is activated. By switching to either the left or right position, that one hydraulic cylinder can be held in a floating state. Switching to the other position activates the other hydraulic cylinder.

[Embodiment] An embodiment of the selection valve 40 according to the present invention will be described below with reference to FIGS. 1 to 4. Components that are the same as those shown in FIGS. 5 to 8 are designated by the same reference numerals, and description thereof will be omitted.

1 to 4, reference numeral 41 denotes a spool inserted into the spool insertion hole 19 of the sleeve 20 so that the operating position can be changed to three positions. ,4
3, 44, 45, 46 are formed, and the lands 42, 43 are formed between the first and second lands 42, 43.
A bypass passage 47 is formed that opens on the outer circumferential surfaces 42a and 43a. And the spool 41
At the neutral position, the outer circumferential surface 43a of the second land 43 touches the inner circumferential surface 1 of the sleeve 20, as shown in FIG.
1, the bypass passage 47 is closed, and the third and fourth annular grooves 14 and 15 and the sixth
and seventh annular grooves 17 and 18 communicate with each other, and in the left position, as shown in FIG.
The fourth annular groove 15 and the bypass passage 47 communicate with the first annular groove 12, respectively, and in the right position, the first and second annular grooves 1 are connected to each other as shown in FIG.
2 and 13 and fourth and fifth annular grooves 15 and 16
are configured so that they communicate with each other. 48,4
9 is a solenoid arranged on both sides of the spool 41, 50 and 51 are springs, and when the spool 41 is not energized, the spring force of the springs 50 and 51
is held in a neutral position.

Next, the operating procedure of the work machine when the selection valve is disposed in the hydraulic circuit between the lift and dump hydraulic cylinders and the hydraulic directional switching valve will be explained as follows.

When raising and lowering the lift arm 2,
The selection valve 40 was held in the neutral position, the bypass passage 47 of the spool 41 was closed, and the ports d and c on the cylinder side were communicated with the ports b and a on the pump side, respectively, as shown in FIG. Afterwards, the directional switching valve 8 is switched from the neutral position to the left position or the right position. Then, the hydraulic oil from the hydraulic pump 30 is sent under pressure to the rear chamber 5b or front chamber 5a of the lift hydraulic cylinder 5 through the oil passages 25, 27 or 24, 26, and the lift arm 2 moves up and down.

Also, while the tractor body 1 is running, the bucket 4
For example, when performing so-called floating work in which the
0 in the neutral position, switch the hydraulic directional control valve 8 to the right position to open the lift hydraulic cylinder 5.
By force-feeding hydraulic fluid to the front chamber 5a of the bucket, the lift arm 2 is lowered to bring the lower surface 4a of the bucket bag 4 into contact with the ground 32. After that, the selection valve 40
When the solenoid 48 is energized and switched from the neutral position to the left position, as shown in FIG. 4
Since the first and third annular grooves 12 and 14 communicate with each other via 7, port a on the pump side communicates with port c on the cylinder side and port b on the pump side.
Therefore, a part of the hydraulic oil pumped from the hydraulic pump 30 flows into the oil tank 31 from the port a through the bypass passage 47 of the spool 41, so that the lift hydraulic cylinder 5 becomes in a floating state. No load from the hydraulic pump 30 acts on the bucket 4. Therefore, even if the ground 32 is uneven, the bucket 4 moves along the ground 32 as the tractor main body 1 travels, and floating work can be performed. In addition, when performing the above-mentioned floating work, after switching the selection valve 40 to the left position, the hydraulic direction switching valve 8 may be switched to the right position to lower the lift arm 5.

When the bucket 4 is to be operated in a dumping operation or in a scooping operation, the selection valve 40 is switched from the neutral position to the right position, and as shown in FIG. 3, ports b and a on the pump side are connected to ports f and e on the cylinder side, respectively. At the same time, the bypass passage 47 is closed.
Thereafter, the directional control valve 8 is switched from the neutral position to the left or right position. Then, the hydraulic oil from the hydraulic pump 30 flows through the oil passages 25, 29 or 2.
4 and 28 to the rear chamber 6b or front chamber 6a of the dumping hydraulic cylinder 6, and the bucket 4 performs a dumping operation or a scooping operation.

Further, the directional switching valve 8 is provided with, for example, a detent mechanism (not shown) capable of holding the valve 8 in the left position, and with the directional switching valve 8 held in the left position by the detent mechanism, Turn on the solenoid 48 of the selection valve 40.
By performing OFF control, the lift arm 2 can be raised and lowered slowly. That is, when the selection valve 40 is held in the neutral position while the directional control valve 8 is switched from the neutral position to the left position, the ports d and c on the cylinder side of the selection valve 40 are connected to the ports b and a on the pump side. The hydraulic oil from the hydraulic pump 30 is communicated with the oil passages 25 and 2.
7 to the rear chamber 5b of the lift hydraulic cylinder 5, and the lift arm 2 rises. Next, when the selection valve 40 is switched to the left position, the ports b and a on the pump side communicate with the ports d and c on the cylinder side as described above, and the ports on the cylinder side are connected via the bypass passage 47 of the spool 41. Since port a on the pump side communicates with port b on the pump side and port b on the pump side, the lift hydraulic cylinder 5 is in an unloaded state, and no load from the hydraulic pump 30 acts on the lift arm 2. 2 slowly descends due to its own weight.

In the above embodiment, the case where the lift hydraulic cylinder and the dump hydraulic cylinder in the work machine are selectively operated has been described, but the present invention is not limited to this, and the first and second hydraulic cylinders are operated selectively. It can be widely used when selectively operating cylinders.

[Effect of idea]

According to the present invention, by using it in combination with a hydraulic directional switching valve for selectively operating two or more hydraulic cylinders, one of the hydraulic cylinders can be reliably floated with a simple switching operation. can be in a state. Therefore,
If the selection valve according to the present invention is used in a working machine,
Floating work for moving the bucket along the ground can be smoothly performed, work efficiency can be improved, and damage to the bucket can be reliably prevented. Furthermore, the structure is simple, piping is easy, and the cost is low. Moreover, by simply replacing the spool of an existing selection valve, the selection valve can be provided with a function for bringing the hydraulic cylinder into a floating state.

[Brief explanation of drawings]

1 to 3 are cross-sectional explanatory views showing an embodiment of the selection valve according to the present invention, in which FIG. 1 shows the neutral position, FIG. 2 shows the left position, and FIG. 3 shows the right position. . FIG. 4 is a hydraulic circuit diagram in which a selection valve according to the present invention is disposed between a hydraulic cylinder and a hydraulic directional valve. Figure 5 is a schematic side view of the work machine;
FIG. 6 is a hydraulic circuit diagram in which a conventional selection valve is disposed between a hydraulic cylinder and a hydraulic directional switching valve, and FIGS. 7 and 8 are cross-sectional explanatory views of the conventional selection valve. 8...Hydraulic directional valve, 11...Inner peripheral surface,
12-18...first to seventh annular grooves, 19...
...Spool insertion hole, 40...Selection valve, 41...
...Spool, 42-46...Land, 42a, 4
3a...outer peripheral surface, 47...bypass passage, a,
b, c, d, e, f... port.

Claims (1)

[Scope of utility model registration request] In the selection valve disposed in the hydraulic circuit between the first and second hydraulic cylinders and the hydraulic directional control valve, the selection valve has first to seventh annular grooves arranged in parallel on its inner peripheral surface. a spool insertion hole formed therein, a port opening into the second, third, fifth, and sixth annular grooves on the cylinder side, and a port opening into the fourth annular groove on the pump side; and a sleeve formed with ports that branch into the first and seventh annular grooves, the sleeve being inserted into the spool insertion hole of the sleeve so that the operating position can be changed to three positions, and forming a plurality of lands, 1st
and a spool forming a bypass passage that opens on the outer peripheral surface of the land between the second land, and in the neutral position, the bypass passage is closed and the third and fourth lands are closed.
The annular groove and the sixth and seventh annular grooves communicate with each other, and at either the left or right position, the third annular groove connects to the first annular groove via the fourth annular groove and the bypass passage. The sixth and seventh grooves communicate with the annular groove.
The annular grooves communicate with each other, and the first and second annular grooves communicate with each other at the other position.
A selection valve characterized in that the annular groove and the fourth and fifth annular grooves are configured to communicate with each other.