JPS5923841Y2 - Agricultural tractor work equipment control valve - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a control valve used in a hydraulic actuation device for controlling the position, draft, etc. of a working machine such as a plow or rotary in an agricultural tractor.

This kind of conventional work control valve switches the spool by operating a lever by external operation, and controls the opening/closing operation of the unload valve to connect the cylinder circuit to the high pressure side or the low pressure side and drive the cylinder. It has become.

Therefore, when in neutral, the unload valve opens and all the hydraulic oil discharged from the pump is returned to the tank, and the cylinder circuit is shut off by the check valve and spool, keeping the cylinder in neutral.

However, in the neutral state, the cylinder is constantly under pressure due to the load from the work equipment, so this pressure acts on the cylinder circuit, and there is some clearance between the outer circumference of the spool and the inner circumference of the sleeve that forms the valve hole. There is oil leakage from this clearance to the low pressure side, causing the cylinder to naturally fall.

For this reason, the present application has developed a work machine control valve for an agricultural tractor that is designed to eliminate as much as possible leakage from the cylinder circuit when in neutral mode (Japanese Patent Laid-Open No. 51-60877).

In the newly developed control valve mentioned above, a valve hole is formed between the main passage on the cylinder side and the tank side, and a truncated conical valve head is placed in the valve hole so that it can open and close freely against the seat. It is equipped with a poppet valve.

However, although this control valve can considerably prevent oil leakage when in neutral, it has the following problems.

In other words, ■ When the poppet valve is lowered and then returned to the neutral position, there is a large amount of leakage until the valve head stably contacts the seat due to unevenness of the seat surface, dirt getting caught on the seat surface, etc.; Due to use, the poppet valve may rattle, and when it returns to neutral, the valve head and seat may not match up perfectly, causing oil leakage. ■If the hydraulic cylinder falls due to internal leakage, its movement may be affected by the feedback link. Although the internal leakage is fed back into the valve, in the poppet type, it is not possible to control the internal leakage to even the slightest extent.

Therefore, an object of the present invention is to provide a work machine control valve for an agricultural tractor that can control the amount of oil leakage as desired regardless of whether or not the valve head of the poppet valve stably contacts the seat.

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

Inside the control valve body 10, there is a pump P side and a cylinder A side.
A vertical pump-side main passage 11 and a cylinder-side main passage 12 are bored to connect the two sides, and one main passage 11 is connected to a valve hole 13 bored in the horizontal direction in the main body 10. .12 are respectively connected to the central valve hole 15.

The main passage 11 communicates with the low pressure side tank T via the JIJ valve 16 and the passage 19, and is also connected to the valve hole 18 via the branch passage 17.
It communicates with the tank T side via a.

The valve hole 13 opens into the low pressure side case 24 at the back, and a main spool 20 is slidably inserted therein, and the tip 21 of the main spool 20 protrudes from the main body 10.
It is pressed by a spring 25 on the back and abuts against an operating lever 23 inside the case 22.

There are two annular grooves 26 and 27 on the outer periphery of the main spool 20.
is cut out, the annular groove 27 communicates with the low pressure side through the hole 28, and an annular groove 29 is also formed on the inner periphery of the valve hole 13, and the annular grooves 26 and 27 in the main spool 20 As the annular groove 29 of the valve hole 13 moves, the annular groove 29 of the valve hole 13 is selectively moved.
It is designed to communicate with

Next, the back of the valve hole 14 is connected to the low pressure side case 2 through the valve seat 44.
4 and has a mushroom-shaped truncated conical valve head 43 inside.
A first check valve 4 which is a poppet valve formed with a
3 is slidably inserted, and its tip 43b is inserted into the main body 10.
The connecting culm 32 is movably inserted into this, and the tip 21 of the main spool 20 is inserted through the connecting culm 32.
Connected to the side.

In this case, in the embodiment of FIG.
The inner end of the nut 43C provided at the end of the nut 43C and the connecting culm 32 are in contact with each other in the neutral state, but in the embodiment shown in FIG.
A wrap L1 is formed between 43C and the connecting culm 32 as a lower side play.

A spring 30 is interposed between the valve head 43 a of the first check valve 43 and the inner surface of the valve hole 14 .

The spring 30 constantly presses the valve head 43a backward in the right direction in the figure with its restoring force, and as a result, the valve head 43a of the check valve 43 comes into contact with the mouth end of the cylindrical valve seat 44. It is supposed to be sealed.

A second check valve 33 having a frusto-conical valve head is slidably inserted into the valve hole 15, and is pressed against the eye end of the branch passage 11a of the passage 11 by a spring 34 at the back when in neutral. It is being

A through hole 35 is bored in the second check valve 33 so that the main passage 12 and the liquid chamber 36 at the back can communicate with each other.

Therefore, in the neutral state, the back pressure of the cylinder A acts on the back liquid chamber 36 of the second check valve 33 through the through hole 35 and the main passage 12, causing the second check valve 33 to move toward the valve seat of the main passage 11. It is designed to ensure that the seat is seated securely.

Furthermore, a truncated conical unload valve 37 is slidably inserted into the other valve hole 18, and is pressed against the end of the neutral channel 17 by a spring 38 at the back. The liquid chamber 39 communicates with the annular groove 29 via a through hole 40 bored in the main body.

As is well known, the actuating lever 23 is rotated clockwise or counterclockwise by operation of an external bundle 41, and is adapted to transmit the linear movement of the main spool 20.

Further, when the cylinder A expands or contracts, the movement is fed back to the actuating lever 23 via the feedback link 42 to return the main spool 20 to the neutral position.

Next, another valve hole 50 is bored in the valve body 10, and a switching spool 51 for regulating the amount of leakage is slidably inserted into this valve hole 50.
0 and protrudes through it, and its tip 51C is connected to two nuts 5.
It is integrally connected to the connecting culm 32 via 2.

The valve hole 50 opens into the cylinder-side main passage 12 and communicates via a passage 53 with the valve hole 14 into which the first check valve 43 is inserted.

Seals 54 and 55 made of O-rings and the like are interposed on the outer periphery of both sides of the switching spool 51 to completely prevent oil in the valve hole 50 from leaking to the low pressure side in the case 22 and 24. .

Also, the switching spool 51 has a small diameter portion 51 that is smaller in diameter than the valve hole 50.
a, a large diameter part 51b having approximately the same diameter as the valve hole 50, and a small diameter part 51a and a land part 51b.
A snot 56 is formed at the border of b.

Moreover, in the embodiment shown in FIG. 1, this slit 56 is blocked by the outer periphery of the land portion 51b and the inner wall of the valve hole 50 in the neutral state.
A wrap U is formed between the slit 56 and the passage 53 as the amount of play on the lower side.

In this case, as described above, the oak l-43C of the first check valve 43 and the connecting culm 32 are in contact with each other.

Further, in the embodiment shown in FIG. 2, approximately half of the slit 56 opens into the passage 53, so that the cylinder side passage communicates with the valve hole 14 via the slit 56 and the passage 53.

However, in this case, as described above, a lap L1 is formed as an amount of play between the oak 43C of the first check valve 43 and the connecting culm 32.

Next, we will discuss the operation.

In the neutral state in Figures 1 and 2, the main spool 2
Both the annular grooves 26 and 27 of the valve hole 13 communicate with the annular groove 29 of the valve hole 13, and the back liquid chamber 39 of the unload valve 37 also communicates with the annular groove 29 of the valve hole 13.
is connected to the low pressure side via the through hole 40 and the groove 29.27, and the second check valve 33 side is also closed by the pressing force of the spunong 34 and the back pressure from the cylinder A, so the pump side main A portion of the hydraulic fluid discharged into the passage 11 flows into the lower pressure side case 24 from the valve hole 13, and a portion flows into the unload valve 3.
Passage 1 is opened by pushing open 7 against spring 36.
9a, each is returned to the tank T side.

Next, in the raised state, the main spool 20 is pushed in the right direction against the spring 25 via the operating lever 23,
One annular groove 27 of the spool 20 is blocked, and the other annular groove 26 is communicated with the annular groove 29 and the through hole 40.

Therefore, high pressure from the main passage 11 is transferred to the valve hole 13 and the annular groove 2.
9. Back liquid chamber 39 of unload valve 37 from through hole 40
As a result, the pressure in the liquid chamber 39 and the passage 17 become the same, so the unload valve 37 is closed and held by the force of the spring tongue 38.

Therefore, the high pressure in the main passage 11 pushes the second check valve 33 open through the passage 11a, and is further led to the cylinder A through the valve hole 15 and the main passage 12, and moves up the cylinder A.

This upward movement is fed back to the actuation lever 23, which is rotated counterclockwise to return the spool 20 to the neutral position.

Next, when in the lowering state, rotate the operating lever 23 counterclockwise to move the main spool 20 to the left by the pressing force of the spring 25, and align the annular groove 27 at the rear of the spool 20 with the annular groove 29 of the valve hole 13. communicate.

At this time, the annular groove 29 and the annular groove 26 of the main spool 20 are interrupted.

Therefore, the back liquid chamber 39 of the unload valve 37 communicates with the low pressure side via the passage 4, the annular groove 29, the annular groove 27, and the hole 28, so that the high pressure in the main passage 11 is transferred to the spring 38.
Push open the unload valve 37 against the
It is all returned to the tank T through the valve hole 18-passage 19a.

When the main spool 20 moves to the left, the first check valve 43 and the switching spool 51 move to the left via the connecting culm 32, thereby causing the valve head 43 of the first check valve 43 to move to the left.
a from the valve seat 44 and fully open the slit 56 of the switching spool 51 to the passage 53 to open the cylinder side main passage 1.
2 through the valve hole 14.

When the valve head 43a and the slit 56 are fully opened, the cylinder side main passage 12 communicates with the low pressure side case 24 via the valve hole 50, slit 56, passage 53, and valve hole 14, so that the cylinder A descends under its own weight.

Also, this movement is fed back to the main spool 20, as described above, to return the spool 20 to the neutral position.

What should be noted here is that when the main spool returns to neutral, the first check valve 43 is pushed to the right by the restoring force of the spring 30, and the switching spool 51 is pushed to the right in conjunction with the connecting culm 32. In the other check valve 43, the valve head 43a closes the mouth end of the valve seat 44, and on the switching spool 51 side, the slit 56 is blocked or partially opened, so the return oil from the cylinder A is blocked at two locations. Therefore, cylinder A is held in neutral.

Therefore, when the valve head 43a comes into contact with the valve seat 44, the valve head 43a
Even if flow resistance is to occur between the outer periphery of the valve seat 44 and the end of the valve seat 44, the slit 56 will not close to the cylinder side main passage 12.
When the main passage 12 on the cylinder side is closed or half-open, the amount of leakage from the cylinder-side main passage 12 to the passage 53 and the valve hole 14 is extremely small.Therefore, since there is almost no flow resistance, the valve head 43a smoothly contacts the valve seat 44. It is something.

In addition, due to long-term use, the first check valve 43 may have rattling, the seat surface of the valve seat 43 may be tilted, or dirt may be caught in the seat surface. Even if it takes some time for the valve head 43a of 43 to stably contact the sea I, the amount of leakage is regulated on the switching spool 51 side, so the amount of leakage can be small.

Furthermore, even if the leakage amount is regulated in two stages by the switching spool 51 and the first check valve 43, if there is still a leakage amount, the cylinder A is lowered according to this leakage amount, and the movement at this time is switched. This is fed back to the spool 51 to further increase the width of the wrap L2.

Also, when the cylinder A is lowered by slight movement, the width of the wrap L2 on the land portion 51 b side in FIG. 1 or the wrap L1 on the check valve 43 side in FIG. Or half open slit 5
6 is formed, the first check valve 43
, when the switching spool 51 is moved slightly to the left, cylinder A
The return oil flows from the slit 56 to the low pressure side, ensuring fine movement operation and improving so-called inching performance.

Next, FIG. 3 is a hydraulic circuit diagram of the control valve according to FIG. 1 or 2.

The illustrated state shows a neutral state, with the main spool 20 in the right position and one side of the unload valve 37 passing through the tank T via the circuit 40. Pushed upwards, it connects circuit 17 to circuit 19a through the lower position.

For this reason, the pressure oil in the cylinder side main circuit 11 is transferred to the circuit 19 through the lower position of the circuit 17-unload valve 37.
It is returned to tank T from a.

Further, the first check valve 43 is held at the left position, and the switching spool 51 is held at the intermediate position, so that the cow cylinder side 74-in circuit 12 is cut off from the tank side by the first check valve 43. , cylinder A is stopped at an arbitrary position.

When the connecting culm 32 is pushed in the right direction via the lever 23 from the above state, the main spool 20 and the switching spool 51
is switched to the left position, and pump circuit 11 is switched to circuit 4.
0, and the cylinder side main circuit 20 is cut off.

For this reason, the unload valve 3 is connected to the pressure side from the main circuit 11.
7 switches to the upper position to cut off the circuit 17, whereby the pressure oil in the main circuit 11 pushes open the second check valve 33 and is supplied to the cylinder A, causing the cylinder A to extend.

On the other hand, when the connecting culm 32 is tensioned to the left via the lever 23, the main spool 20 is switched to the right position, and the first check valve 43 and the switching spool 51 are also switched to the right position.

As a result, the unload valve 37 is switched to the lower position, and the pressure oil in the main circuit 11 is returned to the tank T via the circuit 17, the unload valve 37, and the circuit 19a.

Also, at this time, the cylinder side main circuit 12 is connected to the switching spool 51.
- the first check valve 43 - is returned to the tank T via the circuit 19 a, and the cylinder A is to be lowered.

As described above, the present invention provides the switching spool 51 between the cylinder A and the first check valve 43 to regulate the amount of leakage, and therefore has the following unique effects.

■ The internal leaf of the cylinder side passage 12 is first prevented by the neutral switching spool 51, and then the oil leaking internally from this switching spool 51 is prevented by the first check valve 41, thereby doubly managing internal leakage. This completely prevents oil leaks.

■ If the first check valve 43 becomes rattled and the shaft center shifts, or if dirt or the like gets caught in the seat surface, it may take time for the first check valve 43 to return to the neutral position from the lowering operation. , then - then the switching spool 51
Since the amount of leakage is regulated on the side, the amount of leakage from the outer periphery of the valve head of the first check valve 43 can be reduced.

■ Even if the leakage amount is controlled in two stages by the switching spool 51 and the first check valve 43, if there is still a no-noise amount, the cylinder A will be slightly lowered according to this leakage amount, and the movement of this cylinder A will be reduced. Since this is fed back to the switching spool 51 and pushed in deeper, the wrap width of the switching spool's outer periphery with respect to the valve hole becomes larger, making it possible to further reduce the amount of internal leakage.

Note that when the switching spool 53 is provided with a large diameter part and a small diameter part, and a slit 56 is provided at the boundary between the large diameter part and the small diameter part, and the flow rate is controlled through this slit 56, the first check valve 43 When the switching spool 51 is slightly moved, the return oil of the cylinder A flows from the slit 56 to the low pressure side, so that fine movement operation is reliably performed and so-called inching performance can be improved.

Furthermore, when O-rings 54 and 55 are provided at both ends of the spool 51, all internal leakage from the cylinder side main passage 12 can go to the seat surface of the first check valve 43.

Moreover, a slit 56 is provided in the spool 51 so that a fine movement operation range can be appropriately set.

[Brief explanation of drawings]

1 and 2 are longitudinal sectional side views of a control valve according to an embodiment of the present invention, and FIG. 3 is a hydraulic circuit diagram. 10...Valve body, 12...Cylinder side main passage, 14...Valve hole, 20...
Main spool, 32...Connected culm, 43...
...First check valve, 50...Valve hole,
51...Switching spool, 51a...
Small diameter part, 51 b...Large diameter part, 53...
・Aisle, 54.55...Seal, 56...
··slit.

Claims (4)

[Scope of utility model registration request] (1) A pump-side main passage and a cylinder-side main passage connecting the pump and cylinder are formed in the valve body, and a second check valve is installed in these main passages to allow flow only from the pump to the cylinder. The main passage on the pump side is selectively opened and closed to the tank side via an unload valve, and this unload valve selectively communicates the back liquid chamber to the pump side or the tank side by switching the main spool. Alternatively, the valve body is opened and closed by opening and closing the valve, and a valve hole communicating with the low pressure side through the valve seat is bored in the valve body, and a first check valve is inserted into this valve hole to open and close the valve seat. The first check valve is a hydraulically actuated device that opens the valve seat in conjunction with the spool during the lowering operation, and has another valve hole in the valve body, and this valve hole is connected to the cylinder side main passage. The switching spool is slidably inserted into the valve hole, and the switching spool protrudes from the valve body and connects to the main spool side. By connecting to the connecting culm and switching the switching spool, the cylinder side
A work equipment control valve for an agricultural tractor in which a first check valve is inserted to open and close the air passage. (2) A work machine control valve for an agricultural tractor as set forth in claim 1, which has seals interposed on both sides of the switching spool. (3) A work machine control valve for an agricultural tractor according to claim 1, wherein the switching spool has a large diameter portion and a small diameter portion. (4) A working machine control valve for an agricultural tractor as set forth in claim 3 of the utility model registration, which has a slit formed at the boundary between the large diameter portion and the small diameter portion.