JPS5929122Y2 - Agricultural tractor work equipment control valve - Google Patents

Description

[Detailed description of the invention] This invention relates to a work machine control valve for agricultural tractors.
More specifically, the present invention relates to a control valve used in a hydraulically operated device for controlling the position, draft, etc. of a working machine such as a plow or a rotary tractor in an agricultural tractor.

This type of conventional work equipment control valve switches the spool by operating a lever by external operation, and connects the cylinder circuit to the high pressure side or low pressure side by controlling the opening and closing operation of the unload valve. It is designed to be driven.

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 always under pressure due to the load from the work machine, so this pressure acts on the cylinder circuit7, and there is some clearance between the outer circumference of the spool and the inner circumference of the sleeve that forms the valve hole. If there is, oil will leak from this clearance to the low pressure side and the cylinder will naturally fall.

In addition, in order to increase durability, the part of the sleeve that comes into contact with the spool requires surface hardness, which makes machining difficult.

Furthermore, conventional control valves tend to be expensive because they use a 01J ring or the like to separate the high pressure section and the low pressure section.

Therefore, in order to solve the above-mentioned conventional drawbacks, the present applicant has eliminated leakage from the cylinder circuit in the neutral state, and made the body in contact with the spool sufficiently durable with gray cast iron, which does not require special surface hardness. At the same time, we have developed an inexpensive work equipment control valve for agricultural tractors that eliminates the use of 01J rings or backings in areas that do not cause external leakage, manages the clearance appropriately, and allows leakage. 49-134754).

However, in general, the performance value of a control valve is determined by the amount of l-pitch movement, which is the minimum control of the cylinder, but in the newly developed control valve mentioned above, a The dimensional difference between the width of the annular groove and the width of the land portion of the spool facing it can be determined by adjustment, but machining the annular groove and land in this valve hole is troublesome, so it is necessary to achieve sufficient accuracy. Such machining is extremely difficult.

Therefore, the purpose of this invention is to provide two spools to switch the pilot passage without the above-mentioned processing.
To provide a control valve in which the amount of movement required for switching the passage of a spool is adjustable so that performance requirements can be freely met.

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

Inside the control valve body 10 are the pump P side and the cylinder A.
A pump-side main passage 11 and a cylinder-side main passage 12 are bored in the vertical direction to connect the sides, and one passage 11 has a first valve hole 13 and a second valve hole 5 bored in the horizontal direction in the main body 10.
Similarly, the other passage 12 is connected to the upper valve hole 14, and each passage 11, 12 is connected to the central valve hole 15, respectively.

However, the main passage 11 does not necessarily need to be connected to the second valve hole 53.

Main passage 11 is IJ IJ-F valve 16, passage 54
The valve hole 18 is connected to the low-pressure side tank T via the branch passage 17, and is connected to the valve hole 18 via the branch passage 17.
It communicates with the tank T side via.

The valve holes 13.53 open into the low-pressure side case 24 at the back, and inside each of these valve holes 13, 53 there is a first
A spool 19 and a second spool 20 are slidably inserted, the tip of the one spool 19 protrudes from the main body 10 and is connected to the connecting frame 32 with a nut 56, and the back is pressed by a spring 25. The connecting frame 32 connected to this is pressed, and a bushing rod 57 protruding from approximately the center of the connecting frame 32 is brought into contact with the operating lever 23 inside the case 22.

Furthermore, the other spool 20 is slidably inserted into the valve hole 53, and its tip protrudes from the main body 10 and connects to the connection frame 3.
2 via a nut 58.

The insertion length of each spool 19, 20 into the valve holes 13, 53 can be adjusted by rotating nuts 56, 58.

The outer periphery of the spool 20 has two annular grooves 26 serving as passage means.
．． 27 is notched, the annular groove 27 communicates with the low pressure side through the through hole 28, and an annular groove 29 is also formed on the inner periphery of the valve hole 53.
As the valve 0 moves, it selectively communicates with the annular groove 29 of the valve hole 53.

The valve hole 13 and the other valve hole 53 communicate through a passage 59 which opens into the annular groove 26 of the spool 20 in one valve hole 53 and which opens into the annular groove 26 of the spool 20 in the valve hole 13. An annular groove 60 serving as a passage means of No. 19 is selectively opened and closed.

The wrap of the annular groove 60 is adjusted by adjusting the insertion length of the spool 19 into the valve hole 13.

Next, the back of the valve hole 14 opens into the low pressure side case 24, and the first valve hole 14 has a mushroom-shaped truncated conical valve head 43a formed inside.
A check valve 43 is slidably inserted therein, the rear end valve head 43a of the check valve 43 is pressed against the valve seat 44 by a spring 30, the tip 31 protrudes from the main body 10, and It is inserted into a hole in a connecting frame 32 so that its length can be adjusted freely, and can be moved to the left through the connecting frame 32 in conjunction with the spools 19 and 20 during a lowering operation.

However, during the lifting operation, the connecting frame 32 moves to the right, but the first check valve 43 does not move.

Also, within the valve hole 15 is a second truncated conical check valve 33.
is slidably inserted and is pressed against the mouth end of the passageway 11 by a spring 33 on the back.

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

Therefore, when the back pressure of the cylinder A acts on the back liquid chamber 36 of the second check valve 33, the second check valve 33 is reliably seated on the valve seat of the main passage 11.

Furthermore, a truncated cone-shaped unload valve 37 is slidably inserted into the other valve hole 18, and is constantly pressed against the end of the passage 17 by a spring 38 at the back. 39 communicates with the annular groove 29 via a through hole 40 bored in the main body.

The opening width of the annular groove 29 relative to the through hole 40 is determined by the wrap of the annular groove 29 by adjusting the insertion length of the spool 20 into the valve hole 53.

As is well known, the operating lever 23 is rotated clockwise or counterclockwise by operating an external handle 41, and is connected to the spool 19 through the bushing rod 57 and the connecting frame 32.
It is designed to transmit 20 linear motions.

Further, when the cylinder A expands or contracts, the movement is fed back to the operating lever 23 via a feedback link to return the spools 19, 20 to the neutral position.

Next, we will discuss the operation.

In the neutral state, the annular grooves 26, 27 of the spool 20 both communicate with the annular grooves 29 of the valve bore 53, and the passage 59 is blocked from the valve bore 13.

Further, the back liquid chamber 39 of the unload valve 37 communicates with the low pressure side via a through hole 40 and grooves 29 and 27.

On the other hand, since the second check valve 33 is also closed by the pressing force of the spring 34, the hydraulic fluid discharged into the passage 11 is pushed open against the spring 38 to push the unload valve 37 open, thereby flowing through the passage 55 toward the respective tanks. be returned.

Next, in the raised state, the operating lever 2 is
3 Rotate the lower part counterclockwise to push the bushing rod 57 to the right, thereby connecting the connecting frame 32 and the spools 19, 2.
0 to the right against the spring 25 to block one annular groove 27 of the spool 20 and close the other annular groove 26.
is connected to the groove 29 and through hole 40, and the other spool 19 is connected to the groove 29 and the through hole 40.
Then, the annular groove 60 opens into the passage 59, so that the passage 11 communicates with the liquid chamber 39 via the valve hole 13, the passage 59, the valve hole 53, and the passage 40.

In the above case.

The relationship between the connecting frame 32 and the first check valve is as follows:
2 moves to the right through the hole, and its movement is not transmitted to the first check valve 43;
3 is pressed by a spring 30 to hold the valve seat 44 in a closed state.

For this reason, high pressure oil from the passage 11 is guided to the back liquid chamber 39 of the unload valve 37 through the valve holes 15, 53 and the through hole 40, and as a result, the liquid chamber 39 and the passage 17 have the same pressure, so the unload valve 37 The passage 17 is closed by the force of the spring 38 and is held as it is.

Therefore, the high pressure in the passage 11 pushes the second check valve 33 open and is led to the cylinder A through the passage 12 and the valve hole 14, causing the cylinder A to rise.

This movement is then fed back to the actuating lever 23 via a feedback lever (not shown), which rotates the actuating lever 23 counterclockwise to rotate the spool 19.2.
Return 0 to neutral position.

Next, in the lowered state, when the tip of the actuating lever 23 is rotated clockwise via the handle 41, the actuating lever 23 tries to separate from the bushing rod 57, but at this time, the pressing force of the spring 25 causes the connecting frame 32 and The spools 19 and 20 follow and move to the left, causing the annular groove 27 at the rear of the spool 20 to communicate with the annular groove 29 of the valve hole 53.

For this reason, the back liquid chamber 39 of the unload valve 37 communicates with the low pressure side, so that the high pressure in the passage 11 pushes the unload valve 37 open against the spring 38, causing the tank T to be fully loaded.

Furthermore, when the spools 19 and 20 move to the left, the connecting frame 32 also moves to the left, thereby pushing the nut 61 to the left, causing the first check valve 28 to move to the left at the same time, and the valve head 4 at the rear end to move to the left.
3a is opened from the valve seat 44.

When the first check valve 43 opens, the passage 12 and the valve hole 1
4 communicates with the low pressure side, so the cylinder A slowly descends under its own weight via the throttle S.

Also, this movement is fed back in the same manner as described above to return the spools 19, 20 to their neutral positions.

In the present invention, the opening and closing of the annular groove 60 and the passage 59, which are pilot passages, and the opening and closing of the annular groove 27 and the passage 40 can be adjusted independently using the two spools 19 and 20, so that the minimum controllable l pitch of the cylinder can be adjusted. The amount of movement can be freely selected according to performance requirements, and in the extreme, the l pitch can be reduced to zero.

Also, machining is relatively easy since adjustment can be done with two spools.

Further, in the present invention, a first check valve 43 is provided in the main body,
In the first check valve 43, the force of the spring 30 pushes the valve head and closes the check valve 43.
Since there is a difference in the pressure receiving area between the outer diameter and the inner diameter of the valve seat 44, the valve head is pressed against the valve seat using hydraulic pressure.

That is, even if pressure is generated in the cylinder A due to the load from the working machine in the neutral state, the pressure acts in the direction of closing the valve head through the passage 12 and the valve hole 14, and leakage of oil can be completely prevented.

Furthermore, by providing the second check valve 33, even if pressure is generated in the neutral passage 12, this pressure is led to the liquid chamber 36 through the through hole 35 and acts in the direction of pushing the check valve 33 to close it. leakage is prevented.

Also, the check valve 43 is centered around the spool 19 and 20.
．． 33 and the unload valve 37 are installed in parallel, the thickness of the valve body 10 can be reduced, making it compact and inexpensive.

[Brief explanation of the drawing]

The accompanying drawing is a longitudinal sectional view of a control valve according to an embodiment of the present invention.

Claims (5)

[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 provided in these main passages to allow flow only from the pump to the cylinder. is provided to be openable and closable, the cylinder side main passage is selectively opened and closed to the tank side via the first check valve, and the pump side main passage is selectively opened and closed to the tank side via the unload valve. The unload valve is a hydraulically operated device that is operated to open and close by selectively communicating or blocking the back liquid chamber with the pump side or the tank side, and has a first valve hole in the valve body that communicates with the pump side main passage. and a second valve hole that communicates with the first valve hole and the tank side, and a first spool and a second spool slide into the first and second valve holes, respectively. One end of these first and second spools protrudes outside from the valve body and is connected to a connecting rod so that the length can be adjusted, and the first spool has a main passage on the pump side connected to the second valve body. A passage means is formed for selectively communicating with or blocking the hole, two passage means are formed in the second spool, and one passage means selects the liquid chamber at the back of the unload valve to the first valve hole side. A working machine control valve for an agricultural tractor, in which the other passage means communicates or blocks a liquid chamber at the back of an unload valve with a tank side. (2) The working machine control valve for an agricultural tractor according to claim 1, wherein one ends of the first and second spools are fastened to the connecting rod with a nut. (3) A working machine control valve for an agricultural tractor according to claim 1, wherein the passage means of the first and second spools are annular grooves. (4) The working machine control valve for an agricultural tractor according to claim 1, wherein the first and second valve holes communicate with each other via a passage provided in the valve body. (5) The ramp of the annular groove formed in each spool is adjusted by adjusting the insertion length of the first and second spools into the first and second valve holes with a nut.Claim 1 of Utility Model Registration: A working machine control valve for an agricultural tractor according to item 1 or 3.