JPH0260285B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention provides pressure oil supply, oil drainage, and oil supply/drainage to a single-acting hydraulic cylinder controlled by a spool-type three-position switching control valve. By shutting off, the seedling planting device is raised and lowered and fixed, and the spool of this control valve is switched to operate based on the vertical movement detection of the sensor float installed in the seedling planting device, thereby adjusting the ground level of the seedling planting device. This invention relates to a hydraulic control mechanism for a rice transplanter configured to maintain stability.

[Conventional technology]

The pump port of the control valve is connected to the spool of the control valve with the spool being operated to an intermediate operating position between the neutral position and the raised position of the seedling planting device.
An underlap portion is formed that connects both the drain port to the tank and the cylinder port for supplying pressure oil to the hydraulic cylinder in a constricted state at the same time, and within the action range of this underlap portion, minute cylinder drain oil is removed. There is a device that is constructed so that a neutral stable state is created by the descending state of the seedling planting device and the balance between the supply and discharge hydraulic pressure (for example, Japanese Patent Application Laid-Open No. 1986-
Publication No. 144004).

[Problem that the invention seeks to solve]

In the above conventional means, the raising and lowering operation of the seedling planting device is brought about by a slight displacement of the spool from the neutral stable state due to hydraulic equilibrium, so the response is quick and smooth compared to a general three-position switching control valve. It is possible to perform stable elevation control with little overshoot, and if the spool is manually operated to the upward side when changing the direction of the aircraft at the edge of a ridge, the entire amount is supplied without going through the underlap part. Although it has the characteristic of being able to raise rapidly, the operating range of the underlap portion is small, so in fields where the plowing bed is relatively uneven, the sensor float does not move up and down during planting. As the displacement increases, the spool will more often exceed the action range of the underlap part.
In particular, there was a tendency for overshoot to occur more easily when upward control was performed rapidly with full supply.

The present invention attempts to further stabilize control by improving the control valve.

[Means for solving problems]

In order to achieve the above object, in the present invention, the pump port of the control valve is connected to the spool of the control valve in a state where the spool is operated to an intermediate operating position between a neutral position and a raised position of the seedling planting device. An underlap portion is formed which connects both the drain port to the tank and the cylinder port for supplying pressure oil to the hydraulic cylinder in a constricted state at the same time. It is configured so that a neutral stable state is created by the balance between the descending state of the seedling planting device due to drained oil and the supply/discharge hydraulic pressure, and furthermore, the underlap portion is moved from the neutral position to the raised position of the seedling planting device in the spool axis direction. The point is that it is formed over a certain range that is slightly smaller than the stroke.

[Effect]

According to the above configuration, even if the spool is slightly displaced from the neutral stable state of hydraulic equilibrium via the underlap portion to the upward side, the pressure oil in the pump port oil chamber will flow into the cylinder port oil chamber through the small gap on the outer periphery of the underlap portion. Slow rise control is performed. Then, only when the seedling planting device sinks particularly suddenly and to a large extent, or when the raising operation is performed manually, rapid raising is performed by supplying the entire amount without going through the underlap portion.

〔Effect of the invention〕

Therefore, it has become possible to perform stable level control of the seedling planting device with less pitching by performing slow lifting and lowering control over a wider spool operating range than in the past.

〔Example〕

FIG. 5 shows a riding type rice transplanter equipped with the control mechanism of the present invention, in which a seedling planting device 3 is connected to the rear of a traveling vehicle body 1 via a parallel quadruple link mechanism 2 so as to be able to rise and fall freely, and this link mechanism 2 is moved up and down by a single-acting hydraulic cylinder 4 which is extended by supply of pressure oil and shortened by drained oil.

A spool-type three-position switching control valve 5 that controls the operation of the hydraulic cylinder 4 is connected to the seedling planting device 3.
The seedling planting device 3 is raised and lowered by switching the control valve 5 based on ground pressure fluctuations acting on the sensor float 6 installed in the sensor float 6,
It is configured to perform control to maintain the ground pressure of the sensor float 6 constant and stabilize the ground level of the seedling planting device 3.

FIG. 6 shows the specific structure of the control mechanism, showing the front part of the sensor float 6 that can freely swing up and down about the rear fulcrum X and the fixing member 7 of the seedling planting device 3.
are connected by bending links 8, 8, and the release wire 9 is operated according to the bending and stretching of the bending links 8, 8, and the control valve 5 is switched and operated by the inner wire 9a. In other words, when the ground pressure of the sensor float 6 and the elastic force of the spring 10 that biases the bending links 8, 8 to extend are balanced, the control valve 5 is in a neutral state, the hydraulic cylinder 4 is stopped, and the seedling planting device 3 is maintained constant, and when the vehicle body 1 enters a deep part of the plowing platform and the ground level of the seedling planting device 3 decreases, the ground pressure of the sensor float 6 increases and the bending links 8,
8 is bent against the spring 10 and the inner wire 9a is loosened, whereby the control valve 5 is switched to the pressure oil supply state by the spring 11, and the seedling planting device 3 is raised by the hydraulic cylinder 4. is,
When the sensor float ground pressure decreases to the set value, the neutral state is restored. In addition, as the plowing platform becomes shallower, the subsidence of the vehicle body 1 decreases, and the ground level of the seedling planting device 3 increases, the ground pressure of the sensor float 6 decreases, and the bending links 8, 8 are affected by the elastic force of the spring 10 and the float. When the inner wire 9a is stretched by the weight and pulled, the control valve 5 is switched to the cylinder oil draining state, and the seedling planting device 3 is lowered by its own weight until the sensor float ground pressure increases to the set value. and stabilize in a neutral state. By continuously performing the above control, the level of the seedling planting device 3 relative to the ground is maintained at a substantially constant level regardless of the amount of subsidence of the vehicle body 1.

1 to 4 show the detailed structure of the control valve 5, in which the tip of the spool 12 inserted into the valve casing 5a is thrust into the operation casing 5b, and the spool 12 is attached to the protruding end of the spool 12. The pin 13 is locked by an operation fork 14 pivotally supported on the operation casing 5b, and by rotating the fork shaft 15 connected to the release wire 9 in forward and reverse directions, the spool 12 is moved to the neutral position N and the pressure oil It is configured to switch between a supply position (forced upward position) U and an oil drain position (self-weight downward position) D.

Next, the function of the control valve 5 itself will be explained in detail. When the spool 12 is in the neutral position N as shown in FIG. 1, the oil chamber a communicating with the pump port P and the first oil chamber b communicating with the drain port T are The hydraulic cylinder 4 is locked by being communicated with the large diameter portion 12b so that the oil chamber c communicating with the cylinder port C is closed by the large diameter portion 12b. When the spool 12 is pushed in and switched to the pressure oil supply position U, the first drain oil chamber b is closed by the large diameter portion 12c, and
Pump port oil chamber a and cylinder port oil chamber c are communicated via small diameter portion 12a, and cylinder port C
Pressure oil is sent to. Also, when the spool 12 is pulled out and switched to the oil draining position D, the cylinder oil chamber c
and the second drain oil chamber d communicate with each other via the second small diameter portion 12d, allowing oil to be drained from the hydraulic cylinder 4, and the pump port oil chamber a and the first drain oil chamber b communicate with each other. The short circuit is maintained and the oil is drained. In the figure, 16 is a main relief valve that communicates with the pump port P, and 17 is a lowering lock valve that prevents oil from draining from the cylinder 4 and prevents the oil leaf from unexpectedly lowering the seedling planting device 3. , normally open, but shut off when driving on the road. Further, reference numeral 18 denotes a throttle valve provided in the cylinder oil drain passage, which is used to adjust the rate at which the seedling planting device 3 descends under its own weight.

The configuration described above is not particularly different from the conventional one, and the present invention further adds the following configuration.

That is, an underlap portion A is formed at the end of the large diameter portion 12b of the spool 12 on the pump port oil chamber a side. This underlap portion A has a certain range L (approximately 5
mm), it is configured as a parallel stepped portion so as to have a slightly smaller diameter (about 0.1 mm in radius difference) than the outer diameter of the large diameter portion 12b.

According to the above configuration, the underlap portion A is the fourth
As shown in Figure A, when the cylinder port oil chamber c touches the end of the cylinder port oil chamber c, this oil chamber c
It communicates with the pump port oil chamber a through a minute gap (about 0.1 mm gap) e, and the pump port oil chamber a itself communicates with the first drain port oil chamber b through a small gap f. Therefore, when the amount of overlap between the underlap portion A and the oil chamber c is small, the small gap f becomes relatively large, the drain resistance becomes small, and it becomes possible to drain oil from the hydraulic cylinder 4 in small amounts. A slow descending state of the seedling planting device 3 is brought about. Furthermore, as the amount of overlap between the underlap portion A and the oil chamber c increases, the small gap f becomes smaller and the drain resistance increases, and the back pressure due to this drain resistance becomes in equilibrium with the hydraulic cylinder internal pressure, resulting in a substantial A stable state is brought about in which the hydraulic cylinder 4 stops. Therefore, between the original neutral position N of the spool 12 and the pressure oil supply position U, a slow descending position D' is formed by draining oil via the underlap portion A, and furthermore, this slow descending position D' and A neutral stable position N' is formed between the original pressure oil supply position U and the oil supply/discharge equilibrium.

Moreover, when the spool 12 is displaced a little more upward from this neutral stable position N', as shown in FIG. There is a small gap e between the oil chamber a and the cylinder port oil chamber c on the outer periphery of the underlap part A.
Pressure oil is sent out to the cylinder port C little by little, and a slow rising operation is performed.

Then, when the spool 12 is further displaced to the upward side, the end of the underlap portion A enters the cylinder port oil chamber c, as shown in FIG. The large flow path is shorted to provide rapid rise operation.

The control valve 5 having the above structure can also be switched manually, and its structure will be explained below.

A cylindrical shaft 19 is fitted onto the fork shaft 15,
A contact arm 20 fixed to the inner end of the case is configured to be able to contact the pin 13 only from one side, and a manual operation lever 21 is attached to the outer end of the cylindrical shaft 19.
is installed. When this lever 21 is switched to the forward limit position A as shown in FIG. 6, the contact arm 20 is in a position far away from the pin 13 as shown in FIG.
4 allows forward and reverse operation of the spool, that is, automatic lifting and lowering control.

Moreover, when the lever 21 is operated to the rear limit position C in FIG. It can be forced to rise to a height of .

When the lever 21 is returned to the B position shown in FIG. 6 after being raised to a desired position, the contact arm 20 holds the spool 12 at the neutral position N via the pin 13, and In the position B, the contact arm 20 is held in position by the spring ball 22, and the seedling planting device 3 is fixed at a predetermined raised position. Further, the cylindrical shaft 19 is connected to the seedling planting device 3.
The planting clutch 23 is connected via a link 25 to the operating lever 24 of the planting clutch 23, which connects and disconnects power to the planting clutch 23, so that the planting clutch 23 can be engaged only when the manual operating lever 21 is in the A position.

[Application example]

The present invention can be applied to a walk-behind rice transplanter that stably maintains the level of a seedling planting device directly connected to the machine body by controlling the elevation and descent of the propulsion wheels that are in contact with the tiller.

[Brief explanation of drawings]

The drawings show an embodiment of the hydraulic control mechanism for a rice transplanter according to the present invention, and FIG. 1 is a cross-sectional plan view of a control valve, and FIG.
The figure is a partially cutaway side view of the control valve, Figure 3 is a longitudinal sectional front view of the control valve, Figure 4 A-C is an enlarged plan view of the main parts showing various spool displacement states, and Figure 5 is the entire rice transplanter. The side view, FIG. 6, is a perspective view of the automatic control mechanism. 3...Seedling planting device, 4...Hydraulic cylinder, 5...
...Control valve, 6...Sensor float, 12...Spool, A...Underlap part, a...Pump port oil chamber, b...Drain port oil chamber, c...Cylinder port oil chamber, e...Gap, f...Gap, N
...neutral position, U...raised position.

Claims (1)

[Claims] 1 The seedling planting device 3 is raised and lowered and fixed by supplying and draining pressure oil to the single-acting hydraulic cylinder 4 controlled by the spool-type three-position switching control valve 5, and shutting off the oil supply and drain. At the same time, this control valve 5
This is a hydraulic control mechanism for a rice transplanter configured to operate the spool 12 of the rice transplanter by switching the spool 12 based on the vertical movement detection of the sensor float 6 provided in the seedling planting device 3, thereby stably maintaining the level of the seedling planting device 3 above the ground. hand,
The spool 12 of the control valve 5 has its spool 1
2 is operated to an intermediate operating position between the neutral position N and the raised position U of the seedling planting device, the pump port P of the control valve 5 is connected to the drain port T to the tank,
An underlap part A is formed which communicates with the cylinder port C for supplying pressure oil to the hydraulic cylinder 4 in a constricted state at the same time. It is configured so that a neutral stable state is created by the balance between the descending state of the attached device and the supply/discharge hydraulic pressure, and furthermore, the underlap portion A is moved from the neutral position N to the raised position U of the seedling planting device in the spool axis direction. The hydraulic control mechanism of the rice transplanter is formed over a certain range l that is slightly smaller than the stroke L.