JPH0239090Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a flow force compensation mechanism for a spool of a directional control valve.

<Prior Art> When a spool used in a directional switching valve is switched, a force (flow force) is generated in the direction of the operating force of the switching operation or in the opposite direction due to the flow of pressure oil.

This flow force occurs when the flow velocity of the pressure oil becomes high. That is, in the case of a switching operation of a switching valve, the value becomes large when the flow rate control is minute flow control. If a flow force occurs during minute control of the flow rate, it is necessary to perform control against this flow force, making it difficult to control the flow rate. Note that the flow rate control function is one of the basic functions of the directional switching valve.

Regarding the flow force acting on the spool,
The device shown in Figure 1 is proposed in "Hydraulic Drive and Its Control", Vol. 1, pages 262-277 (10, 3-axis force), published by the limited liability company Sohabo on April 20, 1962. ing.

In the directional control valve shown in Fig. 1, the spool 2 is provided with grooves 5 and 5' having two different cross-sectional shapes, and when the spool 2 is operated, the flow force generated in the groove 5 and the flow force generated in the groove 5' are balanced. This prevents the flow force from affecting the operating lever l. The mechanism of flow force generation in the grooves 5 and 5' will be described below.

First, the generation of flow force when pressure oil flows through the groove 5 having a rectangular cross section will be explained with reference to FIGS. 2a and 2b.

In Figure 2a, 1 is the main body, 2 is the spool,
3 is a high pressure side passage, 4 is a low pressure side passage, and 5 is
The groove has a rectangular cross section. One end of this spool 2 is connected to an operating lever l (see Figure 1).
By operating this operating lever l, the first land portion 2a
opens and closes the gap between the high pressure side passage 3 and the low pressure side passage 4, and also controls the flow rate from the high pressure side passage 3 to the low pressure side passage 4.

When operating the operating lever l to the right in Fig. 1, at the beginning of operating the operating lever l, as shown in Fig. 2 a, there is an orifice with a small opening area between the groove 5 and the low pressure side passage 4. 6 is formed. Therefore, the flow of pressure oil passing through the orifice 6 becomes faster. On the other hand, the flow velocity flowing into the groove 5 from the high-pressure side passage 3 remains slow because no orifice is formed.

Therefore, the pressure near the orifice 6 where the pressure oil flows quickly becomes low pressure. On the other hand, the pressure in the area where the flow rate is slow is high. (From Bernoulli's theorem.) That is, as shown in Figure 2b, there is a pressure on the surface 5a.
Pa acts on the surface 5b, and a pressure Pb acts on the surface 5b. And Pa<Pb. Therefore, in the groove 5 part,
When the orifice 6 is formed, a flow force (hereinafter referred to as positive flow force) in the direction of arrow F1 toward the left in the figure acts.

As the opening degree of the orifice 6 increases, the flow velocity of the pressure oil flowing through it also slows down, so the values of pressure Pa and Pb become closer and the positive flow force also becomes smaller.

Next, the groove 5' portion will be explained. Figure 3a
In the figure, 1 is the main body and 2 is the spool. 3 is a high-pressure side passage, and 4 is a low-pressure side passage, which are formed by enlarging the inner hole 1a of the main body 1 on both sides so as to leave a predetermined length. The spool 2 includes a first land portion 2a that closes off between the high-pressure side passage 3 and the low-pressure side passage 4, and a second
A land portion 2b is provided, and the land portion 2a,
2b fits into the inner hole 1a of the main body 1 to close the gap between the high-pressure side passage 3 and the low-pressure side passage 4 when the spool 2 is operated to the right or left in the figure. A groove 5' is provided between the land portions 2a and 2b,
The inner surface of the groove 5' is formed in a first part 5a' where the first land part 2a side is at a steep angle with respect to the axis of the spool 2, and the second land part 2b side is formed at a steeper angle than the first part 5a'. The second portion 5b' is formed in an angularly opposite direction.

In FIG. 3a, when the spool 2 is operated to the right, an orifice 6' is formed. At this time,
From the high pressure passage side 3 to the low pressure passage 4 side, as shown in _FIG . Outflow at an angle θ ₂ .

The flow force F ₂ at this time is the difference between the inflow momentum and the outflow momentum.

F ₂ = QU〓(Cosθ ₁ −Cosθ ₂ ) ……(1) Q = flow rate 〓 : fluid density U = flow velocity In the above equation (1), if the angle θ ₁ is made larger than the angle θ ₂ , then A flow force (hereinafter referred to as negative flow force) in the direction shown by arrow _F2 in FIG. 3b is generated.

Therefore, as mentioned above, the positive force acting on the grooves 5, 5',
Negative flow force balances out.

Flow force F ₂ explained using Figure 3b
A spool groove shape that generates a similar flow force is disclosed as an improved prior art in Japanese Patent Laid-Open No. 115329/1983. The invention described in the same publication attempts to reduce fluctuations in flow force due to the movement position of the spool valve by specifying the shape of the metering notch in a device having a metering notch, while leaving the basic shape of the groove unchanged. This is what I did. The metering notch is shaped like a relatively shallow groove with a relatively steep slope on the inlet side, or has a relatively steep slope on the inlet side and is shallow only on the outlet side. The reduction in operating force is compensated for by the reaction force of fluid momentum generated by the shape of the metering notch.

Furthermore, Japanese Utility Model Publication No. 58-15710 discloses a spool having a small diameter section between the large diameter sections on both sides, and a notch groove for flow rate control provided in the large diameter section on the inflow side.
The notch groove is formed deeper than the small diameter part, and a sloped step is provided between the large diameter part and the small diameter part on the opposite side of the notch groove. Basically, even when the large diameter part closes, The axial force (flow force) is reduced by making the inflow angle and outflow angle of the fluid substantially the same when the notched groove closes.

<Problems to be Solved by the Invention> Due to the hydraulic circuit in which the directional control valve is used, it is not possible to configure the directional control valve so that the flow force is always balanced as shown in FIG.

That is, the directional control valve shown in FIG. 1 is constructed so that the positive and negative flow forces generated in the grooves 5 and 5' are balanced, but the flow rate to the load is controlled by the grooves 5 or 5'. In most cases, one or the other is done. The groove is controlled on either the inflow side or the outflow side of the load, and the other side is not controlled. (When controlling on both sides, it is necessary to match the degree of restriction of both grooves, which makes processing complicated.) Therefore, with the directional control valve shown in Fig. 1, it is necessary to control the load only on the input side of the load. When trying to control the flow rate, a positive flow force acts, and when controlling the flow rate only on the output side of the load, a negative flow force acts.

In addition, flow control is one of the basic functions of a directional control valve, and in most cases where a directional control valve is used, in order to obtain the necessary flow control characteristics, it is necessary to It is necessary to provide a flow rate control notch for metering in the first land portion 2a. Due to this flow rate control notch, the way the flow rate is generated changes.
In order to adjust this change, it is necessary to change the shape of the other grooves 5 and the opening degree (opening area relative to the stroke) of the orifice 6. In this way, in the conventionally proposed flow force compensation mechanism shown in FIG. 1, the shape of one groove affects the other groove.
Adjustments to eliminate flow force were complicated.

In the case of the valve described in the above-mentioned publication, the shape, length, and depth of the flow rate control notch or cutout groove must be specified so that flow force is difficult to occur in each valve. That is, when determining the shape and dimensions of a notch or groove for flow rate control, both the flow rate control function and the flow force reduction effect must be taken into consideration. Another problem is that the shape is not necessarily simple and processing is not easy.

This idea allows the flow rate control section to have a simple shape and size that is optimal for each individual valve and easy to process without being subject to any restrictions, and allows flow force compensation to be performed in other parts. The challenge is to make it possible.

<Means for solving the problem> The technical means of this invention is to slidably fit a spool into an inner hole of a main body having a high-pressure passage and a low-pressure passage, and a second spool on the high-pressure passage side of the spool. A land portion is provided, and a second land portion is provided on the low pressure passage side, and between the first land portion and the second land portion, when the spool is operated, the land portion is connected to the high pressure side passage and the low pressure side passage. A groove with a width extending over the spool is provided, and the groove is composed of a first part connected to the first land part and a second part connected to the second land part, and the groove has a width that spans the axis of the spool of the first part. The angle with respect to the core is made larger than the angle with respect to the axis of the spool of the second portion, and when the pressure fluid passes through this groove, the second portion
In the spool in which a flow force is generated in the direction from the land portion to the first land portion,
A flow control notch is provided in the first land portion, and the second land portion is provided with a flow control notch.
An annular recess is provided between the part and the second land part, extending over the entire circumference, continuous with the second part, and having a surface parallel to the spool axis, and the spool axis of this recess is It is characterized in that the depth to the plane parallel to the core is such that a pressing force in the opposite direction corresponding to the flow force and the flow force due to the flow rate control notch can be obtained as static pressure.

<Operation> According to this technical means, when the pressure oil from the high pressure passage flows into the groove of the spool in the flow rate control area by the flow rate control notch and flows out to the low pressure passage, the flow rate control notch flows into the second part. A negative flow force is generated by the flow of pressure oil along. However, the hydraulic pressure (static pressure) on the low pressure passage side acts on the recess provided between the second portion and the second land portion. This acts on the spool as a force in the direction opposite to the direction of action of the negative flow force, and its magnitude varies depending on the size of the effective area of the recess, which is the force on the spool of the recess. The size increases by increasing the depth to the plane parallel to the axis.
Therefore, if a spool valve that requires a flow rate control function is provided with an individually optimal flow rate control notch, and the depth of the recess is increased to cancel the flow force caused by the spool, Flow force is compensated. The depth dimension of the recess is determined experimentally.

The basic idea of this invention is to determine the shape of the spool groove and flow control notch so that the negative flow force is generated, and then determine the depth of the recess so as to cancel that flow force. It is. The actual flow force that is of concern occurs in the flow control region associated with the flow control notch. Therefore, the inflow direction and the outflow direction of the fluid flowing into the groove of the spool in the flow rate control region become a problem. The simplest shape of the flow control notch that is commonly used is to cut into the first land part from the groove side with a small diameter end mill in a direction perpendicular to the axis of the spool and feed it a certain length in the spool axis direction. It is formed to form a keyway,
The inner surface of the notch is perpendicular to the axis of the spool. In other cases, the inner surface of the notch is generally perpendicular to the axis, except for special cases. In such a notch, the inflow angle of the fluid flowing into the groove of the spool in the flow rate control area through the notch changes as the spool moves, but during this change, the inflow angle θ ₁ (with respect to the spool axis) changes. angle)
It is well known that the maximum flow force occurs when the temperature approaches 69 degrees. This is because if the deep part of the notch is perpendicular to the spool axis, the inflow angle is considered to change at a large angle close to the right angle, and the direction of the inflow fluid bends toward the spool axis near the bottom of the notch. This is understandable since it is assumed that the momentum in the outflow direction will increase due to the flow of water. For these reasons, the inflow angle θ ₁ of the fluid flowing into the groove from the flow rate control notch may be around 69 degrees when considering the flow force. The outflow angle θ ₂ of the fluid from the groove is bent in the direction of the spool axis at the bottom of the notch in the flow rate control region, and flows out along the second part, so it roughly corresponds to the angle with respect to the axis of the second part. Become something to do. This outflow condition is always a condition that produces the negative flow force. Therefore, this negative flow force is appropriately canceled by adjusting the depth of the recess in the direction perpendicular to the spool axis.

The relationship between the inclination angles of the first part and the second part is the basic concept of the invention, and is such that the negative flow force always occurs.

<Example> An example of the present invention will be described below with reference to FIG. 4a. In this figure, the same parts as those in FIG. 3a are designated by the same reference numerals, and their explanation will be omitted. The difference from the one in FIG. 3a is that a third portion 10 is connected to the second portion 5b' of the groove 5', and a notch 7 for controlling the flow rate is provided.

This third portion 10 is formed around the entire circumference of the spool 2, and consists of a surface 10a perpendicular to the axis of the spool 2 and a surface 10b parallel to the axis of the spool 2.
It has an annular recess shape with respect to the surface of the portion 5b'.

A plurality of flow rate control notches 7 are provided on the edge _2a1 of the land portion 2a, each having a substantially triangular cross section.

In this example, spool 2 is operated;
When the orifice 6' is formed, the pressure oil in the high pressure side passage 3 flows from the orifice 6' in the direction of arrow _a1 ,
It hits the bottom surface 7b of the flow control notch 7, the direction of the flow is changed in the direction of arrow _a3 , and the second portion 5
At point b', the direction of the flow is changed in the direction of arrow _a2 and flows out into the low pressure side passage 4. Due to the flow of pressure oil when passing through this orifice 6', a positive flow force acts on the spool 2, and arrows a ₃ ,
A negative flow force acts on the spool 2 due to the flow indicated by _a2 . As explained in Figure 3a, the relationship between positive and negative flow forces is as follows:
The negative flow force becomes stronger.

The recess, which is the third portion 10, has a depth that is not affected by the flow shown by arrow _a2 , so
As shown in d, pressure on the low pressure side acts on the surface 10a. The hydraulic pressure acting on this surface 10a acts in opposition to the negative flow force. Therefore, by adjusting the pressure receiving area of the surface 10a of the third portion 10, the flow force generated in the groove 5' can be balanced.

Note that the third portion 10 provided in the groove 5' does not necessarily have to have a surface perpendicular to the axis of the spool 2, as shown in FIGS. 4b and 4c, and its depth H
If 1, H2, and H3 are equal, similar thrust can be obtained.

<Effects of the invention> (1) In the present invention, the cross-sectional shape of the groove formed in the spool and in which the flow rate control notch is provided is such that the groove has a cross-sectional shape as shown in Figure 3a where a negative flow force occurs. , this groove is provided with a notch for controlling the flow rate required by the directional valve, so that depending on the strength of the negative flow force, the depth of the recess in the third section is gradually deepened and the positive The generation of flow force in the groove having the flow control notch is prevented by adjusting the degree of generation of flow force so as to oppose the negative flow force. The depth of the recess in the third part is
Since the depth can be increased by cutting, the positive and negative flow rates can be balanced by adjusting the depth of the recess in the third portion very easily, regardless of the flow rate control characteristics.

(2) Since it has the above-mentioned effects, the influence of one groove of the spool does not affect other grooves, making it easy to design the directional control valve and easily obtain desired flow characteristics.

(3) Since the flow force of the directional control valve using this spool is balanced, no extra force is required for its operation, and accurate flow control can be obtained.

(4) Since the notch for flow rate control can be provided without any particular restrictions on its shape or dimensions, it is possible to adopt a notch with an extremely simple shape, which facilitates processing.

[Brief explanation of drawings]

Fig. 1 is a partial vertical side view schematically showing a device having a conventional flow force compensation mechanism, Fig. 2 a and b
are respectively enlarged sectional views of the groove 5 in FIG. 1, and FIGS. 3a and 3b are enlarged sectional views of the groove 5' in FIG.
FIG. 4a is an enlarged sectional view of the main part showing one embodiment of this invention, and FIGS. 4b and 4c are enlarged sectional views of the main part showing a modification of the third part of this invention. DESCRIPTION OF SYMBOLS 1...Main body, 1a...Body internal hole, 2...Spool, 2a...First land portion, 2b...Second land portion, 3...High pressure side passage, 4...Low pressure side passage, 5'
...Groove, 5a'...first part, 5b'...second part,
6'... Orifice, 7... Flow rate control notch, 1
0, 10', 10''... recess (third part), 10b
...A surface parallel to the spool axis.

Claims (1)

[Scope of utility model registration request] A spool is slidably fitted into an inner hole of a main body having a high pressure passage and a low pressure passage, a first land portion is provided on the high pressure passage side of the spool, and a second land portion is provided on the low pressure passage side of the spool, and a second land portion is provided on the low pressure passage side of the spool. A groove having a width spanning the high pressure side passage and the low pressure side passage when the spool is operated is provided between the first land portion and the second land portion, and this groove is formed in the first land portion. and a second portion connected to the second land portion, the angle of the first portion with respect to the axis of the spool is larger than the angle of the second portion with respect to the axis of the spool. In the spool, a flow force is generated in a direction from the second land part to the first land part when the pressure fluid passes through the groove, and the first land part is provided with a flow rate control notch, and the first land part is provided with a flow rate control notch, and the second land part An annular recess is provided between the second land portion and the entire periphery spanning both sides, continuous with the second portion, and having a surface parallel to the spool axis, and the spool axis of this recess is A flow force compensation mechanism for a spool, characterized in that the depth to the parallel surface is such that a pressing force in an opposite direction corresponding to the flow force and the flow force due to the flow rate control notch can be obtained as a static force.