JPS5815710Y2 - Directional control valve spool - Google Patents

Description

[Detailed description of the invention] The present invention is a spool for a directional control valve that is installed in a hydraulic system, and in particular, as shown in Fig. 1, it is used in a neutral circuit that unloads tank C from pump B when spool a is in the neutral state. An object of the present invention is to provide a spool for a directional control valve in a hydraulic system that can reduce the axial force when the valve is closed.

It has long been known that an axial force acts on the spool when switching a hydraulic directional control valve, and in particular, the higher the pressure, the greater the axial force generated.

Various measures have been taken in the past to reduce this axial force (for example, Utility Model Publication No. 50-27626), but these have mainly been concentrated on the notches attached to the spool for finely adjusting the flow rate. .

As a result, the axial force generated when the notch closes has been considerably reduced, but the axial force generated when the large diameter portion of the spool closes has become stronger.

That is, Fig. 2 shows a conventional example in which the groove bottom of the notch d is deeper than the small diameter part, and Fig. A shows the case when the large diameter part is closed, and Fig. B shows the case when the notch part is closed.

The transition of the axial force at this time is as shown by the solid line e in FIG.

In the figure, 1 is when the large diameter part is closed, and ■ is when the notch is closed.From this figure, it can be seen that the axial force is reduced by 1 when the notch is closed, but is larger by 1 when the large diameter part is closed. .

Figure 2C shows the spool before taking measures to reduce the axial force.The change in axial force with respect to the movement of the spool is shown by the chain line f in Figure 3.When the large diameter portion closes, the axial force in ■ is also large; When the section closed, the axial force of H was extremely large.

As a result of the axial force reduction measures mentioned above, when the notch closes, the axial force of H has been reduced, but when the large diameter section closes, the axial force of When the operating pressure of actuators such as cylinders and motors increases and it is necessary to reduce the opening area of the notch, the pressure in the neutral part increases as the large diameter part closes. The axial force has also increased.

The axial force F acting on the spool a is F = pQ (V 1 cos θ1 - V 2 cos
θ2).

Here, ρ is the density of the fluid, Q is the flow rate, ■1 is the inflow velocity, θ
l is the inflow angle and θ2 is the outflow angle.

From the above formula, Vl, +V2tθ1. By determining θ2 fc, the axial force F' acting on the spool a can be reduced.0 Here, a conventional spool in which the axial force is reduced at the position where the notch is closed will be considered with reference to FIG.

The fluid from the large diameter part of spool a flows in at a speed Vl and an angle θl, reverses at the bottom of the notch d, stays on the wall surface of the notch d at the depth h, and jumps out at a speed V1 and an angle θ2. To go.

In this case, θ□ and θ2 become approximately the same (V1 cos θ
1-V2CO3θ2) becomes smaller, and therefore the axial force F becomes smaller.

The outflow angle θ2 at this time is the length g and depth h of the notch d.
Determined by.

On the other hand, in the spool before the axial force reduction measures shown in Figure 2 C, the fluid flowing in from the notch collides with the end face of the adjacent large diameter part.
It stays at this end face and flows out almost perpendicular to the axis, and θ2 is large, so V 2 CO8θ2 becomes extremely small.

Therefore, (V1 cos θ1-V 2 cos θ2) increases, and the axial force F increases.

This is the same when the large diameter part shown in Fig. 2A closes; the outflow angle θ2 on the outflow side is large, and therefore the axial force becomes large because V2CO8θ2 is small, and as a result, the large diameter part closes as shown in Fig. 3. It can be seen that when the button is closed, the axial force when the button and the notch in the example not shown in FIG. 2C are closed becomes large.

From the above, as shown in FIG. It is considered that the axial force at the closed position can be reduced.

However, if the spool a'Q is shaped as shown in Figure 5 and a notch dt is added to this, the result will be as shown in Figure 6, and the depth h of the notch d will change from the state shown in Figure 4. This increases the outflow angle θ2 from the notch, which impairs the reduction of the axial force at the position where the notch d closes.

The present invention was developed in consideration of the above, and its purpose is to reduce the axial force at the position where the large diameter part is closed, without impairing the effect of reducing the axial force at the position where the notch is closed. It is something to do.

In order to achieve the above object, the present invention provides a spool having a large diameter part and a small diameter part with a notch groove that is deeper than the outer circumferential surface of the small diameter part from the large diameter part to the small diameter part, and the notch groove is provided in the small diameter part. A medium diameter portion is provided at a position axially distant from the large diameter portion having a groove, and the step portion of the medium diameter portion facing the large diameter portion is formed into an inclined surface whose diameter increases as the distance from the large diameter portion increases. Also, a notch is provided in an extension of the notch groove in the middle diameter portion.

The operation of the directional control valve having the above configuration is as follows.

That is, when the large diameter part closes, the fluid that flows from the large diameter part to the small diameter part hits the slope of the medium diameter part and flows out from the small diameter part to the outflow port at an angle that is approximately the same as the inflow angle.
The axial force at this time becomes small.

When the sprouted notch groove closes, the fluid that flows into the notch groove from the large diameter part stays in the notch provided in the middle diameter part from the notch groove and flows out at approximately the same angle as the inflow angle, and the axial force at this time also becomes smaller. .

The effects of the above configuration are as follows.

That is, the spool of the direction control valve can be switched with a small axial force.

Further, when switching is performed using spool Th, +Ilot pressure or electromagnetic force from a solenoid, switching can be performed with small hydraulic pressure or small electric power, and the power required for switching can be reduced.

Even more subtle switching operations, such as switching more slowly, become possible.

An embodiment of the present invention will be described below with reference to FIG. 7. The large diameter portion 2 of the spool 1 for switching the neutral position is provided with a cutout groove 4 that connects from this portion to the small diameter portion 3 in the same manner as in the prior art.

A medium diameter portion 5 having a smaller diameter than the large diameter portion 2 and a larger diameter than the small diameter portion 3 is provided at a position away from the large diameter portion 2 having the notch groove 4 of the small diameter portion 3. The stepped portion is a straight or curved slope, and a notch 6 is provided in an extension of the notched groove 4 to be approximately the same size as the small diameter portion 3.

By doing this, at the position where the large diameter section is closed, the fluid flowing in from the large diameter section is reversed on the slope of the middle diameter section and flows out, and the inflow angle and outflow angle at this time are approximately the same, and the axial force is reduced. When considering the formula F-ρQ(Vlcosfi-V2cosθ
2) (V1cosθ1-V2cosθ2) becomes smaller, and the axis at the position where the large diameter portion is closed is reduced.

On the other hand, in the position where the notch is closed, by providing the notch 6 extending from the notch groove 4 in the middle diameter part, the axial force at the position where this part is closed can be kept small as in the conventional case.

The changes in axial force at both positions above are shown in Figure 8.
The axial force at the position where the large diameter part 2 closes ■The position where the button and notch close ■ is shown by the curve j, and the axial force when the large diameter part closes is compared to the axial force k in the conventional case. significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway explanatory diagram of a directional control valve of a hydraulic system to which the present invention is applied, Figs. A diagram showing the transition of axial force in the case of a spool, Fig. 4 is an enlarged sectional view of the main parts of a conventional spool, Figs. An explanatory diagram of the configuration of the spool,
FIG. 8 is a diagram showing the transition of the axial force of the spool in the case of the present invention. 1 is a spool, 2 is a large diameter part, 3 is a small diameter part, 4 is a notched groove,
5 is the middle diameter part, 6 is the notch.

Claims (1)

[Scope of utility model registration request] The valve body is slidably fitted into a valve body having an inflow port and an outflow hole, and has a large diameter portion 2 and a small diameter portion 3 adjacent thereto;
By sliding, communication between the inflow port and the outflow port of the valve body is disconnected between the large diameter portion 2 and the small diameter portion 3, and the spool of the directional control valve is connected from the large diameter portion 2 to the small diameter portion 3. A notched groove 4 that is deeper than the outer circumferential surface of the small diameter portion 3
and a medium diameter portion 5 is provided in the small diameter portion 3 at a position axially away from the large diameter portion 2 having the notch groove 4,
The stepped portion of the medium diameter portion 5 facing the large diameter portion 2 is formed into a slope shape whose diameter gradually increases as the distance from the large diameter portion 2 increases, and a notch 6 is formed in an extension of the notch groove 4 of the medium diameter portion 5 A spool for a directional control valve, comprising: a spool for a directional control valve;