JPS5858538B2 - riyuuriyouseigiyoben - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flow rate control valve that can always supply a flow rate proportional to the opening degree of a flow rate adjustment part to an actuator even if the discharge pressure of a fluid pump changes. The accuracy has been further improved.

Before explaining the flow control valve of the present invention, basic control of a conventional flow control valve will first be explained based on FIG.

That is, in the figure, when fluid is discharged from the fluid pump 1, primary pressure P1 is generated in the front part of the flow rate adjustment part 31 due to the throttle resistance of the flow rate adjustment part 31 which is applied to the flow rate adjustment valve 3, and the primary pressure P1 is generated in the rear part of the flow rate adjustment part 31. A secondary pressure P2 corresponding to the load W of the actuator 4 is generated, and a pressure difference ΔP is generated before and after the flow rate adjustment section 310.
form.

Moreover, at the same time, the secondary pressure P1 acts on the primary ash pressure receiving surface 27 at one end of the spool 22 of the pressure compensation valve 2 through the pilot passage 21, and the secondary pressure P2 acts on the primary ash pressure receiving surface 27 at the other end of the spool 22 through the feedback passage 32. back pressure chamber 23
It acts on the secondary pressure receiving surface 28 at the other end of the NuPool 22.

As a result, the differential pressure △P between the secondary pressure P1 and the secondary pressure P2
is greater than the spring 240 force, the spool 22 is displaced to the left against the spring force K, opening the pressure controlled variable orifice 25.

The pressure compensating valve 2 is of the normally closed type, and when the variable pressure adjustment orifice 25 is opened as described above, a part of the discharge amount Q1 discharged from the fluid pump 1 is diverted to the tank 26, and the primary pressure is Decrease P1.

When the pressure difference △P between the primary pressure P1 and the secondary pressure P2 is equal to the spring force, the pressure control variable orifice 25
The opening degree of is kept constant, and the divided flow rate Q3 is also kept constant.

In other words, if the discharge amount Q1 of the fluid pump 1 is constant, the differential pressure ΔP between the primary pressure P1 and the secondary pressure P2 is also kept constant, and the flow rate supplied to the actuator 4 is also kept constant.

After that, when the movable valve 33 of the flow rate adjustment valve 3 is operated to adjust the opening degree of the flow rate adjustment part 31, the spool 2 of the pressure compensation valve 2
2 is displaced to automatically adjust the opening degree of the pressure control variable orifice 25, and performs control to maintain the differential force ΔP before and after the flow rate adjustment section 310 constant.

However, when performing the above control, the axial thrust F acting on the spool 22 when the fluid is diverted from the variable pressure control orifice 25 cannot be overlooked as a factor that determines the accuracy of the control.

The axial thrust F can be expressed using a generally well-known formula as follows.

That is, with C as a constant, Qupcos fl =F F-(: -Q 3 v'FT =C(Q I Q 2
) s”P'l.

In particular, the conventional flow control valve has an area A1 of the primary ball pressure receiving surface 27 of the spool 22 facing the pressure compensation valve 2 and a secondary ball pressure receiving surface 28 of the spool 22 facing the pressure compensation valve 2.
The area A2 and the area A2 are formed to be the same area, that is, AI=A2, and in such a conventional example, there were the following defects due to the influence of the axial thrust F.

That is, the proportion of the spool 22 shown in FIG. 3 is as shown in the following equation.

Therefore, if K, C, and Ql are each constant (Q
2 may be assumed to be approximately constant here. Therefore, by adjusting the opening degree of the flow rate adjustment section 31 and setting the set flow rate Q2 as shown by the imaginary line in FIG. The larger ΔP becomes, the more the excess flow rate is added to the set flow rate Q2, and the pressure compensation accuracy decreases accordingly.

In other words, the thrust term cannot be ignored.

The present invention has been made in view of the above circumstances, and an object thereof is to eliminate the influence of the axial thrust and improve pressure compensation accuracy.

The structure of the present invention is that a flow rate adjustment valve equipped with a flow rate adjustment section is provided in the supply line of the actuator, and a normally closed pressure compensation valve is interposed between the supply line and the tank in front of the flow rate adjustment valve. , the front part of the flow rate adjusting part is communicated with the primary pressure receiving surface on the opposite spring side of the spool in the pressure compensating valve, and the flow rate adjusting part is connected to the secondary ball pressure receiving surface on the spring side which is buttoned on the spool. This is a flow control valve in which the rear end is communicated with the spool, and the area of the primary pressure receiving surface of the spool is made larger than the area of the secondary ball pressure receiving surface.

Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 1, the spool 22 in the pressure compensation valve 2
The area AI of the primary ball pressure receiving surface 27 is formed larger than the area A2 of the secondary ball pressure receiving surface 28, that is, the area AI>A2.

Note that the parts shown in FIG. 1 by the same reference numerals as in FIG. 3 are the same as the structure described based on FIG. 3, and therefore detailed description of the structure will be omitted.

As a result, in the structure shown in Fig. 1, an area difference of A I - A 2 - △A is formed at both ends of the spool 22, and the pressure is generated from the primary pressure P] that acts on this area difference △A. The resulting force becomes a force that resists the axial thrust F.

Moreover, the force that resists the axial thrust F has a characteristic that as the primary pressure P1 increases, a corresponding force against the axial thrust F is exerted.

This can be expressed as the following formula.

That is, in a range of values of Pl, v'P 1-==
Assuming P1, AIP1=A2P2++-C(Ql-Q2)PIp
2=pl-△P, A2=AI-ΔA, AIPl-
(AI-△A) (PI-ΔP) + +C (Ql-Q2)
PI A1△P-△API-1- +C (Ql-Q2) PI However, △A・△PζO.

Here, it is desirable that A1ΔP=K, but for that, it is necessary that ΔAP1=C(Ql-Q2)PI hold true.

Therefore, △A=C(Ql-Q2), In other words, AI-A2=C(Q3).

Therefore, it is necessary to vary the area AI at both ends of the spool and the difference ΔA between A2 in accordance with the flow rate Q2 flowing into the actuator 4 (more precisely, in correspondence with Q1-Q2).

However, it is impossible to change the area difference ΔA corresponding to the flow rate Q2 each time, so for example, for example, Q
After determining l, AI and A2 can be determined by setting 50% of the rated opening as the design target for Q2 (it may be changed to 60%, 70%, etc. depending on the required flow rate of the actuator).

This is shown in Fig. 4. When the opening degree of the flow rate adjustment section 31 is determined in the vertical direction and pi is determined in the horizontal direction, the closer the opening degree of the flow rate adjustment section 31 is to 0%, the more Pl increases. Q2 tends to increase, and the opening degree of the flow rate adjustment part 31 reaches the rated value, that is, 100.
%, Q2 tends to decrease as Pl increases, but if the opening degree of the flow rate adjustment section 31 is 50 or more, Q2 can always obtain the set amount regardless of changes in Pl. be.

Therefore, in the vicinity of the design target opening of 50φ, even if the primary pressure P1 changes by adjusting the opening of the flow rate adjustment section 31, the set flow rate Q2 is almost proportional to the opening of the flow rate adjustment section 31. It is something that can be controlled.

The embodiment shown in FIG. 1 has a so-called slide spool type pressure compensating valve 2, but the embodiment shown in FIG. 2 has a spool 22.
This shows a structure in which the primary ball pressure receiving surface 27 is made into a sheet type so as to directly face the discharge passage of the pump, and the area A1 of the primary ball pressure receiving surface 27 is larger than the area A2 of the secondary pressure receiving surface 28.

As shown above, in the present invention, the area AI of the primary ball pressure receiving surface 27 buttoned on the spool 22 of the pressure compensating valve 2 is made larger than the area A2 of the secondary pressure receiving surface 28, so that the sudden pressure receiving surface 27 and the secondary ball pressure receiving surface 27 A force resisting the axial thrust F is generated by the primary pressure P1 applied to the area difference ΔA with the pressure receiving pressure surface 28.

The force resisting this axial thrust F is determined by selecting the area difference △A and setting the design target to be the average flow rate that is used most often in the actuator, and set the design target to, for example, 50% of the rated opening as shown in Figure 4. Therefore, no matter how the primary pressure P1 changes in the vicinity of the rated opening of 50, the differential pressure before and after the flow rate adjustment section 31 is always kept constant, and the flow rate Q2 supplied to the actuator is controlled by the flow rate adjustment section 31. It is possible to perform control corresponding to the opening degree of the opening.

Therefore, compared to the conventional spool 220 in which the pressure-receiving areas are the same at both ends and only excessive flow occurs regardless of the opening degree of the flow rate adjusting section 31 as shown in FIG. 5, the characteristics can be improved and the overall Since the error between the set opening degree and the flow rate can be reduced, control accuracy can be significantly improved.

Moreover, since the flow control valve of the present invention is of a meter-in type, there is an effect that the flow rate supplied to the actuator 4 does not change even if the discharge amount of the pump 1 changes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention, FIG. 2 is an explanatory diagram of another embodiment, FIG. 3 is an explanatory diagram of a conventional example, and FIGS. 4 and 5 are a cross-sectional view of the present invention and a conventional example. This is a characteristic comparison chart. 2...Pressure compensation valve, 3...Flow rate adjustment valve, 21...
Pilot passage, 25...pressure control variable orifice,
27... - thrust pressure receiving surface, 28... secondary pressure receiving surface, 31
...Flow rate adjustment section, 32...Feedback passage.

Claims (1)

[Claims] 1. A flow rate adjustment valve 3 equipped with a flow rate adjustment section 31 is provided in the supply line of the actuator 4, and a normally closed pressure compensation valve 2 is interposed between the supply line in front of the flow rate adjustment valve 3 and the tank 26. The front side of the flow rate adjusting section 31 is communicated with the primary ash pressure receiving surface 27 on the side opposite to the spring of the spool 220 in the pressure compensating valve 2, and the spool 22
The rear part of the flow rate adjustment part 31 is communicated with the secondary pressure receiving surface 28 corresponding to the spring side in the spool 22, and the area A1 of the primary ash pressure receiving surface 27 in the spool 22 is made larger than the area A2 of the secondary pressure receiving surface 28. A flow control valve characterized in that: