JPS6146295Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a relief valve such as a balance piston type for hydraulic pressure.

Conventionally, in this type of relief valve, the structure of the contact part (seating part) between the main spool as a balance piston and its seat has generally been
It is as shown in the figure.

To briefly explain its structure with reference to the same figure,
The spool 1 is slidably and loosely fitted inside the body 2 of the relief valve, and has an annular plane 1a perpendicular to the sliding direction formed at one end of the spool 1, and is pressed forward by a main spring 3.

On the other hand, a seat 4 whose outer circumferential edge of the annular plane 1a of the spool 1 is pressed by the main spring 3 into line contact is fixed to one end of the body 1 by press fitting or the like, and its contact surface with the spool 1 is a conical surface. ing. Further, a large distance S is provided between the main passage hole 2a provided in the body 1 and the outer circumference 1e of the spool 1.

In such a configuration, when the main pressure P is smaller than a predetermined value, the force of the main spring 3 causes the outer circumferential edge of the annular plane 1a of the spool 1 to make annular line contact with the conical surface of the seat 4, so that the port "P" ，
When the poppet seal between "T" is performed and the main pressure P becomes larger than a predetermined value, the spool 1 retreats against the main spring 3, and the port "P"→
A relief flow occurs in the direction of "T".

However, with such a conventional poppet seal relief valve structure, stability during relief at cracking pressure is poor, and the relief flow becomes vibratory, making it extremely difficult to apply to minute flow rates.

This invention was made in view of the above points, and aims to improve the stability of a relief valve using a poppet seal during relief, and to provide a relief valve that can be applied to minute flow rates.

Therefore, the relief valve according to this invention is provided with a spool that slides within the body to open and close the main passage hole, and a seat that is pressed against the spool, in a body in which a main passage hole is formed. A poppet seal portion is formed by providing an annular edge on one of the opposing surfaces of the sheet and an annular surface in line contact with the annular edge on the other side, and in a sealed state by the poppet seal portion, the spool is The above object is achieved by closing the main passage hole and positioning it at a sliding position that slightly overlaps the inner peripheral surface of the body.

An embodiment of this invention will be described below with reference to FIGS. 2 to 6, and parts corresponding to those in FIG. 1 are designated by the same reference numerals.

FIGS. 2 and 3 show a first embodiment of this invention. First, the overall structure of the balance piston type relief valve will be briefly explained with reference to FIG.

The spool 1 is slidably and loosely fitted inside a body 2 which has a main passage hole 2a and a drain hole 2b forming ports "T" and "D" communicating with the tank 15 on the outer periphery, and the spool 1 and the body 2 A main spring 3 is held in a compressed state between the main spring 3 and a pilot seat 5 having a through hole 5a fixed thereto, and the spool 1 is pressed against a seat 4 press-fitted to one end of the body 2. The pilot seat 5, together with the poppet 7 which is integrated with the spring receiver 6, controls the opening and closing of the pilot flow.

At the other end of the body 2, a cap 8 is attached to an O-ring 9.
A spring retainer 10 is attached to the end of the cap 8 with an O-ring 1.
The pilot spring 12 is engaged between the spring receiver 10 and the spring receiver 6 which is integrated with the poppet 7, and the poppet 7 is inserted into the pilot seat 5. is being pressed.

The pressure adjustment screw 13 screwed into the rear end of the cap 8 and in contact with the spring receiver 10 is rotated to move the spring receiver 10 forward and backward in the axial direction, thereby changing the pressing force of the pilot spring 12. Adjust the relief pressure to the required value using
In this state, tighten the pressure adjustment screw 13 and lock nut 14.
Fix it by.

Next, the poppet seal section formed by the spool 1 and the sheet 4 will be explained in detail with reference to FIG. It is formed in an annular plane 1a perpendicular to the sliding direction of the spool 1. On the other hand, the seating portion of the sheet 4 facing the annular plane 1a of the spool 1 is formed with an annular edge 4a that makes line contact perpendicularly to the annular plane 1a.

In addition, when the spool 1 and the seat 4 are in contact with each other and are poppet-sealed, the outer circumferential surface 1e of the spool 1 and the inner circumferential surface 2c of the body 2 with which the outer circumferential surface 1e is in sliding contact form a main passage leading to the port "T". Completely close the hole 2a and place the spool 1 in a slightly overlapping sliding position as shown by L in the figure.
is positioned.

With this configuration, while the main pressure P is lower than the set pressure Ps of the relief valve, the annular plane 1a of the spool 1 is in vertical line contact with the annular edge 4a of the seat 4 due to the main spring 3, and the port "P",
Between "T" is in a sealed state.

When the main pressure P rises and becomes higher than the set pressure Ps, the poppet 7 shown in FIG.
A pilot flow is generated in the direction of “P′” → “D”,
The pressure P' at the rear of the spool becomes smaller than the main pressure P, and a pressure difference P-P' is generated before and after the spool 1, and the spool 1 starts moving rearward.

However, in this state, the main passage hole 2a is still closed by the outer circumferential surface 1e of the spool 1 due to the overlap portion L between the outer circumferential surface 1e of the spool 1 and the inner circumferential surface 2c of the body 2, and the main flow does not occur. When the spool 1 retreats further and its displacement x becomes larger than the length of the overlap portion L, the main passage hole 2a begins to open, and a main flow is generated in the direction from port "P" to "T", resulting in a relief state. Become.

Now, the outer diameter of the spool 1 is a, the diameter of the seating part is b, the cross-sectional area of the spool 1 is A, the fluid force acting on the spool 1 due to the flow from port "P" to "T" is f, and the force of the main spring 3 is When the spring constant is k and the amount of displacement of the spool 1 is x, the following balance equation holds true during relief: (P-P')A-f=kx.

Conversely, when the main pressure P becomes lower than the set pressure Ps from the relief state, the poppet 7 shown in FIG. The pressure becomes P=P', and the spool 1 is pushed forward by the main spring 3. First, the overlap portion L of the spool 1 with respect to the main passage hole 2a seals the port "P" → "T", and then the spool 1 is seated on the seat 4 and completely seals between ports "P" and "T".

According to this configuration, since the overlap portion L is provided that closes the main passage hole 2a by the outer circumferential surface 1e of the spool 1 and the inner circumferential surface 2c of the body 2, the flow does not become vibratory at the time of relief. , stability is greatly improved. Therefore, it can be easily applied even in the case of minute flow rates.

In addition, by appropriately selecting the size, quantity, shape, etc. of the main passage hole 2a, ports "P", "T"
The stability can be improved by adjusting the flow rate gain by adjusting the amount of restriction between the two. Further, by adjusting the amount by which the sheet 4 is pushed in, for example, by inserting a shim between the front end surface 2d of the body and the flange portion 4e of the sheet 4 in FIG. 2, the amount of overlap can be adjusted optimally.

Moreover, since a poppet seal structure is used in addition to the overlap structure, the amount of overlap caused by the spool land can be extremely small.
Various performances such as override and response are also excellent.

According to this embodiment, the annular plane 1a of the spool 1 and the annular edge 4a of the sheet 4 are in vertical line contact to form a seal, so that the concentricity and roundness of the spool 1 and the sheet 4 are improved. In addition, the gap between the outer circumferential surface 1e of the spool 1 and the inner circumferential surface 2c of the body 2 can be minimized, and leakage when the valve is closed can be minimized.

Further, as shown in FIG. 3, since the spool outer diameter a is made equal to the seat outer diameter b, turning of the body 2 is extremely easy.

Next, in FIG. 4, the seating surface of the sheet 4 facing the spool 1 is an annular plane 4b perpendicular to the sliding direction of the spool 1, and the surface of the spool 1 facing the sheet 4 is in line contact perpendicular to the annular plane 4b. This figure shows a second embodiment of this invention in which an annular edge 1b is formed, and its operation and effect are exactly the same as those of the previous embodiment.

Further, FIG. 5 shows a third embodiment of this invention, in which the spool 1 is provided with an overlapping portion L similar to the previous embodiment, an annular edge 1f is formed on the spool 1, and the spool 1 of the sheet 4 is provided with an overlapping portion L similar to the previous embodiment. The seating surface in contact is a conical surface 4c.

Furthermore, FIG. 6 shows a fourth embodiment of this invention in which the relationship between the spool 1 and the seat 4 in the third embodiment is reversed, and the seat 4 is formed integrally with the body 2 and faces the spool 1. Annular edge 4 on the surface
d, and a conical surface 1g is formed on the spool 1.

In these two embodiments, the stability of the flow during relief can be ensured, and in particular, in the fourth embodiment, the inner circumferential surface 2c of the body 2 and the inner circumferential surface 4f of the seat 4 are simultaneously processed. As a result, the concentricity is significantly improved and the adhesion of the seating portion is improved.

Note that this invention is applicable not only to balance piston type relief valves but also to direct acting type relief valves.

As described above, according to this invention, the spool and its seat have a poppet seal structure, and when the poppet seal is in a sealed state, the spool closes the main passage hole formed in the body with its outer peripheral surface. Since the sliding position is positioned to slightly overlap the inner circumferential surface of the body, the poppet structure reduces leakage and provides good performance such as response and override. It has the excellent effect of eliminating vibration and greatly improving stability, making it possible to apply it even in the case of minute flow rates.

[Brief explanation of the drawing]

FIG. 1 is a partial cross-sectional view showing the main parts of a conventional balance piston type relief valve, FIG. 2 is a cross-sectional view showing the overall structure of the first embodiment of this invention, and FIG.
The figure is also a partial cross-sectional view showing the main part.
The figure is a partial sectional view showing the main part of the second embodiment of this invention, FIG. 5 is a partial sectional view showing the main part of the third embodiment of this invention, and FIG. 6 is a partial sectional view showing the main part of the third embodiment of this invention. Fourth
FIG. 3 is a partial cross-sectional view showing the main parts of the embodiment. 1...Spool, 2...Body, 2a...Main passage hole, 3...Main spring, 4...Seat, 5...Pilot seat, 7...Poppet,
8...Cap, 12...Pilot spring, 13...Pressure adjustment screw, L...Overlap part.

Claims (1)

[Scope of utility model registration request] A spool that slides within the body to open and close the main passage hole is provided in a body in which a main passage hole is formed, and a seat that is pressed against the spool,
An annular edge is provided on one of the opposing surfaces of the spool and the seat, and an annular surface that is in line contact with the annular edge is provided on the other side to form a poppet seal portion, and
In the sealed state by the poppet seal portion, the spool closes the main passage hole with its outer peripheral surface and is positioned at a sliding position slightly overlapping with the inner peripheral surface of the body. relief valve.