JPH0362921B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides a method for guiding a spool in a spool hole of a housing of a directional control valve so that it slides without leakage.
At least two axially adjacent chambers are formed within the spool bore, the chambers having a ridged bore section therebetween, in which the land of the spool controls the connection of the chambers on both sides, The present invention relates to a hydraulic directional control valve in which the land passes through at least one fine control recess and a relief annular groove surrounding the land and forming a pressure balancing surface.

[Conventional technology]

Such a directional control valve is known from DE 27 17 384 A1, in which the spool of the main control stage guided in the spool bore has a fine control recess and a pressure balancing annular groove in the land. . The land controlling the connection from the motor chamber to the inlet or return chamber is provided with these relief grooves serving the pressure balancing ring only in the area of the motor chamber;
Control notches useful for fine control are formed in the lands on both sides. A disadvantage of this construction of the spool is that in the area of the control notch of the plunger a relatively large surface is formed which does not balance the pressure, increasing the frictional forces exerted on one side of the spool. Even though the spool has control notches to aid in fine control, directional control valves are not well suited for large flow rates and the spool requires large operating forces.

Furthermore, the Federal Republic of Germany patent application publication no.
In the hydraulic directional control valve known from specification 2919109,
The surfaces provided on the walls of the spool and spool hole for mutual contact are precision machined to form the spool and spool hole with very close manufacturing tolerances. Despite careful manufacturing, unavoidable small deviations occur between the cylindrical peripheral part of the spool and the bore wall, forming a flattened pressure pocket into which the pressure medium enters. The pressure of such a pressure pocket forces the opposite circumferential area of the spool firmly against the hole wall, resulting in a large frictional force resisting movement of the spool. As a result, the actuating force of the actuating electromagnet or of the return spring may no longer be sufficient for a reliable movement of the spool. To reduce such frictional forces, an annular relief groove is provided in the wall of the spool hole. Even with this provision of an annular relief groove, particularly large operating forces are generated if the spool remains stationary in a particular position for a long time. For sufficient reliability of the functioning of such directional control valves, the operating electromagnet and the spring must therefore be designed to be stronger and therefore larger than is originally necessary for regular operation. Furthermore, providing an annular relief groove in the inner wall of the housing is more expensive and therefore more expensive than providing such a groove in the outer wall of the spool. Furthermore, this directional control valve has the disadvantage that its spool does not have a fine control recess and is therefore not suitable for proportional control of small pressure medium quantities. Although the relief annular grooves in the housing improve hydraulic centering of the spool, even small pressure pockets are still formed in the wall portions between the relatively narrow relief grooves, increasing frictional forces.

Furthermore, an electromagnetically operated hydraulic directional control valve is known from Figure 10.38 on page 266 of the second edition of "Hydraulic power and its industrial applications" by Walter Ernts, published by McGraw-Hill in 1960. The land is provided with a relief annular groove and a control notch. This directional control valve operates with negative overlap, since in the initial position of the spool the motor chamber is simultaneously connected to the inlet and return chambers via a fine control notch in the spool. In this case, a part of the annular relief groove in the land is in the area of the motor chamber, so that in the initial position of the spool the annular relief groove cannot act at all. The other part of the relief groove in the area of the spool hole is traversed by a fine control notch and therefore cannot be fully activated.
Directional control valves are suitable for controlling small flow rates with the control notch, but this arrangement of the control notch and relief annular groove has the disadvantage that the relief annular groove has a detrimental effect on the flow characteristic curve. . That is, the relief groove exiting from the spool hole to the motor chamber creates a step-like bend in the flow rate characteristic curve. Therefore, the flow rate characteristic curve that extends continuously with a slight curve in such a control notch has abrupt discontinuities depending on the number of relief annular grooves exiting to the motor chamber, and these points have small flow rates. becomes disadvantageous when controlling. Furthermore, the ridge between the two relief annular grooves, after entering the spool hole, forms a pressure pocket which, when subjected to pressure, produces a radial force acting to one side and thus reduces friction. Enlarge.

[Problem that the invention aims to solve]

An object of the present invention is to provide a directional control valve that can further reduce the frictional force of the spool while maintaining the flow characteristics obtained by the fine control recess.

[Means to solve the problem]

In order to solve this problem, according to the invention, the fine control recess intersects only one relief annular groove in the axial direction of the spool, and the width of this relief annular groove in the axial direction of the spool is equal to its depth. The depth of this annular relief groove is very small, so that the course of the flow characteristic curve determined by the fine control recess is approximately maintained.

〔Effect of the invention〕

Thus, according to the invention, by forming the pressure balancing surface by a single relief annular groove that is as wide as possible in the axial direction and very shallow, a better centering of the spool is achieved and thus the operation When does the frictional force inside become so small? Just 1
The two relief annular grooves result in only one discontinuity (step bend) in the flow characteristic curve and are therefore very advantageous for small flow control by fine control recesses. Moreover, the very small depth of the annular relief groove is completely sufficient for the function of pressure equalization, while it does not have a detrimental effect on the flow characteristic curve. Furthermore, the pressure medium for pressure balance to the relief annular groove is supplied using a fine control recess, and there is no need to machine a special through hole in the spool for supplying this pressure medium, so the spool can be easily and inexpensively installed. Manufactured in

〔Example〕

Two embodiments of the invention are shown in the drawings,
This will be explained below.

FIG. 1 shows a part of a directional control valve 10 in which a spool 13 is fitted which is guided in a leak-tight manner into a spool hole 12 in a housing 11 of the valve. A first chamber 14 is formed in the spool hole 12, which is under high pressure, and axially adjacent thereto is a second chamber 15, in which a lower pressure level is present. Between the two chambers 14 and 15, the spool hole 12 is formed with a rib-like hole section 16 into which the land 17 of the spool 13 is guided in a leak-free manner.

The land 17 has a very wide and relatively flat relief annular groove 18, so that the land 17 has a
First control collar 19 closer to first chamber 14
and a second control collar 2 adjacent to the second chamber 15.
1 is formed. The control collars 19, 21 are precision machined and are therefore guided within the spool bore 12 with very close manufacturing tolerances. As fine control recesses, two control notches 22 are formed on the diameter of the land 17, which is also shown in detail in FIG. The maximum opening cross section of the control notch 22 faces the first chamber 14 and its tip faces the second control collar 21
, so that the control notch 22 completely intersects the relief annular groove 18. Control notch 22
The other circumferential surface of the relief annular groove 18 forms the actual pressure equalization surface 23 in the land 17. Since the relief annular groove 18 is designed as wide as possible, the guidance of the spool 13 within the spool 12 also ensures a leak-free separation between the chambers 14 and 15 by the second control collar 21. The depth of the relief annular groove 18 is selected to be small so that a pressure equalization via the annular groove 18 takes place, while the flow characteristic curve defined by the shape of the control recess 22 is hardly influenced. When the outer diameter of the spool 13 is approximately 12 mm, the depth of the relief annular groove 18 is approximately
It is 2.5mm/100th. The depth of the annular groove 18 is therefore shown exaggerated in FIG.

The operation of the directional control valve 10 according to FIG. 1 will be explained below, with reference also to FIG. The characteristic curve in FIG. 3 shows the flow rate Q with respect to the stroke S of the spool 13. In the illustrated cutoff position of the spool 13, the second control collar 21 prevents the connection between the chambers 14 and 15. The high pressure present in the first chamber 14 also occurs via the control cutout 22 in the relief annular groove 18 and centers the land 17. Therefore, in the area between the control collars 19 and 21 there is a land 17.
There is no longer a pressure equalization surface that presses the hole portion 16 radially to one side and increases the frictional force.
When land 17 is moved to the right, control notch 2
2 makes the connection from the first chamber 14 to the second chamber 15. Due to the shape of the control recess 22, a continuously curved characteristic curve 24 is obtained, as shown in FIG. In this case, when the edge between the second control collar 21 and the relief annular groove 18 enters the second chamber 15, a small bend occurs at the point 25 of the characteristic curve 24, but the course of the characteristic curve 24 remains almost unchanged. will be maintained. This is achieved, inter alia, by means of a relief annular groove 18, which has a depth of only a few hundredths of a millimeter, and which has only a slight influence on the effective flow cross section. Even if the stroke of the spool 13 increases, the spool hole 12
The centering of the land 17 within is maintained well.

In comparison to the structure of the invention according to FIGS. 1 to 3, FIG. 4 shows a characteristic curve 26 of a comparable known directional control valve. In this characteristic curve 26, step jumps are clearly visible at points 27, 28 and 29. These jumps occur each time one of a plurality of conventional relief annular grooves exits the spool hole into the chamber. Locations 27 to 29
Such a discontinuous feature in is avoided by providing and forming only one relief annular groove 18 as shown in FIG. The spool 1 is therefore guided with close tolerances in the spool hole 12.
3, there is less risk of pressure pockets being formed due to unavoidable small deviations in the finish and pressing the spool radially into the spool hole, thereby increasing frictional forces. The spool 13 can therefore be moved out of its position particularly easily and requires only low operating forces. The operating electromagnet and the return spring can therefore be designed small with constant reliability of function. Even if the spool 13 remains in its inactive position, the improved hydraulic centering allows the frictional forces to remain low. The directional control valve 10 is advantageously suitable for the control of small flow rates, since the course of the characteristic curve 24 caused by the shape of the fine control recess 22 is maintained and the only small discontinuity at point 25 poses little disturbance. There is.

FIG. 5 shows a second directional control valve 30 configured as a proportionally operated four-port directional control valve. Its housing 31 has an inflow chamber 3 as usual.
2, two motor chambers 33, 34, and return chambers 35, 36 connected to each other, and a spool hole 37 passes through these chambers. The spool 38 is guided so as to slide into the spool hole 37 without leaking.
In order to control the connection of these chambers 32 to 36, it has four lands 39, 41, 42, 43, each land 39 to 43 having two control notches 44 formed on its diameter, which serve as fine control recesses. ing. As in the directional control valve 10 according to FIG. 1, the control recesses 44 each intersect with a corresponding relief annular groove 45, which is designed as wide as possible and very flat. Each land 39 to 43
In the relief annular groove 45 the first control collar 46
is separated from the second control collar 47. Second
A third control collar 49 follows each of the control collars 47 via a relief groove 48 . The depth of this narrow relief groove 48 is significantly larger than the depth of the relief annular groove 45, and in particular, it is 10 times or more. Each land 3
The relief grooves 48 and the third control collar 49 located at 9 to 43 are such that in the initial position of the spool 38,
Outside the ridged hole portions 51 formed between the chambers 32 to 36, respectively. The spool 38 is held in its initial position by a return spring (not shown) and can be moved to either side via a push rod 52 by an electromagnet.

The operation of the directional control valve 30 is as follows. The directional control valve 30 can be used as a conventional proportionally operated four-port directional control valve, and the configuration and placement of the control notch 44 in the land of the spool 38 significantly reduces the frictional forces on the spool 38. However, due to the shape of the fine control recess 44, the flow rate characteristics can be maintained. For sufficient reliability of function, the return spring and the operating electromagnet can therefore be designed relatively small. This is because the operating force required to move the spool 38 can be reduced even in extreme cases.

It is of course possible to modify the illustrated embodiment without departing from the spirit of the invention. For example, instead of the illustrated triangular control recess, control recesses of different shapes, for example U-shaped or trapezoidal fine control recesses, can also be used. The depth of the relief annular groove can also be varied depending on various factors such as the size of the directional valve, the viscosity of the pressure medium and the pressure generated. For example, the diameter of spool 38 is 50
Point 2 of characteristic curve 24 in mm directional control valve
5, the depth of the annular relief groove 45 can be increased to 1/10 mm if a slightly larger inclination is tolerated. However, overall this depth remains below the value of 0.2 to 0.5% of the spool's outer diameter, and is therefore approximately equal to the depth of conventional relief grooves.
It's getting smaller by the 10th power.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a part of the first directional control valve according to the present invention, FIG. 2 is a cross-sectional view of the spool taken along the line - in FIG. 1, and FIG. FIG. 4 is a flow characteristic curve diagram of a known directional control valve, and FIG. 5 is a longitudinal sectional view of a second directional control valve. 10,30...Direction control valve, 11,31...Housing, 12,37...Spool hole, 13,3
8...Spool, 14, 15, 32-36...
Chamber, 16, 51... Hole part, 17, 39, 41,
42, 43... land, 18, 45... relief annular groove, 22, 44... fine control recess (control notch),
23...Pressure equilibrium surface.

Claims (1)

[Claims] 1. A spool is slidably guided in a spool hole of a housing of a directional control valve, and at least two axially adjacent chambers are formed in the spool hole, and a ridge is formed between these chambers. It has a hole section in which the land of the spool controls the connection of both chambers, and for this control the land has at least one fine control recess and a relief around the land that forms a pressure equalization surface. In those with an annular groove, the fine control recess 22, 44 intersects only one relief annular groove 18, 45 in the axial direction of the spool 13, 38, and this relief annular groove 18 in the axial direction of the spool 13 , 45 is several times its depth, and the depth of this relief annular groove 18 is very small, so that the course of the flow characteristic curve 24 determined by the fine control recess 22 is approximately A hydraulic directional control valve, characterized in that: 2. Directional control valve according to claim 1, characterized in that the fine control recesses are configured as control notches 22, 44. 3. characterized in that the length of the fine control recesses 22, 44 in the axial direction of the spools 13, 38 is equal to or larger than half of the lands 17, 39,
A directional control valve according to claim 1 or 2. 4 The individual lands 17, 19 are connected to the control collars 19, 2 by means of at least one relief annular groove 18, 45.
1, 46, 47, relief annular groove 18, 4
Lands 17, 39 having a width of 5 contact the hole portions 16, 51 in the initial position of the spools 13, 38.
Directional control valve according to claim 1, characterized in that the width of the control collar (19, 21, 46, 47) is equal to or greater than the width of the control collar (19, 21, 46, 47). 5 The fine control recesses 22 and 44 intersect with the first control collars 19 and 46 and the relief annular grooves 18 and 45 in order when viewed from the end faces of the lands 17 and 39, and the minimum flow cross section thereof intersects with the second control collars 21 and 45, respectively. 5. Directional control valve according to claim 4, characterized in that it ends in 47. 6. The directional control valve according to claim 1, characterized in that the depth of the relief annular grooves 18, 45 is smaller than about 0.2 to 0.5% of the spool diameter, and is several hundredths of a millimeter. 7 At the initial position of the spools 13, 38, only the control collars 19, 21, 46, 47 have hole portions 16, 51.
Directional control valve according to claim 4, characterized in that the fine control recesses 22, 44 completely or partially intersect the control collar.