solenoid valve

Abstract

To secure flat suction characteristics of a fixed iron core in a wide range even if a moving core moves in an axial direction, concerning an electromagnetic valve in which the fixed iron core attracts the moving core in the axial direction by magnetic force of a coil.SOLUTION: A solenoid valve 1 includes a coil 2, a core body 11 having the coil 2 arranged outside, and a valve 4 opposed to the core body 11 in a reciprocating manner on the same axis. The solenoid valve 1 is configured such that the core body 11 attracts the valve 4 in an axial direction by magnetic force generated by the coil 2 in order to reciprocate the valve 4. The core body 11 has a bore 11b therein, and the valve 4 is disposed so as to be movable in the axial direction so that at least a part of the valve enters and exits the bore 11b. Holding means is provided to keep a constant area where an inner periphery of the bore 11b and an outer periphery of the valve 4 closely face each other when the inner circumference of the boa 11b and the outer periphery of the valve 4 oppose accompanying movement in the axial direction of the valve 4. The holding means is a recessed portion 4c provided on the outer periphery of the valve 4.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a solenoid valve configured such that a fixed core attracts a movable core in the axial direction by a magnetic force generated by a coil to cause the movable core to reciprocate. [Background technology]

[0002] A known example of this type of technology is the "linear solenoid" described in Patent Document 1 below. This linear solenoid includes a coil, a fixed core disposed within the coil, and a movable core coaxially opposed to the fixed core. The fixed core has a first attraction portion formed at its end facing the movable core with a tapered recess that widens toward the movable core, and an annular second attraction portion disposed closer to the movable core than the first attraction portion. The second attraction portion has a cylindrical inner circumferential surface that is continuous with the tapered surface of the recess. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-277327 Summary of the Invention [Problem to be solved by the invention]

[0004] In the linear solenoid described in Patent Document 1, when the movable core enters the recess of the fixed core, the axial attractive force acting on the movable core increases, compensating for the effect of the magnetic force acting in the radial direction of the movable core. That is, when the movable core enters the recess of the fixed core, the magnetic force acting in the radial direction of the movable core increases, while the magnetic force acting in the axial direction of the movable core also increases. The balance between these two magnetic forces creates a region where the fixed core has a flat attractive force characteristic relative to the movable core. However, in the linear solenoid, the attractive force of the fixed core increases when the movable core is too close to the fixed core and decreases when it is too far away. That is, the attractive force of the fixed core is affected by the displacement of the movable core. As a result, the flat attractive force of the fixed core is limited to a narrow range.

[0005] This disclosed technology has been made in consideration of the above circumstances, and its purpose is to ensure, in a solenoid valve configured so that the fixed core attracts the movable core in the axial direction by the magnetic force generated by a coil, flat attraction characteristics of the fixed core over a wide range regardless of axial movement (displacement) of the movable core. [Means for solving the problem]

[0006] In order to achieve the above object, the technology described in claim 1 provides a solenoid valve including a coil that generates a magnetic force when energized, a fixed core around which the coil is disposed, and a movable core that is opposed to the fixed core and capable of reciprocating coaxially, and in which the fixed core attracts the movable core in the axial direction by the magnetic force generated by the coil to cause the movable core to reciprocate, the fixed core having a bore therein, the movable core being disposed so as to be movable in the axial direction so that at least a portion of the movable core enters and leaves the bore, and when the outer periphery of the movable core faces the inner periphery of the bore as the movable core moves in the axial direction, a holding means is provided for maintaining a constant area of close facing between the inner periphery of the bore and the outer periphery of the movable core. The holding means is a non-magnetic body provided on the outer periphery of the movable core so that the exposed area of the outer periphery of the movable core facing the inner periphery of the bore is constant. The purpose of this is to

[0007] According to the configuration of the above technology, the movable core faces the fixed core coaxially and reciprocally, and to reciprocate the movable core, the fixed core attracts the movable core in the axial direction by magnetic force generated by a coil. Here, the movable core is arranged to be movable in the axial direction so that at least a portion of it enters and exits the bore of the fixed core, and a portion of the outer periphery of the movable core forms a magnetic circuit with the fixed core. Then, when the outer periphery of the movable core faces the inner periphery of the bore as the movable core moves in the axial direction, a holding means keeps the close facing area between the inner periphery of the bore and the outer periphery of the movable core constant at that facing point, regardless of the movement of the movable core. Therefore, the magnetic force flowing from the movable core to the fixed core is kept constant regardless of the axial movement (displacement) of the movable core. Furthermore, regardless of the movement of the movable core, the area of the outer periphery of the movable core exposed to the inner periphery of the bore is kept constant by the non-magnetic material, thereby blocking the flow of magnetic force from the movable core to the fixed core. [Effects of the Invention]

[0014] According to the technology described in claim 1, in a solenoid valve configured such that the fixed core attracts the movable core in the axial direction by the magnetic force generated by the coil, it is possible to ensure a flat attraction characteristic of the fixed core over a wide range regardless of the movement (displacement) of the movable core in the axial direction. In addition, stable attraction characteristics of the fixed iron core can be ensured. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 2 is a cross-sectional view showing the solenoid valve according to the first embodiment. [Figure 2] 2 is an enlarged cross-sectional view showing the vicinity of a ring in the solenoid valve of FIG. 1 according to the first embodiment. [Figure 3] 3 is a further enlarged cross-sectional view showing the vicinity of the upper end of the valve in FIG. 2 according to the first embodiment. [Figure 4] 5A to 5C are cross-sectional views showing a stepwise movement process of the valve in the first embodiment. [Figure 5] 5A to 5C are cross-sectional views showing a stepwise movement process of the valve in the first embodiment. [Figure 6] 5A to 5C are cross-sectional views showing a stepwise movement process of the valve in the first embodiment. [Figure 7] 5A to 5C are cross-sectional views showing a stepwise movement process of a valve according to a comparative example of the first embodiment. [Figure 8] 5A to 5C are cross-sectional views showing a stepwise movement process of a valve according to a comparative example of the first embodiment. [Figure 9] 5A to 5C are cross-sectional views showing a stepwise movement process of a valve according to a comparative example of the first embodiment. [Figure 10] 5 is a graph showing an image of the suction force characteristics of the valve by the core body in the first embodiment. [Figure 11] 5 is a graph showing an image of the suction force characteristics of the valve by the core body in the first embodiment. [Figure 12] 10 is a graph showing an image of the suction force characteristics of the valve by the core body, in a comparative example of the first embodiment. [Figure 13] 10 is a graph showing an image of the suction force characteristics of the valve by the core body, in a comparative example of the first embodiment. [Figure 14] 4 is a cross-sectional view equivalent to FIG. 3 showing the vicinity of the upper end of the solenoid valve according to a modified example of the first embodiment. [Figure 15] 4 is a cross-sectional view equivalent to FIG. 3 showing the vicinity of the upper end of the solenoid valve according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] First Embodiment A first embodiment of a solenoid valve will be described in detail below with reference to the drawings.

[0020] [Solenoid valve configuration] 1 shows a cross-sectional view of a solenoid valve 1 of this embodiment. This solenoid valve 1 includes a coil 2 that generates a magnetic force when energized, a substantially cylindrical stator core 3 on the outside of which the coil 2 is arranged and which has bores 11b and 12a on the inside, and a substantially cylindrical valve 4 that is arranged coaxially with the stator core 3 and can reciprocate. The coil 2 is covered by a resin casing 5, and the outside of the casing 5 is covered by a yoke 6 made of a magnetic material. A connector 7 for power supply is formed in a part of the casing 5.

[0021] The stator core 3 is made of a magnetic material and is composed of a core body 11 located at the top of Figure 1 and a cylindrical body 12 extending coaxially downward from the core body 11. The core body 11 has a center hole 11a extending axially and a bore 11b connected to the center hole 11a, while the body 12 has a bore 12a extending axially. The valve 4 is made of iron, a magnetic material, and has a center hole 4a and a tip hole 4b extending from the center hole 4a to a valve seat 14. A ring 13 made of a non-magnetic material is disposed between the core body 11 and the body 12. The core body 11 and the body 12 are connected by the ring 13, and the adjacent inner circumferences have the same inner diameter but are divided by the ring 13 to form a recess. The valve 4 opposes the core body 11 coaxially and is capable of reciprocating. In this embodiment, core body 11 is made of iron and corresponds to an example of a fixed iron core in the disclosed technology, and valve 4 corresponds to an example of a movable iron core in the disclosed technology. A valve seat 14, on which valve 4 can be seated, is disposed at the lower end of body 12 in a position opposite the lower end of valve 4. Valve seat 14 has a valve hole 14a and is made of a non-magnetic material. A spring 15 is provided between the upper end of valve 4 and the lower end of core body 11 to bias valve 4 in a direction to seat valve 4 on valve seat 14 (valve closing direction). When coil 2 is energized, this solenoid valve 1 forms a magnetic circuit 16 between components 4, 6, 11, and 12, as shown by the dashed lines in FIG. 1 .

[0022] This solenoid valve 1 is configured such that the stator core 3 (core body 11) attracts the valve 4 in the axial direction due to the magnetic force generated by the coil 2, causing the valve 4 to reciprocate. That is, when the solenoid valve 1 is opened, the magnetic force generated by the coil 2 causes the stator core 3 (core body 11) to attract the valve 4 in the axial direction against the biasing force of the spring 15. As a result, the valve 4 moves away from the valve seat 14 (opening), and the valve orifice 14a is opened. In this open state, the valve orifice 14a communicates with the center hole 4a of the valve 4 and the bore 11b and center hole 11a of the core body 11, allowing fluid to flow through the flow path. When the solenoid valve 1 is closed, the magnetic force generated by the coil 2 is stopped, and the attraction of the valve 4 by the stator core 3 (core body 11) is stopped. As a result, the biasing force of the spring 15 causes the valve 4 to seat on the valve seat 14 (closing), and the valve orifice 14a is closed. This solenoid valve 1 constitutes a linear solenoid valve in that it reciprocates a valve 4 relative to a stator core 3 (core body 11).

[0023] In this embodiment, the bore 11b of the core body 11 has an inner diameter that is divided into two stages, one large and one small. The valve 4 is arranged so that its upper end (see FIG. 1) can move axially in and out of the bore 11b. This solenoid valve 1 is provided with a retaining means for maintaining a constant close-facing area between the inner periphery of the bore 11b and the outer periphery of the valve 4 when the outer periphery of the upper end of the valve 4 faces the inner periphery of the bore 11b as the valve 4 moves axially.

[0024] [Regarding retention means] The solenoid valve 1 of this embodiment, which is a linear solenoid valve, is configured as a composite type of a cylinder type (a type in which the valve 4 is housed in the core body 11) and an opposed magnetic pole type (a type in which the valve 4 is axially opposed to the core body 11). The proportional range (a range in which the attractive force characteristic is flat relative to the displacement of the valve 4) obtained by this composite type is inherently limited. Therefore, in this embodiment, in order to be able to expand the range in which the attractive force characteristic is flat relative to the displacement of the valve 4, the holding means is specified as follows.

[0025] FIG. 2 is an enlarged cross-sectional view of the solenoid valve 1 of FIG. 1, showing the vicinity of the ring 13. FIG. 3 is a further enlarged cross-sectional view of the vicinity of the upper end of the valve 4 of FIG. 2. In this embodiment, as shown in FIGS. 2 and 3, the retaining means is constituted by a recess 4c provided on the outer periphery of the tip of the valve 4. That is, as shown in FIG. 3, the outer periphery of the tip of the valve 4 has an edge surface 4d adjacent to its edge that can face the inner periphery of the bore 11b of the core body 11, and a recess 4c continuing from the edge surface 4d. This edge surface 4d forms a closely facing surface where the inner periphery of the bore 11b and the outer periphery of the valve 4 face each other closely. In contrast, with the recess 4c, although the outer periphery of the valve 4 can face the inner periphery of the bore 11b, it is separated from the inner periphery of the bore 11b by the depth D1 of the recess 4c (see FIG. 3), forming a magnetic gap and not in close proximity. In this embodiment, the length L1 (see FIG. 3) of the recess 4c in the axial direction of the valve 4 is set to approximate the length of movement (displacement) of the valve 4 in that axial direction.

[0026] [About the action and effect of solenoid valves] According to the configuration of the solenoid valve 1 of this embodiment described above, the valve 4 faces the core body 11 coaxially and reciprocally, and to reciprocate the valve 4, the core body 11 is configured to attract the valve 4 in the axial direction by the magnetic force generated by the coil 2. Here, the valve 4 is arranged so that its upper end (see FIG. 1) can move axially in and out of the bore 11b of the core body 11, and a part of the outer periphery of the upper end of the valve 4 forms a magnetic circuit 16 with the core body 11. Then, when the outer periphery of the valve 4 faces the inner periphery of the bore 11b as the valve 4 moves axially, the recess 4c (retaining means) keeps the close facing area between the inner periphery of the bore 11b and the outer periphery of the valve 4 constant at that facing point regardless of the movement of the valve 4.

[0027] In FIGS. 1 to 3, the valve 4 moves upward due to the suction of the core body 11. FIGS. 4 to 6 show the stepwise movement of the valve 4 in cross-section. FIG. 4 shows the closed state of the valve 4 shown in FIGS. 1 to 3. FIG. 5 shows the state in which the valve 4 has moved upward by "X (X is a predetermined value) (mm)" from the closed state. FIG. 6 shows the state in which the valve 4 has moved upward by "X + α (α is a predetermined value smaller than X) (mm)" from the closed state. As shown in FIGS. 4 to 6, the outer periphery of the tip (upper end) of the valve 4 faces the inner periphery of the bore 11b of the core body 11 as the valve 4 moves. However, the only surface of the outer periphery that faces closely with the inner periphery of the bore 11b is the edge surface 4d. In other words, even when the valve 4 moves upward, the recessed portion 4c does not face closely with the inner periphery of the bore 11b. The area of close contact between the edge surface 4d of the valve 4 and the inner periphery of the bore 11b remains constant regardless of the axial movement (displacement) of the valve 4. Therefore, as shown by the dashed arrows in Figures 4 to 6, the magnetic force flowing from the valve 4 to the core body 11 remains constant regardless of the axial movement (displacement) of the valve 4. For this reason, in this embodiment, for the solenoid valve 1 configured so that the core body 11 attracts the valve 4 in the axial direction by the magnetic force generated by the coil 2, it is possible to ensure a flat attraction characteristic of the core body 11 over a wide range regardless of the axial movement (displacement) of the valve 4.

[0028] 7 to 9 show cross-sectional views of a comparative example of this embodiment that does not have a retaining means (recess 4c) and illustrates the stepwise movement process of valve 4. FIG. 7 shows the closed state of valve 4, FIG. 8 shows the state where valve 4 has moved upward by "X (mm)" from the closed state, and FIG. 9 shows the state where valve 4 has moved upward by "X + α (mm)" from the closed state. As shown in FIGS. 7 to 9, the outer periphery of the tip (upper end) of valve 4 closely faces the inner periphery of bore 11b over the entire portion of valve 4 that is immersed in bore 11b as valve 4 moves. The area of close facing between the outer periphery of valve 4 and the inner periphery of bore 11b increases as valve 4 moves (displaces) in the axial direction. Therefore, as indicated by the dashed arrows in FIGS. 7 to 9, the magnetic force flowing from valve 4 to core body 11 increases as valve 4 moves (displaces) in the axial direction. Therefore, in this comparative example, the suction force of the core body 11 changes due to the axial movement (displacement) of the bulb 4, and the flat suction characteristics of the core body 11 cannot be ensured.

[0029] 10 and 11 are graphs showing the attractive force characteristics of the valve 4 using the core body 11 of this embodiment. Meanwhile, FIGS. 12 and 13 are graphs showing the attractive force characteristics of the valve 4 using a comparative core body 11. In FIGS. 10 and 12, the horizontal axis represents the valve stroke, and the vertical axis represents the attractive force (of the core body 11) and the current value (of the coil 2). In FIGS. 11 and 13, the horizontal axis represents the current value (of the coil 2), and the vertical axis represents the valve stroke (fluid flow rate). In FIGS. 10 to 13, the relationship between the attractive force of the core body 11 and the attractive force required to move the valve 4 is plotted using black dots.

[0030] As shown in Figures 12 and 13, in the comparative example, the slope of the valve stroke (flow rate) decreases as the current value increases. In contrast, as shown in Figures 10 and 11, in this embodiment, the decrease in suction force due to an increase in the valve stroke is suppressed, and therefore the decrease in the slope of the valve stroke (flow rate) due to an increase in the current value is suppressed.

[0031] Furthermore, according to the configuration of this embodiment, the holding means is formed simply by providing a recess 4c on the outer periphery of the valve 4. As a result, the processing of the valve 4 to form the holding means can be simplified.

[0032] [Modification of the first embodiment] A modification of the first embodiment will now be described. Fig. 14 shows a cross-sectional view similar to Fig. 3 of the vicinity of the upper end of the valve 4 of the solenoid valve 1 according to this modification. In the first embodiment, a recess 4c is provided on the outer periphery of the tip of the valve 4 as a retaining means. However, as a modification, as shown in Fig. 14, a non-magnetic body 21 can be provided in the recess 4c. That is, the non-magnetic body 21 is provided on the outer periphery of the valve 4 so that the area of the outer periphery of the tip of the valve 4 that faces the inner periphery of the bore 11b of the core body 11 is constant. The non-magnetic body 21 can be made of steel, cast iron, copper, aluminum, or an alloy thereof.

[0033] [Operation and effect of the modified solenoid valve] In addition to the effects and advantages of the first embodiment, the configuration of this modification provides the following effects and advantages. That is, in this modification, regardless of axial movement of the valve 4, the area of the outer periphery of the valve 4 exposed to the inner periphery of the bore 11b of the core body 11 is kept constant by the non-magnetic body 21. Therefore, the flow of magnetic force from the valve 4 to the core body 11 is blocked by the non-magnetic body 21. This ensures stable attraction characteristics of the core body 11.

[0034] Second Embodiment Next, a second embodiment of the solenoid valve will be described in detail with reference to the drawings. In the following description, the same components as those in the first embodiment will be given the same reference numerals and will not be described again, and the following description will focus on the differences.

[0035] [Regarding retention means] This embodiment differs from the first embodiment in the configuration of the retaining means. FIG. 15 is a cross-sectional view similar to FIG. 3 showing the vicinity of the upper end of the valve 4 in the solenoid valve 1 of this embodiment. As shown in FIG. 15, in this embodiment, the retaining means is formed by a recess 11c provided on the inner periphery of the bore 11b of the core body 11. That is, as shown in FIG. 15, no recess 4c is provided on the outer periphery of the valve 4. Instead, the inner periphery of the bore 11b of the core body 11 has an edge surface 11d adjacent to its open end that can face the outer periphery of the tip of the valve 4, and a recess 11c continuing from the edge surface 11d. This edge surface 11d forms a closely facing surface where the outer periphery of the valve 4 and the inner periphery of the bore 11b face each other closely. In contrast, in the case of the recess 11c, the inner periphery of the bore 11b can face the outer periphery of the valve 4, but is separated from the outer periphery of the valve 4 by the depth of the recess 11c, forming a magnetic gap and not in close proximity. In this embodiment, the length of the recess 11c in the axial direction of the bore 11b is set to approximate the length of movement (displacement) of the valve 4 in that axial direction.

[0036] [About the action and effect of solenoid valves] According to the configuration of the solenoid valve 1 of this embodiment described above, unlike the first embodiment, the holding means is configured simply by providing a recess 11c on the inner periphery of the bore 11b of the core body 11. Therefore, the processing of the core body 11 to configure the holding means can be simplified.

[0037] <Another embodiment> The disclosed technology is not limited to the above-described embodiments, and can be implemented by appropriately modifying part of the configuration within the scope of the disclosed technology.

[0038] (1) In the modified example of the first embodiment, the non-magnetic material 21 is provided in a recess 4c provided on the outer periphery of the bulb 4. However, it is also possible to coat the outer periphery of the bulb with a film of a non-magnetic material or to demagnetize the outer periphery of the bulb without forming a recess on the outer periphery of the bulb.

[0039] (2) In the second embodiment, a recess 11c is provided on the inner periphery of the bore 11b of the core body 11 as a retaining means. However, it is also possible to provide a non-magnetic material in this recess 11c, or to coat the inner periphery of the bore of the core body with a non-magnetic film, or to demagnetize the inner periphery of the bore without providing a recess on the inner periphery of the bore.

[0040] (3) In the above embodiments, the stator core 3 is made up of a plurality of parts, namely the core body 11, the body 12, and the ring 13. However, the stator core can also be made up of a single part. [Industrial Applicability]

[0041] The disclosed technology can be used in linear solenoid type electromagnetic valves used to control fluid flow rates. [Explanation of symbols]

[0042] 1 solenoid valve 2 coils 4 valves (moving iron core) 4c Recess (holding means) 4d edge surface 11 Core body (fixed iron core) 11b Bore 11c Recess (holding means) 11d Edge surface 21 Non-magnetic material

Claims

[Claim 1] A coil that generates magnetic force when energized; a fixed core on the outside of which the coil is disposed; a movable iron core that is coaxially opposed to the fixed iron core and capable of reciprocating; and a solenoid valve configured such that the fixed core attracts the movable core in the axial direction by a magnetic force generated by the coil, so as to reciprocate the movable core, the fixed core has a bore therein, and the movable core is arranged to be movable in the axial direction so that at least a portion of the movable core enters and leaves the bore; a holding means for keeping constant a close opposing area where the inner periphery of the bore and the outer periphery of the movable iron core closely face each other when the outer periphery of the movable iron core faces the inner periphery of the bore as the movable iron core moves in the axial direction, The holding means is a non-magnetic material provided on the outer periphery of the movable core so as to keep constant the exposed area of the outer periphery of the movable core facing the inner periphery of the bore. A solenoid valve characterized by:

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