Solenoid actuator

Abstract

To provide a solenoid actuator capable of efficiently transferring magnetic flux between a stator and a movable element.SOLUTION: A solenoid actuator 1 includes: a coil 3; a first stator 10 that includes a first yoke 14 and a cylindrical guide 30 fixed to an inner peripheral side of the first yoke 14; a second stator 20 which is arranged facing the first stator 10 in an axial direction so as to form a magnetic path 4 around the coil 3 together with the first stator 10; and a movable element 50 configured to move in the axial direction toward the second stator 20 from an original position radially inward of the first stator 10 by a magnetic force generated by energizing the coil 3. The cylindrical guide 30 includes: a magnetic tube 32 disposed in contact with an inner peripheral surface of the first yoke 14; and a non-magnetic layer 34 covering an inner peripheral surface of the magnetic tube 32. A minimum distance d1 between the second stator 20 and the magnetic tube 32 is greater than a minimum distance d2 between the second stator 20 and the movable element 50 at the original position.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a solenoid actuator.

Background Art

[0002] Conventionally, a solenoid actuator is known in which a stator that forms a magnetic path around a coil is arranged, and a mover is attracted by a magnetic force generated by energizing the coil, so that the mover can be moved in the axial direction.

[0003] For example, Patent Document 1 describes an electromagnetic actuator including a first stator provided on the stroke start position (original position) side of a mover and a second stator provided on the stroke end position side of the mover. In the electromagnetic actuator described in Patent Document 1, in order to realize flat attraction characteristics over the entire stroke length of the mover, the outer shapes of the mover and the first stator are devised. Specifically, as the mover moves toward the stroke end position side, a tapered portion is provided on the outer peripheral surface of the mover so as to narrow the gap between the first stator and the mover. On the other hand, a convex curved surface is provided at the end of the first stator on the second stator side so as to widen the gap between the first stator and the mover.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, it is required that a solenoid actuator realizes high thrust without sacrificing compactness. Therefore, it is desirable to improve the shapes of the stator and the mover so that magnetic flux can be efficiently transferred between the stator and the mover. In this regard, Patent Document 1 proposes improvements to the external shape of the movable element and the first stator in order to achieve flat attraction characteristics, but there is still room for improvement in terms of the efficiency of magnetic flux transfer between the stator and the movable element.

[0006] In view of the above circumstances, at least some embodiments of the present invention aim to provide a solenoid actuator capable of efficiently transferring magnetic flux between a stator and a movable element. [Means for solving the problem]

[0007] [1] Some embodiments of the present invention include solenoid actuators, Coil and, A first stator including a first yoke and a cylindrical guide fixed to the inner circumference of the first yoke, A second stator is positioned opposite the first stator in the axial direction so as to form a magnetic path together with the first stator around the coil, A movable element configured to move axially toward the second stator from its original position radially inward of the first stator by the magnetic force generated by energizing the coil, Equipped with, The cylindrical guide is A magnetic cylinder provided in contact with the inner circumferential surface of the first yoke, A non-magnetic layer covering the inner surface of the magnetic cylinder, Includes, The minimum distance d1 between the magnetic cylinder of the cylindrical guide and the second stator is greater than the minimum distance d2 between the movable element and the second stator in the original position.

[0008] [2] In some embodiments, in the configuration of [1] above, The cylindrical guide extends axially beyond the tip of the first yoke towards the second stator.

[0009] [3] In some embodiments, in the configuration of [1] or [2] above, In its original position, the movable element extends axially beyond the tip of the cylindrical guide toward the second stator.

[0010] [4] In some embodiments, in any of the configurations described in [1] to [3] above, The tip of the movable element overlaps with the second stator in the axial direction in its original position.

[0011] [5] In some embodiments, in any of the configurations [1] to [4] above, The cylindrical guide extends axially to the rear end of the movable element in its original position, or beyond the rear end of the movable element to the side opposite the second stator.

[0012] [6] In some embodiments, in any of the configurations [1] to [5] above, The first yoke has a first through hole into which a cylindrical guide is press-fitted, The inner wall of the first through hole is The contact area with the outer surface of the magnetic cylinder, In the axial direction, a non-contact region is located adjacent to the contact region on the opposite side of the second stator, and Includes, The diameter of the first through-hole is the same in the contact area and the non-contact area. [Effects of the Invention]

[0013] According to at least some embodiments of the present invention, the magnetic flux transferred between the movable element in its original position and the first yoke or second stator can be increased, and the magnetic transfer between the movable element in its original position and the first yoke and second stator can be effectively performed. This makes it possible to realize a compact and high-thrust solenoid actuator. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic cross-sectional view showing the configuration of a solenoid actuator according to one embodiment. [Figure 2] This is a cross-sectional view showing the detailed structure of a solenoid actuator in the magnetic flux transfer region between the stator and the movable element according to one embodiment, showing the movable element in its original position. [Figure 3] FIG. 88 is a cross-sectional view showing a detailed structure of a solenoid actuator in a magnetic flux transfer region between a stator and a mover, showing a state where the mover is in an intermediate position. [Figure 4] FIG. 89 is a cross-sectional view showing a detailed structure of a solenoid actuator in a magnetic flux transfer region between a stator and a mover, showing a state where the mover is in a maximum stroke position. [Figure 5] FIG. 90 is a cross-sectional view showing a solenoid actuator according to an embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described as embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0016] FIG. 1 is a cross-sectional view schematically showing the configuration of a solenoid actuator according to an embodiment. In FIG. 1, illustration of the resin mold of the solenoid actuator is omitted. Also, although the magnetic path 4 is shown only for one side (the left side portion in the figure) of the coil 3, similar magnetic paths 4 are formed on both sides (the right side portion in the figure) of the annularly provided coil 3.

[0017] In some embodiments, as shown in FIG. 1, the solenoid actuator 1 includes a coil 3, stators 10 and 20 for forming a magnetic path 4 around the coil 3, and a mover 50 that is axially movable by the magnetic force generated by the coil 3.

[0018] Coil 3 is constructed by winding a wire made of a conductor such as copper or a copper alloy around the central axis O of the solenoid actuator 1. Coil 3 as a whole is roughly annular with respect to the central axis O. Terminals (not shown) are electrically connected to coil 3, and power is supplied to coil 3 through these terminals. When coil 3 is energized, a magnetic force is generated to attract the movable element 50. The coil 3 may also be housed in a bobbin (not shown).

[0019] The stators 10 and 20 include a first stator 10 and a second stator 20 located on either side of the coil 3 in the axial direction of the solenoid actuator 1. The stators 10 and 20 are made of a magnetic material, which may be iron, for example, and are arranged in an annular shape around a central axis O so as to surround the coil 3.

[0020] The first stator 10 and the second stator 20 are arranged so as to face each other in the axial direction, separated by an air gap 11, on the inner circumference side of the coil 3 and on the outer circumference side of the movable element 50, which will be described later. The air gap 11 is provided to restrict the magnetic flux flow from the first stator 10 directly to the second stator 20 without passing through the movable element 50, and to efficiently allow the magnetic flux to flow from the first stator 10 to the second stator 20 via the movable element 50.

[0021] In the example shown in Figure 1, the first stator 10 and the second stator 20 come into contact at the contact portion 12 located on the outer circumference of the coil 3. In this case, the first stator 10 and the second stator 20 may be integrally molded by a resin mold (not shown) with the first stator 10 and the second stator 20 facing each other on the inner circumference side of the coil 3 via an air gap 11 and in contact with each other at the contact portion 12 on the outer circumference side of the coil 3. The position of the contact portion 12 between the first stator 10 and the second stator 20 is not particularly limited. The contact portion 12 may be located at the center of the coil 3 in the axial direction, as in the example in Figure 1, or it may be located at a position different from the center of the coil 3.

[0022] In other embodiments, the solenoid actuator 1 does not have a contact point between the first stator 10 and the second stator 20. For example, if the solenoid actuator 1 includes one or more stators other than the first stator 10 and the second stator 20, the one or more other stators may be located between the first stator 10 and the second stator 20 and together with the first stator 10 and the second stator 20 to form a magnetic path 4. In this way, the presence of other stators between the first stator 10 and the second stator 20 may result in a configuration where the first stator 10 and the second stator 20 do not come into direct contact with each other. Furthermore, gaps may exist between the multiple stators, including the first stator 10 and the second stator 20.

[0023] In some embodiments, as shown in Figure 1, the first stator 10 includes a first yoke 14 and a cylindrical guide 30 fixed to the inner circumference of the first yoke 14.

[0024] The cylindrical guide 30, fixed to the inner circumference of the first yoke 14, faces the second stator 20 in the axial direction, separated by an air gap 11 between the first stator 10 and the second stator 20. That is, the tip 31 of the cylindrical guide 30 does not contact the tip 21 of the second stator 20, but is separated by the air gap 11. Here, the air gap 11 refers to the smallest gap between the first stator 10, which includes the first yoke 14 and the cylindrical guide 30, and the second stator 20 on the inner circumference side of the coil 3.

[0025] The cylindrical guide 30 may be positioned such that its tip 31 is located in a radial position range that at least partially overlaps with the tip 21 of the second stator 20, as shown in Figure 1.

[0026] In some embodiments, as shown in Figure 1, the cylindrical guide 30 is positioned such that its tip 31 protrudes from the first yoke 14 toward the second stator 20. That is, the cylindrical guide 30 extends axially toward the second stator 20 beyond the tip position of the first yoke 14. In this way, by extending the cylindrical guide 30 beyond the tip of the first yoke 14 toward the second stator 20, it becomes easier to secure a magnetic transfer area between the cylindrical guide 30 (magnetic cylinder 32, described later) and the movable element 50, thereby increasing the magnetic flux flowing between the movable element 50 in its original position and the second stator 20.

[0027] Furthermore, the cylindrical guide 30 may extend axially to the rear end 51 of the movable element 50 in its original position, or beyond the rear end 51 of the movable element 50 to the side opposite the second stator 20. In the exemplary embodiment shown in Figure 1, the cylindrical guide 30 extends axially beyond the rear end 51 of the movable element 50 in its original position, toward the side opposite the second stator 20. That is, the base end 33 of the cylindrical guide 30, opposite to the tip end 31, protrudes axially from the rear end 51 of the movable element 50 in its original position toward the side opposite the second stator 20. By extending the cylindrical guide 30 beyond the rear end 51 of the movable element 50 in its original position, toward the side opposite the second stator 20, it becomes easier to secure a magnetic transfer area between the cylindrical guide 30 (magnetic cylinder 32, described later) and the movable element 50. As a result, the overall magnetic resistance of the magnetic path 4 passing through the movable element 50 is reduced, and the magnetic flux flowing between the movable element 50 in its original position and the second stator 20 can be increased.

[0028] The first yoke 14 of the first stator 10 is made of a magnetic material, which may be iron, for example, and is arranged together with the second stator 20 to surround the coil 3. The first yoke 14 may contact the second stator 20 at a contact portion 12 on the outer circumference side of the coil 3. The first yoke 14 has a first through-hole 15 for receiving the cylindrical guide 30. The first through-hole 15 may be a circular hole concentric with the central axis O of the solenoid actuator 1.

[0029] As shown in Figure 1, the inner wall of the first through-hole 15 of the first yoke 14 includes a contact area 15a that contacts the outer circumferential surface of the cylindrical guide 30 and a non-contact area 15b that does not contact the outer circumferential surface of the cylindrical guide 30. The non-contact area 15b is adjacent to the contact area 15a in the axial direction. The non-contact area 15b is located on the opposite side of the contact area 15a from the second stator 20 in the axial direction.

[0030] In some embodiments, the inner diameter of the first through-hole 15 is the same in the contact region 15a and the non-contact region 15b. That is, the inner wall of the first through-hole 15 is not provided with any steps that would restrict the axial position of the cylindrical guide 30 relative to the first yoke 14. Therefore, the step in the inner wall of the first through hole 15 does not obstruct the axial positioning of the cylindrical guide 30 relative to the second stator 20. Thus, when assembling the cylindrical guide 30 to the first yoke 14, it becomes possible to appropriately adjust the axial position of the tip 31 of the cylindrical guide 30, making it easier to control the air gap 11 with high precision.

[0031] In some embodiments, the second stator 20 includes a second yoke 24 and a second cylindrical member 40 fixed to the inner circumference of the second yoke 24, as shown in Figure 1.

[0032] The second yoke 24 is formed of a magnetic material, which may be iron, for example, and is arranged together with the first stator 10 to surround the coil 3. The second yoke 24 may contact the first stator 10 at the contact portion 12 on the outer circumference side of the coil 3. The second yoke 24 has a second through-hole 25 for receiving the second cylindrical member 40. The second through-hole 25 may be a circular hole concentric with the central axis O of the solenoid actuator 1.

[0033] In the exemplary embodiment shown in Figure 1, the second cylindrical member 40 has a tip 21 of the second stator 20 that forms an air gap 11 between it and the first stator 10. In other embodiments, the entire second stator 20 is constructed as a single, integrated unit.

[0034] As shown in the embodiment in Figure 1, by providing the second cylindrical member 40 of the second stator 20, which is directly related to the air gap 11, separately from the second yoke 24, it becomes easier to control the air gap 11 with higher precision compared to when the entire second stator 20 is constructed as a single unit. For example, consider the case where, when assembling the cylindrical guide 30 to the first yoke 14, the position of the tip 31 of the cylindrical guide 30 is adjusted with reference to the reference surface 22 of the second stator 20 (i.e., the axial end face 22 of the second yoke 24 opposite to the first stator 10). In this case, after adjusting the axial position of the tip 31 of the cylindrical guide 30 with respect to the axial end face 22 of the second yoke 24, the second cylindrical member 40 may be axially aligned with respect to the axial end face 22 of the second yoke 24 when assembling the second cylindrical member 40 to the second yoke 24. As a result, the only dimension of the second cylindrical member 40 of the second stator 20 (the axial dimension of the second cylindrical member 40 from the reference surface 22 of the second yoke 24 to the air gap 11) substantially affects the air gap 11, and a highly accurate air gap 11 can be easily formed.

[0035] In some embodiments, as shown in Figure 1, the second cylindrical member 40 is provided so as to protrude from the second yoke 24 toward the first stator 10. In other words, the tip 21 of the second stator 20 formed by the second cylindrical member 40 is located on the first stator 10 side, beyond the tip of the second yoke 24, in the axial direction.

[0036] Some solenoid actuators, such as linear solenoids, are desirable to have a linear characteristic in which the attractive force changes with respect to current. To achieve this linear characteristic, it is advantageous to make the tip of the second stator, which is located downstream in the direction of movement of the movable element from its original position when the coil is energized, tapered toward the air gap. In this regard, as described above, by making the second cylindrical member 40 that forms the air gap 11 protrude axially from the second yoke 24, the overall shape of the second stator 20 formed by the second yoke 24 and the second cylindrical member 40 can be made closer to the tapered shape described above.

[0037] In the exemplary embodiment shown in Figure 1, the second yoke 24 has a thickness t that decreases toward the air gap 11. That is, the second yoke 24 has a tip section 26 in the tip region facing the air gap 11, in which the thickness t decreases toward the air gap 11. Here, the thickness t of the second yoke 24 is the radial dimension of the second yoke 24.

[0038] Thus, the second yoke 24 has a thickness distribution that decreases as it approaches the air gap 11. Combined with the configuration in which the second cylindrical member 40 protrudes from the second yoke 24 toward the first stator 10, the overall shape of the second stator 20 can be made even closer to the aforementioned tapered shape.

[0039] When current is supplied to coil 3, magnetic flux flows through the magnetic path 4 formed around coil 3 by the first stator 10 and second stator 20 of the above configuration. As a result, the movable element 50 moves axially from its original position radially inward of the first stator 10 towards the second stator 20. The second stator 20 forms a cavity 28 radially inward to receive the movable element 50 as it approaches axially when the coil 3 is energized. In the embodiment shown in Figure 1, the cavity 28 is defined by the second cylindrical member 40 of the second stator 20.

[0040] In some embodiments, the movable element 50 is a plunger 52 provided at the end of the shaft 54, which is the output shaft of the solenoid actuator 1, as shown in Figure 1. The plunger 52 has a through hole into which the shaft 54 ​​is press-fitted. The shaft 54 ​​is press-fitted into the through hole of the plunger 52 such that the axis of the shaft 54 ​​aligns with the axis of the plunger 52.

[0041] The plunger 52, which serves as the movable element 50, is made of a magnetic material, which may be iron, for example, and is attached to the outer circumference of the shaft 54. The diameter of the plunger 52 is larger than the diameter of the shaft 54, and smaller than the inner diameter of the cylindrical guide 30 of the first stator 10. Also, the diameter of the plunger 52 is smaller than the diameter of the cavity 28 formed by the second stator 20.

[0042] When coil 3 is de-energized, shaft 54 ​​is biased in the opposite direction to arrow B by a spring (not shown), and plunger 52, acting as the movable element 50, is positioned radially inward of the first stator 10 (cylindrical guide 30). At this time, plunger 52 only needs to be substantially positioned radially inward of the cylindrical guide 30, and the end of plunger 52 may protrude from the first stator 10 (cylindrical guide 30) toward the second stator 20. In contrast, when the coil 3 is energized, the plunger 52, acting as the movable element 50, enters the cavity 28 formed radially inward of the second stator 20. At this time, it is sufficient that at least a portion of the plunger 52 is located within the cavity 28, and the remaining portion of the plunger 52 may protrude from the cavity 28 toward the first stator 10.

[0043] The shaft 54 ​​to which the plunger 52 in the above configuration is fixed extends through the second stator 20 to the outside of the solenoid actuator 1. The shaft 54 ​​moves in the direction of arrow B when the solenoid actuator 1 is operated, transmitting the driving force of the solenoid actuator 1 to an external device (not shown). The external device driven by the solenoid actuator 1 is not particularly limited, but could be, for example, a spool that hydraulically controls the valve timing of the intake and exhaust valves of a vehicle's engine.

[0044] The shaft 54 ​​may be slidably supported toward the second stator 20 by a bearing. In the embodiment shown in Figure 1, the radially inner portion of the second cylindrical member 40, which constitutes a part of the second stator 20, functions as a bearing portion 53, and the shaft 54 ​​is slidably supported by the bearing portion 53 of the second cylindrical member 40.

[0045] Figures 2 to 4 are cross-sectional views showing the detailed structure of a solenoid actuator in the region where magnetic flux is transferred between the stator and the movable part, according to one embodiment. Figure 2 shows the de-energized state of coil 3 with the movable element 50 in its original position. Here, the original position of the movable element 50 is represented as X=0 using the position coordinate X of the end face of the movable element 50, and can be rephrased as the stroke start position where the stroke amount of the solenoid actuator 1 is zero. In contrast, Figure 3 shows the state in which the movable element 50 has moved by a stroke amount X1 relative to its original position, and the position coordinate X of the end face of the movable element 50 is the intermediate position X1. Similarly, Figure 4 shows the state in which the movable element 50 has moved by the maximum stroke amount X2 relative to its original position, and the position coordinate X of the end face of the movable element 50 is the maximum stroke position X2 (>X1).

[0046] In some embodiments, as shown in Figures 2 to 4, the cylindrical guide 30 includes a magnetic cylinder 32 having an outer surface that contacts the inner wall of the first through hole 15 of the first yoke 14, and a non-magnetic layer 34 formed on the inner surface of the magnetic cylinder 32.

[0047] The magnetic cylinder 32 is made of a magnetic material, which may be iron, for example, and faces the second stator 20 across the air gap 11. That is, of the magnetic material portions of the first stator 10, including the first yoke 14 and the cylindrical guide 30, the magnetic cylinder 32 is positioned closest to the tip 21 of the second stator 20. The radial position range of the magnetic cylinder 32 may at least partially overlap with the radial position range of the tip 21 of the second stator 20, which forms an air gap 11 with the magnetic cylinder 32.

[0048] The non-magnetic layer 34 of the cylindrical guide 30 is provided on the inner circumferential surface of the magnetic cylinder 32 so as to face the outer circumferential surface of the movable element 50. As a result, the cylindrical guide 30 can guide the movable element 50 in the axial direction by causing the movable element 50 to slide against the non-magnetic layer 34. The non-magnetic layer 34 may be made of a low-friction material such as copper or PTFE (polytetrafluoroethylene). The non-magnetic layer 34 may be formed on the inner surface of the cylindrical guide 30 by a construction method such as sintering or impregnation. In an exemplary embodiment, the non-magnetic layer 34 is formed by impregnating a porous layer of copper alloy formed by sintering with a resin material containing PTFE.

[0049] Generally, guides (bearings) that constrain the radial position of a movable element and guide it axially are located in a different place from the radial magnetic gap between the yoke and the movable element. In this case, if the axis of the yoke is eccentric with respect to the guide that restricts the radial position of the movable element, the magnetic gap between the movable element and the yoke on the outer circumference of the movable element will also be affected. For this reason, it is necessary to ensure a relatively wide magnetic gap between the movable element and the yoke on the outer circumference of the movable element, taking into account the effect of axial misalignment of the yoke on the guide (bearing). In this regard, as shown in the embodiments in Figures 2 to 4, if a cylindrical guide 30 capable of realizing a guiding function that guides the movable element 50 in the axial direction by a non-magnetic layer 34 is fixed to the inner circumference of the first yoke 14, the influence of axial misalignment of the first yoke 14 on the cylindrical guide 30 can be substantially eliminated. Therefore, the radial gap tr that needs to be secured between the cylindrical guide 30 and the movable element 50 only needs to be large enough to allow the assembly of the movable element 50. As a result, the magnetic gap between the first stator 10 and the movable element 50 can be reduced, and the magnetic flux from the first stator 10 to the movable element 50 can be increased. In this case, the magnetic gap between the first stator 10 and the movable element 50 is the sum of the radial gap tr mentioned above and the thickness of the non-magnetic layer 34.

[0050] As shown in Figure 2, the minimum distance d1 between the magnetic cylinder 32 of the cylindrical guide 30 and the second stator 20 (second cylindrical member 40) is greater than the minimum distance d2 between the movable element 50 and the second stator 20 (second cylindrical member 40) in the original position.

[0051] In this way, by satisfying the relationship d1 > d2, the magnetic resistance in the gap between the magnetic cylinder 32 and the second stator 20 becomes greater than the magnetic resistance in the gap between the movable element 50 in its original position and the second stator 20. As a result, the magnetic flux flowing between the movable element 50 in its original position and the second stator 20 can be increased. In addition, a configuration has been proposed in which an annular movable element is supported by the yoke from the inner circumference via a guide. In this respect, in the solenoid actuator 1, the cylindrical guide 30 is located radially outside the movable element 50, so a larger area of ​​the annular magnetic gap between the magnetic cylinder 32 of the cylindrical guide 30 and the movable element 50 can be secured compared to the conventional proposed structure described above. This is because the area of ​​the magnetic gap is expressed as the product of the circumference and axial length of the magnetic gap, and when the magnetic gap is formed radially outside, the circumference of the magnetic gap becomes relatively larger. In this way, the magnetic transfer area (area of ​​the magnetic gap) between the magnetic cylinder 32 and the movable element 50 increases, which reduces the overall magnetic resistance of the magnetic path 4, and also increases the magnetic flux flowing between the movable element 50 in its original position and the second stator 20. Therefore, it becomes possible to effectively transfer magnetic fields between the movable element 50 and the first stator 10 and the second stator 20 in their original positions (see arrows in Figure 2), thereby realizing a compact and high-thrust solenoid actuator 1.

[0052] Here, in order to increase the magnetic transfer area between the magnetic cylinder 32 and the movable element 50, it is advantageous to make the cylindrical guide 30 as long as possible. On the other hand, in order to ensure the magnetic flux passing through the movable element 50 in its original position, it is desirable to impose constraints on the tip position of the cylindrical guide 30 so that the above-mentioned relationship d1 > d2 holds true. In this regard, as shown in the embodiment described above with reference to Figure 1, by making the diameter of the first through-hole 15 of the first yoke 14 the same in the contact area 15a and the non-contact area 15b of the inner wall of the first through-hole 15 of the first yoke 14, it becomes possible to adjust the position of the tip 31 of the cylindrical guide 30 with high precision. Therefore, the cylindrical guide 30 can be made sufficiently long as long as the relationship d1 > d2 is satisfied, and it is possible to achieve both securing the magnetic transfer area between the magnetic cylinder 32 and the movable element 50 and increasing the magnetic flux passing through the movable element 50 in its original position.

[0053] In some embodiments, as shown in Figures 2 to 4, the cylindrical guide 30 extends axially toward the second stator 20 beyond the tip position X_yoke of the first yoke 14. The minimum distance d1 between the magnetic cylinder 32 of the cylindrical guide 30 and the second stator 20 (second cylindrical member 40) may be smaller than the minimum distance d3 between the first yoke 14 and the second stator 20 (second cylindrical member 40). By extending the cylindrical guide 30 beyond the tip position X of the first yoke 14 toward the second stator 20, it becomes easier to secure a magnetic transfer area between the magnetic cylinder 32 of the cylindrical guide 30 and the movable element 50, thereby increasing the magnetic flux flowing between the movable element 50 in its original position and the second stator 20. On the other hand, if the tip of the cylindrical guide 30 is brought too close to the second stator 20, the magnetic flux flowing between the magnetic cylinder 32 and the second stator 20 without passing through the movable element 50 will increase, and as a result, the magnetic flux between the movable element 50 and the second stator 20 may decrease. In this regard, by imposing a restriction on the tip position of the cylindrical guide 30 (magnetic cylinder 32) so as to satisfy the above-mentioned relationship d1 > d2, it is possible to ensure sufficient magnetic flux flowing between the movable element 50 and the second stator 20 in their original positions.

[0054] In some embodiments, the movable element 50 (plunger 52) in its original position (X=0) extends axially toward the second stator 20 beyond the position of the tip 31 of the cylindrical guide 30. That is, the tip of the movable element 50 in its original position protrudes axially from the cylindrical guide 30 toward the second stator 20. This makes it easier to satisfy the aforementioned relationship (d1>d2), where the minimum distance d2 between the movable element 50 and the second stator 20 is smaller than the minimum distance d1 between the magnetic cylinder 32 and the second stator 20.

[0055] In the exemplary embodiment shown in Figure 2, the tip of the movable element 50 in its original position (X=0) overlaps with the second stator 20 in the axial direction. That is, the tip of the movable element 50 in its original position (X=0) enters the cavity 28 defined by the second stator 20 (second cylindrical member 40). This makes it easier to satisfy the aforementioned relationship (d1>d2), in which the minimum distance d2 between the movable element 50 and the second stator 20 is smaller than the minimum distance d1 between the magnetic cylinder 32 and the second stator 20.

[0056] In the exemplary embodiments shown in Figures 2 to 4, the outer circumferential surface of the movable element 50 (plunger 52) includes a tapered surface 56 that is tapered towards the tip, with the outer diameter decreasing towards the tip, on the tip side of the reference point 55. When the movable element 50 is in its original position X0, the reference point 55 that indicates the boundary of the tapered tip region (tapered surface 56) on the outer circumferential surface of the movable element 50 is located radially inward of the cylindrical guide 30, and the minimum distance d2 between the movable element 50 and the second stator 20 in its original position is the distance between the outer circumferential edge of the tip surface 57 of the movable element 50 and the second cylindrical member 40, as shown in Figure 2. When the movable element 50 is in the intermediate position X1, the axial position of the reference point 55 on the outer surface of the movable element 50 is approximately the same as the tip position of the cylindrical guide 30, and the minimum distance d2' between the movable element 50 and the second stator 20 is the distance between the second cylindrical member 40 and the tapered surface 56 of the movable element 50, as shown in Figure 3. When the movable element 50 is in the maximum stroke position X2, the reference point 55 indicating the boundary of the tapered tip region on the outer circumferential surface of the movable element 50 lies within the cavity 28 formed by the second stator 20 (second cylindrical member 40). At this time, the minimum distance d2'' between the movable element 50 and the second stator 20 is the distance between the region on the outer circumferential surface of the movable element 50 behind the reference point 55 and the second cylindrical member 40, as shown in Figure 4. Furthermore, the minimum distance between the movable element 50 and the second stator 20 decreases as the stroke amount of the movable element 50 increases, and the relationship d2>d2'>d2'' holds true.

[0057] When the movable element 50 is in its original position (X=0), as shown in Figure 2, the magnetic transfer area between the movable element 50 and the second cylindrical member 40 is smaller than the magnetic transfer area between the cylindrical guide 30 and the movable element 50. Furthermore, the magnetic gap (distance d2) between the movable element 50 and the second cylindrical member 40 is larger than the magnetic gap (sum of the radial gap tr and the thickness of the non-magnetic layer 34) between the cylindrical guide 30 and the movable element 50. For this reason, when the movable element 50 is in its original position (X=0), the magnetic gap between the movable element 50 and the second cylindrical member 40, which accounts for the majority of the magnetic resistance of the entire magnetic path, limits the magnetic flux flowing through the magnetic path, and the magnetic flux flowing through the magnetic path when the coil 3 is energized is relatively small. When the movable element 50 moves to the intermediate position X1, the length of the movable element 50's penetration into the cavity 28 increases compared to the original position (X=0) shown in Figure 2. As a result, the magnetic transfer area between the movable element 50 and the second stator 20 (second cylindrical member 40) increases, and the magnetic flux flowing through the magnetic path 4 increases. Note that, compared to the original position (X=0) shown in Figure 2, the magnetic transfer area between the cylindrical guide 30 and the movable element 50 decreases due to the decrease in the axial overlap length between the cylindrical guide 30 and the movable element 50. However, as described above, the magnetic resistance of the magnetic gap between the movable element 50 and the second cylindrical member 40, which accounted for most of the magnetic resistance of the entire magnetic path in the original position (X=0), decreases, so the magnetic flux flowing through the magnetic path 4 increases overall. When the movable element 50 moves to the maximum stroke position X2, the length of penetration of the movable element 50 into the cavity 28 increases further compared to the intermediate position X1 shown in Figure 3. As a result, the magnetic transfer area between the movable element 50 and the second stator 20 (second cylindrical member 40) increases, and the magnetic flux flowing through the magnetic path 4 increases further.

[0058] Here, as the movable element 50 moves from its original position (X=0) towards the maximum stroke position (X=X2), the length of the movable element 50's penetration into the cavity 28 increases. As a result, with increasing stroke of the movable element 50, the radial component of the magnetic flux vector from the movable element 50 to the second stator 20 (second cylindrical member 40) increases and the axial component decreases, which may cause the thrust of the solenoid actuator to decrease. In this regard, as described above, in the embodiments shown in Figures 2 to 4, a tapered surface 56 is formed on the outer circumferential surface of the movable element 50 (plunger 52). As the stroke amount increases, the outer circumferential surface of the movable element 50 approaches the inner circumferential surface of the second stator 20 (second cylindrical member 40). As a result, a decrease in thrust can be suppressed.

[0059] Next, a specific structural example of the solenoid actuator 1 will be explained with reference to Figure 5. In the following, we will omit further explanation of the features mentioned above, referring to Figures 1 to 4.

[0060] Figure 5 is a cross-sectional view showing a solenoid actuator according to one embodiment. As shown in the figure, the solenoid actuator 1 includes a coil 3, a first stator 10 and a second stator 20, and a movable element 50 (plunger 52). Coil 3 is formed by winding a wire made of a conductor such as copper or a copper alloy around a bobbin 60. The bobbin 60 is substantially surrounded by a first stator 10 and a second stator 20. However, the first stator 10 (first yoke 14) has a notch in a certain circumferential area, and the terminal holding portion 62 of the bobbin 60 is exposed at the notch of the first yoke 14. The base end of a terminal 64 is embedded in the terminal holding portion 62 of the bobbin 60. The terminal 64 is electrically connected to the wire making up coil 3 inside the bobbin 60. Furthermore, in the solenoid actuator 1, the coil 3 and bobbin 60, and the first stator 10 and second stator 20 are integrally molded in a resin mold 70 and embedded in the resin mold 70. The terminal 64 penetrates the resin mold 70 from the terminal holding portion 62 of the bobbin 60 and protrudes into a recess 72 provided in the resin mold 70, and is electrically connectable to an external terminal that fits into the recess 72. The resin mold 70 may also have a protrusion (not shown) that contacts the rear end 51 of the movable element 50 (plunger 52) in its original position.

[0061] In this specification, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" shall not only describe such arrangements strictly, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. Furthermore, in this specification, expressions describing shapes such as quadrilaterals and cylindrical shapes shall not only represent geometrically precise quadrilaterals and cylindrical shapes, but also shapes that include uneven surfaces, chamfered surfaces, etc., to the extent that the same effect can be achieved. Furthermore, in this specification, the expressions “equipment,” “includes,” or “possess” of a component are not exclusive expressions that exclude the existence of other components. [Explanation of symbols]

[0062] 1. Solenoid actuator 3 coils 4 magnetic path 10 1st stator 11 Air gap 14. First York 20 Second stator 24 Second York 26. Details 28 Cavity 30 Cylindrical guides 32 Magnetic tube 34 Non-magnetic layer 40 Second cylindrical member 50 mover X0 original position

Claims

1. Coil and, A first stator including a first yoke and a cylindrical guide fixed to the inner circumference of the first yoke, A second stator is positioned opposite the first stator in the axial direction so as to form a magnetic path together with the first stator around the coil, A movable element configured to move in the axial direction toward the second stator from its original position radially inward of the first stator by the magnetic force generated by energizing the coil, Equipped with, The cylindrical guide is, A magnetic cylinder provided in contact with the inner circumferential surface of the first yoke, A non-magnetic layer covering the inner circumferential surface of the magnetic cylinder, Includes, The minimum distance d1 between the magnetic cylinder of the cylindrical guide and the second stator is greater than the minimum distance d2 between the movable element and the second stator in the original position. Solenoid actuator.

2. The cylindrical guide extends axially toward the second stator side beyond the tip position of the first yoke. The solenoid actuator according to claim 1.

3. The movable element extends in the axial direction toward the second stator side beyond the tip position of the cylindrical guide in the original position. The solenoid actuator according to claim 1 or 2.

4. The tip of the movable element overlaps with the second stator in the axial direction in the original position. The solenoid actuator according to claim 1 or 2.

5. The cylindrical guide extends in the axial direction to the rear end of the movable element in its original position, or beyond the rear end of the movable element to the side opposite the second stator. The solenoid actuator according to claim 1 or 2.

6. The first yoke has a first through hole into which the cylindrical guide is press-fitted, The inner wall of the first through hole is The contact region with the outer surface of the magnetic cylinder, In the axial direction, a non-contact region located adjacent to the contact region on the opposite side from the second stator, with the contact region in between, Includes, The diameter of the first through-hole is the same in the contact region and the non-contact region. The solenoid actuator according to claim 1 or 2.

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