Solenoid actuator and method for manufacturing a solenoid actuator

Abstract

To provide a solenoid actuator which attains predetermined electromagnetic characteristics while reducing manufacturing costs, and to provide a method of manufacturing the solenoid actuator.SOLUTION: A solenoid actuator 1 includes: a coil 3; a first stator 10 and a second stator 20 which are arranged forming an air gap 11 therebetween in an axial direction so as to form a magnetic path 4 around the coil 3; 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 second stator 20 includes: a second yoke 24; and a second press component 40 which is formed by a magnetic material and provided at the inner periphery side of the second yoke 24 so as to protrude from the second yoke 24 toward the first stator 10 in the axial direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a solenoid actuator and a method for manufacturing 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 move 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, 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 as the mover moves toward the stroke end position side. 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] Incidentally, the tip shape of the second stator, which is located downstream of the movable element's movement from its original position when the coil is energized, affects the characteristics of the solenoid actuator. For example, in order to achieve a linear characteristic in the change of attractive force with respect to current, a second stator with a tapered tip shape toward the first stator may be desirable. However, if the tapered shape of the second stator is to be achieved solely through machining, the manufacturing cost of the solenoid actuator will increase.

[0006] In view of the above circumstances, at least some embodiments of the present invention aim to provide a solenoid actuator and a method for manufacturing the same that can obtain desired electromagnetic characteristics while suppressing manufacturing costs. [Means for solving the problem]

[0007] [1] Solenoid actuators according to at least some embodiments of the present invention are Coil and, A first stator and a second stator are arranged axially separated by an air gap so as to form a magnetic path 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 second stator is, Second York and A second pressed part, formed of a magnetic material and provided on the inner circumference side of the second yoke so as to protrude axially from the second yoke toward the first stator, Includes.

[0008] [2] In some embodiments, in the configuration of [1] above, The second pressed part has a decreasing thickness in the axial direction towards the first stator.

[0009] [3] In some embodiments, in the configuration of [2] above, The thickness of the second pressed part decreases from the axial position on the first stator side of the tip of the second yoke toward the first stator.

[0010] [4] In some embodiments, in any of the configurations described in [1] to [3] above, The second yoke decreases in thickness in the axial direction toward the first stator.

[0011] [5] In some embodiments, in any of the configurations [1] to [4] above, The second yoke is formed by pressed parts.

[0012] [6] Methods for manufacturing a solenoid actuator according to at least some embodiments of the present invention are as follows: Coil and, A first stator and a second stator are arranged axially separated by an air gap so as to form a magnetic path 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, A method for manufacturing a solenoid actuator comprising: The second stator is formed by attaching a second pressed component made of magnetic material to the inner circumference of the second yoke so as to protrude axially from the second yoke toward the first stator.

[0013] [7] In some embodiments, in the method described in [6] above, By drawing, recesses are formed in the magnetic material. By punching along the outer edge of the recess, the magnetic cylinder with the recess is separated from the magnetic material. By chamfering the fracture surface of the outer edge of the recess in the magnetic cylinder during the punching process, a second pressed part is obtained that has a recess as a cavity for receiving the movable element, and whose thickness decreases in the axial direction toward the first stator.

[0014] [8] In some embodiments, in the method of [6] or [7] above, A recess is formed in the yoke material by drawing, By punching along the outer peripheral edge of the recess, the recess is removed from the yoke material leaving the outer peripheral edge, and a second yoke is obtained whose thickness decreases in the axial direction toward the first stator.

Advantages of the Invention

[0015] According to at least some embodiments of the present invention, the second press part formed of a magnetic material projects axially from the second yoke toward the first stator, so that the overall shape of the second stator formed by the second yoke and the second press part can be made closer to the aforementioned tapered shape. Further, by using the second press part to realize the overall shape of the tapered second stator, the manufacturing cost of the solenoid actuator can be reduced compared to the case of obtaining the tapered second stator solely by cutting.

Brief Description of the Drawings

[0016] [Figure 1] It is a cross-sectional view schematically showing the configuration of a solenoid actuator according to an embodiment. [Figure 2] It is a cross-sectional view showing the detailed structure of a solenoid actuator in the magnetic flux transfer region between the stator and the mover according to an embodiment.}1] [Figure 3A] It is a diagram showing the assembly procedure of a solenoid actuator according to an embodiment. [Figure 3B] It is a diagram showing the assembly procedure of a solenoid actuator according to an embodiment. [Figure 3C] It is a diagram showing the assembly procedure of a solenoid actuator according to an embodiment. [Figure 3D] It is a diagram showing the assembly procedure of a solenoid actuator according to an embodiment. [Figure 4A] It is a diagram showing the processing procedure of a second press part according to an embodiment. [Figure 4B] It is a diagram showing the processing procedure of a second press part according to an embodiment. [Figure 4C] It is a diagram showing the processing procedure of a second press part according to an embodiment. [Figure 5] This is a cross-sectional view showing a solenoid actuator according to one embodiment. [Modes for carrying out the invention]

[0017] Hereinafter, several embodiments of the present invention will be described with reference to the attached 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.

[0018] Figure 1 is a schematic cross-sectional view showing the configuration of a solenoid actuator according to one embodiment. Figure 2 is a cross-sectional view showing a 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.

[0019] Figure 1 omits the illustration of the resin mold for the solenoid actuator. Also, although the magnetic path 4 is shown only for one side of coil 3 (the left side in the figure), similar magnetic paths 4 are formed on both sides of the ring-shaped coil 3 (the right side in the figure).

[0020] In some embodiments, as shown in Figure 1, the solenoid actuator 1 includes a coil 3, stators 10, 20 for forming a magnetic path 4 around the coil 3, and a movable element 50 that is axially movable by the magnetic force generated by the coil 3.

[0021] 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).

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] In some embodiments, as shown in Figures 1 and 2, the first stator 10 includes a first yoke 14 and a cylindrical guide 30 fixed to the inner circumference of the first yoke 14. In other embodiments, the entire first stator 10 is formed as a single piece.

[0027] 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.

[0028] 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 Figures 1 and 2.

[0029] In some embodiments, as shown in Figures 1 and 2, 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.

[0030] 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.

[0031] In some embodiments, as shown in Figure 2, 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.

[0032] 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.

[0033] 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.

[0034] 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 embodiment in Figure 2, 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 side of the first yoke 14, the effect of axial misalignment of the first yoke 14 on the cylindrical guide 30 can be substantially eliminated. For this reason, 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.

[0035] 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 pressed part 40) is greater than the minimum distance d2 between the movable element 50 and the second stator 20 (second pressed part 40) in its original position.

[0036] 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.

[0037] In some embodiments, as shown in Figure 2, 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 pressed part 40) may be smaller than the minimum distance d3 between the first yoke 14 and the second stator 20 (second pressed part 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.

[0038] In some embodiments, the movable element 50 (plunger 52, described later) 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.

[0039] 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 press part 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.

[0040] In the exemplary embodiment shown in Figure 2, 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 surface of the movable element 50 is located radially inward of the cylindrical guide 30.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] In some embodiments, the second stator 20 includes a second yoke 24 and a second pressed part 40 fixed to the inner circumference of the second yoke 24, as shown in Figures 1 and 2.

[0045] 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 pressed part 40. The second through-hole 25 may be a circular hole concentric with the central axis O of the solenoid actuator 1.

[0046] In the exemplary embodiment shown in Figure 1, the second press part 40 is a press-formed product that includes a cylindrical portion 41 and a shoulder portion 42.

[0047] As shown in the embodiment in Figure 1, by providing the second press part 40, which is directly related to the air gap 11, separately from the second yoke 24, the air gap 11 can be controlled with higher precision compared to the case where the entire second stator 20 is made as a single piece. 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 pressed part 40 may be axially aligned with respect to the axial end face 22 of the second yoke 24 when assembling the second pressed part 40 to the second yoke 24. As a result, the only dimension of the second pressed part 40 of the second stator 20 (the axial dimension of the second pressed part 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.

[0048] In the exemplary embodiment shown in Figure 2, the tip portion of the cylindrical part 41 of the second press part 40 includes a convex curved surface 44 and a tapered surface 46. The apex 45 of the cylindrical portion 41 is the part of the second press part 40 that is closest to the first stator 10 in the axial direction. The curved surface 44 connects to the tapered surface 46 at the apex 45. The tip 21 of the second stator 20 is formed by the tip portion of the cylindrical portion 41, which includes the curved surface 44 located radially inward and the tapered surface 46 located radially outward.

[0049] The curved surface 44 may be formed, for example, by a shear droop resulting from the deep drawing process of the second press part 40. The tapered surface 46 may be formed, for example, by chamfering the fracture surface resulting from the punching process. The method for forming the curved surface 44 and the tapered surface 46 will be described in detail later.

[0050] In some embodiments, as shown in Figures 1 and 2, the second press part 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 cylindrical portion 41 of the second press part 40 is located in the axial direction between the tip of the second yoke 24 and the first stator 10.

[0051] 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 press part 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 press part 40 can be made closer to the tapered shape described above.

[0052] In the embodiment shown in Figure 2, the thickness of the second press part 40 decreases in the axial direction toward the first stator 10. That is, the thickness of the leading edge of the second press part 40 decreases as it approaches the first stator 10. This, combined with the configuration in which the second pressed part 40 protrudes axially from the second yoke 24, makes the overall shape of the second stator 20 even closer to the aforementioned tapered shape. In the example shown in Figure 2, the thickness distribution of the second pressed part 40 is achieved by the curved surface 44 and the tapered surface 46.

[0053] Furthermore, the starting point P1 for the thickness reduction of the second pressed part 40 may be located on the first stator 10 side of the tip of the second yoke 24. In other words, the thickness of the second pressed part 40 may decrease toward the first stator 10 from an axial position toward the first stator 10, toward the tip of the second yoke 24. In the example shown in Figure 2, the axial range of the curved surface 44 is wider than that of the tapered surface 46, and the starting point P1 of the thickness reduction of the second press part 40 is at the end opposite to the apex 45 of the curved surface 44. In other embodiments, the axial range of the tapered surface 46 is wider than that of the curved surface 44, and the starting point P1 of the thickness reduction of the second press part 40 is at the end opposite to the apex 45 of the tapered surface 46.

[0054] As the thickness of the second yoke 24 becomes zero at its tip, the overall thickness of the second stator 20 decreases toward the first stator 10. Furthermore, as described above, even on the side of the second yoke 24 toward the first stator 10, the overall thickness of the second stator 20 decreases toward the first stator 10 due to the decrease in the thickness of the second pressed part 40. Therefore, the overall shape of the second stator 20 formed by the second yoke 24 and the second press part 40 can be made even closer to the tapered shape described above.

[0055] In some embodiments, as shown in Figures 1 and 2, 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.

[0056] 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 pressed part 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.

[0057] The second yoke 24 can be formed by press forming. That is, not only the second press part 40, but also the second yoke 24 may be made from a press part. Since the second yoke 24, which constitutes the second stator 20 together with the second press part 40, is also formed from a press part, the manufacturing cost of the solenoid actuator 1 can be further reduced compared to the case where the tapered second stator 20 is obtained solely by machining.

[0058] 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 (see arrow in Figure 2). 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, as indicated by arrow B in Figure 1. 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 pressed part 40 of the second stator 20.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The shaft 54 ​​may be slidably supported toward the second stator 20 by a bearing. In the embodiment shown in Figure 1, the radially inward portion of the second pressed part 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 pressed part 40.

[0064] Next, with reference to Figures 3A to 3D, the manufacturing method of the solenoid actuator 1 with the above configuration will be described.

[0065] Figures 3A to 3D show some of the steps involved in the manufacturing method of a solenoid actuator 1 according to one embodiment.

[0066] First, the first yoke 14 and the second yoke 24, which is part of the second stator 20, are positioned around the coil 3 (see Figure 3A). Then, the cylindrical guide 30 is positioned axially with respect to the reference surface 22 of the second yoke 24.

[0067] When positioning the cylindrical guide 30, a jig 120 may be used to ensure that the tip 31 of the cylindrical guide 30 is in a desired axial position relative to the reference surface 22. In the embodiment shown in Figure 3A, a jig 120 for positioning the cylindrical guide 30 is installed in advance prior to inserting the cylindrical guide 30 into the first through hole 15 of the first yoke 14. The jig 120 has a flat surface 100 and a substantially cylindrical protrusion 122. The protrusion 122 is located on the inner circumference side of the flat surface 100 and is provided projecting upward from the flat surface 100. The jig 120 is installed such that the flat surface 100 of the jig 120 is in contact with the reference surface 22 of the second yoke 24, and the protrusion 122 of the jig 120 is located on the inner circumference side of the second yoke 24. At this time, the upper end surface 124 of the protrusion 122 of the jig 120 is located higher than the reference surface 22 of the second yoke 24 by the amount of protrusion of the protrusion 122 from the flat surface 100. Next, as shown in Figure 3A, the cylindrical guide 30 is inserted into the first through hole 15 of the first yoke 14 from the opposite side of the second yoke 24. When the tip 31 of the cylindrical guide 30 contacts the upper end surface 124 of the protrusion 122 of the jig 120, the insertion of the cylindrical guide 30 is stopped, as shown in Figure 3B. In this way, the cylindrical guide 30 is positioned axially with respect to the reference surface 22 of the second yoke 24, which constitutes a part of the second stator 20.

[0068] The positioned cylindrical guide 30 is fixed to the inner circumference of the first yoke 14 so as to be immovable relative to the first yoke 14. The cylindrical guide 30 can be fixed to the first yoke 14 by press-fitting or welding. When the cylindrical guide 30 is press-fitted into the first through-hole 15 of the first yoke 14, the positioning of the cylindrical guide 30 and the fixing of the cylindrical guide 30 to the first yoke 14 are performed simultaneously. In contrast, when the first cylindrical member 30 is fixed to the first yoke 14 by welding, the fixing of the first cylindrical member 30 to the first yoke 14 is performed after the positioning of the first cylindrical member 30.

[0069] Next, as shown in Figure 3C, the second press part 40, which constitutes a part of the second stator 20, is inserted into the second through hole 25 of the second yoke 24, thereby positioning and fixing the second press part 40 relative to the second yoke 24. Specifically, the second press part 40 is attached to the inner circumference of the second yoke 24 such that it protrudes axially from the second yoke 24 toward the first stator 10.

[0070] Here, when positioning the second press part 40, a jig 130 may be used to achieve a state in which the tip portion of the second press part 40 (i.e., the tip 21 of the second stator 20) is in a desired axial position relative to the reference surface 22 of the second yoke 24. The jig 130 has a flat surface 132 and a recess 134 surrounded by the flat surface 132. The depth of the recess 134 is set to a dimension that can accommodate the bearing portion 53 of the second press part 40. The jig 130 is positioned so that the flat surface 132 of the jig 130 is in contact with the reference surface 22 of the second yoke 24 and the shoulder portion 42 of the second press part 40. By bringing the reference surface 22 of the second yoke 24 and the shoulder portion 42 of the second press part 40 into contact with the flat surface 132 of the jig 130 in this manner, the tip portion of the second press part 40 (i.e., the tip 21 of the second stator 20) is positioned axially relative to the second yoke 24.

[0071] The second pressed part 40, thus positioned, is fixed to the inner circumference of the second yoke 24 so as to be immovable relative to the second yoke 24. As a result, the first stator 10 (first yoke 14 and cylindrical guide 30) and the second stator 20 (second yoke 24 and second pressed part 40) form a magnetic path 4 (see Figure 3) around the coil 3. The second press part 40 can be fixed to the second yoke 24 by press-fitting or welding. When the cylindrical guide 30 is press-fitted into the first through hole 15 of the first yoke 14, the positioning of the cylindrical guide 30 and the fixing of the cylindrical guide 30 to the first yoke 14 are performed simultaneously.

[0072] Subsequently, as shown in Figure 3D, the plunger 52, which serves as the movable element 50, is assembled to the first stator 10 and the second stator 20. The axial position of the movable element 50 (plunger 52) at this stage is not particularly limited. The movable element 50 (plunger 52) may be mounted to be in its original position radially inward of the first stator 10 (cylindrical guide 30) by assembling a spring (not shown). Furthermore, in the example shown in Figure 3D, the shaft 54 ​​is slidably supported by the second pressed part 40 of the second stator 20.

[0073] Finally, the first stator 10 and the second stator 20 can be integrally molded using a resin mold (not shown) to obtain the solenoid actuator 1.

[0074] As described above with reference to Figures 3A to 3D, when assembling the cylindrical guide 30 to the first yoke 14, the axial positioning of the cylindrical guide 30 with respect to the reference plane 22 of the second stator 20 can be performed, thereby reducing the number of related parts that affect the air gap 11. This makes it possible to control the air gap 11 with high precision, and a solenoid actuator 1 with excellent suction characteristics can be realized at low cost.

[0075] Next, we will describe the processing methods for the second press part 40 and the second yoke 24, which constitute the second stator 20.

[0076] Figures 4A to 4C show the processing procedure for the second press part 40 according to one embodiment. First, as shown in Figure 4A, a recess 202 is formed in the plate-shaped magnetic material 200 by drawing. Specifically, a punch 302 is lowered onto the magnetic material 200 placed on the die 300. The punch 302 presses against the magnetic material 200 as it penetrates into the cavity of the die 300. At this time, the magnetic material 200 around the cavity of the die 300 is drawn into the cavity, forming the recess 202. The recess 202 corresponds to the cavity 28 defined by the cylindrical portion 41 of the completed second press part 40. Next, as shown in Figure 4B, punching is performed along the outer edge of the recess 202 to separate the magnetic cylinder 210 having the recess 202 from the rest of the magnetic material 200. Specifically, the punch 312 is lowered over the drawn magnetic material 200 placed on the die 310. The die 310 has a larger inner diameter than the die 300 shown in Figure 4A, creating a small clearance C between it and the outer surface of the magnetic cylinder 210. The punch 312 has an outer diameter that is approximately the same as the inner diameter of the die 310 and has a larger outer diameter than the punch 302 shown in Figure 4A. The die 310 and the punch 312 break the outer edge of the recess 202, forming a fracture surface 212. Next, as shown in Figure 4C, the fracture surface 212 of the magnetic cylinder 210 is chamfered as needed. This forms a cylindrical portion 41 in which a convex curved surface 44 and a tapered surface 46 are connected at the apex 45. The curved surface 44 is caused by a shear droop that occurs on the inner periphery of the recess 202 of the magnetic cylinder 210 during the drawing process shown in Figure 4A. The tapered surface 46 is caused by the chamfering of the fracture surface 212. After this, the shoulder portion 42 and the bearing portion 53 are formed, and the second pressed part 40 is completed.

[0077] The curved surface 44 caused by shear droop during the deep drawing process curves radially outward as it approaches the first stator 10, contributing to the realization of a thickness distribution of the second pressed part 40 that decreases as it approaches the first stator 10. Thus, the aforementioned thickness distribution of the second press part 40 can be achieved by low-cost press forming, and combined with the configuration in which the second press part 40 protrudes axially from the second yoke 24, the overall shape of the second stator 20 can be made even closer to the aforementioned tapered shape. Furthermore, in the example shown in Figures 4A to 4C above, the second press part 40 can be processed using a progressive press, which can further reduce the manufacturing cost of the second press part 40.

[0078] Similar to the second press part 40, the second yoke 24 may also be manufactured by press forming. For example, a yoke material made of magnetic material may be subjected to drawing to form a recess, similar to the procedure shown in Figures 4A and 4B, and the recess may be removed from the yoke material, leaving the outer edge intact, by punching along the outer edge of the recess, thereby obtaining a second yoke 24 whose thickness decreases toward the first stator 10 in the axial direction. Thus, the aforementioned thickness distribution of the second yoke 24 can be achieved by low-cost press forming, and combined with the configuration in which the second press part 40 protrudes axially from the second yoke 24, the overall shape of the second stator 20 can be made even closer to the aforementioned tapered shape.

[0079] A specific structural example of the solenoid actuator 1 described above will be explained with reference to Figure 5.

[0080] 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.

[0081] 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]

[0082] 1. Solenoid actuator 3 coils 4 magnetic path 10 1st stator 11 Air gap 20 Second stator 24 Second York 28 Cavity 40 Second Press Part 41 Cylindrical section 42 Shoulder 44 Curved surface 50 mover 200 Magnetic material 210 Magnetic tube 212 Fracture surface

Claims

1. Coil and, A first stator and a second stator are arranged axially separated by an air gap so as to form a magnetic path 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 second stator is, Second York and, A second pressed part is formed of a magnetic material and is provided on the inner circumference side of the second yoke so as to protrude from the second yoke in the axial direction toward the first stator, including Solenoid actuator.

2. The thickness of the second pressed part decreases in the axial direction toward the first stator. The solenoid actuator according to claim 1.

3. The thickness of the second pressed part decreases from an axial position on the first stator side of the tip of the second yoke toward the first stator. The solenoid actuator according to claim 2.

4. The second yoke has a thickness that decreases toward the first stator in the axial direction. A solenoid actuator according to any one of claims 1 to 3.

5. The second yoke is formed by a pressed part. A solenoid actuator according to any one of claims 1 to 3.

6. Coil and, A first stator and a second stator are arranged axially separated by an air gap so as to form a magnetic path 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, A method for manufacturing a solenoid actuator comprising: The second stator is formed by attaching a second pressed component made of magnetic material to the inner circumference of the second yoke so as to protrude from the second yoke in the axial direction toward the first stator. A method for manufacturing a solenoid actuator.

7. By drawing, recesses are formed in the magnetic material. By punching along the outer edge of the recess, the magnetic cylinder having the recess is separated from the magnetic material. By chamfering the fracture surface of the outer edge of the recess of the magnetic cylinder in the punching process, a second press part is obtained which has the recess as a cavity for receiving the movable element and whose thickness decreases toward the first stator in the axial direction. A method for manufacturing a solenoid actuator according to claim 6.

8. A recess is formed in the yoke material by a drawing process. By punching along the outer edge of the recess, the recess is removed from the yoke material, leaving the outer edge intact, thereby obtaining the second yoke, whose thickness decreases toward the first stator in the axial direction. A method for manufacturing a solenoid actuator according to claim 6 or 7.

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