Solenoid

Abstract

The present invention provides a solenoid wherein manufacturing costs are minimized and the waterproof properties of a bobbin and a molded resin are improved. A solenoid 1 according the present invention comprises: a bobbin 20 that is provided with a cylindrical section 201 and a large diameter section 202 extended radially outward from a location at an axial end section of the cylindrical section 201; a coil 21 that is wound around the cylindrical section 201 of the bobbin 20; and a molded resin outer packaging body that covers the bobbin 20 and the coil 21 with a molded resin, and forms a bond section 25 between the molded resin outer packaging body and the large diameter section 202. The molded resin exterior body is provided with an end section covering section 31 that covers an axial end section of the large diameter section 202 of the bobbin 20 with the molded resin along the radial direction. A region in one portion of the end section covering section 31 is provided with an axially thick section 33 that has a greater thickness in the axial direction than regions in other portions of the end section covering section 31.

Description

Solenoid

[0001] The present invention relates to a solenoid used for opening and closing a valve of a shock absorber.

[0002] A damping force adjustable shock absorber is mounted on a suspension device for vehicles such as automobiles, and the damping force adjustable shock absorber adjusts the damping force by opening and closing a control valve. A solenoid is used to open and close the control valve. The coil used for the solenoid is molded with a mold resin for waterproofing and constitutes a molded coil. The solenoid magnetizes a housing, a yoke, and an armature that form a magnetic circuit by an electric current flowing through the molded coil, and a suction force is generated between an axially movable armature and an anchor fixed to an end of the molded coil. Thereby, a thrust is applied to the valve body of the control valve by a rod fixed integrally with the armature.

[0003] The solenoid used for an automobile shock absorber is installed at a position close to the ground and is exposed to the outside. When water enters the molded coil, the electrical resistance of the coil changes, so that the solenoid does not function properly. Therefore, ensuring the waterproofness of the molded coil becomes an issue in solenoid design.

[0004] As means for solving this, there are, for example, the techniques described in Patent Document 1 and Patent Document 2. Patent Document 1 discloses a structure in which an O-ring is provided on the upstream side of a bobbin of a solenoid for sealing. Further, Patent Document 2 discloses a structure in which a protrusion (projection) is formed on a coil bobbin and the mold resin and the coil bobbin are heat-welded during molding for sealing.

[0005] Japanese Unexamined Patent Application Publication No. 2019-113162 Japanese Unexamined Patent Application Publication No. 2005-5652

[0006] In the technique described in Patent Document 1, since it is necessary to form an O-ring and a groove for accommodating the O-ring, there is an issue that the manufacturing cost increases.

[0007] Furthermore, the technology described in Patent Document 2 seals the mold resin and the coil bobbin by melting the protruding portion of the coil bobbin without using an O-ring. However, in the technology described in Patent Document 2, as the mold resin moves, heat is transferred to the mold and the coil bobbin, resulting in some areas of the mold resin being at a lower temperature and leaving unmelted portions, which leads to a problem of poor waterproofing between the coil bobbin and the mold resin.

[0008] The object of the present invention is to provide a solenoid that reduces manufacturing costs and improves the waterproofness of the bobbin and mold resin.

[0009] To achieve the above objective, the solenoid of the present invention comprises, as an example, a bobbin having a cylindrical portion and a large-diameter portion extending radially outward from the axial end of the cylindrical portion; a coil wound around the cylindrical portion of the bobbin; and a molded resin casing that covers the bobbin and the coil with molded resin and forms a joint between the large-diameter portion and the casing, wherein the molded resin casing includes an end covering portion that covers the axial end of the large-diameter portion of the bobbin radially with the molded resin, and a portion of the end covering portion has an axially thickened portion that is thicker in the axial direction than the other portion of the end covering portion.

[0010] According to the present invention, it is possible to provide a solenoid that reduces manufacturing costs and improves the waterproofness of the bobbin and mold resin.

[0011] Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments.

[0012] This is a cross-sectional view of solenoid 1 cut along the axial direction. This is a top view of the molded coil as seen from the axial direction. This is a cross-sectional view taken along the line IIB-IIB in Figure 2A. This is a top view of the molded coil according to Embodiment 1 of the present invention as seen from the axial direction. This is a cross-sectional view taken along the line IIIB-IIIB in Figure 3A. This is an enlarged view of part IIIC in Figure 3B. This is a top view of the molded coil according to Embodiment 2 of the present invention as seen from the axial direction. This is a cross-sectional view taken along the line IVB-IVB in Figure 3A. This is a top view of the molded coil according to Embodiment 3 of the present invention as seen from the axial direction. This is a cross-sectional view taken along the line VB-VB in Figure 5A. This is a top view of the molded coil according to Modification 1 of Embodiment 3 as seen from the axial direction. This is a cross-sectional view taken along the line VIB-VIB in Figure 6A. This is a top view of the molded coil according to Embodiment 4 of the present invention as seen from the axial direction. This is a cross-sectional view taken along the line VIIB-VIIIB in Figure 7A. This is a top view of the molded coil according to Embodiment 5 of the present invention as seen from the axial direction. This is a cross-sectional view taken along the line VIIIB-VIIIB in Figure 8A.

[0013] The embodiments of the present invention will be described below with reference to the drawings. In principle, the same reference numerals are used for the same elements in all the drawings. Furthermore, descriptions of parts having the same function will be omitted. It should be noted that the configurations described below are merely embodiments, and it is not intended that the embodiments of the present invention are limited to the following specific embodiments.

[0014] In the embodiments described below, for convenience, the upper part of the paper is defined as "top" and the lower part of the paper as "bottom". In addition, in each embodiment, the direction along the rod 8 is defined as the "axial direction", the rotational direction around this axial direction is defined as the "circumferential direction", and the direction perpendicular to the axial direction is defined as the "radial direction".

[0015] <Solenoid Structure> First, an example of a typical solenoid using a molded coil will be explained using Figures 1 and 2. In Figures 1 and 2, an O-ring is not used.

[0016] Figure 1 is a cross-sectional view of the solenoid 1 cut along its axial direction. The solenoid 1 is used to open and close a control valve of a damping force adjustable shock absorber installed in the suspension system of a vehicle such as an automobile. The solenoid 1 comprises a molded coil 2, a yoke 3, a housing 4, a cylinder 5, an armature 6, an anchor 7, a rod 8, a bush 9, and a plate 10. C in the figure indicates the center line.

[0017] The yoke 3 is formed in a cylindrical shape from a magnetic material and is positioned to cover the periphery of the molded coil 2. The housing 4 is made of a magnetic material and is located on the inner circumference of the molded coil 2, positioned to cover one axial side of the armature 6. The cylinder 5 is formed in a cylindrical shape from a non-magnetic material and is positioned to extend axially from the upper surface of the bottom side of the yoke 3. The armature 6 is made of a magnetic material and is fixed to the rod 8. The anchor 7 is formed in a cylindrical shape from a magnetic material and is positioned radially inward from the molded coil 2, positioned to cover the other axial side of the armature 6. A through hole is formed in the center of the anchor 7, communicating in the vertical direction (axial direction), and the rod 8 is inserted into this through hole. A bush 9 is positioned below the through hole of the anchor 7.

[0018] When current flows through the molded coil 2, the yoke 3, housing 4, and armature 6 become magnetized, generating an attractive force between the anchor 7 located at the end of the molded coil 2 and the armature 6. A rod 8 is fixed to the center of the armature 6. The rod 8 is held via a bush 9 so as to be able to move linearly in the axial direction. When an attractive force is generated between the armature 6 and the anchor 7, the rod 8 imparts thrust to the valve body of the control valve.

[0019] <Basic Structure of Molded Coil> Figure 2A is a top view of the molded coil as seen from the axial direction. Figure 2B is a cross-sectional view taken along the line IIB-IIB in Figure 2A.

[0020] As shown in Figures 2A and 2B, the molded coil 2 comprises a bobbin 20 composed of a cylindrical portion 201 and large-diameter portions 202 that extend radially outward from the axial ends of the cylindrical portion 201 (both axial ends in Figure 2B) and have a larger diameter than the cylindrical portion 201; an insulating coated coil 21 wound around the cylindrical portion 201 of the bobbin 20; a molded resin casing 22 that covers the bobbin 20 and the coil 21 with molded resin; and an injection portion 23 formed on the surface of the molded resin casing 22 with a rough surface roughness. The molded resin casing 22 covers the outer circumference of the coil 21, as well as the upper and lower end faces and outer circumference of the large-diameter portions 202 of the bobbin 20 with molded resin.

[0021] A portion of the large-diameter section 202 (one side in Figures 2A and 2B) is provided with a connecting section 24 (radial extension) that extends radially outward from the large-diameter section 202 and connects the coil 21 to an external terminal. The large-diameter section 202 and the connecting section 24 are formed continuously and integrally. The connecting section 24 is covered with a molded resin outer casing 22.

[0022] A joint portion 25 is formed between the molded resin casing 22 and the large-diameter portion 202 of the bobbin 20. The joint portion 25 is located on the axial end face, the radial side, or both of the large-diameter portion 202. In addition, in the configurations of Figures 2A and 2B, a joint portion 25 is also formed between the molded resin casing 22 and the connecting portion 24 (radial extension portion) of the bobbin 20.

[0023] The protruding portions 27 are formed in an uneven manner on the surface of the bobbin 20. The protruding portions 27 are located on the axial end face, the radial side face, or both of these. Furthermore, the protruding portions 27 are melted by the high-temperature molding resin injected from the injection section 23, and the melting of the molding resin and the bobbin 20 promotes the formation of the joint portion 25.

[0024] The projection 29 is located on the inner diameter of the bobbin and can be used for aligning the mold (not shown) and the bobbin 20.

[0025] The end covering portion 31, which constitutes part of the molded resin outer casing 22, covers the axial end of the large diameter portion 202 of the bobbin 20 along the radial direction. The side covering portion 43, which constitutes part of the molded resin outer casing 22, covers the large diameter portion 202 of the bobbin 20 and the radial end of the coil 21 along the axial direction.

[0026] The molded resin outer casing 22 is formed by overmolding the bobbin 20 around which the coil 21 is wound with molded resin. In other words, the molded coil 2 is constructed by overmolding the bobbin 20 around which the coil 21 is wound with molded resin.

[0027] The injection section 23 formed on the surface of the molded resin casing 22 becomes the injection mark of the molten molded resin that makes up the molded resin casing 22. In other words, the injection section 23 is the entrance (injection port) for the molten resin when overmolding the molded resin casing 22, and the molten molded resin is injected from the injection direction indicated by the arrow.

[0028] The joint 25 is formed when the molded resin outer casing 22 and the bobbin 20 melt together and fuse to each other. The joint 25 functions as a sealing portion with sealing properties that can suppress the intrusion of water.

[0029] <Challenges in forming the joint> In order to ensure the waterproofness of the molded coil 2, it is necessary to form a joint 25 around the entire circumference of the bobbin 20. To achieve this, it is necessary to suppress the temperature drop of the molten molded resin around the entire circumference of the bobbin 20. When forming the joint 25 at the end face of the large diameter portion 202 of the bobbin 20, suppressing the temperature drop of the end covering portion 31 is effective, and when forming the joint 25 on the side surface of the large diameter portion 202 of the bobbin 20, suppressing the temperature drop of the side covering portion 43 is effective.

[0030] The following three factors contribute to the temperature drop of the end covering portion 31 and the side covering portion 43: (a) heat dissipation from the mold; (b) delay in reaching the interface due to the flow of mold resin to areas other than the interface between the mold resin and the bobbin; and (c) delay in reaching the interface due to the long distance from the injection port.

[0031] In the following, methods for suppressing at least one of the above factors (a) to (c), which cause a decrease in the temperature of the mold resin, will be explained in each example.

[0032] Figure 3A is a top view of a molded coil according to Embodiment 1 of the present invention, viewed from the axial direction. Figure 3B is a cross-sectional view taken along the line IIIB-IIIB in Figure 3A. Figure 3C is an enlarged view of section IIIC in Figure 3B. Components identical to those in Figures 2A and 2B are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0033] Example 1 describes a method for suppressing temperature drop caused by the following factors: (a) heat dissipation from the mold; (b) delay in the arrival of the mold resin at the interface due to flow of the mold resin to areas other than the interface between the mold resin and the bobbin.

[0034] In Example 1, the region that suppresses the temperature drop of the mold resin is the end face of the large-diameter portion 202 of the bobbin 20.

[0035] In the molded coil 2 shown in Figures 3A and 3B, the connection portion 24 has been omitted from the illustration of the molded coil 2 shown in Figures 2A and 2B in order to make the phenomenon easier to understand. Additional configurations based on the molded coil 2 are shown below.

[0036] In a portion of the end covering portion 31 located in the axial direction of the molded resin, an axially thickened portion 33 is formed, which has a greater axial thickness than the rest of the end covering portion 31 (excluding the portion). The rest of the end covering portion 31 becomes an axially thinned portion 35, which has a thinner axial thickness than the axially thickened portion 33.

[0037] In Example 1, in order to reduce heat dissipation to the mold, an axially thickened portion 33 is provided in a part of the end covering portion 31, where the axial thickness is increased. When molten mold resin is injected into the mold, the amount of mold resin that flows increases in the axially thickened portion 33. As a result, the heat capacity of the mold resin increases in the axially thickened portion 33, which can suppress the temperature drop of the mold resin. However, if the entire end covering portion 31 is thickened, the flow path of the end covering portion 31 expands, which reduces the flow velocity of the mold resin. As a result, at positions far from the injection portion 23 of the mold resin, there is a delay in the arrival of the mold resin at the interface between the mold resin and the bobbin 20. If there is a delay in the arrival of the mold resin, the resin temperature of the mold resin will decrease, and there is a possibility that the joint portion 25 will not be formed in some parts. Therefore, in Example 1, the axially thickened portion 33 is formed only in a part of the end covering portion 31, and the other areas are made into an axially thin portion 35 with a thin thickness. By configuring it in this way, the flow path of the end covering portion 31 can be narrowed, and the flow velocity of the molten mold resin can be increased. As a result, in Example 1, the arrival time of the mold resin at the interface between the mold resin and the bobbin 20 can be shortened over the entire circumference, and a joint portion 25 can be formed over the entire circumference of the end face of the large diameter portion 202 of the bobbin 20.

[0038] The bobbin 20 of Example 1 is provided with a projection 29 that protrudes in the axial direction on the inner diameter portion of the bobbin 20. In addition, the axial end face (surface) of the bobbin 20 is provided with an uneven ridge portion 27.

[0039] In the case of a molded coil 2 having a projection 29 on the inner diameter of the bobbin, the projection 29 protrudes axially beyond the axial end face region of the large diameter portion 202 of the bobbin 20, making it difficult to have an end covering portion 31 with sufficient thickness above the projection 29. Therefore, it is desirable that the axially thickened portion 33 be positioned radially outward from the projection 29 of the bobbin 20.

[0040] In the case of the molded coil 2 having the concavo-convex ridge portion 27 on the axial end face of the bobbin 20, the formation of the joint portion 25 may be aimed at by melting the ridge portion 27 (see FIG. 3C). In this case, suppressing the temperature drop of the molded resin around the ridge portion is advantageous for the formation of the joint portion 25. Therefore, at least a part of the axially thick portion 33 is preferably disposed at a position axially opposed to the ridge portion 27. On the other hand, since the purpose of providing the ridge portion 27 can be considered other than melting of the resin, it is not always necessary to provide the axially thick portion 33 at a position facing all of the ridge portion 27.

[0041] As described above, according to the first embodiment, it is possible to provide a solenoid that suppresses manufacturing costs and improves the waterproof properties of the bobbin and the molded resin.

[0042] <Modification> The present invention is not limited to the configuration of the first embodiment described above. For example, the solenoid of the present invention may be provided with other configurations such as a connection portion 24 in the molded coil. Further, in the first embodiment of the present invention, as shown in FIG. 3B, the axially thick portion 33 is disposed only at the upper part of the molded coil, but the axially thick portion 33 may be disposed only at the lower part, or the axially thick portion 33 may be disposed both above and below.

[0043] Next, a second actual example of the present invention will be described with reference to FIGS. 4A and 4B. FIG. 4A is a top view of the molded coil according to the second embodiment of the present invention as viewed from the axial direction. FIG. 4B is a cross-sectional view taken along line IVB-IVB of FIG. 3A. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

[0044] In the second embodiment, a method for suppressing temperature drop due to the following factors will be described. (a) Heat extraction to the mold. (b) Delay in reaching the interface due to the flow of the molded resin to a location other than the interface between the molded resin and the bobbin.

[0045] In the second embodiment, the region for suppressing the temperature drop of the molded resin is the end face in the large-diameter portion 202 of the bobbin 20.

[0046] In Example 2, a connection part 24 (radial extension part) for connecting the coil 21 and an external terminal extends radially outward from the large-diameter part 202 of the bobbin 20.

[0047] An end covering part 31 that forms part of the molded resin exterior 22 covers the axial ends of the large-diameter part 202 of the bobbin 20 and the connection part 24 along the radial direction. A side covering part 43 that forms part of the molded resin exterior 22 covers the radial ends of the large-diameter part 202 of the bobbin 20 and the coil 21 along the axial direction.

[0048] In a partial region of the end covering part 31 located in the axial direction of the molded resin, an axially thick part 33 having a greater axial thickness than other regions of the end covering part 31 is formed. The other regions of the end covering part 31 become an axially thin part 35 having an axial thickness thinner than that of the axially thick part 33.

[0049] In Example 2, the end covering part 31 that covers one end face (upper face) of the large-diameter part 202 of the bobbin 20 and a part of the end face (upper face) of the connection part 24 is the axially thick part 33. Also, the end covering part 31 that covers a part of the end face (upper face) of the connection part 24 excluding the axially thick part 33 is the axially thin part 35. In other words, the axially thick part 33 of Example 2 is formed so as to straddle the large-diameter part 202 of the bobbin 20 and the connection part 24 in at least a part of the end covering part 31.

[0050] In Example 2, in order to reduce heat extraction from the mold, an axially thick part 33 with an increased axial thickness is provided in a partial region of the end covering part 31. When the molten molded resin is injected into the mold, the amount of the molded resin flowing in the axially thick part 33 increases, and the heat capacity of the molded resin increases, so that a decrease in the temperature of the molded resin can be suppressed.

[0051] Also, when the bobbin 20 includes the connection part 24, the molded resin also flows in the direction of the connection part 24 (radial extension part), and a delay in the arrival of the molded resin at the interface between the molded resin and the bobbin 20 occurs in a predetermined circumferential region (inside the broken-line region in FIG. 4A) of the end covering part 31 corresponding to the connection part 24. As a result, there is a concern that the joint part 25 may not be formed in the vicinity of point P (FIG. 4A) where the arrival of the molded resin is presumed to be the slowest.

[0052] Therefore, in Embodiment 2, an axially thickened portion 33 is provided in a predetermined circumferential region (within the dashed area in Figure 4A) corresponding to the connection portion 24 of the end covering portion 31 that covers the large diameter portion 202, and the axial thickness is greater in the axial direction than the axially thin portion 35 corresponding to the connection portion 24. The axially thickened portion 33 functions as a flow promoting portion that promotes the flow of mold resin from a circumferential region other than the predetermined circumferential region (within the dashed area in Figure 4A) toward the predetermined circumferential region. As a result, the flow path in the predetermined circumferential region corresponding to the connection portion 24 is expanded, and the flow resistance can be reduced, thereby suppressing the delay in the arrival of mold resin near point P. In other words, in the configuration of Embodiment 2, the flow of mold resin from a circumferential region other than the predetermined circumferential region toward the predetermined circumferential region can be promoted. As a result, the arrival of the mold resin at the interface between the mold resin and the bobbin can be accelerated over the entire circumference, so that a joint portion 25 can be formed around the entire circumference of the end face of the large diameter portion 202 of the bobbin 20.

[0053] Furthermore, in the case of a molded coil equipped with a projection 29, it is desirable that the axially thickened portion 33 be positioned radially outward from the projection 29 of the bobbin 20, similar to the first embodiment.

[0054] Furthermore, in the case of a coil having a protruding portion 27, it is preferable, similar to Example 1, that at least a portion of the axially thickened portion 33 be positioned opposite the protruding portion 27 in the axial direction.

[0055] As described above, according to Example 2, a solenoid is provided that has a connection part on the bobbin, which reduces manufacturing costs and improves the waterproofness of the bobbin with the connection part and the molded resin.

[0056] <Modifications> In Example 2, the molding resin injection section 23 is provided at the upper and lower positions in the vertical direction of the molding coil 2, and the molding resin is injected from the radially outer side. The present invention is not limited to the configuration of Example 2 described above. For example, the molding resin injection section 23 may be provided at the central position in the vertical direction of the molding coil 2, and the molding resin may be injected from the radially outer side. Alternatively, the molding resin injection section 23 may be provided at the upper and lower end faces in the vertical direction of the molding coil 2, and the molding resin may be injected from the vertical axis direction.

[0057] Next, a practical example 3 of the present invention will be described using Figures 5A and 5B. Figure 5A is a top view of the molded coil according to Embodiment 3 of the present invention, viewed from the axial direction. Figure 5B is a cross-sectional view taken along the line VB-VB in Figure 5A. Components similar to those in Embodiments 1 and 2 are denoted by the same reference numerals, and their detailed descriptions are omitted. Embodiment 3 describes a method for suppressing temperature drop due to the following factors: (b) Delay in reaching the interface due to the flow of molded resin to locations other than the interface between the molded resin and the bobbin.

[0058] In Example 3, the region that suppresses the temperature drop of the mold resin is the end face of the large-diameter portion 202 of the bobbin 20.

[0059] In Embodiment 3, the bobbin 20 is provided with a connection portion 24 (radial extension portion) that extends radially outward from the large diameter portion 202 and connects the coil 21 to an external terminal.

[0060] The end covering portion 31, which constitutes part of the molded resin outer casing 22, covers the large diameter portion 202 of the bobbin 20 and the axial end of the connecting portion 24 along the radial direction. The side covering portion 43, which constitutes part of the molded resin outer casing 22, covers the large diameter portion 202 of the bobbin 20 and the radial end of the coil 21 along the axial direction.

[0061] Furthermore, Embodiment 3 includes a flow suppression section 36. The flow suppression section 36 suppresses the flow of the mold resin and delays the inflow of the mold resin into the connection section 24, and constitutes a part of the mold resin outer casing 22.

[0062] The end covering portion 31, which covers at least a part of the large-diameter portion 202 and the connecting portion 24 of the bobbin 20, forms an axially thin portion 35. At least a part of the end covering portion 31 that covers the connecting portion 24 forms a connecting portion thick portion 37 (axially thick portion) which is thicker in the axial direction than the axially thin portion 35. In other words, the connecting portion thick portion 37 is a region that is thicker than the end covering portion 31 that covers the connecting portion 24.

[0063] In the molded coil 2 of Embodiment 3, a slit-shaped flow suppression portion 36 is formed between the axially thin portion 35 and the thick portion 37 of the connection portion of the end covering portion 31. The flow suppression portion 36 is a region with a thinner wall thickness than both the axially thin portion 35 and the thick portion 37 of the connection portion. The flow suppression portion 36 also functions to suppress the flow of molded resin into the thick portion 37 of the connection portion.

[0064] If the flow suppression portion 36 is not provided, the thickened portion 37 of the connection portion is thicker than the end covering portion 31 and has less flow resistance, so the resin preferentially flows into the connection portion 24, delaying its arrival at a predetermined circumferential region (within the dashed line area in Figure 5A) of the end covering portion 31 corresponding to the connection portion 24. In Embodiment 3, by providing the flow suppression portion 36, the flow of the mold resin to the connection portion 24 is suppressed, and the mold resin is encouraged to preferentially flow to a predetermined circumferential region of the end covering portion 31 corresponding to the connection portion 24. As a result, the arrival of the mold resin at the interface between the mold resin and the bobbin is accelerated over the entire circumference, so that the joint portion 25 can be formed around the entire circumference of the end face of the large diameter portion 202 of the bobbin 20.

[0065] As described above, according to Example 3, it is possible to provide a solenoid that reduces manufacturing costs and improves the waterproofness of the bobbin and mold resin.

[0066] <Modification> Next, a modification of the practical example 3 of the present invention will be described using Figures 6A and 6B. Figure 6A is a top view of the molded coil according to modification 1 of Example 3, viewed from the axial direction. Figure 6B is a cross-sectional view taken along the line VIB-VIB in Figure 6A.

[0067] In Modification 1, the molded coil 2 has a different shape for the flow suppression portion 36, and a rib 39 is provided on a part of the flow suppression portion 36.

[0068] In Modification 1, the flow suppression portion 36 extends radially outward (towards the connection portion 24) compared to Example 3 (Figure 5A). In addition, a rib 39 is formed in the circumferential center of the flow suppression portion 36, with a thickness in the axial direction greater than that of the flow suppression portion 36.

[0069] In the region surrounding the end covering portion 31 that covers the connection portion 24, the thickness of the end covering portion 31 needs to be increased for product design purposes. Therefore, in the modified example of Embodiment 3, a rib 39, which is thicker than the end covering portion 31, is provided in the region surrounding the end covering portion 31 that covers the connection portion 24. Since the rib 39 is thicker than the end covering portion 31, the flow of mold resin to the connection portion 24 is promoted. However, if the flow suppression portion 36 is arranged in most of the region surrounding the end covering portion 31, the effect shown in Embodiment 3 can be obtained even if a part of the remaining region (rib 39) is thicker than the end covering portion 31.

[0070] In Example 3 and its modified form, the molding resin injection section 23 is provided at the upper and lower positions in the vertical direction of the molding coil 2, and the molding resin is injected from the radially outer side. The present invention is not limited to the configuration of Example 3 and its modified form described above. For example, the molding resin injection section 23 may be provided at the central position in the vertical direction of the molding coil 2, and the molding resin may be injected from the radially outer side. Alternatively, the molding resin injection section 23 may be provided at the upper and lower end faces in the vertical direction of the molding coil 2, and the molding resin may be injected from the vertical axis direction.

[0071] Next, a practical example of the present invention, 4, will be described with reference to Figures 7A and 7B. Figure 7A is a top view of a molded coil according to embodiment 4 of the present invention, viewed from the axial direction. Figure 7B is a cross-sectional view taken along the line VIIB-VIIB in Figure 7A. Components similar to those in embodiments 1 to 3 are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0072] Example 4 describes a method for suppressing temperature drop due to the following factors: (a) heat dissipation from the mold; (c) delay in reaching the interface due to the long distance from the injection port.

[0073] In Example 4, the region that suppresses the temperature drop of the mold resin is the upper and lower end faces of the large-diameter portion 202 of the bobbin 20.

[0074] In the molded coil 2 shown in Figures 7A and 7B, the connection portion 24 has been removed from the molded coil 2 shown in Figures 2A and 2B in order to make the phenomenon easier to understand. Additional configurations based on the molded coil 2 are shown below.

[0075] In a portion of the end covering portion 31 located in the axial direction of the molded resin, an axially thickened portion 33 is formed, which has a greater axial thickness than the rest of the end covering portion 31. The rest of the end covering portion 31 becomes an axially thinned portion 35, which has a thinner axial thickness than the axially thickened portion 33.

[0076] The axially thickened portion 33 is located in the circumferential far region (within the dashed area in Figure 7A), which includes the position furthest from the injection portion 23.

[0077] In the mold coil 2, an axially thickened portion 33 is positioned in the circumferentially distant region, which is the furthest from the injection port 23 and where there is a concern that the joint portion 25 may not be formed due to a drop in the temperature of the mold resin. This reduces the temperature drop in the circumferentially distant region, which is the furthest from the injection port and most likely to result in non-joint formation, and ensures the formation of the joint portion 25 around the entire circumference of the end covering portion 31, including the circumferentially distant region. Furthermore, by thickening only the circumferentially distant region instead of the entire circumference, the amount of mold resin used can be reduced, contributing to a reduction in manufacturing costs.

[0078] In the case of a coil having a projection 29, it is preferable that the axially thickened portion 33 be positioned radially outward from the projection 29 of the bobbin 20, similar to the first embodiment.

[0079] Furthermore, in the case of a coil having a protruding portion 27, it is preferable, similar to Example 1, that at least a portion of the axially thickened portion 33 be positioned opposite the protruding portion 27 in the axial direction.

[0080] As described above, according to Example 4, it is possible to provide a solenoid that reduces manufacturing costs and improves the waterproofness of the bobbin and mold resin.

[0081] <Modification> In Example 4, the axially thickened portion 33 is placed only at the top. The present invention is not limited to the configuration of Example 4 described above. For example, the axially thickened portion 33 may be placed only at the bottom, or it may be placed at both the top and bottom.

[0082] Next, a practical example 5 of the present invention will be described with reference to Figures 8A and 8B. Figure 8A is a top view of a molded coil according to embodiment 5 of the present invention, viewed from the axial direction. Figure 8B is a cross-sectional view taken along the line VIIIB-VIIIB in Figure 8A. Components similar to those in embodiments 1 to 4 are denoted by the same reference numerals, and their detailed descriptions are omitted.

[0083] Example 5 describes a method for suppressing temperature drop caused by the following factors: (a) heat dissipation from the mold; (b) delay in the arrival of the mold resin at the interface due to flow of the mold resin to areas other than the interface between the mold resin and the bobbin.

[0084] The regions that suppress the temperature drop of the mold resin are the end face and side surface of the large-diameter portion 202 of the bobbin 20.

[0085] In the molded coil 2 shown in Figures 8A and 8B, the connection portion 24 has been removed from the molded coil 2 shown in Figures 2A and 2B in order to make the phenomenon easier to understand. Additional configurations based on the molded coil 2 are shown below.

[0086] In a portion of the end covering portion 31 located in the axial direction of the molded resin, an axially thickened portion 33 is formed, which has a greater axial thickness than the rest of the end covering portion 31. The rest of the end covering portion 31 becomes an axially thinned portion 35, which has a thinner axial thickness than the axially thickened portion 33.

[0087] Furthermore, a radially thickened portion 45 is formed in a part of the side covering portion 43 located in the radial direction of the mold resin, with a radial thickness greater than that of the other parts of the side covering portion 43. The other parts of the side covering portion 43 are radially thinned portions 46, with a radial thickness less than that of the radially thickened portion 45. Note that the radially thickened portion 45 is the area other than the connecting portion (not shown). The protruding portion 27 is positioned on both the axial end face and the radial end face (side face) of the large diameter portion 202 of the bobbin 20.

[0088] To reduce heat loss to the mold, a portion of the end covering portion 31 that covers the end face of the large diameter portion 202 of the bobbin 20 is provided with an axially thickened portion 33, in which the thickness in the axial direction is increased. In addition, a portion of the side covering portion 43 that covers the side surface of the large diameter portion 202 of the bobbin 20 is provided with a radially thickened portion 45, in which the thickness in the radial direction is increased. When molten mold resin is injected into the mold, the amount of mold resin that flows increases in the axially thickened portion 33 and the radially thickened portion 45, and the heat capacity of the mold resin increases, so that the temperature drop of the mold resin can be suppressed.

[0089] However, if the entire end covering portion 31 and the side covering portion 43 are thickened, the overall flow path of the end covering portion 31 and the side covering portion 43 will expand, reducing the flow velocity. As a result, at positions far from the injection portion 23, there will be a delay in reaching the interface between the mold resin and the bobbin 20, and the resin temperature of the mold resin will decrease, potentially preventing the formation of the joint portion 25 in some areas. Therefore, the end face of the large diameter portion 202 of the bobbin 20 is provided with an axially thickened portion 33, which is partially thickened as in Example 1, and the side surface of the large diameter portion 202 of the bobbin 20 is provided with a radially thickened portion 45, which is thickened only in part of the side covering portion 43. By configuring it in this way, the flow path of the end covering portion 31 and the side covering portion 43 can be narrowed, and the flow velocity of the molten mold resin can be increased. As a result, the arrival of the mold resin at the interface between the mold resin and the bobbin can be accelerated around the entire circumference, and the joint portion 25 can be formed on the end face and side surface of the large diameter portion 202 of the bobbin 20 around the entire circumference.

[0090] In the case of a coil having a protruding portion 27, for the same reasons as in Embodiment 1, it is preferable to position at least a portion of the axially thickened portion 33 and the radially thickened portion 45 opposite the protruding portion 27.

[0091] As described above, according to Example 5, it is possible to provide a solenoid that reduces manufacturing costs and improves the waterproofness of the bobbin and mold resin.

[0092] <Modification> In Example 5, the protruding portion 27 is arranged on both the end face and the side surface of the large-diameter portion 202 of the bobbin 20. The present invention is not limited to the configuration of Example 5 described above. For example, the protruding portion 27 may be arranged on only one of the end face or side surface of the large-diameter portion 202 of the bobbin 20. Also, the radially thickened portion 45 may be arranged on only one of the upper or lower parts.

[0093] 1...Solenoid, 2...Molded coil, 3...Yoke, 4...Housing, 5...Cylinder, 6...Armature, 7...Anchor, 8...Rod, 9...Bush, 10...Plate, 20...Bobbin, 21...Coil, 22...Molded resin casing, 23...Injection part, 24...Connection part, 25...Joint part, 27...Protrusion, 29...Projection, 31...End covering part, 33...Axial thick part, 35...Axial thin part, 36...Flow suppression part, 37...Connection part thick part, 39...Rib, 43...Side covering part, 45...Radial thick part, 46...Radial thin part, 201...Cylindrical part, 202...Large diameter part

Claims

1. A solenoid for use in a control valve, comprising: a bobbin having a cylindrical portion and a large-diameter portion extending radially outward from the axial end of the cylindrical portion; a coil wound around the cylindrical portion of the bobbin; and a molded resin casing covering the bobbin and the coil with molded resin and forming a joint between the bobbin and the large-diameter portion, wherein the molded resin casing includes an end covering portion that covers the axial end of the large-diameter portion of the bobbin radially with the molded resin, and a portion of the end covering portion has an axially thickened portion that is thicker in the axial direction than the other portion of the end covering portion.

2. A solenoid according to claim 1, characterized in that the bobbin is provided with a projection that protrudes in the axial direction, and the axially thickened portion is positioned radially outward from the projection.

3. A solenoid according to claim 1, characterized in that the axial end face of the bobbin is provided with an uneven ridge portion, and the axially thickened portion is positioned opposite the ridge portion in the axial direction.

4. A solenoid for use in a control valve, comprising: a bobbin having a cylindrical portion, a large-diameter portion extending radially outward from the axial end of the cylindrical portion, and a radial extension portion extending radially from the large-diameter portion; a coil wound around the cylindrical portion of the bobbin; and a molded resin casing covering the bobbin and the coil with molded resin, forming a joint between the large-diameter portion and the radial extension portion, wherein the molded resin casing includes an end covering portion that covers the axial ends of the large-diameter portion and the radial extension portion of the bobbin radially with the molded resin, and a flow promoting portion is provided in a predetermined circumferential region of the end covering portion covering the large-diameter portion corresponding to the radial extension portion, which promotes the flow of the molded resin from another circumferential region different from the predetermined circumferential region toward the predetermined circumferential region.

5. A solenoid according to claim 4, characterized in that the flow-promoting portion is an axially thickened portion that is thicker than the end covering portion that covers the axial end face of the radial extension portion.

6. A solenoid according to claim 5, characterized in that the axial end face of the bobbin is provided with an uneven ridge, and the axially thickened portion is positioned opposite the ridge in the axial direction.

7. A solenoid for use in a control valve, comprising: a bobbin having a cylindrical portion, a large-diameter portion extending radially outward from the axial end of the cylindrical portion, and a radial extension portion extending radially from the large-diameter portion; a coil wound around the cylindrical portion of the bobbin; and a molded resin casing covering the bobbin and the coil with molded resin, forming a joint between the large-diameter portion and the radial extension portion, wherein the molded resin casing includes an end covering portion that covers the axial ends of the large-diameter portion and the radial extension portion of the bobbin radially with the molded resin, and the end covering portion includes an axially thickened portion that covers the radial extension portion and the large-diameter portion of the bobbin, and a flow suppressing portion that suppresses the flow of the molded resin to the axially thickened portion.

8. A solenoid for use in a control valve, comprising: a bobbin having a cylindrical portion and a large-diameter portion extending radially outward from the axial end of the cylindrical portion; a coil wound around the cylindrical portion of the bobbin; and a molded resin casing covering the bobbin and the coil with molded resin and forming a joint between the casing and the large-diameter portion, wherein the molded resin casing has an axially thickened portion in a circumferentially distant region including the position furthest from the injection portion of the molded resin, having a greater axial thickness in the circumferentially distant region than in regions other than the circumferentially distant region.

9. A solenoid according to claim 8, characterized in that the bobbin is provided with a projection that protrudes in the axial direction, and the axially thickened portion is positioned radially outward from the projection.

10. A solenoid according to claim 8, characterized in that the axial end face of the bobbin is provided with an uneven ridge portion, and the axially thickened portion is positioned opposite the ridge portion in the axial direction.

11. A solenoid for use in a control valve, comprising: a bobbin having a cylindrical portion and a large-diameter portion extending radially outward from the axial end of the cylindrical portion; a coil wound around the cylindrical portion of the bobbin; and a molded resin casing covering the bobbin and the coil with molded resin and forming a joint between the casing and the large-diameter portion, wherein the molded resin casing includes a side covering portion that covers the radial end of the large-diameter portion of the bobbin along the axial direction with the molded resin, and a portion of the side covering portion is provided with a radially thickened portion having a radial thickness greater than that of the other portion of the side covering portion.

12. A solenoid according to claim 11, characterized in that the radial end face of the bobbin is provided with an uneven ridge, and the radially thickened portion is positioned radially opposite to the ridge.

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