Solenoid, shock absorber, and method for manufacturing solenoid

Abstract

A purpose of the present invention is to provide a solenoid structure that makes it possible to shorten the axial length.　A solenoid according to the present invention comprises: a bobbin 20 that has a cylindrical portion 201, and a large diameter portion 202 that is formed at one end of the cylindrical portion 201 and extends radially outward from the cylindrical portion 201; a coil 21 that is wound around the cylindrical portion 201 of the bobbin 20; and a primary exterior body 22 that covers an outer periphery of the coil 21 and a side surface 202a of the large diameter portion 202 of the bobbin 20 and constitutes a seal portion 23 between the side surface 202a of the large diameter portion 202 of the bobbin 20 and the primary exterior body. Out of both end surfaces 2021 and 2022 of the large diameter portion 202, at least a portion of the end surface 2022 that is on the opposite side from the winding side of the coil 21 is exposed from the primary exterior body 22.

Description

Solenoid, shock absorber, and method of manufacturing solenoid

[0001] The present invention relates to a solenoid provided in a solenoid valve, a shock absorber, and a method for manufacturing the solenoid.

[0002] Patent Document 1 describes a molded coil in which a coil is wound between frame disks provided near both ends of a cylindrical coil bobbin made of thermoplastic resin, protrusions are formed on the outer and outer peripheral surfaces of the frame disks that continue in the circumferential direction and have thin-walled portions at their tips, and a molten high-temperature molding material made of the same resin is injection-molded onto the outer peripheral part of the coil bobbin, whereby the thin-walled portions are heated and melted by the molding material, and the two are heat-fused together (see abstract).

[0003] Japanese Patent Application Publication No. 9-63835

[0004] The molded coil of Patent Document 1 has a structure in which the protrusions on the end surface of the coil bobbin are melted, so that it is necessary to inject molding material onto the end surface of the coil bobbin, and the molding material on the end surface of the coil bobbin increases the axial length of the coil.

[0005] An object of the present invention is to provide a solenoid structure that can shorten the axial length.

[0006] In order to achieve the above object, the solenoid of the present invention is a solenoid mounted on an electromagnetic valve, the solenoid comprising: a bobbin having a cylindrical portion and a large diameter portion formed at one end of the cylindrical portion and extending radially outward from the cylindrical portion; a coil wound around the cylindrical portion of the bobbin; and a primary outer casing that covers the outer periphery of the coil and a side surface of the large diameter portion of the bobbin and forms a seal between the side surface of the large diameter portion of the bobbin, and at least a portion of both end surfaces of the large diameter portion opposite the side on which the coil is wound is exposed from the primary outer casing.

[0007] According to the present invention, the axial length of the solenoid can be shortened by providing a seal on the side surface of the large diameter portion of the bobbin and eliminating the seal on the end surface of the large diameter portion. By shortening the axial length of the solenoid, it is possible to reduce the size of the shock absorber. Objects, configurations, and effects other than those described above will become clear from the following description of the preferred embodiment of the invention.

[0008] FIG. 1 is a longitudinal sectional view of a solenoid according to an embodiment of the present invention; FIG. 2 is a longitudinal sectional view showing a molded coil extracted from the solenoid of FIG. 1; FIG. 3 is an enlarged view of the vicinity of the side surface of the large diameter portion of the molded coil (part III in FIG. 2); FIG. 4 is a view showing a modified example (first modified example) of the solenoid according to the present invention, and is an enlarged view of the vicinity of the side surface of the large diameter portion of the molded coil; FIG. 5 is a view showing a modified example (second modified example) of the solenoid according to the present invention, and is an enlarged view of the vicinity of the side surface of the large diameter portion of the molded coil; FIG. 6 is an enlarged view of the vicinity of the outer periphery of the molded coil; FIG. 7 is an enlarged view of the vicinity of the outer periphery of the large diameter portion of the bobbin; FIG. 8 is an example of a longitudinal sectional view of a molding die for a primary exterior body; FIG. 9 is a longitudinal sectional view of a shock absorber according to the present invention; FIG. 10 is an enlarged view of the side surface of the large diameter portion of the molded coil in a comparative example to the present invention.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] First, a shock absorber to which the solenoid 1 according to the present invention is applied will be described with reference to Fig. 9. Fig. 9 is a vertical cross-sectional view of a shock absorber 100 according to the present invention. In this embodiment, the damping force adjustable shock absorber 100 will be described as an example.

[0011] The damping force adjustable hydraulic shock absorber (hereinafter referred to as the shock absorber) 100 according to this embodiment has a double-cylinder structure in which an outer cylinder 103 is provided outside a cylinder 102, and a reservoir 104 is formed between the cylinder 102 and the outer cylinder 103. A piston 105 is slidably fitted within the cylinder 102, and the piston 105 divides the interior of the cylinder 102 into two chambers: an upper cylinder chamber 102A and a lower cylinder chamber 102B. One end of a piston rod 106 is connected to the piston 105 by a nut 107, and the other end of the piston rod 106 passes through the upper cylinder chamber 102A and is inserted through a rod guide 108 and an oil seal 109 attached to the upper ends of the cylinder 102 and the outer cylinder 103, and extends outside the cylinder 102. A base valve 110 is provided at the lower end of the cylinder 102, separating the lower cylinder chamber 102B from the reservoir 104.

[0012] The piston 105 is provided with oil passages 111 and 112 that communicate between the upper and lower cylinder chambers 102A and 102B. The oil passage 111 is provided with a check valve 113 that allows oil to flow only from the lower cylinder chamber 102B to the upper cylinder chamber 102A, and the oil passage 112 is provided with a disk valve 114 that opens when the pressure of the oil in the upper cylinder chamber 102A reaches a predetermined pressure to relieve the oil in the upper cylinder chamber 102A to the lower cylinder chamber 102B.

[0013] The base valve 110 is provided with oil passages 115 and 116 that connect the cylinder lower chamber 102B and the reservoir 104. The oil passage 115 is provided with a check valve 117 that only allows oil to flow from the reservoir 104 to the cylinder lower chamber 102B, and the oil passage 116 is provided with a disk valve 118 that opens when the pressure of the oil in the cylinder lower chamber 102B reaches a predetermined pressure to relieve the oil in the cylinder lower chamber 102B to the reservoir 104. The cylinder 102 is filled with oil, and the reservoir 104 is filled with oil and gas.

[0014] Separator tubes 120 are fitted to the upper and lower ends of the cylinder 102 via seal members 119, and an annular oil passage 121 is formed between the cylinder 102 and the separator tube 120. The annular oil passage 121 is connected to the upper cylinder chamber 102A by an oil passage 122 provided in the side wall near the upper end of the cylinder 102. A small-diameter opening 123 is provided in the side wall of the separator tube 120, and a large-diameter opening 124 is provided in the side wall of the outer cylinder 103, approximately concentric with opening 123. A damping force generating mechanism 125 is attached to opening 124 in the side wall of the outer cylinder 103.

[0015] The damping force adjustable shock absorber 100 is mounted, for example, on an automobile suspension device. In general, the damping force adjustable shock absorber 100 has a piston 105 connected to a piston rod 106 slidably fitted inside a cylinder 102 filled with oil, dividing the cylinder 102 into two chambers. The flow of oil generated by the sliding of the piston 105 inside the cylinder 102 is controlled by a damping force generating mechanism 125 including an orifice, a disc valve, etc. to generate a damping force. The damping force is also adjusted by changing the flow resistance of the damping force generating mechanism 125 using a pressure control valve 128. The damping force generating mechanism 125 includes a solenoid 1 for controlling the pressure control valve 128, and constitutes an electromagnetic valve. Hereinafter, the damping force generating mechanism 125 will be referred to as a "solenoid valve."

[0016] The solenoid 1 according to the present invention will now be described. <Structure of the solenoid 1> Figure 1 is a longitudinal cross-sectional view of a solenoid 1 according to one embodiment of the present invention. In the following description, the "axial direction" refers to the direction along the central axis 20a of the bobbin 20, and the radial direction refers to the radial direction of the bobbin 20, i.e., the direction perpendicular to the central axis 20a. As will be described later, the bobbin 20 has a tubular portion (cylindrical portion) 201 (see Figure 2), and the central axis 20a is an axis passing through the center of the cylindrical portion 201.

[0017] The solenoid 1 is used to open and close a pressure control valve 128 of a damping force control shock absorber 100 mounted on a suspension device 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, and a bushing 9. Reference numeral 10 denotes a plate provided at one end of the solenoid 1. When current flows through the molded coil 2, the yoke 3, the housing 4, and the armature 6 are magnetized, and an attractive force is generated between the anchor 7 located at one end of the molded coil 2 and the armature 6. A rod 8 is fixed to the center of the armature 6 and is supported by the anchor 7 via the bushing 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 applies thrust to the valve element of the pressure control valve 128.

[0018] <Basic Structure of Molded Coil 2> Figure 2 is a vertical cross-sectional view showing the molded coil 2 extracted from the solenoid 1 of Figure 1. The molded coil 2 has a bobbin 20 consisting of a cylindrical portion 201 and a large-diameter portion 202 extending radially outward from the cylindrical portion 201, an insulating-coated coil 21 wound around the cylindrical portion 201 of the bobbin 20, and a primary exterior body 22 covering the outer periphery of the coil 21 and a side surface 202a of the large-diameter portion 202 of the bobbin 20. A seal portion 23 is formed between the primary exterior body 22 and the large-diameter portion 202 of the bobbin 20, and the seal portion 23 is located on the side surface 202a of the large-diameter portion 202. The primary exterior body 22 is formed by overmolding the bobbin 20 around which the coil 21 is wound, and the seal portion 23 is formed by melting the interface between the primary exterior body 22 and the bobbin 20.

[0019] Figure 3 is an enlarged view of the vicinity of the large-diameter portion side surface 202a of the molded coil 2 (section III in Figure 2). Hereinafter, "end surface" refers to the axial end surface. The axial position of the end surface 221 of the primary outer casing 22 differs from the axial position of the end surface 2022 opposite to the end surface 2021 connected to the tubular portion 201 of the large-diameter portion 202, and the distance L1 between the end surface 221 of the primary outer casing 22 and the end surface 2021 of the large-diameter portion 202 is greater than the thickness T1 of the large-diameter portion 202. In other words, the end surface 221 of the primary outer casing 22 is located axially away from the end surface 2022 of the large-diameter portion 202, away from the coil 21. In this case, the height H1 of the seal portion 23 in the axial direction is equal to the thickness T1 of the large-diameter portion 202.

[0020] Furthermore, the entire end surface 2022 of the large diameter portion 202 is exposed. Here, "exposed" means that the end surface 2022 is not covered by the primary exterior body 22 but is exposed from the primary exterior body 22. In other words, the end surface 2022 may be covered by the yoke 3 or the plate 10 as shown in FIG. 1 .

[0021] 1 , at least a portion of the end surface 2022 is covered by other members such as the yoke 3 and the plate 10, and therefore, in order to shorten the axial length of the solenoid 1 in relation to these other members, it is sufficient that at least a portion of the end surface 2022 is exposed from the primary exterior body 22. In other words, of both end surfaces 2021, 2022 of the large diameter portion 202, at least a portion of the end surface 2022 opposite to the side on which the coil 21 is wound is exposed from the primary exterior body 22.

[0022] 4 is a diagram showing a modified example (first modified example) of the solenoid 1 according to the present invention, and is an enlarged view of the vicinity of the side surface 202a of the large diameter portion of the molded coil 2. In this example, the axial position of the end surface 221 of the primary outer casing 22 coincides with the axial position of the end surface 2022 of the large diameter portion 202. In this case, the height H1 of the seal portion 23 in the axial direction of the bobbin 20 is equal to the thickness T1 of the large diameter portion 202. In this example, the axial length of the molded coil 2 alone can be shortened compared to the case of FIG. 3, and the axial length of the solenoid 1 can be reliably shortened.

[0023] 5 is a diagram showing a modified example (second modified example) of the solenoid 1 according to the present invention, and is an enlarged view of the vicinity of the side surface 202a of the large diameter portion of the molded coil 2. In this example, the distance L1 between the end surface 221 of the primary outer casing 22 and the end surface 2021 of the large diameter portion 202 is smaller than the thickness T1 of the large diameter portion 202. In this case, the distance L1 between the end surfaces 221 and 2021 is the height H1 of the seal portion 23 in the axial direction, and the height H1 of the seal portion 23 is smaller than the thickness T1 of the large diameter portion 202. If the sealing performance of the seal portion 23 can be ensured, the distance L1 can be made smaller than the thickness T1, allowing the molded coil 2 to be made smaller.

[0024] In the above-described embodiment and modified example, the side surface 202 a of the large diameter portion 202 of the bobbin 20 has a simple cylindrical shape, but the side surface 202 a of the large diameter portion 202 does not necessarily have to be cylindrical. For example, the side surface 202 a of the large diameter portion 202 may have an irregular shape, such as a protrusion.

[0025] As shown in FIGS. 3 to 5, in this embodiment and the modified example, the height H1 of the seal portion 23 in the axial direction is equal to or smaller than the thickness T1 of the large diameter portion 202.

[0026] <Structure of the outer periphery of the coil> Figure 10 is an enlarged view of the side surface 202a of the large diameter portion of a molded coil in a comparative example to the present invention. In this example, the seal portion 23 between the primary outer casing 22 and the bobbin 20 is located on the side surface 202a of the large diameter portion 202. On the other hand, in the comparative example to the present invention, as shown in Figure 10, the primary outer casing 22 is also provided on the end surface 2022 of the large diameter portion, and the seal portion 23 is formed not only on the side surface 202a of the large diameter portion 202 of the bobbin, but also on the end surface 2022 of the large diameter portion. Therefore, the area of ​​the seal portion 23 is larger than in this example.

[0027] In this embodiment, in order to ensure sufficient waterproof performance at the seal portion 23, the molding temperature during overmolding of the primary outer casing 22 is made higher than in the past, and the heat from the primary outer casing 22 reliably melts the resin material on the side surface 202a of the large diameter portion 202.

[0028] 6 is an enlarged view of the outer periphery of the molded coil 2. Protective means 24 is provided between the primary exterior body 22 and the coil 21. Protective means 24 is, for example, a sheet-like member. Hereinafter, the protective means will be referred to as the protective member or protective section. If the molding temperature during overmolding of the primary exterior body 22 is set lower than the melting point of the protective section 24, the protective section 24 will not liquefy during injection molding, thereby avoiding direct contact between the primary exterior body 22 and the coil 21. For this reason, a material with a melting point higher than the heat resistance temperature of the insulating coating of the coil 21 is used for the protective section 24.

[0029] Here, the heat resistance temperature of the insulating coating of coil 21 is the temperature at which the insulating performance of coil 21 deteriorates after primary exterior body 22 is overmolded, and is equal to or lower than the melting point of the insulating coating of coil 21. By providing protective part 24 between primary exterior body 22 and coil 21, the molding temperature of primary exterior body 22 can be set to be equal to or higher than the heat resistance temperature of the insulating coating of coil 21, and primary exterior body 22 can be molded at a higher temperature than before.

[0030] Furthermore, it is preferable to use a material for the protective part 24 that has a lower thermal conductivity than the thermal conductivity of the insulating coating of the coil 21. This makes it possible to reduce the amount of heat that transfers to the coil 21 through the protective part 24 during injection molding of the primary exterior body 22.

[0031] 7 is an enlarged view of the vicinity of the outer periphery of the large diameter portion 202 of the bobbin 20. The diameter of the large diameter portion 202 is smaller at the end face 2021 of the large diameter portion 202 of the molded coil 2, and a step (step portion) 2023 is formed in the large diameter portion 202. If there is a gap between the protective portion 24 and the large diameter portion 202, there is a risk that molten resin will flow into the outer periphery of the coil 21 during molding of the primary outer casing 22, damaging the insulating coating of the coil 21. However, by providing the step 2023, it becomes easier to position the protective portion 24 so that the protective portion 24 reliably covers the axial end of the winding range of the coil 21 when winding the protective portion 24 around the outer periphery of the coil 21, and it is possible to prevent a gap from occurring between the end face 2021 of the large diameter portion 202 and the protective portion 24. In this case, the large diameter portion 202 has a step 2023 on the end surface 2021 on the winding side of the coil 21 , and the protective portion 24 is provided so as to cover the step 2023 .

[0032] 7 , the protective portion 24 is wound around the small diameter portion of the step 2023, and therefore the seal portion 23 is not formed at the step 2023. Therefore, it is desirable to minimize the height of the step 2023 in order to prevent a decrease in the waterproof function of the seal portion 23. Furthermore, it is not always necessary to provide the step 2023; for example, if the protective portion 24 is wound around the outer periphery of the coil 21 using a device with high positioning accuracy, the step 2023 does not necessarily have to be provided.

[0033] In this embodiment, an example is shown in which a sheet-like member is used as the protective portion 24, but other protective means, such as a sprayed coating agent or an overmolded resin layer, may also be used. Furthermore, in this embodiment, an example is shown in which the protective portion 24 is used, but in the case of a material with a small heat of fusion, such as syndiotactic polystyrene resin (SPS), the protective portion 24 may not be provided because sufficient waterproofing can be provided to the seal portion 23 even if the molding temperature of the primary outer casing 22 is below the heat resistance temperature of the insulating coating of the coil 21.

[0034] <Waterproof Performance of Seal Portion 23> The waterproof performance of the seal portion 23 in this example was verified using glass fiber reinforced nylon resin (PA66-GF30). A bobbin 20 having a large-diameter portion with a diameter of 28 mm and a thickness of 3 mm was used. A gate was installed near the side of the large-diameter portion 202 of the bobbin 20 to ensure that the temperature of the primary outer casing 22 reached the large-diameter portion 202 of the bobbin 20 was 280°C or higher. The resulting molded coil 2 was then subjected to a water immersion test to check for leakage. The results showed that leakage was blocked at a 1-mm-thick portion of the large-diameter portion side surface 202a, confirming that the required waterproof function was ensured even when the seal portion between the primary outer casing 20 and the bobbin 20 was provided only on the large-diameter portion side surface 202a.

[0035] The bobbin 20 has a cylindrical portion 201 with a height of 12.5 mm. A protective portion 24 is formed on the outermost periphery of the bobbin 20, and is made of a fluororesin sheet with a thickness of 0.3 mm (thermal conductivity 0.25 W.m -1 .K -1The temperature during molding when the protective layer 24 was wound around the coil 21 was determined by finite element analysis. When injection molding was performed with the gate set at half the height of the cylindrical portion 201, setting the cylinder temperature to 295°C ensures that the temperature of the primary outer casing 22 when it reaches the large diameter portion 202 is between 280°C and 295°C, ensuring the waterproof performance of the seal portion 23. Furthermore, because the melting point of the fluororesin sheet is 312°C, the protective portion 24 does not melt during injection molding, and the insulating coating of the coil 21 (heat-resistant temperature 290°C to 300°C) is not damaged.

[0036] The manufacturing method of the solenoid 1 of this embodiment is to provide a protective portion 24 on the outer surface of the coil 21, the melting point of which is higher than the heat resistance temperature of the insulating coating of the coil 21, heat the primary outer casing 22 to 280°C or higher, and injection mold the primary outer casing 22 so that the outer surface of the primary outer casing 22 and the side surface 202a of the large diameter portion 202 of the bobbin 20 are covered and the end surface 2022 of the large diameter portion 202 is exposed.

[0037] <Method of Manufacturing Molded Coil> Next, an example of a process for manufacturing the molded coil 2 of the solenoid 1 will be described. In this example, an example of using glass fiber reinforced nylon resin (for example, PA66-GF30) will be described.

[0038] 8 is an example of a vertical cross-sectional view of a molding die 30 for the primary exterior body 22. The molding die 30 has restraint portions 301 on both ends in the axial direction, which restrict the flow of the primary exterior body 22 in the axial direction Ax during injection molding.

[0039] The protective portion 24 is provided on the outer periphery of the bobbin 20 around which the coil 21 is wound before injection molding of the primary exterior body 22. After the bobbin 20, the coil 21, and the protective portion 24 are placed inside the molding die 30, the primary exterior body 22 is injected through the gate 302 to fill the molding die 30.

[0040] 8 shows an example in which the gate 302 is provided at one location on the molding die 30. The gate 302 is desirably located at half the height of the cylindrical portion 201 so as to minimize the time it takes for the resin forming the primary outer casing 22 to reach the two large diameter portions 202 in the axial direction Ax during injection molding. In the example shown in FIG. 8, the heating temperature in the cylinder is set to 295°C or higher so that the temperature of the primary outer casing 22 when it reaches the large diameter portions 202 during injection molding is 280°C or higher. In this embodiment, an example is shown in which the gate 302 is located at one location at half the height of the cylindrical portion 201. However, the gate 302 does not necessarily have to be located at half the height of the cylindrical portion 201, and multiple gates may be located instead of one location.

[0041] <Effects> According to the embodiment and its modifications described above, the following effects can be obtained.

[0042] Because the seal portion 23 of the molded coil 2 is located on the side surface 202a of the large diameter portion 202 of the bobbin 20, the end surface 2022 of the large diameter portion 202 is exposed. Therefore, the axial length of the molded coil 2 can be made shorter than that of the molded coil structure of the comparative example shown in Figure 10. This allows the axial lengths of the housing 4 and anchor 6 to be shortened, which in turn shortens the axial length of the solenoid 1 and enables the solenoid valve 125 of the shock absorber 100 to be made smaller.

[0043] Furthermore, if the shapes of the housing 4 and the anchor 6 are maintained, the axial length of the cylindrical portion 201 of the bobbin 20 can be made longer than that of the molded coil structure of the comparative example of the present invention. As a result, the number of turns of the coil 21 can be increased, which increases the attractive force of the armature 6 and the anchor 7 and increases the thrust of the solenoid 1.

[0044] The above-described embodiments of the present invention have the following features: (1) A solenoid 1 mounted on a solenoid valve 125, the solenoid 1 having: a bobbin 20 having a cylindrical portion 201 and a large-diameter portion 202 formed at one end of the cylindrical portion 201 and extending radially outward from the cylindrical portion 201; a coil 21 wound around the cylindrical portion 201 of the bobbin 20; and a primary exterior body 22 covering an outer periphery of the coil 21 and a side surface 202a of the large-diameter portion 202 of the bobbin 20 and constituting a seal portion 23 between the primary exterior body 22 and the side surface 202a of the large-diameter portion 202 of the bobbin 20, wherein at least a portion of the end surface 2022 of the large-diameter portion 202 opposite the side on which the coil 21 is wound is exposed from the primary exterior body 22.

[0045] (2) The height H1 of the seal portion 23 in the axial direction of the bobbin 20 is equal to or smaller than the thickness T1 of the large diameter portion 202.

[0046] (3) Of the two end faces 2021 and 2022 of the large diameter portion 202 , the end face 2022 opposite the side on which the coil 21 is wound is entirely exposed from the primary outer casing 22 .

[0047] (4) The protective portion 24 is provided between the outer circumferential surface of the coil 21 and the primary outer casing 22, and the melting point of the protective portion 24 is higher than the heat resistance temperature of the insulating coating of the coil 21.

[0048] (5) The thermal conductivity of the protective portion 24 is lower than the thermal conductivity of the insulating coating of the coil 21 .

[0049] (7) The protective portion 24 is provided between the outer circumferential surface of the coil 21 and the primary outer casing 22, and the protective portion 24 is made of a sheet-like member.

[0050] (7) The large diameter portion 202 has a step 2023 on the end surface 2021 on the winding side of the coil 21, and the protective portion 24 is provided to cover the step 2023.

[0051] (8) A shock absorber 100 that is mounted on a suspension device of an automobile and has a pressure control valve 128 and a solenoid for controlling the pressure control valve 128, and includes a solenoid 1 as the solenoid.

[0052] (9) A method for manufacturing a solenoid (1), comprising providing a protective portion (24) on the outer peripheral surface of a coil (21) having a melting point higher than the heat resistance temperature of the insulating coating of the coil (21), heating a primary outer casing (22) to 280°C or higher, and injection-molding the primary outer casing (22) so that the outer peripheral surface of the primary outer casing (22) and the side surface (202a) of the large diameter portion (202) of the bobbin (20) are covered and the end surface (2022) of the large diameter portion (202) is exposed.

[0053] (10) A method for manufacturing a solenoid (1), wherein the protective portion (22) has a thermal conductivity lower than that of the insulating coating of the coil (21).

[0054] The present invention is not limited to the above-described embodiments, and other forms conceivable within the scope of the technical concept of the present invention are also included within the scope of the present invention as long as they do not impair the characteristics of the present invention. Furthermore, the present invention is not limited to the above-described embodiments, and various modifications are included. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations. Furthermore, it is possible to add, delete, or replace part of the configuration of the embodiments with other configurations.

[0055] 1... solenoid, 20... bobbin, 21... coil, 22... primary outer casing, 23... sealing portion, 24... protective portion, 100... damping force adjustable shock absorber, 125... solenoid valve, 128... pressure control valve, 201... cylindrical portion, 202... large diameter portion, 202a... side surface of large diameter portion 202, 2021... end surface on the winding side of coil 21, 2022... end surface opposite to the winding side of coil 21, 2023... step

Claims

1. A solenoid mounted on a solenoid valve, the solenoid comprising: a bobbin having a cylindrical portion and a large diameter portion formed at one end of the cylindrical portion and extending radially outward from the cylindrical portion; a coil wound around the cylindrical portion of the bobbin; and a primary exterior body covering the outer periphery of the coil and a side surface of the large diameter portion of the bobbin and constituting a seal between the side surface of the large diameter portion of the bobbin and the side surface, wherein at least a portion of both end surfaces of the large diameter portion opposite the side on which the coil is wound is exposed from the primary exterior body.

2. A solenoid as claimed in claim 1, wherein the height of said seal portion in the axial direction of said bobbin is equal to or smaller than the thickness of said large diameter portion.

3. A solenoid as claimed in claim 1, wherein the end faces of said large diameter section opposite the side on which said coil is wound are entirely exposed from said primary exterior body.

4. A solenoid as claimed in claim 1, further comprising a protective portion between the outer circumferential surface of the coil and the primary exterior body, the protective portion having a melting point higher than the heat resistance temperature of the insulating coating of the coil.

5. A solenoid as claimed in claim 4, wherein the protective portion has a thermal conductivity smaller than that of the insulating coating.

6. A solenoid as claimed in claim 1, further comprising a protective section between the outer circumferential surface of the coil and the primary exterior body, the protective section being made of a sheet-like material.

7. A solenoid as claimed in claim 6, wherein the large diameter portion has a step on an end face on the side where the coil is wound, and the protective portion is provided so as to cover the step.

8. A shock absorber mounted on a suspension device of an automobile and having a pressure control valve and a solenoid for controlling said pressure control valve, said solenoid being the solenoid according to claim 1.

9. A method for manufacturing a solenoid as described in claim 1, comprising providing a protective section on the outer peripheral surface of the coil, the melting point of which is higher than the heat resistance temperature of the insulating coating of the coil, heating the primary exterior body to 280°C or higher, and injection molding the primary exterior body so as to cover the outer peripheral surface of the primary exterior body and the side surface of the large diameter portion of the bobbin and expose the end face of the large diameter portion.

10. A method for manufacturing a solenoid as set forth in claim 9, wherein the protective portion has a thermal conductivity lower than that of the insulating coating.

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