Noise filter

Abstract

To suppress leakage of a magnetic field generated by energization to a coil.SOLUTION: The noise filter A includes the coils 12 connected to the wires 31 constituting the electric circuit 30 and the shielding members 20 including magnetic materials, the shielding members 20 are tubular and arranged to surround the coils 12, and the shielding members 20 are formed with the mounting slits 25 continuous over the entire length in the axial direction of the shielding members 20 and having both ends facing the 20F and the 20R of the front and rear end edges in the axial direction of the shielding members 20. Since the coil 12 is surrounded by the shielding member 20 containing a magnetic material, leakage of a magnetic field generated by energization of the coil 12 is suppressed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to noise filters. [Background technology]

[0002] Patent Document 1 discloses a noise filter in which a ferrite core is housed in a cylindrical portion and an electric wire is wound around the cylindrical portion in a spiral shape. The winding forms a wire harness. When a high-frequency current that generates noise flows through the wire harness, the magnetic field generated around the winding is absorbed by the ferrite core, thereby reducing the noise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-100120 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above noise filter, the winding portion is exposed to the outside of the cylindrical portion, so if another communication circuit is routed near the noise filter, there is a concern that the magnetic field leaking from the winding portion may affect the communication circuit.

[0005] The noise filter of the present disclosure was developed based on the above circumstances, and aims to suppress leakage of a magnetic field generated by energizing a coil. [Means for solving the problem]

[0006] The noise filter of the present disclosure comprises: a coil connected to an electric wire that constitutes an electric circuit; a shielding member including a magnetic material, the shielding member is cylindrical and disposed to surround the coil, The shielding member has an attachment slit formed therein, the attachment slit extending continuously over the entire length of the shielding member in the axial direction and having both ends facing both axial edges of the shielding member. [Effects of the Invention]

[0007] According to the present disclosure, leakage of a magnetic field generated by energizing a coil can be suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a side view of the noise filter of the first embodiment. [Figure 2] FIG. 2 is a plan view of the filter body. [Figure 3] FIG. 3 is a perspective view of the shielding member. [Figure 4] FIG. 4 is a plan view showing an initial step of attaching the filter body to the shielding member. [Figure 5] FIG. 5 is a plan view showing an intermediate step in attaching the filter body to the shielding member. [Figure 6] FIG. 6 is a plan view of the noise filter of the second embodiment. [Figure 7] FIG. 7 is a plan view showing a state in which the shielding member is elastically deformed. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described. Any combination of the following multiple embodiments within a range that does not cause contradictions is also included in the description of the present invention. The noise filter of the present disclosure comprises: (1) A shielding device includes a coil connected to an electric wire that constitutes an electric circuit, and a shielding member containing a magnetic material. The shielding member is cylindrical and disposed to surround the coil. The shielding member has an attachment slit that is continuous along the entire axial length of the shielding member and has both ends facing both axial edges of the shielding member. According to the configuration of the present disclosure, when a noise current flows through the coil, a magnetic field is generated in the coil, thereby reducing noise. Because the coil is surrounded by the shielding member containing a magnetic material, leakage of the magnetic field generated by current flowing through the coil is suppressed. When the coil is housed in the shielding member, the electric wire or coil is passed through the attachment slit. Because the attachment slit is continuous along the entire axial length of the shielding member and has both ends facing both axial edges of the shielding member, the coil can be housed in the shielding member while remaining connected to the electric wire.

[0010] (2) In (1), it is preferable that the shielding member is capable of elastically deforming so as to widen the mounting slits. With this configuration, the width of the mounting slits narrows when the shielding member is not elastically deformed, thereby improving the effect of suppressing leakage of magnetic field.

[0011] (3) In (2), it is preferable that the mounting slit is open when the shielding member is not elastically deformed. With this configuration, it is possible to visually check, by a camera, or the like, whether the coil is housed in the shielding member.

[0012] (4) In (3), the mounting slits preferably include a circumferential slit extending circumferentially in the axial center of the shielding member, a first axial slit extending from one circumferential end of the circumferential slit to one axial edge of the shielding member, and a second axial slit extending from the other circumferential end of the circumferential slit to the other axial edge of the shielding member. In this configuration, when accommodating a coil in the shielding member, first, the electric wire and the circumferential slit are arranged in the same direction, and the electric wire is accommodated in the shielding member through the circumferential slit. Next, the shielding member is rotated so that the first axial slit and the second axial slit approach each other relative to the electric wire or coil. Then, the electric wire or coil is passed through the first axial slit and the second axial slit, and the coil is accommodated in the shielding member. Even if the coil is translated in the radial direction of the shielding member, there is no risk of the coil coming off the shielding member.

[0013] (5) In (2), it is preferable that the mounting slit is spiral-shaped, and the shielding member generates an elastic restoring force capable of keeping the mounting slit closed. This configuration makes it possible to prevent leakage of a magnetic field from the mounting slit.

[0014] [Details of the embodiments of the present disclosure] [Example 1] A noise filter A according to a first embodiment of the present disclosure will be described with reference to FIGS. 1 to 5. The present invention is not limited to these examples, but is defined by the claims, and includes all modifications within the meaning and scope of the claims. In this first embodiment, the F direction in FIGS. 1 to 5 is defined as the front. The H direction in FIGS. 1 and 2 is defined as the up. The R direction in FIGS. 2 to 5 is defined as the right. The front-rear direction and the axial direction are used interchangeably.

[0015] The noise filter A of the first embodiment is connected midway along an electric circuit 30 such as a communication circuit or a power supply circuit, and is a component for suppressing or eliminating noise in the electric circuit 30. The electric circuit 30 has two electric wires 31. Of the two electric wires 31, terminal portions 31E connected to the noise filter A have their axes oriented in the front-rear direction and are coaxially arranged with a gap between them in the axial direction (front-rear direction). The noise filter A is connected to the electric circuit 30 while being disposed between the two terminal portions 31E.

[0016] The noise filter A includes a filter body 10, a shielding member 20, and an exterior body 26. The filter body 10 includes a core 11 and a coil 12. The core 11 is made of a magnetic material such as iron or a magnetic material. The core 11 is cylindrical and has an axis extending in the front-to-rear direction. The coil 12 includes a single wire 15 with a circular cross section. The coil 12 includes a cylindrical magnetic field generating unit 13 and a pair of front and rear connection terminals 14. The magnetic field generating unit 13 is formed by winding the wire 15 coaxially and spirally around the outer periphery of the core 11. The pair of connection terminals 14 extend in the axial direction from both ends of the magnetic field generating unit 13. The pair of connection terminals 14 are connected in series to the terminals 31E of two electric wires 31 by solder 16. The filter body 10 and the terminal portions 31E of the two electric wires 31 constitute a filter module 17.

[0017] The shielding member 20 is a single cylindrical component with both axial end faces open. The shielding member 20 contains a magnetic material and is capable of elastic deformation. Specific examples of the shielding member 20 include a synthetic resin body with a powdered magnetic material (not shown) or a fibrous magnetic material (not shown) embedded therein, and a synthetic resin body with metal foil attached to its inner surface. The filter body 10 and the terminal portions 31E of the two electric wires 31 are housed within the shielding member 20.

[0018] The shielding member 20 has a substrate portion 21, a front covering portion 22F, and a rear covering portion 22R. The substrate portion 21 is flat and has a thickness oriented in the up-down direction. In a plan view of the noise filter A (shielding member 20) from above, the substrate portion 21 is rectangular and has a long side oriented in the front-to-rear direction. The front covering portion 22F and the rear covering portion 22R are point-symmetrical in plan view and are arranged in point-symmetrical positions. The front covering portion 22F and the rear covering portion 22R are plate-like portions with a thickness smaller than that of the substrate portion 21. The front covering portion 22F and the rear covering portion 22R are curved so as to bulge upward in a front view of the noise filter A seen from the front.

[0019] The front cover portion 22F is located at the rear (front side) in a rear view of the noise filter A. The front cover portion 22F is connected to the right edge of the substrate portion 21 and extends leftward to cover the substrate portion 21 from above. The left edge (extending end) of the front cover portion 22F is disposed with a gap in the vertical direction relative to the upper surface of the left edge of the substrate portion 21. An opening between the left edge of the front cover portion 22F and the front end region on the upper surface of the substrate portion 21 functions as a front axial slit 23F that connects the inside and outside of the shielding member 20. The front axial slit 23F is a space for attaching the filter body 10 within the shielding member 20. The front axial slit 23F is continuous over the entire length of the front cover portion 22F in the front-rear direction and opens in the front-rear direction at the front end surface of the front cover portion 22F (the front end edge 20F of the shielding member 20) and the rear end surface of the front cover portion 22F.

[0020] The rear cover portion 22R is located on the near side (rear side) in a rear view of the noise filter A seen from behind. The rear cover portion 22R is connected to the left edge of the substrate portion 21 and extends to the right so as to cover the substrate portion 21 from above. The right edge portion (extending end portion) of the rear cover portion 22R is disposed with a gap in the vertical direction from the upper surface of the right edge portion of the substrate portion 21. The opening between the right edge portion of the rear cover portion 22R and the rear end region on the upper surface of the substrate portion 21 functions as a rear axial slit 23R that connects the inside and outside of the shielding member 20. The rear axial slit 23R is a space for attaching the filter body 10 inside the shielding member 20. The rear axial slit 23R is continuous over the entire length of the rear cover portion 22R in the fore-and-aft direction, and opens in the fore-and-aft direction at the front end surface of the rear cover portion 22R and at the rear end surface of the rear cover portion 22R (the rear end edge 20R of the shielding member 20).

[0021] An opening between the rear end surface of the front covering portion 22F and the front end surface of the rear covering portion 22R functions as a circumferential slit 24 that connects the inside and outside of the shielding member 20. The circumferential slit 24 is a space for attaching the filter body 10 inside the shielding member 20. The circumferential slit 24 is an opening that extends in the circumferential direction along the front covering portion 22F and the rear covering portion 22R. The circumferential slit 24 extends in the left-right direction in a plan view. The left end of the circumferential slit 24 communicates with the rear end of the front axial slit 23F. The right end of the circumferential slit 24 communicates with the front end of the rear axial slit 23R.

[0022] The front axial slit 23F, the rear axial slit 23R, and the circumferential slit 24 are continuous from the front end edge 20F to the rear end edge 20R of the shielding member 20, and form mounting slits 25 that open at both the front and rear ends 20F, 20R of the shielding member 20. The opening width dimensions of the front axial slit 23F, the rear axial slit 23R, and the circumferential slit 24 are all larger than the outer diameters of the electric wires 31 and the wires 15, and smaller than the outer diameter of the magnetic field generating unit 13.

[0023] The procedure for attaching the filter module 17 (filter body 10) to the shielding member 20 will be described. The axis of the filter body 10 and the axis of the terminal portion 31E of the electric wire 31 are oriented in the front-to-rear direction, and the shielding member 20 is oriented so that the front cover portion 22F and the rear cover portion 22R are aligned in the left-to-right direction. In this state, a portion of the terminal portion 31E of one of the electric wires 31 is dropped into the circumferential slit 24 from above the shielding member 20 and accommodated in the shielding member 20 (see FIG. 4). Next, the shielding member 20 is rotated 90° counterclockwise in a plan view (indicated by the arrow in FIG. 4) using the center of the circumferential slit 24 as a fulcrum. During the process of rotating the shielding member 20, the front axial slits 23F and the rear axial slits 23R allow the terminal portions 31E of the electric wires 31 to pass through, and the front covering portion 22F and the rear covering portion 22R are displaced to positions where they cover the terminal portions 31E of the electric wires 31 from above. During the process of rotating the shielding member 20, the shielding member 20 does not undergo elastic deformation.

[0024] When the rotation of the shielding member 20 is completed, as shown in FIG. 5, the terminal portions 31E of the electric wires 31 are housed within the shielding member 20, and are positioned so that the terminal portions 31E of the electric wires 31 penetrate the shielding member 20 in the front-rear direction. The filter body 10 is positioned outside the shielding member 20 in a plan view. After this, the shielding member 20 is slid forward as indicated by the arrows in FIG. 5. This sliding movement houses the filter body 10 within the shielding member 20. Because the openings at the front and rear end edges 20F, 20R of the shielding member 20 are large enough to surround the entire filter body 10 in a front view, the shielding member 20 does not elastically deform as it slides forward. When the filter body 10 is housed within the shielding member 20, a radial clearance is ensured between the outer surface of the filter body 10 (magnetic field generating unit 13) and the inner surface of the shielding member 20.

[0025] After the filter body 10 is housed within the shielding member 20, a synthetic resin adhesive tape (not shown) is wrapped around the entire shielding member 20, the portion of the terminal portion 31E of the electric wire 31 that extends forward from the shielding member 20, and the portion of the terminal portion 31E of the electric wire 31 that extends rearward from the shielding member 20. The adhesive tape wrapped around the shielding member 20 and the terminal portion 31E of the electric wire 31 constitutes the outer casing 26. By wrapping the adhesive tape around the shielding member 20 and the terminal portion 31E of the electric wire 31, the filter body 10 and the terminal portion 31E of the electric wire 31 are restricted from moving axially relative to the shielding member 20, moving radially relative to the shielding member 20, and rotating about the axis relative to the shielding member 20. This completes the assembly of the noise filter A and the connection of the noise filter A to the electric circuit 30.

[0026] The filter module 17 (filter body 10) can be attached to the shielding member 20 by a procedure different from that described above. The axis of the filter body 10 and the axis of the terminal portion 31E of the electric wire 31 are oriented in the front-rear direction, and the shielding member 20 is oriented so that the front cover portion 22F and the rear cover portion 22R are aligned in the left-right direction. At this time, the filter body 10 is positioned closer to the shielding member 20 than the position shown in FIG. 4. From this state, the shielding member 20 is rotated 90° counterclockwise in a plan view, with the center of the circumferential slit 24 as a fulcrum.

[0027] During the rotation, the front cover portion 22F is elastically deformed so as to be displaced upward, thereby expanding the vertical opening width of the front axial slit 23F. Then, the rear end portion of the filter body 10 passes through the front axial slit 23F with the expanded opening width, and the rear end portion of the filter body 10 is accommodated in the front end region (the region covered by the front cover portion 22F) within the shielding member 20. Thereafter, the shielding member 20 is slid forward to accommodate the entire filter body 10 within the shielding member 20. Thereafter, adhesive tape is wound around the exterior body 26 as described above, thereby completing the assembly of the noise filter A.

[0028] When a noise signal flows through the electric circuit 30 and the coil 12, a magnetic field is generated on the inner and outer circumferential sides of the magnetic field generating unit 13. A core 11 is disposed through the magnetic field generating unit 13. The core 11 absorbs the magnetic field and converts it into heat, thereby reducing noise. A magnetic field that is not absorbed by the core 11 exists outside the outer circumferential surface of the magnetic field generating unit 13. Therefore, if a separate communication circuit (not shown) is installed near the noise filter A, there is a concern that the magnetic field generated outside the magnetic field generating unit 13 may affect the separate communication circuit. In this embodiment 1, the coil 12 (magnetic field generating unit 13) is surrounded by a shielding member 20 containing a magnetic material, so there is no risk of the magnetic field generated by the magnetic field generating unit 13 leaking outside the shielding member 20. Therefore, there is no risk that the magnetic field of the filter may affect the separate communication circuit.

[0029] The noise filter A of the first embodiment includes a coil 12 connected to an electric wire 31 that constitutes an electric circuit 30, and a shielding member 20 containing a magnetic material. The shielding member 20 is cylindrical and disposed to surround the coil 12. The shielding member 20 is formed with an attachment slit 25 that extends continuously over the entire axial length of the shielding member 20 and whose ends face both axial edges 20F, 20R of the shielding member 20. When a noise current flows through the coil 12, a magnetic field is generated in the coil 12, thereby reducing the noise. Because the coil 12 is surrounded by the shielding member 20 containing a magnetic material, leakage of the magnetic field generated by current flow through the coil 12 is suppressed. When the coil 12 is housed within the shielding member 20, the electric wire 31 or the coil 12 is passed through the attachment slit 25. The mounting slit 25 is continuous over the entire axial length of the shielding member 20, and both ends face the axial edges 20F, 20R of the shielding member 20, so that the coil 12 can be housed within the shielding member 20 while remaining connected to the electric wire 31.

[0030] The front cover portion 22F of the shielding member 20 can be elastically deformed to widen the front axial slits 23F. The rear cover portion 22R can be elastically deformed to widen the rear axial slits 23R. With this configuration, when the shielding member 20 is not elastically deformed, the opening width of the mounting slits 25 (the front axial slits 23F and the rear axial slits 23R) is narrowed, thereby improving the effect of suppressing leakage of the magnetic field.

[0031] The mounting slits 25 are open when the shielding member 20 is not elastically deformed. With this configuration, it is possible to confirm with the naked eye or with a camera, etc., that the coil 12 (filter body 10) is housed in the shielding member 20.

[0032] The mounting slits 25 include a circumferential slit 24, a front axial slit 23F, and a rear axial slit 23R. The circumferential slit 24 is an opening extending in the circumferential direction in the center of the shielding member 20 in the axial direction. The front axial slit 23F is an opening extending from one circumferential end (left end) of the circumferential slit 24 to one axial edge (front edge 20F) of the shielding member 20. The rear axial slit 23R is an opening extending from the other circumferential end (right end) of the circumferential slit 24 to the other axial edge (rear edge 20R) of the shielding member 20.

[0033] When accommodating the coil 12 (filter body 10) in the shielding member 20, first, the electric wire 31 and the circumferential slits 24 are arranged in the same direction, and the electric wire 31 is accommodated in the shielding member 20 through the circumferential slits 24. Next, the shielding member 20 is rotated so that the front axial slits 23F and the rear axial slits 23R approach each other relative to the electric wire 31 or the coil 12. Then, the electric wire 31 or the coil 12 (filter body 10) is passed through the front axial slits 23F and the rear axial slits 23R, and the filter body 10 (coil 12) is accommodated in the shielding member 20. Even if the coil 12 is translated in the radial direction of the shielding member 20 (left-right or up-down direction), the coil 12 does not interfere with the front covering portion 22F, the rear covering portion 22R, and the substrate portion 21, and therefore there is no risk of the coil 12 detaching to the outside of the shielding member 20.

[0034] [Example 2] A noise filter B according to a second embodiment of the present disclosure will be described with reference to Figures 5 to 7. In this second embodiment, the front-to-rear direction is defined as the F direction in Figures 5 to 7. The up-to-down direction is defined as the H direction in Figures 5 to 7. The front-to-rear direction and the axial direction are used synonymously. The noise filter B according to the second embodiment has a shielding member 40 configured differently from that of the first embodiment. Since the other configurations are the same as those of the first embodiment, the same components are denoted by the same reference numerals, and a description of the structure, operation, and effects will be omitted.

[0035] The shielding member 40 of the second embodiment is a single cylindrical component with both end faces in the axial direction (front-rear direction) open. The shielding member 40 contains a magnetic material and is capable of elastic deformation. Specific examples of the shielding member 40 include a synthetic resin body in which a powdered magnetic material (not shown) or a fibrous magnetic material (not shown) is embedded, and a synthetic resin body with metal foil attached to its inner surface. The filter body 10 and the terminal portions 31E of the two electric wires 31 are housed within the shielding member 40.

[0036] The shielding member 40 has a spiral mounting slit 41. The mounting slit 41 opens at both axial end edges of the shielding member 40. The shielding member 40 can be elastically deformed to expand the axial opening width of the mounting slit 41. When the shielding member 40 is not elastically deformed, the mounting slit 41 is closed over its entire length from the front end to the rear end.

[0037] When the slit body is attached to the shielding member 40, one axial end of the shielding member 40 is elastically deformed so that one end of the attachment slit 41 opens, and a portion of the terminal portion 31E of the electric wire 31 is accommodated in the shielding member 40 through the opening. Next, by elastically deforming the shielding member 40, the opening region of the attachment slit 41 moves axially along its spiral path, and the terminal portion 31E of the electric wire 31 is sequentially accommodated in the shielding member 40 through the opening region. Then, when the opening region of the attachment slit 41 reaches the other end and the terminal portion 31E of the electric wire 31 passes through the attachment slit 41, the terminal portion 31E of the electric wire 31 is accommodated in the shielding member 40 while penetrating the shielding member 40 in the axial direction. In this state, the elastic restoring force of the shielding member 40 returns the entire region of the attachment slit 41 from the front end to the rear end to a closed state. Thereafter, the shielding member 40 is slid in the axial direction, and the entire filter body 10 is housed within the shielding member 40. With the above, the attachment of the filter body 10 to the shielding member 40 is completed.

[0038] The noise filter B of the second embodiment includes a coil connected to an electric wire 31 that constitutes an electric circuit 30, and a shielding member 40 containing a magnetic material. The shielding member 40 is cylindrical and disposed so as to surround the filter body 10 (coil 12). The shielding member 40 is formed with mounting slits 41 that open at a front end edge 40F and a rear end edge 40R in the axial direction of the shielding member 40 and communicate over the entire length of the shielding member 40. When a noise current flows through the coil 12, a magnetic field is generated in the magnetic field generating section 13 of the coil 12, thereby reducing noise.

[0039] The coil 12 is surrounded by the shielding member 40, which contains a magnetic material, which suppresses leakage of the magnetic field generated by passing current through the coil 12. When the filter body 10 (coil 12) is housed within the shielding member 40, the electric wire 31 or the coil 12 is passed through the mounting slit 41. The mounting slit 41 is continuous over the entire length of the shielding member 40 in the axial direction, and both ends face both end edges 40F, 40R of the shielding member 40 in the axial direction. This means that the filter body 10 (coil) can be housed within the shielding member 40 while the coil 12 remains connected to the electric wire 31.

[0040] The shielding member 40 can be elastically deformed so that the mounting slits 41 expand. With this configuration, when the shielding member 40 is not elastically deformed, the width of the mounting slits 41 narrows, thereby improving the effect of suppressing magnetic field leakage. The mounting slits 41 are spiral-shaped. The shielding member 40 can generate an elastic restoring force that can keep the mounting slits 41 closed. With this configuration, it is possible to prevent magnetic field leakage from the mounting slits 41.

[0041] [Other Examples] The present invention is not limited to the examples described above and illustrated in the drawings, but is defined by the claims. The present invention includes the equivalent meaning of the claims and all modifications within the scope of the claims, including the following embodiments. In the first and second embodiments, the inner diameter of each of the axial ends of the shielding member in a free state may be smaller than the outer diameter of the coil. This configuration can prevent the coil from being displaced in the axial direction within the shielding member. In the first and second embodiments, the adhesive tape may not be wound around the outer peripheral surface of the shielding member. In the first embodiment, the first axial slit may be closed when the shielding member is in a free state where it is not elastically deformed. In the first embodiment, the second axial slit may be closed when the shielding member is in a free state where it is not elastically deformed. In the first embodiment, the shielding member may be of a type that does not elastically deform, and in this case, the material of the shielding member is not limited to that containing synthetic resin, and may be made of metal only. In the second embodiment, at least a part of the attachment slit may be open when the shielding member is in a free state where it is not elastically deformed. [Explanation of symbols]

[0042] A...Noise filter B...Noise filter 10...Filter body 11...Core 12...Coil 13...Magnetic field generating unit 14...Connection terminal 15...Elemental wire 16...Solder 17...Filter module 20...Shielding member 20F: Front edge of the shielding member 20R...Rear edge of shielding member 21...Board 22F...Front cover 22R...Rear cover 23F...Front axial slit (first axial slit) 23R...Rear axial slit (second axial slit) 24...Circumferential slit 25...Installation slit 26...Exterior body 30...Electrical circuit 31...Electric wire 31E...End of electric wire 40...Shielding member 40F: Front edge of shielding member 40R...Rear edge of shielding member 41...Installation slit

Claims

1. a coil connected to an electric wire that constitutes an electric circuit; a shielding member including a magnetic material, the shielding member is cylindrical and disposed to surround the coil, The noise filter has mounting slits formed in the shielding member that open at both axial edges of the shielding member and communicate over the entire length of the shielding member.

2. The noise filter according to claim 1 , wherein the shielding member is capable of elastically deforming so that the mounting slits expand.

3. 3. The noise filter according to claim 2, wherein the mounting slit is open when the shielding member is not elastically deformed.

4. The mounting slit is a circumferential slit extending in a circumferential direction in a central portion of the shielding member in the axial direction; a first axial slit extending from one circumferential end of the circumferential opening to one axial end edge of the shielding member; 4. The noise filter according to claim 3, further comprising: a second axial slit extending from the other circumferential end of the circumferential opening to the other axial end edge of the shielding member.

5. The mounting slit is spiral-shaped, 3. The noise filter according to claim 2, wherein the shielding member generates an elastic restoring force capable of keeping the mounting slit closed.

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