JPH0514919U - Anti-scattering device for magnets - Google Patents

Abstract

(57) [Summary] [Structure] The magnet 5 is provided with a central hole 6. A resin holder is insert-molded on the peripheral surface of the center hole 6 to provide a holder 7 for holding the magnet 5. The magnet 5 is press-fitted and fixed to the rotary shaft 1 through the holder 7 and the central hole 6.
An annular recess 5a is provided on the upper surface of the magnet 5. The outer end portion of the holder 7 is fitted into the concave portion 5a so that the holding portion 7
a is provided. [Effect] Since the magnet 5 is held by the holder 7 and the holding portion 7a, it is possible to prevent the broken magnet 5 from scattering around.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a magnet scattering prevention device in a magnet fixing structure.

[0002]

[Prior Art]

 In general, a rotation detection device has a magnetic sensor closely arranged to a magnet fixed to a rotation shaft.For example, the rotation on the transmission side of a vehicle is transmitted to the rotation shaft, and this rotation is converted into a pulse signal by the magnet magnetic sensor. However, this pulse signal is sent to a speedometer or the like. On the other hand, in an overcurrent type instrument used for a speedometer, etc., a magnet is fixed to the rotating shaft, and a guide plate and a mustache spring that covers a part of the magnet are provided on the pointer shaft, and the rotation is transmitted to the rotating shaft. The pointer shaft rotates in a state of being balanced with the elastic force of the beard spring via the guide plate by the action of overcurrent generated by the rotation of the magnet.

As described above, the rotation detection device, the overcurrent type instrument, and the like have a structure in which the magnet is concentrically fixed to the rotating shaft. This magnet fixing structure has a resin layer of the magnet at the end of the rotating shaft. Is press-fitted into the insert-molded center hole, the magnet inserted into the rotary shaft is sandwiched between the peripheral flange of the rotary shaft and the rubber packing, and the rubber packing is fastened with a bush. Various structures are known in which a magnet inserted into a rotary shaft is sandwiched by a pair of bushes and a wave washer, and the magnets are arranged between the shaft flanges.

[0004]

[Problems to be solved by the device]

 In the above-mentioned conventional technology, since the structure that prevents the magnet from scattering is not provided, if the magnet is made of brittle material such as sintered ferrite, the magnet may be cracked by the stress applied to the magnet after assembly. However, if the magnet is broken, the rotating shaft rotates at high speed, causing the broken magnet to scatter and damage surrounding parts. Therefore, an object of the present invention is to provide a magnet scattering prevention device capable of preventing a broken magnet from scattering.

[0005]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the present invention is configured by providing an annular recess on the outer peripheral surface of the magnet, and inserting a part of the holder into the recess to provide a holding portion.

[0006]

【Example】

 An embodiment of the present invention will be described below with reference to the accompanying drawings. 1 and 2 show a first embodiment of the present invention, in which reference numeral 1 denotes a rotating shaft supported by a case 2 via a bearing 3, which is located above the bearing 3 and is supported by a peripheral flange. Although the portion 4 is formed, the support portion 4 may be integral with or separate from the rotary shaft 1, or may be formed by a rotation transmission gear. A magnet 5 has a central hole 6 formed in the magnet 5 and an annular recess 5a formed in a substantially circular shape on the upper surface side of the outer peripheral surface. Reference numeral 7 denotes a holder for press-fitting and fixing the central hole 6 of the magnet 5 onto the rotary shaft 1. The upper surface of the holder 7 is extended to the recess 5a position of the magnet 5 and the outside of the holder 7 corresponding to the recess 5a position. The end portion is fitted in this recess 5a to form a holding portion 7a.

As described above, in this embodiment, the magnet 5 is covered with the holder 7 from the peripheral surface portion of the center hole 6 to the recess 5 a, and the center hole 6 of the magnet 5 is attached to the rotary shaft 1 via the holder 7. It is press-fitted and fixed, and the upper surface of the outer peripheral surface of the magnet 5 is held by a holding portion 7a. Further, the holder 7 is insert-molded between the magnet 5 and the mold, and 8 is a mold hole provided by supporting the magnet 5 with the mold at the time of molding the holder 7.

In the embodiment having such a configuration, even if the magnet 5 is made of a brittle material such as sintered ferrite and the magnet 5 is cracked by the stress applied after the assembly, the magnet 5 is usually provided with a central hole. Since a crack is generated from 6 in the outer peripheral direction and cracks, the magnet 5 can be sufficiently held integrally by the holding portion 7a of the holder 7 fitted into the recess 5a of the magnet 5, and the magnet 5 can be rotated. It is possible to prevent the broken magnet 5 from being scattered by the high speed rotation of the shaft 1 and damaging surrounding parts.

Further, there is no need to provide a new separate component for preventing the magnets from scattering, and there is no increase in the size of the device, which is effective in cost reduction.

In this embodiment, the annular concave portion 5a of the magnet 5 into which the holding portion a of the holder 7 is fitted is provided near the center of the upper surface portion, but the position where the concave portion 5a is provided is the upper surface portion. Further, it may be provided at the outer position, and can be appropriately set if the exposed surface 5b provided at the portion corresponding to the sensor-S position is not covered by the holder 7 in consideration of the magnetic action. Is. Further, the width of the bottom surface of the concave portion 5a and the width of the tip portion of the holding portion 7a corresponding to this portion can be appropriately set as long as the magnet 5 can be held. Further, in this embodiment, the holding portion 7a is provided on the outer end portion of the holder 7. However, the position where the holding portion 7a is provided is such that when the holder 7 is cracked from the central hole 6 of the magnet 5 toward the outer peripheral direction thereof, If the holder 7a is provided by being able to hold the cracked part and by fitting a part of the holder 7 into the recess 5a, the holding part 7a is not limited to this part, for example, inside the outer end part. It may be a part.

FIG. 3 shows a second embodiment of the present invention. The same parts as those of the above-mentioned first embodiment are designated by the same reference numerals, and the description of the same parts will be omitted. In this case, the annular recess 5a of the magnet 5 is provided at substantially the same position on both the upper surface and the lower surface of the magnet 5, and the holder 7 is extended to the position of each recess 5a and the outer end portion of the holder 7 is provided. Is fitted into the concave portion 5a to form the holding portion 7a. As described above, in this embodiment, the holding portion fitted into the recess 5a is provided not only on the upper surface of the magnet 5 but also on the lower surface thereof, so that the magnet 5 can be held more reliably.

In the present embodiment, the recess 5a is provided at substantially the same position on the upper surface and the lower surface of the magnet 5, and the holding portion 7a is formed at a portion corresponding to the recess 5a. However, the recess 5a on the upper surface of the magnet 5 is used. The position of the concave portion 5a on the lower surface is not limited to this, and for example, one may be provided near the central hole 6 and the other far from the central hole 6. Further, this embodiment can be combined with the above-mentioned embodiments.

[0013]

[Effect of the device]

 According to the present invention, a center hole is provided in a magnet fixed to a rotating shaft, a resin is insert-molded on the peripheral surface of the center hole to provide a holder, and the magnet and the rotating shaft are fixed through the holder. In this case, since an annular recess is provided on the outer peripheral surface of the magnet and a holder is provided by fitting a part of the holder into the recess, scattering of the broken magnet can be prevented. Can provide protection.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a first embodiment of the present invention.

FIG. 2 is a perspective view of a main part of the above embodiment.

FIG. 3 is a sectional view of an essential part showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotating shaft 2 case 3 bearing 4 support part 5 magnet 5a recessed part 5b exposed part 6 center hole 7 holder 7a holding part 8 mold hole

Claims (1)

[Scope of utility model registration request] 1. A magnet, which is fixed to a rotary shaft, is provided with a central hole, a resin is insert-molded on a peripheral surface of the central hole to provide a holder, and the magnet and the rotary shaft are fixed through the holder. 2. A magnet scattering prevention device according to claim 1, wherein an annular concave portion is provided on the outer peripheral surface of the magnet, and a holding portion is provided by fitting a part of the holder into the concave portion.