JP6852876B2 - Rotating machine - Google Patents

Description

The present invention relates to a rotary electric machine in which a rotor connected to a shaft rotates with respect to a stator.

Conventionally, a technique for reducing electromagnetic noise generated during the operation of a rotary electric machine has been known.
For example, the rotary electric machine disclosed in Patent Document 1 has a branch portion branched from the intermediate position of the extension portion of the power supply terminal, and the branch portion has an insulating layer adjacent to the outer surface and an insulating layer adjacent to the insulating layer. It is formed from a conductive layer to be formed. A capacitor composed of an insulating layer and a conductive layer suppresses high-frequency noise propagated from the power supply terminal.

Japanese Unexamined Patent Publication No. 2016-5397

The prior art of Patent Document 1 reduces the amount of noise propagation from the power supply terminal to the radiation source, and does not reduce the amount of noise radiation from the radiation source to the outside. Therefore, it is not possible to reduce the radiation of noise propagated to the shaft, which is the radiation source.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a rotary electric machine that reduces the amount of noise emitted from a shaft which is a radiation source.

The rotary electric machine of the present invention includes a shaft (501-504) which is a rotating shaft, a rotor (40) connected to the shaft, a stator (30), a housing (20), and an armature coil (42). And a field generation source (31, 32).
The stator interacts with the rotor to generate a rotational force in the rotor.
The housing accommodates the rotor and stator, or functions as a stator while accommodating the rotor.
The armature coil is wound around either a rotor or a stator and is energized from a power source.
The field source is provided on the other side of the stator or rotor to provide a field to the armature coil.

The shaft has a conductive axis (54), one or more conductive layers (51, 52) and two conductive portions (55, 56).
The one or more conductive layers surround the radial outer side of the axis and are axially divided by one or more annularly divided portions (71, 72).
The two conductive portions are provided on one end side and the other end portion side with respect to the annular divided portion, and conduct between each conductive layer and the axial center.

In the present invention, the noise current propagated to the shaft is divided into a plurality of paths of one or more conductive layers and the axial center from the annular division portion, and flows toward one end portion and the other end portion, and both ends. It merges at the conductive part on the part side. At this time, since the noise currents in opposite directions cancel each other out, the noise radiated to the outside is reduced. This makes it possible to reduce the influence of radio interference on peripheral devices due to radiation noise.

Further , one or more annular division portions in the axial direction of the shaft, between the conductive layers in the radial direction of the shaft, and between the conductive layers and the axial center (61, 62) are filled with an insulating material. Has been done. Here, the "insulating material" is not limited to a material having an infinite resistance of Ω, and includes, for example, a high resistance material having a resistance of several MΩ or more, which is generally interpreted as an insulating material in the art.
As a result, the conductive layer and the axial center can be stably maintained while ensuring the insulation between the noise and current paths.

The rotary electric machine of the present invention is particularly preferably applied to a brushed DC motor. In that case, the rotating electric machine has a commutator (43) including a plurality of commutator pieces fixed to the shaft, and a pair or more brushes (33,) held in the housing and slidably contacted with the commutator when the rotor rotates. 34), and the direction of the current flowing through the armature coil is switched by the contact between the brush and the commutator.
In a brushed motor, the spark generated by the contact between the brush and the commutator becomes a noise source, so that the effect of reducing radiation noise is particularly effective.

Further, in this rotary electric machine, it is preferable that one or more annular split portions are located in a range corresponding to the commutator or the rotor in the axial direction of the shaft. As a result, the annular division portion can be effectively arranged at a position where a large amount of noise current is propagated.

The conductive portion may be composed of each conductive layer and a metal member that abuts on the axis.
Further, in the conductive portion, each conductive layer and the axial center may be in a welded state.

It is sectional drawing in the axial direction of the rotary electric machine of 1st Embodiment. It is the II direction arrow view of the rotary electric machine of FIG. It is a schematic cross-sectional view of the rotary electric machine of FIG. It is a front view of the shaft of 1st Embodiment, and is a partial cross-sectional view which shows the form in which the conductive part made of a metal member is press-fitted. It is sectional drawing in the axial direction of the shaft of 1st Embodiment (a form in which a conductive layer and an axial center are in a welded state in a conductive part). It is a figure which shows the action effect of (a) 1st Embodiment and (b) comparative example. It is sectional drawing in the axial direction of the shaft of 2nd Embodiment. It is sectional drawing in the axial direction of the shaft of 3rd Embodiment. It is sectional drawing in the axial direction of the shaft of 4th Embodiment.

Hereinafter, a plurality of embodiments of the rotary electric machine will be described with reference to the drawings.
(First Embodiment)
The rotary electric machine of the first embodiment will be described with reference to FIGS. 1 to 6.
First, refer to FIGS. 1 to 3 for the overall configuration of the rotary electric machine. The rotary electric machine 10 of the present embodiment is a DC motor with a brush, and includes a housing 20, a stator 30, field generators 31, 32, brushes 33, 34, a rotor 40, an armature coil 42, a commutator 43, and the like. A shaft 501 or the like is provided.

Hereinafter, for convenience of explanation, the upper side of FIG. 1 is referred to as “upper” and the lower side of FIG. 1 is referred to as “lower”. However, the actual rotary electric machine 10 is not limited to the vertical direction, and may be installed in the horizontal direction or the diagonal direction.
Further, FIG. 3 is a schematic radial cross-sectional view showing the operating principle of the brushed DC motor, and does not show the exact cross section of FIG. 1. For example, in FIG. 3, the rotor 40 is simplified and shown as a configuration in which an armature coil 42 is wound around three teeth 41.

The housing 20 includes a field source case 21 and a brush holder 22, and forms an outer shell of the rotary electric machine 10. In the field generation source case 21 constituting the lower part of the housing 20, the field generation sources 31 and 32 are fixed to the inner wall of the cylinder, and the rotor 40 is housed inside the field generation sources 31 and 32. The field generation sources 31 and 32 are typically composed of N-pole and S-pole permanent magnets to provide a field to the armature coil 42.
The rotor 40 is connected to a shaft 501, which is a rotation shaft. The armature coil 42 is wound around the rotor 40 and is energized from a power source.

In the configuration of FIG. 1, the housing 20 to which the field generation sources 31 and 32 are fixed accommodates the rotor 40 and "interacts with the rotor 40 to generate a rotational force in the rotor 40. It also functions as. However, in other embodiments, the stator 30 may be provided independently of the housing 20.
The commutator 43 includes a plurality of commutator pieces fixed to the shaft 501. FIG. 3 illustrates a form in which the commutator includes three commutator pieces.

The brush holder 22 constituting the upper part of the housing 20 holds a pair of brushes 33 and 34 inside while functioning as a lid covering the opening of the field source case 21. Further, positive and negative electrodes 35 and 36 connected to an external DC power supply are provided. The pair of brushes 33 and 34 are connected to the positive and negative electrodes 35 and 36, respectively, and are arranged so as to face each other. The brushes 33 and 34 are in sliding contact with the commutator 43 when the rotor 40 rotates. Two or more pairs of brushes 33 and 34 may be provided.

In the rotary electric machine 10, the rotor 40 rotates continuously with respect to the stator 30 by switching the direction of the current flowing through the armature coil 42 due to the contact between the brushes 33 and 34 and the commutator 43. Since the operating principle of such a brushed DC motor is a well-known technique, detailed description thereof will be omitted.

By the way, as described in Patent Document 1 (Japanese Unexamined Patent Publication No. 2016-5397) and the like, electromagnetic noise generated by the operation of a rotary electric machine may cause radio interference to peripheral devices. In particular, in a brushed motor, sparks generated by contact between the brushes 33 and 34 and the commutator 43 become a noise source, so that a solution to this problem is required more than in a brushless motor or the like.
Regarding noise reduction, in the prior art of Patent Document 1, the amount of noise propagated to the radiation source is reduced by forming a capacitor between the power feeding terminal and the housing.

On the other hand, in the present embodiment, focusing on the fact that the noise radiation source to the outside is mainly the shaft, it is an object of the present invention to reduce the noise radiation amount from the shaft, particularly the high frequency noise radiation amount.
The shaft of a rotary electric machine is generally made of metal, that is, a conductor in order to secure the strength as a rotary shaft. Theoretically, forming the shaft with a non-conductive material such as resin or ceramic is advantageous in reducing noise, but it is not realistic from the viewpoint of ensuring strength. Therefore, we propose a characteristic configuration of the shaft to reduce the amount of noise radiation while ensuring the strength of the rotating shaft.
In FIG. 1, the annular split portion 71 of the shaft 501 shown by the broken line at the position of the commutator 43 is a portion showing its characteristic configuration.

Hereinafter, the configuration of the shaft of each of the present embodiments will be described in detail. As the shaft code of each embodiment, the number of the embodiment is assigned to the third digit following "50".
First, the configuration of the shaft 501 of the first embodiment will be described with reference to FIGS. 4 and 5. For convenience of explanation, the end portion of the shaft 501 shown on the upper side of FIGS. 4 and 5 is referred to as an upper end portion, and the end portion also shown on the lower side is referred to as a lower end portion.

The shaft 501 has a cylindrical shape having a central axis Q, and is made of metal and has a conductive layer 51, a shaft center 54, two conductive portions 55 and 56, and an annular division filled with a resin as an insulating material. It has a portion 71 and an insulating layer 61. That is, the shaft 501 of the first embodiment has a two-layer structure including one conductive layer 51 and the axial center 54 when the axial center 54 is regarded as one layer.
As used herein, the term "insulating material" is not limited to a material having an infinite resistance of Ω, but includes a high resistance material having a resistance of several MΩ or more, which is generally interpreted as an insulating material in the art.

The axial center 54 is formed in an integral solid cylindrical shape without being divided in the axial direction.
The conductive layer 51 surrounds the radial outside of the axis 54 and forms the outermost layer of the shaft 501. The conductive layer 51 is divided into two conductive layer elements 511 and 512 by an annular dividing portion 71 provided in the middle of the axial direction. The position of the annular dividing portion 71 is not limited to the middle in the axial direction, and the lengths of the two conductive layer elements 511 and 512 may be uneven.
A resin is filled between the conductive layer 51 and the axial center 54 in the radial direction to form an insulating layer 61.

The conductive portion 55 conducts the upper end portion of the shaft 501 between the conductive layer element 511 on the upper end portion side and the axial center 54. The conductive portion 56 conducts the lower end portion of the shaft 501 between the conductive layer element 512 on the lower end portion side and the axial center 54.
As shown in the partial cross-sectional view of FIG. 4, the conductive portions 55 and 56 are rings that are press-fitted between the outer wall of the axial center 54 and the inner wall of the conductive layer 51, for example, having an inlay formed at the end portion, and abut against them. It may be composed of a metal member having a shape.
Further, as shown in FIG. 5, the metal member in contact with the end faces of the conductive layer 51 and the axial center 54 may be welded by laser welding, electric welding, or the like, and the conductive layer 51 and the axial center 54 themselves are welded to each other. May be good. Including these cases, the state of the shaft 501 as a product is expressed as "the conductive layer 51 and the axial center 54 are in a welded state".

In the specific design of the shaft 501, parameters such as the total length of the shaft L, the outer diameter of the shaft φD, the thickness Tm of the conductive layer 51, the thickness Tp of the insulating layer 61, and the width W of the annular divided portion 71 are matched. It is preferable to set to.
Next, with reference to FIG. 6, the action and effect of the shaft 501 of the present embodiment will be described in comparison with the comparative example. FIG. 6A shows the shaft 501 of the present embodiment, and FIG. 6B shows the magnitude of radiated noise generated by the noise current propagated from the noise source to the shaft for the shaft 509 of the comparative example. Shown schematically.

The shaft 509 of the comparative example shown in FIG. 6B is a solid metal cylinder. The noise current propagated from the noise source to the axial middle portion of the shaft 509 flows along the side surface of the cylinder to one end 595 and the other end 596, and the noise is radiated to the outside accordingly. The noise current and radiated noise shown by the thick solid line mean that the magnitude of the current and noise is relatively large. This may cause radio interference to peripheral devices.

On the other hand, the shaft 501 of the present embodiment shown in FIG. 6A has a two-layer structure of a conductive layer 51 and an axial center 54 in the radial direction, and the conductive layer 51 is axially divided by an annular dividing portion 71. ing. The noise current propagated from the noise source to the axial intermediate portion of the shaft 501 is divided into two paths of the conductive layer 51 and the axial center 54 starting from the annular dividing portion 71 and heading toward one end and the other end. It flows and merges at the conductive portions 55 and 56 at both ends. As shown in parts E1 and E2, at this time, noise currents in opposite directions cancel each other out, so that noise radiated to the outside is reduced. The noise current and radiated noise illustrated by the dashed line mean that the magnitude of the current and noise is relatively small. As a result, the influence of radio interference on peripheral devices can be reduced.

When the rotary electric machine 10 is a motor with a brush as in the present embodiment, the spark generated by the contact between the brushes 33 and 34 and the commutator 43 becomes a noise source, so that the effect of reducing radiation noise is particularly effectively exhibited. To. Further, as shown in FIG. 1, it is effective that the annular dividing portion 71 is located in a range corresponding to the commutator 43 in the axial direction of the shaft 501. As a result, the annular division portion 71 can be effectively arranged at a position where a large amount of noise current is propagated. Alternatively, the annular dividing portion 71 may be located in a range corresponding to the rotor 40 in the axial direction of the shaft 501.

In the present embodiment, since most of the total product of the shaft 501 is composed of the conductive layer 51 made of metal and the shaft center 54, the strength as a rotating shaft can be ensured. Further, the noise current dispersed in the conductive layer 51 and the axial center 54 merges in the opposite directions at the conductive portions 55 and 56 at the ends and cancels each other, whereby the radiated noise can be suitably reduced.

Further, in the present embodiment, the annular dividing portion 71 and the conductive layer 51 and the axial center 54 are filled with a resin as an insulating material, so that the insulating property between the noise current paths is ensured and the conductive layer is conducted. The layer 51 and the axial center 54 can be stably held. In addition, it can be easily manufactured by a method such as insert molding.

Next, the configuration of the shaft of the second, third, and fourth embodiments will be described with reference to FIGS. 7, 8, and 9, which are axial cross-sectional views corresponding to FIG. 5 of the first embodiment. In the following description of the embodiment, substantially the same configuration as that of the first embodiment is designated by the same reference numerals and the description thereof will be omitted.
As the configuration of the conductive portions 55 and 56 of each embodiment, either the press-fitting or welding configuration described in the first embodiment may be adopted.

(Second Embodiment)
The shaft 502 of the second embodiment shown in FIG. 7 has another conductive layer 52 between the conductive layer 51, which is the outermost layer in the radial direction, and the axial center 54, and has a three-layer structure. Here, the conductive layer 51 is referred to as a "first conductive layer 51", and the conductive layer 52 which is an intermediate layer is referred to as a "second conductive layer 52". The first conductive layer 51 is divided into two conductive layer elements 511 and 512 by the annular dividing portion 71. Similarly, the second conductive layer 52 is divided into two conductive layer elements 521 and 522 by the annular dividing portion 72. Resin is filled between the first conductive layer 51 and the second conductive layer 52 in the radial direction and between the second conductive layer 52 and the axial center 54, respectively, and the first insulating layer 61 and the second insulating layer are filled with resin, respectively. 62 is formed. The conductive portions 55 and 56 at both ends conduct conduction between all the conductive layers 51 and 52 and the axial center 54.

As a modification of the second embodiment, a shaft having a four-layer structure including three conductive layers and a shaft center 54, or a shaft having a multi-layer structure including more conductive layers may be used.
For example, when the diameter of the shaft is relatively large, by providing two or more conductive layers on the outside of the shaft center 54, the cross-sectional area per layer can be reduced and the noise current can be easily dispersed.

(Third Embodiment)
The shaft 503 of the third embodiment shown in FIG. 8 is provided with extended conductive portions 57 and 58 extending from the conductive layer elements 511 and 512, respectively, on the end side in the axial direction with respect to the conductive portions 55 and 56. .. Inside the extended conductive portions 57 and 58, terminal insulating portions 67 and 68 filled with resin are formed.

As described above, one or both of the conductive portions 55 and 56 is not limited to the end portion in the axial direction, and may be provided at a position other than the shaft end portion as long as it is on the end portion side with respect to the annular divided portion 71. Further, the entire cross section of the shaft may be filled with resin without providing the extension conductive portions 57 and 58 on the end side of the conductive portions 55 and 56.

(Fourth Embodiment)
In the shaft 504 of the fourth embodiment shown in FIG. 9, the conductive layer 51 is divided into three conductive layer elements 511, 512, and 513 by two annular division portions 711 and 712 in the axial direction. The intermediate conductive layer element 513 is held by the resin filled in the annular divided portions 711 and 712. One conducting portion 55 is provided on the upper end side with respect to the annular dividing portion 711, and the other conducting portion 56 is provided on the lower end side with respect to the annular dividing portion 712.
In this way, the conductive layer 51 may be divided by the annular dividing portion at two or more points in the axial direction. Further, as a combination with the second embodiment, two or more conductive layers may be divided by an annular dividing portion at two or more places, respectively.

(Other embodiments)
(A) Ceramic or the like may be used instead of the resin as the insulating material to be filled in the annular divided portion, between the conductive layers, and between the conductive layer and the axis. The holding of the conductive layer is possible, it may ensure insulation function by air layers.

(B) The rotary electric machine of the present invention is not limited to the brushed DC motor shown in the above embodiment. For example, a rotor provided with a permanent magnet (field generation source) is applied to a brushless motor or the like that rotates inside the stator by sequentially switching the energization of a multi-phase coil wound around the stator. May be good.
As described above, the present invention is not limited to the above-described embodiment, and can be implemented in various embodiments without departing from the spirit of the invention.

10 ... Rotating machine,
20 ... Housing,
30 ... Stator, 31, 32 ... Field source, 33, 34 ... Brush,
42 ... armature coil, 43 ... commutator,
501-504 ... Shaft,
51, 52 ... conductive layer, 54 ... axis, 55, 56 ... conductive part,
61, 62 ... Insulation layer,
71, 72 ... Circular division.

Claims (5)

A shaft (501-504), which is a rotating shaft, and
The rotor (40) connected to the shaft and
A stator (30) that interacts with the rotor and generates a rotational force in the rotor,
A housing (20) that accommodates the rotor and the stator, or that accommodates the rotor and functions as the stator.
An armature coil (42) wound around one of the rotor and the stator and energized from a power source, and an armature coil (42).
A field generator (31, 32) provided on the other side of the stator or the rotor and giving a field to the armature coil, and
With
The shaft
A conductive axial center (54), one or more conductive layers (51, 52) that surround the radial outer side of the axial center and are axially divided by one or more annular divisions (71, 72), and the one with respect to the annular segmented portion and provided on the other end side, have a two conduction portions (55, 56) for conduction between each said conductive layer and said axis,
An insulating material (61,) is provided between one or more of the annular dividing portions in the axial direction of the shaft, the conductive layers in the radial direction of the shaft, and between the conductive layer and the axial center. A rotary electric machine filled with 62). A commutator (43) including a plurality of commutator pieces fixed to the shaft, and a commutator (43).
A pair or more of brushes (33, 34) held in the housing and slidably contacted with the commutator during rotation of the rotor.
With more
The rotary electric machine according to claim 1 , wherein the direction of the current flowing through the armature coil is switched by the contact between the brush and the commutator. The rotary electric machine according to claim 2 , wherein one or more of the annular dividing portions are located in a range corresponding to the commutator or the rotor in the axial direction of the shaft. The rotary electric machine according to any one of claims 1 to 3 , wherein the conductive portion is composed of each of the conductive layers and a metal member that abuts on the axis. The rotary electric machine according to any one of claims 1 to 3 , wherein each of the conductive layers and the axial center is in a welded state in the conductive portion.

Images