The present invention relates to a direct current (DC) motor.
In a DC motor, radio noise is generated due to a contact state between a brush and a commutator or switching of current.
As a method for reducing the radio noise, it is common to mount a choke coil or a capacitor, or both the choke coil and the capacitor on a power supply circuit inside or outside the electric motor.
Since a radio noise reduction effect is increased when the choke coil and the capacitor are arranged on the power supply circuit near the brush, the choke coil and the capacitor are usually mounted on a brush holder. For example, a structure described in PTL 1 is known in which a choke coil is electrically connected between a plus electrode of a DC power supply and a first brush, and a choke coil is electrically connected between a minus electrode of the DC power supply and a second brush, and further a capacitor is electrically connected between the plus electrode and the minus electrode.
With this brush holder structure, the radio noise of the DC motor is reduced in accordance with frequency characteristics of a filter formed by the choke coil and the capacitor.
PTL 1: JP 2007-267448 A
In a case where the DC motor subjected to the radio noise reduction measure as described above is mounted on, for example, a vehicle, there is generally a limitation on a mounting space in the vehicle, and downsizing of the DC motor is essential.
However, in the above method, since the choke coil and the capacitor are mounted on the brush holder, downsizing of the brush holder is difficult, and further, downsizing of the DC motor is difficult. For downsizing of the brush holder and the DC motor, for example, if a choke coil and a capacitor respectively having small sizes and small capacities are used, the radio noise reduction effect weakens and the noise cannot be reduced in some cases.
An object of the present invention is to provide a DC motor in which downsizing of the DC motor is possible while a choke coil and a capacitor are mounted on a brush holder to reduce radio noise.
To solve the above problems, for example, a configuration described in claims is adopted.
The present application includes a plurality of means for solving the above problems, and its examples include a DC motor including a brush holder, in which the brush holder includes: a brush holder base formed of an insulating material; at least a pair of brushes that supplies power to a commutator; a spring that brings each of the brushes into sliding contact with an outer circumferential portion of the commutator; and a choke coil and a capacitor for reducing radio noise, and the capacitor is provided on a surface of the brush holder, the surface being different from a surface on which the choke coil is provided.
According to the present invention, it is possible to provide a DC motor in which downsizing of the DC motor is possible while the choke coil and the capacitor necessary for reducing radio noise are mounted.
Problems, configurations, and effects other than those described above will be clarified from description of an embodiment below.
Hereinafter, a brush holder structure according to an embodiment of the present invention will be described with reference to the drawings.
A DC motor 1 includes a yoke 2 forming a magnetic circuit while also serving as a motor case, and a plurality of magnets 3 is mounted on the inner surface of the yoke 2, and further, an armature 4 is accommodated in the inner side of the magnets 3 while holding an arbitrary gap from a magnet inner surface. The armature 4 is provided at the radial center with a shaft 5, and the shaft 5 is rotatably supported by the yoke 2 and a bracket 8 via a bearing 6 and a bearing 7. In the armature 4, an armature core 9 and a commutator 12 are fixed to the shaft 5, and a coil 11 is wound to straddle between a plurality of slots 10 formed in a circumferential direction outer circumferential portion of the armature core 9. The commutator 12 is formed in a cylindrical shape with an insulating material such as plastic and includes a plurality of commutator segments 13 made of a conductive material on the outer circumferential portion, and a part of each of the commutator segments 13 is electrically joined to the coil 11 wound between the slots 10.
Meanwhile, a brush holder 14 is accommodated inside the yoke 2, and on the brush holder 14, at least a pair of brushes that supplies power to the commutator segments 13 and a spring 16 are arranged, and further a choke coil 17 and a capacitor 18 are arranged for reducing radio noise. Each of the brushes 15 is electrically connected to an external power supply terminal 19 of the DC motor 1 and is brought into sliding contact with an outer circumferential surface of each of the commutator segments 13 by pressing force of the spring 16 held by the brush holder 14, and the power is supplied to the coil 11 via each of the commutator segments 13.
In the brush holder 14, on a brush holder base 20 formed in a substantially circular shape with an insulating material such as plastic, a brush box 21 that holds each of the brushes and a spring holder 22 that holds the spring 16 are integrally molded or formed with a method such as assembly with separate parts, and each of the brushes 15 that supplies power to each of the commutator segments 13 and the spring 16 that brings each of the brushes 15 into sliding contact with the outer circumferential portion of each of the commutator segments 13 are arranged on the brush holder base 20. Further, the choke coil 17 and the capacitor 18 for reducing radio noise are respectively arranged on different surfaces of the brush holder base 20.
Inside the brush holder base 20, a power supply terminal 23 is included to be connected to the choke coil 17 and the capacitor 18 with a method such as insert molding, and an opening 24 is provided in both surfaces of the brush holder base 20 so that a part of the power supply terminal 23 is exposed on both surfaces of a mounting surface of the choke coil 17 and a mounting surface of the capacitor 18, of the brush holder base 20.
In the present embodiment, the power supply terminal 23 included inside the brush holder base 20 and the external power supply terminal 19 of the DC motor 1 are integrally formed; however, the power supply terminal 23 and the external power supply terminal 19 may be formed, as separate parts, with joining or the like.
In the choke coil 17, one end is connected to the power supply terminal 23 at the opening 24 of the brush holder base 20, and the other end is connected to a lead wire 25 of each of the brushes 15, whereby the power supply terminal 23 and each of the brushes 15 are electrically connected together via the choke coil 17, and further the power is supplied to the coil 11 via each of the commutator segments 13 that is in sliding contact with each of the brushes 15.
In the present embodiment, the choke coil 17 and each of the brushes 15 are arranged on the same surface of the brush holder base 20; however, the choke coil 17 and each of the brushes 15 may be respectively arranged on different surfaces of the brush holder base 20.
The capacitor 18 is arranged on a surface of the brush holder base 20, the surface being different from a surface on which the choke coil 17 is arranged, and one end is connected to the power supply terminal 23 at the opening 24 of the brush holder base 20, and the other end is connected to a connection terminal 26 fixed to the brush holder base 20 and is electrically connected to the yoke 2 via the connection terminal 26.
The connection terminal 26 is formed by, for example, forming a thin plate of a conductive material such as copper, and includes a claw portion 27 to be brought into contact with the yoke 2, a substantially valley-shape formed portion 29 that is a fixing portion to the brush holder base 20, and a bent portion 30 to be connected to the capacitor 18.
As illustrated in
In addition, as illustrated in
The choke coil 17 is electrically connected between a plus terminal 19a of the external power supply terminal 19 and a first brush 15a, and another choke coil 17 is electrically connected between a minus terminal 19b of the external power supply terminal 19 and a second brush 15b, whereby a noise filter is formed between the external power supply terminal 19 and each of the brushes 15. Further, the capacitor 18 is electrically connected between the plus terminal 19a of the external power supply terminal 19 and the yoke 2 via the connection terminal 26, and another capacitor 18 is electrically connected between the minus terminal 19b of the external power supply terminal 19 and the yoke 2 via another connection terminal 26, whereby a noise filter is formed between the plus terminal 19a and the minus terminal 19b of the external power supply terminal 19 via the capacitor 18 and the yoke 2.
In this way, the choke coil 17 and the capacitor 18 are respectively arranged on different surfaces of the brush holder 14, and the power supply terminal 23 to be connected to the choke coil 17 and the capacitor 18 is included inside the brush holder base 20, whereby downsizing of the brush holder 14 is possible, and further, downsizing of the DC motor 1 is possible, while the filter that reduces radio noise is mounted.
Note that, the present invention is not limited to the embodiment described above, and includes various modifications. For example, the embodiment described above has been described in detail for describing the present invention clearly, and is not necessarily limited to that including all the configurations described. For a part of the configuration of the embodiment, it is possible to add, remove, and replace another configuration.
1 DC motor
2 yoke
3 magnet
4 armature
5 shaft
6, 7 bearing
8 bracket
9 armature core
10 slot
11 coil
12 commutator
13 commutator segment
14 brush holder
15 brush
15
a first brush
15
b second brush
16 spring
17 choke coil
18 capacitor
19 external power supply terminal
19
a plus terminal
19
b minus terminal
20 brush holder base
21 brush box
22 spring holder
23 power supply terminal
24 opening
25 lead wire
26 connection terminal
27 claw portion
28 protruding portion
29 substantially valley-shape formed portion
30 bent portion
Number | Date | Country | Kind |
---|---|---|---|
2015-252799 | Dec 2015 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2016/085835 | 12/2/2016 | WO | 00 |