Carbon ground brush assembly

Abstract

This carbon ground brush assembly comprises: a plate having a through-hole in a central portion and a flange for attachment to a housing; and a brush unit. In the brush unit, by crimping a brush holder to the plate, a top surface of a carbon ground brush is brought into contact with the holder, and a bottom surface of the brush is brought into contact with the plate. Further, a rear end of the brush is pressed by a spring to bias the brush toward a rotary shaft. A leaf spring portion for pressing the housing is provided at a rear end of the brush holder, and the brush holder is connected to the housing by pressing the housing. This allows the brush to be reliably grounded to the housing.　

Description

Carbon ground brush assembly

[0001] This invention relates to a carbon ground brush assembly used in rotating electrical machines such as electric motors and generators. This invention relates to a carbon ground brush assembly for grounding the rotating shaft of a rotating electrical machine to the outside through a housing, and particularly relates to the attachment of a unit of carbon ground brushes to an assembly.

[0002] In a rotating electrical machine, an unnecessary current may flow through the rotating shaft. This current is called a shaft current and causes electromagnetic noise and electrical erosion of the bearings supporting the rotating shaft. To ground the rotating shaft of a rotating electrical machine, it is known to contact a brush of conductive fibers with the rotating shaft (for example, Patent Document 1: Patent 6227096). In Patent Document 1, a brush of conductive fibers is supported on an annular ring. Further, it is also known to use a sintered body of carbon (carbon brush) for the ground brush (Patent Document 2: Special Table 2016-525329).

[0003] The contact between the rotating shaft and the ground brush changes due to reversals of the rotational direction of the shaft, vibrations of the shaft, changes in the rotational speed of the shaft, etc. For example, when the rotating electrical machine is a drive motor of an electric vehicle, when the rotational direction is switched from forward rotation during forward movement to reverse rotation during reverse movement, the contact between the rotating shaft and the ground brush changes. The rotating shaft vibrates due to the influence of unevenness of the road surface, etc., and the rotational speed is not constant. These also change the contact between the rotating shaft and the ground brush. Also, when the rotating electrical machine is a wind power generator, etc., the contact between the rotating shaft and the ground brush changes due to strong winds, lightning strikes, etc. Furthermore, reversals of the rotational direction, vibrations of the rotating shaft, changes in the rotational speed, strong winds, lightning strikes, etc. not only affect the connection between the rotating shaft and the ground brush, but also affect the connection between the ground brush and its holder (brush holder), etc. Therefore, it is necessary to reliably ground the rotating shaft regardless of the condition of the rotating shaft.

[0004] Patent 6227096 Special Table 2016-525329

[0005] The objective of this invention is to reliably ground the rotating shaft to the housing regardless of the condition of the rotating shaft. In particular, the objective of this invention is to maintain a consistently good electrical connection from the carbon earth brush to the housing, which houses the carbon earth brush assembly and serves as an external grounding path.

[0006] This invention relates to a carbon earth brush assembly for grounding the rotating shaft of a rotating electric machine, comprising a plate having a through hole in the center for passing the rotating shaft and a flange on the outer circumference for attachment to a housing, and a brush unit, the brush unit comprising a carbon earth brush, a brush holder covering the top surface and both sides of the carbon earth brush and bringing the bottom surface of the carbon earth brush into contact with the plate, and a spring that presses the rear end of the carbon earth brush at a position viewed from the rotating shaft, biasing the carbon earth brush toward the rotating shaft, the invention is characterized by having a leaf spring portion at the rear end of the brush holder at a position viewed from the rotating shaft, configured to electrically connect the top surface of the carbon earth brush to the brush holder and the bottom surface of the carbon earth brush to the plate by crimping the brush holder to the plate, and to electrically connect the brush holder to the housing by pressing the housing. The housing is electrically connected to the outside (ground side). In this invention, the rotating shaft is grounded by electrically connecting the earth brush unit to its housing.

[0007] Preferably, the rear end of the carbon earth brush has an inclined surface that slopes inward from the sliding surface of the carbon earth brush to the rotation axis, and a portion of the biasing force of the spring biases the carbon earth brush against one inner surface of the brush holder. In this way, the spring ensures a connection between the brush and the holder. The biasing inner surface is, for example, the surface against which the carbon earth brush is pressed by the frictional force due to the forward rotation of the rotation axis. Since the rotation axis is most likely to be rotating in the forward direction, the earthing performance during forward rotation is given priority over the earthing performance during reverse rotation.

[0008] Particularly preferable is a torsion spring, in which one end of the torsion spring biases the inclined surface at the rear end of the brush, and the other end is supported by a plate. Using a torsion spring allows for a larger inclination angle of the inclined surface, thus enabling the brush to be pressed against one inner wall of the holder with greater force. Furthermore, since the torsion spring occupies a small size within the holder, the holder can be made smaller.

[0009] Preferably, in addition to connecting the brush holder and the plate by crimping, the brush holder and the plate are electrically connected by lead wires.

[0010] This invention ensures that the carbon earth brush is reliably grounded to the housing. The brush is biased toward the axis of rotation by a spring, ensuring a connection between the axis of rotation and the brush. The holder is crimped to ensure a connection between the top surface of the brush and the holder, the bottom surface of the brush and the plate, and the holder and the plate. The holder and the housing are directly connected by bringing the leaf spring portion at the rear end of the holder, for example, a bent rear end of the holder, into contact with the housing. Furthermore, the plate is electrically connected to the housing by a flange.

[0011] As described above, this invention provides multiple conductive paths from the carbon earth brush to the housing. Therefore, the rotating shaft can be reliably grounded to the housing regardless of changes in the state of the rotating electric machine, such as changes in rotational speed, reversal of rotational direction, or vibration of the rotating shaft.

[0012] Plan view of the carbon earth brush assembly of the embodiment Vertical cross-sectional view of the assembly of the embodiment Vertical cross-sectional view of the main part of the assembly of the embodiment Developed view of the brush holder of the embodiment Plan view showing the pressure of the carbon brush by the coil spring in the embodiment Plan view of the main part of the modified carbon earth brush assembly

[0013] The following shows an optimal embodiment for carrying out the present invention. The present invention is not limited to the embodiments, but is defined based on the claims and can be modified by adding matters known to those skilled in the art to the embodiments.

[0014] Figures 1 to 5 show an embodiment of the carbon earth brush assembly 2. 4 is a plate made of iron or the like, with a through hole 5 in the center through which a rotating shaft 6 passes. The rotating shaft 6 can be the main motor shaft of an electric vehicle, the rotating shaft of a wind turbine, or any other shaft of a rotating electric machine. The outer circumference of the plate 4 has a flange 8, and the assembly 2 is fixed to the housing 10 by fitting the flange 8 into the housing 10 or by fastening it to the housing 10 with bolts and nuts. The surfaces of the plate 4 and flange 8 are electrically conductive. In this embodiment, the plate 4 is annular, but the outer shape of the plate 4 can be other than annular to match the shape of the housing 10.

[0015] One to more brush units 12 are fixed to one side of the plate 4 by crimping, and in this embodiment, two are fixed. The brush unit 12 consists of a brush holder 13 and a carbon earth brush 14. The carbon earth brush 14 is made of carbon or a mixture of carbon and metal, for example, a sintered body of a mixture of carbon and resin binder. For the brush holder 13, a metal that has high conductivity, is easy to process, and whose surface is not insulating is used, such as brass.

[0016] A notch 9 is provided in the flange 8 at the rear end (the end on the housing 10 side) of the brush unit 12, so that the leaf spring portion 26 at the rear end of the brush holder 13 is electrically connected to the housing 10 at all times due to its elasticity. The carbon earth brush (hereinafter referred to as "brush") 14 is biased toward the shaft 6 by the coil spring inside the holder 13, and by crimping the holder 13 to the plate 4, the top surface of the brush 14 is electrically connected to the holder 13, and the bottom surface is electrically connected to the plate 4.

[0017] By orienting the biasing direction of the coil spring at an angle to the direction perpendicular to the axis 6, the brush 14 is pressed against one inner surface of the brush holder 13 and electrically connected. The inner surface of the holder 13 that presses the brush 14 is preferably the inner surface against which the brush 14 is pressed when the axis 6 rotates forward. Furthermore, the holder 13 is electrically connected to the housing 10 by the leaf spring portion 26 at the rear end of the holder 13, and the plate 4 is electrically connected to the housing 10 by the flange 8. In addition, the holder 13 is electrically connected to the plate 4 by, for example, welding or soldering the lead wires 16 to the holder 13 and the plate 4. With the above configuration, the holder 13 is reliably grounded to the housing 10 via the plate 4 or directly.

[0018] Figures 2 to 5 show the details of the brush unit 12 and the electrical connection between the brush unit 12 and the housing 10. The crimping piece 20 of the brush holder 13 is passed through a hole (not shown) in the plate 4 and crimped. In this embodiment, the brush holder 13 is crimped at two locations on the lower part of both sides 29 and 30. Due to the pressure of the crimping, the top surface of the brush 14 contacts the holder 13 and the bottom surface contacts the plate 4. These contact points are shown as shaded areas in Figure 3.

[0019] As shown in Figure 5, the brush 14 is biased primarily toward the shaft 6 by a coil spring 24, ensuring an electrical connection with the shaft 6. The rear end of the brush 14 forms an inclined surface 25 that is inclined from the tangential direction to the shaft 6, and this inclination causes a portion of the pressure from the coil 24 to press the brush 14 against the inner surface of one side 30 of the brush holder 13. Being inclined from the tangential direction to the shaft means being inclined from the sliding surface of the brush 14 relative to the shaft. In this embodiment, when the shaft 6 rotates forward, the brush 14 is pressed against the side surface by the pressure of the coil 24.

[0020] Figure 4 shows an unfolded view of the brush holder 13, with the dashed lines indicating the folding points. There are side portions 29 and 30 on both sides of the top portion 28, and for example, two crimping pieces 20 are provided on each of the side portions 29 and 30. A pair of leaf spring portions 26, 26 are extended from near the rear ends of the side portions 29 and 30 and folded upward to press against the housing 10. This ensures an electrical connection between the holder 13 and the housing 10, as shown in the shaded area of ​​Figure 3. As a result, the electrical connection between the brush 14 and the housing 10 is maintained at all times.

[0021] The coil spring 24 can be replaced with any suitable spring, such as a torsion spring or leaf spring. An example using a torsion spring 34 is shown in Figure 6. The coil of the torsion spring 34 is fixed by a projection 35, and one end of the torsion spring 34 presses against the inclined surface 40 at the rear end of the brush 14, while the other end is supported by a retaining piece 36. A slit 38 is also provided on the side of the holder 13 so that the torsion spring 34 can press against the inclined surface 40. Since there is no support piece 22 at the rear end of the holder 13, the leaf spring portion 32 extends downward from above the rear end of the holder 13. The modified example in Figure 6 is otherwise the same as the embodiments in Figures 1 to 5.

[0022] Since the torsion spring 34 is smaller than the coil spring 24, the holder 13 can be made smaller. Also, as is clear from comparing Figures 5 and 6, the torsion spring 34 can press the brush 14 at a larger inclination angle, making the connection between the brush 14 and the side of the holder 13 more secure.

[0023] The housing may be the outer ring of a rolling bearing or the housing of a bearing. Also, the carbon earth brush may contact the rotating shaft itself, for example, but it may also contact the inner ring of a rolling bearing fixed to the rotating shaft.

[0024] 2 Carbon earth brush assembly 4 Plate 5 Through hole 6 Rotating shaft 8 Flange 9 Notch 10 Housing 12 Brush unit 13 Brush holder 14 Carbon earth brush 16 Lead wire 20 Crimping piece 22 Support piece 24 Coil spring 25 Inclined surface 26 Leaf spring section 28 Top section 29, 30 Side section 32 Leaf spring section 34 Torsion spring 35 Projection 36 Retaining piece 38 Slit 40 Inclined surface

Claims

1. A carbon earth brush assembly for grounding the rotating shaft of a rotating electric machine, comprising a plate having a through hole in the center for passing the rotating shaft and a flange on the outer circumference for mounting to a housing, and a brush unit, wherein the brush unit comprises a carbon earth brush, a brush holder covering the top surface and both sides of the carbon earth brush and bringing the bottom surface of the carbon earth brush into contact with the plate, and a spring that presses the rear end of the carbon earth brush at a position viewed from the rotating shaft, biasing the carbon earth brush toward the rotating shaft, wherein the top surface of the carbon earth brush is electrically connected to the brush holder and the bottom surface of the carbon earth brush is electrically connected to the plate by crimping the brush holder to the plate, and a leaf spring portion is provided at the rear end of the brush holder at a position viewed from the rotating shaft, wherein the brush holder is electrically connected to the housing by pressing the housing.

2. The carbon earth brush assembly according to claim 1, characterized in that the rear end of the carbon earth brush has an inclined surface that is inclined from the sliding surface of the carbon earth brush to the rotation axis, and a portion of the biasing force of the spring biases the carbon earth brush toward one inner surface of the brush holder.

3. The carbon earth brush assembly according to claim 2, characterized in that the spring is a torsion spring, one end of which biases the inclined surface and the other end of which is supported by the plate.

4. A carbon earth brush assembly according to any one of claims 1 to 3, characterized in that the brush holder and the plate are electrically connected by lead wires.

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