Rotary electrical machine

Abstract

This rotary electrical machine includes: a rotor having a winding; a rotor shaft coaxially provided in the rotor; a pair of slip rings provided on the rotor shaft and transmitting electric power to the winding; and a pair of brushes abutting on the pair of slip rings. On the rotor shaft, the pair of slip rings are arranged side by side at a predetermined interval in the axial direction. The slip ring is provided with a plurality of groove parts extending in the axial direction on the surface thereof, and the groove parts are arranged at predetermined intervals in the circumferential direction. In the circumferential direction of the slip ring, the interval between adjacent groove parts is smaller than the interval between the slip rings.

Description

rotating electrical machines

[0001] The present invention relates to a rotating electric machine.

[0002] A rotating electric machine having windings on a rotor is generally configured so that slip rings are provided on the rotor shaft and power is transmitted to the windings using brushes that contact the slip rings.

[0003] JP2871003B2 discloses a configuration in which grooves are formed on the outer peripheral surface of a slip ring, and the grooves are used to wear away any adhesions caused by abrasion powder from the brush, thereby preventing short circuits and other problems caused by the adhesions.

[0004] When the slip ring slides against the brushes, not only does the brush generate wear particles, but the brushes can also scrape the slip ring surface, creating thread-like fragments. In a configuration with two slip rings attached to a rotor shaft, if these fragments come into contact across the gap between the slip rings, an electrical short circuit can cause insulation failure. While conventional configurations can remove wear particles adhering to the brushes, no consideration has been given to preventing insulation failure caused by slip ring fragments.

[0005] The present invention has been made in view of the above problems, and has an object to provide a rotating electric machine that can suppress insulation failure caused by fragments of slip rings.

[0006] According to one aspect of the present invention, the present invention is applied to a rotating electric machine including a rotor having windings, a rotor shaft provided coaxially with the rotor, a set of slip rings provided on the rotor shaft for transmitting power to the windings, and a set of brushes abutting the set of slip rings. The set of slip rings is arranged side by side on the rotor shaft at a predetermined interval in the axial direction. The slip rings have a plurality of grooves on their surfaces extending in the axial direction. The grooves are arranged at a predetermined interval in the circumferential direction. The interval between adjacent grooves in the circumferential direction of the slip rings is smaller than the interval between the slip rings.

[0007] Fig. 1 is a cross-sectional view of a motor according to this embodiment. Fig. 2 is an explanatory diagram of a slip ring. Fig. 3 is an explanatory diagram of a slip ring. Fig. 4 is an explanatory diagram of a slip ring. Fig. 5 is an explanatory diagram of a slip ring. Fig. 6 is an explanatory diagram of a slip ring and a brush. Fig. 7 is an explanatory diagram of a slip ring. Fig. 8 is an explanatory diagram of a slip ring.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0009] FIG. 1 is a schematic diagram illustrating a motor 1 as a rotating electrical machine according to an embodiment of the present invention, and is a cross-sectional view taken along the axis of rotation.

[0010] The rotating electric machine (motor) 1 of this embodiment is configured as a field-winding type synchronous motor, and is rotationally driven by applying electric power to a stator 21 and a rotor 22. The motor 1 is mounted on a vehicle and functions as a driving power source for the vehicle. Note that the motor 1 may also be used as a drive device for devices other than vehicles, such as various types of electrical equipment and industrial machinery.

[0011] As shown in FIG. 1 , the motor 1 is configured by housing 11 containing a stator 21 , a rotor 22 , and a rotor shaft 23 .

[0012] The stator 21 is housed within the housing 11 and includes a rotor 22. The stator 21 is configured by windings wound in slots (not shown).

[0013] The rotor 22 includes a field winding (not shown) and is driven to rotate by the interaction of a magnetic field generated by power applied to the field winding and a magnetic field generated by the stator 21. The rotor 22 includes a rotor shaft 23 coaxially therewith. The rotor shaft 23 is rotatably supported by the housing 11.

[0014] A pair of annular slip rings 30 are provided on the outer periphery of one end (left side in FIG. 1 ) of the rotor shaft 23. A pair of rod-shaped brushes 60 abuts against each slip ring 30. Abutment surfaces 60f (see FIG. 6 ) where the brushes 60 abut against the slip rings 30 are rectangular when viewed from the axial direction of the brushes 60. The brushes 60 transmit DC power supplied from a battery (not shown) to the slip rings 30, and transmit the power to the field winding of the rotor 22 via the slip rings 30.

[0015] The slip ring 30 is composed of a first slip ring 30a on the positive side and a second slip ring 30b on the negative side. A first brush 60a contacts the first slip ring 30a, and a second brush 60b contacts the second slip ring 30b. A positive current is applied to the first brush 60a, and a negative current is applied to the second brush 60b.

[0016] The slip ring 30 is made of a conductive metal such as copper, and the brush 60 is made of a material softer than the slip ring 30 (for example, carbon and a binder).

[0017] In the motor 1 configured as above, fragments that are generated by sliding between the slip ring 30 and the brush 60 will now be described.

[0018] The brushes 60 are in sliding contact with the slip rings 30, and as the rotor shaft 23 rotates, the slip rings 30 rotate relative to the brushes 60, gradually wearing them down. The brushes 60 are made of solidified powdered carbon, and wear generates fine wear particles. Meanwhile, the hard components contained in the brushes 60 can wear away parts of the slip rings 30, causing thread-like fragments to peel off from the surface of the slip rings 30. If these thread-like fragments come into contact across the slip rings 30, an electrical short circuit can occur, potentially resulting in poor insulation.

[0019] In this embodiment, the occurrence of insulation failure is suppressed by the configuration described below.

[0020] 2 and 3 are explanatory views of the rotor shaft 23 in the vicinity of the slip ring 30 of this embodiment. Fig. 2 is a perspective view of the rotor shaft 23, and Fig. 3 is a side view of the rotor shaft 23.

[0021] The slip ring 30 has grooves 40 on its surface that extend from one axial end (right side in FIG. 2 ) to the other axial end (left side in FIG. 2 ). The grooves 40 are formed linearly along the direction of the rotational axis of the rotor shaft 23. A plurality of grooves 40 are arranged at predetermined intervals in parallel with each other around the circumferential direction of the slip ring 30. In the example shown in FIG. 2 , nine grooves 40 are formed at equal intervals on the surface of the slip ring 30.

[0022] The groove width of the groove 40 is set to a width such that when the brush 60 scrapes the surface of the slip ring 30 , the scraped pieces are separated from the surface of the slip ring 30 in the groove 40 .

[0023] Furthermore, the surface of the slip ring 30 wears due to the sliding of the brushes 60, and the depth of the grooves 40 becomes shallower over time. Therefore, the depth of the grooves 40 is set in advance through experiments and simulations so that the surface of the slip ring 30 does not reach the bottom of the grooves 40 even after the product warranty period of the motor 1 has expired. The shape of the grooves 40 may be any shape, such as a V-shape, a U-shape, or a rectangular shape.

[0024] As shown in Figure 3, adjacent grooves 40 on the surface of the slip ring 30 are arranged with a circumferential distance L2 between them. The first slip ring 30a and the second slip ring 30b are arranged with an axial distance L1 between them. The distance L2 between the grooves 40 is configured to be smaller than the distance L1 between the slip rings 30. The circumferential distance between the grooves 40 does not necessarily have to be equal, as long as the distance L2 between the grooves 40 is configured to be smaller than the distance L1.

[0025] With this configuration, even if the surface of the slip ring 30 is scraped by the brush 60, the length of the resulting thread-like breaks is L2 or less. Therefore, no fragments long enough to short-circuit the gap L1 between the slip rings 30 are generated. This prevents poor insulation of the slip rings 30.

[0026] Next, modified examples of the configuration of the groove portion 40 of the slip ring 30 will be described.

[0027] 4 and 5 are side views of the rotor shaft 23 according to a modification of this embodiment.

[0028] 4, the grooves 40 are formed linearly from one end (right side) of the slip ring 30 to the other end (left side), and are formed parallel to each other and inclined (at a predetermined angle with respect to the axial direction) with respect to the axial direction of the rotor shaft 23. Even in this case, the grooves 40 are configured so that the circumferential distance between them is distance L2.

[0029] The inclination direction of the groove portion 40 is configured to be symmetrical (linearly symmetric, mirror-symmetrical) with respect to a midpoint (shown by a dotted line in Figure 4) perpendicular to the axial direction of the rotor shaft 23 between the first slip ring 30a and the second slip ring 30b.

[0030] By forming the grooves 40 at an angle on the surface of the slip ring 30 in this way, when the rotor shaft 23 rotates, the grooves 40 on the surface of the slip ring 30 draw in the surrounding air, and the air flows in the direction of the grooves 40, generating an axial wind near the slip ring 30. As a result, wind is generated in each direction from the end side of the grooves 40, as shown by the white arrows in Figure 4.

[0031] In this way, wind is generated near the slip ring 30, which blows away wear powder from the brush 60 and fragments of the slip ring 30 in the axial direction. This prevents wear powder and fragments from accumulating around the slip ring 30, thereby suppressing the occurrence of insulation failure in the slip ring 30. Furthermore, by preventing wear powder and fragments from accumulating around the brush 60, an increase in the sliding resistance of the brush 60 can also be suppressed.

[0032] As shown in Figure 5, the grooves 40 of the two slip rings 30 may be configured symmetrically so that the inclination directions are the same. In this configuration, the direction of the airflow generated by the grooves 40 of the slip rings 30 is the same, as indicated by the white arrows in Figure 5, and wear powder and debris can be blown away in the same direction. Note that the grooves 40 of the first slip ring 30a and the grooves 40 of the second slip ring 30b do not have to be symmetrical, and the angles of inclination may be different.

[0033] FIG. 6 is an explanatory diagram of the configuration of the slip ring 30 and the brush 60 in the case of the configuration shown in FIG. 4 or FIG.

[0034] As shown in Figures 4 and 5, if the groove portion 40 is formed at an angle in the slip ring 30, when the brush 60 slides on the surface of the slip ring 30, if the size of the area occupied by the groove portion 40 on the abutment surface 60f of the brush 60 changes, the contact area of ​​the abutment surface 60f will change, which may cause vibrations or abnormal noise.

[0035] Therefore, in order to prevent the contact area of ​​the abutting surface 60f of the brush 60 from changing, the following configuration is adopted.

[0036] As shown in FIG. 6, the contact surface 60f of the brush 60 has a rectangular shape, and its four corners are indicated as corner A, corner B, corner C, and corner D, respectively.

[0037] Here, when corner A of brush 60 is in contact with one groove 40a of the multiple grooves 40, corner B located diagonally opposite to corner A is in contact with another groove 40b. At this time, corners C and D, which are located at positions intersecting the diagonal line formed by corners A and B, are both in contact with yet another groove 40c. Groove 40c is disposed between grooves 40a and 40b.

[0038] By defining the positions and shapes of the contact surface 60f of the brush 60 and the groove 40 of the slip ring 30 in this way, the contact area of ​​the contact surface 60f with the surface of the slip ring 30 is always constant when the brush 60 moves on the surface of the slip ring 30. The contact area is the area obtained by subtracting the area occupied by the groove 40 from the area of ​​the contact surface 60f.

[0039] Specifically, in Figure 6, when the brush 60 relative to the slip ring 30 moves from the position indicated by the dotted line to the position indicated by the dashed line, the area occupied by the groove portion 40 on the contact surface 60f changes from the entire groove portion 40c to part of the groove portion 40a and part of the groove portion 40c, but this change does not change the size of the area occupied by the groove portion 40 on the contact surface 60f.

[0040] In this way, the contact area of ​​the abutment surface 60f does not change depending on the position of the groove portion 40 in the slip ring 30, so that vibrations and abnormal noise between the brush 60 and the slip ring 30 can be suppressed.

[0041] FIG. 7 is a side view of a rotor shaft 23 according to yet another modification of the present embodiment.

[0042] In the modified example shown in Figure 7, the groove portion 40 is composed of a first groove portion 40d that extends from one end on the right side of the axial direction of the slip ring 30 to the other end on the left side but does not reach the left end, and a second groove portion 40e that extends from the other end on the left side of the axial direction of the slip ring 30 to one end on the right side but does not reach the right end.

[0043] The first grooves 40d and the second grooves 40e are arranged alternately in the circumferential direction, and the first grooves 40d and the second grooves 40e are configured to partially overlap in the circumferential direction. Note that the other end of the first groove 40d and the one end of the second groove 40e may be at the same position in the circumferential direction.

[0044] As in the modified example shown in Figure 7, the grooves 40 formed on the surface of the slip ring 30 do not necessarily need to be formed from one end to the other in the axial direction, but may be formed in a portion of the surface, and the distance between adjacent grooves 40 may be distance L2 in the axial direction. Note that Figure 7 shows an example in which the grooves 40 are formed parallel to the axial direction of the rotor shaft 23, but as shown in Figures 4 and 5, the grooves 40 may be formed at an angle with respect to the axial direction.

[0045] With this configuration, the groove portion 40 is reduced compared to a configuration in which the groove portion 40 is formed along the axial direction of the slip ring 30, thereby improving the strength and wear resistance of the slip ring 30.

[0046] Furthermore, in the manufacturing process of the slip ring 30, when the groove portion 40 is machined in the slip ring 30 by press working, a press working machine with a small axial width can be used, thereby reducing manufacturing costs.

[0047] FIG. 8 is a side view of a rotor shaft 23 according to yet another modification of the present embodiment.

[0048] In the modification shown in FIG. 8, a protrusion 50 that protrudes in a circular ring shape in the circumferential direction is provided on the rotor shaft 23 between the first slip ring 30a and the second slip ring 30b.

[0049] The protrusions 50 are configured so that their outer diameters are larger than the outer diameters of the slip rings 30, and their heights from the rotor shaft 23 are larger than the heights of the slip rings 30. As a result, the protrusions 50 are configured as wall members between the slip rings 30.

[0050] In this way, by providing the protrusions 50 between the slip rings 30 that are taller than the slip rings 30, the creepage distance between the slip rings 30 can be increased. As a result, even if fragments generated by the brushes 60 and the slip rings 30 become lodged between the slip rings 30, the fragments will not come into contact across the slip rings 30. Note that, since the presence of the protrusions 50 prevents short-circuiting of the fragments between the slip rings 30, the slip rings 30 may not be provided with grooves 40.

[0051] As described above, in this embodiment, the motor 1 includes a rotor 22 having windings, a rotor shaft 23 provided coaxially with the rotor 22, a set of slip rings 30 provided on the rotor shaft 23 and transmitting power to the windings, and a set of brushes 60 abutting against the set of slip rings 30. The set of slip rings 30 are arranged side by side on the rotor shaft 23 at a predetermined interval L1 in the axial direction. The slip ring 30 has a plurality of grooves 40 on its surface extending in the axial direction, and the grooves 40 are arranged at a predetermined interval L2 in the circumferential direction. The interval L2 between adjacent grooves 40 in the circumferential direction of the slip ring 30 is smaller than the interval L1 between the slip rings 30.

[0052] In this configuration, even if the surface of the slip ring 30 is scraped by the brush 60, the length of the resulting thread-like break is L2 or less, so no fragments long enough to short-circuit the gap L1 between the slip rings 30 are generated. This makes it possible to suppress the occurrence of insulation failure in the slip ring 30.

[0053] In this embodiment, the groove 40 is formed linearly from one end to the other end of the slip ring 30 in the axial direction.

[0054] In this configuration, the groove 40 can more reliably keep the length of the thread-like fragments generated from the slip ring 30 to less than L1.

[0055] In this embodiment, the grooves 40 are formed so as to be inclined with respect to the axial direction.

[0056] In this configuration, the rotation of the rotor shaft 23 generates wind in the groove portion 40, which can blow away wear powder and fragments around the slip ring 30, thereby further reducing the occurrence of insulation failure in the slip ring 30.

[0057] In addition, in this embodiment, the direction of inclination of the grooves 40 of the first slip ring 30a and the direction of inclination of the grooves 40 of the second slip ring 30b are symmetrical to each other.

[0058] In this configuration, the rotation of the rotor shaft 23 can effectively generate wind by the grooves 40 of the set of rotor shafts 23, so that the occurrence of insulation failure of the slip ring 30 can be further suppressed.

[0059] In this embodiment, the grooves 40 are made up of a first groove 40d formed from one end on the right side in the axial direction to a position not reaching the other end on the left side, and a second groove 40e formed from the other end on the left side in the axial direction to a position not reaching the one end on the right side, and the first grooves 40d and the second grooves 40e are arranged alternately in the circumferential direction of the slip ring 30. The first grooves 40d and the second grooves 40e are arranged so that they partially overlap in the circumferential direction.

[0060] In this configuration, the number of grooves 40 in the slip ring 30 is reduced compared to a configuration in which the grooves 40 are formed along the axial direction, thereby improving the strength and wear resistance of the slip ring 30.

[0061] In this embodiment, the brush 60 has a rectangular contact surface 60f that contacts the surface of the slip ring 30. When a first corner A of the contact surface 60f is in contact with one of the grooves 40a of the plurality of grooves 40 on the surface of the slip ring 30, a second corner B diagonally opposite the first corner A of the contact surface 60f contacts another groove 40b different from the groove 40a, and a third corner C and a fourth corner D intersecting the diagonal line formed by the first corner A and the second corner B contact yet another groove 40c.

[0062] In this configuration, the abutment surface 60f contacts multiple grooves 40 so that the contact area does not change depending on the position of the grooves 40 in the slip ring 30, thereby suppressing vibration and abnormal noise between the brush 60 and the slip ring 30.

[0063] In this embodiment, the rotor shaft 23 is provided with a protruding portion 50 that protrudes in an annular shape between the pair of slip rings 30 and has an outer diameter larger than that of the slip rings 30 .

[0064] In this configuration, by providing a protrusion 50 between the slip rings 30 that is taller than the slip rings 30, it is possible to prevent fragments from coming into contact across the slip rings 30, thereby suppressing a decrease in electrical insulation.

[0065] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

[0066] The grooves 40 of the slip ring 30 may be filled with a resin or the like to smooth out the irregularities on the surface of the slip ring 30 .

[0067] In this embodiment, the motor 1 is a field-winding type synchronous motor, and power is transmitted to the field winding of the rotor 22 via the brushes 60 and slip rings 30. However, the present invention is not limited to this, and can be applied to a motor in which the rotor has a winding and power is transmitted to the winding via the brushes and slip rings. For example, the present invention may be applied to a DC motor in which the stator has a permanent magnet.

Claims

1. A rotating electric machine comprising: a rotor having windings; a rotor shaft mounted coaxially with the rotor; a pair of slip rings, each consisting of a positive and a negative electrode, mounted on the rotor shaft and transmitting DC power to the windings; and a pair of brushes, each consisting of a positive and a negative electrode, in contact with the pair of slip rings, A set of slip rings is arranged on the rotor shaft at a predetermined distance in the axial direction. The slip ring has a plurality of grooves extending axially on its surface, and the grooves are arranged at predetermined intervals in the circumferential direction. In the circumferential direction of the slip ring, the distance between adjacent grooves is smaller than the distance between slip rings. Rotating electric machine.

2. A rotating electric machine according to claim 1, The groove portion is formed in a straight line from one end to the other in the axial direction of the slip ring. Rotating electric machine.

3. A rotating electric machine according to claim 1, The groove portion is formed inclined with respect to the axial direction. Rotating electric machine.

4. A rotating electric machine according to claim 3, The direction of the inclination of the groove portion of one slip ring and the direction of the inclination of the groove portion of the other slip ring are symmetrical to each other. Rotating electric machine.

5. A rotating electric machine according to claim 1, The groove portion consists of a first groove portion formed from one end in the axial direction to a position not reaching the other end, and a second groove portion formed from the other end in the axial direction to a position not reaching the first end. The first groove and the second groove are arranged alternately in the circumferential direction on the slip ring. The first groove and the second groove are arranged such that a portion of them overlaps in the circumferential direction. Rotating electric machine.

6. A rotating electric machine according to claim 3, The brush has a rectangular contact surface that contacts the surface of the slip ring. When the first corner of the contact surface is in contact with one of the plurality of grooves, the second corner of the contact surface diagonally opposite the first corner is in contact with another groove different from the said groove. The third and fourth corners, which are located at positions that intersect the diagonal formed by the first and second corners, are further in contact with the other grooves. Rotating electric machine.

7. A rotating electric machine according to claim 1, The rotor shaft has an annular projection between a pair of slip rings, the projection having a diameter larger than the outer diameter of the slip rings. Rotating electric machine.