Motor, and motor equipped with speed reducer

Abstract

To provide a motor capable of obtaining necessary durability by taking a measure for damage of a sliding contact point due to a commutation spark when driven at a high voltage (for example, 48 V), while using a rotor and a commutator segment similar to those in the motor driven at a low voltage (for example, 12 V); and to provide a motor equipped with a speed reducer.SOLUTION: The present invention provides a motor 1 and a motor equipped with a speed reducer, wherein, a plurality of coils 4 are connected to respective commutator segments 5, each connected to both ends of each coil 4, while two coils 4 wound at positions displaced from each other by 360 / m (deg) in a circumferential direction of a core 3 are connected in series when the number of magnetic pole pairs is represented by m; and a plurality of brushes 7 each comprise copper, metal sulfide, one selected from metal carbide and metal silicide, and graphite.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a motor and a motor with a reducer that are primarily used in automotive electrical equipment, home appliances, etc. [Background technology]

[0002] Traditionally, motors for automotive electrical equipment have generally been driven by 14V batteries (12V battery voltage). In recent years, with the advancement of hybrid and electrified vehicles, higher voltage batteries have been installed in vehicles and are primarily used as power sources for assist motors used for driving. For example, in a 56V system, a 48V battery is used as the battery voltage.

[0003] Furthermore, there is a movement to use a high-voltage battery to drive other electrical equipment as well. If this could be realized, it would be possible to reduce the current compared to conventional systems, reduce heat generation in the wiring harnesses installed in the automobile, and also reduce the diameter of the wires in the wiring harnesses, thereby reducing the mass, fuel economy, and cost of the automobile.

[0004] In small brushed DC motors, which are widely used in 14V systems as motors for automotive electrical equipment, commutation sparks occur between the brushes and commutator segments when the commutator segments are switched. To apply such small brushed DC motors to a 56V system and meet the same specifications as those for a 14V system, it is necessary to reduce the coil winding diameter and increase the number of turns.

[0005] The aforementioned commutation sparks are caused by electrical energy stored in the coil while the motor is running. However, if the number of coil turns is large, the inductance increases and the electrical energy stored in the coil also increases, resulting in very intense commutation sparks. Such increased commutation sparks shorten the brush life. Conventional approaches to combat commutation sparks have been to increase the number of grooves in the rotor slots and commutator segments (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 186544 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0007] However, increasing the number of slots in the rotor will result in an increase in the size of the motor, and if the number of commutator segments increases, it will be necessary to reduce the width of the brush to prevent conduction between adjacent commutator segments, which will also reduce the volume of the brush and may result in a decrease in the amount of time the motor can be driven.

[0008] On the other hand, it is also possible to use the same rotor and commutator as a conventional 14V motor in a 56V system by adjusting the number of coil turns to achieve the same performance. For example, to change the voltage from 12V to 48V and achieve the same motor performance, the number of coil turns can be increased by four times in proportion to the voltage, but doing so will significantly increase commutation sparks due to the increase in voltage, making the sliding contacts made up of the brushes and commutator more susceptible to damage.

[0009] Specifically, the inventors tested a motor used in a conventional 14V system at 13.5V, which required a product to run at 20,000 cycles or more in a specific test mode. The motor ran for more than 40,000 cycles, twice the required number of cycles. Next, the same motor was tested at 52V. The winding diameter and number of turns were changed so that the output characteristics at 52V were equivalent to those at 13.5V. The motor stopped after only running for 2,000 cycles. Next, the same motor was tested with a ring-shaped varistor attached to the tongue of the commutator segment to suppress commutation sparks. The motor's run time was extended to 14,000 cycles. However, the required number of cycles was not met. It was found that simply attaching a ring-shaped varistor to the commutator segment to prevent commutation sparks was not enough to ensure a sufficient number of cycles.

[0010] Therefore, the object of the present invention is to provide a motor and a motor with a reducer that use the same rotor and commutator segments as motors driven at low voltages (e.g., 12 V), but that take measures to prevent damage to the sliding contacts caused by commutation sparks when driven at high voltages (e.g., 48 V), and that can achieve the required durability. [Means for solving the problem]

[0011] The motor of the present invention comprises a core fixed to a shaft, a plurality of coils wound around the core, a commutator fixed to the shaft and having a plurality of commutator segments insulated from one another, and a plurality of brushes in slidable contact with the commutator segments, wherein, when the number of magnetic pole pairs is m, the plurality of coils are connected in series with two coils wound at positions offset from each other by 360 / m (deg) around the circumferential direction of the core, and both ends of each coil are connected to adjacent commutator segments, and the plurality of brushes contain copper, metal sulfide, one of metal carbide and metal silicide, and graphite.

[0012] It is desirable that the metal sulfide be molybdenum disulfide, the metal carbide be tungsten carbide, and the metal silicide be tungsten silicide.

[0013] It is desirable to further include an annular structure fixed to each of the plurality of commutator segments.

[0014] It is desirable that the device be driven by a DC power supply with a rated voltage of 48V or more and 60V or less.

[0015] It is desirable that the device further comprises a cylindrical housing that rotatably holds the shaft, the axial length of the housing being 200 mm or less, the radial length of the housing being 100 mm or less, and the rated output being 500 W or less.

[0016] A motor with a reducer of the present invention is characterized by comprising the motor and a reducer that reduces the output of the motor. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a motor and a motor with a reducer that use the same rotor and commutator segments as a motor driven at a low voltage (e.g., 12 V), but that takes measures to prevent damage to the sliding contacts caused by commutation sparks when driven at a high voltage (e.g., 48 V), and that has the required durability. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram showing a partial cross section of a motor according to an embodiment of the present invention; [Figure 2] FIG. 10 is a diagram illustrating a winding state of a coil according to the prior art. [Figure 3] 1 is a diagram illustrating a winding state of a coil according to an embodiment of the present invention. FIG. [Figure 4] FIG. 10 is a diagram showing a test mode of a durability test. [Figure 5] FIG. 10 is a diagram showing test results when the winding state of the coil is changed. [Figure 6] FIG. 10 is a diagram showing test results when the brush material contains tungsten carbide and molybdenum disulfide. [Figure 7] FIG. 10 is a diagram showing test results when the brush material contains tungsten silicide and molybdenum disulfide. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partial cross-sectional view of a motor (rotating electric machine) according to one embodiment of the present invention. As shown in FIG. 1, the motor 1 is primarily used in automotive electrical equipment, home appliances, and the like. Specifically, the motor 1 uses the same rotor and commutator segments as motors driven at low voltages (e.g., 12 V), but is designed to prevent damage to the sliding contacts due to commutation sparks when driven at high voltages (e.g., 48 V). As an example, the motor will be described as being used as a drive source for automotive power windows. The motor uses the same rotor and commutator segments as motors driven by conventional 14 V batteries (12 V battery voltage), but can be driven by a 56 V battery (48 V battery voltage) to satisfy the required number of drive cycles as a product. However, the present invention is not limited to this, and can be applied to motors driven by DC power sources with a rated voltage of 48 V or more and 60 V or less.

[0020] The motor 1 comprises a core 3 fixed to a shaft 2, a plurality of coils 4 wound around the core 3, a commutator 6 fixed to the shaft 2 and having a plurality of commutator segments 5 insulated from one another, and a plurality of brushes 7 in slidable contact with the plurality of commutator segments 6.

[0021] The shaft 2 is rotatably supported on the central axis 2a of a cylindrical (e.g., cylindrical) housing 8 via a bearing 12 between a closed bottom 9 of the housing 8 and an end cap 11 fitted to an open top 10 of the housing 8. That is, the motor 1 further includes a cylindrical housing 8 that rotatably supports the shaft 2. In particular, the present invention is directed to a small brushed DC motor in which the axial length L1 of the housing 8 is 200 mm or less, the radial length L2 of the housing 8 is 100 mm or less, and the rated output is 500 W or less. Here, the rotor 14 collectively refers to all components (such as the core 3 and coil 4) that rotate together with the shaft 2. The exposed length of the shaft 2 on the bottom 9 side (left side in the figure) is longer than the exposed length on the top 10 side (right side in the figure). The shaft 2 transmits its rotational force to a reducer unit or the like via a worm gear or the like on the bottom 9 side where the exposed length is longer. The rotor 14 is housed within the housing 8, except for the portion of the shaft 2 that is exposed to the outside. A pair of magnets 15 are fixed in an annular shape along the circumferential direction on the inner circumferential surface of the housing 8. This magnet 15 provides one magnetic pole pair, and the motor 1 is configured with two poles.

[0022] The core 3 is formed by laminating a plurality of annular core sheets 16 in the axial direction, and the shaft 2 is fixed to the core 3 by being press-fitted into the center of the core 3, so that the core 3 rotates integrally with the shaft 2. The core 3 also has a plurality of teeth 17 extending radially outward from the center, and a plurality of slots 18 formed between each pair of adjacent teeth 17, each extending along the axial direction. A winding 19 that forms the coil 4 is wound between the plurality of slots 18.

[0023] When the number of magnetic pole pairs is m, two coils 4 are wound around the core 3 at positions offset from each other by 360 / m (deg), and connected in series, with both ends of each coil 4 connected to the adjacent commutator segment 5. The winding state of the coils 4 will be described in detail later.

[0024] The commutator 6 is fixed to the shaft 2 at a position adjacent to the end cap 11 within the housing 8. A plurality of commutator segments 5 made of a conductive material are attached to the outer circumferential surface of the commutator 6 at predetermined intervals along the circumferential direction. The conductive material is, for example, oxygen-free copper. Each of the commutator segments 5 is formed of a plate-shaped metal piece extending along the axial direction and is fixed while being insulated from one another. A tongue 20 is formed at the end of the commutator segment 5 facing the core 3. The winding start and winding end of the coil 4 are wrapped around the tongue 20 and fixed by fusing. This electrically connects the commutator segment 5 to the corresponding coil 4. An annular structure (ring-shaped varistor) 21 is also provided around the commutator 6. In other words, the motor 1 further includes an annular structure 21 fixed to each of the plurality of commutator segments 5.

[0025] The brushes 7 contain copper, metal sulfide, one of metal carbide and metal silicide, and graphite. Specifically, the metal sulfide is molybdenum disulfide, the metal carbide is tungsten carbide, and the metal silicide is tungsten silicide. The brushes 7 are held in a brush holder 22 attached to the end cap 11 via elastic brush arms 23. Specifically, the pair of brush arms 23 are held so that their tip ends 23a face each other. Terminals 24 are fitted and fixed to the rear ends 23b of the brush arms 23. A brush 7 is fixed to each tip end 23a and electrically connected to the brush arms 23. An inner diameter side end surface 26 of each brush 7 facing the shaft 2 is in sliding contact with the commutator 6, and the brush 7 abuts against the commutator 6 via an elastically deformable portion 27 of the brush arm 23. The brushes 7 are electrically connected to an external power source (not shown) such as a battery via the terminals 24 and the brush arms 23. Power is supplied to the commutator 6 from the external power source via the brush arms 23 and the brushes 7.

[0026] Next, a detailed description will be given of the winding state of the coil 4. Here, to facilitate understanding, before describing the winding state of the coil 4 according to one embodiment of the present invention, the winding state of a coil according to the prior art will be described, and then the winding state of the coil 4 according to this embodiment will be described in comparison with the winding state of the coil 4 according to the prior art.

[0027] Fig. 2 is a diagram illustrating the winding state of a coil according to the prior art. As shown in Fig. 2, in the coil 104 according to the prior art, the winding 119 is wound sequentially between two outer slots 30 that are positioned on either side of two adjacent slots 30. For example, the winding 119 wound around the tongue 120 of the fourth commutator segment 105 is wound 2n turns (n ​​is a natural number) between the slot 30 located between the third tooth 33 and the fourth tooth 33 and the slot 30 located between the sixth tooth 33 and the seventh tooth 33. In other words, one coil 28 with 2n turns is formed between the fourth commutator segment 105 and the fifth commutator segment 105.

[0028] Fig. 3 is a diagram illustrating the winding state of a coil according to one embodiment of the present invention. As shown in Fig. 3, in the coil 4 according to one embodiment of the present invention, similar to the case of Fig. 2, the winding 19 is wound sequentially between two outer slots 18 that are positioned on either side of two adjacent slots 18. However, unlike the case of Fig. 2, for example, the winding 19 wound around the tongue piece 20 of the fourth commutator segment 5 is wound n turns, which is half the number of turns in the case of Fig. 2, between the slot 18 between the seventh tooth 17 and the eighth tooth 17 and the slot 18 between the second tooth 17 and the third tooth 17, to form the first coil 4. Thereafter, the winding 19 is wound n turns in the opposite direction to the first coil 4 between the slot 18 between the sixth tooth 17 and the seventh tooth 17 and the slot 18 between the third tooth 17 and the fourth tooth 17, without being connected to the fifth commutator segment 5, to form a second coil 4. As a result, a pair of coils 4 (the first coil 4 and the second coil 4) are formed between the fourth commutator segment 5 and the fifth commutator segment 5, facing each other across the shaft 2 and connected in series.

[0029] Similarly, the windings 19 connected to the other commutator segments 5 are sequentially configured to form first coils 4 and second coils 4 that are opposed across the shaft 2 and have opposite winding directions, and the rotor coil 7 is formed between adjacent commutator segments 5. As a result, when the motor 1 is driven, the first coils 4 and second coils 4 each generate a rotational force in the same direction, and the motor 1 generates a rotational force equivalent to that of the prior art.

[0030] In the winding state shown in FIG. 3, when the number of magnetic pole pairs is m, two coils 4 wound at positions offset from each other by 360 / m (deg) in the circumferential direction of the core 3 are connected in series, and both ends of each coil 4 are connected to adjacent commutator segments 5. This results in more crossover wires connecting one coil 4 to another than in the winding state shown in FIG. 2. If the number of crossover wires is increased, for example, when the motor 1 is used in an environment with severe vibration, friction may occur at the contact points between the crossover wires. However, this friction can be suppressed by reinforcing the tongue pieces 20 of the commutator segments 5. This reinforcement can be achieved, for example, by attaching the annular structure 21 described above.

[0031] The inventors conducted a durability test under specified conditions to demonstrate the effects of the present invention. First, the test mode of the durability test will be described. FIG. 4 shows the test mode of the durability test. As shown in FIG. 4, the motor was driven under a load of approximately 90 mN m so that the terminal voltage of the motor was 52 V under a normal temperature and humidity environment. The test mode was such that the motor was driven in one direction for 4.5 seconds, constrained for 0.5 seconds, then paused for 25 seconds, driven in the other direction for 4.5 seconds, constrained for another 0.5 second, and then paused for another 25 seconds, each of which was a 60-second series of steps, and this cycle was repeated.

[0032] Next, the test results of the durability test will be explained one by one.

[0033] First, to confirm the effect of changing the coil winding state, we employed the motor structure shown in FIG. 1. We conducted durability tests using a motor according to the present invention (Example 1) with the winding state shown in FIG. 3 as Example 1 and a conventional motor (Comparative Example 1) with the winding state shown in FIG. 2 as Comparative Example 1. The results are described below. However, in both Example 1 and Comparative Example 2, general-purpose graphite brushes were used, and a motor with two stator magnet poles and eight rotor core slots was used. FIG. 5 shows test results for different coil winding states. As shown in FIG. 5, the motor of Example 1 achieved more than twice the lifespan of the motor of Comparative Example 1. In other words, we confirmed that durability in high-voltage environments was significantly improved by adopting a winding state in which two coils wound at positions offset from each other by 360° / m (deg) around the core, where m is the number of magnetic pole pairs, are connected in series, and both ends of each coil are connected to adjacent commutator segments.

[0034] Next, to confirm the effect of incorporating metal carbides and metal sulfides into the brush material, we conducted a similar durability test to that described above for a motor incorporating metal carbides and metal sulfides into the brush material, using the motor structure shown in Figure 1 and the winding pattern shown in Figure 2. However, the motor used had two stator magnet poles and eight rotor core slots. The metal carbides act as an abrasive (coating thickness adjuster) to remove the coating (mainly a buildup of brush wear particles) that forms when the brush slides against the commutator segment surface, adjusting the coating thickness appropriately to improve the contact between the brush and commutator segment. While an appropriate coating thickness can suppress wear between the brush and commutator segment, an excessively thick coating can worsen the contact between the brush and commutator segment and increase wear. Here, the metal carbide used is tungsten carbide, a high-melting-point material that is hard enough to polish the coating and can withstand the high-temperature environment caused by commutation sparks. The metal sulfide also serves as a lubricant, improving the sliding between the brush and commutator segment by providing the brush with low-wear properties in low-humidity environments. Here, molybdenum disulfide, with its low coefficient of friction, is used as the metal sulfide.

[0035] Figure 6 shows the results of a durability test when the brush material contains tungsten carbide and molybdenum disulfide. As shown in Figure 6, it was confirmed that the durability under high voltage environments was improved by including tungsten carbide and molybdenum disulfide.

[0036] Finally, a similar durability test was conducted when metal silicide was used as an alternative to metal carbide. In this durability test, the motor structure shown in Figure 1 and the winding pattern shown in Figure 2 were used, and the brush material contained metal silicide and metal sulfide. However, the motor used had two stator magnet poles and eight rotor core slots. Here, tungsten silicide was used as the metal silicide. Figure 7 shows the test results when metal silicide was used in the brush material. As shown in Figure 7, it was confirmed that the inclusion of metal silicide improved durability in high-voltage environments.

[0037] Although a motor according to one embodiment of the present invention has been described above, the present invention is not limited to this embodiment and various modifications are possible without departing from the spirit of the present invention. For example, while a two-pole motor has been described in the above embodiment, the present invention is also applicable to a four-pole or more motor as long as it has an even number of poles. In the case of four poles, a mechanical angle of 180° corresponds to an electrical angle of 360°, so that radially opposing positions (i.e., positions rotationally symmetric by 180°) in the present invention are rotationally symmetric by a mechanical angle of 90°. [Explanation of symbols]

[0038] 1 motor 2 shafts 2a Center axis 3 cores 4,104 coils 5,105 commutator segments 6 Commitator 7 Brush 8. Housing 9 Bottom part 10 Top part 11 End cap 12 Bearings 14 rotors 15 Magnet 16 Core Sheets 17,117 Teeth 18,118 Slots 19,119 windings 20,120 tongue piece 21 Ring-shaped varistor (ring structure) 22 Brush holder 23 Brush arm 23a Tip 23b Rear end Terminal 24 26 Inner diameter side end face 27 Elastic deformation part

Claims

1. a core fixed to the shaft; a plurality of coils wound around the core; a commutator fixed to the shaft and having a plurality of commutator segments insulated from one another; a plurality of brushes in slidable contact with the plurality of commutator segments; In a motor comprising: When the number of magnetic pole pairs is m, the plurality of coils are wound in positions shifted from each other by 360 / m (deg) in the circumferential direction of the core, and two coils are connected in series, and both ends of each coil are connected to adjacent commutator segments, The plurality of brushes include copper, metal sulfide, one of metal carbide and metal silicide, and graphite. A motor characterized by:

2. The metal sulfide is molybdenum disulfide, the metal carbide is tungsten carbide, and the metal silicide is tungsten silicide. The motor according to claim 1 .

3. The commutator segment further includes an annular structure fixed to each of the plurality of commutator segments. The motor according to claim 2 .

4. It is driven by a DC power supply with a rated voltage of 48V or more and 60V or less. The motor according to claim 3.

5. The drive mechanism further includes a cylindrical housing that rotatably holds the shaft, The axial length of the housing is 200 mm or less, the radial length of the housing is 100 mm or less, and the rated output is 500 W or less.

5. The motor according to claim 4.

6. A motor according to any one of claims 1 to 5; a reducer that reduces the output of the motor; Equipped with A motor with a reducer.

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