JP2019088086A - motor - Google Patents

Abstract

To provide a DC motor capable of suppressing vibration and noise caused by a magnetic flux density distribution waveform.SOLUTION: A motor 100 is a DC motor having a rotor provided with a commutator 7 and being rotatable about a central axis and a stator provided with a brush 10 in contact with the commutator 7. The stator includes two pieces of arcuate magnets 2a, 2b disposed in a second rotational symmetry. Respective magnets 2a, 2b have a N pole and a S pole. Between the N pole and the S pole of respective magnets 2a, 2b, a magnetic pole transition section 12 is provided in which surface magnetic flux density slowly transits from respective centers of the N pole and the S pole toward a boundary of the N pole and the S pole.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a motor comprising a commutator and a brush.

  There is known a DC motor provided with a sintered ferrite magnet on a stator. For example, Patent Document 1 describes a motor including a sintered ferrite magnet divided into four and having a field pole of four poles. In the motor described in Patent Document 1, one magnet is provided with a single field pole.

Japanese Utility Model Application Publication No. 57-159388

  In the configuration using the same number of magnets as the number of field magnetic poles as in the motor described in Patent Document 1, it is conceivable that the number of parts is large and the number of manufacturing steps is increased. Therefore, the inventors examined a DC motor from the viewpoint of suppressing the number of manufacturing steps by reducing the number of magnets for field magnetic poles, and obtained the following recognition.

  In order to reduce the number of magnets for the field poles, it is conceivable to provide the hollow cylindrical ring magnet with a plurality of poles. However, when a cylindrical ring magnet is manufactured using an anisotropic ferrite magnet material having a high BHmax, it has been found that the ring magnet is highly likely to be cracked in the high temperature sintering process. In this case, it is difficult to secure a desired mass production yield.

  In an anisotropic ferrite magnet, it is conceivable to provide a plurality of magnetic poles on a single piece of magnet by reducing the number of divisions in order to reduce the number of parts. As an example, the present inventors examined a motor of a first configuration provided with two magnetic poles on each piece obtained by dividing the ring into two and having four field magnetic poles. In this configuration, it has been found that if the magnetic poles are simply saturated and magnetized, the surface magnetic flux density of the magnet becomes rectangular and the motor vibration and noise deteriorate. Therefore, in order to improve the magnetic flux density distribution waveform, the inventors of the present invention provide a motor of a second configuration in which an air gap is provided between two magnets and an unmagnetized portion is provided between the magnetic poles of one magnet. It was investigated. In the second configuration, although the magnetic flux density distribution waveform was improved somewhat, it was found that the vibration and noise of the motor did not reach the desired level.

  From the above, the inventor has recognized that the DC motor including the sintered ferrite magnet has a problem to be improved in terms of suppressing vibration and noise caused by the magnetic flux density distribution waveform.

  The object of the present invention is made in view of such a subject, and is providing a DC motor which can control vibration and noise resulting from a magnetic flux density distribution waveform.

  In order to solve the above problems, a motor according to an embodiment of the present invention includes a commutator, a DC motor including a rotor rotatable about a central axis and a stator provided with a brush in contact with the commutator. The stator includes two pieces of arc-shaped magnets arranged in two-fold rotational symmetry. Each magnet has a north pole and a south pole. Between the N pole and the S pole of each magnet, there is provided a magnetic pole transition portion in which the surface magnetic flux density gradually transitions from the central portion of each of the N pole and S pole toward the boundary between the N pole and the S pole.

  According to this aspect, by providing the magnetic pole transition portion, it is possible to gently change the surface magnetic flux density.

  Another aspect of the present invention is also a motor. The motor is a DC motor including a rotor provided with a commutator and rotatable about a central axis, and a stator provided with a brush in contact with the commutator, the stator being capable of rotating the rotor And a bearing, a magnet, a motor case, a brush holder for holding the brush, and an end bell. The motor case has a first hollow cylinder and a second hollow cylinder whose outer shape is different from that of the first hollow cylinder. The second hollow column has a bottom that holds the bearing. One end face of the magnet is fixed in contact with the step surface of the first hollow cylinder and the second hollow cylinder, and the other end face of the magnet is pressure-welded by a column extending from the brush holder fixed to the end bell A projection is formed at the tip of the columnar part.

  It is to be noted that any combination of the above-described constituent elements, and one in which the constituent elements and expressions of the present invention are mutually replaced among methods, systems, etc. is also effective as an aspect of the present invention.

  According to the present invention, it is possible to provide a DC motor capable of suppressing vibration and noise caused by a magnetic flux density distribution waveform.

It is an axial sectional view of a motor concerning an embodiment. It is radial direction sectional drawing of the motor of FIG. It is radial direction sectional drawing which shows the periphery of the magnetic pole transfer part of the motor of FIG. It is another radial direction sectional view which shows the periphery of the magnetic pole transition part of the motor of FIG. FIG. 7 is yet another radial cross-sectional view showing the periphery of a magnetic pole transition portion of the motor of FIG. 1; FIG. 7 is yet another radial cross-sectional view showing the periphery of a magnetic pole transition portion of the motor of FIG. 1; It is explanatory drawing explaining the process of magnetizing the magnet of the motor of FIG. It is explanatory drawing explaining the periphery of the projection part of the motor of FIG. It is explanatory drawing explaining the periphery of the flat part of the motor of FIG. It is explanatory drawing explaining the periphery of the slit part of the motor of FIG. It is radial direction sectional drawing which shows the periphery of the inner peripheral recessed part of the motor of FIG. It is an axial sectional view which shows the periphery of the crimp fixing | fixed part of the end bell of the motor of FIG. It is explanatory drawing explaining the arrangement | positioning of the brush holder of each motor of FIG. 1, and each magnet. It is explanatory drawing explaining the motor case of the motor of FIG. It is radial direction sectional drawing of the motor which concerns on a 1st comparative example. It is a wave form diagram which shows magnetic flux density distribution of the motor of FIG. It is a wave form diagram which shows magnetic flux density distribution of the motor of FIG. It is radial direction sectional drawing of the motor which concerns on a 2nd comparative example. It is a wave form diagram which shows magnetic flux density distribution of the motor of FIG. It is an axial sectional view of the motor concerning a 3rd comparative example. It is a comparison figure which shows an example of the performance of the motor of FIG. 1, and the motor of FIG. It is a characteristic view which shows an example of the characteristic of the motor of FIG. 1, and the motor of FIG. It is a comparison figure which shows an example of the torque constant per unit volume of the motor of FIG. 1, and FIG.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. In the embodiment and the modification, the same or equivalent constituent elements and members are denoted by the same reference numerals, and duplicating descriptions will be appropriately omitted. In addition, dimensions of members in each drawing are shown appropriately enlarged or reduced for easy understanding. In each drawing, a part of members which are not important in describing the embodiment is omitted and displayed.
Also, although terms including first and second ordinal numbers are used to describe various components, this term is used only to distinguish one component from another component, and this term The constituent elements are not limited by

  The motor according to the embodiment of the present invention is a small DC motor suitable for driving an electric storage mirror for a vehicle, driving a door lock, driving an air conditioner damper, and the like. In recent years, more than 50 DC motors for automobiles have come to be mounted, and downsizing and weight reduction of the motors have become important issues to be solved in order to improve the fuel consumption performance of automobiles. Further, with the reduction in noise of automobiles, the demand for noise reduction is also increasing in motors, and in particular, the demand for noise reduction in a state where a load is applied to the motors is increasing. In order to reduce the size and weight of the motor, it is possible to use a magnet with a high maximum energy product (BHmax), but for practical purposes the cost, the workability of the magnet, the influence on vibration and noise, the magnet motor It is also necessary to consider the assemblability and the like.

  As an example, in a small DC motor, a magnet (such as a ring-shaped isotropic sintered ferrite magnet) is mounted in a motor case made of a cylindrical magnetic material, and an air gap of about 0.1 mm to 0.5 mm is interposed. An armature is rotatably mounted.

In order to further reduce the size and weight of such a small DC motor, it is necessary to compensate for the reduction in motor performance such as torque due to the reduction in size by using a magnet having a high maximum energy product. The maximum energy product can be increased by using an anisotropic magnet instead of an isotropic magnet or by using a ferrite magnet as a rare earth magnet, but a cylindrical ferrite magnet used for a small DC motor can be used as a cylinder. If an anisotropic magnet is used as it is, there is a problem that the magnet is broken due to the distortion caused by aligning the magnetic domain direction at the time of sintering.
The DC motor according to the embodiment described below was devised based on such thinking, and the contents thereof will be described below.

Embodiment
Hereinafter, a motor 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. The motor 100 is a small DC motor suitable for driving a motorized electric storage mirror, driving a door lock, driving an air conditioner damper, and the like. FIG. 1 is an axial sectional view of a motor 100 according to the embodiment. FIG. 2 is a radial sectional view of the motor 100. In the present application, a direction parallel to the central axis of the motor 100 is referred to as “axial direction”, a direction perpendicular to the central axis of the motor 100 as “radial direction”, and a direction along an arc centered on the central axis of the motor 100 It is referred to as "circumferential direction". FIG. 1 is an axial sectional view of a DC motor composed of a 4-pole field magnet and a rotor in which an armature winding is applied to a 6-groove iron core.

  The motor 100 includes a motor case 1, two pieces of magnets 2a and 2b, a brush holder 23, an end bell 3, a shaft 4, an iron core 5 of an armature, a coil 6, a commutator 7 and a varistor 8 , Bearing 9, a pair of brushes 10, and a motor terminal 11 are mainly included.

(stator)
The motor case 1 is formed by pressing or the like into a bottomed hollow cylindrical body shape from a magnetic material such as iron. The two-piece magnets 2 a and 2 b are attached to the inner peripheral surface of the motor case 1. The motor case 1 forms a magnetic path of the magnets 2a and 2b. An end bell 3 is fixed to the opening of the motor case 1. The end bell 3 may be fixed to the motor case 1 by a method such as press fitting or crimping.

  The brush holder 23 is attached to the end bell 3. The brush holder 23 may be made of resin, for example. A pair of brushes 10 is fixed to the end bell 3 via a brush holder 23. The brush 10 contacts the commutator 7 through the brush arm. The brush arm is supported by the end bell 3 via a brush holder 23 and connected to a motor terminal 11 provided on the end bell 3 opposite to the brush. The brush arm is connected to an external power supply (not shown) via the motor terminal 11.

(Rotor)
The iron core 5 is fixed to the shaft 4. The coil 6 is wound around an iron core 5. The commutator 7 is provided on the shaft 4. The shaft 4 is rotatably supported by bearings 9 fixed to the central portion of the end bell 3 and the central portion of the bottom 25 of the motor case 1. A varistor 8 for reducing surge current is attached to the end of the commutator 7. The shaft 4, the iron core 5, the coil 6, and the commutator 7 constitute a rotor.

(magnet)
The two-piece magnets 2a and 2b are arc-shaped magnets. Each of the magnets 2a and 2b may be an anisotropic ferrite sintered magnet whose magnetic field is oriented in the thickness direction. The two-piece magnets 2a and 2b are symmetrically disposed via the circumferential gap. In particular, the two-piece magnets 2a, 2b are arranged in two-fold rotational symmetry. An angle centered on the central axis of the circumferential gap 14 is denoted as an angle α. The angle α may be set in the range of more than 0 ° and 60 ° or less. If the angle α exceeds 60 °, the efficiency of the motor 100 may be reduced. Further, if the angle α is too small, it is not possible to secure a space into which a fixing pin or the like for fixing the magnets 2a and 2b can enter. From such a point of view, the angle α may be set in the range of 10 ° to 30 °. Each of the magnets 2a and 2b is provided with a magnetic pole of two poles of N pole and S pole, and two pieces constitute a four pole magnetic pole. The magnetic pole transition part 12 is provided in the both ends of each magnetic pole of 4 poles of each magnet 2a, 2b.

The magnetic pole transition portion 12 is a portion where the surface magnetic flux density of the magnetic pole gradually decreases or increases. As shown in FIG. 2, an angle centered on the central axis of the magnetic pole transition portion 12 is denoted as an angle β. Note that β can be defined as an angle between the magnetic poles at a position where the magnetic flux becomes 95% or less and the magnetic flux density starts to decrease when the maximum value of the magnetic flux density of the adjacent magnetic poles is 100%. The angle β may be set larger than the angle α. In particular, the angle α and the angle β may be set to satisfy the equation (1).
Angle β ≧ angle α ··· (1)

  Coils 6 are wound around the six grooved iron cores 5 fixed to the shaft 4 respectively. The rotor and the stator configured in this way constitute a 4-pole, 6-groove DC motor.

  Next, with reference to FIGS. 3 to 6, an example of means for forming the magnetic pole transition portion 12 which is a portion where the surface magnetic flux density of the magnetic pole gradually decreases or increases will be described. Each of FIGS. 3 to 6 is a radial cross-sectional view showing the periphery of the magnetic pole transition portion 12 of the motor 100. Each of FIGS. 3 to 6 corresponds to FIG. The magnetic pole transition portion 12 includes a first transition portion 12a and a second transition portion 12b. The first transition portion 12a is formed at the boundary between the magnetic poles of the magnets 2a and 2b. The second transition portion 12 b is formed with the gap 14 in the circumferential direction between the two pieces of magnets 2 a and 2 b interposed therebetween. For this reason, there is a limit in bringing it close to a sine wave only by the operation of magnetization, and in particular, the second transition portion 12b sandwiching the gap portion 14 in the circumferential direction of the two pieces of magnet has a rectangular waveform of the magnetic flux density distribution. There was a problem that it was easy. In the present specification, it is not essential that the void or void such as the void 14 in the circumferential direction is a void. If necessary, a nonmagnetic material or member such as an adhesive, a resin, or a nonmagnetic metal may be disposed in the void portion. The same applies to the other air gaps and air gaps described below.

(Back part of outer circumference)
In the example of FIGS. 3 to 6, on the outer peripheral surface of each of the magnets 2a and 2b, an outer peripheral receding portion 15 which recedes inward in a region corresponding to the second transition portion 12b is provided. By having the outer circumferential receding portion 15, an end void portion is formed between the outer diameter portion of each of the magnets 2 a and 2 b and the motor case 1. The end void portion is formed between the motor case 1 and the outer diameter portion of the magnet over the second transition portion 12b of the two pieces of magnets 2a and 2b. The end air gaps may be formed to gradually increase in distance as they approach both ends of the magnets 2a and 2b. That is, the end void portion has a minimum distance at or far from the farthest position in the circumferential direction from the both ends of each magnet 2a, 2b of the second transition portion 12b, and the space at each end of each magnet 2a, 2b May be formed to be maximum. In this case, it becomes possible to make the magnetic flux density distribution waveform at both ends of each magnet closer to a sine wave.

  In the example of FIG. 5, FIG. 6, the outer periphery receding part 16 receded inward in the area | region corresponding to the 1st transition part 12a is provided in the outer peripheral surface of each magnet 2a, 2b. By having the outer circumferential receding portion 16, an intermediate gap portion is formed between the outer diameter portion of each of the magnets 2 a and 2 b and the motor case 1. The intermediate gap portion is formed between the motor case 1 and the outer diameter portion of the magnet in all or a part of the region in a region corresponding to the first transition portion 12a of the two pieces of magnets 2a and 2b. . In this case, it becomes possible to make the magnetic flux density distribution waveform at both ends of each magnet closer to a sine wave. Either one or both of the outer circumferential receding portion 15 and the outer circumferential receding portion 16 may be provided. The shapes of the outer circumferential receding portion 15 and the outer circumferential receding portion 16 can be determined by simulation or experiment using parameters such as the shape of the motor and the thickness of the magnet according to the desired magnetic flux density distribution waveform.

  Next, another method of forming the magnetic pole transition portion 12 will be described with reference to FIG. FIG. 7 is an explanatory view for explaining the step of magnetizing the two-piece magnets 2 a and 2 b of the motor 100. FIG. 7 shows a radial cross section of a work including two pieces of magnets 2a and 2b fixed to the motor case 1 and a magnetizing yoke 17 fitted to the work. The magnetizing yoke 17 is inserted into the inner periphery of the magnets 2a and 2b attached to the motor case 1 through a narrow gap.

(Yoke recess)
The outer diameter portion of the magnetizing yoke 17 is provided with a yoke recess 18 in which a portion corresponding to the magnetic pole transition portion 12 is recessed from other portions. The magnetic pole transition portion 12 may be formed using a magnetizing yoke 17 provided with a yoke recess 18 in which a portion corresponding to the magnetic pole transition portion 12 is recessed from other portions. The yoke recess 18 is a portion receding inward from the circumscribed circle of the magnetizing yoke 17. The yoke recesses 18 are provided at four locations corresponding to the first transition portion 12a and the second transition portion 12b. The yoke recess 18 may be formed to have four-fold rotational symmetry. The shape of the yoke recess 18 can be determined by simulation or experiment depending on the desired magnetic flux density distribution waveform. In the example of FIG. 7, the yoke recess 18 has a shape in which the gap gradually increases in the circumferential direction from the center position 18 c in the circumferential direction of the yoke recess 18 in the circumferential direction. In the example of FIG. 7, the main surface which comprises the yoke recessed part 18 is a substantially plane, but the said surface may be a curved surface. By providing the yoke recess 18 in the magnetizing yoke 17, it becomes easy to make the magnetic flux density distribution waveform of each magnet closer to a sine wave.

(protrusion)
Next, with reference to FIG. 8, another means for forming the magnetic pole transition portion 12 will be described. In the example of FIG. 8, a rib-like outward protrusion 21 is provided at a portion facing the magnetic pole transition portion 12 of the motor case 1. FIGS. 8A to 8C are perspective views showing the periphery of the protrusion 21 of the motor 100. FIG. 8D to 8E are radial direction sectional views showing the periphery of the protrusion 21 of the motor 100. FIG. Each of FIGS. 8 (d) to 8 (e) corresponds to FIGS. 8 (a) to 8 (c).

  The protrusion part 21 may be provided corresponding to both the 1st transition part 12a and the 2nd transition part 12b, and may be provided corresponding to any one. In the example of FIG. 8A, the protrusion 21 is provided corresponding to the first transition portion 12a and is not provided in the second transition portion 12b. In the example of FIGS. 8B and 8C, the protrusion 21 is provided corresponding to both the first transition portion 12a and the second transition portion 12b. The protrusions 21 may be provided in a skew shape inclining with respect to the axial direction, as shown in FIG. 8C.

  By providing the protrusion 21, as shown in FIG. 8, an air layer is formed between the motor case 1 and each of the magnets 2a and 2b. By forming the air layer, it becomes easy to make the magnetic flux density distribution waveform of each of the magnets 2a and 2b closer to a sine wave. By bringing the magnetic flux density distribution waveform closer to a sine wave, it is possible to realize a motor with suppressed vibration and noise. The width in the circumferential direction, the height in the radial direction, and the angle of the skew of the protrusion 21 can be determined by simulation or experiment using the shape of the motor, the thickness of the magnet, and the like as parameters. Further, as shown in FIGS. 8A and 8B, by making the outer surface of the protrusion 21 flat, the motor 100 can be easily attached using this flat portion. is there.

(Flat part)
Next, referring to FIG. 9, another means for forming the magnetic pole transition portion 12 will be described. In the example of FIG. 9, the flat portion 37 is provided in a portion facing the magnetic pole transition portion 12 of the motor case 1. FIG. 9A is a perspective view showing the periphery of the flat portion 37 of the motor 100. FIG. FIG. 9 (b) is a radial cross-sectional view showing the periphery of the flat portion 37 of the motor 100. The flat portion 37 is a portion in which a portion facing the magnetic pole transition portion 12 of the cylindrical motor case 1 is receded inward and formed into a substantially flat surface.

  The flat portion 37 may be provided corresponding to both the first transition portion 12a and the second transition portion 12b, or may be provided corresponding to either one. In the example of FIG. 9, the flat portion 37 is provided corresponding to both the first transition portion 12 a and the second transition portion 12 b. By providing the flat portion 37 on the outer peripheral portion of the motor case 1, as shown in FIG. 9, the thickness of the portion corresponding to the flat portion 37 of each of the magnets 2a and 2b becomes thinner than the other portions. In this case, the magnetic flux density decreases as it approaches the circumferential center of the thin portion, and it becomes easy to make the magnetic flux density distribution waveform closer to a sine wave. By bringing the magnetic flux density distribution waveform closer to a sine wave, it is possible to realize a motor with suppressed vibration and noise.

(Slit section)
Next, with reference to FIG. 10, another means of forming the magnetic pole transition portion 12 will be described. In the example of FIG. 10, the slit portion 22 is provided in a portion facing the magnetic pole transition portion 12 of the motor case 1. 10 (a) to 10 (c) are perspective views showing the periphery of the slit portion 22 of the motor 100. FIG. 10D to 10E are radial direction sectional views showing the periphery of the slit portion 22 of the motor 100. FIG. Each of FIGS. 10 (d) to 10 (e) corresponds to FIGS. 10 (a) to 10 (c).

  The slit portion 22 is a cut portion extending in the axial direction at a portion facing the magnetic pole transition portion 12 of the motor case 1. In the example of FIGS. 10 (a) and 10 (b), the slit parts 22 are integrally provided at the respective places, and in the example of FIG. 10 (c), a plurality of the slit parts 22 are provided at the respective places (for example, , 3) may be provided separately.

  The slit portion 22 may be provided corresponding to both the first transition portion 12a and the second transition portion 12b, or may be provided corresponding to either one. In the example of FIG. 10A, the slit portion 22 is provided corresponding to the first transition portion 12a, and is not provided in the second transition portion 12b. In the example of FIG. 10 (b), (c), the slit part 22 is provided corresponding to both the first transition part 12a and the second transition part 12b. The slit portion 22 may be provided in parallel to the axial direction as shown in FIG. 10 (a). As shown in FIGS. 10B and 10C, the slit portion 22 may be provided in a skew shape inclining with respect to the axial direction.

  By providing the slit portions 22 in the outer peripheral portion of the motor case 1, as shown in FIG. 10, the magnetic resistance can be increased in the vicinity of the portions corresponding to the slit portions 22 of the magnets 2a and 2b. As described above, in the region where the magnetic resistance is increased, the magnetic flux density is lowered, and it becomes easy to make the magnetic flux density distribution waveform closer to a sine wave. By bringing the magnetic flux density distribution waveform closer to a sine wave, it is possible to realize a motor with suppressed vibration and noise.

  The shape of the slit portion 22 such as the slit width, the skew angle, and the number of divisions can be determined by simulation or experiment using the shape of the motor, the thickness of the magnet, and the like as parameters. There is no particular limitation on the cut shape of the slit portion 22, and the cut portion of the slit portion 22 may be provided with a circular hole or the like instead of the slit.

(Back part of inner circumference)
Next, with reference to FIG. 11, another means for forming the magnetic pole transition portion 12 will be described. In the example of FIG. 11, an inner circumferential receding portion 24 which recedes outward is provided in the region corresponding to the magnetic pole transition portion 12 on the inner circumferential surface of each magnet 2a, 2b. FIG. 11 is a radial cross-sectional view showing the periphery of the inner circumferential receding portion 24 of the motor 100. As shown in FIG. As shown in FIG. 11, the inner circumferential receding portion 24 is recessed outward on the inner circumferential surface of each of the magnets 2a and 2b.

  The provision of the inner circumferential receding portion 24 at the magnetic pole transition portion 12 enables the air gap between the iron core 5 and the inner circumferential surfaces of the magnets 2a and 2b to be expanded at that portion. The air gap is enlarged at the pole transition portion 12 to increase the magnetic resistance at that portion. As described above, in the region where the magnetic resistance is increased, the magnetic flux density is lowered, and it becomes easy to make the magnetic flux density distribution waveform closer to a sine wave. By bringing the magnetic flux density distribution waveform closer to a sine wave, it is possible to realize a motor with suppressed vibration and noise. The shape of the inner circumferential receding portion 24 can be determined by simulation or experiment using the shape of the motor, the thickness of the magnet, and the like as parameters.

(Other configuration)
Next, other configurations of the motor 100 according to the embodiment will be described. As shown in FIG. 1, the motor case 1 includes a first hollow cylinder 1 a and a second hollow cylinder 1 b whose outer diameter and inner diameter are smaller than those of the first hollow cylinder 1 a. The second hollow column 1 b has a bottom 25 that holds the bearing 9. A stepped surface 1c is formed at the boundary between the first hollow cylinder 1a and the second hollow cylinder 1b.

  One end face in the axial direction of each of the magnets 2a and 2b is in contact with the step surface 1c. The other axial end face of each of the magnets 2 a and 2 b is in contact with a columnar portion 26 extending from a brush holder 23 fixed to the end bell 3. That is, each magnet 2a, 2b is clamped from both sides by the level | step difference surface 1c and the columnar part 26 in the axial direction. When the end bell 3 and the motor case 1 are crimped and fixed to the other end face in the axial direction of each of the magnets 2a and 2b, a columnar portion 26 is in pressure contact. With this configuration, the magnets 2a and 2b can be firmly fixed to the motor case 1. By firmly fixing the magnet, vibration and noise of the motor can be suppressed. The outer contour of the hollow cylinder in the axial direction is not limited to a circle, and may be a polygon, or a combination of a circle and a polygon.

  FIG. 12 is an axial sectional view showing the periphery of the caulking fixing portion of the end bell 3. 12 is an axial sectional view of a portion of the motor 100 excluding the rotor, and corresponds to FIG. FIG. 12 (a) shows a state before the end bell 3 is fixed to the motor case 1 by caulking, and FIG. 12 (b) shows a state after the caulking. The two pieces of magnets 2a and 2b are fixed to the motor case 1 by fixing pins 28 inserted into the circumferential gap 14. The fixing pin 28 applies a force in the circumferential expansion direction to both circumferential ends of each of the magnets 2a and 2b.

  In the state before caulking, one end face in the axial direction of each magnet 2a, 2b is in close contact with the step surface 1c, and the other end face in the axial direction of each magnet 2a, 2b extends from the brush holder 23 It faces the part 26 via a gap. At the tip of the columnar portion 26, a protrusion 27 thinner than the columnar portion 26 is formed. In the process of caulking and fixing the end bell 3 to the motor case 1, as shown in FIG. 12 (b), the projection 27 comes in contact with the other axial end face of each of the magnets 2a and 2b and is gradually pushed further. It will be crushed. The protrusion 27 is pressed and crimped to the other axial end face of each of the magnets 2a and 2b, and the magnets 2a and 2b can be firmly crimped and fixed to the motor case 1.

(Brush holder)
The brush holder 23 will be described. FIGS. 13A and 13B are perspective views of the brush holder 23. FIGS. 13 (c) and 13 (d) are diagrams showing the arrangement of the magnets 2a and 2b viewed from the end bell side. In the example of FIG. 13A, the projection 27 of the columnar part 26 of the brush holder 23 is formed in a quadrangular pyramid shape. In this case, as shown in FIG. 13 (c), when the end bell 3 is crimped and fixed, the projection 27 abuts against the pressure contact portion 29 of the other end face in the axial direction of each magnet 2a, 2b Fix the magnet firmly. In the example of FIG. 13B, the projection 27 of the columnar part 26 of the brush holder 23 is formed in a cylindrical shape. In this case, as shown in FIG. 13 (d), the contact area between the pressure contact portion 29 and each of the magnets 2 a and 2 b is increased, so that the magnets can be fixed more firmly. The shape of the protrusion 27 is not limited to a quadrangular pyramid shape or a cylindrical shape, and may be, for example, a plurality of needle-like protrusions, a plate-like protrusion, a hollow cylindrical protrusion, or the like. The number of columnar portions 26 is not limited to four. The number of columnar portions 26 may be three or less or five or more.

(Case recess)
Next, another fixing means for fixing the magnets 2a and 2b to the motor case 1 will be described. FIG. 14A is a perspective view of a motor 100 to which another fixing means is applied. FIG. 14 (b) is an axial cross-sectional view of a portion excluding the rotor of the motor 100 to which another fixing means is applied, and corresponds to FIG. 1. In the example of FIG. 14, the motor case 1 is provided with a case recess 1 d. The case recess 1 d is provided at the boundary between the cylindrical portion of the motor case 1 and the bottom 25. The case recess 1 d is a portion that partially enters radially and axially inward. A step surface 1c is formed inside the case recess 1d. The step surface 1c is a surface directed in the axial direction in the step between the first hollow cylindrical body 1a and the second hollow cylindrical body 1b. A plurality of case recesses 1 d may be provided, and in the example of FIG. 14, four case recesses 1 d are provided at substantially equal intervals in the circumferential direction.

  One end face in the axial direction of each of the magnets 2a and 2b is in close contact with the step surface 1c. The other end face in the axial direction of each of the magnets 2 a and 2 b faces the columnar portion 26 extended from the brush holder 23 with a gap therebetween. At the tip of the columnar portion 26, a protrusion 27 thinner than the columnar portion 26 is formed. In the process of caulking and fixing the end bell 3 to the motor case 1, the protrusions 27 come in contact with the other axial end faces of the magnets 2 a and 2 b and gradually collapse as they are further pushed. The protrusion 27 is pressed and crimped to the other axial end face of each of the magnets 2a and 2b, and the magnets 2a and 2b can be firmly crimped and fixed to the motor case 1.

  As described above, the magnets 2a and 2b are fixed to the motor case 1 by the fixing pins 28 inserted into the circumferential gap 14. The fixing pin 28 applies a force in the circumferential expansion direction to both circumferential ends of each of the magnets 2a and 2b. The fixing pin 28 of the magnet is inserted out of the range of the case recess 1 d of each magnet 2 a, 2 b, and the tip of the fixing pin 28 can be inserted until it abuts on the bottom 25 of the step surface 1 c. It can be used. By lengthening the fixing pin 28, the fitting length of the fixing pin 28 and each of the magnets 2a and 2b becomes long, and the circumferential fixing of each of the magnets 2a and 2b becomes stronger, and the vibration of the magnets can be suppressed. .

  The motor 200 according to the first comparative example will be described with reference to FIGS. 15 and 16. FIG. 15 is a radial direction cross-sectional view of the motor 200 according to the first comparative example, and corresponds to FIG. FIG. 16 shows a magnetic flux density distribution waveform of the motor 200. In the motor 200, one C-shaped magnet 30 is magnetized to have two poles and one air gap 35 and one unmagnetized portion 32 are provided between the magnetic poles. As shown in FIG. 16, since the magnetic flux density distribution waveform of the motor 200 is a rectangular wave, many harmonic components are superimposed, and vibration and noise at the time of driving are large.

  FIG. 17 is a diagram showing a magnetic flux density distribution of the motor 100 according to the embodiment. The motor 100 can bring the magnetic flux density distribution waveform closer to a sine wave with respect to the motor 200 by providing the above-described configuration. By suppressing the harmonic components of the magnetic flux density distribution waveform, the motor 100 can reduce vibration and noise with respect to the motor 200.

  The motor 300 according to the second comparative example will be described with reference to FIGS. 18 and 19. FIG. 18 is a radial direction cross-sectional view of a motor 300 according to a second comparative example, and corresponds to FIG. FIG. 19 shows a magnetic flux density distribution waveform of the motor 300. The motor 300 is composed of a two-piece magnet and a six-groove armature, the two-piece magnet being disposed across the air gap part θ in the circumferential direction, and the unmagnetized part θ ' It is provided. As shown in FIG. 19, since the magnetic flux density distribution waveform of the motor 300 is rectangular, many harmonic components are superimposed, and vibration and noise at the time of driving are large. In the motor 100 according to the embodiment, the harmonic component of the magnetic flux density distribution waveform is suppressed, whereby the motor 100 can reduce vibration and noise with respect to the motor 300.

  A motor 400 according to a third comparative example will be described with reference to FIG. FIG. 20 is an axial sectional view of a motor 400 according to a third comparative example, and corresponds to FIG. In the motor 400, one end face of the magnets 34a and 34b is in close contact with the bent portion 33 of the motor case, and the other end face of the magnets 34a and 34b is in contact with the stop boss 36. The magnets 34 a, 34 b are fixed between the bent portion 33 and the locking boss 36. In this case, since the bent portion 33 has a small contact area with the magnets 34a and 34b, it is difficult to fix the magnet firmly. Further, in the elongated bosses 36, the bosses are deformed at the time of pressure bonding, and it is difficult to fix the magnet with sufficient strength, so that the magnet may vibrate and the vibration or noise of the motor 400 may be deteriorated.

  In the motor 100 according to the embodiment, one end face of each of the magnets 2a and 2b is in close contact with the step surface 1c of the motor case 1, and the other end face is a projection at the tip of the columnar portion 26 extended from the brush holder 23. It is firmly fixed by 27. The columnar portion 26 has a strength that does not significantly deform due to caulking, and only the protrusion 27 can be crushed to maintain the state in which the magnet is strongly crimped. For this reason, the vibration and noise of the motor 100 are suppressed.

  FIG. 21 is a comparison diagram showing an example of the performance of the motor 200 according to the first comparative example and the performance of the motor 100 according to the embodiment. FIG. 22 is a characteristic diagram showing an example of the characteristics of the motor 200 and the motor 100 in comparison. FIG. 23 is a diagram comparing torque constants Kt per unit volume of the motor 200 and the motor 100. In FIG. The motor 100 according to the embodiment is miniaturized by approximately 40% as compared with the motor 200 of the first comparative example having substantially the same torque constant Kt. In addition, the motor 100 according to the embodiment firmly holds each of the magnets 2a and 2b to make the magnetic flux density distribution waveform sinusoidal, thereby causing noise at a load of 20 gcm as compared with the motor 200 according to the first comparative example. Could be lowered by 1.78 dB. As described above, the motor 100 according to the embodiment can greatly contribute to downsizing, weight reduction, and noise reduction as compared to the motor 200 according to the first comparative example.

  Next, the operation and effects of the motor 100 configured as described above will be described.

  A motor 100 according to the embodiment is a DC motor including a rotor provided with a commutator 7 and rotatable about a central axis, and a stator provided with a brush 10 in contact with the commutator 7, and fixed. The element includes two arc-shaped magnets 2a and 2b arranged in rotational symmetry twice, and each magnet 2a and 2b has an N pole and an S pole, and the N pole and S of each magnet 2a and 2b are Between the poles, there is provided a magnetic pole transition portion 12 in which the surface magnetic flux density gradually transitions from the center of each of the N pole and the S pole toward the boundary between the N pole and the S pole. As described above, since the surface magnetic flux at the boundary between the N pole and the S pole becomes gentle, noise can be reduced. Also, by using anisotropic sintered ferrite for the magnet, a compact high torque and low noise motor can be provided. According to this configuration, the magnetic flux density distribution waveform can be made closer to a sine wave as compared with the case where the magnetic pole transition portion 12 is not provided. By suppressing the harmonic component of the magnetic flux density distribution waveform, vibration and noise of the motor can be reduced.

  In the motor 100 according to the embodiment, the two-piece magnets 2a and 2b are disposed across the air gap 14 provided in the circumferential direction over the angular range of the angle α centering on the central axis, and the magnetic pole transition 12 is It is provided over an angle range of angle β around the axis, and angle β is set to satisfy the relationship of angle β ≧ angle α with respect to angle α. According to this configuration, it is possible to make the magnetic flux density distribution waveform closer to a sine wave. By suppressing the harmonic component of the magnetic flux density distribution waveform, vibration and noise of the motor can be reduced.

  In the motor 100 according to the embodiment, the angle α is set in the range of more than 0 ° and 60 ° or less. If the angle α becomes larger than 60 °, the efficiency of the motor is degraded. On the other hand, if the amount is too small, a space into which a fixing pin or the like for fixing the magnet can not be secured. According to this configuration, it is possible to suppress the decrease in efficiency of the motor while securing the arrangement space for the fixing pin and the like.

  In the motor 100 according to the embodiment, the magnetic pole transition portion 12 is formed using a magnetized yoke 17 provided with a yoke recess 18 in which a portion corresponding to the magnetic pole transition portion 12 is recessed from other portions. According to this configuration, the magnetic flux density of the magnetic pole transition portion 12 can be changed gently as compared to the case of using a magnetized yoke having no yoke recess 18.

  In the motor 100 according to the embodiment, the two-piece magnets 2a and 2b are fixed to the inside of the motor case 1, and the outer peripheral surface of each of the magnets 2a and 2b is inward in the region corresponding to the magnetic pole transition portion 12. An outer peripheral receding portion (15, 16) to be retracted is provided, and a gap is formed between the outer peripheral receding portion (15, 16) and the motor case 1. According to this configuration, it is possible to form an air gap between the motor case 1 and the magnetic flux density in the region corresponding to the magnetic pole transition 12 more gently than in the case where the outer peripheral receding portion is not provided. .

  In the motor 100 according to the embodiment, the two pieces of magnets 2a and 2b are fixed inside the motor case 1, and a rib-like outward protrusion 21 is provided at a portion facing the magnetic pole transition portion 12 of the motor case 1. The flat portion 37 or the slit portion 22 is provided. According to this configuration, an air layer is formed between the motor case 1 and the magnets 2a and 2b, and it becomes easy to make the magnetic flux density distribution waveform of each magnet 2a and 2b approach a sine wave.

  In the motor 100 according to the embodiment, on the inner peripheral surface of each of the magnets 2a and 2b, an inner circumferential receding portion 24 recessed outward in a region corresponding to the magnetic pole transition portion 12 is provided. According to this configuration, it is easy to expand the air gap between the iron core 5 and each of the magnets 2a and 2b in the region of the inner circumferential receding portion 24 so that the magnetic flux density distribution waveform approaches a sine wave.

  A motor 100 according to the embodiment is a DC motor including a rotor provided with a commutator 7 and rotatable about a central axis, and a stator provided with a brush 10 in contact with the commutator 7, and fixed. The rotor includes a bearing 9 rotatably supporting a rotor, magnets 2a and 2b, a motor case 1, a brush holder 23 for holding a brush 10, and an end bell 3. The motor case 1 is a first motor case. A hollow cylindrical body 1a and a second hollow cylindrical body 1b having an outer shape different from that of the first hollow cylindrical body 1a. The second hollow cylindrical body 1b has a bottom 25 for holding the bearing 9, and the magnet 2a, One end face of 2b is fixed in contact with the step surface 1c of the first hollow cylindrical body 1a and the second hollow cylindrical body 1b, and the other end face of the magnets 2a and 2b is a brush holder fixed to the end bell 3 23 are pressed against each other by the columnar portion 26 extended from Protrusion 27 is formed at the distal end. According to this configuration, the magnets 2a and 2b can be sandwiched and fixed between the step surface 1c and the columnar portion 26 of the brush holder 23. Further, since the other end face of each magnet 2a, 2b is pressure-welded by the columnar part 26, it becomes possible to fix each magnet 2a, 2b more firmly, and it is possible to reduce the vibration of the magnet.

  In the motor 100 including the second hollow cylinder, a plurality of small diameter portions or a plurality of case recesses 1d are partially formed on the outer periphery of the second hollow cylinder 1b with respect to the outer periphery of the first hollow cylinder 1a. It is formed. According to this configuration, the magnets 2a and 2b can be firmly fixed by being sandwiched between the case recess 1d and the columnar portion 26 of the brush holder 23.

  The above has been described based on the embodiments of the present invention. It is to be understood by those skilled in the art that these embodiments are exemplifications, and that various modifications and alterations are possible within the scope of the claims of the present invention, and such variations and modifications are also within the scope of the claims of the present invention. It is understood. Accordingly, the descriptions and drawings herein are to be considered as illustrative and not restrictive.

  DESCRIPTION OF SYMBOLS 1 motor case, 2a, 2b magnet, 3 end bell, 4 shaft, 5 iron core, 7 commutator 7, 9 bearing, 10 brush 10, 12 magnetic pole transition part 12, 17 magnetization yoke, 23 brush holder 23, 100 motor.

Claims (9)

A DC motor comprising: a rotor provided with a commutator and rotatable about a central axis; and a stator provided with a brush in contact with the commutator,
The stator includes two arc-shaped magnets arranged in two-fold rotational symmetry,
Each of the magnets has an N pole and an S pole,
Between the N pole and the S pole of each magnet, a magnetic pole whose surface magnetic flux density gradually transitions from the center of each of the N pole and the S pole toward the boundary between the N pole and the S pole A motor characterized in that a transition part is provided. The two-piece magnet is disposed across a gap provided in the circumferential direction over an angular range of the angle α around the central axis,
The magnetic pole transition portion is provided over an angular range of an angle β around the central axis,
The motor according to claim 1, wherein the angle β is set to satisfy the relationship of angle β ≧ angle α with respect to the angle α.   The motor according to claim 2, wherein the angle α is set in a range of more than 0 ° and 60 ° or less.   4. The magnetic pole transition portion according to any one of claims 1 to 3, wherein the magnetic pole transition portion is formed using a magnetized yoke provided with a yoke recess in which a portion corresponding to the magnetic pole transition portion is recessed from other portions. Motor described. The two-piece magnet is fixed to the inside of the motor case,
An outer peripheral receding portion which recedes inward in a region corresponding to the magnetic pole transition portion is provided on an outer peripheral surface of each of the magnets,
The motor according to any one of claims 1 to 4, wherein a gap is formed between the outer peripheral receding portion and the motor case. The two-piece magnet is fixed to the inside of the motor case,
The motor according to any one of claims 1 to 5, wherein a rib-like outward protrusion, a flat portion or a slit is provided at a portion of the motor case facing the magnetic pole transition portion.   The motor according to any one of claims 1 to 6, wherein an inner peripheral receding portion which is recessed outward in an area corresponding to the magnetic pole transition portion is provided on an inner peripheral surface of each of the magnets. A DC motor comprising: a rotor provided with a commutator and rotatable about a central axis; and a stator provided with a brush in contact with the commutator,
The stator includes a bearing rotatably supporting the rotor, a magnet, a motor case, a brush holder for holding the brush, and an end bell.
The motor case has a first hollow cylinder and a second hollow cylinder whose outer shape is different from that of the first hollow cylinder.
The second hollow column has a bottom for holding the bearing,
One end face of the magnet is fixed in contact with the stepped surface of the first hollow cylinder and the second hollow cylinder.
The other end face of the magnet is pressure-welded by a column extending from the brush holder fixed to the end bell,
A motor is characterized in that a projection is formed at the tip of the columnar part.   A plurality of small diameter portions or a plurality of case concave portions are partially formed on an outer peripheral portion of the second hollow cylindrical body with respect to an outer peripheral portion of the first hollow cylindrical body. Motor described.

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