JP2006311661A - Four-pole dc brush motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively utilize a magnetic force of an anisotropic rare-earth bonded magnet, and to improve the torque performance. <P>SOLUTION: In a DC brush motor, having a permanent magnet disposed on the inner circumference of a housing of a motor, the permanent magnet, comprises the four-pole hollow cylindrical anisotropic rare earth bond magnet 13 having a thickness of 0.5-1.3 mm. An outer circumference of the anisotropic rare earth bond magnet 13 is directly pressed to the inner circumference of the housing 12 by the elastic forces of the housing 12 and the anisotropic rare-earth bonded magnet 13. The inner circumference of the anisotropic rare-earth bonded magnet 13 does not have a covering layer. The gap between the inner circumference of the anisotropic rare earth bond magnet 13 and an outer circumference of a core is 0.05-0.4 mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a 4-pole DC brush motor. In particular, the present invention relates to a 4-pole DC brush motor that uses an anisotropic rare-earth bonded magnet as a permanent magnet and can be reduced in size and torque. For example, the present invention is highly effective when a small DC brush motor device having a motor outer diameter of 50 mm or less in the 1 W to 200 W or 300 W class is provided. Although the application is not particularly limited, the effect is sufficiently exhibited when used as a drive source for equipment mounted on an automobile in which miniaturization and weight reduction are essential.

As a 4-pole DC brush motor using an anisotropic rare earth bonded magnet, a motor described in Patent Document 1 is known. In the motor, a bonded magnet is press-fitted into a casing, and a resin coating layer is formed on the inner peripheral surface of the anisotropic rare earth bonded magnet.
JP 2005-033844 A

Therefore, the gap between the rotor core and the inner peripheral surface of the anisotropic rare earth bonded magnet is 0.8 mm or more, and since there is a resin film that is not a magnetic material in the gap, the anisotropic rare earth bonded magnet There is a problem that the magnetic flux does not effectively flow to the rotor core.
That is, there is a problem that the strong magnetic force of the anisotropic rare earth bonded magnet is not effectively used for the motor torque.
The present invention has been made to solve the above-described problems, and an object thereof is to improve torque performance by effectively using the magnetic force of an anisotropic rare earth bonded magnet in a motor.

  The invention of claim 1 is a DC brush motor having a permanent magnet disposed on the inner peripheral portion of the casing of the motor, wherein the permanent magnet is a hollow cylindrical four-pole anisotropic having a thickness of 0.5 mm to 1.3 mm. An anisotropic rare earth bonded magnet, the anisotropic rare earth bonded magnet and the elastic force of the casing make the anisotropic outer surface of the anisotropic rare earth bonded magnet directly in pressure contact with the inner peripheral surface of the casing. 4-pole DC brush motor characterized in that there is no coating layer on the inner peripheral surface of the conductive rare earth bonded magnet, and the distance between the inner peripheral surface and the outer peripheral surface of the core of the rotor is 0.05 mm or more and 0.4 mm or less It is.

  In the invention of claim 2, the anisotropic rare earth bonded magnet is press-fitted into the inner peripheral surface of the casing, so that the outer peripheral surface of the anisotropic rare earth bonded magnet is directly pressed against the inner peripheral surface of the casing. It is a 4 pole DC brush motor of Claim 1 characterized by the above-mentioned.

The invention according to claim 3 is the four-pole DC brush motor according to claim 1 or 2, wherein the permanent magnet has a thickness of 0.7 mm or more and 1.2 mm or less.
According to a fourth aspect of the present invention, the distance between the inner peripheral surface of the anisotropic rare earth bonded magnet and the outer peripheral surface of the rotor core is 0.2 mm or more and 0.4 mm or less. It is a 4-pole DC brush motor of any one of Claim 3.

  In the first aspect of the invention, the distance between the rotor core and the inner peripheral surface of the anisotropic rare earth bonded magnet is set to 0.05 mm or more and 0.4 mm or less, and the elastic force of the anisotropic rare earth bonded magnet and the elastic force of the casing are used. The outer peripheral surface of the anisotropic rare earth bonded magnet is in direct pressure contact with the inner peripheral surface of the housing, and since there is no resin coating layer on the inner peripheral surface, the magnetic resistance of the magnetic circuit can be made very small. The powerful magnetic field lines of the anisotropic rare earth bonded magnet are effectively supplied to the motor core. In order to reduce the gap between the rotor core and the magnet, it is necessary to reduce the outer diameter tolerance A of the magnet and the inner diameter tolerance B of the motor case. This is because when the magnet is fixed to the inner peripheral surface of the casing with an adhesive as in the prior art, the intersection C of the adhesive layer is added and the total tolerance is A + B + C. Since the tolerance increases, the magnet may come into contact with the rotor core if the gap is reduced. However, when the anisotropic rare earth bonded magnet is pressed against the inner peripheral surface of the casing, the crossing C of the adhesive is eliminated, and the total tolerance is A + B. Since it traces to the inner peripheral surface, the total tolerance is A ′ + B (where A ′ <A), which is smaller than the mere tolerance sum A + B. Since the total tolerance can be reduced, the minimum value of the gap necessary for preventing the anisotropic rare earth bonded magnet and the rotor core from contacting each other can be reduced. As a result, the motor torque is improved. Further, by setting the thickness of the anisotropic rare earth bonded magnet to 0.5 mm or more and 1.3 mm or less, the motor torque / magnet volume or the motor torque / motor volume which is a performance index can be improved.

  In the invention of claim 2, the anisotropic rare earth bonded magnet is press-fitted into the inner peripheral surface of the casing, so that the outer peripheral surface of the anisotropic rare earth bonded magnet is directly pressed against the inner peripheral surface of the casing. It is characterized by being. As the press contact method, press fitting is the easiest method from the viewpoint of equipment, technology, and reliability. As a result, since the magnetic resistance of the magnetic circuit can be minimized, the motor torque can be improved, and the motor torque / magnet volume or the motor torque / motor volume, which is a performance index, can be improved. For the above reasons, the gap between the rotor core and the anisotropic rare earth bonded magnet can be reduced by press fitting, and the magnetic resistance of the magnetic circuit can be reduced as much as possible.

In the third aspect of the invention, the permanent magnet has a thickness of 0.7 mm or more and 1.2 mm or less, so that the motor torque / magnet volume as a performance index can be further improved.
According to the invention of claim 4, the distance between the inner peripheral surface of the anisotropic rare earth bonded magnet and the outer peripheral surface of the core of the rotor is set to 0.2 mm or more and 0.4 mm or less, so that the magnetism of the magnetic circuit is further increased. The resistance can be reduced, and the motor torque can be improved.

  Hereinafter, the present invention will be described based on embodiments. In addition, this invention is not limited to the following embodiment.

FIGS. 1A and 1B show an example of the motor of this embodiment. The figures are a side view (a) and a cross-sectional view AA ′ (b). The motor device of the present embodiment is intended to reduce the size and increase the torque constant of the conventional motor device. The motor device of the present embodiment includes a housing 12, an anisotropic rare earth bonded magnet 13 that is a hollow cylindrical permanent magnet provided in the inner peripheral portion of the housing 12, and a rotor core that forms a rotor core provided in the center portion. 14, a coil 15 wound around the rotor core 14, a rotary shaft 11 extending from the center of the rotor core 14, and a back yoke 10 for preventing magnetic flux leakage. The anisotropic rare earth bonded magnet 13 has a maximum energy product of 14 MGOe (111 KJ / m ³ ) or more, so that the maximum energy product is large. Therefore, the magnetoresistance of the magnetic circuit when the present invention is used. Due to the reduction effect, the motor performance is greatly improved. The anisotropic rare earth bonded magnet 13 is magnetized to four poles, and the rotor core 14 has ten slots in which windings are arranged. The motor housing 16 is used as a concept combining the housing 12 and the back yoke 10. The back yoke 10 is not always necessary, and the motor housing may be constituted by the housing 12 alone.

The anisotropic rare earth bonded magnet 13 has been finally mass-produced by the applicant in recent years. For example, the anisotropic rare earth bonded magnet 13 is manufactured by the manufacturing method of Japanese Patent Application Laid-Open No. 2001-76917, Japanese Patent No. 2816668, Japanese Patent No. 3060104, and International Patent Application PCT / JP03 / 04532. This anisotropic rare earth bonded magnet can now be manufactured with a maximum energy product of 17 MGOe to 28 MGOe (135 KJ / m ^{3 to} 223 KJ / m ³ ).

  The motor device of the present embodiment (FIGS. 1A and 1B) employs a thin hollow cylindrical anisotropic rare earth bonded magnet 13 made of Nd—Fe—B. Further, the magnetization is set to 4 poles, the magnetic path length of the magnetic circuit per pole is greatly reduced, and the torque received by the rotor core 14 is increased. The anisotropic rare earth bonded magnet 13 is a magnet that is manufactured by resin molding magnetic powder made of Nd—Fe—B and is strongly magnetized in the radial direction. As the material for the anisotropic rare earth bonded magnet, Nd—Fe—B-based materials, Nd—Fe—B-based materials, for example, materials containing other rare earth elements of Nd and Nd, and other additive elements should be used. Can do. Furthermore, materials containing rare earth elements other than Nd, for example, Sm—Fe—N materials, SmCo materials, Nd—Fe—B materials, and mixtures thereof can be used.

In particular, the anisotropic rare earth bonded magnet 13 is composed of a rare earth element containing yttrium (Y) (hereinafter referred to as “R1”), an R1FeB alloy containing iron (Fe) and boron (B) as main components. R1FeB comprising an R1FeB-based anisotropic magnet powder having an average particle size of 50 to 400 μm obtained by the oxidization treatment and a first surfactant covering the surface of the constituent particles of the R1FeB-based anisotropic magnet powder The average particle size is 50 to 84% by mass (mass%), the rare earth element containing Y (hereinafter referred to as “R2”), Fe and nitrogen (N) or B as main components. R2Fe (N, B) comprising an R2Fe (N, B) -based anisotropic magnet powder of 10 μm and a second surfactant covering the surface of the constituent particles of the R2Fe (N, B) -based anisotropic magnet powder. B) System fine powder is 15-40 mass% The binder resin is 1 to 10 mass%, and the maximum magnetic energy product (BH) _max is 21 MGOe to 28 MGOe (167 to 223 KJ / m ³ ), and is re-magnetized after 1000 hours at 100 ° C. It is preferable to use a composite anisotropic rare earth bonded magnet having a permanent demagnetization factor of 6% or less indicating a reduction rate of the obtained magnetic flux. A method for manufacturing the composite anisotropic rare earth bonded magnet is described in International Patent Application PCT / JP03 / 04532.

One specific example of the R1FeB-based anisotropic magnet powder is NdFeB-based anisotropic magnet powder, and one specific example of the R2Fe (N, B) -based anisotropic magnet powder is SmFeN-based anisotropic magnet powder. It is. By using such a composite anisotropic rare earth bonded magnet, a material having a high maximum energy product (BH) _max of 21 MGOe to 28 MGOe (167 to 223 KJ / m ³ ) can be obtained. In addition, the composite anisotropic rare earth bonded magnet can have a permanent demagnetization rate of 6% or less, which is a rate of demagnetization due to secular change, and can improve weather resistance such as heat resistance and oxidation resistance. it can. As a result, the motor using these composite anisotropic rare earth bonded magnets can achieve the effect of the present invention higher, and can extend the reliability and life.

An anisotropic rare earth bonded magnet is also called a plastic magnet. This magnet is characterized in that the maximum energy product (BH) _max is about 5 times or more compared to a conventional sintered ferrite magnet. That is, the maximum energy product (BH) _{max of} the standard sintered ferrite magnet 23 is 3.5 MGOe (28 KJ / m ³ ). m ³ ) having a maximum energy product of at least.

  The weight ratio of the resin in the anisotropic rare earth bonded magnet 13 was in the range of 2 wt% to 3.5 wt%. There are the following four methods for orientation molding. The first is a method in which anisotropic magnet powder and resin are supplied to a mold and heated, and a magnetic field is applied to orient and compress. The second method is a method in which anisotropic magnet powder and resin are supplied to a mold and heated, and a magnetic field is applied and oriented to form a preform, followed by high-pressure compression molding. Third, at room temperature, anisotropic magnet powder and resin are supplied to a mold and compression molded to form a pre-formed body, and further heated to apply a magnetic field and oriented to light pressure compression. This is a method of forming a preformed body by molding, and then heating to perform high-pressure compression molding. Fourth, at normal temperature, anisotropic magnet powder and resin are supplied to a mold and compression molded to form a pre-formed body, and further heated and applied with a magnetic field to be oriented and light pressure compressed. This is a molding method. In order to obtain sufficient fluidity and thermosetting properties, it is desirable to use an epoxy resin. Of course, other known thermosetting resins may be used. As the resin of the anisotropic rare earth bonded magnet 13, a thermosetting resin that has high fluidity and is thermoset when molded in a heating magnetic field is used. Specifically, bisphenol A type and polycyclic type epoxy resins are used.

  This molded body was cured to improve the curing degree of the resin to 90 to 100%. Thereby, the coupling | bonding between magnetic powder and resin and resin and resin was improved. Next, as shown in FIG. 3, this cylindrical molded body is inserted into a piston 31 having a positioning convex ring 32 of a press-fit cylinder 30, and the molded body of the anisotropic rare earth bonded magnet 13 after curing is made of glass. Heated at a temperature below the transition temperature. The position of the anisotropic rare earth bonded magnet 13 in the piston 31 is determined by the convex ring 32. This heating reduces the strength of the material without breaking the bond between the magnetic powder and the resin or between the resin and the resin, that is, by bringing the cured resin closer to the rubbery region from the glassy region. The mechanical strength was maintained by reducing the stress applied to the anisotropic rare earth bonded magnet when the magnet 13 was press-fitted into the housing 12. In this state, the press-fitting cylinder 30 was driven so that the tip of the piston 31 was in contact with the tip of the housing as shown in FIG. In this state, the position of the anisotropic rare earth bonded magnet 13 in the housing 12 is determined. By the operation of the piston 31, the anisotropic rare earth bonded magnet 13 was press-fitted along the inner peripheral portion of the housing 12 and positioned at a predetermined position. Thereafter, the press-fitting cylinder 30 was driven, the piston 31 was pulled out and cooled, so that the anisotropic rare earth bonded magnet 13 was press-fitted and fixed to the inner peripheral portion of the housing 12.

  In addition, when the weight ratio of resin exceeds 3.5 wt%, since the quantity of magnetic powder will decrease, a magnetic characteristic will fall and a flux value will fall. Further, as the amount of resin increases, the burrs of the molded body increase, the releasability from the mold or the lower punch deteriorates, and it becomes difficult to take out the molded body, and at the same time, many chips and cracks are observed.

  Further, when the weight ratio of the resin is less than 2 W%, the binding force between the magnetic powder and the resin is reduced, and stress is applied to the anisotropic rare earth bond magnet 13 when the anisotropic rare earth bond magnet 13 is pressed into the housing 12. The mechanical strength is lowered, the press-fitting load is reduced, or the tightening allowance for press-fitting is reduced, and the required fixing force cannot be obtained. Or, even if it can be press-fitted, it may be damaged during magnetization.

  The temperature at the time of press-fitting is preferably 60 to 150 ° C. This temperature range does not deteriorate the characteristics of the anisotropic rare earth bonded magnet, and in addition, bonds between the magnetic powder and the resin, and between the resin and the resin. It is optimal for pressing the anisotropic rare earth bonded magnet 13 into the housing 12 by cutting the resin from the glassy region to the rubbery region without cutting.

  In this way, as shown in FIG. 2, the outer peripheral surface of the anisotropic rare earth bonded magnet 13 is more elastic to the inner peripheral surface of the housing 12 than the elastic force of the anisotropic rare earth bonded magnet 13 and the elasticity of the housing 12. Directly pressed by force. That is, there is no gap across the entire surface between the outer peripheral surface of the anisotropic rare earth bonded magnet 13 and the inner peripheral surface of the housing 12. Therefore, the magnetic resistance of the magnetic circuit can be reduced. As a result, the ability of the anisotropic rare earth bonded magnet 13 having a large energy product can be sufficiently exerted, and a motor having a large output torque and motor performance index (torque constant / motor volume) can be obtained.

With the above manufacturing method, as shown in FIG. 4, the thickness of the anisotropic rare earth bonded magnet 13 can be controlled to an arbitrary value within the range of 0.5 mm to 1.3 mm. The gap b between the inner peripheral surface and the rotor core 14 can be controlled to an arbitrary value in the range of 0.05 mm or more and 0.4 mm or less.
In this embodiment, the outer shape of the rotor core 14 is fixed, the gap b between the rotor core 14 and the anisotropic rare earth bonded magnet 13 is 0.3 mm, the thickness of the anisotropic rare earth bonded magnet 13 is 1.0 mm, and the magnet length. Is the same as the magnet of a conventional motor. Compared to a conventional motor, that is, a motor having a resin film formed on the inner peripheral surface of an anisotropic rare earth bonded magnet having a gap of 0.5 mm with the rotor core and an anisotropic rare earth bonded magnet 13 having a thickness of 1.5 mm. The motor torque can be improved to 1.5 times or more of the conventional motor torque.

  Further, it is more desirable that the thickness of the anisotropic rare earth bonded magnet is 0.7 mm or more and 1.2 mm or less. This increases the volume in the mold and reduces the friction between the magnet powder and the mold or between the magnet powder and the magnet powder, so that the degree of orientation of the existing magnet powder is improved and the magnetic flux is further increased. This is because it can. In this case, the motor torque / magnet volume can be further improved. The distance between the inner peripheral surface of the anisotropic rare earth bonded magnet and the outer peripheral surface of the rotor core is more preferably 0.2 mm or greater and 0.4 mm or less. The magnetic resistance of the magnetic circuit can be further reduced.

  As described above, the resin weight ratio of the anisotropic rare earth bonded magnet 13 is set to 2 W% or more and 3 W% or less, compression-molded, cured, and cured to 90 to 100%. The anisotropic rare earth bonded magnet 13 is press-fitted into the inner peripheral portion of the housing 12 by reheating at a temperature below the point and bringing the cured resin closer to the rubbery region from the glassy region. Can be done easily. That is, when the anisotropic rare earth bonded magnet 13 is press-fitted into the inner peripheral portion of the casing 12 by the piston 31 and then the stress applied to the anisotropic rare earth bonded magnet can be reduced when the piston 31 is pulled out, the mechanical strength is reduced. Is not reduced.

  Moreover, the motor as a specific example has the following characteristics. However, although it is not specified for the type of motor device, it is effective when used for a DC brush motor with an output of 300 W or less. A DC brush motor device having a permanent magnet disposed in an inner peripheral portion of a motor casing and a rotor core disposed in a central portion and having a motor outer diameter of 50 mm or less, wherein the permanent magnet is magnetized to four poles. An anisotropic rare earth bonded magnet with a thin hollow cylindrical shape and a maximum energy product of 17 MGOe or more, wherein the radial thickness of the anisotropic rare earth bonded magnet is d, the thickness of the motor housing is w, When the diameter is a, the casing thickness to magnet thickness ratio w / d is more than 1 and 3 or less, and the radial thickness of the anisotropic rare earth bonded magnet to the diameter ratio of the rotor core d / The DC brush motor device is characterized in that a is 0.015 or more and 0.07 or less.

  The motor casing is a concept including a back yoke, and the motor casing outer diameter r is used to mean the outer diameter of the motor device including the back yoke.

  A range of 1 <ratio of casing thickness to magnet thickness w / d ≦ 3 is desirable. In the case of a DC brush motor using a sintered ferrite magnet, since the magnetic force of the magnet is weak, magnetic leakage can be sufficiently prevented even if the casing thickness is smaller than the magnet thickness. On the other hand, when an anisotropic rare earth bonded magnet is used, when w / d is 1 or less, the magnetic force of the magnet is so strong that magnetic leakage cannot be prevented. It needs to be big. If w / d is greater than 3, even if the magnet's magnetic force is strong, the case thickness becomes too thick and magnetic leakage will be eliminated, but the case thickness will be increased unnecessarily, and it will be small enough. As a result, the motor performance index decreases.

On the other hand, a range of 0.015 ≦ magnet thickness to rotor core diameter d / a ≦ 0.07 is desirable. In this range, the motor performance index T (T = torque constant / volume) is more than twice the performance index T (about 1.3) of a motor using a conventional two-pole sintered ferrite magnet. . A drastic reduction in size and weight, which cannot be conceived in the past, can be realized by reducing the volume of the entire motor to about ½ with the same torque constant as that of a conventional motor. On the other hand, compared to a motor using a conventional sintered ferrite magnet, the volume is reduced by about 20% (80% of the conventional volume), and the torque constant is doubled. A periodical effect can be obtained. The volume is evaluated by the volume of the entire motor. Since the brush and commutator are common to the two motors, the volume can be reduced to 37% when the same torque constant is used in terms of the effective portion that generates torque.

When an anisotropic rare earth bonded magnet having a maximum energy product (BH _max ) of 25 MGOe is used, the motor performance index T is 2.56 times in the range of 0.03 ≦ d / a ≦ 0.07. ing. When an anisotropic rare earth bonded magnet having a maximum energy product (BH _max ) of 20 MGOe is used, the motor performance index T is 2.46 times in the range of 0.03 ≦ d / a ≦ 0.07. Has been obtained. Further, when an anisotropic rare earth bonded magnet having a maximum energy product (BH _max ) of 17 MGOe is used, the motor performance index T is 2.39 times in the range of 0.03 ≦ d / a ≦ 0.07. Has been obtained. Therefore, the range of d / a is a desirable range.

Motor performance index T per unit magnet usage (that is, motor performance index T / magnet usage, hereinafter this ratio S is referred to as “magnet efficiency”) is a magnet performance multiple of m times that of a conventional two-pole ferrite motor. The ratio of magnet thickness to rotor core diameter d / a, which is equal to twice this value, is 0.07. Here, the magnet performance multiple m is defined by (performance of anisotropic rare earth bonded magnet [(BH) _max ]) / (performance of sintered ferrite magnet [(BH) _max ]) For example, anisotropic rare earth When the performance (maximum energy product) of the bonded magnet is 17 MGOe and the performance (maximum energy product) of the sintered ferrite magnet is 3.5 MGOe, the magnet performance multiple m is 4.9. When the maximum energy product of the conductive rare earth bonded magnet is 20 MGOe, the magnet performance multiple m is 5.7 times, and when the maximum energy product of the anisotropic rare earth bonded magnet is 25 MGOe, the magnet performance multiple m is 7.1 times.

  The ratio of the magnet thickness to the rotor core diameter d / a when the magnet efficiency S is twice the magnet performance multiple of m times that of the conventional two-pole ferrite motor is the maximum energy of the anisotropic rare earth bonded magnet. When the product is 17 MGOe or more, the value is almost the same 0.07 regardless of the value.

  When the ratio of magnet thickness to rotor core diameter d / a is 0.07 or less, the magnet efficiency S of the motor device of the present invention is more than twice the magnet performance multiple of m times the magnet efficiency of the conventional two-pole ferrite motor. . However, when the magnet thickness to rotor core diameter ratio d / a is close to the lower limit value of 0.015, the magnet efficiency becomes maximum, but the demagnetizing field becomes large due to the thin magnet, and the magnetic flux penetrating the rotor core suddenly increases. Since the motor performance index T decreases to nearly twice that of a motor using a conventional two-pole sintered ferrite magnet, the ratio of magnet thickness to rotor core diameter d / a is preferably 0.015 or more. .

  The above range of the magnet thickness to rotor core diameter ratio d / a means that the casing thickness w and magnet thickness d are both thin when the motor outer diameter is 50 mm or less. If the motor outer diameter is fixed, the diameter of the rotor core can be increased as much as the casing thickness w and the magnet thickness d can both be reduced, and the winding can be increased, leading to an improvement in output torque.

  Further, since this anisotropic rare earth bonded magnet is formed by resin molding, it is easily formed with high accuracy. Thereby, the permanent magnet shape of a motor housing inner peripheral part can be made into an accurate hollow cylindrical shape. That is, the motor internal magnetic field by the permanent magnet can be made rotationally symmetric with high accuracy.

  The present invention can be used as a small, high torque motor.

The block diagram which showed the DC brush motor apparatus which concerns on the specific 1st Example of this invention. The axial direction sectional view showing the state where the anisotropic rare earth bond magnet in the DC brush motor concerning the 1st example was press-fitted into the inner peripheral part of the case. The block diagram of the mechanism which press-fits the anisotropic rare earth bond magnet in the DC brush motor which concerns on 1st Example in a housing | casing inner peripheral part. Sectional drawing which showed the relationship between a rotor core, an anisotropic rare earth bond magnet, and a space | gap.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Back yoke 11 ... Rotating shaft 12 ... Housing 13 ... Anisotropic rare earth bonded magnet 14 ... Rotor core 15 ... Coil 16 ... Motor housing 18 ... Cover film 30 ... Cylinder 31 ... Piston 32 ... Convex ring

Claims (4)

In a DC brush motor having a permanent magnet disposed on the inner periphery of the motor casing,
The permanent magnet is a hollow cylindrical quadrupole anisotropic rare earth bonded magnet having a thickness of 0.5 mm to 1.3 mm,
Due to the elastic force of the anisotropic rare earth bonded magnet and the elastic force of the casing, the outer peripheral surface of the anisotropic rare earth bonded magnet is directly pressed against the inner peripheral surface of the casing,
There is no coating layer on the inner peripheral surface of the anisotropic rare earth bonded magnet, and the distance between the inner peripheral surface and the outer peripheral surface of the rotor core is 0.05 mm or more and 0.4 mm or less. DC brush motor. The anisotropic rare earth bonded magnet is press-fitted into the inner peripheral surface of the casing, so that the outer peripheral surface of the anisotropic rare earth bonded magnet is in direct pressure contact with the inner peripheral surface of the casing. The 4-pole DC brush motor according to claim 1. The 4-pole DC brush motor according to claim 1 or 2, wherein the permanent magnet has a thickness of 0.7 mm or more and 1.2 mm or less. The distance between the inner peripheral surface of the anisotropic rare earth bonded magnet and the outer peripheral surface of the core of the rotor is 0.2 mm or greater and 0.4 mm or less. A 4-pole DC brush motor as described in 1.

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