EP0591555A1 - Cylinder type anisotropic magnets and their manufacturing methods and motors - Google Patents

Abstract

Disclosed is a cylindrical anisotropic magnet, which increases the total magnetic flux generated by the magnetic poles and improves the friction characteristics of motors, and its manufacturing method. Likewise, it improves the profitability of the assembly and its miniaturization is possible by increasing the total magnetic flux generated by the magnetic poles. To obtain an engine that is also less noisy, it is necessary to improve its drive characteristics. A magnetic ring is placed on the outer circumference of an elliptical mold space whose large diameter aligns with the direction of magnetization induced by a pair of magnetic poles, with a pair of magnets placed at opposite ends of that large diameter. . After the sintering of the elliptical body which has been molded with an apparatus where a magnet core is placed in the center, by cylindrical forming, a cylindrical anisotropic ferrite magnet of diameter D1 is obtained, the opposite ends of which exhibit radial anisotropy in a specified angular limit, and the remaining parts of which exhibit orthogonal anisotropy. For example, a motor is obtained by introducing by pressure a ferrite magnet into the internal circumference of a cylindrical caliper to constitute a stator and by placing a rotor in the space of said internal circumference of this ferrite magnet. A cylindrical, sintered anisotropic magnet can be obtained without this operation causing cracks, by using a cylindrical anisotropic magnet, a specific part of which has radial anisotropy and the remaining parts of which have orthogonal anisotropy. The friction is then reduced because it is thus possible to take advantage of the various advantages of this anisotropic magnet.

Description

DESCRIPTION Cylinder Type Anisotropic Magnets and Their Manufacturing Methods and Motors Technical Field

This invention is concerned with a cylinder type anisotropic magnet that can enhance total magnetic flux which is generated from the magnetic pole surface and the improvement of cogging characteristicson motors; furthermore, it is used for two pole motors, and by efficiently placing cylinder type anisotropic magnets in which a specified range is radial anisotropic and the rest is orthogonal anisotropic (orthogonal)and/or isotropic; thus, motor can achieve efficiency in the assembly work, noise abatement and miniaturization.

Background Art

As magnet used for two pole motor, etc, sintered magnets such as ferrite magnet and rare earth magnet and resin-bonded magnet,are known. For example, as shown in Fig.8,Fig.9 and Fig. 10, the motor compositions which utilize ferrite type scinterd magnet (heretofore, referred to as ferrite magnet) as stator and rotor are known.

The composition which is shown in Fig.8, is an example of a motor in which a cylinder type ferrite magnet 81 is utilized on the stator side. It is fastened on the inner circumference of the cylinder type yoke 82, and at the same time, rotor (not shown) is placed in space 83 of the inner circumference side of the said ferrite magnet 81. Usually, in the motor of such composition, since it is difficult to utilize radial anisotropic ferrite magnet forthe reasons stated later, isotropic cylinder ferrite magnet 81 used for relatively low performance motors. The composition shown in Fig.9 is an example of utilizing a pair of segment magnets 81a and 81 b on the stator side. They are fastened to the inner circumference of the cylindrical yoke 82, and at the same time, rotor (not shown) is placed in space 83 in the circumference side facing the said magnets

81a and 81 b. In the segment magnets shown in the figure, since it is possible to utilize magnet having excellent magnetic property such as radial anisotropic ferrite magnet, it is utilized for relatively high output motor.

The composition shown in Fig. 10 is an example of utilizing a pair of segment magnets 91a and 91 b on the rotor side, and they are fastened to the respective outer circumference of the magnet support 93 which is fastened to a central axle 92, and positioned within the specifically shaped stator (not shown). In the segment magnets 91a and 91b, which are similar to the ferrite magnets 81a and 81b as shown in Fig.9, since magnetic radial anisotropic ferrite magnet having excellent magnetic property can be utilized, they are applied to relatively high output motors.

However, in recent years, even in the high output motor, in order to simplify the assembly process (higher efficiency of assembly work) and for prevention of cogging, motor which utilize anisotropic cylinder type ferrite magnet which possesses stronger magnetic characteristic than the above stated radial anisotropic segment ferrite magnet to be utilized.

As anisotropic cylinder type ferrite magnet utilized in two pole motors, depending on the orientation of its anisotropy, the radial anisotropic cylinder type ferrite magnet and the orthogonal anisotropic cylinder type ferrite magnet are known.

When utilizing the above stated radial anisotropic cylinder type ferrite magnet and orthogoral anisotropic cylinder type ferrite magnet in two pole motor, they share the problems stated below.Here, we will explain the composition in which these ferrite magnet are positioned on the stator side of the two pole motor.

In the two pole motor, in which radial anisotropic cylinder type ferrite magnets are positioned, the approximately constant magnet flux is maintained at any given position of the circumference in the middle of space between stator and motor, which results in highly efficient motor. When the magnet materials which possess the identical magnetic characteristic are utilized, it is possible to obtain superior motor output in comparison to the composition which utilizes the orthogoral anisotropic cylinder type ferrite magnet.

However, the above magnetic flux distribution radically changes at each edge of magnetic poles, which will result in ;the motor possessing the poor cogging characteristics.

Therefore, when these motors are utilized as a wiper motor and a fan motor, etc., since noise is generated from cogging, it was necessary to consider its influence to the environment of the people working near the said motor.

Also, if the magnetic characteristic of magnet material is increased to an extent, the molded body will crack when sintering, and for all practical purposes, it is difficult to manufacture a unit body radial anisotropic cylinder type ferrite magnet which has the required strong magnetic properties.

That is to say that as a manufacturing method of a unit body radial anisotropic cylinder type ferrite magnet, after the starting powder such as Sr ferrite pulverized powder and Ba ferrite pulverized powder that are less than 2μm. in the average particle size is molded into a cylinder shape in the » magnetic field by the dry method,etc, it can be sintered; but, since shrinkage _jjp rates for the circumferential direction and radial direction differ when sintering, it easily cracks due to accumulated internal stress, and it never materialized as a practical method.

As a method to prevent cracking in sintering, it was proposed to mold the mixture of the Sr ferrite pulverized powder 50 — 80 wt% with the average particle size less than 2_/zmand Ba ferrite powder isotopic powder 50 -~ 20 wt% with 14 — 200 mesh size in the magnetic field by the dry method (Patent Bulletin Heisei 1 -48643).

However, the magnetic characteristics of radial anisotropic cylinder type ferrite magnet which is industrially sintered by this method has the upper limit of Br 3.4 kG, βHc 2.9 kG, (BH)max 2.6 MGOe, which is not satisfactory for the demand for higher performance in recent years.

Thus, unless the radial anisotropic cylindertype ferrite magnet with the strong magnetic characteristics which is indispensable to realize the high output motor sought after in recent years, it was impossible to satisfy this requirement.

On the other hand, in the orthogoral anisotropic cylindertype ferrite magnet, even when the magnet raw material which is superior in magnetic characteristic, cracking does not take place in the molding when sintered, and a cylindertype of unit body is easily obtained; however, the magnetic flux distribution in the circumferential direction at the center of space between stator and rotor, as the middle of the magnetic pole approaches higher and closer to the both edges, it gradually decreases generating a so-called sine curve. Although, in comparison to the composition in which radial anisotropic cylindertype ferrite magnet is placed, the higher magnetic flux can be achieved at the central part of the magnetic poles, and the total magnet flux which generate from the magnet poles is lower in the orthogoral anisotropic cylindertype ferrite magnet. However, having the above stated magnetic flux distribution, as far as the motor cogging characteristics are concerned, it is superior to the composition which utilizes radial anisotropic cylindertype magnets.

The above stated situation is not limited only to the motor which utilizes ferrite magnet but also to the motor which utilizes rare earth type sintered magnets; furthermore, even in motor that utilizes resin-bonded magnet which does not suffer from cracking in sintering, it is sought similarly to enhance the total magnetic flux generated from the magnetic poles and improve the motor cogging characteristics; but the composition which satisfies both requirements has not been proposed.

As shown above, it is explained that in the composition in which ferrite magnets are placed on the stator side of two-pole motor, whether the said ferrite magnet are radial anisotropic cylindertype ferrite magnet or orthogoral anisotropic cylindertype ferrite magnets, each type of magnets has some problems associated with it. These problem occur even when the above ferrite magnets are placed on the rotor side of the two pole motor.

As a rotor composition that is specifically improved to obtain brushless motor with little cogging characteristics, the following assembly type cylinder shape permanent magnet is proposed.

That is to say, in JP-A-59-92758(theterm "JP-A" as used here signitied "an unexamined published Japanese Patent application"), where assembly type cylinder shape anisotropic permanent magnet is proposed. Assembling from four separately molded anisotropic permanent magnets into a cylinder shape, as shown in Fig. 11, the anisotoripic direction of upper and lower magnets 101 and 102 are aligned in the vertical direction, by being anisotropic magnetized to the direction of magnet thickness; furthermore, right and left permanent magnets 103and 104 are arranged so that the anisotropic direction is right angle to the direction of magnet thickness, and the anisotropic directions of four permanent agnets, 101, 102, 103 and 104 are right angle to the cylinder axis/thus they have the same direction.

Also, in JP-A-59-92759,forthe similar objectives are proposed. As shown in Fig.12, in order for the anisotropic direction of upper and lower permanent magnets 111 and 112 are in vertical directions as shown in the figure, anisotropy is added to the direction of magnetic thickness; also by making right and left permanent magnets 113 and 114 isotropic magnets, and making the anisotropic direction of two permanent magnets 111 and 112 are aligned so that they are right angle to the axis of the cylinder shape permanent magnet, thus creating the assembly type cyfinder shape permanent magnet.

In the above stated assembly type cylinder, since multiple separate molded permanent magnets are assembled by adhesive, etc., to form a unified body. From the point of enhancement of efficiency in assembling, there is no magnet which presently satisfies all technical requirements as the usual radial anisotropicsegment ferrite magnet.

Also, it finally can form a unit cylinder shape, but it can not totally eliminate the space where separately molded permanent magnets are fastened by adhesive. Also, since each separately molded permanent magnet has each distinctive magnetic characteristics, and considering those scattering characteristics, they can not necessarily satisfy requirements in the said technical field from the point of cogging prevention.

When the above stated rotor composition is utilized on the stator side, it still has the similar problems.

The objectives of this invention are concerned with solving problems of the anisotropic magnet with the above composition, and to provide a cylindertype anisotropic magnet which enhances the total magnetic flux generated from magnet poles and improve their motor cogging characteristics. Furthermore, the objectives of this invention are the improvement of the assembly efficiency relative to the motor containing the usual radial anisotropic segment magnets, the increase in the total magnetic flux generated from the magnetic poles relative to the motors which utilize the isotropic cylinder shape ferrite magnet and the orthogoral anisotropic cylinder shape ferrite magnet, and to accomplish miniaturization of the whole motor; furthermore, it is to provide the motor which lowers the noise level by improving cogging characteristicetc. relative to the motors which utilizes the radial anisotropic magnet ferrite magnet and the radial anisotropic cylinder shape ferrite magnet.

Also, the object of this invention is to provide the motor which has the higher efficiency and the better cogging characteristics relative to the so- called assembly type anisotropic magnet which consists of multiple separately molded permanent magnets. Disclosure of Invention

In order to solve the problems of the anisotropic magnet of the above various compositions, various studies were conducted in increasing the total magnetic flux generated from the magnetic poles and to obtain the cylinder shape anisotropic magnet utilized forthe motors with good cogging characteristics. As a result of such studies, we have discovered and propose it here that, by making specified parts of a unit body cylinder shape anisotropic sintered into radial anisotropic and the remainder into either orthogoral anisotropic and/or isotropic, it is possible to effectively capitalize on each magnet's advantages and efficiently mass produce it.

This invention provides, as a practical method to manufacture a unit body cylinder shape anisotropic sintered magnet in which a pair of opposite parts have radial anisotropy within a specified angle and the remainder orthogonal anisotropy and/or isotropy, a process for producing them whereby; molding magnetic raw materials powder in the magnetic field in a molding apparatus provides a molding dies which has an elliptical molding space in which a longer diameter of the said molding space is placed in the magnetizing direction between a pair of the magnet poles, a pair of the magnet are placed opposite to the long diameter in said molding space and an core consisting of a magnetic body similarly shaper to the said molding space; sintering the elliptical molded body; thus producing cylindertype anisotropic magnet which consists of a cylindrical unit sintered body in which a pair of opposing parts show radial anisotropy within a specified range, and the rest shows orthrogoral anisotropy and/or isotropy.

Furthermore, as a practical example of manufacturing this invented unit body cylinder shape anisotropic resin-bonded magnet, the following process is privided; in a molding apparatus privides a molding dies which has an circular molding space between a pair of magnetic poles, a pair of the magnet are placed opposite to the long diameter in said molding space and an core consisting of a magnetic body similarly shaper to the said molding space, after thermal setting resins, coupling agents, and lubricants are added to the magnetic raw materials powder and mixed, it is molded in the magnetic field. Furthermore, according to the binders utilized, the room temperature curing or thermal curing method is chosen to produce a unit body cylinder shape anisotropic resin-bonded magnet, in which a pair of opposing parts are radial anisotropic within a specified angle range and the rest is orthogoral anisotropic and/or isotropic.

As applicable cylinder shape anisotropic magnets in this invented motor, ferrite magnets such as a Sr ferrite magnet and a Ba ferrite magnet, etc., and rare earth magnets such as rare earth-cobait magnets, rare earth-iron-boron magnets, and any other known anisotropic sintered magnets or anisotropic resin-bonded magnets can be utilized. Brief Description of Drawings

Fig.1 shows an example of this invented motor, which shows a plane view explaining a stator parts.

Fig.2 A and B shows examples of conceptual drawings which explains a cylindershape anisotropic magnet which is placed in this invented motor and its manufacturing apparatus.

Fig.3 A and B shows other example of conceptual drawings which explains in this invented cylinder shape anisotropic magnet which is placed a motor and its manufacturing apparatus.

Fig.4 shows other example of conceptual drawings which explains in this invented cylindershape anisotropic magnet which is placed a motor and its manufacturing apparatus.

Fig.5 shows examples of a plane view explaining manufacturing process of this invented cylinder shaped anisotropic magnet cylinder with other composition which is placed in motor.

Fig.6 shows other example of this invention; particularly, the plane view drawing explains only the rotor composition.

Fig.7 shows the graph which is a result of relative measurements of the magnetic flux distribution in the circumferential direction at the center of space between stator and rotor of this invented motor and usual two pole motor.for making the effectiveness of this invented motor clear.

Fig.8 shows a plane vies which explains a motor composition in which usual ferrite magnets are placed at stator and rotor.

Fig.9 shows a plane view which explains motor composition in which usual ferrite magnets are placed at stator and rotor.

Fig.10 shows a plane view which explains a motor composition in which usual ferrite magnets are placed at stator and rotor.

Fig.11 shows an oblique viewwhich explains the usual brushless motor rotor.

Fig.12 shows an oblique viewwhich explains the other brushless motor rotor.

Beat Mode for carving Out the Invention

Fig.1 is a plane view of the stator part as an example of this invented motor. In Fig.1,10 isa ferrite magnet which contains Sr and is obtained from a manufacturing method described later. It isa cylindershape anisotropic ferrite magnet with diameter Dl which consists of a pair of opposing parts 11a and 11b where each has radial anisotropy within the angle range of 01(theta 1) and the parts 12a and 12b of the remainder are orthogoral anisotropic magnets. Here, the cylindtrical process is applied after sintering it to the magnet, and it is pressure fastened to a cylinder shape yoke 82 to form stator.

Furthermore, by placing rotor (not shown) in space 83 of the inner circumference of the said ferrite magnet 10 to obtain the desired motor.

We will explain in detail the manufacturing method of the above ferrite magnet 10. The Fig.2 — Fig.4 show drawings that describe the said ferrite magnet and the molding apparatus with which to manufacture it. The ferrite magnet 10 shown in Fig.2A, as explained before, has a pair of opposing parts 11a and 11b each of which possesses radial anisotropy within the angle range 01(theta 1), and the rest orthogoral anisotropy at parts 12a and 12b and with diameter of Di. M in the figure indicates the magnetizing direction of the molding apparatus which is stated later.

Fig.3 A and B is an example of the molding apparatus to manufacture the above ferrite magnet 10 That is to say, the apparatus is made by placing a molding dies 3, which has an elliptical molding space in which the magnetizing direction (M direction in the figure) conincides with a longer diameter, between a pair of magnetic poles 1a and 1 b to which magnetic coils 2a and 2b are wound; and at the same time, by placing a pair of magnets 4a and 4b at the outer circumference of the said molding space and opposite parts to the longer diameter direction, placing a pair of non-magnetic bodies 5a and 5b opposite to the shorter diameter direction, and placing core 6 which consists of a magnet body similarly shaped to the said molding space at the center of the said molding space.

Furthermore, individual magnet bodies 4a and 4b are placed opposite to the outer circumference of the angle range 03(theta 3) in the elliptical molding space. In the figure, 8 is the ring shape lower punch which is non¬ magnetic, and 9 is the ring shape upper punch which is also non-magnetic.

After insertintg the appropriate amount of the magnetic raw materials powder 7 of a specified composition into the elliptical molding space in the molding dies 3 of the above described molding apparatus, it is compression molded while being magnetized by a pair of magnetic poles along the M direction as shown in the figure by passing the electric current through electomagnetic coils 2a and 2b. When the said magnetic raw materials powder 7 is compression molded, due to action of the magnetic field lines, as shown by the broken lines in the figure, which is generated by placement of a pair of magnets 4a and 4b and a pair of non-magnets 5a and 5b, each opposing part to a pair of magnets 4a and 4b will have radial anisotropy, and each opposing part to a pair of non-magnets 5a and 5b will have orthogonal anisotropy.

Particularly, in the composition of fig. 3, by placing a pair of magnets 4a and 4b directly opposite to the outer circumference of the molding space, the magnetic field from magnet poles can be efectively applied to the magnetic raw materials powder 7.

The molded body thus obtained consists an elliptical molded body 20 with a longer diameter D2 and a shorter diameter D3, as shown in B of Fig.2, has a pair of opposing parts 21 a and 21 b, each of which is radial anisotropic within the angle range 02(theta 2), and the reminders 22a and 22b consist, which is orthogonal anisotropic. M in the figure is the direction of magnetization in the above molding apparatus.

Furthermore, by sintering this elliptical molded body 20 at a specified temperature, as shown in A of Fig.2 A, it is possible to make it into the cylinder type anisotropic ferrite magnet with almost circular shape in cross section in which a pair of opposing parts 21a and 21b are radial anisotropic within each angle range 02(theta 2), and the reminders 22a and 22b are orthogonal anisotropic.

Also, in Fig.2 barriers between a pair of opposing parts and the rest are shown by the continuous line; however, it does not necessarily indicate, for example ,how radial anisotropy and orthogonal anisotropy clearly changes at the said continuous line. As far as the said remaining part is concerned, it results not only in orthogonal anisotropy, but a part or in some cases all of it could result in isotropy according to the composition of the above molding apparatus and the magnetizing direction of magnetic raw materials powder 7 when pressure molding it.

That is to say that, by optimizing shape and size of magnetic bodies 4a and 4b and non-magnetic bodies 5a and 5b that are placed at the outer circumference of the molding space, the change in magnetic characteristics between the radial anisotropic part and the orthogonal anisotropic and/or isotropic part becomes smooth; thus, the smooth magnetic flux distribution which generates little cogging as shown in a later example is achieved, and it is possible to lower incidences of fracturing and cracking of the molded body.

Furthermore, creating the molding space by combining magnetic bodies 4a and 4b and non-magnetic bodies 5a and 5b as shown in Fig.3, and extending edges of the inner circumference of magnetic bodies 4a and 4b from both sides and making contacts, the molding space is created without using non¬ magnetic bodies 5a and 5b. In this composition, the magnetic characteristics distribution between the radial anisotropic part and the orthogonal anisotoropic and/or isotropic part varies, based on thickness and shape of the butting sede of the above altered magnetic bodies 4a and 4b.

In the manufacturing method explained above, the reason behind making the molding body 20 into an elliptical shape is due to the differences in the shrinkage rate of the molding body depending on weather it is alined with the magnetization direction or right angle to it when it is pressure molded in the magnetic field. Since the shrinkage rate in the magnetization direction is usually larger, the molding body is made into an elliptical shape so that the magnetization direction aligns with the longer diameter; and it is made into a cylindershape after sintering to reduce the processing cost in the grinding process, resulting in the increasing the yield, and to lower the cost of manufacturing. Furthermore, the shape and measurement of this molding body 20 are optimized according to its magnetic characteristics together with the shape and measurement of the cylindertype an isotropic ferrite magnet which is finally obtained after sintering; however, usually in the case of cylinder type an isotropic ferrite magnet which is used forthe multi purpose two pole motor, the ratio of the long diameter D2to the short diameter D3 of the molding body 20, D2/D3, is about 1.05 ~ 1.15, and the degree range of radial anisotropy of 100° - 160° is desirable.

That is to say that, if the ratio D2/D3 is outside of the above range, it does not produce cylindrically shaped molding body. Also, if the angle range 02(theta 2) of radial anisotropy is too small, the desired objective can not be achieved, and if it is too large, it cracks when sintering it; thus it is desirable to choose these parameters within the ranges.

In the case of a rare earth cylindertype anisotropic sintered magnet, since the above shrinkage rate is similar to that of a ferrite magnet, the molding apparatus can be composed the same way.

Furthermore, as shown in Fig.4 A and B, in the similar composition as in Fig.3, by having the composition in which a non-magnetic ring 30 is placed in the molding space of the molding dies 3 and between a pair of magnetic bodies 4a and 4b and between a pari of non-magnetic bodies 5a and 5b, fractures and cracks generated when sintering the molded body can be further reduced. Furthermore, in the molding apparatus of Fig.4, by placing the non¬ magnetic ring 30, it is possible to have the composition which does not have a pair of non-magnetic bodies 5a and 5b.

In Fig.4, by using the cylindrical non-magnetic ring 30, it is composed so that the ring thickness between the molding space and a pair of magnetic bodies 4a and 4b is small, and the thickness changes toward the circumferential direction. Also, by utilizing steel carbide as non-magnetic ring material, the dies' longevity is designed.

Therefore/the molding apparatus is not limited to the above composition, but many compositions can be implemented. The composition must at least have a molding dies which has the elliptical molding space with a longer diameter aligned with the magnetization direction between a pair of magnetic poles, a pair of magnetic bodies in the opposite parts of the longer diameter direction of the said molding space, and a core which consists of a magnetic body similar shaped to the molding space at the center of the molding space.

Fig.5, without making the molded body into an elliptical shape to obtain the cylindertype anisotropic ferrite magnet as above, and taking advantage of the characteristics that the shrinkage rate differs in the magnetizing direction and the right angle direction, it explains the manufacturing method of a ferrite magnet which significantly improves the motor cogging characteristics.

That is to say that, if the molded body is obtained by making the molding space cylindrical as in the apparatus in Fig.3, the said molded body becomes a cylindrical molded body 40, in which a pair of opposing parts 41 a and 41 b each of which has anisotropy within the angle rage 02(theta 2), and the remainder parts 42a and 42b have orthogonal anisotropy. In the figure, M is the magnetization direction of the above molding apparatus.

Furthermore, when this cylindrical molded body 40 is sintered at a specified temperature, it produces an elliptical sintered body 50 with a long diameter D2 and a short diameter D3 in which a pair of opposing parts 51a and 51 b each of which has radial anisotropy within the angle range thetai as in Fig.5 B, and the remainder parts 52a and 52b have orthogonal anisotropy. M in the figure is the magnetizaiton direction of the above molding apparatus. Then, by administering the inner diameter processing and the exterior diameter processing (the oblique line area in the figure is eliminated) to the internal circumference parts 53a and 53b and outer circumference parts 54a and 54b, respectively, of this elliptical sintered body 50. As shown in Fig.5 C, a cylindertype anisotropic ferrite magnet shaped almost circle longitudinal section is obtained. The magnet has a pair of opposing parts 61a and 61b each of which has radial anisotropy within the angle range thetai, and the remainder parts 62a and 62b have orthogonal anisotropy.

In this magnetic composition, particularly the inner circumference surface 63a and 63b of the radial anisotropic parts 61a and 61b is mechanically finished into a cylindrical shape by the above inner diameter processing, but the inner circumference surface 64a and 64b of the orthogonal anisotropic parts 62a and 62b are not eliminated by the inner diameter processing and maintain the sintered surface condition. Thus, the change in the magnetic flux distribution as it moves from the radial anisotropic parts 61a and 61b to the orthogonal anisotropic parts 62a and 62b become smooth, which improves the motor cogging characteristics.

Also, by making the shape of the above molded body into an elliptical shape in which a longer diameter aligns with the magnetization direction for the outer diameter, and making the inner diameter cylindrical, the sintered body in which the outer diameter cylindrical and the inner diameter elliptical. As a result, the same effect as the above composition is obtained, the processing cost of the outer diameter is reduced, and the further cost down becomes feasible.

Fig.6 shows the other example of this invention, particularly, it shows only the rotor composition of the motor. That is to say that, 70 of Fig.6 is a cylinder type anisotropic ferrite magnet which is obtained by the above manufacturing, method, in which a pair of opposing parts 71a and 71b each of which has radial anisotropy within the angle range thetai, and the remainder parts 72a and 72b have orthogonal anisotropy. Here, the cylindrical processing is applied after sintering, a rotor axis 92 is fastened to the outer circumference of the magnet support 93 at the center, and it is placed within the stator (not shown) with a specified shape to compose the motor.

In this composition, the technology which is utilized forthe above stator composition can also be applied to a cylindertype anisotropic ferrite magnet 70.

The examples that were explained heretofore are the motor compositions in which sintered magnet type cylindershape ferrite magnet was utilized; however, the similar effect can be obtained even this magnet was a rare earth sintered magnet for the reasons explained before.

Also, even resin-bonded magnets were placed in this invented motor composition, the similar effect is obtained; any of the usual manufacturing methods such as the pressure molding, injection molding and resin impregnation can be utilizeded as the manufacturing method of the interested resin-bonded magnet.

For example, since the thermal sharinkage rate does not need to be considered as in the sintered magnet, the shape of molded body shape can be cylindrical. The molding apparatus is made by placing a molding dies which has a cylindrical molding space between a pair of magnetic poles, placing a pair of magnetic bodies opposite to the magnetic poles of the magnetic body similarly shaped to the said molding space, and placing a core which consists of the said molding space at the center of the molding space. Thermal setting resins, coupling agents,and lubricants are added to the magnetic raw materials powder placed in the molding apparatus in presence of the magnetic field; furthermore, the room temperature curing or the thermal curing can be applied based on the binder utilized.

Particularly, in the resin impregnation method, after pressure molding the magnetic powder, after it is heat treated if needed, and it is impregnated with thermosetting resins.

The filling rate of magnetic powder in the resin-bonded magnet can be optimized according to the above manufacturing method. Synthetic resins used as binder can be either of thermosetting or thermoplastic; however, it is preferable to choose thermally stable resins, and it can be optimally selected from, for example, polyamid, polyimid, phenol resins, flouride resins, silicon resins, and epoxy resins. Example 1

By showing the motor which utilizes a Sr ferrite cylindertypes anisotropic sincetered magnet as an example/the effect of this invention is further clarified.

As the magnetic raw materials powder, Sr ferrite powder which has the basic magnetic characteristics with the residual magnetic flux density Br = 3.77 kG, the coercive force He = 2.97 kOe, and the maximum energy product (BH)max = 3.34 MGOe is compression molded by the molding apparatus (04(theta 4) = 120°) as shown in Fig.4 in the magnetic field of 6kOe under pressure of 1 ton/cm2; and the molded body as shown in Fig.2 B is obtained.

The dimensions of the molded body are a long diameter D2 = 52.6mm, a short diameter D3 = 47.1mm (D2/D3 = 1.12), a height is approximately 12.6mm, and 02(theta 2) = 120° - 130°.

After sintering this molded body for one hour at 1200X1, and mechanically processing it to obtain the invented cylindrical cylindertype anisotropic sintered body shaped almost circle in longitudinal section with an outer diameter 40mm x an inner diameter 30mm x a height 10mm, and placing the said magnet at the sator side of the two pole motor and the magnetic flux distribution in the circumferential direction at the center of the space between rotor and the magnet.

Comparative Example

Also, as a comparative example 1, utilizing the identical magnetic raw materials powder as above, and a cylindertype arthogonal anisotropic sintered magnet with an outer diameter 40mm . x an inner diameter 30mm x a height 10mm was obtained; by usual method by placing the magnet in the same direction as this invented motor, the identical measurement with Example 1 was made.

Furthermore, as a comparative example 2, utilizing the Sr ferrite powder with the magnetic characteristics with the main residual magnetic flux density Br a 3.16kG, the coercive force He = 2.46kOe, and the maximum energy product (BH)max = 2.20MGOe,the cylindertype radial anisotropic sintered magnet was obtained. The magnet has dimensions of an outer diameter 40mm x an inner diameter 30mm x a height 10mm and which is known to have the excellent magnetic characteristics within the range where the cracking does not occur when sintered. When the magnet was placed under the same condition as in this invented motor, the same measurement as in Example 1 was conducted. Effects

Fig.7 shows various magnetic flux distribution The horizontal axis in Fig.7 indicates the measurement angle (degree ° ), and the vertical axis indicates the magnetic flux density Bg(kG) at individual positions.

The magnetic flux distribution which is plotted by O mark of this invented motror relative to the magnetic flux distribution of the comparative example 1 which is plotted by • mark in Fig.7. The magnetic flux which is generated from the magnetic poles, namely the area surrounding the horizontal axis of the graph representing magneticflux and the magneticf lux distribution curve since a part of this invented magnet is radial anisotropic, is clearly largerthan that of the comparative example 1 Therefore, it is possible to increase the motor output.

Also, concerning the magnetic flux distribution as a whole similar to the comparative example 1, as the center of the magnetic pole approaches higher and closer to both edges, it gradually decreases creating a so-called sine curve, thus the cogging characteristics is good.

Since the this invention can be better manufactured without cracking even if it made from the high performing raw materials than the magnet of the comparative example 2 plotted by x mark, the magneticflux which is generated from the magnetic pole surface is greater than the comparative example 2; and it has the good cogging characteristics.

Also, this invented motor has the same level of noises generated from cogging as in the motor of the comparative example 1 ; however, it was confirmed that the revolution torque improved 15% — 20% as the total magnetic flux generated from the magnet increased, Therefore, the relative reduction of noises was accomplished, since the increase in the revolution torque does not increase noises generated from cogging.

Also, the noises generated from cogging is reduced 50% — 60% in this invented motor relative to the motor in the comparative example 2, it was also confirmed that the revolution torque improved 20% to 25% due to the increase in the total magneticflux generated from the magnet.

Similarly, noises generated from cogging in this invented motor is reduced 50% — 60% compared to the motor in the comparative example 2; and it was confirmed that the revolution torque improved 20% - 25% as the total magnetic flux generated from the magnet increased.

Although it is explained in terms of a Sr ferrite cylindertype anisotropic sintered magnet in this example, this inventer confirmed that the same effect in motors in which cylinder type anisotropic sintered magnets which consists of other materials such as rare earths, etc. are utilized.

Furthermore, when Sr ferrite cylinder anisotropic resin-bonded magnets in which epoxy resins is used as binder was made in the identical apparatus as in examples other than making the molding space cylindrical and were measured their various characteristics in a motor, the similar effects as in the above examples were confirmed. Industrial Applicability

This invented motor is concerned with the effective utilization of individual magnet by placing the unit cylinder type anisotropic magnet in which a specified part of it is made radial anisotropic and the remainder made into either orthogonal anisotropic and/or isotropic, and the achieving the enhancement of the motor output which results from the enhancement of the total magneticflux generated from the magnetic poles; and since it improves the cogging characteristics of a motor, it is possible to realize the reduction of noises which generate from the said cogging.

This invented manufacturing method prevents fractures and cracking from occuring when sintering the cylindertype anisotropic sintered magnet and efficiently mass produce it.

Claims

1. A cylindertype anisotropicmagnet which comprises radial anisotropy of a pair of opposing parts within a specified degree range, and the remainder which is orthogonal anisotropic and/or isotropic, and which is a unit body.

2. The cylindertype anisotropic magnet as claimed in claim 1, said magnet is a ferrite magnets contains Sr and/or Ba.

3. The cylindertype anisotropic magnet as claimed in claim 1, said magnet is a rare earth magnets.

4. The cylindertype anisotropic magnet as claimed in claim 1, Claim 2, and Claim 3, said magnet having the radial anisotropic degree range of 02(theta 2) 100° - 160°.

5. A prosess for producing the cylindertype anisotropic magnet, which comprises; molding the magnetic raw materials in the magnetic field in the molding apparatus in which a molding dies which has an elliptical molding space where a long diameter aligns with the magnetizing direction between a pair of magnetic poles, a pair of magnets provided to opposite portion of a pair of magnetic poles in said in said molding space and a core which consists of a magnetic body similarly shaped to said molding space; sintering the elliptical molded body to obtain a unit sintered body shaped almost circle in cross section in which a pair of opposing parts are radial anisotropy within a specified degree range and the remainders orthogonal anisotropic and/or isotropic.

6. The prosess for producing the cylindertype anisotropic magnet as claimed in claim 5, which comprises; the molding space which consists of a pair of magnets which are placed opposite to a long diameter direction of the molding space, and a pair of non- magnets which are placed opposite to a short diameter direction.

7. The prosess for producing the cylindertype anisotropic magnet as claimed in claim 5 and Claim 6, which comprises; creating the molding space by cylindrical non-magnetic rings,and the ring thickness between the molding space and a pair of magnets is made small, and at the same time, the thickness is varied toward the circumferential direction.

8. The prosess for producing the cylindertype anisotropic magnet as claimed in claim 5, Claim 6, or Claim 7, which comprises; the ratio of a long diameter D2 and a short diameter D3, D2/D3, is 1.05 — 1.15, the radial anisotropic degree range 02(theta 2) is 100°- 160° of a molding body.

9. A prosess for producing the cylindertype anisotropic magnet, which comprises; molding the magnetic raw materials in the magnetic field in the molding apparatus in which a molding dies which has an circular molding space between a pair of magnetic poles, a pair of magnets provided to opposite portion of a pair of said magnetic poles in said molding space and a core which consists of a magnetic body similarly shaped to said molding space; sintering the molded body shaped almost circle in cross section to obtain a elliptical unit sintered body in which a pair of opposing parts are radial anisotropy within a specified degree range and the remainders orthogonal anisotropic and/or isotropic; mechanical processing of outer circumference and/or the inner circumference of said sintered body.

10. The prosess for producing the cylinder type anisotropic magnet as claimed in claim 9, which comprises; the molding space which consists of a pair of magnets which are placed opposite portion of a pair of magnetic poles in the molding space, and a pair of non-magnets which are placed at the exterior circumferential part other than the portion of magnets opposing to each other.

11. The prosess for producing the cylinder type anisotropic magnet as claimed in claim 9 and Claim 10, which comprises; the ratio of a long diameter D2 and a short diameter D3, D2/D3, is 1.05 - 1.15, the radial anisotropic degree range 02(theta 2) is 100° — 160° of a molding body.

12. A prosessfor producing the cylindertype anisotropic magnet, which comprises; molding the magnetic raw materials added and mixed with thermosetting resins, coupling agents, and lubricants in the magnetic field in the molding apparatus in which a molding dies which has an circular molding space between a pair of magnetic poles, a pair of magnets provided to opposite portion of a pair of said magnetic poles in said molding space and a core which consists of a magnetic body similarly shaped to said molding space; curing the molded body to obitain a unit dinder type anisotropic resin-bonded magnet in which a pair of opposing parts are radial anisotropy within a specified degree range and the remainders orthogonal anisotropic and/or isotropic.

13.The prosess for producing the cylinder type anisotropic magnet as claimed in claim 12, which comprises; the molding space which consists of a pair of magnets placed opposite portion of a pair of magnetic poles in the molding space, and a pair of non-magnets which is placed at the exterior circumferential part which is other than the portion of magnets opposing to each other.

14. The prosess for producing the cylindertype anisotropic magnet as claimed in claim 12 and Claim 13, which comprises; the radial anisotropic range 02(theta 2) is 100° - 160° of a molding body.

15. A motor which utilizes the unit cylinder type anisotropic magnet, which is characterized by having radial anisotropy within a specified angle range for a pair of opposing parts, and the remainder is either orthogonal anisotropy and/or isotropy; and the motor is characterized by using the magnets as stator or rotor.