JP6655290B2 - Axial gap type rotary electric machine - Google Patents

Description

  The present invention relates to an axial gap rotating electric machine.

  Reduction of iron loss is one of the effective means for increasing the efficiency of a rotating electric machine. Iron loss mainly occurs in the iron core that becomes an electromagnet, but in a permanent magnet motor that uses a permanent magnet on the rotor side, iron loss may also occur in the surrounding magnetic material holding the permanent magnet. Are known. In the radial gap type motor, in order to reduce the iron loss, electromagnetic steel sheets having a thickness of 0.35 mm and 0.5 mm were laminated so that an eddy current does not flow in the axial direction even in a portion holding the magnet. Structures that use things are common.

  Patent Document 1 proposes a structure in which an electromagnetic steel plate or an amorphous metal foil strip is used for a magnet holding member of a rotor of an axial gap motor by using the same method as described above.

  On the other hand, in a radial gap type motor, there is an example in which a design is made in which a magnetic body and a structure are shared for a holding member of a rotor-side magnet. For example, the structure is such that a magnet is adhered and held on the surface of a magnetic material shaft such as iron. In the case of this structure, since the magnetic flux generated from the magnet is a DC magnetic field, no loss occurs in the shaft magnetic body portion. However, the magnetic flux generated by the coil on the stator side generates a magnetic flux that changes the magnetic flux beyond the magnet portion to the magnetic material. At this time, an eddy current for canceling the fluctuation flows through the magnetic material portion according to the change in the magnetic flux, and causes an iron loss called an eddy current loss.

  In order to prevent this, in Patent Document 2, the loss is reduced by using a method in which a shaft surface is subjected to a spiral processing and an adhesive containing magnetic powder is used. Also, in the case of an outer rotor type motor, a loss similar to that described above is provided by a method described in Patent Document 3 to reduce loss.

Japanese Patent No. 5502463 JP-A-11-332147 JP 2007-077476 A

  Patent Literature 1 discloses a structure in which an amorphous metal foil strip having a thickness of about 0.025 mm is wound up as an iron core as a magnet holding member serving as a back yoke (yoke portion) of a rotor. In this structure, a mechanical strength is required for the rotor yoke to mechanically hold the rotor disk and the rotating shaft that rotates. For this reason, the rotor yoke is made of a high-strength material such as an iron alloy, and the portion requiring magnetism is a wound iron core (amorphous spiral lamination), and a permanent magnet for the rotor is bonded to the wound iron core. The structure is held by using the method. In this configuration, in addition to the magnet, three parts, a wound iron core and a rotor yoke, are required. In order to integrate them, a fixing means such as an adhesive is required, and the number of parts is increased. Since the stress at the time of winding changes with time, external stress, vibration, etc., the reliability such as peeling of the adhesive decreases, the man-hour for manufacturing the wound iron core increases, and the number of parts increases. There is a problem that the assemblability is deteriorated due to an increase in the number.

  Patent Literature 2 and Patent Literature 3 propose a structure in which a rotor yoke also serves as a back yoke (yoke portion) of the rotor. This method can also be applied to an axial gap type motor, but when applying this method, the same problem occurs with a radial gap type motor, but it is necessary to perform cutting using a lathe or the like on the rotor yoke. In the cutting process, since each rotor yoke is set on a lathe and work is performed while adjusting their dimensions, it takes a very long time, and the productivity is poor. Further, when deep groove processing is performed, a processing tool having a small width is required, and in this case, there is a problem that a processing speed is reduced. Further, after processing, it is necessary to perform processing such as washing, feeling, and rust prevention of machine oil attached during processing, which causes an increase in cost.

  An object of the present invention is to provide an inexpensive and highly reliable rotor yoke that can reduce eddy currents in a rotor yoke.

  The features of the present invention for solving the above problems are, for example, as follows.

A rotor and a stator, the rotor having a rotor back yoke and a rotor magnet, wherein the rotor back yoke has a central hole, a guide portion for holding the rotor magnet, A plurality of concentric grooves and a protrusion between the plurality of grooves are formed on the entire circumference from the inner peripheral portion to the outer peripheral portion of the child back yoke, and a tip portion of the protrusion has an R-shaped structure, or An axial gap type rotating electric machine with a structure in which projections have a tapered angle .

  According to the present invention, the rotor yoke is composed of one part (material) except for the magnet, so that the number of manufacturing steps can be reduced and the number of bonded parts is reduced, so that the bonding strength is not insufficient. An improvement in reliability can be expected. In addition, the reduction of the eddy current, which is the initial target, and the securing of the induced voltage can both be achieved, and the efficiency of the motor can be increased. Problems, configurations, and effects other than those described above will be apparent from the following description of the embodiments.

It is a perspective view of the rotor of the axial gap type rotary electric machine concerning one embodiment of the present invention. 1 shows a configuration of a rotating electric machine according to an embodiment of the present invention. 6 is a graph showing experimental results for explaining the effect of the groove structure according to one embodiment of the present invention. FIG. 4 is a cross-sectional comparison diagram of a structure illustrating various structures described in FIG. 3. It is a key map explaining the forging manufacturing method concerning one embodiment of the present invention. It is a key map showing the transfer press manufacturing method concerning one embodiment of the present invention. It is a key map showing the manufacturing method by the powder metallurgy technique concerning one embodiment of the present invention. 3 shows various variations of a groove shape according to an embodiment of the present invention. It is a perspective view showing an example of application of an axial gap type motor to which the structure of the present invention is applied.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. The following description shows specific examples of the content of the present invention, and the present invention is not limited to these descriptions, and various modifications by those skilled in the art within the technical idea disclosed in the present specification. Changes and modifications are possible. In all the drawings for describing the present invention, components having the same function are denoted by the same reference numerals, and repeated description thereof may be omitted.

  FIG. 1 is a perspective view of a rotor of an axial gap type rotating electric machine according to one embodiment of the present invention. FIG. 1A is a perspective view of a rotor, and FIG. 1B is a perspective view of a rotor back yoke.

  The rotor 2 of the axial gap type rotating electric machine shown in FIG. 1A is a rotor having a permanent magnet. The rotor 2 has a rotor back yoke 11 and a rotor magnet 20, and is configured by attaching the rotor magnet 20 to the rotor back yoke 11. The rotor magnet 20 and the rotor back yoke 11 are integrated by a method such as bonding. The rotor back yoke 11 is made of a soft magnetic material such as iron.

  The rotor magnet 20 includes a rotor magnet north pole 21 and a rotor magnet south pole 22. The rotor magnet N-pole 21 and the rotor magnet S-pole 22 which are paired with the N pole and the S pole are periodically arranged in the rotation direction. A rotor shaft hole 12 for fastening to a shaft is formed at the center of the rotor 2.

  In FIG. 1A, the ring-shaped disk-shaped magnet has a structure in which ten magnetic poles are arranged in the circumferential direction. One magnetic pole has a fan shape and is arranged on the circumference at an equal angular pitch. The magnetic poles are assembled as a rotor 2 in the form as shown in FIG. 1A, and then magnetized by an electromagnet called a magnetizing yoke to form such magnetic poles. A similar rotor structure can be obtained by attaching one or more divided magnets.

  In one embodiment of the present invention, as shown in FIG. 1B, a plurality of grooves 13 are provided on a surface (joining surface) of the disk-shaped rotor back yoke 11 to be attached to the rotor magnet 20. I have. The figure shows a case where a plurality of concentric grooves 13 are provided on the surface of the disk-shaped rotor back yoke 11 to which the rotor magnet 20 is attached. The projections 113 are formed on the rotor back yoke 11 by forming the concentric grooves 13. This groove 13 can reduce the eddy current generated by a change in magnetic flux density generated by energization of the stator coil.

  FIG. 2 shows a configuration of a rotating electric machine according to one embodiment of the present invention. FIG. 2A shows a configuration of an axial gap type rotating electric machine. The axial gap type rotating electric machine 1 has two rotors 2 in the axial direction. Each rotor 2 is provided with a rotor magnet 20.

  The stator 3 is arranged at a central portion in the axial direction, and includes a stator core 15 having a substantially fan-shaped cross section like the rotor magnet 20, and a stator coil 18 wound therearound. . The magnet magnetic flux flows through the stator core 15 through the gap in the axial plane, and is linked to the stator coil 18 to generate an induced voltage in the stator coil 18.

  The housing 14 holds an outer peripheral portion of the stator 3. The shaft 17 is arranged for connecting the rotors 2 on both sides in the axial direction and outputting the shaft. The lead wire 19 is formed by electrically connecting the three-phase stator coils 18 in a delta or star connection to form a terminal portion.

  FIG. 2B schematically shows the flow of the magnetic flux on a plane. The magnetic flux emitted from the rotor magnet north pole 21 of the rotor 2 flows through the stator core 15 in the axial direction, and flows into the rotor magnet south pole 22 disposed on the opposite side. In the rotor back yoke 11, the magnetic flux of the magnet flows from the rotor magnet N pole 21 in the circumferential direction and flows into the rotor magnet S pole 22 adjacent in the circumferential direction. Since the magnetic flux generated by the magnet is a constant magnetic field, the magnetic field does not fluctuate basically in the rotor back yoke 11, but changes in the magnetic flux density due to the slots of the stator 3 and the influence of the stator winding current cause It is known that a small change in magnetic flux density occurs near the interface between the rotor magnet 20 and the rotor back yoke 11. For this reason, the rotor back yoke 11 generally employs a laminated iron core such as an electromagnetic steel plate in a radial type motor or the like.

  In the axial gap type rotating electric machine, when a laminated core made of an electromagnetic steel plate is used for the rotor back yoke 11, a structure in which the laminated body is laminated in a direction perpendicular to the flow of the magnetic flux is required. Therefore, a rotor back yoke such as an electromagnetic steel sheet iron core wound on a circumference as shown in Patent Document 1 described above or an amorphous foil band wound iron core is required. These structures lead to an increase in the number of parts, an increase in man-hours, and a decrease in reliability. Therefore, a simpler structure is required. Therefore, the eddy current is reduced by the groove structure described above.

  FIG. 2C shows a magnet shape for one pole of the axial gap rotating electric machine. According to the magnetic flux lines shown in FIG. 2B, the flow of the magnetic flux flows in a direction halfway from the center of the rotor magnet 20 so that the magnetic flux of the rotor magnet 20 has a half of the magnetic pole surface area. You can see that it flows to the next. For this reason, the total amount of the magnetic flux can be represented by the product of the magnetic flux density and the surface area, so that the residual magnetic flux density Br of the rotor magnet 20, the average magnet circumference l per pole of the rotor magnet 20, and the rotor From the width W of the magnet 20, it can be considered to be about WＷ / 2 ／ Br.

  FIG. 2D shows the cross-sectional shape of the groove of the rotor back yoke. Since it is considered that an eddy current can be prevented by passing only the protrusion 113 as a magnetic path for passing a magnetic flux between the adjacent magnets, the height H of the protrusion 113, the protrusion 113 and the gap (groove 13) are considered. Is R, the total cross-sectional area of the projection 113 is HWR. If the rotor back yoke 11 is made of iron and its magnetic flux density is 2T, the amount of magnetic flux that can flow can be expressed as 2H.WR. Considering that the magnetic flux of the rotor magnet 20 flows only through the protrusion 113, it can be understood that this condition is satisfied in the case of l · Br <4H · R.

  In the example of the rotating electric machine shown in FIG. 2A, the outer diameter of the rotor magnet 20 is φ63, the inner diameter is φ29, and the rotor magnet 20 is a 10-pole magnet. At this time, the average magnet circumference l per pole is about 14 mm. Since this magnet uses a ferrite magnet, the residual magnetic flux density Br is 0.45T, and if the interval between the projection 113 and the groove 13 is equal, R = 0.5. The length is about 3 mm or more. In the dimensional relationship of FIG. 2A, the eddy current can be prevented by setting the protrusion 113 to 3 mm or more.

  FIG. 3 is a graph showing experimental results for explaining the effect of the groove structure according to one embodiment of the present invention. 3 (a) to 3 (d) show the induced voltage (see FIG. 3 (b)) obtained by actually manufacturing the rotating electric machine shown in FIG. 2 (a) and changing the material and shape of the rotor back yoke. )), No-load loss (FIG. 3 (a)), and the results of measuring the motor efficiency (FIG. 3 (d)) when the rotating electric machine is driven with the voltage kept constant. FIG. 3C shows the relationship between the torque and the rotation speed when the rotating electric machine is driven with the voltage kept constant.

  The respective dimensional relationships have the shape shown in FIG. FIG. 4 is a cross-sectional comparison diagram of a structure illustrating various structures described in FIG. 4 (a) shows a magnetic steel sheet or amorphous using a spiral core 10 yoke, FIG. 4 (b) uses a solid iron as a yoke, and FIG. 4 (c) and FIG. This adopts a groove structure according to an embodiment of the present invention.

  As the rotor yoke of the axial gap type rotating electric machine, those using solid iron as a yoke, those using a magnetic steel sheet wound iron core yoke, and those employing the groove structure according to one embodiment of the present invention are all obtained. There was no significant change in the effective value of the induced voltage or the shape of the waveform. However, the measurement results of the no-load loss show that the loss of the iron solid yoke and the grooved yoke is larger than that of the magnetic steel sheet wound iron core yoke. This is considered to be an increase in yoke loss due to a change in magnetic flux density due to slot harmonics.

  Regarding the efficiency when the rotating electric machine was driven, the result was that the core wound with an electromagnetic steel plate had the highest efficiency, and the iron solid yoke had the lowest efficiency. This is the effect of the yoke loss due to the change in magnetic flux due to the stator winding current. In the grooved rotor yoke according to the embodiment of the present invention, the efficiency is improved as compared with the iron solid yoke, and it has been confirmed that there is an effect of reducing the yoke loss. Further, it was confirmed that the smaller the cross-sectional area of the protrusion, the more effective the relationship between the protrusion dimensions. According to the results of this experiment, the cross-sectional area of the protrusions is small relative to the magnet surface area, and the magnetic flux also passes through the solid part of the rotor yoke, so the loss reduction effect is small. Thus, it is considered that there is an effect of reducing the loss comparable to that of the magnetic steel sheet wound iron core.

  FIG. 5 shows an example of a method of manufacturing this projection structure. FIG. 5 is a conceptual diagram illustrating a forging manufacturing method according to an embodiment of the present invention. As described above, a method using a wound iron core such as an electromagnetic steel sheet causes an increase in manufacturing cost and a decrease in reliability. Therefore, it is desired that the rotor yoke portion be formed of an integral body of the same material. However, the number of steps is increased by performing post-processing, and therefore, it is necessary to make the post-processing in a single step. FIG. 5 shows a means for obtaining a structure according to an embodiment of the present invention from a blank by forging with a press.

  FIG. 5A shows a blank 31 to be a material. A substantially disk-shaped iron-based material that can be a magnetic material is prepared. This material can be prepared at low cost by pressing or cutting out from a bar. In the following description, iron is used as an example, but an alloy such as magnetic stainless steel, a nickel alloy, and a cobalt alloy may be used instead of iron. .

  As shown in FIG. 5 (b), this material is placed in a mold for forging by applying plastic deformation, and a desired shape is formed by applying a molding force to the mold. In FIG. 5B, reference numeral 32 denotes a base of the press equipment. Reference numeral 33 denotes an operating die of the press equipment. Reference numeral 34 denotes a punch for forming a central hole of the upper die attached to the operating die 33. Reference numeral 35 denotes a punch for forming the groove 13 of the upper mold. At this time, since the punch 35 serving as the upper die for forming the groove becomes thin, it is necessary to have strength against buckling or the like. For this reason, when forming is performed by such a method, in order to improve the strength of the root portion of the punch, a structure in which the root portion is rounded, or a punch as shown in FIG. It is desirable to take measures such as providing a taper angle (10 ° in this figure). Therefore, the groove shape when formed by this method has a shape as shown in FIG. In this manner, a plurality of grooves are formed by applying a stress in the thickness direction of the rotor back yoke.

  FIG. 6 shows an example of manufacturing from a flat plate. FIG. 6 is a conceptual diagram illustrating a transfer press manufacturing method according to an embodiment of the present invention. FIG. 6 shows a manufacturing method of obtaining a final shape at a third processing station 44 by repeating molding from a hoop-shaped material through a first forming station 42 and a second processing station 43 and pressing. Since this method can be configured to perform a plurality of pressing steps, there is an advantage that the center hole can be punched and the final accuracy can be adjusted.

  In FIG. 6, reference numeral 41 denotes a hoop-shaped iron material. Reference numeral 42 denotes a first molding station. In the first molding station 42, a center boring process is performed. 43 is a second processing station. In the second processing station 43, processing for providing a seat for securing dimensions for holding a magnet is performed. Reference numeral 44 denotes a third processing station. The third processing station 44 performs groove processing by plastic processing (forging processing). As described above, by dividing each processing step, it is possible to obtain a high quality (highly accurate product shape).

  FIG. 7 shows still another manufacturing method. FIG. 7 is a conceptual diagram illustrating a manufacturing method using a powder metallurgy technique according to an embodiment of the present invention. Reference numeral 51 denotes an iron powder placed in a compression molding die. 52 shows a base plate of the compression molding press equipment. Reference numeral 53 denotes an operation die of the compression molding press equipment. Reference numeral 54 denotes a compression molding punch attached to the operation die 53.

  Iron powder that can be a magnetic material is inserted into a lower mold having a cylindrical cylinder, and compression molding is performed with an upper punch that can be molded into a grooved rotor yoke according to one embodiment of the present invention. Then, it is fired to obtain a rotor yoke as a sintered part. With this method, it is possible to obtain a part by molding with relatively low compressive force, as compared with the method of obtaining a shape by plastic deformation described above. For the time being, the compression force can be reduced by molding to a not too high density, but the sintering causes the irons to bond together and shrink, resulting in a high-density compact. . According to this method, the depth and shape of the groove can be relatively freely configured.

  The manufacturing method described above can be manufactured by molding because it is an axial gap type rotor yoke. This is because the magnet attachment surface is on the wide surface side of the disk, and in the case of a radial type motor, since both the inner rotor type and the outer rotor type have cylindrical surfaces, such forming processing is difficult. .

  FIG. 8 shows various variations of the groove shape according to the embodiment of the present invention.

  FIG. 8A shows an example in which the groove 13 is also inserted in the radial direction. In FIG. 8A, a plurality of grooves 13 are provided on the joining surface of the rotor back yoke 11 and the rotor magnet 12 in the radial direction of the rotor back yoke 11. In order to suppress the generation of the eddy current, the finer the division, the higher the effect. Therefore, it is effective to make the shape of the projection 113 fine. Therefore, according to the flow of the magnetic flux shown in FIG. 2 (b), the center of the magnetic pole of the rotor magnet 20 is a place where the magnetic flux does not flow. By dividing the 113, the projection 113 can be subdivided without obstructing the flow of the magnetic flux.

  FIG. 8B shows a mode in which the width of the protrusion 113 is changed. Although the amount of magnetic flux flowing has been described with the average circumference, the larger the diameter, the larger the magnetic flux actually. For this reason, the ratio R between the protrusion 113 and the groove 13 is not made constant, and the width of the protrusion 113 is increased or the length of the protrusion 113 is increased (the groove 13 is deepened) where the diameter is large. , A structure for increasing the amount of magnetic flux flowing through the protrusion 113 is shown.

  FIG. 8 (c) shows that the guide portion 60 holding the rotor magnet 20 can be simultaneously formed using the above-described feature that the shape can be manufactured by one-shot processing by forging or powder metallurgy. It shows the building. According to this structure, effects such as maintaining the centrifugal force resistance of the rotor magnet 20 and improving the positioning accuracy of the rotor magnet 20 can be expected.

  FIG. 8D shows a structure having the protrusion 213 on the rotor magnet 20 side as well. In FIG. 8D, a plurality of protrusions 213 are provided on the rotor magnet 20 at portions corresponding to the plurality of grooves 13 in the circumferential direction of the rotor back yoke 11. When the rotor magnet 20 is also a sintered magnet, it is manufactured by a mold, so that the projections 213 can be formed relatively easily. The size of the magnet is generally adjusted by polishing its surface. Since this process requires a lot of man-hours, the portion provided with the protrusion is used without any processing. The rotor back yoke 11 according to one embodiment of the present invention also has no post-processing, so that no accuracy is required, and the gap opposing surface of the rotor magnet 20 which is polished on one side to ensure accuracy is assembled as a reference for assembly, and then rotated. A fixing member such as an adhesive is poured between the child back yoke 11 and the rotor magnet 20 to be formed. Since the surface of the rotor magnet 20 and the surface of the rotor back yoke 11 are mutually uneven, a large bonding area can be secured and the strength can be improved.

  FIG. 8E shows an example of a bonded magnet in which the rotor magnet 20 is formed by injection molding. In FIG. 8E, the material of the bond magnet is also arranged in the groove 13 of the rotor back yoke 11 by injection molding. Since the bond magnet is formed by directly injection-molding the rotor back yoke 11, it is possible to reduce man-hours and loss. Since the bonded magnet has a large specific resistance, the magnet loss such as eddy current can be reduced.

  FIG. 8F shows that the grooves 13 and the projections 113 are also formed on the surface of the rotor back yoke 11 opposite to the surface on which the rotor magnet 20 is attached when the manufacturing method according to the embodiment of the present invention is used. Can be formed. In other words, in the circumferential direction of the rotor back yoke 11, a plurality of grooves 13 are provided on the surface of the rotor back yoke 11 opposite to the surface where the rotor back yoke 11 is joined to the rotor magnet 20. For this reason, since the rotating body receives wind, it is possible to obtain a rotor having a high heat radiation effect as a radiation fin.

  FIG. 9 shows a system application example of an axial gap type rotating electric machine using a rotor shape according to an embodiment of the present invention. It can be incorporated into mechanical devices such as pumps and fans, or applied to flywheel devices, etc., and a motor with high motor efficiency due to low rotor loss, in other words, an energy-saving product can be realized.

DESCRIPTION OF SYMBOLS 1 Axial gap rotating electric machine, 2 rotors, 3 stators, 10 spiral iron cores, 11 rotor back yoke, 12 rotor shaft holes, 13 grooves, 14 housings, 15 stator cores, 17 shafts, 18 stator coils, 19 Lead wire, 20 rotor magnet, 21 rotor magnet north pole, 22 rotor magnet south pole, 31 blank, 32 base part, 33 working die, 34 35 punch, 41 iron material, 42 first forming station, 43 Second processing station, 44 Third processing station, 51 Iron powder, 52 Base plate, 53 Working die, 54 Compression molding punch, 60 Guide part, 113 213 Projection

Claims (8)

Having a rotor and a stator,
The rotor has a rotor back yoke and a rotor magnet,
A center hole, a guide portion for holding the rotor magnet, the plurality of concentric grooves and the plurality of concentric circles extending from an inner peripheral portion to an outer peripheral portion of the rotor back yoke; And projections between the grooves are formed,
An axial gap type rotating electric machine , wherein a tip portion of the projection has an R-shaped structure, or the projection has a tapered angle . The rotor back yoke according to claim 1, wherein the rotor back yoke has a disk shape,
Axial gap rotary electric machine before Symbol plurality of grooves in the thickness direction of the rotor back yoke is molded. 3. The axial gap rotating electric machine according to claim 1, wherein the rotor back yoke is made of a soft magnetic material. The plurality of protrusions are formed on the rotor back yoke by the plurality of grooves according to any one of claims 1 to 3,
The residual magnetic flux density of the rotor magnet is Br, and the average magnet circumference l per pole of the rotor magnet is l
An axial gap type rotating electric machine that satisfies l · Br <4H · R, where H is the height of the plurality of protrusions, and R is the ratio of the plurality of protrusions to the plurality of grooves. The axial gap type rotating electric machine according to any one of claims 1 to 4, wherein a plurality of grooves are provided on a joint surface of the rotor back yoke with the rotor magnet in a radial direction of the rotor back yoke. The axial gap rotating electric machine according to any one of claims 1 to 4, wherein the rotor magnet has a plurality of protrusions at portions corresponding to a plurality of grooves in a circumferential direction of the rotor back yoke. The rotor magnet according to any one of claims 1 to 4, wherein the rotor magnet is a bonded magnet,
An axial gap rotary electric machine in which the bond magnet is arranged in a plurality of grooves in a circumferential direction of the rotor back yoke. The axial gap type rotation according to any one of claims 1 to 7, wherein a plurality of grooves are provided on a surface of the rotor back yoke in a circumferential direction of the rotor back yoke opposite to a bonding surface with the rotor magnet. Electric machine.