TWI637583B - Axial gap rotary electric machine - Google Patents

Abstract

The purpose of the present invention is to reduce the eddy current of the rotor yoke and to obtain a rotor yoke which is inexpensive and highly reliable.

An axial gap type rotating electric machine includes a rotor and a stator. The rotor system includes a rotor back yoke and a rotor magnet. A plurality of grooves are provided on a circumferential surface of the rotor back yoke and a joint surface between the rotor back yoke and the rotor magnet. The grooves form a plurality of protrusions on the rotor back yoke, so that the residual magnetic flux density of the rotor magnet is Br, the average pole circumference of one pole of the rotor magnet is l, the height of the plurality of protrusions is H, and the plurality of protrusions When the ratio to the plurality of grooves is R, 1 · Br <4H‧R is satisfied.

Description

Axial gap rotary electric machine

The present invention relates to an axial gap type rotating electrical machine.

In order to improve the efficiency of rotating electrical machines, reducing iron loss is one of the effective methods. Although iron loss mainly occurs in an iron core that becomes an electromagnet, in the case of a permanent magnet motor in which a permanent magnet is used on a rotor side, it is known that the iron loss also occurs in a surrounding magnetic body that holds the permanent magnet. In the radial gap motor, in order to reduce this iron loss, and in terms of holding the magnet, and also to prevent eddy currents from flowing in the axial direction, laminated electromagnetic steel plates with a thickness of 0.35 mm and 0.5 mm are used. The structure of the person is average.

Patent Document 1 proposes a structure using an electromagnetic steel plate, an amorphous metal foil tape, or the like in the same manner as described above for the magnet holding member of the rotor of the axial gap motor.

On the other hand, in the radial gap type motor, there is an example of designing a holding member in which a magnetic body and a structure are shared by a rotor-side magnet. For example, a structure in which a magnet is adhered and held on the surface of a magnetic shaft such as iron. With this structure, the magnetic flux generated from the magnet is straight Since the magnetic field is flowing, the loss does not occur in the axial magnetic part. However, the magnetic flux generated by the coil on the stator side generates a magnetic flux that exceeds the magnet portion and changes the magnetic flux even with the magnetic body. At this time, an iron loss called an eddy current loss is caused in the magnetic body portion due to a change in magnetic flux, and an eddy current for eliminating the variation is caused to flow.

In order to cope with this problem, in Patent Document 2, a method of using a magnetic powder-containing adhesive is used to perform spiral processing on the shaft surface to reduce loss. In the case of an outer rotor type motor, the same groove as described above is provided by the method shown in Patent Document 3 to reduce the loss.

[Prior technical literature] [Patent Literature]

[Patent Document 1] Japanese Invention Patent No. 5502463

[Patent Document 2] Japanese Patent Publication No. Heisei 11-332147

[Patent Document 3] Japanese Patent Publication No. 2007-074776

Patent Document 1 shows a structure in which an amorphous metal foil tape having a plate thickness of approximately 0.025 mm is wound into a core to form a core holding member serving as a back yoke (yoke portion) of a rotor. This structure is In order to mechanically hold the rotating shaft of the rotating rotor disc, mechanical strength is required for the rotor yoke. For this reason, the rotor yoke is made of high-strength materials such as ferroalloys, and the parts that need to be magnetic are used to wind the core (amorphous spiral laminated tape), and it is a method of bonding the permanent magnets for the rotor. The structure is retained in the wound core. In this configuration, in addition to the magnet, three components including a core and a rotor yoke need to be wound. In order to integrate them, a fixing means such as an adhesive is required. As the number of components increases, the core is wound around the core. The stress at the time of winding changes with time, external stress, vibration, etc., so the reliability of the peeling and the like of the bonding is reduced, the man-hours for manufacturing the wound core are increased, and the number of components is increased. Becomes a problem.

Patent Literature 2 and Patent Literature 3 propose a structure in which the rotor yoke also serves as a back yoke (yoke portion) of the rotor. Although this method can also be applied to an axial gap type motor, in the case of applying this method, the radial gap type becomes the same problem, and it is necessary to perform cutting processing using a lathe or the like for the rotor yoke. The cutting process is to set each rotor yoke on a lathe and adjust the dimensions to perform operations, so it is very time consuming and poor in manufacturing. In addition, in the case of deep groove processing, a processing tool with a narrow width is required, and in this case, there are problems such as a delay in processing speed. In addition, after processing, cleaning, drying, rust prevention, and the like of the motor oil adhered during processing are required, which becomes a factor of increasing costs.

The purpose of the present invention is to reduce the eddy current of the rotor yoke and to obtain a rotor yoke which is inexpensive and highly reliable.

The features of the present invention for solving the above-mentioned problems are as follows.

An axial gap rotary electric machine includes a rotor and a stator. The rotor includes a rotor back yoke and a rotor magnet. A plurality of grooves are provided on a circumferential direction of the rotor back yoke on a joint surface of the rotor back yoke and the rotor magnet.

According to the present invention, the rotor yoke system is constituted by one member (material) other than the magnet, so that manufacturing man-hours can be reduced, and the number of members to be bonded can be reduced. Therefore, it is expected that reliability such as insufficient bonding strength will not occur. Promotion. In addition, the reduction of the eddy current and the guarantee of the induced voltage for the original purpose can be established at the same time, which can improve the efficiency of the motor. Problems, structures, and effects other than the above will be demonstrated by the following description of the embodiment.

1‧‧‧Axial gap rotary electric machine

2‧‧‧ rotor

3‧‧‧ stator

10‧‧‧ Spiral Core

11‧‧‧rotor back yoke

12‧‧‧Rotor shaft hole

13‧‧‧ trench

14‧‧‧Shell

15‧‧‧ stator core

17‧‧‧ axis

18‧‧‧ Stator coil

19‧‧‧ Lead

20‧‧‧rotor magnet

21‧‧‧ Rotor magnet N pole

22‧‧‧ Rotor magnet S pole

31‧‧‧ embryo

32‧‧‧ base

33‧‧‧Motion

34, 35‧‧‧ punch

41‧‧‧Iron material

42‧‧‧The first forming station

43‧‧‧Second Processing Station

44‧‧‧3rd processing station

51‧‧‧Iron powder

52‧‧‧ floor

53‧‧‧Motion

54‧‧‧ Punch for compression molding

60‧‧‧Guide

113, 213‧‧‧ protruding

[Fig. 1] A perspective view of a rotor of an axial gap type rotating electrical machine according to an embodiment of the present invention.

FIG. 2 shows a configuration of a rotating electrical machine according to an embodiment of the present invention.

3 is a graph showing an experimental result for explaining the effect of a trench structure according to an embodiment of the present invention.

4 is a cross-sectional comparative view of a structure explained with various structures described in FIG. 3.

FIG. 5 is a conceptual diagram illustrating a forging manufacturing method according to an embodiment of the present invention.

[FIG. 6] A conceptual diagram showing a self-feeding combined pressing method according to an embodiment of the present invention.

[FIG. 7] A conceptual diagram showing a manufacturing method by a powder metallurgy method according to an embodiment of the present invention.

[Fig. 8] Fig. 8 shows various variations of the groove shape according to an embodiment of the present invention.

Fig. 9 is a perspective view illustrating an application example of an axial gap motor with a structure to which the present invention is applied.

Hereinafter, embodiments of the present invention will be described using drawings and the like. The following description is a specific example of the content of the present invention, and the present invention is not limited to those described here. It is disclosed within the scope of the technical idea of this specification. Those with ordinary knowledge in the technical field to which the present invention belongs can make various formulas. Various changes and corrections. In addition, in the entire drawings for explaining the present invention, those having the same functions are denoted by the same reference numerals, and repeated descriptions thereof may be omitted.

[Example 1]

FIG. 1 shows an axial clearance according to an embodiment of the present invention Perspective view of the rotor of a rotary electric machine. Figure 1 (a) is a perspective view of the rotor, and Figure 1 (b) is a perspective view of the rotor back yoke.

The rotor 2 of the axial gap type rotating electrical machine shown in FIG. 1 (a) is a rotor having a permanent magnet. The rotor 2 includes a rotor back yoke 11 and a rotor magnet 20, and the rotor magnet 20 is configured to be adhered 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 N pole 21 and a rotor magnet S pole 22. The rotor magnet N pole 21 and the rotor magnet S pole 22 in which the N pole and the S pole are paired are periodically arranged in the rotation direction. A rotor shaft hole 12 for fastening the shaft is formed in the center of the rotor 2.

In FIG. 1 (a), a ring-shaped disc-shaped magnet has a structure in which magnetic poles of 10 poles are arranged in a circumferential direction. One magnetic pole is fan-shaped and is arranged on the circumference at equal angular intervals. This magnetic pole is assembled as a rotor 2 in the form shown in FIG. 1 (a), and is then magnetized by an electromagnet called a magnetizing yoke to form such a magnetic pole. One pole at a time, or a plurality of divided magnets can be pasted to obtain the same rotor structure.

In one embodiment of the present invention, as shown in FIG. 1 (b), a plurality of grooves 13 are provided on the adhesive surface (joint surface) of the disk-shaped rotor back yoke 11 and the rotor disk 20. The figure shows a case where a plurality of concentrically-shaped grooves 13 are provided on the rotor disk 20 of the disk-shaped rotor back yoke 11 on the adhesive surface. A concentric groove 13 is formed so that a protrusion 113 is formed on the rotor back yoke 11. This groove 13 can reduce the eddy current caused by the change in the magnetic flux density caused by the energization of the stator coil.

FIG. 2 shows a configuration of a rotary electric machine according to an embodiment of the present invention. FIG. 2 (a) shows a configuration of an axial gap type rotating electrical machine. The axial gap type rotating electrical machine 1 is a device having two rotors in the axial direction. A rotor magnet 20 is arranged in each of the rotors 2.

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

The casing 14 holds the outer periphery of the stator 3. The shaft 17 is arranged to connect the rotors 2 on both sides in the axial direction, and outputs the shaft. Lead wires 19 are three-phase stator coils 18 which are electrically delta-connected or star-connected to form terminal portions.

Fig. 2 (b) schematically shows the flow of magnetic flux on a plane. The magnetic flux flowing from the rotor magnet N pole 21 of the rotor 2 flows through the stator core 15 in the axial direction and flows into the rotor magnet S 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 to the circumferential direction. It is known that the magnetic flux generated by a magnet is a fixed magnetic field. Therefore, although the magnetic field fluctuates little in the rotor back yoke 11, the magnetic flux density caused by the slots of the stator 3 and the influence of the stator winding current, etc. In the vicinity of the interface between the rotor magnet 20 and the rotor back yoke 11, a slight change in magnetic flux density is caused. For this reason, the rotor back yoke 11 generally uses a laminated core such as an electromagnetic steel plate in a radial type motor.

In the case of the axial gap type rotating electric machine, when a laminated iron core of an electromagnetic steel plate is used for the rotor back yoke 11, a structure in which the laminated iron core is laminated in a vertical direction with respect to the magnetic flux flow is required. For this reason, as shown in Patent Document 1 described previously, a rotor back yoke such as an electromagnetic steel plate core, an amorphous foil tape wound core, and the like, which are wound around the circumference, is required. These structures require an increase in the number of components, an increase in the number of man-hours, and a decrease in reliability. Therefore, a simpler structure is required. To this end, the eddy current is reduced by the trench structure shown previously.

Fig. 2 (c) shows a magnet shape of one pole of the axial gap type rotating electric machine. According to the magnetic flux line shown in FIG. 2 (b), the flow of the magnetic flux is a flow method which is separated from the center of the rotor magnet 20 by half in the left-right direction. Therefore, it is known that the magnetic flux of the rotor magnet 20 is the surface area of the magnetic pole Half of it flows to the next door. Therefore, the total amount of the magnetic flux can be expressed as the product of the magnetic flux density and the surface area. Therefore, the residual magnetic flux density Br of the rotor magnet 20 and the one-pole average average magnet perimeter l of the rotor magnet 20, the rotor The width W of the magnet 20 can be considered to be about W‧l / 2‧Br.

FIG. 2 (d) is a cross-sectional view showing a groove portion of a rotor back yoke. To create a magnetic circuit that allows the magnetic flux between adjacent magnets to flow, only the protrusion 113 should be used to prevent eddy currents. Therefore, the ratio of the height H of the protrusion 113, the protrusion 113, and the gap (groove 13) is At R, the total cross-sectional area of the protrusion 113 is H‧W‧R. When the material of the rotor back yoke 11 is iron, if the magnetic flux density is 2T, the magnetic flux that can flow is expressed as 2H‧W‧R. Considering that the previous magnetic flux of the rotor magnet 20 only flowed on the protrusion 113, it was found that it became a threshold of l‧Br <4H‧R The case of the system satisfies this.

In the example of the rotating electric machine shown in FIG. 2 (a), the rotor magnet 20 is a magnet having an outer diameter of 63 and an inner diameter of 9 or 10 poles. The average 1-pole average magnet circumference l at this time is about 14 mm. This magnet system uses a ferrite magnet, so the residual magnetic flux density Br is 0.45T, and when the distance between the protrusion 113 and the groove 13 is equal, R = 0.5, so the required height of the protrusion 113 is about 3 mm or more. . In the dimensional relationship of FIG. 2 (a), the protrusion 113 is made 3 mm or more, so that eddy current can be prevented.

FIG. 3 is a graph showing an experimental result for explaining the effect of a trench structure according to an embodiment of the present invention. In FIGS. 3 (a) to 3 (d), the induced voltage under the material and shape of the rotor back yoke (FIG. 3 (b)) and No load loss (Fig. 3 (a)), and the motor efficiency (Fig. 3 (d)) when the rotating electric machine was driven with the voltage fixed was measured. Fig. 3 (c) shows the relationship between the torque and the number of revolutions when the rotating electrical machine is driven with a fixed voltage.

The respective dimensional relationships are the shapes shown in FIG. 4. FIG. 4 is a cross-sectional comparative view of a structure explained with various structures described in FIG. 3. Fig. 4 (a) is a yoke using an electromagnetic steel plate or amorphous as the spiral iron core 10, Fig. 4 (b) is a yoke using solid iron, and Figs. 4 (c) and 4 (d) are using this A ditch constructor related to an embodiment of the invention.

Regarding the rotor yoke of an axial gap type rotating electric machine, a person using solid iron as a yoke and a person using an electromagnetic steel sheet to wind an iron core, There is no significant change in the actual value of the induced voltage, the shape of the waveform, and the like obtained by all the trench constructors according to one embodiment of the present invention. However, in terms of measurement results of no-load loss, the loss of the solid iron yoke and the grooved yoke is larger than that of the wound iron yoke of the electromagnetic steel sheet. This is due to the increase in yoke loss caused by changes in magnetic flux density due to slot harmonics.

In terms of efficiency when driving a rotating electric machine, the system is still the result of the highest efficiency of the electromagnetic steel sheet winding core and the lowest efficiency of the solid iron yoke. This is the effect of yoke loss caused by changes in the magnetic flux caused by the stator winding current. With regard to the grooved rotor yoke according to an embodiment of the present invention, it has been confirmed that the efficiency is improved as compared with a solid iron yoke, and there is an effect of reducing yoke loss. In terms of the relationship between the protrusion sizes, it was confirmed that the smaller the cross-sectional area of the protrusion, the more effective it was. According to the results of this experiment, the cross-sectional area of the protrusion is small compared to the surface area of the magnet, and the magnetic flux also passes through the solid part of the rotor yoke. Therefore, the loss reduction effect is small, but the cross-sectional area of the protrusion is the above ratio, so This electromagnetic steel sheet has an effect of reducing the loss like a wound core.

An example of a method of producing this protrusion structure is shown in FIG. 5. FIG. 5 is a conceptual diagram illustrating a forging manufacturing method according to an embodiment of the present invention. As described previously, a method of winding an iron core with an electromagnetic steel plate or the like causes an increase in manufacturing cost, a decrease in reliability, and the like. Therefore, the rotor yoke portion is preferably formed of a single body of the same material. However, since the post-processing increases the man-hours, it is necessary to use a one-time program. FIG. 5 shows a means for obtaining a structure according to an embodiment of the present invention from a blank by using forging by pressing.

FIG. 5 (a) shows the blank 31 as a material. quasi- It is a disc-shaped, iron-based material that can be used as a magnetic body. This material can be prepared inexpensively by punching or cutting out from a bar. Although iron is described below as an example, other alloys such as magnetic stainless steel, nickel alloy, and cobalt alloy may be used in addition to iron. .

As shown in FIG. 5 (b), this material is placed in a mold for plastic deformation and forging, and a forming force is applied to the mold to form a desired shape. In Fig. 5 (b), the base portion of a 32-series punching equipment. Acting die for 33 series stamping equipment. The 34 is a punch for forming a central hole in the upper die mounted on the movable die 33. 35 is a punch for forming the groove 13 of the upper die. At this time, since the punch 35 used as an upper die for forming a groove is thinner, it is necessary to provide strength for buckling and the like. Therefore, in the case of forming in this way, in order to increase the strength of the root of the punch, a structure is provided in which an R angle is applied to the root, and a demolding angle is applied as shown in FIG. It is ideal to take measures such as 10 ° in the middle. Therefore, the shape of the grooves when formed by this method is as shown in Fig. 5 (c). In this way, a plurality of grooves are formed by applying stress to 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 self-feeding combined pressing method according to an embodiment of the present invention. FIG. 6 shows a manufacturing method in which a hoop-shaped material passes through the first forming station 42 and the second processing station 43 and is repeatedly formed to obtain the final shape at the third processing station 44. Since this method can be made through a plurality of punching processes, there is an advantage that the punching process of the center hole can be performed to the final precision adjustment process.

In FIG. 6, 41 is a hoop-shaped iron material. The 42 series is the first forming station, and the 42 series of the first forming station performs the center hole processing. 43 is the second processing station. Here, the second processing station 43 performs processing for applying a support surface for securing the size of the holding magnet. The 44 series third processing station performs groove processing by plastic processing (forging processing) at the third processing station 44 series. In this way, separating each processing program makes it possible to obtain a high-quality (high-precision) product shape.

FIG. 7 shows another manufacturing method. FIG. 7 is a conceptual diagram illustrating a manufacturing method using a powder metallurgy method according to an embodiment of the present invention. Reference numeral 51 denotes iron powder arranged in a compression molding die. 52, which represents the bottom plate of the compression molding press equipment. The 53 series represents the moving die of the compression molding press equipment. Reference numeral 54 denotes a punching machine for compression molding mounted on the movable die 53.

A powder of iron capable of becoming a magnetic body is inserted into a lower mold having a cylindrical cylinder, and compression-molded using an upper punch that can be shaped into a grooved rotor yoke shape according to an embodiment of the present invention. Thereafter, the rotor yoke is obtained by firing. In this method, a member can be obtained by forming with a relatively low compressive force as compared with a method of obtaining a shape by the plastic deformation shown previously. It is temporarily formed into a relatively low density, so that the compressive force can be reduced, but due to sintering, iron can be combined with each other to shrink, so a high-density formed body is finally obtained. With this method, the depth, shape, and the like of the groove can be relatively freely formed.

In the manufacturing method shown above, the axial yoke type rotor yoke can be manufactured by molding. The adhesive surface of this series of magnets becomes On the surface side, in the case of a radial type motor, both the inner rotor type and the outer rotor type have a cylindrical surface, and thus the forming process is difficult.

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

Fig. 8 (a) shows an example in which the groove 13 is also included in the radial direction. In FIG. 8 (a), a plurality of grooves 13 are provided on the joint 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 occurrence of eddy current, the effect is higher when the system is finer cut, so the shape of the protrusion 113 is effectively reduced. Therefore, according to the above-mentioned magnetic flux flow method shown in FIG. 2 (b), the magnetic flux in the center of the magnetic pole of the rotor magnet 20 does not flow. Therefore, the radial groove 13 is included in this part, and the protrusion is projected. The 113 division allows subdivision of the protrusion 113 without hindering the flow of magnetic flux.

FIG. 8 (b) shows a form in which the width of the protrusion 113 is changed. Previously, although the magnetic flux was expressed as an average perimeter, the magnetic flux actually increased in the larger the diameter. For this reason, it is shown that the ratio R of the protrusions 113 to the grooves 13 is not made the same. Where the diameter is large, the width of the protrusions 113 is increased, or the length of the protrusions 113 is increased (the grooves 13 are made deep) to increase the flow. The structure of the amount of magnetic flux due to the protrusion 113.

FIG. 8 (c) shows a feature in which a shape can be produced in a single process by forging, powder metallurgy, or the like shown previously, and a guide portion 60 that holds the rotor magnet 20 is manufactured at the same time. With this structure, effects such as maintaining the anti-centrifugal strength of the rotor magnet 20 and improving the positioning accuracy of the rotor magnet 20 can be expected.

As shown in FIG. 8 (d), it is also shown on the rotor structure 20 side. Structure of the protrusion 213. In FIG. 8 (d), the rotor magnet 20 is provided, and a plurality of protrusions 213 are provided in a portion corresponding to the plurality of grooves 13 in the circumferential direction of the rotor back yoke 11. The rotor magnet 20 is also made by a mold in the case of a sintered magnet, and thus the protrusion 213 can be relatively easily formed. The magnet system is generally ground and processed to adjust its size. This process consumes man-hours, so portions with protrusions are used without being processed. The rotor back yoke 11 according to an embodiment of the present invention is also manufactured without post-processing without accuracy, and only one side is subjected to grinding processing, and the gap facing surface of the rotor magnet 20 with which accuracy is ensured is assembled as a reference for assembly It is formed by flowing a fixing member such as an adhesive between the rotor back yoke 11 and the rotor magnet 20. The surface of the rotor magnet 20 and the surface of the rotor back yoke 11 are concave and convex with each other, so that the bonding area can be largely ensured, and the strength can be improved.

Next, FIG. 8 (e) shows an example of a soft magnet in which the rotor magnet 20 is formed by injection molding. In FIG. 8 (e), the groove 13 attached to the rotor back yoke 11 is also a material in which a soft magnet is arranged by injection molding. The soft magnet is formed by being directly injection-molded into the rotor back yoke 11. Therefore, the number of man-hours and the loss can be reduced. Flexible magnets have a large resistivity, so magnet losses such as eddy currents can be reduced.

In FIG. 8 (f), when the manufacturing method according to an embodiment of the present invention is adopted, grooves 13, protrusions 113, and the like may be formed on the opposite surface of the rotor back yoke 11 from the adhesive surface of the rotor magnet 20. 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 joint surface of the rotor magnet 20. For this reason, since it receives wind as a rotating body, it is possible to obtain a high heat radiation effect as a heat sink. Rotor.

FIG. 9 shows a system use example of an axial gap type rotating electrical machine in a rotor shape according to an embodiment of the present invention. It can be installed in mechanical equipment such as pumps, fans, etc., or can be applied to flywheel devices, etc. It has low rotor loss and can achieve high motor efficiency, in other words, energy-saving products.

Claims (8)

An axial gap type rotating electric machine includes a rotor and a stator. The rotor includes a rotor back yoke and a rotor magnet. The rotor back yoke is a flat plate. In a circumferential direction of the rotor back yoke, A plurality of grooves are provided on a joint surface of the rotor magnet. For example, the axial gap type rotating electrical machine according to the first patent application range, wherein the rotor back yoke is disc-shaped, and stress is applied in a thickness direction of the rotor back yoke to form the plurality of grooves. For example, the axial gap type rotating electrical machine according to claim 1 or 2, wherein the rotor back yoke is formed of a soft magnetic material whose powder is solidified by compression molding or a soft magnetic material which is provided with irregularities by press molding. For example, the axial gap type rotating electrical machine according to the first or second patent application scope, wherein a plurality of protrusions are formed on the rotor back yoke by the plurality of grooves, so that the residual magnetic flux density of the rotor magnet is Br, and the rotor magnet is When the average length of the 1-pole average magnet is 1, the height of the plurality of protrusions is H, and when the ratio of the plurality of protrusions to the plurality of grooves is R, 1‧Br <4H‧R is satisfied. For example, the axial gap type rotating electrical machine according to item 1 or 2 of the patent application, wherein a plurality of grooves are provided in a radial direction of the rotor back yoke on a joint surface of the rotor back yoke with the rotor magnet. For example, the axial gap type rotating electrical machine according to item 1 or 2 of the patent application scope, wherein the rotor magnet is provided with a plurality of protrusions in a portion of the rotor back yoke in a circumferential direction corresponding to the plurality of grooves. For example, the axial gap type rotating electrical machine according to claim 1 or 2, wherein the rotor magnet is a soft magnet, and the soft magnet is arranged in a plurality of grooves in a circumferential direction of the rotor back yoke. According to the axial gap type rotating electrical machine according to the first or second aspect of the patent application, a plurality of surfaces of the rotor back yoke on a side opposite to a joint surface of the rotor magnet in the circumferential direction of the rotor back yoke are provided. ditch.