Axial air-gap electronic motor

In an axial air-gap electronic motor in which a stator is formed by a plurality of core members, the manpower for assembling the core member is reduced, and the motor is assembled in a shorter period of time. A hook portion 320, which is a first connecting means, is projectingly provided at one end in the circumferential direction of a flange portion 310 of each of the core members 21a to 21i, and a columnar locking shaft 330 to which the hook portion 320 is locked is provided at the other end in the circumferential direction of the flange portion 310, by which the core members 21a to 21i are connected to each other.

TECHNICAL FIELD

The present invention relates to an axial air-gap electronic motor in which a rotor and a stator are arranged so as to face to each other along the axis line direction of a rotor output shaft. More particularly, it relates to an axial air-gap electronic motor that requires less manpower for parts and is capable of being assembled easily in a short period of time.

BACKGROUND ART

As shown, for example, in Patent Document 1 (Japanese Patent Application Publication No. 2004-282989), an axial air-gap electronic motor is an electronic motor in which a rotor is arranged on one side surface or both side surfaces of a stator with a predetermined air gap being provided therebetween, and is characterized in that the thickness in the rotating shaft direction can be decreased, namely, the motor can be made flat as compared with a radial gap electronic motor of, for example, an inner rotor type.

The axial air-gap electronic motor described in Patent Document 1 is configured so that the stator is formed by a plurality of fan-shaped core members connected to each other in a ring form. According to this configuration, the stator can be formed easily by winding a coil in advance on one core member and by merely connecting the core members in a ring form and performing wire connection.

In such a stator construction, the core members have conventionally been assembled into a ring shape by fitting a concave portion provided in one end portion of the flange portion of the core member on a boss provided in the other end portion of the flange portion of the adjacent core member. However, since this assembling process is a temporary one for putting the core members in a mold for the next resin molding, the core members are easily disconnected by a slight shock.

Also, after the coil has been wound on the core member, the coil pulled out of each core member must be connected for each phase, which presents a problem in that the wire connecting work and the jumper wire treatment require much time and labor.

SUMMARY OF THE INVENTION

Accordingly, a problem of the present invention is that in an axial air-gap electronic motor in which a stator is formed by a plurality of core members, the manpower for assembling the core member is decreased, and the motor is assembled in a shorter period of time.

To solve the above-mentioned problem, the present invention has several features described below. The present invention provides an axial air-gap electronic motor in which a stator and a rotor are arranged so as to face to each other along the axis line direction of a rotor output shaft of the rotor with a predetermined air gap being provided therebetween, and the stator has a plurality of core members arranged in a ring form with the axis line of the rotor output shaft being a center, the core members being connected to each other via a predetermined connecting means, wherein each of the core members is formed into a bobbin shape having a stator iron core and an insulator for insulating a winding portion of the stator iron core; the insulator has a pair of flange portions that are parallel with each other along a teeth surface of the stator iron core; a hook portion, which is a first connecting means, is projectingly provided at one end in the circumferential direction of the each flange portion; and a columnar locking shaft to which the hook portion of the adjacent core member is locked is projectingly provided at the other end in the circumferential direction of the flange portion.

According to this configuration, since the hook portion provided in the flange portion of the insulator of a stator core is locked to the locking shaft provided in the flange portion of the insulator of the adjacent stator core, the stator cores can be connected firmly to each other.

The hook portion and the locking shaft are preferably provided on the outer periphery side of the flange portion, and on the inner periphery side of the flange portion, there is preferably provided a second connecting means including a locking convex portion provided at one end in the circumferential direction of the flange portion and a locking concave portion that is provided at the other end in the circumferential direction of the flange portion and engages with the locking convex portion.

According to this configuration, since the first connecting means consisting of the hook portion and the locking shaft is provided on the outer periphery side of the flange portion, and the second connecting means consisting of the locking convex portion and the locking concave portion is provided on the inner periphery side of the flange portion, the accuracy in assembling the stator core can be enhanced.

The flange portion is preferably provided with a guide portion for guiding the hook portion to the locking shaft, and the guide portion is preferably provided with a holding portion for holding a part of the hook portion together with the locking shaft.

According to this configuration, since the guide portion for guiding the hook portion to the locking shaft is provided, and the hook portion is held together with the locking shaft by a part of the guide portion, the hook portion can be guided surely to the locking position of the locking shaft, and the locked state can be maintained.

The guide portion preferably consists of a concave portion formed by recessing a part of the flange portion in the axis line direction of the rotor output shaft, and the holding portion preferably consists of a height difference surface formed between the guide portion and the flange portion.

According to this configuration, since the guide portion is formed by recessing a part of the flange portion, and the hook portion is held by utilizing the height difference surface, not only the hook portion can be guided easily, but also the manpower for parts and the material cost can be reduced.

The surface-to-surface distance of the inner surface of the hook portion is preferably a little smaller than the surface-to-surface distance of the guide portion.

According to this configuration, since the surface-to-surface distance of the hook portion is a little smaller than the surface-to-surface distance of the guide portion, the each guide portion can be held by the each hook portion, so that the core members can be connected more firmly.

The hook portion preferably has an arcuate hook groove locked along the locking shaft, and the core members are preferably connected to each other so as to be turnable around the locking shaft via the hook groove.

According to this configuration, since the hook groove locked along the locking shaft is provided, the core members can be connected while being turned in the state in which the hook portion is hooked to the locking shaft.

The each flange portion is preferably provided with a cylindrical portion for erecting a terminal pin, to which both ends of a coil wound around the winding portion are connected by being entangled individually, substantially perpendicularly from the flange portion.

According to this configuration, since first and second cylindrical portions for directly holding the terminal pin by which the coil is entangledly connected in the flange portion, both ends of the coil after assembly are connected entangledly to the each terminal pin, so that not only the wire connection can be performed easily but also the assembly of the motor itself can be performed easily.

Preferably, the locking shaft is also used as the cylindrical portion. According to this configuration, since the locking shaft is also used as either of the first and second cylindrical portions, the motor can be manufactured at a lower cost.

The locking shaft and/or the cylindrical portion are preferably provided with a reinforcing rib for reinforcement. According to this configuration, since the reinforcing rib is provided at the outer periphery of the cylindrical portion and/or the locking shaft, the strength decreased by the decrease in thickness of the flange portion can be compensated, and also the cylindrical portion and/or the locking shaft can be prevented from being thermally distorted at the time of resin molding.

The flange portion is preferably provided with a positioning portion for providing relative positioning between a mold and the core members when a resin compact is integrally molded in a state in which the core members are connected to each other in a ring form.

According to this configuration, since the positioning portion at the time of resin molding in a part of the flange portion is provided, the positioning of stator of the motor can be performed at a time merely by performing the relative positioning between the stator core and the mold.

Each of the core members is preferably provided with a positioning means for arranging the core members along a predetermined rotating shaft with the teeth surfaces of the flange portions facing to each other.

According to this configuration, since the plurality of stator cores are arranged so that the teeth surfaces face to each other, and the coil can be wound in one turn from one end to the other end, time required for wire connection and assembly can be shortened.

The insulator is preferably provided with a winding protective portion for covering a part of the side surface of the stator iron core to prevent a jumper wire set between the core members from coming into direct contact with the stator iron core.

According to this configuration, since the winding protective portion for covering a part of the side surface of the stator iron core is provided in a part of the insulator, the jumper wire of winding can surely be prevented from coming into direct contact with the stator iron core and being broken or damaged.

DETAILED DESCRIPTION

An embodiment of the present invention will now be described with reference to the accompanying drawings. The present invention is not limited to this embodiment.FIG. 1is a sectional view of an essential portion of an axial air-gap electric motor in accordance with one embodiment of the present invention.FIGS. 2A and 2Bare front and side views of a stator, respectively, andFIG. 3is a perspective view of the stator.

This axial air-gap electric motor1has a stator2embedded in a resin compact200and a pair of rotors3arranged so as to face to both side surfaces of the stator2with a predetermined air gap being provided. The rotors3are fixed coaxially on a rotor output shaft4for delivering a rotational driving force.

The stator2is formed in a ring shape with the axis line of the rotor output shaft4being the center, and is integrally molded together with the resin compact200by insert molding. At both ends of the resin compact200, lid members10aand10bare installed to close both ends of the resin compact200.

At both ends of the resin compact200, there are provided first and second storing sections220and230for storing various motor mechanism portions including the rotors3.

The first storing section220(the left-hand side inFIG. 1) consists of a concave portion recessed along the axis line direction of the rotor output shaft4, and on the bottom surface of the concave portion, teeth surfaces22on one side of core members21ato21iof the stator2are exposed. InFIG. 3, the teeth surfaces22are omitted for the configuration of drawing.

As shown inFIG. 3, the first storing section220is formed into a step shape having three inner peripheral surfaces (a first inner peripheral surface221, a second inner peripheral surface222, and a third inner peripheral surface223) whose inside diameters decrease stepwise from the outside toward the inside.

Between the first inner peripheral surface221and the second inner peripheral surface222, a first height difference surface224that is horizontal along the teeth surface22is provided. As shown inFIG. 1, the first height difference surface224is a support surface for supporting the outer peripheral edge of the lid member10a, and the lid member10ais attached horizontally along the first height difference surface224together with the first inner peripheral surface221.

Between the second inner peripheral surface222and the third inner peripheral surface223, a similarly horizontal second height difference surface225is provided. The second height difference surface225is a support surface for supporting a circuit board5for driving the motor, and is formed one step lower than the first height difference surface224.

As shown in a partially enlarged view ofFIG. 4, on the second height difference surface225, the tip end portions of terminal pins6provided on the stator2are projectingly provided. The terminal pins6are erected substantially perpendicularly from flange portions310of the core members21ato21iof the stator2, and to a part thereof, the start end and the termination end of a coil250are connected in an entangled state respectively.

The terminal pins6are provided in a set of two at three places (a total of six places) for each phase (U phase, V phase, and W phase) of the electric motor. In this example, the terminal pins6are erected from the core members21a,21dand21grespectively.

According to this configuration, as shown inFIG. 1, by mounting the circuit board5along the second height difference surface225, the terminal pins6can be inserted directly in insertion holes, not shown, provided in the circuit board5.

As a more preferred mode, it is preferable that the periphery of the terminal pins6on the second height difference surface225has a recessed portion228which is one step lower from the second height difference surface. According to this configuration, a portion formed into a convex shape by a synthetic resin440entering into a portion around the terminal pin6at the time of insert molding because of insufficient seal between the mold and the pin can be prevented from rising to a convex shape, so that the circuit board5can surely be mounted horizontally.

Also, it is preferable that a part of the second inner peripheral surface222, which is adjacent to the terminal pin6, is further recessed in the radial direction, thereby forming a further recessed portion229. According to this configuration, a short circuit from the tip end of the terminal pin6toward the lid member10acan be prevented.

The second height difference surface225is further formed with guide holes226. As shown inFIG. 5, the guide hole226is formed by insert molding by inserting a guide pin, not shown, in a guide hole361in a positioning portion360provided on the core member21a,21d,21gwhen the stator2is insert molded.

On the second height difference surface225, locking claws227are provided which coincide with notch portions, not shown, provided in the circuit board5and are used to position the circuit board5with respect to the stator2. The locking claw227is provided so as to project toward the inside, and, in this example, is provided at three places at a predetermined angle.

The second storing section230(the right-hand side inFIG. 1) consists of a concave portion recessed along the axis line direction of the rotor output shaft4, and on the bottom surface of the concave portion, teeth surfaces22on the other side of core members21ato21iof the stator2are exposed.

The second storing section230is formed into a step shape having two inner peripheral surfaces (a first inner peripheral surface231and a second inner peripheral surface232) whose inside diameters decrease stepwise from the outside toward the inside.

Between the first inner peripheral surface231and the second inner peripheral surface232, a first height difference surface233that is horizontal along the teeth surface22is provided. As shown inFIG. 1, the first height difference surface233is a support surface for supporting the outer peripheral edge of the other lid member10b, and the lid member10bis attached horizontally along the first height difference surface233together with the first inner peripheral surface231.

In the central portion of the stator2is arranged a bearing section240. In this example, the bearing section240has a pair of radial ball bearings241and242, the inner race thereof being press fitted in the rotor output shaft4, and the outer race side being embedded in the resin compact200. In the present invention, the configuration of the bearing section240may be arbitrary.

In each of the first and second storing sections220and230, a disc-shaped rotor3is arranged so as to be rotatable. The rotor3is provided with a rotor magnet32on the surface facing to the stator2of a disc-shaped rotor back yoke31. On the surface opposite to the surface facing to the opposite stator2(on the circuit board5side) of a disc-shaped rotor back yoke31, a position detecting magnet33is provided which serves as a detected portion of a position detecting sensor51mounted on the circuit board5.

In the present invention, the rotor3may have an arbitrary shape if it has a basic configuration for an axial air-gap electric motor. In this example, the rotors3are arranged on both right and left sides of the stator2; however, the rotor may be arranged only on one side.

Further, although the rotors3has the same rotor output shaft4in common, a two-output shaft type may be used in which each of the rotors3has a respective rotor output shaft. Also, a shaft-less type may be used in which the rotors3are directly supported on the stator2via a radial ball bearing without the use of the rotor output shaft4.

Next, the stator2is explained.FIG. 6is a perspective view of the stator2, andFIGS. 7A and 7Bare front and side views of a stator core, respectively.FIGS. 8A and 8Bare perspective views of a core member,FIG. 9Ais a front view of the core member,FIG. 9Bis a back view,FIG. 9Cis a plan view,FIG. 9Dis a bottom view,FIG. 9Eis a side view, andFIG. 9Fis a sectional view taken along the line A-A.

As shown in these figures, the stator2includes the plurality of (in this example, nine (nine-slot)) core members21ato21iarranged in a ring form with the rotation axis line of the rotor output shaft4being the center axis. Since the core members21ato21ihave the same construction, in this example, the core member21ais explained as an example.

As shown inFIGS. 8A and 8B, the core member21ahas a bobbin-shaped stator iron core23having a pair of right and left flange-shaped teeth surfaces22, and the coil250(refer toFIG. 1) is wound on the stator iron core23. The stator iron core23is formed by laminating H-shaped magnetic steel sheets in the radial direction.

In this example, at both ends of the teeth surface22of the stator iron core23, a skew tilted at a predetermined angle is formed in the circumferential direction to reduce cogging torque. The shape of the teeth surface22, including the presence of the skew, is selected arbitrarily according to the motor specification.

The whole of the stator iron core23excluding the teeth surfaces22is covered by an insulator300consisting of an insulating resin. The insulator300has the flange portions310extending in the radial direction along the teeth surfaces22. These flange portions310also form a part of the bobbin on which the coil250is wound.

Each of the flange portions310is provided with two connecting means for connecting the core members21ato21ito each other. First, as a first connecting means, in the end portions in the circumferential direction of the flange portions310, there are provided hook portions320for connecting the core members21ato21ito each other in a ring form with the rotor output shaft4being the center and locking shafts330to which the hook portions320are locked.

Referring additionally to partially enlarged views ofFIGS. 10A and 10B, the hook portion320is a convex portion provided so as to project from one end portion in the circumferential direction (the right end inFIG. 10A) toward the outside on the outer periphery side of the flange portion310, and on the upper end face of the hook portion320, there is provided a hook groove321locked along the locking shaft330.

The hook groove321consists of an arcuate groove locked along the outer peripheral surface of the locking shaft330. By locking the hook groove321to the locking shaft330of the adjacent core member21ato21i, the core members21ato21iare turnably connected to each other with the locking shaft330being the center.

The hook portion320is provided with first to third guide surfaces322to324for locking the hook portion320to the locking shaft330smoothly. The first guide surface322consists of a taper surface formed slantwise right downward (refer toFIG. 10A) from the edge of the hook groove321toward the tip end.

The second guide surface323consists of a taper surface formed slantwise left downward (refer toFIG. 10A) from the tip end of the first guide surface322toward the flange portion310side, and the third guide member324consists of a taper surface formed slantwise left upward (refer toFIG. 10A) from the end portion of the second guide surface323toward the proximal end of the flange portion310.

In the root portion between the third guide surface324and the flange portion310, there is provided a rounded portion325which comes into contact along a guide portion350when both ends of the core members21ato21iare finally connected after the core members21ato21ihave been connected to each other.

The locking shaft330is provided so as to project to the other end side in the circumferential direction on the outer periphery side of the flange portion310(the end portion on the side opposite to the hook portion320), and is integrally formed on the flange portion310in a columnar form. In this example, the locking shafts330are provided coaxially with the flange portion310being held therebetween.

Of the locking shafts330, one (the front side inFIG. 8B) of the locking shafts330is provided with a support hole331with a predetermined depth along the axial direction. The support hole331consists of an insertion hole for erecting the terminal pin6, and the terminal pin6is erected substantially perpendicularly in the support hole331.

One of the locking shafts330is provided with a reinforcing rib332for compensating the strength of the flange portion310including the locking shaft330lowered by decreased thickness of the guide portion350. In this example, the reinforcing rib332is provided at a position not subjected to an intervention by the hook portion7, namely, on the upper surface side of the locking shaft330. The other of the locking shafts330consists of a simple columnar body.

Although the reinforcing rib332is provided on only one of the locking shafts330, it is a matter of course that the reinforcing rib332may be provided on both of the locking shafts330. Also, the shape and the number of the reinforcing ribs332can be changed arbitrarily if the position thereof does not interfere with the locking position of the hook portion320.

As a preferable mode, as shown inFIG. 9C, the surface-to-surface distance L2between the inner surfaces of the hook portions320is made shorter than the surface-to-surface distance L1between the guide portions350of the flange portions310.

According to this configuration, by installing the hook portions320on the flange portions310, the hook portions320can be fixed more firmly by supporting the flange portions310held therebetween.

In this example, the first connecting means connects the core members21ato21ito each other by locking the hook groove321of the hook portion320to the locking shaft330. Besides, as shown inFIGS. 12A and 12B, the configuration may be such that a convex portion326is provided on the inside in the axial direction of the hook portion320, and a concave portion380is provided in the guide portion350of the flange portion310, by which the convex portion326is fitted in the concave portion380. Although the convex portion326and the concave portion380are formed into a round shape, these portions may have a polygonal shape.

The flange portion310is provided with a locking convex portion341serving as a second connecting means and a locking concave portion342for receiving the locking convex portion341. The locking convex portion341is a convex portion provided so as to project to the outside from one end portion (the right-hand side surface inFIG. 9A) in the circumferential direction of the flange portion310, and, in this example, consists of a tongue element formed into a triangular shape.

On the other hand, the locking concave portion342consists of a notch portion formed so as to be directed toward the inside from the other end portion (the left-hand side surface inFIG. 9A) in the circumferential direction of the flange portion310, and is formed as a triangular shape coinciding with the locking convex341.

In this example, the locking convex portion341and the locking concave portion342are formed into a triangular shape. However, the shape thereof can be changed arbitrary according to the motor specification such as a square or semicircle shape if the shape is such as to be capable of connecting the core members21ato21ito each other in a ring form.

According to this configuration, by engaging the locking convex portion341and the locking concave portion342with each other together with the first connecting means, the pole members21ato21ican be connected to each other in a ring form surely with high accuracy.

As shown inFIGS. 10A and 10B, the flange portion310is further provided with the guide portion350for guiding the hook portion320to the locking shaft330.

The guide portion350consists of a concave portion formed by recessing a part of the flange portion310in the axis line direction of the rotor output shaft4. In a boundary portion between the guide portion350and the flange portion310, a height difference surface351is provided to guide the hook portion320and also to hold a part of the hook portion320together with the locking shaft330.

A part of the height difference surface351is formed into a step shape, and a holding portion352is formed to support the hook portion320by holding it between the locking shaft330and the height difference surface351. According to this configuration, the height difference surface351comes into contact with a part of the hook portion320, by which the hook portion320can be fixed firmly by being held together with the locking shaft330.

As shown inFIGS. 10A and 11B, the flange portion310is provided with a positioning portion360for providing relative positioning between the mold and the core members21ato21iwhen the resin compact200is integrally molded by insert molding after the core members21ato21ihave been connected in a ring form.

The positioning portion360consists of a cylindrical boss projectingly provided in a substantially central portion at the upper end of one flange portion310, and in the center thereof is provided a guide hole361into which a guide pin, not shown, is inserted. The bottom portion of the guide hole361is formed into a conical shape to facilitate the introduction of the guide pin.

In the flange portion310on the front side shown inFIG. 11A, a cylindrical portion370in which the other terminal pin6is erected is further provided. The cylindrical portion370is provided with a support hole371for erecting the terminal pin6so that the terminal pin6is erected substantially perpendicularly via the support hole371.

The flange portion310on the front side shown inFIG. 11Bis also provided with a cylindrical portion373having the same shape as that of the cylindrical portion370. However, the cylindrical portion373consists simply of a columnar body, and is projectingly provided coaxially with the cylindrical portion370with the flange portions310being held therebetween. The cylindrical portion370is provided on a concentric circle with the center axis of the rotor output shaft4being the center.

The flange portion310further has a first positioning portion410and a second positioning portion420as positioning means for arranging the core members21ato21ialong a predetermined horizontal rotating shaft with the teeth surfaces22of the flange portions310facing to each other.

The first positioning portion410has a pair of positioning ribs411and412provided on the outer periphery side of the flange310, and each of the positioning ribs411and412consists of a rectangular plate body provided so as to project perpendicularly from the flange portion310. The positioning ribs411and412are arranged in a state of being shifted relatively in the circumferential direction and the radial direction of the stator2on the flange portion310.

The second positioning portion420has a pair of positioning ribs421and422provided on the inner periphery side of the flange portion310, and each of the positioning ribs421and422consists of a rectangular plate body provided so as to project perpendicularly from the flange portion310. The positioning ribs421and422are also arranged in a state of being shifted relatively in the circumferential direction and the radial direction of the stator2on the flange portion310.

According to this configuration, by engaging the positioning ribs411and412with each other with the teeth surfaces22of the adjacent core members (for example,21aand21b) facing to each other, as shown inFIG. 13, the core members21ato21c(21dto21f,21gto21i) are arranged for each phase along the horizontal rotating shaft O, and thus the coil250can be wound on the core members21ato21cin one turn without being cut.

On the upper end side of the flange portion310, receiving portions390are provided which receive the tip ends of the locking shaft330and the positioning portion360when the teeth surfaces of the core members21ato21iare caused to butt together as shown inFIG. 13.

The receiving portion390consists of a concave portion formed into a U shape on the upper end side of the flange portion310, and the tip ends of the locking shaft330and the positioning portion360are locked to the receiving portions390. In this example, the receiving portion390consists of the concave portion; however, the receiving portion390may be a boss or the like.

As shown inFIG. 13, on one end side in the circumferential direction of the flange portion310, there is provided a winding protective portion430for covering the side surface of the teeth surface22of the stator iron core23from which the flange portion301projects.

The winding protective portion430consists of a rib erected along the side surface of the teeth surface22so that the side surface of the teeth surface22is covered by the rib. According to this configuration, as shown inFIG. 13, a jumper wire set between the core members21ato21ican be prevented from being broken or damaged by a direct contact with the stator iron core23when the coil250is wound in one turn.

Next, one example of a connecting procedure for the core members21ato21iis explained with reference toFIGS. 14A to 14Cand15A to15D. First, as shown inFIG. 14A, the hook groove321in the hook portion320of the core member21ais hooked to the locking shaft330of the adjacent core member21b.

Then, as shown inFIG. 14B, the core member21bis turned to the core member21aside around the locking shaft330in the state in which the hook portion320is hooked to the locking shaft330. Therefore, the tip end portion of the hook portion320passes through the holding portion352formed between the locking shaft330and the height difference surface351while being turned.

When the core member21bis further turned to the core member12aside, as shown inFIG. 14C, the locking concave portion342of the core member21bis inserted toward the locking convex portion341of the core member21a, which is the second connecting means, by which the core member21aand the core member21bare connected to each other. At this time, the holding portion352acts as a stopper to restrain the tip end of the hook portion320, by which the movement of the core member21ain the arrow-marked direction is regulated.

A series of operations described above are repeated for each of the core member21ato21i. Finally, the end portion of the core member21ais connected to the end portion of the core member21i. As shown inFIG. 15A, the tip end portion of the hook portion320of the core member21iis brought into contact with the locking shaft330of the core member21a.

When the hook portion320is pushed into the locking shaft330side in the state in which the hook portion320is in contact, as shown inFIG. 15B, the hook portion320is pushed into the lower side of the locking shaft330along the first guide surface322(refer toFIG. 10A).

When the hook portion320is further pushed in, as shown inFIG. 15C, the second guide surface323of the hook portion320comes into contact with the height difference surface351, and a part of the third guide surface324comes into contact with a corner portion of the teeth surface22, so that the hook portion320passes through a narrow portion between the locking shaft330and the holding portion351while being deformed elastically.

Then, when the hook portion320is further pushed in, as shown inFIG. 15D, the hook portion320is pushed in while the rounded portion325of the third guide surface324is guided along the edge of the teeth surface22. Finally, the locking groove321of the hook portion320fits along the locking shaft330. Thereby, the movement of the tip end of the hook portion320is regulated by the holding portion351, so that the circular shape can be kept. By the series of operations described above, the core members21ato21iare assembled into a ring shape.

The assembled stator2is attached to a special-purpose insert mold (not shown). At this time, guide pins of the mold is caused to coincide with the guide holes361in the positioning portions360of the core members21ato21i, by which the relative positioning between the mold and the stator2can be performed. By this positioning work, not only the positioning of the stator2with respect to the resin compact200but also the relative positioning between the rotors3and the circuit board5can be performed.

After the assembly in the mold has been finished, molten resin is poured into the mold, and the resin compact200is integrally molded. After the bearing section240has been attached to the stator2and the rotors3have been assembled thereto, the circuit board5is fixed on the second height difference surface225of the first storing section220, and the insertion holes in the circuit board5and the terminal pins6are soldered to each other.

After the insulating sheet (not shown) has further been put on the circuit board5, the lid members10aand10bare installed finally on both surfaces of the resin compact200, by which the axial air-gap electric motor1as shown inFIG. 1is completed.

In this embodiment, the axial air-gap electric motor1is of a 9-slot 8-pole type in which the stator2has nine slots and each of the rotors3has eight poles. However, the number of slots of the stator2and the number of poles of the rotor3can be changed arbitrarily according to the motor specification.

The present application is based on, and claims priority from, Japanese Applications Serial Number JP2005-192959, filed Jun. 30, 2005 the disclosure of which is hereby incorporated by reference herein in its entirety.