Electric-motor rotor, electric motor, and air conditioner

To provide an electric-motor rotor including a cylindrical yoke, a resin magnet portion that is formed from resin magnet integrally with the outer periphery of the yoke, a position-detecting magnet that is located on one axial-end side of the resin magnet portion, a plurality of seats that are formed on the axial end surface of the yoke on the side of the position-detecting magnet, each of which includes a pair of protruding portions, and an opening formed between the protruding portions, and a seat connecting portion that is formed with the seats on its top surface, wherein a ribbed runner that supplies the resin magnet to the resin magnet portion through the opening is provided at the opening to form, along with the seat, a seat portion that places thereon the position-detecting magnet.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. national stage application of International Patent Application No. PCT/JP2013/078330 filed on Oct. 18, 2013, the disclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electric-motor rotor, an electric motor, and an air conditioner.

BACKGROUND

Patent Literature 1 discloses an electric-motor rotor including a yoke, a resin magnet portion formed integrally with the outer periphery of the yoke, a position-detecting magnet provided at one axial end of the resin magnet portion, and seats formed at the axial end of the yoke on the position-detecting magnet side, each of which includes a pair of protruding portions, and an opening formed between the pair of protruding portions, wherein the resin magnet portion is molded from resin magnet supplied from a donut-shaped runner that protrudes axially outward from the axial end surface of the yoke on the position-detecting magnet side, and that is positioned on the inner side of the yoke, and from ribbed runners that extend radially outward from the donut-shaped runner, and each of the ribbed runners uses the opening of the seat as a resin-magnet supply path, and is also integrated with the seat to form a seat portion. It is described in Patent Literature 1 that due to the configuration as described above, improvement in the quality of the seat portion on which the position-detecting magnet is set in place, and the quality of a position-detecting-magnet holding protrusion that holds the outer periphery of the position-detecting magnet is achieved.

PATENT LITERATURE

However, in the electric-motor rotor described in Patent Literature 1, when the resin magnet portion and the position-detecting magnet are distanced from each other in the axial direction, the seats to be formed on the yoke are elongated. This makes it difficult to mold the seats. Also, because the opening of the seat is larger-sized, the required amount of resin magnet is increased, which is more costly.

SUMMARY

The present invention has been achieved to solve the above problems, and an object of the present invention is to provide an electric-motor rotor, an electric motor, and an air conditioner that make it possible to improve the quality of the rotor by facilitating formation of seats, and that also make a cost reduction possible by reducing a required amount of resin magnet.

According to an aspect of the present invention in order to solve the above-mentioned problems and achieve the object, there is provided an electric-motor rotor including: a cylindrical yoke; a resin magnet portion that is formed from resin magnet integrally with an outer periphery of this yoke; a position-detecting magnet that is located on one axial-end side of this resin magnet portion; a plurality of seats that are formed in a circumferential direction on an axial end surface of the yoke on a side of the position-detecting magnet, each of which includes a pair of protruding portions, and an opening formed between the pair of protruding portions, and places the position-detecting magnet on the pair of protruding portions; and a seat connecting portion that is formed on the axial end surface, that is formed with the seats on a top surface of the seat connecting portion, and that connects the seats, wherein a runner that supplies the resin magnet to the resin magnet portion through the opening is provided at the opening to form, along with the seat, a seat portion that places thereon the position-detecting magnet.

According to the present invention, it is possible to provide an electric-motor rotor, an electric motor, and an air conditioner that make it possible to improve the quality of the rotor by facilitating formation of seats, and that also make a cost reduction possible by reducing a required amount of resin magnet.

DETAILED DESCRIPTION

Exemplary embodiments of an electric-motor rotor, an electric motor, and an air conditioner according to the present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments.

First Embodiment

FIG. 1is a vertical cross-sectional view illustrating a configuration of an electric-motor rotor according to a first embodiment of the present invention.FIG. 2is a side view illustrating the configuration of the electric-motor rotor according to the present embodiment.

Specifically,FIG. 2is a side view as viewed from the position-detecting magnet side.FIG. 1is a cross-sectional view taken along a line A-A inFIG. 2.FIG. 3are diagrams illustrating a configuration of a yoke, whereFIG. 3(a)is a side view as viewed from the opposite side to the position-detecting magnet,FIG. 3(b)is a cross-sectional view taken along a line B-B inFIG. 3(a), andFIG. 3(c)is a side view as viewed from the position-detecting magnet side.FIG. 4are diagrams illustrating a configuration of a rotor magnet with a donut-shaped runner, whereFIG. 4(a)is a side view as viewed from the opposite side to the position-detecting magnet,FIG. 4(b)is a cross-sectional view taken along a line C-C inFIG. 4(a), andFIG. 4(c)is a side view as viewed from the position-detecting magnet side.FIG. 5are diagrams illustrating a configuration of the rotor magnet after the donut-shaped runner is removed, whereFIG. 5(a)is a side view as viewed from the opposite side to the position-detecting magnet,FIG. 5(b)is a cross-sectional view taken along a line D-D inFIG. 5(a), andFIG. 5(c)is a side view as viewed from the position-detecting magnet side.FIG. 6is a vertical cross-sectional view illustrating a configuration of an electric motor according to the present embodiment. With reference toFIGS. 1 to 6, the electric-motor rotor and the electric motor according to the present embodiment are described below.

An electric-motor rotor100according to the present embodiment relates to a rotor that is formed by molding a resin magnet portion5integrally with the outer periphery of a yoke4that is obtained by molding thermoplastic resin that contains soft magnetic material or ferrite.

The rotor100is molded by setting a shaft (an axis)1, a rotor magnet3, and a position-detecting magnet11in a resin-molding die, and then pouring thermoplastic resin17such as polybutylene terephthalate (PBT) into the resin-molding die.

After the molding, a bearing410(for example, a ball bearing (seeFIG. 6)) is mounted to each side of the rotor magnet3. In the following descriptions, the rotor100, in which the number of magnetic poles is ten, is explained as an example. However, the number of magnetic poles is not limited to ten, and can be any even number. The rotor100is combined with a stator300described later to constitute a brushless DC motor, for example.

The bearing410contacts a surface19that is in contact with, and retains, a cylindrical shaft-outer-peripheral cylinder resin portion31that is formed from the thermoplastic resin17around the outer periphery of the shaft1. A diamond knurl2is given on a portion of the shaft1, which is in contact with the inner-diameter portion of the shaft-outer-peripheral cylinder resin portion31. The diamond knurl2is sometimes simply referred to as “knurl”. The diamond knurl2has a shape of knurled grooves that are given on the outer periphery of mainly a round object (the shaft1in this example), and functions as an anti-skid member. For example, in any non-visible section, mainly the diamond knurl2increases the friction coefficient in a connection portion of a press-fit component (an insert), or engages the knurls in an inner-diameter portion, and is used as an anti-skid and anti-rotation member.

The rotor magnet3and the position-detecting magnet11are described later in detail. First, molding of the rotor100using the thermoplastic resin17such as PBT is described.

Into a lower die (not illustrated) that is set in place in a vertical molding machine (not illustrated), the rotor magnet3is inserted starting from the axial end surface of the yoke4on which concave portions6are provided (the axial end surface on the opposite side to the axial end surface to which the position-detecting magnet11is attached), and then the rotor magnet3is mounted to the lower die.

The lower die includes a convex portion (not illustrated) that is fitted into a tapered notch7provided on the axial end surface of the yoke4on the side of the concave portions6. At the time of fastening the die, the convex portion on the lower die (a core portion) is pressed against the notch7in order to ensure that the outer periphery of the resin magnet portion5is coaxial with the shaft1.

The notch7is provided corresponding to (opposed to) a magnetic pole. Therefore, ten notches7are formed in the circumferential direction with a substantially equal spacing. The reason for providing the notch7corresponding to (opposed to) a magnetic pole is to form a substantially identical magnetic path of the yoke4to each magnetic pole.

The number of convex portions on the lower die, to be fitted into the notches7, is five in this case. These five convex portions are respectively fitted into five (with a substantially equal spacing in the circumferential direction) of the ten notches7. It is adequate that the rotor magnet3is inserted into the lower die starting from the axial end surface of the yoke4on which the concave portions6are provided, and at the time of mounting the rotor magnet3to the lower die, any five of the ten notches7in the yoke4fit therein the five convex portions on the lower die. This is effective to improve workability as compared to the case with five notches7.

Further, at the time of molding when the thermoplastic resin17is filled, the shaft1is set at the center of the rotor magnet3in the lower die. The shaft1is given the diamond knurl2that serves as an anti-rotation member for the shaft-outer-peripheral cylinder resin portion31.

Furthermore, on seat portions50of the rotor magnet3, the position-detecting magnet11is set in place. Thereafter, the die is closed, into which the thermoplastic resin17such as PBT is injected and molded.

While the position-detecting magnet11is described later in detail, the position-detecting magnet11includes a step at each axial end on the inner-diameter side, and is symmetrical in the thickness direction. Due to the configuration as described above, at the time of attaching the position-detecting magnet11to the rotor magnet3, the step on the axial-end side (the outer side) of the rotor magnet3is filled with the thermoplastic resin17such as PBT. This is effective to stop the position-detecting magnet11from slipping off in the axial direction.

A step is provided at each end of the position-detecting magnet11in its thickness direction. Therefore, the position-detecting magnet11can be attached to the rotor magnet3regardless of which is the outer or inner side. However, it is also adequate that a step is provided only on one side of the position-detecting magnet11in its thickness direction, and the step-side is positioned on the axial-end side (the outer side) of the rotor magnet3.

The position-detecting magnet11includes a rib (not illustrated) that serves as an anti-rotation member when the step is filled with the thermoplastic resin17.

It is assumed that the position-detecting magnet11is in a state of being set on the seat portions50of the rotor magnet3. Into the lower die, the rotor magnet3is inserted starting from the axial end surface of the yoke4on which the concave portions6are provided, and is then mounted to the lower die. Therefore, the axial end surface of the yoke4, on which the concave portions6are provided, is a bottom surface of the rotor magnet3, while the opposite axial end surface, on which the position-detecting magnet11is set, is a top surface of the rotor magnet3.

The position-detecting magnet11is located (substantially in a horizontal state) on the top surface of seats34and ribbed runners (a remaining product portion) on the inner side of position-detecting-magnet holding protrusions35bon the seat portions50.

At this time, there is a gap with a predetermined spacing between the outer peripheral surface of the position-detecting magnet11and the inner peripheral surface of the position-detecting-magnet holding protrusion35b. Although detailed descriptions thereof are omitted, the lower die that is set in place on a turn table is rotated by 180° at a predetermined rotating speed, for example, at the time of molding. In a state where the position-detecting magnet11is placed on the seat portions50at the time of resin molding, when the lower die is rotated by 180° at a predetermined rotating speed, for example, then a centrifugal force is applied to the position-detecting magnet11. However, there are the position-detecting-magnet holding protrusions35baround the position-detecting magnet11. Therefore, the position-detecting-magnet holding protrusions35bprevent the position of the position-detecting magnet11from being displaced in the radial direction. The position-detecting magnet11is less likely to be removed from the rotor magnet3. This improves the productivity.

By means of resin molding, the shaft-outer-peripheral cylinder resin portion31is formed from the thermoplastic resin17into a cylindrical shape on the outer periphery of the shaft1to increase the thickness. Around the outer periphery of this shaft-outer-peripheral cylinder resin portion31, gate convex portions32for pouring the thermoplastic resin17are formed radially from the outer periphery of the shaft-outer-peripheral cylinder resin portion31.

The thermoplastic resin17is poured from the axial end surface of the gate convex portions32on the side of the position-detecting magnet11. Therefore, gate processing traces32aremain on the axial end surface of the gate convex portions32on the side of the position-detecting magnet11. The gate convex portions32are formed, for example, by a half of the number of magnetic poles (five gate convex portions that are half the ten magnetic poles in this example).

The gate convex portions32extend with a predetermined length in the radial direction from the shaft-outer-peripheral cylinder resin portion31. The inner peripheral surface of a yoke-inner-peripheral cylinder resin portion37, and the radially distal end of the gate convex portion32are spaced apart from each other by a predetermined distance. The gate convex portion32extends in a radial direction that is substantially the direction along the center of the magnetic pole of the resin magnet portion5.

One axial end surface of the gate convex portions32(on the side of the position-detecting magnet11) is positioned on the inner side of the axial end surface of the rotor magnet3, on which the position-detecting magnet11is provided, by a predetermined dimension (for example, approximately 1 mm). The other axial end surface of the gate convex portions32is positioned at a die-mating-surface track38between the upper die and the lower die of the resin-molding die. Therefore, the axial length of the gate convex portions32is approximately a half of the axial length of the rotor magnet3.

One axial end surface of the gate convex portions32(on the side of the position-detecting magnet11) is positioned on the inner side of the axial end surface of the rotor magnet3, on which the position-detecting magnet11is provided, by a predetermined dimension for the reason described below.

As described already, the thermoplastic resin17is poured from the axial end surface of the gate convex portions32on the side of the position-detecting magnet11. The gate processing traces32aremain on the axial end surface of the gate convex portions32on the side of the position-detecting magnet11.

The gate processing trace32amay sometimes project outward by any length from the axial end surface of the gate convex portion32on the side of the position-detecting magnet11. In a case where there is something that interferes with a projection of the gate processing trace32a, it is preferable that the projection of the gate processing trace32ais accommodated on the inner side of the axial end surface of the rotor magnet3on the side of the position-detecting magnet11.

For example, when the outer diameter of the bearing410(a ball bearing, for example) is smaller than the inner diameter of the yoke-inner-peripheral cylinder resin portion37, the projection of the gate processing trace32ais likely to interfere with the mold of a molded stator350.

Therefore, one axial end surface of the gate convex portions32(on the side of the position-detecting magnet11) is positioned on the inner side of the axial end surface of the rotor magnet3, on which the position-detecting magnet11is provided, by a predetermined dimension, such that the gate processing traces32ado not project outward from the axial end surface of the rotor magnet3. This makes it possible to permit the region of the gate processing traces32ato fall within the above dimension. Accordingly, improvement in the productivity is achieved.

A plurality of ribs18are radially formed between the shaft-outer-peripheral cylinder resin portion31and the yoke-inner-peripheral cylinder resin portion37. In the example illustrated inFIG. 2, five ribs18are radially formed with a substantially equal spacing in the circumferential direction between the shaft-outer-peripheral cylinder resin portion31and the yoke-inner-peripheral cylinder resin portion37(FIG. 2). The ribs18extend in a direction between magnetic poles of the resin magnet portion5.

The thermoplastic resin17reaches the resin magnet portion5and the position-detecting magnet11through the ribs18. Therefore, the yoke4and the resin magnet portion5are integrated into the rotor magnet3. The thermoplastic resin17is injected from the gate convex portions32directly into the shaft-outer-peripheral cylinder resin portion31on the outer periphery of the shaft, and therefore can be filled earlier. Accordingly, improvement in the weld strength of the shaft-outer-peripheral cylinder resin portion31is achieved.

On the other hand, conventionally the thermoplastic resin17is poured into the yoke-inner-peripheral cylinder resin portion37, and is then filled in the shaft-outer-peripheral cylinder resin portion31through the ribs18.

It is adequate that the number of the ribs18, the thickness (in the circumferential direction) and the length (in the axial direction and the radial direction) of the ribs18are minimized as much as possible within a range where the ribs18have a strength to withstand a repetitive stress caused by a generated torque and an intermittent operation of an electric motor, in order to achieve a cost reduction.

Further, it is possible to adjust the transmitted vibration force from the resin magnet portion5to the shaft1by adjusting the rigidity of the ribs18in the circumferential direction by means of changing the number of the ribs18, and the thickness (in the circumferential direction) and the length (in the axial direction and the radial direction) of the ribs18. Therefore, a reduction in noise of an electric motor is achieved, and accordingly the quality of a product is improved.

At the time of molding the electric-motor rotor100using the thermoplastic resin17, both the axial end surfaces of the resin magnet portion5near its outer periphery are pressed by a die to fill the thermoplastic resin17. This prevents formation of a flash on the outer periphery of the resin magnet portion5. Because of no need for a flash removing process, improvement in the productivity and quality is achieved.

Some of the notches7in the yoke4(in this example, five notches7into which the convex portions on the lower die are not fitted), the concave portions6(10concave portions) that serve as a gate for the yoke4, and the seat portions50, are filled with the thermoplastic resin17so as to serve as a torque-transmitting member and an anti-rotation member in the rotating direction.

The concave portions6in the yoke4, and the seat portions50are filled completely with the thermoplastic resin17. Therefore, when the thermoplastic resin17is molded and shrunken in the inner-diameter direction, the thermoplastic resin17is caught by the concave portions6in the yoke4, and by the outer peripheral surface of the seat portions50. This prevents formation of a gap between the thermoplastic resin17and the rotor magnet3, and accordingly can prevent a reduction in the coupling force.

That is, the concave portions6, each of which prevents a projection of a gate processing trace6afrom protruding from the axial end surface of the yoke4, and the seat portions50for positioning the position-detecting magnet11, are used, and therefore there is no need for an additional structure that prevents a reduction in the coupling force. Accordingly, a reduction in costs and a reduction in noise are both achieved.

Next, the yoke4that constitutes the rotor magnet3is described in detail.

The yoke4, provided on the inner side of the rotor magnet3, is obtained by injection molding of thermoplastic resin that contains soft magnetic material or ferrite.

At the time of molding the yoke4, on the outer side of a portion of the die, which forms the outer periphery of the yoke4, a strong magnet is located to provide an oriented magnetic field. Therefore, soft magnetic material or ferrite contained in the yoke4is oriented with anisotropy to the polar direction. Due to the oriented magnetic field as described above, the yoke4is oriented with anisotropy to the polar direction.

The yoke4is formed generally into a cylindrical shape. On the outer periphery of the yoke4, concave portions47and convex portions48are located alternately. The number of the concave portions47is ten, and the number of the convex portions48is also ten.

Each of the concave portions47corresponds to (is opposed to) a magnetic pole of the resin magnet portion5. Each of the convex portions48corresponds to (is opposed to) a portion between magnetic poles of the resin magnet portion5. A configuration is also possible, in which each of the concave portions47corresponds to (is opposed to) a portion between magnetic poles of the resin magnet portion5, and each of the convex portions48corresponds to (is opposed to) a magnetic pole of the resin magnet portion5.

On one axial end surface of the yoke4, a plurality of the concave portions6(with a circular shape, for example), each of which has a predetermined depth in the axial direction, are formed (equal to the number of magnetic poles) with a substantially equal spacing in the circumferential direction. The concave portions6respectively correspond to (are opposed to) the convex portions48(magnetic poles of the resin magnet portion5) on the outer periphery of the yoke4. In this example, because there are ten magnetic poles in the electric-motor rotor, ten concave portions6are formed accordingly.

Thermoplastic resin that contains soft magnetic material or ferrite is poured from the respective concave portions6to the yoke4. Therefore, on the yoke4after the molding, the gate processing traces6aremain at each gate opening for pouring thermoplastic resin.

One reason for providing the concave portions6is to prevent a projection of the gate processing trace6afrom protruding from the axial end surface of the yoke4. Therefore, the depth of the concave portions6in the axial direction is sufficient to prevent the projection of the gate processing trace6afrom protruding from the axial end surface of the yoke4.

Gate openings (remaining as the gate processing traces6a) for pouring thermoplastic resin are provided by the number of magnetic poles (ten magnetic poles in this example). This makes the pouring state of thermoplastic resin that contains soft magnetic material or ferrite even to the magnetic poles at the time of the injection. This also makes the orientation state even. Therefore, improvement in the quality of the yoke4is achieved.

Further, each of the gate openings (remaining as the gate processing traces6a) is provided at the magnetic-pole position, which is an optimal position for the orientation of thermoplastic resin that contains soft magnetic material or ferrite. Therefore, improvement in the quality of the yoke4is achieved.

Furthermore, each of the gate openings (remaining as the gate processing traces6a) is provided on one axial end surface of the yoke4at the center of the concave portion6that has a round shape (a circular shape), and that is notched inward in the axial direction by a predetermined length. This can prevent a flash that remains on the gate processing trace6afrom protruding outward from the axial end surface. Therefore, interference with the positioning during the manufacturing process is suppressed, and formation of waste products is also suppressed. Accordingly, improvement in the manufacturing quality is achieved.

In a cavity portion80of the yoke4, a tapered portion45is defined from the axial end surface, on which the concave portions6are provided, to substantially the center position in the axial direction (the die-mating-surface track46at the time of molding the yoke4). The tapered portion45has a tapered shape that is gradually narrowed inward from the axial end surface on which the concave portions6are provided.

Further, a straight portion44with a constant diameter is defined from the die-mating-surface track46to the axial end surface on the side of the seats34.

The tapered portion45is formed using a fixed-side die. The straight portion44is formed using a movable-side die. The tapered portion45is formed using a fixed-side die, thereby reducing a force of a product (the yoke4) to stick to the fixed-side die at the time of opening the die. Further, the straight portion44is formed using a movable-side die, thereby causing a resistance against the force of a product (the yoke4) to stick to the fixed-side die at the time of opening the die. Therefore, the fixed-side die is smoothly removed from a product (the yoke4), and accordingly improvement in the manufacturing quality is achieved.

On the axial end surface of the yoke4on which the concave portions6are provided, the tapered notches7, each of which reaches the tapered portion45by a predetermined width, are formed at a magnetic-pole position between the concave portions6. The number of the notches7is ten. Each of the notches7is formed so as to ensure that it is coaxial with the straight portion44and the outer periphery of the yoke4.

At the time of molding the resin magnet portion5integrally with the yoke4using resin magnet, or at the time of molding the rotor magnet3integrally with the shaft1using the thermoplastic resin17, the die holds the notches7in a manner to keep them coaxial with each other. This makes it possible for the notches7to ensure the coaxiality and the phase. Therefore, improvement in the manufacturing quality is achieved.

On an axial end surface of the yoke4on the opposite side to the axial end surface of the yoke4on which the concave portions6are provided, the seats34are provided through a seat connecting portion33. The position of the seats34in the circumferential direction corresponds to (is opposed to) a magnetic pole. That is, the seats34are formed with a substantially equal spacing in the circumferential direction, where the number of the seats34is ten. Each of the seats34is configured by a pair of protruding portions34athat protrude outward in the axial direction, and an opening34bthat is formed between the pair of protruding portions34a.

As described later, the opening34bserves as a resin-magnet supply path for molding the resin magnet portion5integrally with the yoke4. The opening34bhas a width substantially identical to the width of resin-magnet supply runners (ribbed runners35described later).

The seats34are connected with each other by the seat connecting portion33, each of which has a protruding shape on the seat connecting portion33. The seat connecting portion33is provided with a predetermined height from the axial end surface of the yoke4on the opposite side to the axial end surface of the yoke4on which the concave portions6are provided. For example, the seat connecting portion33has a flat shape with a constant thickness in the axial direction. On the seats34, the position-detecting magnet11is set in place to be away from the end surface of the yoke4by a distance determined by the sum of the height of the seat connecting portion33and the seat34itself.

The seat connecting portion33has an inner diameter that substantially corresponds with the inner diameter of the yoke4. That is, the inner peripheral surface of the seat connecting portion33is formed by extending the inner peripheral surface of the yoke4in the axial direction, and is continued from the inner peripheral surface of the yoke4. This facilitates manufacturing of a die for the yoke4, and therefore achieves a reduction in costs of a rotor.

A section of the seat connecting portion33, where the seats34are provided, is extended on the radially outer side of a section of the seat connecting portion33, which connects the seats34with each other. That is, the outer peripheral surface of a section of the seat connecting portion33, where the seats34are provided, is positioned on the radially outer side of the outer peripheral surface of a section of the seat connecting portion33, which is between the seats34. The outer peripheral surface of a section of the seat connecting portion33, which is between the seats34, is positioned on the radially inner side of the outer peripheral surface of the seats34.

The rotor magnet3according to the present embodiment is obtained by accommodating the yoke4in a lower die (not illustrated) that is set in place in a vertical molding machine, and then injecting and molding resin magnet of thermoplastic resin that contains, for example, rare earth samarium onto the outer periphery of the yoke4to integrate the resin magnet portion5with the yoke4.

At the time of molding the resin magnet portion5, on the outer side of a portion of the die, which forms the outer periphery of the resin magnet portion5, a strong magnet is located to provide an oriented magnetic field. Therefore, magnetic particles contained in the resin magnet portion5are oriented with anisotropy to the polar direction.

A core portion of the die for molding the resin magnet portion5, which is inserted into the cavity portion80of the yoke4, is formed on a lower die (not illustrated). The core portion is inserted from the axial end surface of the yoke4, on which the concave portions6are provided, into the cavity portion80, and then the yoke4is mounted to the die.

In a state where the yoke4is mounted to the die, the end surface of the core portion on the lower die for forming the resin magnet portion5is positioned at the end surface of the yoke4on which the seats34are provided.

Convex portions (not illustrated), to be fitted into the notches7provided on the axial end surface of the yoke4on the side of the concave portions6, are provided on the core portion (the lower die) of the die for molding the resin magnet portion5. Therefore, the yoke4is positioned in the circumferential direction relative to the position of the magnet that generates an oriented magnetic field.

The convex portions of the core portion, which are fitted into the notches7, are ensured to be coaxial with the outer periphery of the resin magnet portion5, and are pressed against the notches7at the time of fastening the die. This ensures that the outer periphery of the resin magnet portion5is coaxial with the yoke4.

Resin-pouring portions for molding the resin magnet portion5are provided on a donut-shaped runner36that is formed on the end surface of the core portion (the lower die) of the die for molding the resin magnet portion5. The number of the resin-pouring portions is a half of the number of magnetic poles (in this example, five, which is a half of the ten magnetic poles). The resin-pouring portions are provided with a substantially equal pitch in the circumferential direction. The resin-pouring portions for molding the resin magnet portion5remain as resin-pouring portion traces36aon the donut-shaped runner36. The resin-pouring portion traces36aare formed substantially in the middle between every other two adjacent ribbed runners35in the circumferential direction.

The donut-shaped runner36protrudes toward the seats34from the end surface of the resin magnet portion5or the yoke4with substantially a height (in the axial direction) of the seats34on the yoke4. That is, the donut-shaped runner36is located on the inner side of the yoke4, and the axial end surface of the donut-shaped runner36is as high as the top-end surface of the seats34.

From the outer periphery of the donut-shaped runner36, the ribbed runners35extend radially by an equal number of magnetic poles (ten, in this example). The ribbed runners35are provided by an equal number of the seats34. Each of the ribbed runners35extends toward its corresponding seat34. The ribbed runners35are formed with a height (in the axial direction) substantially identical to the donut-shaped runner36.

As already described, the resin-pouring portions (the resin-pouring portion traces36a) for molding the resin magnet portion5are provided at the substantially middle position between the adjacent ribbed runners35.

The donut-shaped runner36and the ribbed runners35are formed using an upper die, and therefore have a tapered shape that is narrowed from the end surface of the core portion (the lower die) toward the axially outer side, in order to reduce sticking of the donut-shaped runner36and the ribbed runners35to the upper die at the time of opening the die.

Further, the donut-shaped runner36is drilled from the end surface of the core portion (the lower die) straightly into a concave shape by a predetermined depth (in the axial direction). This causes a resistance against sticking of the donut-shaped runner36to the upper die at the time of removing the die. Therefore, the upper die is smoothly removed from the donut-shaped runner36.

The ribbed runners35radially extending from the donut-shaped runner36further extend across the axial end surface of the yoke4on the side of the seats34from the axial end surface of the core portion (the lower die) of the die for molding the resin magnet portion5, and then reach the openings34bon the inner peripheral side of the seats34. Furthermore, the ribbed runners35extend outward from the openings34bon the outer peripheral side of the seats34to a predetermined position away from the other periphery of the yoke4on the axial end surface of the resin magnet portion5.

Resin magnet is poured into the resin-pouring portions (the resin-pouring portion traces36a) of the donut-shaped runner36. The resin magnet flows in the axial direction through runners (axial runners (not illustrated)) to the resin-pouring portions (the resin-pouring portion traces36a), and then changes the flow direction at the resin-pouring portions (the resin-pouring portion traces36a) by 90°. That is, the flow of resin magnet splits into two directions perpendicular to the axial direction. Thereafter, each of the two flows of resin magnet enters the nearest ribbed runner35from the resin-pouring portion (the resin-pouring portion trace36a), and further changes the flow direction by 90° to flow into the resin magnet portion5.

At this time, a portion for changing the flow direction of resin magnet (the resin-pouring portion (the resin-pouring portion trace36a), that is a portion for flowing the resin magnet through the axial runner in the axial direction, and splitting the flow into two directions perpendicular to the axial direction) can be located within the die. This is because the donut-shaped runner36including the resin-pouring portions (the resin-pouring portion traces36a) is located on the inner side of the inner periphery of the yoke4.

For example, when the flow direction is changed on the axial end surface of the yoke4, the injection pressure of resin magnet, having flowed through the axial runners in the axial direction, is likely to damage the yoke4, such as forming a hole through the end surface.

In the present embodiment, within the die, there are portions for changing the flow direction of resin magnet (the resin-pouring portions (the resin-pouring portion traces36a), that are portions for splitting a flow of resin magnet through the axial runners in the axial direction into two directions perpendicular to the axial direction). Therefore, the flow of resin magnet through the axial runners in the axial direction is less likely to damage the yoke4and other components. Accordingly, improvement in the manufacturing quality is achieved.

In the cavity portion80of the yoke4, the straight portion44with a substantially constant diameter of the cross-sectional circle is defined from the end surface on the side of the seats34to the die-mating-surface track46. Also, a gap is minimized between the straight portion44and the core portion (the lower die) of the die for forming the resin magnet portion5, where the core portion is fitted into the straight portion44. This makes it possible to suppress leakage of the resin magnet into the gap between the straight portion44and the core portion (the lower die) of the die. Therefore, improvement in the manufacturing quality is achieved.

In a case where a rare-earth resin magnet portion5is formed around the outer periphery of the yoke4, because the material (rare-earth resin magnet) is costly, it is preferable to minimize the thickness of the resin magnet portion5. In this case, a resin-pouring portion for pouring the resin magnet directly into the resin magnet portion5needs to be smaller in size according to the thickness of the resin magnet portion5. As the resin-pouring portion is smaller in size, the molding pressure is increased.

Meanwhile, as described in the present embodiment, the runners are formed of the donut-shaped runner36and the ribbed runners35that extend radially from the outer periphery of the donut-shaped runner36by an equal number of magnetic poles. Also, the resin-pouring portions (the resin-pouring portion traces36a) are provided on the donut-shaped runner36. Therefore, the gate diameter of the resin-pouring portions can be set to any diameter, and accordingly improvement in the manufacturing quality is achieved.

The number of resin-magnet pouring portions (the resin-pouring portion traces36a) is reduced to a half (five) of the number of magnetic poles (ten magnetic poles). Therefore, the ratio of the amount of runners to a product (the resin magnet portion5) can be reduced as compared to the case where the resin-magnet pouring portions are provided by the number of magnetic poles.

The amount of runners is a total amount of the donut-shaped runner36, the ribbed runners35, and other runners (the axial runners (not illustrated)).

The term “runner” is defined as a portion between the resin magnet portion5and the resin-magnet pouring portion of the die, which does not become the product (the resin magnet portion5). Specifically, the term “runner” indicates the donut-shaped runner36, the ribbed runners35, and other runners (not illustrated).

However, in the case with the rotor magnet3according to the present embodiment, a part of the ribbed runner35(a portion from the inner peripheral surface to the radially distal end of the seat34) becomes the product. That is, the donut-shaped runner36, the ribbed runners35(excluding a portion from the inner peripheral surface to the radially distal end of the seat34), and other runners (not illustrated) are removed after the completion of molding the rotor magnet3.

The amount of the runners according to the present embodiment (the donut-shaped runner36, the ribbed runners35(excluding a portion of the yoke4from the inner peripheral surface to the radially distal end of the seat34), and other runners (not illustrated)) can be reduced by approximately 30% as compared to the case where the resin-magnet pouring portions are provided by the number of magnetic poles (ten, in this example).

Although detailed descriptions thereof are omitted, the ratio of the amount of other runners (not illustrated) relative to the entire runner amount is higher as compared to the donut-shaped runner36and the ribbed runners35. Therefore, as the number of resin-pouring portions is reduced, the entire runner amount is also reduced. Accordingly, in the present embodiment, there are five resin-magnet pouring portions, and thus the entire runner amount is reduced as compared to the case where the resin-pouring portions are provided by the number of magnetic poles (ten, in this example).

In the case of reusing the runners which do not become the product, the configuration, in which the resin-magnet pouring portions are provided by a half of the number of magnetic poles, reduces the amount of runners, and therefore decreases the reuse ratio as compared to the case where the resin-magnet pouring portions are provided by the number of magnetic poles (ten, in this example). Accordingly, degradation of the physical properties of resin magnet (mainly, a mechanical strength) can be suppressed, and consequently improvement in the manufacturing quality is achieved.

Further, while the number of resin-pouring portions is a half of the number of magnetic poles, the number of the ribbed runners35is equal to the number of magnetic poles. Therefore, the state of pouring resin magnet becomes uniform to each of the magnetic poles. It is also possible to make the orientation state even. Accordingly, improvement in the manufacturing quality is achieved.

The donut-shaped runner36, the ribbed runners35(excluding a portion from the inner peripheral surface to the radially distal end of the seat34), and other runners (not illustrated) are removed after the completion of molding the rotor magnet3. A portion of the ribbed runner35, which extends from the donut-shaped runner36to the inner peripheral surface of the seat34, is removed.

Therefore, the seat portion50is configured by the protruding portions34aof the seat34and an unremoved portion35aof the ribbed runner35, which extends from between the protruding portions34a(the opening34b) to the radially outer side. Specifically, in the unremoved portion35a, resin magnet, which fills the opening34bto the top end of the protruding portions34a, extends radially outward, and the distal end of the unremoved portion35ais connected integrally with the top-end surface of the resin magnet portion5. The unremoved portion35afurther includes, at its distal end, the position-detecting-magnet holding protrusion35bthat protrudes outward in the axial direction.

As described already, the position-detecting magnet11is located (substantially in a horizontal state) on the top surface of the seats34and the ribbed runners35(a remaining product portion) on the inner side of the position-detecting-magnet holding protrusions35bon the seat portions50. In a state where the position-detecting magnet11is placed on the seat portions50before resin molding, when the lower die is rotated by 180° at a predetermined rotating speed, for example, then a centrifugal force is applied to the position-detecting magnet11. However, there are the position-detecting-magnet holding protrusions35baround the position-detecting magnet11. Therefore, the position-detecting-magnet holding protrusions35bprevent the position of the position-detecting magnet11from being displaced in the radial direction. The position-detecting magnet11is less likely to be removed from the rotor magnet3. This improves the productivity.

A portion of the ribbed runner35, which is formed on the resin magnet portion5on the outer side of the yoke4, is used as a positioning protrusion that positions the rotor magnet3in the circumferential direction at the time of molding the rotor magnet3integrally with the shaft1using the thermoplastic resin17.

For example, there is a case where the positioning protrusion (a portion of the ribbed runner35on the outer side of the yoke4), the position-detecting-magnet holding protrusion35b, and the seat34are formed only from resin magnet. In that case, upon removing the donut-shaped runner36and the ribbed runners35, these protrusions and seat are connected with each other only by a resin-pouring portion into the resin magnet portion5, and therefore there is a problem of low strength.

However, the seats34are provided on the yoke4, and further the central portion of the seats34is opened to provide the openings34bso as to integrate the ribbed runners35with the seats34, thereby improving the strength. Therefore, improvement in the manufacturing quality is achieved.

In order to change the performance of an electric motor, it is necessary to change the axial length of the resin magnet portion5without changing the axially center position of the resin magnet portion5relative to a stator. However, there is a case where the axial position of the position-detecting magnet11relative to the stator cannot be changed. Even in this case, the rotor magnet3can still be formed without increasing the required amount of resin magnet unnecessarily, while ensuring the resin-magnet pouring path by adjusting the height of the seat connecting portion33. Therefore, a reduction in costs of the rotor100can be achieved.

As described above, resin magnet passes from the donut-shaped runner36through the ribbed runners35, fills the outer periphery of the yoke4, and then integrates the yoke4with the resin magnet portion5. Thereafter, a portion of the ribbed runners35on the inner side of the inner-peripheral-side surface of the seats34, and the donut-shaped runner36are removed, thereby obtaining the rotor magnet3according to the present embodiment.

In the above descriptions, the rotor magnet3is used as an example, in which the outer periphery of the yoke4has a concave-convex shape, and the resin magnet portion5is molded integrally with the outer periphery of the yoke4. However, it is adequate that the outer periphery of the yoke4has a circular shape, and is partially provided with a concave shape or a convex shape, and the resin magnet portion5is molded around the outer periphery of the yoke4to form the rotor magnet3.

The rotor magnet3can also be made up of only a resin magnet.

It is also adequate that a sintered magnet or a molded resin magnet is bonded to the yoke4to form the rotor magnet3.

It is apparent that, regardless of the outer-peripheral shape of the yoke4, or the material or fixing method of a magnet to be located around the outer periphery, the same effects are obtained by molding general-purpose thermoplastic resin so as to fill the concave portions6, each of which prevents the gate processing trace6aprovided on one end surface of the yoke4from protruding from the end surface, and then integrating the shaft1, the rotor magnet3, and the position-detecting magnet11with each other.

Next, the position-detecting magnet11is described. The position-detecting magnet11having a ring shape includes a step (not illustrated) at each axial end on the inner-diameter side, and is symmetrical in the thickness direction.

The position-detecting magnet11is provided at one axial end of the electric-motor rotor100. Thermoplastic resin such as PBT is filled in the step at each axial end of the inner-diameter side of the position-detecting magnet11to serve as an anti-skid member in the axial direction for the position-detecting magnet11.

The position-detecting magnet11has a symmetrical shape in the thickness direction, and therefore can be set in a die regardless of the direction. This reduces a work time. Accordingly, improvement in the productivity and a cost reduction are both achieved.

The position-detecting magnet11is not limited to including a step at each axial end on the inner-diameter side, and can include a step at either one of the axial ends. This step can also be positioned on the axial end-side of the electric-motor rotor100.

The position-detecting magnet11includes a rib (not illustrated) that serves as an anti-rotation member when the step is filled with thermoplastic resin.

The electric-motor rotor100according to the present embodiment is combined with an electric-motor stator, for example, to constitute a brushless DC motor (a synchronous electric motor). The stator can be a molded stator formed using mold resin that is thermosetting resin such as a bulk molding compound (BMC).

FIG. 6illustrates a configuration of a molded electric motor. As illustrated inFIG. 6, an electric motor400includes the shaft1, the electric-motor rotor100, the bearing410, a bracket439, a waterproof cap420, the molded stator350formed by molding the electric-motor stator300, a sensor substrate341, and other elements.

The sensor substrate341, connected to an external device, is mounted to the electric-motor stator300. The sensor substrate341and the electric-motor stator300are mechanically and electrically joined, and are thereafter subjected to a molding process to constitute the molded stator350. The sensor substrate341includes a position-detecting Hall element341aon the surface on the side of the position-detecting magnet11.

Next, components, such as the electric-motor rotor100(to which the bearing410is attached) and the bracket439, are mounted to the molded stator350to constitute the electric motor400.

In the manner as described above, by using the electric-motor rotor100and the electric-motor stator300, the electric motor400can be obtained with improved quality at reduced costs.

As described above, in the present embodiment, the seats34, on which the position-detecting magnet11is placed, are formed on the seat connecting portion33, and the unremoved portion35aof the ribbed runner35, which fills the opening34bof the seat34, extends radially outward from between the protruding portions34ato be connected integrally with the axial end surface of the resin magnet portion5.

According to the present embodiment, even when the resin magnet portion5and the position-detecting magnet11are distanced from each other in the axial direction, the height of the seat connecting portion33is adjusted, and therefore there is no need to change the height of the seats34. Accordingly, while ensuring the resin-magnet pouring path, it is possible to reduce the usage amount of resin magnet, and thus achieve a reduction in costs of the rotor100.

For example, in a case of changing performance of the electric motor400under the configuration that uses the molded stator350(FIG. 6) with an identical positional relation between the stator300and the sensor substrate341, it is necessary to change the axial length of the resin magnet portion5. However, there is a case where the axially center position of the resin magnet portion5relative to the stator300cannot be changed. In such a case, the resin magnet portion5and the position-detecting magnet11may sometimes be distanced from each other in the axial direction. According to the present embodiment, even in the case as described above, an electric motor with desired performance can still be configured by adjusting the height of the seat connecting portion33without changing the height of the seats34. Also, the required amount of resin magnet can be reduced.

In the present embodiment, under the configuration that uses the molded stator350(FIG. 6) with an identical positional relation between the stator300and the sensor substrate341, it is possible to use the rotor100with a varied axial length of the resin magnet portion5, and therefore early depreciation of the molded-stator die is possible. Therefore, it is possible to reduce costs of the electric motor400.

In the present embodiment, molding of the seats34is facilitated. This makes it possible to improve the quality of the rotor100. That is, even when the resin magnet portion5and the position-detecting magnet11are distanced from each other in the axial direction, the height of the seat connecting portion33is adjusted, and then there is no need to increase the height of the seats34. This facilitates molding of the seats34.

When the rotor100is integrally molded using the thermoplastic resin17, the thermoplastic resin17tightly holds the outer-diameter side of the seat connecting portion33, and therefore the resin magnet portion5is rigidly held through the yoke4. This makes it possible to improve the quality of the rotor100.

In the present embodiment, the seat connecting portion33has an inner diameter equal to the inner diameter of the yoke4, and is formed at a position to which the inner-diameter side of the yoke4is extended. This facilitates machining of a molding die for the yoke4, and makes it possible to achieve a cost reduction.

In the present embodiment, the outer peripheral surface of a section of the seat connecting portion33, where the seats34are provided, is positioned on the radially outer side of the outer peripheral surface of a section of the seat connecting portion33, which is between the adjacent seats34. Therefore, when the rotor100is molded integrally using the thermoplastic resin17, the outer peripheral surface of the seat connecting portion33serves as an anti-rotation member for the resin magnet portion5, and therefore reliably transmits a torque of the magnet. This makes it possible to improve the quality of the rotor100.

Further, according to the present embodiment, the electric-motor rotor100with improved quality at reduced costs is used, and therefore improvement in the quality of the electric motor400can be achieved.

Second Embodiment

FIG. 7is a diagram illustrating a configuration of an air conditioner according to a second embodiment of the present invention. An air conditioner500according to the present embodiment includes an indoor device542and an outdoor device543that is connected to the indoor device542. The outdoor device543includes an air blower that includes a molded electric motor400band fans544. The indoor device542also includes an air blower that includes a molded electric motor400a. Each of the molded electric motors400aand400bis the electric motor described in the first embodiment. The outdoor device543includes a compressor545.

According to the present embodiment, the electric motor according to the first embodiment with improved quality at reduced costs is used as an electric motor for the air blower, which is the main component of the air conditioner500, and therefore improvement in the quality of the air conditioner500is achieved.

The electric motor according to the first embodiment is applied to the compressor545, and therefore further improvement in the quality of the air conditioner500is achieved.

INDUSTRIAL APPLICABILITY

The present invention is suitable for an electric-motor rotor, an electric motor, and an air conditioner.