JP7636859B2 - Drive motor - Google Patents

Description

The technology disclosed relates to a drive motor that rotates in a specific direction without using a magnet in the rotor, and in particular, to a drive motor that is suitable for ultra-high speed rotation.

In recent years, so-called stick-type vacuum cleaners, which do not include the vacuum cleaner body, hose, electric cord, etc., have been attracting attention. In stick-type vacuum cleaners, it is necessary to rotate a small fan at high speed to generate high suction power. For this reason, there is a demand for a drive motor (mini fan motor) that is small and lightweight, while ensuring a certain level of torque, and can achieve high speed rotation of 50,000 r/min or more, and even ultra-high speed rotation of 100,000 r/min or more.

The magnets generally used in motor rotors have a low allowable tensile stress, and are destroyed and scattered by the centrifugal force generated when rotating at very high speeds, so structures are seen in which the rotor surface is protected by SUS pipes, carbon fiber, or glass fiber. On the other hand, there are also switched reluctance motors that do not use magnets in the rotor, and are made only of electromagnetic steel sheets that have an allowable tensile stress much higher than that of the magnets. Since the rotor of this motor is made only of electromagnetic steel sheets with a high allowable tensile stress, it has a robust structure and, compared to magnet-type motors, there is almost no risk of damage even when the rotor is rotated at very high speeds. Therefore, it is ideal for mini fan motors.

On the other hand, switched reluctance motors rotate only by the attractive force of the iron rotor drawn to the excited stator teeth by passing current through the stator coil, so to increase output, it is necessary to increase the number of coil turns and expand the coil cross-sectional area, which means increasing the amount of copper used, which has a high specific gravity. Therefore, compared to magnet motors, which rotate using magnetic attractive and repulsive forces, switched reluctance motors are disadvantageous in terms of motor output, efficiency, and size and weight reduction.

Therefore, a flux switching motor has been proposed in which a coil and a magnet are placed on the stator, and the rotor teeth excited by the magnetic flux flowing from the magnet placed on the stator and the stator teeth excited by the coil attract each other, thereby strengthening the attractive force (for example, Patent Documents 1 and 2).

JP 2002-199679 A Patent No. 5791713

In general, motors are often made of iron. This makes them prone to becoming heavy. The smaller the motor, the lighter it becomes, but for the mini fan motors mentioned above, even lighter weight (ultra-lightweight) is required.

Therefore, the main objective of the disclosed technology is to realize a drive motor that can achieve both high output, including high speed rotation, and lightweight design.

The disclosed technology relates to a drive motor that rotates in a specific direction.

The drive motor includes a rotatable shaft, a rotor that is integral with the shaft and does not include a magnet and has multiple radially protruding salient poles, and a stator that is installed around the rotor with an air gap between them.

The stator has a stator core having a back yoke portion and multiple teeth extending inward from the back yoke portion, and multiple coils arranged around the teeth.

The stator core has multiple element cores and multiple magnets.

A gap is formed in the salient pole portion. The salient pole portion has a large magnetic path portion with a large cross-sectional area that extends forward in the direction of rotation from the gap, and a small magnetic path portion with a small cross-sectional area that extends backward in the direction of rotation from the gap.

In other words, in this drive motor, the rotor does not have a magnet. Therefore, the rotor of the drive motor is made only of electromagnetic steel sheets with high allowable tensile stress, resulting in a robust structure, so there is almost no risk of damage even when the rotor is rotated at high or ultra-high speeds.

The stator core has multiple element cores and multiple magnets, and corresponds to a so-called flux switching motor. Therefore, a magnetic circuit is formed in which the magnetic flux of the magnet flows from the element core through the air gap into the tip of the salient pole part of the rotor, and the magnetic flux flows out from the tip of another salient pole part, passes through the air gap and the element core, and returns to the other magnet. The salient pole part is magnetized to the north pole or south pole depending on the rotation angle of the rotor, strengthening the magnetic attraction force, and high-output, high-speed rotation can be performed stably.

Gaps are formed in the salient poles of the rotor. The rotor is essentially a mass of metal, so it is heavy. By forming gaps in multiple salient poles of the rotor, the rotor, and therefore the drive motor, can be significantly lightened.

Moreover, the salient pole portion has a large magnetic path section with a large cross-sectional area on the front side in the direction of rotation, and a small magnetic path section with a small cross-sectional area on the rear side in the direction of rotation.

The rotor rotates due to the magnetic attraction force generated between the teeth and the salient poles. At this time, a large amount of magnetic flux flows from the magnet between the teeth and the large magnetic path portion, and a large magnetic attraction force acts on the side moving forward in the direction of rotation. On the other hand, the small magnetic path portion located on the rear side in the direction of rotation has a small cross-sectional area, so only a small amount of magnetic flux flows in and out between the teeth and the small magnetic path portion compared to the large magnetic path portion, and therefore only a small magnetic attraction force acts on the side moving backward in the direction of rotation.

This makes it possible to suppress the magnet torque that occurs in the direction opposite to the rotor's rotation. As a result, the motor torque required in the rotor's rotation direction can be increased, making it possible to obtain high output even with a small size. This makes it possible to achieve both lightweight and high output.

The drive motor may also be configured such that the gap is a slit that penetrates the axial direction and extends radially, and the thickness of the salient pole portion is greater in the forward portion than in the rear portion of the slit in the direction of rotation.

Slits like this can be easily machined. The large magnetic path section and the small magnetic path section can be formed simply and with high precision.

The drive motor may also be configured such that each of the magnets has a pair of inclined side surfaces that move away from each other radially outward, and each of the side surfaces is in surface contact with the teeth.

This will increase the surface area of the magnet's magnetic poles, resulting in a stronger magnetic force.

The motor may also be configured such that the end faces of each of the magnets located on the inner diameter side of the motor are located on the outer diameter side of the motor than the tips of the teeth.

This reduces the amount of exposure of the magnet to leakage flux from the teeth, suppressing irreversible demagnetization, i.e., a decrease in magnetic force, and thus stabilizing motor output. In addition, the eddy currents that are generated when the leakage flux passes through the magnet can also be similarly reduced, making it possible to achieve high motor efficiency.

The drive motor may also be configured such that each magnet is an anisotropic Sm-Fe-N bonded magnet containing 40% or more by volume of a resin component.

If the resin content is 40% or more by volume, the magnet can be made lighter. By using Sm-Fe-N bonded magnets, which have a lower specific gravity than Nd-Fe-B bonded magnets, the magnet can be made even lighter. And because the magnetic force can be strengthened by using anisotropic magnets, it is possible to significantly increase the output density of the motor. Furthermore, by using magnets that contain a large amount of resin, which is an insulator, the eddy current loss that occurs in the magnet is reduced, making it possible to achieve high motor efficiency even if the amount of resin is increased.

The drive motor may also be configured as a fan motor by further comprising an impeller attached to the shaft and a shroud having an air intake in the center and positioned to cover the impeller.

A fan motor is required to rotate at high speed in a specific direction. This drive motor meets that requirement and is extremely effective. An integrated fan motor, which has an impeller attached to a shaft and a shroud placed over the impeller, also works well in combination with a small drive motor.

In this case, it is preferable to configure a mini fan motor with an outer diameter of 100 mm or less, an overall height of 50 mm or less, and a suction power of 250 W or more.

This type of mini fan motor is ideal for stick vacuum cleaners, making it possible to create a highly convenient vacuum cleaner.

Furthermore, in this case, the coil is formed to have a predetermined inside dimension by edgewise winding, which bends a rectangular wire having a rectangular cross section toward its short side, and each of the teeth has an outside dimension that fits into the inside dimension of the coil, and each of the coils is attached to each of the teeth.

The process of attaching the coil to the stator is simplified, making it possible to manufacture even ultra-small sizes. Furthermore, edgewise winding reduces the side area of the rectangular wire exposed to leakage flux from the teeth, making it possible to achieve high efficiency by suppressing eddy currents.

The disclosed technology makes it possible to realize a drive motor that can achieve both high output, including high speed rotation, and lightweight while still ensuring practical torque.

FIG. 1 is a schematic diagram showing an application example (stick type vacuum cleaner) of a mini fan motor configured with a drive motor according to an embodiment. 1 is a schematic perspective view of a mini fan motor including a drive motor according to an embodiment of the present invention; This is an exploded view of a mini fan motor. FIG. 2 is a schematic perspective view showing a drive motor. FIG. 2 is a schematic diagram showing a stator (coils are omitted). FIG. 2 is a schematic diagram showing a stator core. FIG. 2 is a schematic perspective view showing a coil. 5A and 5B are diagrams for explaining a magnetic state when a drive motor rotates. FIG. 13 is a schematic perspective view showing a modified example of the drive motor.

The following describes in detail the embodiments of the disclosed technology with reference to the drawings. However, the following description is essentially merely an example and does not limit the present invention, its applications, or its uses.

For convenience, the up and down directions used in the description refer to the directions indicated by the arrows in FIG. 2. The axial direction refers to the direction in which the rotation axis P extends, the circumferential direction refers to the direction around the rotation axis P, and the radial direction refers to the direction of the radius or diameter centered on the rotation axis P.

<Application examples of the disclosed technology>
1 shows an example of a stick-type vacuum cleaner 1 suitable for the disclosed technology. This vacuum cleaner 1 is a cordless type, and is configured to be powered by the power of a built-in battery 8.

This vacuum cleaner 1 is equipped with a mini fan motor 2 to which the disclosed technology is applied. The vacuum cleaner 1 is composed of a suction section 3, a tube section 4, a main body section 5, a dust case 6, a handle section 7, etc.

The suction unit 3 has a suction port 3a on its underside, and is configured to slide freely along the floor surface by means of rotatable rollers 3b. The tube portion 4 is made of a long, thin, expandable cylindrical member. The lower end of the tube portion 4 is connected to the suction unit 3, and the upper end of the tube portion 4 is connected to the main body portion 5. The tube portion 4 connects the suction port 3a and the main body portion 5.

The main body 5 is formed to be slightly larger than the tube 4. The main body 5 houses the mini fan motor 2, a battery 8, a control unit 9, etc. The control unit 9 controls the operation of the mini fan motor 2. The battery 8 is a rechargeable secondary battery, and supplies power to the mini fan motor 2.

The handle 7 is the part that is gripped by the user and is provided integrally with the main body 5. The handle is provided so as to protrude rearward from the rear side of the main body 5. The vacuum cleaner 1 is configured so that the user can operate it while holding the handle in one hand.

A dust case 6 is installed below the grip. The dust case 6 is configured to be detachable from the main body 5. The mini fan motor 2 is located adjacent to the dust case 6. The mini fan motor 2 is driven by power supplied from the battery 8 under the control of the control unit 9. When the mini fan motor 2 is driven, a strong suction force is generated. As a result, dust sucked in from the suction port 3a passes through the tube portion 4 and accumulates in the dust case 6.

(Mini fan motor 2)
Figure 2 shows the mini fan motor 2. The mini fan motor 2 is a small device in which a fan and a motor are integrated. The fan is a so-called centrifugal fan. When the impeller 20 rotates around the rotation axis P, air is sucked in from the intake port 31 and discharged radially outward.

The outer diameter D and overall height H of the mini fan motor 2 are designed to be very small so that it can be housed in the main body 5. Specifically, the outer diameter D is preferably 100 mm or less, and the overall height H is preferably 50 mm or less. For example, in the case of the mini fan motor 2 shown in the figure, the outer diameter D is approximately 70 mm, and the overall height H is approximately 40 mm (the so-called palm-sized). Therefore, its weight is light, and it can be comfortably held in the palm of your hand.

Moreover, it is configured to provide high efficiency and high output using the power of the battery 8 so that the vacuum cleaner 1 can achieve sufficient performance. In the case of the mini fan motor 2 shown in the figure, it is configured to be able to operate at a high speed of 50,000 r/min or more, or even at an ultra-high speed of 100,000 r/min or more, with a power consumption of 600 W, and to provide a suction power of 250 W or more.

As shown in FIG. 2 and FIG. 3 in an exploded view, the mini fan motor 2 includes a housing 10, an impeller 20, a shroud 30, a substrate 40, and a drive motor 50. The technology disclosed herein is applied to the drive motor 50.

The housing 10 is constructed by butting a first housing 10a and a second housing 10b together vertically. The housing 10 has a pair of upper and lower annular frames and a number of columnar frames that connect these annular frames, and is formed in a cage shape. The drive motor 50 is housed inside the housing 10.

The impeller 20 has a generally conical shape and is disposed on the upper side of the housing 10. A number of vanes 21 are provided on the outer peripheral surface of the impeller 20. The impeller 20 is attached to the tip of the shaft 51 in a non-rotatable state.

The shroud 30 is fixed to the upper side of the housing 10 so as to cover the impeller 20. A circular intake port 31 is formed in the center of the shroud 30.

The substrate 40 is a disk-shaped member that is attached to the underside of the housing 10. Electrical components such as a capacitor 41 and a semiconductor element 42 are provided on the upper and lower surfaces of the substrate 40.

(Drive motor 50)
The drive motor 50 has a shaft 51 , a rotor 52 , and a stator 53 .

The drive motor 50 has a magnet 62 installed on the stator 53, and the rotor 52 is made of only a magnetic material, and the magnet 62 is configured to magnetize the rotor 52. It is a so-called flux switching motor, and is configured to rotate in only one direction, the counterclockwise direction (CCW direction), using magnet torque.

(Shaft 51)
As shown in Fig. 4, the shaft 51 is made of a cylindrical member. The axis of the shaft 51 coincides with the rotation axis P. As shown in Fig. 3, the shaft 51 has a base end 51a located inside the housing 10 and a tip end 51b protruding above the housing 10. A pair of bearings 54, 54 are attached to the upper and lower parts of the base end 51a, and the shaft 51 is rotatably supported by the housing 10 via these bearings 54, 54. A rotor 52 is provided integrally with the shaft 51 at the middle part of the base end 51a.

(Rotor 52)
The rotor 52 has a cylindrical boss portion 52a and a plurality of (six in this embodiment) salient pole portions 52b that protrude radially from the outer circumferential surface of the boss portion 52a. No magnet is installed on the rotor 52. It is made of iron material only. Specifically, the rotor 52 is formed by stacking a plurality of iron plates (magnetic material) in the above-mentioned roughly star shape in the vertical direction.

The rotor 52 is fixed to the shaft 51 by pressing the base end 51a into the shaft hole formed in the center of the boss 52a. Each salient pole 52b protrudes radially outward from the outer circumferential surface of the boss 52a. Each salient pole 52b is arranged at equal intervals in the circumferential direction.

Each salient pole portion 52b has a pair of salient pole side surfaces 521, 523 and a salient pole end surface 522 that is connected to the salient end edges of the salient pole side surfaces 521, 523 on the motor radial outer side. The pair of salient pole side surfaces 521, 523 are both made of flat surfaces and extend approximately parallel to each other while facing the circumferential direction. The salient pole end surface 522 has a salient pole end surface 525 that is connected to the salient pole side surface 523 and a salient pole end surface 524 that is connected to the salient pole side surface 521. A slight curved portion is formed between the salient pole end surface 524 and the salient pole end surface 525, and the air gap at the salient pole end surface 525 is slightly larger. In other words, each salient pole portion 52b has a structure that protrudes by the amount of the salient pole end surface 525 in the rotation direction (CCW direction) of the motor 50 (so-called asymmetric structure). In addition, a slit 52c is formed in each salient pole portion 52b, which will be described later.

(Stator 53)
4, the stator 53 is configured in a generally annular shape by a plurality of members. The stator 53 is installed in the housing 10 with a predetermined air gap G around the rotor 52 (a so-called inner rotor type). The stator 53 has a stator core 60, an insulator 70, and a coil 80.

Figure 5 shows the stator 53 without the coil 80. Figure 6 shows the stator core 60 without the insulator 70.

The stator 53 (stator core 60) has a cylindrical back yoke portion 60a and multiple (eight in this embodiment) tooth portions 60b that extend radially inward from the back yoke portion 60a. The tooth portions 60b are arranged at equal intervals in the circumferential direction. A slot 60c that accommodates the coil 80 is formed between two adjacent tooth portions 60b, 60b.

The width (circumferential size) of the teeth 60b is approximately the same except for the tip portion (the tip portion has a narrow width). The inner diameter of the stator 53 and the outer diameter of the rotor 52 are designed so that a predetermined size air gap G is formed between the tip of each tooth 60b and the tip of the salient pole portion 52b of the rotor 52.

As shown in FIG. 6, the stator core 60 is composed of multiple (eight in this embodiment) element cores 61 that are roughly U-shaped when viewed from above, and multiple (eight in this embodiment) magnets 62.

Each element core 61 is formed by stacking multiple roughly U-shaped iron plates (magnetic material) in the vertical direction. Each element core 61 has a yoke element 61a that is arc-shaped when viewed from above, and a pair of teeth elements 61b, 61b that extend oppositely from both ends of the yoke element 61a, and is configured to have a constant thickness in the vertical direction relative to the axial direction. The yoke element 61a constitutes part of the back yoke portion 60a, and each tooth element 61b constitutes a side portion of the tooth portion 60b.

Each magnet 62 is formed in a generally plate shape using an anisotropic Sm-Fe-N bonded magnet containing 40 vol. % or more of resin. By using an Sm-Fe-N bonded magnet, which has a smaller specific gravity than an Nd-Fe-B bonded magnet, the motor 50 can be made lighter, and the use of an anisotropic magnet can increase the magnetic force, making it possible to significantly increase the output density of the motor 50. Furthermore, by making the resin component, which is an insulator, 40 vol. % or more, eddy currents generated in the magnets are reduced, so the motor 50 can be made more efficient even if the amount of resin is increased.

Each magnet 62, in detail, has a pair of inclined rectangular side surfaces 62a, 62a that move away from each other in the radial direction, a narrow rectangular inner end surface 62b, and a wide rectangular outer end surface 62c. One of the side surfaces 62a constitutes the north pole, and the other side surface 62a constitutes the south pole.

The magnets 62 are arranged radially in the stator core 60 with the same magnetic poles facing each other in the circumferential direction. The element cores 61 and magnets 62 are connected in an annular shape with one magnet 62 sandwiched between the opposing tooth elements 61b, 61b of two adjacent element cores 61, 61.

Each of the side surfaces 62a of the magnets 62 is in surface contact with the opposing tooth elements 61b, 61b of the two adjacent element cores 61, 61. Because the side surfaces 62a of the magnets 62 are inclined, their surface area is larger than when they are not inclined. This makes it possible to generate a stronger magnetic force, thereby enabling the motor 50 to have a higher output.

The inner end surface 62b of each magnet 62 is located further back (radially outward) than the tip of each tooth element 61b. When the drive motor 50 rotates, a magnetic path (flux flow path) is formed between the tip of the tooth portion 60b and the tip of the salient pole portion 52b. At that time, by protruding the tip of each tooth element 61b into the air gap G beyond the inner end surface 62b of the magnet 62, the amount of magnetic flux directed toward the magnet 62, that is, the amount of magnetic flux to which the magnet 62 is exposed, can be suppressed. This has the effect of suppressing irreversible demagnetization of the magnet 62 and the generation of eddy currents.

As shown in FIG. 5, a plastic (insulating material) insulator 70 is attached around the stator cores 60 connected in an annular shape. Specifically, the top surfaces of the teeth 60b, parts of both side surfaces of the teeth 60b, and part of the back yoke 60a (the part facing the slot 60c) are covered with the insulator 70. The stator core 60 located at the tip of the teeth 60b (the part facing the air gap G) is exposed from the insulator 70.

As shown in FIG. 4, a coil 80 is installed in the portion of each tooth portion 60b that is covered by an insulator 70. This drive motor 50 is used in a mini fan motor 2, so its size is very small. The coil 80 is also correspondingly tiny in size.

Figure 7 shows the coil 80. The coil 80 is designed to generate a high magnetic force and to be easy to assemble.

That is, each coil 80 is formed to have a predetermined inside dimension. Each tooth portion 60b has an outside dimension that fits into the inside dimension of the coil 80, and each coil 80 formed to a predetermined shape can be attached to each tooth portion 60b.

Each coil 80 is formed by winding an electric wire made of an electrical conductor such as copper coated with an insulating film. The electric wire is a rectangular wire 80a having a rectangular cross section. The coil 80 is formed by bending the rectangular wire 80a toward the short side of its cross section (edgewise winding).

The flat wire 80a can be wound without gaps, so a higher space factor can be obtained compared to round wire. Moreover, with edgewise winding, the shorter side, which has a smaller thickness, is wound, so the size of the coil 80 in the winding direction (axial direction) can be reduced, making it possible to miniaturize the motor 50. In addition, since the circumferential side area of the flat wire 80a can be reduced, eddy currents generated by exposing the flat wire 80a to the fringing magnetic flux leaking from each tooth portion 60b can be suppressed, and the motor 50 can be made more efficient. Furthermore, even if the short side is small, the cross-sectional area of the flat wire 80a can be increased by increasing the long side, i.e., the electric wire can be made thicker. Therefore, a large current can be passed through it, and a high magnetic force can be generated.

The ends of each coil 80 attached to each tooth portion 60b are connected to a predetermined terminal of the substrate 40 with the insulating film removed. The substrate 40 is supplied with power from a battery 8. The substrate 40 is provided with multiple switching elements that switch the power, and the control unit 9 controls these switching elements so that a predetermined current (AC) is supplied to each coil 80.

In the case of this drive motor 50, two different phase coil groups consisting of phase A and phase B are configured. As shown by the patterns in Figure 4, the coil groups of phase A and phase B are arranged alternately in the circumferential direction. Two currents (AC) of different phases are supplied to these coil groups of each phase.

In this case, each salient pole portion 52b is structured (asymmetrical structure) to protrude by the salient pole end surface 525 in the rotation direction (CCW direction) of the motor 50, thereby ensuring stability at start-up and realizing uniformity of the rotation direction in the CCW direction, even though it is a two-phase motor. Note that the salient pole end surface 525 protruding in the rotation direction is not necessary for a three-phase motor.

The rotational position of the rotor 52 relative to the stator 53 is detected from changes in induced voltage, and the current supply state to each coil group is controlled based on the rotational position. As a result, a magnetic field (rotating magnetic field) that rotates the rotor 52 is formed in the stator 53. The magnetic attraction force (magnetic torque) between the rotating magnetic field and the salient poles 52b magnetized by each magnet 62 causes the rotor 52 to rotate counterclockwise.

(Detailed Structure of Rotor 52)
As described above, a slit 52c (an example of a gap) is formed in each salient pole portion 52b of the rotor 52. The slit 52c penetrates in the axial direction. The slit 52c also extends linearly in the radial direction from the boundary with the boss portion 52a to the tip of the salient pole portion 52b.

The rotor 52 is essentially a lump of iron. Therefore, the rotor 52 is heavy, but by forming slits 52c in each salient pole portion 52b, the rotor 52, and therefore the drive motor 50, can be significantly lightened in weight.

Moreover, as shown in FIG. 4, a portion (large magnetic path portion 52d) that extends radially with a large thickness (width) is provided ahead of the slits 52c of each salient pole portion 52b in the rotational direction (forward side in the rotational direction, CCW side in the case of this drive motor 50). And a portion (small magnetic path portion 52e) that extends radially with a small thickness (width) is provided behind the slits 52c of each salient pole portion 52b in the rotational direction (reverse side in the rotational direction, CW side in the case of this drive motor 50).

That is, the cross-sectional area of the large magnetic path section 52d located at the front in the direction of rotation is larger than the cross-sectional area of the small magnetic path section 52e located at the rear in the direction of rotation. As a result, more of the magnetic flux of the magnet 62 flows into and out of the large magnetic path section 52d, and conversely, the amount of magnetic flux flowing into and out of the small magnetic path section 52e is smaller. As a result, the magnetic attraction force in the direction of rotation of the motor 50 is greater, and conversely, the magnetic attraction force in the counter-rotation direction of the motor 50 (the CW direction in the case of this motor 50) is smaller. Therefore, since it is possible to realize a high torque for the motor 50, it is possible to achieve both high output and light weight.

Figure 8 shows a schematic diagram of a specific magnetic state when the drive motor 50 rotates. The rotor 52 rotates counterclockwise, as indicated by the arrow R.

The large magnetic path section 52d, which is located at the front in the direction of rotation, has a large cross-sectional area, so a lot of magnetic flux flows in and out between the teeth section 60b (the part of the teeth element 61b) and the large magnetic path section 52d, as shown by arrow Y1, and a large attractive force acts on the side moving forward in the direction of rotation.

On the other hand, the small magnetic path section 52e, which is located on the rear side in the direction of rotation, has a small cross-sectional area, so as shown by arrow Y2, only a small amount of magnetic flux flows between the teeth section 60b (the part of the teeth element 61b) and the small magnetic path section 52e compared to the large magnetic path section, and therefore only a small attractive force acts on the side moving backward in the direction of rotation.

This makes it possible to suppress the magnet torque that occurs in the direction opposite to the direction of rotation of the rotor 52. As a result, the torque of the motor 50 can be increased, and high output can be obtained even with a small size, achieving both high output and lightweight design.

<Modification>
9 shows a modified example of the drive motor 50. The drive motor 50 of this modified example uses a rotor 52 having four salient poles 52b. Although there are eight coils 80, the drive motor 50 forms a rotating magnetic field by switching the energization state of one current (AC) (so-called single phase).

For the mini fan motor 2, high speed rotation of 50,000 r/min or more, and even ultra-high speed rotation of 100,000 r/min or more are required. The more salient poles 52b there are, the more current switching control is performed during one rotation. Therefore, if the rotation speed becomes significantly high, the current switching control becomes complicated, and there is a risk that the control will become unstable or impossible to control. Therefore, the drive motor 50 of this modified example, which has fewer salient poles 52b, is advantageous for ultra-high speed rotation.

The drive motor according to the disclosed technology is not limited to the above-described embodiment, but also includes various other configurations.

For example, in the above embodiment, an application example to a stick-type vacuum cleaner is shown, but the disclosed technology can be applied to other appliances as well. For example, it can be applied to drive other home appliances such as juicer mixers and food processors, robots, etc.

The shape of the gap is not limited to a slit. It is sufficient that a gap is formed in the salient pole portion so that a larger magnetic path is formed in the front part of the salient pole portion in the rotational direction than in the rear part. For example, it may be a groove extending in the radial direction, or a space formed inside the salient pole portion. The gap may be divided into multiple small gaps.

The shape of the slit is also one example. Depending on the specifications, it may be slightly curved, may be wider or narrower, or may extend diagonally.

The wire for the coil 80 is preferably rectangular wire, but is not limited to this. It may also be a regular round wire.

Motor 50 operates as a so-called two-phase, eight-slot, six-salient-pole motor, and in a modified example, as a so-called single-phase, eight-slot, four-salient-pole motor, but the motors according to the disclosed technology also include various combinations other than the above-mentioned number of phases, slots, and salient poles, for example, three-phase, twelve-slot, ten-salient-pole.

REFERENCE SIGNS LIST 1 Vacuum cleaner 2 Mini fan motor 10 Housing 20 Impeller 30 Shroud 40 Substrate 50 Drive motor 51 Shaft 52 Rotor 52b Salient pole portion 52c Slit (gap)
52d Large magnetic path portion 52e Small magnetic path portion 53 Stator 60 Stator core 60a Back yoke portion 60b Teeth portion 60c Slot 61 Element core 61a Yoke element 61b Teeth element 62 Magnet 70 Insulator 80 Coil 80a Flat wire P Rotation shaft G Air gap 521 to 525 Salient pole side surface

Claims (8)

A drive motor that rotates in only one predetermined direction,
A rotatable shaft;
a rotor having a boss portion integrally formed with the shaft, no magnet, and a plurality of salient pole portions radially protruding from the boss portion ;
a stator disposed around the rotor with an air gap therebetween;
Equipped with
The stator includes:
a stator core having a back yoke portion and a plurality of teeth portions extending inwardly from the back yoke portion;
A plurality of coils are disposed around the teeth portion;
having
the stator core has a plurality of element cores each having a substantially U-shape in which a pair of tooth elements constituting the teeth portion extend in an opposing manner from both ends of a circular-arc yoke element constituting the back yoke portion, and a plurality of magnets, and is configured by connecting each of the element cores and the magnets in an annular shape with one magnet sandwiched between the opposing tooth elements of two adjacent element cores,
the drive motor constitutes a flux switching motor capable of magnetizing the rotor with the magnet,
a gap is formed in the salient pole portion , extending radially from the boundary with the boss portion to the tip of the salient pole portion and penetrating in the axial direction, the salient pole portion having a large cross-sectional area extending forward in the rotational direction from the gap, and a small magnetic path portion having a small cross-sectional area extending rearward in the rotational direction from the gap, and the magnetic flux of the magnet flows more into and out of the large magnetic path portion than into the small magnetic path portion, thereby causing a magnetic attraction force that is greater in the rotational direction than in the counter-rotational direction. 2. The drive motor according to claim 1,
The thickness of the salient pole portion is greater at a front portion relative to the slit in the direction of rotation than at a rear portion. 2. The drive motor according to claim 1,
Each of the magnets has a pair of inclined side surfaces that are spaced apart radially outward,
A drive motor in which each of the side surfaces is in surface contact with the teeth portion. In the drive motor according to any one of claims 1 to 3,
A drive motor in which each of the magnets is an anisotropic Sm-Fe-N bonded magnet containing 40 vol. % or more of a resin component. In the drive motor according to any one of claims 1 to 4,
A drive motor in which the end faces of the magnets located on the inner diameter side of the motor are located on the outer diameter side of the protruding ends of the teeth. In the drive motor according to any one of claims 1 to 5,
an impeller attached to the shaft;
A shroud having an intake port at a center portion and disposed so as to cover the impeller;
Further comprising:
The drive motor that constitutes the fan motor. 7. The drive motor according to claim 6,
The drive motor constitutes a mini fan motor having an outer diameter of 100 mm or less, an overall height of 50 mm or less, and a suction power of 250 W or more. 8. The drive motor according to claim 7,
The coil is formed to have a predetermined inside dimension by edgewise winding, in which a rectangular wire having a rectangular cross section is bent toward its short side,
each of the teeth has an outer dimension that fits into an inner dimension of the coil,
A drive motor, in which each of the coils is attached to each of the teeth.

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