JP5195450B2 - Slotless motor - Google Patents

Description

  The present invention relates to a slotless motor, and more particularly to an electromagnetic structure.

Unlike a so-called slotted motor, the slotless motor does not have teeth and slots in the stator core, and therefore has the advantage that it does not generate cogging torque theoretically and rotates very smoothly. Therefore, it is widely used as a motor that can obtain high rotational accuracy relatively easily.
A conventional slotless motor has a configuration as shown in FIGS. 7 and 8 (see, for example, Patent Documents 1 and 2).
FIG. 7 is a front sectional view of a conventional slotless motor, and FIG. 8 is a side sectional view.
7 and 8, reference numeral 11 denotes a stator core, 11a denotes a stator core end, and 12 denotes an armature winding. The armature winding 12 is fixed to the inner peripheral surface of the stator core 11, and the stator 10 is formed by the stator core 11 and the armature winding 12. 21 is a rotor core, and 22 is a permanent magnet. 30 is a space | gap and 40 is a rotating shaft.
The permanent magnet 22 is fixed to the outer peripheral surface of the rotor core 21, and the rotor core is formed by the rotor core 21, the permanent magnet 22, and the rotating shaft 40. The rotor 20 is arranged inside the stator 10 so as to be opposed to each other through the gap 30. Bearings (not shown) are installed on both sides of the rotary shaft 40, and the bearings are accommodated in brackets (not shown), and the brackets are fitted to frames (not shown). The rotor 20 is supported.
Next, the operation of the slotless motor configured as described above will be described.
By passing a three-phase alternating current through the armature winding 12, a rotating magnetic field is generated inside the stator 10, and due to the interaction between the rotating magnetic field and the magnetic field created by the permanent magnet 22, the rotor 20 Rotate.
As described above, since the slotless motor does not have the teeth and the slots in the stator core, the cogging torque is theoretically not generated, and the slotless motor has an advantage that it rotates very smoothly. However, unlike the slotted motor, the armature winding 12 of the conventional slotless motor is disposed in the gap 30 between the permanent magnet 22 and the stator core 11, so that the outer circumference of the permanent magnet 22 is A so-called magnetic gap from the surface to the inner peripheral surface of the stator core 11 is significantly larger than that of a slotted motor. Since the magnetic resistance increases as the magnetic gap increases, the winding inductance of a slotless motor is usually much smaller than the winding inductance of a slotted motor. This small winding inductance becomes an obstacle when driving the motor. Normally, the permanent magnet type synchronous motor is driven by a PWM driven driver device. At this time, if the winding inductance is small, the current ripple increases, and as a result, the high frequency loss due to the current ripple increases. As a result, there has been a problem that the rated output of the motor can be kept low.
Further, since this high frequency loss is mainly generated in the permanent magnet, the temperature of the permanent magnet becomes abnormally high, so that the magnet is likely to be thermally demagnetized.
In order to increase the winding inductance, it is the simplest method to add an external reactor separately from the motor. However, a space for installing the reactor is required and the connection with the motor is complicated. There is a drawback (see, for example, Non-Patent Document 1).
One method for solving the above problem is disclosed in Patent Document 3. 9 and 10 show a slotless motor disclosed in Patent Document 3. FIG. The slotless motor of Patent Document 3 is different from the slotless motors of Patent Documents 1 and 2 in that the auxiliary iron core 13 is in contact with the coil end portion 52 of the armature winding 12 at the stator core end portion 11a. It is a point that is installed. Since the auxiliary iron core 13 is provided in the coil end part 52, the leakage magnetic flux of the coil end part 52 increases. Therefore, the winding inductance can be increased without adding a reactor separately to the outside. As described above, the problem that the winding inductance of the slotless motor is small is solved.

Japanese Patent Laid-Open No. 11-234989 (FIG. 1) JP 2002-101595 A (FIGS. 1 and 4) JP 2007-135392 A (FIGS. 1 and 2)

IEEJ Transaction D, July 2003 (Page 814) Design and control of interior permanent magnet synchronous motor Issued on October 25, 2001, Ohmsha (page 108)

However, the slotless motor disclosed in Patent Document 3 has the following problems. That is, since the auxiliary iron core is disposed so as to cover the coil end portion to the inner circumference portion of the winding, the auxiliary iron core protrudes from the inner circumference portion of the winding, making it difficult to insert the rotor.
Further, normally, a permanent magnet type synchronous motor requires an angle sensor for detecting the angular position when the motor is driven. However, this angle sensor increases the outer diameter of the motor, particularly the length in the axial direction. Further, since the angle sensor is generally expensive, there is a problem that the price of the entire motor becomes high. For this reason, various methods for driving a motor without using an angle sensor have been proposed (see, for example, Non-Patent Document 2).
Among the various methods, the change in the magnitude of the winding inductance due to the rotational position, while stably driving a low speed including a stopped state and realizing a stable start with torque control, A technique using so-called rotational position dependency has become common. However, for that purpose, the rotor needs to be a so-called embedded magnet type rotor. This is because in the surface magnet type rotor, the winding inductance is substantially constant regardless of the rotor position, and the above method cannot be applied.
However, when an embedded magnet type rotor is employed, there is a problem that it becomes difficult to provide a large hollow hole in the center of the rotor because the permanent magnet is disposed inside the rotor core.

  The present invention has been made in view of such problems, and without adding an external reactor and without increasing the motor dimensions, the winding inductance is much larger than the conventional one, and the high-frequency loss is reduced. The first object of the present invention is to provide a slotless motor that is small in size and easy to assemble a motor. In addition, the second aspect of the present invention is to provide a slotless motor suitable for sensorless driving using the rotational position dependency of the winding inductance, even if a surface magnet type rotor is used. Objective.

In order to solve the above problems, the present invention is configured as follows.
The invention according to claim 1 is a stator having a cylindrical stator core, an armature winding fixed to an inner peripheral surface of the stator core, and a rotor core fitted to a rotating shaft; A rotor having a permanent magnet fixed to the outer peripheral surface of the rotor core, and the armature winding has a linear portion extending in the rotation axis direction and a coil end bent in a direction perpendicular to the axis direction In the slotless motor, the permanent magnet at the coil end of the armature winding is disposed so as to face the inside of the cylindrical stator via a gap. A portion not facing the armature winding is provided with an auxiliary iron core with the same inner diameter as the armature winding so as not to cover the inner peripheral surface of the armature winding, and on the end side in the axial direction of the permanent magnet, A magnetic ring with the same outer diameter as the permanent magnet is arranged at an axial distance from the permanent magnet. , The auxiliary core and the magnetic ring, is characterized in that opposed to each other through a gap in the radial direction.
The invention according to claim 2 is characterized in that the auxiliary iron core and the magnetic ring are made of an insulating coated iron powder type dust core material.
The invention according to claim 3 is characterized in that the auxiliary iron core and the magnetic ring are made of an insulating coated iron powder type dust core material.
The invention according to claim 4 is characterized in that the distance between the magnetic ring and the permanent magnet in the axial direction is wider than the distance from the permanent magnet surface to the stator core.

The present invention has the following effects.
According to the first aspect of the present invention, the auxiliary iron core is added to the end portion of the armature winding that is not opposed to the permanent magnet, that is, the coil end portion, and the auxiliary iron core is opposed to the rotor side. As the magnetic ring is added, the leakage flux at the coil end can be increased, and the winding inductance can be increased without adding a separate reactor outside and without increasing the motor size. can do. Therefore, the current ripple can be suppressed small, and as a result, the high frequency loss can be suppressed small. Therefore, since the high frequency loss is reduced, the heat generation of the motor is reduced and the motor output can be increased.
The auxiliary iron core has the same inner diameter as the armature winding so as not to cover the inner peripheral surface of the armature winding, and the magnetic ring has the same outer diameter as the permanent magnet. The rotor can be easily inserted and arranged.
Moreover, since the auxiliary iron core and the magnetic ring are arranged not at the straight line portion of the armature winding but at the coil end portion, it may adversely affect the magnetic flux from the armature winding and permanent magnet related to torque generation. Absent. Therefore, even if an auxiliary iron core and a magnetic ring are added, the torque can be prevented from becoming small.
Further, since the high frequency loss is mainly generated in the permanent magnet, the high frequency loss can be suppressed to be small, so that the temperature increase of the permanent magnet can be suppressed low, and as a result, thermal demagnetization of the magnet can be prevented. .
According to the second aspect of the present invention, since the auxiliary iron core and the magnetic ring are made of an insulation-coated iron powder type dust core material, the eddy current inside the auxiliary iron core and the magnetic ring becomes very small, and the auxiliary iron core and the magnetic ring. High frequency loss generated inside can be reduced.
According to the invention described in claim 3, since the coil end portion is covered with the auxiliary iron core and the magnetic ring as in the invention described in claim 1, the winding inductance can be increased. Therefore, the current ripple can be suppressed small, and as a result, the high frequency loss can be suppressed small. Furthermore, since the magnetic ring has a gear shape, the leakage magnetic flux from the coil end of the armature winding has a large leakage at the position of the tooth of the gear-shaped magnetic ring, that is, the inductance becomes large. In position, leakage is reduced and inductance is reduced. As described above, since the winding inductance increases or decreases according to the rotor position, angle sensorless driving using the rotor position dependency of the inductance is possible. Therefore, since angle sensorless driving is possible, the angle sensor can be omitted, and the cost and size of the motor can be reduced. Since the auxiliary iron core and the magnetic ring are disposed in the coil end portion, there is an effect that the torque characteristics inherent in the slotless motor are not adversely affected.
According to the fourth aspect of the present invention, since the distance between the magnetic ring and the permanent magnet in the axial direction is wider than the distance from the permanent magnet surface to the stator core, the axial direction from the permanent magnet to the magnetic ring. Leakage magnetic flux can be reduced. Accordingly, a reduction in motor torque can be suppressed, and the size of the motor can be reduced.

1 is a side sectional view of a slotless motor showing a first embodiment of the present invention. It is an expanded view which shows the stator inner peripheral surface of the slotless motor of 1st Example of this invention. It is a schematic diagram which shows the flow of the magnetic flux by the effect | action of the auxiliary iron core and magnetic ring of 1st Example of this invention. It is a perspective view of the rotor of the slotless motor which shows the 2nd Example of this invention. It is a schematic diagram which shows the flow of the magnetic flux by the effect | action of the auxiliary iron core of 2nd Example of this invention, and a magnetic ring (sectional drawing in the tooth | gear of a magnetic ring). It is a schematic diagram which shows the flow of the magnetic flux by the effect | action of the auxiliary iron core and magnetic ring of 2nd Example of this invention (sectional drawing in the trough of a magnetic ring). It is a front sectional view of a conventional slotless motor. It is a sectional side view of the slotless motor of FIG. FIG. 8 is a side sectional view of a conventional slotless motor different from FIG. 7. FIG. 10 is a development view showing a stator inner peripheral surface of the slotless motor of FIG. 9.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional side view of a slotless motor according to a first embodiment of the present invention.
In FIG. 1, 11 is a stator core, 12 is an armature winding, and 13 is an auxiliary iron core. The armature winding 12 is fixed to the inner peripheral surface of the stator core 11, and the stator 10 is formed by the stator core 11, the armature winding 12, and the auxiliary iron core 13. 21 is a rotor core, 22 is a permanent magnet, and 24 is a magnetic ring. 30 is a space | gap and 40 is a rotating shaft.
The permanent magnet 22 is fixed to the outer peripheral surface of the rotor core 21, and the magnetic ring 24 is disposed on the axial side surface of the permanent magnet 22 and fixed to the outer peripheral surface of the rotor core 21. The magnetic ring 24 has the same or substantially the same outer diameter as the permanent magnet 21 (hereinafter referred to as the same outer diameter). The rotor core 21, the permanent magnet 22, the magnetic ring 24, and the rotating shaft 40 form a rotor 20. The rotor 20 is arranged to face the inside of the stator 10 with a radial gap 30 therebetween. The auxiliary iron core 13 and the magnetic ring 24 are also arranged to face each other with the gap 30 therebetween. Bearings (not shown) are installed on both sides of the rotary shaft 40, and the bearings are housed in load-side brackets and anti-load-side brackets (not shown), and the load-side brackets and the anti-load-side brackets are mounted. Similarly, the rotor 20 is supported by fitting into a frame (not shown).

FIG. 2 is a development view showing an inner circumferential surface of the stator of the slotless motor according to the first embodiment of the present invention. FIG. 2 shows a state where the inner peripheral surface of the cylindrical stator is developed in a flat shape so as to be easily understood.
In FIG. 2, 50 is a molded armature coil, 51 is a straight portion of the armature coil 50, and extends in the rotation axis direction. A coil end portion 52 of the armature coil 50 extends in a direction orthogonal to the rotation axis. The armature coil 50 is formed by winding an insulation-coated copper wire in an oval shape and then bending it into an arc shape along the inner peripheral surface of the stator core 11. A plurality of armature coils 50 are arranged and fixed in the circumferential direction on the inner peripheral surface of the stator iron core 11, and the armature coils 50 are connected to form the armature winding 12. doing.
The permanent magnet 22 is opposed to the linear portion 51 through the gap 30, and the permanent magnet 22 is hardly opposed to the coil end portion 52. This is because the linear portion 51 mainly contributes to the generation of torque, and the coil end portion 52 hardly contributes to the generation of torque.
As shown in FIGS. 1 and 2, the auxiliary iron core 13 is installed on the inner peripheral surface of the armature winding 12 and attached so as to surround the coil end portion 52. However, the auxiliary iron core 13 is disposed only on the side surface in the axial direction of the coil end portion 52 and has the same inner diameter dimension as the armature winding 12 or substantially the same so as not to cover the inner peripheral surface of the armature winding 12. Inner diameter dimensions (hereinafter referred to as the same inner diameter dimension).
As described above, the present invention is different from the prior art shown in FIGS. 7 to 10 in the following two points.
The first is that the auxiliary iron core 13 is installed with the same inner diameter as the armature winding 12 so that the coil end portion 52 of the armature winding 12 does not cover the inner peripheral surface of the armature winding. The second is that a magnetic ring having the same outer diameter as that of the permanent magnet 22 is arranged on the side surface in the axial direction of the permanent magnet 22. A front sectional view of the slotless motor of the present invention is the same as that of FIG.

Next, the operation of the slotless motor according to the first embodiment of the present invention configured as described above will be described.
By passing a three-phase alternating current through the armature winding 12, a rotating magnetic field is generated inside the stator 10, and due to the interaction between the rotating magnetic field and the magnetic field created by the permanent magnet 22, the rotor 20 Rotate. This is the same as in the prior art.
Next, the auxiliary iron core 13 and the magnetic ring 24 newly added in the present invention will be described in detail.
The auxiliary iron core 13 has the same inner diameter as the armature winding 12 and is installed so as to be in close contact with the coil end portion 52. The magnetic ring 24 has the same outer diameter as that of the permanent magnet 22 and is disposed on the side surface in the axial direction with a slight gap from the side surface of the permanent magnet 22. As a material of the auxiliary iron core 13 and the magnetic ring 24, it is a matter of course that the auxiliary iron core 13 and the magnetic ring 24 are laminated with electromagnetic steel plates. This is to reduce the loss due to the eddy current generated in the auxiliary iron core 13.
The functions of the auxiliary iron core 13 and the magnetic ring 24 are as shown in FIG. That is, since the auxiliary iron core 13 and the magnetic ring 24 are installed so as to cover the coil end portion 52 of the armature winding 12, the auxiliary iron core 13 and the magnetic ring 24 are not installed. Thus, the leakage magnetic flux 62 of the coil end portion 52 of the armature winding 12 is increased. As the leakage magnetic flux 62 of the coil end portion 52 increases, the leakage permeance of the coil end portion 52 increases, and as a result, the winding inductance increases.
Further, since the auxiliary iron core 13 and the magnetic ring 24 are disposed in the coil end portion 52, the effective magnetic flux 61 from the armature winding 12 and the permanent magnet 22 related to torque generation is adversely affected. There is nothing.
Thus, by arranging the auxiliary iron core 13 and the magnetic ring 24 in the coil end portion 52 of the armature winding 12, the winding inductance can be increased. Since the winding inductance can be increased, the current ripple can be reduced, and as a result, the high frequency loss caused by the current ripple can be reduced. Therefore, since the high frequency loss is reduced, the heat generation of the motor is reduced and the motor output can be increased.

Next, a second embodiment of the present invention will be described.
The structure, characteristics, and operation of the slotless motor according to the second embodiment of the present invention are substantially the same as those of the slotless motor according to the first embodiment of the present invention shown in FIGS. Therefore, illustration and description of reference numerals are omitted.
The second embodiment differs from the first embodiment only in the materials of the auxiliary iron core 13 and the magnetic ring 24. In the second embodiment, the auxiliary iron core 13 and the magnetic ring 24 are made of an insulating coated iron powder type dust core material. Insulation-coated iron powder-type magnetic core material is a soft magnetic material in which the surface of iron powder is coated with an organic substance such as resin or an inorganic substance such as glass, and then compression-molded. Electrical insulation between iron powder particles It is intended to suppress eddy current loss.
As described above, in the second embodiment, the auxiliary iron core 13 and the magnetic ring 24 are made of an insulation-coated iron powder-type dust core material, so that the lamination work of steel sheets as in the case of using electromagnetic steel sheets is omitted. And increase productivity. In addition, since the insulation-coated iron powder type powder magnetic core material is used, even in the case of a non-stacked one-piece structure, the eddy current generated inside the auxiliary iron core 13 and the magnetic ring 24 becomes extremely small, High frequency loss generated in the auxiliary iron core 13 and the magnetic ring 24 can be reduced.

  FIG. 4 is a perspective view of the rotor of the slotless motor showing the third embodiment of the present invention. In FIG. 4, 22 is a permanent magnet, 23a is the magnetic pole center of the permanent magnet, 24b is between the magnetic pole poles of the permanent magnet, 24a is a tooth, and 24b is a valley. The third embodiment differs from the first embodiment only in the shape of the magnetic ring 24, and the side sectional view and the front sectional view are the same as those in the first embodiment, and the reference numerals are also the same. Therefore, illustration and description of reference numerals are omitted. The third embodiment is different from the first embodiment in the shape of the magnetic ring 24. More specifically, in the third embodiment, the shape of the magnetic ring 24 is changed to the pole of the permanent magnet 22. The gear shape has the same number of teeth as the number. Further, the position of the tooth 24a is aligned with the inter-pole position 24b of the magnetic pole of the motor, and the position of the valley 24b is aligned with the magnetic pole center 23a of the motor magnetic pole.

Next, the operation of the slotless motor according to the third embodiment of the present invention configured as described above will be described.
By passing a three-phase alternating current through the armature winding 12, a rotating magnetic field is generated inside the stator 10, and due to the interaction between the rotating magnetic field and the magnetic field created by the permanent magnet 22, the rotor 20 Rotate. This is the same as in the first embodiment.
Functions of the auxiliary iron core 13 and the magnetic ring 24 are as shown in FIGS. Here, in FIG. 5, 6, 24a is a tooth | gear and 24b is a trough. Other reference numerals are the same as those in FIG.
Since the auxiliary iron core 13 and the magnetic ring 24 are installed so as to cover the coil end portion 52 of the armature winding 12, compared with the case where the auxiliary iron core 13 and the magnetic ring 24 are not installed, The leakage magnetic flux 62 in the coil end portion 52 of the armature winding 12 is increased. As the leakage magnetic flux 62 of the coil end portion 52 increases, the leakage permeance of the coil end portion 52 increases, and as a result, the winding inductance increases. This point is equivalent to the first embodiment.
Further, in the third embodiment, since the shape of the magnetic ring 24 is a gear shape having the same number of teeth as the number of poles of the permanent magnet 22, leakage from the coil end portion 52 of the armature winding 12. The magnetic flux 62 has a large leakage at the position of the tooth of the gear-shaped magnetic ring, that is, the inductance is large. On the other hand, at the valley position, the leakage is small and the inductance is small. As described above, since the winding inductance increases or decreases according to the rotor position, angle sensorless driving using the rotor position dependency of the inductance is possible. Therefore, since angle sensorless driving is possible, the angle sensor can be omitted, and the cost and size of the motor can be reduced.
The reason why the position of the tooth 24a is aligned with the interpole position 24b of the magnetic pole of the motor and the position of the valley 24b is aligned with the magnetic pole center 23a of the motor magnetic pole is the same angle as the magnetic pole center 23a of the permanent magnet 22. When the teeth 24a are arranged, the leakage flux in the axial direction from the permanent magnet 22 to the magnetic ring 24 is increased, the effective magnetic flux is decreased, and the torque is reduced.

Next, a fourth embodiment of the present invention will be described. The structure, characteristics, and operation of the slotless motor of the fourth embodiment of the present invention are substantially the same as those of the slotless motor of the first to third embodiments of the present invention shown in FIGS. Since it is the same, illustration and description of reference numerals are omitted.
The fourth embodiment differs from the first to third embodiments in that the axial distance between the magnetic ring 24 and the permanent magnet 22 is greater than the distance from the surface of the permanent magnet 22 to the stator core 11. It is only the point that is wide. By setting it as such a structure, the axial magnetic flux leakage from the said permanent magnet 22 to the said magnetic ring 24 can be reduced. Accordingly, a reduction in motor torque can be suppressed, and the size of the motor can be reduced.

  By adding an auxiliary iron core and a magnetic ring, the winding inductance can be increased without adding a separate reactor to the outside, so there is a limit to the installation area, and it is not possible to add a reactor outside. Applicable. In addition, by forming the magnetic ring in a gear shape, the winding inductance increases / decreases depending on the rotor position, so that angle sensorless driving using the rotor position dependency of the inductance is possible. Accordingly, since angle sensorless driving is possible, the angle sensor can be omitted, and the present invention can be used for a robot driving motor or the like that has a particularly severe limitation on motor installation dimensions.

DESCRIPTION OF SYMBOLS 10 Stator 11 Stator core 11a End of stator core 12 Armature winding 13 Auxiliary core 20 Rotor 21 Rotor core 22 Permanent magnet 23a Magnetic pole center 23b Between magnetic poles 24 Magnetic ring 24a Teeth 24b Valley 30 Gap 40 Rotating shaft 50 Formed coil 51 Linear portion 52 Coil end portion 61 Effective magnetic flux 62 Leakage magnetic flux

Claims (4)

A stator having a cylindrical stator core, and an armature winding fixed to the inner peripheral surface of the stator core;
A rotor having a rotor core fitted to a rotating shaft, and a permanent magnet fixed to the outer peripheral surface of the rotor core;
The armature winding has a linear portion extending in the rotation axis direction and a coil end portion bent in a direction orthogonal to the axial direction,
In the slotless motor, the rotor is disposed so as to face the inside of the cylindrical stator via a gap,
In the portion of the coil end of the armature winding that does not face the permanent magnet, an auxiliary iron core is provided with the same inner diameter as the armature winding so as not to cover the inner peripheral surface of the armature winding,
And, on the end side in the axial direction of the permanent magnet, a magnetic ring having the same outer diameter as that of the permanent magnet is disposed with an interval in the axial direction from the permanent magnet,
A slotless motor, wherein the auxiliary iron core and the magnetic ring are opposed to each other through a radial gap.   2. The slotless motor according to claim 1, wherein the auxiliary iron core and the magnetic ring are made of an insulation-coated iron powder type dust core material. The magnetic ring has a gear shape having the same number of teeth as the number of poles of the permanent magnet mounted on the rotor, the position of the teeth is aligned with the position between the poles of the motor magnetic pole, and the position of the valley is the center of the magnetic pole of the motor magnetic pole. slotless motor according to claim 1 or 2, characterized in that according to the position. The slotless motor according to any one of claims 1 to 3, wherein an interval between the magnetic ring and the permanent magnet in an axial direction is wider than a distance from a surface of the permanent magnet to a stator core.

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