JPH08205437A - Synchronous motor - Google Patents

Abstract

PURPOSE: To obtain a three-phase synchronous motor employing permanent magnets and utilizing the reluctance torque by providing salient poles in which steep variation in the density of flux passing through the salient pole is prevented as the motor rotates. CONSTITUTION: At the abutting part of a permanent magnet 51 and a salient pole 71, the inner peripheral end part of the permanent magnet 51 is rounded at a predetermined radius of curvature and the outer circumferential end part of the salient pole 71 is rounded at a predetermined curvature. Consequently, the flux passing through the salient pole 71 passes through the corner of the permanent magnet 51 easily and variation in the density of flux passing the back side in the rotational direction of the salient pole 71 is suppressed. This structure prevents steep variation of flux density at the salient pole 71 and suppresses energy loss due to steep variation of flux density and heating. The outer circumferential end part of the salient pole may not be rounded but may be composed of a low permeability member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous motor having salient poles between permanent magnets provided on the outer circumference of a rotor.

[0002]

2. Description of the Related Art Conventionally, as a synchronous motor (synchronous motor) of this type, permanent magnets are provided on the outer circumference of a rotor at equal intervals, as shown in Japanese Unexamined Patent Publication No. 60-121949, and the middle thereof is provided. A permanent magnet type motor having a salient pole is known. This is because the salient poles are provided between the permanent magnets provided on the outer circumference of the rotor so that the magnetic flux in the horizontal axis (d axis) direction due to the armature current can easily pass through the rotor core, and the vertical axis (q axis) The inductance Lq is made larger than the inductance Ld of the d-axis to effectively use the reluctance torque (reaction torque).

In such a conventional example, a permanent magnet and a salient pole may be separated and independent, but if the magnetic flux of the permanent magnet is strengthened and the reluctance torque of the salient pole is effectively used, In many cases, as shown in FIG. 7, there is no gap between the salient pole Q and the permanent magnet.

[0004]

However, in a motor provided with such salient poles, the relative position change between the salient poles and the teeth on the stator side due to rotation facilitates the flow of magnetic flux between the salient poles and the stator. Since it changes, the magnetic flux Mg by the permanent magnet that passes behind the salient pole Q in the rotation direction (part H in FIG. 7).
There is a problem that the combined magnetic flux of the magnetic flux Mq due to the salient poles changes significantly. FIG. 8 is a graph showing this point. FIG. 8 is a graph in which the distribution of the magnetic flux density inside the salient poles existing in the mechanical angle range of ± 15 degrees is plotted with the salient pole center at 0 degree. “■” indicates the magnetic flux density when the salient pole Q is located between the teeth (see FIG. 1),
“●” indicates the magnetic flux density in a state in which the mechanical angle is rotated 3 degrees from this state. Similarly, the distributions of the magnetic flux densities inside the salient poles Q in the state of being further rotated by 3 degrees are shown in the same manner as “◆”, “Δ (the graph is filled in)”, “□”, and “◯”. The graph of "◯" is in a state in which the salient pole Q has reached a position just facing one tooth. As shown in the figure, it is understood that the magnetic flux density on the front side A of the salient pole Q in the rotational direction changes little with rotation, but the magnetic flux density on the rear side B of the rotational direction changes rapidly.

FIG. 9 visually shows such a change in magnetic flux density. As shown in the figure, in this example, there were 29 magnetic fluxes that passed through the salient poles when the electrical angle was 0 degree, whereas the electrical angle was 30 degrees (the salient pole Q faces the teeth. ), The magnetic flux is increased to 34, and it can be seen that the magnetic flux density is rapidly changed. Further, as the rotor rotates, the magnetic flux density drops sharply. Such a sudden change in magnetic flux causes energy loss due to torque ripple and eddy current, and in some cases causes a problem of demagnetization of the permanent magnet due to heat generation due to energy loss.

[0006] The present invention has been made for the purpose of solving such problems associated with changes in magnetic flux between a permanent magnet and a salient pole.
The following composition was adopted.

[0007]

The synchronous motor of the present invention as defined in claim 1 is provided with a plurality of permanent magnets on the outer periphery of the rotor, and the permanent magnets are formed between the permanent magnets. The gist of the synchronous motor is that at least the rear end of the salient pole with respect to the rotation direction of the rotor is made of a member having a low magnetic permeability.

Therefore, this synchronous motor has a simple structure in a usage mode in which a change in the magnetic flux density at the portion where the salient poles shift to the permanent magnets when viewed from the teeth on the stator side is reduced, and in particular when the rotation in one direction is prioritized. With such a configuration, it is possible to enjoy various advantages associated with the reduction of the change in magnetic flux density.

According to another aspect of the synchronous motor of the present invention, the shape of the salient pole itself is specified as one form in which at least the rear end of the salient pole with respect to the rotation direction of the rotor is formed of a member having a low magnetic permeability. The gist is that the shape of the rear end portion is a shape in which the protrusion is reduced by a predetermined shape as compared with the front end portion in the rotation direction. Since the non-protruding portion eventually has the magnetic permeability of air, the structure of the synchronous motor of claim 2 has the same effect as that of claim 1.

A synchronous motor according to a third aspect of the present invention is a synchronous motor in which a plurality of permanent magnets are provided on the outer periphery of a rotor, and salient poles are provided between the permanent magnets. The gist is that it is composed of a member having a low magnetic permeability. This synchronous motor has salient poles between the permanent magnets, but since the ends of the salient poles are made of a material with low magnetic permeability, when viewed from the tooth side, the portion that moves from the permanent magnets to the salient poles. The change in the magnetic flux density is reduced.

According to a fourth aspect of the present invention, there is provided a synchronous motor in which a salient pole having a low magnetic permeability has a shape in which both ends of the salient pole in the rotational direction are rounded with a predetermined curvature. It is a thing. This shape facilitates the wraparound of the magnetic flux and reduces the change in the magnetic flux density at the boundary between the permanent magnet and the salient pole.

According to a fifth aspect of the synchronous motor of the present invention, the maximum radius of curvature of the end portions of the salient poles of the fourth aspect is an arc inscribed between the end faces of the permanent magnets adjacent to the salient poles and the outer peripheral line of the rotor. It is defined as the maximum radius. The radius of curvature of the salient part is
It is important to set the upper limit because the required magnetic flux will not be obtained and the torque performance will decrease if it is made too large.

A synchronous motor according to a sixth aspect is a synchronous motor in which a plurality of permanent magnets are provided on the outer circumference of a rotor, and salient poles are provided between the permanent magnets, and the inner circumference is in contact with the salient poles of the permanent magnet. The gist is that the side end portion is rounded into a predetermined shape.
When the inner peripheral side end of the permanent magnet is rounded, the magnetic flux passing through the salient poles easily wraps around, and it becomes easy to secure the magnetic flux density required for torque performance.

According to a seventh aspect of the synchronous motor, the radius of curvature r of the inner peripheral side end of the permanent magnet according to the sixth aspect is in the range of D / 10≤r≤D / 2 with respect to the thickness D of the permanent magnet. It is what The radius of curvature of the end of the permanent magnet is
It is important to determine this proper range because the required magnetic flux density cannot be obtained if the amount is made too large, and the heat generation due to the change in the magnetic flux density becomes large if the amount is made too small.

[0015]

Preferred embodiments of the present invention will be described below in order to further clarify the structure and operation of the present invention described above. FIG. 1 shows a rotor 50 as an embodiment of the present invention.
2 is a sectional view showing the structure of a synchronous three-phase motor 40 incorporating the rotor 50. FIG.

First, referring to FIG. 2, the synchronous three-phase motor 4
The overall structure of 0 will be described. The synchronous three-phase motor 40 includes a stator 30, a rotor 50, and a case 60 that houses them. The rotor 50 has a permanent magnet 5 on its outer circumference.
1 to 54 are attached, and a hollow rotary shaft 55 provided at the center of the shaft is attached to a bearing 6 provided in a case 60.
1, 62 rotatably supports the shaft.

The rotor 50 is formed by laminating a plurality of rotors 57 formed by punching non-oriented electrical steel sheets.
As shown in FIG. 1, this rotor 57 is provided with salient poles 71 to 74 at four positions on the outer circumference thereof at intervals of 90 degrees. The salient poles 71 to 74 may be formed integrally with the rotor 57, or may be formed as separate members as shown in FIG. The rotor 57 is provided with holes for inserting pins 59 for assembly at four places. After positioning and stacking with the pins 59, the end plates 57A and 57B are arranged before and after the stacked body. In this state, the ends of the pins 59 are welded or caulked to the end plates 57A and 57B to fix the laminated rotor 57. The center portion of the rotor 57 is removed so that the rotating shaft 55 is press-fitted, and a key groove 58 for preventing rotation is further provided. Therefore, the rotating shaft 55 is driven in a state where the key 56 is driven. 55 is inserted into the laminated rotor 57. Thus, the rotor 50 is assembled.

After forming the rotor 50, permanent magnets 51 to 54 having a predetermined thickness are attached to the outer peripheral surface of the rotor 50 in the axial direction. The permanent magnets 51 to 54 are magnetized in the thickness direction. These permanent magnets 51 to 54
When the rotor 50 is assembled to the stator 30, the magnetic path M penetrating the adjacent permanent magnet, rotor 57, and stator 20.
g (see FIG. 1). The positional relationship between the salient poles 71 to 74 and the permanent magnet 51-less 54 will be described later in detail.

The stator 20, which constitutes the stator 30, is formed by punching out a thin sheet of non-oriented electrical steel sheet like the rotor 57, and has a total of 12 teeth 22 as shown in FIG. Also, on the outer periphery of the stator 20,
Eight cutouts 34 are provided for welding for fixing, and four key grooves 36 are provided for inserting a locking key. The stator 30 is fixed by stacking the plate-shaped stators 20 while positioning them using a jig, and welding the notches 34 provided on the outer periphery in this state. In this state, the coil 32 for generating the rotating magnetic field in the stator 30 is wound around the slot 24 formed between the teeth 22.

After assembling the stator 30 in this way, the key groove provided on the case 60 and the key groove on the outer periphery of the stator 30 are aligned with each other, and a key for preventing rotation is interposed therein, and the key groove is provided on the case 60. Assemble the stator 30. Further, the rotor 50 is rotatably assembled with the bearings 61 and 62 of the case 60, whereby the synchronous three-phase motor 40 is completed.

When an exciting current is supplied to the stator coil 32 of the stator 30 so as to generate a rotating magnetic field, a magnetic path Mq penetrating the adjacent salient pole, rotor 57 and stator 20 is thereby formed. The axis through which the magnetic flux formed by the permanent magnet 52 penetrates the rotor 50 in the radial direction is called the d-axis, and the magnetic flux formed by the stator coil 32 of the stator 30 penetrates the rotor 50 in the radial direction. The axis is called the q axis. In this embodiment (four poles), both axes electrically form an angle of 90 degrees.

A salient pole 71 is provided between the permanent magnets 51 to 54.
Through 74. In this embodiment, the shape of the salient poles 71 to 74 and the permanent magnets 51 to 5 are used.
There is a feature in the shape of the inner peripheral side end portion of No. 4, but that point will be described in detail later.

The U-phase, V-phase of the synchronous three-phase motor 40,
As shown in FIG. 3, the W-phase coil has a controller 90.
Is connected to a motor driver 80 controlled by, and by applying an AC voltage of a predetermined frequency with a phase difference of 120 degrees to each phase from the motor driver 80,
Synchronous three-phase motor 40 with a rotation speed corresponding to the frequency
The rotor 50 rotates.

Next, the shape of the portion adjacent to the salient poles 71 to 74 and the permanent magnets 51 to 54, which is a feature of the embodiment corresponding to the invention, will be described. FIG. 5 is an explanatory view showing the shape of a portion adjacent to the permanent magnet 51 and the salient pole 71 together with a partially enlarged view. As shown in the figure, the permanent magnet 51 has a shape along the outer periphery of the rotor 57, but the both ends thereof are not thinned in order to secure the magnetic flux density of the permanent magnet 51 also on the end faces, and are the same as a whole. It is shaped to maintain thickness. That is, the circumferential end surfaces 51a of the permanent magnet 51,
51b is almost parallel. Then, the corners on the inner peripheral side are rounded with a predetermined radius of curvature.

The roundness of this inner peripheral side end of the permanent magnet 51 is
As shown in the enlarged view of FIG. 5, the radius of curvature is r2. If the radius of curvature r2 is too large (broken line B in the figure)
r2), the magnetic flux density at the end of the permanent magnet 51 decreases, and the obtained tokule decreases. On the other hand, if the radius of curvature r2 is too small, the magnetic flux Mq passing through the salient poles 71 is less likely to wrap around the end portions of the permanent magnets 51, so that the change in the magnetic flux density when the salient poles 71 pass through the opposing teeth 22 becomes large. . A sudden change in the magnetic flux density causes energy consumption at the end of the permanent magnet 51, that is, heat generation, which increases the temperature rise, thus reducing the margin (margin) for demagnetizing the permanent magnet 51. The range of the radius of curvature r2 within which the temperature rise is within the allowable range while ensuring the required torque was obtained by experiments. The range of the radius of curvature r2 within which the temperature rise is within 10 ° C./min, where the thickness of the permanent magnet 51 is D,
Empirically, D / 10 ≦ r2 ≦ D / 2.

The inner peripheral side end faces of the permanent magnets 51 to 54 are rounded, and in the embodiment, the outer peripheral side end faces of the salient poles 71 to 74 adjacent to the permanent magnets are also rounded with a predetermined radius of curvature. If the radius of curvature r1 in this case is too small (for example, the broken line Br1 in the drawing), the change in the magnetic flux density when the teeth 22 cross the teeth 22 of the stator 30 becomes large, and the eddy current increases and the heat generation becomes large. Not only that, but also the torque ripple increases. On the other hand, if the radius of curvature r1 is too large, the magnetic flux density of the magnetic path Mq passing through the salient poles decreases, and reluctance torque cannot be obtained sufficiently, and torque performance deteriorates.

In this embodiment, as shown in the enlarged view of FIG. 5, the roundness of the outer peripheral side end of the salient pole has an angle 2θ of 2 ° between the outer periphery of the salient pole 71 and the side end face 51a of the permanent magnet 51. The minimum radius of curvature is r1 among the arcs inscribed on the line of division, which are inscribed in the outer circumference of the salient pole 71 and the side end surface 51a of the permanent magnet.
1, the maximum radius of curvature is defined as r13. The minimum radius r11 is the radius | bh | of the arc in which the arc is in contact with the end b of the circle at the end on the inner peripheral side of the permanent magnet 51, and the maximum radius r13 is the side end surface 51a of the permanent magnet 51.
Radius of an arc that contacts the intersection a extending directly to the inner circumference of the permanent magnet 51 and the outer circumference of the salient pole 71 without rounding
f | The radial distance from the point b to the outer circumference of the salient pole (that is, the distance gd in FIG. 5) is the radius r12.
Arcs such as are allowed.

In FIG. 5, the arcs having the radii of curvature r12 and r13 are drawn so as not to contact the side end surfaces 51a of the permanent magnets 51 in order to avoid the complexity of the drawing, but when the radii of curvature r12 and r13 are adopted, It is desirable to increase the circumferential width of the permanent magnet 51 or increase the circumferential width of the salient pole 71 so that the permanent magnet 51 and the salient pole 71 are in contact with each other.

In the synchronous three-phase motor 40 of this embodiment described above, the salient poles 71 to 74 are provided between the permanent magnets 51 to 54, and the end faces of the adjacent portions thereof are located on the permanent magnets 51 to 54. In this case, the inner peripheral side end surface is rounded, and the salient poles 71 to 74 have the outer peripheral side end surface rounded. Moreover, its roundness (radius of curvature r1 and r
In 2), when the rotor 50 rotates and the salient poles 71 to 74 pass through the teeth 22 of the stator 30, there is little change in the magnetic flux density, and the magnetic paths Mg are formed by the permanent magnets 51 to 54.
And the magnetic flux density of the magnetic path Mq passing through the salient poles 71 to 74 is not reduced. As a result, it is possible to reduce the energy loss due to the change of the magnetic flux density, and further, the temperature rise in the adjacent portions of the salient poles 71 to 74 and the permanent magnets 51 to 54.
It is possible to secure a sufficient margin for keeping the temperature rise of 1 to 54 within a range where demagnetization does not occur.

When the salient poles 71 to 74 have rounded corners as in the above-described embodiment, there is an advantage that a die such as a press for producing these is free from stress concentration and is easy to produce. is there. The permanent magnets 51 to 54 are also easy to manufacture.

Next, a second embodiment of the present invention will be described. The synchronous three-phase motor of the second embodiment has the same structure except the structure of the synchronous three-phase motor 40 and the rotor 150 of the first embodiment. The structure of the rotor 150 of the synchronous three-phase motor of the second embodiment is shown in FIG. As shown in the figure, the rotor 150 includes permanent magnets 51 to 54 having the same shape as that of the first embodiment, and is different only in the shape of salient poles existing therebetween. In the salient poles 171 to 174, about half (B portion in the drawing) on the rear side with respect to the rotation direction of the rotor 150 (X direction in the drawing) is compared with about half on the front side (A portion in the drawing). The shape is such that the amount of protrusion is small. That is, compared to the A portion, the B portion has a shape scraped from the original shape as the salient pole. Although the salient poles 173 and 174 are not shown in FIG. 6, they have the same form as the salient poles 171 and 172.

In this shape, the B portion of the salient poles 171 to 174 has a lower magnetic permeability than the A portion, and the magnetic flux density passing therethrough is low. When the salient poles 171 to 174 pass through the tooth 22, as described with reference to FIGS. 7 and 8, in the normal salient pole, the magnetic flux density sharply decreases with rotation, but the B part is cut in advance. By lowering the magnetic permeability, the density of the magnetic flux passing through the portion B is low from the beginning, so the change in the magnetic flux density can be suppressed to a small level. Therefore, similar to the first embodiment, the energy loss due to the change in the magnetic flux density, and further, the temperature rise in the adjacent portions of the salient poles 171 to 174 and the permanent magnets 51 to 54 can be reduced, and the permanent magnets 51 to 54 can be reduced. A sufficient demagnetization margin can be secured.

In the second embodiment, since the portion B of the salient pole which is on the rear side with respect to the rotation direction is cut away, this synchronous three-phase motor is basically a one-way rotation type. It is a thing. If it rotates in the opposite direction, it may not be possible to reduce the change in magnetic flux density or torque ripple, but when it is used as a drive motor for electric vehicles, the use related to basic performance is unidirectional. (Forward direction)
Since it is sufficient to rotate to, in such a specification, a large effect can be obtained with a simple configuration.

Although some embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, a synchronization having a configuration such as the number of pole pairs 6, 8, 10 ... The present invention has a structure as an electric motor, a structure in which a member having a low magnetic permeability is provided instead of rounding the salient poles in the first embodiment, or deleting the rear side of the salient poles in the second embodiment. Needless to say, the present invention can be implemented in various modes without departing from the above.

[0035]

As described above, the synchronous motor according to the first to seventh aspects of the present invention is excellent in that it is possible to reduce the change in the magnetic flux density due to the rotation of the rotor in the adjacent permanent magnet and salient pole. Produce the effect. Therefore, it is possible to reduce the energy loss due to the change in the magnetic flux density, and further the temperature rise in the adjacent portion of the salient pole and the permanent magnet, and it is possible to sufficiently secure the demagnetization margin of the permanent magnet. As a result, it is also possible to reduce the torque ripple and improve the efficiency accompanying the reduction of energy loss.

In addition, in the synchronous motor according to the sixth and seventh aspects, since the inner peripheral side end of the permanent magnet is rounded into a predetermined shape, the magnetic flux passing through the salient poles easily wraps around, and sufficient tokle performance is secured. It has the advantage of being able to

[Brief description of drawings]

FIG. 1 is a diagram showing a synchronous three-phase motor 40 according to an embodiment of the present invention.
3 is a plan view showing the structure of FIG.

FIG. 2 is a cross-sectional view showing the structure of a synchronous three-phase motor 40 incorporating the rotor 50 of the embodiment.

FIG. 3 shows other salient poles 71 to 7 of the synchronous three-phase motor 40.
It is a top view which shows the structural example of 4.

FIG. 4 is a block diagram showing a motor driver 80 and a controller 90 that drive the synchronous three-phase motor 40.

FIG. 5 is an explanatory view showing a shape of a portion adjacent to a permanent magnet 51 and a salient pole 71 in the first embodiment.

FIG. 6 is an explanatory view showing the shape of a salient pole 171 of the second embodiment.

FIG. 7 is an explanatory diagram showing a relationship between permanent magnets, salient poles, and teeth of a synchronous three-phase motor in a conventional technique.

FIG. 8 is a graph showing how the magnetic flux density inside a salient pole changes in the prior art.

FIG. 9 is an explanatory diagram visually showing how the magnetic flux density inside the salient pole changes as the rotor rotates.

[Explanation of symbols]

 20 ... Stator 22 ... Teeth 24 ... Slot 30 ... Stator 30 ... Stator 32 ... Stator coil 34 ... Notch 36 ... Keyway 40 ... Synchronous three-phase motor 50 ... Rotor 51 or 54 ... Permanent magnets 51a, 51b ... Side End surface 55 ... Rotating shaft 57 ... Rotor 57A, 57B ... End plate 58 ... Key groove 59 ... Pin 60 ... Case 61, 62 ... Bearing 71 to 74 ... Salient pole 80 ... Motor driver 90 ... Controller 150 ... Rotor 171 to 174 ... Salient pole

Front page continued (72) Inventor Eiji Yamada 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Inventor Tetsuya Miura 1 Toyota Town, Toyota City, Aichi Prefecture, Toyota Motor Co., Ltd. (72) Invention Toshifumi Arakawa 1 41, Yokocho, Nagakute-cho, Aichi-gun, Aichi Prefecture Toyota Central Research Institute Co., Ltd. (72) Inventor Yukio Inuma 1-41, Nagakute, Nagakute-cho, Aichi-gun, Aichi Prefecture Toyota Chuo, Ltd. 1 In the laboratory

Claims (7)

[Claims] 1. A synchronous motor having a plurality of permanent magnets on the outer circumference of a rotor, wherein salient poles are provided between the permanent magnets, the rear end of at least the salient poles in the rotational direction of the rotor. A synchronous motor whose part is composed of a member having a low magnetic permeability. 2. The synchronous motor according to claim 1, wherein at least a rear end of the salient pole with respect to the rotation direction of the rotor protrudes by a predetermined shape as compared with a front end with respect to the rotation direction. A synchronous motor with a reduced shape. 3. A synchronous motor having a plurality of permanent magnets on the outer circumference of a rotor, wherein the permanent magnets are formed as salient poles, wherein both ends of the salient poles in the rotational direction have a low magnetic permeability. Synchronous motor composed of members. 4. The synchronous motor according to claim 3, wherein both ends of the salient pole with respect to the rotation direction are rounded with a predetermined curvature. 5. The synchronous motor according to claim 4, wherein the maximum radius of curvature is determined as a maximum radius of an arc inscribed between an end surface of the permanent magnet adjacent to the salient pole and an outer peripheral line of the rotor. Synchronous motor. 6. A synchronous motor comprising a plurality of permanent magnets on the outer circumference of a rotor, wherein the permanent magnets are salient poles, and an inner peripheral side end portion of the permanent magnets in contact with the salient poles. Is a synchronous motor rounded into a predetermined shape. 7. The synchronous motor according to claim 6, wherein a radius of curvature r of an inner peripheral side end portion of the permanent magnet is D / 10 ≦ r ≦ D / 2 with respect to a thickness D of the permanent magnet. Synchronous motor that is in range.