JP3659055B2 - Electric motor rotor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the structure of a rotor of an electric motor in which a permanent magnet is embedded in the rotor, and in particular, can reduce cogging torque without using skew or the like.
[0002]
[Prior art]
As a magnet type synchronous motor (electric motor), there is an IPM motor (embedded magnet type motor) in which a permanent magnet is embedded in a rotor. Since this motor has the characteristics of high efficiency, miniaturization, and high rotation speed, it is currently widely used as a motor suitable for electric vehicles and the like.
[0003]
However, in a motor using such a permanent magnet, the attractive force between the stator and the rotor fluctuates with a change in reluctance due to the iron core, and this fluctuation causes a periodic change with an angular velocity called cogging torque or torque ripple. Torque fluctuations (hereinafter referred to as cogging torque) occur. This cogging torque impairs the smoothness of rotation and causes vibration and abnormal noise, so it is desirable to keep it small.
[0004]
For this reason, various devices for reducing cogging torque have been conventionally used. One of them is to provide a skew (inclination) in the magnetic pole (permanent magnet) of the magnet rotor (for example, Japanese Patent Application Laid-Open No. 63-140645). In addition, there is also disclosed one in which the magnetization direction of the permanent magnet is inclined to cause a skew effect on the rotor (Japanese Patent Laid-Open No. 5-168181).
[0005]
Further, as a method other than skew, for example, the width of the permanent magnet is determined to a predetermined value (or range) at the central angle (Japanese Patent Laid-Open No. 3-98445), and the rotor core is divided so as to divide the magnetic path. A rotor having a non-circular shape provided with a plurality of gaps (Japanese Utility Model Laid-Open No. 5-9147), and changing the outer core shape of the core pieces constituting the rotor in the stacking direction to change the rotor core shape. (Japanese Utility Model Laid-Open No. 3-106851) and the like are disclosed.
[0006]
[Problems to be solved by the invention]
However, in the method of providing a skew in the magnetic poles of the magnet rotor, for example, the laminated rotor core is divided together with the permanent magnets in the laminating direction, and the permanent magnets are inserted into the divided rotor cores, and then stepped by a certain angle. Since it is necessary to shift to the shaft, there is a problem that man-hours increase, labor and time for manufacturing increase, and the cost increases. Even in the method in which the magnetization direction of the permanent magnet is inclined and the skew effect is provided, a special process for making the magnetization direction oblique is required, and it takes time and effort to manufacture.
[0007]
As a method other than skew, first, in the method of determining the width of the magnet, the amount of magnetic flux desired is determined by the width of the magnet, but in this case the width of the magnet cannot be determined arbitrarily. The amount of magnetic flux desired for cogging torque reduction may not be obtained. Also, in the method of making the rotor shape non-circular or changing the rotor core shape, the shape of the rotor or rotor core is not a regular circle, so it is also time-consuming and time-consuming to manufacture, and tends to be expensive. .
[0008]
As described above, in any method, making any change to the permanent magnet itself or changing the shape of the rotor or rotor core itself increases man-hours, requires time and effort for production, and increases the cost. Unavoidable.
[0009]
The present invention has been made in view of such problems of the prior art, and it is possible to reduce the cogging torque without using a skew or the like. The purpose is to provide.
[0010]
[Means for Solving the Problems]
The above object of the present invention is achieved by the following means.
[0011]
(1) The rotor of the electric motor according to the present invention is a rotor of an electric motor in which a plurality of permanent magnets are arranged inside a rotor core, and the plurality of permanent magnets are arranged in a circumferential direction of an outer peripheral portion of the rotor core, A substantially radial magnetic flux blocking portion is provided on the outer peripheral portion of each rotor magnet on the circumferential end surface side of the rotor core, and a protruding portion protruding toward the permanent magnet is provided on the outer peripheral end portion of the magnetic flux blocking portion. And an iron core exists between the protrusion and the permanent magnet .
[0012]
(2) The said magnetic flux interruption | blocking part is in contact with the circumferential direction end surface of the said permanent magnet.
[0013]
(3) The angle between the tip position of the protrusion and the center of the permanent magnet sandwiching the center of the rotor core is an electrical angle of 54 to 59 °.
[0014]
(4) The permanent magnet is a plate-like magnet.
[0015]
(5) The magnetic flux blocking part is a through hole.
[0016]
【The invention's effect】
According to the present invention, the protruding portion protruding to the permanent magnet side is provided at the outer peripheral side end of the magnetic flux blocking portion provided in the rotor core, that is, the magnetic flux blocking portion is substantially L-shaped, and the magnetic flux blocking portions on both sides of the permanent magnet ( The distance between the protrusions) is shorter than the width of the permanent magnet, so that the distribution of magnetic flux by the permanent magnet is optimized, and the cogging torque can be reduced without using skew. At this time, the effect of reducing the cogging torque is given only by the shape of the magnetic flux shielding portion provided in the rotor core, and there is no need to change the permanent magnet itself or the shape of the rotor or rotor core itself. Since points other than the shape are sufficient, the number of man-hours is small, the manufacture is easy, and the cost is low. In addition, since the magnetic flux blocking portion has a shape in which an iron core exists between the protruding portion and the permanent magnet, the magnetic flux of the permanent magnet can be utilized, so that the stator coil and the permanent magnet of the rotor are repelled and attracted. The cogging torque can be reduced without reducing the magnet torque.
[0018]
Further, according to experiments, an angle at which the tip position of the protrusion of the magnetic flux blocking portion and the center of the permanent magnet sandwich the center of the rotor core (hereinafter referred to as “tip angle of magnetic flux blocking portion”) is set to 54 to 59 ° in electrical angle. In this case, the cogging torque rate (= cogging torque maximum value / rated torque) is 1.0%, which is a general target value in motor design (if the cogging torque rate is less than 1.0%, the rotational speed fluctuation is reduced. It is known that vibration and abnormal noise are remarkably improved), and desirable results were obtained. Therefore, the cogging torque can be effectively reduced only by setting the leading end angle of the magnetic flux interrupter to an electrical angle in the range of 54 to 59 °.
[0019]
Further, as described above, the adjustment is based only on the shape of the magnetic flux shielding part, and since there is a large degree of freedom in the shape and arrangement of the magnet, a plate-shaped magnet that is easy to manufacture can be used as a permanent magnet. Combined with this simple rotor structure, it is extremely advantageous in terms of cost.
[0020]
Further, when the magnetic flux blocking part is a through hole, it is only necessary to prepare a predetermined die for punching, and it can be dealt with as it is by a conventional process, so there is no increase in cost in this respect.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a main part front view showing an example of a rotor of an electric motor of the present invention. Here, only one magnetic pole portion is described, and the other magnetic pole portions are omitted because they have the same configuration.
[0023]
This electric motor is a four-pole (two-pole pair) IPM motor (embedded magnet type motor) in which four permanent magnets are embedded in a rotor 10. The rotor 10 includes a rotor core 11 formed by laminating a plurality of thin (for example, 0.5 mm thick) circular silicon steel plates, and a motor shaft (not shown) press-fitted into a shaft hole at the center of the rotor core 11. And four permanent magnets 12 arranged at equal intervals in the circumferential direction of the outer peripheral portion of the rotor core 11. The permanent magnet 12 is a normal plate magnet that is easy to manufacture.
[0024]
Further, substantially radial flux barriers (magnetic flux blocking portions) 13 and 14 are provided on the outer peripheral portion of the permanent magnet 12 of the rotor core 11 on the circumferential end surface side. The flux barriers 13 and 14 are through holes that penetrate in the longitudinal direction of the rotor core 11 and do not pass magnetic flux. Protrusions 13 a and 14 a projecting toward the permanent magnet 12 are provided at the outer peripheral side ends of the flux barriers 13 and 14. That is, the flux barriers 13 and 14 have a substantially L shape, and are arranged such that the interval L between the flux barriers 13 and 14 (projections 13 a and 14 a thereof) is shorter than the width W of the permanent magnet 12. Has been. Further, in order to make use of the magnetic flux of the permanent magnet 12, a gap 15 (dimension d) is provided between the protrusions 13a, 14a of the flux barriers 13, 14 and the permanent magnet 12 so that an iron core also exists in that portion. ing. That is, an iron core is always present on the surface of the permanent magnet 12. The permanent magnet 12 and the flux barriers 13 and 14 are symmetric with respect to a straight line A connecting the center of the permanent magnet 12 and the center of the rotor core 11.
[0025]
FIG. 2 is a drawing showing the relationship between the flux barrier tip position and the cogging torque rate. Here, the tip position of the flux barrier is the angle at which the tip positions of the protrusions 13a, 14a of the flux barriers 13, 14 and the center of the permanent magnet 12 sandwich the center of the rotor core 11 (hereinafter referred to as “flux barrier tip angle”), in other words. Then, the angle formed by the straight line B connecting the tip positions of the protrusions 13a and 14a of the flux barriers 13 and 14 and the center of the rotor core 11 and the straight line A connecting the center of the permanent magnet 12 and the center of the rotor core 11 is electrically Indicated by the angle (θ _F ). Also, the cogging torque rate is expressed by the following equation:
Cogging torque ratio = cogging torque maximum value / rated torque
[0026]
As a result of the experiment, as shown in FIG. 2, the cogging torque rate depends on the flux barrier tip angle θ _F , and it can be seen that there is a desirable range effective in reducing the cogging torque. According to the figure, considering that the general target value of the cogging torque rate in the motor design is 1.0%, the cogging torque rate is 54 to 59 ° (electrical angle) that is 1.0% or less. Is a desirable range as the shape or dimensions of the flux barriers 13 and 14 (projections 13a and 14a thereof). In particular, when the flux barrier tip angle θ _F is 57 ° (electrical angle) or in the vicinity thereof, the effect of reducing the cogging torque is maximized, which is most desirable. When the flux barrier tip angle θ _F is 61 ° (electrical angle), as shown in FIG. 3, the flux barriers 13 and 14 have no protruding portion.
[0027]
Therefore, according to the present embodiment, the protruding portions 13a and 14a protruding toward the permanent magnet 12 are provided at the outer peripheral side end portions of the flux barriers 13 and 14 provided in the rotor core 11, that is, the flux barriers 13 and 14 are substantially omitted. Since the gap L between the flux barriers 13, 14 (projections 13 a, 14 a thereof) on both sides of the permanent magnet 12 is shorter than the width W of the permanent magnet 12, the distribution of magnetic flux by the permanent magnet 12 is made L-shaped. The cogging torque can be reduced without using skew and the like. At this time, the effect of reducing the cogging torque is given only by the shape of the flux barriers 13 and 14 provided in the rotor core 11, and there is no need to change the permanent magnet itself or the shape of the rotor or rotor core itself. Since points other than the shape of 14 are normal, for example, a plate-like magnet can be used as the permanent magnet 12, and the shape of the rotor 10 or the rotor core 11 may be circular, so that the number of steps is small and the production is easy. Inexpensive.
[0028]
In addition, since the iron core is formed between the protrusions 13 a and 14 a of the flux barriers 13 and 14 and the permanent magnet 12, the iron core always exists on the surface of the permanent magnet 12, and the magnetic flux of the permanent magnet 12. Since the stator coil and the permanent magnet 12 of the rotor 10 are repelled and attracted, the cogging torque can be reduced without reducing the magnet torque.
[Brief description of the drawings]
FIG. 1 is a front view of an essential part showing an example of a rotor of an electric motor of the present invention.
FIG. 2 is a drawing showing a relationship between a flux barrier tip position and a cogging torque rate.
3 is a corresponding drawing of FIG. 1 showing the shape of the flux barrier when the flux barrier tip angle is 61 ° (electrical angle).
[Explanation of symbols]
10 ... rotor,
11 ... Rotor core,
12 ... Permanent magnet,
13, 14 ... flux barrier (magnetic flux blocker),
13a, 14a ... protrusions.

Claims (5)

In the rotor of an electric motor in which a plurality of permanent magnets are arranged inside the rotor core,
The plurality of permanent magnets are arranged in the circumferential direction of the outer peripheral portion of the rotor core, and a substantially radial magnetic flux blocking portion is provided on the outer peripheral portion of the rotor core on the circumferential end surface side, and the magnetic flux blocking portion The rotor of the electric motor is characterized in that a projecting portion projecting toward the permanent magnet is provided at an outer peripheral side end portion, and an iron core exists between the projecting portion and the permanent magnet . The rotor of an electric motor according to claim 1 , wherein the magnetic flux blocking portion is in contact with a circumferential end surface of the permanent magnet .   2. The rotor of an electric motor according to claim 1, wherein an angle between an end position of the protruding portion and a center of the permanent magnet sandwiching a center of the rotor core is an electrical angle of 54 to 59 °.   The rotor of an electric motor according to claim 1, wherein the permanent magnet is a plate-shaped magnet.   The rotor of an electric motor according to claim 1, wherein the magnetic flux shielding part is a through hole.

Images