JPH0336939A - Radial rotor structure - Google Patents

Abstract

PURPOSE:To magnetize a magnet perfectly by arranging a wedge type magnet having inner circumferential thickness thinner than the outer circumferential thickness at the inner circumferential side of a rotor. CONSTITUTION:Rotor core 12 held by magnets 14 holds the longitudinal opposite ends of rotor 10 by means of end boards. A shaft 20 is inserted into the end boards and secured thereto. The magnet 14 has wedge type cross section. Consequently, the magnet 14 has low outer circumferential permeance and high inner circumferential permeance. When the magnet is shaped to provide identical permeance at the inner and outer circumferences, the magnet can be magnetized uniformly. By such arrangement, demagnetization resistance is improved resulting in the improvement of torque.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a so-called radial type rotor structure in a synchronous motor, in which the rotor core is held between magnets.

[Conventional technology]

Generally, in the radial type rotor of a synchronous motor,
The magnet is sintered into a rectangular block shape. If the magnets are magnetized individually, the workability will be significantly degraded due to the magnetic force when assembling the magnets into the rotor. Therefore, the magnetization is normally carried out all at once using a dedicated magnetizer after assembly into the rotor.

[Problem to be solved by the invention]

Magnetization by a magnetizer is performed from the outer periphery of the rotor, but in this case, the magnetic path is shorter as it approaches the outer periphery of the rotor, and longer as it approaches the inner periphery. In addition, the magnetic flux passes through the magnets after passing through the rotor core, but since the shape of the magnet is a rectangular parallelepiped, the rotor core inevitably has a fan-shaped (or trapezoidal) cross section, and the magnetic flux passes through the narrow inner circumference of the rotor core. Then, the magnetic flux density increases, and the magnetic permeability decreases accordingly. In other words, out of the celadon magnetic flux, the magnetic flux that passes through the inner circumference of the magnet's rotor is smaller than the magnetic flux that passes through the outer circumference due to the length of the magnetic path when passing through the rotor core and the low permeance caused by the narrowness of the inner circumference of the rotor core. The magnetic flux density becomes smaller than the magnetic flux density of . Therefore, there is a problem in that the inner peripheral portion of the magnet may not be completely magnetized. For this reason, it may be possible to increase the ampere-turn of the magnetizer, but it has been found that even if this is increased, it actually makes almost no contribution to the inner peripheral portion of the magnet, and its effect is weak.

Therefore, in order to solve this problem, the present invention aims to provide a radial type rotor structure in which the magnets can be completely magnetized.

[Means to solve the problem]

In view of the above object, the present invention provides a radial type rotor in which a rotor core is held between magnets, wherein the thickness of the magnet in the inner circumferential direction on the inner circumferential side of the rotor is greater than the thickness on the outer circumferential side. A radial type rotor structure for a synchronous motor is provided, which is characterized by having a thin wedge-shaped cross section.

[For production]

The magnetic permeability of the magnet is very small, and by setting the inner circumferential side thinner than the outer circumferential side, the permeance to the magnetic flux passing through each location is changed. That is, by forming the cross section of the magnet into a wedge shape, it is possible to reduce the permeance on the outer circumferential side and increase the permeance on the inner circumferential side when considering only the magnet. Although the shape of the rotor core changes somewhat due to the change in the shape of the magnet, the length of each magnetic path on the outer and inner circumferential sides basically remains unchanged, so when only the rotor core is considered, the outer and inner magnetic paths Each permeance on the circumferential side remains in the same relationship as a hole and a small hole, respectively. That is, the permeance that takes into account both the rotor core and the magnet acts so that the outer circumferential side and the inner circumferential side have the same value, so that the magnetization performance does not change depending on the location, and the whole can be uniformly and completely magnetized.

〔Example〕

The present invention will be described in more detail below based on embodiments shown in the accompanying drawings. Referring to FIGS. 1 and 2, the rotor core 12 held between the magnets 14 is held between end plates 18 at both ends of the rotor 10 in the longitudinal direction. The fastening method is performed by penetrating and inserting the rod 16. Further, a shaft 20 is inserted into and fastened to the end plate 18.

Conventionally, the cross-sectional shape of the magnet 14 is as shown by broken line 1.
As shown by 4', it is rectangular, and the magnet 14 is formed into a rectangular parallelepiped. However, since the rectangular parallelepiped magnet 14' has the aforementioned drawbacks, the cross-sectional shape of the magnet 14 is wedge-shaped (or can also be expressed as a trapezoid), as shown by the solid line in FIG. to form. That is, the length of the side 14b on the inner circumferential side of the magnet 14 is shorter than the length of the side 14a on the outer circumferential side. Rotor 10
Comparing the magnetic path La that passes near the outer periphery of the magnetic path Lb and the magnetic path Lb that passes near the inner periphery of The length of magnetic path La is longer than that of magnetic path Lb. As shown in the figure, there is a considerable difference in length between the magnetic path La and the magnetic path Lb that pass through the rotor core 12. When the magnet 14 is magnetized by a magnetizer, the generated magnetizing magnetic field is generally quite large, and under such a large magnetic field, the longer the length of the magnetic path, the considerably smaller the permeance becomes.

Therefore, the permeance due to the presence of the rotor core 12 for the magnetic paths La and Lb is considerably smaller for the magnetic path Lb than for the magnetic path La. On the other hand, the permeance due to the presence of the magnet 14 for each magnetic path LaLb is small because the magnetic permeability of the magnet material is considerably smaller than that of the rotor core.

A slight difference in the length of passage of the magnet 14 in Lb makes a considerable difference, and the magnetic path Lb is considerably larger than the magnetic path La. From the above, the permeance of each magnetic path La, Lb depends on the ratio of the sides 14a and 14'b of the magnet 14, the magnetic permeability of the magnet material and the material of the rotor 1a 12, etc. Unlike rotors that use cross-sectional magnets, the rotor core 12 and magnets 14
The difference is considerably reduced when considering both members. This effect is achieved by the magnet 14' of the conventional shape indicated by the broken line in FIG.
As can be seen by comparing the solid line magnet 14 according to the present invention, this can be achieved without changing the amount of magnet material used. Furthermore, if a magnet [4] is used in which the inner circumferential side 14b of the rotor 10 is set shorter than the outer circumferential side 14a, the inner circumferential portion of the rotor core 12 will expand by that amount. Therefore, the reduction in the magnetic permeability of the rotor core material when a large magnetizing magnetic field is applied is small, and as a result, the permeance with respect to the magnetic path Lb becomes larger than in the conventional case. This also applies to both magnetic paths L a
This contributes to making the permeance uniform between Lb and Lb.

In order to quantitatively demonstrate the effects of the rotor structure according to the present invention, an analytical comparison was made with that of a conventional type. The magnet 14 shown in FIG. 3 has a wedge angle θ of approximately 1 as shown in FIG.
This is the case of 5 degrees, and reference numbers 30 and 32 indicate a magnetized core and a magnetized winding, respectively. Reference numeral 12' in Fig. 4 indicates a conventional sector-shaped (or trapezoidal) rotor core when a conventionally shaped magnet 14' is used.The lines in both figures indicate the magnetic path. When a current of 80,000 ampere turns is applied to both of them, the analytical values of the magnetic flux density at the locations PA, PB, PA', and Pa' shown in the figure are 1.62.1.42.
1.76, 1.07·×104 Gauss. That is, in the case of the rotor structure according to the present invention shown in FIG. 3, compared to the case of the conventional rotor structure shown in FIG. has decreased by about 10%, resulting in a decrease in magnet
The difference in magnetic flux density between the outer circumferential side PA and the inner circumferential side PB of 4 is 10
% is no longer too much.

Furthermore, in the rotor of the conventional structure shown in Fig. 4, when the number of ampere turns is 60,000, the locations PA' and P are
The magnetic flux densities at B' are 1.47° and 1.05°, respectively.
XIO' is small, but from this, we simply increase the magnetizing magnetic field of the magnetizer without changing the shape of the magnet 14' (the ratio corresponds to the number of ampere turns from 60,000 to 80,000). It can also be seen that the magnetic flux density at location FB' is hardly improved.

In the above explanation, only the magnetization of the magnet was focused, but in general, a magnet that is completely magnetized has the effect that it is difficult to be demagnetized. This effect is particularly great for rare earth magnets such as neodymium iron magnets and samarium/cobalt magnets.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, in a rotor structure using a magnet with a wedge-shaped or trapezoidal cross section, the difference in permeance with respect to the magnetic path between the outer circumferential side and the inner circumferential side is small. The magnet can be sufficiently magnetized, and as a result of sufficient magnetization, demagnetization resistance is improved and output torque is also improved.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view of a rotor according to the present invention,
2 is a cross-sectional view taken along arrow line II in FIG. 2, FIG. 2 is a vertical cross-sectional view of the rotor according to the present invention, and FIG. 3 is an analysis result diagram showing the magnetic path during magnetization of the rotor magnet according to the present invention. ,
FIG. 4 is an analysis result diagram showing the magnetic path when magnetizing a conventional rotor magnet. 10... Rotor, 12... Rotor core, 14...
Magnet, 20...shaft.

Claims (1)

[Claims] 1. A radial type rotor in which the rotor core is held between magnets, and the magnet has a wedge-shaped cross section in which the circumferential thickness of the magnet on the inner circumferential side of the rotor is thinner than the thickness on the outer circumferential side. A radial type rotor structure of a synchronous motor.