JPS6139842A - Motor - Google Patents

Abstract

PURPOSE:To reduce cogging to the minimum limit and to enhance the efficiency of a motor by providing a nonmagnetic portion or a portion having no magnet at an electric angle of the prescribed range between poles of a permanent magnet of a rotor. CONSTITUTION:A 4n pieces of permanent magnets 2 are mounted on the inner surface of a yoke 1 as a rotor, 3n pieces of salient poles 4a opposed to the magnets 2 over 180 deg. of electric angle and a coil 5 wound on the poles 4 and coupled in 3-phase Y-connection at 120 deg. form an armature, and a nonmagnetic portion or a portion 7 having no magnet is provided at 30 to 60 deg. of an electric angle is provided between the poles of the magnets 2 of the rotor. Thus, a cogging can be suppressed to the minimum limit, and a motor having a high efficiency can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a motor with low cogging and high efficiency, and particularly to a motor suitable for a small-output brushless motor.

[Prior art]

Motors with salient poles narrow the air gap. However, due to the attractive force between the salient poles and the magnetic poles of the permanent magnet, harmful torque unevenness called cogging occurs.In order to reduce this cogging, it is necessary to magnetize the permanent magnet. It is common practice to create a sinusoidal waveform or to make the salient poles or magnetic poles tilted in the direction of rotation (skew), but these all lead to a decrease in motor torque and motor efficiency. This will be further explained with reference to the drawings.

FIG. 1 shows an ideal configuration of a conventional three-phase motor. In this figure, 1 is a yoke, 2 is a permanent magnet,
These constitute the rotor I.

3 is an air gap, 4-1.4-2.4-3. is the salient pole of the armature core (hereinafter collectively referred to as 4).

The same applies to other symbols. ), 5-1°5-2.
A coil 5-3 is wound around each of the salient poles 4-1 to 4-3. 6 is a slot between each salient pole 4-1 to 4-3)
These 4 to 6 constitute armature (2).

In FIG. 1, motor torque is generated by changes in magnetic flux passing through a current-carrying coil 5 as the rotor moves.

That is, in FIG. 1, when the permanent magnet 2 moves to the right, the area of the magnetic pole facing the salient pole 4-1 decreases in the north pole part, increases in the south pole part, and passes through the salient pole 4-1. The magnetic flux changes upward. At this time, the magnetic flux flowing through the salient pole 4-2 changes downward, and the magnetic flux flowing through the salient pole 4-3 does not change.

The same thing applies to any positional relationship between the permanent magnet 2 and the armature (2), and the magnetic flux flowing through the two salient poles 4 always changes in opposite directions, while the magnetic flux flowing through the other salient pole does not change. Therefore, torque can be efficiently generated by energizing only the coil 5 wound around the two salient poles whose magnetic flux changes. Three coils 5-1 to 5-3
The method of energizing only two of them is called 120° energization, and can be easily configured using logic circuits.

By the way, the motor shown in FIG. 1 is not realistic. This is because the salient pole 4 is usually manufactured as a single plate for accuracy reasons, and therefore, it is virtually impossible to wind the coil 5 in a structure in which the slot 6 is closed as shown in FIG. In addition, a portion of the magnetic lines of force flowing into the salient pole 4 from the air gap 3 bypasses the coil 5 through the slot 6, making it impossible to generate sufficient torque.

Therefore, a normal motor has a slot 6a as shown in FIG.
This makes it possible to make the wire larger and wind it, as well as to block the bypass of the magnetic flux.

However, the motor shown in FIG. 2 is inefficient and causes undesirable cogging. That is, in the positional relationship shown in FIG. 2, even if the permanent magnet 2 shifts to the right or left with respect to the armature I, the salient pole 4 whose magnetic flux changes is 1 of the central salient pole 4-2.
If 120' current is applied in this state,
The current flowing through the coil 5-1 or 5-3 wound around the other salient pole 4-1 or 4-3 generates torque,
There will be no reactive current.

Further, in the motor shown in FIG. 2, the areas of the N and S poles facing the salient poles 4 change depending on the positional relationship between the permanent magnet 2 and the armature (2). In such a case, the position where the areas of the N and S poles facing armature I are equal becomes stable due to magnetic attraction,
If they are in any other positional relationship, the force that pulls them toward a stable position will work, causing cogging.

[Summary of the invention]

This invention has been made to solve the above problems. In other words, as a result of studying the cogging generation mechanism, the present inventors found that 1 of the magnetic pole width was set between each N pole and S pole.
By using a 4n-pole permanent magnet with 72 non-magnetized parts or parts without magnets and 3n salient poles with a width of 3/2 of the magnetic pole width, a motor with low cogging and high efficiency is achieved. This invention was completed by discovering that it is possible to construct the following. Hereinafter, the present invention will be explained with respect to the negative side.

[Embodiments of the invention]

FIG. 3 is an explanatory diagram of the principle of this invention, in the case of n=1, that is, the permanent magnet is 2-1.2-2.2-3°2-4. This is a case where the number of salient poles is 4, and the number of salient poles is 4-1.4-2.4-3. In addition, 7 is a non-magnetized part or a part without a magnet (hereinafter simply referred to as a non-magnetized part), and if the magnetic pole width of the permanent magnet 2 is multiplied and the width of the non-magnetized part 7 is d, then d=D/ 2
has been selected.

Further, the width W of the salient pole 4 is selected to be W=(3/2)·D.

As is clear from FIG. 3, in any positional relationship between the permanent magnet 2 and the armature I, the areas of the opposing N or S poles of the two salient poles 4 change, and the areas of the remaining salient poles 4 change. In other words, if the rotor moves in the direction of the arrow in Figure 3, due to the change in positional relationship, the area of the N pole facing the salient pole 4-2 increases, the area of the S pole decreases, and the salient pole For 4-1, the opposing S pole area increases, the N pole area decreases, and no change occurs for salient pole 4-3.Therefore, the magnetic pole area is wound around salient poles 4-2 and 4-1, where the magnetic pole area changes. By energizing the coil 5-2.5-1, torque can be generated with maximum efficiency. Furthermore, since the sum of the areas of the N and S poles facing all the salient poles 4 is equal and constant regardless of the positional relationship between the rotor I and the armature I, the occurrence of cogging is minimized. It can be suppressed.

FIGS. 4 and 5 are a plan view and a side sectional view showing an embodiment of the present invention based on the above principle.

In these figures, 1 to 6a and 7 are the same as in FIG. be done. In order to obtain high output with a small size, it is preferable to use a radially oriented rare earth plastic magnet as the permanent magnet 2. The yoke 1 can be made of any ferromagnetic material, but a pressed iron plate is inexpensive.

The salient pole 4 is formed by stacking punched silicon steel plates,
This is used by being press-fitted into a bearing housing 10 formed by cutting carbon steel. The coil 5 is then connected to a Y connection. A printed circuit board 11 is fixed to the bearing housing 1o, and on this printed circuit board 11 there are three Hall elements 12 (only one is shown in the figure) for detecting the timing of switching the energization to the coil 5, and an energization control circuit. 13 is attached.

Furthermore, a rubber magnet 14 is attached to the surface ring of the rotor I facing the Hall element 12 to make the Hall element 12 sensitive. Generally, this type of motor is driven by speed control, but in order to obtain the speed signal for this purpose, a multi-pole (for example, 160 poles) is superimposed on the magnetized pattern for energization switching on the rubber magnet 14. It is preferable to perform weak magnetization, and the magnetic field change due to this multipole is detected by meandering FG (frequency fist generator) coils formed at opposing positions on the printed circuit board 11.

The detected signal is transmitted using a commercially available IC (e.g., Nippon Electric Corporation; gP
c1043c, etc.), and is directly introduced into an energization control IC (for example, Toshiba's TA7245AP). In this way, the coil 5 can be driven by switching the energization based on the detection of the Hall element 12 and energizing the coil 5 at 120@.

According to the above configuration, as explained in the principle of FIG. 3, a motor that does not cause cogging and has high efficiency can be obtained.

Although the above embodiment shows the case where n=2, in order to prevent the shaft 8 from wobbling, it is preferable to set n to 2 or abnormally so that the driving force is balanced.

〔Effect of the invention〕

As explained in detail above, the present invention provides a 4n-pole permanent magnet having a non-magnetized part or a part without a magnet with a width of 1/2 of the magnetic pole width between the north pole and the south pole, and The radius facing the permanent magnet of each salient pole is 3 of the magnetic pole width.
/2 and 63n salient poles, cogging can be minimized and a highly efficient motor can be obtained. Therefore, it is ideal for brushless motors, especially radial gap type motors, and is expected to find wide use in the future.

[Brief explanation of the drawing]

FIG. 1 is a principle explanatory diagram showing an ideal configuration of a conventional three-phase motor, FIG. 2 is a principle explanatory diagram showing an example of the configuration of a conventional three-phase motor, and FIG. 3 is a principle explanatory diagram of the present invention. FIGS. 4 and 5 are a plan view and a side sectional view showing an embodiment of the present invention. In the diagram, "E" is the rotor, ■ is the armature, 1 is the yoke, and 2 is the rotor.
permanent magnet, 3 is air gap, 4 is salient pole, 5 is coil, 6
a is a slot, 7 is a non-magnetized portion, 8 is a shaft, 9 is a bearing, 1o is a bearing housing, 11 is a printed circuit board, 12 is a Hall element, 13 is an energization control circuit, and 14 is a rubber magnet. Note that the same reference numerals in the figures indicate the same or corresponding parts. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Procedure amendment (Own ship November 28, 1981)

Claims (1)

[Claims] A permanent 4n pole having a non-magnetized part or a part without a magnet with a width of 1/2 of the magnetic pole width between the yoke and the N and S poles attached to the inner surface of the yoke. a rotor having a magnet, 3n salient poles facing the permanent magnet, each of which has a width that is 3/2 of the magnetic pole width, and further wound around each of the salient poles; and an armature having a coil that is energized through 120 degrees in a three-phase Y-connection. However, n is an integer of 1 or more.