JPS61254057A - Flat motor - Google Patents

Abstract

PURPOSE:To enable rotational frequency to be detected without increasing the outer diameter of a motor and without reducing torque, by providing the periphery of some section of a rotor magnet confronting a printed board for detecting the rotational frequency having zigzag pattern, with a rugged section. CONSTITUTION:A rotor magnet 14 is fixed on a shaft 4 via a rotor yoke 2. A stator is provided with a stator yoke 6 and stator coils 5. A printed board 9 for detecting rotational frequency has zigzag pattern, and the full periphery of a partial rotor magnet 14 confronting the printed board 9 is provided with convex sections and concave sections. The phase on the convex sections of the pole N sections is different from the phase on the convex sections of the pole S sections by an angle for one half a cycle on the zigzag pattern of the printed board 9.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a flat electric motor having a rotor magnet and a stator coil that are opposed to each other in a plane, and a rotation detector.

2. Description of the Related Art In recent years, portable type devices such as tape recorders and VTRs have been increasingly used, and flat type electric motors are often used as their driving sources.

With the miniaturization of these devices, there is a strong desire for flat electric motors to be lighter, thinner, and smaller.

An example of the conventional flat type electric motor mentioned above will be described below with reference to the drawings.

FIG. 2 shows a cross section of a conventional flat type electric motor.

In Figure 2, 1 is a rotor magnet, 2 is a rotor yoke,
3 is a rotor post, 4 is a shaft, 5 is a stator coil fixed at a position facing the rotor magnet 1 and formed of self-fused wire or the like to match the magnetic pole shape of the rotor magnet 1, 6 is a stator yoke, and 7 is a Hall element. 8 is a bearing, and 9 is a rotor magnet 1 and a stator coil 50.
This is a printed circuit board for detecting the rotation speed located between the rotor magnets 1 and the stator coils and pasted on the stator coils. It is often constructed from a thin flexible printed circuit board. Furthermore, a pattern to which the Hall element 7 is soldered is formed on the substrate 9.

In order to drive the motor, K requires a drive circuit in addition to this, but it is not directly related to the present invention and will therefore be omitted.

FIG. 3 shows the magnetization pattern of the magnetization surface of the rotor magnet 1 of the conventional example. In the figure, part A is a magnetized part for main magnetic flux, and part B is a magnetized part for rotation detection. Generally, the magnetized part of part B has a motor outer diameter of 40 to 10 oa11.
Most flat type electric motors with a diameter of 2 to 3 pitches are used. In Figure 3, as an example, the main magnetic flux part has 8 poles and the rotation detection part has 6 poles.
The case of 4 poles is shown. This combination of pole numbers will be explained below.

FIG. 4 shows the printed circuit board 9 for rotation speed detection of the conventional example.
This pattern 10 shows the rotation speed detection pattern.
is formed in a zigzag shape, and matches the magnetization pitch and magnetization portion of portion B of the rotor magnet 1, and the number of convex portions in the zigzag pattern is 6%.

The operation of the conventional flat electric motor configured as described above will be described below. When the convex pole part of the zigzag pattern 1o is located at a position facing the N pole of the magnetized part B for rotation speed detection of the rotor magnet 1, the zigzag pattern 10 is linked with positive interlinkage magnetic flux +Φwax, and Zigzag pattern 10
When the convex pole part of is located at a position facing the S pole of the magnetized part B for rotation speed detection of the rotor magnet 1, a negative magnetic linkage -Φ interlinks ax. This situation is shown in FIG. As is clear from Fig. 5, the interlinkage magnetic flux Φ of the zigzag pattern 10 changes from +Φm□ to 1Φ'm&X every time the rotor magnet rotates 360o/64
change between. Therefore, if the rotor continues to rotate, between terminals C and 0 of the zigzag pattern 1o, ・=-
An induced voltage e of ciΦ/dt is generated. This induced voltage e can have a waveform almost like a sine wave with 32 cycles per rotation, making it possible to detect the rotational speed of the motor.

FIG. 6 shows another second embodiment. In the same figure, parts 2 to 8 are completely the same as in the first conventional example, so their explanation will be omitted. In FIG. 6, 11 is a main magnetic flux rotor magnet, 12 is a rotational speed detection magnet, and the rotor magnet 1 of the first conventional example is separated into two parts. Reference numeral 13 is a printed circuit board for detecting the rotation speed, and the difference from the first conventional example is that the rotor yoke 6 and the stator coil 60
It is located in between. This print base 3 has the same zigzag pattern as the first conventional example. The operation of the second conventional example is completely the same as that of the first conventional example, so a description thereof will be omitted.

Problems to be Solved by the Invention However, in the above-mentioned configuration, in the first conventional example, the magnetic flux of the magnetized part for detecting the rotation speed of the rotor magnet 1 does not contribute at all to the torque generated by the electric motor. Therefore, the motor torque decreases in proportion to the magnet diameter. Further, when the magnetized portion for detecting the rotation speed is located on the outer periphery of the magnet, the degree of reduction is particularly large, and the torque may be reduced by about 20%.

Further, in the second conventional example shown in FIG. 6, a separate magnet for detecting the rotation speed is required, which increases the cost and increases the outer diameter of the motor.

The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a flat type electric motor having a rotation speed detector that does not increase the outer diameter of the motor and causes almost no decrease in torque.

Means for Solving the Problems In order to solve the above problems, the flat electric motor of the present invention has the following features:
A printed circuit board for rotation speed detection having a zigzag pattern, a convex portion and a concave portion all around the circumference of the portion of the rotor magnet located opposite to this printed circuit board, and a convex portion on the i-pole portion and a convex portion on the 8-pole portion. In this embodiment, the phases of the zigzag patterns differ by an angle corresponding to a half cycle of the zigzag pattern.

Function The present invention has two cases in which the convex part of the N pole part of the rotor magnet faces the convex pole part of the zigzag pattern, and
The rotor magnet rotates from that position by half a cycle of the zigzag pattern, and the convex part of the S pole of the rotor magnet sometimes faces the convex pole part of the zigzag pattern.As a result, the zigzag pattern The interlinkage magnetic flux changes, and an induced voltage with a frequency proportional to the rotation speed is obtained between the terminals of the zigzag pattern.

In this case, the difference in level between the convex and concave parts of the rotor magnet can be made smaller than the actual air gap including the coil thickness, so there is almost no decrease in the main magnetic flux, and the rotation speed of the separately sealed It becomes possible to create a flat electric motor that does not require a detection magnet.

EXAMPLE Hereinafter, a flat electric motor according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the figure, 2 to 9 are exactly the same as the configuration explained in the first conventional example in FIG. 2, and the rotation speed detection printed circuit board 9 has the zigzag pattern shown in FIG. It has a pattern.

14 is a rotor magnet according to the present invention, a sketch of which is shown in FIG. The rotor magnet 14 has a convex portion and a concave portion formed over the entire circumference of a portion of the magnet, and the width of one of the convex portions and the width of one of the concave portions in the circumferential direction are equal, and the zigzag pattern shown in FIG. The width is equal to the width of 10 convex pole parts or concave pole parts.

Further, the convex portion (concave portion) of the north pole portion of the rotor magnet 14 and the convex portion (concave portion) of the south pole portion are shifted by a half cycle of the zigzag pattern 10 (1800 in electrical angle).

Here, in a resin-molded magnet, the uneven portions of the magnet can be easily formed with high precision using a mold.

Here, the uneven portion of the rotor magnet 14 may be on the inner diameter side, the outer diameter side, or the center portion of the rotor magnet 14, as long as it faces the zigzag pattern 1o of the rotation speed detection printed circuit board 9. In this embodiment, the rotor magnet 14
The number of poles is 8 degrees, and the width of the convex portion or concave portion of the rotor magnet 14 is 360°/64°. Therefore, in this embodiment, eight convex portions and concave portions are formed per pole, but the total number of convex portions and concave portions per pole may be an odd number, and need not be an integer.

The operation of the flat electric motor constructed as described above will be explained using FIG. 8. FIG. 8(a) shows a case where the rotor magnet 10 has come to a position where the convex pole part of the zigzag pattern 10 faces the convex part of the N pole of the rotor magnet 14. In this case, the concave portion of the S pole of the rotor magnet 14 faces the convex pole portion of the zigzag pattern 1o. Therefore, the gap between the convex pole part of the zigzag pattern 10 and the opposing rotor magnet 14 is small at the north pole part, but becomes large at the south pole part. Therefore, the magnetic flux interlinking with the zigzag pattern 1o is dominated by the north pole side. FIG. 8(b) shows that the four-event magnet 14 is rotated for 100 half cycles of the zigzag pattern (18 degrees electrical angle).
0) This is a case of moving to the right, and this time, the convex part of the S pole part faces the convex pole part of the zigzag pattern 10, and the concave part of the N pole part faces. Therefore, the magnetic flux interlinking with the zigzag pattern 1o is dominated by the south pole side.

Through the above-described operation, each time the rotor magnet 14 moves for half a cycle of the zigzag pattern 1o, the polarity of the interlinkage magnetic flux changes as in the conventional example shown in FIG. 5, and as a result, the rotor magnet If continues to rotate, it is possible to obtain an induced voltage waveform between terminals C and D of the zigzag pattern 10 with the number of cycles equal to the convex pole of the zigzag pattern 1o per rotation, making it possible to detect the number of rotations. .

Here, the rotor magnet 14 and the rotation speed detection printed circuit board 9
By making the distance closer to the rotor magnet 14, a practically sufficient rotation speed detection signal can be obtained even if the step between the convex portion and the concave portion of the rotor magnet 14 is reduced. In this case, the rotor magnet 1 including the thickness of the stator coil 6 and the printed circuit board 9 for rotation speed detection.
The amount of step difference between the convex portion and the concave portion of the rotor magnet 14 is relatively very small with respect to the substantial air gap between the rotor magnet 14 and the stator yoke 60. Therefore, the decrease in the main magnetic flux caused by providing a portion of the rotor magnet 14 with a concavo-convex portion for detecting the rotation speed is almost negligible, and there is also almost no decrease in the torque characteristics of the electric motor.

Effects of the Invention As described above, the present invention is capable of detecting rotational speed by simply creating slight irregularities on the periphery of a rotation speed detection printed circuit board having a zigzag pattern and a part of the rotor magnet located opposite to this printed circuit board. , it is possible to obtain a rotation speed detection signal, and there is no large torque reduction due to creating a magnetized part for rotation speed detection on the main magnet as in the conventional example, and there is also no need for a separate rotation speed detection signal. There is no need for a detection magnet, which has great advantages in terms of cost and size, and has great industrial value.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of a flat type motor showing an embodiment of the present invention, Fig. 2 is a cross-sectional view of a flat type motor showing a conventional example, and Fig. 3 is a magnetized state of the rotor magnet in Fig. 2. FIG. 4 is a plan view showing the zigzag pattern of the rotation speed detection printed circuit board in FIG. 2, and FIG. 5 shows the magnetic flux interlinking with the zigzag pattern in FIG. 4. An explanatory diagram showing changes in the number, FIG. 6 is a sectional view of another second conventional example,
FIG. 7 is a schematic diagram showing a rotor magnet in an embodiment of the present invention, and FIGS. 8a and 8b are explanatory diagrams showing the operation of the present invention. 2... Rotor yoke, 4... Group shaft, 6
... Stator coil, 6 ... Stator yoke, 8 ... Bearing, 9 ... Printed circuit board for rotation speed detection. Name of agent: Patent attorney Toshio Nakao and 1 other person
2rI! I Figure 3 Evening 5i! ! ! Cylinder 6 figure

Claims (2)

[Claims] (1) A rotor magnet, a stator coil fixed at a position facing the rotor magnet, and a rotation speed detection printed circuit board located between the rotor magnet and the stator coil and having a zigzag pattern provided on the stator coil. A flat electric motor comprising: a part of the rotor magnet at a position facing the rotation detecting printed circuit board having a convex part and a concave part over the entire circumference, and a convex part of the N pole part and a convex part of the S pole part. , a flat electric motor characterized in that the zigzag pattern has a half-cycle angle, that is, an electrical angle that differs by 180°. (2) A flat electric motor according to claim (1), characterized in that a mold-molded resin magnet is used as the rotor magnet. 6) A flat electric motor according to claim (1), characterized in that a resin magnet is used in which only the concave and convex portions of the rotor magnet are molded.