JPS60134745A - Rotating speed detecting mechanism - Google Patents

Abstract

PURPOSE:To accurately detect a rotating speed by constituting a speed detecting conductor in a symmetrical shape to cross to cancel a leakage magnetic flux component from a drive coil, thereby reducing a noise. CONSTITUTION:A speed detecting conductor 112 of a motor rotating speed detector is circulated counterclockwise in a region (a) from a point (d) to a point (e), and subsequently circulated counterclockwise in a region (b) from the point (e) to a point (f). Thus, the signs of induced voltaged due to leakage magnetic fluxes phia, phib from a drive coil are opposite to each other and generated in a direction to cancel each other. Further, since a magnetic flux phic of a region (c) does not cross the conductor 112, the induced voltage is zero. When the regions (a), (b) are so formed as to have the same area for the drive coil and a symmetry, the induced voltaged due to the magnetic fluxes phia, phib become equal to each other.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a rotational speed detection device for detecting the rotational speed of a motor that has an annular magnet as a rotor and a drive coil that provides rotational force to the rotor as a stator. .

Conventionally, as a means for detecting the rotational speed of the above-mentioned motor,
An annular magnetic pole array magnetized with multiple poles along the circumferential direction of the annular magnet is used as a magnetic pole array for speed detection, and is placed opposite to one end surface of this magnetic pole array, and the magnetic flux generated from the magnetic pole array and A method is adopted in which interlinking conductors are used and the rotational speed is detected based on the frequency of a signal generated in the conductors. However, with this method, noise proportional to the switching frequency of the drive coil current is placed on the speed detection conductor due to leakage magnetic flux due to the current of the drive coil that provides rotational force to the rotor, so the SIN ratio of the speed detection device decreases and the speed per rotation is reduced. Detection accuracy decreases. This will be explained below using the drawings.

Figure 1 shows a side cross-section of a motor equipped with a rotational speed detection device.
] It is a figure. In the figure, a rotating shaft 4 is supported on a base 1 by a plurality of bearings 2 and 5, and a disk-shaped magnet holder 5 with a bent outer circumference is attached to the upper end of the rotating shaft 4. On the inner surface and inner periphery of the bent portion 6a of the magnet holder 5, there are an annular magnet 6 for a main magnetic pole arranged concentrically around the rotating shaft 4 as shown in the figure, and an annular magnet 7 dedicated for rotational speed detection. is installed.

A core 8 is integrally fixed to the base 1, facing the annular magnet 6 in a concentric inner direction, and a coil 9 is disposed on the outer periphery of the core 8. The rounded annular magnet 7 is magnetized so that a predetermined number of magnetic poles are arranged along the circumferential direction. A substrate 10 is attached opposite to this annular magnet 7. This board 10 has a second
As shown in the figure, a series of conductors 11 have a substantially circular shape and are printed wiring such that they protrude at predetermined angles. The conductor 11 faces the magnetic pole array for speed detection of the annular magnet 7, and extends in the radial direction at multiple locations. In other words, the magnetic flux generated from the magnetic pole array for detection of the rotating annular magnet 7 is directed to the It is provided in a zigzag pattern so as to cross and interlink with some parts. The relative positional relationship between the positions of the ON and S poles of the magnet 7 and the radially extending portion of the conductor 11 is determined so that the currents induced in the radially extending portion of the conductor 110 do not cancel each other out. For example, when one of the radially extending portions of the conductor 11 faces the north pole of the magnet 7, the portions on both sides thereof face the south poles on both sides of the north pole of the magnet 7. do.

In this configuration, when a current is applied to the coil 9, the shaft 4 rotates, and the magnet 7 attached to this rotor rotates, the magnetic flux generated from each magnetic pole array crosses the conductor 11 while interlinking. Therefore, a voltage is generated across the conductor 11. Since the frequency of this voltage is proportional to the change in magnetic flux that crosses the conductor 11 within a unit time, that is, the rotation speed of the magnet 70, the rotation speed of the motor can be detected from the frequency.

However, since the magnetic flux generated by the current flowing through the drive coil 9 also intersects with the conductor 11, noise components from the drive coil 9 are superimposed on both ends of the conductor 11. This situation is illustrated in FIG. Describe using.

FIG. 5 is a simplified diagram for describing the influence of noise due to leakage magnetic flux from the drive coil 9 with respect to the conductor 11 of the substrate 10, and zigzag (protruding) portions for obtaining signal components are omitted. . To be sure, FIG. 5(A) shows the case of the conductor 11 arranged in the same manner as in FIG. 2, and the conductor 11 in FIG. A region that generates magnetic flux in the opposite direction is provided in the middle of the conductor. In FIG. 5, the areas through which the leakage magnetic fluxes φα, φb, and φC from the drive coil 9 pass are respectively defined as a semicircular α area on the left side of the drawing, a semicircular annular b area on the right side of the drawing, and a C area in the center. Then, in the case of FIG. 5(a), magnetic flux φα, magnetic flux φb, and magnetic flux φC are all interlinked with the conductor 11, so
The noise voltage eJ induced in the conductor 11 is expressed by the following equation (1).

e, 4-mutual (φα+φb+-〇) ・・・・・・・・・
Formula (1) On the other hand, in the case of 00 in Figure 5, the magnetic flux -〇 is the conductor 1
1, the noise voltage eB induced in the conductor 11 is as shown in (2) below.

eB” 27 (φα+φb) ・・・・・・・・・(
Equation 2) In this case, the noise voltage is reduced compared to Equation (1), but it is not completely counteracted, and there is a problem in terms of rotation detection accuracy.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional problems, and to provide a highly accurate motor rotation speed detection device with less noise.

[Summary of the invention]

The feature of the present invention is that the speed detection conductor is arranged symmetrically so as to cancel the leakage magnetic flux component from the drive filter.
This is because they are configured so that they intersect.

[Embodiment of the Invention] Next, an embodiment of the present invention will be described in detail using the drawings. FIG. 4 is a simplified diagram of wiring of a speed detection conductor of a motor rotation speed detection device according to an embodiment of the present invention. In FIG. 4, the conductor 112 goes around the C area clockwise from the point (A) to the point @), and then the B area from the point ←) to the point Q→
It goes around counterclockwise until the end. Therefore, the sign of the induced voltage due to the linkage with the magnetic flux φa and the induced voltage due to the linkage with the magnetic flux 1IIb are opposite to each other, and they are generated in the directions of canceling each other. Furthermore, since the magnetic flux φC in the C region does not interlink with the conductor 112, the induced voltage due to φC is zero.

Here, if the C region and the h region have the same area and are symmetrical with respect to the drive coil, the induced voltage due to the linkage with the magnetic flux φα and the induced voltage due to the magnetic flux linkage are equal to each other. Become. As described above, the noise voltage ec induced in the conductor 11 is expressed by the following equation (5).

ec = 27 (φa -1IIc) = 0 -
...Equation (3) Therefore, the noise voltage due to leakage magnetic flux from the drive coil can be made zero.

In the above embodiment, the annular conductor is configured so that magnetic flux is generated symmetrically in opposite directions, but the present invention is not limited to this. The back emitter may be 1 or more. Further, the substrate 10 is 1
The substrate 10 is attached opposite to the annular magnet 7 dedicated to rotational speed detection, and the base 1 side of the annular magnet for the main magnetic pole is magnetized so that a predetermined number of magnetic poles are lined up along the circumferential direction. Of course, it may also be applied by being attached opposite to the end face of.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to eliminate noise voltage due to leakage magnetic flux from the drive coil, and therefore it is possible to obtain an inexpensive, low-noise, high-precision detector.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a motor with a rotation speed detection device added.
Fig. 2 is a schematic diagram of the structure of the pattern of the conductor for generating speed detection signals, and Fig. 5 is a simplified diagram of the conventional conductor for generating speed detection signals.
FIG. 4 shows a simplified diagram of a conductor according to one embodiment of the invention. [Explanation of symbols] 6...Annular magnet for main pole. 7...Annular magnetic throat dedicated to detecting rotational speed. 8...Core, 9...Coil, 10...Substrate, 11...Speed detection signal generation conductor. 112] 4′! 121211 Figure 3 (A) a b Figure 4 / \ / ・Conflict b

Claims (1)

[Claims] A rotational speed detection mechanism for a rotating device including a rotational shaft rotatably held by a base and a holder mounted on the rotational shaft so as to face the base, the rotational speed detection mechanism detecting the rotational speed of the rotational device. A ring-shaped magnet having a multi-pole array of magnetic poles along a circumference centered on an axis, and a conductor arranged to interlink with the magnetic flux of the ring-shaped magnet, the conductor or the ring-shaped Rotational speed detection characterized in that magnets are fixed to the base or holder, respectively, and the conductors are crossed so that the sum of components interlinked with the vertical magnetic flux from the annular magnet becomes zero. mechanism.