JPH0258592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational frequency detection device, and in particular, the device includes a permanent magnet that generates magnetic flux on the rotating side, and a conductor that detects changes in the magnetic flux of the permanent magnet on the stationary side. The present invention relates to a rotational frequency detection device that detects rotational frequency.

FIG. 1A provides the background of this invention and shows a sectional view of a motor to which a rotational frequency detection device is attached to which is applied to the invention.

FIG. 1B shows a structural diagram of a permanent magnet of the rotational frequency detection device of FIG. 1A.

FIG. 1C shows a cross-sectional view of the permanent magnet of FIG. 1B in a straight line.

FIG. 1D shows the shape of the conductive foil of the rotational frequency detection device of FIG. 1A.

In the configuration, the rotational frequency detection device 1 includes a permanent magnet 1a and a conductive foil 1b. As the permanent magnet 1a, a ring-shaped ferrite magnet, a rubber magnet, a plastic magnet, or the like is used. As shown in Fig. 1B, the permanent magnet 1a has concavities and convexities of pitch γ _P formed radially in the circumferential direction, and as shown in Fig. 1C, the concave and convex surface is the N pole, and the flat side is the S pole. It is magnetized to a single pole. In addition, the magnetic flux of the N pole on the uneven side is
A relationship is created in which the magnetic flux of the N' pole is smaller than the magnetic flux of the N'' pole of the recess.The permanent magnet 1a formed in this way is attached to the circumferential side of the rotating magnetic disc 2.Magnetic The body disc 2 is fixed to a mounting bracket 4 fixed to the shaft 3.

As shown in FIG. 1D, the conductor foil 1b is formed in a meandering manner along the circumferential direction at intervals of pitch τ _P , and is connected to the output terminals 6 and 7. This conductive foil 1b is attached to the printed board 5, facing the permanent magnet 1a, with a slight gap provided therebetween.

FIG. 2 is a waveform diagram of each component of the rotational frequency detection device, in particular, a shows the magnetic flux change of the permanent magnet, and b shows the output voltage of the conductor foil.

In operation, the permanent magnet 1a in the portion interlinked with the conductive foil 1b generates magnetic flux φ ₁ and magnetic flux φ ₂ that vary in accordance with the concave and convex portions of the uneven portion, as shown in FIG. 2a. When the permanent magnet 1a rotates together with the magnetic disk 2, a voltage corresponding to the time change of the magnetic fluxes φ ₁ and φ ₂ is induced in a certain part of the conductor foil 1b in the circumferential direction. That is, voltages induced in the radial direction are added to the conductor foil 1b, and an averaged AC voltage is obtained as shown in FIG. 2b.

By the way, in the rotational frequency detection device having such a structure, in order to increase the rotation detection accuracy (that is, the frequency), the pitch τ _P of the uneven portion of the permanent magnet 1a is reduced, and the pitch τ _P of the conductor foil 1b is made smaller. It must be made as small as the pitch of the part. However, as the pitch of the uneven parts becomes smaller, the difference between the magnetic flux φ ₁ and the magnetic flux φ ₂ generated in the uneven parts becomes smaller.
In addition, since the permanent magnet 1a is magnetized as a single pole, the magnetic fluxes φ ₁ and φ ₂ of the uneven portion form a uniform long magnetic path with the thickness of the permanent magnet 1a, as shown by the dotted line arrows in FIG. 1A. , the magnetic flux density of the permanent magnet 1a becomes small. Furthermore, the gap between the permanent magnet 1a and the printed board 5 cannot be made shorter due to mechanical constraints.
For this reason, the rotational frequency detection device including a permanent magnet magnetized to a single pole has a drawback that the output voltage of the conductive foil 1b decreases as the rotation detection accuracy increases.

On the other hand, in other rotational frequency detection devices, alternating magnetization of N and S poles is performed in which the uneven portions of the permanent magnet are not formed. Therefore, the magnetic flux of the permanent magnet forms a uniform short magnetic path between the adjacent north and south poles, so the magnetic flux density of the permanent magnet increases. but,
When increasing the frequency, it is difficult to narrow the alternate magnetization pitches of the permanent magnets, so there is a limit to the increase in rotation detection accuracy. That is, in a rotational frequency detection device including alternately magnetized permanent magnets, although the output voltage of the conductor foil increases, there is a drawback in that there is a limit to the increase in rotation detection accuracy.

Therefore, an object of the present invention is to provide a rotation frequency detection device that can increase rotation detection accuracy and generate a relatively high voltage proportional to rotation speed.

In summary, this invention consists of forming permanent magnets in a concave and convex shape in order to improve rotation detection accuracy, and alternately magnetizing the permanent magnets in order to obtain a large voltage proportional to the rotation speed. .

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3A shows a structural diagram of a permanent magnet of a rotational frequency detection device according to an embodiment of the present invention.

FIG. 3B shows the shape of the conductor foil of the rotational frequency detection device according to the embodiment of the present invention.

FIG. 4A shows a cross-sectional view of the permanent magnet of FIG. 3A in a straight line.

FIG. 4B shows a cross-sectional view of a magnetizer that alternately magnetizes the permanent magnets of FIG. 3A.

In terms of configuration, this embodiment differs from FIG. 1B in that the permanent magnet 1a is formed in an uneven shape, and
This is because the poles and S poles are alternately magnetized. That is, as shown in FIGS. 3A and 4A, the permanent magnet 1a is magnetized with N poles and S poles alternately at every pitch 3/2τ _P between the centers of the convex parts, and the pitch τ _P / Convex portions and concave portions are formed alternately every second, and the alternating repetition of the convex portions and concave portions is reversed every time the magnetic pole changes, as shown by the dotted line in FIG. 4A. In other words, the pitch τ _P is repeated a number of times, specifically three times, within the range T _M of the pair of north and south poles.

The permanent magnets 1a are alternately magnetized by a magnetizer shown in FIG. 4B. This magnetizer is composed of a yoke 7 and a coil 8. The yoke 7 is formed with meandering grooves 9 into which coils 8 for passing a large current can be inserted, corresponding to pitches 3/2τ _P of which the permanent magnets 1a are alternately magnetized. For this reason, the groove 9 cannot be made infinitely smaller with the pitch 3/2τ _P being an absolute value. Therefore, the pitches in which the permanent magnets 1a are alternately magnetized are three times as fine as the pitches in which the grooves 9 are formed.

FIG. 5 is a waveform diagram of each component of the rotational frequency detection device of this embodiment, in particular, a shows a change in the magnetic flux of the permanent magnet, and b shows a voltage induced in a portion of the conductive foil.

FIG. 6 shows a waveform diagram of voltages induced in each part of the conductor foil of the rotational frequency detecting device of this embodiment.

Next, the operation of this embodiment will be explained with reference to FIGS. 3B to 6. The part of the permanent magnet 1a interlinked with the conductor foil 1b receives magnetic flux +φ and magnetic flux - which change in accordance with the north and south poles, as shown in FIG. 5a.
φ occurs. In other words, the magnetic flux of N(S) pole +φ(-
φ) is the magnetic flux of the protruding N′ (S′) pole +φ ₁ (−φ ₁ )
is generated so that it is smaller than the magnetic flux +φ ₂ (−φ ₂ ) of the recessed N″ (S″) pole. This permanent magnet 1
When a rotates together with the magnetic disc 2, a temporal change in the magnetic flux interlinking with a portion ω _a in the circumferential direction of the pitch τ _P /2 between the permanent magnet 1 a and the conductor foil 1 b shown in FIG. 3B,
In other words, as shown in Figure 5b and Figure 6a, the induced voltage at the ω _a portion increases when passing through the magnetic pole change area between the N and S poles, and the shape of the uneven portion with the same polarity increases. The voltage decreases when passing through a region where the voltage changes. Similarly, the induced electromotive force at the circumferential portions ω _b and ω _c of the pitch magnetic flux τ _P /2 of the conductor foil 1b has the same waveform as the induced electromotive force at the ω _a portion, as shown in Fig. 6b and c. Yes, the phase is delayed by 360 electrical degrees (120 electrical degrees of distorted AC voltage). Also,
The induced electromotive force in the circumferential portions ω _a ′, ω _b ′, ω _c ′...ω _o of the pitch τ _P /2 of the conductor foil 1b is the same as the induced electromotive force in the portions ω _a , ω _b , ω _c is repeated, and thereafter ω _b ′ (=ω _b ), ω _c ′ (=ω _c ), ω _a , ω _b ……ω _o . Therefore, the output voltage of the conductor foil 1b is
As shown in , the induced electromotive voltages of ω _a to ω _o are summed to form an averaged AC voltage with a constant amplitude.

Note that if the alternating repetition of convex portions and concave portions formed at every pitch τ _P /2 is not reversed each time the magnetic pole changes, the portion ω _a of the conductor foil 1b will have the shape shown by the dotted line in FIG. 5b. In this way, the phase of the voltage generated at each N-pole and S-pole is reversed. That is, the output voltage of the conductor foil 1b becomes zero because it is the sum of the voltages generated at the portion ω _a of the conductor foil 1b.

Therefore, the rotation detection accuracy of the rotation frequency detection device of this embodiment is such that the pitch τ _P of the uneven portion is three with respect to the pair of N and S poles magnetized to the permanent magnet 1a, that is, as shown in FIG. 4A. N′(N″) pole and S′(S″) as shown in
Since the uneven portions are formed at a pitch three times the number of poles in a pair of poles, detection can be performed at three times the frequency of the conventional method. In addition, since the conventional output voltage of the rotational frequency detection device obtained only the voltage corresponding to the change in magnetic flux +φ ₁ , + _{φ 2} shown in FIG.
A voltage corresponding to the difference between φ ₂ and the magnetic fluxes −φ ₁ and −φ ₂ is obtained.

FIG. 7A shows a structural diagram of a permanent magnet of a rotational frequency detection device according to another embodiment.

FIG. 7B shows a cross-sectional view of the permanent magnet of FIG. 7A in a straight line.

In terms of configuration, this embodiment differs from FIG. 3A in that there is a pitch τ _P within the range T _M of the pair of N and S poles.
is repeated an odd number of times, specifically 5 times. Note that the uneven shape of the permanent magnet 1a is 3A.
Formed under the same conditions as in the figure.

FIG. 8 is a waveform diagram of each component of the rotational frequency detecting device of the embodiment shown in FIG. 7A, in particular, a shows the change in the magnetic flux of the permanent magnet, and b shows the output voltage of the conductor foil.

In operation, the magnetic flux +φ (-φ) of the N (S) pole of the permanent magnet 1a in the part interlinked with the conductor foil 1b is the 8th
The magnetic flux of the protruding N′ (S′) pole as shown in Figure a +
φ ₁ and +φ ₃ (−φ ₁ −φ ₃ ) are smaller than the magnetic flux +φ ₂ (−φ ₂ ) of the recessed N″ (S″) pole. In addition,
N'(S') at the center of the N and S poles shown in Figure 8a
Although the magnetic flux +φ ₃ (−φ ₃ ) of the pole is larger than the magnetic flux +φ ₁ (−φ ₁ ) at the magnetic pole change part between the N and S poles,
By using a permanent magnet with anisotropy as the permanent magnet 1 and by performing deep magnetization, the magnetic flux +φ ₃ (−
φ ₃ ) becomes smaller than or equal to the magnetic flux +φ ₁ (−φ ₁ ). When this permanent magnet 1a rotates together with the magnetic disc 2, the induced electromotive force in a circumferential portion ω _a of the conductor foil 1b with pitch τ _P /2 is generated between the N and S poles as shown in FIG. 5b. The voltage increases at the magnetic pole changing portion, and decreases at the portion where the shape of the uneven portion of the same polarity changes. Therefore, the output voltage of the conductor foil 1b becomes an averaged alternating current voltage with a constant amplitude as shown in FIG. 8b.

Therefore, the rotation detection accuracy of the rotation frequency detection device of the other embodiment can be detected at five times the frequency. Also,
The output voltage of the rotation frequency detection device is magnetic flux +φ ₁ , +
A voltage corresponding to the difference between φ ₂ , +φ ₃ and magnetic flux −φ ₁ , −φ ₂ , −φ ₃ is obtained.

FIG. 9 shows a cross-sectional view of another embodiment of the rotational frequency detection device in which the permanent magnet is made straight.

In terms of configuration, the difference between the other embodiments and FIGS. 3A and 7A is that the pitch τ _P is repeated an even number of times, specifically 4 times, within the range T _M of the pair of N and S poles. That's true. In addition, the permanent magnet 1a
The uneven shape is formed under the same conditions as in FIG. 3A.

FIG. 10 is a waveform diagram of each component of the rotational frequency detection device shown in FIG.
indicates the output voltage of the conductor foil.

In operation, the magnetic flux +φ (-φ) of the N (S) pole of the permanent magnet 1a in the part interlinked with the conductor foil 1b is the first
As shown in Figure 0, the magnetic flux of the protruding N'(S') pole + φ ₁ (-φ ₁ ) is the magnetic flux of the recessed N''(S'') pole + φ ₂
(−φ ₂ ). This permanent magnet 1
When a rotates together with the magnetic disk 2, the conductor foil 1
The induced electromotive force in a portion ω _a in the circumferential direction with pitch τ _P /2 of b is the concave N″ pole as shown in Figure 10b.
The protruding N′ pole excluding the magnetic pole change part with the S″ pole
The voltage increases at the magnetic pole changing portion of the S′ pole, and decreases at the portion where the shape of the concavo-convex portion of the same polarity changes. Similarly, the induced electromotive force in other parts of the conductor foil 1b in the circumferential direction with pitch τ _P /2 has the same waveform as that in FIG. 9a, as shown in FIGS. It lags by 90° in voltage potential angle. Therefore, the output voltage of the conductor foil 1b becomes the sum of the induced electromotive voltages b to e in FIG. 10, as shown in FIG. 10f, and becomes an averaged AC voltage.

Therefore, the rotation detection accuracy of the rotation frequency detection device of the other embodiments can detect the rotation at four times the frequency. In addition, the output voltage of the rotation frequency detection device is magnetic flux +φ ₁ ,
A voltage corresponding to the difference between +φ ₂ and the magnetic fluxes −φ ₁ and −φ ₂ is obtained.

In this way, in the rotational frequency detection device, the N pole and the S pole are alternately magnetized at relatively large intervals,
Convex portions and concave portions are alternately formed in each of the N-pole portion and the S-pole portion at intervals relatively smaller than the magnetization interval, and the alternating repetition of the convex portions and concave portions is reversed each time the magnetic pole changes. This selection has the advantage that the output of the rotational frequency detection device can be increased arbitrarily.

As described above, according to the present invention, the unique effects of being able to improve the rotation detection accuracy and generating a relatively high voltage proportional to the rotation speed are achieved.

[Brief explanation of drawings]

FIG. 1A provides the background of this invention and shows a sectional view of a motor to which a rotational frequency detection device is attached to which is applied to this invention. FIG. 1B shows a structural diagram of a permanent magnet of the rotational frequency detection device of FIG. 1A. 1st
Figure C shows a cross-sectional view of the permanent magnet of Figure 1B in a straight line. FIG. 1D shows a shape diagram of the conductor foil of the rotational frequency detection device of FIG. 1A. FIG. 2 shows a waveform diagram of each component of the rotational frequency detection device. FIG. 3A shows a structural diagram of a permanent magnet of a rotational frequency detection device according to an embodiment of the present invention. FIG. 3B shows a shape diagram of a conductor foil of a rotational frequency detection device according to an embodiment of the present invention.
FIG. 4A shows a cross-sectional view of the permanent magnet of FIG. 3A in a straight line. FIG. 4B shows a sectional view of a magnetizing machine that alternately magnetizes the permanent magnets of FIG. 3B. FIG. 5 shows a waveform diagram of each component of the rotational frequency detection device of this embodiment. FIG. 6 shows a waveform diagram of voltages induced in each part of the conductor foil of the rotational frequency detecting device of this embodiment. FIG. 7A shows a structural diagram of a permanent magnet of a rotational frequency detection device according to another embodiment. Figure 7B is the 7th
A cross-sectional view in line with the permanent magnet in Figure A is shown. FIG. 8 shows a waveform diagram of each component of the rotational frequency detection device of FIG. 7A. FIG. 9 shows a structural diagram of a permanent magnet of a rotational frequency detection device according to another embodiment. 1st
FIG. 0 shows a waveform diagram of each component of the rotational frequency detection device of FIG. In the figure, 1 is a rotational frequency detection device, 1a is a permanent magnet, and 1b is a conductive foil.

Claims (1)

[Claims] 1. N poles and S poles are alternately magnetized at relatively large intervals in the circumferential direction of a ring-shaped rotating body, and each N pole portion and S pole portion are magnetized at different intervals. a ring-shaped permanent magnet selected such that convex portions and concave portions are alternately formed at intervals relatively smaller than that of the ring-shaped permanent magnet, and the alternating repetition of the convex portions and concave portions is reversed each time the magnetic pole changes; A rotational frequency detection device comprising a conductor that faces a permanent magnet with a small gap and is formed in a meandering shape at an interval corresponding to the convex portion and the concave portion of the ring-shaped permanent magnet. 2. The rotational frequency detection device according to claim 1, wherein the conductor is a conductive foil formed on a printed board.