JPS6051351B2 - magnetic generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic power generation device that applies interlinking magnetic flux to a power generation coil and generates a power generation voltage in the power generation coil by changing the magnetic flux. The present invention provides a magnetic power generation device suitable for application to a rotational speed signal generator of a rotational speed detection device for a capstan motor, a so-called frequency generator.

An embodiment in which the present invention is applied to a frequency generator will be described below with reference to the drawings and in comparison with a conventional example.

FIG. 1 is a cross-sectional view showing the structure of a frequency generator conventionally used in a capstan motor of a tape recorder, etc., and FIG. 2 is a cross-sectional view of the main parts thereof.

To explain this, the frequency generator includes a first fixing member 16 made of a disc-shaped magnetic material fixed to a housing 14 made of a non-magnetic material of a bearing 12 fixed to a substrate 10, and a first fixed member 16 made of a disk-shaped magnetic material. A second fixing member 18 made of a disk-shaped magnetic material that is provided so that its disk plane faces the fixing member 16 and has a toothed portion 17 on its outer periphery, and an outer circle of the first and second fixing members. The peripheral portion and the second fixing member 18
A rotor 24 as a moving member made of a magnetic material having a toothed part 20 and a flat part 22 facing each other at a required interval, and a disc plane of the first and second fixed members. Between a magnet 26 as a magnetomotive member held between them, and a disk plane of the first and second fixed members held and wound around the bobbin 28 on the outside of the magnet 26, It is made up of a power generation coil 30 that is sandwiched therebetween. The rotor 24 is the rotor 2
The capstan shaft 32 is press-fitted into the capstan shaft 32 and supported by the bearing 12, etc., and is given a rotational movement about the rotation center. Since it is not directly related, it will be omitted here. In FIG. 1, the magnet 26 is planarly magnetized with the upper surface having one polarity and the lower surface having the other polarity.

For convenience of explanation, it is assumed that the upper surface is planarly magnetized with the N pole and the lower surface with the S pole. As is well known, the function of the frequency generator is to cause the generator coil 30 to generate a speed signal having a frequency corresponding to the rotational speed of the rotor 24, and for this purpose, the frequency signal is generated from the magnet 26 and chained to the generator coil 30. The magnitude of the intersecting magnetic flux is
At least one magnetic circuit must be formed that changes as the magnetic head 4 rotates.

Needless to say, a change in the direction of the magnetic flux linkage can also be regarded as a change in magnitude in a broad sense if we consider that the magnetic flux has a negative magnitude. Therefore, the magnetic circuit formed in the frequency generator shown in FIG. 1 and having the configuration described above will be explained with reference to FIG. 2.

There are roughly two types of magnetic circuits formed in the frequency generator shown in FIG.

One of them is shown by the solid line in Figure 2,
The magnetic flux generated from the N pole magnetized on the upper surface of the magnet 26 enters the first fixing member 16, and then sequentially enters the tooth profile 20 of the rotor 24, the tooth profile 17 of the second fixing member 18, and the tooth profile 17 of the second fixing member 18. This path passes through the flat part of the second fixing member 18 and is absorbed by the S pole magnetized on the bottom surface of the magnet 26. The other path is shown by the dashed line in FIG. is from the N pole on the upper surface of the magnet 26 to the first fixing member 16 and the toothed portion 2 of the rotor 24.
0, the plane portion 2 of the rotor 24 is transmitted through the rotor 24;
2. There is a path extending from the flat part of the second fixing member 18 to the S pole on the lower surface of the magnet 26. Of the two magnetic circuits described above, the magnetic circuit shown by the solid line in FIG. 2 is involved in the generation of the speed signal in the frequency generator of FIG. 2 fixing member 18
The opposing state of the toothed portions 17 changes as the rotor 24 rotates, and the magnetic gap between the toothed portions 20 and 17 changes, resulting in a change in magnetic resistance. The magnitude of the intersecting magnetic fluxes can be changed.

The frequency at which the magnitude of the magnetic flux changes is determined by the rotor 24.
The rotational speed of the rotor 24 and the second fixing member 18
The number of teeth in the tooth profile parts 20 and 17 is determined by the number of teeth in the tooth profile parts 20 and 17, and since the number of teeth in the tooth profile parts 20 and 17 is given a required constant number, it uniquely corresponds to the rotational speed of the rotor 24. The resulting speed signal is generated in the generator coil 30. On the other hand, the magnetic circuit shown by the dashed line in FIG.
As long as the rotor 24 rotates ideally with the rotation center at , there is no factor that changes the magnetic resistance of the magnetic circuit, and the normal state is that it is not involved in the generation of the rotational speed signal l of the rotor 24.

However, in reality, it is difficult to maintain the opposed state of the flat part 22 of the rotor 24 and the flat part of the second fixing member 18 constant regardless of the rotational phase of the rotor 24. , for example, the second fixing member 1
8 to the substrate 10 using screws made of iron-based material, and when attempting to attach a rotor magnet or the like to the lower surface of the rotor 24 using screws made of iron-based material,
If the screws made of the above iron-based material form protrusions,
The gap between the protrusions changes as the rotor 24 rotates, and therefore the magnetic resistance changes in accordance with the rotation of the rotor 24. In addition, warpage or distortion of the second fixing member 18, flat portion 2 of the rotor 24, etc.
Although there are conceivable factors for changing the magnetic resistance, such as the occurrence of an error in the flatness of the rotor 24, the largest one is the occurrence of vibration in the axial direction of the capstan shaft 32 of the rotor 24. In particular, a drive rotor magnet (shown in the figure) is attached to the rotor 24 above.
If the rotor 24 is directly mounted and the rotor 24 is rotated by the electromagnetic force between it and a separately provided drive coil (not shown), the electromagnetic force is purely the rotational force of the rotor 24. In addition, it is usual that a thrust force in the axial direction of the capstan shaft 32 is generated at the same time, and furthermore, the thrust force of the capstan shaft 32 described in -F is a thrust bearing made of a viscoelastic material such as oil-impregnated nylon. Since the thrust bearing is generally received and supported, a vibration system is formed having the above-mentioned thrust bearing as a spring and the above-mentioned rotor 24 as a mass, and the thrust force due to the above-mentioned electromagnetic force acts on this vibration system as an external force. It turns out. Furthermore, the electromagnetic force normally acts to maintain the rotation of the rotor 24 by sequentially switching the driving coils that operate as the rotor 24 rotates, and therefore Some variation in the thrust force described above may occur when switching drive coils.

That is, a varying external force is applied to the vibration system, which causes the capstan shaft 32 and the rotor 24 to vibrate in the axial direction of the capstan shaft 32. Due to this axial vibration, the magnetic gap between the flat part of the second fixing member 18 and the flat part 22 of the rotor 24 changes,
As the magnetic resistance changes, the magnitude of the magnetic flux that interlinks with the generator coil 30 through the magnetic circuit shown by the dashed line in FIG. 2 changes. As mentioned above, the magnetic circuit shown by the dashed-dotted line in FIG. 2 should not originally provide a speed signal corresponding to the rotational speed of the rotor 24. The signal generated in the generator coil 30 based on the change in magnetic resistance that occurs in the magnetic field is nothing but a disturbance signal to the original speed signal, and when attempting to control the rotational speed of the rotor 24 based on the speed signal, the control accuracy is degraded. However, in severe cases, this has caused problems such as control becoming impossible.

In order to basically eliminate the above-mentioned problem, the magnetic circuit shown by the dashed line in FIG. One possible method is to reduce the magnitude of the magnetic flux between the flat part 22 and the flat part 22.

In the former method, for example, the flat portion 22 of the rotor 24 is made of a non-magnetic material with high magnetic resistance. Although it is possible to implement by configuring, the tooth profile portion 2 of the rotor 24
It goes without saying that 0 must be made of a magnetic material with low magnetic resistance in order to form a magnetic circuit for generating the original speed signal shown by the solid line in FIG.
However, in this method, the rotor 24 has a two-piece structure having a magnetic part and a non-magnetic part. This will be complicated in manufacturing. The present invention is based on the latter of the above two methods, and this will be explained below.
The figure is a cross-sectional view showing the configuration of the frequency generator of this embodiment, and Figure 4 is a cross-sectional view of its main parts. are given the same number.

As shown in FIG. 3, the feature of the present invention is that a second magnet 34 as a second magnetomotive member is added to the conventional structure shown in FIG.
is provided on the lower surface of the second fixing member 18.

Like the magnet 26, this second magnet 34 is also planarly magnetized with one side having an N pole and the other side having an S pole, and as shown in FIG. The magnetized surfaces of the S poles are arranged to face each other. Third
The magnetic circuit formed in the frequency generator having the configuration shown in the figure is basically the same as that of the frequency generator having the configuration shown in Figure 1, but as described above, the magnetic circuit formed is a flat surface magnetized with the same polarity. The magnetic flux generated from both the magnet 26 and the second magnet 34, which are placed so as to face each other, is the fourth magnet.
As shown in the figure, the second magnet 34 is disposed at a location where the plane part of the second fixing member 18 and the plane part 22 of the rotor 24 are opposed to each other, where they overlap in opposite directions. The existing magnetic flux can be reduced compared to the structure shown in FIG.

In principle, the magnet 26 and the second magnet 3
By controlling the strength of magnetization 4, it is also possible to set the magnetic flux passing through the planar opposing portion and interlinking with the power generating coil 30 to 0. In other words, it is possible to eliminate the magnetic flux in the portion where the magnetic resistance may change due to vibration in the axial direction of the capsulated shaft 32 and rotor 24 as described above or other causes, and of course, the magnetic flux can be reduced. The generation of disturbance signals due to changes in magnitude can also be prevented. As described above, the present invention includes a plurality of fixing members (first fixing member 16 and second fixing member 18 in the embodiment) fixed to a substrate and a plurality of parts facing the fixing member. , a plurality of magnetic circuits (indicated by solid lines and dashed lines in the embodiment) are formed between the fixed members via these plurality of opposing portions, and a moving member ( In the embodiment, a magnetomotive member (magnet 26 in the embodiment) for supplying magnetic flux to the magnetic circuit formed by the rotor 24), the fixed member, and the moving member.
and a power generation coil member (in the embodiment, the power generation coil 30) provided to interlink with the magnetic flux generated by the magnetomotive member and passing through the plurality of magnetic circuits, and the power generation coil member (the power generation coil 30 in the embodiment) Among the magnetic fluxes passing through the plurality of magnetic circuits formed by the members, at least one is configured so that its magnitude changes periodically with the movement of the moving member (in the embodiment, the second fixed member 18 and The rotor 24 is provided with toothed portions 17 and 20 facing each other to periodically change the magnetic resistance of the magnetic circuit shown by the solid line), and the other magnetic circuit (shown by the dashed line in the embodiment). (magnetic circuit), the magnetic flux from the magnetomotive member generated between the fixed member and the moving member (the opposing portion of the flat part of the second fixed member 18 and the flat part 22 of the rotor 24) is canceled out. By providing another magnetomotive member (the second magnet 34), the movement of the moving member causes a change in magnetic flux, and the movement of the moving member generates a signal synchronized with the movement of the moving member. This system is designed to reduce signals mixed in as disturbance signals from other parts of the magnetic generator, thereby allowing the generator coil to generate a power generation voltage that accurately corresponds to the movement of the moving member. When applied to a frequency generator for generating speed signals for a capstan motor such as a tape recorder, a speed signal with a good S/N ratio can be obtained without making major changes to the configuration or structure of each component. This has the excellent effect of making it possible to control the rotational speed with high precision.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing the configuration of a conventional frequency generator;
3 is a sectional view showing the configuration of a frequency generator according to an embodiment of the present invention, and FIG. 4 is a sectional view of the essential part. 10... Board, 16... First fixing member, 17...
- Tooth section, 18... Second fixing member, 20... Tooth section, 22... Plane section, 24... Rotor, 26...
Magnet, 30...Generating coil, 34...Second magnet.

Claims (1)

[Claims] 1. A fixing member fixed to a substrate and a plurality of parts facing the fixing member, forming a plurality of magnetic circuits between the fixing member and the fixing member via these plurality of opposing parts, and a movable member that moves relative to the member; a magnetomotive member for supplying magnetic flux to the plurality of magnetic circuits formed by the fixed member and the movable member; a power generating coil member provided so as to interlink with the magnetic flux passing through the magnetic circuit, and at least one of the magnetic fluxes passing through the plurality of magnetic circuits formed by the fixed member and the moving member is caused by the movement. The size of the member is configured to change periodically in accordance with the movement of the member, and for at least one of the other magnetic circuits, the magnetomotive member generated between the fixed member and the moving member A magnetic power generation device characterized in that another magnetomotive member is provided so as to cancel magnetic flux.