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Description 1, title of the invention
Electromagnetic pickup cartridge
3. Detailed Description of the Invention The present invention relates to an electromagnetic
pickup cartridge configured to be able to greatly improve various characteristics such as
transmission characteristics with a simple structure. In general, many of the electromagnetic
cartridges are referred to as a movable magnet type (M0M type) that generates electric power
according to the principle shown in FIG. That is, the needle tip 2 is attached to the front end of
the bowl Shiba-1 and the movable magnet 3 is attached to the rear end, and this is supported by
the damper 4 formed of an elastic material. When the needle lever 1 is driven and the movable
magnet 3 vibrates, the vibration unit EndPage: 1 is attached to the inner surface of the end of the
yoke 6 made of high permeability material. By changing the magnetic flux flowing through the
yoke 6, an electromotive force is generated in the coil 7 wound around the outer periphery of the
yoke 6. The quality of the electromagnetic pickup cartridge is determined by how to faithfully
transmit the magnetic flux fluctuation generated in the vibration section to the power generation
section composed of the yoke 6 and the coil 7. In particular, the loss of the magnetic circuit is
small. Is important, and its frequency characteristics must be common. Furthermore, in
conventional electromagnetic pickup cartridges for stereo records, it is considered desirable to
use balanced winding ··· using two coils arranged in parallel in order to cancel the external
induction ham. In addition, the left and right channels must be completely separated and
independent, and the magnetic path lengths must be equal and further symmetrical. FIG. 2 is
based on such a problem and shows a conventional electromagnetic pickup cartridge configured
to satisfy the various conditions described above. That is, the vibrating portion is constituted by
the needle lever 8 and the cylindrical movable magnet 9 attached to the rear end portion, and the
magnetic flux fluctuation generated by the vibrating portion is formed by press bending a high
magnetic permeability material such as permalloy. To the magnetic ball assembly. The magnetic
flux fluctuation of the left channel is generated by the coils 13 and 14 wound around the
magnetic pole 10 yoke 11 and the magnetic pole 12. The magnetic flux fluctuation of the left and
right channels passes through the magnetic pole 15 yoke 16 and the magnetic pole 17 and is
generated by the coil 18.19 wound around them. However, considering the magnetic path
lengths of the magnetic flux passing through the pole piece and the yoke of each channel here,
since the coils 13.14 and 18.19 are disposed for the left and right channels respectively, the left
channel The magnetic path lengths of the magnetic pole 10.12 and the magnetic pole 16.17 of
the right channel are different from each other. There is a problem that unbalance occurs in the
magnetic characteristics of the right and left sides.
Also, in this type of cartridge, bending must be performed when forming the magnetic poles and 11 ° 16, and therefore ferrites that are weak in bending can not be used,
Generally, it is made of a single piece of permalloy. For this reason, magnetic losses can not be
avoided, and therefore, as shown in FIG. 3, it is not possible to obtain a flat transfer characteristic
for the entire required frequency band, and a large attenuation occurs in the high frequency
range. Occurs. This is because the eddy current loss is caused mainly by the skin effect caused by
the size or shape of the magnetic pole or yoke made of permalloy or the like. In order to solve
this, a thinner material may be used, but when composed of a thinner material, there arises a
problem that the sensitivity is lowered. Therefore, in order to solve these problems, it can be
considered to use a thin material to form a laminated structure, but even in such a laminated
structure, the magnetic pole and the yoke are as shown in FIG. In the case of the shape, a
magnetic heat treatment step is required after the press bending step, and after heat treatment, a
large number of materials have to be laminated without giving mechanical strain, so that the
manufacturing process is extremely complicated. It is The present invention is intended to
eliminate the above-mentioned problems, and by using ferrite or the like, which is a sintered core
material of metal oxide with excellent high frequency characteristics, the power generation part
is configured in a simple shape, Provided is an electromagnetic pick-up cartridge which is as
small as possible and at the same time the magnetic path lengths of both left and right channels
are completely equal and symmetrical and the necessary frequency band can be obtained with
high sensitivity and completely flat transfer characteristics. It is a thing. An embodiment of the
present invention will be described below with reference to FIGS. 4 to 7. In FIGS. 4 and 5, 2 ° is
a needle lever, 21 is a needle tip attached to the tip of the needle lever 2o, 22 is a cylindrical
movable magnet attached to the rear end of the needle lever 20, A damper 24 made of an elastic
material for supporting the movable magnet 22 is an EndPage: 2 sleeve for supporting the needle
lever 20 via the damper 23. A vibrating portion is constituted by these needle levers 20 to 24.
FIG. 6 is a U-shaped yoke 25.26 machined with ferrite, which is an oxide magnetic material, with
their ends 27, 28 at their ends. 29.30 are made into a magnetic pole portion, and their inner side
surfaces are integrally processed so as to form a magnetic pole surface 27am2 Baa 29a * 30a,
and a coil 31 ° 32 is wound in the yoke portion of the U-shaped yoke 25.26. It is done.
FIG. 7 shows a fixing member 37 made of a nonmagnetic material and provided with guide
grooves 33m34m35 # 36 equally distributed in four places on the inner surface thereof. After
inserting both ends 27 ° 28.29.30 of the pair of U-shaped yokes 25.26 into the guide grooves of the fixing member 37 from opposite sides of the fixing member 37 respectively,
the fixing member 37 In the surface where the pair of U-shaped yokes 25 and 26 are in contact
with each other, a resin-bonded and fixed shaft forms a power generation portion having a
structure shown in FIG. In the above embodiment, if the movable magnets 22 are disposed
substantially at the center of the magnetic pole surfaces 27a * 28a, 29a, 3oaJ, and in the squareshaped space, and at the approximate center in the front-rear direction, the magnetic paths of the
left and right channels are , Magnetic pole 27, U-shaped yoke 25 magnetic pole 28, and magnetic
pole 29. It becomes U-shaped yoke 26, magnetic pole 3o. Therefore, the magnetic path lengths of
the left and right channels are completely equal, and moreover, because of the symmetry, it is
possible to completely eliminate the unbalance of the output voltage 1 frequency characteristic 1
phase characteristic etc. generated between each channel . Also, the above implementation f! In
No.1, when forming the power generation section with a pair of U-shaped yokes 25.26, there is
no need to perform any bending process, and four magnetic poles 27 to 30 can be formed even if
ferrite weak for bending process is used it can. Therefore, in the case of the conventional
permalloy, as shown in FIG. 3, the attenuation in the audio frequency band is large, while in the
above embodiment, the eddy current product is reduced, and the curve a in FIG. As shown, good
transmission characteristics are realized in the audio frequency band as well as outside the audio
frequency band9. ことができる。 In this case, depending on the magnetic characteristics of the
ferrite and the electrical load conditions of the amplifier when used as a pickup cartridge, as
shown by curve b in FIG. 9, a large resonance may be shown in the transfer characteristics.
However, this resonant frequency can be solved by appropriately designing the shape of the Ushaped yoke or the number of turns of the coil. In addition, in the conventional pickup cartridge
shown in FIG. 2 in general, the magnetic pole portion and the yoke portion are magnetically
joined in the coil, so that the degree of coupling varies. However, according to the above
embodiment, the pair of U-shaped yokes 25 and 26 constituting the power generation unit do
not have a magnetic joint portion because the magnetic pole portion and the yoke portion are
integrated. Therefore, the variation in the degree of coupling described above is completely
Furthermore, since the cross section 1 of the yoke portion in the coil 31632 can be reduced, low
impedance, low inductance design can be made, and it is easy to extend the resonance frequency
beyond the audio frequency band without sacrificing the output voltage It is something that can
be Furthermore, according to the above embodiment, the structure of the pair of U-shaped yokes
25 and 26 constituting the power generation unit is extremely simple, and since precision
machining can be easily performed, the mass productivity is excellent. It can be manufactured
inexpensively. And, in the conventional pickup cartridge as shown in FIG. 2, there is a problem
that the channel separation characteristic becomes worse because it is difficult to position the
magnetic pole 10 ° 12 · 15.17 accurately. According to the above embodiment, the magnetic
pole portions 27/28/29 · of the pair of U-shaped yokes 25.26 precisely processed in the guide
grooves 33.34.3e 5.36 of the fixing member 37 precisely molded with resin. By inserting 30 and
bonding and fixing, it is possible to accurately arrange the positional relationship of the magnetic
pole faces 27a + 28aa29am 30a, and it is possible to significantly improve the separation
characteristics. In the above example, the U-shaped yoke was fabricated using EndPage: 311, 7 to
produce a U-shaped yoke. However, the U-shaped yoke was shaped by powder molding and then
sintered. It may be a ferrite, as shown in FIG. 9, and may be a laminated core in which a large
number of thin metal flat plates such as permalloy prepared by pressing, etching, etc. are
laminated. In this case, since each flat plate is not required to be bent at all and is merely a stack
of flat plates, it is not susceptible to mechanical strain even after magnetic heat treatment, and
the assembly becomes extremely easy. Also in this case, since the fixing member is used, the
assembling accuracy is improved, and various characteristics such as the transfer characteristic
and the channel separation characteristic can be remarkably improved. Furthermore, in the
present embodiment, the four magnetic ball surfaces have a flat surface, but after a pair of Ushaped yokes are lock integrated, the magnetic ball surface is formed into a curved surface
having a constant curvature by lapping or the like. Finishing makes it possible to keep the gap
with the cylindrical movable magnet constant all over each magnetic ball plane, and it becomes
possible to lead the magnetic flux uniformly from the magnet on the cylinder, and various
characteristics such as channel separation Can be significantly improved.
As described above, according to the electromagnetic picker-to-cartridge of the present invention,
there is no magnetic bonding surface between the magnetic pole portion and the yoke portion in
the power generation portion, and by further improving the processing accuracy and the
assembly accuracy. The characteristics such as the transfer characteristics and channel
separation% 41 E can be remarkably improved, and the industrial property is extremely large.
4. Brief description of the drawings FIG. 1 is an explanatory view of the operation principle of an
electromagnetic pickup cartridge, FIG. 2 is a perspective view showing a conventional
electromagnetic pickup cartridge, FIG. 3 is a transmission characteristic diagram of the same
cartridge, FIG. FIG. 6 is a perspective view of an electromagnetic pickup cartridge according to an
embodiment of the present invention, FIG. 6 is a partial sectional perspective view thereof, FIG. 6
is a perspective view of a U-shaped yoke according to the present invention, and FIG. FIG. 8 is a
perspective view of a fixing member, FIG. 8 is a transmission characteristic view of the same
cartridge, and FIG. 9 is a perspective view of a U-shaped yoke showing an embodiment of the
electromagnetic pinkup cartridge according to the present invention. 2o ...... needles lever, 21 ......
tip chip, 22 ...... movable magnet, 23 fist ..... damper, 24 ...... scan IJ- 、, 25.26 · · · · · · · ヨ ー ク
shaped yoke, · · · · · · · · · pole, 31.32 fist · · · · coil, 33.34. 36 a 36 · · · · · · Guide
groove, 37 · · · · · · · · · Fixing member. Name of agent Attorney Nakao and others 1 person Figure
2 Figure 3 EndPage: 4