JPH039398Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a front end of a tuner using a small variable capacitor consisting of a plurality of variable capacitor sections including a small capacity variable capacitor section such as UHF.

(Prior art and its problems) Conventionally, receiving circuits using small variable capacitors have been widely used in tuner receiving circuits because the circuit configuration is simple and inexpensive.

However, in extremely high frequency bands such as UHF, coupling between variable condenser sections is likely to occur, and in the past, it has been impossible to use small variable capacitors in close proximity to each variable condenser section in such high frequency reception bands. It was considered possible.

Therefore, in order to enable the use of small variable capacitors even in extremely high reception bands such as UHF, the applicant has achieved this by improving the shielding method inside the variable capacitors (Utility Application No. 85256/1983). .

However, this small multiple variable capacitor is limited by its size and structure that can be mass-produced, so shielding is mainly used between the stages of each variable condenser section, and when looking at the entire receiving circuit including the variable capacitor, there are still no measures against noise and vibration. The necessary parts are left.

In other words, when a tuner board using a small variable capacitor with a high-frequency section is actually incorporated into an electronic device, not only the connections between each section in the variable capacitor or other electrical components, but also the mechanical movement of metal such as switches, etc. Static electricity generated from parts often enters the receiver, is detected through the receiver circuit, and is output as noise. This is particularly likely to occur in tape recorders with radios, which have many mechanical parts such as tape transports.

Also, for those with built-in speakers,
The electrode plate of the variable capacitor vibrates due to the sound pressure and magnetic flux of the speaker, causing microphonic noise and howling.

Particularly in extremely high frequency reception bands such as UHF, these phenomena tend to appear very conspicuously, and a new problem has been posed and a solution has been desired.

In addition, to solve the problem of vibration, measures can be taken, such as fixing the parts of the polyethylene film that is the insulating material between the rotor plates or stator plates of the variable capacitor that protrude from the plate edges, and providing protrusions to support the plates inside the variable capacitor body. However, in the case of a small-capacity variable capacitor with a high receiving frequency band such as the UHF band, the number of rotor plates and stator plates is small, so the above method does not completely suppress vibration. No prevention effect could be obtained, and noise caused by static electricity or the like could hardly be prevented.

(Purpose of the invention) In a tuner configured with a small variable capacitor that includes a section for an extremely high receiving frequency band such as the UHF band, static electricity is generated in each band or from the coupling between each section of the variable capacitor, the mechanical part, etc. It is an object of the present invention to provide a front end that prevents microphonic noise, howling, etc. caused by noise, sound pressure from speakers, vibrations due to magnetic flux, etc.

(Summary of the invention) A small multiple variable capacitor equipped with a plurality of variable capacitor sections including a small capacitance variable capacitor section such as UHF is mounted on a front end board that constitutes a receiving circuit related to the small capacitance variable capacitor section. A part of the shield case for shielding the end board from receiving circuits related to other variable condenser sections is used to shield the sides of the small capacity variable condenser section of the variable capacitor, and together with the shield of the front end board, the shield case of the variable capacitor is This is a new tuner front end that prevents noise, vibration, howling, etc. caused by coupling, static electricity, sound pressure, magnetic flux, etc. in a small capacity section.

(Example) Figures 5 to 8 show an example of a small multiple variable capacitor used in the present invention, and Figure 6 shows a top view.
FIG. 5 is a cross-sectional view taken along line B-B' in FIG.
The figures each show a side view as viewed from the direction of arrow A in FIG. 6.

In each figure, 1 is a variable capacitor main body, and 2 is a polycover. Trimmer capacitors 3a to 3d are arranged on the upper surface of the variable capacitor main body 1, and can be adjusted through holes on the upper surface of the polycover 2.

Between the upper plate 4 and lower plate 5 of the variable condenser main body 1, a UHF local variable condenser section UO,
UHF tuned variable condenser section UA, AM tuned variable condenser section AA.VHF (and FM) tuned variable condenser section FVA, AM station variable condenser section
AO, VHF (and FM) local variable condenser section
They are arranged in a superposed state in the order of FVO, and are provided with square pillars 6a to 6d and pins 7a to 7d which also serve as electrodes and are inserted into these pillars.
Post 8a supporting the UHF variable condenser section,
8b and pins 9a and 9b.

Each variable condenser section can be operated by a common metal rotor shaft 10 rotatably disposed between an upper surface plate 4 and a lower surface plate 5. A rotor plate 11 is attached to each variable condenser section, and stator plates 12 coated with insulation are alternately interwoven with the rotor plates on the pillars 6a to 6d and 8a, 8b facing the rotor plate group of each variable condenser section. It is fixed in this state.

In the AM, VHF (and FM) variable condenser section, each stator plate 12 is inserted into the column to which it is attached and is electrically connected to pins 7a to 7d that fix each variable condenser section. 7 d and the downwardly protruding portions 71 a to 71 d of the bottom plate 5 serve as attachment terminals to the main board 20 .

Regarding the UHF variable condenser section, as is clear from FIG. 8 showing the C-C′ cross section in FIG. They are not connected to the fixing pins 9a, 9b of the stator plates 8a, 8b, and the extensions of the stator plate 12 directly protrude to the side of the variable condenser section to serve as mounting terminals 13a, 13b for mounting on the circuit board. In other words, 13a is the variable condenser section UO from the UHF station.
Among the terminals, 13b is the terminal of the UHF tuned variable condenser section UA.

In addition, grounding shield plates 14 and 15 are arranged on the mutually opposing surfaces of the upper plate 4 and the lower plate 5, respectively, and a grounding terminal 14a is integrally formed on the side edge of the shield plate 14, and the grounding terminal 14a is integrally formed on the side edge of the shield plate 14. The shield plate 15 has a ground terminal 15a on the side edge.
15b is provided by being integrally bent and protruded downward by holding portions 5a and 5b formed on the side edges of the lower surface plate 5.

On the other hand, the UHF variable condenser section has a high reception frequency and is highly susceptible to coupling due to stray capacitance between each variable condenser section.
Unlike other variable condenser sections, it is difficult to place them in the same space without a shield. Therefore
UHF variable condenser section and other AM, VHF (also
FM) In order to prevent coupling due to stray capacitance between the variable condenser sections and between the local variable condenser section UO and the tuned variable condenser section UA in the UHF variable condenser section, ), and local variable condenser section UO and synchronized variable condenser section
Shield plates 14, 16, 1 are installed between the UA and the UA.
7, 15 are arranged, and shield plates 16, 17
Ground terminals 16a and 17a are also integrally formed on the side edges and protrude to the side of the variable condenser in a mutually overlapping state.

Therefore, the UHF variable condenser section UO,
The UA is shielded from other variable condenser sections by shield plates 16, 17, and 15 to prevent coupling between other sections due to stray capacitance.

Also, since the terminals of the UHF variable condenser section protrude to the side of the variable condenser and do not pass through other sections or intersect with other terminals, the terminals of the UHF variable condenser section do not pass through other sections or intersect with other terminals. It can be sufficiently separated from the terminals 71a to 71d of the section, and coupling due to stray capacitance between the terminals can be effectively avoided.

In addition, the terminals of the UHF variable condenser sections UO and UA are not extended downward, but are made to protrude to the side of the variable condenser, and are connected to the UHF front end board 20 on the side of the variable condenser, thereby making the terminals themselves short. Since it can reduce the lead inductance of the terminal, it is extremely effective in the high frequency UHF band.

This small multiple variable capacitor has a UHF variable condenser section on the side as shown in Figure 5.
Terminal 1 is attached to the circuit pattern 201 of the UHF front end board 20, which constitutes the circuit related to UO and UA.
It is attached by soldering 3a, 13b, 14a, 16a, and 17a. With this, variable capacitor 1 and UHF front end board 2
0 is unitized.

Incidentally, on the UHF front end board 20, as is clear from FIGS. 1 and 3, there are coils L ₁ to L ₅ related to the UHF variable condenser sections UO and UA.
Various electronic components are attached, such as a resistor R, an attachment terminal 21 to a tuner board 40, which will be described later.

Also, on the periphery of the UHF front end board 20,
When incorporating it into the shield case 30 described later,
Protrusion 20 for fixing inside shield case 30
a to 20c are formed.

In this way, it is possible to use a small multiple variable capacitor even in extremely high frequency bands such as the UHF band, but when it is actually incorporated into electronic equipment such as a tape recorder, the side of the variable capacitor without a shield plate is However, problems remain, such as noise caused by static electricity from mechanisms, switches, etc., coupling with nearby components, and vibrations caused by the sound pressure and magnetic flux of the speaker that cannot be completely eliminated by the polycondenser cover.

In the present invention, as described below, the shield case 3 for shielding the front end board 20 is
Solved by 0.

The shield case 30, as shown in FIG.
The front-end board 20 is made up of a top plate 31 that is the component mounting surface side, a back plate 32 that is the back side, and a side plate 33 that covers the side surface.Furthermore, a variable capacitor is mounted on the top plate 31 at a portion corresponding to the mounting position of the variable capacitor 1. 1
Shield case 34 for variable capacitor that covers the protruding part of
are arranged.

This shield case 30 is assembled so that the front plate 31 and the back plate 32 are fitted to the side plates 33 from the front and back, and the front end board 20 to which the variable capacitor is attached has protrusions 20a to 20c on its periphery.
The notches 32a to 32c of the back plate 32 and the side plate 33
It is designed to be fixed within the shield case 30 by being held between the shield case 30 and the shield case 30. Each plate is fixed at its contact portion by soldering or the like. In addition, the variable capacitor shield case 34 is inserted into the notch 31a from the back side of the surface plate 31 before attaching the surface plate, and the protrusions 34b, 34
c and 34d (not shown) are attached by soldering to the back surface of the top plate 31.

In addition, the front plate 31, the back plate 32, the side plate 33, and the shield case 34 for the variable capacitor are equipped with adjustment devices so that the coils _L1 to _L5 on the front end board 20 and the trimmer capacitors 3a to 3d of the variable capacitor 1 can be adjusted from the outside. Holes (notches) 31b to 31e, 32
d, 33a to 33c, 34e, and 34f are formed, and as shown in FIG.
0 is assembled, a screwdriver or the like can be inserted through each hole to adjust each adjustment point.

In addition, the surface plate 31 that constitutes the shield case 30
The side plate 33 not only shields the front and side surfaces of the front end board 20, but also protects the coil components L 1 to ₁ on the front end board 20 when the front end board 20 is attached, as shown in FIG. Partition plate 31f inserted between _L5 etc.
33d to 33h are formed to prevent coupling between the coil components on the board.

That is, looking at variable condenser 1, the variable condenser itself was only provided with interstage shield plates 14, 16, and 17 between UHF variable condenser sections UA and UO and other variable condenser sections, as described above. However, when the front end board 20 is housed in the shield case 30, the side surfaces of the variable capacitor 1 are shielded by the variable capacitor shield case 34, the partition plate 31f of the front plate 31, and the partition plate 33g of the side plate 33, respectively. Therefore, it is possible to prevent coupling between the UHF variable condenser section, the tuned variable condenser section UA, the local variable condenser section UO, and other variable condenser sections and circuit components.

Therefore, since both the variable capacitor 1 and the front end board 20 are shielded by the shield case 30, it is possible not only to prevent the above-mentioned coupling but also to prevent noise due to static electricity generated from moving parts such as mechanisms and switches. In addition, the sound pressure of the speaker, which could not be prevented with a polycover,
A strong metal shield case can completely block the effects of magnetic flux.

In addition, in each figure, the protrusions 33i, 3 on the lower edge of the side plate 33
3j and a protrusion 34a on the lower edge of the variable capacitor shield case 34 are terminals for attaching the shield case 30 to a tuner board 40, which will be described later.

With the above configuration, the UHF front end unit is completed, and each unit has VHF, FM,
It can be attached to the tuner board 40 on which a receiving circuit such as AM is configured.

FIG. 4 shows a state in which a UHF front end unit containing a UHF front end board 20 housed in a shield case 30 is mounted on a tuner board 40.

The UHF front end includes terminal 21 of the front end board 20 and terminals 71a to 71 of the variable capacitor 1.
d, 15a, 15b, and the terminals 33i, 33j, 34a at the lower edge of the shield case 30 are mounted on the circuit pattern 401 of the tuner board 40 by soldering together with other parts.

On the tuner board 40, a bar antenna 41,
Components of the receiving circuit other than the UHF band, such as the connection terminal 42, as well as resistors, capacitors, and coils, are attached, but as the tuner board becomes smaller and the mounting density of components increases, each component is mounted closer together. For example, VHF and FM, rather than particularly high frequency bands such as the UHF band,
Even in the band, coupling between the tuning (or antenna) coil LVa and the local oscillator coil LVo is likely to occur, and some kind of shielding measures are required in this area as well.

In this invention, we focused on the fact that the UHF front end unit occupies a relatively large space on the tuner board 40, and we focused on the fact that the UHF front end unit occupies a relatively large space on the tuner board 40. generator coil Lvo
Arranged so that they are located on both sides with the shield case 30 of the UHF front end unit in between,
The shield case 30 is used as a shield plate to prevent coupling between the tuning stage and the local oscillator stage of the VHF (and FM) receiving circuit. This makes it possible to prevent coupling between parts even if close arrangement of parts is unavoidable.

(Effects of the invention) As described above, the present invention is capable of superimposing a plurality of variable condenser sections including small capacity variable condenser sections such as UHF and operating them by the same rotor shaft. A multiple small variable capacitor in which a shield plate is arranged between one capacitive variable condenser section and another variable capacitor section; , consists of a shield case for shielding both the front-end board and the multi-compact variable capacitor, ensuring shielding of small-capacity variable condenser sections such as UHF, where the shield plate inside the variable capacitor alone would not be sufficient. can be done.

In addition, since this side of the variable capacitor can be covered with a metal shield plate, it is also possible to shield noise caused by static electricity generated from other mechanisms, switches, etc., and the noise from speakers that could not be prevented with the variable capacitor's polycover. Since pressure, magnetic flux, etc. can be easily blocked, microphonic noise and howling caused by vibration of the variable capacitor plate can also be prevented.

Furthermore, since the variable capacitor and UHF front-end board are integrated into a unit and housed in a shield case, the configuration is simpler and space-saving compared to the case where shielding measures are taken separately.

[Brief explanation of the drawing]

Each figure shows an example of the present invention, and Figure 1 is a UHF
An exploded perspective view showing the configuration of the front end unit.
Figure 2 is a perspective view of the external appearance of the shield case, Figure 3 is a plan view of the UHF front end board, and Figure 4 is
A plan view showing the UHF front end unit mounted on the tuner board, Fig. 5 is a side sectional view taken along Fig. 6 B-B' of the small multi-variable condenser used in the present invention, and Fig. 6 is the top view of the variable condenser. 7 is a side view seen from the direction of arrow A in FIG. 6, and FIG. 8 is a sectional view taken along line CC' in FIG. 7. Explanation of symbols, 1... Variable capacitor body, 11... Rotor plate, 12... Stator plate, 14
~17... Shield plate, 20... UHF front end board, 30... Shield case, 31...
Front plate, 32...Back plate, 33...Side plate, 34
...Shield case for variable condenser, UO...UHF station source variable condenser section, UA...UHF tuned variable condenser section, L ₁ to _{L 5} ...Coil, VLo...
VHF station coil, VLa...VHF tuning coil.

Claims (1)

[Scope of utility model registration request] A plurality of variable condenser sections including a small capacity variable condenser section such as UHF are overlapped so that they can be operated by the same rotor shaft, and a shield plate is provided between the small capacity variable condenser section and other variable condenser sections. For shielding the multiple small variable capacitors arranged, a front end board connected to the small capacity variable condenser section and forming a receiving circuit of the small capacitance variable capacitor section, and the front end board and the multiple small variable capacitors. The front end of Chuyuna is characterized by consisting of a shield case and a shield case.