JPS62211904A - High-frequency inductor - Google Patents

Abstract

PURPOSE:To improve workability and to exceedingly reduce the number of processing steps by forming a high-frequency inductor by winding a copper wire whose surface is plated with a magnetic substance to increase a relative permeability. CONSTITUTION:A high-frequency inductor is formed by winding a copper wire A whose surface is plated with a magnetic substance to improve a relative permeability. The copper wire A has a higher relative permeability than a copper wire B whose surface is coated with a protective coating film. Accordingly, in case of an air coil using the copper wire A, it is possible to make a wire diameter larger and the number of winding times less compared with that using the copper wire B. Consequently, workability is improved and the number of processing steps can be reduced exceedingly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high frequency inductor forming a resonant circuit used in a high frequency unit for receiving communication broadcasting.

(Prior Art) A conventional high-frequency inductor uses an air-core coil wound with copper wire whose surface is coated with a protective film.

A resonant circuit using the above-mentioned high frequency inductor will be explained with reference to FIGS. 3 to 5. The resonant circuit shown in FIG. 3 includes a high-frequency inductor L□ with an inductance L1,
Capacitor C1 with capacity C1, variable capacitance diode Vcc
and a power supply B that supplies voltage B thereto.

FIG. 4 is a characteristic diagram showing the relationship between the capacitance C2 of the variable capacitance diode Vcc and the voltage B. If the horizontal axis is the voltage B and the vertical axis is the capacitance C2, the relationship resembles a hyperbola.

FIG. 5 is an equivalent circuit of the resonant circuit shown in FIG. 3, which is composed of a capacitance (C□+C2) and an inductance L1, and has a resonant frequency f shown in equation ( ]). can be obtained.

L: inductance [] C: capacitance [F] fo: resonant frequency [7] In the above resonant equivalent circuit, C=C1+C2, and the voltage B supplied to the variable capacitance diode Vcc increases its capacitance C.
2 changes, the circuit configuration allows the resonance frequency to be set arbitrarily.

In order to obtain a predetermined resonant frequency using the above resonant circuit, it is adjusted by the supply voltage B, but since there are variations in the characteristics of the capacitor C and the variable capacitance diode Vcc,
First, after setting the supply voltage B to a constant value, the closeness of the air-core coil constituting the high-frequency inductor L1 was changed to absorb the above-mentioned variations and adjust the resonant frequency to a predetermined value.

(Problem to be solved by the invention) In the second adjustment method, when the frequency becomes low,
In order to increase the inductance, methods were used to reduce the wire diameter of the air-core coil or increase the number of turns. Additionally, if the inductance was too large, the inductance was adjusted by winding a copper wire around a ready-made product, placing a magnetic material inside the coil to increase the inductance, and changing the relative position of the magnetic material and the coil. .

However, when the wire diameter of the air-core coil is made thinner, there are problems in that as the wire diameter becomes thinner, the ease of insertion into a circuit board decreases, the strength of the wire decreases, and the shape of the coil becomes more likely to change. Further, when increasing the number of turns, there is also a problem that the rigidity of the coil decreases and the coil shape tends to change.

When winding copper wire around a ready-made product, there is a problem in that the cost of materials and the number of man-hours increase significantly.

The present invention solves the above two problems and provides a high-frequency inductor that has excellent workability and requires less man-hour adjustment work.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a high-frequency inductor by plating a magnetic material on the surface and winding copper wire with improved relative permeability to form an air-core coil. It is something.

(Function) Copper wire whose surface is plated with a magnetic material has a higher relative magnetic permeability than copper wire whose surface is coated with a protective coating. Compared to an air-core coil with equivalent inductance, the wire diameter is thicker,
The number of turns can be reduced.

This is clear from equation (2) for obtaining the inductance L of the air-core coil.

Here, g: Coil length = πdN S: Coil cross-sectional area = πr2 N: Coil turns number d: Coil winding diameter r: Wire diameter μ0: Vacuum permeability p,: Relative magnetic permeability: Nagaoka coefficient, i.e. It is clear that if the relative magnetic permeability is small, the number of turns N can be reduced, and if the wire diameter r is increased, -N can be further reduced.

(Example) An embodiment according to the present invention will be explained with reference to FIG.

The figure shows a wire plated with a magnetic material according to the present invention with a diameter of 0.1.
Winding diameter of 6mm copper wire is 5. Frequency-inductance characteristic diagram comparing the characteristics of a high-frequency inductor wound in an air-core coil with 10 turns and the characteristics of a conventional high-frequency inductor made of copper wire of the same thickness coated with a protective film and with the same winding diameter and number of turns. The horizontal axis represents the frequency 10cMuzl, and the vertical axis represents the inductance L[n old.

From this data, the relative magnetic permeability of copper wire plated with magnetic material is:
It can be seen that the strength is about 1.25 times that of steel wire coated with a protective coating. Therefore, when the inductance of the air-core coil according to the present invention is made equivalent to that of a conventional copper wire with a protective coating, when only the wire diameter is changed, the wire diameter is 1/3, and when only the number of turns is changed, the number of turns is 1/1. .25.

Note that the above comparative data is an example according to the present invention, and the above ratio can be further increased by further increasing the density of the magnetic material formed on the surface of the copper wire.

Next, an example of use of the high frequency inductor according to the present invention will be described.

Another purpose of high-frequency inductors, which are magnetically plated copper wire wound around an air-core coil, is to improve the resonance sharpness Q at a specific frequency of the resonant circuit that uses them, and is mainly used in radio IF bands. A certain frequency 10.7MHz
and 4.5MI (targeted at z).

However, when used in a higher frequency band than this, it is necessary to reduce the thickness of the magnetic material plated on the surface of the copper wire, and if it is made too thin, a problem arises in that the effectiveness of the magnetic material decreases. There is also the problem that the resonance sharpness Q decreases, and the effect of sharp Q, which is one of the original objectives, cannot be obtained. For example, like a TV tuner, the frequency is 50Mk to 200MT (when targeting z, the resonance sharpness Q
becomes significantly lower.

As mentioned above, as the thickness of the magnetic material plated on the surface of the copper wire is increased, the inductance increases, but an application example that takes advantage of the decreasing property that the sharpness Q of resonance decreases will be explained with reference to FIG. In the figure, the resonant circuit includes a high-frequency inductor L3, a capacitor C3, a variable capacitance diode D, and a power source B? that supplies voltage to these. However, in order to reduce the sharpness Q of the resonance, a resistor R4 is connected in parallel with the high frequency inductor L, and a ferrite bead Fe is connected to the high frequency inductor L, which is an air-core coil connected to the resonant circuit. was inserted. By replacing the above high frequency inductors L2 and 1, 3 with low Q high frequency inductors according to the present invention, the above resistor R
1 and the ferrite beads Fe can be deleted.

(Effects of the Invention) As explained above, according to the present invention, it is possible to change the inductance while using an air-core coil with the same wire diameter, winding diameter, and number of turns. It is possible to eliminate deformation and increase in winding time due to decrease in workability due to use, decrease in rigidity of the air-core coil due to adoption of thin wire or increase in the number of turns.

Furthermore, since the number of turns of the air-core coil is reduced, the mounting area on the circuit board can be reduced, and therefore the mounting density can be increased.

Furthermore, when used in a resonant circuit in a high frequency band exceeding 50 MHz, it is possible to reduce the number of components such as resistors and ferrite beads that are conventionally required to reduce the sharpness Q of resonance.

[Brief explanation of drawings]

Fig. 1 is a characteristic diagram comparing the frequency-inductance characteristics of the high-frequency inductor according to the present invention and a conventional one, Fig. 2 is a resonance circuit diagram used in a high frequency band, Fig. 3 is a conventional resonant circuit diagram, and Fig. 4 is a diagram of a conventional resonant circuit. The figure is a voltage-capacitance characteristic diagram of a variable capacitance diode, and FIG. 5 is a resonance equivalent circuit diagram for FIG. 3. B, B?・Power supply to the variable capacitance diode, C1,
C2, C3... Capacitor, Fe-ferrite bead, L, , L2. L3...High frequency inductor (air core coil), R1...Resistor. Patent applicant Matsushita Electric Industrial Co., Ltd. Figure 1 1 Io 50 100
(M)-1z)f. Figure 2 Figure 3 Figure 5

Claims (1)

[Claims] A high-frequency inductor characterized by winding copper wire with a magnetic material plated on its surface.