JPH0215298Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current controlled variable inductor used in electronic tuning circuits such as car tuners.

FIG. 1 is a side view of a conventional variable inductor of this type, in which a U-shaped core 1 and an I-shaped core 2 of magnetic material are combined, and a control coil 3 and a tuning coil 4 are wound around the core 1. be. The tuned coil 4 is wound through a groove 5 provided at the tip of the core 1. Then, by passing a direct current or low frequency current through the control coil 3, a closed magnetic path is formed between the cores 1 and 2 as shown by the dotted line 6, and by changing the magnetic flux density with the current, a closed magnetic path is formed in the tuned coil 4. The effective magnetic permeability of the core 1 is controlled and its inductance is changed. The dotted line 7 is a magnetic path by the tuning coil 4, and the groove 5 is provided mainly for structurally adjusting the magnetic flux density of the control coil 3 passing through the tuning coil 4.

However, in such a structure in which the magnetic path between the control coil 3 and the tuning coil 4 is completely closed, the inductance and temperature characteristics, which are the characteristics of the tuning coil 4, tend to vary depending on the contact state of the core 1 and the core 2. . In other words, slight variations in the mirror-finished state and dimensions of the surface of the contact portion 8 between the core 1 and the core 2 affect various characteristics. Since the cores 1 and 2 are usually fixed together with an adhesive, the state of contact may change due to the adhesive entering the contact portion 8. Furthermore, since the control coil 3 and the tuning coil 4 cannot be directly wound around the U-shaped core 1, they must be wound separately and fitted into the core 1. Furthermore, as described above, bonding work between core 1 and core 2 is also required. As described above, the conventional structure requires high assembly precision between the cores, especially precision at the contact portion, so it is difficult to reduce variations in characteristics and the assembly work is troublesome.

An object of the present invention is to provide a highly practical variable inductor structure by improving the conventional drawbacks.

In the current-controlled variable inductor of the present invention, a tuning coil is wound around the winding part of a core having flanges at both ends, and a cylindrical first cover that covers the tuning coil and forms a magnetic path therein is placed outside the first cover. A control coil is wound around the control coil, and a second cover is further disposed to cover the control coil and form a magnetic path of the control coil.

Embodiments of the current controlled variable inductor of the present invention will be described below with reference to FIGS. 2 and 3. FIG. 2 is an exploded perspective view showing the windings removed, and FIG. 3 is a longitudinal sectional view.

In FIGS. 2 and 3, 10 is a drum-shaped core, 11 is a first cover that can be formed into a cylindrical shape by combining two halves, 12 is a pot-shaped second cover, and 13 is a base. The core 10, the first cover 11, and the second cover 12 are all made of ferrite, which is a magnetic material. The base 13 is made of synthetic resin.

The winding portion 15 of the core 10, which has circular flanges 14 at both ends, is formed into two stages, with the center being thinner and the ends thicker so that winding can be easily performed inside and outside. A tuning coil 16 is wound on the inside, and a control coil 17 is wound on the outside. Control coil 17 is tuning coil 1
6 and is wound onto the first cover 11 which is fitted into the thick part of the winding part 15. A terminal pin 23 for connecting the lead wires of the tuning coil 16 and the control coil 17 is implanted on the lower surface of the circular base 13.

The core 10 placed on the base 13 is housed in the second cover 12, but the winding part 15 is
is perpendicular to the bottom surface 18 of the cover 12. The convex portion 19 of the collar 14 on the core 10 fits into the concave portion of the bottom surface 18, making it easy to determine the horizontal position of the core 10. The side surface of the base 13 is fixed to the inner surface 20 of the second cover 12.

And the collar 14 under the core 10 and the second cover 1
The seams of the first core 11 and the inner surface 20 of the first core 11 are slightly apart from each other. Note that the contact area between the upper flange 14 of the core 10 and the bottom surface 18, the contact area between the first cover 11 and the winding part 15 of the core 10, and the seam of the first core 11 are made, for example, in order to prevent damage due to vibration. The contact may be made through a Mylar film or an adhesive.

In the variable inductor of the present invention configured as described above, the magnetic path 21 by the control coil 17 connects the winding portion 15 of the core 10, the upper collar 14, the second cover 12, and the lower collar of the core 10, as shown by the dotted line. It mainly extends to 14. On the other hand, the magnetic path 22 by the tuned coil 16 is connected to the core 1
0 winding part 15, which mainly extends to the first cover 11. The magnetic path 21 caused by the control coil 17 and the magnetic path 22 caused by the tuning coil 16 overlap most in the winding part 15, and by changing the magnetic flux density by the control coil 17, the effective magnetic permeability of the winding part 15 is controlled and the tuning is performed. The inductance of the coil 16 can be varied. Note that if the influence of an external magnetic field is considered, the second cover 12 may be covered with a metal case.

FIG. 4 is a longitudinal sectional view showing another embodiment of the variable inductor of the present invention, which differs from FIGS. 2 and 3 in that the second cover 30 is cylindrical. Second
The cover 30 has a control coil 31 and a tuning coil 32.
It is fixed on the base 34 together with the core 33 wound around it. 35 is a first cover. In the case of FIG. 4, the magnetic path 36 caused by the control coil 31 is more divergent than in the first embodiment, so that the inductance of the tuning coil 32 corresponding to the current in the control coil 31 changes more slowly. Note that the second cover 30 may be made by combining two halves in the same manner as the first cover 35.

FIG. 5 is a longitudinal sectional view showing still another embodiment of the variable inductor of the present invention.

A step 42 is formed along the periphery of the lower flange 41 of the core 40, and a cylindrical second cover 43 is fitted into the step 42. 44 and 45 are a tuning coil and a control coil, respectively, and 46 and 47 are
are the first cover and the base, respectively. In the case of FIG. 5, the magnetic path 48 caused by the control coil 45 is in almost the same state as in the cases of FIGS. 2 and 3, and does not diverge as in the case of FIG. 4.

As described above, in the current controlled variable inductor of the present invention, the tuning coil and the control coil are wound around the same core, and the magnetic path formed by each coil is not a completely closed magnetic path. Therefore, compared to the conventional closed magnetic circuit structure as shown in FIG. 1, there is no need for mirror finishing of the contact portions, and variations in characteristics can be reduced. Furthermore, since the tuning coil and the control coil can be sequentially wound around the same core using high-frequency coil winding technology, workability is good and assembly is easy. Note that the tuning coil may be wound in multiple turns. Thus, according to the present invention, a highly practical current-controlled variable inductor can be provided.

[Brief explanation of drawings]

Fig. 1 is a side view of a conventional current-controlled variable inductor, Fig. 2 is an exploded perspective view showing an embodiment of the current-controlled variable inductor of the present invention, Fig. 3 is a vertical cross-sectional view, and Fig. 4 is the present invention. FIG. 5 is a longitudinal sectional view showing still another embodiment of the current controlled variable inductor. 10, 33, 40: core, 11, 35, 46:
First cover, 12, 30, 43: Second cover, 13, 34, 47: Base, 14, 41:
Tsuba, 15: Winding section, 16, 32, 44: Tuning coil, 17, 31, 45: Control coil, 18: Bottom surface, 20: Inner surface, 21, 22, 36, 48: Magnetic path, 42: Step section .

Claims (1)

[Scope of utility model registration request] A tuning coil is wound around the winding portion of the core having flanges at both ends, and a control coil is wound around the outside of a cylindrical first cover that covers the tuning coil and forms a magnetic path for the tuning coil. A current controlled variable inductor, further comprising a second cover that covers the control coil and forms a magnetic path of the control coil.