JPS643404B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a piezoelectric oscillator whose frequency can be adjusted from outside a sealed container.

[Prior art] In a piezoelectric oscillator, especially a commonly used crystal oscillator, a volume is placed in a container to adjust the frequency by voltage using a variable capacitor or a variable cap, and a hole is made in a part of the container. I opened it and adjusted the variable capacity or volume using an adjustment rod such as a screwdriver, and fine-tuned the frequency.

FIG. 1 is a cross-sectional view showing an example of a conventional piezoelectric oscillator. There is a can 2 that covers the parts attached to the board 1. A hole is made in a part of the can 2, and the variable capacitance or volume 3 is adjusted from there with an adjustment rod to finely adjust the frequency.

However, in recent years, there has been a demand for crystal oscillators in small sealed containers, and in order to adjust the frequency it is necessary to attach external variable capacitors, volume controllers, etc. When these parts are attached externally, the area occupied increases, making it difficult to downsize. It was becoming an obstacle.

OBJECTS OF THE INVENTION The object of the invention is to eliminate the above-mentioned drawbacks and to enable frequency tuning of piezoelectric oscillators in a compact and sealed construction. Hereinafter, examples will be given and explained in detail.

[Example] In the present invention, a coil is formed by winding a wire around a U-shaped magnetic core. The piezoelectric oscillator utilizes the fact that by moving a permanent magnet closer to or farther away from the coil, the magnetic flux density inside the magnetic core changes, and the magnetic permeability changes, resulting in a change in the inductance of the coil. FIG. 2 shows the wire 5 and the permanent magnet 6 wound around the magnetic core 4. FIG. 2a is a side view, and FIG. 2b is a plan view. A wire 5 is wound around a U-shaped magnetic core 4 to form a coil 7. When the permanent magnet 6 is brought closer to this magnetic core 4,
The magnetic flux density of the permanent magnet 6 changes, and the inductance L of the coil 7 becomes smaller as the distance d between the permanent magnet 6 and the coil 7 becomes smaller. In FIG. 2, the permanent magnet 6 is shaped like a disk so that it can be rotated around the permanent magnet and the magnetic flux density can be changed in the same way as moving it closer or farther away.

FIG. 3 shows an example in which it is incorporated into a crystal oscillation circuit. The configuration of the oscillation circuit is as follows: a coil ₇ and a piezoelectric _vibrator Two resistors R ₁ and R ₂ are connected in series, and these two capacitors C ₁ and C ₂
and the midpoint of the two resistors R ₁ and R ₂ are connected.
The collector is connected to a power supply, and in this example, the midpoint between the two resistors is used as the oscillation output. When the permanent magnet 6 is moved closer or closer to the coil 7 wound around the magnetic core 4, the output frequency of the oscillator changes.

FIG. 4 is a graph showing the relationship between the distance between the coil and the permanent magnet and the inductance of the coil. As the permanent magnet 6 of the coil 7 is brought closer, the inductance L decreases, and as a result, the output frequency of the oscillator becomes higher. Therefore, the frequency of the crystal oscillator was set somewhat high, and the permanent magnet was brought closer to match the desired frequency.

FIG. 5 is a sectional view showing an example of the embodiment of the present invention implemented in a crystal oscillator.

The components attached to the board 8 are covered with a can 9 for shielding, and a wire 5 is attached to the magnetic core 4 on the inner wall side of the can 9.
A shaft 10 for positioning the permanent magnet is provided on the outer wall of the can 9 near the coil, a hole is made in advance in the permanent magnet 6, and the shaft is inserted into the shaft. Note that the shaft is fixed to the can by spot welding or the like. Frequency adjustment is achieved by rotating a permanent magnet around the shaft while measuring the oscillation frequency with a frequency counter or the like. Make a groove in the permanent magnet so that you can insert a screwdriver or the like and turn it. After the adjustment is completed, the permanent magnet 6 is fixed with an adhesive or the like.

FIG. 6 shows another embodiment of the invention. Kan9
An example is shown in which a recess 11 is provided in a part of the recess, and the permanent magnet 6 is placed in the recess 11 and rotated within the recess. This prevents the permanent magnet 6 from jumping out of the can 9 as shown in FIG. 5, and further miniaturization is possible.

In the present invention, a U-shaped magnetic core is used, but it may be rod-shaped, and the permanent magnet is not limited to a disk, but may be U-shaped, prismatic, or the like. Also,
The material used for the magnetic core is a ferromagnetic material such as ferrite or nickel-iron alloy.

[Effects] The present invention eliminates the need to drill holes for variable capacitance and volume in the can, which was conventionally required, and it becomes possible to clean the printed circuit board with an organic solvent or the like while the oscillator is attached, which could not be done conventionally. Additionally, it has become possible to install a crystal resonator that is not sealed inside the can. Moreover, the effect of being able to adjust the frequency from outside the sealed container is great.

In addition, in the present invention, when changing the position of the permanent magnet, an example was shown in which it was rotated on the outer wall of the can, but the frequency can be adjusted by increasing or decreasing the distance between the coil and the permanent magnet, and it is possible to change the position of the permanent magnet by moving it along the outer wall of the can. The results are similar.

In the present invention, quartz is used as the piezoelectric material, but other materials such as lithium tantalate, lithium niobate, or piezoelectric ceramic may also be used.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional oscillator, and Fig. 2 is a sectional view of a conventional oscillator.
The positional relationship between the coil and permanent magnet is shown. Figure 3 shows
This figure shows the circuit of an oscillator in a sealed container that allows frequency adjustment. FIG. 4 is a graph showing the relationship between the inductance of the coil and the distance between the permanent magnet and the coil. FIG. 5 is a sectional view showing an embodiment of a crystal oscillator housed in a sealed container according to the present invention, and FIG. 6 is a sectional view showing another embodiment.

Claims (1)

[Claims] 1. In a piezoelectric oscillator that includes a coil wound around a magnetic core made of ferromagnetic material, a piezoelectric vibrator, and an oscillation circuit inside a sealed container, the coil and the piezoelectric vibrator are connected in series between the base of a transistor and ground, An oscillation circuit consists of two capacitors connected in series between the base and ground, two resistors connected in series between the emitter and ground, and the midpoint between the two capacitors and the two resistors connected. A piezoelectric oscillator characterized in that the coil is disposed near the inner wall of a sealed container, and a permanent magnet is provided for frequency adjustment by moving the coil near the outer wall of the sealed container.