JPH0211796Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a bimorph for VTR, optical communication, etc., and a piezoelectric ceramic plate having a coefficient of thermal expansion equal to that of the bimorph is used as an insulating material for mounting the bimorph made of piezoelectric ceramic on a metal base. It is characterized by having been glued.

Bimorphs for VTRs, optical communications, etc. are used by fixing one end of the bimorph to a metal base, applying an electric field to the bimorph to distort the tip, and using this distortion to control switching of the magnetic head sensor, switching of the optical path, etc. However, due to room temperature changes, at low temperatures the sensor warps toward the insulating board as shown exaggeratedly in Figure 1a, and at high temperatures the sensor warps as shown exaggeratedly in Figure 1b. This causes the tip to be misaligned against the side, which prevents its mass use in precision applications. However, the bimorph itself does not have temperature characteristics that would cause the tip to shift due to changes in indoor temperature, so when we investigated the real cause, we found that the coefficient of thermal expansion between the bimorph and the insulating plate that attaches it to the metal base. It was suspected that this was due to a discrepancy.

In other words, in the past, glass epoxy plates were exclusively used as the insulating material between the bimorph and the metal base plate, but the coefficient of thermal expansion of the bimorph is quite different from that of the piezoelectric ceramic, and measurement results indicate that positional deviations may occur. became clear. The present invention aims to eliminate such drawbacks.

Figures 2 to 4 show an embodiment of the present invention, in which a shim 1 is sandwiched between the sides, for example, Pb (Zr,
Piezoelectric ceramic plates 2 and 3 made of a known piezoelectric material such as Ti)O ₃ are joined, and baked silver electrodes 2a and
3a to form a bimorph 4, a sensor electrode 5 is provided on one side of the silver electrode 2a, a lead wire is connected to each electrode, and one end of the silver electrode 3a is connected to the piezoelectric ceramic plates 2 and 3 for thermal expansion. Insulating plates 6 made of, for example, the piezoelectric ceramic described above and having the same coefficient are bonded.

Document A is an example product in which the distance between the insulating plate 6 and the tip of the bimorph 4 is 25 mm according to the above example, and Document B is a conventional product in which only the insulating plate is a glass epoxy plate and the other parts are the same. , Material A uses two materials A ₁ and A ₂ , and Material B uses two materials B ₁ ,
Using _B2 , the temperature change was repeated as follows: 0°C → room temperature → 45°C → room temperature → 0°C → room temperature, and the positional deviation of the tip was measured, and the formation shown in FIG. 5 was obtained. That is, in Material A, the maximum misalignment of the tip was -20 to 20 μm, and the maximum amplitude of the misalignment was 40 μm, whereas in Material B, the maximum misalignment was -40 to 80 μm, and the maximum amplitude of the misalignment was 120 μm. In this way, we were able to prove the superiority of the present invention.

As clarified by the above embodiments, the present invention is to attach a piezoelectric ceramic plate having the same coefficient of thermal expansion as the piezoelectric ceramic plate constituting the bimorph to the bimorph 4 as an insulating material for mounting on a metal base (mainly aluminum). With this configuration, it was possible to prevent the insulating plate 6 itself from undergoing thermal expansion and contraction different from that of the bimorph 4.

[Brief explanation of drawings]

Figures 1a and 1b are side views illustrating the displacement of the tip due to room temperature changes in a conventional product in which a glass epoxy plate is bonded as an insulating plate; Figures 2 to 4 show an embodiment of the present invention; is a side view, Figure 3 is a plan view,
FIG. 4 is a plan view of the back side, and FIG. 5 is a curve diagram of the positional numerical values of the tip of material A based on the present invention and material B of the conventional product. 2, 3...piezoelectric ceramic plate, 4...bimorph, 6
...Insulating board.

Claims (1)

[Scope of utility model registration request] 1. A bimorph for VTR, etc., characterized in that a piezoelectric ceramic plate having the same coefficient of thermal expansion as the bimorph is adhered as an insulating material for mounting the bimorph made of piezoelectric ceramic on a metal base.