JPS61215932A - Piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To make small the equivalent serial resistance, to make high the sensitivity, to make wide a vacuum degree measuring scope, to make small-sized and to make light by arranging the exciting electrode at both edge parts and the central part of the vibrator. CONSTITUTION:For a piezoelectric vibrator 1, the supporting pat 3 is fixed by adhesives 4, etc., on a supporting base 2 composed of a ceramics material, etc. The exciting electrode is arranged on the four surfaces of respective arms, the number of electrodes is three pieces each on respective surfaces and arranged so that the adjoining electrode can be the different electrode. Namely, at one side arm, electrodes 5, 6, 7, 8, 9 and 10 and electrodes, which respectively go to be the same electrodes to these facing surfaces, are arranged, for example, electrodes 6, 8, and 10 and electrodes 5, 7 and 9 are connected so that respective electrodes can be the same electrodes. Electrodes 11, 12, 13, 14, 15, 16, etc., of other arm are in the same manner, and the polarity is made opposite. Thus, by making easy the both edge fixing bending mode the third higher harmonic vibration is made easy, thereby the equivalent serial resistance can be made smaller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vacuum sensor piezoelectric vibrator used as a vacuum sensor to measure the degree of vacuum. In particular, it relates to the electrode arrangement of a bending mode piezoelectric lifter with both ends fixed.

[Summary of the invention]

The present invention provides an optimal electrode arrangement of the vibrator that can widen the range of vacuum measurement when a piezoelectric vibrator with both ends fixed is used as a vacuum sensor for measuring the degree of vacuum.

[Conventional technology]

Vacuum gauges have been used in equipment in various fields since ancient times.

Among them, the Pirani vacuum gauge is especially frequently used! Ta.

[Problem that the invention seeks to solve]

However, recently, as devices have become smaller and lighter,
There is also a similar demand for vacuum gauges to be smaller and lighter. The Villany vacuum gauge mentioned above is large in size and penetrates, so it is a recent model! The reality is that %I2 cannot be fully met. or,
Conventional vacuum gauges that use vacuum sensors cannot measure the degree of vacuum in equipment that generates high-voltage fields, such as thruster furnaces. Therefore, the present invention proposes a new sensor for vacuum gauges that improves the above-mentioned drawbacks, and includes an electrode arrangement that efficiently excites piezoelectric vibrators in which two fixed-end type vibrators are connected to the back; It provides structure. In other words, it is compact, has a low equivalent series resistance R, and is strong against impact.
The present invention provides a vacuum sensor piezoelectric vibrator with excellent reliability.

[Problem t-Means for solving]

Figure 3 shows the relationship between the degree of vacuum and the equivalent row resistance R1 of the piezoelectric vibrator in the third-order harmonic vibration in the bending mode with both ends fixed according to the present invention. , (KΩ).For example, in the case of crystal as the piezoelectric material, experiments show that 1!, increases with the deterioration of the degree of vacuum.

When the degree of vacuum changes from 0 to 1 Torr, R increases accordingly.
By focusing on the vacuum degree dependence of y, the degree of vacuum can be accurately measured from this relationship.

In reality, a change in R of the vibrator is equivalent to a change in the current Nn flowing through the piezoelectric vibrator, and in an actual vacuum gauge, the current Kn is converted into the degree of vacuum and displayed. Further, in order to make the vibrator of the present invention strong against shock, a fixed-end type is used, unlike a cantilever type. To explain more specifically, the piezoelectric vibrator is set on a support pedestal made of a material such as ceramics, and is supported and fixed with an adhesive or the like using support parts provided at both ends of the piezoelectric vibrator. Ru. Therefore, the piezoelectric vibrator of the present invention has features with respect to disturbances and loads. Next, the relationship between the degree of vacuum and the equal series resistance R is shown. The sensitivity S to the degree of vacuum of the piezoelectric vibrator is equal series resistance R1 at high vacuum (more than 10"""l'or'r), and n'ft: R at atmospheric pressure.

Then, n is expressed by the following formula.

However, ΔR=R1−R.

As is clear from equation (2), in order to increase the sensitivity Bt-, it is sufficient to reduce R1 of the piezoelectric vibrator and increase 1ΔR1. Here, 1ΔR1 is determined by the shape and dimensions of the vibrator, and if the width W and length L of the bar are inversely proportional to @W and proportional to the length L. Therefore, in order to increase IΔR1t, the thinner the rod is and the longer it is, the larger 1ΔR1 becomes. However, if an excitation electric mark is arranged on the piezoelectric vibrator so that this long n vibrates in the bending mode of the fundamental wave, R becomes large, and the actual sensitivity does not become very large. Therefore, in the present invention, by arranging the excitation electrode vi- which easily causes the eighth harmonic vibration in the bending mode on the elongated rod described above, Rlt- can be further reduced even with the same dimensions, so that the sensitivity g can be significantly increased. Figure 2(a),
Cb) shows the transducer of the rod fixed at both ends of the present invention and the displacement at each position when the transducer vibrates at the eighth harmonic. Here, the length of the vibrator is 1, the width is W, and the thickness is t. As is clear from Figure 2), there are four locations where the displacement is zero. ffOchi, both ends and 0.859L from that end
This is the position of Furthermore, since the four locations where the displacement is zero are the locations where the most strain occurs, the electrodes may be arranged so that the strain occurs at any one of these four locations. As a result, the equivalent series resistance R*' in the third harmonic vibration of the bending mode can be reduced, and the sensitivity can be increased even with a vibrator of the same size.

[Effect]

In this way, the present invention has a pressure of 1! Taking into account the vibration mode order of the vibrator, and more specifically, from the displacement distribution of the third harmonic vibration of the bending mode and the strain distribution generated at that time, the optimum excitation electrode is selected for piezoelectric vibration. By providing it on the child, third harmonic vibration can be easily caused and lk can be reduced. As a result, sensitivity to the degree of vacuum can be increased.

〔Example〕

Embodiments of the present invention will be described below based on the drawings. Figures 1 (6) and 1) are examples of the bending mode piezoelectric vibrator with a fixed number at both ends of the present invention, Figure 1 (c) is a front view of the fixed piezoelectric vibrator, and Figure 1) is Figure 1 b. ) is a side view. A piezoelectric vibrator 1 is set on a support pedestal 2 made of a ceramic material or the like, and is supported and fixed at the end of a support portion 8 of the vibrator with a layer adhesive 4 or the like. And the excitation electrode is 6
They are arranged on four sides of the arm, with eight electrodes on each side, and adjacent electrodes are arranged so that they have different polarities. That is, one arm has electrodes 5, 6, 7, 8, 9.10
However, in addition, although not shown in symbols, there are haimen den spears 5 and 8.
, 9 are also provided with electrodes having the same polarity on their opposing surfaces. The diagonally shaded electrodes 6.8. IQ is connected to have the same polarity, and the nine electrodes 5, 7 and 9 (shown by dots) are connected to have the same polarity (not shown), forming a two-terminal structure.

Just like rifI, the same ladder electrode is placed on the other bowl.
However, they are arranged so that the polarity is opposite. Therefore, electrodes 5, 7, 9, 11, 13, 15 are of the same polarity, and electrodes 6, 8.10, 12, 14.1
6 are provided so that they have the same polarity. This makes it possible to easily prevent the eighth harmonic hyperactivity in the bending mode with both ends fixed, and to reduce s''st.

〔Effect of the invention〕

As described above, in the present invention, in order to reduce the sensitivity S to the degree of vacuum, it is sufficient to reduce the equivalent series resistance R1 of the piezoelectric vibrator. In addition, the present invention has the effect of reducing the size of the R plate by arranging an excitation electrode that easily causes 8th harmonic vibration on a long and thin rod that increases lΔR1.As a result, the sensitivity Bt can be increased and the vacuum degree measurement range can be widened. has. Furthermore, since the piezoelectric vibrator is used as a vacuum sensor, it can be made extremely compact and lightweight, and since the piezoelectric vibrator is mounted on a support base, it has effects such as being resistant to shocks.
Do N. At the same time, since piezoelectric vibrators are strong against high magnetic fields, they also have sound effects that can be used to measure the degree of vacuum even in high field generating devices such as nuclear reactors.

[Brief explanation of the drawing]

FIG. 1 (φ is a front view of fixing the piezoelectric sensor of the present invention, and FIG. 1 is a side view of FIG. 1). The WJz diagram is a diagram showing the piezoelectric vibrator fixed at both ends and the displacement (b) t to explain the present invention, and Figure 8 is a diagram showing the relationship between the degree of vacuum and the equivalent series resistance of the piezoelectric vibrator of the present invention. It is. 1. Piezoelectric camera 20. Support pedestal 80. Support part 46. Coating agent 5, ~160. More than electrode

Claims (1)

[Claims] 1. A piezoelectric vibrator comprising two connected vibrators fixed at both ends that vibrate in a bending mode, characterized in that excitation electrodes are arranged at both ends and the center of the vibrators.