JPS596377B2 - Density conversion mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a density to frequency conversion mechanism.

FIG. 1 is a diagram illustrating the basic configuration of an example of a conventionally known mechanism for converting density into frequency.

In the figure, 1 is a 5 bar with a uniform cross section fixed at both ends;
2 is, for example, a base such as a housing. In such a device, when the rod 1 is placed in a fluid to be measured, there is a relationship between the density ρo of the fluid to be measured and the vibration frequency f in the horizontal direction of the rod as shown in the following equation.

”＝÷”χ.

``'''ρ ι: Length of rod 1 E: Longitudinal elastic modulus of rod 1 151: Second moment of area about the principal axis perpendicular to the vibration direction g: Gravitational acceleration α: Constant ρ determined by the vibration mode : Density of rod 1 20ρo : Density of fluid to be measured A : Proportionality coefficient (determined by the shape and material of the vibrator.

) Since the resonant frequency ω is expressed as 2πf, by measuring the resonant frequency ω of the rod 1, it is possible to measure the density 25ρo of the fluid to be measured.

In such a transducer, the following conditions must be satisfied in order to achieve highly accurate measurement.

(i) Good stability of frequency f.

In other words, the Q of the vibrator 30 (=rod 1) is high. (Ii) Frequency change rate Δf/ρ with respect to density change is large.

fp=|−fp=0 (Δf=) fp=0 35 That is, the quality G of such a transducer can be expressed by the following equation.

In the configuration shown in Fig. 1, if the rod 1 is caused to resonate and its resonance frequency ω is measured, the density ρ of the fluid to be measured can be determined.
.

However, as shown in Figure 2, when the rod is vibrating, a reaction force R is generated at the fixed end of the base 2, and this force is generated when the base is at the ideal fixed end. If not, it becomes a loss and is consumed, causing a decrease in the Q of rod 1. The present invention solves the above problems.

An object of the present invention is to provide an efficient density conversion mechanism with a simple configuration and low vibration energy loss. FIG. 3 is an explanatory diagram of the configuration of one embodiment of the present invention, where A is a front view;
B is a side view.

In the figure, 1 is the vibrator main body, the vibrating part 11, the coupling part 1
2 and a support section 13.

The vibrating part 11 is provided symmetrically in parallel to the central axis A-A,
It is shaped like two plate beams. Both ends of the coupling part 12 are coupled to one end of each of the vibrating parts 11,
The vibration part 11 and the coupling part 12 form a mouth shape. The support portion 13 vibrationally insulates the vibrator body 1 from the base 2 to which the vibrator body 1 is attached, such as a housing, and also provides a center It is designed to prevent the occurrence of errors due to misalignment of the axes, and is made up of plate-shaped flexures 131 and 132 that are perpendicular to each other, and connects the connecting portion 12 and the base 2. As shown in FIG. 3, 3 and 4 are piezoelectric elements respectively attached to the side surfaces of the coupling part 12. In this case, the piezoelectric element 3 is used as an excitation element and is connected to an externally provided amplifier 5. There is.

Furthermore, the piezoelectric element 4 is used as a vibration pickup element, and its output is fed back to the amplifier 5. An oscillation circuit B is configured. 6 is a frequency measuring device.

In the above configuration, the density ρ of the fluid to be measured.

When , the resonant frequency of the vibrator body 1 changes as shown in equation (1) above, and correspondingly, the oscillation frequency of the oscillation circuit B also changes. Therefore, when the oscillation frequency of the oscillation circuit B is measured by the frequency measuring device 6, the density ρ of the fluid to be measured is determined. You can know the value of.

In this case, as shown in FIG. 5, in the vibration mode in which the two vibrating parts 11 vibrate symmetrically about the central axis A-A, the vibrating parts 11 and Joint part 1
Since the reaction force R and moment M generated at the connection point with 2 are in opposite directions and equal in magnitude, they cancel each other out at the joint 12, and no force is generated at all, even if the support is not in an ideal state. , no energy is consumed externally from the vibrator body 1.

As a result, it is possible to obtain a vibrator main body with a high Q (a large value of the goodness level G).

FIG. 6 is an explanatory diagram of the main part configuration of another embodiment of the present invention, in which A is a front view and B is a side view.

2Z addition"";;fu'. 1"2: Four fixed isolation masses 14 are provided.

With such a device, the generated reaction force R can be made smaller, and the small reaction forces are canceled out by each other, so that no force is applied to the support point of the vibrator body 1/to the base 2. You can get something that will not occur more reliably.

In the above embodiment, it was explained that the piezoelectric elements 3 and 4 are attached to the side surface of the coupling part 12, but it goes without saying that they may be attached to the vibrating part 11 as shown in FIG. 7A. It is.

However, a better Q can be obtained near the side surface of the joint portion 12. The relationship between the fixed position of the piezoelectric element and Q is shown in FIG. FIG. 8 is a configuration explanatory diagram of another embodiment of the present invention, in which A is a front view and B is a side view.

In this embodiment, the vibrating part 11/ is composed of two elongated plates that are symmetrically parallel to the central axis A-A and on the same plane, and the connecting part 12/ is also made of the same plate. It is a flat plate-like object.

Since the main parts of the vibrator main body 1 are constructed in a flat plate shape in this way, it is possible to obtain a device that is extremely easy to manufacture, and for example, a manufacturing method such as etching can be employed. In this case, the vibrator is composed of two vibrating parts 11 as shown in FIG.
a, 11b are encouraged to alternately vibrate symmetrically across the plate surfaces symmetrically about the central axis A-A, and in this case, if an isolation mass is provided, as shown in FIG. What is necessary is to provide an isolation mass 14' that protrudes in the left-right direction.

FIG. 11 is an explanatory diagram of the main part configuration of another embodiment of the present invention.

In this embodiment, a vibrator 1 consisting of a vibrating part 11 and a coupling part 12 is provided in a pipe P through which a fluid to be measured flows.
Piezoelectric elements 3 and 4 as excitation and detection elements are provided on the outer surface of the portion of the tube P to which the pipe P is attached. In such a device, since the vibrator 1 is inside the tube P, it is protected by the tube P. Furthermore, since the piezoelectric elements 3 and 4 are attached to the outer surface of the tube P, maintenance and inspection are facilitated. 1st
Figure 2 is an example of how this device can be used to measure density sensitivity to density changes due to changes in air pressure. Note that if the piezoelectric elements 3 and 4 are formed by thin film piezoelectric elements directly on the side surface of the vibrator body 1 by vapor deposition or sputtering, the piezoelectric elements will be more easily formed than by bonding the piezoelectric elements.
In addition to being able to obtain a higher Q, since it is formed directly on the side surface of the main body, products with good productivity can be obtained.

In addition, if the vibrator body 1 is made of a magnetic material and an electromagnetic method is used in which the vibrator is driven and picked up by a coil, the coil as the drive and pick-up element can be made non-contact with the vibrator body 1, resulting in better characteristics. You can get good quality products.

Furthermore, if the vibrator main body 1 is directly composed of a piezoelectric material such as crystal, and the vibrator is constructed by attaching electrodes to the piezoelectric element by vapor deposition, etc., the configuration becomes even simpler, the characteristics are good, and the output is Low impedance can be obtained. In this case, the arrangement of the crystal cut and the flat electrode may be selected so that the vibrating section 11 undergoes bending vibration.

Furthermore, in the above-mentioned embodiment, it was explained that the vibrating part 11 has a plate beam shape, but it is not limited to this, and may be in the shape of a round bar.In short, even if the opposing vibrating parts have a symmetrical structure Bye.

As described above, according to the present invention, it is possible to realize an efficient density conversion mechanism with a simple configuration and low vibration energy loss.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle configuration of an embodiment of a conventionally known Kerr frequency conversion mechanism, FIG. 2 is an explanatory diagram of the operation of FIG. 1, and FIG. 3 is an explanatory diagram of the configuration of an embodiment of the present invention. A is a front view, B is a side view, Fig. 4 is an explanatory diagram of the configuration of the oscillation circuit, and Fig. 5 is the third
Fig. 6 is an explanatory diagram of the configuration of another embodiment of the present invention, where A is a front view, B is a side view, and Figs. 7A and B are the relationship between the fixed position of the piezoelectric element and Q. FIG. 8 is a configuration explanatory diagram of another embodiment of the present invention, A is a front view, B is a side view, FIG. 9 is an explanatory diagram of the operation of FIG. 8, A is a front view, B
is a side view, FIG. 10 is a configuration explanatory diagram of another embodiment of the present invention, A is a front view, B is a side view, FIG. 11 is a configuration explanatory diagram of another embodiment of the present invention, and FIG. This is an example of how this device can be used to measure density sensitivity to changes in density due to changes in air pressure. 1... Vibrator body, 11... Vibrating part,
12...Connection part, 13...Support part, 1
31,132...Flexia, 14...
・Isolation mass, 2...Base, 3,
4...Piezoelectric element, 5...Amplifier, 6...
...Frequency measuring device, A-A... Central axis.

Claims (1)

[Scope of Claims] 1. A vibrator body comprising a substantially long-axis vibrating part provided symmetrically in parallel with a central axis and a coupling part coupling one end of each of the vibrating parts; A density conversion mechanism comprising an excitation means for causing the vibrator to vibrate, and a detection means for detecting vibration of the vibrator body. 2 Using a piezoelectric element as an element of the excitation means and detection means,
2. The density conversion mechanism according to claim 1, wherein the piezoelectric element is provided at a connecting portion of the vibrator body. 3. The density conversion mechanism according to claim 2, characterized in that a thin film vapor-deposited piezoelectric element is used as the piezoelectric element. 4. The density conversion mechanism according to claim 1, wherein the vibrator body is made of a magnetic material, and coils are used as elements of the excitation means and the detection means. 5. The density conversion mechanism according to claim 1, wherein the vibrator main body is composed of a piezoelectric material and an electrode.