JPS6110197Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crystal strain gauge that detects the natural frequency of a gauge that changes in response to applied strain and measures the amount of strain acting on the gauge.

FIG. 1 is an explanatory diagram of the configuration of a conventional example using such a crystal strain gauge, and in the figure, 1 is a support;
2 is an inlet for the pressure to be measured; 3 is a bellows that expands and contracts according to the introduced pressure; 4 is a strain-generating body having a predetermined recess in the center and made of a plate spring, for example; and 5 is an abbreviation of the strain-generating body. Crystal strain gauges 6 and 6' glued to the central part are fasteners 7 and 7', for example screws, for fastening both ends of the strain body 5 to the support 1 and the bellows 3, respectively.
is an adhesive body that adheres the crystal strain gauge 5 to the strain body 4. Further, FIGS. 2 and 3 are enlarged views of the area around the crystal strain gauge 5, showing a state where no strain is acting on the crystal strain gauge 5 and a state where strain is acting, respectively. In Figures 2 and 3,
The same symbols as in FIG. 1 are used with the same meaning, and the explanation here will be omitted. Furthermore, 5a and 5b are long vibrating parts that are symmetrically provided with respect to the central axis of the crystal strain gauge 5, and 5c and 5d are vibrating parts that are connected at both ends of the vibrating parts 5a and 5b, respectively. The connecting portions 5c and 5d and the vibrating portion 5
a and 5b are combined in a square shape to form a crystal gauge 5.

In the conventional embodiment having the above configuration, when the pressure to be measured is not introduced from the inlet 2, the bellows 3 is in a contracted state, and the strain body 4 is kept in a substantially horizontal state and moved around the crystal strain gauge 5. is as shown in Figure 2. Furthermore, when a pressure to be measured is introduced from the inlet 2, the bellows 3 expands in response to the pressure to be measured, thereby applying strain to the strain body 4. The strain of the flexure element 4 is transmitted to the crystal strain gauge 5 via the adhesive bodies 7, 7', causing the crystal strain gauge to change from the state shown in FIG. 2 to the state shown in FIG. 3. In FIG. 3, at the fixed end of the crystal strain gauge 5 to the strain body 4, a reaction force R and a moment M generated at the connection points between the vibrating parts 5a, 5b and the coupling parts 5c, 5d are in opposite directions. Therefore, even if the coupling between the crystal strain gauge 5 and the strain body 4 is not ideal, energy will not be consumed and released from the crystal strain gauge 5 to the outside. The amount of strain transmitted from the flexure element 4 to the crystal strain gauge 5 is accurately detected by the crystal strain gauge 5, and is calculated from the strain amount through predetermined calculation processing (not shown). A measurement pressure is measured.

However, in the above conventional example, the crystal strain gauge 5 is bonded to the starting body 4 using the adhesive bodies 7 and 7', and the pressure to be measured introduced into the bellows 3 is transmitted through the strain body 4 to cause the crystal strain. Since it is configured to be indirectly detected by the gauge 5, the crystal strain gauge 5 and the strain body 4 are connected to each other.
The zero point may exhibit temperature characteristics and fluctuate due to the difference in thermal expansion coefficient between There were some drawbacks, such as:

The present invention has been devised in view of these drawbacks, and its purpose is to provide a quartz crystal strain gauge in which the above-mentioned drawbacks are eliminated and the temperature characteristics at the zero point are improved.

The feature of the present invention is that the crystal strain gauge 5 measures the natural frequency of the gauge, which changes in response to the applied strain, and determines the strain acting on the gauge.
The purpose is to use a composite gauge having one inner vibrator and two outer vibrators to detect the difference in frequency between one of the outer vibrators and the inner vibrator to obtain the distortion. .

Hereinafter, the present invention will be explained in detail using figures. FIG. 4 is an explanatory diagram of the configuration of an embodiment of the present invention. In the figure, the same symbols as in FIG. 1 are used with the same meanings, and the explanation here will be omitted. Also, 8 is 3
9 is a composite crystal strain gauge in which multiple oscillators 81 to 83 are connected by a coupling part 84, and 9 is a composite crystal strain gauge 8 whose lower end (the lower end of the oscillators 81 to 83) is bonded to the strain body 4. 10 and 10' are lead wires, 11 and 11' are oscillation circuits, 12 is a frequency difference detection circuit, 13 is a counter, and 14 is a linearizer. Furthermore, FIG. 5 is an enlarged view of the vicinity of the composite crystal strain gauge 8, and in the figure, the same symbols as in FIG. 4 are used with the same meanings, and the explanation here will be omitted. In addition, the vibrator 81 (or 82, 83) has the vibrating parts 81a, 81b (or 82a, 82
b, 83a, 83b) and small joint parts 81c, 81d
(or 82c, 82d, 83c, 83d), and the vibrating section is formed of two elongated members provided symmetrically with respect to the central axis of each of the vibrators. . Furthermore, the small coupling portions 81c, 81d (or 82c, 82
d, 83c, 83d) have both ends coupled to one end of each of the vibrating parts, and the vibrator 81
(or 82, 83) are each formed into a square shape by the vibrating portion and the small coupling portion.

The operation of the present invention having the above configuration will be explained below. In FIG. 4, when the pressure to be measured is not introduced from the inlet 2, the bellows 3 is in a contracted state, and the strain body 4 is kept in a substantially horizontal state, and each vibrator 81 of the composite crystal strain gauge 5 is in a contracted state. The same force Fo is applied from the strain body 4 to 83. Thus, each of the vibrators 81 to 83 receives the same strain and vibrates at each natural frequency _f1 to _f3 . In addition, inlet 2
When a pressure to be measured is introduced from the bellows 3, the bellows 3 expands in response to the pressure to be measured, thereby applying strain to the strain body 4. The strain is transmitted to the vibrators 81 to 83 of the composite crystal strain gauge 8 via the adhesive 9, and compressive force is applied to the vibrators 81 and 83, respectively, as shown in FIG.
F ₁ and F ₃ are applied, and a tensile force F ₂ is applied to the vibrator 82. Therefore, the vibrators 82 and 83 each have a tensile force.
Under strain corresponding to F ₂ and compressive force F ₃ , respectively,
The natural frequencies of f ₂ and F ₃ are f ₂ ′ and f ₃ ′, respectively (for example,
f ₂ < f ₂ ′, f ₃ > f ₃ ′). The natural frequencies f ₃ ′ and f ₂ ′ pass through oscillation circuits 11 and 11 ′, respectively, and then are subjected to arithmetic processing (f ₃ ′−f ₂ ′) in the frequency difference detection circuit 12, and then the frequency The signal is output as an output Eo through a counter 13 which is a reading circuit and a linearizer 14 which is a linearization calculation circuit. Thus, the pressure to be measured introduced into the bellows 3 is measured from the output Eo.

According to the embodiment of the present invention as described above in detail, the oscillators 81 to 8 of the composite crystal strain gauge 8
Since the lower end of the strain gauge 3 is bonded to the strain body 4 by the adhesive 9, even if the thermal expansion coefficients of the composite crystal strain gauge 8 and the strain body 4 are different, the above-mentioned vibration No force due to temperature change acts in the longitudinal direction of the elements 81 to 83, and this has the advantage of exhibiting superior zero point temperature characteristics compared to the conventional example. Furthermore, since the structure is configured to detect the difference between the natural frequency of the vibrator 82 and the natural frequency of the vibrator 83, the strain body 4 is directed to the vibrator 82 and the vibrator 83 in opposite directions. Force F ₂ , F ₃
In addition to this, there is also the advantage that the detection sensitivity is twice as high as that of the conventional example.
Furthermore, since the difference between the natural frequency of the vibrator 82 and the natural frequency of the vibrator 83 is detected, the linearization calculation in the linearizer 14 has the advantage that an accuracy of 0.5% can be achieved using a first-order approximation formula. It also has

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the configuration of the conventional example, FIGS. 2 and 3 are enlarged views of the vicinity of the crystal strain gauge in FIG. 1, FIG. 4 is an explanatory diagram of the configuration of the embodiment of the present invention, and FIG. 4
FIG. 2 is an enlarged view of the area around the composite type crystal strain gauge shown in the figure. 1... Support, 2... Inlet, 3... Bellows,
4... Strain body, 5... Crystal strain gauge, 5a, 5b
... Vibrating part, 5c, 5d... Coupling part, 6, 6'...
... Fastening body, 7, 7', 9... Adhesive body, 8... Composite crystal strain gauge, 10, 10'... Lead wire, 1
1, 11'... Oscillation circuit, 12... Frequency difference detection circuit, 13... Counter, 14... Linearizer, 81, 82, 83... Vibrator, 81a, 81
b, 82a, 82b, 83a, 83b... vibrating section, 84, 81c, 81d, 82c, 82d, 8
3c, 83d... joint portion.

Claims (1)

[Scope of utility model registration request] First and second elongated vibrating parts provided symmetrically with respect to the central axis and first and second small coupling parts that respectively connect both ends of the first and second vibrating parts. first to third vibrators each formed in a square shape;
a coupling portion coupled to one end of each of the first to third vibrators, and disposing the first and third vibrators on the outside and disposing the second vibrator on the inside; . A composite crystal strain gauge, wherein the amount of strain applied is measured from the difference between the natural frequency of the first or third vibrator and the natural frequency of the second vibrator.