JPH0524184Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention is based on the Karman vortex generator that is inserted into the flow of a fluid, for example, the intake air of an engine such as an automobile, and which generates Karman vortices alternately near both sides of the vortex generator. The present invention relates to a Karman vortex flowmeter that measures the flow velocity or flow rate of a fluid by detecting pressure fluctuations in a vortex, and in particular to the shape of a diaphragm in a vortex detection section.

[Prior art and its problems]

Figure 5 is an overall configuration diagram of a conventional Karman vortex flowmeter, Figures 6 and 7 are schematic configuration diagrams of the vortex detection section, Figure 8 is a plan view of the vibrator, and Figure 9 is the vibration state of the diaphragm. 10 are waveform diagrams in FIG. 9. In FIG. 5, 1 is a pipe, 2 is a pair of Karman vortex generators (vortex generators), 3A and 3B are openings provided in this vortex generator 2, 4 is a vortex detector, and 5
6 is an optical fiber, and 6 is a processing circuit for the eddy detection signal. As shown in FIGS. 6 and 7, the vortex detection unit 4 is formed with a vibration chamber 7 having a rectangular cross section. A diaphragm 9 of the child 8 is provided. As shown in FIG. 8, this oscillator 8 consists of a diaphragm 9 on which pressure fluctuations of Karman vortices act, and a pair of diaphragms 9 on which the diaphragm 9 is held on a line-symmetrical axis including its center of gravity to perform torsional vibration. span band 10
A, 10B and this span band 10A, 10B
The frame portion 11 serving as the fixed end of the 1 has a substantially constant thickness.
Molded from a sheet of metal. In addition, 12A, 12
Reference numeral B designates pressure guiding holes communicating with the openings 3A and 3B, respectively, and is for guiding the pressure change of the Karman vortex to the diaphragm 9. Further, the signal processing section 6 includes a generating element 13, a light receiving element 14, and a waveform shaping circuit 15.

Next, the operation will be explained with reference to FIGS. 5 to 10. When a Karman vortex is generated near both sides of the vortex generator 2 inserted into the flow inside the pipe line 1, the pressure is increased by this vortex to the openings 3A,
The pressure is transmitted to the diaphragm 9 via the pressure guiding hole 12A, the opening 3B, and the pressure guiding hole 12B. As a result, the diaphragm 9 is displaced. Since these vortices are generated alternately in the vicinity of both side surfaces of the vortex generating body 2, the diaphragm 9 torsionally vibrates around the pair of span bands 10A and 10B due to these vortices. The light from the light emitting element 13 of the signal processing circuit 6 is transmitted through the optical fiber 5 to the diaphragm 9.
The irradiated light is reflected on the surface of the diaphragm 9 and transmitted through the optical fiber 5 to the light receiving element 14.
, and the vortex frequency can be detected with an extremely simple configuration. However, in order to detect the reflected light from the diaphragm 9 by the light receiving element 14,
The amount of reflected light also changes due to the deformation of the diaphragm, and the change in the amount of light due to the deformation results in high frequency distortion. That is, ideally the diaphragm 9 needs to be a completely rigid body. However, the diaphragm 9 is a thin metal plate and cannot be made into a rigid body. As shown in FIG. 9, the diaphragm 9 has a rectangular plate shape with a uniform width dimension, so it is easy to manufacture and control of dimensional accuracy is easy. However, this diaphragm 9 has a high vortex frequency, and in a high flow velocity region with large pressure changes, both corners B at the tip of the diaphragm cause bending vibration, which causes the first
As shown in Figure A, the high-frequency distortion of the output waveform of the light receiving element 14 increases, and as a result, the waveform period changes to T ₁ , T ₂ , T ₃ (T ₁ ≠ T ₂ ≠ T ₃ ) as shown in Figure B. Unlike this, the stability of the waveform period deteriorates, which is unfavorable for engine control. Improving the stability of this waveform period was an important issue to be solved. Note that FIG. 10B shows the waveform shaping output of the waveform shaping circuit 15.

[Purpose of invention]

The present invention was devised in view of the above-mentioned problems, and its purpose is to provide a device that is easy to manufacture, has a simple structure, has excellent durability, and can improve the periodic stability of the output waveform. Our objective is to provide a Karman vortex flowmeter.

[Key points of the idea]

In order to achieve this purpose, the present invention
The diaphragm is twisted to form a substantially trapezoidal shape with the width gradually decreasing from the vibration axis toward the tip, and the connection portion of the diaphragm with the span band is formed into an arc shape, and at least an upper housing or a lower housing is formed. A mountain-shaped inclined surface is provided at a location facing the diaphragm of either one of the diaphragms.

[Example of idea]

Next, one embodiment of the present invention will be described in detail based on the drawings.

Fig. 1 shows a schematic configuration diagram of a vortex detection unit to which the present invention is applied, A is a front cross-sectional view thereof, and B is a side cross-sectional view thereof. The figures have the same functions as those in Figs. 5 to 7. The parts are given the same reference numerals. The lower housing 22 has a vortex generator 2 integrally formed on its lower surface, a vibrator 23 on top of the lower housing 22, and an upper housing 21 stacked on top of the vibrator 23 in order to hold the vibrator 23. be done. The vibration chamber 25 is divided by the vibration plate 24 of the vibrator 23 into an upper chamber and a lower chamber that communicate with each other with a small gap, and the torsional vibration axis A-A of the vibration plate 24 (FIG. 2) Including, vertically opposing mountain-shaped inclined surfaces 26 and 27 are formed. 34A, 34
B is a storage chamber that accommodates the span bands 29A and 29B, and 28 is a tension applying means for applying tension to the span bands 29B, which is a leaf spring in this embodiment. Further, 30 and 31 are light emitting elements and light receiving elements, and pressure fluctuations due to Karman vortices alternately generated by the vortex generator 2 are caused by pressure fluctuations in the openings 3A, 3B and the pressure guiding hole 1.
A and 12B, the vibration is introduced into the lower chamber of the vibration chamber 25, and is optically detected as torsional vibration of the vibration plate 24.

Next, FIG. 2 shows a schematic diagram of the main parts of an embodiment of the present invention. In the figure, the oscillator 23 includes a diaphragm 24 on which pressure fluctuations of Karman vortices act, and a pair of span bands that hold the diaphragm 24 on a line-symmetrical axis A-A that includes its center of gravity and cause torsional vibration. 29A, 29B and this span band 29A, 2
The frame body 20 serving as the fixed end of 9B is formed from a single metal plate having a substantially constant thickness. by the way,
The diaphragm 24 is formed into a substantially trapezoidal shape, with the width gradually decreasing toward the tip from the vibration axis A-A, which torsionally vibrates by the span bands 29A and 29B. In addition, the connecting portions of the diaphragm 24 with the span bands 29A and 29B are formed in an arc shape with a radius R to avoid concentration of stress on these connecting portions. By molding the diaphragm 24 in this way, it has a shape in which both the tip corners B of the conventional diaphragm 9 shown in FIG. is removed,
Therefore, as shown in FIG. 2A, the light receiving element 31
The output waveform has high-frequency distortion removed and becomes a periodic clean waveform. Therefore, as shown in FIG.

Next, Figure 3 is a perspective view of the upper housing, and Figure 4 is a perspective view of the upper housing.
The figure shows a perspective view of the lower housing. In FIGS. 3 and 4, the upper and lower housings 2
1 and 22 are provided with grooves 30 and 31 facing each other and having substantially the same shape corresponding to the shape of the vibrator 23. Thus, the grooves 30 and 31 form the upper and lower chambers of the vibration chamber 25 between the grooves 30 and 31 and the span band 29.
It consists of concave grooves 35, 36, 37, 38 forming accommodation chambers 34A, 34B in which A, 29B are accommodated, accommodation chambers 39, 40 in which the tension applying mechanism 28 is accommodated, and the like.

The groove 33 (FIG. 4) is formed in a substantially trapezoidal shape to accommodate the diaphragm 24, and forms a mountain-shaped inclined surface 27 having a peak B-B including the torsional vibration axis A-A of the diaphragm 24.
The inclined surface 27 is always in contact with the bottom surface of the vibration chamber 25 without any gap. The inlet holes 12A and 12B are open in the inclined surface 27, and the pressure fluctuation of the Karman vortex generated in the vortex generator 2 is transmitted to the vibration chamber 25.
is similarly formed in a generally trapezoidal shape to accommodate the diaphragm 24 and to form a mountain-shaped inclined surface 26 .
The top of the mountain-shaped inclined surface 26 is
In order to prevent mechanical interference even if the plate 4 is slightly deformed, a small gap, about 30 μm in this embodiment, is maintained by cutting off the flat surface 41.
Further, the lower housing 22
Positioning pins 42, 43 provided on the vibrator 23 fit into pin holes 44, 45 on the center line of the span bands 29A, 29B of the vibrator 23 and pin holes 46, 47 of the upper housing 21, respectively, for positioning.

By configuring the vibrator 23 and the upper and lower housings 21 and 22 in this manner, the diaphragm 24 is formed into a substantially trapezoidal shape, and the connecting portions with the span bands 29A and 29B are formed into an arc shape. together with upper and lower housings 21, 22
A full cushion of air is created between the grooves 32 and the chevron-shaped inclined surfaces formed in the grooves 32 and 33, so that collisions are softened and deformation thereof is prevented.

[Effect of idea]

As explained above, according to the present invention, the diaphragm is formed into a substantially trapezoidal shape by torsionally reducing the axis from the vibration axis toward the tip, thereby making it easy to manufacture. This is simple and has the effect of eliminating high-frequency distortion of the output waveform of the light receiving element due to the bending vibration of the diaphragm that tends to occur in conventional high-speed ranges, and improving the periodic stability of the output waveform. moreover,
Since the connection portion of the diaphragm with the span band is formed in an arc shape, stress concentration at this connection portion can be avoided and cracks in the diaphragm can be prevented. In addition, a mountain-shaped inclined surface is provided at the part of the housing that faces the diaphragm, and an air cushion is formed between the diaphragm and the housing, so the buffering effect of this space completely prevents deformation of the diaphragm. This further improves the reliability and durability of the Karman vortex flow type, which is equipped with a diaphragm that repeatedly vibrates at a very high frequency, especially in high-speed regions.

[Brief explanation of drawings]

FIG. 1 shows a schematic configuration diagram of a vortex detection section to which the present invention is applied, FIG. Fig. 2A is an explanatory diagram of the output signal obtained when using the diaphragm shown in Fig. 2;
The figure is a perspective view of the upper housing, FIG. 4 is a perspective view of the lower housing, FIG. 8 is a plan view of the vibrator, FIG. 9 is a vibration state diagram of the diaphragm, and FIG. 10 is an explanatory diagram of an output signal obtained when the diaphragm shown in FIG. 9 is used. 2... Vortex generator, 21... Upper housing, 2
2... lower housing, 23... vibrator, 24...
... Vibration plate, 25 ... Vibration chamber, 26, 27 ... Mountain-shaped inclined surface, 29A, 29B ... Spun band, 3
0, 31, 32, 33, 35, 36, 37, 38
...Concave groove, 41...Flat surface.

Claims (1)

[Scope of utility model registration request] A diaphragm that vibrates in response to pressure fluctuations generated alternately near both sides of a Karman vortex generator inserted into a fluid flow; In a Karman vortex flowmeter, which has a pair of span bands that are held and torsionally vibrate, and an upper housing and a lower housing that sandwich the fixed end of the span band, the diaphragm is torsionally vibrated from the axis of vibration toward the tip. gradually decreases to form a substantially trapezoidal shape, and a connecting portion of the diaphragm with the span band is formed into an arc shape, and at least one of the upper housing and the lower housing faces the diaphragm. A Karman vortex flowmeter characterized by having a mountain-shaped sloped surface at the location where the flow is caused.