JPH0418253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a Karman vortex flowmeter for measuring the intake air amount of a fluid, for example, an engine of an automobile.

[Prior art and its problems]

Karman vortex flowmeters vibrate a diaphragm using the pressure fluctuations of Karman vortices generated near the sides of a columnar body inserted into the flow of intake air, and optically detect the vortex frequency from the number of vibrations. , which measures flow velocity or flow rate. This type of Karman vortex flow meter is known, for example, from Japanese Patent Application Laid-Open No. 58-219415 or Japanese Patent Application Laid-Open No. 58-219416.
Fig. 6 is an overall configuration diagram of a conventionally known Karman vortex flowmeter, Fig. 7 is a plan view of the vibrator shown in Fig. 6, Fig. 8 is a front sectional view of the vortex detection section, and Fig. 9 is a diagram of the tension applying mechanism. A schematic configuration diagram is shown. In FIGS. 6 to 9, 1 is a pipe, 2 is a columnar body that generates a Karman vortex, 3 is a vortex detection section, 4 is a throttle tube provided on the upstream side of the columnar body 2, and 5 is a throttle tube 4 This is a rectifier grid installed in front of the In FIG. 7, 6 is a plate-like member (oscillator), which includes a diaphragm 7 that torsionally vibrates in response to the pressure fluctuation of the Karman vortex generated in the pipe 1 by the columnar body 2, and the center of gravity of the diaphragm 7. A pair of span bands 8A, 8B and the span band 8 are held in mass balance with respect to the rotating shaft.
It consists of a frame 9 that serves as the fixed ends of A and 8B, and is a thin metal plate with a thickness of about 20 μm. In addition, 10
A and 10B are punched parts of this diaphragm 7.

In FIG. 8, a housing 12 houses the vibrator 6, and is composed of a lower housing 13 integrally formed with the columnar body 2 and an upper housing 14. In the lower and upper housings 13 and 14, grooves (not shown) of approximately the same shape are formed corresponding to the diaphragm 7 and the span bands 8A and 8B. 13, the vibrator 6 is held and the vibration chamber 15 is
is formed. Further, reference numerals 16 and 17 denote a light emitting element and a light receiving element, which are disposed opposite to the upper surface of the diaphragm 7, and whose optical axes pass through the rotational center axis of the diaphragm 7, and a hole 18 provided in the upper housing 14. The diaphragm 7 is irradiated with light and the reflected light is received to detect the vortex frequency.

In Figure 9, 19 is the span band 8A, 8B
This is a tension adding mechanism for adding tension to. 2
0 is a compression spring, 21 is a cap, and 22 is a lightweight resin presser for pushing the span band 8B, which is formed into a cylindrical shape with a bottom. This presser 2
When the spring 20 is compressed, it is guided into the guide hole 23 of the upper housing 14 and applies tension to the span band 8B. At this time, adjust the span band 8 so that the deflection angle a is about 30 degrees.
Providing a deflection allowance for B is necessary in order to keep the spring force approximately constant. Note that 18 is a fulcrum projection for receiving the span band 8B. By the way, when a sudden temperature change occurs, a transient temperature difference occurs between the vibrator 6 and the lower and upper housings 13 and 14. Due to this temperature difference, even if the materials of the vibrator 6 and the lower and upper housings 13 and 14 are the same, the lengths of the span bands 8A and 8B change due to the difference in thermal expansion. However, as described above, since tension is applied to the span band 8B by the spring, the change in length due to this thermal expansion can be absorbed, and the tension is maintained approximately constant. Therefore, it is possible to prevent the span bands 8A, 8B from being damaged, the vibration resistance of the diaphragm 7 being degraded by external vibrations, and the sensitivity at the lowest flow rate becoming unstable. For this reason, it is necessary to set a deflection allowance in advance for the span band 8B so as to maintain a predetermined deflection angle a during assembly. for example,
By forming a draw in the frame 9 in a direction perpendicular to the span bands 8A, 8B without changing the length of the span bands 8A, 8B, the length of the frame 9 is slightly shortened to provide a deflection allowance. There is a way. However, molding the frame 9 in this way requires complicated molding, and is not necessarily an appropriate method for practical use. Therefore, the setting of this deflection allowance is
This was an important issue in molding the vibrator 6.

[Purpose of the invention]

In view of the above points, the present invention effectively solves the problems of the prior art, and aims to provide a Karman vortex that is easy to manufacture, requires no effort to handle, and has stable detection sensitivity at low flow rates. The purpose of the present invention is to provide a flow meter.

[Key points of the invention]

In order to achieve such an objective, the present invention
The other end of one of the pair of span bands is connected to a fixing part, and the other end is separated from the fixing part, so that the span band is provided with a predetermined deflection margin.

According to an embodiment of the present invention, a connecting piece is provided between the other end of the other span band and the fixed part, and after providing a predetermined deflection allowance for the span band, the connecting piece is be separated.

Furthermore, according to another embodiment of the present invention, the connecting piece is formed so narrow that it can be automatically separated by applying tension to the spun band after the plate member is assembled.

[Embodiments of the invention]

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

FIG. 1 is a block diagram of the main parts of a Karman vortex flowmeter according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of the structure of an embodiment of the present invention. In FIGS. 1 and 2, parts having the same functions as those in FIGS. 4 to 7 are given the same reference numerals. The vibrator 24 is
It is a thin metal plate mainly consisting of a diaphragm 25, a pair of span bands 27A, 27B that hold the diaphragm 25, and a frame 28. Incidentally, one end of the span bands 27A and 27B holds the diaphragm 25 so that the mass is balanced by the rotation axis A-A that includes the center of gravity of the diaphragm 25. Further, the other end of the span band 27A is connected to a frame 28 which is a fixed part. The other end of the span band 27B consists of a relatively long wide part 29 and a span band holding part 30 following the wide part 29, and is separated from the frame 28 through a small gap 40. This wide part 2
9 is formed wide to avoid stress concentration while maintaining the torsional rigidity of the span band 27B. In addition,
The span band holding part 30 is formed wider than the wide part 29, and has an oblong pin hole 32 on the torsional rotation axis A-A. Further, the pin hole 31 is provided in the frame 28 on the runout rotation axis A-A, which is located symmetrically with the pin hole 32. These pin holes 31, 32
and the fixing pin 3 installed in the lower housing 13.
7 and 38, the diaphragm 25 and the span bands 27A and 27B are positioned. At this time, the fixing pin 38 is installed so as to be inscribed in the diaphragm 25 side of the oblong pin hole 32, and when a spring force is applied to the span band 27B by the tension applying mechanism 19, the span band 27B is pulled. The fixing pin 38 comes to be inscribed on the frame 28 side of the pin hole 32, so the movement of the span band holding part 30 becomes the deflection allowance of the span band 27B, and a predetermined deflection is imparted to the span band 27B. . Therefore, even if the deflection margin of the span band 27B suddenly decreases due to thermal expansion of the housing due to a transient temperature rise, the span band 27B can be prevented from being damaged. Furthermore, the pin hole 33 and the pin hole 31 position the frame body 28 using the fixing pins 37 and 39 of the lower housing 13. Furthermore, in FIG. 1, 35 is a space provided in the lower and upper housings 13, 14, and in FIG. 2, 34 is a through hole for a fixing screw (not shown) when stacking the lower housings 14, 36A and 36B are punched parts of the diaphragm 25.

Next, FIG. 3 shows a schematic configuration diagram of another embodiment of the present invention. In the figure, parts having the same functions as those in FIG. 2 are given the same reference numerals. The vibrator 124 includes a span band holding section 30 and a frame body 28.
A connecting piece 41 is provided to connect the two. This connecting piece 41 makes handling of the vibrator 124 extremely easy. That is, the frame body 28 is positioned by the pin holes 31, 33 and the fixing pins 37, 39, and the pin holes 31, 32 and the fixing pin 3
7 and 38, the connecting piece 41 maintains the connected state between the span band holding part 30 and the frame 28 until the diaphragm 25 and the span bands 27A, 27B are positioned. After this positioning, the spun band holding part 30 and the frame 28 are separated by cutting the connecting piece 41 with a knife or the like.

Furthermore, this connecting piece 41 is connected to the span band 27.
After the vibrator 124 is assembled between the lower and upper housings 13 and 14 by forming the width sufficiently narrower than the width dimensions of the span bands 27B and 27B, tension is applied to the span band 27B by the tension applying mechanism 19. It is also easy to make it automatically disconnected.

Next, FIG. 4 shows a schematic configuration diagram of still another embodiment of the present invention. In the figure, parts having the same functions as in FIG. 3 are given the same reference numerals.
The vibrator 224 includes a diaphragm 25 and a diaphragm 2.
A pair of span bands 127A serving as rotation axes of 5,
127B and a frame 128 are provided. Further, a span band holding section 130 is provided at the other end of the span band 127B, and is separated from the frame 128 with a small gap 140 interposed therebetween. Furthermore, the frame body 128 has positioning pin holes 31 and 33.
A pin hole 133 is arranged outside the lower housing 13, and a third fixing pin (not shown) added outside the fixing pins 37 and 38 of the lower housing 13 makes it possible to stably assemble the vibrator 224. .

Next, FIG. 5 shows a schematic configuration diagram of still another embodiment of the present invention. In the figure, parts having the same functions as in FIG. 4 are given the same reference numerals.
The vibrator 324 includes a diaphragm 25 and a diaphragm 2.
A pair of span bands 12 serving as the torsion rotation axis of 5.
7A, 127B and a frame 128 are provided. Further, a span band holding section 130 is provided at the other end of the span band 127B, and a frame body 128
They are separated by a small gap 140 between them. Note that the span band holding portion 130 is provided with a positioning pin hole 134 for the diaphragm 25, and the frame body 128 is provided with a positioning pin hole 135, respectively. The vibrator 324 is positioned by fixing pins (not shown) of the lower housing 13 that correspond to the pin holes 134 and 135. Along with this, a span band 12 which is a torsion rotation axis
Another positioning pin 136 corresponding to the positioning pin 31 is provided on the frame 128 on the extension line of 7A and 127B. In addition to the positioning pin hole 31, there are positioning pin holes 134, 135, 136.
is provided, the assembly of the vibrator 324 is stabilized in a short time, and the axes of the light emitting element 16, the light receiving element 17, the span bands 127A and 127B, and the diaphragm 25 are
The relative position with respect to the center is easily determined, reducing the adjustment effort.

〔Effect of the invention〕

As described above, according to the present invention, one end of the span band is connected to the diaphragm and the other end is separated from the frame body to provide a predetermined deflection allowance for the span band, thereby solving the problems of the prior art. This method effectively solves the problem, is easy to manufacture, requires no effort in handling, and has the effects of stabilizing detection sensitivity at low flow rates.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the main parts of a Karman vortex flowmeter according to an embodiment of the present invention, FIG. 2 is a schematic diagram of an embodiment of the present invention, and FIG. 3 is a schematic diagram of another embodiment of the present invention. 4 and 5 are schematic configuration diagrams of still other embodiments of the present invention, FIG. 6 is an overall configuration diagram of a conventionally known Karman vortex flowmeter, and FIG. 7 is a diagram of the vibrator of FIG. 6. A plan view, FIG. 8 is a front sectional view of the vortex detection section,
FIG. 9 is a schematic diagram of the tension applying mechanism. 3... Vortex detection unit, 19... Tension adding mechanism, 2
4,124,224,324... vibrator, 25...
...Vibration plate, 27A, 27B, 127A, 127B
... Spun band, 28,128 ... Frame, 29
...Wide part, 30,130...Span band holding part, 31,32,33...Pin hole, 37,38,
39...fixing pin, 41...connecting piece.

Claims (1)

[Scope of Claims] 1. A diaphragm that vibrates in response to pressure fluctuations due to Karman vortices that are generated alternately near both sides of a columnar body inserted into the flow of a pipe, and one end of which is coupled to the diaphragm, respectively. A plate-like member formed by integrally molding a pair of span bands serving as a rotation axis of a lever diaphragm and a fixing part to which the span bands are fixed; and a tension applying mechanism for applying tension to the span bands. In the Karman vortex flowmeter, the other end of one of the pair of span bands is connected to the fixed part, and the other end is separated from the fixed part so that the span band has a predetermined deflection. A Karman vortex flow meter characterized by a gap. 2. In the Karman vortex flowmeter according to claim 1, a connecting piece is provided between the other end of the other span band and a fixed part, and a predetermined deflection allowance is provided in the span band. The Karman vortex flowmeter is characterized in that the connecting piece is then separated. 3. In the Karman vortex flowmeter according to claim 2, the connecting piece is narrow enough to be automatically separated by applying tension to the span band after the plate member is assembled. A Karman vortex flowmeter characterized by being molded.