DE3241988A1 - FLOWMETER WITH KARMAN'SCHER VERBELSTRASSE - Google Patents

Description

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FUJI ELECTRIC CO., LTD.
Kawasaki / Japan

My reference is VPA 81 P 8611 DE

Flow meter with Karman's vortex street

The invention relates to a flow meter with Karman's vortex street according to the preamble of claim 1. ■ ■ ·.

In a known flow meter of this type (Japanese Patent application 90813/1981), the first pillar in the direction of flow has a triangular cross-section, and the The pillar behind is designed as a plate. In particular, due to the design of the rear pillar The relatively high flow resistance makes it difficult to measure at low flow rates. Furthermore In such a construction, the eddies in the direction of the current behind the pillars are recorded, thereby providing an accurate Capturing the vertebrae is difficult. Possibly occurring pulsations in the pipe, changes in the flow velocity or the pressure are cause for disturbances here. In general, flow meters of this type still have the disadvantage that the Generation of the vortex is unstable and relatively weak vortices are generated at low flow rates, which is an accurate Makes measurement difficult.

In addition, a flow meter is also known at one pillar is a substantially isosceles triangular one Has cross-section and is arranged so that the base line of the triangle is transverse to the direction of flow and thus vortices can be generated over a relatively wide range of flow rates. Here, however, exists the disadvantage that there is a great loss of pressure due to the pier occurs because the face opposite the flow is flat.

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In addition, another flow meter is known at one pillar has a substantially isosceles trapezoidal shape Has cross-section and is arranged / that the base is vertical to the direction of flow and thus 5 · Vortex over a relatively large range of flow rates be generated". A disadvantage here is that there is a great loss of pressure because the surface, which is opposite to the river, is flat «, with another known vortex generators are a large number of pillars arranged one behind the other in the direction of flow at regular intervals. This construction is, however, by the great constructive Effort and the high production costs disadvantageous »

First, general problems of a vortex detector will be explained. In general, a flow meter of the type mentioned is those produced in Karman's vortex street Vortex behind the pillar or pillars at low flow rates very weak. Thus is a detector with high sensitivity required »arrangements with high sensitivity, e.g.« heating wire or ultrasonic radiation arrangements have the disadvantage that with them small electrical Analog signals have to be amplified and so do the temperature characteristics and the stability of the detector or the detector circuit considerably influences the measuring accuracy and the measuring range «Accordingly, detectors, which are needed for a measurement at low flow rates, relatively insensitive to these Be factors and must continue to have high sensitivity.

A known arrangement in which a vibration plate of a vortex detector is bent by the mirble pressures and the has a simplified signal processing is known from the Japanese utility model Ir «, 21501/1971. Here is

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a vibration chamber with a vortex generator is present, and there is a vibrator with a plate-shaped bottom attached to the wall of this chamber with one end. The speed or amount of flow is determined by the Vibration frequency of the vibrator derived. This known apparatus has advantages in that it is simple in construction is because changes in pressure due to the eddies are directly detected as a deflection or as a force. As well as always, in the event that the vibrator performs bending vibrations, malfunctions due to external vibrations may occur appear. Especially when the flow rate is low and thus the pressure changes caused by the eddies, even small, it is impossible to absorb the vibrations due to the eddy from disturbing external vibrations differentiate, so that an accurate detection of the vortex frequency is impracticable.

In another conventional vortex detector, the relatively sensitive vortex detector on a vibrating part with a plate made of lightweight resin, which is attached so that it can rotate around a centering hole. This vortex detector is disadvantageous in that at high flow rates and thus high vortex pressures, large deflections or large forces act on the detector because the plate part is bent proportionally to the eddy pressure.

In summary, it can be said that it is extremely it is difficult to detect eddies with accuracy without damaging or even destroying the detector.

Another example of such an arrangement, in which a plate part is bent and this bending or twisting is detected, is known from Japanese patent 36933/1980. This device is suitable if ■■ · ... ■■

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the flow rate is very high, but it can Do not detect eddies when the flow rate is low because disturbing bending or other vibrations of the plate part can occur here » ■ 5

The invention is based on the object of a flow meter with a Karmansehen Wirbe'istraße to create that has a pulley generator, which is relatively strong and regular eddies even at low flow rates generated and also causes a slight pressure loss and is little influenced by external influences or through disturbances in the medium to be sneezed »

To solve this problem, a flow meter has the type mentioned at the beginning. Type of characteristics according to the identifying part of claim 1.,

A flow meter according to the invention, in contrast to the known arrangements, has a first pillar with an isosceles triangular cross-section and a second pillar with an isosceles trapezoidal cross-section, both of which have the same projected widths across the direction of flow and are arranged as a pentagon, they also have optimal dimensions based on the results of experiments, whereby the pressure loss is small and the characteristic improvements in terms of linearity can be achieved in a wide measuring range. In contrast to the known arrangements - with sensors for vortex detection in the direction of flow behind the pillars - the arrangement according to the invention also has openings on opposite sides of the second pillar, which can guide pressure fluctuations caused by eddies and thus detection of the eddies through these openings can be carried out _o It thus results that the new "flow meter Mirbel with a good signal noise

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can detect ratio over a wide range of the flow rate without disturbing pressure fluctuations, z. B. caused by pulsations in the river to be influenced.
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With the dependent claims 2 and 3, advantageous embodiments of the flow meter according to the invention are optimal Dimensioning of the pillars for vortex generation specified.

In one embodiment of the flow meter according to the Claim 4 there is a vortex detector which is particularly suitable for removing disruptive external vibrations from those to be detected Vibrations, especially at low flow rates to distinguish. In this embodiment there is a vibrator which is activated by the eddy pressures excited to flexural vibrations around a held end will. This novel vibrator is in a state of equilibrium near a symmetrical bore by the center of gravity of the vibrator; it is carried by the tightening straps in the bore; causing torsional vibration around the center of gravity is made possible. In addition, a mechanical tension is applied to the tensioning straps To prevent bending vibrations, whereby this vibrator cannot be influenced by external vibrations. This embodiment is advantageous because there is a large oscillation resistance and a detection of eddies high sensitivity can be performed regardless of the fact that the torsion spring constant is small.

According to further developments, here is a chamber for wrapping the vibration plate, which is due to torsional vibrations the vortex pressures is excited, which is also formed by the vibrating plate in two essentially equal Subspaces is divided. One of these sub-spaces is divided symmetrically in relation to the centering hole of the

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Vibration plate »The two sub-chambers thus formed are provided with openings for the introduction of the pressure fluctuations of the eddy pressures, - which pass through their walls and allow the torsional vibrations of the vibration plate. The amplitude of these vibrations is limited by that of the vibrating plate opposite walls, whereby the vibrations are essentially the same regardless of the eddy pressure Have amplitude.

The first sub-space is provided with elements for detecting the bending of the vibration plate, which itself is the Subspace in which the eddy pressures are transported from . that of the subspace with the vibration deflection detector seal off. It is thus achieved that the detector hardly comes into contact with the medium to be measured, which makes it possible is to detect eddies without having special experience with possible impurities. The the deflection of the vibration plate detecting parts two optical paths which are open to the first subspace and facing the vibrating plate »This arrangement with a light emitting and a light receiving part is arranged at opposite ends, with a change due to the torsional vibrations of the vibrating plate the intensity of the light reflected on the vibrating plate takes place. The light receiving part detects this Change in intensity as a signal proportional to the oscillation. This novel arrangement is simple to construct and can detect eddies without being influenced by electromagnetic interference.

Advantageous embodiments of this embodiment of the flow meter according to the invention specified in claim k are specified in claims 5 to 12. In particular, the embodiments according to claim 7 enable a flow measurement that is insensitive to temperature changes.

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In the Ausführungsforra according to claim 12 is advantageous Way, a vibrator specified, which despite a relatively low spring constant a good resistance to has disruptive external vibrations. This can improve the sensitivity in the detection of the eddies because the tensioning straps that carry the vibration plate are in a state of equilibrium and thus allow torsional vibrations, however, on the other Side prestressed are prevented by flexural vibrations. ■

In a further embodiment of the flow meter according to claim 13, it is possible to make a particularly precise detection of the eddies of the Karmän ¹ see vortex street over a wide range of the flow rate. By reducing the resonance frequency of the vibrator or adapting the resonance frequency to the characteristics of the change in the vortex pressures, a relatively large deflection of the vibrator can be achieved even at low flow rates (at low vortex frequencies), although exceptionally large deflections at high flow rates (at high eddy frequencies) are prevented. To avoid instabilities in the resonance frequency of the vibration system, this is preferably damped in a suitable manner. In this way, an essentially constant amplitude of the deflection can be achieved over the entire range of the vortex frequencies. Furthermore, this novel arrangement is extremely effective in that the sensitivity is increased at low flow rates while at the same time excessively large deflections of the vibrator plate at high flow rates are prevented. This ensures stable oscillation of the vibrator plate and prevents possible destruction of the arrangement.

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An advantageous design of the flow meter according to Claim 13 is indicated by dependent claim 14.

Claim 15 specifies an embodiment variant in which a reliable detection of the Karman ¹ see vortices is achieved when transient problems of the vibration plate occur. The tightening straps that carry the vibrator are also suitably damped here, so that even if the flow rate changes abruptly, no interference occurs between the eddy frequencies and the resonance frequency of the vibrator. This also allows a precise measurement of a change in flow during transient processes, which is extremely important for practical use. According to a further embodiment, the chambers that enclose the tensioning straps can be completely filled with damping material, so that bending vibrations of the tensioning straps can also be suppressed.

Suitable embodiments of the arrangement according to claim 15 are specified with the dependent claims 16 to 18.

In a further embodiment of the. Flow meter according to claim 19 it is ensured that measurement inaccuracies due to a change in the light receiving parts do not occur which is produced by rectifying said output signal and is then processed in an integrator circuit, "There is obtained here, .that even when the DC component of the output: signal of the detector changes - z _o example, due to a change of the optical components - a. Output signal is generated "that corresponds exactly to the vortex frequency. The

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Changes to the optical components can be made by either Changes to the light-emitting or light-captured parts or caused by impurities in the optics will. In this claimed arrangement, however, there is always a square-wave output signal corresponding to the eddy frequency detachable. This is advantageous because the respective detector can be adjusted easily and freely of impurities is. Further, when the waveform of the output signal of the warpage detecting means changes, the difference between the output signal and the already mentioned DC voltage signal are amplified, whereby the gain is automatically regulated according to the magnitude of the DC voltage signal. Thus, there can be a reduction the light intensity caused by contamination in the optical parts of the electrical circuit which leads to an increase in the reliability of the arrangement.

In dependent claim 20 is an advantageous embodiment of the Arrangement according to claim 19 specified.

With the subclaims 21 to 24 advantageous applications of the flow meter according to the invention with a Karman ¹ see Wirbe.lstraße are specified, in particular in automobile engines.

In an exemplary application in automobile engines in particular a measurement of the air sucked in by the internal combustion engine can be carried out. An arrangement an embodiment of the flow meter with optical detection in the air inlet line of the engine, however, leaves , there is a risk that the optical parts with prolonged use become contaminated, which leads to a reduction in the sensitivity in the detection of the eddies. Farther may be related to the use of a flow meter

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the engine of an automobile may be hindered by influences due to unsuitable temperatures or electrical disturbances in the engine compartment to eliminate. Anyway _e can here when little air (eg. B "when the motor) is drawn, the cooling effect can be greatly reduced, thus possibly a large temperature increase occurred, which" reduces the reliability of the electrical circuit Furthermore, additional components extremely expensive to compensate for the rise in temperature.

In another known flow meter (Japanese Utility model 28998/1980) is a signal processing circuit for processing the detected signal in one Housing housed in a branch line to the lead-in line ^ whereby the circuit is cooled with the air flowing through this branch line. Even here, however, if little air is sucked in by the engine, the signal processing module will get hotter because a relatively small amount of air flows through this branch line due to the greater resistance in the flow than in the inlet line to the motor »

In contrast, according to the specified with deo.Anspruch 21 Arrangement of special device features specified, with which a cleaning and cooling with separately sucked in air is carried out ο in the case of the one characterized by claim 22 Arrangement, the electrical switching elements are housed in such a way that temperature or other influences do not have a disruptive effect «The electrical components are used for this purpose, for example in the driver's compartment of an automobile housed »

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Further advantageous embodiments of an application of the Invention are set out in claims 23 and 24.

The invention is explained with reference to the figures. Fig. 1 shows the principle of construction of a conventional one

Flow meter with Karman ¹ shear vortex street, Fig. 2 shows a view of the vortex detector of the flow meter according to Figure 1,

Fig. 3 shows a cross section of a known vortex generator daring

Fig. 4 shows a cross section through a vortex generator

According to the present invention, Figs. 5 to 10 are characteristic diagrams of the The vortex generator of FIG. 4, FIG. 11 is an enlarged cross-sectional view of a

Vortex detector along the flow direction, Fig. 12 is a sectional view of a vibrator, Fig. 13 is a side elevational view of a vortex detector, Fig. 14 shows the construction of a warpage detection sensor to detect the deflection of the vibrator,

along with its deflection characteristic, Fig. 15 is a view of another embodiment a deflection detection sensor,

Fig. 16 is a cross-section through an embodiment of the sensor with tensioning straps which are pressed by a spring,
Fig. 17 is an enlarged partial cross section of the essential parts of Fig. 16;

Fig. 18 is an enlarged partial cross section of a vortex detector along the direction of flow, with light-emitting and light-receiving elements of the vibrator plate are arranged opposite one another,

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19 is a circuit diagram of a circuit arrangement for further processing of the received signals the Figo 18,

Fig. 20 is a view for explaining the construction A bending detection sensor according to FIG. 18

together with the characteristics of this sensor, Fig. 21 is a view of another embodiment the deflection detection sensor,

Fig. 22 shows the operating characteristics of a vibrator, Fig. 23 shows the characteristic of an output of the

Flow meter according to the invention, FIGS. 24 and 25 show schematic representations Exemplary embodiment of the vibrator, in which the damping material is arranged in the vicinity of the tensioning straps, Fig. 26 shows diagrams with waveforms of the detected eddies,

Figures 27 and 28 are circuit diagrams of a. Embodiment a circuit arrangement for further processing of the detected signals, "- ■

Fig. 29 is a view showing an arrangement of an automobile engine with a vortex flow meter,

Fig. 30 illustrates a particular embodiment of the flow meter according to FIG. 29,

Fig. 31 is a view showing the manner in which in which the flow meter is installed in the automobile,

Fig. 32 shows a similar arrangement to Fig. 31, Fig. 33 illustrates a cross-sectional view of the flowmeter of Figure 32. _Q '
· The embodiments of a flow meter with Karmin'scher Mirbelstrasse shown in FIGS. 1 and 2 are part of an arrangement which is known, for example, from Japanese patent application 90813/1981. In Fig. 1, a pipe 1 is Darges'tellt, also a vortex generator 2 for generating a

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Karman's vortex street, openings 3 and 3 ¹ , a vortex detector 4, optical fiber optic cables 5 and a signal processing circuit 6 for further processing of the detected signal. Said vortex detector arrangement is formed by parts 4 to 6. In FIG. 2, a vortex detector 4 is provided with a vibration chamber 43 which has a substantially isosceles triangular cross section; Furthermore, a .Vibrationsplatte 44 is present, which is excited by vortices in the vicinity of the vortex generator 2 to vibrate. The vibrating plate 44 is also in the vibrating chamber. 43 arranged. Pressure fluctuations caused by Karman vortices are introduced into the vibration chamber 43 through openings 41 and 42. The signal processing circuit 6 has a light emitting part 6a, a light receiving part 6b and a waveform forming circuit 6c.

This flow meter, known from the prior art, functions in such a way that the Karman vortex street in the neighboring area the opposite sides of the vortex generator - arranged in the tube 1 - vortex generated. The through the Pressure fluctuations caused by vortices are passed through the openings 3, 41 or 42 to the vibrating plate 44 and bend them accordingly. The vortices occur alternately in the area of the opposite sides of the vortex generator 2 and therefore cause the plate 44 to vibrate. Light from the light emitting part 6a in the signal processing rack 6 is through an optical fiber line 5a guided onto the vibrating plate 44 and is reflected there by the surface of the vibrating plate. Then will this light transmitted through the light receiving part 6b and through an optical fiber line 5b. Because the edge surfaces the optical fiber lines 5a and 5b opposite - Are arranged essentially 'perpendicular - to the vibrating surface of the plate 44, the changes

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Intensity of the light that the receiving part 6b receives, corresponding to the deflection of the vibration plate 44 «Thus the light receiving part 6b receives a signal corresponding to the interaction of the vibrating plate 44, whereby enables detection of the vibration frequency of the eddy is"

In general, flow meters of this type have the disadvantage that the generation of the eddies is unstable and low Flow relatively weak eddies can be generated, which makes an accurate measurement difficult »

First are the problems that are related to a Vortex generator occur, discussed «, Fig. 3 shows schematically an exemplary embodiment from the prior art known flow meter, in which two pillars (Mirbelkörper) K1 and K2 in a room along are arranged in the direction of flow «The first in the direction of the river Pillar K1 has a triangular cross-section to generate vortices, and the second pillar K2 behind it is shaped like a plate The pillar with a triangular cross-section is essentially the streamlines of the flowing through Mediuffls adapted and is therefore advantageous because it does not cause a great loss of pressure. Anyway, it it is unable to generate eddies with ease, and thus is especially at low flow rates a measurement difficult. In addition, in such one construction detects the eddies in the direction of the current behind the pillars and accordingly there are pulsations in the Pipe, changes in flow rate or pressure Reason for disturbances, whereby an exact recording of the eddies is impossible.

In the Fig «, 4 a first pillar 2a is shown, the an essentially isosceles triangular transverse

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Has section, and there is a second pillar 2b - located behind it in the direction of flow - which has a substantially trapezoidal cross-section. These pillars are arranged so that the base line of the triangular cross section of the first pillar 2a and the base line of the trapezoidal cross section of the second pillar 2b are parallel to each other and are arranged at a predetermined distance "1" in the direction of flow, the base lines being perpendicular to the direction of flow. Furthermore, the projected width of the first pillar 2a and the second pillar 2b (dl or d2) at right angles to the river is the same length. The triangular cross-section of the first pillar 2a has a vertical angle ^ L and the trapezoidal cross-section has a height "h". The same sides of the trapezoidal shape enclose an angle (h . The sizes described are suitably set in a manner to be described later. The second pillar 2b is provided with openings 4a and 4a for introducing the generated eddies on opposite sides near the axial edges Mistake.

The results of experiments, the effect of the angle «£, the angle / S, the height" h ", the distance" l ⁿ and the widths d1 and d2 of the pillars with respect particularly with regard to the generation of vortices and the stability of these production shown below.

1) If the described width of the first pillar in essentially equal to the width of the second pillar (dl = d2 = d), then vortices are generated with the highest stability, and they can with a good signal-to-noise ratio can be detected.

2) If the angle of the first pillar is 90 ° to 120 ° then the pressure loss is lowest and the vortex waveforms detected are very stable. If the

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Angle β is smaller than the range given above, disturbances are generated whose frequency components are below the frequency of the eddy "In the event that the angle exceeds the range described, disturbances are also generated and a large pressure loss is to be expected"

3) If the height ^M h "of the isosceles trapezoidal shape of the second pillar is formed according to the relationship h ^ d / 2 and the Minkel β £ ■ 40 °, it is possible to detect eddies with good linearity even at lower flow rates« In detail, the results of the experiments are made understandable by the representations in FIGS. 5 and 6, where β £> hQ ° and h £ 0.5d; here the Strouhal size (= vortex frequency χ width / flow rate) is essentially constant (<- 3 % ■) ■ and thus a practicable characteristic is given »

4) If the distance 1 between the pillars is chosen so, that it has a size between 0.2d and 0.3d, a wide measuring range and good linearity can be achieved « It will be shown that for the case when the distance is in this range, the velocity at which the vortex occurs can be detected, can be further reduced - as shown in FIG. 7 - and the linearity at high flow rates is improved - as shown in Fig. 8 - "

FIGS. 9 and 10 show examples of characteristics of a flow meter designed according to the above-mentioned results of the experiments. "In this embodiment, the angle" /, of the first pillar is 90 °, the height h -act is d / 3 and the angle β is equal to 40® "It is important here that the measurement was carried out in air with atmospheric pressure" Fig. " 9 shows that the linearity over a range of 1 to 60 o / sec flow rate

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can be kept less than + 3 % , whereby a practicable characteristic of the flow meter is achieved. The curve X of FIG. 10 shows that the pressure loss characteristic of a flow meter in which the second pillar has an isosceles trapezoidal cross section and the widths (d1, d2) of the pillars are the same; In contrast, the curve Y of FIG. 10 shows the pressure loss characteristic of a flow meter according to the present invention. It can be seen from this that the present invention enables the pressure loss to be halved, as a rough approximation.

In further another embodiment of the flow meter with Karman vortex street ¹ shear reference to the figures 11 will be described to 15 °.

11 shows a pipe 1, a vortex generator 2 for generating the Karman vortex street and a vortex detector 4. The vortex generator 2 is constructed taking into account the boundary conditions described, for example, with reference to FIG. The vortex generator 2 has slots 4a and 4b on opposite sides of the second pillar 2b near the axial ends for passing pressure changes due to vortices. In Fig. 12, a vibrator 8 includes a thin metal plate (about 20 micrometers) and a vibrating plate 9 on which the pressure fluctuations of the vortices act. Furthermore, tensioning straps 10a and 10b are provided which carry the plate 9, the plate 9 being arranged symmetrically to a bore through the center of gravity of the plate in order to allow torsional vibrations of the plate; a connecting piece 11 forms the fixed ends of the tensioning straps. These parts are formed from a metal plate which is essentially the same throughout. Having thickness. The vibration plate 9 is in equilibrium with respect to its mass relative to the central axis. the

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Tensioning straps 10a and 10b are designed so that the torsion spring constant - defined by the dimensions of the straps is extremely low in order to allow adequate angular deflection of the vibrating plate even with small changes in the vortex pressure, whereby the resonance frequency is as low as possible _D recesses 11a and 11b are formed by punching out "Mach of FIG." 11, a housing 12 contains the vibrator 8, which in turn has a lower plate 13 and an upper plate 14. The plates 13 and 14 are provided with recesses which are essentially the same and are arranged opposite one another. The recesses here correspond to the bore of the vibrator 8 Flange 15 of the vortex generator 2, the vibrator 8 is supported here; At the same time, a vibration chamber 16 and chambers 17a and 17b for enclosing the tensioning straps are formed. The lower sub-chamber, formed by the vibration plate 9 and the lower plate 13? is also almost equally divided into sub-chambers 19a and 19b by a projection 18 which is arranged on the lower plate 13 opposite the centering hole of the vibration plate 9 »The sub-chambers 19a and 19b communicate with the slots 4a and 4b of the vortex generator 2 through connecting holes 20a or »20b« The projection 18 prevents the medium to be measured from circulating between the sub-chambers 19a and 19b, which means that the vortex pressure changes can be transmitted from the slot 4a or 4b to the vibration plate 9 without losses »

As long as the torsional vibration of the vibrating plate 9 is not hindered, the space between the protrusion should 18 and the vibrating plate 9 be as close as possible; before-

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preferably it is of the order of 0.1 to 0.2 mm. the end for the same reason, the space between the vibrating plate 9 and the vibrating chamber 16 should preferably be in the are of the same order of magnitude.

In the illustration according to FIG. 13 there is an adjusting screw 21 available, with which the tensioning straps 10a and 10b can be subjected to a mechanical tension; these Screw 21 is arranged on the central axis of the tension band 10b. The screw 21 transmits tension to a part of the tension band 10b between the attached ends and a projection 22 together with the lower plate 13 prevents bending vibrations of the vibrator 8. As later in FIG In connection with FIGS. 16 and 17, the tensioning band is preferably via a spring part with the screw 21 connected. In Fig. 11 is further shown that fiber optic lines 5 for the detection of the angular bending of the vibrator 8 have two optical paths - for transmission and for reception. The optical axes are essentially perpendicular to the surface of the vibrating plate 9 of the vibrator 8, and the optical paths are open to the partial space. This means that the optical parts are completely in the subspace 26 inserted. This has the result that the optical parts are not in direct contact with e.g. B. a liquid of the medium to be measured can come. The other ends of the fiber optic lines are provided with a light emitting part 6a and a light receiving part 6b is preferably provided. The reference number 6 denotes a detector circuit, which includes the light emitting part 6a, the light receiving part 6b, an amplifier, and a waveform device (not shown).

The function of the arrangement described above is such that if, for example, a vortex 30 on the upper Vortex generator 2 side (on the slot 4b side)

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is generated, the pressure in the vicinity of the slot 4b decreases compared to the pressure in the vicinity of the opposite slot 4a _o Accordingly, the pressure in the sub-chamber 19b in cooperation with the slot 4b is lower than the pressure in the sub-chamber 19a, which is associated with the opposite slot 4a cooperates »

In connection with FIG. 11, the balance of the forces around the centering hole of the vibration plate is now shown Discussed around 9, “A pressure applied to the upper surface of the vibrating plate 9 is essentially equal over the entire surface. With regard to the underside of the vibrating plate 9, the pressure is in the lower chamber 19b lower than in the sub-chamber 19a, and there may be a clockwise moment due to the Pressure difference on the vibrating plate 9 = Thus the Vibrating plate 9 set in a clockwise rotation, but with the lower surface and the upper surface of the vibration chamber 16 limit the amplitude of the rotation.

Thus, even if a vortex is generated on the opposite side of the vortex generator, the pressure in the Sub-chamber 19a lower than in sub-chamber 19b, causing the vibrating plate to rotate in the opposite direction - (left-. rotating) is displaced »The amplitude is in the same way through the bottom and the upper surface of the vibration chamber 16 limited. Therefore, by generating a pair of vortices, a torsional vibration (an interaction) of the vibrator becomes 8 caused. As this is done through the palms of the hands of the vibration chamber 16 is limited, the amplitude is essentially constant regardless of changes in mirror pressure. The vibration plate 9 is essentially in equilibrium of its mass around the centering hole. Inertial forces caused by external vibrations, are thus suppressed around the centering hole. Through this thus no torsional vibrations occur. Further

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the vibrator 8 hardly becomes vertical external vibrations follow when the tensioning straps 10a and 10b are subjected to tension. The vibrator is thus in this context free from external vibrations. Likewise, when tension is applied to the tensioning straps, the torsion spring constant is hardly affected by this. For the reasons mentioned, the resistance is therefore disruptive in terms of Improved vibrations without reducing the sensitivity with regard to the detection of eddies. 10

It thus results that eddy the vibrator 8 to torsional vibrations excite within the vibration chamber 16. To control these vibrations over a wide range of Vortex frequencies, e.g. B. from 10 Hz to 1 kHz, it is important that the pressure fluctuations of the eddy directly on the vibrating plate 9 to transfer without loss. To this end, the present invention includes slots Aa and 4b in the vortex generator 2, to changes in vortex pressure in the lower caramens 19a and 19b to lead in the shortest possible way, and furthermore, according to the invention, the projection 18 is present, with the leakage flows between the sub-chambers 19a and 19b are minimized. There is also a nozzle between the periphery of the Vibration plate 9 and the wall surfaces of the vibration chamber 16 shaped so that leakage flows between the sub-chamber 26 and the sub-chamber 19a or 19b are minimized.

Changes in the eddy pressure thus act directly on the vibrating plate without losses, which enables stable detection of the eddies.

Detections of a number of deflections, that is to say the vibration frequency, with the vibrator 8 are referred to below -described on Figures 11, 14 and 15.

The vibration frequency "is detected by measuring the Change in the intensity of the reflected light on the

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upper surface of the vibrating plate 9 using the Fiber optic line 5 »In detail, the fiber optic line has two optical paths 5a and 5b, which in any way and way with its end surface 31 of the vibrating plate 9 are arranged opposite on; however, the optical axes are essentially vertical to the surface of the vibrating plate 9 »If the intensity of the light reflected by the vibrating plate 9 decreases - by the rotation of the reflective surface (as shown by the 14b), such an interaction of the vibrator generates two light pulses as an output signal. if the deflection of the vibrator 8 is substantially constant, the light output signals are also substantially constant. As a result, it is possible to adjust the vortex frequency to capture by means of a simple circuit arrangement. Hence, the proposed method for evaluating the reflected light is extremely practical because it only requires a simple arrangement and necessity an exact straight alignment of the optical axes is avoided. Furthermore, the optical parts are within the Subspace 26 of the vibration chamber 16 arranged, so that they do not come into direct contact with the medium to be measured and thus contamination of the optical parts is prevented. ;

In the above-mentioned detection mechanism, the optical axes of the glass fiber lines 5 substantially vertical to the surface of the vibrating plate 9 "But, it is also possible to easily incline the optical axes of the glass fiber cable 5, so that a maxiaale angle deflection θ m of the vibration plate 9 on the vibrating surface is reached (see Fig. 15). This arrangement is advantageous in that even a small angular deflection can be detected with sufficient sensitivity and an output signal with an essentially sinusoidal waveform can be achieved. this

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facilitates further signal processing (see. Fig. 14b), because an essentially constant range of the in Fig. 14 b shown curve can be exploited. The peak of the intensity of the reflected light is thus according to shifted to the right of this curve. It should be noted in this regard that the exemplary embodiment described is not based on an application is limited to a fiber optic construction, but there are other arrangements for detecting Fluctuations in the intensity of the reflected light are conceivable here.

In Figures 16 and 17, a mechanism 30 is shown, with which a mechanical tension can be applied to the tensioning straps 10a and 10b. Furthermore, a compression spring 31, a Cap 32 and a pressing device 33 for pressing down the tensioning band 10b are provided. The printing device is made of one lightweight resin and is made as a hollow cylinder with a bottom having a rectangular protrusion 35, executed. When the spring is compressed, the protrusion will durch.ein rectangular guide hole 34 out, which is arranged in the top plate 14 to prevent the printing device 33 from rotating. The arrangement will one tension is passed on part of the tensioning band 10b between the outer fixed ends, and one on the lower one Plate 13 shaped projection 22 also prevents flexural vibrations of the vibrator 8. The spring 31 is enclosed from the pressure device 33, the cap 32 preventing the spring from popping out.

When a rapid temperature change occurs, a temperature difference arises between the vibrator 8 and the housing -If the parts in question are not made of the same material, This creates a different thermal expansion of the two tensioning straps. Anyway, the compression spring points 31 according to the present invention a small spring

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Λ β

-Zh- VPA 81 P 8611 DE

constant on, and it acts on the tightening straps. with a Tension, so that the tensioning straps are usually somewhat bent and this results in differences in thermal expansion can be absorbed »If the described tension is kept constant, the tightening straps can be injured and reductions in vibration resistance caused by external vibrations are prevented «

According to FIG. 18, an enlarged cross-sectional view of a vortex detector is shown along the direction of flow » Here are a light emitting part 23 and a light receiving part Part 24 arranged so that they face the upper surface of the vibrating plate 9 and their optical axes are in the center of the centering hole Cross vibration plate 9 »A detection circuit 25, which supplies parts 23 and 24 and processes the output signal, contains a coupling circuit 27a for selecting the alternating components of the output signal of the light received Part 24 and a comparator 27b for forming a corresponding square-wave signal, as shown in FIG.

A detection of a number of deflections or the vibration frequency of the vibrator 8 is described with reference to FIGS. 18 to 21. When the deflection of the vibrator 8 is essentially is constant, the light output signal is thus also constant, and there can be an output voltage in the Order of magnitude of 1 V can be taken from part 24 even at low flow rates. Also in this embodiment it is ensured that the optical parts do not come into contact with the medium to be measured and therefore can be kept free from contamination.

In this embodiment a detection mechanism the parts 23 and 24 are arranged so that the maximum of the light intensity is reached when the vibrating plate 9

- 25 - VPA 81 P 8611 DE

is in a horizontal position. As with the 21, the vibration plate 9 can be biased up to the maximum angular amplitude du. Even in this embodiment, the above advantages described are exploited. By taking advantage of the rectilinear parts of the curve in Fig. 20 (b) and therefore a good sensitivity and low susceptibility to interference is achieved will. In this example, an output signal with a pulse for an interaction of the vibratory chain generated.

The function of the flow ^{meter according to the invention with a Karman 1} vortex street is described with reference to FIG. 22, in which some functional characteristics of a vibrator are shown. In general, a vibrator (see, for example, FIG. 12) oscillates according to the frequency of the vortex. According to the invention, the fundamental frequency of the torsional vibration is defined by the moment of inertia of the vibration plate (plate 9 in FIG. 12) and by the torsion spring constant of the tensioning straps (cf. tensioning straps 10a and 10b, e.g. in FIG. 12). This torsional vibration should be substantially equal to the lowest frequency of the vortices being measured, with the length and width of the tensioning straps and the dimensions of the vibrating plate, etc. appropriately selected for the required purpose.

When a vibration force with a predetermined amplitude acts on such a vibration system, the system generates a frequency response as shown in FIG. It can roughly be said that in Fig. 22 (a) the amplitude is proportional increases towards the angular frequency and its peak at the resonance frequency η reached. In the following, the amplitude falls in inverse proportion to the square of the angular frequency mentioned, this characteristic being influenced by the amount of damping. In this figure, the ordinate represents

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- 26 - VPA 81 P 8611 DE

represents an amplitude ratio (dynamic amplitude X / static Amplitude a.) And the abscissa represents the angular frequency ratio as a dimensionless quantity. It has been determined experimentally that the extent of the changes in the eddy pressure essentially proportional to the square of the flow rate falls as shown in Fig. 22b. Because the vortex frequency is proportional to the flow rate is, the amount of change in eddy pressure may decrease in proportion to the square of the eddy frequency o

According to the present invention, the resonance frequency is _ η of the vibrator equals the lowest frequency of the vortex, and therefore the vibrator receives vibratory forces that are proportional increase to the square of the frequency. Thus, the amplitude of the vibration plate of the vibrator Ira is essentially constant, as shown in Fig. 22c »

In FIg. 23 Is shown the characteristic of the output signal of a flow meter according to the invention. In the stationary state, the signal detected with the light-receiving part has a symmetrical waveform, relative to a constant DC component. This equilibrium component DC corresponds to a state of equilibrium of the vibrating plate when it is at rest, as shown in FIG. 23 (A). If the flow rate to be measured rises abruptly in a settling state, a resonance occurs at a resonance frequency which is determined by the Hasse of the vibration plate of the vibrator and by the torsion spring constant of the tensioning straps. If z. B _n, the flow in a manner such as "23 (B) shown in Fig varies, no 'swirls can here be detected, since the waveform of the output signal is disordered" Thus, it can be determined that a resonance point exists in the frequency characteristic of torsional vibration of the vibrator as shown by the broken line in Fig. 22 (A). »

-3ίι--

- VPA 81 P 8611 DE In Fig. 24 are a vibration plate 9 and tensioning straps 10a and 10b. In addition, there is damping material 36, such as B. a rubber-like visco-elastic material, arranged in the region of the tensioning straps 10a and 10b. Experiments have shown that the frequency characteristics of torsional vibrations of a provided with such a damping material Vibrators do not have a defined resonance point, which is indicated by the straight line in Fig. 24 (A). It results it follows that when such an abrupt change in flow occurs, the vibrator will give a correct response of the change in eddy pressure supplies. As shown in Fig. 23 (B), a disordered waveform is prevented when a such change takes place, thereby preventing the impossibility of detecting eddies. Thus, according to the According to the invention, resonance of the vibrator 8 can be prevented at least within the range of the vortex frequency.

Fig. 25 shows a schematic representation of another Embodiment. This embodiment is different differs from the arrangement shown in FIG. 24 in that chambers 17a and 17b are completely filled with damping material 37 are. The tensioning straps 10a and 10b are arranged in these chambers 17a and 17b. This construction is also suppressed a resonance in the torsional vibration of the vibrator and also prevents bending vibrations in vertical or horizontal direction, which can be caused by external vibrations. In this example, the damping material 37 be silicone rubber, for example.

An exemplary embodiment of a flow meter with a Karman vortex street is shown below with reference to FIGS 26, the waveform of detected vortices and in FIGS. 27 and 28 circuit diagrams for further processing of the detected signal are shown in one variant each.

BATH ORIGINAL

- VPA 81 P 8611 DE In Fig. 27 is a light emitting part 61, a light receiving Part 6a, buffer amplifiers 63I and 633 »· a Integration circuit 632, a comparator circuit 634, Resistors R1 to R6, a capacitor C1 and a diode D1 shown.

The output signal of the light-receiving part 62 is fed directly to the comparator 634. In addition, this signal is fed to the integrator circuit 632 via the buffer amplifier 63I. The output signal of the integrator circuit 632 is fed via the buffer amplifier 633 to a second input of the comparator circuit 634. The comparator circuit compares the signals present at its inputs and, if they match, generates an output signal. In detail, the output signal of the light receiving part 62 has a sinusoidal waveform, which is essentially symmetrical to a DC voltage E _q , which in turn corresponds to a constant intensity of the light, which in an equilibrium position of the vibrating plate - in its rest position - shown here with "a" in Fig. 26 (B) is generated »On the other hand, the output of the integrator circuit 632 is the same signal as the DC voltage signal E shown by broken line b in Fig. 26 (B). Consequently, it is thus possible to obtain a rectangular waveform of the output signal in response to the eddy frequency based on a comparison of the input signals of the comparator and thus to carry out a corresponding change in the waveform in the comparator circuit 634 us «, generally have different characteristics and the DC voltage E corresponds to the equilibrium position of the vibrating plate, the output signal changes relative to the DC voltage E» as indicated by a 'in Fig. 26 (B) «In any case, as before

-36-

- 29 - VPA 81 P 8611 DE

described, the output signal a 'compared with the DC voltage b ¹ generated by rectification; this changes the waveform. It is thereby possible to precisely detect eddy frequencies even when the DC voltage E changes. If the DC voltage E drops in the equilibrium position of the vibrating plate, which leads to a drop in the light intensity, for example caused by impurities in the optical parts including the reflective surface, the vibrating plate or the fiber optic cables, a square-wave output signal can be used as a response in the same way can be derived on the vortex frequencies. It must be noted here that the time constant of the integrator circuit 632 is preferably selected to be as large as possible. If the time constant is small, small disturbing additional waves at lower eddy frequencies can lead to a change in the difference between the output signal "a ^11" and the signal "b", which means that the arrangement can be influenced by disturbances. te is greater than the lowest frequency of the vortices In order to prevent disturbing effects, it may be desirable to provide a hysteresis as shown in Fig. 27 in the comparator circuit 634, such as those formed by resistors R5 and R6.

FIG. 28 shows a circuit diagram of a modified embodiment according to FIG. 27. In FIG. 28 there is an amplifier circuit 635 available, which has a differential amplifier 635-, and 635t. A variable resistor 635 ^, whose Resistance value decreases when the voltage applied to it increases, is part of a CDS optocoupler and acts to regulate the gain of amplifier 635 ,. The output A of the buffer amplifier 633 is connected to the variable resistor 635 ^ via a buffer amplifier 635 tied together. The difference according to this amendment to the

- VPA 81 P 8611 DE exemplary implementation of FIG "27 lies _e that the voltage difference between the output signal" is a "and the DC voltage b that the signal" is obtained a "via the integrator circuit 632, amplified, and at the same time the gain of the amplifier 632, is automatically regulated by the amplitude of the voltage E (A) of the said DC voltage signal b «. *

It can thus be summarized that the light intensity which reaches the light receiving part 62 is lowered by impurities in the optical parts, and thus when the output signal of the part 62 changes from "a" to a ', as shown in FIG «, 26B shown« In detail, the direct voltage DC corresponds to the light intensity with a vibrator plate in equilibrium and thus decreases from E to E '. The alternating voltage AC thus corresponds to the changes in the light intensity, caused by vibrations of the vibrating plate, and thus decreases from "a" to a ⁸ "In any case, the differential amplifier 635? ^ ^e detect eddy frequencies with certainty and this even when the direct voltage E changes, because it either amplifies any difference between the output ^{signals "a n} and the direct voltage signal b or the difference between a ¹ and b '". The resistance also decreases of the variable resistor 635 ^ "when the DC voltage drops due to a decrease in the gain of the amplifier 635 ^" It follows that a decrease in the AC voltage AC in response to the eddy frequency can be compensated the amplifier 635, by appropriately selecting the values of resistors RI1 and R12 and resistance ^to control gain 635 ^ "Therefore, it is possible, even when the light intensity falls to perform a stable detection of the vortex frequencies without being affected by this reduction"

-35-

- - & - VPA 81 P 8611 DE

It is shown that the output of the light receiving part 62 in this example is always through the buffer amplifier 631 is led to the integrator circuit 632. This can however, should be omitted if the impedance defined by the resistor R4 and the capacitor C1 is sufficiently larger is as the load resistance R2 of the light receiving part.

In FIG. 29, an engine 101 (for example, the internal combustion engine an automobile) with a feed line 102. Line 102 includes one Air filter 103 and another filter element 104 and an inlet pipe 105, a throttle valve 106 and other elements. A tube 108 forms part of the inlet tube 105, the flow through the tube 108 being provided by a flow equalizer 109 is stabilized. A flow meter 107 with a Karman vortex street contains a vortex generator 2, which is inserted into the tube 108 to generate the vortices, a vortex detector 4, which converts the pressure changes of the vortices generated into light pulses in response to the vortex frequency as well as other parts. An electronic circuit 6 for converting the light signal of the vortex detector 4 into a electrical signal is on via fiber optic cables 5a and 5b turned on the vortex detector.

As can be seen from Fig. 30, the vortex detector 4 is made up of holes 20a and 20b, a chamber 16 which is provided with the holes communicates and a vibration plate 9, which performs torsional vibrations in the chamber, formed. The holes have openings 4a and 4b on opposite sides Sides of the generator 2 are arranged parallel to the river and serve to guide the pressure fluctuations of the eddies.

One ends of the fiber optic cables 5a and 5b are arranged so that their optical axes correspond to the axis of rotation of the Cross vibrators at a certain angle. The ends of the leads 5a and 5b are provided with a light emitting part 6a

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- J £ - VPA 81 P 8611 DE

and a light-captured part 6b provided «These elements are housed in a housing 120 «A cleaning piece. 122 includes a limiter 124 and a filter 123. The one described Chamber is via the restrictor 124 and the filter 123 as well as through an opening 121, which in the housing 120 is close of the light emitting parts is arranged in connection with the atmosphere. ■

The function of the arrangement shown is described as follows » For example, if air flows through the introduction line 102 (see FIG. 29) and thus vortices on the Side of the opening 4a of the vortex generator 2 generated. (See » Fig. 30), the pressure on the side of the opening 4a becomes less than the pressure on side 4b. When a pair of such eddies are created, such pressure differentials cause them a torsional vibration in the vibrator 9 (corresponding to an interaction). A change in the intensity of the reflected Light caused by the bending in this vibration is detected by the light receiving part 6b and transmitted through the fiber optic line 5b for measuring the vortex frequency. Thus is the amount of flown To derive air from this frequency. The pressure in the chamber 26 is lower than the atmospheric pressure because the pressure is known to be lower on the side of the opening 4a than the atmospheric pressure, and the vortex generator 2, which is the introduction line on the opposite side 4b narrows, leads to the reduction of the pressure also on the side of the opening 4b »

Accordingly, it is always when the automobile is driven and thus Air is sucked in ^ the pressure in the chamber 26 is negative. With In other words, if not the engine will have a kickback caused. Air · sucked in by this negative pressure and thereby the inside of the insertion tube in this negative "Pressure kept ^ by keeping the air clean

-> 3 - VPA 81 P 8611 DE

Cleaning part 122 is guided to the light-emitting part and this is thus cleaned or kept free of contamination from the outset. However, when the cleaned air in the introduction pipe 102 flows through the holes 20a, 20b and the openings Aa, 4b, the amount of the air is not measured. However, the limiter 124 limits the amount of air described to less than 0.1 % of the total intake air. This affects neither the measuring accuracy nor the generation of the eddies. 10

In the embodiment described above, the openings are to carry out the fluctuations in eddy pressure on opposite Sides of the vortex generator 10 arranged. These openings can also be in places in the vicinity of the Generator and at locations behind in the direction of flow, as long as they detect eddies at all. As a result, since the pressure within the introduction line 102 is always lower than the atmospheric pressure, the air can be cleaned from outside the pipe.

Another example of an arrangement of a flow meter with a Karman ¹ vortex street is shown in FIG. 31 shows a motor 101 with an inlet line 102, this inlet line having an air filter 103, further filter elements 104, an inlet pipe 105 and a throttle valve 106. A vortex flow meter 107 is mounted within the introduction line 102 and contains a pipe 108 which is part of the introduction pipe 105, a flow limiter 109 for stabilizing the flow in the pipe 108 and a vortex detector 4. This vortex detector 4 is located within the introduction pipe and operates in such a way that it converts pressure fluctuations due to the vortex into light signals for the production of light pulses according to the vortex frequency. These elements are all exemplified in the engine compartment

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ο ο ο «to

- & k - VPA 81 P 8611 DE

wisely installed in an automobile «. An electrical circuit 12 for converting the light signals of the vortex detector 4 In contrast, an electrical signal is in the driver's compartment of the automobile arranged, if possible in an environment in which they are less is affected by the temperature and electrical disturbances etc. than in the engine room. The electrical circuit is with the vortex detector 4 of the flow meter 107 in the engine compartment connected via the fiber optic line 5. With this arrangement, the signals detected due to the eddies are called Light signals are transmitted from the engine compartment to the driver's compartment via line 5 as an optical fiber optic line and accordingly this arrangement cannot be influenced at all by temperature and electromagnetic interference. The energy supply This measuring arrangement described takes place directly with direct current and only requires sufficient stabilization, which can be carried out in a simple manner.

32 shows a further application of one according to the invention Flow meter shown, in which a motor 101, an inlet line 102 - with filter element 104, inlet tube 105, throttle valve 106, etc. - a vortex flow meter 107 inside the inlet tube and a flow limiter 109 is present. There is also a vortex generator here 2 within the lead-in to generate the Vortex arranged, and there is a vortex detector 4 " This illustrated mechanism converts pressure fluctuations due to eddies into light signals and generates a light output signal according to the vortex frequency. In addition, there is a pipe 130 (to be described later) and a flow restrictor 131 available.

To introduce air into a box 134 for cooling the components of a signal processing circuit 25, this box is used Flow meter designed so that the pipe 130 - for guiding the air into the engine at negative pressure - with the box 134

-> 5 -. . VPA 81 P 8611 DE

via the limiter 131 / as shown in FIGS. 32 and 33, connected is. Another lead-in line 132 for lead-in of air in box 134 is via the air filter open to the atmosphere. The exchange of air through the Air filter 133, tube 132, box 134, tube 130 and the lead-in conduit 102 is caused by the negative pressure inside the engine; This ensures that when the temperature inside the engine compartment rises, an increase in temperature in the formwork elements of the Signal processing module 25 is prevented because air is constantly flowing through box 134. If the engine after a Driving at very high speed is issued, the temperature in the engine compartment is very high, however, it can also be in In this case, by the remaining large negative pressure in the engine, the air through the box 134 for sufficient cooling flow.

When the engine throttle is fully open, the negative pressure is low and the flow of air through box 134 decreases; however, in this case a large amount of air flows through the introduction pipe, whereby the temperature within the box 134 is maintained to a sufficient extent here as well. Furthermore, the air sucked in for cooling is only 0.1 % of the total flow, so that the measuring accuracy of the flow meter is not affected.

The openings for admitting the air can be open to the introduction line. In this case it is the air filter unnecessary. In detail, the opening for introducing the air can be behind the vortex generator 2 and in the direction of flow be arranged in front of the throttle valve 106, what with the interrupted Line in Fig. 33 is indicated. Thus, in this embodiment, the amount of sucked air is can already be measured before it reaches the openings.

· ■ · ·

- VPÄ 81 P 8611 DE While the invention in detail in connection with selected Embodiments are described, are of course also a number of changes and variations to create beneficial effects on different ones Embodiments possible without the subject matter of Invention to leave.

24 claims
33 figures

Claims (1)

VPA 81 P 8611 DE claims 1 J flow meter with Karman's isiirbelstrasse for measuring - ' the flow rate or the speed of a medium - two pillars (2a, 2b) (vertebral bodies) ,, which in the direction of flow are arranged one behind the other, characterized in - that - a first pillar (2a) at the front in the direction of flow is present, which has an isosceles triangular cross-section has and - a second, behind in the direction of flow, second Pillar (2b) is present, one of which is isosceles trapezoidal cross-section that - the baseline of the cross-section of the first pillar (2a) is equal to the base line of the cross section of the second pillar (2b) and that - The first pillar (2a) and second pillar (2b) are arranged so that the baselines are parallel to each other in one specified distance (l) and transverse to the direction of flow of the medium to be measured «. (Fig »4) 2 »flow meter according to claim 1, characterized in that - the triangular cross-section of the first pillar (2a) has a vertical angle of 90 ° to 120 °, - the same legs of the trapezoidal cross-section of the second pillar (2b) enclose an angle which is less than 40® and that - The height h of the trapezoidal one in the direction of flow The cross-section of the second pillar (2b) is smaller than d / 2, where d is the length of the baseline and the first and the .. second pillars (2a, 2b) at a distance (1) from 0.2 to 0.3 χ d are arranged «, ■ BATH ORIGINAL - «2 · VPA 81 P 8611 DE 3 flow meter according to claim 1 or 2, characterized in that - the two side surfaces of the second pillar (2b) each are provided with an opening (4a, 4b) through which pressure fluctuations due to the vortices generated (Fig. 4). 4. Flow meter according to one of the preceding claims, characterized in that - for measuring the ^{pressure fluctuations caused by the vortices of the Karmän 1} see vortex street, a vibrator (8). is present, which is acted upon by the pressure fluctuations and detects the frequency of the vortices from the vibrations caused by these pressure fluctuations, and that - the vibrator (8) is arranged in a vibration chamber (16) and is in a mass equilibrium relative to a centering hole |. The center of gravity of the vibrator (8) is located, whereby the vibrator (8) can perform torsional vibrations around the centering hole (Fig. 11). 5. Flow meter according to claim 4,. characterized in that - The vibrator (8) has a vibrating plate (9) and is carried by a pair of tensioning straps (10a, 10b) (Fig. 12). 6. Flow meter according to claim 4 or 5, characterized in that - the tensioning straps (10a, 10b) firmly clamped at their ends, and are subjected to mechanical tension. . ■ 7. Flow meter according to claim 6,
. characterized in that - Part of one of the tightening straps (10b) in the area of the fixed The end is subjected to the mechanical tension ', - '- ■. BATH ORIGINAL . ό- VPA 81 P 8611 DE - being at a support point in a chamber for wrapping of the tightening straps (17a, 17b) a spring (31) with a small spring constant is present which exerts a pressure on the part of the tightening strap (17b) exercises (Fig. 16). 8 ", flow meter according to claim 4, characterized in that - the vibrator is arranged on a plate (9) which is in the Vibration chamber (16) is included, this 10 'plate (9) divides the vibration chamber (16) into two sub-spaces (26; 19a, 19b) and that - A first sub-space (26) with a device for detection the bending of the plate (9) is provided and the other Partial space with inlet channels (4a, 4b) for the to be measured Pressure fluctuations is provided, whereby the detection device (23, 24, 25 ο "ο) and the introduction channels through the plate (9) are isolated from each other (Fig. 18). 9 »flow meter according to claim 8,
characterized in that - The second sub-space is further divided into two sub-chambers (19a, 19b), the centering hole of the plate (9) divides the subspace symmetrically, and that - The sub-chambers (19a, 19b) alternate with the pressure fluctuations are acted upon (Fig. 18). 10 »flow meter according to claim 8 or 9, characterized in that - the detection device has a light-emitting part (23), a light-receiving part (24) and light-transmitting parts connected thereto, that -τ the open ends of the light-transmitting parts (glass fiber line 5) are arranged in such a way that each is opposite one end of the plate (9) in the first sub-space (26), "what through." a change in the intensity of the reflected light resulting from the rotating deflection of the Plate (9) is detected (Fig. 18). BATH ORIGINAL - k " VPA 81 P 8611 DE 11. Flow meter according to claim 10, characterized in that - the surfaces of the open ends are arranged so that they are then parallel to the plate (9) when the plate (9) is in its maximum rotational position, in which further rotation is prevented by the walls of the vibration chamber (Fig. 15). 12. Flow meter according to claim 8 or 9, characterized. , that - At least one pair of devices for emitting and receiving light are present, which are used to detect the oscillating bending of the plate these are arranged opposite one another. 15. Flow meter according to one of claims 4 to 12, characterized in that - The entire vibration detection device is designed so that the natural vibrations (resonance frequency) of the Vibrator is essentially equal to the lowest expected frequency of the vortex. · 14. Flow meter according to claim 13,. characterized in that - the vibrator is arranged on the plate in such a way that this arrangement is in mass equilibrium, whereby the plate can perform torsional vibrations. 15. Flow meter according to one of claims 4 to 14, characterized in that - the vibrator is dampened. 16. Flow meter according to claim 15, characterized in that - The tension straps (10a, 10b) are designed so that they themselves cause the damping. ^{VPA 81 p 8611 DE} 17. Flow meter according to claim 16, characterized in that - The tensioning straps (10a, 10b) with a visco-elastic Material are coated, whereby the tensioning straps (10a, 10b) receive a corresponding damping characteristic » 18. Flow meter according to claim 16, characterized in that - The chamber that encloses the tensioning straps (10a, 10b) with Damping material is filled ", 19. Flow meter according to one of claims 10 to 18, characterized in that - A signal processing circuit for processing the detected signal is present, which is an integrator circuit (632) for integrating the output signal of the detection device (61, 62) and a correlator circuit (634) for comparing the output signal of the integrator circuit (632) with the output signal of the detection device (61, 62) (Fig. 27) ο 20. Flow meter according to claim 19, characterized in that the Signal processing circuit contains the following components: - A differential _{amplifier (635 2} ) ^for amplifying the difference between the output signal of the integrator circuit (632) and the output signal of the detection device (61, 62), - a second amplifier (635 ■ *) for further amplification the output signal of the differential amplifier (635p) and - A gain control device (635 ^) for controlling the , _ Gain of the second amplifier (635 *) as a function of from the output signal of the integrator circuit (632) and to compensate for amplitude reductions in the output signal the detection device (61, 62) (Fig. 28). BATH ORIGINAL -Ό- VPA 81 P 8611 DE 21. Use of a flow meter according to one of the preceding Claims for measuring the amount of energy produced by an automobile engine sucked in air, characterized by a combination of the following features: - it is a pillar arrangement (2) which is located in a path through the intake pipe (102) of the engine (101), present, the pillar arrangement (2) being a Karmän'sche Vortex street generated in the sucked air, - a vibrator is arranged so that it is generated by the Vortex is vibrated and a deflection detection device (4) is effective for the optical detection of the bending of the vibrator, - There is also an arrangement for cleaning the suctioned Air and to limit this air to a predetermined amount and - An optical arrangement which contains the vibrator and the deflection detection device (4) and with the purified air is supplied (Fig. 29). 22. Application of the flow meter according to one of the claims until 20, characterized by a combination of the following features: - a vortex generator built up with a pillar arrangement (2) is provided in the intake manifold of an engine (101) for generating a carmine vortex street, these vortices act alternately on opposite sides of the vortex generator, - A vibrator (8) is provided outside the suction line (102) and vibrates due to the vortex pressure generated by the>. Vortex generator is generated,
- An optical bending detection device (4) with a light emitting part (6a) and a light receiving part (6b) for optical detection of the bending of the vibrator (9), the optical device being arranged outside the suction line (102), BATH ORIGINAL ft O O © ■ O Il β O · 0 β ο Φ O β O QO O O O O . φ O O Q O σ O Φ O O O O VPA 8.1 P 8611 DE - a flow meter housing, which contains the vortex generator, contains the vibrator (9) and the optical device is housed in the engine compartment and - is an electrical signal processing circuit (12) arranged outside the engine compartment and converts the light signals of the flow meter parts in the engine compartment into an electrical one Signal um, with which the amount of air sucked in is detected; the electrical signal processing circuit is with the flow meter housing in the engine compartment through a .10 fiber optic cable (5) connected (Fig, 31) = 23. Application of a flow meter according to claims 1 to. for measuring the air sucked in by an automobile engine, characterized by the combination the following features? - A signal processing module (25) processes the detected ones Vortex signals and - A housing (134), in which the signal processing circuit (2 ^) is housed, communicates on one side with an air intake line via a pipe on the side lying behind a throttle valve in the flow direction, the other side of the housing (134) with the athraosphere is connected, and due to the negative pressure on this side of the throttle valve, air from the atmosphere is passed through the housing for cooling the electrical components of the signal processing circuit (25) (Fig »33) 24 »Use of a flow meter according to claim 23, characterized in that - the air for cooling the electrical components Signal processing circuit (25) through an inlet pipe in -. the housing (134) is inserted, which is in the flow direction • behind the vortex generator and in front of the throttle valve is arranged (Fig. 33) ο
35