JP5422015B2 - Flowmeter - Google Patents

Description

  The present invention relates to a flowmeter that increases the detection sensitivity of a flow rate sensor with respect to a minute flow rate by devising the flow channel structure and widens the measurement dynamic range by the flow rate sensor by suppressing the detection sensitivity with respect to a large flow rate.

  In a flow meter using a thermal type flow sensor, in order to increase the detection sensitivity and detect a minute flow rate, a plurality of parallel flow passages along the direction of fluid flow are provided inside the flow path with the flow sensor attached to the wall surface. It has been proposed that the flow velocity at the wall surface position is increased by partitioning into minute channels, and that the nozzle portion is provided in the middle of the flow channel to increase the flow velocity at the nozzle portion (for example, Patent Document 1). , 2).

Japanese Patent Laid-Open No. 4-69521 Japanese Patent Laid-Open No. 11-173896

  However, as described above, when the detection sensitivity for a very small flow rate is increased, the detection sensitivity for a large flow rate is also increased accordingly. There is a problem to say. Therefore, for example, in a gas meter having a maximum measured flow rate of about 30,000 [L / h], it is difficult to accurately detect even a very small leakage flow rate of about 5 [L / h].

  The present invention has been made in consideration of such circumstances, and its purpose is a flow meter that can easily and accurately detect from a minute flow rate such as gas leakage to a large flow rate in a normal use state of gas. Is to provide.

In order to achieve the above-described object, the flow meter according to the present invention is devised in the flow path structure to saturate the output of the flow sensor, for example, from a minute flow rate of about 5 [L / h] to 30,000 [ L / h] can be measured up to a large flow rate, basically,
<a> A first and a second, which are provided in parallel and which shunt and flow the fluid flowing through the main flow path and passively change the shunt ratio according to the flow rate of the fluid flowing through the main flow path A flow path;
<b> A flow rate sensor provided in at least one of the first and second flow paths is provided. Note that “the shunt ratio changes” means that it is not necessary to supply energy such as current from the outside in order to change the shunt ratio.

  Incidentally, the first and second flow paths are formed by spatially dividing the cross section of the main flow path along the fluid flow direction of the main flow path, for example, the first and second flow paths. At least one of the second flow paths passively changes the flow path resistance with respect to the fluid in accordance with the flow rate of the fluid flowing through the main flow path, thereby diverting between the first and second flow paths. Configured to change the ratio.

  Specifically, the first and second flow paths are formed by partitioning the cross section of the main flow path by, for example, a partition body provided along the fluid flow direction of the main flow path. Preferably, one channel is formed as a channel space having a smaller channel cross section than the second channel. In particular, the first flow path is provided with a predetermined length of a running section for the fluid flow, and a narrow section is provided on the downstream side of the running section to narrow down the flow path cross-sectional area. It is preferable to incorporate a sensor.

  Alternatively, the first flow path is a mesh formed on a part of a mesh body provided so as to cover the entire flow path cross section of the main flow path, for example, as a minute region compared to the flow path cross section of the main flow path. It consists of a laminar flow region formed downstream of the defect. The second flow path is formed as an area other than the laminar flow area on the downstream side of the mesh body, which is formed by equivalently partitioning the cross section of the main flow path with the laminar flow area. Realized. Incidentally, a plurality of mesh bodies having the mesh defect portion may be provided with the positions of the mesh defect portions aligned in the fluid flow direction.

  The first and second flow paths are formed by partitioning the cross section of the main flow path with a partition body provided along the fluid flow direction of the main flow path, and depending on the flow velocity of the fluid. By providing the second flow path with a paddle mechanism that changes the flow path resistance with respect to the fluid, the first and second flow paths are changed according to the flow path resistance of the second flow path that changes depending on the opening degree of the paddle mechanism. It is also possible to configure the diversion ratio between the two flow paths to be variable.

  Preferably, a lattice-like partition plate that divides the flow path into a plurality of parallel fine flow paths along the fluid flow may be provided in the second flow path. Further, the grid-like partition plate is realized as a grid body having a predetermined length, and a plurality of the grid bodies are arranged in series in the flow direction of the fluid in the second flow path, It is also preferable to interpose mesh bodies between these lattice bodies. It is also useful to provide a second flow rate sensor in the second flow path and to compensate for a decrease in measurement accuracy for a large flow rate by performing flow rate measurement using this second flow rate sensor in combination.

  According to the flowmeter having the basic configuration described above, the diversion ratio between the first flow path and the second flow path provided in parallel changes passively according to the flow rate of the fluid flowing through the main flow path. Therefore, for example, when the flow rate of the fluid flowing through the main flow path is small, the flow division ratio with respect to the first flow path is high, and as the flow rate of the fluid flowing through the main flow path increases, the flow division ratio with respect to the first flow path increases. In the case of lowering, by providing a flow rate sensor in the first flow path, it is possible to detect a minute flow rate to a large flow rate with the flow rate sensor.

  That is, in the case described above, when the flow rate flowing through the main flow path is very small, by passing most of the fluid through the first flow path, the small flow rate can be reliably detected. In this case, most of the flow rate can be passed through the second flow path, and the flow rate of the fluid flowing through the first flow path can be suppressed. Therefore, as the flow rate of the fluid flowing through the main flow path increases, the flow rate flowing through the first flow path can be suppressed in accordance with the diversion ratio described above, so that a minute flow rate can be achieved without saturating the flow sensor. To a large flow rate can be collectively detected.

  In addition, after securing a running section for the fluid flow in the first flow path, a narrow portion for narrowing the cross-sectional area of the flow path is provided, and the flow sensor is incorporated in the narrow portion. The flow rate of the minute flow amount guided to the first flow path can be accelerated in the narrow portion. As a result, the detection sensitivity of the flow rate sensor can be substantially increased, and a minute flow rate can be easily detected. In particular, the narrow portion acts as a flow path resistance for a large flow rate, and thus works extremely effectively in passively changing the diversion ratio between the first and second flow paths. Further, since the mesh body and lattice body described above and the paddle mechanism act as a flow path resistance for a small flow rate, they are also extremely effective in passively changing the diversion ratio between the first and second flow paths. Act on.

The figure which shows the basic composition of the flowmeter which concerns on this invention. The figure which equivalently shows the flow-path structure of the flowmeter shown in FIG. The figure which shows the change characteristic of flow-path resistance with respect to the flow volume of the 1st and 2nd flow path of the flowmeter shown in FIG. The figure which shows the change of the shunt ratio between the 1st and 2nd flow paths in the flowmeter shown in FIG. The figure which shows the 1st implementation example of the flow-path structure in the flowmeter shown in FIG. The figure which shows the 2nd implementation example of the flow-path structure in the flowmeter shown in FIG. The figure which shows the 3rd implementation example of the flow-path structure in the flowmeter shown in FIG. The figure which shows the 4th implementation example of the flow-path structure in the flowmeter shown in FIG. The figure which decomposes | disassembles into the fluid flow direction, and shows typically the flow-path structure of the flowmeter which concerns on the 1st Embodiment of this invention. The figure which shows typically the cross-section of the principal part of the flow path in the flowmeter shown in FIG. The figure which shows the change of the flow sensor output with respect to micro flow rate of the experiment which confirmed the improvement of the detection sensitivity with respect to micro flow rate of the flow meter shown in FIG. The figure which shows the change of the flow sensor output with respect to very small flow volume when changing the ratio of flow-path cross-sectional area (frontage width). The figure which compares and shows the sensor output which changes with the presence or absence of a mesh body. The figure which shows the change of the sensor output with respect to the flow volume of the flow sensor for low speeds and the flow sensor for high speeds in 1st Embodiment. The figure which shows the sensor output characteristic which changes with the difference in the length of a lattice body. The figure which decomposes | disassembles into the fluid flow direction, and shows typically the flow-path structure of the flowmeter which concerns on the 2nd Embodiment of this invention. The figure which shows typically the cross-section of the principal part of the flow path in the flowmeter shown in FIG. The figure which shows the change of the sensor output in the micro flow volume which changes with the presence or absence of a mesh defect | deletion part. The figure which shows the change of the sensor output with respect to the flow volume of the flow sensor for low speeds and the flow sensor for high speeds in 2nd Embodiment.

  Hereinafter, a flow meter according to the present invention will be described with reference to the drawings.

  This flow meter is suitable as a gas meter, and is configured using, for example, a thermal flow sensor that detects the mass flow rate of the flow gas. Although not shown in particular, the thermal flow sensor is a thin diaphragm formed on a silicon substrate or glass substrate, for example, and a pair of temperature sensitive resistance elements are provided in the fluid flow direction with a heating resistance element in between. The flow rate (flow velocity) of the fluid is detected from the change in the temperature distribution in the vicinity of the sensor surface due to the fluid flowing along the sensor surface.

  FIG. 1 is a diagram showing a basic configuration of a flow meter according to the present invention. First and second flow paths 2 for dividing and flowing the fluid in the middle of a main flow path 1 for flowing fluid (for example, gas). , 3 are provided in parallel. In particular, the first and second flow paths 2 and 3 correspond to the flow resistance R1 of the first flow path 2 and the second flow according to the flow rate (flow velocity) V of the fluid flowing through the main flow path 1. The flow path resistance R2 of the flow path 3 is passively changed, thereby changing the diversion ratio between the first and second flow paths 2 and 3, equivalently as shown in FIG. Create a resistor circuit. That is, the first and second flow paths 2 and 3 have passive flow resistances R1 and R2 as shown in FIG. 3, depending on the flow rate (flow velocity) V of the fluid flowing through the main flow path 1, for example. According to the flow path resistances R1 and R2, the fluid is divided into flow rates I1 and I2, respectively, and the flow ratio [I1 / (I1 + I2)] is as shown in FIG. The flow path structure changes according to the flow rate (flow velocity) V of.

  Only one of the first and second flow paths 2 and 3 passively changes its flow resistance R1 or flow resistance R2 according to the flow rate (flow velocity) V of the fluid flowing through the main flow path 1. It may be changed. In this case, the diversion ratio [I1 / (I1 + I2)] between the first and second flow paths 2 and 3 changes with the change of the flow path resistance R1 or R2. The thermal flow sensor 4 described above is incorporated in at least one of the first and second flow paths 2 and 3 described above in the flowmeter having such a flow path structure.

  The first and second flow paths 2 and 3 described above are connected to the inside of a pipe (large diameter pipe) 5 forming the main flow path 1 as shown in FIGS. 5 (a) and 5 (b), for example. It is formed by partitioning the internal space of the pipe 5 in the cross-sectional direction of the flow path by a small-diameter pipe 6 as a partition body provided along the flow direction. FIG. 5A shows the longitudinal cross-sectional structure of the flow channel, and FIG. 5B shows the cross-sectional structure of the flow channel.

  In this case, the difference between the cross-sectional areas of the first and second flow paths 2 and 3 formed by dividing the internal space of the pipe 5 by the small-diameter pipe 6 or the laminar flow inside the pipe 5 The flow resistances R1 and R2 of the first and second flow paths 2 and 3 are caused to flow through the pipe 5 due to the difference in the velocity distribution of the pipes and the change of the flow velocity gradient caused by the wall surface of the small diameter pipe 6. Varies depending on the flow rate (flow velocity) V.

  Specifically, when the flow rate (flow velocity) V of the fluid flowing through the pipe 5 is small, the flow path resistance of the first flow path 2 having a small flow path cross-sectional area formed as the internal space of the small-diameter pipe 6. R1 is only slightly larger than the channel resistance R2 of the second channel 3 having a large channel cross-sectional area formed as an external space of the small-diameter pipe 6. However, when the small-diameter pipe 6 is provided in the central portion of the pipe 5, the flow velocity in the central portion of the pipe 5 originally exhibits a speed distribution slightly faster than the peripheral portion thereof, so the first and second flow paths 2, 3 It can be considered that the flow velocities R1 and R2 of the first and second flow paths 2 and 3 are substantially the same.

  However, when the flow rate (flow velocity) V increases, the velocity gradient due to the contact resistance with the fluid on the wall surface of the small-diameter pipe 6 increases accordingly. The channel resistance R1 increases. That is, the channel resistance R1 changes passively according to the flow rate. As a result, as the flow rate (flow velocity) V of the fluid flowing through the pipe 5 increases, it becomes difficult for the fluid to flow into the first flow path 2, and the diversion ratio with the second flow path 3 changes. Become.

  Therefore, if the flow rate sensor 4 is provided in the first flow path 2, when the flow rate (flow velocity) V of the fluid flowing through the pipe 5 is very small, the flow rate is the first and second flow paths 2. The flow rate sensor 4 can reliably detect the minute flow rate. Further, when the flow rate (flow velocity) V of the fluid flowing through the pipe 5 increases, the flow resistance R1 of the first flow path 2 increases with the increase in the flow resistance R1 between the first and second flow paths 2 and 3. Since the diversion ratio changes and an increase in the flow rate of the fluid flowing through the first flow path 2 is suppressed, the flow rate can be detected without saturating the flow rate sensor 4.

  At this time, if the second flow rate sensor 4a capable of detecting a high flow rate with high accuracy is provided in the second flow channel 3, the detection accuracy of the large flow rate in the flow rate sensor 4 provided in the first flow channel 2 is provided. Can be compensated for. However, since the minute flow rate cannot be detected with high accuracy by the second flow rate sensor 4a, the detection of the minute flow rate is left to the flow rate sensor 4 provided in the first flow path 2 as described above. Become.

  As shown in FIGS. 6A and 6B, if a narrow portion (nozzle portion) 6a in which the pipe diameter (channel cross-sectional area) is narrowed is provided in the middle of the small-diameter pipe 6, piping can be provided. As the flow rate (flow velocity) V of the fluid flowing through the flow channel 5 increases, the flow channel resistance R1 of the first flow channel 2 can be changed further greatly. That is, when the narrow portion (nozzle portion) 6a exists in the middle of the small diameter pipe 6, the fluid that has entered the small diameter pipe 6 flows while being compressed through the small diameter pipe 6, and the flow rate is increased in the above state. It will pass through the narrow part 6a. At this time, when the flow rate (flow velocity) V of the fluid flowing through the pipe 5 is small, the degree of fluid compression in the small-diameter pipe 6 is small, and the small-diameter pipe 6 increases as the flow rate (flow velocity) V increases. The degree of compression of the fluid increases. This means that when the flow rate is small, the flow channel resistance R1 of the first flow channel 2 having a small flow channel cross-sectional area is small, and as the flow rate increases, the flow channel resistance R1 of the first flow channel 2 gradually increases. means. On the other hand, the channel resistance R2 of the second channel 3 having a large channel cross-sectional area hardly changes regardless of the change in the flow rate (flow velocity) V.

  Therefore, by providing the flow rate sensor 4 in the first flow path 2 having the above-described flow path structure, the diversion ratio between the first and second flow paths 2 and 3 is changed according to the flow rate, so that the flow rate is high. Therefore, it is possible to reliably detect a low flow rate to a high flow rate without saturating the flow rate sensor 4. In particular, if the flow rate sensor 4 is provided in the narrow portion 6a described above, the speed of the fluid flowing through the first flow path 2 can be increased in the narrow portion 6a. However, this can be detected with high sensitivity.

  In addition, the flow rate sensor 4 and the second flow rate sensor 4a are provided in the same circumferential direction of the flow channel circumferential surface without providing different flow rate regions along the longitudinal direction of the flow channel as in the prior art. ing. For this reason, in the prior art, the flow path length required for each flow area is required along the longitudinal direction for each of the large flow area and the small flow area, but in the present invention, different flow areas are provided. At this time, since each flow rate sensor is provided in the same circumferential direction of the flow channel circumferential surface, only one flow channel length is required for the flow rate region. For this reason, since the flow path length does not become longer than that of the prior art, the flow meter can be reduced in size.

  By the way, the first and second flow paths 2 and 3 are arranged so as to cover the cross section of the flow path inside the pipe 5 forming the main flow path 1 as shown in FIGS. 7 (a) and 7 (b), for example. A space on the downstream side of the mesh body 7 can also be formed by dividing the mesh body 7 in the flow path cross-sectional direction of the pipe 5 by the provided mesh body 7. FIG. 7A shows the vertical cross-sectional structure of the flow path, and FIG. 7B shows the cross-sectional structure of the flow path.

  The mesh body 7 has a mesh deficient portion (notch) 7a formed in a part thereof, and the pipe is arranged such that the mesh deficient portion 7a is positioned in a part of the flow path cross section of the pipe 5. 5 is provided orthogonal to the fluid flow direction. The mesh body 7 incorporated in the pipe 5 in this way causes the mesh defect 7a to act as a region where the flow path resistance R1 is zero [0], and the mesh body 7 itself is a fluid that flows through the pipe 5. It functions as a passive body whose flow path resistance R2 changes according to the flow rate (flow velocity) V.

  The first and second flow paths 2 and 3 are equivalently divided into the interior of the pipe 5 as a portion where the flow of fluid formed in the downstream area of the mesh body 7 by the mesh body 7 is different. Formed. Specifically, the first flow path 2 is realized as a laminar flow region that passes through the mesh defect 7a and is formed on the downstream side of the mesh defect 7a. The second flow path 3 is realized as a region other than the laminar flow region on the downstream side of the mesh body 7, that is, a flow passage region for the fluid that has passed through the mesh body 7.

  According to the flow path structure provided with such a mesh body 7, the fluid flowing through the pipe 5 receives different flow path resistances depending on whether the fluid passes through the mesh defect 7 a or the mesh body 7. become. In other words, when the flow rate (velocity) V of the fluid flowing through the pipe 5 is very small, since the flow path resistance (pressure loss) in the mesh body 7 is large, most of the fluid does not have a flow path resistance. It flows through part 7a. Accordingly, the flow rate flowing through the formation region of the first flow path 2 on the downstream side of the mesh defect portion 7a is increased, and the formation region of the second flow path 3 on the downstream side of the mesh body 7 is increased. There is almost no flow through. However, when the flow rate (flow velocity) V of the fluid flowing through the pipe 5 increases, the amount of fluid flowing through the mesh body 7 gradually increases by overcoming the flow path resistance (pressure loss) in the mesh body 7. Further, the diversion ratio of the fluid passing through the mesh defect portion 7a, that is, the diversion ratio of the fluid flowing into the first and second flow paths 2 and 3 changes.

  Therefore, if the flow rate sensor 4 is provided in the first flow path 2, when the flow rate (flow velocity) V of the fluid flowing through the pipe 5 is very small, most of the small flow rate is the first flow path. 2 (mesh defect portion 7a), the flow rate sensor 4 can reliably detect the minute flow rate. Further, when the flow rate (flow velocity) V of the fluid flowing through the pipe 5 increases, the fluid flows to the second flow path 3 through the mesh body 7, and accordingly, the first flow path 2 (mesh) The flow rate flowing through the defect portion 7a) is suppressed. As the flow resistance R1 of the first flow path 2 increases, the diversion ratio between the first and second flow paths 2 and 3 changes, and the flow rate of the fluid flowing through the first flow path 2 changes. Since the increase is suppressed, the flow rate can be detected without saturating the flow rate sensor 4 as in the above-described embodiment.

  At this time, if the second flow rate sensor 4a capable of detecting a high flow rate with high accuracy is provided in the second flow channel 3, the detection accuracy of the large flow rate in the flow rate sensor 4 provided in the first flow channel 2 is provided. Can be compensated for. However, when the flow rate (flow velocity) V is very small, the minute flow rate cannot be detected by the second flow rate sensor 4a in combination with the fact that almost no fluid flows through the second flow path 3. It is. Therefore, the detection of the minute flow rate is left to the flow rate sensor 4 provided in the first flow path 2 (downstream of the mesh defect portion 7a).

  By the way, the first and second flow paths 2 and 3 described above can be realized as shown in FIGS. 8A and 8B, for example. FIG. 8A shows the longitudinal cross-sectional structure of the flow path, and FIG. 8B shows the cross-sectional structure of the flow path. In this flow path structure, a plate-like partition body 8 is provided in the pipe 5 constituting the main flow path 1 along the direction of fluid flow so that the internal space of the main flow path 1 is flown through the first and second flow paths. A paddle mechanism 9 is provided to partition the passages 2 and 3 and further partition the second space 3 in the fluid flow direction.

  The paddle mechanism 9 includes a valve body 9a that is supported in a tiltable manner via, for example, a hinge so as to close the second flow path 3, and passes through the second flow path 3. The flow path resistor is configured to tilt by receiving the pressure of the flowing fluid to form a gap in the second flow path 3 and to allow the fluid to flow through the gap. In particular, the paddle mechanism 9 changes the size (opening) of the gap formed by the plate body 9a according to the flow rate (flow velocity) V of the fluid flowing through the second flow path 3. It functions as a variable resistance element that passively changes the road resistance.

  According to the flowmeter having the flow path structure provided with such a paddle mechanism 9, when the flow rate of the fluid flowing through the main flow path 1 is very small, the paddle mechanism provided in the second flow path 3. Since 9 closes the second flow path 3, the minute flow rate fluid flows exclusively through the first flow path 2. Then, as the flow rate of the fluid flowing through the main flow path 1 increases, the valve element 9a of the paddle mechanism 9 opens due to the fluid pressure, and the flow path resistance decreases. The flow is divided into two flow paths 2 and 3.

  Therefore, if the flow rate sensor 4 is provided in the first flow path 2, most of the fluid flows through the first flow path 2 when the flow rate is very small, so that it is possible to reliably detect the very small flow rate. Further, when the flow rate increases, the valve element 9a of the paddle mechanism 9 opens with the increase of the flow rate, and thereby the fluid is divided into the first and second flow paths 2 and 3, so that the first flow path 2 An increase in the flow rate of the fluid flowing therethrough is suppressed. As a result, since it is possible to detect the flow rate while suppressing the saturation of the flow rate sensor 4, it is possible to consistently detect from the minute flow rate to the large flow rate described above.

  In addition, since the flow volume which flows through the 1st flow path 2 is suppressed at the time of the flow of a large flow volume as mentioned above, the flow volume detection accuracy by the flow sensor 4 falls correspondingly. Therefore, if the second flow rate sensor 4a capable of detecting a high flow rate with high accuracy is provided in the second flow channel 3, the detection accuracy of the large flow rate in the flow rate sensor 4 provided in the first flow channel 2 is lowered. Can be supplemented. However, when the flow rate (velocity) V is very small, almost no fluid flows through the second flow path 3, so that the minute flow rate can hardly be detected by the second flow rate sensor 4a. . Therefore, the detection of the minute flow rate is left to the flow rate sensor 4 provided in the first flow path 2.

  As described above, referring to FIGS. 5 (a), (b) to 8 (a), (b), the configurations of the first and second flow paths 2, 3 in which the diversion ratio changes according to the flow rate of the fluid. As described with respect to the example, the flowmeter according to the present invention has the first and second flow paths 2 and 3 in which the diversion ratio passively changes between the flow of a small flow rate and the flow of a large flow rate. The flow sensor 4 is incorporated in at least one of the above. In particular, by incorporating the flow sensor 4 in the flow path on the side where the flow ratio becomes high at a small flow rate and becomes low at a large flow rate, the flow sensor 4 can detect from a small flow rate to a large flow rate consistently. I am doing so.

  Specifically, most of the minute flow rate is led to a flow path (the first flow path 2 in the example described above) provided with the flow sensor 4 to substantially increase the flow velocity (apparent flow rate). Therefore, a minute flow rate can be reliably detected. On the other hand, with respect to a large flow rate, the flow rate introduced to the flow path (first flow path 2) provided with the flow rate sensor 4 is suppressed to suppress an increase in the flow velocity, thereby saturating the flow rate sensor 4. The flow rate is detected without any problems. Therefore, according to the flow meter of the present invention, for example, from a very small flow rate of about 5 [L / h] due to gas leakage caused by cracks or scratches in the pipe 5, for example, a maximum of 30,000 [L / h] in a normal gas use state. It is possible to consistently measure up to about a large flow rate with one flow rate sensor 4, and its practical advantages are great. If the second flow rate sensor 4a for large flow rate capable of detecting the flow rate in the normal gas use state with high accuracy is provided in the other flow channel (the second flow channel 3 in the above-described example), the above-described operation is performed. Since it is possible to compensate for the detection accuracy of the flow rate sensor 4 becoming rough at a large flow rate, the gas flow rate can be measured practically without any problem.

  In addition, the flow rate sensor 4 and the second flow rate sensor 4a are provided in the same circumferential direction of the flow path circumferential surface without separately providing a large flow rate region and a small flow rate region along the longitudinal direction as in the prior art, A large flow rate region and a small flow rate region are formed in the determined flow path length. Therefore, it is possible to share the flow path length necessary for forming the large flow rate measurement region and the small flow rate measurement region, respectively. Therefore, it can be set as the structure which can miniaturize a flowmeter.

  Next, a specific configuration example of the flow meter according to the present invention will be described.

  FIG. 9 is a diagram schematically showing the flow channel structure of the flow meter according to the first embodiment of the present invention in an exploded manner in the fluid flow direction, and FIG. 10 is a schematic cross-sectional view of the main part thereof. FIG. This flow meter is mainly composed of a lattice body 12 that divides an internal space of a pipe 11 having a rectangular channel cross section into a plurality of minute channels in the direction of the channel cross section. The lattice body 12 is configured by combining a plurality of plate-like partition walls provided in parallel along the fluid flow direction of the pipe 11 in a lattice shape. In particular, the grid body 12 used in this embodiment includes, for example, a sensor grid body 12a in which a flow sensor is incorporated as described later, and first and second front grid bodies 12b provided on the upstream side of the sensor grid body 12a. 12c, and first and second rear lattice bodies 12d and 12e provided on the downstream side of the sensor lattice body 12a.

  Incidentally, these lattice bodies 12 (12a, 12b to 12e) have, for example, a plurality of (multiple) microchannels 13 having a substantially square channel cross-sectional shape arranged in a matrix and a substantially rectangular channel cross-sectional shape. And two micro channels 14 having a channel cross-sectional area approximately twice that of the micro channel 13 are formed. These two microchannels 14 are formed, for example, by removing a plate-shaped partition wall that partitions two adjacent microchannels 13 at the side of the lattice body 12. These lattice bodies 12 (12a, 12b to 12e) are, as shown in FIG. 9, a mesh body (wire mesh) 15 (15a, 15b, 15c, 15d) between the lattice bodies 12 (12a, 12b to 12e). Are overlapped in the direction of fluid flow to form a plurality of flow paths that are continuous in the direction of fluid flow. Each mesh body (wire net) 15 has a role of rectifying the fluid flowing through the lattice body 12 described above.

  By the way, it is considered that the plurality (large number) of microchannels 13 partitioned by the lattice bodies 12 (12a, 12b to 12e) form a channel having a large channel cross-sectional area by grasping them as a group. Can do. Moreover, these microchannels 13 and 14 show different channel resistances with respect to the flow of the fluid due to differences in the channel cross-sectional areas. Therefore, for example, it can be considered that the group of the microchannels 13 corresponds to the second channel 3 described above, and the two microchannels 14 correspond to the first channel 2 described above.

  In addition, as shown in FIG. 10, a nozzle 14a is provided at one of the two micro flow paths 14 formed in the sensor grid 12a at a substantially intermediate position of the flow path, and the cross-sectional area of the flow path is narrowed down. Yes. The micro flow path 14 provided with the nozzle 14a is used for detecting a micro flow rate (for low speed), and a low speed flow sensor 16a is incorporated at a position where the flow path cross-sectional area is narrowed by the nozzle 14a. The other micro flow path 14 is used for large flow rate detection (for high speed), and a high speed flow rate sensor 16b is incorporated at a substantially intermediate position. These two microchannels 14 are regarded as channels separated from the above-described group of microchannels 13, so that the first and second channels whose diversion ratio changes according to the above-described flow rate. It can also be understood as 3.

  According to the flowmeter having a flow channel structure in which the flow channel is partitioned using such a lattice body 12, each flow channel cross-sectional area of the plurality of micro flow channels 13 forming the second flow channel 3 is a flow sensor. 16a and 16b are narrower than the micro flow path 14 into which the flow path 16 is incorporated, and the flow path resistance is large. Therefore, when the fluid flowing through the pipe 11 is a very small flow rate, the fluid mainly has a small flow path resistance. It flows into the flow path 14. As the flow rate of the fluid flowing through the pipe 11 increases, the fluid resistance of the microchannel 13 is overcome and the fluid flows into the microchannel 13.

  As a result, as the fluid flow rate increases, the diversion ratio between the fluid flow rate flowing into the micro flow channel 13 and the fluid flow rate flowing into the micro flow channel 14 changes. The flow rate of the fluid flowing through the microchannel 14 provided with the flow rate sensors 16a and 16b is gradually suppressed as the flow rate increases. Accordingly, the detection sensitivity of the flow rate sensors 16a and 16b provided in the micro flow channel 14 with respect to a small flow rate can be increased, and the flow rate of the divided flow into the micro flow channel 14 when flowing through a large flow rate can be suppressed. It is possible to detect the flow rate while suppressing the saturation of the flow rate sensors 16a and 16b.

  Further, in the flowmeter having the above-described flow channel structure, as described above, the nozzle portion 14a that narrows the flow channel cross-sectional area is provided at the substantially central position of one of the micro flow channels 14 in which the low-speed flow sensor 16a is incorporated. It has been. The first and second front grid bodies 12b and 12c provided on the upstream side of the sensor grid body 12a provided with the nozzle portion 14a form a running section for the fluid flowing into the micro flow path 14. All of the fluid that has flowed into the run-up section is sent to the nozzle portion 14a. As a result, the flow rate of the fluid that has flowed into the microchannel 14 is increased by narrowing the channel cross-sectional area by the nozzle portion 14a, so that the low-speed flow sensor 16a provided in the nozzle portion 14a of the microchannel 14 is used. Makes it possible to detect a minute flow rate with higher accuracy. In particular, the low-speed flow sensor 16a can detect a minute flow rate with higher sensitivity than the high-speed flow sensor 16b provided in the other minute flow path 14 not forming the nozzle portion 14a.

  FIG. 11 shows experimental data for confirming improvement in flow rate detection sensitivity in the flow channel structure in which the grid body 12 is provided and the flow path is divided into a plurality of micro flow channels 13 and 14 as described above. The change of the flow sensor output in the case where it is not provided and the case where the lattice body 12 is provided is shown in comparison. This experimental data confirms that the flow rate detection sensitivity of the flow rate sensors 16a and 16b is improved when the grid body 12 is provided and the flow path is divided into the micro flow paths 13 and 14, rather than when the grid body 12 is not provided. It was. Although not particularly illustrated, it has also been found that the detection sensitivity can be improved by increasing the length of the lattice body 12. This is considered to be because the difference in the flow resistance between the plurality of micro flow channels 13 and 14 with respect to the flow rate increases as the length of the lattice body 12 (flow channel length) increases.

  FIG. 12 shows a change in the flow rate sensor output with respect to the minute flow rate when the ratio of the channel cross-sectional area (frontage width) of the plurality of minute channels 13 and 14 formed by the lattice body 12 is changed. . In FIG. 11, the reference refers to the case where the opening width (channel cross-sectional area) of the microchannel 14 provided with the flow sensor 16 is equal to the opening width (channel cross-sectional area) of the other microchannel 13. Is shown. The parameters indicated as 4 times and 8 times are respectively set to 4 times and 8 times the front width (flow cross-sectional area) of the micro flow path 14 in which the flow rate sensor 16 is provided, and the front width (flow cross-sectional area) of the micro flow path 13. The case where it is set to double is shown.

  From the experimental data shown in FIG. 12, the opening width (channel cross-sectional area) of the microchannel 14 provided with the flow sensor 16 is made larger than the opening width (channel cross-sectional area) of the other microchannel 13. Therefore, the fluid in the minute flow rate region is less likely to flow into the minute flow path 13, and accordingly, a larger flow rate flows into the minute flow path 14 provided with the flow rate sensor 16, and the sensitivity of detection of the minute flow rate by the flow rate sensor 16 is increased. It is supported that it will increase.

  FIG. 13 shows the effect of the presence or absence of the mesh body (wire net) 15 described above, and shows the change in sensor output from a small flow rate to a large flow rate. The case where the mesh body (metal mesh) 15 is not provided is a case where the mesh body (wire mesh) 15 is omitted from the flow channel structure shown in FIG. Is shown.

  As is apparent from the characteristics shown in FIG. 13, the provision of the mesh body (wire net) 15 increases the rectifying effect on the fluid flowing through the microchannels 13 and 14, respectively, and enables stable flow rate detection. In addition, it can be seen that instantaneous flow rate measurement accuracy can be improved. From the experimental data shown in FIG. 13, it can be seen that the change in sensor output with respect to the change in flow rate in the minute flow rate region is steep, and the detection sensitivity of the flow sensor 16 in the minute flow rate region is high. At the same time, since the change in sensor output with respect to the change in flow rate becomes broader as the flow rate increases, it can be seen that the detection sensitivity of the flow rate sensor 16 in the large flow rate region is gradually reduced.

  The suppression of the detection sensitivity of the flow rate sensor 16 in this large flow rate range is caused by the fact that the pressure loss at the nozzle portion 14a described above increases in proportion to the square of the flow velocity (flow rate). As a result, the nozzle portion 14a ( This is because the flow rate passing through the micro flow channel 14) is limited and the flow rate flowing into the micro flow channel 13 increases. And according to the flowmeter employing the above-mentioned flow path structure, it is proved that it is possible to consistently measure from a minute flow rate to a large flow rate without saturating the flow rate sensor 16.

  FIG. 14 shows changes in sensor output with respect to the flow rates of the low-speed flow rate sensor 16a and the high-speed flow rate sensor 16b provided in the above-described two microchannels 14, respectively. As is apparent from the data shown in FIG. 14, the output of the low-speed flow sensor 16a provided in the micro flow channel 14 provided with the nozzle portion 14a to narrow the flow channel cross-sectional area is the rate of change as the flow rate increases. Is suppressed and exhibits a broad change. This phenomenon is because the flow rate of the fluid passing through the nozzle portion 14a is suppressed in accordance with the pressure loss at the nozzle portion 14a. On the other hand, since the nozzle portion 14a is not provided in the micro flow path 14 on the side where the high-speed flow sensor 16b is provided, suppression of the change rate of the sensor output accompanying the increase in the flow rate is suppressed. And the amount depending on the change in the diversion ratio between the microchannel 13 and the microchannel 13 described above.

  From this experimental result, it is possible to further change the flow rate in the microchannel 14 where the diversion ratio changes with the microchannel 13 depending on whether or not the nozzle portion 14a is provided in the microchannel 14, It can be seen that by providing 14a, the rate of change in the diversion ratio can be further increased to further increase the detection sensitivity in the minute flow rate region. Therefore, if the low-speed flow sensor 16a and the high-speed flow sensor 16b are provided in the two minute flow paths 14 described above, the measurement is performed consistently from the minute flow area to the large flow area with different detection characteristics. It becomes possible to compensate for the lack of measurement accuracy on the low flow rate side and the high flow rate side in each of the flow rate sensors 16a and 16b.

  FIG. 15 shows sensor output characteristics that change depending on the length of the lattice body 12 (flow path length). From this experimental data, it can be seen that the longer the length of the lattice body 12, the less affected by the pressure loss at the nozzle portion 14a, the higher the sensor output. This phenomenon is caused by the compressibility of the fluid (gas) as the flow path length of the micro flow paths 13 and 14 partitioned by the lattice body 12 is longer, particularly as the run-up section on the upstream side of the nozzle portion 14a is longer. This is thought to be because the flow rate flowing into the microchannel 14 does not change much compared to the change in the flow rate flowing through. Therefore, if the run-up section in the microchannel 14 is secured to some extent and the length of the grid 12a is increased to stabilize the channel resistance, the shunt ratio between the microchannels 13 and 14 is increased. Regardless of the presence of the nozzle portion 14a, it can be changed in accordance with the flow rate (flow velocity) of the fluid flowing through the pipe 11, so that it can be said that it is very preferable for detecting a minute flow rate with high sensitivity.

  By the way, if the mesh defect part 7a is provided in a part of the mesh body 7 previously provided so as to cover the cross section of the flow path, the fluid flows between the fluid passing through the mesh defect part 7a and the fluid passing through the mesh body 7. It has been described that the difference (1) and the second flow path (2) and (3) are formed on the downstream side of the mesh body (7). Therefore, by detecting a minute flow rate by incorporating a mesh body (wire net) having a mesh defect portion into a flow channel structure in which two types of micro flow channels 13 and 14 are formed using the lattice body 12 shown in FIG. The accuracy can be further increased.

  FIG. 16 is a diagram schematically showing the flow channel structure of the flowmeter according to the second embodiment of the present invention realized based on such a viewpoint, disassembled in the fluid flow direction. 17 is a view schematically showing a cross-sectional structure of the main part. The lattice body 12 (12a, 12b to 12e) shown in this embodiment is the same as that in the above-described embodiment. Further, in the second embodiment, the mesh bodies sandwiched between the respective lattice bodies 12 (12a, 12b to 12e) are made to correspond to the formation positions of the microchannels 14 on the side where the nozzle portions 14a are provided. The difference from the first embodiment is that a mesh body (wire mesh) 17 having a rectangular mesh defect 17a is used.

  According to the flow meter realized by forming the flow channel structure described above, the flow channel resistance (pressure loss) in the micro flow channel 14 that is positioned in the mesh defect portion 17a and does not have a mesh body (wire mesh) is small. Since the flow rate flowing into the micro flow path 14 in the minute flow rate region increases, the detection sensitivity for the minute flow rate can be increased more than in the previous embodiment. In order to confirm such an effect, when the mesh body (metal mesh) 17 in which the mesh defect portion 17a is formed is not used (first embodiment), only one mesh body (metal mesh) 17 in which the mesh defect portion 17a is formed is used. The sensor output in the minute flow rate region was examined for the used one, the two used similarly, the three used further, and the case where the mesh defect portion 17a was formed in all of them, as shown in FIG. Experimental results were obtained.

  As is apparent from the experimental data shown in FIG. 18, the sensor output increases as the mesh body 17 having the mesh defect 17a formed therein is used more and the flow resistance (pressure loss) by the mesh body 17 becomes smaller. It can be seen that it functions effectively in increasing the diversion ratio between the channels 13 and 14 and guiding most of the minute flow rate to the micro flow channel 14 incorporating the flow rate sensor 16. Therefore, it was confirmed that a minute flow rate of about 5 [L / h] due to leakage can be detected with high sensitivity.

  FIG. 19 shows output characteristics of the low-speed flow sensor 16a and the high-speed flow sensor 16b in the flowmeter configured as described above. As shown by the output characteristics of each of these sensors 16a and 16b, according to the low-speed flow sensor 16a provided with the nozzle portion 14a and incorporated in the micro flow channel 14 positioned at the formation position of the mesh defect portion 17a, The detection sensitivity in the minute flow rate region can be sufficiently increased. However, the detection sensitivity in the large flow rate region is lowered by the amount that the detection sensitivity in the very small flow rate region is sufficiently increased.

  On the other hand, in the high-speed flow rate sensor 16b incorporated in the micro flow channel 14 that does not have the nozzle portion 14a and the mesh body 17 is provided in the flow channel, the detection sensitivity in the micro flow rate region cannot be increased so much. However, the detection sensitivity can be made substantially constant over the entire measurement range from the minute flow rate region to the large flow rate region. Accordingly, by monitoring the outputs of the low-speed flow rate sensor 16a and the high-speed flow rate sensor 16b, from a minute flow rate of about 5 [L / h] caused by leakage, a maximum of 30000 [L / h in the normal use state is obtained. ] Over the entire measurement range up to a large flow rate, it is possible to detect the flow rate with high accuracy, and there is a great practical advantage. Further, by comparing the outputs of these flow sensors 16a and 16b, effects such as the ability to monitor changes in sensor characteristics over time can be obtained.

  The present invention is not limited to the embodiment described above. For example, the ratio of the channel cross-sectional areas of the first and second channels 2 and 3 may be determined according to the measurement specifications, etc. Also good. In the embodiments shown in FIGS. 8 and 17, lattice bodies are provided on the upstream side and the downstream side of the sensor lattice body 12a, respectively, and the flow path structure is symmetric with respect to the fluid flow direction. Such a symmetrical flow path structure takes into consideration that the flow direction of the fluid may be reversed in the forward and reverse directions, but in the case where the flow direction of the fluid is determined in a unified manner. The grid bodies 12b and 12c may be provided only on the upstream side of the sensor grid body 12a. Further, the length of the flow path formed by the lattice body 12 in this way may be determined according to the specification.

  The mesh bodies 7, 15, and 17 described above may be not only a wire mesh but also a honeycomb structure or a punching metal. Further, the lattice body 12 described above may be a so-called honeycomb type hexagonal channel cross section or triangular channel cross section instead of the rectangular channel cross section. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

DESCRIPTION OF SYMBOLS 1 Main flow path 2 1st flow path 3 2nd flow path 4 Flow rate sensor 5 Piping 6 Small diameter pipe (partition body)
7 Mesh body (wire mesh)
7a Mesh defect part 8 Partition body 9 Paddle mechanism 9a Valve body 11 Piping 12 Grid body 13,14 Micro flow path 14a Nozzle part 15 Mesh body (metal mesh)
16a Flow sensor for low speed 16b Flow sensor for high speed 17 Mesh body (metal mesh)
17a Mesh defect

Claims (8)

A first flow path and a second flow path, which are provided in parallel, branch the fluid flowing through the main flow path and flow passively according to the flow rate of the fluid flowing through the main flow path. A flow path;
A first flow sensor provided in the first flow path,
The first flow path comprises a laminar flow region formed on the downstream side of a mesh defect provided in a part of the mesh body provided to cover the entire flow path cross section of the main flow path,
The second flow path is formed by equivalently partitioning the cross section of the main flow path with the laminar flow region as a region other than the laminar flow region on the downstream side of the mesh body. There is a flow meter characterized by that.   The flow meter according to claim 1, wherein the mesh defect portion provided in a part of the mesh body is formed as a minute region portion as compared with a cross section of the main flow path.   The flowmeter according to claim 2, wherein a plurality of mesh bodies including the mesh defect portion are provided with the positions of the mesh defect portions aligned in a fluid flow direction. At least one of the first flow path and the second flow path is configured to passively change a flow path resistance with respect to the fluid in accordance with a flow rate of the fluid flowing through the main flow path. Changing the diversion ratio between the path and the second flow path;
The said 2nd flow path is provided with the grid | lattice-like partition plate which divides the said 2nd flow path into several parallel fine flow paths along the flow of the fluid. The flow meter described in 1. The grid-like partition plate is a grid body having a predetermined length,
5. The second flow path is formed by arranging a plurality of the lattice bodies in series in the flow direction of the fluid, and interposing the mesh bodies between the lattice bodies. 6. Flow meter. A first flow path and a second flow path, which are provided in parallel, branch the fluid flowing through the main flow path and flow passively according to the flow rate of the fluid flowing through the main flow path. A flow path;
A first flow sensor provided in the first flow path,
The first flow path and the second flow path are formed by partitioning the cross section of the main flow path by a partition body provided along the fluid flow direction of the main flow path. ,
The second flow path is provided with a paddle mechanism in which the flow path resistance with respect to the fluid changes according to the flow velocity of the fluid, and the flow resistance of the second flow path changes with the opening degree of the paddle mechanism. Accordingly, the flow dividing ratio between the first flow path and the second flow path can be varied. A first flow path and a second flow path, which are provided in parallel, branch the fluid flowing through the main flow path and flow passively according to the flow rate of the fluid flowing through the main flow path. A flow path;
A first flow sensor provided in the first flow path,
At least one of the first flow path and the second flow path is configured to passively change a flow path resistance with respect to the fluid in accordance with a flow rate of the fluid flowing through the main flow path. Changing the diversion ratio between the path and the second flow path;
The second flow path is provided with a grid-like partition plate that divides the second flow path into a plurality of parallel fine flow paths along the flow of fluid. .   The flowmeter according to claim 1, further comprising a second flow sensor in the second flow path.

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