JP5567626B2 - Axial flow sensor - Google Patents

Description

  The present invention relates to an axial flow sensor that detects a flow rate of a fluid by detecting a rotational speed when an impeller provided in a passage rotates by the flow of the fluid.

  Various types of sensors are known as sensors for detecting the flow rate of a fluid (water or the like) flowing through the passage, and one of them is an axial flow rate sensor. This axial flow type flow sensor rotates the impeller by flowing a fluid from the direction of the rotating shaft to the impeller provided in the passage, and detects the flow rate based on the rotational speed of the impeller at that time. Since the axial flow sensor has a simple structure, the axial flow sensor is highly reliable, can be manufactured at low cost, and has an excellent characteristic that an output proportional to the flow rate can be obtained.

  However, this axial flow type flow rate sensor has a drawback that the detection accuracy is lowered unless the direction of the flow flowing into the impeller is uniform. For example, since the rotational speed of the impeller changes between when the fluid flows straight toward the impeller and when it flows while turning slightly, the detected flow rate changes. Alternatively, even when the air flows while turning, the impeller is used in the case where it turns uniformly over the entire cross section of the passage and in the case where the portion turning strongly and the portion turning weakly are mixed on the cross section of the passage. The rotation speed of the sensor changes and the detected flow rate changes. In view of this, a technology has been proposed in which a flow straightening plate is provided upstream of the impeller to rectify the flow direction and then flow into the impeller (Patent Document 1, Patent Document 2, etc.).

JP 2003-302263 A JP 2004-333402 A

  However, there is a problem that the detection accuracy of the axial flow type flow sensor may not be sufficiently improved only by providing a current plate on the upstream side of the impeller. This is because the detection accuracy of the axial flow sensor is affected not only by the direction of the flow flowing into the impeller but also by the flow velocity distribution in the passage cross section, so the flow direction is simply aligned by providing a rectifying plate. This is because the detection accuracy may not be sufficiently improved.

  The present invention has been made in response to the above-mentioned problems of the prior art, and is an axis capable of detecting a flow rate with sufficient detection accuracy without being affected by the flow direction or the flow velocity distribution in the passage cross section. The purpose is to provide a flow-type flow sensor.

In order to solve the above-described problems, the axial flow type flow sensor of the present invention employs the following configuration. That is,
A body case in which a passage through which a fluid flows is formed; an impeller that is provided in the passage and rotates about the direction of the flow by the fluid flow; and the passage on the upstream side of the impeller. In an axial flow type flow sensor comprising a rectification unit that rectifies the direction of the flow that flows across and flows into the impeller, and a detection means that detects the rotational speed of the impeller,
In the rectifying unit, a plurality of communication holes for communicating the upstream side and the downstream side of the rectifying unit are provided across the cross section of the passage.
Each of the communication holes is provided with a deforming portion that deforms in a direction in which the area of the communication hole decreases when the rectifying unit receives the pressure of the fluid from the upstream side.

  In such an axial flow sensor of the present invention, when a fluid flows in the passage of the main body case, the impeller provided in the passage rotates. On the upstream side of the impeller, there is provided a rectification unit having a plurality of communication holes formed across the cross section of the passage, and the fluid flows into the impeller after the flow direction is rectified by the rectification unit. The flow rectified by the rectification unit may be a flow that goes straight toward the impeller or a flow that turns. Here, each communication hole is provided with a deforming portion that is deformed in a direction in which the area of the communication hole is reduced when fluid pressure is received from the upstream side.

  If it carries out like this, in the location where the flow velocity which flows into a rectification | straightening part is large, since the area of a communicating hole will receive small big pressure from a fluid and the flow in that location will decelerate. Moreover, since the part for which the flow volume decreased by having decelerated goes around to another location, the flow velocity at the location where the flow velocity is small is increased. For this reason, the flow velocity distribution is flattened on the downstream side of the rectifying unit, and the flow velocity distribution flowing into the rectifying unit is almost the same as that on the downstream side of the rectifying unit. can do. In addition, since the plurality of communication holes are formed in the rectifying unit, the flow direction is also adjusted. In the end, the flow direction and flow velocity distribution are always the same on the downstream side of the rectification unit, and the impeller can be rotated by such a flow, greatly improving the flow rate detection accuracy. It becomes possible to make it.

  In the above-described axial flow type flow sensor of the present invention, the deformed portion is formed by passing a plurality of communication holes parallel to the rotation shaft of the impeller through an elastic member having a plate thickness corresponding to the length of the communication hole. It may be formed. And it is good also as supporting the elastic member in which the communicating hole was formed by the support part from the downstream of the flow.

  If it carries out like this, the communication hole which has a deformation | transformation part can be easily manufactured only by providing a some communication hole in the elastic member which has predetermined | prescribed plate | board thickness. Further, if the elastic member is supported by the support portion from the downstream side, the elastic member will not be bent by the pressure of the fluid.

  Further, in the above-described axial flow sensor of the present invention, a plurality of communication holes are formed in a substrate formed of a material that is not deformed by the pressure of the fluid, and a deforming portion by an elastic member is formed at a portion where the communication holes open in the substrate It is good also as providing.

  Even in this case, it is possible to reduce the area of the communication hole by deforming the deformation portion provided in the opening of the communication hole with the pressure of the fluid. As a result, even if the flow velocity distribution on the upstream side of the rectifying unit in which the communication hole is formed is different, substantially the same flow velocity distribution is obtained on the downstream side. In addition, the flow can be rectified by the communication hole formed in the substrate. As a result, the downstream impeller is supplied with a flow having the same flow direction and flow velocity distribution, and the flow rate detection accuracy can be greatly improved.

It is an exploded view showing the structure of the axial flow type flow sensor 1 of the present embodiment. It is explanatory drawing which illustrated a mode that the flow-velocity distribution in a pipe line changed with the difference in the piping shape of the upstream of the axial flow type flow sensor 1. FIG. It is explanatory drawing which shows the reason for the rotational speed of the impeller 30 changing with the difference in the flow velocity distribution in a pipe cross section. 4 is an explanatory diagram showing a basic operation of the rectifying unit 10. FIG. It is explanatory drawing which showed the mechanism in which the rectification | straightening part 10 absorbs the difference of the upstream flow velocity distribution, and converts into a flat flow velocity distribution. It is explanatory drawing about the rectification | straightening part 80 of a 1st modification. It is an exploded assembly figure showing the structure of axial flow type flow sensor 1 provided with rectification part 90 of the 2nd modification.

  FIG. 1 is an exploded view showing the structure of the axial flow type flow sensor 1 of the present embodiment. The axial flow type flow sensor 1 of the present embodiment includes a main body case 60 in which a circular cross-section passage 60c through which a fluid such as water flows is formed, an impeller 30 accommodated in the passage 60c, and the impeller 30. Bearing parts 40 and 50 which are supported by being sandwiched from above and below, a magnetic sensor 70 provided on the outer surface of the main body case 60, and the like are provided.

  The passage 60c is formed so that the inner diameter of the portion (housing portion 62) in which the impeller 30 is housed is slightly smaller, and the bearing portions 40 and 50 are the end surfaces of the housing portion 62 (the portion in which the inner diameter of the passage 60c is smaller). ). Further, in the passage 60c on the upstream side of the bearing portion 40, a plurality of communication holes 10c are formed to rectify the flow direction, and a support plate 20 that supports the rectification unit 10 from the downstream side is accommodated. ing. Since the support plate 20 has a plurality of openings 22 at the same position as the communication hole 10c of the rectifying unit 10, the support plate 20 prevents the flow of fluid passing through the communication hole 10c of the rectifying unit 10. There is nothing. In this embodiment, the support plate 20 corresponds to a “support portion” in the present invention. In the example shown in FIG. 1, the upper end of the impeller 30 is pivotally supported by the bearing portion 40. However, the bearing portion 40 may be omitted, and a bearing that pivotally supports the upper end of the impeller 30 may be provided in the center of the support plate 20 instead. In the portion where the support plate 20 is provided with the bearing, the flow from the rectifying unit 10 is hindered. However, since the fluid originally does not flow in the portion of the bearing, no problem occurs even if the flow is hindered.

  The impeller 30 includes a cylindrical blade base 34, projecting shafts 32 protruding from both ends of the blade base 34, and a plurality of blades 36 erected radially from the outer peripheral side surface of the blade base 34. Yes. The blade 36 extends from the upper end side to the lower end side of the blade base 34 and is further formed in a spiral shape around the central axis of the blade base 34. The impeller 30 is pivotally supported by fitting the projecting shafts 32 at both ends to the bearing portions 40 and 50.

  The tip portion of the blade 36 is magnetized so that the adjacent blades 36 have opposite polarities alternately. When the impeller 30 rotates, the switching of the magnetic pole can be detected using the magnetic sensor 70. Since the impeller 30 rotates at a speed corresponding to the flow rate flowing into the passage 60c, the magnetic sensor 70 detects the rotational speed of the impeller 30 from the number of times the polarity of the magnetic pole is switched per unit time. The flow rate flowing into 60c can be detected. In this embodiment, the magnetic sensor 70 corresponds to the “detecting means” in the present invention.

  The rectifying unit 10 has a disk shape having an outer diameter that is substantially the same as the inner diameter of the passage 60c, and has a plurality of communication holes 10c parallel to the central axis of the passage 60c (the rotation axis of the impeller 30). For this reason, the flow flowing into the rectifying unit 10 from the upstream side is rectified in the flow direction when passing through the plurality of communication holes 10 c, and is parallel to the rotation axis of the impeller 30 on the downstream side of the rectifying unit 10. It becomes a flow of direction.

  Moreover, the rectification | straightening part 10 is formed using the rubber material, and the support plate 20 which supports the rectification | straightening part 10 from the downstream is formed with rigid materials, such as a metal and hard resin. For this reason, even if the flow velocity distribution flowing into the rectification unit 10 changes due to the difference in the pipe shape on the upstream side of the rectification unit 10, the influence is not transmitted to the downstream side of the rectification unit 10. The flow of the same flow velocity distribution can always flow into the impeller 30. As a result, the flow rate detection accuracy can be greatly improved. This point will be described in detail later. From the viewpoint of not transmitting the fluctuation of the flow velocity distribution to the downstream side, the rectifying unit 10 is desirably formed using a rubber material having a hardness of 50 to 60 degrees. In view of water resistance and heat resistance, the rubber material is particularly preferably silicon rubber or EPDM (ethylene / propylene / diene rubber).

  FIG. 2 is an explanatory view exemplifying how the flow velocity distribution in the pipe changes due to the difference in the pipe shape on the upstream side of the axial flow sensor 1. When the pipe shape is straight as shown in FIG. 2 (a), the central portion of the pipe cross section has the highest flow velocity, and the lower the outer portion, the lower the flow velocity, and the portion in contact with the inner wall of the pipe has zero flow velocity. Flow velocity distribution. On the other hand, when the pipe is bent as illustrated in FIG. 2B, the portion where the flow velocity is highest is the flow velocity distribution that moves from the center to the outside. Such a difference in the flow velocity distribution affects the rotational speed of the impeller 30 provided on the downstream side, thereby reducing the flow rate detection accuracy.

  FIG. 3 is an explanatory diagram showing the reason why the rotational speed of the impeller 30 changes due to the difference in the flow velocity distribution in the pipe cross section. For example, when attention is paid to a fluid flowing into the impeller 30 at a position Ra from the rotation axis of the impeller 30, the fluid rotates the impeller 30 by pushing the blade 36. At this time, the force (rotational torque) for rotating the impeller 30 is a value obtained by multiplying the distance Ra by the component in the rotational direction of the force with which the fluid pushes the blades 36. Similarly, for the fluid flowing into the impeller 30 at a distance Rb from the rotation axis of the impeller 30, the force (rotational torque) that causes the fluid to rotate the impeller 30 is the force by which the fluid pushes the impeller 36. A value obtained by multiplying the component in the rotation direction by the distance Rb.

  And if the flow velocity is the same, the force that the fluid pushes the blades 36 may be considered to be the same. Therefore, the rotational torque that rotates the impeller 30 when it flows into the distance Rb than when it flows into the position of the distance Ra. Becomes larger. For this reason, the rotational torque for rotating the impeller 30 is different between the flow velocity distribution shown in FIG. 2A and the flow velocity distribution shown in FIG. For these reasons, the rotational speed of the impeller 30 is different even at the same flow rate, and the detected flow rate is also different. Conversely, if the difference in flow velocity distribution can be eliminated, the flow rate detection accuracy can be greatly improved. The axial flow type flow sensor 1 of this embodiment not only rectifies the direction of flow by the rectification unit 10 provided on the upstream side of the impeller 30, but also uniformizes the difference in flow velocity distribution, thereby detecting the flow rate detection accuracy. Has been greatly improved.

  FIG. 4 is an explanatory diagram showing the basic operation of the rectifying unit 10 that equalizes the difference in flow velocity distribution. 4A shows an enlarged cross-sectional view of a part of the rectification unit 10 when there is no flow, and FIG. 4B shows a part of the rectification unit 10 when there is a flow. An enlarged cross-sectional view is shown. The white arrow shown in FIG. 4 represents the flow of the fluid. When there is no flow as shown in FIG. 4A, no flow pressure is applied to the rectifying unit 10, and therefore the inner diameter da of the communication hole 10c is the as-formed inner diameter da. On the other hand, when there is a flow as shown in FIG. 4B, the rectifying unit 10 receives the flow pressure from the upstream side, and the downstream side of the rectifying unit 10 is supported by the support plate 20. Therefore, the rectifying unit 10 is compressed in the thickness direction. As a result, the inner diameter of the communication hole 10c is reduced from the inner diameter da at the time of molding to the inner diameter db. Furthermore, as shown in FIG. 4C, when the flow velocity increases, the pressure of the flow applied to the rectifying unit 10 also increases, so that the compression amount of the rectifying unit 10 also increases. As a result, the communication hole 10c is further reduced in inner diameter to become the inner diameter dc.

  Thus, since the rectification | straightening part 10 is formed with the rubber material and the downstream side is supported by the support plate 20, the internal diameter of the communicating hole 10c becomes small in the part which received the pressure of the flow. Moreover, the larger the pressure received from the flow, the smaller the inner diameter of the communication hole 10c. If such a rectification part 10 is provided in a pipe line, even if it is a flow of any flow velocity distribution, it can be set as the substantially same flow velocity distribution in the downstream of the rectification part 10. FIG. In this embodiment, since the entire rectifying section 10 made of a rubber material is deformed by the flow pressure, the entire rectifying section 10 of the present embodiment corresponds to the “deformed section” in the present invention. ing.

  FIG. 5 is an explanatory diagram showing how the rectifying unit 10 absorbs the difference in the upstream flow velocity distribution and converts it to a similar flow velocity distribution. For example, as shown in FIG. 5 (a), the flow on the upstream side of the rectifying unit 10 has a flow velocity distribution such that the flow velocity at the center portion of the conduit is the highest, and the flow velocity becomes smaller toward the outside. Shall be. This corresponds to the case where the rectifying unit 10 is placed on the downstream side of the straight pipe shape (see FIG. 2A).

  As described above with reference to FIG. 4, in the rectifying unit 10 of the present embodiment, the inner diameter of the communication hole 10 c existing in that portion becomes smaller as the flow velocity increases, so the inner diameter of the communication hole 10 c in the central portion of the pipe line. Becomes the smallest and the flow of fluid is greatly decelerated. Further, since the flow velocity decreases from the center of the pipe to the outside, the degree to which the communication hole 10c is reduced in diameter is reduced, and the degree to which the flow is decelerated is also reduced. As a result of the diameter of the communication hole 10c being reduced in accordance with the flow velocity in this way, the flow velocity is suppressed in the portion where the flow is fast, and the flow velocity in the portion where the flow is slow is increased by that amount. On the side, the flow velocity distribution becomes flatter than the flow velocity distribution on the upstream side.

  FIG. 5B shows a case where the upstream pipe shape of the rectifying unit 10 is bent. As described above with reference to FIG. 2B, on the downstream side of the portion where the pipe shape is bent, a portion having the largest flow velocity has a flow velocity distribution that is biased outward from the center of the pipe. Even in such a case, since the communication hole 10c of the rectifying unit 10 has the smallest diameter reduction in the portion with the highest flow velocity, the fluid flow in that portion is greatly decelerated. In other portions, the communication hole 10c is reduced in diameter when the flow velocity is large, and the flow velocity is suppressed. In the portion where the flow velocity is small, the flow of the portion where the flow velocity is suppressed wraps around and the flow velocity increases. As a result, the flow velocity distribution is flattened on the downstream side of the rectifying unit 10 than on the upstream side.

  As described above, the rectifying unit 10 has a function of converting almost the same flow velocity distribution on the downstream side, regardless of what flow velocity distribution flows from the upstream side. Moreover, since the plurality of communication holes 10c formed in the rectifying unit 10 are formed in parallel with the rotation shaft of the impeller 30, the rectifying unit 10 also has a function of rectifying the flow in the same direction. . As a result, the flow direction always flows in the impeller 30 on the downstream side of the rectification unit 10 and the flow velocity distribution is the same, so that the flow rate detection accuracy can be greatly improved. Become.

  In the embodiment described above, the entire rectifying unit 10 is formed of a rubber material. When the flow pressure is received, the rectifying unit 10 is deformed in the thickness direction, and the inner diameter of the communication hole 10c is reduced. explained. However, if the diameter of the communication hole 10c is reduced by receiving the pressure of the flow, the entire rectifying unit 10 does not necessarily need to be deformed in the thickness direction.

  FIG. 6 is an explanatory view illustrating the rectifying unit 80 of the first modified example. FIG. 6A shows a rough external shape of the rectifying unit 80 of the first modification. The rectifying unit 80 of the first modified example includes a disk-shaped substrate 82 formed of a rigid material such as metal or hard resin, and a circle formed of a rubber material and provided on the upstream surface of the substrate 82. And a plate-shaped deformation portion 84. A plurality of communication holes 80 c are formed in the substrate 82 in parallel with the rotation axis of the impeller 30, and the deformation portion 84 is provided with an opening 84 c at a position where the communication hole 80 c of the substrate 82 is opened. .

  FIG. 6B shows the cross-sectional shapes of the communication hole 80c and the opening 84c. As shown in the drawing, a tongue 86 is projected from the opening 84c obliquely inward toward the upstream side. Therefore, when a flow pressure is applied from the upstream side as indicated by an arrow in the figure, the tongue 86 of the deformation portion 84 is deformed as indicated by a broken line, and the area of the opening portion 84c (therefore, the communication hole 80c). The opening area) is reduced. Furthermore, the faster the flow, the greater the deformation of the tongue 86, and the smaller the opening area of the communication hole 80c. As a result, the mechanism similar to that of the rectifying unit 10 of the present embodiment described above absorbs the difference in the flow velocity distribution on the upstream side and is converted into a substantially similar flow velocity distribution, thereby greatly improving the flow rate detection accuracy. It becomes possible to make it.

  Further, in the rectifying unit 80 of the first modification described above, the substrate 82 can be formed of a rigid material, so that it is not necessary to support the downstream side of the rectifying unit 80 with the support plate 20. For this reason, if the rectification | straightening part 80 of a 1st modification is used, the support plate 20 can be abbreviate | omitted and the structure of the axial flow type flow sensor 1 can be made simpler. Furthermore, if the bearing which supports the upper end of the impeller 30 is provided on the substrate 82, the bearing portion 40 can also be omitted, so that the structure of the axial flow type flow sensor 1 can be further simplified.

  In the above description, the rectifying unit 80 of the first modification has been described as having the deforming portion 84 (tongue portion 86) on the upstream side of the communication hole 80c. However, as is apparent from the function of the deformation portion 84 (tongue portion 86) described above, the deformation portion 84 (tongue portion 86) is not limited to the upstream side of the communication hole 80c, and may be provided at any position. . Therefore, for example, as shown in FIG. 6C, a deformable portion 84 (tongue portion 86) can be provided on the downstream side of the communication hole 80c.

  Further, the flow passing through the rectifying unit 10 of the above-described embodiment and the rectifying unit 80 of the first modified example has been described as being rectified into a flow that goes straight toward the impeller 30. However, the flow may be rectified so as to turn while flowing toward the impeller 30.

  FIG. 7 shows an exploded view of the axial flow type flow sensor 1 including the rectifying unit 90 of the second modified example. The axial flow type flow sensor 1 shown in FIG. 7 is configured so that the shape of the blade 39 of the impeller 38 is straight and parallel to the central axis of the blade base 34 with respect to the axial flow type flow sensor 1 described above with reference to FIG. The extended point is different from the point that the rectifying unit 10 is replaced with the rectifying unit 90. Further, in the rectifying unit 90 of the second modified example, the communication hole 90c formed in the substrate 92 is inclined with respect to the rotation axis of the impeller 38 with respect to the rectifying unit 80 of the first modified example shown in FIG. Therefore, the difference is that the flow that has passed through the rectifying unit 90 is rectified into a swirling flow.

  Also in the axial flow type flow sensor 1 including the rectifying unit 90 of the second modified example, the tongue 86 of the deforming unit 84 is deformed similarly to the rectifying unit 80 of the first modified example described above. Differences in upstream flow velocity distribution can be absorbed. Further, the flow direction can be rectified by the communication hole 90c of the substrate 92 to generate a swirling flow. As a result, on the downstream side of the rectifying unit 90 of the second modified example, it is possible to always obtain the same swirling flow with the same flow velocity distribution, so that the flow rate detection accuracy can be greatly improved. .

  In the case of the rectifying unit 90 of the second modified example shown in FIG. 7, the bearing unit 40 can also be omitted if a bearing that pivotally supports the upper end of the impeller 38 is provided on the substrate 92. By doing so, the structure of the axial flow sensor 1 can be simplified.

  The axial flow sensor 1 according to this embodiment and various modifications has been described above, but the present invention is not limited to the above-described embodiments and modifications, and can be implemented in various modes without departing from the spirit of the present invention. Is possible.

DESCRIPTION OF SYMBOLS 1 ... Axial flow sensor, 10 ... Rectification part, 10c ... Communication hole,
20 ... support plate, 22 ... opening, 30 ... impeller,
32 ... protruding shaft, 34 ... blade base, 36 ... blade,
38 ... impeller, 39 ... vane, 40 ... bearing part,
60 ... Main body case, 60c ... Passage, 62 ... Storage part,
70 ... Magnetic sensor, 80 ... Rectification part, 80c ... Communication hole,
82 ... Substrate, 84 ... Deformation part, 84c ... Opening part,
86 ... tongue part, 90 ... rectification part, 90c ... communication hole,
92 ... Substrate

Claims (3)

A body case in which a passage through which a fluid flows is formed; an impeller that is provided in the passage and rotates about the direction of the flow by the fluid flow; and the passage on the upstream side of the impeller. In an axial flow type flow sensor comprising a rectification unit that rectifies the direction of the flow that flows across and flows into the impeller, and a detection means that detects the rotational speed of the impeller,
In the rectifying unit, a plurality of communication holes for communicating the upstream side and the downstream side of the rectifying unit are provided across the cross section of the passage.
Each of the communication holes is provided with a deforming portion that deforms in a direction in which the area of the communication hole decreases when the rectifying portion receives the pressure of the fluid from the upstream side. Flow sensor. The axial flow type flow sensor according to claim 1,
The deformation portion is formed by penetrating a plurality of the communication holes parallel to the rotation shaft of the impeller through an elastic member having a thickness corresponding to the length of the communication holes.
The axial flow rate sensor, wherein the elastic member in which the communication hole is formed is supported by a support portion from the downstream side of the flow. The axial flow type flow sensor according to claim 1,
The communication hole is formed in a substrate formed of a material that is not deformed by the pressure of the fluid,
The deformation portion is an elastic member provided in a portion where the communication hole is opened in the substrate.

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