volumetric flow meter

Abstract

To provide a positive displacement flow meter capable of accurately measuring flow rate even when the amount of liquid being measured is minute. [Solution] This positive displacement flow meter comprises a measuring chamber 23 having an inlet and outlet for the liquid to be measured, a rotor 50 housed eccentrically and rotatably along the inner circumferential surface of the measuring chamber, a magnet 55 embedded on the upper surface of the rotor at an eccentric position from the center, and a magnetic sensor 63 that measures the amount of rotation of the rotor by detecting the magnet. With this positive displacement flow meter, since the magnet is positioned eccentrically from the center of the rotor, the radius of rotation is increased, making detection by the magnetic sensor possible. Therefore, even if the measuring chamber and rotor are miniaturized, detection of the magnet by the magnetic sensor is possible, making it possible to measure minute flow rates.

Description

Technical Field

[0001] The present invention relates to a positive displacement flowmeter that detects the rotation of a rotor that rotates according to the flow rate of a liquid to be measured in a measurement chamber and measures the flow rate of the liquid to be measured from the rotation speed thereof.

Background Art

[0002] Conventionally, when accurately measuring the flow rate of a liquid to be measured flowing through a pipe installed in various plants and devices, a positive displacement flowmeter is used. Among them, when measuring a liquid to be measured with a small flow rate to a minute flow rate, the positive displacement flowmeter A100 described in Patent Document 1 (hereinafter referred to as the flowmeter A100) is frequently used. As shown in FIG. 10, this type of flowmeter A100 includes a lower main body A110 in which an inflow path A111 and an outflow path A112 to which an inflow side connection pipe and an outflow side connection pipe are connected, and a measurement chamber A113 continuous with these inflow path A111 and outflow path A112 are formed, an upper main body A120 that closes the upper opening of the measurement chamber A113, and a rotor A130 that swings and rotates while moving along the inner wall of the measurement chamber A113. At the center of the measurement chamber A113, an annular groove A116 is formed by an annular protrusion A114 and a central axis A115 provided around the annular protrusion A114. Further, as shown in FIG. 11, a partition plate A117 that extends from the inner peripheral surface of the measurement chamber A113 to the outer peripheral surface of the annular protrusion A114 and blocks between the inflow path A111 and the outflow path A112 is installed in the measurement chamber 113. Further, the rotor A130 is configured in a bottomed cylindrical shape with a disc portion A132 provided at the upper end of a cylindrical body A131, and a mounting portion A133 of a magnet A135 protruding upward and a guide shaft A134 protruding downward are provided at the center of the disc. The rotor A130 is accommodated in the measurement chamber A113 with the guide shaft A134 inserted into the guide groove A116, and the guide shaft A134 rotates along the guide groove A116, so that the rotor A130 swings and rotates in the measurement chamber A113. Therefore, when the liquid to be measured flowing in from the inflow path A111 flows into the measurement chamber A113, the rotor A130 rotates toward the outlet side by the inflow pressure of the liquid to be measured, and the liquid to be measured in the measurement chamber A113 is sent out from the outlet to the outflow path A112.

[0003] Furthermore, the upper body A120 is provided with a relief groove A121 for the mounting portion A133 to rotate, and is equipped with a magnetic sensor A122 capable of detecting the magnet A135 attached to the mounting portion A133. In this way, each time the rotor A130 rotates, a predetermined amount of the liquid to be measured is sent to the outflow path A112, and the magnet is detected once by the magnetic sensor A122. Therefore, the flow rate can be calculated from the product of the rotation speed of the rotor A130 measured by the magnetic sensor A122 and the amount of discharged per rotation of the rotor A130. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 05-142010 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, conventional positive displacement flow meters, in order to measure minute amounts of liquid, reduce the volume of the measuring chamber and the rotor, which in turn reduces the rotor's radius of rotation. This leads to a problem where the magnetic sensor cannot detect the magnet.

[0006] The present invention aims to provide a volumetric flow meter capable of measuring minute flow rates of a liquid under test. [Means for solving the problem]

[0007] The above problem can be solved by a positive displacement flow meter comprising a measuring chamber having an inlet and outlet for the liquid to be measured, a rotor housed eccentrically rotatably along the inner circumferential surface of the measuring chamber, a magnet embedded on the upper surface of the rotor at an eccentric position from the center, and a magnetic sensor that measures the amount of rotation of the rotor by detecting the magnet. Furthermore, it is preferable that the magnet moves along an elliptical orbit as the rotor rotates, and that the magnetic sensor is positioned to detect when the magnet reaches the end of the elliptical orbit on the major axis side. [Effects of the Invention]

[0008] According to the above invention, since the magnet is positioned eccentrically from the center of the rotor, the radius of rotation is increased, making detection by a magnetic sensor possible. Therefore, even if the measuring chamber and rotor are miniaturized, detection of the magnet by a magnetic sensor is possible, making it possible to provide a positive displacement flow meter capable of measuring minute flow rates. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of the positive displacement flow meter according to the present invention. [Figure 2] This is an exploded perspective view of the positive displacement flow meter according to the present invention. [Figure 3] This is a plan view showing the structure of the lower body of the positive displacement flow meter according to the present invention. [Figure 4] This is a cross-sectional view AA in Figure 3. [Figure 5] This is an enlarged view of section C in Figure 4. [Figure 6] This is an enlarged view of section B in Figure 3. [Figure 7] Figure 6 shows an enlarged view of section B, illustrating the transition from the previous state. [Figure 8] Figure 7 shows an enlarged view of section B, illustrating the transition from the previous state to the current state. [Figure 9] Figure 8 shows an enlarged view of section B, illustrating the transition from the previous state. [Figure 10] This is a side cross-sectional view showing the structure of a conventional flow meter. [Figure 11] This is a plan view showing the structure of a conventional flow meter. [Modes for carrying out the invention]

[0010] Hereinafter, a positive displacement flow meter 10 (hereinafter referred to as "flow meter 10") according to an embodiment of the present invention will be described with reference to the drawings. As shown in Figure 1, this flow meter 10 has a lower body 20 to which an inlet-side connecting pipe (not shown) and an outlet-side connecting pipe (not shown) are connected, and an upper body 60 fixed to the lower body 20.

[0011] As shown in Figure 3, a fitting recess 21 is formed on the upper surface of the lower body 20 that can be fitted with the upper body 60. At the bottom of this fitting recess 21, an annular seal groove 22 and a measuring chamber 23 located inside the seal groove 22 are formed to open upward. A ring-shaped sealing member 221 is housed in the seal groove 22. As a result, as shown in Figure 4, when the upper body 60 is fixed above the lower body 20, the space between the lower body 20 and the upper body 60 is sealed by the sealing member 221. This prevents the liquid to be measured supplied into the measuring chamber 23 from flowing out to the outside.

[0012] As shown in Figures 2 and 3, the measuring chamber 23 is a space configured in a substantially cylindrical shape. An inlet 24 and an outlet 25 are formed on the bottom surface 231 of the measuring chamber 23, and an inlet path 241 and an outlet path 251 are continuous to these inlet 24 and outlet 25, respectively. These inlet path 241 and outlet path 251 are continuous to the outer surface of the lower body 20, and connection parts 242 and 252 are formed at the outer openings thereto to which the inlet-side connecting pipe (not shown) and the outlet-side connecting pipe (not shown) are connected.

[0013] As shown in Figure 6, a partition plate 30 is provided between the inlet 24 and the outlet 25 in the measuring chamber 23. This partition plate 30 is a plate-shaped member that extends radially inward from the inner wall 232 of the measuring chamber 23, and is designed so that its thickness is approximately the same as the depth of the measuring chamber 23. Therefore, the liquid to be measured that flows into the measuring chamber 23 from the inlet 24 flows around the partition plate 30 and flows out from the outlet 25. The partition plate 30 is sandwiched in a groove 233 formed in the inner wall 232 of the measuring chamber 23, and is fixed by inserting a fixing pin 26 that is erected at the bottom of the groove 233 of the measuring chamber 23. As the partition plate 30 is sandwiched in the groove 233 and the fixing pin 26 is inserted through it, the partition plate 30 will not shift position even when subjected to the pressure of the liquid being measured or vibrations caused by the rotation of the rotor 50 described later. Furthermore, the partition plate 30 can be easily replaced. In addition, the radial inner end of the partition plate 30 is configured in an arc shape, so when the inner circumference of the notch 53 of the rotor 50 described later comes into contact with the inner end of the partition plate 30, it is less likely to get caught and the rotor 50 can slide smoothly.

[0014] Furthermore, as shown in Figures 5 and 6, a circular guide hole 27 is formed in the center of the bottom surface 231 of the weighing chamber 23. A guide pin 28 is erected in the center of the bottom of this guide hole 27, and this guide pin 28 forms an annular space inside the guide hole 27. A substantially cylindrical eccentric bearing 40, which is rotatably supported by the guide pin 28, is housed in this annular space, and a retaining groove 41 extending in the axial direction is cut out from the outer circumferential surface of the eccentric bearing 40. This retaining groove 41 is configured to be substantially U-shaped in plan view, and its circumferential width and the maximum radial gap between it and the guide hole 27 are approximately the same dimension. Therefore, the guide shaft 52, which is inserted into the retaining groove 41, is held in place by the U-shaped portion of the retaining groove 41 and the inner circumferential surface of the guide hole 27 so as not to tilt.

[0015] As shown in FIGS. 6 to 9, a rotor 50 that can swing and rotate along the inner wall 232 is accommodated in the metering chamber 23 having the above structure. This rotor 50 is composed of a solid disk portion 51 whose plate thickness is substantially the same as the depth dimension of the metering chamber 23, and a cylindrical guide shaft 52 that protrudes from the center of the lower surface of the disk portion 51. This guide shaft 52 is fitted into the holding groove 41 of the eccentric bearing 40 and is rotatably held by the inner peripheral surfaces of the holding groove 41 and the guide hole 27. Further, a notch 53 through which the partition plate 30 can be inserted is provided in the disk portion 51 of the rotor 50. When the guide shaft 52 directed by the eccentric bearing 40 revolves in the guide hole 27, this notch 53 is designed so as not to bite into the partition plate 30, to always have contact at one or more points, and to prevent the disk portion 51 from completely closing the inlet 24 and the outlet 25. Since the notch 53 is fitted to the partition plate 30 in this way, when the guide shaft 52 revolves in the guide hole 27, the disk portion 51 swings around the partition plate 30 as shown in FIGS. 6 to 9. Further, since the inlet 24 and the outlet 25 are always blocked by the disk portion 51 of the rotor 50 and the partition plate 30, the measured liquid flowing into the metering chamber 23 through the inlet 24 presses the rotor 50 toward the outlet 25 and swings and rotates the rotor 50 in the metering chamber 23. Furthermore, the notch 53 is configured such that the opening thereof has the same width L2 as the partition plate 30. Therefore, as shown in FIG. 8, even when the rotor 50 is in the state of being farthest from the partition plate 30, the vicinity of the opening of the notch 53 and the partition plate 30 are in contact with each other, and the inlet 24 and the outlet 25 can continue to be blocked.

[0016] Also, as shown in FIG. 6, a receiving hole 54 is formed through the disk portion 51 of the rotor 50 at a position separated from the notch 53, and a magnet 55 is accommodated in this receiving hole 54. Since this magnet 55 is formed at a position where the receiving hole 54 is eccentric from the center of the rotor 50, when the rotor 50 swings and rotates, it moves along an elliptical orbit having a major diameter L4 longer than the diameter L3 of the circular orbit of the guide shaft 52, as shown by the two-dot chain line in FIG. 9. It is preferable that the dimension of the major diameter L4 of the elliptical orbit is 1.3 times or more the dimension of the diameter L3 of the circular orbit. Further, the magnet 55 is configured to be slightly thinner than the rotor 50 so as not to be caught by the upper main body 60 or the bottom surface 231 of the metering chamber 23 when the rotor 50 swings and rotates.

[0017] Furthermore, the diameter L1 of the rotor 50 is designed to be 5 to 10 times the lateral width L2 of the partition plate 30. Since the diameter L1 of the rotor 50 is designed to be 5 times or more the lateral width L2 of the partition plate 30 in this way, when the rotor 50 swings and rotates, the notch 53 is continuous with both the inlet 24 and the outlet 25, and the situation where the partition plate 30 does not block the space between the inlet 24 and the outlet 25 can be prevented. That is, when the diameter L1 of the rotor 50 is 5 times or more the lateral width L2 of the partition plate 30, it is possible to prevent the measured liquid from flowing directly from the inlet 24 to the outlet 25, thereby preventing a decrease in measurement accuracy. On the other hand, since the diameter L1 of the rotor 50 is designed to be 10 times or less the lateral width L2 of the partition plate 30, the notch 53 through which the partition plate 30 is inserted has a relatively large structure with respect to the diameter L1 of the rotor 50. In particular, when the diameter L1 of the rotor 50 is designed to be 6 to 7 times the lateral width L2 of the partition plate 30, the notch 53 becomes wider with respect to the diameter L1 of the rotor 50, and the space between the inlet 24 and the outlet 25 is blocked by the partition plate 30 and the rotor 50. As a result, the rotor 50 can rotate smoothly even when the flow rate of the measured liquid is very small. As a result, when the diameter L1 of the rotor 50 is designed to be 6 to 7 times the lateral width L2 of the partition plate 30, the flow rate of the measured liquid can be measured with particularly high accuracy.

[0018] The upper body 60 has a fitting projection 61 formed on its lower surface that fits into a fitting recess 21 of the lower body 20, while a bottomed sensor housing 62 is formed on its upper surface. A magnetic sensor 63 is housed in the bottom of this sensor housing 62, as shown in Figure 2, and the magnetic sensor 63 is positioned so that its detection range 64 is located near the vertex on the major axis side of the elliptical orbit of the magnet 55. The magnetic sensor 63 is connected to a display device (not shown) that measures the flow rate of the liquid being measured, and is configured to output a pulse signal to the display device each time the magnet 55 reaches the detection range 64, as shown in Figure 7. The bottom of the sensor housing 62 is set to a thickness that allows the magnetic sensor 63 to detect the magnet 55 mounted on the rotor 50 and does not deform due to the pressure of the liquid being measured.

[0019] The display device includes a storage unit that stores in advance a set discharge amount of the liquid to be measured that is discharged each time the rotor 50 oscillates once, a counter that counts the number of rotations of the rotor 50 from the number of pulse signals from the magnetic sensor 63, and a display screen that calculates and displays the total flow rate of the liquid to be measured from the product of the set discharge amount and the number of rotations of the rotor 50.

[0020] The operation of the flow meter 10, configured as described above, will be explained below. The liquid to be measured, supplied from the inlet piping, flows into the metering chamber 23 through the inlet path 241 and the inlet 24. At this time, since the inlet 24 and the outlet 25 are separated by the rotor 50, the liquid to be measured that has flowed into the metering chamber 23 presses against the outer surface of the rotor 50. As a result, the rotor 50 is pushed towards the outlet 25, and as shown in Figures 6 to 9, the guide shaft 52 revolves along the guide hole 27 and swings around the partition plate 30 while constantly blocking the space between the inlet 24 and the outlet 25. At this time, the liquid to be measured that had accumulated inside the metering chamber 23 is pressed by the swinging rotor 50 and flows out into the outlet piping through the outlet 25 and the outflow path 251.

[0021] When the liquid to be measured flows in, each time the guide shaft 52 rotates once and the rotor 50 oscillates once, the magnet 55 attached to the rotor 50 passes through the detection range 64, and the magnetic sensor 63 transmits a pulse signal to the display device. Therefore, the display device can detect the number of oscillations of the rotor 50 from the received pulse signal, and can calculate and display the flow rate of the liquid to be measured from the product of the set discharge amount and the number of pulse signals.

[0022] When the rotor 50 oscillates, the magnet 55 is eccentrically positioned away from the partition plate 30 and guide shaft 52, which are the center of the rotor 50's oscillation. As a result, the magnet 55 moves along an elliptical path with a major axis L4 that is longer than the diameter L3 of the circular path of the guide shaft 52, as shown in Figure 9. This allows the magnet 55 to move back and forth between the detection range 64 of the magnetic sensor 63, as shown in Figure 7, and a position sufficiently far from the detection range 64 of the magnetic sensor 63, as shown in Figure 9. Consequently, sensing defects such as the magnetic sensor 63 constantly detecting the magnet 55 can be prevented. In other words, because the magnet 55 is eccentrically positioned from the guide shaft 52, the flow meter 10 of this invention has the effect of reducing the travel distance of the magnet 55 compared to when the magnet 55 is on the guide shaft 52, thus reducing the likelihood of sensing defects. As a result, it is possible to reduce the size of the metering chamber 23 and the rotor 50 compared to the conventional flow meter A100, and it becomes possible to measure even minute flow rates.

[0023] In the flow meter 10 with the above structure, the rotor 50 has a solid structure consisting of a disc portion 51 and a guide shaft 52 protruding from the lower surface of the disc portion 51, so that a guide hole 27 can be provided in the bottom surface 231 of the metering chamber 23. This eliminates the cylindrical body A131 and the annular projection A114 located inside the cylindrical body A131, which are prone to damage when the conventional flow meter A100 is scaled down. Furthermore, since the rotor 50 does not have a cylindrical body A131, the disc portion 51 that is pressed by the liquid being measured has a thickness dimension that is approximately the same as the depth of the metering chamber 23, making it possible to have higher strength compared to the rotor A130 of the conventional flow meter A100. Thus, because the rotor 50 of the flow meter 10 of the present invention has a solid structure, when scaled down there are no excessively thin and weak parts, and it has the effect of being less prone to damage and wear during operation.

[0024] Furthermore, since the magnet 55 is housed in a housing hole 54 formed in the disc portion 51 of the rotor 50 rather than in the mounting portion A133, it is possible to maintain the size of the magnet 55 even when the rotor 50 is reduced in size, and there is no risk of the magnet 55 coming off the rotor 50 when the rotor 50 is oscillating.

[0025] Furthermore, since the rotor 50 does not have a cylindrical section A131, the metering chamber 23 can be designed to be shallower by the amount of the cylindrical section A131. This reduces the volume of the metering chamber 23, making it possible to measure even minute flow rates. In addition, because the metering chamber 23 is designed to be shallow, the radial dimensions of the metering chamber 23 and rotor 50 can be increased compared to a conventional flow meter A100 designed with the same volume. As a result, the outer surface of the rotor 50, which is pressed by the liquid being measured, and the guide pin 28, which is the center of the rotor 50's oscillating rotation, are separated. Therefore, even a small force from the liquid being measured with an extremely small flow rate can cause the rotor 50 to oscillate smoothly, resulting in more accurate measurements. Moreover, the notch 53 of the rotor 50 is configured to be relatively large, and the inner surface of the notch 53 is also wide, so the inner surface of the notch 53 is also more easily subjected to pressure from the liquid being measured. Therefore, the rotor 50 can oscillate more smoothly.

[0026] Furthermore, since the rotor 50 does not have a mounting portion A133, the relief groove A121, which would cause the mounting portion A133 to rotate, can be eliminated. Also, since the eccentric bearing 40 is housed in the guide hole 27, there is almost no void in the guide hole 27 through which the liquid to be measured can enter. As a result, measurement errors caused by the liquid to be measured flowing into the relief groove A121 and guide groove A116, which were a problem with conventional flow meters A100, do not occur, and flow rate measurement can be performed with high accuracy.

[0027] Furthermore, the specific configuration of each part is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the present invention. For example, the inflow direction of the liquid to be measured and the eccentric rotation direction of the rotor 50 can be in the opposite direction to those of the embodiments described above without any problem. In addition, the volumetric flow meter 1 according to the present invention can measure the flow rate of water, oil, and various chemical solutions, and by pre-setting the discharge volume according to the type of liquid to be measured, it is possible to measure the flow rate of various liquids to be measured. [Explanation of symbols]

[0028] 10…Positive flow meter 20 … Lower body 23…Measuring room 231… Bottom 24 … Inlet 25 … Outlet 27 … Guide hole 28… Guide pin 30… Partition plate 40... Eccentric bearing 41 … Retaining groove 50… Rotor 51 ... Disc section 52… Guide axis 53… trigger 54 ... Intake 55… Magnet 60… Upper body 63… Magnetic sensor

Claims

1. A measuring chamber equipped with an inlet and outlet for the liquid to be measured, A rotor is housed eccentrically and rotatably along the inner circumferential surface of the metering chamber, A magnet embedded in the upper surface of the rotor at an eccentric position from the center, A magnetic sensor that measures the amount of rotation of the rotor by detecting the aforementioned magnet, A positive displacement flow meter characterized by having the following features.

2. The positive displacement flow meter according to claim 1, characterized in that the magnet moves along an elliptical orbit in accordance with the rotation of the rotor, and the magnetic sensor is arranged to detect when the magnet has reached the end on the major axis side of the elliptical orbit.

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