Positive displacement flow meter

0001The present invention relates to a positive displacement flow meter that is optimal not only for measuring a liquid to be measured with a small flow rate to a minute flow rate but also for measuring a liquid to be measured with a very small flow rate such as an intravenous drip.

0002Conventionally, a positive displacement flow meter has been used to accurately measure the flow rate of the liquid to be measured flowing through the pipes installed in various plants and equipment. Among them, the liquid to be measured has a small to minute flow rate. The rotary piston type flowmeter (hereinafter referred to as a flowmeter) described in Japanese Patent Application Laid-Open No. 9-297045 (Patent Document 1) is often used for the measurement. This type of flow meter 101 includes a flow meter main body 102 to which an inflow side connecting pipe (not shown) and an outflow side connecting pipe (not shown) are connected, as shown in FIG. 13 attached to the present specification. It is composed of an upper lid 103 having a gap 103a in which a magnetoresistive element 115 described later and a display unit 116 for displaying a flow rate from the detection signal thereof are arranged. The flowmeter main body 102 is provided with an annular groove-like measuring chamber S101 including a circumferential wall surface 102a, a partition wall outer peripheral wall surface 102ba of a cylindrical partition wall 102b provided on the center side thereof, and a bottom surface 102c connecting them. ing. Further, the bottom surface 102c has an inflow port (not shown) and an outflow port (not shown) of the liquid to be measured, and the inflow side connection pipe and the outflow side connection pipe are connected to these inflow port and outflow port, respectively. Communicating.

0003The measuring chamber S101 is blocked by a non-magnetic isolation plate 117 on the upper side and a partition plate (not shown) between the inflow port and the outflow port, and the liquid to be measured flowing in from the inflow port is annular. It is configured to pass along the groove-like measuring chamber S101 and flow out from the outlet. Further, in the measuring chamber S101, a bottomed cylindrical rotor 105 composed of a tubular portion 105a and a bottom portion 105b has a bottom portion 105b upward, and a part of the tubular portion outer peripheral surface 105aa is a circumferential wall surface 102a of the measuring chamber S101. In addition, a part of the inner peripheral surface 105ab of the cylinder portion is arranged in contact with the outer peripheral wall surface 102ba of the partition wall.

0004The rotor 105 is provided with a notch (not shown) for guiding the partition plate over the cylinder portion 105a and the bottom portion 105b so that the rotor 105 can swing with the rotation of the rotor shaft 105c described later. It is configured in. Further, a rotor shaft 105c is fixed to the rotor 105 at its center position, and the rotor shaft 105c is rotatably held by a rotatable eccentric bearing 118 in the partition wall 102b, and with the rotation of the eccentric bearing 118. It is configured to revolve and swing the rotor 105 in the measuring chamber S101.

0005In this flow meter 101, when the liquid under test flows in from the inlet, the rotor 105 receives the pressure of the liquid under test and is pushed out to the outlet side, and the rotor shaft 105c revolves (rotates) together with the eccentric bearing 118. At this time, since the rotor shaft 105c can rotate with respect to the eccentric bearing 118, the rotor 105 swings around the partition plate while constantly blocking between the inflow port and the outflow port, and is covered in the measuring chamber S101. The measuring liquid flows out from the outlet. During this period, the rotor shaft 105c, that is, the center position of the rotor 105 rotates with the rotation of the eccentric bearing 118. Therefore, the number of swings of the rotor 105 can be detected by detecting this rotation speed. Therefore, the discharge amount during one reciprocating swing of the rotor 105 is calculated in advance from the volume surrounded by the circumferential wall surface 102a, the volume surrounded by the partition wall outer peripheral wall surface 102ba, the volume of the cylinder portion 105a and the bottom portion 105b of the rotor 105, and the like. Then, the flow rate of the liquid to be measured can be accurately measured from the discharge amount and the number of swings of the rotor 105.

<p num="0006"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 9-297045</text></patcit></p>

<p num="0007"> In the flow meter, when detecting the number of swings of the rotor 105, the bottom 105b of the rotor 105 swings in the measuring chamber S101 in order to detect the number of rotations of the rotor shaft 105c that matches the number of swings of the rotor 105. A magnet 119 is embedded in the center position. The change in the magnetic field generated by the rotation of the magnet 119 is detected by the magnetic resistance element 115 arranged in the gap 103a of the upper lid 103, and the rotation speed of the magnet 119 is also calculated from this rotation speed of the rotor shaft 105c. That is, the number of swings of the rotor 105 is detected. Therefore, the wall thickness of the rotor 105 needs to be thickened so that the magnet 119 can be embedded, and the mass of the rotor 105 is increased accordingly. As a result, the frictional resistance between the rotor 105 and each wall surface of the measuring chamber S101 increases, but the pressure of the liquid to be measured flowing from the inflow port is sufficient for measuring the flow rate of the liquid to be measured from a small flow rate to a minute flow rate. Since the rotor 105 swings in the measuring chamber S101 without any trouble, accurate measurement is possible. However, the liquid to be measured flowing in from the inflow port has a very small flow rate such as drip. Then, since the pressure of the liquid to be measured is extremely small, it becomes difficult for the rotor 105 to swing smoothly because the mass becomes large and the frictional resistance at the contact portion with each wall surface of the measuring chamber S101 becomes large as described above. .. Therefore, it is not possible to obtain an accurate number of swings of the rotor 105 for a very small flow rate of the liquid to be measured, and therefore, there is a problem that accurate measurement cannot be performed.</p><p num="0008"> Further, in the above-mentioned flow meter, the rotation speed of the rotor shaft 105c, that is, the number of swings of the rotor 105 is detected by detecting the change in the magnetic field due to the rotation of the magnet 119 embedded in the rotor 105 by the magnetic resistance element 115. It has been. Therefore, the isolation plate 117 that shields the measuring chamber S101 from the inside of the gap 103a in which the magnetoresistive element 115 and the display unit 116 are arranged must be made as thin as possible, and the pressure resistance of the measuring chamber S101 is lowered. However, there is a problem that it is not suitable for measuring a high-pressure liquid under test.</p><p num="0009"> Furthermore, in the above-mentioned flowmeter, since the magnet 119 is embedded in the rotor 105, it is necessary to apply a corrosion-resistant resin coating treatment to the magnet 119. Therefore, deterioration of the corrosion resistance due to aging must be taken into consideration. This has caused problems such as shortening the life of the flow meter.</p><p num="0010"> An object of the present invention is to eliminate the problems exemplified above, and accurately measure not only a liquid to be measured with a small flow rate to a minute flow rate but also a liquid to be measured with a very small flow rate such as an intravenous drip. To provide the optimum positive displacement flowmeter for this purpose.</p>

<p num="0011"> In order to achieve the above object, the present invention is formed by a peripheral wall surface, a partition wall outer peripheral wall surface of a partition wall provided on the center side thereof, and a bottom surface connecting them and having an inlet and an outlet for the liquid to be measured. A flow meter main body provided with a measuring chamber, a cylinder portion and a bottom portion, and the bottom portion is arranged to face the bottom surface via the cylinder portion, and a part of the outer peripheral surface of the cylinder portion is placed on the circumferential wall surface of the measuring chamber and inside the cylinder portion. A rotor that swings in the measuring chamber while a part of the peripheral surface is in contact with or close to the outer peripheral wall surface of the partition wall, and a rotor is guided so that the rotor swings while maintaining contact with or close to each wall surface of the measuring chamber. It is a positive displacement flow meter having a rotor shaft, and is characterized in that an ultrasonic transmitting unit and an ultrasonic receiving unit are arranged at a position where the passage of a rotor in the measuring chamber is detected. According to this configuration, since the number of swings of the rotor having a predetermined discharge amount is detected by the ultrasonic receiving unit arranged in the flow meter main body, it is not necessary to embed a magnet in the bottom of the rotor. Therefore, the frictional resistance between the rotor and each surface of the measuring chamber can be reduced by reducing the wall thickness of the bottom of the rotor to reduce the weight of the rotor. As a result, the rotor can swing smoothly, and the contact between the rotor and each surface of the measuring chamber or the leakage of the liquid to be measured from the vicinity is reduced, and the liquid to be measured is measured from a small flow rate to a minute flow rate. Not only can the above be performed more accurately, but even if the liquid to be measured has a very small flow rate such as drip, the rotor swings smoothly due to the pressure, and accurate measurement can be performed. It is possible to provide an optimum flow meter not only for measuring a liquid to be measured but also for measuring a liquid to be measured having a very small flow rate.</p><p num="0012"> In addition, since a magnet is not used to detect the number of swings of the rotor, not only can a steel top lid be used to seal the measuring chamber, but also a non-magnetic material even when a separating plate is used in addition to the top lid. Eliminates the need to use. In addition, it is not necessary to consider the thickness of the isolation plate of the measuring chamber, and it is possible to provide a positive displacement flow meter with a high withstand voltage design by making it sufficiently thick, as well as machining for embedding a magnet in the rotor and a magnet. It is not necessary to apply a corrosion-resistant resin coating treatment to the magnet, and it is possible to provide a positive displacement flowmeter that is inexpensive to manufacture and has a long life.</p><p num="0013"> Furthermore, in order to improve the resolution of the flow rate per rotation of the rotor by generating four pulse signals from the detection signal of the ultrasonic receiver while the rotor swings once, the outer peripheral surface of the rotor cylinder and weighing When the line connecting the contact point on the circumferential wall surface of the chamber and the contact point on the inner peripheral surface of the cylinder part of the rotor and the contact point on the outer peripheral wall surface of the partition wall is at or near the position where it overlaps with the ultrasonic receiver, and from this position, the rotor shaft rotates 180 degrees. It is desirable to arrange the ultrasonic receiver at a position away from the circumferential wall surface, the outer peripheral wall surface of the partition wall, or both in a plan view, at least when it is at or near the position. Specifically, the ultrasonic receiving unit may be arranged at the above-mentioned position so as not to detect or substantially detect the cylinder portion of the rotor.</p><p num="0014"> On top of that, the rotor axis is 90 degrees from the position where the line connecting the contacts on the outer peripheral surface of the rotor cylinder and the circumferential wall surface of the measuring chamber and the contacts on the inner peripheral surface of the rotor cylinder and the outer peripheral wall surface of the partition wall overlaps the ultrasonic receiver. It is even more desirable to arrange the ultrasonic receiver so that the cylinder of the rotor is detected at the maximum when it is at or near the rotating position and the 270 degree rotating position.</p>

<p num="0015"> According to the present invention described above, the wall thickness of the bottom of the rotor is determined by detecting the number of swings of the rotor that swings in the measuring chamber due to the inflow of the liquid to be measured by the ultrasonic transmitter and the ultrasonic receiver. By making the rotor thinner, we can reduce the weight of the rotor, and provide a positive displacement flow meter that is ideal not only for measuring liquids to be measured from small to minute flow rates, but also for measuring liquids to be measured with extremely small flow rates such as drip. can do.</p>

0016<figref num="1">The vertical sectional view of the positive displacement flow meter which concerns on 1st Embodiment of this invention.</figref><figref num="2">Exploded view of the positive displacement flow meter according to the first embodiment of the present invention.</figref><figref num="3">AA line sectional view of FIG.</figref><figref num="4">Explanatory drawing of the first half part of one rotation of a rotor shaft which shows the positional relationship between the ultrasonic wave receiving part and the rotor and the receiving state of the ultrasonic wave receiving part by 45 degree rotation of the rotor shaft which concerns on 1st Embodiment of this invention.</figref><figref num="5">Explanatory drawing of the latter half of one rotation of a rotor shaft which shows the positional relationship between the ultrasonic wave receiving part and the rotor and the receiving state of the ultrasonic wave receiving part which concerns on 1st Embodiment of this invention every 45 degree rotation of a rotor shaft.</figref><figref num="6">The waveform diagram which processed the output signal of the ultrasonic wave receiving part which concerns on 1st Embodiment of this invention.</figref><figref num="7">The vertical sectional view of the positive displacement flow meter which concerns on 2nd Embodiment of this invention.</figref><figref num="8">BB line sectional view of FIG.</figref><figref num="9">Explanatory drawing of the first half part of one rotation of a rotor shaft which shows the positional relationship between the ultrasonic wave receiving part and the rotor and the receiving state of the ultrasonic wave receiving part which concerns on 2nd Embodiment of this invention every 45 degree rotation of a rotor shaft.</figref><figref num="10">Explanatory drawing of the latter half of one rotation of a rotor shaft which shows the positional relationship between the ultrasonic wave receiving part and the rotor and the receiving state of the ultrasonic wave receiving part which concerns on 2nd Embodiment of this invention every 45 degree rotation of a rotor shaft.</figref><figref num="11">The waveform diagram which processed the output signal of the ultrasonic wave receiving part which concerns on 2nd Embodiment of this invention.</figref><figref num="12">The explanatory view which shows the modification of the positional relationship between the ultrasonic wave receiving part and the rotor which concerns on 2nd Embodiment of this invention.</figref><figref num="13">Sectional drawing of the positive displacement flow meter which concerns on a conventional example.</figref>

0017(First Embodiment) Hereinafter, a rotary piston type flowmeter (hereinafter referred to as a flowmeter) according to the first embodiment of the present invention will be described with reference to the drawings. As shown in FIGS. 1 to 3, the flow meter 1 covers the flow meter main body 2 having an inflow side connecting pipe (not shown) and an outflow side connecting pipe (not shown), and the upper portion thereof. It has an upper lid 3 that seals the measuring chamber S1 described later. The flowmeter main body 2 is provided with an annular groove-like measuring chamber S1 composed of a circumferential wall surface 2a, a partition wall outer peripheral wall surface 2ba of a cylindrical partition wall 2b formed on the center side thereof, and a bottom surface 2c connecting them. ing. The bottom surface 2c of the measuring chamber S1 is provided with an inflow port 2d and an outflow port 2e, and the inflow side connection pipe and the outflow side connection pipe communicate with each other at the inflow port 2d and the outflow port 2e. Further, a partition plate 4 is arranged between the circumferential wall surface 2a and the partition wall 2b of the measuring chamber S1 so as to block the inflow port 2d and the outflow port 2e, and the inflow from the inflow side connection pipe is measured. The liquid is configured to pass through the inflow port 2d, the annular groove-like measuring chamber S1 and the outflow port 2e in this order, and flow out from the outflow side connecting pipe. Even if the upper lid 3 has a site display type structure including an isolation plate (not shown) for sealing the measuring chamber S1 and a gap (not shown) for accommodating the display unit (not shown). Good.

0018The upper end of the partition wall 2b of the flow meter main body 2 is formed so as to recede from the upper end surface of the circumferential wall surface 2a, and the bottom portion 5b of the rotor 5 described later can be positioned so as to face the upper lid 3. It has become. Further, a guide shaft 6 is press-fitted inside the partition wall 2b of the flow meter main body 2 at the center thereof, and the guide shaft 6 and the partition wall inner peripheral wall surface 2bb guide the rotor shaft 5c described later. Guide groove S2 is formed.

0019In the measuring chamber S1, a bottomed cylindrical rotor 5 having a cylinder portion 5a and a bottom portion 5b arranges the bottom portion 5b of the bottom portion 5b with the cylinder portion 5a facing the bottom surface 2c, and further, the outer peripheral surface of the cylinder portion 5aa. A part of the measuring chamber S1 is arranged on the circumferential wall surface 2a, and a part of the inner peripheral surface 5ab of the cylinder portion is arranged in contact with or close to the partition wall outer peripheral wall surface 2ba. The bottom portion 5b of the rotor 5 is formed with a recess located on the upper surface side thereof and a communication hole 5d that communicates the recess and the inside of the cylinder portion 5a so that the rotor 5 and the upper lid 3 do not stick to each other. It has become. The rotor 5 has a rotor shaft 5c formed so as to project downward from the center of the bottom portion 5b, and the rotor shaft 5c is guided by the guide groove S2 and is configured to revolve. Further, the rotor shaft 5c may be formed integrally with the rotor 5 or may be formed separately.

0020The rotor 5 is provided with a notch 5e for guiding the partition plate 4 over the tubular portion 5a and the bottom portion 5b, and when the rotor shaft 5c is guided by the guide groove S2 and revolves, the notch 5e is provided. It is configured so that it does not bite into the partition plate 4. With this configuration, the bottom side of the rotor 5 is in contact with the upper lid 3, a part of the outer peripheral surface 5aa of the cylinder is in contact with the circumferential wall surface 2a of the measuring chamber S1, and a part of the inner peripheral surface 5ab of the cylinder is in contact with the outer wall surface 2ba of the partition wall. It is possible to swing around the partition plate 4 while the rotation is restricted by the partition plate 4 while maintaining a close state.

0021Next, an ultrasonic transmitting unit and an ultrasonic receiving unit for detecting the swing of the rotor 5, which is a main part of the present invention, will be described. The ultrasonic wave transmitting unit and the ultrasonic wave receiving unit are a disk-shaped transmitting side piezoelectric element 7 and a receiving side piezoelectric element 8, which are examples of an oscillator, respectively. The transmitting side piezoelectric element 7 can transmit ultrasonic waves when a voltage is applied between the two electrodes, and the receiving side piezoelectric element 8 receives a mechanical force from the ultrasonic waves between the two electrodes. It has a structure that generates a voltage. Further, the transmitting side piezoelectric element 7 and the receiving side piezoelectric element 8 are housed in the end portions of the transmitting side sensor holder 9 and the receiving side sensor holder 10, respectively, and these are housed in the measuring chamber S1 with the receiving side piezoelectric element 8 facing upward. It is arranged so as to sandwich it. That is, the transmitting side piezoelectric element 7 and the transmitting side sensor holder 9 are placed in the stepped storage hole 2f formed on the lower surface side of the flow meter main body 2 by the transmitting side holder holder 12 via the packing 11, and the receiving side piezoelectric element. Similarly, the 8 and the receiving side sensor holder 10 are attached to the upper surface of the upper lid 3 by the receiving side holder holder 14 via the packing 13. Glycerin (not shown) is injected between the upper surface of the transmitting side piezoelectric element 7 and the ceiling surface of the stepped storage hole 2f, and between the lower surface of the receiving side piezoelectric element 8 and the upper surface of the upper lid 3. The degree of adhesion is increased. As a result, the ultrasonic waves transmitted from the transmitting side piezoelectric element 7 are transmitted toward the receiving side piezoelectric element 8 without being blocked by the air layer, and the ultrasonic waves reaching the upper surface of the upper lid 3 are blocked by the air layer. A structure is obtained in which the piezoelectric element 8 on the receiving side is reached without being damaged. Due to its characteristics, the ultrasonic waves are attenuated according to the number of media transmitted before reaching the receiving side piezoelectric element 8 and the transmission distance thereof. The larger the number of transmitted media and the longer the transmission distance, the more attenuated. The amount will be large. Due to this characteristic, as the rotor 5 passes between the transmitting side piezoelectric element 7 and the receiving side piezoelectric element 8, the detection signal of the receiving side piezoelectric element 8 reached by the ultrasonic waves changes every moment.

0022As shown in FIG. 3, the mounting position of the receiving side piezoelectric element 8 is on an extension of the line connecting the partition plate 4 and the center of the partition wall 2b in a plan view, and the edge of the receiving side piezoelectric element 8 is a measuring chamber. It is in contact with the circumferential wall surface 2a forming S1, and the edge on the opposite side is the position where the wall thickness of the cylinder portion 5a of the rotor 5 is separated from the partition wall outer wall surface 2ba (hereinafter referred to as the rotor shaft original position). The mounting position of the receiving side piezoelectric element 8 provides a configuration in which the receiving side piezoelectric element 8 does not detect the tubular portion 5a of the rotor 5 when the rotor shaft 5c is at a 180 ° rotation position from the rotor shaft original position.

0023The lead wires 15a and 15b connected to the electrodes (not shown) of the transmitting side piezoelectric element 7 and the receiving side piezoelectric element 8 are the sensor holders 9 of the transmitting side and the receiving side, respectively, as shown in FIGS. 1 and 2. , 10, packings 11, 13 and holder retainers 12, 14 are taken out through the through holes 9a, 10a, 11a, 13a, 12a, 14a, respectively. The lead wire 15a of the transmitting side piezoelectric element 7 is guided by a lead wire taking-out groove 2g provided in communication with the stepped storage hole 2f, and the lead wire 15b of the receiving side piezoelectric element 8 is directly connected to the receiving side holder. It is taken out from the retainer 14.

0024In the above flowmeter, when the liquid to be measured flows into the measuring chamber S1 from the inflow port 2d, the rotor 5 receives the pressure of the liquid to be measured and is pushed out to the outflow port 2e side as shown in FIG. 4A. The rotor shaft 5c revolves along the annular guide groove S2 in the bulkhead 2b. At this time, as shown in FIGS. 4 (b) to 4 (d) and 5 (e) to 5 (h), the rotor 5 is a partition plate while constantly blocking between the inflow port 2d and the outflow port 2e. It swings around 4 so that the liquid under test in the measuring chamber S1 can flow out from the outlet 2e. During this period, the ultrasonic waves transmitted from the transmitting side piezoelectric element 7 (transmitted by the voltage applied in a predetermined cycle) are transmitted from the rotor 5 as shown in FIGS. 4 (a), 4 (b) and 5 (h). When the notch 5e is closer to the partition wall 2b, that is, when the rotor shaft 5c is in the rotor shaft original position (0 °), 45 ° rotation position from the rotor shaft original position, and 315 ° rotation position, ultrasonic waves are emitted. The number of permeating media increases. Further, since the area of the tubular portion 5a having a long transmission distance is also large, the amount of attenuation of the ultrasonic wave is large, and the detection signal of the receiving side piezoelectric element 8 reached by the ultrasonic wave is a small value.

0025On the other hand, as shown in FIGS. 4 (d), 5 (e) and 5 (f), when the notch 5e of the rotor 5 is closer to the circumferential wall surface 2a side of the measuring chamber S1, that is, the rotor shaft. When 5c is near the rotation position of 135 °, the rotation position of 180 °, and the rotation position of 225 ° from the original position of the rotor axis, the medium through which ultrasonic waves pass is only the liquid under test, and the number is the minimum. Therefore, the amount of attenuation of the ultrasonic wave is small, and the detection signal of the receiving side piezoelectric element 8 reached by the ultrasonic wave becomes a large value. As a result, each time the rotor shaft 5c makes one rotation and the rotor 5 reciprocates once, the receiving side piezoelectric element 8 outputs a detection signal of output characteristics in which one peak value is obtained as shown in FIG. can do. Therefore, since the number of swings of the rotor 5 can be detected from this detection signal, it is not necessary to embed a magnet in the bottom 5b of the rotor 5. As a result, the wall thickness of the bottom portion 5b of the rotor 5 can be reduced to reduce the weight of the rotor 5, and the frictional resistance between the rotor 5 and each surface of the measuring chamber S1 can be reduced, so that the rotor 5 can swing smoothly. Along with this, leakage of the liquid to be measured from the contact portion between the rotor 5 and each wall surface of the measuring chamber S1 is reduced, and the measurement of the liquid to be measured from a small flow rate to a minute flow rate can be performed more accurately. In addition, even if the liquid to be measured has a very small flow rate such as an intravenous drip, the rotor 5 can swing smoothly even with the pressure, so accurate measurement is possible, and the flow rate is small to small. It is possible to provide an optimum flow meter not only for measuring the liquid to be measured at a flow rate but also for measuring a liquid to be measured at a very small flow rate.

0026Further, since the number of swings of the rotor 5 is detected from the detection signal of the receiving side piezoelectric element 8, it is not necessary to use a magnet when detecting the number of swings of the rotor 5, and the measuring chamber S1 is sealed. A steel top lid 3 can be used. Further, even when a separating plate (not shown) is used in addition to the upper lid 3, it is not necessary to use a non-magnetic material, and it is not necessary to consider the thickness thereof. It is possible to provide a positive displacement flow meter that is sufficiently thick and has a high withstand voltage design. Moreover, it is not necessary to perform machining for embedding the magnet in the rotor 5 or to apply a corrosion-resistant resin coating treatment to the magnet, and it is possible to provide a positive displacement flowmeter that is inexpensive to manufacture and has a long life.

0027(Second embodiment) Next, the flow meter according to the second embodiment of the present invention will be described. As shown in FIGS. 7 and 8, the flow meter 51 has the same structure as the flow meter of the first embodiment, and has a configuration in which only the mounting positions of the transmitting side piezoelectric element 57 and the receiving side piezoelectric element 58 are different. The description of the overall structure and the mounting structure of the transmitting side piezoelectric element 57 and the receiving side piezoelectric element 58 will be omitted. The transmitting side piezoelectric element 57 and the receiving side piezoelectric element 58 are arranged at positions sandwiching the measuring chamber S51 with the receiving side piezoelectric element 58 facing upward as in the first embodiment. The mounting positions of the transmitting side piezoelectric element 57 and the receiving side piezoelectric element 58 are on an extension of the line connecting the partition plate 54 of the measuring chamber S51 formed in the plan view flow meter main body 52 and the center of the partition wall 52b. The edge of the receiving side piezoelectric element 58 is at a position where the wall thickness of at least the cylinder portion 55a of the rotor 55 is separated from the circumferential wall surface 52a of the measuring chamber S51, and the opposite edge is at a position where it is in contact with the outer peripheral wall surface 52ba of the partition wall. There is. The mounting position of the receiving side piezoelectric element 58 provides a configuration in which the receiving side piezoelectric element 58 does not detect the tubular portion 55a of the rotor 55 when the rotor shaft 55 is in the rotor shaft original position. Further, this mounting position provides a configuration in which the cylinder portion of the rotor 55 is detected at the maximum when the rotor shaft 55c is at or near the position where the rotor shaft 55c is rotated 90 degrees and 270 degrees from the original position of the rotor shaft. The above-mentioned mounting position is not limited to the extension of the line connecting the partition plate 54 and the center of the partition wall 52b, but is not limited to the contact points of the outer peripheral surface 55aa of the cylinder portion of the rotor 55 and the circumferential wall surface 52a of the measuring chamber S51. The same setting can be made as long as the line connecting the contact points of the inner peripheral surface 55ab of the cylinder portion of the rotor 55 and the outer peripheral wall surface 52ba of the partition wall overlaps with the receiving side piezoelectric element 58.

0028In the above flow meter, when the liquid to be measured flows into the measuring chamber S51 from the inflow port 52d, the rotor 55 receives the pressure of the liquid to be measured and is pushed out to the outflow port 52e side as shown in FIG. 9A. The rotor shaft 55c revolves (rotates) along the annular guide groove S52 in the partition wall 52b. At this time, as shown in FIGS. 9 (b) to 9 (d) and 10 (e) to 10 (h), the rotor 55 is a partition plate while constantly blocking between the inflow port 52d and the outflow port 52e. It swings around 54, and the liquid under test in the measuring chamber S51 can flow out from the outlet 52d. During this period, the ultrasonic waves transmitted from the transmitting side piezoelectric element 57 (transmitted by the voltage applied in a predetermined cycle) are transmitted from the rotor 55 as shown in FIGS. 9 (a), 9 (b) and 10 (h). When the notch 55e is closer to the bulkhead 52b, that is, between the rotor shaft 55c rotation position of 315 ° from the rotor shaft original position and the rotation position of 45 ° from the rotor shaft original position including the rotor shaft original position (0 °). Most pass through the bottom 55b of the rotor 55 when in the vicinity. As a result, this ultrasonic wave is attenuated by passing through the bottom portion 55b, but the amount of attenuation is small because it is not affected by the tubular portion 55a and the transmission distance of the ultrasonic wave is short. Therefore, the detection signal of the receiving side piezoelectric element 58 reached by this ultrasonic wave becomes a large value. Further, as shown in FIGS. 9 (d), 10 (e) and 10 (f), when the notch 55e of the rotor 55 is closer to the circumferential wall surface 52a side of the measuring chamber S51, that is, the rotor shaft 55c is the rotor. When it is in the vicinity between the rotation position of 225 ° including the rotation position of 135 ° and the rotation position of 180 ° from the original position of the axis, the medium through which most ultrasonic waves pass is slightly affected by the cylinder 55a. The number of the liquid under test is the smallest, and the amount of attenuation is small. Therefore, the detection signal of the receiving side piezoelectric element 58 reached by this ultrasonic wave becomes a large value.

0029On the other hand, in the ultrasonic wave, as shown in FIGS. 9 (c) and 10 (g), when the notch 55e of the rotor 55 is at an intermediate position between the circumferential wall surface 52a and the partition wall 52b of the measuring chamber S51, that is, When the rotor shaft 55c is at or near the rotation position of 90 ° and 270 ° from the original position of the rotor shaft, the area of the cylinder portion 55a of the rotor 55 passing in front of the receiving side piezoelectric element 58 is maximized. .. Further, since the tubular portion 55a has a long tubular portion and a long transmission distance, the ultrasonic wave is greatly attenuated by that amount, so that the detection signal of the receiving side piezoelectric element 58 reached by the ultrasonic wave becomes a small value. Therefore, each time the rotor shaft 55c makes one rotation and the rotor 55 reciprocates once, the receiving side piezoelectric element 58 outputs a detection signal of output characteristics having two peak values as shown in FIG. Can be done. Therefore, not only can the number of swings of the rotor 55 be reliably detected from this detection signal, but also two pulse signals, for a total of four pulse signals, can be generated from each of the peak values, and the rotor 55 swings once. It is possible to generate four flow rate pulses per number of times to improve the resolution of the flow rate per rotation of the rotor.

0030As a modification of the positional relationship between the transmitting side piezoelectric element 57 and the receiving side piezoelectric element 58 according to the second embodiment of the present invention, as shown in FIG. 12, the mounting position of the receiving side piezoelectric element 58 is set in a plan view measuring chamber. On the extension line connecting the partition plate 54 of S51 and the center of the partition wall 52b, the edge of the receiving side piezoelectric element 58 is from the circumferential wall surface 52a and the partition wall outer peripheral wall surface 52ba of the measuring chamber S51 to the cylinder portion 55a of the rotor 55, respectively. It may be a position where the wall thickness is separated. In this case, when the notch 55e of the rotor 55 is closer to the circumferential wall surface 52a side of the measuring chamber S51, that is, the rotor shaft 55c is 225 ° including the rotation position of 135 ° and the rotation position of 180 ° from the original position of the rotor shaft. When it is near between the rotation positions, the ultrasonic waves from the transmitting side piezoelectric element 57 can be improved so as to reach the receiving side piezoelectric element 58 with almost no transmission through the cylinder portion 55a of the rotor 55. Therefore, when the notch 55e of the rotor 55 is closer to the circumferential wall surface 52a side of the measuring chamber S51, the amount of attenuation of the ultrasonic wave is further smaller than that of the second embodiment, so that the receiving side where the ultrasonic wave reaches. The detection signal of the piezoelectric element 58 becomes an even larger value. As a result, the receiving side piezoelectric element 58 can output a detection signal having a large height difference characteristic that facilitates signal processing for obtaining a flow rate signal, and four flow rate pulses per number of swings of the rotor. Can be reliably generated. Further, in the flowmeter according to any of the embodiments, the mounting position of the above-mentioned receiving side piezoelectric elements 8 and 58 is not limited to the position where the cylinder portions 5a and 55a of the rotors 5 and 55 are not detected. , It may be a position where it is hardly detected, that is, a position where the cylinder portions 5a, 55a of the rotors 5, 55 are slightly detected. Further, the mounting position of the receiving side piezoelectric elements 8,58 may be any position as long as it can detect the passage of the rotors 5,55, and may be a position where the ultrasonic waves reflected by the rotors 5,55 are detected. In this case, the area through which the tubular portions 5a, 55a of the rotors 5, 55 pass is detected, and the rotor 5, 55 is detected from this area. The number of swings of 55 can be detected. Moreover, in the flowmeter according to any embodiment, the receiving side piezoelectric elements 8 and 58 are not limited to the disk shape, and may be a rectangular plate shape.

0031Although the embodiment of the present invention has been described, the specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

00321 ... Rotary piston type flow meter 2 ... Flowmeter body 2a ... Circumferential wall 2b ... bulkhead 2ba ... partition wall outer wall 2c ... bottom 2d ... inlet 2e ... outlet 5 ... rotor 5a ... Cylinder 5aa ... Cylinder outer peripheral surface 5ab ... Inner circumference of cylinder 5b ... bottom 5c ... rotor shaft 7 ... Transmitter piezoelectric element 8 ... Piezoelectric element on the receiving side S1 ... Weighing room