JP4954177B2 - Flow sensor - Google Patents

Description

  The present invention relates to a flow rate sensor including an impeller provided in a conduit through which a fluid flows and a magnetic sensor that detects a magnetic field of a magnetic pole provided on the outer periphery of the impeller from the outside of the conduit.

  As a conventional flow sensor of this type, for example, a sensor in which an impeller is provided in a pipe and the impeller is rotated by the flow of fluid in the pipe is known. The tip of the impeller blade is magnetized and provided with a magnetic pole. The rotational speed of the impeller increases and decreases in proportion to the flow velocity. On the other hand, a magnetic sensor is attached to the outside of the pipe, and a magnetic field that changes as the impeller rotates is detected by the magnetic sensor.

The rotational speed of the impeller can be detected from the output signal from the magnetic sensor. Since the number of rotations is proportional to the flow velocity in the pipeline as described above, the flow rate of the fluid in the pipeline can be obtained from the cross-sectional area in the pipeline and the flow velocity (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2000-009503 (FIG. 1)

  In the flow rate sensor as described above, the impeller is rotated by the fluid flow. However, if the impeller is formed relatively large, the impeller does not rotate with a small force, so the sensitivity at a low flow rate becomes dull. Does not rotate in proportion to the flow velocity. On the other hand, if the impeller is formed to be relatively small, the impeller's own weight is reduced, and it is possible to rotate the impeller stably even at a low flow rate. There arises a problem that the bearing portion is easily worn.

  In view of the above problems, an object of the present invention is to provide a flow sensor capable of improving sensitivity at a low flow rate and solving problems such as wear at a large flow rate.

  In order to solve the above problems, a flow sensor according to the present invention is provided with an impeller having a magnetic pole at the tip of a blade and rotating by the flow of the fluid in the middle of a conduit through which the fluid flows, and detecting the number of rotations of the impeller. Therefore, in the flow rate sensor having a magnetic sensor for detecting the magnetic field generated by the magnetic pole at the tip of the impeller from the outside of the conduit, the impeller is provided to be movable in the flow direction, and the flow of the fluid is received. The impeller is provided with a fluid receiving portion for moving the vehicle downstream, the braking impeller that rotates without moving in the flow direction due to the flow of the fluid is provided on the downstream side of the impeller, and the impeller and the braking impeller An urging means for urging in a direction to separate them from each other, and when the impeller approaches the braking impeller to a predetermined distance against the urging force of the urging means, the impeller and the braking impeller Connect both impellers Providing the coupling mechanism for rotating at a speed characterized.

  According to the above configuration, since the force for moving the impeller generated by the fluid receiving portion receiving the flow at the low flow rate is small, the impeller is moved downstream against the elastic force of the elastic means. Never move. Therefore, the impeller rotates independently from the braking impeller.

  As the flow velocity increases, the force that moves the impeller downstream increases, and the impeller gradually approaches the braking impeller against the biasing force. When the distance between the two impellers approaches a predetermined distance, the impeller and the braking impeller are connected by the connection mechanism, so that the mass of the impeller has increased to the total mass of both impellers, and the rotational speed of the impeller is Decelerated. When the flow velocity decreases, the urging means separates the distance between the impeller and the braking impeller again, so that the connection by the connecting mechanism is released.

  In addition, the said impeller can be rotatably attached to the rotating shaft extended in the upstream along the rotating shaft line of the said brake impeller.

  As is apparent from the above description, the present invention is highly sensitive because the impeller can rotate independently at a low flow rate, and the impeller rotates in conjunction with the braking impeller as the flow rate increases. It does not easily occur and does not cause problems such as wear.

  Referring to FIG. 1, P is a conduit through which water as a fluid flows. A resin sleeve 1 was inserted into the pipe P, and a braking impeller 2 was rotatably held by the sleeve 1. A rectifying fin 11 for rotating the water flow is provided at the upstream end of the sleeve 1. An impeller 3 is attached to a rotating shaft 21 extending upstream from the braking impeller 2. The impeller 3 is rotatable with respect to the rotation shaft 21 and is movable with respect to the axis of the rotation shaft 21, that is, the water flow direction. Further, a spring member 4 as an urging means is inserted between the impeller 3 and the braking impeller 2 so that the urging force acts in the direction of widening the interval between the impeller 3 and the braking impeller 2. Is formed. A magnetic sensor 5 is attached to the outer periphery of the pipe P, and an output signal of the magnetic sensor 5 is input to the arithmetic unit 6.

  Referring to FIG. 2, the braking impeller 2 is formed with four blades 2a, 2b, 2c, 2d, and a rotating shaft 21 is provided on the upper part. Of each blade, the tip of the blade 2a is magnetized to the N pole, and the tip of the blade 2b is magnetized to the S pole. The remaining blades 2c and 2d are not magnetized, and therefore no magnetic pole is provided at the tip.

  In addition, a concave engagement recess 23 serving as a coupling mechanism is formed on the upper edge of the blade 2a, and a notch-shaped relief portion 22 is formed on the upper edge of the remaining blades 2b, 2c, 2d. Yes.

  Four blades 3a, 3b, 3c, 3d are formed on the impeller 3, and a fluid receiving portion 31 formed of a cross-shaped horizontal surface is formed on the upper surface of each blade 3a, 3b, 3c, 3d. . In addition, an engaging convex portion 32 that engages with the engaging concave portion 23 to form a coupling mechanism is formed at the lower portion of the blade 3a. The blades 3a and 3c are both magnetized to the N pole, and the blades 3b and 3d are magnetized to the S pole.

  The spring member 4 includes two upper and lower washers 41 and a belt-like elastic deformation portion 42 that connects both washers 41. When an external force in the compression direction is applied from the up and down direction, the elastic deformation portion 42 is deformed and the interval between both washers 41 is reduced. However, when there is no external force, the elastic deformation portion 42 is restored and the interval between both washer portions 41 is increased. Function as.

  According to the above configuration, when the water flow passes through the rectifying fins 11 and becomes a rotating flow, the rotating flow acts on each blade of the impeller 3 and the braking impeller 2 to rotate both the impellers 2 and 3. However, since the impeller 3 is located upstream from the braking impeller 2 and the frictional force and mass that inhibit the rotation are small, the impeller 3 starts rotating at a low flow rate, and the rotation speed rapidly increases in response to the increase in the flow rate. To do. On the other hand, the braking impeller 2 has low sensitivity at a low flow rate, and the increase speed of the rotational speed is slow as the flow rate increases.

  Referring to FIG. 3, in a state where the flow velocity is low and the distance between impeller 3 and braking impeller 2 is widened by spring member 4, engagement convex portion 32 engages with engagement concave portion 23. Therefore, as shown in FIG. 3A, the blade 3a and the blade 2a rotate individually without being synchronized with each other. As described above, the rotation speed of the blade 3a is faster than the rotation speed of the blade 2a.

  When the flow velocity increases and the impeller 3 moves to the downstream side, that is, the braking impeller 2 side by the water flow received by the fluid receiving portion 31, the engaging convex portion 32 becomes the engaging concave portion 23 as shown in FIG. Engage. Since the impeller 3 always tries to rotate at a higher speed than the braking impeller 2, the engaging convex portion 32 keeps being pressed against the engaging concave portion 23, and therefore the impeller 3 and the braking impeller 2 and rotate at the same speed in synchronization. When the flow velocity decreases and the impeller 3 returns to the upstream side, the state returns to the state shown in FIG. 3A, and the impeller 3 and the braking impeller 2 again rotate independently of each other.

  Referring to FIG. 4, L1 is a graph showing the relationship between the flow rate and the rotational speed when the impeller 3 rotates alone, and L2 rotates with the impeller 3 and the braking impeller 2 connected to each other. It is a graph which shows the relationship between the flow volume in case, and rotation speed.

  When the flow velocity gradually increases from the state where the flow is stopped, the impeller 3 immediately starts rotating (point a), and the rotational speed increases along L1. When the speed is increased to the point b, the impeller 3 and the braking impeller 2 are connected as described above, so that the rotational speed is rapidly decelerated to the point c. Thereafter, the rotational speed increases along L2 while maintaining the connected state.

  Next, when the flow velocity decreases from that state, the connection between the impeller 3 and the braking impeller 2 is released when the rotational speed decelerates to point d along L2, and the rotational speed increases rapidly to point e. Thereafter, the rotational speed of the impeller 3 decelerates along L1.

  This change in the rotational speed of the impeller 3 can be detected by the magnetic sensor 5. And the detected signal is arithmetically processed by the calculating part 6, and a flow volume is calculated | required.

  By the way, since only the detection signal from the magnetic sensor 5 is input to the calculation unit 6, it is necessary to determine from the detection signal whether the impeller 3 and the braking impeller 2 are connected.

  A signal due to the rotation of the impeller 3 and a signal due to the rotation of the braking impeller 2 are superimposed on this detection signal. The arithmetic unit 6 first separates both signals to obtain two signals shown in FIG. FIG. 5A shows a signal due to the rotation of the impeller 3, and FIG. 5B shows a signal due to the rotation of the braking impeller 2.

  In a state where the impeller 3 and the braking impeller 2 are not connected to each other, the wavelength F2 in (b) is longer than twice the wavelength F1 in (a). Therefore, if F1 <0.5F2, it can be seen that the impeller 3 and the braking impeller 2 are not connected to each other, and the calculation unit 6 obtains the flow rate using L1 in FIG.

  When the impeller 3 and the braking impeller 2 are connected to each other, F1 = 0.5F2, the blade 3a and the blade 2a are both magnetized to the N pole, and the blade 3b and the blade 2b are both the S pole. Due to the magnetism, the signal shown in FIG. 5B cannot be separated from the detection signal. Therefore, the calculation unit 6 determines that the impeller 3 and the braking impeller 2 are connected to each other, and calculates the flow rate using L2 in FIG.

  In addition, this invention is not limited to an above-described form, You may add a various change in the range which does not deviate from the summary of this invention. For example, in the above embodiment, the fluid receiving portion 31 is provided on the upper surface of the impeller, but a hook-like protrusion is provided in the horizontal direction from each blade 3a, 3b, 3c, 3d, and the upper surface of the protrusion is the fluid receiving portion. By functioning as 31, the total area of the fluid receiving portion 31 may be increased.

The figure which shows the structure of one embodiment of this invention Perspective view showing impeller and braking impeller The figure explaining the connection state of an impeller and a braking impeller Diagram showing the relationship between flow velocity and rotation speed The figure which shows the signal superimposed on the detection signal

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sleeve 2 Brake impeller 3 Impeller 4 Spring member 5 Magnetic sensor 6 Calculation part 11 Current flow fin 21 Rotating shaft 23 Engagement recessed part 32 Engagement convex part P Pipe line

Claims (2)

  In the middle of the conduit through which the fluid flows, an impeller that has a magnetic pole at the tip of the blade and rotates by the flow of the fluid is provided, and the magnetic pole at the tip of the impeller from the outside of the conduit is detected in order to detect the rotational speed of the impeller. In the flow rate sensor having a magnetic sensor for detecting the magnetic field by the impeller, the impeller is provided with the impeller so as to be movable in the flow direction, and receives a fluid flow and moves the impeller downstream. And a biasing means provided on the downstream side of the impeller to provide a braking impeller that rotates without moving in the flow direction due to a fluid flow, and to bias the impeller and the braking impeller in a separating direction. And a connecting mechanism for connecting the impeller and the braking impeller to rotate both impellers at a constant speed when the impeller approaches the braking impeller to a predetermined distance against the urging force of the urging means. A flow characterized by the provision of Sensor.   The flow sensor according to claim 1, wherein the impeller is rotatably attached to a rotation shaft that extends upstream along a rotation axis of the braking impeller.

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