JP3764533B2 - Flow meter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow meter of a type that magnetically detects the rotation of an impeller by a magnetic sensor. More specifically, the present invention relates to a structure for increasing the upper temperature limit of a fluid that can be passed through a flow meter.
[0002]
[Prior art]
As shown in FIG. 3, a flow meter such as a hot water meter has a metering chamber 117 in which a fluid 40 such as hot water flows in a meter case by a pressure receiving case 155, and a sensor arrangement chamber 150 (recessed portion) into which a lower end portion of the measuring unit 20 is fitted. ) And is divided. An impeller 31 that rotates according to the flow rate is disposed in the measuring chamber 117, and a magnet 35 is attached to the upper end of the rotating shaft 32. On the other hand, the measurement unit 20 includes a magnetic sensor 21 at the lower end. Therefore, since the magnetic sensor 21 can magnetically detect the rotation of the impeller 31 via the magnet 35, the flow rate can be obtained from the number of rotations.
[0003]
[Problems to be solved by the invention]
In the type of flow meter that magnetically detects the rotation of the impeller 31 by the magnetic sensor 21, the upper limit of the usable temperature of the magnetic sensor 21 is low, and if it exceeds that, the flow rate cannot be measured accurately. Nevertheless, since the conventional flow meter 1 has a structure that only relies on the heat radiation from the cast meter case itself, the heat of the hot water flowing through the flow meter is easily transmitted to the magnetic sensor 21, and the magnetic sensor 21 is Temperature rises easily. For this reason, the conventional magnetic detection type flow meter has a problem that the upper temperature limit of the fluid 40 that can flow is low.
[0004]
Accordingly, an object of the present invention is to solve the above-described problem, and in a flow meter of a type that magnetically detects the rotation of the impeller by a magnetic sensor, the upper temperature limit of the fluid that can flow in the flow meter is set. It is to provide a configuration that can be enhanced.
[0005]
[Means for Solving the Problems]
In order to solve the above-described problems, the flow meter of the present invention has a meter case interior partitioned by a pressure plate, and an impeller that rotates in accordance with the flow rate of the fluid flowing through the inside of the pressure plate. A magnet attached to the rotating shaft of the impeller is disposed, and a measuring unit having a built-in magnetic sensor for detecting the rotation of the magnet and the measuring unit are fitted on the other side of the pressure plate. A concave sensor arrangement chamber is disposed, and the magnetic sensor is opposed to the magnet via a bottom surface portion of the sensor arrangement chamber and the pressure plate, and a side surface portion of the sensor arrangement chamber is a metal. The bottom surface portion is made of synthetic resin, and the outer periphery of the sensor placement chamber is covered with a heat insulating air chamber for suppressing heat conduction from the fluid flowing through the sensor to the magnetic sensor. It is characterized in that is.
[0006]
The bottom surface of the sensor placement chamber of the present invention is made of synthetic resin and also serves as a heat insulating plate. This heat insulating plate suppresses heat conduction from the fluid flowing inside the meter case to the magnetic sensor. Therefore, even if a fluid having a high temperature is allowed to flow through the flow meter, the upper limit of the temperature of the fluid that can be flowed through the flow meter can be increased as much as the temperature rise of the magnetic sensor can be suppressed.
[0008]
In the present invention, heat conduction from the fluid flowing through the measuring chamber to the magnetic sensor can be suppressed by the air layer in the heat insulating air chamber. Therefore, even if a fluid having a high temperature is allowed to flow through the flow meter, the temperature rise of the magnetic sensor can be suppressed, so that the upper temperature limit of the fluid that can flow through the flow meter can be further increased.
[0009]
In the present invention, a heat radiating vent is formed in the outer peripheral wall of the heat insulating air chamber. With this configuration, air enters and exits between the heat-insulating air chamber and the outside of the case through the heat dissipation vent. Therefore, since the heat dissipation efficiency from the heat insulating air chamber to the outside of the case is high, the upper limit of the temperature of the fluid that can flow in the flow meter can be further increased.
[0010]
In the present invention, heat radiating fins are formed at positions adjacent to the heat radiating vents on the outer surface of the outer peripheral wall of the heat insulating air chamber. If comprised in this way, since the thermal radiation efficiency to the exterior of a case will increase, the temperature upper limit of the fluid which can pass the inside of a flow meter can further be raised.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0012]
(Overall configuration of flow meter)
FIG. 1 is a longitudinal sectional view showing a flow meter to which the present invention is applied.
[0013]
As shown in FIG. 1, the flow meter 1 includes a meter case 10, an impeller 31 that rotates according to the flow rate of the fluid 40 that flows inside the meter case 10, a rotating shaft 32 to which the impeller 31 is attached, The magnet 35 attached to the upper end portion of the rotating shaft 32 and the magnetic sensor 21 for detecting the rotation of the impeller 31 by magnetically detecting the rotation of the magnet 35 are generally composed of the built-in measuring unit 20. Has been.
[0014]
The meter case 10 is configured by a plurality of cylindrical or ring-shaped case components such as a metal case body 11 such as a casting, an inner case 12, and the like, and their main configurations will be briefly described.
[0015]
Of the case components, the case body 11 has an inflow port 111 and an outflow port 112 of the fluid 40 in opposite directions in the lower half, and the inner case 12 is fitted and fixed in the upper half of the case body 11. A cylindrical body 114 is formed. The inner case 12 has an upper end portion (flange portion) engaged with a step 113 c formed in an upper end inner peripheral portion of the cylindrical body 114 of the case main body 11, and a lower end portion of the inner case 12 being an inner peripheral surface of the case main body 11. It is in the state supported on the partition part 115 which protrudes from. An upper end portion of the inner case 12 is covered with a metal pressure plate 13 such as a casting so as to cover the upper end opening, and the pressure plate 13 is gasketed by a metal pressure plate fixing case 14 such as a casting. It is being fixed to case body 12 via.
[0016]
In the present embodiment, the measuring chamber 117 is defined in the meter case 10 by the case body 11, the inner case 12, and the pressure plate 13, and the lower half of the inside of the measuring chamber 117. The impeller 31 is arranged in the part so that the rotary shaft 32 is directed in the vertical direction. Here, a support shaft 33 is fixed upward by a nut 331 on the bottom surface portion 116 of the case body 11, and the lower end portion of the rotary shaft 32 is rotatably supported by the support shaft 33. On the other hand, the pressure plate 131 is formed with a recess 132 that opens downward, and the support shaft 34 is fixed downward from the central position of the recess 132. The upper end portion of the rotating shaft 32 is rotatably supported by the support shaft 34. A magnet 35 is fixed to the upper end of the rotating shaft 32 by a magnet holder (not shown).
[0017]
At a position above the measuring chamber 117, the measurement unit fixing case 15 is stacked and fixed on the pressure plate fixing case 14 so as to cover the pressure plate 13. In the measurement unit fixing case 15, a concave sensor arrangement chamber 150 that opens upward is formed, and the lower end of the measurement unit 20 is fitted into the sensor arrangement chamber 150. The measuring unit 20 has a cylindrical shape as a whole, and a lower side is a detection unit 22 having a built-in magnetic sensor 21. Accordingly, the magnetic sensor 21 is in a state of facing the magnet 35 through the partition wall made of the bottom surface portion of the measurement unit fixing case 15 and the pressure-resistant plate 13 and can detect the rotation of the magnet 35. A display unit (not shown) for displaying data is formed on the upper end surface of the measurement unit 20, and this display unit is covered with the open / close lid 24. A signal cable (not shown) is drawn from the measurement unit 20. The measurement unit 20 includes a flange portion 25 projecting in an annular shape on the outer periphery, and the flange portion 25 is sandwiched between the upper case 16 and the measurement unit fixing case 15 via a gasket, so that measurement is performed. The unit 20 is fixed to the meter case 10.
[0018]
[Structure to prevent heat conduction to magnetic sensor]
When hot water is flowed as the fluid 40 in the flow meter 1 configured as described above, if the heat of the fluid 40 is transmitted to the magnetic sensor 21 of the measurement unit 20 and the temperature of the magnetic sensor 21 exceeds the upper limit, the magnetic sensor 21 is The rotational speed of the magnet 35 may be erroneously detected. Therefore, the present invention is configured as described below to prevent heat transfer from the fluid 40 to the magnetic sensor 21.
[0019]
(Heat conduction prevention structure with heat insulating plate)
First, in this embodiment, the measurement unit fixing case 15 is made of a metal whose side surface portion is made of a casting or the like, but the bottom surface portion interposed between the magnetic sensor 21 and the magnet 35 is formed of a synthetic resin plate, The heat insulating plate 154 that suppresses heat conduction from the fluid 40 flowing through the measuring chamber 117 to the magnetic sensor 21 is configured.
[0020]
Therefore, in this embodiment, the heat insulating plate 154 suppresses heat conduction from the fluid 40 flowing through the measuring chamber 117 to the magnetic sensor 21, so that the temperature of the magnetic sensor 21 can be increased even when the high-temperature fluid 40 flows through the flow meter 1. The rise can be suppressed. Therefore, according to this embodiment, the temperature upper limit of the fluid 40 that can pass through the flow meter 1 can be increased by the amount that the temperature rise of the magnetic sensor 21 can be suppressed by the heat insulation structure using the heat insulation plate 154. .
[0021]
(Heat conduction prevention structure by air layer)
Next, in this embodiment, the measurement unit fixing case 15 has an outer periphery with a predetermined interval between the inner cylindrical body 152 constituting the side wall of the sensor placement chamber 150 and the inner cylindrical body 152. It has a double structure with the outer cylindrical body 151 located on the side. Unlike the bottom surface part that functions as the heat insulating plate 154, the inner cylindrical body part 152 and the outer cylindrical body part 151 are both made of metal such as casting and have high thermal conductivity. The inner cylindrical body 152 and the outer cylindrical body 151 are connected to each other at the upper end portion thereof by a connecting portion 163, and their lower openings are closed by the pressure plate 13 and the pressure plate fixing case 14. It has a structure. Therefore, in the flow meter 1 according to the present embodiment, a heat insulating air chamber 50 for suppressing heat conduction from the measuring chamber 117 to the magnetic sensor 21 is defined between the sensor arrangement chamber 150 and the measuring chamber 117. It has a structure.
[0022]
Therefore, in the flow meter 1 according to the present embodiment, heat conduction from the fluid 40 flowing through the measuring chamber 117 to the magnetic sensor 21 by avoiding the heat insulating plate 154 is suppressed by the air layer in the heat insulating air chamber 50, and the heat is The pressure plate 13 and the pressure plate fixing case 14 are discharged to the outside of the case. Further, when the air in the heat insulating air chamber 50 is warmed, the heat is transmitted to the outer cylindrical body 151 by air convection, and is radiated from there to the outside of the case. For this reason, even if the fluid 40 with a high temperature is passed through the flow meter 1, the temperature rise of the magnetic sensor 21 can be more effectively suppressed. For example, in a conventional flow meter having neither a heat insulating structure using such an air layer (heat insulating air chamber 50) nor a heat insulating structure using a heat insulating plate 154, the temperature rise of the magnetic sensor 21 is a fluid In contrast to the temperature rise corresponding to about 90% of the temperature of 40, a flow meter having a heat insulating structure using both the air layer (heat insulating air chamber 50) and the heat insulating plate 54 as in the present embodiment. 1, the temperature rise of the magnetic sensor 21 can be suppressed to about 60% of the temperature of the fluid 40. Therefore, according to this embodiment, the upper limit of the temperature of the fluid 40 that can flow in the flow meter 1 can be increased by the amount that the temperature increase of the magnetic sensor 21 can be suppressed using the air layer and the heat insulating plate 54. it can.
[0023]
(Heat dissipation structure from insulated air chamber)
When the air in the heat insulating air chamber 50 is warmed, the heat is transmitted to the outer cylindrical body 151 by air convection and can be dissipated from the case to the outside of the case. On the lower end side of the outer cylindrical body 151 of the measurement unit fixing case 15, a heat radiating air hole 153 is provided that allows the heat insulating air chamber 50 to communicate with the outside of the case. For this reason, when the fluid 40 having a high temperature is caused to flow through the flow meter 1 and the temperature of the air layer in the heat insulating air chamber 50 rises due to the heat, an air flow occurs due to the convection indicated by the arrow A, thereby insulating the heat. As shown by an arrow B, the air heated in the air chamber 50 exits from the heat dissipation vent 153 to the outside of the case. Further, as indicated by an arrow C, cool new air enters the heat insulating air chamber 50 from the heat radiating vent hole 153.
[0024]
Accordingly, since heat is efficiently released from the heat insulating air chamber 50 to the outside of the case, for example, in a conventional flow meter that does not have such a heat dissipation structure or the above-described heat insulation structure, the temperature rise of the magnetic sensor 21 is While there was a temperature rise corresponding to about 90% of the temperature of the fluid 40, a heat insulating structure using the heat insulating plate 154 and the air layer and a heat radiating structure using the heat radiating vent 153 as in this embodiment. , The temperature increase of the magnetic sensor 21 can be suppressed to about 50% of the temperature of the fluid 40. Therefore, according to this embodiment, the upper limit of the temperature of the fluid 40 that can pass through the flow meter 1 can be further increased by the amount that can suppress the temperature increase of the magnetic sensor 21.
[0025]
Further, in this embodiment, the radiating fin 60 is formed on the outer peripheral wall of the outer cylindrical body 151 of the measurement unit fixing case 15 so as to protrude toward the outside of the case. Therefore, the heat transmitted to the meter case 10 can be efficiently radiated through the heat radiating fins 60, and the heat in the heat insulating air chamber 50 can be radiated efficiently through the heat radiating fins 60. Therefore, the temperature rise of the magnetic sensor 21 can be reliably prevented. Therefore, the temperature upper limit of the fluid 40 that can flow through the flow meter 1 can be further increased.
[0026]
(Other embodiments)
Note that the number and opening positions of the heat radiating vents 153 are not limited to those shown in FIG. 1, but may be any positions as long as air can enter and exit between the heat insulating air chamber 50 and the outside of the case. As shown in FIG. 2, the heat dissipating vent holes 153 may be provided at a plurality of places such as three places. In addition, although the radiation fins 60 are not shown in FIG. 2, it is a matter of course that both the plurality of heat radiation vents 153 and the radiation fins 60 may be provided.
[0027]
Further, in the above embodiment, the position for forming the heat insulating air chamber 50 is defined at the side position of the magnet 35. However, it may be provided at a position below that, that is, at a side position of the measuring chamber 117.
[0028]
【The invention's effect】
As described above, in the flow meter according to the present invention, a heat insulating plate or a heat insulating air chamber for suppressing heat conduction from the fluid flowing through the measuring chamber to the magnetic sensor is provided between the magnetic sensor and the measuring chamber. (Air layer). Therefore, according to the present invention, the heat insulating plate or the heat insulating air chamber suppresses heat conduction to the magnetic sensor and suppresses the temperature increase of the magnetic sensor. Therefore, even if a high-temperature fluid is allowed to flow through the flow meter, the upper limit of the temperature of the fluid that can flow through the flow meter can be increased by the amount that can suppress the temperature increase of the magnetic sensor.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing a flow meter to which the present invention is applied.
FIG. 2 is a longitudinal sectional view showing a flow meter according to another embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing a conventional flow meter.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Flowmeter 10 Meter case 14 Pressure-resistant plate fixing case 15 Measuring unit fixing case 20 Measuring unit 21 Magnetic sensor 31 Impeller 32 Rotating shaft 35 Magnet 40 Fluid 50 Heat insulation air chamber 60 Radiation fin 117 Measuring chamber 150 Sensor arrangement chamber 153 Ventilation holes 154 for heat dissipation

Claims (1)

The inside of the meter case is partitioned by a pressure plate,
On one side of the pressure plate, an impeller that rotates according to the flow rate of the fluid flowing through the inside, and a magnet attached to the rotating shaft of the impeller are arranged,
On the other side of the pressure plate, a measurement unit incorporating a magnetic sensor for detecting rotation of the magnet, and a concave sensor arrangement chamber in which the measurement unit is fitted, are arranged.
The magnetic sensor faces the magnet via the bottom surface of the sensor placement chamber and the pressure plate.
The sensor arrangement chamber has a side surface made of metal, while the bottom surface is made of synthetic resin.
The outer periphery of the sensor placement chamber is covered with a heat insulating air chamber for suppressing heat conduction from the fluid flowing through the sensor to the magnetic sensor,
A heat radiating vent is formed in the outer peripheral wall of the heat insulating air chamber,
A flow meter, wherein a heat radiating fin is formed at a position adjacent to the heat radiating vent on the outer surface of the outer peripheral wall.

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