Flowmeter

Abstract

The invention provides a flow meter suitable for measuring the flow of extremely low temperature fluid and high temperature fluid. A flow meter according to the present invention is provided with: a flow path pipe having a flow path through which a fluid flows; an impeller that is rotatably supported inside the flow path pipe; and a sensor for measuring the flow rate of the fluid flowing through the flow path by the rotation of the impeller, the sensor having a wiring board made of a metal base material in a sensor housing provided outside the flow path pipe, the wiring board having mounted thereon: a magnetic sensor package for detecting the magnetic force of the impeller; a heater that heats the wiring substrate; and a temperature control circuit that controls the on / off of the power supply of the heater on the basis of the temperature of the wiring substrate, and maintains a uniform substrate temperature by using the wiring substrate made of a metal base material. And a heat storage effect for maintaining a temperature at which the sensor can operate during a transient stop or an abnormal stop, and a heat dissipation effect for absorbing heat in the vicinity of the sensor and dissipating heat are obtained.

Description

Technical Field

[0001] The present invention relates to a flow meter suitable for measuring the flow rate of a fluid in a wide temperature range from extremely low temperature to high temperature. Background Art

[0002] In recent years, the flow measurement of extremely low temperature fluids has been sought in the semiconductor manufacturing process. When measuring the flow of extremely low temperature (e.g. -120°C) fluids (e.g. fluorine-based refrigerants), impeller flow meters are usually used. Since impeller flow meters use semiconductor sensors such as Hall ICs as magnetic sensors, they have poor temperature characteristics at low temperatures, and cannot be detected if the fluid temperature is below -40°C. Therefore, the following flow meters are known: By adopting a detection method using a pickup coil as a magnetic sensor, the flow measurement of extremely low temperature fluids can be performed (see Patent Document 1 below).

[0003] However, since the pickup coil is a copper winding, it becomes an antenna and is susceptible to noise from external magnetic fields in all directions. In addition, in recent semiconductor manufacturing plants, the installation area of ​​the device is reduced, and the distance between the components in the device is shortened. In addition, there are motors, solenoid valves, electromagnetic switches, inverters, power lines, etc. near the flow meter, which is in an environment that is prone to malfunction due to these magnetic field noises. Therefore, the flow meter needs to be configured as far away as possible in the device, which gradually becomes difficult to use.

[0004] On the other hand, if a semiconductor sensor such as a Hall IC is used as in the past, it has directivity in detection and is not easily affected by noise of the external magnetic field, but particularly when a low-temperature fluid is used, the detection sensitivity of the Hall element decreases, and there is a problem of being unable to detect. Therefore, in order to prevent the decrease in the detection sensitivity of the Hall element, a hot water supply device having a water amount sensor is known, and the water amount sensor has a Hall element and a heater (see Patent Document 2 below).

[0005] However, the hot water supply device is a device that is controlled based on the ambient temperature outside the water quantity sensor, and does not measure the temperature near the Hall element, so it is not possible to accurately control the temperature of the Hall element. In addition, when used for extremely low-temperature fluids, in order to prevent condensation and freezing on the outside of the product, it is necessary to cover almost the entire outer packaging surface with insulating materials. Since the ambient temperature and the sensor temperature will deviate due to their insulating properties, there is a problem that the temperature cannot be correctly controlled. In addition, it is necessary to assume that the semiconductor manufacturing equipment has a momentary stop or abnormal stop, and heat storage is required to maintain a temperature that can operate even if the heat is taken away by the low-temperature fluid for a period of time when the power is disconnected, but there is no such countermeasure.

[0006] Prior art literature Patent Literature Patent Document 1: Japanese Patent No. 6257833 Patent Document 2: Japanese Patent Application Publication No. 2004-294020 Summary of the invention

[0007] Technical issues The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a flow meter suitable for measuring the flow rates of extremely low-temperature fluids and high-temperature fluids.

[0008] Technical Solution In order to solve the above-mentioned problem, the flow meter of the present invention is characterized in that it comprises: a flow tube having a flow path for fluid circulation; an impeller supported in a rotatable manner inside the flow tube; and a sensor for measuring the flow rate of the fluid flowing in the flow path by the rotation of the impeller, the sensor having a wiring substrate with a metal base material inside a sensor housing arranged outside the flow tube, and mounted on the wiring substrate are: a magnetic sensor package for detecting the magnetic force of the impeller; a heater for heating the wiring substrate; and a temperature control circuit for controlling the power on / off of the heater based on the temperature of the wiring substrate, and the magnetic sensor package is mounted on the wiring substrate by welding.

[0009] In the flow meter of the present invention, the following structure may be adopted: the magnetic sensor package is a magnetic sensor package with a thermal pad in which a magnetic sensor element is mounted on a thermal pad.

[0010] In the flow meter of the present invention, the wiring substrate may be designed so that the substrate width of a portion where the magnetic sensor package is mounted is narrower than the substrate width of other portions.

[0011] In addition, the following structure can also be adopted in the flow meter of the present invention: the flow path tube is composed of an inlet tube having an inlet and an outlet tube having an outlet, and a chamber is accommodated in the space between the inlet tube and the outflow tube, and an impeller with a diameter larger than the inner diameter of the flow path is contained in the chamber.

[0012] In the flow meter of the present invention, a corrugated gasket may be inserted between the chamber and the inlet pipe, and a metal seal may be inserted between the joint surfaces of the inlet pipe and the outlet pipe.

[0013] Technical Effects According to the flowmeter of the present invention, the semiconductor sensor of the magnetic sensor package (Hall IC, etc.) is used, so that it is not easily affected by the noise of the external magnetic field. The temperature control is performed by installing the magnetic sensor package, the heater and the temperature control circuit on the wiring substrate of the metal substrate, so that the temperature of the sensor can be accurately controlled. Therefore, the wiring substrate of the metal substrate is used to maintain a uniform substrate temperature, and a heat storage effect is obtained for maintaining a temperature at which the sensor can operate during an instantaneous stop or abnormal stop. In particular, the semiconductor sensor of the magnetic sensor package (Hall IC, etc.) has an action guarantee temperature. Although it cannot be detected if the fluid temperature becomes below -40°C, it is possible to achieve the effect of flow measurement suitable for extremely low temperature fluids by heating the wiring substrate of the metal substrate with a heater to maintain it above -40°C. In addition, since the wiring substrate of the metal substrate can efficiently absorb the heat near the sensor and dissipate the heat to the outside, it has the effect of being able to perform flow measurement suitable for high temperature fluids. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a perspective view showing the appearance of the flow meter of the present invention.

[0015] Figure 2 It is a top view showing the appearance of the flow meter.

[0016] Figure 3 This shows the flow meter Figure 2 Cross-section along line AA.

[0017] Figure 4 This is the flow meter Figure 3 Enlarged cross-sectional view of section C in the middle.

[0018] Figure 5 This is the flow meter Figure 2 Cross-section along line BB.

[0019] Figure 6 1 is a schematic diagram showing an example of a wiring board of a metal base material in the flow meter.

[0020] Figure 7 This is an enlarged view of the vicinity of the Hall IC in this flow meter.

[0021] Figure 8 This is a cross-sectional view showing a state where a waterproof connector cable is mounted on the waterproof connector of the flow meter.

[0022] Explanation of symbols 1: Flow meter 2: Flow pipe 3: Sensor 4: Inflow pipe 5: Outflow pipe 6: Inflow 7: Upstream flow path 8: downstream flow path; 9: Outflow 10: Cabin 11: Impeller 12: concave part 13: Bearings 14: Bearings 15: Rectifier 16: Axis 17: Blade 18: Magnet 19: Wave washer 20: Metal seals 21: Bolt with hexagonal hole 22: Sensor housing 23: Self-tapping screws 24: Wiring substrate 24a: Electrode 25: Magnetic sensor package (Hall IC) 25a: Magnetic sensor element (Hall element) 25b: terminal 26: Heater 27: Temperature control circuit 28: Temperature sensor 29: Thermal pad 30: Base plate pressure plate 31: Rubber lining 32: Waterproof connector 32a: Pin 33: Internal cables 34: Filling material 35: External cables 36: Waterproof connector cable DETAILED DESCRIPTION

[0023] Hereinafter, a mode for carrying out the present invention will be described with reference to the drawings.

[0024] like Figure 1 and Figure 2As shown, the flow meter 1 of this embodiment is an impeller flow meter that detects an impeller rotating in proportion to the flow velocity to measure the flow rate of a fluid, and is a sensor-integrated flow meter in which a sensor 3 for measuring the flow rate of the fluid based on the rotation speed of the impeller is installed outside a flow path pipe 2 having a flow path for the fluid to flow. As a use of the flow meter 1, for example, it can be connected to a horizontal piping of a temperature control cooler of a semiconductor manufacturing device and can be used for flow measurement of a fluorine-based inert liquid. The flow rate can be measured in a wide temperature range from an extremely low temperature of -120°C to a high temperature of +150°C.

[0025] Figure 3 2 is a cross-sectional view showing the internal structure of the flow path tube 2. As shown in the figure, in order to prevent magnetism due to heat during welding and / or processing, the flow path tube 2 is composed of two parts, an inlet pipe 4 and an outlet pipe 5 made of stainless steel (for example, SUS316). An upstream flow path 7 connected to an inlet 6 opened at one end is formed in the inlet pipe 4, and a downstream flow path 8 connected to an outlet 9 opened at the other end is formed in the outlet pipe 5. An impeller 11 built into a chamber 10 is provided in the space between the upstream flow path 7 and the downstream flow path 8. In an impeller flowmeter, in order to reduce pressure loss, it is preferred to make the impeller diameter larger than the flow path diameter. Therefore, in this embodiment, a recess 12 having a diameter larger than the inner diameter D1 of the flow path (upstream flow path 7 and downstream flow path 8) is provided on the inner side of the outflow pipe 5, and a structure is adopted in which the chamber 10 with the impeller 11 built into the recess 12 is accommodated.

[0026] The chamber 10 is made of a thermoplastic resin (e.g., PPS) having excellent heat resistance. Ceramic (e.g., alumina) bearings 13 and 14 are arranged opposite to each other in the center of the chamber 10, and a rectifying plate (e.g., PPS) 15 is integrally formed radially around the bearing 13 on the side of the inflow pipe 4. The impeller 11 has four blades 17, 17, ... made of a thermoplastic resin (e.g., PPS) arranged radially and spirally on the outer periphery of a rotating shaft 16 made of ceramic (e.g., alumina). Magnets 18 made of samarium cobalt or the like having excellent heat resistance and corrosion resistance are buried in two blades 17 (17B and 17D) of the four blades 17 (17A, 17B, 17C, 17D) that are 180 degrees opposite to each other. The impeller 11 is designed to have an outer diameter D2 larger than an inner diameter D1 of the flow path (the upstream flow path 7 and the downstream flow path 8 ), and is supported rotatably around the axis of a rotation shaft 16 supported by bearings 13 and 14 .

[0027] In the flow path pipe 2, the fluid flowing into the chamber 10 from the inlet 6 through the upstream flow path 7 becomes a vortex through the rectifying plate 15 and the spiral blades 17, and flows out from the outlet 9 through the downstream flow path 8. In this embodiment, since an axial flow type is adopted in which the fluid vertically collides with the rotating surface of the impeller 11, there is no restriction on the installation posture (vertical or horizontal) of the flow meter 1 to the piping, and there is no problem because the axial stress is small, so there are few failures and a long life can be achieved. In addition, since the chamber 10 obtained by unitizing the impeller 11, the bearings 13, 14, and the rectifying plate 15 in advance only needs to be accommodated in the recess 12, the assembly work of the components can be simplified, and maintenance work can also be easily performed.

[0028] Since the flow meter 1 of this embodiment adopts a chamber housing structure that is unitized and does not easily cause the centers of the bearings 13 and 14 supporting the impeller 11 to deviate from each other, for the purpose of reducing pressure loss, a sealing portion is required at the joint surface between the inlet pipe 4 and the outlet pipe 5. Generally, although a rubber gasket such as an O-ring is used in the sealing portion, the rubber gasket becomes hard below -50°C and becomes unable to seal, so a metal seal is used in this embodiment. That is, a metal (for example, SUS304) wave washer 19 is inserted between the chamber 10 and the inlet pipe 4 to prevent the shaking of the chamber 10, and a metal seal 20 is inserted into a part of the joint surface between the inlet pipe 4 and the outflow pipe 5. In addition, a plurality of hexagonal bolts 21, 21, ... are fastened to the inlet pipe 4 from the outside of the inlet pipe 4, thereby sealing the joint surface between the inlet pipe 4 and the outflow pipe 5.

[0029] In the case of a conventional metal seal, the yield rate during manufacturing is lower than that of a rubber gasket. Therefore, in this embodiment, the yield rate is greatly improved by setting the gasket shape to limit the contact area. That is, if the hexagonal bolt is used for fastening, the Figure 4 As shown in the figure, although the product is pressed in the direction of the arrow and the gasket is crushed, the gasket is usually pressed against the entire surface and the load per unit area is dispersed, so there is a problem that the force is not concentrated in a certain part and the sealing performance is poor. Therefore, for the metal seal 20 of this embodiment, by reducing the contact surface a between the inlet pipe 4 and the contact surface b between the outlet pipe 5 to limit the contact area, the force is applied only to the part marked with the circular mark in the figure, and a high sealing performance can be maintained with a weak tightening force.

[0030] In addition, the conventional metal seal is tightened by rotating the whole body, so there is a problem that the gasket slides in the direction of rotation during rotation, and the surface is corroded due to the friction heat and bite generated at this time, thereby damaging the sealing performance. Therefore, in this embodiment, by adopting a tightening structure with hexagonal bolts 21, force is applied only in the vertical direction, and the friction heat and bite of the surface will not be generated, and the surface will not be corroded. Therefore, high sealing performance can be achieved, and metal sealing can be performed economically without the need for components for solving the problem.

[0031] It should be noted that conventional pipe threads such as Rc threads are sealed using sealing tapes, rubber or resin sealants. However, when these sealing components are connected to metal joints such as stainless steel, there is a problem that the thermal contraction at low temperatures is greater than the thermal contraction of metals and leakage is likely to occur. Therefore, in this embodiment, the outer shape of the inlet pipe 4 and the outlet pipe 5 does not adopt a pipe thread but a pipe extension structure. Therefore, it is possible to install a double-ferrule Swagelok pipe joint (Swagelok Company, trade name) at the front end of the welded pipe and install a VCR joint (Swagelok Company, trade name), etc. on the flow tube 2. As a result, the flow tube 2 and the joint are made of the same material, and the thermal expansion coefficient is the same even at low temperatures. Therefore, even if a low-temperature fluid is used, there is no need to worry about the generation of gaps or leakage, and high air tightness can be maintained.

[0032] Figure 5 2 is a cross-sectional view showing the internal structure of the sensor 3. As shown in the figure, the sensor 3 is housed in a sensor housing 22 made of a thermoplastic resin (such as PPS) having excellent heat resistance. The sensor housing 22 is fixed to the flow tube 2 by self-tapping screws 23 and is arranged outside the flow tube 2. A wiring substrate 24 made of a metal base material with high thermal conductivity is built into the sensor housing 22.

[0033] The wiring substrate 24 of the metal base material refers to a wiring substrate including Figure 6 The metal base substrate 24-1, the metal core substrate 24-2, and the metal column substrate 24-3 are all shown. The metal base substrate 24-1 is formed by laminating an insulating layer on the surface of a metal plate (aluminum plate, copper plate) that becomes a base (substrate), and forming an outer layer circuit thereon. The metal core substrate 24-2 is formed by laminating an insulating layer on the surface and back of a metal plate (aluminum plate, copper plate) that becomes a core (substrate), forming an outer layer circuit thereon, and providing through holes. The metal column substrate 24-3 is formed by laminating an insulating layer on the surface of a metal plate (aluminum plate, copper plate) that becomes a base (substrate), forming an outer layer circuit thereon, and exposing the metal plate.

[0034] On the wiring substrate 24 of the metal base material, a non-contact magnetic sensor package 25 for detecting the magnetic force of the impeller 11 is installed at a position opposite to the impeller 11 in the flow tube 2. The magnetic sensor package 25 of this embodiment is a Hall IC with a built-in Hall element, which converts magnetic force into voltage using the Hall effect as a magnetic sensor element. The magnetic sensor package (Hall IC) 25 is a package of electronic components composed of a chip circuit, and has a function of detecting the rotation speed using magnetic force. The chip circuit is composed of a Hall element, a power supply circuit, an operational amplifier, a Schmitt trigger, and a transistor. If the fluid passes through the inside of the flow tube 2, the magnet 18 also rotates with the rotation of the impeller 11, and outputs magnetic force to the outside of the flow tube 2 every time the magnet 18 passes. If the magnetic sensor element (Hall element) of the magnetic sensor package (Hall IC) 25 detects the magnetic force, a potential difference is generated, and the potential difference is amplified by the operational amplifier. If it is detected that the Schmitt trigger is above the upper limit value or below the lower limit value, the transistor outputs an on / off (Lo / Hi) digital signal.

[0035] A heater 26 for heating the wiring substrate 24, a temperature control circuit 27 for controlling the power on / off of the heater 26, and a temperature sensor 28 for detecting the temperature of the wiring substrate 24 are also mounted on the wiring substrate 24 of the metal base material. The heater 26 is composed of a resistor. When the power is turned on and the current flows, the heater 26 generates heat to heat the wiring substrate 24, thereby preventing the temperature of the magnetic sensor element (Hall element) of the magnetic sensor package (Hall IC) 25 from decreasing. The temperature sensor 28 detects the temperature of the wiring substrate 24 using a thermistor or the like. If the temperature of the wiring substrate 24 is detected to be below the set temperature (lower limit value), the temperature control circuit 27 turns on the power of the heater 26, and if the temperature of the wiring substrate 24 is detected to be above the set temperature (upper limit value), the heater 26 is turned off to control the temperature of the wiring substrate 24. It should be noted that although the temperature control circuit 27 and the temperature sensor 28 are provided as separate components, a single-chip electronic component such as a temperature control circuit with a built-in temperature sensor may be used.

[0036] In this embodiment, the magnetic sensor package (Hall IC) 25 is mounted on the wiring substrate 24 of the metal base material by soldering. Figure 7As shown in (A), the following structure can be adopted: the terminal 25b connected to the magnetic sensor element (Hall element) 25a is mounted on the electrode 24a of the wiring substrate 24 through the solder s. In this way, the magnetic sensor element (Hall element) 25a can be positioned stably and accurately for a long time by fixing the metals to each other. In addition, even if it is assumed that it is repeatedly used in a wide temperature range of -120°C to +150°C, since the metals have similar thermal expansion coefficients, it is possible to prevent the electronic components from peeling off due to thermal cycles. In addition, since the temperature of the wiring substrate 24 is easily transmitted directly to the magnetic sensor element (Hall element) 25a via the solder s and the metal with good thermal conductivity such as the terminal 25b, it has the effect of being able to achieve high-precision temperature control.

[0037] In addition, if Figure 7 As shown in (B), as another example of the magnetic sensor package (Hall IC) 25, a magnetic sensor package with a thermal pad may be used. That is, the following structure may be adopted: a magnetic sensor package (Hall IC) 25 having a magnetic sensor element (Hall element) 25a mounted on the surface of a thermal pad 29 made of a copper plate is used, and the thermal pad 29 on the back is mounted on the electrode 24a of the wiring substrate 24 using solder s. As a result, copper with good thermal conductivity exists between the wiring substrate 24 and the magnetic sensor element (Hall element) 25a, and the wiring substrate 24 and the magnetic sensor element (Hall element) 25a can be maintained at approximately the same temperature, which has the effect of being able to achieve high-precision temperature control based on extremely high thermal conductivity.

[0038] like Figure 5 As shown, the wiring substrate 24 of the metal base material is inserted into the interior of the sensor housing 22 through the substrate pressing plate 30 made of resin, and the rubber gasket 31 is used to prevent moisture from entering from the outside, and the waterproof connector 32 for the M12 connector is used to prevent detachment and waterproof protection. Although the internal cables 33 such as the power supply wire and the signal wire are arranged inside the sensor housing 22, the filling material (for example, heat-resistant epoxy resin) 34 is bonded and fixed in a manner covering the outer periphery of these internal cables 33. Therefore, air convection does not occur in the internal space of the sensor housing 22, and even if a high-temperature fluid flows in the flow path, heat transfer from the flow path tube 2 to the wiring substrate 24 can be prevented. On the contrary, even if a low-temperature fluid flows in the flow path, condensation on the wiring substrate 24 can be suppressed, and even if the flow path tube 2 condenses and freezes, the internal wires will not rust and poor contact of the internal cables 33 can be prevented. In addition, even if the filling material 34 and the sensor housing 22 are bonded and peeled due to thermal fluctuations, the wiring substrate 24 can be stably fixed by the substrate pressing plate 30 without falling off.

[0039] Thus, in this embodiment, the magnetic sensor package (Hall IC) 25, the heater 26, the temperature control circuit 27, and the temperature sensor 28 are mounted on a piece of metal-based wiring substrate 24, and inserted into the sensor case 22 to independently perform temperature control outside the flow tube 2. As a result, the temperature near the magnetic sensor package (Hall IC) 25 can be accurately controlled. Therefore, a heat storage effect is obtained for maintaining a uniform substrate temperature by using the wiring substrate 24 of the metal substrate while maintaining a temperature at which the sensor 3 can operate during an instantaneous stop or abnormal stop. In particular, the semiconductor sensor of the magnetic sensor package (Hall IC) 25 has an operating guarantee temperature. Although it cannot be detected if the fluid temperature becomes below -40°C, it has the effect of being able to achieve flow measurement suitable for extremely low temperature fluids by heating the wiring substrate 24 of the metal substrate with the heater 26 to maintain it above -40°C.

[0040] In addition, the magnetic sensor package (Hall IC) 25 is arranged close to the magnet 18 so as to be able to detect the magnetic force of the magnet 18 more strongly, and is not easily affected by the external magnetic field by using a Hall element with the lowest sensitivity possible. Therefore, since the sensor 3 is arranged near the flow path of the flow path tube 2, there is a problem that it is easy to be directly subjected to the heat of the fluid. Therefore, if Figure 2 As shown, for the wiring substrate 24 of this embodiment, the substrate width W1 of the portion where the magnetic sensor package (Hall IC) 25 closest to the flow path is mounted is designed to be extremely narrow compared to the substrate width W2 of the other portion where the heater 26, the temperature control circuit 27, and the temperature sensor 28 are mounted. This has the advantage of being able to reduce the heat input received by the wiring substrate 24 from the flow path side.

[0041] In addition, although the fluid can be heated by the heater 26 when the fluid is at a low temperature, if the heat can be dissipated when the fluid is at a high temperature, there is an advantage that even a fluid at a higher temperature can be used. In this embodiment, since the magnetic sensor package (Hall IC) 25 is mounted on the wiring substrate 24 of the metal base material by welding, the heat received by the magnetic sensor element (Hall element) 25a is efficiently absorbed by the wiring substrate 24 of the metal base material with high thermal conductivity. In addition, as Figure 8 As shown, the heat absorbed by the wiring substrate 24 is efficiently transferred from the internal cable 33 to the external cable 35 via the pins 32a of the waterproof connector 32, and is dissipated to the outside air from the waterproof connector cable 36 exposed to the outside air. In this way, since the heat dissipation effect of enabling the magnetic sensor element (Hall element) 25a to dissipate heat efficiently from the flow path to the outside of the flow meter can be obtained, the flow measurement suitable for high-temperature fluid can also be performed.

[0042] It should be noted that in the above-mentioned embodiment, although a Hall element is used as the magnetic sensor element 25a of the magnetic sensor package 25 for detecting the magnetic force of the impeller 11, the type of the magnetic sensor element 25a is not limited thereto. For example, a Hall element that directly outputs a Hall voltage, or a linear Hall IC that amplifies the Hall voltage and outputs it linearly can be used as a Hall sensor using the Hall effect. In addition, a GMR sensor element based on the giant magnetoresistance (GMR) effect, a TMR sensor element based on the tunnel magnetoresistance (TMR), etc. can also be used as an MR sensor using the magnetoresistance (MR) effect. In addition, although PPS is used as the material of the sensor housing 22, foamed PPS with excellent heat insulation properties can also be used.

[0043] Industrial Applicability In the above embodiment, the flow meter of the present invention is used for measuring the flow rate of a fluorine-based inert liquid in a temperature control cooling device of a semiconductor manufacturing device. However, the flow meter of the present invention can also be used for measuring the flow rate of hydraulic equipment.

Claims

1. A flow meter, characterized in that: have: A flow path tube having a flow path for fluid to flow; an impeller rotatably supported inside the flow tube; and a sensor for measuring the flow rate of the fluid flowing in the flow path by the rotation of the impeller, The sensor includes a wiring substrate made of a metal base material in a sensor case provided outside the flow tube. The wiring substrate is provided with: a magnetic sensor package for detecting the magnetic force of the impeller; a heater for heating the wiring substrate; and a temperature control circuit for controlling the power on / off of the heater based on the temperature of the wiring substrate. The magnetic sensor package is mounted on the wiring substrate by soldering.

2. The flow meter according to claim 1, characterized in that The magnetic sensor package is a magnetic sensor package with a thermal conductive pad, in which a magnetic sensor element is mounted on the thermal conductive pad.

3. The flow meter according to claim 1 or 2, characterized in that: The wiring substrate is designed so that the substrate width of a portion where the magnetic sensor package is mounted is narrower than the substrate width of other portions.

4. The flow meter according to claim 1, characterized in that: The flow path pipe is composed of an inlet pipe having an inlet and an outlet pipe having an outlet. A chamber is accommodated in the space between the inlet pipe and the outlet pipe. An impeller having a diameter larger than an inner diameter of the flow path is housed in the chamber.

5. The flow meter according to claim 4, characterized in that: A corrugated gasket is inserted between the chamber and the inlet pipe, and a metal seal is inserted between the joint surfaces of the inlet pipe and the outlet pipe.

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