JP2017219402A - Thermal flow rate sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the transmission of heat generated by a heater to a temperature sensor.SOLUTION: A thermal flow rate sensor includes: piping 1 in which a fluid flows; a sensor chip 2 which has a heater 22 and is pasted to the piping 1; and a sensor chip 3 which has a temperature sensor 31, and is pasted to the piping 1 while keeping a clearance from the sensor chip 2. The piping 1 has a piping portion 12 to which the sensor chip 2 is pasted; a piping portion 13 to which the sensor chip 3 is pasted; and a piping portion 14 which is connected between the piping portion 12 and the piping portion 13, and is configured from a member with low heat conductivity to a member configuring the piping portions 12 and 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal flow sensor in which a sensor chip is attached to a pipe.

  2. Description of the Related Art Conventionally, a thermal flow sensor that measures the flow rate of a fluid flowing in a pipe using a heater is known (see, for example, Patent Document 1). In this thermal flow sensor, a sensor chip provided with a heater and a sensor chip provided with a temperature sensor are attached to a pipe. And a heater heats so that it may become fixed temperature higher than the temperature measured by the temperature sensor.

International Publication No. 2001/088407

However, in the conventional thermal flow sensor, the heater and the temperature sensor are bonded to the same pipe, and the heat generated by the heater is transmitted to the temperature sensor through the pipe, affecting the measurement by the temperature sensor, There is a problem that an error occurs in the heating temperature of the heater. As a result, in the thermal flow sensor, the flow measurement accuracy in a minute flow rate range is lowered, and particularly when the maximum measured flow rate is reduced, the accuracy guaranteed flow range is narrowed. On the other hand, thermal flow sensors are used in various fields for measuring flow rate, and stable measurement is required in a measurement environment.
In addition, if the entire pipe is made of a material having low thermal conductivity in order to suppress heat transfer, heat generated from the heater will not be transferred to the fluid in the pipe, so that sufficient sensitivity cannot be obtained. In addition, measurement by the temperature sensor cannot be performed correctly.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thermal flow sensor that can suppress the heat generated by the heater from being transmitted to the temperature sensor.

  A thermal flow sensor according to the present invention includes a pipe through which a fluid flows, a heater, a first sensor chip attached to the pipe, a temperature sensor, and a gap with respect to the first sensor chip. A second sensor chip provided and attached to the pipe, and the pipe includes a first pipe part to which the first sensor chip is attached and a second sensor chip to which the second sensor chip is attached. A third pipe is connected between the pipe section, the first pipe section and the second pipe section, and is composed of a member having low thermal conductivity with respect to the members constituting the first and second pipe sections. And a piping part.

  According to this invention, since it comprised as mentioned above, it can suppress that the heat generated by the heater is transmitted to the temperature sensor.

1A and 1B are diagrams showing a configuration example of a thermal flow sensor according to Embodiment 1 of the present invention, and are a perspective view and a bottom view. 2A and 2B are diagrams showing an example of pipe connection in Embodiment 1 of the present invention, and are a perspective view showing a state before connection and a perspective view showing a state after connection. 3A to 3C are diagrams showing another example of connection of piping in Embodiment 1 of the present invention, a perspective view showing a state before connection, and a perspective view and a cross-sectional view showing a state after connection. . It is a figure explaining the effect of the thermal type flow sensor concerning Embodiment 1 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1 FIG.
1 is a diagram showing a configuration example of a thermal flow sensor according to Embodiment 1 of the present invention. In FIG. 1, the signal lines connecting the sensor chips 2 and 3 and the substrate 4 are not shown.
The thermal flow sensor is a sensor that measures the flow rate of a fluid (liquid or gas) flowing through the pipe (capillary) 1 using the heater 22. As shown in FIG. 1, the thermal flow sensor includes a pipe 1 through which fluid flows, sensor chips (first and second sensor chips) 2 and 3 attached to a countersink surface 11 of the pipe 1, and a sensor. And a substrate 4 connected to the chips 2 and 3 for inputting and outputting signals.

  The pipe 1 has pipe parts (first to third pipe parts) 12 to 14. The sensor chip 2 is affixed to the piping part 12. In addition, the sensor chip 3 is attached to the pipe portion 13. The piping unit 14 is connected between the piping unit 12 and the piping unit 13. Moreover, the piping part 14 is comprised from a member with low heat conductivity with respect to the member which comprises the piping parts 12 and 13. FIG. For example, the piping parts 12 and 13 are made of quartz glass, and the piping part 14 is made of a member having a lower thermal conductivity than quartz glass, such as a resin such as PTFE.

The sensor chip 2 is provided with a heater 22 that applies heat to the fluid in the pipe 1 in a diaphragm portion 21 that is a thin film attached to the pipe 1.
The sensor chip 3 is provided with a temperature sensor 31 that measures the temperature of the fluid in the pipe 1. A gap is provided between the sensor chip 2 and the sensor chip 3.

The substrate 4 is provided with a connecting portion 41 protruding from one side. This connecting portion 41 is affixed to the counterbore surface 11.
And the board | substrate 4 acquires the signal which shows the temperature measured by the temperature sensor 31, and controls the heater 22 so that it may become a fixed temperature higher than the said temperature. And the board | substrate 4 acquires the signal which shows the power in the heater 22, and measures the flow volume of a fluid. That is, in the thermal type flow rate sensor, when the fluid in the pipe 1 is stationary, the amount of heat when the heater 22 applies heat so that the temperature is higher than the surroundings and the fluid in the pipe 1 is upstream. When the heat flows to the downstream side, a difference is generated in the amount of heat when heat is applied by the heater 22 so as to be higher than the surrounding by a certain temperature. This difference in the amount of heat has a correlation with the flow rate of the fluid in the pipe 1. Therefore, in the thermal type flow sensor, the flow rate of the fluid flowing in the pipe 1 can be measured from the difference in the amount of heat.

  As described above, in the pipe 1, the portion (pipe section 14) between the sensor chip 2 and the sensor chip 3 is formed of a member having low thermal conductivity, and thus is generated by the heater 22 provided in the sensor chip 2. It is possible to suppress the heat transferred to the temperature sensor 31 provided in the sensor chip 3.

Next, the connection method of the piping parts 12 and 13 and the piping part 14 is demonstrated.
As a method of connecting the piping parts 12 and 13 and the piping part 14, for example, as shown in FIG. In the example of FIG. 2, male screws 141 and 142 are formed at both ends of the piping portion 14, a female screw 121 that is screwed with the male screw 141 is formed at one end of the piping portion 12, and a male screw 142 is formed at one end of the piping portion 13. A female screw 131 is formed to be screwed together. In the case of the configuration shown in FIG. 2, the sensor chips 2 and 3 are affixed to the outside of the male screws 141 and 142 of the piping part 14. Thus, by connecting the pipe parts 12 and 13 and the pipe part 14 with screws, the pipe 1 can be downsized with a simple configuration.
In contrast to FIG. 2, a female screw may be formed at both ends of the pipe part 14 and a male screw may be formed at one end of the pipe parts 12 and 13.

Moreover, as a connection method of the piping parts 12 and 13 and the piping part 14, the method of connecting with the adhesive agent 5 as shown, for example in FIG. 3 is also mentioned. In addition, illustration of the adhesive agent 5 is abbreviate | omitted in FIG. 3C. In the example of FIG. 3, convex tapers 143 and 144 are formed at both ends of the pipe portion 14, a concave taper 122 along the taper 143 is formed at one end of the pipe portion 12, and one end of the pipe portion 13 is formed. A concave taper 132 is formed along the taper 144. Thus, by providing the tapers 122, 132, 143, and 144 on the connection surfaces of the pipe parts 12 to 14, the axial deviation of the pipe parts 12 to 14 can be eliminated.
In contrast to FIG. 3, a concave taper may be formed at both ends of the pipe part 14, and a convex taper may be formed at one end of the pipe parts 12 and 13. Moreover, even if the fluid which flows through the piping 1 is corrosive fluids, such as a chemical | medical solution, it can respond by using the fluorine-type thing as the adhesive agent 5. FIG.

  Next, the effect of the thermal flow sensor according to the first embodiment will be described with reference to FIG. In FIG. 4, the analysis result of the temperature distribution on the countersink surface 11 in the conventional configuration (when the entire pipe 1 is made of quartz glass) is indicated by a broken line. Moreover, the analysis result of the temperature distribution in the countersink surface 11 in the configuration according to Embodiment 1 (when the piping parts 12 and 13 are made of quartz glass and the piping part 14 is made of PTFE) is shown by a solid line. .

  In the analysis shown in FIG. 4, the fluid temperature in the pipe 1 is 25 ° C., and the driving temperature of the heater 22 is 35 ° C. (fluid temperature + 10 ° C.). Further, the thermal conductivity of quartz glass is 1.38 W / m · K, and the thermal conductivity of PTFE is 0.12 W / m · K. In FIG. 4, reference numeral 401 indicates the installation position of the heater 22 on the countersink surface 11, and reference numeral 402 indicates the installation position of the temperature sensor 31 on the countersink surface 11. Reference numerals 403 to 405 denote the installation positions of the piping parts 12 to 14 in the configuration according to the first embodiment.

  As shown in FIG. 4, in the conventional configuration, the measurement result by the temperature sensor 31 is 0.92 ° C. higher than the fluid temperature (25 ° C.). On the other hand, in the configuration according to the first embodiment, the measurement result by the temperature sensor 31 is 0.37 ° C. higher than the fluid temperature (25 ° C.). That is, in the configuration according to Embodiment 1, the heat generated by the heater 22 is less likely to be transmitted to the temperature sensor 31 side compared to the conventional configuration.

  As described above, according to the first embodiment, the pipe 1 through which the fluid flows, the heater 22, the sensor chip 2 attached to the pipe 1, the temperature sensor 31, and the sensor chip 2 The sensor chip 3 is attached to the pipe 1 with a gap therebetween. The pipe 1 includes a pipe part 12 to which the sensor chip 2 is attached, a pipe part 13 to which the sensor chip 3 is attached, Since it was comprised between the piping part 12 and the piping part 13, and it comprised so that it might have the piping part 14 comprised from the member with low heat conductivity with respect to the member which comprises the said piping parts 12 and 13, it is a heater. It is possible to suppress the heat generated by 22 from being transmitted to the temperature sensor 31.

  In addition, although the case where the piping parts 12 and 13 were comprised from quartz glass was shown above, it is not restricted to this, What is necessary is just a member in which the heat transfer by the heater 22 and the measurement by the temperature sensor 31 are not prevented.

  In the present invention, any constituent element of the embodiment can be modified or any constituent element of the embodiment can be omitted within the scope of the invention.

1 Piping 2 Sensor chip (first sensor chip)
3 Sensor chip (second sensor chip)
4 Substrate 5 Adhesive 11 Countersink surface 12 Piping part (first piping part)
13 Piping section (second piping section)
14 Piping section (third piping section)
21 Diaphragm portion 22 Heater 31 Temperature sensor 41 Connection portion 121 Female screw 122 Taper 131 Female screw 132 Taper 141, 142 Male screw 143, 144 Taper

Claims (5)

Piping through which fluid flows;
A first sensor chip having a heater and affixed to the pipe;
A temperature sensor, and a second sensor chip attached to the pipe with a gap with respect to the first sensor chip,
The piping is
A first piping part to which the first sensor chip is attached;
A second piping part to which the second sensor chip is attached;
The 3rd piping part comprised between the member connected between the said 1st piping part and the said 2nd piping part, and having low heat conductivity with respect to the member which comprises the said 1st, 2nd piping part A thermal flow sensor characterized by comprising: The thermal flow sensor according to claim 1, wherein the first and second piping parts and the third piping part are connected by screws. The thermal flow sensor according to claim 1, wherein the first and second piping parts and the third piping part are connected by an adhesive. The thermal flow sensor according to claim 3, wherein the first and second piping parts and the third piping part have a tapered connection surface. The thermal flow sensor according to any one of claims 1 to 4, wherein the third piping portion is made of resin.

Images