JP4981308B2 - Flow rate measuring device and fluid discrimination device - Google Patents

Description

  The present invention relates to a flow rate measuring device and a fluid discriminating device, and more specifically, a flow rate measuring device that measures the flow rate of a fluid such as gas or water flowing in a flow path using a flow sensor, and a discrimination target fluid. The present invention relates to a fluid discrimination device for discriminating types.

  As a flow rate measuring device for measuring the flow rate of a fluid such as gas or water that is a flow rate measurement target, a device using a thermal type flow sensor is known. This flow sensor uses the principle that a heater having a temperature higher than the temperature of the fluid is placed in the fluid flow, and the temperature distribution of the fluid heated by the heater changes as the flow velocity increases. It is.

  As such a flow sensor, the one shown in Patent Document 1 is known, and this conventional thermal type flow sensor will be described with reference to FIGS. 6 and 7. 6 is a block diagram showing a configuration of a conventional thermal type flow sensor, and FIG. 7 is a cross-sectional view of the flow sensor shown in FIG.

  In FIG. 6, the flow sensor 1 includes a Si substrate (sensor substrate) 2, a diaphragm 3, a microheater 4 made of platinum or the like formed on the diaphragm 3, and a downstream formed on the diaphragm 3 on the downstream side of the microheater 4. Power is supplied to the side thermopile 5, power terminals 6 A and 6 B for supplying drive current from a power source (not shown) to the microheater 4, and the upstream side thermopile 8 and the upstream side thermopile 8 formed on the diaphragm 3 upstream of the microheater 4. First output terminals 9A and 9B that output upstream temperature signals, and second output terminals 7A and 7B that output downstream temperature signals output from the downstream thermopile 5 are provided.

  The flow sensor 1 is arranged in a direction substantially orthogonal to the fluid flow direction (direction from P to Q) with respect to the microheater 4, detects physical property state information of the fluid, and detects a right side temperature detection signal (third temperature). The right thermopile 11 that outputs the detection signal), the third output terminals 12A and 12B that output the right temperature detection signal output from the right thermopile 11, and the micro heater 4 in a direction substantially perpendicular to the fluid flow direction. A left output thermopile 13 that detects physical property state information of the fluid and outputs a left side temperature detection signal (corresponding to the third temperature detection signal); a fourth output that outputs a left side temperature detection signal output from the left side thermopile 13; Terminals 14A and 14B, resistors 15 and 16 for obtaining fluid temperature, and output terminals 17A and 17B for outputting fluid temperature signals from the resistors 15 and 16 are provided. . The right thermopile 11 and the left thermopile 13 constitute a temperature sensor.

  The upstream thermopile 8, the downstream thermopile 5, the right thermopile 11, and the left thermopile 13 are composed of thermocouples. This thermocouple is composed of p ++-Si and Al, and has cold junctions 5b and 8b and hot junctions 5a and 8a, detects heat, and connects the cold junctions 5b and 8b with the hot junctions 5a and 8a. When a thermoelectromotive force is generated from the temperature difference, a temperature detection signal is output.

  As shown in FIG. 7, a diaphragm 3 is formed on the Si substrate 2. The diaphragm 3 includes a micro heater 4, an upstream thermopile 8, a downstream thermopile 5, a right thermopile 11, and a left thermopile 13. The respective hot junctions are formed.

  According to the flow sensor 1 configured as described above, when the microheater 4 starts to be heated by an external drive current, the heat generated from the microheater 4 is transferred from the downstream thermopile 5 and the upstream side using a fluid as a medium. The temperature is transmitted to the hot junctions 5a and 8a of the thermopile 8. Since the cold junctions 5b, 8b of each thermopile are on the Si substrate (Si substrate), they are at the substrate temperature, and since each hot junction is on the diaphragm, it is heated by the transferred heat, and Si The temperature rises above the substrate temperature. Each thermopile generates a thermoelectric power from the temperature difference between the hot junctions 5a and 8a and the cold junctions 5b and 8b, and outputs a temperature detection signal.

  The heat transferred by using the fluid as a medium is transferred to each thermopile by a synergistic effect of the heat diffusion effect of the fluid and the flow velocity of the fluid flowing from P to Q. That is, when there is no flow rate, the heat is diffused evenly to the upstream thermopile 8 and the downstream thermopile 5, and the difference between the upstream temperature signal from the upstream thermopile 8 and the downstream temperature signal from the downstream thermopile 5 is transmitted. The signal goes to zero.

  On the other hand, when a flow velocity is generated in the fluid, the amount of heat transferred to the hot junction 5a of the downstream thermopile 5 is increased by the flow velocity, and the amount of heat transferred to the hot junction 8a of the upstream thermopile 8 is reduced. The difference signal between the signal and the upstream temperature signal is a positive value corresponding to the flow velocity.

  On the other hand, when the microheater 4 starts to be heated by an external drive current, the heat generated from the microheater 4 is hardly affected by the flow velocity of the fluid and is only affected by the thermal diffusion effect of the fluid. It is transmitted to the right thermopile 11 arranged in a direction substantially orthogonal to the fluid flow direction. In addition, similar heat is transmitted to the left thermopile 13 disposed in a direction substantially orthogonal to the fluid flow direction with respect to the microheater 4. Therefore, the right temperature detection signal output from the third output terminals 12A and 12B by the electromotive force of the right thermopile 11 and / or the left temperature detection output from the fourth output terminals 14A and 14B by the electromotive force of the left thermopile 13 The signal is data correlated with the physical state of the fluid, and the physical state information can also be obtained by appropriate processing.

  The physical state of the fluid also affects the upstream temperature signal output from the upstream thermopile 8, the downstream temperature signal output from the downstream thermopile 5, and the upstream temperature signal, and changes in the same manner as the right and left thermopile outputs. To do. Therefore, in principle, by dividing the upstream temperature signal and the downstream temperature signal, or the difference between these by the right and / or left thermopile output, even with different fluids such as thermal diffusion constants, That is, an accurate flow rate can be calculated for any type of fluid.

  Therefore, the flow rate measuring device (not shown) is based on the right side temperature detection signal output from the third output terminals 12A and 12B and / or the left side temperature detection signal output from the fourth output terminals 14A and 14B. By calculating the information and correcting the difference signal between the upstream temperature signal from the upstream thermopile 8 and the downstream temperature signal from the downstream thermopile 5 with the physical property state information, high-precision measurement is realized. I have done it.

  On the other hand, the flow sensor 101 without the lateral temperature sensor shown in FIG. 10 is also used as the flow rate measuring device. FIG. 7 is also a cross-sectional view of FIG.

  When such a flow sensor 101 is used, it is necessary to devise control of the micro heater 104 so that the output does not change depending on the physical property state that changes depending on the temperature, pressure, and type of the fluid. For example, a method is known in which the temperature of the heated microheater 104 is controlled to rise by a certain temperature from the substrate temperature (ambient temperature) (Patent Document 2). This is done by arranging temperature sensors 15 and 16 for measuring the ambient temperature on the substrate 102, measuring the ambient temperature, and controlling with an analog circuit so that the temperature of the heater 104 is raised by a constant temperature from the ambient temperature output. To do.

  In the case of such a flow rate measuring device, the microheater 104 is controlled to a temperature that is higher than the ambient temperature by a certain temperature, so the temperature distribution with respect to the ambient temperature measured by the upstream thermopile 108 and the downstream thermopile 105 It was affected only by the flow velocity of the fluid, and was less affected by the physical properties of the fluid, enabling high-accuracy measurement.

  However, in the flow sensors 1 and 101 described above, there is a problem that the reproducibility of the measurement accuracy is poor despite the correction and control according to the physical property state of the fluid. In particular, when measuring a large flow rate, that is, when the flow velocity is high, the reproducibility is poor, which is a factor in limiting the flow rate measurement range.

  As a result of intensive investigation of this problem, it was found that the output changed even when no current flowed through the microheater 4, that is, when the flow sensor 1 was not driven. Details will be described below.

  FIG. 8 is a schematic diagram showing a thermopile output due to a conventional temperature difference, and FIG. 9 is a relationship between a temperature difference between a fluid temperature and a substrate temperature measured by a conventional flow sensor and a sensor output device difference (measurement error). It is the graph which showed. And the measurement is measured at 100 L / min in the standard state of the fluid.

  The unit indicated by the vertical axis in FIG. 9 is% RD (% of Reading: percentage of reading). For example, when the meter output is 9 L / min when the flow rate of 10 L / min is measured in a meter having a maximum flow rate of 100 L / min, this% RD indicates the instrumental difference as -10% RD. . And the tolerance at this time can be shown by -1% FS (percentage with respect to the maximum measured value of a meter).

  As shown in FIG. 8, when there is no temperature difference, the temperature sensor output is output V0 when no power is applied to the heater, and the output is V2 when power is applied to the heater. When the gas temperature rises above the substrate temperature in the flow sensor 1 in this state, the output V0 and the output V2 rise correspondingly, and become an output V1 and an output V3, respectively. However, since the power is always applied to the flow sensor 1, the output V0 and the output V1 cannot be measured, and the output that is originally the output V2 changes to the output V3.

  FIG. 9 shows the result of actually measuring the output of the flow sensor 1 shown in FIG. 6 and evaluating the error. The instrumental error was found to be about + 20% RD at a temperature difference of -30 degrees and about -20% RD at a temperature difference of +30 degrees.

  In the case of the flow sensor 1 shown in FIG. 6 (see Patent Document 1), the voltage applied to the heater is always substantially constant. Therefore, the temperature of the gas and the sensor base is the output of the upstream thermopile 8 and the downstream thermopile 5. The output due to the difference is almost the same, and when the difference output is measured, it is automatically canceled. However, the right and left thermopile outputs cannot be canceled because they do not take the difference output. If the difference output between the upstream thermopile 8 and the downstream thermopile 5 is not corrected by the right and / or left thermopile output, accurate measurement cannot be performed, and the output accuracy of the flow sensor 1 is deteriorated. That is, it has been found that the output of the flow sensor 1 changes in proportion to the temperature difference between the gas and the sensor base.

  On the other hand, in the case of the flow sensor 101 of FIG. 10, since the temperature sensors 15 and 16 for measuring the ambient temperature are on the substrate 102, the substrate temperature is measured instead of the ambient temperature and becomes higher by a certain temperature than the substrate temperature. Thus, the heater temperature is set. Therefore, when there is a temperature difference between the fluid and the substrate, the heater temperature rise relative to the substrate temperature is different from the temperature rise at which the microheater 104 heats the fluid. For this reason, the differential output between the upstream thermopile 108 and the downstream thermopile 105 is proportional to the temperature increase heated by the microheater 104, and the upstream thermopile 108 and the downstream are in proportion to the set temperature increase being controlled. The differential output of the side thermopile 105 has changed, resulting in an error in flow rate measurement.

As means for solving this, Patent Document 3 proposes a method of correcting the sensor output when the flow sensor 101 is pulse-driven and the heater is driven by the sensor output caused only by the temperature difference between the fluid and the substrate. . However, this method has a problem that the flow rate cannot be continuously measured.
JP 2001-12988 A Japanese Patent Laid-Open No. 04-034315 JP 2004-117157 A

  Therefore, in view of the above-described problems, an object of the present invention is to provide a flow rate measuring device capable of improving measurement accuracy even in continuous measurement.

In order to solve the above problems, the flow rate measuring device according to claim 1 according to the present invention is provided on a diaphragm 3 provided on the surface of a base 2 and on the diaphragm 3, as shown in a basic configuration diagram of FIG. A heater 4 that heats the fluid flowing in the flow path, and an upstream side that is provided on the diaphragm 3 upstream of the flow path with respect to the heater 4 and that detects the temperature of the fluid and outputs an upstream temperature signal A flow sensor having a temperature sensor 8 and a downstream temperature sensor 5 provided on the diaphragm 3 on the downstream side of the flow path with respect to the heater 4 to detect the temperature of the fluid and output a downstream temperature signal. In the flow rate measuring apparatus for measuring the flow rate of the fluid using 1, the reference base 2 </ b> A formed by the same constituent members as the base 2 and the same constituent members as the diaphragm 3 are used. The reference diaphragm 3A formed on the surface of the reference substrate 2A and the upstream side temperature sensor 8 on the diaphragm 3 are arranged on the reference diaphragm 3A so as to be the same as the arrangement of the fluid. The reference upstream temperature sensor 8A that detects the temperature of the reference and outputs a reference upstream temperature signal is placed on the reference diaphragm 3A so as to have the same arrangement as the downstream temperature sensor 5 on the diaphragm 3. And a reference downstream temperature sensor 5A that detects the temperature of the fluid and outputs a reference downstream temperature signal so as to be influenced by the same fluid flow as the flow sensor 1. The non-heating reference member 1A provided in the flow path, the downstream temperature signal output from the downstream temperature sensor 5 and the upstream temperature sensor 8 output. From the temperature difference output Von is a difference signal of the flow-side temperature signal, the reference downstream temperature signal and the reference upstream temperature signal said reference upstream temperature sensor 8A outputs the reference downstream temperature sensor 5A outputs The flow direction subtraction means 41d for calculating the same output as that obtained by subtracting the temperature difference output Voff , which is a difference signal of the flow rate, and the flow rate calculation for calculating the flow rate of the fluid based on the calculation result by the flow direction subtraction means 41d And means 41c.

According to the first aspect of the present invention, the non-heating reference member 1A is affected by the same fluid flow as the flow sensor 1 in the flow path in which the flow sensor 1 is provided. Provided. Then, when the heater 4 is heated by external control or the like, the downstream temperature signal and the upstream temperature signal are taken in from the downstream temperature sensor 5 and the upstream temperature sensor 8 of the flow sensor 1, respectively. The reference downstream temperature signal and the reference upstream temperature signal corresponding to the temperature signal are taken in from the reference downstream temperature sensor 5A and the reference upstream temperature sensor 8A of the non-heating reference member 1A. Then, the flow direction subtracting means 41d converts the temperature difference output Voff, which is the difference signal between the reference downstream temperature signal and the reference upstream temperature signal, from the temperature difference output Von, which is the difference signal between the downstream temperature signal and the upstream temperature signal. The same output as that obtained by subtracting is calculated , and the flow rate of the fluid based on the calculation result is calculated by the flow rate calculation means 41c.

As shown in the basic configuration diagram of FIG. 1, the flow rate measuring device according to Item 2 includes a diaphragm 3 provided on the surface of the base 2 and a heater that is provided on the diaphragm 3 and heats the fluid flowing in the flow path. 4, an upstream temperature sensor 8 provided on the diaphragm 3 upstream of the flow path with respect to the heater 4 to detect the temperature of the fluid and output an upstream temperature signal, and the flow with respect to the heater 4 A downstream temperature sensor 5 provided on the diaphragm 3 on the downstream side of the path to detect the temperature of the fluid and output a downstream temperature signal; and provided on the diaphragm 3 and substantially the flow direction of the fluid. By using a flow sensor 1 having lateral temperature sensors 11 and 13 that detect the temperature of the fluid in a substantially orthogonal direction passing through the heater 4 and output a lateral temperature signal, the fluid flow 2A, a reference base 2A formed of the same constituent members as the base 2, a reference diaphragm 3A formed of the same constituents as the diaphragm 3, and the diaphragm 3 on the diaphragm 3 A reference lateral temperature sensor provided on the reference diaphragm 3A for detecting the temperature of the fluid and outputting a reference lateral temperature signal so as to be substantially the same as the arrangement of the lateral temperature sensors 11 and 13. 11A, 13A, a non-heating reference member 1A provided in the flow path so as to be influenced by the same fluid flow as the flow sensor 1, and the lateral temperature sensors 11, 13 Side subtracting means 41a for subtracting the reference lateral temperature signal output from the reference lateral temperature sensors 11A, 13A from the lateral temperature signal output by the reference side, and the lateral side subtracting means 4 a based on the lateral side temperature signal obtained by subtracting the, and the temperature distribution property status information detecting means 41b for detecting the physical property state information indicating the physical properties condition of the fluid in accordance with in the substantially perpendicular direction, the downstream temperature sensor 5 The flow rate calculation means 41c for calculating the flow rate of the fluid based on the downstream temperature signal output from the upstream temperature sensor 8 and the upstream temperature signal output from the upstream temperature sensor 8 and the physical property state information detected by the physical property state information detection means 41b. It is characterized by having.

According to the second aspect of the present invention, the non-heating reference member 1A is affected by the same fluid flow as the flow sensor 1 in the flow path in which the flow sensor 1 is provided. Provided. When the heater 4 is in a heated state, the lateral temperature signal is taken from the lateral temperature sensors 11 and 13 of the flow sensor 1 and the reference lateral temperature signal corresponding to the lateral temperature signal is not heated. It is taken in from the reference lateral temperature sensors 11A and 13A of the reference member 1A. Then, based on the lateral temperature signal obtained by subtracting the reference lateral temperature signal from the captured lateral temperature signal , the physical properties of the fluid in accordance with the spread, change, etc. of the temperature distribution in the substantially orthogonal direction indicating the physical state of the fluid Physical property state information indicating the state is calculated by the physical property state information detecting means 41c. Then, the flow rate calculation means 41c calculates the flow rate of the fluid based on the captured upstream temperature signal and downstream temperature signal and the detected physical property state information.

As shown in the basic configuration diagram of FIG. 1, the invention described in item 3 is the flow rate measuring device according to claim 2, wherein the non-heating reference member 1 </ b> A further includes the upstream temperature sensor 8 on the diaphragm 3. The reference upstream temperature sensor 8A provided on the reference diaphragm 3A to detect the temperature of the fluid and output a reference upstream temperature signal so as to be the same as the arrangement of A reference downstream temperature sensor 5A provided on the reference diaphragm 3A so as to be the same as the arrangement of the downstream temperature sensor 5 and detecting the temperature of the fluid and outputting a reference downstream temperature signal; from a configured, the a difference signal of the upstream-side temperature signal downstream temperature signal and said upstream temperature sensor 8 outputs the downstream temperature sensor 5 outputs the temperature difference output Von, Identical to that serial reference downstream temperature sensor 5A is obtained by subtracting the temperature difference output Voff which is a difference signal of the reference downstream temperature signal and the reference upstream temperature signal said reference upstream temperature sensor 8A is outputted to the output The flow direction subtracting means 41c is further provided so that the flow rate calculating means 41c is based on the calculation result by the flow direction subtracting means 41d and the physical property state information detected by the physical property state information detecting means 41b. The flow rate of the fluid is calculated.

According to the third aspect of the present invention, each of the reference upstream temperature sensor 8A and the reference downstream temperature sensor 5A provided on the non-heating reference member 1A is thermally generated by the heater 4 of the flow sensor 1. The temperature of the fluid that is not affected is detected, and a reference upstream temperature signal and a reference downstream temperature signal are output. When the reference upstream temperature signal and the reference downstream temperature signal are taken in, the difference signal between the downstream temperature signal output from the downstream temperature sensor 5 and the upstream temperature signal output from the upstream temperature sensor 8 is output. The same output as that obtained by subtracting the temperature difference output Voff, which is the difference signal between the reference upstream temperature signal and the reference downstream temperature signal , is calculated from the temperature difference output Von . Then, the flow rate of the fluid based on those calculation results and physical property state information is calculated by the flow rate calculation means 41c.

  In the flow rate measuring device according to any one of claims 1 to 3, the non-heating reference member 1A is the flow sensor, as shown in the basic configuration diagram of FIG. 1 is another flow sensor having the same configuration as that of No. 1.

  According to the present invention described in claim 4, when a flow sensor is provided in the flow path, another flow sensor having the same configuration as the flow sensor is used as a non-heating reference member on the upstream side of the flow sensor or the like. Is provided.

In order to solve the above problems, the fluid discrimination device according to claim 5 according to the present invention is provided on a diaphragm 3 provided on the surface of a base 2 and on the diaphragm 3, as shown in a basic configuration diagram of FIG. A heater 4 that heats the fluid flowing in the flow path, and a temperature that is provided on the diaphragm 3 and is substantially orthogonal to the fluid flow direction and passes through the heater 4 to detect the temperature of the fluid. In a fluid discrimination device that discriminates the type of fluid to be discriminated using a flow sensor 1 having lateral temperature sensors 11 and 13 that output a side temperature signal, a reference formed by the same component as the base 2 Substrate 2A, a reference diaphragm 3A formed of the same components as the diaphragm 3, and the arrangement of the lateral temperature sensors 11 and 13 on the diaphragm 3 are substantially the same. The reference side temperature sensors 11A and 13A provided on the reference diaphragm 3A for detecting the temperature of the fluid and outputting a reference side temperature signal. From the non-heating reference member 1A provided in the flow path so as to be affected by the same fluid flow as that of the sensor 1, and the lateral temperature signal output from the lateral temperature sensors 11 and 13, the reference Based on the lateral subtraction means 41a for subtracting the reference lateral temperature signal output from the lateral temperature sensors 11A and 13A, and the lateral temperature signal subtracted by the lateral subtraction means 41a , in the substantially orthogonal direction. Physical state information detecting means 41b for detecting physical state information indicating the physical state of the fluid according to the temperature distribution, and based on the physical state information detected by the physical state information detecting means 41b. There is characterized in that so as to determine the type of the determination target fluid.

According to the present invention described in claim 5, the non-heating reference member 1A is provided in the flow path in which the flow sensor 1 is provided so as not to be affected by the temperature distribution generated by the heater 4, for example. When the heater 4 is in a heated state, the lateral temperature signal is taken from the lateral temperature sensors 11 and 13 of the flow sensor 1 and the reference lateral temperature signal corresponding to the lateral temperature signal is not heated. It is taken in from the reference lateral temperature sensors 11A and 13A of the reference member 1A. Then, based on the lateral temperature signal obtained by subtracting the reference lateral temperature signal from the captured lateral temperature signal , the physical properties of the fluid in accordance with the spread, change, etc. of the temperature distribution in the substantially orthogonal direction indicating the physical state of the fluid Physical property state information indicating the state is calculated by the physical property state information detecting means 41c. Then, the type of the discrimination target fluid is discriminated based on the physical property state information.

As described above, according to the flow rate measuring device of the present invention described in claim 1, the non-heating reference member having the same configuration of the base body, the diaphragm, the downstream temperature sensor, and the upstream temperature sensor in the flow sensor is flown. provided in the sensor and the same flow channel, and captures the downstream temperature signal and the upstream side temperature signal at the time of heating from the flow sensor heater, participants from unheated reference member which is not affected by heat from the heater Teruyo The downstream temperature signal and the reference upstream temperature signal are taken in , and the difference signal between the reference downstream temperature signal and the reference upstream temperature signal is obtained from the temperature difference output Von which is the difference signal between the downstream temperature signal and the upstream temperature signal. from what has been to calculate the flow rate of the fluid compensation to the basis a certain temperature difference same output as the output Voff obtained by subtracting the result of the operation, even in a heated state of the heater The reference downstream temperature signal and the reference upstream temperature according to the temperature difference between the latest substrate temperature and the fluid temperature are always measured during the fluid measurement period from the non-heating reference member not affected by the heating of the sensor. Since the signal can be captured, even if there is a temperature difference between the substrate and the fluid due to a temperature change outside the flow path, etc., the temperature sensor generated when the temperature difference occurs between the substrate temperature and the fluid temperature. Since the offset output can be canceled, the flow sensor output accuracy can be maintained in a good state even if a temperature difference occurs between the substrate temperature and the fluid temperature. Further, since the non-heating reference member is provided in the flow path so as to be affected by the same fluid flow as that of the flow sensor, the same influence as the fluid flowing into the flow sensor is obtained. Therefore, even when the heater of the flow sensor is driven, the downstream and upstream temperature signals corresponding to the non-driven state can always be taken in, so the heater drive control and correction processing in the flow measuring device are complicated. Therefore, the measurement accuracy for the fluid can be improved.

As described above, according to the flow rate measuring device of the present invention described in claim 2, the non-heating reference member having the same configuration of the base body, the diaphragm, and the lateral temperature sensor in the flow sensor is used as the heater of the flow sensor. Provided in the flow path so as not to be affected by the generated temperature distribution, and when the heater is heated, the lateral temperature signal from the lateral temperature sensor of the flow sensor, the reference lateral temperature of the non-heating reference member Based on the upstream temperature signal and the downstream temperature signal corrected based on the physical property state information detected based on the lateral temperature signal obtained by subtracting the reference lateral temperature signal , respectively. Since the fluid flow rate is measured, the reference side temperature signal that is not always affected by the heating of the heater can be captured even in the heating state of the heater. It is possible to always obtain the latest physical property information during the body measurement period, and even if a temperature difference occurs between the substrate and the fluid due to a temperature change outside the flow path, the temperature between the substrate temperature and the fluid temperature Since the offset output of the temperature sensor generated when a difference occurs can be canceled, the flow sensor output accuracy can be maintained in a good state even if a temperature difference occurs between the substrate temperature and the fluid temperature. Further, since the non-heating reference member is provided in the flow path so as to be affected by the same fluid flow as that of the flow sensor, the same influence as the fluid flowing into the flow sensor is obtained. Therefore, since the lateral temperature signal corresponding to the non-driving state can always be taken even when the heater of the flow sensor is driven, control of the heater driving in the flow measuring device, correction processing, etc. are not complicated. Measurement accuracy for various types of fluids can be improved.

According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, the non-heating reference member is provided with the reference upstream temperature sensor and the reference downstream temperature sensor, and for reference thereof. The reference upstream temperature signal and the reference downstream temperature signal are further fetched from the sensor of the sensor, and the reference downstream temperature signal and the reference upstream are obtained from the temperature difference output Von which is a difference signal between the downstream temperature signal and the upstream temperature signal. Since the same output as that obtained by subtracting the temperature difference output Voff which is the difference signal of the side temperature signal is calculated , the error factor of the measurement accuracy can be further reduced, so that the measurement accuracy can be further improved. Can do.

  According to the invention described in claim 4, in addition to the effect of the invention described in any one of claims 1-3, another flow sensor having the same configuration as the flow sensor is used as the non-heating reference member. As a result, errors due to differences in configuration between the flow sensor and the non-heating reference member can be almost eliminated, and there is no need to use individual components as the non-heating reference member. And can be manufactured inexpensively.

As described above, according to the fluid discrimination device of the present invention described in claim 5, the non-heating reference member having the same configuration of the base body, the diaphragm, and the lateral temperature sensor in the flow sensor is used as the heater of the flow sensor. Provided in the flow path so as not to be affected by the generated temperature distribution, and when the heater is heated, the lateral temperature signal from the lateral temperature sensor of the flow sensor, the reference lateral temperature of the non-heating reference member Since the physical property state information of the fluid is detected based on the lateral temperature signal obtained by subtracting the reference lateral temperature signal, and the type of the discrimination target fluid is determined based on the physical property state information. Even if a temperature difference occurs between the fluid temperature and the substrate temperature of the flow sensor, the error due to the temperature difference can be eliminated. Therefore, the physical property state information is based on the accurate lateral temperature signal. It is possible to accurately determine the fluid detection to. Therefore, the accuracy of discrimination can be improved for various types of fluids.

  Hereinafter, an embodiment of a flow rate measuring apparatus according to the present invention that measures the flow rate of a fluid using the flow sensors 1 and 101 (see FIGS. 6, 7, and 10) described in the background art will be described with reference to FIG. Description will be made with reference to the drawings of FIGS. Since the basic configuration of the flow sensors 1 and 101 has been described in the background art, a detailed description thereof will be omitted.

  Here, FIG. 2 is a diagram for explaining an installation example of the flow rate measuring device of the present invention using a flow sensor, and FIG. 3 is a block diagram showing an example of the configuration of the flow rate measuring device shown in FIG. FIG. 4 is a flowchart showing an example of a flow rate measurement process according to the present invention executed by the CPU of FIG.

[First best mode]
In FIG. 2, a flow rate measuring device 20 of the present invention measures the flow rate of a gas, which is a fluid, using the flow sensor 1 described in the background art. The flow sensor 1 heats the fluid at a temperature higher than the temperature of the diaphragm 3 provided on the surface of the base body while being insulated from the base body 2, and the gas provided on the diaphragm 3 and flowing in the flow path 70. And a micro heater (heater) 4 that generates a predetermined temperature distribution, and a temperature difference between the base 2 and the diaphragm 3 provided on the diaphragm 3 on the upstream side of the flow path 70 with respect to the heater 4. An upstream thermopile (upstream temperature sensor) 8 that detects the temperature of the gas and outputs an upstream temperature signal, and the base 2 provided on the diaphragm 3 downstream of the flow path 70 with respect to the microheater 4. And a downstream thermopile (downstream temperature sensor) that detects the temperature of the fluid based on a temperature difference between the diaphragm 3 and the diaphragm 3 and outputs a downstream temperature signal. 5), and a temperature signal of the fluid corresponding to the temperature distribution in a substantially orthogonal direction passing through the heater 4 substantially orthogonal to the fluid flow direction provided on the diaphragm 3 and outputting a lateral temperature signal. A right thermopile 11 and a left thermopile 13 (lateral temperature sensor).

  The flow rate measuring device 20 amplifies a differential signal between the above-described downstream temperature signal from the downstream thermopile 5 in the flow sensor 1 and the upstream temperature signal from the upstream thermopile 8 in the flow sensor 1. And an amplifier 35a for amplifying the right temperature detection signal from the right thermopile 11 in the flow sensor 1, an amplifier 35b for amplifying the left temperature detection signal from the left thermopile 13 in the flow sensor 1, and a predetermined program A microprocessor (MPU) 40 that operates and a drive unit 50 that is controlled by the MPU 40 and drives the microheater 4 are configured. Each of the differential amplifier 33, the amplifiers 35a and 35b, and the drive unit 50 is connected to the MPU 40.

  Furthermore, the flow rate measuring device 20 has a non-heating reference member 1A provided in the flow path 70 so as not to be affected by the temperature distribution generated by the heater 4 of the flow sensor 1. As shown in FIG. 2, the non-heating reference member 1A is on the cross section of the flow path 70 which is substantially perpendicular to the flow direction of gas flowing in the flow path 70 (the direction from P to Q in FIG. 2). In FIG. 5, the flow sensor 70 is provided on the inner wall below the flow path 70 so as to face the flow sensor 1 provided above.

  Note that the arrangement relationship between the flow sensor 1 and the non-heating reference member 1A is not changed in the cross-sectional shape, etc., which are arranged at positions substantially orthogonal to the flow on an arbitrary wall surface in the flow path 70. The linear flow path 70 can have various different arrangement relationships, such as arranging the non-heating reference member 1A upstream and the flow sensor 1 downstream.

  Further, it is conceivable to arrange the non-heating reference member 1A at a position where there is almost no flow in the flow path 70, a position where the flow is not affected, etc., but the gas at the position where there is no flow (stagnation position) Since it is not always the same temperature as the flowing gas, it is not appropriate to arrange at such a position, and the above-described arrangement relationship is preferable.

  Furthermore, as long as the flow path 70 is arranged at the same position in the same cross-sectional shape, there is no big problem even if the distance between them is long. Are preferably close to each other.

  The non-heating reference member 1A has the same basic configuration as that of the flow sensor 1 described above. The reference base 2A is formed of the same constituent member as the base 2 of the flow sensor 1, and is insulated from the reference base 2A. A reference diaphragm 3A provided on the surface of the flow sensor 1 and formed of the same components as the diaphragm 3 of the flow sensor 1, and a right thermopile 11 and a left thermopile 13 (horizontal) with respect to the gas flow direction. The temperature of the fluid is detected on the basis of the temperature difference between the reference substrate 2A and the gas on the hot junction provided on the reference diaphragm 3A so as to be in the same direction as the side temperature sensor). A reference right thermopile 11A that outputs a side temperature signal and a reference left thermopile 13A (reference side temperature sensor).

  Further, the non-heating reference member 1A is provided on the reference diaphragm 3A on the upstream side of the flow path 70, and the temperature of the fluid is determined based on the temperature difference between the upstream reference base 2A and the gas on the hot junction. And a reference upstream temperature sensor 8A that outputs a reference upstream temperature signal and a reference diaphragm 3A on the downstream side of the flow path 70, and the reference base 2A on the downstream side and the hot junction A reference downstream temperature sensor 5A that detects the temperature of the fluid based on the temperature difference from the gas and outputs a reference downstream temperature signal.

  Further, the flow rate measuring device 20 generates a reference downstream temperature signal from the reference downstream thermopile 5A in the non-heating reference member 1A and a reference upstream temperature signal from the reference upstream thermopile 8A. A differential amplifier 34 that amplifies the difference signal, an amplifier 36a that amplifies the right temperature detection signal from the reference right thermopile 11A in the non-heating reference member 1A, and a left temperature detection signal from the reference left thermopile 13A. And an amplifier 36b for amplifying. Each of the differential amplifier 34 and the amplifiers 36a and 36b is connected to the MPU 40.

  In the best mode, since the non-heating reference member 1A is constituted by another flow sensor having the same configuration as the flow sensor 1, the heater 4 of the flow sensor 1 is also provided to the non-heating reference member 1A. Although there is a heater corresponding to the above, the heater is not driven. The non-heating reference member 1 </ b> A is not limited to the configuration, and for example, only the reference right thermopile 11 </ b> A and the reference left thermopile 13 </ b> A are formed on the reference diaphragm 3 </ b> A formed in the same shape as the diaphragm 3. Various forms such as a form using the reference diaphragm 3A formed smaller than the outer shape of the diaphragm 3 can be used.

  As is well known, the MPU 40 includes a central processing unit (CPU) 41 that performs various processes and controls according to a predetermined program, a ROM 42 that is a read-only memory storing programs for the CPU 41, and various data. And a RAM 43, which is a readable / writable memory having an area necessary for processing operations of the CPU 41, and the like.

In the ROM 42, when the flow rate of gas is measured using the flow sensor 1, the CPU 41 (computer) includes a subtracting means for lateral side , a physical property state information detecting means, a flow rate calculating means, and a flow in the above-mentioned claims. Various programs for functioning as direction subtraction means are stored.

  The CPU 41 receives a difference signal, which is a difference between the downstream temperature signal from the downstream thermopile 5 and the upstream thermopile 8 and the upstream temperature signal, via the differential amplifier 33, and the reference downstream thermopile 5A and A difference signal that is a difference between the reference downstream temperature signal from the reference upstream thermopile 8 </ b> A and the reference upstream temperature signal is input via the differential amplifier 34.

  In the best mode, the case where the differential amplifier 33 is used will be described. However, the present invention is not limited to this, and the downstream temperature signal and the upstream temperature signal are directly input to the CPU 41 after being amplified by the amplifier. For example, various forms can be adopted.

  The CPU 41 receives the right temperature signal from the right thermopile 11 via the amplifier 35a, the left temperature signal from the left thermopile 13 via the amplifier 35b, and the reference from the reference right thermopile 11A. The right temperature signal is input via the amplifier 36a, and the left temperature signal from the reference left thermopile 13A is input via the amplifier 36b.

  In this best mode, a method using two amplifiers 35a and 35b and two amplifiers 36a and 36b will be described. For example, a method of constructing an amplifier circuit that outputs the sum of two signals by one amplifier, etc. Different methods can be used.

  The drive unit 50 is connected to the MPU 40, and includes a drive circuit that drives the microheater 4 by controlling power supply to the microheater 4 in accordance with an instruction from the MPU 40.

  Next, an example of the flow rate measurement process executed by the CPU 41 of the microcomputer 40 having the above-described configuration will be described below with reference to the flowchart shown in FIG.

  When the flow rate measurement process shown in FIG. 4 is started, the driving unit 50 is instructed to start heating the microheater 4 in step S11, and then the process proceeds to step S12. In response to this instruction, the driving unit 50 drives the micro heater 4 so that a constant voltage is applied. As a result, the gas around the microheater 4 is heated and a predetermined temperature distribution is generated.

  In step S12, the right side temperature detection signal and the left side temperature detection signal are taken in from the right side thermopile 11 and the left side thermopile 13 via the amplifiers 35a and 35b, and these signal values are stored in the RAM 43 as the temperature distribution output V3on when the microheater 4 is driven. And then the process proceeds to step S13.

  In step S13, the right side temperature detection signal and the left side temperature detection signal (corresponding to the lateral side temperature signal) are taken in from the reference right thermopile 11A and the reference left thermopile 13A via the amplifiers 35a and 35b, and the signal values thereof are micronized. The temperature distribution output V3off when the heater 4 is not driven is stored in the RAM 43, and then the process proceeds to step S14.

  In step S14, the difference signal between the upstream temperature signal and the downstream temperature signal output from the downstream thermopile 5 and the upstream thermopile 8 of the flow sensor 1 corresponding to the temperature distribution output V3on at the time of heating is the differential amplifier 33. The signal value is stored in the RAM 43 as the temperature difference output Von at the time of heating, and then the process proceeds to step S15.

  In step S15, corresponding to the temperature distribution output V3off at the time of non-heating, the reference upstream temperature signal and the reference reference output from the reference downstream thermopile 5A and the reference upstream thermopile 8A of the non-heating reference member 1A, respectively. The difference signal of the downstream temperature signal is taken in via the differential amplifier 34, and the signal value is stored in the RAM 43 as the temperature difference output Voff at the time of non-heating, and then the process proceeds to step S16.

In step S16 ( lateral side subtracting means , physical property state information detecting means), the difference between the temperature distribution output V3on and the temperature distribution output V3off of the RAM 43 is obtained, whereby the physical property state information corresponding to the physical property of the fluid (V3on−V3off) Is calculated and stored in the RAM 43, and then the process proceeds to step S17. Note that the physical properties of the fluid can be determined to some extent based on the physical property state information.

In step S17 ( flow direction subtraction means , flow rate calculation means), the temperature difference outputs Von and Voff of the RAM 43, physical property state information (V3on-V3off), and a flow rate calculation formula described later are used for one measurement. The winning flow rate is calculated and stored in the RAM 43 as flow rate information. Thereafter, in step S18, the flow rate information is output to a predetermined display device, for example, and displayed on the display device.

  In this best mode, a calculation program for calculating (Von−Voff) / (V3on−V3off) which is a flow rate calculation formula is stored in the ROM 42 in advance, but correction of the temperature difference output Von is not necessary. In such a case, a calculation program for calculating a flow rate calculation formula of Von / (V3on−V3off) is stored in the RAM 42, and the processing in step S12 described above can be deleted.

  In step S19, it is determined whether an end request has been received. If it is determined that an end request has not been received (N in S19), the process returns to step S12, and a series of processing is repeated. Note that it is not necessary to immediately return to step S12, and it may be possible to return after a predetermined time has elapsed. On the other hand, if it is determined that the end request has been received (Y in S19), the driving unit 50 is instructed to end the heating of the microheater 4 in step S20, and when the driving of the microheater 4 is stopped, the subsequent processing is performed. Is terminated.

  Here, the reason why the flow rate measuring apparatus having the above-described configuration is effective will be described in comparison with a conventional measuring apparatus and its measuring method.

  In the conventional measurement, since one flow sensor 1 is used, the temperature sensor output when the microheater 4 is not driven is not measured during the measurement of driving the microheater 4. Therefore, the data output as the flow sensor 1 is Von / V3on. On the other hand, the output data of the present invention is Von / (V3on-V3off). If the output V3off when the heater is not driven is 0, the output is the same. The temperature of the diaphragm 3 on which the (thermopile hot junction) is mounted also rises, the output V3off is not 0, and V3off> 0. Since the output V3on when the heater is driven is similarly affected by the temperature rise of the diaphragm 3 due to the temperature difference, the output becomes larger by the output V3off than when there is no temperature difference.

  The same applies to the case where the temperature of the fluid is lower than that of the substrate 2, and the temperature of the diaphragm 3 on which the thermopile hot junction is mounted decreases, the output V3off is not zero, and V3off <0. The output V3on when the heater is driven is also reduced by an amount corresponding to V3off compared to when there is no temperature difference. Thus, since the V3on output changes and is unstable due to the temperature difference between the fluid and the substrate 2, the output is unstable and the measurement error is large in the conventional flow sensor output Von / V3on. Since the output is stable at the flow sensor output Von / (V3on−V3off), the measurement error is greatly reduced.

  When (Von−Voff) / (V3on−V3off) is used as the flow sensor output, there is an effect of further improving the measurement accuracy. Since Von is a differential output between the upstream thermopile 8 and the downstream thermopile 5, there is an effect that the amount of change in the thermopile output due to the temperature change of each hot junction is canceled, and Von / (V3on− V3off) alone can improve the measurement error. However, Von slightly changes due to changes in the thermal resistance, heat capacity, etc. of the diaphragm 3 due to the temperature change of the diaphragm 3. Therefore, the difference output by Voff is taken, and (Von−Voff) / (V3on−V3off) is used as the flow sensor output, thereby further improving the measurement accuracy.

  Next, an example of the operation (action) in the flow rate measuring device 20 having the above-described configuration will be described with reference to the drawing in FIG. FIG. 5 is a graph showing the relationship between temperature difference and instrumental error according to the present invention.

  When the flow rate measuring process described above is executed by the flow rate measuring device 20, the microheater 4 is driven. The flow rate measuring device 20 takes in the temperature distribution output V3on from the right side thermopile 11 and the left side thermopile 13 of the flow sensor 1, and takes in the temperature difference output Von from the upstream side thermopile 8 and the downstream side thermopile 5, respectively. The temperature distribution output V3off is taken from the reference right thermopile 11A and the reference left thermopile 13A of 1A, and the temperature difference output Voff is taken from the reference upstream thermopile 8A and the reference downstream thermopile 5A, respectively.

  Physical property state information is detected based on the difference between the captured temperature distribution output V3on and the temperature distribution output V3off, and the gas flow rate is calculated using the physical property state information, the captured temperature difference outputs Von, Voff and the flow rate calculation formula. Then, the flow rate is output as flow rate information to, for example, a display device and displayed.

  Thereafter, during the gas measurement period, the above-described processing is repeated, so that the physical property state information is always detected when the flow rate is measured, and the upstream and downstream temperature sensor outputs are corrected with this physical property state information to calculate the flow rate. Do.

  When the relationship between the temperature difference and the instrumental difference was confirmed under the same measurement conditions as those described in the problem to be solved by the above-described invention, the result shown in FIG. 5 was obtained. Specifically, when the sensor base and the gas temperature difference are changed in a range of about -30 to 30 degrees, as shown in FIG. 5, the instrumental difference is about 1% when the temperature is -30 degrees, and -15 degrees. The measurement result is about 0% at -5 degrees, about 0.5% at -5 degrees, about 0% at 5 degrees, about 0% at 15 degrees, and about -1% at 30 degrees. I was able to get it. That is, in this way, the flow rate measuring device 20 of the present invention can eliminate the occurrence of an instrumental error due to a change in temperature difference.

  As described above, according to the flow rate measuring device 20 of the present invention, the non-heating reference member 1A having the same configuration of the base 2, the diaphragm 3, the right thermopile 11 and the left thermopile 13 (lateral temperature sensor) in the flow sensor 1 is used. Is provided in the flow path so as not to be affected by the temperature distribution generated by the micro heater (heater) 4 of the flow sensor 1, and the right thermopile 11 and the left side of the flow sensor 1 are heated when the micro heater 4 is heated. Each lateral temperature signal and each reference lateral temperature signal of the non-heating reference member 1A are taken in from the thermopile 13, respectively, and the physical property state information of the fluid is detected based on these lateral temperature signals, and the physical property state information is obtained. Since the flow rate of the fluid is measured based on the upstream temperature signal and the downstream temperature signal corrected based on the microheater 4 The temperature sensor offset that occurs when the temperature difference between the substrate temperature and the fluid temperature can be corrected by the reference temperature signal that is not affected by the heating, even in the heated state. Since the output can be canceled, the flow sensor output accuracy can be maintained in a good state even if a temperature difference occurs between the substrate temperature and the fluid temperature. Therefore, even when the micro heater 4 of the flow sensor 1 is driven, the lateral temperature signal corresponding to the non-driven state can always be taken in, so that the heater driving control and correction processing in the flow rate measuring device 20 are complicated. Even if it is continuous measurement, the measurement precision with respect to various kinds of fluids can be improved.

  Further, since the non-heating reference member 1A is provided on the side wall surface opposite to the flow sensor 1 in the flow path 70 so as to be affected by the flow of gas (fluid), the same temperature as the gas flowing into the flow sensor 1 is obtained. The reference side that is not affected by the heat generated by the micro heater 4 of the flow sensor 1 by the reference right thermopile 11A and the reference left thermopile 13A (reference side temperature sensor). A temperature signal can be captured. Therefore, since the lateral temperature signal can always be corrected more accurately, the measurement accuracy for various types of fluids can be further improved.

  Further, a reference upstream temperature sensor 8A and a reference downstream temperature sensor 5A are provided on the non-heating reference member 1A, and a reference upstream temperature signal and a reference downstream temperature signal are received from each of these reference sensors. Further, since the upstream temperature signal and the downstream temperature signal are also corrected and corrected, the error factor of the measurement accuracy can be further reduced, so that the measurement accuracy can be further improved.

  In addition, since the other flow sensor having the same configuration as the flow sensor 1 is used as the non-heating reference member 1A, an error due to a difference in configuration between the flow sensor 1 and the non-heating reference member 1A is almost eliminated. This can be eliminated, and since it is not necessary to use individual components as the non-heating reference member 1A, the measurement accuracy can be further improved.

  In the above-described best mode, the case where each unit in the claims is realized by the MPU 40 has been described. However, the present invention is not limited to this. For example, a digital signal processor (DSP), an ASIC (application) It can be in various forms such as realization with specific IC).

  Further, each signal from the right thermopile 11 and the left thermopile 13 is amplified by the amplifiers 35a and 35b, and each signal from the reference right thermopile 11A and the reference left thermopile 13A is amplified by the amplifiers 36a and 36b to the MPU 40. Although the case of inputting is described, the present invention is not limited to this. The differential amplifiers 33 and 34 for the upstream temperature signal and the downstream temperature signal are different from the amplifiers 35a and 35b and 36a and 36b described above. It is possible to further simplify the arithmetic processing in the MPU 40 by automatically correcting (subtracting) on the analog circuit such as replacement with a dynamic amplifier.

  Further, in the above-described best mode, the flow rate measuring device 20 has been described. However, the present invention is not limited to this, and can be realized by incorporating the flow rate measuring device 20 in a gas meter, or a fluid such as water or chemicals. Various forms such as realization as a measuring instrument can be adopted.

[Second best mode]
In the first best mode described above, the case where the downstream side and upstream side temperature signals are corrected based on the physical property state information of the fluid has been described. However, the present invention is not limited to this and is corrected by the physical property state information. It is also effective for a flow rate measuring device that does not. Therefore, in the second best mode, flow rate measurement in which the flow rate is measured by correcting the downstream and upstream temperature signals without detecting the physical property state information will be described.

  Since each of the flow sensor 1, the non-heating reference member 1A, and the flow rate measuring device 20 has the same basic configuration as the first best mode described above, only different portions will be described.

  First, in FIG. 3, a flow sensor 1 includes a substrate 2, a diaphragm 3, a micro heater 4, a downstream thermopile (temperature sensor) 5, an upstream thermopile (temperature sensor) 8, and a resistance (substrate temperature) for detecting the temperature of the substrate 2. (Detection means: see FIG. 6) 15 and 16 only. The non-heating reference member 1A includes only the reference substrate 2A, the reference diaphragm 3A, the reference downstream thermopile 5A, and the reference upstream thermopile 8A (reference side temperature sensor).

  The configuration of the flow rate measuring device 20 is dealt with by deleting the configuration corresponding to the right thermopile 11, the left thermopile 13, the reference right thermopile 11A, and the reference left thermopile 13A in FIG.

In the ROM 42 of the flow rate measuring device 20, the reference downstream temperature thermopile 5 </ b> A is output from the downstream temperature signal output from the downstream temperature thermopile 5 and the upstream temperature signal output from the upstream temperature thermopile 8 . downstream temperature signal and the flow direction for subtracting means said reference upstream temperature thermopile 8A subtracts the reference upstream temperature signal output, to the downstream side temperature signal and the upstream side temperature signal the flow direction for subtracting means subtracting Various programs for causing the CPU 41 to function as various means such as a flow rate calculating means for calculating the flow rate of the fluid based on the above are stored in advance.

  When the flow rate measuring device 20 detects the substrate temperature of the substrate 2 detected by the resistors 15 and 16, the flow rate measuring device 20 controls the power supply of the microheater 4 so as to keep the substrate temperature higher than the substrate temperature. In the heating state, the downstream temperature signal ad and the upstream temperature signal au are taken in from the downstream temperature sensor 5 and the upstream temperature sensor 8 of the flow sensor 1, respectively, and non-heating is performed corresponding to each temperature signal. The reference downstream temperature signal bd and the reference upstream temperature signal bu of the reference member 1A are taken from the reference downstream temperature sensor 5A and the reference upstream temperature sensor 8A of the non-heating reference member 1A. For example, a correction calculation formula (Q1 = ad−au−) determined in advance by each of the upstream temperature signal au, the downstream temperature signal ad, the reference upstream temperature signal bd, and the reference downstream temperature signal bu, for example. bd + bu) is calculated, and the fluid flow rate is calculated based on the correction data Q1.

  According to the flow rate measuring device 20 having such a configuration, the latest substrate temperature is always maintained during the fluid measurement period from the non-heating reference member 1A that is not affected by the heating even when the microheater 4 is heated. Since the reference downstream temperature signal and the reference upstream temperature signal corresponding to the temperature difference between the fluid and the fluid temperature can be captured, the temperature between the base 2 and the diaphragm 3 due to a temperature change or the like outside the flow path 70 can be obtained. Even if a difference occurs, the offset output of the temperature sensor that occurs when a temperature difference occurs between the substrate temperature and the fluid temperature can be canceled, so even if a temperature difference occurs between the substrate temperature and the fluid temperature, the flow sensor The output accuracy can be kept in a good state. Accordingly, even when the micro heater 4 of the flow sensor 1 is driven, the downstream side and upstream side temperature signals corresponding to the non-driven state can always be captured. Even if it is a continuous measurement without complication, the measurement accuracy with respect to the fluid can be improved.

[Third best mode]
Next, the best mode of the fluid discriminating apparatus for discriminating the fluid type using the flow sensor 1 and the non-heating reference member 1A described in the first best mode will be described below. The same or corresponding parts as those described in the prior art and the first and second best modes are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fluid discriminating device includes an amplifier 35a, 35b, 36a, 36b, a microprocessor (MPU) 40, and a drive unit 50 in the configuration of the flow rate measuring device 20 shown in FIG. 6 described in the first best mode. And have. The flow sensor 1 includes a base body 2, a diaphragm 3, a micro heater (heater) 4, a right thermopile 11 and a left thermopile 13 (lateral temperature sensor), a flow sensor 1, and a non-heating reference member 1A. Have. The non-heating reference member 1A includes a reference base 2A, a reference diaphragm 3A, a reference right thermopile 11A, and a reference left thermopile 13A (reference side temperature sensor).

The ROM 42 further includes a lateral subtracting means for subtracting a reference lateral temperature signal output from the reference right thermopile 11A and the left thermopile 13A from a lateral temperature signal output from the right thermopile 11 and the left thermopile 13, the lateral side Based on the lateral temperature signal subtracted by the subtracting means , physical property state information indicating the physical property state of the fluid corresponding to the temperature distribution in the substantially orthogonal direction passing through the microheater 4 substantially orthogonal to the fluid flow direction is detected. Storing a fluid discrimination program for causing the CPU 41 to function as various means such as a fluid discrimination means for discriminating the type of the discrimination target fluid based on the physical property status information detected by the physical property status information detection means 41 b. is doing.

  When the fluid discrimination program executes the fluid discrimination program, it instructs the drive unit 50 to start heating the microheater 4 and drives the drive unit 50 to generate a predetermined temperature distribution around the microheater 4. In the heating state, the right temperature signal and the left temperature signal are taken in from the right thermopile 11 and the left thermopile 13 of the flow sensor 1, and are referenced from the reference right thermopile 11A and the reference left thermopile 13A of the non-heating reference member 1A. The right side temperature signal for reference and the left side temperature signal for reference are captured.

  The right temperature signal and the left temperature signal are corrected based on the reference right temperature signal and the reference left temperature signal, the temperature distribution indicated by the corrected right temperature signal and the left temperature signal is detected, and the fluid is detected based on the temperature distribution. The physical property state information corresponding to the physical property is detected. Then, the fluid type is determined based on a comparison result between the physical property state information and predetermined physical property determination information, and the determination result information indicating the determination result is output to a display device, a communication device, an audio output device, etc. (not shown). As a result, the determination result is notified.

  According to the fluid discriminating apparatus described above, the non-heating reference member 1A having the same arrangement configuration of the base body 2, the diaphragm 3, the right thermopile 11 and the left thermopile 13 (lateral temperature sensor) in the flow sensor 1 is used as the flow sensor 1. The micro heater 4 is provided in the flow path so as not to be affected by the temperature distribution generated by the micro heater 4, and when the micro heater 4 is in a heated state, the side temperature signal from the side temperature sensor of the flow sensor 1 is not heated. The reference lateral temperature signal of the reference member 1A is captured and corrected, the physical property state information of the fluid is detected based on the corrected lateral temperature signal, and the type of the discrimination target fluid is determined based on the physical property state information Therefore, even if there is a temperature difference between the fluid temperature and the substrate temperature, errors due to the temperature difference can be eliminated. It is possible to accurately determine the fluid by detecting a physical property status information based on the item. Therefore, the accuracy of discrimination can be improved for various types of fluids.

It is a block diagram which shows the basic composition of the flow measuring device which concerns on this invention. It is a figure for demonstrating the example of installation of the flow measuring device of this invention using a flow sensor. It is a block diagram which shows an example of a structure of the flow measuring device shown in FIG. It is a flowchart which shows an example of the flow volume measurement process which concerns on this invention which CPU of FIG. 3 performs. It is a graph which shows the relationship between the temperature difference by this invention, and an instrumental difference. It is a block diagram which shows the structure of the conventional thermal type flow sensor. It is sectional drawing of the flow sensor shown in FIG. It is a schematic diagram which shows the output of the thermopile by the conventional temperature difference. It is the graph which showed the relationship between the temperature difference of the fluid temperature measured with the conventional flow sensor, and substrate temperature, and a sensor output device difference (measurement error). It is a block diagram which shows the structure of the flow sensor without a conventional side temperature sensor.

Explanation of symbols

1 Flow sensor (flow sensor)
1A Non-heating reference member 3 Diaphragm 3A Reference diaphragm 4 Heater 5 Downstream temperature sensor 8 Upstream temperature sensor 11, 13 Lateral temperature sensor 11A, 13A Reference lateral temperature sensor 20 Flow rate measuring device 41a Lateral subtraction means (CPU)
41b Physical property state information detecting means (CPU)
41c Flow rate calculation means (CPU)
41d Flow direction subtraction means (CPU)

Claims (5)

A diaphragm provided on the surface of the substrate; a heater provided on the diaphragm for heating a fluid flowing in the flow path; and provided on the diaphragm upstream of the flow path with respect to the heater to adjust the temperature of the fluid. An upstream temperature sensor that detects and outputs an upstream temperature signal, and a downstream side that is provided on the diaphragm downstream of the flow path with respect to the heater and detects the temperature of the fluid and outputs a downstream temperature signal In a flow rate measuring device that measures the flow rate of the fluid using a flow sensor having a temperature sensor,
A reference base formed of the same constituent member as the base, a reference diaphragm formed of the same constituent member as the diaphragm and provided on the surface of the reference base, and the upstream temperature sensor on the diaphragm A reference upstream temperature sensor provided on the reference diaphragm to detect the temperature of the fluid and outputting a reference upstream temperature signal, and the downstream temperature on the diaphragm A reference downstream temperature sensor that is provided on the reference diaphragm so as to have the same sensor arrangement and detects a temperature of the fluid and outputs a reference downstream temperature signal. A non-heating reference member provided in the flow path so as to be affected by the same fluid flow as the sensor;
Reference downstream side output by the reference downstream temperature sensor from a temperature difference output Von that is a difference signal between the downstream temperature signal output by the downstream temperature sensor and the upstream temperature signal output by the upstream temperature sensor. Subtracting means for flow direction that calculates the same output as the subtracted temperature difference output Voff that is a difference signal between the temperature signal and the reference upstream temperature signal output by the reference upstream temperature sensor;
A flow rate calculating means for calculating a flow rate of the fluid based on a calculation result by the flow direction subtracting means;
A flow rate measuring device comprising: A diaphragm provided on the surface of the substrate; a heater provided on the diaphragm for heating a fluid flowing in the flow path; and provided on the diaphragm upstream of the flow path with respect to the heater to adjust the temperature of the fluid. An upstream temperature sensor that detects and outputs an upstream temperature signal, and a downstream side that is provided on the diaphragm downstream of the flow path with respect to the heater and detects the temperature of the fluid and outputs a downstream temperature signal A temperature sensor, a lateral temperature sensor that is provided on the diaphragm and detects a temperature of the fluid in a substantially orthogonal direction passing through the heater and approximately orthogonal to the flow direction of the fluid, and outputs a lateral temperature signal; In a flow measurement device that measures the flow rate of a fluid using a flow sensor having
The reference base formed of the same constituent member as the base, the reference diaphragm formed of the same constituent member as the diaphragm, and the arrangement of the lateral temperature sensor on the diaphragm are substantially the same. A reference lateral temperature sensor provided on the reference diaphragm for detecting a temperature of the fluid and outputting a reference lateral temperature signal, and the same fluid flow as the flow sensor. A non-heating reference member provided in the flow path so as to be affected by
A lateral subtraction means for subtracting a reference lateral temperature signal output by the reference lateral temperature sensor from a lateral temperature signal output by the lateral temperature sensor;
Physical property state information detecting means for detecting physical property state information indicating the physical state of the fluid according to the temperature distribution in the substantially orthogonal direction based on the lateral temperature signal subtracted by the lateral subtracting unit ;
A flow rate for calculating the flow rate of the fluid based on the downstream temperature signal output from the downstream temperature sensor, the upstream temperature signal output from the upstream temperature sensor, and the physical property state information detected by the physical property state information detecting means. A calculation means;
A flow rate measuring device comprising: A non-heating reference member is further provided on the reference diaphragm so as to be the same as the arrangement of the upstream temperature sensor on the diaphragm, and detects the temperature of the fluid and outputs a reference upstream temperature signal. The reference upstream temperature sensor is provided on the reference diaphragm so as to be the same as the arrangement of the downstream temperature sensor on the diaphragm, and detects the temperature of the fluid to generate a reference downstream temperature signal. A downstream reference temperature sensor for output, and
Reference downstream side output by the reference downstream temperature sensor from a temperature difference output Von that is a difference signal between the downstream temperature signal output by the downstream temperature sensor and the upstream temperature signal output by the upstream temperature sensor. A flow direction subtraction means for calculating the same output as the difference signal obtained by subtracting the temperature difference output Voff , which is a difference signal between the temperature signal and the reference upstream temperature signal output from the reference upstream temperature sensor;
3. The flow rate of the fluid is calculated by the flow rate calculation unit based on a calculation result by the subtraction unit for the flow direction and physical property state information detected by the physical property state information detection unit. The flow rate measuring device described in 1.   The flow rate measuring device according to claim 1, wherein the non-heating reference member is another flow sensor having the same configuration as the flow sensor. A diaphragm provided on the surface of the substrate, a heater provided on the diaphragm for heating the fluid flowing in the flow path, and a substantially provided on the diaphragm and passing through the heater substantially orthogonal to the fluid flow direction. In a fluid discrimination apparatus that discriminates the type of fluid to be discriminated using a flow sensor having a lateral temperature sensor that detects a temperature of the fluid in an orthogonal direction and outputs a lateral temperature signal.
The reference base formed of the same constituent member as the base, the reference diaphragm formed of the same constituent member as the diaphragm, and the arrangement of the lateral temperature sensor on the diaphragm are substantially the same. A reference lateral temperature sensor provided on the reference diaphragm for detecting a temperature of the fluid and outputting a reference lateral temperature signal, and the same fluid flow as the flow sensor. A non-heating reference member provided in the flow path so as to be affected by
A lateral subtraction means for subtracting a reference lateral temperature signal output by the reference lateral temperature sensor from a lateral temperature signal output by the lateral temperature sensor;
Physical property state information detecting means for detecting physical property state information indicating the physical property state of the fluid according to the temperature distribution in the substantially orthogonal direction based on the lateral temperature signal subtracted by the lateral subtracting unit. With
A fluid discriminating apparatus characterized in that the type of the discrimination target fluid is discriminated based on the physical property state information detected by the physical property state information detecting means.

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