JP7078481B2 - Heat ray type flow meter - Google Patents

Description

The present invention relates to a heat ray type flow meter that measures the flow rate of the fluid to be measured.

Conventionally, various techniques related to a heat ray type flow meter for measuring the flow rate of the fluid to be measured have been proposed.

For example, the flow rate measuring device described in Patent Document 1 below heats a fluid flowing through a flow path with a heater, detects the temperature of the heated fluid with a temperature sensor on the downstream side, and determines the flow rate based on the detected value. Measure.

Similar to this flow rate measuring device, the temperature of the heated fluid is detected by the temperature sensor on the downstream side, but unlike this flow rate measuring device, the temperature of the heated fluid is detected by two temperature sensors on the downstream side, and the two are detected. In some cases, the flow rate is measured based on the detected value.

FIG. 15 shows an example of a flow rate measuring method using a heat ray type flow meter, which is the latter conventional flow rate measuring device. The conventional heat ray type flow meter used in the flow rate measurement method shown in the figure has one heater and two temperature measurement sensors (hereinafter referred to as the upstream temperature sensor) in the flow path from the upstream side to the downstream side. The temperature measurement sensor on the downstream side is referred to as a "second temperature measurement sensor"), which is referred to as a "first temperature measurement sensor").

First, a predetermined voltage is applied to the heater to generate a heat signal s50 having a temperature change of one peak from the heater. Next, the heat signals s50 flow to the downstream side, and the heat signals corresponding to the heat signals s50 whose temperature is measured by the first and second temperature measurement sensors are the heat signals s51 and s52, respectively. The same threshold value Th is set for each of the first and second temperature measurement sensors, and the temperature exceeding the threshold value Th is detected by the first and second temperature measurement sensors from the time when the voltage application to the heater is started. Measure the time to the point in time.

For example, the time from the time when the voltage application to the heater is started to the time when the first temperature sensor detects the temperature exceeding the threshold Th is set as "A", and the time from the time when the voltage application to the heater is started is the second measurement. Assuming that the time until the temperature sensor detects the temperature exceeding the threshold Th is "B", the time difference BA between the time B and the time A is that the measured fluid is the first temperature sensor and the second temperature measurement. It is the time elapsed when flowing between the sensor and the sensor.

Then, if the distance from the first temperature measurement sensor to the second temperature measurement sensor is L, the flow velocity V is calculated by the distance L / time difference BA, and if the cross-sectional area of the flow path is S, the flow rate is the flow velocity. It is calculated by V × cross-sectional area S.

In the conventional flow rate measuring method shown in FIG. 15, the flow rate of the fluid to be measured is measured in this way.

Japanese Patent No. 4947463

However, in the above-mentioned conventional flow rate measuring method, if the fluid to be measured has a temperature change, the flow rate of the fluid to be measured may not be measured accurately.

FIG. 16 is a diagram for explaining an example in this case. In the figure, the straight line V1 shown by the alternate long and short dash line indicates the temperature change of the fluid to be measured.

As described with reference to FIG. 15, the heat signal s50 generated from the heater flows to the downstream side according to the flow of the fluid to be measured, and the temperature is measured by the first and second temperature measurement sensors. In FIG. 16, the heat signals s53 and s54 indicate the heat signals corresponding to the heat signals s50 measured by the first and second temperature measurement sensors, respectively.

As shown in FIG. 16, the heat signals s53 and s54 are obtained by increasing the heat signal s50 from the heater by the temperature change of the fluid to be measured. In such a situation, when the same threshold value Th is set and the time A'and B'corresponding to the above-mentioned times A and B are measured, the time A'and the time B'are on the curve of the thermal signal s50, respectively. Will be measured at different locations. Therefore, since the time difference B'-A'does not match the time difference BA described above, it cannot be said that the flow rate calculated based on this time difference B'-A'is measured accurately.

In the example of FIG. 16, the temperature change V1 is linear, that is, constant for convenience of explanation. Therefore, if different threshold values are set for the first temperature measurement sensor and the second temperature measurement sensor, the time difference B'- Although it is possible to bring A'close to the correct time difference B-A, the temperature change of the fluid under test is usually not constant, so even if different thresholds are set, the time difference B'-A'is accurate. is not.

As described above, with the conventional heat ray type flow meter, it is difficult to accurately measure the flow rate of the fluid to be measured when the fluid to be measured has a temperature change.

Therefore, in order to deal with the above problems, the present invention provides a heat ray type flow meter capable of accurately measuring the flow rate of the fluid to be measured even when the fluid to be measured has a temperature change. The purpose is.

The invention according to claim 1 made to solve this problem includes a flow path through which the fluid to be measured flows, a heating means for heating the fluid to be measured, which is arranged in the flow path, and the flow path. The temperature of the first temperature measuring means for measuring the temperature of the fluid to be measured, which is arranged on the downstream side of the heating means, and the temperature of the fluid to be measured, which is arranged on the downstream side of the first temperature measuring means in the flow path. The heating means is controlled so as to generate a heat signal having at least two peaks from the second temperature measuring means for measuring the temperature and the heating means so that the heat signal is superimposed on the fluid to be measured flowing in the flow path. The temperature of the fluid to be measured exceeds the threshold for each of the control means, the generation means for generating a plurality of thresholds for the temperature of the fluid to be measured, and the threshold generated by the generation means. The temperature of the fluid to be measured measured by the second temperature measuring means exceeds the threshold for each threshold generated by the first measuring means for measuring the first time from the time to the time when the temperature is exceeded again, and then again. The second time measuring means for measuring the second time until the time is exceeded, and the third time from the end of the first time measuring by the first time measuring means to the end of the second time measuring by the second time measuring means. It is characterized by having a third timing means for measuring and a calculation means for calculating the flow rate of the fluid to be measured based on the first to third hours timed by the first to third timing means, respectively.

The invention according to claim 2 is the heat ray type flow meter according to claim 1, and when at least one of the first and second hours is not timed, the calculation means is the flow rate of the fluid to be measured. It is characterized in that no calculation is performed.

The invention according to claim 3 is the heat ray type flow meter according to claim 1, and when both the first time and the second time are timed, the calculation means is equal to the first time and the second time. In this case, the flow rate of the fluid to be measured is calculated, but when the first time and the second time are different, the flow rate of the fluid to be measured is not calculated.

The invention according to claim 4 is the heat ray type flow meter according to claim 1, wherein among the thresholds generated by the generation means, the temperature of the measured fluid on which the thermal signal is superimposed exceeds the threshold twice. It further has a hypothetical means of assuming the elapsed time from the first crossing to the second crossing, and when both the first and second hours are timed, the calculating means is the elapsed time, the first hour and the second hour. If all are equal, the flow rate of the measured fluid is calculated, but if the elapsed time and at least one of the first and second hours are different, the flow rate of the measured fluid is not calculated. It is characterized by that.

The invention according to claim 5 is the heat ray type flow meter according to any one of claims 1 to 4, wherein the peaks of the thermal signal have the same height.

The invention according to claim 6 is the heat ray type flow meter according to any one of claims 1 to 5, wherein the calculation means is a second from a position in the flow path where the first temperature measuring means is arranged. By dividing the distance to the position where the temperature measuring means is placed by the third time measured by the third measuring means to calculate the flow velocity of the fluid to be measured, and multiplying the flow velocity by the cross-sectional area of the flow path. It is characterized by calculating the flow rate of the fluid to be measured.

According to the first aspect of the invention, as the heat signal generated from the heating means, a special shape having at least two peaks is generated and superimposed on the fluid to be measured, and the first and second temperature measuring means are used. The temperature of the fluid to be measured measured by is the same threshold value (however, it does not mean that the threshold values set for the first temperature measuring means and the second temperature measuring means are the same, but for one thermal signal. Since the time exceeding (meaning that the thresholds used by each of the first or second temperature measuring means are the same) twice is measured as the first and second hours, the heat having a shape with one mountain is measured. Compared with the conventional heat ray type flow meter that superimposes the signal on the fluid to be measured and measures the time exceeding the same threshold once, it accurately determines whether or not the heat signal caused by the heating means is detected. be able to.

And since the third time is timed based on the accurately determined first and second hours, the third time is also accurate, and based on such accurate first to third hours. The calculated flow rate of the fluid to be measured is also highly accurate.

Further, in the invention according to claim 1, since a plurality of threshold values are generated and the first to third hours are measured for each of the generated threshold values, the first to third time is measured even when the fluid to be measured has a temperature change. The 1st to 3rd hours can be measured accurately.

Therefore, according to the first aspect of the present invention, it is possible to accurately measure the flow rate of the fluid to be measured even when the fluid to be measured has a temperature change.

According to the second aspect of the present invention, the flow rate of the fluid to be measured is not calculated when at least one of the first and second hours is not timed.

That is, the fact that at least one of the first and second hours is not timed means that the temperature measurement derived from the thermal signal was not made correctly.

Therefore, according to the invention of claim 2, the flow rate of the fluid to be measured is calculated based only on the correct measurement result by excluding the incorrect measurement result, so that the flow rate of the fluid to be measured can be accurately measured. It becomes possible to measure.

According to the invention of claim 3, when both the first time and the second time are timed, the flow rate of the measured fluid is calculated when the first time and the second time are equal to each other. If the first time and the second time are different, the flow rate of the fluid to be measured is not calculated.

That is, even if both the first and second hours are timed, if both are not the same time, the temperature of the fluid to be measured is measured, such as detecting different positions of the heat signals generated by the heating means. Means that was not done correctly.

Therefore, according to the invention of claim 3, the flow rate of the fluid to be measured is calculated based only on the truly correct measurement result, excluding the incorrect measurement result that may be correctly determined. , The flow rate of the fluid to be measured can be measured more accurately.

According to the invention of claim 4, when both the first time and the second time are timed, the flow rate of the measured fluid is calculated when the elapsed time, the first time and the second time are all equal. On the other hand, if the elapsed time and at least one of the first time and the second time are different, the flow rate of the fluid to be measured is not calculated.

That is, even if both the first and second hours are timed, if the elapsed time and at least one of the first and second hours are different, the thermal signal generated by the heating means. It means that the temperature of the fluid to be measured was not measured correctly, such as detecting a different position.

Therefore, the invention according to claim 4 also excludes incorrect measurement results that may be correctly determined, and is measured based only on the truly correct measurement results, as in the invention according to claim 3. Since the flow rate of the fluid is calculated, it is possible to measure the flow rate of the measured fluid with higher accuracy.

It is a schematic diagram ((a)) and the vertical sectional view ((b)) which show the schematic structure of the heat ray type flow meter which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the control circuit provided in the heat ray type flow meter of FIG. It is a figure which shows an example of the shape, wavelength and transmission time of the heat signal generated by the heat ray type flowmeter of FIG. It is a figure which shows an example of the operation of the 1st to 3rd counter provided in the control circuit of FIG. It is a flowchart which shows the procedure of the control processing which the 3rd determination part provided in the control circuit of FIG. 2 executes. It is a figure which shows an example of the heat signal measured by the 1st and 2nd temperature measuring sensors provided in the heat ray type flow meter of FIG. It is a figure which shows an example of the thermal signal different from the example of FIG. 6 measured by the 1st and 2nd temperature measuring sensors provided in the heat ray type flow meter of FIG. It is a figure which shows an example of the thermal signal measured by the 1st and 2nd temperature measuring sensors provided in the heat ray type flowmeter of FIG. 1 when there is a temperature change in the fluid to be measured. It is a block diagram which shows the structure of the control circuit provided in the heat ray type flow meter which concerns on the 2nd Embodiment of this invention. It is a figure which shows an example of the operation of the 1st to 3rd counter provided in the control circuit of FIG. It is a block diagram which shows the structure of the control circuit provided in the heat ray type flow meter which concerns on 3rd Embodiment of this invention. It is a figure which shows an example of the operation of the 1st 1, the 1st 2, the 2nd 1, the 2nd 2 and the 3rd counter provided in the control circuit of FIG. It is a figure which shows an example of the operation different from FIG. 11 is a diagram showing an example of operation further different from FIGS. 12 and 13 of the first 1, first 2, second 1, second 2, and third counters provided in the control circuit of FIG. 11. .. It is a figure which shows an example of the flow rate measuring method by the conventional heat ray type flow meter. It is a figure for demonstrating the erroneous measurement which occurs when the flow rate measurement is performed using the flow rate measurement method of FIG. 15 when there is a temperature change in the fluid to be measured.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
The heat ray type flow meter according to the first embodiment of the present invention is a heat ray type MEMS (Micro Electro Mechanical Systems) flow meter, which measures the flow rate of the fluid to be measured by a TOF (Time of Flight) method. be. Possible uses include controlling the flow rate of trace amounts of medical chemicals and managing reagents and culture solutions for biochemical tests. The flow rate range of the fluid to be measured is assumed to be 1 to 100 μl / min, but is not limited to this.

As shown in FIG. 1A, the heat ray type flow meter 100 of the present embodiment includes a heater 101, a first temperature measuring sensor 102, a second temperature measuring sensor 103, signal lines 104 to 106, a flow path 107, and the like. I have. The heat ray type flow meter 100 of the present embodiment has a rectangular shape in a plan view, and its dimensions are, for example, 10 mm (vertical) × 20 mm (horizontal).

The heater 101 and the first and second temperature measuring sensors 102 and 103 are formed on the silicon wafer 108 (see FIG. 1 (b)).

The flow path 107 is formed by superimposing a flow path forming portion 109 having a rectangular groove formed on the surface of the silicon wafer 108. The flow path forming portion 109 forms holes 109a and 109b at positions corresponding to both ends of the flow path 107, respectively. Silicon tubes 110 and 111 are inserted into the holes 109a and 109b, respectively.

The silicon tube 110 serves as an introduction pipe for introducing the fluid to be measured into the flow path 107, and the silicon tube 111 serves as a discharge pipe for discharging the fluid to be measured from the flow path 107.

The heater 101, the first temperature measurement sensor 102, and the second temperature measurement sensor 103 are arranged in the flow path 107 from the upstream side to the downstream side in this order.

One end of the signal lines 104 to 106 is connected to the heater 101 and the first and second temperature measurement sensors 102 and 103, respectively, and the other end is connected to the control circuit 200 shown in FIG.

A heat signal having a predetermined shape is generated from the heater 101 while the fluid to be measured passes through the flow path 107. FIG. 3A shows an example of this thermal signal s1. As shown in FIG. 3A, the heat signal s1 has an M-shape having two peaks of temperature change, and has an amplitude value (temperature rise width) of 10 ° C. In the illustrated example, the height of each mountain is the same, but may be different (see FIGS. 6 to 8). Further, the amplitude value is not limited to 10 ° C, and any temperature may be adopted. The amplitude value can be freely changed by changing the voltage value applied to the heater 101.

The fluid to be measured on which the thermal signal s1 is superimposed, that is, the fluid to be measured in which the original temperature of the fluid to be measured (hereinafter referred to as “pre-control temperature”) is raised by the thermal signal s1 follows the flow of the fluid to be measured. It flows to the downstream side. Then, the first temperature measurement sensor 102 first measures the temperature of the fluid to be measured whose temperature has risen, and then the second temperature measurement sensor 103 measures the temperature of the fluid to be measured whose temperature has risen.

FIG. 3B shows an example of the result of measuring the temperature of the fluid to be measured by the first temperature measurement sensor 102, and FIG. 3C shows the temperature of the fluid to be measured by the second temperature measurement sensor 103. An example of the result is shown.

The temperature change of the fluid to be measured measured by the first temperature measurement sensor 102, that is, the temperature change according to the heat signal s1 (hereinafter, also referred to as “heat signal” (heat signal s2)) is shown in FIG. 3 (b). In the example of, it is not different from the temperature change of the thermal signal s1. Therefore, the amplitude value of the thermal signal s2 is also 10 ° C, similarly to the thermal signal s1. Further, since the wavelength of the thermal signal s2 is 100 msec, the wavelength of the thermal signal s1 is also 100 msec, although it is not shown in FIG. 3 (a).

The temperature change of the fluid to be measured measured by the second temperature measurement sensor 103, that is, the heat signal s3 is not different from the temperature change of the heat signal s1 in the example of FIG. 3C. Therefore, the amplitude value and wavelength of the thermal signal s3 are also not shown in FIG. 3 (c), but are 10 ° C and 100 msec, respectively.

The flow rate of the fluid to be measured is the measurement method described above in the [Background Art] column, specifically, the time elapsed for the fluid to be measured to flow a predetermined distance even in the heat ray type flow meter 100 of the present embodiment (hereinafter, By measuring (referred to as "movement time") and dividing the measured movement time by a predetermined distance, the flow velocity of the fluid to be measured is calculated, and the calculated flow velocity is multiplied by the cross-sectional area of the flow path 107. Measures the flow rate of the fluid to be measured. The feature of the present invention lies in the method of measuring the movement time of the fluid to be measured, that is, the method from the measurement of the movement time to the calculation of the flow rate is the same as that of the above-mentioned conventional heat ray type flow meter. Since there is no difference, the method of measuring the travel time will be mainly described below.

The details of the movement time will be described later, but a plurality of threshold values are set, and for each threshold value, the time from exceeding the threshold value to exceeding the threshold value is measured and the thermal signal is measured. The time from when s2 exceeded the threshold value again until the thermal signal s3 exceeded the threshold value (however, this threshold value may differ between the thermal signal s2 and the thermal signal s3) was measured and measured. It is done on the basis of three types of time.

In FIG. 3 (b), the threshold value Th at 5 ° C indicates one of a plurality of set threshold values. Further, the threshold value Th in FIG. 3 (c) is also the same as the threshold value Th in FIG. 3 (b), which is 5 ° C. Since the time from when the thermal signals s2 and s3 exceed the threshold value Th to when the threshold value Th3 is exceeded again is the same 50 msec, the thermal signal s2 and the thermal signal s3 are determined to be correct measurement results. , The time from when the heat signal s2 exceeds the threshold value Th again until the heat signal s3 exceeds the threshold value Th again, that is, the fluid to be measured moves from the position of the first temperature measurement sensor 102 to the position of the second temperature measurement sensor 103. The time taken is measured as 10 msec.

As the threshold value Th, the one to which the pre-control temperature is added is actually used. This is because the first and second temperature measurement sensors 102 and 103 measure the temperature of the fluid to be measured in which the thermal signals s2 and s3 are superimposed on the pre-control temperature. Therefore, the temperature axis of each graph in FIG. 3 excludes the pre-control temperature of the fluid to be measured, that is, shows the “temperature difference”. This situation is the same in the other FIGS. 4 and 6 to 8.

As shown in FIG. 2, the control circuit 200 includes a control unit 201, a heat application unit 202, a first temperature detection unit 203, and a second temperature detection unit 204. Although not shown in FIG. 2, the signal lines 104 to 106 are connected to the heat application unit 202, the first temperature detection unit 203, and the second temperature detection unit 204, respectively.

The control unit 201 is connected to the heat application unit 202, the first temperature detection unit 203, and the threshold value generation unit 205. The control unit 201 generates the M-shaped heat signal from the heater 101 by instructing the heat application unit 202 of the applied voltage value.

Further, the control unit 201 acquires the temperature of the fluid to be measured around the first temperature measurement sensor 102 before generating the heat signal, that is, the temperature before control, from the first temperature detection unit 203. The control unit 201 outputs the acquired pre-control temperature and the amplitude value of the heat signal generated from the heater 101 to the threshold value generation unit 205. Here, since the amplitude value of the heat signal generated from the heater 101 can be determined in advance from the applied voltage value instructed to the heat application unit 202, the control unit 201 outputs this determined value to the threshold value generation unit 205. do.

The threshold generation unit 205 determines the temperature rise width of the fluid to be measured based on the above-mentioned definite value, adds a predetermined margin to the temperature rise width, divides the addition result into a predetermined number, and sets a threshold value. To generate. Specifically, as shown in FIG. 3A, it is assumed that the amplitude value of the heat signal s1 generated from the heater 101 is 10 ° C, and the margin is 5 ° C. When 15 ° C, which is the result of this addition, is divided into, for example, 6 equal parts, the difference between the threshold values is 2.5 ° C. Assuming that the pre-control temperature of the fluid to be measured is 50 ° C, the threshold generation unit 205 has 52.5 ° C, 55 ° C, 57.5 ° C, 60 ° C, 62.5 ° C, Generates 6 thresholds at 65 ° C.

The threshold value generation unit 205 outputs the plurality of threshold values thus generated to the first and second determination units 206 and 208.

The first temperature detection unit 203 is connected to the first determination unit 206, and the first determination unit 206 is connected to the first counter 207 and the third counter 210. Further, a threshold value generation unit 205 is also connected to the first determination unit 206.

The first determination unit 206 stores a plurality of threshold values output from the threshold value generation unit 205 as described above, and stores the respective threshold values and the temperature of the fluid to be measured output from the first temperature detection unit 203. By comparison, it is determined whether or not the temperature of the fluid to be measured exceeds each of the threshold values.

As shown in FIG. 3B or FIG. 4, the first determination unit 206 compares the temperature of the fluid to be measured with the threshold value Th, and when the temperature of the fluid to be measured exceeds the threshold value Th, the first counter 207 Start (ON) counting. FIG. 4 shows a state in which the temperature of the fluid to be measured exceeds the threshold value Th and the first counter 207 is turned on at time T1. In FIG. 4, the time T0 indicates the time when the voltage application to the heater 101 is started.

The first determination unit 206 continues the comparison operation between the temperature of the fluid to be measured and the threshold value Th, and when the temperature of the fluid to be measured exceeds the threshold value Th again, the count of the first counter 207 is stopped (OFF) and the count is stopped (OFF). The count of the third counter 210 is started (ON). FIG. 4 shows a state in which the temperature of the fluid to be measured exceeds the threshold value Th again at time T2, the first counter 207 is turned off, and the third counter 210 is turned on.

Similarly, the second temperature detection unit 204 is connected to the second determination unit 208, the second determination unit 208 is connected to the second counter 209 and the third counter 210, and further, the second determination unit 208 is connected to the second determination unit 208. The threshold generation unit 205 is also connected.

The difference between the operations of the second temperature detection unit 204, the second determination unit 208 and the second counter 209 and the operations of the first temperature detection unit 203, the first determination unit 206 and the first counter 207 described above is the former. Controls based on the temperature measured from the first temperature measurement sensor 102, whereas the latter controls based on the temperature measured from the second temperature measurement sensor 103, and the second determination unit 208 is the second. 3 The control performed on the counter 210 is different. Therefore, only the control performed by the second determination unit 208 on the third counter 210 will be described.

Even if the temperature of the fluid to be measured exceeds the threshold value Th, the second determination unit 208 does not give any instruction to the third counter 210, so that the third counter 210 continues to be in the ON state. Then, when the temperature of the fluid to be measured exceeds the threshold value Th again, the second determination unit 208 stops (OFF) the counts of both the second and third counters 209 and 210. In FIG. 4, after the temperature of the fluid to be measured exceeds the threshold value Th at time T3 and the second counter 209 is turned on, the temperature of the fluid to be measured exceeds the threshold value Th again at time T4, and the second counter is turned on. It is shown that both the third counters 209 and 210 are turned off.

The third counter 210 is connected to the third determination unit 211, and the third determination unit 211 is connected to the first and second counters 207 and 209 and the output unit 212.

The third determination unit 211 compares the count value counted by the first counter 207 with the count value counted by the second counter 209, and if both count values match, counts by the third counter 210. The counted value is output to the output unit 212.

Since the first to third counters 207, 209, and 210 each count up by "1" at predetermined time intervals, the count values of the first to third counters 207, 209, and 210 are indirectly counted. It shows the elapsed time. That is, in FIG. 4, the times a, b, and T are obtained by multiplying the count values of the first to third counters 207, 209, and 210 by the predetermined time, respectively. Here, the time a indicates the time from when the heat signal s2 exceeds the threshold value Th to when the threshold value Th is exceeded again, and the time b is the time from when the heat signal s3 exceeds the threshold value Th to when the threshold value Th is exceeded again. The time T indicates the time elapsed when the fluid to be measured moves from the position of the first temperature measurement sensor 102 to the position of the second temperature measurement sensor 103.

In FIG. 4, the graph showing the temperature transition according to the passage of time of the heat signals s2 and s3 is different from the actual measurement result. As described above with reference to FIG. 3, the time for the fluid to be measured to move from the position of the first temperature measurement sensor 102 to the position of the second temperature measurement sensor 103 is 10 msec, whereas the thermal signals s2 and s3 The wavelength of is 100 msec. Therefore, when two thermal signals s2 and s3 are arranged on the time axis, most of them overlap, but in FIG. 4, they do not overlap. This is done for convenience of explanation, and there is no other reason. Of course, there is no contradiction in FIG. 4 when viewed with respect to the fluid to be measured, which is different from that in FIG. This situation is the same for FIGS. 6 to 8.

The output unit 212 outputs the count value of the third counter 210 to the outside. An arithmetic processing unit (not shown) is provided outside this, and the arithmetic processing unit calculates the movement time of the fluid to be measured based on the output count value, and as described above, this movement time. The flow velocity of the fluid to be measured is calculated from, and the flow rate of the fluid to be measured is calculated from this flow velocity.

Hereinafter, the control process executed by the heat ray type flow meter 100 configured as described above will be described in more detail.

FIG. 5 shows a procedure of the measurement data determination process executed by the third determination unit 211, and the measurement data determination process will be described with reference to FIGS. 6 to 8.

FIG. 6 shows the thermal signals s11 and s12 measured by the first and second temperature measurement sensors 102 and 103, respectively. Although not shown in FIG. 6, the heater 101 generates a thermal signal s10 (see FIG. 8) similar to the thermal signals s11 and s12. In the example of FIG. 6, it is shown that the heat signal s10 generated from the heater 101 reaches the first and second temperature measurement sensors 102 and 103 without losing its shape.

Returning to FIG. 5, when the measurement data determination process is started, the third determination unit 211 first determines whether or not a predetermined time has elapsed since the heater 101 was turned on, that is, the heat signal s10 from the heater 101 is second. It is determined whether or not the temperature measurement sensor 103 has passed the position (step 1). This is because the subsequent processing after step 2 is desired to be executed after the thermal signal s10 has passed the position of the second temperature measuring sensor 103. The predetermined time can be easily estimated from the duration of the voltage applied to the heater 101, the distance from the heater 101 to the second temperature measuring sensor 103, the approximate flow velocity of the fluid to be measured, and the like.

As a result of the determination in step 1, when the predetermined time has not elapsed since the heater 101 was turned on, the measurement data determination process is terminated, while when the predetermined time has elapsed since the heater 101 was turned on, the next step 2 is performed. move on.

In step 2, the third determination unit 211 determines whether or not the count value of the first counter 207 (hereinafter, referred to as “first counter value”) is “1” or more. This determines whether the first counter 207 is counting a valid count value. When the first counter 207 counts more than a predetermined count value, the third determination unit 211 stops the count of the first counter 207 and resets it.

In FIG. 6, for example, when the threshold value Th1 is set, the thermal signal s11 does not exceed the threshold value Th1 again, so that the first counter 207 continues without stopping the counting operation. Therefore, when the first counter 207 counts for a time corresponding to, for example, the wavelength of the thermal signal s11 or longer, the third determination unit 211 stops the count of the first counter 207 and resets it.

Therefore, when the count value of the first counter 207 is “0”, it means that the first counter 207 is not counting a valid count value. This situation is the same for the second counter 209.

As a result of the determination in step 2, when the first counter value is “1” or more, the process proceeds to the next step 3, while when the first counter value is “0”, the process proceeds to step 6, and the third determination unit 211 advances to step 6. After stopping the counting of the first to third counters 207, 209, 210, the first to third counters 207, 209, 210 are reset.

Further, the third determination unit 211 outputs a value indicating an erroneous determination to the output unit 212 (step 7), and then ends the measurement data determination process.

In step 3, the third determination unit 211 determines whether or not the count value of the second counter 209 (hereinafter referred to as “second counter value”) is “1” or more. As a result of this determination, when the second counter value is "1" or more, the process proceeds to the next step 4, while when the second counter value is "0", the process proceeds to the above step 6.

In step 4, the third determination unit 211 determines whether or not the first counter value and the second counter value are equal to each other. This determination is made to determine whether the thermal signal measured by the first temperature measuring sensor 102 and the thermal signal measured by the second temperature measuring sensor 103 are both correct thermal signals. That is, when the first counter value = the second counter value, it is determined that each of the heat signals correctly detects the heat signal from the heater 101. On the other hand, when the first counter value ≠ the second counter value, it is determined that either one or both of the two thermal signals is not correctly detected from the heater 101.

As a result of the determination in step 4, when the first counter value = the second counter value, the process proceeds to the next step 5, while when the first counter value ≠ the second counter value, the process proceeds to the above step 6.

In step 5, the third determination unit 211 outputs the count value of the third counter 210 (hereinafter, referred to as “third counter value”) to the output unit 212. When the third counter value is output from the third determination unit 211, the output unit 212 outputs the third counter value to the outside. Since the subsequent processing has been described above, the description thereof will be omitted.

In the example of FIG. 6, since the heat signal s11 and the heat signal s12 both correctly detect the heat signal s10 from the heater 101, when the threshold value Th2 is set, the first counter 207 starts from the time T1. The second counter 209 counts the count value corresponding to the time b from the time T3 to the time T4, while counting the count value corresponding to the time a until the time T2. Then, since the time a and the time b are equal, the count value corresponding to the time T from the time T2 to the time T4 counted by the third counter 210 is output to the output unit 212.

In FIG. 7, the heat signal s21 measured by the first temperature measurement sensor 102 correctly detects the heat signal s10 from the heater 101, whereas the heat signal s10 measured by the second temperature measurement sensor 103 is a heat signal. s22 shows an example in which the heat signal s10 from the heater 101 is not correctly detected due to a sudden change in the ambient temperature.

In FIG. 7, the triangular curve V2 shown by the two-dot chain line shows an example of the temperature change of the fluid to be measured around the second temperature measurement sensor 103.

When the measurement result of FIG. 7 is applied to the measurement data determination process described above, when the threshold value Th2 is set, the thermal signal s21 is set to the time by the first counter 207, similarly to the thermal signal s11 in FIG. Although the thermal signal s22 is counted from T1 to the time T2, the second counter 209 does not exceed the threshold value Th1 to Th5 again regardless of which of the threshold values Th1 to Th5 including the threshold value Th2 is set. Is stopped and reset.

Therefore, in this case, in step 3 of FIG. 5, the second counter value = 0, and in step 7, a value indicating an erroneous determination is output to the output unit 212. As a result, the arithmetic processing unit does not calculate the flow velocity and the flow rate of the fluid to be measured.

FIG. 8 shows an example when the movement time of the fluid to be measured is correctly detected even when the ambient temperature of the first and second temperature measurement sensors 102 and 103 changes. In the figure, the straight line V1 shown by the two-dot chain line shows the temperature change of the fluid to be measured similar to the straight line V1 in FIG.

When the measurement result of FIG. 8 is applied to the measurement data determination process described above, when the threshold value Th12 is set, the thermal signal s31 is set to the time by the first counter 207, similarly to the thermal signal s11 in FIG. Although the data is counted from T1 to the time T2, the thermal signal s32 does not exceed the threshold value Th12 again, so that the second counter 209 is stopped and reset.

However, when the threshold value Th13 is set for the second counter 209, the thermal signal s32 exceeds the threshold value Th13 at the time T3 and further exceeds the threshold value Th13 at the time T4. Since the time a from time T1 to time T2 and the time b from time T3 to time T4 are equal, it is necessary to determine that both the thermal signal s31 and the thermal signal s32 are correct measurement results.

Therefore, in order to deal with this, it is necessary to change the above-mentioned measurement data determination process. Specifically, it may be changed as follows. That is,
(1) The counting of the third counter 210 is continued until the first counter 207 receives the reset instruction.
(2) After the first counter 207 counts a valid count value even for one of the set plurality of threshold values, the counting operation of the third counter 210 is continued.
(3) If the temperature measured by the second temperature measuring sensor 103 exceeds the set threshold value again while the third counter 210 continues the counting operation, the corresponding threshold value is exceeded again. The third counter value of the third counter 210 is stored in association with each threshold value.
(4) The third counter value stored in association with each threshold value erases the third counter value associated with the threshold value each time the second counter 209 is reset.
(5) When both the first counter value and the second counter value are valid count values and are equal to each other, the remaining third counter value that is not erased is output to the output unit 212.

As described above, in the heat ray type flow meter 100 of the present embodiment, the flow path 107 through which the fluid to be measured flows, the heater 101 for heating the fluid to be measured, and the flow path 107 arranged in the flow path 107. The first temperature measuring sensor 102 for measuring the temperature of the fluid to be measured, which is arranged on the downstream side of the heater 101, and the subject, which is arranged on the downstream side of the first temperature measuring sensor 102 in the flow path 107. A second temperature measuring sensor 103 for measuring the temperature of the measuring fluid is provided.

Further, in the heat ray type flow meter 100 of the present embodiment, the heat signal having at least two peaks is generated from the heater 101, and the heat signal is superimposed on the fluid to be measured flowing in the flow path 107. Measured by the first temperature measuring sensor 102 for each of the control unit 201 that controls the heater 101, the threshold generation unit 205 that generates a plurality of thresholds for the temperature of the fluid to be measured, and the threshold generation unit 205. The temperature of the fluid to be measured is measured by the second temperature measuring sensor 103 for each threshold generated by the first counter 207 and the threshold generation unit 205, which counts the first time from the time when the temperature of the fluid to be measured exceeds the threshold to the time when the temperature exceeds the threshold again. The second counter 209 counts the second time from the time when the temperature of the fluid to be measured exceeds the threshold value to the time when the temperature exceeds the threshold value again, and the second counter 209 completes the counting of the first time by the first counter 207. A third counter 210 for counting the third time until the counting of the second time is completed is provided.

Then, in the heat ray type flow meter 100 of the present embodiment, the flow rate of the fluid to be measured is calculated based on the first to third hours counted by the first to third counters 207, 209, 210, respectively.

That is, in the heat ray type flow meter 100 of the present embodiment, as the heat signal generated from the heater 101, a special shape having at least two peaks is generated and superimposed on the measured fluid, and the first and second measurements are made. It does not mean that the temperature of the fluid to be measured measured by the temperature sensors 102 and 103 has the same threshold value (however, the threshold values set for the first temperature measurement sensor 102 and the second temperature measurement sensor 103 are the same). The time that exceeds (meaning that the thresholds used for each of the first and second temperature measurement sensors 102 and 103 are the same) twice for one thermal signal is counted as the first and second time. Therefore, the heat signal caused by the heater 101 is detected as compared with the conventional heat ray type flow meter that superimposes a heat signal having a shape with one peak on the fluid to be measured and measures the time exceeding the same threshold once. It is possible to accurately determine whether or not it is done.

And since the third time is counted based on the accurately determined first and second hours, the third time is also accurate, and based on such accurate first to third hours. The calculated flow rate of the fluid to be measured is also highly accurate.

Further, in the heat ray type flow meter 100 of the present embodiment, a plurality of threshold values are generated and the first to third hours are counted for each of the generated threshold values, so that even when the fluid to be measured has a temperature change. , The first to third hours can be counted accurately.

Therefore, according to the heat ray type flow meter 100 of the present embodiment, it is possible to accurately measure the flow rate of the fluid to be measured even when the fluid to be measured has a temperature change.

Further, in the heat ray type flow meter 100 of the present embodiment, the flow rate of the fluid to be measured is not calculated when at least one of the first and second hours is not counted.

That is, the fact that at least one of the first and second hours is not counted means that the temperature measurement derived from the thermal signal was not performed correctly.

Therefore, according to the heat ray type flow meter 100 of the present embodiment, the flow rate of the fluid to be measured is calculated based only on the correct measurement result by excluding the incorrect measurement result. Therefore, the flow rate of the fluid to be measured is calculated. It is possible to measure with high accuracy.

Further, when both the first time and the second time are counted, the flow rate of the fluid to be measured is calculated when the first time and the second time are equal to each other, while the first time and the second time are counted. If they are different, the flow rate of the fluid to be measured is not calculated.

That is, even if both the first and second hours are counted, if both are not the same time, the temperature of the fluid to be measured is measured, such as detecting different positions of the heat signals generated by the heater 101. Means that was not done correctly.

Therefore, according to the heat ray type flow meter 100 of the present embodiment, the incorrect measurement result that may be correctly determined is excluded, and the flow rate of the fluid to be measured is calculated based only on the truly correct measurement result. Therefore, it becomes possible to measure the flow rate of the fluid to be measured with higher accuracy.

Incidentally, in the present embodiment, the heater 101 is an example of "heating means". The first and second temperature measuring sensors 102 and 103 are examples of the "first and second temperature measuring means". The control unit 201 is an example of "control means". The threshold value generation unit 205 is an example of the “generation means”. The first to third counters 207, 209, 210 are examples of "first to third timekeeping means".

[Second Embodiment]
When the heat ray type flow meter 100 of the first embodiment outputs the third counter value of the third counter 210 to the output unit 212, that is, the temperature measurement derived from the heat signal generated from the heater 101 is correctly performed. As a criterion for determining the case, "the first counter value = the second counter value" is adopted. On the other hand, in the heat ray type flow meter according to the second embodiment of the present invention, as the above-mentioned determination standard, "the temperature of the fluid to be measured on which the heat signal generated from the heater 101 is superimposed has a predetermined threshold value. The difference is that the time from the time when the value is exceeded to the time when the value is exceeded again is the first counter value and the time temperature is the second counter value.

Since such a determination criterion is adopted, the heat ray type flow meter of the present embodiment is executed by a part of the components of the control circuit 200 and each component with respect to the heat ray type flow meter 100 of the first embodiment. Some of the processing to be done is changed. Therefore, in the control circuit 300 (see FIG. 9) of the heat ray type flow meter of the present embodiment, the same components as the control circuit 200 (see FIG. 2) of the heat ray type flow meter 100 of the first embodiment are the same. Reference numerals are given, and detailed description thereof will be omitted.

In FIG. 9, the control unit 201'is connected to the third determination unit 311 and the third counter 210 is inserted between the third determination unit 311 and the output unit 212.

The control unit 201'sets the threshold value again after the temperature of the fluid to be measured on which the M-shaped heat signal generated from the heater 101 is superimposed exceeds the threshold value for each threshold value generated by the threshold value generation unit 205. Assuming the time to exceed. Here, the thermal signal does not always exceed the threshold value twice for all the generated threshold values, and some of them exceed the threshold value only once.

For example, in FIG. 6 of the first embodiment, the thermal signal s10 (see FIG. 8), which is the basis of the thermal signals s11 and s12, exceeds the threshold Th1 only once, but the thermal signal s1 shown in FIG. Exceeds the threshold Th twice.

In the latter case, the control unit 201'calculates (assumes) the time from when the thermal signal s1 first exceeds the threshold value Th to when it exceeds the threshold value Th again. The time table calculated by the control unit 201'is actually a "count value" corresponding to the time table, not a "time". However, hereinafter, both the time teat and the count value corresponding to the time teat will be referred to as "time teat".

Next, the control unit 201'outputs the calculated time Teat to the third determination unit 311. The third determination unit 311 stores the time This time.

Similar to the first determination unit 206 in the first embodiment, the first determination unit 306 starts (ON) the count of the first counter 207 when the temperature of the fluid to be measured exceeds the threshold value Th. In this embodiment, the first determination unit 306 is not connected to the third counter 210, and therefore does not control the third counter 210. FIG. 10 shows a state in which the temperature of the fluid to be measured exceeds the threshold value Th and the first counter 207 is turned on at time T1.

The first determination unit 306 continues the comparison operation between the temperature of the fluid to be measured and the threshold value Th, and when the temperature of the fluid to be measured exceeds the threshold value Th again, the count of the first counter 207 is stopped (OFF). At the same time, the third determination unit 311 starts (ON) the count of the third counter 210. FIG. 10 shows a state in which the temperature of the fluid to be measured exceeds the threshold value Th again at time T2, the first counter 207 is turned off, and the third counter 210 is turned on.

Similar to the second determination unit 208 in the first embodiment, the second determination unit 308 also starts (ON) the count of the second counter 209 when the temperature of the fluid to be measured exceeds the threshold value Th. In this embodiment, the second determination unit 308 is also not connected to the third counter 210, so that the third counter 210 is not controlled. FIG. 10 shows that at time T3, the temperature of the fluid to be measured exceeds the threshold value Th, the second counter 207 is turned on, and the third counter 210 is continuously turned on.

The second determination unit 308 continues the comparison operation between the temperature of the fluid to be measured and the threshold value Th, and when the temperature of the fluid to be measured exceeds the threshold value Th again, the count of the second counter 209 is stopped (OFF). At the same time, the third determination unit 311 stops (OFF) the count of the third counter 210. FIG. 10 shows how the temperature of the fluid to be measured exceeds the threshold value Th again at time T4, and the second and third counters 209 and 210 are both turned off.

The third determination unit 311 compares the count value (first counter value) of the first counter 207 with the time table, and compares the count value (second counter value) of the second counter 209 with the time table. As a result of this comparison, when the first counter value = time Teat and the second counter value = time Teat, the third determination unit 311 outputs the count value (third counter value) of the third counter 210 to the output unit 212. do.

In the example of FIG. 10, since the first counter value a = time Teat and the second counter value b = time Teat, the third determination unit 311 outputs the third counter value, that is, the count value corresponding to the time T. Output to 212.

When at least one of the first counter value ≠ time Teat and the second counter value ≠ time Teat is satisfied, the third determination unit 311 is the third counter, as in the first embodiment. Instead of the value, a value indicating an erroneous determination is output to the output unit 212.

As described above, the heat ray type flow meter of the present embodiment can also perform the same control as the heat ray type flow meter of the first embodiment.

In the heat ray type flow meter of the present embodiment, when both the first time and the second time (the first and second count values) are timed, when the time Teat, the first time and the second time are all equal. While the flow rate of the fluid to be measured is calculated, if the time Teat is different from at least one of the first time and the second time, the flow rate of the fluid to be measured is not calculated.

That is, even if both the first and second hours are timed, if the time temperature and at least one of the first and second hours are different, the thermal signal generated by the heater 101 It means that the temperature of the fluid to be measured was not measured correctly, such as detecting a different position.

Therefore, the heat ray type flow meter of the present embodiment also excludes incorrect measurement results that may be correctly determined, and only truly correct measurement results, as in the case of the heat ray type flow meter of the first embodiment. Since the flow rate of the fluid to be measured is calculated based on the above, it is possible to measure the flow rate of the fluid to be measured with higher accuracy.

Incidentally, in the present embodiment, the control unit 201'is an example of the "assuming means".

[Third Embodiment]
The heat ray type flow meter according to the third embodiment of the present invention is provided with two counters corresponding to the first and second counters 207 and 209, respectively, with respect to the heat ray type flow meter of the second embodiment. The point is different. Therefore, in the control circuit 400 of the heat ray type flow meter of the present embodiment, the same components as the control circuit 300 of the heat ray type flow meter of the second embodiment are designated by the same reference numerals, and detailed description thereof will be given. Omit.

In FIG. 11, the first temperature detection unit 203 is connected to the first 1 determination unit 406a and the first 2 determination unit 406b. Further, a threshold value generation unit 205 is also connected to the first 1 determination unit 406a and the first 2 determination unit 406b. The first 1 determination unit 406a and the first 2 determination unit 406b are connected to the first 1 counter 407a and the first 2 counter 407b, respectively. Further, the first 1 counter 407a and the first 2 counter 407b are connected to the third determination unit 411.

Similarly, the second temperature detection unit 204 is connected to the second 1 determination unit 408a and the second 2 determination unit 408b. Further, a threshold value generation unit 205 is also connected to the second 1 determination unit 408a and the second 2 determination unit 408b. Then, the second 1 determination unit 408a and the second 2 determination unit 408b are connected to the second 1 counter 409a and the second 2 counter 409b, respectively. Further, the second counter 409a and the second counter 409b are connected to the third determination unit 411.

Similar to the control unit 201'in the second embodiment, the control unit 201'calculates the time from when the M-shaped heat signal generated from the heater 101 exceeds one threshold value to when the same threshold value is exceeded again. (Suppose. For example, the thermal signal s1 (see FIG. 10 in the second embodiment) that is the basis of the thermal signals s2 and s3 shown in FIG. 12 exceeds the threshold value Th22 twice. Therefore, in this case, the control unit 201'calculates the time Heat from the first time the heat signal s1 exceeds the threshold value Th22 to the time when the heat signal s1 first exceeds the threshold value Th22, as in the control unit 201'in the second embodiment. Is output to the third determination unit 411. The third determination unit 411 stores this time Heat as in the third determination unit 311 in the second embodiment.

Different thresholds are output from the threshold generation unit 205 and stored in the first 1 determination unit 406a and the first 2 determination unit 406b, respectively. In the example of FIG. 12, the threshold value Th21 is stored in the first 1 determination unit 406a, and the threshold value Th22 is stored in the first 2 determination unit 406b.

Similarly, different threshold values are output from the threshold value generation unit 205 and stored in the second 1 determination unit 408a and the second 2 determination unit 408b, respectively. In the example of FIG. 12, the threshold value Th21 is stored in the second 1 determination unit 408a, and the threshold value Th22 is stored in the second 2 determination unit 408b.

The first 1 determination unit 406a compares the temperature of the fluid to be measured with the threshold value Th21, and when the temperature of the fluid to be measured exceeds the threshold value Th21, the count of the first counter 407a is started (ON). FIG. 12 shows a state in which the temperature of the fluid to be measured exceeds the threshold value Th21 and the first counter 407a is turned on at time T11.

The first 1 determination unit 406a continues the comparison operation between the temperature of the fluid to be measured and the threshold value Th21, and when the temperature of the fluid to be measured exceeds the threshold value Th21 again, the count of the first counter 407a is stopped (OFF). ). In the example of FIG. 12, since the temperature of the fluid to be measured exceeds the threshold value Th21 only once and does not exceed the threshold value Th21 again, the first counter 407a continues the counting operation.

In this case, the third determination unit 211 in the first embodiment time-outs when the first and second counters 207 and 209 count a predetermined count value, that is, a count value corresponding to the wavelength of the thermal signal s1 or more. It is considered that (Timeout) has occurred, the count is stopped, and the count is reset.

The same operation as the operation of the third determination unit 211 is also executed by the first determination unit 406a. Therefore, as shown in FIG. 12, when the first 1 counter 407a counts at least the wavelength of the thermal signal s2, the first 1 determination unit 406a considers that the time-out has occurred and the first 1 counter. The count of 407a is stopped (OFF) and reset.

On the other hand, the first 2 determination unit 406b performs the same control processing as the control processing performed on the first 2 counter 407b by the first 1 determination unit 406a on the first 1 counter 407a. However, the first 2 determination unit 406b is different in that the comparison target to be compared with the temperature of the fluid to be measured is not the threshold value Th21 but the threshold value Th22. Therefore, the description of the control process performed by the first 2 determination unit 406b on the first 2 counter 407b will be omitted.

In the example of FIG. 12, the temperature of the fluid to be measured exceeds the threshold value Th22 twice. Therefore, in the figure, the temperature of the fluid to be measured exceeds the threshold value Th22 at time T12, and the first 2 counter 407b is turned on. After that, at time T13, it is shown that the temperature of the fluid to be measured exceeds the threshold value Th22 again and the first 2 counter 407b is turned off.

The second 1 determination unit 408a and the second 2 determination unit 408b also compare the temperature of the fluid to be measured with the threshold Th21 and the threshold Th22, respectively, and at the timing when the temperature of the fluid to be measured exceeds the threshold Th21 and the threshold Th22, respectively. For the second 1 counter 409a and the second 2 counter 409b, the first 1 determination unit 406a and the first 2 determination unit 406b are for the first 1 counter 407a and the first 2 counter 407b, respectively. Performs the same control processing as the above control processing. Therefore, the description of the control processing performed by the second 1 determination unit 408a and the second 2 determination unit 408b on the second 1 counter 409a and the second 2 counter 409b, respectively, will be omitted.

In the example of FIG. 12, as described above, the temperature of the fluid to be measured exceeds the threshold value Th21 only once and exceeds the threshold value Th22 twice. Therefore, in the figure, at time T14, the temperature of the fluid to be measured exceeds the threshold value Th21, and the second counter 409a is turned on, but after that, it is regarded as a timeout and is stopped in the middle of counting. And the state of being reset is shown. Then, in the figure, after the temperature of the fluid to be measured exceeds the threshold value Th22 at the time T15 and the second counter 409b is turned on, the temperature of the fluid to be measured again sets the threshold value Th22 at the time T16. It is also shown that the second counter 409b is turned off.

When any one of the first counter 407a and the first two counters 407b stops counting, the third determination unit 411 compares the count value of the counter that stopped the counting with the time table. .. As a result of the comparison, when the count value and the time Table are equal, the third determination unit 411 starts (ON) the count of the third counter 210.

Further, when any one of the second 1 counter 409a and the second 2 counter 409b stops counting, the third determination unit 411 sets the count value of the counter that stopped the counting and the above time Teat. compare. As a result of the comparison, when the count value and the time Table are equal, the third determination unit 411 stops (OFF) the count of the third counter 210.

In FIG. 12, since the count value a2 of the first 2 counters 407b = time Teat, the third counter 210 is turned on at the time T13 when the first 2 counters 407b stop counting, and the second counter 210 is turned on. Since the count value b2 of the two counters 409b = time Teat, it is shown that the third counter 210 is turned off at the time T16 when the second counter 409b stops counting.

Further, the third determination unit 411 outputs the count value of the third counter 210 to the output unit 212.

FIG. 13 shows each count value of the first counter 407a and the second counter 409a ≠ time Teat, and each count value of the first two counters 407b and the second counter 409b = time Teat. In this case, it is a figure which shows the count operation of the 3rd counter 210.

As described above, each time either the first counter 407a or the first two counters 407b stops counting, the third determination unit 411 compares the count value of the stopped counter with the time table. , The count of the third counter 210 is started (ON) only when both of them match. In the example of FIG. 15, since the count value a1 ≠ time Teat when the first counter 407a is stopped, the third determination unit 411 starts counting the third counter 210 at this timing (time T23). I won't let you. After that, since the count value a2 = time Teat when the first 2 counters 407b are stopped, the third determination unit 411 starts counting the third counter 210 at this timing (time T24).

Further, as described above, each time any of the second counter 409a and the second counter 409b stops counting, the third determination unit 411 sets the count value and the time teat of the stopped counter. The count of the third counter 210 is stopped (OFF) only when the two are compared and they match. In the example of FIG. 13, since the count value b1 ≠ time Teat when the second counter 409a is stopped, the third determination unit 411 stops the count of the third counter 210 at this timing (time T27). I won't let you. After that, since the count value b2 = time Teat when the second 2 counters 409b are stopped, the third determination unit 411 stops the count of the third counter 210 at this timing (time T28).

FIG. 14 is a diagram showing the counting operation of the third counter 210 when each count value of all the counters 407a, 407b, 409a, and 409b = time Teat.

As described above, each time either the first counter 407a or the first two counters 407b stops counting, the third determination unit 411 compares the count value of the stopped counter with the time table. , The count of the third counter 210 is started (ON) only when both of them match. Therefore, in the example of FIG. 14, since the count value a1 = time Teat when the first counter 407a is stopped, the third determination unit 411 counts the third counter 210 at this timing (time T33). To start. That is, the third determination unit 411 does not control the counting operation of the third counter 210 at that timing (time T24) even if the first two counters 407b are stopped and the count value a2 = time Teat. ..

Further, as described above, each time any of the second counter 409a and the second counter 409b stops counting, the third determination unit 411 sets the count value and the time teat of the stopped counter. The count of the third counter 210 is stopped (OFF) only when the two are compared and they match. Therefore, in the example of FIG. 14, since the count value b1 = time Teat when the second counter 409a is stopped, the third determination unit 411 counts the third counter 210 at this timing (time T37). To stop. That is, the third determination unit 411 does not control the counting operation of the third counter 210 at the timing (time T28) even if the second counter 409b is stopped and the count value b2 = time Teat. ..

In the example of FIG. 13, the count values a1 and b1 of the first counter 407a and the second counter 409a are both not equal to the time table, and the counts of the first two counters 407b and the second counter 409b are each. It shows the case where the values a2 and b2 are both equal to the time Teat. However, the count values a2 and b1 of the first two counters 407b and the second counter 409a are not equal to the time table, and the count values a1 and b2 of the first counter 407a and the second counter 409b are both equal to each other. Can both be equal to the time Teat.

The fluid to be measured shown in FIG. 8 in the first embodiment is applied to the heat ray type flow meter of the present embodiment, the threshold value Th12 is set in the first determination unit 406a and the second determination unit 408a, and the first It is assumed that the threshold value Th13 is set in the 2 determination unit 406b and the 2nd 2 determination unit 408b.

In this case, the first counter 407a counts the time a. Since this time a is equal to the time Teat, the third counter 210 is turned on at the time T2.

On the other hand, although the second 1 counter 409a times out, the second 2 counter 409b counts the time b. Since this time b is equal to the time Teat, the third counter 210 is turned off at the time T4.

Therefore, according to the heat ray type flow meter of the present embodiment, even when the ambient temperature of the first and second temperature measuring sensors 102 and 103 changes, the moving time of the fluid to be measured can be correctly detected.

The present invention is not limited to each of the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

(1) In each of the above embodiments, an M-shaped thermal signal having two peaks of temperature change is generated from the heater 101, but the number of peaks is not limited to two, but three or more. There may be.

(2) In the first to third embodiments, one counter is used for each temperature detection unit, and in the fourth embodiment, two counters are used for each temperature detection unit, and the temperature of the fluid to be measured is a threshold value. The time from exceeding to exceeding again is counted, but the number of counters is not limited to this, and may be any number. However, as the number of counters increases, the processing becomes complicated and the memory capacity increases.

101 Heater 102 1st temperature measurement sensor 103 2nd temperature measurement sensor 107 Flow path 200, 300, 400 Control circuit 201, 201 ′ Control unit 202 Heat application unit 203 1st temperature detection unit 204 2nd temperature detection unit 205 Threshold generation unit 206, 306 1st judgment unit 208, 308 2nd judgment unit 211, 311, 411 3rd judgment unit 207 1st counter 209 2nd counter 210 3rd counter 406a 1st 1 judgment unit 406b 1st 2 judgment unit 408a 2nd 1 determination unit 408b 2nd 2 determination unit 407a 1st 1 counter 407b 1st 2 counter 409a 2nd 1 counter 409b 2nd 2 counter 212 Output unit

Claims (6)

The flow path through which the fluid to be measured flows and
A heating means for heating the fluid to be measured, which is arranged in the flow path, and
In the flow path, a first temperature measuring means for measuring the temperature of the fluid to be measured, which is arranged on the downstream side of the heating means, and
In the flow path, a second temperature measuring means for measuring the temperature of the fluid to be measured, which is arranged on the downstream side of the first temperature measuring means, and
A control means for controlling the heating means so as to generate a heat signal having at least two peaks from the heating means and superimpose the heat signal on the fluid to be measured flowing in the flow path.
A generation means that generates multiple thresholds for the temperature of the fluid under test,
For each threshold value generated by the generation means, a first timekeeping means for measuring the first time from when the temperature of the fluid to be measured measured by the first temperature measuring means exceeds the threshold value to when the temperature exceeds the threshold value again.
For each threshold value generated by the generation means, a second timekeeping means for measuring the second time from when the temperature of the fluid to be measured measured by the second temperature measuring means exceeds the threshold value to when the temperature exceeds the threshold value again, and
A third timekeeping means for measuring the third time from the end of the timekeeping of the first hour by the first timekeeping means to the end of the timekeeping of the second time by the second timekeeping means.
A calculation means for calculating the flow rate of the fluid to be measured based on the first to third hours timed by the first to third timekeeping means, respectively.
A heat ray type flow meter characterized by having. The heat ray type flow meter according to claim 1, wherein the calculation means does not calculate the flow rate of the fluid to be measured when at least one of the first and second hours is not timed. When both the first time and the second time are timed, the calculation means calculates the flow rate of the fluid to be measured when the first time and the second time are equal to each other, while the first time. The heat ray type flow meter according to claim 1, wherein the flow rate of the fluid to be measured is not calculated when the second time is different from that of the second time. Among the threshold values generated by the generation means, there is further a hypothetical means for assuming the elapsed time from the first exceeding to the threshold value where the temperature of the fluid to be measured on which the thermal signal is superimposed exceeds twice. ,
When both the first time and the second time are timed, the calculation means calculates the flow rate of the fluid to be measured when the elapsed time, the first time and the second time are all equal. The heat ray type according to claim 1, wherein the flow rate of the fluid to be measured is not calculated when the elapsed time is different from at least one of the first time and the second time. Flowmeter. The heat ray type flow meter according to any one of claims 1 to 4, wherein the peaks of the thermal signal have the same height. The calculation means measures the distance from the position where the first temperature measuring means is arranged in the flow path to the position where the second temperature measuring means is arranged by the third measuring means for the third time. Any one of claims 1 to 5, wherein the flow rate of the fluid to be measured is calculated by dividing by, and the flow rate of the fluid to be measured is calculated by multiplying the flow rate by the cross-sectional area of the flow path. The heat ray type flowmeter described in the section.

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