JP4571898B2 - Current meter and flow meter - Google Patents

Description

  The present invention relates to a velocimeter and a flow meter that measure the flow velocity or flow rate of a fluid such as a gas on the flow path.

For example, when measuring the flow rate of a fluid such as gas on the flow path, it is placed on the flow path as a technique for detecting the velocity of the fluid flowing in the flow path, which is necessary to obtain the flow rate by multiplying the known cross-sectional area of the flow path. The heater is energized and driven by an AC drive signal, and the temperature sensor arranged at an interval in the flow direction of the fluid in the flow path from the heater outputs the AC flow velocity output in accordance with the propagation speed of the heat released from the heater A method for obtaining a phase difference between a signal and an AC driving signal used for energization driving of a heater is known (for example, Patent Document 1).
JP-A-5-264567

  The above-described method for obtaining the flow velocity of the fluid from the phase difference between the flow velocity signal output from the temperature sensor and the AC drive signal used for energization driving of the heater is output from the temperature sensor when the flow velocity of the fluid flowing through the flow path changes. The flow rate of the fluid is calculated by changing the phase of the flow rate signal by an amount corresponding to the flow rate, and the accuracy is determined with respect to the time when the phase difference between the drive signal and the flow rate signal is measured. It depends on the resolution.

  The phase difference between the drive signal and the flow velocity signal is reversed, for example, by using a flip-flop circuit that uses the drive signal and the flow velocity signal as the R and S inputs, respectively, and the R and S inputs are inverted at the time of the zero crossing of each signal. The measurement can be performed from the difference in timing, and the factors governing the measurement resolution at that time include the cycle of the clock of the flip-flop circuit and the frequency of the drive signal and the flow velocity signal.

  Of these, the shorter the cycle of the clock of the flip-flop circuit, the higher the measurement resolution of the phase difference between the drive signal and the flow velocity signal and thus the measurement accuracy, but the clock cycle of the flip-flop circuit is temporarily shortened. If there is a situation that cannot be done, lower the frequency of the drive signal (and hence the flow rate signal) (and increase the cycle) to increase the number of clocks of the flip-flop circuit generated during one cycle of the drive signal or flow rate signal As a result, the measurement resolution of the phase difference between the drive signal and the flow velocity signal, and thus the measurement accuracy, are to be improved in the same situation as when the clock cycle is shortened.

  However, detecting the difference between the arrival timing of a specific phase location of the drive signal and the arrival timing of the same phase location of the flow velocity signal, such as the timing difference between the drive signal and the flow velocity signal described above, for example. Since the phase difference between the two signals measured in step 1 can only be measured once in one period, if the frequency of the drive signal is lowered, the measurement period of the phase difference between the drive signal and the flow rate signal becomes longer, resulting in a measured phase difference. The followability of the flow velocity of the fluid on the flow path obtained based on the change in the actual flow velocity of the fluid flowing through the flow path is lowered, and as a result, the accuracy of the flow velocity measurement of the fluid is lowered.

  The above-described problem is not limited to the case where the energization drive is performed by the AC drive signal in a heater in which the amount of heat released changes depending on the energization amount. This also applies to the case where a heat source that switches between emission and absorption and whose amount of heat released or absorbed changes depending on the amount of energization is used as a heat source.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to use the heat source and the temperature sensor arranged at intervals in the flow direction of the fluid in the flow path, and use the AC signal described above or a signal obtained by linearly shifting the AC signal. Based on the phase difference from the drive signal of the flow velocity signal output by the temperature sensor that detects the heat propagated from the heat source that is energized and driven by the drive signal of the periodic voltage waveform whose voltage changes at a constant cycle, such as When measuring the flow velocity or flow rate of the fluid flowing through the flow path, the flow velocity of the fluid on the flow path obtained based on the measured phase difference while increasing the measurement accuracy of the phase difference between the drive signal and the flow velocity signal An object of the present invention is to provide a flowmeter and a flowmeter that can prevent deterioration in followability of the flow rate with respect to changes in the actual flow rate or flow rate of the fluid flowing through the flow path, and can ensure the accuracy of the flow rate or flow rate measurement of the fluid.

  The present invention according to claim 1 and claim 2 that achieves the above object relates to a flow meter, and the present invention according to claim 3 relates to a flow meter.

  The current meter according to the first aspect of the present invention detects a heat source that is energized and driven by a drive signal having a periodic voltage waveform whose voltage changes at a constant period, and heat that is released or absorbed by the heat source. A flow sensor having a temperature sensor that outputs a flow velocity signal corresponding to the flow rate is arranged on the flow path of the fluid to be measured so that the heat source and the temperature sensor are spaced apart from each other in the flow direction of the fluid in the flow path. A flowmeter that measures the flow velocity of the fluid flowing through the flow path based on the phase difference signal output by the phase difference signal output means that detects the phase difference between the flow velocity signal and the drive signal according to the phase difference. In the flow path, the flow sensor disposed at each of the n locations where the fluid flow conditions are equal (integer of n = 2 or more), and thermal insulation means for thermally insulating the flow sensors from each other, Each flow Drive means for energizing and driving the heat source of the sensor by the drive signals that are shifted in phase by 1 / n period, and sequentially by the phase difference signal output means every 1 / n period of the drive signal. Based on the phase difference signal corresponding to the phase difference between the flow velocity signal and the drive signal for each detected flow sensor, the flow velocity of the fluid flowing through the flow path is determined every 1 / n period of the drive signal. It is characterized by measuring.

  Moreover, the flowmeter of the present invention described in claim 2 is the flowmeter of the present invention described in claim 1, wherein each flow sensor includes an insulating layer film in which the heat source and the temperature sensor are disposed, The heat source of the insulating film layer and a silicon base provided in the peripheral area of the diaphragm area where the temperature sensor is arranged, and n pieces are obtained by connecting the silicon bases of the respective flow sensors. The flow sensor is integrally formed, and the thermal insulation means is constituted by the silicon base of each flow sensor.

  Furthermore, the flow meter of the present invention described in claim 3 detects a heat source that is energized and driven by a drive signal having a periodic voltage waveform whose voltage changes at a constant period, and detects the heat released or absorbed by the heat source. A flow sensor having a temperature sensor that outputs a flow velocity signal corresponding to the flow rate is arranged on the flow path of the fluid to be measured so that the heat source and the temperature sensor are spaced apart from each other in the flow direction of the fluid in the flow path. And a flowmeter for measuring the flow rate of the fluid flowing through the flow path based on the phase difference signal output in accordance with the phase difference by the phase difference signal output means that detects the phase difference between the flow velocity signal and the drive signal. The flow rate is measured using the flow velocity of the fluid flowing through the flow path measured by the flow velocity meter and the known cross-sectional area of the flow path. Measure the flow rate of flowing fluid And features.

  According to the velocimeter of the present invention as set forth in claim 1, when the driving means drives the heat source of each flow sensor by the drive signal of the signal of the periodic voltage waveform, the energization amount or the emission (or absorption) heat amount of the heat source is increased. The flow rate signal is increased or decreased continuously, and the level of the flow rate signal output from the temperature sensor of each flow sensor increases or decreases accordingly. Therefore, the flow rate signal is a signal component having the same frequency as the drive signal or twice the frequency of the drive signal. It becomes a periodic voltage waveform including the frequency component.

  By the way, the signal component of the same frequency as the drive signal or the frequency component of the frequency of the drive signal included in the flow velocity signal of the periodic voltage waveform output from the temperature sensor of each flow sensor is determined by the drive means of each flow sensor. Since the phase difference from the drive signal used for energization drive of the heat source changes according to the flow velocity of the fluid flowing through the flow path, the flow rate signal of the periodic voltage waveform output from the temperature sensor of each flow sensor is driven by each flow sensor. If the means monitors the fluctuation of the phase difference from the drive signal used for energization driving of the heat source, the flow velocity of the fluid flowing through the flow path is measured.

  Then, the drive means drives the heat sources of the n flow sensors by drive signals that are out of phase with each other by 1 / n period, so that the phase difference signal output means arrives at a specific phase portion of the drive signal. The timing for detecting the difference between the timing and the timing at which the same phase portion of the flow velocity signal arrives and outputting the phase difference signal arrives with a shift of 1 / n period for each flow sensor.

  In addition, since the flow sensors are thermally insulated from each other by the thermal insulation means, even if the heat sources of the n flow sensors are energized and driven simultaneously by the drive means, the respective heat sources are released or absorbed. The output of the temperature sensor of the other flow sensor is not affected by heat.

  Therefore, the phase difference signal corresponding to the phase difference between the drive signal of the heat source of each flow sensor and the flow rate signal of the temperature sensor, which is output by the phase difference detection means every 1 / n cycle of the drive signal, is 1 / n of the drive signal. Since it corresponds to the flow velocity of the fluid flowing through the flow path at different timings by n cycles, even if the timing for measuring the phase difference between the drive signal and the flow velocity signal comes only once in one cycle of the drive signal, The flow velocity of the fluid flowing in the flow path is measured at every fine timing obtained by dividing one cycle of the drive signal by the number of flow sensors arranged in the flow path.

  Therefore, in order to increase the measurement resolution of the phase difference between the drive signal and the flow velocity signal, if the clock cycle used for phase difference measurement cannot be shortened, the drive signal can be reduced by lowering the frequency of the drive signal instead. As the frequency of the flow sensor is lowered, the measurement period of the flow velocity of the fluid flowing in the flow path becomes longer even if the timing of measuring the phase difference between the drive signal and the flow velocity signal in the flow sensor becomes longer. To prevent the fluid flow velocity on the flow path obtained based on the measured phase difference from deteriorating following the change in the actual flow velocity of the fluid flowing through the flow path, and to ensure the accuracy of fluid flow velocity measurement. it can.

  Further, according to the flowmeter of the present invention described in claim 2, in the flowmeter of the present invention described in claim 1, each flow sensor is integrated with the flow sensor by integrating n flow sensors. It can be easily arranged at a location where the flowing conditions are equal.

  According to the flowmeter of the present invention described in claim 3, the flow rate of the fluid flowing through the flow path, which is measured with high accuracy by the flowmeter of the present invention described in claim 1 or 2, is used. The flow rate of the fluid flowing through the passage can be measured with high accuracy.

  Hereinafter, an embodiment of a flow meter according to the present invention will be described together with an embodiment of a current meter with reference to the drawings.

  First, a schematic configuration of a flow sensor used in a gas flow meter according to a first embodiment of the present invention to which a current meter according to the present invention is applied and a gas flow meter according to a third embodiment of the present invention to be described later. A description will be given with reference to FIGS.

  The flow sensor indicated by reference numeral 3 in the explanatory diagram of FIG. 1 is shown in a sectional view of FIG. 2 as described with reference to FIG. 1 in, for example, Japanese Patent Laid-Open No. 9-257821. By removing the central portion of the Si substrate 31 (corresponding to the silicon base in the claims) having the insulating film 32 laminated on the upper surface by illegal etching, a diaphragm region 32a is formed in the central portion of the insulating film 32, On the diaphragm region 32a, as shown in FIG. 1, a micro heater 33 (corresponding to a heat source in claims) and a thermopile 35 (corresponding to a temperature sensor in claims) are formed by micromachining. The microheater 33 is disposed on the upstream side in the fluid flow direction on the flow path S of the gas (corresponding to the fluid to be measured in the claims). There are disposed so as to be positioned downstream.

  In this flow sensor 3, the microheater 33 emits heat by energizing and driving the microheater 33 with a drive signal, and an electromotive force corresponding to the temperature of the heat transmitted from the microheater 33 is generated in the thermopile 35. The electromotive force is configured to be output from the thermopile 35 as a flow velocity signal corresponding to the flow rate of the gas flowing through the flow path S.

  Further, in the flow sensor 3, the heat capacity of the diaphragm region 32a is very small as compared with the heat capacity of the other insulating coating 32, so that the heat generated by the microheater 33 is other than the gas flowing through the flow path S. On the other hand, the insulating coating 32 excluding the diaphragm region 32a is not easily transmitted to the thermopile 35 through the medium of the medium, and the surrounding area is provided by the Si substrate 31 that is much easier to transfer heat than the diaphragm region 32a. Therefore, the heat distribution in the diaphragm region 32a is thermally insulated from the surroundings.

  Next, a schematic configuration of the gas flowmeter according to the first embodiment of the present invention that measures the flow rate of the gas flowing through the flow path S using the flow sensor 3 described above will be described with reference to the block diagram of FIG. To do.

  The gas flow meter of the first embodiment indicated by reference numeral 1 in FIG. 3 is a drive circuit 5 (corresponding to drive means in claims) for energizing and driving the flow sensor 3 and the microheater 33 with a sinusoidal drive signal. ), An amplifier 7 that amplifies the flow velocity signal output from the thermopile 35, a bandpass filter 9 that passes only the same frequency component as the drive signal of the drive circuit 5 from the flow velocity signal amplified by the amplifier 7, and a drive circuit A phase difference detection circuit 11 for detecting a phase difference of the flow velocity signal that has passed through the band pass filter 9 with respect to the phase of the drive signal 5 and outputting a phase difference detection signal (corresponding to the phase difference signal in the claims). Three flow velocity measuring units A having a phase difference signal output means).

  Further, the gas flow meter 1 of the first embodiment is an arithmetic device such as a microcomputer that calculates the flow velocity or flow rate of the gas flowing through the flow path S from the phase difference detection signal from the phase difference detection circuit 11 of each flow velocity measurement unit A. 13 is provided.

  The flow sensors 3 of the respective flow velocity measuring units A are arranged apart from each other at the same flow conditions of the gas in the flow path S, and the heat generated by each microheater 33 is the thermopile of the other flow sensor 3. The flow sensors 3 are thermally insulated from each other by the respective Si substrates 31 so as not to be sensed by 35.

  Further, as shown in the circuit diagram of FIG. 4, the driving circuit 5 of each flow velocity measuring unit A outputs a sine wave signal corresponding to the oscillation frequency of the crystal oscillator 51 over the entire width of its amplitude. The signal is shifted by a direct-current amplifier 53 so that it becomes a potential, and a signal based on a positive or negative sine wave is output to the micro heater 33 of the flow sensor 3 as the drive signal. In addition, the drive signals are output with the phases shifted by 1/3, which is one-third of the number of the flow velocity measuring units A.

  Further, as shown in the circuit diagram of FIG. 5, the phase difference detection circuit 11 of each flow velocity measuring unit A couples the drive signal of the drive circuit 5 with a capacitor C1, and supplies power Vcc (DC5V in this embodiment). After the pull-up resistor R1 pulls up to a potential determined by the voltage dividing ratio between the resistor R2 and the pull-up resistor R1, the intermediate potential of the amplitude of the drive signal generated at the midpoint of the resistors R3 and R4 (in this embodiment, 2). .5V) is compared with the DC voltage of the comparator A1, the comparison output of the comparator A1 is input to the input S of the RS flip-flop F / F, and the flow rate signal that has passed through the bandpass filter 9 is coupled by the capacitor C2. After pulling up to a potential determined by the voltage dividing ratio of the resistor R6 and the pull-up resistor R5 by the power source Vcc and the pull-up resistor R5, the resistor R3 The comparator A2 compares the DC voltage of the intermediate potential of the drive signal generated at the midpoint of R4 with the comparator A2, inputs the comparison output of the comparator A2 to the input R of the RS flip-flop F / F, and drives the drive circuit 5 The phase difference detection signal of H level is output from the RS flip-flop F / F during a period in which the phase of the flow velocity signal that has passed through the bandpass filter 9 is shifted with respect to the phase of the signal.

  In the present embodiment, the resistors R1, R2, R3, R4, R5, and R6 have the same resistance value.

  Further, the arithmetic device 13 is configured to convert the phase difference detection signal output from the phase difference detection circuit 11 of each flow velocity measurement unit A into data relating to a conversion formula for converting the phase difference detection signal into the flow velocity of the gas flowing through the flow path S, The data of the cross-sectional area of the flow path S and the like necessary for calculating the flow rate of the gas flowing through the flow path S from the flow velocity of the gas is stored in the internal memory.

  In the gas flow meter 1 of the first embodiment having the above-described configuration, the drive circuit 5 of each flow velocity measurement unit A is used to drive the microheater 33 by energization. The signal does not invert between the positive and negative polarities, and the potential merely changes in a sine wave form. The energization amount of the micro heater 33 is also increased or decreased in a sine wave form. The waveform of the flow velocity signal output from the thermopile 35 that has detected the heat released from is a waveform having the same frequency as the drive signal.

  Although the waveform has the same frequency as that of the drive signal, the flow velocity signal output from the thermopile 35 is superimposed with other frequency components in addition to the same basic frequency component as that of the drive signal. Since the change in the phase difference of the flow velocity signal is determined depending on the frequency of the flow velocity signal, if the flow velocity signal from the thermopile 35 containing frequency components other than the fundamental frequency is used as it is, the phase difference detection circuit 11 In this case, it is impossible to accurately detect the phase difference from the drive signal.

  However, since the frequency components other than the fundamental frequency included in the flow velocity signal are removed by the bandpass filter 9, what is input to the phase difference detection circuit 11 is a sine wave based on the fundamental frequency of the drive signal.

  The waveform of the flow velocity signal output from the thermopile 35 of each flow velocity measuring unit A is such that the higher the flow velocity of the gas flowing through the flow path S, the more the phase is advanced and the phase delay with respect to the drive signal is reduced. The phase difference detection of each flow velocity measuring unit A has an H level period corresponding to the phase difference of the flow velocity signal that has passed through the band-pass filter 9 with respect to the phase of the drive signal of the drive circuit 5. The duty ratio of the phase difference detection signal from the circuit 11 is a value reflecting the flow velocity of the gas flowing through the flow path S.

  Further, since the phases of the drive signals output from the drive circuits 5 of the three flow velocity measuring units A to the micro heater 33 are shifted from each other by 1/3, the RS of the phase difference detection circuit 11 of each flow velocity measurement unit A The period during which the H-level phase difference detection signal is output from the flip-flop F / F is also shifted by 1/3 of one cycle of the drive signal.

  For this reason, the data stored in the internal memory in the arithmetic unit 13 that has fetched the phase difference detection signal output from the phase difference detection circuit 11 of each flow velocity measurement unit A with a shift of 1/3 of one cycle of the drive signal. Based on the above, the flow rate or flow rate of the gas flowing through the flow path S is measured every 1/3 period of one period of the drive signal.

  Therefore, the clock cycle of the RS flip-flop F / F cannot be shortened in order to increase the resolution of the flow velocity measurement. Instead, the frequency of the drive signal output from the drive circuit 5 is lowered (the cycle is increased). Even so, the flow rate or flow rate of the gas can be measured in a cycle that is 1/3 of one cycle of the drive signal, and the flow rate of the gas on the flow path S obtained based on the measured phase difference is It is possible to prevent a decrease in followability with respect to a change in the actual flow velocity of the gas flowing through the flow path S and to ensure the accuracy of the gas flow rate measurement.

  Next, a schematic configuration of a flow sensor used in the gas flow meter according to the second embodiment of the present invention to which the current meter according to the present invention is applied and the gas flow meter according to the fourth embodiment of the present invention to be described later. Will be described with reference to the explanatory diagram of FIG.

  The flow sensor denoted by reference numeral 3A in FIG. 6 is configured by using a Peltier element 37 instead of the micro heater 33 of the flow sensor 3 described with reference to FIGS. On the path S, the Peltier element 37 is disposed on the upstream side in the fluid flow direction, and the thermopile 35 is positioned on the downstream side.

  In this flow sensor 3A, the Peltier element 37 is energized and driven by a drive signal, whereby the Peltier element 37 releases or absorbs heat according to the direction of current flow, and according to the temperature of the heat transmitted from the Peltier element 37. An electromotive force is generated in the thermopile 35, and the electromotive force is output from the thermopile 35 as a flow velocity signal corresponding to the flow rate of the gas flowing through the flow path S.

  In addition, the diaphragm region 32a is formed by the Si substrate 31 with respect to the insulating coating 32 except for the heat that the Peltier element 37 emits or absorbs to the thermopile 35 through a medium other than the gas flowing in the flow path S. It is the same as the flow sensor 3 described with reference to FIGS. 1 and 2 in that it is thermally insulated.

  Next, a schematic configuration of the gas flowmeter according to the second embodiment of the present invention that measures the flow rate of the gas flowing through the flow path S using the flow sensor 3A described above will be described with reference to the block diagram of FIG. To do.

  In the gas flow meter of the second embodiment indicated by reference numeral 1A in FIG. 7, the flow sensor 3 of each flow velocity measuring unit A is replaced with the flow sensor 3A, and the DC shift amplifier 53 is omitted from the drive circuit 5. The gas according to the first embodiment is used except that the drive circuit 5A is used to output an AC signal based on a sine wave of a potential across a positive potential and a negative potential to the Peltier element 37 of the flow sensor 3A as the drive signal. The configuration is the same as that of the flow meter 1.

  In the gas flowmeter 1A of the second embodiment having the above configuration, the drive circuit 5A of each flow velocity measuring unit A energizes the Peltier element 37 with an alternating drive signal by a sine wave of a potential straddling a positive potential and a negative potential. Even if it is driven, the direction of the current flowing through the Peltier element 37 is reversed when the polarity is reversed between the positive and negative, and the Peltier effect (warm → cold) opposite to the Peltier effect generated in the Peltier element 37 before the reversal. Or cold / warm), and the increase / decrease tendency of the emission or absorption heat amount of the Peltier element 37 with respect to the increase / decrease of the energization amount of the Peltier element 37 is reversed before and after the reversal of the direction of current flowing through the Peltier element 37. Since the phenomenon does not occur, the waveform of the flow velocity signal output from the thermopile 35 that detects the heat released or absorbed by the Peltier element 37 of each flow velocity measurement unit A is the drive signal whose polarity is Whether the AC signal is inverted between positive and negative mutual, or its polarity regardless of whether the non inverting DC (shift) signal between positive and negative mutual, a sinusoidal with the same frequency as the drive signal.

  The waveform of the flow velocity signal output from the thermopile 35 of each flow velocity measuring unit A is such that the higher the flow velocity of the gas flowing through the flow path S, the more the phase is advanced and the phase delay with respect to the drive signal is reduced. The phase difference detection of each flow velocity measuring unit A has an H level period corresponding to the phase difference of the flow velocity signal that has passed through the band-pass filter 9 with respect to the phase of the drive signal of the drive circuit 5. The duty ratio of the phase difference detection signal from the circuit 11 is a value reflecting the flow velocity of the gas flowing through the flow path S.

  Furthermore, since the phases of the drive signals output from the drive circuits 5 of the three flow velocity measuring units A to the Peltier element 37 are shifted from each other by 1/3, the RS of the phase difference detection circuit 11 of each flow velocity measuring unit A The period during which the H-level phase difference detection signal is output from the flip-flop F / F is also shifted by 1/3 of one cycle of the drive signal.

  For this reason, the data stored in the internal memory in the arithmetic unit 13 that has fetched the phase difference detection signal output from the phase difference detection circuit 11 of each flow velocity measurement unit A with a shift of 1/3 of one cycle of the drive signal. Based on the above, the flow rate or flow rate of the gas flowing through the flow path S is measured every 1/3 period of one period of the drive signal.

  Therefore, in the gas flow meter 1A of the second embodiment, similarly to the gas flow meter 1 of the first embodiment, the clock cycle of the RS flip-flop F / F can be shortened in order to increase the resolution of the flow velocity measurement. Instead, even if the frequency of the drive signal output from the drive circuit 5 is lowered (the cycle is increased), the flow rate or flow rate of the gas can be measured in a cycle that is 1/3 of one cycle of the drive signal. The flow rate of the gas on the flow path S obtained based on the measured phase difference can be prevented from being lowered in the followability to the change in the actual flow speed of the gas flowing through the flow path S. Can be secured.

  In the gas flow meter 1 of the first embodiment described above, the microheater 33 is driven by a positive potential or negative potential drive signal obtained by direct-shifting a sine wave. However, the present invention is constant like a square wave. The present invention can also be applied to the case where the microheater 33 is driven by a drive signal having a positive potential or a negative potential obtained by direct-shifting a signal having a periodic voltage waveform in which the voltage changes with the period of.

  Accordingly, the third embodiment of the present invention corresponds to a modification of the gas flow meter 1 of the first embodiment described above, and the microheater 33 is driven by a positive or negative potential drive signal obtained by direct-shifting a square wave. A schematic configuration of the gas flowmeter according to the present invention will be described with reference to the block diagram of FIG.

  The gas flow meter of the third embodiment indicated by reference numeral 1B in FIG. 8 is a positive flow rate measurement unit A of the gas flow meter 1 of the first embodiment, in which a square wave is DC-shifted instead of the drive circuit 5. Except for the point of using a drive circuit 5B (corresponding to the drive means in the claims) for driving the microheater 33 by a drive signal of potential or negative potential, the other configuration is the same as the gas flow meter 1 of the first embodiment. Has been.

  As the drive circuit 5B, although not shown and described again, for example, a known astable multivibrator can be used.

  In the gas flow meter 1B of the third embodiment having the above-described configuration, the driving circuit 5B of each flow velocity measuring unit A is used to drive the microheater 33 by energization. The signal does not invert between the positive and negative polarities, and the potential merely changes in a square wave shape. Therefore, the energization amount of the microheater 33 is also increased or decreased in a square wave shape. The waveform of the flow velocity signal output from the thermopile 35 that detects the heat released from the micro heater 33 of each flow velocity measurement unit A is also a drive signal. It becomes a square wave shape in which deformation due to a slight delay occurs at the rise and fall of the same frequency.

  By the way, since the drive signal of the positive potential or negative potential micro heater 33 obtained by DC-shifting the square wave includes a harmonic component in addition to the fundamental frequency component, the square output from the thermopile 35 of each flow velocity measuring unit A is output. The wavy flow velocity signal also includes harmonic components other than the fundamental frequency, like the drive signal used by the drive circuit 5B to energize and drive the micro heater 33 of each flow velocity measurement unit A. Since the amount of change in the phase difference of the flow velocity signal with respect to the flow velocity signal is determined depending on the frequency of the flow velocity signal, if the flow velocity signal from the thermopile 35 containing harmonic components other than the fundamental frequency is used as it is, the phase difference The detection circuit 11 cannot accurately detect the phase difference from the drive signal.

  However, since the harmonic component contained in this flow velocity signal is removed by the bandpass filter 9, what is input to the phase difference detection circuit 11 of each flow velocity measurement unit A is a sine wave based on the fundamental frequency of the drive signal. .

  The sine wave flow velocity signal output from the thermopile 35 of each flow velocity measurement unit A and passed through the band-pass filter 9 is advanced in phase as the flow velocity of the gas flowing through the flow path S is higher, and the phase relative to the drive signal is increased. The delay is reduced and the amplitude is increased so that the phase of the flow rate signal passing through the band-pass filter 9 with respect to the phase of the drive signal of the drive circuit 5B has an H level period. The duty ratio of the phase difference detection signal from the phase difference detection circuit 11 of each flow velocity measurement unit A is a value reflecting the flow velocity of the gas flowing through the flow path S.

  For this reason, the data stored in the internal memory in the arithmetic unit 13 that has fetched the phase difference detection signal output from the phase difference detection circuit 11 of each flow velocity measurement unit A with a shift of 1/3 of one cycle of the drive signal. Based on the above, the flow rate or flow rate of the gas flowing through the flow path S is measured every 1/3 period of one period of the drive signal.

  Therefore, in the gas flow meter 1B of the third embodiment, similarly to the gas flow meter 1 of the first embodiment, the clock cycle of the RS flip-flop F / F can be shortened in order to increase the resolution of the flow velocity measurement. Instead, even if the frequency of the drive signal output from the drive circuit 5B is lowered (the cycle is increased), the flow rate or flow rate of the gas can be measured in a short cycle of 1/3 of one cycle of the drive signal. The flow rate of the gas on the flow path S obtained based on the measured phase difference can be prevented from being lowered in the followability to the change in the actual flow speed of the gas flowing through the flow path S. Can be secured.

  In the gas flowmeter 1A of the second embodiment described above, the microheater 33 is driven by an AC drive signal by a sine wave of a potential straddling a positive potential and a negative potential. The present invention can also be applied to the case where the Peltier element 37 is driven by an AC drive signal having a potential that straddles a positive potential and a negative potential in a periodic voltage waveform in which the voltage changes at a constant cycle such as a wave.

  Accordingly, this corresponds to a modification of the gas flow meter 1A of the second embodiment described above, and the Peltier element 37 is driven by an alternating drive signal by a square wave of a potential across a positive potential and a negative potential. A schematic configuration of the gas flowmeter according to the fourth embodiment will be described with reference to the block diagram of FIG.

  The gas flow meter of the fourth embodiment shown by reference numeral 1C in FIG. 9 is the gas flow meter of the third embodiment, instead of the drive circuit 5A, for each flow velocity measuring unit A of the gas flow meter 1A of the second embodiment. A driving circuit that omits the DC shift configuration from the driving circuit 5B of 1B and outputs an AC signal by a square wave of a potential straddling a positive potential and a negative potential to the Peltier element 37 of the flow sensor 3A as the driving signal. Except for the point using 5C (corresponding to the driving means in the claims), the rest is configured in the same manner as the gas flow meter 1B of the second embodiment.

  As the drive circuit 5C, for example, a well-known astable multivibrator can be used, although the illustration and illustration are omitted.

  In the gas flow meter 1C of the fourth embodiment having the above-described configuration, the drive circuit 5C of each flow velocity measurement unit A energizes the Peltier element 37 with an alternating drive signal by a square wave of a potential straddling a positive potential and a negative potential. Even if it is driven, the direction of the current flowing through the Peltier element 37 is reversed when the polarity is reversed between the positive and negative, and the Peltier effect (warm → cold) opposite to the Peltier effect generated in the Peltier element 37 before the reversal. Or cold / warm), and the increase / decrease tendency of the emission or absorption heat amount of the Peltier element 37 with respect to the increase / decrease of the energization amount of the Peltier element 37 is reversed before and after the reversal of the direction of current flowing through the Peltier element 37. Since the phenomenon does not occur, the waveform of the flow velocity signal output from the thermopile 35 that detects the heat released or absorbed by the Peltier element 37 of each flow velocity measurement unit A is the drive signal whose polarity is Regardless of whether the signal is an AC signal that is inverted between positive and negative or a DC signal that is not inverted between the positive and negative polarities (shift), there is a slight rise and fall at the same frequency as the drive signal. It becomes a square wave with deformation caused by delay.

  By the way, since the drive signal of the Peltier element 37 by the square wave of the potential straddling the positive potential and the negative potential includes the harmonic component in addition to the fundamental frequency component, the thermopile 35 of each flow velocity measuring unit A outputs. Similarly to the drive signal used for the drive circuit 5C to energize and drive the Peltier element 37 of each flow velocity measurement unit A, the square wave flow velocity signal includes harmonic components other than the fundamental frequency. Since the amount of change in the phase difference of the flow velocity signal with respect to the change is determined depending on the frequency of the flow velocity signal, the flow velocity signal from the thermopile 35 containing harmonic components other than the fundamental frequency is used as it is in the waveform. The phase difference with the drive signal in the phase difference detection circuit 11 cannot be accurately detected.

  However, since the harmonic component contained in this flow velocity signal is removed by the bandpass filter 9, what is input to the phase difference detection circuit 11 of each flow velocity measurement unit A is a sine wave based on the fundamental frequency of the drive signal. .

  The sine wave flow velocity signal output from the thermopile 35 of each flow velocity measurement unit A and passed through the band-pass filter 9 is advanced in phase as the flow velocity of the gas flowing through the flow path S is higher, and the phase relative to the drive signal is increased. The delay is reduced and the amplitude is increased so that the phase of the flow rate signal passing through the band-pass filter 9 with respect to the phase of the drive signal of the drive circuit 5C has an H level period. The duty ratio of the phase difference detection signal from the phase difference detection circuit 11 of each flow velocity measurement unit A is a value reflecting the flow velocity of the gas flowing through the flow path S.

  For this reason, the data stored in the internal memory in the arithmetic unit 13 that has fetched the phase difference detection signal output from the phase difference detection circuit 11 of each flow velocity measurement unit A with a shift of 1/3 of one cycle of the drive signal. Based on the above, the flow rate or flow rate of the gas flowing through the flow path S is measured every 1/3 period of one period of the drive signal.

  Therefore, in the gas flow meter 1C of the fourth embodiment, similarly to the gas flow meter 1A of the second embodiment, the clock cycle of the RS flip-flop F / F can be shortened in order to increase the resolution of the flow velocity measurement. Instead, even if the frequency of the drive signal output from the drive circuit 5C is lowered (longer cycle), the flow rate or flow rate of the gas can be measured in a cycle shorter than 1/3 of one cycle of the drive signal. The flow rate of the gas on the flow path S obtained based on the measured phase difference can be prevented from being lowered in the followability to the change in the actual flow speed of the gas flowing through the flow path S. Can be secured.

  Incidentally, the drive circuit 5 of each flow velocity measurement unit A used in the gas flow meter 1 of the first embodiment is DC-shifted from the drive circuit 5 used in each flow velocity measurement unit A of the gas flow meter 1A of the second embodiment. The amplifier 53 may be omitted and replaced with the drive circuit 5A that outputs an AC signal as a drive signal by a sine wave having a potential straddling a positive potential and a negative potential.

  In that case, the sine wave drive signal used by the drive circuit 5A of each flow velocity measurement unit A to drive the microheater 33 is reversed between the positive and negative polarities, and the current flow of the microheater 33 is so-called. Since the heat dissipation amount of the microheater 33, which has a half-wave rectified wave shape and is proportional to the power that is the product of current and voltage, becomes a sine wave having a frequency twice that of the drive signal used for energization driving of the microheater 33, The waveform of the flow velocity signal output from the thermopile 35 of each flow velocity measurement unit A that has detected the heat released from the microheater 33 follows the amount of heat released from the microheater 33 and becomes a sine wave having a frequency twice that of the drive signal. .

  Therefore, the phase difference detection circuit 11 of each flow velocity measuring unit A detects the phase difference between the drive signal and the flow velocity signal from the thermopile 35 that is a sine wave having a frequency twice that of the drive signal.

  Therefore, even if the gas flow meter 1 of the first embodiment is configured such that the microheater 33 is energized and driven by the drive circuit 5A, the same effect as the gas flow meter 1 of the first embodiment can be obtained.

  In each of the above embodiments, the case where the thermopile 35 is located downstream of the microheater 33 and the Peltier element 37 in the fluid flow direction has been described. However, in the present invention, the thermopile 35 is the microheater 33 and the Peltier element. The present invention can also be applied to a case where it is located upstream of 37 in the fluid flow direction.

  Also in this case, the waveform of the flow velocity signal output from the thermopile 35 is the flow velocity of the gas flowing through the flow path S, as in the case where the thermopile 35 is located downstream of the micro heater 33 and the Peltier element 37 in the fluid flow direction. The higher the speed is, the more the phase is advanced and the phase delay with respect to the drive signal is reduced so that the phase of the flow rate signal that has passed through the band-pass filter 9 with respect to the phase of the drive signal of the drive circuits 5, 5A, 5B, 5C. The duty ratio of the phase difference detection signal from the phase difference detection circuit 11 having an H level period corresponding to the phase difference is a value reflecting the flow velocity of the gas flowing through the flow path S.

  For this reason, even when the thermopile 35 is located upstream of the micro heater 33 in the fluid flow direction, the position of each flow velocity measurement unit A in the gas flow meters 1, 1A, 1B, 1C of the first to fourth embodiments. In the arithmetic unit 13 that has captured the phase difference detection signal from the phase difference detection circuit 11, the flow rate or flow rate of the gas flowing through the flow path S is set to 1 / cycle of one cycle of the drive signal based on the data stored in the internal memory. It is possible to measure with high accuracy every three periods.

  Further, in the gas flowmeters 1, 1A, 1B, and 1C of the first to fourth embodiments described above, the three flow sensors 3 and 3A are arranged separately at locations where the gas flow conditions in the flow path S are equal. The heat generated by the micro heater 33 of each flow sensor 3 or the heat released or absorbed by the Peltier element 37 of each flow sensor 3A is converted into the other flow sensors 3, 3A using the interval between the flow sensors 3 and 3A. It was configured not to be sensed by the 3A thermopile 35.

  However, as shown in the explanatory diagram of FIG. 10, the flow sensor unit B in which the Si bases 31 of the three flow sensors 3, 3 </ b> A are connected and integrated is connected to the flow path S with the micro heater 33 being a fluid. By arranging the thermopile 35 and the thermopile 35 on the upstream side in the flow direction so as to be located on the downstream side, the three flow sensors 3 and 3A are arranged at locations where the gas flow conditions in the flow path S are equal. Also good.

  In this case, the thermopile 35 of each flow sensor 3, 3 </ b> A is connected to each Si that is integrally connected to the heat generated by the micro heater 33 of the other flow sensor 3, 3 </ b> A and the heat released or absorbed by the Peltier element 37. What is necessary is just to thermally insulate with the board | substrate 31.

  And if comprised in this way, each flow sensor 3 and 3A can each be easily arrange | positioned in the location where the conditions where the gas flows in the flow path S are equal.

  Further, in each of the above embodiments, the case where the three flow sensors 3 and 3A are used and the flow sensors 3 and 3A are used has been described. However, the micro heater 33 and the Peltier element 37 of the flow sensors 3 and 3A are connected to the flow velocity measurement unit A. In the above description, the energization driving is performed using the drive signals whose phases are shifted by 1/3, which is one-third of the number of the flow sensors. However, the number of the flow sensors 3 and 3A may be any number as long as it is two or more. The drive signal used for energization driving of the micro heater 33 and the Peltier element 37 of each flow sensor 3, 3 A is 1 / the number of the flow sensors 3, 3 A to be used (when n flow sensors 3, 3 A are used) Can be shifted by 1 / n).

  In each of the above embodiments, the gas flowmeter for measuring the gas flow rate has been described as an example. However, the present invention is applicable to the measurement of the flow rate or flow rate of various fluids such as gases and liquids other than gas. In addition, it goes without saying that the present invention can be widely applied to the case where only the flow velocity at the previous stage is measured without measuring the flow rate.

It is explanatory drawing which shows schematic structure of the flow sensor used in the gas flowmeter which concerns on 1st and 3rd embodiment of this invention. It is sectional drawing of the flow sensor shown in FIG. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 1st Embodiment of this invention to which the current meter by this invention is applied. FIG. 4 is a circuit diagram showing an internal configuration of the drive circuit of FIG. 3. FIG. 4 is a circuit diagram showing an internal configuration of the phase difference detection circuit of FIG. 3. It is explanatory drawing which shows schematic structure of the flow sensor used in the gas flowmeter which concerns on 3rd and 4th embodiment of this invention. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 2nd Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 3rd Embodiment of this invention to which the current meter by this invention is applied. It is a block diagram which shows schematic structure of the gas flowmeter which concerns on 4th Embodiment of this invention to which the current meter by this invention is applied. It is explanatory drawing which shows schematic structure of the flow sensor used in the gas flowmeter which concerns on other embodiment of this invention.

Explanation of symbols

1, 1A, 1B, 1C Gas flow meter 3, 3A Flow sensor 5, 5A, 5B, 5C Drive circuit (drive means)
11 Phase difference detection circuit (phase difference signal output means)
31 Si substrate (silicon base, thermal insulation means)
32 Insulating layer film 32a Diaphragm region 33 Micro heater (heat source)
35 Thermopile (temperature sensor)
37 Peltier element (heat source)
S channel

Claims (3)

A flow sensor having a heat source that is energized and driven by a drive signal having a periodic voltage waveform whose voltage changes at a constant period, and a temperature sensor that detects heat released or absorbed by the heat source and outputs a flow rate signal according to the temperature Is disposed on the flow path of the fluid to be measured so that the heat source and the temperature sensor are spaced apart from each other in the flow direction of the fluid in the flow path, and the phase difference between the flow velocity signal and the drive signal is detected. In the velocimeter for measuring the flow velocity of the fluid flowing through the flow path based on the phase difference signal output by the phase difference signal output means according to the phase difference,
The flow sensors respectively arranged at n locations (n = 2 or more integers) where the fluid flows in the flow path are equal;
Thermal insulation means for thermally insulating the flow sensors from each other;
Drive means for energizing and driving the heat sources of the flow sensors by the drive signals that are out of phase with each other by 1 / n period of the drive signal,
Based on the phase difference signal corresponding to the phase difference between the flow velocity signal and the drive signal for each flow sensor detected by the phase difference signal output means sequentially every 1 / n cycle of the drive signal, Measuring the flow velocity of the fluid flowing through the flow path every 1 / n period of the drive signal;
An anemometer characterized by that.   Each flow sensor is configured by providing a silicon base in a peripheral region of the insulating layer film in which the heat source and the temperature sensor are disposed, and a diaphragm region of the insulating layer film in which the heat source and the temperature sensor are disposed. The n flow sensors are integrally formed by connecting the silicon bases, and the thermal insulation means is constituted by the silicon bases of the flow sensors. The anemometer described. A flow sensor having a heat source that is energized and driven by a drive signal having a periodic voltage waveform whose voltage changes at a constant period, and a temperature sensor that detects heat released or absorbed by the heat source and outputs a flow rate signal according to the temperature Is arranged on the flow path of the fluid to be measured so that the heat source and the temperature sensor are spaced apart from each other in the flow direction of the fluid in the flow path, and the phase difference between the flow velocity signal and the drive signal is detected. A flowmeter that measures the flow rate of the fluid flowing through the flow path based on the phase difference signal output by the phase difference signal output means according to the phase difference,
The anemometer according to claim 1 or 2,
Using the flow velocity of the fluid flowing through the flow path measured by the anemometer and the known cross-sectional area of the flow path, the flow rate of the fluid flowing through the flow path is measured.
A flow meter characterized by that.

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