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WO2003052355A1 - Debitmetre - Google Patents

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Publication number
WO2003052355A1
WO2003052355A1 PCT/JP2001/010958 JP0110958W WO03052355A1 WO 2003052355 A1 WO2003052355 A1 WO 2003052355A1 JP 0110958 W JP0110958 W JP 0110958W WO 03052355 A1 WO03052355 A1 WO 03052355A1
Authority
WO
WIPO (PCT)
Prior art keywords
resistors
sensor
temperature
heating
flow
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/JP2001/010958
Other languages
English (en)
Japanese (ja)
Inventor
Tsukasa Matsuura
Naoki Yutani
Kazuhiko Tsutsumi
Yuji Ariyoshi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Mitsubishi Electric Corp
Original Assignee
Mitsubishi Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Mitsubishi Electric Corp filed Critical Mitsubishi Electric Corp
Priority to JP2003553200A priority Critical patent/JPWO2003052355A1/ja
Priority to PCT/JP2001/010958 priority patent/WO2003052355A1/fr
Publication of WO2003052355A1 publication Critical patent/WO2003052355A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
    • G01F1/6845—Micromachined devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
    • G01F1/696—Circuits therefor, e.g. constant-current flow meters

Definitions

  • the present invention relates to a flow sensor for measuring a gas flow, and more particularly to a flow sensor for an automobile.
  • thermal type flow sensor that can directly detect the mass air flow has become mainstream.
  • a thermal type flow sensor that controls two sets of heat generating resistors and a temperature sensor so that the temperatures thereof are equal to each other is disclosed in Japanese Patent Laid-Open Publication No. H11-326600. It is proposed in Japanese Patent Publication No.
  • FIG. 9 is a diagram showing the configuration and operation principle of the flow sensor.
  • R1 to R6 are resistors
  • 100 is a flow tube through which the measurement fluid flows
  • resistors R1 to R4 are arranged in the flow tube 20 through which the measurement fluid flows, and are exposed to the flow.
  • R 1 and R 4 are heating resistors
  • R 2 and R 3 are temperature sensors
  • heating resistor R 1 and temperature sensor R 2 temperature sensor R 3 and heating resistor R 4 is configured as a pair.
  • Ql and Q2 are switches
  • 102 is a comparator
  • 104 is an inverter.
  • control is performed such that the temperature of the resistors Rl and R2 and the temperature of the resistors R3 and R4 are always equal by the repetition of such switch switching operation, that is, the oscillation of the circuit.
  • the output from the circuit ie, the sensor output, is a digital output from the comparator 102 as indicated by “info out”.
  • the sensor output is high during the time t].
  • switch Q1 is on and conducting to resistor R1
  • switch Q2 is on and resistor R4
  • the sensor output is low during the time t2 when power is supplied to the switch.
  • the switching of this circuit occurs spontaneously, and its period t1 + t2 is determined by the thermal time constants of resistors Rl, R2 and resistors R3, R4.
  • FIG. 11 is a graph showing the flow rate and the temperature distribution on the sensor. The method of measuring the flow rate will be described below with reference to this figure.
  • the horizontal axis is position
  • the vertical axis is temperature (all are arbitrary units).
  • FIG. 12 shows an example of the structure of a conventional flow sensor.
  • 105 is silicon 106 is a groove formed by etching silicon
  • 107 is a bridge supporting resistors R1 to R4.
  • the bridge is made of a thin film and has resistors Rl and R2 and resistors R3 and R4.
  • the thermal type flow sensor proposed in Japanese Patent Application Laid-Open No. H11-132603 is configured as described above, and the measured flow rate information is digitized by a comparator and output. These outputs are then input to a signal processing circuit, where they are processed as useful data.
  • the output signal of an automotive flow sensor is input to an engine control unit (ECU) and processed along with data from other sensors, such as air pressure and temperature, to determine the optimal fuel injection quantity.
  • ECU engine control unit
  • signal processing circuits such as engine-control units sample the signal from the flow sensor at a certain frequency to make the processed data meaningful.
  • the higher the response system the higher the sampling frequency. Therefore, it is meaningless if the digitizing frequency of the sensor signal, that is, the sensor output frequency, is lower than this sampling frequency, and it is necessary that the frequency be at least the same or higher.
  • the present invention has been made in view of the above-mentioned problems of the related art, and it is possible to appropriately set the output frequency of the flow sensor.
  • the output frequency is set to be equal to or higher than the sampling frequency.
  • the purpose is to provide a reliable flow sensor that can be applied to highly responsive systems such as automobiles. Disclosure of the invention
  • the present invention provides a silicon substrate, a support film of an insulating thin film formed on the surface of the silicon substrate, and a support film formed on the support film and supported by the support film. It has two sets of heating resistors and a temperature sensor, and the temperature of the heating resistor and the temperature sensor on the upstream side and the temperature of the heating resistor and the temperature sensor on the downstream side in the flow direction of the measurement fluid. So that the upstream and downstream heating resistors are alternately heated so that the flow rate of the measurement fluid is measured based on the ratio of the heating time of the upstream and downstream heating resistors.
  • f (H z) is the switching frequency for alternately heating the upstream and downstream heating resistors
  • d ( ⁇ m) is the distance between each pair of heating resistors and the temperature sensor
  • k 1 is the constant.
  • k 1 1900 000, 0 ⁇ k 2 ⁇ 200.
  • the structure for achieving the output frequency required for the flow sensor that is, the switching frequency f, can be determined by the distance d between the heating resistor and the temperature sensor. It can be applied to a flow sensor for
  • the distance d between the heating resistor and the temperature sensor of each set is preferably 1 m or more and 30 ⁇ m or less.
  • the sampling frequency of the automotive engine control unit is around 800 Hz
  • the switching frequency for heating the heating resistors alternately that is, the output frequency is desirably higher.
  • the output frequency is set to 80 OHz or more, which is desirable when the flow sensor of the present method is applied to a flow sensor for an automobile.
  • FIGS. 1A and 1B show a flow sensor according to a first embodiment of the present invention, wherein FIG. 1A is a plan view thereof, and FIG. 1B is a cross-sectional view taken along line Ib-Ib in FIG. is there.
  • FIG. 2 is a process chart for explaining a method of manufacturing the flow sensor of FIG.
  • FIG. 3 is a control circuit diagram of the flow sensor of FIG.
  • FIG. 4 is an output waveform diagram of the flow sensor of FIG.
  • FIG. 5 is a graph showing the relationship between the distance between the heating resistor and the temperature sensor and the output frequency in the flow sensor of FIG.
  • Figure 6 shows the output frequency, heating resistor, and temperature sensor of the flow sensor in Figure 1. It is a graph which shows the relationship with distance.
  • FIG. 7A and 7B show a flow sensor according to a second embodiment of the present invention, wherein FIG. 7A is a plan view thereof, and FIG. 7B is a cross-sectional view taken along line VEb-VHb in FIG.
  • FIG. 8 shows a flow sensor according to a third embodiment of the present invention, (a) is a plan view thereof, and (b) is a cross-sectional view taken along line Mb-Mb in (a).
  • FIG. 9 is a control circuit diagram of a conventional flow sensor.
  • FIG. 10 is an output waveform diagram of the conventional flow sensor of FIG.
  • FIG. 11 is a graph showing the temperature distribution on the surface of the conventional flow sensor of FIG.
  • FIG. 12 is a longitudinal sectional view of the conventional flow sensor of FIG. BEST MODE FOR CARRYING OUT THE INVENTION
  • FIG. 1 shows a flow sensor S1 according to the first embodiment of the present invention.
  • the flow sensor S 1 includes an upstream temperature sensor 1, an upstream heating resistor 2, a downstream heating resistor 3, and a downstream heating resistor arranged in order from the upstream side to the downstream side of the flow.
  • a side temperature sensor 4 is provided, and all of these resistors 1 to 4 are supported on a supporting film 6 which is made of a silicon nitride film and is a diaphragm-like insulating thin film.
  • Each of the resistors 1 to 4 is formed of a platinum thin film having a line width of 5 / im and a thickness of 2 m, and a line interval of 5 / m.
  • the minimum distance between the upstream-side temperature sensor 1 and the upstream-side heating resistor 2 and the minimum distance between the downstream-side heating resistor 3 and the upstream-side temperature sensor 4 are d and the deviation is d.
  • the dimensions of the diaphragm indicated by broken lines in (a) are 0.75 mm or 1.5 mm in width a, 2 mm in height b, and 3 ⁇ in thickness t. Further, as shown in FIG. 1B, the support film 6 is supported on the silicon substrate 5 via the thermal oxidation film 9. Reference numeral 8 denotes a bonding pad for wire bonding. Next, a manufacturing process of the flow rate sensor S1 according to the present invention will be described with reference to FIG.
  • a thermal oxide film 9 with a thickness of 0.5 m is formed on both sides.
  • a silicon wafer 5 having a plane orientation (100) and a thickness of 380 / m is prepared.
  • a silicon nitride film 11 having a thickness of about 2 / im was formed on one of the thermal oxide films 9 by sputtering.
  • a platinum film 7 having a thickness of about 0.2 / zm is further formed on the silicon nitride film 11 by sputtering.
  • the platinum film 7 was patterned using photolithography, and the temperature sensors 1, 4, the heating resistors 2, 3, and the wiring portion were formed.
  • Form 10 (the wiring 10 is not shown in FIG. 2 (d)).
  • a silicon nitride film having a thickness of about 1 im is formed as a protective film by sputtering, and then, although not shown, a pad portion for wire bonding is formed by dry etching. Open.
  • the thermal oxide film 9 on the back surface is patterned and the silicon substrate 5 is anisotropically etched from the back surface using this as a mask.
  • TM AH tetra'methylammonium'hydroxide
  • FIG. 3 is a view showing the operation principle of the flow sensor S1 according to the present invention.
  • the flow sensor S1 includes a plurality of (in this case, six) resistors R1 to R6, and among the resistors R1 to R6, the resistors R1 to R4. Is arranged in a flow tube 20 through which the measurement fluid flows, and is exposed to the flow of the measurement fluid.
  • resistor R 1 is the upstream temperature sensor 1
  • resistor R 2 is the upstream heating resistor 2
  • resistor R 3 is the downstream heating resistor 3
  • resistor R 4 is the downstream temperature sensor 4. It is.
  • the resistors R5 and R6 are resistors forming a bridge circuit together with the resistors R1 and R4.
  • the resistors R2 and R3 are turned on / off by switches Q1 and Q2, respectively, which are composed of transistors.
  • the bridge circuit is connected to the comparator 22. Have been.
  • the output of the comparator 22 is directly input to the switch Q1 and is also input to the switch Q2 via the inverter 24, and is also output to, for example, an engine control unit (ECU) or an output monitor. .
  • ECU engine control unit
  • control is performed so that the temperature of the resistors Rl and R2 and the temperature of the resistors R3 and R4 are always equal by the repetition of such a switch switching operation, that is, the oscillation of the circuit.
  • the output from the circuit ie, the sensor output, is a digital output from the comparator 22.
  • the sensor output is high during time t1 when switch Q1 is on and resistor R2 is energized, while switch Q2 is on and resistor R3
  • the sensor output is low during the time t2 during which power is supplied to the sensor.
  • the temperature of the resistors R1, R2 and the temperatures of the resistors R3, R4 are controlled to be always equal.
  • the resistors R l and R 2 on the upstream side take more heat than the resistors R 3 and R 4 on the downstream side.
  • the relationship between the time t1 when the resistor R1 is energized and the time t2 when the resistor R4 on the downstream side is energized is t1> t2, and the duty ratio of the sensor output changes.
  • the duty ratio and the flow rate have a one-to-one relationship, the force, the flow rate, and the like can be measured.
  • the switching frequency for heating the heating resistors alternately that is, the output frequency f
  • the output frequency f is linear with the reciprocal 1 / d of the distance between the heating resistors and the temperature sensor.
  • Fig. 5 is a graph showing the relationship between the reciprocal 1 / d of the distance between the heating resistor and the temperature sensor and the frequency f of the flow sensor output.
  • the four points are on a straight line, and it can be seen that the smaller the d (the larger the lZd), the higher the output frequency f of the flow sensor.
  • the prototype sensor was actually operated, and power consumption and heat loss were measured.
  • the power consumption at a flow rate of 8 m / s (30 g / s in flow rate) was 61 mW.
  • the air temperature was 23 ° C
  • the temperature of the heating resistor was 143 ° C.
  • the amount of heat Q that escapes from the heating resistor through the diaphragm to the silicon substrate that is, the value of heat loss
  • the value of heat loss can be calculated as follows. In this method, switching is performed, so it is only necessary to consider the heat loss from either the upstream heating resistor or the downstream heating resistor.
  • the length L of the upstream heating resistor 2 is 1 mm
  • the thickness t of the support film 6 is 3 ⁇ m
  • the distance L ′ (m) from the upstream heating resistor 2 to the left silicon substrate 5 is the width of the diaphragm a.
  • the thermal conductivity k of the silicon nitride film 11 is 2.79 W / mK
  • the temperature Th of the upstream heating resistor 2 is 143 ° C
  • the temperature T s of the silicon substrate 5 is 23 ° C
  • the cross-sectional area A is
  • the heat loss under the above operating conditions must be less than 10%, and above that, the normal operation of the flow sensor may not be performed.
  • the heat loss of a sensor with a diaphragm width a of 1.5 mm is 1.6 mW, and the power consumption is equivalent to 2.6% of 61 mW, so there is no problem in characteristics.
  • the lower limit of the diaphragm width is 0.75 mm
  • the value of k 2 is in the range 0 ⁇ k 2 200. That is, the flow rate sensor shown in the present embodiment has a relation between the distance d between the heating resistor and the temperature sensor and the output frequency f.
  • the output signal from the flow sensor is input to an external engine-control unit (ECU) and processed together with data from other sensors, such as air pressure and temperature, to optimize Used to determine the fuel injection amount. Since the sampling frequency of the engine control unit for automobiles is mainly around 80 OHz, the output frequency must be 800 Hz or more.
  • Figure 5 shows the relationship between the output frequency f and the distance d between the heating resistor and the temperature sensor.
  • d 25; um when there is almost no heat loss (the curve shown by the broken line in the figure), and usually less than that. Need to be designed with d.
  • the sampling frequency of the control unit is currently around 800 Hz, but there are also low-frequency ones.
  • a heating resistor and a temperature sensor are used as a flow sensor applied to automobiles.
  • the distance should be d ⁇ 30 im, preferably d ⁇ 25 im. Since the minimum gap between the heating resistor and the temperature sensor is manufactured using photolithography, the lower limit of d is 1 // m. Therefore, the distance d between the heating resistor and the temperature sensor is 1 111 to 30 / im, preferably 1 x rn to 25 / im.
  • platinum is used as the heating resistor, but the material is nickel, nickel-iron, nickel-aluminum, tungsten, iron-palladium, nickel silicide, molybdenum silicide, titanium silicide, low-resistance
  • a metal, alloy, silicide, silicon, or the like such as silicon or polysilicon may be used, and has the same effect as the above embodiment.
  • a platinum resistor was used as the temperature sensor, but the material may be the above-mentioned metal, alloy, silicide, silicon, or the like, or a thermistor-thermocouple. This has the same effect as the above embodiment.
  • the silicon nitride film is used as the support base material.
  • the material may be any material as long as the portion in contact with the heating resistor and the temperature sensor is an insulator, and may be a material other than the silicon nitride film.
  • the temperature control circuit is shown in FIG. 3 in the present embodiment, a control method that alternately heats the heating resistors so that the temperature of the upstream heating resistor and the temperature of the downstream heating resistor become the same is used.
  • other circuit configurations may be used, and the same effects as in the above embodiment can be obtained.
  • FIG. 7 shows a flow sensor S2 according to the second embodiment of the present invention.
  • the support film 6 is formed not in a diaphragm shape but in a bridge shape.
  • the bridge can be formed by forming an opening in the support film 6 by dry etching and performing anisotropic etching of the silicon substrate 5 from both the support film side and the back surface.
  • the heat loss from the heat generating resistor to the silicon substrate 5 can be reduced, and the same effect as in Embodiment 1 can be obtained by increasing the size of the diaphragm.
  • FIG. 8 shows a flow sensor S3 according to the third embodiment of the present invention.
  • the components denoted by the same reference numerals as those in FIG. 1 are the same or equivalent components.
  • the support film 6 is formed not in a diaphragm shape but in a bridge shape, and the support film 6 is supported on the cavities 12 of the silicon substrate 5 as shown in FIG. 1 (b). .
  • the cavities 12 can be formed by forming an opening in the support film 6 by dry etching and performing anisotropic etching of the silicon substrate 5 from the support film side. According to this embodiment, can heat loss reduction from the heating resistor to the silicon ⁇ substrate 5, there same effect force s and to increase the size of the diaphragm in the first embodiment.
  • the output frequency of the flow sensor according to the present invention can be appropriately set to be equal to or higher than the sampling frequency, the flow sensor is suitable for use as a flow sensor for an automobile requiring high-speed response.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

L'invention concerne un débitmètre conçu de manière à satisfaire la relation f = k1/d K2, dans laquelle K1 = 19'000, 0 ≤ k2 ≤ 200, f désigne la fréquence de commutation (en Hz) à laquelle des résistances chauffantes sont chauffées, d désigne la distance (en νm) entre la résistance chauffante et une sonde de température et k1 et k2 sont des constantes. La distance entre la résistance chauffante et la sonde de température est comprise entre 1 et 30 νm. Par conséquent, le débitmètre peut être utilisé dans un véhicule automobile pour régler le débit à la fréquence d'échantillonnage d'un système de commande moteur ou à une fréquence supérieure.
PCT/JP2001/010958 2001-12-14 2001-12-14 Debitmetre Ceased WO2003052355A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2003553200A JPWO2003052355A1 (ja) 2001-12-14 2001-12-14 流量センサ
PCT/JP2001/010958 WO2003052355A1 (fr) 2001-12-14 2001-12-14 Debitmetre

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/JP2001/010958 WO2003052355A1 (fr) 2001-12-14 2001-12-14 Debitmetre

Publications (1)

Publication Number Publication Date
WO2003052355A1 true WO2003052355A1 (fr) 2003-06-26

Family

ID=11738034

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2001/010958 Ceased WO2003052355A1 (fr) 2001-12-14 2001-12-14 Debitmetre

Country Status (2)

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JP (1) JPWO2003052355A1 (fr)
WO (1) WO2003052355A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010133897A (ja) * 2008-12-08 2010-06-17 Hitachi Automotive Systems Ltd 熱式流体流量センサおよびその製造方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0943900A1 (fr) * 1998-03-20 1999-09-22 Berkin B.V. Dispositif de mesure de l'écoulement d'un milieu
JPH11344369A (ja) * 1998-06-03 1999-12-14 Mitsubishi Electric Corp 流量検出素子及び流量センサ

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0943900A1 (fr) * 1998-03-20 1999-09-22 Berkin B.V. Dispositif de mesure de l'écoulement d'un milieu
JPH11344369A (ja) * 1998-06-03 1999-12-14 Mitsubishi Electric Corp 流量検出素子及び流量センサ

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010133897A (ja) * 2008-12-08 2010-06-17 Hitachi Automotive Systems Ltd 熱式流体流量センサおよびその製造方法
US8429964B2 (en) 2008-12-08 2013-04-30 Hitachi Automotive Systems, Ltd. Thermal fluid flow sensor having stacked insulating films above and below heater and temperature-measuring resistive elements

Also Published As

Publication number Publication date
JPWO2003052355A1 (ja) 2005-04-28

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