WO2013187226A1 - 熱式流量計 - Google Patents
熱式流量計 Download PDFInfo
- Publication number
- WO2013187226A1 WO2013187226A1 PCT/JP2013/064823 JP2013064823W WO2013187226A1 WO 2013187226 A1 WO2013187226 A1 WO 2013187226A1 JP 2013064823 W JP2013064823 W JP 2013064823W WO 2013187226 A1 WO2013187226 A1 WO 2013187226A1
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- WIPO (PCT)
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- circuit package
- flow meter
- passage
- protrusion
- flow rate
- Prior art date
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F5/00—Measuring a proportion of the volume flow
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- 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
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- 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
- G01F1/6842—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow with means for influencing the fluid flow
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- 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
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- 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
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- 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
- G01F1/6965—Circuits therefor, e.g. constant-current flow meters comprising means to store calibration data for flow signal calculation or correction
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- 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
- G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
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- 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
- G01F1/698—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
- G01F1/699—Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters by control of a separate heating or cooling element
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/006—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus characterised by the use of a particular material, e.g. anti-corrosive material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/02—Compensating or correcting for variations in pressure, density or temperature
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/02—Compensating or correcting for variations in pressure, density or temperature
- G01F15/04—Compensating or correcting for variations in pressure, density or temperature of gases to be measured
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/02—Compensating or correcting for variations in pressure, density or temperature
- G01F15/04—Compensating or correcting for variations in pressure, density or temperature of gases to be measured
- G01F15/043—Compensating or correcting for variations in pressure, density or temperature of gases to be measured using electrical means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/14—Casings, e.g. of special material
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/18—Supports or connecting means for meters
- G01F15/185—Connecting means, e.g. bypass conduits
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D2200/00—Input parameters for engine control
- F02D2200/02—Input parameters for engine control the parameters being related to the engine
- F02D2200/04—Engine intake system parameters
- F02D2200/0414—Air temperature
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/14—Introducing closed-loop corrections
- F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
- F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
- F02D41/1454—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being an oxygen content or concentration or the air-fuel ratio
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
- F02D41/02—Circuit arrangements for generating control signals
- F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
- F02D41/182—Circuit arrangements for generating control signals by measuring intake air flow for the control of a fuel injection device
Definitions
- the present invention relates to a thermal flow meter.
- a flow meter for measuring the flow rate of gas and the temperature of the gas are used.
- a measuring device for measurement was provided separately.
- a flow meter that has a function of measuring the temperature of a gas to a flow meter that measures the flow rate of the gas is considered.
- Such a technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-209243.
- This technology is a thermal flow meter that measures the flow rate of gas, with a sensor that measures the temperature of the gas, and has the function of measuring the amount of intake air and the intake air temperature that are supplied to the internal combustion engine. ing.
- Equipment that measures control parameters should always have high reliability.
- control parameters such as thermal flow meters and intake air temperature sensors
- elements that perform each measurement are individually arranged in a gas to be measured, and the respective elements are individually electrically connected in the gas to be measured. In such a structure, there are various difficult problems to maintain high reliability.
- An object of the present invention is to provide a reliable thermal flow meter having a gas temperature detection unit.
- the thermal flow meter of the present invention performs heat transfer between a sub-passage for taking in and flowing the gas to be measured flowing through the main passage and the gas to be measured flowing through the sub-passage.
- a circuit package having a flow rate measurement circuit for measuring a flow rate and a temperature detection unit for detecting the temperature of the gas to be measured, and an electric signal representing the flow rate and an electric signal representing the temperature of the gas to be measured are output.
- An external terminal and a case for supporting the circuit package, and the circuit package includes a configuration in which the flow rate measurement circuit and the temperature detection unit are included in a resin, and the temperature detection unit is formed from the circuit package body. It has a projecting portion that protrudes, and the base of the projecting portion is thicker than the tip, and further, the base of the projecting portion becomes gradually narrower toward the tip.
- a highly reliable thermal flow meter having a gas temperature detection unit can be obtained.
- FIG. 1 is a system diagram showing an embodiment in which a thermal flow meter according to the present invention is used in an internal combustion engine control system. It is a figure which shows the external appearance of a thermal type flow meter, (A) is a left view, (B) is a front view. It is a figure which shows the external appearance of a thermal type flow meter, (A) is a right view, (B) is a rear view. It is a figure which shows the external appearance of a thermal type flow meter, (A) is a top view, (B) is a bottom view. It is a figure which shows the housing of a thermal type flow meter, (A) is a left view of a housing, (B) is a front view of a housing.
- FIG. 1 It is a figure which shows the housing of a thermal type flow meter, (A) is a right view of a housing, (B) is a rear view of a housing. It is the elements on larger scale which show the state of the flow-path surface arrange
- FIG. 12 is a view showing another embodiment of the circuit package shown in FIG. 11, wherein (A) is a front view of the circuit package and (B) is a rear view. It is a figure which shows the production process of a circuit package.
- the form for carrying out the invention described below solves various problems that are demanded as actual products, and particularly as a measuring device for measuring the intake air amount of a vehicle. It solves various problems that are desirable for use, and has various effects.
- One of the various problems solved by the following embodiment is the contents described in the column of the problem to be solved by the above-described invention, and one of the various effects exhibited by the following embodiment is It is the effect described in the column of the effect of the invention.
- Various problems solved by the following embodiments, and various effects produced by the following embodiments will be described in the description of the following embodiments. Therefore, the problems and effects solved by the embodiments described in the following embodiments are also described in the contents other than the contents of the problem column to be solved by the invention and the effect column of the invention.
- FIG. 1 shows an embodiment in which a thermal flow meter according to the present invention is used in an internal combustion engine control system of an electronic fuel injection system. It is a system diagram. Based on the operation of the internal combustion engine 110 including the engine cylinder 112 and the engine piston 114, the intake air is sucked from the air cleaner 122 as the measurement target gas 30 and passes through the main passage 124 such as the intake body, the throttle body 126, and the intake manifold 128. Guided to the combustion chamber of the engine cylinder 112. The flow rate of the gas 30 to be measured, which is the intake air led to the combustion chamber, is measured by the thermal flow meter 300 according to the present invention, and fuel is supplied from the fuel injection valve 152 based on the measured flow rate.
- the gas to be measured is introduced into the combustion chamber together with a certain gas 30 to be measured.
- the fuel injection valve 152 is provided in the intake port of the internal combustion engine, and the fuel injected into the intake port forms an air-fuel mixture together with the measured gas 30 that is intake air, and passes through the intake valve 116. It is guided to the combustion chamber and burns to generate mechanical energy.
- the thermal flow meter 300 can be used not only for the method of injecting fuel into the intake port of the internal combustion engine shown in FIG. 1 but also for the method of directly injecting fuel into each combustion chamber.
- the basic concept of the control parameter measurement method including the method of using the thermal flow meter 300 and the control method of the internal combustion engine including the fuel supply amount and ignition timing are substantially the same. A method of injecting fuel into the port is shown in FIG.
- the fuel and air guided to the combustion chamber are in a mixed state of fuel and air, and are ignited explosively by spark ignition of the spark plug 154 to generate mechanical energy.
- the combusted gas is guided from the exhaust valve 118 to the exhaust pipe, and is discharged from the exhaust pipe to the outside as the exhaust gas 24.
- the flow rate of the gas 30 to be measured which is the intake air led to the combustion chamber, is controlled by the throttle valve 132 whose opening degree changes based on the operation of the accelerator pedal.
- the fuel supply amount is controlled based on the flow rate of the intake air guided to the combustion chamber, and the driver controls the flow rate of the intake air guided to the combustion chamber by controlling the opening degree of the throttle valve 132, thereby
- the mechanical energy generated by the engine can be controlled.
- the flow rate and temperature of the measurement target gas 30 that is the intake air that is taken in from the air cleaner 122 and flows through the main passage 124 are measured by the thermal flow meter 300, and from the thermal flow meter 300
- An electric signal indicating the flow rate and temperature of the intake air is input to the control device 200.
- the output of the throttle angle sensor 144 for measuring the opening degree of the throttle valve 132 is input to the control device 200, and further the positions and states of the engine piston 114, the intake valve 116 and the exhaust valve 118 of the internal combustion engine, and the rotation of the internal combustion engine.
- the output of the rotation angle sensor 146 is input to the control device 200.
- the output of the oxygen sensor 148 is input to the control device 200.
- the control device 200 calculates the fuel injection amount and the ignition timing based on the flow rate of the intake air, which is the output of the thermal flow meter 300, and the rotational speed of the internal combustion engine measured based on the output of the rotation angle sensor 146. Based on these calculation results, the amount of fuel supplied from the fuel injection valve 152 and the ignition timing ignited by the spark plug 154 are controlled. The fuel supply amount and ignition timing are actually based on the intake air temperature and throttle angle change state measured by the thermal flow meter 300, the engine rotational speed change state, and the air-fuel ratio state measured by the oxygen sensor 148. It is finely controlled. The control device 200 further controls the amount of air that bypasses the throttle valve 132 by the idle air control valve 156 in the idle operation state of the internal combustion engine, thereby controlling the rotational speed of the internal combustion engine in the idle operation state.
- the vehicle on which the thermal flow meter 300 is mounted is used in an environment with a large temperature change, and is also used in wind and rain or snow. When a vehicle travels on a snowy road, it travels on a road on which an antifreezing agent is sprayed. It is desirable for the thermal flow meter 300 to take into account the response to temperature changes in the environment in which it is used and the response to dust and contaminants. Further, the thermal flow meter 300 is installed in an environment that receives vibrations of the internal combustion engine. It is required to maintain high reliability against vibration.
- the thermal flow meter 300 is attached to an intake pipe that is affected by heat generated from the internal combustion engine. Therefore, heat generated by the internal combustion engine is transmitted to the thermal flow meter 300 via the intake pipe which is the main passage 124. Since the thermal flow meter 300 measures the flow rate of the gas to be measured by performing heat transfer with the gas to be measured, it is important to suppress the influence of heat from the outside as much as possible.
- the thermal flow meter 300 mounted on the vehicle simply solves the problem described in the column of the problem to be solved by the invention, and exhibits the effect described in the column of the effect of the invention.
- the above-described various problems are fully considered, and various problems required as products are solved, and various effects are produced. Specific problems to be solved by the thermal flow meter 300 and specific effects achieved will be described in the description of the following examples.
- FIGS. 2, 3, and 4 are views showing the external appearance of the thermal flow meter 300, and FIG. 2B is a front view, FIG. 3A is a right side view, FIG. 3B is a rear view, FIG. 4A is a plan view, and FIG. It is a bottom view.
- the thermal flow meter 300 includes a case 301, and the case 301 includes a housing 302, a front cover 303, and a back cover 304.
- the housing 302 includes a flange 312 for fixing the thermal flow meter 300 to the intake body that is the main passage 124, an external connection portion 305 having an external terminal 306 for electrical connection with an external device, and a flow rate.
- a measuring unit 310 is provided.
- a sub-passage groove for creating a sub-passage is provided inside the measuring unit 310, and a flow rate detection for measuring the flow rate of the gas 30 to be measured flowing through the main passage 124 is provided inside the measuring unit 310.
- the thermal type flow meter 300 can measure the flow rate and temperature of the gas in the part away from the inner wall surface of the main passage 124, and can suppress a decrease in measurement accuracy due to the influence of heat or the like.
- the temperature of the measurement target gas 30 is easily affected by the temperature of the main passage 124 and is different from the original temperature of the gas. It will be different from the state.
- the main passage 124 is an intake body of an engine, it is often maintained at a high temperature under the influence of heat from the engine. For this reason, the gas in the vicinity of the inner wall surface of the main passage 124 is often higher than the original temperature of the main passage 124, which causes a reduction in measurement accuracy.
- the fluid resistance is large, and the flow velocity is lower than the average flow velocity of the main passage 124. For this reason, if the gas in the vicinity of the inner wall surface of the main passage 124 is taken into the sub passage as the gas to be measured 30, a decrease in the flow velocity with respect to the average flow velocity in the main passage 124 may lead to a measurement error.
- the inlet 350 is provided at the tip of the thin and long measuring unit 310 extending from the flange 312 toward the center of the main passage 124, so that the flow velocity in the vicinity of the inner wall surface is provided. Measurement errors related to the reduction can be reduced.
- the inlet 350 is provided at the distal end portion of the measuring unit 310 extending from the flange 312 toward the center of the main passage 124, but also the outlet of the sub passage. Is also provided at the tip of the measurement unit 310, so that measurement errors can be further reduced.
- the measurement unit 310 of the thermal flow meter 300 has a shape that extends long from the flange 312 toward the center of the main passage 124, and a portion of the gas to be measured 30 such as intake air is taken into the sub-passage at the tip. There are provided an inlet 350 and an outlet 352 for returning the gas 30 to be measured from the auxiliary passage to the main passage 124.
- the measuring section 310 has a shape that extends long along the axis from the outer wall of the main passage 124 toward the center, but the width has a narrow shape as shown in FIGS. 2A and 3A. is doing. That is, the measurement unit 310 of the thermal flow meter 300 has a side surface with a thin width and a substantially rectangular front surface.
- the thermal flow meter 300 can be provided with a sufficiently long sub-passage, and the fluid resistance of the measurement target gas 30 can be suppressed to a small value. For this reason, the thermal type flow meter 300 can measure the flow rate of the measurement target gas 30 with high accuracy while suppressing the fluid resistance to a small value.
- Upstream side projection 317 and downstream side projection 318 are provided on the upstream side surface and the downstream side surface of measurement unit 310 constituting thermal flow meter 300, respectively. Is provided.
- the upstream protrusion 317 and the downstream protrusion 318 have a shape that becomes narrower toward the tip with respect to the root, and the fluid resistance of the measurement target gas 30 that is the intake air flowing in the main passage 124 can be reduced.
- An upstream protrusion 317 is provided between the heat insulating portion 315 and the inlet 343.
- the upstream protrusion 317 has a large cross-sectional area and large heat conduction from the flange 312 or the heat insulating portion 315, but the upstream protrusion 317 is interrupted before the inlet 343, and further, the upstream protrusion 317 has a temperature detecting portion 452 side.
- the distance from the temperature detection unit 452 to the temperature detection unit 452 is long due to the depression of the outer wall on the upstream side of the housing 302 as will be described later. For this reason, the heat conduction from the heat insulation part 315 to the support part of the temperature detection part 452 is suppressed.
- a gap including a terminal connection portion 320 and a terminal connection portion 320 described later is formed between the flange 312 or the heat insulating portion 315 and the temperature detection portion 452. For this reason, the gap between the flange 312 or the heat insulation part 315 and the temperature detection part 452 is long, and the front cover 303 and the back cover 304 are provided in this long part, and this part acts as a cooling surface. Therefore, the influence of the temperature of the wall surface of the main passage 124 on the temperature detection unit 452 can be reduced.
- the gap between the flange 312 or the heat insulating portion 315 and the temperature detecting portion 452 becomes long, the intake portion of the gas 30 to be measured leading to the sub passage can be brought closer to the center of the main passage 124. A decrease in measurement accuracy related to the wall surface of the main passage 124 can be suppressed.
- the measurement unit 310 inserted into the main passage 124 has a very narrow side surface, and the downstream protrusion 318 and the upstream protrusion 317 provide air resistance.
- the tip has a narrow shape with respect to the root to be reduced. For this reason, an increase in fluid resistance due to the insertion of the thermal flow meter 300 into the main passage 124 can be suppressed. Further, in the portion where the downstream protrusion 318 and the upstream protrusion 317 are provided, the upstream protrusion 317 and the downstream protrusion 318 protrude from both sides of the front cover 303 and the back cover 304. .
- the upstream protrusion 317 and the downstream protrusion 318 are made of a resin mold, the upstream protrusion 317 and the downstream cover 304 are easily formed into a shape with low air resistance, while the front cover 303 and the back cover 304 have a shape with a wide cooling surface. For this reason, the thermal flow meter 300 has an effect that air resistance is reduced and the air to be measured that flows through the main passage 124 is easily cooled.
- the flange 312 is provided with a plurality of recesses 314 in the lower surface of the flange 312 facing the main passage 124, reducing the heat transfer surface between the flange 312 and the main passage 124.
- the thermal flow meter 300 is less susceptible to heat.
- the screw hole 313 of the flange 312 is for fixing the thermal type flow meter 300 to the main passage 124, and the surface of the screw hole 313 around the screw passage 313 facing the main passage 124 is separated from the main passage 124.
- a space is formed between the main passage 124 and a surface around the screw hole 313 facing the main passage 124.
- the recess 314 functions not only to reduce the heat conduction but also to reduce the influence of shrinkage of the resin constituting the flange 312 when the housing 302 is molded.
- a heat insulating part 315 is provided on the measurement part 310 side of the flange 312.
- the measurement part 310 of the thermal type flow meter 300 is inserted into the inside from an attachment hole provided in the main passage 124, and the thermal insulation part 315 faces the inner surface of the attachment hole of the main passage 124.
- the main passage 124 is, for example, an intake body, and the main passage 124 is often maintained at a high temperature. Conversely, when starting in a cold region, the main passage 124 may be at a very low temperature. If such a high or low temperature state of the main passage 124 affects the temperature detection unit 452 or the flow rate measurement described later, the measurement accuracy decreases.
- a plurality of recesses 316 are arranged in the heat insulating portion 315 adjacent to the inner surface of the hole of the main passage 124, and the width of the heat insulating portion 315 adjacent to the inner surface of the hole is extremely large between the adjacent recesses 316. It is thin and less than one third of the width of the recess 316 in the fluid flow direction. Thereby, the influence of temperature can be reduced.
- the heat insulating portion 315 has a thick resin. During resin molding of the housing 302, volume shrinkage occurs when the resin cools from a high temperature state to a low temperature and cures, and distortion due to the generation of stress occurs. By forming the depression 316 in the heat insulating portion 315, the volume shrinkage can be made more uniform, and the stress concentration can be reduced.
- the measuring unit 310 of the thermal flow meter 300 is inserted into the inside through an attachment hole provided in the main passage 124 and is fixed to the main passage 124 with a screw by the flange 312 of the thermal flow meter 300. It is desirable that the thermal flow meter 300 is fixed in a predetermined positional relationship with respect to the mounting hole provided in the main passage 124.
- a recess 314 provided in the flange 312 can be used for positioning the main passage 124 and the thermal flow meter 300.
- FIG. 4A is a plan view of the thermal flow meter 300.
- FIG. Four external terminals 306 and a correction terminal 307 are provided in the external connection portion 305.
- the external terminal 306 is a terminal for outputting a flow rate and temperature as a measurement result of the thermal flow meter 300 and a power supply terminal for supplying DC power for operating the thermal flow meter 300.
- the correction terminal 307 is used to measure the produced thermal flow meter 300, obtain a correction value related to each thermal flow meter 300, and store the correction value in a memory inside the thermal flow meter 300. In the subsequent measurement operation of the thermal flow meter 300, the correction data representing the correction value stored in the memory is used, and the correction terminal 307 is not used.
- the correction terminal 307 has a shape different from that of the external terminal 306 so that the correction terminal 307 does not get in the way when the external terminal 306 is connected to another external device.
- the correction terminal 307 is shorter than the external terminal 306, and even if a connection terminal to an external device connected to the external terminal 306 is inserted into the external connection unit 305, the connection is not hindered. It has become.
- a plurality of depressions 308 are provided along the external terminals 306 inside the external connection portion 305, and these depressions 308 concentrate stress due to resin shrinkage when the resin that is the material of the flange 312 cools and hardens. It is for reducing.
- a correction terminal 307 is provided to measure the characteristics of each of the thermal flow meter 300 before shipping and to measure product variations.
- the correction value for reducing the variation can be stored in the memory inside the thermal flow meter 300.
- the correction terminal 307 is formed in a shape different from that of the external terminal 306 so that the correction terminal 307 does not interfere with the connection between the external terminal 306 and the external device. In this way, the thermal flow meter 300 can reduce the variation of each before shipping and can improve the measurement accuracy.
- FIGS. 5 and 6 show the state of the housing 302 with the front cover 303 and the back cover 304 removed from the thermal flow meter 300.
- FIG. 5A is a left side view of the housing 302
- FIG. 5B is a front view of the housing 302
- FIG. 6A is a right side view of the housing 302
- FIG. 4 is a rear view of the housing 302.
- the housing 302 has a structure in which the measuring unit 310 extends from the flange 312 toward the center of the main passage 124, and a sub-passage groove for forming the sub-passage is provided on the tip side thereof.
- the sub-passage grooves are provided on both the front and back surfaces of the housing 302.
- FIG. 5B shows the front-side sub-passage groove 332
- FIG. 6B shows the back-side sub-passage groove 334.
- An inlet groove 351 for forming the inlet 350 of the sub-passage and an outlet groove 353 for forming the outlet 352 are provided at the distal end portion of the housing 302, so that the gas in a portion away from the inner wall surface of the main passage 124 In other words, the gas flowing in the portion close to the central portion of the main passage 124 can be taken in from the inlet 350 as the gas 30 to be measured.
- the gas flowing in the vicinity of the inner wall surface of the main passage 124 is affected by the wall surface temperature of the main passage 124 and often has a temperature different from the average temperature of the gas flowing through the main passage 124 such as the measurement target gas 30 as intake air. . Further, the gas flowing in the vicinity of the inner wall surface of the main passage 124 often exhibits a flow rate that is slower than the average flow velocity of the gas flowing through the main passage 124. Since the thermal flow meter 300 of the embodiment is not easily affected by this, it is possible to suppress a decrease in measurement accuracy.
- the auxiliary passages formed by the front side auxiliary passage groove 332 and the back side auxiliary passage groove 334 described above are connected to the heat insulating portion 315 by the outer wall recess 366, the upstream outer wall 335, and the downstream outer wall 336.
- the upstream outer wall 335 is provided with an upstream protrusion 317
- the downstream outer wall 336 is provided with a downstream protrusion 318.
- the sub-passage groove for forming the sub-passage is formed in the housing 302, and the sub-passage is completed by the sub-passage groove and the cover by covering the cover with the front and back surfaces of the housing 302. .
- all the sub-passage grooves can be formed as a part of the housing 302 in the resin molding process of the housing 302.
- both the front side sub-passage groove 332 and the back side sub-passage groove 334 are all part of the housing 302. It becomes possible to mold.
- the secondary passages on both sides of the housing 302 can be completed.
- the secondary passage can be formed with high accuracy. Moreover, high productivity is obtained.
- a part of the measurement target gas 30 flowing through the main passage 124 is taken into the back side sub-passage groove 334 from the 351 forming the inlet 350 and flows through the back side sub-passage groove 334.
- the back side sub-passage groove 334 has a shape that becomes deeper as it advances, and as the gas flows along the groove, the measured gas 30 gradually moves in the front side direction.
- the rear side sub-passage groove 334 is provided with a steeply inclined portion 347 that becomes deeper and deeper before the hole 342, and a part of the air having a small mass moves along the steeply inclined portion 347, and passes through the hole 342 in FIG. It flows in the direction of the measurement flow path surface 430 described in B).
- a foreign substance with a large mass is difficult to change rapidly, it moves on the back surface 431 for measurement flow path surface shown in FIG. After that, it passes through the hole 341 and flows through the measurement flow path surface 430 shown in FIG.
- the air to be measured 30 that has moved from the hole 342 to the front side sub-passage groove 332 flows along the measurement channel surface 430 and is used for measurement. Heat is transferred to and from the flow rate detector 602 for measuring the flow rate through the heat transfer surface exposed portion 436 provided on the flow path surface 430, and the flow rate is measured. Both the gas to be measured 30 that has passed through the measurement flow path surface 430 and the air that has flowed from the hole 341 to the front side sub-passage groove 332 flow along the front side sub-passage groove 332, and from the outlet groove 353 for forming the outlet 352. It is discharged into the passage 124.
- a substance having a large mass such as dust mixed in the measurement target gas 30 has a large inertial force, and along the surface of the portion of the steeply inclined portion 347 shown in FIG. It is difficult to change the course rapidly in the deep direction of the groove. For this reason, the foreign matter having a large mass moves toward the measurement channel surface rear surface 431, and the foreign matter can be prevented from passing near the heat transfer surface exposed portion 436.
- many foreign substances having a large mass other than gas pass through the measurement channel surface rear surface 431 which is the back surface of the measurement channel surface 430, they are caused by foreign matters such as oil, carbon, and dust.
- the influence of dirt can be reduced, and the decrease in measurement accuracy can be suppressed. That is, since it has a shape in which the path of the gas to be measured 30 is suddenly changed along an axis that crosses the flow axis of the main passage 124, the influence of foreign matter mixed in the gas to be measured 30 can be reduced.
- the flow path formed by the back side sub-passage groove 334 draws a curve from the front end of the housing 302 toward the flange, and the gas flowing through the sub-passage flows into the main passage 124 at the position closest to the flange.
- the flow is in the reverse direction, and the sub-passage on the back surface, which is one side in the flow portion in the reverse direction, is connected to the sub-passage formed on the surface side, which is the other side.
- a hole 342 and a hole 341 penetrating the back side sub-passage groove 334 and the front side sub-passage groove 332 are provided in the flow direction of the measurement flow path surface 430 for measuring the flow rate.
- the measurement target gas 30 moves in a shape in which the through-hole 342 and the hole 341 are provided to move the measured gas 30 from the back side sub-passage groove 334 formed on one surface of the housing 302 to the front side sub-passage groove 332 formed on the other surface of the housing 302.
- a passage is formed.
- a mold for forming the holes 342 and 341 in these holes is used to form the measurement flow path surface 430. It is possible to prevent the resin from flowing into the exposed heat transfer surface exposed portion 436. Further, when the circuit package 400 is fixed to the housing 302 with a resin mold by using the formation of the holes 342 and 341 on the upstream side and the downstream side of the measurement flow path surface 430, the mold is arranged using these holes. The circuit package 400 can be positioned and fixed by this mold.
- two holes are provided as holes penetrating the back side auxiliary passage groove 334 and the front side auxiliary passage groove 332.
- the shape of the sub-passage that connects the back side sub-passage groove 334 and the front side sub-passage groove 332 with one of the holes is formed by one resin molding process. Is possible.
- a back side sub-passage inner peripheral wall 391 and a back side sub-passage outer peripheral wall 392 are provided on both sides of the back side sub-passage groove 334, and the height direction ends of the back side sub-passage inner peripheral wall 391 and the back side sub-passage outer peripheral wall 392 are respectively provided.
- the back side sub-passage of the housing 302 is formed by the close contact between the portion and the inner surface of the back cover 304.
- a front side sub-passage inner peripheral wall 393 and a front side sub-passage outer peripheral wall 394 are provided on both sides of the front side sub-passage groove 332, and the front end and the back of the front side sub-passage inner peripheral wall 393 and the front-side sub-passage outer peripheral wall 394 in the height direction.
- the front side sub-passage of the housing 302 is formed by closely contacting the inner surface of the cover 304.
- the measurement target gas 30 is divided into both the measurement flow path surface 430 and the back surface thereof, and the heat transfer surface exposed portion 436 for measuring the flow rate is provided on one side.
- the measurement channel surface 430 may be passed.
- the foreign matter mixed in the measurement target gas 30 can be removed on one side where the second axis is less bent.
- the measurement flow path surface 430 and the heat transfer surface exposed portion 436 are provided at the connecting portion between the front side sub passage groove 332 and the back side sub passage groove 334.
- it may be provided in the front side sub-passage groove 334 or in the back side sub-passage groove 334 instead of the connecting portion between the front side sub-passage groove 332 and the back side sub-passage groove 334.
- the throttle shape is formed in the portion of the heat transfer surface exposed portion 436 for measuring the flow rate provided on the measurement flow path surface 430, and this throttle effect increases the flow velocity and improves the measurement accuracy. Even if a vortex is generated in the gas flow on the upstream side of the heat transfer surface exposed portion 436, the vortex can be eliminated or reduced by the restriction, and the measurement accuracy is improved.
- the outer wall 335 is provided with an outer wall recess 366 that has a shape in which the upstream outer wall 335 is recessed downstream at the root of the temperature detector 452.
- the outer wall recess 366 increases the distance between the temperature detection unit 452 and the outer wall recess 366, thereby reducing the influence of heat transmitted through the upstream outer wall 335.
- the circuit package 400 is fixed by wrapping the circuit package 400 in the fixing portion 372.
- the fixed portion 372 includes the circuit package 400 in a direction along the flow axis of the measurement target gas 30.
- the outer wall recess 366 includes the circuit package 400 in a direction crossing the flow axis of the measurement target gas 30. That is, the circuit package 400 is included in such a manner that the direction in which the fixing portion 372 is included is different. Since the circuit package 400 is included in two different directions, the securing force is increased.
- the outer wall recess 366 is a part of the upstream outer wall 335
- the circuit package 400 is arranged in a different direction from the fixing portion 372 on the downstream outer wall 336 instead of the upstream outer wall 335 for increasing the fixing force.
- the downstream outer wall 336 may include the plate portion of the circuit package 400, or the downstream outer wall 336 may include a recess recessed in the upstream direction or a protrusion projecting in the upstream direction to include the circuit package 400. good.
- the inclusion of the circuit package 400 by providing the outer wall recess 366 on the upstream outer wall 335 has the effect of increasing the thermal resistance between the temperature detector 452 and the upstream outer wall 335 in addition to fixing the circuit package 400. This is because they were held.
- the outer wall recess 366 is provided at the base of the temperature detection unit 452, thereby reducing the influence of heat transmitted from the flange 312 or the heat insulating unit 315 through the upstream outer wall 335. Further, a temperature measurement recess 368 formed by a notch between the upstream protrusion 317 and the temperature detection unit 452 is provided.
- the temperature measurement depression 368 can reduce the transfer of heat provided to the temperature detector 452 via the upstream protrusion 317. Thereby, the detection accuracy of the temperature detector 452 is improved.
- the upstream protrusion 317 has a large cross-sectional area, heat is easily transmitted, and the function of the temperature measuring recess 368 for preventing heat transfer is important.
- FIG. 7 is a partially enlarged view showing a state in which the flow path surface 430 of the circuit package 400 is disposed inside the sub-passage groove, and is shown in FIG. It is sectional drawing. Note that this figure is a conceptual diagram, and the details shown in FIGS. 5 and 6 are omitted and simplified in detail in FIG. 7, and the details are slightly modified.
- the left portion in FIG. 7 is the end portion of the back side auxiliary passage groove 334, and the right side portion is the starting end portion of the front side auxiliary passage groove 332.
- holes 342 and 341 are provided on the left and right sides of the circuit package 400 having the measurement channel surface 430, and the circuit package 400 having the measurement channel surface 430 is provided.
- the back side sub-passage groove 334 and the front side sub-passage groove 332 are connected on both the left and right sides.
- the gas to be measured 30 taken from the inlet 350 and flowing through the back side sub-passage formed by the back side sub-passage groove 334 is guided from the left side of FIG. 7, and a part of the gas to be measured 30 is passed through the hole 342.
- the measurement target gas 30 flows in the direction of the flow path 386 formed by the surface of the measurement flow path surface 430 of the circuit package 400 and the projection 356 provided on the front cover 303, and the other measurement target gas 30 is the measurement flow path surface back surface 431 and the back cover 304. It flows in the direction of the flow path 387.
- the gas to be measured 30 that has flowed through the flow path 387 moves toward the front side sub-passage groove 332 through the hole 341, merges with the gas to be measured 30 that is flowing through the flow path 386, and The flow is discharged from the outlet 352 to the main passage 124.
- a protrusion 358 provided on the back cover 304 protrudes from the flow channel 387 toward the measurement flow channel surface rear surface 431.
- the sub passage groove is formed so that the measured gas 30 guided from the back side sub passage groove 334 to the flow path 386 through the hole 342 is bent more than the flow path guided to the flow path 387. Therefore, a substance having a large mass, such as dust, contained in the measurement target gas 30 gathers in the flow path 387 with less bending. For this reason, almost no foreign substance flows into the flow path 386.
- a structure is formed in which the throttle is formed by the protrusion 356 provided on the front cover 303 projecting gradually toward the measurement flow path surface 430 continuously from the most distal portion of the front side sub-passage groove 332. Is made.
- a flow path surface for measurement 430 is arranged on one side of the throttle part of the flow path 386, and a heat transfer surface exposed part for allowing the flow rate detection unit 602 to transfer heat to the measurement target gas 30 on the flow path surface for measurement 430. 436 is provided.
- the measurement target gas 30 is a laminar flow with few vortices in the heat transfer surface exposed portion 436.
- the measurement accuracy is improved when the flow velocity is high.
- the diaphragm is formed by the projection 356 provided on the front cover 303 facing the measurement channel surface 430 smoothly projecting toward the measurement channel surface 430. This restriction acts to reduce the vortex of the measured gas 30 and bring it closer to the laminar flow.
- the flow velocity is increased in the throttle portion, and the heat transfer surface exposed portion 436 for measuring the flow rate is arranged in the throttle portion, so that the flow rate measurement accuracy is improved.
- a diaphragm is formed by projecting the protrusion 356 into the sub-passage groove so as to face the heat transfer surface exposed portion 436 provided on the flow path surface 430, and the measurement accuracy can be improved.
- the protrusion 356 for forming the aperture is provided on the cover facing the heat transfer surface exposed portion 436 provided on the flow path surface 430.
- the front cover 303 is provided with the heat transfer surface exposed portion 436.
- 304 may be provided on the cover facing the heat transfer surface exposed portion 436 provided on the flow path surface 430 in 304.
- the distribution of the gas 30 to be measured between the flow path 386 and the flow path 387 is also related to high-precision measurement.
- the flow path 386 Adjustment such as distribution of the measurement target gas 30 with the flow path 387 is performed.
- the flow velocity is increased, and foreign substances such as dust are drawn into the flow path 387.
- a restriction by the projection 358 is used as one of various adjustment means for the flow path 386 and the flow path 387.
- the trace of the mold used in the resin molding process of the circuit package 400 is applied to the measurement channel surface rear surface 431 which is the back surface of the heat transfer surface exposed portion 436 provided on the measurement channel surface 430. 442 remains.
- the press mark 442 does not particularly hinder measurement of the flow rate, and there is no problem even if the press mark 442 remains as it is.
- the measurement flow path surface 430 including the heat transfer surface exposed portion 436 is surrounded by a mold, and the back surface of the heat transfer surface exposed portion 436 is pressed by another mold to prevent the inflow of resin.
- the circuit package 400 is made by transfer molding, the pressure of the resin is high, and it is important to press the heat transfer surface exposed portion 436 from the back surface.
- a semiconductor diaphragm is used for the flow rate detection unit 602, and it is desirable to form a ventilation passage formed by the semiconductor diaphragm. In order to hold and fix a plate or the like for forming the ventilation passage, it is important to press the heat transfer surface exposed portion 436 from the back surface.
- FIG. 8 is a diagram showing the appearance of the front cover 303
- FIG. 8 (A) is a left side view
- FIG. 8 (B) is a front view
- FIG. C) is a plan view
- 9A and 9B are views showing the appearance of the back cover 304.
- FIG. 9A is a left side view
- FIG. 9B is a front view
- FIG. 9C is a plan view.
- the front cover 303 and the back cover 304 are used to make a secondary passage by closing the secondary passage groove of the housing 302.
- a projection 356 is provided and used to make a diaphragm. For this reason, it is desirable that the molding accuracy be high. Since the front cover 303 and the back cover 304 are made by a resin molding process in which a thermoplastic resin is injected into a mold, the front cover 303 and the back cover 304 can be made with high molding accuracy.
- a front protection part 322 and a rear protection part 325 are formed on the front cover 303 and the rear cover 304 shown in FIGS.
- a front protection part 322 provided on the front cover 303 is disposed on the front side surface of the inlet 343, and a back protection part 325 provided on the back cover 304 is provided on the rear side surface of the inlet 343.
- the temperature detection unit 452 disposed inside the entrance 343 is protected by the front protection unit 322 and the back protection unit 325, and the machine of the temperature detection unit 452 due to a collision with the temperature detection unit 452 during production or when mounted on a vehicle. Damage can be prevented.
- a projection 356 is provided on the inner side surface of the front cover 303, and as shown in FIG. 7, the projection 356 is disposed to face the measurement channel surface 430 and extends long in the direction along the axis of the channel of the sub-passage. It has a different shape.
- the measurement channel surface 430 and the projections 356 form a throttle in the above-described channel 386 to reduce the vortices generated in the measurement target gas 30 and cause a laminar flow.
- the sub-flow path having the throttle portion is divided into a groove portion and a lid portion that closes the groove and completes the flow passage having the throttle, and the groove portion is used for molding the housing 302.
- the sub-passage is formed by forming the front cover 303 having the projections 356 by the second resin molding process, and then forming the front cover 303 by another resin molding process, and covering the groove with the front cover 303 as a groove lid.
- the circuit package 400 having the measurement flow path surface 430 is also fixed to the housing 302. In this way, by forming a complicated groove in the resin molding process and providing the projection 356 for drawing on the front cover 303, the flow path 386 shown in FIG. 7 can be formed with high accuracy.
- the positional relationship between the groove and the measurement flow path surface 430 and the heat transfer surface exposed portion 436 can be maintained with high accuracy, the variation in mass-produced products can be reduced, resulting in high measurement results. Productivity is also improved.
- the molding of the channel 387 by the back cover 304 and the measurement channel surface rear surface 431 is the same.
- the channel portion 386 is divided into a groove portion and a lid portion, the groove portion is formed by a second resin molding process for molding the housing 302, and then the channel 387 is covered with a back cover 304 having a projection 358. Molding.
- the flow path 387 By making the flow path 387 in this way, the flow path 386 can be made with high accuracy, and productivity is improved.
- a restriction is provided in the flow path 387, but it is also possible to use a flow path 387 without a restriction without using the protrusion 358.
- a notch 323 for forming the outlet 352 is provided on the front end side of the front cover 303. As shown in FIG. 2B, the outlet 352 extends not only on the right side surface of the housing 302 but also on the front side of the housing 302 by the notch 323. As a result, the fluid resistance of the entire sub-passage decreases, and the gas to be measured 30 introduced into the sub-passage from the inlet 350 increases. This improves the flow rate measurement accuracy.
- FIG. 10 is an enlarged view of the terminal connection part 320 of the housing 302 shown in FIGS. 5 and 6.
- the following points are a little different. 5 and FIG. 6 is different from the description in FIG. 5 and FIG. 6 in that each external terminal inner end 361 is cut off, whereas in FIG. 10, the state before each external terminal inner end 361 is cut off.
- the external terminal inner ends 361 are connected by connecting portions 365, respectively.
- the external terminal inner ends 361 projecting to the circuit package 400 side of the external terminals 306 overlap with the corresponding connection terminals 412 or in the vicinity of the corresponding connection terminals 412.
- the external terminal 306 is fixed to the housing 302 by resin molding.
- a resin molding process for molding the housing 302 in a state where the external terminal inner ends 361 are connected to each other by a connecting portion 365.
- the external terminal 306 is fixed to the housing 302 by the process.
- the connection terminal 412 and the external terminal inner end 361 may be fixed first, and then the external terminal 306 may be fixed to the housing 302 by the second molding step.
- the number of terminals included in the circuit package 400 is larger than the number of external terminal inner ends 361.
- the connection terminal 412 is connected to the external terminal inner end 361, and the terminal 414 is not connected to the external terminal inner end 361. That is, the terminal 414 is a terminal that is provided in the circuit package 400 but is not connected to the external terminal inner end 361.
- a terminal 414 not connected to the external terminal inner end 361 is provided. After the circuit package 400 is produced in the first resin molding process, it is inspected whether the circuit package 400 operates correctly or whether an abnormality has occurred in electrical connection in the first resin molding process. By doing so, high reliability can be maintained for each circuit package 400.
- the terminal 414 that is not connected to the external terminal inner end 361 is used for such inspection of the circuit package 400. Since the terminals 414 are not used after the inspection work, these unused terminals 414 may be cut at the base of the circuit package 400 after the inspection, or inside the resin that is the terminal side fixing portion 362 as shown in FIG. It may be buried in. Thus, by providing the terminal 414 that is not connected to the external terminal inner end 361, it is possible to inspect whether or not an abnormality has occurred in the circuit package 400 produced in the first resin molding process, and high reliability can be maintained.
- a hole 364 is provided in the housing 302.
- the hole 364 is connected to an opening 309 provided inside the external connection portion 305 shown in FIG.
- both sides of the housing 302 are sealed with a front cover 303 and a back cover 304. If the hole 364 is not provided, a difference occurs between the atmospheric pressure in the air gap and the external air pressure due to the temperature change of the air in the air gap including the terminal connection portion 320. Such a pressure difference is desirably as small as possible. Therefore, a hole 364 connected to the opening 309 provided in the external connection portion 305 is provided in the gap of the housing 302.
- the external connection part 305 has a structure that is not adversely affected by water or the like in order to improve the reliability of electrical connection, and by providing the opening 309 in the external connection part 305, water can be prevented from entering from the opening 309. Furthermore, it is possible to prevent foreign substances such as dust and dirt from entering.
- a portion for embedding and fixing the circuit package 400 in the housing 302 with a resin mold is provided as a fixing portion 372 for embedding and fixing the circuit package 400 in the housing 302 on the flange 312 side slightly from the sub-passage groove.
- the fixing portion 372 is embedded so as to cover the outer periphery of the circuit package 400 formed by the first resin molding process.
- a recess 376 and a recess 378 are provided on the front side surface of the fixed portion 372. Further, as shown in FIG. 6B, a recess 373 is formed on the back side surface of the fixing portion 372.
- These depressions can alleviate shrinkage when the temperature of the resin cools when the fixing portion 372 is molded, and the concentration of stress applied to the circuit package 400 can be reduced. Further, the flow of the resin through the mold for forming the above-described depression is restricted, thereby slowing down the temperature of the resin, and the fixing portion 372 is formed deeply in the unevenness provided on the surface of the circuit package 400. Resin can be made easy to enter.
- the entire surface of the circuit package 400 is not covered with the resin for molding the housing 302, but a portion where the outer wall of the circuit package 400 is exposed is provided on the flange 312 side of the fixing portion 372. 5 and 6, the area of the outer peripheral surface of the circuit package 400 that is included in the resin of the housing 302 is exposed from the resin of the housing 302 without being included in the resin of the housing 302. The area is wider. Further, the part of the measurement flow path surface 430 of the circuit package 400 is also exposed from the resin forming the housing 302.
- the periphery of the circuit package 400 is formed by forming depressions on the front and back surfaces of the fixing portion 372 that covers the entire outer wall of the circuit package 400 in a strip shape.
- the excessive stress concentration due to the volume shrinkage in the process of hardening the fixing portion 372 is reduced. Excessive stress concentration may also adversely affect the circuit package 400.
- the circuit package 400 can be strengthened with a smaller area. In order to fix, it is desirable to improve the adhesiveness with the outer wall of the circuit package 400 in the fixing
- FIG. When a thermoplastic resin is used for the purpose of molding the housing 302, the thermoplastic resin enters the fine irregularities of the outer wall of the circuit package 400 in a state where the viscosity of the thermoplastic resin is low, and the thermoplastic resin enters the fine irregularities of the outer wall. It is desirable for the resin to cure.
- thermoplastic resin increases in viscosity based on a decrease in temperature and hardens. Accordingly, by pouring the high temperature thermoplastic resin into or from the fixing portion 372, the low viscosity thermoplastic resin can be brought into close contact with the outer wall of the circuit package 400 and cured.
- an obstacle portion that restricts the flow of the thermoplastic resin is formed by a mold for making these recesses, and the heat in the fixing portion 372 is formed. The moving speed of the plastic resin decreases. This suppresses the temperature drop of the thermoplastic resin, prolongs the low viscosity state, and improves the adhesion between the circuit package 400 and the fixing portion 372.
- a roughening method for applying fine irregularities to the surface of the circuit package 400 can be roughened by sandblasting. Further, it can be roughened by laser processing.
- a sheet with irregularities is attached to the inner surface of the mold used in the first resin molding step, and the resin is press-fitted into the mold provided with the sheet on the surface.
- fine irregularities can be formed on the surface of the circuit package 400 to be roughened.
- the surface of the circuit package 400 can be roughened by providing irregularities inside the mold for molding the circuit package 400.
- the surface portion of the circuit package 400 that performs such roughening is a portion where at least the fixing portion 372 is provided.
- the degree of adhesion is further increased by roughening the surface portion of the circuit package 400 in which the outer wall recess 366 is provided.
- the depth of the groove depends on the thickness of the circuit package 400 when the surface of the circuit package 400 is processed using the above-described sheet.
- the thickness of the sheet is increased, molding in the first resin molding process becomes difficult, so there is a limit to the thickness of the sheet, and when the thickness of the sheet is thin, there is a limit to the depth of unevenness provided in advance in the sheet. Out.
- corrugated bottom and a vertex is 10 micrometers or more and 20 micrometers or less. At a depth of less than 10 ⁇ m, the adhesion effect is weak. A depth greater than 20 ⁇ m is difficult due to the thickness of the sheet.
- the resin thickness in the first resin molding process for forming the circuit package 400 is desirably 2 mm or less, It is difficult to make the depth of the unevenness between 1 mm and 1 mm or more.
- the degree of adhesion between the resin that covers the circuit package 400 and the resin that forms the housing 302 increases.
- the depth of the unevenness between the bottom and the top of the unevenness is preferably 1 mm or less. That is, it is desirable to increase the degree of adhesion between the resin that covers the circuit package 400 and the resin that molds the housing 302 by providing irregularities in the range of 10 ⁇ m or more and 1 mm or less on the surface of the circuit package 400.
- thermosetting resin that forms the circuit package 400 there is a difference in the thermal expansion coefficient between the thermosetting resin that forms the circuit package 400 and the thermoplastic resin that forms the housing 302 including the fixing portion 372, and an excessive stress generated based on the difference in the thermal expansion coefficient causes the circuit package. It is desirable not to join 400. By providing the depression 373, the depression 378, and the depression 376, the stress applied to the circuit package 400 can be reduced.
- the stress due to the difference in thermal expansion coefficient applied to the circuit package 400 can be reduced by forming the fixed portion 372 including the outer periphery of the circuit package 400 in a band shape and narrowing the width of the band. It is desirable that the width of the band of the fixing portion 372 is 10 mm or less, preferably 8 mm or less. In the present embodiment, not only the fixing portion 372 but also the outer wall recess 366 that is a part of the upstream outer wall 335 of the housing 302 includes the circuit package 400 and fixes the circuit package 400. The width of the band 372 can be further reduced. For example, if there is a width of 3 mm or more, the circuit package 400 can be fixed.
- the surface of the circuit package 400 is provided with a portion covered with a resin for molding the housing 302 and a portion exposed without being covered for the purpose of reducing stress due to a difference in thermal expansion coefficient.
- a plurality of portions where the surface of the circuit package 400 is exposed from the resin of the housing 302 are provided, one of which is the measurement flow path surface 430 having the heat transfer surface exposed portion 436 described above.
- a portion exposed to the flange 312 side from the fixing portion 372 is provided.
- an outer wall recess 366 is formed, and a portion upstream of the outer wall recess 366 is exposed, and this exposed portion is used as a support for supporting the temperature detector 452.
- the portion of the outer surface of the circuit package 400 closer to the flange 312 than the fixing portion 372 extends from the outer periphery, particularly from the downstream side of the circuit package 400 to the side facing the flange 312, and further to the upstream side of the portion close to the terminal of the circuit package 400.
- the air gap is formed so as to surround the circuit package 400. Since the gap is formed around the portion where the surface of the circuit package 400 is exposed in this way, the amount of heat transferred from the main passage 124 to the circuit package 400 via the flange 312 can be reduced, and measurement due to the influence of heat. The decrease in accuracy is suppressed.
- a gap is formed between the circuit package 400 and the flange 312, and this gap portion acts as the terminal connection portion 320.
- the connection terminal 412 of the circuit package 400 and the external terminal inner end 361 located on the housing 302 side of the external terminal 306 are electrically connected by spot welding or laser welding, respectively.
- the gap of the terminal connection portion 320 has an effect of suppressing heat transfer from the housing 302 to the circuit package 400, and the connection work between the connection terminal 412 of the circuit package 400 and the external terminal inner end 361 of the external terminal 306. Because of the space available for use.
- the circuit package 400 including the flow rate detection unit 602 and the processing unit 604 is formed by the first resin molding process.
- the housing 302 having, for example, the front side sub-passage groove 332 and the back side sub-passage groove 334 for forming the sub-passage through which the gas to be measured 30 flows is manufactured in the second resin molding step.
- the circuit package 400 is built in the resin of the housing 302 and fixed in the housing 302 by a resin mold.
- the heat transfer surface exposed portion 436 and the sub-passage for example, the front-side sub-passage groove 332 and the back-side sub-passage for the heat-flow detecting unit 602 to perform heat transfer with the measurement target gas 30 and measure the flow rate. It becomes possible to maintain the relationship with the shape of the passage groove 334, for example, the positional relationship and the direction relationship, with extremely high accuracy. It is possible to suppress errors and variations occurring in each circuit package 400 to a very small value. As a result, the measurement accuracy of the circuit package 400 can be greatly improved. For example, the measurement accuracy can be improved by a factor of two or more compared to a conventional method of fixing using an adhesive.
- the thermal flow meter 300 is often produced by mass production, and the method of adhering with an adhesive while strictly measuring here has a limit in improving measurement accuracy.
- the circuit package 400 is manufactured by the first resin molding process, and then the sub-passage is formed in the second resin molding process in which the sub-passage for flowing the measurement target gas 30 is formed.
- variation in measurement accuracy can be greatly reduced, and the measurement accuracy of each thermal flow meter 300 can be greatly improved. This applies not only to the embodiment shown in FIGS. 5 and 6, but also to the embodiment shown in FIG.
- the relationship among the front side sub-passage groove 332, the back side sub-passage groove 334, and the heat transfer surface exposed portion 436 is set with high accuracy so as to be a prescribed relationship.
- the circuit package 400 can be fixed to the housing 302.
- the positional relationship and the shape relationship between the heat transfer surface exposed portion 436 and the sub passage of each circuit package 400 can be constantly obtained with very high accuracy. Is possible.
- the sub-passage groove for example, the front-side sub-passage groove 332 and the back-side sub-passage groove 334, to which the heat transfer surface exposed portion 436 of the circuit package 400 is fixed can be formed with very high accuracy
- the sub-passage is formed from the sub-passage groove.
- the work is a work of covering both surfaces of the housing 302 with the front cover 303 and the back cover 304. This work is very simple and is a work process with few factors that reduce the measurement accuracy. Further, the front cover 303 and the back cover 304 are produced with high molding accuracy. Accordingly, it is possible to complete the sub-passage provided in a defined relationship with the heat transfer surface exposed portion 436 of the circuit package 400 with high accuracy. By such a method, in addition to improvement of measurement accuracy, high productivity can be obtained.
- a thermal flow meter was produced by manufacturing a secondary passage and then adhering a measuring section to the secondary passage with an adhesive.
- the method of using the adhesive has a large variation in the thickness of the adhesive, and the bonding position and the bonding angle vary from product to product. For this reason, there was a limit to increasing the measurement accuracy. Furthermore, when performing these operations in a mass production process, it is very difficult to improve measurement accuracy.
- the circuit package 400 including the flow rate detecting unit 602 is produced by the first resin mold, and then the circuit package 400 is fixed by the resin mold and at the same time, the auxiliary passage is formed by the resin mold.
- a secondary passage groove is formed by the second resin mold.
- a portion related to the measurement of the flow rate for example, the measurement flow path surface 430 to which the heat transfer surface exposed portion 436 and the heat transfer surface exposed portion 436 of the flow rate detection unit 602 are attached is formed on the surface of the circuit package 400. Thereafter, the measurement channel surface 430 and the heat transfer surface exposed portion 436 are exposed from the resin for molding the housing 302. That is, the heat transfer surface exposed portion 436 and the measurement flow path surface 430 around the heat transfer surface exposed portion 436 are not covered with the resin for molding the housing 302.
- the flow passage surface 430 for measurement and the heat transfer surface exposed portion 436 formed by the resin mold of the circuit package 400 or the temperature detection portion 452 are also used as they are after the resin molding of the housing 302 to measure the flow rate of the thermal flow meter 300. Used for temperature measurement. By doing so, the measurement accuracy is improved.
- the circuit package 400 is fixed to the housing 302 with a small fixed area because the circuit package 400 is fixed to the housing 302 having the sub passage by integrally forming the circuit package 400 with the housing 302. it can. That is, the surface area of the circuit package 400 that is not in contact with the housing 302 can be increased. The surface of the circuit package 400 that is not in contact with the housing 302 is exposed to a gap, for example. The heat of the intake pipe is transmitted to the housing 302 and is transmitted from the housing 302 to the circuit package 400.
- the housing 302 does not include the entire surface or most of the circuit package 400, but the circuit package 400 can be maintained with high accuracy and high reliability even when the contact area between the housing 302 and the circuit package 400 is reduced. It can be fixed to the housing 302. For this reason, heat transfer from the housing 302 to the circuit package 400 can be suppressed to a low level, and a decrease in measurement accuracy can be suppressed.
- the area A of the exposed surface of the circuit package 400 may be equal to the area B covered with the molding material of the housing 302 or the area A may be larger than the area B. Is possible. In the embodiment, the area A is larger than the area B. By doing so, heat transfer from the housing 302 to the circuit package 400 can be suppressed. Further, the stress due to the difference between the thermal expansion coefficient of the thermosetting resin forming the circuit package 400 and the expansion coefficient of the thermoplastic resin forming the housing 302 can be reduced.
- the hatched portion is the second resin molding process in order to fix circuit package 400 to housing 302 in the second resin molding process.
- a fixing surface 432 and a fixing surface 434 for covering the circuit package 400 with the thermoplastic resin to be used are shown.
- the relationship between the measurement channel surface 430 and the heat transfer surface exposed portion 436 provided on the measurement channel surface 430 and the shape of the sub-passage is a prescribed relationship.
- the circuit package 400 is fixed to the housing 302 that molds the sub-passage and at the same time forms the sub-passage. It can be maintained with extremely high accuracy.
- the circuit package 400 since the circuit package 400 is fixed to the housing 302 in the second resin molding step, the circuit package 400 can be positioned and fixed with high accuracy in a mold for forming the housing 302 having the sub-passage. It is possible, and by injecting a high-temperature thermoplastic resin into the mold, the circuit package 400 is fixed to the sub-passage after molding with high accuracy.
- the entire surface of the circuit package 400 is not the fixing surface 432 that is covered with the resin for molding the housing 302, but the surface is exposed to the connection terminal 412 side of the circuit package 400, that is, the housing is covered with the resin for the housing 302. The part which is not broken is provided.
- the surface of the circuit package 400 is not included in the resin of the housing 302 and is exposed from the resin of the housing 302 because of the area of the fixing surface 432 included in the resin for the housing 302 and the area of the fixing surface 434. The area is wider.
- thermosetting resin that forms the circuit package 400 there is a difference in the thermal expansion coefficient between the thermosetting resin that forms the circuit package 400 and the thermoplastic resin that forms the housing 302 including the fixing portion 372, and stress based on this difference in thermal expansion coefficient is not applied to the circuit package 400 as much as possible. It is desirable to do so.
- the fixed surface 432 on the surface of the circuit package 400 By reducing the fixed surface 432 on the surface of the circuit package 400, the influence based on the difference in thermal expansion coefficient can be reduced.
- the fixed surface 432 on the surface of the circuit package 400 can be reduced by forming a belt with a width L.
- the mechanical strength of the projecting portion 424 can be increased by providing the fixing surface 432 at the base of the projecting portion 424.
- the circuit package 400 On the surface of the circuit package 400, by providing a band-shaped fixed surface in a direction along the axis through which the measured gas 30 flows, and further providing a fixed surface in a direction intersecting with the axis through which the measured gas 30 flows, the circuit package is more firmly provided 400 and the housing 302 can be fixed to each other.
- a portion surrounding the circuit package 400 in a band shape with a width L along the measurement flow path surface 430 is a fixed surface in the direction along the flow axis of the measurement target gas 30 described above, and the root of the protrusion 424.
- the portion that covers is a fixed surface in the direction crossing the flow axis of the measurement target gas 30.
- the circuit package 400 is manufactured by the first resin molding process as described above.
- the hatched portion described on the appearance of the circuit package 400 is a resin used in the second resin molding process when the housing 302 is molded in the second resin molding process after the circuit package 400 is manufactured in the first resin molding process.
- 11A is a left side view of the circuit package 400
- FIG. 11B is a front view of the circuit package 400
- FIG. 11C is a rear view of the circuit package 400.
- the circuit package 400 incorporates a flow rate detection unit 602 and a processing unit 604, which will be described later, and these are molded with a thermosetting resin and integrally molded.
- a measurement channel surface 430 that functions as a surface for flowing the measurement target gas 30 is formed in a shape that extends long in the flow direction of the measurement target gas 30.
- the measurement flow path surface 430 has a rectangular shape that extends long in the flow direction of the measurement target gas 30.
- the measurement channel surface 430 is made thinner than other portions, and a heat transfer surface exposed portion 436 is provided in a part thereof.
- the built-in flow rate detection unit 602 performs heat transfer with the measurement target gas 30 via the heat transfer surface exposure unit 436, measures the state of the measurement target gas 30, for example, the flow velocity of the measurement target gas 30, and the main passage 124. An electric signal representing the flow rate flowing through the is output.
- the built-in flow rate detection unit 602 (see FIG. 19) to measure the state of the gas 30 to be measured with high accuracy, the gas flowing in the vicinity of the heat transfer surface exposed portion 436 is laminar and less disturbed. desirable. For this reason, it is preferable that there is no step between the side surface of the heat transfer surface exposed portion 436 and the surface of the measurement channel surface 430 that guides the gas. With such a configuration, it is possible to suppress uneven stress and distortion from acting on the flow rate detection unit 602 while maintaining high accuracy in flow rate measurement. The step may be provided as long as it does not affect the flow rate measurement accuracy.
- the heat transfer surface exposed part 436 is a place used for exchanging heat with the gas to be measured 30.
- the flow detection part 602 and the object to be measured are used. It is desirable that heat transfer with the measurement gas 30 be performed satisfactorily. For this reason, it is necessary to avoid that the heat transfer surface exposed portion 436 is covered with the resin in the first resin molding step.
- a mold is applied to both the heat transfer surface exposed portion 436 and the measurement flow path surface back surface 431 which is the back surface thereof, and the mold prevents the resin from flowing into the heat transfer surface exposed portion 436.
- a recessed trace 442 is formed on the back surface of the heat transfer surface exposed portion 436.
- elements constituting the flow rate detection unit 602 and the like are arranged close to each other, and it is desirable to dissipate heat generated by these elements to the outside as much as possible.
- the molded recess has an effect of being easy to dissipate heat with little influence of the resin.
- a semiconductor diaphragm constituting the flow rate detection unit 602 is disposed inside the heat transfer surface exposed portion 436, and a gap is formed on the back surface of the semiconductor diaphragm.
- the semiconductor diaphragm is deformed due to a change in pressure in the gap due to a temperature change, and the measurement accuracy is lowered. Therefore, in this embodiment, an opening 438 communicating with the gap on the back surface of the semiconductor diaphragm is provided on the surface of the circuit package 400, and a communication path connecting the gap on the back surface of the semiconductor diaphragm and the opening 438 is provided inside the circuit package 400.
- the opening 438 is provided in a portion where the hatched lines shown in FIG. 11 are not described so that the opening 438 is not blocked by the resin in the second resin molding step.
- opening 438 It is necessary to mold the opening 438 in the first resin molding step. A mold is applied to the opening 438 and the back surface thereof, and both the front and back surfaces are pressed with the mold, so that the resin to the opening 438 can be formed. Inflow is blocked and opening 438 is formed. The formation of the communication path that connects the opening 438 and the gap on the back surface of the semiconductor diaphragm and the opening 438 will be described later.
- a pressing trace 442 remains on the back surface of the circuit package 400 where the heat transfer surface exposed portion 436 is formed.
- a mold for example, a insert piece is applied to the heat transfer surface exposed portion 436, and the pressing trace 442 on the opposite surface is further formed.
- a mold is applied to the portion, and both molds prevent the resin from flowing into the heat transfer surface exposed portion 436.
- FIG. 12 shows a frame frame 512 of the circuit package 400 and a chip mounting state of the circuit component 516 mounted on the frame frame 512.
- a broken line portion 508 indicates a portion covered with a mold used when the circuit package 400 is molded.
- a lead 514 is mechanically connected to the frame frame 512, a plate 532 is mounted at the center of the frame frame 512, and a chip-shaped flow rate detection unit 602 and a processing unit 604 made as an LSI are mounted on the plate 532. Has been.
- the flow rate detection unit 602 is provided with a diaphragm 672, and terminals of the flow rate detection unit 602 described below and the processing unit 604 are electrically connected by wires 542. Further, each terminal of the processing unit 604 and the corresponding lead 514 are connected by a wire 543.
- the lead 514 located between the portion serving as the connection terminal of the circuit package 400 and the plate 532 has a chip-like circuit component 516 connected between them.
- the flow rate detection unit 602 having the diaphragm 672 is disposed at the most distal end side, and the processing unit 604 is in an LSI state to be a connection terminal with respect to the flow rate detection unit 602. Further, a connection wire 543 is disposed on the terminal side of the processing unit 604. In this manner, the flow rate detection unit 602, the processing unit 604, the wire 543, the circuit component 516, and the connection lead 514 are arranged in order from the front end side of the circuit package 400 to the connection terminal, thereby simplifying the entire configuration. Is a concise arrangement.
- a thick lead is provided to support the plate 532, and this lead is fixed to the frame 512 by a lead 556 and a lead 558.
- a lower surface of the plate 532 is provided with a lead surface (not shown) having the same area as the plate 532 connected to the thick lead, and the plate 532 is mounted on the lead surface. These lead surfaces are grounded. Thus, noise can be suppressed by performing grounding in the circuits of the flow rate detection unit 602 and the processing unit 604 via the lead surface in common, and the measurement accuracy of the measurement target gas 30 is improved.
- a lead 544 is provided so as to protrude from the plate 532 toward the upstream side of the flow path, that is, along the axis in the direction crossing the axis of the above-described flow rate detection unit 602 or processing unit 604 circuit component 516.
- a temperature detection element 518 for example, a chip-like thermistor is connected to the lead 544.
- a lead 548 is provided near the processing portion 604 that is the base of the protruding portion, and the lead 544 and the lead 548 are electrically connected by a thin connection line 546.
- the thermal resistance between the lead 548 and the lead 544 can be increased by connecting with a line having a small cross-sectional area and a large thermal resistance. Thereby, the influence of heat does not reach the temperature detection element 518, and the measurement accuracy of the temperature of the measurement target gas 30 is improved.
- the lead 548 is fixed to the frame 512 by a lead 552 and a lead 554.
- the connecting portion between the lead 552 and the lead 554 and the frame 512 is fixed to the frame 512 in an inclined state with respect to the protruding direction of the protruding temperature detecting element 518, and the mold is also disposed obliquely at this portion. It becomes.
- the molding resin flows along this oblique state in the first resin molding step, the molding resin in the first resin molding step flows smoothly to the tip portion where the temperature detection element 518 is provided, and reliability is improved. improves.
- FIG. 12 shows an arrow 592 indicating the resin press-fitting direction.
- the lead frame on which the circuit components are mounted is covered with a mold, and a press-fitting hole 590 for injecting resin is provided in the position of the circle, and a thermosetting resin is injected into the mold from the direction of the arrow 592.
- a circuit component 516 and a temperature detection element 518 there are a circuit component 516 and a temperature detection element 518, and a lead 544 for holding the temperature detection element 518.
- a plate 532, a processing unit 604, and a flow rate detection unit 602 are provided in a direction close to the direction of the arrow 592.
- thermosetting resin In the first resin molding step, a thermosetting resin is used, and it is important to spread the resin throughout before curing. For this reason, the relationship between the arrangement of circuit components and wiring in the lead 514 and the press-fitting hole 590 and the press-fitting direction is very important.
- FIG. 13 is a diagram showing a part of the CC cross section of FIG. 12, and the gap 674 and the hole 520 provided inside the diaphragm 672 and the diaphragm 672 It is explanatory drawing explaining the communicating hole 676 which connects.
- a diaphragm 672 is provided in the flow rate detection unit 602 that measures the flow rate of the gas 30 to be measured, and a gap 674 is provided in the back surface of the diaphragm 672.
- the diaphragm 672 is provided with an element for exchanging heat with the measurement target gas 30 and thereby measuring the flow rate. If heat is transmitted between the elements via the diaphragm 672 separately from the exchange of heat with the gas to be measured 30 between the elements formed in the diaphragm 672, it is difficult to accurately measure the flow rate. For this reason, the diaphragm 672 needs to increase the thermal resistance, and the diaphragm 672 is made as thin as possible.
- the diaphragm 672 is embedded and fixed in the first resin of the circuit package 400 formed by the first resin molding process, and the element (not shown) is provided on the surface of the diaphragm 672, and the element is a heat transfer surface exposed portion.
- heat is transmitted to the measurement target gas 30 (not shown) via the heat transfer surface 437 on the element surface.
- the heat transfer surface 437 may be constituted by the surface of each element, or a thin protective film may be provided thereon. It is desirable that the heat transfer between the element and the measurement target gas 30 is performed smoothly, while the direct heat transfer between the elements is as small as possible.
- the portion of the diaphragm 672 where the element is provided is disposed in the heat transfer surface exposed portion 436 of the measurement channel surface 430, and the heat transfer surface 437 is exposed from the resin forming the measurement channel surface 430. ing.
- the outer peripheral portion of the diaphragm 672 is covered with the thermosetting resin used in the first resin molding process for forming the measurement flow path surface 430.
- the stress generated in the resin forming the measurement channel surface 430 Will be received only by the side surface of the diaphragm 672, and the diaphragm 672 may be distorted to deteriorate its characteristics. As shown in FIG. 13, the distortion of the diaphragm 672 is reduced by making the outer peripheral portion of the front side of the diaphragm 672 also covered with the thermosetting resin.
- the step W between the heat transfer surface 437 and the measurement flow path surface 430 through which the measurement target gas 30 flows is small.
- the diaphragm 672 is made very thin in order to suppress heat transfer between the elements, and a gap 674 is formed on the back surface of the diaphragm 672.
- a gap 674 is formed on the back surface of the diaphragm 672.
- the pressure of the gap 674 formed on the back surface of the diaphragm 672 changes based on the temperature due to a temperature change.
- the diaphragm 672 receives a pressure to cause distortion, and high-precision measurement becomes difficult. Therefore, the plate 532 is provided with a hole 520 connected to the opening 438 that opens to the outside, and a communication hole 676 that connects the hole 520 and the diaphragm 672 is provided.
- the communication hole 676 is made of two plates, for example, a first plate 534 and a second plate 536.
- the first plate 534 is provided with a hole 520 and a hole 521, and further a groove for forming the communication hole 676.
- the communication hole 676 is formed by closing the groove and the hole 520 and the hole 521 with the second plate 536.
- the communication hole 676 can be formed by closing the groove and the hole 520 and the hole 521 with the second plate 536.
- the lead frame can be used as the second plate 536.
- an LSI that operates as a diaphragm 672 and a processing unit 604 is provided on the plate 532.
- a lead frame for supporting a plate 532 on which the diaphragm 672 and the processing unit 604 are mounted is provided below these. Therefore, the structure becomes simpler by using this lead frame.
- the lead frame can be used as a ground electrode.
- the role of the second plate 536 is given to the lead frame, and the lead frame is used to close the hole 520 and the hole 521 formed in the first plate 534 and to form the groove formed in the first plate 534.
- the communication hole 676 By forming the communication hole 676 by covering the lead frame so as to cover the lead frame, the entire structure is simplified, and the lead frame acts as a ground electrode, so that the diaphragm 672 and the processing unit 604 are externally connected. The influence of noise can be reduced.
- a pressing trace 442 remains on the back surface of the circuit package 400 where the heat transfer surface exposed portion 436 is formed.
- a mold for example, a insert piece is applied to the heat transfer surface exposed portion 436, and the pressing trace 442 on the opposite surface is further formed.
- a mold is applied to the portion, and both molds prevent the resin from flowing into the heat transfer surface exposed portion 436.
- FIG. 14 shows a state in which the frame frame shown in FIG. 12 is molded with a thermosetting resin and covered with the thermosetting resin in the first resin molding step.
- the measurement flow path surface 430 is formed on the surface of the circuit package 400, and the heat transfer surface exposed portion 436 is provided on the measurement flow path surface 430. Further, the gap 674 on the back surface of the diaphragm 672 disposed inside the heat transfer surface exposed portion 436 is connected to the opening 438.
- a temperature detection unit 452 for measuring the temperature of the measurement target gas 30 is provided at the tip of the protrusion 424, and a temperature detection element 518 is incorporated therein.
- a lead for taking out an electric signal of the temperature detection element 518 is divided, and a connection line 546 having a large thermal resistance is disposed. Thereby, the heat transfer from the base of the protrusion part 424 to the temperature detection part 452 is suppressed, and the influence by heat is suppressed.
- an inclined portion 594 and an inclined portion 596 are formed at the base of the protruding portion 424. While the flow of the resin in the first resin molding step is smooth, the measurement target gas 30 measured by the temperature detection unit 452 is measured by the inclined portion 594 and the inclined portion 596 in a state where the resin is mounted on the vehicle and operating. The projection flows smoothly from the protrusion 424 toward the root, and the root of the protrusion 424 is cooled, so that the effect of heat on the temperature detection unit 452 can be reduced. After the state shown in FIG. 14, the lead 514 is disconnected for each terminal to become the connection terminal 412 and the terminal 414.
- the resin flow is blocked at the position of the heat transfer surface exposed portion 436 and the opening 438, for example, a piece larger than the diaphragm 672 is applied, and the back surface is pressed and sandwiched from both sides.
- the pressing trace 442 and the pressing trace 441 are formed on the heat transfer surface exposed portion 436 and the opening 438 in FIG. 14 or the back surface corresponding to the heat transfer surface exposed portion 436 and the opening 438 in FIG. Remaining.
- the cut surface of the lead separated from the frame 512 is exposed from the resin surface, so that moisture or the like may enter the inside from the cut surface of the lead during use. It is important to prevent this from the viewpoint of improving durability and improving reliability.
- the portion of the fixed surface 434 in FIG. 14 is covered with resin in the second resin molding step, and the cut surface is not exposed.
- the lead cutting portions of the inclined portion 594 and the inclined portion 596 are covered with resin in the second resin molding step, and the cutting surfaces of the leads 552 and the leads 554 shown in FIG. 12 with the frame 512 are covered with the resin. This prevents corrosion of the cut surfaces of the lead 552 and the lead 554 and intrusion of water from the cut portion.
- the cut surfaces of the lead 552 and the lead 554 are close to an important lead portion that transmits an electrical signal of the temperature detection unit 452. Therefore, it is desirable to cover the cut surface with the second resin molding process.
- FIG. 15 shows another example of the circuit package 400.
- the circuit package 400 has the connection terminals 412 and the terminals 414 provided on the same side of the circuit package 400.
- the connection terminal 412 and the terminal 414 are provided on different sides.
- the terminal 414 is a terminal that is not connected to an external connection terminal of the thermal flow meter 300.
- connection terminal 414 by extending the terminal 414 in a direction different from that of the connection terminal 412, it is possible to reduce the concentration of the leads in the frame 512 to a part, and the arrangement of the leads in the frame 512 is facilitated.
- a chip capacitor which is a circuit component 516, is connected to a lead portion corresponding to the connection terminal 412.
- a slightly large space is required. In the embodiment of FIG. 15, there is an effect that it is easy to secure a lead space corresponding to the connection terminal 412.
- the circuit package 400 shown in FIG. 15 is formed with an inclined portion 462 and an inclined portion 464 whose thickness gradually changes at the base portion of the protruding portion 424 protruding from the package body 422. Yes.
- the same effect as described in FIG. 11 is obtained. That is, as shown in FIG. 15, the protruding portion 424 protrudes from the side surface of the package main body 422 in a shape extending in the upstream direction of the measurement target gas 30.
- a temperature detection unit 452 is provided at the tip of the protrusion 424, and a temperature detection element 518 is embedded in the temperature detection unit 452.
- Inclined portions 462 and 464 are provided at a connection portion between the protruding portion 424 and the package main body 422.
- the base of the protruding portion 424 is thickened by the inclined portion 462 or the inclined portion 464, and a shape that gradually narrows as the tip proceeds is formed at the root of the protruding portion 424. That is, a shape in which the cross-sectional area crossing the axis in the projecting direction gradually decreases when the projecting direction is used as an axis is provided at the root of the projecting part 424.
- the protrusion 424 has low mechanical strength and is easily broken at the root. With the shape in which the base of the protruding portion 424 is thickened and gradually becomes narrower in the direction of the tip, stress concentration on the base can be alleviated and the mechanical strength is excellent. In addition, when the protruding portion 424 is formed by a resin mold, warpage or the like is likely to occur due to an influence of a volume change when the resin is hardened. Such influence can be reduced.
- the base of the protruding portion 424 is thickened, and the base of the protruding portion 424 is surrounded by the housing 302 so that the circuit package 400 is fixed to the housing 302.
- the base of the protruding portion 424 is covered by the resin of the housing 302, it is possible to prevent the protruding portion 424 from being damaged by a mechanical impact.
- FIG. 16 shows a production process of the circuit package 400 in the production process of the thermal flow meter 300.
- FIG. 17 shows the production process of the thermal flow meter, and
- FIG. 18 shows another embodiment of the production process of the thermal flow meter.
- step 1 shows the process of producing the frame shown in FIG. This frame is made by, for example, press working.
- Step 2 the plate 532 is first mounted on the frame frame formed in Step 1, and the flow rate detection unit 602 and the processing unit 604 are further mounted on the plate 532, and circuit components such as the temperature detection element 518 and the chip capacitor are further mounted. Mount.
- electrical wiring is performed between circuit components, between circuit components and leads, and between leads.
- the lead 544 and the lead 548 are connected by a connection line 546 for increasing the thermal resistance.
- the circuit component shown in FIG. 12 is mounted on the frame frame 512, and an electric circuit in which electrical connection is further made is produced.
- step 3 it is molded with a thermosetting resin by the first resin molding process.
- FIG. 14 shows the circuit package 400 in a molded state.
- the connected leads are separated from the frame frame 512, and the leads are also separated, and the circuit package 400 shown in FIGS. 11 and 15 is completed.
- a measurement flow path surface 430 and a heat transfer surface exposed portion 436 are formed.
- step 4 the appearance inspection and operation inspection of the completed circuit package 400 are performed.
- the first resin molding step of Step 3 transfer molding is performed. Since the electric circuit produced in step 2 is fixed in the mold and high temperature resin is injected into the mold at a high pressure, it is desirable to inspect whether there are any abnormalities in the electrical components and the electrical wiring.
- a terminal 414 is used in addition to the connection terminal 412 shown in FIGS. Since the terminal 414 is not used thereafter, the terminal 414 may be cut from the root after this inspection. For example, in FIG. 15, the used terminal 414 is cut at the root.
- step 5 the housing 302 is made by the second resin molding process.
- the housing 302 has a resin-made sub-passage groove, a flange 312 and an external connection portion 305, and the hatched portion of the circuit package 400 shown in FIG. 11 is covered with the resin in the second resin molding process, so that the circuit package 400 is the housing. 302 is fixed.
- the combination of the production of the circuit package 400 by the first resin molding process (step 3) and the molding of the housing 302 of the thermal flow meter 300 by the second resin molding process significantly improves the flow rate detection accuracy.
- step 6 the external terminal inner ends 361 shown in FIG. 10 are disconnected, and the connection terminal 412 and the external terminal inner end 361 are connected in step 7.
- step 8 the front cover 303 and the back cover 304 are attached to the housing 302, the inside of the housing 302 is sealed with the front cover 303 and the back cover 304, and the measured gas 30 Is completed, and the thermal flow meter 300 is completed.
- the diaphragm structure described with reference to FIG. 7 is formed by the protrusions 356 provided on the front cover 303 or the back cover 304.
- the front cover 303 is made by molding in step 10
- the back cover 304 is made by molding in step 11.
- the front cover 303 and the back cover 304 are made in different processes, and are made by molding with different molds.
- step 9 the gas is actually introduced into the sub-passage and the characteristics are tested.
- the relationship between the sub passage and the flow rate detection unit is maintained with high accuracy, very high measurement accuracy can be obtained by correcting the characteristic by the characteristic test.
- the positioning and shape-related molding that affects the relationship between the sub-passage and the flow rate detection unit are performed in the first resin molding process and the second resin molding process, there is little change in characteristics even with long-term use, and high accuracy. In addition, high reliability is ensured.
- step 12 the connection terminal 412 of the circuit package 400 and the external terminal inner end 361 are connected.
- step 13 the housing 302 is formed by the second resin molding process.
- the housing 302 has a resin-made sub-passage groove, a flange 312 and an external connection portion 305, and the hatched portion of the circuit package 400 shown in FIG. 11 is covered with the resin in the second resin molding process, so that the circuit package 400 is the housing. 302 is fixed.
- the combination of the production of the circuit package 400 by the first resin molding process (step 3) and the molding of the housing 302 of the thermal flow meter 300 by the second resin molding process significantly improves the flow rate detection accuracy.
- step 8 the front cover 303 and the back cover 304 are attached to the housing 302, the inside of the housing 302 is sealed with the front cover 303 and the back cover 304, and the measured gas 30 A sub-passage for the flow is completed.
- the diaphragm structure described with reference to FIG. 7 is formed by the protrusions 356 provided on the front cover 303 or the back cover 304.
- the front cover 303 is made by molding in step 10
- the back cover 304 is made by molding in step 11.
- the front cover 303 and the back cover 304 are made in different processes, and are made by molding with different molds.
- step 9 the gas is actually introduced into the sub-passage and the characteristics are tested.
- the relationship between the sub passage and the flow rate detection unit is maintained with high accuracy, very high measurement accuracy can be obtained by performing characteristic correction by a characteristic test.
- the positioning and shape-related molding that affects the relationship between the sub-passage and the flow rate detection unit are performed in the first resin molding process and the second resin molding process, there is little change in characteristics even with long-term use, and high accuracy. In addition, high reliability is ensured.
- FIG. 19 is a circuit diagram showing a flow rate detection circuit 601 of the thermal flow meter 300. Note that a measurement circuit related to the temperature detection unit 452 described in the embodiment is also provided in the thermal flow meter 300, but is omitted in FIG.
- the flow rate detection circuit 601 of the thermal type flow meter 300 includes a flow rate detection unit 602 having a heating element 608 and a processing unit 604.
- the processing unit 604 controls the amount of heat generated by the heating element 608 of the flow rate detection unit 602 and outputs a signal indicating the flow rate based on the output of the flow rate detection unit 602 via the terminal 662.
- the processing unit 604 includes a central processing unit (hereinafter referred to as a CPU) 612, an input circuit 614, an output circuit 616, a memory 618 that holds data representing a relationship between a correction value, a measured value, and a flow rate,
- a power supply circuit 622 is provided to supply a constant voltage to each necessary circuit.
- the power supply circuit 622 is supplied with DC power from an external power source such as an in-vehicle battery via a terminal 664 and a ground terminal (not shown).
- the flow rate detection unit 602 is provided with a heating element 608 for heating the air to be measured 30.
- the voltage V1 is supplied from the power supply circuit 622 to the collector of the transistor 606 constituting the current supply circuit of the heating element 608, and a control signal is applied from the CPU 612 to the base of the transistor 606 via the output circuit 616. Accordingly, a current is supplied from the transistor 606 to the heating element 608 through the terminal 624.
- the amount of current supplied to the heating element 608 is controlled by a control signal applied from the CPU 612 to the transistor 606 constituting the current supply circuit of the heating element 608 via the output circuit 616.
- the processing unit 604 controls the amount of heat generated by the heating element 608 so that the temperature of the air to be measured 30 is higher than the initial temperature by a predetermined temperature, for example, 100 ° C. by being heated by the heating element 608.
- the flow rate detection unit 602 has a heat generation control bridge 640 for controlling the heat generation amount of the heating element 608 and a flow rate detection bridge 650 for measuring the flow rate.
- One end of the heat generation control bridge 640 is supplied with a constant voltage V3 from the power supply circuit 622 via a terminal 626, and the other end of the heat generation control bridge 640 is connected to the ground terminal 630.
- a constant voltage V2 is supplied from one end of the flow rate detection bridge 650 from the power supply circuit 622 via a terminal 625, and the other end of the flow rate detection bridge 650 is connected to the ground terminal 630.
- the heat generation control bridge 640 includes a resistor 642 that is a resistance temperature detector whose resistance value changes based on the temperature of the heated air 30 to be measured, and the resistor 642, the resistor 644, the resistor 646, and the resistor 648 are bridges.
- the circuit is configured.
- the potential difference between the intersection A of the resistor 642 and the resistor 646 and the potential B at the intersection B of the resistor 644 and 648 is input to the input circuit 614 via the terminal 627 and the terminal 628, and the CPU 612 has a predetermined potential difference between the intersection A and the intersection B.
- the amount of heat generated by the heating element 608 is controlled by controlling the current supplied from the transistor 606 so as to be zero volts.
- the flow rate detection circuit 601 illustrated in FIG. 19 heats the air to be measured 30 with the heating element 608 so as to be higher than the original temperature of the air to be measured 30 by a constant temperature, for example, 100 ° C. at all times.
- a constant temperature for example, 100 ° C. at all times.
- the intersection A and the intersection A The resistance value of each resistor constituting the heat generation control bridge 640 is set so that the potential difference between B becomes zero volts. Accordingly, in the flow rate detection circuit 601 shown in FIG. 19, the CPU 612 controls the current supplied to the heating element 608 so that the potential difference between the intersection A and the intersection B becomes zero volts.
- the flow rate detection bridge 650 includes four resistance temperature detectors, a resistor 652, a resistor 654, a resistor 656, and a resistor 658. These four resistance temperature detectors are arranged along the flow of the air to be measured 30, and the resistor 652 and the resistor 654 are arranged upstream of the heating element 608 in the flow path of the air to be measured 30, and the resistor 656. And the resistor 658 are arranged on the downstream side in the flow path of the air to be measured 30 with respect to the heating element 608. In order to increase the measurement accuracy, the resistor 652 and the resistor 654 are arranged so that the distance to the heating element 608 is substantially the same, and the resistor 656 and the resistor 658 are substantially the same distance to the heating element 608. Has been placed.
- each resistance of the flow rate detection bridge 650 is set so that the potential difference between the intersection C and the intersection D becomes zero when the flow of the air 30 to be measured is zero. Therefore, when the potential difference between the intersection C and the intersection D is, for example, zero volts, the CPU 612 generates an electric signal indicating that the flow rate of the main passage 124 is zero based on the measurement result that the flow rate of the air to be measured 30 is zero. Output from the terminal 662.
- the resistor 652 and the resistor 654 arranged on the upstream side are cooled by the measured air 30 and arranged on the downstream side of the measured air 30.
- the resistors 656 and 658 are heated by the air 30 to be measured heated by the heating element 608, and the temperatures of the resistors 656 and 658 rise. Therefore, a potential difference is generated between the intersection C and the intersection D of the flow rate detection bridge 650, and this potential difference is input to the input circuit 614 via the terminal 631 and the terminal 632.
- the CPU 612 retrieves data representing the relationship between the potential difference stored in the memory 618 and the flow rate of the main passage 124 based on the potential difference between the intersection C and the intersection D of the flow rate detection bridge 650, and Find the flow rate.
- An electrical signal representing the flow rate of the main passage 124 obtained in this way is output via the terminal 662. Note that the terminal 664 and the terminal 662 shown in FIG. 19 are newly described with reference numerals, but are included in the connection terminal 412 shown in FIG. 5, FIG. 6, or FIG.
- the memory 618 stores data representing the relationship between the potential difference between the intersection C and the intersection D and the flow rate of the main passage 124, and is obtained based on the actual measured value of gas after the circuit package 400 is produced.
- correction data for reducing measurement errors such as variations is stored.
- the actual measurement of the gas after production of the circuit package 400 and the writing of the correction value based on it into the memory 618 are performed using the external terminal 306 and the correction terminal 307 shown in FIG.
- the arrangement relationship between the sub-passage through which the measurement target gas 30 flows and the measurement flow path surface 430 and the arrangement relationship between the sub-passage through which the measurement target gas 30 flows and the heat transfer surface exposed portion 436 are highly accurate. Since the circuit package 400 is produced in a state where there is little variation, the measurement result with extremely high accuracy can be obtained by the correction using the correction value.
- FIG. 20 is a circuit configuration diagram showing the circuit arrangement of the flow rate detection circuit 601 of FIG. 19 described above.
- the flow rate detection circuit 601 is made as a rectangular semiconductor chip, and the measured air 30 flows in the direction of the arrow from the left side to the right side of the flow rate detection circuit 601 shown in FIG.
- a rectangular diaphragm 672 is formed in the flow rate detection unit 602, and a thin region 603 indicated by a broken line in which the thickness of the semiconductor chip is reduced is provided in the diaphragm 672.
- the thin region 603 is formed with a gap on the back surface side, and the gap communicates with the opening 438 shown in FIGS. 11 and 5, and the atmospheric pressure in the gap depends on the atmospheric pressure introduced from the opening 438.
- the diaphragm 672 thin region 603 has a low thermal conductivity by reducing the thickness, and the heat through the diaphragm 672 to the resistor 652, the resistor 654, the resistor 658, and the resistor 656 provided in the thin region 603 is reduced. Transmission is suppressed, and the temperature of these resistors is substantially determined by heat transfer with the measurement target gas 30.
- a heating element 608 is provided at the center of the thin region 603 of the diaphragm 672, and a resistor 642 constituting a heating control bridge 640 is provided around the heating element 608.
- Resistors 644, 646, and 648 constituting the heat generation control bridge 640 are provided outside the thin region 603.
- the resistors 642, 644, 646, and 648 formed in this way constitute a heat generation control bridge 640.
- a resistor 652 and a resistor 654 that are upstream temperature measuring resistors and a resistor 656 and a resistor 658 that are downstream temperature measuring resistors are arranged so as to sandwich the heating element 608, and the air to be measured is placed on the heating element 608.
- An upstream resistance temperature detector 652 and a resistance 654 are arranged on the upstream side in the direction of the arrow through which 30 flows, and a downstream resistance temperature detector on the downstream side in the direction of the arrow in which the measured gas 30 flows with respect to the heating element 608.
- a certain resistor 656 and resistor 658 are arranged. In this manner, the flow rate detection bridge 650 is formed by the resistor 652, the resistor 654, the resistor 656, and the resistor 658 arranged in the thin region 603.
- both ends of the heating element 608 are connected to terminals 624 and 629 described at the lower side of FIG.
- a current supplied from the transistor 606 to the heating element 608 is applied to the terminal 624, and the terminal 629 is grounded as a ground.
- the resistor 642, the resistor 644, the resistor 646, and the resistor 648 constituting the heat generation control bridge 640 are connected to the terminals 626 and 630, respectively.
- a constant voltage V3 is supplied from the power supply circuit 622 to the terminal 626, and the terminal 630 is grounded.
- a connection point between the resistor 642 and the resistor 646 and between the resistor 646 and the resistor 648 is connected to a terminal 627 and a terminal 628.
- the terminal 627 outputs the potential at the intersection A between the resistor 642 and the resistor 646, and the terminal 627 outputs the potential at the intersection B between the resistor 644 and the resistor 648.
- FIG. 20 As shown in FIG.
- a constant voltage V2 is supplied to the terminal 625 from the power supply circuit 622, and the terminal 630 is grounded as a ground terminal.
- the connection point between the resistor 654 and the resistor 658 is connected to the terminal 631, and the terminal 631 outputs the potential at the point B in FIG.
- a connection point between the resistor 652 and the resistor 656 is connected to a terminal 632, and the terminal 632 outputs a potential at the intersection C shown in FIG.
- the resistor 642 constituting the heat generation control bridge 640 is formed in the vicinity of the heating element 608, so that the temperature of the gas warmed by the heat generation from the heating element 608 can be accurately measured. it can.
- the resistors 644, 646, and 648 constituting the heat generation control bridge 640 are arranged away from the heat generating body 608, and thus are configured not to be affected by heat generated from the heat generating body 608.
- the resistor 642 is configured to react sensitively to the temperature of the gas heated by the heating element 608, and the resistor 644, the resistance 646, and the resistance 648 are configured not to be affected by the heating element 608. For this reason, the detection accuracy of the measurement target gas 30 by the heat generation control bridge 640 is high, and the control for increasing the measurement target gas 30 by a predetermined temperature with respect to the initial temperature can be performed with high accuracy.
- an air gap is formed on the back surface side of the diaphragm 672, and this air space communicates with the opening 438 shown in FIGS. 11 and 5.
- the pressure on the back surface side air gap of the diaphragm 672 and the front side of the diaphragm 672 The difference from the pressure is not increased. Distortion of the diaphragm 672 due to this pressure difference can be suppressed. This leads to an improvement in flow rate measurement accuracy.
- the diaphragm 672 forms the thin region 603, and the thickness of the thin region 603 is very thin, and heat conduction through the diaphragm 672 is suppressed as much as possible. Therefore, the flow rate detection bridge 650 and the heat generation control bridge 640 are less affected by heat conduction through the diaphragm 672, and the tendency to operate depending on the temperature of the measurement target gas 30 is further increased, and the measurement operation is improved. For this reason, high measurement accuracy is obtained.
- Measurement of gas temperature in thermal flow meter 300 8.1 Structure of temperature detection unit 452 in thermal flow meter 300 In FIGS. A passage is provided. An inlet 343 that opens toward the upstream side of the flow of the gas 30 to be measured is formed on the flange 312 side of the auxiliary passage as shown in FIG. Inside the inlet 343, a temperature detector 452 for measuring the temperature of the measurement target gas 30 is disposed so as to protrude from the inside of the housing 302. In the central part of the measurement unit 310 provided with the inlet 343, the upstream outer wall of the measurement unit 310 constituting the housing 302 is recessed toward the downstream side, that is, toward the inside of the housing 302, and the depression shape is formed.
- the temperature detection part 452 has a shape that protrudes outward from the housing 302 toward the upstream side from the upstream outer wall. Further, a front cover 303 and a back cover 304 are provided on both side portions of the hollow outer wall, and upstream ends of the front cover 303 and the rear cover 304 are directed upstream from the hollow outer wall. It has a protruding shape. Therefore, an inlet 343 for taking in the measurement target gas 30 is formed by the hollow outer wall and the front cover 303 and the back cover 304 on both sides thereof. The gas 30 to be measured taken from the inlet 343 comes into contact with the temperature detector 452 provided inside the inlet 343, and the temperature is measured by the temperature detector 452.
- the gas to be measured 30 flows along the portion supporting the temperature detection unit 452 protruding upstream from the outer wall of the housing 302 having a hollow shape, and the front side outlet 344 and the back side outlet 345 provided in the front cover 303 and the back cover 304. Is discharged into the main passage 124.
- the temperature detection unit 452 protrudes out of the housing 302 and directly contacts the measurement target gas 30, thereby improving detection accuracy. To do. Further, the temperature of the gas flowing into the inlet 343 from the upstream side in the direction along the flow of the measurement target gas 30 is measured by the temperature detection unit 452, and further, the base of the temperature detection unit 452 that is a part that supports the temperature detection unit 452. By flowing toward the portion, the temperature of the portion supporting the temperature detection unit 452 is cooled in a direction approaching the temperature of the gas 30 to be measured.
- the temperature of the intake pipe which is the main passage 124, is normally high, and heat is transmitted from the flange 312 or the heat insulating portion 315 to the portion supporting the temperature detecting portion 452 through the upstream outer wall in the measuring portion 310, and the temperature measurement accuracy There is a risk of affecting.
- the support portion is cooled by flowing along the support portion of the temperature detection unit 452. Therefore, it is possible to suppress the heat from being transmitted from the flange 312 or the heat insulating portion 315 to the portion supporting the temperature detecting portion 452 through the upstream outer wall in the measuring portion 310.
- the upstream outer wall in the measurement unit 310 has a shape that is recessed toward the downstream side, so that there is a gap between the upstream outer wall in the measurement unit 310 and the temperature detection unit 452. Can be made longer. As the heat transfer distance becomes longer, the distance of the cooling portion by the measured gas 30 becomes longer. Accordingly, it is possible to reduce the influence of heat generated from the flange 312 or the heat insulating portion 315. As a result, the measurement accuracy is improved.
- the upstream outer wall has a shape that is recessed toward the downstream side, that is, toward the inside of the housing 302, the upstream outer wall 335 of the housing 302 can be fixed, and the circuit package 400 can be easily fixed. Become.
- the protrusion 424 (see FIG. 11) having the temperature detector 452 is also reinforced.
- the inlet 343 is provided on the upstream side of the measurement target gas 30 in the case 301, and the measurement target gas 30 guided from the inlet 343 passes around the temperature detection unit 452, It is led from the front side outlet 344 and the back side outlet 345 to the main passage 124.
- the temperature detection unit 452 measures the temperature of the measurement target gas 30 and outputs an electrical signal representing the measured temperature from the external terminal 306 of the external connection unit 305.
- a case 301 included in the thermal flow meter 300 includes a front cover 303, a back cover 304, and a housing 302.
- the housing 302 has a recess for forming an inlet 343, and the recess is an outer wall recess 366 (see FIG.
- the front side outlet 344 and the back side outlet 345 are formed by holes provided in the front cover 303 and the back cover 304.
- the temperature detection unit 452 is provided at the tip of the protrusion 424 and is mechanically weak.
- the front cover 303 and the back cover 304 serve to protect the protrusions 424 from mechanical impact.
- the front cover 303 and 304 shown in FIGS. 8 and 9 are formed with a front protection part 322 and a back protection part 325.
- a front protection part 322 provided on the front cover 303 is disposed on the front side surface of the inlet 343, and a back protection part 325 provided on the back cover 304 is provided on the rear side surface of the inlet 343.
- the temperature detection unit 452 disposed inside the entrance 343 is protected by the front protection unit 322 and the back protection unit 325, and the machine of the temperature detection unit 452 due to a collision with the temperature detection unit 452 during production or when mounted on a vehicle. Damage can be prevented.
- the base of the protrusion 424 that supports the temperature detector 452 is gradually thicker with respect to the tip, and the gas 30 to be measured that has entered from the inlet 343 gradually increases. Since it flows along the base part which becomes thick, a cooling effect increases.
- the root portion of the protrusion 424 is close to the flow rate detection circuit and is easily affected by the heat generated by the flow rate detection circuit.
- a lead 548 for connecting a temperature detection element 518 provided in the temperature detection unit 452 is embedded in the root portion of the protrusion 424. For this reason, heat may be transmitted through the lead 548.
- the cooling effect can be increased by increasing the contact area with the measurement target gas 30 by thickening the base of the protrusion 424.
- the circuit package 400 includes a circuit package body 422 and a protrusion 424 that incorporate a flow rate detection unit 602 and a processing unit 604, which will be described later, for measuring the flow rate. have.
- the protruding portion 424 protrudes from the side surface of the circuit package main body 422 in a shape extending in the upstream direction of the measurement target gas 30.
- a temperature detection unit 452 is provided at the tip of the protrusion 424, and a temperature detection element 518 is embedded in the temperature detection unit 452 as shown in FIG. As shown in FIGS.
- inclined portions 462 and 464 are provided at the connection portion between the protruding portion 424 and the circuit package body 422.
- the base of the protruding portion 424 is thickened by the inclined portion 462 or the inclined portion 464, and a shape that gradually narrows as the tip proceeds is formed at the root of the protruding portion 424.
- the cross-sectional area that crosses the axis in the protruding direction has a shape that decreases at the root of the protruding portion 424 as it advances in the distal direction. In this way, in the shape in which the circuit package 400 partially protrudes, the protrusion 424 has a weak mechanical strength, so the base of the protrusion 424 is thickened and gradually becomes thinner as it advances in the tip direction.
- the concentration of stress on the root can be relaxed and the mechanical strength can be improved.
- the protruding portion 424 is formed by a resin mold, warpage or the like is likely to occur due to an influence of a volume change when the resin is hardened. By thickening the root, it is possible to reduce the influence on such a problem.
- the base of the protruding portion 424 is thickened, and the base of the protruding portion 424 is surrounded by the resin of the housing 302 to fix the circuit package 400 to the housing 302. In this manner, by covering the base of the protruding portion 424 with the resin of the housing 302, it is possible to prevent the protruding portion 424 from being damaged by a mechanical impact.
- the protrusion 424 that supports the temperature detection unit 452 has a tip that is narrower than the base, and the temperature detection unit 452 is provided at the tip. With such a shape, the influence of heat from the base portion of the protruding portion 424 on the temperature detecting portion 452 is reduced.
- the measurement target gas 30 flows along the protrusion 424, and acts to bring the temperature of the protrusion 424 close to the temperature of the measurement target gas 30.
- the influence of the temperature of the base portion of the protrusion 424 on the temperature detection unit 452 is suppressed.
- the vicinity of the protruding portion 424 including the temperature detecting portion 452 is thin, and becomes thicker toward the root of the protruding portion 424. For this reason, the measurement target gas 30 flows along the shape of the protruding portion 424, and the protruding portion 424 is efficiently cooled.
- the hatched portion at the base portion of the protruding portion 424 is a fixed surface 432 that is covered with the resin that forms the housing 302 in the second resin molding step.
- a depression is provided in the shaded portion at the base of the protrusion 424. This indicates that a hollow portion that is not covered with the resin of the housing 302 is provided.
- the protrusion 424 is further easily cooled by the measurement target gas 30.
- the display of the hatched portion is omitted, but it is the same as FIG.
- the circuit package 400 is provided with a connection terminal 412 in order to supply power for operating the built-in flow rate detection unit 602 and processing unit 604 and to output a flow rate measurement value and a temperature measurement value. Further, a terminal 414 is provided to inspect whether the circuit package 400 operates correctly and whether an abnormality has occurred in the circuit components or their connections.
- the circuit package 400 is made by transfer molding the flow rate detection unit 602 and the processing unit 604 using a thermosetting resin in the first resin molding step. By performing transfer molding, the dimensional accuracy of the circuit package 400 can be improved. However, in the transfer molding process, a high-temperature pressure is applied to the inside of the sealed mold containing the flow rate detection unit 602 and the processing unit 604.
- each circuit package 400 produced is inspected. Since the inspection terminal 414 is not used for measurement, the terminal 414 is not connected to the external terminal inner end 361 as described above.
- Each connection terminal 412 is provided with a bending portion 416 in order to increase mechanical elastic force. By giving each connection terminal 412 a mechanical elastic force, it is possible to absorb stress generated due to a difference in thermal expansion coefficient between the resin in the first resin molding process and the resin in the second resin molding process.
- each connection terminal 412 is affected by thermal expansion due to the first resin molding process, and the external terminal inner end 361 connected to each connection terminal 412 is affected by resin due to the second resin molding process.
- production of the stress resulting from these resin differences can be absorbed.
- inclined portions 462 and 464 are provided at the base of the protruding portion 424.
- the base of the protruding portion 424 is thickened by the inclined portion 462 or the inclined portion 464, and a shape that gradually narrows as the tip proceeds is formed at the root of the protruding portion 424. That is, a shape in which the cross-sectional area crossing the axis in the projecting direction gradually decreases when the projecting direction is used as an axis is provided at the root of the projecting part 424.
- the base of the projecting portion 424 is thickened, and the shape gradually narrows as it advances in the tip direction, thereby reducing the concentration of stress on the root and mechanical strength. Can be improved.
- the protruding portion 424 is formed by a resin mold, warpage or the like is likely to occur due to an influence of a volume change or the like when the resin is hardened. By thickening the root, it is possible to reduce the influence on such a problem.
- the base of the protruding portion 424 is thickened, and the base of the protruding portion 424 is surrounded by the housing 302 so that the circuit package 400 is fixed to the housing 302.
- the protrusion 424 can be prevented from being damaged by a mechanical impact.
- FIG. 21 shows another example of the protrusion 424 of the circuit package 400.
- the same reference numerals as those in the above-described drawings have the same structure and the same effect. . Therefore, the description is omitted.
- the protruding portion 424 protruding from the circuit package main body 422 has a protrusion 446 and a protrusion 447 on the flat surface side and the back surface side. Only one of the protrusion 446 and the protrusion 447 is effective. In this embodiment, one projection is formed on each of the plane side and the back side, but a plurality of projections may be provided.
- Each protrusion has a root portion 448 and a tip portion 449, and the height thereof decreases from the root portion 448 toward the tip portion 449.
- the base portion of the protruding portion 424 is covered with a resin forming the housing 302. For this reason, in the second resin molding process, the base 448 of the protrusion 446 and the base 448 of the protrusion 447 are also covered with the resin.
- the mechanical strength of the protruding portion 424 increases. Further, since the area in contact with the measurement target gas 30 is increased, the cooling effect is increased. Further, the adhesiveness of the housing 302 to which the circuit package 400 is fixed to the resin is improved, and the circuit package 400 is fixed to the housing 302 more firmly. This increases the reliability.
- FIG. 22 is a partially enlarged view of the protruding portion 424 protruding from the package body 422, and FIG. 22 (A) is the same as FIG. 11 (B) or FIG. 15 (A).
- FIG. 22B is a partially enlarged view of the front view described in FIG.
- An inclined portion 462 and an inclined portion 464 shown in FIG. 22A are further curved with respect to the inclined portion 462 and the inclined portion 464 shown in FIG. 11B and FIG. That is, the inclined portion 462 and the inclined portion 464 shown in FIGS. 11B and 15A may be straight lines or curved lines. However, in any case, substantially the same effect can be obtained.
- the tip of the projecting portion 424 has a narrow shape with respect to the thickness direction of the package main body 422.
- the inclined portions 466 and 468 are provided when the thickness of the package main body 422 and the width of the temperature detecting portion 452 are different, and the inclined portions 462 and the inclined portions 464 are formed so as to be gradually thinner in the thickness direction. The same effect as described above with respect to
- FIG. 21 The structure of FIG. 21 can be added to FIG. By doing in this way, the effect demonstrated in FIG. 21 is brought also with respect to the Example of FIG.
- FIGS. 23 to 25 show still another embodiment.
- FIG. 23 is a diagram in which a circuit package 400 according to another embodiment is fixed by a housing 302, and is an alternative to the embodiment described in FIG. 5 or FIG.
- FIG. 24 shows another embodiment described in FIGS. 11 and 15.
- FIG. 25 shows another embodiment of FIG. 12, and shows a state in which circuit components are mounted on the frame of the circuit package 400 of the other embodiment shown in FIG.
- a protrusion 424 protrudes from the package body 422 of the circuit package 400 toward the center of the main passage 124.
- the inlet and outlet of the sub-passage are formed on the center side of the main passage 124, which is the distal end side of the measurement unit 310 of the housing 302.
- the entrance is the back side and does not appear in the figure.
- An exit groove 353 for forming an exit is provided on the distal end side of the measurement unit 310.
- the gas to be measured 30 is taken in from the inlet formed on the back surface side of FIG. 23, and a sub-passage (hereinafter referred to as a sub-passage measuring unit 435) connecting the inlet and the outlet is formed in the wall surface direction of the main passage 124.
- the passage measurement unit 435 is provided with a measurement channel surface 430 for measuring the flow rate.
- a hole 399 that opens to the main passage 124 is provided between the sub-passage measuring unit 435 and the inlet and outlet sides, and a temperature detector 452 is disposed in the hole 399.
- the hole 399 opens into the main passage 124, and the gas to be measured 30 flowing through the main passage 124 passes through the hole 399. Therefore, the temperature detection unit 452 provided in the circuit package 400 in the gas to be measured 30 passing through the hole 399. Is constantly exposed, and the temperature of the gas 30 to be measured flowing through the main passage 124 can be measured.
- the hole 399 has different shapes on the front side and the back side, and a difference in the pressure of the gas 30 to be measured due to the difference in shape between the front side and the back side of the hole 399 occurs. Gas flows in the direction.
- FIG. 24 shows the external shape of the circuit package 400 shown in FIG.
- the difference from FIG. 11 is that the protruding direction of the protruding portion 424 from the package main body 422 is different.
- 24A is a left side view
- FIG. 24B is a front view
- FIG. 24C is a rear view.
- the side 472 of the package body 422 extends as it is to form the protrusion 424, and the temperature detection element 518 is held inside the tip of the protrusion 424.
- a gently sloping portion 463 is formed at the base of the other side of the protruding portion 424.
- the base of the protruding portion 424 can be thickened, and a shape that gradually decreases in the distal direction can be provided at the root portion of the protruding portion 424. Since the protrusion 424 has a low mechanical strength, the base of the protrusion 424 is thickened, and the shape gradually becomes narrower as it advances toward the tip, thereby reducing the concentration of stress on the root and mechanical strength. Can be improved. In addition, when the protruding portion 424 is formed by a resin mold, warpage or the like is likely to occur due to an influence of a volume change when the resin is hardened.
- the protrusion length of the protrusion 424 can be increased, thereby detecting the temperature.
- the detection accuracy of the temperature detection element 518 provided in the part 452 is improved.
- the base of the protrusion 424 is thickened, and the base of the protrusion 424 is surrounded by the housing 302 so as to be surrounded by the resin of the housing 302 so as to be strong against mechanical shock.
- the protrusion 424 can be prevented from being damaged.
- the hatched portion described on the appearance of the circuit package 400 is used in the second resin molding process when the housing 302 is molded in the second resin molding process after the circuit package 400 is manufactured in the first resin molding process.
- 3 shows a fixed surface 432, a fixed surface 433, and a fixed surface 434 on which the circuit package 400 is covered with resin. That is, the mechanical strength of the circuit package 400 is increased by these fixing surfaces, and in particular, the mechanical strength at the base of the protruding portion 424 can be improved by the fixing surface 432.
- the hatched portion in FIG. 24 is a portion covered with a resin for forming the housing 302 in the second resin molding step, as described with reference to FIG. Covering the base of the protrusion 424 provides mechanical reinforcement. Further, since the portion of the fixed surface 432 is covered with the resin forming the housing 302 and both sides thereof are covered with the resin across the measurement channel surface 430, the sub-passage, the measurement channel surface 430, the heat transfer surface exposed portion 436, and the like. Is firmly fixed with high accuracy. Further, since the fixing portion 433 is also formed in the protruding portion 426, the circuit package 400 can be firmly fixed.
- the fixing portion 433 is located away from the fixing surface 432 and the fixing surface 434, and the length direction of the fixing portion is a direction in which the longitudinal axes intersect with each other, the fixing becomes easy. . Conversely, the area that the housing 302 covers the circuit package 400 can be reduced, and stress due to a difference in thermal expansion can be reduced.
- the present invention can be applied to the measuring device for measuring the gas flow rate described above.
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Abstract
Description
図1は、電子燃料噴射方式の内燃機関制御システムに、本発明に係る熱式流量計を使用した一実施例を示す、システム図である。エンジンシリンダ112とエンジンピストン114を備える内燃機関110の動作に基づき、吸入空気が被計測気体30としてエアクリーナ122から吸入され、主通路124である例えば吸気ボディ、スロットルボディ126、吸気マニホールド128を介してエンジンシリンダ112の燃焼室に導かれる。前記燃焼室に導かれる吸入空気である被計測気体30の流量は本発明に係る熱式流量計300で計測され、計測された流量に基づいて燃料噴射弁152より燃料が供給され、吸入空気である被計測気体30と共に混合気の状態で燃焼室に導かれる。なお、本実施例では、燃料噴射弁152は内燃機関の吸気ポートに設けられ、吸気ポートに噴射された燃料が吸入空気である被計測気体30と共に混合気を成形し、吸入弁116を介して燃焼室に導かれ、燃焼して機械エネルギを発生する。
エアクリーナ122から取り込まれ主通路124を流れる吸入空気である被計測気体30の流量および温度が、熱式流量計300により計測され、熱式流量計300から吸入空気の流量および温度を表す電気信号が制御装置200に入力される。また、スロットルバルブ132の開度を計測するスロットル角度センサ144の出力が制御装置200に入力され、さらに内燃機関のエンジンピストン114や吸入弁116や排気弁118の位置や状態、さらに内燃機関の回転速度を計測するために、回転角度センサ146の出力が、制御装置200に入力される。排気ガス24の状態から燃料量と空気量との混合比の状態を計測するために、酸素センサ148の出力が制御装置200に入力される。
内燃機関の主要な制御量である燃料供給量や点火時期はいずれも熱式流量計300の出力を主パラメータとして演算される。また必要に応じて吸入空気の温度に基づいて制御パラメータの補正などが行われる。熱式流量計300の計測精度の向上や経時変化の抑制、信頼性の向上が、車両の制御精度の向上や信頼性の確保に関して重要である。特に近年、車両の省燃費に関する要望が非常に高く、また排気ガス浄化に関する要望が非常に高い。これらの要望に応えるには熱式流量計300により計測される吸入空気である被計測気体30の流量の計測精度の向上が極めて重要である。また熱式流量計300が高い信頼性を維持していることも大切である。
2.1 熱式流量計300の外観構造
図2および図3、図4は、熱式流量計300の外観を示す図であり、図2(A)は熱式流量計300の左側面図、図2(B)は正面図、図3(A)は右側面図、図3(B)は背面図、図4(A)は平面図、図4(B)は下面図である。熱式流量計300はケース301を有し、ケース301はハウジング302と表カバー303と裏カバー304とを備えている。ハウジング302は、熱式流量計300を主通路124である吸気ボディに固定するためのフランジ312と、外部機器との電気的な接続を行うための外部端子306を有する外部接続部305と、流量等を計測するための計測部310を備えている。計測部310の内部には、副通路を作るための副通路溝が設けられており、さらに計測部310の内部には、主通路124を流れる被計測気体30の流量を計測するための流量検出部602(図19参照)や主通路124を流れる被計測気体30の温度を計測するための温度検出部452を備える回路パッケージ400が設けられている。
熱式流量計300の入口350が、フランジ312から主通路124の中心方向に向かって延びる計測部310の先端側に設けられているので、主通路124の内壁面近傍ではなく、内壁面から離れた中央部に近い部分の気体を副通路に取り込むことができる。このため熱式流量計300は主通路124の内壁面から離れた部分の気体の流量や温度を測定することができ、熱などの影響による計測精度の低下を抑制できる。主通路124の内壁面近傍では、主通路124の温度の影響を受け易く、気体の本来の温度に対して被計測気体30の温度が異なる状態となり、主通路124内の主気体の平均的な状態と異なることになる。特に主通路124がエンジンの吸気ボディである場合は、エンジンからの熱の影響を受け、高温に維持されていることが多い。このため主通路124の内壁面近傍の気体は、主通路124の本来の気温に対して高いことが多く、計測精度を低下させる要因となる。
熱式流量計300を構成する計測部310の上流側側面と下流側側面にそれぞれ上流側突起317と下流側突起318とが設けられている。上流側突起317と下流側突起318は根元に対して先端に行くに従い細くなる形状を成しており、主通路124内を流れる吸入空気である被計測気体30の流体抵抗を低減できる。熱絶縁部315と入口343との間に上流側突起317が設けられている。上流側突起317は断面積が大きく、フランジ312あるいは熱絶縁部315からの熱伝導が大きいが、入口343の手前で上流側突起317が途切れており、さらに上流側突起317の温度検出部452側から温度検出部452への距離が、後述するようにハウジング302の上流側外壁の窪みにより、長くなる形状を成している。このため温度検出部452の支え部分への熱絶縁部315からの熱伝導が抑制される。
フランジ312には、その下面である主通路124と対向する部分に、窪み314が複数個設けられており、主通路124との間の熱伝達面を低減し、熱式流量計300が熱の影響を受け難くしている。フランジ312のねじ孔313は熱式流量計300を主通路124に固定するためのもので、これらのねじ孔313の周囲の主通路124に対向する面が主通路124から遠ざけられるように、各ねじ孔313の周囲の主通路124に対向する面と主通路124との間に空間が成形されている。このようにすることで、熱式流量計300に対する主通路124からの熱伝達を低減し、熱による測定精度の低下を防止できる構造をしている。さらにまた前記窪み314は、熱伝導の低減効果だけでなく、ハウジング302の成形時にフランジ312を構成する樹脂の収縮の影響を低減する作用をしている。
図4(A)は熱式流量計300の平面図である。外部接続部305の内部に4本の外部端子306と補正用端子307が設けられている。外部端子306は熱式流量計300の計測結果である流量と温度を出力するための端子および熱式流量計300が動作するための直流電力を供給するための電源端子である。補正用端子307は生産された熱式流量計300の計測を行い、それぞれの熱式流量計300に関する補正値を求めて、熱式流量計300内部のメモリに補正値を記憶するのに使用する端子であり、その後の熱式流量計300の計測動作では上述のメモリに記憶された補正値を表す補正データが使用され、この補正用端子307は使用されない。従って外部端子306が他の外部機器との接続において、補正用端子307が邪魔にならないように、補正用端子307は外部端子306とは異なる形状をしている。この実施例では外部端子306より補正用端子307が短い形状をしており、外部端子306に接続される外部機器への接続端子が外部接続部305に挿入されても、接続の障害にならないようになっている。また外部接続部305の内部には外部端子306に沿って複数個の窪み308が設けられており、これら窪み308は、フランジ312の材料である樹脂が冷えて固まる時の樹脂の収縮による応力集中を低減するためのものである。
3.1 副通路と流量検出部の構造と効果
熱式流量計300から表カバー303および裏カバー304を取り外したハウジング302の状態を図5および図6に示す。図5(A)はハウジング302の左側面図であり、図5(B)はハウジング302の正面図であり、図6(A)はハウジング302の右側面図であり、図6(B)はハウジング302の背面図である。ハウジング302はフランジ312から計測部310が主通路124の中心方向に延びる構造を成しており、その先端側に副通路を成形するための副通路溝が設けられている。この実施例ではハウジング302の表裏両面に副通路溝が設けられており、図5(B)に表側副通路溝332を示し、図6(B)に裏側副通路溝334を示す。副通路の入口350を成形するための入口溝351と出口352を成形するための出口溝353が、ハウジング302の先端部に設けられているので、主通路124の内壁面から離れた部分の気体を、言い換えると主通路124の中央部分に近い部分を流れている気体を被計測気体30として入口350から取り込むことができる。主通路124の内壁面近傍を流れる気体は、主通路124の壁面温度の影響を受け、吸入空気である被計測気体30などの主通路124を流れる気体の平均温度と異なる温度を有することが多い。また主通路124の内壁面近傍を流れる気体は、主通路124を流れる気体の平均流速より遅い流速を示すことが多い。実施例の熱式流量計300ではこのような影響を受け難いので、計測精度の低下を抑制できる。
図7は、回路パッケージ400の流路面430が副通路溝の内部に配置されている状態を示す部分拡大図であり、図6のA-A断面図である。なお、この図は概念図であり、図5や図6に示す詳細形状に対して、図7では細部の省略および単純化を行っており、細部に関して少し変形している。図7の左部分が裏側副通路溝334の終端部であり、右側部分が表側副通路溝332の始端部分である。図7では明確に記載していないが、計測用流路面430を有する回路パッケージ400の左右両側には、孔342と孔341とが設けられていて、計測用流路面430を有する回路パッケージ400の左右両側で裏側副通路溝334と表側副通路溝332とが繋がっている。
図8は表カバー303の外観を示す図であり、図8(A)は左側面図、図8(B)は正面図、図8(C)は平面図である。図9は裏カバー304の外観を示す図であり、図9(A)は左側面図、図9(B)は正面図、図9(C)は平面図である。図8および図9において、表カバー303や裏カバー304はハウジング302の副通路溝を塞ぐことにより、副通路を作るのに使用される。また突起部356が備え絞りを作るのに使用される。このため成形精度が高いことが望ましい。表カバー303や裏カバー304は金型に熱可塑性樹脂を注入する樹脂モールド工程により、作られるので、高い成形精度で作ることができる。
図10は図5および図6に示すハウジング302の端子接続部320の拡大図である。しかし次の点が少し異なっている。図5および図6の記載と異なる点は、図5および図6では各外部端子内端361がそれぞれ切り離されているのに対し、図10では各外部端子内端361が切り離される前の状態を示しており、各外部端子内端361はそれぞれ繋ぎ部365で繋がっている。外部端子306の回路パッケージ400側に突出する外部端子内端361が、それぞれ対応する接続端子412と重なり合うように、あるいは対応する接続端子412の近傍に来るようにして、第2モールド工程で、各外部端子306が樹脂モールドによりハウジング302に固定されている。各外部端子306の変形や配置のずれを防ぐために、一実施例として、外部端子内端361が互いに繋ぎ部365でつながった状態で、ハウジング302を成形するための樹脂モールド工程(第2樹脂モールド工程)により外部端子306をハウジング302に固定する。ただし、先に接続端子412と外部端子内端361とを固定して、その後第2モールド工程により外部端子306をハウジング302に固定しても良い。
図10に示す実施例では、外部端子内端361の数より回路パッケージ400が有する端子の数が多い。回路パッケージ400が有する端子の内、接続端子412が外部端子内端361にそれぞれ接続されており、端子414は外部端子内端361に接続されない。すなわち端子414は、回路パッケージ400に設けられているが、外部端子内端361に接続されない端子である。
図10の部分拡大図に示す如く、ハウジング302には孔364が設けられている。孔364は図4(A)に示す外部接続部305の内部に設けられた開口309につながっている。実施例では、ハウジング302の両面が表カバー303と裏カバー304で密閉されている。もし孔364が設けられていないと、端子接続部320を含む空隙内の空気の温度変化により、前記空隙内の気圧と外気圧との間に差が生じる。このような圧力差はできるだけ小さいことが望ましい。このため外部接続部305内に設けられた開口309につながる孔364がハウジング302の空隙内に設けられている。外部接続部305は電気的接続の信頼性向上のため、水などによる悪影響を受けない構造としており、開口309を外部接続部305内に設けることで、開口309からの水の浸入を防止でき、さらにごみや埃などの異物の侵入も防止できる。
4.1 ハウジング302の固定部などによる回路パッケージ400の固定構造
次に再び図5および図6を参照して、回路パッケージ400のハウジング302への樹脂モールド工程による固定について説明する。副通路を成形する副通路溝の所定の場所、例えば図5および図6に示す実施例では、表側副通路溝332と裏側副通路溝334のつながりの部分に、回路パッケージ400の表面に成形された計測用流路面430が配置されるように、回路パッケージ400がハウジング302に配置され固定されている。回路パッケージ400をハウジング302に樹脂モールドにより埋設して固定する部分が、副通路溝より少しフランジ312側に、回路パッケージ400をハウジング302に埋設固定するための固定部372として設けられている。固定部372は第1樹脂モールド工程により成形された回路パッケージ400の外周を覆うようにして埋設している。
また回路パッケージ400の外周面の内のハウジング302の樹脂に包含される部分の面積を少なくして、少ない面積で、より強固に回路パッケージ400を固定するには、固定部372における回路パッケージ400の外壁との密着性を高めることが望ましい。ハウジング302を成形する趣旨として熱可塑性樹脂を使用する場合には、熱可塑性樹脂の粘性が低い状態で回路パッケージ400の外壁の細かい凹凸に入り込み、前記外壁の細かい凹凸に入り込んだ状態で、熱可塑性樹脂が硬化することが望ましい。ハウジング302を成形する樹脂モールド工程において、熱可塑性樹脂の入口を固定部372にあるいはその近傍に設けることが望ましい。熱可塑性樹脂は温度の低下に基づいて粘性が増大し、硬化する。従って高温状態の熱可塑性樹脂を固定部372にあるいはその近傍から流し込むことで、粘性の低い状態の熱可塑性樹脂を回路パッケージ400の外壁に密着させ、硬化させることができる。また、固定部372に窪み376や窪み378、窪み373を成形することで、これら窪みを作るための金型により、熱可塑性樹脂の流れを制限する障害部が作られ、固定部372での熱可塑性樹脂の移動速度が低下する。このことにより熱可塑性樹脂の温度低下が抑えられ、低粘性状態を長引かせ、回路パッケージ400と固定部372との密着性が向上する。
上述した図5および図6に示すハウジング302において、流量検出部602や処理部604を備える回路パッケージ400を第1樹脂モールド工程により製造し、次に、被計測気体30を流す副通路を成形する例えば表側副通路溝332や裏側副通路溝334を有するハウジング302を、第2樹脂モールド工程にて製造する。この第2樹脂モールド工程で、前記回路パッケージ400をハウジング302の樹脂内に内蔵して、ハウジング302内に樹脂モールドにより固定する。このようにすることで、流量検出部602が被計測気体30との間で熱伝達を行って流量を計測するための熱伝達面露出部436と副通路、例えば表側副通路溝332や裏側副通路溝334の形状との関係、例えば位置関係や方向の関係を、極めて高い精度で維持することが可能となる。回路パッケージ400毎に生じる誤差やばらつきを非常に小さい値に抑え込むことが可能となる。結果として回路パッケージ400の計測精度を大きく改善できる。例えば従来の接着剤を使用して固定する方式に比べ、2倍以上、計測精度を向上できる。熱式流量計300は量産により生産されることが多く、ここに厳密に計測しながら接着剤で接着する方法には、計測精度の向上に関して限界がある。しかし、本実施例のように第1樹脂モールド工程により回路パッケージ400を製造し、その後被計測気体30を流す副通路を成形する第2樹脂モールド工程にて副通路を成形すると同時に回路パッケージ400と前記副通路とを固定することで、計測精度のばらつきを大幅に低減でき、各熱式流量計300の計測精度を大幅に向上することが可能となる。このことは、図5や図6に示す実施例だけでなく、図7に示す実施例においても同様である。
図11で斜線の部分は、第2樹脂モールド工程において、ハウジング302に回路パッケージ400を固定するために、第2樹脂モールド工程で使用する熱可塑性樹脂で回路パッケージ400を覆うための、固定面432および固定面434を示している。図5や図6を用いて説明したとおり、計測用流路面430および計測用流路面430に設けられている熱伝達面露出部436と副通路の形状との関係が、規定の関係となるように、高い精度で維持されることが重要である。第2樹脂モールド工程において、副通路を成形すると共に同時に副通路を成形するハウジング302に回路パッケージ400を固定するので、前記副通路と計測用流路面430および熱伝達面露出部436との関係を極めて高い精度で維持できる。すなわち、第2樹脂モールド工程において回路パッケージ400をハウジング302に固定するので、副通路を備えたハウジング302を成形するための金型内に、回路パッケージ400を高い精度で位置決めして固定することが可能であり、この金型内に高温の熱可塑性樹脂を注入することで、成型後の副通路に対して、回路パッケージ400が高い精度で固定される。
5.1 回路パッケージのフレーム枠と回路部品の搭載
図12に回路パッケージ400のフレーム枠512およびフレーム枠512に搭載された回路部品516のチップの搭載状態を示す。なお、破線部508は、回路パッケージ400のモールド成形時に用いられる金型により覆われる部分を示す。フレーム枠512にリード514が機械的に接続されており、フレーム枠512の中央に、プレート532が搭載され、プレート532にチップ状の流量検出部602およびLSIとして作られている処理部604が搭載されている。流量検出部602にはダイヤフラム672が設けられており、以下に説明する流量検出部602の各端子と処理部604とがワイヤ542で電気的に接続されている。さらに処理部604の各端子と対応するリード514とがワイヤ543で接続されている。また回路パッケージ400の接続端子となる部分とプレート532との間に位置するリード514は、それらの間にチップ状の回路部品516が接続されている。
図13は、図12のC-C断面の一部を示す図であり、ダイヤフラム672およびダイヤフラム672の内部に設けられた空隙674と孔520とを繋ぐ連通孔676を説明する、説明図である。
図15は回路パッケージ400の他の実施例である。他の図に示されている符号と同じ符号は同じ作用をする構成である。先に説明した図11に示す実施例では、回路パッケージ400は、接続端子412と端子414とが回路パッケージ400の同じ辺に設けられている。これに対して図15に示す実施例では、接続端子412と端子414は異なる辺に設けられている。端子414は、熱式流量計300が有する外部との接続端子に接続されない端子である。このように、熱式流量計300が有する外部に接続する接続端子412と外部に接続しない端子414とを異なる方向に設けることにより、接続端子412の端子間を広くでき、その後の作業性が向上する。また端子414を接続端子412と異なる方向に延びるようにすることで、枠512内のリードが一部に集中するのを低減でき、枠512内でのリードの配置が容易となる。とくに接続端子412に対応するリードの部分には、回路部品516であるチップコンデンサなどが接続される。これら回路部品516を設けるにはやや広いスペースが必要となる。図15の実施例では、接続端子412に対応するリードのスペースを確保し易い効果がある。
6.1 回路パッケージ400の生産工程
図16は熱式流量計300の生産工程の内の回路パッケージ400の生産工程を示す。図17は熱式流量計の生産工程を示し、図18は熱式流量計の生産工程の他の実施例を示す。図16において、ステップ1は図12に示すフレーム枠を生産する工程を示す。このフレーム枠は例えばプレス加工によって作られる。ステップ2では、ステップ1で作られたフレーム枠に、まずプレート532を搭載し、さらにプレート532に流量検出部602や処理部604を搭載し、さらに温度検出素子518、チップコンデンサなどの回路部品を搭載する。またステップ2では、回路部品間や回路部品とリード間、リード同士の電気的な配線を行う。このステップ2において、リード544とリード548の間を、熱抵抗を大きくするための接続線546で接続する。ステップ2では、図12に示す、回路部品がフレーム枠512に搭載され、さらに電気的な接続がなされた電気回路が作られる。
図17では、図16により既に生産されている回路パッケージ400と既に図示しない方法で生産されている外部端子306とが使用される。ステップ5では、第2樹脂モールド工程によりハウジング302がつくられる。このハウジング302は樹脂製の副通路溝やフランジ312や外部接続部305が作られると共に、図11に示す回路パッケージ400の斜線部分が第2樹脂モールド工程の樹脂で覆われ、回路パッケージ400がハウジング302に固定される。前記第1樹脂モールド工程による回路パッケージ400の生産(ステップ3)と第2樹脂モールド工程による熱式流量計300のハウジング302の成形との組み合わせにより、流量検出精度が大幅に改善される。ステップ6で図10に示す各外部端子内端361の切り離しが行われ、接続端子412と外部端子内端361との接続がステップ7で行われる。
図18で、図16により既に生産された回路パッケージ400と図示しない方法で既に生産された外部端子306とが使用され、第2樹脂モールド工程の前にステップ12で、回路パッケージ400の接続端子412と外部端子内端361との接続が行われる。この際、若しくはステップ12よりも前の工程で図10に示す各外部端子内端361の切り離しが行われる。ステップ13で第2樹脂モールド工程によりハウジング302がつくられる。このハウジング302は樹脂製の副通路溝やフランジ312や外部接続部305が作られると共に、図11に示す回路パッケージ400の斜線部分が第2樹脂モールド工程の樹脂で覆われ、回路パッケージ400がハウジング302に固定される。前記第1樹脂モールド工程による回路パッケージ400の生産(ステップ3)と第2樹脂モールド工程による熱式流量計300のハウジング302の成形との組み合わせにより、流量検出精度が大幅に改善される。
7.1 熱式流量計300の回路構成の全体
図19は熱式流量計300の流量検出回路601を示す回路図である。なお、先に実施例で説明した温度検出部452に関する計測回路も熱式流量計300に設けられているが、図19では省略している。熱式流量計300の流量検出回路601は、発熱体608を有する流量検出部602と処理部604とを備えている。処理部604は、流量検出部602の発熱体608の発熱量を制御すると共に、流量検出部602の出力に基づいて流量を表す信号を、端子662を介して出力する。前記処理を行うために、処理部604は、Central Processing Unit(以下CPUと記す)612と入力回路614、出力回路616、補正値や計測値と流量との関係を表すデータを保持するメモリ618、一定電圧をそれぞれ必要な回路に供給する電源回路622を備えている。電源回路622には車載バッテリなどの外部電源から、端子664と図示していないグランド端子を介して直流電力が供給される。
図20は、上述した図19の流量検出回路601の回路配置を示す回路構成図である。流量検出回路601は矩形形状の半導体チップとして作られており、図20に示す流量検出回路601の左側から右側に向って、矢印の方向に、被計測空気30が流れる。
8.1 熱式流量計300における温度検出部452の構造
図2および図3において、計測部310の先端側である、主通路124の中央側に、副通路が設けられている。前記副通路よりもフランジ312側に、被計測気体30の流れの上流側に向かって開口する入口343が図2(A)に示すように形成されている。入口343の内部には被計測気体30の温度を計測するための温度検出部452が、ハウジング302の内部から突出するようにして配置されている。入口343が設けられている計測部310の中央部では、ハウジング302を構成する計測部310の上流側外壁が下流側に向かって、すなわちハウジング302の内側に向かって、窪んでおり、前記窪み形状の上流側外壁から温度検出部452が上流側に向かってハウジング302から外に突出する形状を成している。また前記窪み形状の外壁の両側部には表カバー303と裏カバー304が設けられており、前記表カバー303と裏カバー304の上流側端部が、前記窪み形状の外壁より上流側に向かって突出した形状を成している。このため前記窪み形状の外壁とその両側の表カバー303と裏カバー304とにより、被計測気体30を取り込むための入口343が成形される。入口343から取り込まれた被計測気体30は入口343の内部に設けられた温度検出部452に接触することで、温度検出部452によって温度が計測される。さらに窪み形状を成すハウジング302の外壁から上流側に突出した温度検出部452を支える部分に沿って被計測気体30が流れ、表カバー303と裏カバー304に設けられた表側出口344および裏側出口345が主通路124に排出される。
図2や図3に示す如く、温度検出部452がハウジング302から外に突出して、直接被計測気体30に触れる構造となっているので、検出精度が向上する。また被計測気体30の流れに沿う方向の上流側から入口343に流入する気体の温度が温度検出部452により計測され、さらにその気体が温度検出部452を支える部分である温度検出部452の根元部分に向かって流れることにより、温度検出部452を支える部分の温度を被計測気体30の温度に近づく方向に冷却する作用を為す。主通路124である吸気管の温度が通常高くなり、フランジ312あるいは熱絶縁部315から計測部310内の上流側外壁を通って、温度検出部452を支える部分に熱が伝わり、温度の計測精度に影響を与える恐れがある。上述のように、被計測気体30が温度検出部452により計測された後、温度検出部452の支える部分に沿って流れることにより、前記支える部分が冷却される。従ってフランジ312あるいは熱絶縁部315から計測部310内の上流側外壁を通って温度検出部452を支える部分に熱が伝わるのを抑制できる。
回路パッケージ400は、流量を計測するための後述する流量検出部602や処理部604を内蔵している回路パッケージ本体422と突出部424とを有している。図2に示すように回路パッケージ本体422の側面から突出部424が被計測気体30の上流方向に延びている形状で突出している。突出部424の先端部に温度検出部452が設けられ、温度検出部452の内部に、図12に示す如く、温度検出素子518が埋設されている。突出部424と回路パッケージ本体422とのつながり部には、図11や図15に示す如く、傾斜部462および464が設けられている。この傾斜部462あるいは傾斜部464により突出部424の根元を太くし、先端方向に進むにつれて徐々に細くなる形状が突出部424の根元部に作られる。突出方向の軸に対して前記軸を横切る断面積が、突出部424の根元部で、先端方向に進むにつれて減少する形状を有している。このように、回路パッケージ400が一部突出した形状においては、突出部424は機械的な強度が弱いため、突出部424の根元を太くし、先端方向に進むにつれて徐々に細くなる形状とすることにより、根元への応力の集中を緩和するとともに機械的な強度を向上することができる。また樹脂モールドで突出部424を作る場合に、樹脂が固まるときの体積変化などの影響で、反りなどが生じやすい。根元を太くすることで、このような課題に対しても影響を低減できる。さらに、被計測気体30の温度をできるだけ正確に検出するためには突出長さを長くすることが望ましく、根元を太くすることで突出部424の突出長さを長くすることが可能となり、温度検出部452に設けられた温度検出素子518の検出精度が向上する。
図11や図15で説明したごとく、突出部424の根元部に傾斜部462および464が設けられている。この傾斜部462あるいは傾斜部464により突出部424の根元を太くし、先端方向に進むにつれて徐々に細くなる形状が突出部424の根元部に作られる。すなわち突出方向を軸とした場合に前記突出方向の軸を横切る断面積が徐々に減少する形状が、突出部424の根元部に設けられている。
図21は回路パッケージ400の突出部424の他の実施例であり、先に説明した図面と同じ参照符号は、同じ構造であり、同じ作用効果を為す。従って説明を省略する。回路パッケージ本体422から突出している突出部424は、平面側および裏面側に突起446および突起447を有している。これら突起446および突起447はどちらか一方だけでも効果がある。またこの実施例では、平面側および裏面側に1本ずつ突起が成形されているが、複数本の突起を備えても良い。各突起は根元部448と先端部449とを有し、根元部448から先端部449に向かうにしたがってその高さが低くなっている。図11に示す如く、突出部424の根元部はハウジング302を成形する樹脂に覆われる。このため、第2樹脂モールド工程で、突出部424の根元部と共に突起446や突起447の根元部448も樹脂で覆われる。
図22は、パッケージ本体422から突出する突出部424の部分拡大図であり、図22(A)は、図11(B)や図15(A)に記載の正面図の部分拡大図であり、図22(B)は平面図である。図22(A)に示す傾斜部462や傾斜部464は、図11(B)や図15(A)に示す傾斜部462や傾斜部464に対してさらに曲線を描いている。すなわち図11(B)や図15(A)に示す傾斜部462や傾斜部464は直線または曲線であってもよい。しかし、どちらにしても略同じような効果が得られる。
図23乃至図25はさらに他の実施例を示す。図23は他の実施例である回路パッケージ400をハウジング302によって固定した図であり、図5あるいは図6で説明した実施例の代案である。また図24は図11や図15で説明した実施例の他の実施例である。図25は図12の他の実施例であり、図24で示す他の実施例の回路パッケージ400のフレーム枠に回路部品を搭載した状態を示す図である。図23乃至図25の実施例では、回路パッケージ400のパッケージ本体422から主通路124の中心方向に向かって突出部424が突出している。ハウジング302の計測部310の先端側である、主通路124の中心側に副通路の入口および出口が成形されている。図23では入口が裏面側となり図には表れない。出口を形成するための出口溝353が計測部310の先端側に設けられている。図23の裏面側に形成されている入口から被計測気体30が取り込まれ、主通路124の壁面方向に入口と出口とを繋ぐ副通路(以下副通路計測部435と記す)が形成され、副通路計測部435に流量を計測するための計測用流路面430が設けられている。
302 ハウジング
303 表カバー
304 裏カバー
305 外部接続部
306 外部端子
307 補正用端子
310 計測部
320 端子接続部
332 表側副通路溝
334 裏側副通路溝
356、358 突起部
359 樹脂部
361 外部端子内端
365 繋ぎ部
372、374 固定部
400 回路パッケージ
412 接続端子
414 端子
422 パッケージ本体
424 突出部
430 計測用流路面
432、434 固定面
436 熱伝達面露出部
438 開口
452 温度検出部
590 圧入孔
594、596 傾斜部
601 流量検出回路
602 流量検出部
604 処理部
608 発熱体
640 発熱制御ブリッジ
650 流量検知ブリッジ
672 ダイヤフラム
Claims (14)
- 主通路を流れる被計測気体を取り込んで流すための副通路と、前記副通路を流れる被計測気体との間で熱伝達を行うことにより流量を計測するための流量計測回路と前記被計測気体の温度を検出する温度検出部とを有する回路パッケージと、前記流量を表す電気信号や前記被計測気体の温度を表す電気信号を出力する外部端子を備えると共に前記回路パッケージを支持するケースと、を備え、
前記回路パッケージは、前記流量計測回路や前記温度検出部を樹脂で包含された構成からなり、前記温度検出部が回路パッケージ本体から突出した突出部を有し、
前記突出部の根元がその先端部より太く、さらに前記突出部の根元部において、先端に向かって徐々に細くなる形状を有している、ことを特徴とする熱式流量計。 - 請求項1に記載の熱式流量計において、
前記突出部の根元は、突出方向に対して垂直な断面においてその先端部より大きく、前記突出部の先端に向かって前記断面が徐々に小さくなる形状を有している、ことを特徴とする熱式流量計。 - 請求項1に記載の熱式流量計において、
前記突出部の外周から外に向かう突起が形成されており、
前記突起は、前記突出部の前記根元から前記突出部の前記先端の方に向かって延びている、ことを特徴とする熱式流量計。 - 請求項3に記載の熱式流量計において、
前記突起は、前記突出部の前記根元部で前記ハウジングの樹脂に覆われている、ことを特徴とする熱式流量計。 - 請求項1に記載の熱式流量計において、
前記パッケージ本体は、平らな二面と、前記各二面の外周に形成され、前記各二面を繋ぐ側面と、を有し、前記側面から前記突出部が突出する形状を成し、前記側面と前記突出部のつながり部分が前記根元部を構成し、対向する前記つながり部分の間が先端に向かって徐々に細くなる形状を有している、ことを特徴とする熱式流量計。 - 請求項1に記載の熱式流量計において、
前記パッケージ本体は、平らな二面と、前記各二面の外周に形成され、前記各二面を繋ぐ側面と、を有し、前記側面から前記突出部が突出する形状を成し、前記平らな二面の間の厚さが前記突出部の前記温度検出部より厚い形状を成し、
前記厚さが、先端に向かって徐々に細くなる形状を有している、ことを特徴とする熱式流量計。 - 請求項1乃至請求項6の内の一に記載の熱式流量計において、
前記パッケージ本体から突出している前記突出部は、主通路を流れる被計測気体の流れの上流方向に向かって突出している、ことを特徴とする熱式流量計。 - 請求項1乃至請求項6の内の一に記載の熱式流量計において、
前記パッケージ本体から突出している前記突出部は、前記副通路の方向に向かって突出している、ことを特徴とする熱式流量計。 - 請求項8に記載の熱式流量計において、
副通路は、前記主通路の中央側に入口および出口を有し、前記入口および前記出口を繋ぐ通路を、前記入口および前記出口より前記主通路の壁面側に有し、
前記入口および前記出口と、前記入口および前記出口を繋ぐ前記通路と、の間に前記主通路に開口する孔を設け、
前記パッケージ本体から突出している前記突出部を、前記副通路の方向に向かって突出させ、前記突出部の先端に設けられた温度検出部が前記主通路に開口する前記孔に配置される、ことを特徴とする熱式流量計。 - 請求項1乃至請求項9の内の一に記載の熱式流量計において、
前記パッケージ本体から突出している前記突出部は、その内部にリードを備えており、前記リードの先端部に温度検出素子が電気的に接続されている、ことを特徴とする熱式流量計。 - 請求項10に記載の熱式流量計において、
前記突出部は、その内部に、前記温度検出素子が接続された第1のリードと、前記パッケージ本体の内部の電気回路と接続される第2のリードと、前記第1のリードと前記第2のリードとの間に設けられ、前記第1のリードと前記第2のリードとを電気的に接続するための接続線と、を有する、ことを特徴とする熱式流量計。 - 請求項7に記載の熱式流量計において、
前記回路パッケージを保持すると共に前記回路パッケージで計測された流量を表す電気信号および気体の温度を表す電気信号を出力するための外部端子を備えるハウジングを有し、
前記回路パッケージの前記回路パッケージ本体が前記ハウジングの内部に設けられ、前記回路パッケージが有する前記突出部が前記ハウジングから外に突出している、ことを特徴とする熱式流量計。 - 請求項7に記載の熱式流量計において、回路パッケージ本体はその内部に流量を計測するためのダイヤフラムと流量を出力する処理部とを有しており、前記ダイヤフラムの位置と前記処理部の位置とを結ぶ線に対して前記線を横切る方向に、前記突出部が前記回路パッケージ本体から突出している、ことを特徴とする熱式流量計。
- 請求項8に記載の熱式流量計において、回路パッケージ本体はその内部に流量を計測するためのダイヤフラムと流量を出力する処理部とを有しており、前記ダイヤフラムの位置と前記処理部の位置とを結ぶ線に対して前記線に沿う方向に、前記突出部が前記回路パッケージ本体から突出している、ことを特徴とする熱式流量計。
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US14/407,152 US9541437B2 (en) | 2012-06-15 | 2013-05-29 | Thermal flow meter with a circuit package having an air flow measurement circuit for measuring an air flow |
DE112013002965.0T DE112013002965T5 (de) | 2012-06-15 | 2013-05-29 | Thermischer Durchflussmesser |
CN201380031595.0A CN104380055B (zh) | 2012-06-15 | 2013-05-29 | 热式流量计 |
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DE102017206226A1 (de) * | 2017-04-11 | 2018-10-11 | Robert Bosch Gmbh | Sensor zur Erfassung mindestens einer Eigenschaft eines fluiden Mediums |
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