JP6775650B2 - Thermal flow meter - Google Patents

Description

The present invention relates to a thermal flow meter.

The thermal flow meter for measuring the flow rate of a gas is provided with a flow rate detecting unit for measuring the flow rate, and the flow rate of the gas is measured by transferring heat between the flow rate detecting unit and the gas to be measured. It is configured to measure. The flow rate measured by a thermal flow meter is widely used as an important control parameter for various devices. A feature of the thermal flow meter is that it can measure the flow rate of gas, for example, mass flow rate, with relatively high accuracy compared to other types of flow meters.

However, further improvement in measurement accuracy of gas flow rate is desired. For example, in a vehicle equipped with an internal combustion engine, there is a very high demand for fuel saving and exhaust gas purification. To meet these demands
It is required to measure the intake air amount, which is a main parameter of an internal combustion engine, with high accuracy. The thermal flow meter that measures the amount of intake air guided to the internal combustion engine includes a sub-passage that takes in a part of the intake air amount and a flow rate detection unit arranged in the sub-passage, and the flow rate detection unit is the gas to be measured. By transferring heat to and from, the state of the gas to be measured flowing through the sub-passage is measured, and an electric signal representing the amount of intake air guided to the internal combustion engine is output. Such a technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 2011-252996 (Patent Document 1).

Japanese Unexamined Patent Publication No. 2011-252996

In order to measure the flow rate of gas with high accuracy by the thermal flow meter, the flow rate detection unit of the thermal flow meter is installed in the sub passage provided in the thermal flow meter for taking in the gas flowing through the main passage. It is required to position and fix with high accuracy. In the technique described in Patent Document 1, a housing having a sub-passage in which a hole for fitting a flow rate detection unit is formed is manufactured in advance from resin, and a sensor assembly having a flow rate detection unit is provided separately from this housing. The sensor assembly is fixed to the housing in a state where the flow rate detection unit is inserted into the hole of the sub-passage after manufacturing. An elastic adhesive is filled in the gap between the hole of the sub-passage and the flow rate detecting portion and the gap of the fitting portion of the sensor assembly into the housing, and the difference in linear expansion between the two is absorbed by the elastic force of the adhesive. To do.

With such a structure, it is difficult to accurately set and fix the positional relationship and the angular relationship between the flow rate detection unit and the sub-passage when the sensor assembly is fitted into the housing. That is, there is a problem that the positional relationship and the angular relationship between the sensor assembly and the sub-passage provided in the housing easily change depending on the state of the adhesive and the like. Therefore, it has been difficult to further improve the flow rate detection accuracy with the conventional thermal flow meter. In general, thermal flowmeters are mass-produced. In this mass production process, when the flow rate detection unit is fixed to the sub-passage in a predetermined positional relationship or angle relationship using an adhesive, the flow rate detection unit is used during bonding using the adhesive and in the solidification process of the adhesive. It was difficult to determine the positional relationship and the angular relationship between the and the sub-passage, and it was extremely difficult to maintain and fix these positional relationships with high accuracy. For this reason, it has been difficult to further improve the measurement accuracy of the thermal flowmeter in the past.

An object of the present invention is to provide a thermal flow meter with high measurement accuracy.

In order to solve the above problems, the thermal flowmeter of the present invention transfers heat 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 measuring circuit for measuring the flow rate and a first resin for sealing the flow rate measuring circuit, and for accommodating the circuit package and connecting to an external device. A housing made of a second resin having an external connection portion and having a thermal expansion coefficient different from that of the first resin is provided, and the circuit package is for at least outputting the measurement result of the flow rate measurement circuit. It has a measurement terminal and an inspection terminal for inspecting the flow rate measurement circuit after sealing with the first resin, and the measurement terminal and the inspection terminal are different from each other in the circuit package. Provided on the side, the inspection terminal has a shorter shape than the measurement terminal.

According to the present invention, a thermal flowmeter with high measurement accuracy can be obtained.

It is a system diagram which shows an Example which used the thermal flow meter which concerns on this invention in an internal combustion engine control system. It is a figure which shows the appearance of the thermal flowmeter, FIG. 2A is a left side view, and FIG. 2B is a front view. It is a figure which shows the appearance of the thermal flowmeter, FIG. 3A is a right side view, and FIG. 3B is a rear view. It is a figure which shows the appearance of the thermal flowmeter, FIG. 4A is a plan view, and FIG. 4B is a bottom view. It is a figure which shows the housing of the thermal flowmeter, FIG. 5A is a left side view of the housing, and FIG. 5B is a front view of the housing. It is a figure which shows the housing of the thermal flowmeter, FIG. 6A is a right side view of the housing, and FIG. 6B is a rear view of the housing. FIG. 7 (A) is a partially enlarged view showing a state of the flow path surface arranged in the sub-passage, and FIG. 7 (B) is a partially enlarged view showing another embodiment of FIG. 7 (A). 8A is a left side view, FIG. 8B is a front view, and FIG. 8C is a plan view, showing the appearance of the front cover. 9 (A) is a left side view, FIG. 9 (B) is a front view, and FIG. 9 (C) is a plan view, showing the appearance of the back cover 304. It is a partially enlarged view which shows the other Example of the Example shown in FIG. 7. It is a block diagram which shows still another Example of the Example shown in FIG. 5 and FIG. It is a partially enlarged view which shows a part of the BB cross section of FIG. It is a partially enlarged view of the terminal connection part. It is an external view of a circuit package, FIG. 14A is a left side view, FIG. 14B is a front view, and FIG. 14C is a rear view. It is a figure which shows the state which the circuit component is mounted on the frame frame of a circuit package. It is explanatory drawing explaining the diaphragm and the communication passage connecting a gap and an opening inside a diaphragm. It is a figure which shows the state of the circuit package after the 1st resin molding process. 14 is a diagram showing another embodiment of the circuit package shown in FIG. 14, FIG. 18A is a front view of the circuit package, and FIG. 18B is a rear view. It is a figure which shows the outline of the manufacturing process of a thermal flow meter, and is the figure which shows the production process of a circuit package. It is a figure which shows the outline of the manufacturing process of a thermal flow meter, and is the figure which shows the production process of a thermal flow meter. It is a figure which shows the outline of the manufacturing process of a thermal flow meter, and is the figure which shows the other embodiment of the production process of a thermal flow meter. It is a circuit diagram which shows the flow rate detection circuit of a thermal flow meter. It is explanatory drawing explaining the flow rate detection part of the flow rate detection circuit.

The embodiment for carrying out the invention (hereinafter referred to as an embodiment) described below solves various problems requested as an actual product, 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 produces various effects. One of the various problems solved by the following examples is the content described in the column of the problems to be solved by the invention described above, and one of the various effects of the following examples is. It is the effect described in the column of effect of the invention. The various problems solved by the following examples and the various effects produced by the following examples will be described in the description of the following examples. Therefore, the problems and effects described in the following Examples, which are solved by the Examples, include contents other than the contents of the problem column to be solved by the invention and the effect column of the invention.

In the following examples, the same reference numerals show the same configuration even if the drawing numbers are different.
It has the same effect. For the configurations already described, only reference numerals may be added to the drawings and the description may be omitted.

1. 1. One Example Using the Thermal Flowmeter According to the Present Invention for the Internal Combustion Engine Control System FIG. 1 shows an embodiment using the thermal flowmeter according to the present invention for the electronic fuel injection type internal combustion engine control system. , It is a system diagram. Engine cylinder 112 and engine piston 1
Based on the operation of the internal combustion engine 110 including 14, the intake air is sucked from the air cleaner 122 as the gas to be measured 30, and the main passage 124, for example, the intake body and the throttle body 12
6. It is guided to the combustion chamber of the engine cylinder 112 via the intake manifold 128. The flow rate of the gas to be measured 30 which is the intake air guided to the combustion chamber is the thermal flow meter 300 according to the present invention.
Fuel is supplied from the fuel injection valve 152 based on the measured flow rate, and is guided to the combustion chamber in the state of an air-fuel mixture together with the gas to be measured 30 which is the intake air. In this embodiment, the fuel injection valve 152 is provided at 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 which is the intake air, and the fuel is formed through the intake valve 116. It is guided to the combustion chamber and burns to generate mechanical energy.

In recent years, many vehicles have adopted a method in which a fuel injection valve 152 is attached to the cylinder head of an internal combustion engine and fuel is directly injected from the fuel injection valve 152 into each combustion chamber as a method excellent in exhaust purification and fuel efficiency improvement. .. The thermal flow meter 300 can be used not only in the method of injecting fuel into the intake port of the internal combustion engine shown in FIG. 1 but also in the method of injecting fuel directly into each combustion chamber. In both methods, the basic concept of the control parameter measurement method including the usage of the thermal flow meter 300 and the control method of the internal combustion engine including the fuel supply amount and the ignition timing are almost the same, and intake is a typical example of both methods. FIG. 1 shows a method of injecting fuel into the port.

The fuel and air guided to the combustion chamber are in a mixed state of fuel and air, and are explosively burned by spark ignition of the spark plug 154 to generate mechanical energy. The gas after combustion is guided from the exhaust valve 118 to the exhaust pipe, and is discharged to the outside of the vehicle from the exhaust pipe as exhaust 24. The flow rate of the gas to be measured 30, which is the intake air guided 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 opening degree of the throttle valve 132 to control the flow rate of the intake air guided to the combustion chamber. The mechanical energy generated by the engine can be controlled.

1.1 Outline of control of internal combustion engine control system Gas to be measured 3 which is intake air taken from the air cleaner 122 and flows through the main passage 124.
The flow rate and temperature of 0 are measured by the thermal flow meter 300, and an electric signal representing the flow rate and temperature of the intake air is input to the control device 200 from the thermal flow meter 300. Further, the output of the throttle angle sensor 144 that measures the opening degree of the throttle valve 132 is input to the control device 200, and 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. In order to measure the speed, 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 in order to measure the state of the mixing ratio of the fuel amount and the air amount from the state of the exhaust 24.

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 rotation 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,
Further, the ignition timing of ignition is controlled by the spark plug 154. The fuel supply amount and ignition timing are actually the changes in the intake air temperature and throttle angle measured by the thermal flow meter 300.
Based on the state of change in engine speed and the state of air-fuel ratio measured by the oxygen sensor 148,
It is finely controlled. The control device 200 further adjusts the amount of air bypassing the throttle valve 132 in the idle operation state of the internal combustion engine.
It is controlled by 56 to control the rotation speed of the internal combustion engine in the idle operation state.

1.2 Importance of improving the measurement accuracy of the thermal flowmeter and the installation environment of the thermal flowmeter The main parameters of the fuel supply amount and ignition timing, which are the main control amounts of the internal combustion engine, are the output of the thermal flowmeter 300. Is calculated as. Therefore, it is important to improve the measurement accuracy of the thermal flowmeter 300, suppress the change with time, and improve the reliability in order to improve the control accuracy and reliability of the vehicle.
Particularly in recent years, there has been a very high demand for fuel efficiency of vehicles, and a very high demand for exhaust gas purification. In order to meet these demands, it is extremely important to improve the measurement accuracy of the flow rate of the gas to be measured 30, which is the intake air measured by the thermal flow meter 300. It is also important that the thermal flowmeter 300 maintains high reliability.

The vehicle equipped with the thermal flow meter 300 is used in an environment where the temperature changes greatly, and is also used in wind, rain and snow. When a car travels on a snowy road, it travels on a road on which an antifreeze agent is sprayed. It is desirable that the thermal flowmeter 300 also considers the response to temperature changes in the usage environment and the response to dust and pollutants. Further, the thermal flow meter 300 is installed in an environment that receives vibration of the internal combustion engine. It is required to maintain high reliability against vibration.

Further, the thermal flow meter 300 is mounted on an intake pipe that is affected by heat generated from the internal combustion engine. Therefore, the 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 transferring heat to 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 problems described in the problem column to be solved by the invention and exerts the effects described in the effect column of the invention, as described below. Not only that, as will be explained below, the various problems described above are fully considered, the various problems required for the product are solved, and various effects are achieved. Specific problems to be solved by the thermal flow meter 300 and specific effects to be achieved will be described in the description of the following examples.

2. Configuration of Thermal Flowmeter 300 2.1 External Structure of Thermal Flowmeter 300 FIGS. 2, 3 and 4 are views showing the external appearance of the thermal flowmeter 300, and FIG. 2A is a thermal flow rate. A total of 300 left side views, FIG. 2 (B) is a front view, FIG. 3 (A) is a right side view, FIG. 3 (B) is a rear view, FIG. 4 (A) is a plan view, and FIG. 4 (B) is a plan view. It is a bottom view. The thermal flow meter 300 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 which is the main passage 124, an external connection portion 305 having an external terminal 306 for making an electrical connection with an external device, and a flow rate. It is provided with a measuring unit 310 for measuring and the like. A sub-passage groove for forming a sub-passage is provided inside the measuring unit 310, and a flow rate detection for measuring the flow rate of the gas to be measured 30 flowing through the main passage 124 is further inside the measuring unit 310. A circuit package 400 including a unit 602 (see FIG. 20) and a temperature detection unit 452 for measuring the temperature of the gas to be measured 30 flowing through the main passage 124 is provided.

2.2 Effect based on the external structure of the thermal flowmeter 300 Since the inlet 350 of the thermal flowmeter 300 is provided on the tip side of the measuring unit 310 extending from the flange 312 toward the center of the main passage 124. The gas in the portion near the central portion away from the inner wall surface, not near the inner wall surface of the main passage 124, can be taken into the sub-passage. Therefore, the thermal flow meter 300 can measure the flow rate and temperature of the gas in the portion 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. In the vicinity of the inner wall surface of the main passage 124, the temperature of the main passage 124 is easily affected, and the temperature of the gas to be measured 30 differs from the original temperature of the gas, and the average of the main gas in the main passage 124 is average. It will be different from the state. In particular, when the main passage 124 is the intake body of the engine, it is often maintained at a high temperature due to the influence of heat from the engine. Therefore, the gas near the inner wall surface of the main passage 124 is often higher than the original temperature of the main passage 124, which causes a decrease in measurement accuracy.

The fluid resistance is large in the vicinity of the inner wall surface of the main passage 124, and the flow velocity is lower than the average flow velocity of the main passage 124. Therefore, if the gas near 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 of the main passage 124 may lead to a measurement error. In the thermal flowmeter 300 shown in FIGS. 2 to 4, the flange 312 to the main passage 1
Since the inlet 350 is provided at the tip of the thin and long measuring unit 310 extending toward the center of the 24, it is possible to reduce the measurement error related to the decrease in the flow velocity near the inner wall surface. In addition, FIGS. 2 to 4
In the thermal flow meter 300 shown in the above, not only the inlet 350 is provided at the tip 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 the tip of the measuring unit 310. Since it is provided in, the measurement error can be further reduced.

The measuring 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 part of the gas to be measured 30 such as intake air is taken into the sub-passage at the tip thereof. An outlet 350 for returning the gas to be measured 30 from the sub-passage to the main passage 124 is provided. The measuring unit 310 has a shape extending long along an axis from the outer wall of the main passage 124 toward the center, but the width has a narrow shape as shown in FIGS. 2 (A) and 3 (A). doing. That is, the measuring unit 310 of the thermal flow meter 300 has a thin side surface and a substantially rectangular front surface. As a result, the thermal flow meter 300 can be provided with a sub-passage having a sufficient length, and the fluid resistance to the gas to be measured 30 can be suppressed to a small value. Therefore, the thermal flow meter 300 can suppress the fluid resistance to a small value and can measure the flow rate of the gas to be measured 30 with high accuracy.

2.3 Structure of temperature detection unit 452 The flow of the gas to be measured 30 is located closer to the flange 312 side than the sub-passage provided on the tip side of the measurement unit 310, as shown in FIGS. 2 and 3. Entrance 34 that opens toward the upstream side
3 is molded, and a temperature detection unit 452 for measuring the temperature of the gas to be measured 30 is arranged inside the inlet 343. In the central portion of the measurement unit 310 provided with the inlet 343, the upstream outer wall in the measurement unit 310 constituting the housing 302 is recessed toward the downstream side, and the temperature detection unit 452 is recessed from the recessed upstream outer wall. Has a shape that protrudes toward the upstream side. Further, a front cover 303 and a back cover 304 are provided on both sides of the recessed outer wall, and the upstream end portions of the front cover 303 and the back cover 304 are directed toward the upstream side from the recessed outer wall. It has a protruding shape. Therefore, the recessed outer wall and the front cover 303 and the back cover 304 on both sides thereof form an inlet 343 for taking in the gas to be measured 30. The temperature of the gas to be measured 30 taken in from the inlet 343 is measured by the temperature detection unit 452 by coming into contact with the temperature detection unit 452 provided inside the inlet 343. Further, the temperature detection unit 4 projecting upstream from the outer wall of the housing 302 having a recessed shape.
The gas to be measured 30 flows along the portion supporting the 52, and the front side outlet 344 and the back side outlet 345 provided on the front cover 303 and the back cover 304 are discharged to the main passage 124.

2.4 Effect related to temperature detection unit 452 The temperature of the gas flowing into the inlet 343 from the upstream side in the direction along the flow of the gas to be measured 30 is measured by the temperature detection unit 452, and the gas further causes the temperature detection unit 452. By flowing toward the root portion of the temperature detection unit 452, which is the supporting portion, the temperature of the portion supporting the temperature detection unit 452 is cooled in a direction approaching the temperature of the gas to be measured 30. The temperature of the intake pipe, which is the main passage 124, usually rises, and the flange 312 or the heat insulating part 315 to the measuring part 310
Heat is transferred to the portion supporting the temperature detection unit 452 through the inner upstream outer wall, which may affect the temperature measurement accuracy. As described above, after the gas to be measured 30 is measured by the temperature detection unit 452, the supporting portion is cooled by flowing along the supporting portion of the temperature detecting unit 452. Therefore, it is possible to suppress heat transfer from the flange 312 or the thermal insulation unit 315 to the portion supporting the temperature detection unit 452 through the upstream outer wall in the measurement unit 310.

In particular, the support portion of the temperature detection unit 452 has a shape in which the outer wall on the upstream side in the measurement unit 310 is recessed toward the downstream side (described below with reference to FIGS. 5 and 6). 31
The distance between the upstream outer wall in 0 and the temperature detection unit 452 can be increased. As the heat conduction distance becomes longer, the distance of the cooling portion by the gas to be measured 30 becomes longer. Therefore, the influence of heat generated from the flange 312 or the heat insulating portion 315 can be reduced. From these things, the measurement accuracy is improved. Since the upstream outer wall has a shape recessed toward the downstream side (described below with reference to FIGS. 5 and 6), the circuit package 400 (see FIGS. 5 and 6) described below is fixed. Becomes easier.

2.5 Structures and effects of upstream and downstream sides of the measuring unit 310 On the upstream and downstream sides of the measuring unit 310 that constitutes the thermal flowmeter 300, there are upstream protrusions 317 and downstream protrusions 318, respectively. It is provided. Upstream protrusion 317 and downstream protrusion 31
Reference numeral 8 has a shape that becomes thinner toward the tip with respect to the root, and the fluid resistance of the gas to be measured 30 which 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 has a large heat conduction from the flange 312 or the heat insulating portion 315, but the upstream protrusion 317 is interrupted in front of the inlet 343, and the temperature detection portion 452 side of the upstream protrusion 317. As will be described later, the distance from the temperature detection unit 452 to the temperature detection unit 452 is increased due to the depression of the outer wall on the upstream side of the housing 302. Therefore, heat conduction from the heat insulating portion 315 to the supporting portion of the temperature detecting portion 452 is suppressed.

Further, a gap including a terminal connection portion 320 and a terminal connection portion 320, which will be described later, is formed between the flange 312 or the thermal insulation portion 315 and the temperature detection portion 452. Therefore, the flange 3
12 or the space between the heat insulating portion 315 and the temperature detecting portion 452 is long, and the front cover 303 and the back cover 304 are provided in this long portion, and this portion 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. Further, the distance between the flange 312 or the heat insulating portion 315 and the temperature detecting portion 452 becomes longer, so that
The intake portion of the gas to be measured 30 leading to the sub-passage can be brought closer to the center of the main passage 124. It is possible to suppress a decrease in measurement accuracy due to heat transfer from the main passage 124 wall surface.

As shown in FIGS. 2 (B) and 3 (B), the measuring unit 310 inserted into the main passage 124 is
Both sides thereof are very narrow, and the downstream protrusion 318 and the upstream protrusion 317 have a shape in which the tip is narrow with respect to the root for reducing air resistance. Therefore, the thermal flow meter 300 is used in the main passage 12
It is possible to suppress an increase in fluid resistance due to insertion into 4. Further, in the portion where the downstream side protrusion 318 and the upstream side protrusion 317 are provided, the upstream side protrusion 317 and the downstream side protrusion 318 have a shape protruding from both sides of the front cover 303 and the back cover 304 to both sides. .. Upstream protrusion 3
Since the 17 and the downstream protrusion 318 are made of a resin mold, it is easy to form a shape having low air resistance, while the front cover 303 and the back cover 304 have a shape having a wide cooling surface. Therefore, the thermal flow meter 300 has the effect that the air resistance is reduced and the air to be measured flowing through the main passage 124 easily cools the flow meter 300.

2.6 Structure and effect of flange 312 The flange 312 is provided with a plurality of recesses 314 on the lower surface of the flange 312 facing the main passage 124 to reduce the heat transfer surface between the flange 312 and the main passage 124. , The thermal flow meter 300 makes it less susceptible to heat. The screw hole 313 of the flange 312 is the main passage 1 of the thermal flow meter 300.
It is for fixing to 24, and the surface facing the main passage 124 around each screw hole 313 and the main passage so that the surface facing the main passage 124 around these screw holes 313 is kept away from the main passage 124. A space is formed between the passage and the passage 124. By doing so, the heat transfer from the main passage 124 to the thermal flowmeter 300 can be reduced, and the structure can prevent the measurement accuracy from being lowered due to heat. Furthermore, the recess 314 not only has the effect of reducing heat conduction, but also has the effect of reducing the effect of shrinkage of the resin constituting the flange 312 during molding of the housing 302.

A thermal insulation unit 315 is provided on the measurement unit 310 side of the flange 312. Thermal flowmeter 30
The measuring unit 310 of 0 is inserted into the inside through the mounting hole provided in the main passage 124, and the heat insulating portion 315 faces the inner surface of the mounting 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. On the contrary, it is considered that the main passage 124 has an extremely low temperature at the time of starting in a cold region. Such a main passage 124
If the high temperature or low temperature state affects the temperature detection unit 452 and the flow rate measurement described later, the measurement accuracy is lowered. For this reason, a plurality of recesses 316 are provided side by side in the heat insulating portion 315 close to the inner surface of the hole of the main passage 124, and the width of the heat insulating portion 315 close to the inner surface of the hole between the adjacent recesses 316 is extremely thin. , Is less than one-third of the width of the depression 316 in the fluid flow direction. This can reduce the influence of temperature. Further, the resin becomes thicker in the heat insulating portion 315. When the resin of the housing 302 is molded, volume shrinkage occurs when the resin cools from a high temperature state to a low temperature and hardens, and strain due to the generation of stress occurs. By forming the recess 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 flowmeter 300 is inserted into the inside through a mounting hole provided in the main passage 124, and is fixed to the main passage 124 by a flange 312 of the thermal flowmeter 300 with a screw.
It is desirable that the thermal flow meter 300 be fixed to the mounting holes provided in the main passage 124 in a predetermined positional relationship. The recess 314 provided in the flange 312 can be used for positioning the main passage 124 and the thermal flowmeter 300. By forming a convex portion in the main passage 124, it is possible to form a shape in which the convex portion and the recess 314 have a fitting relationship, and the thermal flow meter 300
Can be fixed in the main passage 124 at an accurate position.

2.7 Structure and effect of external connection portion 305 and flange 312 FIG. 4A is a plan view of the thermal flowmeter 300. Four external terminals 306 and correction terminals 307 are provided inside the external connection portion 305. The external terminal 306 is a terminal for outputting the flow rate and temperature which is the 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 measures the produced thermal flowmeter 300, obtains a correction value for each thermal flowmeter 300, and is used to store the correction value in the memory inside the thermal flowmeter 300. Terminal, then thermal flowmeter 3
In the measurement operation of 00, the correction data representing the correction value stored in the above-mentioned memory is used, and the correction terminal 307 is not used. Therefore, 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. In this embodiment, the correction terminal 307 has a shorter shape than the external terminal 306, so that even if the connection terminal to the external device connected to the external terminal 306 is inserted into the external connection portion 305, it does not interfere with the connection. It has become. Further, a plurality of recesses 308 are provided inside the external connection portion 305 along the external terminal 306, and these recesses 308 are stress-concentrated due to shrinkage of the resin when the resin, which is the material of the flange 312, cools and hardens. It is for reducing.

In addition to the external terminal 306 used during the measurement operation of the thermal flowmeter 300, the correction terminal 307
By providing, it is possible to measure the characteristics of each of the thermal flowmeters 300 before shipping, measure the variation of the product, and store the correction value for reducing the variation in the memory inside the thermal flowmeter 300. It will be possible. After the above correction value setting step, the correction terminal 307 is the external terminal 30.
The correction terminal 307 is made to have a shape different from that of the external terminal 306 so as not to interfere with the connection between the 6 and the external device. In this way, the thermal flowmeter 300 can reduce variations in each of the thermal flowmeters 300 before shipment, and can improve the measurement accuracy.

3. 3. Overall structure of housing 302 and its effect 3.1 Structure and effect of sub-passage and flow rate detection unit Housing 3 with front cover 303 and back cover 304 removed from thermal flow meter 300
The state of 02 is shown in FIGS. 5 and 6. FIG. 5A is a left side view of the housing 302.
5 (B) is a front view of the housing 302, FIG. 6 (A) is a right side view of the housing 302, and FIG. 6 (B) 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 end side thereof. In this embodiment the housing 30
Sub-passage grooves are provided on both the front and back surfaces of No. 2, and FIG. 5 (B) shows the front-side sub-passage groove 332, and FIG. 6 (B) shows the back-side sub-passage groove 334. Inlet groove 35 for forming the inlet 350 of the sub-passage
Since the outlet groove 353 for forming 1 and the outlet 352 is provided at the tip end portion of the housing 302, the gas in the portion away from the inner wall surface of the main passage 124, in other words, the main passage 124.
The gas flowing in the portion close to the central portion of the above can be taken in from the inlet 350 as the gas to be measured 30. The gas flowing near 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 intake air. Further, the gas flowing near the inner wall surface of the main passage 124 often shows a flow velocity 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 such an influence, it is possible to suppress a decrease in measurement accuracy.

The sub-passage formed by the front-side sub-passage groove 332 and the back-side sub-passage groove 334 described above is the outer wall recess 36.
6 and the upstream side outer wall 335 and the downstream side outer wall 336 are connected to the heat insulating portion 315. Further, the upstream side outer wall 335 is provided with the upstream side protrusion 317, and the downstream side outer wall 336 is provided with the downstream side protrusion 31.
8 is provided. With such a structure, the thermal flow meter 300 is fixed to the main passage 124 by the flange 312, so that the measuring unit 310 having the circuit package 400 is fixed to the main passage 124 with high reliability.

In this embodiment, the housing 302 is provided with a sub-passage groove for forming the sub-passage, and the sub-passage groove and the cover complete the sub-passage by covering the front surface and the back surface of the housing 302 with the cover. .. With such a structure, all the sub-passage grooves can be formed as a part of the housing 302 in the resin molding process of the housing 302. Further, since molds are provided on both sides of the housing 302 when the housing 302 is molded, by using both molds, both the front side sub-passage groove 332 and the back side sub-passage groove 334 can be used as a part of the housing 302. It becomes possible to mold. By providing the front cover 303 and the back cover 304 on both sides of the housing 302, the auxiliary passages on both sides of the housing 302 can be completed. Front side sub-passage grooves 33 on both sides of the housing 302 using a mold
By forming 2 and the back side sub-passage groove 334, the sub-passage can be formed with high accuracy. In addition, high productivity can be obtained.

In FIG. 6B, a part of the gas to be measured 30 flowing through the main passage 124 is taken into the back side sub-passage groove 334 from the inlet groove 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 the gas to be measured 30 gradually moves in the front side direction as it flows along the groove. In particular, the back side sub-passage groove 334 is provided with a steeply inclined portion 347 that suddenly deepens at the upstream portion 342 of the circuit package 400, and a part of the air having a small mass moves along the steeply inclined portion 347, and the circuit package 400 In the upstream portion 342 of the above, the air flows toward the measurement flow path surface 430 shown in FIG. 5 (B). On the other hand, since it is difficult for a foreign matter having a large mass to change its course suddenly due to inertial force, it moves toward the back surface 431 of the flow path surface for measurement shown in FIG. 6B. After that, it passes through the downstream portion 341 of the circuit package 400 and flows toward the measurement flow path surface 430 shown in FIG. 5 (B).

The flow of the gas to be measured 30 in the vicinity of the heat transfer surface exposed portion 436 will be described with reference to FIG. In the front side sub-passage groove 332 shown in FIG. 5 (B), the upstream portion 3 of the circuit package 400 described above.
The air, which is the gas to be measured 30 that has moved from 42 to the front side sub-passage groove 332 side, is the measurement flow path surface 4
It flows along 30 and heat is transferred to and from the flow rate detection unit 602 for measuring the flow rate via the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430, and the flow rate is measured. .. The gas to be measured 30 that has passed through the measurement flow path surface 430 and the air that has flowed from the downstream portion 341 of the circuit package 400 to the front side sub-passage groove 332 both flow along the front side sub-passage groove 332 and exit 35.
2 is discharged from the outlet groove 353 for molding into the main passage 124.

A substance with a large mass such as dust mixed in the gas to be measured 30 has a large inertial force, and the depth of the groove sharply deepens along the surface of the steeply inclined portion 347 shown in FIG. 6 (B). It is difficult to change course suddenly in the deep direction of the groove. Therefore, the foreign matter having a large mass can move toward the back surface 431 of the flow path surface for measurement, and can prevent the foreign matter from passing near the heat transfer surface exposed portion 436. In this embodiment, most of the foreign substances having a large mass other than gas pass through the back surface 431 of the measurement flow path surface, which is the back surface of the measurement flow path surface 430, and thus are caused by foreign substances 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 that suddenly changes the course of the gas to be measured 30 along the axis that crosses the axis of the flow of the main passage 124, the influence of foreign matter mixed in the gas to be measured 30 can be reduced.

In this embodiment, the flow path formed by the back side sub-passage groove 334 faces the flange direction from the tip of the housing 302 while drawing a curve, and the gas flowing through the sub-passage at the position on the most flange side becomes the flow of the main passage 124. On the other hand, the flow is in the opposite direction, and the sub-passage on the back side, which is one side of the flow in the reverse direction, is connected to the sub-passage formed on the front side, which is the other side. By doing so, the heat transfer surface exposed portion 436 of the circuit package 400 can be easily fixed to the sub-passage, and the gas to be measured 30 can be easily taken in at a position close to the central portion of the main passage 124.

In this embodiment, the measurement flow path surface 430 for measuring the flow rate is configured to penetrate the back side sub-passage groove 334 and the front side sub-passage groove 332 in the flow direction in the flow direction, and the tip side of the circuit package 400 is a housing. It has a cavity 382 instead of the configuration supported by 302, and the space of the upstream portion 342 of the circuit package 400 and the space of the downstream portion 341 of the circuit package 400 are connected. The upstream part 342 of this circuit package 400 and the circuit package 400
The gas to be measured 3 is configured to penetrate the downstream portion 341 of the housing 302 from the back side sub-passage groove 334 formed on one surface of the housing 302 to the front sub-passage groove 332 formed on the other surface of the housing 302.
The sub-passage is formed in a shape in which 0 moves. With such a configuration, it is possible to form the sub-passage groove on both sides of the housing 302 in one resin molding step, and it is possible to form the structure connecting the sub-passage grooves on both sides together.

When molding the housing 302, the measurement flow path surface 43 formed on the circuit package 400
By clamping both sides of 0 with a molding die, it is possible to form a structure that penetrates the upstream portion 342 of the circuit package 400 and the downstream portion 341 of the circuit package 400, and at the same time as resin molding the housing 302, the circuit package. The 400 can be mounted in the housing 302. By inserting and molding the circuit package 400 into the molding die of the housing 302 in this way, the circuit package 400 and the heat transfer surface exposed portion 436 can be mounted on the sub-passage with high accuracy.

In this embodiment, the upstream portion 342 of the circuit package 400 and the downstream portion 341 of the circuit package 400 are penetrated. However, the upstream part 342 of the circuit package 400
It is also possible to form a sub-passage shape connecting the back side sub-passage groove 334 and the front side sub-passage groove 332 in one resin molding step by forming the structure so as to penetrate either the back side sub-passage groove 341 and the downstream portion 341.

In addition, on both sides of the back side sub-passage groove 334, the back side sub-passage inner peripheral wall 391 and the back side sub-passage outer peripheral wall 39
2 is provided, and the back side sub-passage of the housing 302 is formed by the tip portions of the back-side sub-passage inner peripheral wall 391 and the back-side sub-passage outer wall 392 in the height direction and the inner surface of the back cover 304 being in close contact with each other. Will be done. Further, on both sides of the front side sub-passage groove 332, a front side sub-passage inner peripheral wall 393 and a front side sub-passage outer peripheral wall 394 are provided, and these front side sub-passage inner peripheral wall 393 and the front side sub-passage outer peripheral wall 39.
The housing 302 is brought into close contact with the tip of the height direction 4 and the inner surface of the front cover 303.
The front side sub-passage is formed.

In this embodiment, the gas to be measured 30 flows separately on both the flow path surface 430 for measurement and the back surface thereof, and the heat transfer surface exposed portion 436 for measuring the flow rate is provided on one side. Instead of dividing into one passage, it may pass only on the surface side of the measurement flow path surface 430. By bending the sub-passage along the second axis in the direction crossing the first axis in the flow direction of the main passage 124, foreign matter mixed in the gas to be measured 30 can be removed from one side of the second shaft with a small bend. The influence of foreign matter can be reduced by providing the measurement flow path surface 430 and the heat transfer surface exposed portion 436 on the side of the second axis having a large bend.

Further, in this embodiment, 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. However, instead of the connecting portion between the front side sub-passage groove 332 and the back side sub-passage groove 334, the front side sub-passage groove 332 or the back side sub-passage groove 3
It may be provided in 34.

A diaphragm shape is formed on the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430 for measuring the flow rate (described below with reference to FIG. 7), and the flow velocity is increased by this throttle effect. Therefore, the measurement accuracy is improved. Further, 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 above throttle, and the measurement accuracy is improved.

In FIGS. 5 and 6, the upstream side outer wall 335 is provided with an outer wall recessed portion 366 having a shape of being recessed to the downstream side at the root portion of the temperature detecting portion 452. The temperature detection unit 45 is provided by the outer wall recess portion 366.
The distance between 2 and the outer wall recessed portion 366 becomes longer, and the influence of heat transmitted through the upstream outer wall 335 can be reduced.

Further, by wrapping the circuit package 400 with the fixing portion 372, the circuit package 400
However, by further fixing the circuit package 400 by the outer wall recessed portion 366, the force for fixing the circuit package 400 can be increased. The fixing portion 372 includes the circuit package 400 in the direction along the flow axis of the gas to be measured 30. On the other hand, the outer wall recessed portion 366 includes the circuit package 400 in the direction across the flow axis of the gas to be measured 30. That is, the circuit package 400 is included in different directions with respect to the fixed portion 372.
Includes. Since the circuit package 400 is included in two different directions, the fixing force is increased. The outer wall recess 366 is a part of the upstream outer wall 335, but if it is to increase the fixing force, the downstream outer wall 336 is used instead of the upstream outer wall 335 to increase the fixing force 37.
The circuit package 400 may be included in a direction different from 2. For example, the downstream outer wall 336 may include the plate portion of the circuit package 400, or the downstream outer wall 336 may be provided with a recessed portion in the upstream direction or a protruding portion protruding in the upstream direction to include the circuit package 400. good. The circuit package 400 is included by providing the outer wall recess 366 on the upstream outer wall 335 because, in addition to fixing the circuit package 400, the effect of increasing the thermal resistance between the temperature detection unit 452 and the upstream outer wall 335 is increased. This is because it was given.

An outer wall recess 366 is provided at the base of the temperature detection unit 452, whereby the flange 312 is provided.
Alternatively, the influence of heat transmitted from the heat insulating portion 315 through the upstream outer wall 335 can be reduced. Further, a temperature measuring recess 368 formed by a notch between the upstream protrusion 317 and the temperature detection unit 452 is provided. The temperature measuring recess 368 can reduce the heat transfer to the temperature detection unit 452 via the upstream protrusion 317. As a result, the detection accuracy of the temperature detection unit 452 is improved. In particular, the upstream protrusion 317 has a large cross-sectional area, so heat is easily transferred.
The function of the temperature measuring recess 368 that blocks heat transfer is important.

3.2 Structure and effect of the flow rate detection unit of the sub-passage FIG. 7 is a partially enlarged view showing a state in which the measurement flow path surface 430 of the circuit package 400 is arranged inside the sub-passage groove, and is A of FIG. −A sectional view. It should be noted that this figure is a conceptual diagram, and the detailed shapes shown in FIGS. 5 and 6 are omitted and simplified in FIG. 7, and the details are slightly deformed. The left portion of FIG. 7 is the end portion of the back side sub-passage groove 334.
The right side portion is the starting end portion of the front side sub-passage groove 332. Although not clearly described in FIG. 7, penetration portions are provided on both the left and right sides of the circuit package 400 having the measurement flow path surface 430, and the back sides on the left and right sides of the circuit package 400 having the measurement flow path surface 430. Sub passage groove 334
And the front side sub-passage groove 332 are connected.

The gas to be measured 30 taken in 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 the circuit package 4.
It flows through the through portion of the upstream portion 342 of 00 toward the surface of the measurement flow path surface 430 of the circuit package 400 and the flow path 386 formed by the protrusion 356 provided on the front cover 303, and other gas to be measured. Reference numeral 30 denotes a flow path 387 formed by the back surface 431 of the flow path surface for measurement and the back cover 304. After that, the gas to be measured 30 flowing through the flow path 387 is transferred to the downstream portion 3 of the circuit package 400.
It moves toward the front side sub-passage groove 332 through the through portion of 41, merges with the gas to be measured 30 flowing through the flow path 386, flows through the front side sub-passage groove 332, and is discharged from the outlet 352 to the main passage 124. .. As shown in FIG. 7B, the flow path 387 has a protrusion 3 provided on the back cover 304.
58 may protrude toward the back surface 431 of the flow path surface for measurement.

The flow path 3 from the back side sub-passage groove 334 via the through portion of the upstream portion 342 of the circuit package 400.
Since the sub-passage groove is formed so that the gas to be measured 30 guided by the 86 has a larger bend than the flow path guided to the flow path 387, the mass of dust and the like contained in the gas to be measured 30 is formed. Larger substances collect in the less curved flow path 387. Therefore, there is almost no inflow of foreign matter into the flow path 386.

The flow path 386 has a structure in which a throttle is formed by continuously projecting from the most advanced portion of the front side sub-passage groove 332 to the protrusion 356 provided on the front cover 303 toward the measurement flow path surface 430. Is made up of. A measurement flow path surface 430 is arranged on one side of the throttle portion of the flow path 386, and a heat transfer surface exposed portion for the flow rate detection unit 602 to transfer heat to and from the gas to be measured 30 on the measurement flow path surface 430. 436 is provided. In order for the flow rate detection unit 602 to measure with high accuracy, it is desirable that the gas to be measured 30 is a laminar flow with few vortices in the heat transfer surface exposed portion 436. Moreover, the faster the flow velocity, the better the measurement accuracy. For this purpose, the protrusion 356 provided on the front cover 303 facing the measurement flow path surface 430 projects smoothly toward the measurement flow path surface 430, whereby the diaphragm is formed. This diaphragm acts to reduce the vortex of the gas to be measured 30 and bring it closer to the laminar flow. Further, the flow velocity becomes faster in the throttle portion, and the heat transfer surface exposed portion 436 for measuring the flow rate is arranged in this throttle portion, so that the measurement accuracy of the flow rate is improved.

A protrusion 356 facing the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430.
The diaphragm can be formed by projecting the squeeze into the sub-passage groove to improve the measurement accuracy. The protrusion 356 for forming the diaphragm is a heat transfer surface exposed portion 436 provided on the measurement flow path surface 430.
It will be provided on the cover facing the. In FIG. 7, since the cover facing the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430 is the front cover 303, the front cover 303 is provided with the protrusion 356, but the front cover 303 or the back cover 304 Flow path surface for measurement 4
It may be provided on the cover facing the heat transfer surface exposed portion 436 provided in 30. The cover facing the heat transfer surface exposed portion 436 changes depending on which surface the measurement flow path surface 430 and the heat transfer surface exposed portion 436 are provided in the circuit package 400.

The distribution of the gas to be measured 30 between the flow path 386 and the flow path 387 is also related to high-precision measurement, and as shown in FIG.
The distribution of the gas to be measured 30 between the flow path 386 and the flow path 387 may be adjusted by projecting the gas into the flow path 386. Further, by providing a throttle portion in the flow path 387, the flow velocity is increased, and a foreign matter such as dust is drawn into the flow path 387. In the embodiment shown in FIG. 7B, a diaphragm with a protrusion 358 is used as one of various means for adjusting the flow path 386 and the flow path 387.
By adjusting the width between the back surface 431 of the flow path surface for measurement and the back cover 304, etc., the above-mentioned flow path 38
The distribution of the flow rate between 6 and the flow path 387 may be adjusted. In this case, as shown in FIG. 7A, the protrusion 358 provided on the back cover 304 becomes unnecessary.

5 and 6, on the back surface of the measurement flow path surface 431, which is the back surface of the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430, the pressing marks of the mold used in the resin molding process of the circuit package 400. 442 remains. The pressing mark 442 does not particularly hinder the measurement of the flow rate, and there is no problem even if the pressing mark 442 remains as it is. Further, as will be described later, when the circuit package 400 is molded by the resin mold, it is important to protect the semiconductor diaphragm of the flow rate detection unit 602. For this reason, it is important to hold down the back surface of the heat transfer surface exposed portion 436. Further, it is important to prevent the resin covering the circuit package 400 from flowing into the heat transfer surface exposed portion 436. From this point of view, 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. Since the circuit package 400 is made of transfer mold, the pressure of the resin is high, and it is important to press the heat transfer surface exposed portion 436 from the back surface. Further, a semiconductor diaphragm is used in the flow rate detection unit 602, and it is desired to form a ventilation passage of a gap formed by the semiconductor diaphragm. In order to hold and fix the 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.

3.3 Shape and effect of front cover 303 and back cover 304 FIG. 8 is a view showing the appearance of the front cover 303, FIG. 8 (A) is a left side view, FIG. 8 (B) is a front view, and FIG. C) is a plan view. FIG. 9 is a view showing the appearance of the back cover 304, which is shown in FIG.
A) is a left side view, FIG. 9B is a front view, and FIG. 9C is a plan view. In FIGS. 8 and 9, the front cover 303 and the back cover 304 are used to form the sub-passage by closing the sub-passage groove of the housing 302. It also has a protrusion 356 and is used to provide a throttle in the flow path. Therefore, it is desirable that the molding accuracy is high. Since the front cover 303 and the back cover 304 are made by a resin molding process of injecting a thermoplastic resin into a mold, they can be made with high molding accuracy. Further, the front cover 303 and the back cover 304 are formed with a protrusion 380 and a protrusion 381, and when the housing 302 is fitted, FIGS. 5 (B) and 6 (B) are formed.
At the same time as filling the gap of the cavity 382 on the tip side of the circuit package 400 described in the above, the tip of the circuit package 400 is covered.

The front cover 303 and the back cover 304 shown in FIGS. 8 and 9 include the front protection portion 322 and the back protection portion 3.
25 is molded. As shown in FIGS. 2 and 3, a front cover 303 is provided on the front side surface of the entrance 343.
The front protection portion 322 provided in the above is arranged, and the back cover 304 is provided on the back side surface of the entrance 343.
The back protection portion 325 provided in the above is arranged. The temperature detection unit 452 arranged inside the inlet 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 the temperature detection unit 452 colliding with something during production or when mounted on a vehicle. Damage can be prevented.

A protrusion 356 is provided on the inner surface of the front cover 303, and as shown in the example of FIG. 7, the protrusion 3 is provided.
56 is arranged to face the measurement flow path surface 430 and has a shape that extends long in the direction along the axis of the flow path of the sub-passage. As shown in FIG. 8C, the cross-sectional shape of the protrusion 356 may be inclined toward the downstream side with the apex of the protrusion as a boundary. A diaphragm is formed in the above-mentioned flow path 386 by the measurement flow path surface 430 and the protrusion 356, and the vortex generated in the gas to be measured 30 is reduced to cause a laminar flow. In this embodiment, the sub-passage having the throttle portion is divided into a groove portion and a lid portion that closes the groove to complete the flow path with the throttle portion, and the groove portion is divided into a housing 3
By making it in the second resin molding step for molding 02, then molding the front cover 303 having the protrusion 356 in another resin molding step, and using the front cover 303 as the lid of the groove to cover the groove, the sub-passage Is making. In the second resin molding step of molding the housing 302, the circuit package 400 having the measurement flow path surface 430 is also fixed to the housing 302. The groove having a complicated shape is formed in the resin molding process, and the protrusion 35 for drawing
By providing 6 on the front cover 303, the flow path 386 shown in FIG. 7 can be formed with high accuracy. Further, since the arrangement 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 the mass-produced product can be reduced, and as a result, a high measurement result can be obtained. It also improves productivity.

The same applies to the molding of the flow path 387 by the back cover 304 and the back surface 431 of the flow path surface for measurement. The flow path 387 is formed by dividing the flow path 387 into a groove portion and a lid portion, forming the groove portion in the second resin molding step of molding the housing 302, and covering the groove with the back cover 304. By making the flow path 387 in this way, the flow path 387 can be made with high accuracy, and the productivity is also improved. In this embodiment, the flow path 386 is provided with a throttle, but as shown in FIG. 7B, it is also possible to provide a protrusion 358 and use the flow path 387 having the throttle.

3.4 Other Examples of the Example shown in FIG. 7 FIG. 10 is an enlarged view showing another example of the flow rate measuring portion shown in FIG. 7, and is A of FIG. 6 (B).
-A is another embodiment of the portion corresponding to the cross section. Similar to FIG. 7, the gas to be measured 30 taken in from the inlet groove (not shown) flows through the sub-passage provided on the tip side of the measuring unit 310 (not shown in FIG. 10) as shown by the broken line arrow, and is on the left side of the drawing. It is led to the passage 386 from the groove located on the terminal side of the back side sub-passage groove located. In this passage 386, the flow rate is measured by the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430. After that, it was guided to the front side sub-passage groove and again shown in FIG.
It flows through the sub-passage provided on the tip end side of the measuring unit 310, which is not shown in 0, as shown by the broken line arrow, and is discharged from the outlet 352 shown in FIG. 2 (B) to the main passage 124.

The back side of the measurement flow path surface 430 provided in the circuit package 400 is embedded in the resin portion 359 for forming the sub-passage. By embedding the back side of the measurement flow path surface 430 of the circuit package 400 in the resin portion 359 for forming the sub-passage, the back side sub-passage groove 334
The measurement flow path surface 430 formed in the circuit package 400 is arranged so as to be continuous along the inner surface of the groove, and the gas to be measured 30 is the inner surface of the back side sub-passage groove 334 and the measurement flow path surface 430.
The flow rate is measured by the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430. Although not shown, the sub-passage groove formed on the back surface of the measuring unit 310 is the back cover 30.
Covered by 4, a secondary passage is created.

Front cover 30 at a position facing the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430
3 is provided with a protrusion 356 projecting inside the flow path 386, and the drawing is formed by the protrusion 356 and the measurement flow path surface 430. Similar to the flow path 386 shown in FIG. 7, the flow path 38
By forming the diaphragm into 6, the vortex of the gas to be measured 30 flowing through the flow path 386 is reduced, and the gas to be measured 30 approaches the laminar flow. Therefore, the measurement accuracy of the flow rate measured by the flow rate detection unit 602 is improved. Further, the flow velocity of the flow rate measuring portion is increased by the throttle provided in the passage flow path 386.
This leads to improved accuracy of flow measurement.

The major difference from the structure shown in FIG. 7 is that in FIG. 7, sub-passages are formed on both sides of the measurement flow path surface 430 formed on the circuit package 400 and the measurement flow path surface back surface 431 on the back surface thereof. On the other hand, in FIG. 10, the sub-passage is formed only on the measurement flow path surface 430.
The structure shown in FIG. 10 has an effect that the flow rate flowing along the measurement flow path surface 430 is larger and the flow velocity of the measured gas 30 to be measured can be increased.

In FIG. 10, the housing 302 is provided so that the measurement flow path surface 430 is continuous with the back side sub-passage groove.
The circuit package 400 was fixed to. Therefore, the protrusion 356 is provided on the front cover 303. Therefore, the back cover 304 does not need a protrusion. However, the measurement flow path surface 43 is in the front side sub-passage groove.
The circuit package 400 may be fixed to the housing 302 so that the zeros are continuous. In this case, the protrusion 356 is provided on the back cover 304, and the front cover 303 does not need a protrusion.

3.5 Further Examples of Examples shown in FIGS. 5 and 6 FIG. 11 is a configuration diagram showing other examples of the examples shown in FIGS. 5 and 6, and is a configuration diagram showing the main passages of FIGS. 5 and 6. A portion for forming a sub-passage groove corresponding to the tip end side of the measuring unit 310 inserted into 124 is shown. The flange 312 and the external connection portion 305 are omitted. In the embodiment shown in FIGS. 5 and 6, a sub-passage groove for forming both front and back sub-passages of the housing 302 of the thermal flow meter 300 is provided. FIG. 11 shows a structure in which the sub-passage is provided on either the front surface or the back surface of the housing 302, and has a simple structure. The technical contents are substantially the same regardless of whether the sub-passage is provided on the front surface or the back surface of the housing 302. FIG. 11 shows an example in which the sub-passage is provided on the front surface, and FIG. 11 will be described as a representative example.

A cover is provided on the front side where the sub-passage is provided, and a cover is not provided on the back side because the passage is not formed. That is, the back side of the housing 302 is the housing 30 instead of the cover.
The back surface is covered with the resin forming 2. The cover is made of a thermoplastic resin by a resin molding step as in the examples of FIGS. 5 and 6.

The sub-passage is made of a sub-passage groove and a resin cover covering the groove, and an inlet groove 351 for forming an inlet 350 is formed on the upstream side in the flow direction of the gas to be measured 30, and is formed on the downstream side. An outlet groove 353 for forming the outlet 352 is formed. The gas to be measured 30 taken in from the inlet groove 351 is guided by the front side sub-passage groove 332 and approaches the circuit package 400.
Further, the flow flows along the surface of the measurement flow path surface 430, the flow rate is measured by the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430, and the flow rate is discharged from the outlet groove 353 to the main passage 124 after the flow rate is measured.

The circuit package 400 made in the first resin molding step is fixed to the housing 302 in the second resin molding step, and at the same time, the front side sub-passage groove 332, the outer wall recessed portion 366, the upstream side outer wall 335 and the downstream side outer wall 336, and the figure. A housing 302 having a flange 312 and an external connection 305 (not shown) is molded in the second resin molding step. The effect associated with this is shown in Fig. 5.
And as described above in the description of FIG.

FIG. 12 is a cross-sectional view taken along the line AA of FIG. The back surface of the housing 302 is entirely covered with the resin portion 359, and the back surface of the measurement flow path surface 431 and the side surface of the measurement flow path surface 430 of the circuit package 400 are embedded and fixed in the resin portion 359. Front side sub-passage groove 332
A sub-passage for flowing the gas to be measured 30 is formed by the front cover 303 covering the surface, and a protrusion provided at a position facing the measurement flow path surface 430 following the sub-passage formed in the front sub-passage groove 332. A flow path 386 with a portion 356 is formed. The protrusion 356 is provided on the front cover 303, which is a cover at a position facing the heat transfer surface exposed portion 436. A diaphragm shape is formed by the measurement flow path surface 430 and the protrusion 356, and the heat transfer surface exposed portion 436 is provided at a position forming the diaphragm shape. Therefore, as described with reference to FIGS. 7 and 10, due to the aperture shape, the gas to be measured 30 measured by the heat transfer surface exposed portion 436 becomes a substantially laminar flow with few vortices, and the measurement accuracy is improved. Further, the shape of the diaphragm increases the flow velocity of the gas to be measured 30, which leads to improvement in measurement accuracy for measuring the flow rate.

3.6 Fixing structure and effect of the circuit package 400 by the housing 302 Next, the fixing of the circuit package 400 to the housing 302 by the resin molding process will be described with reference to FIGS. 5 and 6 again. Predetermined location of the sub-passage groove for forming the sub-passage,
For example, in the embodiment shown in FIGS. 5 and 6, the measurement flow path surface 430 formed on the surface of the circuit package 400 is arranged at the connecting portion between the front side sub-passage groove 332 and the back side sub-passage groove 334. The circuit package 400 is arranged and fixed to the housing 302. A portion for embedding and fixing the circuit package 400 in the housing 302 by 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 step.

As shown in FIG. 5B, the circuit package 400 is fixed by the fixing portion 372.
The fixed portion 372 has a surface having a height in contact with the front cover 303 and a thin portion 376, so that the circuit package 4
00 is included. By reducing the thickness of the resin that covers 376 points, the fixing part 372
It has the effect of alleviating the shrinkage when the temperature of the resin cools during molding and reducing the concentration of stress applied to the circuit package 400. As shown in FIG. 6B, if the back side of the circuit package 400 is also shaped as described above, more effect can be obtained.

Further, instead of covering the entire surface of the circuit package 400 with the resin forming the housing 302, 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. In the examples of FIGS. 5 and 6, the area of the portion 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 larger. Further, the portion of the measurement flow path surface 430 of the circuit package 400 is also exposed from the resin forming the housing 302.

In the second resin molding step for molding the housing 302 by thinning a part of the fixing portion 372 that covers the outer wall of the circuit package 400 in a strip shape over the entire circumference.
Excessive stress concentration due to volume shrinkage in the process of curing the fixed portion 372 is reduced so as to include the periphery of the circuit package 400. Excessive stress concentration is circuit package 40
There is a possibility that it will have an adverse effect on 0.

Further, in order to reduce the area of the portion of the outer peripheral surface of the circuit package 400 that is included in the resin of the housing 302 and to fix the circuit package 400 more firmly with a small area.
It is desirable to improve the adhesion of the fixed portion 372 to the outer wall of the circuit package 400.
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 that the resin is cured. Housing 30
In the resin molding step of molding 2, it is desirable to provide the inlet of the thermoplastic resin in or near the fixing portion 372. Thermoplastics increase in viscosity as the temperature decreases,
Cure. Therefore, by pouring the thermoplastic resin in a high temperature state into or near the fixing portion 372, the thermoplastic resin in a low viscosity state can be brought into close contact with the outer wall of the circuit package 400 and cured. As a result, the temperature drop of the thermoplastic resin is suppressed, the low viscosity state is prolonged, and the adhesion between the circuit package 400 and the fixed portion 372 is improved.

By roughening the outer wall surface of the circuit package 400, the circuit package 400 and the fixing portion 3
Adhesion with 72 can be improved. As a method of roughening the outer wall surface of the circuit package 400, after molding the circuit package 400 in the first resin molding step, a roughening method of forming fine irregularities on the surface of the circuit package 400, for example, a treatment method called satin finish. There is. As a roughening method for applying fine unevenness processing to the surface of the circuit package 400, it can be roughened by, for example, sandblasting. Further, it can be roughened by laser processing.

As another roughening method, a sheet having 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. Even in this way, fine irregularities can be formed on the surface of the circuit package 400 and roughened. Further, the surface of the circuit package 400 can be roughened by making unevenness inside the mold for molding the circuit package 400. The surface portion of the circuit package 400 that performs such roughening is
At least the portion where the fixing portion 372 is provided. Furthermore, by roughening the surface portion of the circuit package 400 provided with the outer wall recessed portion 366, the degree of adhesion is further strengthened.

Further, the depth of the groove depends on the thickness of the sheet when the surface of the circuit package 400 is unevenly processed by using the above-mentioned sheet. If the thickness of the sheet is increased, it becomes difficult to mold in the first resin molding step. Therefore, there is a limit to the thickness of the sheet, and if the thickness of the sheet is thin, the depth of unevenness provided in advance on the sheet is limited. Out. Therefore, when the sheet is used, it is desirable that the depth of the unevenness between the bottom and the apex of the unevenness is 10 μm or more and 20 μm or less. At depths less than 10 μm, the effect of adhesion is weak. Depths greater than 20 μm are difficult due to the thickness of the sheet.

In the case of a roughening method other than the above-mentioned sheet, the bottom and apex of the unevenness are formed because it is desirable that the thickness of the resin in the first resin molding step of molding the circuit package 400 is 2 mm or less. It is difficult to make the depth of the unevenness between them 1 mm or more. Conceptually, increasing the depth of the unevenness between the bottom and the apex of the unevenness on the surface of the circuit package 400 increases the degree of adhesion between the resin covering the circuit package 400 and the resin forming the housing 302. However, for the above reason, the depth of the unevenness between the bottom and the apex of the unevenness is preferably 1 mm or less. That is, it is desirable to increase the degree of adhesion between the resin covering the circuit package 400 and the resin forming the housing 302 by providing the surface of the circuit package 400 with irregularities in a range of 10 μm or more and 1 mm or less.

Housing 30 with thermosetting resin for molding circuit package 400 and fixing portion 372
There is a difference in the coefficient of thermal expansion from the thermoplastic resin that molds 2, and it is desirable that excessive stress generated based on this difference in coefficient of thermal expansion is not applied to the circuit package 400.

Further, by forming the shape of the fixing portion 372 including the outer periphery of the circuit package 400 into a band shape and narrowing the width of the band, the stress due to the difference in the coefficient of thermal expansion applied to the circuit package 400 can be reduced. It is desirable that the width of the band of the fixed portion 372 is 10 mm or less, preferably 8 mm or less. In this embodiment, the circuit package 400 is fixed not only at the fixing portion 372 but also at the outer wall recessed portion 366 which is a part of the upstream outer wall 335 of the housing 302 because the circuit package 400 is included and the circuit package 400 is fixed. The width of the band of 372 can be further reduced. For example, if the width is 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 forming the housing 302 and a portion exposed without being covered for the purpose of reducing stress due to the difference in the coefficient of thermal expansion. The portion where the surface of these circuit packages 400 is exposed from the resin of the housing 302 is
A plurality of measurement flow path surfaces 4 are provided, one of which has the heat transfer surface exposed portion 436 described above.
The number is 30, and in addition, a portion exposed on the flange 312 side of the fixing portion 372 is provided. Further, an outer wall recessed portion 366 is formed to expose a portion upstream of the outer wall recessed portion 366, and this exposed portion is used as a support portion for supporting the temperature detecting portion 452. Circuit package 4
The portion of 00 on the flange 312 side of the fixing portion 372 on the outer surface is further from the outer circumference, particularly from the downstream side of the circuit package 400 to the side facing the flange 312, and further the circuit package 4
A gap is formed so as to surround the circuit package 400 toward the upstream side of the portion close to the terminal of 00. By forming a gap around the exposed surface of the circuit package 400 in this way, the circuit package 4 is formed from the main passage 124 via the flange 312.
The amount of heat transferred to 00 can be reduced, and the decrease in measurement accuracy due to the influence of heat is suppressed.

A gap is formed between the circuit package 400 and the flange 312, and this gap portion acts as a terminal connection portion 320. In 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. Terminal connection 32
As described above, the gap of 0 has the effect of suppressing heat transfer from the housing 302 to the circuit package 400, and for 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. It is secured as a usable space.

3.7 Structure and effect of terminal connection portion 320 FIG. 13 is an enlarged view of the terminal connection portion 320 of the housing 302 shown in FIGS. 5 and 6.
However, the following points are slightly different. The differences from the descriptions in FIGS. 5 and 6 are in FIGS.
In, while each external terminal inner end 361 is separated, FIG. 13 shows a state before each external terminal inner end 361 is separated, and each external terminal inner end 361 is connected by a connecting portion 365, respectively. ing. In the second molding step, each of the external terminal inner ends 361 protruding toward the circuit package 400 side of the external terminal 306 is placed so as to overlap the corresponding connection terminals 412 or to be in the vicinity of the corresponding connection terminals 412. The external terminal 306 is fixed to the housing 302 by a resin mold. In order to prevent deformation and misalignment of each external terminal 306, as an embodiment, a resin molding step (second resin mold) for molding the housing 302 in a state where the outer 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 step). However, the connection terminal 412 and the outer terminal inner end 361 may be fixed first, and then the outer terminal 306 may be fixed to the housing 302 by the second molding step.

3.8 Inspection of finished product by the first resin molding process In the embodiment shown in FIG. 13, the number of terminals included in the circuit package 400 is larger than the number of the inner ends 361 of the external terminals. Of the terminals included in the circuit package 400, the connection terminal 412 is connected to the outer terminal inner end 361, and the terminal 414 is not connected to the outer terminal inner end 361.
That is, the terminal 414 is provided in the circuit package 400, but the outer terminal inner end 361
It is a terminal that is not connected to.

In FIG. 13, in addition to the connection terminal 412 connected to the external terminal inner end 361, the external terminal inner end 36
A terminal 414 that is not connected to 1 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 and whether an abnormality has occurred in the electrical connection in the first resin molding process. By doing so, high reliability can be maintained for each circuit package 400. The terminal 414, which is not connected to the inner end 361 of the external terminal, is used for inspection of such a circuit package 400. Since the terminals 414 are not used after the inspection work, these unused terminals 414 may be cut at the root of the circuit package 400 after the inspection, or as shown in FIG. 13, the inside of the resin which is the terminal side fixing portion 362. You may bury it in. Terminal 414 not connected to the inner end 361 of the external terminal in this way
By providing the above, it is possible to inspect whether or not an abnormality has occurred in the circuit package 400 produced in the first resin molding step, and it is possible to maintain high reliability.

3.9 Communication structure and effect between the air gap inside the housing 302 and the outside of the thermal flowmeter 300 As shown in the partially enlarged view of FIG. 13, the housing 302 is provided with a hole 364. The hole 364 is connected to an opening 309 provided inside the external connection portion 305 shown in FIG. 4 (A). In the embodiment, both sides of the housing 302 are sealed by the front cover 303 and the back cover 304. If the holes 364 are not provided, a difference occurs between the air pressure in the air pressure and the outside air pressure due to the temperature change of the air in the air pressure including the terminal connection portion 320. It is desirable that such a pressure difference be 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 portion 305 has a structure that is not adversely affected by water or the like in order to improve the reliability of the electrical connection, and the opening 30
By providing 9 in the external connection portion 305, it is possible to prevent water from entering through the opening 309, and further prevent foreign matter such as dust and dirt from entering.

3.10 Housing 302 molding and effect by the second resin molding process In the housing 302 shown in FIGS. 5 and 6 described above, a circuit package 400 including a flow rate detection unit 602 and a processing unit 604 is manufactured by the first resin molding process. Next, a housing 302 having, for example, a front side sub-passage groove 332 and a back side sub-passage groove 334 for forming a sub-passage through which the gas to be measured 30 flows is manufactured in the second resin molding step. In this second resin molding step, the circuit package 400 is built in the resin of the housing 302, and the housing 3
It is fixed in 02 by a resin mold. By doing so, the heat transfer surface exposed portion 436 and the sub-passage for the flow rate detection unit 602 to transfer heat to the gas to be measured 30 and measure the flow rate, for example, the front sub-passage groove 332 and the back sub-passage It is 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 that occur 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 more than twice as compared with the conventional method of fixing using an adhesive. The thermal flowmeter 300 is often produced by mass production, and there is a limit in improving the measurement accuracy in the method of adhering with an adhesive while strictly measuring the flow meter 300. However, as in this embodiment, the circuit package 400 is manufactured by the first resin molding step, and then the sub-passage is formed in the second resin molding step of forming the sub-passage through which the gas to be measured 30 flows. By fixing the sub-passage, the variation in measurement accuracy can be significantly reduced, and the measurement accuracy of each thermal flow meter 300 can be significantly improved. This applies not only to the examples shown in FIGS. 5 and 6, but also to FIG. 7 or FIG.
The same applies to the examples shown in.

For example, further explaining with reference to the embodiment shown in FIGS. 5 and 6, the relationship between the front side sub-passage groove 332, the back side sub-passage groove 334, and the heat transfer surface exposed portion 436 can be determined with high accuracy so as to have a specified relationship. The circuit package 400 can be fixed to the housing 302. As a result, in each of the mass-produced thermal flowmeters 300, the positional relationship and shape of the heat transfer surface exposed portion 436 of each circuit package 400 and the sub-passage can be constantly obtained with extremely high accuracy. It becomes possible. Since the sub-passage groove to which the heat transfer surface exposed portion 436 of the circuit package 400 is fixed, for example, the front side sub-passage groove 332 and the back side sub-passage groove 334 can be formed with extremely high accuracy, the sub-passage is formed from this sub-passage groove. The work is a work of covering both sides of the housing 302 with the front cover 303 and the back cover 304. This work is very simple, and there are few factors that reduce the measurement accuracy. Further, the front cover 303 and the back cover 304 are produced by a resin molding process with high molding accuracy. Therefore, it is possible to complete the sub-passage provided in the specified relationship with the heat transfer surface exposed portion 436 of the circuit package 400 with high accuracy. By such a method, high productivity can be obtained in addition to improvement of measurement accuracy.

On the other hand, conventionally, a thermal flowmeter has been produced by manufacturing a sub-passage and then adhering a measuring unit to the sub-passage with an adhesive. In the method of using the adhesive in this way, the thickness of the adhesive varies widely, and the bonding position and the bonding angle vary from product to product. Therefore, there is a limit to improving the measurement accuracy. Further, when these operations are performed in the mass production process, it becomes very difficult to improve the measurement accuracy.

In the embodiment according to the present invention, first, the circuit package 400 including the flow rate detection unit 602 is produced by the first resin mold, then the circuit package 400 is fixed by the resin mold, and at the same time, the sub-passage is formed by the resin mold. The sub-passage groove for this purpose is formed by a second resin mold. By doing so, the flow rate detection unit 602 can be fixed to the shape of the sub-passage groove and the sub-passage groove with extremely high accuracy.

A portion related to the measurement of the flow rate, for example, a 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. After that, the measurement flow path surface 430 and the heat transfer surface exposed portion 436 are exposed from the resin forming the housing 302. That is, the heat transfer surface exposed portion 436 and the heat transfer surface exposed portion 436
The peripheral measurement flow path surface 430 is not covered with the resin forming the housing 302.
Measurement flow path surface 430 and heat transfer surface exposed portion 4 molded by the resin mold of the circuit package 400
The 36 or the temperature detection unit 452 is used as it is even after the resin molding of the housing 302, and is used for the flow rate measurement and the temperature measurement of the thermal flow meter 300. By doing so, the measurement accuracy is improved.

In the embodiment according to the present invention, since the circuit package 400 is integrally molded with the housing 302 to fix the circuit package 400 to the housing 302 having a sub-passage, the circuit package 400 is fixed to the housing 302 with a small fixed area. it can. That is,
A large surface area of the circuit package 400 that is not in contact with the housing 302 can be taken. The surface of the circuit package 400 that is not in contact with the housing 302 is exposed to, for example, a gap. The heat of the intake pipe is transferred to the housing 302, and is transferred from the housing 302 to the circuit package 400. The housing 302 does not cover the entire surface or most of the circuit package 400, and even if the contact area between the housing 302 and the circuit package 400 is reduced, the circuit package 400 is provided with high accuracy and high reliability. Housing 3
Can be fixed to 02. Therefore, the 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.

In the embodiment shown in FIGS. 5 and 6, the area A of the exposed surface of the circuit package 400 may be equal to the area B covered with the molding material for molding of the housing 302, or the area A may be larger than the area B. It 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 coefficient of thermal expansion of the thermosetting resin forming the circuit package 400 and the housing 3
The stress due to the difference in the expansion coefficient of the thermoplastic resin forming 02 can be reduced.

4. Appearance of circuit package 400 4.1 Molding of measurement flow path surface 430 provided with heat transfer surface exposed portion 436 FIG. 14 shows the appearance of the circuit package 400 produced in the first resin molding step. In addition, it should be noted
The shaded portion described on the appearance of the circuit package 400 is used in the second resin molding step when the housing 302 is molded in the second resin molding step after the circuit package 400 is manufactured in the first resin molding step. The fixed surface 432 in which the circuit package 400 is covered with the resin is shown. 14 (A) is a left side view of the circuit package 400, FIG. 14 (B) is a front view of the circuit package 400, and FIG. 14 (C) 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.

On the surface of the circuit package 400 shown in FIG. 11B, a measurement flow path surface 430 that acts as a surface for flowing the gas to be measured 30 is formed in a shape that extends long in the flow direction of the gas to be measured 30. In this embodiment, the measurement flow path surface 430 has a rectangular shape that extends long in the flow direction of the gas to be measured 30. As shown in FIG. 14A, the measurement flow path surface 430 is made thinner than the other parts, and a heat transfer surface exposed portion 436 is provided in a part thereof. The built-in flow rate detection unit 602 transfers heat to the gas to be measured 30 via the heat transfer surface exposed unit 436, measures the state of the gas to be measured 30, for example, the flow velocity of the gas to be measured 30, and measures the flow velocity of the gas to be measured 30, and the main passage 124 Outputs an electrical signal that represents the flow rate flowing through.

In order for the built-in flow rate detection unit 602 (see FIG. 20) to measure the state of the gas to be measured 30 with high accuracy, the gas flowing in the vicinity of the heat transfer surface exposed unit 436 must be a laminar flow and have less turbulence. desirable. Therefore, it is preferable that there is no step between the flow path side surface of the heat transfer surface exposed portion 436 and the surface of the measurement flow path surface 430 that guides the gas. With such a configuration, it is possible to suppress the action of uneven stress and strain on the flow rate detection unit 602 while maintaining the flow rate measurement accuracy with high accuracy. The step may be provided as long as it does not affect the flow rate measurement accuracy.

As shown in FIG. 14C, on the back surface of the measurement flow path surface 430 having the heat transfer surface exposed portion 436, the pressing marks 442 of the mold retainer that supports the internal substrate or the plate during resin molding of the circuit package 400. Remains. The heat transfer surface exposed portion 436 is a place used for exchanging heat with the gas to be measured 30, and in order to accurately measure the state of the gas 30 to be measured, the flow rate detection unit 602 and the subject are covered. It is desirable that heat transfer with the measurement gas 30 is performed well. Therefore, it is necessary to avoid covering the exposed portion 436 of the heat transfer surface with the resin in the first resin molding step. A mold is applied to both sides of the heat transfer surface exposed portion 436 and the back surface of the measurement flow path 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 concave-shaped pressing mark 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 this portion, and it is desirable to dissipate heat generated by these elements to the outside as much as possible. The molded recess is less affected by the resin and has the effect of easily dissipating heat.

The flow rate detection unit (flow rate detection element) 602 composed of semiconductor elements has a heat transfer surface exposed portion 43.
A semiconductor diaphragm corresponding to No. 6 is formed, and the semiconductor diaphragm can be obtained by forming a gap on the back surface of the flow rate detecting element 602. When the void is sealed, the semiconductor diaphragm is deformed due to the change in pressure in the void due to the temperature change, and the measurement accuracy is lowered. Therefore, in this embodiment, the opening 43 communicating with the void on the back surface of the semiconductor diaphragm
8 is provided on the surface of the circuit package 400, and a communication passage 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 the second
In the resin molding step, it is provided in a portion where the diagonal line shown in FIG. 14 is not shown so that the resin does not block the resin.

It is necessary to mold the opening 438 in the first resin molding step, and by applying a mold to the portion of the opening 438 and the back surface thereof and pressing both the front and back surfaces with the mold, the resin can be pressed into the portion of the opening 438. The inflow is blocked and the opening 438 is formed. The molding of the communication passage connecting the opening 438 and the gap on the back surface of the semiconductor diaphragm and the opening 438 will be described later.

4.2 Molding and effect of temperature detection unit 452 and protrusion 424 The temperature detection unit 452 provided in the circuit package 400 is a protrusion extending in the upstream direction of the gas to be measured 30 in order to support the temperature detection unit 452. The tip of the 424 is also provided, and has a function of detecting the temperature of the gas to be measured 30. In order to detect the temperature of the gas to be measured 30 with high accuracy, it is desirable to minimize the heat transfer to the portion other than the gas to be measured 30. The protruding portion 424 that supports the temperature detecting portion 452 has a shape in which the tip portion is thinner than the root portion.
A temperature detection unit 452 is provided at the tip portion thereof. Due to such a shape, the temperature detection unit 45
The influence of heat from the root portion of the protruding portion 424 on 2 is reduced.

Further, after the temperature of the gas to be measured 30 is detected by the temperature detection unit 452, the gas to be measured 30 flows along the protrusion 424 and acts to bring the temperature of the protrusion 424 closer to the temperature of the gas to be measured 30. As a result, the influence of the temperature at the base of the protruding portion 424 on the temperature detecting portion 452 is suppressed. In particular, in this embodiment, 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. Therefore, the gas to be measured 30 flows along the shape of the protrusion 424, and the protrusion 424 is efficiently cooled.

At the base of the protruding portion 424, the shaded portion is a fixed surface 432 covered with the resin that molds the housing 302 in the second resin molding step. A recess is provided in the shaded portion at the base of the protruding portion 424. This indicates that the housing 302 is provided with a recessed portion that is not covered with resin. By forming a recessed portion of the housing 302 at the base of the protrusion 424 that is not covered with the resin in this way, the protrusion 424 is further facilitated to be cooled by the gas to be measured 30.

4.3 Terminals of circuit package 400 The circuit package 400 is connected to supply power for operating the built-in flow rate detection unit 602 and processing unit 604, and to output flow rate measurement values and temperature measurement values. Terminal 412
Is provided. Further, a terminal 414 is provided in order to inspect whether the circuit package 400 operates correctly and whether or not an abnormality has occurred in the circuit components and their connections.
In this embodiment, the circuit package 400 is made by transfer-molding the flow rate detection unit 602 and the processing unit 604 with a thermosetting resin in the first resin molding step. The dimensional accuracy of the circuit package 400 can be improved by performing transfer molding, but in the transfer molding process, the high temperature pressurized inside the sealed mold containing the flow rate detection unit 602 and the processing unit 604. Since the resin is press-fitted, it is desirable to inspect the completed circuit package 400 for damage to the flow rate detection unit 602, the processing unit 604, and their wiring relationships. In this embodiment, terminals 414 for inspection are provided, and each circuit package 400 produced is inspected. Terminal for inspection 4
Since 14 is not used for measurement, as described above, terminal 414 is an external terminal inner end 361.
Not connected to. Note that each connection terminal 412 has a curved portion 41 in order to increase the mechanical elastic force.
6 is provided. By giving each connection terminal 412 a mechanical elastic force, it is possible to absorb the stress generated due to the difference in the coefficient of thermal expansion of the resin by the first resin molding step and the resin by the second resin molding step. That is, each connection terminal 412 is affected by thermal expansion due to the first resin molding process, and further, the outer terminal inner end 361 connected to each connection terminal 412.
Is affected by the resin produced by the second resin molding process. It is possible to absorb the generation of stress caused by the difference between these resins.

4.4 Fixing the circuit package 400 by the second resin molding step and its effect In FIG. 14, the shaded area is the second resin molding step in order to fix the circuit package 400 to the housing 302 in the second resin molding step. A fixed surface 432 is shown for covering the circuit package 400 with the thermoplastic resin used. As described with reference to FIGS. 5 and 6, the relationship between the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430 and the measurement flow path surface 430 and the shape of the sub-passage is a defined relationship. As such, it is important to maintain high accuracy. In the second resin molding step, since the circuit package 400 is fixed to the housing 302 in which the sub-passage is molded and the sub-passage is molded at the same time, the relationship between the sub-passage and the measurement flow path surface 430 and the heat transfer surface exposed portion 436 is established. Can be maintained with extremely high accuracy.
That is, 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 the mold for molding the housing 302 having the sub-passage. It will be possible. By injecting a high-temperature thermoplastic resin into this mold, the sub-passage is molded with high accuracy, and the circuit package 40
0 is fixed with high accuracy.

In this embodiment, the entire surface of the circuit package 400 is not a fixed surface 432 covered with a resin for molding the housing 302, but the surface is exposed on the connection terminal 412 side of the circuit package 400, that is, covered with a resin for the housing 302. There is a part that is not broken. In the embodiment shown in FIG. 14, the area of the surface of the circuit package 400 that is exposed from the resin for the housing 302 without being included in the resin of the housing 302 is larger than the area of the fixed surface 432 included in the resin for the housing 302. Is wider.

Housing 30 with thermosetting resin for molding circuit package 400 and fixing portion 372
There is a difference in the coefficient of thermal expansion from the thermoplastic resin that forms No. 2, and it is desirable that stress based on this difference in coefficient of thermal expansion is not applied to the circuit package 400 as much as possible. By reducing the number of fixed surfaces 432 on the surface of the circuit package 400, the influence based on the difference in the coefficient of thermal expansion can be reduced. For example, by forming a strip with a width L, the fixed surface 4 on the surface of the circuit package 400
32 can be reduced.

Further, by providing the fixing surface 432 at the base of the protruding portion 424, the mechanical strength of the protruding portion 424 can be increased. On the surface of the circuit package 400, a band-shaped fixed surface is provided along the axis through which the gas to be measured 30 flows, and a fixed surface in the direction intersecting the axis through which the gas to be measured 30 flows is provided to make the circuit package stronger. The 400 and the housing 302 can be fixed to each other. In the fixed surface 432, the portion surrounding the circuit package 400 in a band shape with a width L along the measurement flow path surface 430 is the fixed surface in the direction along the flow axis of the gas to be measured 30 described above, and is the root of the protruding portion 424. The portion covering the gas 30 is a fixed surface in the direction crossing the flow axis of the gas to be measured 30.

5. Mounting circuit components in a circuit package 5.1 Frame frame of a circuit package FIG. 15 shows a mounting state of chips of the frame frame 512 of the circuit package 400 and the circuit components 516 mounted on the frame frame 512. The broken line portion 508 is the circuit package 4.
The part covered by the mold used at the time of molding 00 is shown. A lead 514 is mechanically connected to the frame frame 512, a plate 532 is mounted in 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 done. The flow rate detecting unit 602 is provided with a diaphragm 672, which corresponds to the heat transfer surface exposed portion 436 described above by the molding molding described above. Further, each terminal of the flow rate detection unit 602 described below and the processing unit 604 are electrically connected by a wire 542. Further, each terminal of the processing unit 604 and the corresponding lead 514 are connected by a wire 543. In addition, the portion serving as the connection terminal of the circuit package 400 and the plate 5
A chip-shaped circuit component 516 is connected to the lead 514 located between the lead 514 and the lead 514.

When the circuit package 400 is completed in this way, the flow rate detection unit 602 having the diaphragm 672 is arranged on the most advanced side, and the processing unit 604 is in the LSI state so as to serve as a connection terminal to the flow rate detection unit 602. Further, a wire 543 for connection is arranged on the terminal side of the processing unit 604. By arranging the flow rate detection unit 602, the processing unit 604, the wire 543, the circuit component 516, and the connection lead 514 in this order from the tip side of the circuit package 400 in the direction of the connection terminal, the whole becomes simple and the whole Is a concise arrangement.

A lead is provided to support the plate 532, and this lead is a lead 556.
And leads 558 are fixed to the frame 512. A lead surface (not shown) having an area equivalent to that of the plate 532 connected to the lead is provided on the lower surface of the plate 532, and the plate 532 is mounted on the lead surface. These lead surfaces are grounded. As a result, noise can be suppressed by commonly grounding the inside of the circuit of the flow rate detection unit 602 and the processing unit 604 through the lead surface, and the measurement accuracy of the gas to be measured 30 is improved. Further, the lead 544 is provided so as to project from the plate 532 toward the upstream side of the flow path, that is, along the axis in the direction crossing the axes of the flow rate detection unit 602, the processing unit 604, and the circuit component 516 described above. There is. A temperature detection element 518, for example, a chip-shaped thermistor, is connected to the lead 544. Further, the processing unit 604, which is the base of the protruding portion.
A lead 548 is provided closer to the lead 548, and the lead 544 and the lead 548 are electrically connected by a thin wire 546 such as an Au wire. When the lead 548 and the lead 544 are directly connected, heat is transferred to the temperature detection element 518 via the lead 548 and the lead 544, and the temperature of the gas to be measured 30 cannot be accurately measured. Therefore, the thermal resistance between the lead 548 and the lead 544 can be increased by connecting with a wire having a small cross-sectional area and a large thermal resistance. As a result, the influence of heat is prevented from reaching the temperature detecting element 518, and the measurement accuracy of the temperature of the gas to be measured 30 is improved.

The lead 548 is fixed to the frame 512 by the lead 552 and the lead 554.
The connecting portions of the leads 552 and the leads 554 and the frame 512 are fixed to the frame 512 in a state of being inclined with respect to the protruding direction of the protruding temperature detecting element 518, and the mold is also arranged diagonally at this portion. It becomes. Since the molding resin flows along this diagonal state in the first resin molding step, the molding resin in the first resin molding step smoothly flows to the tip portion where the temperature detection element 518 is provided, and the reliability is improved. improves.

FIG. 15 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 resin injection is provided in the mold at the position marked with a circle.
The thermosetting resin is injected into the mold from the direction of 92. Arrow 592 from the press-fit hole 590
There is a circuit component 516 and a temperature detecting element 518 in the direction of the above, and there is a lead 544 for holding the temperature detecting element 518. Further, a plate 532, a processing unit 604, and a flow rate detecting unit 602 are provided in a direction close to the direction of arrow 592. By arranging in this way, the resin flows smoothly in the first resin molding step. In the first resin molding step, a thermosetting resin is used, and it is important to spread the resin throughout before curing. Therefore lead 5
The relationship between the arrangement of the circuit components and wiring in No. 14 and the press-fitting hole 590 and the press-fitting direction is very important.

5.2 Structure connecting the gap and the opening on the back surface of the diaphragm FIG. 16 is a diagram showing a part of the CC cross section of FIG. 15, which is provided inside the diaphragm 672 and the flow rate detection unit (flow rate detection element) 602. It is explanatory drawing explaining the communication hole 676 which connects a gap 674 and a hole 520.

As will be described later, the flow rate detecting unit 602 for measuring the flow rate of the gas to be measured 30 has a diaphragm 6
72 is provided, and a gap 674 is provided on the back surface of the diaphragm 672. Although not shown, the diaphragm 672 is provided with an element for exchanging heat with the gas to be measured 30 and measuring the flow rate by the exchange of heat. If heat is transferred between the elements formed in the diaphragm 672, apart from the exchange of heat with the gas to be measured 30, between the elements via the diaphragm 672, it becomes difficult to accurately measure the flow rate. For this reason, diaphragm 67
No. 2 needs to have a large thermal resistance, and the diaphragm 672 is made as thin as possible.

The flow rate detection unit (flow rate detection element) 602 is embedded and fixed in the first resin of the circuit package 400 formed by the first resin molding step so that the heat transfer surface 437 of the diaphragm 672 is exposed. The surface of the diaphragm 672 is provided with the elements (heating element 608 shown in FIG. 21, resistance 652 which is an upstream resistance temperature detector, resistance 654 and resistance 656, resistance 658 which are downstream resistance temperature detectors, etc.) which are not shown. .. The element transfers heat to and from the gas to be measured 30 (not shown) via the heat transfer surface 437 on the surface of the element in the heat transfer surface exposed portion 436 corresponding to the diaphragm 672. The heat transfer surface 437 may be formed on the surface of each element, or a thin protective film may be provided on the surface. It is desirable that heat transfer between the element and the gas to be measured 30 is performed smoothly, while direct heat transfer between the elements is as small as possible.

The portion of the flow rate detection unit (flow rate detection element) 602 in which the element is provided is arranged on the heat transfer surface exposed portion 436 of the measurement flow path surface 430, and the heat transfer surface 437 is the measurement flow path surface 430.
Is exposed from the resin that is molding. The outer peripheral portion of the flow rate detection element 602 is a flow path surface 43 for measurement.
It is covered with the thermosetting resin used in the first resin molding step of molding 0. Assuming that only the side surface of the flow rate detecting element 602 is covered with the thermosetting resin, and the surface side of the outer peripheral portion of the flow rate detecting element 602 (that is, the region around the diaphragm 672) is not covered with the thermosetting resin. The stress generated in the resin forming the flow path surface 430 for measurement is measured by the flow rate detection element 602.
Since it is received only on the side surface of the diaphragm 672, the diaphragm 672 may be distorted and its characteristics may be deteriorated. As shown in FIG. 16, the distortion of the diaphragm 672 is reduced by setting the outer peripheral portion on the front side of the flow rate detecting element 602 to be covered with the thermosetting resin. On the other hand, if the step between the heat transfer surface 437 and the measurement flow path surface 430 through which the gas to be measured 30 flows is large, the flow of the gas to be measured 30 is disturbed and the measurement accuracy is lowered. Therefore, it is desirable that the step W between the heat transfer surface 437 and the measurement flow path surface 430 through which the gas to be measured 30 flows is small.

The diaphragm 672 is made very thin in order to suppress heat transfer between the elements, and the thickness is reduced by forming a gap 674 on the back surface of the flow rate detecting element 602. When the gap 674 is sealed, the pressure of the gap 674 formed on the back surface of the diaphragm 672 changes based on the temperature due to the temperature change. When the pressure difference between the gap 674 and the surface of the diaphragm 672 becomes large, the diaphragm 672 receives pressure and causes distortion, which makes high-precision measurement difficult. Therefore, the plate 532 is provided with a hole 520 connected to the opening 438 that opens to the outside, and is provided with a communication hole 676 connecting the hole 520 and the gap 674. The communication hole 676 is made of, for example, two plates, a first plate 532 and a second plate 536.
The first plate 532 is provided with holes 520 and 521, and is further provided with a groove for forming a communication hole 676. By closing the groove and the hole 520 and the hole 521 with the second plate 536, the communication hole 676 is created. The diaphragm 672 is provided by the communication hole 676 and the hole 520.
The air pressure acting on the front and back surfaces of the is substantially equal, and the measurement accuracy is improved.

As described above, by closing the grooves and holes 520 and 521 with the second plate 536,
Communication holes 676 can be made, but another method is to use the lead frame in the second plate 5
It can be used as 36. As shown in FIG. 15, an LSI that operates as a diaphragm 672 and a processing unit 604 is provided on the plate 532. Below these, a lead frame for supporting the plate 532 on which the diaphragm 672 and the processing unit 604 are mounted is provided. Therefore, by using this lead frame,
The structure becomes simpler. Further, the lead frame can be used as a ground electrode. In this way, the lead frame is given the role of the second plate 536, and the lead frame is used to close the holes 520 and 521 formed in the first plate 534 and to form a groove formed in the first plate 534. By forming the communication hole 676 by covering it with the lead frame, the overall structure is simplified, and by acting as the ground electrode of the lead frame, the diaphragm 672 and the processing unit 604 are externally formed. The influence of noise can be reduced.

In the circuit package 400, a pressing mark 442 remains on the back surface of the circuit package 400 in which the heat transfer surface exposed portion 436 is formed. In the first resin molding step, in order to prevent the resin from flowing into the heat transfer surface exposed portion 436, a mold is formed on the heat transfer surface exposed portion 436.
For example, a insert piece is applied, and a mold is applied to the portion of the pressing mark 442 on the opposite surface thereof, and both molds prevent the resin from flowing into the heat transfer surface exposed portion 436. In this way, the heat transfer surface exposed portion 4
By molding the 36 portions, the flow rate of the gas to be measured 30 can be measured with extremely high accuracy.

FIG. 17 shows a state in which the frame shown in FIG. 15 is molded with a thermosetting resin by the first resin molding step and covered with the thermosetting resin. By this molding, the circuit package 4
The measurement flow path surface 430 is formed on the surface of 00, and the heat transfer surface exposed portion 436 is the measurement flow path surface 43.
It is provided at 0. Further, the gap 674 on the back surface of the diaphragm 672 corresponding to the heat transfer surface exposed portion 436 is configured to be connected to the opening 438. A temperature detection unit 452 for measuring the temperature of the gas to be measured 30 is provided at the tip of the protrusion 424, and a temperature detection element 518 is built in the temperature detection unit 452. Inside the protrusion 424, in order to suppress heat transfer, the lead for extracting the electric signal of the temperature detection element 518 is divided, and the connection wire 546 having a large thermal resistance.
Is placed. As a result, heat transfer from the root of the protruding portion 424 to the temperature detecting portion 452 is suppressed, and the influence of heat is suppressed.

Further, an inclined portion 594 and an inclined portion 596 are formed at the base of the protruding portion 424. In addition to smoothing the flow of resin in the first resin molding process, the gas 30 to be measured measured by the temperature detection unit 452 by the inclined portion 594 and the inclined portion 596 while being mounted on the vehicle and operating It has the effect of smoothly flowing from the protruding portion 424 toward the root thereof, cooling the root of the protruding portion 424, and reducing the influence of heat on the temperature detecting portion 452. After the state of FIG. 17, the lead 51
4 is separated for each terminal and becomes a connection terminal 412 and a terminal 414.

In the first resin molding step, it is necessary to prevent the resin from flowing into the heat transfer surface exposed portion 436 and the opening 438. Therefore, in the first resin molding step, the heat transfer surface exposed portion 43
At the positions of 6 and the opening 438, an insert piece larger than, for example, a diaphragm 672, which prevents the inflow of resin is applied, a presser is applied to the back surface thereof, and the resin is sandwiched from both sides. 14 (C) shows the heat transfer surface exposed portion 436 and opening 438 of FIG. 17, or the heat transfer surface exposed portion 436 of FIG. 14 (B).
A pressing mark 442 and a pressing mark 441 remain on the back surface corresponding to the opening 438 and the opening 438.

Since the cut surface of the reed separated from the frame 512 in FIG. 17 is exposed from the resin surface, moisture or the like may enter the inside from the cut surface of the lead during use. It is important to prevent such a situation from the viewpoint of improving durability and reliability. For example, the lead cutting portion of the inclined portion 594 and the inclined portion 596 is covered with resin in the second resin molding step, and FIG.
The cut surface of the lead 552 and the lead 554 with the frame 512 shown in 5 is covered with the resin. This prevents corrosion of the cut surface of the lead 552 and lead 554 and water intrusion from the cut portion. The cut surface of the lead 552 and the lead 554 is in close proximity to an important lead portion that transmits an electric signal of the temperature detection unit 452. Therefore, it is desirable to cover the cut surface with the second resin molding step.

5.3 Other Examples of Circuit Package 400 FIG. 18 is another embodiment of circuit package 400. The same code as the code shown in the other figures has the same function. In the embodiment shown in FIG. 14 described above, in the circuit package 400, the connection terminal 412 and the terminal 414 are provided on the same side of the circuit package 400. On the other hand, in the embodiment shown in FIG. 18, the connection terminal 412 and the terminal 414 are provided on different sides. The terminal 414 is a terminal that is not connected to the external connection terminal of the thermal flowmeter 300. In this way, the connection terminal 41 connected to the outside of the thermal flowmeter 300
By providing the terminal 2 and the terminal 414 not connected to the outside in different directions, the distance between the terminals of the connection terminal 412 can be widened, and the subsequent workability is improved. Further, 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 in a part.
The arrangement of leads within the frame 512 becomes easy. In particular, a chip capacitor or the like, which is a circuit component 516, is connected to the lead portion corresponding to the connection terminal 412. These circuit parts 51
A slightly large space is required to provide 6. In the embodiment of FIG. 18, there is an effect that it is easy to secure the lead space corresponding to the connection terminal 412.

Opening 438, heat transfer surface exposed portion 436, measurement flow path surface 430, pressing mark 4 in FIG.
41. The description of the pressing mark 442 is substantially the same as the above-mentioned content, and has the same effect. The specific description will be omitted because the description will be repeated.

6. Production process of the thermal flow meter 300 6.1 Production process of the circuit package 400 FIGS. 19A to 19C show the production process of the thermal flow meter 300, FIG. 19A shows the production process of the circuit package 400, and FIG. 19B shows the heat. The production process of the type flow meter is shown, and FIG. 19C shows another embodiment of the production process of the thermal flow meter. In FIG. 19A, step 1 shows a step of producing the frame shown in FIG. This frame frame is made, for example, by press working.

In step 2, the plate 532 is first mounted on the frame made in step 1, the flow rate detection unit 602 and the processing unit 604 are mounted on the plate 532, and the temperature detection element 5 is further mounted.
18. Mount circuit parts such as chip capacitors. Further, in step 2, electrical wiring is performed between circuit components, between circuit components and leads, and between leads. In this step 2, the lead 54
4 and the lead 548 are connected by a connecting wire 546 for increasing the thermal resistance. Step 2
Then, the circuit component shown in FIG. 15 is mounted on the frame frame 512, and an electric circuit is further electrically connected.

Next, in step 3, the thermosetting resin is molded by the first resin molding step. This state is shown in FIG. Further, in step 3, the connected leads are separated from the frame 512, and the leads are also separated from each other, and the circuit package 400 shown in FIG. 14 is separated.
To complete. As shown in FIG. 14, the circuit package 400 is formed with a measurement flow path surface 430 and a heat transfer surface exposed portion 436.

In step 4, the appearance inspection and the operation inspection of the completed circuit package 400 are performed. In the first resin molding step of step 3, the electric circuit made in step 2 is fixed in the mold, and the high-temperature resin is injected into the mold at a high pressure, so that an abnormality occurs in the electric parts and the electric wiring. It is desirable to inspect for the presence. Connection terminal 412 shown in FIGS. 14 and 18 for this inspection
In addition, terminal 414 is used. Since the terminal 414 is not used after that, it may be cut from the root after this inspection. For example, in FIG. 18, the used terminal 414 is cut at the root.

6.2 Production process and characteristic correction of the thermal flow meter 300 In the process shown in FIG. 19B, the circuit package 400 produced in FIG. 19A and the external terminal 306 are used, and the housing is housed by the second resin molding process in step 5. 302 is made. The housing 302 includes a resin sub-passage groove, a flange 312, and an external connection portion 305.
Is formed, the shaded portion of the circuit package 400 shown in FIG. 14 is covered with the resin in the second resin molding step, and the circuit package 400 is fixed to the housing 302. The combination of the production of the circuit package 400 by the first resin molding step (step 3) and the molding of the housing 302 of the thermal flow meter 300 by the second resin molding step greatly improves the flow rate detection accuracy. In step 6, each external terminal inner end 361 shown in FIG. 13 is disconnected, and the connection terminal 412 and the external terminal inner end 361 are connected in step 7.

When the housing 302 is completed in step 7, then in 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 by the front cover 303 and the back cover 304, and the gas to be measured 30 The sub-passage for flowing the gas is completed. Further, the diaphragm structure described with reference to FIGS. 7, 10 and 12 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, and the back cover 304 is made by molding in step 11. Further, the front cover 303 and the back cover 304 are manufactured in separate processes, and are molded by different molds.

In step 9, the gas is actually guided to the sub-passage and the characteristics are tested. Since the relationship between the sub-passage and the flow rate detection unit is maintained with high accuracy as described above, extremely high measurement accuracy can be obtained by performing characteristic correction by the characteristic test. In addition, since positioning and shape-related molding that affect the relationship between the sub-passage and the flow rate detector are performed in the first resin molding process and the second resin molding process, there is little change in characteristics even after long-term use, and high accuracy is achieved. In addition, high reliability is ensured.

6.3 Production process of thermal flowmeter 300 and another embodiment of characteristic correction In FIG. 19C, the circuit package 400 and external terminal 306 produced in FIG. 19A are used and before the second resin molding process. Connection terminal 412 and external terminal inner end 36 in step 12
The connection with 1 is made. At this time, or in a step prior to step 12, the inner end 361 of each external terminal shown in FIG. 13 is separated. In step 13, the housing 302 is made by the second resin molding step. The housing 302 has a resin sub-passage groove and a flange 3
12 and the external connection portion 305 are formed, the shaded portion of the circuit package 400 shown in FIG. 14 is covered with the resin in the second resin molding step, and the circuit package 400 is fixed to the housing 302. Production of circuit package 400 by the first resin molding step (step 3)
) And the molding of the housing 302 of the thermal flow meter 300 by the second resin molding step, the flow rate detection accuracy is significantly improved.

When the housing 302 is completed in step 13, then in step 8, the front cover 30
3 and the back cover 304 are attached to the housing 302, the inside of the housing 302 is sealed by the front cover 303 and the back cover 304, and a sub-passage for flowing the gas to be measured 30 is completed. Further, the diaphragm structure described with reference to FIGS. 7, 10 and 12 is formed by the protrusions 356 provided on the front cover 303 or the back cover 304. In addition, this table cover 30
3 is made by molding in step 10, and the back cover 304 is made by molding in step 11. Further, the front cover 303 and the back cover 304 are manufactured in separate processes, and are molded by different molds.

In step 9, the gas is actually guided to the sub-passage and the characteristics are tested. As described above, since the relationship between the sub-passage and the flow rate detection unit is maintained with high accuracy, extremely high measurement accuracy can be obtained by performing characteristic correction by the characteristic test. In addition, since positioning and shape-related molding that affect the relationship between the sub-passage and the flow rate detector are performed in the first resin molding process and the second resin molding process, there is little change in characteristics even after long-term use, and high accuracy is achieved. In addition, high reliability is ensured.

7. Circuit configuration of the thermal flowmeter 300 7.1 Overall circuit configuration of the thermal flowmeter 300 FIG. 20 is a circuit diagram showing the flow rate detection circuit 601 of the thermal flowmeter 300. The measurement circuit for the temperature detection unit 452 described above in the embodiment is also provided in the thermal flow meter 300, but is omitted in FIG. 20. The flow rate detection circuit 601 of the thermal flow meter 300 includes a flow rate detection unit 602 having a heating element 608 and a processing unit 604. The processing unit 604 is a flow rate detecting unit 6.
While controlling the amount of heat generated by the heating element 608 of 02, a signal representing the flow rate is output via the terminal 662 based on the output of the flow rate detection unit 602. In order to perform the above processing, the processing unit 604
Central Processing Unit (hereinafter referred to as CPU) 612, input circuit 614, output circuit 61
6. It is provided with a memory 618 for holding data showing the relationship between a correction value or a measured value and a flow rate, and a power supply circuit 622 for supplying a constant voltage to a required circuit. DC power is supplied to the power supply circuit 622 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 gas to be measured 30.
A 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 to this control signal. Based on the transistor 606
A current is supplied to the heating element 608 via 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 transistors 606 forming the current supply circuit of the heating element 608 via the output circuit 616. The processing unit 604 controls the calorific value of the heating element 608 so that the temperature of the gas 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 is a heat generation control bridge 640 for controlling the amount of heat generated by the heating element 608.
And a flow rate detection bridge 650 for measuring the flow rate. A constant voltage V3 is supplied from the power supply circuit 622 to one end of the heat generation control bridge 640 via the 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 the power supply circuit 622 to one end of the flow rate detection bridge 650 via the 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 has a resistance 642, which is a resistance temperature detector whose resistance value changes based on the temperature of the heated gas 30 to be measured, and has a resistance 642, a resistance 644, and a resistance 646.
The resistor 648 constitutes a bridge circuit. The potential difference between the intersection A of the resistor 642 and the resistor 646 and the intersection B between the resistor 644 and the resistor 648 is input to the input circuit 614 via the terminals 627 and 628, and the CPU 612 has a predetermined value for the potential difference between the intersection A and the intersection B. In this embodiment, the heating element 60 is controlled by controlling the current supplied from the transistor 606 so as to be zero volt.
The calorific value of 8 is controlled. The flow rate detection circuit 601 shown in FIG. 20 heats the gas 30 to be measured by the heating element 608 so that the temperature is constant, for example, 100 ° C. higher than the original temperature of the gas 30 to be measured. In order to perform this heating control with high accuracy, when the temperature of the measurement gas 30 heated by the heating element 608 becomes a constant temperature, for example, always 100 ° C. higher than the initial temperature, it intersects with the intersection A. The resistance value of each resistance constituting the heating control bridge 640 is set so that the potential difference between B is zero volt. Therefore, in the flow rate detection circuit 601 shown in FIG. 20, the CPU 612 controls the supply current to the heating element 608 so that the potential difference between the intersection A and the intersection B becomes zero volt.

The flow rate detection bridge 650 is composed of 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 gas to be measured 30, and the resistors 652 and 654 are arranged upstream of the heating element 608 in the flow path of the gas 30 to be measured, and the resistance 656. And the resistor 658 are arranged on the downstream side in the flow path of the gas to be measured 30 with respect to the heating element 608. Also, resistance 652 to improve measurement accuracy
And the resistor 654 are arranged so that the distances to the heating element 608 are substantially the same, and the resistors 656 and the resistor 658 are arranged so that the distances to the heating element 608 are substantially the same.

The potential difference between the intersection C of the resistor 652 and the resistor 656 and the intersection D of the resistor 654 and the resistor 658 is input to the input circuit 614 via the terminals 631 and 632. In order to improve the measurement accuracy, for example, each resistor 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 gas to be measured 30 is zero. Therefore, when the potential difference between the intersection C and the intersection D is, for example, zero volt, the CPU 612 outputs an electric signal meaning that the flow rate of the main passage 124 is zero based on the measurement result that the flow rate of the gas to be measured 30 is zero. Output from terminal 662.

When the gas to be measured 30 is flowing in the direction of the arrow in FIG. 20, the resistor 6 arranged on the upstream side
The 52 and the resistor 654 are cooled by the gas to be measured 30, and the resistors 656 and the resistor 658 arranged on the downstream side of the gas 30 to be measured are warmed by the gas 30 to be measured warmed by the heating element 608, and these resistors. The temperature of 656 and resistor 658 rises. 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 terminals 631 and 632. CPU 612 is a flow detection bridge 650
Based on the potential difference between the intersection C and the intersection D, the data representing the relationship between the potential difference stored in the memory 618 and the flow rate of the main passage 124 is searched, and the flow rate of the main passage 124 is obtained. An electric signal representing the flow rate of the main passage 124 thus obtained is output via the terminal 662. Although the terminal 664 and the terminal 662 shown in FIG. 20 have new reference numbers, they are included in the connection terminals 412 shown in FIGS. 5, 6 or 13 described above.

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 further obtained after the circuit package 400 is produced based on the measured value of the gas. In addition, correction data for reducing measurement errors such as variations are stored. The actual measurement of the gas after the production of the circuit package 400 and the writing of the correction value based on the actual measurement to the memory 618 are performed by using the external terminal 306 and the correction terminal 307 shown in FIG. In this embodiment, the arrangement relationship between the sub-passage through which the gas to be measured 30 flows and the flow path surface for measurement 430 and the arrangement relationship between the sub-passage through which the gas to be measured 30 flows and the heat transfer surface exposed portion 436 are extremely accurate. Since the circuit package 400 is produced in a state where there is little variation in the gas, the measurement result with extremely high accuracy can be obtained by the correction by the correction value.

7.2 Configuration of Flow Rate Detection Circuit 601 FIG. 21 is a circuit configuration diagram showing the circuit arrangement of the flow rate detection circuit 601 of FIG. 20 described above.
The flow rate detection circuit 601 is made as a rectangular semiconductor chip, and the gas to be measured 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 having a reduced thickness of the semiconductor chip is formed in the flow rate detection unit (flow rate detection element) 602 composed of a semiconductor chip, and the diaphragm 672 has a thin region indicated by a broken line (that is, described above). The heat transfer surface) 603 is provided. The above-mentioned gap is formed on the back surface side of the thin region 603, and the gap communicates with the opening 438 shown in FIGS. 14 and 5, and the air pressure in the gap depends on the air pressure derived from the opening 438. ..

By reducing the thickness of the diaphragm 672, the thermal conductivity is lowered, and the resistance 652, the resistance 654, and the resistance 65 provided in the thin region (heat transfer surface) 603 of the diaphragm 672 are reduced.
8. Heat transfer to the resistor 656 via the diaphragm 672 is suppressed, and the temperature of these resistors is roughly determined by the heat transfer with the gas to be measured 30.

A heating element 608 is provided in the center of the thin region 603 of the diaphragm 672.
A resistor 642 forming a heat generation control bridge 640 is provided around the heating element 608. Then, the resistors 644 and 6 forming the heat generation control bridge 640 outside the thin region 603
46 and 648 are provided. Resistors 642, 644, 646, 6 thus formed
The heat generation control bridge 640 is configured by 48.

Further, a resistor 652 and a resistor 654 which are upstream resistance temperature detectors and a resistor 656 and a resistor 658 which are downstream resistance temperature detectors are arranged so as to sandwich the heating element 608, and the gas to be measured is arranged with respect to the heating element 608. Resistors 652 and 65, which are upstream resistance temperature detectors, are on the upstream side in the direction of the arrow through which 30 flows.
4 is arranged, and resistors 656 and 658, which are downstream resistance temperature detectors, are arranged on the downstream side in the direction of the arrow in which the gas to be measured 30 flows with respect to the heating element 608. In this way, the thin region 6
The flow rate detection bridge 650 is formed by the resistor 652, the resistor 654, the resistor 656, and the resistor 658 arranged at 03.

Further, both ends of the heating element 608 have terminals 624 and 6 shown on the lower side of FIG. 21.
Each is connected to 29. Here, as shown in FIG. 20, 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.

Resistor 642, resistor 644, resistor 646, resistor 648 constituting the heat generation control bridge 640
Are connected and connected to terminals 626 and 630, respectively. As shown in FIG. 20, a constant voltage V3 is supplied to the terminal 626 from the power supply circuit 622, and the terminal 630 is grounded as a ground. Further, the connection point between the resistor 642 and the resistor 646 and between the resistor 646 and the resistor 648 is connected to the terminal 627 and the terminal 628. As described in FIG. 21, terminal 627 outputs the potential at the intersection A of resistor 642 and resistor 646, and terminal 627 outputs resistor 644 and resistor 64.
The potential of the intersection B with 8 is output. As shown in FIG. 20, the terminal 625 has a power supply circuit 622.
A constant voltage V2 is supplied from the terminal 630, and the terminal 630 is grounded as a ground terminal. Further, the connection point between the resistor 654 and the resistor 658 is connected to the terminal 631, and the terminal 631 is shown in FIG.
The potential at point B of 0 is output. The connection point between the resistor 652 and the resistor 656 is connected to the terminal 632, and the terminal 632 outputs the potential at the intersection C shown in FIG.

As shown in FIG. 21, the resistor 642 constituting the heat generation control bridge 640 is a heating element 608.
Since it is formed in the vicinity of, the temperature of the gas warmed by the heat generated from the heating element 608 can be measured with high accuracy. On the other hand, the resistors 644 and 646 constituting the heat generation control bridge 640
, 648 are arranged apart from the heating element 608, so that they are not easily affected by the heat generated from the heating element 608. The resistor 642 is configured to react sensitively to the temperature of the gas warmed by the heating element 608, and the resistance 644, the resistor 646, and the resistor 648 are the heating element 60.
It has a structure that is not easily affected by 8. Therefore, the detection accuracy of the gas to be measured 30 by the heat generation control bridge 640 is high, and the control for raising the gas to be measured 30 by a predetermined temperature with respect to the initial temperature can be performed with high accuracy.

In this embodiment, a gap is formed on the back surface side of the diaphragm 672, and the gap communicates with the opening 438 shown in FIGS. 14 and 5, the pressure of the gap on the back surface side of the diaphragm 672 and the front side of the diaphragm 672. The difference with the pressure of is not large. The distortion of the diaphragm 672 due to this pressure difference can be suppressed. This leads to improvement in flow rate measurement accuracy.

As described above, the diaphragm 672 forms the thin region 603, and the thickness of the portion including the thin region 603 is made very thin, so that 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 have a diaphragm 672.
The influence of heat conduction through the gas is suppressed, the tendency to operate depending on the temperature of the gas to be measured 30 becomes stronger, and the measurement operation is improved. Therefore, high measurement accuracy can be obtained.

The present invention can be applied to the above-mentioned measuring device for measuring the flow rate of gas.

300 Thermal flowmeter 302 Housing 303 Front cover 304 Back cover 305 External connection part 306 External terminal 307 Correction terminal 310 Measuring part 320 Terminal connection part 332 Front side sub-passage groove 334 Back side sub-passage groove 356, 358 Protrusion part 359 Resin part 361 External terminal Inner end 365 Connection part 372 Fixing part 400 Circuit package 412 Connection terminal 414 Terminal 424 Protruding part 430 Measuring flow path surface 432 Fixed surface 436 Heat transfer surface Exposed part 438 Opening 452 Temperature detection part 590 Press-fit hole 594, 596 Inclined part 601 Flow rate detection circuit 602 Flow rate detection unit 604 Processing unit 608 Heating element 640 Heating control bridge 650 Flow rate detection bridge 672 Diaphragm

Claims (8)

A sub-passage for taking in and flowing the gas to be measured flowing through the main passage,
A flow rate measurement circuit for measuring the flow rate by transferring heat to the gas to be measured flowing through the sub-passage, and
A circuit package having a first resin for sealing the flow rate measurement circuit, and
A housing made of a second resin having an external connection portion for accommodating the circuit package and connecting to an external device and having a coefficient of thermal expansion different from that of the first resin is provided.
The circuit package is at least
A measuring terminal for outputting a measurement result of the flow rate measuring circuit,
An inspection terminal for inspecting the flow rate measurement circuit after sealing with the first resin,
Have and
The measurement terminal and the inspection terminal are provided on different sides of the circuit package.
The inspection terminal is a thermal flow meter characterized in having a shorter shape than the measurement terminal. In the thermal flow meter according to claim 1,
Further, the circuit package is a thermal flow meter including a correction terminal for reading adjustment data from the outside after the circuit package is housed in the housing. In the thermal flow meter according to claim 1,
The housing comprises the external connection and a sub-passage groove for forming the sub-passage.
By covering the housing cover, wherein the thermal flow meter the bypass passage sub passage groove is covered with the cover is formed. In the thermal flow meter according to claim 2,
A thermal flowmeter having a different shape between the end of the external connection portion connected to the external device and the end of the correction terminal connected to the external device. In the thermal flow meter according to claim 2,
The measurement terminal and the correction terminal are thermal flowmeters having a bent portion. In the thermal flow meter according to claim 2,
The inspection terminal is a thermal flowmeter having a shorter shape than the correction terminal. In the thermal flow meter according to claim 2,
The electrical connection portion between the measurement terminal and the external connection portion is a thermal flow meter covered with the second resin. It is a manufacturing method of a thermal flow meter for measuring the flow rate by transferring heat to and from the gas to be measured flowing through the sub-passage.
A flow rate measurement circuit for measuring the flow rate, a measurement terminal for outputting the measurement result of the flow rate measurement circuit, and an inspection terminal provided on a side different from the measurement terminal to inspect the flow rate measurement circuit. A resin molding process that seals the terminals with resin,
An inspection step of inspecting the flow rate measurement circuit using the inspection terminal after the resin molding step,
A method for manufacturing a thermal diversion meter, which comprises a cutting step of cutting the inspection terminal after the inspection step.

Images