JP2014001934A - Thermal type flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal type flowmeter having high reliability and including a gas temperature detecting part.SOLUTION: A thermal type flowmeter comprises: a sub-passage for taking in measured gas flowing through a main passage, and making the measured gas flow through; a flow rate measuring circuit for measuring a flow rate by performing heat transfer between the measured gas flowing through the sub-passage and itself; and a case for housing the flow rate measuring circuit, with an external terminal for connecting with an external device. The flow rate measuring circuit includes a measuring terminal for outputting a measurement result, an inspecting terminal for inspecting the flow rate measuring circuit, and an adjusting terminal. The measuring terminal and the adjusting terminal are projected from the flow rate measuring circuit, and electrically connected to the external terminal provided on the case and the external adjusting terminal, respectively. The inspecting terminal is electrically disconnected from the external terminal and the external adjusting terminal.

Description

  The present invention relates to a thermal flow meter.

  A thermal flow meter for measuring a gas flow rate includes a flow rate detection unit for measuring a flow rate, and performs heat transfer between the flow rate detection unit and a measurement target gas to be measured. It is configured to measure the flow rate. The flow rate measured by the 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 a gas flow rate, for example, a mass flow rate, with relatively high accuracy compared to other types of flow meters.

  However, when the thermal flow meter is mass-produced, it is important to reduce variations in order to maintain high measurement accuracy. Conventionally, it is known that an adjustment terminal is provided in addition to a measurement terminal. Such a technique is described in, for example, Japanese Patent Application Laid-Open No. 2011-106868 (Patent Document 1). However, it does not mention how and for what purpose the adjustment terminal is used.

JP 2011-106868 A

  When a thermal flow meter is mass-produced, it is desirable to reduce variations associated with mass production. It is desirable to maintain high reliability. For example, in a thermal type flow meter used for vehicle control, if an abnormality occurs in the thermal type flow meter, it may be difficult to travel the vehicle. Even if the vehicle can travel, a big problem arises from the viewpoint of exhaust purification of the car. Patent Document 1 discloses that an adjustment terminal is provided, but does not discuss improvement of reliability.

  An object of the present invention is to provide a thermal flow meter in which high reliability is maintained.

  In order to solve the above problems, the thermal flow meter of the present invention performs heat transfer between a sub-passage for taking in and flowing the gas to be measured flowing through the main passage and the gas to be measured flowing through the sub-passage. And a case having an external terminal for housing the flow measurement circuit and connecting to an external device, and the flow measurement circuit outputs an output of a measurement result. A measuring terminal for inspecting the flow measuring circuit and an adjusting terminal, and the measuring terminal and the adjusting terminal project from the flow measuring circuit and are provided in the case. The external terminal and the external adjustment terminal are electrically connected to each other, and the inspection terminal is electrically disconnected from the external terminal and the external adjustment terminal.

  Alternatively, heat transfer is performed between a case having a sub-passage for taking in and flowing the gas to be measured flowing through the main passage and an external terminal for connection to an external device, and the gas to be measured flowing through the sub-passage. A circuit package molded with a first resin containing a flow rate measurement circuit for measuring a flow rate by the case, and the case includes the external terminal and the circuit package, and a sub-passage for forming the sub-passage. A housing formed with a second resin, provided with a passage groove, and a cover that forms the sub passage by covering the sub passage groove; and the external terminal is formed on the second resin constituting the housing. The external terminal has an inner terminal for connecting with the circuit package, the housing has a gap inside, and the front of the external terminal is embedded and held. The inner terminal of the external terminal protrudes from the second resin forming the housing into the gap, the terminal of the circuit package is disposed in the gap, and the inner end of the external terminal and the terminal of the circuit package are They are connected in the gap.

  According to the present invention, it is possible to provide a thermal flow meter with excellent reliability.

1 is a system diagram showing an embodiment in which a thermal flow meter according to the present invention is used in an internal combustion engine control system. It is a figure which shows the external appearance of a thermal type flow meter, (A) is a left view, (B) is a front view. It is a figure which shows the external appearance of a thermal type flow meter, (A) is a right view, (B) is a rear view. It is a figure which shows the external appearance of a thermal type flow meter, (A) is a top view, (B) is a bottom view. It is a figure which shows the housing of a thermal type flow meter, (A) is a left view of a housing, (B) is a front view of a housing. It is a figure which shows the housing of a thermal type flow meter, (A) is a right view of a housing, (B) is a rear view of a housing. It is the elements on larger scale which show the state of the flow-path surface arrange | positioned at a subchannel | path. It is a figure which shows the external appearance of a table | surface cover, (A) is a left view, (B) is a front view, (C) is a top view. It is a figure which shows the external appearance of the back cover 304, (A) is a left view, (B) is a front view, (C) is a top view. It is the elements on larger scale of a terminal connection part. It is an external view of a circuit package, (A) is a left side view, (B) is a front view, and (C) is a rear view. It is a figure which shows the state which mounted the circuit components in the frame frame of the circuit package. It is explanatory drawing explaining the communicating path which connects the space | gap and opening inside a diaphragm and a diaphragm. It is a figure which shows the state of the circuit package after a 1st resin mold process. FIG. 12 is a view showing another embodiment of the circuit package shown in FIG. 11, wherein (A) is a front view of the circuit package and (B) is a rear view. It is a figure which shows the outline | summary of the production process of a thermal type flow meter. It is a circuit diagram which shows the flow volume detection circuit of a thermal type flow meter. It is explanatory drawing explaining the flow volume detection part of a flow volume detection circuit. It is a front view which shows the other Example of the housing which comprises a thermal type flow meter. It is explanatory drawing explaining the state which connected the connector of the external apparatus to the external connection part. It is a front view which shows the other Example of the temperature detection part of a circuit package main body. It is explanatory drawing which shows an example of utilization of the correction | amendment data of flow volume.

  The form for carrying out the invention described below (hereinafter referred to as an embodiment) solves various problems that are demanded as actual products, and particularly as a measuring device for measuring the intake air amount of a vehicle. It solves various problems that are desirable for use, and has various effects. One of the various problems solved by the following embodiment is the contents described in the column of the problem to be solved by the above-described invention, and one of the various effects exhibited by the following embodiment is It is the effect described in the column of the effect of the invention. Various problems solved by the following embodiments, and various effects produced by the following embodiments will be described in the description of the following embodiments. Therefore, the problems and effects solved by the embodiments described in the following embodiments are also described in the contents other than the contents of the problem column to be solved by the invention and the effect column of the invention.

  In the following embodiments, the same reference numerals indicate the same configuration even when the figure numbers are different, and the same effects are achieved. For configurations that have already been described, only the reference numerals are attached to the drawings, and the description may be omitted.

1. FIG. 1 shows an embodiment in which the thermal flow meter according to the present invention is used for an electronic fuel injection internal combustion engine control system. It is a system diagram. Based on the operation of the internal combustion engine 110 including the engine cylinder 112 and the engine piston 114, the intake air is sucked from the air cleaner 122 as the measurement target gas 30 and passes through the main passage 124 such as the intake body, the throttle body 126, and the intake manifold 128. Guided to the combustion chamber of the engine cylinder 112. The flow rate of the gas 30 to be measured, which is the intake air led to the combustion chamber, is measured by the thermal flow meter 300 according to the present invention, and fuel is supplied from the fuel injection valve 152 based on the measured flow rate. The gas to be measured is introduced into the combustion chamber together with a certain gas 30 to be measured. In the present embodiment, the fuel injection valve 152 is provided in the intake port of the internal combustion engine, and the fuel injected into the intake port forms an air-fuel mixture with the measured gas 30 that is intake air, and is connected via the intake valve 116. It is guided to the combustion chamber and burns to generate mechanical energy.

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

  The fuel and air guided to the combustion chamber are in a mixed state of fuel and air, and are burned explosively by spark ignition of the spark plug 154 to generate mechanical energy. The combusted gas is guided from the exhaust valve 118 to the exhaust pipe, and exhausted as exhaust 24 from the exhaust pipe to the outside of the vehicle. The flow rate of the gas 30 to be measured, which is the intake air led to the combustion chamber, is controlled by the throttle valve 132 whose opening degree changes based on the operation of the accelerator pedal. The fuel supply amount is controlled based on the flow rate of the intake air guided to the combustion chamber, and the driver controls the flow rate of the intake air guided to the combustion chamber by controlling the opening degree of the throttle valve 132, thereby The mechanical energy generated by the engine can be controlled.

1.1 Outline of Control of Internal Combustion Engine Control System The flow rate and temperature of the measurement target gas 30 that is the intake air that is taken in from the air cleaner 122 and flows through the main passage 124 are measured by the thermal flow meter 300, and from the thermal flow meter 300 An electric signal indicating the flow rate and temperature of the intake air is input to the control device 200. Further, the output of the throttle angle sensor 144 for measuring the opening degree of the throttle valve 132 is input to the control device 200, and further the positions and states of the engine piston 114, the intake valve 116 and the exhaust valve 118 of the internal combustion engine, and the rotation of the internal combustion engine. 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 mixture ratio between 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 intake air that is the output of the thermal flow meter 300 and the rotational speed of the internal combustion engine that is measured based on the output of the rotation angle sensor 146. Based on these calculation results, the amount of fuel supplied from the fuel injection valve 152 and the ignition timing ignited by the spark plug 154 are controlled. The fuel supply amount and ignition timing are actually based on the intake air temperature and throttle angle change state measured by the thermal flow meter 300, the engine rotational speed change state, and the air-fuel ratio state measured by the oxygen sensor 148. It is finely controlled. The control device 200 further controls the amount of air that bypasses the throttle valve 132 by the idle air control valve 156 in the idle operation state of the internal combustion engine, thereby controlling the rotational speed of the internal combustion engine in the idle operation state.

1.2 Improvement of measurement accuracy and installation environment of thermal flow meter equipped with intake air temperature detection function Both the fuel supply amount and ignition timing, which are the main control variables of the internal combustion engine, mainly output from the thermal flow meter 300 Calculated as a parameter. Further, control parameters are corrected based on the temperature of the intake air as necessary. Improvement in measurement accuracy of the thermal flow meter 300, suppression of changes over time, and improvement in reliability are important for improving vehicle control accuracy and ensuring reliability. In particular, 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 measurement target gas 30 that is the intake air measured by the thermal flow meter 300. It is also important that the thermal flow meter 300 maintains high reliability.

  The vehicle on which the thermal flow meter 300 is mounted is used in an environment with a large temperature change, and is used in wind and rain or snow. When a vehicle travels on a snowy road, it travels on a road on which an antifreezing agent is sprayed. It is desirable for the thermal flow meter 300 to take into account the response to temperature changes in the environment in which it is used and the response to dust and contaminants. Further, the thermal flow meter 300 is installed in an environment that receives vibrations of the internal combustion engine. It is required to maintain high reliability against vibration.

  The thermal flow meter 300 is attached to an intake pipe that is affected by heat generated from the internal combustion engine. Therefore, heat generated by the internal combustion engine is transmitted to the thermal flow meter 300 via the intake pipe which is the main passage 124. Since the thermal flow meter 300 measures the flow rate of the gas to be measured by performing heat transfer with the gas to be measured, it is important to suppress the influence of heat from the outside as much as possible.

  As described below, the thermal flow meter 300 mounted on the vehicle simply solves the problem described in the column of the problem to be solved by the invention, and exhibits the effect described in the column of the effect of the invention. In addition, as will be described below, the above-described various problems are fully considered, and various problems required as products are solved, and various effects are produced. Specific problems to be solved by the thermal flow meter 300 and specific effects achieved will be described in the description of the following examples.

2. 2.1 Configuration of Thermal Flow Meter 300 2.1 External Structure of Thermal Flow Meter 300 FIGS. 2, 3, and 4 are views showing the external appearance of the thermal flow meter 300, and FIG. 2B is a front view, FIG. 3A is a right side view, FIG. 3B is a rear view, FIG. 4A is a plan view, and FIG. It is a bottom view. The thermal flow meter 300 includes a case 301, and the case 301 includes a housing 302, a front cover 303, and a back cover 304. The housing 302 includes a flange 312 for fixing the thermal flow meter 300 to the intake body that is the main passage 124, an external connection portion 305 having an external terminal 306 for electrical connection with an external device, and a flow rate. Etc., a measuring unit 310 is provided. A sub-passage groove for creating a sub-passage is provided inside the measuring unit 310, and a flow rate detection for measuring the flow rate of the gas 30 to be measured flowing through the main passage 124 is provided inside the measuring unit 310. A circuit package 400 including a temperature detection unit 452 for measuring the temperature of the measurement target gas 30 flowing through the unit 602 (see FIG. 17) and the main passage 124 is provided.

2.2 Effects based on the external structure of the thermal flow meter 300 Since the inlet 350 of the thermal flow meter 300 is provided on the distal end side of the measuring unit 310 extending from the flange 312 toward the center of the main passage 124, A portion of the gas that is not near the inner wall surface of the passage 124 but near the center away from the inner wall surface can be taken into the sub-passage. For this reason, the thermal type flow meter 300 can measure the flow rate and temperature of the gas in the part away from the inner wall surface of the main passage 124, and can suppress a decrease in measurement accuracy due to the influence of heat or the like. In the vicinity of the inner wall surface of the main passage 124, the temperature of the measurement target gas 30 is easily affected by the temperature of the main passage 124 and is different from the original temperature of the gas. It will be different from the state. In particular, when the main passage 124 is an intake body of an engine, it is often maintained at a high temperature under the influence of heat from the engine. For this reason, the gas in the vicinity of the inner wall surface of the main passage 124 is often higher than the original temperature of the main passage 124, which causes a reduction in measurement accuracy.

  In the vicinity of the inner wall surface of the main passage 124, the fluid resistance is large, and the flow velocity is lower than the average flow velocity of the main passage 124. For this reason, if the gas in the vicinity of the inner wall surface of the main passage 124 is taken into the sub passage as the gas to be measured 30, a decrease in the flow velocity with respect to the average flow velocity in the main passage 124 may lead to a measurement error. In the thermal flow meter 300 shown in FIGS. 2 to 4, the inlet 350 is provided at the tip of the thin and long measuring unit 310 extending from the flange 312 toward the center of the main passage 124, so that the flow velocity in the vicinity of the inner wall surface is provided. Measurement errors related to the reduction can be reduced. In addition, in the thermal type flow meter 300 shown in FIGS. 2 to 4, not only the inlet 350 is provided at the distal end portion of the measuring unit 310 extending from the flange 312 toward the center of the main passage 124, but also the outlet of the sub passage. Is also provided at the tip of the measurement unit 310, so that measurement errors can be further reduced.

  The measurement unit 310 of the thermal flow meter 300 has a shape that extends long from the flange 312 toward the center of the main passage 124, and a portion of the gas to be measured 30 such as intake air is taken into the sub-passage at the tip. There are provided an inlet 350 and an outlet 352 for returning the gas 30 to be measured from the auxiliary passage to the main passage 124. The measuring section 310 has a shape that extends long along the axis from the outer wall of the main passage 124 toward the center, but the width has a narrow shape as shown in FIGS. 2 (A) and 3 (A). doing. That is, the measurement unit 310 of the thermal flow meter 300 has a side surface with a thin width and a substantially rectangular front surface. Thereby, the thermal flow meter 300 can be provided with a sufficiently long sub-passage, and the fluid resistance of the measurement target gas 30 can be suppressed to a small value. For this reason, the thermal type flow meter 300 can measure the flow rate of the measurement target gas 30 with high accuracy while suppressing the fluid resistance to a small value.

2.3 Structure and effect of upstream side surface and downstream side surface of measurement unit 310 Upstream side projection 317 and downstream side projection 318 are provided on the upstream side surface and the downstream side surface of measurement unit 310 constituting thermal flow meter 300, respectively. Is provided. The upstream protrusion 317 and the downstream protrusion 318 have a shape that becomes narrower toward the tip with respect to the root, and the fluid resistance of the intake air 20 flowing in the main passage 124 can be reduced. An upstream protrusion 317 is provided between the heat insulating portion 315 and the inlet 343. The upstream protrusion 317 has a large cross-sectional area and large heat conduction from the flange 312 or the heat insulating portion 315, but the upstream protrusion 317 is interrupted before the inlet 343, and further, the upstream protrusion 317 has a temperature detecting portion 452 side. The distance from the temperature detection unit 452 to the temperature detection unit 452 is long due to the depression of the outer wall on the upstream side of the housing 302 as will be described later. For this reason, the heat conduction from the heat insulation part 315 to the support part of the temperature detection part 452 is suppressed.

  In addition, a gap including a terminal connection portion 320 and a terminal connection portion 320 described later is formed between the flange 312 or the heat insulating portion 315 and the temperature detection portion 452. For this reason, the gap between the flange 312 or the heat insulation part 315 and the temperature detection part 452 is long, and the front cover 303 and the back cover 304 are provided in this long part, and this part acts as a cooling surface. Therefore, the influence of the temperature of the wall surface of the main passage 124 on the temperature detection unit 452 can be reduced. In addition, since the gap between the flange 312 or the heat insulating portion 315 and the temperature detecting portion 452 becomes long, the intake portion of the gas 30 to be measured leading to the sub passage can be brought closer to the center of the main passage 124. A decrease in measurement accuracy related to the wall surface of the main passage 124 can be suppressed.

  As shown in FIGS. 2B and 3B, the measurement unit 310 inserted into the main passage 124 has a very narrow side surface, and the downstream protrusion 318 and the upstream protrusion 317 provide air resistance. The tip has a narrow shape with respect to the root to be reduced. For this reason, an increase in fluid resistance due to the insertion of the thermal flow meter 300 into the main passage 124 can be suppressed. Further, in the portion where the downstream protrusion 318 and the upstream protrusion 317 are provided, the upstream protrusion 317 and the downstream protrusion 318 protrude from both sides of the front cover 303 and the back cover 304. . Since the upstream protrusion 317 and the downstream protrusion 318 are made of a resin mold, the upstream protrusion 317 and the downstream cover 304 are easily formed into a shape with low air resistance, while the front cover 303 and the back cover 304 have a shape with a wide cooling surface. For this reason, the thermal flow meter 300 has an effect that air resistance is reduced and the air to be measured that flows through the main passage 124 is easily cooled.

2.4 Structure and Effect of Flange 312 The flange 312 is provided with a plurality of recesses 314 in the lower surface of the flange 312 facing the main passage 124, reducing the heat transfer surface between the flange 312 and the main passage 124. The thermal flow meter 300 is less susceptible to heat. The screw hole 313 of the flange 312 is for fixing the thermal type flow meter 300 to the main passage 124, and the surface of the screw hole 313 around the screw passage 313 facing the main passage 124 is separated from the main passage 124. A space is formed between the main passage 124 and a surface around the screw hole 313 facing the main passage 124. By doing in this way, it has the structure which can reduce the heat transfer from the main channel | path 124 with respect to the thermal type flow meter 300, and can prevent the fall of the measurement precision by heat | fever. Furthermore, the recess 314 functions not only to reduce the heat conduction but also to reduce the influence of shrinkage of the resin constituting the flange 312 when the housing 302 is molded.

  A heat insulating part 315 is provided on the measurement part 310 side of the flange 312. The measurement part 310 of the thermal type flow meter 300 is inserted into the inside from an attachment hole provided in the main passage 124, and the thermal insulation part 315 faces the inner surface of the attachment hole of the main passage 124. The main passage 124 is, for example, an intake body, and the main passage 124 is often maintained at a high temperature. Conversely, when starting in a cold region, the main passage 124 may be at a very low temperature. If such a high or low temperature state of the main passage 124 affects the temperature detection unit 452 or the flow rate measurement described later, the measurement accuracy decreases. For this reason, a plurality of recesses 316 are arranged in the heat insulating portion 315 adjacent to the inner surface of the hole of the main passage 124, and the width of the heat insulating portion 315 adjacent to the inner surface of the hole is extremely large between the adjacent recesses 316. It is thin and less than one third of the width of the recess 316 in the fluid flow direction. Thereby, the influence of temperature can be reduced. In addition, the heat insulating portion 315 has a thick resin. During resin molding of the housing 302, volume shrinkage occurs when the resin cools from a high temperature state to a low temperature and cures, and distortion due to the generation of stress occurs. By forming the depression 316 in the heat insulating portion 315, the volume shrinkage can be made more uniform, and the stress concentration can be reduced.

  The measurement unit 310 of the thermal flow meter 300 is inserted into the inside through an attachment hole provided in the main passage 124 and is fixed to the main passage 124 with a screw by the flange 312 of the thermal flow meter 300. It is desirable that the thermal flow meter 300 is fixed in a predetermined positional relationship with respect to the mounting hole provided in the main passage 124. A recess 314 provided in the flange 312 can be used for positioning the main passage 124 and the thermal flow meter 300. By forming the convex portion in the main passage 124, the convex portion and the recess 314 can be formed into a fitting relationship, and the thermal flow meter 300 can be fixed to the main passage 124 at an accurate position.

2.5 Structure and Effect of External Connection 305 and Flange 312 FIG. 4A is a plan view of the thermal flow meter 300. FIG. Four external terminals 306 and an external adjustment terminal 307 are provided inside the external connection portion 305. The external terminal 306 is a terminal for outputting a flow rate and temperature as a measurement result of the thermal flow meter 300 and a power supply terminal for supplying DC power for operating the thermal flow meter 300. The external adjustment terminal 307 is a terminal for writing correction data in a memory 618 (FIG. 17) built in a thermal flow meter 300 described later.

  That is, the external adjustment terminal 307 supplies a gas having a known flow rate to the mass-produced thermal flow meter 300 to measure the gas flow rate, and in each mass-produced thermal flow meter 300, the known flow rate is measured. From the measurement result, the correction data for increasing the detection accuracy of each thermal flow meter 300 is calculated, and the correction data is stored in the memory 618 inside the thermal flow meter 300. In the subsequent measurement operation of the thermal flow meter 300, the correction data stored in the memory 618 is used, and the variation of each thermal flow meter 300 is adjusted. The external adjustment terminal 307 is not used for normal control. Therefore, the external adjustment terminal 307 has a different shape from the external terminal 306 so that the external adjustment terminal 307 does not get in the way when the external terminal 306 is connected to other external devices. In this embodiment, the external adjustment terminal 307 is shorter than the external terminal 306, and even if the connector 311 (FIG. 20) to the external device connected to the external terminal 306 is inserted into the external connection unit 305, the connection is possible. It is designed not to become an obstacle. In addition, a plurality of depressions 308 are provided along the external terminals 306 inside the external connection portion 305, and these depressions 308 concentrate stress due to resin shrinkage when the resin that is the material of the flange 312 cools and hardens. It is for reducing.

  As described above, by providing the external adjustment terminal 307 in addition to the external terminal 306 used during the measurement operation of the thermal flow meter 300, the characteristics of each of the thermal flow meter 300 are measured before shipping. It is possible to measure the product variation and store a correction value for reducing the variation in the memory in the thermal flow meter 300. After the correction value setting step, the external adjustment terminal 307 is formed in a shape different from that of the external terminal 306 so that the external adjustment terminal 307 does not interfere with the connection between the external terminal 306 and the external device. In this way, the thermal flow meter 300 can reduce the variation of each before shipping and can improve the measurement accuracy.

  In particular, in this embodiment, the measurement part for measuring the flow rate of gas and the formation of the sub-passage for flowing the gas 30 to be measured are performed within the resin molding process, so that the above-described variation correction maintains extremely high measurement accuracy. it can. For this reason, when the fixing of the measuring unit and the molding of the auxiliary passage are completed, the correction data is obtained by supplying a known gas flow rate, and the correction data is stored in the memory 618 (FIG. 17). Use 307 to store.

3. 3. Overall structure of housing 302 and its effect 3.1 Structure and effect of sub-passage and flow rate detection unit FIGS. 5 and 6 show the state of the housing 302 with the front cover 303 and the back cover 304 removed from the thermal flow meter 300. FIG. 5A is a left side view of the housing 302, FIG. 5B is a front view of the housing 302, FIG. 6A is a right side view of the housing 302, and FIG. 4 is a rear view of the housing 302. FIG. The housing 302 has a structure in which the measuring unit 310 extends from the flange 312 toward the center of the main passage 124, and a sub-passage groove for forming the sub-passage is provided on the tip side thereof. In this embodiment, the sub-passage grooves are provided on both the front and back surfaces of the housing 302. FIG. 5B shows the front-side sub-passage groove 332, and FIG. 6B shows the back-side sub-passage groove 334. An inlet groove 351 for forming the inlet 350 of the sub-passage and an outlet groove 353 for forming the outlet 352 are provided at the distal end portion of the housing 302, so that the gas in a portion away from the inner wall surface of the main passage 124 In other words, the gas flowing in the portion close to the central portion of the main passage 124 can be taken in from the inlet 350 as the gas 30 to be measured. The gas flowing in the vicinity of the inner wall surface of the main passage 124 is affected by the wall surface temperature of the main passage 124 and often has a temperature different from the average temperature of the gas flowing through the main passage 124 such as intake air. Further, the gas flowing in the vicinity of the inner wall surface of the main passage 124 often exhibits a flow rate that is slower than the average flow velocity of the gas flowing through the main passage 124. Since the thermal flow meter 300 of the embodiment is not easily affected by this, it is possible to suppress a decrease in measurement accuracy.

  The sub passages formed by the front side sub passage groove 332 and the back side sub passage groove 334 described above are connected to the heat insulating portion 315 by the outer wall recess 366, the upstream outer wall 335, and the downstream outer wall 336. The upstream outer wall 335 is provided with an upstream protrusion 317, and the downstream outer wall 336 is provided with a downstream protrusion 318. With such a structure, the thermal flow meter 300 is fixed to the main passage 124 by the flange 312, whereby the measuring unit 310 having the circuit package 400 is fixed to the main passage 124 with high reliability.

  In this embodiment, the sub-passage groove for forming the sub-passage is formed in the housing 302, and the sub-passage is completed by the sub-passage groove and the cover by covering the cover with the front and back surfaces of the housing 302. . 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. In addition, 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 are all 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 secondary passages on both sides of the housing 302 can be completed. By forming the front side secondary passage groove 332 and the back side secondary passage groove 334 on both surfaces of the housing 302 using a mold, the secondary passage can be formed with high accuracy. Moreover, high productivity is obtained.

  In FIG. 6B, a part of the measurement target gas 30 flowing through the main passage 124 is taken into the back side sub passage groove 334 from the inlet groove 351 that forms the inlet 350 and flows through the back side sub passage groove 334. The back side sub-passage groove 334 has a shape that becomes deeper as it advances, and as the gas flows along the groove, the measured gas 30 gradually moves in the front side direction. In particular, the rear side sub-passage groove 334 is provided with a steeply inclined portion 347 that becomes deeper and deeper before the hole 342, and a part of the air having a small mass moves along the steeply inclined portion 347, and passes through the hole 342 in FIG. It flows in the direction of the measurement flow path surface 430 described in B). On the other hand, a foreign substance having a large mass is difficult to change rapidly due to the action of inertial force, and therefore moves toward the measurement channel surface rear surface 431 shown in FIG. After that, it passes through the hole 341 and flows through the measurement flow path surface 430 shown in FIG.

  In the front side sub-passage groove 332 shown in FIG. 5B, the air to be measured 30 that has moved from the hole 342 to the front side sub-passage groove 332 flows along the measurement channel surface 430 and is used for measurement. Heat is transferred to and from the flow rate detector 602 for measuring the flow rate through the heat transfer surface exposed portion 436 provided on the flow path surface 430, and the flow rate is measured. Both the gas to be measured 30 that has passed through the measurement flow path surface 430 and the air that has flowed from the hole 341 to the front side sub-passage groove 332 flow along the front side sub-passage groove 332, and from the outlet groove 353 for forming the outlet 352. It is discharged into the passage 124.

  A substance having a large mass such as dust mixed in the measurement target gas 30 has a large inertial force, and along the surface of the portion of the steeply inclined portion 347 shown in FIG. It is difficult to change the course rapidly in the deep direction of the groove. For this reason, the foreign matter having a large mass moves toward the measurement channel surface rear surface 431, and the foreign matter can be prevented from passing near the heat transfer surface exposed portion 436. In this embodiment, since many foreign substances having a large mass other than gas pass through the measurement channel surface rear surface 431 which is the back surface of the measurement channel surface 430, they are caused by foreign matters such as oil, carbon, and dust. The influence of dirt can be reduced, and the decrease in measurement accuracy can be suppressed. That is, since it has a shape in which the path of the gas to be measured 30 is suddenly changed along an axis that crosses the flow axis of the main passage 124, the influence of foreign matter mixed in the gas to be measured 30 can be reduced.

  In this embodiment, the flow path formed by the back side sub-passage groove 334 draws a curve from the front end of the housing 302 toward the flange, and the gas flowing through the sub-passage flows into the main passage 124 at the position closest to the flange. On the other hand, the flow is in the reverse direction, and the sub-passage on the back surface, which is one side in the flow portion in the reverse direction, is connected to the sub-passage formed on the surface side, which is the other side. By doing so, it becomes easy to fix the heat transfer surface exposed portion 436 of the circuit package 400 to the sub-passage, and further, it becomes easy to take in the gas 30 to be measured at a position close to the central portion of the main passage 124.

  In this embodiment, a hole 342 and a hole 341 penetrating the back side sub-passage groove 334 and the front side sub-passage groove 332 are provided before and after the measurement flow path surface 430 for measuring the flow rate in the flow direction. The measurement target gas 30 moves in a shape in which the through-hole 342 and the hole 341 are provided to move the measured gas 30 from the back side sub-passage groove 334 formed on one surface of the housing 302 to the front side sub-passage groove 332 formed on the other surface of the housing 302. A passage is formed. By doing in this way, it is possible to form the sub-passage grooves on both surfaces of the housing 302 in one resin molding process, and to form the structure connecting both surfaces together.

  Further, by providing the holes 342 and 341 on both sides of the measurement flow path surface 430 formed in the circuit package 400, a mold for forming the holes 342 and 341 in these holes is used to form the measurement flow path surface 430. It is possible to prevent the resin from flowing into the exposed heat transfer surface exposed portion 436. Further, when the circuit package 400 is fixed to the housing 302 with a resin mold by using the formation of the holes 342 and 341 on the upstream side and the downstream side of the measurement flow path surface 430, the mold is arranged using these holes. The circuit package 400 can be positioned and fixed by this mold.

  In this embodiment, two holes, a hole 342 and a hole 341, are provided as holes penetrating the back side sub passage groove 334 and the front side sub passage groove 332. However, even if two holes consisting of the hole 342 and the hole 341 are not provided, the shape of the sub-passage that connects the back side sub-passage groove 334 and the front side sub-passage groove 332 with one of the holes is formed by one resin molding process. Is possible.

  A back side sub-passage inner peripheral wall 391 and a back side sub-passage outer peripheral wall 392 are provided on both sides of the back side sub-passage groove 334, and the height direction ends of the back side sub-passage inner peripheral wall 391 and the back side sub-passage outer peripheral wall 392 are respectively provided. The back side sub-passage of the housing 302 is formed by the close contact between the portion and the inner surface of the back cover 304. Further, a front side sub-passage inner peripheral wall 393 and a front side sub-passage outer peripheral wall 394 are provided on both sides of the front side sub-passage groove 332. The front side sub-passage inner peripheral wall 393 and the front-side sub-passage outer peripheral wall 394 and the front end portion in the height direction and the front side. When the inner surface of the cover 303 is in close contact, the front side sub-passage of the housing 302 is formed.

  In this embodiment, the measurement target gas 30 is divided into both the measurement flow path surface 430 and the back surface thereof, and the heat transfer surface exposed portion 436 for measuring the flow rate is provided on one side. Instead of dividing into two passages, only the surface side of the measurement channel surface 430 may be passed. By bending the sub-passage along the second axis in a direction crossing the first axis in the flow direction of the main passage 124, the foreign matter mixed in the measurement target gas 30 can be removed on one side where the second axis is less bent. By providing the measurement flow path surface 430 and the heat transfer surface exposed portion 436 on the side with the larger curvature of the second axis, the influence of foreign matter can be reduced.

  Further, in this embodiment, a measurement flow path surface 430 and a 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, it may be provided in the front side sub-passage groove 334 or in the back side sub-passage groove 334 instead of the connecting portion between the front side sub-passage groove 332 and the back side sub-passage groove 334.

  A throttle shape is formed in the portion of the heat transfer surface exposed portion 436 for measuring the flow rate provided on the measurement flow path surface 430. Due to this throttle effect, the flow velocity is increased and the measurement accuracy is improved. Even if a vortex is generated in the gas flow on the upstream side of the heat transfer surface exposed portion 436, the vortex can be eliminated or reduced by the restriction, and the measurement accuracy is improved.

  5 and 6, the upstream outer wall 335 includes an outer wall recess 366 that has a shape that is recessed downstream at the root of the temperature detector 452. The outer wall recess 366 increases the distance between the temperature detection unit 452 and the outer wall recess 366, thereby reducing the influence of heat transmitted through the upstream outer wall 335.

  Further, the circuit package 400 is fixed by wrapping the circuit package 400 in the fixing portion 372. However, by further fixing the circuit package 400 by the outer wall recess portion 366, the force for fixing the circuit package 400 is increased. Can do. The fixed portion 372 includes the circuit package 400 in a direction along the flow axis of the measurement target gas 30. On the other hand, the outer wall recess 366 includes the circuit package 400 in a direction crossing the flow axis of the measurement target gas 30. That is, the circuit package 400 is included in such a manner that the direction in which the fixing portion 372 is included is different. Since the circuit package 400 is included in two different directions, the securing force is increased. Although the outer wall recess 366 is a part of the upstream outer wall 335, the circuit package 400 is arranged in a different direction from the fixing portion 372 on the downstream outer wall 336 instead of the upstream outer wall 335 for increasing the fixing force. May be included. For example, the downstream outer wall 336 may include the plate portion of the circuit package 400, or the downstream outer wall 336 may include a recess recessed in the upstream direction or a protrusion projecting in the upstream direction to include the circuit package 400. good. The inclusion of the circuit package 400 by providing the outer wall recess 366 on the upstream outer wall 335 has the effect of increasing the thermal resistance between the temperature detector 452 and the upstream outer wall 335 in addition to fixing the circuit package 400. This is because they were held.

  The outer wall recess 366 is provided at the base of the temperature detection unit 452, and thereby the influence of heat transmitted from the flange 312 or the heat insulating unit 315 through the upstream outer wall 335 can be reduced. Further, a temperature measurement recess 368 formed by a notch between the upstream protrusion 317 and the temperature detection unit 452 is provided. The temperature measurement depression 368 can reduce the transfer of heat provided to the temperature detector 452 via the upstream protrusion 317. Thereby, the detection accuracy of the temperature detector 452 is improved. In particular, since the upstream protrusion 317 has a large cross-sectional area, heat is easily transmitted, and the function of the temperature measuring recess 368 for preventing heat transfer is important.

3.2 Structure and Effect of Sub-Flow Rate Detection Unit FIG. 7 is a partially enlarged view showing a state in which the measurement flow path surface 430 of the circuit package 400 is disposed inside the sub-passage groove, and FIG. It is -A sectional drawing. Note that this figure is a conceptual diagram, and the details shown in FIGS. 5 and 6 are omitted and simplified in detail in FIG. 7, and the details are slightly modified. The left portion in FIG. 7 is the end portion of the back side auxiliary passage groove 334, and the right side portion is the starting end portion of the front side auxiliary passage groove 332. Although not clearly shown in FIG. 7, holes 342 and 341 are provided on the left and right sides of the circuit package 400 having the measurement channel surface 430, and the circuit package 400 having the measurement channel surface 430 is provided. The back side sub-passage groove 334 and the front side sub-passage groove 332 are connected on both the left and right sides.

  The gas to be measured 30 taken from the inlet 350 and flowing through the back side sub-passage formed by the back side sub-passage groove 334 is guided from the left side of FIG. 7, and a part of the gas to be measured 30 is passed through the hole 342. The measurement target gas 30 flows in the direction of the flow path 386 formed by the surface of the measurement flow path surface 430 of the circuit package 400 and the projection 356 provided on the front cover 303, and the other measurement target gas 30 is the measurement flow path surface back surface 431 and the back cover 304. It flows in the direction of the flow path 387. Thereafter, the gas to be measured 30 that has flowed through the flow path 387 moves toward the front side sub-passage groove 332 through the hole 341, merges with the gas to be measured 30 that is flowing through the flow path 386, and The flow is discharged from the outlet 352 to the main passage 124. As shown in FIG. 7B, a protrusion 358 provided on the back cover 304 protrudes toward the measurement channel surface rear surface 431 in the channel 387.

  The sub passage groove is formed so that the measured gas 30 guided from the back side sub passage groove 334 to the flow path 386 through the hole 342 is bent more than the flow path guided to the flow path 387. Therefore, a substance having a large mass, such as dust, contained in the measurement target gas 30 gathers in the flow path 387 with less bending. For this reason, almost no foreign substance flows into the flow path 386.

  In the flow path 386, a structure is formed in which the throttle is formed by the protrusion 356 provided on the front cover 303 projecting gradually toward the measurement flow path surface 430 continuously from the most distal portion of the front side sub-passage groove 332. Is made. A flow path surface for measurement 430 is arranged on one side of the throttle part of the flow path 386, and a heat transfer surface exposed part for allowing the flow rate detection unit 602 to transfer heat to the measurement target gas 30 on the flow path surface for measurement 430. 436 is provided. In order to measure the flow rate detection unit 602 with high accuracy, it is desirable that the measurement target gas 30 is a laminar flow with few vortices in the heat transfer surface exposed portion 436. In addition, the measurement accuracy improves when the flow velocity is faster. For this purpose, the diaphragm is formed by the projection 356 provided on the front cover 303 facing the measurement channel surface 430 smoothly projecting toward the measurement channel surface 430. This restriction acts to reduce the vortex of the measured gas 30 and bring it closer to the laminar flow. Further, the flow velocity is increased in the throttle portion, and the heat transfer surface exposed portion 436 for measuring the flow rate is arranged in the throttle portion, so that the flow rate measurement accuracy is improved.

  By making the protrusion 356 project into the sub-passage groove so as to face the heat transfer surface exposed portion 436 provided on the flow path surface 430, a diaphragm can be formed and measurement accuracy can be improved. The protrusion 356 for forming the aperture is provided on the cover facing the heat transfer surface exposed portion 436 provided on the flow path surface 430. In FIG. 7, since the cover facing the heat transfer surface exposed portion 436 provided on the flow path surface 430 is the front cover 303, the front cover 303 is provided with the heat transfer surface exposed portion 436. 304 may be provided on the cover facing the heat transfer surface exposed portion 436 provided on the flow path surface 430 in 304. Depending on which side of the circuit package 400 the flow path surface 430 and the surface on which the heat transfer surface exposed portion 436 is provided, which cover is opposite to the heat transfer surface exposed portion 436 is changed.

  The distribution of the gas 30 to be measured between the flow path 386 and the flow path 387 is also related to high-precision measurement. By projecting the protrusion 358 provided on the back cover 304 into the flow path 387, the flow path 386 Adjustment such as distribution of the measurement target gas 30 with the flow path 387 is performed. In addition, by providing a throttle portion in the flow path 387, the flow velocity is increased, and foreign substances such as dust are drawn into the flow path 387. In this embodiment, as one of various adjustment means for the flow path 386 and the flow path 387, a restriction by the projection 358 is used. However, the width between the measurement flow path surface back surface 431 and the back cover 304, etc. By adjustment, the distribution of the flow rate between the flow path 386 and the flow path 387 described above may be adjusted. In this case, the protrusion 358 provided on the back cover 304 is not necessary.

  In FIG. 5 and FIG. 6, the trace of the mold used in the resin molding process of the circuit package 400 is applied to the measurement channel surface rear surface 431 which is the back surface of the heat transfer surface exposed portion 436 provided on the measurement channel surface 430. 442 remains. The press mark 442 does not particularly hinder measurement of the flow rate, and there is no problem even if the press mark 442 remains as it is. As will be described later, when the circuit package 400 is molded with a 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 the back surface of the heat transfer surface exposed portion 436. It is also important that the resin that covers the circuit package 400 does not flow 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 by transfer molding, the pressure of the resin is high, and it is important to press the heat transfer surface exposed portion 436 from the back surface. Further, a semiconductor diaphragm is used for the flow rate detection unit 602, and it is desirable to form a ventilation passage formed by the semiconductor diaphragm. In order to hold and fix a plate or the like for forming the ventilation passage, it is important to press the heat transfer surface exposed portion 436 from the back surface.

3.3 Shapes and Effects of Front Cover 303 and Back Cover 304 FIG. 8 is a diagram showing the appearance of the front cover 303, FIG. 8 (A) is a left side view, FIG. 8 (B) is a front view, and FIG. C) is a plan view. 9A and 9B are views showing the appearance of the back cover 304. FIG. 9A is a left side view, FIG. 9B is a front view, and FIG. 9C is a plan view. In FIGS. 8 and 9, the front cover 303 and the back cover 304 are used to make a secondary passage by closing the secondary passage groove of the housing 302. Further, the protrusion 356 is provided and used to provide a restriction in the flow path. For this reason, it is desirable that the molding accuracy be high. Since the front cover 303 and the back cover 304 are made by a resin molding process in which a thermoplastic resin is injected into a mold, they can be made with high molding accuracy.

  A front protection part 322 and a back protection part 325 are formed on the front cover 303 and the back cover 304 shown in FIGS. As shown in FIGS. 2 and 3, a front protection part 322 provided on the front cover 303 is disposed on the front side surface of the inlet 343, and a back protection part 325 provided on the back cover 304 is provided on the rear side surface of the inlet 343. Is arranged. The temperature detection unit 452 disposed inside the entrance 343 is protected by the front protection unit 322 and the back protection unit 325, and the machine of the temperature detection unit 452 due to a collision with the temperature detection unit 452 during production or when mounted on a vehicle. Damage can be prevented.

  A projection 356 is provided on the inner side surface of the front cover 303, and as shown in FIG. 7, the projection 356 is disposed to face the measurement channel surface 430 and extends long in the direction along the axis of the channel of the sub-passage. It has a different shape. The cross-sectional shape of the protrusion 356 may be inclined toward the downstream side with the apex of the protrusion as a boundary as shown in FIG. A restriction is formed in the flow path 386 described above by the measurement flow path surface 430 and the protrusions 356, and the vortex generated in the measurement target gas 30 is reduced, thereby causing 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 and completes the flow path having the throttle, and the groove portion is used for molding the housing 302. Next, the front cover 303 having the projections 356 is formed by another resin molding process, and the front cover 303 is used as a lid of the groove to cover the groove. In the second resin molding step for molding the housing 302, the circuit package 400 having the measurement flow path surface 430 is also fixed to the housing 302. In this way, by forming the groove having a complicated shape in the resin molding process and providing the projection 356 for drawing on the front cover 303, the flow path 386 shown in FIG. 7 can be formed with high accuracy. In addition, since the positional relationship between the groove and the measurement flow path surface 430 and the heat transfer surface exposed portion 436 can be maintained with high accuracy, the variation in mass-produced products can be reduced, resulting in high measurement results. Productivity is also improved.

  The configuration of the channel 387 by the back cover 304 and the measurement channel surface rear surface 431 is the same. The flow path 387 is divided into a groove portion and a lid portion, the groove portion is formed by a second resin molding process for molding the housing 302, and then the flow path 387 is formed by covering the groove with a back cover 304 having a projection 358. Forming. By making the flow path 387 in this way, the flow path 387 can be made with high accuracy, and productivity is improved. In this embodiment, a restriction is provided in the flow path 387, but it is also possible to use a flow path 387 without a restriction without using the protrusion 358.

  In FIG. 8B, a notch 323 for forming an outlet 352 is provided on the front end side of the front cover 303. As shown in FIG. 2B, the outlet 352 extends not only on the right side surface of the housing 302 but also on the front side of the housing 302 by the notch 323. As a result, the fluid resistance of the entire sub-passage is reduced, and the amount of the measurement target gas 30 guided from the inlet 350 into the sub-passage is increased. This improves the flow rate measurement accuracy.

3.4 Structure and Effect of Terminal Connection Part 320 FIG. 10 is an enlarged view of the terminal connection part 320 of the housing 302 shown in FIGS. 5 and 6. However, the following points are a little different. 5 and FIG. 6 is different from the description in FIG. 5 and FIG. 6 in that each external terminal inner end 361 is cut off, whereas in FIG. 10, the state before each external terminal inner end 361 is cut off. In the figure, the external terminal inner ends 361 are connected by connecting portions 365, respectively.

  The projecting end of the external terminal 306 to the inside of the circuit package 400 is an external terminal inner end 361, and the projecting end of the external adjustment terminal 307 to the inside of the circuit package 400 is an external adjustment terminal inner end 367. The external terminal inner end 361 and the external adjustment terminal inner end 367 overlap the measurement terminal 412 and the adjustment terminal 415, respectively. Alternatively, the external terminal inner end 361 and the external adjustment terminal inner end 367 are arranged in the vicinity of the corresponding measurement terminal 412 and adjustment terminal 415, respectively. These are then electrically and mechanically connected.

  In the second molding step, the external terminals 306 and the external adjustment terminals 307 are fixed to the housing 302 by resin molding. In order to prevent deformation and displacement of each external terminal 306 and external adjustment terminal 307, as an example, the external terminal inner end 361 and the external adjustment terminal inner end 367 are connected to each other by a connecting portion 365. It is fixed to the housing 302 by a resin molding process (second resin molding process) for molding 302. However, the measurement terminal 412 and the external terminal inner end 361 may be fixed first, and then the external terminal 306 may be fixed to the housing 302 by the second molding step.

  The external adjustment terminal inner end 367 stores the correction data obtained by an external device such as a measuring device in the memory 618 (FIG. 17) from the external adjustment terminal 307 to the adjustment terminal 415 for correction. A communication signal for writing data is transmitted, the processing unit 604 is ready to perform data write communication, and the correction data is stored in the memory 618 (FIG. 17) via the external terminal 306.

3.5 Inspection of Finished Product by First Resin Molding Process In the embodiment shown in FIG. 10, the circuit package 400 has a larger number of terminals than the total of the external terminal inner ends 361 and the external adjustment terminal inner ends 367. Among the terminals included in the circuit package 400, the measurement terminal 412 and the adjustment terminal 415 are connected to the external terminal inner end 361 and the external adjustment terminal inner end 367, respectively, and the inspection terminal 414 includes the external terminal inner end 361 and It is not connected to the inner end 367 of the external adjustment terminal. That is, the inspection terminal 414 is a terminal that is provided in the circuit package 400 but is not connected to the external terminal inner end 361 or the external adjustment terminal inner end 367.

  In FIG. 10, in addition to the measuring terminal 412 connected to the external terminal inner end 361 and the adjusting terminal 415 connected to the external adjusting terminal inner end 367, an inspection terminal 414 that is not connected is provided. After the circuit package 400 is produced in the first resin molding process, it is inspected whether the circuit package 400 operates correctly or whether an abnormality has occurred in electrical connection in the first resin molding process. By doing so, high reliability can be maintained for each circuit package 400. The inspection terminal 414 that is not connected is used for such inspection of the circuit package 400. Since the inspection terminals 414 are not used after the inspection work, these unused inspection terminals 414 may be cut off at the base of the circuit package 400 after the inspection, or by the terminal side fixing portion 362 as shown in FIG. It may be buried inside a certain resin. By providing the inspection terminals 414 that are not connected, 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 high reliability can be maintained. In particular, in the first resin molding process, transfer molding with high resin pressure is performed, so there is a possibility that circuit disconnection or stress concentration on the LSI may occur, and inspection of the molded circuit after the first resin molding process is performed. desirable.

3.6 Communication structure and effect between gap inside housing 302 and outside of thermal flow meter 300 As shown in the partially enlarged view of FIG. 10, a hole 364 is provided in the housing 302. The hole 364 is connected to an opening 309 provided inside the external connection portion 305 shown in FIG. In the embodiment, both sides of the housing 302 are sealed with a front cover 303 and a back cover 304. If the hole 364 is not provided, a difference occurs between the atmospheric pressure in the air gap and the external air pressure due to the temperature change of the air in the air gap including the terminal connection portion 320. Such a pressure difference is desirably as small as possible. Therefore, a hole 364 connected to the opening 309 provided in the external connection portion 305 is provided in the gap of the housing 302. The external connection part 305 has a structure that is not adversely affected by water or the like in order to improve the reliability of electrical connection, and by providing the opening 309 in the external connection part 305, water can be prevented from entering from the opening 309. Furthermore, it is possible to prevent foreign substances such as dust and dirt from entering.

4). 4.1 Fixing Structure of Circuit Package 400 by Housing 302 4.1 Fixing Structure of Circuit Package 400 by Fixing Part of Housing 302 Next, referring to FIGS. 5 and 6 again, a resin mold process for housing 302 of circuit package 400 is performed. The fixing will be described. In a predetermined position of the sub-passage groove forming the sub-passage, for example, in the embodiment shown in FIGS. The circuit package 400 is arranged and fixed to the housing 302 so that the measurement flow path surface 430 is arranged. A portion for embedding and fixing the circuit package 400 in the housing 302 with a resin mold is provided as a fixing portion 372 for embedding and fixing the circuit package 400 in the housing 302 on the flange 312 side slightly from the sub-passage groove. The fixing portion 372 is embedded so as to cover the outer periphery of the circuit package 400 molded by the first resin molding process.

  As shown in FIG. 5B, a recess 376 and a recess 378 are provided on the front side surface of the fixed portion 372. Further, as shown in FIG. 6B, a recess 373 is formed on the back side surface of the fixing portion 372. These depressions can alleviate shrinkage when the temperature of the resin cools when the fixing portion 372 is molded, and the concentration of stress applied to the circuit package 400 can be reduced. Further, the above-described depression restricts the flow of the resin by the mold, thereby slowing down the resin temperature and penetrating the resin constituting the fixing portion 372 to the depth of the unevenness provided on the surface of the circuit package 400. Can be made easier.

  Further, the entire surface of the circuit package 400 is not covered with the resin for molding the housing 302, but a portion where the outer wall of the circuit package 400 is exposed is provided on the flange 312 side of the fixing portion 372. 5 and 6, the area of the outer peripheral surface of the circuit package 400 that is included in the resin of the housing 302 is exposed from the resin of the housing 302 without being included in the resin of the housing 302. The area is wider. Further, the part of the measurement flow path surface 430 of the circuit package 400 is also exposed from the resin forming the housing 302.

  In the second resin molding step for forming the housing 302, the periphery of the circuit package 400 is formed by forming depressions on the front and back surfaces of the fixing portion 372 that covers the entire outer wall of the circuit package 400 in a strip shape. The excessive stress concentration due to the volume shrinkage in the process of hardening the fixing portion 372 is reduced. Excessive stress concentration may also adversely affect the circuit package 400.

4.2 Improvement of Adhesion between Housing 302 and Circuit Package 400 Further, by reducing the area of the outer surface of the circuit package 400 that is included in the resin of the housing 302, the circuit package 400 can be strengthened with a smaller area. In order to fix, it is desirable to improve the adhesiveness of the fixing part 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 for the resin to cure. In the resin molding process for molding the housing 302, it is desirable to provide an inlet for the thermoplastic resin at or near the fixed portion 372. The thermoplastic resin increases in viscosity based on a decrease in temperature and hardens. Accordingly, by pouring the high temperature thermoplastic resin into or from the fixing portion 372, the low viscosity thermoplastic resin can be brought into close contact with the outer wall of the circuit package 400 and cured. Further, by forming the recess 376, the recess 378, and the recess 373 in the fixed portion 372, an obstacle portion that restricts the flow of the thermoplastic resin is created by the mold for making these recesses, and the heat in the fixing portion 372 is formed. The moving speed of the plastic resin is reduced, and the resin pressure in the region where the flow of the resin is restricted is maintained in a normal state. This suppresses the temperature drop of the thermoplastic resin, prolongs the low viscosity state, and improves the adhesion between the circuit package 400 and the fixing portion 372.

  By roughening the outer wall surface of the circuit package 400, the adhesion between the circuit package 400 and the fixing portion 372 can be improved. As a method for roughening the outer wall surface of the circuit package 400, a roughening method for forming fine irregularities on the surface of the circuit package 400 after the circuit package 400 is formed in the first resin molding step, for example, a treatment method called matte treatment. There is. A roughening method for applying fine irregularities to the surface of the circuit package 400, for example, can be roughened by sandblasting. Further, it can be roughened by laser processing.

  As another roughening method, a sheet with irregularities is attached to the inner surface of a mold used in the first resin molding step, and the resin is press-fitted into a mold provided with the sheet on the surface. In this way, fine irregularities can be formed on the surface of the circuit package 400 to be roughened. Further, the surface of the circuit package 400 can be roughened by providing irregularities inside the mold for molding the circuit package 400. The surface portion of the circuit package 400 that performs such roughening is a portion where at least the fixing portion 372 is provided. In addition, the degree of adhesion is further increased by roughening the surface portion of the circuit package 400 in which the outer wall recess 366 is provided.

  Further, the depth of the groove depends on the thickness of the sheet when the surface of the circuit package 400 is processed by using the above-described sheet. When the thickness of the sheet is increased, molding in the first resin molding process becomes difficult, so there is a limit to the thickness of the sheet, and when the thickness of the sheet is thin, there is a limit to the depth of unevenness provided in advance in the sheet. Out. For this reason, when using the said sheet | seat, it is desirable that the depth of the unevenness | corrugation between the bottom and the vertex of an unevenness | corrugation is 10 micrometers or more and 20 micrometers or less. At a depth of less than 10 μm, the adhesion effect is weak. A depth greater than 20 μm is difficult due to the thickness of the sheet.

  In the case of the roughening method other than the sheet, since the resin thickness in the first resin molding process for forming the circuit package 400 is desirably 2 mm or less, It is difficult to make the depth of the unevenness between 1 mm and 1 mm or more. Conceptually, when the depth of the unevenness between the bottom and apex of the unevenness on the surface of the circuit package 400 is increased, the degree of adhesion between the resin that covers the circuit package 400 and the resin that forms the housing 302 increases. However, for the above reason, the depth of the unevenness between the bottom and the top of the unevenness is preferably 1 mm or less. That is, it is desirable to increase the degree of adhesion between the resin that covers the circuit package 400 and the resin that molds the housing 302 by providing irregularities in the range of 10 μm or more and 1 mm or less on the surface of the circuit package 400.

  There is a difference in thermal expansion coefficient between the thermosetting resin forming the circuit package 400 and the thermoplastic resin forming the housing 302 including the fixing portion 372, and an excessive stress generated based on the difference in the thermal expansion coefficient causes a circuit package. It is desirable not to join 400. By providing the depression 373, the depression 378, and the depression 376, the stress applied to the circuit package 400 can be reduced.

  Furthermore, by making 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 thermal expansion coefficient applied to the circuit package 400 can be reduced. It is desirable that the width of the band of the fixing portion 372 is 10 mm or less, preferably 8 mm or less. In the present embodiment, not only the fixing portion 372 but also the outer wall recess 366 that is a part of the upstream outer wall 335 of the housing 302 includes the circuit package 400 and fixes the circuit package 400. The width of the band 372 can be further reduced. For example, if there is a width of 3 mm or more, the circuit package 400 can be fixed.

  The surface of the circuit package 400 is provided with a portion covered with the resin for molding the housing 302 and a portion exposed without being covered for the purpose of reducing stress due to the difference in thermal expansion coefficient. A plurality of portions where the surface of the circuit package 400 is exposed from the resin of the housing 302 are provided, one of which is the measurement flow path surface 430 having the heat transfer surface exposed portion 436 described above. A portion exposed to the flange 312 side from the fixing portion 372 is provided. Further, an outer wall recess 366 is formed, and a portion upstream of the outer wall recess 366 is exposed, and this exposed portion is used as a support for supporting the temperature detector 452. The portion of the outer surface of the circuit package 400 closer to the flange 312 than the fixing portion 372 extends from the outer periphery, particularly from the downstream side of the circuit package 400 to the side facing the flange 312 and further to the upstream side of the portion close to the terminal of the circuit package 400. A gap is formed so as to surround the circuit package 400. Since the air gap is formed around the portion where the surface of the circuit package 400 is exposed in this manner, the amount of heat transferred from the main passage 124 to the circuit package 400 via the flange 312 can be reduced, and measurement due to the influence of heat. The decrease in accuracy is suppressed.

  A gap is formed between the circuit package 400 and the flange 312, and this gap portion functions as the terminal connection portion 320. At the terminal connection portion 320, the measurement 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 and mechanically connected by spot welding or laser welding, respectively. Similarly, the adjustment terminal 415 is electrically and mechanically connected to the inner end 367 of the external adjustment terminal described in FIG. 10 by spot welding or laser welding. As described above, the gap of the terminal connection portion 320 has an effect of suppressing heat transfer from the housing 302 to the circuit package 400 and also connects the measurement terminal 412 of the circuit package 400 and the external terminal inner end 361 of the external terminal 306. There is enough space available for work.

4.3 Molding of Housing 302 and Improvement of Measurement Accuracy by Second Resin Molding Process In the housing 302 shown in FIGS. 5 and 6 described above, the circuit package 400 including the flow rate detection unit 602 and the processing unit 604 is formed by the first resin molding process. Next, the housing 302 having, for example, the front side sub-passage groove 332 and the back side sub-passage groove 334 for forming the sub-passage through which the gas to be measured 30 flows is manufactured in the second resin molding step. In the second resin molding step, the circuit package 400 is built in the resin of the housing 302 and fixed in the housing 302 by a resin mold. By doing so, the heat transfer surface exposed portion 436 and the sub-passage, for example, the front-side sub-passage groove 332 and the back-side sub-passage for the heat-flow detecting unit 602 to perform heat transfer with the measurement target gas 30 to measure the flow rate It becomes possible to maintain the relationship with the shape of the passage groove 334, for example, the positional relationship and the direction relationship, with extremely high accuracy. It is possible to suppress errors and variations occurring in each circuit package 400 to a very small value. As a result, the measurement accuracy of the circuit package 400 can be greatly improved. For example, the measurement accuracy can be improved by a factor of two or more compared to a conventional method of fixing using an adhesive. The thermal flow meter 300 is often produced by mass production, and the method of adhering with an adhesive while strictly measuring here has a limit in improving measurement accuracy. However, as in the present embodiment, the circuit package 400 is manufactured by the first resin molding process, and then the sub-passage is formed in the second resin molding process in which the sub-passage for flowing the measurement target gas 30 is formed. By fixing the auxiliary passage, variation in measurement accuracy can be greatly reduced, and the measurement accuracy of each thermal flow meter 300 can be greatly improved. This applies not only to the embodiment shown in FIGS. 5 and 6, but also to the embodiment shown in FIG.

  For example, in the embodiment shown in FIG. 5 and FIG. 6, the relationship among the front side sub-passage groove 332, the back side sub-passage groove 334, and the heat transfer surface exposed portion 436 is set with high accuracy so as to be a prescribed relationship. The circuit package 400 can be fixed to the housing 302. Thus, in the mass production type thermal flow meter 300, the positional relationship and the shape relationship between the heat transfer surface exposed portion 436 and the sub passage of each circuit package 400 can be constantly obtained with very high accuracy. Is possible. The sub-passage groove, for example, the front-side sub-passage groove 332 and the back-side sub-passage groove 334, to which the heat transfer surface exposed portion 436 of the circuit package 400 is fixed, can be molded with very high accuracy. The work is a work of covering both surfaces of the housing 302 with the front cover 303 and the back cover 304. This work is very simple and is a work process with few factors that reduce the measurement accuracy. The front cover 303 and the back cover 304 are produced by a resin molding process with high molding accuracy. Accordingly, it is possible to complete the sub-passage provided in a defined relationship with the heat transfer surface exposed portion 436 of the circuit package 400 with high accuracy. By such a method, in addition to improvement of measurement accuracy, high productivity can be obtained.

  On the other hand, in the past, a thermal flow meter was produced by manufacturing a sub-passage and then adhering a measuring unit to the sub-passage with an adhesive. As described above, the method of using the adhesive has a large variation in the thickness of the adhesive, and the bonding position and the bonding angle vary from product to product. For this reason, there was a limit to increasing the measurement accuracy. Furthermore, when performing these operations in a mass production process, it is very difficult to improve measurement accuracy.

  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, and then the circuit package 400 is fixed by the resin mold and at the same time, the secondary path is formed by the resin mold. A secondary passage groove for molding is molded by the second resin mold. By doing in this way, the flow volume detection part 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. Thereafter, the measurement channel surface 430 and the heat transfer surface exposed portion 436 are exposed from the resin for molding the housing 302. That is, the heat transfer surface exposed portion 436 and the measurement flow path surface 430 around the heat transfer surface exposed portion 436 are not covered with the resin for molding the housing 302. The flow path surface 430 for measurement and the heat transfer surface exposed part 436 molded by the resin mold of the circuit package 400 or the temperature detection part 452 are also used as they are after the resin molding of the housing 302 to measure the flow rate of the thermal flow meter 300. Used for temperature measurement. By doing so, the measurement accuracy is improved.

  In the embodiment according to the present invention, the circuit package 400 is fixed to the housing 302 with a small fixed area because the circuit package 400 is fixed to the housing 302 having the auxiliary passage by integrally molding the circuit package 400 with the housing 302. it can. That is, the surface area of the circuit package 400 that is not in contact with the housing 302 can be increased. The surface of the circuit package 400 that is not in contact with the housing 302 is exposed to a gap, for example. The heat of the intake pipe is transmitted to the housing 302 and is transmitted from the housing 302 to the circuit package 400. The housing 302 does not include the entire surface or most of the circuit package 400, but the circuit package 400 can be maintained with high accuracy and high reliability even when the contact area between the housing 302 and the circuit package 400 is reduced. It can be fixed to the housing 302. For this reason, heat transfer from the housing 302 to the circuit package 400 can be suppressed to a low level, and a decrease in measurement accuracy can be suppressed.

  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 of the housing 302 or the area A may be larger than the area B. Is possible. In the embodiment, the area A is larger than the area B. By doing so, heat transfer from the housing 302 to the circuit package 400 can be suppressed. In addition, the stress due to the difference between the thermal expansion coefficient of the thermosetting resin forming the circuit package 400 and the expansion coefficient of the thermoplastic resin forming the housing 302 can be reduced.

4.4 Fixing of Circuit Package 400 by Second Resin Molding Process and Its Effect In FIG. 11, the hatched portion is the second resin molding process in order to fix circuit package 400 to housing 302 in the second resin molding process. A fixing surface 432 and a fixing surface 434 for covering the circuit package 400 with the thermoplastic resin to be used are shown. As described with reference to FIGS. 5 and 6, the relationship between the measurement channel surface 430 and the heat transfer surface exposed portion 436 provided on the measurement channel surface 430 and the shape of the sub passage is maintained with high accuracy. This is very important. In the second resin molding step, the circuit package 400 is fixed to the housing 302 that forms the sub-passage and at the same time forms the sub-passage. It 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 a mold for molding the housing 302 having the sub-passage. It becomes possible. By injecting a high-temperature thermoplastic resin into the mold, the sub-passage is formed with high accuracy, and the circuit package 400 is fixed with high accuracy.

  In this embodiment, the entire surface of the circuit package 400 is not the fixed surface 432 that is covered with the resin forming the housing 302, but the surface is exposed to the measurement terminal 412 side of the circuit package 400, that is, the resin for the housing 302. The part which is not covered is provided. In the embodiment shown in FIG. 11, the surface of the circuit package 400 is not included in the resin of the housing 302 and is exposed from the resin of the housing 302 because of the area of the fixing surface 432 included in the resin for the housing 302 and the area of the fixing surface 434. The area is wider.

  There is a difference in thermal expansion coefficient between the thermosetting resin forming the circuit package 400 and the thermoplastic resin forming the housing 302 including the fixing portion 372, and stress based on the difference in thermal expansion coefficient is not applied to the circuit package 400 as much as possible. It is desirable to do so. By reducing the fixed surface 432 on the surface of the circuit package 400, the influence based on the difference in thermal expansion coefficient can be reduced. For example, the fixed surface 432 on the surface of the circuit package 400 can be reduced by forming a belt with a width L.

  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, by providing a band-shaped fixed surface in a direction along the axis through which the measured gas 30 flows, and further providing a fixed surface in a direction intersecting with the axis through which the measured gas 30 flows, the circuit package is more firmly provided 400 and the housing 302 can be fixed to each other. In the fixed surface 432, a portion surrounding the circuit package 400 in a band shape with a width L along the measurement flow path surface 430 is a fixed surface in the direction along the flow axis of the measurement target gas 30 described above, and the root of the protrusion 424. The portion that covers is a fixed surface in the direction crossing the flow axis of the measurement target gas 30.

  In FIG. 11, the circuit package 400 is manufactured by the first resin molding process as described above. The hatched portion described on the appearance of the circuit package 400 is a resin used in the second resin molding process when the housing 302 is formed in the second resin molding process after the circuit package 400 is manufactured in the first resin molding process. Shows a fixed surface 432 and a fixed surface 434 on which the circuit package 400 is covered. 11A is a left side view of the circuit package 400, FIG. 11B is a front view of the circuit package 400, and FIG. 11C is a rear view of the circuit package 400. The circuit package 400 incorporates a flow rate detection unit 602 and a processing unit 604, which will be described later, and these are molded with a thermosetting resin and integrally molded. On the surface of the circuit package 400 shown in FIG. 11B, a measurement channel surface 430 that functions as a surface for flowing the measurement target gas 30 is formed in a shape that extends long in the flow direction of the measurement target gas 30. In this embodiment, the measurement flow path surface 430 has a rectangular shape that extends long in the flow direction of the measurement target gas 30. As shown in FIG. 11A, the measurement channel surface 430 is made thinner than other portions, and a heat transfer surface exposed portion 436 is provided in a part thereof. The built-in flow rate detection unit 602 performs heat transfer with the measurement target gas 30 via the heat transfer surface exposure unit 436, measures the state of the measurement target gas 30, for example, the flow velocity of the measurement target gas 30, and the main passage 124. An electric signal representing the flow rate flowing through the is output.

  In order for the built-in flow rate detector 602 (see FIG. 17) to measure the state of the gas 30 to be measured with high accuracy, the gas flowing in the vicinity of the heat transfer surface exposed portion 436 is laminar and has little turbulence. desirable. For this reason, it is preferable that there is no step between the side surface of the heat transfer surface exposed portion 436 and the surface of the measurement channel surface 430 that guides the gas. With such a configuration, it is possible to suppress uneven stress and distortion from acting on the flow rate detection unit 602 while maintaining high accuracy in flow rate measurement. The step may be provided as long as it does not affect the flow rate measurement accuracy.

  On the back surface of the measurement flow path surface 430 having the heat transfer surface exposed portion 436, as shown in FIG. 11 (C), a pressing mark 442 for pressing the mold that supports the internal substrate or plate during resin molding of the circuit package 400. Remains. The heat transfer surface exposed part 436 is a place used for exchanging heat with the gas to be measured 30. In order to accurately measure the state of the gas to be measured 30, the flow detection part 602 and the object to be measured are used. It is desirable that heat transfer with the measurement gas 30 be performed satisfactorily. For this reason, it is necessary to avoid that the heat transfer surface exposed portion 436 is covered with the resin in the first resin molding step. A mold is applied to both the heat transfer surface exposed portion 436 and the measurement flow path surface back surface 431 which is the back surface thereof, and the mold prevents the resin from flowing into the heat transfer surface exposed portion 436. A recessed trace 442 is formed on the back surface of the heat transfer surface exposed portion 436. In this portion, elements constituting the flow rate detection unit 602 and the like are arranged close to each other, and it is desirable to dissipate heat generated by these elements to the outside as much as possible. The formed recess is less affected by the resin and has an effect of easily radiating heat.

  A semiconductor diaphragm constituting the flow rate detection unit 602 is disposed inside the heat transfer surface exposed portion 436, and a gap is formed on the back surface of the semiconductor diaphragm. When the gap is sealed, the semiconductor diaphragm is deformed due to a change in pressure in the gap due to a temperature change, and the measurement accuracy is lowered. Therefore, in this embodiment, an opening 438 communicating with the gap on the back surface of the semiconductor diaphragm is provided on the surface of the circuit package 400, and a communication path connecting the gap on the back surface of the semiconductor diaphragm and the opening 438 is provided inside the circuit package 400. Note that the opening 438 is provided in a portion where the hatched lines shown in FIG. 11 are not described so that the opening 438 is not blocked by the resin in the second resin molding step.

  It is necessary to mold the opening 438 in the first resin molding step. A mold is applied to the opening 438 and the back surface thereof, and both the front and back surfaces are pressed with the mold, so that the resin to the opening 438 can be formed. Inflow is blocked and opening 438 is formed. The formation of the communication path that connects the opening 438 and the gap on the back surface of the semiconductor diaphragm and the opening 438 will be described later.

  In the circuit package 400, the pressing trace 442 remains on the back surface of the circuit package 400 where 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, for example, a insert piece is applied to the heat transfer surface exposed portion 436, and the pressing trace 442 on the opposite surface is further formed. A mold is applied to the portion, and both molds prevent the resin from flowing into the heat transfer surface exposed portion 436. By forming the heat transfer surface exposed portion 436 in this manner, the flow rate of the measurement target gas 30 can be measured with extremely high accuracy. Further, since the portion of the pressing mark 442 has no or almost no resin in the second resin molding step, the heat dissipation effect is great. In the case where a lead is used as the second plate 536, there is an effect that heat generated in an adjacent circuit through the lead can be radiated.

5. Mounting of Circuit Components on Circuit Package 5.1 Frame Frame of Circuit Package and Mounting of Circuit Components FIG. 12 shows a frame frame 512 of the circuit package 400 and a chip mounting state of the circuit component 516 mounted on the frame frame 512. A broken line portion 508 indicates a portion covered with a mold used when the circuit package 400 is molded. A lead 514 is mechanically connected to the frame frame 512, a plate 532 is mounted at the center of the frame frame 512, and a chip-shaped flow rate detection unit 602 and a processing unit 604 made as an LSI are mounted on the plate 532. Has been. The flow rate detection unit 602 is provided with a diaphragm 672, and terminals of the flow rate detection unit 602 described below and the processing unit 604 are electrically connected by wires 542. Further, each terminal of the processing unit 604 and the corresponding lead 514 are connected by a wire 543. The lead 514 located between the portion serving as the connection terminal of the circuit package 400 and the plate 532 has a chip-like circuit component 516 connected between them.

  In this way, when the circuit package 400 is completed, the flow rate detection unit 602 having the diaphragm 672 is disposed at the most distal end side, and the processing unit 604 is in an LSI state to be a connection terminal with respect to the flow rate detection unit 602. Further, a connection wire 543 is disposed on the terminal side of the processing unit 604. In this manner, the flow rate detection unit 602, the processing unit 604, the wire 543, the circuit component 516, and the connection lead 514 are arranged in order from the front end side of the circuit package 400 to the connection terminal, thereby simplifying the entire configuration. Is a concise arrangement.

  A thick lead is provided to support the plate 532, and this lead is fixed to the frame 512 by a lead 556 and a lead 558. A lower surface of the plate 532 is provided with a lead surface (not shown) having the same area as the plate 532 connected to the thick lead, and the plate 532 is mounted on the lead surface. These lead surfaces are grounded. Thus, noise can be suppressed by performing grounding in the circuits of the flow rate detection unit 602 and the processing unit 604 via the lead surface in common, and the measurement accuracy of the measurement target gas 30 is improved. Further, a lead 544 is provided so as to protrude from the plate 532 toward the upstream side of the flow path, that is, along the axis in a direction crossing the axis of the flow rate detection unit 602, the processing unit 604, and the circuit component 516 described above. Yes. A temperature detection element 518, for example, a chip-like thermistor is connected to the lead 544. Furthermore, a lead 548 is provided near the processing portion 604 that is the base of the protruding portion, and the lead 544 and the lead 548 are electrically connected by a thin wire 546 such as an Au wire. When the lead 548 and the lead 544 are directly connected, heat is transmitted to the temperature detection element 518 through the lead 548 and the lead 544, and the temperature of the measurement target gas 30 cannot be measured accurately. For this reason, the thermal resistance between the lead 548 and the lead 544 can be increased by connecting with a line having a small cross-sectional area and a large thermal resistance. Thereby, the influence of heat does not reach the temperature detection element 518, and the measurement accuracy of the temperature of the measurement target gas 30 is improved.

  The lead 548 is fixed to the frame 512 by a lead 552 and a lead 554. The connecting portion between the lead 552 and the lead 554 and the frame 512 is fixed to the frame 512 in an inclined state with respect to the protruding direction of the protruding temperature detecting element 518, and the mold is also disposed obliquely at this portion. It becomes. As the molding resin flows along this oblique state in the first resin molding step, the molding resin in the first resin molding step flows smoothly to the tip portion where the temperature detection element 518 is provided, and reliability is improved. improves.

  FIG. 12 shows an arrow 592 indicating the resin press-fitting direction. The lead frame on which the circuit components are mounted is covered with a mold, and a press-fitting hole 590 for injecting resin is provided in the position of the circle, and a thermosetting resin is injected into the mold from the direction of the arrow 592. In the direction of the arrow 592 from the press-fitting hole 590, there are a circuit component 516 and a temperature detection element 518, and a lead 544 for holding the temperature detection element 518. Further, a plate 532, a processing unit 604, and a flow rate detection unit 602 are provided in a direction close to the direction of the arrow 592. 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. For this reason, the relationship between the arrangement of circuit components and wiring in the lead 514 and the press-fitting hole 590 and the press-fitting direction is very important.

5.2 Structure for Connecting the Gap and Opening on the Back of the Diaphragm FIG. 13 is a diagram showing a part of the CC cross section of FIG. 12, and is provided inside the diaphragm 672 and the flow rate detection unit (flow rate detection element) 602. It is explanatory drawing explaining the communicating hole 676 which connects the gap | interval 674 and the hole 520. FIG.

  As will be described later, a diaphragm 672 is provided in the flow rate detection unit 602 that measures the flow rate of the gas 30 to be measured, and a gap 674 is provided on the back surface of the diaphragm 672. Although not shown in the drawing, the diaphragm 672 is provided with an element for exchanging heat with the measurement target gas 30 and thereby measuring the flow rate. If heat is transmitted between the elements via the diaphragm 672 separately from the exchange of heat with the measurement target gas 30 between the elements formed in the diaphragm 672, it is difficult to accurately measure the flow rate. For this reason, the diaphragm 672 needs to increase the thermal resistance, and the diaphragm 672 is made as thin as possible.

  The flow rate detection unit (flow rate detection element) 602 is embedded and fixed in the first resin of the circuit package 400 molded by the first resin molding process so that the heat transfer surface 437 of the diaphragm 672 is exposed. The element (not shown) is provided on the surface of the diaphragm 672. The element transmits heat to the measurement target gas 30 (not shown) through the heat transfer surface 437 on the element surface in the heat transfer surface exposed portion 436 corresponding to the diaphragm 672. The heat transfer surface 437 may be constituted by the surface of each element, or a thin protective film may be provided thereon. It is desirable that the heat transfer between the element and the measurement target gas 30 is performed smoothly, while the direct heat transfer between the elements is as small as possible.

  The portion of the flow rate detection unit (flow rate detection element) 602 where the element is provided is disposed in the heat transfer surface exposed portion 436 of the measurement flow channel surface 430, and the heat transfer surface 437 forms the measurement flow channel surface 430. Exposed from the resin. The outer peripheral portion of the flow rate detection element 602 is covered with the thermosetting resin used in the first resin molding process that forms the measurement flow path surface 430. If only the side surface of the flow rate detection element 602 is covered with the thermosetting resin, and the surface side of the outer peripheral portion of the flow rate detection 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 measurement flow path surface 430 is received only by the side surface of the flow rate detection element 602, so that the diaphragm 672 may be distorted and the characteristics may be deteriorated. As shown in FIG. 13, the distortion of the diaphragm 672 is reduced by setting the front side outer peripheral portion of the flow rate detection element 602 to be covered with the thermosetting resin. On the other hand, if the level difference between the heat transfer surface 437 and the measurement flow path surface 430 through which the measurement target gas 30 flows is large, the flow of the measurement target gas 30 is disturbed, and the measurement accuracy decreases. Therefore, it is desirable that the step W between the heat transfer surface 437 and the measurement flow path surface 430 through which the measurement target gas 30 flows is small.

  The diaphragm 672 is made very thin in order to suppress heat transfer between the elements, and a gap 674 is formed on the back surface of the flow rate detection unit (flow rate detection 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 a temperature change. When the pressure difference between the gap 674 and the surface of the diaphragm 672 becomes large, the diaphragm 672 receives a pressure to cause distortion, and high-precision measurement becomes difficult. For this reason, the plate 532 is provided with a hole 520 that is connected to the opening 438 that opens to the outside, and a communication hole 676 that connects the hole 520 and the gap 674. The communication hole 676 is made of two plates, for example, a first plate 534 and a second plate 536. The first plate 534 is provided with a hole 520 and a hole 521, and further a groove for forming the communication hole 676. The communication hole 676 is formed by closing the groove and the hole 520 and the hole 521 with the second plate 536. By the communication hole 676 and the hole 520, the air pressure acting on the front surface and the back surface of the diaphragm 672 becomes substantially equal, and the measurement accuracy is improved.

  As described above, the communication hole 676 can be formed by closing the groove and the hole 520 and the hole 521 with the second plate 536. Alternatively, the lead frame can be used as the second plate 536. As illustrated in FIG. 12, an LSI that operates as a diaphragm 672 and a processing unit 604 is provided on the plate 532. A lead frame for supporting a plate 532 on which the diaphragm 672 and the processing unit 604 are mounted is provided below these. Therefore, the structure becomes simpler by using this lead frame. The lead frame can be used as a ground electrode. In this way, the lead frame has the role of the second plate 536, and the lead frame is used to block the hole 520 and the hole 521 formed in the first plate 534 and to form the groove formed in the first plate 534. By forming the communication hole 676 by covering the lead frame so as to cover the lead frame, the entire structure is simplified, and the lead frame acts as a ground electrode, so that the diaphragm 672 and the processing unit 604 are externally connected. The influence of noise can be reduced.

  In the circuit package 400, the pressing trace 442 remains on the back surface of the circuit package 400 where 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, for example, a insert piece is applied to the heat transfer surface exposed portion 436, and the pressing trace 442 on the opposite surface is further formed. A mold is applied to the portion, and both molds prevent the resin from flowing into the heat transfer surface exposed portion 436. By forming the heat transfer surface exposed portion 436 in this manner, the flow rate of the measurement target gas 30 can be measured with extremely high accuracy.

  FIG. 14 shows a state in which the frame shown in FIG. 12 is molded with a thermosetting resin and covered with the thermosetting resin in the first resin molding step. By this molding, a measurement channel surface 430 is formed on the surface of the circuit package 400, and a heat transfer surface exposed portion 436 is provided on the measurement channel surface 430. Further, the gap 674 on the back surface of the diaphragm 672 disposed inside the heat transfer surface exposed portion 436 is connected to the opening 438. A temperature detection unit 452 for measuring the temperature of the measurement target gas 30 is provided at the tip of the protrusion 424, and a temperature detection element 518 is incorporated therein. Inside the protruding portion 424, in order to suppress heat transfer, a lead for taking out an electric signal of the temperature detection element 518 is divided, and a connection line 546 having a large thermal resistance is disposed. Thereby, the heat transfer from the base of the protrusion part 424 to the temperature detection part 452 is suppressed, and the influence by heat is suppressed.

  Further, an inclined portion 594 and an inclined portion 596 are formed at the base of the protruding portion 424. While the flow of the resin in the first resin molding step is smooth, the measurement target gas 30 measured by the temperature detection unit 452 is measured by the inclined portion 594 and the inclined portion 596 in a state where the resin is mounted on the vehicle and operating. The projection flows smoothly from the protrusion 424 toward the root, and the root of the protrusion 424 is cooled, so that the effect of heat on the temperature detection unit 452 can be reduced. After the state of FIG. 14, the lead 514 is cut for each terminal, and becomes a measurement terminal 412 or an inspection 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. For this reason, in the first resin molding step, the resin flow is blocked at the position of the heat transfer surface exposed portion 436 and the opening 438, for example, a piece larger than the diaphragm 672 is applied, and the back surface is pressed and sandwiched from both sides. . In FIG. 11C, the pressing trace 442 and the pressing trace 441 are formed on the heat transfer surface exposed portion 436 and the opening 438 in FIG. 14 or the back surface corresponding to the heat transfer surface exposed portion 436 and the opening 438 in FIG. Remaining.

  When the cut surface of the lead cut off from the frame 512 in FIG. 14 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 this from the viewpoint of improving durability and improving reliability. For example, the portion of the fixed surface 434 in FIG. 14 is covered with resin in the second resin molding step, and the cut surface is not exposed. Further, the lead cutting portions of the inclined portion 594 and the inclined portion 596 are covered with resin in the second resin molding step, and the cutting surfaces of the leads 552 and the leads 554 shown in FIG. 12 with the frame 512 are covered with the resin. This prevents corrosion of the cut surfaces of the lead 552 and the lead 554 and intrusion of water from the cut portion. The cut surfaces of the lead 552 and the lead 554 are close to an important lead portion that transmits an electrical signal of the temperature detection unit 452. Therefore, it is desirable to cover the cut surface with the second resin molding process.

5.3 Another Example of Circuit Package 400 FIG. 15 shows another example of the circuit package 400. The same reference numerals as those shown in other figures are the same. In the embodiment shown in FIG. 11 described above, the circuit package 400 includes a measurement terminal 412, an adjustment terminal 415, and an inspection terminal 414 provided on the same side of the circuit package 400. On the other hand, in the embodiment shown in FIG. 15, the measurement terminal 412, the adjustment terminal 415, and the inspection terminal 414 are provided on different sides. The inspection terminal 414 is a terminal that is not connected to an external connection terminal of the thermal flow meter 300. As described above, the measurement terminal 412 and the adjustment terminal 415 that are connected to the outside of the thermal flow meter 300 and the inspection terminal 414 that is not connected to the outside are provided in different directions, whereby the measurement terminal 412 and the adjustment terminal are provided. The space between the terminals 415 can be widened, and the subsequent workability is improved. Further, by extending the inspection terminal 414 and the adjustment terminal 415 in a direction different from the measurement terminal 412, it is possible to reduce the concentration of the leads in the frame 512, and the arrangement of the leads in the frame 512. Becomes easy. In particular, a chip capacitor, which is a circuit component 516, is connected to a lead portion corresponding to the measurement terminal 412. In order to provide these circuit components 516, a slightly large space is required. The embodiment of FIG. 15 has an effect that it is easy to secure a lead space corresponding to the measurement terminal 412 and the adjustment terminal 415.

  Similarly to the circuit package 400 shown in FIG. 11, the circuit package 400 shown in FIG. 15 is formed with an inclined portion 462 and an inclined portion 464 whose thickness gradually changes at the base portion of the protruding portion 424 protruding from the package body 422. Yes. The same effect as described in FIG. 11 is obtained. That is, as shown in FIG. 15, the protruding portion 424 protrudes from the side surface of the package main body 422 in a shape extending in the upstream direction of the measurement target gas 30. A temperature detection unit 452 is provided at the tip of the protrusion 424, and a temperature detection element 518 is embedded in the temperature detection unit 452. Inclined portions 462 and 464 are provided at a connection portion between the protruding portion 424 and the package main body 422. The base of the protruding portion 424 is thickened by the inclined portion 462 or the inclined portion 464, and a shape that gradually narrows as the tip proceeds is formed at the root of the protruding portion 424. That is, a shape in which the cross-sectional area crossing the axis in the projecting direction gradually decreases when the projecting direction is used as an axis is provided at the root of the projecting part 424.

  By having such a shape, when the circuit package 400 is molded by a resin mold, it is possible to use a method in which a sheet is applied to the inside of the mold to flow the resin for the purpose of protecting the element. Improves the reliability. Further, the protrusion 424 has low mechanical strength and is easily broken at the root. With the shape in which the base of the protruding portion 424 is thickened and gradually becomes narrower in the direction of the tip, stress concentration on the base can be alleviated and the mechanical strength is excellent. In addition, when the protruding portion 424 is formed by a resin mold, warpage or the like is likely to occur due to an influence of a volume change when the resin is hardened. Such influence can be reduced. In order to detect the temperature of the gas 30 to be measured as accurately as possible, it is desirable to increase the protruding length. Heat transfer from the package body 422 to the temperature detection element 518 provided in the temperature detection unit 452 can be easily reduced by increasing the protrusion length of the protrusion 424.

  As shown in FIGS. 11B and 11C, the base of the protruding portion 424 is thickened, and the base of the protruding portion 424 is surrounded by the housing 302 to fix the circuit package 400 to the housing 302. In this manner, by covering the base of the protruding portion 424 with the resin of the housing 302, it is possible to prevent the protruding portion 424 from being damaged by a mechanical impact. In addition, various effects described with reference to FIG.

  The description of the opening 438, the heat transfer surface exposed portion 436, the measurement flow path surface 430, the pressing trace 441, and the pressing trace 442 in FIG. 15 is substantially the same as the above-described content, and has the same effects. A specific description will be omitted because it will be repeated.

6). Production Process of Thermal Flow Meter 300 6.1 Production Process of Circuit Package 400 FIG. 16 shows a production process of the circuit package 400 in the production process of the thermal flow meter 300. In FIG. 16, step 1 shows the process of producing the frame shown in FIG. This frame is made by, for example, press working. In Step 2, the plate 532 is first mounted on the frame frame formed in Step 1, and the flow rate detection unit 602 and the processing unit 604 are further mounted on the plate 532, and circuit components such as the temperature detection element 518 and the chip capacitor are further mounted. Mount. In step 2, electrical wiring is performed between circuit components, between circuit components and leads, and between leads. In step 2, the lead 544 and the lead 548 are connected by a connection line 546 for increasing the thermal resistance. In step 2, the circuit component shown in FIG. 12 is mounted on the frame frame 512, and an electric circuit in which electrical connection is further made is produced.

  Next, in step 3, it is molded with a thermosetting resin by the first resin molding process. The molded circuit package 400 is as shown in FIG. In step 3, the connected leads are separated from the frame frame 512, and the leads are also separated, whereby the circuit package 400 shown in FIGS. 11 and 15 is completed. In this 400, as shown in FIGS. 11 and 15, a measurement channel surface 430 and a heat transfer surface exposed portion 436 are formed.

  In step 4, an appearance inspection of the completed circuit package 400 and an inspection of whether the electric circuit operates correctly are performed using the inspection terminal 414 in addition to the measurement terminal 412. In the first resin molding step of Step 3, transfer molding is performed. Since the electric circuit produced in step 2 is fixed in the mold and high temperature resin is injected into the mold at a high pressure, it is desirable to inspect whether there are any abnormalities in the electrical components and the electrical wiring. For this inspection, an inspection terminal 414 is used in addition to the measurement terminal 412 shown in FIGS. Since the inspection terminal 414 is not used thereafter, it may be cut from the root after this inspection. For example, in FIG. 15, the used inspection terminal 414 is cut at the root.

6.2 Adjustment of Production Process and Measurement Characteristics of Thermal Flow Meter 300 In Step 5, a circuit package 400 that has already been produced and an external terminal 306 that has already been produced by a method not shown are used. In step 5, the housing 302 is formed by the second resin molding process. The housing 302 has a resin-made sub-passage groove, a flange 312 and an external connection portion 305, and the hatched portion of the circuit package 400 shown in FIG. 11 is covered with the resin in the second resin molding process, so that the circuit package 400 is the housing. 302 is fixed. The combination of the production of the circuit package 400 by the first resin molding process (step 3) and the molding of the housing 302 of the thermal flow meter 300 by the second resin molding process significantly improves the flow rate detection accuracy. In step 6, each external terminal inner end 361 shown in FIG. 10 is disconnected, and the measurement terminal 412 and the external terminal inner end 361 are connected in step 7.

  When the housing 302 is completed in step 7, next, 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 with the front cover 303 and the back cover 304, and the measured gas 30 Is completed, and the thermal flow meter 300 is completed. Further, the diaphragm structure described with reference to FIG. 7 is formed by the protrusions 356 provided on the front cover 303 or the back cover 304. The front cover 303 is made by molding in step 10, and the back cover 304 is made by molding in step 11. Further, the front cover 303 and the back cover 304 are made in separate steps, and are made by molding with different molds.

  In step 9, a gas having a known flow rate is actually supplied to the sub-passage, and a characteristic test is performed. As described above, since the relationship between the sub passage and the flow rate detection unit is maintained with high accuracy, very high measurement accuracy can be obtained by correcting the characteristic by the characteristic test. In addition, since the positioning and shape-related molding that affects the relationship between the sub-passage and the flow rate detection unit are performed in the first resin molding process and the second resin molding process, there is little change in characteristics even with long-term use, and high accuracy. In addition, high reliability is ensured.

7). Circuit Configuration of Thermal Flow Meter 300 7.1 Overall Circuit Configuration of Thermal Flow Meter 300 FIG. 17 is a circuit diagram showing a flow rate detection circuit 601 of the thermal flow meter 300. Note that a measurement circuit related to the temperature detection unit 452 described in the embodiment is also provided in the thermal flow meter 300, but is omitted in FIG. The flow rate detection circuit 601 of the thermal type flow meter 300 includes a flow rate detection unit 602 having a heating element 608 and a processing unit 604. The processing unit 604 controls the amount of heat generated by the heating element 608 of the flow rate detection unit 602 and outputs a signal indicating the flow rate based on the output of the flow rate detection unit 602 via the terminal 662. In order to perform the processing, the processing unit 604 includes a central processing unit (hereinafter referred to as a CPU) 612, an input circuit 614, an output circuit 616, a memory 618 that holds data representing a relationship between a correction value, a measured value, and a flow rate, A power supply circuit 622 is provided to supply a constant voltage to each necessary circuit. The power supply circuit 622 is supplied with DC power from an external power source such as an in-vehicle battery via a terminal 664 and a ground terminal (not shown).

  The flow rate detector 602 is provided with a heating element 608 for heating the air to be measured 30. The voltage V1 is supplied from the power supply circuit 622 to the collector of the transistor 606 constituting the current supply circuit of the heating element 608, and a control signal is applied from the CPU 612 to the base of the transistor 606 via the output circuit 616. Accordingly, a current is supplied from the transistor 606 to the heating element 608 through the terminal 624. The amount of current supplied to the heating element 608 is controlled by a control signal applied from the CPU 612 to the transistor 606 constituting the current supply circuit of the heating element 608 via the output circuit 616. The processing unit 604 controls the amount of heat generated by the heating element 608 so that the temperature of the air to be measured 30 is higher than the initial temperature by a predetermined temperature, for example, 100 ° C. by being heated by the heating element 608.

  The flow rate detection unit 602 includes 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. One end of the heat generation control bridge 640 is supplied with a constant voltage V3 from the power supply circuit 622 via a terminal 626, and the other end of the heat generation control bridge 640 is connected to the ground terminal 630. A constant voltage V2 is supplied from one end of the flow rate detection bridge 650 from the power supply circuit 622 via a terminal 625, and the other end of the flow rate detection bridge 650 is connected to the ground terminal 630.

  The heat generation control bridge 640 includes a resistor 642 that is a resistance temperature detector whose resistance value changes based on the temperature of the heated air 30 to be measured, and the resistor 642, the resistor 644, the resistor 646, and the resistor 648 are bridges. The circuit is configured. The potential difference between the intersection A of the resistor 642 and the resistor 646 and the potential B at the intersection B of the resistor 644 and 648 is input to the input circuit 614 via the terminal 627 and the terminal 628, and the CPU 612 has a predetermined potential difference between the intersection A and the intersection B. In this embodiment, the amount of heat generated by the heating element 608 is controlled by controlling the current supplied from the transistor 606 so as to be zero volts. The flow rate detection circuit 601 illustrated in FIG. 17 heats the air to be measured 30 with the heating element 608 so as to be higher than the original temperature of the air to be measured 30 by a constant temperature, for example, 100 ° C. at all times. In order to perform this heating control with high accuracy, when the temperature of the air to be measured 30 heated by the heating element 608 becomes higher than the initial temperature by a certain temperature, for example, 100 ° C., the intersection A and the intersection A The resistance value of each resistor constituting the heat generation control bridge 640 is set so that the potential difference between B becomes zero volts. Therefore, in the flow rate detection circuit 601 shown in FIG. 17, 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 volts.

  The flow rate detection bridge 650 includes four resistance temperature detectors, a resistor 652, a resistor 654, a resistor 656, and a resistor 658. These four resistance temperature detectors are arranged along the flow of the air to be measured 30, and the resistor 652 and the resistor 654 are arranged upstream of the heating element 608 in the flow path of the air to be measured 30, and the resistor 656. And the resistor 658 are arranged on the downstream side in the flow path of the air to be measured 30 with respect to the heating element 608. In order to increase the measurement accuracy, the resistor 652 and the resistor 654 are arranged so that the distance to the heating element 608 is substantially the same, and the resistor 656 and the resistor 658 are substantially the same distance to the heating element 608. Has been placed.

  A potential difference between an intersection C of the resistor 652 and the resistor 656 and an intersection D of the resistor 654 and the resistor 658 is input to the input circuit 614 through the terminal 631 and the terminal 632. In order to improve the measurement accuracy, for example, each resistance of the flow rate detection bridge 650 is set so that the potential difference between the intersection C and the intersection D becomes zero when the flow of the air 30 to be measured is zero. Therefore, when the potential difference between the intersection C and the intersection D is, for example, zero volts, the CPU 612 generates an electric signal indicating that the flow rate of the main passage 124 is zero based on the measurement result that the flow rate of the air to be measured 30 is zero. Output from the terminal 662.

  When the measured air 30 flows in the direction of the arrow in FIG. 17, the resistor 652 and the resistor 654 arranged on the upstream side are cooled by the measured air 30 and arranged on the downstream side of the measured air 30. The resistors 656 and 658 are heated by the air 30 to be measured heated by the heating element 608, and the temperatures of the resistors 656 and 658 rise. Therefore, a potential difference is generated between the intersection C and the intersection D of the flow rate detection bridge 650, and this potential difference is input to the input circuit 614 via the terminal 631 and the terminal 632. The CPU 612 retrieves data representing the relationship between the potential difference stored in the memory 618 and the flow rate of the main passage 124 based on the potential difference between the intersection C and the intersection D of the flow rate detection bridge 650, and Find the flow rate. An electrical signal representing the flow rate of the main passage 124 obtained in this way is output via the terminal 662. Note that the terminal 664 and the terminal 662 shown in FIG. 17 are newly described with reference numerals, but are included in the measurement terminal 412 shown in FIG. 5, FIG. 6 or FIG.

  The memory 618 stores data representing the relationship between the potential difference between the intersection C and the intersection D and the flow rate of the main passage 124, and is obtained based on the actual measured value of gas after the circuit package 400 is produced. In addition, correction data for reducing measurement errors such as variations is stored. Note that the actual measurement of the gas after production of the circuit package 400 and the writing of the correction value based on the measurement into the memory 618 are performed using the external terminal 306 and the external adjustment terminal 307 shown in FIG. In the present embodiment, the arrangement relationship between the sub-passage through which the measurement target gas 30 flows and the measurement flow path surface 430 and the arrangement relationship between the sub-passage through which the measurement target gas 30 flows and the heat transfer surface exposed portion 436 are highly accurate. Since the circuit package 400 is produced in a state where there is little variation, the measurement result with extremely high accuracy can be obtained by the correction using the correction value.

7.2 Configuration of Flow Rate Detection Circuit 601 FIG. 18 is a circuit configuration diagram showing a circuit arrangement of the flow rate detection circuit 601 of FIG. 17 described above. The flow rate detection circuit 601 is made as a rectangular semiconductor chip, and the measured air 30 flows in the direction of the arrow from the left side to the right side of the flow rate detection circuit 601 shown in FIG.

  The flow rate detection unit 602 is formed with a rectangular diaphragm 672, and the diaphragm 672 is provided with a thin region 603 indicated by a broken line in which the thickness of the semiconductor chip is reduced. The thin region 603 is formed with a gap on the back surface side, and the gap communicates with the opening 438 shown in FIGS. 11 and 5, and the atmospheric pressure in the gap depends on the pressure introduced from the opening 438.

  The diaphragm 672 thin region 603 has a low thermal conductivity by reducing the thickness, and the heat through the diaphragm 672 to the resistor 652, the resistor 654, the resistor 658, and the resistor 656 provided in the thin region 603 is reduced. Transmission is suppressed, and the temperature of these resistors is substantially determined by heat transfer with the measurement target gas 30.

  A heating element 608 is provided at the center of the thin region 603 of the diaphragm 672, and a resistor 642 constituting the heating control bridge 640 is provided around the heating element 608. Resistors 644, 646, and 648 constituting the heat generation control bridge 640 are provided outside the thin region 603. The resistors 642, 644, 646, and 648 formed in this way constitute a heat generation control bridge 640.

  In addition, a resistor 652 and a resistor 654 that are upstream temperature measuring resistors and a resistor 656 and a resistor 658 that are downstream temperature measuring resistors are arranged so as to sandwich the heating element 608, and the air to be measured is placed on the heating element 608. An upstream resistance temperature detector 652 and a resistance 654 are arranged on the upstream side in the direction of the arrow through which 30 flows, and a downstream resistance temperature detector on the downstream side in the direction of the arrow in which the measured gas 30 flows with respect to the heating element 608. A certain resistor 656 and resistor 658 are arranged. In this manner, the flow rate detection bridge 650 is formed by the resistor 652, the resistor 654, the resistor 656, and the resistor 658 arranged in the thin region 603.

  Further, both end portions of the heating element 608 are connected to terminals 624 and 629 described on the lower side of FIG. Here, as shown in FIG. 17, a current supplied from the transistor 606 to the heating element 608 is applied to the terminal 624, and the terminal 629 is grounded as a ground.

  The resistor 642, the resistor 644, the resistor 646, and the resistor 648 that constitute the heat generation control bridge 640 are connected to the terminals 626 and 630, respectively. As shown in FIG. 17, 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, connection points between the resistor 642 and the resistor 646 and between the resistor 646 and the resistor 648 are connected to a terminal 627 and a terminal 628. As shown in FIG. 18, the terminal 627 outputs the potential at the intersection A between the resistor 642 and the resistor 646, and the terminal 627 outputs the potential at the intersection B between the resistor 644 and the resistor 648. As shown in FIG. 17, a constant voltage V2 is supplied to the terminal 625 from the power supply circuit 622, and the terminal 630 is grounded as a ground terminal. The connection point between the resistor 654 and the resistor 658 is connected to the terminal 631, and the terminal 631 outputs the potential at the point B in FIG. A connection point between the resistor 652 and the resistor 656 is connected to a terminal 632, and the terminal 632 outputs a potential at the intersection C shown in FIG.

  As shown in FIG. 18, since the resistor 642 constituting the heat generation control bridge 640 is formed in the vicinity of the heating element 608, the temperature of the gas warmed by the heat generation from the heating element 608 can be accurately measured. it can. On the other hand, the resistors 644, 646, and 648 constituting the heat generation control bridge 640 are arranged away from the heat generating body 608, and thus are configured not to be affected by heat generated from the heat generating body 608. The resistor 642 is configured to react sensitively to the temperature of the gas heated by the heating element 608, and the resistor 644, the resistance 646, and the resistance 648 are configured not to be affected by the heating element 608. For this reason, the detection accuracy of the measurement target gas 30 by the heat generation control bridge 640 is high, and the control for increasing the measurement target gas 30 by a predetermined temperature with respect to the initial temperature can be performed with high accuracy.

  In this embodiment, an air gap is formed on the back surface side of the diaphragm 672, and this air space communicates with the opening 438 shown in FIGS. 11 and 5. The pressure on the back surface side air gap of the diaphragm 672 and the front side of the diaphragm 672 The difference from the pressure is not increased. Distortion of the diaphragm 672 due to this pressure difference can be suppressed. This leads to an improvement in flow rate measurement accuracy.

  As described above, the diaphragm 672 forms the thin region 603, and the thickness of the thin region 603 is very thin, so that the heat conduction through the diaphragm 672 is suppressed as much as possible. Therefore, the flow rate detection bridge 650 and the heat generation control bridge 640 are less affected by heat conduction through the diaphragm 672, and the tendency to operate depending on the temperature of the measurement target gas 30 is further increased, and the measurement operation is improved. For this reason, high measurement accuracy is obtained.

8). 8.1 Measurement of gas temperature in thermal flow meter 300 8.1 Structure of temperature detection unit 452 in thermal flow meter 300 In FIGS. 2 and 3, a sub-portion is formed at the center of main passage 124, which is the distal end side of measurement unit 310. A passage is provided. An inlet 343 that opens toward the upstream side of the flow of the gas 30 to be measured is formed on the flange 312 side of the auxiliary passage as shown in FIG. Inside the inlet 343, a temperature detector 452 for measuring the temperature of the measurement target gas 30 is disposed so as to protrude from the inside of the housing 302. In the central part of the measurement unit 310 provided with the inlet 343, the upstream outer wall of the measurement unit 310 constituting the housing 302 is recessed toward the downstream side, that is, toward the inside of the housing 302, and the depression shape is formed. The temperature detection part 452 has a shape that protrudes outward from the housing 302 toward the upstream side from the upstream outer wall. Further, a front cover 303 and a back cover 304 are provided on both side portions of the hollow outer wall, and upstream ends of the front cover 303 and the rear cover 304 are directed upstream from the hollow outer wall. It has a protruding shape. Therefore, an inlet 343 for taking in the measurement target gas 30 is formed by the hollow outer wall and the front cover 303 and the back cover 304 on both sides thereof. The gas 30 to be measured taken from the inlet 343 comes into contact with the temperature detector 452 provided inside the inlet 343, and the temperature is measured by the temperature detector 452. Further, the gas to be measured 30 flows along a portion supporting the temperature detection unit 452 protruding upstream from the outer wall of the housing 302 having a hollow shape, and the front side outlet 344 and the back side outlet 345 provided in the front cover 303 and the back cover 304. Is discharged into the main passage 124.

8.2 Effect of Temperature Detection Unit 452 As shown in FIGS. 2 and 3, the temperature detection unit 452 protrudes out of the housing 302 and directly contacts the measurement target gas 30, thereby improving detection accuracy. To do. Further, the temperature of the gas flowing into the inlet 343 from the upstream side in the direction along the flow of the measurement target gas 30 is measured by the temperature detection unit 452, and further, the base of the temperature detection unit 452 that is a part that supports the temperature detection unit 452. By flowing toward the portion, the temperature of the portion supporting the temperature detection unit 452 is cooled in a direction approaching the temperature of the gas 30 to be measured. The temperature of the intake pipe, which is the main passage 124, is usually high, and heat is transferred from the flange 312 or the abutting portion 315 to the portion supporting the temperature detecting portion 452 through the upstream outer wall in the measuring portion 310, thereby measuring the temperature. There is a risk of affecting. As described above, after the gas to be measured 30 is measured by the temperature detection unit 452, the support portion is cooled by flowing along the support portion of the temperature detection unit 452. Therefore, it is possible to suppress heat from being transmitted from the flange 312 or the contact portion 315 to the portion supporting the temperature detection portion 452 through the upstream outer wall in the measurement portion 310.

  In particular, in the support portion of the temperature detection unit 452, the upstream outer wall in the measurement unit 310 has a shape that is recessed toward the downstream side, so that there is a gap between the upstream outer wall in the measurement unit 310 and the temperature detection unit 452. Can be made longer. As the heat transfer distance becomes longer, the distance of the cooling portion by the measured gas 30 becomes longer. Therefore, the influence of heat generated from the flange 312 or the contact portion 315 can be reduced. As a result, the measurement accuracy is improved.

  Since the upstream outer wall has a shape that is recessed toward the downstream side, that is, toward the inside of the housing 302, the upstream outer wall 335 of the housing 302 can be fixed, and the circuit package 400 can be easily fixed. Become. In addition, the protrusion 424 (see FIG. 11) having the temperature detector 452 is also reinforced.

  As described above with reference to FIGS. 2 and 3, the inlet 343 is provided on the upstream side of the measurement target gas 30 in the case 301, and the measurement target gas 30 guided from the inlet 343 passes around the temperature detection unit 452, It is led from the front side outlet 344 and the back side outlet 345 to the main passage 124. The temperature detection unit 452 measures the temperature of the measurement target gas 30 and outputs an electrical signal representing the measured temperature from the external terminal 306 of the external connection unit 305. A case 301 included in the thermal flow meter 300 includes a front cover 303, a back cover 304, and a housing 302. The housing 302 has a recess for forming an inlet 343, and the recess is an outer wall recess 366 (see FIG. 5 and FIG. 6). The front side outlet 344 and the back side outlet 345 are formed by holes provided in the front cover 303 and the back cover 304. As will be described below, the temperature detection unit 452 is provided at the tip of the protrusion 424 and is mechanically weak. The front cover 303 and the back cover 304 serve to protect the protrusions 424 from mechanical impact.

  Further, a front protection part 322 and a rear protection part 325 are formed on the front cover 303 and the back cover 304 shown in FIGS. As shown in FIGS. 2 and 3, a front protection part 322 provided on the front cover 303 is disposed on the front side surface of the inlet 343, and a back protection part 325 provided on the back cover 304 is provided on the rear side surface of the inlet 343. Is arranged. The temperature detection unit 452 disposed inside the entrance 343 is protected by the front protection unit 322 and the back protection unit 325, and the machine of the temperature detection unit 452 due to a collision with the temperature detection unit 452 during production or when mounted on a vehicle. Damage can be prevented.

  As shown in FIGS. 11 and 15, the base of the protrusion 424 that supports the temperature detector 452 is gradually thicker with respect to the tip, and the gas 30 to be measured that has entered from the inlet 343 gradually increases. Since it flows along the base part which becomes thick, a cooling effect increases. The root portion of the protrusion 424 is close to the flow rate detection circuit and is easily affected by the heat generated by the flow rate detection circuit. Furthermore, a lead 548 for connecting a temperature detection element 518 provided in the temperature detection unit 452 is embedded in the root portion of the protrusion 424. For this reason, heat may be transmitted through the lead 548. The cooling effect can be increased by increasing the contact area with the measurement target gas 30 by thickening the base of the protrusion 424.

8.3 Molding and Effect of Temperature Detection Unit 452 and Protrusion 424 The circuit package 400 includes a circuit package body 422 and a protrusion 424 that incorporate a flow rate detection unit 602 and a processing unit 604, which will be described later, for measuring the flow rate. have. As shown in FIG. 2, the protruding portion 424 protrudes from the side surface of the circuit package main body 422 in a shape extending in the upstream direction of the measurement target gas 30. A temperature detection unit 452 is provided at the tip of the protrusion 424, and a temperature detection element 518 is embedded in the temperature detection unit 452 as shown in FIG. As shown in FIGS. 11 and 15, inclined portions 462 and 464 are provided at the connection portion between the protruding portion 424 and the circuit package body 422. The base of the protruding portion 424 is thickened by the inclined portion 462 or the inclined portion 464, and a shape that gradually narrows as the tip proceeds is formed at the root of the protruding portion 424. The cross-sectional area that crosses the axis in the protruding direction has a shape that decreases at the root of the protruding portion 424 as it advances in the distal direction.

  As described above, the connection between the outer wall surface of the circuit package 400 and the outer wall surface of the projecting portion 424 is connected with a structure that gradually changes. Thus, a method can be used in which a sheet is applied to the inside of the mold and the resin is allowed to flow. When the outer wall surface changes abruptly, an excessive force is applied to the sheet, and there is a problem that the contact between the inner wall surface of the mold and the sheet is displaced and the resin molding is not performed well. Further, the protrusion 424 has low mechanical strength and is easily broken at the root. With the shape in which the base of the protruding portion 424 is thickened and gradually becomes narrower in the direction of the tip, stress concentration on the base can be alleviated and the mechanical strength is excellent. In addition, when the protruding portion 424 is formed by a resin mold, warpage or the like is likely to occur due to an influence of a volume change when the resin is hardened. Such influence can be reduced. In order to detect the temperature of the gas 30 to be measured as accurately as possible, it is desirable to increase the protruding length. Heat transfer from the circuit package body 422 to the temperature detection element 518 provided in the temperature detection unit 452 can be easily reduced by increasing the protrusion length of the protrusion 424.

  As shown in FIGS. 11B and 11C, the base of the protruding portion 424 is thickened, and the base of the protruding portion 424 is surrounded by the resin of the housing 302 to fix the circuit package 400 to the housing 302. In this manner, by covering the base of the protruding portion 424 with the resin of the housing 302, it is possible to prevent the protruding portion 424 from being damaged by a mechanical impact.

  In order to detect the temperature of the gas to be measured 30 with high accuracy, it is desirable to reduce the heat transfer with the portion other than the gas to be measured 30 as much as possible. The protrusion 424 that supports the temperature detection unit 452 has a tip that is narrower than the base, and the temperature detection unit 452 is provided at the tip. With such a shape, the influence of heat from the base portion of the protruding portion 424 on the temperature detecting portion 452 is reduced.

  In addition, after the temperature of the measurement target gas 30 is detected by the temperature detection unit 452, the measurement target gas 30 flows along the protrusion 424, and acts to bring the temperature of the protrusion 424 close to the temperature of the measurement target gas 30. As a result, the influence of the temperature of the base portion of the protrusion 424 on the temperature detection unit 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. For this reason, the measurement target gas 30 flows along the shape of the protruding portion 424, and the protruding portion 424 is efficiently cooled.

  In FIG. 11, the hatched portion at the base portion of the protruding portion 424 is a fixing surface 432 covered with the resin forming the housing 302 in the second resin molding process. A depression is provided in the shaded portion at the base of the protrusion 424. This indicates that a hollow portion that is not covered with the resin of the housing 302 is provided. In this way, by forming a hollow-shaped portion that is not covered with the resin of the root portion housing 302 of the protrusion 424, the protrusion 424 is further easily cooled by the measurement target gas 30. In FIG. 15, the display of the hatched portion is omitted, but it is the same as FIG.

  The circuit package 400 is provided with a measurement terminal 412 for supplying power for operating the built-in flow rate detection unit 602 and the processing unit 604 and outputting a flow rate measurement value and a temperature measurement value. . Further, an inspection terminal 414 is provided for inspecting whether the circuit package 400 operates correctly and whether an abnormality has occurred in circuit components or 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 using a thermosetting resin in the first resin molding step. By performing transfer molding, the dimensional accuracy of the circuit package 400 can be improved. However, in the transfer molding process, high-temperature pressure is applied to the inside of the sealed mold containing the flow rate detection unit 602 and the processing unit 604. Since the resin is injected, 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 relationship. In this embodiment, an inspection terminal 414 for inspection is provided, and each produced circuit package 400 is inspected. Since the inspection terminal 414 for inspection is not used for measurement, the inspection terminal 414 is not connected to the external terminal inner end 361 as described above. Each measurement terminal 412 is provided with a bent portion 416 in order to increase mechanical elasticity. By giving each measurement terminal 412 a mechanical elastic force, it is possible to absorb the stress generated due to the difference in thermal expansion coefficient between the resin in the first resin molding step and the resin in the second resin molding step. . That is, each measurement terminal 412 is affected by thermal expansion due to the first resin molding process, and the external terminal inner end 361 connected to each measurement terminal 412 is affected by resin due to the second resin molding process. Generation | occurrence | production of the stress resulting from these resin differences can be absorbed.

8.4 Effects and Effects of Inclined Portions 462 and 464 Formed at the Base of the Protruding Portion 424 As described with reference to FIGS. 11 and 15, inclined portions 462 and 464 are provided at the base of the protruding portion 424. The base of the protruding portion 424 is thickened by the inclined portion 462 or the inclined portion 464, and a shape that gradually narrows as the tip proceeds is formed at the root of the protruding portion 424. That is, a shape in which the cross-sectional area crossing the axis in the projecting direction gradually decreases when the projecting direction is used as an axis is provided at the root of the projecting part 424.

  When the circuit package 400 is molded by resin molding, when the sheet is applied to the inside of the mold for the purpose of protecting the element and the resin flows, the adhesion between the sheet and the inner surface of the mold is improved and the reliability is improved. To do. Further, the protrusion 424 has low mechanical strength and is easily broken at the root. With the shape in which the base of the protruding portion 424 is thickened and gradually becomes narrower in the direction of the tip, stress concentration on the base can be alleviated and the mechanical strength is excellent. In addition, when the protruding portion 424 is formed by a resin mold, warpage or the like is likely to occur due to an influence of a volume change when the resin is hardened. Such influence can be reduced. In order to detect the temperature of the gas 30 to be measured as accurately as possible, it is desirable to increase the protruding length. Heat transfer from the package body 422 to the temperature detection element 518 provided in the temperature detection unit 452 can be easily reduced by increasing the protrusion length of the protrusion 424.

  As shown in FIGS. 11B and 11C, the base of the protruding portion 424 is thickened, and the base of the protruding portion 424 is surrounded by the housing 302 to fix the circuit package 400 to the housing 302. Thus, by covering the base of the protrusion 424 with the resin of the housing 302, the protrusion 424 can be prevented from being damaged by a mechanical impact.

8.5 Another Example of Housing 302 FIG. 19 shows another example of FIGS. 5 and 6. In FIGS. 5 and 6, a gap is formed in the terminal connection portion 320, and a measurement terminal is formed in the gap. 412 is electrically and mechanically connected at the inner end 361 of the external terminal, and the adjustment terminal 415 is electrically and mechanically connected to the inner end 367 of the external adjustment terminal. On the other hand, in the embodiment shown in FIG. 19, before the second resin molding step, the measurement terminal 412 and the external terminal inner end 361 are electrically and mechanically connected, and the adjustment terminal 415 and the external adjustment terminal are further connected. Electrical and mechanical connection with the inner end 367 is made. After these connections, the housing 302 is molded in a second resin molding process. In this embodiment, the gap between the flange 312 side end of the circuit package 400 and the flange 312 or between the flange 312 side end of the circuit package 400 and the terminal fixing portion 363 is entirely covered with resin. By doing so, the inspection terminal 414, the measurement terminal 412, the adjustment terminal 415, the external terminal inner end 361, and the external adjustment terminal inner end 367 are all covered with the resin, and there is no fear of corrosion. Further, there is no possibility that moisture or the like enters the inside of the circuit package 400 from the bases of the inspection terminal 414, the measurement terminal 412, and the adjustment terminal 415 that are each terminal of the circuit package 400. This leads to improved reliability. Furthermore, it is excellent from the viewpoint of fixing the circuit package 400 to the housing 302.

8.6 Connection Structure between External Connection Portion 305 and Connector 311 FIG. 20 is a conceptual diagram in which a connector 311 of an external device is inserted into the external connection portion 305 in FIG. The external adjustment terminal 307 has a different shape from the external terminal 306. Therefore, the connection between the connector terminal 319 of the connector 311 and the external terminal 306 is not affected. In this embodiment, the external adjustment terminal 307 is positioned at the end of the external terminal 306 so that the external adjustment terminal 307 does not affect the connection of the connector 311 as described above. Also, the dimensions are shortened.

  On the other hand, in writing correction data, the other connection terminal is connected to the external adjustment terminal 307 to send correction data to be stored. The external adjustment terminal 307 is hardly affected by moisture and is provided inside the external connection portion 305, so that the influence of corrosion is small. In addition, since it is inside the external connection unit 305, it does not get in the way when the thermal flow meter 300 is attached or the thermal flow meter 300 is transported.

8.7 Another Example of Temperature Detection Unit 452 of Protrusion 424 FIG. 21 shows another example relating to the temperature detection unit 452 of the protrusion 424 of the circuit package body 422 described with reference to FIGS. 11 and 15. In the embodiment shown in FIGS. 11 and 15, when the protrusion 424 is manufactured in the first resin molding process, the temperature detection unit 452 is covered with the resin used in the first resin molding process. In the heat transfer surface exposed portion 436 provided on the measurement flow path surface 430, the heat transfer surface exposed portion 436 is not covered with resin in the first resin molding step in order to improve the flow rate measurement sensitivity. I have to. Similarly, in another embodiment shown in FIG. 21, in the first resin molding step, the temperature detector 452 is molded so that the temperature detector 452 at the tip of the protrusion 424 is not covered with resin. The measurement accuracy of 452 can be improved. Since the temperature detection unit 452 is not covered with resin, a depression 454 is formed in the resin of the temperature detection unit 452 portion. In the portion of the depression 454, the temperature detecting element 518 shown in FIG. 12 can come into contact with the measurement target gas 30 in a nearly direct state, and measurement sensitivity is improved and measurement accuracy is improved. Note that the same reference numerals as those in the other drawings indicate the same configuration and have the same function and effect, and thus the description is omitted to avoid duplication of explanation.

9. Description of Use Example of Correction Data FIG. 22 illustrates an example of writing and using correction data from the external adjustment terminal 307. There are various ways of obtaining and using the correction data. The present embodiment is an example. Since the sub-passage is formed in the second resin molding step, the flow rate is actually measured by flowing a known flow rate through the sub-passage, and the correction data is calculated by an external measuring device. The correction data calculated by the step adjustment terminal 415 is written into the memory 618 shown in FIG. 17 via the external adjustment terminal 307, the external adjustment terminal inner end 367, and the adjustment terminal 415. This correction data is obtained before shipping the thermal flow meter 300, for example, and is written in the memory 618.

  Next, in actual measurement of the gas flow rate, the CPU 612 receives the measurement result of the flow rate detection unit 602 of FIG. Next, based on the measurement result of the flow rate detection unit 602, the flow rate is obtained by calculation such as search from the data stored in the memory 618 in advance. In step 23, the calculation result is temporarily stored. In step 24, the correction data written and stored in step 415 is read, and in steps 25 and 26, the flow rate obtained in step 22 is corrected based on the correction data. Due to this correction, the mass-produced thermal flow meter 300 corrects the variation and outputs a highly accurate measurement result. In step 412, the gas flow rate, which is a highly accurate measurement value corrected based on the request from the external device, is output via the measurement terminal 412.

  Since the circuit package 400 includes the inspection terminal 414 and the adjustment terminal 415 in this manner, high reliability can be maintained and high detection accuracy can be obtained.

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

300 Thermal Flowmeter 302 Housing 303 Front Cover 304 Back Cover 305 External Connection Portion 306 External Terminal 307 Correction Terminal 310 Measurement Unit 320 Terminal Connection Portion 332 Front Side Secondary Passage Groove 334 Back Side Secondary Passage Groove 356, 358 Protrusion 359 Resin 361 External terminal inner end 365 Connecting portion 372, 374 Fixed portion 400 Circuit package 412 Connection terminal 414 Terminal 422 Package body 424 Projection portion 430 Measurement flow path surface 432, 434 Fixed surface 436 Heat transfer surface exposed portion 438 Opening 452 Temperature detection portion 590 Press fit Hole 594, 596 Inclination part 601 Flow rate detection circuit 602 Flow rate detection part 604 Processing part 608 Heating element 640 Heat generation control bridge 650 Flow rate detection bridge 672 Diaphragm

Claims (17)

A flow rate measuring circuit for measuring a flow rate by performing heat transfer between a sub passage for taking in and flowing the gas to be measured flowing through the main passage and the gas to be measured flowing through the sub passage;
A case having an external terminal for housing the flow rate measurement circuit and connecting to an external device, and
The flow measurement circuit has a measurement terminal for outputting a measurement result, an inspection terminal for inspecting the flow measurement circuit, and an adjustment terminal,
The measurement terminal and the adjustment terminal protrude from the flow rate measurement circuit and are electrically connected to an external terminal and an external adjustment terminal provided on the case, respectively, and the inspection terminal is connected to the external terminal and the external terminal. A thermal flowmeter characterized in that it is electrically disconnected from the adjustment terminal. The thermal flow meter according to claim 1,
The flow measurement circuit is molded with resin to form a circuit package, and the measurement terminal, the inspection terminal, and the adjustment terminal protrude outside from the circuit package, and the measurement terminal and the adjustment terminal Are electrically connected to an external terminal and an external adjustment terminal provided in the case, respectively, and the inspection terminal is electrically disconnected from the external terminal and the external adjustment terminal. Thermal flow meter to do. The thermal flow meter according to claim 2,
The case includes a housing and a cover, and the housing includes the external terminal and a sub-passage groove for forming the sub-passage,
By covering the housing with the cover, the auxiliary passage groove is covered with the cover to form the auxiliary passage,
The measurement terminal and the adjustment terminal are electrically connected to an external terminal and an external adjustment terminal provided in the housing, respectively, and the inspection terminal is electrically connected to the external terminal and the external adjustment terminal. A thermal flow meter characterized by being cut off. In the thermal type flow meter according to claim 1 or claim 2,
An end of the case connected to an external device of the external terminal and the external adjustment terminal has a different shape between the external terminal and the external adjustment terminal. In the thermal type flow meter according to claim 3,
The circuit package is made in a first resin molding process, and the measurement terminal and the inspection terminal protrude from the circuit package,
The housing is made by a second resin molding process;
The measurement terminal and the adjustment terminal are connected to the external terminal and the external adjustment terminal, and a tip portion of the inspection terminal is included by a molded resin in which the housing is molded. Thermal flow meter. In the thermal type flow meter according to claim 3,
The circuit package is made in a first resin molding process, and the measurement terminal and the inspection terminal protrude from the circuit package,
The housing is made by a second resin molding process;
The measurement terminal and the adjustment terminal are connected to the external terminal and the external adjustment terminal, and the inspection terminal has a shorter shape than the measurement terminal and the adjustment terminal. Thermal flow meter to do. In the thermal type flow meter according to claim 3,
The thermal flow meter according to claim 1, wherein the measurement terminal, the inspection terminal, and the adjustment terminal included in the circuit package are provided on the same side of the sides constituting the circuit package. In the thermal type flow meter according to claim 3,
The circuit package has a shape having a plurality of sides in appearance.
The thermal flow meter, wherein the measurement terminal and the inspection terminal of the circuit package are provided on different sides. In the thermal type flow meter according to claim 3,
The circuit package is made in a first resin molding process, and the measurement terminal and the inspection terminal protrude from the circuit package,
The housing is made by a second resin molding process;
The housing has a gap inside,
The external terminal and the external adjustment terminal are embedded and held in a resin constituting the housing,
Each of the external terminals and the external adjustment terminal has an external terminal inner end and an external adjustment terminal inner end for connecting to the measurement terminal and the inspection terminal of the circuit package,
The external terminal inner end and the external adjustment terminal inner end of each external terminal and external adjustment terminal protrude from the resin constituting the housing into the gap inside the housing,
An end of the circuit package measurement terminal and an end of the adjustment terminal are disposed in the gap, and the external terminal inner end and the external adjustment terminal inner end projecting from the resin constituting the housing; The thermal flow meter, wherein the connection terminal and the adjustment terminal of the circuit package are connected in the gap. The thermal flow meter according to claim 5 or 6, wherein:
The measurement terminal and the adjustment terminal of the circuit package have a bent portion between the connection portion of the external terminal inner end and the external adjustment terminal inner end and the circuit package. Characteristic thermal flow meter. In the thermal type flow meter according to claim 3,
The circuit package is made in a first resin molding process, and the measurement terminal and the inspection terminal protrude from the circuit package,
The housing having the external terminals is made by a second resin molding process,
The measurement terminal and the adjustment terminal are connected to the external terminal and the external adjustment terminal,
The external terminal and the external adjustment terminal are embedded and held in a resin constituting the housing, and the measurement terminal and the adjustment terminal of the circuit package, the inner end of the external terminal of the external terminal, and the external adjustment terminal Each of the external adjustment terminal inner ends are electrically connected to form an electrical connection portion, and the external terminal inner end and the external adjustment terminal inner end and each of the electrical connection portions. Both are covered with a resin that molds the housing. A case having a sub-passage for taking in and flowing the gas to be measured flowing through the main passage and an external terminal for connection to an external device;
A circuit package molded in a first resin molding step that incorporates a flow rate measurement circuit that measures a flow rate by performing heat transfer with the gas to be measured flowing through the sub-passage,
The case includes the external terminal and the circuit package, and includes a sub-passage groove for forming the sub-passage, and a housing molded in a second resin molding process, and covers the sub-passage groove. A cover that forms a secondary passage,
The external terminal is embedded and held in the second resin constituting the housing, and the external terminal has an external terminal inner end for connecting to the circuit package,
The housing has a gap inside, the inner terminal of the external terminal protrudes from the second resin forming the housing into the gap, and the terminal of the circuit package is disposed in the gap. The thermal flow meter, wherein an inner end of the external terminal and the terminal of the circuit package are connected in the gap. The thermal flow meter according to claim 12,
In the first resin molding step, the circuit package including the flow rate measurement circuit is formed with the first resin,
The thermal flow rate characterized in that, in the second resin molding step, the housing in which the circuit package and the external terminal are held and fixed and the sub passage groove is formed is formed by the second resin. Total. The thermal flow meter according to claim 13,
In the molding of the housing in the second resin molding step, the gap is formed inside the housing, and the inner terminal of the external terminal protrudes from the resin forming the housing into the gap. The thermal flow meter according to claim 1, wherein the external terminal is held and fixed by the housing, and the circuit package is held and fixed by the housing so that the terminal of the circuit package is positioned in the gap. The thermal flow meter according to claim 14,
The housing has a flange for fixing the thermal flow meter to the main passage, and an upstream outer wall and a downstream outer wall for fixing the sub passage groove to the flange,
The gap is formed between the flange and the auxiliary passage groove,
The circuit package is held and fixed by the housing such that at least the flange side of the circuit package is positioned in the gap,
From the surface facing the flange on the side of the flange side of the circuit package, the terminal of the circuit package protrudes toward the flange,
On the other hand, the external terminal inner end of the external terminal protrudes from the flange toward the circuit package, and the external terminal inner end of the external terminal and the terminal of the circuit package are connected in the gap. A thermal flow meter characterized by that. The thermal flow meter according to claim 15,
A thermal flow meter, wherein a gap is formed between an inner side of the downstream outer wall and a side surface of the circuit package facing the inner side of the downstream outer wall. The thermal flow meter according to claim 15 or claim 16,
A thermal flow meter characterized in that a gap is formed between the inner side of the upstream outer wall and the side surface of the circuit package facing the inner side of the upstream outer wall on the flange side. .