Thermal flow meter

Abstract

Thermal flow meter, comprising: a bypass line for receiving and flowing measurement target gas (30) flowing in a main line (124); a circuit package (400) having an air flow measuring circuit for measuring an air flow by performing heat transfer with respect to the measurement target gas (30) flowing in the bypass line, and having a temperature detecting section (452) that detects a temperature of the measurement target gas (30); and a housing (302) provided with an external contact (306) which outputs an electrical signal indicating the air flow and an electrical signal indicating the temperature of the measurement target gas (30) and carries the circuit package (400), wherein the circuit package (400) is constructed such that the air flow measuring circuit and the temperature detecting section (452) are bonded in resin, and the temperature detecting section (452) has a first projection (424) projecting from a circuit package main body (422), characterized in that the first projection (424) is formed in a shape which is thicker at its root than at the leading end portion and whose neck portion gradually narrows towards the front end, wherein the circuit package main body (422) has two flat end surfaces and side surfaces formed on outer peripheries of the end surfaces and connecting the end surfaces, and is formed in a shape such that the first projection (424) projects from the side surfaces, wherein Connecting portions between the side surfaces and the first projection (424) construct the neck portion and are formed in a shape that narrows toward the leading edge between the mutually facing connecting portions.

Description

field of technology

[0001] The present invention relates to a thermal flow meter State of the art

[0002] In the case where an air flow of gas and a temperature of the gas are measured, and a measured value of the measured flow and a measured value of the temperature are used as parameters for control, a flow meter that measures the air flow of the gas and a measuring device that measures the temperature of the gas have conventionally been provided separately. For convenience, a flow meter has been devised that is provided with a function of measuring the temperature of the gas in the flow meter that measures the air flow of the gas. The above-mentioned technique is disclosed, for example, in JP 2008-209243 A. The technique is configured such that a gas temperature measuring sensor is attached to a thermal flow meter that measures the air flow of the gas and has a function of measuring an intake air amount supplied to an internal combustion engine and an intake air temperature.

[0003] Patent Application Publication No. 2 (PTL) shows a thermal-type air flow sensor comprising a semiconductor sensor element having a sensing point with a temperature sensing resistor. Furthermore, Patent Application Publication No. 2 shows a heat-generating resistor formed on a semiconductor substrate and a cavity provided on the semiconductor. A control circuit of Patent Application Publication No. 2 supplies heating current to the heat-generating resistor, and a terminal outputs the air flow rate signal to an external part.

[0004] Patent Publication No. 3 discloses an apparatus and method for manufacturing a printed circuit board and an electronic device equipped with a printed circuit board. The printed circuit board of Patent Publication No. 3 further includes an outer lead frame, an inner lead frame, and a supporting projection member.

[0005] Patent Application Publication No. 4 (PTL) shows a flow sensor structure for sealing the surface of an electrical control circuit. Patent Application Publication No. 4 (PTL) further provides a part of a semiconductor device through a manufacturing method. The flow sensor structure of Patent Application Publication No. 4 includes a semiconductor device with an air flow detection unit and a diaphragm formed thereon.

[0006] PTL 5 shows an air flow measuring device module mounted in the wall of an air duct. The PTL 5 module is electrically connected to a heating resistor and a temperature sensing resistor. Reference listPatent literature PTL 1: JP 2008-209243 A PTL 2: JP H11- 6 752 A PTL 3: US 2011 / 0 272 768 A1 PTL 4: US 2011 / 0 140 211 A1 PTL 5: DE 196 01 871 A1 Summary of the inventionTechnical problem

[0007] A device that measures parameters for control, such as a thermal flow meter and an intake air temperature sensor, desirably has high reliability. For example, in control of an internal combustion engine for a vehicle, it is desirable to respond to a request for saving the vehicle's fuel consumption and to respond to a request for exhaust gas purification, and high reliability is desired in the intake air flow measurement and the intake air temperature measurement. In the technique disclosed in PTL 1, elements that perform the respective measurements are independently arranged in the measurement target gas, and the respective elements are independently electrically connected in the measurement target gas. In the above structure, there are several objects to maintain high reliability.

[0008] An object of the present invention is to provide a thermal flow meter having high reliability and a gas temperature detecting section. Technical solution

[0009] To achieve this, a thermal flow meter according to the invention is provided, which achieves the above-mentioned objects according to the features of claim 1. The dependent claims relate to advantageous embodiments and further developments of the invention. In particular, a bypass line for introducing and flowing measurement target gas flowing in a main line, a circuit package with an air flow measurement circuit for measuring an air flow by performing heat transfer with respect to the measurement target gas flowing in the bypass line and a temperature detection section that detects a temperature of the measurement target gas, and a housing provided with an external contact that outputs an electrical signal indicative of the air flow and an electrical signal indicative of the temperature of the measurement target gas and supports the circuit package, wherein the circuit package is constructed such thatthat the air flow measuring circuit and the temperature detecting section are bonded in resin, the temperature detecting section has a projection that projects from the circuit package main body, and the projection is formed in a shape that is thicker at its root than at the leading end portion and whose neck portion gradually narrows towards the leading end., Advantageous effects of the invention

[0010] According to the present invention, it is possible to obtain the thermal flow meter having high reliability and the gas temperature detecting section. Short description of the drawings [FIG. [1] Fig. 1 is a system diagram illustrating an internal combustion engine control system using a thermal flow meter according to an embodiment of the invention. [FIG. [2] Fig. 2(A) and Fig. 2(B) are diagrams illustrating an appearance of the thermal flow meter, where Fig. 2(A) a side view from the left and Fig. 2(B) is a front view. [FIG. [3] Fig. 3(A) and Fig. 3(B) are diagrams illustrating an appearance of the thermal flow meter, where Fig. 3(A) a side view from the right and Fig. 3(B) is a rear view. [FIG. [4] Fig. 4(A) and Fig. 4(B) are diagrams illustrating an appearance of the thermal flow meter, where Fig. 4(A) a plan view and Fig. 4(B) is a bottom view. [FIG. [5] Fig. 5(A) and Fig. 5(B) are diagrams illustrating a casing of the thermal flow meter, where Fig. 5(A) a side view of the housing from the left and Fig. 5(B) is a front view of the housing. [FIG. [6] Fig. 6(A) and Fig. 6(B) are diagrams illustrating a casing of the thermal flow meter, wherein Fig. 6(A) a side view of the housing from the right and Fig. 6(B) is a rear view of the housing. [FIG. [7] Fig. 7 is a partially enlarged view illustrating a state of the flow path surface arranged in the bypass passage. [FIG. [8] Fig. 8(A) to 8(B) are diagrams illustrating an appearance of a front cover, wherein Fig. 8(A) a side view from the left, Fig. 8(A) a front view and Fig. 8(B) is a plan view. [FIG. [9] Fig. 9(A) and Fig. 9(B) are diagrams illustrating an appearance of a rear cover 304, wherein Fig. 9(A) a side view from the left, Fig. 9(B) a front view and Fig. 9(C) is a plan view. [FIG.

[10] Fig. 10 is a partially enlarged view of a contact terminal. [FIG.

[11] Fig. 11(A) and Fig. 11(B) are external views illustrating a circuit package, wherein Fig. 11(A) a side view from the left, Fig. 11(B) a front view and Fig. 11(C) is a rear view. [FIG.

[12] Fig. 12 is a diagram illustrating a state in which circuit components are mounted on a frame of the circuit package. [FIG.

[13] Fig. 13 is an explanatory diagram illustrating a diaphragm and a connecting channel connecting an opening and a gap in the diaphragm. [FIG.

[14] Fig. 14 is a diagram illustrating a state of the circuit package after a first resin molding process. [FIG.

[15] Fig. 15(A) and Fig. 15(B) are views showing the other embodiment of the Fig. 11(A) to 11(C), Fig. 15(A) is a front elevational view of the circuit package and Fig. 15(B) a rear elevational view. [FIG.

[16] Fig. 16 is a view showing a manufacturing process of the circuit package. [FIG.

[17] Fig. 17 is a view illustrating a manufacturing process of the thermal flow meter. [FIG.

[18] Fig. 18 is a view illustrating the other embodiment of the manufacturing process of the thermal flow meter. [FIG.

[19] Fig. Figure 19 is a circuit diagram showing an air flow detection circuit of the thermal flow meter. [FIG.

[20] Fig. 20 is an explanatory view describing an air flow detecting portion of the air flow detecting circuit. [FIG.

[21] Fig. 21(A) to 21(C) are the other embodiment and illustrate the shape of an external appearance of a circuit package 400, Fig. 21(A) is a side elevation view from the left, Fig. 21(B) is a front elevational view and Fig. 21(B) is a bottom elevation view. [FIG.

[22] Fig. 22(A) and Fig. 22(B) are partially enlarged views of a projection, Fig. 22(B) is a front elevational view and Fig. 22(C) is a plan view. [FIG.

[23] Fig. 23 is a view illustrating a casing of a thermal flow meter according to the other embodiment. [FIG.

[24] Fig. 24(A) to 24(C) are the other embodiment and illustrate the shape of an external appearance of the circuit package 400, Fig. 24(A) is a side elevation view from the left, Fig. 24(B) is a front elevational view and Fig. 24(C) is a rear view. Description of the embodiments

[0011] Embodiments of the invention described below (hereinafter referred to as embodiments) achieve various objects and are desired as a practical product. In particular, the embodiments achieve various objects when used in a meter for measuring an intake air amount of a vehicle and exhibit various effects. One of the various objects addressed by the following embodiments is described under the above-described "Technical Object of the Invention", and one of the various effects achieved by the following embodiments is described under "Effects of the Invention". Various objects achieved by the following embodiments and various effects achieved by the following embodiments are further described under "Description of Embodiments".Therefore, it would be apparent that the following embodiments also include other effects or objects achieved or addressed by the embodiments than those described in "Technical Problem of the Invention" or "Effects of the Invention".

[0012] In the following embodiments, like reference numerals denote like elements even if they are inserted in different drawings, and they have the same functional effects. The components described in previous sections may not be described by identifying reference numerals and symbols in the drawings.

[0013] 1. Internal combustion engine control system with a thermal flow meter according to an embodiment of the invention.

[0014] Fig. 1 is a system diagram illustrating a control system for an electric fuel injection internal combustion engine including a thermal flow meter according to an embodiment of the invention. During operation of an internal combustion engine 110 having an engine cylinder 112 and an engine piston 114, intake air as a measurement target gas 30 is drawn from an air cleaner 122 and guided into a combustion chamber of the engine cylinder 112 through a main passage 124 including, for example, an intake body, a throttle body 126, and an intake manifold 128. A flow rate of the measurement target gas 30 as intake air supplied to the combustion chamber is measured by the thermal flow meter 300 according to the invention. Fuel is supplied from a fuel injection valve 152 based on the measured flow rate and mixed with the measurement target gas 30 as intake air, so that the mixture gas is supplied to the combustion chamber.It is noted that in this embodiment, the fuel injection valve 152 is provided in an intake port of the internal combustion engine, and the fuel injected into the intake port is mixed with the measurement target gas 30 as intake air to form a mixture gas, so that the mixture gas is supplied to the combustion chamber through an intake valve 116 to generate mechanical energy by burning.

[0015] In recent years, a direct fuel injection system has been used in many vehicles with excellent results in exhaust gas purification or fuel saving, wherein a fuel injection valve 152 is used in a cylinder head of the internal combustion engine and fuel is injected from the fuel injection valve 152 directly into each combustion chamber. The thermal flow meter 300 can also be used in an engine type in which the fuel is injected directly into each combustion chamber, as well as in an engine type in which the fuel is injected into the intake port of the internal combustion engine from Fig. 1. A method for measuring control parameters, including a method for deploying the thermal flow meter 300, and a method for controlling the internal combustion engine, including a fuel supply amount or ignition timing, are substantially similar when compared between the two types. A representative example of both types, a type in which fuel is injected into the intake port, is shown in Fig. 1 illustrates.

[0016] The fuel and air supplied into the combustion chamber are in a fuel-air mixture state and are explosively combusted by spark ignition from the spark plug 154 to generate mechanical energy. After combustion, the gas is guided into an exhaust pipe through the exhaust valve 118 and discharged from the exhaust pipe as exhaust gas 24 to the outside of the vehicle. The flow rate of the measurement target gas 30 as intake air supplied to the combustion chamber is controlled by the throttle valve 132, the opening degree of which changes in response to the operation of the accelerator pedal. The fuel supply amount is controlled based on the flow rate of intake air supplied to the combustion chamber, and a driver controls an opening degree of the throttle valve 132, so that the flow rate of intake air supplied to the combustion chamber is controlled. As a result, it is possible to control the mechanical energy generated by the internal combustion engine. 1.1 Overview of the control of the combustion engine control system

[0017] The flow rate and temperature of the measurement target gas 30 as intake air obtained from the air cleaner 122 and flowing through the main line 124 are measured by the thermal flow meter 300, and an electrical signal representing the flow rate and temperature of the intake air is input from the thermal flow meter 300 to the control unit 200. Furthermore, an output of the throttle angle sensor 144, which measures an opening degree of the throttle valve 132, is input to the control unit 200, and an output of a rotation angle sensor 146 is input to the control unit 200 to measure a position or state of the engine piston 114, the intake valve 116, or the exhaust valve 118 of the internal combustion engine, and a rotational speed of the internal combustion engine. In order to measure a mixture ratio state between the amount of fuel and the amount of air from the state of the exhaust gas 24, an output of an oxygen sensor 148 is fed into the control unit 200.

[0018] The control unit 200 calculates a fuel injection amount or ignition timing based on an intake air flow rate as the output of the thermal flow meter 300 and an engine speed measured at the output of the rotation angle sensor 146. Based on their calculation results, a fuel amount supplied to the fuel injection valve 152 and an ignition timing for igniting the spark plug 154 are controlled. In practice, the fuel supply amount or ignition timing is further precisely controlled based on a change in the intake temperature or throttle angle, each measured by the thermal flow meter 300, a change in the engine speed, or an air-fuel ratio state measured by the oxygen sensor 148.In the idle state of the internal combustion engine, the control unit 200 further regulates the amount of air that is passed past the throttle valve 132 with an idle control valve 156 and regulates a speed of the internal combustion engine in the idle state. 1.2 Improvement of the measurement accuracy of the thermal flow meter with temperature detection function for the inlet air and installation environment

[0019] A fuel supply amount and ignition timing, which correspond to the main control variables of the internal combustion engine, are both calculated using the output of the thermal flow meter 300 as the main parameter. Furthermore, calibration of the control parameter is performed based on the intake air temperature when necessary. Improving measurement accuracy, suppressing deterioration with age, and improving reliability in the thermal flow meter 300 are important for improving vehicle control accuracy and ensuring reliability. In particular, in recent years, the demand for saving vehicle fuel consumption has become very strong, and the demand for exhaust gas purification has also become very strong.To meet these requirements, it is extremely important to improve the measurement accuracy of the air flow of the measurement target gas 30, which is the intake air measured by the thermal flow meter 300. It is also important that the thermal flow meter 300 maintains high reliability.

[0020] A vehicle incorporating the thermal flow meter 300 is used in an environment where temperature changes are significant or where severe weather such as storms or snow is present. When a vehicle travels on a snowy road, it travels over a road surface on which antifreeze has been sprayed. Preferably, the thermal flow meter 300 is designed taking into account a countermeasure for temperature changes or a countermeasure against dust and contaminants in such an environment. Furthermore, the thermal flow meter 300 is installed in an environment where the internal combustion engine is subject to vibration. It is also desirable to maintain high reliability against vibration.

[0021] The thermal flow meter 300 is installed in the intake pipe, which is exposed to heat from the internal combustion engine. Therefore, the heat generated by the internal combustion engine is conducted to the thermal flow meter 300 via the intake pipe, which is a main pipe 124. Since the thermal flow meter 300 measures the flow rate of the target gas by transferring heat from the target gas, it is important to minimize the influence of external heat.

[0022] The vehicle-mounted thermal flow meter 300 achieves the objects described in "Technical Object of the Invention" and provides the effects described below in "Effects of the Invention." Furthermore, it achieves various objects required as a product, as described below, and provides various effects with respect to various objects described above. Specific objects or effects achieved or provided by the thermal flow meter 300 are described in the following description of embodiments. 2. Structure of the thermal flow meter 3002.1 Structure of the external appearance of the thermal flow meter 300

[0023] Fig. 2(A), Fig. 2(B), Fig. 3(A), Fig. 3(B), Fig. 4 (A) and Fig. 4 (B) are views illustrating an external appearance of the thermal flow meter 300, Fig. 2(A) is a left elevational side view of the thermal flow meter 300, Fig. 2(B) is a front elevation view, Fig. 3(A) is a right elevational side view, Fig. 3(B) a rear elevation view, Fig. 4(A) a plan view and Fig. 4 (B) is a bottom elevation view. The thermal flow meter 300 includes a housing 301, and the housing 301 is provided with a case 302, a front cover 303, and a rear cover 304. The housing 302 is provided with a flange 312 for attaching the thermal flow meter 300 to an inlet body, which is the main line 124, an external terminal 305 with an external contact 306 for electrically connecting to an external device, and a measuring section 310 for measuring the air flow. An inner section of the measuring section 310 is provided with a bypass line groove for forming a bypass line, and the inner section of the measuring section 310 is further provided with a circuit package 400 with an air flow detection section 602 (see Fig. 19) for measuring an air flow of the measurement target gas 30 flowing in the main line 124 and a temperature detecting section 452 for measuring a temperature of the measurement target gas 30 flowing in the main line 124. 2.2 Effects based on the external structure of the thermal flow meter 300

[0024] Since the inlet port 350 of the thermal flow meter 300 is provided on the leading end side of the measuring section 310 extending toward the center of the main pipe 124 from the flange 312, the gas located near the center portion away from the inner wall surface can be introduced into the bypass pipe instead of near the inner wall surface of the main pipe 124. For this reason, the thermal flow meter 300 can measure a flow rate or a temperature of the air that is distant from the inner wall surface of the main pipe 124 of the thermal flow meter 300, making it possible to suppress a decrease in measurement accuracy caused by heat influence and the like.Near the inner wall surface of the main pipe 124, the thermal flow meter 300 is easily affected by the temperature of the main pipe 124, so the temperature of the measurement target gas 30 is subject to a condition different from the original temperature of the gas and has a state different from the average state of the main gas in the main pipe 124. In particular, when the main pipe 124 functions as an intake body of the engine, it may be affected by heat from the engine and remain at a high temperature. For this reason, the gas near the inner wall surface of the main pipe 124 often has a higher temperature than the original temperature of the main pipe 124, thus deteriorating the measurement accuracy.

[0025] Near the inner wall surface of the main line 124, a fluid resistance increases and a flow rate decreases compared to an average flow rate in the main line 124. For this reason, when the gas as the measurement target gas 30 is introduced into the bypass line near the inner wall surface of the main line 124, a decrease in the flow rate compared to the average flow rate in the main line 124 may generate a measurement error. In the thermal flow meter 300 illustrated in Fig. 2(A), 2(B), 3(A), 3(B), and 4(A) to 4(C), since the inlet channel 350 is provided in the leading end of the thin and long measuring section 310 extending from the flange 312 to the center of the main pipe 124, it is possible to reduce a measurement error associated with a decrease in the flow rate near the inner wall surface. In the thermal flow meter 300 illustrated in Fig. 2(A), 2(B), 3(A), 3(B), and 4(A) to 4(C), in addition to the inlet port 350 provided at the leading end of the measuring section 310 extending from the flange 312 to the center of the main channel, an outlet port of the bypass line is provided in the leading end of the measuring section 310. Therefore, it is possible to further reduce the measurement error.

[0026] The measuring section 310 of the thermal flow meter 300 has a shape extending from the flange 312 toward the center of the main line 124, and its leading end is provided with the inlet port 350 for introducing a part of the measurement target gas 30, for example, inlet air to the bypass line, and the outlet port 352 for returning the measurement target gas 30 from the bypass line to the main line 124. While the measuring section 310 has a shape extending along an axis extending from the outer wall of the main line 124 toward the center, its width is narrower, as shown in Fig. 2(A) and Fig. 3(A). That is, the measuring section 310 of the thermal flow meter 300 has a front surface with an approximately rectangular shape and a side surface with a thin width. As a result, the thermal flow meter 300 can have a bypass line of sufficient length, and it is possible to suppress fluid resistance for measuring the measurement target gas 30 to a small value. For this reason, with the thermal flow meter 300, it is possible to suppress the flow resistance to a small value and measure the flow rate of the measurement target gas 30 with high accuracy. 2.3 Structure and effects of the upstream surface and the downstream surface of the measuring section 310

[0027] An upstream protrusion 317 and a downstream protrusion 318 are provided on the upstream surface and the downstream surface of the measuring section 310 in the thermal flow meter 300, respectively. The upstream protrusion 317 and the downstream protrusion 318 have a shape that tapers along the leading end toward the base, making it possible to reduce fluid resistance of the measurement target gas 30 as inlet air through the main pipe 124. The upstream protrusion 317 is provided between the heat insulator 315 and the inlet port 343. The upstream protrusion 317 has a large cross-sectional area and absorbs a large amount of heat transferred from the flange 312 or the heat insulator 315.However, the upstream protrusion 317 is notched near the inlet port 343, and a length of the temperature sensing portion 452 of the upstream protrusion 317 increases due to the hollow space of the upstream outer wall of the housing 302, as described below. For this reason, heat conduction from the thermal insulator 315 to the support portion of the temperature sensing portion 452 is suppressed.

[0028] Furthermore, a later-mentioned contact terminal 320 and a gap with the contact terminal 320 are formed between the flange 312 or the thermal insulator 315 and the temperature detecting portion 452. As a result, a distance between the flange 312 or the thermal insulator 315 and the temperature detecting portion 452 is long, a front cover 303 and a rear cover 304 are provided in the long part, and the part functions as a cooling surface. Therefore, it is possible to reduce the influence that the temperature of the wall surface of the main pipe 124 exerts on the temperature detecting portion 452. Furthermore, since the distance between the flange 312 or the thermal insulator 315 and the temperature detecting portion 452 is long, it is possible to shift the inlet portion of the measurement target gas 30 supplied to the bypass pipe near the center of the main pipe 124.It is possible to prevent the measurement accuracy from being reduced around the wall surface of the main pipe 124.

[0029] As in Fig. 2(B) or Fig. As illustrated in Fig. 3(B), both side surfaces of the measuring portion 310 inserted into the main pipe 124 have a very narrow shape, and a leading end of the downstream protrusion 318 or the upstream protrusion 317 has a narrow shape compared to the base, where the air resistance is smaller. For this reason, it is possible to suppress an increase in flow resistance caused by inserting the thermal flow meter 300 into the main pipe 124. Further, at the portion where the downstream protrusion 318 or the upstream protrusion 317 is provided, the upstream protrusion 317 or the downstream protrusion 318 protrudes toward both sides with respect to both side portions of the front cover 303 or the rear cover 304.Since the upstream protrusion 317 or the downstream protrusion 318 is formed from a resin molding, it is easy to mold them in a shape with negligible air resistance. Meanwhile, the front cover 303 or the rear cover 304 is designed to have a wide cooling surface. For this reason, the thermal flow meter 300 has reduced air resistance and can be easily cooled by the measurement target air flowing through the main pipe 124. 2.4 Structure and effects of the flange 312

[0030] The flange 312 is provided with a plurality of concave portions 314 on its underside, which is a part facing the main line 124, to reduce a heat transfer surface to the main line 124 and make it difficult for the thermal flow meter 300 to be affected by heat. The screw hole 313 of the flange 312 is provided for fixing the thermal flow meter 300 to the main line 124, and a space is formed between a surface around each screw hole facing the main line 124 and the main line 124, so that the surface around the screw hole 313 facing the main line 124 is recessed from the main line 124. As a result, the flange 312 has a structure capable of reducing heat transfer from the main line 124 to the thermal flow meter 300 and preventing deterioration in measurement accuracy caused by heat.Furthermore, in addition to the effect of reducing heat transfer, the cavity 314 can reduce the influence of shrinkage of the resin of the flange 312 during molding of the housing 302.

[0031] The thermal insulation 315 is provided on the measuring section 310 side of the flange 312. The measuring section 310 of the thermal flow meter 300 is inserted into the interior of the main pipe 124 via an installation hole, so that the thermal insulation 315 faces the inner surface of the installation hole of the main pipe 124. The main pipe 124 serves as an inlet body, for example, and is often kept at a high temperature. On the other hand, it is understood that the main pipe 124 is kept at a particularly low temperature when operating in a cold region. If such a high or low temperature condition of the main pipe 124 affects the temperature detection section 452 or the flow rate measurement described below, the measurement accuracy deteriorates.For this reason, a plurality of cavities 316 are provided side by side in the thermal insulation 315 adjacent to the inner surface of the opening of the main pipe 124, and a width of the thermal insulation 315 adjacent to the inner surface of the opening between the adjacent cavities 316 is particularly thin, which is equal to or less than 1 / 3 of the width of the fluid flow direction of the cavity 316. As a result, it is possible to reduce the influence of temperature. In addition, a part of the thermal insulation 315 is thickened. During resin molding of the housing 302, when the resin is cooled from a high temperature to a low temperature and solidifies, volume shrinkage occurs, so deformation is generated when stress occurs. By forming the cavity 316 in the thermal insulation 315, it is possible to make the volume shrinkage more uniform and reduce stress concentration.

[0032] The measuring section 310 of the thermal flow meter 300 is inserted inward from an installation hole in the main line 124 and fastened to the main line 124 with screws using the flange 312 of the thermal flow meter 300. The thermal flow meter 300 is preferably attached to the installation hole in the main line 124 with a predetermined positional relationship. The recess 314 in the flange 312 can be used to determine a positional relationship between the main line 124 and the thermal flow meter 300. By forming the convex part in the main line 124, it is possible to provide an insertion relationship between the convex part and the recess 314 and to fix the thermal flow meter 300 in a precise position on the main line 124. 2.5 Structure and effects of the external connection 305 and the flange 312

[0033] Fig. 4 (A) is a plan view illustrating the thermal flow meter 300. Four external contacts 306 and one calibration contact 307 are provided in the external terminal 305. The external contacts 306 include contacts for outputting the flow rate and temperature as the measurement result of the thermal flow meter 300, and a power terminal for supplying DC power for operating the thermal flow meter 300. The calibration contact 307 is used to measure the manufactured thermal flow meter 300, obtain a calibration value for each thermal flow meter 300, and store the calibration value in an internal memory of the thermal flow meter 300. In the subsequent measurement operation of the thermal flow meter 300, the calibration data representing the calibration value stored in the memory is used, and the calibration contact 307 is not used.Therefore, in order to prevent the calibration contact 307 from interfering with the connection of other external devices to the external contacts 306, the calibration contact 307 has a different shape than the external contact 306. In this embodiment, since the calibration contact 307 is shorter than the external contact 306, the calibration contact 307 does not interfere with the connection even when the terminal contact connected to the external contact 306 for connecting external devices is inserted into the external terminal 305. Furthermore, since a plurality of concaves 308 are provided along the external contact 306 in the external terminal 305, the concaves 308 reduce stress concentration caused by shrinkage of the resin when the resin as the material of the flange 312 is cooled and solidified.

[0034] Since the calibration contact 307 is provided in addition to the external contact 306 used in the measurement operation of the thermal flow meter 300, it is possible to measure characteristics of each thermal flow meter 300 before shipment to obtain a fluctuation in the product and store a calibration value for reducing the fluctuation in the internal memory of the thermal flow meter 300. The calibration contact 307 is formed in a shape different from that of the external contact 306 to prevent the calibration contact 307 from interfering with the connection between the external contact 306 and external devices after the calibration value is set. In this way, when using the thermal flow meter 300, it is possible to reduce fluctuation in each thermal flow meter 300 before shipment and improve measurement accuracy. 3. Overall structure of the housing 302 and its effects 3.1 Structure and effects of the bypass line and the air flow detection section

[0035] Fig. 5(A), Fig. 5(B), Fig. 6(A) and Fig. 6(B) illustrates a state of the housing 302 when the front and rear covers 303 and 304 are removed from the thermal flow meter 300. Fig. 5(A) is a left side view illustrating the housing 302, Fig. 5(B) is a front view illustrating the housing 302, Fig. 6(A) is a right side view illustrating the housing 302, and Fig. 6(B) is a rear view illustrating the housing 302. In the housing 302, the measuring section 310 extends from the flange 312 toward the center of the main line 124, and a bypass line groove for forming the bypass line is provided on its leading end side. In this embodiment, the bypass line groove is provided on both the front and rear sides of the housing 302. Fig. 5(B) illustrates a bypass line groove at the front 332, and Fig. 6(B) illustrates a bypass passage groove at the rear side 334. Since an inlet groove 351 for forming the bypass passage intake port 350 and an outlet groove 353 for forming the outlet port 352 are provided at the leading end of the housing 302, the gas distant from the inner wall surface of the main passage 124, that is, the gas flow passing through the main passage 124 near the center, can be taken out from the intake port 350 as the measurement target gas 30. The gas flowing through the main passage 124 near the inner wall surface is affected by the temperature of the wall surface of the main passage 124 and has a different temperature than the average temperature of the gas flowing through the main passage 124, such as the intake air, which is the measurement target gas 30 in many cases.In addition, the gas flowing near the inner wall surface of the main pipe 124 often has a lower flow rate than the average flow rate of the gas flowing through the main pipe 124. Since the thermal flow meter 300 according to the embodiment is resistant to such influences, it is possible to suppress a reduction in measurement accuracy.

[0036] The bypass passage formed by the above-described front-side bypass passage groove 332 or the rear-side bypass passage groove 334 is connected to the thermal insulator 315 through the hollowed outer wall portion 366, the upstream outer wall 335, or the downstream outer wall 336. Furthermore, the upstream outer wall 335 is provided with the upstream protrusion 317, and the downstream outer wall 336 is provided with the downstream protrusion 318. With this structure, since the thermal flow meter 300 is fixed to the main line 124 using the flange 312, the measuring section 310 with the circuit package 400 is fixed to the main line 124 with high reliability.

[0037] In this embodiment, the housing 302 is provided with the bypass passage groove for forming the bypass passage, and the covers are attached to the front and rear sides of the housing 302, so that the bypass passage is formed by the bypass passage groove and the covers. With this structure, it is possible to form entire bypass passage grooves as part of the housing 302 during the resin molding process of the housing 302. Since the molds are provided in both surfaces of the housing 302 during the molding of the housing 302, it is possible to form both the bypass passage groove on the front side 332 and the bypass passage groove on the rear side 334 as part of the housing 302 by using the molds for both surfaces. Since the front and rear covers 303 and 304 are provided in both surfaces of the housing 302, it is possible to obtain the bypass lines in both surfaces of the housing 302.Since the front bypass line groove 332 and the rear bypass line groove 334 are formed on both surfaces of the casing 302 by means of molds, it is possible to form the bypass line with high accuracy and achieve high productivity.

[0038] A portion of the target gas 30, which is in the main line 124 in Fig. 6(B) is taken into the bypass passage groove at the rear side 334 by 351, which forms an inlet opening 350, and flows in the bypass passage groove at the rear side 334. The bypass passage groove at the rear side 334 is formed in a shape that is deeper toward the front, and the measurement target gas 30 gradually moves toward the front while flowing along the groove. Specifically, the bypass passage groove at the rear side 334 is provided with a steep slope portion 347 that rapidly deepens from the hole 342, and a portion of the air with a smaller mass moves along the steep slope portion 347 and flows from the hole 342 to the measurement surface 430, which is in Fig. 5(B). On the other hand, since foreign matter with a large mass is difficult to change course quickly, the foreign matter moves to the rear of the Fig. 6(B). After that, the foreign matter flows through the hole 341 and flows to the Fig. 5(B) described measuring surface 430.

[0039] In the bypass line channel at the front 332 from Fig. 5(B), the air as the measurement target gas 30, which moves from the hole 342 to the bypass passage groove on the front side 332, flows along the measurement surface 430, and with the air flow detection portion 602, heat transfer is performed to measure a flow rate by means of an exposed portion of the heat transfer surface 436 provided in the measurement surface 430. Both the measurement target gas 30 flowing through the measurement surface 430 and the air flowing from the hole 341 to the bypass passage groove on the front side 332 flow along the bypass passage groove on the front side 332 and are discharged from the exhaust groove 353, which forms the exhaust channel 352 to the main line 124.

[0040] A substance with a heavy mass, such as an impurity mixed into a measurement target gas 30, has a high inertial force and has difficulty making its way to the deep side of the groove along the surface of the steep slope part 347 of Fig. 6(B) where a depth of the groove deepens steeply. For this reason, since a foreign matter with heavy mass flows through the back side of the measuring surface 431, it is possible to prevent a foreign matter from flowing near the exposed portion of the heat transfer surface 436. In this embodiment, since most foreign matters with heavy mass, other than the gas, flow through the back side of the measuring surface 431, which is a rear surface of the measuring surface 430, it is possible to suppress the influence of contamination caused by a foreign matter such as an oil component, carbon, or a contaminant and deterioration of measurement accuracy. That is, since the path of the measurement target gas 30 changes steeply along an axis transverse to the flow axis of the main pipe 124, it is possible to reduce the influence of a foreign matter mixed with the measurement target gas 30.

[0041] In this embodiment, the flow path including the bypass passage groove at the rear side 334 is directed from the leading end of the housing 302 toward the flange along a curved line, and the gas flowing through the bypass passage on the side closest to the flange flows inversely to the flow of the main passage 124, so that the bypass passage at the rear side, as one side of this reverse flow, is connected to the bypass passage formed at the front side as the other side. As a result, it is possible to easily attach the exposed portion of the heat transfer surface 436 of the circuit package 400 to the bypass passage and easily sample the measurement target gas 30 from a location close to the center of the main passage 124.

[0042] In this embodiment, a hole 342 and a hole 341 passing through the rear bypass passage groove 334 and the front bypass passage groove 332 are provided at the front and rear sides of the flow direction of the measurement surface 430 for measuring the air flow. The bypass passage is formed in a shape such that the measurement target gas 30 moves from the rear bypass passage groove 334 formed in one surface of the housing 302 and provided with the through holes 342 and 341 to the front bypass passage groove 332 formed in the other surface of the housing 302. As a result, it is possible to form the bypass passage groove in both surfaces of the housing 302 by resin molding, and it is possible to additionally form a structure connecting both surfaces.

[0043] Since the hole 342 and the hole 341 are provided on both sides of the measuring surface 430 formed in the circuit package 400, it is possible to prevent the resin from flowing into the exposed portion of the heat transfer surface 436 formed in the measuring surface 430 by using a mold that forms the hole 342 and the hole 341 therein. Furthermore, in the case where the circuit package 400 is fixed to the housing 302 during resin molding by utilizing the formation of the hole 342 and the hole 341 on an upstream side and a downstream side of the measuring surface 430, it is possible to arrange the mold based on the holes and position and fix the circuit package 400 to the mold.

[0044] In this embodiment, two holes 342 and 341 are provided as the holes passing through the rear bypass passage groove 334 and the front bypass passage groove 332. However, it is possible to form the bypass passage shape connecting the rear bypass passage groove 334 and the front bypass passage groove 332 in a resin molding process through an arbitrary hole without providing two holes formed by the hole 342 and the hole 341.

[0045] A rear bypass passage inner wall 391 and a rear bypass passage outer wall 392 are provided on both sides of the rear bypass passage groove 334, and the inner surface of the rear cover 304 abuts the leading end portions of the height direction of each of the rear bypass passage inner wall 391 and the rear bypass passage outer wall 392, so that the rear bypass passage is formed in the case 302.In addition, a front bypass passage inner wall 393 and a front bypass passage outer wall 394 are provided on both sides of the front bypass passage groove 332, and the inner surface of the rear cover 304 abuts the leading end portions of the height direction of the front bypass passage inner wall 393 and the front bypass passage outer wall 394, so that the front bypass passage is formed in the housing 302.

[0046] In this embodiment, the measurement target gas 30 flows dividedly through the measurement surface 430 and its rear surface, and the exposed portion of the heat transfer surface 436 for measuring the flow rate is provided in one of them. However, the measurement target gas 30 may flow only through the front surface of the measurement surface 430, instead of dividing the measurement target gas 30 into two lines. By curving the bypass line to follow a second axis transverse to a first axis of the flow direction of the main line 124, it is possible to collect a foreign matter mixed in the measurement target gas 30 on the side where the curvature of the second axis is insignificant. By providing the measurement surface 430 and the exposed portion of the heat transfer surface 436 on the side where the curvature of the second axis is significant, it is possible to reduce the influence of a foreign matter.

[0047] In this embodiment, the measuring surface 430 and the exposed portion of the heat transfer surface 436 are provided in a connecting part between the front-side bypass passage groove 332 and the rear-side bypass passage groove 334. However, the measuring surface 430 and the exposed portion of the heat transfer surface 436 may be provided in the front-side bypass passage groove 332 or the rear-side bypass passage groove 334 instead of the connecting part between the front-side bypass passage groove 332 and the rear-side bypass passage groove 334.

[0048] An orifice structure is formed in a part of the exposed portion of the heat transfer surface 436 provided in the measuring surface 430 to measure a flow rate, so that the flow rate increases due to the orifice effect and measurement accuracy is improved. In addition, even if a vortex is generated in a gas flow on the upstream side of the exposed portion of the heat transfer surface 436, it is possible to eliminate or reduce the vortex by means of the orifice and improve measurement accuracy.

[0049] On Fig. 5(A), Fig. 5(B), Fig. 6(A) and Fig. Referring to FIG. 6(B), a hollowed outer wall portion 366 is provided in which the upstream outer wall 335 has a hollow shape hollowed toward the downstream side in a neck portion of the temperature detecting portion 452. Due to this hollowed outer wall portion 366, a distance between the temperature detecting portion 452 and the hollowed outer wall portion 366 increases, so it is possible to reduce the influence of heat transmitted via the upstream outer wall 335.

[0050] Although the circuit package 400 is wrapped by the fastening portion 372 for fixing the circuit package 400, it is possible to increase a fastening force for the circuit package 400 by further fixing the circuit package 400 using the hollowed outer wall portion 366. The fastening portion 372 wraps the circuit package 400 along a flow axis of the measurement target gas 30. Meanwhile, the hollowed outer wall portion 366 wraps the circuit package 400 across the flow axis of the measurement target gas 30. That is, the circuit package 400 is wrapped so that the wrapping direction is different from the fastening portion 372. Since the circuit package 400 is wrapped along the two different directions, the fastening force is increased.Although the hollowed outer wall portion 366 is part of the upstream outer wall 335, the circuit package 400 may be wrapped in a direction different from that of the fastening portion 372 by using the downstream outer wall 336 instead of the upstream outer wall 335 to increase the fastening force. For example, a plate portion of the circuit package 400 may be wrapped by the downstream outer wall 336, or the circuit package 400 may be wrapped by means of a hollow hollowed in the upstream direction or a protrusion projecting in the upstream direction provided in the downstream outer wall 336.Since the hollowed outer wall portion 366 is provided in the upstream outer wall 335 to enclose the circuit package 400, it is possible to provide an effect of increasing a thermal resistance between the temperature detecting portion 452 and the upstream outer wall 335 in addition to fixing the circuit package 400.

[0051] Since the hollowed outer wall portion 366 is provided in a neck portion of the temperature sensing portion 452, it is possible to reduce the influence of heat transmitted from the flange 312 or the heat insulator 315 through the upstream outer wall 335. Furthermore, a temperature sensing cavity 368 is provided, formed by a notch, between the upstream protrusion 317 and the temperature sensing portion 452. By means of the temperature sensing cavity 368, it is possible to reduce heat transmission to the temperature sensing portion 452 through the upstream protrusion 317. As a result, it is possible to improve the detection accuracy of the temperature sensing portion 452.In particular, since the upstream protrusion 317 has a large cross section, it easily transfers heat, and a functionality of the temperature measuring cavity 368 that suppresses heat transfer becomes important. 3.2 Structure and effects of the air flow detection section of the bypass line

[0052] Fig. 7(A) and Fig. 7(B) are partially enlarged views showing a state in which the flow path 430 of the circuit package 400 is arranged inside the bypass line groove, as a sectional view taken along the line AA of Fig. 6(A) and Fig. 6(B). It should be noted that Fig. 7(A) and Fig. 7(B) shows a conceptual diagram with omissions and simplifications, compared to the specific configuration of Fig. 5(A), Fig. 5(B), Fig. 6(A) and Fig. 6(B), and details may be slightly different. The left side of Fig. 7(A) and Fig. 7(B) is a terminal end portion of the bypass line groove at the rear side 334, and the right side is a starting end portion of the bypass line groove at the front side 332. Even if in Fig. 7(A) and Fig. 7(B) is not clearly illustrated, the hole 342 and the hole 341 are provided in both the left and right sides of the circuit package 400 having the measurement surface 430, and the rear side bypass line groove 334 and the front side bypass line groove 332 are connected to the left and right sides of the circuit package 400 having the measurement surface 430.

[0053] The measurement target gas 30, which is taken in from the inlet port 350 and flows through the rear bypass line including the rear bypass line groove 334, is supplied from the left side Fig. 7(A) and Fig. 7(B). Part of the measurement target gas 30 flows through the hole 342 into a flow path 386 including the front side of the measurement surface 430 of the circuit package 400 and the protrusion 356 provided in the front cover 303. The other measurement target gas 30 flows into a flow path 387 formed by the back side of the measurement surface 431 and the back cover 304. Then, the measurement target gas 30 flowing through the flow path 387 moves through the hole 341 to the bypass passage groove at the front side 332 and is combined with the measurement target gas 30 flowing through the flow path 386, so that it flows through the bypass passage groove at the front side 332 and is discharged from the exhaust port 352 into the main passage 124. It is noted that in the flow path 387, the projection 358 provided in the rear cover 304 projects toward the back of the measuring surface 431.

[0054] Since the bypass duct groove is designed such that the flow path of the measurement target gas 30, which is guided through the hole 342 from the bypass duct groove on the rear side 334 to the flow path 386, has a wider curvature than the flow path leading to the flow path 387, a substance with a heavy mass, such as an impurity contained in the measurement target gas 30, is collected in the less curved flow path 387. For this reason, there is almost no foreign matter flow in the flow path 386.

[0055] The flow path 386 is structured to form an opening such that the front cover 303 is provided sequentially for the leading front end portion of the bypass passage groove at the front side 332, and the protrusion 356 slightly protrudes to the side of the measurement surface 430. The measurement surface 430 is arranged on one side of the opening portion of the flow path 386 and is provided with the exposed portion of the heat transfer surface 436 to perform heat transfer between the air flow detection portion 602 and the measurement target gas 30. In order to perform the measurement through the air flow detection portion 602 with high accuracy, the measurement target gas 30 preferably flows laminarly with little swirl in the exposed portion of the heat transfer surface 436. With the faster flow rate, the measurement accuracy is further improved.For this reason, the opening is designed such that the protrusion 356 provided in the front cover 303 facing the measuring surface 430 protrudes slightly toward the measuring surface 430. This opening reduces turbulence in the measurement target gas 30 to make the flow more laminar. Since the flow rate increases in the opening portion and the exposed portion of the heat transfer surface 436 for measuring the flow rate is arranged in the opening portion, the measurement accuracy of the flow rate is improved.

[0056] Since the opening is formed such that the projection 356 protrudes toward the inside of the bypass passage groove to face the exposed portion of the heat transfer surface 436 provided in the flow path 430, it is possible to improve the measurement accuracy. The projection 356 for forming the opening is provided on the cover facing the exposed portion of the heat transfer surface 436 provided in the flow path 430. Fig. 7(A) and Fig. 7(B), the exposed portion of the heat transfer surface 436 is provided in the front cover 303 because the cover facing the exposed portion of the heat transfer surface 436 provided in the flow path 430 is the front cover 303. Alternatively, the exposed portion of the heat transfer surface 436 may also be provided in the cover facing the exposed portion of the heat transfer surface 436 provided in the flow path 430 of the front or rear cover 303 or 304. Depending on which of the surfaces of the flow path 430 and the exposed portion of the heat transfer surface 436 are provided in the circuit package 400, the cover facing the exposed portion of the heat transfer surface 436 is changed.

[0057] A distribution of the measurement target gas 30 between the flow paths 386 and 387 also relates to the high-accuracy measurement. A distribution of the measurement target gas 30 between the flow paths 386 and 387 is adjusted by causing the protrusion 358 provided in the rear cover 304 to protrude into the flow path 387. In addition, since the opening portion is provided in the flow part 387, it is possible to increase the flow rate and guide a foreign matter such as a contaminant to the flow path 387. In the embodiment, the opening formed by the protrusion 358 serves as one of means for adjusting between the flow paths 386 and 387. Alternatively, the above-mentioned distribution of the flow rate between the flow paths 386 and 387 can be adjusted by adjusting a width between the back of the measurement surface 431 and the rear cover 304 and the like.In this case, the projection 358 provided in the rear cover 304 is not necessary.

[0058] On Fig. 5(A), Fig. 5(B), Fig. 6(A) and Fig. Referring to FIG. 6(B), a press mark 442 of the mold used in the resin molding process for the circuit package 400 remains on the back of the measurement surface 431 as the rear surface of the exposed portion of the heat transfer surface 436 provided in the measurement surface 430. The press mark 442 does not particularly hinder the measurement of the flow rate and is not problematic even if the press mark 442 remains. Furthermore, as described below, it is important to protect a semiconductor diaphragm of the air flow sensing portion 602 when the circuit package 400 is formed by resin molding. For this reason, pressing the rear surface of the exposed portion of the heat transfer surface 436 is important. It is also important to prevent resin covering the circuit package 400 from flowing into the exposed portion of the heat transfer surface 436.From this perspective, resin inflow is suppressed by encasing the sensing surface 430 including the exposed portion of the heat transfer surface 436 using one mold and pressing the rear surface of the exposed portion of the heat transfer surface 436 using another mold. Since the circuit package 400 is manufactured by transfer molding, resin pressure is high, and pressing from the rear surface of the exposed portion of the heat transfer surface 436 is important. In addition, since a semiconductor diaphragm is used in the airflow sensing section 602, a vent duct is preferably formed for a gap created by the semiconductor diaphragm. In order to hold and fix a plate and the like for forming the vent duct, pressing from the rear surface of the exposed portion of the heat transfer surface 436 is important. 3.3 Forms and effects of the front and rear covers 303 and 304

[0059] Fig. 8(A) to 8(C) are diagrams illustrating an appearance of the front cover 303, wherein Fig. 8(A) a side view from the left, Fig. 8(B) a front view and Fig. 8(C) is a plan view. Fig. 9(A) and Fig. 9(B) are diagrams illustrating an appearance of the rear cover 304, wherein Fig. 9(A) a side view from the left, Fig. 9(B) a front view and Fig. 9(C) is a plan view. In Fig. 8(A), Fig. 8(B), Fig. 8(C), Fig. 9(A), Fig. 9(B) and Fig. 9(C), the front or rear cover 303 or 304 serves to form the bypass passage by covering the bypass passage groove of the housing 302. Furthermore, the front or rear cover 303 or 304 serves to form an opening in conjunction with the projection 356. For this reason, it is preferable to increase the molding accuracy. Since the front or rear cover 303 or 304 is manufactured by a resin molding process by injecting a thermoplastic resin into a mold, it is possible to mold the front or rear cover 303 or 304 with high molding accuracy.

[0060] The front protective portion 322 or the rear protective portion 325 is formed in the front or rear cover 303 or 304, respectively, which in Fig. 8(A) to 8(C) and 9(A) to 9(C) respectively. As shown in FIG. Fig. 2(A), Fig. 2(B), Fig. 3(A) or Fig. As illustrated in Fig. 3(B), the front protecting portion 322 provided on the front cover 303 is disposed at the front side of the intake port 343, and the rear protecting portion 325 provided on the rear cover 304 is disposed at the rear side of the intake port 343. The temperature detecting portion 452 disposed inside the intake port 343 is protected by the front protecting portion 322 and the rear protecting portion 325, so it is possible to prevent mechanical damage to the temperature detecting portion 452 caused when the temperature detecting portion 452 collides with something during manufacturing or when loading a vehicle.

[0061] The inner surface of the front cover 303 is provided with the projection 356. As in Fig. As illustrated in Figure 7, the protrusion 356 is arranged to face the measurement surface 430 and has a shape extending along an axis of the flow path of the bypass passage. An opening is formed in the above-described flow path 386 using the measurement surface 430 and the protrusion 356 to reduce a vortex generated in the measurement target gas 30 and to generate laminar flow. In this embodiment, the bypass passage having the opening part is divided into a groove part and a lid part covering the groove to form a flow path with an opening, and the groove part is formed by a second resin molding process to form the case 302. Then, the front cover 303 having the protrusion 356 is formed by another resin molding process, and the groove is covered by using the front cover 303 as the lid of the groove to form the bypass passage.In the second resin molding process for molding the housing 302, the circuit package 400 having the measuring surface 430 is also fixed to the housing 302. Since the molding of the groove with such a complicated shape is performed by a resin molding process, and a projection 356 for the opening is provided on the front cover 303, it is possible to form the flow path 386 of FIG. Fig. 7(A) and Fig. 7(B) with high accuracy. Furthermore, since the alignment relationship between the groove and the measurement surface 430 or the exposed portion of the heat transfer surface 436 can be maintained with high accuracy, it is possible to reduce product fluctuation and, as a result, obtain a highly accurate measurement result. Therefore, it is possible to increase productivity.

[0062] The flow path 387 is formed in the same way through the rear cover 304 and the back of the measuring surface 431. The flow path 387 is formed by separating the flow path 386 into a groove part and a lid part, wherein the groove part is prepared in a second resin molding process that forms the housing 302, and next, the groove is covered with the rear cover 304 having the protrusion 358. Since the flow path 387 is prepared as mentioned above, it is possible to prepare the flow path 386 with high accuracy, and productivity is improved. In this embodiment, the opening is provided in the flow path 387, however, it is possible to use a flow path 387 without an opening without using a protrusion 358.

[0063] In Fig. 8 (B), a notch 323 for forming the exhaust passage 352 is provided on a leading end side of the front cover 303. As shown in Fig. As shown in Figure 2(B), not only is the exhaust port 352 extended toward a right surface of the housing 302, but the exhaust port 352 is also extended toward the front of the housing 302 through the notch 323. As a result, the flow resistance of an entire bypass passage is reduced, and the measurement target gas 30 discharged from the inlet channel 350 to the bypass passage is increased. As a result, the measurement accuracy of the air flow is improved. 3.4 Structure and effect of the contact terminal 320

[0064] Fig. Figure 10 shows an enlarged view of the contact terminal 320 of the housing 302 shown in Fig. 5 and Fig. 6. However, they are slightly different in the following points. Different points from the description in Fig. 5 and Fig. 6, each inner socket of the external contacts 361 is made of Fig. 5 and Fig. 6 separated, but shows Fig. 10 shows a state in which each of the inner sockets of the external contact 361 is separated, and each of the inner sockets of the external contact 361 is connected by a connecting portion 365. Each of the external contacts 306 is fixed to the housing 302 according to resin molding in a second resin molding process such that the inner sockets of the external contact 361, which protrude toward the circuit package 400 side of the external contact 306, respectively overlap the corresponding terminal contacts 412 or come close to the corresponding terminal contacts 412. In order to prevent deformation and displacement in the arrangement of each of the external contacts 306, according to the embodiment, the external contact 306 is fixed to the housing 302 according to a resin molding process (second resin molding process) to form the housing 302 in a state in which the inner sockets of the external contact 361 are connected by the connecting portion 365.The terminal contact 412 and inner socket of the external contact 361 may be attached beforehand, and the external contact 306 may be attached to the housing 302 thereafter according to the second molding process. 3.5 Test of the finished product according to the first resin molding process

[0065] In a Fig. In the embodiment illustrated in Figure 10, the number of contacts included in the circuit package 400 is greater than the number of internal sockets of the external contact 361. The terminal contacts 412 among the contacts included in the circuit package 400 are respectively connected to the internal sockets of the external contact 361, and the contacts 414 are not connected to the internal sockets of the external contact 361. In other words, the contacts 414 are the contacts provided in the circuit package 400 but not connected to the internal sockets of the external contact 361.

[0066] In Fig. 10, the contacts 414 that are not connected to the inner sockets of the external contact 361 are provided, in addition to the terminal contacts 412 that are connected to the inner sockets of the external contact 361. After the circuit package 400 is manufactured in the first resin molding process, it is tested whether the circuit package 400 operates properly and whether an abnormality in the electrical connection is generated in the first resin molding process. High reliability can be maintained in each of the circuit packages 400 in this way. The contacts 414 that are not connected to the inner sockets of the external contact 361 are used for testing the circuit package 400.Since the contacts 414 are not used after the test work, the unused contacts 414 may be cut off at the root of the circuit package 400 after the test or may be buried in an inner portion of the resin corresponding to the contact-side fixing portion 362, as shown in FIG. Fig. 10. Since the contacts 414 that are not connected to the inner sockets of the external contact 361 are provided as mentioned above, it is possible to test whether an abnormality is generated in the circuit package 400 manufactured in the first resin molding process, and high reliability can be maintained. 3.6 Connection structure between the gap in the inner portion of the housing 302 and the external portion of the thermal flow meter 300 and effect

[0067] As shown in a partially enlarged view in Fig. 10, a hole 364 is provided in the housing 302. The hole 364 is connected to an opening 309 formed in an inner portion of the Fig. 4(A). In the embodiment, both surfaces of the housing 302 are hermetically sealed by the front cover 303 and the rear cover 304. If the hole 364 is not provided, a difference is generated between the air pressure in the gap and the ambient air pressure due to the temperature change of the air in the gap including the contact terminal 320. The pressure difference is desirably as small as possible. As a result, the vent hole 364, which communicates with the opening 309 provided in the external terminal 305, is provided in the gap of the housing 302.The external terminal 305 is structured so that the external terminal 305 is not adversely affected by the water to improve the reliability of an electrical connection, and it is possible to prevent the intrusion of water from the opening 309 and further prevent the intrusion of foreign substances such as foreign particles and dusts by setting the opening 309 in the external terminal 305. 4. Fixing structure of the circuit package 400 by the housing 3024.1 Fixing structure of the circuit package 400 by a fixing portion of the housing 302

[0068] Next, the attachment of the circuit package 400 to the housing by a resin molding process is described again with reference to Fig. 5(A), Fig. 5(B), Fig. 6(A) and Fig. 6(B). The circuit package 400 is arranged and fixed in the housing 302 such that the measuring surface 430 formed on the front surface of the circuit package 400 is arranged in a predetermined position of the bypass line groove to measure the bypass line, for example, a connecting portion between the bypass line groove on the front side 332 and the bypass line groove on the rear side 334 in the embodiment of Fig. 5(A), Fig. 5 (B), Fig. 6(A) and Fig. 6(B). A part for burying and fixing the circuit package 400 in the housing 302 by resin molding is provided as a fixing portion 372 for burying and fixing the circuit package 400 in the housing 302 on the side slightly closer to the flange 312 from the bypass passage groove. The fixing portion 372 is buried so as to cover the outer periphery of the circuit package 400 formed by the first resin molding process.

[0069] As in Fig. 5(B), a recess 376 and a recess 378 are provided on a front side of the fixing portion 372. As shown in Fig. Further, as shown in Fig. 6(B), a concavity 373 is formed on a back side of the fixing portion 372. Based on the concavities, it is possible to reduce deflation when the resin temperature drops in the case of molding the fixing portion 372, and it is possible to reduce the concentration of stress acting on the circuit package 400. Furthermore, by restricting the flow of the resin through the mold for forming the above-mentioned cavities, the rate of drop in the resin temperature can be reduced, and the resin constituting the fixing portion 372 can easily penetrate deep into the concavities and bulges provided on the front side of the circuit package 400.

[0070] The entire surface of the circuit package 400 is not covered by a resin used to mold the housing 302, but a portion where the outer wall of the circuit package 400 is exposed is provided in the side of the flange 312 of the fixing portion 372. In the embodiment of Fig. 5(A), Fig. 5(B), Fig. 6(A) and Fig. 6(B), the area of a portion exposed to the resin of the package 302 but not enclosed by the package 302 is larger than the area of a portion enclosed by the resin of the package 302 outside the outer peripheral surface of the circuit package 400. Furthermore, a portion of the measurement surface 430 of the circuit package 400 is also exposed to the resin of the package 302.

[0071] Excessive stress concentration due to volume shrinkage is reduced in a process of hardening the fixing portion 372 to include the periphery of the circuit package 400 in a second resin molding process for forming the housing 302 by forming the concaves on the front and back sides of the fixing portion 372, which covers an outer wall of the circuit package 400 like a band over an entire circumference. The excessive stress concentration may adversely affect the circuit package 400. 4.2 Improving the adhesion level between the housing 302 and the circuit package 400

[0072] In order to fix the circuit package 400 with a small area by reducing the area of a resin-wrapped portion of the case 302 on the outer peripheral surface of the circuit package 400, it is preferable to increase the adhesion of the circuit package 400 to the outer wall in the fixing portion 372. When a thermoplastic resin is used to mold the case 302, it is preferable that the thermoplastic resin penetrates into the fine unevenness on the outer wall of the circuit package 400 while having a low viscosity, and the thermoplastic resin solidifies while penetrating the fine unevenness of the outer wall. In the resin molding process for molding the case 302, it is preferable that the inlet port of the thermoplastic resin be provided in and near the fixing portion 372. The viscosity of the thermoplastic resin increases with decreasing temperature, so it solidifies.Therefore, by injecting the thermoplastic resin at high temperature into or near the fixing portion 372, it is possible to solidify the thermoplastic resin having a low viscosity while impacting the outer wall of the circuit package 400. Furthermore, since the concave portion 376, the concave portion 378, and the concave portion 373 are formed in the fixing portion 372, a barrier portion that restricts the flow of the thermoplastic resin is formed by the mold for forming the concave portions, and a moving speed of the thermoplastic resin in the fixing portion 372 is reduced. Thus, the temperature drop of the thermoplastic resin is suppressed, a low viscosity state is prolonged, and adhesion between the circuit package 400 and the fixing portion 372 is improved.

[0073] By roughening the outer wall surface of the circuit package 400, it is possible to improve the adhesion between the circuit package 400 and the fixing portion 372. As a method for roughening the outer wall surface of the circuit package 400, a roughening method for forming fine unevenness on the surface of the circuit package 400 is known, for example, a satin finishing treatment after molding the circuit package 400 through the first resin molding process. As a roughening method for forming fine unevenness on the surface of the circuit package 400, the roughening can be achieved, for example, by sandblasting. Further, the roughening can be performed by laser machining.

[0074] As another roughening method, an uneven sheet is attached to an inner surface of the mold used in the first resin molding process, and the resin is pressed against the mold with the sheet on the surface. With this method, fine unevenness can be formed and roughened on a surface of the circuit package 400. Alternatively, unevenness can be applied to an inner surface of the mold for molding the circuit package 400 to roughen the surface of the circuit package 400. The surface portion of the circuit package 400 for such roughening is at least a portion where the fixing portion 372 is disposed. In addition, adhesion is increased by roughening a surface portion of the circuit package 400 where the hollowed outer wall portion 366 is disposed.

[0075] When applying asperities to the surface of the circuit package 400 using the above-mentioned sheet, the depth of the groove depends on the thickness of the sheet. As the thickness of the sheet increases, molding in the initial resin molding process becomes difficult, so the thickness of the sheet is limited. As the thickness of the sheet decreases, the depth of the asperities arranged on the sheet is limited in advance. For this reason, when using the above-mentioned sheet, the depth of the asperities between the bottom and top surfaces of the asperities is preferably 10 μm or more and 20 μm or less. If the depth is less than 10 μm, the adhesion effect is impaired. If the depth is greater than 20 μm, it is difficult to achieve with the above-mentioned sheet thickness.

[0076] In roughening methods other than the above-mentioned method using the sheet, the thickness of the resin in the first resin molding process for molding the circuit package 400 is preferably 2 mm or less. For this reason, the depth of the unevenness between the bottom and top of the unevenness is difficult to increase to 1 mm or more. Conceptually, it is expected that the adhesion between the resin covering the circuit package 400 and the resin for molding the case 302 increases as the depth of the unevenness between the bottom and top of the unevenness on the surface of the circuit package 400 increases. However, for the reason described above, the depth of the unevenness between the bottom and top of the unevenness is preferably 1 mm or less.That is, when the unevenness having a thickness of 10 μm or more and 1 mm or less is provided on the surface of the circuit package 400, the adhesion between the resin covering the circuit package 400 and the resin for molding the case 302 is preferably increased.

[0077] A thermal expansion coefficient differs between the thermosetting resin for molding the circuit package 400 and the thermoplastic resin for molding the housing 302 with the fixing portion 372. It is preferable to avoid applying excessive stress to the circuit package 400 caused by this difference in thermal expansion coefficient. It is possible to reduce the stress applied to the circuit package 400 by providing the recess 373 and the recess 378, as well as the aforementioned recess 376.

[0078] By forming the fixing portion 372 surrounding the outer periphery of the circuit package 400 in a band shape and reducing the width of the band, the effect of stress generated by a difference in thermal expansion coefficient on the circuit package 400 can be reduced. A width of the band of the fixing portion 372 is 10 mm or less, and preferably 8 mm or less. In this embodiment, since the hollowed outer wall portion 366 as a part of the upstream outer wall 335 of the housing 302 and the fixing portion 372 wrap the circuit package 400 to fix the circuit package 400, it is possible to further reduce the width of the band of the fixing portion 372. For example, the circuit package 400 can be fixed when the width is 3 mm or more.

[0079] To reduce stress generated by the difference in thermal expansion coefficient, a portion covered by the resin used to mold the housing 302 and an exposed portion without a cover are arranged on the surface of the circuit package 400. A plurality of portions in which the surface of the circuit package 400 is exposed by the resin of the housing 302 are provided, and one of them is the measurement surface 430 having the above-described exposed portion of the heat transfer surface 436. In addition, an exposed portion is arranged on a part of the flange 312 side relative to the fixing portion 372. Further, the outer wall hollow portion 366 is formed to expose a portion of the upstream side relative to the outer wall hollow portion 366, and this exposed portion serves as a support portion that supports the temperature detection portion 452.A gap is formed so that a portion of the outer surface of the circuit package 400 on the side of the flange 312 with respect to the fixing portion 372 surrounds the circuit package 400 around its outer periphery, specifically, the side facing the flange 312 from the downstream side of the circuit package 400 and further over the downstream side of the portion near the contact of the circuit package 400. Since the gap is formed around the portion where the surface of the circuit package 400 is exposed, the amount of heat transferred to the circuit package 400 through the flange 312 from the main line 124 can be reduced, and the deterioration of the measurement accuracy by the heat can be suppressed.

[0080] A gap is formed between the circuit package 400 and the flange 312, and this gap serves as a contact terminal 320. The terminal contact 412 of the circuit package 400 and the inner socket of the external contact 361 on the housing 302 side of the external contact 306 are electrically connected to this contact terminal 320 by spot welding, laser welding, etc. The gap of the contact terminal 320 can suppress heat transfer from the housing 302 to the circuit package 400 as described above and is provided as a space that can be used for performing connection work between the terminal contact 412 of the circuit package 400 and the inner socket of the external contact 361 of the external contact 306. 4.3 Formation of the housing 302 by a second resin molding process and improvement of the measurement accuracy

[0081] In the previously described Fig. 5(A), Fig. 5(B), Fig. 6(A) and Fig. In the case 302 illustrated in FIG. 6(B), the circuit package 400 including the airflow detection section 602 or the processing unit 604 is manufactured through the first resin molding process. Subsequently, the case 302 including, for example, the front side bypass passage groove 332 or the rear side bypass passage groove 334 for forming the bypass passage through which the measurement target gas 30 flows is manufactured through the second resin molding process. Through this second resin molding process, the circuit package 400 is embedded in the resin of the case 302 and fixed to the inside of the case 302 by resin molding.As a result, the air flow detection section 602 performs heat transfer with the measurement target gas 30, so that a configuration relationship such as a positional relationship or a directional relationship between the exposed portion of the heat transfer surface 436 for measuring the flow rate and the bypass passage, including, for example, the front-side bypass passage groove 332 or the rear-side bypass passage groove 334, can be achieved with remarkably high accuracy. In addition, it is possible to reduce errors or deviations generated in each circuit package 400 to a very low value. As a result, it is possible to significantly improve the measurement accuracy of the circuit package 400. For example, it is possible to double or even more increase the measurement accuracy compared to a conventional method in which attachment is performed with an adhesive.Since the thermal flow meter 300 is typically mass-produced, the method using an adhesive and strict measurement has limitations in improving measurement accuracy. However, if the circuit package 400 is manufactured through the first resin molding process as in this embodiment, and then the bypass passage is formed in the second resin molding process to form the bypass passage in which the measurement target gas 30 flows while fixing the circuit package 400 and the bypass passage, fluctuation in measurement accuracy can be significantly reduced and the measurement accuracy of each thermal flow meter 300 can be significantly improved. This is similar to the embodiment of FIG. Fig. 7 and the embodiment from Fig. 5(A), Fig. 5(B), Fig. 6(A) or Fig. 6(B).

[0082] Further on the embodiment of for example Fig. 5(A), Fig. 5(B), Fig. 6(A) or Fig. Referring to FIG. 6(B), it is possible to fix the circuit package 400 to the housing 302 such that a relationship between the front-side bypass passage groove 332, the rear-side bypass passage groove 334, and the exposed portion of the heat transfer surface 436 is set to a specific relationship. Thus, in each of the mass-produced thermal flow meters 300, a positional relationship or a configuration relationship between the exposed portion of the heat transfer surface 436 of each circuit package 400 and the bypass passage can be regularly achieved with remarkably high accuracy.Since the bypass passage groove in which the exposed portion of the heat transfer surface 436 of the circuit package 400 is mounted, for example, the front side bypass passage groove 332 and the rear side bypass passage groove 334, can be formed with remarkably high accuracy, one work of forming the bypass passage in this bypass passage groove is a work of covering both sides of the housing 302 with the front or rear cover 303 or 304. This work is very simple and is a process with few factors of deteriorating measurement accuracy. In addition, the front or rear cover 303 or 304 is formed by a resin molding process with high molding accuracy. Therefore, it is possible to form the bypass passage provided in a specific relationship with the exposed portion of the heat transfer surface 436 of the circuit package 400 with high accuracy.In this way, high productivity can be achieved in addition to improving measurement accuracy.

[0083] In comparison, the prior art thermal flowmeter was manufactured by fabricating the bypass line and then bonding the measuring section to the bypass line using an adhesive. This adhesive-based method has disadvantages because the adhesive has an uneven thickness, and the position or angle of the adhesive varies in each product. Therefore, there were limitations to improving measurement accuracy. When this work is performed in mass production, improving measurement accuracy is even more difficult.

[0084] In the embodiment of the present invention, the circuit package 400 including the airflow sensing portion 602 is first manufactured through a first resin molding process, and then the circuit package 400 is fixed by resin molding, while the bypass passage groove for forming the bypass passage is formed by resin molding through a second resin molding process. Thus, the shape of the bypass passage groove can be formed and the airflow sensing portion 602 can be fixed to the bypass passage groove with significantly high precision.

[0085] A portion related to flow rate measurement, such as the exposed portion of the heat transfer surface 436 of the air flow detection portion 602 or the measuring surface 430 mounted in the exposed portion of the heat transfer surface 436, is formed on the surface of the circuit package 400. Subsequently, the measuring surface 430 and the exposed portion of the heat transfer surface 436 are exposed from the resin used to mold the housing 302. That is, the exposed portion of the heat transfer surface 436 and the measuring surface 430 around the exposed portion of the heat transfer surface 436 are not covered by the resin used to mold the housing 302.The measuring surface 430 formed by resin molding the circuit package 400, the exposed portion of the heat transfer surface 436, or the temperature detection portion 452 is directly used to measure a flow rate of the thermal flow meter 300 or a temperature even after resin molding the housing 302. Thus, the measurement accuracy is improved.

[0086] In the embodiment of the present invention, the circuit package 400 is formed with the housing 302 into a single component to fix the circuit package 400 to the housing 302 with the bypass line. Therefore, the circuit package 400 can be fixed to the housing 302 with a small fixing area. That is, the surface of the circuit package 400 that is not in contact with the housing 302 can be enlarged. For example, the surface of the circuit package 400 that is not in contact with the housing 302 is exposed to form a gap. The temperature of the intake pipe is transferred to the housing 302 and then transferred from the housing 302 to the circuit package 400.Even if the contact area between the housing 302 and the circuit package 400 is reduced, instead of surrounding the entire surface or most of the surface of the circuit package 400 with the housing 302, it is possible to achieve high reliability with high accuracy and fix the circuit package 400 to the housing 302. For this reason, it is possible to suppress heat transfer from the housing 302 to the circuit package 400 and a decrease in measurement accuracy.

[0087] At the Fig. 5(A), Fig. 5(B), Fig. 6(A) or Fig. In the embodiment illustrated in FIG. 6(B), the area A of the exposed surface of the circuit package 400 can be greater than or equal to the area B covered by a molding material used to mold the housing 302. In the embodiment, the area A is greater than the area B. Thus, heat transfer from the housing 302 to the circuit package 400 can be suppressed. In addition, it is possible to reduce stress due to a difference between a thermal expansion coefficient of the thermosetting resin used to form the circuit package 400 and a thermal expansion coefficient of the thermoplastic resin used to form the housing 302. 4.4 Fixing the circuit package 400 by a second resin molding process and its effect

[0088] A hatched section in Fig. 11(A) to 11(C) indicate a mounting surface 432 and a mounting surface 434 for covering the circuit package 400 with the thermoplastic resin used in the second resin molding process, which is used in the second resin molding process to mount the circuit package 400 to the housing 302. As described above with reference to Fig. 5 and Fig. 6, it is important to maintain high accuracy so that the relationship between the measurement surface 430 and the exposed portion of the heat transfer surface 436 provided in the measurement surface 430 and the shape of the bypass line assumes a prescribed relationship. Since the circuit package 400 is attached to the housing 302, with the bypass line being molded simultaneously with the molding of the bypass line in the resin molding process, the relationship between the bypass line and the measurement surface 430 and the exposed portion of the heat transfer surface 436 can be maintained with extremely high accuracy.In other words, since the circuit package 400 is fixed to the housing 302 in the second resin molding process, the circuit package 400 can be positioned and fixed in the mold for molding the housing 302 with the bypass line with high accuracy, and the circuit package 400 is fixed with high accuracy after molding by injecting the hot thermoplastic resin into the mold.

[0089] In this embodiment, the entire surface of the circuit package 400 is not a mounting surface 432 covered by the resin used to mold the housing 302, but the front surface is exposed to the side of the terminal contact 412 of the circuit package 400. That is, there is a portion not covered by the resin used to mold the housing 302. In the Fig. 11(A) to 11(C), of the front surface of the circuit package 400, the area not surrounded by the resin used to mold the housing 302 but exposed by the resin used to mold the housing 302 is larger than the area of the mounting surface 432 and mounting surface 434 wrapped by the resin used to mold the housing 302.

[0090] A thermal expansion coefficient differs between the thermosetting resin for molding the circuit package 400 and the thermoplastic resin for molding the housing 302 with the fixing portion 372. It is preferable to avoid applying excessive stress to the circuit package 400 caused by this difference in thermal expansion coefficient as long as possible. By reducing the size of the front surface of the circuit package 400 and the fixing surface 432, the influence due to the difference in thermal expansion coefficient can be reduced. For example, the fixing surface 432 on the front surface of the circuit package 400 can be reduced by providing a band shape with a width L.

[0091] The mechanical strength of the protrusion 424 can be increased by disposing the fastening surface 432 at the base of the protrusion 424. The circuit package 400 and the housing 302 can be more securely fastened to each other by disposing, on the front surface of the circuit package 400, a band-shaped fastening surface along a flow axis of the measurement target gas 30 and a fastening surface transverse to the flow axis of the measurement target gas 30. On the fastening surface 432, a portion surrounding the circuit package 400 in a band shape with a width L along the measurement surface 430 is the fastening surface along the flow axis of the measurement target gas 30 as described above, and a portion covering the base of the protrusion 424 is the fastening surface transverse to the flow axis of the measurement target gas 30.

[0092] In Fig. 11(A) to 11(C), the circuit package 400 is molded in the first resin molding process as mentioned above. The hatched portion described in the external appearance of the circuit package 400 indicates the mounting surface 432 and the mounting surface 434 on which the circuit package 400 is covered with the resin used in the second resin molding process when the housing 302 is molded in the second resin molding process after the circuit package 400 is manufactured in the first resin molding process. Fig. 11(A) is a left elevational side view of the circuit package 400, Fig. 11(A) is a front elevational view of the circuit package 400 and Fig. Figure 11(C) is a rear elevational view of the circuit package 400. The circuit package 400 includes an airflow detection section 602 and a processing unit 604 described below, which are molded into one piece using a thermosetting resin. The measurement surface 430, which acts as a surface for flowing the measurement gas 30, is formed on one end face of the circuit package 400. Fig. 11(B) is formed into a shape extending longitudinally in the flow direction of the measurement target gas 30. In the embodiment, the measurement surface 430 is formed in a rectangular shape extending longitudinally in the flow direction of the measurement target gas. The measurement surface 430 is formed thinner than the other sections, as shown in Fig. 11(A), and the exposed portion of the heat transfer surface 436 is provided in a part thereof. The built-in air flow detection section 602 performs heat transfer with the measurement target gas 30 via the exposed portion of the heat transfer surface 436, measures a state of the measurement target gas 30, for example, a flow rate of the measurement target gas 30, and outputs an electrical signal expressing the air flow flowing in the main line 124.

[0093] In order for the built-in air flow detection section 602 (see Fig. 19) to measure the state of the measurement target gas 30 with high accuracy, it is desirable that the gas flowing near the exposed portion of the heat transfer surface 436 be a laminar flow with little turbulence. Thus, it is preferable that no step be provided between the flow path side surface of the exposed portion of the heat transfer surface 436 and the gas-carrying surface of the measurement surface 430. According to the structure, non-uniform stress and strain can be prevented from acting on the air flow detection portion 602 while maintaining the accuracy of the air flow measurement at a high level. The step can be provided as long as the step does not affect the accuracy of the air flow measurement.

[0094] A press impression 442 of a molding press, which supports an internal substrate or plate during resin molding of the circuit package 400, remains on a back side of the measurement surface 430 with the exposed portion of the heat transfer surface 436, as shown in Fig. 11(C). The exposed portion of the heat transfer surface 436 is a location for exchanging heat with the measurement target gas 30, and it is desirable that heat transfer between the air flow detection section 602 and the measurement target gas 30 be well performed in order to accurately measure the state of the measurement target gas 30. Thus, it is necessary to prevent the situation that the exposed portion of the heat transfer surface 436 is covered with resin in the first resin molding process. The mold is applied to both surfaces of the exposed portion of the heat transfer surface 436 and the back surface of the measurement surface 431, which is the back surface of the exposed portion of the heat transfer surface, and the resin is prevented from flowing into the exposed portion of the heat transfer surface 436 by the mold.The press impression 442 with a concave shape is formed on the back of the exposed portion of the heat transfer surface 436. The elements constituting the airflow sensing portion 602 are arranged close to the portion, and it is desirable to radiate the heat generation of the elements to the outer portion as much as possible. The formed concave part is less affected by the resin and achieves a simple radiation effect.

[0095] A semiconductor diaphragm constituting the air flow detection section 602 is disposed in the inner part of the exposed portion of the heat transfer surface 436, and a gap is formed on the back of the semiconductor diaphragm. If the gap is hermetically sealed, the semiconductor diaphragm is deformed by the pressure change in the gap due to temperature changes, and the measurement accuracy is reduced. Thus, in the embodiment, an opening 438 communicating with the gap on the back of the semiconductor diaphragm is provided in a front side of the circuit package 400, and a communication duct connecting the gap in the back of the semiconductor diaphragm and the opening 438 is provided in the inner portion of the circuit package 400. The opening 438 is in a portion where the Fig. 11(A) to 11(V) is not described, provided in a manner that the opening 438 is not clogged by the resin in the second resin molding process.

[0096] It is necessary to form the opening 438 in the first resin molding process. The resin flow into the opening 438 portion is blocked by applying the mold to the opening 438 portion and its back surface, and pressing the front and back surfaces with the mold, and the opening 438 is formed. The molding of the opening 438 and the connecting channel connecting the gap in the back surface of the semiconductor diaphragm and the opening 438 will be mentioned below.

[0097] In the circuit package 400, the press mark 442 remains on the back of the circuit package 400, on which the exposed portion of the heat transfer surface 436 is formed. In the first resin molding process, a mold, such as an insert mold, is attached to the exposed portion of the heat transfer surface 436 to prevent resin from flowing into the exposed portion of the heat transfer surface 436. The mold is further attached to the portion of the press mark 442 on an opposite surface, and the resin from flowing into the exposed portion of the heat transfer surface 436 is blocked by both molds. As a result, by molding the portion of the exposed portion of the heat transfer surface 436, it is possible to measure the air flow of the measurement target gas 30 with extremely high accuracy.Furthermore, since the portion of the press impression 442 has no or little resin in the second resin molding process, the heat radiation effect is large. In the case where a conductor is used as the second plate 536, there is an effect that heat generation in the adjacent circuit is radiated through the conductor. 5. Mounting the circuit parts to the circuit package 5.1 Frame of the circuit package and mounting the circuit parts

[0098] Fig. 12 illustrates a frame 512 of the circuit package 400 and a mounting state of a chip as a circuit component 516 mounted on the frame 512. Note that the dotted line 508 indicates a portion covered by the mold used to mold the circuit package 400. A conductor 514 is mechanically connected to the frame 512, and a board 532 is mounted in the center of the frame 512. A chip-like airflow sensing section 602 and a processing unit 604 as a large-scale integrated (LSI) circuit are mounted on the board 532. A diaphragm 672 is provided in the airflow sensing section 602, and each contact of the airflow sensing section 602 and the processing unit 604 described below is connected with a wire 542. In addition, each contact of the processing unit 604 and a corresponding conductor 514 are connected to a wire 543.In addition, the conductor 514 positioned between a portion corresponding to the terminal contact of the circuit package 400 and the plate 532 is connected with the chip-like circuit component 516 therebetween.

[0099] The airflow sensing section 602 with the diaphragm 672 is arranged on the leading-end side when the circuit package 400 is obtained in this way. The processing unit 604 is arranged on the side corresponding to the terminal for the airflow sensing section 602 in an LSI state. In addition, a connecting wire 543 is arranged on the contact side of the processing unit 604. By arranging the airflow sensing section 602, the processing unit 604, the wire 543, the circuit component 516, and the connecting conductor 514 sequentially in this order from the leading-end side of the circuit package 400 to the terminal, the entire circuit package 400 becomes simple and compact.

[0100] A thick conductor is provided to support the plate 532, and this conductor is fixed to the frame 512 using the conductor 556 or 558. Note that a conductor surface with the same area as that of the plate 532, which is connected to the thick conductor, is provided on the underside of the plate 532, and the plate 532 is mounted on the conductor surface. This conductor surface is connected to the ground. As a result, it is possible to suppress noise by generally connecting the circuit of the air flow detection section 602 or the processing unit 604 to the ground using the conductor surface, thus improving the measurement accuracy of the measurement target gas 30.Additionally, a conductor 544 is provided on the upstream side of the flow path from the plate 532, namely, so as to protrude along an axis transverse to the axis of the air flow detection section 602, the processing unit 604, or the above-described circuit component 516. A temperature detection element 518, such as a chip-type thermistor, is connected to this conductor 544. In addition, a conductor 548 is provided near the processing unit 604, which is a base of the projection, and the conductors 544 and 548 are electrically connected with a thin connecting line 546. Since the conductors 548 and 544 are directly connected, heat is transferred to the temperature detection element 518 through the conductors 548 and 544, so it may be difficult to accurately measure a temperature of the measurement target gas 30.For this reason, by connecting a wire with a small cross-sectional area and a large resistance, it is possible to increase the thermal resistance between the leads 548 and 544. As a result, it is possible to improve the accuracy of temperature measurement of the measurement target gas 30 to prevent the influence of heat from reaching the temperature detection element 518.

[0101] The conductor 548 is fixed to the frame 512 through the conductor 552 or 554. A connecting portion between the conductor 552 or 554 and the frame 512 is fixed to the frame 512 while being inclined against the protruding direction of the protruding temperature detection element 518, and the mold is also inclined in this area. As the molding resin flows along this incline in the first resin molding process, the molding resin from the first resin molding process flows smoothly to the leading end portion where the temperature detection element 518 is provided, thus improving reliability.

[0102] In Fig. In FIG. 12, an arrow 592 indicates a resin injection direction. The lead frame on which a circuit component is mounted is covered by the resin, and a pressed fitting hole 590 for resin injection into the mold is provided at a circled position, so that a thermosetting resin is injected into the mold along the direction of the arrow 592. The circuit component 516 or the temperature sensing element 518 and the lead 544 for holding the temperature sensing element 518 are provided from the pressed fitting hole 590 along the direction of the arrow 592. In addition, the board 532, the processing unit 604, and the air flow sensing section 602 are arranged in a direction close to the arrow 592. With this arrangement, the resin flows smoothly in the first resin molding process. The first resin molding process uses a thermosetting resin, so it is important to expand the resin before it solidifies.For this reason, the arrangement of a circuit component of the conductor 514 or a wire and a relationship between the pressed fitting hole 590 and the injection direction become important. 5.2 Structure for the connecting gap on the rear surface of the diaphragm and the opening

[0103] Fig. 13 is a diagram showing a part of the cross section along a line CC of Fig. 12 to describe a communication hole 676 connecting a gap 674 provided in and inside the diaphragm 672 and the hole 520.

[0104] As described below, the air flow detection section 602 for measuring the flow rate of the measurement target gas 30 is provided with a diaphragm 672, and a gap 674 is provided on the rear surface of the diaphragm 672. Although not illustrated, the diaphragm 672 is provided with an element for exchanging heat with the measurement target gas 30 and thereby measuring the flow rate. If the heat is transferred to the elements formed in the diaphragm 672 through the diaphragm 672 separately from the heat exchange with the measurement target gas 30, it is difficult to accurately measure the flow rate. For this reason, it is necessary to increase a thermal resistance of the diaphragm 672 and form the diaphragm 672 as thin as possible.

[0105] The diaphragm 672 is fixed while being buried in the first resin of the circuit package 400 formed in the first resin molding process. A front side of the diaphragm 672 is provided with the element (not shown), and the element performs heat transfer with the measurement target gas 30 (not shown) via the heat transfer surface 437 on the front side of the element in the exposed portion of the heat transfer surface 436. The heat transfer surface 437 may be constructed through the front side of each of the elements or may be provided with a thin protective film thereon. It is desirable that heat transfer between the element and the measurement target gas 30 be performed smoothly, and direct heat transfer between the elements be minimized as much as possible.

[0106] A portion of the diaphragm 672 where the elements are provided is disposed in the exposed portion of the heat transfer surface 436 of the measuring surface 430, and the heat transfer surface 437 is exposed from the resin used to mold the measuring surface 430. The outer periphery of the diaphragm 672 is covered by the thermosetting resin used in the first resin molding process to mold the measuring surface 430. If only the lateral side of the diaphragm 672 is covered by the thermosetting resin and the upper surface of the outer periphery of the diaphragm 672 is not covered by the thermosetting resin, stress generated in the resin used to mold the measuring surface 430 will be absorbed only by the lateral side of the diaphragm 672, so distortion may occur in the diaphragm 672 and properties may deteriorate.The distortion of the diaphragm 672 is reduced by covering the outer peripheral portion of the diaphragm 672 with the thermosetting resin, as shown in FIG. Fig. 13. Meanwhile, if the height difference between the heat transfer surface 437 and the measurement surface 430 over which the measurement target gas 30 flows is large, the flow of the measurement target gas 30 will be disturbed, thus deteriorating the measurement accuracy. Therefore, it is preferable that the height difference W between the heat transfer surface 437 and the measurement surface 430 over which the measurement target gas 30 flows is small.

[0107] The diaphragm 672 is formed thin to suppress heat transfer between the elements, and a gap 674 is formed in the rear surface of the diaphragm 672. When this gap 674 is sealed, a pressure in the gap 674 formed on the rear surface of the diaphragm 672 changes depending on a temperature change. As a pressure difference between the gap 674 and the surface of the diaphragm 672 increases, the diaphragm 672 absorbs the pressure, and distortion is generated, making it difficult to perform high-accuracy measurements. For this reason, a hole 520 is provided in the plate 532, which is connected to the opening 438 opened to the outside, and a communication hole 676 is provided that connects this hole 520 to the diaphragm 672.This communication hole 676 is composed, for example, of a pair of plates including first and second plates 534 and 536. The first plate 534 has holes 520 and 521 and a groove for forming the communication hole 676. The communication hole 676 is formed by covering the groove and holes 520 and 521 with the second plate 536. By using the communication hole 676 and the hole 520, the pressure applied to the front and rear surfaces of the diaphragm 672 is almost equalized, thus improving measurement accuracy.

[0108] As described above, the connection hole 676 may be formed by covering the groove and the holes 520 and 521 with the second plate 536. Alternatively, the lead frame may be used as the second plate 536. As described with reference to Fig. As described in Fig. 12, the diaphragm 672 and the LSI circuit serving as the processing unit 604 are provided on the first board 532. A lead frame for supporting the first board 532, on which the diaphragm 672 and the processing unit 604 are mounted, is provided below. Thus, the structure becomes simpler using the lead frame. In addition, the lead frame can be used as a ground electrode. When the lead frame serves as the second board 536 and the connection hole 676 is formed by covering the holes 520 and 521 formed in the first board 534 using the lead frame and by covering the groove formed in the first board 534 using the lead frame in this way, it is possible to simplify the entire structure.In addition, it is possible to reduce the influence of noise from outside the diaphragm 672 and the processing unit 604 because the lead frame serves as a ground electrode.

[0109] In the circuit package 400, the press mark 442 remains on the rear surface of the circuit package 400, where the exposed portion of the heat transfer surface 436 is formed. In the first resin molding process, in order to prevent resin from flowing into the exposed portion of the heat transfer surface 436, a mold such as an insert mold is installed in a portion in the exposed portion of the heat transfer surface 436, and a mold is installed in a portion of the press mark 442 opposite thereto, so that resin from flowing into the exposed portion of the heat transfer surface 436 is suppressed. By forming a portion of the exposed portion of the heat transfer surface 436 in this way, it is possible to measure the flow rate of the measurement target gas 30 with particularly high accuracy.

[0110] Fig. 14 represents a condition in which the Fig. 12 is molded with the thermosetting resin in the first resin molding process and covered with the thermosetting resin. According to this molding process, the measurement surface 430 is formed on the front surface of the circuit package 400, and the exposed portion of the heat transfer surface 436 is provided on the measurement surface 430. In addition, the gap 674 on the rear surface of the diaphragm 672, which is arranged in the inner portion of the exposed portion of the heat transfer surface 436, is structured to communicate with the opening 438. A temperature detection portion 452 for measuring the temperature of the measurement target gas 30 is provided at the leading end of the projection 424, and a temperature detection element 518 is embedded in an inner portion thereof.In the inner part of the protrusion 424, a conductor for extracting the electrical signal from the temperature sensing element 518 is segmented to suppress heat transfer, and a connecting line 546 with high thermal resistance is arranged. As a result, heat transfer from a root of the protrusion 424 to the temperature sensing portion 452 is suppressed, and the influence of heat is suppressed.

[0111] A slope portion 594 or 596 is formed at the root of the protrusion 424. A resin flow in the first resin molding process flows smoothly. In addition, the measurement target gas 30 measured by the temperature detection portion 452 flows smoothly from the protrusion 424 via the slope portion 594 or 596 to its base while the temperature detection portion 452 is installed in a vehicle and operated to cool the base of the protrusion 424. Thus, it is possible to reduce the influence of heat on the temperature detection portion 452. According to the state of Fig. 21, conductor 514 is separated from each contact to correspond to terminal contact 412 or contact 414.

[0112] In the first resin molding process, it is necessary to prevent resin from flowing into the exposed portion of the heat transfer surface 436 or the opening 438. For this reason, in the first resin molding process, resin flow into a position of the exposed portion of the heat transfer surface 436 or the opening 438 is suppressed. For example, an insert mold larger than the diaphragm 672 is installed, and a press is installed on the rear surface thereof so that pressing is performed from both surfaces. Fig. 11(C), the press mark 442 or 441 remains on the rear surface corresponding to the exposed portion of the heat transfer surface 436 or the opening 438 of Fig. 14 or the exposed portion of the heat transfer surface 436 or the opening 438 Fig. 11(B).

[0113] Since the cut surface of the conductor, which is drawn from the frame 512 in Fig. 14 is separated from the resin surface, there is a risk that the water content will penetrate from the cut surface of the conductor into the inner portion during use. In order to improve durability and reliability, it is important to prevent this risk. For example, the section of the fixing surface 434 is made of Fig. 14 is covered with the resin in the second resin molding process, and the cut surface is not exposed. Furthermore, the cut conductor portions of the slope portion 594 and the slope portion 596 are covered with the resin in the second resin molding process, and the cut surfaces of the conductor 552 and the conductor 554 are Fig. The frames 512 shown in Figure 12 are covered with the resin. As a result, corrosion of the cut surfaces of the conductor 552 and the conductor 554 and water penetration from the cut portions are prevented. The cut surfaces of the conductor 552 and the conductor 554 are close to the important conductor portion that transmits the electrical signal of the temperature sensing portion 452. Thus, the cut surface is desirably covered in the second resin molding process. 5.3 Further embodiment of the circuit package 400

[0114] Fig. Figure 15 illustrates another embodiment of the circuit package 400. Like reference numerals denote like elements as in the other drawings. In the embodiment described above with respect to Fig. 11, the terminal contact 412 and the contact 414 of the circuit package 400 are provided on the same side of the circuit package 400. In comparison, in the embodiment of Fig. 15, the terminal contact 412 and the contact 414 are provided on different sides. The contact 414 is a contact that is not connected to the terminal contact connected to the outside in the thermal flow meter 300. When the terminal contact 412 connected to the outside in the thermal flow meter 300 and the contact 414 not connected to the outside are provided in different directions in this way, it is possible to widen a distance between the terminal contact 412 and the contact and improve workability. In addition, when the contact 414 extends in a direction different from that of the terminal contact 412, it is possible to prevent the conductor within the frame 512 from being concentrated on one part and to facilitate the arrangement of the conductor within the frame 512.In particular, a chip capacitor as the circuit component 516 is connected to a portion of the conductor corresponding to the terminal contact 412. A somewhat large space is necessary to provide such a circuit component 516. In the embodiment of FIG. Fig. 15 it is possible to easily obtain a space for the conductor corresponding to the terminal contact 412.

[0115] In the Fig. 15(A) and Fig. 15(B), the slope portion 462 and the slope portion 464 having gradually changing thicknesses are formed in the neck portion of the projection 424 projecting from the package main body 422 in the same manner as the circuit package 400 shown in Fig. 11(A) to 11(C). The same effects as in Fig. 11(A) to 11(C). In other words, as described in Fig. 5(A) and Fig. As shown in Fig. 15(B), the protrusion 424 protrudes from the side surface of the package main body 422 in a shape extending in an upstream direction of the measurement target gas 30. The temperature detection portion 452 is provided in the leading end portion of the protrusion 424, and the temperature detection element 518 is buried in the inner portion of the temperature detection portion 452. The slope portions 462 and 464 are provided in a connected portion between the protrusion 424 and the package main body 422. The shape that makes the root of the protrusion 424 thick and gradually narrows toward the end of the leading end portion is formed in the neck portion of the protrusion 424 by the slope portion 462 or the slope portion 464.In other words, the neck portion of the projection 424 is provided in a shape in which a cross-sectional area intersecting an axis in the protruding direction is gradually reduced in the case that the protruding direction corresponds to the axis.

[0116] Since the above-mentioned mold is provided, it is possible to use a method of flowing the resin while attaching a sheet to the inner portion of the mold for the purpose of protecting the elements. In the case where the circuit package 400 is molded by resin molding, the adhesion between the sheet and the inner surface of the mold is improved, and reliability is improved. Furthermore, the protrusion 424 is weak in mechanical strength and tends to be bent at the root. The stress concentration at the root can be reduced by the mold that thickens the root of the protrusion 424 and gradually narrows toward the leading end, and excellent mechanical strength can be achieved. Furthermore, in the case where the protrusion 424 is molded by resin molding, there is a tendency for warpage to be generated due to the volume change upon solidification of the resin.It is possible to reduce the influence. It is desirable to lengthen the protrusion length to detect the temperature of the measurement target gas 30 as accurately as possible. It becomes easy to reduce heat transfer from the package main body 422 to the temperature sensing element 518 provided in the temperature sensing section 452 by lengthening the protrusion length of the protrusion 424.

[0117] As in Fig. 11(B) and Fig. As shown in Fig. 11(C), the root of the protrusion 424 is thickened, and the circuit package 400 is fixed to the housing 302 in such a way as to surround the root of the protrusion 424 with the housing 302. It is possible to prevent the protrusion 424 from breaking off due to a mechanical impact by covering the root of the protrusion 424 with the resin of the housing 302 as described above. In addition, the Fig. 11(A) to 11(C).

[0118] Descriptions of the opening 438, the exposed portion of the heat transfer surface 436, the measuring surface 430, the press impression 441 and the press impression 442 in Fig. 15 are similar to those described above and have the same functional effects. Detailed descriptions are not repeated for the sake of simplicity. 6. Manufacturing process of the thermal flow meter 3006.1 Manufacturing process of the circuit package 400

[0119] Fig. 16 illustrates a manufacturing process of the circuit package 400 from the manufacturing process of the thermal flow meter 300. Fig. 17 shows a manufacturing process of the thermal flow meter, and Fig. 18 shows the other embodiment of the manufacturing process of the thermal flow meter. In Fig. 16, a step 1 denotes a process of producing the Fig. 12. The frame is manufactured, for example, by press molding. In step 2, the plate 532 is first mounted on the frame formed in step 1, the air flow sensing section 602 and the processing unit 604 are further mounted on the plate 532, and the circuit parts, such as the temperature sensing element 518 and the chip capacitors, are further mounted. Furthermore, in step 2, electrical wiring is performed between the circuit parts, between the circuit parts and the conductor, and between the conductors. In step 2, the conductor 544 and the conductor 548 are connected therebetween with a lead wire 546 to increase the thermal resistance. In step 2, the Fig. 12 are mounted on the frame 512, and the electrically connected electrical circuit is further formed.

[0120] Next, in step 3, the first resin molding process involves molding with a thermosetting resin. The circuit package 400 in the molded state is shown in Fig. 14. Furthermore, in step 3, each of the connected conductors is separated from the frame 512, the conductors are separated from each other, and the Fig. 11 and Fig. The circuit package 400 shown in Figure 15 is complete. At 400, the measurement surface 430 and the exposed portion of the heat transfer surface 436 are formed, as shown in Fig. 11 and Fig. 15 shown.

[0121] In step 4, an external appearance inspection and a movement test of the finished circuit package 400 are performed. In the first resin molding process in step 3, transfer molding is performed. Since the electrical circuit formed in step 2 is fixed in the mold and the hot resin is injected into the mold at high pressure, it is desirable to check whether an abnormality is generated in the electrical parts and the electrical wiring. For the test, the contact 414 is used in addition to the terminal contact 412, which are shown in Fig. 11 and Fig. 15. Since contact 414 is not used afterward, contact 414 can be cut off from the root after testing. For example, the used contact 414 is shown in Fig. 15(A) and Fig. 15 (B) cut off at the root. 6.2 Manufacturing process of the thermal flow meter 300 and setting the measuring properties

[0122] In Fig. 17 are already in accordance with Fig. 16 and the external contact 306 already manufactured by a process (not shown) are used. In a step 5, the housing 302 is formed by the second resin molding process. The resin bypass line groove, the flange 312, and the external terminal 305 are formed in the housing 302, which is shown in Fig. The hatched portion of the circuit package 400 shown in Figures 11(A) to 11(C) is covered with resin in the second resin molding process, and the circuit package 400 is fixed to the housing 302. The accuracy of air flow detection is greatly improved based on the combination of the manufacturing (step 3) of the circuit package 400 by the first resin molding process and the molding of the housing 302 of the thermal flow meter 300 by the second resin molding process. In a step 6, each of the inner bushings of the Fig. 10, and the connection between the connection contact 412 and the inner socket of the external contact 361 takes place in a step 7.

[0123] When the housing 302 is completed by step 7, the front cover 303 and the rear cover 304 are attached to the housing in step 8, the inner portion of the housing 302 is hermetically sealed by the front cover 303 and the rear cover 304, the bypass line for flowing the measurement target gas 30 is completed, and the thermal flow meter 30 is completed. Furthermore, the Fig. 7 is formed by the protrusion 356 provided on the front cover 303 or the rear cover 304. The front cover 303 is formed by the molding in a step 10, and the rear cover 304 is formed by the molding in a step 11. Further, the front cover 303 and the rear cover 304 are each formed by separate processes and are each formed by the different molds.

[0124] In step 9, the gas is actually supplied to the bypass line, and the property test is performed. As stated above, very high measurement accuracy can be achieved by performing property calibration according to the property test, since the relationship between the bypass line and the airflow detection section is maintained with high accuracy. Furthermore, since positioning and molding with a positional relationship that affects the relationship between the bypass line and the airflow detection section are performed in the first resin molding process and the second resin molding process, the property does not change significantly even during long-term use, and it is possible to ensure high reliability in addition to high accuracy. 6.3 Another embodiment of the manufacturing process of the thermal flow meter 300

[0125] In Fig. 18 are already in accordance with Fig. 16 and the external contact 306 already manufactured by a process (not shown) are used, and the connection between the terminal contact 412 of the circuit package 400 and the inner socket of the external contact 361 is performed in a step 12 before the second resin molding process. At this time, or in a process before step 12, the separation of each of the inner sockets of the Fig. 10 is performed. In a step 13, the housing 302 is formed by the second resin molding process. The resin bypass groove, the flange 312, and the external terminal 305 are formed in the housing 302, which is shown in Fig. The hatched portion of the circuit package 400 shown in FIGS. 11(A) to 11(C) is covered with resin in the second resin molding process, and the circuit package 400 is fixed to the housing 302. The accuracy of air flow detection is greatly improved by combining the manufacturing (step 3) of the circuit package 400 according to the first resin molding process and the molding of the housing 302 of the thermal flow meter 300 by the second resin molding process.

[0126] The housing 302 is obtained in step 13. Then, in step 8, the front and rear covers 303 and 304 are installed in the housing 302, so that the interior of the housing 302 is sealed with the front and rear covers 303 and 304, and the bypass passage for flowing the measurement target gas 30 is obtained. In addition, an opening structure described with reference to Fig. 7(A) and Fig. 7(B), the projection 356 is formed in the front or rear cover 303 or 304. Note that the front cover 303 is formed by the molding in a step 10, and the rear cover 304 is formed by the molding in a step 11. In addition, the front and rear covers 303 and 304 are formed in different processes with different molds.

[0127] In step 9, a feature test is performed by actually introducing air into the bypass line. Since the relationship between the bypass line and the airflow detection section is maintained with high accuracy as described above, particularly high measurement accuracy is achieved by performing feature calibration through a feature test. Furthermore, since molding is determined with a positional or configurational relationship between the bypass line and the airflow detection section in the first resin molding process and the second resin molding process, the feature does not change significantly even during long-term use, and high reliability is achieved in addition to high accuracy. 7. Circuit configuration of the thermal flow meter 3007.1 Overall circuit configuration of the thermal flow meter 300

[0128] Fig. Fig. 19 is a circuit diagram illustrating the flow rate detection circuit 601 of the thermal flow meter 300. It should be noted that the measuring circuit associated with the temperature detection section 452 described in the aforementioned embodiment is also provided in the thermal flow meter 300, but is intentionally not included in Fig. 19. The flow rate detection circuit 601 of the thermal flow meter 300 includes the air flow detection section 602 with the heat generator 608 and the processing unit 604. The processing unit 604 controls a heat amount of the heat generator 608 of the air flow detection section 602 and outputs a signal representing the flow rate through the contact 662 based on the output of the air flow detection section 602. For this processing, the processing unit 604 includes a central processing unit (hereinafter referred to as "CPU") 612, an input circuit 614, an output circuit 616, a memory 618 for storing data representing a relationship between the calibration value or the measured value and the flow rate, and a power supply circuit 622 for providing a specific voltage to each required circuit.The voltage supply circuit 622 is supplied with DC voltage from an external voltage supply, such as a battery installed in the vehicle, via a contact 664 and a ground contact (not shown).

[0129] The air flow detection section 602 includes a heat generator 608 for heating the measurement target gas 30. A voltage V1 is supplied from the power supply circuit 622 to a collector of a transistor 606 included in a power supply circuit of the heat generator 608, and a control signal is applied from the CPU 612 through the output circuit 616 to a base of the transistor 606. Based on this control signal, a current is transmitted from the transistor 606 to the heat generator 608 via the contact 624. The amount of current supplied to the heat generator 608 is controlled by a control signal applied from the CPU 612 to the transistor 606 of the power supply circuit of the heat generator 608 via the output circuit 616.The processing unit 604 controls the heat amount of the heat generator 608 so that a temperature of the measurement target gas 30 increases by a predetermined temperature, for example, by 100 °C from an initial temperature using the heat generator 608.

[0130] The airflow detection section 602 includes a heater control bridge 640 for controlling a heat quantity of the heat generator 608 and an airflow detection bridge circuit 650 for measuring a flow rate. A predetermined voltage V3 is connected from the power supply circuit 622 to one end of the heater control bridge 640 via contact 626, and the other end of the heater control bridge 640 is connected to the ground contact 630. In addition, a predetermined voltage V2 is connected from the power supply circuit 622 to one end of the airflow detection bridge circuit 650 via contact 625, and the other end of the airflow detection bridge circuit 650 is connected to the ground contact 630.

[0131] The heating control bridge 640 includes a resistor 642, which is a resistance temperature sensor with a resistance value that changes depending on the temperature of the heated measurement target gas 30. The resistors 642, 644, 646, and 648 form a bridge circuit. A potential difference between a node A between resistors 642 and 646 and a node B between resistors 644 and 648 is input to the input circuit 614 via contacts 627 and 628, and the CPU 612 controls the current supplied by the transistor 606 for controlling the heat quantity of the heat generator 608 so that the potential difference between nodes A and B is set to a predetermined value, for example, zero volts in this embodiment. The Fig. The flow detection circuit 601 shown in Fig. 19 heats the measurement target gas 30 with the heat generator 608 so that a temperature rises by a predetermined temperature, for example, always by 100°C from an initial temperature of the measurement target gas 30. In order to perform this heating control with high accuracy, resistance values of each resistor of the heating control bridge 640 are set so that the potential difference between nodes A and B decreases to zero when the temperature of the measurement target gas 30 heated by the heat generator 608 rises by a predetermined temperature, for example, always by 100°C from an initial temperature. Thus, the CPU 612 in the flow detection circuit 601 controls Fig. 19 the electric current provided by the heat generator 608 so that the potential difference between nodes A and B drops to zero.

[0132] The bridge circuit of the air flow detection 650 includes four resistance temperature sensors 652, 654, 656, and 658. The four resistance temperature sensors are arranged along the flow of the measurement target gas 30 such that the resistors 652 and 654 are arranged upstream of the heat generator 608 in the flow path of the measurement target gas 30, and the resistors 656 and 658 are arranged downstream of the heat generator 608 in the flow path of the measurement target gas 30. In addition, to increase measurement accuracy, the resistors 652 and 654 are arranged so that the distances to the heat generator 608 are approximately equal, and the resistors 656 and 658 are arranged so that the distances to the heat generator 608 are approximately equal.

[0133] A potential difference between a node C between resistors 652 and 656 and a node D between resistors 654 and 658 is input to the input circuit 614 through contacts 631 and 632. To increase measurement accuracy, each resistor of the bridge circuit of the air flow detector 650 is set, for example, so that a positional difference between nodes C and D is set to zero when the flow of the measurement target gas 30 is set to zero. Thus, while the potential difference between nodes C and D is set to zero, for example, the CPU 612 outputs an electrical signal indicating that the flow rate of the main line 124 is zero via contact 662 based on the measurement result that the flow rate of the measurement target gas 30 is zero.

[0134] If the target gas is 30 in Fig. 19 flows in the direction of the arrow, the upstream resistor 652 or 654 is cooled by the measurement target gas 30, and the resistors 656 and 658 arranged downstream in the measurement target gas 30 are heated by the measurement target gas 30 heated by the heat generator 608, so that the temperature of the resistors 656 and 658 rises. For this reason, a potential difference is generated between the nodes C and D of the bridge circuit of the air flow detection 650, and this potential difference is input to the input circuit 614 via the contacts 631 and 632. The CPU 612 searches for data indicating a relationship between the flow rate in the main line 124 and the aforementioned potential difference stored in the memory 618 based on the potential difference between nodes C and D of the bridge circuit of the air flow detection 650 to obtain the flow rate of the main line 124.An electrical signal indicating the flow rate of the main line 124 thus obtained is output via contact 662. It is noted that the value shown in . Fig. 19, although designated by new reference numbers, in the terminal contact 412 described above from Fig. 5(A), Fig. 5(B), Fig. 6(A), Fig. 6(B) or Fig. 10 are included.

[0135] The memory 618 stores the data indicating a relationship between the potential difference between nodes C and D and the flow rate in the main line 124, as well as calibration data for reducing a measurement error, such as a deviation, obtained based on the actual measured value of the gas after the manufacture of the circuit package 400. It is noted that the actual measured value of the gas after the manufacture of the circuit package 400 and the calibration value based thereon using the external contact 306 or the calibration contact 307, illustrated in Fig. 4(A) and Fig. 4(B), stored in the memory 618. In this embodiment, the circuit package 400 is manufactured while maintaining a high-accuracy, low-variance arrangement relationship between the bypass passage for flowing the measurement target gas 30 and the measurement surface 430, or a high-accuracy arrangement relationship between the bypass passage for flowing the measurement target gas 30 and the heat transfer surface 436 exposed portion. Thus, it is possible to obtain a measurement result with remarkably high accuracy by calibrating with the calibration value. 7.2 Configuration of the flow rate detection circuit 601

[0136] Fig. 20 is a circuit configuration diagram showing a circuit arrangement of the above-described flow rate detection circuit 601 of Fig. 19. The flow detection circuit 601 is made of a semiconductor chip with a rectangular shape. The measurement target gas 30 flows along the arrow direction from the left side to the right side of the Fig. 20 illustrated flow detection circuit 601.

[0137] A rectangular diaphragm 672 is formed in the airflow detection section 602, and the diaphragm 672 is provided with a thin region 603 obtained by reducing a thickness of the semiconductor chip and shown by a dashed line. The thin region 603 is formed in a gap on its rear side, which gap is in contact with the Fig. 11 and Fig. 5, and the air pressure in the gap depends on the air pressure delivered from the opening 438.

[0138] The thin portion 603 of the diaphragm 672 has reduced thermal conductivity by reducing the thickness, and heat transfer through the diaphragm 672 to the resistor 652 and resistor 654 provided in the thin portion 603 and resistor 658 and 656 is suppressed, and the temperatures of the resistors are approximately fixed by heat transfer with the measurement target gas 30.

[0139] The heat generator 608 is provided in the center of the thin portion 603 of the diaphragm 672, and the resistor 642 of the heater control bridge 640 is provided around the heat generator 608. Additionally, resistors 644, 646, and 648 of the heater control bridge 640 are provided on the outside of the thin portion 603. The resistors 642, 644, 646, and 648 thus formed constitute the heater control bridge 640.

[0140] In addition, resistors 652 and 654 are arranged as upstream resistance temperature sensors, and resistors 656 and 658 are arranged as downstream resistance temperature sensors to be connected between the heat generator 608. The resistors 652 and 654 as upstream resistance temperature sensors are arranged on the upstream side of the heat generator 608 in the direction of the arrow in which the measurement target gas 30 flows. The resistors 656 and 658 as downstream resistance temperature sensors are arranged on the downstream side of the heat generator 608 in the direction of the arrow in which the measurement target gas 30 flows. In this way, the bridge circuit of the air flow detection 650 is formed by the resistors 652, 654, 656, and 658 in the thin region 603.

[0141] Both ends of the heat generator 608 are connected to each of the lower half of Fig. 20 illustrated contacts 624 and 629 are connected. As in Fig. 19, the current applied by transistor 606 to heat generator 608 is applied to contact 624 and contact 629 is grounded.

[0142] The resistors 642, 644, 646 and 648 of the heating control bridge 640 are connected to each other and are also connected to the contacts 626 and 630. As in Fig. As illustrated in Figure 19, contact 626 is supplied with a predetermined voltage V3 from voltage supply circuit 622, and contact 630 is grounded. In addition, the node between resistors 642 and 646 and the node between resistors 646 and 648 are connected to contact 627 and 628, respectively. As shown in Fig. 20, contact 627 outputs an electrical potential of node A between resistors 642 and 646, and contact 627 outputs an electrical potential of node B between resistors 644 and 648. As shown in Fig. As illustrated in Figure 19, contact 625 is supplied with a predetermined voltage V2 from voltage supply circuit 622, and contact 630 is grounded. Additionally, a node between resistors 654 and 658 is connected to contact 631, and contact 631 outputs an electrical potential of node B. Fig. 19. The node between resistors 652 and 656 is connected to contact 632, and contact 632 outputs an electrical potential of node C, as shown in Fig. 19 illustrates.

[0143] Since the resistor 642 of the heating control bridge 640, as in Fig. 20, is formed near the heat generator 608, it is possible to measure the temperature of the gas heated by the heat from the heat generator 608 with high accuracy. Meanwhile, since the resistors 644, 646, and 648 of the heater control bridge 640 are arranged away from the heat generator 608, they are not easily affected by the heat generated by the heat generator 608. The resistor 642 is configured to be sensitive to the temperature of the gas heated by the heat generator 608, and the resistors 644, 646, and 648 are configured not to be affected by the heat generator 608. For this reason, the detection accuracy of the measurement target gas 30 using the heater control bridge 640 is high, and the control for heating the measurement target gas 30 by only a predetermined temperature from its original temperature can be performed with high accuracy.

[0144] In this embodiment, a gap is formed in the rear surface of the diaphragm 672 and communicates with the opening 438 formed in Fig. 11(A) to 11(C) or 5(A) and 5(B), so that a difference between the pressure of the gap on the back side of the diaphragm 672 and the pressure at the front side of the diaphragm 672 does not increase. It is possible to suppress distortion of the diaphragm 672 caused by this pressure difference. This contributes to improving the measurement accuracy of the flow rate.

[0145] As mentioned above, the diaphragm 672 forms the thin portion 603, making the thickness of the thin portion 603 very thin, and heat transfer through the diaphragm 672 is suppressed as much as possible. Thus, in the air flow detection bridge circuit 650 and the heating control bridge 640, the influence of heat transfer through the diaphragm 672 is suppressed, and they are more likely to trigger depending on the temperature of the measurement target gas 30, and the measurement movement is improved. As a result, high measurement accuracy is achieved. 8. Measurement of gas temperature in thermal flowmeter 3008.1 Structure of temperature detection section 452 in thermal flowmeter 300

[0146] In Fig. 2 and Fig. 3, the bypass line is provided on the middle side of the main line 124, on the leading end side of the measuring section 310. A suction port 343, which is open to an upstream side of the flow of the measurement target gas 30, is formed on the side of the flange 312, narrower than that shown in Fig. 2(A). A temperature detecting portion 452 for measuring the temperature of the measurement target gas 30 is disposed in an inner portion of the intake port 343 so as to protrude from the inner portion of the casing 302. In the central portion of the measuring portion 310 provided with the intake port 343, an upstream outer wall of the measuring portion 310 constituting the casing is pressed downstream, that is, against the inner side of the casing 302, and the temperature detecting portion 452 is formed in a shape such that the temperature detecting portion protrudes from the casing 302 from the upstream outer wall of the cavity toward the upstream side.Further, the front cover 303 and the rear cover 304 are provided on both lateral portions of the outer wall of the cavity and are formed in a shape such that the upstream end portions of the front cover 303 and the rear cover 304 protrude upstream from the outer wall of the cavity. As a result, the inlet port 343 for introducing the measurement target gas 30 is formed through the outer wall of the cavity and the front cover 303 and the rear cover 304 on both sides thereof. The measurement target gas 30 taken out from the suction port 343 has its temperature measured by the temperature detection portion 452 based on contact with the temperature detection portion 452 provided in the inner portion of the suction port 343.Further, the measurement target gas 30 flows along the portion supporting the temperature detecting portion 452 protruding upstream from the outer wall of the housing 302 formed in the cavity, and the front outlet port 344 and the rear outlet port 345 provided in the front cover 303 and the rear cover 304 are discharged into the main line 124. 8.2 Functions and effects of the temperature detection section 452

[0147] As in Fig. 2 and Fig. 3, since the temperature detecting portion 452 is structured to protrude outward from the casing 302 and directly contact the measurement target gas 30, the detection accuracy is improved. Furthermore, the temperature of the gas flowing into the inlet port 343 from the upstream side in the direction along the flow of the measurement target gas 30 is measured by the temperature detecting portion 452, and the gas flows to the neck portion of the temperature detecting portion 452, which is the portion supporting the temperature detecting portion 452, thereby acting to cool the temperature of the portion supporting the temperature detecting portion 452 closer to the temperature of the measurement target gas 30.There is a risk that the temperature of the intake pipe corresponding to the main line 124 normally becomes high, and heat is transferred to the portion supporting the temperature detection section 452 from the flange 312 or the heat insulator 313 through the upstream outer wall within the measuring section 310, affecting the accuracy of temperature measurement. As mentioned above, since the measurement target gas 30 is measured by the temperature detection section 452 and then flows along the portion supporting the temperature detection section 452, the supporting section is cooled. Thus, it is possible to prevent heat from being transferred from the flange 312 or the heat insulator 315 through the upstream outer wall within the measuring section 310 to the portion supporting the temperature detection section 452.

[0148] In particular, since the upstream outer wall within the measuring section 310 is formed in such a way that the upstream outer wall is concave toward the downstream side in the support portion of the temperature detection section 452, it is possible to lengthen the distance between the upstream outer wall within the measuring section 310 and the temperature detection section 452. The heat transfer distance thereby becomes longer, and the cooling section by the measurement target gas 30 becomes longer. Thus, it is possible to reduce the heat influence from the flange 312 or the heat insulator 315. Accordingly, the measurement accuracy is improved.

[0149] Since the upstream outer wall is formed in such a way that the upstream outer wall is concave toward the downstream side, that is, toward the inner portion of the housing 302, it is possible to fix it with the outer wall 335 of the housing 302, and it is easy to fix the circuit package 400. Furthermore, it is possible to reinforce the projection 424 (see Fig. 11(A) to 11(C)), which has the temperature detecting section 452.

[0150] As previously by Fig. 2 and Fig. 3, the inlet port 343 is provided on the upstream side of the measurement target gas 30 in the housing 301, and the measurement target gas 30 guided from the inlet port 343 is guided from the front outlet port 344 and the rear outlet port 345 through the periphery of the temperature detecting section 452 to the main pipe 124. The temperature of the measurement target gas 30 is measured by the temperature detecting section 452, and the electrical signal indicative of the measured temperature is output from the external contact 306 included in the external terminal 305. The housing 301 included in the thermal flow meter 300 is provided with the front cover 303 and the rear cover 304 and the housing 302, the housing 302 has the cavity for forming the inlet port 343, and the cavity is formed by the hollowed outer wall portion 366 (see Fig. 5 and Fig. 6). Further, the front exhaust port 344 and the rear exhaust port 345 are formed through the holes provided in the front cover 303 and the rear cover 304. As described next, the temperature sensing portion 452 is provided in the leading end portion of the projection 424 and is mechanically weak. The front cover 303 and the rear cover 304 serve to protect the projection 424 from mechanical shock.

[0151] Further, a front protection portion 322 and a rear protection portion 325 are formed in the front cover 303 and 304, shown in Fig. 8 and Fig. 9. As in Fig. 2 or Fig. 3, the front protecting portion 322 provided in the front cover 303 is disposed on a front surface of the intake port 343, and a rear protecting portion 325 provided in the rear cover 304 is disposed on a rear surface of the intake port 343. The temperature detecting portion 452 disposed in the inner portion of the intake port 343 is protected by the front protecting portion 322 and the rear protecting portion 325, and it is possible to prevent mechanical damage to the temperature detecting portion 452 due to collision of the temperature detecting portion 452 with an object during manufacturing or when mounted on the vehicle.

[0152] Furthermore, a cooling effect is increased, as in Fig. 11 and Fig. 15, the neck portion of the protrusion 424 supporting the temperature detecting portion 452 gradually thickens in its neck portion relative to the leading end, and the measurement target gas 30 entering from the intake port 343 flows along the gradually thickened neck portion. The neck portion of the protrusion 424 is close to the airflow detecting circuit and is likely to be affected by heat generation from the airflow detecting circuit. Further, the conductor 548 for connecting the temperature detecting element 518 provided in the temperature detecting portion 452 is buried in the neck portion of the protrusion 424. As a result, there is a possibility that heat is transferred via the conductor 548. The cooling effect can be increased by thickening the neck portion of the protrusion 424 to increase the contact area with the measurement target gas 30. 8.3 Formation and action of the temperature sensing section 452 and the projection 424

[0153] The circuit package 400 includes the circuit package main body 422, which includes the air flow detection section 602 and the processing unit 604, which are provided for measuring the air flow and are mentioned below, and the projection 424. As shown in Fig. 2(A) and Fig. As shown in Figure 2(B), the protrusion 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. The temperature detection portion 452 is provided in the leading end portion of the protrusion 424, and the temperature detection element 518 is buried in the inner portion of the temperature detection portion 452, as shown in Figure 2(B). Fig. 12. The slope portions 462 and 464 are provided in the connected portion between the projection 424 and the circuit package main body 422, as shown in Fig. 11 and Fig. 15. The root of the protrusion 424 is thickened by the slope portion 462 or the slope portion 464, and the shape that gradually thins toward the leading end is formed in the neck portion of the protrusion 424. A cross-sectional area that intersects the axis with respect to the axis in the protruding direction has a shape that tapers toward the leading end in the neck portion of the protrusion 424. As mentioned above, in the shape in which the circuit package 400 partially protrudes, since the protrusion 424 is weak in mechanical strength, the stress concentration at the root can be reduced and the mechanical strength can be improved by thickening the root of the protrusion 424 and forming it in the shape that gradually narrows toward the leading end.Furthermore, in the case where the protrusion 424 is formed by resin molding, warpage tends to occur due to the volume change upon resin solidification. It is possible to reduce the influence of the above-mentioned problem by thickening the root. Furthermore, it is desirable to lengthen the protrusion length in order to detect the temperature of the measurement target gas 30 as accurately as possible. It is possible to lengthen the protrusion length of the protrusion 424 by thickening the root, and the detection accuracy of the temperature detection element 518 provided in the temperature detection section 452 is improved.

[0154] The circuit package 400 is fixed to the housing 302 such that the root of the projection 424 is thickened and the root of the projection 424 is surrounded by the resin of the housing 302, as shown in Fig. 11(B) and Fig. 11(C). It is possible to prevent the protrusion 424 from breaking off due to mechanical impact by covering the root of the protrusion 424 with the resin of the housing 302 as mentioned above.

[0155] In order to detect the temperature of the measurement target gas 30 with high accuracy, it is desirable to structure it so that heat conduction transmitted from the main pipe 124, to which the thermal flow meter 300 is attached, via the housing 302 or the circuit package 400 is suppressed as much as possible. The protrusion 424 supporting the temperature detecting portion 452 is formed in a shape such that the leading end portion is narrower than the root and is provided with the temperature detecting portion 452 in its leading end portion. According to the above-mentioned shape, the thermal influence exerted by the neck portion of the protrusion 424 on the temperature detecting portion 452 can be reduced.

[0156] Furthermore, after the temperature of the measurement target gas 30 is detected by the temperature detection section 452, the measurement target gas 30 flows along the protrusion 424 and serves to bring the temperature of the protrusion 424 closer to the temperature of the measurement target gas 30. As a result, the influence of the temperature of the neck portion of the protrusion 424 on the temperature detection section 452 is suppressed. Specifically, in the embodiment, the proximity of the protrusion 424 to the temperature detection section 452 is narrow, and the protrusion 424 thickens toward the root. As a result, the measurement target gas 30 flows along the shape of the protrusion 424 and efficiently cools the protrusion 424.

[0157] In Fig. In FIGS. 11(A) to 11(C), the hatched portion in the neck portion of the protrusion 424 is the mounting surface 432 covered with the resin that forms the housing 302 in the second resin molding process. The hollow portion is provided in the hatched portion of the neck portion of the protrusion 424. This means that the hollow portion is provided that is not covered by the resin of the housing 302. The protrusion 424 is further easily cooled by the measurement target gas 30 by forming the hollow portion that is not covered with the resin of the housing 302 in the neck portion of the protrusion 424. Fig. 15(A) and Fig. 15(B), the illustration of the hatched portion is omitted, but it is the same as in Fig. 11(A) to 11(C)

[0158] The terminal contact 412 is provided in the circuit package 400 to supply electric power for actuating the built-in airflow sensing section 602 and the processing unit 604, and to output the measured airflow value and the measured temperature value. Furthermore, the contact 414 is provided for checking whether the circuit package 400 is properly activated and whether an abnormality has been generated in the circuit parts and their connection. In the embodiment, the circuit package 400 is formed by transfer molding the airflow sensing section 602 and the processing unit 604 in the first resin molding process using the thermosetting resin.It is possible to further improve the dimensional accuracy of the circuit package 400 by transfer molding. However, since the transfer molding process forces the pressurized hot resin into the inner portion of the hermetically sealed mold incorporating the air flow sensing portion 602 and the processing unit 604, it is desirable to test whether damage occurs in the air flow sensing portion 602 and the processing unit 604 and their wiring relationship relative to the finished circuit package 400. In the embodiment, the contact 414 for testing is provided, and the test is performed on each of the manufactured circuit packages 400. Since the contact 414 for testing is not used for measurement, the contact 414 is not connected to the inner socket of the external contact 361, as mentioned above.A curved portion 416 is provided in each of the terminal contacts 412 to increase a mechanical elastic force. By applying the mechanical elastic force to each of the terminal contacts 412, it is possible to absorb the stress caused by the difference between the thermal expansion coefficient in the resin of the first resin molding process and the resin of the second resin molding process. In other words, each of the terminal contacts 412 is affected by the thermal expansion due to the first resin molding process, and the inner socket of the external contact 361, which is connected to each of the terminal contacts 412, is affected by the resin in the second resin molding process. It is possible to absorb the occurrence of stress due to differences in the resin. 8.4 Function and effect of the inclined sections 462 and 464 formed in the neck section of the projection 424

[0159] As in Fig. 11 and Fig. As described in FIG. 15, the slope portions 462 and 464 are provided in the neck portion of the protrusion 424. The shape that thickens the root of the protrusion 424 by the slope portion 462 or the slope portion 464 and gradually narrows toward the leading end is formed in the neck portion of the protrusion 424. In other words, the shape in which a cross-sectional area intersecting an axis in the protruding direction is gradually reduced in the case where the protruding portion lies on the axis is provided in the neck portion of the protrusion 424.

[0160] Since the protrusion 424 is weak in mechanical strength, it is possible to improve the mechanical strength and reduce stress concentration at the root by thickening the root of the protrusion 424 and forming a shape that gradually narrows toward the leading end. Furthermore, in the case where the protrusion 424 is formed by resin molding, warpage tends to be generated due to the volume change upon resin solidification. It is possible to reduce the influence of this problem by thickening the root. Furthermore, it is desirable to lengthen the protrusion length in order to detect the temperature of the measurement target gas 30 as accurately as possible. It is possible to lengthen the protrusion length of the protrusion 424 by thickening the root, and the detection accuracy of the temperature detection element 518 provided in the temperature detection section 452 is improved.

[0161] The circuit package 400 is attached to the housing 302 such that the root of the projection 424 is thickened, as shown in Fig. 11(B) and Fig. 11(C), and the root of the protrusion 424 is surrounded by the resin of the housing 302. As mentioned above, it is possible to prevent the protrusion 424 from breaking off due to mechanical impact by covering the root of the protrusion 424 with the resin of the housing 302. 8.5 Other embodiment of the projection 424

[0162] Fig. 21(A) to 21(C) illustrate the other embodiment of the protrusion 424 of the circuit package 400, and the same reference numerals as those in the previously described drawings denote the same structures and have the same operations and effects. Therefore, their description will be omitted. The protrusion 424, which protrudes from the circuit package main body 422, has a protrusion 446 and a protrusion 447 on a smooth side and a back side. The protrusion 446 and the protrusion 447 have an effect even if only one is provided. Further, in the embodiment, the protrusion is formed individually on the smooth side and the back side, but a plurality of protrusions may be provided. Each of the protrusions has a neck portion 448 and a leading end portion 449, and is lower from the neck portion 448 to the leading end portion 449. As shown in Fig. As shown in FIGS. 11(A) to 11(C), the neck portion of the protrusion 424 is covered with the resin forming the housing 302. As a result, the neck portions 448 of the protrusion 445 and the protrusion 447 are covered with the resin together with the neck portion of the protrusion 424 in the second resin molding process.

[0163] The mechanical strength of the protrusion 424 is increased by providing the protrusion 447 and the neck portion 448. Furthermore, the cooling effect is enhanced because an area in contact with the measurement target gas 30 is increased. Furthermore, adhesion with the resin of the case 302, with which the circuit package 400 is fixed, is improved, and the circuit package is more firmly fixed to the case 302. Thus, reliability is improved. 8.6 Further embodiment of the projection 424

[0164] Fig. 22(A) and Fig. 22(B) are partially enlarged views of the projection 424 projecting from the package main body 422, Fig. 22(A) is a partially enlarged view of the Fig. 11(B) and Fig. 15(A) described front elevation, and Fig. 22(B) is a plan view. A slope portion 462 and a slope portion 464 shown in Fig. 22(A), bend in relation to the Fig. 11(B) and Fig. 15(A) and the inclination section 462 and the inclination section 464. In other words, the inclination section 462 and the inclination section 464 shown in Fig. 11(B) and Fig. 15(A), can be straight lines or curved lines. In either case, however, approximately the same effect can be achieved.

[0165] In Fig. 22(B), a leading end portion of the protrusion 424 is formed in a narrower shape relative to a thickness direction of the package main body 422. The same effect as the above-mentioned description about the slope portion 462 and the slope portion 464 can be achieved in the case where there is a difference between the thickness of the package main body 422 and the width of the temperature sensing portion 452 and the shape that gradually narrows in the thickness direction by providing the slope portions 466 and 468 as mentioned above.

[0166] The structure in Fig. 21(A) to 21(C) may lead to Fig. 22(A) and Fig. 22(B). According to this structure, the Fig. 21(A) to 21(C) described effect in the embodiment in Fig. 22(A) and Fig. 22(B). 8.7 Further embodiments of the projection 424

[0167] Fig. 23 to 25 represent further alternative versions. Fig. Fig. 23 is a view in which a circuit package 400 according to the other embodiment is fixed by the housing 302, and an alternative concept to the one shown in Fig. 5(A), Fig. 5(B), Fig. 6(A) or Fig. 6(B). Furthermore, Fig. 24(A) to 24(C) the other embodiment of the Fig. 11 and Fig. 15 described embodiment. Fig. 25 is the other embodiment of Fig. 12 and is a view showing a state in which the circuit parts corresponding to the other in Fig. 24 are mounted on a frame of a circuit package 400. In the embodiments in Fig. 23 to 25, the projection 424 protrudes from the package main body 422 of the circuit package 400 toward the center of the main line 124. The inlet port and the outlet port of the bypass line are formed on the middle side of the main line 124, which is the leading end side of the measuring section 310 of the housing 302. In Fig. 23, the inlet port is the rear side and does not appear in the drawing. An outlet groove 353 for forming the outlet port is provided on the leading end side of the measuring section 310. The measurement target gas 30 is introduced from the inlet port, which is shown in Fig. 23 is formed on the back side, a bypass passage (hereinafter referred to as a bypass passage measuring portion 435) connecting the inlet port and the outlet port is formed in a direction of the wall surface of the main passage 124, and the bypass passage measuring portion 435 is provided with a measuring surface 430 for measuring an air flow.

[0168] A hole 399 open to the main line 124 is provided between the bypass line measuring section 435 and the inlet and outlet sides, and a temperature detecting section 452 is disposed in the hole 399. As mentioned above, since the hole 399 is open to the main line 124 and the measurement target gas 30 flows through the hole 399, the temperature detecting section 452 provided in the circuit package is always exposed to the measurement target gas 30 flowing through the hole 399 and can measure the temperature of the measurement target gas flowing in the main line 124. The hole 399 differs in shape between its front and back sides, the pressure difference of the measurement target gas 30 is generated due to the shape difference between the front and back sides of the hole 399, and the gas always flows in one direction or the other in the hole 399 due to the pressure difference.

[0169] Fig. 24 represents an external manifestation of the Fig. 23. A circuit package 400 shown in Fig. 11(A) to 11(C) is that the protruding direction of the projection 424 is different from the package main body 422. Fig. 24(A) is a side elevation view from the left, Fig. 24 (B) is a front elevation view, and Fig. 24(C) is a rear elevational view. One side 472 of the package main body 422 extends as it is to form the protrusion 424, and a temperature sensing element 518 is held in an inner portion of a leading end portion of the protrusion 424. On the other hand, a gently inclined slope portion 463 is formed at the root of the other side of the protrusion 424.

[0170] The root of the protrusion 424 can be thickened by providing the slope portion 463 at the root of the protrusion 424 as mentioned above, and the shape that gradually narrows toward the leading end can be formed in the neck portion of the protrusion 424. Since the protrusion 424 is weak in mechanical strength, it is possible to reduce the stress concentration at the root, and it is possible to increase the mechanical strength by thickening the root of the protrusion 424 and forming the shape that gradually narrows toward the leading end. Furthermore, in the case where the protrusion 424 is formed by resin molding, there is a tendency for warpage to be generated due to the volume change upon resin solidification. It is possible to reduce the influence on the problem by thickening the root.Further, it is desirable to lengthen the protruding length in order to detect the temperature of the measurement target gas 30 as accurately as possible, it is possible to lengthen the protruding length of the protrusion 424 by thickening the root, and the detection accuracy of the temperature detecting element 518 provided in the temperature detecting section 452 is improved.

[0171] In Fig. 23, by thickening the root of the protrusion 424 and covering the root of the protrusion 424 with the resin of the case forming the bypass passage to surround the case 302, the protrusion 424 becomes more resistant to mechanical impact, and it is possible to prevent the protrusion 424 from being broken off. The hatched portion described in the external appearance of the circuit package 400 indicates the mounting surface 432, the mounting surface 433, and the mounting surface 434 on which the circuit package 400 is covered with the resin used in the second resin molding process when the case 302 is molded in the second resin molding process after the circuit package 400 is manufactured in the first resin molding process.In other words, the mechanical strength of the circuit package 400 is increased by these fixing surfaces, and it is possible to improve the mechanical strength of the root of the protrusion 424 particularly by the fixing surface 432. In addition, the fixing surfaces shown in FIG. Fig. 11(A) to 11(C).

[0172] The hatched section in Fig. 24 is a portion covered with the resin that forms the housing 302 in the second resin molding process, as shown in Fig.11(A) to 11(C). Mechanical reinforcement is obtained by covering the neck portion of the protrusion 424. Furthermore, since the portion of the fixing surface 432 is covered with the resin constituting the case 302 and the measuring surface 430 is covered on both sides while being sandwiched, the bypass line, the measuring surface 430, and the exposed portion of the heat transfer surface 436 are firmly fixed with high accuracy. Furthermore, since the fixing portion 433 is formed in the portion of the protrusion 426, it is possible to firmly fix the circuit package 400. Since the fixing portion 433 is provided at a position away from the fixing portion 432 and the fixing surface 434, and the direction of the length of the fixing portion corresponds to the direction in which the axes in the length directions intersect, it is easy to fix.On the other hand, it is possible to reduce the area with which the housing 302 covers the circuit package 400, and it is possible to reduce the stress due to the difference in thermal expansion. Industrial availability

[0173] The present invention is applicable as a measuring device for measuring a gas flow rate as mentioned above. List of reference symbols 300 thermal flow meter 302 housing 303 front cover 304 rear cover 305 external connection 306 external contact 307 Calibration contact 310 measuring section 320 contact connection 332 Bypass line channel on the front 334 Bypass line channel at the rear 356, 358 lead 359 Harz section 361 inner socket of the external contact 365 connecting section 372, 374 fastening section 400 circuit package 412 connection contact 414 Contact 422 Circuit package main body 424 lead 430 measuring surface 432, 434 mounting surface 436 exposed section of the heat transfer surface 438 Opening 452 Temperature detection section 590 pressed fitting hole 594, 596 incline section 601 Flow rate detection circuit 602 Air flow detection section 604 processing unit 608 Heat generator 640 Heating control bridge 650 Bridge circuit of air flow detection 672 Diaphragm

Claims

[1] Thermal flow meter comprising: a bypass line for receiving and flowing measurement target gas (30) flowing in a main line (124); a circuit package (400) having an air flow measuring circuit for measuring an air flow by performing heat transfer with respect to the measurement target gas (30) flowing in the bypass line, and having a temperature detecting section (452) that detects a temperature of the measurement target gas (30); and a housing (302) provided with an external contact (306) which outputs an electrical signal indicating the air flow and an electrical signal indicating the temperature of the measurement target gas (30) and carries the circuit package (400), wherein the circuit package (400) is constructed such that the air flow measuring circuit and the temperature detecting section (452) are bonded in resin, and the temperature detecting section (452) has a first projection (424) projecting from a circuit package main body (422), characterized by , that the first projection (424) is formed in a shape which is thicker at its root than at the leading end portion and whose neck portion gradually narrows towards the front end, wherein the circuit package main body (422) has two flat end surfaces and side surfaces formed on outer peripheries of the end surfaces and connecting the end surfaces, and is formed in a shape such that the first projection (424) projects from the side surfaces, wherein Connecting portions between the side surfaces and the first projection (424) construct the neck portion and are formed in a shape that narrows toward the leading edge between the mutually facing connecting portions. [2] A thermal flow meter according to claim 1, wherein the root of the first projection (424) is larger than its leading end portion in a vertical cross section of a protruding direction and has a shape in which the cross section gradually tapers toward the leading end portion of the first projection (424). [3] Thermal flow meter according to claim 1, wherein a second projection is formed projecting outwardly from an outer periphery of the first projection (424), and the second projection extends from the root of the first projection (424) to the leading end portion of the first projection (424). [4] A thermal flow meter according to claim 3, wherein the second projection in the neck portion (448) of the first projection (424) is covered with a resin of the housing (302). [5] Thermal flow meter according to claim 1, wherein the circuit package main body (422) is formed in a shape such that a thickness between the two end surfaces is thicker than the temperature detecting portion (452) of the first projection (424), and the thickness has a shape that gradually narrows towards the leading end section. [6] The thermal flow meter according to any one of claims 1 to 5, wherein the first projection (424) projecting from the circuit package main body (422) projects in an upstream direction of the flow of the measurement target gas (30) flowing in the main pipe (124). [7] A thermal flow meter according to any one of claims 1 to 5, wherein the first projection (424) projecting from the circuit package main body (422) projects in a direction of the bypass passage. [8] Thermal flow meter according to claim 7, wherein the bypass line has an inlet opening (343) and an outlet opening (352, 344, 345) on the middle side of the main line (124) and laterally to the wall surface of the main line (124), and provides a passage such that the inlet opening (343) and the outlet opening (352, 344, 345) are connected closer to a wall surface of the main line (124) than the inlet opening (343) and the outlet opening (352, 344, 345) without the passage, wherein a hole (399) open to the main line (124) is provided between the inlet opening (343) and the outlet opening (352, 344, 345), and the passage connects the inlet opening (343) and the outlet opening (352, 344, 345), and the first projection (424) projecting from the circuit package main body (422) projects toward the bypass line, and the temperature detecting portion (452) provided at the leading end portion of the first projection (424) is disposed in the hole (399) open to the main line (124). [9] A thermal flow meter according to any one of claims 1 to 8, wherein the first projection (424) projecting from the circuit package main body (422) is provided with a conductor in its inner portion, and the temperature detecting element is electrically connected to a leading end portion (449) of the conductor. [10] A thermal flow meter according to claim 9, wherein the first projection (424) has in its inner portion a first conductor to which the temperature detecting element is connected, a second conductor connected to an electrical circuit in the inner portion of the circuit package main body (422), and a lead wire provided between the first conductor and the second conductor and provided for electrically connecting the first conductor and the second conductor. [11] Thermal flow meter according to claim 6, further comprising: a housing which accommodates the circuit package (400) and has an external contact (306) for outputting an electrical signal indicative of an air flow and an electrical signal indicative of a gas temperature measured by the circuit package (400), wherein the circuit package main body (422) of the circuit package (400) is provided in the inner portion of the housing (302), and the first projection (424) provided in the circuit package (400) projects from the housing (302). [12] A thermal flow meter according to claim 6, wherein the circuit package main body (422) has, in its inner portion, a diaphragm (672) for measuring an air flow and a processing unit (604) for outputting the air flow, and the first projection (424) projects from the circuit package main body (422) in a direction intersecting a line connecting a position of the diaphragm (672) and a position of the processing unit (604). [13] The thermal flow meter according to claim 7, wherein the circuit package main body (422) has, in its inner portion, a diaphragm (672) for measuring an air flow and a processing unit (604) for outputting the air flow, and the first projection (424) projects from the circuit package main body (422) in a direction along a line connecting a position of the diaphragm (672) and a position of the processing unit (604).

Images