Physical quantity detecting device with a circuit board that has projections to repel water

Provided is a physical-quantity detecting device having high reliability by preventing water droplets from attaching to a diaphragm area. A physical-quantity detecting device according to the present invention includes: a circuit board having provided thereon at least one detecting unit that detects a physical quantity of gas to be measured that passes through a main passage and also having provided thereon a circuit unit that executes computational processing on the physical quantity detected by the detecting unit; and a housing accommodating the circuit board, wherein the physical-quantity detecting unit on the circuit board is constructed to be exposed to the main passage. Furthermore, convex projections are provided around a through hole directly communicating with the physical-quantity detecting unit implemented on the circuit board.

TECHNICAL FIELD

The present invention relates to a physical quantity measurement device for intake air in an internal combustion engine.

BACKGROUND ART

In PTL 1, in order to prevent a thin film diaphragm from being damaged due to boiling in a case where water drops are attached to the diaphragm serving as a sensing element in a thermal flowmeter, a convex structure made of a water repellent material is formed on an outer periphery of the thin film diaphragm.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

The invention disclosed in PTL 1 relates to a structure of the thermal flowmeter in which, in order to prevent the thin film diaphragm from being damaged by boiling in water drops attached to the diaphragm, the protrusion structure which is provided to be spaced from the outer periphery of the thin film diaphragm with a gap and is made of a water repellent material is provided on a surface of the thin film diaphragm, but it is very difficult to practically form a convex structure by using a water repellent material repelling water.

Regarding a method of forming a protrusion shape on a diaphragm surface of several mm, there may be a method using a process of printing and curing a resin paste, and a process of adhering a protrusion member (for example, a film-like sheet) formed in a convex shape in advance to a diaphragm surface, but product cost increases since an expensive water repellent material is used. A processing process is established by a special step and special equipment, and thus there is a disadvantage that product cost further increases.

In a case where water permeates into a diaphragm serving as a sensing portion of silicon semiconductor via a through-hole which is provided in a circuit board and is directly connected to the diaphragm, there is concern that the diaphragm is damaged by boiling in the water permeating into the diaphragm, and thus characteristics thereof are influenced.

Therefore, an object of the invention is to provide a physical quantity measurement device with high reliability by preventing water drops being attached to a diaphragm area.

Solution to Problem

In order to solve the problems, according to the present invention, there is provided a physical quantity measurement device including a circuit board that is provided with a measurement portion measuring a physical quantity of a gas to be measured passing through a main passage and a circuit portion performing a calculation process on the physical quantity measured by the measurement portion; and a housing in which the circuit board is stored, in which, in the circuit board, a physical quantity measurement portion mounted on a part of the circuit board and a part of the circuit board are exposed to a physical quantity measurement space, and, in which a plurality of projections which are individually electrically disconnected from a circuit wiring are provided on a part of the circuit board.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a physical quantity measurement device with high reliability by preventing water drops from being attached to a diaphragm area by repelling water drops. Objects, configurations, and effects other than those described above will become apparent through description of the following embodiments.

DESCRIPTION OF EMBODIMENTS

In the following description, the best mode for carrying out the invention (hereinafter, referred to as, an Example) solves various problems desired to be solved in an actual product, and, particularly solves various problems desired to be solved in a measurement device measuring a physical quantity of intake air in a vehicle, so as to achieve various effects. One of various problems solved by the following Examples is the content described in the section of Solution to Problem, and one of various effects achieved by the following Examples is the effect described in the section of Advantageous Effects of Invention. Problems solved by the following Examples and various effects achieved by the following Examples will be described in description of the following Examples. Therefore, the content of problems solved by Examples or effects, described in the following Examples, may be the content other than the content described in the section of Solution to Problem and the section of Advantageous Effects of Invention.

In the following Examples, the same reference numeral indicates the same constituent element throughout the drawings, and thus the same advantageous effect is achieved. A constituent element which has already been described is given only a reference numeral, and description thereof is omitted, in some cases.

1. One Example in which Physical Quantity Measurement Device According to the Present Invention is Used in Internal Combustion Engine Control System

FIG. 1is a system diagram illustrating one Example in which a physical quantity measurement device according to the present invention is used in an internal combustion engine control system of an electronic fuel injection type. Intake air which is sucked from an air cleaner122as a gas30to be measured is guided to a combustion chamber of an engine cylinder112via, for example, a main passage124such as an intake body, a throttle body126, an intake manifold128on the basis of an operation of an internal combustion engine110including the engine cylinder112and an engine piston114. A physical quantity of the gas30to be measured which is intake air guided to the combustion chamber is measured by a physical quantity measurement device300according to the present invention, and a fuel is supplied from a fuel injection valve152on the basis of the measured physical quantity, and is guided to the combustion chamber in a state of a mixed gas along with intake air20. In the present example, the fuel injection valve152is provided at an intake port of the internal combustion engine, a fuel injected into the intake port forms a mixed gas along with the gas30to be measured which is intake air, and is guided to the combustion chamber via an intake valve116so as to be burnt and to generate mechanical energy.

The fuel and the air guided to the combustion chamber are in a mixed state of the fuel and the air, and are explosively burnt due to spark ignition of an ignition plug154so as to generate mechanical energy. The burnt gas is guided to an exhaust tube via an exhaust valve118, and is exhausted to the outside of a vehicle from the exhaust tube as an exhaust gas24. A flow rate of the gas30to be measured which is intake air guided to the combustion chamber is controlled by a throttle valve132of which an opening degree changes on the basis of an operation on an accelerator pedal. A fuel supply amount is controlled on the basis of a flow rate of intake air guided to the combustion chamber, and a driver controls an opening degree of the throttle valve132so as to control a flow rate of intake air guided to the combustion chamber, and can thus control mechanical energy generated by the internal combustion engine.

1.1 Summary of Control of Internal Combustion Engine Control System

A physical quantity such as a flow rate, the temperature, humidity, or pressure of the gas30to be measured which is intake air taken in from the air cleaner122and flowing through the main passage124are measured by the physical quantity measurement device300, and an electric signal indicating the physical quantity of the intake air is input to a control device200from the physical quantity measurement device300. An output from a throttle angle sensor144measuring an opening degree of the throttle valve132is input to the control device200, and an output from a rotation angle sensor146is input to the control device200in order to measure a position or a state of the engine piston114, the intake valve116, or the exhaust valve118of the internal combustion engine, and a rotation speed of the internal combustion engine. An output from an oxygen sensor148is input to the control device200in order to measure a state of a mixture ratio between a fuel amount and an air amount on the basis of a state of the exhaust gas24.

The control device200calculates a fuel injection amount or an ignition timing on the basis of the physical quantity of the intake air which is an output from the physical quantity measurement device300, and the rotation speed of the internal combustion engine which is measured by using the output from the rotation angle sensor146. A fuel amount supplied from the fuel injection valve152and the ignition timing at which a fuel is ignited by the ignition plug154. A fuel supply amount or an ignition timing is actually finely controlled on the basis of a temperature or a change state of a throttle angle measured by the physical quantity measurement device300, a change state of an engine rotation speed, and a state of a fuel air ratio measured by the oxygen sensor148. The control device200controls an amount of air bypassing the throttle valve132with an idle air control valve156in an idle operation state of the internal combustion engine, and controls a rotation speed of the internal combustion engine in the idle operation state.

1.2 Importance of Improvement of Measurement Accuracy in Physical Quantity Measurement Device and Mounting Environment of Physical Quantity Measurement Device

Both of a fuel supply amount and an ignition timing which are primary control amounts of the internal combustion engine are calculated by using outputs from the physical quantity measurement device300as main parameters. Therefore, improvement of measurement accuracy in the physical quantity measurement device300, suppression of a change over time, and improvement of reliability are important in improvement of control accuracy of a vehicle or ensuring of reliability thereof.

Particularly, in recent years, the demand for fuel saving of vehicles is very high, and the demand for purification of exhaust gas is very high. In order to cope with these demands, it is considerably important to improve measurement accuracy of a physical quantity of the intake air20measured by the physical quantity measurement device300. It is also important for the physical quantity measurement device300to maintain high reliability.

A vehicle on which the physical quantity measurement device300is mounted is used in an environment in which a change in a temperature or humidity is great. It is desirable in the physical quantity measurement device300that coping with a change in a temperature or humidity in the usage environment, or coping with dust or contaminants is also taken into consideration.

The physical quantity measurement device300is attached to the intake tube influenced by heat generated from the internal combustion engine. Thus, heat generated from the internal combustion engine is delivered to the physical quantity measurement device300via the intake tube which is the main passage124. The physical quantity measurement device300performs heat transfer with a gas to be measured so as to measure a flow rate of the gas to be measured, and thus it is important to suppress the influence of heat from the outside as much as possible.

The physical quantity measurement device300mounted on a vehicle solves the problem described in the section of Solution to Problem and achieves the effect described in the section of Advantageous Effects of Invention, and also solves various problems desired to be solved in a product so as to achieve various effects as described below by taking into sufficient consideration of the above-described various problems. Specific problems solved or specific effects achieved by the physical quantity measurement device300will be described in the following Examples.

2. Configuration of Physical Quantity Measurement Device300

2.1 Exterior Structure of Physical Quantity Measurement Device300

FIGS. 2-1 to 2-6are diagrams illustrating an exterior of the physical quantity measurement device300, in whichFIG. 2-1is a front view of the physical quantity measurement device300,FIG. 2-2is a rear view thereof,FIG. 2-3is a left side view thereof,FIG. 2-4is a right side view thereof,FIG. 2-5is a plan view thereof, andFIG. 2-6is a bottom view thereof.

The physical quantity measurement device300includes a housing302, a front cover303, and a rear cover304. The housing302is formed by molding a synthetic resin material, and includes a flange311which fixes the physical quantity measurement device300to the intake body which is the main passage124, an external connection portion321having a connector protruding from the flange311and used for electrical connection to an external apparatus, and a measurement portion331extending to protrude toward the center of the main passage124from the flange311.

A circuit board400is integrally provided with the measurement portion331through insert molding when the housing302is formed through molding (refer toFIGS. 3-1 and 3-2). The circuit board400is provided with at least one measurement portion measuring a physical quantity of the gas30to be measured flowing through the main passage124, and a circuit portion processing a signal measured by the measurement portion. The measurement portion is disposed at a position exposed to the gas30to be measured, and the circuit portion is disposed in a circuit chamber sealed with the front cover303.

A subsidiary passage is provided between a front surface and a rear surface of the measurement portion331, and a first subsidiary passage305is formed through cooperation with the front cover303and the rear cover304. A distal end part of the measurement portion331is provided with a first subsidiary passage inlet305afor incorporating a part of the gas30to be measured such as intake air into the first subsidiary passage305, and a first subsidiary passage outlet305bfor returning the gas30to be measured to the main passage124from the first subsidiary passage305. A part of the circuit board400protrudes in the middle of the first subsidiary passage305, and a flow rate measurement portion602(refer toFIG. 3-1) which is the measurement portion is disposed in the protruding portion so as to measure a flow rate of the gas30to be measured.

A second subsidiary passage306for incorporating a part of the gas30to be measured such as intake air into a sensor chamber Rs is provided in an intermediate part of the measurement portion331located further toward the flange311than the first subsidiary passage305. The second subsidiary passage306is formed through cooperation with the measurement portion331and the rear cover304. The second subsidiary passage306has a second subsidiary passage inlet306awhich is open in an upstream side outer wall336in order to incorporate the gas30to be measured, and a second subsidiary passage outlet306bwhich is open in a downstream side outer wall338in order to return the gas30to be measured to the main passage124from the second subsidiary passage306. The second subsidiary passage306communicates with the sensor chamber Rs formed on the back surface side of the measurement portion331. A pressure sensor and a humidity sensor which are measurement portions provided on a rear surface of the circuit board400are provided in the sensor chamber Rs.

2.2 Effects Based on Exterior Structure of Physical Quantity Measurement Device300

In the physical quantity measurement device300, the second subsidiary passage inlet306ais provided in the intermediate part of the measurement portion331extending toward the center of the main passage124from the flange311, and the first subsidiary passage inlet305ais provided in the distal end part of the measurement portion331. Therefore, a gas in a portion close to the central portion of the main passage124separated from an inner wall surface instead of the vicinity of the inner wall surface can be incorporated into the first subsidiary passage305and the second subsidiary passage306. Therefore, the physical quantity measurement device300can measure a physical quantity of a gas in the portion separated from the inner wall surface of the main passage124, and can thus reduce a measurement error of a physical quantity due to heat or a flow velocity reduction near the inner wall surface.

The measurement portion331has a long shape extending along an axis from an outer wall of the main passage124toward the center, but has a narrow shape since a thickness width is small as illustrated inFIGS. 2-3 and 2-4. In other words, the measurement portion331of the physical quantity measurement device300has a substantially rectangular shape in a front view since a width of a side surface thereof is small. Consequently, the physical quantity measurement device300can be provided with the sufficiently long first subsidiary passage305, and can thus reduce fluid resistance to a small value with respect to the gas30to be measured. Thus, the physical quantity measurement device300can measure a flow rate of the gas30to be measured with high accuracy while reducing fluid resistance to a small value.

2.3 Structure and Effect of Flange311

A plurality of depressions313are provided on a lower surface312facing the main passage124in the flange311, and thus reduce a heat transfer surface with the main passage124, so that the physical quantity measurement device300is hardly influenced by heat. In the physical quantity measurement device300, the measurement portion331is inserted into the main passage124through an attachment hole provided in the main passage124, and thus the lower surface312of the flange311faces the main passage124. The main passage124is, for example, the intake body, and the main passage124is often maintained at a high temperature. In contrast, the temperature of the main passage124may be considerably low at the time of starting in a cold district. If a high temperature or low temperature state of the main passage124influences measurement of various physical quantities, measurement accuracy deteriorates. The flange311has the depressions313on the lower surface312, and a space is formed between the lower surface312facing the main passage124, and the main passage124. Therefore, heat transfer from the main passage124to the physical quantity measurement device300can be reduced, and thus deterioration in measurement accuracy due to heat can be prevented.

Screw holes314of the flange311are used to fix the physical quantity measurement device300to the main passage124, and a space is formed between a surface facing the main passage124around each of the screw holes314and the main passage124such that the surface facing the main passage124around each of the screw holes314is separated from the main passage124. In the above-described way, a structure is provided in which heat transfer from the main passage124to the physical quantity measurement device300can be reduced, and thus deterioration in measurement accuracy due to heat can be prevented.

2.4 Structure of External Connection Portion321

The external connection portion321has a connector322which is provided on an upper surface of the flange311, and protrudes toward a downstream side of the flow direction of the gas30to be measured from the flange311. The connector322is provided with an insertion hole322ainto which a communication cable for connection to the control device200is inserted. As illustrated inFIG. 2-4, four external terminals323are provided in the insertion hole322a. The external terminals323are terminals for outputting information regarding a physical quantity which is a measurement result in the physical quantity measurement device300and power supply terminals for supplying DC power for operating the physical quantity measurement device300.

The connector322has a shape which protrudes the downstream side in the flow direction of the gas30to be measured from the flange311and is inserted from the downstream side toward the upstream side in the flow direction, but is not limited to this shape, and may have, for example, a shape which protrudes vertically from the upper surface of the flange311and is inserted in an extending direction of the measurement portion331, and may cover various modifications.

3. Entire Structure and Effects of Housing302

3.1 Entire Structure of Housing302

Next, the entire structure of the housing302will be described with reference toFIGS. 3-1 to 3-5.FIGS. 3-1 to 3-5are diagrams illustrating a state of the housing302in which the front cover303and the rear cover304are detached from the physical quantity measurement device300, in whichFIG. 3-1is a front view of the housing302,FIG. 3-2is a rear view of the housing302,FIG. 3-3is a right side view of the housing302,FIG. 3-4is a left side view of the housing302, andFIG. 3-5is a sectional view taken along the line A-A inFIG. 3-1.

The housing302has a structure in which the measurement portion331extends toward the center of the main passage124from the flange311. The circuit board400is formed on a basal end side of the measurement portion331through insert molding. The circuit board400is disposed in parallel along and to the surfaces of the measurement portion331at an intermediate position between the front surface and the rear surface of the measurement portion331, and is integrally molded into the housing302, so as to divide the basal end side of the measurement portion331into one side and the other side in a thickness direction.

A circuit chamber Rc in which the circuit portion of the circuit board400is stored is formed on the front surface side of the measurement portion331, and the sensor chamber Rs in which a pressure sensor421and a humidity sensor422are stored is formed on the rear surface side thereof. The circuit chamber Rc is closed by attaching the front cover303to the housing302, and is completely isolated from the outside. On the other hand, the second subsidiary passage306, and the sensor chamber Rs which is an internal space communicating with the outside of the measurement portion331via the second subsidiary passage306are formed by attaching the rear cover304to the housing302. A part of the circuit board400protrudes (a protrusion part403) into the first subsidiary passage305from a partition wall335which partitions the measurement portion331into the circuit chamber Rc and the first subsidiary passage305, and the flow rate measurement portion602is provided on a measurement channel surface430of the protrusion part.

3.2 Structure of Subsidiary Passage Groove

Subsidiary passage grooves for forming the first subsidiary passage305are provided on the distal end side of the measurement portion331in a length direction. The subsidiary passage grooves for forming the first subsidiary passage305have a front side subsidiary passage groove332illustrated inFIG. 3-1and a rear side subsidiary passage groove334illustrated inFIG. 3-2. As illustrated inFIG. 3-1, the front side subsidiary passage groove332is gradually curved toward the flange311side which is the distal end side of the measurement portion331from the first subsidiary passage outlet305bwhich is open in the downstream side outer wall338of the measurement portion331toward the upstream side outer wall336, and communicates with an opening part333which penetrates through the measurement portion331in the thickness direction at a position near the upstream side outer wall336. The opening part333is formed along the flow direction of the gas30to be measured of the main passage124so as to extend from the upstream side outer wall336to the downstream side outer wall338.

As illustrated inFIG. 3-2, the rear side subsidiary passage groove334is divided into two ways at an intermediate position between the upstream side outer wall336and the downstream side outer wall338from the upstream side outer wall336toward the downstream side outer wall338, one way extends linearly as a discharge passage and is open in a discharge port305cof the downstream side outer wall338, and the other way is gradually curved to the flange311side which is the basal end side of the measurement portion331toward the downstream side outer wall338, and communicates with the opening part333at a position near the downstream side outer wall338.

The rear side subsidiary passage groove334forms an inlet groove through which the gas30to be measured flows from the main passage124, and the front side subsidiary passage groove332forms an outlet groove through which the gas30to be measured incorporated from the rear side subsidiary passage groove334is returned to the main passage124. Since the front side subsidiary passage groove332and the rear side subsidiary passage groove334are provided at the distal end part of the housing302, a gas in a portion separated from the inner wall surface of the main passage124, that is, a gas flowing through a portion close to the central portion of the main passage124can be incorporated as the gas30to be measured. A gas flowing near the inner wall surface of the main passage124tends to have a temperature which is different from an average temperature of gases flowing through the main passage124, such as the intake air20, due to the influence of the temperature of the wall surface of the main passage124. A gas flowing near the inner wall surface of the main passage124tends to have a flow velocity lower than an average flow velocity of gases flowing through the main passage124. The physical quantity measurement device300of the Example is hardly influenced thereby, and thus it is possible to prevent deterioration in measurement accuracy.

As illustrated inFIG. 3-2, a part of the gas30to be measured flowing through the main passage124is incorporated into the rear side subsidiary passage groove334from the first subsidiary passage inlet305a, and flows through the rear side subsidiary passage groove334. A foreign substance having great mass included in the gas30to be measured flows into the discharge passage which extends linearly from the branch, along with the part of the gas to be measured, and is discharged to the main passage124from the discharge port305cof the downstream side outer wall338.

The rear side subsidiary passage groove334has a shape which is gradually deepened, and thus the gas30to be measured is gradually moved to the front side of the measurement portion331while flowing along the rear side subsidiary passage groove334. Particularly, the rear side subsidiary passage groove334is provided with a steep part334awhich is rapidly deepened in front of the opening part333, and thus part of air having small mass is moved along the steep part334aso as to flow through the measurement channel surface430side of the circuit board400in the opening part333. On the other hand, a foreign substance having great mass hardly changes its course, and thus flows through a rear surface431side of the measurement channel surface.

As illustrated inFIG. 3-1, the gas30to be measured moved to the front side in the opening part333flows along the measurement channel surface430of the circuit board, and is brought into heat transfer with the flow rate measurement portion602provided on the measurement channel surface430, and thus a flow rate is measured. The air which flows into the front side subsidiary passage groove332from the opening part333flows along the front side subsidiary passage groove332, and is discharged to the main passage124from the first subsidiary passage outlet305bwhich is open in the downstream side outer wall338.

A substance having great mass, such as waste matter mixed with the gas30to be measured, has large inertial force, and thus hardly rapidly changes its course in a depth direction of the groove along a surface of a portion of the steep part334ain which the depth of the groove steeply increases. Thus, a foreign substance having great mass is moved to the rear surface431side of the measurement channel surface, and thus the foreign substance can be prevented from passing the vicinity of the flow rate measurement portion602. In the present example, most of foreign substances having great mass other than a gas are configured to pass through the rear surface431of the measurement channel surface which is a back surface of the measurement channel surface430, and thus it is possible to reduce the influence of contamination due to a foreign substance such as oil, carbon, or waste matter, and thus to prevent deterioration in measurement accuracy. In other words, the shape is formed such that a course of the gas30to be measured rapidly changes along an axis crossing the flow axis of the main passage124, and thus it is possible to reduce the influence of a foreign substance mixed with the gas30to be measured.

3.3 Structures and Effects of Second Subsidiary Passage and Sensor Chamber

The second subsidiary passage306is formed linearly from the second subsidiary passage inlet306ato the second subsidiary passage outlet306bin parallel to the flange311along the flow direction of the gas30to be measured. The second subsidiary passage inlet306ais formed by notching a part of the upstream side outer wall336, and the second subsidiary passage outlet306bis formed by notching a part of the downstream side outer wall338. Specifically, as illustrated inFIG. 3-3, the second subsidiary passage inlet and outlet are formed by notching a part of the upstream side outer wall336and a part of the downstream side outer wall338from the rear surface side of the measurement portion331at a position continuing to and along an upper surface of the partition wall335. The second subsidiary passage inlet306aand the second subsidiary passage outlet306bare notched to a depth position which is coplanar with the rear surface of the circuit board400. The second subsidiary passage306is a pass through which the gas30to be measured passes along a rear surface of a board main body401of the circuit board400, and thus functions as a cooling channel for cooling the board main body401. The circuit board400such as an LSI or a microcomputer often holds heat, and such heat can be transferred to the rear surface of the board main body401so as to be dissipated by the gas30to be measured passing through the second subsidiary passage306.

The sensor chamber Rs is provided further toward the basal end side of the measurement portion331than the second subsidiary passage306. A part of the gas30to be measured which has flowed into the second subsidiary passage306from the second subsidiary passage inlet306aflows into the sensor chamber Rs, and thus pressure and relative humidity thereof are respectively measured by the pressure sensor421and the humidity sensor422in the sensor chamber Rs. The sensor chamber Rs is disposed further toward the basal end side of the measurement portion331than the second subsidiary passage306, and thus it is possible to reduce the influence of dynamic pressure of the gas30to be measured passing through the second subsidiary passage306. Therefore, it is possible to improve measurement accuracy in the pressure sensor421in the sensor chamber Rs.

Since the sensor chamber Rs is disposed further toward the basal end side of the measurement portion331than the second subsidiary passage306, for example, in a case where the distal end side of the measurement portion331is attached to the intake passage so as to be directed downward, it is possible to prevent contaminants or water drops flowing into the second subsidiary passage306along with the gas30to be measured from being attached to the pressure sensor421or the humidity sensor422disposed on the downstream side thereof.

Particularly, in the present example, since, in the sensor chamber Rs, the pressure sensor421with a relatively large exterior is disposed on the upstream side, and the humidity sensor422with a relatively small exterior is disposed on the downstream side of the pressure sensor421, contaminants or water drops flowing into the second subsidiary passage along with the gas30to be measured from are attached to the pressure sensor421, and are prevented from being attached to the humidity sensor422. Therefore, it is possible to protect the humidity sensor422with low resistance to contaminants or water drops.

The pressure sensor421and the humidity sensor422are hardly influenced by a flow of the gas30to be measured compared with the flow rate measurement portion602, and, especially, the humidity sensor422has only to secure a diffusion level of moisture in the gas30to be measured, and can thus be provided in the sensor chamber Rs adjacent to the linear second subsidiary passage306. In contrast, regarding the flow rate measurement portion602, a certain flow velocity or more is required, it is necessary to keep dust and contaminants away, and the influence of pulsation is also required to be taken into consideration. Therefore, the flow rate measurement portion602is provided in the first subsidiary passage305which has a shape circulating in a loop form.

FIGS. 4-1 and 4-2are diagram illustrating another form of the second subsidiary passage. In this form, a through-hole337is provided in the upstream side outer wall336and the downstream side outer wall338so as to form the second subsidiary passage inlet306aand the second subsidiary passage outlet306binstead of notching the upstream side outer wall336and the downstream side outer wall338. In a case where the second subsidiary passage inlet306aand the second subsidiary passage outlet306bare respectively formed by notching the upstream side outer wall336and the downstream side outer wall338as in the second subsidiary passage illustrated inFIGS. 3-2 to 3-5described above, a width of the upstream side outer wall336and a width of the downstream side outer wall338at these positions are locally reduced, and thus there is concern that the measurement portion331may be distorted in a substantially C shape with the notches as starting points due to thermoforming in molding. According to this form, the through-hole is provided instead of the notches, and thus it is possible to prevent the measurement portion331from being bent in a substantially C shape. Therefore, it is possible to prevent measurement accuracy from being influenced by a change in a position or a direction of the measurement portion for the gas30to be measured due to distortion of the housing302, and thus to ensure normally constant measurement accuracy without an individual difference.

FIGS. 8-1, 8-2 and 8-3are diagrams illustrating still another form of the second subsidiary passage.

A partition wall for partition into the second subsidiary passage306and the sensor chamber Rs may be provided on the rear cover304. According to this configuration, the gas30to be measured can be caused to indirectly flow into the sensor chamber Rs from the second subsidiary passage306, so that the influence of dynamic pressure on the pressure sensor, and thus it is possible to prevent contaminants or water drops being attached to the humidity sensor.

In the example illustrated inFIG. 8-1, two pressure sensors421A and421B are provided to be arranged in a line along the second subsidiary passage306, and a single humidity sensor422is provided on the downstream side thereof, in the sensor chamber Rs. Partition walls352A and352B are provided on the rear cover304, and are disposed to extend between the second subsidiary passage306and the sensor chamber Rs by attaching the rear cover304to the housing302. Specifically, the partition wall352A is disposed between the pressure sensor on the upstream side and an upstream wall of the sensor chamber Rs, and the partition wall352B is disposed along the humidity sensor between the pressure sensor on the downstream side and a downstream wall of the sensor chamber Rs.

In the example illustrated inFIG. 8-2, only the pressure sensor421B on the downstream side is provided, the pressure sensor421A on the upstream side is omitted, and thus a partition wall352C is lengthened. A partition wall352D on the downstream side is disposed along the humidity sensor between the pressure sensor on the downstream side and a downstream wall of the sensor chamber Rs, in the same manner as the partition wall352B inFIG. 8-1. Therefore, the partition walls352A and352C prevent the gas30to be measured from coming into direct contact with the pressure sensor, and can thus reduce the influence of dynamic pressure. The partition walls352B and352D can prevent contaminants or water drops from being attached to the humidity sensor.

In the example illustrated inFIG. 8-3, both of the two pressure sensors421A and421B are omitted, and only a single humidity sensor422is provided in the sensor chamber Rs. A partition wall352E on the upstream side has a substantially L shape which extends from the upstream wall of the sensor chamber Rs to an upstream position of the humidity sensor between the second subsidiary passage306and the sensor chamber Rs, and is bent at a downstream end so as to face the upstream side of the humidity sensor. A partition wall352F is disposed along the humidity sensor between the pressure sensor on the downstream side and the downstream wall of the sensor chamber Rs in the same manner as the partition walls352B and352D. Therefore, the partition wall352E can prevent contaminants or water drops contained in the gas30to be measured passing through the second subsidiary passage306being moved to the humidity sensor, and thus to protect the humidity sensor from such contaminants or the like.

3.4 Shapes and Effects of Front Cover303and Rear Cover304

FIG. 5is a diagram illustrating an exterior of the front cover303, in whichFIG. 5(a)is a front view, andFIG. 5(b)is a sectional view taken along the line B-B inFIG. 5(a).FIG. 6is a diagram illustrating an exterior of the rear cover304, in whichFIG. 6(a)is a front view, andFIG. 6(b)is a sectional view taken along the line B-B inFIG. 6(a).

InFIGS. 5 and 6, the front cover303or the rear cover304forms the first subsidiary passage305by closing the front side subsidiary passage groove332and the rear side subsidiary passage groove334of the housing302. The front cover303forms the closed circuit chamber Rc, and the rear cover304forms the second subsidiary passage306and the sensor chamber Rs communicating with the second subsidiary passage306by closing a recessed part of the measurement portion331on the rear surface side.

The front cover303is provided with a projection part356at a position facing the flow rate measurement portion602, and is used to form a stop with the measurement channel surface430. Thus, it is desirable that molding accuracy is high. The front cover303or the rear cover304is formed through a resin mold process in which a thermosetting resin is injected into a metal mold, and can be formed with high molding accuracy.

A plurality of fixation holes351into which a plurality of fixation pins350protruding from the measurement portion331are inserted are provided in the front cover303and the rear cover304. The front cover303and the rear cover304are respectively attached to the front surface and the rear surface of the measurement portion331, and, in this case, the fixation pins350are inserted into the fixation holes351such that positioning is performed. The front cover and the rear cover are bonded to each other through laser welding or the like performed along edges of the front side subsidiary passage groove332and the rear side subsidiary passage groove334, and are similarly bonded to each other through laser welding or the like performed along edges of the circuit chamber Rc and the sensor chamber Rs.

3.5 Fixation Structure of Circuit Board400to Housing302and Effects

Next, a description will be made of a resin mold process of fixing the circuit board400to the housing302. The circuit board400is integrally molded into the housing302such that the flow rate measurement portion602of the circuit board400is disposed at a predetermined location of the subsidiary passage groove forming the subsidiary passage, for example, in the present example, in the opening part333which connects the front side subsidiary passage groove332to the rear side subsidiary passage groove334.

Portions which bury and fix an outer peripheral edge of a base portion402of the circuit board400in and to the housing302by using a resin mold are provided on the measurement portion331of the housing302as fixation portions372and373. The fixation portions372and373fix the outer peripheral edge of the base portion402of the circuit board400by interposing the outer peripheral edge therebetween.

The housing302is manufactured in the resin mold process. In this resin mold process, the circuit board400is embedded in a resin of the housing302, and is fixed to the inside of the housing302with a resin mold. In the above-described way, it is possible to maintain, with considerably high accuracy, a positional relationship or a directional relationship which is a relationship between shapes of subsidiary passages, for example, the front side subsidiary passage groove332and the rear side subsidiary passage groove334for measuring a flow rate through heat transfer between the flow rate measurement portion602and the gas30to be measured, and thus to reduce an error or variation occurring in each circuit board400to a very small value. As a result, it is possible to considerably improve measurement accuracy in the circuit board400. For example, it is possible to remarkably improve measurement accuracy compared with a method in which fixation is performed by using an adhesive in the related art.

The physical quantity measurement device300tends to be produced through mass production, and thus there is a limit in accurate measurement and improvement of measurement accuracy in the fixation method using an adhesive. However, as in the present example, since the subsidiary passages are formed and the circuit board400is also fixed in the resin mold process of forming subsidiary passages through which the gas30to be measured flows, it is possible to considerably reduce a variation in measurement accuracy, and thus to considerably improve measurement accuracy in each physical quantity measurement device300.

For example, when further described with the Example illustrated inFIGS. 3-1 to 3-5, the circuit board400can be fixed to the housing302such that a relationship among the front side subsidiary passage groove332, the rear side subsidiary passage groove334, and the flow rate measurement portion602is a defined relationship. Consequently, in each of the physical quantity measurement devices300which are mass-produced, a positional relationship between the flow rate measurement portion602of each circuit board400and the first subsidiary passage305or a relationship between shapes can be normally obtained with considerably high accuracy.

Since the first subsidiary passage305to and in which the flow rate measurement portion602of the circuit board400is fixed and disposed is formed by using, for example, the front side subsidiary passage groove332and the rear side subsidiary passage groove334with considerably high accuracy, work of forming the first subsidiary passage305by using the subsidiary passage grooves332and334is work of covering both sides of the housing302with the front cover303and the rear cover304. This work is very simple, and is thus a work process in which there are few factors to reduce measurement accuracy. The front cover303and the rear cover304are produced in the resin mold process in which molding accuracy is high. Therefore, the subsidiary passages provided to have a defined relationship with the flow rate measurement portion602of the circuit board400can be formed with high accuracy. According to this method, it is possible to achieve high productivity in addition to improvement of measurement accuracy.

In contrast, in the related art, a subsidiary passage is manufactured, and then a measurement portion is adhered to the subsidiary passage via an adhesive, so that a thermal flowmeter is produced. In a method using an adhesive as mentioned above, a variation in a thickness of an adhesive is great, and an adhesion position or an adhesion angle varies in each product. Thus, there is a limit in increasing measurement accuracy. In a case where such work is performed in a mass production process, it is considerably hard to improve measurement accuracy.

In the Example of the present invention, the circuit board400is fixed via a resin mold, and the subsidiary passage grooves for forming the first subsidiary passage305are formed by using the resin mold. In the above-described way, it is possible to form shapes of the subsidiary passage grooves and fix the flow rate measurement portion602to the subsidiary passage grooves with considerably high accuracy.

A portion related to measurement of a flow rate, for example, the flow rate measurement portion602or the measurement channel surface430to which the flow rate measurement portion602is attached is provided on the front surface of the circuit board400. The flow rate measurement portion602and the measurement channel surface430are exposed from the resin molding the housing302. In other words, the flow rate measurement portion602and the measurement channel surface430are not covered with the resin molding the housing302. The flow rate measurement portion602or the measurement channel surface430of the circuit board400is used without being changed after resin molding of the housing302, and is used to measure a flow rate in the physical quantity measurement device300. Measurement accuracy is improved in the above-described way.

In the Example of the present invention, since the circuit board400is integrally molded into the housing302, and thus the circuit board400is fixed to the housing302having the first subsidiary passage305, the circuit board400can be reliably fixed to the housing302. Particularly, since the protrusion part403of the circuit board400is configured to protrude to the first subsidiary passage305through the partition wall335, sealing between the first subsidiary passage305and the circuit chamber Rc is high, the gas30to be measured can be prevented from leaking into the circuit chamber Rc out of the first subsidiary passage305, and thus it is possible to prevent circuit components or wirings of the circuit board400from being corroded due to contact with the gas30to be measured.

3.6 Structure and Effect of Terminal Connection Portion320

Next, a description will be made of a structure of a terminal connection portion with reference toFIGS. 10-1 to 10-4.FIG. 10-1is a diagram for explaining a structure of the terminal connection portion,FIG. 10-2is a diagram for explaining a structure of the terminal connection portion,FIG. 10-3is a sectional view taken along the line F-F inFIG. 10-1, andFIG. 10-4is a sectional view taken along the line G-G inFIG. 10-2.

The terminal connection portion320has a configuration in which inner end parts361of the external terminals323are connected to connection terminals412of the circuit board400via gold wires413. As illustrated inFIG. 10-1, the inner end parts361of the respective external terminals323protrude into the circuit chamber Rc from the flange311side, and are disposed to be arranged with a predetermined gap in accordance with positions of the connection terminals412of the circuit board400.

The inner end parts361are disposed at positions which are substantially coplanar with the front surface of the circuit board400as illustrated inFIG. 10-3. A front end thereof is bent in a substantially L shape from the front surface of the measurement portion331toward the rear surface thereof, and protrudes to the rear surface of the measurement portion331. As illustrated inFIG. 10-4(a), the front ends of the inner end parts361are connected to a connection part365, and, as illustrated inFIG. 10-4(b), the connection part365is cut off after molding, and thus the front ends are divided into individual parts.

Each inner end part361is fixed to the housing302via a resin mold such that the inner end parts361and the circuit board400are coplanar with each other in a mold process. The respective inner end parts361are fixed to the housing302in the resin mold process in a state of being integrally connected to each other via the connection part365in order to prevent deformation or deviation in arrangement. The inner end parts are fixed to the housing302, and then the connection part365is cut off.

The inner end part361is resin-molded in a state of being interposed between the front surface side and the rear surface side of the measurement portion331, and, at this time, a metal mold is brought into contact with the entire front surface of the inner end part361, and a fixation pin is brought into contact with a rear surface of the inner end part361. Therefore, the front surface of the inner end part361to which a gold wire is welded can be completely exposed without being covered with the mold resin, and thus the gold wire can be easily welded. A pin hole340which is a trace of pressing the inner end part361with the fixation pin is formed in the measurement portion331.

The front end of the inner end part361protrudes into a recessed part341formed on the rear surface of the measurement portion331. The recessed part341is covered with the rear cover304, and the periphery of the recessed part341is continuously bonded to the rear cover304through laser welding or the like so as to form a closed inner space. Therefore, the inner end part361can be prevented from being corroded due to contact with the gas30to be measured.

4. Exterior of Circuit Board400

4.1 Molding of Measurement Channel Surface430with Flow Rate Measurement Portion602

FIGS. 7-1 to 7-6illustrate an exterior of the circuit board400. Diagonal line portions drawn on the exterior of the circuit board400indicate a fixation surface432and a fixation surface434which are fixed in a state in which the circuit board400is covered with a resin during molding of the housing302in the resin mold process.

FIG. 7-1is a front view of the circuit board,FIG. 7-2is a right side view of the circuit board,FIG. 7-3is a rear view of the circuit board,FIG. 7-4is a left side view of the circuit board,FIG. 7-5is a sectional view taken along the line B-B, indicating a section of an LSI portion inFIG. 7-1, andFIG. 7-6is a sectional view taken along the line C-C of a measurement portion inFIG. 7-1.

The circuit board400has the board main body401, the circuit portion and the flow rate measurement portion602which is a sensing element are provided on the front surface of the board main body401, and the pressure sensor421and the humidity sensor422which are sensing elements are provided on the rear surface of the board main body401. The board main body401is made of a glass epoxy resin material, and has a value which is the same as or similar to a thermal expansion coefficient of a thermosetting resin molding the housing302. Therefore, it is possible to reduce stress due to a difference between thermal expansion coefficients when the housing302is brought into insert molding, and thus to reduce distortion of the circuit board400.

The board main body401has a plate shape with a predetermined thickness, includes the substantially square-shaped base portion402, and the substantially square-shaped protrusion part403which protrudes from one side of the base portion402and is smaller than the base portion402, and thus has a substantially T shape in a plan view. The circuit portion is provided on the front surface of the base portion402. The circuit portion is formed of electronic components including an LSI414, a microcomputer415, a power source regulator416, chip components417such as a resistor or a capacitor mounted on circuit wirings (not illustrated). The power source regulator416generates a relatively large amount of heat compared with other electrical connections such as the microcomputer415or the LSI414, and is thus disposed on the relatively upstream side in the circuit chamber Rc. The LSI414is entirely sealed with a synthetic resin material419so as to include a gold wire411, and thus improves handling property of the circuit board400during insert molding.

As illustrated inFIG. 7-5, a recessed part402ainto which the LSI414is fitted is provided to be recessed on the front surface of the board main body401. The recessed part402amay be formed by performing laser processing on the board main body401. The board main body401made of the glass epoxy resin can be easily processed such that the recessed part402acan be easily provided, compared with a board main body made of ceramics. The recessed part402ahas a depth in which a front surface of the LSI414is coplanar with the front surface of the board main body401. As mentioned above, since the front surface of the LSI414matches the front surface of the board main body401in heights, wire bonding of connecting the LSI414to the board main body401via the gold wire411is facilitated, and thus it becomes easier to manufacture the circuit board400. The LSI414may be directly provided on the front surface of the board main body401as illustrated inFIG. 7-6. In a case of such a structure, a synthetic resin material419coating the LSI414further protrudes, but processing for forming the recessed part402ain the board main body401is not necessary, and thus manufacturing can be simplified.

The protrusion part403is disposed in the first subsidiary passage305when the circuit board400is inserted and molded into the housing302, and the measurement channel surface430which is a front surface of the protrusion part403extends along the flow direction of the gas30to be measured. The flow rate measurement portion602is provided on the measurement channel surface430of the protrusion part403. The flow rate measurement portion602performs heat transfer with the gas30to be measured so as to measure a state of the gas30to be measured, for example, a flow velocity of the gas30to be measured, and outputs an electric signal indicating a flow rate thereof flowing through the main passage124. In order for the flow rate measurement portion602to measure a state of the gas30to be measured with high accuracy, it is desirable that a gas flowing in the vicinity of the measurement channel surface430is a laminar flow, and disturbance is small. Thus, it is desirable that the front surface of the flow rate measurement portion602is coplanar with the measurement channel surface430, or a difference therebetween is equal to or less than a predetermined value.

A recessed part403ais provided to be recessed on the front surface of the measurement channel surface430, and the flow rate measurement portion602is fitted thereinto. The recessed part403amay also be formed by performing laser processing. The recessed part403ahas a depth in which a front surface of the flow rate measurement portion602is coplanar with the front surface of the measurement channel surface430. The flow rate measurement portion602and a wiring portion thereof are coated with a synthetic resin material418, and thus the occurrence of electro-corrosion due to attachment of salt water is prevented.

Two pressure sensors421A and421B and a single humidity sensor422are provided on the rear surface of the board main body401. The two pressure sensors421A and421B are respectively disposed in a line on the upstream side and the downstream side. The humidity sensor422is disposed on the downstream side of the pressure sensor421B. The two pressure sensors421A and421B and the single humidity sensor422are disposed in the sensor chamber Rs. In the example illustrated inFIG. 7-3, a description has been made of a case where the two pressure sensors421A and421B and the single humidity sensor422are provided, but, as illustrated inFIG. 8-2(a), only the pressure sensor421B and the humidity sensor422may be provided, and, as illustrated inFIG. 8-3(a), only the humidity sensor422may be provided.

In the circuit board400, the second subsidiary passage306is disposed on the rear surface side of the board main body401. Therefore, the entire board main body401can be cooled by the gas30to be measured passing through the second subsidiary passage306.

4.2 Structure of Temperature Measurement Portion451

A temperature measurement portion451is provided at an end side of the base portion402on the upstream side and a corner thereof on the protrusion part403side. The temperature measurement portion451forms one of measurement portions for measuring a physical quantity of the gas30to be measured flowing through the main passage124, and is provided on the circuit board400. The circuit board400has a protrusion part450which protrudes toward the upstream of the gas30to be measured from the second subsidiary passage inlet306aof the second subsidiary passage306, and the temperature measurement portion451includes a chip type temperature sensor453provided on the rear surface of the circuit board400in the protrusion part450. The temperature sensor453and a wiring portion thereof are coated with a synthetic resin material, and thus the occurrence of electro-corrosion due to attachment of salt water is prevented.

For example, as illustrated inFIG. 3-2, the upstream side outer wall336in the measurement portion331forming the housing302is depressed toward the downstream side at the central part of the measurement portion331in which the second subsidiary passage inlet306ais provided, and the protrusion part450of the circuit board400protrudes toward the upstream side from the depressed upstream side outer wall336. A distal end of the protrusion part450is disposed at a position recessed more than the surface of the upstream side outer wall336on the most upstream side. The temperature measurement portion451is provided in the protrusion part450so as to face the rear surface of the circuit board400, that is, the second subsidiary passage306side.

Since the second subsidiary passage inlet306ais formed on the downstream side of the temperature measurement portion451, the gas30to be measured flowing into the second subsidiary passage306from the second subsidiary passage inlet306acomes into contact with the temperature measurement portion451, and then flows into the second subsidiary passage inlet306a, and thus the temperature thereof is measured when the gas to be measured comes into contact with the temperature measurement portion451. The gas30to be measured having come into contact with the temperature measurement portion451flows into the second subsidiary passage306from the second subsidiary passage inlet306ain this state, passes through the second subsidiary passage306, and is discharged to the main passage123from the second subsidiary passage outlet306b.

4.3 Fixation of Circuit Board400in Resin Mold Process and Effect Thereof

A diagonal line portion inFIG. 9-1indicates the fixation surface432and the fixation surface434for covering the circuit board400with a thermosetting resin used in the resin mold process in order to fix the circuit board400to the housing302. It is important that high accuracy is maintained such that a relationship between the measurement channel surface430and the flow rate measurement portion602provided on the measurement channel surface430and shapes of the subsidiary passages is a defined relationship.

Since, in the resin mold process, the subsidiary passages are molded, and the circuit board400is also fixed to the housing302molding the subsidiary passages, a relationship between the subsidiary passages, and the measurement channel surface430and the flow rate measurement portion602can be maintained with considerably high accuracy. In other words, since the circuit board400is fixed to the housing302in the resin mold process, the circuit board400can be positioned in and fixed to a metal mold for molding the housing302having the subsidiary passages with high accuracy. A thermosetting resin with a high temperature is injected into the metal mold, and thus the subsidiary passages are molded with high accuracy, and the circuit board400is also fixed with high accuracy. Therefore, an error or a variation occurring in each circuit board400can be reduced to a very small value. As a result, it is possible to considerably improve measurement accuracy in the circuit board400.

In the present example, the outer periphery of the base portion402of the board main body401is covered with fixation portions372and373of a mold resin molding the housing302, which are used as the fixation surfaces432and434. In the Example illustrated inFIG. 9-1, as fixation means for stronger fixation, through-holes404is provided in the board main body401of the circuit board400, the through-holes404are buried in a mold resin, and thus fixation force of the board main body401is increased. The through-holes404are provided in a location fixed by the partition wall335, and a front side and a rear side of the partition wall335are connected to each other via the through-holes404.

The through-holes404are preferably provided in a location corresponding to the partition wall335. Since the mold resin is a thermosetting resin, and the board main body401is made of glass epoxy, mutual chemical bonding action is low, and adhesion hardly occurs. The partition wall335has a length larger than a width, and is configured to easily spread in a direction of becoming distant from the board main body401. Therefore, the through-holes404are provided in a location corresponding to the partition wall335, and thus the partition walls335with the board main body401interposed therebetween can be physically coupled to each other via the through-holes404. Therefore, the circuit board400can be more strongly fixed to the housing302, and thus it is possible to prevent a gap from being formed between the partition wall and the protrusion part403. Therefore, the gas30to be measured can be prevented from permeating into the circuit chamber Rc through a gap between the partition wall335and the protrusion part403, and thus the circuit chamber Rc can be completely sealed.

In the Example illustrated inFIG. 9-2, in addition to the through-holes404, round hole-shaped through-holes405are provided in the end side on the upstream side and the downstream side of the base portion402, and the through-holes405are buried in a mold resin, and thus fixation force of the board main body401is further increased. The end side on the upstream side and the end side on the downstream side of the base portion402are interposed between the fixation portions372and373from both sides in the thickness direction, and the front side and the rear side thereof are connected to each other via the through-holes405. Therefore, the circuit board400can be more strongly fixed to the housing302.

The through-holes404are preferably provided in the partition wall335, but, in a case where the partition wall335is fixed to the board main body401with predetermined fixation force, the through-holes404may be omitted. In the Example illustrated inFIG. 9-3, the through-holes404are omitted, and the through-holes405are provided in the end side on the upstream side and the end side on the downstream side of the base portion402. According to this configuration, the board main body401of the circuit board400can also be strongly fixed to the housing302.

The through-hole is not limited to a round hole shape, and, for example, as illustrated inFIG. 9-4, may be a long hole-shaped through-hole406. In the present example, the long hole-shaped through-holes406are provided to extend along the end side on the upstream side and the end side on the downstream side of the base portion402. The through-hole406increases an amount of resins connecting the front side and the rear side of the measurement portion331, and thus higher fixation force can be obtained, compared with a round hole-shaped through-hole.

In the above-described respective Examples, the through-holes404,405and406have been described as an example of fixation means, but a through-hole is only an example. For example, in the Example illustrated inFIG. 9-5, large notch portions407which extend in a length direction thereof are provided in the end side on the upstream side and the end side on the downstream side of the base portion402. In the Example illustrated inFIG. 9-6, notch portions408are provided between the base portion402and the protrusion part403. In the Example illustrated inFIG. 9-7, a plurality of notch portions409are provided to be arranged with predetermined intervals in the end side on the upstream side and the end side on the downstream side of the base portion402. In the Example illustrated inFIG. 9-8, a pair of notch portions410are provided to be notched toward the base portion402from both sides of the protrusion part403. According to this configuration, the board main body401of the circuit board400can also be strongly fixed to the housing302.

4.4 Convex Projection Provided on Circuit Board and Effect Thereof

FIG. 12-1(a) is a front view (front surface) of the circuit board,FIG. 12-1(b) is an enlarged view of an A portion inFIG. 12-1(a), andFIG. 12-1(c) is a sectional view taken along the line B-B inFIG. 12-1(b).FIG. 12-2(a) is a rear view (rear surface) of the circuit board,FIG. 12-2(b) is an enlarged view of a C portion inFIG. 12-2(a), andFIG. 12-2(c) is a sectional view taken along the line D-D inFIG. 12-2(b).

In the present invention, the board main body401of the circuit board400has been description, and thus only a target portion of the present invention will be described in the following description. In the circuit board400, the recessed part403ais formed in a part of the measurement channel surface430of the protrusion part403protruding into the subsidiary passage which is a measurement space in the board main body401. The flow rate measurement portion (physical quantity measurement portion)602measuring a flow rate of a fluid (that is, a gas to be measured) which is a physical quantity is mounted on the recessed part403a. A through-hole462reaching the rear surface431of the measurement channel surface from the recessed part403aformed on the measurement channel surface430side is disposed in the circuit board400. The through-hole462is provided for ventilation between a diaphragm space formed by the flow rate measurement portion602stored in the recessed part403aand outside air, and penetrates through the circuit board400. The sealed diaphragm space is formed between a diaphragm of the flow rate measurement portion602and the recessed part403a, and the through-hole462communicates with the diaphragm space.

A convex projection460is formed on at least one of the measurement channel surface430and the rear surface431of the measurement channel surface of the protrusion part403. As illustrated inFIG. 12-1(c), the entire front surface and rear surface of the circuit board400are coated with a resist coat461.

FIG. 12-1(c) illustrates a structure in which a plurality of projecting parts460aare provided as the convex projection460on both of the measurement channel surface430and the rear surface431of the measurement channel surface of the circuit board400, andFIG. 12-2(c) illustrates a structure in which a plurality of projecting parts460aare provided on only the rear surface431of the measurement channel surface side. The plurality of projecting parts460aare provided around the flow rate measurement portion602on the measurement channel surface430, and are provided around the through-hole462on the rear surface431of the measurement channel surface.

In the present invention, hereinafter, regarding a description of implementation in a circuit board, an embodiment will be described by using a printed board as a model, but an effect is also the same for a ceramic board or a multilayer board (LTCC, HTCC) laminated with glass/ceramic, which are regarded as a circuit board in the present invention.

In a case where the circuit board400is a printed board, the convex projection460presented in the present invention can be easily formed by using a pattern forming technique. The printed board is laminated with a core material and a prepreg, and circuit wiring patterns are formed even in an interlayer and on front and rear surfaces. Wirings in respective layers are electrically connected to each other via plated through-holes, so as to form a circuit network. Regarding patterns using copper on respective interlayers and the front and rear surfaces, copper foils are etched to form circuit patterns, copper foils as wiring patterns are laminated in the respective interlayers, and are disposed on the front and rear surfaces so as to be brought into hot press, and a resin is cured and stabilized. Thereafter, a resist coat is formed on the front and rear surfaces, and is cured, and thus a printed board is formed.

In the printed board, as described above, patterns using copper foils formed on a prepreg surface are formed through etching processing (chemical treatment), there is no limit in a shape of a protection mask of when a circuit board is etched, and thus most of shapes such as thin lines and geometrical land shapes can be realized through etching. Therefore the printed board is used as a board of many electronic circuits. In the present invention, the convex projections460are disposed on the measurement channel surface430and the rear surface431of the measurement channel surface of the protrusion part403of the circuit board400, but, in a case where the circuit board400is formed of a printed board, the convex projection460can be formed in an etching process of when the printed board is formed, and the convex projection460can be formed simultaneously with execution of etching processing for forming a circuit wiring pattern of a product circuit. Therefore, a general technique of the related art can be used, and thus the convex projection460can be formed without increasing the number of processes and cost.

Regarding an effect expected in the present invention, if water drops flowing into the subsidiary passage from the main passage124are attached to the protrusion part403of the circuit board400, and are attached to the flow rate measurement portion602mounted on the recessed part403aof the measurement channel surface430, there is concern that the diaphragm is heated and is damaged until the attached water drops are boiled, and thus detaching the water drops attached to the measurement channel surface430early from the circuit board400is essential in improvement of reliability of the physical quantity measurement device300.

One end of the through-hole462is open in the rear surface431of the measurement channel surface of the circuit board400. The through-hole462communicates with the diaphragm space between the diaphragm of the flow rate measurement portion602mounted on the recessed part403aof the circuit board400and the recessed part403a, and penetrates to the rear surface431of the measurement channel surface of the circuit board400from the recessed part403a.

As mentioned above, in a structure in which the diaphragm space inside the flow rate measurement portion602is directly ventilated through the through-hole462, there is concern that a water drop permeates into the through-hole462, and reaches the diaphragm space inside the flow rate measurement portion602. If the diaphragm is filled with water drops, the diaphragm is heated until the attached water drops are boiled, and thus there is concern that the diaphragm is damaged. In a case where water drops fill the diaphragm space and are frozen in this state, stress is applied to the diaphragm and the flow rate measurement portion602due to volume expansion, and thus there is a probability that the diaphragm and the flow rate measurement portion may be damaged. Therefore, it is an important quality issue to realize a structure of preventing water drops from entering the through-hole462by repelling and removing water drops attached to the protrusion part403of the circuit board400early.

In a printed board as the circuit board400of the present invention, a solder resist coat461is formed on a front surface and a rear surface thereof. The resist coat461is generally formed by using an epoxy-based resin, the material is an organic compound having weak water repellency, and a contact angle with water is about 80 degrees. However, in order to repel and remove a water drop through water repelling, a super-water repellent surface state in which a contact angle with water exceeds 100 degrees is necessary. Such a super-water repellent state is a physical property value which is difficult to realize unless a fluorine-based resin or a silicone-based resin is used. The object of the present invention may be achieved by applying a coat using the above-described super-water repellent material on a surface of a circuit board, but very expensive materials, cumbersome coating, and a drying process are required, and thus cost is increased. Therefore, such coping is not appropriate for a general purpose product.

According to the present invention, the convex projection460formed on the circuit board400by using a pattern forming technique of a printed board copes such that characteristics of surface tension which is a feature of a water drop can be used. When a water drop is in a steady state, force is applied thereto such that the water drop tends to have a spherical shape, which becomes the most stable energy state as a state due to the surface tension. In this case, if the surface of the circuit board400to which the water drop is attached is uneven instead of being flat, the water drop cannot stay in a constant location. Therefore, the water drop is moved, and thus the water drop is repelled from the circuit board400due to kinetic energy. Therefore, the surface of the circuit board400preferably has a fine surface state in order to repel a water drop.

The convex projection460formed on the surface of the printed board may be formed by etching copper foils. A shape which can be formed is the convex projection460from the surface of the printed board. A sectional shape of the convex projection460is a trapezoidal sectional shape in which a dimension of a lower bottom is larger than a dimension of an upper bottom. A planar shape may be a circular shape. This is because a circular shape requires the minimum surface area in forming a sphere due to the surface tension of water, and an effect of more easily forming a water drop as a sphere is high.

As illustrated inFIG. 12-1(c), the convex projection460may be formed both of the measurement channel surface430and the rear surface431of the measurement channel surface of the protrusion part403of the circuit board400, and may be formed on only the rear surface431of the measurement channel surface in which one end of the through-hole462is open and is exposed, as illustrated inFIG. 12-2(c). In the Example, the plurality of projecting parts460aforming the convex projection460are provided to be spread over the entire surfaces of the measurement channel surface430and the rear surface431of the measurement channel surface. The projecting part460ahas a substantially circular shape in a plan view, and has a trapezoidal sectional shape in which a dimension of a lower bottom is larger than a dimension of an upper bottom. The plurality of projecting parts460aare individually formed electrically separately from circuit wirings at a part of the circuit board400.

FIG. 12-3(a) is a diagram illustrating the rear surface431of the measurement channel surface of the protrusion part403, andFIG. 12-3(b) is an enlarged view of an E portion inFIG. 12-3(a). The convex projection460is provided on the rear surface431of the measurement channel surface, and the plurality of projecting parts460aof the convex projection460are disposed in a grid form centering on the through-hole462so as to surround the periphery of the through-hole462.

FIGS. 12-4(a),12-4(b) and12-4(c) are diagrams illustrating that arrangement of the convex projections460formed on the rear surface431of the measurement channel surface is defined. In the configuration example illustrated inFIG. 12-4(a), the convex projections460are disposed in a zigzag form centering on the through-hole462. In the configuration example illustrated inFIG. 12-4(b), the plurality of projecting parts460aof the convex projection460are disposed in a square form centering on the through-hole462while intersecting each other in series. In the configuration example illustrated inFIG. 12-4(c), the plurality of projecting parts460aof the convex projection460are disposed radially centering on the through-hole462.

FIGS. 12-5(a) and12-5(b) are front views illustrating that arrangement of the convex projections460formed on the rear surface431of the measurement channel surface is defined. In the configuration example illustrated inFIG. 12-5(a), the convex projection460has a plurality of projecting parts460beach of which has an elliptical shape as a planar shape. The plurality of projecting parts460bare disposed such that a major axis of the elliptical shape is directed along the flow direction (FLOW) of a fluid. The projecting parts are disposed in a zigzag form centering on the through-hole462so as to be alternately located.

The elliptical shape of the projecting part460bis effective in a case where a water drop horizontally scatters toward the projecting part460balong the flow direction. In this case, the water drop comes into contact with a long side (large arc portion) of the projecting part430b, and the water drop can be subdivided into an upper drop and a lower drop with this location as a starting point, and can be repelled and fly backward.

In the configuration example illustrated inFIG. 12-5(b), the convex projection460has rectangular projecting parts460ceach of which has a rectangular shape as a planar shape. Each of the plurality of projecting parts460cis disposed such that one side on the flow direction upstream side is orthogonal to the flow direction of a fluid. The projecting parts are disposed in a zigzag form centering on the through-hole462so as to be alternately located. A water drop contained in a fluid collides with one side of the projecting part460c, and the water drop is subdivided into drops with this location as a starting point, and is repelled and fly backward. Therefore, it is possible to repel and remove a water drop attached to the circuit board400from the circuit board400, and thus to prevent a water drop from entering the through-hole462.

A recommended dimension of the convex projection460formed on the circuit board400based on specific verification will be presented. For example, as illustrated inFIG. 12-6, in a case where an inner diameter of the through-hole462is indicated by ϕd, a dimension of a convex projection upper bottom is indicated by L1, a dimension of a convex projection lower bottom is indicated by L2, and a dimension of a space between the convex projection lower bottom and an adjacent lower bottom is indicated by L3, dimensions are selected to satisfy a relationship of ϕd≥L2≥L3(here, L1<L2), and thus a combination is obtained such that a water drop hardly enters the through-hole462which is open in the rear surface431of the measurement channel surface.

For example, in a case where the inner diameter ϕd of the through-hole462is ϕ0.1 to ϕ0.5, the lower bottom L2of the convex projection460is 75 μm to 200 μm, and the space L3between the lower bottom of the convex projection460and an adjacent lower bottom is 80 to 150 μm, a combination in which a water drop does not enter the through-hole462is obtained.

As an actual verification result, a combination of ϕd=ϕ0.3, L2=100 μm, and L3=75 μm has a relationship achieving an effect in which a water drop is repelled and flies most. The above-described dimension relationship is an example based on verification, and all dimensions and positional relationships are not defined in this relational expression.

FIG. 13-1(a) is a front view of the rear surface431of the measurement channel surface of the protrusion part403, andFIG. 13-1(b) is an enlarged view of an F portion inFIG. 13-1(a). In the present example, a feature is that the convex projection460is disposed on the front side which is a flow direction upstream side of a fluid as a front obstacle of the through-hole462, and thus a water drop does not enter the through-hole462. In a structural system in a case where a flow of a fluid with a physical quantity to be measured from the main passage124to the circuit board400is constant with respect to the flow rate measurement portion602mounted on the protrusion part403of the circuit board400disposed in the main passage124, the convex projection460is provided as a front obstacle in front of the through-hole462with respect to an inflow direction of a flow rate of the through-hole462provided in the rear surface431of the measurement channel surface of the circuit board400. In other words, the convex projection460is disposed as a front obstacle in front of the through-hole462. A water drop which flows in from the main passage124collides with the convex projection430disposed in front of the through-hole462, so that the water drop is subdivided, and thus it is possible that the water drop does not come into direct contact with the through-hole462.

In a case where the circuit board400is a printed board, the convex projection460can be easily formed through a copper etching process of forming a circuit wiring pattern formed on the printed board presented inFIGS. 12-1 to 12-6. For example, a size of the projecting part forming the convex projection430is made larger than an inner diameter of the through-hole462, and thus it is possible to promote a water drop scattering effect using a front obstacle. The convex projection460is formed of the projecting part460aof which a planar shape is a circular shape, and is formed in a diameter larger than that of the through-hole462as illustrated inFIG. 13-1(b).

FIGS. 13-2(a) and13-2(b) illustrate other embodiments of the convex projection460used as the front obstacle presented inFIG. 13-1.

In a configuration illustrated inFIG. 13-2(a), the convex projection460has a projecting part460cdisposed in front of the through-hole462. The projecting part460cfundamentally has a rectangular shape along the flow direction, and is disposed such that a long side thereof is along the inflow direction of a fluid, and a short side thereof is along a direction which is orthogonal to the inflow direction of the fluid. A length of the short side of the projecting part460cis larger than a dimension of the through-hole462, and thus the through-hole462is hidden on the rear side of the projecting part. The projecting part460cserves as a front obstacle of the through-hole462, and can thus prevent a water drop flowing in along with a fluid from coming into direct contact with the through-hole462. There is no difference in an effect even if a collision surface of the projecting part460cdisposed on the inflow direction upstream side of a fluid may be chamfered or formed in an R shape.

In a structure illustrated inFIG. 13-2(b), a projecting part460dof which a planar shape is a tuning fork shape is provided in front of the through-hole462as the convex projection460. The projecting part460dhas a shape which extends along the flow direction of a fluid, and branches into two ways in the middle position. The through-hole462is disposed inside of the branches of the projecting part460d. The projecting part460dhas a tuning fork shape which branches into two ways from a single way in the inflow direction of a fluid, and can thus cause a water drop to flow to the downstream side by avoiding the through-hole462without the water drop being directly attached thereto even if the water drop flows in.

FIGS. 14-1(a) and14-1(b) illustrate embodiments other than the convex projection460presented inFIGS. 12 and 13. InFIG. 14-1(a), in a structural system in a case where a flow of a fluid with a physical quantity to be measured from the main passage124to the circuit board400is constant with respect to the flow rate measurement portion602mounted on the protrusion part403of the circuit board400disposed in the main passage124, the projecting part460aand slits460eare provided as the convex projection460with respect to the inflow direction of a flow rate of the through-hole462provided in the rear surface431of the measurement channel surface of the circuit board400. The projecting part460ais larger than the through-hole462, and is disposed as a front obstacle in front of the through-hole462. The slit460eis disposed to be an elongated slit-shaped convex projection in a state of being along the inflow direction of a fluid at a position of being separated from the distal end side and the basal end side of the protrusion part403with respect to the through-hole462.

The projecting part460ahas a shape larger than the through-hole462, and is disposed in front of the through-hole462. A plurality of slits460eare respectively disposed on the distal end side and the basal end side of the protrusion part403with respect to the through-hole462, and are disposed along the flow direction of a fluid. Therefore, even if water drops scatter from the inflow direction, most of the water drops are subdivided at the projecting part460aserving as a front obstacle, and water drops riding the slits460eare slid and moved to the downstream position of the through-hole462without being changed. Therefore, it is possible that the through-hole462does not come into direct contact with a water drop.

FIG. 14-1(b) illustrates another Example of the Example of the invention presented inFIG. 14-1(a). The central axis of the projecting part460aas a front obstacle is disposed at a deviated position relative to the through-hole462which is open in the rear surface431of the measurement channel surface of the circuit board400. There is a structure in which central line of the through-hole462is located at a position lower than the central axis of the projecting part460a, and slits460ewhich are elongated slit-shaped projections are disposed in a state of being inclined obliquely downward with respect to the inflow direction of a fluid on upper and lower sides of the through-hole462. According to this structure, it is possible to prevent a water drop from coming into direct contact with the through-hole462.

FIGS. 14-2(a) and14-2(b) illustrate other embodiments of the convex projection462and the front obstacle463presented inFIGS. 12 and 13. In a structure illustrated inFIG. 14-2(a), the convex projection460has a structure of being disposed in the entire outer circumference of the through-hole462. In other words, the convex projection460has a ring-shaped projecting part460fwhich is circumferentially continued so as to surround the circumference of an opening of the through-hole462which is open in the rear surface431of the measurement channel surface. Therefore, in a structural system in which a fluid with a physical quantity to be measured flows into the subsidiary passage from the main passage124, and flows through the subsidiary passage along the circuit board400, even if a water drop flows in, the water drop can be caused to come into contact with the projecting part460fearlier than the through-hole462. Therefore, it is possible to prevent a water drop from coming into direct contact with the through-hole462.

In a structure illustrated inFIG. 14-2(b), the convex projection460has a structure of being disposed on the entire outer circumference of the through-hole462, and a notch460gis provided at a part on the downstream side of the through-hole462in the inflow direction of a physical quantity.

In other words, the projecting part460fof the convex projection460has a ring shape which is circumferentially continued so as to surround the circumference of an opening of the through-hole462which is open in the rear surface431of the measurement channel surface, and the notch460gwhich is partially notched on the downstream side is provided. In a case where a water drop scatters and reaches the through-hole462crossing over the projecting part460g, the notch460gis used to discharge the water drop to the downstream side which is a lower side of the through-hole462. Preferably, the notch460gis disposed along a flow line of the inflow direction of a physical quantity and is disposed on the downstream side of the through-hole462.

5. Circuit Configuration of Physical Quantity Measurement Device300

5.1 Entire Circuit Configuration of Physical Quantity Measurement Device300

FIG. 11-1is a circuit diagram of the physical quantity measurement device300. The physical quantity measurement device300includes a flow rate measurement circuit601and a temperature/humidity measurement circuit701.

The flow rate measurement circuit601includes the flow rate measurement portion602having a heat generation body608, and a processing portion604. The processing portion604controls a heating value of the heat generation body608of the flow rate measurement portion602, and outputs a signal indicating a flow rate to the microcomputer415via a terminal662on the basis of an output from the flow rate measurement portion602. In order to perform the process, the processing portion604includes a central processing unit (CPU)612, an input circuit614, an output circuit616, a memory618holding data indicating a relationship between a correction value or a measurement value and a flow rate, and a power source circuit622which supplies a predetermined voltage to each necessary circuit. DC power is supplied to the power source circuit622from an external power source such as an on-vehicle battery via a terminal664and a ground terminal (not illustrated).

The flow rate measurement portion602is provided with the heat generation body608heating the gas30to be measured. The power source circuit622supplies a voltage V1to a collector of a transistor606forming a current supply circuit of the heat generation body608, a control signal is applied to a base of the transistor606from the CPU612via the output circuit616, and a current is supplied to the heat generation body608from the transistor606via a terminal624on the basis of the control signal. A current amount supplied to the heat generation body608is controlled on the basis of a control signal applied to the transistor606forming the current supply circuit of the heat generation body608from the CPU612via the output circuit616. The processing portion604controls a heating value of the heat generation body608such that the temperature of the gas30to be measured is increased from an initial temperature to a predetermined temperature, for example, 100° C. through heating in the heat generation body608.

The flow rate measurement portion602includes a heat generation control bridge640for controlling a heating value of the heat generation body608and a flow rate sensing bridge650for measuring a flow rate. A predetermined voltage V3is supplied to one end of the heat generation control bridge640from the power source circuit622via a terminal626, and the other end of the heat generation control bridge640is connected to a ground terminal630. A predetermined voltage V2is supplied to one end of the flow rate sensing bridge650from the power source circuit622via a terminal625, and the other end of the flow rate sensing bridge650is connected to the ground terminal630.

The heat generation control bridge640has a resistor642which is a temperature measurement resistor of which a resistance value changes depending on the temperature of the gas30to be measured, and the resistor642, a resistor644, a resistor646, and a resistor648form a bridge circuit. A potential difference between an intersection A between the resistor642and the resistor646and an intersection B between the resistor644and the resistor648is input to the input circuit614via a terminal627and a terminal628, and the CPU612controls a current supplied from the transistor606such that the potential difference between the intersection A and the intersection B becomes a predetermined value, for example, a zero volts in this Example, and thus controls a heating value of the heat generation body608. The flow rate measurement circuit601illustrated inFIG. 11-1heats the gas30to be measured with the heat generation body608such that the initial temperature of the gas30to be measured is increased to a predetermined temperature, for example, 100° C. at all times. In order to perform the heating control with high accuracy, when the temperature of the gas30to be measured which is warmed by the heat generation body608is increased from an initial temperature to a predetermined temperature, for example, 100° C. at all times, a resistance value of each resistor forming the heat generation control bridge640is set such that a potential difference between the intersection A and the intersection B becomes zero volts. Therefore, in the flow rate measurement circuit601, the CPU612controls a current supplied to the heat generation body608such that a potential difference between the intersection A and the intersection B becomes zero volts.

The flow rate sensing bridge650is formed of four temperature measurement resistors such as a resistor652, a resistor654, a resistor656, and a resistor658. The four temperature measurement resistors are disposed along a flow of the gas30to be measured, the resistor652and the resistor654are disposed on an upstream side of a channel of the gas30to be measured with respect to the heat generation body608, and the resistor656and the resistor658are disposed on a downstream side of the channel of the gas30to be measured with respect to the heat generation body608. In order to increase measurement accuracy, the resistor652and the resistor654are disposed such that distances thereof to the heat generation body608are substantially the same as each other, and the resistor656and the resistor658are disposed such that distances thereof to the heat generation body608are substantially the same as each other.

A potential difference between an intersection C between the resistor652and the resistor656and an intersection D between the resistor654and the resistor658is input to the input circuit614via a terminal631and a terminal632. Each resistance of the flow rate sensing bridge650is set such that a potential difference between the intersection C and the intersection D becomes zero, for example, in a state in which a flow of the gas30to be measured is zero in order to increase measurement accuracy. Therefore, in a state in which a potential difference between the intersection C and the intersection D is, for example, zero volts, the CPU612outputs an electric signal indicating that a flow rate of the main passage124is zero from the terminal662on the basis of a measurement result of the flow rate of the gas30to be measured being zero.

In a case where the gas30to be measured flows in an arrow direction inFIG. 11-1, the resistor652or the resistor654disposed on the upstream side is cooled by the gas30to be measured, the resistor656or the resistor658disposed on the downstream side of the gas30to be measured is warmed by the gas30to be measured which is warmed by the heat generation body608, and thus the temperatures of the resistor656and the resistor658are increased. Thus, a potential difference occurs between the intersection C and the intersection D of the flow rate sensing bridge650, and this potential difference is input to the input circuit614via the terminal631and the terminal632. The CPU612searches for data indicating a relationship between the potential difference and a flow rate of the main passage124stored in the memory618on the basis of the potential difference occurs between the intersection C and the intersection D of the flow rate sensing bridge650, so as to obtain a flow rate of the main passage124. An electric signal indicating the flow rate of the main passage124obtained in the above-described way is output via the terminal662. A terminal664and the terminal662illustrated inFIG. 11-1are given new reference numerals, but are included in the connection terminal412illustrated inFIG. 9-1described above.

The memory618stores data indicating a relationship between a potential difference between the intersection C and the intersection D and a flow rate of the main passage124, and also stores correction data for reducing a measurement error such as a variation, obtained on the basis of an actually measured value of a gas after the circuit board400is produced.

The temperature/humidity measurement circuit701includes an input circuit such as an amplifier/A/D converter to which measurement signals from the temperature sensor453and the humidity sensor422are input, an output circuit, a memory which holds data indicating a relationship between a correction value or a temperature and absolute humidity, and the power source circuit622which supplies a predetermined voltage to a necessary circuit. Signals output from the flow rate measurement circuit601and the temperature/humidity measurement circuit701are input to the microcomputer415. The microcomputer415includes a flow rate computation unit, a temperature computation unit, and an absolute humidity computation unit, calculates a flow rate, a temperature, and absolute humidity which are physical quantities of the gas30to be measured on the basis of the signals, and outputs the calculated physical quantities to an ECU200.

The physical quantity measurement device300and the ECU200are connected to each other via a communication cable, and perform communication using digital signals based on a communication standard such as SENT, LIN, or CAN. In the present example, a signal is input to a LIN driver420from the microcomputer415, and LIN communication is performed from the LIN driver420. Information which is output to the ECU200from the LIN driver of the physical quantity measurement device300is output in a superimposed manner through digital communication by using a single-wire or two-wire communication cable.

The absolute humidity computation unit of the microcomputer415performs a process of computing absolute humidity on the basis of information regarding relative humidity which is output from the humidity sensor422and temperature information, and correcting the absolute humidity on the basis of an error. The corrected absolute humidity computed by the absolute humidity computation unit is used for various pieces of engine operation control in a control unit62of an ECU18. The ECU18may directly use comprehensive error information for various pieces of engine operation control.

In the Example illustrated inFIG. 11, a description has been made of a case where the physical quantity measurement device300includes the LIN driver420and performs LIN communication, but the present invention is not limited thereto, and direct communication with the microcomputer415may be performed without using LIN communication as illustrated inFIG. 11-2.

As mentioned above, the embodiments of the present invention have been described in detail, but the present invention is not limited to the embodiments, and various design modifications may occur within the scope without departing from the spirit of the present invention disclosed in the claims. The embodiments have been described in detail for better understanding of the present invention, and thus are not necessarily limited to including all of the above-described configurations. Some configurations of a certain embodiment may be replaced with some configurations of another embodiment, and some configurations or all configurations of another embodiment may be added to configurations of a certain embodiment. The configurations of other embodiments may be added to, deleted from, and replaced with some of the configurations of each embodiment.

REFERENCE SIGNS LIST