JP6941172B2 - Physical quantity detector - Google Patents

Description

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

Currently, a physical quantity detecting device inserted into an intake pipe is required to have a passage structure that protects an electronic circuit against adhesion between a housing case and a cover and has an excellent air flow rate. Metal wire bonding that electrically connects to a circuit board on which electronic components such as microcomputers, capacitors, and chip resistors are mounted must be protected from corrosive gas, water, oil, and the like. Further, the characteristics of the air flow rate can be maintained by wrapping the circuit chamber with a cover.

In the technique described in Patent Document 1, a sub-passage that takes in a part of the fluid to be measured, a sensor chip that is arranged in the sub-passage and measures the flow rate of the fluid to be measured, and a fluid flow rate detected by the sensor chip are electrically signals. It has an electronic component having a resistor inside, and a substrate on which the sensor chip and the electronic component are mounted. The surface of the substrate on the side on which the electronic component is mounted is covered with a filler. A physical quantity measuring device is disclosed.

Japanese Unexamined Patent Publication No. 2016-90413

As shown in Patent Document 1, the filler is filled in a space including a circuit board and a housing on which electronic components are mounted so as to cover the electronic components. For example, an epoxy resin is used as the filler. In addition, the structure is such that the cover is in close contact with the housing surface.

However, in such a structure, after the resin filler is put into the circuit portion in the coating process, the surface tension of the filler is generated with the time until the curing work, and the resin gets wet to the wall surface of the housing. There is a concern that the front cover adhesion will be poor. Due to the poor flatness of the front cover, the gas flow of the flow rate detection unit arranged in the sub-passage is disturbed.

Furthermore, since the resin filler applied to the central portion of the circuit board is pulled to the side surface of the housing due to the generation of surface tension, the final height after thermosetting is lower than immediately after application. Metal wire bonding, which has a height with respect to this change in the height of the filler, tends to be exposed without being completely covered. Therefore, a coating film design for a filler is required.

Therefore, an object of the present invention is to provide a structure of a physical quantity detecting device that suppresses the rising of the filler and protects the metal wire bonding.

The system diagram which shows an Example which used the physical quantity detection device which concerns on this invention in an internal combustion engine control system. Front view of physical quantity detection device. The rear view of the physical quantity detection device. Left side view of the physical quantity detector. Right side view of the physical quantity detector. Top view of the physical quantity detector. Bottom view of the physical quantity detection device. The front view which shows the state which the front cover was removed from the physical quantity detection device. The rear view which shows the state which removed the back cover from a physical quantity detection device. The front view which shows after sealing the resin filler of FIG. 3-1. FIG. 4-1 is a cross-sectional view taken along the line BB. An embodiment of a step structure in a physical quantity detection device. The front view which shows after the epoxy filling of FIG. FIG. 6-1 is a cross-sectional view taken along the line AA.

Examples of the present invention will be described in detail below with reference to the drawings. In the following examples, the same reference numerals show the same configuration even if the drawing numbers are different, and have the same effect. For the configurations already described, only reference numerals may be added to the drawings and the description may be omitted.

[Example 1]
As shown in FIG. 1, the physical quantity detecting device 300 according to the present invention is attached to an intake pipe which is a main air passage so as to measure the physical use of intake air of an internal combustion engine. The physical quantity of the gas to be measured 30 which is the intake air guided to the combustion chamber is detected by the physical quantity detection device 300 according to the present invention, fuel is supplied from the fuel injection valve 152 based on the detected physical quantity, and the intake air 20 It is guided to the combustion chamber in the state of air-fuel mixture.

2-1 to 2-6 are views showing the appearance of the physical quantity detection device 300, FIG. 2-1 is a front view of the physical quantity detection device 300, FIG. 2-2 is a rear view, and FIG. 2-3 is a left side view. 2-4 is a right side view, 2-5 is a plan view, and 2-6 is a bottom view.

The physical quantity detecting device 300 includes a housing 302, a front cover 303, and a back cover 304. The housing 302 is formed by molding a synthetic resin material, and has a flange 311 for fixing the physical quantity detection device 300 to the intake body which is the main passage 124, and electricity with an external device protruding from the flange 311. It has an external connection unit 321 having a connector for making a specific connection, and a measurement unit 331 extending from the flange 311 toward the center of the main passage 124.

The measurement unit 331 is integrally provided with the circuit board 400 by insert molding when the housing 302 is molded (see FIGS. 3-1 and 3-2). The circuit board 400 is provided with at least one detection unit for detecting the physical quantity of the gas to be measured 30 flowing through the main passage 124, and a circuit unit for processing the signal detected by the detection unit. The detection unit is arranged at a position exposed to the gas to be measured 30, and the circuit unit is arranged in a circuit chamber sealed by the front cover 303.

Sub-passage grooves are provided on the front surface and the back surface of the measuring unit 331, and the first sub-passage 305 is formed in cooperation with the front cover 303 and the back cover 304. A part of the circuit board 400 protrudes in the middle of the first sub-passage 305, and a flow rate detection unit 602 (see FIG. 3-1), which is a detection unit, is arranged in the protruding portion to be measured. The flow rate of the gas 30 is detected.

A second sub-passage 306 for taking a part of the gas to be measured 30 such as intake air into the sensor chamber Rs is provided in the middle portion of the measuring unit 331 closer to the flange 311 than the first sub-passage 305. The second sub-passage 306 is formed by the cooperation of the measuring unit 331 and the back cover 304. In the sensor chamber Rs, a pressure sensor and a humidity sensor, which are detection units provided on the back surface of the circuit board 400, are arranged.

The measuring unit 331 has a shape extending long along an axis from the outer wall of the main passage 124 toward the center, but the thickness width has a narrow shape as shown in FIGS. 2-3 and 2-4. It is made up. That is, the measurement unit 331 of the physical quantity detection device 300 has a shape in which the width of the side surface is thin and the front surface is substantially rectangular. As a result, the physical quantity detection device 300 can be provided with the first sub-passage 305 having a sufficient length, and the fluid resistance to the gas to be measured 30 can be suppressed to a small value. Therefore, the physical quantity detecting device 300 can suppress the fluid resistance to a small value and measure the flow rate of the gas to be measured 30 with high accuracy.

Next, the overall structure of the housing 302 will be described with reference to FIGS. 3-1 to 3-5. 3 to 3-5 are views showing a state of the housing 302 in which the front cover 303 and the back cover 304 are removed from the physical quantity detecting device 300, and FIG. 3-1 is a front view of the housing 302 and FIG. 3-. 2 is a rear view of the housing 302, FIG. 3-3 is a right side view of the housing 302, FIG. 3-4 is a left side view of the housing 302, and FIG. 3-5 is a sectional view taken along line AA of FIG. 3-1. ..

The housing 302 has a structure in which the measuring unit 331 extends from the flange 311 toward the center of the main passage 124. A circuit board 400 is insert-molded on the base end side of the measurement unit 331. The circuit board 400 is arranged parallel to the surface of the measuring unit 331 at an intermediate position between the front surface and the back surface of the measuring unit 331, and is integrally molded with the housing 302, and the base end side of the measuring unit 331 is thickened. It is divided into one side and the other side in the parallel direction.

A circuit chamber Rc for accommodating the circuit portion of the circuit board 400 is formed on the front surface side of the measurement unit 331, and a sensor chamber Rs for accommodating the pressure sensor 421 and the humidity sensor 422 is formed on the back surface side. The circuit chamber Rc is sealed and completely isolated from the outside by attaching the front cover 303 to the housing 302. On the other hand, by attaching the back cover 304 to the housing 302, the second sub-passage 306 and the sensor chamber Rs, which is an indoor space communicating with the outside of the measurement unit 331 via the second sub-passage 306, are formed. A part of the circuit board 400 protrudes into the first sub-passage 305 from the partition wall 335 that divides the circuit chamber Rc of the measurement unit 331 and the first sub-passage 305, and the protruding portion of the flow path surface for measurement The flow rate detection unit 602 is provided in the 430.

The second sub-passage 306 is formed in a straight line between the second sub-passage inlet 306a and the second sub-passage outlet 306b in parallel with the flange 311 so as to follow the flow direction of the gas to be measured 30. .. The second sub-passage inlet 306a is formed by cutting out a part of the upstream side outer wall 336, and the second sub-passage outlet 306b is formed by cutting out a part of the downstream side outer wall 338. Specifically, as shown in FIG. 3-3, a part of the upstream side outer wall 336 and a part of the downstream side outer wall 338 are formed from the back surface side of the measuring unit 331 at a position continuously along the upper surface of the partition wall 335. It is formed by cutting out. The second sub-passage inlet 306a and the second sub-passage outlet 306b are cut out to a depth position where they are flush with the back surface of the circuit board 400. Since the gas to be measured 30 passes along the back surface of the substrate body 401 of the circuit board 400, the second sub-passage 306 functions as a cooling channel for cooling the substrate body 401. Many of the circuit boards 400 have heat such as LSIs and microcomputers, and these heats can be transferred to the back surface of the substrate main body 401 and dissipated by the gas to be measured 30 passing through the second sub-passage 306.

The sensor chamber Rs is provided on the base end side of the measuring unit 331 with respect to the second sub-passage 306. A part of the gas to be measured 30 that has flowed from the second sub-passage inlet 306a into the second sub-passage 306 flows into the sensor chamber Rs, and the pressure and relative humidity are measured by the pressure sensor 421 and the humidity sensor 422 in the sensor chamber Rs, respectively. Detected. Since the sensor chambers Rs are arranged closer to the proximal end side of the measuring unit 331 than the second sub-passage 306, the influence of the dynamic pressure of the gas to be measured 30 passing through the second sub-passage 306 can be reduced. Therefore, the detection accuracy of the pressure sensor 421 in the sensor chamber Rs can be improved.

The pressure sensor 421 and the humidity sensor 422 are less affected by the flow of the gas to be measured 30 than the flow rate detection unit 602. In particular, the humidity sensor 422 only needs to secure the diffusion level of water in the gas to be measured 30. It can be provided in the sensor chamber Rs adjacent to the linear second sub-passage 306. On the other hand, the flow rate detection unit 602 requires a flow velocity of a certain level or higher, needs to keep dust and dirt away, and needs to consider the influence on pulsation. Therefore, the flow rate detection unit 602 is provided in the first sub-passage 305 having a curved shape.

The housing 302 is manufactured in the resin molding process. In this resin molding step, the circuit board 400 is built in the resin of the housing 302 and fixed in the housing 302 by the resin mold. By doing so, the shape of the sub-passage for the flow rate detection unit 602 to transfer heat to the gas to be measured 30 and measure the flow rate, for example, the shape of the front side sub-passage groove 332 and the back side sub-passage groove 334. It is possible to maintain the positional relationship and the directional relationship, which are relationships, with extremely high accuracy, and it is possible to suppress errors and variations that occur for each circuit board 400 to extremely small values. As a result, the measurement accuracy of the circuit board 400 can be greatly improved.

The physical quantity detecting device 300 is often produced by mass production, and there is a limit in improving the measurement accuracy in the method of adhering with an adhesive while strictly measuring the physical quantity. However, by molding the sub-passage in the resin molding step of forming the sub-passage through which the gas to be measured 30 flows as in this embodiment and fixing the circuit board 400 at the same time, the variation in measurement accuracy can be significantly reduced. It is possible to significantly improve the measurement accuracy of the physical quantity detecting device 300.

A portion related to flow rate measurement, for example, a measurement flow path surface 430 to which a flow rate detection unit 602 and a flow rate detection unit 602 are attached is provided on the surface of the circuit board 400. The flow rate detection unit 602 and the measurement flow path surface 430 are exposed from the resin forming the housing 302. That is, the flow rate detection unit 602 and the measurement flow path surface 430 are not covered with the resin that forms the housing 302.

The circuit board 400 is fixed by the resin mold, and at the same time, the sub-passage groove for molding the first sub-passage 305 is formed by the resin mold. By doing so, the flow rate detection unit 602 can be fixed to the shape of the sub-passage groove and the sub-passage groove with extremely high accuracy. By integrally molding the circuit board 400 with the housing 302, the circuit board 400 is fixed to the housing 302 having the first sub-passage 305, so that the circuit board 400 can be reliably fixed to the housing 302. In particular, since the protruding portion 403 of the circuit board 400 penetrates the partition wall 335 and protrudes into the first sub-passage 305, the sealing property between the first sub-passage 305 and the circuit chamber Rc is high. It is possible to prevent the gas to be measured 30 from leaking from the first sub-passage 305 into the circuit chamber Rc, and to prevent the circuit parts and wiring of the circuit board 400 from coming into contact with the gas to be measured 30 and corroding.

[Example 2]
A second embodiment of the present invention will be described with reference to FIG. The description of the same configuration as that of the first embodiment will be omitted.

In this embodiment, the inside of the circuit chamber Rc is sealed with a filler 6 which is a circuit protective material. In this embodiment, a resin material such as epoxy is used as the filler.

Since a voltage is applied to the resistor in the electronic component 15 in the circuit chamber Rc, the resistor 7 generates heat. Electronic components include, for example, a transceiver, a microcomputer, and a thermistor. Due to this heat generation, the temperature of the physical quantity detecting device rises and the difference from the environmental temperature becomes large, so that the flow rate measurement accuracy decreases. Therefore, it is necessary to suppress the temperature rise due to heat generation around the circuit chamber Rc. In this embodiment, the circuit chamber Rc is filled with the filler 6 to cover the electronic component 15 that generates heat. By adopting a member having good thermal conductivity to the atmosphere such as epoxy for the filler 6, the heat of the circuit component 15 can be efficiently propagated to the air flowing through the main passage. Therefore, the heat of the electronic component 15 can be easily dissipated, and the temperature rise can be suppressed.

Further, since the physical quantity measuring device 300 is used for measuring the flow rate of a vehicle equipped with an internal combustion engine, it is exposed to an atmosphere such as exhaust gas, gasoline, or salt water. By covering the electronic component 15 with the filler 6, the electronic component 3 is prevented from being exposed to the atmosphere, so that the characteristic fluctuation of the electronic component 15 can be prevented, and a more accurate thermal air flow meter can be provided.

Further, the circuit board 400 is electrically connected to the external terminal 323 by the bonding wire 413. The material of the bonding wire 413 is, for example, Al, Au, or Cu. The loop height of the wire 413 is set lower than that of the fixing portion 372 so as not to come into contact with the front cover 303.

As a further effect of the filler 6, since the wire bonding 413 is fixed, deformation of the wire bonding 413 that is strain-dependent due to vibration can be suppressed. Further, since the wire bonding is lower (completely covered) than the surface of the filler 6, corrosion can be prevented as in the circuit component 15. Therefore, a more reliable physical quantity measuring device can be provided. In particular, when it is used for controlling an internal combustion engine of an automobile, it is particularly effective because it is necessary to consider the reliability of engine vibration.

The filler 6 is filled in the circuit chamber Rc in the form of a liquid or gel, and then cured by heat treatment. Due to the relationship between the surface tension of the wall surface of the circuit chamber Rc and the resin shrinkage, the wall surface side rises, and the center side is dragged by it and becomes lower in height than at the time of filling. As a result, the final product is provided with an inclined shape in which the thickness of the filler 6 is thicker on the wall surface side than on the center side.

The wire loop shape is configured to have an apex on the connection terminal side and a gentle slope toward the pad side of the circuit board 400 so as to follow the inclined shape. It becomes possible to cope with the rise.

The physical quantity measuring device 300 inserted and mounted in the main flow path is required not to be a resistance to the flow in the main flow path. Therefore, when a method is adopted in which the wires are not exposed by simply increasing the thickness of the circuit chamber Rs, the thickness of the physical quantity measuring device 300 increases. According to this embodiment, the amount of the filler 6 injected can be reduced by forming the loop shape in consideration of the shrinkage and the rise of the filler 6, and the increase in the thickness of the housing can be suppressed and efficiently. It is possible to prevent the wire from being exposed.

In particular, when a double-sided mounting structure in which these sensors, circuit components, etc. are mounted on both sides of the circuit board 400 is adopted in order to measure physical quantities of a plurality of fluids such as flow rate, pressure, and humidity, the physical quantity measuring device 300 The thickness is limited. This embodiment is particularly effective in improving the wire reliability while suppressing the fluid resistance of the physical quantity measuring device 300 in the structure in which the thickness of the circuit chamber Rs is limited.

[Example 3]
A third embodiment of the present invention will be described with reference to FIGS. 5, 6-1 and 6-2. The description of the same configuration as that of the second embodiment will be omitted.

In this embodiment, in addition to the configuration of the second embodiment, stepped portions 13a, 13b, 13c, 13d, and 13e are formed in the corners of the circuit chamber Rs at an angle of 90 ° or less.

The stepped portions 13a to 13e have a shape having a larger angle than the corners, and more preferably have an R-shaped shape as shown in FIG. The R shape makes it possible to effectively utilize the limited space of the circuit room Rc.

In the corners where the angle is small, the resin is more likely to rise due to surface tension. Since the thickness (height) of the circuit chamber Rc varies due to the variation in parts, the filler 6 may rise and partially cover the laser welded portion 372b when the thickness is small. In that case, poor adhesion occurs in the laser welding between the front cover 303 and the laser welding portion 372b, and the yield deteriorates.

Further, after the filler 6 is filled, the rising may progress even if a time elapses until the curing occurs. In this case as well, the yield deteriorates.

When the stepped portions 13a to 13e are present, the filler 6 charged into the circuit chamber Rc can flow in a wider direction at the corners and suppress the rising of the filler 6 reaching the laser welded portion 372b at the corners. You can.

When the step portions 13a to 13e are made higher than the central portion (minimum thickness portion) of the filler 6, the rising of the filler 6 can be suppressed more effectively. Due to surface tension and shrinkage, the central portion of the filler 6 becomes low, and the resin (filler) in the central portion is brought closer to the corner side. In this embodiment, the rise can be suppressed by reducing the amount of resin in the corners by the stepped portion. Further, since the rising of the step portion and the corner portion can be discontinuous, the amount of rising can be reduced. More preferably, by making the height of the step portion higher than the injection height at which the filler 6 is injected, it is possible to further prevent the laser welding portion from reaching the welded portion 372b.

Rc circuit chamber 6 Filling material 13a, 13b, 13c, 13d, 13e Step portion 124 ... Main passage 300 ... Physical quantity detection device 302 ... Housing 303 ... Front cover 304 ... Back cover 305 ... First subpassage 311 ... Flange 321 ... External connection Unit 331 ... Measuring unit 372 Fixing unit 372b Laser welding unit 400 Circuit board 602 ... Flow detection unit 421 ... Pressure sensor 422 ... Humidity sensor 413 ... Wire

Claims (7)

A circuit board on which circuit components are mounted and
A housing for accommodating the circuit board and
A physical quantity detecting device including an external connection terminal electrically connected to the circuit board via a bonding wire, and the housing including a wall surface forming a circuit chamber for accommodating the circuit components.
The circuit protection material to be filled in the circuit chamber is provided.
The circuit protective material has a shape that is thicker on the external connection terminal side than on the pad side connected to the bonding wire of the circuit board.
The loop apex of the bonding wire is on the external connection terminal side.
The circuit board has the circuit board as the bottom surface, and when the surface parallel to the circuit board is viewed from a direction perpendicular to the circuit board, the angle formed by the two wall surfaces forming the corners of the circuit board is It is 90 degrees, and the two walls forming the corner of the circuit room are perpendicular to the circuit board.
A stepped portion having a stepped surface parallel to the circuit board is provided between the two wall surfaces.
A first curved surface is provided in a region perpendicular to the circuit board from the stepped surface of the stepped portion.
A second curved surface having a radius of curvature larger than that of the first curved surface is provided in a region in a direction perpendicular to the circuit board from the step surface of the step portion.
A physical quantity detection device characterized in that. The physical quantity detecting device according to claim 1, wherein the circuit chamber is formed by the cooperation of the housing and a cover welded by laser welding to the housing. The physical quantity detecting device according to claim 1, wherein the height of the stepped surface of the stepped portion is larger than the minimum height of the circuit protective material. The physical quantity detecting device according to claim 1, wherein the circuit board is a double-sided mounting board on which at least one of a sensor or an electronic component is mounted on both sides. The physical quantity detecting device according to claim 4, wherein the circuit board is inserted into a housing. The physical quantity detecting device according to claim 5, wherein the circuit board has a flow sensor and an electronic component mounted on one side thereof, and a pressure sensor and a humidity sensor mounted on the other side. The method for manufacturing a physical quantity detecting device according to claim 1.
An insert process in which a double-sided mounting board on which a circuit component is mounted on one surface and a detection element is mounted on the other surface is inserted into the housing.
It comprises an injection step of injecting a circuit protective material into the one surface of the double-sided mounting board.
In the insert step, the step portion, the first curved surface, and the second curved surface are formed at the corners of the circuit chamber.
A method for manufacturing a physical quantity detecting device, which comprises injecting the circuit protective material so as not to exceed the stepped surface of the stepped portion in the injection step.

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