Wärmeflussmesser

Abstract

Heat flow meter (20) comprising: a flow detection element (321) configured to detect an air flow; and a printed circuit board (300) arranged such that a part of the printed circuit board (300) faces a detection surface (322) of the flow detection element (321), the printed circuit board (300) being provided with a conductive resin element (400) comprising a conductive substance and a resin as components on at least a part of a section of the printed circuit board (300) which is provided in an auxiliary channel (135) on a surface facing the detection surface (322) of the flow detection element (321).

Description

Technical field

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

[0002] For example, the technique described in PTL 1 is used in conjunction with a heat flow meter to measure the flow rate of a target gas. Citation list of patent literature

[0003] PTL 1: JP 2019-7902 A Summary of the invention TECHNICAL PROBLEM

[0004] In the heat flow meter described in PTL 1, part or all of the plate-shaped element facing a flow detection unit is made of a conductive material, and this conductive material neutralizes charged impurities present in the target gas. However, in the heat flow meter described in PTL 1, the main channel must have a complex shape, and there is room for improvement to reduce the cost of the neutralization function.

[0005] The present invention was made in consideration of the above, and one object of the present invention is to provide an extremely reliable heat flow meter. Solution to the problem

[0006] To solve the aforementioned problems, a heat flow meter according to the present invention comprises: a flow detection element configured to detect airflow; and a printed circuit board arranged such that a portion of the board faces a detection surface of the flow detection element. The printed circuit board is provided with a conductive resin component comprising a conductive substance and a resin as constituent elements on at least a portion of a section provided in an auxiliary channel on a surface facing the detection surface of the flow detection element. Advantageous effects of the invention

[0007] According to the present invention, a very reliable heat flow meter can be provided.

[0008] Tasks, configurations and effects that go beyond the above description will become clear through the explanation of the following embodiments. List of characters Fig. Figure 1 is a diagram showing the configuration of a control system for electric fuel injection for an internal combustion engine using a heat flow meter according to the present embodiment. Fig. Figure 2 is a front view of the heat flow meter according to the present embodiment. Fig. Figure 3 is a cross-sectional view of the heat flow meter along the line shown in Fig. 2 shown line AA. Fig. 4 is a front view of a printed circuit board from which a housing is made. Fig. 2 was removed. Fig. Figure 5 is a front view of a printed circuit board, from which a circuit component, such as a chip package, is shown. Fig. 4 is away. Fig. 6 is a schematic cross-sectional view of the in Fig. 5 printed circuit board shown along line BB. Fig. Figure 7 is a view to illustrate modification 1 of the printed circuit board and a conductive coating film. Fig. 8 is a schematic cross-sectional view of the in Fig. 7 printed circuit board shown along line CC. Fig. Figure 9 is a view to illustrate modification 2 of the printed circuit board and the conductive coating film. Fig. 10 is a schematic cross-sectional view of the in Fig. 9 shown circuit board along line DD. Fig. Figure 11 is a view to illustrate modification 3 of the printed circuit board and the conductive coating film. Fig. 12 is a schematic cross-sectional view of the in Fig. 11 printed circuit boards shown along line EE. Description of embodiments

[0009] One embodiment of the present invention is described below with reference to the drawings. Configurations designated by the same reference numerals in the respective embodiments have similar functions in those embodiments unless otherwise specified, so their description is omitted. Furthermore, orthogonal coordinate axes are described in the necessary drawings to clarify the description of the positions of the respective parts.

[0010] As in Fig. As shown in Figure 1, a heat flow meter 20 mounted on a vehicle is used, which is attached to a main channel 22 representing the intake manifold of an internal combustion engine 10. As described below, the heat flow meter 20 not only solves the problems described in the "Technical Problem" section and produces the effects described in the "Advantages of the Invention" section, but also solves various problems that are necessary as a product of adequately addressing the various problems described above, and produces various effects. Specific problems to be solved with the heat flow meter 20 and specific effects to be achieved with it are explained below.

[0011] Fig. Figure 2 is a front view of the heat flow meter 20 according to the present embodiment. Fig. Figure 2 shows a state in which a cover is 200 away from a housing 100. Fig. Figure 3 is a cross-sectional view of the heat flow meter 20 along the line shown in Fig. 2 shown line AA. Fig. Figure 4 is a front view of a printed circuit board 300, where the housing 100 is made of Fig. 2 was removed. In the following description, it is assumed that a target gas 2 is located along a central axis 22a of the in Fig. The main channel 22 shown in 1 flows.

[0012] The heat flow meter 20 is used in a state in which it is inserted into the main channel 22 through a mounting opening provided in a channel wall of the main channel 22 and is attached to the main channel 22. The heat flow meter 20 comprises a housing arranged in the main channel 22 through which the target gas 2 flows. The housing of the heat flow meter 20 consists of the housing 100 and the cover 200 attached to the front of the housing 100.

[0013] The housing 100 is manufactured, for example, by injection molding a synthetic resin material.

[0014] The cover 200 consists, for example, of a plate-shaped element made of a metal or a synthetic resin material. In the present embodiment, an aluminum alloy or a synthetic resin material is formed by injection molding. The cover 200 is large enough to completely cover the front of the housing 100.

[0015] The housing 100 has a flange 111 for attaching the heat flux meter 20 to the main channel 22 and a connector 112 that projects from the flange 111 and is exposed on the outside of the main channel 22 for electrical connection to an external device. Furthermore, the housing 100 includes a measuring unit 113 that extends from the flange 111 in the direction of the central axis 22a of the main channel 22 in order to measure the physical quantity of the target gas 2 flowing through the main channel 22.

[0016] The measuring unit 113 has a thin and elongated shape, extending straight from the flange 111. The measuring unit 113 comprises a wide front surface 121 and a wide rear surface 122, a pair of narrow side surfaces 123 and 124, and a narrow bottom surface 125.

[0017] The front surface 121 and the rear surface 122 are rectangular surfaces with long sides and short sides in the longitudinal and transverse directions, respectively, of the measuring unit 113 and are main surfaces that have a large surface area comprising the surfaces that form the measuring unit 113. The front surface 121 and the rear surface 122 are arranged parallel to each other along the central axis 22a of the main channel 22 when the heat flow meter 20 is attached to the main channel 22. The side surface 123 is located on one side in the lateral direction of the measuring unit 113 and is arranged to face the upstream side of the main channel 22 when the heat flow meter 20 is attached to the main channel 22. The side surface 124 is located on the other side in the lateral direction of the measuring unit 113 and is arranged so that it faces the downstream side of the main channel 22 when the heat flux meter 20 is attached to the main channel 22.The lower surface 125 is connected to the front surface 121, the rear surface 122, the side surface 123, and the side surface 124. The lower surface 125 is located at the tip section of the measuring unit 113, which is separated from the flange 111, and is arranged parallel to the central axis 22a of the main channel 22 when the heat flow meter 20 is attached to the main channel 22. Since the side surfaces 123 and 124, which face the upstream and downstream sides of the main channel 22, respectively, have a narrow shape in the heat flow meter 20, it is possible to reduce the fluid resistance to a small value with respect to the target gas 2.

[0018] In the present embodiment, the position of the heat flow meter 20 when attached to the main channel 22 is such that the base section of the measuring unit 113 is located near the flange 111 on the upper side, and the tip section of the measuring unit 113, separated from the flange 111, is located on the lower side. However, the position of the heat flow meter 20 when attached to the main channel 22 is not limited to the present embodiment, and various positions are possible. For example, the position of the heat flow meter 20 can be such that the base section and the tip section of the measuring unit 113 are mounted horizontally at the same height.

[0019] In the measuring unit 113, an inlet 131 of auxiliary channels 134 and 135 is provided in the side surface 123, and a first outlet 132 and a second outlet 133 are provided in the side surface 124. The inlet 131, the first outlet 132, and the second outlet 133 are located at the apex of the measuring unit 113, which extends from the flange 111 toward the central axis 22a of the main channel 22. Therefore, the measuring unit 113 can direct the target gas 2, which flows in a section near the central axis 22a, away from the inner surface of the channel wall of the main channel 22 into the auxiliary channels 134 and 135. This allows the heat flow meter 20 to measure the flow rate of the target gas 2 flowing in the area near the central axis 22a and to suppress a decrease in measurement accuracy due to the influence of heat or similar factors.

[0020] The measuring unit 113 is equipped with a flow detection element 321, an intake air temperature sensor 331 and a humidity sensor 333.

[0021] The flow detection element 321 has a membrane-like (thin-film) detection surface 322 and is located in the center of the auxiliary channels 134 and 135. The flow detection element 321 detects the flow of the target gas 2 flowing through the main channel 22, i.e., the air flow. The intake air temperature sensor 331 is located in the center of a temperature detection channel 141, one end of which opens near the inlet 131 provided in the side surface 123, and the other end opens towards both the front surface 121 and the rear surface 122 of the measuring unit 113. The intake air temperature sensor 331 detects the temperature of the target gas 2 flowing through the main channel 22. The humidity sensor 333 is located in a humidity measuring chamber 142 of the measuring unit 113.The humidity sensor 333 measures the humidity of the target gas 2, which enters the humidity measuring chamber 142 through a window section 143 opened in the rear surface 122 of the measuring unit 113.

[0022] The measuring unit 113 is provided with auxiliary channel slots 151 and 152 for forming the auxiliary channels 134 and 135 and a circuit chamber 140 for receiving the circuit board 300.

[0023] The circuit chamber 140 and the auxiliary channel grooves 151 and 152 are recessed into the front surface 121 of the measuring unit 113 and are covered by attaching the cover 200 to the front surface of the housing 100. The circuit chamber 140 is located in an area near the side surface 123 in the measuring unit 113. The auxiliary channel grooves 151 and 152 are located in an area closer to the lower surface 125 than the circuit chamber 140, and in an area closer to the side surface 124 than the circuit chamber 140 in the measuring unit 113.

[0024] The auxiliary channel grooves 151 and 152 form the auxiliary channels 134 and 135 in conjunction with the cover 200, which covers the front surface 121 of the measuring unit 113. The auxiliary channel grooves 151 and 152 comprise the first auxiliary channel groove 151 and the second auxiliary channel groove 152.

[0025] The first auxiliary channel groove 151 is shaped such that it extends along the lateral direction of the measuring unit 113 between the inlet 131, which opens towards the side surface 123 of the measuring unit 113, and the first outlet 132, which opens towards the side surface 124 of the measuring unit 113. The first auxiliary channel groove 151, in conjunction with the cover 200, forms the first auxiliary channel 134. The first auxiliary channel 134 receives the target gas 2 flowing through the main channel 22 from the inlet 131 and returns the extracted target gas 2 from the first outlet 132 back into the main channel 22. The first auxiliary channel 134 has a flow path that extends from the inlet 131 along the flow direction of the target gas 2 in the main channel 22 and leads to the first outlet 132.

[0026] The second auxiliary channel groove 152 branches off from the center of the first auxiliary channel groove 151, bends towards the base section of the measuring unit 113 (towards the flange 111), and extends longitudinally along the measuring unit 113. The second auxiliary channel groove 152 is then bent towards the side surface 124 at the base section of the measuring unit 113, folded back towards the tip section of the measuring unit 113 (towards the lower surface 125) to form a U-turn, and extends again longitudinally along the measuring unit 113. The second auxiliary channel groove 152 is bent towards the side surface 124 in front of the first outlet 132 and is designed to be continuous with the second outlet 133, which opens towards the side surface 124. The second outlet 133 is arranged so that it faces the downstream side of the main channel 22.The second outlet 133 has an opening area that is slightly larger than that of the first outlet 132 and is formed at a position adjacent to the side of the base section of the measuring unit 113 in relation to the first outlet 132.

[0027] The second auxiliary channel groove 152, in conjunction with the cover 200, forms the second auxiliary channel 135. The second auxiliary channel 135 allows the target gas 2, branched off and flowing in from the first auxiliary channel 134, to pass through and returns the target gas 2 from the second outlet 133 to the main channel 22. The second auxiliary channel 135 has a flow path that moves back and forth along the longitudinal direction of the measuring unit 113. That is, the second auxiliary channel 135 comprises a forward path section 136 branching off in the middle of the first auxiliary channel 134 and extending towards the base section of the measuring unit 113 (towards the flange 111), and a backward path section 137 which is folded back at the base section of the measuring unit 113 to make a U-turn and extends towards the tip section of the measuring unit 113 (towards the lower surface 125).The forward path section 136 branches off in the middle of the first auxiliary channel 134 and extends away from the first auxiliary channel 134. The reverse path section 137 is bent at an end section of the forward path section 136 to make a U-turn and extends in a direction approaching the first auxiliary channel 134. The reverse path section 137 has a flow path leading to the second outlet 133, which is open to the downstream side of the main channel 22 at a position on the downstream side of the main channel 22 with respect to the inlet 131.

[0028] In the second auxiliary channel 135, the flow detection element 321 is located in the middle of the forward path section 136. Since the second auxiliary channel 135 is designed to extend longitudinally along the measuring unit 113 and to move back and forth, a greater channel length can be ensured, and the influence on the flow detection element 321 can be reduced if pulsation occurs in the main channel 22. The flow detection element 321 is housed in a chip package 310, and the chip package 310 is mounted on the printed circuit board 300. The chip package 310 is a carrier body that supports the flow detection element 321.

[0029] In the present embodiment, an example of the resin-sealed chip package 310, which exposes at least the detection surface 322 (thin section) of the flow detection element 321, is shown as a carrier body that supports the flow detection element 321, but the present invention is not limited thereto. Since the throttle shape can be integrally formed in the chip package 310 when the flow detection element 321 is resin-sealed, it is possible to reduce the variation in the positional relationship between the flow detection element 321 and the throttle shape, and there is the advantage that the flow detection accuracy is improved.

[0030] Circuit components such as the chip package 310, the intake air temperature sensor 331, the humidity sensor 333, and a pressure sensor 335 are mounted on a mounting surface 300a of the circuit board 300. The intake air temperature sensor 331, the humidity sensor 333, and the pressure sensor 335 are not strictly necessary, and different sensors can be selected for mounting depending on the requirements. The circuit board 300 has a substantially rectangular shape in plan view. As shown in Fig. As shown in Figure 2, the circuit board 300 is arranged in the measuring unit 113 such that the longitudinal direction of the circuit board 300 extends from the base section to the tip section of the measuring unit 113, and the transverse direction of the circuit board 300 extends from the side surface 123 to the side surface 124 of the measuring unit 113.

[0031] As in Fig. As shown in Figure 4, the circuit board 300 comprises the main body 301, which is arranged in the circuit chamber 140, a first projection 302, which is arranged in the temperature detection channel 141, a second projection 303, which is arranged in the humidity measurement chamber 142, and a third projection 304, which is arranged in the forward path section 136 of the second auxiliary channel 135. The pressure sensor 335 and the chip package 310 are mounted on the main body 301, the intake air temperature sensor 331 is mounted on the tip section of the first projection 302, and the humidity sensor 333 is mounted on the second projection 303.

[0032] The third projection 304 is designed to extend from the circuit chamber 140 to the auxiliary channel slots 151 and 152. Specifically, the third projection 304 extends from the main body 301 located in the circuit chamber 140 towards the forward path section 136 of the second auxiliary channel 135. The third projection 304 has a section 305 facing the detection surface 322 of the flow detection element 321 provided in the chip package 310. In other words, the facing section 305 is formed by the third projection 304 of the printed circuit board 300.

[0033] As in Fig. Figure 3 shows that the chip package 310 has a resin housing in which the flow detection element 321, an LSI 324, and a conductor frame 325 are formed by a resin element 326. The flow detection element 321 and the LSI 324 are mounted on the conductor frame 325. The resin element 326 seals the conductor frame 325 on which the flow detection element 321 and the LSI 324 are mounted, so that the membrane-shaped detection surface 322 of the flow detection element 321 is exposed.

[0034] The chip package 310 is formed in the shape of a rectangular, flat plate with a predetermined thickness. The chip package 310 has a front surface 310a facing the cover 200 and a rear surface 310b, which is a surface opposite the front surface 310a in the direction of the thickness of the chip package 310. The front surface 310a and the rear surface 310b of the chip package 310 are large main surfaces and lie along the mounting surface 300a of the printed circuit board 300.

[0035] As in the Fig. 3 and Fig. As shown in Figure 4, the chip package 310 comprises a mounting section 311 which is attached to the main body 301 of the printed circuit board 300 in the circuit chamber 140, and a projecting section 312 which projects from the mounting section 311 in the direction of the second auxiliary channel 135.

[0036] The mounting section 311 of the chip package 310 is provided with a plurality of terminals 313. The plurality of terminals 313 are arranged to project from both ends of the mounting section 311 of the chip package 310 in directions away from each other along the width of the mounting section 311. The tip of each terminal 313 is bent in the direction of the thickness of the mounting section 311 and is located at a point that protrudes from the rear surface 310b of the mounting section 311. The mounting section 311 of the chip package 310 is attached to the main body 301 of the printed circuit board 300 by connecting the tip of the terminal 313 to the mounting surface 300a of the main body 301 of the printed circuit board 300 using solder or the like.The mounting section 311 of the chip package 310 is attached such that the rear surface 310b of the mounting section 311 and the mounting surface 300a of the main body 301 of the circuit board 300 form a gap in the direction of the thickness of the mounting section 311.

[0037] The forward section 312 of the chip package 310 is arranged such that it faces the third projection 304 (facing section 305) of the printed circuit board 300 in the forward path section 136 of the second auxiliary channel 135. A recessed groove 314 is formed in the forward section 312 of the chip package 310, extending from the rear surface 310b of the forward section 312 towards the front surface 310a. The recessed groove 314 is formed on the rear surface 310b of the forward section 312 such that it extends across the width direction of the forward section 312. The detection surface 322 of the flow detection element 321 is arranged such that it is exposed in an intermediate position in the extension direction of the recessed groove 314.

[0038] The chip package 310 is arranged such that the recessed groove 314 extends along the forward path section 136 of the second auxiliary channel 135. The chip package 310 is arranged such that the detection surface 322 of the flow detection element 321 faces the third projection 304 (facing section 305), which is part of the circuit board 300. In the chip package 310, a channel P is formed between the recessed groove 314 of the projecting section 312 and the third projection 304 (facing section 305) of the circuit board 300. That is, the recessed groove 314 forms the channel P in conjunction with the third projection 304 (facing section 305). The channel P is part of the forward path section 136 of the second auxiliary channel 135, through which the target gas 2 flows. The target gas 2 flowing through the second auxiliary channel 135 passes through channel P, and the detection surface 322 of the flow detection element 321 is exposed.

[0039] The detection surface 322 of the flow detection element 321 has a pair of temperature sensor resistors and a heater and detects a change in the temperature distribution of the target gas 2 along the channel P. The flow detection element 321 detects the flow of the target gas 2 flowing through the passage P based on the change in temperature distribution detected by the detection surface 322. This allows the heat flow meter 20 to measure the flow of the intake air, i.e., the target gas 2, which is directed from the main channel 22 into the secondary channels 134 and 135, and to output a signal indicating the measurement result to a control device 4.

[0040] The intake air, used as the target gas 2 for measurement, can contain contaminants such as dust, oil, carbon, or similar substances. Most contaminants, such as dust, are almost completely removed by an air purifier 21, but contaminants consisting of fine particles can pass through the air purifier 21 and enter the secondary channels 134 and 135 to a small extent. It is known that these fine-particle contaminants collide with each other to generate a charge transfer and are, for example, charged to act as a positive electrode.

[0041] If the target gas 2, which contains the charged impurities, is directed into the auxiliary channels 134 and 135 for an extended period, the charged impurities can accumulate on the detection surface 322 of the flow detection element 321 provided in the auxiliary channels 134 and 135. If impurities are deposited on the detection surface 322, the flow detection element 321 cannot adequately detect the temperature distribution of the target gas 2, and the flow rate of the target gas 2 may not be adequately detected. Therefore, it is important that no charged impurities are deposited on the detection surface 322.

[0042] As one method for reducing the deposition of charged impurities on the detection surface 322, it is conceivable to equip the heat flow meter 20 with a neutralization function to electrically neutralize the charged impurities contained in the gas 2 being measured and thus reduce their deposition on the detection surface 322. This neutralization function is a function of setting the potential of the adjacent section 305 of the circuit board 300, which forms the channel P where the detection surface 322 is exposed, to a potential capable of neutralizing charged impurities. In this neutralization function, the adjacent section 305 of the circuit board 300 can be conductive, but preferably has a predetermined potential.This is because the charged impurities easily come into contact with the facing section 305, which performs the neutralization function, due to the Coulomb force generated between them and this section, thus promoting the neutralization of the charged impurities. Examples of the specified potential are a power supply potential and a ground potential.

[0043] This neutralization function can be achieved, for example, by exposing a wiring pattern that has a ground potential of the printed circuit board 300 at the mounting surface 300a of the printed circuit board 300 on the adjacent section 305 of the printed circuit board 300. Since the wiring pattern of the printed circuit board 300 usually consists of a corrosion-prone metal foil, e.g., a copper foil, the plating is carried out with corrosion protection in mind.

[0044] Since the heat flow meter 20 is a product requiring high reliability, such as in a vehicle, it is necessary to apply multiple layers to the exposed wiring pattern on mounting surface 300a of the printed circuit board 300. For example, if the exposed wiring pattern on mounting surface 300a of the printed circuit board 300 is a copper foil, an electroplated nickel plating is applied to the wiring pattern, an electroplated Pd plating is applied to the electroplated nickel plating, and then an electroplated gold replacement plating is applied. Applying such a large number of layers to the exposed wiring pattern on the surface of the printed circuit board 300 can significantly increase the cost of the heat flow meter 20.

[0045] Furthermore, the exposed wiring pattern on mounting area 300a of the printed circuit board 300 is typically surrounded by an insulating film, such as a solder mask, in one direction along the mounting area 300a of the printed circuit board 300. Therefore, even when the plating is applied to the exposed wiring pattern on mounting area 300a of the printed circuit board 300, it only covers the top surface of the wiring pattern, and it is difficult to completely cover the side surface of the wiring pattern that borders the insulating film, such as the solder mask. In particular, when applying electroplated nickel plating, there is a high probability that the electroplated nickel plating will be exposed on the side surface of the wiring pattern and will corrode.If the electroplated nickel plating is corroded, the wiring pattern of the circuit board 300 is also likely to corrode, so that the potential of the facing section 305 of the circuit board 300 is not adequately stabilized, and there is a possibility that the neutralization function of impurities is impaired. As a result, charged impurities can easily accumulate on the detection surface 322 of the heat flow meter 20. Consequently, the heat flow meter 20 may not be able to adequately detect the flow rate of the target gas 2 over a longer period of time.

[0046] In the heat flow meter 20 according to the present embodiment, the neutralization function of impurities is reliably realized at low cost and a long service life is achieved by sealing a second conductive section 309, which is a wiring pattern exposed on the mounting surface 300a of the circuit board 300, with a conductive coating film 400 described below.

[0047] Fig. Figure 5 is a front view of the circuit board 300, from which circuit components such as the chip package 310 are mounted. Fig. 4 are away. Fig. Figure 6 is a schematic cross-sectional view of the printed circuit board 300 along the in Fig. 5 shown line BB.

[0048] As in Fig. As shown in Figure 6, the printed circuit board 300 has a multi-layered structure in which the insulations 306 and 307 and the conductive sections 308 and 309 are laminated.

[0049] The insulations 306 and 307 comprise the first insulation 306, which is provided as an inner layer of the printed circuit board 300 and consists of an insulating substrate such as a glass-epoxy substrate or a paper-phenol substrate, and the second insulation 307, which is provided as the outermost layer of the printed circuit board 300 and consists of an insulating film such as a solder mask. The first insulation 306 encloses the conductive sections 308 and 309, which are provided as an inner layer of the printed circuit board 300. The second insulation 307 surrounds the conductive sections 308 and 309, which are provided as the outermost layer of the printed circuit board 300, extending from the mounting surface 300a of the printed circuit board 300.

[0050] Conductive sections 308 and 309 are wiring patterns consisting of a metal foil, e.g., a copper foil. Conductive sections 308 and 309 comprise the first conductive section 308, which has a potential different from the ground potential of the circuit board 300, and the second conductive section 309, which has the ground potential. The ground potential of the circuit board 300 can be a potential that can remove charged impurities contained in the target gas 2. If the potential of the charged impurities is the positive electrode, the ground potential of the circuit board 300 can be the negative electrode.

[0051] The first conductive section 308 comprises a wiring pattern that is provided as a layer inside the printed circuit board 300, as shown in Fig. 6 shown, and a wiring pattern that is provided as the outermost layer of the printed circuit board 300, as shown in Fig. Figure 5 shows the wiring pattern formed as the outermost layer of the printed circuit board 300. For example, the wiring pattern is a metal pad to which the terminal 313 of the chip package 310 is connected. The first conductive section 308 is placed above the main body 301, the first protrusion 302, the second protrusion 303, and the third protrusion 304 of the printed circuit board 300.

[0052] The second conductive section 309 is a wiring pattern that is electrically connected to a wiring pattern on the ground of the printed circuit board 300. That is, the second conductive section 309 has the ground potential of the printed circuit board 300. The second conductive section 309 is provided as the outermost layer of the printed circuit board 300. The second conductive section 309 is a section that extends from the insulations 306 and 307 of the printed circuit board 300 to the mounting surface 300a of the printed circuit board 300. The second conductive section 309 is provided at the facing section 305 (third projection 304) of the printed circuit board 300, which faces the detection surface 322 of the flow detection element 321.

[0053] As in Fig. As shown in Figure 5, the second conductive section 309 has a rectangular shape along the mounting surface 300a of the printed circuit board 300. The second conductive section 309 is configured to extend along the longitudinal direction of the forward path section 136 of the second auxiliary channel 135 and the lateral direction of the forward path section 136 of the second auxiliary channel 135. That is, the second conductive section 309 is shaped to extend along the longitudinal direction of the channel P formed by the recessed groove 314 of the chip package 310 and the lateral direction of the channel P.

[0054] The second conductive section 309 is designed to face the conductive coating film 400 on the inside of channel P, which is part of the forward path section 136 of the second auxiliary channel 135 through which the target gas 2 flows. The second conductive section 309 is designed to seal the inside of channel P from the side of the circuit board 300 at the facing section 305 of the circuit board 300. The second conductive section 309 is designed to span channel P in the width direction. The second conductive section 309 is designed to extend beyond the width of channel P to a section 312a that is closer to the circuit chamber 140 than channel P of the preceding section 312. In other words, the second conductive section 309 is designed such that its length W1 extends along the width of the second auxiliary channel 135, i.e.,The length W1 along the width of the channel P is longer than the width W3 of the channel P or the width W4 of the forward path section 136 of the second auxiliary channel 135. However, the length W1 of the second conductive section 309 along the width of the channel P is preferably equal to or longer than the width W2 of the detection surface 322 of the flow detection element 321 provided in the channel P, but is not particularly limited.

[0055] The conductive coating film 400 is an example of a conductive resin element containing a conductive substance and a resin as components. It is applied to the printed circuit board 300 and formed into a film. The conductive substance that is a component of the conductive coating film 400 can be, for example, carbon or a metal such as silver, copper, or aluminum, or a metal oxide such as tin oxide, tin-doped indium oxide (ITO), or antimony-doped tin oxide (ATO). The resin that is a component of the conductive coating film 400 can be, for example, a resin that adheres to the printed circuit board 300, such as an epoxy resin, a phenolic resin, a fluorinated resin, or a polyester resin.From the perspective of improving corrosion resistance, the conductive substance as a component of the conductive coating film 400 is carbon, and from the perspective of improving chemical resistance and heat resistance, the synthetic resin as a component of the conductive coating film 400 is preferably an epoxy resin or a phenolic resin. To increase heat resistance, the synthetic resin that is a component of the conductive coating film 400 is preferably an epoxy resin.

[0056] The conductive coating film 400 can be easily bonded to the printed circuit board 300 by printing or spraying it onto the board and then drying and curing it in a thermostatic bath or similar environment. Bonding the conductive coating film 400 to the printed circuit board 300 is simpler than plating, and production costs are low. The conductive coating film 400 is cheaper in terms of material costs than plating.

[0057] As in Fig. As shown in Figure 5, the conductive coating film 400 is located on the facing section 305 of the circuit board 300, which faces the detection surface 322 of the flow detection element 321. The conductive coating film 400 seals the second conductive section 309, which is located on the facing section 305 of the detection surface 322. That is, the conductive coating film 400 seals the second conductive section 309, which is located on the third projection 304, forming the facing section 305. As shown in Fig. As shown in Figure 6, the conductive coating film 400 covers an upper surface 309a, which faces the detection surface 322 of the second conductive section 309, and a side surface 309b, which abuts the upper surface 309a of the second conductive section 309 without a gap. In this way, the conductive coating film 400 can seal the second conductive section 309, which is a wiring pattern exposed on the mounting surface 300a of the printed circuit board 300. The conductive coating film 400 is in contact with the second conductive section 309, which has a ground potential of the printed circuit board 300 and the same ground potential as the second conductive section 309.

[0058] The conductive coating film 400 is provided in the facing section 305 of the printed circuit board 300 such that it faces the inside of channel P, which is part of the forward path section 136 of the second auxiliary channel 135 through which the target gas 2 flows. The conductive coating film 400 seals the second conductive section 309, which is provided such that the inside of channel P is sealed from the side of the printed circuit board 300. The conductive coating film 400 seals the second conductive section 309, which lies transversely to channel P in the width direction. The conductive coating film 400 seals the second conductive section 309, which is provided such that it extends beyond the width of channel P to section 312a, which is closer to the circuit chamber 140 than channel P of the preceding section 312.In other words, the conductive coating film 400 is configured such that the length W along the width of the second auxiliary channel 135, i.e., the length W along the width of channel P, is longer than the length W1 along the width of channel P of the second conductive section 309. Preferably, the conductive coating film 400 is configured such that the length W along the width of channel P is greater than the width W3 of channel P or the width W4 of the forward path section 136 of the second auxiliary channel 135.

[0059] The conductive coating film 400 comes into contact with the second insulation 307, which surrounds the second conductive section 309, from the direction along the mounting surface 300a of the printed circuit board 300, in order to seal the second conductive section 309. In particular, the conductive coating film 400 comes into contact with at least one upper surface 307a of the second insulation 307, which is adjacent to the second conductive section 309 in the direction along the mounting surface 300a of the printed circuit board 300 and opposite the detection surface 322, and a side surface 307b, which is connected to the upper surface 307a of the second insulation 307, in order to seal the second conductive section 309.

[0060] In the heat flow meter 20 according to the present embodiment, the detection surface 322 of the flow detection element 321 and a part of the printed circuit board 300 are arranged such that they face each other, and a conductive element is provided on at least a part of the facing section 305, which is provided in the second auxiliary channel 135, which is a surface facing the detection surface 322 of the printed circuit board 300. Since the neutralization function in the heat flow meter 20 is implemented on the printed circuit board 300 by a conductive resin that has higher corrosion resistance than a plating, it is possible to extend the service life even at low cost and to ensure the reliability of the flow detection accuracy.

[0061] In the heat flow meter 20, the conductive resin element that performs the neutralization function is preferably the conductive coating film 400, which is formed by applying it to the circuit board 300 in a film form. As a result, the neutralization function in the heat flow meter 20 can be implemented in a simple process, thus further reducing costs.

[0062] In the heat flow meter 20, the carrier body, which carries the flow detection element 321, is mounted on the circuit board 300 as a chip package 310, and the detection surface 322 of the flow detection element 321 and the circuit board 300 are arranged so that they face each other, thus forming the channel P as the flow detection channel. As a result, in the heat flow meter 20, the influence of the housing 100, the cover 200, and the circuit board 300 on the mounting variation of channel P, which is the flow detection channel, can be eliminated, and the reliability of the flow detection accuracy can be improved.

[0063] If the conductive coating film 400, which is a conductive resin element provided on the circuit board 300, has a predetermined potential, the charged impurities in the heat flow meter 20 can be attracted to the conductive coating film 400 by the Coulomb force and moved away from the flow detection element 321, even if the target gas 2, which contains charged impurities, flows towards the flow detection element 321. Since the conductive coating film 400 can neutralize the charged impurities after attraction, it is also possible in the heat flow meter 20 to suppress the accumulation of impurities on the detection surface 322 of the flow detection element 321.

[0064] If the conductive coating film 400 is designed to overlap the exposed part (second conductive section 309) of the wiring of the printed circuit board 300, the conductive coating film 400 can have a predetermined potential. The predetermined potential can be ground or a power supply potential. Since most contaminants that have passed through the air purifier 21 are charged to + (positive electrode), it is preferable that the second conductive section 309, which is covered by the conductive coating film 400, is used as the ground conductor and the conductive coating film 400 as the ground potential. Furthermore, because the conductive coating film 400 overlaps the second conductive section 309, there is the advantage that the neutralization function can be formed with a simple configuration.In a case where the neutralization function is to be formed on an element, such as the cover 200, which is not equipped with a signal line, a complex mechanism is required to connect the circuit board 300 and the cover 200 in order to establish a connection at a predetermined potential. On the other hand, by forming a film by applying a conductive resin to a portion of the circuit board 300 to cover a connection at a predetermined potential, the neutralization function exhibiting a predetermined potential can be easily implemented.

[0065] Furthermore, in the heat flow meter 20, the facing section 305, which faces the flow detection element 321 of the printed circuit board 300, is configured by the third projection 304, which extends into the second auxiliary channel 135. In the heat flow meter 20, it is advantageous that the second conductive section 309 is provided on the third projection 304 and that the conductive coating film 400 seals the second conductive section 309, which is provided on the third projection 304.

[0066] In the configuration described above, in the heat flow meter 20, the second conductive section 309, which serves as a supply source for a potential capable of neutralizing impurities, is positioned via the conductive coating film 400 such that it faces the inside of the second auxiliary channel 135 through which the target gas 2 flows. In the heat flow meter 20, the distance between the conductive coating film 400, which faces the inside of the second auxiliary channel 135 through which the target gas 2 flows, and the second conductive section 309 is extremely short, and the charge supplied to the conductive coating film 400 by the second conductive section 309 can be immediately distributed over the entire surface of the conductive coating film 400.In the heat flow meter 20, the impurity neutralization function can be initiated immediately, since the potential of the conductive coating film 400, which faces the inside of the second auxiliary channel 135, can be immediately equated with the potential of the second conductive section 309. As a result, the deposition of impurities on the detection surface 322 in the heat flow meter 20 can be further suppressed.

[0067] Furthermore, in the heat flow meter 20, the length W1 of the second conductive section 309 along the width of the second auxiliary channel 135 is equal to or longer than the width W4 of the second auxiliary channel 135, and the length W of the conductive coating film 400 along the width of the second auxiliary channel 135 is longer than the length W1 of the second conductive section 309. That is, in the heat flow meter 20, both the length W of the conductive coating film 400 and the length W1 of the second conductive section 309 are preferably equal to or greater than the width W4 of the second auxiliary channel 135.

[0068] With the above configuration, the potential of the conductive coating film 400, which faces the inside of the second auxiliary channel 135 through which the target gas 2 flows, can be easily and uniformly distributed across the entire second auxiliary channel 135 in the lateral direction within the heat flow meter 20. In the heat flow meter 20, it is possible to suppress variations in the neutralization function of impurities in the lateral direction of the second auxiliary channel 135. Furthermore, since the surface of the conductive coating film 400, which faces the inside of the second auxiliary channel 135, can be kept smooth, the target gas 2 can flow stably in the heat flow meter 20, allowing its flow rate to be accurately detected.In the heat flow meter 20, it is not only possible to adequately detect the flow rate of the target gas 2 over a long period of time by reducing the deposition of impurities on the detection surface 322, but also to improve the detection accuracy of the flow rate. This allows the service life of the heat flow meter 20 to be extended at low cost and the detection accuracy to be improved.

[0069] In the heat flux meter 20, the conductive coating film 400 preferably comes into contact with the second insulation 307, which surrounds the second conductive section 309 from the direction along the mounting surface 300a of the circuit board 300 in order to seal the second conductive section 309.

[0070] With the above configuration, the conductive coating film 400 in the heat flow meter 20 can reliably seal the second conductive section 309, and the adhesion between the conductive coating film 400 and the circuit board 300 can be improved, thus further extending the neutralization function for contaminants. In the heat flow meter 20, the deposition of contaminants on the detection surface 322 can be further reduced, and the flow rate of the target gas 2 can be adequately detected over a longer period. This allows the service life of the heat flow meter 20 to be extended even at a low cost.

[0071] Furthermore, in the heat flow meter 20, the conductive substance, which is a component of the conductive coating film 400, is preferably carbon with high corrosion resistance, and the synthetic resin, which is a component of the conductive coating film 400, is preferably an epoxy resin or a phenolic resin with high chemical resistance and heat resistance.

[0072] With the above configuration, the corrosion resistance, chemical resistance, and heat resistance of the conductive coating film 400 in the heat flow meter 20 can be improved, thus further extending the service life of the impurity neutralization function. In the heat flow meter 20, the deposition of impurities on the detection surface 322 can be further reduced, and the flow rate of the target gas 2 can be reliably detected over a longer period. This allows the service life of the heat flow meter 20 to be extended even at a low cost.

[0073] [Changes to the printed circuit board and the conductive coating film] Fig. Figure 7 is a view to illustrate a first modification of the printed circuit board 300 and the conductive coating film 400. Fig. 7 corresponds to the Fig. 5. Fig. Figure 8 is a schematic cross-sectional view of the printed circuit board 300 along the line shown. Fig. Line CC shown in 7. Fig. 8 corresponds to the Fig. 6.

[0074] At the in Fig. 5 and Fig. In the printed circuit board 300 shown in Figure 6, the second conductive section 309 is positioned over the conductive coating film 400 such that it faces the inside of channel P, which is part of the forward path section 136 of the second auxiliary channel 135 through which the target gas 2 flows. In the Fig. 7 and Fig. In contrast, in the printed circuit board 300 shown in Figure 8, it is possible that the second conductive section 309 is not provided over the conductive coating film 400, so that it faces the inside of channel P, which is part of the forward path section 136 of the second auxiliary channel 135. The conductive coating film 400, which is in Fig. 7 and Fig. Figure 8 is designed to face the inside of channel P, which is part of the forward path section 136 of the second auxiliary channel 135, similar to the conductive coating film 400, as shown in Fig. 5 and Fig. 6 shown.

[0075] The heat flow meter 20 of the first modification, which is in the Fig. 7 and Fig. As shown in Figure 8, even if the second conductive section 309 does not point towards the inside of the channel P via the conductive coating film 400, the conductive coating film 400 points towards the inside of the channel P, and thus it is possible to reliably realize the neutralization function of impurities even at low cost.

[0076] Furthermore, in the Fig. 5 and Fig. In the printed circuit board 300 shown in Figure 6, the size of the second conductive section 309 is slightly smaller than the size of the conductive coating film 400, and there is no significant difference between the sizes. On the other hand, in the Fig. 7 and Fig. In the printed circuit board 300 shown in Figure 8, the size of the second conductive section 309 is significantly smaller than the size of the conductive coating film 400. For example, in the circuit board shown in Figure 8, the size of the second conductive section 309 is significantly smaller than the size of the conductive coating film 400. Fig. 5 and Fig. In the circuit board 300 shown in Figure 6, the length W1 of the second conductive section 309 is equal to or greater than the width W4 of the second auxiliary channel 135, whereas in the Fig. 7 and Fig. In the circuit board 300 shown in Figure 8, the length W1 of the second conductive section 309 can be smaller than the width W4 of the second auxiliary channel 135. In the Fig. 7 and Fig. In the conductive coating film 400 shown in Figure 8, the length W along the width of the second auxiliary channel 135 is equal to or greater than the width W4 of the second auxiliary channel 135, similar to the one shown in the Fig. 5 and Fig. 6 shown conductive coating film 400.

[0077] In the Fig. 7 and Fig. In the first modification of the heat flow meter 20 shown in Figure 8, the size of the second conductive section 309 is remarkably small compared to the size of the conductive coating film 400, so that the conductive coating film 400 can reliably seal the second conductive section 309 and improve adhesion to the printed circuit board 300. Furthermore, the heat flow meter 20 of the first modification, which is shown in the Fig. 7 and Fig. As shown in Figure 8, the quantity of the second conductive section 309, which consists of a relatively expensive material such as copper foil, can be reduced, thus lowering material costs. Therefore, the thermal flow meter 20 of the first modification, which is shown in the Fig. 7 and Fig. As shown in Figure 8, the service life of the impurity neutralization function can be further extended while simultaneously reducing costs. Therefore, in the case of the first modification of the heat flow meter 20, which is shown in the Fig. 7 and Fig. As shown in Figure 8, it is possible to further extend the service life even at low costs while simultaneously reducing costs further.

[0078] Fig. Figure 9 is a view to illustrate a second modification of the printed circuit board 300 and the conductive coating film 400. Fig. 9 corresponds to the Fig. 7. Fig. Figure 10 is a schematic cross-sectional view of the printed circuit board 300 along the in Fig. 9 shown line DD. Fig. 10 corresponds to the Fig. 8.

[0079] During the Fig. 7 and Fig. In the printed circuit board 300 shown in Figure 8, the second conductive section 309 consists of a metal foil, e.g., a copper foil, which is significantly smaller than the size of the conductive coating film 400. On the other hand, in the Fig. 9 and Fig. In the printed circuit board 300 shown in Figure 10, the second conductive section 309 is formed by a through-hole. The second conductive section 309 formed by the through-hole is electrically connected to a ground wiring pattern 309', which is provided as a layer within the printed circuit board 300.

[0080] Similar to the heat flow meter 20 of the first modification, which was used in the Fig. 7 and Fig. As shown in section 8, the heat flow meter 20 of the second modification, which is in the Fig. 9 and Fig. As shown in Figure 10, the service life of the impurity neutralization function can be extended while simultaneously reducing costs. Therefore, the service life of the heat flow meter 20 in the second modification, which is shown in the Fig. 9 and Fig. As shown in point 10, it can also be extended at low cost.

[0081] Fig. Figure 11 is a view illustrating a third modification of the printed circuit board 300 and the conductive coating film 400. Fig. 11 corresponds to the Fig. 7. Fig. Figure 12 is a schematic cross-sectional view of the printed circuit board 300 along the in Fig. Line EE shown in 11. Fig. 12 corresponds to the Fig. 8.

[0082] At the in Fig. 7 and Fig. In the circuit board 300 shown in section 8, the second conductive section 309 is provided on the third projection 304 of the circuit board 300. The section shown in the Fig. 7 and Fig. The conductive coating film 400 shown in Figure 8 seals the second conductive section 309, which is located on the third projection 304. On the other hand, in the Fig. 11 and Fig. The second conductive section 309 is provided in the main body 301 of the printed circuit board 300 shown in section 12. The section shown in the Fig. 11 and Fig. 12 The conductive coating film 400 shown can be applied from the third projection 304 of the circuit board 300 to the main body 301 to seal the second conductive section 309 provided in the main body 301.

[0083] In the Fig. 11 and Fig. In the third modification of the heat flow meter 20 shown in Figure 12, the heat from the second conductive section 309 is hardly transferred to the target gas 2 flowing through channel P, since the second conductive section 309 is located in the main body 301, which is separate from channel P. In the third modification of the heat flow meter 20 shown in the Fig. 11 and Fig. As shown in Figure 12, the temperature distribution of the target gas 2, which is detected on the detection surface 322, is hardly affected by the heat of the second conductive section 309, so that the flow rate of the target gas 2 can be detected more accurately. Therefore, with the heat flow meter 20 of the third modification, which is shown in the Fig. 11 and Fig. As shown in Figure 12, the service life can be extended even at low cost and the detection accuracy increased.

[0084] In the embodiment described above, the case where the second conductive section 309 has the ground potential of the printed circuit board 300 was described as an example. However, the second conductive section 309 only needs to have a potential capable of removing charged contaminants and can have a different potential than the ground potential of the printed circuit board 300. In this case, the second conductive section 309 can be a conductive section, such as a wiring pattern, that is exposed from the insulations 306 and 307 of the printed circuit board 300 to the mounting surface 300a and is insulated from a wiring pattern that has the ground potential of the printed circuit board 300.

[0085] [Further details] It should be noted that the present invention is not limited to the embodiments mentioned above and includes various modifications.

[0086] For example, the embodiments of the present invention described above have been described in detail in a clearly understandable manner and are not necessarily limited to those with all the described configurations. Furthermore, some of the configurations of a particular embodiment can be replaced by the configurations of the other embodiments, and the configurations of the other embodiments can be added to the configurations of the embodiment in question. Moreover, some of the configurations of each embodiment can be omitted, replaced by other configurations, and added to other configurations.

[0087] Each of the configurations, functions, processing units, processing means, and the like mentioned above can be partially or completely achieved through hardware, for example, by designing an integrated circuit. Alternatively, the configurations and functions can be implemented in software, with a processor analyzing and executing a program that implements each function. Information such as a program, tape, or file for implementing each function can be stored in a recording device such as memory, a hard disk drive, or a solid-state drive (SSD), or on a recording medium such as an IC card, an SD card, or a DVD.

[0088] Furthermore, only the control and information lines necessary for explanation are shown, but not all control and information lines for the product. In practice, almost all configurations can be considered interconnected. Reference symbol list 2 Target gas 20 heat flow meters 22 Main Channel 135 second auxiliary channel 140 circuit chamber 300 circuit boards 301 Main body 304 third lead 305 facing section 307 second insulation 309 second leading section 310 chip package 321 Flow detection element 322 detection area 400 conductive coating film QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] JP 2019007902 A

[0003]

Claims

[1] Heat flux meter, comprising: a flow detection element configured to detect airflow; and a printed circuit board arranged such that a part of the printed circuit board faces a detection surface of the flow detection element, wherein the printed circuit board is provided with a conductive resin element comprising a conductive substance and a resin as components on at least a part of a section provided in an auxiliary channel on a surface facing the detection surface of the flow detection element. [2] Heat flow meter according to claim 1, wherein the conductive resin element is a conductive coating film which is formed into a film form by application to the circuit board. [3] Heat flow meter according to claim 2, wherein the conductive coating film is provided such that it seals a conductive section formed on the circuit board with a predetermined potential. [4] Heat flow meter according to claim 3, wherein The circuit board also contains wiring and an insulating film designed to cover the wiring, and The conductive section is a section of the wiring exposed by the insulating foil. [5] Heat flow meter according to one of claims 3 or 4, further comprising: a circuit chamber adjacent to the auxiliary channel for receiving the printed circuit board, wherein The auxiliary channel is a channel that receives a portion of the target gas being measured. that flows through the main channel, the circuit board has a main body arranged in the circuit chamber and a projection extending from the circuit chamber into the auxiliary channel, the guiding part is provided on the ledge, and the conductive coating film is applied to the projection. [6] Heat flow meter according to claim 5, wherein a length of the conducting section along a width of the auxiliary channel is equal to or greater than the width of the auxiliary channel, and in the conductive coating film, the length along the width of the auxiliary channel is greater than the length of the conductive section along the width of the auxiliary channel. [7] Heat flow meter according to claim 5, wherein a length of the conducting section along a width of the auxiliary channel is smaller than the width of the auxiliary channel, and in the conductive coating film, the length along the width of the auxiliary channel is equal to or greater than the width of the auxiliary channel. [8] Heat flow meter according to one of claims 3 or 4, further comprising: a circuit chamber next to the auxiliary channel for receiving the printed circuit board, wherein The auxiliary channel is a channel that receives a portion of the target gas being measured. that flows through a main channel, the circuit board has a main body arranged in the circuit chamber and a projection extending from the circuit chamber into the auxiliary channel, the conductive section is provided on the main body, and the conductive coating film is attached from the projection towards the main body. [9] Heat flux meter according to claim 3, wherein the predetermined potential is a mass potential. [10] Heat flow meter according to claim 1, wherein The conductive substance is carbon, and The synthetic resin is either an epoxy resin or a phenolic resin. [11] Heat flux meter according to any one of claims 1 to 10, further comprising: a carrier body configured to carry the flow detection element, wherein the carrier body is mounted on the circuit board in such a way that the detection surface of the detection element faces a part of the circuit board. [12] Heat flow meter according to claim 11, wherein the carrier body is a chip package formed by sealing with a synthetic resin, such that at least the detection surface of the flow detection element is exposed.