CN-115023591-B - Thermal flowmeter

Abstract

The invention provides a thermal flowmeter with high reliability. The thermal flowmeter (20) has a flow rate detection element (321) for detecting the flow rate of air, and a conductive coating film (400) containing a conductive material and a resin as constituent elements is provided on at least a part of the surface facing the detection surface (322) of the flow rate detection element (321) and provided in the sub-passage 135).

Inventors

• SHIBATA MIZUKI
• YOGO TAKAYUKI
• UENODAN AKIRA
• ABE HIROYUKI
• Fadin fahana bintiharidan

Assignees

• 日立安斯泰莫株式会社

Dates

Publication Date

20260508

Application Date

20201222

Priority Date

20200220

Claims (10)

1. 1. A thermal flowmeter, comprising: a flow rate detecting element for detecting the flow rate of the air, and A circuit board having a part arranged to face the detection surface of the flow rate detection element, The circuit board is provided with a conductive resin member containing a conductive material and a resin as constituent elements on at least a part of a surface of the circuit board facing the detection surface of the flow rate detection element and provided in a position within the sub-passage, The conductive resin member is a conductive coating film formed in a film shape by coating on the circuit substrate, The conductive coating film is provided so as to seal a conductor portion of a predetermined potential formed on the circuit board.
2. 2. The thermal flowmeter of claim 1, wherein, The circuit board further includes a wiring and an insulating film provided so as to cover the wiring, The conductor portion is a portion exposed from the insulating film of the wiring.
3. 3. A thermal flowmeter according to claim 1 or 2, wherein, Further comprises a circuit chamber adjacent to the sub-path and accommodating the circuit board, The sub-passage is a passage for taking in a part of the gas to be measured flowing in the main passage, The circuit board has a main body portion disposed in the circuit chamber and a protruding portion protruding from the circuit chamber toward the sub-passage, The conductor portion is provided on the protruding portion, The conductive coating film is provided on the protruding portion.
4. 4. The thermal flowmeter of claim 3, wherein, The length of the conductor portion along the width of the sub-via is equal to or greater than the width of the sub-via, A length of the conductive coating film along the width of the sub-via is longer than the length of the conductor portion along the width of the sub-via.
5. 5. The thermal flowmeter of claim 3, wherein, A length of the conductor portion along a width of the sub-via is less than the width of the sub-via, The length of the conductive coating film along the width of the sub-via is equal to or greater than the width of the sub-via.
6. 6. A thermal flowmeter according to claim 1 or 2, wherein, Further comprises a circuit chamber adjacent to the sub-path and accommodating the circuit board, The sub-passage is a passage for taking in a part of the gas to be measured flowing in the main passage, The circuit board has a main body portion disposed in the circuit chamber and a protruding portion protruding from the circuit chamber toward the sub-passage, The conductor portion is disposed on the body portion, The conductive coating film is provided from the protruding portion to the main body portion.
7. 7. The thermal flowmeter of claim 1, wherein, The predetermined potential is a ground potential.
8. 8. The thermal flowmeter of claim 1, wherein, The conductive material is carbon and the conductive material is carbon, The resin is an epoxy resin or a phenolic resin.
9. 9. A thermal flowmeter according to claim 1 or 2, wherein, Further comprises a support body for supporting the flow rate detection element, The support is mounted on the circuit board such that the detection surface of the detection element faces a part of the circuit board.
10. 10. The thermal flowmeter of claim 9, wherein, The support is a chip package formed by sealing with a resin so as to expose at least the detection surface of the flow rate detection element.

Description

Thermal flowmeter Technical Field The present invention relates to a thermal flowmeter. Background As a technique related to a thermal flowmeter for measuring a flow rate of a gas to be measured, for example, a technique described in patent document 1 is known. Prior art literature Patent literature Patent document 1 Japanese patent laid-open publication No. 2019-7902 Disclosure of Invention Problems to be solved by the invention In the thermal flowmeter described in patent document 1, a part or all of the plate-like member facing the flow rate detection unit is formed of a conductive material that removes charged contaminants contained in the gas to be measured. However, in the thermal flowmeter described in patent document 1, the main passage must be formed in a complicated shape, and there is room for improvement in terms of cost reduction for achieving the charge removing function. The present invention has been made in view of the above circumstances, and an object thereof is to provide a highly reliable thermal flowmeter. Technical means for solving the problems In order to solve the above problems, the thermal flowmeter of the present invention is characterized by comprising a flow rate detection element that detects an air flow rate, and a circuit board that is disposed so that a part thereof faces a detection surface of the flow rate detection element, wherein the circuit board is provided with a conductive resin member that contains a conductive material and a resin as constituent elements on at least a part of a surface facing the detection surface of the flow rate detection element and that is provided at a position within a sub-passage. ADVANTAGEOUS EFFECTS OF INVENTION According to the present invention, a highly reliable thermal flowmeter can be provided. The problems, configurations, and effects other than those described above will be apparent from the following description of the embodiments. Drawings Fig. 1 is a diagram showing a configuration of an internal combustion engine control system of an electronic fuel injection system using a thermal flowmeter according to the present embodiment. Fig. 2 is a front view of the thermal flowmeter according to the present embodiment. Fig. 3 is a cross-sectional view of the thermal flowmeter taken along line A-A shown in fig. 2. Fig. 4 is a front view of the circuit board with the housing removed from fig. 2. Fig. 5 is a front view of the circuit board from which the circuit components such as the chip package are removed from fig. 4. Fig. 6 is a schematic view of a cross section of the circuit board cut along line B-B shown in fig. 5. Fig. 7 is a diagram illustrating modification 1 of the circuit board and the conductive coating film. Fig. 8 is a schematic view of a cross section of the circuit substrate cut along line C-C shown in fig. 7. Fig. 9 is a diagram illustrating modification 2 of the circuit board and the conductive coating film. Fig. 10 is a schematic view of a cross section of the circuit substrate cut along line D-D shown in fig. 9. Fig. 11 is a diagram illustrating modification 3 of the circuit board and the conductive coating film. Fig. 12 is a schematic view of a section of the circuit substrate cut along the line E-E shown in fig. 11. Detailed Description Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same reference numerals are given to the respective embodiments, and the same functions are provided in the respective embodiments unless otherwise specified, so that the description thereof is omitted. In the drawings, orthogonal coordinate axes are described for the purpose of clarifying the description of the positions of the respective portions. As shown in fig. 1, a thermal flowmeter 20 mounted on a vehicle is mounted on a main passage 22 that is an intake passage of an internal combustion engine 10 and is used. As described in the following description, the thermal flowmeter 20 not only solves the problems described in the problem section to be solved by the present invention, and achieves the effects described in the effect section of the present invention, but also fully considers the various problems described above, solves various problems required as a product, and achieves various effects. Specific problems to be solved and specific effects to be achieved by the thermal flowmeter 20 are described in the following description. Fig. 2 is a front view of the thermal flowmeter 20 of the present embodiment. In fig. 2, a state in which the cover 200 is removed from the housing 100 is shown. Fig. 3 is a cross-sectional view of the thermal flowmeter 20 taken along line A-A shown in fig. 2. Fig. 4 is a front view of the circuit substrate 300 after the housing 100 is removed from fig. 2. In the following description, it is assumed that the measured gas 2 flows along the central axis 22a of the main passage 22 shown in fig. 1. The thermal flowmeter 20 is inserted into