THERMAL FLOWMETER

• US 20190323871A1
• Filed: 09/27/2017
• Published: 10/24/2019
• Est. Priority Date: 01/26/2017
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: UENODAN, Akira, FUKAYA, Masashi, SAITO, Tomoaki, TASHIRO, Shinobu, WATANABE, Tsubasa
• Granted Patent: US 11,112,286 B2
• Time in Patent Office: Days
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 2400/18 Packaging of the electronic circuit in a casing
• CPC Class Codes: F02D 41/18 by measuring intake air flow
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 15/04 of gases to be measured
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow
• CPC Class Codes: G01K 13/02 for measuring temperature of moving fluids or granular materials capable of flow
• CPC Class Codes: G01K 13/024 of moving gases
• CPC Class Codes: G01K 2205/02 for measuring inlet gas temperature

Abstract

A thermal flowmeter includes a plurality of measuring units for stabilizing air flowing in a sub-passage, and improves noise performance or a pulsation characteristic of a flow rate sensor. The thermal flowmeter includes a flange fixed to an attachment part of a main passage, a sub-passage takes in a part of measured gas flowing in the main passage, a flow rate measuring unit measures a flow rate of the measured gas in the sub-passage, a circuit component controls the flow rate measuring unit, and the flow rate measuring unit and an electronic component are mounted on a circuit substrate. The sub-passage is formed in a substrate of the circuit substrate, the sub-passage on a surface side of the circuit substrate and a second space on a rear surface side are separated by the circuit substrate, and a pressure measuring unit and the circuit component are arranged in the second space.

Claims

1. A thermal flowmeter used by being inserted from an attachment hole provided in a passage wall of a main passage into an inside of the main passage, comprising:

a flange to be fixed to an attachment part of the main passage;

a sub-passage that takes in a part of measured gas flowing in the main passage;

a flow rate measuring unit that measures a flow rate of the measured gas in the sub-passage;

a circuit component that controls the flow rate measuring unit; and

a circuit substrate on which the flow rate measuring unit and the circuit component are mounted,

wherein the sub-passage is formed in a substrate of the circuit substrate.

2. The thermal flowmeter according to claim 1, wherein a sub-passage on a surface side of the circuit substrate on which side the flow rate measuring unit is provided and a second space, which is different from the sub-passage, on a rear surface side of the circuit substrate are separated by the circuit substrate, and at least one physical sensor other than the flow rate measuring unit, and a circuit component are arranged in the second space.

3. The thermal flowmeter according to claim 1, wherein the flange, the flow rate measuring unit, and the circuit component are installed in this order in an insertion direction of the thermal flowmeter.

4. The thermal flowmeter according to claim 1, wherein the circuit substrate has a partially-molded resin, and an inner wall of the sub-passage has a surface on a side on which the flow rate measuring unit is provided and a surface of the resin of the circuit substrate.

5. The thermal flowmeter according to claim 4, wherein the resin includes a cover that is included in a part of the inner wall of the sub-passage by being adhered or welded.

6. The thermal flowmeter according to claim 1, further comprising a resin body having a recessed part, wherein the resin body is included in a part of an inner wall of the sub-passage by being adhered or crimped to a surface on a side on which the flow rate measuring unit is provided of the circuit substrate.

7. The thermal flowmeter according to claim 1, wherein the sub-passage includes a main passage connecting an inlet and an outlet, and a bypass passage that bypasses the main passage, and the flow rate measuring unit is included in the bypass passage.

8. The thermal flowmeter according to claim 7, wherein the circuit substrate configures whole one side wall surface among four side wall surfaces of the bypass passage.

9. The thermal flowmeter according to claim 7, wherein a third space is included between the main passage and the bypass passage, and at least one physical sensor other than the flow rate measuring unit is installed in the third space.

10. The thermal flowmeter according to claim 1, wherein the flow rate measuring unit is electrically connected to the circuit component through a bonding wire, one end side thereof being connected to the flow rate measuring unit, and includes a seal material that covers the bonding wire, the seal material being provided on a circuit component side of the flow rate measuring unit.

11. The thermal flowmeter according to claim 1, wherein the circuit component is LSI or a microcomputer or both.

12. The thermal flowmeter according to claim 1, wherein the flow rate measuring unit and the circuit component are an integrated one-chip component.

13. The thermal flowmeter according to claim 1, wherein the circuit substrate is a printed substrate.

14. The thermal flowmeter according to claim 7, wherein a resist film or a surface treated film having a hydrophilic property or a water-repellent property is included on a surface of the circuit substrate included in a part of the bypass passage.

15. The thermal flowmeter according to claim 7, wherein a surface of the circuit substrate included in a part of the bypass passage is grounded by pattern exposure or surface treating.

16. The thermal flowmeter according to claim 1, further comprising a temperature measuring unit that measures a temperature of the measured gas flowing in the main passage,

wherein the temperature measuring unit is provided in such a manner as to be protruded to a leading end side of a chassis extended toward a center of the main passage from the flange.