Thermal Flow Meter

• US 20150177043A1
• Filed: 11/19/2012
• Published: 06/25/2015
• Est. Priority Date: 12/07/2011
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Incorporated (Hitachi, Ltd.)
• Inventors: Tokuyasu, Noboru, Tashiro, Shinobu, Hanzawa, Keiji, Morino, Takeshi, Doi, Ryosuke
• Granted Patent: US 9,658,094 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F01N 11/002 the diagnostic devices measuring or estimating temperature or pressure in, or downstream of the exhaust apparatus
• CPC Class Codes: F01N 2560/07 the means being an exhaust gas flow rate or velocity meter or sensor, intake flow meters only when exclusively used to determine exhaust gas parameters
• CPC Class Codes: F02D 41/187 using a hot wire flow sensor
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 1/692 Thin-film arrangements
• CPC Class Codes: G01F 15/04 of gases to be measured
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow

Abstract

In order to provide a thermal-type flowmeter highly accurate, with high reliability, and simple in construction, while being available at a lower price, a thermal-type flowmeter as proposed includes a sub-path that takes in a fluid under measurement; a sensor element that measures a flow-rate of the fluid under measurement in the sub-path; a temperature detection element that detects a temperature of the fluid under measurement; a drive circuit that controls a heating temperature of the sensor element; and a protection circuit that protects the drive circuit from noise, a cavity being formed on a substrate of the sensor element, an exothermic resistor being provided on a thin-film part on the cavity through the intermediary of an electrically insulating film, and a flow rate being detected on the basis of temperature distribution in the thin-film part.

Claims

1. A thermal-type flowmeter comprising:

a sub-path that takes in a fluid under measurement;

a sensor element that measures a flow-rate of the fluid under measurement in the sub-path;

a temperature detection element that detects a temperature of the fluid under measurement;

a drive circuit that controls a heating temperature of the sensor element; and

a protection circuit that protects the drive circuit from noise,

a cavity being formed on a substrate of the sensor element, an exothermic resistor being provided on a thin-film part on the cavity through the intermediary of an electrically insulating film, and a flow rate being detected on the basis of temperature distribution in the thin-film part,

wherein the sensor element and the drive circuit are mounted on a metal lead fame,

wherein the entire periphery of the sensor element, the drive circuit, and the lead fame is encapsulated with a thermosetting resin to thereby complete a chip package, and

wherein at least one of a chip component that protects the drive circuit and an air-temperature detecting element is consolidated inside the chip package.

2. The thermal-type flowmeter according to claim 1, wherein the thin-film part is partially exposed out of the thermosetting resin.

3. The thermal-type flowmeter according to claim 1, wherein the chip package is provided with a communication mechanism for causing the cavity to communicate with the outside of the thermosetting resin.

4. The thermal-type flowmeter according to claim 1, wherein the sensor element, the drive circuit, and a hole for causing the cavity to communicate with the outside of the thermosetting resin are disposed in the same straight-line direction.

5. The thermal-type flowmeter according to claim 1, wherein the drive circuit is disposed between the sensor element and the hole for causing the cavity to communicate with the outside of the thermosetting resin

6. The thermal-type flowmeter according to claim 1, wherein the air-temperature detecting element is consolidated inside the chip package, and the sensor element is disposed in a flow path differing from a flow path where the air-temperature detecting element is disposed.

7. The thermal-type flowmeter according to claim 6, wherein the chip package is in a shape with only a portion thereof, where the air-temperature detecting element is mounted, being protruded, and the air-temperature detecting element is disposed in an upstream direction of the flow of the fluid under measurement.

8. The thermal-type flowmeter according to claim 6, wherein a part of the lead fame is protruded from the chip package, and the air-temperature detecting element is disposed at a position on the opposite side from a direction of the protrusion.

9. The thermal-type flowmeter according to claim 5, wherein the sensor element differs in chip height from the drive circuit.

10. The thermal-type flowmeter according to claim 9, wherein the chip height of the drive circuit is lower than the chip height of the sensor element.