Thermal flow meter

• US 9,658,094 B2
• Filed: 11/19/2012
• Issued: 05/23/2017
• Est. Priority Date: 12/07/2011
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: Tokuyasu, Noboru, Tashiro, Shinobu, Hanzawa, Keiji, Morino, Takeshi, Doi, Ryosuke
• Primary Examiner(s): Walsh, Ryan
• Application Number:
  US14/363,002
• Publication Number:
  US 20150177043A1
• Time in Patent Office: 1,646 Days
• 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. An apparatus that detects a physical quantity of air flow, the apparatus comprising:

a chip package including a sensor element, wherein the chip package includes

a drive circuit electrically connected to the sensor element,

a chip capacitor that protects the drive circuit,

a metal lead frame on which the drive circuit and the chip capacitor are mounted,

a resin mold within which the drive circuit and the chip capacitor are encapsulated, and

a temperature detecting element which is mounted on the metal lead frame and which is also encapsulated within the resin mold, wherein the temperature detecting element is directly mounted on the metal lead frame via an electrically conductive adhesive, wherein

the chip capacitor is mounted directly on the metal lead frame via an electrically conductive adhesive, so that the chip capacitor is fixed directly to the lead frame.

2. The apparatus according to claim 1, wherein the sensor element has a substrate, a thin film part formed on a cavity of the substrate, and an exothermic resistor provided on the thin film part, and the sensor element is also encapsulated within the resin mold, so that the thin film part is partially exposed out of the resin mold.

3. The apparatus according claim 2, wherein the chip package is provided with a communication mechanism that causes the cavity to communicate with the outside of the resin mold.

4. The apparatus according claim 3, wherein the mechanism includes a hole, and the hole, the sensor element, and the drive circuit are disposed in a same straight-line direction.

5. The apparatus according to claim 4, wherein the drive circuit is disposed between the sensor element and the hole.

6. The apparatus according to claim 1, further comprising a bypass passage in which the sensor element is disposed, wherein the temperature detecting element is disposed outside of the bypass passage.

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

8. The apparatus according to claim 6, wherein a part of the metal lead frame is protruded from the chip package, and the temperature detecting element is disposed at a position on the opposite side from a direction of the protrusion.

9. The apparatus according to claim 6, wherein the sensor element differs in chip height from the drive circuit.

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

11. An apparatus that detects a physical quantity of air flow, the apparatus comprising:

a chip package including a sensor element, wherein the chip package includes,

a drive circuit that is electrically connected to the sensor element,

a temperature detecting element,

a metal lead frame on which the drive circuit and the temperature detecting element are mounted,

a resin mold within which the drive circuit and the temperature detecting element are encapsulated, wherein

the temperature detecting element is directly mounted on the metal lead frame via an electrically conductive adhesive, such that the temperature detecting element is fixedly bonded to the metal lead frame, and

the chip package is mounted directly on the metal lead frame via an electrically conductive adhesive, so that the chip package is fixed directly to the lead frame.

12. An apparatus that detects a physical quantity of air flow, the apparatus comprising:

a chip package including a sensor element, wherein the chip package includes

a drive circuit electrically connected to the sensor element,

a chip capacitor that protects the drive circuit,

a metal lead frame on which the drive circuit and the chip capacitor are mounted, and

a resin mold within which the drive circuit and the chip capacitor are encapsulated, wherein

the chip capacitor is mounted directly on the metal lead frame via an electrically conductive adhesive, so that the chip capacitor is fixed directly to the lead frame, and

the sensor element has a substrate, a thin film part formed on a cavity of the substrate, and an exothermic resistor provided on the thin film part, and the sensor element is also encapsulated within the resin mold, so that the thin film part is partially exposed out of the resin mold.