Thermal flow meter

Patent metadata

Field	Value
Publication number	US-9746362-B2
Application number	US-201314407142-A
Country	US
Kind code	B2
Filing date	May 29, 2013
Priority date	Jun 15, 2012
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

The present invention provides a thermal flow meter 300 which reduces a stress applied from a fixing portion 3721 , which is used to hold and fix a circuit package 400 with respect to a housing 302 , to the circuit package 400 and has high reliability. In the thermal flow meter of the invention, the circuit package 400 embedded with a flow rate measurement circuit is formed through a first resin molding process, the fixing portion 3721 is formed along with the housing 302 through a second resin molding process, and the circuit package 400 is enveloped by the fixing portion 3721 , whereby the circuit package 400 is held by and fixed to the housing 302 . In order to reduce the influence of a stress, generated based on a temperature change of the fixing portion 3721 , on the circuit package 400 , the fixing portion 3721 is constituted of a thick portion 4714 and a thin portion 4710 . Since thickness of a resin of the thin portion 4710 is small, the stress to be generated is small, and a force applied to the circuit package 400 can be reduced.

First claim

The invention claimed is:

1. An air flow meter including an air flow sensing portion, comprising:
a housing;
a circuit comprising a processing unit which connects to the air flow sensing portion electrically, and a first mold resin within which the processing unit is encapsulated;
a second mold resin having a thermal expansion coefficient that is different from a thermal expansion coefficient of the first mold resin, and which envelopes the portion of the first mold resin of a chip package, wherein
the second mold resin comprises a thick portion, and a thin portion, and
the thin portion extends from the processing unit to a first distance, the thick portion extends from the processing unit to a second distance, and the second distance is larger than the first distance.

2. The air flow meter according to claim 1 , wherein in order to hold the circuit package by the housing, the fixing portion provided in the housing has the thick portion and the thin portion enveloping the circuit package,
an area of a surface of the circuit package in which the thin portion envelops the circuit package is larger than an area of the circuit package surface in which the thick portion envelops the circuit package.

3. The air flow meter according to claim 1 , wherein the housing has a flange, a bypass passage trench portion in which the bypass passage is formed, an upstream-side outer wall connecting the flange and the bypass passage groove portion, and a downstream-side outer wall, the fixing portion for holding the circuit package is provided to connect the upstream-side outer wall and the downstream-side outer wall,
the fixing portion has a thick portion and a thin portion, and as to thickness of a resin covering the surface of the circuit package and formed in the second resin molding process.

4. The air flow meter according to claim 3 , wherein the thick portion constituting the fixing portion is formed on the opposite as the flange of the fixing portion,
the thin portion is formed on the side of the flange of the fixing portion, and the thick portion and the thin portion are connected.

5. The air flow meter according to claim 3 , wherein the thick portion constituting the fixing portion is formed on the opposite as the flange of the fixing portion,
the thin portion is formed on the side of the flange of the first thick portion, and
a second thick portion is formed on the flange side of the thin portion.

6. The air flow meter according to claim 1 , wherein the housing has a flange, a bypass passage trench portion in which the bypass passage is formed, an upstream-side outer wall connecting the flange and the bypass passage groove portion, and a downstream-side outer wall,
the outer wall which is at least one of the upstream-side outer wall and the downstream-side outer wall envelops the circuit package, whereby the circuit package is fixed by the housing,
the outer wall enveloping the circuit package further has a thin portion enveloping a part of the circuit package, and the thin portion has a shape in which the thickness of a portion covering the circuit package is smaller than the thickness of the outer wall enveloping the circuit package, and
the outer wall enveloping the circuit package and the thin portion are integrally connected.

7. The air flow meter according to claim 1 , wherein at least a resin surface of the circuit package has a roughened texture.

8. The air flow meter according to claim 1 , wherein the circuit package is formed of a thermosetting resin, and the housing is formed of a thermoplastic resin.

9. The air flow meter according to claim 1 , wherein a side of the thick portion of the fixing portion that is farthest from the circuit package is adhered to an inner surface of the cover.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Tashiro Shinobu
• Hanzawa Keiji
• Tokuyasu Noboru
• Morino Takeshi
• Doi Ryosuke
• Uenodan Akira

Classifications

• G01F5/00

  Measuring a proportion of the volume flow · CPC title

• G01F1/696

  Circuits therefor, e.g. constant-current flow meters · CPC title

• G01F1/699

  by control of a separate heating or cooling element · CPC title

• G01F1/6842 Primary

  with means for influencing the fluid flow · CPC title

• G01F15/14

  Casings, e.g. of special material · CPC title