THERMAL FLOW METER

• US 20150168193A1
• Filed: 05/31/2013
• Published: 06/18/2015
• Est. Priority Date: 06/15/2012
• Status: Active Grant

• Current Assignee: Hitachi Astemo Ltd. (Hitachi, Ltd.)
• Original Assignee: Hitachi Automotive Systems Limited (Hitachi, Ltd.)
• Inventors: Morino, Takeshi, Tashiro, Shinobu, Tokuyasu, Noboru, Hanzawa, Keiji, Inoue, Atsushi, Uenodan, Akira
• Granted Patent: US 9,709,428 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/696 Circuits therefor, e.g. constant-current flow meters
• CPC Class Codes: G01F 1/6965 comprising means to store calibration data for flow signal calculation or correction
• CPC Class Codes: G01F 15/14 Casings, e.g. of special material
• CPC Class Codes: G01F 5/00 Measuring a proportion of the volume flow

Abstract

To improve measurement accuracy of a thermal flow meter. The present invention provides a thermal flow meter, in which a protrusion 356 having an orifice surface 503 and a recovery surface 505 is provided on a wall surface 501 of a bypass passage, an intersection line 506 between the orifice surface 503 and the wall surface 501 is arranged in an upstream side from an upstream side end 401 of a circuit package 400, an intersection line 507 between the recovery surface 505 and the wall surface 501 is arranged in a downstream side from a downstream side end 402 of the circuit package 400, and an apex 504 of the protrusion 356 is arranged in a downstream side from a heat transfer surface of an air flow sensing portion 602 and in an upstream side from the downstream side end 402 of the circuit package 400.

Claims

1. A thermal flow meter comprising a bypass passage for flowing a measurement target gas received from a main passage, an air flow sensing portion that measures a heat amount by performing heat transfer with the measurement target gas flowing through the bypass passage using a heat transfer surface, and a support body that supports an air flow sensing portion inside the bypass passage to expose at least the heat transfer surface,

wherein a wall surface facing the measurement surface out of wall surfaces of the bypass passage, where the heat transfer surface of the air flow sensing portion of the support body is exposed, is provided with a protrusion including an orifice surface approaching the support body from the wall surface along a flow direction of the measurement target gas and a recovery surface returning from a downstream side end of the orifice surface to the wall surface,

an intersection line between the orifice surface and the wall surface is arranged in an upstream side from an upstream side end of the support body in a flow direction of the measurement target gas,

an intersection line between the recovery surface and the wall surface is arranged in a downstream side from a downstream side end of the support body in a flow direction of the measurement target gas, and

a portion of the protrusion farthest from the wall surface is arranged in a downstream side from the heat transfer surface of the air flow sensing portion in a flow direction of the measurement target gas and in an upstream side from a downstream side end of the support body.

2. The thermal flow meter according to claim 1, wherein the orifice surface and/or the recovery surface has at least one of a plane or a curved surface.

3. The thermal flow meter according to claim 1, wherein the orifice surface and/or the recovery surface has a shape convex to the support body or concave to the support body.

4. The thermal flow meter according to claim 1, wherein the orifice surface and/or the recovery surface has a plurality of planes having different inclinations or a plurality of curved surfaces having different curvatures.

5. The thermal flow meter according to claim 4, wherein the orifice surface has a plurality of planes having different inclinations and has a shape convex to the support body, and

at least one of intersection lines between neighboring planes of the plurality of planes is arranged to face a heat transfer surface of the air flow sensing portion in a flow direction of the measurement target gas.

6. The thermal flow meter according to claim 5, wherein the at least one of intersection lines between the neighboring planes is arranged in an upstream side from a center of the heat transfer surface of the air flow sensing portion in a flow direction of the measurement target gas.

7. The thermal flow meter according to claim 1, wherein the orifice surface has a plane parallel to the heat transfer surface of the air flow sensing portion,

an upstream side end of the parallel plane is arranged in an upstream side from the heat transfer surface of the air flow sensing portion in a flow direction of the measurement target gas,

a downstream side end of the parallel plane is arranged in a downstream side from the heat transfer surface of the air flow sensing portion in a flow direction of the measurement target gas.

8. The thermal flow meter according to claim 1, wherein the orifice surface and the recovery surface are asymmetrical to a plane perpendicular to a flow direction of the measurement target gas.

9. The thermal flow meter according to claim 1, wherein the recovery surface has a plane perpendicular to the wall surface.

10. The thermal flow meter according to claim 9, wherein the perpendicular plane is provided in a downstream side from a downstream side end of the support body in a flow direction of the measurement target gas.

11. The thermal flow meter according to claim 10, wherein the perpendicular plane is provided in a downstream side end of the recovery surface.

12. The thermal flow meter according to claim 1, wherein sloped surfaces widened toward the wall surface facing the measurement surface are provided around the heat transfer surface of the air flow sensing portion out of the support body.

13. The thermal flow meter according to claim 12, wherein a sloped surface provided along the flow direction of the measurement target gas out of the sloped surfaces extends from the upstream side end of the support body to the downstream side end.

14. The thermal flow meter according to claim 1, wherein the measurement target gas flowing through the bypass passage also flows to a backside of the measurement surface opposite to the measurement surface of the support body, and

a backside wall surface facing the backside of the measurement surface out of the wall surfaces of the bypass passage is provided with a backside protrusion including a backside orifice surface approaching the support body along a flow direction of the measurement target gas and a backside recovery surface returning from a downstream side end of the backside orifice surface to the wall surface.

15. The thermal flow meter according to claim 14, wherein the backside protrusion is symmetrical to a plane passing through a center of the heat transfer surface out of planes perpendicular to a flow direction of the measurement target gas.

16. The thermal flow meter according to claim 14, wherein the backside protrusion is asymmetrical to a plane perpendicular to a flow direction of the measurement target gas.

17. The thermal flow meter according to claim 14, wherein an intersection line between the backside orifice surface and the backside wall surface is arranged in a downstream side from an upstream side end of the support body in a flow direction of the measurement target gas, and

an intersection line between the backside recovery surface and the backside wall surface is arranged in an upstream side from a downstream side end of the support body in a flow direction of the measurement target gas.

18. The thermal flow meter according to claim 1, wherein the measurement target gas flowing through the bypass passage only flows to the measurement surface side of the support body.