Pressure Sensor, Differential Pressure Sensor, and Mass Flow Rate Control Device Using Same

• US 20170299456A1
• Filed: 10/06/2015
• Published: 10/19/2017
• Est. Priority Date: 10/07/2014
• Status: Active Grant

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Metals (Thailand) Ltd.
• Inventors: SUZUKI, Kengo, SAKAGUCHI, Isao, UMEYAMA, Takahiro
• Granted Patent: US 10,175,132 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/12 Manufacturing methods specially adapted for producing sensors for in-vivo measurements
• CPC Class Codes: A61B 5/0008 Temperature signals
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/03 Detecting, measuring or recording fluid pressure within the body other than blood pressure, e.g. cerebral pressure; Measuring pressure in body tissues or organs A61B5/205 takes precedence
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• CPC Class Codes: G01L 1/22 using resistance strain gauges
• CPC Class Codes: G01L 1/2231 the supports being disc- or ring-shaped, adapted for measuring a force along a single direction
• CPC Class Codes: G01L 13/02 using elastically-deformable members or pistons as sensing elements
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 19/02 Arrangements for preventing, or for compensating for, effects of inclination or acceleration of the measuring device; Zero-setting means for aneroid barometers G01L7/14
• CPC Class Codes: G01L 19/04 Means for compensating for effects of changes of temperature , i.e. other than electric compensation
• CPC Class Codes: G01L 27/007 Malfunction diagnosis, i.e. diagnosing a sensor defect
• CPC Class Codes: G01L 9/0055 bonded on a diaphragm
• CPC Class Codes: G01L 9/04 of resistance-strain gauges
• CPC Class Codes: G01L 9/125 with temperature compensating means non electric temperature compensating means G01L19/04

Abstract

The present invention makes it possible to, even when a stainless steel is adopted in a diaphragm: prevent the diaphragm and a strain sensor from exfoliating from each other; be hardly susceptible to the influence of temperature in an operating environment; not allow the sensitivity of a pressure sensor to be dominated only by the mechanical characteristic of a material constituting the diaphragm; and increase the degree of freedom in design of members constituting the pressure sensor. A pressure sensor according to the present invention is, in order to solve the above problems, characterized in that: the pressure sensor has a diaphragm deforming by the pressure of a fluid, an elastic body covering the whole surface of the diaphragm and joining to the diaphragm on one side, and a strain sensor being arranged by joining on the other side of the elastic body and on an end side apart from a position corresponding to the center of the diaphragm and detecting the deformation of the elastic body working together with the deformation of the diaphragm as a strain; and the elastic body is formed of a material having a linear expansion coefficient close to the linear expansion coefficient of a material constituting the strain sensor.

Claims

1. A pressure sensor comprising:

a diaphragm deforming by a pressure of a fluid;

an elastic body covering the whole surface of the diaphragm and joining to the diaphragm on one side; and

a strain sensor being arranged by joining on the other side of the elastic body and on an end side apart from a position corresponding to a center of the diaphragm and detecting a deformation of the elastic body working together with a deformation of the diaphragm as a strain,

wherein the elastic body is formed of a material having a linear expansion coefficient close to the linear expansion coefficient of a material constituting the strain sensor.

2. A pressure sensor according to claim 1,

wherein the diaphragm is formed of a stainless steel or a clad material including the stainless steel and another metal material.

3. A pressure sensor according to claim 1,

wherein the diaphragm has a cylindrical shape and is configured so that a center part is thinner than an end part, a center of the thinner center part bulges, and the bulging part joins to the elastic body.

4. A pressure sensor according to claim 3,

wherein:

the strain sensor includes silicon; and

the elastic body includes any one of a kovar alloy, a 42 alloy, and an invar alloy, each of which has a linear expansion coefficient close to the linear expansion coefficient of the silicon.

5. A pressure sensor according to claim 4,

wherein the elastic body has a cylindrical shape and is configured so that a center part is thinner than an end part and a hole is formed at a part other than a part where the strain sensor is arranged in the elastic body.

6. A pressure sensor according to claim 5,

wherein:

the hole includes two slits being formed in a manner of interposing the strain sensor and extending from an end to the other end of the elastic body; and

the slits penetrate the elastic body.

7. A pressure sensor according to claim 5,

wherein the hole includes:

a first through hole being formed in a manner of interposing the strain sensor and penetrating the elastic body; and

a second through hole communicating with the first through hole and being formed in the elastic body on the side opposite to the side where the strain sensor is arranged.

8. A pressure sensor according to claim 5,

wherein:

the hole includes two recesses (concavities) being formed in a manner of interposing the strain sensor and extending from an end to the other end of the elastic body; and

the recesses do not penetrate the elastic body.

9. A pressure sensor according to claim 6,

wherein the elastic body has a width equal to or larger than a size of the strain sensor and joins at least to two sites of a center part and an outer periphery of the diaphragm.

10. A pressure sensor according to claim 9,

wherein the elastic body joins to the center part of the diaphragm at one point and to the outer periphery of the diaphragm around the whole circumference.

11. A pressure sensor according to claim 10,

wherein the elastic body joins to the strain sensor with a metal or a low-melting-point glass.

12. A pressure sensor according to claim 11,

wherein the metal for joining the elastic body to the strain sensor is Au/Sn or Au/Ge.

13. A pressure sensor according to claim 11,

wherein the low-melting-point glass for joining the elastic body to the strain sensor is a vanadium-based glass.

14. A pressure sensor according to claim 13,

wherein the diaphragm has a plurality of bends between a center part of the diaphragm and an end.

15. A pressure sensor according to claim 1,

wherein:

the pressure sensor has a support fixing an outer periphery of the diaphragm and an airtight housing fixed to the support and arranged in a manner of surrounding the diaphragm, the elastic body, and the strain sensor; and

the support and the airtight housing are fixed so as to retain airtightness.

16. A pressure sensor according to claim 15,

wherein a brim is formed at the outer periphery of the support, the airtight housing is fixed to the brim, and the thickness of the brim is 0.10 mm to 0.20 mm.

17. A pressure sensor according to claim 16,

wherein the support is formed of a forged material and a direction of forged stream lines formed by forging coincides with an in-plane direction of the brim.

19. A mass flow controller which monitors the pressure of a fluid,

the mass flow controller comprising a pressure sensor according to claim 14.

18. A differential pressure sensor comprising:

a first diaphragm and a second diaphragm which are arranged so as to face each other and deforming by a pressure of a fluid;

an elastic body being arranged between the first diaphragm and the second diaphragm and joining to the first diaphragm on one side and the second diaphragm on the other side; and

a strain sensor being arranged on one side or the other side of the elastic body and on an end side apart from a position corresponding to a center of the first diaphragm and the second diaphragm and detecting a deformation of the elastic body working together with a deformation of the first diaphragm and the second diaphragm as a strain; and

wherein the elastic body is formed of a material having a linear expansion coefficient close to the linear expansion coefficient of a material constituting the strain sensor.

20. A mass flow controller which monitors the pressure of a fluid,

the mass flow controller comprising a differential pressure sensor according to claim 18.