Thermosensitive flow rate detecting element and flow rate sensor using same

• US 5,936,157 A
• Filed: 11/12/1997
• Issued: 08/10/1999
• Est. Priority Date: 07/03/1997
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kawai, Masahiro, Yamashita, Akira, Ohashi, Yutaka, Yamakawa, Tomoya
• Primary Examiner(s): Dombroske, George
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US08/968,569
• Time in Patent Office: 636 Days
• Field of Search: 73/204.26, 73/204.25, 73/204.24
• US Class Current: 73/204.26
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/692 Thin-film arrangements

Abstract

A thermosensitive flow rate detecting element having a flat substrate is provided with a gap having an opening on at least one side thereof for the flow of a fluid, an insulating support film provided on the one side of the substrate, a sensor unit which has a heating element for heating the fluid and a thermosensitive element for detecting temperature of the fluid provided in the upper position of the opening on the insulating support film, and a fluid temperature measuring element, provided at a distance from the sensor unit on the one side of the flat substrate, for detecting temperature of the fluid. The thermosensitive flow rate detecting element measures flow rate or flow velocity of the fluid on the basis of a temperature detected by the thermosensitive element, by keeping heating temperature of the heating element at a level higher than a temperature detected by the fluid temperature measuring element by a prescribed difference in temperature. A first notch is provided on the flat substrate near the fluid temperature measuring element and is formed by removing a part of the flat substrate from either side thereof so as not to reach the remaining side thereof.

Claims

1. A thermosensitive flow rate detecting element comprising:

a flat substrate provided with a gap having an opening on at least one side thereof for the flow of a fluid;

an insulating support film provided on said one side of said flat substrate;

a sensor unit which comprises a heating element for heating said fluid and a thereoosensitive element for detecting temperature of said fluid provided in the upper position of said opening on said insulating support film; and

a fluid temperature measuring element, provided at a distance from said sensor unit on said one side of said flat substrate, for detecting temperature of said fluid,

wherein said thermosensitive flow rate detecting element measures flow rate or flow velocity of said fluid on the basis of a temperature detected by said thermosensitive element, by keeping heating temperature of said heating element at a level higher than a temperature detected by said fluid temperature measuring element by a prescribed difference in temperature, and

wherein a first notch is provided on said flat substrate near said fluid temperature measuring element and is formed by removing a part of said flat substrate from either side thereof so as not to reach the remaining side thereof.

2. The thermosensitive flow rate detecting element according to claim 1, wherein said first notch is formed under the arrangement region of said fluid temperature measuring element on the other side of the flat substrate.

3. The thermosensitive flow rate detecting element according to claim 2, further comprising said first notchs formed on the outer periphery of said fluid temperature measuring element on said one side of the flat substrate.

4. The thermosensitive flow rate detecting element according to claim 2, further comprising said first notchs formed on the outer periphery of said fluid temperature measuring element on the other side of the flat substrate.

5. The thermosensitive flow rate detecting element according to claim 2, further comprising a thin film made of a conductive material which is provided on the upper portion of said fluid temperature measuring element in a state insulated from said fluid temperature measuring element.

6. The thermosensitive flow rate detecting element according to claim 2, further comprising a second notch formed by removing a part of the flat substrate which is provided on a portion of said flat substrate between said sensor unit and the fluid temperature measuring element, so as to cross a thermal conduction path from said sensor unit to said fluid temperature measuring element.

7. The thermosensitive flow rate detecting element according to claim 2, further comprising a thermal conduction inhibiting member made of a low-thermal-conductivity material which is provided between said sensor unit and said fluid temperature measuring element so as to cross a thermal conduction path from said sensor unit to said fluid temperature measuring element.

8. The thermosensitive flow rate detecting element according to claim 1, wherein said first notchs are formed on the outer periphery of said fluid temperature measuring element on said one side of the flat substrate.

9. The thermosensitive flow rate detecting element according to claim 1, wherein said first notchs are formed on the outer periphery of said fluid temperature measuring element on the other side of the flat substrate.

10. The thermosensitive flow rate detecting element according to claim 1, further comprising a thin film made of a 112 conductive material which is provided on the upper portion of said fluid temperature measuring element in a state insulated from said fluid temperature measuring element.

11. The thermosensitive flow rate detecting element according to claim 1, further comprising a second notch formed by removing a part of the flat substrate which is provided on a portion of said flat substrate between the sensor unit and the fluid temperature measuring element, so as to cross a thermal conduction path from said sensor unit to said fluid temperature measuring element.

12. The thermosensitive flow rate detecting element according to claim 11, wherein said second notch is formed on the other side of the flat substrate.

13. The thermosensitive flow rate detecting element according to claim 11, wherein said second notch is formed on said one side of the flat substrate.

14. The thermosensitive flow rate detecting element according to claim 1, further comprising a thermal conduction inhibiting member made of a low-thermal-conductivity material which is provided between said sensor unit and said fluid temperature measuring element so as to cross a thermal conduction path from said sensor unit to said fluid temperature measuring element.

15. A thermosensitive flow rate detecting element comprising;

a flat substrate provided with a gap having an opening on at least one side thereof for the flow of a fluid;

an insulating support film provided on said one side of the substrate;

a sensor unit which comprises a heating element for heating said fluid and a thermosensitive element for detecting temperature of said fluid provided in the upper position of said opening on said insulating support film; and

a fluid temperature measuring element, provided at a distance from said sensor unit on said one side of said flat substrate, for detecting temperature of said fluid,

wherein said thermosensitive flow rate detecting element measures flow rate or flow velocity of said fluid on the basis of a temperature detected by said thermosensitive element, by keeping heating temperature of said heating element at a level higher than a temperature detected by said fluid temperature measuring element by a prescribed difference in temperature, and

wherein a second notch formed by removing a part of the flat substrate is provided on a portion of said flat substrate between the sensor unit and the fluid temperature measuring element, so as to cross a thermal conduction path from said sensor unit to said fluid temperature measuring element.

16. A flow rate sensor comprising:

a measuring duct, having a cylindrical shape, arranged within a path of a fluid to be measured with the axial direction thereof substantially in alignment with the flow direction of the fluid to be measured;

a thermosensitive flow rate detecting element comprising a flat substrate provided with a gap having an opening on at least one side, an insulating support film provided on one side of the substrate, a sensor unit which comprises a heating element for heating said fluid and a thermosensitive element for detecting temperature of said fluid provided in the upper position of said opening on said insulating support film, and a fluid temperature measuring element, provided at a distance from said sensor unit on said one side of said flat substrate, for detecting temperature of said fluid, and a notch provided on said flat substrate near said fluid temperature measuring element and formed by removing a part of said flat substrate from either side thereof so as not to reach the remaining side thereof, said thermosensitive flow rate detecting element being provided in said measuring duct with the arranging direction of said heating element and said thermosensitive element in alignment with the axial direction of said measuring duct; and

a control unit for controlling electric current supplied to said heating resistance element so as to keep the temperature of said heating resistance element at a prescribed value higher than the temperature of said fluid temperature measuring element;

whereby

a flow rate or a flow velocity of said fluid being measured on the basis of thermal conduction phenomenon from the portion heated by said heating resistance element to said fluid to be measured.