Thermal type flow measuring device

• US 20040211253A1
• Filed: 02/11/2004
• Published: 10/28/2004
• Est. Priority Date: 08/14/2001
• Status: Active Grant

• Current Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Original Assignee: Hitachi Car Engineering Company Limited (Hitachi, Ltd.), Hitachi, Ltd.
• Inventors: Igarashi, Shinya, Horie, Junichi, Nakada, Keiichi, Ueyama, Kei, Watanabe, Izumi
• Granted Patent: US 6,935,172 B2
• Time in Patent Office: Days
• US Class Current: 73/204.15
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/698 Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters

Abstract

A thermal type flow measuring device comprises a heating resistor(HF), a temperature measuring resistor(Ru) upstream of the heating resistor(HF) with respect to a fluid(Q), and a temperature measuring resistor(Rd) downstream of the heating resistor(HF). A heat sensitive resistance element(CF), the upstream temperature measuring resistor(Ru) and the downstream temperature measuring resistor(Rd) form a first bridge circuit, and this first bridge circuit and the heating resistor(HF) form a second bridge circuit. Feedback control means(OP1, Tr) heat the heating resistor(HF) in accordance with an output for keeping a balance of the second bridge circuit. The distance between the heat sensitive resistance element(CF) and the heating resistor(HF) is larger than the distance between the upstream temperature measuring resistor(Ru) or the downstream temperature sensitive resistor(Rd) and the heating resistor(HF) so that the heat sensitive resistance element(CF) is positioned to receive less thermal influences from the heating resistor(HF) than the upstream temperature measuring resistor(Ru) and the downstream temperature sensitive resistor(Rd). The upstream temperature measuring resistor or the downstream temperature measuring resistor is heated by the heating resistor, and the flow rate of the fluid is measured based on an output for keeping a balance of the first bridge circuit.

Claims

1. A thermal type flow measuring device including a heating resistor (HF) disposed in a fluid (Q), upstream temperature measuring resistors (Ru1, Ru2) disposed upstream of said heating resistor (HF) with respect to said fluid (Q), and downstream temperature measuring resistors (Rd1, Rd2) disposed downstream of said heating resistor (HF) with respect to said fluid, thereby measuring the flow rate of said fluid, said thermal type flow measuring device comprising:

a first bridge circuit including said upstream temperature measuring resistors (Ru1, Ru2) and said downstream temperature measuring resistors (Rd1, Rd2);

a second bridge circuit including said first bridge circuit and said heating resistor (HF); and

feedback control means (OP1, Tr) for heating said heating resistor (HF) in accordance with an output for keeping a balance of said second bridge circuit,

wherein said upstream temperature measuring resistors or said downstream temperature measuring resistors are heated by said heating resistor, and the flow rate of said fluid is measured based on an output for keeping a balance of said first bridge circuit.

5. A thermal type flow measuring device according to claim 1, wherein the flow direction of said fluid is detected based on the output of said first bridge circuit.

6. A thermal type flow measuring device according to claim 1, wherein the flow direction of said fluid is detected based on the output of said second bridge circuit.

7. A thermal type flow measuring device according to claim 1, wherein the flow direction of said fluid is detected based on the outputs of said first bridge circuit and said second bridge circuit.

2. A thermal type flow measuring device including a heating resistor (HF) disposed in a fluid (Q), an upstream temperature measuring resistor (Ru) disposed upstream of said heating resistor (HF) with respect to said fluid (Q), and a downstream temperature measuring resistor (Rd) disposed downstream of said heating resistor (HF) with respect to said fluid, thereby measuring the flow rate of said fluid, said thermal type flow measuring device comprising:

a first bridge circuit including a heat sensitive resistance element (CF), said upstream temperature measuring resistor (Ru) and said downstream temperature measuring resistor (Rd);

a second bridge circuit including said first bridge circuit and said heating resistor (HF); and

feedback control means (OP1, Tr) for heating said heating resistor (HF) in accordance with an output for keeping a balance of said second bridge circuit,

wherein the distance between said heat sensitive resistance element (CF) and said heating resistor (HF) is larger than the distance between said upstream temperature measuring resistor (Ru) or said downstream temperature sensitive resistor (Rd) and said heating resistor (HF) so that said heat sensitive resistance element (CF) is positioned to receive less thermal influences from said heating resistor (HF) than said upstream temperature measuring resistor (Ru) and said downstream temperature sensitive resistor (Rd), and said upstream temperature measuring resistor or said downstream temperature measuring resistor is heated by said heating resistor, and the flow rate of said fluid is measured based on an output for keeping a balance of said first bridge circuit.

10. A thermal type flow measuring device according to claim 2, wherein the flow direction of said fluid is detected based on the output of said first bridge circuit.

13. A thermal type flow measuring device according to claim 2, wherein the flow direction of said fluid is detected based on the output of said second bridge circuit.

16. A thermal type flow measuring device according to claim 2, wherein the flow direction of said fluid is detected based on the outputs of said first bridge circuit and said second bridge circuit.

3. A thermal type flow measuring device including a heating resistor (HF) disposed in a fluid (Q), upstream temperature measuring resistors (Ru1, Ru2) disposed upstream of said heating resistor (HF) with respect to said fluid (Q), and downstream temperature measuring resistors (Rd1, Rd2) disposed downstream of said heating resistor (HF) with respect to said fluid, thereby measuring the flow rate of said fluid, said thermal type flow measuring device comprising:

a first bridge circuit including said upstream temperature measuring resistors (Ru1, Ru2) and said downstream temperature measuring resistors (Rd1, Rd2);

a second bridge circuit including a heat sensitive resistance element (CF) and said heating resistor (HF); and

feedback control means (OP1, Tr) for heating said heating resistor (HF) in accordance with an output for keeping a balance of said second bridge circuit,

wherein said heat sensitive resistance element (CF) is heated by said heating resistor, and the flow rate of said fluid is measured based on an output for keeping a balance of said first bridge circuit.

11. A thermal type flow measuring device according to claim 3, wherein the flow direction of said fluid is detected based on the output of said first bridge circuit.

14. A thermal type flow measuring device according to claim 3, wherein the flow direction of said fluid is detected based on the output of said second bridge circuit.

17. A thermal type flow measuring device according to claim 3, wherein the flow direction of said fluid is detected based on the outputs of said first bridge circuit and said second bridge circuit.

4. A thermal type flow measuring device including a heating resistor (HF) disposed in a fluid (Q), upstream temperature measuring resistors (Ru1, Ru2) disposed upstream of said heating resistor (HF) with respect to said fluid (Q), and downstream temperature measuring resistors (Rd1, Rd2) disposed downstream of said heating resistor (HF) with respect to said fluid, thereby measuring the flow rate of said fluid, said thermal type flow measuring device comprising:

a first bridge circuit including said upstream temperature measuring resistors (Ru1, Ru2) and said downstream temperature measuring resistors (Rd1, Rd2);

a second bridge circuit including a heat sensitive resistance element (CF) and said heating resistor (HF);

feedback control means (OP1, Tr) for heating said heating resistor (HF) in accordance with an output for keeping a balance of said second bridge circuit;

a heating resistor (HF′

) for heating said heat sensitive resistance element (CF); and

heating control means (R3) for heating said heating resistor (HF′

) in accordance with an output of said feedback control means (OP1, Tr),

wherein the flow rate of said fluid is measured based on an output for keeping a balance of said first bridge circuit.

12. A thermal type flow measuring device according to claim 4, wherein the flow direction of said fluid is detected based on the output of said first bridge circuit.

15. A thermal type flow measuring device according to claim 4, wherein the flow direction of said fluid is detected based on the output of said second bridge circuit.

18. A thermal type flow measuring device according to claim 4, wherein the flow direction of said fluid is detected based on the outputs of said first bridge circuit and said second bridge circuit.

8. A control device for an internal combustion engine, which includes flow measuring means for measuring the flow rate of gas supplied to said internal combustion engine, said flow measuring means comprising:

a heating resistor (HF) disposed in a fluid (Q);

upstream temperature measuring resistors (Ru1, Ru2) disposed upstream of said heating resistor (HF) with respect to said fluid (Q);

downstream temperature measuring resistors (Rd1, Rd2) disposed downstream of said heating resistor (HF) with respect to said fluid;

a first bridge circuit including said upstream temperature measuring resistors (Ru1, Ru2) and said downstream temperature measuring resistors (Rd1, Rd2);

a second bridge circuit including said first bridge circuit and said heating resistor (HF); and

feedback control means (OP1, Tr) for heating said heating resistor (HF) in accordance with an output for keeping a balance of said second bridge circuit,

wherein said upstream temperature measuring resistors or said downstream temperature measuring resistors are heated by said heating resistor, and the flow rate of said fluid is measured based on an output for keeping a balance of said first bridge circuit.

9. A control device for a fuel cell, which including flow measuring means for measuring the flow rate of gas used in said fuel cell, said flow measuring means comprising:

a heating resistor (HF) disposed in a fluid (Q);

upstream temperature measuring resistors (Ru1, Ru2) disposed upstream of said heating resistor (HF) with respect to said fluid (Q);

downstream temperature measuring resistors (Rd1, Rd2) disposed downstream of said heating resistor (HF) with respect to said fluid;

a first bridge circuit including said upstream temperature measuring resistors (Ru1, Ru2) and said downstream temperature measuring resistors (Rd1, Rd2);

a second bridge circuit including said first bridge circuit and said heating resistor (HF); and

feedback control means (OP1, Tr) for heating said heating resistor (HF) in accordance with an output for keeping a balance of said second bridge circuit,

wherein said upstream temperature measuring resistors or said downstream temperature measuring resistors are heated by said heating resistor, and the flow rate of said fluid is measured based on an output for keeping a balance of said first bridge circuit.