Thermal mass-flow meter and mass-flow control device using same
A thermal mass-flow meter and mass-flow controller using the mass-flow meter are disclosed. The mass flow meter includes a base having an installation surface, a passage for fluid, and a bypass in the middle of the passage. The mass-flow meter also includes a case in contact with the installation surface of the base and housing a sensor tube and sensor wires. The mass flow sensor also includes a sensor circuit including a bridge circuit including the sensor wires and other resistive elements. A heat-transfer block is positioned adjacent to the case and in contact with the installation surface of the base. A bottom surface of the heat-transfer block and the installation surface of the base are in surface contact with each other, and at least one lateral surface of said heat-transfer block and a lateral surface of said case are in surface contact with each other.
1. A thermal mass-flow meter including:
a base having an installation surface and a passage for fluid;
a bypass in the middle of said passage;
a flow sensor comprising a sensor tube that branches from said passage on an upstream side of said bypass, bypasses to an outside of said installation surface, and joins said passage on a downstream side of said bypass, a pair of sensor wires wound around said sensor tube, and a case in contact with said installation surface of said base and housing said sensor tube and said sensor wires; and
a sensor circuit including a bridge circuit constituted by said sensor wires and other resistive elements;
a heat-transfer block formed of heat-transfer material and positioned adjacent to said case and in contact with said installation surface of said base, wherein:
a bottom surface of said heat-transfer block and said installation surface of said base are in surface contact with each other, and
at least one lateral surface of said heat-transfer block and a lateral surface of said case are in surface contact with each other.
2. The thermal mass-flow meter according to claim 1 , including:
a heat-transfer sheet formed of heat-transfer material and in contact with a lateral surface of said base,
a surface of said heat-transfer sheet and said lateral surface of said base are in surface contact with each other, and
a surface of said heat-transfer sheet and at least one lateral surface of said heat-transfer block are in surface contact with each other.
3. The thermal mass-flow meter according to claim 1 , including:
a heat insulator covering an upper surface of said heat-transfer block.
4. The thermal mass-flow meter according to claim 1 , including:
a heater which heats said base and/or a cooler which cools said base.
5. The thermal mass-flow meter according to claim 1 , including:
a temperature control block in contact with a lateral surface of said base, at least, and
said temperature control block is formed of heat-transfer material and has a heating element which heats said temperature control block and/or a cooling element which cools said temperature control block.
6. The thermal mass-flow meter according to claim 5 , wherein:
said heat-transfer block is in surface contact with an upper surface and/or at least one lateral surface of said temperature control block.
7. The thermal mass-flow meter according to claim 5 , wherein:
said heat-transfer block is formed, as a part of said temperature control block, integrally and inseparably with said temperature control block.
8. The thermal mass-flow meter of claim 5 , wherein:
said thermal mass-flow meter further has a heat insulator covering an upper surface of said heat-transfer block or said temperature control block, at least.
9. The thermal mass-flow meter of claim 1 , wherein:
said case includes a leg part.
10. The thermal mass-flow meter according to claim 1 , wherein:
an absolute value of difference between a temperature of a fluid which flows through said passage and a temperature of a fluid which flows through said sensor tube becomes less than 10 degrees Celsius.
11. A mass-flow control device including:
a base having an installation surface and a passage for fluid;
a bypass in the middle of said passage;
a flow sensor comprising a sensor tube that branches from said passage on an upstream side of said bypass, bypasses to an outside of said installation surface,
and joins said passage on a downstream side of said bypass, a pair of sensor wires wound around said sensor tube, and a case in contact with said installation surface of said base and housing said sensor tube and said sensor wires; and
a sensor circuit including a bridge circuit constituted by said sensor wires and other resistive elements;
a heat-transfer block formed of heat-transfer material and positioned adjacent to said case and in contact with said installation surface of said base, wherein:
a bottom surface of said heat-transfer block and said installation surface of said base are in surface contact with each other, and
at least one lateral surface of said heat-transfer block and a lateral surface of said case are in surface contact with each other,
a flow control valve in contact with said installation surface of said base and configured to control a flow rate of the fluid which flows through said passage, and
a control circuit which outputs a control signal to said flow control valve based on the flow rate of the fluid detected by said thermal mass-flow meter.
12. The mass-flow control device according to claim 11 , including:
a heat-transfer sheet formed of heat-transfer material and in contact with a lateral surface of said base,
a surface of said heat-transfer sheet and said lateral surface of said base are in surface contact with each other, and
a surface of said heat-transfer sheet and at least one lateral surface of said heat-transfer block are in surface contact with each other.
13. The mass-flow control device according to claim 11 , including:
a heat insulator covering an upper surface of said heat-transfer block.
14. The mass-flow control device according to claim 11 , including:
a heater which heats said base and/or a cooler which cools said base.
15. The mass-flow control device according to claim 11 , including:
a temperature control block in contact with a lateral surface of said base, at least, and
said temperature control block is formed of heat-transfer material and has a heating element which heats said temperature control block and/or a cooling element which cools said temperature control block.
16. The mass-flow control device according to claim 15 , wherein:
said heat-transfer block is in surface contact with an upper surface and/or at least one lateral surface of said temperature control block.
17. The mass-flow control device according to claim 15 , wherein:
said heat-transfer block is formed, as a part of said temperature control block, integrally and inseparably with said temperature control block.
18. The mass-flow control device of claim 15 , wherein:
said thermal mass-flow meter further has a heat insulator covering an upper surface of said heat-transfer block or said temperature control block, at least.
19. The mass-flow control device of claim 11 , wherein:
said case includes a leg part.
20. The mass-flow control device according to claim 11 , wherein:
an absolute value of difference between a temperature of a fluid which flows through said passage and a temperature of a fluid which flows through said sensor tube becomes less than 10 degrees Celsius.