In a thermal sensor with a detection part and a circuit part formed on the same substrate, an insulating film for protection of the circuit part causes problems of lowering in sensitivity of a heater, deterioration in accuracy due to variation of a residual stress in the detection part, etc. A layered film including insulating films is formed on a heating resistor, an intermediate layer is formed thereon, and a layered film including insulating films is formed further thereon. The intermediate layer is specified to be a layer made up of any one of aluminum nitride, aluminum oxide, silicon carbide, titanium nitride, tungsten nitride, and titanium tungsten. This configuration enables the layered film on the upper part of the detection part to be removed using the intermediate layer as an etch stop layer, which solves problems of lowering in sensitivity, a variation in residual stress, etc. resulting from these.

Thermal fluid flow sensor and method of manufacturing the same

A thermal-type flow sensor capable of generating a monotonously increasing output over a time period of transition from a reverse flow to a forward flow with a simplified structure while exhibiting high sensitivity in the measurement of flow rate in the forward direction. The flow sensor includes a plurality of heat generating portions implemented by upstream heat-sensitive resistor (4) and downstream heat-sensitive resistor (5) within a passage (19) as viewed in a direction in which fluid flows through the passage (19), for thereby measuring a flow rate or a flowing speed of the fluid on the basis of heat transfer phenomenon taking place between the heat generating portions and the fluid. The flow sensor includes a heating current control means (30, 31, 32) for controlling heating currents flowing through the heat-sensitive resistors (4, 5) so that temperatures of the plurality of heat generating portions increase by predetermined values relative to the temperature of the fluid, a means (34) for determining difference between heating currents flowing through the upstream heat generating portion and the downstream heat generating portion, and means (35 to 37) for detecting the flowing speed or the flow rate of the fluid on the basis of the difference between the heating currents.

Thermal-type flow sensor

A thermal type flow measuring device comprising: an 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) on the basis of the balance keeping output 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 heat sensitive resistor (Rd) and the heating resistor (HF) so that the heat sensitive resistor element (CF) is positioned to receive less thermal influences from the heating resistor (HF) than the upstream temperature measuring resistor (Ru) and the downstream heat sensitive resistor (Rd), and so that the upstream temperature measuring resistor or the downstream temperature measuring resistor is heated by the heating resistor thereby to measure the flow rate of the fluid on the basis of an output for keeping the balance of the first bridge circuit.

Thermal type flow measuring device

A flow rate detecting element has a flat substrate 1 provided with a gap opening 18 on at least one side surface, a sensor section 15 including a heating resistance element 4 and a pair of temperature detecting resistance elements 5, 6 arranged on opposite sides of the heating resistance element and wrapped by an insulating supporting film 2 and an insulating protecting film 3 from above and below. The sensor section is arranged on a plane substantially parallel with a surface of the flat substrate and at least one end of the supporting film is held by the flat substrate to locate the sensor section over the gap, whereby the most part of the sensor section is disposed in a non-contact state with the flat substrate. A thin-film-shaped thermal conduction promoting member 11 is provided in a heat transmitting path of the sensor section between the heating resistance element and the pair of temperature detecting resistance elements, and has a higher thermal conductivity than the supporting film and the protecting film.

Flow rate detecting element and flow rate sensor using same

A flow sensor eliminates turbulence of fluid flow due to a structure of the temperature detecting portion so that a temperature of the temperature detecting portions does not fluctuate due to the turbulence of the fluid. The flow sensor is formed on a substrate. Each of a first temperature detecting portion and a second temperature detecting portion has a heating function and a temperature detecting function, and are arranged along a direction of flow of the fluid. A supporting portion is formed on the substrate for supporting the first and second temperature detecting portions thereon. The supporting portion does not have a side surface facing substantially in the direction of flow of the fluid. A side surface of the supporting portion is protected by a guard portion formed along the side surface.

Jiei Booree Fuiritsupu

Papers

Flow rate sensor