A thermal air flowmeter in which a heat generating resistive element having temperature dependence is arranged in an air flow passage to measure the air flow rate on the basis of an output V2 of a gauge circuit having this element. The flowmeter is also provided with an operation circuit for correcting the output characteristic by using a polynomial the second order or a higher order than the second order. By providing such an operation circuit, higher precision of the thermal air flowmeter can be achieved by a method in place of laser trimming, with a small-scale circuit configuration.

Thermal air flowmeter

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 heating resistor type air flow rate measuring apparatus is provided with a couple of heating resistors (2a, 2b) placed at the positions where those resistors may interfere thermally each other with respect to an air flow, and a couple of driving circuits for driving those heating resistors. The air flow rate signal is obtained by calculating the difference between the output signals of a couple of heating resistors (2a, 2b) in terms of heat radiation rate effected by an air flow, and adding the difference value onto the output signal of one of heating resistors.

Heating resistor type air flow rate measuring apparatus

In regard to an output of an intake flow meter for an internal combustion engine, a pulsation error can be reduced and dispersion in correction at the time of correction of response delay (a recovering of response delay) is reduced. A digital device is used for pre-processing of a control unit for inputting a flow rate measuring signal. An output voltage of the flow sensor is converted into a digital value, the digital value is converted into a flow rate and adds a response delay. The control unit detects a degree of response delay in reference to dispersion in a clock signal so as to perform response delay recovering and reduce dispersion of the response delay.

Thermal flow meter and control system

A flow measuring device includes a housing, a support, and a flow measurement element. The housing defines a passage therein and includes a passage narrowing part, which reduces a cross-sectional area of the passage, in a predetermined part of the passage. The support has a platy shape and is disposed along a flow direction of fluid flowing in the passage. The flow measurement element is located inside the passage narrowing part and is disposed on a surface of the support. The flow measurement element detects a flow rate of fluid flowing in the passage. The passage narrowing part has an inner wall surface that gradually reduces a width of the passage from a center side to both end sides of the passage in a height direction of the passage, which is perpendicular to a direction of the width of the passage.

Flow measuring device

An intake air flow measuring apparatus for internal combustion engine apparatus has a thermal type air flow meter, a unit for correcting the response delay of the thermal type air flow meter, and a unit for detecting the direction of the flow of intake air so that an amount of reverse air flow is detected by the response delay correcting unit and air flow direction unit, and that a true amount of sucked air flow is calculated from the output of the thermal type air flow meter and the amount of reverse air flow.

Yutaka Nishimura

Papers

Intake air flow measuring apparatus for internal combustion engine