The present invention provides a thermal flow meter which can suppress a degradation of measurement accuracy caused by deformation of a diaphragm and a stained rear surface thereof even in a case where a gap is provided in order to form the diaphragm in an air flow sensing element. The present invention relates to a thermal flow meter 300 which includes a bypass passage through which a measurement target gas 30 received from a main passage 124 flows, and an air flow sensing element which measures a flow rate of the measurement target gas 30 by performing heat transfer with the measurement target gas 30 flowing through the bypass passage. The thermal flow meter 300 includes at least a circuit package 400 which contains the air flow sensing element 602. A gap 674 is formed in a rear surface of the air flow sensing element 602 to form a diaphragm 672 in an air flow sensing area 437 of the air flow sensing element 602, and the gap 674 becomes a sealed space reduced in pressure compared to an atmospheric pressure.

A flow sensing module is provided for determining a flow rate of a fluid flowing through a flow channel. The flow sensing module may include an integrated flow restrictor, sometimes including a plurality of concentric ribs defining a plurality of orifices shaped to match the curvature of the wall of the flow channel. A first sensing port may open into the flow channel upstream of the flow restrictor, and a second sensing port may open into the flow channel downstream of the flow restrictor. A flow rate of a fluid flowing through the flow channel may be determining using a differential pressure between the first and second ports created by the flow restrictor, either using a flow sensor or a pressure sensor. The particular arrangement and relative dimensions of the orifices of the flow restrictor and the pressure ports can result in substantially reduced noise.

The present invention has been made to improve measurement accuracy of a thermal flow meter. In the thermal flowmeter according to the invention, a circuit package (400) that measures a flow rate is molded in a first resin molding process. In a second resin molding process, a housing (302) having an inlet trench (351), a bypass passage trench on frontside (332), an outlet trench (353), and the like are formed through resin molding, and an outer circumferential surface of the circuit package (400) produced in the first resin molding process is enveloped by a resin in the second resin molding process to fix the circuit package (400) to the housing (302).

Traditional flow sensors include an upstream resistive sensor element, a downstream resistive sensor element and an intervening heater resistive element. To help reduce the size and/or cost of such flow sensor, it is contemplated that the heater resistor may be eliminated. When so provided, the space required for the heater resistive element, as well as the corresponding heater control circuit, may be eliminated. This can reduce the cost, size and complexity of the flow sensor. Coupling a resistive sensor element of such flow sensor to ground through a low temperature coefficient of resistance (TCR) resistor can reduce the variation of span of an output of the flow sensor which can improve resolution and accuracy of such sensor.

A flow sensor includes an auxiliary channel having an opening into which a fluid to be measured is taken; a sensor element that measures the flow of the fluid to be measured; a housing that accommodates electronic parts; and a resin cover. The flow sensor is configured such that junctions of the housing and the cover are formed in locations where first target weld portions, which are formed so that the circuit chamber is surrounded, face each other and second target weld portions, which are disposed for additional reinforcement of the joints, face each other on a bonding face of the housing and a bonding face of the cover with a step being provided. The positioning of the housing and the cover is determined, and the first target weld portions are welded to each other and second target weld portions are welded to each other by way of laser radiation.

Provided is a thermal type airflow volume meter improving measurement accuracy, a method for manufacturing the same, and an adhesive sheet for use therein, the adhesive sheet divided into at least two or more per adherend and having a thickness of approximately 0.1 mm or less is divided to correspond to a shape of the adherend and generates or increases adhesion or stickiness by external energy.

A flow rate sensor includes: a housing made from a resin material and having a bottom base portion and a side wall, at least one surface side of the housing being open; a cover made from a resin material, covering the one surface side of the housing, welded to an upper surface of the side wall of the housing, and defining, with the bottom base portion and the side wall of the housing, an auxiliary passage within which a gas to be measured flows that is taken in from a main passage; and a flow rate detection unit disposed within the auxiliary passage. A protruding portion for height control is provided to one of the housing and the cover at least in a vicinity of the side wall around the flow rate detection unit so as to suppress sinking in of the cover during welding.

The purpose of this invention obtain a physical-quantity detection device, the external shape of the housing of which can be reduced in size. Said physical-quantity detection device, which detects a plurality of physical quantities of a gas being measured that flows through a main channel, is characterized by having a housing positioned inside said main channel, a circuit board insert-molded into said housing, and a plurality of detection sensors mounted on both sides of the circuit board.

The present invention provides a thermal flow meter 300 which reduces a stress applied from a fixing portion 3721, which is used to hold and fix a circuit package 400 with respect to a housing 302, to the circuit package 400 and has high reliability. In the thermal flow meter of the invention, the circuit package 400 embedded with a flow rate measurement circuit is formed through a first resin molding process, the fixing portion 3721 is formed along with the housing 302 through a second resin molding process, and the circuit package 400 is enveloped by the fixing portion 3721, whereby the circuit package 400 is held by and fixed to the housing 302. In order to reduce the influence of a stress, generated based on a temperature change of the fixing portion 3721, on the circuit package 400, the fixing portion 3721 is constituted of a thick portion 4714 and a thin portion 4710. Since thickness of a resin of the thin portion 4710 is small, the stress to be generated is small, and a force applied to the circuit package 400 can be reduced.

A gas flow sensing device, and related method of manufacturing, comprising a conductive layer encapsulated in dielectric film, suspended over a cavity to form a diaphragm. The conductive layer functions as both a heating a sensing element and is patterned to provide uniform heat distribution across the diaphragm. The device is designed to sense flow from any direction relative to the device and the design of the dielectric film and diaphragm reduces sensor drift during prolonged operation.