Abstract: A highly accurate thermosensitive flow rate sensor is able to reduce the detection error of a flow rate even in the case of a flow accompanied by considerable intake air pulsation in an automotive engine or the like. A flow rate detecting section disposed in a main pipe is equipped with a support member having a first guide surface and a second guide surface for guiding a fluid on opposite sides thereof, and a flow rate detection element provided on the second guide surface of the support member. The second guide surface of the support member, on which the flow rate detection element is mounted, extends longer than the first guide surface in the downstream direction.

Abstract: A flow rate sensor comprises: a main fluid passage for a fluid to flow therealong; a detecting pipe conduit coaxially disposed in the main fluid passage; a temperature sensing element for sensing the temperature of the fluid; a flow rate sensing element including a flow rate detecting resistance made of a thermo-sensitive electrically resistant material, the flow rate detecting element being disposed in the main fluid passage in a manner such that the flow rate detecting resistance is exposed to the fluid flowing therethrough; and a control circuit for controlling an electric current flowing to the flow rate detecting resistance such that the temperature of the flow rate detecting resistance may be maintained at a predetermined value which is higher to some extent than a fluid temperature detected by the temperature sensing element. The main fluid passage involves a converged section whose passage cross sectional area becomes gradually smaller towards the downstream side thereof.

Abstract: A flow rate measuring device includes a flow rate measuring duct for placement in a primary passage for a fluid, extending substantially parallel to the primary passage, and a flow rate detector in the flow rate measuring duct for measuring a flow rate of the fluid in the primary passage, the flow rate measuring duct having a downstream wall including a notch or a through hole. The downstream wall may include an air-permeable member. The flow rate measuring device may include a projection on an outer wall of the flow rate measuring duct upstream of the notch, through hole, or air-permeable member, the projection extending in a circumferential direction with respect to the flow rate measuring duct.

Abstract: A flow rate sensor comprises a fluid passage for a fluid to flow therealong; a main body structure arranged so as to turn its front end to the upstream side of the fluid and coaxially positioned within the fluid passage; and a detecting element disposed between the main body structure and the internal surface of the fluid passage. The main body structure is formed such that its cross section perpendicular to its central axis, at first becomes gradually larger from its front end towards its rear end and then becomes gradually smaller. The detecting element includes a ceramic substrate coated with a film made of a thermo-sensitive electrically resistant material. The film is formed into a meander pattern so as to form a flow rate detecting resistance. The detecting element further includes a fluid temperature compensating resistance.

Abstract: A heat sensitive flow amount sensor of the invention includes a measuring pipe disposed in the inlet pipe of an internal combustion engine, an air flow amount detecting element disposed in the measuring pipe for detecting the flow amount of intake air flowing in the inlet pipe making use of the fact that a quantity of heat loss corresponds to the flow amount of the intake air, and a straightening member disposed on the outer periphery of the measuring pipe along the axial line thereof for straightening the intake air flowing into the measuring pipe by straightening the intake air flowing in the inlet pipe. With this arrangement, even if the heat sensitive flow amount sensor is disposed in the vicinity of a throttle valve, the measuring accuracy of the flow amount of air is not lowered and the size of an internal combustion engine can be reduced by the employment of the heat sensitive flow amount sensor.

Abstract: Plate-like straightening members are provided between a main conduit and a metering pipe stored in the main conduit to suppress the deviation of a flow of a fluid in the main conduit and stabilize a flow in the metering pipe.