Flow measuring device

Abstract

A flow measuring device has a flow channel block including a main flow channel whose both ends are open, and an auxiliary flow channel that branches from the main flow channel, a flow amount measurement element provided for the auxiliary flow channel, and a branch entrance and a collection exit that open in a wall surface of the main flow channel, and that communicate to the auxiliary flow channel, so that a part of a gaseous body that flows through the main flow channel is directed to the auxiliary flow channel through the branch entrance, and the gaseous body that has passed through the auxiliary flow channel is directed back to the main flow channel through the collection exit. A holding member containing portion is provided in a depressed manner for an area excluding an area including the branch entrance and an area including the collection exit in a circumference surface of a space of the flow channel block that configures the main flow channel. An orifice is contained within the main flow channel. An orifice holding member fitted into the holding member containing portion holds the orifice by being brought into contact with the orifice. The wall surface of the main flow channel is configured by a wall surface excluding the area for which the holding member containing portion is formed out of the main flow channel and an inner surface of the orifice holding member.

Description

BACKGROUND OF THE INVENTION[0001]1. Technical Field[0002]The present invention relates to flow measuring devices, in particular, to a flow measuring device for measuring a flow amount of a gaseous body.[0003]2. Related Art[0004]A straight-tube type flow measuring device typically measures a flow velocity V of a gaseous body that flows through a flow channel 12 using a flow detection element 11, as shown in FIG. 1A or 1B, and measures a flow amount of the gaseous body within the flow channel 12 based on the measured flow velocity V and a flow channel cross-sectional area.[0005]When a certain amount of the gaseous body flows through the flow channel 12 in the flow measuring device having such a structure, the flow velocity V of the gaseous body increases if the flow channel cross-sectional area is small as shown in FIG. 1A, and the flow velocity V of the gaseous body decreases if the flow channel cross-sectional area is large as shown in FIG. 1B. On the other hand, the flow detection ...

AI Technical Summary

Benefits of technology

[0016]The displacement of the positions of the vent hole 33 and the inlet 23 in this manner gives an influence on the flow of the gaseous body that flows from the main flow channel 13 into the auxiliary flow channel 14, and thus can produce variation in the flow ratio between the main flow channel 13 and the auxiliary flow channel 14, thereby causing the decrease of the measurement accuracy of the flow measuring device.

[0034]Moreover, according to this aspect, a resilient member can be sandwiched between the end surface of the orifice holding member and the end cap. By sandwiching the resilient member between the end surface of the orifice holding member and the end cap, it is possible to press the orifice holding member against the orifice by the resilient repulsion of the resilient member, thereby securely holding the orifice.

Problems solved by technology

As a result, preparing flow measuring devices of flow amount ranges for various purposes becomes expensive and requires a large storage space.

However, even with this method, a stepped section was generated between the vent hole 33 and the inlet 23, and the flow of the gaseous body directed to the auxiliary flow channel 14 was disturbed by this stepped section, and thus it was not possible to reduce the variation of the flow ratio.

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