Measuring and testing – Volume or rate of flow – Thermal type
Patent
1998-08-18
2000-09-05
Patel, Harshad
Measuring and testing
Volume or rate of flow
Thermal type
731182, G01F 168
Patent
active
061125903
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a device for measuring the mass of a flowing medium. A device has already been disclosed (EP-PS 0 458 998), which has a measuring element accommodated in a measurement fitting, wherein a flow rectifier and a grating are accommodated upstream of the measuring element. The flow rectifier is provided to generate as uniform a flow as possible over the entire inner cross section. The grating permanently fastened to the flow rectifier is intended to produce extremely fine eddies in the flow in order to produce flow conditions that are as constant as possible downstream of the grating so that a stabilization of the measurement signal is produced at the measuring element. In order to prevent a dispersion of the characteristic curve of the measurement signal emitted by the measuring element, it is particularly important that the grating be disposed in a precise alignment to the flow rectifier. This is carried out in the known device by embedding the grating in a heated state into a ring of the flow rectifier. The grating is a wire grating that has individual wires that are woven with one another into a grating structure. In the course of this, the wires retain a certain ability to shift in relation to one another. Embedding the wire grating in the plastic results in the disadvantage that with a change in temperature and with the aging of the plastic of the flow rectifier due to creeping processes, a buckling of the wire grating can occur. The buckling of the wire grating, though, leads to a disadvantageous change in the characteristic curve of the measuring element. The permanent fastening of the grating to the flow rectifier results in the further disadvantage that only relatively costly flow rectifiers with gratings of different mesh widths can be combined with one another. Furthermore, the provided embedding of the grating into the plastic of the flow rectifier is relatively costly for technical manufacturing reasons. Moreover, there is the danger that in the embedding of the grating in the heated state into the ring of the flow rectifier, expelled plastic remains in the flow rectifier so that hindrances in the flow arise that could lead to a signal scattering, particularly in a mass production.
ADVANTAGES OF THE INVENTION
The device according to the invention for measuring the mass of a flowing medium, has the advantage over the prior art that it produces a simple manufacturing method and installation of the device. It is advantageous that the flow rectifier can be produced in a particularly simple manner as a compact standard component with a grating with a varying mesh width or a varying opening cross section, wherein a precise alignment of the through flow openings of the flow rectifier to the through flow openings of the grating is produced. It is also advantageous that a buckling of the grating can be prevented, by means of which the measurement precision and in particular, the measurement stability increase during continuous operation of the device. Furthermore, for a scheduled disassembly of the device, it turns out that the flow rectifier and the grating exist individually and can be separated without destroying them, by means of which it is possible to simply reuse these parts.
Advantageous improvements and updates of the device are possible by means of the measures taken herein.
The provided manufacturing method of the grating, in which it is stamped out of a thin metal strip, is also advantageous and permits the through flow cross sections of the grating to be produced with a very high precision without increasing the manufacturing costs of the grating in so doing. It is advantageous that gratings with various mesh widths or with various through flow cross sections can be produced in a particularly simple manner.
BRIEF DESCRIPTION OF THE DRAWINGS
An exemplary embodiment of the invention is shown in a simplified manner in the drawings and will be explained in more detail in the description that follows.
FIG. 1 shows a device according to the invention in a pa
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Greigg Edwin E.
Greigg Ronald E.
Patel Harshad
Robert & Bosch GmbH
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