Measuring and testing – Simulating operating condition – Marine
Patent
1996-08-26
1998-01-27
Dombroske, George M.
Measuring and testing
Simulating operating condition
Marine
732025, G01M 1900
Patent
active
057124256
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a device for measuring the mass of a flowing medium, or for a flow rate meter. German Patent Application P 44 07 209.0 (U.S. patent application Ser. No. 08/545,583, filed Nov. 3, 1995) sets forth a device that has a carrier body which extends crosswise to the flow of the medium and which is introduced in plug-in fashion into an opening made in a boundary wall of the flow. The boundary wall is for instance a wall of an intake tube through which an internal combustion engine aspirates air from its surroundings. The carrier body is elongated in shape, and in its free end region that protrudes into the flowing medium, it has a measuring channel through which the medium flows. A temperature-dependent measuring resistor, embodied by so-called micromechanical construction, is accommodated in the measuring channel. Such measurement elements have a sensor zone, produced on a platelike carrier by etching out a silicon wafer; the sensor zone, together with a plurality of resistor layers, forms at least one temperature-dependent measuring resistor. The sensor zone encloses only a small recess on the carrier and is extremely slight in thickness, making it capable, with a fast reaction time, of detecting changes in the flow velocity, such as changes in the mass of the flowing medium.
In engine operation, the opening and closing of the engine inlet valves causes a highly pulsating flow to prevail in the intake tube, which as in nearly all technical flows is turbulent in nature. The influence of the pulsations in the flow is partly damped by accommodating the measuring element in the measuring channel, but because of the turbulence in the flow, especially with micromechanical measuring elements, the measurement signal output by the measuring element has so-called background noise. The background noise of the electrical measurement signal output by the measuring element makes precise measurement of the flow velocity more difficult, however.
In the aforementioned prior art, the boundary walls of the measuring channel downstream of an inlet opening of the measuring channel are made rounded, to achieve a maximally unimpeded inflow without flow detachments into the measuring channel and a parallel flow in the measuring channel, especially in the region of the measuring element. However, this is only limitedly attainable with the rounded boundary walls, since the desired small structural size of the device makes the inlet region of the measuring channel too short in the flow direction to allow optimal inflow without flow separations, especially when the flow is turbulent. Under certain flow conditions, flow separations can therefore occur especially in the inlet region of the measuring channel; they are intrinically unstable chronologically and affect the flow in the region of the measuring element in such a way as to increase the measuring signal noise and hence worsen the outcome of measurement.
ADVANTAGES OF THE INVENTION
The device of the invention has the advantage over the prior art that the device has markedly reduced measuring signal noise, thus enabling an improvement in the outcome of measurement, compared with the prior art.
By the provisions recited herein, advantageous further features of and improvements to the device as defined hereinafter are possible.
BRIEF DESCRIPTION OF THE DRAWINGS
One exemplary embodiment of the invention is shown in simplified form in the drawings and described in further detail in the ensuing description. FIG. 1, partly in section, shows a side view of a device embodied according to the invention; FIG. 2 shows an enlarged detail of FIG. 1; and FIG. 3 is a modification of FIGS. 1 and 2 which includes a trip wire.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT
FIG. 1, partly in section, shows a side view of a device 1 that is used to measure the mass of a flowing medium, in particular the aspirated air mass of internal combustion engines. The device 1 has preferably a slender blocklike shape extending radially longitudinally in the direction o
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Hecht Hans
Konzelmann Uwe
Lehenberger Stefan
Rilling Heinz
Artis Jewel V.
Dombroske George M.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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