Title of Invention

A DEVICE FOR DETERMINING AT LEAST ONE PARAMETER OF A MEDIUM FLOWING IN THE LINE

Abstract

A measuring element in a device for determining at least one parameter of a medium flowing in the line, according to the prior art, is not sufficiently protected against extraneous particles, such as, for example, solid particles. A device (1) according to the invention has a bypass duct (11) with a partition (27) which shields off a measuring element (30) or, by virtue of a special arrangement of an inner wall surface (16), prevents extraneous particles from being capabe of flowing to the measuring element (30). (Figure 2a)

Full Text

The invention proceeds from a device for determining at least one parameter of a medium flowing in the line, in particular of the intake air mass of an internal combustion engine. DE 41 06 842 Al discloses a hot-wire sensor for the measurement of a gas volume flow, said hot-wire sensor being arranged in a bypass duct in which there is, downstream of the orifice of the bypass duct, a wall surface running parallel to the orifice of the bypass duct. However, the sensor is not arranged in a shaded-off region of the bypass duct, and it is therefore not protected against contamination. EP 803 712 A2 discloses an airflow meter which has a separating point or a partition in the bypass duct. Moreover, in the bypass duct, there is a wall which is parallel to the inlet orifice of the bypass duct and also completely covers this orifice. However, the sensor is not protected against inflowing liquids. DE 198 15 654 Al discloses a measuring device for measuring the mass of a medium flowing in the line, in which measuring device there is in the bypass duct a separating point or a partition which is intended to protect the measuring element against solid particles and other impurities. However, because of reflections of the solid particles which impinge onto an inner wall in the bypass duct, these solid particles are reflected into the measuring duct and may impinge onto the measuring element there. No indication is given that, by virtue of the law of reflection, the reflections of solid particles can be influenced by a modification of the inner wall A publication discloses a bypass geometry in which there is, in the bypass duct, a partition extending parallel in the direction of flow, and there is a wall surface which runs parallel to the inlet orifice of the bypass duct. The wall surface lies downstream of the measuring element. The measuring element is in this case protected from the main flow by the partition and a lower-lying inlet orifice. The different run of the main duct and the measuring duct leads to increased signal noise. In the case of backflows, liquid, particles and oil may pass directly into the measuring duct and may contaminate or destroy the measuring element. Advantages of the invention By contrast, the advantage of the device according to the invention, as described herein, is that the at least one measuring element is protected against action by liquids arid particles in a simple way. Advantageous developments and improvements of the device as described herein are possible as a result of the measures described herein. It is advantageous if the inlet orifice of the bypass duct has a breakaway edge for liquids, because a liquid wall film can consequently no longer form in the bypass duct in the region of the inlet orifice and possibly reach the measuring element. The outlet orifice of the bypass duct may advantageously be oriented laterally, downward or in the direction of flow. The partition advantageously has at least one U-shaped portion, in order thereby to protect the sensor appropriately both in the case of forward flow and in the case of back flow. Drawing Exemplary embodiments of the invention are illustrated in simplified form in the drawing and are explained in more detail in the following description. In the accompanying drawing: Figure 1 shows a device for determining at least one parameter of a flowing medium in the installed state, figures 2a to d show a bypass duct in a measuring housing of the device according to the invention. Description of the exemplary embodiment Figure 1 shows diagrammatically how a device 1 is installed in a line 2 in which the medium to be measured flows. The device 1 for determining at least one parameter consists of a measuring housing 6, identified by a lower rectangle depicted by dashes and dots, and of a carrier part 7, identified by an upper rectangle depicted by dashes and dots, in which, for example, evaluation electronics are accommodated. In this exemplary embodiment of the device 1, a measuring element 30 (fig. 2) is used, which, for example, determines the volume flow of the flowing medium. Further parameters which can be measured are, for example, the pressure, temperature and concentration of a medium constituent or a flow velocity, which are determined by means of suitable sensors. The measuring housing 6 and the carrier part 7 have, for example, a common longitudinal axis 8 which runs in the installation direction and which, for example, may also be the center axis. The device 1 is introduced, for example in plug-in manner, into a wall 5 of the line 2. The wall 5 delimits a flow cross section of the line 2, in the center of which flow cross section a center axis 4 extends parallel to the wall 5 in the direction of the flowing medium. The direction of the flowing medium, designated below as the main flow direction, is identified by corresponding arrows 3 and runs from left to right there. Figure 2a shows the measuring housing 6 with the bypass duct 11. The bypass duct 11 has an inlet orifice 13, through which the medium flows into the bypass duct 11. Downstream of the inlet orifice 13 and upstream of the measuring element 30, there is an inner wall surface 16 which runs approximately parallel to the inlet orifice 13 and onto which particles, such as solid particles and liquid particles, entering in the main flow direction 3 impinge frontally, theit is to say perpendicularly. A projection of the inlet orifice 13 is reproduced in full on the inner wall surface 16. The inlet orifice 13 is delimited at the top by a breakaway edge 18, so that a liquid wall film which may reach the measuring element 30 does not form there on the bypass duct wall. Downstream of the inlet orifice 13, an inlet duct 21 commences as a portion of the bypass duct 11. Thereafter, the bypass duct 11 executes, for example, a bend of about 90 degrees toward the carrier part 7, then runs approximately parallel to the* flow direction 3 in a middle part 20 and then executes, for example, a bend of 90 degrees downward, that is to say away from the carrier part 7, to form what may be; referred to as an outlet duct 23, in order then to leave the measuring housing 6 again through an outlet crifice 25. The bypass duct 11 therefore has, for example, at least one U-shaped portion. The outlet orifice 25 may be present laterally of the measuring housing 6, or is designed in such a way that the medium leaves the bypass duct 11 again, downward in the flow direction 3 or perpendicularly to the flow dire-*--— ** The measuring element 30 is arranged in the middle part 20. The measuring element 30 projects partially into the carrier part 7, Below the measuring- element 30 and the carrier part 7, there is, in the middle part 20, a partition 27 which runs perpendicularly to the drawing plane and has, for example, a U-shape matched to the run of the bypass duct 11, The partition 27 commences upstream at a separating point 33 which lies in a shaded-off region 35 - The shaded-off region 35 is that part of the bypass duct 11 which is not covered by a projection of the inlet orifice 13 perpendicular to the flow direction 3, that is to say particles entering the bypass duct 11 parallel to the flow direction 3 first have to be deflected in order to entei: the shaded-off region 35. The partition 27 extending completely or almost completely from one wall side to the other wall side of the bypass duct 11 divides the bypass duct 11 into two ducts, a measuring duct 40 having the measuring element 3 0 and the detour duct 42 lying at a geodetic height below the latter. The measuring duct 40 comprises, for example, parts of the inlet duct 21 and outlet duct 23. Downstream of the measuring element 30, the measuring duct 40 and the detour duct 42 are combined again. This may also take place directly upstream of the outlet orifice 25. An axial arrangement of the inner wall surface 16 lies, in the flow direction 3, between the separating point 33, the upstream start of the partition 27 and a downstream end 34 of the partition 27. When the flowing medium in the line 2 contains liquid particles and these flow into the bypass duct 11, a liquid wall film, which may travel in the direction of the measuring element 30, does not form on account of the breakaway edge 18. Downstream of the inlet orifice 13, the liquid par^^i^R -imninae onto the inner wall surface 16 and there form a wall film which moves through the detour duct 42 in the direction of the outlet orifice 25. Solid particles, too, do not pass into the measuring duct 40 because of their inertia. Solid particles, such as, for example, dust particles, impinge onto the inner wall surface 16 frontally, that is say perpendicularly, and are reflected back there and leave the bypass duct 11 again through the inlet orifice 13 or are entrained into the detour duct 42 by the flow. The detour duct 42 is designed in such a way and has a width such that, even when there is a pronounced introduction of liquid, no capillary effect occurs. The effects described afford the advantage that, downstream of the inlet orifice 13, a part of the medium which is free of liquid droplets and of solid particles is deflected in the upward direction to the carrier part 7 and flows via the measuring duct 40 and the measuring element 30, while, as a result of the separation by means of the partition 27, that part of the medium which is laden with liquid and with solid particles is led past said measuring duct and measuring element via the detour duct 42 lying below them. Figure 2b shows a further possibility for the configuration of the bypass duct 11, which corresponds essentially approximately to a U-shape in the region of the middle part 20. As compared with fig. 2a, the outlet orifice 25 lies below the inlet orifice 13, that is to say the distance of the outlet orifice 25 from the measuring element 30 in the direction of the center axis 4 is greater than that of the inlet orifice 13. The outlet orifice 25 may also be opened downward, that is to say the flowing medium leaves the bypass duct 11 perpendicularly to the flow direction 3. The partition 27 extends, for example, only in the measuring duct 40 and is U-shaped. In figure 2c, in contrast to figure 2a, the outlet orifice 25 is arranged parallel to the inlet orifice 13, that is to say the flowing medium leaves the bypass duct 11 in the flow direction 3. The partition 27 extends in the measuring duct 40 as far as the outlet duct 23 and, for example, is S-shaped. In figure 2d, the outlet duct 23 also executes, starting from the end of the outlet duct 23 of figure 2b, another bend opposite to the flow direction 3, for example of 90°, so that, forming a further U-shape, it runs at least partially opposite to the flow direction 3. The outlet orifice 25 may be configured in such a way that the flowing medium leaves the bypass duct 11 perpendicularly (fig. 2d) or opposite to the flow direction 3. The possibilities for the configuration of the bypass duct 11 are selected according to requirements to be met by the device 1, such as, for example, pulsation behavior, backflows, etc. WE CLAIM : 1. A device for determining at least one parameter of a medium flowing in the line, in particular of the intake air mass of an internal combustion engine, with at least one measuring element around which the flowing medium flows, with a bypass duct which extends along a flow direction between an inlet orifice connected to the line and at least one outlet orifice issuing into the line downstream of the inlet orifice, the bypass duct having, between the inlet orifice and the measuring element, at least one separating point which divides the bypass duct into a measuring duct, in which the at least one measuring element is arranged, and into a detour duct, which detours the measuring element in the flow direction, characterized in that, downstream of the inlet orifice, there is, in the bypass duct (11), an inner wall surface (16) which runs parallel to the inlet orifice (13) and which completely covers a projection of the inlet orifice (13) in the flow direction (3) and in that the separating point (33), lying outside this projection, is formed by a partition (27), and in that the inner wall surface (16) is arranged between the separating point (33), the upstream start of the partition (27) and a downstream end (34) of the partition (27). 2. The device as claimed in claim 1, wherein the partition (27) has at least one U-shape. 3. The device as claimed in claim 1 or 2, wherein the partition (27) is matched to the run of the bypass duct (11). 4. The device as claimed in claim 1, wherein the inlet orifice (13) has a breakaway edge (18). 5. The device as claimed in claim 2 or 3, wherein the partition (27) defines a detour duct (42), in which the liquid flows, and in that no capillary effect occurs in the detour duct (42). 6. The device as claimed in claim 1, wherein the bypass duct (11) has at least one U-shaped portion.

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in-pct-2002-1171-che drawings-duplicate.pdf

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in-pct-2002-1171-che-correspondance others.pdf

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