Sensor arrangement for determining at least one parameter of a fluid medium flowing through a measuring channel

Abstract

Sensor arrangement (10) for determining at least one parameter of a fluid medium flowing through a measuring channel (28), in particular an intake air mass flow of an internal combustion engine, wherein the sensor arrangement (10) comprises a sensor housing (12), in particular a plug-in sensor inserted or insertable into a flow tube, and at least one sensor chip (42) arranged in the measuring channel (28) for determining the parameter of the fluid medium, wherein the sensor housing (12) comprises a housing body (14), a measuring channel cover (16) in which the measuring channel (28) is formed, an electronics compartment (18), an inlet (34) into the measuring channel (28) and at least one outlet (32) from the measuring channel (28), wherein the measuring channel (28) is separated at least in the region of the sensor chip (42) by the housing body (14), the measuring channel cover (16), a wall section (66) facing the electronics compartment and a wall section (68) facing away from the electronics compartment. is limitedwherein the measuring channel cover (16) has a stop surface (80) for bearing against the housing body (14), wherein the wall section (66) facing the electronics compartment is formed at an angle to the stop surface (80) of -10° to +20° and preferably of 0° to +10° such that the measuring channel (28) has a convergent course at least in the area of ​​a sensor carrier (40), characterized in that the wall section (66) facing the electronics compartment has at least one base section (100) and at least one drop section (102), wherein the drop section (102) has a lower wall height than the base section (100), wherein the drop section (102) is arranged in the area of ​​the sensor chip (42).

Description

State of the art

[0001] Numerous methods and devices for determining the flow properties of fluid media, i.e., liquids and / or gases, are known from the prior art. These flow properties can be any physically and / or chemically measurable properties that qualify or quantify the flow of the fluid medium. In particular, they can be flow velocity and / or mass flow rate and / or volume flow rate.

[0002] The invention is described below in particular with reference to so-called hot-film air mass meters, as described, for example, in Konrad Reif (ed.): Sensors in Motor Vehicles, 1st edition 2010, pages 146-148. Such hot-film air mass meters are generally based on a sensor chip, in particular a silicon sensor chip, with a sensor membrane as the measuring surface or sensor area, which is permeable to the flowing fluid medium. The sensor chip generally comprises at least one heating element and at least two temperature sensors, which are arranged, for example, on the measuring surface of the sensor chip. An asymmetry in the temperature profile detected by the temperature sensors, which is influenced by the flow of the fluid medium, allows conclusions to be drawn about the mass flow and / or volume flow of the fluid medium.Hot-film air mass meters are typically designed as plug-in sensors that can be permanently or interchangeably inserted into a flow pipe. This flow pipe could, for example, be the intake manifold of an internal combustion engine.

[0003] In this system, a partial flow of the medium passes through at least one main channel provided in the hot-film air mass meter. A bypass channel is formed between the inlet and outlet of the main channel. Specifically, the bypass channel is designed such that it has a curved section for deflecting the partial flow of the medium entering through the inlet of the main channel. This curved section then transitions into a section in which the sensor chip is located. This latter section constitutes the actual measuring channel in which the sensor chip is positioned. A flow guide is provided in the bypass channel to direct the flow and prevent the flow of the partial medium stream from separating from the channel walls of the measuring channel.Furthermore, the inlet area of ​​the main channel, in the region of its opening which faces the opposite direction of flow, is provided with inclined or curved surfaces designed in such a way that the medium flowing into the inlet area is deflected away from the part of the main channel leading to the sensor chip. This prevents liquid or solid particles contained in the medium from reaching the sensor chip and contaminating it due to their inertia.

[0004] In practice, such hot-film air mass meters must meet a multitude of requirements and boundary conditions. Besides the goal of reducing the overall pressure drop across the hot-film air mass meter through suitable flow-optimized designs, one of the main challenges is to further improve the signal quality and the robustness of such devices against contamination by oil and water droplets, as well as soot, dust, and other solid particles. This signal quality relates, for example, to the mass flow rate of the medium through the measuring channel leading to the sensor chip, and potentially to the reduction of signal drift and the improvement of the signal-to-noise ratio.Signal drift refers to the deviation, for example, of the medium's mass flow rate, in the sense of a change in the characteristic curve relationship between the actual mass flow rate and the signal determined during calibration in manufacturing. When determining the signal-to-noise ratio, the sensor signals output in rapid succession are considered, whereas characteristic curve or signal drift refers to a change in the mean value.

[0005] In typical hot-film air mass meters of the type described, a sensor carrier with a sensor chip attached to or embedded in it usually protrudes into the measuring channel. For example, the sensor chip can be glued into or onto the sensor carrier. The sensor carrier can form a single unit with a metal base plate, onto which electronics, a control and evaluation circuit in the form of a printed circuit board, may also be glued. Alternatively, the sensor carrier can be designed as an injection-molded plastic part of an electronic module. The sensor chip and the control and evaluation circuit can be connected, for example, by bonding. The resulting electronic module can then be glued into a sensor housing, and the entire plug-in sensor can be sealed with a cover.

[0006] Despite the improvements brought about by this sensor arrangement, there is still potential for improvement regarding signal acquisition accuracy.

[0007] For the hot-film air mass meter to deliver the most accurate air mass signal possible, a uniform flow to the sensor and through the measuring channel within it, and especially across the measuring surface of the sensor chip, is crucial. A gap exists between one end face of the sensor carrier and the wall of the measuring channel; its width is subject to manufacturing variations. In the area of ​​the sensor carrier, the fluid flowing in the measuring channel splits into three partial mass flows. A first partial mass flow flows over the sensor carrier and the sensor chip, a second partial mass flow flows under the sensor carrier, and a third partial mass flow flows through the gap. After the flow has passed around the sensor carrier, an unstable wake forms with fluctuating flow velocities and pressures.This leads to fluctuating flow rates upstream, especially in the area of ​​the sensor chip, which result in fluctuations in the measurement signal, particularly with oscillation modes typical for the dimensions of the sensor carrier and the flow velocity.

[0008] From DE 197 41 031 A1 a generic sensor arrangement for determining at least one parameter of a fluid medium flowing through a measuring channel is known.

[0009] Another sensor arrangement for determining at least one parameter of a fluid medium flowing through a measuring channel is known from DE 199 27 818 A1. Disclosure of the invention

[0010] Therefore, a sensor arrangement for determining at least one parameter of a fluid medium flowing through a measuring channel is proposed, which can at least largely avoid the disadvantages of known methods and strategies and in which, in particular, the characteristic curve reproducibility and the adjustability are improved, as well as the signal noise and the inflow sensitivity are reduced.

[0011] The sensor arrangement for determining at least one parameter of a fluid medium flowing through a measuring channel, in particular an intake air mass flow rate of an internal combustion engine, comprises a sensor housing, in particular a plug-in sensor inserted or insertable into a flow tube, and at least one sensor chip arranged in the measuring channel for determining the parameter of the fluid medium. The sensor housing has a housing body, a measuring channel cover in which the measuring channel is formed, an electronics compartment, an inlet to the measuring channel, and at least one outlet from the measuring channel. The measuring channel is bounded, at least in the region of the sensor chip, by the housing body, the measuring channel cover, a wall section facing the electronics compartment, and a wall section facing away from the electronics compartment. The measuring channel cover has a stop surface for bearing against the housing body.The wall section facing the electronics compartment is formed at an angle to the stop surface of -10° to +20° and preferably from 0° to +10° such that the measuring channel has a convergent profile, at least in the area of ​​the sensor carrier. According to the invention, the wall section facing the electronics compartment has at least a base section and at least one drop section, wherein the drop section has a lower wall height than the base section and wherein the drop section is arranged in the area of ​​the sensor chip.

[0012] The sensor chip can be arranged on a sensor carrier that projects from the electronics compartment into the measuring channel. The contact surface can be located adjacent to the sensor carrier. The wall section facing the electronics compartment can have a downstream end when viewed in a main flow direction of the fluid medium in the measuring channel. The sensor chip can be arranged on a sensor carrier that projects from the electronics compartment into the measuring channel. A measuring channel wall section can be arranged downstream in the main flow direction. The downstream end of the wall section facing the electronics compartment can be arranged such that a discontinuous transition, in particular by means of a recessed step, is formed between the wall section facing the electronics compartment and the measuring channel wall section. The wall section facing the electronics compartment can have a downstream end when viewed in a main flow direction of the fluid medium in the measuring channel.The sensor chip can be arranged on a sensor carrier that projects from the electronics compartment into the measuring channel. Downstream in the main flow direction, a measuring channel wall section can be arranged, the downstream end of the wall section facing the electronics compartment transitioning into the measuring channel wall section at a radius, in particular tangentially. The sensor chip can have a sensor membrane over which the fluid medium flows. The wall section facing the electronics compartment can be adjacent to or spaced apart from a side edge of the sensor membrane facing the electronics compartment. The sensor chip can be arranged on a sensor carrier that projects from the electronics compartment into the measuring channel. The wall section facing the electronics compartment can have a surface facing the sensor carrier. The surface facing the sensor carrier can have at least one recess for receiving adhesive.The surface facing the sensor carrier can have several recesses for receiving adhesive, with at least one of the recesses being channel-shaped. The surface facing the sensor carrier can have several recesses for receiving adhesive, with at least one of the recesses having a shallower depth than the other recesses. The wall section facing the electronics compartment can have a continuous profile, at least in the area of ​​the sensor carrier.

[0013] Within the scope of the present invention, the main flow direction is understood to be the local flow direction of the fluid medium at the location of the sensor or sensor arrangement, whereby, for example, local irregularities such as turbulence can be disregarded. In particular, the main flow direction can thus be understood as the locally averaged transport direction of the flowing fluid medium. The main flow direction can therefore refer either to the flow direction at the location of the sensor arrangement itself or to the flow direction in the channel within the sensor housing, such as at the location of the sensor carrier or the sensor chip, whereby these two main flow directions may differ. Within the scope of the present invention, it is therefore always specified to which location the main flow direction refers.Unless otherwise specified, the main flow direction refers to the location of the sensor arrangement.

[0014] In the context of the present invention, a downstream arrangement is understood to mean the arrangement of a component at a point which the fluid medium reaches later in time than a reference point when flowing in the main flow direction.

[0015] Similarly, within the scope of the present invention, an upstream arrangement of a component is understood to mean an arrangement of the component at a location which the fluid medium flowing in the main flow direction reaches earlier in time than a reference point.

[0016] Within the scope of the present invention, the sensor carrier can be configured wholly or partially as a circuit carrier, in particular as a printed circuit board, or can be part of a circuit carrier, in particular a printed circuit board. For example, the circuit carrier, in particular the printed circuit board, can have a projection which forms the sensor carrier and which projects into the channel, for example the measuring channel of a hot-film air mass meter. The remaining part of the circuit carrier, in particular the printed circuit board, can be housed, for example, in an electronics compartment, in a housing of the sensor arrangement, or in a plug-in probe of the sensor arrangement.

[0017] In the context of the present invention, a printed circuit board (PCB) is generally understood to be a substantially plate-shaped element that can also be used as a carrier for electronic structures, such as conductive traces, terminal contacts, or the like, and preferably also has one or more such structures. In principle, at least slight deviations from the plate shape are also conceivable and are included in the definition. The PCB can, for example, be made of a plastic material and / or a ceramic material, such as an epoxy resin, in particular a fiber-reinforced epoxy resin. In particular, the PCB can, for example, be designed as a printed circuit board (PCB) with conductive traces, in particular printed conductive traces.

[0018] In this way, the electronics module of the sensor assembly can be greatly simplified, eliminating the need for a base plate and a separate sensor carrier, for example. The base plate and sensor carrier can be replaced by a single circuit board, which can also house, in whole or in part, the control and evaluation circuitry for the sensor assembly. This control and evaluation circuitry is used to control the at least one sensor chip and / or to evaluate the signals generated by this sensor chip. By combining these elements, the manufacturing effort for the sensor assembly can be significantly reduced, and the space required for the electronics module can be greatly minimized.

[0019] The sensor arrangement can, in particular, comprise at least one housing, wherein the channel is formed within the housing. For example, the channel can include a main channel and a bypass or measuring channel, wherein the sensor carrier and the sensor chip can, for example, be arranged in the bypass or measuring channel. Furthermore, the housing can have an electronics compartment separate from the bypass channel, wherein the electronic module or the printed circuit board is essentially housed in the electronics compartment. The sensor carrier can then be designed as an extension of the printed circuit board projecting into the channel. This arrangement is technically comparatively simple to implement, in contrast to the complex electronic modules known from the prior art.

[0020] Particularly when a printed circuit board is used as a sensor substrate, but also in other cases and / or when using other media as sensor substrates, the sensor substrate can be designed, at least partially, as a multilayer sensor substrate. Thus, the sensor substrate can be designed using a so-called multilayer technique and have two or more interconnected substrate layers. For example, these substrate layers can be made of a metal, a plastic, a ceramic material, or a composite material and be bonded together using bonding techniques such as adhesive bonding.

[0021] In this case, where a multilayer technique is used with several sensor layers of the sensor carrier, the leading edge can be at least partially stepped by varying the dimensions of the carrier layers, oriented against the main flow direction of the fluid medium. In this way, the profiles can be approximated, at least in a stepped manner. For example, rectangular profiles, or—approximately—round, rounded, or wedge-shaped profiles (at least approximately rounded, rounded, or wedge-shaped profiles in a cross-sectional plane perpendicular to the plane of extension of the sensor carrier, can be formed in this way. The sensor chip can be arranged on or in the sensor carrier such that it is oriented perpendicular to the local main flow direction.For example, the sensor chip can be rectangular in shape, with one side of this rectangle arranged perpendicular or substantially perpendicular, for example with an orientation that deviates from the vertical by no more than 10 degrees, to the local main flow direction.

[0022] The sensor chip can be electrically contacted via at least one electrical connection. For example, the sensor carrier, in particular a printed circuit board forming the sensor carrier or an extension of this printed circuit board, can have one or more conductive traces and / or contact pads which are connected to corresponding contacts on the sensor chip, for example by a bonding process. In this case, the electrical connection can be protected by at least one cover and separated from the fluid medium. This cover can be designed, in particular, as a so-called glob top, for example as a drop of plastic and / or adhesive, which covers the electrical connection, for example the bond wires. In this way, influences on the flow caused by the electrical connection can also be reduced, since the glob top has a smooth surface.

[0023] Furthermore, the sensor chip can have at least one sensor area. This sensor area can be, for example, a sensor surface made of a porous ceramic material and / or, in particular, a sensor membrane. The sensor membrane, as the measuring surface or sensor area, can be permeable to the flowing fluid medium. The sensor chip comprises, for example, at least one heating element and at least two temperature sensors, which are arranged, for example, on the measuring surface of the sensor chip, with one temperature sensor located upstream of the heating element and the other temperature sensor located downstream of the heating element. An asymmetry in the temperature profile detected by the temperature sensors, which is influenced by the flow of the fluid medium, can be used to infer the mass flow rate and / or volume flow rate of the fluid medium.

[0024] Furthermore, the sensor assembly can include a temperature sensor protruding into the duct. For example, the temperature sensor can be designed as an electrical resistor, such as an NTC (negative temperature coefficient) thermistor, which is used to measure the temperature of the intake air. The temperature sensor can, for example, be part of a control circuit that ensures that changes in the intake air temperature do not affect the measurement accuracy of the sensor assembly.

[0025] Within the scope of the present invention, the specification of the angles for the wall section facing the electronics room is to be understood as an inclined arrangement of this section to the stop surface, wherein a negative sign indicates that this inclination has a course rotated counterclockwise with respect to the stop surface, and a positive sign indicates a course rotated clockwise with respect to the stop surface.

[0026] In the context of the present invention, a continuous course of the wall section facing the electronics room is understood to mean a uniform or steady, uninterrupted course without abrupt changes in direction and, in particular, without kinks. When the course is described by a mathematical function, this course corresponds to a differentiable function.

[0027] A fundamental concept of the present invention is a modified routing of the bypass or measurement channel wall in the area of ​​the sensor carrier on the side of the sensor chip with the micromechanical sensor membrane. The contour of the bypass or measurement channel wall facing the electronics compartment, according to the invention, runs without kinks, particularly in the area of ​​the sensor chip, closer to the sensor chip, and at an angle that generates a convergent channel profile directly above the sensor chip. A larger useful signal with simultaneously lower interference, reduced characteristic curve tolerances, improved tunability, and lower signal noise can be achieved by shifting a pulse-rich wall beam towards the micromechanical sensor membrane.

[0028] Another fundamental concept is a modified design of the grooves, channels, and reservoirs in the bypass or measuring channel cover to ensure reliable adhesive retention. The inventive design prevents the adhesive from flowing onto the sensor chip. Brief description of the drawings

[0029] Further optional details and features of the invention will become apparent from the following description of preferred embodiments, which are shown schematically in the figures.

[0030] They show: Fig. 1. A perspective view of a sensor arrangement, Fig. 2 an enlarged view of an electronic module of the sensor assembly, Fig. 3 a top view of the measuring channel cover with the measuring channel and the sensor carrier, Fig. 4 a cross-sectional view of the measuring channel cover, Fig. 5 a perspective cross-sectional view of the measuring channel cover, Fig. 6 a top view of the channel structure in the measuring channel cover, Fig. 7 a distribution of flow velocities in the measuring channel, Fig. 8 a section of a measuring channel cover according to a first embodiment of the invention, Fig. 9 a perspective view of a section of the measuring channel cover, Fig. 10 another perspective view of a section of the measuring channel cover, Fig. 11 a sectional view of the measuring channel cover, Fig. 12 a perspective view of a section of a measuring channel cover according to a second embodiment of the present invention, Fig. 13 a perspective view of a section of a measuring channel cover according to a third embodiment of the invention, Fig. 14 a perspective view of a section of a measuring channel cover according to a fourth embodiment of the invention, Fig. 15 a perspective view of a section of a measuring channel cover according to a fifth embodiment of the invention, Fig. 16 a perspective view of a section of a measuring channel cover according to a sixth embodiment of the invention, Fig. 17 a perspective view of a section of a measuring channel cover according to a seventh embodiment of the invention and Fig. 18 a perspective view of a section of a measuring channel cover according to an eighth embodiment of the invention. Detailed description of the embodiments of the invention

[0031] Fig. Figure 1 shows a perspective view of a sensor arrangement 10 for determining a parameter of a fluid medium. The sensor arrangement 10 is designed as a hot-film air mass meter and comprises a sensor housing 12 designed as a plug-in sensor, which can be inserted, for example, into a flow pipe, in particular an intake manifold of an internal combustion engine. The sensor housing 12 has a housing body 14, a measuring channel cover 16, an electronics compartment 18, and an electronics compartment cover 20 for closing the electronics compartment 18. A channel structure 22 is formed in the measuring channel cover 16. The channel structure 22 has a main channel 24, which terminates in a main flow outlet (not shown) on the underside 26, as shown in Figure 1. Fig. The sensor housing 12 has a main channel 1, as well as a bypass or measuring channel 28 branching off from the main channel 24, which opens into a bypass or measuring channel outlet 32 ​​located on an end face 30 of the sensor housing 12. A representative quantity of the fluid medium can flow through the channel structure 22 via an inlet opening 34, which, in the installed state, points against a main flow direction 36 of the fluid medium at the location of the sensor housing 12.

[0032] Fig. Figure 2 shows an enlarged view of an electronic module 38 of the sensor arrangement 10. In the installed state of the electronic module 38, a sensor carrier 40 in the form of a wing projects into the measuring channel 28. A sensor chip 42 is embedded in this sensor carrier 40 such that a micromechanical sensor membrane 44, designed as the sensor area of ​​the sensor chip 42, is permeable to the fluid medium. The sensor carrier 42 and the sensor chip 42 are components of the electronic module 38. The electronic module 38 further comprises a curved base plate 46 and a printed circuit board 48, for example glued to it, with a control and evaluation circuit 50. The sensor chip 42 is electrically connected to the control and evaluation circuit 50 via electrical connections 52, which are implemented here as wire bonds.The resulting electronic module 38 is inserted into the electronics compartment 18 within the housing body 14 of the sensor housing 12, for example by gluing. The sensor carrier 40 projects into the channel structure 22. The electronics compartment 18 is then closed by the electronics compartment cover 20.

[0033] Fig. Figure 3 shows a top view of the channel structure 22 in the measuring channel cover 16. A centrifugal deflection device 54 is arranged in the measuring channel cover 16. The measuring channel cover 16 is further designed such that a measuring channel ramp 56 is formed in the measuring channel 28. Furthermore, the following is made of Fig. 3. The arrangement of the sensor carrier 40 can be seen. In its inserted state, the sensor carrier 40 protrudes into the measuring channel 28. Viewing the Fig. Figure 3 shows the sensor carrier 40 with its rear or underside 58. The rear or underside 58 is the side of the sensor carrier 40 opposite the sensor membrane 44. The sensor carrier 40 further has a leading edge 62, which may be rounded and which points against the main flow direction 60 of the fluid medium in the measuring channel 28, and a trailing edge 64 downstream of the leading edge 62. The measuring channel ramp 56 extends in the area between the centrifugal deflection 54 and the trailing edge 64 of the sensor carrier 40. The measuring channel 28 is bounded, at least in the area of ​​the sensor chip 42, by the housing body 14, the measuring channel cover 16, a wall section 66 facing the electronics compartment, and a wall section 68 facing away from the electronics compartment.

[0034] Fig. Figure 4 shows a cross-sectional view of the measuring channel cover 16, where the section also extends through the sensor carrier 40. From the representation of the Fig. Figure 4 shows that the flow cross-section in the measuring channel 28 decreases with increasing length due to the measuring channel ramp 56. This, together with a reduction in cross-section caused by the sensor carrier 40, leads to an acceleration of the flow and a reduction in the fluctuation component of the flowing fluid medium. A flattening or near-parallel shape of the measuring channel ramp 56 is clearly visible in the region of the trailing edge 64 of the sensor carrier 40.

[0035] Fig. Figure 5 shows a perspective cross-sectional view of the measuring channel cover 16 in the area of ​​the sensor carrier 40. A gap 70 can be seen between the side of the sensor carrier 40 in which the sensor chip 42 with the sensor membrane 44 is embedded and the measuring channel ramp 56. A partial flow of the fluid medium flowing within the measuring channel 28 flows through this gap 70. Furthermore, it is evident from Fig. 5 to recognize that the guidance and conditioning of the flowing fluid medium are significantly influenced by the measuring channel ramp 56 and the sensor carrier 40.

[0036] Fig. Figure 6 shows a top view of the channel structure 22 in the measuring channel cover 16 with the position of the sensor carrier 40 and the sensor chip 42 with the sensor membrane 44 indicated. From the representation of the Fig. Figure 6 clearly shows that, in the conventional measuring channel cover 16, the wall section 66 facing the electronics compartment and the opposite wall section 68 facing away from the electronics compartment run parallel downstream of the centrifugal deflection 54 up to the rear edge 64 of the sensor carrier 40. From the illustration of the Fig. Figure 6 further shows that the wall section 66 facing the electronics compartment has a kink 72 in the area of ​​the trailing edge 64 of the sensor carrier 40. The kink 72 contributes, among other things, to influencing the flow and velocity distribution of the fluid medium within the measuring channel 28, as described in more detail below.

[0037] Fig. Figure 7 shows a distribution of the flow velocities of the fluid medium in the channel structure 22 relative to each other. Accordingly, in Fig. 7. No absolute flow velocities are given, but only their exemplary ratios to each other. From the representation of the Fig. A pulse-rich wall beam 74 can be identified as a high-velocity region. However, this beam 74 does not lie above the micromechanical sensor membrane 44, but extends along the wall section 66 facing the electronics compartment. This results in a loss of signal amplitude. Furthermore, it is evident from Fig. A clearly inhomogeneous velocity field 76 can be observed in the flow space directly above the micromechanical sensor membrane 44. The shape of the velocity field 76 above the sensor membrane 44, i.e., the relative and absolute values ​​of the velocity field 76, fluctuate, for example, with the mass flow rate of the fluid medium. Different velocity profiles even with small changes, such as in the mass flow rate, indicate a relatively unstable flow topology. This instability in the near field of the micromechanical sensor membrane 44 leads to further deviations in the measurement signal when other flow parameters, such as the turbulence intensity or the air temperature, are changed. Geometric boundary conditions, such as tolerances in the installation of the sensor housing 12 in the flow tube, can also lead to signal changes due to the described inhomogeneous, unstable velocity field 76 above the micromechanical sensor membrane 44.In particular, the micromechanical sensor membrane 44 is located in an area of ​​relatively low flow velocities and strong gradients of flow velocities.

[0038] All these undesirable phenomena are counteracted by the embodiments of the sensor arrangement 10 according to the invention described below. In particular, the differences from the previously described conventional sensor arrangement 10 are described. For example, with the sensor arrangement 10 according to the invention, better values ​​with regard to signal noise, characteristic curve reproducibility, and adjustability are likely due to a displacement of the pulse-rich wall beam 74 across the sensor membrane 44. For this reason, possible embodiments that effect such a displacement are described below.

[0039] A first embodiment of the sensor arrangement 10 according to the invention is described in Fig. 8 shown. Fig. Figure 8 shows a section of a top view of the channel structure 22 in the measuring channel cover 16. From the representation of the Fig. Figure 8 shows that the measuring channel cover 16 has a stop surface 80. The stop surface 80 is located adjacent to the area where the sensor carrier 40 projects into the measuring channel 28. The stop surface 80 serves to abut the measuring channel cover 16 against the housing body 14 during the assembly of the sensor arrangement 10. For assembly, the sensor carrier 40 is guided through an opening 82 or recess in the wall section 66 facing the electronics compartment, so that the sensor carrier 40 projects into the measuring channel 28. The stop surface 80 is located downstream of the opening 82 with respect to the main flow direction 66 of the fluid medium within the measuring channel 28.According to the invention, it is proposed that the wall section 66 facing the electronics compartment is formed at an angle 84 to the stop surface 80 of -10° to +10°, and preferably of 0° to +10°, such that the measuring channel 28 has a convergent path, at least in the region of the sensor carrier 40. A fundamental concept of the invention is a modified guidance of the wall section 66 facing the electronics compartment in the region of the sensor carrier 40 on the side of the sensor chip 42 with the micromechanical sensor membrane 44. The contour of the wall section 66 facing the electronics compartment according to the invention runs continuously and without kinks in the region of the trailing edge 64 of the sensor chip 42, generally closer to the sensor chip 42, and in the region of the sensor chip 42 at the angle 84, which generates a convergent path of the measuring channel 28 directly above the sensor chip 42.A larger useful signal with simultaneously lower interference, both lower characteristic curve tolerances and improved adjustability and lower signal noise, can thus be achieved by shifting the pulse-rich wall beam 74 towards the micromechanical sensor membrane 44. In the case of... Fig. In the embodiment of the measuring channel cover 16 shown in Figure 8, the wall section 66 facing the electronics compartment is formed at an angle 84 of 4.6° to the stop surface 80. This brings the wall section 66 facing the electronics compartment closer to the micromechanical sensor membrane 44.

[0040] Fig. Figure 9 shows a perspective view of a section of the measuring channel cover 16. Fig. Figure 9 shows further optional aspects of the present invention, which are described in more detail below. For bonding the measuring channel cover 16, the housing body 14, the electronics module cover 20, and the sensor carrier 40, adhesive is metered into a channel 86 formed in the measuring channel cover 16. The channel 86 is formed, in particular, in that area of ​​the wall section 66 facing the electronics compartment in which the opening 82 is formed. The channel 86 extends along an edge 88 of the measuring channel cover 16 such that the channel 86 can be covered, at least partially, by the sensor carrier 40 in order to bond the measuring channel cover 16 to the sensor carrier 40.

[0041] The wall section 66 facing the electronics compartment also has a surface 90 facing the sensor carrier 40. The surface 90 is preferably arranged parallel to the sensor carrier 40 and the base plate 46 of the electronics module 38. This configuration is neutral with respect to pulsation and water contamination, i.e., it does not generate any additional errors compared to the prior art. Optionally, at least one recess 92 for receiving adhesive can be formed in the surface 90. For example, a first recess 94 is channel-shaped and serves as a barrier channel, as described in more detail below. Furthermore, for example, a second recess 96 is configured as a reservoir for receiving adhesive in the surface 90 and has an approximately triangular shape in a top view, the apex of which, connecting the longest sides, points approximately opposite to the main flow direction 60 of the fluid medium in the measuring channel 28.Downstream of the opening 82 with respect to the main flow direction 60 of the fluid medium in the measuring channel 28, a measuring channel wall section 98 is arranged, which has the stop surface 80. The second recess 96 adjoins this measuring channel wall section 98. The second recess 96 has a shallower depth than the first recess 94.

[0042] The recesses 94 and 96 can collect excess adhesive from the channel 86. This prevents excess adhesive, potentially facilitated by capillary action from the wall section 66 facing the electronics compartment (located closer to the sensor membrane 44), from flowing into the flow-relevant area over the sensor chip 42. Such quantities of adhesive on the sensor chip 42 would alter the flow field in the immediate vicinity of the micromechanical sensor membrane 44 and the heat balance of the thermal measuring principle, leading, among other things, to deviations in the characteristic curves. Due to the statistical nature of such adhesive contamination, these deviations cannot be compensated for during series production, which would result in a widening of specified tolerances.

[0043] Fig. Figure 10 shows another perspective view of a section of the measuring channel cover 16. Fig. Figure 10 shows further optional aspects of the present invention, which are described in more detail below. Fig. Figure 10 clearly shows that the wall section 66 facing the electronics compartment has at least one base section 100 and at least one drop section 102. The base section 102 has surface 90. The drop section 102 has a lower wall height than the base section 100. The drop section 102 is located in the area of ​​the sensor chip 42. In other words, the drop section 102 extends parallel to an edge 104 facing the electronics compartment 18 ( Fig. 6) of the sensor chip 42. This recessed section 102 provides further protection against the contamination of the sensor chip 42 by excess adhesive as described above. The recessed section 102 has a wall height of 0 mm to 3.5 mm, for example 2.0 mm.

[0044] Fig. Figure 11 shows a sectional view of the measuring channel cover 16, the section extending along one dimension of the sensor carrier 40 and perpendicular to one dimension of the measuring channel 28. The section also passes through the sensor carrier 40. Due to the increased clear width between the recessed section 102 and the sensor chip 42, two gaps 106 are formed between the measuring channel cover 16 and the side of the sensor carrier 40 in which the sensor chip 42 is embedded, on the one hand, and between the housing body 14 and the rear or underside 58 of the sensor carrier 40, on the other. This is intended to prevent the adhesive from flowing onto the sensor chip 42 due to capillary action.

[0045] Fig. Figure 12 shows a perspective view of a section of a measuring channel cover 16 according to a second embodiment of the present invention. Only the differences from the previous embodiment are described below, and identical components are designated with the same reference numerals. The features described above as optional aspects may also be implemented in the second embodiment, even if this is not explicitly shown.

[0046] The wall section 66 facing the electronics compartment has a downstream end 108 with respect to the main flow direction 60 of the fluid medium in the measuring channel 28. The downstream end 108 of the wall section 66 facing the electronics compartment is arranged such that a discontinuous transition 110 is formed between the wall section 66 facing the electronics compartment and the measuring channel wall section 98. The discontinuous transition 110 is formed, for example, by means of a recessed step 112 between the wall section 66 facing the electronics compartment and the measuring channel wall section 104. The height of the downstream end 108 of the wall section 66 facing the electronics room, downstream of the base section 98 described above in the form of the step 112 above the base level of the measuring channel 28, can vary from flush, i.e. 0 mm, to the level of the sensor carrier 40, depending on the positioning of the sensor carrier 40 and the height of the measuring channel 28, up to approximately3 mm above the base level of measuring channel 28.

[0047] Fig. Figure 13 shows a perspective view of a section of a measuring channel cover 16 according to a third embodiment of the present invention. Only the differences from the preceding embodiments are described below, and identical components are designated with the same reference numerals. The features described above as optional aspects may also be implemented in the third embodiment, even if this is not explicitly shown.

[0048] The outlet of the wall section 66 facing the electronics room, i.e., the downstream end 108, can transition into the measuring channel wall section 98 in a first radius 114. For example, the first radius 114 can be designed as a transition radius between the downstream end 108 and the measuring channel wall section 98, so that a transition 116 between the downstream end 108 and the measuring channel wall section 98 is realized in a blended manner. In other words, the transition of the wall section 66 facing the electronics room into the measuring channel wall section 98 is achieved by means of a transition radius to the contour of the downstream measuring channel wall section 98. A filling, i.e., a displacement of the measuring channel wall section 98 above the base height of the downstream end 108 of the wall section 66 facing the electronics room, or, in other words, a "forward" of the measuring channel wall section 98, is also conceivable.This would create a continuous wall of the measuring channel 28 over its entire height, for example also with a radial transition. Optionally, and with or without the recesses 92, 94, 96 described above, the surface 90 can have slight inclinations in the range of a few degrees.

[0049] Fig. Figure 14 shows a perspective view of a section of a measuring channel cover 16 according to a fourth embodiment of the present invention. Only the differences from the preceding embodiments are described below, and identical components are designated with the same reference numerals. The features described above as optional aspects may also be implemented in the fourth embodiment, even if this is not explicitly shown.

[0050] As from Fig. As can be seen from Figure 14, the downstream end 108 of the wall section 66 facing the electronics compartment can transition tangentially into the measuring channel wall section 98. In other words, the first radius 114 is identical to a radius of the measuring channel wall section 98. Optionally, the measuring channel wall section 98 can have an additional or second radius 118, which, with respect to the main flow direction 60 of the fluid medium within the measuring channel 28, is located upstream of the first radius 114 and above the measuring channel wall section 98.

[0051] Fig. Figure 15 shows a perspective view of a section of a measuring channel cover according to a fifth embodiment of the present invention. Only the differences from the preceding embodiments are described below, and identical components are designated with the same reference numerals. The features described above as optional aspects may also be implemented in the fifth embodiment, even if this is not explicitly shown.

[0052] As from Fig. As can be seen in Figure 15, the wall section 66 facing the electronics compartment extends from the leading edge 62 of the sensor carrier 40 to the trailing edge 64 of the sensor carrier 40. The wall section 66 facing the electronics compartment is arranged at an angle 84 of approximately -2.0° to the stop surface 80. The wall section 66 facing the electronics compartment can be arranged adjacent to the side edge 120 of the sensor membrane 44 facing the electronics compartment. Accordingly, a distance of 0 mm between the wall section 66 facing the electronics compartment and the sensor membrane 44 is provided. The center 122 of the side edge 120 of the sensor membrane 44 facing the electronics compartment can be used as a reference for this distance. In general, with regard to the distance of the wall section 66 facing the electronics room from the sensor membrane 44, a range from 0 mm up to the distance resulting from the extension of the upstream contour of the measuring channel wall is conceivable.

[0053] Fig. Figure 16 shows a perspective view of a section of a measuring channel cover 16 according to a sixth embodiment of the present invention. Only the differences from the preceding embodiments are described below, and identical components are designated with the same reference numerals. The features described above as optional aspects may also be implemented in the sixth embodiment, even if this is not explicitly shown.

[0054] At the in Fig. In the sixth embodiment shown in Figure 16, the wall section 66 facing the electronics compartment is arranged at an angle 84 of +20° to the stop surface 80 and, in an overlapping view, touches the sensor carrier 40 and the measuring channel 28 as shown in Figure 16. Fig. 16 The sensor membrane 44 is seen only at a downstream end 124 of the electronics compartment-facing side edge 120 of the sensor membrane 44. In general, with regard to the distance of the electronics compartment-facing wall section 66 from the sensor membrane 44, a distance resulting from the extension of the upstream contour of the measuring channel wall is conceivable.

[0055] Fig. Figure 17 shows a perspective view of a section of a measuring channel cover 16 according to a seventh embodiment of the present invention. Only the differences from the preceding embodiments are described below, and identical components are designated with the same reference numerals. The features described above as optional aspects may also be implemented in the seventh embodiment, even if this is not explicitly shown.

[0056] At the in Fig. In the embodiment shown in Figure 17, the wall section 66 facing the electronics compartment is arranged at an angle 84 of -10° to the stop surface 80 of the measuring channel cover 16. The wall section 66 facing the electronics compartment extends from an area upstream of the leading edge 62 of the sensor carrier 40 to the trailing edge 64 of the sensor carrier 40. For example, the wall section 66 facing the electronics compartment begins at an ascending section of the measuring channel ramp 56.

[0057] Fig. Figure 18 shows a perspective view of a section of a measuring channel cover 16 according to an eighth embodiment of the present invention. Only the differences from the preceding embodiments are described below, and identical components are designated with the same reference numerals. The features described above as optional aspects may also be implemented in the eighth embodiment, even if this is not explicitly shown.

[0058] At the in Fig. In the embodiment shown in Figure 18, the wall section 66 facing the electronics compartment is arranged at an angle of 0° to the stop surface 80 of the measuring channel cover 16. The wall section 66 facing the electronics compartment extends directly upstream of the sensor chip 42 with respect to the main flow direction of the fluid medium within the measuring channel 28 to downstream of the trailing edge 64 of the sensor carrier 40.

[0059] It is explicitly emphasized that in all previously described embodiments, a fundamental principle is the displacement or relocation of the wall section 66 facing the electronics compartment along a line perpendicular to and through the center 122 of the side edge 120 of the sensor membrane 44 facing the electronics compartment, compared to the conventional sensor arrangement described above. This results in a displacement of the pulse-rich wall beam 74 described above across the sensor membrane 44. Accordingly, improved values ​​regarding signal noise, characteristic curve reproducibility, and adjustability can be achieved.

Claims

[1] Sensor arrangement (10) for determining at least one parameter of a fluid medium flowing through a measuring channel (28), in particular an intake air mass flow of an internal combustion engine, wherein the sensor arrangement (10) comprises a sensor housing (12), in particular a plug-in sensor inserted or insertable into a flow tube, and at least one sensor chip (42) arranged in the measuring channel (28) for determining the parameter of the fluid medium, wherein the sensor housing (12) comprises a housing body (14), a measuring channel cover (16) in which the measuring channel (28) is formed, an electronics compartment (18), an inlet (34) into the measuring channel (28) and at least one outlet (32) from the measuring channel (28), wherein the measuring channel (28) is separated at least in the region of the sensor chip (42) by the housing body (14), the measuring channel cover (16), a wall section (66) facing the electronics compartment and a wall section facing away from the electronics compartment (68) is limited,wherein the measuring channel cover (16) has a stop surface (80) for contact with the housing body (14), wherein the wall section (66) facing the electronics compartment is formed at an angle to the stop surface (80) of -10° to +20° and preferably of 0° to +10°, such that the measuring channel (28) has a convergent course at least in the area of ​​a sensor carrier (40), characterized by , that the wall section (66) facing the electronics room has at least one base section (100) and at least one drop section (102), wherein the drop section (102) has a lower wall height than the base section (100), wherein the drop section (102) is located in the area of ​​the sensor chip (42). [2] Sensor arrangement (10) according to the preceding claim, wherein the sensor chip (42) is arranged on the sensor carrier (40) which projects from the electronics room (18) into the measuring channel (28), wherein the stop surface (80) is arranged adjacent to the sensor carrier (40). [3] Sensor arrangement (10) according to one of the preceding claims, wherein the wall section (66) facing the electronics compartment has a downstream end (108) viewed in a main flow direction (60) of the fluid medium in the measuring channel (28), wherein the sensor chip (42) is arranged on the sensor carrier (40) which projects from the electronics compartment (18) into the measuring channel (28), wherein a measuring channel wall section (98) is arranged downstream in the main flow direction (60) of the fluid medium in the measuring channel (28), wherein the downstream end (108) of the wall section (66) facing the electronics compartment is arranged such that a discontinuous transition (110), in particular by means of a recessed step (112), is formed between the wall section (66) facing the electronics compartment and the measuring channel wall section (98). [4] Sensor arrangement (10) according to one of claims 1 to 2, wherein the wall section (66) facing the electronics compartment has a downstream end (108) as seen in a main flow direction (60) of the fluid medium in the measuring channel (28), wherein the sensor chip (42) is arranged on the sensor carrier (40) which projects from the electronics compartment (18) into the measuring channel (28), wherein a measuring channel wall section (98) is arranged downstream in the main flow direction (60), wherein the downstream end (108) of the wall section (66) facing the electronics compartment transitions into the measuring channel wall section (98) in a radius (114), in particular tangentially. [5] Sensor arrangement (10) according to one of the preceding claims, wherein the sensor chip (42) has a sensor membrane (44) over which the fluid medium can flow, wherein the wall section (66) facing the electronics space is arranged adjacent to or spaced apart from a side edge (120) of the sensor membrane (44) facing that side edge. [6] Sensor arrangement (10) according to one of the preceding claims, wherein the sensor chip (42) is arranged on the sensor carrier (40) which projects from the electronics compartment (18) into the measuring channel (28), wherein the wall section (66) facing the electronics compartment has a surface (90) facing the sensor carrier (28), wherein the surface (90) facing the sensor carrier (40) has at least one recess (92, 94, 96) for receiving adhesive. [7] Sensor arrangement (10) according to the preceding claim, wherein the surface (90) facing the sensor carrier (40) has several recesses (92, 94, 96) for receiving adhesive, wherein at least one (96) of the several recesses (92, 94, 96) is channel-shaped. [8] Sensor arrangement (10) according to one of the two preceding claims, wherein the surface (90) facing the sensor carrier (40) has several recesses (92, 94, 96) for receiving adhesive, wherein at least one (96) of the several recesses (92, 94, 96) has a shallower depth than the other recesses (92, 94). [9] Sensor arrangement (10) according to one of the preceding claims, wherein the wall section (66) facing the electronics room has a continuous course at least in the area of ​​the sensor carrier (40).

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