Abstract:
A sensor device for detecting a flow property of fluid medium, e.g., an air flow in the intake tract or the charge air tract of an internal combustion engine, includes: a sensor housing introduced into the air flow and having at least one housing body, at least one cover, and at least one channel through which the fluid medium flows; a sensor element for detecting the flow property, the sensor element being held on a top side of a carrier. The carrier is situated at least partially in the channel and has a cross section which becomes wider in parallel with the main flow direction of the fluid medium at the location of the sensor element in a sectional plane in parallel to the main flow direction of the fluid medium in the channel.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a sensor device for detecting at least one flow property of a fluid medium, e.g., in the intake tract or the charge tract of an internal combustion engine. 
         [0003]    2. Description of the Related Art 
         [0004]    Flow meters are used to ascertain the air flow in the intake tract or the charge tract of an internal combustion engine. Since the weight ratios are important in the chemical process of combustion, the mass flow rate of the intake/charge air is to be measured, for which volume measuring methods or impact pressure measuring methods are used to some extent. 
         [0005]    Various types of sensors are known for measuring the air mass throughput. One such type of sensor is the so-called hot-film mass airflow sensor, such as that described in one possible specific embodiment in published German patent application document DE 103 45 584 A1. The flow meter according to published German patent application document DE 103 45 584 A1 has a sensor housing having a cavity for accommodating an electronic module, which is separated from a bypass measuring channel. The electronic module here has a carrier profile, which is formed essentially on a bottom plate having side webs molded on the opposing longitudinal sides. The electronic module also has a plastic carrier tongue, which is situated on one of the head sides of the carrier profile and, as a carrier, accommodates the sensor element. A circuit board equipped with electronic components and printed conductors is usually attached to the bottom plate of the carrier profile to provide an evaluating electronic unit. 
         [0006]    Published German patent application document DE 103 45 584 A1 also describes how the electronic module is held by the side webs in the cavity provided here after being inserted into the sensor housing, while achieving a clamping effect. The carrier here protrudes into the bypass measuring channel through an outlet opening between the latter and this cavity. 
         [0007]    In addition, published German patent application document DE 44 26 102 A1 describes a sensor carrier for a device for measuring the mass of a flowing medium, which is characterized in that the sensor carrier has a frame element and a holding element, the frame element having an opening which is covered by the holding element situated at the rear, thereby forming the recess for the sensor element. 
       BRIEF SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a sensor device for detecting at least one flow property of a fluid medium, in particular for detecting the air flow rate in the intake tract or the charge air tract of an internal combustion engine. The sensor device has at least one sensor housing, which may be introduced into the fluid medium and has at least one housing body and at least one cover. In addition, the sensor housing preferably has at least one channel through which the fluid medium may flow. In addition, the sensor device has a sensor element for detecting the flow property of the fluid medium, which is preferably mounted on a top side of a carrier, the carrier having a bottom side opposite the top side. The carrier is preferably situated at least partially in the channel. The channel may also be a side channel or a bypass channel branching off from a main flow channel or a main channel. 
         [0009]    With the sensor device according to the present invention, it is also provided that, at the location of the sensor element in a sectional plane parallel to a main flow direction of the fluid medium in the channel, the carrier has a cross section which becomes wider in at least some sections parallel to the main flow direction of the fluid medium. In other words, the thickness of the carrier increases along the main flow direction and decreases, preferably steadily, opposite the main flow direction accordingly. Furthermore, it is important in particular that the cross section becomes wider in the main flow direction, at least up to the rear of the sensor element. 
         [0010]    With the resulting tapering or constriction of the measuring channel, preferably steadily, in particular upstream from and in the area of the sensor element, it has advantageously been found that it is possible in this way to have an effective influence on the oncoming flow of the fluid medium against the sensor element and thereby substantially improve the stability, in particular the reproducibility, of the measurements, the comparability and signal-to-noise ratio. In this context, it is desirable in particular that an equally steady increase in the velocity of the fluid medium is achieved due to this steady tapering of the measuring channel, thus also improving the advantages mentioned above. 
         [0011]    In addition, the dependence of the comparability of the positioning of the housing body, of the cover and of the carrier in relation to one another is reduced in an advantageous manner, which permits a higher precision of the sensor devices compared and decreases rejects due to the production technology accordingly in an advantageous manner with the same manufacturing tolerances. As has also been found here, the influence of the position of the cover and the housing body is reduced significantly because the sensor element in particular is positioned on the carrier and the carrier contributes significantly toward the tapering of the channel. It is conceivable here in particular that complete independence of the position of the cover and the housing body is achieved when tapering of the channel is implemented completely by the carrier. Due to the widening of the cross section of the carrier according to the present invention and the associated tapering of the channel, in particular a reduction in the cross section of the channel, the flow velocity and the pressure of the fluid medium are influenced in the area of the sensor element and therefore an increase in accuracy is possible in an advantageous manner. 
         [0012]    It may also be advantageous if the carrier is designed to be wedge-shaped in at least some sections at the location of the sensor element. A corresponding wedge shape of the carrier thus also has advantageous effects in the manner described above by a widening of the cross section of the carrier and a corresponding tapering of the cross section of the channel. 
         [0013]    According to the idea on which the present invention is based, it may also be provided that the carrier has an inflow edge, in particular a contoured inflow edge. In other words, the inflow edge preferably has a fluidically optimized contour, the inflow edge having a contour having a shape starting from a tip or an apex point—as viewed in the main flow direction of the fluid medium—such that the cross section of the carrier also widens increasingly in the main flow direction of the fluid medium in the area of the inflow edge starting from the tip of the carrier. 
         [0014]    According to another specific embodiment of the present invention, it may be provided that the carrier of the sensor device has an apex angle γ, as viewed in the main flow direction. This apex angle is defined in particular by the two straight lines spanning the apex angle, these lines being obtained by drawing two lines in tangent to both the top side and the bottom side of the carrier. These two straight lines usually intersect in front of the carrier, as viewed in the main flow direction. “Drawing a tangent” is understood here in particular to mean that the straight line does not pass through the cross-sectional area of the carrier but instead merely contacts the carrier, under formation of one or multiple contact points. 
         [0015]    In addition, it may advantageously be provided that the carrier of the sensor device has a recess on the top side, the sensor element being introduced into the recess in such a way that the measuring surface of the sensor element has fluid medium flowing over it. It may also advantageously be provided that the sensor element completely fills up the recess and the measuring surface is flush with the top side of the carrier. 
         [0016]    The measuring surface may be equipped, for example, with at least one heating element and at least two temperature sensors, the sensor device optionally being equipped, for example, to detect, with the aid of the temperature sensors, an influence on a temperature distribution due to the flow of the fluid medium. For this purpose, one temperature sensor is preferably situated, viewed in the flow direction of the fluid medium, upstream and one temperature sensor is situated downstream from the heating element. 
         [0017]    According to another embodiment of the proposed sensor device, it may be provided that at least the bottom side and/or the top side of the carrier has/have a planar shape in at least some sections. 
         [0018]    Alternatively or additionally, it may also be provided that at least the bottom side and/or the top side of the carrier has/have a shape which is concave and/or convex, in particular being curved in at least some sections. 
         [0019]    This advantageously creates the possibility of having an advantageous influence on the flow of the fluid medium through a corresponding design of a surface contour on the bottom side and/or the top side of the carrier. 
         [0020]    In addition, with the proposed sensor device, it may also be provided that at least on the bottom side and/or the top side of the carrier two or more regions of a different shape abut in pairs, forming a transitional edge. 
         [0021]    The design of the carrier is not limited to symmetrical or conical geometries in particular. Consequently, a variety of possible designs of the shape of the bottom side and/or the top side of the carrier are conceivable. With another embodiment of the sensor device in particular, it may be provided that the top side and the bottom side have a shape, which is described in greater detail in the following itemization. In particular, it may be provided here that the top side and the bottom side have a planar shape in at least some sections and the top side runs at a first pitch, preferably &gt;0°, in particular &gt;10°, to the main flow direction, and the bottom side runs at a second pitch, preferably &gt;0°, in particular &gt;10°, to the main flow direction. Furthermore, the first pitch and the second pitch are equal. In general, the pitch refers to the angle which is enclosed or spanned in a sectional plane by a vector of the main flow direction in the area of the carrier and a vector tangentially along the shape of either the top side or the bottom side of the carrier or a wall section of the housing body or of the cover. 
         [0022]    Alternatively, the shape of the top side and the bottom side may be designed in such a way that the top side and the bottom side each have a planar shape in at least some sections, the top side running at a first pitch, preferably &gt;0°, in particular &gt;10°, to the main flow direction, and the bottom side running at a second pitch, preferably &gt;0°, in particular &gt;10°, to the main flow direction, the first pitch and the second pitch being different. 
         [0023]    According to another alternative embodiment, it may be provided for the top side and the bottom side to each have a planar shape in at least some sections, the top side running in parallel to the main flow direction, and the bottom side running at a second pitch, preferably &gt;0°, in particular &gt;10°, to the main flow direction. 
         [0024]    Conversely, it may likewise be provided that the top side and the bottom side each have a planar shape in at least some sections, the top side running at a first pitch, preferably &gt;0°, in particular &gt;10°, to the main flow direction, and the bottom side running in parallel to the main flow direction. 
         [0025]    It is likewise conceivable that the top side has a shape with a concave curvature in at least some sections. A concave shape is understood in particular to mean that the curvature bulges centrally toward a straight sectional line running essentially in parallel to the main flow direction through the carrier. In other words, the cross-sectional area of the carrier is reduced by the concave curvature, whereas it would increase due to a convex curvature having the same edge points of the curvature. 
         [0026]    It may likewise correspondingly be provided that the bottom side has a concave curvature in at least some sections. 
         [0027]    In addition, it is possible to design the shape of the carrier in such a way that the bottom side has a first section having a first shape in the main flow direction and a second section having a second shape connected to the first section in the main flow direction, a transitional edge being situated essentially across the main flow direction between the first section and the second section. 
         [0028]    The proposed sensor device may also be designed in such a way that the carrier tapers on its downstream end, i.e., at its rear end in the main flow direction, in particular so that the shape of the top side and the shape of the bottom side meet and merge at an apex. 
         [0029]    According to another embodiment of the sensor device, it may also be provided that the housing body and/or the cover has/have a geometry in which the housing body and/or the cover is/are designed to cause the channel to taper in the area of the carrier. This yields in particular the advantage that the influence of the carrier on the flow of the fluid medium is advantageously supported by the geometry of the housing body and/or that of the cover. 
         [0030]    In addition, it may also be provided that the cross-sectional shape of the carrier is adapted essentially to the geometry of the housing body and/or that of the cover. This means in particular that the shape of the top side of the carrier cooperates with the geometry of the cover in such a way that the flow of the fluid medium between the carrier and the cover may be influenced in a targeted manner. Furthermore, the bottom side of the carrier here also has a shape which cooperates with the geometry of the housing body in particular and seeks to influence the flow of the fluid medium between the bottom side of the carrier and the housing body, optionally in the same way as the flow of the fluid medium between the top side of the carrier and the cover, or to induce a different flow through a different influence. 
         [0031]    In general, it may also be provided that the sensor device, in particular the sensor housing of the sensor device, is designed at least partially as a plug sensor, and the plug sensor is introducible into a flow tube of the fluid medium. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]      FIG. 1  shows a schematic diagram of the sensor housing of a sensor device according to the present invention without a cover placed on the housing body. 
           [0033]      FIG. 2  shows a sectional diagram of a possible specific embodiment along line A-A′ in  FIG. 1 . 
           [0034]      FIG. 3  shows a sectional diagram of another specific embodiment along line A-A′ in  FIG. 1 . 
           [0035]      FIGS. 4   a  through  4   f  illustrate various diagrams of possible embodiments of the carrier. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]      FIG. 1  shows a schematic diagram of one possible specific embodiment of sensor device  10  according to the present invention, which shows in particular a sensor housing  12  having an open housing body  14 , in other words, without a cover  16 , which is provided for closing housing body  14 . 
         [0037]    The diagram in  FIG. 1  also indicates that a channel  18 , which has an inflow opening  20  and an outflow opening  22 , is situated in housing body  14 . Inflow opening  20  is preferably situated on an end face of housing body  14  directed opposite main flow direction  24 , outflow opening  22  preferably at the same time being situated at a right angle to inflow opening  20  within a chamber carrying the fluid medium. In addition, the preferred specific embodiment of sensor device  10  according to the present invention has another outlet opening  26 , which is formed following inflow opening  20 , as viewed along main flow direction  24 . This permits a preferred embodiment of channel  18  as a bypass channel. 
         [0038]    As also shown in  FIG. 1 , sensor device  10  has a carrier  28  situated in channel  18  in at least some sections, a sensor element  30  being held on this carrier inside channel  18 . It may thus be ensured that a substream of the fluid medium flows along main flow direction  24  through inflow opening  20  following the course of channel  18  to outflow opening  22  and flows over carrier  28  and sensor element  30 . 
         [0039]      FIG. 2  shows a sectional diagram of one possible specific embodiment along line A-A′ as shown in  FIG. 1 . 
         [0040]    The diagram in  FIG. 2  shows in particular that housing body  14  has a pitch a which reduces the cross section of channel  18  in front of and in the area of carrier  28 . In addition, cover  16  has a pitch β which may be designed to be different from pitch α of housing body  14 , for example, as shown here, and influences the cross section of channel  18  only in an area in front of carrier  28 . Geometry  32  of housing body  14  is described by the wall section of housing body  14  with pitch α as well as the wall section in channel  18  adjacent thereto and aligned in parallel to main flow direction  24 . A corresponding geometry  34  of cover  16  is described by the wall section of cover  16 , which runs at pitch β in some sections, and the section of cover  16  runs adjacent thereto downstream and essentially in parallel to main flow direction  24 . 
         [0041]      FIG. 2  also shows that in the specific embodiment of sensor device  10  shown here, sensor element  30  is situated in a recess  36 , preferably on top side  38  of carrier  28 . Carrier  28  also has a bottom side  40  situated opposite top side  38 . The shape of top side  38  and bottom side  40  of carrier  28  shown here form in particular an inflow edge  42  directed opposite main flow direction  24 . When viewed in main flow direction  24 , the shape of top side  38  and of bottom side  40  of carrier  28  thus contributes to the tapering of channel  18  in accordance with the idea according to the present invention. Carrier  28  here has a apex angle γ, which corresponds to the angle between a straight line applied to top side  38  and to bottom side  40 . 
         [0042]    Thus, in general, the pressure and/or the flow velocity of the fluid medium may be influenced indirectly by the tapering of channel  18 , in particular a reduction in the cross section of channel  18  in the area of carrier  28 . As shown in  FIG. 2 , the flow velocity along top side  38  of carrier  28  may differ from the flow velocity on bottom side  40  of carrier  28 , in particular due to the difference in design of geometry  32  of housing body  14  and geometry  34  of cover  16 . 
         [0043]      FIG. 3  shows a sectional diagram of another specific embodiment of sensor device  10  along line A-A′ in  FIG. 1 . Sensor device  10  illustrated in  FIG. 3  differs from sensor device  10  illustrated in  FIG. 2  only in geometry  32  of housing body  14 , geometry  34  of cover  16 , the design of carrier  28  and the resulting different design of channel  18 . 
         [0044]    As may be derived in detail from the diagram in  FIG. 3 , geometry  32  of housing body  14  is formed by a wall section, which is merely planar. At the same time, geometry  34  of cover  16  is formed by a wall section in parallel to main flow direction  24 . According to this specific embodiment of sensor housing  12  of sensor device  10 , no tapering of channel  18  is achieved by geometry  32  of housing body  14  and geometry  34  of cover  16 , when considered alone. The tapering of channel  18 , in particular a reduction in the channel cross section, is created exclusively by carrier  28  according to the specific embodiment shown in  FIG. 3 . Carrier  28  also reveals that apex angle γ is obtained from two partial angles δ, γ, partial angle δ corresponding to the pitch of top side  38  of carrier  28  in relation to main flow direction  24 . Accordingly, partial angle ε is formed by the pitch of bottom side  40  of carrier  28  in relation to main flow direction  24 . 
         [0045]    In addition, the diagram in  FIG. 3  indicates that top side  38  of carrier  28  is formed by an area  44  having a planar shape and by an additional area adjacent to area  44  downstream and having a different angle of inclination. Accordingly, a transitional edge  46  is formed on top side  38  of carrier  28  in the transition of the two areas into one another. According to the specific embodiment of sensor device  10  shown in  FIG. 3 , it may also be provided that top side  38  and bottom side  40  of carrier  28  contact one another in a shared vertex on a side of carrier  28  opposite inflow edge  42  in main flow direction  24 . However, it is not absolutely necessary for this vertex to lie on a plane of inflow edge  42 , as viewed in main flow direction  24 . This may optionally be situated in particular on a side facing top side  38  or bottom side  40  in relation to inflow edge  42  in main flow direction  24  due to an asymmetrical design of top side  38  and bottom side  40  of carrier  28 . 
         [0046]    In the following individual diagrams a) through f) of  FIG. 4 , various possible embodiments of carrier  28  are shown, in particular the shape of top side  38  or of bottom side  40 . The individual diagrams of different embodiments of carrier  28  are described below essentially on the basis of their differences in comparison with one another, in particular the differences in comparison with the preceding diagram. 
         [0047]      FIG. 4   a  thus shows a carrier  28  having an area  44  of a planar shape provided on top side  38  as well as on bottom side  40  of carrier  28 . 
         [0048]      FIG. 4   b  shows a carrier  28 , which also has an area  44  having a planar shape on top side  38  as well as on bottom side  40  of carrier  28 , but top side  38  of carrier  28  runs essentially in parallel to main flow direction  24  (not shown), whereas bottom side  40  of carrier  28  is set at an angle in relation to main flow direction  24 . 
         [0049]    However, the diagram in  FIG. 4   c  shows a carrier  28 , whose bottom side  40  runs essentially in parallel to main flow direction  24  (not shown), so that top side  38  of carrier  28  has a pitch in relation to main flow direction  24 . 
         [0050]    Carrier  28  according to the diagram in  FIG. 4   d  has an area  48  having a concave shape on top side  38  as well as on bottom side  40 . 
         [0051]    However, the diagram in  FIG. 4   e  shows that carrier  28  illustrated here has an area  44  on top side  38  having a planar shape, which runs obliquely to main flow direction  24 . Bottom side  40  of carrier  28  illustrated here also has an inclined area  44  having a planar shape, when viewed in main flow direction  24 , to which an additional area  44  also having a planar shape but in parallel to main flow direction  24  is connected, forming a transitional edge  46 . However, the diagram in  FIG. 4   f  indicates that top side  38  of carrier  28  shown here is formed from an area  48  having a concave shape, whereas bottom side  40  initially also has an area  48  having a concave shape in main flow direction  24 , an additional area  50  having a convex shape connected to same, forming a transitional edge  46 . 
         [0052]    The possible embodiments of carrier  28  are not exhausted in the diagrams of  FIGS. 2 through 4  but instead may be formed by any combination of different features of top side  38  or bottom side  40  of carrier  28  in planar, convex or concave sections in arbitrary apex angles γ, in particular pitches δ, ε.