Abstract:
A device for measuring the filling level of a liquid in a container with an ultrasound sensor and electronic components attached to the ultrasound sensor. A damping cup is arranged above the ultrasound sensor. The electronic components attached to the ultrasound sensor are separated from the liquid to be measured by a cover arranged above the electronic components. The cover has a recess in the vicinity of the ultrasound sensor, rests against the ultrasound sensor with the rim of the recess and is sealingly glued to the same.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0001]    The invention relates to a device for measuring the filling level of a liquid in a container with an ultrasound sensor and electronic components attached to the ultrasound sensor, wherein a damping cup is arranged above the ultrasound sensor. 
       Brief Discussion of the Related Art 
       [0002]    A device of this kind has been described for example in the DE 10 2014 009 610 A1. Such devices are used in particular for measuring the filling level of engine oil in an oil-lubricated engine, in particular in a motor vehicle. The filling level of the liquid is ascertained with the aid of ultrasound sensors. These emit sound waves, which are reflected at the interface between two media, here between air and oil, and which are received back by the ultrasound sensor. The recorded travel time of the sound waves is then used as a basis for ascertaining the filling level in the container holding the liquid. With a running engine, in particular in a motor vehicle, it is difficult, however, to ascertain the filling level of the oil, because the oil is very foamy and the sound waves are reflected at the gas bubbles in the oil. The values detected therefore vary widely across a wide area. In order to obtain measurements which can be evaluated, a unique interface is required between the gaseous medium such as air in this case, and the oil. In order to achieve this, the ultrasound sensors have so-called damping cups assigned to them. The damping cups usually comprise an ante-chamber. Within these damping cups, which surround the measuring section of the ultrasound sensor, the liquid to be measured is calmed and its connection to the container is limited to merely a small opening in the damping cup to the container. Due to the small opening in the damping cup to the container the amount of gas bubbles reaching the damping cup is reduced. The damping cups also serve to retard fluctuations generated e.g. by acceleration or by driving through bends and to take the mean of resulting fluctuations. In order to ensure maximum service life for the device, the ultrasound sensor with its electronic components is overmoulded in one known embodiment using a thermosetting plastic. In order to ensure that subsequent assembly processes can be carried out, the electrical connections are excluded from the overmoulding process. 
       SUMMARY OF THE INVENTION 
       [0003]    The invention is based on the requirement to propose a device of the kind mentioned in the beginning, which is particularly robust and long-lasting. This requirement is met with a device having the characteristics of patent claim  1 . Advantageous developments are proposed in the subclaims. 
         [0004]    With a device for measuring the filling level of a liquid in a container comprising an ultrasound sensor and electronic components connected to the ultrasound sensor, wherein a damping cup is arranged above the ultrasound sensor, provision is made according to the invention for the electronic components connected to the ultrasound sensor to be separated from the liquid to be measured by a cover arranged above the electronic components, for the cover to comprise a recess in the vicinity of the ultrasound sensor and for the cover with the edge of the recess to rest against the ultrasound sensor and to be sealingly glued to the same. In this way a protected space is created around the ultrasound sensor and in particular below the same, which is sealed against the medium above it or against the liquid above it. The electronic components may be circuit elements and/or electrical lines and connections. 
         [0005]    In the outer area the cover is also glued to a bottom arranged below it, so that cavities are created in which electronic components are arranged which are associated with the ultrasound sensor. As a result the electronic components and also their terminals and connections do not reside in the liquid to be measured, in particular not in the oil, and are therefore not attacked. Furthermore, with this embodiment there is no danger that any materials, which may be encasing the electronic components, may become detached due to vibrations or temperature fluctuations. 
         [0006]    The cover is preferably configured as a circular disc with a central recess. This embodiment ensures that the cover is well adapted to the device. The central recess is provided for connection to the ultrasound sensor, enabling the ultrasound sensor to emit through this recess and allowing the ultrasound waves to reach the damping cup arranged above it. 
         [0007]    With a preferred development of the invention the top of the cover forms the bottom of the damping cup. The damping cup can then be produced as a part which is open at the bottom and which is placed on top of the cover. On its top the cover is preferably equipped with holding structures for attaching the damping cup. In particular, the holding structures are formed as ring-shaped elevations, against which corresponding walls of the damping cup rest. In particular two ring-shaped elevations or annular edges surrounding each other are provided, between which an ante-chamber is formed within the damping cup. Furthermore the cover, on its top, conveniently comprises structures for forming an antechamber in the damping cup. 
         [0008]    With another preferred development of the invention the cover, at its bottom, comprises downwardly extending structures perpendicular to the cover plane, which are attached, in particular glued, to the bottom. Gluing is in particular effected with a flange, which at the bottom can be inserted into the respective container, in which the filling level is measured. The whole device is preferably mounted onto a flange, which can be inserted, in particular inserted from below, into the container with the liquid to be measured. The device with the damping cup then extends preferably vertically upwards. 
         [0009]    Below the cover liquid-free spaces are preferably formed, which house the electronic components and in which the electrical connection to the ultrasound sensor extends. In this case there is no need for overmoulding the electrical connections and the electronic components, since protection against the liquid to be measured is provided by the cover. 
         [0010]    With another preferred development of the invention the cover at the central recess is provided with a roughly vertical section extending along the side of the ultrasound sensor, and a horizontal section extending to a certain extent across the ultrasound sensor. As a result the cover is, to some extent, guided around the upper corner of the ultrasound sensor, so that in this area a narrow area enclosing the upper rim of the ultrasound sensor is formed, in which an adhesive connection is made between the ultrasound sensor and the cover. Especially preferably the cover in this rim area, comprises a projection, which lies directly adjacent to the upper rim edge of the ultrasound sensor and in which the distance between the ultrasound sensor and the cover is minimal. This design results in a particularly effective adhesive connection. 
         [0011]    With another preferred development of the invention the recess in the cover above the ultrasound sensor is configured as an opening. Here the cover rests against the ultrasound sensor and is continuously connected to the same by means of a ring-shaped adhesive connection. This ensures that the cover is altogether tight again, since the recess, which preferably is circular, is closed due to the ultrasound sensor arranged in the recess and the ring-shaped adhesive connection between the ultrasound sensor and the recess, specifically the rim of the recess. 
         [0012]    A further aspect of the invention relates to an oil-lubricated engine wherein the engine comprises an above-described device for measuring the engine oil level. In other respects the invention relates to a motor vehicle with the above-mentioned device, in particular with the previously mentioned oil-lubricated motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The invention will now be described in more detail by way of the embodiment depicted in the drawing. In detail, in the schematic representations: 
           [0014]      FIG. 1  shows a schematic view of a device according to the invention; 
           [0015]      FIG. 2  shows a sectional view of a damping cup of the device according to the invention; 
           [0016]      FIG. 3  shows a sectional view through a lower area of the device according to the invention with ultrasound sensor and cover; 
           [0017]      FIG. 4  shows a perspective view of  FIG. 3 ; 
           [0018]      FIG. 5  shows a perspective view in another section through the lower part of the device according to the invention; 
           [0019]      FIG. 6  shows an enlarged view of the ultrasound sensor with the cover arranged above it and the ring-shaped adhesive connection. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]      FIG. 1  shows a device  1 , which in its upper area comprises a damping cup  2 , inside which a measuring section extends. The ultrasound sensor not visible here emits ultrasound waves within this measuring section. In the lower area of the device  1  the damping cup comprises a pre-volume or antechamber  5 . This antechamber  5  here essentially has an outer wall  4  and a lid  6 .  FIG. 2  shows a cross-section through the upper part of the device  1  with the damping cup  2 . The measuring section  3 , at the bottom of which the ultrasound sensor not shown here is arranged, extends through the measuring section  2 . Here the antechamber  5  consists of an inner ring  8  and an outer ring  7 . These are formed by the outer wall  4  and an inner wall  9 . In the view according to  FIG. 2  the inflow  10  for the entry of the liquid from the container into the antechamber  5  can be recognised. This initially leads into the inner ring  7 . The inflow  10  is essentially a breakthrough through the outer wall  4 . This is located close to the bottom, in particular directly adjacent to the bottom of the device  1 . The liquid can enter through an inflow  11  from the outer ring  7  into the inner ring  8 . The inflow  11  is offset by 180° from the inflow  10 . The liquid is then able to get into the measuring section  3  from the inner ring  8  through an inflow  12 . The inflow into the measuring section  3  is offset by 180° from the inflow  11 . Due to this arrangement of the inflows  10 ,  11  and  12  it is ensured that the liquid travels for a maximum possible distance in the antechamber  5 , during which time it is calmed and outgassed thus resulting in a minimum of gas bubbles in the liquid, on which the ultrasound waves could reflect and interfere with the measuring result. 
         [0021]      FIG. 3  shows a cross-section through the lower part of the device  1 , in particular through the bottom area of the antechamber, which is not shown in  FIGS. 1 and 2 . In particular this figure shows the ultrasound sensor  13  with its electronic contacts  14 , which are connected in downward direction. The electronic contacts  14  are part of the electronic components connected to the ultrasound sensor  13 . The ultrasound sensor  13  is mounted onto a lower flange  19  and mounted centrally below the damping cup  2  and emits within the damping cup  2  into the vertically upward directed measuring section  3 . Essential to the present invention is the cover  16  provided here, which comprises a central recess  30 , which as regards size essentially corresponds to the diameter of the measuring section  3 . The cover  16  with the recess  30 , which could also be called a freed-up space, is configured and positioned such that the ultrasound sensor  13 , the recess  30  and the measuring section  3  are arranged one above another and in alignment with each other. The cover  16  comprises ring-shaped structures on its top, which are used for connection to the antechamber  5 . An inner annular edge  17  and an outer annular edge  18  are provided here, in particular. The inner annular edge  17  is joined here to the wall  2  of the damping cup. The outer annular edge  18  is joined to the inner wall  9  of the antechamber. Preferably the inner annular edge  17  is chamfered or sloped towards the inside and the outer annular edge  18  is chamfered or sloped towards the outside. Conversely the lower rim of the damping cup  2  is chamfered outwards, and the lower rim of the inner wall  9  is chamfered inwards. The chamfers correspond to each other, respectively. This leads to an automatic self-adjustment during assembly of the damping cup  2  with the antechamber  5  on the cover  16 . Moreover the cover  16  comprises lower projections  22  and is connected here via an adhesive connection  26  to the flange  19 . In the rim area of the cover  16  there is provided a connection area  23  of the cover  16  to the flange  19 . Here an adhesive connection  26  is established between the cover  16  and the flange  19  using basically known construction and assembly technology. In the area of the recess  30  an adhesive connection  24  is provided between the cover  16  and the ultrasound sensor  13 . This is provided in the shape of a ring around the upper outer edge of the ultrasound sensor  13 . On the rim of the recess  16  a vertical part  27  and a horizontal part  28  of the cover can be recognised, which surround this upper rim of the ultrasound sensor  13 . This produces an approximately uniform area for the adhesive connection  24  both horizontally and vertically. The vertical area is however distinctly longer than the horizontal area  28 . Moreover the rim of the recess  30  shows a step  29  in the cover  16 , which represents the minimum distance between the edge of the ultrasound sensor  13  and the cover  16 . This allows a particularly good distribution of the adhesive compound in the area of the adhesive connection  24 . For due to capillary forces substantially less adhesive spreads from the vertical part  27  onto the ultrasound sensor  13 , thereby forming a particularly good adhesive connection. 
         [0022]      FIG. 4  is a perspective sectional view onto the lower area of the device  1 , which roughly corresponds to the area depicted in  FIG. 3 . Identical parts have been marked with identical reference symbols. Here the view upon the cover  16  is more from the top, so that, in particular the inner annular edge and the outer annular edge can be recognised. The inner annular edge  17  comprises a breakthrough  31 , through which the liquid to be measured, in particular the oil, reaches the measuring section  3 . Also the recess  30  or freed-up space and the adhesive connection  24  circumventing the recess  30  like a ring between the cover  16  and the ultrasound sensor  13  can be recognised here. 
         [0023]      FIG. 5  shows a perspective view of the lower part of the device  1 . This figure corresponds more or less to  FIGS. 3 and 4 , but it is viewed from a different perspective and using a different section. In particular the inner annular edge  17  with the breakthrough  31  and the outer annular edge  18  with the breakthrough  32  can be recognised. The breakthroughs  31  and  32  are offset by 180° from one another, so that the liquid dwells for a maximum duration in the ante-chamber  5 . Furthermore it shows the flange ring  21 , which was merely indicated in  FIGS. 3 and 4 . The outer wall  4  of the antechamber  5  is placed onto this outer flange ring  21 . To this end it is convenient if the outer wall  4 , different from the view in  FIG. 2 , is shorter than the inner wall  9  and the wall of the damping cup  2 , i.e. if it does not extend as far in downward direction. 
         [0024]      FIG. 6  shows an enlarged cross-section in the area of the ultrasound sensor  13 . The ultrasound sensor  13  can be recognised here with its contacts  14 . The cover  16  extends at the rim and around the ultrasound sensor  13 . The cover comprises the central recess  30  so that the ultrasound sensor  13  can emit in an upward direction and can receive from above. Between the cover  16  and the ultrasound sensor  13 , in particular in the area of the upper annular edge or, in cross-section of the upper corner of the ultrasound sensor  13 , the cover  16  and the ultrasound sensor  13  are in close proximity to each other, and this is also where the adhesive connection  24  is formed, with which the cover  16  is sealingly connected to the ultrasound sensor  13 . The cover  16 , to this end, comprises a vertical part  27  on the rim of the recess  30 , which extends parallel to a part of the side wall of the ultrasound sensor  13 . Furthermore the cover  16  comprises a horizontal part  28  shorter relative to this vertical part  27 , wherein the horizontal part  28 , within a short rim area, extends across the ultrasound sensor  13 . In the transition area between this vertical part  27  and the horizontal part  28  a step  29  of the cover  16  is provided on the rim of the recess  30 . This could also be called a C-groove. Here, due to a kind of projection in the cover, a projection comparable in shape and size to the corner of the ultrasound sensor  13  is formed, which lies opposite the upper corner of the ultrasound sensor  13  thus representing a minimum distance for forming an adhesive connection. In the area of this step  29  of the cover  16  the thickness of the adhesive connection  24  is approximately only half the thickness of the adhesive connection  24  at the widest point from the ultrasound sensor  13  to the horizontal part  28  of the cover  16 . 
         [0025]    All features mentioned in the above description and in the claims can be combined at random with the features of the independent claim. The disclosure of the invention is thus not limited to the described or claimed feature combinations, rather all feature combinations meaningful in terms of the invention are considered to have been disclosed.