Abstract:
An air mass sensor has a three-part configuration formed of an insertion element, a measuring channel element and a housing element for accommodating an evaluation device. In order to be able to provide flexible insertion elements for a device having a short overall height, the measuring channel element and the housing element are joined to one another along a side of the measuring channel element that is perpendicular to the main direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation of copending International Application No. PCT/DE03/01311, filed Apr. 22, 2003, which designated the United States and was not published in English. 

   BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The invention relates to a device for measuring the mass of air flowing inside a line. A device of this type is also referred to for short as an air mass measuring device or an air mass sensor. 
   The device is inserted into the intake channel for the air mass, as a result of which a defined portion of the total air flow flows through this device. The known insertion channel air mass measuring devices is formed essentially of a measuring channel in which a sensor is disposed, the electronics for the sensor which are disposed in a housing, and also an insertion element which inserts the measuring channel into the line. 
   Air mass sensors in the induction port of internal combustion engines are sufficiently known. They are used in order to detect the air mass taken in for the cylinders of the internal combustion engine and thus to enable the engine control unit to correctly set the air/fuel mixture along with other operational parameters. The mode of operation of the air mass sensor will not be described in detail in this patent specification. 
   A device for measuring the mass of a medium flowing in a line is known from Published, Non-Prosecuted German Patent Application DE 44 07 209 A1, corresponding to U.S. Pat. No. 6,422,070, whereby the housing for the electronics for the sensor projects into the intake line. Downstream of the electronics housing in the insertion direction follows the bypass channel with the sensor carrier. With regard to this configuration, the insertion element, the electronics for evaluating the sensor signals and the measuring channel are situated in series in the insertion direction. The disadvantage of this configuration for the air mass sensor is the fact that the latter requires a large construction length that can lead to installation problems, particularly in the case of small pipe diameters or low space availability in the engine area. 
   An air mass measuring device is known from U.S Pat. No. 5,939,628, whereby the electronics for evaluating the measuring sensors are integrated into the insertion element and in this situation are located outside the intake line. Although the air mass measuring device has a shorter overall construction, the integration of the electronics into the insertion element does however lead to the fact that minor constructional changes to the insertion element are comparatively costly. In particular, a constructional change to the insertion element makes it necessary to carry out a costly adaptation to the mounting support for the evaluation electronics and possibly to the electronics themselves if an electrical plug-in connection for connecting the measuring device to an engine control unit needs to be differently aligned or needs to be configured for other plug-in connections. 
   SUMMARY OF THE INVENTION 
   It is accordingly an object of the invention to provide a device for measuring the mass of air flowing inside a line which overcomes the above-mentioned disadvantages of the prior art devices of this general type, which has a short construction length that permits flexible adaptation to a wide variety of installation situations. 
   With the foregoing and other objects in view there is provided, in accordance with the invention, a device for measuring an air mass flowing inside a line. The device contains at least one measuring sensor, and a measuring channel element having a side, an outlet opening formed therein, and an inlet opening formed therein and into which a portion of the air mass flowing in a main direction of flow enters, flows around the measuring sensor and exits back into the line by way of the outlet opening. An insertion element is provided and when placed into an opening in the line projects into the line. An evaluation device receives signals generated by the measuring sensor. A housing element accommodates the evaluation device. The insertion element holds the housing element and the measuring channel element in the line. The housing element is disposed against the side of the measuring channel element plugged into the line, and the housing element is disposed perpendicular to the main direction of flow of the air mass. 
   The device according to the invention has a measuring channel element, into which a defined portion of the air mass to be measured enters by way of an inlet opening as an air stream. The air stream flows around at least one measuring element and exits into the line by way of an outlet opening. In its installed position the measuring channel element is plugged into the line. The air mass measuring device according to the invention has an insertion element which when placed into an opening in the line plugs the measuring channel element into the line. In addition, the device according to the invention has a housing element that has an evaluation device for receiving signals from the sensor elements. The housing element and/or the measuring channel element can be connected to the insertion element and, when connected, are held by the latter. With regard to the air mass measuring device according to the invention, the housing element and/or the measuring channel element is provided with a connection device which holds the housing element in the line against a side of the measuring channel element disposed perpendicularly with respect to the main direction of flow. The main direction of flow is the direction of flow of the undisturbed air mass in the line. In the connected state, the housing element and the measuring channel element are therefore connected to one another laterally. With regard to the solution according to the invention, an excessively long construction length is avoided as a result of the lateral configuration of the elements. At the same time, as a result of incorporating the evaluation device into the housing element and into the line, this ensures that concrete requirements applying to the insertion element can be realized independently of the evaluation device. A further advantage that has become apparent is the fact that the small distance between sensors in the measuring channel and evaluation electronics results in good electromagnetic compatibility. 
   The housing element has an essentially flat electronics substrate as the evaluation device, whereby the normal direction of the electronics substrate is disposed parallel to the main direction of flow in the line. 
   In a preferred embodiment, the housing element is provided with devices for electrical and mechanical connection with the insertion element. With regard to the air mass measuring device according to the invention, the housing element is connected to the insertion element and the measuring channel element is connected to the housing element. The connection of the housing element to the insertion element is also effected by way of electrical devices such that the signals from the evaluation device can be forwarded by way of the insertion element to a control unit. 
   By preference, the housing element is constructed with a base element and a cover element, between which is disposed the electronics substrate. The cover element is provided with cross-pieces which are connected to the measuring channel element when the device is in the assembled state. 
   The housing element is preferably disposed on the upstream facing side of the measuring channel element and has a convex shaped cover element. 
   In accordance with the invention, the base element has solder tags connecting the measuring sensor to the evaluation device on a side of the housing element facing the measuring channel element. The base element has a recess formed therein through which the solder tags connect the measuring sensor to the evaluation device. 
   In a preferred embodiment, the evaluation device has a substantially flat element which is connected to the base element by way of a shaped adhesive part provided with an adhesive on both sides and which seals the recess. The use of shaped adhesive parts is already known. With regard to this embodiment, a substantially flat element, preferably the electronics substrate, is secured in such a manner in the evaluation device that its recess is sealed. 
   In another embodiment, the insertion element additionally has a pin-shaped temperature sensor that protrudes from the insertion element and through the opening into the line. 
   In a further embodiment, the housing element is provided with a drainage recess located crosswise with respect to the insertion direction. The recess prevents the ingress of splashing water, which has condensed on the housing element, into the inlet opening. 
   Other features which are considered as characteristic for the invention are set forth in the appended claims. 
   Although the invention is illustrated and described herein as embodied in a device for measuring the mass of air flowing inside a line, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
   The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic, side-elevational view of an air mass sensor according to the invention; 
       FIG. 2  is a diagrammatic, exploded, perspective view of a connector element with a temperature sensor; 
       FIG. 3  is a perspective view of a measuring channel with an electronics housing; 
       FIG. 4  is diagrammatic, exploded, perspective view of the measuring channel and the electronics housing; and 
       FIG. 5  is diagrammatic, exploded, perspective view of the electronics housing. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the figures of the drawing in detail and first, particularly, to  FIG. 1  thereof, there is shown a side view of an air mass sensor  10 . The air mass sensor  10  is inserted into an intake line  12 . A main direction of flow of air is indicated by arrow A. One portion of the air mass stream enters a bypass channel of a bypass element  16  by way of an inlet opening (see FIG.  3 ). In the channel  16 , the air is directed past two sensors  18  and  20  (FIG.  4 ). The sensors  18 ,  20  take the form for example of temperature-dependent resistors with resistance layers, so-called hot-film resistors, for measuring the mass of the air flowing past. The measuring principles for determining an air mass flowing past in the bypass channel  16  are known and do not require further description here. 
   On its upstream facing side the bypass channel  16  is provided with an electronics housing  22 . The housing  22  is connected to the bypass channel  16 , as illustrated in  FIG. 3 , which is described in detail below. 
   The electronics housing  22  is in turn connected to a connector element  24 . The connector element  24  is inserted into an opening in the line  12  and holds both the electronics housing  22  and also the bypass channel  16 . The connector element  24  is used as an insertion element. 
     FIG. 2  shows a perspective view of the connector element  24  in more detail. The connector element  24  has a cover  26  that is provided with an orientation arrow for indicating the main direction of flow. A body  28  of the connector element  24  has a slotted hole  30  containing electrical contacts  32 . A connector terminal  34  leads away from the connector body  28  for forwarding the measurement signals to a non-illustrated engine control unit. 
   The connector body  28  is additionally provided with a temperature sensor  36 . The temperature sensor takes the form of a so-called negative temperature coefficient (NTC) temperature sensor. When the measuring device is in the assembled state, the temperature sensor  36  is situated laterally beside the bypass channel  16  and downstream of the electronics housing  22 . 
   As illustrated in  FIG. 3 , the electronics housing  22  is provided with the contact pins  38  which when inserted establish an electrical connection between evaluation electronics  48  and the connector element  24 . 
     FIG. 4  shows the bypass element  16  with its opening  14  for the bypass channel. The bypass channel has a first section for the inflowing air and a second section that is connected to the first section by way of a deflection section. In the area of the deflection section, the first and second sections are separated from one another by a wall  40 . The sensor carriers bearing the sensors  18  and  20  are disposed in the bypass channel. The channel element  16  has a flange  42  running around it, onto which a housing base element  44  is placed. The housing base element  44  is provided with the contact pins  38 . The contact pins  38  project from a pedestal  46 . Disposed in the base element  44  is the flat electronics substrate  48  that evaluates the measurement signals from the sensors  18  and  20  and forwards its results by way of the contact pins  38 . Mounted onto the base element  44  is a housing cover  50  that is provided laterally with cross-pieces  52 . The cross-pieces  52  are each disposed on longitudinal sides of the housing cover  50  close to the corners. 
   In order to connect the housing element  22  to the channel element  16 , the electronics substrate  48  is inserted into the base element  44 , as described in detail in the following with reference to FIG.  5 . The cover  50  is put in place and the cross-pieces  52  are guided laterally past the base element  44  through recesses  54 . On the flange  42  of the channel element  16  the cross-pieces  52  are connected to the latter for example by an adhesive or welding. The unit formed in this manner is inserted into the connector element  24  and the projection  46  is stuck or welded in the slotted hole  30 . Subsequently, an. electrically conducting connection is established between the contact pins  38  and  32 , by soldering for example. 
     FIG. 5  illustrates the mounting of the electronics substrate  48  in the base element  44 . The base element  44  has a non-illustrated spray-coated metal insert. A shaped adhesive part  56  with an adhesive on both sides is inserted into the base element  44 . The shaped adhesive part  56  is provided with an opening  58 . In the area of the opening  58 , two solder tags  60  and  62  are provided for each of the sensor elements  18 ,  20 . Only one of each pair of the two pairs of solder tags  60 ,  62  is visible in FIG.  5 . The opening  58  is disposed such that the measuring sensors can be soldered to the solder tags  60  and  62  through the opening. The electronics substrate  48  mounted on the shaped adhesive part  56  seals an opening in the base element  44  and thus also the measuring channel element. 
     FIG. 1  additionally shows a drainage recess  64  running crosswise with respect to the direction of flow A which collects any water splashes occurring and drains the water off to the side in order to prevent it entering the inlet opening.