Abstract:
In order to improve a system for monitoring the working area atmosphere of an operating engine, measuring devices ( 2 ) for determining readings for a gas and/or an aerosol in the working area ( 4 ) of an operating engine are used as a starting point. Each measuring device comprises a suction means ( 8 ) which extracts a gas and/or a mixture of an aerosol from the working area ( 4 ) of the operating engine and feeds it to a sensor unit ( 16, 17, 18 ). An electronics module for operating the sensor unit ( 16, 17, 18 ) is also present. The suction means is designed as a convection pump ( 8 ) preferably with a heating device ( 42 ) and a cooling device ( 44 ).

Description:
[0001]    This application claims priority from PCT Application No. PCT/EP2011/051885 filed Feb. 9, 2011 which claims priority from European Application No. EP 10162870.9 filed on May 14, 2010, which applications are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to a system with measuring devices for determining readings of gases and/or an aerosol for an operating engine and to a monitoring method by means of which readings of gases and/or an aerosol in an operating engine, in particular readings of the aerosol concentration in an internal combustion engine, are determined. 
       BACKGROUND OF THE INVENTION 
       [0003]    The monitoring of gases and aerosol concentrations, particularly of lubricating oil mist in working areas of internal combustion engines or in casings of power transmission gears, is of considerable interest for avoiding damages. A rapid increase of the oil mist concentration is indicative of damages, for example of the tearing off of a lubricating film. As a result of frictional heat thus formed, oil vapors are formed which condensate to oil mist in the working area and thus result in a rapid increase of the oil mist concentration. If the resulting hazard is quickly recognized, then explosions and a concomitant threat to persons and further damages to the operating engine can be prevented with appropriate counteractions such as shutting down of the operating engine or of individual components of the operating engine. However, it is also possible to study specific gas components in such a working atmosphere by means of other sensors. 
         [0004]    Furthermore, in addition to the tearing off of the lubricating film, so-called blow-throughs may occur between the piston and the associated cylinder wall in bearings of piston engines due to damaged piston rings, which cause a total damage of the piston/cylinder aggregate (“piston seizure”). An increase of the oil mist density with simultaneous rise in temperature due to the hot combustion gases is indicative of such blow-throughs. 
         [0005]    First approaches for measuring the oil mist concentration are known from EP-A-0 071 391. In EP-A-0 071 391 it is suggested to draw the aerosol from the working area through a measuring compartment by means of a winged wheel blower and to carry out therein a reflection measurement by means of a radiation source and a radiation sensor. The winged wheel blower suggested therein is intended for use with a plurality of compartments arranged parallel to each other. 
         [0006]    The disadvantages of such an arrangement were already shown in WO-A-98/11331. In addition to the considerable constructive and operating expenses of such arrangement, the use of a blower for drawing out has been found to be insufficient, meaning that such a solution should be avoided. Moreover, the drawing out operation also draws dirty air through the pipe system, and thus oil accumulations in the form of oil bags can form which clog the lines, thus rendering the operation of the measuring device difficult or impossible. 
         [0007]    In contrast thereto, in DD-A-239 474 and in GB-A-2 166 232 it is suggested to arrange, for each working area of the driving gear of an internal combustion engine, a sensor unit directly in the interior of the respective working area and to connect it via an optical or electrical transmission path to an evaluation unit arranged outside of the internal, combustion engine. However, such a solution is associated with the disadvantage that the base concentration of oil mist and splash oil in the long run contaminates the sensors and, therefore, also leads to false alarms. 
         [0008]    In contrast, in the already mentioned WO-A-98/11331 it is suggested to provide, in each working area to be monitored, a sensor unit with an extraction based on a venturi nozzle. Such a measuring device operates without mechanically moving parts and is, therefore, almost wearless. However, it has been found that the air flow generated solely by the crank movement of the crankshaft cannot produce a sufficient perfusion of the vacuum suction nozzle, so that the effectivity of the measuring device is not ensured. In WO 2007/140640 A it was suggested to provide a common external compressed air supply for supplying all of the venturi nozzles of an engine and to ensure supply to the individual measuring points with appropriate supply lines. However, this approach has the disadvantage of requiring complex supply lines. 
         [0009]    From DE 26 08 390 A1 it is generally known that a measuring device for indicating the formation of oil mist—and/or oil smoke in engine rooms of internal combustion engines can be configured with an air jet pump, with DE 26 08 390 A1 suggesting to have all of the sampling lines lead into a common collection chamber. But in this manner a differentiated monitoring of the combustion room by means of multiple measuring points, which would allow for localization of the damage site, is not possible. 
       SUMMARY OF THE INVENTION 
       [0010]    It is an object of the invention to provide an improved system with measuring devices of the above mentioned type for determining readings of a gas and/or aerosol for an operating engine. In doing so, the various samples taken shall remain unmixed with each other. On the other hand, the individual measuring points shall be supplied with only a single cable. Furthermore, it appears essential that no moving parts such as a rotary blower etc. with reduced acceptance regarding the atmosphere :of the working area of an internal combustion engine shall be used. 
         [0011]    Here, the measures of the invention initially have the result that without moving parts, at least without a propeller that can quickly become contaminated by the atmosphere of an internal combustion engine, an analysis of the gas mixture and/or of an aerosol from the working area can be achieved with only a single electrical supply line. 
         [0012]    For the analysis of an aerosol it is customary to use an optical sensor. Generally, it is possible for the convection pump to have only one heating device or one cooling device. However, a good circulating performance is achieved by having a heating device plus a cooling device. In this case the sensor unit or a plurality of sensor units, respectively, are arranged in the flow channel between the heating device and the cooling device. 
         [0013]    In an advantageous embodiment, the heating element of the heating device is configured e.g. as a conventional resistive heating or as an inductive heating, and the cooling element of the cooling device is configured as a passive heat exchanger against the environment. Thereby, the device has to be configured in such a way that the ambient temperature allows for a sufficient temperature difference. 
         [0014]    An alternative embodiment is provided by a conventional heating element and a peltier element as the cooling element, wherein the peltier element is used for cooling, and the—warm—counter side of the peltier element is coupled to the environment via a heat exchanger. 
         [0015]    Furthermore, it is possible to realize the heating device and the cooling device of the convection pump by means of a peltier element for heating the gas or aerosol/gas mixture of the sensor unit and for cooling behind the sensor unit. 
         [0016]    In all of these embodiments, the suction point and the recovery point will advantageously be adjacent to each other. The flow channel can be configured as two concentrically arranged pipes, in which case the suction point and the recovery point are concentrically arranged. 
         [0017]    If only one heating device or one cooling device is provided, the suction point can be arranged above the recovery point, in which case the convection pump comprises a cooling device, or else the suction point can be arranged below the recovery point, in which case the convection pump comprises a heating device. 
         [0018]    Through the advantageous embodiment of a flow channel it will be possible in many cases to avoid having a separation means for separating off coarse components, but otherwise such separation means—a so called pipe or a labyrinth for separating off, in particular, oil droplets from the oil mist can be provided before the sensor. 
         [0019]    It is advantageous to have a temperature sensor arranged in the flow channel. In a simple embodiment, a temperature sensor is arranged in the heating side of the flow channel and the system comprises a device for warning when the temperature measured by the temperature sensor is excessive. At a temperature of for example 150° the system will issue a warning and optionally the engine will be checked. It is even more advantageous to provide two temperature sensors for monitoring the temperature difference between the heating side and the cooling side of the flow channel. In this manner the temperature difference, which represents a measure for the flow and accordingly a monitoring value therefor, can be used as a criterion for a sufficient flow. In a further development, a controlling device is provided for controlling the power of the heating element and the cooling element by means of the temperature difference, the temperature in the heating side or the temperature in the cooling side of the flow channel. 
         [0020]    The aforementioned elements as well as those claimed and described in the following exemplary embodiments, to be used according to the invention, are not subject to any particular conditions by way of exclusion in terms of their size, shape, use of material and technical design, with the result that the selection criteria known in the respective field of application can be used without restrictions. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    Further details, advantages and features of the object of the present invention will become apparent from the following description and the corresponding drawings, in which measuring devices according to the present invention are illustrated by way of example. The drawings show: 
           [0022]      FIG. 1  a schematic view of a measuring device in the working area of an internal combustion engine according to a first embodiment of the present invention, with a conventional heating device and a cooling device with a passive heat exchanger that conducts away the heat to the environment; 
           [0023]      FIG. 2  the measuring device according to  FIG. 1  in a perspective view from the side; 
           [0024]      FIG. 3  a side view of the measuring device according to  FIG. 1 ; 
           [0025]      FIG. 4  the measuring device according to  FIG. 1  as a sectional view taken from the side with a view onto the fins of the heat exchanger in the flow channel; 
           [0026]      FIG. 5  a schematic view of an alternative embodiment of the measuring device with a conventional heating device and an active cooling device that conducts away the heat via a peltier element and a heat exchanger to the environment; 
           [0027]      FIG. 6  the measuring device according to  FIG. 5  in a perspective view taken from the side; 
           [0028]      FIG. 7  a side view of the measuring device according to  FIG. 5 ; 
           [0029]      FIG. 8  the measuring device according to  FIG. 5  as a sectional view taken from the side with a view onto the fins of the heat exchanger in the flow channel; 
           [0030]      FIG. 9  a schematic view of a further, third embodiment of the measuring device with a heating device and a cooling device that is configured via a peltier element (heating pump) between the heat exchangers of the heating side and the cooling side of the flow channel; 
           [0031]      FIG. 10  the measuring device according to  FIG. 9  in a perspective view taken from the side; 
           [0032]      FIG. 11  a side view of the measuring device according to  FIG. 9 ; 
           [0033]      FIG. 12  the measuring device according to  FIG. 9  as a sectional view taken from the side with a view onto the fins of the heat exchanger in the flow channel. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    The  FIGS. 1 to 4  show a measuring device  2  of the system according to a first embodiment of the present invention. The measuring device is built by means of a flange  22  into the wall  6  of the operating engine, in the present case into the working area  4  of an internal combustion engine. The flange  22  comprises a feed line  12  for a gas/aerosol mixture which is drawn in from the working area  4  by the pumping action of a convection pump  8 , and which is again fed back into the working area  4  by means of a recovery line  20 . 
         [0035]    In the present embodiment, the recovery line  20  is arranged close to the feed line  12  and, therefore, the suction point  12   a  and the recovery point  20   a  of the gas/aerosol mixture are located close to each other. 
         [0036]    The two lines  12 ,  20 —as seen from the suction point and recovery point, respectively, and starting out from the flange—initially comprise a substantially horizontal section, which—after a bent section—leads into the actual convection pump area. 
         [0037]    The latter comprises in the feed line  12  thereof a heating device  42  with a resistive heating element  42   a  and a heat exchanger  42   b,  and in the recovery lines  20  thereof a cooling device  44  with a heat exchanger  44   a  in the recovery line and a further heat exchanger  44   b  that conducts the heat to the environment. 
         [0038]    By means of the heating device  42  with the resistive heating element  42   a  and the heat exchanger  42   b  the gas/aerosol mixture is heated up within the feed area  12  and due to its concomitant expansion rises up into the actual measuring region  26 . On the other hand the gas/aerosol mixture that has already been measured is cooled down in the recovery area by means of the cooling device  44  with the heat exchangers  44   a  and  44   b  and contracts, which leads to an amplification of the above mentioned current all the way to the recovery point in the working area of the internal combustion engine. 
         [0039]    This embodiment stands out in that it needs only a single active thermal element, namely, a conventional heating element. In this manner, this embodiment is not only very easy to set up and also easily operated without much effort, but also particularly reliable. 
         [0040]    In the present embodiment, the actual measuring region comprises a transmission light measuring path on the one hand and a scattered light measuring path on the other hand. The transmission light measuring path is implemented with the light source  17 , namely a light emitting diode, and the optical sensor  16 ; the light intensity transmitted of the light source  17  is measured. The scattered light path is implemented by the light source  18  and by the sensor  16  also used for the transmission light path; the light scattered from the aerosol present in the light path is measured. The measurement of transmission and scattered light with only one sensor is carried out intermittently in time. The sensor and the light source, respectively, are coupled to the measuring area by means of optical windows  30  that are adapted to the optical properties of the sensors and the light source, respectively. 
         [0041]    The temperature of the heating side can be regulated via the heating power of the resistive heating depending on the temperature of the cooling side in such a manner that—at least over a wide region of ambient temperatures and temperatures of the working area—there is a constant temperature difference between the heating side and the cooling side, which difference can be e.g. 50° C., i.e. at 45° C. and 70° C., respectively, on the cooling side, the temperature of the heating side is 95° C. and 120° C., respectively. A minimum temperature difference between the heating and the cooling side shall be maintained to ensure a sufficient flow. If the temperature difference falls short of this, an alarm can be triggered. 
         [0042]    As typical values for the embodiment described herein, the heating device will have an average supplied power of about 5 watts and a normal working temperature of 120° C. The diameter of the feed line is about 15 to 20 mm. 
         [0043]    The  FIGS. 5 to 8  show an alternative embodiment that again comprises a heating device  42  with a conventional heating element  42   a  that is also configured as an electrical resistive heating and a heat exchanger  42   b  and an active cooling device  46 , this embodiment comprising a peltier element  46   a  with a heat exchanger  46   b  coupled thereto and a heat exchanger  46   c  coupled to the environment. The feed and recovery of the heat of the gas/aerosol mixture, respectively, occurs via the heat exchangers  42   b ,  46   b . 
         [0044]    The heating device is again configured in such manner that the inflowing gas/aerosol mixture reaches a temperature of e.g. 120° C. The cooling element in this embodiment is configured so that the gas/aerosol mixture flowing back which has already been analyzed is cooled down to a temperature of about 30° C. so that a convection flow is maintained. The heating side of the peltier element in this embodiment reaches a temperature of about 60°. This embodiment has the advantage that the ambient temperatures are higher and that the temperature difference between the heating side and the cooling side can be chosen larger in favor of a higher pump power, although this requires a larger expenditure for the cooling performance. 
         [0045]    In a further embodiment according to the  FIGS. 9 to 12  both the heating and the cooling are achieved with a peltier element  50  coupled to the heating and to the cooling by means of heat exchanger elements  50   a  and  50   b.  In this embodiment the peltier element  50  is arranged in the middle between the adjacent feed line and recovery line  12 ,  20  and thermally coupled to the feed line  12  and recovery line  20  by means of two heat exchangers  50   a,    50   b —which in the present embodiment are aluminum strip profiles with a size of 50×29×25 mm. The peltier element  50  is arranged in such a manner that its heating side cooperates thermally with the feed by means of the heat exchanger  50   a  and that its cooling side cooperates thermally with the recovery by means of the heat exchanger  50   b.    
         [0046]    As a typical value for this embodiment, the peltier element  40  will have an average power supplied of about 5 watt, a maximum temperature of 150° C. and a size of 20×20×3.6 mm. The diameter of the feed line is about 15 to 20 mm, and the operating temperature of the heat exchanger elements  50   a ,  50   b  is 50 to 60° C. on the heating side and 30° C. on the cooling side, which is above the gas/aerosol temperature in the working area. 
       LIST OF REFERENCE NUMERALS 
       [0000]    
       
           2  measuring device 
           4  working area 
           6  wall of the operating engine 
           8  convection pump 
           12  gas/aerosol feed line 
           12   a  suction point 
           16  sensor 
           17  transmission light source for the sensor 
           18  scattered light light source for the sensor 
           20  gas/aerosol recovery 
           20   a  recovery point 
           22  flange 
           26  measuring region 
           30  optical windows 
           42  heating device 
           42   a  heating element 
           42   b  heat exchanger for the heating device, coupled to the gas/aerosol 
           44  cooling device 
           44   a  heat exchanger for the cooling device, coupled to the gas/aerosol 
           44   b  heat exchanger for the cooling device, coupled to the environment 
           46  cooling device with peltier element 
           46   a  peltier element 
           46   b  heat exchanger for the cooling device, coupled to the gas/aerosol and to the peltier element 
           46   c  heat exchanger for the cooling device, coupled to the environment and to the peltier element 
           50  peltier element 
           50   a  heat exchanger for the heating device, coupled to the gas/aerosol 
           50   b  heat exchanger for the cooling device, coupled to the gas/aerosol