Abstract:
A method according to the invention makes it possible to make a check of the correct installation and operation of piston cooling nozzles ( 10 ) in a cold text prior to the final assembly of the engine by applying compressed air to each piston cooling nozzle ( 10 ) and directing the jet of compressed air emitted by the piston cooling nozzle ( 10 ) to be checked toward a surface pressure sensor ( 24 ). This makes it possible to record the position of the compressed air jet generated by the piston cooling nozzle ( 10 ) and preferably also the geometry of the jet. It is thereupon possible to draw conclusions concerning the proper operation and installation of the respectively checked piston cooling nozzle ( 10 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   The invention relates to a method for checking nozzles of internal-combustion engines, with the nozzles being installed and in particular checked for their correct installation and/or operation prior to the complete assembly of the respective internal-combustion engine. 
   2. Prior Art. 
   Internal-combustion engines are usually equipped with fuel injection nozzles. In addition, more modern internal-combustion engines, in particular high-performance engines, have piston cooling nozzles, which spray oil against the bottom end of the piston, in particular in cooling ducts or supply ducts emanating from the bottom end of the pistons. These types of nozzles must not only generate a jet having a certain geometry, in particular a certain cross-section, but more importantly the jet must also follow a precisely determined direction in order that the oil of the piston cooling nozzles reaches the respective cooling duct or supply duct at the lower end of each piston. Consequently, the checking of injection nozzles as well as piston cooling nozzles must primarily be capable of determining jet geometry and jet direction. 
   Known prior to the invention has been the checking of nozzles, in particular injection nozzles, after they have been installed in the cylinder head but before the cylinder head has been mounted on the engine block. Here only the function of the injection nozzles is checked by an operating test, which merely shows whether or not the injection nozzle is in order. However, the jet geometry and particularly the jet direction cannot be determined by this known test. The same holds true for piston cooling nozzles. Here it is particularly crucial to test their jet direction in order to ensure that the jet of oil emitted from the piston cooling nozzles in the assembled engine also reaches the correct position at the bottom side of the respective piston, in particular the piston cooling duct or supply duct. 
   BRIEF SUMMARY OF THE INVENTION 
   Proceeding from the above, the object of the invention is to provide a method by means of which nozzles of internal-combustion engines, in particular injection nozzles and piston cooling nozzles, can be checked simply and reliably at least with respect to their jet direction, and preferably also with respect to their jet geometry. 
   A method for achieving this object is A method for checking nozzles of internal-combustion engines, with the nozzles being installed and in particular checked for their correct installation and/or operation prior to the complete assembly of the respective internal-combustion engine, characterized in that each nozzle is checked with a jet of fluid medium directed toward at least one pressure sensor. Accordingly, each nozzle, in particular each injection nozzle or piston cooling nozzle, is checked with a jet of fluid medium which is directed toward at least one pressure sensor. The use of the at least one pressure sensor allows one to determine the direction of the liquid jet emitted by the nozzle because the at least one pressure sensor, due to its pre-specified positioning, generates a signal only when the respective pressure sensor is struck. If the pressure sensor is only partially struck by the jet of air emitted by the respective nozzle, it generates an attenuated signal, which also allows one to draw conclusions about a jet direction deviating from the pre-determined direction. The intensity of the pressure signal registered by the pressure sensor also allows one to draw conclusions about the nozzle&#39;s jet geometry. 
   Pursuant to a preferred further development of the method according to the invention, a surface pressure sensor is employed which can also be formed from a plurality of individual pressure sensors arranged in an array or grid-like pattern. Accordingly, any reference to a surface pressure sensor made in the following also includes a sensor comprising a plurality of pressure sensors arranged in an array or grid. 
   Each surface pressure sensor can determine, or more precisely scan, the pressure of the liquid jet emitted by the nozzle to be checked in the pre-specified surface region. The checking method according to the invention is even capable of establishing the position at which the tested jet emitted by the nozzle to be checked strikes the surface scanned by the surface pressure sensor (test surface). This enable one to make precise conclusions concerning the direction of the liquid or tested jet emitted by the nozzle to be checked. The jet geometry of the tested jet can be determined by the size and shape of the surface area on which the liquid jet emitted by the nozzle has generated a pressure signal on the surface pressure sensor. The pressure signal can be represented by the surface pressure sensor as a three-dimensional image, with the pressure value being spatially plotted on a reference line perpendicular to the test surface. Thus, a pressure distribution pattern of the tested jet can be determined over the cross-sectional area of the test surface, namely the plane occupied by the surface pressure sensor. 
   The invention also provides that pressure sensors, in particular surface pressure sensors, can determine a pressure across the preferably entire surface area of a respective cylinder bore (when checking a piston cooling nozzle) in the engine block or, (when checking an injection nozzle) of a combustion chamber in the cylinder head. By virtue of this arrangement, a largest possible surface area is available for checking the jet direction and preferably also the jet geometry exhibited by the tested jet of the injection nozzle or piston cooling nozzle. It is possible to determine the pressure across practically the entire cross-sectional area of the cylinder bore in the engine block or of the combustion chamber in the region of the bearing surface of the cylinder head on the engine block. This makes it possible to make a check of the direction and geometry of the injection jet of injection nozzles and the cooling jet of piston cooling nozzles which has the greatest possible statistical significance. 
   According to a further embodiment of the invention, for the purpose of checking piston cooling nozzles, it is possible to attach the surface pressure sensor associated to each piston cooling nozzle or cylinder bore to the side of the engine block facing the cylinder head via the respective cylinder bore during the check of the piston cooling nozzles. Preferably, all piston cooling nozzles of the internal-combustion engine are tested simultaneously. Thus, for a six-cylinder internal-combustion engine having one piston cooling nozzle per cylinder, six surface pressure sensors would be temporarily attached through the respective cylinder bore. To simplify the checking process, it is possible to attach all or only a group of surface pressure sensors to a common carrier so that all or at least a plurality of surface pressure sensors can be attached simultaneously and in the correct position relative to the engine block in a single operation and also subsequently detached. The surface pressure sensors are impinged by the end of the tested jet, which extends through the entire cylinder bore, on the side of the engine block lying opposite the piston cooling nozzle. 
   The check of the injection nozzles provides for the assignment of each injection nozzle to a surface pressure sensor arranged on the side of the cylinder head bearing on the engine block. The surface pressure sensor is then situated at the front of the combustion chamber, specifically at its greatest cross-section, because the surface of the combustion chamber has its greatest area at the side of the cylinder head which bears upon the engine block. For this purpose each injection nozzle or each cylinder is to be assigned its own surface pressure sensor. All or part of the surface pressure sensors can be assigned to a common carrier. 
   Pursuant to a preferred embodiment of the method, the respective surface pressure sensor covers either the entire opening of the combustion chamber at the bearing side of the cylinder head on the engine block or the entire cylinder bore in the engine block. As a result, the largest possible surface area of the cylinder bore or of the combustion chamber can be assessed by the respective surface pressure sensor concerning the impact and the cross-section of the tested jet which is emitted by the respective nozzle for testing of the latter. 
   Preferably, the injection nozzles or piston cooling nozzles are continually impinged with compressed air during the checking operation, with the surface pressure sensors determining at least the location and the pressure of the compressed air emitted by the nozzles, and preferably also the distribution of pressure across the cross-section of the compressed air jet. This ensures a significant checking of the piston cooling nozzles as well as of the injection nozzles with respect to their mode of operation, correct nozzle bore and above all the proper mounting of the piston cooling nozzles in the engine block or of the injection nozzles in the cylinder head. The compressed air allows for a contaminant-free cold test without falsifying the test or measured results in a non-reproducible manner. 
   During checking, a continuous jet of compressed air is generated by the piston cooling nozzles or injection nozzles, preferably throughout the entire checking procedure. This means that measurements can be taken continually over a certain period of time, thus ensuring significant, i.e. stable, measurements over a certain period of time due to the time recording of the measured results of the surface pressure sensors. If a constant measurement result cannot be shown within at least a certain period of time during the test, one can draw conclusions about errors in the measurement device. One can therefore see that a test result which might suggest improperly functioning nozzles or their incorrect installation cannot be evaluated because the testing device and/or a measuring calculation for evaluating the results of checking are faulty. 
   Pursuant to a preferred embodiment of the method, compressed air kept at room temperature is used to check the piston cooling nozzles as well as the injection nozzles. Thus, the compressed air used for the check can be taken from the usually present supply of compressed air and does not require any additional treatment. The method according to the invention can therefore be successfully employed at a minimum additional cost to the user. 
   It is also intended to use air compressed at a pressure of 1 to 5 bar, preferably 2 to 3 bar, for checking the injection nozzles as well as the piston cooling nozzles. Air pressurized at such a level is also available in common compressed air networks and thus the method can be realized in this respect at a low cost. Due to the use of surface pressure sensors or an array or grid comprising a plurality of pressure sensors, air pressurized between 1 and 5 bar, in particular 2 to 3 bar, is sufficient for checking the piston cooling nozzles and injection nozzles in order to obtain significant results as measured by the employed pressure sensors, in particular surface pressure sensors. The pressure level of compressed air may lie at the lower limit of the aforementioned pressure range if the distance between the nozzle to be checked and the surface pressure sensor is relatively small, as is the case, for example, when checking injection nozzles in the cylinder head. If the distance between the piston cooling nozzles and the surface pressure sensor is greater, in particular in long-stroke internal-combustion engines, air compressed at a pressure in the upper region of the specified ranges can be used to check the piston cooling nozzles. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Two preferred exemplary embodiments of the invention will be discussed in more detail in the following on the basis of the drawings, which show: 
       FIG. 1  is a schematic vertical section through a piston with a piston cooling duct. 
       FIG. 2  is a schematic view of part of a cylinder head in the region of a cylinder bore with its associated piston cooling nozzle. 
       FIG. 3  is a schematic view of part of a cylinder head in the region of an injector nozzle. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The method according to the invention for checking piston cooling nozzles  10  of internal-combustion engines will be illustrated in conjunction with  FIGS. 1 and 2 . Each cylinder  12  or each pair of adjacent cylinders of the internal-combustion engine is assigned a piston cooling nozzle  10 . Thus, for a six-cylinder internal-combustion engine a total of six piston cooling nozzles  10  are present. These nozzles are checked simultaneously in the operating test prior to the complete assembly of the internal-combustion engine, particularly if the pistons  11  have not yet been installed in the cylinder bores  13  of the engine block  14 . 
     FIG. 1  shows a longitudinal section through the piston  11 . Inside the piston  11  is a preferably annular cooling duct  15 . This is disposed in the upper region of the piston  11 , namely encompassing a combustion chamber recess  16  which proceeds from the top side  17  of the piston  11  to form part of the combustion chamber. In place of the cooling duct  15 , one can also provide cooling coils or more complex cooling spaces (in two-part pistons). The cooling duct  15  is provided with liquid coolant, in particular oil, through a usually vertical, straight supply duct  18 . The supply duct  18  is open in the region of the bottom side  19  of the piston  11  and its upper end opens out at a point in the cooling duct  15  ( FIG. 1 ). 
   The piston cooling nozzle  10  is attached at a bottom side of the engine block  14 . The piston cooling nozzle  10  can be configured to have a center coolant feeder  20  which is supplied by the crankcase with oil from the oil pan. The piston cooling nozzle  10  with the coolant feeder  20  is then screwed on under the engine block  14 . In the shown exemplary embodiment two opposite tube sections  21  branch off the coolant feeder  20  and lead to the bottom side of the adjacent cylinder  12 . One piston cooling nozzle  10  then provides coolant, in particular oil, simultaneously but separately to two pistons  11  in different cylinder bores  13 . Each tube section  21  of the piston cooling nozzle  10  is formed such that a nozzle-like cooling nozzle end  22  extends from below into the respective cylinder  12 , specifically in such a manner that coolant is sprayed from the cooling nozzle end  22  parallel to the cylinder center axis  23  upwards in a vertical and eccentric direction under the pistons  11 . This is carried out in such a manner that the coolant jet emitted from the cooling nozzle end  22  of the piston cooling nozzle  10  is directed exactly into the coolant supply duct  18  running parallel to the cylinder center axis  23  to the cooling duct  15 . The piston cooling nozzle  10  must be mounted under the engine block  14  such that the cooling oil emitted from the cooling nozzle end  22  enters the supply duct  18  in the piston  11  from below. In addition, the oil jet must have a geometry, in particular a jet cross-section, which matches the diameter of the supply duct  18  in order that at least a large part of the coolant oil sprayed out of the cooling nozzle end  22  against the piston  11  from below reaches the supply duct  18 . As an alternative, the piston cooling nozzle can also be configured such that its supplies cooling oil to a single piston  11  only. Then each piston  11  or cylinder is provided with its own piston cooling nozzle. 
   According to the method of the invention, a cold test is made to check the positioning and preferably also the geometry and cross-section of the coolant jet before the internal-combustion engine is assembled, in particular before the pistons  11  have been inserted in the engine block  14 . During this test, all piston cooling nozzles  10  of the internal-combustion engine are simultaneously and continuously supplied with a pressurized fluid medium. The fluid is then emitted through each cooling nozzle end  22 , and in the process passes through each cylinder bore  13  in the engine block  14  of the internal-combustion engine from the bottom to the top. The fluid medium used is preferably compressed air. The air pressure applied is 1 to 5 bar, preferably 2 to 3 bar. The air pressure itself is approximately 2 bar. Air having the ambient temperature is used. Thus, the air is neither cooled nor warmed with respect to the ambient temperature. Such compressed air can be taken from the normally present compressed air supply network. 
   According to a preferred embodiment of the invention, a surface pressure sensor checks the position of each tested air jet, in particular its geometry, and above all its cross-section. At least a qualitative, and preferably also a quantitative determination is made of the dominant pressure at every position of the surface pressure sensor. The surface pressure sensor can also be formed from a grid or array of many individual pressure sensors, which by virtue of their uniform grid-like distribution over a certain surface area can make an even scan of the measured pressure area thus formed. As a result, it is possible to determine the location at which the jet of test fluid, in particular the jet of compressed air, strikes the measuring surface of the surface pressure sensor or the grid of a plurality of identical pressure sensors. In addition, the surface pressure sensor can determine the cross-section of the test jet, in particular the test air jet, striking the measuring surface of the surface pressure sensor, thus making it possible to draw conclusions concerning the jet geometry of the test jet or test air jet. 
   Each of the surface pressure sensors  24 , which are identical to each other, is dimensioned such that it completely covers the top surface area of a cylinder bore  13  of the engine block  14 , preferably with a circular overlapping of the top side  25  of the engine block  14  facing the cylinder head  28 . The surface pressure sensor  24  is thus located on the side of the cylinder bore  13  which is opposite the cooling nozzle end  22 . By virtue of the complete covering of the top side of the cylinder bore  13  by the surface pressure sensor  24 , the latter is capable of determining the pressure of the test air jet emitted upwards from the respective cooling nozzle end  22  in the entire region of the cylinder bore  13 . 
   For the realization of the method according to the invention, each of the individual surface pressure sensors  24  assigned to a cylinder bore  13  can be detachably affixed above the respective cylinder bore  13  on the top side  25  of the engine block  14 . Provided for this function is an attachment device (not shown in the figures) which is configured such that it can be easily attached to the top side  25  of the engine block  24  and detached from it just as easily. As an alternative, it is conceivable to design the attachment device such that it simultaneously locks all identically configured surface pressure sensors  24 , which are to be associated with cylinder bores  13  arranged in a row in the engine block  14 , on the top side  25  of the engine block  14  in a detachable manner. By means of this arrangement, it is possible for all surface pressure sensors  24  for a row of cylinder bores  13  in the engine block  14  to be fixed simultaneously in their proper position above the respective cylinder bore  13  in a single assembly work step. After testing, all surface pressure sensors  24  can be simultaneously detached in common from the top side  25  of the engine block  14 . 
   The method according to the invention for the preferably simultaneous checking of all piston cooling nozzles  10  of an internal-combustion engine proceeds as follows in the cold test: 
   After all piston cooling nozzles  10  have been installed at the underside of the engine block  14 , but no cylinder  12  has yet been placed in the cylinder bores  13  of the engine block  14 , a surface pressure sensor  24  is attached on the top side  25  of the engine block  14  through each cylinder bore  13 , covering the latter with its full surface. The surface pressure sensors  24  can be attached either in common or individually to the top side  25  of the engine block  14  for executing the checking operation. All surface pressure sensors  24  are permanently provided with test leads which are connected to a preferably single, common test computer. If necessary, these leads can also be used to supply energy to the surface pressure sensors  24 . All cooling nozzles  10  are now impinged with a test fluid medium, in particular with compressed air. This is preferably accomplished by attaching the coolant feeder  20  of each piston cooling nozzle  10  to a compressed air supply. 
   After the compressed air has been released from the compressed air supply, the compressed air to be used for testing flows out of the cooling nozzle ends  22  of the piston cooling nozzles  10 . If the piston cooling nozzles  10  are intact and correctly installed, a thin jet of compressed air flows out of the cooling nozzle ends  22  parallel to the cylinder center axis  23  in the direction of the surface pressure sensors  24  at the top side  25  of the engine block  14 . The respective surface pressure sensor  24  now determines the position where the test air jet has struck the surface pressure sensor  24 . 
   Besides determining the position where the respective jet of compressed air or test air has struck the surface pressure sensor  24 , preferably at its underside, it is also possible to determine whether the test air jet has been properly mounted. One can also determine the pressure with which the test air jet strikes the surface pressure sensor  24 . This can then be used to determine whether the piston cooling nozzle  10 —in particular the cooling nozzle end  22  where the test compressed air escapes from the piston cooling nozzle  10 —has been properly manufactured. It is also possible to determine the shape and size of the surface area struck by the test air jet on the surface pressure sensor  24  and thus establish its geometry. 
     FIG. 3  illustrates the use of the method according to the invention for checking injection nozzles  26  in a cold test. The check is made after all injection nozzles  26  and all spark plugs  27  have been installed in the cylinder head  28  of the internal-combustion engine. At the same time, however, the cylinder head  28  with the injection nozzles  26  and the spark plugs  27  has not yet been placed on the engine block  14 . The bottom side  29  of the cylinder head  28  facing the top side  25  of the engine block  14  is therefore still freely accessible. Preferably the injection nozzles  26  have not yet been connected to fuel lines. Nor must the spark plugs  27  yet be connected to the circuit of the ignition system. 
   All injection nozzles  26  are checked simultaneously in an operating test. Accordingly, during the check the injection nozzles  26  are not supplied with fuel but instead with a fluid test medium, in particular compressed air at room temperature and having a pressure between 1 and 5 bar, preferably 2 to 3 bar. The compressed air can be taken from a usual source of compressed air. 
   Likewise employed for checking the injection nozzles  26  is a surface pressure sensor  30  arranged at the bottom side  29  of the cylinder head  28  in the region of each combustion chamber  31 . The surface pressure sensor  30  can have the configuration and operation mode of the previously described surface pressure sensor  24 . In this respect, reference will be made to the remarks describing the checking of piston cooling nozzles  10  in conjunction with  FIGS. 1 and 2 . 
   A surface pressure sensor  30  is arranged under each combustion chamber  31  located at the bottom side  29  of the cylinder head  28 . The surface pressure sensor  30  is dimensioned such that it completely covers the respective combustion chamber  31 , preferably with a circular overlapping of the marginal region of the bottom side  29  of the cylinder head  28  around the combustion chamber  31 . The surface pressure sensors  30 , which are preferably identical to one another, are also detachably affixed individually or in groups to the bottom side  29  of the cylinder head  28  by means of an attachment device (not shown). The checking of the injection nozzles  26  is in principle carried out in the same manner as the checking of the piston cooling nozzles  10 . 
   The injection nozzles  26  mounted in the cylinder head  28  are checked in the cold test before the cylinder head  28  is joined with the engine block  14 . To this end, each combustion chamber  31  is assigned its own surface pressure sensor  30 , which is affixed at its bottom side  29  which is still open for access. Either all of the surface pressure sensors  30  (or groups comprising a plurality thereof) are arranged together, i.e. simultaneously, under the bottom side  29  of the cylinder head  28 , or the surface pressure sensors  30  are individually attached at these positions in succession. In the process, each surface pressure sensor  30  covers a combustion chamber  31 . 
   The injection nozzles  26  are checked simultaneously. To this end, each injection nozzle  26  is provided with a continuous, i.e. non-interrupted, supply of compressed air during the checking operation. The compressed air emitted from each injection nozzle  26  forms a test jet which strikes the surface pressure sensor  30  located opposite the respective injection nozzle  26 . In the process, the surface pressure sensor  30  measures the compressed air or test jet emitted from the injection nozzle  26 . On the basis of this measurement, the surface pressure sensor  30  can, on one hand, determine the position of impact of the test jet. On the other hand, it can also determine the pressure at which the test jet strikes the surface pressure sensor  30  as well as the form and dimensions of the test jet. 
   The above detailed description of the preferred embodiments, examples, and the appended figures are for illustrative purposes only and are not intended to limit the scope and spirit of the invention, and its equivalents, as defined by the appended claims. One skilled in the art will recognize that many variations can be made to the invention disclosed in this specification without departing from the scope and spirit of the invention. 
   LIST OF DESIGNATIONS 
   
       
       
         
             10  piston cooling nozzle 
             11  piston 
             12  cylinder 
             13  cylinder bore 
             14  engine block 
             15  cooling duct 
             16  combustion chamber recess 
             17  top side 
             18  supply duct 
             19  bottom side 
             20  coolant feeder 
             21  tube section 
             22  cooling nozzle end 
             23  cylinder center axis 
             24  surface pressure sensor 
             25  top side 
             26  injection nozzle 
             27  spark plug 
             28  cylinder head 
             29  bottom side 
             30  surface pressure sensor 
             31  combustion chamber