Abstract:
A system and method for testing partially assembled engines for possible oil leaks. The system includes engine pressurizing devices that are automatically controlled by a controller according to a predetermined control program based upon the engine model type being tested. The pressurizing devices introduce pressurized air into the engine oil system. A leak testing unit monitors the pressurized engine for pressure drops indicative of an oil seal leak. Air pressure leaks resulting from inherently air-porous EGR valves are compensated for by an EGR compensating unit, which provides pressurized air to an intake side of the EGR valve. The flow of pressurized air through the EGR compensating unit is monitored to determine whether there is a problem with the EGR valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application is related to U.S. patent application Ser. No. ______, filed Jan. 5, 2006 (Rankin Hill Docket No. HON-16433), the disclosure of which is expressly incorporated herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is generally directed toward manufacturing and testing methods and, more particularly, toward a system and method for testing an engine on a production line for oil leaks. 
         [0004]    2. Description of Related Art 
         [0005]    During the manufacture of an automobile engine, it is necessary to confirm that the engine&#39;s oil system does not leak. In the past, oil leak testing has been a manual operation in which an associate on the production line manually connects a flow leak tester to the engine, and the flow leak tester measures the amount of air flowing through, and out of, the oil passage. If the flow rate is greater that a predetermined limit, an alarm is sounded and the engine is sent to the repair area to be checked. Because the engine is not completely sealed during the manual leak test, some of the air flows past the piston rings, into the combustion chambers, and out the open exhaust and intake valves. The amount of air that flows past the piston rings is dependent on variables that are difficult, if not impossible, to control. For example, these variables include the amount of oil on the piston and piston rings, how long the engine has set on the production line, and the orientation of the crankshaft. 
         [0006]    Because of these variables, the manual leak testing method requires that the alarm limits be set high to compensate for the amount of air that blows by the piston rings (hereinafter referred to as ‘blow-by’) and the fluctuation in the blow-by, due to the uncontrollable variables. Since many of the oil leaks are smaller than the blow-by, many small oil leaks cannot be detected by the manual leak testing method. 
         [0007]    Therefore, there exists a need in the art for a system and method to more accurately and reliably detect oil leaks in an engine. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is directed toward a system and method for testing an engine for possible oil leaks, wherein the system is automated and wherein the method can be performed on an engine production line without interrupting the production timing or sequence. 
         [0009]    In accordance with the present invention, the system includes a series of head seal units that are individually associated with portions of the engine. The head seal units are adapted to seal against the associated portions of the engine, and to provide a flow of pressurized air to the engine. 
         [0010]    In further accordance with the present invention, some of the head seal units are adapted to introduce pressurized air into the engine oil system, while at least one other head seal unit is adapted to provide pressurized air to an intake side of an EGR valve and thereby offset or compensate for air leakage inherent in the EGR valve. 
         [0011]    In further accordance with the present invention, a leak testing unit and an EGR compensation unit are provided. The leak testing unit controls pressurization of the engine, and is adapted to sense a drop in air pressure within the pressurized engine that is indicative of a possible oil seal leak. The EGR compensation unit is adapted to monitor a rate of air flow to the EGR valve, and is operable to determine whether the EGR valve is leaking air at a rate indicative of a possibly faulty EGR valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    These and further features of the invention will be apparent with reference to the following description and drawings, wherein: 
           [0013]      FIG. 1  is a schematic front view of an engine and a pressurizing apparatus; 
           [0014]      FIG. 2  is a schematic top plan view of the engine and portions of the pressurizing apparatus; 
           [0015]      FIG. 3  is a schematic side view of the engine and portions of the pressurizing apparatus; 
           [0016]      FIG. 4  is a schematic illustration of a control system for the leak testing station; 
           [0017]      FIG. 5  is a schematic illustration of pneumatic connections for the leak testing station; 
           [0018]      FIG. 6  schematically illustrates a leak testing station and engine prior to a leak testing procedure; 
           [0019]      FIG. 7  schematically illustrates a similar leak testing station and engine during a leak testing procedure 
           [0020]      FIG. 8  schematically illustrates a leak testing station as in  FIG. 7 , but with an adaptor for accommodating an engine with an exhaust manifold outlet secured thereto; and, 
           [0021]      FIG. 9  is a flowchart showing steps of a leak testing method according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    With reference to  FIGS. 6-8 , a portion of a production line incorporating an engine oil leak testing station  100  is schematically illustrated. The production line includes a conveyor belt  102  that extends through the testing station  100 . The conveyor  102  transports partially assembled engines  10 , each disposed upon a pallet  11 , toward the testing station  100 . The conveyor  102  also transports tested engines away from the testing station for further assembly or repair, depending upon the results of the oil leak test, as described hereinafter. 
         [0023]    With reference to  FIGS. 1-3 , the engine  10  includes a cast engine block  12 , a crankcase  14 , an air intake base  16 , a pair of exhaust manifolds  18 , first and second head covers  20 ,  22 , and an exhaust gas recirculation (EGR) valve  24 . 
         [0024]    The EGR valve  24  permits exhaust gas to be communicated from an exhaust of one or more of the engine cylinders back to an intake manifold (not shown) via the air intake base  16 , so as to mix exhaust gas with incoming fresh combustion air and thereby improve engine efficiency. As such, the EGR valve  24  has an exhaust side that communicates with the exhaust of the engine  10 , and an intake side that communicates with the intake manifold via an EGR port  26  formed on the top surface of the air intake base  16 , as shown best in  FIG. 2 . 
         [0025]    The first head cover  20  includes an oil fill tube  28  and the second head cover  22  includes a port  30 , which is sometimes referred to as a breather port. 
         [0026]    The air intake base  16  receives fresh combustion air and recirculated exhaust gases from the air intake manifold (not shown) and communicates a combustion air mixture to each of the cylinders. The air intake base  16  includes a series of air intake passageways  31 , each of the passageways  31  being dedicated to a particular cylinder. 
         [0027]    Each exhaust manifold  18  receives exhaust gases from cylinders on an associated side of the engine  10 , and includes an exhaust port  32  that is connected to a vehicle exhaust system (not shown) and through which the exhaust gases flow. 
         [0028]    It is noted that the engine  10  described to this point is relatively conventional and well known in the art, and that the engine structure forms no part of the present invention. It is further noted that the engine oil leak testing system and method of the present invention is not limited to the engine structure described herein, which is exemplary in nature. Rather, it is considered apparent that, with the principles described herein, one skilled in the art could easily adapt the system and method of the present invention to any engine design. 
         [0029]    The engine  10  includes a series of oil seals that prevent engine oil, which is held in the crankcase  14  and distributed throughout the engine (i.e., oil system), from leaking out of the engine  10 . These oil seals include one or more seals installed in the engine block  12  and the crankcase  14 , and between the head covers  20 ,  22  and the engine block  12 . The testing station tests the oil seals for leaks by pressurizing the engine  10  and monitoring the pressurized engine for air leaks indicative of a leak at one or more engine oil seals. 
         [0030]    With continued reference to  FIGS. 1-3 , portions of a pressurizing apparatus provided by the testing station  100  are schematically illustrated in connection with the engine  10  that is to be tested. The pressurizing apparatus includes a series of pressure or pneumatic connectors that sealingly engage associated portions of the engine  10  and that are used to introduce pressurizing air into the engine  10  so as to pressurize the oil system and the intake and exhaust passages of the engine  10 . 
         [0031]    The pressure connectors are provided by a pair of exhaust manifold seal head units  40 , an engine oil fill tube seal head unit  42 , a head cover port seal head unit  44 , an injector base seal head unit  45 . As will be apparent from the following description, the injector base seal head unit  45  includes pressure connectors for the individual air passages  31  as well as for the EGR port  26 . For purposes of clarity of description, the air passage pressure connectors will be referred to hereinafter as being provided by the air intake seal head unit  46  and the EGR port pressure connector will be referred to hereinafter as being provided by the EGR port seal head unit  48 , although they are actually all disposed on the injector base seal head unit  45 . 
         [0032]    As will be appreciated, the exhaust manifold seal head units  40  are adapted to sealingly engage the exhaust manifolds  18 ; the engine oil fill tube seal head unit  42  is adapted to sealingly engage the oil fill tube  28 ; the head cover port seal head unit  44  is adapted to sealingly engage the head cover port (breather port)  30 ; the injector base seal head unit  46  is adapted to sealingly engage the air intake passageways  31  in the air intake base  16 ; and the EGR port seal head unit  48  is adapted to sealingly engage the EGR port  26  formed in the air intake base  16 . 
         [0033]    The seal head units  40 ,  42 ,  44 ,  45  are disposed on associated mechanisms, described hereinafter, so as to be movable toward and away from the engine  10 . Accordingly, the seal head units  40 ,  42 ,  44 ,  45  are normally in a relatively retracted position between testing procedures and during a testing procedure are moved into an extended position in sealing engagement with associated portions of the engine  10 . Shortly thereafter, pressurized air from a source of pressurized air is introduced via the seal head units  40 ,  42 ,  44 ,  46  into the engine  10 . 
         [0034]    More specifically, pressurized air is introduced into the engine  10  via the oil fill tube  28 , the exhaust manifold ports  32 , the air intake passageways  31 , and the head cover port  30 , which are hereafter collectively referred to as the engine pressurizing ports, and used to pressurize the engine  10 . Pressurized air is also provided to the EGR valve  24  via the EGR port  26  and the EGR port seal head unit  48 . As will be appreciated from the following description, pressurized air provided via the EGR port  26  is used to compensate or offset for leakage inherent in the EGR valve  24 , and thereby eliminates the leaky EGR valve  24  as a source of error in the engine oil leak testing method. 
         [0035]    With reference to  FIG. 4 , a control system for the leak testing station  100  is schematically illustrated. The control system includes a programmable logic controller  50  (PLC), an RF reader  52 , a series of sensors and remote input/output devices  54 , an EGR compensation unit  60 , a leak testing unit  62 , actuators  64  and robots  66 . 
         [0036]    The RF reader  52  includes an RF control board  56  and RF antenna  58 . The sensors  54  include a sensor for detecting the presence of a pallet/engine at the entrance of the testing station, a sensor for detecting the presence of a pallet/engine at a testing location within the testing station, and various sensors and interlocks for safe operation of the testing station. 
         [0037]    The PLC  50  controls activation of the RF reader  52 , receives information from the RF reader  52  (i.e., RF control board  56  and RF antenna  58 ) and the sensors  54 , and initiates desired operating programs to control components of the testing station  100 , such as the EGR compensation unit  60  and the leak testing unit  62 , so as to automatically perform an engine oil leak testing procedure, as will be described hereinafter. The PLC program controls operation of the EGR compensation unit  60  and leak testing unit  62 , as well as movable components of the testing station  100 , such as actuators  64  for moving associated sealing head units (i.e.,  42 ,  44 ,  45 ) into engagement with their corresponding engine ports, and robots  66  that carry sealing head units (i.e.,  40 ) thereon. 
         [0038]    With reference to  FIG. 5 , a pneumatic system for the engine leak testing station is schematically illustrated. In addition to the previously described leak testing unit  62  and EGR compensation unit  60 , the pneumatic system includes quick charge valves  68  and pressure regulators  70 ,  72 . The quick charge valves  68  receive plant air and, under the control of the leak testing unit  62 , output a high volume of air, at a predetermined reduced pressure, to the engine pressurizing ports for introduction into the engine  10 . 
         [0039]    Similarly, the leak testing unit  62  receives reduced pressure air from the pressure regulator  72 , and supplies this reduced pressure air to the engine pressurizing ports. Preferably, the outputs of the quick charge valves  68  and the leak testing unit  62  are fluidly connected to the exhaust manifold seal head units  40 , the engine oil fill tube seal head unit  42 , the head cover port seal head unit  44 , the air intake seal head unit  46  so as to provide pressurized air to the corresponding engine pressurizing ports. Further, the air supplied to the engine pressurizing ports via the quick charge valves  68  is at the same pressure as the air supplied to the engine pressurizing ports via the leak testing unit  62 , with the quick charge valves  68  serving to quickly fill the engine  10  with pressurized air, and the leak testing unit  62  serving to subsequently monitor air leakage from the pressurized engine, as will be apparent from the following discussion. 
         [0040]    Likewise, the EGR compensation unit  60  receives reduced pressure air from the pressure regulator  70  and supplies this reduced pressure air to the EGR intake port  26  via the EGR port seal head unit  48 . The air supplied to the EGR intake port  26  via the EGR compensation unit  60  is at the same pressure as the air supplied to the engine pressurizing ports by the quick charge valves  68  and the leak testing unit  62 , with the EGR compensation unit  60  serving to offset or compensate for leakage of air from the EGR valve  24  and thereby permit more accurate detecting of engine oil leaks, as will be discussed further hereinafter. 
         [0041]    With reference to the drawings of  FIG. 6-7 , and the flow chart of  FIG. 9 , the leak testing station  100  is integrated or incorporated into the engine production line, and is fully automated. The engine  10  is disposed on the engine pallet  11 , and moves with the assembly conveyor  102 , which runs through the leak testing station  100 . The pallet  11 , with the engine  10  to be tested, arrive at an entrance of the testing station on the conveyor. When the engine  10  and pallet  11  are detected at the entrance of the testing station  100 , the PLC program turns on an output to the RF control board  56  to start an engine pallet RF read cycle, which reads the engine&#39;s serial number from an RF data storage tag (not shown) located on the side of the pallet  11 . The information on the RF tag is read by the RF antenna  58  and into the RF control board  56 . The engine data is transferred to the PLC  50 , and the PLC  50  decodes the engine model or type from the engine serial number (step  200 ). The PLC  50  compares the engine model type to information on a model lookup table stored in the PLC memory or elsewhere to confirm that the model type is valid (step  202 ). Should the model type not be present in the PLC lookup table, the PLC  50  turns on an alarm output indicating that the engine should be removed (step  204 ) and stops the automatic cycle. If the model type exists, the PLC  50  selects and loads a predetermined test program for that engine model type to control subsequent operation of the leak testing unit  62 , the EGR compensation unit  60  as well as the robots  66  and actuators  64  (step  206 ). 
         [0042]    For example, the predetermined test programs may vary between various model types by changing the predetermined time for charging the engine with pressurized fluid (to accommodate differences in the internal volume of the oil system between different engine models) and by changing the operation of the robots  66  to correctly seat the exhaust manifold seal head units  40  against the exhaust manifolds  18  (and to accommodate different exhaust manifold configurations—i.e.,  FIG. 8 , described hereinafter). In this regard, it is considered apparent that other methods of indicating or inputting the engine model type may be employed, such as a bar code scanner or equivalent optical methods, or that the predetermined program may be a default program or a user-selected program should the assembly line handle only one or a limited number of engine models. 
         [0043]    If the model number is valid (i.e., in the model lookup table), the PLC program releases the engine  10  and pallet  11  to move into the testing station  100 . The engine  10  and pallet  11  move from the station entrance to a work location inside the test station  100 . Once the engine is detected at the work location, the PLC program engages the pressure connectors or seal head units with the engine (step  208 ). 
         [0044]    More specifically, the PLC program first advances the intake manifold seal head unit  45  onto the intake manifold (injector base  16 ) by activating the appropriate actuator  64 . The EGR port opening  26  and the intake openings (ports)  31  on the injector base  16  are individually sealed by associated pressure connectors provided by the intake manifold seal head unit  45  upon actuation of the corresponding actuator  64 . As noted previously, the air passage pressure connectors are pneumatically connected to each other by way of pneumatic circuits, which are preferably provided within the intake manifold seal head unit  45 , while the EGR port pressure connector is fluidly isolated from the air passage pressure connectors. The oil fill opening seal head unit  42  advances to seal the oil fill opening  28  by actuation of the associated actuator  64 . The PLC program then activates appropriate actuator  64  to advance the head cover port seal head unit  44  and seal the head cover port  30 . 
         [0045]    The PLC program then sends a robot cycle start signal to the exhaust manifold sealing robots  66 . The robots simultaneously advance and move the exhaust manifold seal head units  40  into sealing engagement with the exhaust manifolds  18  (ports  32 ). At this point, all of the openings in the engine  10  where air could normally leak out to atmosphere are sealed, and the PLC program sends a start signal to the leak testing unit  62 . 
         [0046]    Thereafter, a charging step (step  210 ) is initiated, whereby the leak testing unit  62  activates the quick charge valve  68  to provide a large volume of air at a predetermined pressure to fill the engine  10  being leak tested in a short period of time. The output airlines of the quick charge valve  68  are connected to all of the seal head units for the engine pressurizing ports (i.e., exhaust manifold seal head unit  40 , intake manifold seal head unit  46 , oil fill opening seal head unit  42 , and breather port seal head unit  44 ). This pneumatic configuration provides a quick and even pressurization of the engine oil system. The quick charge valve remains on for a predetermined amount of time and then is turned off, while the leak testing unit  62  continues supplying air pressure during the charge cycle of the test to the engine  10  at a predetermined pressure and charge time. 
         [0047]    At a predetermined time during the leak testing unit&#39;s charge cycle, the PLC program sends a start signal to the EGR compensation unit  60  to zero a mass air flow meter, which is inside the EGR compensation unit  60 , at the flow rate of air leaking through the intake side of the EGR valve  24 . The air supplied to the intake side of the EGR valve  24  is at an equal pressure, with large flow capacity, to the air supplied by the leak testing unit  62  to the EGR valve exhaust side by way of the engine  10  to which the valve  24  is connected. 
         [0048]    After the EGR compensation unit  60  is zeroed, and once the leak testing unit  62  completes the charge cycle (i.e., after a predetermined amount of time), the leak testing unit  62  will cut off the supply of pressurized air to the engine via the engine pressurization ports, and will pause for a predetermined amount of time to allow the engine pneumatics to equalize or balance. During this time, pressurized air flow to the EGR valve  24  from the EGR compensation unit  60  is maintained (step  212 ). 
         [0049]    After the balancing step, the leak testing unit  62  will monitor the pressure inside the engine for a predetermined period of time to detect any changes in the pressure of the air that has been trapped inside the engine (known hereinafter as the detect cycle). The change (drop) in air pressure during the detect cycle is compared to a predetermined alarm limit by the leak testing unit  62 . If the air pressure change exceeds the predetermined alarm limit in the leak testing unit  62 , the leak testing unit  62  sends an alarm signal to the PLC  50 . At the same time (i.e., after the EGR compensation unit  60  receives the zero signal from the PLC  50 ), the air flow rate from the EGR compensation unit  60  is measured and monitored by the mass air flow meter and compared to predetermined upper and lower alarm limits (step  214 ). If the rate of air flow from the EGR compensation unit  60  exceeds the alarm limit during the test (after the zero function) an alarm output is sent to the PLC  50  from the EGR compensation unit  60 . Specifically, air flow rates through the EGR compensation unit  60  above the alarm limits are consistent with a problem in the EGR valve  24 , and warrant further inspection prior to passing the engine for further assembly. 
         [0050]    The PLC  50  receives the test results from the EGR compensation unit  60  and the leak testing unit  62  (step  216 ). When a no-good test result occurs (i.e., when one of the alarm limits is exceeded), the PLC program returns the seal head units to their home positions by actuation of the robots  66  and actuators  64 , and turns on a pallet repair pin set output to set a repair pin on the pallet  11  (indicating a no-good test occurred) (step  218 ). If the test results from EGR compensation unit  60  and the leak testing unit  62  do not exceed the predetermined alarm limits (i.e., test result is ‘ok’), the PLC  50  returns all of the seal head units to their home position. When the test results are ‘ok’, the pallet repair pin is not set (step  220 ). 
         [0051]    The PLC  50  retrieves the temporarily stored engine serial number (previously read from the pallet RF tag) and combines it with the test result data from the EGR compensation unit  60  and the leak test unit  62 . The engine number and the test result data is then compiled by the PLC program into a predetermined format and transmitted to the printer  80  and to a data storage system  82  ( FIG. 4 ). The engine is then released from the testing station  100 , and the PLC program returns to its initial or start condition to prepare for receipt and testing of another engine. 
         [0052]    It is believed apparent that the engine oil leak testing method and system of the present invention is capable of use with many different engine designs, and at different stages of the engine assembly. For example,  FIG. 8  illustrates an alternative engine  10 ′ to which an exhaust manifold extension  18   a  has been assembled prior to initiation of the leak testing procedure. Due to manufacturing considerations, it may be desirable to install such an extension  18 a prior to the leak test. The illustrated extension includes an open port that is adapted to receive a sensor, such as an oxygen sensor. To prevent leakage of air from the open port, a modified exhaust manifold head seal unit  40   a  is provided, and includes a plug  40   a ′ that fits into the open port and a pressure connection  40   a ″ that sealing engages an open end of the extension  18   a  and through which pressurizing air is introduced into the exhaust manifold  18 . With the method and system of the present invention, when an engine  10 ′ having such an extension  18   a  is detected at the testing station entrance (i.e., via the RF tag/engine serial number), the robots  66  will preferably exchange the exhaust manifold seal head unit  40  for a modified exhaust manifold seal head unit  40   a  and the predetermined operating program will activate the robot  66  so as to properly position and seal the modified head unit  40   a  with the extension  18   a , as described above. 
         [0053]    Accordingly, the leak testing station and method described hereinbefore permits automated testing of partially manufactured engines for oil leaks. The entire testing procedure, from detection of the engine to release of the engine, only takes about 20-30 seconds. The actual pressurizing and testing steps (charging to leak detection) is performed in about 12-17 seconds. Accordingly, the leak testing station maybe incorporated into the production line, and the testing method may be performed on each engine without slowing the production line. Further, it is noted that the pressure developed within the engine is relatively low (i.e., about 0.20 kg/cm 2 ) so the time to charge the engine is relatively small, and the pressure developed on the oil seals is below the rated limits of such oil seals.