Abstract:
A method and apparatus for developing a test for determining if an engine has oil seal leaks. The engine is charged with a predetermined pressure of air and monitored by a leak tester. A digital valve is set to provide a certain leak rate based upon signals received from a digital valve controller. Thereafter, based upon signals received from a PC and a main control unit, a variety of trials are completed. The results and programs are stored in the PC. Results of the trials allow an optimized testing program to be selected that would be best suited for use on a manufacturing assembly line.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention generally relates to engine leak testing and more specifically, toward a method for developing a program for engine leak testing that will subsequently be used on a manufacturing assembly line. 
   2. Description of Related Art 
   During the manufacture of engines, it is desirable to test the assembled engine to determine if any of the various oil seals are leaking. Due to the construction of modern engines, it has proven difficult to develop engine leak testing methods that can be employed quickly, as is required for manufacturing efficiency. Furthermore, the testing methods are usually specific to individual engine types and thus new testing programs must be developed every time a new engine design is produced. 
   Development of these testing programs can be very labor intensive and requires a large amount of time. For example, when developing the testing programs, one of the set parameters, the leak rate, may range from 100 cc/min to 5000 cc/min, in increments of 25 cc/min. This results in about 200 different trials that must be run in order to properly develop a new program. 
   One known testing method that has been employed in the past involves having a user manually adjust and confirm the leak rate for each incremental change. Running the trials at different leak rates requires that the user change orifices to adjust the set leak rate. And, as each trial is typically run 3 to 5 times, development of a single program can require several hundred iterations. Furthermore, a wait time of typically two minutes is used between trials to ensure that any fluid pressure in the engine from the previous trial has dissipated. Accordingly, the known testing method is not an effective technique for developing a program for detecting engine oil leaks. 
   Therefore, there exists a need in the art for a method of efficiently developing testing programs for an engine. 
   SUMMARY OF THE INVENTION 
   The present invention is directed toward a method for developing a testing program to analyze an engine for oil leaks. In accordance with the present invention, a plurality of leak testing programs may be sequentially run on a subject engine. During each testing program, the engine is charged with pressurized air. After the engine is pressurized, the supply of pressurized air to the engine is discontinued and a digital valve is opened to allow pressurized air to leak from the engine at a predetermined controlled rate while the engine pressure is measured for a predetermined period of time. The measured pressure drop is used to establish the rate at which the engine leaks. After running several test programs, it can be determined which program would be best suited for use on the assembly line to test new engines. Therefore, the testing procedure of the present invention permits selection of the optimum testing program for subsequent use on the assembly line to permit leak testing of each engine during assembly or manufacture thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and further features of the invention will be apparent with reference to the following description and drawings, wherein: 
       FIG. 1  is a schematic view of a leak tester development system; 
       FIG. 2  is a schematic view of a digital valve of the leak tester development system; and 
       FIG. 3  is a flow chart illustrating a method of using the leak tester development system. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIG. 1 , a leak tester development system  10  is illustrated. The leak tester development system  10  includes a main control unit  12 , a leak tester  14 , a computer (PC)  16 , a digital valve controller  18 , and a digital valve  20 . Further, an engine  22  is attached to the leak tester  14  and the digital valve  20  by a supply hose  24  and a discharge tube  26 , respectively. The supply hose  24  and discharge tube  26  are fluidly connected to the same cavity in the engine  22 . 
   The main control unit  12  includes an MCU CPU  28 , three quad optical isolators  30 ,  32 ,  34 , a driver chip  36 , a voltage regulator  38 , and a filter capacitor  40 . A cable CF is connected between a port C of the main control unit  12  and a port F of the leak tester  14 . Further, a cable DE is connected between a port D of the main control unit  12  and a port E of the leak tester  14 . The main control unit  12  communicates with the PC  16  through the port B, cable BG, and port G. Finally, the main control unit  12  communicates with the digital valve controller  18  via port A, cable AH, and port H. 
   The digital valve controller  18  includes an integrated circuit converter  42 , a digital control valve (DVC) CPU  44 , optical isolators  46 , and a terminal strip  48 . The digital valve controller  18  communicates with the digital valve  20  through the terminal strip  48  and a cable IJ. 
   With reference to  FIGS. 1 and 2 , the digital valve  20  includes a manifold  50  and a plurality of individual valves  52 . Each of the individual valves  52  includes a calibrated orifice  54 . Further, the digital valve  20  has port J for communication with the digital valve controller  18 . 
   With continued reference to  FIG. 1 , the leak tester development system  10  is shown in connection with the engine  22  that is to be tested. The supply hose  24  and discharge tube  26  sealingly engage associated portions of the engine  22 . The supply hose  24  is used to introduce pressurized air into the engine  22  so as to pressurize a cavity the engine  22  (e.g., oil passages), while the discharge tube  26  is used to controllably vent or remove air from the engine  22 . 
   It is noted that the engine  22  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 leak tester development system  10  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 method of the present invention to any engine design. 
   While the components of the leak tester development system  10  are illustrated as being connected to each other with various types of cables or wires, it is considered apparent that other connection means/methods could be utilized to provide the necessary communication between the components. For example, wireless communication methods could be employed to provide communication between the components. 
   With reference to  FIGS. 1 and 2 , assembly and operation of the leak tester development system  10  will now be discussed. A user (not shown) inputs requested data into the PC  16 . Although not limited thereto, the requested data preferably includes a speed that the leak tester  14  and the main control unit  12  will communicate, a first program that will be run, a last program that will be run, a beginning leak rate, an ending leak rate, a leak rate interval, a number of cycles per increment, and a wait time between trials. Alternatively, the requested data may simply be the program to run should the stored programs include all the necessary testing parameters. The programs to be run are pre-loaded or stored in the main control unit  12 . The programs can include an input by the user that represents a first length of time that the system  10  is allowed to charge the engine  22  with air before the digital valve  20  is opened. The programs can also include an input by the user that represents a second length of time that the digital valve  20  is to be open to allow air to escape. The data is then communicated to the main control unit  12  with commercially available terminal software such as Procomm Plus by Symantec of Cupertino, Calif. 
   Power is provided to the main control unit  12  through the voltage regulator  38  and the filter capacitor  40 . The MCU CPU  28  contains software necessary for operation of the leak tester development system  10 . Further, the MCU CPU  28  is connected to two quad optical isolators  30 ,  32  for control of the output to the leak tester  14 , and to one quad optical isolator  34  for the input from the leak tester  14 . The MCU CPU  28  is also connected to the driver chip  36 . The driver chip  36  conditions serial communication between the MCU CPU  28  and the digital valve controller  18  and the PC  16 . 
   The main control unit  12  sends a signal through the port D, via the cable DE, to port E of the leak tester  14 , of the starting and ending programs to be executed. Further, the main control unit  12  instructs the digital valve controller  18  via the port A and the port H (connected by the cable AH), of the starting and ending leak rates, the leak rate interval, the number of cycles per increment, and the wait time between trials. 
   The signals from the main control unit  12 , via cable AH, are converted by the integrated circuit converter  42  into a signal compatible with the DVC CPU  44 . The DVC CPU  44  then responds to the main control unit  12  that the digital valve controller  18  is ready to receive data. After receiving the requested leak rates, the DVC CPU  44  outputs binary coded decimal code that is conditioned by the optical isolators  46 . The optical isolators  46  amplify an output current from the DVC CPU  44  and then send a signal to the terminal strip  48 . 
   In the preferred embodiment, the leak tester development system  10  provides air at about 0.2 kg/cm 2 . However, other air pressures are possible and contemplated. The pressurized air, at the predetermined pressure, is provided to the engine  22  via the leak tester  14 . After the engine  22  is pressurized for a set time as input by the user or the program, the digital valve  20  is set to the desired leak rate and measurements begin. As will be apparent to those skilled in the art, the leak tester  14  is adapted, once the engine  22  is pressurized, to monitor leakage of air from the pressurized engine  22  by sensing or measuring drops in engine pressure. A suitable leak tester is sold by Cosmo Instruments Co., Ltd. of Tokyo, Japan, as model number LS-1841. 
   The port J of the digital valve  20  receives the signals from the terminal strip  48  of the digital valve controller  18  through the cable IJ. These signals control which of the individual valves  52  are opened. When the valves  52  are open, air can flow from the engine  22 , through the discharge tube  26 , the manifold  50 , and then through orifice  54 . Each orifice  54  has a specific flow rate at a specific pressure. As is illustrated in  FIG. 2 , the flow rate of each orifice  54  is binary weighted so that a flow rate from 1 cc/min to over 4000 cc/min, in 1 cc/min intervals is possible. That is, by having valves  52  with flow rates of 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, and 2048 cc/min, a variable flow rate (by 1 cc/min) intervals is achievable. 
   Also, after the trial is completed, test results and settings associated with the specific trial are sent from the port F of the leak tester to the port C of the main control unit  12  through the cable CF. Then, the test results and associated settings are communicated via the port B of the main control unit  12  and the cable BG, to the port G of the PC  16 . Subsequently, a file is created on the PC  16  to record the test results and associated settings. 
   With reference to  FIG. 1  and specifically  FIG. 3 , steps in developing a testing procedure will be described. Initially, the leak tester  14  and the digital valve  20  are sealingly engaged with the engine  22  (step  100 ) and power is supplied to the system  10  (step  102 ). A variety of operating parameters, such as a speed that the leak tester  14  and the main controller  12  will communicate, a first program that will be run, a last program that will be run, a beginning leak rate, an ending leak rate, a leak rate interval, a number of cycles per increment, and a wait time between trials are input into the PC  16  and are subsequently transmitted to other components in the system  10  (step  104 ). Then, air is provided to the engine  22  via the supply hose  24  to charge the engine  22  with pressurized air (step  106 ). After reaching a desired pressure, the air supply is turned off (step  108 ) and the digital valve  20  is set to allow the inputted leak rate (step  110 ) occur. After a required time has passed, engine air pressure is measured (step  112 ) and the leak rate is calculated (step  114 ). The calculated leak rate and operating parameters are then sent to the PC  16  to be recorded (step  116 ). If required by instructions as inputted by the user, the trial can be repeated with alternative leak rates, and durations, all without manual adjustment of the digital valve  20  by the user. 
   While the present invention has been described with particularity herein, it is considered apparent that the numerous modifications or additions may be resorted to without departing from the scope and spirit of the present invention. Rather, taken broadly, the present invention teaches a method of developing programs for pressure testing an engine for possible oil leaks. Accordingly, the present invention is not limited to the preferred embodiment that has been described with particularity hereinbefore, but rather is only to be defined by the claims appended hereto.