Abstract:
A system designed to simulate an internal combustion engine having improper valve timing is provided. The purpose of the simulation system is to calibrate and/or validate a proprietary cam-crank correlation diagnostic algorithm. The simulation system includes a simulator module that communicates with crankshaft and camshaft position sensors and an engine control module. The simulator module includes: a first selector that selects a shift value for shifting a periodic signal; and a modification module that receives a camshaft position signal from the camshaft position sensor and that generates a modified camshaft position signal based on the crankshaft position signal and the shift value.

Description:
FIELD 
     The present invention relates to diagnostic systems for internal combustion engines. 
     BACKGROUND 
     The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
     An internal combustion engine can include one or more intake and/or exhaust camshafts that regulate the timing of intake and/or exhaust valves. A camshaft position sensor generates a camshaft position signal indicating a position of the camshaft. A control module monitors the camshaft position signal to determine engine position. The control module performs diagnostics to ensure that the engine position is reliable. 
     During development of the diagnostics, technicians disassemble the engine and reinstall the camshafts in a manner such that they are either advanced or retarded with respect to the crankshaft. The diagnostics are then tested to verify proper operation. For example, the diagnostics should be able to diagnose whether the rotation of the camshaft and the crankshaft are properly synchronized. This method of disassembling and reassembling the engine is costly and time consuming. 
     SUMMARY 
     Accordingly, A diagnostic system for an internal combustion engine is provided. The diagnostic system includes a diagnostic module that communicates with camshaft position sensor and an engine control module. The diagnostic module includes: a first selector that selects a shift value for shifting a periodic signal; and a modification module that receives a camshaft position signal from the camshaft position sensor and that generates a modified camshaft position signal based on the camshaft position signal and the shift value. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a functional block diagram of an engine system according to various aspects of the present disclosure. 
         FIG. 2  is a functional block diagram of the engine system of  FIG. 1  including a correlation simulation module according to various aspects of the present disclosure. 
         FIG. 3  is a functional block diagram illustrating the correlation simulation module of  FIG. 2  according to various aspects of the present disclosure. 
         FIG. 4  is an illustration of modified camshaft position signals generated by the correlation simulation module according to various aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     Referring now to  FIG. 1 , an engine system  10  includes an engine  12  that combusts an air and fuel mixture to produce drive torque. Air is drawn into an intake manifold  14  through a throttle  16 . The throttle  16  regulates mass air flow into the intake manifold  14 . Air within the intake manifold  14  is distributed into cylinders  18 . Although four cylinders  18  are illustrated, it can be appreciated that the engine  12  can have a plurality of cylinders  18 , including, but not limited to, 2, 3, 5, 6, 8, 10, 12 and 16 cylinders. 
     A fuel injector (not shown) injects fuel that is combined with the air as it is drawn into the cylinder  18  through an intake port. An intake valve  22  selectively opens and closes to enable the air/fuel mixture to enter the cylinder  18 . The intake valve position is regulated by an intake camshaft  24 . A piston (not shown) compresses the air/fuel mixture within the cylinder  18 . A spark plug  26  initiates combustion of the air/fuel mixture, driving the piston in the cylinder  18 . The piston drives a crankshaft (not shown) to produce drive torque. Combustion exhaust within the cylinder  18  is forced out through an exhaust manifold  28  when an exhaust valve  30  is in an open position. The exhaust valve position is regulated by an exhaust camshaft  32 . The exhaust gas flows into an exhaust system (not shown). Although single intake and exhaust valves  22 , 30  are illustrated, it can be appreciated that the engine  12  can include multiple intake and exhaust valves  22 , 30  per cylinder  18 . 
     The engine system  10  can include an intake cam phaser  34  and/or an exhaust cam phaser  36  that respectively regulate the rotational timing of the intake and exhaust camshafts  24 , 32 . More specifically, the timing or phase angle of the respective intake and exhaust camshafts  24 , 32  can be retarded or advanced with respect to each other or with respect to a location of the piston within the cylinder  18  or crankshaft position. In this manner, the position of the intake and exhaust valves  22 , 30  can be regulated with respect to each other or with respect to a location of the piston within the cylinder  18 . By regulating the position of the intake valve  22  and the exhaust valve  30 , the quantity of air/fuel mixture ingested into the cylinder  18  and, therefore, the engine torque is regulated. A control module  40  controls the phase angle of the intake cam phaser  34  and exhaust cam phaser  36  based on a desired torque. 
     Referring now to  FIG. 2 , a side view of the engine system  10  is shown. The exhaust camshaft  32  ( FIG. 1 ) and the intake camshaft  24  ( FIG. 1 ) are coupled to the crankshaft (not shown) via sprockets  52 A,  52 B, and  52 C and a timing chain  54 . The engine system  10  outputs a crankshaft signal  59  indicating the position of the crankshaft. The crankshaft signal  59  is generated by the rotation of a wheel  56  coupled to the crankshaft. The wheel  56  can have a plurality of teeth. A crankshaft position sensor  58  senses the teeth of the wheel and generates the crankshaft signal  59  in a periodic form. The control module  40  decodes the crankshaft signal  59  to a specific tooth number of the wheel  56 . The crankshaft position is determined from the decoded tooth number of the wheel  56 . 
     Similarly, a camshaft position sensor  60  senses the teeth of a wheel  62  coupled to the exhaust camshaft  32  ( FIG. 1 ) and generates a camshaft signal  63   a . A camshaft position is determined from the camshaft signal  63   a . As can be appreciated, a wheel (not shown) and camshaft position sensor (not shown) can be coupled to the intake camshaft  24  ( FIG. 1 ), either additionally or alternatively. From the camshaft position and the crankshaft position, the control module  40  can determine an overall engine position. In addition, the control module  40  can diagnose the operation of the exhaust camshaft  32  and crankshaft. 
     To verify proper operation of the diagnostics performed by the control module  40  and/or to permit calibration development, a correlation simulation module  64  can be disposed between the camshaft position sensor  60 , the crankshaft sensor  58 , and the control module  40 . The correlation simulation module  64  permits real-time modification of the camshaft position signal  63   a . The modification can have a selectable magnitude. 
     In an exemplary embodiment, as shown in  FIG. 3  and with continued reference to  FIG. 2 , the correlation simulation module includes one or more selectors such as a switches (e.g., rotary switches) that allow an operator to selectively alter the camshaft signal  63   a . In various other embodiments, the selectors can be implemented by other selection devices, such as, the use of jumpers or potentiometers. 
     In various embodiments, a first selector  70  selects which camshaft signal  63   a  to be modified (for engine systems  10  with more than one camshaft sensor  60 ). A second selector  72  selects the number of teeth or a pulse value by which the camshaft signal  63   a  is to be shifted. A third selector  74  selects whether the camshaft signal  63   a  is to be advanced or retarded. 
     A modification module  76  receives as input the crankshaft signal  59 , a signal  73  indicating the camshaft signal  63   a  to be modified, a signal  75  indicating the number of teeth by which to shift the selected camshaft signal  63   a , and a signal  77  indicating whether to advance or retard the selected camshaft signal  63   a . The modification module  76  monitors the crankshaft signal  59  for a position of the crankshaft and the number of teeth per revolution of the wheel  56 . In various embodiments, the modification module  76  maintains a memory of the selected camshaft signal  63   a  waveform for each revolution. Based on the selected inputs  73 ,  75 , and/or  77  and the stored waveform, the modification module  76  generates a modified camshaft signal  63   b . In various embodiments, the modified camshaft signal  63   b  is either retarded or advanced relative to the crankshaft signal  59  by the selected pulse value or number of teeth. 
     For example, as shown in  FIG. 4  and with continued reference to  FIGS. 2 and 3 , an exemplary crankshaft signal  59  is shown at  80 . An exemplary camshaft signal  63   a  is shown at  82 . Modified camshaft signals are shown at  84  and  86 . When “two teeth” and “retarded” are the selected inputs, the modification module  76  generates a modified camshaft signal  84  that is retarded by two pulses or teeth as shown at  88 . When “two teeth” and “advanced” are the selected inputs, the modification module  76  generates a modified camshaft signal  86  that is advanced by two pulses or teeth as shown at  90 . The modified camshaft signal  63   b  and the crankshaft signal  59  are output to the control module  40  for diagnosing. The modified camshaft signal  63   a  allows the control module  40  to diagnose errors without altering engine system components. 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure has been described in connection with particular examples thereof, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and the following claims.