Abstract:
A system for detecting conditions indicative of substandard performance of cylinders in a diesel engine includes an engine control unit disposed in operable communication with the engine and a computer disposed in informational communication with the engine control unit. The engine control unit is in operable communication with the engine through a communication element. The system measures the required fuel with all cylinders operating and enables a recommendation to be made with respect to corrective or maintenance measures that should be undertaken with respect to the cylinder. A method for utilizing the system includes comparing fuel requirements of the engine operating under power of all cylinders and under the successive arrest of each of the cylinders. The process is repeated until each cylinder is individually removed and all of the data can be compiled and considered to determine the performance of each individual cylinder.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of and claims the benefit of U.S. patent application Ser. No. 09/788,737, filed Feb. 20, 2001, which claims the benefit of U.S. Provisional Patent Application No. 60/183,214, filed Feb. 17, 2000, the contents of both applications being incorporated herein by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to diesel engines, and, more particularly, to a system and process for detecting conditions indicative of substandard performance of the cylinders within a large scale multi-cylinder diesel engine. 
     BACKGROUND 
     Diesel engines are internal combustion devices in which high compression ratios produce auto ignition of an air/fuel mixture. In such devices, because the air/fuel mixture is ignited under a compressive force, conventional ignition processes (e.g., those utilizing spark ignition, such as that found in an Otto cycle engine) are inapplicable. Thus, fewer options for influencing the combustion method are available. Control of the engines are attained primarily through the influence of a fuel injection process and the amount of fuel injected. Differences in tolerances of the components of an engine oftentimes result in variation in the behavior of each of the individual cylinders of the engine. This variation causes less than optimum performance to be realized by the engine. Such performance is characterized by low power output as a result of weak cylinders. Operation of the engine on a weak cylinder generally results in increased fuel consumption, emission of harmful substances, vibration, excessive noise, and shortened service life. 
     While increased fuel consumption, emission of harmful substances, vibration, excessive noise, and shortened service life are generally indicative of a weak cylinder condition, such indicators require lengthy periods of monitoring of a large number of attributes of the engine. Direct methods of weak cylinder detection have been performed by highly skilled artisans using solely their experience-trained senses. Such methods are more characteristic of art forms than of technical diagnostic processes. In these methods, an operator of a diesel engine brings the engine up to a load and a speed and allows the engine to reach a steady state condition. Thereafter, the operator adjusts the fuel volume flowing from one of the fuel pumps to one of the cylinders. For each cylinder, the skilled operator listens to the sound emanating from the cylinder and makes a determination regarding the response of the cylinder to the changed volume of fuel being supplied. Given even a narrow range of environmental and other conditions, such a determination is generally highly subjective and open to various interpretations even by the same operator. Based on the determination itself, the operator makes a judgment as to the condition of the components of each cylinder and thereby recommends remedial or other action. 
     While such methods have been effective for many years, they are not the most economical, effective, or accurate means of determining the condition of diesel engines. Furthermore, they are certainly not the most time-efficient methods or a means that can be carried out with the frequency required by the operation of large scale equipment into which the diesel engine is incorporated. 
     SUMMARY 
     A method and system for overcoming the drawbacks associated with the detection of conditions indicative of substandard performance of the cylinders in a diesel engine is described herein. The system provides for diagnostic monitoring of the cylinders of the engine by monitoring the system response to the selective temporary arrest of each cylinder as the engine is maintained at a constant load and speed. The method includes making a comparison of the average fuel required per cylinder of the engine operating under the power of all cylinders and a subsequent average fuel requirement for each cylinder of the engine operating under the successive arrest of each of the cylinders or a group of cylinders (at a selected engine speed and load). The process is repeated until each cylinder is individually (or collectively) removed and operationally restored and all of the data can be compiled and considered in order to statistically rank the performance of each cylinder, thereby allowing recommendations to be made concerning corrective measures regarding cylinders that are not performing up to predetermined standards. 
     The system includes an engine control unit disposed in operable communication with the engine and a computer disposed in informational communication with the engine control unit. The engine control unit is in operable communication with the engine through a communication element that includes a valve. The communication element may be a wiring harness. The informational communication with the engine control unit includes a dynamic signal, which controls the amount of fuel being dispensed to each cylinder, and a feedback signal, which provides a quantitative value representative of the amount of fuel being dispensed to each cylinder. The system takes into account speed and load and measures the amount of time over which fuel is dispensed to the cylinder. The time value is compared to an associated value in a linearization or lookup table, thereby allowing a determination to be made regarding the amount of fuel required by the cylinder to maintain the speed and load. Such a determination allows a recommendation to be made with respect to desirable, remedial, or modification measures that should be undertaken with respect to the cylinder. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of the system for the detection of conditions indicative of substandard performance of cylinders in a diesel engine. 
     FIG. 2 is a flowchart illustrating the method of operation of the system for the detection of conditions indicative of substandard performance of cylinders in a diesel engine. 
     FIG. 3 is a flowchart illustrating an alternate method of operation of the system for the detection of conditions indicative of substandard performance of cylinders in a diesel engine. 
     FIG. 4 is a graphical interpretation of a fuel requirement measurement of a cylinder of the engine. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a system for the detection of conditions indicative of substandard performance of the cylinders of a diesel engine is shown generally at  10  and is hereinafter referred to as “system  10 .” System  10  is a diagnostic tool capable of measuring the required fuel per cylinder for an engine having all of its cylinders operational. System  10  is, furthermore, capable of temporarily arresting the operation of each individual cylinder in succession while operating in an analysis mode (i.e., while maintaining a select constant speed and load of the engine) and re-measuring the fuel requirement per cylinder of the engine with all but one cylinder (or all but a group of cylinders) functioning. The conditions detectable by system  10  are generally those indicative of weakened cylinder structure, although other conditions may be detectable. Based on the detected conditions, diagnostic recommendations pertaining to the operation of the engine can thereby be made. 
     System  10  comprises an engine, shown generally at  12 , an engine control unit  14  in informational communication with engine  12 , and a computer  16  in informational communication with engine control unit  14 . Informational communication between engine  12  and engine control unit  14  is maintained through a wiring harness, shown generally at  18 . Computer  16  is installed on board a motor vehicle (not shown) into which engine  12  is incorporated and is integrally configured with other control elements of engine  12 . The motor vehicle may be a railway locomotive. Alternately, a portable computer (not shown) having the requisite software can be used to provide an interface between the operator and system  10 . 
     Engine  12  comprises a plurality of cylinders  24 . Typically, engine  12  comprises eight, twelve, or sixteen cylinders, although it should be understood by one of ordinary skill in the art that any number of cylinders may be assembled to form engine  12 . Each cylinder  24  includes a fuel injection system (not shown) that provides the fuel required for combustion to its respective cylinder  24 . 
     Wiring harness  18  comprises a plurality of connections  26  between each individual cylinder  24  and engine control unit  14 . Each connection  26  includes a valve (not shown) disposed therein to provide control of the fuel flow to each individual cylinder  24 . It should be understood by one of ordinary skill in the art that each connection  26  may be in direct communication with engine control unit  14 . Each individual connection terminates in a single node  28 , which is in turn maintained in communication with engine control unit  14  through a single communication element  30 . As shown, wiring harness  18  includes two nodes  28 , each of which are maintained in communication with engine control unit  14  through communication elements  30 . 
     Computer  16  is communicatively connected to engine control unit  14  such that informational control can be maintained over the operation of engine control unit  14 . The communicative connection between computer  16  and engine control unit  14  is characterized by a dynamic signal  32  and a feedback signal  34 . Control through such signals  32 ,  34  provides for the monitoring of various parameters associated with the operation of engine  12 . In particular, feedback signal  34  enables computer  16  to measure the time over which fuel is dispensed to each cylinder  24  through its respective fuel pump injection system while dynamic signal  32  enables computer  16  to provide control of the amount of fuel dispensed through the fuel pump injection systems. Such control is transparent to the operator. In such a manner the amount of fuel dispensed to each individual cylinder  24  can be obtained, compared to a derived value in a linearization table compiled from calibration data characteristic of the particular design of engine  12 , and independently adjusted, thereby further allowing for the selective operational arrest of any cylinder  24  or combination of cylinders  24  from operation while enabling the remaining cylinders  24  of engine  12  to continue to run. Such a procedure enables information pertinent to each cylinder  24  to be received individually and interpreted collectively. 
     Referring now to FIG. 2, a test sequence of events by which the computer monitors and controls the engine control unit and ultimately the engine is illustrated with a flowchart, shown generally at  36 . Such monitoring and control of the engine through the test sequence of events (as stated above) is transparent to the operator of the motor vehicle. As shown in flowchart  36  the test sequence is initiated with a start command  38 . Start command  38  initiates a command  40  to run the engine at a specified speed and load. The specified speed and load values are selected by control software (not shown). Execution of command  40  to run the engine effectuates the stabilization of the engine at the specified speed and load values. The stabilization generally encompasses the raising of the temperatures of engine oil and water up to steady state operating temperatures. 
     Upon attainment of steady state operating temperatures, a testing sequence is initiated wherein fuel value readings for the engine as it operates under the power of all cylinders are obtained. Such fuel value readings correspond with fuel volumes, which are obtained from the measurement of the flow of the fuel over a time period. A first executable loop is defined by a first acquisition command  42  and a first comparison decision  44 . Upon execution of first acquisition command  42  and first comparison decision  44 , a first set of fuel value readings representative of the total number of fuel value readings are acquired by the computer through the engine control unit. A default value is used to define the number of readings taken for further calculations. Typically, this default value is 250. Mean and standard deviation values of the readings are calculated. The standard deviation value is compared to a first selected maximum allowable value. The first selected maximum value shown in first comparison decision  44  is 10, although any positive value can be programmed into the software code that defines the loop. If the standard deviation value is greater than the first selected maximum allowable value, then control is passed from first comparison decision  44  back to first acquisition command  42  and the first set of fuel value readings is re-collected. If, on the other hand, the standard deviation value is less than the first selected maximum allowable value, then an average of the first set of fuel valve readings is taken and stored and control is passed to a second executable loop defined by a second acquisition command  46  and a second comparison decision  48 . In the second executable loop, a second set of fuel value readings is acquired by the computer. If, in a manner similar to that characteristic of the first set of fuel value readings, the standard deviation of the second set of fuel valve readings is greater than a second selected maximum value (which is the same as the first selected maximum value), then the second set of fuel valve readings is re-collected. However, as above, if the standard deviation value is less than the second selected maximum allowable value, then an average value of the second set of readings is taken. 
     The average values of each set of readings are then compared in an overall comparison decision  50 . If the comparison of the averages is greater than a maximum selected allowable value (which is shown as being 3, although any positive value can be programmed into the software), then both sets of fuel value readings are re-collected. If the value of overall comparison decision  50  is less than the maximum selected allowable value, then control passes to a testing sequence  52  that proceeds such that fuel valve readings are obtained wherein each individual cylinder of the engine is arrested or “cut out” by having its incoming fuel flow reduced to zero, thereby causing the engine to operate on all cylinders except the one arrested while maintaining the selected speed and load. As alluded to above, groups of cylinders or “inquiry sets” that comprise one or more cylinders may also be arrested, thereby allowing the monitoring of the engine to be abbreviated. Combinations and permutations of individual cylinders and inquiry sets are arrested to provide a representation of the overall functioning of the engine. Testing sequence  52  is continued until each individual cylinder or inquiry set of cylinders has been successively arrested and restored to operation. 
     Upon completion of testing sequence  52 , a decision  54  is executed. If, per decision  54 , all cylinders have not been arrested in the engine and data obtained therefor, control is passed back to the first executable loop and the entire procedure is reinitiated. If, however, all cylinders have been successively arrested, control is passed to an analysis function  56  and the data obtained are analyzed by the computer. In analysis function  56 , the amount of fuel consumption for each cylinder for the engine operating on all cylinders is statistically compared with the amounts of fuel consumption for each cylinder for the engine operating with the fuel flow to each of the various cylinders being reduced to zero. Such analysis enables the relative contribution of each cylinder to be ascertained and further used to determine the relative power output of each cylinder. Based on the data, control is passed to a recommendation function  58  wherein recommendations can be made concerning which, if any, components of the engine (particularly the cylinder components) should be replaced. 
     Alternately, testing sequence  52  may be performed immediately subsequent to the execution of command  40 . Referring now to FIG. 3, flowchart  36  is rearranged to illustrate an alternate sequence of monitoring and controlling events. In FIG. 3 control is passed to the first and second executable loops subsequent to the temporary arrest of each cylinder or inquiry set. Data values corresponding to the arrest of the cylinders or inquiry sets are stored in a register and retrieved for analysis as needed upon completion of the second executable loop and prior to decision  54 . 
     Execution of recommendation function  58  may be at a location remote from the operation of the engine. In particular, the data obtained from analysis function  56  may be relayed by any one of a variety of means including, but not being limited to, satellite transmission to a distally located control and command center. In the event that a defective cylinder is found, the decision for maintenance can be made at the control and command center and relayed back to the engine, where it can be carried out by the operator or specified maintenance personnel. 
     Referring now to FIG. 4, a graphical interpretation of a fuel requirement measurement of a cylinder of the engine is shown generally at  60  and is hereinafter referred to as “graph  60 .” In graph  60 , the fuel requirement of the engine per cylinder is plotted as a function of the time over which one or more cylinders are arrested. As can be seen, the fuel requirement of the engine per cylinder at a steady state value  62  is substantially constant over a period of time (t 0  to t 1 ) in which all cylinders of the engine are operational. When the fuel flow to one or more cylinders of the engine is restricted, thereby arresting the cylinder, the fuel requirement of the engine per cylinder increases over a period of time (t 1  to t 2 ) in order to compensate for the loss of power experienced as a result of the arrest of the cylinder. During a period of time (t 2  to t 3 ) in which the cylinder is completely arrested, the fuel requirement of the engine per cylinder reaches a new steady state value  64 . A difference  66  between steady state value  62  and new steady state value  64  is the relative power contributed by one cylinder. For example, in a fourteen cylinder engine, the arrest of one cylinder yields a theoretical overall increase in total fuel consumption per cylinder of 7.14%. The introduction of fuel back into the cylinder over a period of time (t 3  to t 4 ) then causes the fuel requirement of the engine per cylinder with all cylinders operational to decrease back to its original steady state value  62 . Upon reaching the original steady state value  62 , a successive cylinder can be arrested. 
     A diagnostic recommendation of each cylinder can then be made based on analysis of the actual change in the fuel requirement associated with the respective cylinder. The analysis of the diagnostic recommendation may be converted into a quantifiable value from which an objective determination of the condition of the cylinder can be made. If for example, the actual increase in fuel requirement per cylinder of a fourteen cylinder engine upon arrest of a particular cylinder varies substantially from 7.14%, then an operator can conclude that the arrested cylinder is not contributing to the power output at its full potential and that it may be defective and may warrant maintenance or replacement, The analyzing method as described above may be performed when the motor vehicle is in operational travel. 
     While the above-described system for the detection of substandard conditions present in the cylinders of a diesel engine has been described with reference to a preferred embodiment thereof, it should be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.