IDENTIFICATION OF DIESEL ENGINE INJECTOR CHARACTERISTICS

Abstract: A method for identifying particular characteristics of a fuel injection system places a characterization resistor into a power circuit for each fuel injector. The resistance is selected once the characteristics of the fuel injector have been tested after assembly. The control for the fuel injector is able to query the particular fuel injector and determine its characteristics based upon a voltage which has been influenced by the characterization resistance. In another feature of this invention, coded information, such as the characterization resistance, is assigned to a number of possible combinations of characteristics in a spiral fashion if the characteristics were stored in a two dimensional array.

Description: IDENTIFICATION OF DIESEL ENGINE INJECTOR CHARACTERISTICS BACKGROUND OF THE INVENTION The present invention relates to a method and apparatus for incorporating an identifying resistance into a fuel injector to provide an indication of characteristics of the particular injector. Fuel injectors are utilized to assist in the injection of fuel duπng operation of a diesel engine With manufactuπng tolerances, etc.. each fuel injector has distinct characteπstics Fuel injectors have two characteristics that are important to control of the fuel injection process. First, an offset characteristic is defined, and second, a slope of change of the fuel injection ability is defined. As these two characteπstics vary, an optimum control for the particular fuel injector also vanes. Thus, an optimum control would be aware of the characteπstics for a particular injector. An OEM customer of applicant's has proposed that each fuel injector be tested to determine both the offset and slope, and that an identifier be put into the fuel injector to tell an engine control the offset and slope which applies for the particular injector The OEM proposed having a dedicated control, such as a microprocessor, incorporated into the fuel injector to send an identifying signal. The present invention is directed to achieving the identification with a much simpler and lower cost solution. SUMMARY OF THE INVENTION In a disclosed embodiment of this invention, a fuel injector is tested after assembly, and its offset and slope determined. The offset and slope information is then used to characteπze the fuel injection into one of several particular types. A characteπzation resistor of a value indicative of the "type" of injector is then incorporated into a circuit associated with the fuel injector. The diesel engine control can query the fuel injector, and read the voltage due to the characteπzation resistor to determine the "type" of fuel injector. The "type" is then associated with a particular offset and slope for the fuel injector The control will then know how to optimally control the particular fuel injector. In a preferred embodiment of this invention, the fuel injector is provided a coil to open the injector, and a separate coil to close the injector. Each coil is provided with a high side and a low side dnver which are powered to operate the coils in normal operation. As the engine is being started, the system automatically scans the characteπzation resistor of each injector to determine each cylinder's injector "type" Identification current is passed through the characteπzation resistor, which is connected to the high side of coil A and the low side of coil B. By applying the "48 V" power to a resistor network and returning the current to ground via the low side dnver The voltage across the characteπzation resistor is measured at the high side of coil A This voltage is then associated with a prestored code, which in turn tells the control which type of fuel injector is associated with the particular voltage. The present invention thus provides a simple way of identifying each fuel injector type. One particular benefit of this invention is that the wire harness to the fuel injector need not have any additional wire to provide the identification feature. A control method is also disclosed wherein the identification of the particular fuel injector is only performed if the temperature of the control module is below a predetermined temperature. Applicant recognizes that if the control module is above a relatively high predetermined temperature, then the vehicle has not been stopped for any length of time. The need to redetermine each fuel injector type only occurs when a fuel injector has been replaced. The replacement of a fuel injector would require a long shutdown time for the engine. If the temperature of the control is above the predetermined temperature, an assumption can be made that the vehicle has not been shut down long enough to replace a fuel injector. However, if the control temperature is below the predetermined temperature, then it is possible a fuel injector has been replaced. Of course, it may also simply be the vehicle has been shut down for a length of time, but no fuel injectors have been replaced. Even so, in a preferred method, in such a situation, each of the fuel mjectors are again quened. A control signal is sent to each of the fuel injectors, and the voltage from the charactenzation resistor is read. The voltage is again associated with a particular type of fuel injector, and the particular type of fuel injector is stored at the control. The control then knows how to optimally operate the particular fuel injector. A second distinct feature of this invention relates to the types of characteπstics associated with an identifying quantity which increases. The increasing quantities increase such that each next voltage is assigned to a combination of the two characteπstics that only changes in one of the two charactenstics This will be explained with reference to a two-dimensional arra> . where the "types" are stored in a spiral fashion These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a bπef descπption. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a graph of a test result for identifying particular types of fuel injectors. Figure 2 shows a way of stoπng information from the test results of Figure 1. Figure 3 is a first flow chart of the present invention. Figure 4 is a continuation of Figure 3 flow chart according to the present invention. Figure 5 is a schematic view of an overall diesel engine injector identification circuit. Figure 6A shows the injector identification circuit associated with one of the fuel injectors. Figure 6B shows the circuit of Figure 6A as it would effectively be duπng an identification mode. Figure 7 shows the identification circuitry for the present invention. Figure 8 is a logic state diagram for the fuel injector identification according to this invention Figure 9 is a chart of preferred charactenzation resistances DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT As shown Figure 1, fuel injectors can be charactenzed by a first quantity called "offset" and a second quantity called "slope" The offset and slope are determined by testing the fuel injector for two qualities The two qualities are the time it takes to inject three cubic millimeters of fuel, and second the time to inject eight cubic millimeters of fuel The amounts of injected fuel would maintain the engine at a low idle It should be understood that the charactenzation of an offset and a slope for a fuel injector is pnor art, and developed by one of Applicant's customers This characteπzation forms no portion of the invention As shown for example at line 20, Figure 1, a particular fuel injector has its first time at an intermediate position and its second time at a relatively high position The line 20 crosses the axis C at a low point This would thus be a "low" offset A fuel injector defined by line 22 crosses the line C at a much higher offset Notably, the line 22 has a much lower slope than the line 20 The fuel injector defined by line 24 crosses axis C at an intermediate offset position, and further has a slope which is between the slopes of the lines 20 and 22 Assuming that each injector has high, medium, and low as possible values of slope and high, medium, and low for possible values of offset then the fuel injector charactenzed by the line 20 could be said to have a low offset and a high slope The fuel injector characterized by the line 22 could be said to have a high offset, but a low slope The fuel injector charactenzed by the line 24 could be said to have a medium offset and a medium slope Nine distinct combinations of the three values of the two charactenstics exist Figure 2 shows a way of assigning an incremental value to each of the nine possible combinations of characteπstics As shown, a two-dimensional array is provided which graphs slope between low, medium and high and offset between low, medium and high Each possible combination of the values is graphically represented by a particular incrementally advancing number Applicant has found that by stonng these numbers in a spiral fashion, the likelihood of a misreading will be reduced It should be understood that each of the increasing numbers is associated with an increasing voltage (or other electπcal charactenstic) If the voltage values were assigned increasing in a fashion such that at the end of a row, one moves to the beginning of the row to begin assigning numbers, then a greater misreading could occur than would occur with a spiral array This is because if the values increase, a misreading of a voltage would most likely occur between two adjacent values Thus, a misreading between three and eight is unlikely, whereas a misreading between three and four is more likely With the arrangement as set forth in Figure 2, a misreading between three and four would still result in the proper offset (high) being determined. Moreover, one would only be off one value in the slope (that is, high has been misread as a medium). On the other hand, if the value four had been assigned to the far middle row, where the number eight is illustrated, that same misreading between three and four would result in both charactenstics being off, and one of the charactenstics (offset) being off by two values (that is, a high value has been misread as a low value). By stonng and assigning values in a spiral array, the present invention thus provides the benefit of minimizing detnmental effect due to a voltage misreading. While the spiral array is most preferred, simply moving nght to left, then left to πght and then nght to left, or alternatively up, then down, then up would also provide a similar benefit. While this data storage is an important second feature of this application, the main features of this application go to the identification of a fuel injector type, as will be explained with reference to Figures 3-8. As mentioned above, the present invention incorporates a characteπzation resistor into each fuel injector once the particular "type" of fuel injector has been determined. The details of this incorporation will be explained below The basic flow chart and method of this invention can be understood from Figures 3 and 4. As shown in Figure 3, at power up to the control, any existing initialization that may also be included in the control is performed The fuel injector identification steps then begin The control first asks if the module or engine temperature is above a predetermined temperature, here sixty degrees centigrade The reason for this is to determine whether the vehicle has been shut down for a length of time. If the vehicle is above the predetermined temperature, then it can be assumed the vehicle has not been shut down for any length of time The identification must be repeated each time a fuel injector has been replaced. If the vehicle has not been shut down for a particular length of time, then it is most unlikely that a fuel injector has been replaced If the temperature is above the predetermined temperature, then the previously stored values for each of the injectors are used for the injectors dunng engine operation If the temperature is below the predetermined temperature, then the system moves into the identification loop Reading the resistor at lower temperature minimizes the effect of FET leakage current, and this additionally improves system accuracy by not reading the characterization resistor value when it is hot and its value has been changed by temperature An insert B into the Figure 3 flow chart is shown in Figure 4, as is output A For each of the fuel injectors or cylinders, a code is sent which controls an identification circuit to power up one portion of each of the fuel injector circuits and to energize the characterization resistor The voltage from that fuel injector is then read. As can be seen in Figure 4, at step A, the voltage is compared to a minimum and maximum value to determine the validity of the sensed voltage. As an example, if the voltage is lower than a predetermined value, then the system declares an error and uses the previously stored value for that particular fuel injector If the voltage is above the low predetermined value then the voltage is compared to a high value. Again, if the voltage is above that high value, an enor is reported and the previous value is utilized If an enor is reported, the flow chart then goes to incrementally increasing the cylinder number, and asking if the cylinder number is the last (here 8) If the answer is yes, then the control moves to running the injectors. If additional cylinders need to be identified, the system returns to point B in the Figure 3 flow chart. If the voltage appears to be proper (that is between the high and low values), then the voltage is compared to prestored values to assign a particular fuel injector type to the fuel injector. The assigned type is then used to associate slope and offset. Either the type or the slope and offset are stored at the control for each fuel injector When the control begins to run the fuel injectors, this information is utilized to optimize the operation of each fuel injector. Figure 5 shows a partial schematic diagram for the control of the diesel engine and its fuel injectors. Each fuel injector 30 is shown with its characteπzation resistor 32. As can be seen, each of the injectors have an individual characteπzation resistor 32 The characterization resistors may be of several types across any one diesel engine, and there may be more than one of any one type Again, this is determined based upon the characteristics of each fuel injector as manufactured. Figure 6 A shows the circuitry 30 for dπving each injector. An important feature of this circuit configuration is that no additional wiπng is required within the engine to control module harness. Each injector has an open 34 and close 40 coil. The open coil 34 causes the injector to open and the close coil 40 causes the injector to close. The open coil 34 is provided with a high dnver 36 and a low dnver 38. A charactenzation resistance 32, the only component of this circuit not located in the control module, is placed in seπes with a resistance 33, which is in turn connected to a power supply 35, which is preferably 48 volts. The close coil 40 is provided with a high side dnver 42 and a low side dnver 44. The charactenzation resistor 32 is selected to have such a high resistance that duπng normal operation very little current will flow through the characterization resistance, and thus the operation of the coil 40 is not affected by the inclusion of the characteπzation resistor. The value of the characterization resistor is preferably low enough that the leakage current of the high side driver 36 at the module temperature duπng the injector identification process is insignificant However, the control is provided with the ability to turn on only dnver 44 for coil 40 such that the current must flow through the charactenzation resistor 32. When this occuis. the circuit effectively becomes that which is shown in Figure 6B The charactenzation resistor 32 now controls the voltage leaving the circuit at 46, and being read by the control. In Figure 6B, a resistance 69 is shown, which is the effective resistance which is vaπed by the vanable characteπzation resistors 32 As shown in Figure 6 A, resistors 60 and 61 scale the voltage to the output 46, even duπng normal operation As shown in Figure 6B, the resistances 62 and 69 are effectively set by a combination of the resistances including resistor 32 Preferably, the other resistances are selected to be sufficiently high such that differentiations between the individual charactenzation resistor 32 still can be detected at output 46 The control thus has the ability to turn on one dnver for one coil and read the characterization resistance Preferably, the low side dnver 44 for the close coil 40 is connected such that when it is on and the other dnvers are off, the charactenzation resistance will result in an expected unique range of charactenzation voltage being readable on the output 46 for each type classification. Figure 7 schematically shows the systems for energizing the particular dnvers at the particular time Inputs 50, 52, 54 and 56 selectively dnve the particular dnvers. The system is shown with only two low side dnvers 100 with one being shared by all open and all close coils of all the fuel injectors. In other systems a separate low side dnver may be associated with each coil and cylinder. By controlling the inputs 50, 52, 54 and 56, each fuel injector at each cylinder is quened with the proper low side dnver powered. A worker in this art would recognize how to provide this function, and the circuit of Figure 7 is but one example. Figure 8 is a timing diagram showing the inputs to points 50, 52, 54 and 56 to result in control of each of the eight fuel injectors such that each of the injectors is queried in order The exact details of how the particular cylinder is quened are within the skill of a worker in this art It is the inclusion of the identification resistance, and the relatively inexpensive and simple result of providing an identification of each fuel injector type which is the mam inventive feature here. Normal signal processing, such as scaling the output of the characteπzation resistor, and reading through an analog to digital converter are preferably utilized. Preferably, the value of the characteπzation resistor 32 is chosen to be high (as an example greater than 500 OHMS), such that its effect on normal operation is undetectable. The wetting current for the charactenzation resistor when its dnver is energized is accomplished by the resistor 33 in combination with the other resistors in the circuit, such as is shown in Figure 6A. The senes combination of the resistors 60 and 61 is preferably high enough such that it does not affect the ability to differentiate different values of the charactenzation resistor 32 The use of the resistors 60 and 61 will ensure that the output 46 going to the multiplexing portion of the control will not be the full 48 volts, even under normal operation. Additionally, the "high" impedance of the resistor combination permits the addition of a simple voltage limiting diode to line 46 assunng that the full 48 V cannot reach the multiplexer even when the injector is miswired. It is desirable for a much lower voltage to be the maximum input to most multiplexers. The level shifters 150 as shown in Figure 7 may be eliminated if they are unnecessary to the circuit operation. The elements 152 are a plurality of analogy switches which is associated with each of the individual cylinders. While the characteπzation assigning feature of Figure 2 is shown with regard to two characteπstics, each having three potential values, it should be understood that additional characteπstics having additional numbers of potential values can also benefit from this invention. Preferred embodiments of this invention have been disclosed; however, a worker in this art would recognize that modifications come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims: CLAIMS 1. A fuel injector system compnsing: a plurality of injectors; a control for dnving said fuel injectors; an electπcal component inserted into each of said injectors, said electπcal component modifying an electπcal charactenstic sent from said injector to said control, and said electncal component being selected to provide an indication of particular charactenstics which have been determined to exist for each said fuel injector 2 A fuel injection system as recited in Claim 1, wherein said electncal component is a resistor inserted into a circuit for dnving said fuel injector, said resistor being selected to provide an identifying code to said control selected to identify charactenstics of said fuel injector. 3. A fuel injection system as recited in Claim 2, wherein said characteπstics include an offset and slope for the operation of said fuel injector. 4. A fuel injection system as recited in Claim 2, wherein said resistor is incorporated into a circuit associated with one dnver for dnving a coil for powenng said fuel injector. 5. A fuel injection system as recited in Claim 4, wherein said resistor is selected to have a sufficiently high resistance that it blocks flow of current dunng normal operation of said coil. 6. A fuel injection system as recited in Claim 4, wherein said fuel injector having an open coil and a close coil tor selectively opening and closing said fuel injector, and each of said coils being provided with a low and high side dnver, and said one dnver being one of said dnvers for one of said coils. 7 A fuel injection system as recited in Claim 6, wherein said close coil includes said one dnver 8 A fuel injection system as recited in Claim 7, wherein a low side dnver for said close coil is said one dnver. 9 A fuel injection system as recited in Claim 1 , wherein said electncal characteristic is assigned with increasing electπcal values in such a fashion that each incrementally increasing number changes only one of two charactenstics associated with said electrical characteπstics. 10 A fuel injection system as set forth in Claim 9, wherein said code is associated with a two dimensional array, and said electπcal output increases in a spiral fashion in said two-dimensional array. 11 A fuel injection system as set forth in Claim 1, wherein said control determines a system temperature at start-up, and performing an identification query if said system temperature is below a predetermined temperature. 12 A fuel injection system compnsing. a plurality of fuel injectors, each of said fuel injectors incorporating an open coil and a close coil, said open and close coil being operable to move said injector between open and close positions, and said open and close coils each having a high side and a low side dnver; and a charactenzation resistor associated with at least one driver for one of said coils in each of said fuel injectors, said charactenzation resistor being selected to provide an electncal output from said fuel injector that provides an identifying code relating to a particular operational charactenstic of said fuel injector 13 A fuel injection system as recited in Claim 12, wherein said closed coil and its low side dnver are associated with said charactenzation resistor 14 A fuel injection system as recited in Claim 12, wherein said code is assigned with increasing electπcal values in such a fashion that each incrementally increasing number changes only one of two charactenstics of said fuel injector 15 A fuel injection system as recited in Claim 14, wherein said two charactenstics of said fuel injector include an offset and a slope value 16 A method of operating a fuel injection system compnsing the steps of (1) testing fuel injectors and determining operational characteπstics of each said fuel injector, (2) providing an electncal component in a circuit for dnving said fuel injector, said electπcal component having an electncal charactenstic which is associated with a particular code stored in a control, said code being associated with particular sets of charactenstics relative to said fuel injector; (3) reading said electncal charactenstic from said fuel injector at said control, and associating a particular set of charactenstics with said fuel injector once said electπcal charactenstic has been read by said control; and (4) operating said fuel injector based upon said set of charactenstics 17 A method as set forth in Claim 16, wherein said code is assigned with increasing electncal values in such a fashion that each increasing value changes only one of two charactenstics 18 A method as set forth in Claim 17, wherein said codes are associated with a two dimensional array, and said numbers increase in a spiral fashion 19. A method as set forth in Claim 16, wherein a system temperature reading is performed prior to Step (3) and Step (3) is only performed if said system temperature is below a predetermined temperature. 20. A method as set forth in Claim 16, wherein if the read electrical characteristic of Step (3) is outside a predetermined envelope, then previously read values are used. 21. A method of assigning increasing values to provide an identification code for a component having at least two characteristics of varying amounts comprising the steps of: (1) obtaining information with regard to said at least two characteristics; (2) assigning an identification code to said component based upon the combination of said at least two characteristics, said identification code being associated with a particular electrical characteristic, said particular electrical characteristic increasing with each increasing code; and (3) each increasing code being assigned to a particular combination of characteristics such that between any two adjacent increasing codes, only one of the two characteristics is changed. 22. A method as set forth in Claim 21, wherein said codes are assigned in a spiral array. 23. A method as set forth in Claim 21, wherein said codes are utilized to provide characteristics relative to a fuel injection system.

Inventors: MCCOY JOHN C, VIERLING LOU, MCCOY, JOHN, C., VIERLING, LOU
Applicants: SIEMENS AUTOMOTIVE CORP LP, SIEMENS AUTOMOTIVE CORPORATION
Application year: 2000
Main classification: F02D41
IPC codes: F02D41, F02D45, F02M51, G01M15