CN108361139B - Fuel injector small oil quantity control method - Google Patents

Fuel injector small oil quantity control method Download PDF

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CN108361139B
CN108361139B CN201810082016.XA CN201810082016A CN108361139B CN 108361139 B CN108361139 B CN 108361139B CN 201810082016 A CN201810082016 A CN 201810082016A CN 108361139 B CN108361139 B CN 108361139B
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oil
injection
rail pressure
injector
fuel
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CN108361139A (en
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施华传
居钰生
顾欣
吴逸庭
马涛
邱云
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FAW Group Corp
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FAW Group Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M65/00—Testing fuel-injection apparatus, e.g. testing injection timing ; Cleaning of fuel-injection apparatus
    • F02M65/001—Measuring fuel delivery of a fuel injector
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2441—Methods of calibrating or learning characterised by the learning conditions
    • F02D41/2445—Methods of calibrating or learning characterised by the learning conditions characterised by a plurality of learning conditions or ranges
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/24—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means
    • F02D41/2406—Electrical control of supply of combustible mixture or its constituents characterised by the use of digital means using essentially read only memories
    • F02D41/2425—Particular ways of programming the data
    • F02D41/2429—Methods of calibrating or learning
    • F02D41/2477—Methods of calibrating or learning characterised by the method used for learning
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/30—Controlling fuel injection
    • F02D41/38—Controlling fuel injection of the high pressure type
    • F02D41/40—Controlling fuel injection of the high pressure type with means for controlling injection timing or duration
    • F02D41/402—Multiple injections
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D2200/00—Input parameters for engine control
    • F02D2200/02—Input parameters for engine control the parameters being related to the engine
    • F02D2200/06—Fuel or fuel supply system parameters
    • F02D2200/0614—Actual fuel mass or fuel injection amount

Abstract

The invention relates to a small oil quantity control method of a fuel injector, which is characterized by comprising the following steps: the control method comprises the steps of estimating the oil quantity by using rail pressure drop of the ejector to be detected before and after multiple times of small oil quantity injection, comparing the estimated oil quantity with a basic oil quantity characteristic curve of the ejector to obtain a deviation coefficient of the estimated oil quantity relative to the basic oil quantity, and filling the deviation coefficient into an oil quantity deviation coefficient learning table; after learning of the oil quantity deviation coefficient learning table is completed, the oil quantity pulse width conversion table Q2T unique to each injector is obtained by using the deviation coefficient corresponding to the working condition in the small oil quantity nonlinear regioniAnd using the corrected Q2TiThe look-up table obtains the final corrected injection pulsewidth. The invention can obviously improve the small oil quantity consistency and control precision of the ejector, solve the problems of small oil quantity ejection height deviation and aging correction among ejectors, and meet the requirements of higher emission and oil consumption regulations on the precision and oil quantity consistency of the small oil quantity ejection of the ejector.

Description

Fuel injector small oil quantity control method
Technical Field
The invention relates to a small oil mass control method for a fuel injector, in particular to a control method for injector oil mass compensation used in fuel injection of an internal combustion engine, which is suitable for a control method for fuel injection consistency during small oil mass injection of any engine and belongs to the technical field of engine injector control.
Background
Increasingly strict emission and fuel consumption regulations in China are becoming the driving force for the revolution of the engine market. In view of lower emissions and fuel consumption, engines need more advanced and sophisticated control strategies to be adapted to, and these also place higher demands on the control accuracy and consistency of the small fuel injection of the fuel injectors. Therefore, a new fuel injector injection control technique is needed to improve the control accuracy and consistency of the small fuel injection of the fuel injector.
In the prior art, patent applications CN201110355679 and CN201310224482 of marayl corporation disclose a solution for inconsistency of small oil amount, and the implementation process is that a multi-injection excitation injector is used for small pulse width injection, rail pressure drop before and after the small pulse width injection is measured to estimate the small oil amount actually injected, and the accuracy of the estimated oil amount is ensured by a statistical averaging method; and finally, compiling the estimated oil quantity into an oil quantity compensation table to realize oil quantity compensation and enhance the spraying consistency.
The bosch co patent application CN103328796 is to trigger the injector with a pulse width injection without opening the injector needle during the intake and exhaust stroke (when the injector is idle), and at this time there is no injection, and the rail pressure drop is completely caused by the return oil, and the return oil amount can be determined by measuring the rail pressure drop; in the normal injection, the rail pressure drop is caused by the total amount of the injected oil and the returned oil, and the injected oil amount (total amount-returned oil amount) can be calculated by the rail pressure drop. And finally, calibrating the injectors by using the oil injection quantity and the oil return quantity to adjust the oil injection dispersion difference among the injectors and realize injector aging compensation.
Chinese patent application CN201110355679 discloses a method for determining an injection rule of a fuel injector, and discloses how to obtain the injection rule of each injector and a related oil amount control method on line, where the injection rule of the fuel injector can be divided into four regions: in the initial unopened area A, the injector is basically in a static state and can not inject oil due to the over short driving time; a rapid acting region (Batyliscitic zone) B in which the injection quantity Q rapidly increases as the drive pulse width becomes larger, and which is substantially in an approximately linear curve; and a linear region D in which the injector is fully open and the injection quantity Q increases in a linear manner as the drive pulse width becomes larger. The union region C connects the rapid-action region B to the linear region D, and is largely non-linear, so that the use of fuel injectors is not recommended in this connection region C. This patent application discloses a method of determining the injection law of each injector, which may be approximated by a straight line R1 and a straight line R2, the straight line R1 fitting the fast acting region B, and the straight line R2 fitting the linear region D and intersecting the straight line R1. The line R1 is defined by feature points P1 and P2, and the line R2 is defined by feature points P3 and P4. The characteristic points P1-P4 can be used as a whole to approximately and accurately reconstruct the injection rule of the injector. Since the rail pressure has an influence on the injection law, each characteristic point P1-P4 of the injection law needs to be determined at a different fuel pressure P. The respective injection rule of each injector is stored in a memory of the ECU; in use the ECU controls each injector using the previously stored injection law for each injector.
The method for determining the injection rule of each injector comprises the following steps:
a. completely interrupting the supply of fuel from the oil pump to the rail pipe, avoiding the opening of all the other injectors except the injector to be tested, and measuring the initial fuel pressure Pi in the rail pipe by means of a pressure sensor before opening the injector to be tested, then the ECU driving the injector with the same injection pulse width L, injecting N times in succession, then measuring the final fuel pressure Pf in the rail pipe after terminating the injection of the injector, and then deriving a pressure drop Δ P in the rail pipe before and after the injection of the quantity of oil, which is equal to the difference between Pi and Pf;
b. according to the total oil quantity Q flowing out of the rail pipeTOTAnd the pressure drop delta P in the rail pipe, and obtaining QTOTBy subtracting the lost fuel quantity Q from Δ P × K, the single fuel injection quantity Q can be obtained (Q)TOT-QDecrease in the thickness of the steel) N; the ECU statistically processes a series of measured values of the pressure drop delta P so as to determine the average pressure drop delta P, so that the accuracy of the delta P and the single injection oil quantity Q can be improved, the characteristic points P1-P4 of the actual injection rule of the injector are determined through the process, and the whole injection rule can be reconstructed;
c. the implementation method of N times of continuous injection comprises two methods: the first is to connect the internal combustion engine to an external drive which can maintain internal combustion constant speed operation regardless of the actual amount of oil injected into the cylinder. This allows the injector to be tested to perform a large number N of consecutive injections (N being greater than 50) so that the pressure drop Δ P is relatively high and therefore relatively accurate. The second method is that the required fuel quantity Qd of the internal combustion engine can be changed within a certain error interval during the normal running of the engine, so that the oil quantity Q sprayed within the test action time T is just an integer factor of Qd, and the high required fuel quantity Qd is optimized as much as possible, so that the injector to be tested can be opened continuously for several times, and the test precision of pressure drop can be improved. Therefore, the total oil amount of the N successive injections is exactly equal to the required oil amount Qd, so that the normal operation of the internal combustion engine is not affected.
Chinese patent application CN201310224482, for a method for updating injection laws of fuel injectors (mally corporation), discloses a method how to update the injection laws of the individual injectors in the case where the engine is operating normally and the normal driving of the vehicle by the driver is not affected. The basic principle and the idea are similar to those of the above-mentioned chinese patent CN201110355679, except that after the ECU drives the injector to continuously inject N times with the same injection pulse width L (the total oil amount of the N injections is Q1), a second injection is executed to compensate the total injected oil amount to obtain the requirement of the required oil amount Qd, so that the total oil amount of each cylinder is substantially consistent, and the engine can normally operate without driving and feeling abnormal. The total oil amount Q2(Q2 — Q1) of the second injection is required to fall within the linear region of the injection characteristic, so that the total oil amount to the required oil amount Qd can be satisfied.
Chinese patent application CN103328796A discloses a method for determining injector control quantity, which is used for determining injector control quantity (bosch corporation). In the method, during the intake and exhaust stroke (when the injector is idle), the injector is triggered by pulse width injection without opening an injector needle valve, no oil injection occurs at the moment, the rail pressure drop is completely caused by oil return, and the oil return amount can be determined by measuring the rail pressure drop; in normal injection, the rail pressure drop is caused by the total amount of injected oil and returned oil, and the total oil amount can be calculated by the rail pressure drop, and then the injected oil amount (total amount-returned oil amount) is calculated. And finally, calibrating the injectors by using the oil injection quantity and the oil return quantity to adjust the oil injection dispersion difference among the injectors and realize injector aging compensation. Specifically, the injector of each cylinder is triggered to inject through predefined oil injection pulse width and rail pressure, and the learning value of the oil injection quantity and the oil return quantity of the injector to be tested is calculated according to the rail pressure drop and is stored in the oil quantity characteristic learning table. When learning is completed, these learned values can be used to compensate for the amount of oil.
The disadvantages of marayl corporation's patent applications CN201110355679 and CN201310224482 are as follows:
(1) under each rail pressure, the Maryleigh company selects four characteristic points P1-P4 to determine the rail pressure drop estimated oil quantity, wherein the characteristic points P1 and P2 are in a small oil quantity nonlinear region, and the characteristic points P3 and P4 are in an oil quantity linear region, and the injection rule of the injector can be approximately and accurately reconstructed by using four straight lines and two straight lines. However, the calculation method used by marayleigh is to estimate the absolute value of the fuel quantity to reconstruct the fuel injection law, but the absolute value of the fuel quantity cannot represent the degree of aging of the injector relative to the original basic fuel quantity characteristic curve.
(2) In the multiple injection process of implementing the oil mass self-learning, the rail pressure during injection is gradually reduced along with the increase of the injection times, although the pulse width of multiple injections is the same, the oil injection quantity under different rail pressures is different, and the MaRayleigh simply divides the estimated total oil injection quantity by the injection times to obtain the average single oil injection quantity which is used as the actual single oil injection quantity under the initial rail pressure and the pulse width, and the influence of the continuous reduction of the pressure in the injection process on the oil injection quantity is not considered; the mally algorithm must be premised on a small pulse width and a small number of injections, resulting in a small rail pressure drop. However, if the rail pressure drop is small, the measurement of the rail pressure drop itself may be inaccurate because the pressure drop is of an order of magnitude similar to the magnitude of the error of the pressure sensor and the minimum resolution in reading the pressure sensor. This is a dilemma and the algorithm must be refined to avoid such inherent misreconciliation conflicts. The mally corporation attempts to ensure the accuracy of the rail pressure drop by making statistical measures of the captured rail pressure drop, and although the accuracy of measuring the rail pressure drop is theoretically improved after several hundred orders of magnitude of statistics, it is not necessarily satisfactory in practice. Meanwhile, the method greatly increases the data processing burden of the ECU, reduces the operation efficiency of the algorithm, and needs to consume longer time for the algorithm.
(3) The Maryleigh assumption that the system will generate fuel loss when the rail pressure is high can be used for estimating the fuel loss and deducting the influence of the fuel loss when estimating the fuel injection quantity. First, a first fuel loss is determined, which is directly proportional to the measured duration, then a second fuel loss is determined, which is directly proportional to the number of openings of the fuel injector, and finally the fuel loss is determined by adding these two values. It is clear that the marayl approach to fuel loss estimation is relatively straightforward, and that fuel loss is different under different conditions, e.g. in relation to rail pressure and drive pulse width, while taking into account the effect of injector aging on fuel loss.
(4) During the implementation of the fuel quantity self-learning multiple injection, in order to enable the fuel injection quantity of the injector to be tested to be consistent with the fuel demand quantity Qd, and therefore to ensure that the internal combustion engine can normally operate during the fuel quantity self-learning, after the MaRayleigh measurement injection is carried out, if the total fuel injection quantity injected during the test is Q1, the ECU also carries out a second injection, wherein the fuel injection quantity is Q2(Q2 is Qd-Q1, and Qd is the fuel injection quantity required by the injector), so that the total fuel injection quantity of the injector to be tested is the same as that of other injectors. However, after the oil mass self-learning is started, the injector to be tested performs small-oil-mass multiple injection, the injection of the small oil mass in the self-learning stage is definitely inaccurate, so that the total oil mass is different from the injection quantities of other cylinders, and the combustion effect in the multiple injection mode can be influenced, so that the engine finally runs unstably or slightly shakes.
The bosch company, however, in patent application CN103328796, only describes the principle of oil compensation and the compensation means in a directional manner, and does not refer specifically to the specific steps of determining the injection amount according to the rail pressure drop.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, and provides a small oil quantity control method of a fuel injector, which can obviously improve the small oil quantity consistency and control precision of the injector, solve the problems of small oil quantity injection height deviation and aging correction among the injectors, and meet the requirements of higher emission and oil consumption regulations on the precision and oil quantity consistency of small oil quantity injection of the injector.
According to the technical scheme provided by the invention, the small oil quantity control method of the fuel injector is characterized by comprising the following steps: the control method comprises the steps of estimating the oil quantity by using rail pressure drop of the ejector to be detected before and after multiple times of small oil quantity injection, comparing the estimated oil quantity with a basic oil quantity characteristic curve of the ejector to obtain a deviation coefficient of the estimated oil quantity relative to the basic oil quantity, and filling the deviation coefficient into an oil quantity deviation coefficient learning table; after learning of the oil quantity deviation coefficient learning table is completed, the oil quantity pulse width conversion table Q2T unique to each injector is obtained by using the deviation coefficient corresponding to the working condition in the small oil quantity nonlinear regioniAnd using the corrected Q2TiLooking up a table to obtain the final corrected injection pulse width; the method specifically comprises the following steps:
(1) oil mass self-learning starting judgment: judging whether the fuel injector needs to be started or not;
(2) oil quantity estimation enabling judgment: after the oil mass self-learning function is started, external condition judgment is carried out: evaluating whether the vehicle meets the external state or working condition requirement of the oil quantity estimation; and performing internal condition judgment: detecting the tightness of the fuel system to judge whether the fuel system meets the requirement of estimating the internal tightness of the fuel quantity; enabling the oil quantity estimation function when the internal and external conditions are met;
(3) collecting rail pressure before oil injection: after the oil quantity estimation function is enabled, the oil pumping function and the oil injection function are closed, and rail pressure collection reasonableness judgment before the injection of the injector to be tested is started are carried out under the conditions that the fuel system has no fuel input and output and the rail pressure is stable;
(4) injecting by an injector: after the rail pressure collection before injection is finished, executing the injection function of the injector, selecting proper injection times and injection pulse width, and under the condition that the pump oil is closed and other cylinders except the cylinder to be detected do not inject oil, triggering the injector to be detected to execute N +1 times of injection by using a multi-injection mode, wherein the injection comprises N times of continuous injection with the same short pulse width and 1 additional time of micro closed-loop compensation injection;
(5) and (3) rail pressure acquisition after oil injection: after the ejector completes N times of continuous ejection with the same short pulse width, the rail pressure acquisition and the rail pressure acquisition rationality judgment of the ejector to be detected after ejection are carried out again;
(6) rail pressure drop calculation: calculating the pressure drop of the injection rail of the injector to be detected according to the pressure difference before and after injection, and carrying out rationality judgment on the rail pressure drop so as to obtain a final rail pressure drop output average value;
(7) estimating the total oil quantity: according to the rail pressure drop mean value and the correlation coefficient obtained by calculation, the total oil quantity Q of the rail pipe outflow estimated under the current working condition is obtainedGeneral assembly；
(8) Calculating oil return amount: determining basic oil return amount corresponding to different rail pressures and driving pulse widths through testing before the injector leaves a factory, and filling the basic oil return amount table; calculating an oil return aging factor lambda under different rail pressures, and correcting a basic oil return amount meter by using the aging factor to obtain the aged oil return amount;
(9) estimating the single injection oil quantity: according to the total oil quantity Q of the rail pipe outflow estimated under the current working conditionGeneral assemblyAnd the amount of oil returned QTotal returnCalculating the single injection estimated oil quantity Q of the injector to be tested currentlyEstimating，QEstimating＝α*(QGeneral assembly–QTotal return) α is a correction coefficient of rail pressure dynamic reduction to single injection oil quantity, and N is the injection times;
(10) updating an oil quantity deviation coefficient learning table: obtaining single estimated injection oil quantity Q under different rail pressures and different corresponding pulse widthsEstimatingCalculating the deviation coefficient gamma of the estimated single injection oil quantity relative to the basic oil quantity, and updating the oil quantity deviation coefficient learning table of each injector;
(11) aging faults of the oil sprayer: according to the oil mass deviation coefficient gamma of the aged oil injectorAging ofRelative to the deviation coefficient gamma obtained by self-learning of oil mass when leaving factoryLeave factoryJudging the aging degree of the oil atomizer according to the drift amount delta gamma, and comparing the aging degree with a preset fault threshold value to determine whether the oil atomizer has an aging fault;
(12) and (3) coordinating oil injection pulse width: and after the self-learning is completed, obtaining a corrected oil quantity pulse width conversion table of each injector according to the oil quantity deviation coefficient, and checking the corrected oil quantity pulse width conversion table to obtain the final corrected injection pulse width.
Further, the condition of oil amount self-learning opening comprises that the group of injectors has never been subjected to oil amount self-learning since the group of injectors was shipped or has been subjected to oil amount self-learning but needs aging correction on the injectors; the aging-corrected oil mass self-learning starting condition comprises that the engine runs for a certain time from the last aging correction, or the vehicle runs for a certain mileage from the last aging correction, or the offset of the current deviation coefficient obtained by starting the oil mass estimation function under the characteristic working condition point relative to the deviation coefficient when the aging correction is carried out last time exceeds the threshold value of the aging correction.
Further, after the oil quantity self-learning is started, judging external conditions and internal conditions; the external judgment conditions comprise that the vehicle runs in a fault-free state, the rail pressure sensor collects fault-free conditions, the power supply voltage of the power supply is stable, and the rail pressure fluctuation range is smaller than a threshold value and is stable for more than a period of time; the internal condition judgment method comprises the following steps: when the vehicle is in a state that oil injection and pumping are forbidden to enable the fuel system to have no oil inlet and no oil outlet, the rail pressure drop in unit time under different rail pressures is recorded, the updating of a rail pressure drop leakage table is completed, the rail pressure drop under the current rail pressure is compared with a predefined rail pressure drop leakage threshold under the current rail pressure, and when the rail pressure drop is smaller than the threshold, the tightness of the fuel system is considered to meet the internal judgment condition.
Further, before the oil quantity is estimated, the leakage rail pressure drop of the fuel system is used for correcting the oil quantity, and the specific method is that the fuel leakage pressure drop delta P under the duration of the fuel injection pulse width of the injector to be detected and the current rail pressure is calculated according to the fuel leakage rail pressure drop in unit timeLeakage ofUsing the leakage rail pressure drop Δ PLeakage ofAnd correcting the rail pressure drop used for estimating the fuel injection quantity and the oil return quantity of the injector to be measured so as to remove the influence of the rail pressure drop caused by fuel leakage and enhance the estimation precision.
Furthermore, after the oil mass estimation function is enabled, the torque difference characterization signals of the cylinders are detected, the torque of the cylinder to be measured is compared with the average torque of the cylinders not to be measured, and micro-closed loop control adjustment is carried out on the oil mass of the cylinder to be measured, so that the micro-closed loop adjustment oil mass delta Q of the cylinder to be measured is obtained, and the consistency requirement of the torque of each cylinder is met.
Further, after the oil return amount is deviated due to the aging of the injector, compensating and correcting the basic oil return amount table by using an oil return aging factor; the conditions for obtaining the aging factor by calculation are as follows: the vehicle is in a state without the ejector to work, in the state, the oil quantity estimation function of the ejector to be tested is triggered by a standard pulse width, the standard pulse width can not open the needle valve of the ejector to actuate the ejector, but oil return of the ejector is generated, the oil return aging factor lambda is the ratio of the estimated oil return quantity and the basic oil return quantity obtained by a table look-up according to the standard pulse width, namely lambda is QEstimating oil return/QBasic oil returnAnd obtaining aging factors under different rail pressures, and correcting the basic oil return amount table by using the aging factors under different rail pressures to obtain the aged oil return amount.
Furthermore, the correction coefficient α of the rail pressure dynamic reduction to the single injection oil quantity is obtained by gradually reducing the rail pressure during the injection process, so that the actual injection oil quantity is relative to the average rail pressure P during the rail pressure dynamic reduction processmAverage injected oil amount Q ofmUsing the correction factor α for QmMaking a correction to obtain the initial injection rail pressure PInitialLower single injection oil quantity QEstimatingWhen the driving pulse width is fixed, the fuel injection quantity can be obtained according to a rail pressure check Q2T table, namely Q is Map (P), and the correction coefficient α is Map (P)Initial)/Map(Pm) The method of multiple iterations α is used to improve accuracy.
Further, obtaining the estimated oil quantity Q of single injection under the driving pulse widths corresponding to different rail pressures and basic oil quantitiesEstimatingThen, a deviation coefficient γ of the estimated fuel amount with respect to the base fuel amount is calculated, where γ is (Q)Estimating-QBasic)/QBasicAnd filling the deviation coefficient into the oil quantity deviation coefficient learning table of the test injector according to the basic oil quantity and the rail pressure.
Further, when the amount of oil is not finishedDuring learning, the injection pulse width during non-learning is obtained according to a rail pressure and oil quantity checking Q2T table; after learning is finished, the learned injection pulse width can be obtained by looking up a table through respective oil mass pulse width conversion tables of the injectors; Q2T for each injectoriThe table determination method comprises the following steps: firstly, according to the oil quantity deviation coefficient learning table, the estimated oil quantity corresponding to each oil quantity coordinate value under a certain rail pressure in the basic Q2T table, namely QEstimating＝(1+γ)*QBasic(ii) a Thus, a temporary estimated oil quantity lookup table reflecting the relationship between the estimated oil quantity and the driving pulse width under the current rail pressure is obtained; then, the current injector Q2T is calculated by interpolation according to the oil quantity estimation lookup tableiActual drive pulse width corresponding to each oil mass coordinate value under the current rail pressure in the table; repeating the method under different rail pressures to finish the Q2T corresponding to the fuel injector to be testediAnd (4) updating the table.
The small oil quantity control method of the fuel injector can enable the injector to achieve a high-precision control effect and maintain the consistency of oil injection when injecting fuel, can meet the requirement of multiple injections under a higher emission regulation and achieves the purposes of energy conservation and emission reduction of an engine.
Drawings
Fig. 1 is a schematic diagram of a fuel injection system.
FIG. 2 is a pulse width versus injected fuel quantity plot for each injector in a fuel injection system.
FIG. 3 is a fuel system leak rail pressure monitoring curve.
Fig. 4 is a graph relating fuel quantity to rail pressure drop for an injector of the fuel system.
Fig. 5 is a curve of oil quantity with rail pressure at a certain pulse width.
FIG. 6 is a schematic diagram of an algorithm for estimating fuel injection quantity and pulse width correction based on rail pressure drop.
Fig. 7 is a graph showing the degradation of the fuel quantity characteristic curve of the injector.
FIG. 8 is a graph illustrating the pulse width conversion table Q2T for updating the fuel quantity pulse width of the injector to be testediSchematic representation.
Detailed Description
The invention aims at the small oil quantity of the existing fuel nozzle of the electric control engineThe method comprises the steps of solving the problems of high dispersion and poor consistency of injection characteristics, estimating the oil quantity by calculating rail pressure drop of an injector to be detected before and after multiple times of small oil quantity injection, comparing the estimated oil quantity with a basic oil quantity characteristic curve of the injector to obtain a deviation coefficient of the estimated oil quantity relative to the basic oil quantity, and filling the deviation coefficient into an oil quantity deviation coefficient learning table; after learning of the oil quantity deviation coefficient learning table is completed, the deviation coefficient of the corresponding working condition is used for solving the oil quantity pulse width conversion table Q2T of each injector independently in the small oil quantity nonlinear regioniAnd using the corrected oil quantity pulse width conversion table Q2TiAnd (4) obtaining the final corrected injection pulse width by looking up a table so as to improve the oil quantity consistency in the non-linear region of the oil injection.
Theoretically, the leakage of the fuel system is an abnormal state of the system, and generally the leakage is avoided as much as possible, but in practice, the fuel system can not avoid the leakage, and the invention considers that the leakage of the fuel system is ensured to meet the requirement before the rail pressure drop estimation of the fuel quantity; specifically, under the working condition that the injector does not inject (such as vehicle dragging), the oil injection is forbidden, at the moment, no oil is fed into or discharged from the fuel system, the rail pressure drop detected by the ECU along with time is mainly caused by the leakage of the fuel system, the rail pressure drops in different rail pressures and unit time are recorded, and the rail pressure drops are filled into a rail pressure drop leakage meter. Before oil quantity estimation, rail pressure drop in a rail pressure drop leakage meter is acquired according to current rail pressure and is compared with a rail pressure drop fault threshold value under the current rail pressure defined in advance, and the fuel system tightness is considered to meet the requirement only when the rail pressure drop is smaller than the threshold value.
In order to ensure the accuracy of oil quantity estimation even if the leakage of the fuel system per unit time is less than a threshold value, the leakage of the fuel system can be used for correcting after the rail pressure drop delta P' is calculated during the oil quantity estimationLeakage ofThen, the rail pressure drop Δ P, which is affected by the fuel leakage, is removed as Δ P' - Δ PLeakage of. Note that reference herein to rail pressure drops such as Δ P, Δ POil returnEtc. are rail pressure drops that subtract from fuel system leakage.
In order to improve the rail pressure acquisition precision of the injector to be detected before and after injection, the rail pressure acquisition is carried out for multiple times before and after injection, the deviation degree of the rail pressure acquisition values is judged, and rail pressure acquisition points with the deviation exceeding a threshold value are removed. And only after the rail pressure acquisition value with small deviation degree is acquired for multiple times, the final output average value of the rail pressure before and after acquisition is confirmed. After the inter-tooth spacing rail pressure is used for collecting, the whole collecting process can be completed in the working cycle of the ejector to be detected.
The invention uses a multi-injection method to control injection so as to enhance the reduction degree of rail pressure and improve the rail pressure drop identification precision. After injection is completed and rail pressure collection before and after injection is completed, the injection rail pressure drop can be calculated and obtained. In order to enhance the accuracy of rail pressure drop calculation, the method also judges the rail pressure drop deviation degree obtained by multiple times of calculation so as to eliminate the rail pressure drop with the deviation exceeding the threshold value. When enough rail pressure drops with small deviation degrees are collected, the final output average value of the rail pressure drops can be calculated.
In order to ensure that the oil quantity of the multiple injections does not influence each other, the minimum oil injection interval angle of the multiple injections is specified, and the minimum oil injection interval angle without influencing the oil quantity is confirmed by using a theoretical calculation method or an experimental method. The minimum injection interval is used as one of limiting conditions for the oil quantity function of rail pressure drop confirmation, and the oil quantity estimation function can be started only when the injection pulse width is required to be long enough and the requirements of the pulse width and the minimum interval angle of multiple times of small oil quantity injection are met.
Studies have found that there is a strong correlation between the amount of oil Q flowing out of the rail tube and the pressure drop Δ P in the rail tube. Specifically, the correlation coefficient K between the oil amount Q and the pressure drop Δ P in the rail pipe is mainly determined by the internal volume of the rail pipe and the compression modulus of the fuel. The internal volume of the rail is fixed, and the compression modulus of the fuel is determined by the type of fuel, the bearing capacity (rail pressure) of the fuel, the temperature of the fuel, and the like. The coefficient of correlation is therefore a function of the rail pressure and the oil temperature, i.e., K — Fun (P, T). The invention constructs a correlation coefficient lookup table, and determines the value taking conditions of the correlation coefficient under different rail pressures and oil temperatures by using a theoretical calculation combined with an experimental method. After the correlation coefficient is determined, the oil quantity Q flowing out of the rail pipe can be obtained according to the rail pressure drop obtained by calculation by using a formula Q ═ Δ P × K.
It has also been found that the total oil Q that normally flows from the rail pipeGeneral assembly(fuel system leakage has been subtracted) can be made up of two parts: (1) when the ejector works, the width of the injected oil pulse is short and is not enough to open the needle valve of the ejector, and at the moment, although the ejector does not inject oil, the inside of the ejector is subjected to oil return; (2) and (4) injecting oil, wherein when the injector can open the pulse width work of the needle valve of the injector, oil return is generated, and the injector is triggered to inject oil. Therefore, it is desirable to use a method that first determines the return Q of the fuel system under the current operating conditionsTotal returnThen determining the total oil quantity Q flowing out of the rail pipe after the injector sprays under the current working conditionGeneral assemblyAnd finally the quantity of oil injected by the injector QTotal spraying＝QGeneral assembly–QTotal return。
The oil return amount corresponding to a certain injection pulse width under a certain rail pressure of a delivery injector can be determined by using a test mode, and the oil return amount is filled into an oil return amount look-up table; thus, ideally, the amount of oil returned for a single injection, i.e., Q, is obtained from a table look-up of rail pressure and injection pulsewidthOil return＝Map(P、T)。
During actual engine operation, each injector gradually ages, and the oil return amount of each injector generates creep deformation, and the oil return amount obtained by looking up a table is not accurate any more. The present invention provides a method to determine the amount of fuel returned after injector aging. The method specifically comprises the steps of stopping oil injection of the injector and oil pumping of the oil pump under the condition of vehicle back-dragging working condition or ventilation stroke (at the moment, the injector does not work), enabling a fuel oil system not to pump fuel oil and not to spray the fuel oil, triggering the injector to be tested to inject for multiple times by standard pulse width, enabling the needle valve of the injector not to be opened to actuate the injector under the pulse width, enabling oil return of the injector to occur, collecting and calculating the pressure drop of an oil return rail under the standard pulse width, and converting the pressure drop into an oil return estimated quantity Q under the standard pulseEstimating oil return. When injector degradation occurs, QEstimating oil returnBasic oil return Q obtained by looking up table with standard pulse widthBasic oil returnWill produceGenerating difference, defining the oil return aging factor as lambda, wherein
Figure BDA0001561283380000081
After the oil return quantity aging factor is determined, the invention designs a method for determining the oil quantity of the ejector to be tested. When the engine normally runs, the injector to be tested is triggered to spray by using a multi-time spraying method, because the spray pulse width is greater than the minimum opening pulse width of the injector, the needle valve of the injector is opened, the rail pressure drop at the moment is formed by the oil injection quantity and the oil return quantity together, the rail pressure drop caused by the total oil quantity flowing out of the rail pipe is collected and recorded, and the rail pressure drop is converted into the total estimated oil quantity QGeneral assembly(ii) a Meanwhile, the basic oil return amount is calculated according to the pulse width and the rail pressure table look-up, and the total oil return Q of the fuel system is calculated according to the oil return aging factorTotal returnCorrecting; the total estimated fuel quantity Q injected by the injectorTotal spraying＝QGeneral assembly–QGeneral assemblyAnd (6) returning.
During multiple injections, the rail pressure at the time of injection gradually decreases with each fuel injection, and therefore, the starting rail pressure of each injection is different, which results in a difference in the amount of injected fuel. If the influence of the rail pressure dynamic drop is not considered, the estimated fuel quantity Q is obtained in the process of obtaining the total injection of the injectorTotal sprayingThen, the single fuel injection quantity Q can be directly calculated according to the injection times NEstimating，QEstimating＝QTotal sprayingN, whereas the present invention recognizes that the same drive pulse width, but due to the initial injection rail pressure PInitialUnlike this, Q cannot be simply convertedGeneral assemblyN as initial injection rail pressure PInitialThe lower single injection oil amount. That is to say, QGeneral assemblyThe average injected oil quantity Q in the dynamic reduction process of the rail pressure is obtained by dividing by NmThe rail pressure P corresponding to the average fuel injection quantity is used according to the change relation of the fuel quantity along with the rail pressure under the current driving pulse widthmTo QmCorrected to obtain the actual single injection oil quantity Q at the initial injection rail pressureEstimating. Specifically, since the relationship between the amount of oil and the rail pressure can be represented in the table Q2T, when the driving pulse width is fixed, the table Q2T is checked to obtain the amount of injected oil, i.e., Q ═ map (p), and then the correction system is executedNumber α ═ Map (P)Initial)/Map(Pm) Then single injection quantity Q of initial injection rail pressureEstimating＝α*Qm＝α*QTotal spraying/N＝α*(QGeneral assembly–QTotal return) Since the initial standard injector characteristic data Q2T table used in the first fuel quantity self-learning is not accurate enough, the correction coefficient α obtained by the first calculation has a certain deviation, but as the first fuel quantity self-learning is completed, the second self-learning will use the updated individual Q2T table of each injector to calculate the correction coefficient α, after several iterations of the self-learning, the accuracy of the correction coefficient α will gradually increase, and the accuracy of the small fuel quantity estimation will further increase.
The invention designs an oil quantity deviation coefficient learning table of each injector, and the oil quantity Q estimated by single injection under different rail pressures and pulse widths is obtainedEstimatingThen, a deviation coefficient gamma of the estimated oil amount relative to the basic oil amount is calculated, wherein
Figure BDA0001561283380000082
And filling the deviation coefficient into the oil quantity deviation coefficient learning table of the test injector. The number of learning operating points in the fuel quantity deviation coefficient learning table (generally, the learning operating points are deleted on the basis of the basic fuel quantity Q2T table) can be defined according to the fuel injection precision required by the project, so that the learning efficiency and the learning accuracy are balanced.
The deviation coefficient of the injector represents the deviation degree of the injector relative to the basic oil injection characteristic, and when the injector leaves the factory, the deviation coefficient gamma of the injector is estimated to be used for determining the deviation degree of the oil quantity of the injector relative to the basic oil quantity so as to carry out small oil quantity compensation control; when the injector is aged, the fuel injection characteristic curve is generally deviated, the fuel quantity estimation learning is started to calculate the fuel quantity deviation coefficient gamma for aging, the purpose is to determine the influence of aging on the fuel injection curve, and the deviation delta gamma of the fuel quantity deviation coefficient is equal to gammaAging of–γLeave factoryThe amount of drift may be used to characterize the age of the injector. The invention defines a deviation drift aging fault threshold value, and reminds a driver to drive when delta gamma exceeds the aging threshold valueThe driver injector has aged very much, at which point fault handling and fuel quantity shut-down estimation self-learning are performed. Meanwhile, the deviation coefficient can be used for judging the accuracy of oil quantity estimation, if the deviation coefficient obtained by calculation under a certain working condition is far larger than the deviation coefficients of other working condition points after the oil quantity estimation learning is carried out, or the deviation coefficient obtained by calculation at the time is far larger than the deviation coefficient obtained by calculation under the same working condition at the last time, the accuracy of oil quantity estimation is questioned, and the ECU recalculates the deviation coefficient of the questioned point.
In order to determine the aging correction time, the mileage or the engine running time from the last aging correction is used for judgment, and the deviation coefficient gamma of the engine running at the characteristic working point can be detected at the set characteristic working pointCharacteristic (i)And calculating its deviation coefficient gamma with respect to the last aging correctionFeature (i-1)And determining whether the fuel injector needs aging correction by judging whether the delta gamma' is larger than an aging correction threshold value.
The fuel quantity estimation and self-learning of the injector to be tested can be completed during normal operation of the engine. In the running process of the internal combustion engine, when the injection working condition is in a linear large pulse width region, one-time long pulse width injection of the injector to be tested can be divided into N short pulse width continuous injection and one-time compensation injection for a limited time, and the injection function of the injector N +1 times is completed by using a multi-time injection mode. Wherein the N injections are for oil mass estimation, and the total oil mass of the injections is Q1; and the remaining 1 injection is a compensation injection, which has the effect of ensuring that the torque before and after the estimation of the opening oil amount is consistent, the compensation oil injection amount Q2 is the Qd-Q1, wherein Qd is the fuel injection amount required by the injector.
The injector to be tested performs injection with a small oil quantity for N times, the injection with the small oil quantity in the self-learning stage is not accurate enough, although the target is Q1, the actual oil quantity is definitely deviated from Q1, so that the total oil quantity of the injector to be tested is different from the total oil quantity of injectors of other cylinders, and the combustion effect in a multi-injection mode is possibly influenced, so that the torque generated by the cylinder to be tested (namely the cylinder to which the injector to be tested belongs, the same below) is different from that of the other cylinders, and therefore the engine speed fluctuation is shown, and the vehicle runs unstably or slightly shakes.
In order to solve the problems, the invention adopts a method of closed-loop control compensation for the torque of the cylinder to be measured after the oil mass self-learning function is started. Because the difference of the torque generated by each cylinder is reflected on the transient rotation speed of each cylinder (it should be noted that the adopted torque difference characterization quantity includes but is not limited to the transient rotation speed, for example, the transient rotation speed increment, the cylinder pressure, etc. can also characterize the torque difference of each cylinder, in the embodiment, the transient rotation speed of each cylinder is taken as an example), the ECU can perform the micro-closed loop adjustment on the oil mass Δ Q of the cylinder to be measured by detecting the transient rotation speed of each cylinder, and then comparing the transient rotation speed of the cylinder to be measured with the average transient rotation speed of the cylinder not to be measured, so as to make the torque of the cylinder to be measured the same as that of other cylinders, or control the torque difference of the cylinder to be measured and other cylinders within a micro range, and the micro-torque difference is generally allowed and is difficult to be.
The specific implementation steps are that after the self-learning of the oil quantity is started, the ECU immediately starts the detection function of the transient rotating speed or the transient rotating speed increment of each cylinder of the engine and calculates the rotating speed N of the cylinder to be detectedTransient stateRelative to the mean value N of the transient rotating speed of the cylinder not to be measuredAverageA difference of (2), a difference of Δ NDifference in＝|NTransient state-NAverageL. The speed difference threshold value can be determined through a calibration test when delta N isDifference inWhen the threshold value is smaller than the threshold value, the vehicle runs stably; on the contrary, when Δ NDifference inWhen the torque is larger than the threshold value, the vehicle is considered to be unstable in operation, the torque micro closed-loop control of the cylinder to be tested is required, and the ECU controls the torque micro closed-loop control according to the delta NDifference inTo calculate the regulated oil quantity Δ Q (specifically, may be represented by Δ N)Difference inThe Δ Q is calculated by a method of PID control for the feedback amount, but is not limited to this method. ) And further performing closed-loop adjustment on the compensated fuel injection quantity Q2 (at the moment, Q2 is Qd-Q1+ delta Q) of the cylinder to be measured so as to enable delta NDifference inAnd if the torque is smaller than the threshold value, the torque of the cylinder to be tested is consistent with that of other cylinders, so that the vehicle can stably run when the oil quantity is started for self-learning.
After the oil quantity estimation and the oil quantity deviation are finishedAfter the self-learning of the difference coefficient, the oil quantity pulse width conversion table Q2T unique to each injector can be obtained by using the basic Q2T table and the oil quantity deviation coefficient learning table of each injectoriSo as to compensate the oil quantity in the small oil quantity nonlinear region. Typically, the oil quantity pulse width conversion table Q2TiThe coordinate axis of (2) is consistent with the number of operating points and the oil quantity deviation coefficient learning table, and is initialized to the pulse width data in the basic oil quantity Q2T table. After the oil quantity deviation coefficient learning table is completed, firstly, the oil quantity deviation coefficient learning table can be used for calculating the estimated oil quantity corresponding to each oil quantity coordinate working point under a certain rail pressure in the Q2T table, namely QEstimating＝(1+γ)*QBasicWherein Q isBasicThe coordinate value of each oil quantity in the basic Q2T oil quantity meter; thus, a temporary estimated oil quantity lookup table reflecting the relationship between the estimated oil quantity and the driving pulse width under the current rail pressure is obtained; finally, Q2T is calculated by interpolation according to the oil quantity estimation lookup tableiAnd actual driving pulse widths corresponding to the working points of the oil quantity coordinates under the current rail pressure in the table. Repeating the above method under each rail pressure coordinate value to complete Q2T corresponding to the fuel injector to be testediAnd (4) updating the table.
The present invention will be further described with reference to the following embodiments.
Fig. 1 shows a schematic diagram of a fuel injection system. In fig. 1, fuel is sucked into a fuel fine filter 2 from a fuel tank 1 with a coarse filter, wherein a part of the fuel is pressurized in a plunger cavity of a fuel pump 3 to form pressurized fuel and flows through an oil pipe from an oil outlet valve port of the fuel pump 3 to be collected into a high-pressure pipe 5 to provide a stable and continuous pressure fuel source for the injection of an injector 7, and the surplus part of the fuel flows back to the fuel tank 1 together with return oil of the injector 7 from an overflow valve on the fuel pump 3; the pressure fuel flows from the pressure pipe 5 to the injectors 7 of the cylinders through the pressure oil pipes respectively; the injector 7 injects fuel into the combustion chamber of each cylinder of the engine according to a characteristic injection characteristic at a given timing and a given width of a pulse output from the electronic control unit ECU 8. Rail pressure sensor 6 is installed to 5 one end in the pressure pipe, and the rail pressure condition in the real time monitoring pressure pipe 5 when the rail pressure exceedes the maximum value that allows, relief valve 4 opens, and the rail pressure in the pressure pipe 5 reduces rapidly to the safety range in to guarantee entire system's safety. The electronic control unit 8 of the pressure system collects the state parameters of the engine and the pressure system detected by each sensor in real time, sends out accurate current pulse signals through a built-in control strategy and stored data, and enables corresponding pressure pump electromagnetic valves, injector electromagnetic valves and the like to generate electromagnetic force to drive corresponding actuators to act, so that the oil supply quantity, rail pressure, oil injection angle and oil injection quantity are subjected to feedback regulation according to requirements. The sensor 9 used in the pressure injection system comprises: revolution speed sensor, pressure sensor, coolant temperature sensor, fuel temperature sensor, bent axle angle sensor (or camshaft angle sensor), multiple such as accelerator pedal sensor still are equipped with on some engines: vehicle speed sensors, air flow sensors, barometric pressure sensors, boost pressure sensors, and barometric temperature sensors. The actuator drive signal 10 of the electronic control unit 8 comprises: injector solenoid and high pressure oil pump solenoid drive signals.
In the present embodiment, the electronic control unit ECU8 functions as a fuel injection controller. The EUC8 is a recognized microcomputer that grasps the operating state of the engine and the driver's demand based on various sensor signals and responds to the control demand by a pump injection driving signal. The ECU8 roughly includes a computing device (CPU), a storage device (program storage Rom, data storage EEPROM, backup RAM), a signal processing device (a/D converter and clock generation circuit), and a communication device (serial communication, CAN communication device).
As shown in fig. 2, for the pulse width-injection quantity curve of each injector in a certain fuel injection system, in fig. 2, the injection quantity difference between each injector is large, and the problem is particularly acute in a ballistic region, because the height dispersion of the injection characteristics between the injectors in the ballistic region is mainly related to the dispersion of the manufacturing process size of the parts of the injector; however, reducing the dispersion of the ejection features in the ballistic area by reducing the dispersion in the component manufacturing process dimensions is very complex and therefore extremely costly. Also, even though the dispersion between fuel injectors is good at the time of shipment, the problem of injection variation is further complicated by the fact that fuel injector degradation, which can lead to creep of the injection characteristics over time, can lead to poor consistency.
As shown in fig. 3, for a rail pressure monitoring curve of fuel system leakage, theoretically, fuel system leakage is an abnormal state of the system, and should be avoided as much as possible, but in practice, fuel system leakage is inevitable, and the present invention considers that before oil quantity estimation based on rail pressure drop, the fuel system leakage should be ensured to meet the requirement; specifically, under the working condition that the injector does not inject (such as vehicle dragging), the oil injection is forbidden, at the moment, no oil is fed into or discharged from the fuel system, the rail pressure drop detected by the ECU along with time is mainly caused by the leakage of the fuel system, the rail pressure drop in unit time under different rail pressures is recorded, and the rail pressure drop is filled into a rail pressure drop leakage meter. Before oil quantity estimation, rail pressure drop in a rail pressure drop leakage meter is acquired according to current rail pressure, the rail pressure drop is compared with a pre-defined rail pressure drop fault threshold value under the current rail pressure, and the fuel system tightness is considered to meet the requirement only when the rail pressure drop is smaller than the threshold value. The rail pressure drop shown in fig. 3 is formed within 1min, and in practical application, a reasonable unit time can be set according to specific working condition conditions, and a rail pressure drop threshold caused by fuel leakage is estimated.
In order to ensure the accuracy of oil quantity estimation even if the leakage of the fuel system per unit time is less than a threshold value, the leakage rail pressure drop delta P ' of the fuel system can be used for correcting the leakage rail pressure drop delta P ' after the rail pressure drop delta P ' is calculated during the oil quantity estimationLeakage ofSpecific current rail pressure leakage amount Δ PLeakage of＝TSpraying×ΔPUnit leak÷TUnit ofWherein T isUnit ofAs unit detection time, TSprayingIs the jet pulse width. The rail pressure drop Δ P ═ Δ P' - Δ P with the effect of fuel leakage removedLeakage of. Note that the rail pressure drops such as Δ P, Δ P mentioned in the present embodimentOil returnEtc. are rail pressure drops that subtract from fuel system leakage.
In order to improve the rail pressure acquisition precision of the ejector to be detected before and after the ejection, the rail pressure acquisition is carried out for multiple times before and after the ejection, the deviation degree of the rail pressure acquisition values is judged, and rail pressure acquisition points with the deviation exceeding a threshold value are removed. And only after the rail pressure acquisition value with small deviation degree is acquired for multiple times, the final output average value of the rail pressure before and after acquisition is confirmed. After the inter-tooth spacing rail pressure is used for collecting, the whole collecting process can be completed in the working cycle of the ejector to be detected.
The method of using multiple injections to control injector injection may enhance the degree of rail pressure reduction to improve rail pressure drop identification accuracy. After injection is completed and rail pressure collection before and after injection is completed, the injection rail pressure drop can be calculated and obtained. In order to enhance the accuracy of rail pressure drop calculation, the method also judges the rail pressure drop deviation degree obtained by multiple times of calculation so as to eliminate the rail pressure drop with the deviation exceeding the threshold value. And when enough rail pressure drops with small deviation degrees are collected, calculating the final output average value of the rail pressure drops.
In order to prevent adjacent injections from affecting each other in the multiple injections, a minimum injection interval angle of the multiple injections is specified. And confirming the minimum oil injection interval angle without influencing the oil quantity by using a theoretical calculation or experimental method, and filling the minimum oil injection intervals determined under different injection working conditions into a minimum interval query table. The minimum injection interval is used as one of limiting conditions of the oil quantity function for confirming the rail pressure drop, and the oil quantity estimation function can be started only when the required injection pulse width is long enough and the pulse width and the minimum interval angle requirements of multiple times of small oil quantity injection are met. When multiple times of injection are carried out, the minimum oil injection interval angle is obtained according to the injection working condition table look-up, and the adjacent injection interval is specified to be not smaller than the minimum oil injection interval angle.
Fig. 4 shows a correlation curve between fuel quantity and rail pressure drop of each injector of the fuel system. Studies have found that there is a strong correlation between the amount of oil Q flowing out of the rail tube and the pressure drop Δ P in the rail tube. Specifically, the correlation coefficient K between the oil amount Q and the pressure drop Δ P in the rail pipe is mainly determined by the internal volume of the rail pipe and the compression modulus of the fuel. The internal volume of the rail is fixed, and the compression modulus of the fuel is determined by the type of fuel, the bearing capacity (rail pressure) of the fuel, the temperature of the fuel, and the like. Since the fuel type on a particular engine is constant, the correlation coefficient is a function of rail pressure and oil temperature, i.e., K — Fun (P, T). The invention constructs a correlation coefficient lookup table, and determines the value taking conditions of the correlation coefficient under different rail pressures and oil temperatures by using a theoretical calculation combined with an experimental method. After the correlation coefficient is determined, the oil quantity Q flowing out of the rail pipe can be obtained according to the rail pressure drop obtained by calculation by using a formula Q ═ Δ P × K.
As shown in FIG. 1, the total oil flow Q from the rail pipe is generally obtained after N consecutive injections of the same short pulse widthGeneral assembly(fuel system leakage has been subtracted) can be made up of two parts of oil volume: the return oil of the ejector 7 and the injection oil of the ejector 7. Therefore, it is desirable to use a method for determining the total oil return Q of a fuel system under current operating conditionsTotal returnThen determining the total oil quantity Q flowing out of the rail pipe after the injector sprays under the current working conditionGeneral assemblyAnd finally the total quantity of oil injected Q of the injectorTotal spraying＝QGeneral assembly–QTotal return. The oil return amount corresponding to a certain injection pulse width under a certain orbit pressure can be determined by using a test mode, and the oil return amount is filled into an oil return amount look-up table; therefore, when the fuel injector is not aged, the oil return amount of single injection, namely Q, can be obtained according to the rail pressure and the injection pulse width look-up tableOil returnMap (P, L), the total oil return Q of N consecutive injections of the same short pulse widthTotal return＝N*QOil return＝N*Map(P、L)。
During actual engine operation, each injector gradually ages, and the oil return amount of each injector generates creep deformation, and the oil return amount obtained by looking up a table is not accurate any more. The invention defines and calculates the return oil aging factor as lambda to determine the return oil quantity after the injector is aged. The aging factor is calculated by, but not limited to, stopping oil injection and oil pump oil pumping of an injector under the condition of vehicle back-dragging working condition or ventilation stroke (at the moment, the injector does not work), so that the fuel oil system has no fuel oil pumping or fuel oil spraying, then triggering the injector to be tested to inject for multiple times by standard pulse width, wherein the injector needle valve can not be opened under the pulse width to actuate the injector, but oil return of the injector can occur, and the rail pressure drop generated according to the oil returnCalculating an oil return estimation quantity QEstimating oil return. When injector degradation occurs, QEstimating oil returnAnd the basic oil return Q obtained by a standard pulse width look-up tableBasic oil returnWill make a difference, then
Figure BDA0001561283380000121
And correcting the basic oil return quantity query table by using the aging factor, and solving the aged oil return quantity by using the corrected oil return query table.
As shown in fig. 5, which is a correlation curve between the fuel quantity and the rail pressure of an injector of the fuel system at different pulse widths, it can be known from fig. 5 that the fuel injection quantity will change with the rail pressure after the pulse width is determined. In the fuel quantity estimation multi-injection process, the rail pressure at the time of injection is gradually decreased with each fuel injection, and therefore the starting rail pressure of each injection is different, and as can be seen from fig. 5, although the injection pulse width is the same, the change in the starting rail pressure causes the fuel injection quantity to change. If the influence of the rail pressure dynamic drop is not considered, the estimated fuel quantity Q is obtained in the process of obtaining the total injection of the injectorTotal sprayingThereafter, the initial injection rail pressure P can be calculated directly from the number of injections NInitialSingle fuel injection quantity QEstimating，QEstimating＝QTotal sprayingN, however, due to the drop in initial injection rail pressure, Q is actuallyTotal sprayingDividing by N to obtain the average rail pressure P in the dynamic descending process of the rail pressuremCorresponding average injected oil quantity QmThe average rail pressure P is required to be used according to the change relation of the oil quantity with the rail pressure under the current driving pulse widthmTo obtain a correction coefficient α, and for QmCorrected to obtain the initial injection rail pressure PInitialActual single injection oil quantity QEstimatingSpecifically, since the relationship between the amount of oil and the rail pressure can be represented in the table Q2T, when the drive pulse width is fixed, the table Q2T is checked to obtain the amount of oil injected, i.e., Q ═ Map (P), and then the correction coefficient α is equal to Map (P ═ Map (P))Initial)/Map(Pm) Then single injection quantity Q of initial injection rail pressureEstimating＝α*Qm＝α*QTotal spraying/N＝α*(QGeneral assembly–QTotal return)/N。
P used in calculating αmIs the average injected oil quantity QmCorresponding rail pressure, a preferred finding PmExample of (1) setting PmThe rail pressure is the average of the rail pressures collected before and after the oil mass estimation multiple injection. Of course, the description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, and other different methods of finding P may be usedmSince the standard injector base oil quantity pulse width conversion table Q2T is used in the first self-learning process, the accuracy of each injector is not sufficient, so the correction coefficient α obtained in the first calculation has a certain deviation, but as the first self-learning process is completed, the second estimated oil quantity will use the updated individual Q2T of each injectoriThe table is used to calculate the correction factor α, and after several iterations, the accuracy of the correction factor α will gradually increase, and the accuracy of the small oil amount estimation will further increase.
Fig. 6 is a schematic diagram of an algorithm for estimating fuel injection quantity and pulse width correction based on rail pressure drop. When the condition is satisfied, step 602 starts fuel quantity estimation learning, and completes fuel quantity estimation and self-learning of the injector to be tested when the engine normally operates. The injection pulse width is long enough to open the injector needle valve, the rail pressure drop at this time is composed of the fuel injection quantity and the oil return quantity, step 607 is to collect and record the rail pressure drop of the total oil quantity, and the total estimated oil quantity Q is converted according to the correlation coefficient obtained by looking up the table in step 606General assembly(ii) a The total estimated fuel quantity Q of the injector can be calculated by subtracting the fuel return quantity calculated in step 608 from the total estimated fuel quantityTotal sprayingThe final single fuel injection quantity Q can be obtained after the rail pressure dynamic reduction coefficient is corrected and divided by the injection timesEstimating。
As shown in fig. 7, the aging diagram of the oil quantity characteristic curve of a certain injector is shown, where a curve 1 is a basic oil quantity characteristic curve of a series of injectors, a curve 2 is an actual oil quantity characteristic curve of a certain injector when the injector leaves a factory, and a curve 3 is an aged oil quantity characteristic curve of the injector; the deviation coefficient 1 is the deviation of the oil quantity characteristic of a certain oil injector when the oil injector leaves the factory relative to the basic oil quantity characteristic curve, and the deviation coefficient 2 isDeviation of the aged fuel quantity characteristic of a certain injector from the basic fuel quantity characteristic curve. Determining the driving pulse width of multiple injections when the oil quantity estimation function is implemented according to the table of checking the rail pressure and the basic oil quantity Q2T at different working points, driving the injector to inject for N times continuously according to the pulse width, and estimating the oil quantity to obtain the single injection oil quantity QEstimatingIn step 609, a deviation factor γ of the estimated fuel quantity relative to the base fuel quantity is calculated, wherein
Figure BDA0001561283380000131
And filling the deviation coefficient into the oil quantity deviation coefficient learning table of the tested injector. According to the fuel injection precision required by the project, the number of learning operating points in the fuel quantity deviation coefficient learning table is defined (generally, the learning operating points are deleted on the basis of the operating points of the basic Q2T table, and the number of the learning operating points is defined to be the same as the operating points of the Q2T table in the specification) so as to balance the learning efficiency and the fuel quantity precision. After the deviation coefficient of a certain working condition point is obtained through calculation, if the deviation coefficient is far larger than the deviation coefficients of other working condition points or the deviation coefficient obtained through calculation at the time is far larger than the deviation coefficient obtained through calculation at the same working condition at the last time, the accuracy of oil quantity estimation is questioned, and the ECU recalculates the deviation coefficient of the suspicious point.
The injector deviation factor dotted curves 1, 2 in fig. 7 each represent the degree of deviation of the injector from the basic injection characteristic, but differ from each other. The deviation coefficient dotted curve 1 represents the deviation of the oil mass characteristic of a certain oil injector when leaving a factory relative to the basic oil mass characteristic curve; the deviation factor dotted curve 2 represents the deviation of the aged oil quantity characteristic of a certain injector from the basic oil quantity characteristic curve. In step 602 of fig. 6, there are two conditions for starting fuel quantity self-learning, the first condition is that the engine or the whole vehicle is just delivered, the fuel injector never performs fuel quantity estimation learning, and the purpose of performing injector fuel quantity self-learning to obtain the deviation coefficient is to determine the deviation degree γ of each injector fuel quantity from the basic fuel quantityLeave factoryFor small oil amount compensation control, the deviation coefficient 1 is the same(ii) a condition; in the second case, when the injector is aged, the fuel injection characteristic curve is shifted overall, and in this case, although the fuel quantity estimation learning has been performed, in order to determine the influence of the aging on the fuel injection curve, the injector fuel quantity deviation coefficient γ is estimated againAging ofSo as to meet the requirement of aging correction of the oil injector, and the deviation coefficient 2 is the condition. The drift Δ γ (Δ γ ═ γ) of the two deviation coefficients can therefore be usedAging of-γLeave factory) To characterize the age of the injector. The invention defines the deviation drift aging fault threshold, compares the oil mass deviation coefficient drift delta gamma with the aging fault threshold, and reminds a driver of needing to process in time when the surface of the oil sprayer aging fault occurs when the deviation coefficient drift exceeds the aging fault threshold.
In step 602, in the self-learning condition calculation of the aging correction oil quantity of the starting oil injector, in order to determine the aging correction time, the mileage or the engine running time which is the last aging correction is used for judgment, and the deviation coefficient gamma of the engine which runs at the characteristic working point can be detected at the set characteristic working pointCharacteristic (i)And calculating its deviation coefficient gamma with respect to the last aging correctionFeature (i-1)Determining whether the fuel injector needs aging correction or not by judging whether the offset is larger than an aging correction threshold or not; the characteristic working condition points are calibrated when the fuel injector leaves a factory, and the working condition points which obviously affect the performance of the fuel injector or the working condition points which are frequently used for operating the engine can be preferentially selected as the characteristic working condition points. It is noted that the current deviation coefficient γ obtained by the detectionCharacteristic (i)It is also possible to confirm the degree of degradation of the injector, that is, the characteristic operating point deviation coefficient drift amount Δ γ ═ γ ″Characteristic (i)-γCharacteristic (leave factory)Wherein γ isCharacteristic (leave factory)When the average deviation degree of the characteristic working condition point relative to the basic oil quantity is just before the engine or the whole vehicle leaves a factory, when the delta gamma' exceeds the aging fault threshold value, the condition that the fuel injector is also seriously aged can be also shown.
It should be noted that the above calculation of the deviation coefficient γ and the drift amount Δ γ can be performed by different methods, and the present invention is described by referring to a preferred embodiment, which is merely exemplary in nature and is in no way intended to limit the application or use of the present invention. The method for averaging the deviation coefficients under all working conditions is used when the deviation coefficient gamma of a certain oil sprayer is obtained, and the deviation of the average value is compared with a fault threshold value or an aging correction threshold value; the other method for obtaining the characteristic value of the deviation coefficient further comprises the steps of carrying out weighted average on the deviation coefficients under all the working conditions so as to increase the influence of important working condition points, or respectively comparing whether the deviation coefficient drift amount of each working condition point is larger than a threshold value, and determining aging fault or aging correction when the deviation coefficient drift of more than 50% of the working condition points is larger than the threshold value.
The fuel quantity estimation and self-learning of the injector to be tested can be done during normal operation of the engine. In the running process of the internal combustion engine, the step 605 is used for calculating and implementing multiple injections, specifically, the invention divides the long pulse width injection of the injector to be tested into limited N times of continuous injection with the same short pulse width and one time of compensation injection, and completes the injection function of the injector N +1 times by using a multiple injection mode. Wherein the N times of continuous injection with the same short pulse width are used for estimating the oil quantity, and the total oil quantity injected is Q1; and the rest 1 injection is compensation injection Q2 (required to fall in a linear region of an oil quantity characteristic curve to ensure the accuracy of oil quantity injection), the function of the compensation injection is to ensure that the torques before and after the oil quantity estimation function are consistent, and the compensation injection quantity Q2 is Qd-Q1+ delta Q, wherein Qd is the injection quantity required by the injector, and delta Q is the micro-closed loop oil quantity adjustment.
The injector to be tested performs injection with a small oil quantity for N times, the injection with the small oil quantity in the self-learning stage is not accurate enough, although the target is Q1, the actual oil quantity is definitely deviated from Q1, so that the total oil quantity of the injector to be tested is different from the total oil quantity of injectors of other cylinders, and the combustion effect in a multi-injection mode is possibly influenced, so that the torque generated by the cylinder to be tested (namely the cylinder to which the injector to be tested belongs, the same below) is different from that of the other cylinders, and therefore the engine speed fluctuation is shown, and the vehicle runs unstably or slightly shakes.
In order to solve the problems, the invention adopts a method of closed-loop control compensation for the torque of the cylinder to be measured after the oil mass self-learning function is started. Because the difference of the torque generated by each cylinder is reflected on the transient rotation speed of each cylinder (it should be noted that the adopted torque difference characterization quantity includes but is not limited to the transient rotation speed, for example, the transient rotation speed increment, the cylinder pressure, etc. can also characterize the torque difference of each cylinder, and in this embodiment, the transient rotation speed of each cylinder is taken as an example), the ECU can perform micro-closed loop adjustment on the oil mass of the cylinder to be measured by detecting the transient rotation speed of each cylinder and then comparing the transient rotation speed of the cylinder to be measured with the average transient rotation speed of the cylinder not to be measured, so as to make the torque of the cylinder to be measured the same as that of other cylinders, or control the torque difference of the cylinder to be measured and that of other cylinders within a micro range, and the micro torque difference is generally allowed and is difficult for a driver to.
The specific implementation steps are that after the oil quantity self-learning is started, the ECU immediately starts the transient rotating speed detection function of each cylinder of the engine, and calculates the transient rotating speed N of the cylinder to be detectedTransient stateRelative to the mean value N of the transient rotating speed of the cylinder not to be measuredAverageA difference of (2), a difference of Δ NDifference in＝|NTransient state-NAverageL. The speed difference threshold value can be determined through a calibration test when delta N isDifference inWhen the threshold value is smaller than the threshold value, the vehicle runs stably; on the contrary, when Δ NDifference inWhen the torque is larger than the threshold value, the vehicle is considered to be unstable in operation, the torque micro closed-loop control of the cylinder to be tested is required, and the ECU controls the torque micro closed-loop control according to the delta NDifference inTo calculate the regulated oil quantity Δ Q (specifically, may be represented by Δ N)Difference inThe Δ Q is calculated by a method of PID control for the feedback amount, but is not limited to this method. ) And further, the compensated oil injection quantity Q2 of the cylinder to be measured is adjusted in a closed loop mode to enable delta NDifference inAnd if the torque is smaller than the threshold value, the torque of the cylinder to be tested is consistent with that of other cylinders, so that the vehicle can stably run when the oil quantity is started for self-learning.
As shown in fig. 8, to update the pulse width conversion table Q2T for a given injector fuel quantityiAfter completing the fuel quantity estimation and the self-learning of the fuel quantity deviation factor, the base Q2T table and the fuel quantity deviation system for each injector may be used in step 610Obtaining an oil quantity pulse width conversion table Q2T unique to each injector from a number learning tableiSo as to compensate the oil quantity in the small oil quantity nonlinear region. Typically, the oil quantity pulse width conversion table Q2TiThe coordinate axis of (2) is consistent with the number of operating points and the oil quantity deviation coefficient learning table, and is initialized to the pulse width data in the basic oil quantity Q2T table. After the oil quantity deviation coefficient learning table is completed, firstly, the oil quantity deviation coefficient learning table can be used for calculating the estimated oil quantity corresponding to each oil quantity coordinate working point under a certain rail pressure in the Q2T table, namely QEstimating＝(1+γ)*QBasicWherein Q isBasicThe coordinate value of each oil quantity in the basic Q2T oil quantity meter; thus, a temporary estimated oil quantity lookup table reflecting the relationship between the estimated oil quantity and the driving pulse width under the current rail pressure is obtained; finally, Q2T is calculated by interpolation according to the oil quantity estimation lookup tableiAnd actual driving pulse widths corresponding to the working points of the oil quantity coordinates under the current rail pressure in the table. Repeating the above method under each rail pressure coordinate value to complete Q2T corresponding to the fuel injector to be testediAnd (4) updating the table.
As shown in FIG. 8, the method determines the Q2T of the fuel injector to be tested according to the fuel quantity deviation coefficient learning table of the fuel injector and the characteristic table of the basic fuel quantity Q2TiTable shows one example of the actual drive pulse width at 50 bar. First, respective estimated oil amounts obtained by performing injection at 50bar at respective drive pulse widths in the basic Q2T characteristic table are determined from the deviation coefficient learning table; thus, a temporary oil quantity estimation lookup table reflecting the relationship between the estimated oil quantity and the driving pulse width at the current 50bar rail pressure is obtained, but the oil quantity coordinate values of all points in the oil quantity estimation lookup table are different from the oil quantity coordinate values of all points in the basic Q2Ti table, so that the basic Q2T needs to be obtained by an interpolation method according to the oil quantity estimation lookup tableiThe driving pulse width corresponding to the oil mass coordinate value of each point in the table is backfilled into Q2TiAnd covering the original pulse width data in the row with the rail pressure of 50bar corresponding to the table. The method is repeated under each rail pressure coordinate value, and the whole Q2T of the current fuel injector can be completediThe table update work.
Finally, the fuel system is fedAnd performing oil quantity correction control in a small oil quantity nonlinear region. As shown in fig. 6, when no fuel quantity estimation learning is performed in step 601, step 604 uses a table lookup of a given basic Q2T table to find the fuel injection pulse width and determines whether fuel quantity estimation self-learning is required. And in step 603, self-learning is completed to obtain an oil quantity pulse width conversion table Q2T unique to each injectoriThereafter, Q2T may be usediThe table is looked up to obtain the corrected fuel injection pulse width so as to ensure the consistency of the small fuel injection of the injector. When aging compensation is required, the fuel amount estimation learning can still be performed again to correct the aging of the injector. Before the aging correction learning is completed, the original Q2T obtained in step 610 is usediThe table obtains the final injection pulsewidth, and after the aging correction learning is complete, the updated Q2T is usediThe table obtains the final corrected injection pulse width.
The differences between the solution of the present invention and the prior art are as follows:
(1) in order to improve the accuracy of the fuel quantity estimation of the injectors to be tested, the prior art solutions (mally) use statistical methods to ensure that the rail pressure drop is calculated correctly, although after a few hundred estimates, the estimated fuel quantity can be accurate to within ± 0.1 mg. However, the method greatly reduces the operation efficiency of the algorithm and increases the data processing burden of the ECU.
The rail pressure acquisition is carried out for multiple times before and after the injection, the deviation degree of the rail pressure acquisition values is judged, and rail pressure acquisition points with the deviation exceeding a threshold value are removed. Only after rail pressure acquisition values with small deviation degrees are acquired for multiple times, the final output mean value of the rail pressure before and after acquisition is confirmed; the invention also judges the rail pressure drop deviation degree obtained by multiple times of calculation to eliminate the rail pressure drop with the deviation exceeding the threshold value, and the final output average value of the rail pressure drop is calculated only after enough rail pressure drops with smaller deviation degrees are collected. The method ensures the accuracy of rail pressure acquisition and rail pressure drop calculation at the source, and avoids the reduction of algorithm operation efficiency due to big data statistical processing.
(2) In the prior art, in the solution (marayleigh corporation), four characteristic points P1-P4 are selected for determining the estimated oil quantity of the rail pressure drop under each rail pressure, wherein the characteristic points P1 and P2 are in a small oil quantity nonlinear region, and the characteristic points P3 and P4 are in an oil quantity linear region, and the injection rule of the injector can be approximately and accurately reconstructed by using four points and two straight lines. The method used by marayl estimates the absolute value of the fuel quantity to reconstruct the injection law, but the absolute value of the fuel quantity does not account for the degree of deviation of the injector from the basic fuel quantity characteristic curve.
In order to overcome the defect, the invention designs an oil quantity deviation coefficient learning table of each injector, and the oil quantity Q is estimated by single injection under the condition of obtaining a certain rail pressure and a certain pulse widthEstimatingThen, a deviation coefficient gamma of the estimated oil amount relative to the basic oil amount is calculated, wherein
Figure BDA0001561283380000171
The deviation factor is then filled into the fuel quantity deviation factor learning table for the test injector. The number of operating points in the fuel quantity deviation coefficient learning table (which is generally truncated on the basis of the operating points of the table of the base fuel quantity Q2T) may be defined according to the actual injector characteristic curve conditions and the fuel injection accuracy required for the items to balance the learning efficiency with the fuel quantity control accuracy. The deviation coefficient of the injector represents the deviation degree of the injector relative to the injection characteristic of the basic Q2T, when the injector is aged, the injection characteristic curve is generally deviated, the integral deviation degree of the injection characteristic curve is continuously shifted to be larger along with the increase of the aging degree, so that the aging degree of the injector can be represented by using the deviation amount delta gamma of the deviation coefficient. Meanwhile, the deviation coefficient can be used for judging the accuracy of oil quantity estimation, if the deviation coefficient obtained by calculation under a certain working condition is far larger than the deviation coefficients of other working condition points after the oil quantity estimation learning is carried out, or the deviation coefficient obtained by calculation at the time is far larger than the deviation coefficient obtained by calculation under the same working condition at the last time, the accuracy of oil quantity estimation is questioned, and the ECU carries out the renewed judgment on the deviation coefficient of the questioned pointAnd (4) calculating.
(3) When the fuel quantity self-learning algorithm is used for injecting for a plurality of times under the same pulse width, the rail pressure during injection is gradually reduced along with each fuel injection, so that the initial rail pressure P of each injectionInitialAll are different, which results in the difference of fuel injection quantity between each injection, and the marayl patent does not consider the influence of different initial rail pressure of each injection on fuel quantity in the process of multiple injections, and only according to the formula Q ═ QGeneral assemblyCalculating initial injection rail pressure PInitialAnd the lower single fuel injection quantity Q. The invention considers that although the driving pulse width is the same, the Q can not be simply adjusted due to different initial rail voltagesGeneral assemblyThe actual injection oil amount at the initial starting injection rail pressure is set to be/N. That is to say, QGeneral assemblyThe division by N gives the mean rail pressure P during the dynamic drop of rail pressuremCorresponding average injected oil quantity QmThus obtaining QmThen, the average fuel injection quantity Q is used according to the change relation of the fuel quantity under the current driving pulse width along with the rail pressuremCorresponding rail pressure PmCorrected to obtain the initial injection rail pressure PInitialLower actual injection oil quantity QEstimating. Since the change of oil quantity along with the rail pressure can be shown in the Q2T table, after the drive pulse width is determined, the Q2T is checkediThe fuel injection quantity, i.e. Q ═ Map (P), is tabulated, and the correction factor α ═ Map (P)Initial)/Map(Pm) Then, the single injection quantity Q at the initial injection rail pressure is α QmSince the correction factor α at the first self-learning of the fuel quantity is calculated based on the initial standard injector profile Q2T table, which is different from the characteristic data of each individual injector, the correction factor α calculated at the first self-learning of the fuel quantity has a certain error, but as the first self-learning of the fuel quantity is completed, the second self-learning will use the updated Q2T of each individual injector individuallyiThe table is used to calculate the correction factor α, and after several self-learning iterations, the accuracy of the correction factor α will gradually increase, and the accuracy of the small oil amount estimation will further increase.
(4) The prior art solutions (Bosch Corp.) are believed to beThe injector is driven by the pulse width without opening the needle valve of the injector, no oil injection is performed at the moment, the rail pressure reduction is completely caused by oil return, and the oil return amount can be determined by measuring the rail pressure reduction; and when in normal injection, determining the total oil quantity Q flowing out of the rail pipe after the injector under the current working condition injects through the rail pressure dropGeneral assemblyAnd finally the quantity of oil injected by the injector QTotal spraying＝QGeneral assembly–QTotal return. Although the calculation of the oil return amount and the oil injection amount is summarized in terms of implementation conditions and directions, the detailed implementation steps are not specifically mentioned. Another solution (mally) considers that the system generates fuel losses when the rail pressure is high, and estimates them and deducts the effect of the fuel losses when estimating the injected quantity. First, a first fuel loss is determined, which is directly proportional to the measured duration, then a second fuel loss is determined, which is directly proportional to the number of openings of the fuel injector, and finally the fuel loss is determined by adding these two values. It is clear that the marayl approach to fuel loss estimation is relatively simple and does not take into account the effects of injector aging on leakage.
Theoretically, the leakage of the fuel system is an abnormal state of the system, the leakage is generally avoided as much as possible, but in reality, the fuel system can not avoid the leakage, the invention considers that before the self-learning of the oil quantity, the leakage of the fuel system can meet the requirement, specifically, under the working condition that an injector does not inject (such as the over run working condition of a vehicle), the injection of pump oil is forbidden, no oil is fed into or discharged from the fuel system, the rail pressure detected by an ECU (electronic control unit) is mainly caused by the leakage of the fuel system along with the time, the rail pressure drop in different rail pressures and unit time is recorded, and the rail pressure drop in the fuel leakage is filled into a rail pressure drop table. Before oil mass self-learning, rail pressure drop in a fuel leakage rail pressure drop table is acquired according to current rail pressure, and is compared with a rail pressure drop fault threshold value under the current rail pressure defined in advance, and the fuel system tightness is considered to meet the requirement only when the rail pressure drop is smaller than the threshold value. In order to ensure the accuracy of oil quantity estimation even if the leakage of the fuel system per unit time is less than a threshold value, the leakage of the fuel system can still be used after the rail pressure drop delta P' is calculated during the self-learning of the oil quantityCorrecting the pressure difference by calculating the pressure drop delta P of the fuel leakage rail under the oil injection pulse width duration of the injector to be tested according to the pressure drop of the leakage rail in unit timeLeakage ofThen, the rail pressure drop Δ P, which is affected by the fuel leakage, is removed as Δ P' - Δ PLeakage of. Note that reference herein to rail pressure drops such as Δ P, Δ POil returnEtc. are rail pressure drops that subtract from fuel system leakage.
In the invention, the oil return amount corresponding to a certain injection pulse width under a certain rail pressure is determined by using a test mode, and the oil return amount is filled into an oil return amount look-up table; thus, ideally, the amount of oil returned for a single injection, i.e., Q, is obtained from a table look-up of rail pressure and injection pulsewidthOil returnMap (P, L). In the actual operation process of the engine, each injector gradually ages, so that the oil return amount of each injector generates creep deformation, and the oil return amount obtained by looking up the table is not accurate any more. The present invention provides a method to determine the amount of fuel returned after injector aging. The specific method comprises the steps of triggering the ejector to be tested to carry out multiple injection under the working condition that the ejector does not carry out injection (such as the vehicle dragging working condition or the ventilation stroke), triggering the ejector to be tested to carry out multiple injection by using a standard pulse width, enabling the needle valve of the ejector not to be opened under the pulse width to actuate the ejector, but causing oil return of the ejector, collecting and calculating the pressure drop delta P of an oil return rail under the standard pulse widthOil returnAnd converting the correlation coefficient into an oil return estimation quantity Q under the standard pulse widthEstimating oil return. When injector degradation occurs, QEstimating oil returnLook-up table for oil return quantity Q based on standard pulse widthBasic oil returnWill generate a difference, and define the oil return aging factor as lambda
Figure BDA0001561283380000181
After the oil return aging factor is determined, the invention designs a specific implementation step for determining the oil quantity of the ejector to be tested. When the engine normally runs, the injector to be tested is triggered to inject by using a multi-injection method, the injector needle valve is opened due to the fact that the injection pulse width is long enough, the rail pressure drop at the moment is composed of the oil injection quantity and the oil return quantity, the rail pressure drop of the total oil quantity is collected and recorded, and the rail pressure drop is converted into the total oil quantity Q flowing out of the rail pipeGeneral assembly(ii) a Calculating the basic oil return amount according to the pulse width and the rail pressure table, and performing oil return Q on the fuel system according to the oil return aging factorTotal returnCorrecting to confirm the return oil quantity after aging of the injector, and finally estimating the oil quantity Q of the total injection of the injectorTotal spraying＝QGeneral assembly–QTotal return。
(5) In order to ensure that the fuel quantity self-learning function can be executed during normal operation of the engine, the current solution (mally corporation) is to first record the total fuel quantity of multiple injections as Q1 after the multiple injections are executed; and then, executing compensation injection again, wherein the injection quantity is Q2(Q2 is Qd-Q1, and Qd is the injection quantity required by the injector) so as to make up for the shortage of the injection quantity. The injector to be tested performs small-oil-amount multiple injection, the injection of the small oil amount in the self-learning stage is not accurate enough, although the target is Q1, the actual oil amount is definitely deviated from Q1, so that the total oil amount of the injector to be tested is different from the total oil amount of injectors of other cylinders, and the combustion effect in the multiple injection mode is possibly influenced, so that the torque generated by the cylinder to be tested (namely the cylinder to which the injector to be tested belongs, the same below) is different from that of the other cylinders, and therefore signal fluctuation such as the rotating speed of an engine is represented, and the vehicle runs unstably or slightly shakes.
In order to solve the problems, the invention adopts a method of closed-loop control compensation for the torque of the cylinder to be measured after the oil mass self-learning function is started. Because the difference of the torque generated by each cylinder is reflected on the transient rotation speed of each cylinder (it should be noted that the adopted torque difference characterization quantity includes but is not limited to the transient rotation speed, for example, the transient rotation speed increment, the cylinder pressure, etc. can also characterize the torque difference of each cylinder, and the transient rotation speed of each cylinder is taken as an example in the description), the ECU can perform Δ Q micro-closed loop adjustment on the oil mass of the cylinder to be measured by detecting the transient rotation speed of each cylinder and then comparing the transient rotation speed of the cylinder to be measured with the average transient rotation speed of the cylinder not to be measured, so as to make the torque of the cylinder to be measured identical to that of other cylinders, or control the torque difference of the cylinder to be measured and that of other cylinders within a micro range, and the micro torque difference is generally allowable and is difficult for a driver to perceive.
The specific implementation steps are that after the self-learning of the oil quantity is started, the ECU immediately starts the detection function of the transient rotating speed or the transient rotating speed increment of each cylinder of the engine and calculates the rotating speed N of the cylinder to be detectedTransient stateRelative to the mean value N of the transient rotating speed of the cylinder not to be measuredAverageA difference of (2), a difference of Δ NDifference in＝|NTransient state-NAverageL. The speed difference threshold value can be determined through a calibration test when delta N isDifference inWhen the threshold value is smaller than the threshold value, the vehicle runs stably; on the contrary, when Δ NDifference inWhen the torque is larger than the threshold value, the vehicle is considered to be unstable in operation, the torque micro closed-loop control of the cylinder to be tested is required, and the ECU controls the torque micro closed-loop control according to the delta NDifference inTo calculate the regulated oil quantity Δ Q (specifically, may be represented by Δ N)Difference inThe Δ Q is calculated by a method of PID control for the feedback amount, but is not limited to this method. ) And further performing closed-loop adjustment on the compensated fuel injection quantity Q2 (at the moment, Q2 is Qd-Q1+ delta Q) of the cylinder to be measured so as to enable delta NDifference inAnd if the torque is smaller than the threshold value, the torque of the cylinder to be tested is consistent with that of other cylinders, so that the vehicle can stably run when the oil quantity is started for self-learning.

Claims (9)

1. A method for controlling the small oil quantity of a fuel injector is characterized in that: the control method comprises the steps of estimating the oil quantity by using rail pressure drop of the ejector to be detected before and after multiple times of small oil quantity injection, comparing the estimated oil quantity with a basic oil quantity characteristic curve of the ejector to obtain a deviation coefficient of the estimated oil quantity relative to the basic oil quantity, and filling the deviation coefficient into an oil quantity deviation coefficient learning table; after learning of the oil quantity deviation coefficient learning table is completed, the oil quantity pulse width conversion table Q2T unique to each injector is obtained by using the deviation coefficient corresponding to the working condition in the small oil quantity nonlinear regioniAnd using the corrected oil quantity pulse width conversion table Q2TiLooking up a table to obtain the final corrected injection pulse width; the ejector to be tested is a group of ejectors and comprises a plurality of ejectors; the method specifically comprises the following steps:
(1) oil mass self-learning starting judgment: judging whether the fuel injector needs to be started or not;
(2) oil quantity estimation enabling judgment: after the oil mass self-learning function is started, external condition judgment is carried out: evaluating whether the vehicle meets the external state or working condition requirement of the oil quantity estimation; and performing internal condition judgment: detecting the tightness of the fuel system to judge whether the fuel system meets the requirement of estimating the internal tightness of the fuel quantity; enabling the oil quantity estimation function when the internal and external conditions are met;
(3) collecting rail pressure before oil injection: after the oil quantity estimation function is enabled, the oil pumping function and the oil injection function are closed, and rail pressure collection reasonableness judgment before the injection of the injector to be tested is started are carried out under the conditions that the fuel system has no fuel input and output and the rail pressure is stable;
(4) injecting by an injector: after the rail pressure collection before injection is finished, executing the injection function of the injector, selecting proper injection times and injection pulse width, and under the condition that the pump oil is closed and other cylinders except the cylinder to be detected do not inject oil, triggering the injector to be detected to execute N +1 times of injection by using a multi-injection mode, wherein the injection comprises N times of continuous injection with the same short pulse width and 1 additional time of micro closed-loop compensation injection;
(5) and (3) rail pressure acquisition after oil injection: after the ejector completes N times of continuous ejection with the same short pulse width, the rail pressure acquisition and the rail pressure acquisition rationality judgment of the ejector to be detected after ejection are carried out again;
(6) rail pressure drop calculation: calculating the pressure drop of the injection rail of the injector to be detected according to the pressure difference before and after injection, and carrying out rationality judgment on the rail pressure drop so as to obtain a final rail pressure drop output average value;
(7) estimating the total oil quantity: according to the rail pressure drop mean value and the correlation coefficient obtained by calculation, the total oil quantity Q of the rail pipe outflow estimated under the current working condition is obtainedGeneral assembly；
(8) Calculating oil return amount: determining basic oil return amount corresponding to different rail pressures and driving pulse widths through testing before the injector leaves a factory, and filling the basic oil return amount table; calculating an oil return aging factor lambda under different rail pressures, and correcting a basic oil return amount meter by using the aging factor to obtain the aged oil return amount;
(9) estimating the single injection oil quantity: according to the total oil quantity Q of the rail pipe outflow estimated under the current working conditionGeneral assemblyAnd the amount of oil returned QTotal returnCalculating the single injection estimated oil quantity Q of the injector to be tested currentlyEstimating，QEstimating＝α*(QGeneral assembly–QTotal return) α is a correction coefficient of rail pressure dynamic reduction to single injection oil quantity, and N is the injection times;
(10) updating an oil quantity deviation coefficient learning table: obtaining the estimated oil quantity Q of single injection under different rail pressures and different corresponding pulse widthsEstimatingCalculating the deviation coefficient gamma of the estimated single injection oil quantity relative to the basic oil quantity, and updating the oil quantity deviation coefficient learning table of each injector;
(11) aging faults of the oil sprayer: according to the oil mass deviation coefficient gamma of the aged oil injectorAging ofRelative to the deviation coefficient gamma obtained by self-learning of oil mass when leaving factoryLeave factoryJudging the aging degree of the oil atomizer according to the drift amount delta gamma, and comparing the aging degree with a preset fault threshold value to determine whether the oil atomizer has an aging fault;
(12) and (3) coordinating oil injection pulse width: after the self-learning is completed, the corrected oil quantity pulse width conversion table Q2T of each injector is obtained according to the oil quantity deviation coefficientiAnd checking the corrected oil quantity pulse width conversion table Q2TiA final corrected injection pulsewidth is obtained.
2. The fuel injector small oil amount control method according to claim 1, characterized by: the condition of oil quantity self-learning opening comprises that the group of injectors never carries out oil quantity self-learning since the group of injectors leaves a factory or carries out oil quantity self-learning but needs aging correction on the injectors; the aging-corrected oil mass self-learning starting condition comprises that the engine runs for a certain time from the last aging correction, or the vehicle runs for a certain mileage from the last aging correction, or the offset of the current deviation coefficient obtained by starting the oil mass estimation function under the characteristic working condition point relative to the deviation coefficient when the aging correction is carried out last time exceeds the threshold value of the aging correction.
3. The fuel injector small oil amount control method according to claim 1, characterized by: after the oil quantity self-learning is started, judging external conditions and internal conditions; the external condition judging method comprises the steps that when a vehicle runs in a fault-free state, a rail pressure sensor collects fault-free state, the power supply voltage of a power supply is stable, and the rail pressure fluctuation range is smaller than a threshold value and is stable for more than a period of time, the external judging condition is met; the internal condition judgment method comprises the following steps: when the vehicle is in a state that oil injection and pumping are forbidden to enable the fuel system to have no oil inlet and no oil outlet, the rail pressure drop in unit time under different rail pressures is recorded, the updating of a rail pressure drop leakage table is completed, the rail pressure drop under the current rail pressure is compared with a predefined rail pressure drop leakage threshold under the current rail pressure, and when the rail pressure drop is smaller than the threshold, the tightness of the fuel system is considered to meet the internal judgment condition.
4. The fuel injector small oil amount control method according to claim 1, characterized by: before the oil quantity is estimated, the leakage rail pressure drop of the fuel system is used for correcting the oil quantity, and the specific method is that the fuel leakage pressure drop delta P under the duration of the fuel injection pulse width of the injector to be detected and the current rail pressure is calculated according to the fuel leakage rail pressure drop in unit timeLeakage ofUsing the leakage rail pressure drop Δ PLeakage ofAnd correcting the rail pressure drop used for estimating the fuel injection quantity and the oil return quantity of the injector to be measured so as to remove the influence of the rail pressure drop caused by fuel leakage and enhance the estimation precision.
5. The fuel injector small oil amount control method according to claim 1, characterized by: after the oil mass estimation function is enabled, the torque of the cylinder to be measured is compared with the average torque of the cylinder not to be measured by detecting the torque difference representation signal of each cylinder, so that micro-closed loop control adjustment is performed on the oil mass of the cylinder to be measured, the micro-closed loop adjustment oil mass delta Q of the cylinder to be measured is obtained, and the consistency requirement of the torque of each cylinder is met.
6. The fuel injector small oil amount control method according to claim 1, characterized by: after the oil return amount is deviated due to the aging of the ejector, compensating and correcting the basic oil return amount meter by using an oil return aging factor; the conditions for obtaining the aging factor by calculation are as follows: the vehicle is in a state in which the injector does not need to be operated, in which state the fuel quantity estimation function of the injector to be tested is triggered with a standard pulse widthThe standard pulse width can not open the needle valve of the injector to actuate the injector, but the return oil of the injector is generated, the return oil rail pressure drop under the standard pulse width is collected and calculated, and the return oil rail pressure drop is converted into the return oil estimated quantity Q under the standard pulse widthEstimating oil return(ii) a When injector degradation occurs, QEstimating oil returnBasic oil return Q obtained by looking up table with standard pulse widthBasic oil returnDefining the difference as the return oil aging factor lambda, and then the return oil aging factor lambda is the return oil estimated quantity QEstimating oil returnAnd the basic oil return quantity Q obtained by looking up a table according to the standard pulse widthBasic oil returnI.e. λ ═ QEstimating oil return/QBasic oil returnAnd obtaining aging factors under different rail pressures, and correcting the basic oil return amount table by using the aging factors under different rail pressures to obtain the aged oil return amount.
7. The method of claim 1 wherein said correction factor α of the dynamic drop in rail pressure versus the quantity of fuel injected in a single injection event is determined by gradually dropping rail pressure during an injection event resulting in an actual quantity of fuel injected relative to an average rail pressure P during the dynamic drop in rail pressuremAverage injected oil amount Q ofmUsing the correction factor α for QmMaking a correction to obtain the initial injection rail pressure PInitialSingle injection estimation of oil quantity QEstimatingWhen the driving pulse width is fixed, the fuel injection quantity can be obtained according to the rail pressure check standard fuel quantity pulse width conversion table Q2T, namely Q is Map (P), and the correction coefficient α is Map (P)Initial)/Map(Pm) The method of multiple iterations α is used to improve accuracy.
8. The fuel injector small oil amount control method according to claim 1, characterized by: obtaining the estimated oil quantity Q of single injection under the driving pulse widths corresponding to different rail pressures and basic oil quantitiesEstimatingThen, a deviation coefficient γ of the estimated fuel amount with respect to the base fuel amount is calculated, where γ is (Q)Estimating-QBasic)/QBasic，QBasicConverting the standard oil quantity pulse width into the coordinate value of each oil quantity in the Q2T, and according to the basic oil quantity and the rail pressureThe deviation coefficient is filled in the oil quantity deviation coefficient learning table of the test injector.
9. The fuel injector small oil amount control method according to claim 1, characterized by: when the self-learning of the oil quantity is not finished, the injection pulse width which is not learned is obtained according to a rail pressure and oil quantity check standard oil quantity pulse width conversion table Q2T; after learning is finished, the learned injection pulse width can be obtained by looking up a table through respective oil mass pulse width conversion tables of the injectors; Q2T for each injectoriThe table determination method comprises the following steps: firstly, according to the oil quantity deviation coefficient learning table, the estimated oil quantity corresponding to each oil quantity coordinate value under a certain rail pressure in the standard oil quantity pulse width conversion table Q2T, namely QEstimating＝(1+γ)*QBasic；QBasicThe coordinate values of the oil quantities in the standard oil quantity pulse width conversion table Q2T are respectively; thus, a temporary estimated oil quantity lookup table reflecting the relationship between the estimated oil quantity and the driving pulse width under the current rail pressure is obtained; then, the current injector Q2T is calculated by interpolation according to the oil quantity estimation lookup tableiActual drive pulse width corresponding to each oil mass coordinate value under the current rail pressure in the table; repeating the method under different rail pressures to finish the Q2T corresponding to the fuel injector to be testediAnd (4) updating the table.
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