Closed-loop control method for injection flow of gasoline injector of gasoline direct injection engine

Abstract

The invention relates to a closed-loop control method for injection flow of an oil injector of a gasoline direct injection engine. The method comprises the following steps: performing second-order filtering processing on fuel rail pressure P to output Pfilt; carrying out discrete difference on the Pfilt to obtain a fuel rail pressure deviation Pdef; the fuel rail pressure deviation Pdef is subjected to first-order filtering processing, and Pdef-filt is output; the absolute value of the Pdef-filt is summed to obtain the fuel index FIinj of the current fuel injector; the fuel index difference delta FI between the single fuel injector and the reference fuel injector is multiplied by the fuel injection pulse width proportional gain gain to obtain a compensation fuel injection pulse width delta pw; and the fuel injection pulse width pwinj of the compensated single fuel injector is obtained by adding the fuel injection pulse width pwmaster of the reference fuel injector to the compensation fuel injection pulse width delta pw. Compared with the prior art, accurate fuel control of the fuel injector in a nonlinear area is met, and emission of a direct injection engine in a high-pressure gasoline cylinder is effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of engine electronic control systems and relates to a closed-loop control method for injection flow of an injector of a direct-injection gasoline engine. Background Art

[0002] Gasoline direct injection (GDI), a widely adopted engine control technology, improves engine power and fuel economy while also reducing engine weight and enhancing in-cylinder atomization. With the development of high-pressure direct injection technology, fuel rail pressure has increased from the initial 15MPa to the latest 50MPa. During the operation of a direct-injection gasoline engine, precise control of the injector plays a crucial role in engine performance and emissions.

[0003] Currently, direct injection engine injectors face several pressing challenges. When the injection duration is short, the linearity between injection quantity and injection timing is poor, making precise control of injection quantity difficult by simply manipulating the injection timing. Specifically, in the so-called ballistic region, due to the injector's hardware structure and electromagnetic physics, the needle valve has not yet reached full open travel. This rebound of the needle valve causes the relationship between injected fuel mass and pulse width to exhibit a uniquely nonlinear relationship in the ballistic region. This deviation from the linearity between injection quantity and injection pulse width directly impacts engine combustion and emissions. If the injection quantity is too small, the air-fuel ratio in the engine cylinder becomes lean, resulting in poor combustion and increased emissions. If the injection quantity is too large, excessive fuel enters the cylinder, leading to a rich air-fuel ratio and increased hydrocarbon and carbon monoxide emissions. Furthermore, the relationship between injection quantity and injection timing varies significantly between different injectors, making precise and uniform control of injector injection quantity difficult during mass production and actual use.

[0004] With increasingly stringent engine emissions requirements, precise control of fuel injection volume has become crucial for reducing emissions in direct-injection engines. Traditional open-loop control methods are no longer able to meet the injection precision requirements of modern engines and are unable to adapt to individual injector variations and complex operating conditions. Therefore, a method and system for precise closed-loop control of injector flow is needed to achieve precise control of the injector opening time and, consequently, the injection volume.

[0005] In the previous injector closed-loop control (ICLC) control loop, patent US2014 / 0014072A1 discloses a fuel injection control for an internal combustion engine. The pulse width compensation for the fuel error of a single injector consists of two parts: one is the opening delay time, called the minimum injection pulse (MDP); the other is the closing response (CR), which is the sum of the actuator closing delay and the injector fuel flight time. The minimum injection pulse and closing response are extracted from the electrical signal. To obtain the detectable minimum injection pulse, the system defines a threshold, but in practice, the minimum detectable pulse width may be artificially increased. Secondly, in the ballistic region with low fuel injection volume, it is difficult to detect the second-order derivative of the voltage. In addition, even small voltage changes may affect the detection of the closing response because as the pulse width becomes shorter, the voltage change caused by the ball hitting the valve seat becomes smaller.

[0006] Patent CN108361139A discloses a method for controlling low-volume fuel injectors. The method uses the rail pressure drop before and after multiple low-volume injections of the injector to estimate the fuel volume. The estimated fuel volume is compared with the basic fuel volume characteristic curve of the injector to obtain its deviation coefficient relative to the basic fuel volume, which is then entered into a fuel volume deviation coefficient learning table. After completing the learning of the fuel volume deviation coefficient learning table, the deviation coefficient corresponding to the operating condition in the low-volume nonlinear region is used to calculate the fuel volume pulse width conversion table Q2T for each injector. i , and using the modified Q2T i The final corrected injection pulse width is obtained by looking up the table. However, the patent does not explain or analyze the principle behind rail pressure compensation for fuel quantity. Furthermore, the patent requires multiple injections to enhance the stability and robustness of rail pressure drop, improve the discernibility of rail pressure drop, and then find the correlation coefficient between injection quantity and rail pressure drop. This requires learning under different rail pressure conditions, which is time-consuming and detrimental to energy consumption. Furthermore, the patent does not consider the differences between the design reference injector and the mass-produced injector. Furthermore, the patent is primarily targeted at high-viscosity diesel systems and is less suitable for low-viscosity gasoline systems. Summary of the Invention

[0007] The purpose of the present invention is to provide a closed-loop control method for the injection flow of a direct-injection gasoline engine injector in order to overcome at least one of the defects of the above-mentioned existing direct-injection engine injector technology, such as poor linearity between the injection amount and the injection time when the injection duration is short, and large differences between different injectors, which makes it difficult to accurately control the injection amount. The present invention satisfies the requirement of precise fuel control of the injector in the nonlinear region, thereby effectively reducing emissions of high-pressure gasoline direct-injection engines.

[0008] The purpose of the present invention can be achieved by the following technical solutions:

[0009] One of the technical solutions of the present invention is to provide a closed-loop control method for injection flow rate of a direct-injection gasoline engine injector. The method is based on the responsiveness of fuel pressure to injection pulse width pw and utilizes fluctuations in the engine's high-pressure rail pressure to calculate a compensated injection pulse width δpw. The engine's high-pressure rail pressure is filtered, differentiated, refiltered, and integrated in sequence to obtain a fuel index FI corresponding to the rail pressure change rate. The fuel index FI is then multiplied by the injection pulse width proportional gain gain to calculate the compensated injection pulse width δpw. The method comprises the following steps:

[0010] S1. In order to remove the noise in the signal and make the fuel rail pressure signal smoother, multiple filter coefficients are used to perform second-order filtering on the fuel rail pressure P, and the output is P filt ;

[0011] S2. In order to obtain P filt The rate of change reflects the speed of change of the fuel rail pressure P. filt Perform discrete difference to obtain the fuel rail pressure deviation P def ;

[0012] S3. In order to smooth the rate of change and reduce noise interference, the first-order differential result of the fuel rail pressure deviation P is again calculated. def Perform first-order filtering and the output is P def-filt ;

[0013] S4, the filtered P def-filt Take the absolute value and sum it to get the fuel index FI of the current injector inj ;

[0014] S5, the fuel index FI of the current injector inj , minus the fuel index FI of the reference injector obtained by looking up the table in the electronic control unit (ECU) master , get the fuel index difference δFI, then multiply it by the injection pulse width proportional gain gain to get the compensated injection pulse width δpw;

[0015] S6, injection pulse width pw of a single injector after compensation inj The injection pulse width pw of the reference injector master Add the compensation injection pulse width δpw to obtain.

[0016] The motion characteristics of the injector needle valve are described, which are divided into the long injection pulse width and short injection pulse width of the injector:

[0017] When the electronic control unit sends out an injection pulse command, due to the influence of the seating spring force, the injector needle valve takes a while to respond, and then the needle valve starts to open. The time from the pulse command being sent to the needle valve to start opening is defined as the valve opening delay; the time from the needle valve starting to open to the maximum opening is defined as the valve opening time; if the injection pulse width is long enough, the needle valve will be in a fully open state for a considerable period of time; when the injection pulse ends, due to the influence of electromagnetic induction lag, the needle valve will still be fully open for a period of time, and the time from the end of the pulse to the beginning of the needle valve closing is defined as the valve closing delay; then, under the influence of the seating spring force, the needle valve begins to close, and the time from the needle valve starting to close to being fully seated is defined as the valve closing time;

[0018] The difference between short pulse width and long pulse width is that the needle valve starts to close before it reaches the maximum opening, and the injector does not have enough time to fully open, resulting in the fuel flow being unable to enter the steady-state flow area, and thus the injection flow exhibits nonlinear characteristics.

[0019] The responsiveness of fuel pressure to injection pulse width pw is as follows: For the high-pressure fuel system, if an injection pulse event occurs in the engine control electronic control unit during the cycle, the high-pressure rail fuel pressure will change accordingly; if the injection pulse width pw is long enough, the high-pressure rail fuel pressure will drop; if the injection pulse width pw is small, the injector needle valve will not actually open due to the influence of the spring preload, no fuel will be injected into the cylinder, and the high-pressure rail fuel pressure will not drop; if the injection pulse width pw is between the two, it is the nonlinear region of the injector, and fuel will be injected into the cylinder, and the high-pressure rail fuel pressure will also drop.

[0020] As a preferred technical solution, the electronic control unit stores the charts required for the calculation.

[0021] Furthermore, in step S1, P filt The calculation formula is as follows:

[0022] P filt_当前循环 =P 当前循环 ×k1+P 前1循环 ×k2+P 前2循环 ×k3-P filt_前1循环 ×k4-P filt_前2循环 ×k5

[0023] Among them, P filt_当前循环 is the filtered engine fuel rail pressure for the current cycle,

[0024] k1 to k5 are filter coefficients, which are single values ​​ranging from 0.01 to 0.2.

[0025] P 当前循环 The engine's raw fuel rail pressure measured for the current cycle,

[0026] P 前1循环 The original fuel rail pressure of the engine measured for the first cycle,

[0027] P 前2循环 The original fuel rail pressure of the engine measured for the first 2 cycles,

[0028] P filt_前1循环 is the filtered engine fuel rail pressure of the previous cycle,

[0029] P filt_前2循环 This is the filtered engine fuel rail pressure for the first two cycles.

[0030] Furthermore, in step S2, the fuel rail pressure deviation P def The calculation formula is as follows:

[0031] P def_当前循环 =P filt_当前循环 -P filt_前1循环

[0032] Among them, P def_当前循环 is the fuel rail pressure deviation of the current cycle discrete difference,

[0033] P filt_当前循环 is the filtered engine fuel rail pressure for the current cycle,

[0034] P filt_前1循环 It is the filtered engine fuel rail pressure of the previous cycle.

[0035] Furthermore, in step S3, P def-filt The calculation formula is as follows:

[0036] P def-filt_当前循环 =P def_当前循环 ×k6+P def-filt_前1循环 ×(1-k6)

[0037] Among them, P def-filt_当前循环 is the fuel rail pressure deviation after discrete difference and filtering in the current cycle,

[0038] k6 is the filter coefficient, which is a single value and ranges from 0.01 to 0.2.

[0039] P def_当前循环 is the fuel rail pressure deviation of the current cycle discrete difference,

[0040] P def-filt_前1循环 It is the fuel rail pressure deviation after discrete difference and filtering in the previous cycle.

[0041] Furthermore, in step S4, the fuel index FI of the current injector inj The calculation formula is as follows:

[0042]

[0043] Among them, n represents the current cycle,

[0044] n-1 represents the first cycle,

[0045] P def-filt is the fuel rail pressure deviation after discrete differentiation and filtering.

[0046] Furthermore, in step S5, the fuel index difference δFI between the single injector and the reference injector is used to calculate the compensation injection pulse width δpw between the two injectors. The calculation formula of the compensation injection pulse width δpw is as follows:

[0047] δpw=k×δFI

[0048] Wherein, k is the injection pulse width proportional gain, which can be calibrated in three dimensions with respect to the injection pulse width and ambient temperature;

[0049] δFI=FI inj -FI master ,

[0050] FI inj The fuel index of a single injector is calculated based on the test results of a single independent injector produced in the engineering design.

[0051] FI master For the reference fuel index of the injector, it is calculated after testing the median value of the injector produced according to the design on the engine bench during engineering, and stored in the record table of the electronic control unit.

[0052] Furthermore, the injection pulse width pw of a single injector after compensation in step S6 is inj The calculation formula is as follows:

[0053] pw inj =pw master +k×δFI

[0054] Among them, k is the injection pulse width proportional gain, which can be calibrated in three dimensions with respect to the injection pulse width and ambient temperature.

[0055] pw master is the injection pulse width of the reference injector;

[0056] δFI=FI inj -FI master ,

[0057] FI inj The fuel index of a single injector is calculated based on the test results of a single independent injector produced in the engineering design.

[0058] FI master For the reference fuel index of the injector, it is calculated after testing the median value of the injector produced according to the design on the engine bench during engineering, and stored in the record table of the electronic control unit.

[0059] Furthermore, in step S5, the injection pulse width proportional gain, i.e., k, is calculated as follows:

[0060] k=k s / k e

[0061] Among them, k s is the regression proportional coefficient, reflecting the influence of fuel index on fuel quality. is the partial derivative of the fuel mass mass with respect to the injection pulse width pw, in the reference injector injection pulse width pw master In this state, when the injection pulse width pw changes slightly, the corresponding change rate of the fuel mass mass.

[0062] Furthermore, for the convenience of analysis, the median sample of injectors with the same design but different production batches is generally selected as the injector master, and the other injectors are mass-produced parts. The relationship between them is established based on the theoretical model of the linear regression equation. The linear relationship between the fuel mass M and the fuel index FI of different injectors is proposed through linear regression. The relationship between the fuel mass M and the fuel index FI is as follows:

[0063] M=k s ×FI+M0

[0064] Wherein, M is the fuel mass, in mg,

[0065] FI is the fuel index, which is the independent variable of the relationship and reflects the change in fuel quality caused by the change in fuel rail pressure.

[0066] k s is the regression proportional coefficient, reflecting the influence of fuel index on fuel quality.

[0067] M0 is the intercept, that is, the fuel quality value when the fuel index is 0. It is a constant term that reflects the impact of other factors on fuel quality except the fuel index;

[0068] The fuel mass difference δM between a single injector and the reference injector is proportional to the fuel index difference δFI, and the proportionality coefficient is the regression proportionality coefficient k s , the derivation formula is as follows:

[0069] δM=k s ×δFI

[0070] According to the derived formula, the difference in fuel mass M can be calculated through the deviation of the fuel index FI, and used to analyze the fuel quantity deviation of the injector.

[0071] Furthermore, the influence of the injection pulse width pw on the fuel mass M changes with the change of the injection pulse width pw; the fuel mass change rate k of the reference injector e , and then multiplied by the compensation injection pulse width δpw between a single injector and a reference injector, the fuel mass difference δM between a single injector and a reference injector is obtained. The derivation formula is as follows:

[0072]

[0073] Among them, the injection pulse width pw of the reference injector master Take the derivative of the injection mass mass and get the fuel mass change rate k of the reference injector e .

[0074] One of the technical solutions of the present invention is to provide an injection flow closed-loop control device for a direct injection gasoline engine injector, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the steps of the described method.

[0075] One of the technical solutions of the present invention is to provide a computer-readable storage medium having a computer program stored thereon, which implements the steps of the method when executed by a processor.

[0076] One of the technical solutions of the present invention is to provide a computer program product, comprising a computer program, which implements the steps of the method when executed by a processor.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] (1) The present invention provides a closed-loop control method for injector injection flow rate based on rail pressure to compensate for pulse width. The method does not rely on minimum injection pulse width (MDP) and injector closing response time (CR) to adjust the flow deviation of a single injector. Instead, the method uses a fuel index derived from fuel pressure to compensate for pulse width. This method can meet the requirements of precise fuel control of the injector in a nonlinear region, effectively reducing the emission level of a high-pressure gasoline direct injection (GDI) engine.

[0079] (2) When the direct injection engine injector is operating under a short injection pulse duration, the linearity between the injection amount and the injection pulse duration is poor, and there are also large variations among different injectors. To accurately control the injection amount, it is necessary to perform closed-loop control on the injector. The present invention calculates the fuel index based on the rail pressure change by filtering, differentiation, integration, etc., and achieves consistency in the injection amount by indicating the injection pulse duration that needs to be compensated according to the fuel index;

[0080] (3) The present invention uses the fuel rail pressure of a direct injection engine to establish the relationship between injection quality and injection timing, and on this basis, realizes closed-loop control of the injector. The present invention only uses existing sensors in the system and is insensitive to the material of the injector, thus providing a low-cost and efficient solution.

[0081] (4) The present invention performs closed-loop control on the fuel injector, accurately controls the fuel injector opening time, corrects the fuel injection pulse width, effectively controls the injection amount of the fuel injector, improves the fuel amount consistency in the nonlinear area of ​​the fuel injector, and improves the injection accuracy in the small flow area, thereby reducing the emissions of the direct injection engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 Schematic diagram of the needle valve movement of the fuel injector in the linear region according to an embodiment of the present invention;

[0083] Figure 2 Schematic diagram of the needle valve movement of the fuel injector in the nonlinear region according to an embodiment of the present invention;

[0084] Figure 3 Schematic diagram of the change trend between fuel quality and fuel index in an embodiment of the present invention;

[0085] Figure 4 Schematic diagram of the relationship between the injection pulse width and the fuel mass of the injector flow curve in an embodiment of the present invention;

[0086] Figure 5 Schematic diagram of the injector compensation control method in an embodiment of the present invention. DETAILED DESCRIPTION

[0087] The present invention is described in detail below with reference to specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0088] Example:

[0089] A closed-loop control method for injection flow of a direct-injection gasoline engine injector includes a fuel index indication compensation injection pulse width algorithm and a rail pressure variation indication fuel index algorithm.

[0090] The motion characteristics of the injector needle valve are described, which are divided into the long injection pulse width and short injection pulse width of the injector:

[0091] like Figure 1 As shown, when the electronic control unit (ECU) sends an injection pulse command, due to the influence of the seating spring force, the injector needle valve takes a while to respond, and then the needle valve starts to open. The time from the pulse command to the needle valve starting to open is defined as the valve opening delay; the time from the needle valve starting to open to the maximum opening is defined as the valve opening time; if the injection pulse width is long enough, the needle valve will be in a fully open state for a considerable period of time; when the injection pulse ends, due to the influence of electromagnetic induction lag, the needle valve will still be fully open for a period of time, and the time from the end of the pulse to the needle valve starting to close is defined as the valve closing delay; then, under the influence of the seating spring force, the needle valve begins to close, and the time from the needle valve starting to close to being fully seated is defined as the valve closing time;

[0092] like Figure 2 As shown in the figure, the difference between the short pulse width and the long pulse width is that the needle valve starts to close before it reaches the maximum opening, and the injector does not have enough time to fully open, resulting in the fuel flow being unable to enter the steady-state flow area, and thus the injection flow exhibits nonlinear characteristics.

[0093] Compensate the injection pulse width by using the fuel index indicator. The specific steps are as follows:

[0094] For ease of analysis, the median sample is generally selected as the master injector from injectors of the same design but different production batches, and the other injectors are mass-produced parts. The relationship between them is established based on a theoretical model of a linear regression equation. The linear relationship between the fuel mass M and the fuel index FI of the different injectors is proposed through linear regression. The relationship between the fuel mass M and the fuel index FI is as follows:

[0095] M=k s ×FI+M0

[0096] Wherein, M is the fuel mass, in mg,

[0097] FI is the fuel index, which is the independent variable of the relationship and reflects the change in fuel quality caused by the change in fuel rail pressure.

[0098] k s is the regression proportional coefficient, reflecting the influence of fuel index on fuel quality.

[0099] M0 is the intercept, that is, the fuel quality value when the fuel index is 0. It is a constant term that reflects the impact of other factors on fuel quality except the fuel index;

[0100] like Figure 3As shown, injectors inj.1 to inj.5 represent corresponding data of fuel mass M and fuel index FI of 5 different injectors, and injector master represents corresponding data of fuel mass M and fuel index FI of a reference injector;

[0101] Taking injector inj.1 as an example, the corresponding fuel mass is M1, which is different from the fuel mass M of the reference injector. master The difference between the two is δM, and the fuel index difference between the injector inj.1 and the reference injector is δFI;

[0102] According to the linear relationship between fuel mass M and fuel index FI, the fuel mass difference δM between other injectors and the reference injector is proportional to the fuel index difference δFI, and the proportional coefficient is the regression proportional coefficient k s , the derivation formula is as follows:

[0103] δM=k s ×δFI

[0104] According to the derivation formula, the difference in fuel mass M can be calculated through the deviation of fuel index FI, and used to analyze the fuel quantity deviation of the injector;

[0105] like Figure 4 As shown in the figure, the influence of the injection pulse width pw on the fuel mass M changes with the change of the injection pulse width pw; master is the injection pulse width of the reference injector, M master Is the reference injector in pw master The fuel mass corresponding to the injection pulse width is in mg; M1 is the fuel mass of injector inj.1 when the injection pulse width is pw1. The fuel mass difference between injector inj.1 and the reference injector is δM, and the injection pulse width difference is δpw. master Take the derivative of the injection mass mass and get the fuel mass change rate k of the reference injector e , and then multiply it by the injection pulse width difference δpw between injector inj.1 and the reference injector to obtain the fuel mass difference δM between injector inj.1 and the reference injector. The derivation formula is as follows:

[0106]

[0107] Combining the relationship between the fuel mass difference δM and the fuel index difference δFI and the relationship between the fuel mass difference δM and the injection pulse width difference δpw, the following formula is derived:

[0108] δpw=k×δFI

[0109] Where k = k s / k e The injection pulse width proportional gain is calibrated in three dimensions with respect to the injection pulse width and the ambient temperature. is the partial derivative of the fuel mass mass with respect to the injection pulse width pw, in the reference injector injection pulse width pw master In this state, when the injection pulse width pw changes slightly, the corresponding change rate of the fuel mass mass;

[0110] According to the relationship between the injection pulse width difference δpw and the fuel index difference δFI, if the fuel index difference δFI between a single injector and a reference injector can be obtained, the injection pulse width difference δpw between the two injectors can be obtained.

[0111] The final compensated injection pulse width pw of a single injector inj The injection pulse width pw of the reference injector master The fuel injection pulse width difference δpw is added to obtain the fuel injection pulse width difference δpw, which is characterized by the fuel index FI. The calculation formula is as follows:

[0112] pw inj =pw master +k×δFI

[0113] Where, δFI=FI inj -FI master ,

[0114] FI inj The fuel index of a single injector is calculated based on the test results of a single independent injector produced in the engineering design.

[0115] FI master For the reference fuel index of the injector, it is calculated after testing the median value of the injector produced according to the design on the engine bench during engineering, and stored in the record table of the electronic control unit.

[0116] The fuel index is indicated by rail pressure changes, such as Figure 5 The specific steps are as follows:

[0117] For the high-pressure fuel system, if an injection pulse event occurs in the engine control electronic control unit during the cycle, the high-pressure rail fuel pressure will change accordingly. If the injection pulse width pw is long enough, such as >0.5ms, the high-pressure rail fuel pressure will drop. If the injection pulse width pw is small, such as pw < 0.2ms, the injector needle valve will not actually open due to the influence of spring preload, no fuel will be injected into the cylinder, and the high-pressure rail fuel pressure will not drop. If the injection pulse width pw is between the two, such as 0.2ms≤pw≤0.5ms, it is the nonlinear region of the injector. Even if fuel is injected into the cylinder, the high-pressure rail fuel pressure will also drop.

[0118] Based on the responsiveness of fuel pressure to injection pulse width pw, the compensated injection pulse width δpw is calculated using the fluctuation of the engine's high-pressure rail pressure. The engine's high-pressure rail pressure is filtered, differentiated, refiltered, and integrated in sequence to obtain the fuel index FI corresponding to the rail pressure change rate. This is then multiplied by the injection pulse width proportional gain gain to calculate the compensated injection pulse width δpw.

[0119] S1. In order to remove the noise in the signal and make the fuel rail pressure signal smoother, multiple filter coefficients are used to perform second-order filtering on the fuel rail pressure P, and the output is P filt , P filt The calculation formula is as follows:

[0120] P filt_当前循环 =P 当前循环 ×k1+P 前1循环 ×k2+P 前2循环 ×k3-P filt_前1循环 ×k4-P filt_前2循环 ×k5

[0121] Among them, P filt_当前循环 is the filtered engine fuel rail pressure for the current cycle,

[0122] k1 to k5 are filter coefficients, which are single values ​​ranging from 0.01 to 0.2.

[0123] P 当前循环 The engine's raw fuel rail pressure measured for the current cycle,

[0124] P 前1循环 The original fuel rail pressure of the engine measured for the first cycle,

[0125] P 前2循环 The original fuel rail pressure of the engine measured for the first 2 cycles,

[0126] P filt_前1循环 is the filtered engine fuel rail pressure of the previous cycle,

[0127] P filt_前2循环 The filtered engine fuel rail pressure for the first two cycles;

[0128] S2. In order to obtain P filt The rate of change reflects the speed of change of the fuel rail pressure P. filt Perform discrete difference to obtain the fuel rail pressure deviation P def , fuel rail pressure deviation P def The calculation formula is as follows:

[0129] P def_当前循环 =P filt_当前循环 -P filt_前1循环

[0130] Among them, P def_当前循环 is the fuel rail pressure deviation of the current cycle discrete difference;

[0131] S3. In order to smooth the rate of change and reduce noise interference, the first-order differential result of the fuel rail pressure deviation P is again calculated. def Perform first-order filtering and the output is P def-filt , P def-filt The calculation formula is as follows:

[0132] P def-filt_当前循环 =P def_当前循环 ×k6+P def-filt_前1循环 ×(1-k6)

[0133] Among them, P def-filt_当前循环 is the fuel rail pressure deviation after discrete difference and filtering in the current cycle,

[0134] k6 is the filter coefficient, which is a single value and ranges from 0.01 to 0.2.

[0135] P def-filt_前1循环 The fuel rail pressure deviation after discrete differentiation and filtering in the previous cycle;

[0136] S4, the filtered P def-filt Take the absolute value and sum it to get the fuel index FI of the current injector inj , the current injector fuel index FI inj The calculation formula is as follows:

[0137]

[0138] Among them, n represents the current cycle,

[0139] n-1 represents the first cycle,

[0140] P def-filt is the fuel rail pressure deviation after discrete differentiation and filtering;

[0141] S5, the fuel index FI of the current injector inj , minus the fuel index FI of the reference injector obtained from the table in the electronic control unit master , get the fuel index difference δFI, and then multiply it by the injection pulse width proportional gain gain to get the compensated injection pulse width δpw.

[0142] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A closed-loop control method for injection flow of a direct injection gasoline engine injector, characterized in that: The method comprises the following steps: S1, use multiple filter coefficients to perform second-order filtering on the fuel rail pressure P, and the output is P filt ; S2, the filtered P filt Perform discrete difference to obtain the fuel rail pressure deviation P def ; S3, again calculate the fuel rail pressure deviation P of the first-order differential result def Perform first-order filtering and the output is P def-filt ; S4, the filtered P def-filt Take the absolute value and sum it to get the fuel index FI of the current injector inj ; S5, the fuel index FI of the current injector inj Subtract the fuel index FI of the reference injector master , get the fuel index difference δFI, then multiply it by the injection pulse width proportional gain gain to get the compensated injection pulse width δpw; S6, injection pulse width pw of a single injector after compensation inj The injection pulse width pw of the reference injector master Add the compensation injection pulse width δpw to obtain.

2. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 1, characterized in that: In step S1, P filt The calculation formula is as follows: P filt_当前循环 =P 当前循环 ×k1+P 前1循环 ×k2+P 前2循环 ×k3-P filt_前1循环 ×k4-P filt_前2循环 ×k5 Among them, P filt_当前循环 is the filtered engine fuel rail pressure for the current cycle, k1 to k5 are filter coefficients, which are single values ​​ranging from 0.01 to 0.

2. P 当前循环 The engine's raw fuel rail pressure measured for the current cycle, P 前1循环 The original fuel rail pressure of the engine measured for the first cycle, P 前2循环 The original fuel rail pressure of the engine measured for the first 2 cycles, P filt_前1循环 is the filtered engine fuel rail pressure of the previous cycle, P filt_前2循环 This is the filtered engine fuel rail pressure for the first two cycles.

3. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 1, characterized in that: In step S2, the fuel rail pressure deviation P def The calculation formula is as follows: P def_当前循环 =P filt_当前循环 -P filt_前1循环 Among them, P def_当前循环 is the fuel rail pressure deviation of the current cycle discrete difference, P filt_当前循环 is the filtered engine fuel rail pressure for the current cycle, P filt_前1循环 It is the filtered engine fuel rail pressure of the previous cycle.

4. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 1, characterized in that: In step S3, P def-filt The calculation formula is as follows: P def-filt_当前循环 =P def_当前循环 ×k6+P def-filt_前1循环 ×(1-d6) Among them, P def-filt_当前循环 is the fuel rail pressure deviation after discrete difference and filtering in the current cycle, k6 is the filter coefficient, which is a single value and ranges from 0.01 to 0.

2. P def_当前循环 is the fuel rail pressure deviation of the current cycle discrete difference, P def-filt_前1循环 It is the fuel rail pressure deviation after discrete difference and filtering in the previous cycle.

5. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 1, characterized in that: The fuel index FI of the current injector in step S4 inj The calculation formula is as follows: Among them, n represents the current cycle, n-1 represents the first cycle, P def-filt is the fuel rail pressure deviation after discrete differentiation and filtering.

6. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 1, characterized in that: In step S5, the fuel index difference δFI between the single injector and the reference injector is used to calculate the compensation injection pulse width δpw between the two injectors. The calculation formula of the compensation injection pulse width δpw is as follows: δpw=k×δFI Wherein, k is the injection pulse width proportional gain, which can be calibrated in three dimensions with respect to the injection pulse width and ambient temperature; δFI=FI inj -BE master , FI inj The fuel index of a single injector is calculated based on the test results of a single independent injector produced in the engineering design. FI master The fuel index of the reference injector is calculated after testing the median injector produced according to the design on the engine bench during engineering.

7. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 1, characterized in that: The injection pulse width pw of a single injector after compensation in step S6 inj The calculation formula is as follows: pw inj =pw master +k×δFI Among them, k is the injection pulse width proportional gain, which can be calibrated in three dimensions with respect to the injection pulse width and ambient temperature. pw master is the injection pulse width of the reference injector; δFI=FI inj -BE master , FI inj The fuel index of a single injector is calculated based on the test results of a single independent injector produced in the engineering design. FI master The fuel index of the reference injector is calculated after testing the median injector produced according to the design on the engine bench during engineering.

8. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 1, characterized in that: The injection pulse width proportional gain, i.e., k, in step S5 is calculated as follows: k=k s / k e Among them, k s is the regression proportional coefficient, reflecting the influence of fuel index on fuel quality. is the partial derivative of the fuel mass mass with respect to the injection pulse width pw, in the reference injector injection pulse width pw master In this state, when the injection pulse width pw changes slightly, the corresponding change rate of the fuel mass mass.

9. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 8, characterized in that: The fuel mass M and fuel index FI of different injectors are linearly related through linear regression. The relationship between fuel mass M and fuel index FI is as follows: M=k s ×FI+M0 Wherein, M is the fuel mass, in mg, FI is the fuel index, which is the independent variable of the relationship and reflects the change in fuel quality caused by the change in fuel rail pressure. k s is the regression proportional coefficient, reflecting the influence of fuel index on fuel quality. M0 is the intercept, that is, the fuel quality value when the fuel index is 0. It is a constant term that reflects the impact of other factors on fuel quality except the fuel index; The fuel mass difference δM between a single injector and the reference injector is proportional to the fuel index difference δFI, and the proportionality coefficient is the regression proportionality coefficient k s , the derivation formula is as follows: δM=k s ×δFI According to the derived formula, the difference in fuel mass M can be calculated through the deviation of the fuel index FI, and used to analyze the fuel quantity deviation of the injector.

10. The closed-loop control method for injection flow of a direct injection gasoline engine injector according to claim 8, characterized in that: The influence of the injection pulse width pw on the fuel mass M changes with the change of the injection pulse width pw; the fuel mass change rate k of the reference injector e , and then multiplied by the compensation injection pulse width δpw between a single injector and a reference injector, the fuel mass difference δM between a single injector and a reference injector is obtained. The derivation formula is as follows: Among them, the injection pulse width pw of the reference injector master Take the derivative of the injection mass mass and get the fuel mass change rate k of the reference injector e .

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