Control device of injector

Abstract

To suppress a variation of torque in an internal combustion engine.SOLUTION: A memory stores correction information showing a correspondence between torque difference ΔT being a value obtained by reducing all cylinder torque from individual torque and a correction coefficient N for correcting a fuel injection quantity by an injector when torque of each cylinder is regarded as the individual torque and an average value of torque of all cylinders is regarded as the all cylinder torque. In the correction information, the correction coefficient N in the case that the torque difference ΔT is positive is a value for performing decrease correction of the fuel injection quantity, the correction coefficient N in the case that the torque difference ΔT is negative is a value for performing increase correction of the fuel injection quantity, and the correction width of the increase correction is larger than the correction width of the decrease correction when correction width of the decrease correction and correction width of the increase correction are compared with a case in which absolute values of the torque difference ΔT are the same as an object. A CPU makes the injector of each cylinder inject a correction injection quantity obtained by correcting a basic injection quantity by the correction coefficient N corresponding to the torque difference ΔT.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a control device for an injector. [Background technology]

[0002] The internal combustion engine disclosed in Patent Document 1 includes multiple cylinders and an injector for each cylinder. The injector supplies fuel to a target cylinder. A control device for this internal combustion engine monitors the air-fuel ratio of each of the multiple cylinders. If the air-fuel ratio of any of the multiple cylinders is leaner than the air-fuel ratios of the other cylinders, the control device increases the amount of fuel supplied to that cylinder. The greater the deviation in the air-fuel ratio, the greater the amount of fuel to be increased. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-065714 Summary of the Invention [Problem to be solved by the invention]

[0004] In an internal combustion engine with multiple cylinders, such as that described in Patent Document 1, the air-fuel ratios of the cylinders vary. Large variations in the air-fuel ratios among the cylinders undesirably increase the torque differences between the cylinders. Therefore, correcting the amount of fuel supplied to each cylinder is considered to eliminate such torque differences. However, if the correction amount is uniformly increased depending on the degree of deviation in the air-fuel ratio, as in Patent Document 1, the air-fuel ratio in cylinders with large deviations in the air-fuel ratio will be suddenly changed, resulting in sudden changes in torque. Meanwhile, depending on the air-fuel ratio, there may be cylinders in which the combustion state of the air-fuel mixture in the cylinder is unstable, resulting in torque fluctuations. Gradual changes in the air-fuel ratio in such cylinders would not quickly eliminate the torque fluctuations. [Means for solving the problem]

[0005] An injector control device for solving the above problem controls an injector for each cylinder in an internal combustion engine having a plurality of cylinders for supplying fuel to the cylinders, and includes an execution unit and a storage unit. When an average value of the torque for each cylinder over a certain period during operation of the internal combustion engine is defined as an individual torque, and an average value of the torque of all of the cylinders over the certain period is defined as an all-cylinder torque, the storage unit stores correction information indicating a correspondence between a torque difference, which is a difference between the individual torque and the all-cylinder torque, and a correction value for the amount of fuel injected by the injector, and in the correction information, when the individual torque is greater than the all-cylinder torque, the correction value is a value indicating a decrease correction to decrease the amount of fuel injection, and when the individual torque is smaller than the all-cylinder torque, the correction value is a value indicating an increase correction to increase the amount of fuel injection. and when a correction width of the decrease correction and a correction width of the increase correction are compared for the case where the absolute value of the torque difference is the same, the correction width of the increase correction is larger than the correction width of the decrease correction, and the execution unit repeatedly executes injection control that performs the following steps during operation of the internal combustion engine: a first process of calculating the torque difference for each of the cylinders for the certain period; a second process of calculating, based on the correction information, the correction value of the fuel injection amount for each of the cylinders corresponding to the torque difference calculated in the first process; a third process of calculating a corrected injection amount for each of the cylinders by correcting a basic injection amount corresponding to the operating state of the internal combustion engine using the correction value for each of the cylinders calculated in the second process; and a fourth process of supplying the corrected injection amount for each of the cylinders through control of the injector for each predetermined cycle during the certain period. [Effects of the Invention]

[0006] The above technical concept makes it possible to suppress fluctuations in torque in an internal combustion engine. [Brief explanation of the drawings]

[0007] [Figure 1]FIG. 1 is a schematic diagram of an internal combustion engine. [Figure 2] FIG. 2 is a flowchart showing the processing contents of the injection control. [Figure 3] FIG. 3 is a graph showing the correction information. [Figure 4] FIG. 4 is a graph showing the relationship between the air-fuel ratio and the torque. DETAILED DESCRIPTION OF THE INVENTION

[0008] <Overall structure> An embodiment of an injector control device will be described below with reference to the drawings. As shown in FIG. 1, a vehicle 10 is equipped with an internal combustion engine 20. The internal combustion engine 20 is a drive source for the vehicle 10. The internal combustion engine 20 is equipped with a plurality of cylinders 22 and a crankshaft 28. There are four cylinders 22. The cylinders 22 are spaces defined by an engine body 20A. The cylinders 22 are spaces for burning a mixture of fuel and intake air. Although not shown, each cylinder 22 houses a piston. The piston reciprocates within the cylinder 22 in response to the combustion of the mixture. The crankshaft 28 rotates in response to the reciprocating movement of the piston.

[0009] The internal combustion engine 20 includes a plurality of injectors 25 and a plurality of spark plugs 26. An injector 25 is provided for each cylinder 22. The injection ports of the injectors 25 are located inside the cylinders 22. The injectors 25 inject fuel into the cylinders 22. The injectors 25 supply fuel, such as gasoline, into the cylinders 22. An ignition plug 26 is provided for each cylinder 22. The spark plug 26 ignites the air-fuel mixture in the cylinders 22 by spark discharge.

[0010] The internal combustion engine 20 includes an intake passage 23 and an exhaust passage 27. The intake passage 23 is a passage for introducing intake air into each cylinder 22. The intake passage 23 is connected to each cylinder 22. An adjustable throttle valve 24 is located in the intake passage 23. The amount of intake air changes depending on the opening of the throttle valve 24. The exhaust passage 27 is a passage for discharging exhaust gas from each cylinder 22. The exhaust passage 27 is connected to each cylinder 22. Although not shown, a three-way catalyst or the like for purifying exhaust gas is located in the exhaust passage 27.

[0011] The internal combustion engine 20 is equipped with multiple sensors. For example, the internal combustion engine 20 is equipped with a crank angle sensor 61, an air flow meter 62, a water temperature sensor 63, and an air-fuel ratio sensor 64. The crank angle sensor 61 detects the rotation angle of the crankshaft 28. The air flow meter 62 detects the flow rate of gas flowing through the intake passage 23 as the intake air amount. The water temperature sensor 63 detects the outlet temperature of the coolant flowing through a water jacket defined within the engine body 20A as the engine water temperature. The air-fuel ratio sensor 64 detects the air-fuel ratio of the exhaust gas. The vehicle 10 is also equipped with an accelerator sensor 68 and a vehicle speed sensor 69. The accelerator sensor 68 detects the depression amount of the accelerator pedal of the vehicle 10 as the accelerator operation amount. The vehicle speed sensor 69 detects the traveling speed of the vehicle 10 as the vehicle speed. Each of these sensors repeatedly transmits a signal corresponding to the information detected by itself to a control device 90 (described later).

[0012] The vehicle 10 is equipped with a control device 90. The control device 90 is equipped with a CPU 91 and a memory 92. The CPU 91 is an execution unit. The memory 92 includes three types of storage media: RAM, ROM, and electrically rewritable non-volatile memory. In this embodiment, these three types of storage media are collectively referred to as the memory 92. The memory 92 stores in advance various programs that describe the processes to be executed by the CPU 91. The memory 92 also stores in advance various data required for the CPU 91 to execute the various programs. The memory 92 is a storage unit.

[0013] The CPU 91 repeatedly receives detection signals from various sensors attached to the vehicle 10. The CPU 91 calculates necessary parameters as needed based on the detection signals received from the various sensors. For example, the CPU 91 calculates the engine rotation speed, which is the rotation speed of the crankshaft 28, based on the detection signal from the crank angle sensor 61.

[0014] The CPU 91 controls various controllable devices in the internal combustion engine 20. The controllable devices include the injector 25, the spark plug 26, the throttle valve 24, and the like. When the ignition switch of the vehicle 10 is turned on, the CPU 91 starts the internal combustion engine 20 by controlling the various controllable devices. After the start of the internal combustion engine 20 is completed, the CPU 91 repeats injection control of the injector 25 until the ignition switch is turned off. In parallel with the injection control, the CPU 91 repeats ignition timing control of the spark plug 26 and opening adjustment control of the throttle valve 24. Through these controls, the CPU 91 continues operation of the internal combustion engine 20. That is, the CPU 91 repeats injection control of the injector 25 while the internal combustion engine 20 is operating. Hereinafter, a certain period during operation of the internal combustion engine 20 will be referred to as a control period. The control period is predetermined to be, for example, a time shorter than one second. The control period is longer than the time required for one combustion cycle when the internal combustion engine 20 is operating at its minimum engine speed. One combustion cycle is a series of periods in which one cylinder 22 undergoes one intake stroke, one compression stroke, one expansion stroke, and one exhaust stroke.

[0015] <Injection control> A series of processes in the injection control will be described below. As shown in FIG. 2, when the CPU 91 starts the injection control, it first executes the process of step S10. In step S10, the CPU 91 calculates the torque difference ΔT for each cylinder 22 over the control period. The torque difference ΔT is a value obtained by subtracting the all-cylinder torque from the individual torque. The individual torque is the average value of the torque of a given cylinder 22 over the control period. The all-cylinder torque is the average value of the torque of all cylinders 22 over the control period. Strictly speaking, the torque of a given cylinder 22 is the torque of the crankshaft 28 corresponding to the combustion of the air-fuel mixture in that cylinder 22. As a premise for the CPU 91 to calculate the torque difference ΔT for each cylinder 22, the memory 92 stores a time series of changes in the engine speed from when the ignition switch is turned on until the time step S10 is executed. In step S10, the CPU 91 first refers to this time series. The CPU 91 then extracts, from this time series, data from the period going back from the execution of step S10 to the time before the control period as previous data. As will be described later, in the process of step S60, the CPU 91 causes the injector 25 to inject fuel over the control period. The previous data corresponds to the transition of the engine speed over the period during which the CPU 91 performed the process of step S60 in the previous injection control. After extracting the previous data, the CPU 91 calculates the transition of the derivative value of the engine speed over the control period based on the previous data. The derivative value of the engine speed reflects the torque of the crankshaft 28. Therefore, the CPU 91 calculates the individual torque for each cylinder 22 and the torque for all cylinders based on the transition of the calculated derivative value of the engine speed. The CPU 91 then calculates the torque difference ΔT for each cylinder 22 based on the individual torque for each cylinder 22 and the torque for all cylinders. As can be seen from the period covered by the previous data, each value calculated by the CPU 91 covers the control period in which the process of step S60 was previously performed.

[0016] In step S10, after calculating the individual torque for each cylinder 22, the CPU 91 stores the calculated individual torque for each cylinder 22 in the memory 92. That is, in step S10, the CPU 91 stores the individual torque for each cylinder 22 obtained as a result of performing the processing of step S60 of the previous injection control in the memory 92. When storing the individual torque, the CPU 91 stores the individual torque for each cylinder 22 in the memory 92 in association with identification information that distinguishes each cylinder 22. In this embodiment, a cylinder number, which is a number assigned in advance to each cylinder 22, is used as an example of the identification information. When storing the individual torque for each cylinder 22 in the memory 92, the CPU 91 stores the new individual torque in the memory 92 in a chronological order relative to the individual torque stored in the previous step S10. Therefore, the memory 92 stores the transition of the individual torque for each cylinder 22 in chronological order. For example, for a certain cylinder 22, the latest individual torque in the time series of individual torque is the individual torque obtained as a result of performing the process of step S60 during the control period in the previous injection control. In the time series of individual torque, the individual torque at the timing one timing back from the latest individual torque is the individual torque obtained as a result of performing the process of step S60 during the control period in the injection control two times before the latest individual torque. As described above, in step S10, the CPU 91 calculates the torque difference ΔT for each cylinder 22 and stores the individual torque for each cylinder 22. The process of step S10 is part of the first process. After completing the process of step S10, the CPU 91 proceeds to step S20. Note that, since there is insufficient time series data of individual torque required for the series of processes in the first and second injection controls, the CPU 91 cancels the process of step S20 and proceeds to step S100.

[0017] In step S20, the CPU 91 determines whether or not special measures are necessary to correct the fuel injection amount of the injector 25. As a prerequisite for the CPU 91 to perform the processing of step S20, the memory 92 stores in advance a list of boost cylinders. The list of boost cylinders is information describing the cylinder numbers of the cylinders 22 designated as boost cylinders. The type of cylinders 22 designated as boost cylinders will be explained in the processing of step S50, which will be described later. The cylinder numbers described in the list of boost cylinders are updated every time the processing of step S50, which will be described later, is performed. That is, the cylinder numbers currently described in the list of boost cylinders are the cylinder numbers stored in the memory 92 as boost cylinders in step S50 of the previous injection control. Now, in step S20, the CPU 91 refers to the list of boost cylinders. Then, the CPU 91 identifies the cylinders 22 currently designated as boost cylinders. Then, the CPU 91 performs the following for the boost cylinders. That is, the CPU 91 refers to a time series of the transition of the individual torque for the boosted cylinder among the transitions of the individual torque for each cylinder 22 stored in the memory 92. Then, the CPU 91 performs a necessity determination for this time series. In the necessity determination, the CPU 91 determines whether the latest individual torque in the time series of the individual torque is smaller than the individual torque at the immediately previous timing. If there are multiple boosted cylinders, the CPU 91 performs a necessity determination for each boosted cylinder. If the determination results of the necessity determinations for all boosted cylinders are negative, the CPU 91 determines that no special measures are required to correct the fuel injection amount (step S20: NO). In this case, the CPU 91 proceeds to step S100. The processing of step S20 is part of the first processing.

[0018] In step S100, the CPU 91 calculates a correction coefficient N for each cylinder 22 in a normal manner. The correction coefficient N is a correction value for the amount of fuel injected by the injector 25. As a prerequisite for the CPU 91 to calculate the correction coefficient N, the memory 92 stores correction information in advance. As shown in FIG. 3, the correction information indicates the correspondence relationship between the torque difference ΔT and the correction coefficient N. In the correction information, a region where the torque difference ΔT is a positive value is referred to as a first region R1. In the correction information, a region where the torque difference ΔT is a negative value is referred to as a second region R2. The correction information has the following characteristics: When the torque difference ΔT is "0", the correction coefficient N is "1". The correction coefficient N in the first region R1 is smaller than "1". The correction coefficient N in the second region R2 is larger than "1". The correction coefficient N in the first region R1 decreases as the torque difference ΔT increases. The correction coefficient N in the first region R1 changes approximately linearly according to the torque difference ΔT. The correction coefficient N in the second region R2 increases as the absolute value of the torque difference ΔT increases. The correction coefficient N in the second region R2 changes nonlinearly according to the absolute value of the torque difference ΔT. Specifically, the correction coefficient N in the second region R2 increases exponentially according to the absolute value of the torque difference ΔT. For each torque difference ΔT, the absolute value of the difference between the correction coefficient N and "1" is referred to as the difference value Q. The difference value Q in the first region R1 and the difference value Q in the second region R2 are compared for cases where the absolute value of the torque difference ΔT is the same. In this case, for each absolute value of the torque difference ΔT, the difference value Q in the second region R2 is greater than the difference value Q in the first region R1.

[0019] In step S100, the CPU 91 refers to the correction information and the torque difference ΔT for each cylinder 22 calculated in step S10 to calculate the correction coefficient N for each cylinder 22. The CPU 91 then calculates the correction coefficient N for each cylinder 22 using a normal method. The normal method will be described using one particular cylinder 22 as the target. In the normal method, the CPU 91 calculates the correction coefficient N corresponding to the current torque difference ΔT in the correction information as the correction coefficient N to be applied at the current time. In this way, in step S100, the CPU 91 sets the correction coefficient N to a value corresponding to the current torque difference ΔT for each cylinder 22 based on the correction information. As shown in FIG. 2, after calculating the correction coefficient N for each cylinder 22, the CPU 91 proceeds to step S40. The process in step S100 is the second process.

[0020] On the other hand, in step S20, if the determination result of the necessity determination is positive for one or more increased cylinders, the CPU 91 determines that special measures are required to correct the fuel injection amount (step S20: YES). In this case, the CPU 91 proceeds to the process of step S30.

[0021] In step S30, the CPU 91 calculates the correction coefficient N for each cylinder 22 in a special mode. Here, among the cylinders for which the necessity determination was made in step S20, the cylinders 22 for which the determination result of the necessity determination is positive are referred to as specific cylinders for which the amount of increase is specified. In the special mode, the CPU 91 calculates the correction coefficient N only for the specific cylinders for which the amount of increase is specified among the multiple cylinders 22 by a method different from the normal method, and calculates the correction coefficient N for the other cylinders 22 by the normal method. The other cylinders 22 are cylinders 22 that are required for the amount of increase and for which the determination result of the necessity determination is negative, and cylinders 22 that are not designated as cylinders for which the amount of increase is specified.

[0022] A special mode countermeasure will be described for one specific boost cylinder. In this countermeasure, the CPU 91 sets a specific correction value NX as the correction coefficient N to be applied to the specific boost cylinder. The specific correction value NX will be described. As a premise, of the current torque difference ΔT calculated in step S10, the torque difference ΔTA of the specific boost cylinder is a negative value, as shown in FIG. 3. The reason why the torque difference ΔTA of the specific boost cylinder is a negative value will be described later. Note that the magnitude of the torque difference ΔTA shown in FIG. 3 is an example. A positive value that has the same absolute value as the torque difference ΔTA of the specific boost cylinder is referred to as the symmetric torque difference ΔTX. The specific correction value NX is predetermined as the correction coefficient N corresponding to the symmetric torque difference ΔTX in the correction information. In this countermeasure, the CPU 91 sets this specific correction value NX as the correction coefficient N to be applied to the specific boost cylinder. If there are multiple specific increase cylinders, the CPU 91 applies a countermeasure to each specific increase cylinder to determine the correction coefficient N that should be applied to each specific increase cylinder at this time. As shown in Fig. 2, after setting the correction coefficient N for each specific increase cylinder and each of the other cylinders 22, the CPU 91 proceeds to step S40. The process of step S30 is the second process.

[0023] In step S40, the CPU 91 calculates a basic injection amount FB. The basic injection amount FB is a base value of the fuel injection amount according to the current operating state of the internal combustion engine 20. The basic injection amount FB is a value for one cylinder 22. The CPU 91 calculates the basic injection amount FB based on the torque required for the internal combustion engine 20, which is determined from the accelerator operation amount and the vehicle speed, as well as the operating state of the internal combustion engine 20, such as the engine rotation speed and the intake air amount. In this embodiment, the target air-fuel ratio for each cylinder 22 is the stoichiometric air-fuel ratio AS. That is, in theory, the basic injection amount FB in this embodiment is calculated so that the air-fuel ratio in the cylinder 22 coincides with the stoichiometric air-fuel ratio AS. After calculating the basic injection amount FB according to the operating state of the internal combustion engine 20, the CPU 91 proceeds to step S50.

[0024] In step S50, the CPU 91 calculates a corrected injection amount FH for each cylinder 22. The corrected injection amount FH is a value obtained by correcting the basic injection amount FB by the correction coefficient N. As a specific process of step S50, the CPU 91 performs the following for each cylinder 22. For a given cylinder 22, the CPU 91 calculates the corrected injection amount FH as the product of the correction coefficient N for that cylinder 22 calculated in step S30 or step S100 and the basic injection amount FB calculated in step S40. After calculating the corrected injection amount FH for each cylinder 22, the CPU 91 also updates the contents of the increase cylinder list stored in the memory 92. Specifically, the CPU 91 clears the contents of the current increase cylinder list and then writes the cylinder number of the cylinder 22 corresponding to the increase cylinder in the increase cylinder list. The increased cylinder is a cylinder 22 for which the correction coefficient N calculated in step S30 or step S100 is greater than "1." That is, the CPU 91 stores in the memory 92 as an increased cylinder a cylinder 22 for which the correction injection amount FH is greater than the basic injection amount FB. The processing of step S50 is the third processing. After completing the processing of step S50, the CPU 91 proceeds to step S60.

[0025] In step S60, the CPU 91 controls the injector 25 for each cylinder 22 based on the corrected injection amount FH calculated in step S50. A particular cylinder 22 is referred to as a target cylinder. The CPU 91 can execute a supply process for the target cylinder. The supply process controls the injector 25 of the target cylinder so that the injector 25 injects the corrected injection amount FH for the target cylinder within a predetermined cycle. In this embodiment, the predetermined cycle is predetermined as one combustion cycle. In the supply process, if a predetermined multi-stage injection condition is satisfied, the CPU 91 divides the corrected injection amount FH for the target cylinder into multiple parts and supplies the divided parts to the target cylinder in multiple stages during one combustion cycle. One example of the multi-stage injection condition is that the engine water temperature is lower than a predetermined value. If the multi-stage injection condition is not satisfied, the CPU 91 injects the corrected injection amount FH for the target cylinder in a single fuel injection within one combustion cycle. In step S60, the CPU 91 continues the supply process for each cylinder 22 over the control period. That is, during the control period, the CPU 91 supplies the corrected injection amount FH for each cylinder 22 to each cylinder 22 through control of the injector 25 at each predetermined cycle. The process of step S60 is the fourth process. When the control period has elapsed since the start of step S60, the CPU 91 ends the process of step S60. Then, the CPU 91 temporarily ends the series of processes for injection control. After this, the CPU 91 promptly starts the process of step S10 for new injection control.

[0026] <About correction information> As explained in the processing of step S50, the CPU 91 calculates the product of the basic injection amount FB and the correction coefficient N as the corrected injection amount FH. As can be seen from this, if the correction coefficient N is smaller than "1", the CPU 91 will perform a decrease correction on the basic injection amount FB. That is, the correction coefficient N in the first region R1 in the correction information shown in FIG. 3 is a value indicating a decrease correction that reduces the fuel injection amount. On the other hand, if the correction coefficient N is larger than "1", the CPU 91 will perform an increase correction on the basic injection amount FB. That is, the correction coefficient N in the second region R2 in the correction information is a value indicating an increase correction that increases the fuel injection amount.

[0027] The absolute value of the difference between the corrected injection amount FH and the basic injection amount FB is referred to as the correction range. The correction range increases as the difference value Q, which is the absolute value of the difference between the correction coefficient N and "1," increases. In other words, the difference value Q is a parameter that reflects the correction range. As shown in FIG. 3, in the first region R1 of the correction information, the difference value Q increases as the torque difference ΔT increases. In other words, in the first region R1, the correction range for the decrease correction increases as the torque difference ΔT increases. Furthermore, in the second region R2 of the correction information, the difference value Q increases as the absolute value of the torque difference ΔT increases. In other words, in the second region R2, the correction range for the increase correction increases as the absolute value of the torque difference ΔT increases. Furthermore, as described above, when the difference value Q in the first region R1 and the difference value Q in the second region R2 are compared for the same absolute value of the torque difference ΔT, the difference value Q in the second region R2 is greater than the difference value Q in the first region R1. That is, with respect to the absolute value of each torque difference ΔT, the correction range of the increasing correction is larger than the correction range of the decreasing correction.

[0028] <Actions and Effects of the Embodiment> (1) The overall flow of injection control will be described. In injection control, the CPU 91 calculates the torque difference ΔT for each cylinder 22 in step S10, and then calculates a correction coefficient N for each cylinder 22 by processing in step S30 or step S100. The CPU 91 then calculates a corrected injection amount FH for each cylinder 22 based on the calculated correction coefficient N (step S50). The CPU 91 then causes each injector 25 to inject the corrected injection amount FH for each cylinder 22 (step S60). When calculating the correction coefficient N for each cylinder 22, the CPU 91 basically calculates the correction coefficient N by processing in step S100. In step S100, the CPU 91 corrects the basic injection amount FB for a cylinder 22 for which the torque difference ΔT is a positive value, i.e., for a high-torque cylinder whose individual torque is large relative to the total cylinder torque, using the correction coefficient N in the first region R1 in the correction information. That is, the CPU 91 reduces the basic injection amount FB for the high-torque cylinder. On the other hand, in step S100, for the cylinder 22 having a negative torque difference ΔT, i.e., a low-torque cylinder whose individual torque is small relative to the total cylinder torque, the CPU 91 corrects the basic injection amount FB by using the correction coefficient N in the second region R2 in the correction information. That is, the CPU 91 corrects the basic injection amount FB of the low-torque cylinder by increasing it.

[0029] Here, if the air-fuel ratio in the cylinder 22 is lean, the combustion state of the mixture in the cylinder 22 becomes unstable and the torque of the cylinder 22 is more likely to fluctuate due to misfires and other factors. As described above, when the correction information compares the correction range of the increase correction and the correction range of the decrease correction for the same absolute value of the torque difference ΔT, the correction range of the increase correction is set larger than the correction range of the decrease correction. By correcting the basic injection amount FB using this correction information, the correction range for the basic injection amount FB is increased for the low-torque cylinder with a negative torque difference ΔT. Therefore, in the low-torque cylinder, the instability of the combustion state of the mixture can be quickly resolved while the individual torque of the low-torque cylinder can be brought closer to the torque of all cylinders. This eliminates the situation in the low-torque cylinder where the torque is more likely to fluctuate due to a lean air-fuel ratio and eliminates the torque difference ΔT between the low-torque cylinder and the other cylinders 22. Therefore, overall, torque fluctuations in the internal combustion engine 20 can be suppressed. On the other hand, for the high-torque cylinders with a positive torque difference ΔT, the basic injection amount FB is corrected using the correction information, thereby narrowing the correction range for the basic injection amount FB. Therefore, for the high-torque cylinders, the individual torque of the cylinders can be made closer to the total cylinder torque without abruptly changing the air-fuel ratio. In other words, for the high-torque cylinders, the torque difference ΔT between the high-torque cylinders and the other cylinders 22 can be eliminated without abruptly changing the torque. Therefore, overall, torque fluctuations in the internal combustion engine 20 can be suppressed. Overall, the configuration of this embodiment can suppress torque fluctuations in the internal combustion engine 20.

[0030] (2) The leaner the air-fuel ratio in the cylinder 22, the more unstable the combustion state of the mixture in the cylinder 22. Therefore, the leaner the air-fuel ratio in the cylinder 22, the more quickly it is necessary to resolve the unstable combustion state. In the second region R2 of the correction information of this embodiment, the larger the absolute value of the torque difference ΔT, the larger the correction range of the increase correction. Therefore, when the absolute value of the torque difference ΔT is large, the torque difference ΔT can be resolved quickly. In other words, the unstable combustion state can be resolved quickly.

[0031] On the other hand, in the case of a high-torque cylinder in which the air-fuel ratio in cylinder 22 is on the rich side, although it is desirable to avoid a sudden change in the air-fuel ratio in that cylinder, if the air-fuel ratio is gradually changed when the deviation of individual torque from the total cylinder torque is relatively large, the torque difference ΔT will persist for a long time. In the first region R1 of the correction information in this embodiment, the correction range of the decrease correction becomes larger as the torque difference ΔT becomes larger. Therefore, when the torque difference ΔT is large, the torque difference ΔT can be quickly eliminated.

[0032] (3) For example, to improve exhaust emissions, fuel injection may be performed in multiple stages during a single combustion cycle. When fuel injection is performed in multiple stages, the amount of fuel injected per injection is reduced. When the amount of fuel injected per injection is small, the error in the amount of fuel injected from the injector 25 tends to increase due to the structure of the injector 25. Therefore, when fuel injection is performed in multiple stages, if fuel injection is performed without any countermeasures, there is a high possibility that the air-fuel ratio and therefore torque variations between the cylinders 22 will increase. In other words, when fuel injection is performed in multiple stages, it is particularly required to suppress the torque difference ΔT between the cylinders 22. In response to this requirement, the configuration of this embodiment, which uses correction information to control the amount of fuel supplied to each cylinder 22, is particularly effective in suppressing torque variations in the internal combustion engine 20 that performs fuel injection in multiple stages.

[0033] (4) The reason for providing the processes of steps S20 and S30 will be explained. As a premise, as shown in FIG. 4, when the air-fuel ratio in the cylinder 22 is richer than the stoichiometric air-fuel ratio AS, the torque of the cylinder 22 is maximized at the maximum air-fuel ratio AM. When the air-fuel ratio in the cylinder 22 is richer than the maximum air-fuel ratio AM, the torque of the cylinder 22 decreases as the air-fuel ratio becomes richer. In relation to this, if a cylinder 22 with an excessively rich air-fuel ratio exists during operation of the internal combustion engine 20, the individual torque of that cylinder 22 may fall below the torque of all cylinders. Accordingly, the torque difference ΔT of that cylinder 22 may become negative. When the torque difference ΔT is negative, the correction coefficient N corresponding to the torque difference ΔT in the correction information becomes positive. This means that the basic injection amount FB is corrected to increase. In other words, when the correction coefficient N is calculated using the correction information, if there is a cylinder 22 whose air-fuel ratio is excessively rich, the fuel injection amount of that cylinder 22 may be increased. However, ideally, the fuel injection amount of the cylinder 22 whose air-fuel ratio is excessively rich should be decreased. To deal with this situation, the injection control employs the following configuration. Specifically, in step S10, the CPU 91 stores the individual torque for each cylinder 22 in chronological order. That is, the CPU 91 monitors the progress of the individual torque for each cylinder 22. Then, in step S20, the CPU 91 determines whether the individual torque of the increased cylinder, which is the cylinder 22 whose fuel injection amount was increased in the previous injection control, is increased. That is, the CPU 91 determines whether the latest individual torque in the time series of the individual torque of the increased cylinder is smaller than the individual torque immediately before. The latest individual torque is the individual torque obtained as a result of the previous injection control. The previous individual torque is the individual torque obtained as a result of the injection control performed two times before. As shown in Fig. 4, if the latest individual torque TP1 is smaller than the previous individual torque TP2 in the necessity determination, the torque of the target cylinder to be increased has decreased despite the fuel injection amount being increased. In other words, if the determination result of step S20 is positive (step S20: YES), it can be estimated that the air-fuel ratio of the target cylinder to be increased is excessively rich.Therefore, if the determination result of step S20 is positive, the CPU 91 treats the target cylinder for increase as a specific cylinder for increase, and proceeds to step S30. Then, in step S30, the CPU 91 uses a countermeasure to set a correction value for the fuel injection amount for the specific cylinder for increase. Here, the specific cylinder for increase is cylinder 22, whose fuel injection amount was increased in consideration of the fact that the torque difference ΔT was negative in the previous injection control. Reflecting this, as illustrated in FIG. 3, the torque difference ΔTA for the specific cylinder for increase is currently negative. In the countermeasure, the CPU 91 treats a positive value having the same absolute value as the negative torque difference ΔTA as a symmetric torque difference ΔTX. Furthermore, the CPU 91 treats the correction coefficient N corresponding to the symmetric torque difference ΔTX in the correction information as a specific correction value NX. The specific correction value NX is a value in the first region R1 in the correction information. In other words, the specific correction value NX is a value indicating a decrease correction. In the countermeasure, the CPU 91 forcibly specifies this specific correction value NX as the correction coefficient N to be applied to the specific increase cylinder. That is, in the countermeasure, the CPU 91 sets the correction coefficient N of the specific increase cylinder to the specific correction value NX regardless of the torque difference ΔT of the specific increase cylinder. Then, in steps S50 and S60, the CPU 91 causes the injector 25 to inject a corrected injection amount FH obtained by reducing the basic injection amount FB using this specific correction value NX. As a result of reducing the fuel injection amount, the excessively rich air-fuel ratio of the specific increase cylinder can be eliminated. The air-fuel ratio of the specific increase cylinder can then return to a slightly rich value between the maximum air-fuel ratio AM and the stoichiometric air-fuel ratio AS in FIG. 4. Accordingly, the torque difference ΔT of the specific increase cylinder can return to a positive value. If the relationship that the torque difference ΔT is a positive value when the air-fuel ratio in the cylinder 22 is rich is satisfied, the correspondence relationship between the torque difference ΔT and the correction coefficient N in the correction information can be used to set an appropriate correction coefficient N corresponding to the torque difference ΔT. Therefore, as the CPU 91 subsequently repeats injection control, that is, as the CPU 91 sequentially sets the correction coefficient N in correspondence with the torque difference ΔT using the normal method, the correction coefficient N of the specific boost cylinder gradually returns to a value appropriate for eliminating the torque difference ΔT. At the same time, the torque difference ΔT between the specific boost cylinder and the other cylinders 22 becomes smaller.

[0034] (5) As described in (4) above, the specific correction value NX in this embodiment is set to a value indicating a decrease correction corresponding to the symmetric torque difference ΔTX. This specific correction value NX is expected to have a relatively large correction range for the decrease correction. If the correction range for the decrease correction is relatively large, there is a high possibility that an excessively rich air-fuel ratio state can be quickly resolved. Furthermore, there is a high possibility that the time required for the correction coefficient N to return to an appropriate value can be shortened thereafter.

[0035] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0036] The specific correction value NX is not limited to the example in the above embodiment, and may be any value that indicates a decrease correction. The processing of steps S20 and S30 is not essential. That is, the processing of step S100 may be always performed after step S10. After step S100, the processing may proceed to step S40. If the processing of steps S20 and S30 is eliminated, the processing of storing the time series of the individual torque for each cylinder 22 in step S10 and the processing of storing the boosted cylinder in step S50 may also be eliminated.

[0037] The correction information is not limited to the example of the above embodiment. The correction information may indicate the correspondence between the difference between the individual torque and the all-cylinder torque and the correction value of the fuel injection amount by the injector 25, and may satisfy the first, second, and third conditions. The first condition is that the correction value in the first region R1 is a value indicating a decrease correction. The second condition is that the correction value in the second region R2 is a value indicating an increase correction. The third condition is that, when the correction ranges of the decrease correction and the increase correction are compared for the same absolute value of the torque difference ΔT, the correction range of the increase correction is larger than the correction range of the decrease correction for each absolute value of the torque difference ΔT. Note that, in the first region R1, satisfying the following fourth condition is preferable for correcting the fuel injection amount to eliminate a positive torque difference ΔT. The fourth condition is that when the torque difference ΔT is a positive first value, the correction range of the decrease correction is larger than when the torque difference ΔT is a positive second value smaller than the first value. Similarly, in the second region R2, if the following fifth condition is satisfied, it is preferable to correct the fuel injection amount to eliminate the negative torque difference ΔT. The fifth condition is that when the torque difference ΔT is a negative third value, the correction range of the increase correction is larger than when the torque difference ΔT is a negative fourth value that is larger than the third value. However, it is not essential that the fourth condition be satisfied. It is also not essential that the fifth condition be satisfied.

[0038] The torque difference ΔT may be calculated by subtracting the individual torque from the total cylinder torque. The correction information may be changed accordingly. The correction value of the fuel injection amount is not limited to a value that corrects the basic injection amount FB by multiplication. For example, the correction value may be a value that corrects the basic injection amount FB by addition.

[0039] The target air-fuel ratio may be set to a value different from the stoichiometric air-fuel ratio AS. It is not essential to employ a mode in which fuel is injected in multiple stages into one cylinder 22 during one combustion cycle. In other words, fuel may be injected only once into one cylinder 22 during one combustion cycle.

[0040] The overall configuration of the internal combustion engine 20 is not limited to the example of the above embodiment. For example, if multi-stage fuel injection is not adopted, the injector 25 may be of a type that supplies fuel to the cylinders 22 via the intake passage 23. Furthermore, the number of cylinders 22 is not limited to four.

[0041] The predetermined cycle is not limited to one combustion cycle. For example, the predetermined cycle may be multiple combustion cycles. The basic injection amount FB and other parameters may be changed as appropriate to handle the predetermined cycle. [Explanation of symbols]

[0042] 20... internal combustion engine 22... cylinder 25... injector 90... control device 91... CPU 92... memory

Claims

1. The control target is an injector for each cylinder in an internal combustion engine having a plurality of cylinders, the injector being for supplying fuel to each of the cylinders; An execution unit and a storage unit, When an average value of the torque for each cylinder for a certain period during operation of the internal combustion engine is defined as an individual torque, and an average value of the torque for all of the cylinders for the certain period is defined as a total cylinder torque, the storage unit stores correction information indicating a correspondence relationship between a torque difference, which is a difference between the individual torque and the all-cylinder torque, and a correction value of a fuel injection amount by the injector; In the correction information, when the individual torque is greater than the all-cylinder torque, the correction value is a value indicating a decrease correction for decreasing the fuel injection amount, and when the individual torque is less than the all-cylinder torque, the correction value is a value indicating an increase correction for increasing the fuel injection amount, and when a correction width of the decrease correction and a correction width of the increase correction are compared for cases where the absolute value of the torque difference is the same, the correction width of the increase correction is larger than the correction width of the decrease correction, The execution unit, during operation of the internal combustion engine, a first process for calculating the torque difference for each cylinder over the fixed period; a second process for calculating, based on the correction information, the correction value of the fuel injection amount for each cylinder according to the torque difference calculated in the first process; a third process for calculating a corrected injection amount for each cylinder by correcting a basic injection amount according to an operating state of the internal combustion engine using the correction value for each cylinder calculated in the second process; a fourth process of supplying the corrected injection amount for each cylinder through control of the injector at every predetermined cycle during the certain period; and Injector control device.

2. the torque difference is a value obtained by subtracting the all-cylinder torque from the individual torque, In the correction information, when the torque difference is a positive first value, the correction width of the decrease correction is larger than when the torque difference is a positive second value that is smaller than the first value, and when the torque difference is a negative third value, the correction width of the increase correction is larger than when the torque difference is a negative fourth value that is larger than the third value. The injector control device according to claim 1 .

3. the predetermined cycle is a series of periods in which one cylinder undergoes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke, respectively, once, In the fourth process, the execution unit divides the corrected injection amount into a plurality of parts and supplies the divided parts to the cylinder in multiple stages through control of the injector during one predetermined cycle. The injector control device according to claim 1 .

4. The execution unit: In each injection control, In the first process, the individual torque of each of the cylinders obtained as a result of performing the fourth process of the previous injection control is stored in the storage unit; In the third process, the cylinder in which the correction injection amount is made larger than the basic injection amount is stored in the storage unit as an increased injection cylinder, Regarding the newly performed injection control, In the first process, for the cylinder stored as the increased cylinder in the third process of the previous injection control, it is determined whether or not the individual torque obtained as a result of performing the fourth process for the certain period in the previous injection control is smaller than the individual torque obtained as a result of performing the fourth process for the certain period in the injection control before last, In the second process, if the result of the determination is positive, the correction value of the increased cylinder is set to a predetermined specific correction value that indicates the decrease correction regardless of the torque difference of the increased cylinder, and if the result of the determination is negative, the correction value of the increased cylinder is set to a value corresponding to the torque difference of the increased cylinder based on the correction information. The injector control device according to claim 1 .

5. the torque difference is a value obtained by subtracting the all-cylinder torque from the individual torque, Regarding the newly performed injection control, when the torque difference for each cylinder calculated in the first process is a symmetric torque difference that has the same absolute value as the torque difference for the increased cylinder and is a positive value, The specific correction value is set to a value indicating the decrease correction corresponding to the symmetric torque difference in the correction information. The injector control device according to claim 4.

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