Control device for internal combustion engines

Abstract

To suppress discharge of unburned fuel caused by misfire in post injection and attain a required air-fuel ratio and required torque.SOLUTION: A fuel injection amount calculation section 110 calculates a reference fuel injection amount QF from a required air-fuel ratio AFt and a sucked intake air amount Ga, and each injection amount calculation section 120 divides the reference fuel injection amount Qf into a main injection amount Qm and a post injection amount Qp. On the basis of required torque TQr, an injection timing calculation section 130 calculates main injection timing Im and post injection timing Ip. A post combustion period determination section 150 determines whether post combustion completion timing Ipf calculated by a post combustion completion timing calculation section 140 is a set crank angle Ct. A correction section 160 corrects the post injection timing Ip and the main injection amount Qm so that the post combustion completion timing IPf becomes the set crank angle Ct.SELECTED DRAWING: Figure 3

Description

Technical Field

[0004] , ,

[0005] , ,

[0001] The present disclosure relates to a control device for an internal combustion engine.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2011-32949 (Patent Document 1) describes that in a compression self-ignition internal combustion engine, a post-injection is performed following a main injection of fuel to increase the exhaust temperature. In this Patent Document 1, the in-cylinder temperature at the post-injection timing (post-injection period) is controlled within a predetermined temperature range with the combustion temperature of the post-injected fuel as the lower limit temperature and the temperature at which the torque generated by the combustion of the post-injected fuel becomes smaller than an allowable value as the upper limit temperature, so that the fuel injected by the post-injection is sufficiently combusted and the torque generated by the combustion of the fuel injected by the post-injection is suppressed to a value within an allowable range. Thereby, it is said that the exhaust temperature can be increased and the torque fluctuation of the internal combustion engine can be suppressed from becoming larger than an allowable amount.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, the post-injection timing is controlled by paying attention to the ignition limit of the post-injection, but it is assumed that there are cases where it becomes difficult to achieve both a suitable air-fuel ratio (required air-fuel ratio, required air excess ratio) and required torque for increasing the exhaust temperature. In the present disclosure, a post-injection that is injected into the cylinder (combustion chamber) following the main injection and ignites and burns in the combustion chamber is referred to as a post-injection.

[0005] The purpose of this disclosure is to suppress the emission of unburned fuel due to post-injection misfires while simultaneously achieving the required air-fuel ratio and torque. [Means for solving the problem]

[0006] The control device for an internal combustion engine of the present disclosure is a control device for a compression autoignition type internal combustion engine. The control device includes: a fuel injection amount calculation means for calculating a reference fuel injection amount to achieve a required air-fuel ratio; an injection amount calculation means for distributing the reference fuel injection amount to a main injection amount injected in the main injection and a post injection amount which is the injection amount of a post injection injected at a retarded angle compared to the main injection, based on the operating state of the internal combustion engine; an injection timing calculation means for calculating a main injection timing which is the injection timing of the main injection and a post injection timing which is the injection timing of the post injection, based on the required torque; a post combustion period determination means for determining whether the combustion end time of the post injection is at a set crank angle; and a correction means for correcting the post injection timing and the main injection amount if the combustion end time is not at a set crank angle.

[0007] In this configuration, the fuel injection amount calculation means of the control device calculates a reference fuel injection amount to achieve the required air-fuel ratio, and each injection amount calculation means distributes the reference fuel injection amount to a main injection amount and a post-injection amount. Since the reference fuel injection amount is calculated to achieve the required air-fuel ratio, the air-fuel ratio becomes the required air-fuel ratio.

[0008] The injection timing calculation means calculates the main injection timing, which is the injection timing for the main injection, and the post-injection timing, which is the injection timing for the post-injection, based on the required torque. The post-combustion period determination means determines whether the combustion end time of the post-injection is at the set crank angle, and the correction means corrects the post-injection timing and main injection amount if the combustion end time is not at the set crank angle. Since the main injection timing and post-injection timing are calculated based on the required torque, and the post-injection timing and main injection amount are corrected if the combustion end time of the post-injection is not at the set crank angle, the required torque can be achieved and misfires in the post-injection can be suppressed.

[0009] Therefore, this configuration makes it possible to suppress the emission of unburned fuel due to post-injection misfires while simultaneously achieving the required air-fuel ratio and torque.

[0010] The correction means may correct the post-injection timing to the retarded side and increase the main injection amount when the combustion end time is advanced compared to the set crank angle, and correct the post-injection timing to the advanced side and decrease the main injection amount when the combustion end time is retarded compared to the set crank angle.

[0011] With this configuration, when the combustion termination time is advanced beyond the set crank angle, the post-injection timing is corrected to the retarded side, allowing for appropriate control of the post-injection combustion termination time and maintaining good emissions. Furthermore, the decrease in output torque caused by the retarded post-injection timing is suppressed by increasing the main injection amount. When the combustion termination time is retarded beyond the set crank angle, the post-injection timing is corrected to the advanced side, allowing for appropriate control of the post-injection combustion termination time and maintaining good emissions. Furthermore, the increase in output torque caused by the advanced post-injection timing is suppressed by decreasing the main injection amount.

[0012] An exhaust catalytic converter is provided in the exhaust passage of the internal combustion engine, and the required air-fuel ratio may be the air-fuel ratio set when the exhaust catalytic converter is warmed up.

[0013] With this configuration, the air-fuel ratio required to raise the exhaust temperature is set as the required air-fuel ratio when the exhaust purification device is warming up, allowing the exhaust purification device to warm up more quickly. [Effects of the Invention]

[0014] According to this disclosure, it is possible to suppress the emission of unburned fuel due to misfires in post-injection while simultaneously achieving the required air-fuel ratio and required torque. [Brief explanation of the drawing]

[0015] [Figure 1]This diagram schematically shows the overall configuration of the internal combustion engine according to this embodiment. [Figure 2] This diagram illustrates an example of fuel injection and combustion in the warm-up mode. [Figure 3] This figure shows an example of a functional block configured in the ECU in this embodiment. [Figure 4] This flowchart shows an example of the fuel injection control process performed in the ECU during the warm-up mode. [Figure 5] This flowchart shows an example of the processing in the post-combustion end time calculation routine. [Modes for carrying out the invention]

[0016] The embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated.

[0017] Figure 1 is a schematic diagram showing the overall configuration of the internal combustion engine according to this embodiment. Referring to Figure 1, the engine (internal combustion engine) 1 is a compression-ignition type internal combustion engine (diesel engine) equipped with an exhaust gas purification device 70. The engine 1 is used, for example, as a power source for a vehicle. The engine 1 is an internal combustion engine that injects fuel from a fuel injector 14 into the combustion chamber formed in the cylinder 12 of the engine body 10 and performs compression auto-ignition. In this embodiment, the engine 1 has four cylinders. The intake passage 20 of the engine 1 is provided with an air cleaner 22, an intercooler 24, and an intake throttle valve (diesel throttle valve) 26. Fresh air from which foreign matter has been removed by the air cleaner 22 is supercharged (compressed) by the compressor 32 of the turbocharger 30, cooled by the intercooler 24, supplied to the intake manifold 28, and supplied to each combustion chamber from the intake port.

[0018] Fuel is stored in the fuel tank 40. The fuel in the fuel tank 40 is supplied to the high-pressure fuel pump 42 by the feed pump 41, and the high-pressure fuel discharged from the high-pressure fuel pump 42 is pumped to the common rail 44 through the fuel passage 43. The high-pressure fuel stored in the common rail 44 is injected into the combustion chamber (inside the cylinder) from the injector 14.

[0019] The exhaust gas discharged from the combustion chamber is collected in the exhaust manifold 50 and discharged to the outside air through the exhaust passage 52. Also, a part of the exhaust gas is recirculated to the intake manifold 28 through the EGR (Exhaust Gas Recirculation) passage 60. The EGR passage 60 is provided with an EGR cooler 62 and an EGR valve 64.

[0020] The turbine 34 of the turbocharger 30 is provided in the exhaust passage 52, and downstream of the turbine 34, as an exhaust gas purification device 70, an oxidation catalyst 71, a DPF (Diesel Particulate Filter) 72, a selective reduction catalyst (hereinafter also referred to as an SCR (Selective Catalytic Reduction) catalyst) 73, and an oxidation catalyst 74 are provided. The oxidation catalyst 71 oxidizes and purifies CO (carbon monoxide), HC (hydrocarbons), and SOF (Soluble Organic Fraction) contained in the exhaust gas. Also, when the oxidation catalyst 71 burns and removes the particulate matter (PM) collected by the DPF 72, it burns (oxidizes) the supplied HC to raise the exhaust gas temperature.

[0021] An SCR catalyst 73 is disposed in an exhaust passage 52 downstream of the DPF 72. The SCR catalyst 73 is, for example, one in which copper (Cu) ion-exchanged zeolite is supported on a ceramic carrier as a catalyst, and exhibits a high NOx purification rate by using ammonia (NH3) as a reducing agent. The ammonia used as the reducing agent is generated by hydrolyzing and thermally decomposing the aqueous urea supplied to the exhaust passage 52 upstream of the SCR catalyst 73. An urea addition valve (aqueous urea injection injector) 80 is provided in the exhaust passage upstream of the SCR catalyst 73, and the aqueous urea pumped from an urea water tank 81 by a pump 82 is injected from the urea addition valve 80 into the exhaust passage 52 upstream of the SCR catalyst 73.

[0022] An oxidation catalyst 74 is provided in the exhaust passage 52 downstream of the SCR catalyst 73, and oxidizes and purifies the ammonia (slipped) discharged from the SCR catalyst 73.

[0023] The ECU (Electronic Control Unit) 100 includes a CPU (Central Processing Unit) 101, a memory 102 composed of a ROM (Read Only Memory) and a RAM (Random Access Memory), an input / output port (not shown) for inputting / outputting various signals, etc., and executes predetermined arithmetic processing based on the information stored in the memory 102 and the information from various sensors, and controls an injector 14, an intake throttle valve 26, an EGR valve 64, etc. The ECU 100 corresponds to an example of the "control device" of the present disclosure.

[0024] Examples of the various sensors input to the ECU 100 include a crank angle sensor 111, a cam position sensor 112, an intake air amount sensor 113, an accelerator opening sensor 114, an intake air temperature sensor 115, a vehicle speed sensor 116, etc.

[0025] The crank angle sensor 111 detects the crank angle CA of engine 1. The ECU 100 calculates the rotational speed NE of engine 1 based on the crank angle CA. The cam position sensor 112 detects the cam position (rotational position) CP of the intake camshaft and / or exhaust camshaft. The ECU 100 performs cylinder identification (for example, identification of the cylinder in the intake stroke) based on the crank angle CA and cam position CP.

[0026] The intake air volume sensor 113 detects the intake air volume Ga. The accelerator pedal position sensor 114 detects the accelerator pedal position AP, which is the amount the accelerator pedal is pressed. The intake air temperature sensor 115 detects the intake air temperature TA, which is the temperature of the intake air. The vehicle speed sensor 116 detects the vehicle speed SPD of the vehicle in which engine 1 is installed. The ECU 100 also receives signals from various sensors not shown in the diagram, such as coolant temperature THW, boost pressure BP, and common rail pressure Pc.

[0027] The ECU 100 calculates the fuel injection amount from the accelerator opening AP and rotational speed NE, or from the accelerator opening AP and the required torque TQr set by the vehicle speed SPD. It also calculates the fuel injection timing from the accelerator opening AP and rotational speed NE, or from the required torque TQr and rotational speed NE. Then, at the fuel injection timing, it controls the injector 14 so that fuel corresponding to the fuel injection amount is injected into the combustion chamber (cylinder).

[0028] In oxidation catalysts 71, SCR catalysts 74, etc., the purification performance deteriorates when the catalyst bed temperature falls below the activation temperature. When the catalyst bed temperature is low and the exhaust purification catalyst needs to be warmed up, or when the exhaust temperature needs to be raised, the ECU 100 controls the engine 1 in a "warm-up mode" that uses post-injection following the main injection to raise the exhaust temperature.

[0029] Figure 2 illustrates an example of fuel injection and combustion in the warm-up mode. As shown in the upper part of Figure 2, in the warm-up mode of this embodiment, pilot injection is performed prior to main injection, and post-injection is performed after the main injection. The fuel injected by post-injection burns in the combustion chamber (cylinder). Since post-injection is injected at a retarded injection timing compared to main injection, its contribution is lower than that of main injection, but it generates the output torque of engine 1. In this disclosure, this injection following main injection is referred to as "post-injection," but it may also be referred to as "after-injection."

[0030] To warm up the exhaust gas purification catalyst, it is preferable to set the air-fuel ratio to be lower (resulting in a lower air purification rate) compared to normal operation when raising the exhaust gas temperature (during warm-up mode). By performing post-injection, the amount of fuel supplied to the combustion chamber (inside the cylinder) can be increased without increasing the amount of main injection injected during the main injection, making it possible to reduce the air-fuel ratio while suppressing an increase in output torque.

[0031] As shown in the lower part of Figure 2, post-injection fuel ignites and burns after the main injection combustion. When the post-injection timing is advanced, the contribution of post-injection to power torque increases, resulting in increased power torque. Conversely, when the post-injection timing is retarded, misfires may occur due to a decrease in combustion chamber temperature (cylinder temperature), potentially leading to the discharge of unburned fuel.

[0032] In this embodiment, by controlling the timing of the end of post-injection combustion to coincide with the set crank angle, it is possible to suppress the emission of unburned fuel due to misfires in post-injection while simultaneously achieving the required air-fuel ratio and torque in the warm-up mode.

[0033] Figure 3 shows an example of a functional block configured in the ECU 100 in this embodiment. The fuel injection amount calculation unit 110 calculates a reference fuel injection amount Qf, which is the total amount of fuel injected into the combustion chamber (cylinder), based on the required air-fuel ratio AFt and the intake air amount Ga. The required air-fuel ratio AFt is the air-fuel ratio set during the warm-up operation mode, which is determined in advance by experiments or the like and stored in the memory 102. The reference fuel injection amount Qf may be calculated, for example, based on the intake air amount per revolution (Ga / NE) obtained from the engine rotation speed NE and the intake air amount Ga, so that the air-fuel ratio becomes the required air-fuel ratio AFt. The fuel injection amount calculation unit 110 corresponds to an example of the "fuel injection amount calculation means" in this disclosure.

[0034] Each injection amount calculation unit 120 distributes the reference fuel injection amount Qf to a pilot injection amount Qo, a main injection amount Qm, and a post-injection amount Qp based on the operating state of the engine 1. For example, the minimum injection amount that can be injected from the injector 14 is set to the pilot injection amount Qo. The main injection amount Qm is calculated from a main injection amount calculation map with accelerator opening AP and rotational speed NE as parameters. Then, the post-injection amount Qp is calculated by subtracting the pilot injection amount Qo and the main injection amount Qm from the reference fuel injection amount Qf (Qp = Qf - Qo - Qm). Each injection amount calculation unit 120 corresponds to an example of the "each injection amount calculation means" in this disclosure.

[0035] The injection timing calculation unit 130 calculates the main injection timing Im, which is the injection timing for the main injection, and the post injection timing Ip, which is the injection timing for the post injection, based on the required torque TQr and the rotational speed NE. The required torque TQr may be determined, for example, by the accelerator opening AP and the vehicle speed SPD. The main injection timing Im is determined from a main injection timing map with the required torque TQr and rotational speed NE as parameters, and the post injection timing Ip may be determined from a post injection timing map with the required torque TQr and rotational speed NE as parameters. The injection timing calculation unit 130 also sets the pilot injection timing Io to a timing (crank angle) advanced by a predetermined crank angle from the main injection timing Im. The pilot injection timing Io may also be determined by map search, similar to the main injection timing Im. The injection timing calculation unit 130 corresponds to an example of the "injection timing calculation means" in this disclosure.

[0036] The post-combustion termination timing calculation unit 140 calculates the post-injection combustion termination timing Ipf. For example, the post-combustion termination timing calculation unit 140 uses a combustion model to calculate the in-cylinder temperature, in-cylinder oxygen partial pressure, etc., at the time of post-injection from parameters such as the main injection amount Qm, post-injection amount Qp, intake air amount Ga, intake air temperature TA, rotational speed NE, EGR amount (ERG rate), and common rail pressure Pc. Next, it uses a heat generation rate combustion model to determine the heat generation rate (combustion rate) of post-injection from this in-cylinder temperature, in-cylinder oxygen concentration, post-injection amount Qp, etc. Then, based on the calculated heat generation rate, it determines the post-combustion period (crank angle), which is the combustion period of post-injection, and calculates the post-combustion termination timing Ipf by adding the post-combustion period to the post-injection timing Ip.

[0037] The post-combustion period determination unit 150 determines whether the post-combustion end time Ipf is advanced beyond the set crank angle Ct, or whether it is advanced beyond the set crank angle Ct. The set crank angle Ct is set in advance by experimentation or the like and stored in the memory 102. The set crank angle Ct may be a constant value regardless of the operating state of the engine 1, or multiple values ​​may be set according to the operating state of the engine 1 (for example, multiple regions partitioned by rotational speed NE). The post-combustion period determination unit 150 corresponds to an example of the "post-combustion period determination means" of this disclosure.

[0038] The correction unit 160 corrects the post-injection timing Ip, main injection amount Qm, etc., based on the determination result in the post-combustion period determination unit 150. In this embodiment, the post-injection timing Ip is expressed in terms of ATDC (After Top Dead Center) (the post-injection timing Ip is expressed as the crank angle after top dead center). The correction unit 160 corresponds to an example of the "correction means" of this disclosure.

[0039] If the post-combustion end timing Ipf is advanced beyond the set crank angle Ct, the correction unit 160 corrects the post-injection timing Ip to the retarded side and increases the main injection amount Qm. For example, the new post-injection timing Ip is the current post-injection timing Ip plus a predetermined value A (Ip ← Ip + A). As the retardation of the post-injection timing Ip reduces the contribution rate of post-injection output torque, the main injection amount Qm is increased. For example, the new main injection amount Qm is the current main injection amount Qm plus a predetermined amount q (Qm ← Qm + q). In this case, it is desirable to determine the amount of decrease in the output torque contribution rate due to retarding the post-injection timing Ip and set the predetermined amount q to a value corresponding to this decrease. The post-injection amount Qp is recalculated using the new main injection amount Qm (Qp = Qf - Qo - Qm).

[0040] If the post-combustion end timing Ipf is advanced beyond the set crank angle Ct, the correction unit 160 corrects the post-injection timing Ip to the advanced side and reduces the main injection amount Qm. For example, the new post-injection timing Ip is the current post-injection timing Ip minus a predetermined value B (Ip ← Ip - B). As the post-injection timing Ip advances, the contribution rate of post-injection to the output torque increases, so the main injection amount Qm is reduced. For example, the new main injection amount Qm is the current main injection amount Qm minus a predetermined amount q (Qm ← Qm - q). In this case, it is desirable to determine the amount of increase in the output torque contribution rate due to advancing the post-injection timing Ip and set the predetermined amount q to a value corresponding to this increase. The post-injection amount Qp is recalculated using the new main injection amount Qm (Qp = Qf - Qo - Qm).

[0041] Figure 4 is a flowchart showing an example of the fuel injection control process executed in the ECU 100 during warm-up mode. This flowchart is executed, for example, when it becomes necessary to raise the temperature of the exhaust gas to increase the temperature of the SCR catalyst 74 of the exhaust gas purification device 70. This flowchart is repeated at predetermined intervals during warm-up mode.

[0042] In step 10 (hereinafter, steps are abbreviated as "S"), various parameters such as intake air volume Ga, rotational speed NE, accelerator opening AP, and vehicle speed SPD are acquired. In the following step S11, the standard fuel injection amount Qf is calculated based on the required air-fuel ratio AFt, intake air volume Ga, and rotational speed NE. The required air-fuel ratio AFt during warm-up mode is pre-stored in memory 102.

[0043] In S12, the minimum injection amount that can be injected from injector 14 is set to pilot injection amount Qo, and the main injection amount Qm is calculated from the main injection fuel calculation map using the accelerator opening AP and rotational speed NE. In addition, the post-injection amount Qp is calculated from the formula QP = Qf - Qo - Qm.

[0044] In S13, the required torque TQr is calculated from the accelerator opening AP and vehicle speed SPD. Based on the required torque TQr and rotational speed NE, the main injection timing Im is calculated from the main injection timing map. Based on the required torque TQr and rotational speed NE, the post-injection timing Ip is calculated from the post-injection timing map. In addition, the timing (crank angle) advanced by a predetermined crank angle from the main injection timing Im is set to the pilot injection timing Io.

[0045] In the subsequent S14, the post-combustion end time Ipf is calculated. The post-combustion end time Ipf is calculated in a subroutine. Figure 5 is a flowchart showing an example of the processing of the post-combustion end time calculation routine. This flowchart is repeated at predetermined intervals during the warm-up mode.

[0046] Referring to Figure 5, in S20, various parameters such as the main injection amount Qm, post-injection amount Qp, intake air amount Ga, intake air temperature TA, rotational speed NE, EGR amount (ERG rate), and common rail pressure Pc are acquired. In the following S21, the in-cylinder temperature, in-cylinder oxygen partial pressure, etc., at the time of post-injection are calculated using a combustion model based on the parameters acquired in S20, and then the process proceeds to S22.

[0047] In S22, the heat generation rate (combustion rate) of post-injection is determined using a heat generation rate model based on the in-cylinder temperature, in-cylinder oxygen concentration, post-injection amount Qp, etc. In the following S23, the post-combustion period (crank angle), which is the combustion period of post-injection, is determined based on the heat generation rate of post-injection, and the post-combustion end time Ipf is calculated by adding the post-combustion period to the post-injection time Ip, thus ending this routine.

[0048] Returning to Figure 4, in S15, it is determined whether the post-combustion termination time Ipf is greater than or equal to the "set crank angle Ct + α". α is a value for control hysteresis, and its magnitude may be set in advance through experiments, etc. If the post-combustion termination time Ipf is less than the "set crank angle Ct + α" (i.e., the post-combustion termination time Ipf is advanced from the "set crank angle Ct + α"), it is judged negative and the process proceeds to S16. If the post-combustion termination time Ipf is greater than or equal to the "set crank angle Ct + α" (i.e., the post-combustion termination time Ipf is retarded from the "set crank angle Ct + α"), it is judged positive and the process proceeds to S18.

[0049] In S16, it is determined whether the post-combustion end time Ipf is less than or equal to the "set crank angle Ct-α". If the post-combustion end time Ipf is greater than the "set crank angle Ct-α" (i.e., the post-combustion end time Ipf is retarded compared to the "set crank angle Ct-α"), the determination is negative and the routine ends. If the post-combustion end time Ipf is less than or equal to the "set crank angle Ct-α" (i.e., the post-combustion end time Ipf is advanced compared to the "set crank angle Ct-α"), the determination is positive and the process proceeds to S17.

[0050] In S17, the current post-injection timing Ip is added to a predetermined value A to calculate the new post-injection timing Ip (Ip ← Ip + A). The decrease in the output torque contribution rate of post-injection due to retarding the post-injection timing Ip by the predetermined value A is determined, a predetermined amount q corresponding to this decrease is calculated, and the current main injection amount Qm is added to the predetermined amount q to calculate the new main injection amount Qm (Qm ← Qm + q). Then, the post-injection amount Qp is recalculated using the new main injection amount Qm (Qp = Qf - Qo - Qm), and the routine ends.

[0051] In S18, the current post-injection timing Ip is subtracted by a predetermined value B to calculate the new post-injection timing Ip (Ip ← Ip - B). The increase in the output torque contribution rate of post-injection due to advancing the post-injection timing Ip by the predetermined value B is determined, a predetermined amount q corresponding to this increase is calculated, and the current main injection amount Qm is subtracted by the predetermined amount q to calculate the new main injection amount Qm (Qm ← Qm - q). Then, the post-injection amount Qp is recalculated using the new main injection amount Qm (Qp = Qf - Qo - Qm), and the routine ends.

[0052] According to this embodiment, the fuel injection amount calculation unit 110 of the ECU 100 calculates a reference fuel injection amount Qf so ​​that it becomes the required air-fuel ratio AFt, and the individual injection amount calculation units 120 distribute the reference fuel injection amount Qf to the pilot injection amount Qo, the main injection amount Qm, and the post-injection amount Qp. Since the reference fuel injection amount Qf is calculated so that it becomes the required air-fuel ratio AFt, the air-fuel ratio during the warm-up operation mode becomes the required air-fuel ratio AFt. In addition, the injection timing calculation unit 130 calculates the main injection timing Im and the post-injection timing Ip based on the required torque TQr. The post-combustion period determination unit 150 determines whether the post-combustion end timing Ipf is the set crank angle Ct, and the correction unit 160 corrects the post-injection timing Ip and the main injection amount Qm if the post-combustion end timing Ipf is not the set crank angle Ct. Based on the required torque TQr, the main injection timing Im and post-injection timing Ip are calculated. If the post-combustion end timing Ipf is not equal to the set crank angle Ct, the post-injection timing Ip and main injection amount Qm are corrected, thereby achieving the required torque TQr and suppressing post-injection misfires.

[0053] According to this embodiment, when the post-combustion termination timing Ipf is advanced compared to the set crank angle Ct, the post-injection timing Ip is corrected to the retarded side and the main injection amount Qm is increased. This allows for appropriate control of the post-combustion termination timing Ipf, good emission maintenance, and suppression of the decrease in output torque caused by the correction of the post-injection timing Ip to the retarded side by increasing the main injection amount Qm. When the post-combustion termination timing Ipf is retarded compared to the set crank angle Ct, the post-injection timing Ip is corrected to the advanced side and the main injection amount Qm is decreased. This allows for appropriate control of the post-combustion termination timing Ipf, good emission maintenance, and suppression of the increase in output torque caused by the correction of the post-injection timing Ip to the advanced side by decreasing the main injection amount Qm.

[0054] In the above embodiment, the post-combustion termination time calculation routine in Figure 5 used a combustion model and a heat generation rate model to determine the post-combustion termination time Ipf. However, the method for calculating the post-combustion termination time Ipf is not limited to this. For example, an in-cylinder pressure sensor may be provided, and the heat generation rate waveform may be estimated based on the change in in-cylinder pressure detected by the in-cylinder pressure sensor. The post-combustion termination time Ipf may then be determined using this heat generation rate waveform.

[0055] In the above embodiment, the process shown in the flowchart of Figure 4 is repeatedly executed during the warm-up mode. However, even if the process in Figure 4 is repeatedly executed, it is conceivable that a negative determination may not be made in S16 depending on the driving environment and usage environment. (It is also conceivable that even if the process in Figure 4 is repeatedly executed, the post-combustion end time Ipf may not converge to within the range of the set crank angle Ct±α.) If a negative determination is not made in S16 even after a predetermined time has elapsed since the start of fuel injection control by the warm-up mode, the routine may be terminated after the process in S13 without executing the procedures from S14 onwards. This makes it possible to reduce the computational load on the ECU 100 when the post-combustion end time Ipf does not converge to within the range of the set crank angle Ct±α depending on the driving environment and usage environment.

[0056] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of symbols]

[0057] 1 Engine, 10 Engine block, 12 Cylinder, 14 Injector, 20 Intake passage, 22 Air cleaner, 24 Intercooler, 26 Intake throttle valve, 28 Intake manifold, 30 Turbocharger, 32 Compressor, 34 Turbine, 40 Fuel tank, 41 Feed pump, 42 High-pressure fuel pump, 43 Fuel passage, 44 Common rail, 50 Exhaust manifold, 52 Exhaust passage, 60 EGR passage, 62 EGR cooler, 64 EGR valve, 70 Exhaust gas purification device, 71 Oxidation catalyst, 72 DPF, 73 Selective catalytic reduction (SCR catalyst), 74 Oxidation catalyst, 80 Urea additive valve, 81 Urea tank, 82 Pump, 100 ECU, 101 CPU, 102 Memory, 110 Fuel injection amount calculation unit, 111 Crank angle sensor, 112 Cam position sensor, 113 Intake air volume sensor, 114 accelerator pedal position sensor, 115 intake air temperature sensor, 116 vehicle speed sensor, 120 injection volume calculation unit, 130 injection timing calculation unit, 140 post-combustion end timing calculation unit, 150 post-combustion period determination unit, 160 correction unit.

Claims

1. A control device for a compression-ignition type internal combustion engine, A fuel injection amount calculation means for calculating a reference fuel injection amount to achieve the required air-fuel ratio, Each injection amount calculation means allocates the reference fuel injection amount to a main injection amount injected in the main injection and a post-injection amount which is the injection amount of a post-injection injected at a retarded angle compared to the main injection, based on the operating state of the internal combustion engine. An injection timing calculation means calculates the main injection timing, which is the injection timing of the main injection, and the post-injection timing, which is the injection timing of the post-injection, based on the required torque. A post-burning period determination means for determining whether the end time of the post-injection combustion is at a set crank angle, A control device for an internal combustion engine, comprising: correction means for correcting the post-injection timing and the main injection amount when the combustion termination timing is not the set crank angle.

2. The correction means is When the combustion termination time is advanced compared to the set crank angle, the post-injection timing is corrected to retard the angle and the main injection amount is corrected to increase it. The control device for an internal combustion engine according to claim 1, wherein when the combustion termination time is retarded compared to the set crank angle, the post-injection timing is advanced and the main injection amount is reduced.

3. The exhaust passage of the aforementioned internal combustion engine is equipped with an exhaust gas purification catalyst. The control device for an internal combustion engine according to claim 1 or claim 2, wherein the required air-fuel ratio is the air-fuel ratio set when the exhaust gas purification catalyst is warmed up.

Images