JP5273307B1 - Control device for internal combustion engine - Google Patents

Abstract

  An internal combustion engine is equipped with an EGR device that returns a part of the exhaust gas flowing through the exhaust passage to the intake passage for recirculation. The electronic control unit executes a process of specifying and storing a cetane number region to which the cetane number of the fuel supplied to the internal combustion engine belongs. The electronic control unit determines the EGR opening degree (VR) during idle operation when the engine is in an execution period immediately after the start of the internal combustion engine and the low cetane number region is stored (t11 to t12). In addition, the required injection timing (Tst) during idling is set to a retarded timing as compared to when not in a specific situation.

Description

  The present invention relates to a control device for an internal combustion engine that estimates the cetane number of fuel supplied to the internal combustion engine and executes engine operation control according to the estimated cetane number.

  In a self-ignition type internal combustion engine, fuel injected into a cylinder by a fuel injection valve is ignited after a predetermined time (so-called ignition delay) has elapsed since injection. In order to improve the output performance and emission performance of an internal combustion engine, a control device that controls the execution mode of engine control such as injection timing and injection amount in fuel injection in consideration of such ignition delay is widely adopted. .

  In an internal combustion engine, the lower the cetane number of the fuel used, the longer the ignition delay. For this reason, for example, even if the engine control execution mode is set assuming that a standard cetane number fuel is used at the time of shipment of the internal combustion engine, a fuel with a relatively low cetane number such as winter fuel is used as a fuel tank. When the fuel is replenished, the ignition timing of the fuel is delayed and the combustion state is deteriorated. In some cases, misfire occurs.

  In order to suppress the occurrence of such inconvenience, it is desirable to correct the engine control execution mode based on the actual cetane number of the fuel injected into the cylinder.

  For example, Patent Document 1 discloses an internal combustion engine equipped with an exhaust gas recirculation (EGR) device that recirculates a part of exhaust gas flowing through an exhaust passage of an internal combustion engine to an intake passage, and supplies fuel to the internal combustion engine. It has been proposed to estimate the cetane number and correct the amount of exhaust (EGR amount) returned to the intake passage by the EGR device in accordance with the estimated cetane number. In this apparatus, as the estimated cetane number is lower, the EGR amount is corrected to decrease, thereby improving the combustion state of the fuel and suppressing the occurrence of misfire.

JP 2007-285195 A

  Usually, an EGR device includes an EGR passage that communicates an intake passage and an exhaust passage of an internal combustion engine, and an EGR valve that changes a passage sectional area of the EGR passage. In the EGR device, the EGR amount is adjusted through operation control of the EGR valve. In such an EGR device, due to the volume of the EGR passage and the volume of the portion from the connection portion of the intake passage of the internal combustion engine to the cylinder of the internal combustion engine to the change in the EGR amount with respect to the change in the opening degree of the EGR valve. A delay is inevitable. For this reason, the responsiveness and stability of the change in the EGR amount with respect to the change in the opening degree of the EGR valve is low, and precise adjustment of the EGR amount by the EGR device is difficult. It can be said that it is easy.

  In particular, during the idling operation immediately after the start of the internal combustion engine, since the absolute amount of intake air is small, the influence of the adjustment error of the EGR amount on the engine operation state is likely to increase, Since the temperature is low, the combustion state of the fuel tends to become unstable. Therefore, at this time, if the amount of EGR is excessively increased due to the adjustment error, there is a high possibility that the occurrence of misfire cannot be properly suppressed. On the other hand, if the EGR amount becomes too small due to the adjustment error at this time, the combustion temperature of the fuel in the cylinder becomes high, so that the amount of nitrogen oxide (NOx) in the exhaust increases accordingly.

  The present invention has been made in view of such a situation, and an object thereof is an internal combustion engine capable of achieving both suppression of misfire and suppression of nitrogen oxide emission when using a low cetane number fuel. It is to provide a control device.

  In order to achieve the above object, a control device for an internal combustion engine according to the present invention comprises an EGR device for returning a part of exhaust gas flowing through the exhaust passage of the internal combustion engine to the intake passage and recirculating the fuel, and is supplied to the internal combustion engine. Estimate the cetane number. When the cetane number estimated by the estimation unit is low and the execution period is immediately after the start of the internal combustion engine, the EGR amount by the EGR device during idle operation is reduced compared to when it is not. .

  As a result, when the idling operation is performed immediately after the start of the internal combustion engine in a situation where the cetane number estimated by the estimation unit is low, that is, the influence of the EGR amount adjustment error on the fuel combustion state is likely to be large and the fuel combustion When the state tends to become unstable, the adjustment error of the EGR amount can be reduced by the amount that the absolute amount of the EGR amount decreases. Therefore, the influence on the combustion state of the fuel due to the adjustment error of the EGR amount can be suppressed small. Moreover, the fuel injection timing is retarded in accordance with such a decrease in the EGR amount. Therefore, the combustion state of the fuel can be set through the adjustment of the fuel injection timing capable of setting the combustion state of the fuel in the cylinder of the internal combustion engine with higher accuracy than the adjustment of the EGR amount.

  Therefore, according to the above apparatus, since the combustion state of the fuel in the cylinder of the internal combustion engine when using the low cetane number fuel can be appropriately set, it is possible to suppress misfire occurrence and reduce the amount of nitrogen oxide (NOx) emission. Coexistence with suppression can be achieved.

  Preferably, the control unit sets the EGR amount by the EGR device to “0”. According to such an apparatus, the influence on the combustion state of the fuel due to the adjustment error of the EGR amount can be eliminated, so that the combustion state of the fuel can be set with higher accuracy.

  In one aspect of the present invention, the retarding of the fuel injection timing by the control unit is executed on condition that the external air pressure is equal to or higher than a predetermined determination pressure. When the outside air pressure is low, the amount of oxygen contained in the intake air is small because the air density is low. For this reason, the combustion state of the fuel in the cylinder of the internal combustion engine is likely to deteriorate, and misfire is likely to occur. According to the above apparatus, when the external pressure is low and misfire is likely to occur, the change of the fuel injection timing to the retarded side, in other words, the change to the side of deteriorating the combustion state of the fuel is prohibited. Can be reliably suppressed. In addition, when the external air pressure is high and misfire is relatively difficult to occur, the change of the fuel injection timing to the retard side is permitted, so that the NOx emission amount can be suppressed.

  In one aspect of the present invention, the execution period is set to a period from when the internal combustion engine is started to when the accelerator operation member is opened. According to such a device, when the temperature in the cylinder of the internal combustion engine is low immediately after the start of the internal combustion engine, in other words, only in a period during which the instability of the combustion state of the fuel in the cylinder is likely to be caused with high accuracy. The reduction of the EGR amount and the retardation of the fuel injection timing for realizing the setting of the combustion state can be executed.

1 is a schematic diagram illustrating a schematic configuration of a control device for an internal combustion engine according to an embodiment of the present invention. Sectional drawing which shows the cross-section of a fuel injection valve. The time chart which shows the relationship between transition of fuel pressure and the detection time waveform of a fuel injection rate. The flowchart which shows the execution procedure of a correction process. The time chart which shows an example of the relationship between a detection time waveform and a basic time waveform. The flowchart which shows the specific execution procedure of an index value detection process. Explanatory drawing explaining the calculation method of rotation fluctuation amount. The flowchart which shows the execution procedure of an EGR control process. The flowchart which shows the execution procedure of the injection timing retardation process. The timing chart which shows an example of the execution aspect of each process.

  A control apparatus for an internal combustion engine according to an embodiment embodying the present invention will be described below.

  As shown in FIG. 1, the vehicle 10 is equipped with an internal combustion engine 11 as a drive source. A crankshaft 12 of the internal combustion engine 11 is connected to wheels 15 via a clutch mechanism 13 and a manual transmission 14. In the vehicle 10, when a clutch operating member (for example, a clutch pedal) is operated by an occupant, the clutch mechanism 13 is in an operating state in which the connection between the crankshaft 12 and the manual transmission 14 is released.

  An intake passage 17 is connected to the cylinder 16 of the internal combustion engine 11. Air is sucked into the cylinder 16 of the internal combustion engine 11 through the intake passage 17. Further, as the internal combustion engine 11, one having a plurality of (four [# 1 to # 4] in the present embodiment) cylinders 16 is employed. A direct injection type fuel injection valve 20 that directly injects fuel into the cylinder 16 is attached to the internal combustion engine 11 for each cylinder 16. The fuel injected by opening the fuel injection valve 20 is ignited and burned in contact with the intake air compressed and heated in the cylinder 16 of the internal combustion engine 11. In the internal combustion engine 11, the piston 18 is pushed down by the energy generated by the combustion of fuel in the cylinder 16, and the crankshaft 12 is forcibly rotated. Combustion gas burned in the cylinder 16 of the internal combustion engine 11 is discharged as an exhaust gas into an exhaust passage 19 of the internal combustion engine 11.

  The internal combustion engine 11 is provided with an exhaust gas recirculation (EGR) device 50 for returning a part of the exhaust gas flowing in the exhaust passage 19 to the intake passage 17 for recirculation. The EGR device 50 includes an EGR passage 51 that communicates the intake passage 17 and the exhaust passage 19 of the internal combustion engine 11, and an EGR valve 52 that is attached to the EGR passage 51 and adjusts the cross-sectional area of the EGR passage 51. . In the EGR device 50, the amount of exhaust gas (EGR gas) returned from the exhaust passage 19 to the intake passage 17, the so-called EGR amount, is adjusted by changing the opening degree of the EGR valve 52.

  Each fuel injection valve 20 is individually connected to a common rail 34 via a branch passage 31a, and the common rail 34 is connected to a fuel tank 32 via a supply passage 31b. A fuel pump 33 that pumps fuel is provided in the supply passage 31b. In the present embodiment, the fuel boosted by the pumping by the fuel pump 33 is stored in the common rail 34 and supplied to each fuel injection valve 20. A return passage 35 is connected to each fuel injection valve 20, and each return passage 35 is connected to a fuel tank 32. Part of the fuel inside the fuel injection valve 20 is returned to the fuel tank 32 through the return passage 35.

  Hereinafter, the internal structure of the fuel injection valve 20 will be described.

  As shown in FIG. 2, a needle valve 22 is provided inside the housing 21 of the fuel injection valve 20. The needle valve 22 is provided in a state capable of reciprocating in the housing 21 (moving up and down in the figure). Inside the housing 21 is provided a spring 24 that constantly urges the needle valve 22 toward the injection hole 23 (the lower side in the figure). A nozzle chamber 25 is formed in the housing 21 at a position on one side (lower side in the figure) with the needle valve 22 interposed therebetween, and on the other side (upper side in the figure). A pressure chamber 26 is formed.

  The nozzle chamber 25 is formed with a plurality of injection holes 23 that communicate the inside with the outside of the housing 21, and fuel is supplied from the branch passage 31 a (common rail 34) through the introduction passage 27. The pressure chamber 26 is connected to the nozzle chamber 25 and the branch passage 31a (common rail 34) via a communication passage 28. The pressure chamber 26 is connected to a return passage 35 (fuel tank 32) via a discharge passage 30.

  The fuel injection valve 20 employs an electrically driven type, and a piezoelectric actuator 29 in which a plurality of piezoelectric elements (for example, piezo elements) that expand and contract by input of a drive signal is provided in the housing 21. It has been. A valve body 29 a is attached to the piezoelectric actuator 29, and the valve body 29 a is provided inside the pressure chamber 26. Then, through the movement of the valve element 29 a by the operation of the piezoelectric actuator 29, one of the communication path 28 (nozzle chamber 25) and the discharge path 30 (return path 35) is selectively communicated with the pressure chamber 26. It has become.

  In this fuel injection valve 20, when a valve closing signal is input to the piezoelectric actuator 29, the piezoelectric actuator 29 contracts and the valve body 29 a moves, and the communication path 28 and the pressure chamber 26 are in communication with each other. The communication between the return passage 35 and the pressure chamber 26 is cut off. Thereby, the nozzle chamber 25 and the pressure chamber 26 are communicated with each other in a state where the discharge of the fuel in the pressure chamber 26 to the return passage 35 (fuel tank 32) is prohibited. Therefore, the pressure difference between the nozzle chamber 25 and the pressure chamber 26 becomes very small, and the needle valve 22 moves to a position where the injection hole 23 is closed by the urging force of the spring 24. At this time, the fuel injection valve 20 does not inject fuel. State (valve closed).

  On the other hand, when a valve opening signal is input to the piezoelectric actuator 29, the piezoelectric actuator 29 expands to move the valve element 29a, the communication between the communication passage 28 and the pressure chamber 26 is cut off, and the return passage. 35 and the pressure chamber 26 are in communication with each other. As a result, part of the fuel in the pressure chamber 26 is returned to the fuel tank 32 via the return passage 35 in a state where fuel outflow from the nozzle chamber 25 to the pressure chamber 26 is prohibited. As a result, the pressure of the fuel in the pressure chamber 26 decreases and the pressure difference between the pressure chamber 26 and the nozzle chamber 25 increases, and the pressure difference causes the needle valve 22 to move against the biasing force of the spring 24 and inject. Apart from the hole 23, the fuel injection valve 20 is in a state in which fuel is injected (opened state) at this time.

  A pressure sensor 41 that outputs a signal corresponding to the fuel pressure PQ inside the introduction passage 27 is integrally attached to the fuel injection valve 20. For this reason, for example, the fuel in a portion near the injection hole 23 of the fuel injection valve 20 as compared with a device that detects the fuel pressure at a position away from the fuel injection valve 20 such as the fuel pressure in the common rail 34 (see FIG. 1). The pressure can be detected, and the change in the fuel pressure inside the fuel injection valve 20 accompanying the opening of the fuel injection valve 20 can be detected with high accuracy. One pressure sensor 41 is provided for each fuel injection valve 20, that is, for each cylinder 16 of the internal combustion engine 11.

  As shown in FIG. 1, the internal combustion engine 11 is provided with various sensors as peripheral devices for detecting an operation state. As these sensors, in addition to the pressure sensor 41, for example, the crank sensor 42 for detecting the rotational phase and rotational speed (engine rotational speed NE) of the crankshaft 12, and the operation amount of an accelerator operating member (for example, an accelerator pedal). An accelerator sensor 43 for detecting (accelerator operation amount ACC) is provided. In addition, an external air pressure sensor 44 for detecting the pressure of external air (external air pressure) of the internal combustion engine 11, an intake air amount sensor 45 for detecting the amount of intake air passing through the intake air passage 17 (passage air intake amount GA), An intake pressure sensor 46 for detecting the pressure (intake pressure PM) in the intake passage 17 is provided. In addition, an opening sensor 47 for detecting the opening of the EGR valve 52 (EGR opening VR), an operation switch 48 that is turned on when the internal combustion engine 11 is started and turned off when the operation is stopped are also provided. It has been.

  Further, as peripheral devices of the internal combustion engine 11, for example, an electronic control unit 40 configured with a microcomputer is also provided. The electronic control unit 40 functions as an estimation unit and a control unit, takes in output signals from various sensors, performs various calculations based on the output signals, and controls the operation of the EGR valve 52 (EGR) according to the calculation results. Control) and driving control of the fuel injection valve 20 (fuel injection control) and the like.

  The EGR control of the present embodiment is basically executed as follows.

  First, based on the engine rotational speed NE, the passage intake air amount GA, and the intake pressure PM, an estimated value (EGR rate) of the ratio (EGR rate) occupied by the EGR amount in the amount of gas sucked into the cylinder 16 of the internal combustion engine 11 ( The actual EGR rate Regr) is calculated. The actual EGR rate can be estimated based on the following idea. Based on the intake pressure PM and the engine rotational speed NE, the amount of gas (a gas including fresh air and EGR gas) sucked into the cylinder 16 of the internal combustion engine 11 can be estimated. Further, it is possible to estimate the amount of air (fresh air amount) taken into each cylinder 16 during one rotation of the crankshaft 12 based on the passage intake amount GA and the engine rotational speed NE. An amount obtained by subtracting the fresh air amount from the gas amount (= gas amount−fresh air amount) can be obtained as an amount corresponding to the actual EGR amount, and the actual EGR is calculated from the same amount and the gas amount. The rate (= “gas amount−fresh air amount” / gas amount) can be estimated.

  Further, a control target value (target EGR rate Tegr) for the EGR rate is set based on the engine speed NE and the fuel injection amount (specifically, a required injection amount TAU described later). Thereafter, a control target value (target EGR opening degree Tvr) for the EGR opening degree VR is set based on the target EGR rate Tegr.

  Then, operation control of the EGR valve 52 is executed based on the target EGR opening degree Tvr, the target EGR rate Tegr, and the actual EGR rate Regr. Specifically, as the operation control of the EGR valve 52, a prospective control using the target EGR opening degree Tvr as a prospective control amount and a feedback control based on a deviation between the target EGR rate Tegr and the actual EGR rate Regr are executed.

  Further, the fuel injection control of the present embodiment is basically executed as follows.

  First, a control target value (required injection amount TAU) for the fuel injection amount for operating the internal combustion engine 11 is calculated based on the accelerator operation amount ACC, the engine speed NE, and the like. Thereafter, a control target value for fuel injection timing (required injection timing Tst) and a control target value for fuel injection time (required injection time Ttm) are calculated based on the required injection amount TAU and the engine speed NE. Based on the required injection timing Tst and the required injection time Ttm, the valve opening drive of each fuel injection valve 20 is executed. Thereby, an amount of fuel commensurate with the operation state of the internal combustion engine 11 at that time is injected from each fuel injection valve 20 and supplied into each cylinder 16 of the internal combustion engine 11.

  In the fuel injection control of the present embodiment, the engine rotational speed NE is set to a predetermined value during the deceleration of the traveling speed of the vehicle 10 and the engine rotational speed NE by releasing the operation of the accelerator operation member (accelerator operation amount ACC = “0”). When the speed is within the speed range, control (so-called fuel cut control) for temporarily stopping fuel injection for operation of the internal combustion engine 11 is executed.

  Further, in the fuel injection control of the present embodiment, there are three areas: a low cetane number area (low cetane number area), a medium area (medium cetane number area), and a high area (high cetane number area). While being set, the fuel injection control is executed in a different execution mode for each region. For example, the required injection timing Tst is set to the advance timing for the region with the lower cetane number. Specifically, for each of the three cetane number regions, the relationship between the engine operating state determined by the required injection amount TAU and the engine speed NE and the required injection timing Tst corresponding to the cetane number region is the result of various experiments and simulations. And the same relationship is stored in the electronic control unit 40 as a calculation map (ML, MM, MH). Then, based on the required injection amount TAU and the engine speed NE at that time, the calculation map ML is used for the low cetane number region, the calculation map MM is used for the medium cetane number region, and the calculation is performed for the high cetane number region. The required injection timing Tst is calculated from each map MH.

  When the fuel injection from the fuel injection valve 20 is executed in this way, an error may occur in the execution timing and the injection amount due to the initial individual difference or change with time of the fuel injection valve 20. Such an error is undesirable because it changes the output torque of the internal combustion engine 11. Therefore, in the present embodiment, in order to properly execute the fuel injection from each fuel injection valve 20 in accordance with the operation state of the internal combustion engine 11, the fuel is based on the fuel pressure PQ detected by the pressure sensor 41. A correction process for forming the injection rate detection time waveform and correcting the required injection timing Tst and the required injection time Ttm based on the detection time waveform is executed. This correction process is executed separately for each cylinder 16 of the internal combustion engine 11.

  The fuel pressure inside the fuel injection valve 20 is reduced when the fuel injection valve 20 is opened, and then increased when the fuel injection valve 20 is closed. It fluctuates with it. Therefore, by monitoring the fluctuation waveform of the fuel pressure inside the fuel injection valve 20 at the time of executing the fuel injection, the actual operation characteristics of the fuel injection valve 20 (for example, the actual fuel injection amount and the valve opening operation are started). And when the valve closing operation is started). Therefore, by correcting the required injection timing Tst and the required injection time Ttm based on the actual operating characteristics of the fuel injection valve 20, the fuel injection timing and the fuel injection amount can be accurately adjusted in accordance with the operating state of the internal combustion engine 11. Can be set.

  Hereinafter, such correction processing will be described in detail.

  Here, first, a procedure for forming a fuel pressure fluctuation mode (in this embodiment, a detection time waveform of the fuel injection rate) during execution of fuel injection will be described.

  FIG. 3 shows the relationship between the transition of the fuel pressure PQ and the detection time waveform of the fuel injection rate.

  As shown in FIG. 3, in the present embodiment, the timing at which the fuel injection valve 20 opens (specifically, the movement of the needle valve 22 toward the valve opening side) starts (valve opening operation start timing Tos), When the fuel injection rate becomes maximum (maximum injection rate arrival time Toe), when the fuel injection rate starts to decrease (injection rate decrease start time Tcs), and when the fuel injection valve 20 closes (specifically, the needle valve 22) ) (The movement to the valve closing side) is completed (valve closing operation completion timing Tce).

  First, the average value of the fuel pressure PQ in a predetermined period T1 immediately before the start of the valve opening operation of the fuel injection valve 20 is calculated, and the average value is stored as the reference pressure Pbs. The reference pressure Pbs is used as a pressure corresponding to the fuel pressure inside the fuel injection valve 20 when the valve is closed.

  Next, a value obtained by subtracting the predetermined pressure P1 from the reference pressure Pbs is calculated as the operating pressure Pac (= Pbse−P1). The predetermined pressure P1 corresponds to the change in the fuel pressure PQ, that is, the movement of the needle valve 22 even when the needle valve 22 is in the closed position when the fuel injection valve 20 is driven to open or close. This is a pressure corresponding to a change in the fuel pressure PQ that does not contribute.

  Thereafter, a first-order differential value d (PQ) / dt is calculated according to the time of the fuel pressure PQ in a period in which the fuel pressure PQ drops immediately after the start of fuel injection. Then, the tangent L1 of the time waveform of the fuel pressure PQ at the point where the first-order differential value becomes the minimum, that is, the point where the downward slope of the fuel pressure PQ becomes the largest is obtained, and the intersection of the tangent L1 and the operating pressure Pac is obtained. A is calculated. The timing corresponding to the point AA where the intersection A is returned to the past timing by the following detection delay of the fuel pressure PQ is specified as the valve opening operation start timing Tos. The detection delay is a period corresponding to the delay of the change timing of the fuel pressure PQ with respect to the pressure change timing of the nozzle chamber 25 (see FIG. 2) of the fuel injection valve 20, and the distance between the nozzle chamber 25 and the pressure sensor 41. This is a delay caused by the above.

  Further, the first-order differential value of the fuel pressure PQ in the period in which the fuel pressure PQ rises after dropping once immediately after the start of fuel injection is calculated. Then, the tangent L2 of the time waveform of the fuel pressure PQ at the point where the first-order differential value becomes the maximum, that is, the point where the upward slope of the fuel pressure PQ becomes the largest, is obtained, and the intersection of the tangent L2 and the operating pressure Pac B is calculated. The timing corresponding to the point BB where the intersection B is returned to the past timing by the detection delay is specified as the valve closing operation completion timing Tce.

  Further, an intersection C between the tangent line L1 and the tangent line L2 is calculated, and a difference between the fuel pressure PQ and the operating pressure Pac at the intersection point C (virtual pressure drop ΔP [= Pac−PQ]) is obtained. Further, a value obtained by multiplying the virtual pressure drop ΔP by a gain G1 set based on the required injection amount TAU is calculated as a virtual maximum fuel injection rate VRt (= ΔP × G1). Further, a value obtained by multiplying the virtual maximum fuel injection rate VRt by a gain G2 set based on the required injection amount TAU is calculated as the maximum injection rate Rt (= VRt × G2).

  Thereafter, a time CC at which the intersection C is returned to the past time by the detection delay is calculated, and a point D that becomes the virtual maximum fuel injection rate VRt in the simultaneous CC is specified. The timing corresponding to the intersection E between the straight line L3 connecting the point D and the valve opening operation start timing Tos (specifically, the point at which the fuel injection rate becomes “0” at the same time Tos) and the maximum injection rate Rt is obtained. It is specified as the maximum injection rate arrival time Toe.

  Further, the timing corresponding to the intersection F between the straight line L4 and the maximum injection rate Rt connecting the point D and the valve closing operation completion timing Tce (specifically, the point at which the fuel injection rate becomes “0” at the same time Tce) is injected. It is specified as the rate drop start time Tcs.

  Further, the trapezoidal time waveform formed by the valve opening operation start timing Tos, the maximum injection rate arrival timing Toe, the injection rate drop start timing Tcs, the valve closing operation completion timing Tce and the maximum injection rate Rt is a fuel injection rate in fuel injection. Is used as a detection time waveform.

  Next, with reference to FIGS. 4 and 5, the processing procedure of the process (correction process) for correcting various control target values of the fuel injection control based on such a detection time waveform will be described in detail.

  FIG. 4 is a flowchart showing a specific processing procedure of the correction processing. The series of processes shown in this flowchart conceptually shows the execution procedure of the correction process, and the actual process is executed by the electronic control unit 40 as an interrupt process at predetermined intervals. FIG. 5 shows an example of the relationship between the detection time waveform and the following basic time waveform.

  As shown in FIG. 4, in this correction process, first, as described above, a detection time waveform at the time of execution of fuel injection is formed based on the fuel pressure PQ (step S101). Further, based on the operating state of the internal combustion engine 11 such as the accelerator operation amount ACC and the engine speed NE, a basic value (basic time waveform) for the time waveform of the fuel injection rate at the time of execution of fuel injection is set (step). S102). In the present embodiment, the relationship between the operating state of the internal combustion engine 11 and the basic time waveform suitable for the operating state is obtained in advance based on the results of experiments and simulations and stored in the electronic control unit 40. In the process of step S102, a basic time waveform is set from the above relationship based on the operating state of the internal combustion engine 11 at that time.

  As shown in FIG. 5, the basic time waveform (one-dot chain line) includes the valve opening operation start timing Tosb, the maximum injection rate arrival timing Toeb, the injection rate drop start timing Tcsb, the valve closing operation completion timing Tceb, and the maximum injection rate. The specified trapezoidal time waveform is set.

  Then, the basic time waveform and the detection time waveform (solid line) are compared, and a correction term for correcting the control target value (the required injection timing Tst) of the fuel injection start timing based on the comparison result. K1 and a correction term K2 for correcting the control target value (required injection time Ttm) of the execution time of the same fuel injection are respectively calculated. Specifically, a difference ΔTos (= Tosb−Tos) between the valve opening operation start timing Tosb in the basic time waveform and the valve opening operation start timing Tos in the detection time waveform is calculated, and the difference ΔTos is stored as the correction term K1. (Step S103 in FIG. 4). Further, a difference ΔTcs (= Tcsb−Tcs) between the injection rate decrease start timing Tcsb (FIG. 5) in the basic time waveform and the injection rate decrease start timing Tcs in the detection time waveform is calculated, and the difference ΔTcs is corrected by the correction term K2. (Step S104 in FIG. 4).

  After the correction terms K1 and K2 are calculated in this way, the present process is temporarily terminated.

  When executing the fuel injection control, a value obtained by correcting the required injection timing Tst by the correction term K1 (in this embodiment, a value obtained by adding the correction term K1 to the required injection timing Tst) is calculated as the final required injection timing Tst. Is done. By calculating the required injection timing Tst in this way, the deviation between the valve opening operation start timing Tosb in the basic time waveform and the valve opening operation start timing Tos in the detection time waveform can be suppressed to be small. The start timing of injection is accurately set according to the operating state of the internal combustion engine 11.

  Further, a value obtained by correcting the required injection time Ttm by the correction term K2 (in this embodiment, a value obtained by adding the correction term K2 to the required injection time Ttm) is calculated as the final required injection time Ttm. By calculating the required injection time Ttm in this way, the deviation between the injection rate decrease start timing Tcsb in the basic time waveform and the injection rate decrease start timing Tcs in the detection time waveform can be suppressed to be small. The timing at which the fuel injection rate starts to decrease in the fuel injection is set with high accuracy in accordance with the operating state of the internal combustion engine 11.

  As described above, in the present embodiment, the required injection timing is based on the difference between the actual operating characteristic (specifically, the detection time waveform) of the fuel injection valve 20 and the predetermined basic operating characteristic (specifically, the basic time waveform). Since the Tst and the required injection time Ttm are corrected, the deviation between the actual operating characteristics of the fuel injector 20 and the basic operating characteristics (the operating characteristics of the fuel injector having standard characteristics) can be suppressed. Therefore, the injection timing and the injection amount in the fuel injection from each fuel injection valve 20 are set appropriately so as to match the operating state of the internal combustion engine 11.

  In the present embodiment, control (index value detection processing) for detecting the cetane number index value of the fuel provided for combustion in the internal combustion engine 11 is executed. The outline of the index value detection process will be described below.

  In this index value detection process, an execution condition including a condition that the above-described fuel cut control is being executed ([Condition 1] described later) is set. Then, when this execution condition is satisfied, fuel injection to the internal combustion engine 11 at a predetermined small predetermined amount FQ (for example, several cubic millimeters) is executed, and the internal combustion generated along with the execution of the fuel injection An index value of the output torque of the engine 11 (rotational fluctuation amount ΣΔNE described later) is detected as a fuel cetane number index value. As the rotational fluctuation amount ΣΔNE, a larger value is detected as a larger output torque is generated in the internal combustion engine 11.

  The higher the cetane number of the fuel supplied to the internal combustion engine 11, the easier it is to ignite the fuel, and the less unburned fuel of the fuel decreases, so the engine torque generated with the combustion of the fuel increases. In the estimation control of the present embodiment, the cetane number index value of the fuel is detected based on the relationship between the cetane number of the fuel and the output torque of the internal combustion engine 11.

  Hereinafter, the execution procedure of the index value detection process will be described in detail.

  FIG. 6 is a flowchart showing a specific execution procedure of the index value detection process. Note that the series of processes shown in this flowchart conceptually shows the execution procedure of the index value detection process, and the actual process is executed by the electronic control unit 40 as an interrupt process at predetermined intervals.

As shown in FIG. 6, in this process, it is first determined whether or not an execution condition is satisfied (step S201). Here, it is determined that the execution condition is satisfied when all of the following [Condition 1] to [Condition 3] are satisfied.
[Condition 1] The fuel cut control is executed.
[Condition 2] The clutch mechanism 13 is in an operating state in which the connection between the crankshaft 12 and the manual transmission 14 is released. Specifically, the clutch operating member is operated.
[Condition 3] The correction process is properly executed. Specifically, each correction term K1, K2 calculated in the correction process is neither an upper limit nor a lower limit.

  If the execution condition is not satisfied (step S201: NO), this process is temporarily terminated without executing the following process, that is, the process of detecting the cetane number index value of the fuel.

  Thereafter, when this process is repeatedly executed and the execution condition is satisfied (step S201: YES), execution of the process for detecting the cetane number index value of the fuel is started.

  Specifically, first, a predetermined control target value for fuel injection timing (target injection timing TQst) and a control target value for fuel injection time (target injection time TQtm) are obtained by the correction processing described above with reference to FIGS. Correction is performed by the calculated correction terms K1 and K2 (step S202 in FIG. 6). Specifically, a value obtained by adding the correction term K1 to the target injection timing TQst is set as a new target injection timing TQst, and a value obtained by adding the correction term K2 to the target injection time TQtm is set as a new target injection time TQtm. The

  Then, drive control of the fuel injection valve 20 based on the target injection timing TQst and the target injection time TQtm is executed, and fuel injection from the fuel injection valve 20 is executed (step S203). Through such drive control of the fuel injection valve 20, a predetermined amount FQ of fuel is injected from the fuel injection valve 20 at a timing at which variations in the rotational fluctuation amount ΣΔNE are suppressed. In the present embodiment, the fuel injection in the process of step S203 is a predetermined one of the plurality of fuel injection valves 20 (in this embodiment, the fuel injection valve 20 attached to the cylinder 16 [# 1]). It is executed using Similarly, the correction terms K1 and K2 used in this process are also predetermined ones of the fuel injection valves 20 (in this embodiment, the fuel injection valves 20 attached to the cylinders 16 [# 1]). The value calculated corresponding to is used.

  Thereafter, after the rotational fluctuation amount ΣΔNE is detected and stored as an index value of the output torque of the internal combustion engine 11 generated by the fuel injection at the predetermined amount FQ (step S204), the present process is temporarily terminated. Specifically, the rotation fluctuation amount ΣΔNE is detected as follows. As shown in FIG. 7, in the apparatus according to the present embodiment, the engine rotational speed NE is detected every predetermined time, and at each detection, the engine rotational speed NE and the previous engine rotational speed NE are detected several times (in the present embodiment). The difference ΔNE (= NE−NEi) from the engine speed NEi detected three times before) is calculated. Then, an integrated value (a value corresponding to the area of the hatched portion in FIG. 7) for the change in the difference ΔNE accompanying the execution of the fuel injection is calculated, and this integrated value is calculated as the rotational fluctuation amount. Stored as ΣΔNE. Note that the transition of the engine speed NE and the difference ΔNE shown in FIG. 7 are slightly different from the actual transition because they are shown in a simplified manner to facilitate understanding of the calculation method of the rotational fluctuation amount ΣΔNE.

  In the present embodiment, basically, the low cetane number region, the medium cetane number region, or the high cetane number region is specified based on the rotational fluctuation amount ΣΔNE detected through the index value detection process. At the same time, the specified area is stored in the electronic control unit 40. Specifically, when the rotational fluctuation amount ΣΔNE is less than the predetermined value PL (ΣΔNE <PL), it is determined that the region is in the low cetane number region, and when the rotational fluctuation amount ΣΔNE is less than the predetermined value PH (PL ≦ ΣΔNE <PH). Is determined to be in the medium cetane number region, and if it is equal to or greater than the predetermined value PH (ΣΔNE ≧ PH), it is determined to be in the high cetane number region. Then, the fuel injection control is executed in an execution manner commensurate with the cetane number region thus specified.

  Here, when the cetane number of the fuel supplied to the internal combustion engine 11 is low, the ignition delay becomes long, so that the combustion state of the fuel is likely to deteriorate. Further, at the time of idle operation immediately after the start of the internal combustion engine 11, the amount of fuel injected into the cylinder 16 is small and the temperature in the cylinder 16 is low, so the combustion state of the fuel is likely to deteriorate. Therefore, in the apparatus of the present embodiment, in particular, when the engine is idling immediately after the start of the internal combustion engine 11 and is determined to be in the low cetane number region, the combustion state of the fuel is likely to deteriorate, resulting in the occurrence of misfire. It can be said that it is easy.

  In view of this point, in the present embodiment, the target EGR rate Tegr at the time of idling is set to “EGR rate Tegr” when the engine is in the execution period immediately after the start of the internal combustion engine 11 and the low cetane number region is stored (specific situation). It is set to “0” and the EGR amount by the EGR device 50 is set to “0”. Thus, when the idling operation is performed immediately after the start of the internal combustion engine 11 in a state where the low cetane number region is stored, that is, the influence of the adjustment error of the EGR amount on the combustion state of the fuel is likely to increase and the combustion of the fuel When the state tends to become unstable, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 can be improved by the amount that the recirculation of the EGR gas is stopped, so that the occurrence of misfire can be suppressed. Become.

  In order to improve the combustion state of the fuel during idle operation in such a specific situation, the EGR amount during idle operation is not limited to “0”, but the EGR amount is reduced compared to when not in the specific situation. It is also possible to do. In the EGR device 50, the EGR amount with respect to the opening change of the EGR valve 52 due to the volume of the EGR passage 51 and the volume of the portion of the intake passage 17 from the connection portion with the EGR passage 51 to the cylinder 16 of the internal combustion engine 11. It is inevitable that there will be a delay in the change of Therefore, the responsiveness and stability of the change in the EGR amount with respect to the change in the opening degree of the EGR valve 52 are low, and precise adjustment of the EGR amount by the EGR device 50 is difficult. Therefore, when the EGR device 50 adjusts the EGR amount It can be said that errors are likely to occur. If the EGR amount is excessively increased due to the adjustment error, the fuel combustion state may be deteriorated. Further, if the EGR amount becomes too small due to the adjustment error, the combustion temperature of the fuel in the cylinder 16 becomes high, which may cause an increase in nitrogen oxide (NOx) in the exhaust.

  In this regard, in the present embodiment, when the influence of the EGR amount adjustment error on the fuel combustion state is likely to be large and the fuel combustion state is likely to be unstable, the EGR amount adjustment error is the same. Since it disappears, the influence of the adjustment error on the combustion state of the fuel can be eliminated.

  As described above, by setting the EGR amount during idle operation in a specific situation to “0”, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is improved, so that the occurrence of misfire can be suppressed. become. However, if the EGR amount is simply set to “0”, the combustion temperature of the fuel in the cylinder 16 of the internal combustion engine 11 becomes extremely high, which may cause a significant increase in the NOx amount in the exhaust gas.

  In view of this point, in the present embodiment, in a specific situation, the fuel injection timing in the idle operation is delayed compared to the case where the EGR amount in the idle operation is set to “0”. It is set to the corner time. In the present embodiment, when not in a specific situation, the execution period elapses when the medium cetane number region is stored, when the high cetane number region is stored, or after the start of the internal combustion engine 11 is started. When

  By setting the retarded timing as the fuel injection timing, the ignition timing of the fuel in the cylinder 16 of the internal combustion engine 11 is delayed, so that the combustion temperature of the fuel is lowered by that amount and the amount of NOx in the exhaust is reduced. Less. In the present embodiment, the fuel injection timing (specifically, the required injection timing Tst) is set through the fuel injection control so as to achieve both suppression of deterioration of the combustion state and suppression of the NOx emission amount.

  In addition, in the present embodiment, it is possible to set the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 with higher accuracy than the setting by adjusting the EGR amount during the idling operation in a specific situation. This can be done through setting by adjusting the fuel injection timing. As described above, according to the present embodiment, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 when using the low cetane number fuel can be appropriately set. It is possible to achieve both suppression.

  Hereinafter, the process for setting the EGR amount to “0” and the process for delaying the fuel injection timing in a specific situation will be described in detail.

  First, a process for setting the EGR amount to “0” during idling in a specific situation will be described with reference to FIG.

  FIG. 8 shows an execution procedure of a process related to EGR control (EGR control process). A series of processes shown in the flowchart of FIG. 6 is executed by the electronic control unit 40 as an interrupt process at predetermined intervals.

As shown in FIG. 8, in this process, first, it is determined whether or not both of the following [Condition 4] and [Condition 5] are satisfied (step S301).
[Condition 4] A low cetane number region is specified and stored in the electronic control unit 40.
[Condition 5] An execution period from the start of the internal combustion engine 11 to the start of an opening operation of the accelerator operation member (an operation to make the accelerator operation amount ACC larger than “0”). Specifically, after the operation switch 48 is operated to start the operation of the internal combustion engine 11, the state where the accelerator operation amount ACC is “0” is continued.

  When both [Condition 4] and [Condition 5] are satisfied (step S301: YES), the influence of the EGR amount adjustment error on the fuel combustion state tends to be large and the fuel combustion state is unstable. As a result, “0” is set as the target EGR rate Tegr and the EGR amount is set to “0” (step S302).

  On the other hand, when [Condition 4] and [Condition 5] are not satisfied (step S301: NO), normal control is performed as the EGR control processing (specifically, the target EGR rate Tegr set based on the engine speed NE and the required injection amount TAU). The operation control of the EGR valve 52 according to the control is executed (step S303). Specifically, if [Condition 4] is not satisfied, the medium cetane number region or the high cetane number region is specified and stored in the electronic control unit 40 at this time, so that the combustion state of the fuel is excessively deteriorated. The normal control is executed as the EGR control process on the assumption that there is a low possibility of this. If [Condition 5] is not satisfied, the temperature in the cylinder 16 of the internal combustion engine 11 increases as the engine operation continues after the start, so that the fuel combustion state may deteriorate excessively. If it is low, normal control is executed as the EGR control process.

  Next, processing for retarding the fuel injection timing (injection timing retarding processing) will be described with reference to FIG.

  FIG. 9 shows an execution procedure of the injection timing retarding process. A series of processes shown in the flowchart of FIG. 6 is executed by the electronic control unit 40 as an interrupt process at predetermined intervals.

  As shown in FIG. 9, in this process, it is first determined whether or not the EGR opening VR is equal to or less than a predetermined opening (for example, an opening slightly larger than the opening at the time of closing the valve) (step S401). In this process, it is determined whether or not the engine rotational speed NE is equal to or lower than a predetermined speed (for example, a speed corresponding to the upper limit of the engine rotational speed NE during idle operation [1300 revolutions / minute]). In step S402, it is determined whether the required injection amount TAU is equal to or less than a predetermined amount (for example, an amount corresponding to the upper limit of the fuel injection amount during idle operation) (step S403).

  When the EGR opening VR is equal to or less than the predetermined opening (step S401: YES), it is determined that the EGR amount is set to “0” at this time. Further, when the engine speed NE is equal to or lower than the predetermined speed (step S402: YES) and the required injection amount TAU is equal to or lower than the predetermined amount (step S403: YES), it is determined that the internal combustion engine 11 is in the idling operation state. The Therefore, if all the determinations in steps S401 to S403 are affirmative, both [condition 4] and [condition 5] are satisfied and the EGR amount is set to “0” in the EGR control process (see FIG. 8). It is determined that That is, since the low cetane number region is stored at this time and the execution period is from the start of the internal combustion engine 11 to the start of the opening operation of the accelerator operation member, the fuel combustion state is improved. Thus, it is determined that the EGR amount is set to “0” to suppress the occurrence of misfire.

  In this case (steps S401 to S403 are all “YES”), it is further determined whether or not the external air pressure is higher than a determination pressure (for example, 80 kPa) (step S404). If the external pressure is equal to or higher than the determination pressure (step S404: YES), fuel injection control (retarding control) is executed in an execution mode in which a retarded side timing is set as the fuel injection timing ( Step S405).

  In the present embodiment, as a calculation map used for setting the required injection timing Tst, in addition to the calculation maps ML, MM, and MH described above, the EGR amount is set to “0” during idle operation in a specific situation. An operation map MLF is set that is suitable for the above and that sets a relatively retarded timing. More specifically, the relationship between the engine operating state determined by the required injection amount TAU and the engine rotational speed NE and the required injection timing Tst corresponding to the situation where the EGR amount is set to “0” during idle operation in a specific situation is variously tested. And the same relationship is stored in the electronic control unit 40 as the operation map MLF.

  Specifically, in the process of step S405, an operation map MLF is selected from these operation maps. In the subsequent fuel injection control, the required injection timing Tst is set based on the required injection amount TAU and the engine rotational speed NE based on the calculation map MLF.

  On the other hand, if the EGR opening VR is larger than the predetermined opening (step S401: NO), the advance timing is set as the fuel injection timing, assuming that the EGR amount is not set to “0” at this time. Fuel injection control (normal control) in the execution mode is executed (step S406). Specifically, in this normal control, one of the calculation maps corresponding to the cetane number area stored at this time, that is, one of the calculation maps ML, MM, and MH is selected, and thereafter, based on the selected calculation map. The required injection timing Tst is set based on the required injection amount TAU and the engine speed NE. Further, when the engine speed NE is higher than the predetermined speed (step S402: NO) or when the required injection amount TAU is larger than the predetermined amount (step S403: NO), it is assumed that the internal combustion engine 11 is not in the idling operation state and the normal control is performed. Is executed (step S406).

  Thus, according to the present embodiment, the process of setting the EGR amount to “0” (the process of step S302 in FIG. 8) and the process of setting the retarded side timing as the fuel injection timing (step of FIG. 9). The process of S405 is executed only during the execution period from the start of the internal combustion engine 11 to the start of the opening operation of the accelerator operation member. Therefore, when the temperature in the cylinder 16 of the internal combustion engine 11 is low immediately after the start of the engine, in other words, the combustion state of the fuel with high accuracy only during the period when the combustion state of the fuel in the cylinder 16 tends to be unstable. (A process for setting the EGR amount to “0” and a process for setting the retard side timing as the fuel injection timing) can be executed.

  On the other hand, when the atmospheric pressure is equal to or lower than the determination pressure (step S404: NO), normal control is executed (step S406). Here, when the external air pressure is low, the amount of oxygen contained in the intake air is small because the air density is low. Therefore, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is likely to deteriorate, and misfire is likely to occur. According to the present embodiment, when misfire is likely to occur because the external air pressure is low, the calculation map MLF is selected and the required injection timing Tst is set to the retarded timing, in other words, the fuel combustion state is set. Since the change of the required injection timing Tst to the worsening side can be prohibited, the occurrence of misfire can be reliably suppressed. When the external pressure is higher than the determination pressure (step S404: YES), in other words, when it is relatively difficult for misfire to occur, the retarded timing is set as the required injection timing Tst based on the calculation map MLF. In addition, the amount of NOx emission can be suitably suppressed. In the present embodiment, a determination pressure that reliably suppresses misfire occurrence during idling in a specific situation is obtained in advance based on the results of various experiments and simulations, and stored in the electronic control unit 40. Has been.

  Hereinafter, an execution mode of the process for setting the EGR amount to “0” and the process for delaying the fuel injection timing during the idling operation in the specific situation will be described with reference to FIG.

  FIG. 10 shows an example of how these processes are executed. In the figure, the solid line indicates the execution mode of each process in the apparatus according to the present embodiment, and the alternate long and short dash line indicates each process in the comparative apparatus that does not set the EGR amount to “0” and does not retard the fuel injection timing. The execution mode of a process is shown. The two-dot chain line in the figure shows the transition of the NOx emission amount when the EGR amount is “0” and the fuel injection timing is not retarded.

  In the example shown in FIG. 10, at time t <b> 11, the operation switch 48 is turned on and the internal combustion engine 11 is started. At this time, since the low cetane number region is stored and the accelerator operation member is not opened (accelerator operation amount ACC = “0”), “0” is set as the target EGR rate Tegr, and the EGR opening degree VR becomes the opening degree (VR = “0”) corresponding to the closed state. Further, at this time, as the required injection timing Tst, the timing on the retard side is set based on the calculation map MLF by the amount indicated by the white arrow in the drawing as compared with the case where the execution period is not immediately after the engine start. .

  At this time, in the apparatus of the comparative example indicated by the alternate long and short dash line in the figure, the amount of NOx emission is suppressed to a very low level, but since the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is deteriorated, misfires and smoke are generated. Will be invited. On the other hand, in the apparatus shown by the two-dot chain line in the figure, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is sufficiently improved to prevent misfire and smoke, but the combustion temperature of the fuel becomes extremely high. Therefore, the NOx emission amount is greatly increased.

  On the other hand, in the apparatus according to the present embodiment, the EGR amount is set to “0” and the retarded timing is set as the fuel injection timing at times t11 to t12. No significant increase in NOx emissions is caused as in the device shown in FIG. 5, and no misfire or smoke is caused in the device in the comparative example shown by the alternate long and short dash line. As described above, according to the present embodiment, when the low cetane number fuel is used, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 can be appropriately set. It is possible to achieve both reduction of the amount.

  In this example, when the opening operation of the accelerator operation member is started at time t12, the execution of the process for setting the EGR amount to “0” and the process for delaying the fuel injection timing is stopped thereafter. Is done. At this time, the operation control of the EGR valve 52 is executed according to the target EGR rate Tegr set based on the engine speed NE and the required injection amount TAU, and the calculation map ML, based on the accelerator operation amount ACC and the engine speed NE. Drive control of the fuel injection valve 20 is executed in accordance with the required injection timing Tst set based on either MM or MH.

  As described above, according to the present embodiment, the effects described below can be obtained.

  (1) In a specific situation that is an execution period immediately after the start of the internal combustion engine 11 and in which a low cetane number region is stored, the EGR amount during idle operation is set to “0” and compared to when the specific situation is not Thus, the required ignition timing Tst during idle operation is set to the retarded timing. Therefore, when the low cetane number fuel is used, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 can be set appropriately, and both the suppression of misfire and the suppression of NOx emission can be achieved.

  (2) Since the EGR amount during idle operation in a specific situation is set to “0”, the influence of the adjustment error of the EGR amount on the fuel combustion state can be eliminated, and the fuel combustion state can be further improved. It becomes possible to set with high accuracy.

  (3) On the condition that the external air pressure is equal to or higher than the determination pressure, the process of setting the advance side as the fuel injection timing (the process of step S405 in FIG. 9) is executed. For this reason, it is possible to prohibit the change of the required injection timing Tst to the side that deteriorates the combustion state of the fuel when the external air pressure is low and easily causes misfire, and the occurrence of misfire can be reliably suppressed. In addition, when the misfire is relatively difficult to occur due to the high external pressure, since the change of the required injection timing Tst to the retard side is permitted, the NOx emission amount can be suitably suppressed.

  (4) The process of setting the EGR amount to “0” (the process of step S302 of FIG. 8) and the process of setting the retard side timing as the fuel injection timing (the process of step S405 of FIG. 9) 11 is executed only during the execution period from the start of the start of 11 until the opening operation of the accelerator operating member is started. Therefore, the process for realizing the setting of the combustion state of the fuel with high accuracy can be executed only during the period in which the instability of the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is likely to occur.

  The embodiment described above may be modified as follows.

  -Instead of the process of step S401 to step S403, a process of determining whether or not both [condition 4] and [condition 5] are satisfied may be executed. Even in such a device, the required ignition timing Tst during idle operation is retarded in a specific situation in which the internal combustion engine 11 is started immediately after the start and a low cetane number region is stored as compared with a non-specific situation. Can be set to the time of the side.

  The setting of the required injection timing Tst is not limited to being executed using the calculation map, but may be executed using an arithmetic expression.

  -You may make it perform the setting of the request | requirement injection timing Tst at the time of the idle driving | running in a specific condition as follows. That is, the required injection timing Tst is set from the calculation map ML based on the engine rotational speed NE and the required injection amount TAU, and the retard correction term is calculated based on the engine rotational speed NE and the required injection amount TAU. A value obtained by correcting Tst by the retardation correction term is set as the final required injection timing Tst.

  -The process of step S404 of FIG. 9 may be omitted. That is, the process of setting the retarded time as the required injection time Tst (the process of step S405 in FIG. 9) may be executed without depending on the external air pressure.

  In a specific situation, the EGR amount during idle operation is not limited to “0”, and the EGR valve 52 may be slightly opened to recirculate a small amount of EGR gas. In short, it is only necessary that the EGR amount during idle operation in a specific situation can be reduced as compared with the EGR amount when not in a specific situation. Even with such a device, the absolute amount of the EGR amount when idling in a specific situation, that is, when the influence of the adjustment error of the EGR amount on the fuel combustion state tends to be large and the fuel combustion state tends to become unstable. Therefore, it becomes possible to reduce the adjustment error of the EGR amount by the amount of decrease. Therefore, the influence on the combustion state of the fuel due to the adjustment error of the EGR amount can be suppressed small.

  The process of setting the EGR amount to “0” (the process of step S302 in FIG. 8) and the fuel only during the execution period from the start of the internal combustion engine 11 to the start of the opening operation of the accelerator operating member The process of setting the retard side timing as the injection timing (the process of step S405 in FIG. 9) is executed. Instead of this, these processes may be executed only during an execution period from when the internal combustion engine 11 is started until a predetermined time period elapses. Examples of the fixed period include a fixed time (for example, several seconds to several tens of seconds), a period until the integrated value of the fuel injection amount reaches a predetermined value, a period until the integrated value of the intake air amount reaches a predetermined value, and the like. be able to. The point is that in the execution period until the temperature in the cylinder 16 of the internal combustion engine 11 becomes sufficiently high and the combustion state of the fuel becomes good, the processing for setting the EGR amount to “0” and the fuel injection timing are retarded. It is only necessary to be able to execute the process of setting the period of time.

  If the errors in the fuel injection timing and the fuel injection amount due to the initial individual differences and changes with time of the fuel injection valve 20 can be appropriately suppressed, the target injection timing TQst and the target injection time TQtm are corrected by the correction terms K1, K2. May be omitted (step S202 in FIG. 6).

  The control device according to the above embodiment is a device that determines which of the two regions divided by the fuel cetane number index value (rotational fluctuation amount ΣΔNE), or any of the four or more regions. The present invention can also be applied to a device that determines whether the region is the region after the configuration is appropriately changed.

  The control device according to the embodiment described above is based on the rotational fluctuation amount ΣΔNE stored in the electronic control unit 40, and the cetane of fuel supplied to the internal combustion engine 11 with the rotational fluctuation amount ΣΔNE without specifying the cetane number region. The present invention can also be applied to an apparatus used as a value corresponding to a valence (specifically, a cetane number index value) with the configuration changed as appropriate. In such an apparatus, when the rotational fluctuation amount ΣΔNE is smaller than a predetermined value, it is determined that the cetane number of the fuel supplied to the internal combustion engine 11 is low, and the EGR amount during idle operation in a specific situation is determined as “ The process of setting to “0” and the process of setting the retard side timing as the fuel injection timing may be executed.

  A value other than the rotational fluctuation amount ΣΔNE may be calculated as an index value of the output torque of the internal combustion engine 11. For example, during the execution of the index value detection process, the engine rotational speed NE at the time of execution of fuel injection and the engine rotational speed NE immediately before the execution of the fuel injection are respectively detected and the difference between these speeds is calculated. It can be used as an index value.

  The pressure sensor 41 is mounted in an appropriate manner so that the fuel pressure indicator in the fuel injection valve 20 (specifically, in the nozzle chamber 25), in other words, the fuel pressure that changes with the change in the fuel pressure is appropriately set. As long as it can be detected, the present invention is not limited to the mode of being directly attached to the fuel injection valve 20, but can be arbitrarily changed. Specifically, the pressure sensor may be attached to the branch passage 31 a or the common rail 34.

  Instead of the type of fuel injection valve 20 driven by the piezoelectric actuator 29, a type of fuel injection valve driven by an electromagnetic actuator having a solenoid coil or the like may be employed.

  The control device according to the above embodiment can be applied not only to the vehicle 10 on which the clutch mechanism 13 and the manual transmission 14 are mounted, but also to a vehicle on which a torque converter and an automatic transmission are mounted. In such a vehicle, for example, when [Condition 1] and [Condition 3] are satisfied, fuel injection for estimating the cetane number of fuel may be executed. In a vehicle in which a torque converter with a built-in lockup clutch is adopted, [Condition 6] that the lockup clutch is not engaged is newly set and the [Condition 6] is satisfied. The fuel injection for detecting the cetane number index value of the fuel may be executed on the condition that

  The present invention is not limited to a device that performs fuel injection for estimating the cetane number of fuel supplied to an internal combustion engine, but is applicable to any device that performs a process for estimating the cetane number of the fuel. be able to. Examples of such a device include the following devices. That is, first, the pressure in the cylinder (in-cylinder pressure) of the internal combustion engine is detected by the in-cylinder pressure sensor at the time of fuel injection for the operation of the internal combustion engine. Based on this in-cylinder pressure, the time when the fuel is actually ignited is calculated, and the ignition delay time is calculated based on the same period. Thereafter, a cetane number index value is calculated based on the calculated ignition delay time.

  The present invention is not limited to an internal combustion engine having four cylinders, but also to a single cylinder internal combustion engine, an internal combustion engine having two cylinders, an internal combustion engine having three cylinders, or an internal combustion engine having five or more cylinders. Can be applied.

  DESCRIPTION OF SYMBOLS 10 ... Vehicle, 11 ... Internal combustion engine, 12 ... Crankshaft, 13 ... Clutch mechanism, 14 ... Manual transmission, 15 ... Wheel, 16 ... Cylinder, 17 ... Intake passage, 18 ... Piston, 19 ... Exhaust passage, 20 ... Fuel Injection valve, 21 ... housing, 22 ... needle valve, 23 ... injection hole, 24 ... spring, 25 ... nozzle chamber, 26 ... pressure chamber, 27 ... introduction passage, 28 ... communication passage, 29 ... piezoelectric actuator, 29a ... valve body , 30 ... discharge passage, 31a ... branch passage, 31b ... supply passage, 32 ... fuel tank, 33 ... fuel pump, 34 ... common rail, 35 ... return passage, 40 ... electronic control unit, 41 ... pressure sensor, 42 ... crank sensor 43 ... Accelerator sensor, 44 ... External air pressure sensor, 45 ... Intake amount sensor, 46 ... Intake pressure sensor, 47 ... Opening sensor, 48 ... Operation switch, 50 ... E R device, 51 ... EGR passage, 52 ... EGR valve.

Claims (4)

An EGR device for returning a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine to the intake passage for recirculation;
An estimation unit for estimating a cetane number of fuel supplied to the internal combustion engine;
When the cetane number estimated by the estimator is low and during the execution period immediately after the start of the internal combustion engine, the EGR amount by the EGR device during idle operation is reduced compared to when it is not A control device for an internal combustion engine, comprising: a control unit that retards fuel injection timing. The control apparatus for an internal combustion engine according to claim 1,
The control unit for an internal combustion engine, wherein the control unit sets the EGR amount to “0”. The control apparatus for an internal combustion engine according to claim 1 or 2,
The control unit for an internal combustion engine, wherein the control unit executes the retardation of the fuel injection timing on the condition that the external air pressure is equal to or higher than a predetermined determination pressure. The control apparatus for an internal combustion engine according to any one of claims 1 to 3,
The control apparatus for an internal combustion engine, wherein the execution period is a period from when the start of the internal combustion engine is started to when an opening operation of the accelerator operation member is started.

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