CN103038489A - Internal combustion engine control apparatus - Google Patents

Abstract

A control device for an internal combustion engine equipped with an EGR device for recirculating a part of exhaust gas flowing through an exhaust passage by returning it to an intake passage. The electronic control unit executes a process of determining and storing a cetane number region to which the cetane number of fuel supplied to the internal combustion engine belongs. During the execution period immediately after the start of the internal combustion engine and when the specific situation of the low cetane number region is stored (t11~t12), the ECU sets the EGR opening (VR) at idling to "0", and , the required injection timing (Tst) at the time of idling is set to a time on the retard side compared to when it is not a specific situation.

Description

Control devices for internal combustion engines

technical field

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 performs engine operation control based on the estimated cetane number.

Background technique

In a self-ignition internal combustion engine, fuel injected into a cylinder by a fuel injection valve is ignited after a predetermined time (so-called ignition delay) elapses from injection. In order to improve the output performance and emission performance of the internal combustion engine, control devices that control the execution of engine control such as the injection timing and injection amount of fuel injection are widely used in consideration of such ignition delay.

In internal combustion engines, the lower the cetane number of the fuel used, the longer the ignition delay. Therefore, even if the execution mode of the engine control is set under the assumption that the fuel with a standard cetane number is used when the internal combustion engine is shipped from the factory, the fuel tank with a relatively low cetane number such as winter fuel will be replenished. In some cases, the ignition timing of the fuel is also delayed and its combustion state deteriorates, and misfire may occur depending on the situation.

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

For example, Patent Document 1 proposes that, in an internal combustion engine provided with an exhaust gas recirculation (EGR) device for recirculating a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine by returning it to the intake passage, it is proposed that the exhaust gas supplied to the internal combustion engine The cetane number of the fuel is calculated, and the amount of exhaust gas returned to the intake passage (EGR amount) is corrected by the EGR device based on the estimated cetane number. In this device, the lower the estimated cetane number, the more the EGR amount is corrected to decrease, thereby improving the combustion state of the fuel and suppressing the occurrence of misfire.

Patent Document 1: Japanese Patent Laid-Open No. 2007-285195

Contents of the invention

Generally, an EGR device includes an EGR passage for communicating an intake passage and an exhaust passage of an internal combustion engine, and an EGR valve for changing a passage cross-sectional area of the EGR passage. Furthermore, in the EGR device, the EGR amount is adjusted by the 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 connected to the EGR passage in the intake passage of the internal combustion engine to the cylinder of the internal combustion engine, etc., EGR with respect to the opening degree of the EGR valve cannot be avoided. Changes in volume create delays. Therefore, the responsiveness and stability of the change of the EGR amount with respect to the change of the opening degree of the EGR valve are poor, and the precise adjustment of the EGR amount by the EGR device is difficult. An adjustment error occurs.

Especially when the internal combustion engine is idling immediately after starting, the absolute amount of intake air is small, so the influence of the adjustment error of the above-mentioned EGR amount on the engine operating state tends to be large, and because the temperature in the cylinder of the internal combustion engine is low, Therefore, the combustion state of the fuel tends to become unstable. Therefore, at this time, when the EGR amount is too large due to the adjustment error described above, there is a high possibility that the occurrence of misfire cannot be properly suppressed. On the other hand, at this time, if the EGR amount is too small due to the above-mentioned adjustment error, the combustion temperature of the fuel in the cylinder becomes high, which leads to a corresponding increase in nitrogen oxides (NOx) in the exhaust gas.

The present invention was developed in view of such circumstances, and an object of the present invention is to provide a control device for an internal combustion engine capable of suppressing the occurrence of misfire when fuel with a low cetane number is used and suppressing the emission of nitrogen oxides.

In order to achieve the above objects, the present invention provides a control device for an internal combustion engine, which includes an EGR device for recirculating a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine back to the intake passage, and estimates the percentage of fuel supplied to the internal combustion engine. Hexane number. Furthermore, when the cetane number estimated by the estimating unit is low and the execution period is performed immediately after the start of the internal combustion engine, the EGR amount of the EGR device during idling operation is reduced compared to that not the case.

Therefore, when the internal combustion engine is idling immediately after the start of the internal combustion engine under the condition that the cetane number estimated by the estimation unit is low, that is, the influence of the adjustment error of the EGR amount on the combustion state of the fuel tends to be large and the combustion of the fuel tends to increase. When the state tends to become unstable, the adjustment error of the EGR amount can be reduced by an amount in which the absolute amount of the EGR amount decreases. Therefore, it is possible to suppress the influence of the adjustment error of the EGR amount on the combustion state of the fuel to be small. Furthermore, the fuel injection timing is retarded in response to such a decrease in the EGR amount. Therefore, by adjusting the fuel injection timing that can set the combustion state of the fuel in the cylinder of the internal combustion engine more accurately than the adjustment of the EGR amount, the combustion state of the fuel can be set.

Therefore, according to the above device, it is possible to appropriately set the combustion state of the fuel in the cylinder of the internal combustion engine when using low-cetane number fuel, and therefore, it is possible to achieve both suppression of misfire occurrence and emission of nitrogen oxides (NOx).

Preferably, the control unit sets the EGR amount of the EGR device to "0". According to such an apparatus, the influence of the adjustment error of the EGR amount on the combustion state of the fuel can be eliminated, and therefore the combustion state of the fuel can be set with higher accuracy.

In one aspect of the present invention, the hysteresis of the fuel injection timing is performed on the condition that the air pressure outside the control unit is equal to or higher than a predetermined determination pressure. When the external air pressure is low, the intake air contains less oxygen due to the lower air density. Therefore, the combustion state of the fuel in the cylinder of the internal combustion engine tends to deteriorate, and misfire tends to occur. According to the above device, when the external air 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 that deteriorates the combustion state of the fuel is prohibited, so that it is possible to reliably Suppress fire from occurring. 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 allowed, so that the emission amount of NOx can be suppressed.

In one aspect of the present invention, a period from the start of the internal combustion engine to the start of the opening operation of the accelerator operating member is set as the execution period. According to such an apparatus, 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, limited to the period when the combustion state of the fuel in the cylinder tends to become unstable, the high precision can be performed. The reduction of the set EGR amount of the combustion state and the delay of the fuel injection timing.

Description of drawings

FIG. 1 is a schematic diagram showing a schematic configuration of a control device for an internal combustion engine according to an embodiment of the present invention;

2 is a cross-sectional view showing a cross-sectional structure of a fuel injection valve;

FIG. 3 is a time chart showing the relationship between the transition of fuel pressure and the detection time waveform of the fuel injection rate;

Fig. 4 is a flow chart showing the execution steps of the correction process;

Fig. 5 is a time chart showing an example of the relationship between the detection time waveform and the basic time waveform;

FIG. 6 is a flow chart showing specific execution steps of index value detection processing;

FIG. 7 is an explanatory diagram for explaining a calculation method of a rotation fluctuation amount;

FIG. 8 is a flowchart showing the execution procedure of EGR control processing;

FIG. 9 is a flowchart showing execution steps of injection timing delay processing;

FIG. 10 is a time chart showing an example of an execution method of each process.

Detailed ways

Next, a control device for an internal combustion engine according to an embodiment of the present invention will be described.

As shown in FIG. 1 , an internal combustion engine 11 as a drive source is mounted on a vehicle 10 . A crankshaft 12 of the internal combustion engine 11 is coupled to wheels 15 via a clutch mechanism 13 and a manual transmission 14 . In the vehicle 10 , when the occupant operates a clutch operating member (for example, a clutch pedal), 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 cylinders 16 of the internal combustion engine 11 through the intake passage 17 . In addition, as the internal combustion engine 11 , an internal combustion engine having a plurality of (four [#1 to #4] in this embodiment) cylinders 16 can be employed. In the internal combustion engine 11 , a direct injection type fuel injection valve 20 for directly injecting fuel into the cylinder 16 is installed for each cylinder 16 . The fuel injected by the valve opening drive of the fuel injection valve 20 contacts compressed and heated intake air in the cylinder 16 of the internal combustion engine 11 to ignite and burn. Further, in the internal combustion engine 11 , the piston 18 is pushed down by energy generated with the combustion of fuel in the cylinder 16 to forcibly rotate the crankshaft 12 . Combustion gas combusted in the cylinders 16 of the internal combustion engine 11 is discharged to an exhaust passage 19 of the internal combustion engine 11 as exhaust gas.

The internal combustion engine 11 is equipped with an exhaust gas recirculation (EGR) device 50 for recirculating a part of the exhaust gas flowing through the exhaust passage 19 back into the intake passage 17 . The EGR device 50 includes an EGR passage 51 communicating with the intake passage 17 and the exhaust passage 19 of the internal combustion engine 11 , and an EGR valve 52 attached to the EGR passage 51 to adjust the passage cross-sectional area of the EGR passage 51 . In this EGR device 50 , by changing the opening degree of the EGR valve 52 , the amount of exhaust gas (EGR gas) returning from the exhaust passage 19 to the intake passage 17 , that is, a so-called EGR amount, is adjusted.

Each fuel injection valve 20 is connected to a common rail 34 via a branch passage 31 a, and the common rail 34 is connected to a fuel tank 32 via a supply passage 31 b. A fuel pump 33 that pressurizes and feeds fuel is provided in the supply passage 31b. In the present embodiment, the fuel pressurized by the fuel pump 33 is stored in the common fuel supply pipe 34 and supplied to the inside of each fuel injection valve 20 . In addition, return passages 35 are connected to each fuel injection valve 20 , and the return passages 35 are connected to fuel tanks 32 , respectively. Part of the fuel inside the fuel injection valve 20 is returned to the fuel tank 32 through the return passage 35 .

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

As shown in FIG. 2 , a needle valve 22 is provided inside a housing 21 of the fuel injection valve 20 . The needle valve 22 is provided in a state capable of reciprocating movement (moving in the vertical direction in the drawing) inside the housing 21 . Inside the casing 21 is provided a spring 24 that always urges the above-mentioned needle valve 22 toward the injection hole 23 side (downward side in the figure). In addition, in the inside of the housing 21, the nozzle chamber 25 is formed by sandwiching the above-mentioned needle valve 22 at a position on one side (lower side in the figure), and a nozzle chamber 25 is formed on the other side (upper side in the figure). The location is formed with a pressure chamber 26 .

A plurality of injection holes 23 communicating the inside of the nozzle chamber 25 with the outside of the housing 21 are formed, and fuel is supplied to the nozzle chamber 25 from the branch passage 31 a (common fuel supply pipe 34 ) via the introduction passage 27 . The above-described nozzle chamber 25 and branch passage 31 a (common oil supply pipe 34 ) are connected to the pressure chamber 26 via a communication passage 28 . In addition, the pressure chamber 26 is connected to a return passage 35 (fuel tank 32 ) via a discharge passage 30 .

As the above-mentioned fuel injection valve 20, an electrically driven type can be used, and a piezoelectric actuator 29 is provided inside the casing 21. The piezoelectric actuator 29 is composed of a plurality of piezoelectric elements ( Such as piezoelectric ceramic elements) are stacked. A spool 29 a is attached to the piezoelectric actuator 29 , and the spool 29 a is provided inside the pressure chamber 26 . Then, one of the communication passage 28 (nozzle chamber 25 ) and the discharge passage 30 (return passage 35 ) selectively communicates with the pressure chamber 26 by the movement of the spool 29 a caused by the operation of the piezoelectric actuator 29 .

In this fuel injection valve 20, when a valve closing signal is input to the piezo actuator 29, the piezo actuator 29 contracts and the spool 29a moves, and the communication passage 28 and the pressure chamber 26 are in a state of communication, and also serve as a return passage. The communication between 35 and pressure chamber 26 is blocked. Accordingly, the nozzle chamber 25 and the pressure chamber 26 communicate 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 extremely small, and the needle valve 22 moves to the position where the injection hole 23 is blocked by the biasing force of the spring 24. At this time, the fuel injection valve 20 becomes a state of not injecting fuel (closed). valve state).

On the other hand, when a valve opening signal is input to the piezo actuator 29, the piezo actuator 29 expands and the valve body 29a moves, and the communication between the communication passage 28 and the pressure chamber 26 is cut off, and the return passage is communicated. 35 and the state of the pressure chamber 26. As a result, part of the fuel in the pressure chamber 26 returns to the fuel tank 32 through the return passage 35 in a state where the fuel is prohibited from flowing out from the nozzle chamber 25 to the pressure chamber 26 . Therefore, the pressure of the fuel in the pressure chamber 26 decreases, the pressure difference between the pressure chamber 26 and the nozzle chamber 25 increases, and the needle valve 22 moves away from the injection hole 23 against the biasing force of the spring 24 by utilizing the pressure difference. The fuel injection valve 20 is in a state of injecting fuel (valve open state).

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 . Therefore, 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 fuel supply pipe 34 (see FIG. 1 ), it is possible to detect the fuel at a location near the injection hole 23 of the fuel injection valve 20 . As for the pressure, a 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. In addition, the above-mentioned pressure sensors 41 are provided one by one for each fuel injection valve 20 , that is, for each cylinder 16 of the internal combustion engine 11 .

As shown in FIG. 1 , various sensors for detecting an operating state are provided in the internal combustion engine 11 as peripheral devices. As these sensors, in addition to the above-mentioned pressure sensor 41, for example, a crank sensor 42 for detecting the rotational phase and rotation speed (engine speed NE) of the crankshaft 12, and a crank sensor 42 for detecting the operation of an accelerator operating member (such as an accelerator pedal) are provided. The accelerator sensor 43 of the amount (accelerator operation amount ACC). In addition, an external air pressure sensor 44 for detecting the pressure of the external air (outside air pressure) of the internal combustion engine 11, an intake air sensor 45 for detecting the amount of intake air passing through the intake passage 17 (passage intake air amount GA), An intake pressure sensor 46 for detecting the pressure (intake pressure PM) in the intake passage 17 . In addition, an opening sensor 47 for detecting the opening degree of the EGR valve 52 (EGR opening degree VR), and an operation switch 48 for turning on when the operation of the internal combustion engine 11 starts and turning off when the operation stops are provided. wait.

In addition, as peripheral equipment of the internal combustion engine 11 , for example, an electronic control unit 40 including a microcomputer is also provided. The electronic control unit 40 functions as an estimation unit and a control unit, takes in output signals of various sensors, performs various calculations based on these output signals, and executes operation control (EGR control) and Various controls related to the operation of the internal combustion engine 11 such as drive control of the fuel injection valve 20 (fuel injection control).

Basically, the EGR control of the present embodiment is performed as follows.

First, based on the engine speed NE, the passage intake air amount GA, and the intake pressure PM, an estimated value (actual EGR rate) related to the ratio (EGR rate) of the EGR amount to the gas amount sucked into the cylinder 16 of the internal combustion engine 11 is calculated. Regr). In addition, the actual EGR rate can be estimated based on the following idea. The amount of gas (gas including fresh gas and EGR gas) sucked into the cylinder 16 of the internal combustion engine 11 can be estimated based on the intake pressure PM and the engine speed NE. Also, based on the passage intake air amount GA and the engine speed NE, the amount of air (fresh gas amount) sucked into each cylinder 16 during one revolution of the crankshaft 12 can be estimated. Furthermore, the amount obtained by subtracting the new gas amount (=gas amount-new gas amount) from the above-mentioned gas amount can be obtained as an amount corresponding to the actual EGR amount, and the actual EGR rate can be estimated using this amount and the gas amount (= "Amount of Gas - Amount of New Gas"/Amount of Gas).

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

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

In addition, basically, the fuel injection control of the present embodiment is performed as follows.

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

In addition, in the fuel injection control of the present embodiment, when the running speed of the vehicle 10 and the engine speed NE are decelerated due to the release of the operation of the accelerator operation member (accelerator operation amount ACC=“0”), the engine speed NE is When the speed is within a predetermined speed range, control for temporarily stopping fuel injection for operation of the internal combustion engine 11 (so-called fuel cut control) is executed.

In addition, in the fuel injection control of the present embodiment, a region where the cetane number of the fuel is low (low cetane number region) and a region where the cetane number is moderate (middle cetane number region) are set. and the region where the cetane number is high (high cetane number region), and the fuel injection control is executed differently in each of these regions. For example, the required injection timing Tst is set to a timing on the earlier side in a region on the lower side of the cetane number. Specifically, for the three cetane number regions, based on the results of various experiments and simulations, the engine operating state determined by the required injection amount TAU and the engine speed NE and the engine operating state that matches the cetane number region are obtained in advance. The relationship of the injection timing Tst is requested, and the relationship is stored in the electronic control unit 40 as an operation map (ML, MM, MH). Then, based on the required injection amount TAU and the engine speed NE at each period, the required injection timing Tst is calculated using the operation map ML in the low cetane number region, and the required injection timing Tst is calculated using the operation map MM in the middle cetane number region. The required injection timing Tst is calculated, and in the case of a high cetane number range, the required injection timing Tst is calculated using the calculation 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 and the time change of the fuel injection valve 20 , and the like. Such an error changes the output torque of the internal combustion engine 11, which is not preferable. Therefore, in the present embodiment, in order to appropriately perform fuel injection from each fuel injection valve 20 in accordance with the operating state of the internal combustion engine 11, the detection timing of the fuel injection rate is formed based on the fuel pressure PQ detected by the pressure sensor 41. waveform, and a correction process of correcting the required injection timing Tst and the required injection time Ttm is performed based on the detected time waveform. This correction processing is performed individually for each cylinder 16 of the internal combustion engine 11 .

The fuel pressure inside the fuel injection valve 20 fluctuates with the opening and closing operation of the fuel injection valve 20 such that it decreases with the opening of the fuel injection valve 20 and rises with the subsequent closing of the fuel injection valve 20 . . Therefore, by monitoring the fluctuation waveform of the fuel pressure inside the fuel injection valve 20 during fuel injection, it is possible to grasp the actual operating characteristics of the fuel injection valve 20 (for example, the actual fuel injection amount, the timing at which the valve opening operation starts) with high precision. , the period when the valve closing action starts, etc.). 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 as described above, the fuel injection timing and the fuel injection amount can be accurately set in accordance with the operating state of the internal combustion engine 11 .

Hereinafter, such correction processing will be described in detail.

Here, first, a procedure for forming a variation pattern of the fuel pressure (in this embodiment, a detection time waveform of the fuel injection rate) at the time 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 valve opening operation of the fuel injection valve 20 (specifically, the movement of the needle valve 22 to the valve opening side) starts is detected (valve opening operation start timing Tos). , the timing when the fuel injection rate becomes the maximum (maximum injection rate reaching time Toe), the timing when the fuel injection rate starts to decrease (injection rate decrease start time Tcs), the valve closing operation of the fuel injection valve 20 (specifically, the needle valve 22 movement to the valve closing side) ends (valve closing action end timing Tce).

First, the average value of the fuel pressure PQ in the 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. This 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, the value obtained by subtracting the predetermined pressure P1 from the reference pressure Pbs is calculated as the operating pressure Pac (=Pbse−P1). This predetermined pressure P1 is the amount by which the fuel pressure PQ changes regardless of whether the needle valve 22 is in the valve closed position when the fuel injection valve 20 is opened or closed, that is, the fuel that does not contribute to the movement of the needle valve 22 The amount of change in pressure PQ corresponds to the pressure.

Then, a time-based first-order differential value d(PQ)/dt of the fuel pressure PQ during a period in which the fuel pressure PQ decreases immediately after the start of fuel injection is calculated. Then, the tangent line L1 of the time waveform of the fuel pressure PQ at the point where the first-order differential value becomes the smallest, that is, the point where the downward slope of the fuel pressure PQ becomes the largest, is obtained, and the relationship between the tangent line L1 and the above-mentioned operating pressure Pac is calculated. Intersection A. The timing corresponding to the intersection point A and the point AA at which the fuel pressure PQ returns to the previous timing by a later-described detection delay amount is determined as the valve opening operation start timing Tos. In addition, the above detection delay amount is a period corresponding to the delay of the change timing of the fuel pressure PQ relative to the pressure change timing of the nozzle chamber 25 (see FIG. 2 ) of the fuel injection valve 20 , and is due to the distance between the nozzle chamber 25 and the pressure sensor 41 . and so on for the amount of delay generated.

In addition, the first-order differential value of the fuel pressure PQ is calculated while the fuel pressure PQ temporarily drops and then rises immediately after the start of the fuel injection. Then, the tangent line L2 of the time waveform of the fuel pressure PQ at the point where the first-order differential value becomes the largest, that is, the point where the upward slope of the fuel pressure PQ becomes the largest, is obtained, and the relationship between the tangent line L2 and the above-mentioned operating pressure Pac is calculated. Intersection B. The timing corresponding to the intersection point B and the point BB at which the detection delay returns to the past timing is determined as the valve closing operation end timing Tce.

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

Then, the time period CC at which the intersection point C is returned to the previous time period by the detection delay amount is calculated, and the point D at which the virtual maximum fuel injection rate VRt becomes is determined in this time period CC. Then, the timing corresponding to the intersection point E of 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 timing Tos) and the above-mentioned maximum injection rate Rt is determined. Time Toe is reached as the maximum injection rate.

In addition, the timing corresponding to the intersection point F of the straight line L4 connecting the above-mentioned point D and the valve closing operation end timing Tce (specifically, the point at which the fuel injection rate becomes "0" at this timing Tce) and the maximum injection rate Rt is determined as Injection rate reduction start period Tcs.

In addition, the trapezoidal time waveform formed by the valve opening operation start timing Tos, the maximum injection rate reaching timing Toe, the injection rate reduction starting timing Tcs, the valve closing operation ending timing Tce, and the maximum injection rate Rt is used as the fuel injection rate related to fuel injection. related to the detection time waveform used.

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

In addition, FIG. 4 is a flowchart showing specific processing procedures of the above-mentioned correction processing. The series of processing shown in this flowchart conceptually represents the execution procedure of the calibration processing, and the actual processing is executed by the electronic control unit 40 as interrupt processing every predetermined cycle. In addition, 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 fuel injection execution is formed based on the fuel pressure PQ (step S101 ). In addition, 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) related to the time waveform of the fuel injection rate when fuel injection is performed is set (step S102). In the present embodiment, the relationship between the operating state of the internal combustion engine 11 and a basic time waveform suitable for the operating state is obtained in advance based on the results of experiments or simulations, and is stored in the electronic control unit 40 . In the process of step S102, based on the operating state of the internal combustion engine 11 in each period, the basic time waveform is set in accordance with the relationship described above.

As shown in FIG. 5, a trapezoidal time waveform defined by the valve opening operation start timing Tosb, the maximum injection rate reaching timing Toeb, the injection rate reduction starting timing Tcsb, the valve closing operation ending time Tceb, and the maximum injection rate is set as the above-mentioned basic Time waveform (dot-dash line).

Then, such a basic time waveform is compared with the above-mentioned detection time waveform (solid line), and based on the comparison result, the correction term K1 for correcting the control target value (the above-mentioned required injection timing Tst) of the start timing of fuel injection and the correction term K1 are respectively calculated. The correction term K2 is used to correct the control target value (required injection time Ttm) of the execution time of the fuel injection. Specifically, the 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 this difference ΔTos is stored as a correction term K1 ( Step S103 in Fig. 4). Also, the difference ΔTcs (=Tcsb−Tcs) between the injection rate reduction start timing Tcsb ( FIG. 5 ) in the basic time waveform and the injection rate reduction start timing Tcs in the detection time waveform is calculated, and the difference ΔTcs is stored as a correction term K2 (step S104 in FIG. 4 ).

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

When executing fuel injection control, a value obtained by correcting the required injection timing Tst with 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. 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 starting timing Tos in the detection time waveform can be suppressed to be small, and therefore, it is consistent with the operation of the internal combustion engine 11. The state-dependent form sets the start timing of fuel injection with high precision.

In addition, a value obtained by correcting the required injection time Ttm with 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 reduction start timing Tcsb in the basic time waveform and the injection rate reduction start timing Tcs in the detection time waveform can be suppressed to be small, and therefore, in fuel injection, The timing at which the fuel injection rate starts to decrease is set with high precision in a manner corresponding to the operating state of the internal combustion engine 11 .

Thus, in the present embodiment, the required injection timing Tst and the required injection timing Tst are corrected based on the difference between the actual operating characteristics of the fuel injection valve 20 (specifically, the detected time waveform) and predetermined basic operating characteristics (specifically, the basic time waveform). The injection time Ttm, therefore, can suppress the deviation between the actual operating characteristics of the fuel injection valve 20 and the basic operating characteristics (operating characteristics of the fuel injection valve having standard characteristics). Therefore, the injection timing and the injection amount of the fuel injection from each fuel injection valve 20 are appropriately set so as to match the operating state of the internal combustion engine 11 .

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

In this index value detection process, execution conditions including the conditions for executing the above-mentioned fuel cut control ([Condition 1] described later) are set. Then, when the execution condition is satisfied, fuel injection is executed to the internal combustion engine 11 with a predetermined small quantity FQ (for example, several cubic millimeters), and the output rotation speed of the internal combustion engine 11 accompanying the execution of the fuel injection is detected. The index value of the moment (rotation variation ΣΔNE described later) is used as the cetane number index value of the fuel. In addition, as the above-mentioned rotational fluctuation amount ΣΔNE, a larger value is detected when 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 smaller the number of embers of the fuel, so the engine torque generated by the combustion of the fuel increases. In the estimation control of the present embodiment, based on such a relationship between the cetane number of the fuel and the output torque of the internal combustion engine 11 , the cetane number index value of the fuel is detected.

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

FIG. 6 is a flowchart showing specific execution procedures of the above-mentioned index value detection processing. In addition, the series of processing shown in this flowchart conceptually shows the execution procedure of the index value detection processing, and the actual processing is executed by the electronic control unit 40 as interrupt processing every predetermined cycle.

As shown in FIG. 6 , in this process, first, it is determined whether or not an execution condition is established (step S201 ). Here, it is judged that the execution condition is satisfied because all of the following [Condition 1] to [Condition 3] are satisfied.

[Condition 1] The above-mentioned fuel cut control has been 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 has been operated.

[Condition 3] Correction processing has been properly performed. Specifically, each of the correction terms K1 and K2 calculated in the correction process has neither an upper limit value nor a lower limit value.

When the execution condition described above is not satisfied (step S201 : NO), the following process of detecting the cetane number index value of the fuel is not executed, and this process is temporarily terminated.

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

Specifically, first, the control target value of the scheduled fuel injection timing (target injection timing TQst) and the control target value of the fuel injection timing are corrected using the correction terms K1 and K2 calculated by the above-mentioned correction processing in FIGS. 4 and 5 . (Target injection time TQtm) (step S202 of FIG. 6 ). Specifically, the value obtained by adding the correction term K1 to the target injection timing TQst is set as the new target injection timing TQst, and the value obtained by adding the correction term K2 to the target injection time TQtm is set as the new target injection time TQtm.

Then, drive control of the fuel injection valve 20 based on the target injection timing TQst and the target injection time TQtm is performed, and fuel injection from the fuel injection valve 20 is performed (step S203 ). By such driving control of the fuel injection valve 20 , the predetermined amount of fuel FQ is injected from the fuel injection valve 20 at the timing when the variation in the rotational fluctuation amount ΣΔNE is suppressed. In addition, in the present embodiment, the fuel injection in the process of step S203 is performed using a predetermined fuel injection valve among the plurality of fuel injection valves 20 (in the present embodiment, the fuel injection valve 20 attached to the cylinder 16 [﹟1]). injection. In addition, the correction terms K1 and K2 used in this process are similarly used, and the fuel injection valve corresponding to the predetermined fuel injection valve 20 (in the present embodiment, the fuel injection valve 20 attached to the cylinder 16 [﹟1]) is used. calculated value.

Then, after the rotation fluctuation amount ΣΔNE is detected and stored as an index value of the output torque of the internal combustion engine 11 associated with the fuel injection of the predetermined amount FQ (step S204 ), this process is temporarily terminated. Specifically, detection of the amount of rotation fluctuation ΣΔNE is performed as follows. As shown in FIG. 7, in the device of this embodiment, the engine speed NE is detected every predetermined time, and the engine speed NE is calculated each time the detection is performed and the number of times before (in this embodiment, three times before) is calculated. ) The difference ΔNE (=NE−NEi) of the detected engine speed NEi. Then, an integrated value (a value corresponding to the area of the shaded portion in FIG. 7 ) related to the amount of change in the above-mentioned difference ΔNE accompanying the execution of the above-mentioned fuel injection is calculated, and this integrated value is used as the above-mentioned rotation The variation ΣΔNE is stored. In order to make the calculation method of the rotation fluctuation amount ΣΔNE easier to understand, the transition of the engine speed NE and the difference ΔNE shown in FIG. 7 is shown in a simplified form, and therefore it is slightly different from the actual transition.

In the present embodiment, basically, which of the low cetane number region, the middle cetane number region, and the high cetane number region is determined based on the rotation fluctuation amount ΣΔNE detected by the index value detection process, And, the specified area is stored in the electronic control unit 40 . More specifically, when the amount of rotation fluctuation ΣΔNE is less than the predetermined value PL (ΣΔNE<PL), it is determined to be in the low cetane number range, and when the amount of rotation fluctuation ΣΔNE is greater than or equal to the predetermined value PL and less than the predetermined value PH ( PL≤ΣΔNE<PH), it is judged to be in the middle cetane number range, and when the amount of rotation variation ΣΔNE is equal to or greater than the predetermined value PH (ΣΔNE≥PH), it is judged to be in the high cetane number range. Also, fuel injection control is performed in an execution manner matched to the thus determined cetane number region.

Here, when the cetane number of the fuel supplied to the internal combustion engine 11 is low, the ignition delay becomes long, and thus the combustion state of the fuel tends to deteriorate. In addition, when the internal combustion engine 11 is idling immediately after starting, the amount of fuel injected into the cylinder 16 is small and the temperature inside the cylinder 16 is low, so the combustion state of the fuel tends to deteriorate. Therefore, in the apparatus of the present embodiment, it can be said that the combustion state of fuel tends to deteriorate, and misfire tends to occur, especially during idling immediately after starting the internal combustion engine 11 and when it is judged to be in the low cetane number range.

Based on this point, in the present embodiment, the target EGR rate Tegr at the time of idling is set to "0" when the low cetane number range is stored (specific situation) during the execution period immediately after the start of the internal combustion engine 11, The EGR amount of the EGR device 50 is set to "0". As a result, when the internal combustion engine 11 is idling immediately after the startup of the internal combustion engine 11 in a state where the low cetane number region is stored, that is, when the influence of the adjustment error of the EGR amount on the combustion state of the fuel tends to be large and the combustion state of the fuel When it tends to become unstable, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 can be improved according to the stop of the recirculation of EGR gas, and thus the occurrence of misfire can be suppressed.

In such a specific situation, in order to improve the combustion state of fuel during idling, it is not limited to setting the EGR amount during idling to "0", but it is also conceivable to decrease the EGR amount compared to when not in the specific situation. In the above-mentioned EGR device 50, due to the volume of the EGR passage 51 and the volume of the portion from the connection portion of the intake passage 17 to the EGR passage 51 to the cylinder 16 of the internal combustion engine 11, it is unavoidable to change the opening degree of the EGR valve 52. A change in the EGR amount produces a delay. 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 it is difficult to adjust the EGR amount of the EGR device 50 accurately. Therefore, it can be said that it is easy to adjust the EGR amount of the EGR device 50 An adjustment error occurs. Furthermore, when the EGR amount is too large due to the adjustment error described above, the combustion state of the fuel may deteriorate. Also, when the EGR amount is too small due to the above-mentioned adjustment error, the combustion temperature of the fuel in the cylinder 16 becomes high, which may lead to an increase in nitrogen oxides (NOx) in the exhaust gas.

In this regard, in the present embodiment, in a specific situation, that is, when the influence of the adjustment error of the EGR amount on the combustion state of the fuel tends to become large and the combustion state of the fuel tends to become unstable, the adjustment error itself of the EGR amount disappears, Therefore, the influence of this adjustment error on the combustion state of the fuel can be eliminated.

As described above, by setting the EGR amount during idling under specific conditions to "0", the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is improved, thereby suppressing the occurrence of misfire. However, when only the EGR amount is 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 large increase in the amount of NOx in the exhaust gas.

Based on this point, in this embodiment, in a specific situation, the EGR amount during idling is set to "0", and the fuel injection timing during idling is set to be retarded compared to when the specific situation is not. side period. Note that, in this embodiment, when not in a specific situation means when a middle cetane number range is stored, when a high cetane number range is stored, or when the execution period has elapsed after the start of the internal combustion engine 11 .

By setting the timing on the retard side as the fuel injection timing, the ignition timing of the fuel in the cylinder 16 of the internal combustion engine 11 becomes retarded, and accordingly the combustion temperature of the fuel decreases and the NOx amount in the exhaust gas decreases. In the present embodiment, fuel injection control can set a fuel injection timing (specifically, a required injection timing Tst) that takes into account both the suppression of deterioration of the combustion state and the suppression of the NOx emission amount.

Furthermore, in the present embodiment, at the time of idling under specific conditions, the adjustment of the internal combustion engine 11 can be performed by setting the adjustment based on the fuel injection timing that can be performed more accurately than the setting based on the adjustment based on the EGR amount. The setting of the combustion state of the fuel in the cylinder 16. Thus, according to the present embodiment, it is possible to appropriately set the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 when low cetane number fuel is used, and thus suppress the occurrence of misfire and suppress the NOx emission amount at the same time.

Next, the processing for setting the EGR amount to "0" and the processing for retarding the fuel injection timing under specific conditions will be described in detail.

Here, first, processing for setting the EGR amount at the time of idling in a specific situation to "0" will be described with reference to FIG. 8 .

FIG. 8 shows the execution procedure of the EGR control process (EGR control process). A series of processing shown in the flowchart of the figure is executed by the electronic control unit 40 as interrupt processing every predetermined cycle.

As shown in FIG. 8 , in this process, first, it is judged whether or not the following [Condition 4] and [Condition 5] are simultaneously satisfied (step S301 ).

[Condition 4] The low cetane region is determined and stored in the electronic control unit 40 .

[Condition 5] is the execution period from the start of the internal combustion engine 11 to the start of the opening operation of the accelerator operating member (operation to make the accelerator operation amount ACC larger than “0”). Specifically, it is a case where the state in which the accelerator operation amount ACC is "0" continues after the operation switch 48 is operated to start the operation of the internal combustion engine 11 .

Furthermore, when [Condition 4] and [Condition 5] are satisfied at the same time (step S301: YES), it is considered that the influence of the adjustment error of the EGR amount on the combustion state of the fuel tends to become large and the combustion state of the fuel tends to become unstable at this time. , set "0" as the target EGR rate Tegr, and set the EGR amount to "0" (step S302 ).

On the other hand, when [Condition 4] and [Condition 5] are not satisfied (step S301: NO), normal control (specifically, corresponding to the target EGR rate Tegr set based on the engine speed NE and the required injection amount TAU) is executed (step S301: NO). Operation control of the EGR valve 52) as the EGR control process (step S303). Specifically, in the case where [Condition 4] is not satisfied, it is considered that the middle cetane number region or the high cetane number region is determined and stored in the electronic control unit 40 at this time, so there is a possibility that the combustion state of the fuel deteriorates excessively. low, so that normal control is performed as EGR control processing. In addition, when [Condition 5] is not satisfied, it is considered that the temperature in the cylinder 16 of the internal combustion engine 11 increases as the engine operation continues after starting, so the possibility of excessive deterioration of the combustion state of the fuel is low, and the normal operation is executed. The control is handled as EGR control.

Next, processing for retarding the fuel injection timing (injection timing retardation processing) will be described with reference to FIG. 9 .

FIG. 9 shows the execution procedure of the injection timing lag process. A series of processing shown in the flowchart of the figure is executed by the electronic control unit 40 as interrupt processing every predetermined cycle.

As shown in FIG. 9 , in this process, first, it is determined whether the EGR opening degree VR is equal to or less than a predetermined opening degree (for example, an opening degree slightly larger than the valve closing degree) (step S401 ). In addition, in this process, it is judged whether or not the engine speed NE is below a predetermined speed (for example, a speed corresponding to the upper limit of the engine speed NE during idling [1300 rpm]) or not (step S402), and the required injection amount is judged Is TAU equal to or less than a predetermined amount (for example, an amount corresponding to the upper limit of the fuel injection amount during idling) (step S403 ).

Then, it is determined that the EGR amount is set to "0" at this time because the EGR opening degree VR is equal to or less than a predetermined opening degree (step S401: YES). Further, it is determined that the internal combustion engine 11 is in the idling state based on the fact that the engine speed NE is equal to or lower than a predetermined speed (step S402: YES) and the requested injection amount TAU is equal to or lower than a predetermined amount (step S403: YES). Therefore, if all the determinations in these steps S401 to S403 are affirmative, it is determined that the above-mentioned [Condition 4] and [Condition 5] are both satisfied and the EGR amount is set to "0" in the EGR control process (see FIG. 8 ). . That is, at this time, the low cetane number range is stored and it is 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 amount is set to "0".

In this case (“YES” in all steps S401 to S403 ), it is further determined whether the external air pressure is higher than the determination pressure (for example, 80 kPa) (step S404 ). Then, when the external air pressure is equal to or higher than the determination pressure (step S404: YES), fuel injection control (hysteresis control) is performed in the execution mode in which a delay side timing is set as the fuel injection timing (step S405).

In the present embodiment, as the calculation map used for setting the required injection timing Tst, in addition to the above-mentioned calculation maps ML, MM, and MH, it is also set to set the EGR amount at the time of idling in a specific situation. In the operation map of the status matching of "0", the operation map MLF is set at the time on the lag side of the comparison. Specifically, based on the results of various experiments and simulations, the engine operating state determined by the required injection amount TAU and the engine speed NE and the EGR amount set to "0" when idling under specific conditions are obtained in advance. The relationship of the condition matching the required injection timing Tst, and this relationship is stored in the electronic control unit 40 as a calculation map MLF.

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

On the other hand, when the EGR opening degree VR is larger than the predetermined opening degree (step S401: NO), it is considered that the EGR amount is not set to "0" at this time, and the timing of setting the advance side as the timing of the fuel injection timing is executed. Fuel injection control (normal control) in the execution mode (step S406 ). In this normal control, in detail, any one of the operation maps ML, MM, and MH that is an operation map corresponding to the cetane number area stored at this time is selected, and thereafter based on the selected operation map, based on requirements The injection amount TAU and the engine speed NE set the required injection timing Tst. Also, when the engine speed NE is higher than the predetermined speed (step S402: NO) or the required injection amount TAU is larger than the predetermined amount (step S403: NO), the internal combustion engine 11 is considered not to be idling, and normal control is executed (step S406).

Thus, according to the present embodiment, the processing of setting the EGR amount to "0" (processing of step S302 in FIG. 8 ) and the processing of setting a fuel injection timing on the retard side (processing of step S405 in FIG. It is executed 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. Therefore, when the temperature inside the cylinder 16 of the internal combustion engine 11 is low immediately after the start-up, in other words, only during the period when the combustion state of the fuel in the cylinder 16 tends to become unstable, it is possible to execute high-accuracy fuel injection. The process of setting the combustion state (the process of setting the EGR amount to "0" and the process of setting the timing on the retard side as the fuel injection timing).

On the other hand, when the external air 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 air density is low, so the amount of oxygen contained in the intake air is small. Therefore, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 tends to deteriorate, and misfire tends to occur. According to this embodiment, when the external air pressure is low and misfire is likely to occur, the calculation map MLF can be selected and the required injection timing Tst can be set to a retarded timing. Since the side where the state deteriorates is changed, it is possible to reliably suppress the occurrence of misfire. In addition, when the external air pressure is higher than the determination pressure (step S404: YES), in other words, when misfire is relatively difficult to occur, a delay side timing is set as the required injection timing Tst on the basis of the calculation map MLF, so that it can be appropriately reduce the emission of NOx. In addition, in the present embodiment, based on the results of various experiments and simulations, the determination pressure capable of reliably suppressing the occurrence of misfire during idling under specific conditions is obtained in advance and stored in the electronic control unit 40 .

Next, the manner in which the processing for setting the EGR amount to "0" and the processing for retarding the fuel injection timing at the time of idling under the above-mentioned specific conditions will be described with reference to FIG. 10 .

FIG. 10 shows an example of how these processes are executed. In addition, in the figure, the solid line indicates the execution mode of each process in the device of this embodiment, and the dashed-dotted line indicates each process in the device of the comparative example in which the EGR amount is not set to "0" and the fuel injection timing is not retarded. How the processing is performed. In addition, the dashed-two dotted line in the figure shows the transition of the NOx emission amount when the EGR amount is set to "0" and the fuel injection timing is not retarded.

In the example shown in FIG. 10 , the operation switch 48 is turned on at time t11 to start the internal combustion engine 11 . 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 equal to Opening degree corresponding to closed valve state (VR="0"). At this time, based on the calculation map MLF, a timing that is delayed by an amount indicated by a hollow arrow in the figure is set as the required injection timing Tst when it is not an execution period immediately after the start of the engine.

At this time, in the device of the comparative example shown by the dotted line in the figure, although the amount of NOx emission is suppressed to a very small amount, the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is caused to deteriorate, thus causing misfire and smoke. generation. On the other hand, in the device indicated by the two-dot chain line in the figure, although the combustion state of the fuel in the cylinder 16 of the internal combustion engine 11 is good enough to avoid misfire and smoke generation, the combustion temperature of the fuel is extremely high, therefore, resulting in NOx emissions increased significantly.

On the other hand, in the device of this embodiment, the EGR amount is set to "0" at times t11 to t12, and the timing on the retard side is set as the fuel injection timing. The amount of NOx emission is greatly increased like the device shown by the line, and it does not cause fire and smoke generation like the device of the comparative example shown by the dotted line. As described above, according to the present embodiment, when 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, so that both misfire suppression and NOx emission reduction can be achieved.

In this example, when the opening operation of the accelerator operating member starts at time t12, the processing for setting the EGR amount to "0" and the processing for retarding the fuel injection timing are stopped thereafter. Furthermore, at this time, the operation control of the EGR valve 52 is executed based on the target EGR rate Tegr set based on the engine speed NE and the required injection amount TAU, and the calculation maps ML, MM, Any one of MH executes drive control of the fuel injection valve 20 based on the set requested injection timing Tst.

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

(1) In the execution period immediately after the start of the internal combustion engine 11 and in a specific situation in which a low cetane number region is stored, the EGR amount at the time of idling is set to "0", and compared to when it is not in the specific situation , the required ignition timing Tst during idling is set to a retarded timing. Therefore, when 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, and both suppression of misfire occurrence and NOx emission can be achieved.

(2) Since the EGR amount during idling operation under specific conditions has been set to "0", the influence of the adjustment error of the EGR amount on the combustion state of the fuel can be eliminated, and the combustion state of the fuel can be set with higher accuracy .

(3) The process of setting the timing on the advance side as the fuel injection timing is performed on the condition that the external air pressure is equal to or higher than the determination pressure (processing of step S405 in FIG. 9 ). Therefore, it is possible to prevent the required injection timing Tst from being changed to a side that deteriorates the fuel combustion state when the external air pressure is low and misfire is likely to occur, thereby reliably suppressing the occurrence of misfire. In addition, when the external air pressure is high and misfire is relatively difficult to occur, the required injection timing Tst is allowed to be changed to the retard side, so that the emission amount of NOx can be appropriately suppressed.

(4) The process of setting the EGR amount to "0" (the process of step S302 in FIG. 8 ) and setting the hysteresis side are limited to 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 timing is processed as the fuel injection timing (processing of step S405 in FIG. 9 ). Therefore, it is possible to perform processing for setting the fuel combustion state with high precision only during the period when the fuel combustion state in the cylinder 16 of the internal combustion engine 11 is likely to become unstable.

In addition, the above-described embodiment may be modified as follows.

· Instead of the processing of steps S401 to S403, a process of judging whether or not the above-mentioned [condition 4] and [condition 5] are satisfied at the same time may be performed. With such a device, in the execution period immediately after the start of the internal combustion engine 11 and under a specific situation in which a low cetane number region is stored, the required ignition timing Tst at the time of idling can be set to The period of the lag side.

- The setting of the required injection timing Tst is not limited to using the calculation map, and the setting of the required injection timing Tst may be performed using a calculation expression.

• The setting of the requested injection timing Tst during idling under specific conditions may also be performed as follows. That is, based on the engine speed NE and the required injection amount TAU, the required injection timing Tst is set according to the calculation map ML, and the hysteresis correction term is calculated based on the engine speed NE and the required injection amount TAU, and the required injection timing Tst is corrected using the hysteresis correction term. The latter value is set as the final required injection timing Tst.

· The processing of step S404 in FIG. 9 may be omitted. That is, instead of using the external air pressure, a process of setting a lag-side timing as the required injection timing Tst (processing of step S405 in FIG. 9 ) may be executed.

·In a specific situation, instead of setting the EGR amount at idling to "0", 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 idling under specific conditions can be reduced compared to the EGR amount during non-specific conditions. With such a device, during idling operation under specific conditions, that is, when the influence of the adjustment error of the EGR amount on the combustion state of the fuel tends to become large and the combustion state of the fuel tends to become unstable, the absolute amount of the EGR amount can also be changed. A small amount reduces the adjustment error of the EGR amount. Therefore, it is possible to suppress the influence of the adjustment error of the EGR amount on the combustion state of the fuel to be small.

・The process of setting the EGR amount to "0" (the process of step S302 in FIG. 8 ) and the timing of setting the lag side are performed 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 Processing as fuel injection timing (processing of step S405 in FIG. 9 ). Instead, these processes may be executed only during the execution period from the start of the internal combustion engine 11 to the elapse of a predetermined fixed period of time. Examples of the certain period include a certain period of 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, and a period until the integrated value of the intake air amount reaches a predetermined value. In short, as long as the process of setting the EGR amount to "0" and setting the timing on the retard side as the fuel injection timing can be executed until the temperature inside the cylinder 16 of the internal combustion engine 11 is sufficiently high and the combustion state of the fuel is good can be processed.

If errors in fuel injection timing and fuel injection amount caused by initial individual differences and aging changes of the fuel injection valve 20 can be properly suppressed, the process of correcting the target injection timing TQst and target injection time TQtm using the correction terms K1 and K2 can also be omitted (step S202 of FIG. 6 ).

・The control device of the above-mentioned embodiment may be applied to a device for judging which of the two regions divided by the index value of the cetane number of the fuel (rotation variation ΣΔNE) is used after appropriately changing its structure. Which area is the device in the four or more areas.

The control device of the above-mentioned embodiment may also be applied to an internal combustion engine in which the cetane number region is not determined based on the rotation fluctuation amount ΣΔNE stored in the electronic control unit 40 but the rotation fluctuation amount ΣΔNE is supplied to the internal combustion engine after appropriately changing its structure. 11 is a value equivalent to the cetane number of the fuel (specifically, the cetane number index value) used in the device. In such an apparatus, when the rotation fluctuation amount ΣΔNE is smaller than a predetermined value, it is judged that the cetane number of the fuel supplied to the internal combustion engine 11 is low, and the EGR amount at the time of idling under a specific condition is set to The processing of "0" and the processing of setting the timing on the retard side as the fuel injection timing are sufficient.

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

・As for the mounting method of the pressure sensor 41 , as long as it can appropriately detect the pressure that becomes an index of the fuel pressure inside the fuel injection valve 20 (specifically, inside the nozzle chamber 25 ), in other words, the pressure that changes with the change of the fuel pressure The fuel pressure is not limited to the form directly attached to the fuel injection valve 20, and can be changed arbitrarily. Specifically, a pressure sensor may be attached to the branch passage 31 a and the common oil supply pipe 34 .

• Instead of the fuel injection valve 20 driven by the piezoelectric actuator 29, a fuel injection valve driven by an electromagnetic actuator including, for example, a solenoid coil may be used.

- The control device of the above-described embodiment is not limited to the vehicle 10 equipped with the clutch mechanism 13 and the manual transmission 14 , and may be applied to a vehicle equipped with a torque converter and an automatic transmission. In such a vehicle, it is only necessary to perform fuel injection for estimating the cetane number of the fuel when, for example, [Condition 1] and [Condition 3] are satisfied. In addition, in a vehicle employing a device with a built-in lock-up clutch as a torque converter, as long as [Condition 6] in which the lock-up clutch is not engaged is reset and the [Condition 6] is satisfied, the The fuel injection for detecting the cetane number index value of the fuel is sufficient.

- The present invention is not limited to a device that executes fuel injection for estimating the cetane number of fuel supplied to an internal combustion engine, and is applicable to any device that executes processing for estimating the cetane number of the fuel. Examples of such devices include the following devices. That is, first, when performing fuel injection for operation of the internal combustion engine, the cylinder internal pressure sensor detects the pressure in the cylinder of the internal combustion engine (cylinder internal pressure). Then, the timing at which the fuel is actually ignited is calculated based on the cylinder internal pressure, and the ignition delay time is calculated based on the timing. Then, the cetane number index value is calculated based on the calculated ignition delay time.

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

Label description

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... Spool, 30...discharge passage, 31a...branch passage, 31b...supply passage, 32...fuel tank, 33...fuel pump, 34...common oil supply pipe, 35...return passage, 40...electronic control unit, 41...pressure sensor , 42...crankshaft sensor, 43...throttle sensor, 44...external air pressure sensor, 45...intake air sensor, 46...intake air pressure sensor, 47...opening sensor, 48...operation switch, 50...EGR device, 51...EGR passage , 52...EGR valve.

Claims (4)

1. the control gear of an internal-combustion engine is characterized in that, possesses:

The EGR device makes the part of the exhaust of the exhaust passageway that flows through internal-combustion engine turn back to inlet air pathway and carry out recirculation;

Infer section, infer to the cetane number of the fuel of described internal-combustion engine supply; And

Control device, in the cetane number of being inferred out by the described section of inferring lower and be in described internal-combustion engine and just begun to start after when term of execution, compare the EGR amount of the described EGR device when reducing idle running and the fuel injection timing is lagged behind during with non-this situation.

2. the control gear of internal-combustion engine as claimed in claim 1 is characterized in that,

Described control device is made as " 0 " with described EGR amount.

3. the control gear of internal-combustion engine as claimed in claim 1 or 2 is characterized in that,

Air pressure is the predetermined hysteresis of carrying out described fuel injection timing more than the pressure as condition of judging beyond the described control device.

4. such as the control gear of each described internal-combustion engine in the claim 1～3, it is characterized in that,

The term of execution of described be till beginning to the open operation of throttle operation parts after beginning to start from described internal-combustion engine during.

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