WO2013011580A1

WO2013011580A1 - Controller for internal combustion engine

Info

Publication number: WO2013011580A1
Application number: PCT/JP2011/066470
Authority: WO
Inventors: 守谷口
Original assignee: トヨタ自動車株式会社
Priority date: 2011-07-20
Filing date: 2011-07-20
Publication date: 2013-01-24

Abstract

An estimate is made of a cetane value region to which fuel supplied to an internal combustion engine belongs, and fuel-injection control is performed (before (t11)) in a first performance mode according to the estimated cetane value region. Whether or not misfiring in the internal combustion engine has occurred is determined; and, if a misfire is determined to have occurred (t11), fuel-injection control is performed in a second performance mode according to a cetane value region that is lower than the estimated cetane value region. It is then determined if any fuel has been supplied to the fuel tank. Until it is determined that fuel has been supplied when fuel-injection control is performed in the second performance mode ((t11) to (t15)), switching from the second performance mode to the first performance mode for controlling fuel injection is prohibited.

Description

Control device for internal combustion engine

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 based on the estimated cetane number.

In a compression 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 the 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.

Therefore, conventionally, as in the apparatus described in Patent Document 1, it has been proposed to estimate the cetane number of the fuel injected into the cylinder of the internal combustion engine and to execute the engine operation control in accordance with the estimated cetane number. Has been. Moreover, in the apparatus described in Patent Document 1, when misfiring has occurred despite the engine operation control being executed in accordance with the estimated cetane number, the estimated cetane number does not depend on the estimated range. The engine operation control is executed in an execution mode commensurate with the lowest cetane number.

JP 2007-56776 A

In the device described in Patent Document 1, when a misfire has occurred, the execution mode of engine operation control is switched from the execution mode according to the estimated cetane number to the execution mode according to the low cetane number fuel. It is possible to prevent the delay from becoming longer than the expected time. Thereby, the deterioration of the combustion state of the fuel is suppressed and the occurrence of misfire is suppressed.

However, in such a device, the engine operation control is returned to the execution mode before the switching, that is, the execution mode based on the estimated cetane number, because the misfire does not occur after the execution mode of the engine operation control is once switched due to the occurrence of the misfire. Then, the operating state of the internal combustion engine returns to the original state. In this case, there is a high possibility that misfire will occur again.

The present invention has been made in view of such circumstances, and an object thereof is to provide a control device for an internal combustion engine that can suitably suppress the occurrence of misfire.

In order to achieve the above object, in the control device for an internal combustion engine according to the present invention, the estimation unit estimates the cetane number of the fuel supplied to the internal combustion engine, and the first control unit responds to the estimated estimation cetane number. Combustion control related to fuel combustion is executed in the first execution mode. Thereby, combustion control can be executed in a manner corresponding to the cetane number of the fuel supplied to the internal combustion engine.

In the above apparatus, the misfire determination unit determines whether or not misfire has occurred in the internal combustion engine. When the misfire determination unit determines that misfire has occurred, the combustion control is executed in a second execution mode corresponding to fuel having a cetane number lower than the estimated cetane number estimated by the estimation unit. Therefore, even if a misfire occurs during the execution of the combustion control in the first execution mode, the subsequent misfire occurrence is suppressed.

Moreover, after the execution mode of the combustion control is once switched to the second execution mode, unless the fuel supply determination unit determines that there is fuel supply, that is, unless the cetane number of the fuel stored in the fuel tank changes. Switching from the second execution mode of combustion control to the first execution mode according to the estimated cetane number is prohibited. As a result, after the occurrence of misfire has temporarily subsided with the switching of the execution mode of the combustion control to the second execution mode, the execution mode of the combustion control is returned to the first execution mode causing the occurrence of misfire, thereby again. A situation in which a misfire occurs is avoided.

Therefore, according to the above apparatus, it is possible to suitably suppress the occurrence of misfire in the internal combustion engine.

In one aspect of the present invention, the estimation unit estimates which region of the plurality of cetane number regions the cetane number of the fuel supplied to the internal combustion engine belongs to, and the first control unit estimates the cetane number estimated by the estimation unit. The combustion control is executed in the first execution mode corresponding to the region, and the second control unit executes the combustion control in the second execution mode corresponding to the region on the cetane number side lower than the cetane number region estimated by the estimation unit.

In one aspect of the present invention, the estimation unit performs auxiliary injection for performing fuel injection for estimating the cetane number of fuel separately from basic injection control in which fuel injection is performed in an amount corresponding to the operating state of the internal combustion engine. While executing the control, an index value of the engine torque generated along with the execution of the auxiliary injection control is detected, and the detected index value is stored as the estimated cetane number.

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 flag operation processing. The flowchart which shows the execution procedure of a cetane number area | region specific process. The timing chart which shows an example of the execution aspect of a cetane number area | region specific process.

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

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. As the internal combustion engine 11, one having a plurality of (four [# 1 to # 4] in the present embodiment) cylinders 16 is employed. In the internal combustion engine 11, a direct injection type fuel injection valve 20 that directly injects fuel into the cylinder 16, in this embodiment, diesel fuel, is attached to 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.

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.

The fuel injection valve 20 is integrally attached with a pressure sensor 41 that outputs a signal corresponding to the fuel pressure PQ inside the introduction passage 27. 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. Further, a vehicle speed sensor 44 for detecting the traveling speed of the vehicle 10, a clutch switch 45 for detecting whether or not the clutch operating member is operated, and the amount of fuel stored in the fuel tank 32 (the amount of stored fuel) A stockpiling amount sensor 46 for detecting SP) is provided. In addition, an operation switch 47 that is turned on when the operation of the internal combustion engine 11 is started and turned off when the operation is stopped is also provided.

Further, as a peripheral device 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, a first control unit, a second control unit, a misfire determination unit, a replenishment determination unit, and a prohibition unit. The electronic control unit 40 captures output signals of various sensors and performs various types based on the output signals. And various controls relating to the operation of the internal combustion engine 11 such as drive control (fuel injection control) of the fuel injection valve 20 are executed according to the calculation result.

The fuel injection control of this embodiment is basically executed as follows.

First, a control target value (required injection amount TAU) for the fuel injection amount for operation of 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 present embodiment, the drive control of each fuel injection valve 20 based on the required injection timing Tst and the required injection time Ttm functions as equivalent to the basic injection control.

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

In the fuel injection control of the present embodiment, three regions are set, a region where the cetane number of the fuel is low (low cetane number region), a medium region (medium cetane number region), and a high region (high cetane number region). At the same time, 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 of the fuel injection valve 20 and the change over time. 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 according to the operating state of the internal combustion engine 11, the fuel injection is performed based on the fuel pressure PQ detected by the pressure sensor 41. A correction process for forming the 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 fuel injection execution, 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, the procedure for forming the fuel pressure fluctuation mode (in this embodiment, the 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, a timing at which the valve opening operation of the fuel injection valve 20 (specifically, movement of the needle valve 22 toward the valve opening side) is started (valve opening operation start timing Tos), fuel When the 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 is closed (specifically, the needle valve 22 The timing at which the movement toward the valve closing side is completed (valve closing operation completion timing Tce) is detected.

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. 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.

Also, the first-order differential value of the fuel pressure PQ during 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.

Furthermore, the intersection C between the tangent line L1 and the tangent line L2 is calculated, and the difference (virtual pressure drop ΔP [= Pac−PQ]) between the fuel pressure PQ and the operating pressure Pac at the intersection C 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 at which the virtual maximum fuel injection rate VRt is reached at the same time 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, a processing procedure of correcting (controlling) various control target values for 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, this process is temporarily terminated.

When the fuel injection control is executed, 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. The 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.

Also, 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 Tst 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 required injection time Ttm is corrected, the deviation between the actual operating characteristics of the fuel injection valve 20 and the basic operating characteristics (the operating characteristics of the fuel injection valve 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 this embodiment, control (index value detection processing) for detecting the cetane number index value of the fuel to be used 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 as the fuel burns increases. In the estimation control of this 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 above 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 above 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 uses 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]). Executed. Similarly, the correction terms K1 and K2 used in the present processing are also set to predetermined ones of the fuel injection valves 20 (in this embodiment, the fuel injection valves 20 attached to the cylinder 16 [# 1]). Correspondingly calculated values are used. In the present embodiment, the drive control of the fuel injection valve 20 based on the target injection timing TQst and the target injection time TQtm by the process of step S203 functions as equivalent to the auxiliary injection control.

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 engine rotational speed NE are detected several times before (in this embodiment, three times). A difference ΔNE (= NE−NEi) with respect to the engine speed NEi detected before the rotation 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. 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.

Further, in the present embodiment, misfire determination processing for determining whether or not misfire has occurred in the internal combustion engine 11 is executed. In this misfire determination process, first, in the combustion stroke of each cylinder of the internal combustion engine 11, a time T required for the crankshaft 12 to rotate 30 ° CA starting from the compression top dead center is detected. Then, a difference ΔT (= T−Ti) between this time T and the same time (Ti) detected last time is calculated. Then, it is determined that misfire has occurred when the difference ΔT exceeds a predetermined threshold.

In the present embodiment, when a misfire has occurred despite the execution of fuel injection control in accordance with the cetane number region stored in the electronic control unit 40, the cetane number region stored at this time. The fuel injection control is executed in an execution manner corresponding to a lower cetane number region. Thereby, when misfire occurs in the internal combustion engine 11, the execution mode of the fuel injection control is an execution mode corresponding to the cetane number region stored in the electronic control unit 40, that is, the execution mode that has caused the misfire. The first execution mode is switched to the execution mode (second execution mode) corresponding to the low cetane number fuel. Therefore, it is possible to execute the fuel injection control on the assumption that the ignition delay is longer than before the change of the execution mode, and it is possible to improve the combustion state of the fuel. Therefore, even if a misfire occurs during the execution of the fuel injection control in the first execution mode, the subsequent misfire can be suppressed.

By the way, when the occurrence of misfire in the internal combustion engine 11 is suppressed by switching the execution mode of the fuel injection control, the return from the second execution mode of the fuel injection control to the original first execution mode is performed at an appropriate timing thereafter. Failure to do so may lead to the following inconveniences. That is, once the fuel injection control is switched to the second execution mode in association with the occurrence of misfire in the internal combustion engine 11, when the fuel injection control is immediately returned to the first execution mode before the switching because the misfire does not occur, Since the operating state of the internal combustion engine 11 returns to the original state, there is a high possibility that misfire will occur again.

Therefore, in the present embodiment, the fuel supply determination process for determining whether or not fuel is supplied to the fuel tank 32 is executed, and it is determined that fuel supply is performed through the fuel supply determination process when the fuel injection control is performed in the second execution mode. In the meantime, switching from the second execution mode of the fuel injection control to the first execution mode is prohibited.

Thereby, after the execution mode of the fuel injection control is once switched to the second execution mode, unless the fuel tank 32 is refueled, that is, the cetane number of the fuel stored in the fuel tank 32. As long as does not change, switching from the second execution mode to the first execution mode for fuel injection control is prohibited. Therefore, after the misfire occurrence has temporarily subsided with the switching to the second execution mode of the fuel injection control, the misfire occurs again by returning the execution mode of the fuel injection control to the first execution mode causing the misfire occurrence. Can be avoided, and the occurrence of misfire in the internal combustion engine 11 can be suitably suppressed.

Hereinafter, the execution procedure of the processing related to switching of the execution mode of such fuel injection control will be described in detail.

Here, first, a process (flag operation process) for operating a refueling flag for determining whether or not fuel has been supplied to the fuel tank 32 and a misfire detection flag for determining whether or not misfiring has occurred will be described.

Fig. 8 shows the specific execution procedure of the flag operation 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, when it is determined that misfire has occurred through the misfire determination process described above (step S301: YES), the misfire detection flag is turned on (step S302).

The refueling flag is turned on when it is determined that the fuel tank 32 is refueled through the refueling determination process.

This refueling determination process is executed based on the following idea. In this embodiment, the reserve fuel amount SP detected by the reserve amount sensor 46 when the operation switch 47 is turned off is the amount of fuel stored in the fuel tank 32 at the start of fuel supply (the reserve amount V1 before supply). ) Is stored in the electronic control unit 40. Further, the stored fuel amount SP detected by the stored amount sensor 46 when the operation switch 47 is turned on is used as the amount of fuel stored in the fuel tank 32 after refueling (replenished stock amount VP). Then, when the operation switch 47 is turned on, the amount of fuel replenished to the fuel tank 32 (fuel replenishment amount V2 [= VP−V1]) and the stock amount change from the pre-replenishment stock amount V1 and the post-supplement stock amount VP The rate RP (= VP / V1) is calculated respectively. When the fuel supply amount V2 is greater than or equal to a predetermined amount, or when the stockpiling amount change rate RP is greater than or equal to a predetermined value, it is determined that fuel supply has been performed.

When the fuel tank 32 is refueled and the refueling flag is turned on (step S303: YES), the misfire detection flag is turned off (step S304), and then the refueling flag is turned off (step S304). Step S305).

As described above, in the present embodiment, the misfire detection flag is turned on when a misfire occurs in the internal combustion engine 11 and is turned off when fuel is supplied to the fuel tank 32 thereafter. Is called.

In the present embodiment, the execution mode of the fuel injection control, specifically the specific mode of the cetane number region of the fuel, is switched according to the operation state of the misfire detection flag.

Hereinafter, the execution procedure of the process for specifying the cetane number region of fuel (cetane number region specifying process) will be described.

Figure 9 shows the execution procedure of the cetane number area identification process. The 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, first, it is determined whether or not the misfire detection flag is turned off (step S401). When the misfire flag is turned off (step S401: YES), it is stored in the electronic control unit 40 every time the rotational fluctuation amount ΣΔNE is calculated, assuming that no misfire has occurred in the internal combustion engine 11 at this time. A process for updating the cetane number area is executed. Specifically, when the rotational fluctuation amount ΣΔNE is newly calculated and stored between the previous execution of this process and the current execution (step S402: YES), cetane is set based on the rotational fluctuation amount ΣΔNE. A valence area is specified and stored in the electronic control unit 40 (step S403). In this case, the fuel injection control is executed in the first execution mode corresponding to the cetane number region specified and stored based on the rotational fluctuation amount ΣΔNE.

Thereafter, when this process is repeatedly executed and the misfire detection flag is turned on (step S401: NO), it is determined that a misfire has occurred between the previous execution of this process and the current execution (step S401). (S404: YES), the cetane number region stored in the electronic control unit 40 is changed to a region on the low cetane number side by one step (step S406). Specifically, when the high cetane number region is stored in the electronic control unit 40, the medium cetane number region is changed to be stored in the electronic control unit 40, and the medium cetane number region is stored in the electronic control unit 40. Sometimes, the low cetane number region is changed to be stored in the electronic control unit 40. In this case, the fuel injection control is executed in the second execution mode corresponding to the cetane number region lower than the cetane number region stored in the electronic control unit 40 at this time. However, when the low cetane number region is stored in the electronic control unit 40 (step S405: YES), the cetane number region is changed because it cannot be changed to a lower cetane number side region and stored. Is not performed (the process of step S406 is jumped).

In this process, once the cetane number area is changed to the low cetane number area and then it is determined again that misfire has occurred through the misfire determination process (step S404: YES), it is stored in the electronic control unit 40. The existing cetane number region is further changed to a region on the low cetane number side by one step (step S406). Specifically, once the cetane number region is changed from the high cetane number region to the medium cetane number region, if it is determined again that misfire has occurred through the misfire determination process, the medium cetane number region is changed to the low cetane number region. .

Thereafter, when this process is repeatedly executed and the misfire detection flag is turned off (step S401: YES), the cetane number region is specified based on the rotational fluctuation amount ΣΔNE every time the rotational fluctuation amount ΣΔNE is calculated. The storing process is executed (step S402 and step S403). That is, in this case, assuming that the fuel tank 32 has been refueled with the occurrence of misfire in the internal combustion engine 11, switching to the fuel injection control in the first execution mode based on the rotational fluctuation amount ΣΔNE is permitted. Is done.

Hereinafter, the effect of executing the cetane number region specifying process will be described.

FIG. 10 shows an example of an execution mode of the cetane number region specifying process.

In the example shown in FIG. 10, before the time t11, the misfire detection flag is turned off because no misfire has occurred in the internal combustion engine 11, and the refueling flag is turned off. Further, since fuel with a relatively high cetane number is stored in the fuel tank 32, a high cetane number region is specified based on the rotational fluctuation amount ΣΔNE and stored in the electronic control unit 40.

When it is determined that misfire has occurred through the misfire determination process at time t11, the misfire detection flag is turned on, and the cetane number region is changed to a region on the low cetane number side (medium cetane number region) by one step. The Thereby, the execution mode of the fuel injection control is switched from the first execution mode based on the rotational fluctuation amount ΣΔNE to the second execution mode commensurate with the low cetane number fuel.

Thereafter, even if the operation switch 47 is turned off to stop the operation of the internal combustion engine 11 (time t12, t14) or the operation switch 47 is turned on to start the operation (time t13), the fuel tank As long as the fuel supply to 32 is not performed, the misfire detection flag is maintained in the ON state. Therefore, at this time, the cetane number region is not changed and is maintained in the medium cetane number region. Accordingly, switching from the second execution mode of the fuel injection control to the first execution mode is prohibited.

When the fuel tank 32 is refueled while the operation switch 47 is turned off (time t14 to t15), the refueling flag is turned on at the timing when the operation switch 47 is turned on thereafter (time t15). At the same time, the misfire detection flag is turned off. Therefore, thereafter, switching to the fuel injection control in the first execution mode based on the rotational fluctuation amount ΣΔNE is permitted.

At the subsequent time t16, when the rotational fluctuation amount ΣΔNE is detected and stored, the cetane number region is specified and stored based on the rotational fluctuation amount ΣΔNE. Specifically, a high cetane number region is specified based on the rotational fluctuation amount ΣΔNE and stored in the electronic control unit 40. Thereafter, the fuel injection control in the first execution mode based on the rotational fluctuation amount ΣΔNE is executed.

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

(1) From the second execution mode of the fuel injection control to the first execution mode until it is determined through the fuel supply determination process that there is fuel replenishment during execution of the fuel injection control in the second execution mode commensurate with the low cetane number fuel. Switching to is prohibited. Therefore, after the misfire occurrence has temporarily subsided with the switching to the second execution mode of the fuel injection control, the misfire occurs again by returning the execution mode of the fuel injection control to the first execution mode causing the misfire occurrence. Can be avoided, and the occurrence of misfire in the internal combustion engine 11 can be suitably suppressed.

Note that the above embodiment may be modified as follows.

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 embodiment described above is a device for determining which of the two cetane number regions divided by the fuel cetane number index value (rotational fluctuation amount ΣΔNE) or four or more cetane numbers. The present invention can also be applied to a device that determines which area of the area the structure is changed as appropriate.

-As control for changing the execution mode according to the cetane number region stored in the electronic control unit 40, instead of or in addition to adopting control for setting the required injection timing Tst, EGR control or pilot injection Control or the like may be employed. The point is that the combustion control related to the combustion of fuel in the internal combustion engine 11, in other words, the combustion control for adjusting the combustion state of the fuel in the internal combustion engine 11, is adopted as the control for changing the execution mode according to the cetane number region. be able to. In an apparatus that employs EGR control as such combustion control, the EGR control may be executed so that the EGR amount decreases as it is in the low cetane number region. Further, in an apparatus that employs pilot injection control as combustion control, pilot injection control may be executed so that the pilot injection amount increases, for example, when the region is on the low cetane number side.

-The control apparatus concerning the said embodiment determines the execution aspect of fuel-injection control according to the rotation fluctuation amount (SIGMA) ΔNE itself, without specifying a cetane number area | region based on rotation fluctuation amount (SIGMA) ΔNE memorize | stored in the electronic control unit 40. The present invention can also be applied to the apparatus after changing its configuration as appropriate. In such an apparatus, for example, the rotational fluctuation amount ΣΔNE stored in the electronic control unit 40 when the misfire occurrence determination is determined through the misfire determination process is corrected by a predetermined amount, and thereafter the fuel tank 32 is corrected. Until the fuel is refueled, the cancellation of the reduction correction of the rotation fluctuation amount ΣΔNE may be prohibited.

The control device according to the above embodiment estimates the cetane number of the fuel itself based on the rotational fluctuation amount ΣΔNE stored in the electronic control unit 40 and executes the fuel injection control in an execution mode corresponding to the estimated cetane number. The present invention can also be applied to an apparatus that changes the configuration as appropriate. In such an apparatus, for example, when it is determined that misfire has occurred through misfire determination processing, the estimated cetane number stored in the electronic control unit 40 is corrected to a value on the cetane number side lower by a predetermined value, Thereafter, cancellation of the correction of the estimated cetane number may be prohibited until the fuel tank 32 is refueled.

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, for example, a type of fuel injection valve driven by an electromagnetic actuator provided with 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 lockup clutch is incorporated as a torque converter, [Condition 4] that the lockup clutch is not engaged is newly set and the [Condition 4] 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 (auxiliary fuel injection) for estimating the cetane number, and estimates the cetane number of the fuel supplied to the internal combustion engine 11 and responds to the estimated cetane number. Any device that performs combustion control in an execution mode can be applied. Examples of such a device include the following devices. That is, first, when the fuel injection for the operation of the internal combustion engine is executed when the predetermined execution condition is satisfied, the pressure in the cylinder (in-cylinder pressure) of the internal combustion engine is detected by the in-cylinder pressure sensor. 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, an average value of the calculated ignition delay time is calculated, and a cetane number index value is calculated based on the average value. And combustion control is performed in the execution mode according to this cetane number index value.

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 ... Vehicle speed sensor, 45 ... Clutch switch, 46 ... Reserve amount sensor, 47 ... Operation switch.

Claims

An estimation unit for estimating a cetane number of fuel supplied to the internal combustion engine;
A first control unit that executes combustion control related to fuel combustion in a first execution mode according to the estimated cetane number estimated by the estimation unit;
A misfire determination unit that determines the presence or absence of misfire occurrence in the internal combustion engine;
A second control unit that executes the combustion control in a second execution mode according to fuel having a cetane number lower than the estimated cetane number estimated by the estimation unit when the misfire determination unit determines that misfire has occurred;
A replenishment determination unit that determines whether or not fuel is supplied to the fuel tank;
A prohibition unit for prohibiting switching from the second execution mode to the first execution mode until the replenishment determination unit determines that there is fuel replenishment during execution of the combustion control in the second execution mode; A control device for an internal combustion engine.
The control apparatus for an internal combustion engine according to claim 1,
The estimation unit estimates which region of the plurality of cetane number regions the cetane number of the fuel supplied to the internal combustion engine belongs to,
The first control unit executes the combustion control in the first execution mode according to the cetane number region estimated by the estimation unit,
The control device for an internal combustion engine, wherein the second control unit executes the combustion control in the second execution mode corresponding to a region on the cetane number side lower than the cetane number region estimated by the estimation unit.
The control apparatus for an internal combustion engine according to claim 1 or 2,
The estimation unit executes auxiliary injection control for performing fuel injection for estimating the cetane number of the fuel, separately from basic injection control in which fuel injection is performed in an amount corresponding to an operating state of the internal combustion engine. A control device for an internal combustion engine, wherein an index value of engine torque generated with the execution of the auxiliary injection control is detected and the detected index value is stored as the estimated cetane number.