JP2009209860A - Control device for direct fuel injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of combustion by determining deterioration of combustion due to a change of the fuel injection state even in the case wherein the fuel injection quantity is not changed by deposit. <P>SOLUTION: Ignition time is advanced by a set quantity in an operating condition, in which burning condition is determined (S3), and a check whether a knocking margin is reduced or not is done (S4), and in the case wherein the knocking margin is reduced, the deposit eliminating treatment is carried out (S5), and ignition time is advanced again (S6). A check whether the knocking margin is improved or not is done (S7), and in the case wherein the knocking margin is improved, it is determined that the cause of deterioration of combustion is a change of the fuel injection state by deposit (S8), and in the case wherein the knocking margin is not improved, it is determined that the cause of deterioration of combustion is deterioration of particulate characteristics of the injected fuel outside an allowable range by abnormality of an injector (S9). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control apparatus for an in-cylinder fuel injection engine that injects fuel from an injector into a cylinder and burns an air-fuel mixture in the cylinder by spark ignition.

  In an in-cylinder fuel injection engine that directly injects fuel into a cylinder, the tip of the injector that injects fuel into the cylinder is exposed to combustion gas, so that the temperature at the tip of the injector rises to the vicinity of the fuel injection hole. There is a problem that carbonized components in fuel such as gasoline are easily generated as deposits.

  When this deposit accumulates, not only the fuel injection hole is narrowed and the injection amount is reduced, but also the spray characteristics are deteriorated, the mixture distribution in the cylinder is deteriorated, and the combustion is deteriorated. For this reason, conventionally, various techniques for preventing the deterioration of combustion due to the influence of deposit have been proposed.

  For example, Patent Document 1 discloses a nozzle of a fuel injection valve (injector) by increasing a fuel injection pressure when an injection pulse width during air-fuel ratio feedback exceeds a predetermined value with respect to an initial set value. There has been proposed a technique for increasing the penetration force of the fuel in the part and removing the deposit.

Further, Patent Document 2 discloses that a fuel injection valve and / or a fuel injection valve and / or a fuel injection valve and / or Techniques have been proposed for detecting the presence or absence of deposits on the inside of a cylinder.
JP 10-339196 A Japanese Patent Laid-Open No. 2004-22560

  However, in Patent Document 1, deposit accumulation is detected based on a change in the fuel injection pulse width. Therefore, the deposit is effective only until the deposit is narrowed, and the deposit narrows the fuel injector. It is difficult to cope with the case where the spray shape changes at least, and the combustion deteriorates due to the change in the spray shape. Moreover, in patent document 2, it is effective only for the lean burn engine in which the change of the spray shape due to the deposit greatly affects the output fluctuation, and the application range is limited.

  The present invention has been made in view of the above circumstances, and even in the case where the fuel injection amount does not change due to deposit, the cylinder fuel injection engine that can determine the deterioration of combustion due to the change in fuel spray shape and prevent the deterioration of combustion. It aims to provide a control device.

  In order to achieve the above object, a control device for an in-cylinder fuel injection engine according to the present invention is a control device for an in-cylinder fuel injection engine that injects fuel from an injector into a cylinder and burns an air-fuel mixture in the cylinder by spark ignition. The set ignition timing set corresponding to the driving state is controlled to the advance side under a predetermined driving condition, and the difference between the ignition timing when knocking occurs and the set ignition timing is calculated as the knock margin A knock margin calculation unit and a deposit removal processing unit that executes a process of removing deposits near the fuel injection holes of the injector when the knock margin decreases.

  Further, the control device for an in-cylinder fuel injection engine according to the present invention is a control device for an in-cylinder fuel injection engine that injects fuel from an injector into a cylinder and burns an air-fuel mixture in the cylinder by spark ignition. A knock learning value monitor unit for monitoring the knock learning value of the ignition timing based on the time series, and when the monitoring result of the knock learning value is changing to the retard side, the deposit near the injection hole of the injector is removed And a deposit removal processing unit for executing the processing.

  According to the present invention, even when the fuel injection amount does not change due to deposit, it is possible to determine the deterioration of combustion due to the change of the fuel spray shape, and it is possible to prevent the deterioration of combustion.

be able to.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 relate to a first embodiment of the present invention, FIG. 1 is a schematic diagram showing the overall configuration of an in-cylinder fuel injection engine, FIG. 2 is a functional block diagram relating to deposit determination processing, and FIG. It is a flowchart of a routine.

  In FIG. 1, reference numeral 1 denotes an in-cylinder fuel injection engine (hereinafter simply referred to as “engine”) in which fuel is directly injected into a cylinder and an air-fuel mixture is burned by spark ignition. In the cylinder 1a of the engine 1, a piston 4 connected to the crankshaft 3 via a connecting rod 2 is disposed so as to reciprocate. A combustion chamber 5 is formed in the upper portion of the piston 4, and an intake port 6 that is opened and closed by an intake valve (not shown) and an exhaust valve (not shown) are opened and closed on the inclined roof surface of the combustion chamber 5. An exhaust port 7 is formed.

  A spark plug 8 is attached to a substantially central roof surface between the intake port 6 and the exhaust port 7 of the combustion chamber 5, and a discharge electrode of the spark plug 8 faces the combustion chamber 5. An injector 9 that sprays high-pressure fuel directly into the combustion chamber 5 is disposed on the inclined roof surface on the intake side of the combustion chamber 5. The injector 9 communicates with a fuel delivery pipe 11 to which high pressure fuel is supplied from a high pressure fuel pump 10.

  In addition, as a configuration of an intake system that sucks air into the combustion chamber 5 of the engine 1, an intake port 6 is communicated with an intake manifold 12, and the amount of air sucked into the intake manifold 12 via an air cleaner (not shown). A throttle valve 13 for adjusting the above is interposed. An air chamber 14 is connected to the downstream side of the throttle valve 13. The throttle valve 13 is an electronically controlled throttle valve that is driven by an actuator (not shown) such as an electric motor, and its opening (throttle opening) is controlled by an electronic control unit (ECU) 50.

  On the other hand, as an exhaust system configuration for exhausting exhaust gas remaining in the combustion chamber 5 of the engine 1, an exhaust port 7 is communicated with an exhaust manifold 15, and a catalytic converter 16 for purifying exhaust gas is connected to the exhaust manifold 15. Has been. The exhaust manifold 15 is communicated with the air chamber 14 of the intake manifold 12 via an EGR valve (exhaust gas recirculation valve) 17. The EGR valve 17 is driven by, for example, a step motor or the like, and its opening degree (EGR opening degree) is controlled by the ECU 50 similarly to the throttle valve 13.

  Further, the engine 1 is provided with various sensors for detecting the operating state. Typically, it is disposed in the vicinity of the outer periphery of a crank rotor 3a that rotates integrally with the crankshaft 3, a crank angle sensor 20 that detects the crank angle from the rotation of the crank rotor 3a, and a cam mechanism 18 that drives the intake valve to open and close. The cam angle sensor 21 detects the cam angle from the rotational displacement of the cam, and is disposed immediately downstream of the air cleaner (not shown) connected to the upstream side of the throttle valve 13 to reduce the intake air amount. An intake air amount sensor 22 to be detected, a throttle opening sensor 23 to detect the throttle opening, a water jacket formed around the combustion chamber 5, etc. There is a water temperature sensor 24 for detecting the temperature.

  Further, as sensors, an accelerator opening sensor 25 that is disposed in the vicinity of the accelerator pedal and detects the accelerator opening from the amount of depression of the accelerator pedal, the fuel delivery pipe 11, and the fuel pressure in the fuel delivery pipe 11 is provided. An injection pressure sensor 26 for detecting (injection pressure from the injector 9) and a knock sensor 27 for detecting knocking of the engine 1 are provided. Signals from these various sensors are sent to the ECU 50 for processing, and the operating state Is detected.

  The ECU 50 is configured around a microcomputer including a CPU, ROM, RAM, I / O interface, and the like, and includes peripheral circuits such as an A / D converter, a timer, a counter, and various logic circuits. The ECU 50 receives detection signals from the above-described various sensors, and a plurality of other ECUs connected to an in-vehicle network (not shown) based on a communication protocol such as CAN (Controller Area Network), for example, Various control information is input by data communication with a plurality of other ECUs such as a transmission ECU for controlling the transmission and a brake ECU for controlling the brake.

  The ECU 50 executes engine control such as fuel injection control, ignition timing control, and EGR control based on signals from various sensors that detect the engine operating state and various control information input via the in-vehicle network. In this engine control, the ECU 50 is based on the engine speed based on the signal from the crank angle sensor 20 and the required load based on the signal from the accelerator opening sensor 25, and the fuel injection amount, fuel injection timing, ignition timing, etc. The control amount is calculated by referring to a map or the like, and control amounts such as the intake air amount, fuel injection amount, ignition timing, etc., which are optimum for realizing the required load, are set. Then, a drive signal corresponding to these control amounts is output, fuel is directly injected from the injector 9 into the cylinder, and the opening of the throttle valve 13 is controlled via the actuator, and the spark plug 8 is discharged at an optimal timing. By generating spark discharge at the electrode and igniting the air-fuel mixture in the cylinder, torque is ensured while reducing exhaust gas emission, and occurrence of knocking is avoided.

  At this time, the ECU 50 executes a process of determining deposit adhesion under a predetermined operation state in order to prevent combustion deterioration due to the deposit effect around the fuel injection hole of the injector 9. The deterioration of combustion due to the adhesion of the deposit is caused by monitoring parameters such as a change in the drive pulse width of the injector 9, an air-fuel ratio deviation, and output fluctuations (engine revolution fluctuations and torque fluctuations) when the amount of injected fuel decreases due to the deposits. Although it can be determined, it is difficult to determine the deterioration of combustion due to the change in the spray shape without the change in the fuel amount from these parameters.

  Therefore, the ECU 50 monitors the occurrence of knocking due to the deterioration of the in-cylinder cooling effect of the in-cylinder fuel injection engine, thereby preventing the deterioration of combustion due to the change in the spray shape caused by the deposit. That is, in an internal combustion engine in which the injected fuel is mixed with the intake air and combusted, when the injected fuel evaporates in the intake air, the intake air is cooled by the latent heat of vaporization of the injected fuel, and the density of the intake air increases. . In particular, in-cylinder fuel injection engines have a large in-cylinder cooling effect in which the air filled in the cylinder is cooled by the latent heat of vaporization of the fuel injected into the cylinder, and the ignition timing is also set to a value that takes this cooling effect into account. Has been.

  However, if deposits accumulate around the injection holes of the injector and the spray shape changes and the fuel is not dispersed efficiently in the cylinder, the mixing with the air becomes non-uniform and the cooling effect in the cylinder is relatively Knocking is likely to occur at the ignition timing considering the in-cylinder cooling effect when there is no deposit adherence. Therefore, the ECU 50 estimates the deposit accumulation based on the output of the knock sensor 27 and executes a process for reliably preventing deterioration of combustion.

  For this reason, the ECU 50 includes a knock margin calculation unit 51, a deposit removal processing unit 52, and an abnormality diagnosis unit 53 as functions of each means related to deposit determination, as shown in FIG.

  The knock margin calculation unit 51 advances the set ignition timing set corresponding to the operation state based on the engine speed and the load such as the fuel injection amount and the intake air amount under a predetermined operation condition, A knock margin is calculated based on the detection result of knocking. The knock margin is the difference between the ignition timing when knocking occurs and the set ignition timing corresponding to the operating state, and is an index showing how much margin the current combustion state has before the combustion state where knocking occurs It becomes.

  The deposit removal processing unit 52 reads the knock margin calculated by the knock margin calculation unit 51, and when the knock margin decreases due to the ignition timing advance under a predetermined operating condition, the deposit removal processing unit 52 reads the injected fuel from the injector 9. A process of removing deposits in the vicinity of the fuel injection hole of the injector 9 is executed based on the judgment that the spray shape is deteriorated and the combustion is deteriorated. This deposit removal process is executed, for example, alone or in combination with conditions such as increasing the fuel injection pressure of the injector 9, increasing the fuel injection amount, and changing the fuel injection timing.

  The abnormality diagnosis unit 53 examines the change in the knock margin before and after the deposit removal process, and when the knock margin decreased due to the ignition timing advance does not increase even after the deposit removal process is executed, the valve oil tightness of the injector 9 is poor. It is determined that an abnormality such as

  More specifically, the processing related to deposit determination is executed by a deposit determination routine shown in the flowchart of FIG. Hereinafter, the deposit determination routine of FIG. 3 will be described.

  First, in the first step S1, it is checked whether or not the current operation state is under the operation condition for determining the combustion state. The operating condition for determining the combustion state is that the normal ignition timing corresponding to the operating state is gradually advanced, and the knock margin, which is the difference between the ignition timing when knocking occurs and the normal ignition timing, is determined. This is an operating condition to be examined, and is a condition that is set at the time of driving without deteriorating the drive feel, for example, at the time of steady driving in the middle load range. If the combustion condition determination is already in the operating condition, the process jumps from step S1 to step S3. If the combustion condition determination is not in the operating condition, the operation condition such as the ignition timing advance amount is set in step S2. Then, the process proceeds to step S3.

  In step S3, the current ignition timing is advanced by a set amount, and in step S4, it is checked whether or not the knock margin is reduced based on the signal from the knock sensor 27. As a result, if the knock margin has not decreased, the routine is exited. If the knock margin has decreased, it is determined that the combustion state is likely to be knocking, and the deposit removal process is performed in step S5. Execute.

  This deposit removal process is a process executed in preparation for the case where deposits are attached around the injection hole of the injector 9 as a cause of combustion deterioration. For example, the fuel pressure and the injection timing in the fuel delivery pipe 11 are changed. Then, processing such as increasing the injection pressure from the injector 9 or increasing the in-cylinder combustion temperature by increasing the fuel injection amount or changing the injection timing is performed. By this deposit removal process, when deposits are attached to the injector 9, the deposits are effectively removed by blowing the deposits at high pressure or incinerating the deposits by raising the combustion temperature of the air-fuel mixture in the vicinity of the injection holes. can do.

  After performing the deposit removal process in step S5, the process proceeds to step S6, and the ignition timing is advanced again. Next, it is checked in step S7 whether or not the knock margin has been improved by the deposit removal process (whether or not the reduced knock margin has increased). If the knock margin is improved by the deposit removal process, it is determined in step S8 that the cause of the deterioration of combustion is a change in the spray shape of the injected fuel due to the deposit, and the routine is exited.

  On the other hand, if the knock margin is not improved even after the deposit removal process is executed, the process proceeds from step S7 to step S9. In step S9, the cause of the deterioration of combustion is not due to deposit adhesion to the injector 9, but due to poor valve oil tightness of the injector 9 itself, a coarse particle size fuel is injected into the cylinder from the injector 9 into droplets, It is determined that the cause is that the atomization characteristics of the injected fuel deteriorated unacceptably, and the routine is exited.

  If it is determined that the valve oil-tight state of this injector is set poorly, it is determined that the valve oil-tightness is not a temporary failure due to the adhering of dust or the like and is a failure that does not recover. Abnormal processing such as turning on the lamp is performed.

  As described above, in the present embodiment, even when the deposit amount is not so small as to narrow the fuel injection hole of the injector, it is possible to determine the combustion deterioration due to the change in the fuel spray shape and remove the deposit. Thus, it is possible to always maintain a good combustion state and to contribute to the improvement of exhaust emission.

  Next, a second embodiment of the present invention will be described. 4 and 5 relate to a second embodiment of the present invention, FIG. 4 is a functional block diagram relating to deposit determination processing, and FIG. 5 is a flowchart of a deposit determination routine.

  In the second mode, the knock learning value of the ignition timing based on the detection result of knocking is monitored in time series to check the change in the combustion state. For this reason, in the second embodiment, as shown in FIG. 4, a knock learning value monitoring unit 55 for monitoring the knock learning value of the ignition timing based on the detection result of knocking in time series is added to the first embodiment. The deposit removal processing unit 52A and the abnormality diagnosing unit 53A are slightly changed in function.

  As is well known, in engine ignition timing control, when knocking occurs, knocking is avoided by retarding the ignition timing and suppressing engine output, depending on whether knocking occurs or not. In general, learning control for learning the advance angle and retard angle amount of the ignition timing is adopted. Therefore, by monitoring the time-series change of the ignition timing learning value (knock learning value) based on this knocking, the current combustion state can be grasped, and the knock learning value is retarded in time series. It can be determined that the combustion state is likely to cause knocking.

  Therefore, the deposit removal processing unit 52A determines that the combustion state has deteriorated when the knock learning value changes to the retard side in time series based on the monitoring result of the knock learning value, and the first A deposit removal process similar to that of the embodiment is executed.

  Abnormality diagnosis unit 53A checks whether or not the knock learning value that has changed to the retard side changes to the advance side by the deposit removal process and is improved, and when the knock learning value is improved, the cause of the combustion deterioration is When the knock learning value is not improved when it is determined that it is due to deposit, the injector 9 is broken if an abnormality such as a defective valve oil tightness occurs.

  Specifically, in the first step S11 of the deposit determination routine of FIG. 5, the knock learning value is monitored, and in step S12, it is determined whether or not the monitoring result of the knock learning value changes to the retard side in time series. Investigate. When the knock learning value does not change to the retard angle side, the routine exits from step S12, and when the knock learning value changes to the retard angle side, the combustion state deteriorates and knocking is likely to occur. The process proceeds to step S13.

  In step S13, as in the first embodiment, it is assumed that the cause of the deterioration of combustion is the deterioration of the spray shape due to the deposit adhering to the injector 9, and a process of removing the deposit is executed. Then, in step S14, the knock learning value is monitored again, and in step S15, whether or not the knock learning value has been improved by the deposit removal process (the knock learning value that has been changed to the retard side is advanced by the deposit removal process). To see if it has changed to the side).

  As a result, if the knock learning value is improved by the deposit removal process, it is determined in step S16 that the cause of the combustion deterioration is the change in the spray shape of the injected fuel due to the deposit, and the routine is exited. On the other hand, if the knock learning value is not improved even after the deposit removal process is executed, the process proceeds from step S15 to step S17, and the cause of the combustion deterioration is not due to deposit adhesion on the injector 9, but the injector 9 itself. Due to the poor valve oil tightness, it is determined that the fuel having a coarse particle diameter is injected into the cylinder from the injector 9 into droplets, and the atomization characteristics of the injected fuel are deteriorated unacceptably, and the routine is exited.

  In the second mode, not only the same effect as in the first mode is obtained, but also the time series change of the knock learning value is compared with the active determination control of the first mode in which the ignition timing is advanced to check the combustion state. Therefore, the determination process can be simplified and the determination can be performed without depending on the driving state.

The outline which shows the whole structure of the cylinder fuel-injection engine which concerns on 1st Embodiment of this invention. Same as above, functional block diagram related to deposit determination processing Same as above, deposit determination routine flow chart The functional block diagram which concerns on the 2nd Embodiment of this invention and which concerns on the deposit determination process Same as above, deposit determination routine flow chart

Explanation of symbols

1 Engine 9 Injector 27 Knock Sensor 50 Electronic Control Unit 51 Knock Margin Calculation Unit 52, 52A Deposit Removal Processing Unit 53, 53A Abnormality Diagnosis Unit 55 Knock Learning Value Monitor Unit

Claims (4)

In a control apparatus for an in-cylinder fuel injection engine that injects fuel from an injector into a cylinder and burns an air-fuel mixture in the cylinder by spark ignition,
A knock that calculates the difference between the ignition timing when knocking occurs and the set ignition timing as a knock margin by controlling the set ignition timing that is set according to the operating condition to the advanced side under predetermined operating conditions A margin calculation unit;
A control device for a cylinder fuel injection engine, comprising: a deposit removal processing unit that executes a process of removing deposits in the vicinity of the fuel injection hole of the injector when the knock margin decreases.   2. The control apparatus for an in-cylinder fuel injection engine according to claim 1, further comprising an abnormality diagnosing unit that diagnoses that the injector is abnormal when the knock margin does not increase after the deposit removal process. In a control apparatus for an in-cylinder fuel injection engine that injects fuel from an injector into a cylinder and burns an air-fuel mixture in the cylinder by spark ignition,
A knock learning value monitor unit for monitoring the knock learning value of the ignition timing based on the detection result of knocking in time series;
A cylinder removal fuel injection engine comprising: a deposit removal processing unit that performs a process of removing deposits in the vicinity of the injection hole of the injector when the monitoring result of the knock learning value changes to the retard side. Control device.   The in-cylinder fuel injection engine according to claim 3, further comprising an abnormality diagnosing unit that diagnoses that the injector is abnormal when the knock learning value does not change to the advance side after the deposit removal process. Control device.

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