JP2008050975A - Start control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide technology surely improving startability in an internal combustion engine executing auxiliary pre-injection before main-injection in cold start of the internal combustion engine. <P>SOLUTION: In the internal combustion engine executing pre-injection before main-injection in cold starting, a combustion condition based on pre-injection is detected independently from a combustion condition based on main-injection by detecting cylinder pressure before TDC (S102), and injection timing of pre-injection is advanced to improve combustion (S104) if combustion based on pre-injection is not sufficient (S103). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a start control device for an internal combustion engine that performs main injection for injecting fuel to be used for combustion and pre-injection for injecting secondary fuel prior to the start of the internal combustion engine. About.

  In an internal combustion engine, premixed combustion may be performed for the purpose of suppressing exhausted NOx and white smoke. In this premixed combustion, fuel is generally injected into a cylinder at a time earlier than the top dead center of the compression stroke, thereby forming a uniform premixed gas in the combustion chamber. In order to implement this premixed combustion, the compression ratio of the internal combustion engine is set low from the viewpoint of preventing premature ignition. Therefore, there is a strong demand for improvement in startability at the time of cold start of the internal combustion engine.

  Regarding the problem of improving the startability, a start control device has been conventionally known in which pre-injection is performed prior to main injection when starting an internal combustion engine. This is to increase the in-cylinder temperature and the pressure before the main injection by the combustion based on the pre-injection in order to smoothly perform the combustion after the TDC directly connected to the torque.

  In this connection, at the start of the internal combustion engine, the main injection is executed after a plurality of pre-injections, and the final pre-injection of the plurality of pre-injections is performed after 30 degrees before TDC. A technique has been proposed in which premixed combustion is performed by pre-injection performed at a relatively early time and diffusion combustion is performed by final pre-injection (see, for example, Patent Document 1).

However, in the above technique, the combustion based on the pre-injection and the main injection is a combustion that places importance on the connection between the TDC, and therefore the combustion by the pre-injection is too close to the TDC and the combustion becomes insufficient. There was a possibility that the sex would deteriorate. Further, in the state where the fuel by the pre-injection and the fuel by the main injection are burned in duplicate, the amount of pre-injection is large, which may cause smoke.
Japanese Patent Laid-Open No. 10-274086 JP 2005-48703 A JP 2001-227393 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to ensure startability more reliably with respect to an internal combustion engine in which pre-injection is executed auxiliaryly before main injection during cold start. It is to provide technology to improve.

  In order to achieve the above object, the present invention provides an internal combustion engine in which pre-injection is executed before main injection at a cold start, and the state of combustion based on pre-injection is the state of combustion based on main injection. If the combustion based on the pre-injection is detected independently and the pre-injection is insufficient, the greatest feature is to improve the combustion by advancing the injection timing of the pre-injection.

More specifically, main injection means for injecting main fuel to be burned into the cylinder of the internal combustion engine,
Pre-injection means for injecting secondary fuel prior to injection of main fuel by the main injection means;
Pre-combustion state detection means for detecting the combustion state based on the fuel injection of the pre-injection means independently of the combustion state based on the fuel injection of the main injection means;
Pre-startup injection timing changing means for changing the injection timing of fuel injection by the pre-injection means at the start of the internal combustion engine;
An internal combustion engine start control device comprising:
When the internal combustion engine is started, when the pre-combustion state detecting means detects that the combustion based on the fuel injection of the pre-injecting means is insufficient, the pre-start-up injection timing changing means performs the front injection time changing means. The timing of fuel injection by the injection means is advanced.

  Here, when the internal combustion engine is cold-started as described above, pre-injection that is a secondary injection may be performed before the main injection for main combustion. In this method, the in-cylinder temperature and pressure are increased in advance by combustion based on pre-injection, main injection is performed in that state, combustion based on main injection is performed smoothly, and startability is improved.

  Here, in the conventional control, emphasis was placed on ensuring ignitability and stability in the combustion of the main injection by continuously generating the combustion based on the pre-injection and the combustion based on the main injection. Then, the combustion based on the pre-injection is too close to TDC, and the combustion itself based on the pre-injection becomes insufficient, and as a result, it may be difficult to increase the engine speed smoothly. Further, when the combustion based on the pre-injection is close to TDC, the combustion based on the main injection is performed in a state where a large amount of fuel from the pre-injection remains, which may cause smoke.

  Therefore, in the present invention, a pre-combustion state detection means for detecting the combustion state based on the pre-injection independently of the combustion state based on the main injection is provided, and combustion based on the pre-injection is not detected by the pre-combustion state detection means. When it is detected that the state is sufficient, the injection timing of the pre-injection is advanced by the fuel injection timing changing means before starting.

  By doing so, it is possible to stabilize the combustion based on the pre-injection by gradually increasing the temperature by the combustion based on the pre-injection from the state where the in-cylinder pressure is lower, and the combustion based on the pre-injection can be sufficiently performed. As a result, the ignitability and stability of the main injection can be improved, and the engine speed at the cold start can be increased more smoothly. Therefore, the startability of the internal combustion engine can be improved.

  Here, the fact that the combustion based on the pre-injection is sufficiently performed means that the pre-injection timing is sufficiently early or the amount of the pre-injection is sufficiently large. This means that the in-cylinder temperature and the in-cylinder pressure can be increased to a degree sufficient to ensure the ignitability and stability of the main injection, starting early.

Further, in the present invention, when starting the internal combustion engine, it is further provided with a pre-startup injection amount changing means for changing the amount of fuel injection by the pre-injection means,
When the internal combustion engine is started, if it is detected by the pre-combustion state detection means that the combustion based on the fuel injection of the pre-injection means is insufficient, the pre-injection means changes by the pre-injection means at the start time. The fuel injection timing may be advanced, and the fuel injection amount by the pre-injection means may be increased by the pre-startup injection amount changing means.

  If it does so, the combustion by pre-injection will fully be performed, and as a result, the startability of an internal combustion engine can be improved more reliably.

Further, in the present invention, a main combustion state detection means for detecting the combustion state based on the fuel injection of the main injection means independently of the combustion state based on the fuel injection of the pre-injection means,
A startup main injection timing changing means for changing the injection timing of the fuel injection by the main injection means at the start of the internal combustion engine; and at the start of the internal combustion engine, the main combustion state detecting means When it is detected that combustion based on fuel injection is insufficient, the timing of fuel injection by the main injection means may be advanced by the start main injection timing changing means.

  That is, when it is detected by the main combustion state detection means that the combustion based on the main injection is insufficient, the main injection timing changing means at the start time advances the injection timing of the main injection. If it does so, main injection can be injected in the state where compression pressure is higher, and combustion based on main injection can be performed more certainly.

Further, in the present invention, at the time of starting the internal combustion engine, it further includes a starting main injection amount changing means for changing the amount of fuel injection by the main injection means,
When the internal combustion engine is started, when the main combustion state detection means detects that the combustion based on the fuel injection of the main injection means is insufficient, the main injection timing changing means at the start time causes the fuel injection by the main injection means. The timing may be advanced and the amount of fuel injection by the main injection means may be increased by the starting main injection amount changing means.

  If it does so, combustion by main injection will fully be performed, and, as a result, the startability of an internal combustion engine can be improved more reliably.

  The present invention further includes a fuel property detecting means for detecting the property of the fuel injected by the pre-injecting means, and the starting pre-injection timing changing means is detected by the pre-injecting means detected by the fuel property detecting means. When the cetane number of the fuel to be injected is larger than the reference value, the pre-startup injection timing changing means retards the timing of fuel injection by the pre-injection means, and when the cetane number is smaller than the reference value, The timing of fuel injection by the pre-injection means may be advanced.

  Here, if the fuel property of the fuel that is actually injected is different from the assumed fuel property when setting the fuel injection timing of the internal combustion engine, the fuel ignitability is different from the assumed condition. In some cases, combustion deteriorates with changes in fuel properties. Therefore, in the present invention, fuel property detecting means for detecting the property of the fuel is provided, and in particular, the injection timing is injected for the pre-injection that is difficult to establish an optimum atmosphere for combustion and is easily influenced by the property of the fuel. The correction was made according to the cetane number of the fuel.

  By doing so, the pre-injection can be sufficiently performed regardless of the properties of the fuel that is actually injected, and the startability of the internal combustion engine can be improved.

  Further, in the present invention, in addition to the above-described control for correcting the injection timing of the pre-injection according to the cetane number of the injected fuel, the pre-start-up injection amount changing means is detected by the fuel property detecting means. When the cetane number of the fuel injected by the injection means is larger than the reference value, the amount of fuel injection by the pre-injection means is decreased, and when the cetane number is smaller than the reference value, the fuel injection by the previous injection means is reduced. The amount may be increased.

  By doing so, the combustion based on the pre-injection can be performed more reliably regardless of the properties of the fuel that is actually injected, and the startability of the internal combustion engine can be improved more reliably.

  The means for solving the problems in the present invention can be used in combination as much as possible.

  In the present invention, the startability can be improved more reliably for the internal combustion engine in which the pre-injection is auxiliaryly executed before the main injection at the cold start.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine, an intake / exhaust system, and a control system to which the present invention is applied. An internal combustion engine 1 shown in FIG. 1 is a diesel engine having four cylinders 2.

  Each cylinder 2 of the internal combustion engine 1 is provided with a fuel injection valve 3 that directly injects fuel into the combustion chambers 2. The fuel to be injected from the fuel injection valve 3 is stored in the fuel tank 26 and is supplied to the fuel injection valve 3 via the common rail 4 by being pumped by the fuel pump 27.

  An intake manifold 8 is connected to the internal combustion engine 1, and each branch pipe of the intake manifold 8 is communicated with a combustion chamber of each cylinder 2 through an intake port. An intercooler 13 for cooling the gas flowing through the intake pipe 9 is provided upstream of the connection portion between the intake manifold 8 and the intake pipe 9. A compressor housing 6 in which a compressor of the centrifugal supercharger 10 that operates using exhaust energy as a drive source is provided upstream of the intercooler 13. A throttle valve 12 capable of changing the cross-sectional area of the intake pipe 9 is provided on the upstream side of the compressor housing 6 in the intake pipe 9. The throttle valve 12 is connected to an ECU 22 which will be described later via an electric wiring, and the flow rate of the intake air flowing through the intake pipe 9 can be adjusted by controlling the valve opening degree based on a control signal from the ECU 22. it can. Further upstream of the throttle valve 12, an air flow meter 24 for detecting the amount of intake air passing through the intake pipe 9 and an air cleaner 25 for removing dust floating in the fresh air are provided.

  On the other hand, an exhaust manifold 18 is connected to the internal combustion engine 1, and each branch pipe of the exhaust manifold 18 communicates with the combustion chamber of each cylinder 2 through an exhaust port. A turbine housing 7 in which the turbine of the centrifugal supercharger 10 is stored is connected to the exhaust manifold 18 via a collecting pipe 16. An exhaust pipe 19 is connected to an opening through which the exhaust of the turbine housing 7 flows out. The exhaust pipe 19 is provided with a filter 20 that collects particulate matter in the exhaust. An exhaust throttle valve 11 capable of changing the cross-sectional area of the exhaust pipe 19 is provided downstream of the filter 20. The exhaust pipe 19 is open to the atmosphere downstream of the exhaust throttle valve 11. The exhaust throttle valve 11 is connected to the ECU 22 via electrical wiring, and the flow rate of the exhaust gas flowing through the exhaust pipe 19 can be adjusted by controlling the valve opening degree based on a control signal from the ECU 22. .

  A portion of the exhaust pipe 19 downstream of the filter 20 and upstream of the exhaust throttle valve 11 and a portion of the intake pipe 9 upstream of the compressor housing 6 are communicated by a low pressure EGR passage 23. The low-pressure EGR passage 23 is provided with a low-pressure EGR cooler 14 that cools the exhaust gas flowing through the low-pressure EGR passage 23 and a low-pressure EGR valve 5 that can change the flow passage cross-sectional area of the low-pressure EGR passage 23. The low pressure EGR valve 5 is connected to the ECU 22 via an electric wiring, and the amount of exhaust flowing through the low pressure EGR passage 23 may be adjusted by controlling the valve opening degree based on a control signal from the ECU 22. it can.

On the other hand, the exhaust manifold 18 and the intake manifold 8 are communicated with each other by a high pressure EGR passage 15. The high-pressure EGR passage 15 is provided with a high-pressure EGR valve 21 that can change the flow path cross-sectional area of the high-pressure EGR passage 15. The high-pressure EGR valve 21 is connected to the ECU 22 via electric wiring, and the amount of exhaust flowing through the high-pressure EGR passage 15 can be adjusted by controlling the valve opening degree based on a control signal from the ECU 22. it can.

  The internal combustion engine 1 is also provided with an ECU 22 that is an electronic control computer that controls the internal combustion engine 1. The ECU 22 includes a ROM, a RAM, a CPU, an input port, an output port, and the like (not shown), and performs known control such as fuel injection according to the operation state of the internal combustion engine 1 detected by the various sensors and a request from the driver. At the same time, an opening degree command signal is output to the high pressure EGR valve 21, the low pressure EGR valve 5, the throttle valve 12, and the exhaust throttle valve 11.

  The fuel tank 26 has a fuel property sensor 30 for detecting the properties of the fuel, the internal combustion engine 1 has a water temperature sensor 31 for detecting the temperature of the cooling water, and an in-cylinder pressure sensor 32 for detecting the in-cylinder pressure of each cylinder 2. These output signals are input to the ECU 22.

  Here, the control at the start of the internal combustion engine 1 will be described. At the time of cold start of the internal combustion engine 1, since the atmosphere temperature in the combustion chamber is low and combustion is not stable, the pre-injection is executed prior to the main injection performed after TDC. By the combustion based on the pre-injection, the temperature and pressure in the cylinder 2 are increased before the main injection can be performed to improve the ignitability of the fuel related to the main injection, and the combustion based on the main injection is performed more smoothly. It is supposed to be.

  In this case, if the combustion based on the pre-injection is not sufficiently performed, the temperature and pressure in the cylinder cannot be increased as planned, and the combustion based on the main injection may not be performed smoothly. As a result, the startability of the internal combustion engine 1 may not be sufficiently improved. On the other hand, the start timing may be increased by delaying the injection timing of the pre-injection and maintaining the combustion based on the pre-injection and the combustion based on the main injection. If there is a lot of fuel due to, there is a risk that smoke will be generated. In addition, the fuel injection timing of the pre-injection is too close to TDC, and combustion based on the pre-injection may become insufficient.

  Therefore, in the present embodiment, the in-cylinder pressure sensor 32 detects combustion based on the pre-injection and combustion based on the main injection independently, and if any of the combustions is insufficient, it relates to insufficient combustion. Combustion was improved by changing the injection timing of the fuel injection.

  FIG. 2 shows an ideal change in in-cylinder pressure at the start. Ideally, the combustion based on the pre-injection is completed before the TDC, and the combustion based on the main injection is started after the TDC, as shown by the solid line in FIG. However, if the combustion based on the pre-injection is unnecessarily prolonged as shown by the broken line in FIG. 2, both the temperature and the pressure may not rise to the extent that the combustion based on the main injection is smoothly performed. was there. In addition, smoke may be generated as described above.

  Therefore, in this embodiment, the in-cylinder pressure at the time of combustion based on the pre-injection and at the time of combustion based on the main injection is detected independently. Then, the combustion is improved by advancing the fuel injection timing in the injection where the combustion is not sufficient.

  FIG. 3 shows a start-up combustion improvement routine in this embodiment. This routine is a program stored in the ROM of the ECU 22, and is a routine executed for each cylinder 2 at predetermined intervals while the internal combustion engine 1 is in operation.

When this routine is executed, it is first determined in S101 whether or not it is a cold start. Specifically, the cooling water temperature T is detected by the water temperature sensor 31, and it is determined that the cooling water temperature T is lower than a predetermined threshold value. If a negative determination is made here, it is determined that the internal combustion engine 1 has been warmed up and the improvement of combustion by this routine is unnecessary, and thus the process proceeds to S107. On the other hand, if a positive determination is made, the process proceeds to S102.

  In S102, the in-cylinder pressure is detected. Specifically, the detection is performed by reading the output signal of the in-cylinder pressure sensor 32 into the ECU 22. When the process of S102 ends, the process proceeds to S103.

  In S103, it is determined whether or not the combustion based on the pre-injection is sufficiently performed. Specifically, the determination is made based on whether or not the peak of the output of the in-cylinder pressure sensor 32 before TDC in each cylinder 2 is equal to or greater than P1, which is a threshold value for determining that combustion based on the previous injection is sufficiently performed. Here, when it is determined that the combustion based on the pre-injection is not sufficiently performed, the process proceeds to S104, and a measure for improving the combustion based on the pre-injection is taken. On the other hand, if it is determined that the combustion based on the pre-injection is sufficiently performed, the process skips S104 and proceeds to S105.

  In S104, the fuel injection timing of the pre-injection is advanced by a predetermined angle A1. By doing so, when combustion based on the pre-injection is performed, the temperature and pressure can be gradually increased from the stage where the in-cylinder pressure is lower, and the combustion can be more easily completed. Thereby, combustion based on pre-injection can be performed more reliably. When the process of S104 ends, the process proceeds to S105. The predetermined angle A1 may be a predetermined constant value, but in this embodiment, the predetermined angle A1 is based on a map that stores the relationship between the peak value of the in-cylinder pressure during combustion based on the previous injection and the advance angle A1. The value of A1 corresponding to the in-cylinder pressure detected in S102 is obtained by reading it one by one.

  Next, in S105, it is determined whether or not the combustion based on the main injection is sufficiently performed. Specifically, the determination is made based on whether or not the peak of the output of the in-cylinder pressure sensor 32 after TDC is equal to or greater than P2, which is a threshold value for determining that combustion based on main injection is sufficiently performed. If it is determined that the combustion based on the main injection is not sufficiently performed, the process proceeds to S106, and measures are taken to improve the combustion based on the main injection. On the other hand, when it is determined that the combustion based on the main injection is sufficiently performed, S106 is skipped, and this routine is ended once.

  In the process of S106, the fuel injection timing of the main injection is advanced by a predetermined angle A2. By doing so, the main injection can be performed at a time when the compression pressure is higher, and the combustion based on the main injection can be performed more stably. When the process of S106 ends, this routine is temporarily ended.

  If it is determined in S101 that the engine is not cold start, that is, the warm-up of the internal combustion engine 1 has been completed, the process proceeds to S107. In S107, when an affirmative determination is made in S101 during the previous execution of this routine (immediately after the end of warm-up), the fuel injection timings of the previous injection and the main injection are returned to the reference values. Thereafter, the fuel injection timing after the warm-up of the internal combustion engine 1 is controlled by another routine. When the process of S107 ends, this routine is temporarily ended.

  As described above, in this routine, the in-cylinder pressure due to combustion based on the pre-injection and the in-cylinder pressure due to combustion based on the main injection are independently detected, and the fuel related to the injection with the insufficient combustion Combustion was improved by advancing the injection timing. According to this, the combustion which is the main cause that the startability is deteriorated can be selectively improved, and the startability at the cold start can be improved more reliably. Further, since the combustion of the pre-injection is improved by advancing the fuel injection timing of the pre-injection, the combustion itself based on the pre-injection can be improved more reliably, and the inconvenience such as the occurrence of smoke is suppressed. Can do.

  In the above description, the in-cylinder pressure sensor 32 and the ECU 22 that detect the in-cylinder pressure before TDC in S102 correspond to the pre-combustion state detection means in the present embodiment. Further, the in-cylinder pressure sensor 32 and the ECU 22 for detecting the in-cylinder pressure after TDC in S102 correspond to the main combustion state detecting means in the present embodiment. Moreover, ECU22 which performs the process of S104 comprises the injection time change means before starting in a present Example. Similarly, ECU22 which performs the process of S106 comprises the main injection timing change means at the time of a start in a present Example.

  Next, another mode of control for improving combustion at the time of starting in this embodiment will be described. In this aspect, when improving the combustion of the pre-injection and the main injection, the fuel injection timing is advanced and the fuel injection amount is increased.

  FIG. 4 shows the starting combustion improvement routine 2 according to this aspect. The difference between this routine and the above-described start-up combustion improvement routine is that the processing of S201 is performed after the processing of S104, the processing of S202 is performed after the processing of S106, and the processing of S203 is further performed after the processing of S107. That is. Here, only the difference between this routine and the starting combustion improvement routine will be described.

  In this routine, advance processing is performed for the fuel injection timing of the previous injection in the process of S104, and then the process proceeds to S201, where the fuel injection amount of the previous injection is increased by F1. Further, in step S106, the fuel injection timing of the main injection is advanced, and the process proceeds to step S202, where the fuel injection amount of the previous injection is increased by F2. Here, the value of F1 is the value of F1 corresponding to the peak value of the in-cylinder pressure before TDC detected in S102 from the map storing the relationship between the peak value of the in-cylinder pressure before TDC and F1. Acquired by reading. Further, as the value of F2, the value of F2 corresponding to the peak value of the in-cylinder pressure after TDC detected in S102 is read out from the map storing the relationship between the peak value of the in-cylinder pressure after TDC and F2. Is obtained by

  Further, in the process of S107, after returning the fuel injection timing of the pre-injection and the main injection to the reference value when it is immediately after the warm-up end, the process proceeds to S203, and when it is immediately after the warm-up end, the pre-injection and the main injection are performed. Return the fuel injection amount to the reference value.

  As described above, in the start-up combustion improvement routine 2 in this aspect, in order to improve the combustion in the pre-injection and the main injection, if the combustion in any of the injections is insufficient, the insufficient injection is performed. The fuel injection timing is advanced and the fuel injection amount is increased. As a result, it is possible to improve the combustion that is insufficient between the combustion based on the pre-injection and the combustion based on the main injection, and to improve the startability of the internal combustion engine more reliably.

  In addition, ECU22 which performs the process of S201 in the above is corresponded to the injection amount change means before starting in a present Example. Moreover, ECU22 which performs the process of S202 is corresponded to the main injection amount change means at the time of start in a present Example.

  In this embodiment, the combustion state based on the pre-injection and the main injection is detected by the in-cylinder pressure, but the combustion state of both injections is detected by the in-cylinder temperature, vibration during combustion, impact, and the like. It may be.

Next, a second embodiment of the present invention will be described. In this embodiment, the fuel property of the fuel injected in the pre-injection is detected, and the advance amount of the fuel injection timing when the combustion based on the pre-injection is insufficient based on the detected fuel property (cetane number) An example of correcting the will be described. That is, if the cetane number of the fuel injected in the pre-injection is different, the ignitability of the injected fuel is also different. On the other hand, when the advance amount A1 of the fuel injection timing in the start-up combustion improvement routine is determined, when the cetane number of the used fuel is different from the cetane number of the fuel in actual control, the advance amount It corrects itself.

  FIG. 5 shows a flowchart of the starting combustion improvement routine 3 in this embodiment. The difference between this routine and the starting combustion improvement routine described in the first embodiment is that the processing of S301 and S302 is inserted between the processing of S101 and S102, and the processing of S303 instead of the processing of S104. Is the point where is executed. Here, only the difference between this routine and the above-described start-up combustion improvement routine will be described.

  When the process of S101 is completed in this routine, the process proceeds to S301. In S301, the fuel property is detected. Specifically, the fuel property (cetane number) may be detected by detecting the density of the fuel with the fuel property sensor 30 provided in the fuel tank 26. The fuel property sensor 30 may detect the viscosity of the fuel. When the process of S301 ends, the process proceeds to S302.

  In S302, a correction coefficient C1 determined by the cetane number of the fuel is derived with respect to the advance amount A1 of the fuel injection timing when it is determined in S103 that the combustion based on the previous injection is not sufficient. Specifically, a map storing the relationship between the cetane number of the fuel and the correction coefficient C1 is prepared experimentally in advance, and the value of the correction coefficient C1 corresponding to the cetane number of the fuel detected in S301 is read out. Derived by

  In this embodiment, the value of the cetane number of the fuel used or assumed when the map storing the value of A1 is created is used as the reference value. When the actual cetane number of the fuel detected in S301 is larger than the reference value, the correction coefficient C1 is a value less than 1. That is, in this case, the retard side correction is performed. Further, when the cetane number of the actual fuel detected in S301 is smaller than the reference value, the correction coefficient C1 becomes a value larger than 1. That is, in this case, the advance side correction is performed. When the process of S302 ends, the process proceeds to S102.

  Further, in this embodiment, when it is determined in S103 that the combustion based on the pre-injection is not sufficient, the process proceeds to S303. In S303, the advance angle of the fuel injection timing of the pre-injection is implemented as in S104, but the advance angle at that time is not A1, but is advanced by the value C1 · A1 multiplied by the correction coefficient C1 derived in S302. The When the process of S303 ends, the process proceeds to S105.

  As described above, in this embodiment, the cetane number of the pre-injected fuel is detected, and when the cetane number is larger than the reference value, the advance amount of the fuel injection timing is corrected to the retard side. When the cetane number is smaller than the reference value, the advance amount of the fuel injection timing is further corrected to the advance side.

  Therefore, when it is determined that the combustion of the pre-injection is not sufficient regardless of the actual change in the fuel property, the advance angle can be corrected to an appropriate fuel injection timing.

  Next, another aspect of control in the present embodiment will be described. FIG. 6 shows a flowchart of the starting combustion improvement routine 4 in the present embodiment. The difference between this routine and the startup combustion improvement routine 3 is that the process of S401 is executed instead of the process of S302, and the process of S104 in the startup combustion improvement routine is executed instead of the process of S303. It is a point.

That is, in S302 of the starting combustion improvement routine 3, the correction coefficient C1 for the advance amount A1 of the fuel injection timing is derived based on the cetane number of the fuel detected in S301, whereas in S401 in this aspect, Based on the cetane number of the fuel detected in S301, the fuel injection timing of the previous injection is changed by A3.

  Here, specifically, the value of A3 is determined according to the cetane number of the fuel detected in S301 from a map in which a map storing the relationship between the cetane number of fuel and A3 is prepared in advance. The value of the change amount A3 of the fuel injection timing is read out, and the fuel injection timings of the pre-injection and main injection are changed based on the value of A3.

  Here, when the cetane number detected in S301 is larger than the reference value, A3 is a retarded side (+) value, and when the cetane number detected in S301 is smaller than the reference value, A3 is an advance angle. It becomes the value of the side (-).

  As a result, there is no need to correct the value of A1, so in the processing after this routine, the processing in S104 in the starting combustion improvement routine is executed instead of the processing in S303.

  As described above, in this routine, when the cetane number of the fuel is detected, the fuel injection timing of the pre-injection is changed according to the cetane number of the fuel. Regardless, the influence of fuel properties can be canceled out in advance. Further, when the actual cetane number of the fuel is extremely larger than the reference value, it is possible to finally change the injection timing of the pre-injection to the retard side at the end of the processing of S401 and S104.

  Note that the fuel property sensor 30 and the ECU 22 that execute the processing of S301 in the above constitute fuel property detection means in the present embodiment.

  In this embodiment, the control for changing the fuel injection timing of the pre-injection according to the actual cetane number of the fuel has been described, but the same control may be applied to the fuel injection amount of the pre-injection. Good. FIG. 7 shows a flowchart of the starting combustion improvement routine 5 in that case.

  In the starting combustion improvement routine 5, the processes of S301 and S501 are inserted between S101 and S102 of the starting combustion improvement routine 2 shown in FIG. 4, and the process of S303 is executed instead of the process of S104. The process of S502 is executed instead of the process of S201.

  In S501, a correction coefficient C1 determined by the cetane number of the fuel is derived with respect to the advance amount A1 of the fuel injection timing when it is determined in S103 that the combustion based on the previous injection is not sufficient, and the fuel injection timing increase F1 is derived. A correction coefficient C2 for is derived. Specifically, a map storing the relationship between the cetane number of the fuel and the correction coefficients C1 and C2 is experimentally prepared in advance, and the correction coefficients C1 and C2 corresponding to the cetane number of the fuel detected in S301 are set. Derived by reading the value.

  C2 in this case is set to a value less than 1 when the actual fuel cetane number detected in S301 is larger than the reference value, and C2 in the actual fuel detected in S301 is smaller than the reference value. C2 should be greater than 1.

  In S502, as in the process of S201 shown in FIG. 2, the fuel injection amount of the pre-injection is increased, but the advance amount at that time is not F1, but the correction coefficient C2 derived in S501 is used. The amount is increased by the multiplied value C2 · F1.

  As described above, when the cetane number of the actual fuel is larger than the reference value, the advance amount of the fuel injection timing of the pre-injection is corrected to the retard side and the increase of the fuel injection amount is corrected to the decrease side. When the cetane number is smaller than the reference value, the advance amount of the fuel injection timing is further corrected to the advance side, and the increase of the fuel injection amount is further corrected to the increase side.

  Therefore, when it is determined that the combustion of the pre-injection is not sufficient regardless of the actual change in the fuel property, the advance angle can be corrected to an appropriate fuel injection timing and an appropriate amount of fuel can be injected. Can do.

  In the present embodiment, the control for changing the fuel injection timing of the pre-injection according to the actual cetane number of the fuel has been described, but the same control is performed on the fuel injection timing or the fuel injection amount of the main injection. You may apply.

  The internal combustion engine to which the present invention is applied may be an engine premised on the implementation of premixed combustion, but the present invention is not necessarily limited to application to such an engine.

It is a figure which shows schematic structure of the internal combustion engine in the Example of this invention, its intake / exhaust system, and a control system. It is a graph which shows the change of the cylinder pressure by the pre-injection at the time of the cold start in the Example of this invention, and main injection. It is a flowchart which shows the combustion improvement routine at the time of start in Example 1 of this invention. It is a flowchart which shows the combustion improvement routine 2 at the time of start in Example 1 of this invention. It is a flowchart which shows the combustion improvement routine 3 at the time of start in Example 2 of this invention. It is a flowchart which shows the combustion improvement routine 4 at the time of start in Example 2 of this invention. It is a flowchart which shows the combustion improvement routine 5 at the time of start in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Common rail 5 ... Low pressure EGR valve 6 ... Compressor housing 7 ... Turbine housing 8 ... Intake manifold 9. .... Intake pipe 10 ... Centrifugal supercharger 11 ... Exhaust throttle valve 12 ... Throttle valve 13 ... Intercooler 14 ... EGR cooler 15 ... High pressure EGR passage 16 ... Collecting pipe 18 ... Exhaust manifold 19 ... Exhaust pipe 20 ... Filter 21 ... High pressure EGR valve 22 ... ECU
23 ... Low pressure EGR passage 24 ... Air flow meter 25 ... Air cleaner 26 ... Fuel tank 27 ... Fuel pump 30 ... Fuel property sensor 31 ... Water temperature sensor 32 ... In-cylinder pressure sensor

Claims (6)

Main injection means for injecting main fuel to be burned into a cylinder of the internal combustion engine;
Pre-injection means for injecting secondary fuel prior to injection of main fuel by the main injection means;
Pre-combustion state detection means for detecting the combustion state based on the fuel injection of the pre-injection means independently of the combustion state based on the fuel injection of the main injection means;
Pre-startup injection timing changing means for changing the injection timing of fuel injection by the pre-injection means at the start of the internal combustion engine;
An internal combustion engine start control device comprising:
When the internal combustion engine is started, when the pre-combustion state detecting means detects that the combustion based on the fuel injection of the pre-injecting means is insufficient, the pre-start-up injection timing changing means performs the front injection time changing means. A start control device for an internal combustion engine, characterized in that the timing of fuel injection by the injection means is advanced. A pre-startup injection amount changing means for changing the amount of fuel injection by the pre-injection means when the internal combustion engine is started;
When the internal combustion engine is started, when the pre-combustion state detecting means detects that the combustion based on the fuel injection of the pre-injecting means is insufficient, the pre-start-up injection timing changing means performs the front injection time changing means. 2. The internal combustion engine according to claim 1, wherein the timing of fuel injection by the injection means is advanced and the amount of fuel injection by the pre-injection means is increased by the pre-starting injection amount changing means. Start control device. Main combustion state detection means for detecting the combustion state based on the fuel injection of the main injection means independently of the combustion state based on the fuel injection of the pre-injection means;
A starting main injection timing changing means for changing an injection timing of fuel injection by the main injection means at the start of the internal combustion engine, and at the start of the internal combustion engine, by the main combustion state detecting means, When it is detected that combustion based on fuel injection of the main injection means is insufficient, the timing of fuel injection by the main injection means is advanced by the starting main injection timing changing means. The start control device for an internal combustion engine according to claim 1 or 2. A start main injection amount changing means for changing the amount of fuel injection by the main injection means at the time of starting the internal combustion engine;
When the internal combustion engine is started, when the main combustion state detecting means detects that the combustion based on the fuel injection of the main injection means is insufficient, the main injection timing changing means at the start is used to change the main injection timing changing means. 4. The internal combustion engine according to claim 3, wherein the timing of fuel injection by the injection means is advanced and the amount of fuel injection by the main injection means is increased by the starting main injection amount changing means. Start control device. A fuel property detection means for detecting the property of the fuel injected by the pre-injection means;
The pre-start-up injection timing changing means, when the cetane number of the fuel injected by the pre-injection means detected by the fuel property detection means is larger than a reference value, the timing of fuel injection by the pre-injection means The start control of the internal combustion engine according to claim 1 or 2, wherein when the cetane number is smaller than the reference value, the timing of fuel injection by the pre-injection means is advanced. apparatus. A fuel property detection means for detecting the property of the fuel injected by the pre-injection means;
The pre-start-up injection timing changing means, when the cetane number of the fuel injected by the pre-injection means detected by the fuel property detection means is larger than a reference value, the fuel injection timing by the pre-injection means When the cetane number is smaller than the reference value, the timing of fuel injection by the pre-injection means is advanced,
When the cetane number of the fuel injected by the pre-injection means detected by the fuel property detection means is greater than a reference value, the pre-start-time injection amount changing means is the amount of fuel injection by the pre-injection means The start control device for an internal combustion engine according to claim 2, wherein when the cetane number is smaller than the reference value, the amount of fuel injection by the pre-injection means is increased.

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