JP2007285195A - Ignition timing control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of preventing ignition timing from being varied when the ignitionability of working fuel changes, in an ignition timing control system for an internal combustion engine that prolongs a period of time of premixing fuel and gas in cylinders by introducing a large amount of EGR gas into the cylinders. <P>SOLUTION: In the ignition timing control system for an internal combustion engine that prolongs the ignition delay period of fuel by introducing a large amount of EGR gas into the cylinders of the internal combustion engine, the cetane number of the fuel used in the internal combustion engine is determined, and as the determined cetane number is smaller, the amount of the EGR gas is more decreased, whereby an increase of the ignition delay period due to a reduction of the cetane number is canceled by a decrease of the ignition delay period due to a reduction of the amount of the EGR gas. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for controlling the ignition timing of a compression ignition type internal combustion engine.

  In a compression ignition type internal combustion engine, when the ignitability (ignition point) of the fuel used changes, the fuel ignition delay period changes. For this reason, there is a possibility that the ignition timing of the fuel is far from the desired timing.

  For example, if the ignitability of the fuel used decreases (ignition point increases), the ignition delay period of the fuel becomes longer, and the ignition timing becomes later than the desired timing. If the ignition timing of the fuel is later than the desired timing, the fuel is likely to misfire, which may cause a decrease in engine output and the occurrence of smoke.

In contrast, a technique has been proposed in which the change in the ignition timing is suppressed by increasing the fuel injection timing as the ignitability of the fuel decreases (see, for example, Patent Document 1).
JP 2004-340026 A JP 2005-48704 A

  By the way, in recent years, a compression ignition type internal combustion engine has been developed in which a large amount of EGR gas is introduced into the cylinder of the internal combustion engine, thereby prolonging the ignition delay period of the fuel and premixing the fuel and the gas in the cylinder. ing.

  In such a compression ignition type internal combustion engine, it is difficult to suppress a delay in the ignition timing even if the fuel injection timing is advanced when the ignitability of the fuel used becomes low.

  The present invention has been made in view of the various circumstances as described above, and an object thereof is to prolong the premixing period of the fuel and the gas in the cylinder by introducing a large amount of EGR gas into the cylinder. An ignition timing control system for an internal combustion engine is to provide a technique capable of suppressing a change in the ignition timing when the ignitability of the fuel used changes.

  In order to solve the above-described problems, the present invention ignites an internal combustion engine that prolongs a fuel ignition delay period (a premixing period of fuel and gas in the cylinder) by introducing a large amount of EGR gas into the cylinder. In the timing control system, the internal combustion engine is controlled so that the ignition delay period becomes shorter as the ignitability of the fuel used becomes lower.

  More specifically, the present invention is used in an internal combustion engine ignition timing control system that prolongs the ignition delay period (premixing period) of fuel by introducing a large amount of EGR gas into the cylinder of the internal combustion engine. And a control means for controlling the operating state of the internal combustion engine so that the ignition delay period becomes shorter as the ignitability determined by the determination means becomes lower. .

  According to such an ignition timing control system for an internal combustion engine, in an operating state in which a large amount of EGR gas is introduced into the cylinder, an excessively long ignition delay period is suppressed even if the ignitability becomes low due to a change in the properties of the fuel used. Therefore, it is possible to suppress the ignition timing from being separated from the desired timing.

  As a method of shortening the ignition delay period, a method of reducing the amount of EGR gas introduced into the cylinder as the ignitability of the fuel used decreases, and post-injection is performed when the ignitability of the fuel used decreases from a reference value. In addition, a method of increasing the post-injection amount as the ignitability of the fuel used decreases or a method of increasing the heat generation amount of the glow plug as the ignitability of the fuel used decreases can be exemplified.

  When the amount of EGR gas introduced into the cylinder is reduced, the ignition delay period is shortened. Therefore, the increase in the ignition delay period due to the decrease in the ignitability of the fuel used is reduced by the decrease in the ignition delay period due to the decrease in the EGR gas amount. If canceling out, it becomes possible to suppress the change in the ignition timing.

  When post-injection is performed after normal fuel injection (main injection), the post-injected fuel becomes a fire type, and the main injection fuel is ignited and burned. . However, if the ignitability of the fuel used decreases, the ignitability of the post-injected fuel also decreases. Therefore, it is preferable to increase the post injection amount as the ignitability of the fuel used decreases.

  When the heat generation amount of the glow plug increases, the temperature of the fuel easily reaches the ignition point. Therefore, if the heat generation amount of the glow plug increases as the ignitability of the fuel decreases, the ignition delay period is prevented from becoming longer.

  Incidentally, there is a response delay from the time when the EGR valve, the intake throttle valve, etc. are controlled to reduce the EGR gas amount until the EGR gas amount actually introduced into the cylinder decreases to the target amount. For this reason, the control means executes the post-injection and increases the post-injection amount as the ignitability becomes lower for a predetermined period (EGR gas response delay period) from the start of the EGR gas amount reduction process. The ignition delay period may be shortened by shortening the delay period or increasing the heat generation amount of the glow plug as the ignitability decreases.

  Further, when post injection is used as means for shortening the ignition delay period, the post injection amount is preferably limited to a predetermined amount or less. This is because if the post-injection amount becomes excessive, pre-ignition or misfire may be induced depending on the engine operating state at that time.

  When it is necessary to further shorten the ignition delay period after the post injection amount reaches the predetermined amount, the ignition delay period can be shortened by increasing the heat generation amount of the glow plug or decreasing the EGR gas amount. That's fine.

  According to the present invention, in an ignition timing control system for an internal combustion engine that premixes fuel and gas in a cylinder by introducing a large amount of EGR gas into the cylinder, the ignition timing when the ignitability of the fuel used changes. It becomes possible to suppress the change of.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

<Example 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied.

  An internal combustion engine 1 shown in FIG. 1 is a compression ignition internal combustion engine (diesel engine) capable of switching between a premixed combustion operation and a diffusion combustion operation.

  A fuel injection valve 5 that directly injects fuel into the cylinder 4 is disposed on the surface of the cylinder head 2 of the internal combustion engine 1 that faces the top surface of the piston 3.

  The internal combustion engine 1 is provided with an intake passage 6 that guides gas into the cylinder 4 and an exhaust passage 7 that discharges the gas in the cylinder 4. The intake passage 6 and the exhaust passage 7 communicate with each other by an EGR passage 8. The EGR passage 8 is a passage for recirculating a part of the exhaust gas flowing through the exhaust passage 7 (hereinafter referred to as “EGR gas”) to the intake passage 6.

  The EGR passage 8 includes an EGR cooler 9 that cools the EGR gas that flows through the EGR passage 8, and a flow rate adjustment valve (hereinafter referred to as “EGR valve”) 10 that adjusts the amount of EGR gas that flows through the EGR passage 8. Is provided.

  The fuel injection valve 5 and the EGR valve 10 described above are electrically controlled by the ECU 11. The ECU 11 is an electronic control unit that includes a CPU, ROM, RAM, backup RAM, and the like.

  The ECU 11 is electrically connected to a crank position sensor 12 that outputs a pulse signal each time a crankshaft (not shown) of the internal combustion engine 1 rotates by a predetermined angle, an accelerator position sensor 13 that outputs an electric signal corresponding to the depression amount of an accelerator pedal, and the like. It is connected.

  ECU11 discriminate | determines the driving | running state of the internal combustion engine 1 based on output signals, such as above-mentioned crank position sensor 12 and accelerator position sensor 13, and controls the fuel injection valve 5 and the EGR valve 10 according to the discriminating driving | running state. .

  For example, the ECU 11 shows the operation state of the internal combustion engine determined from the output signal (accelerator opening) Accp of the accelerator position sensor 13 and the engine speed (value calculated from the output signal of the crank position sensor 12) Ne in FIG. When in the diffusion combustion operation region, the fuel injection valve 5 is controlled to cause the internal combustion engine 1 to perform diffusion combustion operation.

  Specifically, as shown in FIG. 3, the ECU 11 injects fuel from the fuel injection valve 5 when the cylinder 4 is near the compression top dead center. In this case, since the fuel injection valve 5 injects fuel under the condition that the inside of the cylinder 4 is at a high temperature and high pressure, the fuel injected from the fuel injection valve 5 burns while diffusing into the cylinder 4.

  Further, when the operating state of the internal combustion engine determined from the accelerator opening degree Accp and the engine speed Ne is in the premixed combustion operation region shown in FIG. 2, the ECU 11 sets the fuel injection valve 5 to perform the premixed combustion operation of the internal combustion engine 1. Control.

  Specifically, as shown in FIG. 4, the ECU 11 injects fuel from the fuel injection valve 5 when the cylinder 4 is in the initial stage to the middle stage of the compression stroke (for example, 180 ° CA to 60 ° CA before the top dead center of the compression stroke). (Premix injection) is performed to form a premixed gas, and the premixed gas is compressed and ignited by raising the piston 3.

  By the way, when the internal combustion engine 1 is in a premixed combustion operation, the fuel premixed and injected from the fuel injection valve 5 is compressed by the rise of the piston 3, so that it is ignited at an earlier time than the vicinity of the compression top dead center ( There is a possibility of premature ignition).

On the other hand, the ECU 11 controls the EGR valve 10 to introduce a sufficient amount of EGR gas into the cylinder 4 as compared with the diffusion combustion operation. When a large amount of EGR gas is introduced into the cylinder 4 in this way, the ignition delay period of the premixed fuel becomes long, and thus premature ignition is suppressed.

  However, depending on the refueling conditions and the like, the properties of the fuel used in the internal combustion engine 1 may change, and the ignitability (ignition point) of the fuel may change accordingly. For this reason, the ignitability of the fuel assumed at the time of designing the internal combustion engine 1 and the ignitability of the fuel actually used may be separated.

  In such a case, the fuel ignition timing is far from the desired ignition timing, and various problems such as fuel misfire, increased combustion noise, increased smoke, or decreased engine output may be induced. For such problems, a method has been proposed in which the fuel injection timing is advanced as the ignitability of the fuel used decreases.

  The above method is effective when the internal combustion engine 1 is operated by diffusion combustion, but it is difficult to obtain an effect when the internal combustion engine 1 is operated by premix combustion, and may cause problems such as bore flushing. There is also.

  Therefore, in this embodiment, the ignitability of the fuel used is determined, and if the determined ignitability is lower than the assumed ignitability, the amount of EGR gas during the premixed combustion operation is reduced to reduce the ignition timing. The change was suppressed.

  Hereinafter, ignition timing control when the internal combustion engine 1 is in the premixed combustion operation will be described with reference to FIG. FIG. 5 is a flowchart showing an ignition timing control routine when the internal combustion engine 1 is in the premixed combustion operation. This ignition timing control routine is a routine that is stored in advance in the ROM of the ECU 11, and is a routine that is repeatedly executed by the ECU 11 during the premixed combustion operation of the internal combustion engine 1.

  In the ignition timing control routine, the ECU 11 first determines the ignitability of the fuel actually used by the internal combustion engine 1 in S101. Since the ignitability of the fuel correlates with the cetane number, the ECU 11 may determine the cetane number Cr of the used fuel in S101.

  Various known methods can be used as a method of determining the cetane number of the fuel used. For example, fuel is injected into the cylinder 4 at the beginning of the compression stroke, such as during fuel cut operation, and the ignition timing and ignition delay period of the fuel are detected. Based on the detected parameters, the cetane number Cr of the fuel used is determined. An example of the determination method is illustrated.

  Note that the fuel ignition timing and the ignition delay period can be exemplified by a method of specifying the rise timing of the in-cylinder pressure or the increase timing of the engine rotation speed from the measured values of the in-cylinder pressure sensor and the crank position sensor 12 due to fuel combustion. .

  The measurement of the cetane number Cr as described above may be performed only once after refueling, but the newly refueled fuel and the fuel remaining in the fuel tank are not immediately mixed but gradually mixed. Since mixing is performed, it is preferable to be performed each time this routine is executed.

  In S102, the ECU 11 determines whether or not the cetane number Cr determined in S101 is lower than a reference value Crbase. The reference value Crbase corresponds to the lower limit value of the cetane number assumed in advance when the internal combustion engine 1 is designed.

  If an affirmative determination is made in S102 (Cr <Crbase), the ECU 11 proceeds to S103. In S103, the ECU 11 calculates a deviation ΔCr1 (= Crbase−Cr) by subtracting the cetane number Cr from the reference value Crbase.

  In S104, the ECU 11 calculates a correction amount ΔEGR (= f (ΔCr1)) of the opening degree of the EGR valve 10 based on the deviation ΔCr1 calculated in S103. Here, as shown in FIG. 6, f (ΔCr1) is determined such that the correction amount ΔEGR increases as the deviation ΔCr1 increases.

  In S105, the ECU 11 calculates a target opening Aegr of the EGR valve 10. Specifically, the ECU 11 first obtains a reference value (hereinafter referred to as “reference target opening”) Aegrbase of a target opening determined from the operating state of the internal combustion engine 1 (accelerator opening Accp, engine speed Ne, etc.). . Next, the ECU 11 calculates the target opening Aegr (= Aegrbase−ΔEGR) of the EGR valve 10 by subtracting the correction amount ΔEGR from the reference target opening Aegrbase.

  In this case, the target opening degree Aegr of the EGR valve 10 becomes smaller as the cetane number of the used fuel becomes lower. As a result, as shown in FIG. 7, the amount of EGR gas introduced into the cylinder 4 of the internal combustion engine 1 decreases as the cetane number Cr of the fuel used decreases.

  When the EGR gas amount decreases as the cetane number Cr of the fuel used decreases, the increase in the ignition delay period due to the decrease in the cetane number is offset by the decrease in the ignition delay period due to the decrease in the EGR gas amount. A significant delay is avoided. As a result, fuel misfire, reduction in engine output, increase in combustion noise, increase in smoke, and the like are suppressed.

  Further, when a negative determination is made in S102 (Cr ≧ Crbase), the ECU 11 proceeds to S106. In S106, the ECU 11 sets the reference target opening degree Aegrbase to the target opening degree Aegr (= Aegrbase) of the EGR valve 10.

  As described above, when the ECU 11 executes the ignition timing control routine of FIG. 5, the determination means and control means according to the present invention are realized. Therefore, the EGR gas amount when the internal combustion engine 1 is in the premixed combustion operation decreases as the cetane number decreases. As a result, even when the ignitability (cetane number) of the fuel changes during the premixed combustion operation of the internal combustion engine 1, it is possible to suppress the fluctuation of the ignition timing, thereby suppressing the occurrence of problems due to the delay of the ignition timing. .

<Example 2>
Next, a second embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the first embodiment described above, when the cetane number Cr of the fuel used during the premixed combustion operation of the internal combustion engine 1 is lower than the reference value Crbase, an increase in the ignition delay period is suppressed by reducing the EGR gas amount. However, in the present embodiment, an example will be described in which, when the cetane number Cr of the fuel used during the premixed combustion operation of the internal combustion engine 1 becomes lower than the reference value Crbase, post-injection is performed to suppress the lengthening of the ignition delay period.

  When the ignitability (cetane number Cr) of the fuel used is lower than the reference value Crbase, as shown in FIG. 8, the ECU 11 is near the compression top dead center (preferably the compression) after the premixed injection described above is performed. Post-injection before top dead center). When post-injection is performed after premixed injection in this way, the post-injected fuel becomes a fire type and the premixed injected fuel burns in the vicinity of compression top dead center.

  However, when the cetane number Cr of the fuel used decreases, the ignitability of the post-injected fuel also decreases. Therefore, it is preferable to increase the post injection amount as the cetane number Cr of the fuel used decreases.

  Further, the total fuel injection amount (the sum of the premixed injection amount and the post injection amount) when the post injection as described above is performed is the total fuel injection amount when only the premixed injection is performed (= premixed injection amount). ) Is preferably the same amount. This is to suppress an increase in torque of the internal combustion engine 1 due to the addition of post injection. Accordingly, the ECU 11 decreases the premixed injection amount as the post injection amount increases.

  Hereinafter, ignition timing control when the internal combustion engine 1 is in the premixed combustion operation will be described with reference to FIG. FIG. 9 is a flowchart showing an ignition timing control routine when the internal combustion engine 1 is in the premixed combustion operation.

  In the ignition timing control routine, the processing of S101 to S102 is the same as the ignition timing control routine of the first embodiment described above.

  If an affirmative determination is made in S102 (Cr <Crbase), the ECU 11 proceeds to S201. In S201, the ECU 11 calculates a post injection amount Qpst (= g (Cr)) based on the cetane number Cr determined in S101. Here, as shown in FIG. 10, g (Cr) is determined so that the post injection amount Qpst increases as the cetane number Cr decreases.

  By the way, if the post injection amount Qpst becomes excessive, the following problems may occur. For example, if the post-injection amount Qpst is excessive when the amount of EGR gas is relatively small, the fuel may ignite prematurely, leading to an increase in combustion noise, smoke, or the like. On the other hand, if the post-injection amount Qpst is excessive when the amount of EGR gas is relatively large, the in-cylinder temperature may decrease due to the latent heat of vaporization of the fuel, and the fuel may misfire.

  Therefore, in this embodiment, the upper limit value A is set for the post injection amount Qpst. The upper limit value A is a value determined so as not to cause the above-described various problems, and is obtained experimentally in advance.

  Here, returning to FIG. 9, the ECU 11 determines in S202 whether or not the post injection amount Qpst calculated in S201 is equal to or less than the upper limit value A. Note that the ECU 11 does not compare the post injection amount Qpst and the upper limit value post in S202, but the cetane number Cr determined in S101 and the cetane number when the post injection amount Qpst reaches the upper limit value A ( Refer to Cr0 in Fig. 10. Hereinafter, the cetane number Cr0 may be referred to as "boundary value Cr0").

  If an affirmative determination is made in S202 (Qpst ≦ A or Cr ≧ Cr0), the ECU 11 proceeds to S203 and executes post-injection according to the post-injection amount Qpst calculated in S201. At this time, the ECU 11 reduces the injection amount equal to the post injection amount Qpst from the premixed injection amount in order to suppress an unnecessary increase in torque of the internal combustion engine 1.

  On the other hand, when a negative determination is made in S202 (Qpst> A or Cr <Cr0), the ECU 11 proceeds to S204 and limits the post injection amount Qpst to the upper limit value A.

  In S205, the ECU 11 performs post injection according to the post injection amount Qpst determined in S204.

By the way, when the cetane number Cr of the fuel used is lower than the boundary value Cr0, it becomes difficult to suppress the ignition delay of the fuel only by performing the post injection. Therefore, the ECU 11 performs S20.
In step 6, the EGR gas is reduced.

  In the EGR gas reduction process, the ECU 11 first sets the EGR valve 10 so that the EGR gas amount decreases as the difference ΔCr2 (= Cr0−Cr) between the cetane number Cr determined in S101 and the boundary value Cr0 increases. Correct the target opening.

  When the target opening degree of the EGR valve 10 is corrected in this way, the fuel ignition delay can be suppressed even when the cetane number Cr of the fuel used is lower than the boundary value Cr0. This makes it possible to set the ignition timing to a desired timing.

  If a negative determination is made in S102, the ECU 11 proceeds to S207. In S207, the ECU 11 sets the post injection amount Qpst to zero (post injection stop), and ends the execution of this routine.

  According to the embodiment described above, it is possible to obtain the same effect as that of the first embodiment described above. Furthermore, switching between post-injection execution / non-execution and change in the post-injection amount Qpst is more responsive than change in the EGR gas amount, so the cetane number of the fuel used changes every moment as just after refueling. In this case, the ignition timing control method of this embodiment is effective.

  The ignition timing control method according to the present embodiment is the same as that in the first embodiment described above until the actual EGR gas amount reaches a desired amount from the time when the opening degree of the EGR valve 10 is changed to change the EGR gas amount. It may be executed during the response delay period.

<Example 3>
Next, a third embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the first embodiment described above, when the cetane number Cr of the fuel used during the premixed combustion operation of the internal combustion engine 1 is lower than the reference value Crbase, an increase in the ignition delay period is suppressed by reducing the EGR gas amount. In this embodiment, an example is described in which, when the cetane number Cr of the fuel used during the premixed combustion operation of the internal combustion engine 1 becomes lower than the reference value Crbase, the glow plug generates heat, thereby suppressing the lengthening of the ignition delay period. .

  FIG. 11 is a diagram showing a schematic configuration of the internal combustion engine 1 in the present embodiment. The internal combustion engine 1 shown in FIG. 11 includes a glow plug 14 disposed in the vicinity of the fuel injection valve 5. The glow plug 14 is electrically controlled by the ECU 11.

  For example, the ECU 11 increases the energization amount (heat generation amount) of the glow plug 14 as the cetane number Cr decreases when the cetane number Cr of the fuel used decreases during the premixed combustion operation of the internal combustion engine 1 from the reference value Crbase.

  When the cetane number Cr of the fuel becomes low, the ignition point of the fuel becomes high, so that the fuel ignition delay period becomes long. This becomes more prominent as the cetane number Cr of the fuel decreases. On the other hand, when the amount of heat generated by the glow plug 14 increases, the time until the fuel reaches the ignition point is shortened. This becomes more prominent as the amount of heat generated by the glow plug 14 increases.

Therefore, if the heat generation amount of the glow plug 14 is increased as the cetane number Cr of the fuel is decreased, the increase in the ignition delay period due to the decrease in the cetane number Cr is offset by the decrease in the ignition delay period due to the heat generation of the glow plug 14. The As a result, it is possible to avoid a significant delay in the ignition timing.

  Hereinafter, ignition timing control when the internal combustion engine 1 is in the premixed combustion operation will be described with reference to FIG. FIG. 12 is a flowchart showing an ignition timing control routine when the internal combustion engine 1 is in the premixed combustion operation.

  In the ignition timing control routine of FIG. 12, the processing of S101 to S102 is the same as the ignition timing control routine of the first embodiment described above.

  If an affirmative determination is made in S102 (Cr <Crbase), the ECU 11 proceeds to S301. In S301, the ECU 11 calculates the energization amount Cglow (= h (Cr)) of the glow plug 14 based on the cetane number Cr determined in S101. Here, as shown in FIG. 13, h (Cr) is determined so that the energization amount Cglow increases as the cetane number Cr decreases.

  Returning to FIG. 12, the ECU 11 energizes the glow plug 14 in S302 according to the energization amount Cglow calculated in S301.

  On the other hand, if a negative determination is made in S102 (Cr> Crbase), the ECU 11 proceeds to S303. In S303, the ECU 11 sets the energization amount Cglow of the glow plug 14 to zero and ends the execution of this routine.

  According to the embodiment described above, it is possible to obtain the same effect as that of the first embodiment described above. Further, switching between energization / non-energization of the glow plug 14 and change in the energization amount Cglow are more responsive than changes in the EGR gas amount, so that the cetane number of the fuel used changes every moment as just after refueling. In this case, the ignition timing control method of this embodiment is effective.

  The ignition timing control method according to the present embodiment is the same as that in the first embodiment described above until the actual EGR gas amount reaches a desired amount from the time when the opening degree of the EGR valve 10 is changed to change the EGR gas amount. It may be executed during the response delay period.

1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied. It is a figure which shows the map which defined the pre-mixing combustion operation area | region and diffusion combustion operation area | region of an internal combustion engine. It is a timing chart which shows the fuel-injection method at the time of diffusion combustion operation. It is a timing chart which shows the fuel-injection method at the time of a premix combustion operation. It is a flowchart which shows the ignition timing control routine in a 1st Example. It is a figure which shows the relationship between correction amount (DELTA) EGR of EGR valve opening degree, and deviation (DELTA) Cr1. It is a figure which shows the relationship between the cetane number of used fuel, and the amount of EGR gas. It is a timing chart which shows the fuel-injection method at the time of a premixed combustion driving | operation in a 2nd Example. It is a flowchart which shows the ignition timing control routine in a 2nd Example. It is a figure which shows the relationship between the cetane number Cr of the used fuel, and the post injection quantity Qpst. It is a figure which shows schematic structure of the internal combustion engine in a 3rd Example. It is a flowchart which shows the ignition timing control routine in a 3rd Example. It is a figure which shows the relationship between the cetane number Cr of use fuel, and the energization amount Cglow of a glow plug.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 5 ... Fuel injection valve 8 ... EGR passage 9 ... EGR cooler 10 ... EGR valve 11 ... ECU
14. Glow plug

Claims (7)

In an ignition timing control system for an internal combustion engine that premixes fuel and gas in a cylinder by introducing EGR gas into the cylinder,
Discriminating means for discriminating the ignitability of the fuel used in the internal combustion engine;
Control means for controlling the operating state of the internal combustion engine so that the ignition delay period decreases as the ignitability determined by the determination means decreases;
An ignition timing control system for an internal combustion engine, comprising:   2. The internal combustion engine according to claim 1, wherein the control means shortens the ignition delay period by reducing the amount of EGR gas introduced into the cylinder as the ignitability determined by the determination means decreases. Engine ignition timing control system.   3. The control unit according to claim 2, wherein the control unit causes the fuel injection valve to perform post injection for a predetermined period from the start of the EGR gas amount reduction processing, and the post-injection amount as the ignitability determined by the determination unit decreases. An ignition timing control system for an internal combustion engine characterized by increasing the engine.   2. The control device according to claim 1, wherein when the ignitability determined by the determination unit is lower than a predetermined reference value, post-injection is performed from the fuel injection valve, and the ignitability determined by the determination unit decreases. An ignition timing control system for an internal combustion engine characterized by shortening an ignition delay period by increasing a post injection amount.   5. The ignition timing control system for an internal combustion engine according to claim 4, wherein the control means limits the post injection amount to a predetermined amount or less.   6. The control unit according to claim 5, wherein when the post injection amount reaches a predetermined amount, the control unit ignites by reducing the amount of EGR gas introduced into the cylinder as the ignitability determined by the determination unit decreases. An ignition timing control system for an internal combustion engine characterized by shortening a delay period. The internal combustion engine according to claim 1, comprising a glow plug,
An ignition timing control system for an internal combustion engine, characterized in that the control means shortens the ignition delay period by increasing the amount of heat generated by the glow plug as the ignitability determined by the determination means decreases.

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