JP4702214B2 - Start control device for in-cylinder internal combustion engine - Google Patents

Description

  The present invention relates to a start control device for a spray guide type in-cylinder injection internal combustion engine, and more particularly, in-cylinder injection that can improve startability and emission by promoting fuel vaporization and reducing wall surface adhesion. The present invention relates to a start control device for an internal combustion engine.

  A cylinder injection type internal combustion engine in which fuel is directly injected into a combustion chamber by a fuel injection valve is known. In this in-cylinder internal combustion engine, the electrode portion of the spark plug is laid out at the center of the upper wall of the combustion chamber so as to be located in the vicinity of the fuel spray from the fuel injection valve or in the vicinity of the fuel spray ridgeline. A technique called a spray guide system that directly ignites the fuel spray is known.

  Such an in-cylinder injection internal combustion engine ensures ignitability by injecting fuel in the compression stroke at least when the engine is under a low load to form an air-fuel mixture having good ignitability only around the spark plug. As a whole in the cylinder, stratified combustion is performed to enable lean air-fuel mixture combustion. Thereby, effects such as improvement in fuel consumption, reduction of hydrocarbon (HC), suppression of smoke, and the like can be obtained.

  However, even when trying to perform such stratified combustion at the time of cold start of the engine, the fuel injected in the compression stroke is not sufficiently vaporized in the short time until ignition because the in-cylinder temperature is low, and around the spark plug It is impossible to form an air-fuel mixture with good ignitability.

  Therefore, in order to ensure the ignitability at the cold start, in the direct injection internal combustion engine in which ignition is started after the normal fuel injection is started at the cold start, the normal fuel injection (main injection) Prior to this, a technique has been proposed in which preliminary fuel injection (pilot injection) is performed when the piston is within a range of a crank angle of approximately 180 ° centered at bottom dead center (see, for example, Patent Document 1).

  As a related art, it is required in the combustion chamber for the first mixture formation before the start of the start-up phase of the internal combustion engine, in order to improve the mixture formation at the start of the internal combustion engine, in particular during the warm start. A technique has been proposed in which fuel mass is provided to a combustion chamber by a plurality of continuous fuel injections (see, for example, Patent Document 2).

JP 11-153050 A JP 2004-197736 A

  However, at the time of cold start, since the temperature of the intake air, the temperature of the cylinder wall surface, and the temperature of the fuel are all low, fuel vaporization is poor and so-called wall surface adhesion of the fuel is likely to occur. For this reason, in the above-described prior art in which preliminary fuel injection is performed, startability may not be improved, and emissions may be deteriorated, particularly hydrocarbon (HC), carbon monoxide (CO), It was necessary to suppress the occurrence of smoke.

  The present invention has been made in view of the above. By performing pilot combustion before main combustion is performed at the time of cold start to increase the in-cylinder temperature, thereby promoting fuel vaporization and reducing wall surface adhesion. An object of the present invention is to provide a start control device for a direct injection internal combustion engine that can improve startability and emission.

In order to solve the above-described problems and achieve the object, a start control device for a direct injection internal combustion engine according to claim 1 of the present invention includes a fuel injection valve that directly injects fuel into a combustion chamber, and the fuel injection And at least a spark plug disposed so that the electrode portion is positioned near the ridge line of the fuel spray from the valve, and fuel is injected in the second half of the compression stroke or the first half of the expansion stroke when the internal combustion engine is cold started In the in-cylinder internal combustion engine start control device for performing main combustion that performs spark ignition and pilot combustion that performs preliminary fuel injection and spark ignition prior to the main combustion, the fuel injection during the pilot combustion and it is performed by the intake stroke first half or the intake bottom dead center near the ignition, fuel injection amount at the time of the pilot combustion, fuel injected during the main combustion of the pilot combustion The raw heat is characterized in that the set small amounts so as not to self-ignition.

Therefore, according to the present invention, fuel vaporization is promoted by the in-cylinder warm-up effect of the pilot combustion at the cold start, and the amount of fuel adhering to the piston or the like is reduced, so that the combustibility of the main combustion is improved, Startability and emissions are improved.
Further, according to the present invention, the fuel injected during the main combustion is prevented from burning suddenly by self-ignition, and the generation of smoke is suppressed.

  According to a second aspect of the present invention, there is provided a start control device for a direct injection internal combustion engine according to the first aspect, wherein the pilot combustion is performed during the first half of the intake stroke when the pilot combustion is performed in the first half of the intake stroke. The fuel injection start timing and ignition start timing are after the later of the time when the air amount necessary for pilot combustion can be secured by opening the intake valve and the time when the amount of fuel adhering to the piston becomes less than the allowable value. In addition, it is set before the time when the same amount of air as the amount of in-cylinder gas increased by the pilot combustion can be secured.

  Therefore, according to the present invention, the amount of air necessary for pilot combustion (intake amount) is ensured, and pilot combustion can be performed in a state where the amount of fuel attached to the piston or the like is minimized. Further improvement.

  According to a third aspect of the present invention, there is provided a start control device for a direct injection internal combustion engine according to the first aspect, wherein the pilot combustion is performed when the pilot combustion is performed in the vicinity of the intake bottom dead center. In this case, the fuel injection start timing and the ignition start timing are set so that heat generation by the pilot combustion starts after the intake valve is closed.

  Therefore, according to the present invention, it is possible to suppress the backflow of the pilot combustion combustion gas to the intake port, reduce the intake loss, and ensure good combustion.

According to a fourth aspect of the present invention, there is provided a start control device for a direct injection internal combustion engine according to the third aspect, wherein the air in the cylinder flows backward to the intake port under a predetermined condition. The fuel injection start timing at the time of pilot combustion is set after the intake valve is closed.

  Therefore, according to the present invention, the injection fuel for pilot combustion and the combustion gas thereof are reliably suppressed from flowing back to the intake port, the intake loss is reduced, and good combustion is ensured.

According to the start control device for a direct injection internal combustion engine according to the present invention (Claim 1), the vaporization of fuel is promoted by the in-cylinder warm-up effect of the pilot combustion at the cold start, and the fuel adheres to the piston or the like. Since the amount decreases, the combustibility of the main combustion can be improved, and the startability and emission can be improved.
In addition, it is possible to avoid the fuel that is injected during the main combustion from being rapidly burned by self-ignition, and it is possible to suppress the occurrence of smoke.

  Further, according to the start control device for a direct injection internal combustion engine according to the present invention (Claim 2), an air amount (intake amount) necessary for pilot combustion is ensured, and an amount of fuel adhering to the piston or the like is reduced. Since pilot combustion can be performed in a minimized state, emissions can be further improved.

  Further, according to the start control device for a direct injection internal combustion engine according to the present invention (claim 3), it is possible to suppress the backflow of the combustion gas of the pilot combustion to the intake port, thereby reducing the intake loss. Good combustion can be ensured.

Further, according to the start control device for a cylinder injection internal combustion engine according to the present invention (claim 4 ), it is possible to reliably suppress the backflow of the injected fuel for the pilot combustion and the combustion gas thereof to the intake port. Therefore, intake loss can be reduced and good combustion can be ensured.

  Embodiments of a start control device for a direct injection internal combustion engine according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  First, a schematic configuration of a spray guide type cylinder injection internal combustion engine (hereinafter, referred to as an engine as appropriate) to which the present invention is applied will be described with reference to FIG. Here, FIG. 2 is a cross-sectional view showing a schematic configuration of the engine.

  As shown in FIG. 2, the engine 10 is a four-cycle gasoline engine that directly injects a fuel spray 23 a into the combustion chamber 10 a by a fuel injection valve 23 and ignites sparks by an ignition plug 14, and is configured by a known technique.

  That is, the combustion chamber 10 a of the engine 10 is constituted by a cylinder bore 11, a cylinder head 13, and a piston 12 that is disposed in the cylinder bore 11 so as to be reciprocally movable. The fuel injection valve 23 is disposed at the center of the upper wall of the combustion chamber 10a.

  The spark plug 14 is disposed so that the electrode portion is located in the fuel spray 23 a injected from the fuel injection valve 23 or in the vicinity of the ridge line of the fuel spray 23 a. The spark plug 14 sparks the fuel spray 23a during or immediately after fuel injection.

  An intake valve (intake valve) 16 is disposed at the intake port 15 facing the combustion chamber 10a, and an exhaust valve 20 is disposed at the exhaust port 18 facing the combustion chamber 10a. These valves 16 and 20 are controlled to be opened and closed by a variable valve timing mechanism 28 that variably controls the opening and closing operation timing.

  Although not shown, the exhaust passage of the engine 10 is provided with a catalyst device for purifying smoke, NOx, HC and the like in the exhaust gas.

  Each component of the engine 10, such as a variable valve timing mechanism 28 that variably controls the valves 16 and 20, a spark plug 14, and a fuel injection valve 23, is controlled by an electronic control unit (ECU) 30. The ECU 30 functions as a start control device according to the present invention and executes a control operation described later.

  As shown in FIG. 1, the engine 10 configured as described above has a main combustion in which fuel is injected and spark-ignited in the latter half of the compression stroke at the time of cold start, and a small amount is preliminarily preliminary in the first half of the intake stroke prior to the main combustion. Pilot combustion with fuel injection and spark ignition is performed. That is, stratified combustion is performed in the main combustion. Here, FIG. 1 is a conceptual diagram showing the timing of pilot combustion according to Embodiment 1 of the present invention.

  This control method will be described in more detail with reference to FIGS. This control is executed at predetermined time intervals by the ECU 30 described above. Here, FIG. 3 is a flowchart showing the control method, and FIG. 4 is an explanatory diagram showing the relationship between the cooling water temperature of the engine 10 and the fuel vaporization rate, and is used when determining the necessity of in-cylinder warming. Is.

  FIG. 5 is an explanatory diagram showing the relationship between the required injection amount at the time of pilot injection and the coolant temperature, and is used when determining the fuel injection amount at the time of pilot injection. 4 and 5, the cooling water temperature is simply abbreviated as the water temperature.

  FIG. 6 is an explanatory diagram showing the temporal transition of the in-cylinder air amount, FIG. 7 is an explanatory diagram showing the temporal transition of the distance between the tip of the fuel injection valve 23 and the top surface of the piston 12, and FIG. FIG. 6 is an explanatory diagram showing a temporal transition of the amount of fuel adhering to the piston 12.

  As shown in FIG. 3, it is first determined at the time of cold start, that is, whether or not in-cylinder warm-up is necessary (step S10). As shown in FIG. 4, the current cooling water temperature detected by a cooling water temperature sensor (not shown) indicates that the vaporization rate at the ignition timing of the fuel injected into the cylinder is a predetermined value, for example, 90%. It can be determined by whether or not the specified water temperature Tws has been reached.

  That is, if the current cooling water temperature does not reach the specified water temperature Tws, it can be determined that it is during cold start, fuel vaporization is poor, wall surface adhesion occurs, and emissions deteriorate. Therefore, it is determined that in-cylinder warm-up is necessary (Yes at step S10). On the other hand, if the in-cylinder warm-up is not necessary (No at Step S10), the control is terminated because it is not the target of this control.

  If it is determined that in-cylinder warm-up is necessary (Yes at Step S10), a fuel injection amount for pilot injection is determined (Step S20). For example, the fuel injection amount required at the current coolant temperature is determined from the graph shown in FIG.

  Further, this fuel injection amount is set to a small amount so that the fuel (main injection fuel) injected at the time of main combustion performed later does not cause self-ignition due to heat generated by pilot combustion. This is because smoke is easily generated when the main injection fuel suddenly burns due to self-ignition, so that this smoke generation is suppressed.

  Next, the injection start timing for pilot injection is determined (step S30). This is determined so that the air amount (intake amount) necessary for pilot combustion can be secured and the amount of fuel adhering to the piston 12 is minimized. That is, for example, the time t1 shown in FIG. 6 and the time t3 shown in FIG. 8 are compared, and it may be set after the later one and before the time t2 shown in FIG.

  Here, the time t1 is a time when the air amount ap necessary for pilot combustion can be secured. Moreover, the time t2 is a time when the air amount ag that is the same as the in-cylinder gas amount that increases due to pilot combustion can be secured.

  Moreover, the time t3 is a time when the fuel adhesion amount falls below the allowable fuel adhesion amount s. Note that the specified values s of the air amounts ap and ag and the fuel adhesion amount vary depending on the fuel injection amount, and therefore optimum values are set in advance for each fuel injection amount.

  Thus, the pilot injection start timing set in the first half of the intake stroke is a timing when the distance between the tip of the fuel injection valve 23 and the top surface of the piston 12 remains to some extent, as can be seen with reference to FIG. It corresponds.

  Next, the ignition start timing for pilot combustion is determined (step S40). This can be determined in consideration of the injection period determined by the injection start timing determined in step S30 and the fuel injection amount determined in step S20.

  When the pilot combustion is executed based on the fuel injection amount, the injection start timing, and the ignition start timing determined in this way, the cylinder is warmed up and the combustibility of the main combustion executed in the latter half of the compression stroke is improved. . In addition, since control regarding main combustion can be performed by a well-known technique, detailed description is abbreviate | omitted.

  As described above, according to the start control device for a direct injection internal combustion engine according to the first embodiment, fuel vaporization is promoted by the in-cylinder warm-up effect of the pilot combustion during the cold start. Further, in the latter half of the compression stroke (near TDC) in FIG. 8, the amount of fuel adhering to the piston 12 decreases as shown by the solid line graph from the broken line graph. Therefore, the combustion property of the main combustion can be improved by the in-cylinder warm-up effect by the pilot combustion, so that the startability and the emission can be improved.

  Although the first embodiment has been described as applying the present invention to the engine 10 including the fuel injection valve 23 disposed in the central portion of the upper wall of the combustion chamber 10a, the present invention is not limited to this. For example, as shown in FIG. 9, the present invention may be applied to an engine 10 that includes a fuel injection valve 23 disposed at the end of the upper wall of the combustion chamber 10 a. Here, FIG. 9 is a cross-sectional view showing an engine having another configuration.

  In the first embodiment, the example in which the pilot combustion is executed in the first half of the intake stroke is shown. However, in the second embodiment, the pilot combustion is executed in the vicinity of the intake bottom dead center (BDC) as shown in FIG. is there. Further, the second embodiment is applied to the engine 10 shown in FIG. 2 or 9 of the first embodiment. Since the engine 10 is a spray guide system, it can ignite the fuel injected near the intake bottom dead center (BDC).

  In addition, the pilot combustion may cause a phenomenon in which the air in the cylinder flows backward to the intake port 15 under predetermined conditions. For this reason, in the present Example 2, the coping method which suppresses this backflow was also implemented.

  Here, FIG. 10 is a conceptual diagram showing the timing of pilot combustion according to Embodiment 2 of the present invention. In the following description, the same or corresponding parts as those already described are denoted by the same reference numerals, and redundant description is omitted or simplified.

  Hereinafter, a control method according to the second embodiment will be described with reference to FIG. This control is executed at predetermined time intervals by the ECU 30 described above. Here, FIG. 11 is a flowchart showing a control method.

  As shown in FIG. 11, if it is determined that the in-cylinder warm-up is necessary (Yes at Step S10), it is then determined whether or not a phenomenon occurs in which the air in the cylinder flows backward to the intake port 15 (Step S15). ).

  When the lift amount of the intake valve 16 is large, as shown in FIG. 12, when the piston 12 moves at a low speed and rises after the intake bottom dead center (BDC), the same air amount ag as the in-cylinder gas amount increased by pilot combustion is secured. A phenomenon occurs in which the air in the cylinder flows backward to the intake port 15.

  In order to suppress this backflow, first, it is determined whether or not the backflow has occurred (step S15), and if it has occurred (step S15 affirmative), it is dealt with after step S50 described later. is there. Here, FIG. 12 is an explanatory diagram showing a temporal transition of the in-cylinder air amount.

  If the backflow has not occurred (No at Step S15), the fuel injection amount for pilot injection is determined in the same manner as in the first embodiment (Step S20). Then, an injection start timing for pilot injection and an ignition start timing for pilot combustion are determined (steps S30 and S40), and the control is terminated.

  In this case, as shown in FIG. 13, the injection start timing and the ignition start timing are set so that the heat generation of the pilot combustion occurs after the timing t4 when the intake valve 16 is almost closed. Thereby, the backflow of combustion gas to the intake port 15 can be reliably suppressed. Here, FIG. 13 is a conceptual diagram showing the timing of heat generation of pilot combustion.

  On the other hand, if the reverse flow has occurred (Yes at Step S15), it is determined whether or not the variable valve timing mechanism 28 can be used (Step S50). In the second embodiment, since the variable valve timing mechanism 28 is provided and is in a usable state (Yes at Step S50), it is determined whether or not it can be dealt with by the countermeasure 1 described later (Step S60).

  As shown in FIG. 14, the countermeasure 1 is such that the operating angle of the intake valve 16 is reduced by the variable valve timing mechanism 28 so that the intake valve 16 is substantially closed near the intake bottom dead center (BDC). is there.

  As a result, as shown in FIG. 15, an air amount ag that is the same as the in-cylinder gas amount that is increased by pilot combustion can be secured, and the in-cylinder air can be prevented from flowing back to the intake port 15. Here, FIG. 14 is an explanatory diagram showing a temporal transition of the lift amount of the intake valve 16 according to the countermeasure 1, and FIG. 15 is an explanatory diagram showing a temporal transition of the in-cylinder air amount according to the countermeasure 1. .

  Therefore, if it is possible to cope with this countermeasure 1 (Yes in step S60), countermeasure 1 is implemented (step S65), and the fuel injection amount for pilot injection is determined in step S20.

  In this countermeasure 1, since the operating angle of the intake valve 16 is made a predetermined amount smaller than the reference timing, a sudden air inflow into the cylinder occurs. Thereby, as shown in FIG. 16, it is possible to obtain an effect of increasing the in-cylinder temperature according to the opening timing retardation amount of the intake valve 16.

  Accordingly, in step S20, the fuel injection amount for pilot injection is determined in consideration of the effect of increasing the in-cylinder temperature. When the fuel injection amount is determined, the injection start timing for pilot injection and the ignition start timing for pilot combustion are determined (steps S30 and S40). Here, FIG. 16 is an explanatory diagram showing the relationship between the opening timing retardation amount of the intake valve 16 and the in-cylinder temperature rise effect.

  On the other hand, if it is not possible to cope with the countermeasure 1 (No at Step S60), it is determined whether or not the countermeasure 1 can be handled by adding the countermeasure 2 described later to the countermeasure 1 (Step S70).

  As shown in FIG. 17, the countermeasure 2 is to reduce the lift amount of the intake valve 16 by the variable valve timing mechanism 28 so that the intake continues after the intake bottom dead center (BDC).

  As a result, as shown in FIG. 18, an air amount ag that is the same as the in-cylinder gas amount that increases due to pilot combustion can be secured, and the in-cylinder air can be prevented from flowing back to the intake port 15. Here, FIG. 17 is an explanatory diagram showing a temporal transition of the lift amount of the intake valve 16 according to the countermeasure 2, and FIG. 18 is an explanatory diagram showing a temporal transition of the in-cylinder air amount according to the countermeasure 2. .

  Therefore, if it is possible to cope with the countermeasures according to the countermeasure 1 and the countermeasure 2 (Yes in Step S70), this countermeasure is implemented (Step S75), and the air in the cylinder is prevented from flowing back to the intake port 15. To do.

  Thereafter, similarly to the above, the fuel injection amount for pilot injection and the injection start timing are determined (steps S20 and S30), and the ignition start timing for pilot combustion is determined (step S40).

  Further, if the countermeasure 2 added to the countermeasure 1 cannot be dealt with (No at Step S70), it is determined whether or not the countermeasure can be dealt with by adding the countermeasure 3 to be described later (Step S80). ).

  As shown in FIG. 19, in the third countermeasure, the entire valve timing of the intake valve 16 is advanced by the variable valve timing mechanism 28 so that the intake valve 16 is substantially closed in the vicinity of the intake bottom dead center (BDC). Is.

  As a result, as shown in FIG. 20, an air amount ag that is the same as the in-cylinder gas amount that is increased by pilot combustion can be secured, and the in-cylinder air can be prevented from flowing back to the intake port 15. Here, FIG. 19 is an explanatory diagram showing a temporal transition of the lift amount of the intake valve 16 according to the countermeasure 3, and FIG. 20 is an explanatory diagram showing a temporal transition of the in-cylinder air amount according to the countermeasure 3. .

  Therefore, if it is possible to cope with the countermeasures by the countermeasure 1, the countermeasure 2, and the countermeasure 3 (Yes at Step S80), this countermeasure is implemented (Step S90), and the air in the cylinder flows back to the intake port 15 To suppress.

  Thereafter, similarly to the above, the fuel injection amount for pilot injection and the injection start timing are determined (steps S20 and S30), and the ignition start timing for pilot combustion is determined (step S40).

  By the way, in the second embodiment, the variable valve timing mechanism 28 is in a usable state, but it may not be usable for some reason (No in step S50). Even if the variable valve timing mechanism 28 can be used, it may not be possible to cope with the above-described countermeasures 1, 2, and 3 (No in step S80). In these cases, the process proceeds to step S100, and after determining the fuel injection amount for pilot injection, the injection start timing for pilot injection and the ignition start timing for pilot combustion are determined (steps S110 and S120).

  At this time, as shown in FIG. 21, the injection start timing and the ignition start timing are set after time t4 when the intake valve 16 is substantially closed. As a result, fuel injection and ignition are performed after the intake valve 16 is almost closed, and then heat generation by pilot combustion occurs, so that it is ensured that the injected fuel for pilot combustion or its combustion gas flows backward to the intake port 15. Can be suppressed. FIG. 21 is a conceptual diagram showing the injection start timing for pilot injection and the ignition start timing for pilot combustion.

  The above control (steps S100 to S120) can also be applied to a spray guide type direct injection engine that does not include a variable valve timing mechanism.

  As described above, according to the start control device for the direct injection internal combustion engine according to the second embodiment, the fuel vaporization is promoted by the in-cylinder warm-up effect of the pilot combustion at the cold start, and the piston 12 and the like. Therefore, the startability and emission can be improved.

  Furthermore, since it is possible to suppress the injection fuel for pilot combustion or the combustion gas thereof from flowing back to the intake port 15, intake loss can be reduced and good combustion can be ensured.

  In the first and second embodiments, the main combustion is described as being executed in the latter half of the compression stroke. However, the present invention is not limited to this, and may be executed in the first half of the expansion stroke. Can be expected.

  As described above, the start control device for a direct injection internal combustion engine according to the present invention is useful for a spray guide type direct injection internal combustion engine, and in particular, by promoting fuel vaporization and reducing wall surface adhesion. It is suitable for a direct injection internal combustion engine that aims to improve startability and emission.

It is a conceptual diagram which shows the timing of the pilot combustion which concerns on Example 1 of this invention. It is sectional drawing which shows schematic structure of an engine. It is a flowchart which shows a control method. It is explanatory drawing which shows the relationship between a cooling water temperature of an engine, and a fuel vaporization rate. It is explanatory drawing which shows the relationship between the request | requirement injection quantity at the time of pilot injection, and cooling water temperature. It is explanatory drawing which shows time transition of the amount of cylinder air. It is explanatory drawing which shows time transition of the distance of the front-end | tip of a fuel injection valve, and the top surface of a piston. It is explanatory drawing which shows the time transition of the fuel adhesion amount to a piston. It is sectional drawing which shows the engine of another structure. It is a conceptual diagram which shows the timing of the pilot combustion which concerns on Example 2 of this invention. It is a flowchart which shows a control method. It is explanatory drawing which shows time transition of the amount of cylinder air. It is a conceptual diagram which shows the timing of the heat generation of pilot combustion. It is explanatory drawing which shows the time transition of the lift amount of the intake valve which concerns on the countermeasure 1. FIG. It is explanatory drawing which shows the time transition of the in-cylinder air amount which concerns on the countermeasure 1. FIG. It is explanatory drawing which shows the relationship between the opening timing retard amount of an intake valve, and the cylinder temperature rise effect. It is explanatory drawing which shows the time transition of the lift amount of the intake valve which concerns on the countermeasure 2. It is explanatory drawing which shows the time transition of the in-cylinder air amount which concerns on the countermeasure 2. FIG. 10 is an explanatory diagram showing a time transition of the lift amount of the intake valve according to countermeasure 3; It is explanatory drawing which shows the time transition of the air quantity in a cylinder which concerns on the countermeasure 3. It is a conceptual diagram which shows the injection start timing for pilot injection, and the ignition start timing for pilot combustion.

Explanation of symbols

10 engine (in-cylinder internal combustion engine)
10a Combustion chamber 12 Piston 14 Spark plug 15 Intake port 16 Intake valve (intake valve)
23 Fuel Injection Valve 23a Fuel Spray 28 Variable Valve Timing Mechanism 30 ECU (Starting Control Device)
t1 Time when the amount of air ap required for pilot combustion can be secured t2 Time when the same amount of air ag as the in-cylinder gas amount increased by pilot combustion can be secured t3 Fuel attachment amount falls below the allowable fuel attachment amount s Timing t4 Timing when the intake valve is almost closed

Claims (4)

A fuel injection valve that injects fuel directly into the combustion chamber;
An ignition plug disposed so that an electrode portion is positioned during fuel spray from the fuel injection valve or in the vicinity of a ridge line of the fuel spray;
Comprising at least
Main combustion in which fuel is injected and spark ignited in the second half of the compression stroke or the first half of the expansion stroke when the internal combustion engine is cold started;
Pilot combustion that preliminarily injects fuel and ignites sparks prior to the main combustion,
In a start control device for a direct injection internal combustion engine that performs
The are performed by the intake stroke first half or the intake bottom dead center near the fuel injection and the ignition time of the pilot combustion,
The fuel injection amount at the time of the pilot combustion is set so small that the fuel injected at the time of the main combustion is not self-ignited by the generated heat of the pilot combustion . Start control device.   When the pilot combustion is performed in the first half of the intake stroke, the fuel injection start timing and ignition start timing at the time of the pilot combustion are the timing at which the air amount necessary for the pilot combustion can be secured by opening the intake valve and the piston It is set after the later of the times when the amount of fuel adhering to or below the allowable value and before the time when the same amount of air as the in-cylinder gas amount increased by the pilot combustion can be secured. The start control device for a direct injection internal combustion engine according to claim 1, wherein the start control device is a cylinder injection type internal combustion engine.   When the pilot combustion is performed near the intake bottom dead center, the fuel injection start timing and ignition start timing during the pilot combustion are set so that heat generation by the pilot combustion starts after the intake valve is closed. The start control apparatus for a direct injection internal combustion engine according to claim 1, wherein the start control apparatus is a cylinder injection internal combustion engine. The fuel injection start timing at the time of the pilot combustion is set after the intake valve is closed when the air in the cylinder flows backward to the intake port under a predetermined condition. A start control device for a direct injection internal combustion engine.

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