JP2016130495A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of stably obtaining satisfactory stratified combustion.SOLUTION: An ignition plug 16 is disposed at a center in an upper portion of a cylinder 12. A tumble flow 36 is generated within the cylinder 12. An internal combustion engine comprises a cylinder injection valve 18 that injects fuel into the cylinder 12. The cylinder injection valve 18 injects the fuel toward a high-speed part 38 of the tumble flow 36 with timing when the high-speed part 38 moves toward the cylinder injection valve 18 set as injection timing θa. The high-speed part 38 is a part of the tumble flow 36 which a part thereof at a higher flow speed than an average flow speed of the tumble flow 36.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine suitable for mounting on a vehicle.

  Patent Document 1 discloses a cylinder injection type spark ignition internal combustion engine including an in-cylinder injection valve that directly injects fuel into a cylinder, and an ignition plug disposed in the upper center of the cylinder. The intake system of the internal combustion engine is provided so that a tumble flow is generated in the cylinder by the flow of intake air. Patent Document 1 discloses that good stratified combustion can be obtained by injecting fuel so as to collide with a tumble flow blown from the upper surface of the piston toward the in-cylinder injection valve.

  When the atomized fuel collides with the tumble flow blown up from the upper surface of the piston, the fuel can be deflected toward the center side of the tumble flow. The pressure around the center of the tumble flow is lower than that around it. For this reason, the fuel deflected to the center side of the tumble flow is easily held at the center portion. If the compression stroke is advanced in this state, a high-concentration air-fuel mixture can be stratified at the upper center in the cylinder, that is, at the position where the spark plug is installed. For this reason, according to the conventional internal combustion engine, good stratified combustion can be obtained with high probability.

JP 2004-162577 A JP 2002-030969 A JP 2002-332849 A JP 2009-114916 A

  By the way, the tumble flow generated in the cylinder does not have a uniform flow velocity. For this reason, even if the fuel is injected so as to collide with the tumble flow, if the flow velocity at the collision portion is not sufficient, the fuel penetrates the tumble flow and the desired deflection may not be obtained. In this case, a high-concentration air-fuel mixture cannot be induced around the spark plug, and a situation where good stratified combustion cannot be obtained may occur.

  The present invention has been made to solve the above-described problems, and provides an internal combustion engine that can stably suppress the penetration force of sprayed fuel by a tumble flow and stably obtain good stratified combustion. The purpose is to do.

In order to achieve the above object, a first invention is an internal combustion engine,
A spark plug located in the upper center of the cylinder;
A tumble generating mechanism for generating a tumble flow in the cylinder;
An in-cylinder injection valve for injecting fuel into the cylinder,
The in-cylinder injection valve injects fuel toward the high-speed portion, with the timing at which the high-speed portion of the tumble flow moves toward the in-cylinder injection valve as an injection timing,
The high-speed portion is a part of the tumble flow, and is a series of portions having a flow velocity faster than the average flow velocity of the tumble flow.

The second invention is the first invention, wherein
The injection timing includes a time point corresponding to a crank angle within 160 to 180 ° CA after intake top dead center,
The in-cylinder injection valve is configured to inject fuel in a direction that collides with a high speed portion of a tumble flow at 160 to 180 ° CA after intake top dead center.

The third invention is the first or second invention, wherein
A control unit for determining a fast idle execution condition for setting the idle rotation speed immediately after the start of the internal combustion engine to a higher rotation speed than the normal idle rotation speed after the end of warm-up;
The in-cylinder injection valve injects fuel at the injection timing while the fast idle execution condition is satisfied.

In addition, a fourth invention is any one of the first to third inventions,
A control unit for determining whether or not the execution condition of the lean burn operation in which the target air-fuel ratio is thinner than the stoichiometric lean air-fuel ratio is satisfied,
The in-cylinder injection valve injects fuel at the injection timing while the execution condition of the lean burn operation is satisfied.

In addition, a fifth invention is any one of the first to fourth inventions,
The tumble generating mechanism is
The in-cylinder injection valve;
A control unit that causes the in-cylinder injection valve to perform pre-injection of fuel at a timing at which an airflow in the same direction as the tumble flow is generated in the cylinder,
The injection timing is advanced as the fuel injection amount by the pre-injection increases.

In addition, a sixth aspect of the present invention provides any one of the first to fifth aspects,
It has a throttle valve provided in the intake passage,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The injection timing is advanced as the opening of the throttle valve increases.

In addition, a seventh invention is any one of the first to sixth inventions,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
A tumble control valve that controls the flow of intake air that generates the tumble flow;
The injection timing is advanced as the opening degree of the tumble control valve is controlled to increase the strength of the tumble flow.

Further, an eighth invention is any one of the first to seventh inventions,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The injection timing is advanced as the engine speed increases.

Further, a ninth invention is any one of the first to eighth inventions,
A variable valve mechanism for changing the opening timing of the intake valve of the internal combustion engine,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The injection timing is advanced as the intake valve opening timing is advanced.

According to a tenth invention, in any one of the first to ninth inventions,
The injection timing is set a plurality of times during one cycle, and the fuel injection amount to be injected during one cycle is divided into the plurality of times and injected.

The eleventh aspect of the invention is the tenth aspect of the invention,
A control unit that calculates the ratio of fuel that is divided and injected multiple times,
The control unit calculates the ratio so that the fuel injection amount becomes smaller as the order of injection in one cycle is slower.

The twelfth invention is the tenth or eleventh invention,
It has a throttle valve provided in the intake passage,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The interval between the plurality of injection timings is shorter as the opening of the throttle valve is larger.

The thirteenth aspect of the invention is any one of the tenth to twelfth aspects of the invention,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
A tumble control valve that controls the flow of intake air that generates the tumble flow;
The interval between the plurality of injection timings is shortened as the opening of the tumble control valve is controlled in a direction to increase the strength of the tumble flow.

In addition, a fourteenth invention is any one of the tenth to thirteenth inventions,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The interval between the plurality of injection timings is shorter as the engine speed is higher.

The fifteenth aspect of the invention is any one of the tenth to fourteenth aspects of the invention,
A variable valve mechanism for changing the opening timing of the intake valve of the internal combustion engine,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The interval between the plurality of injection timings is shorter as the opening timing of the intake valve is advanced.

  According to the first aspect of the invention, the fuel injected from the in-cylinder injection valve can collide with the high speed portion of the tumble flow. Since the high speed portion is a portion having a high flow velocity in the tumble flow, the penetration force of the fuel can be satisfactorily suppressed. Therefore, according to the present invention, a high-concentration air-fuel mixture layer can be stably guided around the spark plug located in the upper center of the cylinder, and good stratified combustion can be stably generated.

  According to the second invention, fuel can be injected from the in-cylinder injection valve at a time corresponding to a crank angle within 160 to 180 ° CA after the intake top dead center. From 160 to 180 ° CA after the intake top dead center, a period in which the high-speed air flow sucked in the vicinity of 90 ° CA after the intake top dead center where the moving speed of the piston is the fastest becomes a tumble flow and starts toward the injection valve It is. According to the present invention, the fuel penetration force can be satisfactorily suppressed by causing the fuel to collide with the high-speed airflow.

  According to the third aspect of the present invention, it is possible to stably introduce a high-concentration air-fuel mixture around the spark plug during execution of fast idle. For this reason, according to the present invention, it is possible to provide an internal combustion engine having excellent combustion characteristics during fast idling.

  According to the fourth aspect of the invention, it is possible to stably introduce a high-concentration air-fuel mixture around the spark plug during the lean burn operation. For this reason, according to the present invention, it is possible to provide an internal combustion engine having excellent combustion characteristics during lean burn operation.

  According to the fifth aspect, the tumble flow can be generated by the pre-injection of fuel. The tumble flow becomes faster as the fuel injection amount by the pre-injection increases. The time when the high speed portion of the tumble flow begins to move toward the in-cylinder injection valve becomes faster as the flow velocity becomes higher. According to the present invention, since the injection timing can be matched to the change in the timing, the fuel penetration force can be stably suppressed.

  According to the sixth aspect, a tumble flow can be generated by the flow of intake air. This tumble flow becomes faster as the throttle opening is larger and the intake air amount is larger. Therefore, the timing at which the high speed portion of the tumble flow starts to move toward the in-cylinder injection valve is earlier as the throttle opening is larger. According to the present invention, since the injection timing can be matched to the change in the timing, the fuel penetration force can be stably suppressed.

  According to the seventh aspect, a tumble flow can be generated by the flow of intake air, and the flow velocity can be controlled by the tumble control valve. Then, by changing the injection timing in accordance with the state of the tumble control valve, the timing at which the high speed portion of the tumble flow starts to move toward the in-cylinder injection valve can be stably synchronized with the fuel injection timing. For this reason, also by this invention, the penetration force of a fuel can be suppressed stably.

  According to the eighth aspect, a tumble flow can be generated by the flow of intake air. The flow rate of the tumble flow becomes higher as the engine speed is higher. Accordingly, the timing at which the high speed portion of the tumble flow starts to move toward the in-cylinder injection valve becomes faster as the engine speed increases. According to the present invention, since the injection timing can be matched to the change in the timing, the fuel penetration force can be stably suppressed.

  According to the ninth aspect, a tumble flow can be generated by the flow of intake air. The flow rate of the tumble flow becomes higher as the opening timing of the intake valve is advanced. Therefore, the timing at which the high speed portion of the tumble flow starts to move toward the in-cylinder injection valve becomes earlier as the valve opening timing is advanced. According to the present invention, since the injection timing can be matched to the change in the timing, the fuel penetration force can be stably suppressed.

  According to the tenth invention, the injection timing can be set a plurality of times in one cycle in accordance with the timing at which the high speed portion of the tumble flow comes toward the in-cylinder injection valve. If the injection is divided into a plurality of times, the fuel injection amount at each time is reduced as compared with the case where the injection is performed at a time. The penetration force of the injected fuel becomes weaker as the injection amount is smaller. Therefore, according to the present invention, the penetration force of the injected fuel can be suppressed as compared with the case where the fuel is injected all at once, and good stratified combustion can be generated more stably.

  According to the eleventh aspect, it is possible to reduce the ratio of the fuel that is divided and injected during one cycle as the injection proceeds. The flow rate of the tumble flow becomes slower as the compression stroke proceeds after the first fuel injection. The effect of suppressing the tumble flow with respect to the penetrating force of the injected fuel decreases as the flow velocity becomes slower. According to the present invention, it is possible to achieve a high penetration suppression effect as a whole by changing the fuel injection amount in accordance with the magnitude of the suppression force.

  According to the twelfth aspect, the flow rate of the tumble flow decreases as the throttle opening decreases. The tumble flow is more likely to decline as the flow velocity is lower. Further, the cycle of the high speed portion of the tumble flow toward the in-cylinder injection valve becomes longer as the flow velocity of the tumble flow decreases. According to the present invention, by changing the injection timing interval according to the throttle opening, it is possible to match the cycle. For this reason, according to this invention, the high penetration force suppression effect can be generated with respect to each of the separately injected fuel.

  According to the thirteenth aspect, the cycle of the high speed portion of the tumble flow toward the in-cylinder injection valve varies depending on the state of the tumble control valve. According to the present invention, by changing the interval of the injection timing according to the state of the tumble control valve, it is possible to match the cycle. For this reason, according to this invention, the high penetration force suppression effect can be generated with respect to each of the separately injected fuel.

  According to the fourteenth aspect, the period during which the high-speed portion of the tumble flow is directed to the in-cylinder injection valve changes according to the engine speed. According to the present invention, the interval of the injection timing can be adjusted to the cycle by changing it according to the engine speed. For this reason, according to this invention, the high penetration force suppression effect can be generated with respect to each of the separately injected fuel.

  According to the fifteenth aspect, the cycle of the high speed portion of the tumble flow toward the in-cylinder injection valve changes according to the opening timing of the intake valve. According to the present invention, by changing the injection timing interval according to the opening timing of the intake valve, it is possible to match the cycle. For this reason, according to this invention, the high penetration force suppression effect can be generated with respect to each of the separately injected fuel.

It is a figure which shows the structure of Embodiment 1 of this invention. It is a figure for demonstrating the conditions which the injection timing (theta) a which Embodiment 1 of this invention uses should satisfy | fill. It is a figure which shows the relationship between the fuel injection timing (theta) a and throttle opening in Embodiment 1 of this invention. It is a figure which shows the relationship between the fuel injection timing (theta) a in Embodiment 1 of this invention, and a tumble control valve (TCV) opening degree. It is a flowchart of the process routine performed in Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the injection timing (theta) a of a fuel, and an engine speed. It is a figure for demonstrating the relationship between the fuel injection timing (theta) a and the valve opening period of an intake valve. It is a figure for demonstrating the relationship between the fuel injection timing (theta) a and the valve opening timing of an intake valve. It is a figure for demonstrating the conditions which injection timing (theta) a and (theta) b which Embodiment 2 of this invention should satisfy | fill. It is a figure for demonstrating the relationship between several injection timing (theta) a, (theta) b and throttle opening in Embodiment 2 of this invention. It is a figure for demonstrating the relationship between several injection timing (theta) a, (theta) b, (theta) c in Embodiment 2 of this invention, TCV opening degree, and throttle opening degree. It is a figure for demonstrating the relationship between the flow velocity of the tumble flow high-speed part in injection timing (theta) a, (theta) b, and the ratio of the fuel amount injected in injection timing (theta) a, (theta) b. It is a flowchart of the process routine performed in Embodiment 2 of this invention. It is a figure for demonstrating the relationship between several injection timing (theta) a, (theta) b, and an engine speed. It is a figure for demonstrating the relationship between several injection timing (theta) a, (theta) b, and the valve opening period of an intake valve. It is a figure for demonstrating the relationship between several injection timing (theta) a, (theta) b, and the valve opening timing of an intake valve. It is a figure for demonstrating the relationship between the pre-injection of fuel performed in Embodiment 3 of this invention, main injection, and the phase of a tumble flow high-speed part. It is a figure for demonstrating the principle for determining the fuel ratio of pre-injection in Embodiment 3 of this invention. It is a figure for defining the interval of pre-injection and main injection. It is a figure which shows the relationship between the fuel quantity and the interval which are pre-injected. It is the figure which represented typically the relationship between the fuel quantity pre-injected, an interval, and the fuel quantity injected main. It is a flowchart of the process routine performed in Embodiment 3 of this invention. It is a figure showing the state which made the fuel collide with the high-speed part of a reverse tumble flow.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the element which is common or respond | corresponds, and the overlapping description is abbreviate | omitted. The present invention is not limited to the following embodiments.

Embodiment 1 FIG.
[Configuration of Embodiment 1]
FIG. 1 shows a configuration of an internal combustion engine 10 (hereinafter simply referred to as “internal combustion engine 10”) according to Embodiment 1 of the present invention. The internal combustion engine 10 includes a piston 14 in a cylinder 12. A spark plug 16 is provided in the upper center of the cylinder 12. The spark plug 16 is assembled so that a spark generating portion protrudes from the top surface of the cylinder 12.

  An in-cylinder injection valve 18 for injecting fuel into the cylinder 12 is further provided on the upper surface of the cylinder 12. The in-cylinder injection valve 18 receives high-pressure fuel supply, and can inject an amount of fuel into the cylinder 12 according to the valve opening time TAU. In the present embodiment, the in-cylinder injection valve 18 is configured to inject fuel obliquely from the intake side upper side in the cylinder 12 toward the upper surface of the piston 14.

  An intake passage 20 communicates with the cylinder 12. An intake valve 22 is disposed in a port portion 21 where the intake passage 20 communicates with the cylinder 12. In the present embodiment, the port portion 21 of the intake passage 20 is formed such that a strong vertical rotation vortex, that is, a strong tumble flow is generated in the cylinder 12 by the flow of intake air.

  A tumble control valve (TCV) 24 is disposed upstream of the intake valve 22. The TCV 24 is a butterfly-type valve mechanism that changes the flow passage area of the intake passage 20 and can change the strength of the tumble flow by applying a drift according to the opening degree to the intake air. In the present embodiment, specifically, the tumble strength in the cylinder 12 can be increased by increasing the opening of the TCV 24.

  A throttle valve 26 is disposed in the intake passage 20 at a position further upstream of the TCV 24. The throttle valve 26 is an electronically controlled valve mechanism that operates according to the accelerator opening, and the intake air amount can be changed according to the opening.

  An exhaust passage 28 communicates with the cylinder 12 of the internal combustion engine 10. An exhaust valve 30 is incorporated in the exhaust passage 28 at a portion communicating with the cylinder 12. The internal combustion engine 10 also includes a crank angle sensor 32 mounted on a crankcase below the piston 14. The crank angle sensor 32 is a sensor that emits a signal corresponding to the rotation of a crankshaft (not shown).

  As shown in FIG. 1, the system according to the present embodiment includes an electronic control unit (ECU) 34. The aforementioned crank angle sensor 32 is connected to the ECU 34. Based on the output signal of the crank angle sensor 32, the ECU 34 can detect the rotational position of the crankshaft, that is, the crank angle and the engine rotational speed NE.

  The ECU 34 is also connected to the TCV 24 and the throttle valve 26 described above. The ECU 34 can supply opening degree instruction signals to the TCV 24 and the throttle valve 26, respectively, and can detect the opening degrees based on the signals supplied from them.

  Further, the ignition plug 16 and the in-cylinder injection valve 18 described above are connected to the ECU 34. The ECU 34 can instruct the spark plug 16 to generate a spark at a desired ignition timing, and can instruct the in-cylinder injection valve 18 to inject a desired amount of fuel at a desired injection timing. Can do.

  Although not shown, the ECU 34 includes various sensors that are generally mounted in an internal combustion engine, such as an air flow meter that detects the intake air amount and a water temperature sensor that detects the cooling water temperature, in addition to the sensors and actuators described above. Is connected.

[Conditions for fuel injection timing θa]
Next, features of the internal combustion engine 10 of the present embodiment will be described with reference to FIGS. FIG. 2 is a diagram for explaining the condition of the fuel injection timing θa used by the internal combustion engine 10 in the present embodiment.

  In FIG. 2, the graphic shown on the left side shows a state when the crank angle has changed by about 90 ° CA from the intake top dead center (TDC) to the intake bottom dead center (BDC). In the figure, an arcuate curve indicated by reference numeral 36 indicates a “tumble flow” generated in the cylinder 12, and an open arrow curve indicated by reference numeral 38 indicates a “high-speed portion” of the tumble flow 36. Represents each.

  In the internal combustion engine 10 of the present embodiment, a tumble flow 36 is generated in the cylinder 12 as air flows into the cylinder 12 during the intake process. The speed of the piston 14 becomes the highest at about 90 ° CA after the intake TDC. At this time, since the flow velocity of the intake air is also increased, a high speed portion 38 having a higher flow velocity than other portions is generated in the tumble flow 36. In the present embodiment, a series of portions having a flow velocity faster than the average flow velocity of the tumble flow 36, particularly a series of portions having a flow velocity about 20% or more faster than the average flow velocity is used as the high speed portion 38.

  In FIG. 2, the graphic shown in the center shows a state where the vortex of the high speed portion 38 has moved to a phase in contact with the upper surface of the piston 14. This state is formed at a time of about 160 to 180 ° CA after the intake TDC.

  Here, a white triangle indicated by reference numeral 40 in the figure represents an image of injection by the in-cylinder injection valve 18. Also, a thick arrow indicated by reference numeral 42 represents the flow of injected fuel (hereinafter referred to as “spray flow”). As shown in this figure, in this embodiment, an appropriate time when the vortex of the high speed portion 38 of the tumble flow 36 comes into contact with the upper surface of the piston 14, that is, an appropriate time within 160 to 180 ° CA after the intake TDC. Is determined as the fuel injection timing. Hereinafter, this injection timing is represented by the crank angle “θa” at that time.

  In the figure shown in the center of FIG. 2, the high speed portion 38 of the tumble flow 36 is about to give up the upper surface of the piston 14 and change the traveling direction upward. That is, the high speed unit 38 starts to have a speed component in the direction toward the in-cylinder injection valve 18 at this time.

  As described above, the in-cylinder injection valve 18 is configured to inject fuel from above the cylinder 12 toward the piston 14, but the in-cylinder injection valve 18 of the present embodiment is more specific. Is configured such that fuel can be injected toward the upper surface of the central portion of the piston 14 in a positional relationship of about 160 to 180 ° CA after the intake TDC. For this reason, if the time corresponding to the central graphic in FIG. 2 is determined as the injection timing θa, the spray flow 42 can collide with the high-speed portion 38 of the tumble flow 36 traveling toward this.

  The graphic shown on the right side of FIG. 2 represents the state of the spray flow 42 immediately after the injection timing θa. The high-speed part 38 having a high flow rate has a higher ability than the other regions of the tumble flow 36 and suppresses the penetration force of the injected fuel. As a result, the spray flow 42 cannot maintain straight travel, and changes the traveling direction toward the rotation center of the tumble flow and then toward the top surface of the cylinder 12.

  The inside and outside of the vortex of the tumble flow 36 has a lower pressure than that of the vortex portion. For this reason, when the spray flow 42 moves toward the center of the tumble flow 36, the fuel having a high concentration remains in the tumble flow 36 from the intake to the compression stroke, and as a result, finally, the top surface of the cylinder 12, that is, A high concentration air-fuel mixture layer is generated around the spark plug 16. On the other hand, if the fuel penetrates the tumble flow 36, the fuel is not guided to the top surface of the cylinder 12, and it is difficult to form a high-concentration mixture layer around the spark plug 16.

  As described above, when the injection timing θa is determined so that the spray flow 42 collides with the high-speed portion 38 of the tumble flow 36, the spray flow 42 is prevented from penetrating the tumble flow 36, and the traveling direction thereof is changed to the tumble flow. Can be directed to the center of the cylinder (the top surface of the cylinder 12). In this case, a high-concentration air-fuel mixture layer can be stably generated around the spark plug 16. Therefore, in the present embodiment, the injection timing θa is determined so that the above condition is satisfied.

[Method for Determining Fuel Injection Timing θa]
Next, a method for determining the fuel injection timing θa will be described.
The internal combustion engine 10 of this embodiment is required to operate by stratified combustion under specific conditions. Stratified combustion is required, for example, during lean burn operation or fast idle operation. The lean burn operation is performed with a desired lean air-fuel ratio as a target, which is thinner than stoichiometric, in a specific engine speed region or the like. Under lean burn operation, stratified combustion is required to obtain stable ignition and combustion propagation. The fast idle operation is performed to maintain the idle rotation speed higher than the normal idle rotation speed after the warm-up is completed, for example, immediately after the cold start of the internal combustion engine 10. If stratified combustion is performed during fast idling, an air-fuel mixture layer having a high fuel concentration can be generated only around the spark plug 16 without greatly enriching the air-fuel ratio. The operating state of the engine 10 can be stabilized.

  Stratified combustion is usually required under the specific environment as described above, but the operating state of the internal combustion engine 10 is not always constant even under such an environment. Specifically, even in an environment where stratified combustion is required, for example, the throttle opening or the TCV opening may change. When the throttle opening changes, the intake air amount of the internal combustion engine 10 changes, and the tumble flow speed changes. Similarly, a change appears in the tumble ratio due to a change in the TCV opening.

  If the speed of the tumble flow changes, the relationship between the crank angle and the time when the high speed portion 38 of the tumble flow 36 gives up the upper surface of the piston 14, that is, the time when the high speed portion 38 starts to have a speed component toward the in-cylinder injection valve 18. Changes also occur. Therefore, in order to sufficiently enhance the effect of preventing fuel penetration by the tumble flow 36, it is necessary to finely correct the injection timing θa in accordance with the speed of the tumble flow.

  FIG. 3 shows the relationship between the throttle opening and the fuel injection timing θa. In addition, WOT (Wide Open Throttle) shown in FIG. 3 means a full opening degree. In the internal combustion engine 10 of the present embodiment, the tumble flow becomes faster as the throttle opening is opened, and the time at which the high speed portion 38 starts to face the in-cylinder injection valve 18 over the upper surface of the piston 14 is advanced. For this reason, as shown in FIG. 3, the injection timing θa needs to be advanced as the throttle opening increases.

  FIG. 4 shows the relationship between the TCV opening and the fuel injection timing θa. In the internal combustion engine 10 of the present embodiment, the larger the TCV opening, the stronger the drift of intake air, and the higher the tumble flow. For this reason, as shown in FIG. 4, the injection timing θa needs to be advanced as the TCV opening increases.

[Control of Embodiment 1]
The ECU 34 stores a two-dimensional map in which the trends in FIGS. 3 and 4 are mapped, and when stratified fuel is obtained, the injection timing θa is set with reference to the map. Hereinafter, characteristic control executed by the ECU 34 in the present embodiment will be described with reference to FIG.

  FIG. 5 is a flowchart of a routine executed by the ECU 34. This routine is executed for each cycle of the internal combustion engine 10. When this routine is started, first, various parameters relating to the operating state of the internal combustion engine 10 are read (step 100). Specifically, in addition to the engine speed, the throttle opening, and the TCV opening, the intake air amount, the cooling water temperature, and the like are read from various sensors.

  Next, it is determined whether or not a stratification condition is established in the internal combustion engine 10 (step 102). In this embodiment, when it is determined from the various parameters of the internal combustion engine 10 that execution of lean burn operation is required and when it is determined that execution of fast idle operation is required, the stratification condition is It is judged that it is established.

  If it is determined in step 102 that the stratification condition is not satisfied, since it is not necessary to stratify the high-concentration mixture around the spark plug 16, the normal fuel injection timing without stratified combustion is calculated. (Step 104).

  On the other hand, when it is determined that the stratification condition is established, the above-described calculation of the injection timing θa is performed (step 106). In the present embodiment, the stratification condition is satisfied in several scenes where stratified combustion is required. The ECU 34 has a two-dimensional map of the above-described injection timing θa for each scene. Specifically, in this step, first, a two-dimensional map corresponding to the current scene is specified. Next, the injection timing θa corresponding to the current throttle opening and TCV opening is determined from the two-dimensional map. According to the above processing, the injection timing θa is accurately aligned with the timing when the high speed portion 38 of the tumble flow 36 starts moving toward the in-cylinder injection valve 18 over the upper surface of the piston 14 under the current operating conditions. Can be decided.

  When the above process is completed, a process of injecting fuel at the calculated injection timing is executed (step 108), and the current routine ends. According to the above processing, when the stratification condition is satisfied, the fuel can collide with the high speed portion 38 of the tumble flow 36, and the spray flow 42 can be stably directed toward the center of the tumble flow 36. For this reason, according to this embodiment, in a scene where stratified combustion is required, a state in which a high concentration air-fuel mixture layer is generated around the spark plug 16 can be stably created.

[Modification of Embodiment 1]
In the first embodiment described above, the injection timing θa is calculated based on the two-dimensional map of the throttle opening and the TCV opening, but the calculation method is not limited to this. For example, a method may be used in which a one-dimensional map relating to each of the throttle opening and the TCV opening is prepared, and the injection timing θa is calculated by substituting values obtained from the two maps into functional expressions.

  Moreover, in Embodiment 1 mentioned above, although the internal combustion engine 10 is equipped with TCV24, TCV24 is not an essential element for this invention. When the internal combustion engine 10 does not include the TCV 24, the injection timing θa can be calculated based on the throttle opening without considering the TCV opening.

  In the above-described first embodiment, the opening degree is reflected in the injection timing θa in consideration of the influence of the throttle opening degree and the TCV opening degree on the speed of the tumble flow. Is not an essential element. That is, the injection timing θa may be fixed at a specific crank angle as long as the injected fuel can collide with the high speed portion 38.

  In Embodiment 1 described above, a two-dimensional map is prepared for each scene where stratified combustion is required, but the present invention is not limited to this. That is, the same two-dimensional map may be used in all scenes where the stratification condition is satisfied, ignoring the influence of other parameters except the throttle opening and the TCV opening.

  About the above modification, it can expand | deploy similarly about Embodiment 2 demonstrated below. In order to avoid redundant description, description of these will be omitted in the column of the second embodiment.

  In the first embodiment described above, on the premise that only the throttle opening and the TCV opening are the parameters that greatly affect the speed of the tumble flow when the stratification condition is satisfied, those influences are reflected in the injection timing θa. I am going to let you. However, these two parameters do not affect the tumble flow speed in the internal combustion engine 10. For example, the tumble flow speed is also affected by the engine speed. When the internal combustion engine 10 is provided with a variable valve mechanism that changes the opening timing of the intake valve 22, the speed of the tumble flow also changes depending on the opening timing. For this reason, if a large change occurs in the stratification conditions, the engine speed and the opening timing of the intake valve 22 are injected in addition to or instead of the throttle opening and the TCV opening. It may be reflected in the timing θa.

  FIG. 6 shows the relationship between the engine speed and the fuel injection timing θa. In the internal combustion engine 10 of the present embodiment, the higher the engine rotation speed, the faster the flow rate of intake air, resulting in a higher tumble flow. For this reason, when the engine speed is reflected in the injection timing θa, as shown in FIG. 3, the higher the engine speed, the more advanced θa.

  FIG. 7 shows the relationship between the valve opening period of the intake valve 22 and the fuel injection timing θa. FIG. 8 shows the relationship between the opening timing of the intake valve 22 and the fuel injection timing θa. In the internal combustion engine 10 of the present embodiment, the flow rate of intake air becomes faster as the valve opening timing (opening period) of the intake valve 22 is advanced, and as a result, the tumble flow becomes faster. For this reason, when the valve opening timing (valve opening period) of the intake valve 22 is reflected in the injection timing θa, as the valve opening timing (valve opening period) is advanced, as shown in FIG. 7 or FIG. The injection timing θa is also advanced.

  The trends shown in FIG. 6 or the trends shown in FIGS. 7 and 8 can be reflected in the injection timing θa by reflecting those tendencies in the map or function equation used for calculating θa.

  In the first embodiment described above, the entire intake system structure including the port portion 21 corresponds to the “tumble generating mechanism” in the first invention.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. 9 to 13 together with FIG. The second embodiment of the present invention can be realized by the hardware configuration shown in FIG. 1 as in the first embodiment.

[First Feature of Embodiment 2]
FIG. 9 is a diagram for explaining the conditions to be satisfied by the plurality of injection timings θa and θb used in the present embodiment. The three figures shown in the upper part of FIG. 9 are the same as the three figures shown in FIG. 2 and represent the state change in the first half of the intake compression stroke. On the other hand, the three figures shown in the lower part of FIG. 9 represent the state change in the latter half of the intake compression stroke.

  In the cylinder 12 of the internal combustion engine 10, the tumble flow 36 rotates vertically several times in one intake compression stroke. For this reason, the point when the high speed portion 38 starts to face the in-cylinder injection valve 18 after giving up the upper surface of the piston 14 occurs a plurality of times during one cycle. In the series of movements shown in FIG. 9, the state is formed at the time point shown at the center of the upper stage (time point of crank angle = θa) and the time point shown on the right side of the lower stage (time point of crank angle = θb). .

  The state in the upper center of FIG. 9 is formed at a time of about 160 to 180 ° CA after the intake TDC, similarly to the state in the center of FIG. On the other hand, the state on the right side of the lower stage of FIG. 9 is formed in the range of 80 to 100 ° CA before compression TDC. Here, a white triangle indicated by a reference numeral 44 in the figure on the right side of the lower stage of FIG. 9 is an image of injection by the in-cylinder injection valve 18. A thick arrow indicated by reference numeral 46 indicates the flow of the fuel injected here, that is, the spray flow. As shown in the figure, in the present embodiment, the second fuel injection is performed at the second timing when the high speed portion 38 starts to face the in-cylinder injection valve 18. Hereinafter, this injection timing is represented by a crank angle “θb” at that time.

  The fuel injected by the in-cylinder injection valve 18 at the injection timing θb collides with the high speed portion 38 of the tumble flow 36. As a result, the spray flow 46 changes the traveling direction toward the rotation center of the tumble flow 36 and then toward the top surface of the cylinder 12, similarly to the first spray flow 42. For this reason, the fuel injected for the second time is finally led to the periphery of the spark plug 16 together with the fuel injected for the first time.

  If the fuel to be injected during one cycle is divided and injected, the amount of fuel injected at each time is smaller than when the fuel is injected all at once. The force with which the injected fuel penetrates the tumble flow increases as the amount of fuel increases. For this reason, if the fuel is divided and injected, the suppression force of the tumble flow against the penetration force of the injected fuel can be relatively increased, and the amount of fuel penetrating the tumble flow can be reduced. Therefore, according to the present embodiment, a high-concentration air-fuel mixture layer can be created around the spark plug 16 more stably than in the case of the first embodiment.

[Second feature of the second embodiment]
FIG. 10 shows the relationship between the plurality of fuel injection timings θa, θb and the throttle opening used in the present embodiment. FIG. 10 is the same as in the case of the first embodiment (FIG. 3) in that the injection timing θa is advanced as the throttle opening is larger and the tumble flow is faster. A similar tendency appears in the second injection timing θb, but the advance amount given to θb is not the same as the advance amount given to θa.

  That is, the tumble flow generated in the cylinder 12 is less likely to be attenuated as the flow velocity is higher. Then, the period from the first timing to the second timing at which the high speed portion 38 of the tumble flow 36 starts moving toward the in-cylinder injection valve 18 becomes so short that the tumble flow is difficult to decay. Therefore, in FIG. 10, the second injection timing θb is set such that the larger the throttle opening, the shorter the interval between θa and θb.

  FIG. 11 shows a relationship between a plurality of fuel injection timings θa and θb and a TCV opening degree used in the present embodiment. As in the case of the first embodiment (FIG. 4), the first injection timing θa shown in FIG. 11 is advanced as the TCV opening is larger and the tumble flow is faster. Further, the second injection timing θb shown in FIG. 11 is set so that the interval between θa and θb becomes shorter as the TCV opening degree is larger and the tumble flow is faster, similarly to θb shown in FIG. Yes.

  When the second injection timing θb is set as described above, the fuel can be caused to collide with the high speed portion 38 accurately even at the time of the second injection timing θb regardless of how the tumble flow is attenuated. it can. For this reason, according to the present embodiment, the fuel can be appropriately prevented from penetrating by the tumble flow 36 every time the fuel is divided and injected.

  In FIG. 11, the third injection timing θc is drawn with respect to the TCV opening that maximizes the tumble strength. In the internal combustion engine 10, when the TCV 24 is operated to the vicinity of the maximum opening, the state in which the high speed portion 38 gives up the upper surface of the piston 14 and starts to the in-cylinder injection valve 18 may be repeated three times in one cycle. . In the present embodiment, in such a case, the third injection timing θc is set as shown in FIG.

[Third feature of the second embodiment]
FIG. 12 shows the relationship between the flow velocity of the high-speed part 38 of the tumble flow and the ratio of the fuel amount to be dividedly injected. The graphic on the left side of FIG. 12 represents the flow velocity of the high speed portion 38 at the first injection timing θa and the flow velocity of the high speed portion 38 at the second injection timing θb. The tumble flow 36 is crushed as the intake compression stroke proceeds to reduce the flow velocity. For this reason, as this figure shows, the flow velocity at θa is sufficiently higher than the flow velocity at θb.

  The graphic on the right side of FIG. 12 represents the fuel injection amount calculated in this embodiment in comparison. As shown in this figure, in the present embodiment, the injection amount at the first injection timing θa is set to be larger than the injection amount at the second injection timing θb in accordance with the flow velocity of the high speed unit 38. More specifically, in this embodiment, the fuel injection amount at each time is determined so that the injection amount ratio at θa and θb matches the flow rate ratio of the high speed portion 38 at θa and θb. .

  The high speed portion 38 of the tumble flow 36 exhibits an excellent effect for preventing the penetration of fuel as the flow velocity increases. On the other hand, the greater the amount of fuel, the higher the penetration power. For this reason, in order to divide and inject a certain amount of fuel and minimize the total fuel penetration amount, a large amount of fuel is caused to collide with the high speed portion 38 having a high flow velocity, and the high speed portion 38 having a low flow velocity is caused to collide. It is desirable to use a small amount of fuel for collision. In the present embodiment, as described above, the amount of fuel for each split injection is set so that this requirement is satisfied. For this reason, according to the present embodiment, penetration of the injected fuel can be sufficiently suppressed, and a favorable state suitable for stratified combustion can be stably formed.

[Control of Embodiment 2]
The routine shown in FIG. 13 is the same as the routine shown in FIG. 5 except that step 106 is replaced with steps 110 to 114 and step 108 is replaced with step 116. Here, a description specific to this routine will be mainly described while avoiding redundant description.

  In the routine shown in FIG. 13, if the establishment of the stratification condition is recognized in step 102, next, a plurality of injection timings θa, θb, and θc (only when θc exists) are calculated (step 110). In the present embodiment, the ECU 34 stores a two-dimensional map in which the trends in FIGS. 10 and 11 are mapped. Further, as in the case of the first embodiment, the ECU 34 has a two-dimensional map for each of several scenes where stratified combustion is required. In this step, as in the case of step 106 shown in FIG. 5, first, a two-dimensional map corresponding to the current stratified combustion scene is selected. Next, a plurality of injection timings θa, θb, and θc corresponding to the current throttle opening and TCV opening are determined from the map. According to the processing in this step, it is possible to determine a plurality of injection timings θa, θb, and θc that accurately correspond to the flow velocity and attenuation of the tumble flow 36.

  When the above processing is completed, the flow velocity of the high speed unit 38 at each time of θa, θb, and θc is calculated (step 112). In the present embodiment, the ECU 34 stores a map in which the operating speed of the internal combustion engine 10 is used as a parameter and the flow velocity of the high speed unit 38 is determined in relation to the crank angle. In this step, the flow velocity corresponding to each of θa, θb, and θc is calculated by referring to this map.

  Next, the ratio of fuel that is divided and injected is calculated (step 114). Here, specifically, the ratio of the flow velocity of the high speed section 38 calculated in step 112 as corresponding to each of θa, θb, and θc is directly the fuel injection ratio in each of θa, θb, and θc. Thus, the fuel ratio of each time is calculated.

In the routine shown in FIG. 13, fuel injection processing is performed following step 104 or step 114 (step 116). The processing in this step is the same as that in step 108 shown in FIG. 5 when this step is executed following step 104. On the other hand, when this step is executed after step 114, the following processing is performed.
1. Read the total amount of fuel to be injected in this cycle.
2. By multiplying the total fuel amount by the injection ratio calculated in step 114, the fuel injection amount for each split injection is calculated.
3. The calculated injection amount at each time is injected to the in-cylinder injection valve 18 at crank angle injection timings of θa, θb, and θc.

  According to the above processing, (1) the amount of fuel injected at a time is small, (2) the fuel always collides with the high speed portion 38 accurately regardless of the attenuation of the tumble flow, and (3) The fuel can be effectively guided to the periphery of the spark plug 16 by the three points that the penetration force (injection amount) of the fuel is suppressed according to the suppression force (flow velocity) of the high speed portion 38. For this reason, according to the present embodiment, it is possible to create a state where a high-concentration air-fuel mixture layer is generated around the spark plug 16 more stably than in the case of the first embodiment.

[Modification of Embodiment 2]

  In the second embodiment described above, the plurality of injection timings θa, θb, and θc are set based on the throttle opening and the TCV opening. However, the present invention is not limited to this. For example, the engine rotation speed or the opening timing of the intake valve 22 when the internal combustion engine 10 includes a variable valve mechanism may be reflected in the injection timings θa, θb, and θc.

  FIG. 14 shows the relationship between the engine speed and a plurality of fuel injection timings θa and θb. In the internal combustion engine 10 of the present embodiment, the higher the engine rotational speed, the faster the flow rate of the intake air, and the tumble flow becomes difficult to attenuate. For this reason, when the engine speed is reflected in the injection timings θa and θb, as shown in FIG. 14, the interval between θa and θb is set to be shorter as the engine speed is higher.

  FIG. 15 shows the relationship between the valve opening period of the intake valve 22 and the plurality of fuel injection timings θa and θb. FIG. 16 shows the relationship between the opening timing of the intake valve 22 and a plurality of fuel injection timings θa and θb. In the internal combustion engine 10 of the present embodiment, the flow rate of the intake air becomes faster as the valve opening timing (opening period) of the intake valve 22 is advanced, and as a result, the tumble flow becomes difficult to attenuate. Therefore, when the valve opening timing (valve opening period) of the intake valve 22 is reflected in the injection timings θa and θb, the valve opening timing (valve opening period) is advanced as shown in FIG. The interval between the injection timings θa and θb is set to be shorter.

  The trends shown in FIG. 14 or the trends shown in FIGS. 15 and 16 are reflected in the injection timings θa, θb, and θc by reflecting those tendencies in the map or function expression used for the calculation of θa, θb, and θc. Can be made.

  In the second embodiment described above, as in the first embodiment, the entire intake system structure including the port portion 21 corresponds to the “tumble generating mechanism” in the first invention.

Embodiment 3 FIG.
[Configuration of Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIG. 1 and FIGS. In the present embodiment, an internal combustion engine having the same structure as that shown in FIG. 1 is used except for the following points. For convenience, this embodiment will also be described with reference to FIG. 1, and the reference numeral 10 is assigned to the internal combustion engine.

  When a strong tumble flow is generated in the cylinder 12 of the internal combustion engine 10, the heat in the cylinder 12 is likely to be lost due to cold damage due to the influence of the air flow. The internal combustion engine 10 of the present embodiment has a configuration aimed at spatial combustion by weakening the tumble flow with the aim of reducing this cooling loss. In the first and second embodiments, the intake port portion 21 is formed so as to generate a strong tumble flow. However, in this embodiment, the port portion 21 does not generate a strong tumble flow. Yes. In the present embodiment, it is assumed that the intake passage 20 is not provided with the TCV 24.

[First Feature of Embodiment 3]
In the internal combustion engine 10 of the present embodiment, the in-cylinder injection valve 18 is pre-injected with fuel at an appropriate timing of the intake stroke, whereby the flow rate of intake air can be increased and a tumble flow can be generated in the cylinder 12. The graphic at the left end of FIG. 17 represents a state where the tumble flow 36 and the high speed portion 38 are generated in the cylinder 12 by the pre-injection 48.

  Although the tumble flow 36 and the high speed portion 38 generated by the pre-injection 48 are at a lower speed than in the case of the first or second embodiment, the tumble flow 36 and the high speed section 38 rotate in the longitudinal direction in the cylinder 12 while the intake compression stroke proceeds. The graphic at the right end of FIG. 17 represents a state at the time when the high-speed portion 38 that continues to rotate starts to face the in-cylinder injection valve 18 with the upper surface of the piston 14 being given up. A white triangle denoted by reference numeral 50 in the figure represents an image of main injection performed by the in-cylinder injection valve 18 with this point in time as the injection timing.

  When the main injection 50 is executed at the above injection timing, the injected fuel collides with the high speed portion 38 of the tumble flow 36. As a result, as in the case of the first or second embodiment, the fuel is guided to the vicinity of the top surface of the cylinder 12 and a high-concentration air-fuel mixture layer is generated around the spark plug 16. For this reason, according to the internal combustion engine 10 of the present embodiment, it is possible to stably create a state suitable for stratified combustion as needed while adopting a configuration aimed at reducing the cooling loss.

[Ratio of pre-injection and main injection]
FIG. 18 shows the relationship between the pre-injection 48 ratio and the combustion rate (solid line) and the relationship between the pre-injection ratio and the degree of stratification achieved (broken line). Since the total amount of fuel injected during one cycle is determined according to the state of the internal combustion engine 10, the ratio of the main injection 50 decreases as the ratio of the pre-injection 48 increases. For this reason, the ratio of the pre-injection 48 affects the combustion speed and the stratification degree as shown in FIG.

  The combustion speed and the stratification degree to be realized in the internal combustion engine 10 are determined according to the operating state of the internal combustion engine 10. Therefore, the proportion of pre-injection to be realized in the internal combustion engine 10 is also automatically determined from the relationship shown in FIG. In the present embodiment, the ECU 34 stores the pre-injection ratio determined in this way in relation to the operating state of the internal combustion engine 10. ECU34 determines the ratio of pre-injection with reference to the relationship, when the driving | operation by stratified combustion is calculated | required.

[Second Feature of Embodiment 3]
FIG. 19 is a diagram for defining an interval between the pre-injection 48 and the main injection 50. As shown in FIG. 19, here, the interval from the end of the pre-injection 48 to the start of the main injection 50 is defined as the “interval” between them.

  FIG. 20 shows the relationship between the fuel amount of the pre-injection 48 and the above interval. In the present embodiment, the pre-injection 48 is performed at a timing that promotes the tumble flow 36. Therefore, the flow rate of the tumble flow 36 increases as the fuel amount of the pre-injection 48 increases. The time required for the high speed portion 38 (see the left end in FIG. 17) generated by the pre-injection 48 to rotate to the phase toward the in-cylinder injection valve 18 (see the right end in FIG. 17) over the top surface of the piston 14 is tumble. The faster the flow velocity of the flow 36, the shorter the time. For this reason, as shown in FIG. 20, the interval from the pre-injection to the main injection becomes shorter as the fuel amount of the pre-injection 48 increases.

The pre-injection 48 is executed on the assumption that the main injection 50 is performed after the interval. For this reason, the interval cannot be shorter than the minimum injection period tau _{min of} the in-cylinder injection valve 18, that is, the minimum time required to open and close the in-cylinder injection valve 18. On the other hand, the fuel amount of the pre-injection 48 cannot be increased beyond the value at which the interval reaches the minimum value. For this reason, the minimum value of the interval and the maximum fuel amount of the pre-injection are determined in relation to the minimum injection period tau _min . FIG. 20 also shows the relationship between them for reference.

  FIG. 21 is a diagram schematically showing the relationship between the fuel ratio of the pre-injection 48 and the injection timing of the main injection 50. As shown in FIG. 21, in this embodiment, the larger the fuel ratio of the pre-injection 48, the smaller the fuel amount of the main injection 50 and the advance timing of the main injection 50. According to such a method, the fuel of the main injection 50 can be accurately collided with the high speed portion 38 of the tumble flow 36, and a state suitable for realizing a desired stratification degree can be stably created. .

[Control of Embodiment 3]
The routine shown in FIG. 22 is the same as the routine shown in FIG. 5 except that step 106 is replaced with steps 120 and 122 and step 108 is replaced with step 124. Here, a description specific to this routine will be mainly described while avoiding redundant description.

  In the routine shown in FIG. 22, if the establishment of the stratification condition is recognized in step 102, then the fuel ratio of the pre-injection 48 is calculated (step 120). As described above, the ECU 34 stores a map that defines the injection ratio of the pre-injection 48 in relation to the operating state of the internal combustion engine 10 based on the relationship shown in FIG. In this step, the injection ratio of the pre-injection 48 that matches the current operating state is calculated according to the map.

  Next, the injection timing of the main injection 50 is calculated (step 122). In the present embodiment, the ECU 34 stores a map that determines the injection timing of the main injection 50 in relation to the crank angle so that the tendency shown in FIG. 21 is reflected. In step 122, the injection timing of the main injection 50 corresponding to the injection ratio of the pre-injection 48 is determined according to this map. According to this process, the injection timing of the main injection 50 can be set to a time point at which the fuel can collide with the high speed portion 38 accurately.

In the routine shown in FIG. 22, fuel injection processing is performed following step 104 or step 122 (step 124). The processing in this step is the same as that in step 108 shown in FIG. 5 when this step is executed following step 104. On the other hand, when this step is executed next to step 122, the following processing is performed.
1. Read the total amount of fuel to be injected in this cycle.
2. The fuel amount of the pre-injection 48 is calculated by multiplying the total fuel amount by the injection ratio of the pre-injection 48 calculated in step 120 above.
3. The injection amount of the main injection 50 is calculated by subtracting the injection amount of the pre-injection 48 from the total fuel amount.
4). The calculated injection amount at each time is injected into the in-cylinder injection valve 18 at the injection timing (fixed) of the pre-injection 48 and the injection timing of the main injection 50 determined in step 122.

  According to the above process, in the internal combustion engine 10 having the intake system aimed at reducing the cooling loss, the stratification required for the operation of the stratified combustion can be stably generated as necessary.

[Modification of Embodiment 3]
In Embodiment 3 described above, the injection timing of the pre-injection 48 is fixed to a specific crank angle, but the present invention is not limited to this. That is, the injection timing of the pre-injection 48 that can generate (promote) the tumble flow most efficiently is predetermined in relation to the operating state of the internal combustion engine 10, and the injection timing is determined based on the operating state of the internal combustion engine 10. It is good also as setting suitably according to.

  In the third embodiment described above, a strong tumble flow is not generated in the intake port portion 21, but the present invention is not limited to this. That is, the idea of generating (promoting) a tumble flow by the pre-injection 48 and determining the injection timing of the main injection 50 according to the injection ratio of the pre-injection 48 may be used in combination with the configuration of the first or second embodiment. Good.

  In the third embodiment described above, the in-cylinder injection valve 18 and the ECU 34 that causes the in-cylinder injection valve 18 to perform the pre-injection 48 correspond to the “tumble flow generating mechanism” in the first aspect of the invention. Yes.

[Modification Common to Embodiments 1 to 3]
In the first to third embodiments described above, the tumble flow is a positive tumble flow that rises on the intake side and descends on the exhaust side. However, the tumble flow to which the present invention can be applied is not limited to this.

  FIG. 23 shows a state in which a reverse tumble flow 52 that descends on the intake side and rises on the exhaust side is generated in the cylinder 12, and fuel collides with the high speed portion 54 of the reverse tumble flow 52. Yes. As shown in this figure, the present invention can also be applied to an internal combustion engine that generates a reverse tumble flow 52.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder 16 Spark plug 18 In-cylinder injection valve 21 Port part 24 Tumble control valve (TCV)
26 Throttle valve 34 Control unit (ECU)
36; 52 Tumble flow 38; 44; 54 High speed section 42; 46 Spray flow 48 Pre-injection 50 Main injection θa, θb, θc Injection timing

Claims (15)

A spark plug located in the upper center of the cylinder;
A tumble generating mechanism for generating a tumble flow in the cylinder;
An in-cylinder injection valve for injecting fuel into the cylinder,
The in-cylinder injection valve injects fuel toward the high-speed portion, with the timing at which the high-speed portion of the tumble flow moves toward the in-cylinder injection valve as an injection timing,
The internal combustion engine, wherein the high-speed portion is a part of the tumble flow, and is a series of portions having a flow velocity faster than an average flow velocity of the tumble flow. The injection timing includes a time point corresponding to a crank angle within 160 to 180 ° CA after intake top dead center,
The in-cylinder injection valve is configured to inject fuel in a direction that collides with a high speed portion of a tumble flow at 160 to 180 ° CA after intake top dead center. Internal combustion engine. A control unit for determining a fast idle execution condition for setting the idle rotation speed immediately after the start of the internal combustion engine to a higher rotation speed than the normal idle rotation speed after the end of warm-up;
The internal combustion engine according to claim 1, wherein the in-cylinder injection valve injects fuel at the injection timing while the fast idle execution condition is satisfied. A control unit for determining whether or not the execution condition of the lean burn operation in which the target air-fuel ratio is thinner than the stoichiometric lean air-fuel ratio is satisfied,
The internal combustion engine according to any one of claims 1 to 3, wherein the in-cylinder injection valve injects fuel at the injection timing while an execution condition for the lean burn operation is satisfied. The tumble generating mechanism is
The in-cylinder injection valve;
A control unit that causes the in-cylinder injection valve to perform pre-injection of fuel at a timing at which an airflow in the same direction as the tumble flow is generated in the cylinder,
The internal combustion engine according to any one of claims 1 to 4, wherein the injection timing is advanced as the fuel injection amount by the pre-injection increases. It has a throttle valve provided in the intake passage,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The internal combustion engine according to any one of claims 1 to 5, wherein the injection timing is advanced as the opening of the throttle valve increases. The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
A tumble control valve that controls the flow of intake air that generates the tumble flow;
The internal combustion engine according to any one of claims 1 to 6, wherein the injection timing is advanced as the opening degree of the tumble control valve is controlled in a direction in which the strength of the tumble flow is increased. The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The internal combustion engine according to any one of claims 1 to 7, wherein the injection timing is advanced as the engine speed increases. A variable valve mechanism for changing the opening timing of the intake valve of the internal combustion engine,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The internal combustion engine according to any one of claims 1 to 8, wherein the injection timing is advanced as the valve opening timing of the intake valve is advanced.   The injection timing is set a plurality of times in one cycle, and a fuel injection amount to be injected in one cycle is divided and injected in the plurality of times. The internal combustion engine according to item. A control unit that calculates the ratio of fuel that is divided and injected multiple times,
11. The internal combustion engine according to claim 10, wherein the control unit calculates the ratio so that the fuel injection amount becomes smaller as the order of injection in one cycle is slower. It has a throttle valve provided in the intake passage,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The internal combustion engine according to claim 10 or 11, wherein an interval between the plurality of injection timings becomes shorter as an opening of the throttle valve is larger. The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
A tumble control valve that controls the flow of intake air that generates the tumble flow;
The interval between the plurality of injection timings becomes shorter as the opening degree of the tumble control valve is controlled in a direction to increase the strength of the tumble flow. Internal combustion engine. The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The internal combustion engine according to any one of claims 10 to 13, wherein the interval between the plurality of injection timings becomes shorter as the engine rotational speed becomes higher. A variable valve mechanism for changing the opening timing of the intake valve of the internal combustion engine,
The tumble generating mechanism includes an intake system structure configured to generate the tumble flow by an intake flow,
The internal combustion engine according to any one of claims 10 to 14, wherein the interval between the plurality of injection timings becomes shorter as the opening timing of the intake valve is advanced.

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