JP4161828B2 - Control device for internal combustion engine and knocking suppression method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for controlling the operating state of an internal combustion engine, and more particularly to an apparatus for suppressing the occurrence of knocking.
[0002]
[Prior art]
In general, in a gasoline engine (hereinafter simply referred to as an engine), the torque (output) generated increases as the compression ratio increases. However, knocking tends to occur more easily as the compression ratio becomes higher. Knocking occurs when unburned gas at the end portion self-ignites before the flame propagating from the spark plug reaches the end portion.
[0003]
In response to such a problem, for example, the apparatus described in Patent Document 1 injects high-pressure air into the combustion chamber when igniting the fuel (fuel mixture of fuel and air) supplied into the combustion chamber, and immediately before ignition. Or, the air-fuel mixture immediately after ignition is disturbed. In this way, by causing disturbance in the air-fuel mixture immediately before or after ignition, the interface of the air-fuel mixture in the combustion process is disturbed, and the flame propagation speed is increased. As a result, the occurrence of knocking is suppressed.
[0004]
[Patent Document 1]
JP 2001-20745 A
[0005]
[Problems to be solved by the invention]
However, the device of Patent Document 1 requires the addition of a special device configuration in order to inject high-pressure air into the combustion chamber. In addition, it is necessary to control the injection timing of the high-pressure air very precisely.
[0006]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a control device for an internal combustion engine that can effectively suppress the occurrence of knocking while increasing the engine output. There is to do.
[0007]
[Means for Solving the Problems]
  To achieve the above objective,
  (1) The present invention provides a control device for an internal combustion engine that directly injects fuel into a combustion chamber of the engine during a compression stroke of the internal combustion engine and ignites the injected fuel to operate the engine. Due to the turbulence of fuel spray that increases as pressure increasesWhile suppressing the occurrence of knocking,The difference between the ignition timing at which knocking occurs and MBT is minimized.BeforeThe gist is to determine the injection timing of the injected fuel.
  According to this configuration, in the compression stroke of the internal combustion engine, the injected fuel is increased in pressure and directly injected into the combustion chamber, whereby the spray surface of the injected fuel becomes rough (disturbance occurs in the fuel spray). Further, since the injection timing is determined so that the difference between the ignition timing at which knocking occurs and MBT is minimized due to the disturbance of the fuel spray, the propagation speed of the flame spreading along the fuel spray is substantially increased. As a result, the ignition timing can be brought close to MBT (Minimum Spark Advance for Best Torque) while suppressing the occurrence of knocking.
  Note that “increasing the pressure of the injected fuel” does not mean that the control for increasing the pressure of the injected fuel is performed, but means that the disturbance of the fuel spray that increases as the injected fuel becomes higher is used. For example, if a fuel having a pressure of a certain level or more is injected to generate a sufficiently high turbulence intensity in the gas in the combustion chamber, the knocking suppression action unique to the present invention occurs. However, naturally, control for increasing the pressure of the injected fuel may be performed in order to generate a sufficiently high turbulence intensity.
[0008]
  (2) In another invention, after forming a fuel spray in a combustion chamber of an internal combustion engine, direct injection of fuel into the combustion chamber and ignition of gas in the previous combustion chamber are performed in a compression stroke of the engine, A control device for an internal combustion engine that operates an engine, which is caused by disturbance of fuel spray that increases with an increase in pressure of fuel directly injected into the combustion chamber in a compression stroke.While suppressing the occurrence of knocking,The difference between the ignition timing at which knocking occurs and MBT is minimized.PressureThe gist of the present invention is to determine the timing for directly injecting fuel into the combustion chamber in the contraction stroke.
  Even in this configuration, in the compression stroke of the internal combustion engine, the injected fuel is increased in pressure and directly injected into the combustion chamber, so that the turbulence occurs due to the collision between the injected fuel and the surrounding air. As a result, the propagation speed of the flame is substantially increased, and the ignition timing can be brought close to MBT while suppressing the occurrence of knocking.
[0009]
(3) An ignition means provided on the ceiling surface of the cylindrical combustion chamber of the internal combustion engine for igniting the fuel supplied into the combustion chamber, and the spray of fuel injected in two directions is the inner peripheral wall of the combustion chamber And injecting the fuel directly into the combustion chamber with the fuel directed in two directions so as to face the ignition means.
According to this configuration, the spray of fuel injected in two directions becomes a jet while entraining the surrounding air, travels in opposite directions along the inner wall surface of the combustion chamber, then faces each other (collision), and the combustion chamber Head toward the ignition means along the ceiling surface. The more the gas in the combustion chamber is compressed, the more the turbulence is generated in the gas in the combustion chamber. Due to the occurrence of this turbulence, the propagation speed of the flame is substantially increased after ignition of the fuel, so that it is easy to spread the flame throughout the combustion chamber before the self-ignition of the end gas that causes knocking occurs. Become.
[0010]
(4) The ignition means is provided at substantially the center of the ceiling surface of the cylindrical combustion chamber of the engine, for example.
[0011]
(5) An ignition means provided near the inner peripheral wall and exhaust port of the cylindrical combustion chamber of the internal combustion engine for igniting fuel supplied to the combustion chamber; and an inner peripheral wall of the combustion chamber and the vicinity of the intake port And a fuel injection means for directly injecting fuel into the combustion chamber.
According to this configuration, the flame propagating from the ignition means starts to drop into droplets and hits a fuel spray with high turbulence intensity. Therefore, the combustion of the gas in the combustion chamber proceeds very efficiently, and the occurrence of knocking is effectively suppressed.
[0012]
(6) Moreover, it is preferable that the said injection fuel shall be 100 Mpa or more. According to this configuration, a sufficiently large turbulence is effectively generated in order to affect the flame propagation speed (and thus suppress the occurrence of knocking) in the fuel spray.
[0013]
(7) It is preferable to provide a projection provided on the inner wall of the combustion chamber and in contact with the spray of the injected fuel.
According to this configuration, when the spray of fuel injected into the combustion chamber comes into contact with the protrusion, the atomization of the droplets forming the fuel spray is promoted. As a result, the disturbance generated on the surface of the fuel spray is difficult to attenuate.
[0014]
  (8) Still another invention is a method for suppressing knocking of an internal combustion engine that generates engine torque by igniting fuel directly injected into a combustion chamber in a compression stroke, and accompanying the increase in pressure of the injected fuel Due to increased fuel spray disturbancesWhile suppressing the occurrence of knocking,The difference between the ignition timing at which knocking occurs and MBT is minimized.BeforeThe gist is to determine the injection timing of the injected fuel.
[0015]
  (9) In addition, such a knockerDepressPreferably, the control method includes a step of controlling the fuel spray disturbance that increases as the pressure of the injected fuel increases as the pressure is increased by controlling the fuel injection timing.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described.
[0017]
[Basic engine structure and functions]
FIG. 1A is a side sectional view showing a schematic configuration of a main part of the internal combustion engine according to the first embodiment. As shown in FIG. 1A, the engine 1 is an internal combustion engine that obtains output by repeating four cycles of an intake stroke, a compression stroke, an explosion stroke (expansion stroke), and an exhaust stroke. The engine 1 forms a cylindrical combustion chamber (cylinder) 2 therein. The explosive force of the fuel (gasoline) generated in the combustion chamber 2 is converted into the rotational force of a crankshaft (not shown) via the piston 3 and the connecting rod 4. Further, the combustion chamber 2 is provided with an intake port 5A that forms the most downstream portion of the intake passage 5 and an exhaust port 6A that forms the most upstream portion of the exhaust passage 6. The boundary between the intake port 5A and the combustion chamber 2 is opened and closed by an intake valve 5B. Further, the boundary between the exhaust port 6A and the combustion chamber 2 is opened and closed by an exhaust valve 6B.
[0018]
The engine 1 includes a high-pressure pump (not shown) capable of pressurizing fuel stored in a fuel tank (not shown) to an ultra-high pressure of at least 100 MPa, and fuel pressurized by the high-pressure pump A pressure accumulating chamber (not shown) or the like for holding it as it is is provided. The engine 1 also includes a fuel injection valve 10 having two injection holes facing the combustion chamber 2. The fuel injection valve 10 is provided in the vicinity of the side inner wall 2a on the ceiling surface 2b of the combustion chamber 2 and in the vicinity of the intake port 5A. The fuel injection valve 10 is an electromagnetically driven on-off valve that supplies an ultrahigh pressure fuel held in a pressure accumulating chamber into the combustion chamber 2 at an appropriate amount and at an appropriate timing. An arrow in the combustion chamber 2 indicates a traveling path of fuel spray injected through the fuel injection valve 10 (the same applies to other drawings). The two injection holes of the fuel injection valve 10 are directed in different directions, and the fuel spray injected in the two directions from the two injection holes of the fuel injection valve 10 flows in the recess 3 a of the combustion chamber 2. Advancing in opposite directions along the inner peripheral wall 2a. A depression 3 a is provided on the top surface of the piston 3 that forms the bottom surface of the combustion chamber 2. The recess 3a has a function of guiding the traveling direction of the fuel spray injected in two directions and a function of preventing bore flushing by making the fuel spray difficult to contact the inner peripheral wall 2a of the combustion chamber 2.
[0019]
In addition, the engine 1 includes a spark plug 20 at substantially the center of the ceiling surface 2 b of the combustion chamber 2. The spark plug 20 is energized at an appropriate timing to generate an electric spark in the combustion chamber 2 to ignite the fuel in the combustion chamber 2.
[0020]
The engine 1 includes an accelerator position sensor (not shown) that outputs a signal corresponding to a depression amount of an accelerator pedal (not shown) by a driver, and a rotation speed that outputs a rotation speed (engine speed) of a crankshaft (not shown). A sensor, a temperature sensor that outputs a signal corresponding to the temperature of the cooling water circulating in the engine 1 (cooling water temperature), and a signal corresponding to the flow rate (intake air amount) of the air introduced into the combustion chamber 2 through the intake passage 5 Various sensors such as an air flow meter for output are provided. Signals from various sensors are input to an electronic control unit (ECU) 30.
[0021]
The ECU 30 includes a logical operation circuit including a CPU, a RAM, a ROM, and the like, and comprehensively controls various components of the engine 1 based on signals from various sensors. For example, the ECU 30 operates the fuel injection valve 10 (fuel injection control) based on signals from various sensors, thereby supplying an appropriate amount of fuel to the combustion chamber 2 at an appropriate timing, and at an appropriate timing. By energizing the ignition plug 20 (ignition timing control), the output of the engine 1 is controlled. The fuel injection control and ignition timing control executed by the ECU 30 are collectively referred to as operation control.
[0022]
FIG. 1B is a top view showing the IB-IB cross section of FIG. 1A, and particularly shows the movement of the fuel spray injected from the fuel injection valve 10. As shown by arrows in FIG. 1B, the fuel spray injected in two directions from the two injection holes of the fuel injection valve 10 passes through the inner peripheral wall 2a in the recess 3a on the top surface of the piston 3. After traveling in opposite directions, they face each other (collision), and head toward the spark plug 20 along the ceiling surface of the combustion chamber 2. In the present embodiment, an example in which the fuel injection valve 10 is used to form a two-way spray has been shown. However, instead of such a fuel injection valve 10, a slit-like injection hole is provided and is flattened. A fuel injection valve capable of forming a spray may be employed.
[0023]
[Effects of knocking suppression by turbulence of fuel spray surface]
(1) Relationship between knocking and ignition timing
A gasoline engine basically generates output according to the following combustion process.
[0024]
First, fuel is injected into the combustion chamber through a fuel injection valve provided in the combustion chamber or the intake port, and the spray is diffused in the combustion chamber to form a mixture of fuel and air. Next, the spark plug provided in the combustion chamber emits an electric spark, so that the air-fuel mixture in the combustion chamber is ignited and burned. Due to the combustion of the air-fuel mixture, the pressure in the combustion chamber increases explosively, and a force pushing the piston, that is, engine output is generated.
[0025]
  FIG. 2 is a graph illustrating a general relationship between an ignition timing (a timing at which an ignition plug generates an electric spark) in a gasoline engine and a torque generated by the engine (hereinafter referred to as a generated torque). As shown in FIG. 2, in a gasoline engine, the ignition timing that maximizes the generated torque, the so-called MBT.(Minimum Spark Advance for Best Torque) exists. In FIG. 2, the generated torque can be maximized by performing ignition at a predetermined timing (A) with a crank angle. On the other hand, in a normal engine, the ignition timing at which knocking occurs is on the retard side with respect to the predetermined value MBT. Thus, since the ignition timing (B) at which knocking occurs is on the retarded side with respect to MBT, the engine must be operated at the knocking occurrence point, and the ignition timing cannot be advanced to MBT. The ignition timing MBT tends to shift to the retard side as the engine compression ratio increases. The ignition timing MBT varies depending on the engine speed, the engine load, and the like. Here, the difference (absolute value) between the ignition timing (MBT) that maximizes the generated torque and the ignition timing at which knocking occurs is defined as knock sensitivity ΔSA. The smaller the knock sensitivity ΔSA, the closer the knocking ignition timing (B) can be to MBT, and the generated torque can be increased.
[0026]
(2) Reduction of knock sensitivity by injection of ultra-high pressure fuel
FIG. 3 is a graph showing the relationship between the ignition timing and the generated torque in a gasoline engine that directly injects 100 MPa of ultrahigh pressure fuel into the combustion chamber, and in particular, the fuel injection timing (the timing at which fuel is injected from the fuel injection valve). ) Are knock sensitivities corresponding to three conditions different from each other. As shown in FIG. 3, the relationship between the ignition timing and the generated torque hardly changes even if the fuel injection timing is changed. However, the knock sensitivity ΔSA1 corresponding to the fuel injection timing 60 ° BTDC, the knock sensitivity ΔSA2 corresponding to the fuel injection timing 80 ° BTDC, and the knock sensitivity ΔSA3 corresponding to the fuel injection timing 180 ° BTDC are apparently compared with each other. In addition, the knock sensitivity ΔSA decreases as the fuel injection timing is retarded. That is, in a gasoline engine that directly injects fuel into the combustion chamber, if the fuel injection timing is retarded to reduce the knock sensitivity ΔSA, the knocking ignition timing can be advanced to approach MBT and the generated torque is increased. It becomes possible.
[0027]
(3) Relationship between injection timing and turbulence intensity transition
The reason why the knock sensitivity ΔSA changes in accordance with the change of the fuel injection timing when performing fuel injection with ultra-high pressure fuel will be described below.
[0028]
FIG. 4 is a time chart showing the transition of the turbulence intensity of the gas in the combustion chamber as the crank angle (time) changes in a gasoline engine that directly injects fuel into the combustion chamber. In the intake stroke, when fuel injection is performed under the conditions that the fuel injection timing is 240 ° BTDC and the fuel pressure (fuel pressure) is 12 MPa, the turbulence intensity hardly changes in the combustion chamber (broken line). Also, under the condition that the fuel pressure (fuel pressure) is 12 MPa, even if the fuel injection timing is 60 ° BTDC, the turbulence intensity slightly increases with fuel injection and then quickly returns to the level before fuel injection (broken line) ).
[0029]
On the other hand, as shown in FIG. 4, in the compression stroke, when the fuel injection is performed under the condition that the fuel injection timing is 60 ° BTDC and the fuel pressure (fuel pressure) is 100 MPa, the turbulence intensity increases with the fuel injection. To do. The turbulence intensity once increases and reaches a maximum value, and then attenuates. However, even when the crank angle reaches around 0 ° BTDC (ignition timing), it is maintained at a relatively high level (solid line). However, if the fuel injection timing is advanced to 80 ° BTDC under the condition that the fuel pressure (fuel pressure) is 100 MPa, the turbulence intensity reaches the maximum value earlier and attenuates earlier by that amount. As a result, the turbulence intensity at the time when the crank angle reaches around 0 ° BTDC (ignition timing) is smaller than when the injection timing is set to 60 ° BTDC. Further, when the fuel injection timing is advanced to 180 ° BTDC, the turbulence intensity when the crank angle reaches around 0 ° BTDC (ignition timing) is almost the same as that before fuel injection (two-dot chain line).
[0030]
Thus, in the compression stroke, when fuel injection is performed under the condition that the fuel pressure (fuel pressure) is 100 MPa, the gas in the combustion chamber (the surface of the fuel spray) is disturbed (the gas turbulence intensity is increased). If ignition is performed while the turbulence remains, the propagation speed of the flame that spreads along the fuel spray starting from the spark plug is substantially increased, and the occurrence of knocking is suppressed (the knock sensitivity ΔSA is reduced). (See also FIGS. 3 and 4).
[0031]
FIG. 5 is a graph showing changes in the generated torque (generated torque when the ignition timing is set to the optimal ignition timing) corresponding to the change in the fuel injection timing for the engine 1. As shown in FIG. 5, the generated torque is increased by performing the fuel injection in the compression stroke as compared with the case of performing the fuel injection in the intake stroke. In the compression stroke, the maximum generated torque can be ensured by setting the fuel injection timing in the vicinity of 60 ° BTDC. That is, by performing fuel injection in the compression stroke using ultrahigh pressure fuel, the surface of the fuel spray injected into the combustion chamber 2 is disturbed, and the timing at which the disturbance is attenuated through adjustment of the fuel injection timing. Is adjusted, the ignition can be performed at the timing when the fuel spray is in a moderately disturbed state, and the knock sensitivity ΔSA can be minimized. As the knock sensitivity ΔSA is minimized, the actual ignition timing can be made closer to the ignition timing (see FIG. 2) corresponding to the maximum value of the generated torque, as compared with the conventional case.
[0032]
[Specific examples of operation control]
As specific operation control, the ECU 30 of the engine 1 may execute, for example, a control routine including the following processing contents (1) to (4) at a predetermined cycle.
[0033]
(1) Information necessary for operation control (for example, engine speed, accelerator pedal depression amount, etc.) is acquired based on outputs from various sensors.
(2) The fuel injection timing that minimizes the knock sensitivity ΔSA is estimated.
(3) An optimal ignition timing corresponding to the estimated fuel injection timing is calculated.
(4) The fuel injection valve 10 is opened at the estimated fuel injection timing, and control for energizing the spark plug 20 at the optimal ignition timing is executed.
[0034]
Further, the relationship between the outputs of the various sensors and the target fuel injection timing and ignition timing may be set in advance on the control map. In this case, the ECU 30 uniquely determines the fuel injection timing and the ignition timing based on the outputs of various sensors by referring to the control map.
[0035]
According to the first embodiment in which such a control structure is applied to the engine 1 having the configuration as shown in FIG. 1, the spray of fuel injected in two directions in the combustion chamber 2 entrains the surrounding air. It becomes a jet and travels in opposite directions along the inner peripheral wall 2 a in the recess 3 a on the top surface of the piston 3, then faces (collises), and travels toward the spark plug 20 along the ceiling surface 2 b of the combustion chamber 2. The more the gas in the combustion chamber is compressed, the more the turbulence is generated in the gas in the combustion chamber. Due to the occurrence of this turbulence, the propagation speed of the flame is substantially increased after the ignition of the fuel, so that it is easy to spread the flame over the entire combustion chamber 2 before the self-ignition of the end gas that causes knocking occurs. It becomes. As a result, for example, even if the compression ratio of the engine 1 is increased or the ignition timing is advanced, knocking hardly occurs. Accordingly, the generated torque can be increased while suppressing the occurrence of knocking.
[0036]
(Second Embodiment)
Next, a second embodiment that embodies the present invention will be described focusing on differences from the first embodiment. In the second embodiment, among the engines to be applied, those having the same structure and function as the components of the engine 1 (see FIG. 1) according to the first embodiment are the same. A member number is attached | subjected and the overlapping description here is abbreviate | omitted.
[0037]
FIG. 6A is a side sectional view showing a schematic configuration of a main part of the engine 1A according to the second embodiment, and FIG. 6B is a top view showing the inside of the cylinder of the engine 1A. is there. As shown in FIGS. 6A and 6B, the engine 1A includes a protrusion 2c on the side of the ceiling surface 2b of the cylinder (combustion chamber) 2 or on the side inner wall 2a. The protrusion 2c is preferably made of a metal material or alloy material having a relatively high thermal conductivity, such as titanium. Further, the direction and arrangement of the two nozzle holes provided in the fuel injection valve 10 are set so that the fuel spray injected from each nozzle contacts the protrusion 2c in the process of traveling toward the spark plug 20. . In such an engine 1B, the ECU 30 performs the same operation control as in the first embodiment.
[0038]
According to the second embodiment, the spray of fuel injected into the combustion chamber 2 in the compression stroke comes into contact with the protrusion 2c, thereby promoting the atomization of droplets forming the fuel spray. As a result, the disturbance generated on the surface of the fuel spray is difficult to attenuate. That is, the effect of suppressing knocking due to this disturbance is further enhanced.
[0039]
(Third embodiment)
Next, a second embodiment that embodies the present invention will be described focusing on differences from the first embodiment. In the second embodiment, among the engines to be applied, those having the same structure and function as the components of the engine 1 (see FIG. 1) according to the first embodiment are the same. A member number is attached | subjected and the overlapping description here is abbreviate | omitted.
[0040]
FIG. 7 is a side sectional view showing a schematic configuration of a main part of an engine 1B according to the third embodiment. As shown in FIG. 7, the engine 1B according to the third embodiment includes an intake port in addition to a fuel injection valve 10 (hereinafter referred to as a first fuel injection valve) 10 that faces the injection hole in the combustion chamber 2. The second embodiment is different from the first embodiment in that a second fuel injection valve 11 is provided to face the injection hole in 5A. The second fuel injection valve 11 is an electromagnetically driven on / off valve that injects an appropriate amount of fuel into the intake port at an appropriate timing. Like the first fuel injection valve 10, the second fuel injection valve 11 opens and closes according to a command signal from the ECU 30. To do.
[0041]
The ECU 30 of the engine 1B according to the present embodiment uses the following procedures (1), (2), (1) as the first fuel injection valve 10, the second fuel injection valve 11, and the spark plug 20 as operation control of the engine 1B. Operate according to 3).
[0042]
(1) First, in the intake stroke, fuel is injected into the intake port 5A through the second fuel injection valve 11. As a result, the fuel spray diffuses in the combustion chamber 2 and is distributed almost uniformly.
(2) In the compression stroke, ultra high pressure fuel is injected into the combustion chamber 2 through the first fuel injection valve 10. Here, the sum of the amount of fuel supplied through the first fuel injection valve 10 and the amount of fuel supplied through the second fuel injection valve 11 is necessary and sufficient to generate the torque required for the engine 1. The amount of fuel injected through each of the fuel injection valves 10 and 11 is adjusted so that the amount of fuel becomes a proper amount.
(3) Energize the spark plug 20 to perform ignition.
[0043]
In performing the above-described operation control, it is preferable that the ECU 30 determines the operation timing (fuel injection timing) of the first fuel injection valve 10 so that the knock sensitivity ΔSA is as small as possible and ignites the MBT. This is the same as in the first embodiment.
[0044]
Also according to the third embodiment, it is possible to increase the generated torque while suppressing the occurrence of knocking.
[0045]
(Fourth embodiment)
Next, a fourth embodiment embodying the present invention will be described focusing on differences from the first embodiment. In the fourth embodiment, among the engines to be applied, those having the same structure and function as the components of the engine 1 (see FIG. 1) according to the first embodiment are the same. A member number is attached | subjected and the overlapping description here is abbreviate | omitted.
[0046]
FIG. 8 is a side sectional view showing a schematic configuration of a main part of an engine 1C according to the fourth embodiment. The engine 1 according to the first embodiment includes a spark plug 20 near the center of the ceiling surface 2b of the combustion chamber 2 (see FIG. 1). On the other hand, the engine 1C according to the fourth embodiment includes the spark plug 20 in the vicinity of the side inner wall 2a on the ceiling surface 2b of the combustion chamber 2 and in the vicinity of the exhaust port 6A. Further, the fuel spray is made to travel along the side inner wall 2a of the combustion chamber 2 and then travels along the ceiling surface 2b to reach the spark plug 20 (the configuration of the first embodiment: see FIG. 1). In the engine 1C, the direction and arrangement of the injection port of the fuel injection valve 10 and the shape of the recess 3a formed on the top surface of the piston 3 so that the fuel spray is directed directly from the recess 3a on the piston top surface to the vicinity of the spark plug 20. Etc. are set. In the first embodiment, the fuel spray tends to travel along a plane orthogonal to the reciprocating motion direction (axis) of the piston 3, whereas in the fourth embodiment, the fuel spray. Tends to travel along the axis of the piston 3.
[0047]
In such an engine 1B, the ECU 30 performs the same operation control as in the first embodiment.
[0048]
According to the fourth embodiment, since the amount of heat received by the fuel spray from the top surface of the piston 3 is increased, the atomization of droplets forming the fuel spray is promoted. Further, the flame propagating from the spark plug 20 collides with the fuel spray wound up from the depression 3a ′ on the top surface of the piston. The fuel spray wound up from the recess 3a '(the fuel spray almost directly above the recess 3a') has a relatively short distance from the injection port of the fuel injection valve 10 and a high turbulence intensity.
[0049]
As a result, the flame propagating from the spark plug 20 starts to collide with a fuel spray having a high turbulence intensity as the droplets become finer. Therefore, the combustion of the gas in the combustion chamber 2 proceeds very efficiently, and the occurrence of knocking is effectively suppressed.
[0050]
In each of the above embodiments, the fuel injection timing and the ignition timing are controlled in order to ensure an appropriate turbulence intensity for the gas in the combustion chamber 2 in the vicinity of the ignition timing. Not limited to this, the magnitude of the turbulence intensity of the gas in the combustion chamber 2 is controlled by variably controlling the pressure of the ultrahigh pressure fuel injected through the fuel injection valve 10 so as to enhance the knocking suppression effect. It may be.
[0051]
【The invention's effect】
As described above, according to the present invention, the propagation speed of the flame in the combustion chamber is substantially increased due to the disturbance of the fuel spray that increases as the pressure of the injected fuel increases. As a result, the generated torque of the internal combustion engine can be increased while suppressing the occurrence of knocking.
[Brief description of the drawings]
FIG. 1 is a side sectional view showing a schematic configuration of a main part of an internal combustion engine according to a first embodiment of the present invention.
FIG. 2 is a graph illustrating a general relationship between ignition timing and generated torque in a gasoline engine.
FIG. 3 is a graph showing the relationship between ignition timing and generated torque in a gasoline engine that directly injects ultrahigh pressure fuel into a combustion chamber.
FIG. 4 is a time chart showing the transition of the turbulence intensity of the gas in the combustion chamber accompanying the change in crank angle (time) in a gasoline engine that directly injects fuel into the combustion chamber.
FIG. 5 is a graph showing a change in generated torque corresponding to a change in fuel injection timing.
FIG. 6 is a side sectional view showing a schematic configuration of a main part of an internal combustion engine according to a second embodiment of the present invention.
FIG. 7 is a side sectional view showing a schematic configuration of a main part of an internal combustion engine according to a third embodiment of the present invention.
FIG. 8 is a side sectional view showing a schematic configuration of a main part of an internal combustion engine according to a fourth embodiment of the present invention.
[Explanation of symbols]
1 engine (internal combustion engine)
2 Combustion chamber
3 Piston
5 Intake passage
5A Intake port
5B Intake valve
6 Exhaust passage
6A Exhaust port
6B Exhaust valve
10 Fuel injection valve (for ultra high pressure fuel injection)
11 Second fuel injection valve
20 Spark plug (ignition means)
30 Electronic control unit (ECU)

Claims (8)

In a control device for an internal combustion engine that directly injects fuel into a combustion chamber of the engine during a compression stroke of the internal combustion engine and ignites the injected fuel to operate the engine.
The injection is suppressed from occurring by Ri knocking disturbance of fuel spray increases with pressure of the fuel injection timing of pre-Symbol injected fuel such that the difference between the ignition timing and the MBT of occurrence of knocking is minimized A control device for an internal combustion engine, characterized in that After the fuel spray is formed in the combustion chamber of the internal combustion engine, the direct injection of the fuel into the combustion chamber and the ignition of the gas in the combustion chamber are performed in the compression stroke of the engine, and the control of the internal combustion engine that operates the engine A device,
Suppresses the generation of by Ri knocking disturbance of fuel spray increases with pressure of fuel to be injected directly into the combustion chamber during the compression stroke, the difference between the ignition timing and the MBT of occurrence of knocking is minimized control apparatus for an internal combustion engine and determines when to inject fuel directly into the combustion chamber in the compression stroke as. Ignition means provided on the ceiling surface of the cylindrical combustion chamber of the internal combustion engine for igniting fuel supplied to the combustion chamber;
After the spray of fuel injected in two directions travels in opposite directions along the inner peripheral wall of the combustion chamber and faces each other, the fuel is directed in two directions to the ignition means and enters the combustion chamber. Fuel injection means for directly injecting fuel;
The control apparatus for an internal combustion engine according to claim 1, further comprising:   4. The control apparatus for an internal combustion engine according to claim 3, wherein the ignition means is provided at substantially the center of the ceiling surface of the cylindrical combustion chamber of the engine. Ignition means for igniting the fuel provided in the vicinity of the inner peripheral wall of the cylindrical combustion chamber and the exhaust port of the internal combustion engine and supplied to the combustion chamber;
Fuel injection means provided in the vicinity of the inner peripheral wall of the combustion chamber and the intake port and directly injecting fuel into the combustion chamber;
The control apparatus for an internal combustion engine according to claim 1, further comprising: The control device for an internal combustion engine according to any one of claims 1 to 5, wherein the injected fuel is 100 MPa or more. The control device for an internal combustion engine according to claim 1, further comprising a protrusion provided on an inner wall of the combustion chamber and in contact with the spray of the injected fuel. In an internal combustion engine that generates engine torque by igniting fuel directly injected into the combustion chamber during the compression stroke,
The injection is suppressed from occurring by Ri knocking disturbance of fuel spray increases with pressure of the fuel injection timing of pre-Symbol injected fuel such that the difference between the ignition timing and the MBT of occurrence of knocking is minimized Determining the knocking of the internal combustion engine.

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