JP5884407B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine that operates by switching between premixed compression self-ignition combustion and spark ignition combustion.

  An internal combustion engine switches between spark ignition type combustion in which fuel is directly injected into a combustion chamber and the air-fuel mixture is burned by spark ignition, and premixed compression self-ignition type (hereinafter also referred to as compression self-ignition) combustion. Therefore, an in-cylinder injection gasoline engine with a high degree of freedom in fuel injection timing is known (see, for example, Patent Document 1). In a general in-cylinder injection gasoline engine, one injector is attached to each cylinder, and fuel is directly injected into the cylinder by a high-pressure fuel pump.

JP 2001-342883 A

  In the above-described in-cylinder injection gasoline engine, in order to switch from normal spark ignition combustion to compression auto-ignition combustion at low load, not only the fuel injection amount and injection timing but also the change in in-cylinder pressure due to the engine operating state. Accordingly, it is necessary to appropriately adjust the in-cylinder injection pressure of the fuel within an extremely short time. However, the responsiveness of high-pressure fuel pumps and injectors is limited. Therefore, in such an in-cylinder injection gasoline engine, when switching from the spark ignition combustion mode to the compression ignition combustion mode, the engine operating state is switched from the state where the fuel injection pressure is still high to the compression ignition combustion mode. Instead, it starts lean burn. Thus, in a state where the fuel injection pressure is still high, the fuel injection amount in the combustion chamber tends to be excessive, and the fuel concentration tends to be uneven. Therefore, in this state, there is a problem that the ignitability and combustibility of the sprayed fuel are inferior and the discharge amount of the unburned gas component increases. Further, in such an in-cylinder injection gasoline engine, if the pressure of fuel injected into the cylinder is too high compared to the in-cylinder pressure immediately after switching from the spark ignition combustion mode to the compression ignition combustion mode, the vaporization is performed. As a result, the sprayed fuel is crushed and becomes a factor that goes against fuel atomization. Furthermore, in such an in-cylinder injection gasoline engine, when the fuel injected at high pressure has a large penetration force with respect to the atmosphere in the combustion chamber, the fuel remains in a liquid state and adheres to the piston top surface and the cylinder wall surface. If the fuel adheres to the piston top surface or the cylinder wall surface in the liquid state as described above, it affects the air-fuel ratio in the combustion chamber and the like, thereby preventing stable combustion and causing smoke.

On the other hand, in such an in-cylinder injection gasoline engine, when switching from the compression ignition combustion mode to the spark ignition combustion mode of medium to high load operation, it is necessary to instantaneously increase the fuel injection pressure from a low fuel injection pressure state. It is also difficult to supply an optimal fuel injection amount for spark ignition combustion. Therefore, in this direct injection gasoline engine, the air-fuel ratio becomes too lean in the first few cycles after switching to spark ignition combustion, and unstable combustion and misfire are likely to occur. Further, in such a direct injection gasoline engine, when switching from the compression ignition mode to the spark ignition combustion mode medium and high load operation, due to the combustion temperature becomes higher, the discharge amount of the NO _x increases There are concerns.

  As described above, in a cylinder injection gasoline engine, in order to suppress a deviation from the target air-fuel ratio due to a sudden change in cylinder pressure, or to reduce an error in the fuel injection amount, the response of the cylinder fuel injection pressure control. It is important to be able to improve performance and accuracy. In such an in-cylinder injection gasoline engine, it is important to optimize the fuel injection shape, reach distance, concentration distribution, and the like by adjusting the fuel injection pressure in accordance with the engine operating state.

  The present invention has been made in view of the above problems, and prevents pre-ignition and misfiring in a lean combustion operation region between a spark ignition combustion operation region and a compression auto-ignition combustion operation region and Aiming to realize an internal combustion engine that can ensure ignition and combustion and reduce the amount of unburned gas emission, prevent the generation of smoke, and obtain stable combustion over a wide operating range. To do.

In order to solve the above-described problems and achieve the object, an aspect of the present invention includes a fuel injection valve that directly injects fuel delivered from a high-pressure fuel pump into a combustion chamber, and a spark plug, and at least a low load. Or, in an internal combustion engine that performs premixed compression self-ignition combustion in which the air-fuel mixture is combusted by compression self-ignition by the compression action of the piston in the low-rotation operation region, and performs spark ignition combustion in the high-load or high-rotation operation region The fuel injection valve is connected to the high-pressure fuel pump via a pressure adjustment valve that lowers the fuel injection pressure of the fuel sent from the high-pressure fuel pump to a predetermined pressure. A low-pressure fuel injection valve that injects fuel at a low fuel injection pressure, and a high-pressure fuel that is directly connected to the high-pressure fuel pump and injects fuel at the fuel injection pressure delivered from the high-pressure fuel pump An injection valve, in it, in compression stroke that put the load or middle speed operation region in the transition region to switch between HCCI combustion and spark ignition combustion, is primarily injecting fuel from the low-pressure fuel injector Further, as a supplement, fuel is injected from the high-pressure fuel injection valve with a fuel injection amount smaller than the amount of fuel injected from the low- pressure fuel injection valve, and spark ignition is performed by an ignition plug to perform lean stratified combustion.

  As the above aspect, it is preferable that fuel is mainly injected from the high-pressure fuel injection valve in the intake stroke of the premixed compression auto-ignition combustion, and fuel is injected mainly from the high-pressure fuel injection valve in the intake stroke of the spark ignition combustion. .

  In the above aspect, the low-pressure fuel injection valve and the spark plug are arranged at the center of the top surface of the combustion chamber, and the high-pressure fuel injection valve is generated when the fuel injection direction descends toward the bottom dead center. It is preferable that it is arrange | positioned at the side part of a combustion chamber so that it may face the approximate center of the tumble flow of air.

  According to the present invention, premature ignition and misfire are prevented in a lean combustion operation region that is a transition region between a spark ignition combustion operation region and a compression auto-ignition combustion operation region, and fuel ignitability and combustibility are ensured. Thus, it is possible to realize an internal combustion engine that can reduce the amount of unburned gas emission, prevent the generation of smoke, and obtain stable combustion over a wide operating range.

FIG. 1 is a schematic configuration diagram of an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a configuration diagram showing the control device for the internal combustion engine according to the embodiment of the present invention. FIG. 3 is a diagram showing the relationship between the boundary between the spark ignition combustion operation region and the compression auto-ignition combustion operation region of the internal combustion engine and the engine speed or the engine load in the medium rotation region or medium load region. FIG. 4 is a diagram showing a relationship between a region of spark ignition combustion, lean stratified combustion (during transient), compression auto-ignition combustion, and engine speed or engine load performed in the internal combustion engine according to the embodiment of the present invention. It is. FIG. 5-1 is a flowchart showing a control process mainly in a compression auto-ignition combustion mode of the internal combustion engine according to the embodiment of the present invention. FIG. 5-2 is a flowchart showing a control process mainly in a lean stratified combustion mode of the internal combustion engine according to the embodiment of the present invention. FIG. 5-3 is a flowchart showing a control process mainly in a spark ignition combustion mode of the internal combustion engine according to the embodiment of the present invention. FIG. 6 is an explanatory diagram showing control operations in the compression auto-ignition combustion mode, the lean stratified combustion mode, and the spark ignition combustion mode of the internal combustion engine according to the embodiment of the present invention. FIG. 7A is an explanatory view showing a cylinder liner wet state, and FIG. 7B is an explanatory view showing a piston wet state.

  Details of an internal combustion engine according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an internal combustion engine 1 according to an embodiment of the present invention, and FIG. 2 is a block diagram showing a configuration of a control device (hereinafter referred to as ECU) 20 of the internal combustion engine 1.

First, the configuration of the internal combustion engine 1 will be described with reference to FIG. As shown in FIG. 1, the internal combustion engine 1 according to the present embodiment burns in a spark ignition combustion (SI: Spark Ignition) operation region and a homogeneous air-fuel mixture by a compression action by a piston in the operation region. Premixed compression auto-ignition combustion (HCCI: Homogeneous Charge)
Compression Ignition) operation region and lean stratified combustion (SI) operation region, and can be operated by switching between spark ignition combustion, compression auto-ignition combustion, and lean stratified combustion.

  As shown in FIG. 1, the internal combustion engine 1 according to the present embodiment includes a cylinder 2 (cylinder), a cylinder head 3, and a piston 4 that reciprocates up and down within the cylinder 2. A space between the inner surface 2 a of the cylinder 2, the lower surface 3 a of the cylinder head 3 facing the cylinder 2, and the upper surface 4 a of the piston 4 is a combustion chamber 5. The piston 4 is connected to a crankshaft (not shown) via a connecting rod 6. The vertical movement of the piston 4 is converted to a rotational movement of a crankshaft (not shown) via a connecting rod 6.

  The cylinder head 3 is formed with a pair of intake ports 7 communicating with the combustion chamber 5 and a pair of exhaust ports 8 disposed at positions facing the intake ports 7 respectively. The cylinder head 3 is provided with a pair of intake valves 9 for opening and closing the openings 7 a of the respective intake ports 7 and a pair of exhaust valves 10 for opening and closing the openings 8 a of the respective exhaust ports 8. Yes. The intake valve 9 can introduce air into the combustion chamber 5, and the exhaust valve 10 can exhaust the exhaust in the combustion chamber 5 from the opening 8 a to the exhaust port 8. A valve operating mechanism (not shown) that opens the intake valve 9 and the exhaust valve 10 at a predetermined timing is provided.

At the center of the lower surface 3a of the cylinder head 3 (the top surface of the combustion chamber 5), a plug 11 used in the spark ignition combustion operation is provided. Further, a low pressure center injector 12 as a low pressure fuel injection valve disposed in the vicinity of the plug 11 is provided at the center of the lower surface 3 a of the cylinder head 3. The low-pressure center injector 12 is set so that a low-pressure highly dispersed fuel layer is formed in the vicinity of the ceiling of the combustion chamber 5 so that the spray can be diffused. A high-pressure side injector 13 as a high-pressure fuel injection valve is provided at a lower portion (a side portion in the combustion chamber 5) between the pair of intake valves 9 in the cylinder head 3. As shown in FIG. 1, the fuel injection direction of the high-pressure side injector 13 is such that the tumble flow of air generated when the piston 4 descends toward the bottom dead center (shown by a dashed line arrow T in FIG. 1). The cylinder head 3 is disposed at a position to be a side portion of the combustion chamber 5 so as to inject fuel toward the substantially center (indicated by arrow F in FIG. 1). In addition, FIG. 1 shows the tumble flow T in a state where the piston 4 has reached the bottom dead center as indicated by the alternate long and short dash line.

  The high-pressure side injector 13 is directly connected to the high-pressure fuel pump 14. Therefore, high pressure fuel is supplied to the high pressure side injector 13. The low pressure center injector 12 is connected to the high pressure fuel pump 14 via a regulator 15 as a pressure regulating valve. The regulator 15 regulates the high pressure fuel from the high pressure fuel pump 14 to a predetermined low pressure. Therefore, the fuel injection pressure of the low-pressure center injector 12 becomes a fuel injection pressure lower than that of the high-pressure side injector 13. As shown in FIG. 2, the fuel overflowed by the regulator 15 is returned to a fuel tank (not shown) through the pipe 16.

  The low-pressure center injector 12 and the high-pressure side injector 13 have a well-known configuration in which a plunger (not shown) is operated by controlling a solenoid (not shown) of fuel introduced through a fuel filter (not shown). For this reason, the low pressure center injector 12 and the high pressure side injector 13 can freely perform a fuel injection operation, a closing operation, and a multistage injection operation.

  The internal combustion engine 1 configured as described above directly moves fuel from the low-pressure center injector 12 and the high-pressure side injector 13 into the combustion chamber 5 while vertically moving the piston 4 and opening and closing the intake valve 9 and the exhaust valve 10 at a predetermined timing. The piston 4 can be moved up and down by an explosive force when injected and burned by spark ignition combustion and lean stratified combustion by the plug 11 or compression self-ignition combustion without using the plug 11. In the internal combustion engine 1, the intake of combustion air in the combustion chamber 5, the compression / combustion of the air-fuel mixture, the expansion due to this combustion, and the exhaust of the combustion gas are repeated.

  Next, the ECU 20 of the internal combustion engine 1 of the present embodiment will be described using FIG. The ECU 20 performs control for switching between spark ignition combustion, compression self-ignition combustion, and lean stratified combustion according to the engine operating region as shown in FIG.

  The ECU 20 includes a combustion region determination unit 21 that determines in which mode the internal combustion engine 1 operates, a low-pressure center injector control unit 22 that controls the injection timing and injection time of the low-pressure center injector 12, and a high-pressure side injector. 13 includes a high-pressure side injector control unit 23 that controls the injection timing, the injection time, and the like, and a plug control unit 24 that controls the ignition timing of the plug 11.

  The ECU 20 receives an engine speed signal, a throttle opening signal, an air-fuel ratio (A / F) signal, a crank angle signal, a fuel injection pressure signal, and an in-cylinder temperature signal that are detected by various sensors (not shown). It is like that.

  The combustion region determination unit 21 determines the operation region based on the engine speed signal and the throttle opening signal, and determines in which mode the operation is performed among spark ignition combustion, compression auto-ignition combustion, and lean stratified combustion. judge. In addition, as shown in FIG. 2, the low pressure center injector control unit 22 and the high pressure side injector control unit 23 determine the number of fuel injections per cycle, the fuel injection timing, and the fuel injection amount based on various detection signals. Control signals are output to the low pressure center injector 12 and the high pressure side injector 13. The plug control unit 24 outputs a control signal for causing the plug 11 to perform ignition at a predetermined timing when the combustion region determination unit 21 determines that the operation mode is the spark ignition combustion mode and the lean stratified combustion mode.

  Next, the operation, action, and effect of the internal combustion engine 1 according to the present embodiment will be described. As shown in FIG. 3, generally, the combustion mode of an internal combustion engine is determined by the engine speed and the engine load (motion load). In the internal combustion engine 1 according to the present embodiment, when switching the combustion mode from spark ignition combustion to compression self-ignition combustion, it differs depending on the low pressure center injector 12 and the high pressure side injector 13 according to the operation region shown in FIG. By controlling the fuel injection from the direction, a homogeneous and lean fuel injection is instantaneously formed in the combustion chamber 5. In particular, in the present embodiment, the low pressure center injector 12 is mainly used in the compression stroke of the fuel in the lean load stratified combustion operation region, which is the intermediate load or intermediate rotation operation region, which is a transition region in which compression auto-ignition combustion and spark ignition combustion are switched. The fuel is injected from the start and spark ignition is performed. A specific control method for the internal combustion engine 1 according to the present embodiment will be described later.

  The internal combustion engine 1 according to the present embodiment determines whether to mainly perform injection from one of the low-pressure center injector 12 and the high-pressure side injector 13, and makes these injections multistage injections. It is possible to arbitrarily control the fuel injection amount required for combustion. Therefore, in the present embodiment, it is not necessary to adjust the fuel injection pressures of the low pressure center injector 12 and the high pressure side injector 13 according to the change of the combustion mode when the operating state of the internal combustion engine changes abruptly. For this reason, as compared with the case where the pressure level is adjusted on the high-pressure fuel pump side using a single injector as in the prior art, in this embodiment, an appropriate control of the fuel injection amount can be instantaneously achieved. It becomes possible.

  In the internal combustion engine 1 according to the present embodiment, although only the high-pressure fuel pump 14 is driven at a single pressure, a plurality of stages of fuel are supplied to the low-pressure center injector 12 and the high-pressure side injector 13 in a state close to the target injection pressure. By injecting the fuel at a pressure of and introducing it into the combustion chamber 5, an optimal fuel spray form can be generated.

  In particular, in the present embodiment, such a fuel injection mode requires a lean dilution to reduce torque fluctuation caused by combustion instability when switching the combustion mode from spark ignition combustion to compression autoignition combustion. Ensures the stability of stratified combustion. That is, in the region of lean stratified combustion at the time of transition shown in FIG. 4, the fuel injection is mainly performed by the low pressure center injector 12 in the compression stroke and the high pressure side injector 13 is used as an assist to achieve stratification of the air-fuel mixture, and spark ignition Leads to combustion. As shown in FIG. 4, since the compression ignition combustion cannot be stably performed in the extremely low rotation region or the extremely low load region of the internal combustion engine 1, the spark ignition combustion operation is also performed in this region.

  Further, in the internal combustion engine 1 according to the present embodiment, fuel is mainly injected from the high pressure side injector 13 in the intake stroke of the compression ignition combustion, and fuel is mainly injected from the high pressure side injector 13 in the intake stroke of the spark ignition combustion. By igniting, reliable ignitability and combustibility can be ensured.

  In the internal combustion engine 1 according to the present embodiment, the combustion chamber 5 is determined by determining which of the low-pressure center injector 12 and the high-pressure side injector 13 is the main in accordance with a change in fuel injection timing accompanying stratified combustion or homogeneous combustion. It prevents the fuel from adhering and recombining inside and promotes atomization of the fuel. The fuel can be made finer and a homogeneous mixture can be formed, and fuel efficiency can be improved by improving combustion.

  In the case of performing stratified combustion, the low pressure center injector 12 is mainly used to inject necessary fuel at a low pressure and reduce the penetration (penetration) of the spray. Therefore, it is possible to prevent the piston 4 from being wet, in which the upper surface 4a of the piston 4 gets wet. In FIG. 7A, an elliptical portion indicated by a broken line indicates a region where the piston is in a wet state.

  On the other hand, in homogeneous combustion, as the piston 4 descends toward the bottom dead center, a tumble flow T (see FIG. 1) is generated, so that the high pressure side injector 13 is the main component and the low pressure center injector 12 is the auxiliary. Are simultaneously driven to perform a diffusion spray to produce a homogeneous fuel spray. By generating the diffusion spray in this way, the ignitability of stable compression autoignition combustion is improved, and the occurrence of knocking due to the uneven fuel concentration distribution is suppressed.

  In the internal combustion engine 1 according to the present embodiment, the required fuel state can be achieved instantaneously with the two injectors of the low pressure center injector 12 and the high pressure side injector 13 having different fuel injection pressures. Therefore, it is possible to suppress the occurrence of smoke by suppressing the occurrence of the cylinder liner wet state in the above-described piston wet state and the region indicated by the dashed ellipse in FIG.

  In general, when switching from spark ignition combustion to compression self-ignition combustion, a lean stratified combustion region is required, so it is considered desirable to form fuel injection at low pressure in the combustion chamber 5 uniformly. Conventionally, the pressure response is delayed because the pressure adjustment of only the high-pressure fuel pump 14 is switched between the compression ignition combustion and the spark ignition combustion. In this embodiment, the combination of the low-pressure center injector 12 and the high-pressure side injector 13 is used. Thus, it is possible to create a homogeneous spray that is easy to concentrate in the combustion chamber 5 and prevent premature ignition or misfire. Further, in the internal combustion engine 1 according to the present embodiment, the fuel injection amount can be controlled from a large state to a small state by combining the low pressure center injector 12 and the high pressure side injector 13, so the pressure of the high pressure fuel pump 14 is There is an advantage that it can be set lower than the pressure of the conventional high-pressure fuel pump.

  Further, in the internal combustion engine 1 according to the present embodiment, the drive of the low pressure center injector 12 and the high pressure side injector 13 is shifted so as to be in different time zones, thereby performing fuel injection along the combustion chamber 5 and spraying. The flow can be utilized to accelerate the airflow in the combustion chamber 5 and improve the turbulence intensity. Further, in the internal combustion engine 1 according to the present embodiment, the fuel is uniformly injected into the combustion chamber 5 simultaneously from the low pressure center injector 12 and the high pressure side injector 13, thereby instantaneously cooling the gas in the combustion chamber 5. It also has the effect of increasing the fuel filling rate.

  As described above, the internal combustion engine 1 according to the present embodiment is configured such that the low pressure center injector 12 and the high pressure side injector 13 can simultaneously inject fuel into the combustion chamber 5 at two stages of pressure. By shortening, more accurate fuel injection start timing, fuel injection end timing, and fuel injection amount can be controlled. Further, in the internal combustion engine 1 according to the present embodiment, in the situation where the fuel injection is multistage as described above, the response of the fuel injection pressure is slow with respect to the change of the engine operating condition as in the conventional case. Thus, the problem of insufficient fuel injection amount can be avoided.

  Next, a control flow of the internal combustion engine 1 according to the present embodiment will be described with reference to the flowcharts of FIGS. 5-1, 5-2, and 5-3.

  First, as shown in FIG. 5A, the combustion region determination unit 21 in the ECU 20 determines whether or not the engine is in the compression auto-ignition combustion (HCCI) mode based on the engine speed signal and the throttle opening signal. (Step S1).

  Here, when the operation mode of the internal combustion engine 1 is the compression ignition combustion mode, the high pressure side injector 13 is mainly used and the low pressure center injector 12 is assisted based on the engine speed signal and the throttle opening (engine load) signal. As a result, the fuel injection pressure required in one cycle is calculated (step S2). In step S2, the fuel injection timing and the position of the piston 4 are considered from the crank angle signal.

  Subsequently, the target fuel injection amounts in the low pressure center injector 12 and the high pressure side injector 13 in the intake stroke based on the fuel injection pressure calculated in step S2 in the low pressure center injector control unit 22 and the high pressure side injector control unit 23. Then, multistage fuel injection timing is determined (step S3).

  Based on the target fuel injection amount and fuel injection timing determined in step S3, the low pressure center injector control unit 22 and the high pressure side injector control unit 23 control signals to the corresponding low pressure center injector 12 and high pressure side injector 13, respectively. Is output, and the air-fuel mixture in the combustion chamber 5 is subjected to compression self-ignition combustion (step S4).

  Thereafter, in the compression ignition combustion operation, the combustion stability state is detected based on the in-cylinder temperature signal and the A / F signal, and the low pressure center injector control unit 22 and the high pressure side injector control are performed based on the combustion stability state. Fuel injection correction control is performed from the unit 23 to the low pressure center injector 12 and the high pressure side injector 13 (step S5).

  Next, the fuel region determination unit 21 determines whether or not the engine operation is continuing based on the engine speed signal, the throttle opening signal, and the like (step S6). In step S6, when the operation is continuing (YES), the process returns to the determination of step S1, and when the operation is determined to be stopped (NO), the control is ended.

  If it is determined in step S1 that the operation mode is not the compression auto-ignition combustion mode, it is determined whether or not the operation mode is the lean stratified combustion (SI) mode according to the control flow A shown in the flowchart of FIG. (Step S7). The determination in step S7 is performed by the combustion region determination unit 21 based on the engine speed signal and the throttle opening signal.

  When the lean stratified combustion mode is determined, based on the engine speed signal and the throttle opening (engine load) signal, the low pressure center injector 12 mainly assists the high pressure side injector 13, and the low pressure center injector 12 and high pressure side injector. The fuel injection control pressure required at 13 is calculated (step S8).

  Next, in the compression stroke of the internal combustion engine 1, the target fuel injection amount and injection timing from the low pressure center injector 12 and the high pressure side injector 13 are determined (step S9). In this lean stratified combustion mode, as shown in FIG. 6, control is performed to form a fuel spray state suitable for stratified combustion by performing low-pressure fuel injection mainly in the low-pressure center injector 12 during the compression stroke.

  Thereafter, based on the target fuel injection amount and fuel injection timing determined in step S9, the low-pressure center injector control unit 22 and the high-pressure side injector control unit 23 apply the corresponding low-pressure center injector 12 and high-pressure side injector 13 respectively. A control signal is output to inject the fuel mixture in the combustion chamber 5 into a state suitable for lean stratified combustion. The plug control unit 24 outputs an ignition control signal to the plug 11 and performs ignition at a predetermined timing (step S10). After step S10, the control of step S5 is performed according to the flow of C in the flowchart of FIG.

  Next, when it is determined in step S7 that it is not the lean stratified combustion mode, that is, when it is determined that it is the spark ignition combustion mode, step S11 is performed according to the flow of B shown in FIG. Control. In this step S11, the necessity of the low pressure center injector 12 and the high pressure side injector 13 is based on the high pressure side injector 13 based on the engine speed signal and the throttle opening (engine load) signal and with the low pressure center injector 12 as an auxiliary. The fuel injection control pressure to be calculated is calculated.

  Next, in this spark ignition combustion mode, the target fuel injection amount and fuel injection timing (injection timing in the intake stroke) in the low pressure center injector 12 and the high pressure side injector 13 in the intake stroke are determined (step S12). In this spark ignition combustion mode, since the engine speed and the engine load are also in a high range, it is not necessary for the high-pressure side injectors 13 to be dispersed and injected in multiple stages as in the compression auto-ignition combustion mode.

  Next, based on the target fuel injection amount and injection timing determined in step S12, the low pressure center injector control unit 22 and the high pressure side injector control unit 23 control the corresponding low pressure center injector 12 and high pressure side injector 13 respectively. A signal is output to inject fuel in the combustion chamber 5 into a state suitable for spark ignition combustion, and an ignition control signal is output from the plug control unit 24 to the plug 11 to perform ignition at a predetermined timing ( Step S13). Incidentally, in this spark ignition combustion mode, fuel injection is performed from the high-pressure side injector 13 toward the approximate center of the tumble flow in the intake stroke, so that the turbulence intensity can be increased, so that the fuel in the combustion chamber 5 can be made homogeneous, The filling efficiency can be increased by instantaneous cooling of the gas. After step S13, the control of step S5 is performed according to the flow of C in the flowchart of FIG.

  As mentioned above, although embodiment of this invention was described, it should not be understood that the description and drawing which make a part of disclosure of this embodiment limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the fuel injection pressure of the high-pressure fuel pump 14 is fixed at a constant high pressure, but the high-pressure fuel pump 14 may of course have a pressure adjustment function.

  In the above embodiment, the low pressure center injector 12 is disposed on the ceiling of the combustion chamber 5 and the high pressure side injector 13 is disposed on the side of the combustion chamber 5. However, the fuel of the low pressure center injector 12 and the high pressure side injector 13 is not limited. Needless to say, changing the arrangement by changing the injection direction is also within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Cylinder head 4 Piston 5 Combustion chamber 7 Intake port 8 Exhaust port 9 Intake valve 10 Exhaust valve 11 Plug (ignition plug)
12 Low pressure center injector 13 High pressure side injector 14 High pressure fuel pump 15 Regulator (pressure regulating valve)
DESCRIPTION OF SYMBOLS 20 Control apparatus 21 Combustion area | region determination part 22 Low pressure center injector control part 23 High pressure side injector control part 24 Plug control part

Claims (3)

A fuel injection valve that directly injects fuel delivered from the high-pressure fuel pump into the combustion chamber and an ignition plug, and at least in a low-load or low-rotation operation region, the air-fuel mixture is compressed and self-ignited by the compression action of the piston. An internal combustion engine that performs premixed compression self-ignition combustion to perform combustion, and performs spark ignition combustion in a high load or high rotation operation region,
The fuel injection valve is
A fuel injection pressure that is lower than the fuel injection pressure that is connected to the high-pressure fuel pump via a pressure regulating valve that lowers the fuel injection pressure of the fuel that is sent from the high-pressure fuel pump to a predetermined pressure. A low-pressure fuel injection valve for fuel injection;
A high-pressure fuel injection valve that is directly connected to the high-pressure fuel pump and injects fuel at a fuel injection pressure delivered from the high-pressure fuel pump;
Wherein at compression stroke that put the load or middle speed operation region in the transition region to switch between HCCI combustion and the spark ignition combustion, fuel is injected mainly from the low-pressure fuel injection valve, wherein as auxiliary An internal combustion engine characterized in that fuel is injected from the high-pressure fuel injection valve with a fuel injection amount smaller than the amount of fuel injected from the low-pressure fuel injection valve, spark ignition is performed by the spark plug, and lean stratified combustion is performed.
In the intake stroke of the premixed compression auto-ignition combustion, fuel is mainly injected from the high-pressure fuel injection valve in multiple stages,
The internal combustion engine according to claim 1, wherein fuel is injected mainly from the high-pressure fuel injection valve in an intake stroke of the spark ignition combustion. The low-pressure fuel injection valve and the spark plug are arranged at the center of the top surface of the combustion chamber,
The high-pressure fuel injection valve is disposed on the side of the combustion chamber so that the fuel injection direction is directed to the approximate center of the tumble flow of air generated when the piston descends toward the bottom dead center. The internal combustion engine according to claim 1 or 2, characterized by the above.

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