JP3852230B2 - In-cylinder injection spark ignition engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a direct injection spark ignition engine.
[0002]
[Prior art]
A fuel injection valve that directly injects fuel into the combustion chamber and an ignition plug are provided, and stratified combustion is performed by injecting fuel during the compression stroke in the low load region of the engine, while intake stroke is performed in the high load region of the engine. In a cylinder injection spark ignition engine in which fuel is injected into the cylinder to perform homogeneous combustion, in order to establish the above-described stratified combustion, a strong in-cylinder flow is applied to the intake air in the combustion chamber during the intake stroke. Granting is essential.
[0003]
Therefore, in general, the intake port has a helical port structure, or a swirl flow enhancing means is provided in the intake port so as to impart a strong swirl flow to the intake stroke in the intake stroke.
[0004]
[Problems to be solved by the invention]
Even if a strong swirl flow is applied to the intake air during the intake stroke, it cannot be denied that the in-cylinder flow is attenuated by the compression action during the compression stroke.
[0005]
On the other hand, Japanese Patent Laid-Open No. 5-180123 discloses a fuel supply system that uses a two-fluid fuel injection valve that supplies fuel and pressurized air, and increases the amount of pressurized air in a specific operating region of the engine. Therefore, it is conceivable to reinforce the in-cylinder flow with the pressurized air using the two-fluid fuel injection valve, but even if the pressurized air is simply used as the in-cylinder flow enhancing means. The stratified combustion may become unstable due to the fuel atomization and vaporization promoting action by the pressurized air and the fuel diffusing action.
[0006]
Therefore, the present invention employs the above-described two-fluid fuel injection valve as the fuel injection valve, and finely supplies the pressurized air in accordance with the operating conditions in any of the stratified combustion operation and the homogeneous combustion operation. Provided is an in-cylinder injection spark ignition engine that can be controlled and can obtain an optimal in-cylinder flow for each operating condition, and can realize stabilization of combustion, improvement of engine output, and improvement of exhaust emission. .
[0007]
[Means for Solving the Problems]
  According to the first aspect of the present invention, the fuel injection valve for directly injecting fuel into the combustion chamber and the spark plug are provided, and fuel is injected during the compression stroke in a low load region to perform stratified combustion, and In a direct injection spark ignition engine in which fuel is injected during an intake stroke in a load range to perform homogeneous combustion, the fuel injection valve is a two-fluid type capable of individually injecting fuel and pressurized air In addition to using the fuel injection valve, there is provided an injection timing / period variable means for variably controlling the injection timing and injection period of the pressurized air of the fuel injection valve according to the operating condition of the engine during the stratified combustion operation and the homogeneous combustion operationIn the stratified charge combustion operation, the lower the engine speed, the longer the injection period of pressurized airIt is characterized by that.
[0008]
According to a second aspect of the present invention, the injection timing / period variable means according to the first aspect is configured such that, during the stratified charge combustion operation, the injection timing and the injection timing of the pressurized air according to the engine speed, the load, and the oil / water temperature. It is characterized by changing the period.
[0010]
  Claim3In the invention of claim2The injection timing / period variable means described above is characterized in that, during the stratified combustion operation, the injection period of the pressurized air is lengthened as the engine load increases.
[0011]
  Claim4In the invention of claim 2, claim 2, 3In the stratified charge combustion operation, the injection timing / period variable means described in 1 is characterized in that the injection period of the pressurized air is lengthened as the oil / water temperature is low.
[0012]
  Claim5In the present invention, claims 1 to4The injection timing / period variable means described in 1) is characterized in that the pressurized air injection end timing is set after the fuel injection end timing.
[0013]
  Claim6In the invention of claim5In the stratified combustion operation, the injection timing / period variable means described in (1) is characterized in that the period from the fuel injection end timing to the pressurized air injection end timing becomes longer as the oil / water temperature is lower.
[0014]
  Claim7In the present invention, claims 1 to6The injection timing / period variable means described in (1) is characterized in that only the pressurized air is injected into the combustion chamber during the compression stroke during the homogeneous combustion operation.
[0015]
  Claim8In the invention of claim7The injection timing / period variable means described in the item (1) changes the pressurized air injection period into the combustion chamber during the compression stroke according to the engine speed, load, and oil / water temperature during homogeneous combustion operation. It is a feature.
[0016]
  Claim9In the invention of claim8The injection timing / period variable means described in (1) is characterized in that the pressurized air injection period is lengthened as the engine load increases during the homogeneous combustion operation.
[0017]
【The invention's effect】
  According to the first aspect of the present invention, the two-fluid fuel injection valve capable of injecting fuel and pressurized air is used as the fuel injection valve, and the engine operation is performed during the stratified combustion operation and the homogeneous combustion operation, respectively. Because the injection timing and the injection period of the pressurized air of the fuel injection valve are variably controlled according to the conditions, the control of the injection timing and the injection period of the pressurized air according to the operating conditions during the stratified combustion operation, In-cylinder flow that brings about optimal combustion under all operating conditions can be positively generated, combustion can be stabilized and combustion efficiency can be improved, and fuel consumption rate and exhaust properties can be improved.
  In particular, when the engine speed is low even during stratified charge combustion operation, the in-cylinder flow generated in the intake stroke is weak, resulting in insufficient mixture formation and transport of the mixture around the spark plug. However, since the injection period of pressurized air is controlled to be longer as the engine speed is lower, the strong cylinder suitable for stratification and transportability of the air-fuel mixture can be achieved even when the engine speed is low. Flow can be obtained and stable stratified combustion can be performed.
  On the other hand, when the engine speed is high, good mixture formation and good transportability of the mixture around the spark plug can be obtained by in-cylinder flow generated in the intake stroke. On the other hand, when the air pressure is high, the injection period of the pressurized air is shortened, contrary to the above, so that an appropriate in-cylinder flow that does not inhibit the stratification of the air-fuel mixture can be achieved.
[0018]
In addition, in the homogeneous combustion operation, as in the stratified combustion operation, the in-cylinder flow that brings about optimal combustion under all operating conditions can be positively created, so that the in-cylinder air-fuel mixture can be further homogenized. It is promoted to improve engine output and exhaust properties.
[0019]
According to the second aspect of the present invention, in addition to the effect of the first aspect of the invention, during the stratified charge combustion operation, based on detection signals of engine speed, load, and oil / water temperature, which are main parameters representing operating conditions. Thus, the injection timing and injection period of the pressurized air can be finely and appropriately controlled in accordance with the operating conditions, so that more stable stratified combustion can be performed.
[0022]
  Claim3According to the invention described in claim2In addition to the effects of the invention, normally, when the engine load is high even during stratified combustion operation, a large amount of fuel is injected into the combustion chamber during the compression stroke, and good mixing is achieved only with the in-cylinder flow generated during the intake stroke. Although the formation of the air becomes insufficient, it is controlled so that the injection period of the pressurized air becomes longer as the engine load increases, so that it is suitable for stratification of the air-fuel mixture even when the engine load is high. Strong in-cylinder flow can be obtained and stable stratified combustion can be performed.
[0023]
On the other hand, when the engine load is low, the amount of fuel injected into the combustion chamber in the compression stroke is small, and a good mixture is formed by the in-cylinder flow generated in the intake stroke, but this engine load is low On the contrary, since the injection period of the pressurized air is shortened contrary to the above, it is possible to achieve an appropriate in-cylinder flow that does not inhibit the stratification of the air-fuel mixture.
[0024]
  Claim4According to the invention described in claim 2,, 3In addition to the effects of the present invention, when the oil / water temperature is low even during the stratified combustion operation, that is, when the engine is cold, the fuel is injected into the combustion chamber in the compression stroke and adheres as a liquid film to the piston crown surface. Vaporization becomes difficult and instability of combustion and generation of unburned HC, smoke and deposits are a problem. However, the lower the oil water temperature, the longer the injection period of pressurized air is controlled. Further, the in-cylinder flow can be strengthened to promote the vaporization of the attached fuel, and the stratified combustion can be stabilized and the exhaust properties can be improved.
[0025]
On the other hand, when the temperature of the oil / water is sufficiently increased and the warm-up is completed, the pressurized air injection period is shortened, contrary to the above, so that an appropriate in-cylinder flow that does not inhibit the stratification of the air-fuel mixture can be achieved. .
[0026]
  Claim5According to the invention described in claim 1,4In addition to the effects of the present invention, the pressurized air injection end timing is later than the fuel injection end timing, so that the fuel liquid film remaining in the nozzle hole of the fuel injection valve particularly during the stratified combustion operation By blowing off by injection, the inside of the nozzle hole and the vicinity of the outlet can always be kept clean, deposit adhesion at the nozzle tip can be avoided, the fuel spray shape can be stabilized, and the engine stability can be improved.
[0027]
  Claim6According to the invention described in claim5In addition to the effects of the present invention, when the engine is cold, the oil temperature is low even during stratified combustion operation, fuel is injected into the combustion chamber during the compression stroke, and it is difficult to vaporize the fuel adhering to the piston crown as a liquid film Therefore, instability of combustion, generation of unburned HC, smoke and deposit accumulation are problems, but the lower the oil water temperature, the longer the period from the fuel injection end timing to the pressurized air injection end timing, Vaporization of the adhering fuel can be promoted, and stratified combustion can be stabilized and exhaust properties can be improved.
[0028]
On the other hand, when the temperature of the oil / water is sufficiently increased to reach the warm-up completion state, the period from the fuel injection end timing to the pressurized air injection end timing is shortened contrary to the above, so that appropriate stratification of the mixture is not hindered. It can be in-cylinder flow.
[0029]
  Claim7According to the invention described in claim 1,6In addition to the effect of the present invention, during the homogeneous combustion operation, only the compressed air is injected into the combustion chamber during the compression stroke, so that the in-cylinder flow generated in the intake stroke is made homogeneous by the injection of pressurized air in the compression stroke. Strengthening adjustment can be performed so that the in-cylinder flow strength is optimal for combustion, and stable homogeneous combustion can be performed.
[0030]
  Claim8According to the invention described in claim7In addition to the effects of the present invention, during homogeneous combustion operation, injection of pressurized air that is injected during the compression stroke based on detection signals of engine speed, load, and oil / water temperature, which are main parameters representing operating conditions The period can be finely and appropriately controlled in accordance with the operating conditions, and more stable homogeneous combustion can be performed.
[0031]
  Claim9According to the invention described in claim8In addition to the effects of the invention, normally, when the engine load is high even during homogeneous combustion operation, the amount of fuel injected into the combustion chamber during the intake stroke is large, and only the in-cylinder flow generated during the intake stroke is good. However, since the injection period of the pressurized air is controlled to be longer as the engine load is increased, the mixture mixture is reduced even when the engine load is high. Strong in-cylinder flow suitable for homogenization is obtained, and stable homogeneous combustion can be performed.
[0032]
On the other hand, when the engine load is low, the amount of fuel injected into the combustion chamber in the intake stroke is small, and a good homogeneous mixture is formed by the in-cylinder flow generated in the intake stroke. When the pressure is low, the injection period of the pressurized air is shortened, contrary to the above, so that an appropriate in-cylinder flow that can prevent the in-cylinder flow from becoming too strong and blowing off the combustion flame can be achieved.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0034]
In FIG. 1, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, and 4 is a combustion chamber formed by the cylinder block 1, the piston 2 and the cylinder head 3.
[0035]
The cylinder head 3 is provided with an intake port 6 that is opened and closed by an intake valve 5 and an exhaust port 8 that is opened and closed by an exhaust valve 7, and an ignition plug 9 is disposed at a position almost facing the center of the combustion chamber 4. It is.
[0036]
  There is an intake valve at the peripheral side of the combustion chamber 45A fuel injection valve 10 for directly injecting fuel into the combustion chamber 4 is disposed at a position near the position.
[0037]
As the fuel injection valve 10, a two-fluid fuel injection valve capable of individually injecting fuel and pressurized air is used, and its operation is controlled as described later by an output signal of an engine control unit 11 as a control device. The
[0038]
The engine control unit 11 has an air amount signal detected by an air flow meter 13 provided in an intake passage 12 connected to the intake port 6, a load signal detected by a throttle sensor provided in a throttle valve 14 downstream of the air flow meter 13, The rotation speed signal detected by the crank angle sensor, the oil / water temperature signal detected by the temperature sensor, etc. are input (the throttle sensor, the crank angle sensor, and the temperature sensor are not shown), and based on the detection signals of these various sensors. The engine control unit 11 comprehensively controls the operation of the ignition plug 9, the fuel injection valve 10, the valve operating device (not shown), and the like.
[0039]
A pressurized air passage 15 for supplying pressurized air to the fuel injection valve 10 communicates with the intake passage 12 and bypasses the air pump 16 provided in the pressurized air passage 15 with the air taken in from the intake passage 12 and the air pump 16. The air pressure regulator 18 provided in the bypass passage 17 is pressurized and pressure-adjusted and supplied to the fuel injection valve 10.
[0040]
As will be described later, in order to inject pressurized air into the combustion chamber 4 against the in-cylinder pressure during the compression stroke of the engine, the pressurized air supplied to the fuel injection valve 10 is adjusted to an air pressure of 1 MPa or more.
[0041]
Here, the pressurized air passage 15 communicates between the air flow meter 13 and the throttle valve 14 in the intake passage 12, and the amount of air supplied from the intake port 6 and the amount of air injected from the fuel injection valve 10 are The total is detected by the air flow meter 13 so that air-fuel ratio control can be properly performed.
[0042]
The intake port 6 is set at a predetermined inclination angle so that a required swirling flow, for example, a forward tumble flow, can be formed in the air flow sucked into the combustion chamber 4 during the intake stroke. The mounting angle is set so that pressurized air can be injected in substantially the same direction as the in-cylinder flow generated in the intake stroke.
[0043]
During the stratified combustion operation, the fuel-air mixture is stratified by injecting fuel directly from the fuel injection valve 10 toward the in-cylinder flow generated in the intake stroke into the combustion chamber 4 during the compression stroke of the engine. While igniting and performing stratified combustion, during homogeneous combustion operation, fuel is directly injected into the combustion chamber 4 from the fuel injection valve 10 during the intake stroke of the engine to homogenize the air-fuel mixture, and spark ignition is performed by the spark plug 9. Make homogeneous combustion.
[0044]
The engine control unit 11 includes a pressurized air injection period varying means 11A and a pressurized air injection timing varying means 11B configured as software, and pressurized air is supplied from the fuel injection valve 10 simultaneously with, for example, fuel injection or In addition to being injected with a slight delay, during the stratified combustion operation and the homogeneous combustion operation, the injection timing and the injection period are variably controlled by changing the injection pulse signal of the pressurized air according to the respective operating conditions.
[0045]
As the signals indicating the engine operating conditions described above, detection signals of the engine speed, load, and oil / water temperature, which are main parameters indicating the operating conditions, are used. Based on these detection signals, the pressurized air is detected. The injection timing and injection period are finely variably controlled in accordance with the operating conditions so that an appropriate in-cylinder flow can be formed, so that stratified combustion and homogeneous combustion can be performed stably according to the respective operating conditions. ing.
[0046]
More specifically, the pressurized air injection period varying means 11A and the pressurized air injection timing varying means 11B of the engine control unit 11 include, for example, control of pressurized air injection during the stratified combustion operation shown in FIG. A map and a control map of pressurized air injection during the homogeneous combustion operation shown in FIG. 3 are stored in memory.
[0047]
In order to judge the stratified combustion operation and the homogeneous combustion operation, the high engine speed and the high load region are generally not established unless the homogeneous combustion operation is performed. Therefore, as shown in the maps of FIGS. -The stratified combustion operation region and the homogeneous combustion operation region are separated by load.
[0048]
In the map shown in FIG. 2, in the stratified combustion operation region, the injection period from the start of injection of the pressurized air to the end of injection becomes longer as the engine speed decreases, and the injection period of the pressurized air increases as the load increases. Is set to be long.
[0049]
In the map shown in FIG. 3, in the homogeneous combustion operation region, the injection period from the start of injection of the pressurized air to the end of injection is set longer as the engine load increases.
[0050]
The pressurized air injection period during the stratified combustion operation and the homogeneous combustion operation is based on the basic injection period (pulse width) obtained from the rotation speed-load shown in each map according to the change in the oil temperature and a predetermined value. The correction is calculated by the product of the oil / water temperature correction coefficient, and as shown in FIG. 4, the lower the oil / water temperature, the longer the injection period.
[0051]
On the other hand, the injection timing of the pressurized air during the stratified combustion operation and the homogeneous combustion operation is controlled by the pressurized air injection timing varying means 11B of the engine control unit 11 based on the maps of FIGS. During the combustion operation, only pressurized air is injected into the combustion chamber 4 during the compression stroke.
[0052]
Further, the pressurized air injection end timing is set after the fuel injection end timing. However, as shown in FIG. 5, for example, as the engine oil / water temperature decreases, the pressurized air injection end timing increases from the fuel injection end timing. The period until the end of the pressurized air injection is made longer. Although FIG. 5 shows a change state at the end of the pressurized air injection with respect to the oil / water temperature change during the stratified combustion operation, similar control may be performed during the homogeneous combustion operation.
[0053]
FIG. 6 is a flowchart showing the pressurized air injection control operation by the engine control unit 11 described above.
[0054]
In FIG. 6, the engine speed signal, load signal, oil / water temperature signal, and air amount signal are read in step S1, and based on these various input signals, it is determined whether the stratified combustion operation condition or the homogeneous combustion operation condition in step S2. To do.
[0055]
When it is determined in step S2 that the stratified combustion operation condition is satisfied, the process proceeds to step S3, and the operation is performed in the stratified combustion operation mode in which fuel injection is performed during the compression stroke. In this stratified combustion operation mode, in the next step S4, based on the rotation speed signal, load signal and oil / water temperature signal, the map shown in FIG. 2 and the correction calculation of the pressurized air injection period by the oil / water temperature (see FIG. 4) At the same time as the pressurized air injection period is set, the correction calculation of the pressurized air injection end timing based on the map and the oil / water temperature shown in FIG. 2 based on the rotational speed signal, the load signal, and the oil / water temperature signal in step S5. (Refer to FIG. 5), the injection timing of the pressurized air is set. During the compression stroke, the pressurized air is introduced into the combustion chamber 4 together with the fuel from the fuel injection valve 10 in the injection period and the injection timing optimum for the operating conditions at that time. Be injected.
[0056]
If it is determined in step S2 that the operation state is not the stratified combustion operation condition but the homogeneous combustion operation condition, the process proceeds to step S6 and the operation is performed in the homogeneous combustion operation mode in which fuel injection is performed during the intake stroke.
[0057]
In this homogeneous combustion operation mode, in the next step S7, based on the rotation speed signal, load signal and oil / water temperature signal, the map shown in FIG. 3 and the correction calculation of the pressurized air injection period based on the oil / water temperature (see FIG. 4). At the same time as the pressurized air injection period is set, correction calculation of the pressurized air injection end time based on the map and the oil / water temperature shown in FIG. 3 based on the rotation speed signal, the load signal, and the oil / water temperature signal in step S8. (Similar to FIG. 5), the injection timing of the pressurized air is set. During the intake stroke, the pressurized air is injected into the combustion chamber 4 together with the fuel from the fuel injection valve 10 in the injection period and the injection timing optimum for the operating conditions at that time. In addition, only pressurized air is again injected into the combustion chamber 4 from the fuel injection valve 10 during the compression stroke.
[0058]
FIG. 7 shows the in-cylinder flow in the case where the pressurized air injection period is controlled to be longer as the engine speed is lower, according to the engine speed during the stratified combustion operation (however, the load is constant). The behavior is schematically shown.
[0059]
Since the intake air flow rate and the intake air flow velocity are almost proportional to the engine speed, the in-cylinder flow generated in the intake stroke is weak as shown in FIG. In addition, the transportability of the air-fuel mixture around the spark plug 9 tends to be insufficient.
[0060]
However, in-cylinder flow is energized by injecting pressurized air in the compression stroke in which fuel injection is performed, and the air-fuel mixture is finally stratified by extending the injection period of the pressurized air. In addition, a strong in-cylinder flow suitable for transportability can be formed, and stable stratified combustion can be performed.
[0061]
As shown in (b) and (c) of the figure, when the engine speed shifts to a high speed, the in-cylinder flow generated in the intake stroke increases, but the injection period of the pressurized air injected in the compression stroke is Since it is shortened, an appropriate in-cylinder flow that does not inhibit the stratification of the air-fuel mixture can be achieved. The stratified combustion can be stabilized by providing a sufficient and appropriate flow for the property.
[0062]
FIG. 8 shows the in-cylinder flow when the pressurized air injection period is controlled to be longer as the engine load increases (however, the rotation speed is constant) according to the engine load during stratified combustion operation. The behavior of mixture formation is schematically shown.
[0063]
Since the fuel injection amount is almost proportional to the engine load, the amount of fuel injected into the combustion chamber 4 during the compression stroke is small during the compression stroke and the cylinder generated in the intake stroke is low, as shown in FIG. A good air-fuel mixture is formed by the flow, and therefore, it is not necessary to strengthen the in-cylinder flow. In-cylinder flow can be adjusted.
[0064]
When the engine shifts to a high load as shown in (b) and (c) in the figure, the amount of fuel injected into the combustion chamber 4 in the compression stroke increases, and only the in-cylinder flow generated in the intake stroke A good mixture formation tends to be insufficient.
[0065]
However, since the in-cylinder flow is further strengthened by increasing the injection period of the pressurized air as the engine load increases, the in-cylinder flow suitable for stratification of the air-fuel mixture is achieved even when the engine load is high. And stable stratified combustion can be performed.
[0066]
FIG. 9 schematically shows the behavior of in-cylinder flow in the case where control is performed so that the injection period of pressurized air becomes longer as the oil / water temperature is lower in accordance with the oil / water temperature during the stratified combustion operation.
[0067]
Even during stratified combustion operation, when the oil temperature is low and the engine is not warmed up, fuel is injected into the combustion chamber 4 in the compression stroke as shown in FIG. If it adheres, it is difficult to vaporize the fuel, and it adheres to the piston crown in the form of a liquid film, which causes problems such as unstable combustion, generation of unburned HC and smoke, and deposit buildup. Since the injection period of the pressurized air injected in the stroke is lengthened, the in-cylinder flow is strengthened and the vaporization of the fuel F adhering to the piston crown surface is promoted, so that the stratified combustion is stabilized and the exhaust property is improved. Can be performed.
[0068]
As shown in (b) and (c) of the figure, the fuel F adhering to the piston crown surface is favorably vaporized as the oil water temperature rises and the warm-up is completed. In contrast to the above, since the injection period of the pressurized air is shortened, the in-cylinder flow can be adjusted to such an extent that the stratification of the air-fuel mixture is not hindered.
[0069]
Here, even in each of the stratified combustion operation states described above, the injection end timing of the pressurized air injected together with the fuel in the compression stroke is set after the fuel injection timing. It is possible to take measures for removing the residual fuel in the nozzle hole.
[0070]
This will be described with reference to FIG. 10. When the fuel injection end timing and the pressurized air injection end timing are substantially the same in the compression stroke as shown in FIG. After fuel and pressurized air are injected from the hole 10a, the fuel F adheres and remains in a liquid film form in the nozzle hole 10a, and this gradually carbonizes at the outlet of the nozzle hole 10a and tends to generate deposits. Become.
[0071]
However, as shown in (b) of the figure, since the injection end timing of the pressurized air injected in the compression stroke is set after the fuel injection end timing, the fuel is injected from the nozzle hole 10a of the fuel injection valve 10 into the fuel. Even if the fuel injection is stopped and the fuel adheres in the form of a liquid film in the nozzle hole 10a, this residual fuel remains outside the nozzle hole 10a by the pressurized air that continues to be injected. It is blown away and the inner surface of the nozzle hole 10a and the vicinity of the outlet can always be kept clean.
[0072]
As a result, it is possible to avoid deposit adhesion at the nozzle tip, stabilize the fuel spray shape, and improve engine stability.
[0073]
Since the injection end timing of the pressurized air is controlled according to the oil temperature, the stratified combustion can be stabilized and the exhaust properties can be improved more effectively.
[0074]
FIG. 11 schematically shows the behavior of in-cylinder flow when the control is performed so that the period from the fuel injection end timing to the pressurized air injection end timing becomes longer as the oil / water temperature is lower during the stratified combustion operation.
[0075]
When the oil / water temperature is low and the engine is not fully warmed up, the fuel injected by the compression stroke and adhering to the piston crown is insufficiently vaporized as described above, resulting in unstable combustion and exhaust properties. However, when the oil / water temperature is low, the period from the fuel injection end timing to the pressurized air injection end timing becomes longer as shown in FIG. Vaporization of the fuel F adhering to the crown surface in the form of a liquid film can be promoted, and stratified combustion can be stabilized and exhaust properties can be improved.
[0076]
On the other hand, as shown in (b) and (c) in the figure, as the oil temperature rises and the warm-up is completed, the fuel F adhering to the piston crown surface is better vaporized. In this case, contrary to the above, since the period from the fuel injection end timing to the pressurized air injection end timing is shortened, the in-cylinder flow can be adjusted to such an extent that the stratification of the air-fuel mixture is not hindered.
[0077]
FIG. 12 shows the behavior of in-cylinder flow by pressurized air injection control during homogeneous combustion operation.
[0078]
In homogeneous combustion operation, fuel mixture is injected during the intake stroke to homogenize the mixture. When fuel is injected during the intake stroke as shown in the figure, pressurized air is also injected almost simultaneously with the intake port. The mixture and atomization of the air-fuel mixture are generated by the in-cylinder flow generated in the intake stroke by the pressurized air injection, and vaporization is promoted by stirring.
[0079]
When a transition is made to the compression stroke, only pressurized air is injected during the compression stroke, so the in-cylinder flow generated during the intake stroke is reinforced by the pressurized air injected during the compression stroke, and homogeneous combustion is performed. Therefore, the flow strength can be adjusted (corrected) to an optimum flow strength, and stable homogeneous combustion can be performed.
[0080]
Even during the homogeneous combustion operation, similarly to the stratified combustion operation, the injection control of the pressurized air is appropriately controlled according to the engine speed, load, and oil / water temperature, which are the main parameters of the engine operation.
[0081]
As an example, FIG. 13 schematically shows the behavior of in-cylinder flow in a case where the pressurized air injection period is controlled to become longer as the load increases (however, the rotation speed is constant) according to the engine load. Show.
[0082]
As described above, since the fuel injection amount is almost proportional to the engine load, the amount of fuel injected into the combustion chamber 4 during the intake stroke is small and generated during the intake stroke as shown in FIG. Therefore, it is not necessary to reinforce the in-cylinder flow, but when the engine load is low, the compressed air injected in the compressor stroke is not required. The injection period is shortened.
[0083]
As a result, the in-cylinder flow having an appropriate strength can be achieved to such an extent that the in-cylinder flow can be prevented from excessively blowing out the combustion flame.
[0084]
When the engine shifts to a high load as shown in (b) and (c) of the figure, the amount of fuel injected into the combustion chamber 4 in the intake stroke increases, and only the in-cylinder flow generated in the intake stroke Although the formation of a good homogeneous mixture becomes insufficient, the injection period of the pressurized air injected in the compression stroke becomes longer as the engine load increases.
[0085]
As a result, even when the engine load is high, a strong in-cylinder flow suitable for homogenization of the air-fuel mixture can be obtained, and stable homogeneous combustion can be performed.
[0086]
In this homogeneous combustion operation, after the fuel injection in the intake stroke as described above, only the compressed air is injected in the compression stroke, so the end timing of the pressurized air injection in the intake stroke is set to be higher than the fuel injection end timing. Even if it is not set later, residual fuel in the nozzle hole can be removed by injection of pressurized air in the compression stroke, but in some cases, the pressurized air injection end timing in the intake stroke may be more than the fuel injection end timing. It may be set later and thorough measures to remove residual fuel in the nozzle holes may be used.
[Brief description of the drawings]
FIG. 1 is a system diagram showing an embodiment of the present invention.
FIG. 2 is a map of pressurized air control during stratified combustion operation.
FIG. 3 is a map of pressurized air control during homogeneous combustion operation.
FIG. 4 is a map diagram of a pressurized air injection correction period according to oil / water temperature.
FIG. 5 is a control map diagram of the end time of pressurized air injection according to the oil temperature during stratified combustion operation.
FIG. 6 is a control operation flowchart of the control device.
FIG. 7 is a schematic diagram showing the behavior of in-cylinder flow accompanying a change in rotational speed during stratified charge combustion operation.
FIG. 8 is a schematic diagram showing the behavior of in-cylinder flow accompanying a load change during stratified charge combustion operation.
FIG. 9 is a schematic diagram showing the behavior of in-cylinder flow associated with oil / water temperature change during stratified combustion operation.
FIG. 10 is an explanatory diagram showing a nozzle cleaning state by pressurized air injection during stratified combustion operation.
FIG. 11 is a schematic diagram showing the behavior of in-cylinder flow by pressurized air injection end timing control according to oil temperature change during stratified combustion operation.
FIG. 12 is a schematic diagram showing the behavior of in-cylinder flow by pressurized air injection control during homogeneous combustion operation.
FIG. 13 is a schematic diagram showing the behavior of in-cylinder flow accompanying a load change during homogeneous combustion operation.
[Explanation of symbols]
4 Combustion chamber
9 Spark plug
10 Fuel injection valve
10a Nozzle hole
11 Control device
11A Injection timing variable means
11B Injection period variable means

Claims (9)

It has a fuel injection valve that directly injects fuel into the combustion chamber and an ignition plug, and injects fuel during the compression stroke in the low load range to perform stratified combustion, and injects fuel during the intake stroke in the high load range In the in-cylinder injection spark ignition engine configured to perform homogeneous combustion, a two-fluid fuel injection valve capable of injecting fuel and pressurized air is used as the fuel injection valve, and during stratified combustion operation and During homogeneous combustion operation, there is provided injection timing / period variable means for variably controlling the injection timing and injection period of the pressurized air of the fuel injection valve according to the operating conditions of the engine, and the lower the engine speed during stratified combustion operation An in- cylinder spark-ignition engine characterized by extending the injection period of pressurized air .   The injection timing / period variable means changes the injection timing and the injection period of the pressurized air according to the engine speed, the load, and the oil / water temperature during the stratified combustion operation. The in-cylinder injection spark ignition engine described in 1. The in-cylinder injection spark ignition engine according to claim 2, wherein the injection timing / period variable means extends the injection period of the pressurized air as the engine load increases during the stratified combustion operation. The in-cylinder injection spark ignition engine according to claim 2 or 3 , wherein the injection timing / period variable means lengthens the injection period of the pressurized air as the oil / water temperature is lower during the stratified combustion operation. . Injection timing and duration varying means, cylinder injection type spark according to any one of claims 1-4, characterized in that it is set later than the pressurized air injection end timing is fuel injection termination timing Ignition engine. 6. The cylinder according to claim 5 , wherein the injection timing / period variable means lengthens the period from the fuel injection end timing to the pressurized air injection end timing as the oil / water temperature decreases during the stratified combustion operation. An internal injection spark ignition engine. Injection timing and duration varying means, at the time of homogeneous combustion operation, the cylinder according to any one of claims 1-6 which is in the compression stroke and characterized in that for ejecting only pressurized air into the combustion chamber An internal injection spark ignition engine. The injection timing / period variable means changes the pressurized air injection period into the combustion chamber during the compression stroke according to the engine speed, load, and oil / water temperature during the homogeneous combustion operation. The in-cylinder injection spark ignition engine according to claim 7 . 9. The direct injection spark ignition engine according to claim 8 , wherein the injection timing / period variable means lengthens the pressurized air injection period as the engine load increases during the homogeneous combustion operation.

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