JP2010121591A - Multi-fuel internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suitably improve ignition performance in compression-ignition diffusing combustion using a fuel with low-compression ignitability while avoiding the generations of exhaust emission, fuel consumption deterioration and lubricating failure in a multi-fuel internal combustion engine. <P>SOLUTION: The multi-fuel internal combustion engine is equipped with a piston 32 on whose top surface a cavity 32a is formed and a fuel injection valve 44 for injecting light oil and gasoline or a blended fuel of light oil and gasoline toward an inside of a combustion chamber 34. When a fuel injection is performed under the condition where the piston 32 is positioned between a -25 degrees CA posterior to an air intake top dead center and a 25 degrees CA posterior to the air intake top dead center, the fuel is prevented from running off the cavity 32a. Based on an ignition performance index value made for compression-ignition performance of the fuel introduced into the combustion chamber 34, when performing the compression-ignition diffusing combustion using gasoline, prior to the main injection, during a period of time elapsing from a 5 degrees CA posterior to the air intake top dead center to the 25 degrees CA posterior to the air intake top dead center, an control operation is performed so that an intake-stroke injection using gasoline is carried out. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a multi-fuel internal combustion engine, and in particular, is operated by introducing at least one fuel of at least two types of fuel having different properties or a mixed fuel composed of the at least two types of fuel into a combustion chamber. The present invention relates to a fuel internal combustion engine.

  Conventionally, for example, Patent Document 1 discloses a multi-fuel internal combustion engine that is operated using a plurality of types of fuels having different properties. This conventional multi-fuel internal combustion engine is provided with fuel characteristic detecting means for detecting an ignitability index value obtained by indexing the compression ignitability of the fuel introduced into the combustion chamber. In addition, the conventional multi-fuel internal combustion engine has a period of time from the intake stroke to the compression stroke when the fuel is subjected to compression self-ignition diffusion combustion using the fuel determined to be low compression ignitability based on the ignitability index value. There is provided fuel injection control means for injecting the fuel prior to the predetermined time, and then injecting the fuel with low compression ignition property into the combustion chamber by main injection.

JP 2008-121641 A JP-A-3-26841 Special table 2003-532827 gazette Japanese Patent Laid-Open No. 5-1574 JP 2005-98159 A JP-A-2005-315211 JP 2003-83119 A

  In the multi-fuel internal combustion engine described in Patent Document 1, as described above, when performing compression auto-ignition diffusion combustion using a low compression ignition fuel, a predetermined time during the period from the intake stroke to the compression stroke Prior to the injection, the injection is performed. Although Patent Document 1 describes that the earlier injection timing is advanced as the ignitability index value of the fuel is smaller, the prior injection timing is not specifically specified. If the injection is performed in advance at the timing when the fuel hits the cylinder wall surface, an increase in the HC emission amount or dilution of the lubricating oil is caused as the fuel adheres to the cylinder wall surface. As a result, exhaust emission and fuel consumption may be deteriorated and lubrication failure may occur.

  The present invention has been made to solve the above-described problems, and at the time of compression autoignition diffusion combustion using a low compression ignitable fuel while avoiding deterioration of exhaust emission, fuel consumption and poor lubrication. An object of the present invention is to provide a multi-fuel internal combustion engine that can improve the ignitability of the fuel.

The first invention is a multi-fuel internal combustion engine,
A piston with a cavity formed on the top surface;
A fuel injection valve that injects into the combustion chamber at least one kind of fuel of at least two kinds of fuels having different properties or a mixed fuel composed of the at least two kinds of fuel,
When fuel injection is performed under the condition where the piston is located between −25 ° CA after intake top dead center and 25 ° CA after intake top dead center, the fuel is prevented from protruding from the cavity. Has been
Fuel characteristic acquisition means for acquiring an ignitability index value indexed for the compression ignitability of the fuel led into the combustion chamber;
When performing compression auto-ignition diffusion combustion using fuel determined to be low compression ignitability based on the ignitability index value, prior to main injection, after intake top dead center from −25 ° CA to after intake top dead center Fuel injection control means for controlling the intake stroke injection using the low compression ignitable fuel at least in part during the period up to 25 ° CA;
Is further provided.

The second invention is the first invention, wherein
A variable valve mechanism that can change the closing timing of the exhaust valve;
The fuel injection control means includes injection start timing setting means for setting a start timing of the intake stroke injection in accordance with a closing timing of the exhaust valve changed by the variable valve mechanism.

The third invention is the first invention, wherein
A variable valve mechanism that can change the closing timing of the exhaust valve;
The fuel injection control means includes exhaust retard amount restriction means for restricting the retard amount of the exhaust valve closing timing so that the end timing of the intake stroke injection is not later than 25 ° CA after the intake top dead center. It is characterized by including.

According to a fourth invention, in any one of the first to third inventions,
The fuel injection control means includes injection control correction means for changing at least one of a fuel injection timing and a fuel injection amount in accordance with the ignitability index value by the fuel characteristic acquisition means.

According to a fifth invention, in any one of the first to fourth inventions,
The fuel injection control means includes an injection amount correction means for reducing the intake stroke injection amount as the load of the multi-fuel internal combustion engine is higher.

According to a sixth invention, in any one of the first to fifth inventions,
The fuel injection control means controls so that pilot injection using the low compression ignitable fuel is performed between the intake stroke injection and the main injection,
The fuel injection control means includes an injection amount adjusting means for increasing the amount of pilot injection and decreasing the amount of intake stroke injection as the load of the internal combustion engine decreases.

  According to the first aspect of the present invention, it is possible to reliably prevent the fuel from protruding outside the cavity of the piston when performing the intake stroke injection. As a result, by performing the intake stroke injection while avoiding the deterioration of exhaust emission and fuel consumption due to the discharge of unburned HC and the occurrence of poor lubrication, it is possible to perform the compression self-ignition diffusion combustion using the low compression ignitable fuel. It becomes possible to improve the ignitability of.

  According to the second invention, it is possible to realize the intake stroke injection while further reliably suppressing the discharge of unburned HC to the exhaust system. Thereby, exhaust emission and fuel consumption can be improved satisfactorily.

  According to the third aspect of the present invention, the fuel injected by the intake stroke injection can be retained in the cavity while effectively utilizing the increase in internal EGR due to the retard control of the closing timing of the exhaust valve. The emission of fuel HC can be satisfactorily suppressed.

  According to the fourth invention, even when at least two types of fuel are mixed at an arbitrary mixing ratio, at least one of the fuel injection amount and the fuel injection timing suitable for the arbitrary mixing ratio can be obtained. Accurate combustion control is possible.

  When the load of the internal combustion engine becomes high, the fuel injected by the intake stroke injection is easily ignited in the compression stroke due to the rise of the intake air temperature, the increase of the intake air amount, the rise of the in-cylinder wall surface temperature, etc. Combustion is likely to occur before the main injection is performed. For this reason, there is a concern that the controllability of diffusion combustion with the fuel injected by the main injection is deteriorated (deterioration of fuel consumption due to deterioration of combustion noise, increase of NOx emission amount, deterioration of isovolume, etc.). On the other hand, according to the fifth aspect of the invention, it is possible to achieve the optimum diffusion combustion while avoiding the above problem.

  If the intake stroke injection amount is uniformly set regardless of the load level of the internal combustion engine, the unburned HC associated with the intake stroke injection at a low load where the ratio of the intake stroke injection amount to the main injection amount relatively increases. Will be emitted as emissions and fuel consumption will also deteriorate. On the other hand, according to the sixth aspect of the invention, the above problem can be avoided, the amount of unburned HC discharged in the low load region associated with intake stroke injection can be reduced, and exhaust emission and fuel consumption can be improved. Can do.

Embodiment 1 FIG.
[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to the first embodiment of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10, an intake system that supplies air to the internal combustion engine 10, an exhaust system that exhausts exhaust gas from the internal combustion engine 10, and a control system that controls the operation of the internal combustion engine 10. ing. The internal combustion engine 10 is mounted on a vehicle and used as a power source.

  An intake passage 12 is provided in the intake system of the internal combustion engine 10. An air cleaner 14 is attached to the inlet of the intake passage 12. An air flow meter 16 that outputs a signal corresponding to the flow rate of air taken into the intake passage 12 is provided in the vicinity of the downstream side of the air cleaner 14.

  Further, an intercooler 18 for cooling the compressed air is provided downstream of the intake passage 12. A throttle valve 20 is provided downstream of the intercooler 18. The throttle valve 20 is an electronically controlled throttle valve that can control the throttle opening independently of the accelerator opening. Further, downstream of the throttle valve 20, an intake pressure sensor 22 that outputs a signal corresponding to the pressure in the intake passage 12, and an intake air temperature sensor 24 that outputs a signal corresponding to the temperature of the air flowing in the intake passage 12, Are arranged respectively.

  A compressor 26 a of a variable nozzle type turbocharger 26 is provided in the intake passage 12 from the air flow meter 16 to the intercooler 18. More specifically, the turbocharger 26 is integrally connected to the turbine 26b that operates by the exhaust energy of the exhaust gas, and is rotated by the exhaust energy of the exhaust gas that is input to the turbine 26b. And a compressor 26a. Further, the turbocharger 26 has a variable nozzle (VN) 26c for adjusting the flow rate of the exhaust gas supplied to the turbine 26b.

  An exhaust passage 28 is provided in the exhaust system of the internal combustion engine 10. In the middle of the exhaust passage 28, the turbine 26b of the turbocharger 26 described above is disposed. A catalyst 30 capable of purifying exhaust gas is disposed downstream of the turbine 26b.

  In the cylinder of the internal combustion engine 10, a piston 32 having a cavity 32a formed on the top surface thereof is disposed. A combustion chamber 34 is formed in the cylinder of the internal combustion engine 10 on the top surface side of the piston 32. In the respective port portions of the intake passage 12 and the exhaust passage 28, there are an intake valve 36 and an exhaust valve 38 for bringing the combustion chamber 34 and the intake passage 12 and the combustion chamber 34 and the exhaust passage 28 into a conductive state or a cut-off state, respectively. Is provided. The intake valve 36 and the exhaust valve 38 are driven by an intake variable valve mechanism 40 and an exhaust variable valve mechanism 42, respectively. Specific configurations of these variable valve mechanisms 40 and 42 are not particularly limited, but here, a VVT mechanism that continuously varies the phase of a cam (not shown) that drives the intake valve 36 and the exhaust valve 38. Suppose that

  The internal combustion engine 10 also includes a fuel injection valve 44 for directly injecting fuel into the combustion chamber 34. The fuel injection valve 44 is disposed at the center of the cylinder head 46 so as to face the cavity 32 a of the piston 32.

FIG. 2 is a view for explaining the relationship between the spray angle θ of the fuel injection valve 44 near the top dead center and the shape of the cavity 32 a of the piston 32.
As shown in FIG. 2, the fuel injection valve 44 is arranged such that the center of the injection hole is located on the center line of the piston 32. In the present embodiment, when the piston 32 is 25 ° CA (25ATDC) or less after the intake top dead center, the fuel sprayed from the fuel injection valve 44 is prevented from spraying out of the cavity 32a. The angle θ and the shape of the cavity 32a are set.

  Referring to FIG. 1 again, the description of the system configuration is continued. The fuel injection valve 44 is connected to the fuel tank 50 via the fuel supply passage 48. It is assumed that the fuel tank 50 of the present embodiment receives a plurality of fuels having different properties. More specifically, it is assumed that fuel with good compression ignitability (for example, light oil) and fuel with poor compression ignitability (for example, gasoline) are supplied.

  In the middle of the fuel supply passage 48, a high-pressure pump 52 for pumping the fuel in the fuel tank 50, and high-pressure fuel pressurized by the high-pressure pump 52 are stored and distributed to the fuel injection valves 44 of each cylinder. A common rail 54 is arranged for this purpose. The fuel tank 50 is provided with a fuel property sensor 56 for detecting the specific gravity, viscosity, conductivity, etc. of the fuel in the fuel tank 50. According to such a fuel property sensor 56, it becomes possible to estimate and obtain an ignitability index value (for example, octane number or cetane number) indexed for the compression ignitability of fuel. The ignitability index value may be estimated from the in-cylinder pressure of the cylinder in which combustion is performed.

  The control system of the internal combustion engine 10 includes an ECU (Electronic Control Unit) 60. The ECU 60 is a control device that comprehensively controls the entire system shown in FIG. In addition to the various sensors described above, various sensors such as an accelerator opening sensor 62 and a crank angle sensor 64 are connected to the input side of the ECU 60. The accelerator opening sensor 62 is a sensor that outputs a signal corresponding to the amount of depression of the accelerator pedal (accelerator opening). The crank angle sensor 64 is a sensor that outputs a signal corresponding to the rotation angle of the crankshaft 66. The various actuators described above are connected to the output side of the ECU 60. More specifically, the fuel injection valve 44 is connected to the ECU 60 via an injector EDU (Electrical Driver Unit) 68 for driving the fuel injection valve 44.

  The internal combustion engine 10 of the present embodiment configured as described above has a hardware configuration that is mainly assumed to perform compression auto-ignition diffusion combustion using light oil as fuel, and gasoline that is inferior in compression ignitability to light oil. The internal combustion engine is compatible with various fuels and has a system configuration in which diffusion combustion is established even when used. The basic system configuration of such a multi-fuel internal combustion engine is described in detail in, for example, Japanese Patent Application Laid-Open No. 2008-121641.

FIG. 3 is a diagram for explaining the injection timing for each fuel used in the first embodiment of the present invention. More specifically, FIG. 3 (A) shows the fuel injection timing when using gasoline as fuel, and FIG. 3 (B) shows the fuel injection timing when using light oil as fuel.
First, when using light oil as fuel, as shown in FIG. 3 (B), as in the case of compression auto-ignition diffusion combustion in a normal diesel engine using light oil, it is divided into two during the compression stroke. The pilot injection (PL1 and PL2) is performed, and the main injection is performed at a predetermined time after the compression top dead center (compression TDC) has elapsed.

  On the other hand, when gasoline is used as fuel, as shown in FIG. 3A, intake stroke injection is performed prior to pilot injection (PL1 and PL2) and main injection performed in the same manner as in the case of light oil. . The intake stroke injection starts after several degrees (5 ° CA) has elapsed from the intake top dead center (intake TDC) after the exhaust valve 38 is closed, and ends by 25 ° CA after the intake top dead center. Is set to In other words, the intake stroke injection of the present embodiment can prevent the fuel from being blown into the exhaust system, and the fuel is reliably injected into the cavity 32a of the piston 32 so that the fuel protrudes outside the cavity 32a. The timing is set to prevent this.

Next, with reference to FIG. 4 and FIG. 5, the specific process which ECU60 performs in order to control the intake stroke injection mentioned above is demonstrated.
FIG. 4 is a flowchart of a routine executed by the ECU 60 in order to set the intake stroke injection amount q_tdc and the intake stroke injection start timing θ_qtdc.
In the routine shown in FIG. 4, first, the output value of the fuel property sensor 56 is acquired (step 100). Next, based on the fuel ignitability index value (e.g., octane number) estimated from the output of the fuel property sensor 56, it is determined whether the currently used fuel is gasoline or light oil (step 102).

  If it is determined in step 102 that the currently used fuel is light oil instead of gasoline, the intake stroke injection flag is turned OFF (step 104). On the other hand, if it is determined in step 102 that the currently used fuel is gasoline, the intake stroke injection flag is turned ON (step 106).

  After the intake stroke injection flag is turned ON, the intake stroke injection amount q_tdc is then set to a value corresponding to the operating state such as the load of the internal combustion engine 10 (step 108). Further, the intake stroke injection start timing θ_qtdc is set to 5 ° CA after the intake top dead center as shown in FIG. 3 (step 110).

FIG. 5 is a flowchart of a routine executed by the ECU 60 in order to control the intake stroke injection based on the setting shown in FIG.
In the routine shown in FIG. 5, first, the crank angle is acquired based on the output of the crank angle sensor 64 (step 200).

  Next, it is determined whether or not the intake stroke injection flag is turned on and the current crank angle has reached the intake stroke injection start timing θ_qtdc set in step 110 (step 202).

  As a result, when the determination in step 202 is established, the start time and the end time of the injector timer are respectively calculated so that the intake stroke injection is performed between 5 and 25 ° CA after the intake top dead center. (Steps 204 and 206). Next, an injector timer is set (step 208). As a result, the fuel injection valve 44 is driven to open using the injector EDU 68 during the operation period of the injector timer.

  According to the routine shown in FIGS. 4 and 5 described above, when gasoline is used as fuel, 5-25 ° after intake top dead center prior to pilot injection (PL1 and PL2) and main injection. During the CA period, the intake stroke injection is executed. By performing the intake stroke injection at such timing, it is possible to reliably prevent the fuel from protruding out of the cavity 32a of the piston 32 during the intake stroke injection.

  At the time of compression self-ignition diffusion combustion, the pressure of fuel (injection pressure) is very high. For this reason, when performing the intake stroke injection, if the fuel is not injected so as to hit the cavity 32a, the fuel strikes the cylinder wall surface vigorously. As a result, fuel adheres to the cylinder wall surface, and the fuel in the quench area (flame extinguishing layer) is scraped out without burning, which may increase the HC emission amount. Further, the fuel is taken into the lubricating oil present on the cylinder wall surface, and there is a possibility that problems such as dilution of the lubricating oil and engine seizure due to a decrease in viscosity may occur. On the other hand, according to the control of the intake stroke injection timing of the present embodiment, the intake stroke injection is performed while avoiding the deterioration of exhaust emission and fuel consumption caused by the discharge of unburned HC and poor lubrication. Further, it becomes possible to satisfactorily improve the ignitability at the time of compression self-ignition diffusion combustion using low compression ignitable fuel (gasoline).

  In the first embodiment described above, the ECU 60 executes the processing of step 100, so that the “fuel characteristic acquisition means” in the first invention is a series of the routines shown in FIGS. By executing the process, the “fuel injection control means” in the first aspect of the present invention is realized.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 6 described later together with a routine shown in FIG. 5 instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG. It can be done.

  The system of this embodiment is characterized in that the intake stroke injection start timing θ_qtdc is set according to the closing timing θ_excl of the exhaust valve 38 changed by the exhaust variable valve mechanism 42. More specifically, in this embodiment, the crank angle delayed by 3 ° CA from the closing timing θ_excl of the exhaust valve 38 is set as the intake stroke injection starting timing θ_qtdc. Note that this 3 ° CA is a margin that assumes that air does not enter and exit sufficiently in the ramp portion where the exhaust valve 38 is open.

  Further, in the system of the present embodiment, the intake stroke injection start timing θ_qtdc is limited so as not to be earlier than −25 ° CA after the intake top dead center in order to ensure injection into the cavity 32a of the piston 32. I tried to do it.

  FIG. 6 is a flowchart of a routine executed by the ECU 60 in the second embodiment to realize the above function. In FIG. 6, the same steps as those shown in FIG. 4 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 6, after the intake stroke injection amount q_tdc is set (step 108) under the condition that the intake stroke injection flag is ON (step 106), the exhaust cam angle sensor (not shown) is then set. Based on the output of the crank angle sensor 64, the exhaust VVT advance amount (the advance amount of the opening / closing timing of the exhaust valve 38) is acquired (step 300). Next, the exhaust valve closing timing θ_excl is calculated based on the exhaust VVT advance amount (step 302).

  Next, the intake stroke injection start timing θ_qtdc is set to be the exhaust valve closing timing θ_excl plus 3 ° CA (step 304). Next, it is determined whether or not the intake stroke injection start timing θ_qtdc is smaller (not earlier) than −25 ° CA after the intake top dead center (step 306).

  As a result, if the determination in step 306 is not established, the intake stroke injection start timing θ_qtdc set in step 304 is used as it is. On the other hand, if the determination in step 306 is established, the intake stroke is determined. The injection start timing θ_qtdc is corrected to be −25 ° CA after the intake top dead center (step 308).

  According to the setting of the intake stroke injection start timing θ_qtdc in the routine shown in FIG. 6 described above, when the closing timing θ_excl of the exhaust valve 38 is varied according to the operating state, the unburned HC is discharged to the exhaust system. Further, intake stroke injection can be realized while being reliably suppressed. Thereby, exhaust emission and fuel consumption can be improved satisfactorily.

  Further, according to the above routine, when the closing timing θ_excl of the exhaust valve 38 is advanced, the intake stroke injection starts under a certain limit (the closing timing θ_excl is limited to −25 ° CA after the intake top dead center). The timing θ_qtdc is advanced. For this reason, the time (time until combustion) required for vaporization of the fuel injected by the intake stroke injection can be increased. As a result, unburned HC can be sufficiently reduced, and exhaust emission and fuel consumption can be improved satisfactorily.

  In the second embodiment described above, the “injection start time setting means” according to the second aspect of the present invention is realized by the ECU 60 executing the processing of steps 300 to 304.

Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to FIG.
The system of the present embodiment can be realized by causing the ECU 60 to execute the routine shown in FIG. 7 described later together with the routine shown in FIG. 5 instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG. It can be done.

  Also in the system of the present embodiment, as in the second embodiment described above, the control of the intake stroke injection timing and the control of the closing timing θ_excl of the exhaust valve 38 are coordinated. However, the present embodiment is characterized in that the retard amount of the closing timing θ_excl of the exhaust valve 38 is limited so that the intake stroke injection end timing θ_qtdcend does not come after 25 ° CA after the intake upper start point.

  FIG. 7 is a flowchart of a routine executed by the ECU 60 in the third embodiment in order to realize the above function. In FIG. 7, the same steps as those shown in FIG. 4 in the first embodiment or in FIG. 6 in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

  In the routine shown in FIG. 7, after the intake stroke injection amount q_tdc is set (step 108) under the situation where the intake stroke injection flag is ON (step 106), the intake stroke injection end timing θ_qtdcend is then set to the intake stroke. It is set to 25 ° CA (maximum intake stroke injection end timing) after top dead center (step 400). Next, the intake stroke injection start timing θ_qtdc is calculated as the maximum intake stroke injection start timing θmax that can obtain the maximum intake stroke injection period according to the operating state of the internal combustion engine 10 with the intake stroke injection end timing θ_qtdcend as an end point. (Step 402).

  Next, when the intake stroke injection start timing θ_qtdc <−25 ° CA after intake top dead center is established by the processing of steps 306 and 308, the intake stroke injection start timing θ_qtdc calculated in step 402 is It is corrected to be −25 ° CA after dead center.

  Next, the exhaust valve closing timing θ_excl is calculated so as to be the intake stroke injection start timing θ_qtdc minus 3 ° CA (step 404). Next, the exhaust VVT advance amount is calculated based on the exhaust valve closing timing θ_excl thus calculated (step 406). In this step 406, when the intake stroke injection flag is OFF, the exhaust VVT advance amount is calculated according to the operating state of the internal combustion engine 10 as usual. Next, based on the calculated exhaust VVT advance amount, exhaust VVT advance control (control of the opening / closing timing of the exhaust valve 38 using the exhaust variable valve mechanism 42) is executed (step 408).

  According to the routine shown in FIG. 7 described above, the intake stroke injection end timing θ_qtdcend is set to be 25 ° CA after the intake top dead center, and the fuel injected during the intake stroke injection protrudes from the cavity 32a. The intake stroke injection start timing θ_qtdc is determined within a range not to be performed (after -25 ° CA after intake top dead center). Then, based on the intake stroke injection start timing θ_qtdc determined as described above, the exhaust valve closing timing θ_excl is set to the intake stroke injection start timing θ_qtdc minus 3 ° so that fuel does not blow through the exhaust system during the intake stroke injection. Determined as CA. According to the above processing, the fuel injected by the intake stroke injection is put into the cavity 32a while effectively using the increase in the internal EGR by the exhaust VVT retard control (the retard control of the exhaust valve 38 closing timing θ_excl). It can be made to stop and discharge | emission of unburned HC can be suppressed favorably.

  In the third embodiment described above, the “exhaust retard amount limiting means” according to the third aspect of the present invention is realized by the ECU 60 executing the processing of steps 400 to 408.

Embodiment 4 FIG.
Next, a fourth embodiment of the present invention will be described with reference to FIGS.
The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 9 described later together with the routine shown in FIG. 5 instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG. It can be done.

  In the system of this embodiment, the fuel supplied to the fuel injection valve 44 is 100% gasoline according to the oil type selected by the user of the vehicle at the time of refueling, the amount of fuel refueling, the amount of remaining fuel in the fuel tank 50, and the like. It can vary between fuel, 100% diesel fuel, or any blend of gasoline and diesel oil in any blending ratio.

Therefore, in this embodiment, based on the ignitability index values such as the octane number and the cetane number acquired by the fuel property sensor 56, the fuel injection timing and the fuel injection for each injection such as the intake stroke injection, the pilot injection, and the main injection The amount was linearly variable.

  Specifically, in this embodiment, an injection control value (fuel injection timing and fuel injection amount) in the case of 100% light oil and an injection control value in the case of 100% gasoline fuel are prepared in advance by experiments. Keep it. And the injection control value at the time of mixing light oil and gasoline by arbitrary mixing ratios was obtained by interpolation according to the ignitability index value at each mixing ratio.

  FIG. 8 is a diagram illustrating a specific example of the injection control in the fourth embodiment of the present invention. More specifically, FIG. 8A shows the injection control in the case of 100% gasoline fuel (octane number 90), and FIG. 8B shows the fuel in which light oil and gasoline are mixed at an arbitrary mixing ratio. FIG. 8C shows the injection control in the case of (octane number a), and FIG. 8C shows the injection control in the case of 100% light oil (octane number 14). As described above, since the intake stroke injection is not performed in the case of 100% light oil, the intake stroke injection amount q_tdc_14 in this case is zero as shown in FIG. 8C. .

Here, the main injection will be described as an example, but the same applies to other intake stroke injections and post injections. That is, in this embodiment, the main injection amount q_m_a and the main fuel injection start timing θ_qm_a in the case of the octane number a are calculated according to the following equations (1) and (2), respectively.
q_m_a = q_m_14.x + q_m_90. (1-x) (1)
θ_qm_a = θ_qm_14 · x + θ_qm_90 · (1-x) (2)
However, in the above formulas (1) and (2), x is 0 when the octane number is 14 (light oil 100%), 1 when the octane number is 90 (gasoline 100%), and the octane number a is 14 A variable that changes between 0 and 1 while changing between ˜90.

  FIG. 9 is a flowchart of a routine executed by the ECU 60 in the present fourth embodiment in order to realize variable injection control according to the ignitability index value. In FIG. 9, the same steps as those shown in FIG. 4 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified. In FIG. 9, the description is given by taking the intake stroke injection as an example.

  In the routine shown in FIG. 9, after the output value (octane number a) of the fuel property sensor 56 is acquired (step 100), each parameter in the above equation (1) is then set during intake stroke injection as shown in FIG. The intake stroke injection amount q_tdc_a at the current octane number a is calculated using the equation obtained by substituting these parameters (step 500). Next, similarly to step 500, the intake stroke injection start timing θ_qtdc_a at the current octane number a is calculated using the modified equation (2) (step 502).

  Next, it is determined whether or not the intake stroke injection amount q_tdc_a calculated as described above is larger than 0 (step 504). As a result, when it is determined that q_tdc_a> 0 is not established, that is, when it can be determined that the currently used fuel is 100% light oil, the intake stroke injection flag is turned OFF (step 506). . On the other hand, when it is determined that q_tdc_a> 0 is established, that is, when it can be determined that the currently used fuel is a fuel of 100% gasoline or a fuel in which an arbitrary mixture ratio of gasoline is mixed, The intake stroke injection flag is turned on (step 508).

  According to the routine shown in FIG. 9 described above, the fuel injection amount q and the fuel injection timing θ suitable for an arbitrary mixing ratio can be obtained even when light oil and gasoline are mixed at an arbitrary mixing ratio. Therefore, accurate combustion control is possible. In addition, since it is not necessary to provide an appropriate value for the fuel injection amount q and the fuel injection timing θ for each mixing ratio, the number of experimental points, the storage area of the ECU, and the cost can be reduced. Can do.

  In the fourth embodiment described above, the “injection control correcting means” according to the fourth aspect of the present invention is realized by the ECU 60 executing the processing of steps 100, 500, and 502 described above.

Embodiment 5 FIG.
Next, Embodiment 5 of the present invention will be described with reference to FIG. 10 and FIG.
The system of the present embodiment can be realized by causing the ECU 60 to execute the routine shown in FIG. 11 described later together with the routine shown in FIG. 5 instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG. It can be done.

  FIG. 10 is a view for explaining characteristic intake stroke injection control in the fifth embodiment of the present invention. More specifically, FIG. 10 shows a waveform of each fuel injection amount q (intake stroke injection amount q_tdc, main injection amount q_m, and the total injection amount of both) with respect to the total fuel injection amount q_total.

  The system of the present embodiment is characterized in that the intake stroke injection amount q_tdc is decreased as the total fuel injection amount q_total is increased (the engine load is higher). More specifically, as shown in FIG. 10, as the total fuel injection amount q_total increases, the ratio of the intake stroke injection amount q_tdc to the main injection amount q_m is reduced. In a diesel engine, generally, the throttle loss due to the throttle valve is small (0 when EGR is not introduced), and the ratio (A / F) between the intake air amount and the fuel injection amount is not constant. For this reason, the intake pressure and the engine load do not have a linear relationship.

FIG. 11 is a flowchart of a routine executed by the ECU 60 in the fifth embodiment in order to realize the above function. In FIG. 11, the same steps as those shown in FIG. 4 in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the routine shown in FIG. 11, when it is determined in step 102 that the currently used fuel is light oil instead of gasoline, the intake stroke injection flag is turned off (step 104) and the air flow meter 16 An intake air amount is acquired based on the output (step 600).

  Next, the total fuel injection amount q_total (engine load) is calculated based on information such as the intake air amount and the engine speed (step 602). Next, the main injection amount q_m is set from the total fuel injection amount q_total according to the setting of a predetermined map or the like (step 604).

  On the other hand, if it is determined in step 102 that the currently used fuel is gasoline, the intake stroke injection flag is turned on (step 106), and the intake is performed by the same processing as in steps 600 and 602. Acquisition of the air amount (step 606) and calculation of the total fuel injection amount q_total (step 608) are executed.

  Further, when the fuel used is gasoline, the main injection amount q_m and the intake stroke injection amount q_tdc are respectively set from the total fuel injection amount q_total according to the map having the tendency shown in FIG. 10 (step 610 and 612).

  When the engine load increases, the fuel injected by the intake stroke injection is likely to self-ignite during the compression stroke due to the rise of the intake air temperature, the amount of intake air, the temperature of the cylinder wall surface, etc. Combustion is likely to occur before this is done. For this reason, there is a concern that the controllability of diffusion combustion with the fuel injected by the main injection is deteriorated (deterioration of fuel consumption due to deterioration of combustion noise, increase of NOx emission amount, deterioration of isovolume, etc.).

  In contrast, according to the routine shown in FIG. 11 described above, when the intake stroke injection is performed, the intake stroke injection amount is set such that the larger the total fuel injection amount q_total, the smaller the ratio to the main injection amount q_m. q_tdc is set. According to such a setting, the above problem can be avoided and optimal diffusion combustion can be realized.

  In addition, the ignitability of the fuel injected by the main injection is improved by increasing the intake air temperature, increasing the intake air amount, increasing the cylinder wall surface temperature and the like. As a result, the intake stroke injection amount q_tdc can be reduced, and the exhaust emission and fuel consumption are improved by reducing the unburned HC emission amount.

  In the fifth embodiment described above, the “injection amount correcting means” according to the fifth aspect of the present invention is implemented when the ECU 60 executes the processing of steps 608 to 612.

Embodiment 6 FIG.
Next, a sixth embodiment of the present invention will be described with reference to FIG. 12 and FIG.
The system of the present embodiment can be realized by causing the ECU 60 to execute a routine shown in FIG. 13 described later together with a routine shown in FIG. 5 instead of the routine shown in FIG. 4 using the hardware configuration shown in FIG. It can be done.

  FIG. 12 is a view for explaining characteristic intake stroke injection control in Embodiment 6 of the present invention. More specifically, FIG. 12 shows the waveform of each fuel injection amount q (intake stroke injection amount q_tdc, pilot 1 injection amount q_pl1, pilot 2 injection amount q_pl2, and their total injection amount) with respect to the total fuel injection amount q_total. Show.

  As shown in FIG. 12, in the system of this embodiment, in the low load region where the unburned HC emission amount increases (region where the total fuel injection amount q_total is small), the pilot load 1 q_pl1 and the pilot are reduced as the engine load decreases. This is characterized in that the two injection amount q_pl2 is increased and the intake stroke injection amount q_tdc is decreased. Further, these total injection amounts are set to be equal to the intake stroke injection amount q_tdc shown in FIG.

FIG. 13 is a flowchart of a routine executed by the ECU 60 in the sixth embodiment to realize the above function. In FIG. 13, the same steps as the steps shown in FIG. 4 in the first embodiment or FIG. 11 in the fifth embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the routine shown in FIG. 13, if it is determined in step 102 that the currently used fuel is light oil instead of gasoline, the intake stroke injection flag is set to OFF (step 104) and the intake air amount is acquired (step 600). ) And calculation of the total fuel injection amount q_total (step 602). Then, according to the setting of a predetermined map or the like, the setting of the pilot 1 injection amount q_pl1 (step 700) and the setting of the pilot 2 injection amount q_pl2 (step 702) are performed from the total fuel injection amount q_total.

  On the other hand, if it is determined in step 102 that the currently used fuel is gasoline, the intake stroke injection flag is turned on (step 106), and the intake is performed by the same processing as in steps 600 and 602. Acquisition of the air amount (step 606) and calculation of the total fuel injection amount q_total (step 608) are executed.

  Further, when the fuel used is gasoline, the pilot fuel injection amount q_pl1, pilot fuel injection amount q_pl2, and intake stroke injection amount q_tdc are then calculated from the total fuel injection amount q_total according to the map having the tendency shown in FIG. Each is set (steps 704, 706, and 708).

  If the intake stroke injection amount q_tdc is uniformly set regardless of the engine load level, the unburned state associated with the intake stroke injection at a low load where the ratio of the intake stroke injection amount q_tdc to the main injection amount q_m increases relatively. HC is discharged as emissions, and fuel consumption is also deteriorated.

  On the other hand, according to the routine shown in FIG. 13 described above, when the intake stroke injection is performed, the pilot 1 injection amount q_pl1 and the pilot 2 injection amount q_pl2 are increased as the engine load decreases, and the intake stroke injection is performed. The quantity q_tdc is reduced. According to such a setting, the above problem can be avoided, the amount of unburned HC discharged in the low load region associated with intake stroke injection can be reduced, and exhaust emission and fuel consumption can be improved.

  Further, the total injection amount (total heat amount) of pilot 1 injection amount q_pl1 and pilot 2 injection amount q_pl2 and intake stroke injection amount q_tdc is set when pilot injections 1 and 2 are not performed (setting shown in FIG. 10 above). By making them equal, it is possible to simplify the control logic, reduce the man-hours, and reduce the cost without changing the adaptation of the main injection.

  In the sixth embodiment described above, the “injection amount adjusting means” according to the sixth aspect of the present invention is implemented when the ECU 60 executes the processing of steps 608 and 704 to 708.

It is a figure for demonstrating the system configuration | structure of Embodiment 1 of this invention. It is a figure for demonstrating the relationship between the spray angle (theta) of the fuel injection valve in the vicinity of a top dead center, and the shape of the cavity of a piston. It is a figure for demonstrating the injection timing for every fuel used in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention. It is a flowchart of the routine performed in Embodiment 2 of this invention. It is a flowchart of the routine performed in Embodiment 3 of the present invention. It is a figure which shows the specific example of the injection control in Embodiment 4 of this invention. It is a flowchart of the routine performed in Embodiment 4 of this invention. It is a figure for demonstrating the characteristic intake stroke injection control in Embodiment 5 of this invention. It is a flowchart of the routine performed in Embodiment 5 of this invention. It is a figure for demonstrating the characteristic intake stroke injection control in Embodiment 6 of this invention. It is a flowchart of the routine performed in Embodiment 6 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Intake passage 28 Exhaust passage 32 Piston 32a Piston cavity 34 Combustion chamber 36 Intake valve 38 Exhaust valve 40 Intake variable valve mechanism 42 Exhaust variable valve mechanism 44 Fuel injection valve 48 Fuel supply passage 50 Fuel tank 56 Fuel property Sensor 60 ECU (Electronic Control Unit)
68 Injector EDU
q_m Main injection amount q_pl1 Pilot 1 injection amount q_pl2 Pilot 2 injection amount q_tdc Intake stroke injection amount q_total Total fuel injection amount θ Fuel injection timing θ_excl Exhaust valve closing timing θ_qm Main fuel injection start timing θ_qpl1 Pilot 1 injection start timing θ_qpl2 Pilot 2 injection Start timing θ_qtdc Intake stroke injection start timing θ_qtdcend Intake stroke injection end timing

Claims (6)

A piston with a cavity formed on the top surface;
A fuel injection valve that injects into the combustion chamber at least one kind of fuel of at least two kinds of fuels having different properties or a mixed fuel composed of the at least two kinds of fuel,
When fuel injection is performed under the condition where the piston is located between −25 ° CA after intake top dead center and 25 ° CA after intake top dead center, the fuel is prevented from protruding from the cavity. Has been
Fuel characteristic acquisition means for acquiring an ignitability index value indexed for the compression ignitability of the fuel led into the combustion chamber;
When performing compression auto-ignition diffusion combustion using fuel determined to be low compression ignitability based on the ignitability index value, prior to main injection, after intake top dead center from −25 ° CA to after intake top dead center Fuel injection control means for controlling the intake stroke injection using the low compression ignitable fuel at least in part during the period up to 25 ° CA;
A multi-fuel internal combustion engine, further comprising: A variable valve mechanism that can change the closing timing of the exhaust valve;
The fuel injection control means includes injection start timing setting means for setting a start timing of the intake stroke injection in accordance with a closing timing of the exhaust valve changed by the variable valve mechanism. The multifuel internal combustion engine according to 1. A variable valve mechanism that can change the closing timing of the exhaust valve;
The fuel injection control means includes exhaust retard amount restriction means for restricting the retard amount of the exhaust valve closing timing so that the end timing of the intake stroke injection is not later than 25 ° CA after the intake top dead center. The multifuel internal combustion engine according to claim 1, further comprising:   The fuel injection control means includes injection control correction means for changing at least one of a fuel injection timing and a fuel injection amount in accordance with the ignitability index value by the fuel characteristic acquisition means. 4. The multifuel internal combustion engine according to any one of 3 above.   5. The fuel injection control means according to claim 1, wherein the fuel injection control means includes injection amount correction means for reducing the amount of intake stroke injection as the load of the multi-fuel internal combustion engine increases. Multi-fuel internal combustion engine. The fuel injection control means controls so that pilot injection using the low compression ignitable fuel is performed between the intake stroke injection and the main injection,
6. The fuel injection control means according to claim 1, further comprising an injection amount adjusting means for increasing the amount of pilot injection and decreasing the amount of intake stroke injection as the load on the internal combustion engine decreases. A multifuel internal combustion engine according to any one of the preceding claims.

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