JP3680335B2 - Injection control device for in-cylinder internal combustion engine - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an injection control device for a direct injection internal combustion engine, and more particularly to an injection control device for a direct injection internal combustion engine that injects fuel in a compression stroke with reference to an injection end timing.
[0002]
[Prior art]
Japanese Patent Laid-Open No. 5-113146 has a fuel injection valve capable of directly injecting fuel into an engine cylinder, and an ignition plug in the engine cylinder is used for the entire required fuel injection amount determined according to the engine operating state in the compression stroke. In-cylinder internal combustion engine that determines the fuel injection timing in the compression stroke based on the fuel injection amount and the ignition timing in the compression stroke in an engine that is injected in the vicinity to create a good mixture for ignition around the spark plug Is disclosed. In addition, a large amount of fuel is injected into the engine cylinder in the intake stroke to create a premixed gas, and a small amount of fuel is injected into the engine cylinder in the compression stroke to create a mixture of fire types in the vicinity of the spark plug. An in-cylinder injection internal combustion engine is disclosed that determines an injection timing in a compression stroke based on a fuel injection amount in a compression stroke, an ignition timing, and a fuel injection amount in an intake stroke.
[0003]
FIG. 16 is an explanatory diagram of problems of the prior art in a direct injection internal combustion engine, where (A) is a swirl flow, (B) is a fuel distribution after compression stroke injection, and (C) is an injection timing and misfire rate. It is a figure which shows a relationship. FIG. 16A is a view of the cylinder as viewed from above, and shows the location where the fuel A injected from the fuel injection valve 5 toward the spark plug 65 is diffused by the swirl flow. FIG. 16B shows the fuel distribution in the cylinder of the fuel A injected in the compression stroke. The vertical axis represents the air-fuel ratio, and the horizontal axis represents the position in the cylinder circumferential direction. When the air-fuel ratio mixture in the cylinder circumferential positions a and b shown in the figure comes close to the spark plug 65, ignition is possible. In FIG. 16C, the horizontal axis indicates the injection timing when the ignition timing is point c, and the vertical axis indicates the misfire rate when fuel is injected at the injection timing. When the air-fuel mixture in the a region and the b region corresponding to FIG. 16B shown in FIG. 16C comes to the vicinity of the spark plug 65 at the ignition timing, the region other than the a region and the b region is ignited. Is not ignited when the air-fuel mixture in the air reaches the vicinity of the spark plug 65 at the ignition timing.
[0004]
[Problems to be solved by the invention]
The above-described injection control device for a direct injection internal combustion engine disclosed in Japanese Patent Application Laid-Open No. 5-113145 determines the fuel injection amount and the injection timing in the compression stroke so that an air-fuel mixture good for ignition is created near the ignition plug at the ignition timing. However, if the air-fuel ratio of the air-fuel mixture in the vicinity of the spark plug deviates from the target air-fuel ratio due to the effect of canister purge or the like, and the fluctuation of the air-fuel ratio increases, the spray diffusion time after fuel injection changes and the ignition timing is reached. There arises a problem in that an air-fuel mixture favorable for ignition is not generated in the vicinity of the spark plug and misfire occurs.
[0005]
Therefore, the present invention solves the above-mentioned problem, that is, the spray after the injection so that the fuel injected in the compression stroke is not affected by the canister purge or the like and generates a combustible mixture in the vicinity of the ignition plug at the ignition timing. It is an object of the present invention to provide an injection control device for a direct injection internal combustion engine that makes the diffusion time of the cylinder appropriate.
[0006]
[Means for Solving the Problems]
  An injection control device for a direct injection internal combustion engine according to the present invention that achieves the above object includes a fuel injection valve that directly injects fuel into a cylinder of the engine, wherein the fuel injection valve is a swirl type, and the injected fuel is the cylinder. An injection amount calculating means which is disposed at the top of the head in the cylinder so as to face the spark plug located in the center of the inner head, and which calculates the fuel injection amount injected from the fuel injection valve during the compression stroke; and the engine The injection end timing is set so that the fuel injected from the fuel injection valve and the intake air are diffused by the swirl flow based on the basic fuel injection amount required for one combustion cycle and reach the vicinity of the spark plug at the ignition timing. Based on the injection end timing calculation means to calculate and the injection end timingAn injection start time is calculated, and from the injection start time to the injection end time,And an injection control means for controlling to inject a fuel injection amount in the compression stroke from the fuel injection valve.
[0007]
[Action]
  An injection control device for a direct injection internal combustion engine according to the present invention is obtained based on a basic fuel injection amount required for one combustion cycle of the engine.RuThe injection end timeThe fuel and intake air injected from the swirl type fuel injection valve are diffused by the swirl flow and calculated so as to reach the vicinity of the spark plug at the ignition timing.The injection start timing corresponding to the fuel injection amount injected in the compression stroke is calculated as a reference, and from the injection start timing to the injection end timing,SwirlOpen the fuel injection valve and adjust the fuel injection amount in the compression stroke.Inject and diffuse by intake air and swirl flowSince it did in this way, spray spreads after injection until ignition timing, and the combustible air-fuel mixture good for ignition is generated near the ignition plug at ignition timing.
[0008]
【Example】
FIG. 1 is a configuration diagram of a four-cylinder gasoline engine employed in an embodiment of the present invention. In this figure, 1 is an engine body, 2 is a surge tank, 3 is an air cleaner, 4 is an intake pipe that connects the surge tank 2 and the air cleaner 3, 5 is an electrostrictive high-pressure fuel injection valve that injects fuel into each cylinder, 6 is a high-pressure reservoir tank, 7 is a high-pressure fuel pump capable of controlling the discharge pressure for pumping high-pressure fuel to the reservoir tank 6 via a high-pressure conduit 8, 9 is a fuel tank, 10 is a fuel tank 9 via a conduit 11 Reference numeral 65 denotes a low pressure fuel pump for supplying fuel to the high pressure fuel pump 7. The discharge side of the low-pressure fuel pump 10 is connected to a piezoelectric element cooling introduction pipe 12 for cooling the piezoelectric element of each fuel injection valve 5. The piezoelectric element cooling return pipe 13 is connected to the fuel tank 9, and the fuel flowing through the piezoelectric element cooling introduction pipe 12 through the piezoelectric element cooling return pipe 13 is collected in the fuel tank 9. Each branch pipe 14 connects each high-pressure fuel injection valve 5 to the high-pressure reservoir tank 6.
[0009]
The electronic control unit 20 is composed of a digital computer and includes a ROM (Read Only Memory) 22, a RAM (Random Access Memory), a CPU (Central Processing Unit) 24, and an input port 25 which are connected to each other via a bidirectional bus 21. And an output port 26. A pressure sensor 27 attached to the high-pressure reservoir tank 6 detects the pressure in the high-pressure reservoir tank 6, and the detection signal is input to the input port 25 via the A / D converter 28. An output pulse of the crank angle sensor 29 that generates an output pulse proportional to the engine speed NE is input to the input port 25. The output voltage of the load sensor 30 that generates an output voltage proportional to the depression amount L of an accelerator pedal (not shown) is input to the input port 25 via the A / D converter 31. A water temperature sensor 32 attached to the engine body 1 detects the engine cooling water temperature, and the detection signal is input to the input port 25 via the A / D converter 33. On the other hand, each fuel injection valve 5 is connected to the output port 26 via each drive circuit 34. Each spark plug 65 is connected to the output port 26 via each drive circuit 35. The high pressure fuel pump 7 is connected to the output port 26 via the drive circuit 36. The engine fuel injection control routine according to the present invention is executed by the electronic control unit 20.
[0010]
FIG. 2 is a side sectional view of the fuel injection valve 5. In this figure, 40 is a needle inserted into the nozzle 50, 41 is a pressure rod, 42 is a movable plunger, 43 is a compression spring disposed in the spring accommodating chamber 44 and presses the needle 40 downward, 45 A pressure piston, 46 is a piezoelectric element, 47 is a pressure chamber formed between the top of the movable plunger 42 and the piston 45 and filled with fuel, and 48 is a needle pressure chamber. The needle pressurizing chamber 48 is connected to the high-pressure reservoir tank 6 (FIG. 1) via the fuel passage 49 and the branch pipe 14, so that the high-pressure fuel in the high-pressure reservoir tank 6 passes through the branch pipe 14 and the fuel passage 49. It is supplied into the needle pressurizing chamber 48. When the piezo piezoelectric element 46 is charged, the piezo piezoelectric element 46 expands, whereby the fuel pressure in the pressurizing chamber 47 is increased. As a result, the movable plunger 42 is pressed downward, and the nozzle port 53 is held in the closed state by the needle 40. On the other hand, when the electric charge charged in the piezoelectric element 46 is discharged, the piezoelectric element 46 contracts and the fuel pressure in the pressurizing chamber 47 decreases. As a result, the movable plunger 42 rises, so that the needle 40 rises and fuel is injected from the nozzle port 53. The fuel injection valve 5 may be a solenoid type instead of the piezo element type described above.
[0011]
FIG. 3 is a longitudinal sectional view of the engine of the embodiment. This figure shows the engine during fuel injection in the latter half of the compression stroke. In this figure, 60 is a cylinder block, 61 is a cylinder head, 62 is a piston, 63 is a substantially cylindrical recess formed on the top surface of the piston 62, and 64 is formed between the top surface of the piston 62 and the inner wall surface of the cylinder head 61. Each cylinder chamber is shown. The spark plug 65 faces the cylinder chamber 64 and is attached to the substantially central portion of the cylinder head 61. Although not shown, an intake port and an exhaust port are formed in the cylinder head 61, and an intake valve 66 (see FIG. 4A) and an exhaust are provided in openings of the intake port and the exhaust port into the cylinder chamber 64, respectively. A valve is arranged. The fuel injection valve 5 is a swirl type fuel injection valve, and injects a spray-like fuel having a wide divergence angle and a large spray dispersion and a low penetration force. The fuel injection valve 5 is disposed at the top of the cylinder chamber 64 so as to be directed obliquely downward, and is disposed so as to inject fuel toward the vicinity of the spark plug 65. The fuel injection direction and fuel injection timing of the fuel injection valve 5 are determined so that the injected fuel is directed to the recess 63 formed at the top of the piston 62.
[0012]
FIG. 4 is an explanatory diagram of the operation of the engine shown in FIG. 1, where (a) is the initial stage of the intake stroke, (b) is the late stage of the intake stroke to the early stage of the compression stroke, (c) is the late stage of the compression stroke, and (d) is the combustion stage. It is a figure which shows the state in the cylinder of the engine in a stroke. In the embodiment of the present invention, at the time of low load operation of the engine, the entire required fuel injection amount obtained in accordance with the operation state of the engine is injected in the latter half of the compression stroke shown in FIG. Fuel is injected from the fuel injection valve 5 toward the spark plug 65 and the recess 63 on the top surface of the piston 62. Since this injected fuel has a low penetration force, a high pressure in the cylinder chamber 64 and a weak air flow, the injected fuel is unevenly distributed in the region K near the spark plug 65. The fuel distribution in this region K is non-uniform and changes from a rich air-fuel mixture layer to an air layer, so that there is a combustible air-fuel mixture in the region K near the stoichiometric air-fuel ratio that is most likely to burn. Therefore, the combustible mixture layer in the vicinity of the spark plug 65 is easily ignited, and this ignition flame propagates to the entire heterogeneous mixture layer to complete the combustion. In this way, in the low load region, by injecting fuel in the vicinity of the spark plug 65 in the latter half of the compression stroke, a combustible air-fuel mixture layer is formed in the vicinity of the spark plug 65, and good ignition and combustion can be obtained.
[0013]
During medium-load operation of the engine, the total required fuel injection amount determined according to the engine operating state is divided into an initial intake stroke shown in FIG. 4 (a) and a late compression stroke shown in FIG. 4 (c). Spray. First, as shown in FIG. 4A, fuel is injected from the fuel injection valve 5 toward the spark plug 65 and the concave portion 63 on the top surface of the piston 62 in the intake stroke. This injected fuel is a spray-like fuel having a large spread angle and a weak penetration force. A part of the injected fuel floats in the cylinder chamber 64 and the other collides with the recess 63. These injected fuels are diffused into the cylinder chamber 64 due to the turbulence R in the cylinder chamber 64 caused by the intake air flow flowing into the cylinder chamber 64 from the intake port, and compressed from the intake stroke as shown in FIG. A premixed gas P is produced during the process. The air-fuel ratio of the premixed gas P is such that the ignition flame can propagate. In the state of FIG. 4 (b), the extension of the central axis of the injected fuel is directed to the cylinder wall. Therefore, when the penetration force of the injected fuel is strong, there is a possibility that a part of the spray directly adheres to the cylinder wall. By making this period a non-injection period, the effect of preventing the fuel from adhering to the cylinder wall surface is enhanced.
[0014]
As shown in FIG. 4C, fuel is injected from the fuel injection valve 5 toward the spark plug 65 and toward the recess 63 on the top surface of the piston 62 in the latter half of the compression stroke. This injected fuel originally has a weak penetrating force directed to the spark plug 65, and the pressure in the cylinder chamber 64 is large, so that the injected fuel is unevenly distributed in the region K near the spark plug 65. The fuel distribution in this region K is also non-uniform and changes from a rich air-fuel mixture layer to an air layer. Therefore, in this region K, there is a combustible air-fuel mixture layer near the stoichiometric air-fuel ratio that is most likely to burn. Therefore, in the combustion stroke of FIG. 4D, when the combustible air-fuel mixture layer in the vicinity of the spark plug 65 is ignited, the combustion proceeds around the non-uniform air-fuel mixture region K. The flame propagates to the premixed gas P sequentially from the periphery of the combustion gas B that has undergone volume expansion in this combustion process, and combustion is completed. In this way, in the middle load region, fuel is injected in the initial stage of the intake stroke to create a mixture for flame propagation throughout the cylinder chamber 64, and in the vicinity of the spark plug 65 by injecting fuel in the latter stage of the compression stroke. A relatively rich air-fuel mixture can be produced, and good ignition and combustion with high air utilization can be obtained.
[0015]
During high-load operation of the engine, since the fuel injection amount is large, the concentration of the premixed gas in the cylinder chamber created by the intake stroke injection is high enough to ignite, so stop the compression stroke injection for ignition and respond to the operating state of the engine The entire required fuel injection amount obtained in this way is injected in the intake stroke.
[0016]
FIG. 5 is a diagram showing the fuel injection amount and the fuel injection timing according to the engine load. In this figure, the horizontal axis L indicates the amount of depression of an accelerator pedal (not shown), and the upper vertical axis indicates the fuel injection amount Q._allThe lower vertical axis indicates the injection timing. This figure shows the fuel injection amount Q for convenience of explanation._allIndicates the basic fuel injection amount calculated from the engine speed and the load, as will be described in FIG._allA is the basic fuel injection amount Q_allIs multiplied by a correction coefficient such as an air-fuel ratio correction coefficient FAF and the other correction coefficient is added to obtain the intake stroke injection amount Q₁And compression stroke injection quantity Q₂Is equal to the injection amount obtained by adding
Q_allA = Q_all× (FAF + α) + β = Q₁+ Q₂
Here, α represents a correction coefficient other than FAF, and β represents another correction term. The air-fuel ratio correction coefficient FAF is a coefficient for correcting the fuel injection amount by feedback control so that the air-fuel ratio of the engine becomes the target air-fuel ratio according to the output of the air-fuel ratio sensor provided in the exhaust system of the engine. .
[0017]
As can be seen from this figure, the accelerator pedal depression amount L is L₁When the engine load is smaller than the injection amount Q at the end of the compression stroke₂Only fuel injection is performed. On the other hand, the depression amount L of the accelerator pedal is L₁And L₂During medium-load operation during the period, the injection quantity Q during the intake stroke₁Only the fuel is injected, and the injection amount Q₂Only fuel is injected. That is, at the time of engine medium load operation, fuel injection is performed in two steps, that is, the intake stroke and the end of the compression stroke. The accelerator pedal depression amount L is L₂During engine high load operation, the injection amount Q during the intake stroke₁Only fuel is injected. In this figure, θS1 and θE1 are the fuel injection amounts Q performed during the intake stroke.₁The injection start timing and the injection end timing are respectively shown, and θS2 and θE2 are fuel injection amounts Q performed at the end of the compression stroke.₂The injection start time and the injection end time are respectively shown.
[0018]
FIG. 6 is a flowchart showing a fuel injection control routine of the engine according to the present invention. In the figure, the number following S indicates a step number. The injection amount calculating means for calculating the fuel injection amount to be injected in the compression stroke of the present invention is processed by steps S1 to S3 of this routine, and the injection end timing calculating means for calculating the injection end timing based on the fuel injection amount of the present invention. Is processed by steps S4 to S6 of this routine, the injection start timing is determined to be advanced from the injection end timing for the time of injecting the fuel injection amount of the present invention, and the fuel injection valve is set from the injection start timing to the injection end timing. The valve opening control means for controlling the valve opening time of the fuel injection valve so as to open is processed by steps S7 to S10 of this routine. This routine is executed for each injection valve by interruption every constant crank angle of the engine. In the case of a 4-cylinder engine, it is executed every 180 ° CA (crank angle).
[0019]
First, at step S1, the engine speed NE and the accelerator pedal depression amount L are read. In step S2, the basis (air-fuel ratio correction coefficient FAF) necessary for one combustion cycle of the engine is determined based on the engine speed NE and the accelerator pedal depression amount L (representing the engine load state) from the map 1 shown in FIG. = 1, α = 0, β = 0) Basic fuel injection amount Q of each cylinder_allIs calculated. As shown in FIG. 7, the basic fuel injection amount Q_allIt can be seen that as the accelerator pedal depression amount L increases, it increases as the engine speed NE increases, and the engine speed NE reaches its maximum value at the highest speed of 6000 rpm.
[0020]
In step S3, the actual fuel injection amount Q_allA is the basic fuel injection amount Q_allIs multiplied by an air-fuel ratio correction coefficient FAF or the like to obtain from the above equation.
Q_allA = Q_all× (FAF + α) + β
Next, in step S4, the injection method CQN is determined. As described with reference to FIG. 5, the engine load state is divided into low, middle and high regions from the accelerator pedal depression amount L representing the engine load state, and only the compression stroke of CQN = 0 is injected in the low load region. The compression stroke injection method is set, the medium stroke region is set to the compression stroke of CQN = 1 and the double injection method of injection to the intake stroke, and the high load region is set to the intake stroke injection method of injecting only the intake stroke of CQN = 2.
[0021]
In step S5, it is determined whether the injection method is a compression stroke injection method or a double injection method of CQN = 0 or 1, or an intake stroke injection method of CQN = 2. If CQN = 0 or 1, the process proceeds to step S6. When CQN = 2, the process proceeds to step S11.
[0022]
In step S6, the engine speed NE and the basic fuel injection amount Q_allTherefore, the injection end timing AINJ2 in the compression stroke is calculated from the map 2 shown in FIG. 8 when CQN = 0, and is calculated from a map (not shown) similar to the map 2 when CQN = 1. Basic fuel injection amount Q_allThe actual fuel injection amount Q obtained by multiplying the air-fuel ratio correction coefficient FAF by the other correction term_allA is the intake stroke injection amount Q₁And compression stroke injection quantity Q₂Is equal to the injection amount.
[0023]
10A and 10B are explanatory diagrams of a method for calculating the fuel injection timing in the compression stroke. FIG. 10A shows a case where the fuel injection time is shorter than the crank angle interruption period, and FIG. 10B shows a case where the fuel injection time is longer than the crank angle interruption period. It is each explanatory drawing. In step S7, first, the actual fuel injection amount Q_allCompression stroke injection quantity Q in A₂Fuel injection time τ corresponding to₂Is calculated from the map 3 shown in FIG. This map 3 is calculated for each fuel injection valve based on the fuel injection amount obtained from the fuel pressure in the fuel accumulator, the engine speed and the load state. Next, the determined fuel injection time τ₂Injection time τ for opening the fuel injection valve from the injection end timing AINJ2 obtained in step S6₂The count value CINJ2 (see FIG. 10) that counts how many pulses of the interrupt signal of the crank angle sensor that is output every 10 ° CA or 30 ° CA is generated, and the injection end timing obtained in step S6 A time RINJ2 (see FIG. 10) from AINJ2 until receiving the next crank angle sensor interrupt signal is calculated.
[0024]
In step S8, (τ₂It is determined whether or not + RINJ2) <TNE is established. If YES (in the case of (A) in FIG. 10), the process proceeds to step S9. If NO (in the case of (B) in FIG. 10), the process proceeds to step S10. move on. This TNE is an output cycle of the crank angle sensor that is calculated momentarily as the engine rotates. Therefore, (τ₂If + RINJ2) <TNE is established, it means that there is no output pulse of the crank angle sensor within one cycle of the crank angle sensor, and (τ₂The fact that + RINJ2) <TNE does not hold means that one output pulse of the crank angle sensor exists within one cycle of the crank angle sensor.
[0025]
In step S9, the following equation is calculated (in the case of FIG. 10A), and the process proceeds to step S11.
TINJ2 = TNE- (τ₂+ RINJ2)
Here, TINJ2 indicates the time from the interrupt signal of the crank angle sensor one before the injection end timing AINJ2 to the start of fuel injection. Fuel injection time τ₂Since there is no crank angle interruption signal, CINJ2 is 0, and the injection start timing AINJ02 in the compression stroke is retarded by TINJ2 from the crank angle interruption signal on the advance side by one pulse from the injection end timing AINJ2.
[0026]
In step S10, the following equation is calculated (in the case of FIG. 10B), and the process proceeds to step S11.
CINJ2 = CINJ2-1
TINJ2 = 2TNE- (τ₂+ RINJ2)
Here, TINJ2 indicates the time from the interrupt signal of the crank angle sensor two before the injection end timing AINJ2 to the start of fuel injection. Fuel injection time τ₂Since there is one crank angle interruption signal, CINJ2 is 1, and the injection start timing AINJ02 in the compression stroke is retarded by TINJ2 from the crank angle interruption signal on the advance side of two pulses from the injection end timing AINJ2. The calculation of CINJ2 = CINJ2-1 is executed to calculate the injection start timing AINJ02.
[0027]
12A and 12B are explanatory diagrams of a method for calculating the fuel injection timing in the intake stroke. FIG. 12A shows a case where the fuel injection time is shorter than the crank angle interruption cycle, and FIG. 12B shows a case where the fuel injection time is longer than the crank angle interruption cycle. It is explanatory drawing. In step S11 of the flowchart of FIG. 6, it is determined whether the injection method is a double injection method or an intake stroke injection method with CQN = 1 or 2, or a compression stroke injection method with CQN = 0, and when CQN = 1 or 2 Proceeding to step S12, when CQN = 0, this routine is terminated. In step S12, the injection start timing AINJ1 of the intake stroke injection is calculated from the map 4 shown in FIG. In step S13, first, the actual fuel injection amount Q_allIntake stroke injection amount Q in A₁Fuel injection time τ corresponding to₁Is calculated from the map 3 shown in FIG. Next, the determined fuel injection time τ₁Injection time τ for opening the fuel injection valve from the injection start timing AINJ1 obtained in step S12₁The count value CINJ1 (see FIG. 12) for counting the number of pulses generated by the crank angle sensor output signal every 10 ° CA or 30 ° CA is calculated, and the injection end obtained in step S12 is completed. Fuel injection time τ from time AINJ1₁Only a time RINJ1 (see FIG. 12) until the interruption signal of the crank angle sensor at the first crank angle position on the advance side is received is calculated. Next, in step S14, this routine is ended with TINJ1 = RINJ1.
[0028]
FIG. 13 is a flowchart of an injection start timing calculation routine. This routine is executed every 10 ° CA or 30 ° CA crank angle interruption period. In step S21, it is determined whether CINJ (CINJ1 or CINJ2) coincides with the crank angle interruption signal generation timing (timing) CRNK. If the determination result is YES, the process proceeds to step S22. The routine is terminated, the next crank angle interruption signal is received, the process returns to step S21 again, and this process is repeated. By executing step 21, the crank angle position corresponding to the injection start timing of the first cylinder of the engine is calculated. In step S22, a compare register CPR obtained by adding the crank angle interruption time ASRNE and TINJ2 calculated in steps S9 and S10 or TINJ1 calculated in step S14 is calculated from the following equation.
CPR = ASRNE + TINJ
Next, based on the value of the compare register CPR calculated in step S22, the first cylinder fuel injection valve opening bit YINJ is set to ON, and this routine is terminated.
[0029]
FIG. 14 is a flowchart of an injection end timing calculation routine. This routine is executed every 10 ° CA or 30 ° CA crank angle interruption period. In step S31, it is determined whether the fuel injection valve opening bit YINJ of the first cylinder is on or off. If the determination result is YES, the process proceeds to step S32, and if it is NO, this routine is terminated and the next crank angle interruption is performed. Upon receipt of the signal, the process returns to step S31 again to repeat this process. In step S32, the fuel injection valve of the first cylinder is closed at the injection end timing based on the value of the compare register obtained by calculating CPR = CPR + τ, and this routine is ended.
[0030]
As described above, the internal combustion engine of the embodiment calculates the fuel injection amount to be injected during the compression stroke, and uses the injection end timing AINJ2 obtained based on the basic fuel injection amount required for one combustion cycle of the engine as a reference. Thus, the fuel injection valve is controlled to open and the fuel is injected, so that the spray after the injection diffuses and a combustible air-fuel mixture that is well ignited at the ignition timing is created in the vicinity of the spark plug.
[0031]
The injection start timing and injection end timing of the fuel injection valve for the first cylinder of the engine have been described above with reference to FIGS. 13 and 14. However, the injection start timing and injection end timing of the fuel injection valve for the second to fourth cylinders have been described. Is also obtained in the same manner, and the description thereof is omitted.
[0032]
FIGS. 15A and 15B are diagrams showing the fuel distribution after the compression stroke injection of the direct injection internal combustion engine according to the present invention. FIG. 15A shows the fuel distribution when there is no canister purge, and FIG. 15B shows the fuel distribution when there is a canister purge. FIG. In this figure, the vertical axis indicates the air-fuel ratio, and the horizontal axis indicates the position in the cylinder circumferential direction. The fuel injected into the cylinder is diffused by the swirl flow with the fuel distribution shown in the figure. The actual fuel injection amount Q when there is a canister purge and when there is no canister purge_allA is smaller when the canister purge is present because the amount of fuel contained in the purge gas is reduced than when there is no canister purge, and as shown in FIG. 15, (A) in FIG. It can be seen that the fuel richer than that is distributed in the cylinder. As shown in FIG. 15B, when the canister purge is performed, the fuel injection amount is reduced by the amount of fuel contained in the purge gas. Actual fuel injection amount Q_allSince A is calculated from the following equation, it is understood that the fuel injection amount by canister purge is reduced.
Q_allA = Q_all× (FAF + FPG + α) + β
Where Q_allIs the basic fuel injection amount calculated according to the engine speed and load, FAF is the air-fuel ratio correction coefficient, FPG is the reduction correction coefficient calculated according to the purge rate of the canister purge gas, α is the other correction coefficient, β Indicates other correction terms.
[0033]
Next, features of the present invention will be described with reference to FIG. According to the prior art, since the fuel injection start timing is used as a reference, the point c in FIG. 15A and the point c ′ in FIG. 15B become reference points. Therefore, the combustible mixture in the region a in FIG. 15A, which is a combustible range favorable for ignition, and the combustible mixture in the region a ′ in FIG. The time to reach is different. This is because the time required for the combustible mixture in the region a to move to the point c by the swirl flow is different from the time required for the combustible mixture in the region a ′ to move to the point c ′. On the other hand, since the present invention is based on the injection end timing, the combustible mixture in the region a when there is no canister purge and the region a ′ when there is a canister purge reaches the vicinity of the spark plug at the ignition timing. The misfire due to the influence of the canister purge can be prevented. Note that the region b in FIG. 15A and the region a ′ in FIG. 15B are ignited without adopting the region b in FIG. 15A and the region b ′ in FIG. 15B for ignition. The reason for adopting is that the former air-fuel ratio changes more abruptly than the latter, narrowing the region, and the latter can take longer time from the start of injection to ignition and promote evaporation. Because.
[0034]
The internal combustion engine of the embodiment described above is an engine that is not provided with a port injection valve that is arranged in the intake pipe and injects fuel toward the intake port, but the present invention is a fuel injection valve that directly injects into the cylinder shown in FIG. In addition, the present invention can be applied to a cylinder injection internal combustion engine in which such a port injection valve is provided in an intake pipe. In this internal combustion engine, the in-cylinder direct injection valve that directly injects fuel into the cylinder performs the intake stroke injection and the compression stroke injection according to the engine load as described above, and the fuel injection timing of the compression stroke is the main injection timing. The port injection valve, which is controlled by the invention and injects fuel toward the intake port, performs normal intake stroke injection.
[0035]
【The invention's effect】
As described above, according to the injection control device for a direct injection internal combustion engine of the present invention, fuel injection is performed in the compression stroke based on the injection end timing obtained based on the basic fuel injection amount. The spray diffusion time becomes appropriate, and a combustible air-fuel mixture good for ignition at the ignition timing is generated in the vicinity of the spark plug.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a four-cylinder gasoline engine employed in an embodiment of the present invention.
FIG. 2 is a side sectional view of a fuel injection valve.
FIG. 3 is a longitudinal sectional view of an engine according to an embodiment.
4 is an explanatory diagram of the operation of the engine shown in FIG. 1, where (a) is the initial stage of the intake stroke, (b) is the late stage of the intake stroke to the early stage of the compression stroke, (c) is the late stage of the compression stroke, and (d) It is a figure which shows the state in the cylinder of the engine in a combustion stroke.
FIG. 5 is a diagram showing a fuel injection amount and a fuel injection timing according to an engine load.
FIG. 6 is a flowchart showing a fuel injection control routine of the engine according to the present invention.
FIG. 7 is a diagram showing a map 1 for calculating a basic fuel injection amount based on an engine speed and an accelerator opening.
FIG. 8 is a diagram showing a map 2 for calculating an injection timing in a compression stroke from an engine speed and a basic fuel injection amount.
FIG. 9 is a diagram showing a map 3 for calculating a fuel injection time with respect to a fuel injection amount.
10A and 10B are explanatory diagrams of a fuel injection timing calculation method in a compression stroke, where FIG. 10A shows a case where the fuel injection time is shorter than the crank angle interruption period, and FIG. 10B shows a case where the fuel injection time is longer than the crank angle interruption period. It is each explanatory drawing.
FIG. 11 is a diagram showing a map 4 for calculating the injection timing in the intake stroke from the engine speed and the basic fuel injection amount.
FIGS. 12A and 12B are explanatory diagrams of a fuel injection timing calculation method in the intake stroke, where FIG. 12A shows the case where the fuel injection time is shorter than the crank angle interruption period, and FIG. 12B shows the case where the fuel injection time is longer than the crank angle interruption period. It is each explanatory drawing.
FIG. 13 is a flowchart of an injection start timing calculation routine.
FIG. 14 is a flowchart of an injection end timing calculation routine.
FIGS. 15A and 15B are diagrams showing the fuel distribution after the compression stroke injection of the direct injection internal combustion engine according to the present invention, where FIG. 15A shows the fuel distribution when there is no canister purge, and FIG. 15B shows the fuel distribution when there is a canister purge. FIG.
FIGS. 16A and 16B are explanatory diagrams of problems of the prior art in a cylinder injection internal combustion engine, where FIG. 16A is a swirl flow, FIG. 16B is a fuel distribution after compression stroke injection, and FIG. 16C is an injection timing and a misfire rate; It is a figure which shows the relationship.
[Explanation of symbols]
5 ... Fuel injection valve
20 ... Electronic control unit
29 ... Crank angle sensor
32 ... Water temperature sensor
61 ... Cylinder head
62 ... Piston
63 ... concave combustion chamber
64 ... Cylinder chamber

Claims (1)

In an in-cylinder injection internal combustion engine injection control device including a fuel injection valve that directly injects fuel into a cylinder of an engine,
The fuel injection valve is a swirl type, and is arranged at the top of the head in the cylinder so that the injected fuel is directed to a spark plug located in the center of the head in the cylinder.
An injection amount calculating means for calculating a fuel injection amount injected from the fuel injection valve during the compression stroke;
The injection ends so that the fuel injected from the fuel injection valve and the intake air are diffused by the swirl flow based on the basic fuel injection amount required for one combustion cycle of the engine and reach the vicinity of the spark plug at the ignition timing. Injection end timing calculating means for calculating the timing;
An injection control means for calculating an injection start timing based on the injection end timing and controlling to inject a fuel injection amount in the compression stroke from the fuel injection valve from the injection start timing to the injection end timing. When,
An injection control device for a cylinder injection internal combustion engine, comprising:

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