JP2005002967A - Control device of spark ignition type direct-injection engine with turbo supercharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for a spark ignition type direct-injection engine equipped with a turbo supercharger capable of suppressing generation of smokes by injecting the fuel at the time of acceleration during the suction stroke and improving the turbo lag by controlling the injection timing at this time. <P>SOLUTION: A fuel injection valve 5 is arranged so that the injected fuel is directed toward the neighborhood of a spark plug 7 on the side more in the circumferential direction than the suction valve 2 of a combustion chamber 4. The engine 1 is equipped with the turbo supercharger 15. When the fuel is injected during the suction stroke from the injection valve 5, it is conducted in such a way as avoiding the restriction period DR so that the injected fuel does not attach to the valve element of the suction valve 2 which is opened, and during the normal operation, the fuel injection is implemented in the first period D1 on the angle advance side from the restriction period DR, and at the time of acceleration, the fuel injection is conducted in the second period D2 on the angle delay side from the restriction period DR. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a spark ignition engine control device, and particularly to a fuel injection control technique for a direct injection engine that includes a turbocharger and directly injects fuel into a combustion chamber when an intake valve is open. It is.
[0002]
[Prior art]
In general, a spark plug is disposed in a combustion chamber defined by an inner cylinder wall of an engine, a cylinder head lower surface, a piston top, and the like, and a spark that obtains combustion torque by igniting an air-fuel mixture containing fuel and intake air by the spark plug. A so-called direct injection engine in which a fuel injection valve is arranged so as to face a combustion chamber and fuel is directly injected from the injection valve into the combustion chamber is known.
Further, in Patent Document 1 below, spark ignition with a turbocharger is provided in such a spark ignition type direct injection engine, which is provided with a turbocharger that supercharges intake air using the exhaust energy of the engine. The fuel injection control of the direct injection engine is disclosed. In this patent document 1, in the initial stage of acceleration, fuel is dividedly injected in the intake stroke and the compression stroke, thereby increasing the exhaust energy and raising the exhaust gas temperature, thereby reducing the turbo lag of the turbocharger during acceleration. The technology to prevent is also disclosed.
[0003]
Further, in Patent Document 2 below, when fuel injection is performed during an intake stroke in a spark ignition direct injection engine, fuel injection is prohibited during a period in which the valve opening amount (lift amount) of the intake valve is near the maximum. A technique for suppressing the occurrence of soot and the like is disclosed.
Specifically, when the combustion chamber of such a direct injection engine is viewed from the reciprocating direction of a piston that reciprocates in the cylinder, the ignition plug is disposed near the center of the combustion chamber, and the intake valve and the exhaust valve are the ignition plug. The fuel injection valve is disposed further on the outer peripheral side than the intake valve in the direction in which the intake valve is located. For such a structure, the fuel is supplied from the fuel injection valve to the ignition plug. The spark portion is injected toward a position slightly on the piston side of the spark portion, that is, a slightly lower position in the engine vertical direction. In such a configuration, when fuel is injected with a large opening amount of the intake valve, a part of the fuel injected from the fuel injection valve adheres to the opened intake valve, and soot is generated. There's a problem. Therefore, the occurrence of soot is prevented by controlling the injection timing so that the injected fuel does not adhere to the intake valve.
[0004]
[Patent Document 1]
JP 2000-54894 A
[Patent Document 2]
Japanese Patent Application Laid-Open No. 08-8578
[0005]
[Problems to be solved by the invention]
By the way, in the engine with a turbocharger disclosed in Patent Document 1 described above, the turbo lag in the turbocharger is improved by increasing the exhaust gas temperature. However, fuel injection is performed in the intake stroke and the compression stroke. There is a problem that a lot of smoke occurs when executed. This is because a large amount of fuel is injected during the compression stroke at the time of acceleration. In such an injection mode, the period from the fuel injection execution timing to the ignition timing in the compression stroke is short, and fuel vaporization is insufficient. Thus, it is considered that a lot of smoke is generated due to the ignition of the air-fuel mixture in such a state.
On the other hand, in order to reduce smoke, it is conceivable to inject fuel during the intake stroke while prohibiting fuel injection during the compression stroke, but by simply performing injection during the intake stroke, the exhaust energy can be used efficiently. Therefore, the turbo lag cannot be improved.
Further, as disclosed in Patent Document 2 described above, in a spark ignition type direct injection engine, if fuel injection is performed during an intake stroke, the occurrence of smoke such as soot may be a problem, and the fuel injection timing is appropriately set. If it is not set, it is difficult to achieve both suppression of smoke generation and improvement of turbo lag.
[0006]
The present invention has been made in consideration of the above-described problems, and its purpose is to devise the timing of fuel injection during the intake stroke in a spark ignition direct injection engine with a turbocharger. The purpose is to improve the turbo lag while suppressing the occurrence of smoke.
[0007]
[Means for Solving the Problems]
In order to achieve such an object, according to a first aspect of the present invention, a turbocharger that supercharges intake air by exhaust gas discharged from a combustion chamber of an engine, an intake passage, and the combustion An intake valve for supplying intake air supercharged by the turbocharger to the combustion chamber by opening the valve during at least a predetermined period of the intake stroke, and fuel in the combustion chamber In the state where the combustion chamber is viewed from the reciprocating direction of the piston, the fuel is injected from the outer peripheral side of the combustion chamber toward the vicinity of the spark plug disposed in the combustion chamber. In the control device for a spark-ignition direct injection engine with a turbocharger, comprising a fuel injection valve and an injection timing control means for controlling the fuel injection timing by the fuel injection valve, the injection timing control means When the fuel injection timing is set in the stroke, a restriction period for restricting fuel injection is provided in the vicinity of the maximum valve opening timing at which the valve opening amount of the intake valve becomes maximum, and when the engine is in a steady operation state, the intake stroke The fuel injection is executed during the first period that is advanced from the regulation period, and during the acceleration from the steady operation state, the fuel injection is executed during the second period that is retarded from the regulation period during the intake stroke. It is characterized by controlling as follows.
[0008]
With this configuration, when the engine is in a steady operation state, fuel injection is performed in the first period that is more advanced than the regulation period, avoiding the regulation period during which smoke is likely to be generated due to fuel injection during the intake stroke. Therefore, it is possible to execute fuel injection during the intake stroke, where the generation of smoke is originally low, while further suppressing the generation of smoke. Further, at this time, since fuel injection is performed at an early stage, fuel is sufficiently mixed with intake air over a long period from injection execution to ignition execution, and is generated by combustion. HC (hydrocarbon) can be reduced.
Also, during acceleration, fuel injection is performed in the second period that is retarded from the regulation period during the intake stroke, but at this time, the piston is in a state of being lowered to the bottom dead center side in the cylinder, The fuel injected in such a state improves the mixing with the air by the intake air flow in the cylinder and lowers the intake temperature in the cylinder in a short time by the latent heat of vaporization. Thereby, the intake of a large amount of intake air into the cylinder is promoted, the intake charge amount is increased, and the exhaust gas amount is increased, so that the supercharging performance of the turbocharger can be improved. In addition, by improving the mixing of fuel and air as described above, the combustibility is promoted and the generation of smoke can be suppressed. Therefore, during acceleration, the fuel injection is performed during the intake stroke while avoiding the regulation period, so that the occurrence of smoke can be suppressed and the turbocharger supercharging caused by the increase in the intake charge amount can be suppressed. The performance can be improved and the turbo lag can be improved.
[0009]
According to a second aspect of the present invention, in the first aspect, the injection timing control means performs the first fuel injection in the late stage of acceleration such that the engine torque increased by the turbocharger approaches a predetermined value after the start of acceleration. It is characterized by controlling to be executed during a period.
When fuel injection is executed in the second period, HC discharged from the combustion chamber by combustion is relatively larger than that in the first period.
However, with the configuration according to the second aspect, even during acceleration, fuel injection is performed in the first period after the engine torque is increased by the turbocharger. While maintaining the torque, exhaust of HC from the combustion chamber can be suppressed as a whole.
[0010]
According to a third aspect of the present invention, in the first aspect, the injection timing control means performs the first fuel injection after the start of acceleration at a later stage of acceleration such that the engine torque increased by the turbocharger approaches a predetermined value. It is characterized by performing control in the period and the second period.
With such a configuration, fuel injection can be performed in a state where the intake air flow in the cylinder is fast near the middle of the intake stroke excluding the regulation period, so that mixing characteristics between injected fuel and air can be improved and acceleration is being performed. Thus, smoke and HC emissions from the combustion chamber can be suppressed as a whole while maintaining a high torque.
[0011]
According to a fourth aspect of the present invention, in the first aspect, when the supercharging pressure of the intake air supercharged by the turbocharger exceeds a predetermined value, a part of the exhaust gas upstream of the turbocharger is A wastegate valve that opens to bypass the turbocharger is provided, and the engine's steady operating state is that the engine operating state is placed in the intake passage and the throttle valve that adjusts the intake air amount is fully opened. At this time, the wastegate valve is in a lower rotational speed range than the engine rotational speed at which the wastegate valve shifts from the fully closed state to the open state.
With such a configuration, when the throttle valve arranged in the intake passage is fully opened, the wastegate valve that bypasses the exhaust gas supplied to the turbocharger is lower than the engine speed at which the engine shifts from the fully closed state to the open state. The fuel injection in the second period is executed only at the time of acceleration from the operating state that becomes the rotation region. Therefore, in a steady operation state where the engine speed is in a low engine speed range, fuel injection in the second period is not executed, so that HC emission from the combustion chamber can be suppressed. Further, this steady operation state is a state in which the supercharging capability of the turbocharger is low. Only when accelerating from this operation state, fuel injection is executed in the second period, thereby increasing the HC emission amount. While suppressing, the exhaust energy that is insufficient due to the low rotation state can be compensated, and the turbo lag can be reduced and the HC emission amount can be reduced.
[0012]
According to the fifth aspect of the present invention, the exhaust gas discharged from the combustion chamber of the engine enables communication between the turbocharger that supercharges intake air, the intake passage, and the combustion chamber, and at least a predetermined intake stroke. The intake valve that supplies the intake air supercharged by the turbocharger to the combustion chamber and directly injects fuel into the combustion chamber, and the combustion chamber is reciprocated in the piston reciprocating direction. The fuel injection valve is disposed so that fuel is injected from the outer peripheral side of the combustion chamber toward the vicinity of the spark plug disposed in the combustion chamber, and the fuel injection by the fuel injection valve In a control device for a spark-ignition direct injection engine with a turbocharger, comprising: an injection timing control means for controlling the timing; the injection timing control means is configured to operate when the fuel injection timing is set in the intake stroke. A restriction period for restricting fuel injection is provided in the vicinity of the maximum valve opening timing at which the valve opening amount of the intake valve is maximized. When the engine is in a steady operation state, a first position that is advanced from the restriction period during the intake stroke. During at least one of the period or the second period that is retarded from the regulation period during the intake stroke, the fuel injection is performed in the first period and the second period during acceleration from the steady operation state. And the injection amount of the fuel injection executed in the second period is made larger than the injection amount of the fuel injection executed in the first period.
With this configuration, during acceleration, fuel injection is performed within a period in which the reciprocating speed of the piston is high and the intake air flow in the cylinder is fast, avoiding the restriction period during the intake stroke. Can be greatly suppressed. Further, by increasing the fuel injection amount in the second period more than the fuel injection amount in the first period and executing the injection in the second period, the exhaust gas amount can be increased due to the increase in the intake charge amount, Thereby, the supercharging performance of the turbocharger can be improved and the turbo lag can be improved.
[0013]
A sixth aspect of the present invention is the method according to the fifth aspect, wherein when the supercharging pressure of the intake air supercharged by the turbocharger exceeds a predetermined value, a part of the exhaust gas upstream of the turbocharger is A wastegate valve that opens to bypass the turbocharger is provided, and the engine's steady operating state is that the engine operating state is placed in the intake passage and the throttle valve that adjusts the intake air amount is fully opened. The wastegate valve is in a state where the engine speed is lower than the engine speed at which the wastegate valve shifts from the fully closed state to the open state, and the injection control means The fuel injection is executed in one of the period or the second period, and control is performed so that the fuel injection is executed in both the first period and the second period when the engine is in a high rotation state in the low rotation range. It is a symptom.
With such a configuration, when accelerating from an operating state where the engine speed is relatively high in a low engine speed range where the engine speed is low, both during the intake stroke and before and after the regulation period avoiding the regulation period, By executing the fuel injection, fuel injection can be performed in a state where the intake air flow in the cylinder is faster, and the generation of smoke can be significantly suppressed by improving the mixing of fuel and air.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
[0015]
(First embodiment)
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
[0016]
(overall structure)
As shown in FIG. 1, a spark-ignition direct injection engine 1 with turbocharger (hereinafter referred to as “engine 1”) according to the present invention has wheels (not shown) with respect to a vehicle (not shown). It is mounted so that it can be driven. Further, when two intake valves 2 (only one intake valve is shown) are opened, the engine 1 draws intake air for fuel combustion from the intake passage 3 into the combustion chamber 4 formed in the cylinder 1a. It is like that. Then, fuel (gasoline) is directly injected into the combustion chamber 4 from the fuel injection valve 5 at a predetermined time, and an air-fuel mixture is formed.
[0017]
This air-fuel mixture is compressed by the piston 6 and is ignited and burned by a spark plug 7 (spark ignition device) at a predetermined timing. Combustion gas, that is, exhaust gas, is discharged into the exhaust passage 9 when the exhaust valve 8 is opened.
[0018]
Fuel is supplied to the fuel injection valve 5 by a high-pressure fuel pump 11 through a fuel supply passage 10. Thus, since the high-pressure fuel pump 11 is used, fuel injection can be performed without any trouble even in the latter half of the compression stroke in which the inside of the combustion chamber 4 becomes high pressure. The fuel injection valve 5 is a swirl nozzle type injector, and is arranged so that the tip of the fuel injection valve 5 in which the fuel injection hole is formed directly faces the combustion chamber 4. A cavity 6 a is formed at the top of the piston 6.
[0019]
In the intake passage 3, a throttle valve 12 that can adjust the intake air amount, a surge tank 3 a that stabilizes the intake air flow, and a tumble in the combustion chamber 4 are generated in order from the upstream side in the intake air flow direction. Therefore, a flow control valve 13 for adjusting the inflow direction of the intake air to the combustion chamber 4 is provided. Here, the throttle valve 12 is driven by an electric actuator 12a that operates according to a control signal output from a control unit 22 (ECU) described later. In addition, a bypass passage that bypasses the throttle valve 12 is formed in the intake passage 3, and a bypass valve is provided in the bypass passage so as to open and close, thereby forming an idle speed control device that controls the intake air amount during idle operation. You can also.
In the intake passage 3 upstream of the throttle valve 12, an air cleaner (not shown) for removing dust and the like contained in the intake air directly sucked from the atmosphere in order from the upstream, an air flow sensor (not shown) for detecting the intake air amount. A compressor 15b and an intercooler 18 of a turbocharger 15 to be described later are provided.
[0020]
In the exhaust passage 9, a linear O that linearly detects the oxygen concentration in the exhaust gas and thus the air-fuel ratio in order from the upstream side in the exhaust flow direction. ₂ Sensor 14 (Note that the normal air-fuel ratio, that is, a normal λO whose output reverses in the vicinity of λ = 1 ₂ Sensor), a turbine 15a of the turbocharger 15, a first catalytic converter 16a, and a second catalytic converter 16b.
[0021]
The turbocharger 15 is mechanically connected to the turbine 15a that is rotated by contact with the exhaust gas flow, and is provided in the intake passage 3 and rotates according to the rotation of the turbine 15a. And a compressor 15b capable of supercharging intake air. In addition, an intercooler 18 that cools the intake air that has been supercharged by the compressor 15 b to a high temperature with traveling wind or the like to increase the intake charge amount in the combustion chamber 4, and intake air between the compressor 15 b and the throttle valve 12. It is provided in the passage 3.
[0022]
In the exhaust passage 9, a waste gate valve 17b is provided in a bypass passage 17a that bypasses the upstream and downstream of the turbine 15a. The wastegate valve 17b is configured such that supercharged intake air between the compressor 15b and the throttle valve 12 is introduced into the intake passage 6 with respect to the diaphragm type actuator 17c, and is thereby opened and closed. . Specifically, when the supercharging pressure (positive pressure) of the supercharged intake air is greater than the atmospheric pressure but below a predetermined pressure, the wastegate valve 17b is closed, and substantially the entire amount of exhaust gas passes through the turbine 15a. However, when the supercharging pressure becomes larger than a predetermined pressure, a part of the exhaust gas bypasses the turbine 15a and the excessive supercharging is suppressed by opening the waste gate valve 17b. The reliability of the engine 1 is maintained. In this case, in a state where the throttle valve 12 is fully opened, the engine speed when the supercharging pressure becomes a predetermined pressure and the wastegate valve 17b starts to shift from the closed state to the open state is generally called the intercept speed. It is out.
[0023]
Both the first catalytic converter 16a and the second catalytic converter 16b are loaded with a honeycomb carrier (not shown), and the exhaust gas atmosphere sandwiches the exhaust gas atmosphere corresponding to the stoichiometric air-fuel ratio on the surface of the honeycomb carrier. Thus, the three-way catalyst material that can purify NOx, HC, CO, etc. in the exhaust gas is coated by periodically switching between the oxidizing atmosphere and the reducing atmosphere. In addition, any catalytic converter 16a, 16b exhibits a sufficient purification power when its temperature is higher than the activation temperature, but a sufficient purification power cannot be obtained when the temperature is lower than the activation temperature.
The turbine 15a and linear O ₂ A catalytic converter 16 a may be disposed between the sensor 14 and the sensor 14.
[0024]
The engine 1 is provided with an EGR passage 19 (EGR is an abbreviation of “Exhaust Gas Recirculation”) for returning a part of the exhaust gas in the exhaust passage 9 to the intake passage 3, and the EGR passage 19 is provided with an EGR gas flow rate. An EGR control valve 20 to be controlled is interposed.
Further, the intake valve 2 can change the valve opening timing and the valve closing timing according to the operating state by the variable valve timing mechanism 21.
[0025]
The control unit 22 is a comprehensive control device for the engine 1 and performs various engine controls based on various control information. Specifically, the control unit 22 receives information on the intake air amount from the air flow sensor, accelerator opening information of an accelerator pedal (not shown) provided in the passenger compartment, and a crankshaft ( Crank angle information (not shown), engine coolant temperature information (engine temperature), linear O ₂ Various control information such as air-fuel ratio information from the sensor 14 is input. Based on these control information, the control unit 22 controls the fuel injection control including the fuel injection amount control and the injection timing control of the fuel injection valve 5, controls the ignition timing of the spark plug 7 (ignition timing control), throttle valve 12, control of the opening of the EGR control valve 20, control of the opening of the flow control valve 13, control of the opening period and opening / closing timing of the intake valve 2, and the like.
In the fuel injection control of the engine 1 in the present embodiment, the air-fuel ratio is in the vicinity of the theoretical air-fuel ratio based on the oxygen concentration in the exhaust gas when the operating state of the engine 1 is in a region other than the high rotation and high load states. The air-fuel ratio feedback control is executed so that
[0026]
Next, with reference to FIG. 2, the spray form of the fuel injected from the fuel injection valve 5 will be described in detail.
As shown in FIG. 2, the injection port 5 a of the fuel injection valve 5 is formed on the inner wall of the combustion chamber 4 on the lower side (crankshaft side) in the reciprocating direction of the piston 6 of the communication opening 2 a between the intake passage 3 and the combustion chamber 4. When viewed from the reciprocating direction of the piston 6, it is located near the outer peripheral side of the intake valve 2, that is, on the outer peripheral side of the cylinder 1 a between the two intake valves 2. The fuel is atomized and injected from the injection port 5a toward the obliquely lower side in the reciprocating direction and in a conical shape. Specifically, the inclination angle θ1 of the fuel injection valve (substantially the same as the inclination angle θ1 ′ with respect to the center line of the spray having a substantially conical shape) is set with respect to the horizontal plane (that is, the plane perpendicular to the reciprocating direction). The spray angle θ2 is set between 35 ° and 50 ° (however, under atmospheric pressure conditions).
[0027]
Further, the spray reach distance by such fuel injection slightly passes through the spark portion 7a of the spark plug 7 or a slightly lower position on the upper side of the spray (on the spark plug 7 side), and the exhaust valve 8 Alternatively, the distance is set shorter than the inner wall of the cylinder 1a on the exhaust valve 8 side.
By defining the spray region S as described above, the fuel can be prevented from adhering to the inner wall of the cylinder 1a, and the fuel can be appropriately present around the spark portion 7a. While reducing, ignitability can be improved.
[0028]
By the way, as described above, when the fuel spray region S is defined for improving the ignitability, the following problems occur.
That is, when fuel is injected from the fuel injection valve 5 while the intake valve 2 is open during the intake stroke, the fuel is injected when the valve opening amount (lift amount) of the intake valve 2 is close to the maximum. As shown in FIG. 2, a part of the valve body of the intake valve 2 is located in the spray region S, so that a part of the injected fuel adheres to the valve body of the intake valve 2. Will do.
The fuel adhering in this way is not substantially vaporized and atomized, and smoke is generated by the subsequent combustion. The smoke thus generated is discharged from the combustion chamber together with the exhaust gas, thereby deteriorating the emission.
[0029]
FIG. 3 is an experimental result showing such a phenomenon. During the intake stroke of the engine 1, the amount of smoke generated when the fuel injection start timing (the fuel injection is executed once) is changed (from the combustion chamber). Emission amount) and torque (engine torque) are shown. Further, as will be described later, in order to examine the setting of the optimum fuel injection timing, the intake charge amount and the exhaust amount of HC from the combustion chamber are also shown.
As can be seen from this figure, the intake valve 2 reaches approximately 120 ° CA from a crank angle of approximately 80 ° (hereinafter referred to as CA) after the intake stroke top dead center (TDC) at which the valve opening amount becomes close to the maximum. In the regulation period DR, part of the fuel injected from the fuel injection valve 5 adheres to the opened intake valve 2, so that the amount of smoke generated increases and the torque slightly decreases.
Further, when the fuel injection start timing is gradually advanced from the regulation period DR, the amount of smoke generated gradually decreases but then increases as it approaches TDC. At this time, the HC emission amount shows a tendency similar to the smoke generation amount, and the torque and the intake charge amount decrease as the fuel injection start timing approaches TDC.
On the other hand, when the fuel injection start timing is gradually retarded from the regulation period DR, the smoke generation amount gradually decreases and then gradually increases from the vicinity of BDC (intake stroke bottom dead center). At this time, the torque greatly decreases as it approaches the BDC, the intake charge amount gradually increases, and the HC exhaust amount gradually increases and then rapidly increases from the vicinity of the BDC.
[0030]
The reason why the smoke generation amount and torque are improved by setting the fuel injection start timing to a slightly advanced side or a retarded side with respect to the regulation period DR is because the intake flow in the cylinder 1a becomes fast. In a predetermined crank angle range (that is, a range excluding the crank angle period near TDC and BDC where the speed associated with the reciprocating motion of the piston 6 increases in the geometrical relationship of the crank mechanism and the intake air flow becomes slightly faster). This is because the injected fuel and air are mixed well by being injected, and the amount of the injected fuel adhering to the intake valve 2 is gradually reduced.
The reason why the amount of smoke generated and the torque becomes worse as the fuel injection start timing is made closer to TDC or BDC is that the amount of injected fuel adhering to the top of the piston 6 increases and the intake air in the cylinder 1a. This is probably because the vaporization and atomization of the fuel is not promoted as a whole due to the slow flow and the mixing property between the injected fuel and air being lowered.
[0031]
Further, the reason why the intake charge amount increases by gradually retarding the fuel injection start timing during the intake stroke is considered to be due to the intake air cooling effect resulting from the fuel injection. That is, the peripheral intake air is cooled by the vaporization of the injected fuel, whereby the intake air volume is reduced, and more intake air can be introduced into the combustion chamber 4. Therefore, when fuel is injected at the later stage of the intake stroke, a large amount of intake air can be introduced into the combustion chamber 4 immediately before the intake valve 2 is closed by such intake air cooling. On the other hand, when fuel is injected in the first half of the intake stroke, such an intake cooling effect is once obtained, but the intake air that has been cooled as the piston 6 descends comes into contact with the wall surface of the cylinder 1a and is warmed. When the intake valve 2 is closed, the intake air cooling effect cannot be obtained. Therefore, even if fuel is injected in the first half of the intake stroke, the intake charge amount is not increased.
[0032]
Further, the reason why the HC emission amount is improved by setting the fuel injection start timing to the middle of the first half of the intake stroke is that the fuel injection is performed early in addition to the use of the fast intake flow in the cylinder 1a. This is because the period until ignition becomes longer, and vaporization of the fuel injected during this time is promoted for a long time. If the injection timing is advanced to the vicinity of TDC, a large amount of the injected fuel adheres to the top of the piston 6 and the like, and it is considered that HC deteriorates due to this large amount of attached fuel.
[0033]
(Fuel injection control)
In the present embodiment related to the direct injection engine 1 equipped with the turbocharger 15 based on the experimental results as described above, the fuel injection timing is set as shown in FIG.
A steady operation state in an operation region in which the engine speed is equal to or lower than the intercept rotation number, specifically, an operation region in which the engine speed is low and in a low load state (however, an operation region in a medium rotation and medium load state may be included. In the steady operation state at), fuel injection is executed at a predetermined time within the first period D1 advanced from the regulation period DR. The first period D1 is a region where the intake air flow in the cylinder 1a is fast and the amount of smoke generated is small. At this time, the torque is relatively large and the HC emission amount is small, but the intake charge amount is slightly small. Therefore, the amount of exhaust gas (that is, exhaust energy) is not so large. Specifically, the first period D1 is preferably in the range of 40 ° CA to 80 ° CA after the intake stroke top dead center. Note that if the fuel injection is executed at a further advanced angle than the first period D1, the amount of smoke generated and the amount of HC discharged increase, and the torque also decreases.
[0034]
When the engine operating state shifts from such a steady operation region to acceleration, fuel injection is executed at a predetermined time within the second period D2 in the initial stage of acceleration immediately after the start of acceleration. The second period D2 is a period retarded from the regulation period DR and is a region where the intake air flow in the cylinder 1a is fast and the amount of smoke generated is small. At this time, the torque is large and the intake charge amount is also large. Further, the exhaust energy can be increased, and the turbocharging efficiency of the turbocharger 15 can be improved. On the other hand, the HC emission amount is larger than that in the case where fuel injection is executed in the first period D1. Specifically, the second period D2 is preferably in the range of 120 ° CA to 160 ° CA after the intake stroke top dead center (before the intake stroke bottom dead center, 20 ° CA to 60 ° CA). When the operation is executed with a delay from the second period D2, the amount of smoke generated and the amount of HC discharged increases, and the torque also decreases.
In the latter half of the acceleration after the start of acceleration, for example, the engine torque is the fully open torque (the engine torque that can be generated with respect to the intake charge amount obtained in this state during steady operation when the opening of the throttle valve 12 is fully open). In this state, the fuel injection timing is returned to the first period D1 so that the amount of HC emission is small. Accelerate with.
[0035]
By controlling the fuel injection timing in this way, it is possible to suppress the generation of smoke and HC during steady operation or in the later stage of acceleration where the torque increase effect due to supercharging can be sufficiently obtained. Then, it is possible to improve the turbo lag of the turbocharger 15 by increasing the intake charge amount while suppressing the occurrence of smoke.
In the latter half of the acceleration, the fuel injection may be executed in both the first period D1 and the second period D2, and may be returned to the first period D1 after the acceleration is completed. In the vicinity of the middle stage of the removed intake stroke, fuel injection can be performed in a state where the intake air flow in the cylinder 1a is fast, and further, the fuel injected in the first period D1 is heavier than the fuel injected in the first period D1. (In other words, when a large amount of fuel is injected all at once, the fuel spray at the initial stage of injection does not overlap with the spray of fuel injected thereafter), so mixing of the injected fuel and air As a result, the high torque can be secured while suppressing the generation of smoke and HC. (Refer to one form of injection shown by the broken line in FIG. 4)
[0036]
Next, the control procedure in this embodiment will be described in detail with reference to the control flowchart of FIG.
FIG. 5 shows a flowchart that starts each time the crank angle reaches a predetermined angle. After the start, crank angle information, intake air amount information, and the like are input in step S1. The engine speed is determined based on the crank angle information, and the engine load is determined based on the intake air amount information. In addition to the fuel injection control, the engine control unit 22 controls the opening of the throttle valve 12 based on an accelerator opening signal or the like, thereby adjusting the intake air amount.
Next, in step S2, it is determined whether or not the acceleration is sudden from a low rotation and low load operation region. If the acceleration request is a high acceleration, go to step S3, otherwise steady operation or slow acceleration. The process proceeds to step S4 on the assumption that the vehicle is in a state of rapid acceleration from a high rotation region where the turbo lag is extremely small. The determination of sudden acceleration at this time is determined as acceleration when the rate of change of the intake air amount (change amount per unit time) exceeds a predetermined value within a low rotation range where the engine speed is equal to or lower than the intercept speed. . Note that the rapid acceleration determination is not limited to this, and the amount of change in the accelerator opening, or its annealing value, within a low speed range where the engine speed is equal to or lower than the intercept speed based on the characteristics of the turbocharger 15. Alternatively, the determination may be made based on when the related value such as is equal to or greater than a predetermined value.
[0037]
In step S4, an injection form is set based on a control map (not shown). Specifically, the control map has the horizontal axis as the engine speed and the vertical axis as the engine load, and based on these, the mode of fuel injection timing and the injection amount are stored for each operating state. As a result, the fuel injection timing is set to a predetermined timing within the first period D1 in the operating state where the engine speed is in the low rotation speed range. In addition, since high output is required in the high engine speed range where the engine speed is equal to or higher than the intercept engine speed, the fuel can be used regardless of the change rate of the intake air amount (that is, regardless of whether it is suddenly or slowly accelerated). The injection timing is set to two times, a predetermined time in the first period D1 and a predetermined time in the second period D2.
In this control map, the fuel injection amount is set to increase as the engine speed increases or the engine load increases.
[0038]
In step S3, it is determined whether or not it is in the initial stage of acceleration. If it is in the initial stage of acceleration, the process proceeds to step S5.
The determination at this time is determined by the control map of FIG. 6, and according to this control map, the fully open torque of the engine 1 is obtained in advance according to the engine speed. At the time of acceleration determination, when the current torque at the current engine speed is smaller than the line L in the control map of FIG. 6 (point A in FIG. 6), it is determined that the acceleration is in the initial stage. When it is within the range defined between L and the line L ′ that is smaller than the line L by a predetermined torque and approaches the line L (point B in the figure), it is determined that it is the late stage of acceleration. The current torque is obtained from the intake air amount and the fuel injection amount.
Note that the determination at the initial stage of acceleration is not limited to this. For example, after the start of acceleration, a period after a predetermined time may be determined as the initial stage of acceleration, and after a predetermined period may be determined as the late stage of acceleration.
[0039]
In step S5, since the acceleration is early, the fuel injection timing is set to a predetermined timing within the second period D2. In step S6, since it is the late stage of acceleration, the fuel injection timing is set within the first period D1, or a predetermined time within the first period D1 and a predetermined time within the second period D2. In these steps S5 and S6, the fuel injection amount is set by the fuel injection amount control map set in the same manner as the fuel injection amount characteristic of the control map in step S4.
After each fuel injection mode is set in steps S4, S5, and S6, fuel injection is executed with the set fuel injection amount when the set fuel injection timing is reached by the fuel injection valve (step S4). S7), return.
[0040]
(Second Embodiment)
In the first embodiment of the present invention, the engine 1 that performs fuel injection only in the second period D2 in the initial stage of acceleration has been described, but instead, the fuel injection is performed in the first period D1 in the initial stage of acceleration. And the second period D2, both of which may be described in detail below. In this case, the overall configuration and basic control of the second embodiment are the same as those of the first embodiment.
As shown in FIG. 7, as in the first embodiment, in the steady operation state, fuel injection is performed at a predetermined time within the first period D1. Depending on the operating state, fuel injection may be performed additionally at a predetermined time within the second period D2, or instead of fuel injection within the first period D1. (Refer to the fuel injection Fadd indicated by the broken line in FIG. 7) Specifically, in a region where the operation state is a steady operation state and the engine speed is low, the predetermined time within the first period D1 is reached. Fuel injection is performed or fuel is injected at a predetermined time within the second period D2, and when the operating state is a steady operating state and the engine speed is high, the predetermined period within the first period D1. The fuel may be injected at the time and at a predetermined time within the second period D2.
[0041]
In the early stage of acceleration and the late stage of acceleration, fuel is injected at predetermined timings in the first period D1 and the second period D2. In this case, the fuel injection amount in the fuel injection in the second period D2 is larger than the injection amount in the fuel injection in the first period D1. On the other hand, in the later stage of acceleration, the fuel injection amount in the fuel injection in the second period D2 is smaller than the injection amount in the fuel injection in the first period D1.
Even with such a configuration, fuel injection can be performed in a state where the intake air flow in the cylinder 1a is faster near the middle of the intake stroke excluding the regulation period DR, and further, the fuel injected in the first period D1 Since the fuel injected in the second period D2 does not overlap, the mixing property between the injected fuel and air is improved, and the turbo lag can be improved while suppressing the generation of smoke and HC.
[0042]
(Other embodiments)
In the above-described embodiment, the engine that performs the operation with the air-fuel ratio of the engine 1 set to the stoichiometric air-fuel ratio in a region other than the high-rotation and high-load operation state has been described. However, the present invention is not limited to this. Instead, the engine 1 may be a lean burn engine that performs a so-called lean burn operation. That is, in the lean burn engine, as shown in FIG. 8, the engine air-fuel ratio (A / F) is changed to the stoichiometric air-fuel ratio (A / F = A / F) in the region R1 where the engine operating state is low rotation and low load. For example, the fuel injection is performed at a predetermined time from the middle stage to the latter stage of the compression stroke. Further, in the region R2 on the higher speed and higher load side than the region R1, the air-fuel ratio is set to the stoichiometric air-fuel ratio. At this time, the fuel injection is performed within the first period D1 or the second period D2 in the intake stroke. , Set to a predetermined time.
[0043]
In such an engine, when the operation state is a steady operation in the region R1, fuel injection is performed in the middle of the compression stroke, and lean burn by stratified combustion is performed (C1 in FIG. 8). If acceleration is determined from this state, fuel injection is executed at a predetermined time within the second period D2 in the intake stroke at the initial stage of acceleration even if the operating state is within the region R1 (C2 in FIG. 8). At this time, fuel less than half of the total fuel injection amount may be additionally executed in a predetermined period within the first period D1. Then, when it shifts to the latter half of acceleration, fuel injection is performed at a predetermined time within the first period D1 in the intake stroke.
[0044]
With such a configuration, even in a direct-injection lean burn engine with a turbocharger, it is possible to improve the acceleration performance by improving the turbo lag of the turbocharger 15 in the early stage of acceleration while suppressing the generation of smoke during acceleration. .
[0045]
In the above embodiment, the fuel injection at a predetermined time in the first period D1 or the second period D2 has been described as one time. However, the injection is performed in a plurality of times within the first period D1. Alternatively, the injection may be performed in a plurality of times within the second period D2.
Further, in the above embodiment, the swirl nozzle type injector is used as the fuel injection valve 5, but the present invention is not limited to this. For example, the fuel injection valve 5 is a type having a narrow spray angle and a high penetration force. In the state where the piston 6 is located on the top dead center side, the fuel may be injected so as to collide with the top of the piston 6 or the intake air flow.
Further, the variable valve timing mechanism 21 obtains the time when the intake valve 2 reaches the maximum valve opening amount according to the operating state, and the first period D1 and the second period D2 are changed according to the operating state based on this. You may control as follows.
[0046]
【The invention's effect】
As described above, in the first invention according to the present invention, when the engine is in a steady operation state, fuel injection is performed in the first period that is more advanced than the regulation period during the intake stroke. It is possible to execute fuel injection during the intake stroke with less occurrence of smoke while further suppressing the occurrence of smoke. At this time, since fuel injection is performed at an early stage, the generation of HC can be suppressed. In addition, during acceleration, fuel injection is performed in the second period that is retarded from the regulation period during the intake stroke, so excessive turbocharger excess due to an increase in the intake charge amount is suppressed while suppressing the occurrence of smoke. Turbo lag can be improved by improving the feed performance.
In the second invention according to the present invention, during the acceleration, the fuel injection in the second period retarded from the regulation period during the intake stroke is set to be greater than the fuel injection in the first period. Since the fuel injection is performed in an increased amount, the fuel and air mixing characteristics can be improved by split fuel injection, thereby suppressing the occurrence of smoke and reducing the turbocharger excess due to the increase in the intake charge amount. The turbo lag can be improved by improving the feed performance.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing an outline of an engine 1 according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a spray form of fuel injected from a fuel injection valve 5 into a combustion chamber 4;
FIG. 3 is a graph showing experimental results regarding various data such as smoke generation amount when the fuel injection timing is changed in the intake stroke.
FIG. 4 is a schematic diagram showing a form of fuel injection operation according to the first embodiment.
FIG. 5 is a flowchart showing a control procedure according to the first embodiment.
FIG. 6 is a schematic diagram illustrating a determination method at the early stage of acceleration.
FIG. 7 is a schematic view showing a form of fuel injection operation according to the second embodiment.
FIG. 8 is a schematic diagram showing an operating state of a lean burn engine.
[Explanation of symbols]
2: Intake valve
4: Combustion chamber
5: Fuel injection valve
7: Spark plug
15: Turbocharger
D1: First period
D2: Second period
DR: Regulatory period

Claims (6)

A turbocharger that supercharges intake air by exhaust gas discharged from the combustion chamber of the engine;
An intake valve that allows the intake passage and the combustion chamber to communicate with each other, and that opens the valve during at least a predetermined period of the intake stroke to supply the intake air supercharged by the turbocharger to the combustion chamber;
The fuel is directly injected into the combustion chamber, and the fuel is injected from the outer peripheral side of the combustion chamber toward the vicinity of a spark plug disposed in the combustion chamber when the combustion chamber is viewed from the reciprocating direction of the piston. A fuel injection valve arranged to be
In a control device for a spark ignition direct injection engine with a turbocharger, comprising an injection timing control means for controlling the injection timing of fuel by the fuel injection valve,
The injection timing control means provides a regulation period for regulating fuel injection in the vicinity of the maximum valve opening timing at which the valve opening amount of the intake valve becomes maximum when the fuel injection timing is set in the intake stroke,
When the engine is in a steady operation state, fuel injection is performed in a first period that is more advanced than the regulation period during the intake stroke, and during acceleration from the steady operation state, the fuel injection is delayed from the regulation period during the intake stroke. A control device for a spark-ignition direct injection engine with a turbocharger, wherein control is performed so that fuel injection is performed during the second period. The injection timing control means controls the fuel injection to be executed in the first period after the start of acceleration, at a later stage of acceleration such that the engine torque increased by the turbocharger approaches a predetermined value. Item 2. A control device for a spark ignition direct injection engine with a turbocharger according to Item 1. The injection timing control means performs control so that fuel injection is executed in the first period and the second period in the latter period of acceleration such that the engine torque increased by the turbocharger approaches a predetermined value after the start of acceleration. The control device for a spark ignition direct injection engine with a turbocharger according to claim 1. When the supercharging pressure of the intake air supercharged by the turbocharger exceeds a predetermined value, the valve is opened so as to bypass a part of the exhaust gas upstream of the turbocharger downstream of the turbocharger. With operating wastegate valve,
The engine operating state is lower than the engine speed at which the wastegate valve shifts from a fully closed state to an open state when the throttle valve that is disposed in the intake passage and adjusts the intake air amount is fully opened. The control device for a spark ignition direct injection engine with a turbocharger according to claim 1, wherein the control device is in a rotation range. A turbocharger that supercharges intake air by exhaust gas discharged from the combustion chamber of the engine;
An intake valve that allows the intake passage and the combustion chamber to communicate with each other, and that opens the valve during at least a predetermined period of the intake stroke to supply the intake air supercharged by the turbocharger to the combustion chamber;
The fuel is directly injected into the combustion chamber, and the fuel is injected from the outer peripheral side of the combustion chamber toward the vicinity of a spark plug disposed in the combustion chamber when the combustion chamber is viewed from the reciprocating direction of the piston. A fuel injection valve arranged to be
In a control device for a spark ignition direct injection engine with a turbocharger, comprising an injection timing control means for controlling the injection timing of fuel by the fuel injection valve,
When the fuel injection timing is set in the intake stroke, the injection timing control means provides a regulation period for restricting fuel injection in the vicinity of the maximum valve opening timing at which the valve opening amount of the intake valve is maximized. During the steady operation state, fuel injection is performed at least in the first period that is advanced from the regulation period during the intake stroke or the second period that is retarded from the regulation period during the intake stroke. During acceleration from the steady operation state, the fuel injection is executed in the first period and the second period, and the injection amount of the fuel injection executed in the second period is the same as the fuel injection executed in the first period. A control device for a spark-ignition direct injection engine with a turbocharger, characterized in that it is greater than the injection amount. When the supercharging pressure of the intake air supercharged by the turbocharger exceeds a predetermined value, the valve is opened so as to bypass a part of the exhaust gas upstream of the turbocharger downstream of the turbocharger. With operating wastegate valve,
The engine operating state is lower than the engine speed at which the wastegate valve shifts from a fully closed state to an open state when the throttle valve that is disposed in the intake passage and adjusts the intake air amount is fully opened. In a state of rotation,
The injection control means executes fuel injection during one of the first period and the second period when the engine is in a lower rotation state within the low rotation region, and when the engine is in the high rotation state within the low rotation region. 7. The control device for a spark ignition direct injection engine with a turbocharger according to claim 6, wherein control is performed so that fuel injection is performed both in the second period.

Images