JP5625544B2 - Control unit for direct injection gasoline engine - Google Patents

Description

  The technology disclosed herein relates to a control device for a direct injection gasoline engine that directly injects fuel into a cylinder.

  In a direct injection gasoline engine that injects fuel containing gasoline directly into the cylinder through the fuel injection valve, the fuel is injected at a relatively early timing of the intake stroke such that the piston is located near the top dead center. In this case, the fuel adhering to the top surface of the piston increases, and smoke due to unburned fuel tends to occur, while the intake stroke in which the piston is located in the middle or later of the stroke When the fuel is injected at this timing, the amount of fuel adhering to the cylinder inner wall facing the fuel injection valve increases, so that the amount of fuel entering the oil pan increases and oil dilution is likely to occur. Thus, when the fuel injection timing is early, smoke tends to increase, and when the fuel injection timing is late, oil dilution tends to increase.

  On the other hand, for example, Patent Document 1 describes a configuration in which fuel adhering to a piston top surface or a cylinder inner wall surface is reduced by split injection of fuel to reduce oil dilution and smoke. This document also describes that the deterioration of fuel consumption and the occurrence of smoke are suppressed by advancing the timing of divided injection when the engine is cold compared to the divided injection timing during warm.

JP 2009-121416 A

  However, as described above, since the oil dilution and the generation of smoke have opposite characteristics with respect to the delay of the fuel injection timing, the engine is warmed up as described in Patent Document 1. In the meantime, if the fuel injection timing is only advanced, the oil dilution and the generation of smoke are only within an allowable range.

  The technology disclosed herein has been made in view of the above points, and the purpose of the technology is to avoid the adverse effects on the engine caused by oil dilution before the engine warm-up is completed. It is to further suppress the occurrence of.

  After the engine is completely warmed up, the temperature of the oil is relatively high, so that the fuel mixed therein can evaporate. For this reason, after the engine is completely warmed up, adverse effects on the engine due to oil dilution can be eliminated. Oil dilution can be most problematic when the engine is shut down before it is completely warmed up and fuel that is mixed into the oil gradually accumulates.

  Therefore, the technology disclosed here is a situation in which oil dilution does not become a problem or hardly becomes a problem. Specifically, when the engine is completely warmed up when the engine was stopped last time, At the time of starting the engine this time, there is no or little fuel in the oil, and it is acceptable that some fuel is allowed to enter the oil when the engine is not warmed up Therefore, by performing control giving priority to smoke suppression over oil dilution, it was decided to suppress the occurrence of smoke as much as possible while avoiding adverse effects on the engine due to oil dilution.

Specifically, a control device for a direct injection gasoline engine disclosed herein includes an engine main body to which fuel containing gasoline is supplied, and fuel injection for injecting the fuel into a cylinder in which a piston is inserted in the engine main body. a valve, through control of the fuel injection valve, and control means for controlling the fuel supply to the cylinder.

The fuel injection valve is set so that the fuel injection direction in the cylinder is directed to the inner wall surface of the cylinder or the top surface of the piston in the vicinity of top dead center, and the control means includes the engine body Based on the temperature of the engine main body detected when the engine main body was stopped by the previous key-off in the unwarmed state before the warm-up of the engine is completed, the temperature at the previous stop is equal to or higher than the complete warm-up temperature of the engine main body. When the fuel injection timing during the intake stroke is set to a predetermined timing on the retard side, when the previous stop temperature is lower than the complete warm-up temperature of the engine body, the fuel injection timing during the intake stroke is set. The advance angle is set with respect to the predetermined time.

  Here, more specifically, the fuel injection valve indicates that the fuel injection direction in the cylinder is directed to the inner surface of the cylinder or the top surface of the piston in the vicinity of the top dead center. When the fuel is injected from the fuel injection valve when the piston is located near the top dead center at a relatively early time, the fuel tends to adhere to the top surface of the piston, while the intake air This means that when fuel is injected when the piston is located at the middle or after the stroke at a relatively late time in the stroke, the fuel tends to adhere to the inner wall surface of the cylinder. This may include the case where the fuel injection valve is located, for example, on one side of the cylinder head and below the intake port.

  In addition, “an unwarmed state before the engine warm-up is completed” is defined as a state before the engine temperature, that is, the engine water temperature or the oil temperature reaches a preset warm-up temperature. Is possible.

“When the previous stop temperature is equal to or higher than the complete warm-up temperature of the engine body, the fuel injection timing during the intake stroke is set to a predetermined timing on the retard side” means that the previous stop temperature is equal to or higher than the complete warm-up temperature. As a result, it is assumed that no or little fuel is mixed in the oil at the start of this time, so smoke is sufficiently suppressed even if it is somewhat disadvantageous for oil dilution. This means that the fuel injection timing is set to a predetermined timing on the retard side. As a result, the occurrence of smoke is sufficiently reduced while avoiding adverse effects on the engine due to oil dilution.

In contrast, "when the previous stop temperature is lower than the full warm-up temperature of the engine body, the fuel injection timing during the intake stroke is set to the advance side than the predetermined time" means that, at the last stop Since the temperature is lower than the complete warm-up temperature, there is a possibility that fuel is mixed in the oil at the time of starting this time, so that the predetermined dilution described above is performed so that the oil dilution is sufficiently suppressed and the smoke is also suppressed. Compared to the injection timing at the timing, the injection timing is advantageous for oil dilution but disadvantageous for smoke (however, the injection timing that can reduce both oil dilution and the occurrence of smoke as much as possible) ) Can be defined.

  According to the above configuration, when the engine body is not warmed up, the control for changing the fuel injection timing is executed according to the temperature of the engine body at the previous stop. In other words, when the temperature of the engine body at the time of the previous stop is lower than the complete warm-up temperature, the fuel mixed in the oil does not evaporate sufficiently, and there is a high possibility that the fuel is mixed in the oil when the engine is started. Therefore, in order to sufficiently suppress the occurrence of oil dilution and reduce the occurrence of smoke, the fuel injection timing is set relatively on the advance side. As a result, as described above, both oil dilution and smoke can be reduced as much as possible. Therefore, it is possible to reliably avoid the accumulation of fuel in the oil and to prevent the engine due to oil dilution. Smoke can be suppressed as much as possible while avoiding adverse effects.

  On the other hand, when the temperature of the engine body at the time of the previous stop is equal to or higher than the complete warm-up temperature, even if the fuel is mixed in the oil, it is evaporated, and the fuel is not mixed in the oil when the engine is started this time Or it can be estimated that there is almost no contamination. For this reason, even if some amount of fuel is mixed in the oil, it can be allowed without causing a serious problem. Therefore, the fuel injection timing is set to a predetermined timing on the relatively retarded side. Thereby, the generation of smoke can be reduced as compared with the case where the fuel injection timing is set to the advance side. Therefore, in this case, the generation of smoke can be further reduced while avoiding adverse effects on the engine due to oil dilution.

  The control means sets the start timing of the fuel injection to the middle period when the intake stroke is divided into the first period, the middle period, and the second period when the previous stop temperature is equal to or higher than the complete warm-up temperature of the engine body. It is good. By doing so, it is possible to reduce smoke most, and as described above, it is possible to further reduce the occurrence of smoke while avoiding adverse effects on the engine due to oil dilution.

  When the temperature at the previous stop is lower than the complete warm-up temperature of the engine body, the control means determines that the start-up temperature is lower than a predetermined temperature based on the temperature of the engine body detected at the current start-up of the engine body. When the temperature is low, the fuel injection timing at the intake stroke is set to a second predetermined timing on the advance side, and when the starting temperature is equal to or higher than the predetermined temperature, the fuel injection timing at the intake stroke is set to the second predetermined timing. It is good also as setting to the retard side rather than time.

  According to this configuration, when the temperature at the previous stop is lower than the complete warm-up temperature of the engine body, in other words, it is estimated that fuel is mixed in the oil when the engine is started. When it should be sufficiently suppressed, control for changing the fuel injection timing is executed in accordance with the temperature of the engine body detected at the time of the current start. That is, when the starting temperature is lower than the predetermined temperature, the temperature difference between the starting temperature and the complete warm-up temperature of the engine body is large, so it takes a relatively long time for the engine body to reach full warm-up, In the meantime, a relatively large amount of fuel is mixed in the oil, and there is a possibility that the fuel accumulates in the oil. Therefore, when the starting temperature is lower than the predetermined temperature, the fuel injection timing is set to the second predetermined timing on the advance side in order to surely prevent the fuel from being mixed into the oil. Thereby, smoke is also suppressed while sufficiently suppressing oil dilution.

  On the other hand, when the starting temperature is equal to or higher than the predetermined temperature, the temperature difference between the starting temperature and the complete warm-up temperature of the engine body is small. Less fuel is mixed. For this reason, even if some fuel is allowed to be mixed in the oil until the engine main body is completely warmed up, all or almost all of the fuel mixed in the oil after the engine main body is fully warmed up Can evaporate. That is, fuel does not accumulate in the oil, and adverse effects on the engine can be avoided. Therefore, in the above configuration, when the starting temperature is equal to or higher than the predetermined temperature, the fuel injection timing is set to be higher than the second predetermined timing in order to further suppress the generation of smoke while allowing the fuel to be mixed into the oil somewhat. Set to the retard side. As a result, the generation of smoke can be suppressed as much as possible while avoiding adverse effects on the engine due to oil dilution.

  As described above, the control device for the direct injection gasoline engine estimates the amount of fuel mixed in the oil at the start of the current engine body according to the temperature of the engine body at the previous stop, Accordingly, the fuel injection timing is changed into a relatively advanced timing that takes into account both oil dilution and smoke generation, and a relatively retarded timing that emphasizes smoke. Thus, it is possible to reduce the occurrence of smoke as much as possible while reliably avoiding an adverse effect on the engine due to fuel accumulation.

It is the schematic which shows the structure of a direct injection gasoline engine and its control apparatus. It is a figure which shows the relationship between smoke generation and oil dilution with respect to fuel injection timing. It is a figure explaining the difference in the adhesion state of the fuel to a cylinder inner wall surface and a piston top surface with respect to injection time, (a) When injection time is relatively late, (b) When injection time is relatively early . It is a flowchart which concerns on control of the fuel injection timing which an engine controller performs. It is an example of the map of the fuel injection timing with respect to the engine water temperature at the time of starting.

  Hereinafter, a control device for a direct injection gasoline engine will be described with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature. As shown in FIG. 1, the engine system includes an engine (engine body) 1, various actuators associated with the engine 1, various sensors, and an engine controller 100 that controls the actuators based on signals from the sensors. .

  The engine 1 is a spark ignition type internal combustion engine, and has first to fourth four cylinders 11, 11,. The engine 1 is mounted on a vehicle such as an automobile, and its output shaft is connected to drive wheels via a transmission, although not shown. The vehicle is propelled by the output of the engine 1 being transmitted to the drive wheels. The engine 1 includes a cylinder block 12 and a cylinder head 13 mounted thereon, and cylinders 11, 11,... Are formed inside the block 12. As is well known, a crankshaft 14 is rotatably supported on the cylinder block 12 by a journal, a bearing or the like, and this crankshaft 14 is connected to a piston 15 via a connecting rod 16.

  The piston 15 is slidably inserted into each cylinder 11, and defines a combustion chamber 17 together with the cylinder 11 and the cylinder head 13. Although only one is shown in FIG. 1, two intake ports 18 are formed in the cylinder head 13 for each cylinder 11, and each communicates with the combustion chamber 17. Similarly, two exhaust ports 19 are formed in the cylinder head 13 for each cylinder 11, and each communicates with the combustion chamber 17. As shown in the figure, the intake valve 21 and the exhaust valve 22 are arranged so that the intake port 18 and the exhaust port 19 can be shut off (closed) from the combustion chamber 17, respectively. The intake valve 21 is driven by the intake valve drive mechanism 30 and the exhaust valve 22 is driven by the exhaust valve drive mechanism 40, thereby reciprocating at a predetermined timing to open and close the intake port 18 and the exhaust port 19.

  The intake valve drive mechanism 30 and the exhaust valve drive mechanism 40 have an intake camshaft 31 and an exhaust camshaft 41, respectively. The camshafts 31 and 41 are connected to the crankshaft 14 via a power transmission mechanism such as a known chain / sprocket mechanism. As is well known, the power transmission mechanism rotates the camshafts 31 and 41 once while the crankshaft 14 rotates twice.

  The intake valve drive mechanism 30 includes a hydraulic or mechanical phase variable mechanism (VVT) 32 that can continuously change the phase of the intake camshaft 31 within a predetermined angle range. Yes. Although not shown, the VVT 32 is attached to the front end portion of the engine 1 in the intake camshaft 31. The phase angle of intake camshaft 31 is detected by cam phase sensor 35, and the output signal is input to engine controller 100.

  The spark plug 51 is attached to the cylinder head 13 by a known structure such as a screw. The electrode of the spark plug 51 faces the ceiling of the combustion chamber 17. The ignition system 52 receives a control signal from the engine controller 100 and energizes the spark plug 51 so that a spark is generated at a desired ignition timing.

  The fuel injection valve 53 has a known structure, for example, using a bracket. In this embodiment, the fuel injection valve 53 is attached to one side (the intake side in the illustrated example) of the cylinder head 13. The tip of the fuel injection valve 53 faces the combustion chamber 17 so as to be positioned below the two intake ports 18 in the vertical direction and in the middle of the two intake ports 18 in the horizontal direction. The arrangement of the fuel injection valve 53 is not limited to this. The fuel injection valve 53 is, for example, a multi-injection type fuel injection valve, but is not limited thereto.

  The fuel supply system 54 includes a high-pressure pump (fuel injection pump) that boosts and supplies fuel to the fuel injection valve 53, piping and hoses that supply fuel from a fuel tank to the high-pressure pump, and the fuel injection valve 53. And an electric circuit for driving. As described above, when the fuel injection valve 53 is a multi-injection type, the fuel injection pressure is set to be relatively high in order to inject fuel from the minute injection port. The electric circuit receives a control signal from the engine controller 100 and operates the fuel injection valve 53 to inject a desired amount of fuel into the combustion chamber 17 at a predetermined timing. The engine 1 is a so-called direct injection engine.

  The intake port 18 communicates with the surge tank 55 a through an intake path 55 b in the intake manifold 55. An intake air flow from an air cleaner (not shown) passes through the throttle body 56 and is supplied to the surge tank 55a. A throttle valve 57 is disposed on the throttle body 56. The throttle valve 57 throttles the intake air flow toward the surge tank 55a and adjusts the flow rate as is well known. The throttle actuator 58 receives the control signal from the engine controller 100 and adjusts the opening degree of the throttle valve 57.

  The exhaust port 19 communicates with a passage in the exhaust pipe as is well known by an exhaust path in the exhaust manifold 60. An exhaust gas purification system having one or more catalytic converters 61 is disposed in the exhaust passage downstream of the exhaust manifold 60. The catalytic converter 61 can be a well-known three-way catalyst, lean NOx catalyst, oxidation catalyst, or the like, and any other type that can meet the purpose of exhaust gas purification by a specific fuel control method. It may be a catalyst.

  Further, in order to circulate a part of the exhaust gas to the intake system (hereinafter also referred to as EGR), the intake manifold 55 (downstream from the throttle valve 57) and the exhaust manifold 60 are connected by an EGR pipe 62. Yes. Since the pressure on the exhaust side is higher than that on the intake side, a part of the exhaust gas flows into the intake manifold 55 (referred to as EGR gas), and is mixed with fresh air drawn from the intake manifold 55 into the combustion chamber 17. become. An EGR valve 63 is disposed in the EGR pipe 62, and the flow rate of EGR gas is adjusted by the valve 63. The EGR valve actuator 64 receives a control signal from the engine controller 100 and adjusts the opening degree of the EGR valve 63.

  The engine controller 100 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory that is configured by, for example, RAM and ROM, and stores a program and data, And an input / output (I / O) bus for inputting and outputting signals.

  The engine controller 100 has various inputs such as an intake air flow rate from the air flow sensor 71, an intake manifold pressure from the intake pressure sensor 72, a crank angle pulse signal from the crank angle sensor 73, and an engine water temperature from the water temperature sensor 78. Receive. The engine controller 100 calculates the engine speed based on, for example, a crank angle pulse signal. The engine controller 100 also receives an input of the oxygen concentration of the exhaust gas from the oxygen concentration sensor 74. Further, the engine controller 100 receives an accelerator opening signal from an accelerator opening sensor 75 that detects the amount of depression of the accelerator pedal. The engine controller 100 also receives a vehicle speed signal from a vehicle speed sensor 76 that detects the rotational speed of the output shaft of the transmission. Further, a knock sensor 77 including an acceleration sensor that converts the vibration of the cylinder block 12 into a voltage signal and outputs the voltage signal is attached to the cylinder block 12, and the output signal is also input to the engine controller 100.

  The engine controller 100 calculates the following control parameters of the engine 1 based on the input as described above. For example, a desired throttle opening signal, fuel injection pulse, ignition signal, valve phase angle signal, EGR opening signal, and the like. The engine controller 100 outputs these signals to the throttle actuator 58, the fuel supply system 54, the ignition system 52, the VVT 32, the EGR valve actuator 64, and the like.

  The most characteristic point regarding the control of the engine 1 executed by the engine controller 100 is control related to the fuel injection timing when the engine 1 is started, more specifically, when the engine 1 is not warmed up. By executing the above, the occurrence of smoke in the unwarmed state of the engine 1 is reduced as much as possible while avoiding adverse effects on the engine 1 due to oil dilution. Hereinafter, this fuel injection control will be described with reference to the drawings.

  FIG. 2 shows a case where the fuel injection timing during the intake stroke, more precisely, the fuel injection end timing is changed under the condition that the engine 1 is operated at a rotation speed of 1500 rpm and a water temperature of 50 degrees (that is, an unwarmed state). The relationship between the oil dilution rate and the amount of smoke generated is shown. As can be seen in the figure, setting the fuel injection end timing to the retarded side (left side in FIG. 2) reduces the smoke, which is advantageous for the generation of smoke, but increases the oil dilution ratio. , Disadvantageous for oil dilution. As schematically shown in FIG. 3 (a), when the fuel injection timing is set in the middle or late period of the intake stroke, the piston 15 is positioned in the middle or later of the piston stroke. Since the fuel is injected through the fuel injection valve 53, a large amount of the injected fuel adheres to the inner wall surface of the cylinder 11 facing the fuel injection valve 53 (see the hatching in the figure), while the top surface of the piston 15. This is because the amount of fuel adhering to the fuel is reduced. Conversely, setting the fuel injection timing to the advance side (right side in FIG. 2) is advantageous for oil dilution, but disadvantageous for the generation of smoke. As shown in FIG. 3B, the fuel injection timing is set in the first half of the intake stroke, so that fuel is injected through the fuel injection valve 53 when the piston 15 is located near the intake top dead center. Therefore, a large amount of injected fuel adheres to the top surface of the piston 15 (see hatching in the figure), while the amount of fuel adhering to the inner wall surface of the cylinder 11 decreases. Thus, since the oil dilution characteristic and the smoke characteristic with respect to the early fuel injection timing are opposite to each other, there is no fuel injection timing that minimizes both oil dilution and smoke generation. Therefore, if both the oil dilution and the generation of smoke are to be suppressed, the fuel injection timing is set so that the oil dilution is within the allowable range and the smoke generation is also within the allowable range. Specifically, the engine controller 100 determines the end time of fuel injection (hereinafter referred to as this fuel) in order to keep both oil dilution and smoke generation within an allowable range when the engine 1 is not warmed up (when the engine is cold). The end timing of injection may be simply referred to as fuel injection timing) is set to BTDC285 ° CA, which is a relatively advanced angle side. Hereinafter, this fuel injection timing may be referred to as cold injection timing (see also FIG. 5).

  On the other hand, after the engine 1 is completely warmed up, even if some fuel adheres to the inner wall surface of the cylinder 11, it is easy to vaporize, so that the amount of fuel mixed in the oil is reduced and the fuel is mixed into the oil temporarily. Even if the temperature of the oil is high, it is easy for the fuel to evaporate, and the accumulation of the fuel in the oil is suppressed. For this reason, after the engine 1 is completely warmed up, the fuel injection timing is set to be retarded from the cold injection timing so that the generation of smoke is most suppressed. Specifically, after the engine controller 100 is completely warmed up (more specifically, as described later, when the engine water temperature is a second temperature or higher, which is lower than the fully warmed-up temperature), The fuel injection timing is set to BTDC 260 ° CA. This is equivalent to setting the start timing of fuel injection to the middle period when the intake stroke is divided into the first, middle and latter periods, and this injection timing is sometimes called warm injection timing with an emphasis on smoke. Yes (see also FIG. 5).

  However, as described above, setting the fuel injection timing to the cold injection timing can only keep the oil dilution and the generation of smoke within the allowable range. When the machine reaches the machine, almost no oil remains in the oil, and the adverse effects on the engine due to the oil dilution can be eliminated. That is, the oil dilution can be a problem substantially because the engine 1 is stopped before the engine is completely warmed up, and the fuel mixed in the oil is gradually accumulated.

  Therefore, the engine controller 100 avoids adverse effects on the engine 1 due to oil dilution, and further reduces the occurrence of smoke. When the engine 1 is stopped, control for changing the fuel injection timing in the unwarmed state at the time of starting the engine is executed according to whether or not the engine 1 has been completely warmed up. More specifically, when the engine water temperature was equal to or higher than the complete warm-up temperature when the engine was stopped last time, the fuel is not mixed or hardly mixed in the oil at the start of this time. From the standpoint that it is acceptable to allow some fuel to enter the oil in an unwarmed state, the retarded fuel injection timing, that is, the warm injection timing, which emphasizes the suppression of smoke rather than oil dilution. Set to (predetermined time).

  On the other hand, when the engine water temperature is lower than the fully warmed-up temperature when the engine is stopped last time, there is a high possibility that fuel is mixed in the oil at the time of the current start-up. It is preferable to consider both smoke generation. However, from the viewpoint of suppressing the generation of smoke as much as possible, the fuel injection timing is changed between the cold injection timing and the warm injection timing according to the water temperature at the time of starting the engine.

  That is, when the engine water temperature is relatively high, since the temperature difference between the water temperature at the time of starting and the complete warm-up temperature is small, the time until the engine 1 reaches the complete warm-up is short, and the fuel mixed in the oil during that time is short. The amount is reduced. For this reason, even if some fuel is allowed to be mixed into the oil until the engine 1 is completely warmed up, all of the fuel mixed in the oil after the engine 1 is completely warmed up or its Most can evaporate. That is, fuel does not accumulate in the oil, and adverse effects on the engine 1 can be avoided. Therefore, the engine controller 100 sets the fuel injection timing to the cold injection timing (second predetermined timing) when the water temperature at the start of the engine 1 is lower than the predetermined temperature (first temperature). When the water temperature at the time of starting the engine 1 is equal to or higher than the first temperature, the fuel injection timing is delayed from the cold injection timing in order to further suppress the generation of smoke while allowing the fuel to be mixed somewhat. Set to the corner side.

  Next, the above-described fuel injection timing control executed by the engine controller 100 will be described with reference to the flowchart shown in FIG. This flow starts by stopping the engine 1 in the operating state. First, in step S41, the water temperature at the time of key-off, in other words, when the engine 1 is stopped is read based on the signal from the water temperature sensor 78, and is read. Stored in the engine controller 100.

  The subsequent step S42 is related to the start of the engine 1. In this step S42, the engine water temperature at the previous key-off saved in the engine controller 100 in the previous step S41 is read, and based on the signal from the water temperature sensor 78, this time Read the engine water temperature when the engine starts. Then, in step S43, it is determined whether or not the engine water temperature at the previous key-off is less than a preset complete warm-up temperature (for example, 80 degrees). When the engine water temperature at the time of key-off is equal to or higher than the complete warm-up temperature (NO), the process proceeds to step S44, while when the engine water temperature at the time of key-off is lower than the complete warm-up temperature (when YES). The process proceeds to step S45.

  In step S44, the engine water temperature at the time of key-off is equal to or higher than the complete warm-up temperature, and as described above, it can be estimated that the amount of fuel mixed in the oil at the time of engine startup this time is zero or relatively small. Even if some oil dilution is allowed when the engine is not warmed up, there is little or no influence on the engine 1. Therefore, in order to attach importance to the suppression of smoke, the fuel injection timing is set to the retarded warm injection timing, that is, BTDC 260 ° CA as shown in FIG.

  On the other hand, in step S45, it is determined whether or not the engine water temperature at the current engine start is less than a preset first temperature. As shown in FIG. 5, when the first temperature is relatively low and the engine water temperature is lower than the first temperature, the fuel adhering to the inner wall surface of the cylinder 11 is difficult to vaporize, and the engine 1 Since it takes a long time to complete warm-up, the temperature is appropriately set as a temperature during which a relatively large amount of fuel may be mixed into the oil, for example, about 10 degrees. In step S45, when the water temperature at the time of starting the engine this time is lower than the first temperature (when YES), the process proceeds to step S46 assuming that the engine 1 is cold, and as shown in FIG. Fuel injection is executed at the injection timing (BTDC285 ° CA). Thereafter, the fuel injection timing is retarded in accordance with the increase in the engine water temperature. In this way, in step S46, it is possible to keep the generation of smoke within an allowable range while sufficiently suppressing oil dilution.

  On the other hand, in step S45, when the engine water temperature at the time of the current engine start is equal to or higher than the first temperature (NO), the process proceeds to step S47. In step S47, the engine water temperature at the time of the current engine start is It is determined whether the temperature is lower than the second temperature. As shown in FIG. 5, when the second temperature is lower than the complete warm-up temperature of the engine 1 and higher than the first temperature, and the engine water temperature is higher than the second temperature, the cylinder 11 Since the fuel adhering to the inner wall is easy to vaporize and it takes almost no time until the engine 1 is completely warmed up, the amount of fuel mixed in the oil is small during that time. The temperature is appropriately set as a temperature at which the fuel does not (almost) exist in the oil, and is set to about 60 degrees, for example. In step S47, when the engine water temperature at the start of the current engine is equal to or higher than the second temperature (NO), the engine 1 is warm and the routine proceeds to step S48, where the warm injection timing (BTDC 260 °) is reached. The fuel injection is executed at CA). Thus, in step S48, it is possible to sufficiently suppress the occurrence of smoke while avoiding adverse effects on the engine due to oil dilution.

  On the other hand, in step S47, when the engine water temperature at the current engine start is less than the second temperature (YES), it is determined that the engine 1 is semi-warm and the process proceeds to step S49. In step S49, a correction value of the injection timing is calculated based on the difference between the engine water temperature at the start and the water temperature at the complete warm-up, and the timing is retarded by the correction value from the cold injection timing. Perform fuel injection. Thus, for example, as shown in FIG. 5, when the water temperature at the start of the engine is between the first temperature and the second temperature, linear interpolation is performed between the cold injection timing and the warm injection timing. Fuel injection is executed at the set injection timing. After that, the injection timing is changed to the retard side as the engine water temperature rises. For example, the injection timing may be changed to the retard side along the oblique line in FIG. Thus, in step S49, it is possible to reduce the occurrence of smoke as much as possible while avoiding adverse effects on the engine 1 due to oil dilution.

  Thus, according to the fuel injection control of the engine 1 described above, even when the engine 1 is not warmed up, when the water temperature of the engine 1 at the previous stop is equal to or higher than the complete warm-up temperature, the engine 1 is started. Since it can be estimated that there is (almost) no fuel in the oil, the fuel injection timing is retarded in order to suppress the generation of smoke while allowing some fuel to enter the oil. The warm injection time is set (step S44). As a result, the occurrence of smoke can be significantly suppressed while avoiding adverse effects on the engine 1 due to oil dilution.

  On the other hand, when the water temperature of the engine 1 at the previous stop is less than the complete warm-up temperature, the start-up water temperature is relatively high according to the water temperature at the start of the engine 1, and the engine can be fully warmed up in a short time. In such a case, in the same manner as described above, the fuel injection timing is retarded from the cold injection timing in order to suppress the generation of smoke while allowing the fuel to be mixed somewhat into the oil. (Steps S48 and S49). As a result, the generation of smoke can be suppressed as much as possible while avoiding adverse effects on the engine due to oil dilution.

  Such control is performed when the fuel spray penetrating force becomes relatively strong by setting the fuel injection valve 53 to be a multi-injection type and a relatively high fuel injection pressure, in other words, to the inner wall surface of the cylinder 11. This is particularly effective when the amount of fuel attached increases and oil dilution tends to occur. Of course, the above-described control can be performed when a single injection type fuel injection valve is employed.

  In the flowchart shown in FIG. 4 and the map shown in FIG. 5, the fuel injection timing is changed based on the engine water temperature. Instead, the fuel injection timing is changed based on the temperature of the engine oil. You may make it perform.

  The fuel injection described above can include both a case where a required amount of fuel is injected once and a case where fuel is divided into a plurality of times and injected. For example, in the case of split injection, changing the timing may be performed by changing the entire fuel injection to the retard side and the advance side.

1 Direct-injection gasoline engine (engine body)
100 Engine controller (control means)
11 cylinder 15 piston 53 fuel injection valve

Claims (3)

An engine body supplied with fuel containing gasoline;
A fuel injection valve that injects the fuel into a cylinder in which a piston is inserted in the engine body;
Through the control of the fuel injection valve, and control means for controlling the fuel supply to the cylinder,
The fuel injection valve is set so that the fuel injection direction in the cylinder is directed to the inner wall surface of the cylinder or the top surface of the piston in the vicinity of the top dead center,
Based on the temperature of the engine main body detected when the engine main body was stopped by the previous key-off in the unwarmed state before the completion of warming up of the engine main body, the control means determines that the temperature at the previous stop is the engine When the temperature is equal to or higher than the complete warm-up temperature of the main body, the fuel injection timing during the intake stroke is set to a predetermined timing on the retard side, while when the previous stop temperature is lower than the complete warm-up temperature of the engine main body, the intake stroke control device for a direct injection gasoline engine for setting the fuel injection timing to the advance side than the predetermined timing during.
In the direct injection gasoline engine control device according to claim 1,
When the temperature at the previous stop is equal to or higher than the complete warm-up temperature of the engine body, the control means sets the start timing of the fuel injection to the middle period when the intake stroke is divided into the first period, the middle period, and the second period. A control unit for an injection gasoline engine. In the direct injection gasoline engine control device according to claim 1,
When the previous stop temperature is lower than the complete warm-up temperature of the engine body,
When the starting temperature is lower than a predetermined temperature based on the temperature of the engine body detected at the current start of the engine body, the fuel injection timing at the intake stroke is set to a second predetermined timing on the advance side. On the other hand, a control device for a direct-injection gasoline engine that sets the fuel injection timing during the intake stroke to a more retarded side than the second predetermined timing when the starting temperature is equal to or higher than the predetermined temperature.

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