JP2011140934A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem of becoming unable to properly start an engine, when time until fuel pressure (actual fuel pressure) in a delivery pipe 44 becomes its target value, becomes long after starting cranking, due to a machine difference in a high pressure fuel pump 16 and the deterioration with the lapse of time. <P>SOLUTION: A fuel injection mode of a fuel injection valve 46 is selected in the timing when a predetermined time passes, based on the fact that the actual fuel pressure becomes less than a target value in the timing when the predetermined time passes after starting the cranking and that an increase quantity of the actual fuel pressure becomes less than a predetermined value during the finishing timing of one delivery stroke of the high pressure fuel pump 16. Actually, among a mode when a fuel injection period of the fuel injection valve 46 is both an intake stroke and a compression stroke and a mode when the fuel injection period of the fuel injection valve 46 is limited to the intake stroke, a mode of being limited to the intake stroke is selected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine that is applied to a fuel injection system of an internal combustion engine that directly injects fuel supplied from a pressure accumulating vessel capable of accumulating fuel in a high pressure state into a combustion chamber of the internal combustion engine.

  This type of control device includes a pressure accumulator that can accumulate fuel in a high pressure state, a fuel injection valve that directly injects fuel supplied from the pressure accumulator into a combustion chamber of an internal combustion engine, and fuel from a fuel tank. 2. Description of the Related Art There is known a fuel injection system for an internal combustion engine that includes an engine-driven fuel pump that supplies and discharges the pressure accumulating vessel and a fuel pressure detecting unit that detects a fuel pressure of the pressure accumulating vessel. In addition, as shown in, for example, Patent Document 1 below, from when the initial rotation is started to be applied to the crankshaft of the internal combustion engine (after cranking is started), until the fuel pressure of the pressure accumulator becomes equal to or higher than a predetermined value. A fuel injection valve that prohibits fuel injection is also known. Specifically, the fuel injection pressure at the start of the internal combustion engine is increased by quickly increasing the fuel pressure in the pressure accumulator vessel after cranking is started. As a result, it is possible to suppress the deterioration of the combustion state by promoting atomization of the fuel injected from the fuel injection valve, thereby improving the startability of the internal combustion engine.

JP-A-11-270385

  By the way, when the fuel injection system is used in an environment where the temperature is low (low temperature environment), the rotation of the crankshaft is hindered by an increase in mechanical friction due to an increase in the viscosity of engine oil or fuel. The power can increase. In this case, the rotational speed of the crankshaft at the time of cranking may decrease, and the discharge amount per unit time of the fuel pump may decrease. In addition, if the battery charge amount decreases due to the use of the battery as a power supply source of the starter for cranking in a low temperature environment, deterioration of the battery over time, insufficient charging of the battery, etc., the crankshaft at the time of cranking The rotational speed of the fuel pump may decrease, and the discharge amount of the fuel pump may decrease. Furthermore, the discharge amount of the fuel pump may decrease due to mechanical individual differences of the fuel pump or deterioration with time. Here, when the discharge amount of the fuel pump decreases, the pressure of the fuel supplied to the fuel injection valve decreases due to a delay in the increase in the fuel pressure in the pressure accumulating container after cranking is started. For this reason, there is a possibility that the internal combustion engine cannot be started properly due to the fact that fuel injection for starting the internal combustion engine cannot be performed properly.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine that can appropriately start the internal combustion engine.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  The invention according to claim 1 is a pressure accumulating container capable of accumulating fuel in a high pressure state, a fuel injection valve for directly injecting fuel supplied from the pressure accumulating container into a combustion chamber of an internal combustion engine, and fuel from a fuel tank. Applied to a fuel injection system of an internal combustion engine comprising an engine-driven fuel pump that supplies and discharges to the pressure accumulator and a fuel pressure detecting means for detecting the fuel pressure of the pressure accumulator, and cranking is started Fuel injection at the start of fuel injection of the fuel injection valve based on the degree of increase in the detected fuel pressure during a specified timing including one discharge stroke of the fuel pump before fuel injection of the fuel injection valve is started An injection mode selection means for selecting a mode is provided.

  There is a correlation between the discharge amount of the fuel pump and the increase in the fuel pressure of the pressure accumulating container before the fuel injection of the fuel injection valve is started. For this reason, the degree of increase in the fuel pressure of the pressure accumulator vessel during the specified timing including one discharge stroke of the fuel pump is a parameter for grasping the fuel pressure of the pressure accumulator vessel at the fuel injection start timing. In view of this point, in the above invention, fuel injection is performed based on the degree of increase in the detected fuel pressure (actual fuel pressure) between the specified timings before cranking is started and before fuel injection of the fuel injection valve is started. The fuel injection mode at the start of fuel injection of the valve is selected. Thereby, it is possible to set an appropriate fuel injection mode in accordance with the fuel injection pressure at the time of starting the internal combustion engine, and thus to appropriately start the internal combustion engine.

  The invention of claim 2 further comprises permission means for permitting fuel injection of the fuel injection valve in a specified mode based on the detected fuel pressure being equal to or higher than a specified pressure in the invention of claim 1. The injection mode selection means determines whether or not to change the fuel injection mode from the specified mode when the fuel injection is not permitted by the permission means until a predetermined time elapses after the cranking is started. It is characterized by.

  In the above-described invention, by providing the permission means, the fuel injection pressure at the fuel injection start timing is increased to promote atomization of the injected fuel, thereby improving the startability of the internal combustion engine. However, when the discharge amount of the fuel pump decreases due to mechanical individual differences of the fuel pump, the degree of increase in the fuel pressure of the pressure accumulator vessel decreases. For this reason, it takes a long time until fuel injection of the fuel injection valve is permitted, and the internal combustion engine may not be started properly. Therefore, in the above invention, when fuel injection is not permitted until a predetermined time elapses after cranking is started, it is determined whether or not to change the fuel injection mode from the specified mode. Thereby, the fuel injection mode according to the fuel injection pressure can be set appropriately, and as a result, the internal combustion engine can be started more appropriately.

  The invention according to claim 3 is the invention according to claim 2, wherein the detected fuel pressure at the timing when the predetermined time elapses is less than the specified pressure, and the increase degree of the detected fuel pressure is greater than or equal to a predetermined value. And further comprising an extension means for extending the predetermined time.

  The predetermined time is usually set to a short time in order to avoid a decrease in startability of the internal combustion engine due to a long time until fuel injection of the fuel injection valve is permitted. Then, the shorter the predetermined time, the lower the actual fuel pressure at the timing when the predetermined time elapses. Here, when the actual fuel pressure is less than the specified pressure at the timing when the predetermined time elapses and the actual fuel pressure is increased, the actual fuel pressure may be increased to the specified pressure within a short time. . In view of this point, in the above-described invention, the predetermined time is extended based on the increase degree of the actual fuel pressure becoming a predetermined value or more. Thereby, it is possible to suitably satisfy both requirements of setting the predetermined time to a short time and setting the fuel injection mode corresponding to the fuel injection pressure as early as possible after cranking is started. .

  The invention according to claim 4 is the invention according to claim 3, wherein the fuel injection system further includes an in-vehicle storage battery and a starter that performs the cranking by being fed from the in-vehicle storage battery. The extending means extends the predetermined time only once.

  If the predetermined time is excessively extended, the drive time of the starter becomes long, so that the amount of power stored in the in-vehicle storage battery decreases excessively, and cranking may not be performed properly. In this regard, in the above invention, since the number of times of extension of the predetermined time is set to one, it is possible to avoid an excessive decrease in the amount of power stored in the in-vehicle storage battery, and thus it becomes impossible to perform cranking appropriately. It can be suitably avoided.

  According to a fifth aspect of the present invention, in the third or fourth aspect of the invention, the extension time of the predetermined time is variably set based on at least one of the temperature of the cooling water for cooling the internal combustion engine and the engine speed. The apparatus further comprises means.

  In the said invention, predetermined time can be extended appropriately by using the said parameter.

  The invention according to claim 6 is the invention according to any one of claims 2 to 5, wherein the injection mode selection means is configured such that the detected fuel pressure at a timing when the predetermined time elapses is less than the specified pressure. And selecting a mode in which the degree of separation between the fuel injection start timing of the fuel injection valve and the compression top dead center is greater than the specified mode based on the detected increase in the fuel pressure being less than a predetermined value. The fuel injection of the fuel injection valve is permitted at the timing when the predetermined time elapses.

  When the actual fuel pressure at the timing when the predetermined time elapses is less than the specified pressure and the degree of increase in the actual fuel pressure is small, it is usually difficult to increase the actual fuel pressure to the specified pressure within a short time thereafter. For this reason, there is a possibility that the internal combustion engine cannot be started properly due to a long time until fuel injection of the fuel injection valve is permitted. Here, in the above invention, in view of the fact that the pressure in the combustion chamber decreases as the degree of separation between the compression top dead center and the fuel injection start timing increases, the fuel injection mode of the above aspect is selected and the fuel injection valve performs fuel injection. to approve. Thereby, even if it is a case where the discharge amount of a fuel pump falls and the raise of an actual fuel pressure is delayed, an internal combustion engine can be started appropriately.

  According to a seventh aspect of the present invention, in the sixth aspect of the invention, the specified pressure is set to a first specified pressure, and a second specified pressure that is lower than the first specified pressure is set. And a mode larger than the specified mode is selected based on the fact that the detected fuel pressure at the timing when the predetermined time elapses is less than the second specified pressure.

  In the above invention, even if the actual fuel pressure at the timing when the predetermined time elapses becomes less than the first specified pressure, it is possible to inject fuel in the vicinity of the compression top dead center as long as it becomes equal to or higher than the second specified pressure. For this reason, the first specified pressure can be set to a relatively high value, and when the actual fuel pressure becomes equal to or higher than the first specified pressure by the timing when the predetermined time elapses, the fuel injection pressure is sufficiently high. It is possible to inject fuel.

  The invention according to claim 8 is the invention according to claim 7, wherein the specified pressure setting means variably sets the second specified pressure based on a temperature of cooling water for cooling the internal combustion engine. To do.

  In the above invention, by variably setting the second specified pressure in the above aspect, it is possible to suppress the deterioration of the combustion state at the start of the internal combustion engine as much as possible.

  The invention according to claim 9 is the invention according to any one of claims 2 to 8, wherein the predetermined time is determined based on at least one of a temperature of cooling water for cooling the internal combustion engine and an engine speed. It further comprises means for variably setting.

  In the said invention, predetermined time can be set appropriately according to the condition where the said fuel injection system is used.

  The invention according to claim 10 is the invention according to any one of claims 1 to 9, wherein the fuel injection mode includes a mode in which a fuel injection period of the fuel injection valve includes a compression stroke of the internal combustion engine; The fuel injection period includes a mode limited to an intake stroke of the internal combustion engine.

  The fuel injection pressure required for the fuel injection valve is lower in the intake stroke than in the compression stroke of the fuel injection period. Here, in the above invention, by including the mode of the above aspect as the fuel injection mode, it is possible to set a more appropriate fuel injection mode in accordance with the fuel injection pressure when the internal combustion engine is started.

  According to an eleventh aspect of the present invention, in the invention according to any one of the first to tenth aspects, the specified timing is between end timings of one discharge stroke of the fuel pump.

  In the said invention, the raise degree of an actual fuel pressure can be grasped | ascertained in a short time and with high precision.

The system block diagram concerning one Embodiment. The figure which shows the setting method of the determination time concerning one Embodiment. The time chart which shows the outline | summary of the basic injection control process concerning one Embodiment. The figure which shows the setting method of the extended time concerning one Embodiment. The time chart which shows the outline | summary of the determination time extension process concerning one Embodiment. The figure which shows the setting method of the pressure | voltage rise start fuel pressure concerning one Embodiment. The time chart which shows the outline | summary of the injection mode change process concerning one Embodiment. The time chart which shows the outline | summary of the injection mode change process concerning one Embodiment. The flowchart which shows the procedure of the pressure | voltage rise control process at the time of start concerning one Embodiment.

  Hereinafter, an embodiment in which a fuel injection control device for an internal combustion engine according to the present invention is applied to an accumulator fuel injection system of a direct injection gasoline engine will be described with reference to the drawings.

  FIG. 1 shows a system configuration according to the present embodiment.

  As shown in the figure, the fuel in the fuel tank 10 is pumped up by an electric feed pump 14 through a low-pressure passage 12. The pumped fuel is adjusted to a predetermined low pressure by a low pressure regulator (not shown) and then supplied to the high pressure fuel pump 16.

  The high-pressure fuel pump 16 sucks fuel supplied from the cylinder 18, a plunger 20 that reciprocates in the cylinder 18, a pump chamber 22 that is defined by the inner peripheral wall surface of the cylinder 18 and the plunger 20, and the feed pump 14. The suction valve 26 communicates or blocks the suction port 24 and the pump chamber 22, the electromagnetic solenoid 28 that electromagnetically drives the suction valve 26, and the pump chamber 22 and the discharge port 30 that discharges fuel. It is a plunger pump configured to include a discharge valve 32. Here, the suction valve 26 is a normally open type valve element that is opened when the electromagnetic solenoid 28 is not energized, and is closed when the electromagnetic solenoid 28 is energized.

  In the high-pressure fuel pump 16 configured as described above, the plunger 20 is driven by a pump cam 36 connected to the drive shaft 34. Specifically, the drive shaft 34 is mechanically connected to the intake-side or exhaust-side cam shaft 38 and rotates in synchronization with the cam shaft 38. The camshaft 38 is rotated by rotational energy supplied from the crankshaft 40 and rotates with a predetermined speed ratio (for example, 1/2) with respect to the crankshaft 40. The pump cam 36 has a shape (pump cam profile) in which the distance between the drive shaft 34 and the outer periphery of the cam changes. As a result, the plunger 20 reciprocates in the cylinder 18 in synchronization with the rotation of the drive shaft 34. The period during which the volume in the pump chamber 22 increases due to the lowering of the plunger 20 is the suction stroke of the high-pressure fuel pump 16, and the period during which the volume in the pump chamber 22 decreases as the plunger 20 moves up is the discharge stroke of the high-pressure fuel pump 16. It becomes. Specifically, in the suction stroke of the high-pressure fuel pump 16, the fuel from the feed pump 14 is sucked into the pump chamber 22 through the suction port 24 by opening the suction valve 26. Thereafter, when the volume in the pump chamber 22 is reduced by raising the plunger 20, the fuel in the pump chamber 22 is pressurized by closing the intake valve 26 by energizing the electromagnetic solenoid 28. The When the pressure in the pump chamber 22 exceeds the valve opening pressure of the discharge valve 32, the fuel in the pump chamber 22 is discharged from the discharge port 30 through the discharge valve 32.

  The fuel discharged from the high-pressure fuel pump 16 is supplied to the pressure accumulation container (delivery pipe 44) via the high-pressure passage 42. The delivery pipe 44 stores fuel discharged and supplied from the high-pressure fuel pump 16 in a high-pressure state, and supplies high-pressure fuel to the fuel injection valve 46 of each cylinder of the engine.

  The fuel injection valve 46 is disposed so that its injection port protrudes into the combustion chamber 48 of the engine, and directly injects and supplies fuel to the combustion chamber 48. An air-fuel mixture of fuel injected from the fuel injection valve 46 and intake air introduced into the combustion chamber 48 via an intake valve (not shown) sparks from the spark plug 50 disposed so as to protrude into the combustion chamber 48. It is ignited by discharge and used for combustion. Here, when the fuel pressure (actual fuel pressure) in the delivery pipe 44 is increased, the fuel injection pressure of the fuel injection valve 46 is increased, thereby promoting atomization of the injected fuel. Thereby, the atomization of the injected fuel can be promoted, and the combustion state can be improved.

  A starter 52 is connected to the crankshaft 40. The starter 52 is started by being supplied with power from the battery 56 when the starter switch (SW54) is turned on, and applies initial rotation (cranking) to the crankshaft 40 to start the engine.

  A crank angle sensor 58 that detects the rotation angle of the crankshaft 40 is provided in the vicinity of the crankshaft 40. On the other hand, a cam angle sensor 60 that detects the rotation angle of the cam shaft 38 is provided in the vicinity of the cam shaft 38.

  The electronic control unit (ECU 62) is a control unit that operates various actuators necessary for various controls of the pressure accumulation type fuel injection system. The ECU 62 detects detection signals from a water temperature sensor 64 that detects the temperature (cooling water temperature) of the cooling water for cooling the engine, a fuel pressure sensor 66 that detects the actual fuel pressure, a crank angle sensor 58, and a cam angle sensor 60. Are input sequentially. The ECU 62 performs start control by the starter 52 based on these input signals.

  In particular, after the cranking is started, the ECU 62 performs a start-up pressure increase control process to quickly increase the actual fuel pressure to the target value (injection permission fuel pressure). In the start-up pressure increase control process, the electromagnetic solenoid 28 is energized so that the discharge amount of the high-pressure fuel pump 16 is maximized, and the fuel injection of the fuel injection valve 46 is permitted at a timing when the actual fuel pressure becomes equal to or higher than the injection permission fuel pressure. It is. This is for improving the startability of the engine and suppressing the deterioration of the exhaust characteristics. In other words, if the vehicle leaving time becomes longer and the actual fuel pressure when starting the engine decreases to atmospheric pressure, the fuel injection pressure at the start of injection becomes lower and atomization of the injected fuel is not promoted. In addition, the combustion state at the start of the engine may deteriorate, and the startability of the engine may deteriorate or the exhaust characteristics may deteriorate. For this reason, by maximizing the discharge amount of the high-pressure fuel pump 16 and waiting the fuel injection of the fuel injection valve 46 until the actual fuel pressure becomes equal to or higher than the permitted fuel pressure in order to avoid a decrease in the actual fuel pressure accompanying the fuel injection. Then, the actual fuel pressure is quickly increased to the fuel pressure permitted for injection. As a result, it is possible to improve engine startability and to suppress deterioration of exhaust characteristics.

  In addition, the ECU 62 performs intake compression split injection control at the time of starting the engine, triggered by permission of fuel injection. The intake compression split injection control is a control in which the fuel injection period of the fuel injection valve 46 is both an intake stroke and a compression stroke, and is intended to further improve engine startability and the like. Specifically, first, fuel is injected from the fuel injection valve 46 in the intake stroke. Thereby, the atomization of the fuel is sufficiently accelerated using the time until the discharge spark of the spark plug 50 is generated in the vicinity of the timing at which the top dead center of the compression stroke is generated, and a homogeneous air-fuel mixture is generated in the combustion chamber 48. . Next, a rich air-fuel mixture is generated around the spark plug 50 by injecting fuel before the occurrence of the discharge spark in the compression stroke. Thereafter, the rich air-fuel mixture is ignited by the discharge spark of the spark plug 50, and the homogeneous air-fuel mixture is used for combustion by using this as a fire type. As a result, the combustion state can be improved, and the engine startability and the like can be improved. The fuel injection amount of the fuel injection valve 46 is determined from, for example, the engine rotation speed (cranking rotation speed) during cranking based on the output value of the crank angle sensor 58, the cooling water temperature based on the output value of the water temperature sensor 64, or the like. What is necessary is just to calculate. Specifically, the fuel injection amount required for one combustion cycle may be calculated based on the cranking rotation speed, the cooling water temperature, and the like, and the calculated fuel injection amount may be assigned to each of the intake stroke and the compression stroke. Further, instead of the intake compression split injection control, control (compression stroke injection control) may be performed in which the fuel injection period of the fuel injection valve 46 is only the compression stroke. Specifically, one of the intake compression split injection control and the compression stroke injection control may be selected based on the cranking rotation speed, the cooling water temperature, and the like.

  In view of the fact that intake compression split injection control (or compression stroke injection control) is performed when the engine is started, in the present embodiment, the actual fuel pressure that can be increased by the high-pressure fuel pump 16 during the cranking. And a pressure sufficiently higher than the maximum pressure of the combustion chamber 48 assumed when the fuel injection period is the compression stroke. Thereby, fuel injection of the fuel injection valve 46 becomes possible in the compression stroke. In view of the fact that the atomization of the injected fuel is not promoted and the combustion state is deteriorated as the cooling water temperature is low, it is desirable to variably set the injection permission fuel pressure based on the cooling water temperature. Specifically, the injection permission fuel pressure may be increased as the cooling water temperature is lower.

  By the way, since the discharge amount of the high-pressure fuel pump 16 at the time of cranking decreases, the time (arrival time) from when the cranking is started until the actual fuel pressure becomes the injection permission fuel pressure becomes longer, and the engine is started appropriately. There is a risk that it will not be possible. Here, there are mainly the following three factors that decrease the discharge amount of the high-pressure fuel pump 16. First, there are mechanical individual differences (machine differences) and deterioration with time of the high-pressure fuel pump 16. In other words, when the high-pressure fuel pump 16 is mass-produced, the actual discharge amount of the high-pressure fuel pump 16 is less than the discharge amount corresponding to the discharge characteristic that becomes the central characteristic (machine difference central product), or due to deterioration over time. As a result, the discharge amount of the high-pressure fuel pump 16 decreases. Secondly, there is a storage amount of the battery 56. That is, when the amount of stored electricity (voltage) of the battery 56 is reduced, the rotation speed of the starter 52 is reduced, and the discharge amount per unit time of the high-pressure fuel pump 16 is reduced. Third, there are environments where vehicles are used. That is, under an environment where the temperature is low (low temperature environment), the viscosity of the engine oil or fuel increases, so that the force in the direction of preventing the rotation of the crankshaft 40 increases or the amount of power stored in the battery 56 decreases. As a result, the cranking rotation speed decreases, and the discharge amount per unit time of the high-pressure fuel pump 16 decreases. If the discharge amount of the high-pressure fuel pump 16 decreases due to these factors, the speed of increase of the actual fuel pressure decreases, so that the arrival time becomes longer and the time for which the starter 52 is driven can be lengthened. In this case, since the drive time of the starter 52 becomes longer, the amount of power stored in the battery 56 is excessively reduced, and the engine cannot be started properly due to the inability to properly perform cranking. .

Therefore, in the present embodiment, the engine is appropriately operated by performing the following processes <1> to <3> based on the actual fuel pressure or the like at the timing (determination timing) when the determination time T1 elapses after the cranking is started. Avoid situations where the engine cannot be started. Hereinafter, these processes will be described in detail with reference to FIGS.
<1. Basic injection control processing>
In the basic injection control process, when the actual fuel pressure is equal to or higher than the injection permitted fuel pressure before the determination timing, the fuel injection of the fuel injection valve 46 is permitted at the timing when the actual fuel pressure becomes the injection permitted fuel pressure, and the fuel injection mode is set to the specified mode. It is a process to set. Here, in the present embodiment, the prescribed mode is intake compression split injection control (or compression stroke injection control). In the present embodiment, the determination time T1 is set to a short time so that the amount of power stored in the battery 56 does not decrease excessively with cranking, and is variably set based on the cranking rotation speed and the cooling water temperature. Specifically, as shown in FIG. 2, the determination time T1 is set longer as the coolant temperature THW is higher, and the determination time T1 is set shorter as the cranking rotation speed is higher. This is done in view of the situation where the high-pressure fuel pump 16 is used affects the arrival time. That is, when the coolant temperature THW is high, the fuel temperature is increased, the fuel viscosity is lowered, and the amount of leak fuel in the pump accompanying the discharge operation of the high-pressure fuel pump 16 increases. As a result, the discharge amount of the high-pressure fuel pump 16 decreases and the arrival time becomes longer. Further, when the cranking rotation speed is increased, the discharge time per unit time of the high-pressure fuel pump 16 is increased, so that the arrival time is shortened. For this reason, by making the determination time T1 variably set based on the above parameters, the determination time T1 is made appropriate according to the situation in which the high-pressure fuel pump 16 is used.

  FIG. 3 shows an example of the basic injection control process. Specifically, FIG. 3 (a) shows the transition of the engine speed NE and the voltage V of the battery 56, FIG. 3 (b) shows the transition of the actual fuel pressure Pr, and FIG. 3 (c) shows the transition of the fuel injection time. Show. FIG. 3A shows the transition of the engine speed NE from the timing at which the ECU 62 can grasp the engine speed NE. Further, FIG. 3C shows that the fuel injection amount increases as the fuel injection time increases. However, the fuel injection amount for the same fuel injection time is different between the case where the fuel injection period is the intake stroke and the case where the compression stroke is used. This is because the fuel injection pressure required in each stroke is different.

In the example shown in the figure, it is determined that cranking has been started by determining that the starter 52 has been started by turning on the SW 54 at time t1. Thereafter, the actual fuel pressure Pr reaches the injection permission fuel pressure Pi at a timing (time t2) before the determination timing (time t3). For this reason, fuel injection of the fuel injection valve 46 is permitted at time t2, and intake compression split injection control is started.
<2. Judgment time extension processing>
In the determination time extension process, the actual fuel pressure Pr at the determination timing becomes less than the injection permission fuel pressure Pi, and the actual fuel pressure Pr between the end timings of one discharge stroke of the high-pressure fuel pump 16 from the start of cranking to the determination timing. When the amount of increase (the amount of increase in fuel pressure) is equal to or greater than the predetermined value Pd, the determination time T1 is increased by the extension time T2. This process is a process for determining whether or not the actual fuel pressure Pr is likely to rise to the injection permission fuel pressure Pi within a short time after the determination timing. That is, as described above, if the determination time T1 is shortened in order to realize the request to set the determination time T1 to a short time, the actual fuel pressure Pr at the determination timing is lowered. Here, even if the actual fuel pressure Pr at the determination timing is less than the permitted injection fuel pressure Pi, if the fuel pressure increase amount is large, the actual fuel pressure Pr can be increased to the permitted injection fuel pressure Pi within a short time thereafter. Sometimes. For this reason, by providing the determination time extension process, both the determination time T1 is set to a short time and the fuel injection pressure accompanying the start of fuel injection is increased in order to improve the combustion state. Balance requirements.

  Here, in the present embodiment, the extension time T2 is variably set based on the cranking rotation speed and the cooling water temperature THW. Specifically, as shown in FIG. 4, the longer the cooling water temperature THW, the longer the extension time T2, and the higher the cranking rotation speed, the shorter the determination time T1. In view of the fact that the arrival time changes according to the cranking rotation speed and the coolant temperature THW as described above, this is to suppress the drive time of the starter 52 from becoming longer as the determination time T1 is extended as much as possible. is there. Further, the determination time extension process is performed only once. This is to avoid a situation where cranking cannot be performed properly due to excessive reduction in the amount of power stored in the battery 56 as the starter 52 is driven if the determination time T1 is excessively extended. . The predetermined value Pd may be a value that can determine whether it is difficult to increase the actual fuel pressure Pr to the injection permission fuel pressure Pi even by the determination time extension process. Specifically, the fuel pressure increase amount in a specific pressure region (for example, in the vicinity of the injection permission fuel pressure Pi) when the high pressure fuel pump 16 has a boosting capability for increasing the actual fuel pressure Pr to the injection permission fuel pressure Pi. Is set to the lower limit.

  FIG. 5 shows an example of the determination time extension process. Specifically, FIGS. 5A to 5C correspond to FIGS. 3A to 3C.

  In the example shown in the figure, the cranking is started at time t1, and the fuel pressure increase amount ΔPr during the one discharge stroke end timing of the high-pressure fuel pump 16 is calculated in the period until the determination timing (time t4) thereafter. Specifically, the fuel pressure increase amount ΔPr is calculated as a deviation between the actual fuel pressure Pr at the previous discharge stroke end timing (time t2) of the high-pressure fuel pump 16 and the actual fuel pressure Pr at the current discharge stroke end timing (time t3). Is done. At time t4, although the actual fuel pressure Pr at the determination timing is less than the injection permission fuel pressure Pi, the fuel pressure increase amount ΔPr is equal to or greater than the predetermined value Pd, so the determination time T1 is extended by the extension time T2. Thereafter, since the actual fuel pressure Pr becomes the injection permission fuel pressure Pi by the timing (time t6) when the extension time T2 elapses, the fuel injection of the fuel injection valve 46 at the timing (time t5) when the actual fuel pressure Pr becomes the injection permission fuel pressure Pi. Is permitted, and intake compression split injection control is started.

Here, in the present embodiment, it is assumed that the fuel pressure increase amount ΔPr used in the determination time extension process is calculated immediately before the determination timing. This is to improve the determination accuracy as to whether or not the actual fuel pressure Pr is likely to rise to the injection-permitted fuel pressure Pi within a short time thereafter at the determination timing. That is, when the actual fuel pressure Pr increases, the amount of leakage in the pump accompanying the discharge operation of the high-pressure fuel pump 16 increases, and the discharge amount of the high-pressure fuel pump 16 decreases, so the fuel pressure increase amount ΔPr decreases. Become. In view of this, by using the fuel pressure increase amount ΔPr immediately before the determination timing, it is possible to improve the determination accuracy as to whether or not the actual fuel pressure Pr can be increased to the injection permission fuel pressure Pi within a short time thereafter.
<3. Injection mode change processing>
The injection mode changing process is a case where the actual fuel pressure Pr at the determination timing is less than a specified pressure (a boost start fuel pressure) that is lower than the injection permission fuel pressure Pi, and the fuel pressure increase amount ΔPr is less than the predetermined value Pd. In this case, the fuel injection mode at the start of fuel injection of the fuel injection valve 46 is changed from intake compression split injection control (or compression stroke injection control) to control (intake stroke injection control) in which the fuel injection period is set only to the intake stroke. Thus, the fuel injection of the fuel injection valve 46 is permitted at the determination timing. This process is a process for avoiding a situation where the engine cannot be started properly in a situation where it is difficult to increase the actual fuel pressure Pr to the injection permission fuel pressure Pi within a short time after the determination timing. It is. That is, the fuel injection pressure required for the fuel injection valve 46 is lower in the intake stroke than in the compression stroke of the fuel injection period. Therefore, by changing the fuel injection mode to the intake stroke injection control in which the required fuel injection pressure is low, fuel injection is realized even when it is difficult to increase the actual fuel pressure Pr. As a result, the crankshaft 40 is rotated by the combustion of fuel, and the engine can be started.

  Here, in the present embodiment, the boosted starting fuel pressure is equal to or lower than the maximum value of the actual fuel pressure that can be boosted by the high-pressure fuel pump 16 during cranking, and the combustion chamber is assumed when the fuel injection period is the compression stroke. The pressure is set slightly higher than 48 pressure. In order to avoid the deterioration of the combustion state at the start of the engine as much as possible, the boost start fuel pressure is variably set based on the coolant temperature THW. Specifically, as shown in FIG. 6, when the coolant temperature THW is lower than a specified temperature (for example, the temperature at which it is determined that the engine has been warmed up), the boost start fuel pressure Pi2 is increased as the coolant temperature THW is lower. When the cooling water temperature THW is equal to or higher than the specified temperature, the cooling water temperature THW is fixed.

  FIG. 7 shows an example of the injection mode change process. Specifically, FIGS. 7A to 7C correspond to FIGS. 3A to 3C.

  In the example shown in the figure, after cranking is started at time t1, the actual fuel pressure Pr at the determination timing (time t4) becomes less than the boost start fuel pressure Pi2 and the end of one discharge stroke of the high-pressure fuel pump 16 (time The fuel pressure increase amount ΔPr from t2 to t3) is less than the predetermined value Pd. Therefore, by changing the fuel injection mode from the intake compression split injection control to the intake stroke injection control, the fuel injection of the fuel injection valve 46 is permitted at the determination timing.

  On the other hand, if the actual fuel pressure Pr at the determination timing is less than the injection permission fuel pressure Pi and the fuel pressure increase amount ΔPr is less than the predetermined value Pd, the actual fuel pressure Pr at the determination timing is equal to or higher than the boost start fuel pressure Pi2. While setting the injection mode to the intake compression split injection control, the fuel injection of the fuel injection valve 46 is permitted at the determination timing. This is in consideration of the fact that fuel injection is possible in the compression stroke because the boost start fuel pressure Pi2 is set as described above.

  FIG. 8 shows an example of the above process. Specifically, FIGS. 8A to 8C correspond to FIGS. 3A to 3C.

  In the example shown in the figure, after cranking is started at time t1, the actual fuel pressure Pr at the determination timing (time t4) becomes equal to or higher than the boost start fuel pressure Pi2 and the end of one discharge stroke of the high-pressure fuel pump 16 (time The fuel pressure increase amount ΔPr from t2 to t3) is less than the predetermined value Pd. Therefore, the fuel injection of the fuel injection valve 46 is permitted at the determination timing while the fuel injection mode is set to the intake compression split injection control.

  FIG. 9 shows the procedure of the startup boost control process according to this embodiment. This process is executed when the ECU 62 determines that cranking has started.

  In this series of processing, first, in step S10, the extension determination flag F is set to “0”. Here, the extension determination flag F indicates that the determination time extension process has already been performed by “0”, and indicates that the determination time extension process has not been performed by “1”.

  In the subsequent step S12, the fuel pressure increase amount ΔPr is calculated at the end of each discharge stroke of the high-pressure fuel pump 16. The discharge stroke end timing may be grasped based on the output values of both the crank angle sensor 58 and the cam angle sensor 60.

  In the subsequent step S14, it is determined whether or not the actual fuel pressure Pr becomes equal to or higher than the injection permission fuel pressure Pi before the determination time T1 elapses after the cranking is started. The determination time T1 is set by the map shown in FIG. Specifically, the determination time T1 may be set based on the cranking rotation speed and the coolant temperature THW at the timing at which the ECU 62 can grasp the engine rotation speed using the map.

  If it is determined in step S14 that the actual fuel pressure Pr becomes equal to or higher than the injection-permitted fuel pressure Pi between the start of cranking and the determination timing, the process proceeds to step S16, and the fuel injection mode is changed to the intake compression split injection control (or compression stroke). Set to injection control) and allow fuel injection.

  On the other hand, if a negative determination is made in step S14, the process proceeds to step S18 to determine whether or not the fuel pressure increase amount ΔPr calculated immediately before the determination timing is less than the predetermined value Pd. This process is a process for determining whether or not the actual fuel pressure Pr is likely to rise to the injection permission fuel pressure Pi within a short time after the determination timing.

  If it is determined in step S18 that the fuel pressure increase amount ΔPr is equal to or greater than the predetermined value Pd, it is determined that the actual fuel pressure Pr is likely to rise to the injection permission fuel pressure Pi. In step S20, the extension determination flag F is set to “1”. It is determined whether it is set to "."

  When it is determined in step S20 that the extension determination flag F is set to “0”, determination time extension processing is performed in steps S22 and S24. Specifically, in step S22, the determination time T1 is extended by the extension time T2, and in the subsequent step S24, the extension determination flag F is set to “1”, and then the process returns to step S14. The extension time T2 is set by the map shown in FIG. Specifically, the extension time T2 may be set based on the cranking rotation speed and the coolant temperature THW at the determination timing using the map.

  On the other hand, when an affirmative determination is made in steps S18 and S20, the process proceeds to step S26 to determine whether or not the actual fuel pressure Pr is less than the boost start fuel pressure Pi2.

  If it is determined in step S26 that the actual fuel pressure Pr is equal to or higher than the boost start fuel pressure Pi2, the process proceeds to step S16, and determination is made while setting the fuel injection mode to intake compression split injection control (or compression stroke injection control). The fuel injection of the fuel injection valve 46 is permitted at the timing. On the other hand, when it is determined in step S26 that the actual fuel pressure Pr is less than the boost start fuel pressure Pi2, the process proceeds to step S28, and the fuel injection mode is changed from intake compression split injection control (or compression stroke injection control) to intake stroke injection. It changes to control and permits the fuel injection of the fuel injection valve 46 at the determination timing.

  In addition, when the process of step S16, S28 is completed, this series of processes is once complete | finished.

  As described above, in this embodiment, the engine is selected by selecting one of the fuel injection modes of the intake compression split injection control (or the compression stroke injection control) and the intake stroke injection control based on the actual fuel pressure or the like at the determination timing. Therefore, an appropriate fuel injection mode at the start of fuel injection of the fuel injection valve 46 can be set at the time of starting, and thus the engine can be started properly.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) When it is determined that the actual fuel pressure Pr becomes equal to or higher than the injection permission fuel pressure Pi before the determination timing, the fuel injection of the fuel injection valve 46 is permitted and the intake compression split injection control (or compression stroke injection control) is performed. Thereby, the startability of an engine can be made favorable.

  (2) When it is determined that the actual fuel pressure Pr at the determination timing is less than the injection permitted fuel pressure Pi and the fuel pressure increase amount ΔPr is equal to or greater than the predetermined value Pd, a determination time extension process is performed. Thereby, it is possible to suitably satisfy both the requirements of setting the determination time T1 to a short time and setting the fuel injection mode corresponding to the fuel injection pressure as early as possible after the cranking is started. it can. Further, since the deviation between the actual fuel pressure Pr at the previous discharge stroke end timing and the actual fuel pressure Pr at the current discharge stroke end timing is calculated as the fuel pressure increase amount ΔPr, the time from when the cranking is started until the determination time T1 elapses. Therefore, the fuel pressure increase amount ΔPr can be grasped in a short time and with high accuracy.

  (3) Although it is determined that the actual fuel pressure Pr at the determination timing is less than the injection permission fuel pressure Pi and the fuel pressure increase amount ΔPr is less than the predetermined value Pd, it is determined that the actual fuel pressure Pr at the determination timing is equal to or higher than the boost start fuel pressure Pi2. When the fuel injection mode is set, the fuel injection mode 46 is set to intake compression split injection control (or compression stroke injection control), and the fuel injection of the fuel injection valve 46 is permitted at the determination timing. Accordingly, it can be determined as early as possible that it is difficult to increase the actual fuel pressure Pr to the injection permitted fuel pressure Pi, and fuel injection can be started as soon as possible after cranking is started as fail-safe. it can. Moreover, the injection permission fuel pressure Pi can be made sufficiently higher than the lower limit value at which the compression stroke injection can be performed, and can be set to an optimum pressure or the like for improving exhaust characteristics.

  (4) When it is determined that the actual fuel pressure Pr at the determination timing is less than the boost start fuel pressure Pi2 and the fuel pressure increase amount ΔPr is less than the predetermined value Pd, an injection mode change process is performed. Thereby, fuel injection mode can be set appropriately as fail safe.

  (5) The determination time T1 is variably set based on the cranking rotation speed and the coolant temperature THW. Thereby, the determination time T1 is made appropriate according to the situation in which the high-pressure fuel pump 16 is used.

  (6) The determination time extension process was performed only once. Thereby, it is possible to avoid an excessive decrease in the amount of power stored in the battery 56, and it is possible to suitably avoid a situation in which cranking cannot be performed appropriately.

  (7) The extension time T2 is variably set based on the cranking rotation speed and the cooling water temperature THW. Thereby, it can suppress as much as possible that the drive time of the starter 52 becomes long with extension of determination time T1.

  (8) The boost start fuel pressure Pi2 is variably set based on the coolant temperature THW. Thereby, the deterioration of the combustion state at the time of engine start-up can be suppressed as much as possible.

  (9) Based on the SW 54 being turned on, it is determined that cranking is started. Thereby, it is possible to accurately grasp the timing at which the determination time T1 elapses after the cranking is started and the timing at which the extension time T2 elapses.

(Other embodiments)
The above embodiment may be modified as follows.

  The setting method of the determination time T1 and the extension time T2 is not limited to the method exemplified in the above embodiment. For example, the determination time T1 and the extension time T2 may be variably set based on any one of the cranking rotation speed and the cooling water temperature THW. For example, the determination time T1 and the extension time T2 are not limited to variable values, and may be fixed values.

  In the above embodiment, the fuel pressure increase amount ΔPr is calculated based on the actual fuel pressure Pr at each end of one discharge stroke of the high-pressure fuel pump 16, but is not limited thereto. For example, it may be calculated based on the actual fuel pressure at every two or more discharge stroke end timings of the high-pressure fuel pump 16.

  -In the said embodiment, even if it performs the determination time extension process twice or more, the effect of said (1) in the said embodiment can be acquired.

  The increase degree of the actual fuel pressure is not limited to the fuel pressure increase amount ΔPr, and for example, the increase speed of the actual fuel pressure may be used. In this case, for example, the deviation between the actual fuel pressure at the current discharge stroke end timing of the high-pressure fuel pump 16 and the actual fuel pressure at the previous discharge stroke end timing is divided by the time corresponding to the current and previous discharge stroke end timing. Thus, the above ascending speed may be calculated.

  In the above embodiment, when it is determined that the SW 54 is turned on, it is determined that the cranking is started, but the present invention is not limited to this. For example, a sensor that detects the voltage of the battery 56 may be provided, and it may be determined that cranking has started based on a decrease in the voltage of the battery 56 based on the output value of the sensor by a predetermined amount.

  In the above embodiment, the fuel pressure increase amount ΔPr for comparison with the predetermined value Pd is calculated immediately before the determination timing, but is not limited thereto. For example, an arbitrary fuel pressure increase amount ΔPr among a plurality of fuel pressure increase amounts ΔPr calculated from when cranking is started until the determination time T1 elapses, or an average value of the plurality of fuel pressure increase amounts ΔPr may be used. Good.

  In the above embodiment, when the actual fuel pressure Pr at the determination timing is less than the boost start fuel pressure Pi2, the actual fuel pressure Pr at the determination timing is equal to or higher than the boost start fuel pressure Pi2 with respect to the degree of separation between the fuel injection start timing and the compression top dead center. The intake stroke injection control is selected as the fuel injection mode to be larger than the case, but is not limited thereto. For example, for the intake compression split injection control or the compression stroke injection control, control for shifting (advancing) the fuel injection period in the compression stroke in the direction in which the pressure in the combustion chamber is lowered may be selected. Further, for example, a fuel injection valve (port injection valve) may be provided on an intake passage for supplying intake air to the combustion chamber 48, and control for fuel injection from the port injection valve may be selected.

  -As an injection mode change processing method, it is not restricted to what was illustrated to the said embodiment. For example, the determination is based on the actual fuel pressure Pr and cranking rotation speed at a specific timing before the determination timing, and the fuel pressure increase ΔPr between the discharge stroke end timings of the high-pressure fuel pump 16 calculated immediately after the specific timing. The actual fuel pressure Pr at the timing is predicted, and the fuel injection mode may be changed from the intake compression split injection control (or the compression stroke injection control) to the intake stroke injection control based on the predicted actual fuel pressure Pr and the fuel pressure increase amount ΔPr. . Further, for example, the fuel injection mode may be changed based on the fact that the fuel pressure increase amount ΔPr before the determination time T1 elapses after cranking is started is less than a predetermined value Pd. This is based on the fact that when the fuel pressure increase amount ΔPr is small, it is considered difficult to make the actual fuel pressure Pr at the determination timing equal to or higher than the boost start fuel pressure Pi2.

  In the above embodiment, a normally open type is used as the suction valve 26, but the present invention is not limited to this. For example, a normally closed type in which the valve is opened when the electromagnetic solenoid 28 is energized and the valve is closed when the electromagnetic solenoid 28 is not energized may be used.

  The fuel injection system of the internal combustion engine to which the present invention is applied is not limited to that of a spark ignition type internal combustion engine such as a cylinder injection type gasoline engine, but for example of a compression ignition type internal combustion engine such as a diesel engine (common rail) Fuel injection system).

  DESCRIPTION OF SYMBOLS 10 ... Fuel tank, 16 ... High pressure fuel pump, 44 ... Delivery pipe, 46 ... Fuel injection valve, 48 ... Combustion chamber, 52 ... Starter, 56 ... Battery, 62 ... ECU (Embodiment of fuel injection control device of internal combustion engine) ), 64 ... Water temperature sensor, 66 ... Fuel pressure sensor.

Claims (11)

An accumulator that can accumulate fuel in a high-pressure state, a fuel injection valve that directly injects fuel supplied from the accumulator into a combustion chamber of an internal combustion engine, and an engine that supplies fuel from a fuel tank to the accumulator Applied to a fuel injection system of an internal combustion engine configured to include a drive type fuel pump and a fuel pressure detecting means for detecting a fuel pressure of the pressure accumulating vessel;
Based on the degree of increase in the detected fuel pressure during a specified timing including one discharge stroke of the fuel pump before the fuel injection of the fuel injection valve is started after the cranking is started, the fuel of the fuel injection valve A fuel injection control device for an internal combustion engine, comprising: an injection mode selection means for selecting a fuel injection mode at the start of injection. Based on the fact that the detected fuel pressure is equal to or higher than a specified pressure, further comprising permission means for permitting fuel injection of the fuel injection valve in a specified mode;
The injection mode selection means determines whether or not to change the fuel injection mode from the specified mode when the fuel injection is not permitted by the permission means until a predetermined time elapses after the cranking is started. The fuel injection control device for an internal combustion engine according to claim 1.   The system further comprises an extension means for extending the predetermined time based on the fact that the detected fuel pressure at the timing when the predetermined time elapses is less than the specified pressure and the degree of increase in the detected fuel pressure is greater than or equal to a predetermined value. The fuel injection control device for an internal combustion engine according to claim 2, wherein: The fuel injection system further includes an in-vehicle storage battery, and a starter that performs the cranking by being fed from the in-vehicle storage battery,
4. The fuel injection control device for an internal combustion engine according to claim 3, wherein the extension means extends the predetermined time only once.   5. The internal combustion engine according to claim 3, further comprising means for variably setting an extension time of the predetermined time based on at least one of a temperature of cooling water for cooling the internal combustion engine and an engine speed. Fuel injection control device.   The fuel injection valve is selected based on the fact that the detected fuel pressure at a timing when the predetermined time elapses is less than the specified pressure, and the degree of increase in the detected fuel pressure is less than a predetermined value. A mode in which the degree of separation between the fuel injection start timing and the compression top dead center is larger than the specified mode is selected, and fuel injection of the fuel injection valve is permitted at the timing when the predetermined time elapses. Item 6. The fuel injection control device for an internal combustion engine according to any one of Items 2 to 5. The specified pressure is further defined as a first specified pressure, and further includes specified pressure setting means for setting a second specified pressure that is lower than the first specified pressure,
7. The internal combustion engine according to claim 6, wherein a mode larger than the prescribed mode is selected based on the detected fuel pressure being less than the second prescribed pressure when the predetermined time elapses. Fuel injection control device.   The fuel injection control device for an internal combustion engine according to claim 7, wherein the specified pressure setting means variably sets the second specified pressure based on a temperature of cooling water for cooling the internal combustion engine.   9. The internal combustion engine according to claim 2, further comprising means for variably setting the predetermined time based on at least one of a temperature of cooling water for cooling the internal combustion engine and an engine speed. Engine fuel injection control device.   The fuel injection mode includes a mode in which a fuel injection period of the fuel injection valve includes a compression stroke of the internal combustion engine and a mode in which the fuel injection period is limited to an intake stroke of the internal combustion engine. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 9.   The fuel injection control device for an internal combustion engine according to any one of claims 1 to 10, wherein the interval between the prescribed timings is an end timing of one discharge stroke of the fuel pump.

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