JP2008121426A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine capable of suppressing variation of fuel injection quantity at a time of feed pressure injection even when pulsation is generated in a fuel pressure when a plunger of an engine drive type high pressure pump reciprocates. <P>SOLUTION: An electronic control device 100 executes split injection injecting fuel by splitting in a plurality of times in the feed pressure injection. The electronic control device 100 detects a half cycle in a reciprocation period of the plunger 22 of the high pressure pump 20 in the split injection, and sets an interval of each injection so that an injection interval Tint of two injections out of the split injections becomes equal to the detected half cycle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for an internal combustion engine, and more particularly to a fuel injection control device for an internal combustion engine including an in-cylinder injector that directly injects fuel into a combustion chamber.

  For example, as described in Patent Document 1, a fuel supply system of an internal combustion engine including an in-cylinder injector is generally supplied from a feed pump that discharges fuel in a fuel tank at a predetermined pressure, and the same feed pump. A high-pressure pump that pressurizes the fuel and a delivery pipe that stores the fuel pressurized by the high-pressure pump are configured. Then, the high-pressure fuel accumulated in the delivery pipe is injected into the combustion chamber from the in-cylinder injector.

  FIGS. 7A and 7B are schematic views showing a general configuration of a high-pressure pump in such a fuel supply system. FIG. 7A shows the suction stroke of the high-pressure pump, and FIG. 7B shows the discharge stroke of the high-pressure pump.

  As shown in FIG. 7A, the high-pressure pump has a pressurizing chamber 3 defined by a cylinder 1 and a plunger 2 fitted into the cylinder 1. A supply passage 4 connected to the discharge side of the feed pump and a discharge passage 5 connected to the delivery pipe are connected to the pressurizing chamber 3. The plunger 2 is in contact with a drive cam 7 connected to a camshaft 6 of the internal combustion engine. Thus, the plunger 2 is driven by the drive cam 7 that rotates in synchronization with the rotation of the camshaft 6 during engine operation, and periodically reciprocates in the cylinder 1 so as to increase or decrease the volume of the pressurizing chamber 3. .

The supply passage 4 is provided with a spill valve 8 for closing and opening the supply passage 4, and the discharge passage 5 is provided with a check valve 9 for preventing a back flow of fuel from the delivery pipe.
When the fuel is pressurized by the high-pressure pump and supplied to the delivery pipe, the spill valve 8 is controlled to open when the plunger 2 descends as the drive cam 7 rotates as shown in FIG. The fuel discharged from the feed pump is supplied to the pressurizing chamber 3. On the other hand, as shown in FIG. 7 (b), when the plunger 2 rises with the rotation of the drive cam 7, the spill valve 8 is controlled to close at an appropriate time. The fuel in 3 is pressurized. When the pressure of the fuel in the pressurizing chamber 3 becomes higher than the pressure of the fuel in the delivery pipe, the check valve 9 is opened and the pressurized fuel is supplied to the delivery pipe. Further, the fuel supply amount at this time is adjusted by the closing timing of the spill valve 8. The fuel pressurized by the high-pressure pump is accumulated in the delivery pipe and injected into the combustion chamber through the in-cylinder injector.

By the way, since the discharge amount of the high-pressure pump is very small with respect to the volume of the delivery pipe, when the fuel is not filled in the delivery pipe as at the time of engine start, the fuel is pressurized to the pressure required for injection. It will take a long time. For this reason, when the engine is started, the spill valve 8 is always kept open and fuel is supplied to the delivery pipe by the discharge force of the feed pump without applying pressure by the high-pressure pump. Feed pressure injection is performed to inject fuel with pressure. According to such feed pressure injection, the inside of the delivery pipe can be quickly filled with fuel, and fuel can be injected.
JP 2004-346852 A

  By the way, since the plunger 2 of the high pressure pump reciprocates with the rotation of the camshaft 6 even during the feed pressure injection, the fuel pressure in the delivery pipe fluctuates due to the influence thereof. Specifically, as shown in FIG. 8, the fuel pressure rises as the plunger 2 rises, the fuel pressure falls as the plunger 2 descends, and the fuel pressure in the delivery pipe changes periodically. It pulsates. FIG. 8 is a timing chart showing the relationship between the reciprocation of the plunger 2 and the change in the fuel pressure in the delivery pipe.

  As shown in FIGS. 7A and 7B, since the drive cam 7 has three cam peaks, the plunger 2 is moved three times during a period of 720 ° CA in which the output shaft of the internal combustion engine rotates twice. Repeat the reciprocating motion. Here, for example, in a 6-cylinder internal combustion engine, fuel is injected into each cylinder at 120 ° CA intervals during this 720 ° CA period. At this time, if there is a pulsation in the fuel pressure in the delivery pipe as described above, the fuel pressure in the delivery pipe may vary during the fuel injections INJ1 to 6 for the first to sixth cylinders as shown in FIG. .

  The fuel injection amount of the internal combustion engine is generally controlled by the fuel pressure and the valve opening control time of the injector, that is, the fuel injection time. Therefore, even if the fuel injection time is the same, if the fuel pressure in the delivery pipe is different as described above, the fuel injection amount varies from cylinder to cylinder. There is a risk that inconveniences such as fluctuation may occur and engine operation may become unstable.

  Further, if the fuel pressure resulting from the reciprocating motion of the plunger is detected and the fuel injection times in the fuel injections INJ1 to INJ6 are set based on the detection result, the variation in the fuel injection amount can be reduced. it can. However, it is actually extremely difficult to detect the fuel pressure at that time and reflect it in the fuel injection time in this way, considering that there is a limitation in the calculation capability of the control device.

  The present invention has been made in view of the above circumstances, and an object of the present invention is an internal combustion engine having an in-cylinder injector, in which fuel pressure pulsates due to reciprocation of a plunger of an engine-driven high-pressure pump. Even so, an object of the present invention is to provide a fuel injection control device for an internal combustion engine capable of suppressing variations in the fuel injection amount between cylinders at the time of feed pressure injection.

In the following, means for achieving the above object and its effects are described.
According to the first aspect of the present invention, there is provided a feed pump that discharges fuel in a fuel tank at a predetermined pressure, and a fuel that is supplied to the pressurizing chamber from the feed pump by reciprocating the plunger by the rotational force of the engine output shaft. A high pressure pump that pressurizes and supplies the delivery pipe, a cylinder injection injector that is provided in each cylinder of the internal combustion engine and that supplies fuel from the delivery pipe, and a pressure chamber of the high pressure pump. A spill valve for metering fuel supplied to the delivery pipe, and normal injection for injecting the fuel pressurized by the high-pressure pump and stored in the delivery pipe from the in-cylinder injector; and the spill The valve is kept open, and the fuel in the delivery pipe is injected from the in-cylinder injector based on the discharge pressure of the feed pump. In the fuel injection control apparatus for an internal combustion engine that executes switching between the feed pressure injection and the detection means for detecting the half cycle of the reciprocation period of the plunger, and the fuel is divided into a plurality of times during the feed pressure injection And injection control means for setting the time interval between two of the divided injections to be equal to the half cycle detected by the detection means. The gist.

  According to the above configuration, at the time of feed pressure injection, the interval between two of the divided injections is equal to the half cycle of the reciprocation of the plunger detected by the detecting means, that is, half of the fuel pressure pulsation. It is set to be equal to the period.

  In the case of two injections that are set to be spaced from each other in this way, when one of the injections is performed at a fuel pressure higher than the average value of the pulsating fuel pressure, the other injection has the same average value. At lower fuel pressures. As a result, the sum of the fuel injection amounts in the pair of injections executed at such an interval is equal to the fuel pressure pulsating fuel pressure average value regardless of the timing of the fuel pressure pulsation cycle. It approaches the fuel injection amount in the case of batch injection.

  As a result, the total amount of fuel injected in each cylinder can be brought close to the fuel injection amount when the fuel is collectively injected with an average value of pulsation, and the fuel pressure is increased by the reciprocating movement of the plunger of the engine-driven high-pressure pump. Even in the case where pulsation occurs, it is possible to suppress variations in the fuel injection amount between the cylinders at the time of feed pressure injection.

In addition, the divided injection in which the fuel is divided into a plurality of times during the feed pressure injection includes not only the number of divisions set to 2 but also those set to 3 or more.
According to a second aspect of the present invention, there is provided a fuel injection control device for an internal combustion engine according to the first aspect, wherein the injection control means performs two injections executed at intervals of a half cycle detected by the detection means. The gist of the present invention is to set each injection time to be equal.

  According to the above configuration, the difference between the sum of the fuel injection amounts of the two injections executed at intervals equal to the half cycle detected by the detection means and the fuel injection amount when the fuel is collectively injected with an average value of pulsation. Thus, it is possible to more suitably suppress the variation in the fuel injection amount between the cylinders due to the pulsation of the fuel pressure during the feed pressure injection.

  According to a third aspect of the present invention, in the fuel injection control device for an internal combustion engine according to the first or second aspect, the injection control means sets the division number of the feed pressure injection to two. The gist.

  As described above, the sum of the fuel injection amounts in the two injections executed at intervals equal to the half cycle detected by the detecting means pulsates regardless of the timing of the fuel pressure pulsation cycle. The fuel injection amount in the case of batch injection with the average value of the fuel pressure approaches.

  However, when the fuel injection in each cylinder is divided into three or more times and executed, the total amount of fuel injected in each cylinder due to fuel injection other than the two injections set at the interval of the half cycle. However, it becomes more susceptible to the pulsation of fuel pressure. In this regard, according to the above configuration, the number of fuel injection divisions in each cylinder during the feed pressure injection is set to two. Therefore, the influence of the pulsation of the fuel pressure can be reduced as much as possible, and the variation in the fuel injection amount between the cylinders due to the pulsation of the fuel pressure during the feed pressure injection can be effectively suppressed.

  In the case of an engine-driven high-pressure pump in which the plunger is reciprocated based on the rotation of the output shaft of the internal combustion engine, the period of reciprocation of the plunger is estimated based on the engine rotational speed of the internal combustion engine. Can do. Therefore, specifically, in the fuel injection control device for an internal combustion engine according to any one of claims 1 to 3, as in the invention according to claim 4, the detection means is an engine speed of the internal combustion engine. It is possible to adopt a configuration in which this is detected by estimating the reciprocating period of the plunger based on the above.

  According to a fifth aspect of the present invention, in the fuel injection control device for an internal combustion engine according to any one of the first to fourth aspects, the injection control means determines the first fuel injection timing in the divided injection based on the engine operating state. And the subsequent fuel injection timing is set based on the set initial fuel injection timing.

  When the split injection is executed, the initial fuel injection timing has a larger contribution than the other fuel injection timings in determining the combustion state such as the diffusion state of the air-fuel mixture. In view of this point, in the invention according to claim 5, the first fuel injection timing in the divided injection is set based on the engine operating state, and the subsequent fuel injection timing based on the set first fuel injection timing. Is set. Accordingly, each fuel injection timing in the split injection can be set to a timing in accordance with the engine operation state, and misfire and a decrease in engine output during the feed pressure injection can be suppressed.

  A fuel injection control device for an internal combustion engine according to the present invention that is embodied as an electronic control device that controls a direct injection type 6-cylinder engine will be described below with reference to FIGS.

  FIG. 1 is a schematic diagram showing a schematic configuration of a fuel supply system controlled by the electronic control unit 100. As shown in FIG. 1, the feed pump 10 provided in the fuel tank 11 is an electric pump, and discharges fuel at a predetermined pressure during engine operation. The feed pump 10 is connected to the high pressure pump 20 by a low pressure passage 31, and the fuel discharged from the feed pump 10 is supplied to the high pressure pump 20 through the low pressure passage 31. Note that the low-pressure passage 31 is provided with a filter 12, and fine foreign matters contained in the fuel are removed through the filter 12.

  Further, a return passage 13 for returning a part of the fuel discharged from the feed pump 10 to the fuel tank 11 is connected to the low pressure passage 31. A pressure regulator 14 is provided in the return passage 13, and when the fuel pressure in the low pressure passage 31 exceeds a predetermined pressure, the pressure regulator 14 connects the low pressure passage 31 and the return passage 13, and the fuel in the low pressure passage 31. Is returned to the fuel tank 11. Thus, the fuel pressure in the low pressure passage 31 is suppressed from becoming excessively high, and the fuel is supplied to the high pressure pump 20 at a predetermined pressure as the feed pump 10 is driven.

  As shown in FIG. 1, a cylinder 21 is formed in the high-pressure pump 20, and a pressurizing chamber 23 is defined by the cylinder 21 and a plunger 22 inserted into the cylinder 21. A lifter 24 is fixed to the end of the plunger 22 opposite to the pressurizing chamber 23. A drive cam 51 is provided at one end of the intake camshaft 50 of the engine. As shown in FIG. 1, the lifter 24 is urged by the urging force of the spring 25 and is in contact with the outer peripheral surface of the drive cam 51. For this reason, the plunger 22 is periodically reciprocated in the cylinder 21 so as to increase or decrease the volume of the pressurizing chamber 23 by the drive cam 51 that rotates in synchronization with the rotation of the intake camshaft 50 during engine operation.

  As shown in FIG. 1, a spill valve 26 that closes and opens the low pressure passage 31 is provided at a portion where the pressurizing chamber 23 and the low pressure passage 31 are connected. The spill valve 26 closes the valve body 27 against the urging force of the spring 28 by electromagnetic force, a valve body 27 that closes and opens the low pressure passage 31, a spring 28 that urges the valve body 27 in the valve opening direction, and electromagnetic force. And a solenoid 29 to be valved. The solenoid 29 is excited based on a control command from the electronic control device 100 to close the valve body 27.

  The pressurizing chamber 23 is connected to the delivery pipe 30 by a high-pressure passage 32. The high-pressure passage 32 is provided with a check valve 33 that prevents a backflow of fuel from the delivery pipe 30 side to the high-pressure pump 20 side.

  When the fuel is pressurized by the high-pressure pump 20 and supplied to the delivery pipe 30, the spill valve 26 is controlled to open when the plunger 22 descends as the drive cam 51 rotates, and is discharged from the feed pump 10. Fuel is supplied to the pressurizing chamber 23. On the other hand, when the plunger 22 rises with the rotation of the drive cam 51, the spill valve 26 is controlled to close at an appropriate time, and the fuel in the pressurizing chamber 23 is pressurized with the plunger 22 rising. When the fuel pressure in the pressurizing chamber 23 becomes larger than the fuel pressure in the delivery pipe 30, the check valve 33 is opened, and the pressurized fuel is supplied to the delivery pipe 30 through the high-pressure passage 32. .

  The delivery pipe 30 is connected to an injector 40 provided in each cylinder of the engine. The injector 40 opens based on a drive signal from a drive circuit 101 provided in the electronic control unit 100, and directly injects fuel accumulated in the delivery pipe 30 into the combustion chamber of the engine.

  A relief passage 34 is connected to the delivery pipe 30 and is connected to the fuel tank 11 by the relief passage 34. A relief valve 35 that opens and closes based on the fuel pressure in the delivery pipe 30 is provided in the relief passage 34. When the fuel pressure in the delivery pipe 30 becomes equal to or higher than a predetermined pressure, the relief valve 35 is opened, and a part of the fuel in the delivery pipe 30 is returned to the fuel tank 11. Thus, the fuel pressure in the delivery pipe 30 is suppressed from becoming excessively high.

  The fuel supply system configured as described above is controlled by the electronic control unit 100. Connected to the electronic control unit 100 are a fuel pressure sensor 61 for detecting the fuel pressure in the delivery pipe 30, a water temperature sensor 62 for detecting the engine cooling water temperature THW, a rotation speed sensor 63 for detecting the engine rotation speed NE, and the like. The electronic control unit 100 reads the detection values of these various sensors, performs calculations, and controls each part of the engine including the spill valve 26 and the injector 40.

  For example, the amount of fuel supplied from the high-pressure pump 20 to the delivery pipe 30 is adjusted based on the fuel pressure in the delivery pipe 30 detected by the fuel pressure sensor 61. Specifically, when the fuel pressure in the delivery pipe 30 is significantly reduced as the fuel is injected, the electronic control unit 100 advances the closing timing of the spill valve 26 in the upward stroke of the plunger 22. As a result, the valve closing period of the spill valve 26 in the ascending stroke of the plunger 22 becomes longer, and the amount of fuel supplied to the delivery pipe 30 increases. On the other hand, when the amount of decrease in fuel pressure accompanying fuel injection is small, the closing timing of the spill valve 26 in the ascending stroke of the plunger 22 is delayed. As a result, the closing period of the spill valve 26 in the ascending stroke of the plunger 22 is shortened, and the amount of fuel supplied to the delivery pipe 30 is reduced.

  By the way, since the maximum discharge amount of the high-pressure pump 20 is very small with respect to the volume of the delivery pipe 30, when the fuel is not filled in the delivery pipe 30 as at the time of starting the engine, the pressure required for injection is increased. It takes a long time to pressurize the fuel.

  For this reason, the electronic control unit 100 supplies the fuel to the delivery pipe 30 by the discharge force of the feed pump 10 without controlling the spill valve 26 to be always open when the engine is started, and without applying pressure by the high-pressure pump 20. Then, feed pressure injection for injecting fuel at the discharge pressure of the feed pump 10 is executed. According to such feed pressure injection, it becomes possible to quickly fill the delivery pipe 30 with the fuel and inject the fuel.

  However, since the plunger 22 of the high-pressure pump 20 driven based on the rotation of the intake camshaft 50 of the engine reciprocates even during such feed pressure injection, the fuel pressure in the delivery pipe 30 is It fluctuates due to the effect of reciprocation. Specifically, the fuel pressure in the delivery pipe 30 rises as the plunger 22 rises, falls as the plunger 22 descends, and periodically pulsates.

  For this reason, the fuel pressure in the delivery pipe 30 may vary during fuel injection to each cylinder. The fuel injection amount is controlled by the fuel pressure and the valve opening control time of the injector 40, that is, the fuel injection time. Therefore, even if the fuel injection time is the same, if the fuel pressure in the delivery pipe 30 is different, the fuel injection amount varies from cylinder to cylinder, so that the air-fuel ratio is disturbed or the torque varies between the cylinders. There is a risk of inconveniences such as occurrence and unstable engine operation.

  In order to suppress the influence of such pulsation of fuel pressure, in this fuel supply system, during the feed pressure injection, the fuel injection in each cylinder is divided into the first injection INJprim and the second injection INJsec. I am doing so.

Hereinafter, this divided injection will be described in detail with reference to FIG. FIG. 2 shows the opening / closing timing of the injector 40 when the fuel is divided and injected in the injection stroke.
As shown in FIG. 2, in this divided injection, the injector 40 is opened at the injection start timing θinj, and the first injection INJprim is started. The injection start timing θinj is set as an advance amount based on the timing at which the piston is located at the top dead center TDC. The injection start timing θinj is set based on the engine coolant temperature THW as will be described later. The injection start timing θinj is set at, for example, 290 to 350 ° CA so that the first injection INJprim is started in the intake stroke. Set by range. When the first injection time Tprim elapses after the injector 40 is opened, the injector 40 is closed and the first injection INJprim ends. When the injection interval Tint elapses from the injection start timing θinj, the injector 40 is opened again, and the second injection INJsec is started. As shown in FIG. 2, when the second injection time Tsec elapses after the second injection INJsec is started, the injector 40 is closed and the fuel injection in this injection stroke is ended.

  The electronic control device 100 calculates the injection start timing θinj, the injection interval Tint, the first injection time Tprim, and the second injection time Tsec based on the detection values of the various sensors described above, and outputs a drive command to the injector 40. In 101, the injection start timing θinj, the injection interval Tint, the first injection time Tprim, and the second injection time Tsec are set.

  Hereinafter, the calculation process when setting the injection start timing θinj, the injection interval Tint, the first injection time Tprim, and the second injection time Tsec during the feed pressure injection will be described with reference to FIGS.

  FIG. 3 is a flowchart showing a series of calculation processes for calculating the set values. This process is repeatedly executed at a predetermined cycle in the electronic control device 100 until a predetermined period elapses from the start of engine start.

  When this process is started, first, in step S100, the total fuel injection amount Qtotal injected in each cylinder is calculated based on the engine cooling water temperature THW detected by the water temperature sensor 62. The calculation of the total fuel injection amount Qtotal is performed with reference to a calculation map stored in advance in the memory of the electronic control unit 100.

  When the engine is cold, the fuel is difficult to atomize, so it is desirable to set the total fuel injection amount Qtotal to be large in order to stabilize the combustion. Therefore, the calculation map for calculating the total fuel injection amount Qtotal is set so that the total fuel injection amount Qtotal increases as the engine coolant temperature THW decreases as shown in FIG.

  Next, in step S110, the injection start timing θinj is calculated based on the engine coolant temperature THW. The calculation of the injection start timing θinj is performed with reference to a calculation map stored in advance in the memory of the electronic control unit 100 as in the calculation of the total fuel injection amount Qtotal.

  During feed pressure injection, fuel is injected during the intake stroke. However, when the engine is cold, if fuel is injected at the beginning of the intake stroke where the distance between the piston and the injector 40 is close, the fuel rebounds at the piston top surface and adheres to the spark plug. It's easy to do. If fuel adheres to the spark plug, it may cause misfire. In order to suppress the occurrence of such misfire, it is desirable to wait for the piston to descend to some extent before injecting the fuel. Therefore, in the calculation map for calculating the injection start timing θinj, as shown in FIG. 5, the lower the engine coolant temperature THW, the more the injection start timing θinj is set to the retard side timing.

  Thus, when the injection start timing θinj is calculated through step S110, the process proceeds to step S120, and based on the total fuel injection amount Qtotal calculated in step S100, the first injection time Tprim which is the fuel injection time in the first injection INJprim. The second injection time Tsec, which is the fuel injection time in the second injection INJsec, is calculated. In step S120, first, a total injection time Ttotal for injecting fuel of the total fuel injection amount Qtotal is calculated based on the discharge pressure of the feed pump 10. Then, half the total injection time Ttotal is calculated as the first injection time Tprim and the second injection time Tsec. That is, the first injection time Tprim and the second injection time Tsec are set to the same value.

  Next, in step S <b> 130, the reciprocating cycle Tcycl of the plunger 22 is calculated based on the engine rotational speed NE detected by the rotational speed sensor 63. The drive cam 51 that drives the high-pressure pump 20 has three cam peaks as shown in FIG. Therefore, the plunger 22 reciprocates three times during a period of 720 ° CA in which the output shaft of the engine rotates twice. In step S110, the time required for the engine output shaft to make two revolutions is calculated based on the engine rotational speed NE, and one third of this time is calculated as the reciprocating cycle Tcycl of the plunger 22.

  When the period Tcycl of the reciprocating motion of the plunger 22 is calculated in this way, the process proceeds to step S140, and the injection interval Tint of the injection divided into two is calculated based on the calculated period Tcycl. Here, a time that is ½ of the calculated cycle Tcycl, that is, a half cycle of the plunger 22 is calculated as the injection interval Tint.

  Thus, when the injection start timing θinj, the injection interval Tint, the first injection time Tprim, and the second injection time Tsec are calculated through steps S100 to 140, the process proceeds to step S150, and in step S150, these calculated injection start times are calculated. θinj, injection interval Tint, first injection time Tprim, and second injection time Tsec are set in the drive circuit 101. And this process is once complete | finished. The drive circuit 101 opens and closes the injector 40 based on the injection start timing θinj, the injection interval Tint, the first injection time Tprim, and the second injection time Tsec set through the above arithmetic processing, and divides the fuel into two times. Let spray.

  Hereinafter, the operation and effect obtained by injecting the fuel by dividing the feed pressure into two in this way will be described with reference to FIG. FIG. 6 is a timing chart showing the relationship between the timing of each injection INJprim, INJsec and the fuel pressure.

  As described above, the fuel pressure in the delivery pipe 30 pulsates with the reciprocating motion of the plunger 22 during the feed pressure injection, and the reciprocating motion of the plunger 22 is between the maximum value Pmax and the minimum value Pmin as shown in FIG. It repeats increasing and decreasing every half cycle.

  Through the arithmetic processing in steps S100 to S150 described above, the injection interval Tint between the first injection INJprim and the second injection INJsec is set equal to the half cycle of this pulsation. Therefore, for example, as shown in FIG. 6, when the fuel pressure in the first injection INJprim indicated by a circle becomes a maximum value Pmax larger by Δa than the average value Pave of the pulsating fuel pressure, The fuel pressure in the second injection INJsec becomes a minimum value Pmin that is smaller than the average value Pave by Δa. On the other hand, when the injection start timing θinj is further delayed, and the fuel pressure in the first injection INJprim becomes a fuel pressure that is larger than the average value Pave by Δb, as indicated by a triangle mark in FIG. The fuel pressure in the second injection INJsec is a fuel pressure that is smaller than the average value Pave by Δb. In this way, when the injection interval Tint of each injection INJprim, INJsec is set equal to the half cycle of the change in fuel pressure, one of the injection pressures at any timing in the pulsation cycle of the fuel pressure When the injection is performed at a fuel pressure higher than the average value Pave by a predetermined amount, the other injection is performed at a fuel pressure lower than the average value Pave by the same amount.

According to the embodiment described above, the following effects can be obtained.
(1) The sum of the fuel injection amounts in each injection INJprim, INJsec is the fuel when the fuel is collectively injected with the average value Pave of the pulsating fuel pressure regardless of the timing of the fuel pressure pulsation cycle. It approaches the injection amount.

As a result, even when the pulsation occurs in the fuel pressure due to the reciprocating movement of the plunger 22 of the engine-driven high-pressure pump 20, it is possible to suppress variations in the fuel injection amount between the cylinders during the feed pressure injection. It becomes like this.
(2) Further, since the first injection time Tprim and the second injection time Tsec are set equal to each other, among the injections INJprim and INJsec, the amount by which the fuel injection amount in one injection increases and the other injection Is substantially equal to the amount by which the fuel injection amount decreases.

As a result, the difference between the sum of the fuel injection amounts in the respective injections INJprim and INJsec and the fuel injection amount when the fuel is collectively injected with the average value Pave of the pulsating fuel pressure can be reduced. Variations in the fuel injection amount between the cylinders accompanying the pulsation of the fuel pressure can be more suitably suppressed.
(3) When the fuel injection in each cylinder is divided into three or more times and executed, the fuel is injected in each cylinder due to fuel injection other than the two injections in which the injection interval is set to the half cycle interval. The total amount of fuel is susceptible to pulsation of fuel pressure. In this regard, in the above embodiment, the number of fuel injection divisions in each cylinder during the feed pressure injection is set to two. Therefore, the influence of the pulsation of the fuel pressure can be reduced as much as possible, and the variation in the fuel injection amount between the cylinders due to the pulsation of the fuel pressure during the feed pressure injection can be effectively suppressed.
(4) When split injection is performed, the initial fuel injection timing has a greater contribution than the other fuel injection timings in determining the combustion state such as the diffusion state of the air-fuel mixture. In view of this point, in the above-described embodiment, the injection start timing θinj in the divided injection is set based on the engine coolant temperature THW having a correlation with the engine operation state, and the subsequent fuel is set based on the set injection start timing θinj. The injection timing is set. Therefore, the injection timing of each injection INJprim and INJsec in the split injection can be set to a timing that is in line with the engine operating state, and misfire and a decrease in engine output during feed pressure injection can be suppressed.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above embodiment, the first injection time Tprim and the second injection time Tsec are set to be equal. However, the first injection time Tprim and the second injection time Tsec are set to different lengths. A configuration may be adopted. Even when the injection times Tprim and Tsec are different, if each injection INJprim and INJsec is executed with an injection interval Tint equal to the half cycle of the reciprocating movement of the plunger, the fuel injection amount in one injection is When it increases, the fuel injection amount in the other injection decreases. Therefore, the sum of the fuel injection amounts in each of the injections INJprim and INJsec is the fuel injection when the fuel is collectively injected with the average value Pave of the pulsating fuel pressure regardless of the timing of the fuel pressure pulsation cycle. Get closer to the amount.

  In the above embodiment, as illustrated in FIGS. 4 and 5, the lower the engine coolant temperature THW, the greater the total fuel injection amount Qtotal, and the lower the engine coolant temperature, the more retarded the injection start timing θinj is. However, the setting mode of the total fuel injection amount Qtotal and the injection start timing θinj is not limited to this. Further, as a parameter for setting the total fuel injection amount Qtotal and the injection start timing θinj, other parameters can be used instead of or in addition to the engine cooling water temperature THW. In short, the total fuel injection amount Qtotal and the injection start timing θinj may be set in accordance with the engine operating state.

  The present invention can be applied to the case where the fuel is divided into a plurality of times and the number of times of division is set to 2 or more when the fuel is divided into feed pressures. That is, if two injections having an interval equal to the half cycle of the reciprocating period of the plunger are included, the average of the fuel pressure at which one injection pulsates with respect to the two injections that are set to each other in this way. When the fuel pressure is higher than the value, the other injection is performed at a fuel pressure lower than the average value of the pulsating fuel pressure. For this reason, the sum of the fuel injection amounts in the pair of injections executed at such intervals is the fuel injection with the average value of the pulsating fuel pressure regardless of the timing of the fuel pressure pulsation cycle. It approaches the fuel injection amount in the case. As a result, the total amount of fuel injected in each cylinder can be brought close to the fuel injection amount when the fuel is collectively injected with an average value of pulsation.

  In the above embodiment, the high pressure pump 20 that adjusts the amount of fuel supplied to the delivery pipe 30 by changing the valve closing period of the spill valve 26 in the ascending stroke of the plunger 22 is shown. On the other hand, even in a fuel supply system having a high-pressure pump that adjusts the amount of fuel supplied to the delivery pipe 30 by changing the valve opening period of the spill valve 26 in the downward stroke of the plunger 22. Can be applied.

  Further, although the high pressure pump 20 driven by the drive cam 51 provided on the intake camshaft 50 of the engine is shown, the engine output such as the high pressure pump driven by the drive cam provided on the exhaust camshaft or the crankshaft is shown. The present invention can be applied to any fuel supply system provided with a high-pressure pump driven by the rotational force of the shaft.

  -Although the structure which performs the division | segmentation injection concerning this invention at the time of engine starting was shown in the said embodiment, this invention is not limited to the feed pressure injection at the time of engine starting. In the feed pressure injection in which the periodic pulsation of the fuel pressure is generated, the occurrence of inconvenience due to the influence of the pulsation can be suppressed by executing the divided injection according to the present invention.

  In the above-described embodiment, an example in which the present invention is applied to the fuel supply system including only the in-cylinder injector 40 as the fuel injection device has been described. However, the present invention is directed to the in-cylinder injector. In addition, the present invention can also be applied to a fuel supply system including a port injection injector that injects fuel into an intake port.

  -Variation in fuel injection amount for each cylinder due to the influence of fuel pressure pulsation during feed pressure injection is not limited to the 6-cylinder internal combustion engine as shown in the above embodiment, but is applicable to internal combustion engines such as 4-cylinder and 8-cylinder. However, the present invention is not limited to a six-cylinder engine, and can be applied to engines such as a four-cylinder engine and an eight-cylinder engine.

1 is a schematic diagram showing a schematic configuration of a vehicle fuel supply system including a fuel injection control device according to an embodiment of the present invention. The timing chart which shows the opening-and-closing timing of the injector in the division | segmentation injection concerning the embodiment. The flowchart which shows the flow of the calculation process of the various setting values concerning the division | segmentation injection. The graph which shows the relationship between the engine coolant temperature and the fuel injection amount in the calculation map for total fuel injection amount calculation. The graph which shows the relationship between the engine coolant temperature and the injection start time in the calculation map for injection start time calculation. The timing chart which shows the relationship between the timing of two divided injections, and fuel pressure. (A), (b) is a schematic diagram which shows the general structure of a high pressure pump. The timing chart which shows the relationship between the reciprocating motion of the plunger in a general high pressure pump, and the fuel pressure in a delivery pipe.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Feed pump, 11 ... Fuel tank, 12 ... Filter, 13 ... Return passage, 14 ... Pressure regulator, 20 ... High pressure pump, 21 ... Cylinder, 22 ... Plunger, 23 ... Pressurizing chamber, 24 ... Lifter, 25 ... Spring 26 ... Spill valve, 27 ... Valve element, 28 ... Spring, 29 ... Solenoid, 30 ... Delivery pipe, 31 ... Low pressure passage, 32 ... High pressure passage, 33 ... Check valve, 34 ... Relief passage, 35 ... Relief valve, DESCRIPTION OF SYMBOLS 40 ... Injector, 50 ... Intake cam shaft, 51 ... Drive cam, 61 ... Fuel pressure sensor, 62 ... Water temperature sensor, 63 ... Rotational speed sensor, 100 ... Electronic control unit, 101 ... Drive circuit.

Claims (5)

A feed pump that discharges fuel in the fuel tank at a predetermined pressure, and a high pressure that reciprocates the plunger by the rotational force of the engine output shaft to pressurize the fuel supplied from the feed pump to the pressurizing chamber and supply it to the delivery pipe A pump, an in-cylinder injector provided in each cylinder of the internal combustion engine to which fuel is distributed and supplied from the delivery pipe, and a fuel provided in the pressurizing chamber of the high-pressure pump and supplied to the delivery pipe. A normal injection for injecting the fuel pressurized by the high-pressure pump and accumulated in the delivery pipe from the in-cylinder injector, and holding the spill valve in an open state. Feed pressure injection for injecting fuel in the delivery pipe from the in-cylinder injector based on the discharge pressure of the feed pump. The fuel injection control device for an internal combustion engine that executes Te Toggles,
Detecting means for detecting a half cycle of the reciprocating period of the plunger;
In the feed pressure injection, divided injection is performed in which the fuel is divided into a plurality of injections, and the time interval between two of the divided injections is equal to the half cycle detected by the detection means. The fuel injection control device for an internal combustion engine, comprising: The fuel injection control device for an internal combustion engine according to claim 1,
The fuel injection control device for an internal combustion engine, wherein the injection control means sets the injection times of two injections executed at intervals of a half cycle detected by the detection means. The fuel injection control device for an internal combustion engine according to claim 1 or 2,
The fuel injection control device for an internal combustion engine, wherein the injection control means sets the number of divisions of the feed pressure injection to two. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 3,
The fuel injection control device for an internal combustion engine, wherein the detection means detects the estimation by estimating a period of reciprocation of the plunger based on an engine rotational speed of the internal combustion engine. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4,
The injection control means sets an initial fuel injection timing in split injection based on an engine operating state, and sets a subsequent fuel injection timing based on the set initial fuel injection timing. Engine fuel injection control device.

Images