JP5076879B2 - Fuel injection control system for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection control system for a compression ignition type internal combustion engine.

Conventionally, as a fuel injection method for a compression ignition type internal combustion engine, a technique of performing pilot injection prior to main injection is known. In such a fuel injection method, a technique has been proposed in which at least one of the advance angle of the main injection timing, the increase of the pilot injection amount, or the increase of the injection pressure is performed as the oxygen concentration in the cylinder decreases ( For example, see Patent Document 1).
JP 2003-129890 A JP 2001-090595 A JP 2001-159360 A JP 2002-138889 A JP 2005-299530 A

  By the way, the fuel injection parameter is determined on the assumption that the oxygen concentration in the cylinder (hereinafter referred to as “cylinder oxygen concentration”) matches the target value (hereinafter referred to as “target cylinder oxygen concentration”). It is done.

  However, when the internal combustion engine is operated transiently, the in-cylinder oxygen concentration may be far from the target in-cylinder oxygen concentration. In such a case, since the fuel injection parameter becomes inappropriate with respect to the actual in-cylinder oxygen concentration, the magnitude of the combustion noise may exceed the allowable range.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is combustion in transient operation in a fuel injection control system of a compression ignition internal combustion engine in which fuel is divided and injected multiple times. The purpose is to keep the noise level within the allowable range as much as possible.

  The present invention employs the following means in order to solve the above-described problems. That is, the present invention relates to a fuel injection control system for an internal combustion engine that injects fuel to be injected into a cylinder into a plurality of times, a determination means for determining a fuel injection parameter based on an operating condition of the internal combustion engine, A first acquisition means for acquiring an actual in-cylinder oxygen concentration that is an actual oxygen concentration of the second cylinder, a second acquisition means for acquiring a target in-cylinder oxygen concentration that is an oxygen concentration in a cylinder that meets the operating conditions of the internal combustion engine, Prediction means for predicting combustion noise generated when fuel injection is performed in accordance with the fuel injection parameter determined by the determination means under the actual in-cylinder oxygen concentration acquired by the first acquisition means, and the second acquisition And predicting combustion noise generated when fuel injection is performed in accordance with the fuel injection parameter determined by the determination means under the target in-cylinder oxygen concentration acquired by the means The setting means for setting the predicted combustion noise as the target combustion noise, and the actual combustion when the difference between the combustion noise predicted by the prediction means and the target combustion noise set by the setting means exceeds an allowable value Correction means for correcting the fuel injection parameter determined by the determination means so that the noise approximates the target combustion noise; and control means for operating the fuel injection valve in accordance with the fuel injection parameter corrected by the correction means. I prepared.

In such an invention, the determining means determines the fuel injection parameter according to the operating condition of the internal combustion engine. At that time, the determining means determines the fuel injection parameter on the assumption that the actual in-cylinder oxygen concentration matches the desired target oxygen concentration. Hereinafter, the fuel injection parameter determined by the determining means is referred to as a basic fuel injection parameter.

  By the way, during transient operation, such as during acceleration operation or when returning from fuel cut operation, the actual in-cylinder oxygen concentration may be far from the target oxygen concentration. If the fuel injection control is performed according to the basic fuel injection parameters when the actual in-cylinder oxygen concentration is far from the target oxygen concentration, the magnitude of combustion noise and the amount of smoke generated may deviate from the allowable range.

  On the other hand, the fuel injection control system for an internal combustion engine according to the present invention is a combustion noise (hereinafter referred to as “actual combustion noise”) that can be generated when fuel injection is performed in accordance with basic fuel injection parameters under an actual in-cylinder oxygen concentration. And the combustion noise (target combustion noise) that can be generated when fuel injection is performed in accordance with the basic fuel injection parameters under the target in-cylinder oxygen concentration. If the difference between the two exceeds the allowable value, the basic fuel injection parameter is corrected so that the difference between the two falls within the allowable value. The fuel injection valve operates according to the corrected fuel injection parameter.

  According to this invention, even when the actual in-cylinder oxygen concentration is different from the target in-cylinder oxygen concentration, such as during transient operation of the internal combustion engine, the actual combustion noise can be approximated to the target combustion noise. .

  According to the knowledge of the inventor of the present application, in an internal combustion engine in which fuel is divided and injected multiple times, a change in combustion noise with respect to a change in in-cylinder oxygen concentration, and a change in combustion noise with respect to a change in fuel injection parameters. It may not be a monotonous change.

  For this reason, the fuel injection control system for an internal combustion engine according to the present invention includes means for storing or calculating a correlation between the in-cylinder oxygen concentration and the combustion noise (hereinafter referred to as “first correlation”). Also good.

  In this case, the predicting means can accurately predict the actual combustion noise predicted value based on the actual in-cylinder oxygen concentration and the first correlation. Further, the setting means can appropriately set the target combustion noise based on the target in-cylinder oxygen concentration and the first correlation.

  The fuel injection control system for an internal combustion engine according to the present invention includes means for specifying a correlation between the fuel injection parameter and the combustion noise under the actual in-cylinder oxygen concentration (hereinafter referred to as “second correlation”). You may make it prepare.

  In this case, the correction means can accurately determine the fuel injection parameter that satisfies the target combustion noise based on the second correlation.

  At this time, there may be a plurality of fuel injection parameters that satisfy the target combustion noise in the second correlation. In such a case, the correcting means may select a fuel injection parameter that produces the smallest amount of smoke among a plurality of fuel injection parameters. In this case, the amount of smoke generated can be reduced as much as possible while keeping the magnitude of the combustion noise within an allowable range.

  The correcting means may select the fuel injection parameter closest to the basic fuel injection parameter from among the plurality of fuel injection parameters. In this case, the influence (for example, change in fuel pressure pulsation, etc.) due to correction of the fuel injection parameter can be minimized.

As the fuel injection parameter according to the present invention, one of the injection amount, the injection interval, the injection timing, or the injection pressure of each time can be exemplified.

  According to the present invention, in a fuel injection control system of a compression ignition internal combustion engine in which fuel is divided and injected multiple times, the magnitude of combustion noise during transient operation can be kept within an allowable range as much as possible.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

<Example 1>
First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of a fuel injection control system for an internal combustion engine according to the present invention.

  An internal combustion engine 1 shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine). The internal combustion engine 1 includes a fuel injection valve 3 that directly injects fuel into the cylinder 2.

  The interior (combustion chamber) of the cylinder 2 communicates with the intake passage 4. A compressor housing 50 and an intercooler 6 of the turbocharger 5 are disposed in the intake passage 4.

  The intake air that has flowed into the intake passage 4 is compressed by the compressor housing 50. The intake air compressed by the compressor housing 50 is guided to the cylinder 2 after being cooled by the intercooler 6. The intake air introduced into the cylinder 2 is ignited and burned in the cylinder 2 together with the fuel injected from the fuel injection valve 3.

  Each cylinder 2 communicates with the exhaust passage 7. In the middle of the exhaust passage 7, a turbine housing 51 and an exhaust purification device 8 are arranged. Gas burned in each cylinder 2 (burned gas) is discharged to the exhaust passage 7. The exhaust discharged into the exhaust passage 7 is discharged into the atmosphere via the turbine housing 51 and the exhaust purification device 8 in order.

  The exhaust purification device 8 includes, for example, an NOx storage reduction catalyst and / or a particulate filter, and purifies harmful gas components in the exhaust.

  A portion of the intake passage 4 downstream of the intercooler 6 and a portion of the exhaust passage 7 upstream of the turbine housing 51 are connected to each other by an EGR passage 9. In the middle of the EGR passage 9, an EGR valve 10 that adjusts the flow rate of exhaust gas (hereinafter referred to as “EGR gas”) flowing through the EGR passage 9, and an EGR cooler for cooling the EGR gas flowing through the EGR passage 9 11 is arranged. An intake throttle valve 12 is disposed in a portion of the intake passage 4 downstream of the intercooler 6 and upstream of the connection portion of the EGR passage 9.

  The internal combustion engine 1 configured as described above is provided with an ECU 13. The ECU 13 is an electronic control unit that includes a CPU, ROM, RAM, backup RAM, and the like. The ECU 13 is electrically connected to various sensors such as an air flow meter 14, a crank position sensor 15, a water temperature sensor 16, an air-fuel ratio sensor 17, and an accelerator position sensor 18.

The air flow meter 14 is attached to the intake passage 4 upstream of the compressor housing 50 and measures the amount of air flowing into the intake passage 4. The crank position sensor 15 is attached to the internal combustion engine 1 and measures the rotational position of an unillustrated engine output shaft (crankshaft). The water temperature sensor 16 is attached to the internal combustion engine 1 and measures the temperature of the cooling water circulating through the internal combustion engine 1. The air-fuel ratio sensor 17 is attached to the exhaust passage 7 and measures the air-fuel ratio of the exhaust flowing through the exhaust passage 7. The accelerator position sensor 18 is attached to an accelerator pedal (not shown) and measures the amount of operation of the accelerator pedal (accelerator opening).

  The ECU 13 electrically controls the fuel injection valve 3, the EGR valve 10, and the intake throttle valve 12 based on the measurement values of various sensors as described above. For example, the ECU 13 performs fuel injection control that is the gist of the present invention. Hereinafter, fuel injection control in this embodiment will be described.

  The ECU 13 determines a fuel injection parameter (basic fuel injection parameter) according to the operating conditions (for example, the engine speed Ne and the accelerator opening degree Accp) of the internal combustion engine 1. The fuel injection parameters here include a pilot injection amount, a main injection amount, a pilot interval (an interval between pilot injections and / or an interval between pilot injection and main injection), main injection timing, injection pressure, and the like.

  By the way, the basic fuel injection parameters are determined on the assumption that the oxygen concentration in the cylinder 2 (in-cylinder oxygen concentration) matches the desired target oxygen concentration. However, during transient operation such as acceleration operation or return from fuel cut operation, the actual in-cylinder oxygen concentration (actual in-cylinder oxygen concentration) may be far from the target oxygen concentration.

  If the fuel injection control is performed according to the basic fuel injection parameter when the actual in-cylinder oxygen concentration is far from the target oxygen concentration, the magnitude of combustion noise and the amount of smoke generated may deviate from the allowable range.

  In contrast, in the fuel injection control of the present embodiment, the basic fuel injection parameters are corrected so that the magnitude of combustion noise and the amount of smoke generated are appropriate. In the following, an example in which the basic fuel injection parameter is corrected by giving priority to the magnitude of combustion noise over the amount of smoke generated will be described. This is because even if the amount of smoke generated from the internal combustion engine 1 is slightly increased, the smoke is purified by the exhaust gas purification device 8.

  The ECU 13 predicts the magnitude of combustion noise that can be generated under the actual in-cylinder oxygen concentration (actual combustion noise predicted value) cntemp, and the magnitude of combustion noise that can be generated under the target oxygen concentration (target combustion noise). ) Cntrg was predicted, and the fuel injection parameter was corrected when the difference exceeded the allowable value.

  First, the prediction method of the actual combustion noise prediction value and the target combustion noise will be described.

  FIG. 2 is a diagram showing a correlation (first correlation) between the in-cylinder oxygen concentration and the combustion noise. In FIG. 2, conditions other than the in-cylinder oxygen concentration (for example, pilot interval, injection timing, injection amount, injection pressure, etc.) are constant.

  In FIG. 2, the in-cylinder oxygen concentration is lower than the in-cylinder oxygen concentration (hereinafter referred to as “first in-cylinder oxygen concentration”) roxc1 when the magnitude of the combustion noise shows the maximum value cnmax (FIG. 2). In the middle region A), the combustion noise increases as the in-cylinder oxygen concentration increases. In the region where the in-cylinder oxygen concentration is higher than the first in-cylinder oxygen concentration roxc1 and lower than the second in-cylinder oxygen concentration roxc2 (region B in FIG. 2), the combustion noise decreases as the in-cylinder oxygen concentration increases. In the region where the in-cylinder oxygen concentration is higher than the second in-cylinder oxygen concentration roxc2 (region C in FIG. 2), the combustion noise decreases as the in-cylinder oxygen concentration increases as in the above-described region B. The degree of decrease (slope) is gentler than that in region B. In FIG. 2, roxcmin represents the minimum value that the actual in-cylinder oxygen concentration can take, and roxcmax represents the maximum value that the actual in-cylinder oxygen concentration can take.

  Thus, the magnitude of the combustion noise does not monotonously increase / decrease with respect to the increase / decrease in the in-cylinder oxygen concentration. Such a tendency becomes more prominent as the number of pilot injections increases. For this reason, when predicting the actual combustion noise predicted value cntemp and the target combustion noise cntrg, it is necessary to specify the first correlation as shown in FIG.

  The first correlation differs depending on the fuel injection parameter. For this reason, the first correlation may be mapped in advance for each fuel injection parameter, but the data amount of the map may be enormous.

  Therefore, the coordinate point a1 when the in-cylinder oxygen concentration becomes the minimum value roxcmin, the coordinate point a2 when the in-cylinder oxygen concentration becomes the first in-cylinder oxygen concentration roxc1, and the in-cylinder oxygen concentration becomes the second in-cylinder oxygen concentration roxc2. The coordinate point a3 when the in-cylinder oxygen concentration becomes the maximum value roxcmax may be mapped for each fuel injection parameter.

  The fuel injection parameter correlates with the engine speed Ne and the engine load (accelerator opening Accp). For this reason, the coordinate points a1 to a4 may be obtained from a map using the engine speed Ne and the accelerator opening degree Accp as parameters.

  When the ECU 13 obtains four coordinate points a1, a2, a3, a4 based on the engine speed Ne and the accelerator opening degree Accp, the first correlation as shown in FIG. 2 is obtained by linearly interpolating these coordinate points. Derive relationships.

  The ECU 13 obtains a predicted value of actual combustion noise (actual combustion noise predicted value) cntemp based on the first correlation and the actual in-cylinder oxygen concentration roxc, and based on the first correlation and the target in-cylinder oxygen concentration roxctrg. The target combustion noise cntrg is obtained (see FIG. 3).

  The actual in-cylinder oxygen concentration roxc may be estimated from the intake air amount, the boost pressure, the intake air temperature, the EGR gas transport delay, or the like, or directly measured by an oxygen concentration sensor attached to the intake manifold or the intake port. Also good. Further, the target in-cylinder oxygen concentration roxctrg may be specified from the target EGR rate, the target intake air amount, the target fuel injection amount, and the like.

  When the actual combustion noise predicted value cntemp and the target combustion noise cntrg are predicted by the method as described above, the ECU 13 determines whether or not the difference between the two exceeds an allowable value.

  When the difference between the actual combustion noise predicted value cntemp and the target combustion noise cntrg is equal to or less than the allowable value, the ECU 13 operates the fuel injection valve 3 according to the basic fuel injection parameter. On the other hand, if the difference between the actual combustion noise predicted value cntemp and the target combustion noise cntrg exceeds the allowable value, the ECU 13 corrects the basic fuel injection parameter so that the difference between the two is less than the allowable value. The fuel injection valve 3 is operated according to the fuel injection parameters.

  Here, a fuel injection parameter correction method will be described. Here, an example in which a pilot interval is used as a fuel injection parameter will be described. Hereinafter, the pilot interval corresponding to the basic fuel injection parameter is referred to as a basic pilot interval.

  FIG. 4 is a diagram showing a correlation (second correlation) between the combustion noise and the pilot interval. The second correlation shown in FIG. 4 is a correlation when the actual in-cylinder oxygen concentration roxc matches the target in-cylinder oxygen concentration roxctrg and the fuel injection parameters other than the pilot interval are constant.

  In FIG. 4, the region where the actual pilot interval becomes shorter than the pilot interval (hereinafter referred to as “first pilot interval”) aint1 when the magnitude of the combustion noise shows the minimum value cminin (region D in FIG. 4). ), The combustion noise decreases as the pilot interval increases. On the other hand, in the region where the actual pilot interval is longer than the first pilot interval aint1 (region E in FIG. 4), the combustion noise increases as the pilot interval increases. In addition, aintmin in FIG. 4 shows the minimum value which a pilot interval can take, and aintmax shows the maximum value which a pilot interval can take.

  Thus, the magnitude of the combustion noise does not monotonously increase / decrease monotonously with changes in the pilot interval. Such a tendency becomes more prominent as the number of pilot injections increases. For this reason, when specifying the pilot interval that satisfies the target combustion noise cntrg, it is necessary to specify the second correlation as shown in FIG.

  The second correlation differs depending on conditions other than the pilot interval. For this reason, the second correlation may be mapped in advance for each condition other than the pilot interval, but the amount of information on the map may be enormous.

  Therefore, a coordinate point b1 when the pilot interval is the minimum value aintmin, a coordinate point b2 when the pilot interval is the first pilot interval aint1, and a coordinate point b3 when the pilot interval is the maximum value aintmax You may make it map for every conditions.

  When the ECU 13 obtains the three coordinate points b1, b2, and b3 based on the above-described map, the ECU 13 derives the second correlation as shown in FIG. 4 by linearly interpolating these coordinate points.

  Incidentally, the second correlation shown in FIG. 4 is a correlation when the actual in-cylinder oxygen concentration roxc matches the target in-cylinder oxygen concentration roxctrg (hereinafter referred to as “basic second correlation”). . For this reason, when the actual in-cylinder oxygen concentration roxc is different from the target in-cylinder oxygen concentration roxctrg as in transient operation, the basic second correlation cannot be used as it is.

  On the other hand, the ECU 13 corrects the basic second correlation based on the first correlation shown in FIG. 2 described above, so that the second correlation (hereinafter referred to as “adapted first”) adapted to the actual in-cylinder oxygen concentration roxc. 2 correlation) ”.

  Specifically, the ECU 13 first determines whether or not the actual combustion noise predicted value cntemp is larger than the target combustion noise cntrg. When the actual combustion noise predicted value cntemp is larger than the target combustion noise cntrg, the ECU 13 shifts the basic second correlation in the increasing direction of the combustion noise. As shown in FIG. 5, the shift amount at that time is determined so that the magnitude of the combustion noise when the pilot interval becomes equal to the basic pilot interval aintbase coincides with the actual combustion noise predicted value cntemp described above. Note that the solid line in FIG. 5 indicates the basic second correlation, and the dashed line in FIG. 5 indicates the compatible second correlation.

  When the adaptive second correlation is specified in this way, the ECU 13, as shown in FIG. 6, the pilot interval that satisfies the target combustion noise cntrg in the adaptive second correlation (hereinafter referred to as “adapted pilot interval”). ) Find aintcom.

In the example shown in FIG. 6, there are two adaptive pilot intervals aintcom (aintcom1 and aintcom2 in FIG. 6). In such a case, the ECU 13
The adaptive pilot interval aintcom2 close to the basic pilot interval aintbase is selected from the two adaptive pilot intervals aintcom1 and aintcom2.

  This is because if the suitable pilot interval aintcom is greatly separated from the basic pilot interval aintbase, the pulsation of the fuel pressure may change in the common rail (not shown) and affect the injection pressure and the injection amount.

  On the other hand, when the actual combustion noise predicted value cntemp is smaller than the target combustion noise cntrg, the ECU 13 shifts the basic second correlation in the reduction direction of the combustion noise. As shown in FIG. 7, the shift amount at that time is determined so that the magnitude of the combustion noise when the pilot interval becomes equal to the basic pilot interval aintbase coincides with the actual combustion noise predicted value cntemp described above. Note that the solid line in FIG. 7 indicates the basic second correlation, and the dashed line in FIG. 7 indicates the compatible second correlation.

  When the adaptive second correlation is specified in this way, the ECU 13 obtains an adaptive pilot interval aintcom that satisfies the target combustion noise cntrg in the adaptive second correlation as shown in FIG.

  In the example shown in FIG. 8, there are two suitable pilot intervals aintcom (aintcom3 and aintcom4 in FIG. 8). Also in this case, similar to the example of FIG. 6 described above, the suitable pilot interval aintcom3 close to the basic pilot interval aintbase is selected.

  When the adaptive pilot interval aintcom is selected by the method described in the description of FIGS. 7 and 8, the ECU 13 performs correction for replacing the selected basic pilot interval aintbase with the adaptive pilot interval aintcom. Then, the ECU 13 operates the fuel injection valve 3 in accordance with the corrected basic pilot interval aintbase (= adapted pilot interval aintcom).

  When the fuel injection valve 3 is operated by the method described above, the actual in-cylinder oxygen concentration roxc and the target in-cylinder oxygen concentration roxctrg are different when the fuel injection valve 3 injects fuel in a plurality of times. Also, it is possible to prevent the combustion noise from deviating from the allowable range.

  Hereafter, the execution procedure of the fuel injection control in a present Example is demonstrated along FIG. FIG. 9 is a flowchart showing a pilot interval determination routine in the present embodiment. This pilot interval determination routine is a routine stored in advance in the ROM of the ECU 13 and is periodically executed by the ECU 13.

  In the pilot interval determination routine, first, in S101, the ECU 13 obtains the operating conditions (the engine speed Ne, the accelerator opening degree Accp) of the internal combustion engine 1.

  In S102, the ECU 13 calculates a basic pilot interval aintbase based on the operating condition acquired in S101.

  In S103, the ECU 13 acquires the actual in-cylinder oxygen concentration roxc.

  In S104, the ECU 13 specifies a first correlation (see FIG. 2) corresponding to the operating condition acquired in S101, and performs actual combustion based on the first correlation and the actual in-cylinder oxygen concentration roxc. The noise prediction value cntemp is predicted.

  In S105, the ECU 13 acquires the target in-cylinder oxygen concentration roxctrg.

  In S106, the ECU 13 predicts the target combustion noise cntrg based on the first correlation specified in S104 and the target in-cylinder oxygen concentration roxctrg acquired in S105.

  In S107, the ECU 13 determines whether or not the difference (= | cntrg−cntemp |) between the actual combustion noise predicted value cntemp predicted in S104 and the target combustion noise cntrg predicted in S106 is larger than the allowable value a. To do.

  If a negative determination is made in S107 (| cntrg−cntemp | ≦ a), the ECU 13 proceeds to S111. In S111, the ECU 13 operates the fuel injection valve 3 in accordance with the basic pilot interval aintbase obtained in S102.

  On the other hand, if an affirmative determination is made in S107 (| cntrg-cntemp |> a), the ECU 13 proceeds to S108. In S108, the ECU 13 first specifies a basic second correlation (see FIG. 4) based on the operating condition acquired in S101 and the target in-cylinder oxygen concentration roxctrg acquired in S105. Subsequently, the ECU 13 specifies the compatible second correlation by correcting the basic second correlation based on the first correlation specified in S104 (see FIGS. 5 and 7).

  In S109, the ECU 13 determines a suitable pilot interval aintcom based on the suitable second correlation specified in S108 and the target combustion noise cntrg predicted in S106 (see FIGS. 6 and 8).

  In S110, the ECU 13 operates the fuel injection valve 3 in accordance with the adapted pilot interval aintcom determined in S109.

  As described above, when the ECU 13 executes the pilot interval determination routine of FIG. 9, the determination means, the first acquisition means, the second acquisition means, the prediction means, the setting means, the correction means, the specifying means, A control means is realized.

  Therefore, according to the fuel injection control system of the internal combustion engine of the present embodiment, in the fuel injection control system of the compression ignition type internal combustion engine in which the fuel is divided and injected multiple times, the magnitude of the combustion noise during the transient operation is reduced. It can be within the allowable range.

<Example 2>
Next, a second embodiment of the present invention will be described with reference to FIGS. Here, a configuration different from that of the first embodiment will be described, and description of the same configuration will be omitted.

  In the first embodiment described above, when there are a plurality of adaptive pilot intervals aintcom satisfying the target combustion noise cntrg, the adaptive pilot interval aintcom closest to the basic pilot interval aintbase is selected from the plurality of adaptive pilot intervals aintcom. An example was given.

On the other hand, in the present embodiment, when there are a plurality of adaptive pilot intervals aintcom that satisfy the target combustion noise cntrg, among the plurality of adaptive pilot intervals aintcom, the adaptive pilot interval aint that generates the least amount of smoke.
An example in which com is selected will be described.

  In this case, it is necessary to specify the correlation between the pilot interval and the amount of smoke generated. Therefore, in the fuel injection control system for the internal combustion engine of the present embodiment, the correlation between the pilot interval and the amount of smoke generated is specified using a method similar to the method for specifying the correlation between the pilot interval and the combustion noise. I did it.

  FIG. 10 is a diagram showing a correlation (third correlation) between the in-cylinder oxygen concentration and the amount of smoke generated. In FIG. 10, conditions other than the in-cylinder oxygen concentration (for example, pilot interval, injection timing, injection amount, injection pressure, etc.) are constant.

  In FIG. 10, the in-cylinder oxygen concentration is lower than the in-cylinder oxygen concentration (hereinafter referred to as “third in-cylinder oxygen concentration”) roxc3 when the amount of smoke generated reaches the maximum value smkmax0 (in FIG. 10). In region F), the amount of smoke generated increases as the in-cylinder oxygen concentration increases. In the region where the in-cylinder oxygen concentration is higher than the third in-cylinder oxygen concentration roxc3 (region G in FIG. 10), the amount of smoke generated decreases as the in-cylinder oxygen concentration increases.

  As shown in FIG. 10, the amount of smoke generated does not monotonously increase / decrease as the in-cylinder oxygen concentration increases / decreases. Such a tendency becomes more prominent as the number of pilot injections increases.

  The third correlation as shown in FIG. 10 is assumed to be mapped for each fuel injection parameter. At that time, the coordinate point c1 when the in-cylinder oxygen concentration becomes the minimum value roxcmin, the coordinate point c2 when the in-cylinder oxygen concentration becomes the third in-cylinder oxygen concentration roxc3, and the in-cylinder oxygen concentration become the maximum value roxcmax. Only the time coordinate point c3 may be mapped for each fuel injection parameter.

  FIG. 11 is a diagram illustrating a correlation (fourth correlation) between the pilot interval and the amount of smoke generated. The fourth correlation shown in FIG. 11 is a correlation when the actual in-cylinder oxygen concentration roxc matches the target in-cylinder oxygen concentration roxctrg and the fuel injection parameters other than the pilot interval are constant.

  In FIG. 11, the region where the actual pilot interval becomes shorter than the pilot interval (hereinafter referred to as “second pilot interval”) aint2 when the amount of smoke generated has the maximum value smkmax1 (region H in FIG. 11). Then, the amount of smoke generated increases as the pilot interval increases. On the other hand, in the region where the actual pilot interval is longer than the second pilot interval aint2 (region I in FIG. 11), the amount of smoke generated decreases as the pilot interval increases.

  Thus, the amount of smoke generated does not monotonously increase / decrease monotonously with changes in the pilot interval. Such a tendency becomes more prominent as the number of pilot injections increases.

  The fourth correlation as shown in FIG. 11 is assumed to be mapped in advance for each condition other than the pilot interval. At that time, only the coordinate point d1 when the pilot interval becomes the minimum value aintmin, the coordinate point d2 when the pilot interval becomes the second pilot interval aint2, and the coordinate point d3 when the pilot interval becomes the maximum value aintmax are only pilots. You may make it map for every conditions other than an interval.

  When the ECU 13 obtains the three coordinate points d1, d2, and d3 based on the above-described map, the ECU 13 derives the fourth correlation as shown in FIG. 11 by linearly interpolating these coordinate points.

  The fourth correlation shown in FIG. 11 is a correlation when the actual in-cylinder oxygen concentration roxc matches the target in-cylinder oxygen concentration roxctrg (hereinafter referred to as “basic fourth correlation”). . For this reason, when the actual in-cylinder oxygen concentration roxc is different from the target in-cylinder oxygen concentration roxctrg as in transient operation, the basic fourth correlation cannot be used as it is.

  On the other hand, the ECU 13 corrects the basic fourth correlation based on the third correlation shown in FIG. 10 described above to thereby adjust the fourth correlation (hereinafter referred to as “adapted first”) that matches the actual in-cylinder oxygen concentration roxc. 4 correlation ").

  Specifically, the ECU 13 firstly generates a smoke amount when the in-cylinder oxygen concentration becomes equal to the actual in-cylinder oxygen concentration roxc in the third correlation of FIG. 10 (hereinafter referred to as “actual smoke generation amount prediction value”). The smktemp and the smoke generation amount (hereinafter referred to as “target smoke generation amount”) smktrg when the in-cylinder oxygen concentration becomes equal to the target in-cylinder oxygen concentration roxctrg are obtained.

  The ECU 13 compares the actual smoke generation amount predicted value smktemp with the target smoke generation amount smktrg. When the actual smoke generation amount predicted value smktemp is larger than the target smoke generation amount smktrg, the ECU 13 shifts the basic fourth correlation in the direction of increasing the smoke generation amount. As shown in FIG. 12, the shift amount at that time is determined so that the smoke generation amount when the pilot interval becomes equal to the basic pilot interval aintbase coincides with the actual smoke generation amount prediction value smktemp described above. Note that the solid line in FIG. 12 indicates the basic fourth correlation, and the dashed line in FIG. 12 indicates the compatible fourth correlation.

  When the adaptive fourth correlation is specified in this way, the ECU 13 selects an adaptive pilot interval aintcom that produces the smallest amount of smoke among a plurality of adaptive pilot intervals aintcom that satisfy the target combustion noise cntrg.

  For example, as shown in FIG. 13, when there are two adapted pilot intervals aintcom (aintcom1 and aintcom2 in FIG. 13) that satisfy the target combustion noise cntrg, the ECU 13 uses the adapted fourth correlation to adapt the adapted pilot. A smoke generation amount smk1 in the interval aintcom1 and a smoke generation amount smk2 in the adaptive pilot interval aintcom2 are obtained. In the example shown in FIG. 13, since the smoke generation amount smk1 in the adaptive pilot interval aintcom1 is smaller than the smoke generation amount smk2 in the adaptive pilot interval aintcom2, the ECU 13 selects the adaptive pilot interval aintcom1.

  When both the smoke generation amount smk1 and the smoke generation amount smk2 are smaller than the target smoke generation amount smktrg described above, the ECU 13 of the two compatible pilot intervals aintcom1 and aintcom2, whichever is closer to the basic pilot interval aintbase, An interval (aintcom2 in the example of FIG. 13) may be selected. In this case, the combustion noise and the amount of smoke generated can be within the allowable ranges, and the influence (change in fuel pressure pulsation in the common rail, etc.) due to the change in the pilot interval can be minimized.

  When the suitable pilot interval aintcom is selected by the method described above, when the actual in-cylinder oxygen concentration roxc and the target in-cylinder oxygen concentration roxctrg are different, the actual combustion noise level is made equal to the target combustion noise cntrg. And the amount of smoke generated can be reduced as much as possible.

  Hereinafter, the execution procedure of the fuel injection control in this embodiment will be described with reference to FIG. FIG. 14 is a flowchart showing a pilot interval determination routine in the present embodiment. In FIG. 14, the same reference numerals are given to the processes equivalent to the pilot interval determination routine (see FIG. 9) of the first embodiment described above.

  In the pilot interval determination routine, the ECU 13 specifies an appropriate pilot interval aintcom that satisfies the target combustion noise cntrg in S109, and then proceeds to S201.

  In S201, the ECU 13 determines whether or not there are a plurality of suitable pilot intervals aintcom specified in S109.

  If an affirmative determination is made in S201, the ECU 13 proceeds to S202. In S202, the ECU 13 first specifies a third correlation (see FIG. 10) corresponding to the operating condition acquired in S101. Subsequently, the ECU 13 specifies a basic fourth correlation (see FIG. 11) based on the operating condition acquired in S101 and the target in-cylinder oxygen concentration roxctrg acquired in S105. Further, the ECU 13 specifies the adapted fourth correlation by correcting the basic fourth correlation based on the third correlation (see FIG. 12).

  In S203, the ECU 13 selects a suitable pilot interval aintcom having the smallest amount of smoke generation based on the plurality of suitable pilot intervals aintcom specified in S109 and the adapted fourth correlation. The ECU 13 executes the process of S110 according to the adapted pilot interval aintcom selected in S203.

  If a negative determination is made in S201, the ECU 13 skips S202 and S203 and proceeds to S110.

  As described above, when the ECU 13 executes the pilot interval determination routine of FIG. 14 and the actual in-cylinder oxygen concentration roxc is different from the target in-cylinder oxygen concentration roxctrg, the actual combustion noise magnitude is set to the target combustion noise. It can be made equal to cntrg, and the amount of smoke generated can be reduced as much as possible.

  In the first and second embodiments described above, the pilot interval is taken as an example of the fuel injection parameter, but it goes without saying that the main injection timing, the pilot injection amount, or the injection pressure may be used. In this case, the ECU 13 correlates the main injection timing and the combustion noise at the actual in-cylinder oxygen concentration roxc (see FIG. 15), and the correlation between the pilot injection amount and the combustion noise at the actual in-cylinder oxygen concentration roxc (see FIG. 15). 16) or the correlation (see FIG. 17) between the injection pressure and the combustion noise at the actual in-cylinder oxygen concentration roxc is specified, and the fuel injection parameter satisfying the target combustion noise cntrg in the specified correlation is obtained. Good. Similar to the pilot interval, the correlation between each parameter described above and the combustion noise may be specified based on the correlation between the in-cylinder oxygen concentration and each parameter.

It is a figure which shows schematic structure of the fuel-injection control system of an internal combustion engine. It is a figure which shows the correlation with a cylinder oxygen concentration and the magnitude | size of a combustion noise. It is a figure which shows the method of estimating an actual combustion noise predicted value and a target combustion noise. It is a figure which shows the correlation with a pilot interval when the in-cylinder oxygen concentration corresponds to the target in-cylinder oxygen concentration, and the magnitude of combustion noise. It is a figure which shows the 1st method of calculating | requiring the correlation with a pilot interval and the magnitude of a combustion noise when the in-cylinder oxygen concentration corresponds with an actual in-cylinder oxygen concentration. It is a figure which shows the method of calculating | requiring a suitable pilot interval in a 1st Example. It is a figure which shows the 2nd method of calculating | requiring the correlation with a pilot interval and the magnitude of a combustion noise when the in-cylinder oxygen concentration corresponds with an actual in-cylinder oxygen concentration. It is a figure which shows the other method of calculating | requiring a suitable pilot interval in a 1st Example. It is a flowchart which shows the pilot interval determination routine in a 1st Example. It is a figure which shows the correlation with a cylinder oxygen concentration and the generation amount of smoke. It is a figure which shows the correlation with a pilot interval when the cylinder oxygen concentration corresponds with a target cylinder oxygen concentration, and the generation amount of smoke. It is a figure which shows the correlation with a pilot interval when the cylinder oxygen concentration corresponds with a target cylinder oxygen concentration, and the generation amount of smoke. It is a figure which shows the method of calculating | requiring a suitable pilot interval in a 2nd Example. It is a flowchart which shows the pilot interval determination routine in a 2nd Example. It is a figure which shows the correlation with the main injection timing and the magnitude | size of a combustion noise. It is a figure which shows the correlation with the amount of pilot injection, and the magnitude | size of a combustion noise. It is a figure which shows the correlation with an injection pressure and the magnitude | size of a combustion noise.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Fuel injection valve 4 ... Intake passage 5 ... Turbocharger 6 ... Intercooler 7.・ ・ ・ ・ Exhaust passage 8 ・ Exhaust gas purification device 9 ・ EGR passage 10 ・ ・ ・ ・ EGR valve 11 ・ ・ ・ ・ EGR cooler 12 ・ ・ ・ ・ Intake throttle valve 13 ・ ・ ・ ・ECU
14 .... Air flow meter 15 .... Crank position sensor 16 .... Water temperature sensor 17 .... Air-fuel ratio sensor 18 .... Accelerator position sensor 50 ... Compressor housing 51 ... Turbine housing

Claims (1)

In a fuel injection control system for an internal combustion engine that injects fuel to be injected into a cylinder into a plurality of times,
Based on the operating condition of the internal combustion engine, each time the injection amount, and determining means for determining a value of fuel injection parameters is one of the injection interval, injection timing, or injection pressure,
First acquisition means for acquiring an actual in-cylinder oxygen concentration that is an actual oxygen concentration in the cylinder;
Second acquisition means for acquiring a target in-cylinder oxygen concentration that is an oxygen concentration in the cylinder that meets the operating conditions of the internal combustion engine;
Prediction means for predicting a combustion noise generated when the value in thus the fuel injection of the fuel injection parameters determined by said determining means under the acquired actual in-cylinder oxygen concentration was has been performed by said first acquisition means ,
With predicting the combustion noise that occurs when a value in thus the fuel injection of the fuel injection parameters determined by said determining means under the acquired target cylinder oxygen concentration is performed by the second acquisition means, prediction Setting means for setting the generated combustion noise as the target combustion noise;
Specifying means for specifying the correlation between the value of the fuel injection parameters under actual in-cylinder oxygen concentration that is acquired and the combustion noise by the first acquisition means,
When the difference between the combustion noise predicted by the prediction means and the target combustion noise set by the setting means exceeds an allowable value, the determination means determines that the actual combustion noise approximates the target combustion noise. and a corrects the value of the fuel injection parameter correction means for determining a value of the fuel injection parameter satisfying a target combustion noise that has been set by the setting unit at the specified correlation by the specifying means are,
And control means for operating a value to thus fuel injection valve in the fuel injection parameter corrected by the correction means,
With
The correction means selects a value that produces the least amount of smoke when there are a plurality of fuel injection parameter values that satisfy the target combustion noise set by the setting means in the correlation specified by the specifying means. A fuel injection control system for an internal combustion engine.

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