JP4144505B2 - Fuel injection device for internal combustion engine - Google Patents

Description

  The present invention relates to a fuel injection device for an internal combustion engine.

  2. Description of the Related Art Conventionally, an internal combustion engine has been proposed that includes a port injector that injects fuel into an intake port and an in-cylinder injector that injects fuel into a combustion chamber, and switches between these injectors according to the engine operating state. ing.

  In such an internal combustion engine, since the in-cylinder injector is exposed to the gas in the combustion chamber, deposits are likely to adhere to the injection holes of the injector. In particular, when using a port injector in which the in-cylinder injector is not used, deposits are accumulated in the injection holes of the in-cylinder injector. This deposit hinders fuel injection from the injection hole, and the fuel injection amount of the injector when the in-cylinder injector is used may be less than an appropriate value.

In order to eliminate such problems, it is necessary to periodically remove deposits adhering to the injection holes of the in-cylinder injector. For example, Patent Document 1 discloses a technique in which carbon adhering to an injection hole of an injection nozzle is blown off by increasing a fuel injection amount when an idle operation is continued for a predetermined time or more. By using this technique for removing deposits in the in-cylinder injector, it is possible to remove deposits accumulated in the injection holes of the injector and to suppress the adhesion of deposits to the injection holes.
Japanese Utility Model Publication No. 63-102940

  However, if the fuel injection amount is increased to remove the deposit, the fuel consumption and exhaust emission are deteriorated accordingly. Further, if the fuel injection amount is increased during the idling operation, the internal combustion engine will be blown accordingly, causing vibration and the like.

  The present invention has been made in view of such circumstances, and its purpose is to suppress deposit adhesion in an in-cylinder injector without causing deterioration of fuel consumption, exhaust emission, vibration, or the like. An object of the present invention is to provide a fuel injection device for an internal combustion engine.

In the following, means for achieving the above object and its effects are described.
(1) According to the first aspect of the present invention, the injection pressure of the in-cylinder injector is controlled based on the engine operating state, and fuel injection is performed using at least one of the port injector and the in-cylinder injector. In a fuel injection device for an internal combustion engine, the lower limit of the injection pressure of the in-cylinder injector that can blow away deposits adhering to the injection holes of the in-cylinder injector by fuel injection is a reference pressure, A region where the injection pressure of the in-cylinder injector is less than the reference pressure is a first operating region, and a region where the injection pressure of the in-cylinder injector is equal to or higher than the reference pressure within the engine low load region The second operating region is a region where at least one of the engine speed and the engine load is higher than the first operating region and the second operating region. A region where the engine output is expected to be improved by fuel injection of the in-cylinder injector is a third operating region, and only the port injector is when the engine operating state is in the first operating region in the engine low load region. When the engine operating state shifts from the first operating region to the second operating region in the engine low load region, the engine output is improved by the fuel injection of the in-cylinder injector. with expected whether to select the fuel injection mode using the in-cylinder injector regardless is, when the engine operating state is in the third operating region selecting fuel injection mode using an injector for the cylinder injection When the engine operating state is in any of the first operating region, the second operating region, and the third operating region Is also the subject matter in that it comprises an injection control means for setting on the basis of the fuel injection amount for at least one of said port injector and the in-cylinder injector in the engine load.
(2) The invention according to claim 2 is the fuel injection device for an internal combustion engine according to claim 1, wherein the injection control means determines that deposits are attached to the injection holes of the in-cylinder injector. The gist of the present invention is that the fuel injection mode is switched based on the fact that the engine operating state has shifted from the first operating region to the second operating region.
(3) The invention according to claim 3 is the fuel injection device for an internal combustion engine according to claim 1 or 2, wherein the injection control means is an air-fuel ratio learning in an air-fuel ratio learning region corresponding to the third operation region. The gist is to determine that deposits are attached to the injection hole of the in-cylinder injector based on the value being equal to or greater than the determination value.

When switching between the port injector and the in-cylinder injector, there is no difference in the fuel injection amount before and after the switching, and the fuel reaches the combustion chamber due to the difference in the injector used. The injector is switched so that the combustion state does not change due to the difference in time and the amount of wall surface adhesion. Here, in the in-cylinder injector, since the periphery of the injection hole is exposed to the combustion chamber, deposits adhere to and accumulate on the injection hole when not in use. However, according to the above-described invention, the in-cylinder injector is forcibly used, whereby the usage frequency of the injector is increased as much as possible, and the frequency at which deposits attached to the injection holes are removed by fuel injection. Is increased. For this reason, it becomes possible to suppress deposits from adhering to the injection hole of the in-cylinder injector. Further, since the fuel injection amount is not increased for deposit removal, the deterioration of fuel consumption, exhaust emission, vibration and the like due to the increase of the fuel injection amount are suppressed.
According to the above invention, the in-cylinder injector is forcibly used when the pressure of the fuel supplied to the injector is a value at which the deposit attached to the injection hole can be blown off by the fuel injection, This is not done when the fuel pressure is so low that the deposit cannot be blown away. For this reason, useless use of the in-cylinder injector in a situation where the deposit cannot be blown away can be eliminated.

(4) The invention according to claim 4 controls the injection pressure of the in-cylinder injector based on the engine operating state, and performs fuel injection using at least one of the port injector and the in-cylinder injector. In a fuel injection device for an internal combustion engine, a region where the injection pressure of the in-cylinder injector is less than a reference pressure is defined as a first operation region, and a region where the injection pressure of the in-cylinder injector is equal to or greater than the reference pressure When the engine operating state is in the first operating region, the port is set as the second operating region, the region where at least one of the engine rotational speed and the engine load is higher than the first operating region and the second operating region is defined as the third operating region. A fuel injection mode that uses only an injector for injection is selected, and only the in-cylinder injector is used when the engine operating state is in the third operating region. When the fuel injection mode is selected and the engine operating state shifts from the first operating region to the second operating region, the fuel injection mode is changed from the fuel injection mode using only the port injector to the in-cylinder injector. In addition to switching to the fuel injection mode, at least one of the port injection injector and the in-cylinder injection injector when the engine operation state is in any of the first operation region, the second operation region, and the third operation region. The fuel injection amount is set for one side based on the engine load, and the in- cylinder injector is determined when an air-fuel ratio learning value in an air-fuel ratio learning region corresponding to the third operation region is equal to or greater than a determination value. When it is determined that deposits are attached to the injection holes of the engine, the engine operating state is changed from the first operating region. The in-cylinder operation is permitted when the fuel injection mode is switched in accordance with the transition to the second operation region, and the air-fuel ratio learning value in the air-fuel ratio learning region corresponding to the third operation region is less than the determination value. When it is determined that no deposit is attached to the injection hole of the injector for injection, switching of the fuel injection mode when the engine operating state shifts from the first operating region to the second operating region is prohibited. The gist is to provide an injection control means.

According to the above invention, even if the pressure of the fuel supplied to the in-cylinder injector is equal to or higher than the reference value, when the deposit is not attached to the injection hole of the injector, the injector is forcibly used. Absent. For this reason, it is possible to eliminate the forced use of the in-cylinder injector in a situation where no deposit is attached.

(5) The invention according to claim 5 is the fuel injection device for an internal combustion engine according to claim 3 or 4, wherein the air-fuel ratio learning value is a deviation of the actual air-fuel ratio from the stoichiometric air-fuel ratio toward the lean side. The average value of the feedback correction value set to be corrected is updated so as to be within a predetermined range, and the amount of deposit adhering to the injection hole of the in-cylinder injector increases. The gist is that it is set to be larger.
  (6) The invention according to claim 6 is the fuel injection device for an internal combustion engine according to claim 4 or 5, wherein the injection control means is configured to obtain a plurality of air-fuel ratio learning values set in the air-fuel ratio learning region. The gist is to determine that deposits are attached to the injection holes of the in-cylinder injector based on at least one learning value being equal to or greater than the determination value.
  (7) The invention according to claim 7 is the fuel injection device for an internal combustion engine according to any one of claims 1 to 6, wherein the injection control means has an engine operation state in the second operation region. Sometimes the gist is to select a fuel injection mode that uses only the in-cylinder injector.
  (8) The invention according to claim 8 is the fuel injection device for an internal combustion engine according to any one of claims 1 to 7, wherein the injection control means has an engine operating state in the third operating region. Sometimes the gist is to select a fuel injection mode that uses only the in-cylinder injector.

(9) The invention according to claim 9 is the fuel injection device for an internal combustion engine according to any one of claims 1 to 8, wherein the engine operating state is defined based on an engine speed and an engine load. The first operating region and the second operating region are operating regions in which the engine speed and the engine load are low and low, and the third operating region is the first operating region and The gist of the present invention is an operation region including a region where the engine rotation speed is high with respect to the second operation region and a region where the engine load is high.
  (10) The invention according to claim 10 is the fuel injection device for an internal combustion engine according to any one of claims 1 to 9, wherein the second operating region is on a higher load side than the first operating region. The gist is that it is set as an operating region.
  (11) The invention according to claim 11 is the fuel injection device for an internal combustion engine according to any one of claims 1 to 10, wherein the second operating region is an operating region adjacent to the first operating region. The gist is that it is set as
  (12) The invention according to a twelfth aspect is the fuel injection device for an internal combustion engine according to any one of the first to eleventh aspects, wherein the injection control means changes the fuel injection form to only the port injection injector. The engine operating state is changed from the first operating region to the second operating region under a mode in which there is no difference in the fuel injection amount before and after switching from the injection mode to be used to the injection mode using the in-cylinder injector. The gist is to switch the fuel injection mode based on the transition.

Hereinafter, an embodiment in which the present invention is embodied in a fuel injection device for an automobile engine will be described with reference to FIGS.
An intake passage 2 of the engine 1 shown in FIG. 1 is provided with a throttle valve 4 that opens and closes to adjust the amount of air taken into the combustion chamber 3 (intake air amount). The opening degree of the throttle valve 4 (throttle opening degree) is adjusted according to the depression amount (accelerator depression amount) of the accelerator pedal 5 that is depressed by the driver of the automobile.

  The engine 1 also includes a port injector 6 that injects fuel from the intake passage 2 toward the intake port 2 a of the combustion chamber 3, and an in-cylinder injector 7 that injects fuel into the combustion chamber 3. Yes. These injectors 6 and 7 are supplied with fuel stored in the fuel tank 8 as fuel for the engine 1. That is, the fuel in the fuel tank 8 is pumped up by the feed pump 9 and supplied to the port injector 6. Further, part of the fuel pumped up by the feed pump 9 is pressurized by the high-pressure fuel pump 10 and then supplied to the in-cylinder injector 7 via the delivery pipe 11.

  In the engine 1, an air-fuel mixture composed of fuel injected from the injectors 6 and 7 and air flowing through the intake passage 2 is filled in the combustion chamber 3, and the air-fuel mixture is ignited by the spark plug 12. When the air-fuel mixture after ignition burns, the piston 13 reciprocates due to the combustion energy at that time, and the crankshaft 14 rotates. Further, the air-fuel mixture after combustion is sent to the exhaust passage 15 as exhaust.

  In addition, an electronic control device 16 that performs various operation controls of the engine 1 is mounted on the automobile. By controlling the injectors 6 and 7 and the high-pressure fuel pump 10 through the electronic control device 16, the fuel injection amount control of the engine 1, the pressure (fuel pressure) control of the fuel supplied to the in-cylinder injector 7, and the injector 6 and 7 are switched. Further, detection signals from various sensors shown below are input to the electronic control device 16.

An accelerator position sensor 17 that detects the amount of accelerator depression.
A throttle position sensor 18 that detects the throttle opening.
A vacuum sensor 19 that detects the pressure on the downstream side of the throttle valve 4 in the intake passage 2.

A crank position sensor 20 that outputs a signal corresponding to the rotation of the crankshaft 14.
A fuel pressure sensor 21 that detects the pressure of the fuel in the delivery pipe 11 as the pressure (fuel pressure) of the fuel supplied to the in-cylinder injector.

An oxygen (O2) sensor 22 that outputs a signal corresponding to the oxygen concentration in the exhaust gas flowing through the exhaust passage 15.
Next, the fuel injection amount control of the engine 1, the fuel pressure control of the in-cylinder injector 7, and the switching control of the injectors 6 and 7 will be described individually for each control.

[Fuel injection amount control of engine 1]
The fuel injection amount control of the engine 1 is performed by using the final fuel injection amount Qfin calculated based on the following equation (1), whereby an amount of fuel corresponding to the final fuel injection amount Qfin is supplied to the port injector 6. Alternatively, fuel is supplied from the in-cylinder injector 7 to the combustion chamber 3.

Qfin = Qbse-FAF-KG (i)-A (1)
Qfin: Final fuel injection amount
Qbse: Basic fuel injection amount
FAF: Feedback correction value
KG (i): Air-fuel ratio learning value
A: Other correction coefficient The basic fuel injection amount Qbse in the equation (1) is calculated based on the engine speed, the engine load, etc., and represents a theoretical fuel injection amount required in the engine operating state. It becomes. The basic fuel injection amount Qbse calculated in this way becomes a larger value as the engine 1 becomes higher in rotation and load. The engine speed is obtained based on a detection signal from the crank position sensor 20. The engine load is calculated from a parameter corresponding to the intake air amount of the engine 1 and the engine rotation speed. The parameters corresponding to the intake air amount include the intake pressure of the engine 1 determined based on the detection signal from the vacuum sensor 19, the throttle opening determined based on the detection signal from the throttle position sensor 18, and the accelerator position sensor 17. The amount of accelerator depression required based on the detection signal from

  The feedback correction value FAF in the equation (1) is a value for correcting the fuel injection amount so as to feedback-control the air-fuel ratio of the engine 1 so as to approach the stoichiometric air-fuel ratio, and the detection signal from the oxygen sensor 22 Depending on whether the value is richer or leaner than the value corresponding to the stoichiometric air-fuel ratio, the value is increased or decreased around “1.0”. That is, in the feedback correction value FAF, when the detection signal from the oxygen sensor 22 is a value on the rich side with respect to the stoichiometric air-fuel ratio, the fuel injection amount is gradually decreased to correct the decrease, and when the detection signal is on the lean side The injection amount is gradually increased to correct the increase. Further, the feedback correction value FAF is reduced by a predetermined amount when the detection signal from the oxygen sensor 22 is inverted from the lean value to the rich value, and is inverted from the rich value to the lean value. Sometimes it is increased by a predetermined amount.

  The air-fuel ratio learning value KG (i) in the expression (1) is converged within a predetermined range centered on “1.0” during the feedback control, the feedback correction value FAF (more precisely, the average value FAFAV). This is a value that increases or decreases to correct the fuel injection amount. The average value FAFAV is a value obtained by averaging the feedback correction value FAF when the detection signal of the oxygen sensor 22 is inverted and the feedback correction value FAF when the detection signal is subsequently inverted. The air-fuel ratio learning value KG (i) is gradually increased when the average value FAFAV deviates from the predetermined range to the increasing side, and is gradually decreased when the average value FAFAV deviates from the predetermined range to the decreasing side. The Thus, by increasing / decreasing the air-fuel ratio learning value KG (i) based on the average value FAFAV, the average value FAFAV converges within the predetermined range. The air-fuel ratio learning value KG (i) when the average value FAFAV converges within a predetermined range is learned as a value corresponding to the amount of deviation of the air-fuel ratio of the engine 1 from the stoichiometric air-fuel ratio. The air-fuel ratio learning value KG (i) is set for each of a plurality of air-fuel ratio learning regions i (i = 0, 1, 2, 3, 4,...) Divided according to the engine load. . Then, learning of the air-fuel ratio learning value KG (i) is performed for each air-fuel ratio learning region i.

[Fuel pressure control of in-cylinder injector 7]
The fuel pressure control of the in-cylinder injector 7 is performed by adjusting the oil discharge amount from the high-pressure fuel pump 10 to the delivery pipe 11 in accordance with the engine operating state such as the engine rotation speed and the engine load. By such fuel pressure control, the pressure (fuel pressure) of the fuel supplied to the in-cylinder injector 7 becomes larger as the engine 1 is operated at higher speed and higher load.

  Here, FIG. 2 shows the relationship between the fuel injection amount, the fuel pressure, and the fuel injection time when the fuel injection from the in-cylinder injector 7 is performed. In the figure, the solid line indicates the combination of the fuel pressure and the fuel injection time required to obtain the fuel injection amount Q, and the rightward direction in the figure is shifted as the fuel injection amount Q increases. The fuel pressure is controlled to a higher value within the predetermined range A as the engine 1 is rotated at a higher load. As can be seen from this figure, in order to obtain the fuel injection amount Q, it is necessary to lengthen the fuel injection time as the fuel pressure decreases. In other words, it is necessary to increase the fuel pressure in order to shorten the fuel injection time after obtaining the fuel injection amount Q.

  The reason why the fuel pressure is set to a larger value as the engine 1 rotates at a higher speed is that the combustion cycle becomes shorter as the engine speed increases, and the period during which fuel can be injected from the in-cylinder injector 7 becomes shorter. That is, it is necessary to increase the fuel pressure as the engine speed increases so that the fuel injection time falls within the fuel injection period that becomes shorter as the engine speed increases. The reason why the fuel pressure is increased as the engine 1 is loaded is that the fuel injection amount increases and the fuel injection time tends to increase as the engine load increases. That is, it is necessary to increase the fuel pressure as the engine becomes higher so that the fuel injection time that becomes longer as the engine becomes higher falls within the fuel injection possible period.

[Switching control of injectors 6 and 7]
In the engine 1, the port injection injector 6 and the in-cylinder injector 7 are switched and used in accordance with the engine operating state such as the engine rotation speed and the engine load. A mode of switching between the port injector 6 and the in-cylinder injector 7 is shown in FIG. As can be seen from the figure, the low rotation / low load region of the engine 1 is a port injection region where the port injector 6 is used, and the high rotation / high load region of the engine 1 is used by the in-cylinder injector 7. This is an in-cylinder injection region.

  Thus, the in-cylinder injector 7 is used at the time of high rotation and high load because the fuel injected from the injector 7 is applied to the piston 13 and the like to take the heat of vaporization of the fuel from the piston 13 and cool the piston 13. To do. Then, by cooling the piston 13 as described above, the intake charging efficiency of the engine 1 is increased, and the output of the engine 1 is improved. Accordingly, the in-cylinder injection region is set to a region in which the output of the engine 1 can be improved by direct fuel injection from the in-cylinder injector 7 into the combustion chamber 3.

  When the port injector 6 and the in-cylinder injector 7 are switched and used, a fuel combustion chamber is created so that there is no difference in the fuel injection amount before and after the switching and the difference in the injector used. The injector is switched so that the combustion state does not change due to the difference between the time to reach 3 and the amount of wall surface adhesion.

  By the way, since the in-cylinder injector 7 is exposed to the gas in the combustion chamber 3, deposits easily adhere to the injection holes of the injector 7. Such deposits are blown off by fuel injection from the in-cylinder injector 7, but when the port injector 6 is not used, that is, when the engine operating state is in the port injection region, the in-cylinder injector. As a result, deposits are deposited on the seven injection holes. This deposit hinders fuel injection from the injection hole, and when the in-cylinder injector 7 is used, the fuel injection amount of the injector 7 may be less than an appropriate value.

  In the present embodiment, even if the engine operating state is in the port injection region, the minimum necessary value that allows the fuel pressure of the in-cylinder injector 7 to blow away the deposit adhering to the injection hole of the injector 7 by fuel injection. When the value is equal to or greater than a reference value, the injector 7 is forcibly used.

  The engine speed and the engine load when the reference value of the fuel pressure is obtained change as indicated by a broken line in FIG. 3, for example. Therefore, the fuel pressure is higher than the reference pressure in the region on the higher rotation side (right side in the figure) and the region on the higher load side (upper side in the figure) than the engine speed and engine load when the reference value is obtained. It becomes a state where it becomes possible to blow away the deposit adhering to the injection hole of the injector 7 by the fuel injection from the in-cylinder injector 7.

  The forcible use of the in-cylinder injector 7 described above is performed when the engine operating state is in the port injection region and the region where the fuel pressure is equal to or higher than the reference value, that is, the region indicated by hatching in the drawing. Therefore, in the region indicated by the oblique lines, the injector 7 is forcibly used regardless of whether or not an improvement in the output of the engine 1 can be expected by fuel injection from the in-cylinder injector 7 into the combustion chamber 3. It will be. By such forced use of the in-cylinder injector 7, the frequency of use of the injector 7, that is, the frequency of fuel injection from the injector 7 is increased as much as possible, and the frequency of deposits attached to the injection holes being removed by fuel injection. Is increased. For this reason, it is possible to suppress deposits from adhering to the injection holes of the in-cylinder injector 7 and to prevent the fuel injection amount of the injectors 7 from becoming less than the appropriate value due to deposit adhesion. .

  Next, the procedure for forcibly using the in-cylinder injector 7 will be described with reference to the flowchart of FIG. 4 showing the fuel injection control routine. This fuel injection control routine is executed through an electronic control unit 16 by, for example, an angle interruption every predetermined crank angle.

  In the fuel injection control routine, it is first determined whether or not the engine operating region is in which the fuel pressure is equal to or higher than the reference pressure, that is, whether or not the engine speed and the engine load are in the region above the broken line in FIG. (S101). Subsequently, it is determined whether or not the engine is operating in the port injection region, that is, whether or not the engine speed and the engine load are in the port injection region of FIG. 3 (S102). If both of these steps S101 and S102 are affirmative, the engine operating state is in the area indicated by the hatched area in FIG.

  If a negative determination is made in either step S101 or step S102, the process proceeds to step S105 and the injector is used as usual. That is, if the engine operating state is in the port injection region, the port injection injector 6 is used, and if the engine operating state is in the in-cylinder injection region, the in-cylinder injector 7 is used.

  On the other hand, if an affirmative determination is made in steps S101 and S102, the process of step S103 for determining whether deposits are attached to the injection holes of the in-cylinder injector 7 is executed. In step S103, it is determined whether any one of the air-fuel ratio learning values KG (i) in the air-fuel ratio learning region corresponding to the in-cylinder injection region is greater than or equal to a predetermined value. The air-fuel ratio learning value KG (i) takes a larger value as the amount of deposit attached to the injection hole of the in-cylinder injector 7 increases.

  That is, when the amount of deposit adhering to the injection hole of the in-cylinder injector 7 increases, the fuel injection amount becomes smaller than the appropriate amount when fuel is injected from the injector 7, and the air-fuel ratio of the engine 1 becomes the theoretical sky. It shifts from the fuel ratio to the lean side. In order to eliminate this deviation, the feedback correction value FAF for correcting the fuel injection amount is increased, and the empty value for correcting the fuel injection amount so that the average value FAFAV of the correction value FAF becomes a value within a predetermined range. The fuel ratio learning value KG (i) is increased.

  The air-fuel ratio learned value KG (i) thus increased is made leaner with respect to the target value of the stoichiometric air-fuel ratio of the engine 1 when the deposit is attached to the injection hole of the in-cylinder injector 7. It becomes a value corresponding to the deviation. Therefore, the air-fuel ratio learned value KG (i) takes a larger value as the deposit amount increases and the amount of deviation of the air-fuel ratio from the stoichiometric air-fuel ratio to the lean side increases. Therefore, based on the fact that the air-fuel ratio learned value KG (i) is equal to or greater than a predetermined value, it can be determined that deposits are accurately attached to the injection holes of the in-cylinder injector 7.

  If an affirmative determination is made in step S103 and it is determined that deposits are attached to the injection holes of the in-cylinder injector 7, the injector 7 is forcibly used even in the port injection region (S104). ). On the other hand, if a negative determination is made in step S103 and it is determined that no deposit is attached to the injection hole of the in-cylinder injector 7, the routine proceeds to step S105, where the normal injector (here, the port injector 6). Is used.

According to the embodiment described in detail above, the following effects can be obtained.
(1) When the fuel pressure of the in-cylinder injector 7 is equal to or higher than the reference value, the in-cylinder injector 7 is forcibly used even if the engine operating state is in the port injection region. By such forced use of the in-cylinder injector 7, the frequency of use of the injector 7, that is, the frequency of fuel injection from the injector 7 is increased as much as possible, and the frequency of deposits attached to the injection holes being removed by fuel injection. Is increased. For this reason, it becomes possible to prevent deposits from adhering to the injection holes of the in-cylinder injector 7. In addition, switching of the injector to be used does not cause a difference in the fuel injection amount before and after the switching, and changes in the combustion state due to the difference in the arrival time of fuel to the combustion chamber 3 and the amount of wall surface adhesion. Not done. For this reason, unlike the conventional case of increasing the fuel injection amount to remove deposits, there is no occurrence of deterioration of fuel consumption, exhaust emission, vibration or the like with the increase of the fuel injection amount.

  (2) The reference value of the fuel pressure is set to a minimum necessary value that allows the deposit attached to the injection hole of the in-cylinder injector 7 to be blown off by fuel injection. For this reason, forced use of the in-cylinder injector 7 is performed when the fuel pressure is a value at which the deposit can be blown away, and is not performed when the fuel pressure is low enough not to blow the deposit. For this reason, useless forcible use of the in-cylinder injector 7 in a situation where the deposit cannot be blown away can be eliminated.

  (3) Forcible use of the in-cylinder injector 7 is performed under the condition that it is determined that deposits are attached to the injection holes of the injectors 7, and is therefore performed when there is no deposits of the deposit. There is no. For this reason, useless forcible use of the in-cylinder injector 7 in a situation where the deposit is not attached can be eliminated.

  (4) Judgment that deposits are attached to the injection holes of the in-cylinder injector 7 is any one of the air-fuel ratio learning values KG (i) in the air-fuel ratio learning region i corresponding to the in-cylinder injection region. This is done based on the fact that it is at least a predetermined value. The air / fuel ratio learning value KG (i) takes a larger value as the deviation of the air / fuel ratio of the engine 1 from the stoichiometric air / fuel ratio to the lean side becomes larger due to the adhesion of the deposit. The larger the value, the larger the value. Therefore, the determination that deposits are attached to the injection holes of the in-cylinder injector 7 can be accurately made based on the fact that the air-fuel ratio learned value KG (i) is not less than a predetermined value.

In addition, the said embodiment can also be changed as follows, for example.
-Forcible use of the in-cylinder injector 7 is performed under the condition that it is determined that deposits are attached to the injection holes of the injector, but such conditions are not necessarily set.

  -Whether the fuel pressure of the in-cylinder injector 7 is equal to or higher than the reference value is determined based on whether the engine speed and the engine load are in the engine operation region where the fuel pressure is equal to or higher than the reference value. Instead of this, the above determination may be made using the measured value of the fuel pressure obtained based on the detection signal from the fuel pressure sensor.

  The reference value of the fuel pressure used for determining whether or not the in-cylinder injector 7 is forcibly used is the minimum necessary value that allows the deposit attached to the injection hole to be blown off by the fuel injection from the injector 7. Although it is set to a value, it can be changed to a lower value or a higher value.

  -When forced use of the in-cylinder injector 7 is executed, the use of the port injector 6 is stopped and fuel injection is performed only by the in-cylinder injector 7, but the present invention is not limited to this. In other words, the in-cylinder injector 7 may be forcibly used while using the port injector 6. In this case, when the forced use of the in-cylinder injector 7 is executed, the port injection injector 6 and the cylinder are set so that there is no difference in the fuel injection amount before and after the start of the execution and no change in the combustion state occurs. The fuel injection ratio with the internal injection injector 7 is determined.

  -Although this invention was applied to the engine 1 which performs fuel injection in two types of modes of using only the injector 6 for port injection, and using only the injector 7 for cylinder injection, this invention is not limited to this. For example, the present invention may be applied to an engine that performs fuel injection in three modes: the use of only the port injector 6, the use of only the in-cylinder injector 7, and the combined use of both the injectors 6 and 7. .

1 is a schematic view showing an entire engine to which a fuel injection device of the present invention is applied. The graph which shows the relationship between fuel injection quantity, fuel pressure, and fuel injection time. The figure which shows the port injection area | region where the injector for port injection is used, and the cylinder injection area | region where the injector for cylinder injection is used. The flowchart which shows the procedure at the time of performing forced use of the injector for cylinder injection.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Intake passage, 2a ... Intake port, 3 ... Combustion chamber, 4 ... Throttle valve, 5 ... Accelerator pedal, 6 ... Port injection injector, 7 ... In-cylinder injector, 8 ... Fuel tank, 9 DESCRIPTION OF SYMBOLS ... Feed pump, 10 ... High pressure fuel pump, 11 ... Delivery pipe, 12 ... Spark plug, 13 ... Piston, 14 ... Crankshaft, 15 ... Exhaust passage, 16 ... Electronic control device (injection control means, air-fuel ratio control means), 17 ... Accelerator position sensor, 18 ... Throttle position sensor, 19 ... Vacuum sensor, 20 ... Crank position sensor, 21 ... Fuel pressure sensor, 22 ... Oxygen sensor.

Claims (12)

In a fuel injection device for an internal combustion engine that controls the injection pressure of an in-cylinder injector based on an engine operating state and performs fuel injection using at least one of a port injector and an in-cylinder injector.
The lower limit of the injection pressure of the in-cylinder injector that can blow off deposits attached to the injection holes of the in-cylinder injector by fuel injection is a reference pressure, and the in-cylinder injector A region where the injection pressure is less than the reference pressure is defined as a first operation region, and a region where the injection pressure of the in-cylinder injector is equal to or greater than the reference pressure within the engine low load region is defined as a second operation region. A region in which at least one of the speed and the engine load is higher than the first operation region and the second operation region and the improvement of the engine output is expected by the fuel injection of the in-cylinder injector is defined as a third operation region.
When the engine operating state is in the first operating region in the engine low load region, a fuel injection mode using only the port injector is selected, and the engine operating state is in the first operating region in the engine low load region. The fuel injection mode using the in-cylinder injector is selected regardless of whether or not the improvement of the engine output is expected by the fuel injection of the in-cylinder injector when the transition to the second operation region is made, and the engine operation is When the state is in the third operating region, the fuel injection mode using the in-cylinder injector is selected , and the engine operating state is any of the first operating region, the second operating region, and the third operating region. In some cases, fuel for at least one of the port injector and the in-cylinder injector is used. The fuel injection system for an internal combustion engine, characterized in that it comprises an injection control means for setting, based on the engine load injection amount.   The fuel injection device for an internal combustion engine according to claim 1,
  The engine operation state has shifted from the first operation region to the second operation region on the condition that the injection control means determines that deposits are attached to the injection holes of the in-cylinder injector. The fuel injection mode is switched based on
  A fuel injection device for an internal combustion engine.   The fuel injection device for an internal combustion engine according to claim 1 or 2,
  In the injection control means, deposit is attached to the injection hole of the in-cylinder injector based on the fact that the air-fuel ratio learning value in the air-fuel ratio learning region corresponding to the third operation region is greater than or equal to the determination value. Judgment
  A fuel injection device for an internal combustion engine. In a fuel injection device for an internal combustion engine that controls the injection pressure of an in-cylinder injector based on an engine operating state and performs fuel injection using at least one of a port injector and an in-cylinder injector.
A region where the injection pressure of the in-cylinder injector is less than a reference pressure is defined as a first operating region, a region where the injection pressure of the in-cylinder injector is equal to or greater than the reference pressure is defined as a second operating region, and the engine speed And a region where at least one of the engine loads is higher than the first operation region and the second operation region as a third operation region,
When the engine operating state is in the first operating region, a fuel injection mode using only the port injector is selected, and when the engine operating state is in the third operating region, fuel injection using only the in-cylinder injector. When a mode is selected and the engine operating state shifts from the first operating region to the second operating region, the fuel injection mode is changed from the fuel injection mode using only the port injection injector to the fuel injection using the in-cylinder injector. And at least one of the port injector and the in-cylinder injector when the engine operating state is in any of the first operating region, the second operating region, and the third operating region. The fuel injection amount is set based on the engine load ,
When it is determined that deposits are attached to the injection holes of the in-cylinder injector when the air-fuel ratio learning value in the air-fuel ratio learning region corresponding to the third operation region is greater than or equal to the determination value, The switching of the fuel injection mode is permitted when the state has shifted from the first operation region to the second operation region, and the air-fuel ratio learning value in the air-fuel ratio learning region corresponding to the third operation region is the determination value. When it is determined that the deposit is not attached to the injection hole of the in-cylinder injector, the engine operating state is shifted from the first operating region to the second operating region. A fuel injection device for an internal combustion engine, comprising: an injection control unit that prohibits switching of a fuel injection mode.   The fuel injection device for an internal combustion engine according to claim 3 or 4,
  The air-fuel ratio learning value is updated so that an average value of feedback correction values set to correct the deviation of the actual air-fuel ratio from the stoichiometric air-fuel ratio to the lean side falls within a predetermined range. And the larger the amount of deposit adhering to the injection hole of the in-cylinder injector, the larger is set.
  A fuel injection device for an internal combustion engine.   The fuel injection device for an internal combustion engine according to claim 4 or 5,
  The injection control means is arranged in the injection hole of the in-cylinder injector based on the fact that at least one learning value among the plurality of air-fuel ratio learning values set in the air-fuel ratio learning region is greater than or equal to the determination value. Determining that deposits are attached
  A fuel injection device for an internal combustion engine.   The fuel injection device for an internal combustion engine according to any one of claims 1 to 6,
  The injection control means selects a fuel injection mode that uses only the in-cylinder injector when the engine operating state is in the second operating region.
  A fuel injection device for an internal combustion engine.   In the fuel-injection apparatus of the internal combustion engine as described in any one of Claims 1-7,
  The injection control means selects a fuel injection mode that uses only the in-cylinder injector when the engine operating state is in the third operating region.
  A fuel injection device for an internal combustion engine.   The fuel injection device for an internal combustion engine according to any one of claims 1 to 8,
  The engine operating state is defined based on the engine rotational speed and the engine load, and the first operating region and the second operating region are operations in which the engine rotational speed and the engine load are low and low. The third operation region is an operation region including a region where the engine rotation speed is high and a region where the engine load is high compared to the first operation region and the second operation region.
  A fuel injection device for an internal combustion engine.   In the fuel-injection apparatus of the internal combustion engine as described in any one of Claims 1-9,
  The second operation region is set as an operation region on the higher load side than the first operation region.
  A fuel injection device for an internal combustion engine.   In the fuel-injection apparatus of the internal combustion engine as described in any one of Claims 1-10,
  The second operation region is set as an operation region adjacent to the first operation region.
  A fuel injection device for an internal combustion engine.   The fuel injection device for an internal combustion engine according to any one of claims 1 to 11,
  The injection control means has a mode in which there is no difference in the fuel injection amount before and after the fuel injection mode is switched from the injection mode using only the port injector to the injection mode using the in-cylinder injector. The fuel injection mode is switched based on the fact that the engine operating state has shifted from the first operating region to the second operating region.
  A fuel injection device for an internal combustion engine.

Images