JP4872823B2 - Start control device for internal combustion engine - Google Patents

Description

  The present invention relates to an engine operation state including an intake stroke fuel supply start in which fuel supply to the combustion chamber is performed only in the intake stroke, and a split fuel supply start in which fuel supply to the combustion chamber is divided into an intake stroke and a compression stroke. The present invention relates to a start control device for an internal combustion engine that is switched according to the conditions.

  Conventionally, Patent Document 1 discloses a start control device for an internal combustion engine that switches between the intake stroke fuel supply start and the split fuel supply start as described above. In the intake stroke fuel supply start, the fuel is supplied into the combustion chamber only during the intake stroke, so that homogeneous combustion is performed in a state where an air-fuel mixture uniformly dispersed in the entire combustion chamber is formed. On the other hand, in the split supply start, an air-fuel mixture that is uniformly dispersed throughout the combustion chamber is formed by the fuel supplied in the intake stroke, and then locally in the vicinity of the spark plug at the time of ignition by the fuel supplied in the compression stroke. Combustion in a state where a dense air-fuel mixture layer is formed, so-called weak stratified combustion is performed.

  The split fuel supply start in such an internal combustion engine is performed for the following purpose. During weakly stratified combustion, the ignition timing can be greatly retarded as compared with homogeneous combustion. Therefore, at the time of split fuel supply start-up, weak stratified combustion is performed and ignition timing is significantly retarded to raise the exhaust temperature to promote warming up of the catalyst at cold start and improve cold emission performance I try to let them.

On the other hand, as is well known, in many internal combustion engines, the starting fuel supply amount is corrected based on the intake air density. More specifically, the starting fuel supply amount is corrected by the atmospheric pressure or the intake air temperature, which are parameters that affect the intake air density. Such correction based on the intake air density is performed for the purpose of adjusting the fuel supply amount at start-up in accordance with the change because the mass of air charged in the combustion chamber and contributing to combustion changes depending on the intake air density. That is, the correction of the starting fuel supply amount based on the intake air density is intended to maintain the air-fuel ratio of the combusted air-fuel mixture at an appropriate value with respect to changes in the air mass that fills the combustion chamber and contributes to combustion. It is done in
JP 2003-328816 A

  By the way, it is conceivable to apply the correction of the starting fuel supply amount based on the intake air density to an internal combustion engine that performs switching between the intake stroke fuel supply start and the split fuel supply start as described above. Even in such a case, when the intake stroke fuel supply start is selected, the air-fuel ratio of the combusted air-fuel mixture can be made appropriate by correcting the start time fuel supply amount based on the intake air density. However, when the split fuel supply start is selected, if the start-up fuel supply amount is corrected based on the intake air density, the following problem occurs.

  As described above, when the split fuel supply start is selected, weak stratified combustion is performed in a state where a rich air-fuel mixture is formed only near the spark plug at the time of ignition. In order to perform such weak stratified combustion satisfactorily, the air-fuel mixture in the vicinity of the spark plug needs to have an appropriate fuel concentration. That is, if the fuel concentration in the air-fuel mixture in the vicinity of the spark plug is too low or too high, the combustion state becomes worse, for example, misfire occurs. However, when the correction based on the intake air density is applied to the fuel supply amount in the compression stroke when the split fuel supply start is selected, the amount of fuel supplied to the vicinity of the spark plug changes accordingly. As a result, the fuel concentration of the air-fuel mixture in the vicinity of the spark plug becomes excessive or deficient, resulting in poor starting due to deterioration of the combustion state.

  The present invention has been made in view of such a situation, and the problem to be solved is an intake stroke fuel supply start in which fuel supply to the combustion chamber is performed only in the intake stroke, and fuel supply to the combustion chamber. Provided is an internal combustion engine start control device capable of appropriately correcting a start time fuel supply amount based on an intake air density, which is an internal combustion engine that switches between split fuel supply start performed in an intake stroke and a compression stroke. There is.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
According to the first aspect of the present invention, an intake stroke fuel supply start in which fuel supply to the combustion chamber is performed only in the intake stroke, and a split fuel supply start in which fuel supply to the combustion chamber is divided into an intake stroke and a compression stroke. In the internal combustion engine start control device that switches the fuel supply amount at the start based on the intake air density, when the split fuel supply start is selected, the intake stroke fuel supply start is selected. In comparison, the gist is to reduce the degree of correction based on the intake air density.

  In the above configuration, when the split fuel supply start with weak stratified combustion is selected, the degree of correction based on the intake air density is reduced, and the increase or decrease of the fuel supply amount at the start due to the correction is reduced, so that the mixture near the spark plug due to the correction is reduced. The change in the fuel concentration can be suppressed. Therefore, when selecting the intake stroke fuel supply start to perform homogeneous combustion, the fuel supply amount at the start is appropriately adjusted according to the change in the intake mass due to the intake density, while the fuel supply amount at the start based on the intake density is corrected. It is possible to suitably suppress the deterioration of the combustion state when selecting split fuel supply start. Therefore, according to the above configuration, in the internal combustion engine that switches between the intake stroke fuel supply start and the split fuel supply start, it is possible to appropriately correct the start time fuel supply amount based on the intake air density.

  According to a second aspect of the present invention, in the start control device for an internal combustion engine according to the first aspect, the degree of correction based on the intake air density when the split fuel supply start is selected is set to the total amount of fuel supply during start-up. The gist is to make it smaller as the ratio of the fuel supply amount in the compression stroke is higher.

  When split fuel supply start is selected, the higher the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at start-up, the higher the degree of stratification of the mixture in the combustion chamber and the correction based on the intake air density The effect on the combustion state increases. Therefore, when the ratio of the fuel supply amount in the compression stroke is higher as in the above configuration, the correction of the fuel supply amount at start-up based on the intake density is more appropriate if the degree of correction based on the intake air density is reduced. To be able to do that.

  According to a third aspect of the present invention, in the internal combustion engine start control device according to the first aspect, the correction based on the intake density is applied to the fuel supply amount of the intake stroke when the split fuel supply start is selected. The gist is that it is not applied to the fuel supply amount in the compression stroke when the split fuel supply start is selected.

  In the split fuel supply start, a dense air-fuel mixture layer is locally formed in the vicinity of the spark plug by the fuel supplied to the combustion chamber during the compression stroke. In that respect, in the above configuration, the correction based on the intake air density is applied only to the fuel supply amount of the intake stroke when the split fuel supply start is selected, and is not applied to the fuel supply amount of the compression stroke. The correction based on the density can suppress the influence on the fuel concentration of the air-fuel mixture formed near the spark plug.

  According to a fourth aspect of the present invention, an intake stroke fuel supply start in which fuel supply to the combustion chamber is performed only in the intake stroke, and a split fuel supply start in which fuel supply to the combustion chamber is divided into an intake stroke and a compression stroke. In the internal combustion engine start control device that corrects the starting fuel supply amount based on the intake air density, and prohibits correction based on the intake air density when the split fuel supply start is selected. This is the gist of this.

  If the correction based on the intake air density is not performed when the split fuel supply start is selected as in the above configuration, the change in the fuel concentration of the air-fuel mixture in the vicinity of the spark plug due to the correction does not occur. As a result of the correction, the combustion state is not deteriorated when the split fuel supply start is selected. Therefore, even with the above configuration, in the internal combustion engine that switches between the intake stroke fuel supply start and the split fuel supply start, it is possible to appropriately correct the start time fuel supply amount based on the intake air density.

  The invention according to claim 5 is the internal combustion engine start control device according to any one of claims 1 to 4, wherein the internal combustion engine includes two injectors of an intake port injector and an in-cylinder injector. It is intended to be applied to the above.

  The present invention can be embodied as a start control device for an internal combustion engine including the two injectors as described above. That is, in such an internal combustion engine, the fuel injection from the intake port injector and the fuel injection from the in-cylinder injector are properly used to switch between the intake stroke fuel supply start and the split fuel supply start as described above. It can be performed. Even in an internal combustion engine that does not include an intake port injector but only an in-cylinder injector, intake stroke fuel supply start and split fuel supply start are performed by appropriately using intake stroke injection and compression stroke injection. It is possible.

  The gist of the invention described in claim 6 is to perform atmospheric pressure correction as the correction based on the intake air density in the start control device for the internal combustion engine according to any one of claims 1 to 5. It is. The gist of the invention according to claim 7 is that in the start control device for the internal combustion engine according to any one of claims 1 to 6, the intake air temperature correction is performed as the correction based on the intake air density. Is.

  The present invention can be applied to a start control device for an internal combustion engine that performs correction based on atmospheric pressure or intake air temperature, which is a parameter affecting the intake air density, as correction of the starting fuel supply amount based on the intake air density.

(First embodiment)
Hereinafter, a first embodiment of a start control device for an internal combustion engine according to the present invention will be described with reference to FIGS. The start control device for an internal combustion engine according to the present embodiment is applied to an internal combustion engine that performs only in-cylinder injection or an internal combustion engine that employs a dual injection system that performs both intake port injection and in-cylinder injection. FIG. 1A shows the configuration around the combustion chamber of the internal combustion engine that performs only in-cylinder injection, and FIG. 1B shows the configuration around the combustion chamber of the internal combustion engine that employs the dual injection system as described above. Show.

  In any internal combustion engine, an intake port 11 and an exhaust port 12 are connected to the combustion chamber 10. Then, intake air is introduced into the combustion chamber 10 from the intake port 11 in response to opening of the intake valve 13, and exhaust gas is discharged from the combustion chamber 10 to the exhaust port 12 in response to opening of the exhaust valve 14. ing. An ignition plug 15 for spark ignition of the air-fuel mixture introduced into the combustion chamber 10 is disposed at the top of the combustion chamber 10. On the other hand, as shown in FIG. 1A, in an internal combustion engine that performs only in-cylinder injection, an in-cylinder injector 16 that directly injects fuel into the combustion chamber 10 is provided. On the other hand, as shown in FIG. 1B, in an internal combustion engine that employs a dual injection system, in addition to the similar in-cylinder injector 16, an intake port injection injector 17 that injects fuel into the intake port 11. Is further provided.

  FIG. 2 schematically shows the electrical configuration of the start control device for an internal combustion engine of the present embodiment applied to these internal combustion engines. As shown in the figure, the start control device of the present embodiment is configured around an electronic control unit 20. The electronic control unit 20 temporarily stores a central processing unit (CPU) that performs various arithmetic processes related to engine control, a read-only memory (ROM) in which programs and data for engine control are stored, CPU arithmetic results, and the like. A random access memory (RAM) for storage and an input / output port (I / O) used for input / output of signals with the outside are provided.

  The input port of the electronic control unit 20 includes a rotation speed sensor 21 for detecting the engine rotation speed, a water temperature sensor 22 for detecting the engine cooling water temperature, an atmospheric pressure sensor 23 for detecting the atmospheric pressure, and an intake air temperature sensor 24 for detecting the intake air temperature. For example, various sensors for detecting the operation status of the internal combustion engine are connected. On the other hand, drive circuits 25 and 26 for the spark plug 15 and the in-cylinder injector 16 are connected to the output port of the electronic control unit 20. When applied to the internal combustion engine that employs the dual injection system shown in FIG. 1B, in addition to this, a drive circuit 27 of the intake port injection injector 17 is connected to the output port of the electronic control unit 20. Will be.

  Now, in the internal combustion engine start control device of the present embodiment configured as described above, the fuel supply mode to the combustion chamber 10 at the time of engine start is switched. Specifically, there are an intake stroke fuel supply start in which fuel supply to the combustion chamber 10 is performed only during the intake stroke, and a split fuel supply start in which fuel supply to the combustion chamber 10 is divided into an intake stroke and a compression stroke. It is switched according to the engine operation status. The intake stroke fuel supply start and the split fuel supply start in both the internal combustion engines are performed in the following manner, respectively.

  First, in an internal combustion engine that performs only in-cylinder injection, the in-cylinder injector 16 performs fuel injection in the intake stroke, thereby supplying fuel to the combustion chamber 10 in the intake stroke. Similarly, the in-cylinder injector 16 performs fuel injection in the latter half of the compression stroke, so that fuel is supplied to the combustion chamber 10 in the compression stroke. That is, the in-cylinder injector 16 performs the intake stroke fuel injection only to perform the intake stroke fuel supply start, and the in-cylinder injector 16 performs the split fuel supply start by combining the intake stroke injection and the compression stroke injection. Each to do.

  On the other hand, in an internal combustion engine that employs a dual injection system, the intake port injection injector 17 performs fuel injection from the expansion stroke to the intake stroke, thereby supplying fuel to the combustion chamber 10 in the intake stroke. The in-cylinder injector 16 performs fuel injection in the latter half of the compression stroke, so that fuel is supplied to the combustion chamber 10 in the compression stroke. That is, the intake stroke fuel supply start is performed by performing only the fuel injection by the intake port injector 17 and the fuel injection by the intake port injector 17 and the fuel injection of the in-cylinder injector 16 in the compression stroke are combined. Thus, the split fuel supply start is performed respectively.

  In any internal combustion engine, an air-fuel mixture that is uniformly dispersed is formed in the entire combustion chamber 10 depending on the fuel supply in the intake stroke, and locally in the vicinity of the spark plug 15 at the time of ignition depending on the fuel supply in the compression stroke. A dense mixture layer is formed. Therefore, when the intake stroke fuel supply start in which fuel is supplied only in the intake stroke is selected, homogeneous combustion is performed in a state where the fuel is uniformly dispersed in the combustion chamber 10, and divided into the intake stroke and the compression stroke. At the time of selection of split fuel supply start for supplying fuel, weak stratified combustion is performed in a state where a locally rich mixture layer is formed in the vicinity of the spark plug 15 at the time of ignition.

  Now, the switching between the intake stroke fuel supply start and the split fuel supply start is performed based on the warm-up state of the internal combustion engine. Specifically, at the time of cold start (for example, when the engine coolant temperature is minus 12 ° C. to 0 ° C.), the split fuel supply start is performed, and at the time of warm start (for example, when the engine coolant temperature is 0 ° C. or more) In this case, the intake stroke fuel supply start is performed. This is because, during cold start, weak stratified combustion is possible, which can significantly retard the ignition timing, and the exhaust temperature is increased by the large retardation of the ignition timing to promote warming up of the catalyst. This is to improve the performance. Note that, under extremely low temperature conditions (for example, when the engine cooling water temperature is less than minus 12 ° C.), it is difficult to secure a very high fuel pressure necessary for the compression stroke injection, so the intake stroke fuel supply start is performed. .

  FIG. 3 shows a flowchart of a “startup injection amount calculation routine” for determining the fuel supply amount of the intake stroke and the compression stroke in the intake stroke fuel supply start and the split fuel supply start. The processing of this routine is repeatedly executed at predetermined control cycles by the electronic control unit 20 during engine startup.

  When this routine is started, the electronic control unit 20 first determines in step S30 whether to perform intake stroke fuel supply start or split fuel supply start based on the engine coolant temperature. When the split fuel supply start is selected here, the electronic control unit 20 also determines the ratio between the fuel supply amount in the intake stroke and the fuel supply amount in the compression stroke.

  Subsequently, in step S31, the electronic control unit 20 calculates a map value qst_map of the starting injection amount using an arithmetic map based on the engine speed and the engine coolant temperature. In subsequent step S32, the atmospheric pressure correction processing of the map value qst_map is performed to calculate the final starting injection amount qst. The startup injection amount qst thus calculated indicates the total amount of fuel supplied to the combustion chamber 10 at startup, that is, the total amount of startup fuel supply.

  When the starting injection amount qst is calculated, the electronic control unit 20 calculates the fuel supply amount for the intake stroke and the compression stroke according to the selected fuel supply mode in the following step S33. When the intake stroke fuel supply start is selected, the starting injection amount qst is directly used as the fuel supply amount in the intake stroke, that is, the fuel injection amount in the intake stroke of the in-cylinder injector 16 in the internal combustion engine that performs only in-cylinder injection, or It is set to the fuel injection amount of the intake port injection injector 17 in the internal combustion engine employing the dual injection system. On the other hand, when the split fuel supply start is selected, the start-time injection amount qst is distributed between the intake stroke fuel supply amount and the compression stroke fuel supply amount according to the ratio set in step S30. That is, in an internal combustion engine that performs only in-cylinder injection, the start-time injection amount qst is distributed between the fuel injection amount in the intake stroke and the fuel injection amount in the compression stroke of the in-cylinder injector 16. In an internal combustion engine that employs a dual injection system, the starting injection quantity qst is distributed to the fuel injection quantity of the intake port injector 17 and the fuel injection quantity in the compression stroke of the in-cylinder injector 16.

  As described above, in the present embodiment, the starting injection quantity qst is calculated by performing atmospheric pressure correction on the map value qst_map of the starting injection quantity. In this atmospheric pressure correction, since the mass of air charged in the combustion chamber 10 changes due to the change in the intake air density depending on the atmospheric pressure, the change in the mass of the air causes the change of the air-fuel mixture to be combusted. This is performed for the purpose of adjusting the fuel supply amount so that the air-fuel ratio is maintained at an appropriate value. However, as described above, when such atmospheric pressure correction is applied up to the fuel supply amount in the compression stroke when the split fuel supply start is selected, the amount of fuel supplied to the vicinity of the spark plug 15 changes accordingly. As a result, the fuel concentration in the air-fuel mixture near the spark plug 15 becomes excessive or insufficient, resulting in a starting failure due to deterioration of the combustion state. Therefore, in the present embodiment, the atmospheric pressure correction is applied only when the intake stroke fuel supply start is selected, and the atmospheric pressure correction is prohibited when the divided fuel supply is started.

  FIG. 4 shows a flowchart of an “atmospheric pressure correction routine” employed by the present embodiment. The processing of this routine is executed by the electronic control unit 20 in step S32 of the “startup injection amount calculation routine”.

  When this routine is started, the electronic control unit 20 first confirms in step S40 which start-up injection mode of intake stroke fuel supply start and split fuel supply start is selected.

  If the intake stroke fuel supply start is selected (S40: NO), the electronic control unit 20 calculates the atmospheric pressure correction coefficient kpa based on the atmospheric pressure detected by the atmospheric pressure sensor 23 in step S41. . The value of the atmospheric pressure correction coefficient kpa calculated here is set such that the value of the standard atmospheric pressure is set to the reference “1” and the value decreases monotonously as the atmospheric pressure decreases. For example, in the present embodiment, a value obtained by dividing the atmospheric pressure [kPa] by the standard atmospheric pressure “101.3 kPa”, which is the standard value of the atmospheric pressure at the sea level “0 m”, is set as the atmospheric pressure correction coefficient kpa. ing. Then, in the following step S42, the electronic control unit 20 sets a value obtained by multiplying the map pressure value qst_map by the atmospheric pressure correction coefficient kpa to the starting injection amount qst, and ends this routine.

  On the other hand, when the split fuel supply start is selected (S40: YES), the electronic control unit 20 sets the value of the map value qst_map as it is as the value of the injection quantity qst at start in step S43. Therefore, the atmospheric pressure correction is prohibited when the split fuel supply start to perform weak stratified combustion is selected.

In the present embodiment described above, the following effects can be obtained.
(1) In the present embodiment, when the split fuel supply start is selected, the atmospheric pressure correction of the starting injection amount qst is prohibited, and the atmospheric pressure correction is applied only when the intake stroke fuel supply start is selected. . Therefore, when selecting the intake stroke fuel supply start to perform homogeneous combustion, the injection amount qst at the start is appropriately adjusted in accordance with the change in the intake density due to the atmospheric pressure, and consequently the change in the mass of the air filled in the combustion chamber 10. However, it is possible to suitably suppress the deterioration of the combustion state due to the atmospheric pressure correction when the split fuel supply start is selected. Therefore, in the internal combustion engine that switches between the intake stroke fuel supply start and the split fuel supply start, it is possible to appropriately correct the start time fuel supply amount based on the atmospheric pressure.

(Second Embodiment)
Next, a second embodiment of the internal combustion engine start control device according to the present invention will be described with reference to FIGS. 5 and 6 focusing on differences from the above embodiment.

  In the first embodiment described above, when the split fuel supply start is selected, the atmospheric pressure correction of the starting injection amount qst is prohibited, and the atmospheric pressure correction is applied only when the intake stroke fuel supply start is selected. Thus, the deterioration of the combustion state when the split fuel supply start is selected is avoided by the atmospheric pressure correction. However, depending on the applied internal combustion engine, it may be desirable to perform atmospheric pressure correction of the starting injection amount qst to some extent even when the divided fuel is supplied. In such a case, if the atmospheric pressure correction is uniformly applied when the split fuel supply start is selected or when the intake stroke fuel supply start is selected, the fuel concentration of the air-fuel mixture in the vicinity of the spark plug 15 is selected when the split fuel supply start is selected. Overs and shorts will occur. Therefore, in the present embodiment, when the split fuel supply start is selected, the degree of correction based on the atmospheric pressure with respect to the start injection amount qst is made smaller than when the intake stroke fuel supply start is selected.

  FIG. 5 shows a flowchart of an “atmospheric pressure correction routine” employed in this embodiment. This routine is executed by the electronic control unit 20 in place of the “atmospheric pressure correction routine” of the first embodiment shown in FIG.

  When this routine is started, the electronic control unit 20 first calculates the atmospheric pressure correction coefficient kpa to the atmospheric pressure detected by the atmospheric pressure sensor 23 in step S50. The calculation of the atmospheric pressure correction coefficient kpa here is performed similarly to step S41 of the atmospheric pressure correction routine in the first embodiment described above.

  Subsequently, in step S51, the electronic control unit 20 confirms which start-up injection mode of the intake stroke fuel supply start and the split fuel supply start is selected. If the intake stroke fuel supply start is selected (S51: NO), the electronic control unit 20 in step S53, the map value qst_map of the starting injection amount calculated in step S31 of the starting injection amount calculation routine. Is multiplied by the atmospheric pressure correction coefficient kpa to set the starting injection quantity qst, and this routine is terminated.

  On the other hand, when the split fuel supply start is selected (S51: YES), the electronic control unit 20 corrects the atmospheric pressure correction coefficient kpa in step S52 and then performs the injection at the start in step S53. The quantity qst is calculated. That is, the starting injection amount qst at this time is set to a value obtained by multiplying the map value qst_map by the atmospheric pressure correction coefficient kpa corrected in step S52. The correction of the atmospheric pressure correction coefficient kpa here is performed based on a correction map as illustrated in FIG. As shown in the figure, the value of the corrected atmospheric pressure correction coefficient kpa is set so that the degree of correction is smaller than the value before correction, that is, the value is closer to “1”. Therefore, when the split fuel supply start is selected, the degree of correction of the start time injection amount qst based on the atmospheric pressure is made smaller than when the intake stroke fuel supply start is selected.

According to the start control device for an internal combustion engine of the present embodiment described above, the following effects can be obtained.
(2) In this embodiment, when the split fuel supply start is selected, the degree of correction of the start time injection amount qst based on the atmospheric pressure is made smaller than when the intake stroke fuel supply start is selected. Therefore, when the split fuel supply start with weak stratified combustion is selected, the degree of atmospheric pressure correction is reduced, and the increase or decrease in the starting injection amount qst due to the correction is reduced, and the fuel of the mixture near the spark plug 15 due to the correction is reduced. Changes in concentration can be suppressed. Therefore, when the intake stroke fuel supply start for performing homogeneous combustion is selected, the start time injection quantity qst is appropriately adjusted in accordance with the change in the intake mass due to the atmospheric pressure, while the divided fuel supply start is selected by the atmospheric pressure correction. It can suppress suitably that a state deteriorates. Therefore, according to the present embodiment, in the internal combustion engine that switches between the intake stroke fuel supply start and the split fuel supply start, it is possible to appropriately correct the starting injection amount qst based on the atmospheric pressure. .

(Third embodiment)
Next, a third embodiment of the internal combustion engine start control device of the present invention will be described with reference to FIGS. 7 and 8 focusing on differences from the above embodiment.

  When the split fuel supply start to perform weak stratified combustion is selected, the starting injection amount qst is distributed between the intake stroke fuel supply amount and the compression stroke fuel supply amount. Here, the degree of stratification in the combustion chamber 10 changes depending on the distribution ratio of the fuel supply amount in both strokes. For example, if the ratio of the fuel supply amount in the intake stroke is high, the degree of stratification becomes low and the combustion becomes close to homogeneous combustion. On the other hand, if the ratio of the fuel supply amount in the intake stroke is high, combustion is performed with a higher degree of stratification. As the degree of stratification of the air-fuel mixture in the combustion chamber 10 increases, the influence of atmospheric pressure correction on the combustion state increases.

  Therefore, in the present embodiment, the degree of reflection of the atmospheric pressure correction with respect to the starting injection amount qst when the split fuel supply start is selected is changed according to the distribution ratio of the fuel supply amount in the intake stroke and the compression stroke. . The higher the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at start time (map value qst_map of the injection amount at start time), the lower the degree of reflection of the atmospheric correction, thereby reducing the mixing in the combustion chamber 10. The atmospheric pressure correction can be appropriately performed according to the degree of stratification.

  FIG. 7 shows a flowchart of an “atmospheric pressure correction routine” employed in this embodiment. This routine is executed by the electronic control unit 20 in place of the “atmospheric pressure correction routine” of the first embodiment shown in FIG.

  When this routine is started, the electronic control unit 20 first calculates the atmospheric pressure correction coefficient kpa to the atmospheric pressure detected by the atmospheric pressure sensor 23 in step S70. The calculation of the atmospheric pressure correction coefficient kpa here is performed similarly to step S41 of the atmospheric pressure correction routine in the first embodiment described above.

  Subsequently, in step S71, the electronic control unit 20 confirms which start-up injection mode of the intake stroke fuel supply start and the split fuel supply start is selected. If the intake stroke fuel supply start is selected (S71: NO), the electronic control unit 20 in step S73, the map value qst_map of the start injection amount calculated in step S31 of the start injection amount calculation routine. Is multiplied by the atmospheric pressure correction coefficient kpa to set the starting injection quantity qst, and this routine is terminated.

  On the other hand, if the split fuel supply start is selected (S71: YES), the electronic control unit 20 determines the atmospheric pressure in step S72 according to the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at the start. Correction of the correction coefficient kpa is performed. This correction is performed based on the following equation.

kpa (after correction) = {1- (1-kpa (before correction)) × correction coefficient correction value α}

FIG. 8 shows an example of a calculation map of such correction coefficient correction value α. As shown in the figure, the correction coefficient correction value α is set to a value not less than “0” and not more than “1”, and the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at start-up increases. That is, the higher the degree of stratification, the smaller the value is set. More specifically, the correction coefficient correction value α is gradually increased from “1” to “1” as the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at start-up increases from “0” to “1”. It is set to approach "0". According to the above equation, the corrected atmospheric pressure correction coefficient kpa is the same as the value before correction when the correction coefficient correction value α is “0”, and the correction coefficient correction value α is “1”. As it approaches, it approaches “1”. Therefore, the value of the corrected atmospheric pressure correction coefficient kpa increases as the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at start-up increases, that is, as the degree of stratification increases, It is set to reduce the reflection degree.

  In addition, after correcting the atmospheric pressure correction coefficient kpa in this way, the electronic control unit 20 shifts the process to step S73 described above. In step S73, the starting injection amount qst is set to a value obtained by multiplying the corrected atmospheric pressure correction coefficient kpa by the map value qst_map of the starting injection amount, and this routine is terminated.

According to the start control device for an internal combustion engine of the present embodiment described above, the following effects can be obtained.
(3) Also in the present embodiment, the degree of correction of the starting injection amount qst based on the atmospheric pressure when the split fuel supply start is selected is smaller than when the intake stroke fuel supply start is selected. Therefore, also in the present embodiment, in the internal combustion engine that switches between the intake stroke fuel supply start and the split fuel supply start, it is possible to appropriately correct the starting injection amount qst based on the atmospheric pressure.

  (4) In the present embodiment, the higher the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at start-up, the smaller the degree of reflection of the atmospheric correction. Therefore, the atmospheric pressure correction can be performed more appropriately according to the degree of stratification of the air-fuel mixture in the combustion chamber 10 when the split fuel supply start is selected.

(Fourth embodiment)
Subsequently, a fourth embodiment of the internal combustion engine start control device of the present invention will be described with reference to FIG.

  As described above, when the split fuel supply start is selected, the start-time injection amount qst is distributed to the intake stroke fuel supply amount (intake stroke injection amount qst_in) and the compression stroke fuel supply amount (compression stroke injection amount qst_co). I am doing so. Here, in the present embodiment, when the split fuel supply start is selected, the atmospheric pressure correction is applied only to the intake stroke injection amount qst_in, and is not applied to the compression stroke injection amount qst_co. The influence of the atmospheric pressure correction on the fuel concentration of the air-fuel mixture formed near the spark plug when starting is selected is kept low.

  FIG. 9 shows a flowchart of a “startup injection amount calculation routine” applied to the present embodiment. The processing of this routine is repeatedly executed at predetermined control intervals by the electronic control unit 20 during engine startup, instead of the startup injection amount calculation routine (FIG. 3) in the first embodiment. It has become.

  When this routine is started, the electronic control unit 20 first determines in step S90 whether to perform intake stroke fuel supply start or split fuel supply start based on the engine coolant temperature. When the split fuel supply start is selected here, the electronic control unit 20 also determines the ratio between the fuel supply amount in the intake stroke and the fuel supply amount in the compression stroke. Subsequently, in step S91, the electronic control unit 20 calculates a map value qst_map of the starting injection amount using an arithmetic map based on the engine speed and the engine coolant temperature.

  Subsequently, in step S92, the electronic control unit 20 confirms which start-up injection mode of the intake stroke fuel supply start and the split fuel supply start is selected. If the intake stroke fuel supply start is selected (S92: NO), the electronic control unit 20 uses, in step S93, the one that has been subjected to the atmospheric pressure correction for the entire map value qst_map as the injection amount at the start. Set and exit this routine. That is, the electronic control unit 20 at this time sets a value obtained by multiplying the map value qst_map of the starting injection amount by the atmospheric pressure correction coefficient kpa as the starting injection amount qst.

  On the other hand, when the split fuel supply start is selected (S92: YES), the electronic control unit 20 distributes the map value qst_map of the start time injection amount to the intake stroke injection amount qst_in and the compression stroke injection amount qst_co in step S94. To do. In step S95, the electronic control unit 20 corrects the atmospheric pressure only for the intake stroke injection amount qst_in, and ends this routine. That is, the electronic control unit 20 at this time sets a value obtained by multiplying the intake stroke injection amount qst_in distributed in the previous step S94 by the atmospheric pressure correction coefficient kpa to the final intake stroke injection amount qst_in. On the other hand, the atmospheric pressure correction is not performed on the compression stroke injection amount qst_co, and the value distributed in the previous step S94 is set as it is as the final compression stroke injection amount qst_co.

According to the start control device for an internal combustion engine of the present embodiment described above, the following effects can be obtained.
(5) In the present embodiment, when the split fuel supply start is selected, the atmospheric pressure correction is applied only to the intake stroke injection amount qst_in and is not applied to the compression stroke injection amount qst_co. Therefore, also in the present embodiment, the correction degree of the starting injection amount qst based on the atmospheric pressure when the split fuel supply start is selected is smaller than that when the intake stroke fuel supply start is selected, and the intake stroke fuel supply start is performed. And the split fuel supply start, the start-up injection amount qst can be corrected appropriately based on the atmospheric pressure.

  (6) Also in the present embodiment, the higher the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at start-up, the smaller the degree of reflection of the atmospheric correction. Therefore, the atmospheric pressure correction can be performed more appropriately according to the degree of stratification of the air-fuel mixture in the combustion chamber 10 when the split fuel supply start is selected.

  (7) In the present embodiment, since the atmospheric pressure correction is not applied to the compression stroke injection amount qst_co in the split fuel supply start, the influence of the atmospheric pressure correction on the fuel concentration of the air-fuel mixture formed near the spark plug is affected. It can be kept low.

Each embodiment described above can be implemented with the following modifications.
In each of the above embodiments, the atmospheric pressure correction is performed by multiplying the starting fuel supply amount by the atmospheric pressure correction coefficient kpa. However, the correction amount calculated based on the atmospheric pressure is used as the starting fuel injection amount. It is also possible to perform atmospheric pressure correction by adding / subtracting to (map value qst_map). Also in this case, when the split fuel supply start is selected, the degree of atmospheric pressure correction is made smaller (the absolute value of the correction amount to be added / subtracted is relatively small) than when the intake stroke fuel supply start is selected, Alternatively, by prohibiting the atmospheric pressure correction, it is possible to suitably suppress the deterioration of the combustion state when the split fuel supply start is selected by applying the atmospheric pressure correction.

  In each of the above embodiments, the case where the correction based on the atmospheric pressure is performed as the correction of the fuel supply amount at the start based on the intake air density has been described. However, the fuel supply at the start is adjusted in accordance with the change in the intake air density according to the intake air temperature. The present invention can be similarly applied when the intake air temperature correction performed for the purpose of adjusting the amount is performed as correction based on the intake air density. That is, by performing the intake air temperature correction of the starting fuel supply amount in a manner similar to or equivalent to the atmospheric pressure correction in each of the above embodiments, the split fuel supply start by applying the intake air temperature correction is performed. The deterioration of the combustion state at the time of selection can be suitably suppressed.

(A) is a schematic diagram showing a schematic structure around a combustion chamber of an internal combustion engine that performs only in-cylinder injection, and (b) is a schematic diagram showing a schematic structure around a combustion chamber of an internal combustion engine that employs a dual injection system. 1 is a block diagram schematically showing the electrical configuration of a start control device for an internal combustion engine according to a first embodiment of the present invention. The flowchart which shows the process sequence of the electronic control unit in the injection quantity calculation routine at the time of employ | adopted as the embodiment. The flowchart which shows the process sequence of the electronic control unit in the atmospheric pressure correction routine employ | adopted for the embodiment. The flowchart which shows the process sequence of the electronic control unit in the atmospheric pressure correction routine employ | adopted as 2nd Embodiment of this invention. The graph which shows the relationship of the atmospheric pressure correction coefficient before and behind correction | amendment in the atmospheric pressure correction coefficient correction map referred by the same atmospheric pressure correction routine. The flowchart which shows the process sequence of the electronic control unit in the atmospheric pressure correction routine employ | adopted as 3rd Embodiment of this invention. The graph which shows the relationship between the compression stroke fuel supply ratio and the correction coefficient correction value in the correction coefficient correction value calculation map referred in the same atmospheric pressure correction routine. The flowchart which shows the process sequence of the electronic control unit in the injection quantity calculation routine at the time of start employ | adopted as 4th Embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Combustion chamber, 11 ... Intake port, 12 ... Exhaust port, 13 ... Intake valve, 14 ... Exhaust valve, 15 ... Spark plug, 16 ... Injector for cylinder injection, 17 ... Injector for intake port, 20 ... Electronic control Unit: 21 ... rotational speed sensor, 22 ... water temperature sensor, 23 ... atmospheric pressure sensor, 24 ... intake air temperature sensor, 25-27 ... drive circuit.

Claims (7)

An intake stroke fuel supply start in which fuel supply to the combustion chamber is performed only in the intake stroke, and a split fuel supply start in which fuel supply to the combustion chamber is divided into an intake stroke and a compression stroke are performed according to engine operating conditions. In the start control device for the internal combustion engine that switches and corrects the fuel supply amount at start based on the intake air density,
The start control device for an internal combustion engine, wherein the degree of correction based on the intake air density is made smaller when the split fuel supply start is selected than when the intake stroke fuel supply start is selected. The degree of correction based on the intake air density when the split fuel supply start is selected is reduced as the ratio of the fuel supply amount in the compression stroke to the total fuel supply amount at the start is higher. The start control device for an internal combustion engine according to claim 1. The correction based on the intake air density is applied to the fuel supply amount of the intake stroke when the split fuel supply start is selected, and is not applied to the fuel supply amount of the compression stroke when the split fuel supply start is selected. Item 2. A start control device for an internal combustion engine according to Item 1. An intake stroke fuel supply start in which fuel supply to the combustion chamber is performed only in the intake stroke, and a split fuel supply start in which fuel supply to the combustion chamber is divided into an intake stroke and a compression stroke are performed according to engine operating conditions. In the start control device for the internal combustion engine that switches and corrects the fuel supply amount at start based on the intake air density,
When the split fuel supply start is selected, correction based on the intake air density is prohibited. The start control device for an internal combustion engine according to any one of claims 1 to 4, which is applied to an internal combustion engine including two injectors, an intake port injector and an in-cylinder injector. The start control device for an internal combustion engine according to any one of claims 1 to 5, wherein an atmospheric pressure correction is performed as the correction based on the intake air density. The start control device for an internal combustion engine according to any one of claims 1 to 6, wherein an intake air temperature correction is performed as the correction based on the intake air density.

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