JP2007032476A - Internal combustion engine control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve quick temperature rise of a catalyst while suppressing the worsening of emissions in a multicylinder internal combustion engine with twin entry turbochargers for example. <P>SOLUTION: The multicylinder internal combustion engine has a plurality of small exhaust gas passage portions 17, 18 consisting of exhaust gas passages ranging from cylinders to the catalyst 15 and extending from the cylinders for differentiating temperature maintaining performance, and collective exhaust gas passage portions 7b, 14 collecting them and extending to the catalyst 15. In order to give temperature rise to the catalyst 15, the control device for the multicylinder internal combustion engine controls combustion air-fuel ratios to be different values in cylinder groups communicated with the small exhaust gas passage portions 17, 18 having different temperature maintaining performance to suppress the temperature drop of whole exhaust gas due to the combination of the exhaust gas from the small exhaust gas passage portion 17 having low temperature maintaining performance when combining the exhaust gas from the small exhaust gas passage portions 17, 18. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control device for a multi-cylinder internal combustion engine.

  In general, in an internal combustion engine, a catalyst is installed in an exhaust gas passage to purify the exhaust gas by removing harmful substances in the exhaust gas. The catalyst used for such a purpose usually exhibits a sufficient exhaust gas purification action when its temperature is high to some extent, that is, when it is above the so-called activation temperature. For this reason, it is desirable to maintain the temperature of the catalyst above the activation temperature during operation of the internal combustion engine, and it is desirable to rapidly increase the temperature of the catalyst particularly during cold start.

  Further, in a multi-cylinder internal combustion engine, for example, a four-cylinder internal combustion engine, each cylinder is divided into a group consisting of cylinders whose exhaust strokes are not adjacent to each other for the purpose of drawing out a high output by eliminating mutual interference of exhaust pulsation. A so-called twin entry turbo is known in which an exhaust pipe is configured so that the exhaust gas from the engine is guided to the turbocharger turbine independently for each group (see, for example, Patent Document 1). That is, in such an internal combustion engine, the exhaust branch pipes from the respective cylinders are first gathered into small exhaust pipes for each group, and these small exhaust pipes are arranged up to the turbine of the supercharger. It has become. In this case, after the turbine, the exhaust gas from the small exhaust pipe is collected and guided to the catalyst through one collecting exhaust pipe.

Japanese Patent Laid-Open No. 2004-1224749 JP 2000-130223 A

  By the way, as described above, it is desirable to quickly increase the temperature of the catalyst at the time of cold start. However, since the temperature of the catalyst is raised by circulation of the exhaust gas, the exhaust gas flowing into the catalyst at the time of cold start. It would be desirable to increase the temperature of the gas. The temperature of the exhaust gas flowing into the catalyst is not only the temperature of the exhaust gas when exhausted from the combustion chamber, but also the unburned fuel contained in the exhaust gas in the exhaust gas passage from the combustion chamber to the catalyst. It is also affected by how much it burns.

  A phenomenon in which unburned fuel contained in the exhaust gas burns in the exhaust gas passage from the combustion chamber to the catalyst (hereinafter referred to as “post-combustion phenomenon”) is caused by the temperature in the exhaust gas passage. (That is, the temperature of the exhaust gas in the exhaust gas passage) is difficult to occur unless the temperature is high to some extent. Therefore, in order to increase the temperature of the exhaust gas flowing into the catalyst, the temperature in the exhaust gas passage must be kept high. Very important. That is, by keeping the temperature in the exhaust gas passage high, the exhaust gas temperature cannot be simply lowered, and the exhaust gas temperature can be increased due to the afterburning phenomenon.

  On the other hand, the exhaust gas passage from each cylinder to the catalyst extends from the collective exhaust gas passage portion connected to the catalyst and at least one cylinder, for example, as in the internal combustion engine having the twin entry turbo described above. And a plurality of small exhaust gas passage portions connected to the collective exhaust gas passage portion, each of the small exhaust gas passage portions maintains the temperature of the exhaust gas flowing therethrough ( In the present application, including the scope of claims, the term “temperature maintenance performance” may differ. That is, for example, when the length of the small exhaust gas passage portion is different due to the arrangement of each cylinder, the surface area and the heat capacity of the members constituting the passage are larger when the length of the passage portion is longer. The temperature maintenance performance is inferior.

  In such a case, if the same control is performed for all the cylinders to raise the temperature of the catalyst, the afterburning phenomenon occurs in the small exhaust gas passage portion where the temperature maintenance performance is high, but the temperature maintenance performance is improved. In the low small exhaust gas passage portion, the above-mentioned post-burn phenomenon does not occur, so that the temperature of the exhaust gas passing there may be lowered. And if this low temperature exhaust gas merges with the exhaust gas from the small exhaust gas passage portion with the above high temperature maintenance performance, the temperature of the exhaust gas as a whole may drop, thereby hindering the subsequent occurrence of the afterburning phenomenon. There is. In this case, the unburned fuel in the exhaust gas is not burned sufficiently and the catalyst cannot be quickly heated, so that the emission may be deteriorated.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an exhaust gas passage from each cylinder to the catalyst, a collective exhaust gas passage portion connected to the catalyst, and at least one A plurality of small exhaust gas passage portions extending from the cylinder and connected to the collective exhaust gas passage portion, and at least two of the plurality of small exhaust gas passage portions are Provided is a control device for a multi-cylinder internal combustion engine capable of rapidly raising the temperature of the catalyst while suppressing deterioration of emissions in a multi-cylinder internal combustion engine configured so that the temperature maintenance performance is different from each other. It is.

  The present invention provides a control device for a multi-cylinder internal combustion engine described in each claim as a means for solving the above-mentioned problems.

  According to the first aspect of the present invention, an exhaust gas passage extending from each cylinder to the catalyst extends from the collective exhaust gas passage portion connected to the catalyst and at least one cylinder to the collective exhaust gas passage portion. A plurality of small exhaust gas passage portions connected to each other, and at least two of the plurality of small exhaust gas passage portions are exhaust gas flowing through the small exhaust gas passage portion. In a multi-cylinder internal combustion engine configured so that the temperature maintenance performance, which is the performance of maintaining the temperature of the engine, is different from each other, when the temperature of the catalyst is to be raised, when the exhaust gas from each small exhaust passage portion joins Different temperature maintenance performance so that the exhaust gas from the small exhaust gas passage part where the temperature maintenance performance is relatively low merges to prevent the temperature of the entire exhaust gas from decreasing. For each cylinder or group of cylinders communicating the small exhaust gas passage portion having, and controlling at least one different value of the ignition timing and the combustion air-fuel ratio, to provide a control apparatus for a multi-cylinder internal combustion engine.

  As described above, from the viewpoint of improving emissions, it is desirable to quickly raise the temperature of the catalyst when the internal combustion engine is cold started. On the other hand, when the temperature of such a catalyst is to be raised and the multi-cylinder internal combustion engine as described above is operated with the combustion air-fuel ratio and ignition timing of all the cylinders being the same, the temperature maintenance performance is In a relatively low small exhaust gas passage portion, the temperature of the exhaust gas is likely to decrease, and therefore, the above-described post-burn phenomenon is unlikely to occur. As a result, the temperature of the exhaust gas passing therethrough has a relatively high temperature maintenance performance. There is a possibility that the temperature of the exhaust gas passing through the small exhaust gas passage is considerably lower. In addition, the exhaust gas having a low temperature from the small exhaust gas passage portion having a relatively low temperature maintaining performance joins to lower the temperature of the entire exhaust gas, and the subsequent afterburn phenomenon is generated. There is also a risk of obstruction. In this case, the unburned fuel in the exhaust gas is not burned sufficiently and the catalyst cannot be quickly heated, so that the emission may be deteriorated.

  On the other hand, in the first aspect of the invention, when the temperature of the catalyst is to be raised, the small exhaust gas passage having relatively low temperature maintenance performance when the exhaust gases from the respective small exhaust passage portions merge. Combustion air-fuel ratio for each cylinder or cylinder group communicating with the small exhaust gas passage portion having different temperature maintaining performance is controlled so that the exhaust gas from the portion merges and the temperature of the entire exhaust gas is prevented from decreasing. At least one of the ignition timings is controlled to a different value. By doing so, it is possible to suppress a decrease in the temperature of the entire exhaust gas when the exhaust gases from the respective small exhaust passage portions merge, so that the above-described afterburning phenomenon is promoted, and thereby, in the exhaust gas. As a result, unburned fuel can be reduced and the temperature of the entire exhaust gas can be further increased. As a result, the temperature of the catalyst can be quickly raised while suppressing the deterioration of emissions.

  In the invention according to claim 2, in the invention according to claim 1, when the temperature of the catalyst is to be raised, the temperature of the entire exhaust gas when the exhaust gas from each small exhaust passage portion joins is predetermined. At least one of the combustion air-fuel ratio and the ignition timing is controlled to a different value for each cylinder or cylinder group communicating with the small exhaust gas passage portion having different temperature maintaining performance so as to be equal to or higher than the first temperature. Yes.

  According to the second aspect of the present invention, the afterburning phenomenon can be reliably generated and promoted after the exhaust gas is merged by appropriately setting the first predetermined temperature. . As a result, as in the first aspect of the invention, the unburned fuel in the exhaust gas can be reduced and the temperature of the entire exhaust gas can be further increased. As a result, the deterioration of emissions can be suppressed. In addition, the temperature of the catalyst can be rapidly increased.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, when the temperature of the catalyst is to be increased, a cylinder or a group of cylinders communicating with a small exhaust gas passage portion having a relatively low temperature maintenance performance. In this case, at least one of the combustion air-fuel ratio and the ignition timing is controlled so that the temperature when the exhaust gas from the small exhaust gas passage portion becomes equal to or higher than a predetermined second temperature.

  In the small exhaust gas passage portion where the temperature maintenance performance is relatively low, the temperature of the exhaust gas tends to decrease, and it is difficult to cause the afterburning phenomenon. For this reason, in a cylinder or a group of cylinders communicating with the small exhaust gas passage portion where the temperature maintenance performance is relatively low when the temperature of the catalyst is to be raised, the afterburning phenomenon is promoted in the small exhaust gas passage portion. However, it is preferable to perform control with an emphasis on suppression of a decrease in the temperature of the entire exhaust gas at the time of exhaust gas merging. For this reason, according to the invention described in claim 3, the same as the invention described in claim 1 can be achieved efficiently and reliably by appropriately setting the predetermined second temperature. Actions and effects can be obtained.

  According to a fourth aspect of the present invention, in the third aspect of the invention, when the temperature of the catalyst is to be increased, in the cylinder or the cylinder group communicating with the small exhaust gas passage portion where the temperature maintaining performance is relatively high, To control at least one of the combustion air-fuel ratio and the ignition timing so that the amount of unburned fuel contained in the exhaust gas when the exhaust gas from the small exhaust gas passage portion merges is equal to or less than a predetermined amount It has become.

  In the small exhaust gas passage portion where the temperature maintaining performance is relatively high, the afterburning phenomenon is likely to occur. For this reason, in a cylinder or a group of cylinders that communicate with the small exhaust gas passage portion where the temperature maintenance performance is relatively high when the temperature of the catalyst is to be increased, the afterburning phenomenon is promoted in the small exhaust gas passage portion. It is preferable to implement control with emphasis.

  On the other hand, according to the invention described in claim 4, when the temperature of the catalyst is to be raised, in the cylinder or the cylinder group communicating with the small exhaust gas passage portion where the temperature maintenance performance is relatively high, At least one of the combustion air-fuel ratio and the ignition timing is controlled so that the amount of unburned fuel contained in the exhaust gas when the exhaust gas from the exhaust gas passage portion merges is equal to or less than a predetermined amount. Yes. This control is intended to reduce the amount of unburned fuel in the exhaust gas at the time of joining the exhaust gas by sufficiently burning the unburned fuel contained in the exhaust gas in the small exhaust gas passage portion. Control, that is, control for promoting the afterburning phenomenon in the small exhaust gas passage portion. For this reason, the operation and effect similar to those of the first aspect of the invention can be obtained efficiently and reliably by the configuration of the fourth aspect of the invention.

  In the invention according to claim 5, in the invention according to any one of claims 1 to 4, the temperature maintenance performance is different because the length of the small exhaust passage portion is different. The diameter of the short small exhaust passage portion is made smaller than the diameter of the long small exhaust passage portion.

  According to the fifth aspect of the present invention, the temperature maintaining performance of the small exhaust passage portion having a short length can be further improved, and the afterburning phenomenon inside thereof can be promoted. As a result, the temperature of the exhaust gas when it reaches the catalyst can be raised, and the amount of unburned fuel contained in the exhaust gas can also be reduced. As a result, emission can be improved.

  When the length of the small exhaust passage portion is short, an internal combustion engine can be provided by connecting a cylinder that does not interfere with the timing of the exhaust stroke to the small exhaust passage portion even if the diameter of the small exhaust passage portion is reduced. The performance problems can be avoided.

  According to a sixth aspect of the invention, in the invention according to any one of the first to fifth aspects, the multi-cylinder internal combustion engine includes a supercharger, and the supercharger is provided to each of the small exhaust gas passage portions. A bypass passage that bypasses the turbine of the machine and has a bypass valve that controls the amount of exhaust gas flowing through the bypass passage, and when the temperature of the catalyst is to be raised, The bypass provided for the small exhaust gas passage portion having a relatively low temperature maintaining performance, and the opening degree of the bypass valve provided for the small exhaust gas passage portion having a relatively high temperature maintaining performance. Control is made to be smaller than the opening of the valve.

  When the opening degree of the bypass valve is reduced, the afterburning phenomenon in the small exhaust gas passage portion corresponding to the bypass passage provided with the bypass valve is promoted. On the other hand, when the opening degree of the bypass valve is increased, exhaust gas having a higher temperature flows into the collective exhaust gas passage portion from the small exhaust gas passage portion corresponding to the bypass passage provided with the bypass valve. Will come to do. For this reason, according to the sixth aspect of the invention, the afterburning phenomenon is further promoted in the small exhaust gas passage portion having a relatively high temperature maintaining performance, and the temperature maintaining performance is improved. From the relatively low small exhaust gas passage portion, higher temperature exhaust gas flows into the collective exhaust gas passage portion. As a result, according to the invention described in claim 6, the temperature of the catalyst can be increased more rapidly while further suppressing the deterioration of emission.

  According to a seventh aspect of the present invention, in the invention according to any one of the first to sixth aspects, a motor generator is connected to the multi-cylinder internal combustion engine, which differs when the temperature of the catalyst should be raised. When controlling at least one of the combustion air-fuel ratio and the ignition timing to a different value for each cylinder or cylinder group communicating with the small exhaust gas passage portion having the temperature maintaining performance, the difference in generated torque between the cylinders is controlled by the motor generator. The motor generator is controlled to absorb.

  If the combustion air-fuel ratio and ignition timing are controlled to different values for each cylinder or cylinder group, there may be a difference in generated torque between the cylinders. According to the seventh aspect of the present invention, since the difference in torque generated between the cylinders is absorbed by the motor generator, the temperature of the catalyst is quickly increased while suppressing the deterioration of the emission as described above. Torque fluctuations that can be caused by carrying out the control for increasing the speed can be suppressed.

  In the invention described in each claim, an exhaust gas passage extending from each cylinder to the catalyst extends from the collective exhaust gas passage portion connected to the catalyst and at least one cylinder to the collective exhaust gas passage portion. A plurality of small exhaust gas passage portions connected to each other, and at least two small exhaust gas passage portions of the plurality of small exhaust gas passage portions are configured to have different temperature maintaining performance from each other. In the multi-cylinder internal combustion engine, there is a common effect that the temperature of the catalyst can be quickly raised while suppressing the deterioration of the emission.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals are assigned to the same members.

  FIG. 1 is a diagram for explaining a case where the present invention is applied to an in-cylinder injection spark ignition type four-cylinder internal combustion engine. Referring to FIG. 1, 1 is an internal combustion engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, 3a is a spark plug, 4 is intake air Each manifold is shown. # 1 to # 4 of each cylinder portion indicate the first cylinder to the fourth cylinder, respectively. Reference numeral 5 denotes a cooling water temperature sensor for detecting the temperature of the engine cooling water, and reference numeral 36 denotes an output shaft of the internal combustion engine.

  The intake manifold 4 is connected to the outlet of the compressor 7 a of the supercharger 7 via the downstream intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 10 via the upstream intake duct 8 and the air flow meter 9. A throttle valve 12 driven by a step motor 11 is arranged in the downstream intake duct 6, and an intercooler 13 for cooling intake air flowing in the intake duct 6 is arranged around the downstream intake duct 6. Is done. In the configuration shown in FIG. 1, the engine cooling water is guided into the intercooler 13, and the intake air is cooled by the engine cooling water.

  On the other hand, as shown in FIG. 1, in this embodiment, the exhaust manifold is configured to guide exhaust gases from the first cylinder and the fourth cylinder to the inlet of the turbine 7 b of the supercharger 7. The small exhaust manifold 17 (which constitutes the first small exhaust gas passage portion) and the exhaust gas from the second cylinder and the third cylinder are guided to the inlet of the turbine 7b of the supercharger 7. And a second small exhaust manifold 18 (which constitutes a second small exhaust gas passage portion).

  In the internal combustion engine of the present embodiment, the explosion is normally performed in the order of the first cylinder, the third cylinder, the fourth cylinder, and the second cylinder. Therefore, the exhaust manifold is configured so that the cylinders whose exhaust strokes are not adjacent to each other are grouped in the same group, and the exhaust gas from each cylinder is guided to the turbine 7b of the supercharger 7 independently for each group. I can say that. In this way, mutual interference between exhaust pulsations can be eliminated, thereby obtaining an effect such as high output.

  The outlet of the turbine 7b of the supercharger 7 is connected via an exhaust pipe 14 to a casing 16 containing a catalyst 15 that purifies exhaust gas. A temperature sensor 21 for detecting or estimating the temperature of the catalyst 15 is attached to the casing 16. Without providing such a temperature sensor 21, the relationship between the operating state of the engine and the temperature of the catalyst 15 can be obtained in advance, and the temperature of the catalyst 15 can be estimated based on the operating state of the engine.

  Further, in the present embodiment, a bypass passage for allowing a part of the exhaust gas to flow through the turbine 7b of the supercharger 7 with respect to each of the first and second small exhaust manifolds 17 and 18. 19 and 20 are provided. Further, the bypass passages 19 and 20 are provided with bypass valves 19a and 20a for controlling the amount of exhaust gas flowing through the respective bypass passages.

  The fuel injection valve 3 is connected to a fuel reservoir, so-called delivery pipe 32, through a fuel supply pipe 31. Fuel is supplied into the delivery pipe 32 from an electrically controlled fuel pump 33 with variable discharge amount, and the fuel supplied into the delivery pipe 32 is supplied to the fuel injection valve 3 via each fuel supply pipe 31. . A fuel pressure sensor 34 for detecting the fuel pressure in the delivery pipe 32 is attached to the delivery pipe 32 so that the fuel pressure in the delivery pipe 32 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 34. The discharge amount of the fuel pump 33 is controlled.

  The electronic control unit 50 is composed of a digital computer, and is connected to each other by a bidirectional bus 51. A ROM (read only memory) 52, a RAM (random access memory) 53, a CPU (microprocessor) 54, an input port 55, and an output port 56. It comprises. Output signals from the air flow meter 9, the coolant temperature sensor 5, the temperature sensor 21, the fuel pressure sensor 34, etc. are input to the input port 55 via the corresponding AD converters 57.

The accelerator pedal 44 is connected to a load sensor 45 that generates an output voltage proportional to the depression amount L of the accelerator pedal 44, and the output voltage of the load sensor 45 is input to the input port 55 via the corresponding AD converter 57. Is done. Further, the input port 55 is connected to a crank angle sensor 46 that generates an output pulse every time the crankshaft rotates, for example, 15 °.
On the other hand, the output port 56 is connected to the fuel injection valve 3, the spark plug 3a, the throttle valve 12 driving step motor 11, the bypass valves 19a and 20a, the fuel pump 33, and the like through corresponding drive circuits 58.

  By the way, in the present embodiment, the catalyst 15 described above has a property of exhibiting a sufficient exhaust gas purifying action when its temperature is high to some extent, that is, when it is above the so-called activation temperature. For this reason, it is desirable to maintain the temperature of the catalyst 15 at the activation temperature or higher during operation of the internal combustion engine, and it is desirable to quickly increase the temperature of the catalyst 15 particularly during cold start.

  Here, since the temperature of the catalyst 15 is raised as the exhaust gas flows, it is desirable to increase the temperature of the exhaust gas flowing into the catalyst 15 at the time of cold start. The temperature of the exhaust gas flowing into the catalyst 15 is not limited to the temperature of the exhaust gas when exhausted from each combustion chamber 2, but is also included in the exhaust gas in the exhaust gas passage from each combustion chamber 2 to the catalyst 15. It is also affected by how much the unburned fuel it contains burns.

  The afterburning phenomenon that unburned fuel contained in the exhaust gas burns in the exhaust gas passage from the combustion chamber 2 to the catalyst 15 is caused by the temperature in the exhaust gas passage (that is, this It has been found that it is difficult to occur unless the temperature of the exhaust gas in the exhaust gas passage is high to some extent. In other words, it can be said that the afterburning phenomenon is likely to occur when the temperature in the exhaust gas passage (that is, the temperature of the exhaust gas in the exhaust gas passage) is equal to or higher than a specific temperature Tα.

  For this reason, in order to increase the temperature of the exhaust gas flowing into the catalyst 15, it is very important to maintain the temperature in the exhaust gas passage higher than the temperature Tα at which the afterburn phenomenon is likely to occur. That is, by maintaining the temperature in the exhaust gas passage higher than the specific temperature Tα, the exhaust gas temperature cannot be simply lowered, and the exhaust gas temperature can be increased by the afterburning phenomenon. .

  On the other hand, as in the internal combustion engine of the present embodiment, the exhaust gas passage from each cylinder to the catalyst 15 is a collective exhaust gas passage portion connected to the catalyst 15 (that is, the turbine 7b of the supercharger 7). A portion extending from the inlet to the catalyst 15) and a plurality of small exhaust gas passage portions extending from at least one cylinder and connected to the collective exhaust gas passage portion (that is, the first and second small exhaust passages). When the exhaust manifolds 17 and 18) are configured, the performance of maintaining the temperature of the exhaust gas flowing through each small exhaust gas passage portion, that is, the temperature maintenance performance may differ.

  That is, for example, as can be seen from FIG. 1, in the present embodiment, the first small exhaust manifold 17 that guides the exhaust gas from the first cylinder and the fourth cylinder is different from the second cylinder in relation to the arrangement of the cylinders. It is longer than the second small exhaust manifold 18 that guides exhaust gas from the third cylinder. In such a case, since the first small exhaust manifold 17 having a longer length has a larger surface area (heat dissipating area) and heat capacity of members constituting the first small exhaust manifold 17, the temperature maintaining performance is inferior.

  In such a case, if the same control is performed in all cylinders in order to raise the temperature of the catalyst 15, the second small exhaust manifold 18, which is a small exhaust gas passage portion having a high temperature maintaining performance, has the rear side. Although the burning phenomenon occurs, in the first small exhaust manifold 17 which is the small exhaust gas passage portion having a low temperature maintaining performance, the post-burning phenomenon does not occur, so the temperature of the exhaust gas passing therethrough becomes low. there is a possibility. Then, when this low temperature exhaust gas joins with the exhaust gas from the second small exhaust manifold 18 which is the small exhaust gas passage portion having a high temperature maintaining performance, the temperature of the entire exhaust gas is lowered, thereby the subsequent after There is a risk of inhibiting the occurrence of a burning phenomenon. In this case, the unburned fuel in the exhaust gas is not burned sufficiently, and the catalyst 15 cannot be rapidly heated, so that the emission may be deteriorated.

  In view of the above, in the present embodiment, special control as described below is performed to rapidly increase the temperature of the catalyst 15 while suppressing deterioration of emissions. The control in the present embodiment described below basically includes the combustion air-fuel ratio (that is, the average air-fuel ratio in the combustion chamber 2) AF, the exhaust gas temperature Teg, and the unburned fuel contained in the exhaust gas. The fact that there is a relationship as shown in FIG. 2 is used. Therefore, before describing specific control, the relationship between the relationship shown in FIG. 2 and the control performed in this embodiment will be briefly described.

  That is, FIG. 2 shows an example of the relationship between the combustion air-fuel ratio AF, the exhaust gas temperature Teg, and the amount Hcq of unburned fuel contained in the exhaust gas when the ignition timing of the internal combustion engine is constant. . More specifically, a curve Teg1 indicated by a solid line in the drawing represents the relationship between the combustion air-fuel ratio AF of the temperature of the exhaust gas from the first small exhaust manifold 17 at the inlet of the turbine 7b of the turbocharger 7. A curve Teg2 indicated by an alternate long and short dash line indicates the relationship between the combustion air-fuel ratio AF of the temperature of the exhaust gas from the second small exhaust manifold 18 at the inlet of the turbine 7b of the turbocharger 7. . Further, a curve Hcq1 indicated by a solid line in the figure shows the combustion of the amount of unburned fuel contained in the exhaust gas from the first small exhaust manifold 17 at the inlet of the turbine 7b of the supercharger 7. A curve Hcq2 that shows the relationship with the air-fuel ratio AF and is indicated by a one-dot chain line is an unburned gas contained in the exhaust gas from the second small exhaust manifold 18 at the inlet of the turbine 7b of the supercharger 7. The relationship between the amount of fuel and the combustion air-fuel ratio AF is shown.

  As is clear from this figure, the exhaust gas temperature Teg and the amount Hcq of unburned fuel contained in the exhaust gas vary depending on the combustion air-fuel ratio AF. These relationships also vary depending on the temperature maintenance performance of the first and second small exhaust manifolds 17 and 18, which are the small exhaust passage portions. Further, in this figure, when the combustion air-fuel ratio AF is AF1, the amount Hcq of unburned fuel in the exhaust gas is equal to the exhaust gas from the first and second small exhaust manifolds 17 and 18, respectively. It is the least. When the combustion air-fuel ratio AF is AF2, the exhaust gas temperature Teg is the highest for the exhaust gases from the first and second small exhaust manifolds 17 and 18, respectively.

  Here, considering the combustion air-fuel ratio control in the case where the temperature of the catalyst 15 is raised when the engine is started based on this figure, in order to quickly raise the temperature of the catalyst 15 while suppressing the deterioration of the emission, If the temperature Teg of the exhaust gas can be kept high to some extent, it is preferable to set the combustion air-fuel ratio AF to a combustion air-fuel ratio AF1 that can reduce the amount Hcq of unburned fuel in the exhaust gas. However, in practice, when the combustion air-fuel ratio AF is set to AF1, the temperature of the exhaust gas becomes low in the first small exhaust manifold 17 which is the small exhaust gas passage portion having a low temperature maintaining performance, and the exhaust gas is reduced. As a result, the temperature of the exhaust gas as a whole may be lowered, and as a result, the subsequent occurrence of the afterburning phenomenon may be hindered.

  In consideration of the above, the cylinder communicated with the second small exhaust manifold 18, which is the small exhaust gas passage portion having a high temperature maintaining performance capable of maintaining the exhaust gas temperature Teg to some extent, that is, the second cylinder. In the cylinder and the third cylinder, it is preferable to set the combustion air-fuel ratio AF to the combustion air-fuel ratio AF1 that promotes the afterburning phenomenon and can reduce the amount Hcq of unburned fuel in the exhaust gas. In the cylinder communicated with the first small exhaust manifold 17 that is the exhaust gas passage portion, that is, in the first cylinder and the fourth cylinder, the combustion air-fuel ratio AF is changed to the combustion air-fuel ratio AF2 that increases the temperature Teg of the exhaust gas. It is considered preferable to do so.

  Control in the present embodiment described below is basically based on such an idea. That is, the control in the present embodiment is simply described. When the temperature of the catalyst 15 is to be raised, the small exhaust gas having a relatively low temperature maintenance performance when the exhaust gases from the small exhaust passage portions merge. The combustion air-fuel ratio is different for each cylinder group communicating with the small exhaust gas passage portion having different temperature maintaining performance so as to suppress the temperature of the entire exhaust gas from being lowered by the exhaust gas from the passage portion joining. It is to control to the value.

  More specifically, in the control according to the present embodiment, when the temperature of the catalyst 15 is to be increased, the temperature of the entire exhaust gas when exhaust gases from the respective small exhaust passage portions join together is determined in advance. The combustion air-fuel ratio is controlled to a different value for each cylinder group communicating with the small exhaust gas passage portion having different temperature maintaining performance so that the temperature Tx becomes equal to or higher than the temperature Tx. Here, the first temperature Tx is, for example, a temperature equal to or higher than the specific temperature Tα described above.

  And when the above control is performed, it is possible to suppress the temperature of the entire exhaust gas from being lowered when the exhaust gases from the respective small exhaust passage portions are merged, so that the temperature can be maintained above the first temperature Tx. Thereafter, the afterburning phenomenon is promoted, whereby unburned fuel in the exhaust gas is reduced and the temperature of the entire exhaust gas can be further increased. As a result, the temperature of the catalyst 15 can be quickly raised while suppressing the deterioration of emissions.

  Hereinafter, the control performed in the present embodiment will be specifically described with reference to FIG. FIG. 3 is a flowchart showing a control routine of control executed in order to set the fuel injection amount, ignition timing, opening degree of the bypass valves 19a, 20a, etc. at the time of engine start in the present embodiment. Here, since the fuel injection amount is set in consideration of the intake air amount to each cylinder, setting the fuel injection amount is synonymous with setting the combustion air-fuel ratio. In the internal combustion engine of the present embodiment, when the engine is started, control is performed based on the fuel injection amount, ignition timing, bypass valve opening, and the like set by executing this control routine. .

  When this control routine starts, it is first determined in step 101 whether or not the internal combustion engine is in operation. If it is determined in step 101 that the internal combustion engine is not in operation, the routine proceeds to step 125. In step 125, the pre-starting value (that is, pre-starting engine cooling water temperature) Twb of the engine cooling water temperature Tw is taken, and the value of an integrated value Av described later is initialized (that is, Av = 0). ) Thereafter, this control routine is once ended and repeated from the beginning.

  On the other hand, if it is determined in step 101 that the internal combustion engine is in operation, the routine proceeds to step 103. In step 103, it is determined whether or not the engine coolant temperature Tw is lower than a predetermined reference coolant temperature Twc. This determination is a determination of whether or not the engine has been cold started, and more specifically, a determination of whether or not the internal combustion engine is in a cold state. The reference cooling water temperature Twc is appropriately set in advance for this purpose.

  If it is determined in step 103 that the engine coolant temperature Tw is not lower than the reference coolant temperature Twc, that is, is equal to or higher than a predetermined reference coolant temperature Twc, it is determined that the internal combustion engine is not already in the cold state. In this case, the process proceeds to step 127. When the routine proceeds to step 127, the value of the integrated value Av is initialized (that is, Av = 0), and then this control routine is once ended and repeated from the beginning.

  On the other hand, when it is determined in step 103 that the engine coolant temperature Tw is lower than the reference coolant temperature Twc, it is determined that the internal combustion engine is still in a cold state. Proceed to When the routine proceeds to step 105, it is determined whether or not the internal combustion engine is in an idling state. In the present embodiment, it is determined that the internal combustion engine is idling when the speed of the vehicle on which the internal combustion engine is mounted is substantially zero and the depression amount L of the accelerator pedal 44 is substantially zero.

  If it is determined in step 105 that the internal combustion engine is not idling, the routine proceeds to step 127 where the value of the integrated value Av is initialized (that is, Av = 0), and then this control routine is executed. Once finished, it is repeated from the beginning again. On the other hand, if it is determined in step 105 that the internal combustion engine is idling, the routine proceeds to step 107.

  In step 107, the integration of the integrated value Av is started or continued. In this embodiment, this integrated value Av is an integrated value of the intake air amount after the internal combustion engine is started. That is, after the current internal combustion engine is started, when the control of step 107 is first performed, the intake air amount starts to be accumulated. In other cases, that is, after the current internal combustion engine is started, the second and subsequent times. If the control in step 107 is performed and if the integration has already been started, the intake air amount integration is continued. This integrated value Av is used in determination in step 113 described later. In other embodiments, the integrated value Av may be the elapsed time after the start of the internal combustion engine.

  Following step 107, the process proceeds to step 109. In step 109, the fuel injection amount and ignition timing in the second cylinder and the third cylinder are determined. Here, both the second cylinder and the third cylinder are cylinders communicating with the second small exhaust manifold 18 having a high temperature maintaining performance described above. Therefore, here, the fuel injection amount is such that the combustion air-fuel ratio in the second cylinder and the third cylinder promotes the afterburning phenomenon, and the amount Hcq of unburned fuel in the exhaust gas decreases when the exhaust gas merges. The fuel injection amount is determined to be a combustion air-fuel ratio (that is, an air-fuel ratio corresponding to AF1 in FIG. 2 described above).

  More specifically, in the present embodiment, the fuel injection amount determined here is the same as the combustion air-fuel ratio in the second cylinder and the third cylinder, and the amount Hcq of unburned fuel in the exhaust gas from these cylinders is merged. The fuel injection amount at which the combustion air-fuel ratio becomes equal to or smaller than a predetermined amount (that is, a reference allowable amount) at the time is set.

  In this embodiment, such a fuel injection amount is obtained in advance in consideration of the intake air amount determined based on the throttle valve opening, the engine speed, etc. in the idling state of the internal combustion engine, and is mapped together with the corresponding ignition timing. In step 109, an appropriate fuel injection amount and ignition timing are obtained based on this map.

  When the fuel injection amount and ignition timing in the second and third cylinders are determined in step 109, the routine proceeds to step 111. In step 111, a reference integrated value Cv is determined. This reference integrated value Cv is compared with the integrated value Av in the subsequent step 113, or the integrated value of the intake air amount after starting the internal combustion engine (or the elapsed time after starting the internal combustion engine in other embodiments). Based on the above, it is for determining whether or not the temperature of the catalyst 15 should still be raised. In the present embodiment, the reference integrated value Cv is appropriately determined based on the pre-starting engine coolant temperature Twb taken in step 125 in consideration of such a purpose. Normally, the reference integrated value Cv increases as the pre-starting engine coolant temperature Twb decreases.

  When the reference integrated value Cv is determined in step 111, the process proceeds to step 113. In step 113, as described above, the reference integrated value Cv and the integrated value Av are compared. If it is determined in step 113 that the reference integrated value Cv is greater than the integrated value Av, it is determined that the temperature of the catalyst 15 is still to be raised. Then, the fuel injection amount and ignition timing in the first cylinder and the fourth cylinder are determined.

  Here, the first cylinder and the fourth cylinder are both cylinders communicating with the first small exhaust manifold 17 having a low temperature maintaining performance. As described above, the process proceeds to step 115 when the temperature of the catalyst 15 is still in a state to be increased. Therefore, here, the fuel injection amount is such that the combustion air-fuel ratio in the first cylinder and the fourth cylinder is such that the temperature Teg becomes high when the exhaust gas from these cylinders merges (that is, in FIG. 2 described above). The fuel injection amount is determined to be an air-fuel ratio corresponding to AF2.

  More specifically, in the present embodiment, the fuel injection amount determined here is determined in advance by the combustion air-fuel ratio in the first cylinder and the fourth cylinder, and the temperature when the exhaust gas from these cylinders merges. This is the fuel injection amount at which the combustion air-fuel ratio becomes higher than the second temperature Ty. Here, the second temperature Ty is a temperature at which, for example, the temperature of the whole exhaust gas when combined is equal to or higher than the first temperature Tx described above, and is appropriately determined in advance.

  In the present embodiment, the fuel injection amount as described above is determined in advance in consideration of the intake air amount determined based on the throttle valve opening, the engine speed, etc. in the idling state of the internal combustion engine, and is mapped together with the corresponding ignition timing. In step 115, an appropriate fuel injection amount and ignition timing are obtained based on this map. Normally, the combustion air-fuel ratio to be realized with the fuel injection amount determined in step 115 is smaller than the combustion air-fuel ratio to be realized with the fuel injection amount determined in step 109.

  When the fuel injection amount and the ignition timing in the first cylinder and the fourth cylinder are determined in step 115, the process proceeds to step 117, and the opening degree of the corresponding bypass valve 19a is determined. The opening degree of the bypass valve 19a determined here bypasses the turbine 7b of the supercharger 7 from the inside of the first small exhaust manifold 17 with an amount of exhaust gas appropriate for raising the temperature of the catalyst 15. It is the opening which makes it flow. That is, in this case, the temperature of the catalyst 15 is rapidly raised by supplying the exhaust gas of high temperature bypassing the turbine 7b of the supercharger 7 to the catalyst 15. In the present embodiment, the appropriate opening as described above is obtained in advance, and in step 117, the opening is taken as the opening of the bypass valve 19a.

  When the opening degree of the bypass valve 19a is determined in step 117, the process proceeds to step 123. In step 123, the opening degree of the bypass valve 20a corresponding to the fuel injection amount and ignition timing in the second and third cylinders determined in step 109 is determined. Here, the opening degree of the bypass valve 20a is smaller than the opening degree of the bypass valve 19a determined in the step 117, and is opened so as to promote the afterburning phenomenon in the second small exhaust manifold 18. Determined in degrees.

  That is, in this case, the opening degree of the bypass valve 20a is reduced to reduce the amount of exhaust gas bypassing the turbine 7b of the supercharger 7, and the pressure upstream of the turbine 7b is increased to promote the afterburning phenomenon. Let's make it. By doing so, the exhaust gas temperature can be raised and the amount of unburned fuel in the exhaust gas can be reduced. In the present embodiment, the appropriate opening as described above is obtained in advance, and in step 123, the opening is taken in as the opening of the bypass valve 20a. When the opening degree of the bypass valve 20a is determined in step 123, this control routine is once ended and repeated from the beginning.

  On the other hand, when it is determined in step 113 that the reference integrated value Cv is equal to or less than the integrated value Av, it is determined that the temperature of the catalyst 15 is not already in a state to be raised. The routine proceeds to step 119, where the fuel injection amount and ignition timing in the first cylinder and the fourth cylinder are determined.

  As described above, the first cylinder and the fourth cylinder are both cylinders communicating with the first small exhaust manifold 17 having low temperature maintenance performance. This is a case where the temperature is not in a state to be raised. For this reason, the fuel injection amount here is such that the combustion air-fuel ratio in the first cylinder and the fourth cylinder promotes the afterburning phenomenon, and the amount Hcq of unburned fuel in the exhaust gas decreases when the exhaust gas merges. The fuel injection amount becomes such a combustion air-fuel ratio (that is, the air-fuel ratio corresponding to AF1 in FIG. 2 described above).

  More specifically, in the present embodiment, the fuel injection amount determined here is the same as the combustion air-fuel ratio in the first cylinder and the fourth cylinder, which is the amount of unburned fuel in the exhaust gas from these cylinders Hcq. The fuel injection amount at which the combustion air-fuel ratio becomes equal to or smaller than a predetermined amount (that is, a reference allowable amount) at the time is set.

  That is, when proceeding to step 119, since the first small exhaust manifold 17 has already been warmed to some extent, it is considered that the afterburn phenomenon can occur there even if the temperature maintenance performance is low. Therefore, here, control is performed with an emphasis on reducing the amount of unburned fuel in the exhaust gas.

  In the present embodiment, the fuel injection amount as described above is determined in advance in consideration of the intake air amount determined based on the throttle valve opening, the engine speed, etc. in the idling state of the internal combustion engine, and is mapped together with the corresponding ignition timing. In step 119, an appropriate fuel injection amount and ignition timing are obtained based on this map.

  When the fuel injection amount and the ignition timing in the first cylinder and the fourth cylinder are determined in step 119, the process proceeds to step 121, and the opening degree of the corresponding bypass valve 19a is determined. Here, the opening degree of the bypass valve 19a is an opening degree smaller than the opening degree of the bypass valve 19a determined in the step 117, similar to the opening degree of the bypass valve 20a in the above-described step 123, and the first small value. The opening degree is determined so as to promote the afterburning phenomenon in the exhaust manifold 17.

That is, in this case, the opening degree of the bypass valve 19a is reduced to reduce the amount of exhaust gas bypassing the turbine 7b of the supercharger 7, and the pressure upstream of the turbine 7b is increased to promote the afterburning phenomenon. I will let you. By doing so, the exhaust gas temperature can be raised and the amount of unburned fuel in the exhaust gas can be reduced. In the present embodiment, the appropriate opening as described above is obtained in advance, and in step 121, the opening is taken as the opening of the bypass valve 19a. When the opening degree of the bypass valve 19a is determined in step 121, the process proceeds to step 123. In step 123, the opening degree of the bypass valve 20a is determined as described above, and then this control routine is once ended and repeated from the beginning.
In other embodiments, the determination in step 113 may be performed based on the temperature of the catalyst 15.

  FIG. 4 shows an example of changes over time in the temperature of the first small exhaust manifold 17 and the combustion air-fuel ratios of the first and fourth cylinders after the internal combustion engine is started when the control routine shown in FIG. 3 is executed. It is a thing. Regarding the temperature of the first small exhaust manifold 17, the case where the control routine shown in FIG. 3 is executed is indicated by a solid line, and the combustion air-fuel ratio of the first and fourth cylinders is the lean-side air-fuel ratio. Is indicated by a one-dot chain line, and a case where the air-fuel ratio on the rich side is AF2 is indicated by a two-dot chain line.

  In the example of this figure, the internal combustion engine is started at time t0, and until that time t1, the combustion air-fuel ratios of the first and fourth cylinders are AF2 that is the rich air-fuel ratio. At time t1, it is determined that the integrated value Av is equal to or higher than the reference integrated value Cv, and the combustion air-fuel ratio of the first and fourth cylinders is switched from AF2 that is the rich air-fuel ratio to AF1 that is the lean air-fuel ratio. It has been. At time t1, the temperature of the first small exhaust manifold 17 exceeds the specific temperature Tα, and the afterburning phenomenon is sufficiently generated in the small exhaust manifold 17.

  In the present embodiment, as shown in FIG. 1, the second small exhaust manifold 18 which is a small exhaust passage portion having a short length is the first small exhaust passage portion having a long diameter. It is smaller than the diameter of the small exhaust manifold 17. By doing so, it is possible to reduce the heat capacity and the heat radiation area of the second small exhaust manifold 18 which is the short small exhaust passage portion, and the temperature maintenance performance can be further improved. The afterburning phenomenon can be promoted. As a result, the temperature of the exhaust gas when it reaches the catalyst can be raised, and the amount of unburned fuel contained in the exhaust gas can also be reduced. As a result, emission can be improved.

  Here, since the length of the second small exhaust manifold 18 is short, even if the diameter thereof is reduced (that is, for example, the diameter corresponding to the exhaust gas amount for one cylinder), the timing of the exhaust stroke there If the cylinders that do not interfere with each other (that is, the second cylinder and the third cylinder) are made to communicate with each other, it is possible to avoid a problem in the performance of the internal combustion engine.

  Further, in the present embodiment, the ignition timing is determined so that the generated torque in each cylinder becomes the same in the determination of the ignition timing in the above-mentioned step 109, step 115 and step 119. That is, as can be understood from the above description, when the control routine shown in FIG. 3 is executed, the first and fourth cylinders and the second and third cylinders are controlled to have different combustion air-fuel ratios. There is a case. In such a case, there is a possibility that a difference occurs in the generated torque between the cylinders. On the other hand, in the present embodiment, the ignition timing is set to a different value for each cylinder group having different combustion air-fuel ratios, so that a difference in generated torque does not occur between the cylinders. More specifically, in the present embodiment, the ignition timing that is retarded is set in a cylinder having a low combustion air-fuel ratio compared to a cylinder having a high combustion air-fuel ratio. By doing so, it is possible to suppress torque fluctuations that may be caused by performing the combustion air-fuel ratio control for each cylinder group as described above.

  In another embodiment, the difference in generated torque between the cylinders as described above may be absorbed by a motor generator. FIG. 5 is a diagram for explaining the configuration in this case. The configuration shown in FIG. 5 is basically the same as the configuration shown in FIG. 1, and the description of common parts is omitted.

  Referring to FIG. 5, in this configuration, a motor generator 37 is connected to the output shaft 36 of the internal combustion engine, and a transmission 35 is further connected. The motor generator 37 has both a function as an electric motor that generates a driving force separately from the driving force of the internal combustion engine and a function as a generator that generates power by being driven by an external force.

  In the configuration shown in FIG. 5, the motor generator 37 is mounted on an output shaft 36 of an internal combustion engine and a rotor 38 having a plurality of permanent magnets mounted on its outer peripheral surface, and a stator wound with an exciting coil for forming a rotating magnetic field. And an AC synchronous motor. The exciting coil of the stator 39 is connected to a motor generator control circuit 40, and this motor generator control circuit 40 is connected to a battery 41 that generates a DC high voltage.

  As described above, when the motor generator 37 is driven by an external force, it can be operated as a generator, and the electric power generated at this time is regenerated in the battery 41. When the motor generator 37 is operated as a generator, the motor generator control circuit 40 controls the battery 41 to regenerate the electric power generated by the motor generator 37.

  In this configuration, various signals representing the gear ratio or speed of the transmission 35 and the rotational speed of the output shaft 30 of the transmission 35 are also input to the input port 55 of the electronic control unit 50. . The output port 56 is also connected to the transmission 35 via a corresponding drive circuit 58. Further, the output port 56 is connected to the motor generator 37 via the motor generator control circuit 40.

  In this embodiment, in the configuration as described above, the difference in generated torque between the cylinders as described above is absorbed by the motor generator 37. That is, the control by the control routine shown in FIG. 3 is performed, and the combustion air-fuel ratio in the first and fourth cylinders is smaller than the combustion air-fuel ratio in the second and third cylinders in order to increase the temperature of the catalyst 15. Taking this case as an example, torque absorption control by the motor generator 37 is performed at the timing when the expansion strokes of the first and fourth cylinders that generate larger torque arrive. That is, in this case, since the occurrence of the torque difference is periodic and predictable, the torque difference can be absorbed by controlling the motor generator 37 accordingly.

  More specifically, first, the combustion air-fuel ratio and ignition timing in the first and fourth cylinders determined by the control by the control routine shown in FIG. 3 and the combustion air-fuel ratio in the second and third cylinders are determined. Based on the ignition timing and the like, the torque generated in the first and fourth cylinders and the torque generated in the second and third cylinders are calculated. Next, the calculated torque difference is calculated, and the torque difference to be absorbed is obtained. The motor generator 37 is controlled so as to absorb the torque corresponding to the torque difference to be absorbed at the timing when the expansion strokes of the first and fourth cylinders at which a larger torque is generated.

  In this way, as described above, torque fluctuations that can be caused by controlling the combustion air-fuel ratio and ignition timing for each cylinder group can be suppressed. Further, in this case, since it is allowed to increase the generated torque difference between the cylinders until the torque absorption limit by the motor generator 37, the object of increasing the temperature of the catalyst 15 more quickly while suppressing the deterioration of the emission is achieved. Therefore, a more suitable combustion air-fuel ratio and ignition timing can be set for each cylinder group.

  In the above description, the case of a four-cylinder internal combustion engine has been described as an example. However, the present invention can also be applied to other multi-cylinder internal combustion engines such as six cylinders, eight cylinders, and ten cylinders. In the above description, an internal combustion engine having a supercharger has been described as an example. However, the present invention is not limited to this and can be applied to an internal combustion engine having no supercharger.

  In the above description, both the combustion air-fuel ratio and the ignition timing are controlled to be different values for each cylinder group communicating with the small exhaust gas passage portions having different temperature maintenance performances. In order to obtain the same effect, one of the combustion air-fuel ratio and the ignition timing is set for each cylinder group (or cylinder) communicating with the small exhaust gas passage portion having different temperature maintaining performance. You may make it control to a different value.

  That is, for example, based on the relationship between the ignition timing when the combustion air-fuel ratio is constant as shown in FIG. 2, the temperature Teg of the exhaust gas, and the amount Hcq of unburned fuel contained in the exhaust gas, The ignition timing may be controlled to a different value for each cylinder group (or cylinder). In such a case, it is effective to use the motor generator as described above in order to suppress the torque fluctuation.

FIG. 1 is a diagram for explaining a case where the present invention is applied to an in-cylinder injection spark ignition type four-cylinder internal combustion engine. FIG. 2 is a diagram showing an example of the relationship between the combustion air-fuel ratio AF, the exhaust gas temperature Teg, and the amount Hcq of unburned fuel contained in the exhaust gas when the ignition timing of the internal combustion engine is constant. FIG. 3 is a flowchart showing a control routine of control executed in order to set the fuel injection amount, ignition timing, opening degree of the bypass valve, etc. at the time of engine start in one embodiment of the present invention. FIG. 4 shows an example of changes over time of the temperature of the first small exhaust manifold and the combustion air-fuel ratios of the first and fourth cylinders after starting the internal combustion engine when the control routine shown in FIG. 3 is executed. Is. FIG. 5 is a diagram for explaining a case where the present invention is applied to a direct injection spark ignition type four cylinder internal combustion engine equipped with a motor generator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine body 3 Fuel injection valve 12 Throttle valve 15 Catalyst 17 First small exhaust manifold 18 Second small exhaust manifold 19a, 20a Bypass valve 37 Motor generator 41 Battery

Claims (7)

An exhaust gas passage extending from each cylinder to the catalyst is connected to the collective exhaust gas passage portion connected to the catalyst, and a plurality of small exhaust gases extending from at least one cylinder and connected to the collective exhaust gas passage portion. At least two small exhaust gas passage portions of the plurality of small exhaust gas passage portions, and the temperature is a performance that maintains the temperature of the exhaust gas flowing through the small exhaust gas passage portion. In a multi-cylinder internal combustion engine configured to have different maintenance performances,
When the temperature of the catalyst is to be raised, the exhaust gas from the small exhaust gas passage portions having relatively low temperature maintenance performance when the exhaust gases from the respective small exhaust passage portions are joined together, so that the entire exhaust gas To control at least one of the combustion air-fuel ratio and the ignition timing to a different value for each cylinder or cylinder group communicating with the small exhaust gas passage portion having different temperature maintaining performance so as to suppress the temperature of the engine from decreasing. A control device for a multi-cylinder internal combustion engine.   When the temperature of the catalyst is to be raised, the small exhaust gas having different temperature maintaining performance is set so that the temperature of the entire exhaust gas when the exhaust gases from the small exhaust passages are merged is equal to or higher than a predetermined first temperature. 2. The control apparatus for a multi-cylinder internal combustion engine according to claim 1, wherein at least one of the combustion air-fuel ratio and the ignition timing is controlled to a different value for each cylinder or a group of cylinders communicating with the exhaust gas passage portion.   When the temperature of the catalyst should be increased, the temperature at which the exhaust gas from the small exhaust gas passage portion joins in the cylinder or the group of cylinders communicating with the small exhaust gas passage portion where the temperature maintenance performance is relatively low. 3. The control device for a multi-cylinder internal combustion engine according to claim 1, wherein at least one of the combustion air-fuel ratio and the ignition timing is controlled to be equal to or higher than a predetermined second temperature.   When the temperature of the catalyst is to be raised, the exhaust gas when the exhaust gas from the small exhaust gas passage portion merges in the cylinder or the cylinder group communicating with the small exhaust gas passage portion having relatively high temperature maintenance performance 4. The control device for a multi-cylinder internal combustion engine according to claim 3, wherein at least one of the combustion air-fuel ratio and the ignition timing is controlled so that the amount of unburned fuel contained therein is equal to or less than a predetermined amount. .   The temperature maintenance performance is different because the length of the small exhaust passage portion is different, and the diameter of the small exhaust passage portion having a short length is made smaller than the diameter of the small exhaust passage portion having a long length. The control device for a multi-cylinder internal combustion engine according to any one of claims 1 to 4, wherein the control device is a multi-cylinder internal combustion engine. The multi-cylinder internal combustion engine includes a supercharger, and each small exhaust gas passage portion is a bypass passage that bypasses the turbine of the supercharger, and the amount of exhaust gas flowing through the bypass passage is reduced. A bypass passage having a bypass valve to be controlled is provided;
When the temperature of the catalyst is to be raised, the small exhaust gas in which the degree of opening of the bypass valve provided for the small exhaust gas passage portion having a relatively high temperature maintaining performance is relatively low. The control device for a multi-cylinder internal combustion engine according to any one of claims 1 to 5, wherein the control device is controlled so as to be smaller than an opening degree of the bypass valve provided for the passage portion. . A motor generator is connected to the multi-cylinder internal combustion engine,
When controlling at least one of the combustion air-fuel ratio and the ignition timing to a different value for each cylinder or cylinder group communicating with the small exhaust gas passage portion having different temperature maintaining performance when the temperature of the catalyst should be raised, 7. The control apparatus for a multi-cylinder internal combustion engine according to claim 1, wherein the motor generator is controlled so that a difference in torque generated between the motor generator is absorbed by the motor generator.

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