JP2017125486A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the deterioration of exhaust emission by improving an exhaust emission control rate and suppressing a combustion variation between cylinders at a cold start of an internal combustion engine.SOLUTION: An in-line four-cylinder internal combustion engine comprises a dynamic valve mechanism which selectively performs a both-valve operation motion for operating both a first exhaust valve and a second exhaust valve, and a single-valve stop motion for operating the second exhaust valve by stopping the first exhaust valve, and performs the single-valve stop motion at a cold start of the internal combustion engine. Second exhaust ports communicating with first and fourth cylinders are formed larger in curvature radii of trajectories than those of first exhaust ports. The first and second exhaust ports sequentially communicate with the first and second cylinders along a direction progressing toward the first cylinder from the fourth cylinder, and the first and second exhaust ports sequentially communicate with the third and fourth cylinders along a direction progressing toward the fourth cylinder from the first cylinder.SELECTED DRAWING: Figure 12

Description

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

  For example, Patent Document 1 discloses an internal combustion engine that includes first and second exhaust ports communicating with each cylinder of an engine block and first and second exhaust valves that open and close the first and second exhaust ports, respectively. Has been. When the catalytic converter provided downstream of the exhaust passage is not activated at a low temperature immediately after starting, it is necessary to raise the temperature of the exhaust port early to promote the oxidation reaction of HC in the exhaust gas. It becomes. In the internal combustion engine of Patent Document 1, among the first and second exhaust valves, the first exhaust valve is deactivated and only the second exhaust valve is operated. At this time, in the internal combustion engine disclosed in Patent Document 1, two second exhaust ports connected to two second exhaust valves that do not stop are adjacent to each other in the cylinder arrangement direction. As a result, the temperature rise of the second exhaust port is promoted, so that the HC contained in the exhaust gas can be effectively oxidized.

JP 2007-162605 A Japanese Patent Laid-Open No. 07-091237

  In an internal combustion engine in which the first exhaust port and the second exhaust port communicate with each cylinder individually, the curvature of the track of the exhaust port may differ between the first exhaust port and the second exhaust port. The turbulent energy of the exhaust passing through the exhaust port varies with the curvature of the exhaust port trajectory. For this reason, in the internal combustion engine of Patent Document 1 in which the magnitude of the turbulent energy is not taken into consideration, there remains room for improvement in terms of raising the temperature of the exhaust port.

  There is also known an internal combustion engine in which a cooling water passage for cooling a whole area around an exhaust port of each cylinder is formed in a cylinder head. When the technique of Patent Document 1 is applied to such an internal combustion engine, the temperature rise of the cooling water around the second exhaust port is partially promoted, so that the water temperature distribution in the cooling water passage becomes uneven. End up. In this case, a difference in the degree of cooling occurs for each cylinder, and there is a risk that combustion fluctuations between the cylinders may occur.

  The present invention has been made in view of the above-described problems, and suppresses deterioration of exhaust emission by improving the exhaust purification rate and suppressing combustion fluctuation between cylinders at the time of cold start of the internal combustion engine. It is an object of the present invention to provide a control device for an internal combustion engine that can be used.

In order to achieve the above object, the present invention provides a control device for an internal combustion engine in which four cylinders are arranged in series in the order of a first cylinder, a second cylinder, a third cylinder, and a fourth cylinder.
A first exhaust port and a second exhaust port formed in a cylinder head of the internal combustion engine and individually communicating with each of the four cylinders;
A first exhaust valve disposed in the first exhaust port;
A second exhaust valve disposed in the second exhaust port;
A both-valve operation for operating both the first exhaust valve and the second exhaust valve; and a one-valve stop operation for operating the second exhaust valve by stopping the first exhaust valve in a closed state; A valve mechanism that performs alternatively,
A cooling water passage extending in the cylinder arrangement direction inside the cylinder head, and for circulating cooling water around the first exhaust port and the second exhaust port of the four cylinders;
A control device for controlling the valve mechanism,
The first exhaust port and the second exhaust port communicate with the first cylinder and the second cylinder in this order along the direction from the fourth cylinder to the first cylinder, respectively.
The first exhaust port and the second exhaust port communicate with the third cylinder and the fourth cylinder in this order along the direction from the first cylinder to the fourth cylinder,
Each of the second exhaust ports communicating with the first cylinder and the fourth cylinder has the first cylinder
A curvature of the orbit is formed larger than each of the first exhaust port communicating with the cylinder and the fourth cylinder;
When the water temperature of the internal combustion engine is lower than a predetermined temperature and the engine rotation speed of the internal combustion engine is higher than a predetermined rotation speed, the control device controls the valve mechanism to stop the one-valve stop. It is characterized by being configured to perform an operation.

  According to the present invention, when the water temperature of the internal combustion engine is lower than the predetermined temperature and the engine rotation speed of the internal combustion engine is higher than the predetermined rotation speed, the exhaust is concentrated on the second exhaust port by the one-valve stop operation. Configured to flow. At this time, in the first cylinder and the fourth cylinder, the exhaust gas concentrates on the exhaust port having a large orbital curvature, so that the turbulent energy of the exhaust gas can be effectively increased to improve the exhaust gas purification rate. In addition, since the second cylinder and the third cylinder are provided with the second exhaust port on the side adjacent to the first exhaust port stopped in the first cylinder and the fourth cylinder adjacent to each other, the temperature in the cooling water channel Distribution nonuniformity can be suppressed. Thereby, at the time of cold start of the internal combustion engine, it is possible to improve the exhaust gas purification rate and suppress the combustion fluctuation between the cylinders, so it is possible to suppress the deterioration of the exhaust emission.

It is a figure which shows the structure of the system of Embodiment 1 of this invention. It is a figure which shows the comparative example of arrangement | positioning of the exhaust port connected to each cylinder. It is a figure which shows typically the behavior of the fuel injected into the intake port. It is a figure which shows the distillation characteristic of a fuel. It is a figure which shows the purification rate of the catalyst with respect to an air fuel ratio. It is a figure which shows the example of arrangement | positioning of the exhaust port connected to each cylinder. It is a figure for demonstrating the effect by turbulent flow energy increasing. It is the figure which showed typically the magnitude | size of the turbulent energy in an exhaust port. It is the figure which showed typically the magnitude | size of the turbulent energy in an exhaust port. FIG. 10 is a diagram comparing the exhaust gas temperature characteristics with respect to the ignition timing between the C pattern and the D pattern in FIG. 9. FIG. 10 is a diagram comparing the HC emission characteristics with respect to the ignition timing between the C pattern and the D pattern in FIG. 9. FIG. 3 is a diagram illustrating an example of selection of exhaust port arrangement in the system according to the first embodiment. It is a figure which shows the other example of arrangement | positioning of the exhaust port in the system of Embodiment 1. FIG. 4 is a flowchart of a routine executed by the system according to the first embodiment. It is a time chart which shows the change of the various state quantities at the time of execution of the routine shown in FIG.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings.

[System Configuration of Embodiment 1]
FIG. 1 is a diagram showing a system configuration according to the first embodiment of the present invention. As shown in this figure, the system according to the first embodiment includes an internal combustion engine 10. The internal combustion engine 10 is configured as a 4-stroke gasoline engine in which four cylinders are arranged in series in the order of a first cylinder, a second cylinder, a third cylinder, and a fourth cylinder. The internal combustion engine includes an intake passage that sucks intake air into a combustion chamber (cylinder) of each cylinder and an exhaust passage from which exhaust gas is discharged from each cylinder. A catalyst for purifying exhaust gas is disposed in the middle of the exhaust passage.

  The main body of the internal combustion engine 10 includes a cylinder head 12 and a cylinder block 14. The cylinder head 12 communicates with first and second intake ports that allow intake air to individually flow into the cylinders of the cylinders and first and second exhaust ports that individually discharge exhaust gases within the cylinders of the cylinders. doing. The first and second exhaust ports of each cylinder gather together in the cylinder head 12, and the gathered exhaust ports open to the side surface of the cylinder head 12. That is, the first and second exhaust ports are configured as branch ports extending from the cylinder end of each cylinder to the collecting portion. In the following description and drawings, the first and second exhaust ports may be referred to as Ex1 and Ex2, respectively. Each cylinder of the internal combustion engine 10 includes an ignition plug that ignites the air-fuel mixture in the cylinder, first and second intake valves that individually open and close the first and second intake ports, and first and second exhausts. First and second exhaust valves that individually open and close the ports are provided. In addition, the internal combustion engine includes a both-valve operation for operating both the first exhaust valve and the second exhaust valve, and a one-valve stop for operating only the second exhaust valve by stopping the first exhaust valve in a closed state. A known valve mechanism 16 is provided for alternatively performing the operation.

  Further, the system of the first embodiment includes a cooling water circulation system 20 for circulating cooling water through the main body of the internal combustion engine 10. The cooling water circulation system 20 includes a cooling water passage 22 formed inside the cylinder block 14 and a cooling water passage 24 formed inside the cylinder head 12. The cooling water passage 24 is provided so as to cover the upper part of the four cylinders from the vicinity of the exhaust port to the vicinity of the intake port. If the cooling water passage 24 is configured to extend in the cylinder arrangement direction in the cylinder head 12 and distribute the cooling water around the first exhaust port and the second exhaust port of each cylinder, There is no limitation on the shape of the flow path. The cooling water passage 22 and the cooling water passage 24 are connected via an opening formed in the mating surface of the cylinder head 12 and the cylinder block 14. A cooling water inlet communicating with the cooling water passage 22 is formed in the cylinder block 14, and a cooling water outlet communicating with the cooling water passage 24 is formed in the cylinder head 12. A cooling water inlet of the cylinder block 14 is connected to a cooling water outlet of the radiator 28 by a cooling water introduction pipe 26, and a cooling water outlet of the cylinder head 12 is connected to a cooling water inlet of the radiator 28 by a cooling water discharge pipe 30. The cooling water introduction pipe 26 and the cooling water discharge pipe 30 are connected by a bypass pipe 32 that bypasses the radiator 28. A thermostat 34 is provided at the junction where the bypass pipe 32 joins the cooling water introduction pipe 26. The cooling water introduction pipe 26 is provided with an electric water pump (hereinafter referred to as electric W / P) 36 that is a pump for circulating the cooling water and can adjust the flow rate by changing the drive duty.

  When the electric W / P 36 is driven, cooling water is introduced from the cooling water inlet to the cooling water passages 22 and 24 and discharged from the cooling water outlet. At this time, the thermostat 34 is closed when the cooling water temperature does not reach a predetermined temperature (for example, 80 ° C.), and is opened when the cooling water temperature reaches the predetermined temperature. When the thermostat 34 is closed, as shown by the solid line in the figure, the cooling water discharged from the cooling water outlet becomes the cooling water discharge pipe 30, the bypass pipe 32, the thermostat 34, the cooling water introduction pipe 26, the electric W / P36 is circulated sequentially to form a cooling water flow path that is introduced into the cooling water inlet. On the other hand, when the thermostat 34 is opened, as shown by the solid line and the dotted line in the figure, the cooling water discharged from the cooling water outlet is supplied to the cooling water discharge pipe 30, the radiator 28, the cooling water introduction pipe 26, and the thermostat 34. Then, a cooling water flow path is formed through the electric W / P 36 in order and introduced to the cooling water inlet.

  The system according to the first embodiment includes an ECU 40 (Electronic Control Unit) as a control device. The ECU 40 includes at least an input / output interface, a memory, and a CPU. The input / output interface is provided to capture sensor signals from various sensors attached to the internal combustion engine and to output an operation signal to an actuator provided in the internal combustion engine. Sensors that the ECU captures a signal include a water temperature sensor 42 that detects the temperature of cooling water that has passed through the internal combustion engine 10 and an air flow meter that detects the amount of intake air. The actuator from which the ECU 40 outputs an operation signal includes the valve mechanism and the electric W / P 36 described above. The memory stores various control programs, maps, and the like for controlling the internal combustion engine. The CPU reads out and executes a control program or the like from the memory, and generates an operation signal based on the acquired sensor signal.

[Operation of Embodiment 1]
Next, the operation of the system according to the first embodiment will be described.

1. Outline of Operation of Valve Mechanism of Exhaust Valve The ECU 40 controls the valve mechanism 16 to selectively execute the both-valve operation operation and one-valve stop operation of the exhaust valve. The both-valve operating operation is an operation performed during normal operation after the catalyst of the internal combustion engine is warmed up. In the both-valve operating operation, both the first and second exhaust valves are operated. In the operation of both valves, the ratio of the mass of burned gas discharged to the exhaust port with respect to the mass of burned gas in the cylinder when the exhaust valve is opened (hereinafter referred to as “scavenging efficiency”) can be maintained high. Therefore, an increase in torque fluctuation between combustion cycles is suppressed.

  However, the above-described two-valve operating operation of the exhaust valve has a problem that the exhaust purification rate is reduced when the internal combustion engine is cold-started. That is, in the both-valve operating operation, both the first and second exhaust valves are opened, so that the exhaust gas is distributed to both the first and second exhaust ports. For this reason, at the time of cold start of the internal combustion engine, it takes time to increase the gas temperature in the exhaust port, and the exhaust purification rate during that time decreases.

  As a control effective for solving the problem of the both-valve operating operation, a single valve stop operation of the exhaust valve is known. The single valve stop operation of the exhaust valve is control for stopping the single valve (first exhaust valve) of the exhaust valve in a closed state at a low temperature start when the catalyst is not active. When the one-valve stop control is executed, the contact area between the combustion gas exhausted from the internal combustion engine and the exhaust port is reduced, so that the heat radiation amount is reduced and the gas temperature in the exhaust port is increased. For this reason, according to the one-valve stop operation, the oxidation reaction rate of unburned HC can be increased by increasing the gas temperature in the exhaust port. Can be improved.

2. Issues of single valve stop operation of exhaust valve 2-1. Problems from the viewpoint of non-uniformity of the cooling water temperature In the system according to the first embodiment, when the internal combustion engine 10 is cold-started, it flows into the internal combustion engine 10 from the viewpoint of improving fuel consumption by early warm-up and reducing PM. Water stop control is performed to control the flow rate of the cooling water to a predetermined low flow rate. More specifically, in the water stop control, when the cooling water temperature is lower than a predetermined temperature, the drive duty of the electric W / P 36 is controlled to control the flow rate of the cooling water to a predetermined low flow rate. The predetermined low flow rate may be a flow rate that exhibits the effect of early warm-up of the internal combustion engine 10, and may be a complete water stop with a flow rate of zero. According to the water stop control, it is possible to improve fuel efficiency by improving combustion and reducing friction when the internal combustion engine 10 is cold, and it is possible to reduce PM emission by promoting fuel vaporization.

  However, when the water stop control is executed during the one-valve stop operation, the one-valve stop operation is performed during a period when the cooling water in the cooling water passage 24 is stagnant or the flow is small. When the one-valve stop operation is performed, exhaust gas concentrates on the second exhaust port. Therefore, depending on the arrangement of the first exhaust port and the second exhaust port communicating with each cylinder, a non-uniform water temperature distribution is generated in the cooling water passage 24. It may occur. FIG. 2 is a diagram showing a comparative example of the arrangement of exhaust ports communicating with each cylinder. In the comparative example shown in this figure, the first exhaust port and the second exhaust port communicate with the # 1 cylinder and the # 3 cylinder in this order along the cylinder arrangement direction from the # 1 cylinder to the # 4 cylinder. ing. Further, in the # 2 cylinder and the # 4 cylinder, the first exhaust port and the second exhaust port are arranged in this order along the cylinder arrangement direction from the # 4 cylinder to the # 1 cylinder. According to such an arrangement of the exhaust ports, the second exhaust ports of the # 1 and # 2 cylinders and the second exhaust ports of the # 3 and # 4 cylinders are adjacent to each other, and the # 2 and # 3 cylinders are adjacent to each other. The first exhaust ports of the cylinders are adjacent to each other. In the region where the second exhaust ports are adjacent to each other, the heat radiation of the exhaust heat is concentrated, so that the cooling water temperature increases every moment. On the other hand, since the exhaust heat is not radiated in the region where the first exhaust ports are adjacent to each other, the cooling water temperature is not so high. As described above, when the exhaust ports are arranged such that the same type of exhaust ports are adjacent to each other in the cylinder arrangement direction, the deviation of the cooling water temperature distribution in the cooling water passage 24 becomes large.

  If the cooling water temperature in the cooling water passage 24 becomes uneven, the cooling water may flow to the intake side while maintaining the water temperature non-uniformity. In this case, the wall temperature of the intake port and the temperature of the intake valve also become uneven. FIG. 3 is a diagram schematically showing the behavior of the fuel injected into the intake port. As shown in this figure, a part of the fuel injected from the fuel injection valve collides with the wall surface of the intake port and the intake valve. At this time, part of the collided fuel evaporates, but there is also fuel that does not evaporate and adheres to the wall surface. Since such attached fuel affects the combustion air-fuel ratio, it is desirable that there is no difference in the amount of attached fuel in each cylinder. However, as described above, if non-uniformity occurs in the cooling water temperature in the cooling water passage 24, a large difference occurs in the degree of cooling of the intake port and the combustion chamber wall surface of each cylinder. In this case, the fuel evaporation amount and the attached fuel amount change transiently, and a difference occurs in the combustion air-fuel ratio of each cylinder. This is the same even if the fuel is directly injected into the cylinder, for example.

  In addition, depending on the fuel used, the above problem may become more prominent. FIG. 4 is a diagram showing the fuel distillation characteristics. As shown in this figure, the evaporation rate of gasoline composed of various hydrocarbons gradually changes depending on the temperature. On the other hand, in a fuel close to a single fuel characteristic, such as high-concentration alcohol, the evaporation rate changes rapidly at a temperature near the boiling point. For this reason, in the case of fuel close to a single fuel characteristic, it is conceivable that a large difference occurs in the fuel evaporation amount and the adhered fuel amount in each cylinder due to the temperature difference of the coolant.

  The catalyst exhibits a function of purifying HC, CO and NOx by reaching the activation temperature. FIG. 5 is a diagram showing the purification rate of the catalyst with respect to the air-fuel ratio. As shown in this figure, the purification rates of HC, CO, and NOx change according to the air-fuel ratio. Further, as shown in this figure, the air-fuel ratio at which all of these exhaust components are purified with a high purification rate is limited to the purification window in the vicinity of the air-fuel ratio 14.6 which is the theoretical air-fuel ratio. For this reason, if the air-fuel ratio of each cylinder changes transiently as described above, the combustion air-fuel ratio deviates from the purification window, and exhaust emission deteriorates.

  As a countermeasure for the above problem, for example, the following arrangement of exhaust ports can be considered. FIG. 6 is a diagram showing an example of the arrangement of exhaust ports communicating with each cylinder. In the example shown in this figure, in all four cylinders, the first exhaust port and the second exhaust port communicate with each other in this order along the cylinder arrangement direction from the # 4 cylinder to the # 1 cylinder. According to such an arrangement of the exhaust ports, the same kind of exhaust ports are not adjacent to each other. For this reason, it is possible to prevent the exhaust heat from being concentrated in a specific region, so that the non-uniformity of the cooling water temperature in the cooling water passage 24 is reduced.

但し、ｖ；反応速度，［ ］；濃度，ｋ；反応速度定数，Ａ；衝突頻度因子，Ｅａ；活性化エネルギー，Ｔ；ガス温度 2-2. Problems from the viewpoint of turbulent energy When the single valve stop operation is executed, the turbulent energy in the exhaust port increases. FIG. 7 is a diagram for explaining an effect due to an increase in turbulent energy. As shown in FIG. 7, when the reactants (unburned HC and oxygen) are turbulent by turbulent mixing, the collision frequency factor increases. As shown in the following equation (1), when the collision frequency factor increases, the reaction speed increases. For this reason, when the turbulent energy in the exhaust port increases, the collision frequency factor between unburned HC and its intermediate products and oxygen increases. Afterburning can be promoted. Thus, according to the one-valve stop operation, the oxidation reaction rate of unburned HC can be increased by increasing the gas temperature in the exhaust port and increasing the turbulent energy, so that the catalyst is not activated at a low temperature. The exhaust gas purification rate at the start can be improved.

Where, v: reaction rate, []; concentration, k: reaction rate constant, A: collision frequency factor, Ea: activation energy, T: gas temperature

  Here, the turbulent energy in the exhaust port is affected by the curvature of the exhaust port orbit. FIG. 8 is a diagram schematically showing the magnitude of the turbulent energy in the exhaust port. As shown in this figure, if the first exhaust port and the second exhaust port have a symmetrical shape, the curvature of the trajectory of each exhaust port is the same. In any arrangement of the B pattern and the B pattern, there is no great difference in the turbulent energy during the single valve stop operation. For this reason, if the first exhaust port and the second exhaust port have a symmetrical shape, the one-valve at the time of cold start is obtained by arranging the exhaust port as shown in FIG. 6 described above. Deterioration of exhaust emissions during the stop operation can be suppressed.

  However, depending on the internal combustion engine 10, the curvatures of the orbits of the first exhaust port and the second exhaust port may be different. FIG. 9 is a diagram schematically showing the magnitude of turbulent energy in the exhaust port. In the example shown in this figure, in the exhaust port where the first exhaust port and the second exhaust port are joined in the middle, the orbital center of the exhaust port after joining is shifted from the cylinder center to one side in the cylinder arrangement direction. The shape is shown. In such an exhaust port shape, the curvature of the track of one exhaust port is larger than the curvature of the track of the other exhaust port. For this reason, the case where the exhaust port having a small orbital curvature is the second exhaust port (C pattern in the figure), and the case where the exhaust port having a large orbital curvature is the second exhaust port (D pattern in the figure). When comparing the turbulent energy during the one-valve stop operation, the arrangement of the D pattern in which the exhaust gas is circulated through the exhaust port having a large orbital curvature generates larger turbulent energy.

  FIG. 10 is a diagram comparing the exhaust gas temperature characteristics with respect to the ignition timing between the C pattern and the D pattern in FIG. FIG. 11 is a diagram comparing the HC emission characteristics with respect to the ignition timing between the C pattern and the D pattern in FIG. As shown in FIG. 10, the D pattern in which the exhaust gas is circulated through the exhaust port having a large curvature of the orbit can generate larger turbulent energy, so that the exhaust gas temperature can be effectively increased. . For this reason, as shown in FIG. 11, it can be seen that the exhaust port arrangement of the D pattern can purify more HC.

3. Features of System of Embodiment 1 As described above, in the one-valve stop operation at the time of cold start of the internal combustion engine, a larger turbulent energy while suppressing the cooling water temperature in the cooling water passage 24 from becoming uneven. Is required to be generated. Therefore, the exhaust port arrangement shown below is employed in the system of the first embodiment.

  FIG. 12 is a diagram illustrating an example of selection of an exhaust port arrangement in the system according to the first embodiment. The exhaust ports shown in this figure show a case where the exhaust ports of the # 1 and # 4 cylinders are asymmetrical exhaust ports, and the exhaust ports of the # 2 and # 3 cylinders are symmetrical exhaust ports. . Such an exhaust port shape is employed, for example, when the exhaust ports of each cylinder are gathered in the vicinity of between the # 2 cylinder and the # 3 cylinder (that is, near the center of the cylinder head 12 in the cylinder arrangement direction). Shape. In the example shown in this figure, the first exhaust port and the second exhaust port communicate with the # 1 cylinder and the # 2 cylinder in this order along the cylinder arrangement direction from the # 4 cylinder to the # 1 cylinder. Yes. Further, in the # 3 cylinder and the # 4 cylinder, the first exhaust port and the second exhaust port are arranged in this order along the cylinder arrangement direction from the # 1 cylinder to the # 4 cylinder. According to such an arrangement of the exhaust ports, since the exhaust port having the larger curvature of the orbit among the exhaust ports communicating with the # 1 cylinder and the # 4 cylinder is selected as the second exhaust port, a larger disturbance. Flow energy can be generated. Further, according to such an arrangement of the exhaust ports, the # 1 cylinder and the # 2 cylinder, and the # 3 cylinder and the # 4 cylinder do not have the same type of exhaust ports adjacent to each other. The area can be limited to a minimum (the area between the # 2 cylinder and the # 3 cylinder). As a result, when the internal combustion engine 10 is cold-started, it is possible to improve the exhaust gas purification rate and suppress the combustion fluctuations between the cylinders, thereby suppressing the deterioration of exhaust emission. Further, according to the arrangement of the exhaust ports shown in FIG. 12, a region where adjacent exhaust ports of the same type can be provided in the central region in the cylinder arrangement direction of the cylinder head 12, so that a temperature gradient is generated during subsequent cooling water circulation. It can be dispersed efficiently.

  FIG. 13 is a diagram showing another selection example of the arrangement of the exhaust ports in the system of the first embodiment. The arrangement of the exhaust port (A) in this figure is the same as the arrangement of the exhaust ports shown in FIG. 12 except that the arrangement of the first exhaust port and the second exhaust port communicating with the # 3 cylinder is reversed. . Also, the arrangement of the exhaust ports in (B) in this figure is the arrangement of the exhaust ports shown in FIG. 12 except that the arrangement of the first exhaust port and the second exhaust port communicating with the # 2 cylinder is reversed. Is the same. Also in the exhaust port arrangement shown in FIG. 13, the region where adjacent exhaust ports of the same type can be kept at a minimum of one place. Therefore, when the internal combustion engine 10 is cold started, the exhaust purification rate is improved and Combustion fluctuation can be suppressed.

4). FIG. 14 is a flowchart of a routine executed by the system according to the first embodiment. FIG. 15 is a time chart showing changes in various state quantities during execution of the routine shown in FIG. The routine shown in FIG. 14 is executed by the ECU 40 when the internal combustion engine is started.

  In the routine shown in FIG. 14, first, it is determined whether or not the starting water temperature ethwst is smaller than a predetermined value 1 (predetermined temperature) (step S10). The predetermined value 1 is a water temperature determination value for determining whether or not there is a request for warming up of the catalyst provided in the internal combustion engine, based on the water temperature at the time of starting, and a temperature (for example, 40 ° C.) stored in advance in the ECU 40. Is read. As a result of the determination in step S10, if the determination that the starting water temperature ethwst <predetermined value 1 is not satisfied, it is determined that the catalyst is already in an active state, and this routine is terminated. In this case, the ECU 40 activates another control routine to execute the both-valve operation of the exhaust valve. On the other hand, if it is determined in step S10 that the starting water temperature ethwst <predetermined value 1 is satisfied, it is determined that the catalyst is not yet in an active state, and the process proceeds to the next step.

  In the next step, it is determined whether or not the engine speed ene is larger than a predetermined value 2 (step S12). The predetermined value 2 is a threshold value of the engine speed for determining whether or not the hydraulic pressure of the valve mechanism has been secured, based on whether or not the internal combustion engine has exploded completely after starting, and is a value stored in advance in the ECU. (For example, 700 rpm) is read. As a result, when the present engine speed ene> predetermined value 2 is not recognized, this step is repeatedly executed. If it is confirmed that the current engine speed ene> predetermined value 2 is established, it is determined that the hydraulic pressure of the valve mechanism has been secured, the process proceeds to the next step, and the after-start determination flag is set to ON. (Step S14).

  In the routine shown in FIG. 14, next, a one-valve stop operation is executed (step S16). Specifically, as shown in the time chart of FIG. 15, the operating angle of the first exhaust valve of each cylinder is set to 0, and the operation of the exhaust valve is stopped.

  Next, it is determined whether or not the integrated air amount egasum is larger than a predetermined value 3 (step S18). The predetermined value 3 is a threshold value of the integrated air amount for determining whether sufficient heat energy is supplied to the catalyst and the catalyst warm-up is completed, and is stored in the ECU as a one-dimensional map based on the water temperature at the start. ing. Here, based on the output signal of the air flow meter, an integrated air amount egasum, which is an integrated value of the air amount since the start of the internal combustion engine, is calculated. Then, the integrated air amount (for example, 200 g, ethwt at 25 ° C.) corresponding to the starting water temperature detected in step S10 is read as a predetermined value 3 and compared with the calculated integrated air amount egasum. As a result, if establishment of the integrated air amount egasum> predetermined value 3 is not recognized, it is determined that the catalyst warm-up has not been completed yet, and the process returns to step S16. On the other hand, if it is determined in step S18 that the accumulated air amount egasum> predetermined value 3 is established, it is determined that catalyst warm-up has been completed, and this routine is terminated. When this routine is completed, the ECU activates another control routine to execute the exhaust valve base control.

  Thus, according to the system of the first embodiment, when the internal combustion engine having a catalyst warm-up request is started, the one-valve stop operation of the exhaust valve is executed. In the internal combustion engine 10 of the first embodiment, the arrangement of adjacent exhaust ports of the same type is kept to a minimum, and an exhaust port having a larger orbital curvature is selected as the second exhaust port in a cylinder having an asymmetrical exhaust port. Yes. As a result, when the internal combustion engine 10 is cold-started, it is possible to improve the exhaust gas purification rate and suppress the combustion fluctuations between the cylinders, thereby suppressing the deterioration of exhaust emission.

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder head 14 Cylinder block 16 Valve mechanism 20 Cooling water circulation system 22, 24 Cooling water path 26 Cooling water introduction pipe 28 Radiator 30 Cooling water discharge pipe 32 Bypass pipe 34 Thermostat 36 Water pump (electric W / P)
40 ECU
42 Water temperature sensor

Claims (1)

In the control device for an internal combustion engine in which four cylinders are arranged in series in the order of the first cylinder, the second cylinder, the third cylinder, and the fourth cylinder,
A first exhaust port and a second exhaust port formed in a cylinder head of the internal combustion engine and individually communicating with each of the four cylinders;
A first exhaust valve disposed in the first exhaust port;
A second exhaust valve disposed in the second exhaust port;
A both-valve operation for operating both the first exhaust valve and the second exhaust valve; and a one-valve stop operation for operating the second exhaust valve by stopping the first exhaust valve in a closed state; A valve mechanism that performs alternatively,
A cooling water passage extending in the cylinder arrangement direction inside the cylinder head, and for circulating cooling water around the first exhaust port and the second exhaust port of the four cylinders;
A control device for controlling the valve mechanism,
The first exhaust port and the second exhaust port communicate with the first cylinder and the second cylinder in this order along the direction from the fourth cylinder to the first cylinder, respectively.
The first exhaust port and the second exhaust port communicate with the third cylinder and the fourth cylinder in this order along the direction from the first cylinder to the fourth cylinder,
Each of the second exhaust ports communicating with the first cylinder and the fourth cylinder has the first cylinder
A curvature of the orbit is formed larger than each of the first exhaust port communicating with the cylinder and the fourth cylinder;
When the water temperature of the internal combustion engine is lower than a predetermined temperature and the engine rotation speed of the internal combustion engine is higher than a predetermined rotation speed, the control device controls the valve mechanism to stop the one-valve stop. A control apparatus for an internal combustion engine configured to execute an operation.

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