Supercharged internal combustion engine control method and supercharged internal combustion engine control device

Abstract

This supercharged internal combustion engine control method is designed for a case in which, when a compressor that rotates in association with a turbine, which receives energy from exhaust gas from an internal combustion engine to rotate, takes in fresh air and supplies the fresh air to the intake side of the internal combustion engine, the exhaust gas is purified by a catalyst disposed between the exhaust side of the internal combustion engine and the turbine. In this case, according to the supercharged internal combustion engine control method, an opening degree is adjusted for a waste gate valve, which is disposed in a branch passage branched from an exhaust passage between the catalyst and the turbine and merged with an exhaust side of the exhaust gas of the turbine and which adjusts a flow amount of the exhaust gas in the branch passage to adjust the exhaust gas to be supplied to the turbine, so as to increase the back pressure of the exhaust gas to increase the temperature of the exhaust gas, thereby warming up the catalyst, wherein the opening degree of the waste gate valve is set to the maximum or substantially maximum at the start of the warm-up of the catalyst and the opening degree of the waste gate valve is subsequently reduced as the temperature of the internal combustion engine increases.

Description

Control method for supercharged internal combustion engine and control device for supercharged internal combustion engine

[0001] The present invention relates to a method for controlling a supercharged internal combustion engine and a control device for a supercharged internal combustion engine.

[0002] JP2020-118832A discloses a configuration in which a catalyst for purifying exhaust gas is arranged in an exhaust passage connecting an internal combustion engine and a turbocharger turbine (turbine wheel), and when warming up the catalyst, a variable nozzle attached in front of the turbine wheel is fully closed, or a wastegate valve arranged in a branch passage that branches off at a position downstream of the catalyst in the exhaust passage is fully closed.

[0003] In the above technology, the wastegate valve or variable nozzle is fully closed when catalyst warm-up begins, increasing the exhaust gas back pressure in the exhaust passage and raising the exhaust gas temperature, thereby facilitating catalyst warm-up. Increasing the exhaust gas back pressure also increases the proportion of residual gas (exhaust gas) in the combustion chamber of the internal combustion engine. As the proportion of residual gas increases, the proportion of harmful components in the exhaust gas generated in the next fuel cycle decreases, improving exhaust performance (exhaust gas cleanliness). However, if the proportion of residual gas increases when the internal combustion engine temperature is low, there is a risk of reduced combustion stability in the next combustion cycle.

[0004] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for controlling a supercharged internal combustion engine and a control device for a supercharged internal combustion engine that maintain good combustion stability and exhaust performance when the catalyst is warmed up.

[0005] According to one aspect of the present invention, there is provided a control method for a turbocharged internal combustion engine in which, when a compressor rotates in conjunction with a turbine that receives energy from exhaust gas emitted from the internal combustion engine and takes in fresh air to supply to the intake side of the internal combustion engine, the exhaust gas is purified by a catalyst disposed between the exhaust side of the internal combustion engine and the turbine, and a branch passage that branches off from an exhaust passage between the catalyst and the turbine and joins the exhaust side of the turbine exhaust gas is adjusted to adjust the flow rate of exhaust gas supplied to the turbine by adjusting the aperture of a wastegate valve, or an aperture of a variable nozzle that adjusts the flow velocity of exhaust gas supplied to the turbine, thereby increasing the back pressure of the exhaust gas and raising the temperature of the exhaust gas, thereby warming up the catalyst. In this control method, the aperture of the wastegate valve is set to a maximum or nearly maximum when catalyst warm-up begins and then reduced as the temperature of the internal combustion engine increases, or the aperture of the variable nozzle is set to a maximum or nearly maximum when catalyst warm-up begins and then reduced as the temperature of the internal combustion engine increases.

[0006] FIG. 1 is an explanatory diagram showing an outline of an internal combustion engine control device (control method) of this embodiment. FIG. 2 is a diagram showing a flow of catalyst warm-up control by the internal combustion engine control device (control method) of this embodiment. FIG. 3 is a time chart of each vehicle parameter in the catalyst warm-up control by the internal combustion engine control device (control method) of this embodiment. FIG. 4 is a diagram showing a flow of a modified example of catalyst warm-up control by the internal combustion engine control device (control method) of this embodiment. FIG. 5 is a time chart of each vehicle parameter in the modified example of catalyst warm-up control by the internal combustion engine control device (control method) of this embodiment.

[0007] FIG. 1 is an explanatory diagram showing an outline of a control device (control method) for an internal combustion engine 1 according to this embodiment.

[0008] The internal combustion engine 1 is, for example, a spark-ignition gasoline engine, and is mounted as a drive source in a vehicle such as an automobile.

[0009] The internal combustion engine 1 is, for example, of a cylinder direct injection type, and each cylinder is provided with a fuel injection valve (not shown) that injects fuel into the cylinder (combustion chamber) and a spark plug (not shown). The injection timing and injection amount of the fuel injection valve and the ignition timing of the spark plug are controlled by control signals from a control unit 7 (controller).

[0010] A cylinder of the internal combustion engine 1 communicates with an intake passage 2 via an intake valve (not shown), and communicates with an exhaust passage 3 via an exhaust valve (not shown).

[0011] The internal combustion engine 1 is incorporated into a cooling water circulation system 5 through which cooling water circulates, and is cooled by the cooling water. The cooling water circulation system 5 includes a pump 51 for circulating the cooling water, and a cooling means 52 (a radiator, a chiller) for cooling the cooling water.

[0012] The intake passage 2 supplies fresh air to the internal combustion engine 1, and is provided with an air cleaner (not shown), a compressor 42, and a TLV 21 (throttle valve) from the upstream side.

[0013] An air cleaner (not shown) collects foreign matter in the fresh air.

[0014] The compressor 42 constitutes the turbocharger 4. The compressor 42 takes in fresh air and supplies it to the TLV 21 side.

[0015] The TLV 21 adjusts the flow rate of fresh air supplied to the internal combustion engine 1 (combustion chamber) by adjusting the opening based on the amount of depression of the accelerator pedal (accelerator opening) during normal operation of the internal combustion engine 1 (for example, while the vehicle is running). The TLV 21 is also subject to control when warming up the catalyst 31, which will be described later.

[0016] A first branch passage 22 branches off from the intake passage 2 at a position where the compressor 42 and the TLV 21 meet, and the first branch passage 22 merges with the intake passage 2 at a position upstream of the compressor 42 of the intake passage 2. An RCV 23 (recirculation valve) is arranged in the first branch passage 22.

[0017] The RCV 23 takes in a portion of the air supplied by the compressor 42 and returns it to the intake side of the compressor 42. The RCV 23 is normally closed, but opens when, for example, the pressure downstream of the compressor 42 becomes high (when the TLV 21 is closed). The RCV 23 is also subject to control when warming up the catalyst 31, which will be described later.

[0018] A catalyst 31 and a turbine 41 are arranged in the exhaust passage 3. A filter (not shown) for collecting particulates in the exhaust gas and a muffler (not shown) are arranged downstream of the turbine 41.

[0019] The catalyst 31 (three-way catalyst) purifies the three components of the inflowing exhaust gas, ie, HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxides).

[0020] The turbine 41 constitutes the turbocharger 4. The turbine 41 (turbine wheel 41 a) is connected to the compressor 42 via a shaft 43, and the turbine 41, shaft 43, and compressor 42 rotate coaxially. The turbine 41 receives energy from the exhaust gas to rotate, and transmits the rotational force to the compressor 42 via the shaft 43 to rotate the compressor 42.

[0021] A second branch passage 32 branches off from the exhaust passage 3 at a position between the catalyst 31 and the turbine 41. The second branch passage 32 is connected to the exhaust passage 3 at a position downstream of the turbine 41, and is arranged to bypass the turbine 41 in the exhaust passage 3. A wastegate valve (WGV) 33 is arranged in the second branch passage 32.

[0022] The opening of the WGV 33 can be adjusted as desired to set the second branch passage 32 to a fully closed state, a predetermined opening state, or a fully open state. Reducing the opening of the WGV 33 increases the flow rate of exhaust gas supplied to the turbine 41, and conversely, increasing the opening decreases the flow rate of exhaust gas supplied to the turbine 41. The WGV 33 appropriately adjusts its opening during normal operation of the internal combustion engine 1 (for example, while the vehicle is running) to prevent an excessive increase in the boost pressure in the exhaust passage 3. The WGV 33 is also subject to control when warming up the catalyst 31.

[0023] Although not shown in the figure, the turbocharger 4 is equipped with a variable nozzle. The variable nozzle is a plurality of nozzle vanes provided on the outer periphery of the turbine wheel 41a inside the turbine 41, and by adjusting the opening degree of the variable nozzle, the opening area of ​​the area through which exhaust gas flows to the turbine wheel 41a is adjusted, thereby adjusting the turbocharging pressure.

[0024] When the opening of the variable nozzle is reduced, the opening area is reduced, the flow rate of the exhaust gas supplied to the turbine wheel 41a is increased, the energy recovered by the turbine wheel 41a is increased, and the boost pressure is increased. Conversely, when the opening of the variable nozzle is increased, the opening area is increased, the flow rate of the exhaust gas supplied to the turbine wheel 41a is reduced, and the energy recovered by the turbine wheel 41a is reduced, and the boost pressure is reduced. The variable nozzle is also subject to control when warming up the catalyst 31.

[0025] The first temperature sensor 61 detects the temperature of the cooling water that cools the internal combustion engine 1 .

[0026] The second temperature sensor 62 detects the temperature of the catalyst 31 .

[0027] The control unit 7 (controller) controls the internal combustion engine 1 (fuel injection valves, intake valves, exhaust valves, spark plugs), the TLV 21, the RCV 23, and the WGV 33 (or variable nozzle).

[0028] The control unit 7 calculates the required load of the internal combustion engine 1 based on the detection value of an accelerator opening sensor (not shown), controls the opening of the TLV 21 based on the required load, and controls the operation timing of the internal combustion engine 1 (fuel injection valve, intake valve, exhaust valve, spark plug) and the rotation speed of the internal combustion engine 1 (crankshaft).

[0029] The control unit 7 opens the RCV 23 at a predetermined opening when the pressure at a position downstream of the TLV 21 in the intake passage 2 exceeds a predetermined upper limit value.

[0030] The control unit 7 opens the WGV 33 at a predetermined opening degree when the pressure at a position upstream of the turbine 41 in the exhaust passage 3 exceeds a predetermined upper limit value.

[0031] When the pressure at a position upstream of the turbine 41 in the exhaust passage 3 falls below a predetermined lower limit, the control unit 7 narrows the opening of the variable nozzle to a predetermined opening to suppress a decrease in the rotational speed of the turbine 41.

[0032] The control unit 7 executes warm-up control of the catalyst 31 when the temperature of the catalyst 31 detected by the second temperature sensor 62 falls below a predetermined lower limit temperature.

[0033] When warming up the catalyst 31, the opening of the WGV 33 is fully closed or the opening of the variable nozzle is fully closed, and the back pressure of the exhaust gas is increased to raise the temperature of the exhaust gas, thereby accelerating the warming up of the catalyst 31. On the other hand, increasing the back pressure of the exhaust gas increases the proportion of residual gas (exhaust gas) in the cylinder of the internal combustion engine 1.

[0034] For example, if the internal combustion engine 1 is a direct injection type, fresh air is supplied to the cylinder in the next combustion cycle to mix with residual gas, and fuel is directly injected (vaporized) into the mixed gas, ignited, and burned. In this case, if the ratio of residual gas to fresh air is increased, the fuel is heated by the high-temperature residual gas and becomes more likely to vaporize, which reduces PN (e.g., soot) and unburned HC in the exhaust gas in the next combustion cycle, and improves the cleanliness of the exhaust gas (exhaust performance).

[0035] On the other hand, as the temperature of the cylinder wall of the internal combustion engine 1 decreases, the proportion of injected fuel that adheres to the cylinder wall as liquid increases, and if the proportion of residual gas increases in this state, the proportion of vaporized fuel that mixes with fresh air (oxygen) decreases, resulting in a deterioration in combustion stability.

[0036] However, as the temperature of the cylinder wall of the internal combustion engine 1 increases, the amount of injected fuel that adheres to the cylinder wall as a liquid decreases, and the proportion of vaporized fuel that mixes with fresh air (oxygen) increases, improving combustion stability. In this case, a predetermined combustion stability can be maintained even if the proportion of residual gas is increased. Here, the combustion stability "σPi" is an index that represents the magnitude of cyclic variation in torque of the internal combustion engine 1, and the larger the combustion stability "σPi", the more the combustion stability deteriorates.

[0037] Incidentally, the first combustion stability "σPi １ (FIGS. 2 and 5) decreases as the temperature of the internal combustion engine 1 increases. However, since no back pressure is applied to the exhaust gas, the warm-up of the catalyst 31 cannot be promoted.

[0038] On the other hand, if the WGV 33 and the variable nozzle are always fully closed during warm-up of the catalyst 31, back pressure can be applied to the exhaust gas. However, the combustion stability in this case is higher than when the WGV 33 or the variable nozzle is fully open from the initial stage of warm-up, making combustion in the internal combustion engine 1 unstable and making it difficult to warm up the catalyst 31.

[0039] Therefore, in this embodiment, when the warm-up of the catalyst 31 is started with the WGV 33 (or the variable nozzle) fully open, for example, when the internal combustion engine 1 is started at a temperature approximately equal to the outside air temperature, the first combustion stability "σPi １ (or the combustion stability "σPi １ ") is set as the target combustion stability "σPit", and the second combustion stability "σPi" is set as the opening degree of the WGV 33 is reduced as the temperature of the internal combustion engine 1 increases. ２ The control is executed to reduce the opening of the WGV 33 as the temperature of the internal combustion engine 1 rises so that "σPit" becomes the target combustion stability "σPit" or a value close to the target combustion stability "σPit". This makes the exhaust performance (exhaust gas cleanliness) and combustion stability good. Note that the target combustion stability "σPit" is constant regardless of the temperature of the internal combustion engine 1.

[0040] Therefore, the control unit 7 estimates the temperature of the internal combustion engine 1 (the temperature of the cylinder wall surface of the internal combustion engine 1) based on the temperature of the coolant detected by the first temperature sensor 61. Alternatively, a temperature sensor (not shown) may be provided to measure the temperature of the cylinder wall surface of the internal combustion engine 1, and the temperature of the cylinder wall surface may be directly detected. Furthermore, a temperature sensor (not shown) may be provided to measure the temperature of the lubricating oil that lubricates the internal combustion engine 1, and the temperature of the cylinder wall surface may be estimated from the temperature detected by the temperature sensor.

[0041] 2 is a diagram showing a flow of catalyst warm-up control of the control device (control method) of this embodiment for the internal combustion engine 1. The flow shown below is based on the premise that the opening of the WGV 33 is reduced (the opening of the variable nozzle is set constant (for example, fully closed)) as the temperature of the internal combustion engine 1 increases, but the same applies when the opening of the variable nozzle is reduced while the opening of the WGV 33 is kept constant (for example, fully closed) as the temperature of the internal combustion engine 1 increases, or when the opening of the WGV 33 and the opening of the variable nozzle are simultaneously reduced as the temperature of the internal combustion engine 1 increases.

[0042] In step S01, the control unit 7 detects the state of the internal combustion engine 1 (whether the internal combustion engine 1 is operating or not, etc.).

[0043] In step S02, the control unit 7 determines whether or not to start warming up the catalyst 31, i.e., whether or not the temperature of the catalyst 31 is lower than a predetermined lower limit temperature. If the answer is YES, the control unit 7 proceeds to step S03, and if the answer is NO, the control unit 7 returns to step S01.

[0044] In step S03, the control unit 7 detects the temperature of the cooling water (corresponding to the temperature of the wall surface of the cylinder of the internal combustion engine 1).

[0045] In step S04, the control unit 7 calculates the temperature of the cooling water (corresponding to the temperature of the cylinder wall surface) and the opening degree of the WGV 33 optimized therefor (the second combustion stability "σPi ２ The opening of the WGV 33 (target WGV opening) is calculated by referring to a map showing the relationship between the second combustion stability "σPi" and the opening of the WGV 33 when the second combustion stability "σPi" coincides with or approaches the target combustion stability "σPit". ２ " is the first combustion stability "σPi １ It may be set arbitrarily within a range of not less than the target combustion stability "σPit" and not more than the target combustion stability "σPit".

[0046] In step S05, the control unit 7 calculates the target air flow rate to be taken into the internal combustion engine 1 based on the accelerator opening, and calculates the opening of the TLV 21 (target TLV opening) based on a map showing the relationship between the target air flow rate and the opening of the WGV 33.

[0047] Here, the multiple lines on the map in step S05 represent equal opening lines of the TLV 21, and the opening of the TLV 21 is constant on the equal opening lines.

[0048] When the opening of the WGV 21 is reduced, the flow rate of exhaust gas supplied to the turbine 41 increases accordingly, the rotation speed of the turbine 41 and the compressor 42 increases, and the flow rate of fresh air taken in by the compressor 42 increases. Therefore, the flow rate of fresh air flowing through the TLV 21 increases by the amount that the flow rate of fresh air taken in by the compressor 42 increases. Therefore, by reducing the opening of the TLV 21 by the amount that the flow rate of fresh air taken in by the compressor 42 increases, control is performed so that the target air flow rate remains constant. This makes it possible to generate the desired torque and maintain that torque constant.

[0049] In step S06, the control unit 7 determines whether or not to end the warm-up of the catalyst 31, i.e., whether or not the temperature of the catalyst 31 has reached a predetermined lower limit temperature, and if YES, proceeds to END, and if NO, returns to step S03. The control unit 7 ends the warm-up when the temperature of the catalyst 31 reaches or exceeds the predetermined lower limit.

[0050] [Time Chart of Warm-Up Control of Catalyst 31] FIG. 3 is a time chart of each vehicle parameter in the control device (control method) of the internal combustion engine 1 according to this embodiment.

[0051] In FIG. 3, it is assumed that the internal combustion engine 1 is started after a long time has passed since the internal combustion engine 1 was stopped and the temperature of the internal combustion engine 1 is approximately the same as the air temperature.

[0052] At the start of the internal combustion engine 1, the temperature of the cylinder is approximately the outside air temperature, and the first combustion stability "σPi １ Therefore, when the internal combustion engine 1 is started, the opening of the WGV 33 (or the variable nozzle) is set to the maximum or substantially the maximum, and the proportion of residual gas remaining in the cylinder is set to the minimum.

[0053] 3 is based on the assumption that torque is constant, and the opening of the TLV 21 (the opening of the TLV 21 and / or the RCV 23) is set to maintain that torque. When the RCV 23 is opened to a predetermined opening, fresh air taken in by the compressor 42 is returned to the intake side of the compressor 42. As a result, fresh air heated through the intake passage 2 is mixed with fresh air from the outside and supplied to the TLV 21, thereby increasing the temperature of the fresh air before it is supplied to the cylinder and facilitating vaporization of the fuel injected into the cylinder.

[0054] After the internal combustion engine 1 is started, the temperature of the internal combustion engine 1 (cylinder wall surface, cooling water) increases monotonically with time, and the first combustion stability "σPi １ " also monotonically decreases and stabilizes as the temperature of the internal combustion engine 1 increases.

[0055] However, in this embodiment, the second combustion stability “σPi ２ " always coincides with the target combustion stability "σPit" or the second combustion stability "σPi ２ The opening of the WGV 33 is reduced as the temperature of the internal combustion engine 1 rises so that "σPit" is always close to the target combustion stability "σPit". This increases the proportion of residual gas in the cylinder, raising the temperature of the mixed gas of fresh air and residual gas, making it easier for the fuel supplied to the cylinder to vaporize. Therefore, the integrated amount of untreated components (integrated concentration of PN, HC, and NOx) in the exhaust gas before it is supplied to the catalyst 31 (thick solid line) can be reduced compared to when the opening of the WGV 33 is fully closed from the start of the internal combustion engine 1 (thin solid line), thereby improving exhaust performance (exhaust gas cleanliness).

[0056] Furthermore, the catalyst 31 is warmed up by supplying the exhaust gas to the catalyst 31, and increasing the back pressure of the exhaust gas increases the temperature of the exhaust gas, thereby accelerating the warming up of the catalyst 31.

[0057] When the opening of the WGV 33 is reduced, the flow rate of exhaust gas supplied to the turbine 41 increases, and the rotation speed of the turbine 41 and the compressor 42 increases, thereby increasing the flow rate of fresh air supplied to the TLV 21. Therefore, by reducing the opening of the TLV 21 in response to the reduction in the opening of the WGV 33, the flow rate of fresh air supplied to the internal combustion engine 1 (cylinder) can be kept constant, and the torque of the internal combustion engine 1 can be kept constant.

[0058] [Modification of Warm-up Control of Catalyst 31] Fig. 4 is a diagram showing a flow of a modification of the catalyst warm-up control of the control device (control method) of the internal combustion engine 1 according to this embodiment. The flow shown in Fig. 4 is obtained by adding step S051 between step S05 and step S06 of the flow shown in Fig. 2.

[0059] In step S051, the control unit 7 controls the ignition timing (target ignition timing) of the spark plug based on the opening of the WGV 33 calculated in step S04 and the target air flow rate calculated in step S05. The multiple lines in the map shown in step S051 are equal-ignition timing lines, and the ignition timing is constant on the equal-ignition timing lines. The ignition timing is shifted more toward the retard side as the opening of the WGV 33 becomes smaller or the target air flow rate becomes larger. By performing this ignition timing retard control, torque is slightly reduced, but the exhaust gas temperature can be increased, thereby facilitating warm-up of the catalyst 31. Note that steps S04 and S05 in FIG. 4 are performed assuming that step S051 is executed. Therefore, the map shown in step S04 in FIG. 4 and the map shown in step S04 in FIG. 2 may be different from each other or may be the same. Similarly, the map shown in step S05 of Fig. 4 and the map shown in step S05 of Fig. 2 may be different from each other, or may be the same. Even if the map shown in step S05 of Fig. 4 and the map shown in step S05 of Fig. 2 are the same, the idle speed control increases the air amount (increases the opening of the TLV 21) by the amount of torque that is reduced by retarding the ignition timing, thereby maintaining equal torque.

[0060] [Time Chart of Modified Example of Warm-Up Control of Catalyst 31] Figure 5 is a time chart of each vehicle parameter in a modified example of catalyst warm-up control of the control device (control method) of the internal combustion engine 1 according to this embodiment. In Figure 5, the modified example (thick solid lines) is a time chart of each vehicle parameter when steps S01 to S05, step S051, and step S06 of Figure 4 are executed, and the basic form (thick dashed lines) is a time chart when steps S01 to S06 of Figure 2 are executed but step S051 of Figure 4 is not executed.

[0061] The initial state is the same for both the basic and modified embodiments. Regarding the ignition timing of the spark plug, the basic embodiment (FIG. 2) does not perform any ignition timing manipulation and keeps it constant, but the modified embodiment (FIG. 4) shifts the ignition timing to the retard side as time passes (as the temperature of the internal combustion engine 1 rises).

[0062] As a result, the torque (solid line) based on the control flow of the modified example (FIG. 4) is slightly lower than the torque (dashed line) based on the control flow of the basic form (FIG. 2).

[0063] The change in the opening of the TLV 21 over time (solid line) based on the control flow of the modified example (FIG. 4) decreases at a slower rate than the change in the opening of the TLV 21 over time (dashed line) based on the control flow of the basic form (FIG. 2). That is, in the modified example, the amount of fresh air supplied to the TLV 21 is greater than the amount of fresh air supplied in the basic form. This reduces the rate of torque decrease.

[0064] As described above, since the amount of fresh air supplied in the modified example is greater than the amount of fresh air supplied in the basic example, the residual gas ratio in the cylinder (solid line) based on the control flow of the modified example (Figure 4) increases at a slower rate than the residual gas ratio in the cylinder (dashed line) based on the control flow of the basic example (Figure 2).

[0065] As a result, the unprocessed component integrated amount (thick solid line) based on the control flow of the modified example (FIG. 4) is slightly higher than the unprocessed component integrated amount (dashed line) based on the control flow of the basic form (FIG. 2).

[0066] By performing the control of the above modified example, torque decreases slightly and the cumulative amount of untreated components increases slightly, but the warming up of the catalyst 31 is accelerated more than in the basic form, and the purification of the three components in the exhaust gas, HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxides), can be achieved more quickly.

[0067] There is almost no difference in the change in cooling water temperature over time between the modified example (solid line) and the basic form (dashed line).

[0068] There is almost no difference in the change in the opening degree of the WGV 33 over time between the modified example (solid line) and the basic form (dashed line).

[0069] Combustion stability (third fuel stability "σPi ３ (solid line)) and the combustion stability based on the basic control flow (Figure 2) (second fuel stability "σPi ２ (bold dashed line)), there is almost no difference.

[0070] [Effects of this embodiment] In the control method for the internal combustion engine 1 with the turbocharger 4 of this embodiment, when the compressor 42, which rotates in conjunction with the turbine 41 that rotates by receiving energy from the exhaust gas discharged from the internal combustion engine 1, takes in fresh air and supplies it to the intake side of the internal combustion engine 1, the exhaust gas is purified by the catalyst 31 arranged between the exhaust side of the internal combustion engine 1 and the turbine 41, the wastegate valve ( This is a control method for an internal combustion engine (1) with a turbocharger (4), which warms up a catalyst (31) by adjusting the opening of a wastegate valve (WGV) (33) or the opening of a variable nozzle (not shown) that adjusts the flow rate of exhaust gas supplied to a turbine (41) to increase the back pressure of the exhaust gas and thereby increase the temperature of the exhaust gas, in which the opening of the wastegate valve (WGV) (33) is set to the maximum or nearly the maximum when warming up of the catalyst (31) begins, and then the opening of the wastegate valve (WGV) (33) is reduced as the temperature of the internal combustion engine (1) increases, or the opening of the variable nozzle (not shown) is set to the maximum or nearly the maximum when warming up of the catalyst (31) begins, and then the opening of the variable nozzle (not shown) is reduced as the temperature of the internal combustion engine (1) increases.

[0071] By using the above method, when the temperature of the internal combustion engine 1 is low, the ratio of residual gas in the cylinder is set low to suppress a decrease in combustion stability, and as the temperature of the internal combustion engine 1 increases, the ratio of residual gas is increased to suppress a decrease in combustion stability (second combustion stability "σPi ２ By increasing the proportion of residual gas in the cylinder so as to maintain the target combustion stability "σPit" at a predetermined value (the target combustion stability "σPit" or a value close to the target combustion stability "σPit"), it is possible to reduce harmful components in the exhaust gas. Therefore, it is possible to maintain good combustion stability and exhaust performance when the catalyst 31 is warming up.

[0072] In this embodiment, when the torque of the internal combustion engine 1 is controlled by adjusting the amount of fresh air supplied from the compressor 42 to the intake side of the internal combustion engine 1 using the throttle (TLV21), the opening of the throttle (TLV21) is reduced when the opening of the wastegate valve (WGV33) is reduced or when the opening of the variable nozzle (not shown) is reduced.

[0073] By using the above method, it is possible to suppress torque fluctuations during warm-up and generate and maintain a desired torque.

[0074] In this embodiment, the torque of the internal combustion engine 1 is controlled by adjusting the amount of fresh air supplied from the compressor 42 to the intake side of the internal combustion engine 1 using the throttle (TLV21), and the flow rate of fresh air supplied to the throttle (TLV21) is adjusted by adjusting the opening of the recirculation valve (RCV23), which returns at least a portion of the fresh air supplied from the compressor 42 to the throttle (TLV21) to the fresh air inlet side of the compressor 42.In this case, when reducing the opening of the wastegate valve (WGV33), the opening of the throttle (TLV21) is reduced and / or the opening of the recirculation valve (RCV23) is increased, or when reducing the opening of the variable nozzle (not shown), the opening of the throttle (TLV21) is reduced and / or the opening of the recirculation valve (RCV23) is increased.

[0075] The above method suppresses torque fluctuations during warm-up, enabling the desired torque to be generated and maintained. Furthermore, when the recirculation valve (RCV 23) is opened to a predetermined opening, fresh air taken in by the compressor 42 is returned to the intake side of the compressor 42. As a result, fresh air heated through the intake passage 2 is mixed with fresh air from the outside and supplied to the throttle (TLV 21), raising the temperature of the fresh air before it is supplied to the cylinder and facilitating vaporization of the fuel injected into the cylinder.

[0076] In this embodiment, the temperature of the internal combustion engine 1 (the temperature of the wall surface of the cylinder) is estimated based on the temperature of the cooling water that cools the internal combustion engine 1.

[0077] The above method makes it possible to estimate the temperature of the internal combustion engine 1 (the temperature of the cylinder wall surface) in a simple manner.

[0078] According to the control device for the internal combustion engine 1 with a turbocharger 4 of this embodiment, the turbocharger 4 includes a turbine 41 that rotates by receiving energy from the exhaust gas discharged from the internal combustion engine 1, and a compressor 42 that rotates in conjunction with the rotation of the turbine 41 to take in fresh air and supply it to the intake side of the internal combustion engine 1, a catalyst 31 that is arranged between the exhaust side of the internal combustion engine 1 and the turbine 41 and purifies the exhaust gas, a wastegate valve (WGV 33) that is arranged in a branch passage (second branch passage 32) that branches off from the exhaust passage 3 between the catalyst 31 and the turbine 41 and joins the exhaust side of the turbine 41, and adjusts the flow rate of the exhaust gas in the branch passage (second branch passage 32) to adjust the flow rate of the exhaust gas supplied to the turbine 41, and and a variable nozzle (not shown) that adjusts the flow rate of exhaust gas entering the catalyst 31, and adjusts the opening of a wastegate valve (WGV 33) or the opening of the variable nozzle (not shown) to increase the back pressure of the exhaust gas and thereby increase the temperature of the exhaust gas, thereby warming up the catalyst 31. The control device (control unit 7) for the internal combustion engine 1 with a turbocharger 4 includes: a variable nozzle (not shown) that adjusts the flow rate of exhaust gas entering the catalyst 31; and the control device (control unit 7) adjusts the opening of the wastegate valve (WGV 33) to a maximum or approximately maximum when the catalyst 31 starts to be warmed up, and then reduces the opening of the wastegate valve (WGV 33) as the temperature of the internal combustion engine 1 increases; or sets the opening of the variable nozzle (not shown) to a maximum or approximately maximum when the catalyst 31 starts to be warmed up, and then reduces the opening of the variable nozzle (not shown) as the temperature of the internal combustion engine 1 increases.

[0079] With the above configuration, when the temperature of the internal combustion engine 1 is low, the ratio of residual gas in the cylinder is set low to suppress a decrease in combustion stability, and as the temperature of the internal combustion engine 1 increases, the ratio of residual gas is increased to suppress a decrease in combustion stability (second combustion stability "σPi ２By increasing the proportion of residual gas in the cylinder so as to maintain the target combustion stability "σPit" at a predetermined value (the target combustion stability "σPit" or a value close to the target combustion stability "σPit"), it is possible to reduce harmful components in the exhaust gas. Therefore, it is possible to maintain good combustion stability and exhaust performance when the catalyst 31 is warming up.

[0080] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate.

Claims

A method for controlling an internal combustion engine with a turbocharger, in which a compressor that rotates in conjunction with a turbine that receives energy from exhaust gas discharged from an internal combustion engine takes in fresh air and supplies it to an intake side of the internal combustion engine, purifying the exhaust gas with a catalyst disposed between an exhaust side of the internal combustion engine and the turbine, the method comprising: adjusting an aperture of a wastegate valve that is disposed in a branch passage that branches off from an exhaust passage between the catalyst and the turbine and joins an exhaust side of the exhaust gas of the turbine, adjusting a flow rate of the exhaust gas supplied to the turbine by adjusting a flow rate of the exhaust gas in the branch passage, or adjusting an aperture of a variable nozzle that adjusts a flow velocity of the exhaust gas supplied to the turbine, thereby increasing a back pressure of the exhaust gas and increasing a temperature of the exhaust gas, thereby warming up the catalyst, A control method for an internal combustion engine with a supercharger, the control method comprising: setting the opening of the wastegate valve to a maximum or approximately maximum when warming up of the catalyst begins; and thereafter reducing the opening of the wastegate valve as the temperature of the internal combustion engine rises; or setting the opening of the variable nozzle to a maximum or approximately maximum when warming up of the catalyst begins; and thereafter reducing the opening of the variable nozzle as the temperature of the internal combustion engine rises. In a case where the torque of the internal combustion engine is controlled by adjusting the amount of fresh air supplied from the compressor to the intake side of the internal combustion engine by a throttle, 2. The method for controlling an internal combustion engine with a supercharger according to claim 1, further comprising the step of reducing an opening degree of the throttle when reducing an opening degree of the wastegate valve or when reducing an opening degree of the variable nozzle. In a case where the torque of the internal combustion engine is controlled by adjusting the amount of fresh air supplied from the compressor to the intake side of the internal combustion engine by using a throttle, and the flow rate of fresh air supplied to the throttle is adjusted by adjusting the opening of a recirculation valve that recirculates at least a portion of the fresh air supplied from the compressor to the throttle to the fresh air introduction side of the compressor, When reducing the opening degree of the wastegate valve, the opening degree of the throttle is reduced and / or the opening degree of the recirculation valve is increased.

2. The method for controlling an internal combustion engine with a supercharger according to claim 1, further comprising the steps of: reducing an opening degree of the throttle and / or increasing an opening degree of the recirculation valve when reducing an opening degree of the variable nozzle.

2. The method for controlling a supercharged internal combustion engine according to claim 1, wherein the temperature of the internal combustion engine is estimated based on a temperature of a cooling water that cools the internal combustion engine. A turbocharger including a turbine that rotates by receiving energy from exhaust gas discharged from an internal combustion engine, and a compressor that rotates in conjunction with the rotation of the turbine to take in fresh air and supply it to an intake side of the internal combustion engine; a catalyst disposed between an exhaust side of the internal combustion engine and the turbine to purify the exhaust gas; a wastegate valve that is disposed in a branch passage that branches off from an exhaust passage between the catalyst and the turbine and joins an exhaust side of the turbine, and adjusts a flow rate of the exhaust gas supplied to the turbine by adjusting a flow rate of the exhaust gas in the branch passage; a variable nozzle for adjusting a flow velocity of the exhaust gas supplied to the turbine, A control device for an internal combustion engine with a turbocharger, which warms up the catalyst by adjusting an opening degree of the wastegate valve or an opening degree of the variable nozzle to increase a back pressure of the exhaust gas and increase a temperature of the exhaust gas. A control device for an internal combustion engine with a supercharger, which sets the opening of the wastegate valve to maximum or nearly maximum when warm-up of the catalyst begins, and then reduces the opening of the wastegate valve as the temperature of the internal combustion engine rises, or sets the opening of the variable nozzle to maximum or nearly maximum when warm-up of the catalyst begins, and then reduces the opening of the variable nozzle as the temperature of the internal combustion engine rises.

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