JP4378829B2 - Control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine control device including a catalyst for purifying exhaust gas from an internal combustion engine.
[0002]
[Prior art]
In recent gasoline engine vehicles, a three-way catalyst is installed in the exhaust pipe to purify HC (hydrocarbon), CO (carbon monoxide), NOx (nitrogen oxide), etc. in the exhaust gas. Yes. However, at the time of cooling immediately after start-up, since the three-way catalyst has not been heated to the activation temperature and is in an inactive state, the three-way catalyst cannot sufficiently purify the exhaust gas, resulting in poor exhaust emission.
[0003]
In recent years, as a countermeasure, it is known that the catalyst is warmed up to the activation temperature at an early stage by executing catalyst early warm-up control such as ignition retard control at the cold start to raise the temperature of the exhaust gas. However, recently, in order to further improve the catalyst warm-up performance, a secondary air introduction device for introducing outside air as secondary air into the exhaust pipe on the upstream side of the catalyst has been provided, and rich components such as HC and CO in the exhaust gas within the catalyst. Is reacted with oxygen in the secondary air, and the catalyst is warmed up by the reaction heat.
[0004]
Furthermore, in addition to the secondary air introduction device, an ignition device is provided in the exhaust pipe on the upstream side of the catalyst. The rich component in the exhaust gas is mixed with the secondary air (oxygen) and ignited by the ignition device to cause afterburning in the exhaust pipe. Some are generated and the combustion heat is used to warm up the catalyst.
[0005]
[Problems to be solved by the invention]
In the former, the rich component and oxygen in the secondary air are reacted in the catalyst to warm up the catalyst. However, if the catalyst temperature does not rise to some extent, the reaction between the rich component and oxygen in the catalyst is promoted. Therefore, the early warm-up of the catalyst is delayed, and it is not possible to sufficiently meet the exhaust gas regulations that are becoming increasingly severe in recent years.
[0006]
On the other hand, in the latter case, since the catalyst is warmed up by generating an afterburn by an ignition device in the exhaust pipe, there is an advantage that the catalyst can be warmed up immediately after starting, but it is necessary to provide an ignition device in the exhaust pipe. Therefore, there is a disadvantage that the system configuration becomes complicated and the cost is increased.
[0007]
The present invention has been made in consideration of such circumstances. Therefore, the object of the present invention is to have a relatively simple structure and to generate afterburning on the upstream side of the catalyst so that the catalyst can be warmed up early. An object of the present invention is to provide a control device for an internal combustion engine that can achieve both improvement in machine performance and simplification of configuration and cost reduction.
[0008]
[Means for Solving the Problems]
To achieve the above object, the claims of the present invention are described. 1's The control device for the internal combustion engine controls the combustion of the internal combustion engine by the exhaust gas temperature rise control means so that the rich component in the exhaust gas becomes an exhaust gas temperature that can be combusted in the exhaust gas passage on the upstream side of the catalyst, and introduces secondary air An air-fuel ratio sensor configured to introduce secondary air for generating afterburning into the exhaust gas passage upstream of the catalyst by operating the secondary air introduction device by the control means and detecting the air-fuel ratio of the exhaust gas The system is equipped with air-fuel ratio feedback control means that feedback-controls the air-fuel ratio of the exhaust gas to the target air-fuel ratio based on the output of. Furthermore, in the invention according to claim 1, when the secondary air is introduced, when the warm-up of the catalyst is required, the air-fuel ratio of the exhaust gas upstream of the secondary air introduction position is set. It is a purification window of the catalyst Control near the theoretical air-fuel ratio First As a feature ,two When the secondary air is introduced, when the vehicle is running, the air-fuel ratio of the exhaust gas upstream of the secondary air introduction position is controlled to be rich so that the air-fuel ratio of the catalyst inflow gas is controlled to be close to the theoretical air-fuel ratio. The Second Features.
[0009]
Claim 1 In the invention according to the present invention, the exhaust gas discharged from the internal combustion engine is heated to a temperature combustible in the exhaust gas passage on the upstream side of the catalyst, so that rich components such as HC and CO in the high-temperature exhaust gas are upstream of the catalyst. When mixed with the oxygen of the secondary air introduced into the exhaust gas passage on the side, afterburning occurs in the exhaust gas passage on the upstream side of the catalyst, and the catalyst can be warmed up early with the combustion heat. Moreover, since the HC discharged from the internal combustion engine is burned by the afterburning, the amount of HC discharged into the atmosphere can be reduced even before the catalyst is activated. Furthermore, since an ignition device for igniting the exhaust gas is not required, the system configuration can be simplified and the demand for cost reduction can be satisfied.
[0010]
Incidentally, it goes without saying that the catalyst is in an inactive state at the time of cold start, but even after the catalyst has warmed up once, depending on the operating state, the catalyst temperature may decrease and the catalyst may become in an inactive state. Claim 2 As described above, it is preferable to introduce the secondary air when a catalyst warm-up request is generated, regardless of whether the catalyst is warmed up or not. In this way, when the temperature of the active catalyst is lowered and becomes inactive, a catalyst warm-up request is generated, and secondary air can be immediately introduced to generate afterburning. Not only at the time of start-up, but even after the catalyst has warmed up once, if the temperature of the catalyst drops to the inactive state, it can be quickly restored to the active state by afterburning.
[0011]
Claims 3 As described above, secondary air may be introduced when a request for reducing hydrocarbons flowing into the catalyst is generated or when a request for reducing nitrogen oxides flowing out from the catalyst is generated. When the amount of HC discharged from the internal combustion engine increases and a request to reduce HC flowing into the catalyst is generated, if secondary combustion is introduced to generate afterburning, the HC discharged from the internal combustion engine is burned. Thus, it is possible to reduce the amount of HC flowing into the catalyst by reducing the amount of HC flowing into the catalyst. Even when the air-fuel ratio of the exhaust gas discharged from the internal combustion engine is rich, if the secondary air is introduced, the air-fuel ratio of the catalyst inflow gas can be adjusted to the vicinity of the theoretical air-fuel ratio (catalyst purification window). It is possible to improve the NOx purification rate in the catalyst and reduce the amount of NOx discharged into the atmosphere.
[0012]
In this case, the claim 4 As described above, it is preferable to introduce secondary air at the exhaust gas temperature at which afterburning is possible. In this way, afterburning can be reliably generated immediately after the introduction of secondary air.
[0013]
Also, when starting 5 As described above, secondary air may be introduced after the first explosion occurs in the cylinder. If the first explosion occurs in the cylinder, the exhaust gas temperature starts to rise. Therefore, if the introduction of secondary air is started after the first explosion has occurred, the exhaust gas is heated to a temperature at which it can be combusted. Afterburning can be generated to start warming up the catalyst.
[0014]
In addition, if the introduction timing of secondary air is made too early at the time of start-up, secondary air is introduced before the exhaust gas temperature rises sufficiently and no afterburning occurs. As a result, the time of occurrence of afterburning is delayed.
[0015]
Therefore, the claim 6 As described above, the introduction of secondary air may be prohibited until a predetermined period has elapsed from the start. In this way, the secondary air can be introduced after the exhaust gas temperature has risen sufficiently at the start, and afterburning can be reliably generated immediately after the introduction of the secondary air.
[0016]
Claims 7 As described above, the introduction of secondary air may be prohibited when a request to lower the exhaust gas temperature is generated. That is, when the catalyst is overheated due to afterburning, a request to lower the exhaust gas temperature is generated, and the introduction of secondary air is prohibited. Thereby, exhaust gas temperature can be lowered | hung and catalyst temperature can be lowered | hung, and the overheat deterioration of the catalyst by afterburning can be prevented.
[0017]
At the start of secondary air introduction, the exhaust gas temperature does not rise until a large amount of afterburn occurs, so if a large amount of secondary air is introduced from the beginning of the introduction of secondary air, the introduction of secondary air There is a risk that afterburning will not occur due to a decrease in the exhaust gas temperature due to, and that afterburning may be delayed.
[0018]
Therefore, the claim 8 As described above, the flow rate of the secondary air may be controlled in accordance with the elapsed time from the start, the elapsed time from the catalyst warm-up request time, or the elapsed time from the exhaust gas temperature drop. For example, if the secondary air introduction flow rate is decreased at the beginning of the introduction of secondary air and then gradually increased, the afterburning can be generated efficiently while suppressing the decrease in exhaust gas temperature due to the introduction of secondary air. The exhaust gas temperature can be raised. Also, in the latter stage of secondary air introduction, if the flow rate of secondary air introduced is made larger than the amount consumed by afterburning, oxygen in the secondary air is also fed into the catalyst to react HC in the catalyst. And the catalyst can be efficiently warmed up by the synergistic effect of afterburning and reaction heat.
[0019]
Claims 1 The air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas is provided, and the air-fuel ratio feedback control means feedback-controls the air-fuel ratio of the exhaust gas to the target air-fuel ratio based on the output of the air-fuel ratio sensor. In this way, even if secondary air is introduced into the exhaust gas passage on the upstream side of the catalyst, the air / fuel ratio of the catalyst inflow gas is detected or estimated from the output of the air / fuel ratio sensor, and the air / fuel ratio of the catalyst inflow gas is set to the target air / fuel ratio. The fuel ratio can be controlled. Since the air-fuel ratio sensor is activated before the catalyst, feedback control can be performed after the air-fuel ratio sensor is activated even before the catalyst is activated.
[0020]
In this case, when introducing the secondary air, when the catalyst is required to warm up, 1 As shown, control the air-fuel ratio of the exhaust gas upstream of the secondary air introduction position to near the stoichiometric air-fuel ratio. Just do it. If you do this Since the air-fuel ratio of the catalyst inflow gas can be controlled to be lean, the amount of HC flowing into the catalyst before activation can be reduced, and the amount of HC discharged into the atmosphere can be reduced.
[0021]
In addition, when introducing the secondary air, when driving the vehicle, the claim 1 As described above, the air-fuel ratio of the catalyst inflow gas may be controlled in the vicinity of the theoretical air-fuel ratio by controlling the air-fuel ratio of the exhaust gas upstream of the secondary air introduction position to be rich. When the vehicle travels, the amount of NOx emitted from the internal combustion engine increases and the catalyst temperature rises to some extent. Therefore, the air-fuel ratio of the catalyst inflow gas (the air-fuel ratio of the exhaust gas downstream from the secondary air introduction position) is reduced. Control to near the theoretical air-fuel ratio (catalyst purification window) can improve the NOx purification rate of the catalyst and reduce the amount of NOx discharged into the atmosphere.
[0022]
Claims when performing air-fuel ratio feedback control 9 As described above, an air-fuel ratio sensor may be installed on the downstream side of the secondary air introduction position. In this way, the air-fuel ratio of the catalyst inflow gas can be directly detected by the air-fuel ratio sensor, and the air-fuel ratio of the catalyst inflow gas can be accurately feedback-controlled.
[0024]
Claims 10 An air pump that pumps secondary air into the secondary air introduction passage connected to the exhaust gas passage, a combination valve that integrates an on-off valve that opens and closes the secondary air introduction passage, and a check valve, and an on-off valve The secondary air introduction device is composed of the switching valve for switching the driving pressure of the secondary air, and the secondary air introduction control means controls the switching valve by the secondary air introduction control means to switch the driving pressure to open and close the opening / closing valve to introduce / introduce the secondary air. You may make it control a stop. If it does in this way, while the introduction timing of secondary air can be arbitrarily set by control of a change-over valve, it can prevent that exhaust gas flows backward to the air pump side by a check valve.
[0025]
Claims 11 As described above, secondary air may be introduced into a plurality of locations in the exhaust gas passage on the upstream side of the catalyst. In this way, after-burning is generated by the secondary air introduced upstream of the exhaust gas passage to raise the exhaust gas temperature, and after-burning is also generated by the secondary air introduced downstream of the exhaust gas temperature. Can be further increased. Thereby, while being able to improve the early warming-up effect of the catalyst and the reduction effect of HC emissions, the secondary air introduced downstream is supplied into the catalyst to promote the reaction of HC in the catalyst, The early heat-up effect of the catalyst can be further improved by the reaction heat.
[0026]
Claims 12 As described above, it is preferable to introduce the secondary air to a position in the exhaust gas passage on the upstream side of the catalyst in a position where the exhaust gas temperature falls within a temperature range in which afterburning is possible. In this case, the secondary air introduction position may be fixed at a fixed position. However, in response to the temperature range in which afterburning can be performed spreading downstream of the exhaust gas passage as the exhaust gas temperature rises, May be sequentially switched to the downstream side of the exhaust gas passage. In this way, as the exhaust gas temperature rises, the afterburning position can be brought closer to the catalyst, and the early warm-up effect of the catalyst due to afterburning can be further improved.
[0027]
Meanwhile, claims 13 As described above, it is preferable to control the ignition timing of the internal combustion engine to be retarded more than after warming up when the engine is cold. In this way, the combustion of the air-fuel mixture in the cylinder can be delayed, exhaust gas having a temperature higher than normal can be discharged to the exhaust gas passage, and the exhaust gas temperature in the exhaust gas passage can be raised to a temperature at which afterburning is possible. Can do.
[0028]
In this case, the claim 14 As described above, the air-fuel ratio of the in-cylinder mixture is preferably controlled to be close to the theoretical air-fuel ratio or slightly rich. As a result, an appropriate amount of rich component for generating afterburning can be supplied to the exhaust gas passage, and the air-fuel ratio of the catalyst inflow gas can be controlled to be weak lean, and the amount of HC flowing into the catalyst before activation. The amount of HC discharged into the atmosphere can be reduced.
[0029]
Further claims 15 The target air-fuel ratio of the exhaust gas is set based on the ignition timing retard amount during the ignition retard control, or 16 As described above, the target air-fuel ratio of the exhaust gas may be set closer to the stoichiometric air-fuel ratio as the ignition timing retard amount during the ignition retard control is larger. In other words, if the target air-fuel ratio of the exhaust gas is set corresponding to the ignition timing retardation amount at that time, the fuel injection amount (air-fuel ratio of the air-fuel mixture in the cylinder) is controlled according to the ignition retardation amount, and the combustion state It is possible to raise the exhaust gas temperature to a temperature at which afterburning can be performed while stabilizing the temperature.
[0030]
Further, when the present invention is applied to an internal combustion engine with a variable valve timing mechanism, 17 As described above, the exhaust gas temperature may be controlled within a temperature range in which afterburning can be performed by controlling the valve overlap amount of the intake valve and the exhaust valve. That is, if the valve overlap amount between the intake valve and the exhaust valve is increased, the internal EGR increases and the combustion speed in the cylinder decreases, so that the peak in the cylinder temperature can be delayed. Thereby, exhaust gas having a temperature higher than usual can be discharged to the exhaust gas passage, and the exhaust gas temperature in the exhaust gas passage can be raised to a temperature at which afterburning can be performed.
[0031]
Or claims 18 As described above, the exhaust gas temperature may be controlled to a temperature range in which after-burning can be performed by controlling the valve opening timing of the exhaust valve to the advance side. In other words, if the opening timing of the exhaust valve is advanced, the exhaust gas can be discharged to the exhaust gas passage near the peak of the in-cylinder temperature, and the exhaust gas temperature in the exhaust gas passage is raised to a temperature at which afterburning can be performed. Can do.
[0032]
Claims 19 As described above, it may be determined whether or not the exhaust gas temperature raising control is to be performed based on the engine operating state. In this way, the exhaust gas temperature increase control can be performed only in an operating state that requires the exhaust gas temperature increase control, so that the exhaust gas temperature is not increased more than necessary, and overheating of the catalyst, the air-fuel ratio sensor, etc. Deterioration can be prevented.
[0033]
Further claims 20 As described above, the exhaust gas temperature raising control may be performed when the engine speed is controlled to be higher than the idling speed after the warm-up at the cold start. In other words, when the engine speed is controlled to a starting speed higher than the idling speed after warm-up, the time from ignition to exhaust becomes shorter than the idling speed after warm-up, and the combustion interval Since the exhaust gas flow rate is increased, the temperature rise effect of the exhaust gas temperature can be further enhanced.
[0034]
Claims 21 As described above, the exhaust gas temperature raising control may be prohibited after a predetermined time has elapsed from the start. In this way, it is possible to prevent the exhaust gas temperature raising control (ignition delay angle control or the like) from being prolonged more than necessary, and it is possible to prevent overheating deterioration of the catalyst, the air-fuel ratio sensor, and the like.
[0035]
Claims 22 As described above, torque fluctuation suppression control that suppresses torque fluctuation may be performed during the exhaust gas temperature raising control. That is, when the exhaust gas temperature raising control is performed, torque fluctuation may occur. Therefore, by suppressing this torque fluctuation by the torque fluctuation suppression control, it is possible to prevent drivability deterioration. In the torque fluctuation suppression control, for example, it is conceivable that ignition operation is performed a plurality of times per one combustion stroke or ignition operations are performed at a plurality of locations. At this time, the ignition interval or the number of ignitions may be changed according to the combustion conditions at that time.
[0036]
DETAILED DESCRIPTION OF THE INVENTION
<< Embodiment (1) >>
Hereinafter, an embodiment (1) of the present invention will be described with reference to FIGS. First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner (not shown) is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 13 for detecting the intake air amount is provided downstream of the air cleaner. A throttle valve 14 and a throttle opening sensor 15 that detects the throttle opening are provided on the downstream side of the air flow meter 13.
[0037]
Further, a fuel injection valve 17 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 16 for introducing air into each cylinder of the engine 11. A spark plug 18 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 18.
[0038]
The intake valve 19 and the exhaust valve 20 of the engine 11 are respectively driven by camshafts 21 and 22, and the intake-side camshaft 21 is provided with a hydraulic variable valve timing mechanism 23 that varies the opening and closing timing of the intake valve 19. On the other hand, the camshaft 22 on the exhaust side is provided with a hydraulic variable valve timing mechanism 24 that varies the opening / closing timing of the exhaust valve 20. The hydraulic pressure for driving each variable valve timing mechanism 23, 24 is controlled by a hydraulic control valve (not shown).
[0039]
The intake-side camshaft 21 is provided with an intake-side cam position sensor 25 that detects the rotational position (advance amount) of the camshaft 21, and the exhaust-side camshaft 22 is provided with a rotational position of the camshaft 22. An exhaust side cam position sensor 26 for detecting (advance amount) is provided. The reference position sensor 27 outputs a pulse signal for cylinder discrimination every 720 ° C., and the rotation angle sensor 28 outputs a pulse signal every finer crank angle (for example, every 30 ° C. A). Based on the pulse signals of these sensors 27 and 28, the reference crank position and the engine speed are detected. A water temperature sensor 29 for detecting the engine cooling water temperature is attached to the cylinder block of the engine 11.
[0040]
On the other hand, the exhaust pipe 30 (exhaust gas passage) of the engine 11 is provided with a catalyst 31 such as a three-way catalyst that purifies HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) in the exhaust gas. ing. An air-fuel ratio sensor 32 (or oxygen sensor) that outputs a linear air-fuel ratio signal corresponding to the air-fuel ratio of the exhaust gas is provided on the upstream side of the catalyst 31. In the present embodiment (1), since a secondary air introduction position of a secondary air introduction device 34 to be described later is set upstream of the air-fuel ratio sensor 32, the exhaust gas flowing into the catalyst 31 (exhaust gas containing secondary air) ) Can be directly detected by the air-fuel ratio sensor 32 and feedback controlled. On the downstream side of the catalyst 31, there is provided an oxygen sensor 33 whose output voltage is inverted depending on whether the air-fuel ratio of the exhaust gas is rich or lean with respect to the stoichiometric air-fuel ratio.
[0041]
Next, the configuration of the secondary air introduction device 34 that introduces outside air into the exhaust pipe 30 as secondary air will be described. A secondary air introduction pipe 35 (secondary air introduction passage) for introducing secondary air is connected to the upstream side of the air-fuel ratio sensor 32 in the exhaust pipe 30. The connection position of the secondary air introduction pipe 35, that is, the secondary air introduction position, is such that the exhaust gas temperature in the exhaust pipe 30 is equal to or higher than the temperature at which the rich component in the exhaust gas burns (eg, 700 ° C.). It is set within the range (see FIG. 2).
[0042]
An air filter 36 is provided at the most upstream portion of the secondary air introduction pipe 35, and an air pump 37 that pumps secondary air is provided downstream of the air filter 36. A combination valve 38 is provided on the downstream side of the air pump 37. The combination valve 38 is configured by integrating a check valve 40 on the downstream side of a pressure-driven on-off valve 39 that opens and closes the secondary air introduction pipe 35. The on-off valve 39 of the combination valve 38 is connected to the intake pipe 12 via an intake pressure introduction pipe 41, and the driving pressure of the on-off valve 39 is switched by an electromagnetically driven switching valve 42 provided in the middle of the intake pressure introduction pipe 41. Is switched between the atmospheric pressure and the intake pressure.
[0043]
When the secondary air is introduced, the on / off valve 39 is opened by switching on the electromagnetically driven switching valve 42 (intake pressure introduction position) and introducing the intake pressure into the pressure driven on / off valve 39. As a result, the secondary air discharged from the air pump 37 passes through the on-off valve 39 and flows to the check valve 40 side, and the check valve 40 is opened by the pressure, and the secondary air is introduced into the exhaust pipe 30. Is done.
[0044]
On the other hand, when stopping the introduction of the secondary air, the switching valve 42 is switched off (atmospheric pressure introduction position) and the atmospheric pressure is introduced into the switching valve 39 to close the switching valve 39. As a result, the introduction of the secondary air into the exhaust pipe 30 is stopped and the pressure of the secondary air does not act on the check valve 40 and the pressure on the exhaust pipe 30 side becomes high. The valve is automatically closed to prevent the exhaust gas in the exhaust pipe 30 from flowing back to the air pump 37 side.
[0045]
Outputs of the various sensors described above are input to an engine control circuit (hereinafter referred to as “ECU”) 43. The ECU 43 is mainly composed of a microcomputer including a CPU 44, a ROM 45, a RAM 46, a backup RAM 47, and the like, and by executing each routine stored in the ROM 45, the fuel injection valve 17, the spark plug 18, the intake side and the exhaust side The variable valve timing mechanisms 23 and 24, the secondary air introduction device 34, and the like are controlled.
[0046]
By the way, at the time of cold start, since the catalyst 31 is in an inactive state, HC, CO, NOx, etc. discharged from the engine 11 cannot be sufficiently purified. Therefore, the ECU 43 executes the ignition timing control routine of FIG. 4 to retard the ignition timing of the spark plug 18 and also executes the VVT control routine of FIG. Is controlled to advance the valve opening timing of the exhaust valve 20 and increase the valve overlap amount of the intake valve 19 and the exhaust valve 20, so that rich components (HC, CO) in the exhaust gas are burned in the exhaust pipe 30. Raise the temperature to a possible exhaust gas temperature.
[0047]
Further, the ECU 43 executes the secondary air control routine shown in FIGS. 6 and 7 to control the secondary air introduction device 34 to generate the secondary air for generating afterburning in the exhaust pipe 30. Introduced as air. As a result, the rich component in the high-temperature exhaust gas discharged from the engine 11 is mixed with the oxygen of the secondary air introduced by the secondary air introduction device 34 and burned afterward in the exhaust pipe 30 upstream of the catalyst 31. Is generated naturally, and the catalyst 31 is warmed up early by the combustion heat. Further, the ECU 43 executes the fuel injection control routine of FIG. 3 so that the air-fuel ratio of the exhaust gas flowing into the catalyst 31 is weakly lean (the in-cylinder mixture is almost the stoichiometric air-fuel ratio or weakly rich) during cold start. The amount of HC flowing into the catalyst 31 is controlled. The processing contents of these routines will be described below.
[0048]
[Fuel injection control]
The fuel injection control routine of FIG. 3 is executed, for example, for each fuel injection of each cylinder (for each six cylinder engine, 120 ° C. A). When this routine is started, first, at steps 101 to 103, it is determined as follows whether or not the weak lean air-fuel ratio control for the catalyst warm-up control is to be performed. First, in step 101, it is determined whether or not a predetermined time (for example, 1 second) has elapsed since the start was completed. The completion of the start is determined by, for example, whether or not the engine rotational speed Ne has exceeded a start determination value. If the predetermined time has elapsed from the completion of the start, the routine proceeds to step 102, where it is determined whether or not the engine cooling water temperature Tw is lower than a predetermined temperature (for example, 60 ° C.), and if the engine cooling water temperature Tw is higher than the predetermined temperature. Then, it is determined that it is not at the time of high temperature restart in which the engine 11 is restarted in a high temperature state, and the process proceeds to step 103 to determine whether or not to continue the catalyst warm-up control. Specifically, it is determined whether or not 20 seconds have elapsed since starter on (start of cranking), or whether or not a non-idle state has been reached, and if 20 seconds have elapsed since starter on, or If it is in the non-idle state, it is determined that the catalyst warm-up control is not continued.
[0049]
If any one of the above steps 101 to 103 is determined as “No”, it is determined that the catalyst warm-up control is unnecessary, and the routine proceeds to step 104 where normal fuel injection control is performed. In this normal fuel injection control, at the start of the engine, start-up fuel injection control such as warm-up increase correction according to the engine coolant temperature Tw is performed. In addition, after the engine warm-up is completed, air-fuel ratio feedback control is performed to correct the basic injection amount according to the engine operating state so that the detected value of the air-fuel ratio sensor 32 matches the target air-fuel ratio. carry out.
[0050]
On the other hand, if it is determined as “Yes” in all of the above steps 101 to 103, it is determined that the catalyst warm-up control is necessary, and the process proceeds to step 105 where the weak lean air-fuel ratio control is performed and flows into the catalyst 31. The fuel injection amount of the fuel injection valve 17 is controlled so that the air-fuel ratio of the exhaust gas (catalyst inflow gas) becomes weak lean (for example, A / F = 16). During the introduction of the secondary air, if the air-fuel ratio of the in-cylinder mixture is controlled to be close to the stoichiometric air-fuel ratio or slightly rich, the air-fuel ratio of the catalyst inflow gas becomes weakly lean due to the introduction of the secondary air and flows into the catalyst 31. The amount of HC discharged into the atmosphere can be reduced by reducing the amount of HC. Further, by controlling the air-fuel ratio of the in-cylinder mixture near the stoichiometric air-fuel ratio or slightly rich, rich components necessary for afterburning can be supplied to the exhaust pipe 30.
[0051]
In this case, before activation of the air-fuel ratio sensor 32, the target air-fuel ratio of the catalyst inflow gas may be set to a weak lean (for example, A / F = 16) and the fuel injection amount may be controlled by open loop control. Is activated before the catalyst 31, so that the air-fuel ratio feedback control can be performed after the air-fuel ratio sensor 32 is activated even before the catalyst 31 is activated.
[0052]
[Ignition timing control]
The ignition timing control routine of FIG. 4 is executed, for example, for each fuel injection of each cylinder and serves as exhaust gas temperature raising control means in the claims. When this routine is started, first, in steps 201 to 203, it is determined whether or not to perform ignition timing retardation control (exhaust gas temperature increase control) for catalyst warm-up control. The processing in steps 201 to 203 is the same as the processing in steps 101 to 103 in FIG.
[0053]
If it is determined “No” in any one of the above steps 201 to 203, the process proceeds to step 204, where it is determined that the catalyst warm-up control is unnecessary, and normal ignition timing control is performed. In this normal ignition timing control, the ignition timing is fixed to 5 ° C. before compression TDC (BTDC), for example, at the beginning of engine startup. Further, after the engine warm-up is completed, idle stabilization correction and knock advance correction are performed on the basic advance angle according to the engine operating state, and the ignition timing is controlled by the optimum advance value.
[0054]
On the other hand, if all of the above steps 201 to 203 are determined as “Yes”, it is determined that the catalyst warm-up control is necessary, and the process proceeds to step 205 where the ignition timing retarding control is performed and the ignition of the spark plug 18 is performed. The timing is retarded to, for example, 10 ° C. after compression TDC (ATDC). As a result, the combustion of the air-fuel mixture in the cylinder is delayed and the temperature of the exhaust gas discharged into the exhaust pipe 30 is increased.
[0055]
[VVT control]
The VVT control routine of FIG. 5 is executed at a predetermined cycle (for example, 64 ms cycle), and serves as exhaust gas temperature raising control means in the claims. When this routine is started, first, in steps 301 to 303, it is determined whether or not to perform valve timing control (exhaust gas temperature increase control) of the intake valve 19 and the exhaust valve 20 for catalyst warm-up control. . The processing in steps 301 to 303 is the same as the processing in steps 101 to 103 in FIG.
[0056]
If it is determined “No” in any one of the above steps 301 to 303, the process proceeds to step 304, where it is determined that the catalyst warm-up control is unnecessary, and normal VVT control is performed. In normal VVT control, the valve timings of the intake valve 19 and the exhaust valve 20 are controlled at the most retarded position at the beginning of engine start. Further, after the engine warm-up is completed, VVT feedback control is performed to set a target advance amount of the valve timing of the intake valve 19 according to the engine operating state, and the target advance amount and the intake side cam position sensor 25 are set. The intake side variable valve timing mechanism 23 is feedback-controlled so that the detected value coincides with the detected value.
[0057]
On the other hand, when all of the above steps 301 to 303 are determined as “Yes”, it is determined that the catalyst warm-up control is necessary, the process proceeds to step 305, the opening timing of the exhaust valve 20 is advanced by 15 ° C., and Further, the valve overlap amount of the intake valve 11 and the exhaust valve 20 is increased to 30 ° C. As described above, when the valve overlap amount is increased, the internal EGR is increased and the combustion speed in the cylinder is decreased, so that the peak of the in-cylinder temperature is delayed. Furthermore, if the opening timing of the exhaust valve 20 is advanced, the exhaust gas is discharged into the exhaust pipe 30 near the peak of the in-cylinder temperature, and the exhaust gas temperature can be increased.
[0058]
[Secondary air introduction control]
The secondary air introduction control routine of FIG. 6 is executed at a predetermined cycle. When this routine is started, first, in step 401, a secondary air introduction determination routine of FIG. 7 described later is executed to set the secondary air introduction flag FAB to “ON”, which means permission of secondary air introduction or Set to “off”, which means prohibition of secondary air introduction.
[0059]
Thereafter, the routine proceeds to step 402, where it is determined whether or not the secondary air introduction flag FAB is on. If the secondary air introduction flag FAB is on, the switching valve 42 is switched on (intake pressure introduction position) and opened and closed. While opening the valve 39, the air pump 37 is operated (steps 403 and 404), and the secondary air is introduced into the exhaust pipe 30.
[0060]
On the other hand, if the secondary air introduction flag FAB is off, the switching valve 42 is switched off (atmospheric pressure introduction position) to close the on-off valve 39 and the air pump 37 is stopped (steps 405 and 406). Stop introducing secondary air.
[0061]
The secondary air introduction control routine of FIG. 6 described above plays a role as secondary air introduction control means in the scope of claims together with a secondary air introduction determination routine of FIG. 7 described later.
[0062]
[Secondary air introduction judgment]
Next, the processing content of the secondary air introduction determination routine of FIG. When this routine is started, first, at step 501, it is determined whether or not the start is completed based on whether or not the engine speed Ne exceeds the start determination value. It is determined whether or not the first explosion has occurred in the cylinder. If the first explosion has not occurred yet, the routine proceeds to step 504, where the secondary air introduction flag FAB is set to OFF, and this routine is terminated. Thereafter, when the first explosion occurs, the process proceeds to step 505, the secondary air introduction flag FAB is set to ON (see FIG. 8), and this routine is terminated.
[0063]
On the other hand, if it is determined in step 501 that the start is completed, the process proceeds to step 503, where it is determined whether the secondary air introduction condition is satisfied. The secondary air introduction conditions are, for example, the following (1) to (3).
(1) The exhaust gas temperature is higher than the temperature at which afterburning is possible (eg 700 ° C).
(2) The catalyst temperature is lower than the specified temperature
(3) The engine 11 is in an operating state where the HC emission amount of the engine 11 is relatively large
[0064]
The above condition (3) is that, for example, fluctuations in the engine speed Ne, the intake pipe pressure PM, the intake air amount Ga, and the like are not less than a predetermined value, and the roughness value representing the degree of instability of combustion is not less than the predetermined value. That is, the engine rotational speed Ne is equal to or greater than a predetermined value and the retard amount of the ignition timing is equal to or greater than a predetermined value, and the point is that the combustion state in the cylinder is unstable to some extent. In such a case, since unburned HC is discharged from the engine 11, HC necessary for afterburning can be supplied into the exhaust pipe 30, and the amount of HC flowing into the catalyst 31 by afterburning (HC discharge into the atmosphere). The amount) can also be reduced.
[0065]
Further, if the above condition (1) is satisfied, afterburning can be reliably generated immediately after the introduction of secondary air. The temperature of the exhaust gas may be estimated from the cooling water temperature or the like, or may be detected by installing a temperature sensor in the exhaust gas passage.
[0066]
Further, the predetermined temperature in the above (2) is set to, for example, the lower limit value of the activation temperature range of the catalyst 31 or a temperature slightly higher than that. Therefore, when the catalyst temperature is lower than the predetermined temperature, it is necessary to warm up the catalyst 31. Therefore, secondary air is introduced and the warming up of the catalyst 31 is promoted by afterburning. On the other hand, when the catalyst temperature is equal to or higher than the predetermined temperature, the catalyst 31 is in an active state, and there is no need to warm up the catalyst 31, so the introduction of secondary air is prohibited and the catalyst 31 is overheated due to afterburning. To prevent. The temperature of the catalyst 31 may be estimated from the exhaust gas temperature or the like, or may be detected by installing a temperature sensor on the catalyst 31.
[0067]
When the conditions (1) and (2) described above are satisfied, or when the conditions (1) and (3) are satisfied, the secondary air introduction condition is satisfied, and the process proceeds to step 505. The secondary air introduction flag FAB is set on, and this routine ends. On the other hand, if the secondary air introduction condition is not satisfied, the routine proceeds to step 504, where the secondary air introduction flag FAB is set to OFF, and this routine ends.
[0068]
The determination method of the secondary air introduction condition can be variously changed. For example, when the condition (2) (catalyst temperature <predetermined temperature) is satisfied, the secondary air introduction condition is satisfied. Alternatively, the secondary air introduction condition may be satisfied when the condition (3) (HC emission increase of the engine 11) is satisfied.
[0069]
According to the embodiment (1) described above, during the catalyst warm-up control (in the exhaust gas temperature increase control), the ignition timing is retarded, the opening timing of the exhaust valve 20 is advanced, and the intake valve 19 is advanced. Since the valve overlap amount of the exhaust valve 20 is increased, the exhaust gas temperature in the exhaust pipe 30 can be quickly raised to a temperature at which afterburning can be performed by the synergistic effect of these controls. Then, as shown in FIG. 8, the secondary air is introduced into the exhaust pipe 30 by the secondary air introduction device 34 immediately after the first explosion occurs in the cylinder at the start, and rich components in the exhaust gas discharged from the engine 11 are removed. After being mixed with oxygen in the secondary air, the exhaust gas is heated to a temperature at which the exhaust gas can be burned, and afterburn is generated. The catalyst 31 is warmed up by the combustion heat. As a result, the catalyst 31 can be warmed up early, and the HC discharged from the engine 11 is burned by the afterburning, so that the amount of HC discharged into the atmosphere can be reduced even before the catalyst is activated. it can. In addition, since it is not necessary to provide an ignition device for igniting the exhaust gas, it is possible to satisfy the demands for simplification of configuration and cost reduction.
[0070]
In addition, if the introduction timing of the secondary air is made too early at the start, the secondary air is introduced before the exhaust gas temperature rises sufficiently and no afterburning occurs. However, in this embodiment (1), by setting the secondary air introduction start timing after the first explosion, the time until that time is reached. Since the introduction of the secondary air is prohibited during the period, the secondary air can be introduced after the exhaust gas temperature starts to rise at the start, and the exhaust gas temperature in the exhaust pipe 31 is prevented from decreasing and the afterburning. Generation delay can be prevented. It should be noted that the introduction of secondary air may be prohibited for a predetermined time from the start.
[0071]
By the way, it goes without saying that the catalyst 31 is in an inactive state at the time of cold start, but even with the activated catalyst 31, the catalyst temperature may be lowered and become inactive depending on the operating state. In this respect, in this embodiment (1), after the start is completed, when the catalyst temperature becomes lower than a predetermined temperature (when there is a request for warming up the catalyst 31), secondary air is introduced. Not only during the intermediate start, but even after the catalyst 31 has warmed up once, if the temperature of the catalyst 31 drops to an inactive state, it can be quickly restored to the active state by afterburning.
[0072]
Further, in the present embodiment (1), secondary air is introduced even when the engine 11 is in an operating state where the amount of HC emission is large (when there is a request to reduce HC flowing into the catalyst 31). The amount of HC discharged into the atmosphere can be reduced by post-burning the HC discharged from the engine 11.
[0073]
Further, in the present embodiment (1), it is determined whether or not the exhaust gas temperature raising control (ignition delay angle control, valve timing control) is performed based on the engine cooling water temperature Tw or the elapsed time from the starter on. Therefore, the exhaust gas temperature raising control can be performed only when the exhaust gas temperature raising control is necessary, and the exhaust gas temperature is not increased more than necessary, and the catalyst 31 and the air-fuel ratio sensor 17 and the like are prevented from being overheated. be able to.
[0074]
In this embodiment (1), when exhaust gas temperature raising control is performed, (1) ignition timing retard control, (2) exhaust valve 20 timing advance control, and (3) valve overlap. The exhaust gas temperature rising effect was enhanced by the synergistic effect of these controls by combining the increase in the amount, but one or two of (1) to (3) were implemented to control the exhaust gas temperature. You may make it heat up to the temperature which can be burned after.
[0075]
<< Embodiment (2) >>
Next, Embodiment (2) of this invention is demonstrated using FIG.9 and FIG.10. The secondary air introduction control routine of FIG. 9 executed in the present embodiment (2) is obtained by changing the process of step 404 of FIG. 6 to the process of step 404a and step 404b. The processing is the same as in FIG. The system configuration of this embodiment (2) is the same as that of the above embodiment (1).
[0076]
In the secondary air introduction control routine of FIG. 9, when it is determined that the secondary air introduction flag FAB is on, the switching valve 42 is turned on to open the on-off valve 39 (steps 401 to 403), and then the process goes to step 404a. Then, a map of the duty ratio Duty of the air pump 37 using the elapsed time from the start (starter on or start completion) as a parameter is searched to calculate the duty ratio Duty of the air pump 37 according to the elapsed time from the start. The map characteristic of the duty ratio Duty is set so that the duty ratio Duty increases according to the elapsed time from the start until a predetermined time elapses from the start, and thereafter the duty ratio Duty becomes a substantially constant value. Yes.
[0077]
Thereafter, the process proceeds to step 404b, where the operating voltage Vp of the air pump 37 is obtained by multiplying the maximum operating voltage Vm of the air pump 37 by the duty ratio Duty (Vp = Vm × Duty), and the air pump 37 is operated at this operating voltage Vp.
[0078]
In the present embodiment (2), as shown in FIG. 10, when the first explosion occurs in the cylinder at the time of starting, the introduction of secondary air by the secondary air introduction device 34 is started, and the air flow rate sent by the air pump 37, That is, the secondary air introduction flow rate APQ is small at the beginning of the introduction of the secondary air, and then gradually increases and then becomes a substantially constant flow rate. As a result, the exhaust gas temperature in the exhaust pipe 31 can be raised by efficiently generating afterburning while suppressing the temperature drop due to the introduction of secondary air. In addition, since the secondary air introduction flow rate APQ is larger than the amount consumed by the afterburning in the latter stage of the secondary air introduction, the oxygen of the secondary air is also supplied into the catalyst 31 and the HC in the catalyst 31 is supplied. The catalyst 31 can be quickly warmed up by the synergistic effect of afterburning and reaction heat.
[0079]
In the embodiment (2), the secondary air introduction flow rate (duty ratio Duty of the air pump 37) is set according to the elapsed time from the start. However, the secondary air is required when the catalyst 31 is warmed up after the start. When the exhaust gas temperature is introduced, the introduction flow rate of the secondary air may be set according to the elapsed time from when the exhaust gas temperature is lowered or when the exhaust gas temperature is requested to rise.
[0080]
<< Embodiment (3) >>
Next, an embodiment (3) of the present invention will be described with reference to FIGS. In the present embodiment (3), as shown in FIG. 11, the downstream portion of the secondary air introduction pipe 48 is branched into three introduction portions 48 a, 48 b, 48 c via an introduction position switching valve 49. The portions 48a, 48b, and 48c are connected to the upstream portion, the midstream portion, and the downstream portion of the exhaust pipe 30 upstream of the air-fuel ratio sensor 32, respectively. In this embodiment (3), considering that the exhaust gas temperature of the exhaust pipe 30 decreases due to heat radiation as it goes downstream, the temperature at which the exhaust gas temperature can be combusted by exhaust heat when the engine 11 is in a state after warming up. The connection positions of the introduction parts 48a, 48b, and 48c are set so that the range becomes up to the connection position of the introduction parts 48a and 48b of the upstream part and the midstream part. Therefore, in a state before the engine 11 is warmed up, the range in which the exhaust gas temperature becomes the temperature at which afterburning can be performed by the exhaust heat is the connection position of the upstream introduction portion 48a.
[0081]
In this case, when the introduction position switching valve 49 is switched to the three introduction positions, all the channels through which the secondary air from the air pump 37 flows to the three introduction portions 48a, 48b, and 48c are opened, and the secondary air is 3 The gas is introduced into the exhaust pipe 30 from the introduction portions 48a, 48b, and 48c. Further, when the introduction position switching valve 49 is switched to the two introduction positions, the flow path to the upstream introduction section 48a is closed, and the secondary air is exhausted from the two introduction sections 48b and 48c in the middle and downstream sections. It is introduced into the tube 30. Other system configurations are the same as those in the embodiment (1).
[0082]
Further, the secondary air introduction control routine of FIG. 12 executed in the present embodiment (3) is obtained by adding the processing of steps 411 to 413 between step 402 and step 403 of FIG. The process of each step is the same as in FIG.
[0083]
In this routine, when the secondary air introduction flag FAB is determined to be on (steps 401 and 402), the routine proceeds to step 411, where it is determined whether or not the cooling water temperature Tw is higher than a predetermined temperature, and the cooling water temperature Tw is predetermined. If the temperature is equal to or lower than the temperature, the engine 11 has not been warmed up, so the exhaust gas temperature is determined to be within the range where the exhaust gas temperature can be combusted up to the connection position of the upstream introduction portion 48a. The introduction position switching valve 49 is switched to the three introduction positions. Then, the switching valve 42 is turned on to open the on-off valve 39 and the air pump 37 is operated (steps 403 and 404), and secondary air is supplied from the three introduction portions 48a, 48b, and 48c into the exhaust pipe 30. To introduce.
[0084]
Before the engine 11 is warmed up, the range in which the exhaust gas temperature can be combusted by exhaust heat is up to the connection position of the upstream introduction portion 48a, but by the secondary air introduced from the upstream introduction portion 48a. Afterburning occurs, the exhaust gas temperature on the downstream side rises, and even the connecting position of the introduction part 48b of the midstream part becomes a temperature at which afterburning is possible, so the secondary air introduced from the introduction part 48 of the midstream part Afterburning occurs and the exhaust gas temperature on the downstream side rises. As a result, the temperature is such that afterburning is possible up to the connection position of the downstream introduction portion 48c, so that afterburning is also caused by the secondary air introduced from the downstream introduction portion 48c, and the catalyst 31 on the downstream side thereof. The exhaust gas temperature in the vicinity rises and the catalyst 31 is warmed up.
[0085]
After that, if it is determined in step 411 that the coolant temperature Tw is higher than the predetermined temperature, the engine 11 has been warmed up, and the range in which the exhaust gas temperature becomes a temperature at which afterburning can be performed by exhaust heat is in the middle It judges that it has extended to the connection position of the introduction part 48b of a part, it progresses to step 413, switches the introduction position switching valve 49 to two introduction positions, and introduces only two introduction parts 48b and 48c of a midstream part and a downstream part Secondary air is introduced into the exhaust pipe 30.
[0086]
In this case, by generating afterburning with the secondary air introduced from the introduction part 48b in the middle stream part and raising the exhaust gas temperature, the range of the temperature at which afterburning is possible extends to the connection position of the introduction part 48c in the downstream part. Therefore, afterburning is also generated by the secondary air introduced from the downstream introduction portion 48c. Moreover, since the flow path to the upstream introduction portion 48a is closed, the flow rate of secondary air introduced from the midstream portion and the downstream introduction portions 48b and 48c increases accordingly (see FIG. 13). Thereby, more afterburning can be generated near the catalyst 31, and the warm-up effect of the catalyst 31 can be enhanced.
[0087]
According to the embodiment (3) described above, since secondary air is introduced from a plurality of locations of the exhaust pipe 30 to generate afterburning at a plurality of locations, afterburning can be generated efficiently. The secondary air (oxygen) introduced into the downstream portion is supplied into the catalyst 31 to promote the reaction of HC in the catalyst 31, and the catalyst warm-up effect can be enhanced by the reaction heat.
[0088]
Further, in the present embodiment (3), after the engine 11 is warmed up, paying attention to the fact that the range where the afterburning temperature becomes possible extends to the downstream side of the exhaust pipe 30 according to the warm-up state of the engine 11. Closed the flow path to the upstream introduction portion 48a and increased the flow rate of the secondary air introduced from the middle flow portion and the downstream introduction portions 48b and 48c by that amount. More afterburning can be generated in the vicinity, and the early warm-up effect of the catalyst 31 due to afterburning can be further improved.
[0089]
In this embodiment (3), the introduction position of the secondary air is switched by the introduction position switching valve 49 provided at the branching section of the three introduction sections 48a, 48b, 48c. As described above, instead of the introduction position switching valve 49, an on-off valve 50 may be provided in the middle of the upstream introduction portion 48a, and switching between the three-position introduction and the two-position introduction may be performed by opening and closing the on-off valve 50. .
[0090]
Alternatively, as in the example of FIG. 15, the opening / closing valves 50 are provided in the middle of the three introduction portions 48a, 48b, 48c, and the opening / closing valves 50 of the introduction portions 48a, 48b, 48c are individually opened and closed. You may make it switch between 3 places introduction and 2 places introduction.
The introduction position of the secondary air is not limited to three places, and may be two places or four places or more, and the switching pattern of the introduction position of the secondary air may be changed as appropriate.
[0091]
<< Embodiment (4) >>
In the embodiment (4) of the present invention shown in FIGS. 16 and 17, after the start is completed, the introduction of secondary air is started, and before the vehicle travels (during idle operation), the detected value of the air-fuel ratio sensor 32, that is, The fuel injection amount of the fuel injection valve 17 is feedback-controlled so that the air-fuel ratio of the exhaust gas (catalyst inflow gas) flowing into the catalyst 31 becomes lean (for example, A / F = 16 to 17.6). However, before the air-fuel ratio sensor 32 is activated, the fuel injection amount is controlled in an open loop. Thereafter, during vehicle travel, the fuel injection amount is feedback-controlled so that the detected value of the air-fuel ratio sensor 32, that is, the air-fuel ratio of the catalyst inflow gas is close to the theoretical air-fuel ratio (for example, A / F = 14.6), When a predetermined time has elapsed from the completion of the start, the introduction of the secondary air is stopped.
[0092]
In the present embodiment (4), during the warm-up of the catalyst 31 before the vehicle travels, the catalyst 31 can be warmed up early by the afterburning by introducing the secondary air, and the air-fuel ratio of the catalyst inflow gas is controlled to be lean. Therefore, the amount of HC flowing into the catalyst 31 can be reduced and the amount of HC discharged into the atmosphere can be reduced. In addition, when the vehicle travels, the NOx emission amount from the engine 11 is increased, and the air-fuel ratio of the catalyst inflow gas is controlled to be close to the stoichiometric air-fuel ratio (purification window of the catalyst 31). Purify. That is, since the catalyst 31 has been activated to some extent during vehicle travel, the NOx purification rate in the catalyst 31 can be improved by controlling the air-fuel ratio of the catalyst inflow gas to be close to the theoretical air-fuel ratio, The amount of NOx discharged into the atmosphere can be reduced.
[0093]
<< Embodiment (5) >>
The air-fuel ratio sensor 32 is not necessarily arranged downstream of the secondary air introduction position. As shown by a dotted line in FIG. 1, the air-fuel ratio sensor 32 may be arranged upstream of the secondary air introduction position. good. In this case, as shown in the embodiment (5) of the present invention shown in FIG. 18, during the warm-up of the catalyst 31 before the vehicle travels, the detected value of the air-fuel ratio sensor 32, that is, the exhaust gas discharged from the engine 11 By performing feedback control of the fuel injection amount so that the air-fuel ratio is close to the theoretical air-fuel ratio (for example, A / F = 14.6), the air-fuel ratio of the catalyst inflow gas is controlled to be lean. Thereafter, when the vehicle travels, the fuel injection amount is set so that the detected value of the air-fuel ratio sensor 32, that is, the air-fuel ratio of the exhaust gas discharged from the engine 11 becomes rich (for example, A / F = 12.6 to 13.2). As a result of feedback control, the air-fuel ratio of the catalyst inflow gas is controlled in the vicinity of the theoretical air-fuel ratio. Further, after the introduction of the secondary air is stopped, the fuel injection amount is feedback controlled so that the air-fuel ratio of the exhaust gas discharged from the engine 11 is in the vicinity of the theoretical air-fuel ratio, and the air-fuel ratio of the catalyst inflow gas is set in the vicinity of the theoretical air-fuel ratio. To control.
[0094]
In the embodiment (5) described above, the same effect as that in the embodiment (4) can be obtained.
[0095]
<< Embodiment (6) >>
Next, Embodiment (6) of this invention is demonstrated using FIG. 19 thru | or FIG. FIG. 19 is a schematic configuration diagram of the entire engine control system in the present embodiment (6). However, substantially the same parts as those in FIG. 1 of the embodiment (1) are denoted by the same reference numerals, description thereof will be omitted, and only differences will be described. In the configuration of FIG. 19, the intake side and exhaust side variable valve timing mechanisms 23, 24 are omitted. A bypass passage 51 that bypasses the throttle valve 14 is provided, and an idle speed control valve (ISC valve) 52 is provided in the bypass passage 51. At the time of cold start, the ISC valve 52 is adjusted to a predetermined opening, the amount of air that bypasses the throttle valve 14 is increased, and the engine speed Ne is higher than the idle speed after warming up (for example, 700 rpm) The rotational speed is controlled (for example, 1200 rpm). Further, the intake pipe 12 is provided with an intake pressure sensor 53 for detecting the intake pipe pressure PM, and an intake air temperature sensor 54 for detecting the intake air temperature Ta, instead of the air flow meter 13.
[0096]
In the present embodiment (6), the secondary air introduction control is performed by the same method as in each of the above embodiments, the catalyst warm-up control condition determination routine in FIG. 20, the ignition timing control routine in FIG. 21, and the in FIG. 22 and FIG. A fuel injection control routine is executed. In the catalyst warm-up control execution condition determination routine of FIG. 20, the catalyst warm-up control execution flag XCAT is set to “1” or “0”. XCAT = 1 means that the catalyst warm-up control execution condition is satisfied, and XCAT = 0 means that the catalyst warm-up control execution condition is not satisfied. In the ignition timing control routine of FIG. 21, when the catalyst warm-up control execution condition is satisfied, the ignition timing retard angle correction value θRE is calculated, and the basic ignition time θBASE is controlled to the retard angle side by this retard angle correction value θRE. Thus, the exhaust gas temperature is raised and multiple ignition is performed to suppress torque fluctuation. In the fuel injection control routine of FIGS. 22 and 23, when the catalyst warm-up control execution condition is satisfied, the target air-fuel ratio AFtg is set according to the ignition timing retard correction value θRE, and the exhaust gas air-fuel ratio is The fuel injection amount is controlled so that the target air-fuel ratio AFtg is obtained. The processing contents of these routines will be described below.
[0097]
[Catalyst warm-up control execution condition judgment]
The catalyst warm-up control execution condition determination routine of FIG. 20 is executed every predetermined time (for example, every 10 ms). First, in steps 601 to 605, it is determined whether the following catalyst warm-up control execution conditions are satisfied. To do.
[0098]
(1) The engine speed Ne is within a predetermined range, for example, 400 to 2000 rpm (step 601).
(2) The engine coolant temperature Tw is within a predetermined range, for example, 0 to 60 ° C. (step 602).
(3) The transmission position of the automatic transmission is in the P range or N range (neutral position in the case of manual transmission) (step 603).
(5) Within a predetermined time from the start, for example, within 15 seconds (step 604)
(6) Various failures have not occurred (step 605).
[0099]
When all of the conditions (1) to (6) are satisfied (that is, when all the determinations in steps 601 to 605 are “Yes”), the catalyst warm-up control execution condition is satisfied, and the process proceeds to step 606. Then, the catalyst warm-up control execution flag XCAT is set to “1”.
[0100]
On the other hand, if any one of the conditions of Steps 601 to 605 is determined as “No”, the catalyst warm-up control execution condition is not satisfied, and the process proceeds to Step 607 where the catalyst warm-up control execution flag XCAT is determined. Is reset to “0”.
[0101]
[Ignition timing control]
The ignition timing control routine of FIG. 21 is executed every predetermined time (for example, every 10 ms). First, in step 701, the engine speed Ne, the intake pipe pressure PM, and the engine cooling water temperature Tw are read, and in the next step 702, Whether or not the start has been completed is determined based on, for example, whether or not the engine speed Ne is equal to or higher than the start determination value. If it is before the start is completed, the routine proceeds to step 703, where a preset fixed ignition timing (for example, BTDC 5 ° C. A) is stored at a predetermined address, and this routine is terminated.
[0102]
On the other hand, if it is after the start is completed, the routine proceeds to step 704, where it is determined whether or not the engine is idle based on whether or not the throttle is fully closed based on the output of the throttle opening sensor 15. If the engine is idling, the routine proceeds to step 705, where the basic ignition timing θBSE is calculated according to the engine speed Ne. If the engine is not idling, the process proceeds to step 706, where the basic ignition timing θBSE is calculated according to the engine speed Ne and the intake pipe pressure PM using a map stored in advance in the ROM 45. In these steps 705 and 706, the basic ignition timing θBSE is set to the advance side as the engine speed increases substantially. Note that, at the beginning of the engine start, the basic ignition timing θBSE is usually set in the vicinity of BTDC 10 ° C., for example.
[0103]
Thereafter, the routine proceeds to step 707, where it is determined whether or not the catalyst warm-up control execution flag XCAT is “1” meaning that the catalyst warm-up control execution condition is satisfied. If XCAT = 0, this routine is terminated as it is. .
[0104]
On the other hand, when XCAT = 1, ignition timing control for catalyst warm-up control is executed in subsequent steps 708 to 710. Specifically, in step 708, the retardation correction value θRE corresponding to the engine coolant temperature Tw is calculated using the map shown in FIG. The map characteristic of FIG. 24 shows that the retard angle correction value θRE increases as the coolant temperature Tw is higher when the engine coolant temperature Tw is in the range of 0 to 20 ° C., for example. θRE is a substantially constant value, and in the range where the cooling water temperature Tw is 40 to 60 ° C., the retardation correction value θRE is set to be smaller as the cooling water temperature Tw is higher.
[0105]
Thereafter, the ignition timing θig is obtained by subtracting the retardation correction value θRE from the basic ignition timing θBSE (θig = θBSE−θRE) and stored in a predetermined address. Thereafter, the process proceeds to step 710, where an ignition interval and the number of ignitions for performing multiple ignition operations per one combustion stroke are set according to various parameters (engine speed, ignition timing, etc.) Torque fluctuations during warm-up control are suppressed by multiple ignition.
[0106]
[Fuel injection control]
The fuel injection control routine shown in FIGS. 22 and 23 is executed at predetermined time intervals (for example, every 10 ms). First, at step 801, the engine speed Ne, the intake pipe pressure PM, the engine cooling water temperature Tw, and the intake air temperature Ta are calculated. In the next step 802, it is determined whether or not the start is completed. If it is before the start is completed, the routine proceeds to step 803, where the start-time injection amount TAUSTA is calculated according to the engine coolant temperature Tw. This starting injection amount TAUSTA generally increases as the engine coolant temperature Tw decreases. Thereafter, the routine proceeds to step 804, where the starting injection amount TAUSTA is corrected by the intake air temperature Ta, the engine rotational speed Ne, etc., and this routine is terminated.
[0107]
Thereafter, when the start is completed and it is determined “Yes” in step 802, the process proceeds from step 802 in FIG. 22 to step 805 in FIG. 23, and the catalyst warm-up control execution flag XCAT means that the catalyst warm-up control execution condition is satisfied. It is determined whether it is “1”. If XCAT = 0, normal fuel injection control is executed in steps 806 to 809, and if XCAT = 1, fuel injection amount control for catalyst warm-up control is executed in steps 810 to 815.
[0108]
When XCAT = 0, first, in step 806, the basic injection amount Tp is calculated according to the engine rotational speed Ne and the intake pipe pressure PM using the normal basic injection amount map. In the next step 807, the air-fuel ratio is calculated. It is determined whether or not a feedback condition (F / B condition) is satisfied. The F / B conditions include that the engine coolant temperature Tw is equal to or higher than a predetermined temperature, that the engine is not in a high rotation / high load state, and that the air-fuel ratio sensor 32 is in an active state.
[0109]
If the F / B condition is not satisfied, the process proceeds to step 808, and the feedback correction coefficient FAF is set to “1.0”. On the other hand, if the feedback condition is satisfied, the routine proceeds to step 809, where the feedback correction coefficient FAF is calculated according to the deviation between the actual air-fuel ratio AFr (detected value of the air-fuel ratio sensor 32) and the target air-fuel ratio AFtg.
[0110]
After calculating the feedback correction coefficient FAF, the routine proceeds to step 816, where the post-startup increase coefficient FASE and the warm-up increase coefficient FWL are calculated according to the engine coolant temperature Tw. In the post-startup increase coefficient FASE, the fuel increase is performed only for several tens of seconds after the engine start, whereas in the warm-up increase coefficient FWL, the fuel increase is performed until the engine cooling water temperature Tw reaches a predetermined temperature. Thereafter, the process proceeds to step 817 to calculate another correction coefficient β such as an electric load increase of an air conditioner, etc., and in the next step 818, various corrections are applied to the basic injection amount Tp, and during normal fuel injection control. The fuel injection amount TAU (when XCAT = 0) is calculated by the following equation.
TAU = Tp × (FAF + FASE + FWL) × β
[0111]
On the other hand, if it is determined in step 805 that XCAT = 1 (catalyst warm-up control execution condition is satisfied), the ignition retard control is performed, so that the routine proceeds to step 810 to stabilize combustion, and FIG. Using the map shown, the target air-fuel ratio AFtg during the ignition retard control is calculated according to the retard correction amount θRE of the ignition timing. In the map of FIG. 25, the target air-fuel ratio AFtg is indicated by a hatched area, and the target air-fuel ratio AFtg is set closer to the stoichiometric air-fuel ratio (stoichiometric) as the retard correction value θRE is larger.
[0112]
After calculating the target air-fuel ratio AFtg, the process proceeds to step 811 and the basic injection amount Tp is calculated according to the engine speed Ne and the intake pipe pressure PM at that time using the map for each target air-fuel ratio AFtg stored in the ROM 45 in advance. To do.
[0113]
Thereafter, the process proceeds to step 812, where it is determined whether the air-fuel ratio sensor 32 is in an active state by, for example, whether the element temperature of the air-fuel ratio sensor 32 or the element resistance has reached a determination value corresponding to the active state, In the next step 813, it is determined whether or not the absolute value of the deviation between the target air-fuel ratio AFtg and the actual air-fuel ratio AFr is greater than or equal to a predetermined value.
[0114]
If “Yes” is determined in both of these steps 812 and 813, the process proceeds to step 815, and the update width ΔFD with respect to the correction value FD is set to an air-fuel ratio shift (AFtg−AFr) using the map shown in FIG. 26. The previous correction value FD is corrected by the update width ΔFD (FD = FD + ΔFD), and the stored value of the correction value FD in the backup RAM 47 is updated. This correction value FD is for quickly eliminating the deviation of the air-fuel ratio due to the open loop control at the start of the engine.
[0115]
On the other hand, if “No” is determined in any one of steps 812 and 813, that is, if the air-fuel ratio sensor 32 is inactive and the actual air-fuel ratio AFr cannot be accurately detected, or if the air-fuel ratio deviation (AFtg If -AFr) is less than the predetermined value and it is not necessary to update the correction value FD, the process proceeds to step 814 to use the correction value FD read from the backup RAM 47 as it is.
[0116]
After determining the correction value FD in step 814 or 815 in this way, the processing of steps 116 to 118 is executed, and the post-startup increase coefficient FASE, the warm-up increase coefficient FWL, and other correction coefficients β are calculated. Then, various corrections are made to the basic injection amount Tp, and the fuel injection amount TAU at the time of catalyst warm-up control (when XCAT = 1) is calculated by the following equation.
TAU = Tp × (1 + FD + FASE + FWL) × β
[0117]
The catalyst warm-up control according to the embodiment (6) described above is performed, for example, as shown in the time chart of FIG. In the example of FIG. 27, after the starter is turned on at time t1 and cranking is started, when the start-up is completed at time t2 and the catalyst warm-up control execution flag XCAT is set to “1”, the ignition timing θig is The exhaust gas temperature is raised by being controlled to the retard side by the retard correction value θRE with respect to the basic ignition timing θBSE. Then, the target air-fuel ratio AFtg of the exhaust gas is set according to this retardation correction value θRE, and the fuel injection amount is corrected.
[0118]
In addition, after time t2, the ISC valve 52 is adjusted to a predetermined opening degree, and the engine speed Ne is controlled to a starting speed (for example, 1200 rpm) higher than the idle speed (for example, 700 rpm) after warming up. . When the air-fuel ratio sensor 32 is activated at time t3, the correction value FD is updated with an update width ΔFD corresponding to the air-fuel ratio deviation (AFtg-AFr).
[0119]
Thereafter, when a predetermined time (for example, 15 seconds) elapses from time t2 and reaches time t4, the catalyst warm-up control execution flag XCAT is reset to "0". Thus, the catalyst warm-up control is completed, the ignition timing is gradually returned to the advance side, and the target air-fuel ratio AFtg is returned to the vicinity of the theoretical air-fuel ratio (stoichiometric).
[0120]
In the embodiment (6) described above, during the catalyst warm-up control, the target air-fuel ratio AFtg of the exhaust gas is set according to the ignition timing retardation correction value θRE, so that the retardation correction value θRE at that time is set. Accordingly, the fuel injection amount can be appropriately controlled, and the exhaust gas temperature can be raised while stabilizing the combustion state.
[0121]
Further, in this embodiment (6), when the engine speed Ne is controlled to a starting speed (for example, 1200 rpm) higher than the idle speed (for example, 700 rpm) after warming up, the catalyst warm-up control (ignition) is performed. (Retard angle control) is implemented, and the temperature rise effect of the exhaust gas temperature can be further enhanced in combination with the exhaust gas temperature increase by the rotational speed control at the start.
[0122]
Furthermore, in the present embodiment (6), the catalyst warm-up control is allowed to be performed during a period until a predetermined time (for example, 15 seconds) elapses after the start of the engine 11 is completed. Prolonging more than necessary can be prevented, and after a predetermined time has elapsed, the combustion state can be quickly stabilized by normal control.
[0123]
Further, in the present embodiment (6), multiple ignition is performed during catalyst warm-up control. Therefore, torque fluctuation during catalyst warm-up control can be suppressed by multiple ignition, and catalyst warm-up control is performed. It is possible to prevent the drivability from being degraded. In addition, instead of multiple ignition, ignition may be performed at a plurality of locations, and even in this case, a torque fluctuation suppressing effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.
FIG. 2 is a diagram for explaining the relationship among the distance from the engine exhaust port end face, the exhaust gas temperature, and the range of the secondary air introduction position;
FIG. 3 is a flowchart showing a flow of processing of a fuel injection control routine of the embodiment (1).
FIG. 4 is a flowchart showing a flow of processing of an ignition timing control routine of the embodiment (1).
FIG. 5 is a flowchart showing a flow of processing of a VVT control routine of the embodiment (1).
FIG. 6 is a flowchart showing a process flow of a secondary air introduction control routine of the embodiment (1).
FIG. 7 is a flowchart showing a process flow of a secondary air introduction determination routine of the embodiment (1).
FIG. 8 is a time chart showing an execution example of secondary air introduction control of the embodiment (1).
FIG. 9 is a flowchart showing a process flow of a secondary air introduction control routine according to the embodiment (2) of the present invention.
FIG. 10 is a time chart showing an execution example of secondary air introduction control of the embodiment (2).
FIG. 11 is a schematic configuration diagram of the main part on the engine exhaust side showing the embodiment (3) of the present invention.
FIG. 12 is a flowchart showing a process flow of a secondary air introduction control routine of the embodiment (3).
FIG. 13 is a time chart showing an execution example of secondary air introduction control of the embodiment (3).
FIG. 14 is a schematic configuration diagram of a main part on the engine exhaust side showing a modification (first example) of the embodiment (3).
FIG. 15 is a schematic configuration diagram of a main part on the engine exhaust side showing a modification (second example) of the embodiment (3).
FIG. 16 is a time chart (part 1) showing an execution example of secondary air introduction control according to the embodiment (4) of the present invention;
FIG. 17 is a time chart showing an execution example of secondary air introduction control of the embodiment (4) (part 2);
FIG. 18 is a time chart showing an execution example of secondary air introduction control according to the embodiment (5) of the present invention.
FIG. 19 is a schematic configuration diagram of an entire engine control system showing an embodiment (6) of the present invention.
FIG. 20 is a flowchart showing a process flow of a catalyst warm-up control execution condition determination routine according to the embodiment (6).
FIG. 21 is a flowchart showing a process flow of an ignition timing control routine according to the embodiment (6).
FIG. 22 is a flowchart (part 1) showing the flow of processing of a fuel injection control routine of the embodiment (6).
FIG. 23 is a flowchart (part 2) showing the flow of processing of the fuel injection control routine of the embodiment (6).
FIG. 24 is a diagram showing an example of a retard angle correction value map according to engine coolant temperature.
FIG. 25 is a diagram showing an example of a target air-fuel ratio map according to a retard angle correction value;
FIG. 26 is a view showing an example of a map of an update width ΔFD corresponding to an air-fuel ratio deviation.
FIG. 27 is a time chart showing an execution example of the embodiment (6).
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 17 ... Fuel injection valve, 18 ... Spark plug, 19 ... Intake valve, 20 ... Exhaust valve, 23, 24 ... Variable valve timing mechanism, 30 ... Exhaust pipe (exhaust gas passage), 31 ... Catalyst 32 ... Air-fuel ratio sensor, 34 ... Secondary air introduction device, 35 ... Secondary air introduction pipe (secondary air introduction passage), 37 ... Air pump, 38 ... Combination valve, 39 ... Open / close valve, 40 ... Check valve, 41 ... Intake pressure introduction pipe, 42 ... Switching valve, 43 ... ECU (exhaust gas temperature rise control means, secondary air introduction control means), 48 ... Secondary air introduction pipe (secondary air introduction passage), 48a-48c ... Introduction 49, an introduction position switching valve, 50 ... an on-off valve.

Claims (22)

In a control device for an internal combustion engine in which a catalyst for purifying exhaust gas is installed in an exhaust gas passage of the internal combustion engine,
An exhaust gas temperature raising control means for controlling combustion of the internal combustion engine so that a rich component in the exhaust gas becomes an exhaust gas temperature that can be burnt afterward in the exhaust gas passage on the upstream side of the catalyst;
A secondary air introduction device for introducing secondary air for generating the afterburning into the exhaust gas passage on the upstream side of the catalyst;
Secondary air introduction control means for controlling the secondary air introduction device;
Air-fuel ratio feedback control means for feedback-controlling the air-fuel ratio of the exhaust gas to the target air-fuel ratio based on the output of the air-fuel ratio sensor for detecting the air-fuel ratio of the exhaust gas,
When the air-fuel ratio feedback control means introduces the secondary air, when the catalyst is required to warm up, the air-fuel ratio of the exhaust gas upstream of the secondary air introduction position is the theoretical air that is the catalyst purification window. Means for controlling near the fuel ratio, and means for controlling the air-fuel ratio of the exhaust gas upstream of the secondary air introduction position to be richer than the stoichiometric air-fuel ratio when the vehicle travels when introducing secondary air A control device for an internal combustion engine. The control apparatus for an internal combustion engine according to claim 1, wherein the secondary air introduction control means introduces secondary air when a warm-up request for the catalyst is generated. The secondary air introduction control means introduces secondary air when a request to reduce hydrocarbons flowing into the catalyst is generated or when a request to reduce nitrogen oxides flowing out from the catalyst is generated. The control apparatus for an internal combustion engine according to claim 1 or 2 . The control apparatus for an internal combustion engine according to any one of claims 1 to 3 , wherein the secondary air introduction control means introduces secondary air when the exhaust gas temperature is combustible. The secondary air induction control means, a control apparatus for an internal combustion engine according to any of claims 1 to 4, characterized in that the introduction of secondary air after the first explosion occurs in the cylinder during starting. The control apparatus for an internal combustion engine according to any one of claims 1 to 5 , wherein the secondary air introduction control means prohibits the introduction of secondary air until a predetermined period has elapsed from the start. The control apparatus for an internal combustion engine according to any one of claims 1 to 5 , wherein the secondary air introduction control means prohibits introduction of secondary air when a request to lower the exhaust gas temperature is generated. The secondary air introduction control means controls the flow rate of the secondary air introduced according to the elapsed time from the start, the elapsed time from the request for warming up of the catalyst, or the elapsed time from the time when the exhaust gas temperature decreases. control apparatus for an internal combustion engine according to any of claims 1 to 7, characterized. The control apparatus for an internal combustion engine according to any one of claims 1 to 8 , wherein the air-fuel ratio sensor is installed downstream of a secondary air introduction position. The secondary air introduction device integrates an air pump that pumps secondary air into a secondary air introduction passage connected to the exhaust gas passage, and an on-off valve and a check valve that open and close the secondary air introduction passage. A combination valve and a switching valve for switching the driving pressure of the on-off valve;
The secondary air introduction control means controls the introduction / introduction of secondary air by controlling the switching valve to switch the driving pressure of the on-off valve to open / close the on-off valve. Item 10. The control device for an internal combustion engine according to any one of Items 1 to 9 . The control apparatus for an internal combustion engine according to any one of claims 1 to 10 , wherein the secondary air introduction device introduces secondary air into a plurality of locations of the exhaust gas passage on the upstream side of the catalyst. The secondary air injection is any one of claims 1 to 11, characterized in that the exhaust gas temperature of the exhaust gas passage of the catalyst upstream introduces secondary air to a position where the after-burning temperature range capable The control apparatus of the internal combustion engine described in 1. The control device for an internal combustion engine according to any one of claims 1 to 12 , wherein the exhaust gas temperature raising control means controls the ignition timing of the internal combustion engine to be retarded from the warm-up time when the engine is cold. . The control device for an internal combustion engine according to claim 13 , wherein the exhaust gas temperature raising control means controls the air-fuel ratio of the in-cylinder mixture to be close to the theoretical air-fuel ratio or slightly rich. The control device for an internal combustion engine according to claim 13 or 14 , wherein the exhaust gas temperature raising control means sets a target air-fuel ratio of exhaust gas based on an ignition timing retard amount during ignition retard control. The internal combustion engine according to claim 15 , wherein the exhaust gas temperature raising control means sets the target air-fuel ratio of the exhaust gas closer to the stoichiometric air-fuel ratio as the ignition timing retard amount during the ignition retard control is larger. Control device. A variable valve timing mechanism that variably controls the opening / closing timing of at least one of an intake valve and an exhaust valve of an internal combustion engine;
The exhaust gas Atsushi Nobori control means, in any one of claims 1 to 16, characterized by controlling the temperature range capable of afterburning of the exhaust gas temperature by controlling the valve overlap amount of the exhaust valve and the intake valve The internal combustion engine control device described. A variable valve timing mechanism that variably controls the opening / closing timing of at least one of an intake valve and an exhaust valve of an internal combustion engine;
The exhaust gas Atsushi Nobori control means, in any one of claims 1 to 17, characterized by controlling the temperature range capable of afterburning of the exhaust gas temperature by controlling the opening timing of the exhaust valve to the advance side The internal combustion engine control device described. The control apparatus for an internal combustion engine according to any one of claims 1 to 18 , wherein the exhaust gas temperature raising control means determines whether or not to perform the exhaust gas temperature raising control based on an engine operating state. The exhaust gas temperature raising control means performs exhaust gas temperature raising control when the engine speed is controlled to be higher than the idling speed after warm-up at the time of cold start. Item 20. The control device for an internal combustion engine according to any one of Items 1 to 19 . The control apparatus for an internal combustion engine according to any one of claims 1 to 20 , wherein the exhaust gas temperature increase control means prohibits the exhaust gas temperature increase control after a predetermined time has elapsed from the start. The control apparatus for an internal combustion engine according to any one of claims 1 to 21 , wherein the exhaust gas temperature increase control means performs torque fluctuation suppression control that suppresses torque fluctuation during the exhaust gas temperature increase control.

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