JP3870430B2 - In-cylinder internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an in-cylinder injection type internal combustion engine that can inject fuel directly into a combustion chamber and perform a lean combustion operation, and in particular, when a lean NOx catalyst is deteriorated due to adhesion of a purification ability reducing substance, the purification ability reduction substance is removed. The present invention relates to a direct injection internal combustion engine that can regenerate a lean NOx catalyst.
[0002]
[Prior art]
There are engines such as an internal combustion engine (hereinafter referred to as an engine) mounted on an automobile that burns a lean air-fuel mixture. In such an engine, the amount of NOx in the exhaust gas increases during lean operation. Therefore, in order to purify the exhaust gas in such an engine, there is an exhaust system in which a lean NOx catalyst or a combination of a lean NOx catalyst and a three-way catalyst is installed.
[0003]
Such a lean NOx catalyst is provided with a NOx absorbent in the exhaust passage that absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean and releases the absorbed NOx when the oxygen concentration in the inflowing exhaust gas decreases. The NOx generated when the lean air-fuel mixture is burned is absorbed by the NOx absorbent, and the air-fuel ratio of the exhaust gas flowing into the NOx absorbent is temporarily made rich before the NOx absorbent capacity is saturated. Then, there is one that reduces NOx from the NOx absorbent and releases it.
[0004]
As described above, when NOx is reduced from the NOx absorbent, the hydrocarbon (HC) is made to exist in the exhaust gas by temporarily enriching the air-fuel ratio of the exhaust gas so that the hydrocarbon (HC) exists in the exhaust gas. ) As a reducing agent to the NOx absorbent. For example, Japanese Patent Laid-Open No. 6-117225 discloses a technique related to such reduction of NOx. With this technology, fuel can be sub-injected during the expansion and exhaust strokes of the engine, and the molecular structure of hydrocarbons (HC) can be decomposed into smaller ones using combustion heat to efficiently reduce NOx. It is to make.
[0005]
By the way, since sulfur is contained in fuel and engine lubricating oil, the exhaust gas contains sulfur such as sulfate (hereinafter simply referred to as sulfur), and this sulfur is also absorbed by the NOx absorbent together with NOx. Is done. However, since this sulfur is not released from the NOx absorbent even if the air-fuel ratio of the exhaust gas flowing into the NOx absorbent is simply made rich, the amount of sulfur in the NOx absorbent gradually increases. As the amount of absorption increases, the amount of NOx that can be absorbed by the NOx absorbent gradually decreases, and eventually the NOx absorbent can hardly adsorb NOx.
[0006]
In addition, the above-mentioned JP-A-6-117225 particularly suggests that a poisoning substance that lowers the purification ability such as sulfur that lowers the performance of such a lean NOx catalyst is adsorbed by the NOx absorbent. Absent.
Sulfur absorbed in the NOx absorbent is decomposed and released from the NOx absorbent by heating the NOx absorbent, and at this time, if the air-fuel ratio is made rich or stoichiometric, it is released from the NOx absorbent. Sulfur is immediately reduced by unburned HC and CO in the exhaust gas.
[0007]
Therefore, for example, in the technique disclosed in Japanese Patent Laid-Open No. 6-66129, focusing on such characteristics, when a specific condition is satisfied, the NOx absorbent is heated to further perform rich operation or stoichiometric operation. By performing this, sulfur is released from the NOx absorbent, and is further oxidized and discharged. The specific condition in this case is that the amount of sulfur absorbed in the NOx absorbent reaches a predetermined amount, and the NOx absorbent is heated by operating an electric heater installed in the exhaust system. It is like that.
[0008]
[Problems to be solved by the invention]
By the way, the above-described conventional techniques have the following problems.
In other words, the technique disclosed in Japanese Patent Laid-Open No. 6-117225 cannot cope with a decrease in the performance of the lean NOx catalyst due to a substance having a reduced purification ability such as sulfur.
In the technique disclosed in Japanese Patent Laid-Open No. 6-66129, a device for heating a catalyst such as an electric heater is required in the exhaust system, resulting in an increase in cost and an increase in the size of the exhaust system.
[0009]
By the way, as a means for heating the catalyst, it is conceivable to supply the fuel to the catalyst and burn the fuel in the vicinity of the catalyst. In order to supply fuel to the catalyst, it is conceivable to operate the engine with the air-fuel ratio in a rich state. For example, if the lean combustion operation and the rich combustion operation are repeated, the cost increases and the exhaust system becomes larger. The catalyst can be heated to a required temperature without being invited, and the purification ability reducing substance can be removed from the lean NOx catalyst to perform the catalyst restoration process.
[0010]
However, if the air-fuel ratio is changed from lean to stoichiometric or rich during driving, torque fluctuations occur and the driving performance is deteriorated. To avoid this, such a catalyst restoration process is performed in a low load region or a low load. It is not used in the rotation region, and it is difficult to perform reliable catalyst recovery.
Furthermore, when the air-fuel ratio is changed from lean to stoichiometric or rich during traveling, there is also a problem that fuel consumption deteriorates.
[0011]
The present invention was devised in view of the above-mentioned problems, and it is possible to reliably and appropriately remove the purification ability-decreasing substance adsorbed on the lean NOx catalyst while preventing torque fluctuations. An object of the present invention is to provide a cylinder injection type internal combustion engine.
[0012]
[Means for Solving the Problems]
  For this reason, the direct injection internal combustion engine according to the first aspect of the present invention includes a fuel injection valve that directly injects fuel into the combustion chamber of the internal combustion engine, and makes the air-fuel ratio larger than the stoichiometric air-fuel ratio to perform a lean combustion operation. In a cylinder injection type internal combustion engine that can perform the operation, an exhaust passage that exhausts exhaust gas from the combustion chamber, and a lean NOx that is installed in the exhaust passage and absorbs nitrogen oxides (NOx) in the exhaust gas during lean combustion operation Based on the operating state of the internal combustion engine detected by the catalyst, the operating state detecting means for detecting the operating state of the internal combustion engine, and the operating state detecting meansIn addition to the normal fuel injection performed for combustion in the combustion chamber, the combustion in the combustion chamber should not be affected.Fuel injection valve control means for operating the fuel injection valve in the exhaust stroke of the internal combustion engine to supply additional fuel to the lean NOx catalyst;The fuel injection valve control means raises the lean NOx catalyst when the temperature of the lean NOx catalyst is lower than a predetermined temperature that is a lower limit value of a decomposable temperature range of the purification ability reducing substance attached to the lean NOx catalyst. When the temperature of the lean NOx catalyst is equal to or higher than the predetermined temperature, the injection amount is adjusted so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio for heating. Adjust the injection amount so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio in order to decompose the reduced purification capacity material adhering to the lean NOx catalyst and reduce it to a less harmful substance. Supplying the additional fuelIt is characterized by that.
[0013]
With this configuration, the engine can be operated while directly injecting fuel from the fuel injection valve into the combustion chamber, and the lean combustion operation can be performed with the air-fuel ratio made larger than the stoichiometric air-fuel ratio.
During the lean combustion operation of such an engine, nitrogen oxide (NOx) generated in the exhaust gas is absorbed by the lean NOx catalyst installed in the exhaust passage, and NOx emission is suppressed.
[0014]
  Such a lean NOx catalyst is gradually attached with a substance having a reduced purification capacity as NOx is adsorbed. However, the fuel injection valve control means appropriately adjusts the exhaust stroke of the engine based on the operating state of the internal combustion engine. The fuel injection valve is operated to supply additional fuel to the lean NOx catalyst.
  Since this additional fuel is injected from the fuel injection valve in the exhaust stroke, it is not used for combustion in the combustion chamber and is supplied to the lean NOx catalyst together with the exhaust. A part of such additional fuel is burned in the process of reaching the lean NOx catalyst by the heat of the high-temperature exhaust gas, and the fuel that has reached the lean NOx catalyst is catalyzed and burned. Due to this combustion, the lean NOx catalyst is heated, and the purification ability reducing substance adhering to the lean NOx catalyst is decomposed and removed. By performing the additional fuel injection in the exhaust stroke, the injection of the additional fuel does not affect the combustion in the normal combustion chamber.
  In addition, when the temperature of the lean NOx catalyst is lower than a predetermined temperature that is the lower limit value of the decomposable temperature range of the purification ability reducing substance attached to the lean NOx catalyst, the air-fuel ratio is increased for the purpose of raising the temperature of the lean NOx catalyst. When the amount of fuel is adjusted so that the fuel injection is adjusted to be leaner than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, additional fuel is supplied, and when the temperature of the lean NOx catalyst is equal to or higher than the predetermined temperature, the purification capacity attached to the lean NOx catalyst decreases. In order to decompose the substance and reduce it to a less harmful substance, by adjusting the injection amount so that the air-fuel ratio is richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, the decomposable temperature of the substance with reduced purification capacity can be obtained. The additional fuel is efficiently supplied without using the additional fuel amount outside the region.
A cylinder injection type internal combustion engine according to a second aspect of the present invention is the cylinder injection internal combustion engine according to the first aspect, wherein the internal combustion engine has a plurality of cylinders, and the fuel injection valve is provided for each cylinder. The operation phase of each of the plurality of cylinders is set such that the opening timings of the respective exhaust ports partially overlap, and the fuel injection control means The cylinders whose exhaust port opening times overlap each other are characterized in that the fuel injection valves provided in the respective cylinders are operated simultaneously. Thereby, the control concerning the drive operation of the fuel injection valve is reduced.
According to a third aspect of the present invention, the direct injection internal combustion engine of the present invention includes a fuel injection valve that directly injects fuel into the combustion chamber of the internal combustion engine, and can perform a lean combustion operation with an air-fuel ratio larger than the stoichiometric air-fuel ratio. In a cylinder injection internal combustion engine, an exhaust passage that exhausts exhaust gas from the combustion chamber, a lean NOx catalyst that is installed in the exhaust passage and absorbs nitrogen oxide (NOx) in the exhaust gas during lean combustion operation, An operating state detecting means for detecting the operating state of the internal combustion engine, and normal fuel injection performed for combustion in the combustion chamber based on the operating state of the internal combustion engine detected by the operating state detecting means And a fuel injection valve control means for operating the fuel injection valve in the exhaust stroke of the internal combustion engine to supply additional fuel to the lean NOx catalyst so as not to affect the combustion in the combustion chamber. Duplicate The fuel injection valve is provided for each cylinder, and the opening timing of each exhaust port partially overlaps among at least some of the plurality of cylinders. Thus, the fuel injection control means operates the fuel injection valves provided in the respective cylinders at the same time for the cylinders in which the operation phases are set so that the opening timings of these exhaust ports overlap each other. Is configured toIt is characterized by that.
[0015]
  Claim4The in-cylinder injection type internal combustion engine of the present invention described in claim 1In any one of ~ 3In the configuration described above, the operation state detection means includes an adhesion amount estimation means for estimating the adhesion amount of the substance having reduced purification ability to the lean NOx catalyst and determining whether or not the adhesion amount has reached a predetermined amount. When the fuel injection valve control means determines that the adhesion amount of the purification ability reducing substance to the lean NOx catalyst has reached a predetermined amount by the adhesion amount estimation means, the fuel injection control unit performs the fuel injection in the exhaust stroke of the internal combustion engine. The additional fuel is supplied to the lean NOx catalyst by operating a valve.
[0016]
  With this configuration, when the purification ability decreasing substance gradually adheres to the lean NOx catalyst while adsorbing NOx, the adhesion amount estimating means estimates the adhesion amount of the purification ability decreasing substance. If it can be determined that the amount of the substance that reduces the purification ability on the lean NOx catalyst has reached the predetermined amount based on the estimation by the adhesion amount estimation means, the fuel injection valve control means operates the fuel injection valve in the exhaust stroke of the engine. To supply additional fuel to the lean NOx catalyst.
[0017]
  Claim5The in-cylinder injection internal combustion engine of the present invention described in claim4In the described configuration, the adhesion amount estimation means is configured to estimate the adhesion amount of the purification ability reducing substance to the lean NOx catalyst based on the integrated value of the intake air amount during the lean combustion operation. It is characterized by.
  Such estimation is based on the following idea. In other words, since the purification ability reducing substance such as sulfur adheres to the lean NOx catalyst together with NOx, the adhesion quantity of the purification ability reducing substance to the lean NOx catalyst is the amount of NOx absorbed and further the amount of NOx generated in the lean combustion operation. Can be guessed. This NOx generation amount is considered to correspond to the intake air amount during the lean combustion operation. Therefore, it is possible to estimate the amount of the purification ability reducing substance adhering to the lean NOx catalyst based on the integrated value of the intake air amount during the lean combustion operation.
[0018]
  Claim6The in-cylinder injection internal combustion engine of the present invention described in claim4In the described configuration, the adhesion amount estimation means is configured to estimate the adhesion amount of the purification ability lowering substance to the lean NOx catalyst based on the integrated value of the fuel consumption during the lean combustion operation. It is characterized by.
  As described above, since the deteriorating ability reducing substance such as sulfur adheres to the lean NOx catalyst together with NOx, the attached amount of the deteriorating ability reducing substance in the lean NOx catalyst is the amount of NOx absorbed and further lean combustion. It can be estimated that this corresponds to the amount of NOx generated during operation, and this amount of NOx generated is considered to correspond to the fuel consumption during the lean combustion operation. Accordingly, it is possible to estimate the amount of the purification ability reducing substance adhering to the lean NOx catalyst based on the integrated value of the fuel consumption during the lean combustion operation.
[0019]
  Claim7The in-cylinder injection internal combustion engine of the present invention described in claim4In the described configuration, the adhesion amount estimation means is configured to estimate the adhesion amount of the purification ability lowering substance to the lean NOx catalyst based on an integrated value of the travel distance by the lean combustion operation. It is said.
  As described above, since the deteriorating ability reducing substance such as sulfur adheres to the lean NOx catalyst together with NOx, the attached amount of the deteriorating ability reducing substance in the lean NOx catalyst is the amount of NOx absorbed and further lean combustion. It can be estimated that this corresponds to the amount of NOx generated during operation, and this amount of NOx generated is considered to correspond to the travel distance of the lean combustion operation. Therefore, it is possible to estimate the amount of the purification ability reducing substance adhering to the lean NOx catalyst based on the integrated value of the travel distance by the lean combustion operation.
[0020]
  Claim8The in-cylinder injection internal combustion engine of the present invention described in claim4In the configuration described above, the adhesion amount estimation means is configured to estimate the adhesion amount of the purification ability lowering substance to the lean NOx catalyst based on an integrated value of the travel time by the lean combustion operation. It is said.
  In the same way as described above, since the purification ability reducing substance such as sulfur adheres to the lean NOx catalyst together with NOx, the attached amount of the purification ability reducing substance in the lean NOx catalyst is the amount of NOx absorbed and further lean combustion. It can be estimated that this corresponds to the amount of NOx generated during operation, and this amount of NOx generated is considered to correspond to the travel time of the lean combustion operation. Therefore, it is possible to estimate the amount of the purification ability reducing substance adhering to the lean NOx catalyst based on the integrated value of the travel time by the lean combustion operation.
[0022]
  Claim9The in-cylinder injection type internal combustion engine of the present invention described in claim 1In any one of -8In the described configuration, the fuel injection valve control means is configured to inject the additional fuel in a plurality of times while operating the fuel injection valve a plurality of times during an exhaust stroke in one operation cycle. It is a feature. In this way, by performing the injection of the additional fuel in a plurality of times, the time for one injection can be shortened, and the drop in the fuel injection pressure, which is likely to occur due to the long-time injection by the fuel injection valve, is avoided. Atomization is reliably performed, and the additional fuel can be burned quickly and without waste.
[0023]
  Claim10The in-cylinder injection type internal combustion engine of the present invention described in claim 1To any one of -9In the configuration described above, a catalyst temperature state detection means for detecting the temperature state of the lean NOx catalyst is provided, and the fuel injection valve control means is based on the detection result of the catalyst temperature state detection means after the supply of the additional fuel is started. Thus, the supply of the additional fuel is stopped when the temperature of the lean NOx catalyst reaches or exceeds a predetermined temperature for a predetermined time or longer.
[0024]
  An in-cylinder injection internal combustion engine according to an eleventh aspect of the present invention is the configuration according to any one of the first to tenth aspects, further comprising catalyst temperature state detection means for detecting the temperature state of the lean NOx catalyst, The fuel injection valve control meansIs, Based on the detection result of the catalyst temperature state detection means,Supplying the additional fuel by adjusting the injection amountIt is characterized by that.
[0025]
  Claim12The in-cylinder injection type internal combustion engine of the present invention described in claim 1To any one of ~ 11In the configuration described above, the lean NOx catalyst is characterized in that it carries at least one component of an alkali metal such as potassium, an alkaline earth such as barium, and a rare earth such as lanthanum.
  A direct injection internal combustion engine according to a thirteenth aspect of the present invention is the cylinder injection internal combustion engine according to any one of the first to twelfth aspects, wherein the fuel injection valve control means raises the lean NOx catalyst to the predetermined temperature. If the lean NOx catalyst is made rich to generate excessive heat and the temperature rises excessively, the normal fuel injection is performed for combustion in the combustion chamber without performing the additional injection. Thus, the air-fuel ratio is stoichiometric or rich.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, a direct injection internal combustion engine as a first embodiment will be described with reference to FIGS.
FIG. 2 is a schematic configuration diagram showing this in-cylinder injection type internal combustion engine. In FIG. 2, reference numeral 1 denotes a gasoline engine body of an automobile internal combustion engine (hereinafter referred to as an engine). The ignition system and the like are configured to be capable of lean combustion.
[0027]
The engine body 1 is particularly configured as an in-cylinder injection engine that directly injects fuel into each cylinder. For this reason, each cylinder has a fuel injection port directly facing the combustion chamber 2 so that the fuel A fuel injection valve (injector) 3 as a supply means is attached.
In this embodiment, the engine body 1 is configured as a four-cylinder in-line engine. However, the number of cylinders is not limited to this, and the engine type is applicable to various engines such as a V-type engine and a horizontally opposed engine. it can.
[0028]
An intake passage 5 communicating with the combustion chamber 2 via an intake valve 4 includes an intake port 5A formed for each cylinder, an intake manifold 5B coupled to each of these intake ports 5A, and an intake manifold 5B. A surge tank 5C provided in the upstream portion and an intake pipe 5D coupled to the upstream end of the intake manifold 5B are configured. The intake passage 5 is provided with an air cleaner 6, an air flow sensor 7 for detecting an intake air amount Af, a throttle valve 8, and an ISC (idle speed control) valve (not shown) from the upstream side. An intake air temperature sensor 9 and an atmospheric pressure sensor 10 are provided in the case of the air cleaner 6.
[0029]
As the air flow sensor 7, for example, a Karman vortex air flow sensor or the like is used. The ISC valve is for controlling the idling speed, and adjusts the valve opening according to the fluctuation of the engine load Le due to the operation of an air conditioner (not shown) to change the intake air amount to perform the idling operation. Stabilize. In addition, this ISC valve operates on the valve opening side at the time of air-fuel ratio correction control, which will be described later, and acts to compensate for a decrease in output accompanying the execution of air-fuel ratio correction.
[0030]
An exhaust passage 12 that communicates with the combustion chamber 2 via an exhaust valve 11 includes an exhaust port 12A formed for each cylinder, an exhaust manifold 12B coupled to each of these exhaust ports 12A, and an exhaust manifold 12B. The exhaust pipe 12C is coupled to the upstream side. An exhaust gas purification catalyst (hereinafter referred to as catalyst) 13 is installed in such an exhaust passage 12.
[0031]
The catalyst 13 is configured, for example, as an underfloor catalyst installed under the floor of the vehicle, and includes two catalysts, a lean NOx catalyst 13A and a three-way catalyst 13B, and the lean NOx catalyst 13A is more than the three-way catalyst 13B. Arranged upstream. The lean NOx catalyst 13A is provided with a NOx absorbent, adsorbs NOx (nitrogen oxides) in an oxidizing atmosphere such as when operating in a lean state of the air-fuel ratio (lean combustion operation), and produces HC (carbonization). In a reducing atmosphere where hydrogen is present, NOx is replaced by N₂It has a function of reducing to (nitrogen) or the like.
[0032]
As the NOx catalyst 13A, for example, a catalyst made of Pt having heat deterioration resistance and an alkali rare earth such as lanthanum or cerium is used. On the other hand, the three-way catalyst 13B has the function of oxidizing HC and CO (carbon monoxide) and reducing NOx. The reduction of NOx by the three-way catalyst 13B is near the stoichiometric air-fuel ratio (14.7). It is to be promoted to the maximum.
[0033]
An air-fuel ratio sensor 14 is provided at a location near the combustion chamber 2 upstream of the catalyst 13. As the air-fuel ratio sensor 14, for example, a linear A / F sensor (global air-fuel ratio sensor) is used, and the air-fuel ratio supplied to the combustion chamber 2 based on the oxygen concentration of the exhaust gas discharged from the combustion chamber 2 is used. The air-fuel ratio can be detected in a wide area.
[0034]
Further, an oxygen sensor 15 is provided at a location near the catalyst 13 on the downstream side of the catalyst 13. The oxygen sensor 15 can detect whether the air-fuel ratio of the air-fuel mixture supplied to the lean NOx catalyst 13A among the catalysts 13 is higher than the stoichiometric air-fuel ratio based on the oxygen concentration of the exhaust gas exhausted from the catalyst 13. Anything is acceptable.
Further, the catalyst 13 is provided with a catalyst temperature sensor 16 for detecting the temperature of the catalyst body. The catalyst temperature sensor 16 detects the temperature of the catalyst body through a catalyst bed (not shown), and is particularly configured as a high temperature sensor that can detect the temperature of the NOx catalyst 13A up to a high temperature range. The catalyst temperature sensor 16 can also function as exhaust temperature estimation means for estimating the exhaust temperature from the engine 1.
[0035]
The engine body 1 is also provided with a spark plug 17 for igniting a mixture of air supplied from the intake port 5A to the combustion chamber 2 and fuel supplied from the injector 3 into the combustion chamber 2 for each cylinder. Is arranged. Reference numeral 18 denotes a throttle opening sensor (throttle sensor) that detects the opening θTH of the throttle valve 7, and 19 is a water temperature sensor that detects the cooling water temperature TW.
[0036]
An ECU (electronic control unit) 23 is installed in order to perform air-fuel ratio control, ignition timing control, intake air amount control, control related to an exhaust gas purification catalyst 13, which will be described later, and the like.
The hardware configuration of the ECU 23 is as shown in FIG. 3. The ECU 23 includes a CPU 27 as a main part thereof, and the CPU 27 includes the intake air temperature sensor 9, the atmospheric pressure sensor 10, and the air-fuel ratio sensor. 14. In addition to detection signals from the oxygen sensor 15, the catalyst temperature sensor 16, the throttle sensor 18, and the water temperature sensor 19, an accelerator position sensor 24 that detects the amount of depression of the accelerator pedal, a battery sensor 25 that detects the battery voltage, and a vehicle Each detection signal from the distance meter 26 that counts the travel distance of the vehicle by a vehicle speed pulse integrated value or the like is also input via the input interface 28 and the analog / digital converter 30.
[0037]
Further, the air flow sensor 7, the cranking switch [or ignition switch (key switch)] 20 for detecting the start time, the crank angle sensor 21 for detecting the crank angle synchronization signal θCR from the encoder linked to the camshaft, the first cylinder (reference) Detection signals from a TDC sensor (cylinder discrimination sensor) 22, an idle switch 33, an ignition switch, and the like for detecting the top dead center of the cylinder) are input via an input interface 29.
[0038]
The engine rotation speed (engine rotation speed) Ne is calculated from the generation time interval of the crank angle synchronization signal θCR detected by the crank angle sensor 21, so the crank angle sensor 21 that detects the crank angle detects the engine rotation speed. Also serves as a rotation speed sensor. The crank angle sensor 21 and the TDC sensor 22 are provided in the distributor.
[0039]
Further, the CPU 27 holds the stored contents while the ROM 31 for storing program data and fixed value data, the RAM 32 to be updated and sequentially rewritten, the free running counter 48 and the battery are connected via the bus line. Thus, data is exchanged with a battery backup RAM (not shown) backed up.
[0040]
The data in the RAM 32 is erased and reset when the ignition switch is turned off.
In FIG. 3, the fuel injection control signal based on the calculation result by the CPU 27 is mainly shown in FIG. 3 regarding the fuel injection control. The injection driver 34 opens and closes the injector 3 while turning on / off the power supply from the battery to the solenoid (injector solenoid) 3a of the injector 3 (more precisely, the transistor for the injector solenoid 3a). It is like that.
[0041]
Now, paying attention to the fuel injection control (air-fuel ratio control), the fuel injection control signal calculated by the CPU 27 is output via the driver 34. For example, in the case of a four-cylinder engine, the four injectors 3 are sequentially driven. It is like that.
And, from the characteristics of the in-cylinder injection engine as described above, in this engine, as a mode of fuel injection, a late injection mode in which fuel injection is performed at the latter stage of the compression stroke in order to realize operation by lean combustion (lean operation); In order to realize the operation by stoichiometric air-fuel ratio combustion (theoretical air-fuel ratio operation or stoichiometric operation), an early-stage injection mode in which fuel injection is terminated at the initial stage or the previous period of the intake stroke is provided. During this theoretical air-fuel ratio operation, if the amount of fuel to be supplied is large, fuel injection may be started from the latter stage or the last stage of the exhaust stroke, and the fuel injection may be terminated at the beginning or the first half of the intake stroke.
[0042]
A description will be given of a part related to the lean NOx catalyst characteristic of the direct injection internal combustion engine among the functions of the ECU 23. As shown in FIG. 1, the ECU 23 includes a lean combustion operation region determination unit 101 and an adhesion amount estimation unit 102. And a fuel injection valve control means 103 are provided.
Among these, the lean combustion operation region determination means 101 is based on the information on the engine speed Ne detected by the engine speed sensor (crank angle sensor) 21 and the information on the throttle opening θTH detected by the throttle sensor 18. For example, the lean combustion operation is performed as the lean combustion operation mode in the low load region or the low rotation region, and the theoretical air fuel ratio operation or the rich combustion operation is performed as the stoichiometric air fuel ratio or the rich combustion operation mode in the high load region or the high rotation region. To do.
[0043]
The adhesion amount estimation means 102 has a function (adhesion amount estimation unit) 102A for estimating the adhesion amount of a deteriorating purification ability substance (poisoning substance) such as sulfur adhering to the lean NOx catalyst 13A, and purifies sulfur and the like from this estimated value. A function (adhesion limit determination unit) 102B for determining that the amount of adhesion of the capacity-decreasing substance has reached a predetermined limit amount.
In other words, since sulfur is contained in the fuel and engine lubricating oil, the exhaust gas contains sulfur such as sulfate (hereinafter simply referred to as sulfur), and this sulfur is also absorbed by the NOx absorbent together with NOx. As the amount of sulfur absorbed increases, the amount of NOx that can be absorbed by the NOx absorbent, that is, the purification capacity decreases.
[0044]
However, it is difficult to detect the amount of the substance having reduced purification ability such as sulfur that has actually adhered to the lean NOx catalyst 13A.
Therefore, the adhesion amount estimation unit 102A of the adhesion amount estimation means 102 estimates the adhesion amount of the purification ability reducing substance using the quantity considered to correspond to the adhesion quantity of the purification ability reducing substance such as sulfur as a parameter. is there.
[0045]
That is, the amount of sulfur or the like attached is considered to correspond to the amount of exhaust gas purification during the lean combustion operation. For example, the lean combustion is premised on the lean operation information from the lean combustion operation region determination means 101. Based on the integrated value of the intake air amount during operation or the integrated value of the fuel consumption amount during lean combustion operation, the attached amount of the purification ability reducing substance such as sulfur adhering to the lean NOx catalyst 13A is estimated in this way. In addition, more simply, the travel distance by the lean combustion operation or the travel time by the lean combustion operation (lean combustion operation time) can be estimated.
[0046]
The integrated value of the intake air amount during the lean combustion operation is the number of pulses AP of the air flow sensor during the lean combustion operation._LEANThe integrated value of the fuel consumption during the lean combustion operation is the injector drive time T during the lean combustion operation._LEANCan be obtained. The travel distance by the lean combustion operation is the count information D from the travel distance meter 26 during the lean combustion operation._LEANThe lean combustion operation time is calculated by operating the timer during the lean combustion operation and counting information TR._LEANCan be obtained from
[0047]
Here, in the adhesion amount estimation unit 102A, the number of pulses AP of these airflow sensors_LEAN, Injector drive time T_LEAN, Mileage meter count information D_LEANOr timer count information TR_LEANAccumulate one of the following.
Then, in the adhesion limit determination unit 102B, such integrated value (lean state integrated value) AP_LEAN, T_LEAN, D_LEANOr TR_LEANIs equal to or higher than a preset threshold value AP0, T0, D0, or TR0, it is determined that a substance having reduced purification capacity such as sulfur has adhered to the lean NOx catalyst 13A up to the limit amount. In this case, lean NOx A catalyst recovery signal (or a catalyst regeneration signal) is output for recovering (or regenerating) the ability of the catalyst 13A by removing a purification ability reducing substance such as sulfur from the catalyst 13A.
[0048]
The fuel injection valve control means 103 has two functions for controlling the fuel injection valve 3, that is, a normal fuel injection control unit 104 and a catalyst reinstatement fuel injection control unit 105. In the normal fuel injection control unit 104, The fuel injection control for combustion in the combustion chamber 2 (injection from the intake stroke to the compression stroke) is performed. The catalyst reinstatement fuel injection control unit 105 performs control for catalyst reinstatement, that is, the lean NOx catalyst 13A. Control of fuel injection for heating and placing in a rich or stoichiometric atmosphere.
[0049]
In the catalyst restoration fuel injection control unit 105, by supplying fuel to the lean NOx catalyst 13A, the temperature of the lean NOx catalyst 13A is increased by combustion of the fuel, and after the temperature of the lean NOx catalyst 13A is increased to a predetermined temperature, In order to place the lean NOx catalyst 13A in a rich or stoichiometric atmosphere, control is performed so that a relatively fuel-rich air-fuel mixture with an air-fuel ratio equal to or lower than the stoichiometric air-fuel ratio is supplied to the lean NOx catalyst 13A.
[0050]
In particular, in this catalyst recovery control, the fuel injection to be supplied to the catalyst is performed within the exhaust stroke of each cylinder (specifically, as shown in FIG. 6 so as not to affect the combustion in the combustion chamber 2). This is performed during the opening of the exhaust valve 5 between the end of the expansion stroke and the exhaust stroke). Note that the injection in the intake stroke shown in FIG. 6 is a normal fuel injection performed for combustion in the combustion chamber 2. Further, the fuel supplied for the catalyst restoration control is referred to as an additional fuel in distinction from the fuel supplied for combustion in the normal combustion chamber 2.
[0051]
The catalyst reinstatement fuel injection control unit 105 includes a function (start / end determination unit) 105A for determining the start and end of catalyst reinstatement control (additional fuel control), and the lean NOx catalyst 13A at the time of catalyst reinstatement control. A function for setting the additional fuel injection amount so that the supply gas is in the lean side (lean or stoichiometric) state or the additional fuel injection amount in the rich side (rich or stoichiometric) state (additional fuel) An injection amount setting unit) 105B is provided.
[0052]
The start / end determination unit 105A determines that the catalyst recovery control should be started upon receiving the catalyst recovery signal from the adhesion amount estimation means 102 as described above, and after the catalyst recovery control starts, the lean NOx catalyst 13A performs the first operation. 1 When the temperature rises to a predetermined temperature (for example, 650 ° C.) and the integrated value of the rich or stoichiometric state becomes a predetermined time (for example, 600 seconds) or more, or when the lean NOx catalyst 13A exceeds the first predetermined temperature When the temperature is raised to a higher second predetermined temperature (for example, 750 ° C.), it is determined that the catalyst restoration is completed and the catalyst restoration control should be terminated. The temperature of the lean NOx catalyst 13A is obtained by the catalyst temperature sensor 16, and the integrated value of time is obtained by a timer value obtained by operating the timer 36 under required conditions.
[0053]
In the additional fuel injection amount setting unit 105B, when the temperature of the lean NOx catalyst 13A is lower than a first predetermined temperature (for example, 650 ° C.), detection information from the oxygen sensor 15 so as to be in a lean side (lean or stoichiometric) state. The additional fuel injection amount is set by feedback control based on the above, and when the temperature of the lean NOx catalyst 13A is equal to or higher than the first predetermined temperature (for example, 650 ° C.), the oxygen sensor 15 is set to be in the rich side (rich or stoichiometric). The additional fuel injection amount is set by feedback control based on the detection information from.
[0054]
During such reactivation mode control, the additional fuel injection amount is adjusted according to the temperature of the lean NOx catalyst 13A because when the temperature of the lean NOx catalyst 13A is lower than the first predetermined temperature, the lean NOx catalyst 13A is heated to rise. The fuel is supplied for heating, and when the temperature of the lean NOx catalyst 13A is equal to or higher than the first predetermined temperature, the degrading substances (poisoning substances) such as sulfur adhering to the lean NOx catalyst 13A are decomposed and less harmful. It is a fuel supply for reducing the substance to discharge.
[0055]
In other words, the sulfur S contained in the fuel and engine lubricating oil is finally barium sulfate B.₂SO_FourSuch a sulfate that is difficult to decompose is adsorbed to the NOx absorbent of the lean NOx catalyst 13A, and this sulfate is not decomposed by simply setting the air-fuel ratio of the exhaust gas to the rich side (rich or stoichiometric). However, this sulfate is decomposed when the NOx absorbent of the lean NOx catalyst 13A rises to the required temperature and sulfate ions SO_Four ^2-Is sulfur trioxide SO_ThreeReleased from the NOx absorbent.
[0056]
And the sulfur trioxide SO released from the NOx absorbent in this way_ThreeSulfur dioxide SO₂In order to reduce and release the unburned gas, the unburned gas may be supplied to the lean NOx catalyst 13A. Therefore, the injection amount of the additional fuel is adjusted so that the exhaust gas with rich or stoichiometric air-fuel ratio is supplied to the lean NOx catalyst 13A so that the reducing action can be obtained by the unburned HC or CO in the exhaust gas. -ing
[0057]
Note that the completion of the catalyst restoration by the start / end determination unit 105A is assumed to be when the catalyst 13A is at a first predetermined temperature or higher for a predetermined time. This is when the catalyst 13A is in a predetermined temperature state. Accordingly, since the sulfate is decomposed, the first predetermined temperature and the predetermined time are set by examining such characteristics in advance. In addition, the completion of the catalyst restoration is determined when the catalyst 13A has reached the second predetermined temperature or higher. This is to prevent the catalyst 13A from excessively warming, and the catalyst 13A is sufficiently increased to the second predetermined temperature or higher. This is because it can be estimated that sufficient sulfate has already been decomposed and released from the NOx absorbent.
[0058]
Since the direct injection internal combustion engine as the first embodiment of the present invention is configured as described above, the catalyst restoration control (additional fuel control) is performed as shown in FIGS. 4 and 5, for example.
The control shown in FIG. 4 is started when the restoration of the catalyst is completed, and is performed at a predetermined control cycle set in advance. First, the lean operation is established based on the operation information from the lean combustion operation region determination means 101. If the lean operation is not established, no operation is performed. If the lean operation is established, the process proceeds to step A20, for example, intake air during the lean combustion operation. Amount (number of airflow sensor pulses AP_LEAN) Or fuel consumption during lean combustion operation (injector drive time T_LEAN) Or mileage D by lean combustion operation_LEANOr travel time TR by lean combustion operation_LEANWhile monitoring the accumulated value (lean state accumulated value) ΣAP_LEAN, ΣT_LEAN, ΣD_LEAN, Or ΣTR_LEANIs calculated. Hereinafter, these lean state integrated values are also referred to as AP._LEAN, T_LEAN, D_LEANOr TR_LEANIs written.
[0059]
Next, the routine proceeds to step A30, where the lean state integrated value AP_LEAN, T_LEAN, D_LEANOr TR_LEANDetermines whether or not a threshold value AP0, T0, D0, or TR0 that is set in advance is reached. Of the thresholds, for example, the threshold D0 of the travel distance can be set to about 5000 km.
Lean state integrated value AP_LEAN, T_LEAN, D_LEANOr TR_LEANSteps A10, A20, and A30 are repeated until the threshold value reaches the threshold value, and the lean state integrated value AP_LEAN, T_LEAN, D_LEANOr TR_LEANWhen the value reaches the threshold value, it is determined that the recovery mode is started, and the process proceeds to step A40 to control the recovery mode.
[0060]
As shown in FIG. 5, this reversion mode control determines whether or not the temperature of the lean NOx catalyst 13A is equal to or higher than a first predetermined temperature (for example, 650 ° C.) (step B10), and the temperature of the lean NOx catalyst 13A. If the temperature is not equal to or higher than the first predetermined temperature, the additional fuel injection amount is controlled by feedback control based on detection information from the oxygen sensor 15 so that the exhaust gas supplied to the lean NOx catalyst 13A is in the lean side (lean or stoichiometric) state. Adjust (step B30). Further, when the temperature of the lean NOx catalyst 13A becomes equal to or higher than the first predetermined temperature, the detection information from the oxygen sensor 15 is used so that the exhaust gas supplied to the lean NOx catalyst 13A becomes rich (rich or stoichiometric). The additional fuel injection amount is adjusted by the feedback control based on the feedback control (step B20).
[0061]
In such a recovery mode control, for example, as shown in FIG. 6, after the start determination of the recovery mode, fuel injection is started from the most recent cylinder in the exhaust stroke of each cylinder. If the temperature of 13A is low and does not reach the first predetermined temperature, additional fuel is injected to simply heat the lean NOx catalyst 13A and raise the temperature. A part of the additional fuel injected at this time is burned by the high heat of the exhaust gas in the exhaust passage 12 before reaching the lean NOx catalyst 13A, and the other additional fuel reaches the lean NOx catalyst 13A and is lean. The NOx catalyst 13A catalyses and burns completely without waste.
[0062]
Further, when the temperature of the lean NOx catalyst 13A rises and reaches the first predetermined temperature, as shown in FIG. 7, for example, the additional fuel is increased appropriately so that rich or stoichiometric exhaust gas is supplied to the lean NOx catalyst 13A. Spray. When the lean NOx catalyst 13A is heated to the required temperature in this way, the purification ability reducing substance (poisoning substance) such as sulfate adsorbed on the lean NOx catalyst 13A is decomposed and released, and further released. Decomposition products (eg sulfur trioxide SO_Three) Is a less harmful substance (eg sulfur dioxide SO) due to unburned HC or CO in the rich or stoichiometric exhaust gas from additional fuel injection.₂) And discharged.
[0063]
When the temperature of the lean NOx catalyst 13A increases and reaches a first predetermined temperature (for example, 650 ° C.), the temperature of the catalyst 13A is changed to the first predetermined temperature as shown in step A60 of FIG. The time in the above state (the state in which the catalyst is being restored) is integrated, and it is determined whether or not this integrated value has reached a predetermined time (for example, 600 seconds) (step A70).
[0064]
As described above, when the accumulated time when the temperature of the catalyst 13A is equal to or higher than the first predetermined temperature reaches the predetermined time, the recovery of the catalyst is completed (step A90), and the recovery mode is terminated. Further, it is determined whether or not the temperature of the catalyst 13A has become equal to or higher than a second predetermined temperature (for example, 750 ° C.) even if the accumulated time when the catalyst temperature is equal to or higher than the first predetermined temperature does not reach the predetermined time ( In step A80), when the temperature of the catalyst 13A becomes equal to or higher than a second predetermined temperature (for example, 750 ° C.), it is determined that the catalyst has been restored (step A90), and the restoration mode is terminated. At the end of the recovery mode, the lean state integrated value AP_LEAN, T_LEAN, D_LEANOr TR_LEANIs cleared to 0 (step A100).
[0065]
In this way, when a purification ability-reducing substance such as sulfur (a poisoning substance) adheres to the lean NOx catalyst 13A, while reducing the attached purification ability-reducing substance, such as sulfur, to a less harmful substance by catalyst reactivation control. Since it is removed, the NOx absorption capacity of the lean NOx catalyst 13A can be restored while purifying the exhaust gas itself at the time of the restoration control, so that the NOx generated in the exhaust gas during the lean operation can be reliably absorbed. become.
[0066]
In particular, since the recovery control, that is, the heating control is performed by the exhaust stroke injection separately from the fuel injection for the normal combustion, the recovery control is performed without affecting the normal combustion and therefore without causing the torque fluctuation. Can be done.
Therefore, for example, there is an advantage that the lean NOx catalyst can be revived and controlled without giving the driver a sense of incongruity even in a low load region or a low rotation region such as during lean driving.
[0067]
In addition, according to the exhaust stroke injection, the injected fuel is hardly supplied to the combustion in the combustion chamber and is supplied almost directly to the catalyst together with the exhaust gas in an unburned state. There is an advantage that the activity can be promoted and the resurrection can be completed.
Further, according to the exhaust stroke injection, even when the recovery control is performed, the additional fuel injection is performed for the control of the normal fuel injection (that is, the fuel injection in the intake stroke from the end of the exhaust stroke). It can be performed in the same manner whether it is present or not.
[0068]
It should be noted that the lean state integrated value AP, which is a reference for starting the restoration mode,_LEAN, T_LEAN, D_LEANOr TR_LEANThe threshold value AP0, T0, D0, or TR0 can be set based on the result of examining the adhesion characteristic of the purification ability reducing substance to the lean NOx catalyst 13A and the like. The rich or stoichiometric exhaust gas supply time in the temperature region can also be set based on the result of examining the recovery characteristics of the lean NOx catalyst 13A.
[0069]
In addition, since there is no adverse effect on normal engine operation in the recovery mode, the lean state integrated value AP as a reference for starting the recovery mode is used._LEAN, T_LEAN, D_LEANOr TR_LEANThe threshold value AP0, T0, D0, or TR0 may be set to a small value on the safe side so that the recovery control is performed more frequently so that the sulfur content does not stay excessively.
[0070]
Further, in the temperature increase stage of the lean NOx catalyst 13A, additional fuel injection in the exhaust stroke is performed so that the air-fuel ratio becomes lean or stoichiometric, so that the catalyst restoration control can be performed while using the fuel efficiently. There is an advantage.
Furthermore, since it is determined that the restoration is completed when the catalyst temperature becomes equal to or higher than the second predetermined temperature, it is possible to prevent the catalyst from being excessively heated.
[0071]
Of course, since the temperature of the catalyst 9 can be increased without adding a hardware configuration such as a heater for heating the catalyst to the apparatus, the catalyst can be restored while suppressing an increase in cost.
If the lean NOx catalyst 13A is made rich after the temperature of the lean NOx catalyst 13A is raised to the first set temperature, the engine itself is operated in stoichio or rich when the heat generation is excessive and the temperature rises excessively. Thus, the exhaust stroke injection may not be performed.
[0072]
That is, when the engine body is operating in a lean state, the exhaust gas is in an excessive oxygen state, and if exhaust stroke injection is performed here, surplus oxygen in the exhaust system reacts with additional fuel to generate heat. Also, a lean NOx catalyst or a three-way catalyst at the subsequent stage reacts to generate heat.
It is conceivable that the temperature of the catalyst is excessively increased due to these heat generations. To prevent this excessive temperature increase, it is only necessary to suppress the heat generation due to the reaction between surplus oxygen in the exhaust system and the additional fuel.
[0073]
That is, if the engine body is operated in a stoichiometric or rich state while the injection of additional fuel by exhaust stroke injection is not performed, the lean NOx catalyst or the three-way catalyst generates heat due to the operation of the engine body in the stoichiometric or rich state. A predetermined time elapses after the temperature is maintained at the first set temperature without excessively increasing the amount of the catalyst, and the restoration of the catalyst is completed.
[0074]
Of course, as described above, if the temperature of the lean NOx catalyst 13A is raised to the first set temperature and the temperature is not excessively raised even in the rich atmosphere, the engine itself is lean operated and supplied to the lean NOx catalyst 13A with additional fuel. It is possible to operate the exhaust gas to be stoichiometric or rich.
Next, a cylinder injection type internal combustion engine as a second embodiment of the present invention will be described. Also in this embodiment, as in the first embodiment, the ECU 23 has a lean combustion operation region determination means 101, and an adhesion amount estimation. The means 102 and the fuel injection valve control means 103 are provided, and the catalyst restoration control is performed. Here, the catalyst restoration, that is, the additional fuel injection is performed as shown in FIG. The injection of the additional fuel in the same stroke can be performed in a plurality of times (here, twice).
[0075]
Here, the injection time t of the additional fuel_exIs a predetermined time (threshold) t set in advance₀ Compared to the injection time t_exIs the threshold t₀ If less, set the number of injections to 1 and the injection time t_exIs the threshold t₀ If it is above, the injection frequency is set to 2 times.
Thus, the fuel is divided into a plurality of times (here, twice) for the following reason.
[0076]
In other words, when additional fuel is injected at a time for a long time, naturally a large amount of fuel is injected at a time, the fuel pressure is reduced in the late stage of injection, and the atomization state is deteriorated compared to the initial stage of injection, The injected fuel may not be mixed uniformly. In this case, a part of the fuel injected as an additional fuel during the exhaust stroke is discharged without being burned, and the fuel efficiency for raising the temperature and activating the catalyst 13A is lowered. .
[0077]
Of course, if the amount of additional fuel to be injected in the exhaust stroke of one operation cycle is small from the beginning, there is no such possibility.
Therefore, when there is a large amount of additional fuel to be injected within the exhaust stroke of one operation cycle so that the above-described atomization state may be deteriorated, if fuel injection is started, the fuel pressure drop in the later stage of injection will decrease. The fuel injection is temporarily stopped within a short time, and the fuel injection is performed again after a short interval.
[0078]
Therefore, the threshold t for determining the number of injections₀ Is set so as to define such a range that may cause a decrease in fuel pressure above a certain level.
In addition, injection time of additional fuel (total injection time within one operation cycle) t_exCan be set according to the engine speed (engine speed) Ne or the like. For example, as the engine speed Ne is higher, the injection time t_exIt is conceivable to set short.
[0079]
This is because the higher the engine speed Ne is, the shorter the time required for one operation cycle is, so the exhaust stroke in one operation cycle is also shortened, and the time during which fuel injection can be performed in the exhaust stroke is also shortened. Therefore, the injection time t of additional fuel increases as the engine speed Ne increases._exIs shortened.
In addition, when the number of injections is 2, the first injection time t_ex1 Than the second injection time t_ex2 Each injection time t so that_ex1 , T_ex2 May be set. Thus, the reason for shortening the injection time of the subsequent injection is as follows.
[0080]
That is, this exhaust gas is immediately after the explosion at the beginning of the exhaust stroke, and therefore contains high temperature oxygen. For this reason, even if the injection amount of the additional fuel is relatively large, the atomization and combustion of the fuel are performed quickly and reliably. However, with the passage of time in the exhaust stroke, the exhaust gas temperature gradually decreases and the oxygen contained in the exhaust gas also gradually decreases. When the amount of fuel injection is large, fuel atomization and combustion can be performed quickly and reliably. It becomes difficult to do.
[0081]
Therefore, the shorter injection time is set to a shorter injection time so that the atomization and combustion of the additional fuel can be performed quickly and reliably.
In addition, since the structure of this other part is the same as that of 1st Embodiment, description is abbreviate | omitted.
Since the direct injection internal combustion engine according to the second embodiment of the present invention is configured as described above, it is possible to obtain substantially the same operations and effects as those of the first embodiment. In particular, the additional fuel is divided and injected. As a result, the fuel efficiency is improved, and there is an advantage that the catalyst can be revived quickly and efficiently at a low cost.
[0082]
Next, a cylinder injection type internal combustion engine as a third embodiment of the present invention will be described. The internal combustion engine (engine) according to this embodiment has 12 cylinders, and is configured as, for example, a V-type 12 cylinder engine. ing. Of course, this engine is also a spark ignition type four-cycle engine, and is configured as an in-cylinder injection engine in which fuel is directly injected into the cylinder.
[0083]
In this embodiment as well, as in the first embodiment, the ECU 23 is provided with the lean combustion operation region determination means 101, the adhesion amount estimation means 102, and the fuel injection valve control means 103, so that the catalyst restoration control is performed. In this embodiment, the catalyst is revived, that is, additional fuel injection is performed simultaneously in a plurality of cylinders.
[0084]
That is, in an engine having a large number of cylinders, the exhaust stroke may overlap (polymerize) between the plurality of cylinders. For example, in the case of a 12-cylinder engine as in this embodiment, as shown in FIG. 9, the exhaust strokes overlap in three cylinders simultaneously.
In the present embodiment, the 12 cylinders are divided into four groups each consisting of three cylinders that overlap each other in the exhaust stroke, and additional fuel injection in the exhaust stroke is performed for each group.
[0085]
In this example, as shown in FIG. 9, a group of the first cylinder (# 1), the second cylinder (# 2), and the ninth cylinder (# 9) (first group), the tenth cylinder (# 10). And the fifth cylinder (# 5) and the sixth cylinder (# 6) (second group), the eleventh cylinder (# 11), the twelfth cylinder (# 12), and the third cylinder (# 3) The group is divided into four groups: a group (third group), a fourth cylinder (# 4), a seventh cylinder (# 7), and an eighth cylinder (# 8) (fourth group). In this cylinder, additional fuel injection in the exhaust stroke is performed at the same time.
[0086]
Incidentally, as shown in FIG. 9, each of the plurality of cylinders in each group has a period during which the exhaust stroke is simultaneously performed. However, this period is naturally shorter than the exhaust stroke of a single cylinder. Thus, in the case of 12 cylinders, the common period of the exhaust stroke for each cylinder in the group is approximately one third of the exhaust stroke period of a single cylinder.
Therefore, the injection time t is set so that the additional fuel injection is performed when each cylinder in the group is in the exhaust stroke._exIs configured to restrict. That is, the injection time t depends on the engine speed Ne._exUpper limit t_ex(Ne)_MAXIs set to the amount of displacement of the crank angle defined by the broken line indicating the group injection region in FIG. 9, and the injection time t_exIs the upper limit t_ex(Ne)_MAXBy restricting with the above, additional fuel injection is performed when each cylinder in the group is in the exhaust stroke.
[0087]
Other parts are configured in the same manner as in the first embodiment.
The in-cylinder injection type internal combustion engine as the third embodiment of the present invention is configured as described above. Therefore, each cylinder is a group of a plurality of (in this case, three) cylinder units simultaneously serving as an exhaust stroke. In both cases, additional fuel injection is performed at the same time while limiting the exhaust stroke, so that the same operation and effect as in the first embodiment can be obtained, and the load on the CPU for controlling the fuel injection valve can be reduced. There is also an advantage that the cost for the CPU can be reduced.
[0088]
In the above-described embodiment, the control amount for the recovery of the catalyst (exhaust stroke fuel injection control or additional fuel control) is performed by estimating the adhesion amount of the purification ability decreasing substance. For example, the catalyst recovery fuel injection control is performed every time a predetermined time elapses, or the catalyst recovery fuel injection control is performed at a time interval according to the operating state of the engine. The effects and effects of can be obtained.
[0089]
The lean NOx catalyst is not limited to the above-described embodiment, and supports at least one component of alkali metals such as potassium, alkaline earths such as barium, and rare earths such as lanthanum. Other configurations such as those may be used.
[0090]
【The invention's effect】
  As detailed above, claim 1, 3According to the cylinder injection type internal combustion engine of the present invention described above, the cylinder is provided with a fuel injection valve that directly injects fuel into the combustion chamber of the internal combustion engine, and can perform a lean combustion operation with an air-fuel ratio larger than the stoichiometric air-fuel ratio. In an internal injection internal combustion engine, an exhaust passage for exhausting exhaust gas from the combustion chamber, a lean NOx catalyst that is installed in the exhaust passage and absorbs nitrogen oxide (NOx) in exhaust gas during lean combustion operation, Based on the operating state of the internal combustion engine detected by the operating state detecting means and the operating state detecting means for detecting the operating state of the internal combustion engineIn addition to the normal fuel injection performed for combustion in the combustion chamber, the combustion in the combustion chamber should not be affected.The fuel injection valve control means for operating the fuel injection valve in the exhaust stroke of the internal combustion engine and supplying additional fuel to the lean NOx catalyst is provided so as not to affect the combustion in the normal combustion chamber. There is an advantage that the lean NOx catalyst can be revived by decomposing / removing the purification ability lowering substance adhering to the lean NOx catalyst while avoiding the torque fluctuation.
  According to the direct injection internal combustion engine of the first aspect of the present invention, the temperature of the lean NOx catalyst is further a lower limit value of a temperature range in which the purification ability reducing substance adhering to the lean NOx catalyst can be decomposed. When the temperature is lower than the temperature, for the purpose of raising the temperature of the lean NOx catalyst, the injection amount is adjusted so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, and additional fuel is supplied. When the temperature of the NOx catalyst is equal to or higher than a predetermined temperature, the air-fuel ratio is set to a richer side than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio in order to decompose the reducing ability reducing substance attached to the lean NOx catalyst and reduce it to a less harmful substance. By adjusting the injection amount so that it becomes, it is possible to avoid using an additional amount of additional fuel outside the decomposable temperature range of the purification ability reducing substance, so that the additional fuel can be supplied efficiently. That.
According to the in-cylinder injection internal combustion engine of the second and third aspects of the present invention, the internal combustion engine has a plurality of cylinders, the fuel injection valve is disposed for each cylinder, and the plurality of the above-mentioned plurality of cylinders The operating phases of the exhaust ports are set so that the opening timings of the exhaust ports partially overlap among at least some of the cylinders, and the fuel injection control means opens the exhaust ports. For cylinders whose timings overlap each other, the fuel injection valve provided for each cylinder is operated at the same time, so that the lean NOx catalyst can be restored at a low cost while simplifying the control. There is an advantage that can be.
[0091]
  Claim4According to the in-cylinder injection internal combustion engine of the present invention,In any one of ~ 3In the configuration described above, the operation state detection means includes an adhesion amount estimation means for estimating the adhesion amount of the substance having reduced purification ability to the lean NOx catalyst and determining whether or not the adhesion amount has reached a predetermined amount. When the fuel injection valve control means determines that the adhesion amount of the purification ability reducing substance to the lean NOx catalyst has reached a predetermined amount by the adhesion amount estimation means, the fuel injection control unit performs the fuel injection in the exhaust stroke of the internal combustion engine. By configuring the additional fuel to be supplied to the lean NOx catalyst by operating a valve, it is possible to prevent the combustion in the normal combustion chamber from being affected when the amount of the deteriorating purification ability reaches a predetermined amount. Thus, there is an advantage that the lean NOx catalyst can be reliably restored by decomposing / removing the purification ability-decreasing material adhering to the lean NOx catalyst while avoiding torque fluctuations.
[0092]
  Claim5According to the cylinder injection type internal combustion engine of the present invention,4In the described configuration, the adhesion amount estimation means is configured to estimate the adhesion amount of the purification ability lowering substance to the lean NOx catalyst based on the integrated value of the intake air amount during the lean combustion operation. In addition, the amount of adhesion of the purification ability lowering substance to the lean NOx catalyst can be easily estimated, and there is an advantage that the lean NOx catalyst can be properly restored.
[0093]
  Claim6According to the cylinder injection type internal combustion engine of the present invention,4In the described configuration, the adhesion amount estimation means is configured to estimate the adhesion amount of the purification ability reducing substance to the lean NOx catalyst based on the integrated value of the fuel consumption amount during the lean combustion operation. In addition, the amount of adhesion of the purification ability lowering substance to the lean NOx catalyst can be easily estimated, and there is an advantage that the lean NOx catalyst can be properly restored.
[0094]
  Claim7According to the cylinder injection type internal combustion engine of the present invention,4In the configuration described above, the adhesion amount estimation means is configured to estimate the adhesion amount of the purification ability lowering substance to the lean NOx catalyst based on the integrated value of the travel distance by the lean combustion operation. There is an advantage that it is possible to easily estimate the amount of the substance that reduces the purification ability to the NOx catalyst, and to properly restore the lean NOx catalyst.
[0095]
  Claim8According to the cylinder injection type internal combustion engine of the present invention,4In the configuration described above, the attachment amount estimating means is configured to estimate the attachment amount of the purification ability lowering substance to the lean NOx catalyst based on the integrated value of the travel time by the lean combustion operation, thereby There is an advantage that it is possible to easily estimate the amount of the substance that reduces the purification ability to the NOx catalyst, and to properly restore the lean NOx catalyst.
[0097]
  Claim9According to the in-cylinder injection internal combustion engine of the present invention,In any one of -8In the configuration described above, the fuel injection valve control means is configured to inject the additional fuel in a plurality of times while operating the fuel injection valve a plurality of times during an exhaust stroke in one operation cycle. There is an advantage that the lean NOx catalyst can be revived promptly at low cost while the additional fuel is injected more efficiently.
[0098]
  Claim10According to the in-cylinder injection internal combustion engine of the present invention,To any one of -9In the configuration described above, a catalyst temperature state detection means for detecting the temperature state of the lean NOx catalyst is provided, and the fuel injection valve control means is based on the detection result of the catalyst temperature state detection means after the supply of the additional fuel is started. By configuring the lean NOx catalyst so that the supply of the additional fuel is stopped when the state where the temperature of the lean NOx catalyst is equal to or higher than the predetermined temperature exceeds the predetermined time, the additional fuel can be injected more efficiently while being wasted at low cost. And there is an advantage that the lean NOx catalyst can be revived.
[0099]
  According to the cylinder injection type internal combustion engine of the present invention as set forth in claim 11, in the configuration according to any one of claims 1 to 10, the catalyst temperature state detection means for detecting the temperature state of the lean NOx catalyst is provided. In addition, the fuel injection valve control meansIs, Based on the detection result of the catalyst temperature state detection means,Supplying the additional fuel by adjusting the injection amountWith such a configuration, there is an advantage that the lean NOx catalyst can be revived quickly and efficiently without incurring additional fuel while being injected more efficiently.
[0100]
  Claim12According to the in-cylinder injection internal combustion engine of the present invention,To any one of ~ 11In the configuration described above, the lean NOx catalyst specifically supports the lean NOx catalyst by supporting at least one component of an alkali metal such as potassium, an alkaline earth such as barium, and a rare earth such as lanthanum. Can be configured.
  According to the cylinder injection internal combustion engine of the thirteenth aspect of the present invention, in the configuration according to any one of the first to twelfth aspects, the fuel injection valve control means brings the lean NOx catalyst to the predetermined temperature. If the lean NOx catalyst is brought to a rich atmosphere after the temperature has been raised and excessive heat is generated due to excessive heat generation, the normal injection performed for combustion in the combustion chamber without performing the additional injection is performed. With the configuration in which the air-fuel ratio becomes stoichiometric or rich by fuel injection, heat generation due to the reaction between surplus oxygen in the exhaust system and additional fuel is suppressed, and excessive temperature rise can be prevented.
[Brief description of the drawings]
FIG. 1 is a control block diagram schematically showing a main configuration of a control system of a direct injection internal combustion engine as a first embodiment of the present invention.
FIG. 2 is a diagram showing an overall configuration of a direct injection internal combustion engine as the first embodiment of the present invention.
FIG. 3 is a hardware block diagram showing a control system of the direct injection internal combustion engine as the first embodiment of the present invention.
FIG. 4 is a flowchart for explaining fuel injection control of the direct injection internal combustion engine as the first embodiment of the present invention.
FIG. 5 is a flowchart for explaining a catalyst recovery mode by fuel injection control of the direct injection internal combustion engine according to the first embodiment of the present invention.
FIG. 6 is a diagram showing the injection timing of additional fuel in the direct injection internal combustion engine as the first embodiment of the present invention.
FIG. 7 is a diagram showing the injection timing of additional fuel in the direct injection internal combustion engine as the first embodiment of the present invention.
FIG. 8 is a diagram showing the injection timing of additional fuel in the direct injection internal combustion engine as the second embodiment of the present invention.
FIG. 9 is a diagram showing the injection timing of additional fuel in a direct injection internal combustion engine as a third embodiment of the present invention.
[Explanation of symbols]
1 Engine body
2 Combustion chamber
3. Fuel injection valve (injector) as fuel supply means
3a Injector solenoid
4 Intake valve
5 Intake passage
5A Intake port
5B Intake manifold
5C surge tank
5D intake pipe
6 Air cleaner
7 Air flow sensor
8 Throttle valve
9 Intake air temperature sensor
10 Atmospheric pressure sensor
11 Intake valve
12 Exhaust passage
12A exhaust port
12B Exhaust manifold
12C exhaust pipe
13 Exhaust gas purification catalyst
13A lean NOx catalyst
13B Three-way catalyst
14 Air-fuel ratio sensor
15 Oxygen sensor
16 Catalyst temperature sensor
17 Spark plug
18 Throttle opening sensor (throttle sensor)
19 Water temperature sensor
20 Cranking switch [Ignition switch (key switch)]
21 crank angle sensor (engine speed sensor)
22 TDC sensor (cylinder discrimination sensor)
23 ECU (Electronic Control Unit)
24 Accelerator position sensor
25 Battery sensor
26 Distance meter
27 CPU
28, 29 Input interface
30 Analog / Digital Converter
31 ROM
32 RAM
33 Idle switch
34 Injection driver (fuel injection valve drive means)
36 timer
48 Free running counter
101 Lean combustion operation region determination means
102 Adhesion amount estimation means
102A adhesion amount estimation unit
102B Adhesion limit judgment part
103 Fuel injection valve control means
104 Normal fuel injection control unit
105 Fuel injection control unit for catalyst recovery
105A start / end determination unit
105B Additional fuel injection amount setting unit

Claims (13)

In a cylinder injection type internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine and capable of performing a lean combustion operation with an air-fuel ratio larger than a theoretical air-fuel ratio,
An exhaust passage for exhausting exhaust gas from the combustion chamber;
A lean NOx catalyst that is installed in the exhaust passage and absorbs nitrogen oxides (NOx) in the exhaust gas during lean combustion operation;
Operating state detecting means for detecting the operating state of the internal combustion engine;
Based on the operating state of the internal combustion engine detected by the operating state detecting means, the internal combustion engine is not affected by the combustion in the combustion chamber separately from the normal fuel injection performed for combustion in the combustion chamber. Fuel injection valve control means for operating the fuel injection valve in the exhaust stroke and supplying additional fuel to the lean NOx catalyst ,
The fuel injection valve control means increases the temperature of the lean NOx catalyst when the temperature of the lean NOx catalyst is lower than a predetermined temperature that is a lower limit value of a decomposable temperature range of the purification ability reducing substance attached to the lean NOx catalyst. Therefore, the additional fuel is supplied by adjusting the injection amount so that the air-fuel ratio is leaner than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio, and when the temperature of the lean NOx catalyst is equal to or higher than the predetermined temperature, In order to decompose the reduced purification capacity substance adhering to the lean NOx catalyst and reduce it to a less harmful substance, the injection amount is adjusted so that the air-fuel ratio becomes richer than the stoichiometric air-fuel ratio or the stoichiometric air-fuel ratio. An in-cylinder injection internal combustion engine characterized in that additional fuel is supplied . The internal combustion engine has a plurality of cylinders, and the fuel injection valve is disposed for each cylinder;
The operation phase of each other is set so that the opening timing of each exhaust port partially overlaps among at least some of the plurality of cylinders.
The fuel injection control means is configured to simultaneously operate the fuel injection valves provided in each cylinder for cylinders whose opening timings of these exhaust ports overlap each other. Item 2. The cylinder injection internal combustion engine according to Item 1 . In a cylinder injection type internal combustion engine having a fuel injection valve for directly injecting fuel into a combustion chamber of an internal combustion engine and capable of performing a lean combustion operation with an air-fuel ratio larger than a theoretical air-fuel ratio,
  An exhaust passage for exhausting exhaust gas from the combustion chamber;
  A lean NOx catalyst that is installed in the exhaust passage and absorbs nitrogen oxides (NOx) in the exhaust gas during lean combustion operation;
  Operating state detecting means for detecting the operating state of the internal combustion engine;
  Based on the operating state of the internal combustion engine detected by the operating state detecting means, the internal combustion engine is not affected by the combustion in the combustion chamber separately from the normal fuel injection performed for combustion in the combustion chamber. Fuel injection valve control means for operating the fuel injection valve in the exhaust stroke and supplying additional fuel to the lean NOx catalyst,
  The internal combustion engine has a plurality of cylinders, and the fuel injection valve is disposed for each cylinder;
  The operation phase of each other is set so that the opening timing of each exhaust port partially overlaps among at least some of the plurality of cylinders,
  The fuel injection control means is configured to simultaneously operate the fuel injection valves provided in each cylinder for cylinders in which the opening timings of these exhaust ports overlap each other.
An in-cylinder injection internal combustion engine. The operating condition detecting means, and estimates the deposition amount of the decreased reducing ability substance into the lean NOx catalyst, comprising a deposition amount estimating means for determining whether said adhesion amount reaches the predetermined amount,
When the fuel injection valve control means, the adhesion amount of the decreased reducing ability substance into the lean NOx catalyst is determined to have reached a predetermined amount by said adhesion amount estimating means, fuel injection in the exhaust stroke of the internal combustion engine The in-cylinder injection internal combustion engine according to any one of claims 1 to 3 , wherein the additional fuel is supplied to the lean NOx catalyst by operating a valve. Said adhesion amount estimating means, characterized in that it is configured to estimate the deposition amount of the decreased reducing ability substance into the lean NOx catalyst based on the integrated value of the intake air amount in the lean burn operation The in-cylinder injection internal combustion engine according to claim 4 . Said adhesion amount estimating means, characterized in that it is configured to estimate the deposition amount of the decreased reducing ability substance into the lean NOx catalyst based on the integrated value of the fuel consumption during the lean burn operation The in-cylinder injection internal combustion engine according to claim 4 . It said adhesion amount estimating means, characterized in that it is configured to estimate the deposition amount of the decreased reducing ability substance into the lean NOx catalyst based on the integrated value of the travel distance by the lean burn operation, wherein Item 5. The cylinder injection internal combustion engine according to Item 4 . It said adhesion amount estimating means, characterized in that it is configured to estimate the deposition amount of the decreased reducing ability substance into the lean NOx catalyst based on the integrated value of the travel time by the lean burn operation, wherein Item 5. The cylinder injection internal combustion engine according to Item 4 . The fuel injection valve control means is configured to inject the additional fuel in a plurality of times while operating the fuel injection valve a plurality of times during an exhaust stroke in one operation cycle. Item 9. The cylinder injection internal combustion engine according to any one of Items 1 to 8 . Catalyst temperature state detection means for detecting the temperature state of the lean NOx catalyst is provided;
When the fuel injection valve control means starts supplying the additional fuel and the temperature of the lean NOx catalyst reaches a predetermined temperature or more after a predetermined time based on the detection result of the catalyst temperature state detection means, the additional fuel The in-cylinder injection internal combustion engine according to any one of claims 1 to 9 , characterized in that the supply is stopped. Catalyst temperature state detection means for detecting the temperature state of the lean NOx catalyst is provided;
Fuel injection valve control means based on the detection result of said catalyst temperature state detecting means, and wherein the <br/> performing the supply of the additional fuel by adjustment of the injection quantity, claims 1 to 10 The cylinder injection type internal combustion engine of any one of these. The lean NOx catalyst, characterized in that it carries at least one of components in the rare earth alkali metals, alkaline earth, and lanthanum such as barium and potassium, more of claims 1 to 11 An in-cylinder injection internal combustion engine as set forth in claim 1 . When the lean NOx catalyst is heated to the predetermined temperature and then the lean NOx catalyst is brought to a rich atmosphere, the fuel injection valve control means performs the additional injection when the heat generation is excessive and the temperature rises excessively. Instead of performing the normal fuel injection for combustion in the combustion chamber, the air-fuel ratio is made stoichiometric or rich.
The in-cylinder injection internal combustion engine according to any one of claims 1 to 12, wherein

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