JP3842092B2 - Exhaust purification device and purification method for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control device and a purification method for an internal combustion engine having a function of regenerating NOx storage catalyst from sulfur oxide poisoning.
[0002]
[Prior art]
In a lean-burn internal combustion engine that burns an air-fuel mixture that is leaner than the stoichiometric air-fuel ratio, an exhaust gas purification device that uses a NOx storage catalyst is used to purify NOx that is exhausted. This purification device absorbs N0x exhausted during the lean operation of the internal combustion engine, and switches the air-fuel ratio to rich every predetermined period to reduce the oxygen concentration in the exhaust gas, thereby being stored in the N0x storage catalyst. N0x is released and reduction treatment is performed to purify the exhaust gas.
[0003]
The exhaust gas of the internal combustion engine contains sulfur oxide (hereinafter referred to as SOx), and this SOx is adsorbed by the NOx storage catalyst together with NOx. Since SOx adsorbed on the N0x storage catalyst is not released even when the air-fuel ratio is switched to rich, the adsorption amount increases with the operation time, and the N0x storage function by the N0x storage catalyst is lowered. In order to prevent this, it is necessary to raise the temperature of the NOx storage catalyst and release SOx, and fuel injection is additionally performed in the combustion stroke and exhaust stroke in addition to the intake stroke and compression stroke, or ignition is performed. The exhaust gas temperature was raised by delaying the timing, and SOx was released from the NOx storage catalyst.
[0004]
Such a technique is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-100168 and Japanese Patent Application Laid-Open No. 11-107813. In the in-cylinder injection internal combustion engine in which the fuel directly injected into the cylinder is ignited and burned, the technique disclosed in the former performs the first fuel injection in the compression stroke, and the first to the middle of the combustion stroke. By performing the second additional injection and igniting the fuel by this additional injection by the flame propagation of the fuel by the first injection, the temperature of the exhaust gas is increased without causing the ignition device to operate repeatedly. The catalyst is activated by the above-mentioned, and either the second additional injection or the retard of the ignition timing is selected according to the operating condition of the internal combustion engine, and the second is performed. When the third additional injection is selected, the third additional injection is performed as necessary.
[0005]
The technique disclosed in the latter has a mode in which the combustion control means injects fuel in two steps, that is, an intake stroke and a combustion stroke, and the operation of the internal combustion engine is performed when SOx is released from the NOx storage catalyst. The exhaust gas temperature is raised by selectively performing either the fuel injection divided into two according to the conditions or the ignition timing retardation control, and the temperature of the NOx storage catalyst is increased by the exhaust gas temperature. The temperature is increased to a temperature necessary for releasing SOx.
[0006]
[Problems to be solved by the invention]
Thus, when the temperature of the NOx storage catalyst is raised by performing additional injection of fuel in the combustion stroke, the main injection is performed particularly in the compression stroke as disclosed in JP-A-8-1000063. In the case of additional injection in the combustion stroke, there is a problem that smoke is generated, so the injection amount in the compression stroke is limited, the injection amount in the combustion stroke must be increased, and the unburned fuel Is easy to be discharged. For this reason, when a three-way catalyst is arranged upstream of the NOx storage catalyst in the exhaust path, the temperature of the three-way catalyst rises abnormally due to the reaction between the three-way catalyst and unburned fuel, and the heat-resistant temperature limit There is a risk of damage beyond that.
[0007]
Further, as disclosed in Japanese Patent Application Laid-Open No. 11-107813, smoke is not generated when fuel is injected in two steps, that is, an intake stroke and a combustion stroke. Although the amount can be reduced to suppress an abnormal increase in the temperature of the three-way catalyst due to unburned fuel, the air-fuel ratio by intake stroke injection is set as lean as possible to raise the temperature of the NOx storage catalyst. There is a problem that the combustion becomes unstable and the rotational fluctuation of the internal combustion engine increases, and the temperature rise effect and the combustion state change greatly due to a slight change in the air-fuel ratio.
[0008]
The additional injection of fuel in the combustion stroke has a greater effect of increasing the temperature of the NOx storage catalyst compared to the retarding control of the ignition timing, and is used for increasing the temperature at low revolutions and low loads when the exhaust gas temperature is low. If the injection timing and injection amount are not controlled to the optimum values, phenomena such as deterioration of exhaust gas and abnormal temperature rise of the three-way catalyst appear. In addition, during the period until SOx is released, the temperature of the NOx storage catalyst must be maintained at a temperature necessary for releasing SOx (usually 600 ° C or higher), and this temperature is maintained by additional injection. Therefore, it is necessary to continue the additional injection until the SOx release is completed, and the implementation period of the additional injection becomes long. In the actual vehicle running state, even if the vehicle is running at a constant speed, if the implementation period of additional injection becomes long in this way, it is possible to avoid the exhaust gas from deteriorating or the temperature of the three-way catalyst to rise abnormally. It was not.
[0009]
The present invention has been made to solve such a problem. While obtaining a large temperature rise effect of the NOx storage catalyst by additional injection, the exhaust gas deteriorates, the abnormal temperature rise of the three-way catalyst, and further, the combustion state An object of the present invention is to obtain an exhaust gas purification apparatus and method for an internal combustion engine capable of preventing deterioration.
[0010]
[Means for Solving the Problems]
  An exhaust gas purification apparatus for an internal combustion engine according to the present invention includes a fuel injection means for injecting fuel into a combustion chamber of the internal combustion engine, an ignition means for igniting fuel in the combustion chamber, and a NOx storage catalyst provided in an exhaust passage of the internal combustion engine. And a control means for controlling the fuel injection amount and fuel injection timing of the fuel injection means and the ignition timing of the ignition means. The control means estimates the amount of SOx adsorbed on the NOx storage catalyst, When it is determined that the amount of adsorption exceeds a predetermined value, fuel is additionally injected for a predetermined period in the combustion stroke or exhaust stroke of the internal combustion engine to raise the NOx storage catalyst to a predetermined temperature.Set to heating modeThe ignition timing for a predetermined period after the completion of the additional injectionAlternately retard and additional injectionMaintain the temperature of the NOx storage catalystTemperature rising maintenance modeIt is what you do.
[0011]
Further, the predetermined period for performing the additional injection is determined in accordance with the operating state of the internal combustion engine.
Further, the predetermined period for performing the additional injection is calculated from the injection amount per one time of the fuel to be additionally injected.
Furthermore, the predetermined period for performing the additional injection is calculated from the amount of heat required to raise the temperature of the NOx storage catalyst to a predetermined temperature and the amount of heat generated by the additionally injected fuel.
Further, the predetermined period for performing the additional injection is corrected in accordance with the operating state of the internal combustion engine.
[0012]
Further, the predetermined period for performing the additional injection is corrected according to the exhaust gas temperature of the internal combustion engine.
Further, the additional injection is performed separately when the temperature of the NOx storage catalyst is raised and when the temperature is maintained after the temperature rise, and after the temperature of the NOx storage catalyst reaches the target value due to the additional injection during the temperature rise. The temperature of the NOx storage catalyst is maintained by alternately repeating the ignition timing retard and the additional injection every predetermined period.
Further, the predetermined period during which the ignition timing is retarded is determined in accordance with the operating state of the internal combustion engine.
[0013]
Further, the predetermined period during which the ignition timing is retarded is determined in accordance with the amount of SOx adsorbed on the NOx storage catalyst.
Furthermore, the ignition timing is retarded for a period of time until the temperature of the NOx storage catalyst decreases to a predetermined value, and when the temperature of the NOx storage catalyst decreases to a predetermined value, an additional is added to maintain the temperature of the NOx storage catalyst. It is intended to shift to injection.
Further, the predetermined value of the NOx storage catalyst temperature that determines the retarding period of the ignition timing is determined in accordance with the adsorption amount of SOx adsorbed on the NOx storage catalyst.
[0014]
Further, the predetermined temperature when the NOx storage catalyst is raised to a predetermined temperature by additional injection is determined in accordance with the adsorption amount of SOx adsorbed on the NOx storage catalyst.
Furthermore, the ignition timing retardation for maintaining the temperature of the NOx storage catalyst, or the ignition timing retardation for maintaining the temperature and the implementation period of the additional injection are the amounts of SOx adsorbed on the NOx storage catalyst. It is determined correspondingly.
[0015]
  In addition, the exhaust gas purification method for an internal combustion engine according to the present invention provides a fuel injection means in a combustion chamber of the internal combustion engine to inject fuel, ignites this by the ignition means, and a NOx storage catalyst in the exhaust gas passage. In an internal combustion engine that stores and reduces NOx, when it is estimated that the amount of SOx adsorbed on the NOx storage catalyst exceeds a predetermined value, additional fuel is injected during the combustion stroke or exhaust stroke of the internal combustion engine to store NOx. Raise the catalyst to a certain temperatureSet to heating modeAfter the temperature rise of NOx storage catalystIs a pointOf ignition timing by fire meansAlternate retard and additional injectionMaintain the temperature of the NOx storage catalystTemperature rise maintenance modeThus, SOx is released from the NOx storage catalyst.
[0016]
Furthermore, the execution period of the additional injection is calculated from the amount of heat required to raise the NOx storage catalyst temperature to a predetermined value and the heat generation amount of the additionally injected fuel.
Further, the additional injection is divided into a temperature rising time and a temperature maintaining time of the NOx storage catalyst, and after completing the additional injection at the time of the temperature rising, the retard of the ignition timing and the additional injection for maintaining the temperature are performed. Are alternately performed to maintain the temperature of the NOx storage catalyst.
[0017]
In addition, the retard of the ignition timing for maintaining the temperature is continued until the NOx storage catalyst temperature decreases to a predetermined value, and when the NOx storage catalyst temperature decreases to the predetermined value, the temperature is increased again by additional injection. Is.
Furthermore, the NOx storage catalyst is adsorbed during the additional injection period when the NOx storage catalyst is heated to a predetermined temperature by additional injection, and / or the ignition timing retard period for maintaining the temperature. It is determined according to the amount of adsorption of SOx.
Furthermore, the NOx occlusion period is defined as the period for performing the additional injection when the NOx occlusion catalyst is heated to a predetermined temperature by the additional injection, and / or the period for performing the ignition timing retardation and the additional injection for maintaining the temperature. This is determined according to the amount of SOx adsorbed on the catalyst.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Reference Form 1
  FIG. 1 shows the present invention.Shown as reference form 1 to understand the basic concept of1 is a configuration diagram of an exhaust gas purification apparatus for an internal combustion engine, and illustrates the configuration by extracting one cylinder of a multi-cylinder internal combustion engine. FIG. FIG. 2 is a flow chart for explaining the operation of the control means 16, and FIG. 3 is a characteristic explanatory view for explaining the execution period of the additional injection.
[0019]
In FIG. 1, an air flow sensor 3 and a throttle valve 4 are provided in an intake passage 2 of the internal combustion engine 1, and the intake air amount is controlled by the throttle valve 4 and introduced into the combustion chamber 5. Is measured by the air flow sensor 3, and the opening of the throttle valve 4 is measured by the throttle opening sensor 6. The combustion chamber 5 is provided with an injector 7 as fuel injection means and a spark plug 8 as ignition means. Fuel is injected from the injector 7 into the intake air to form an air-fuel mixture. The ignition plug 8 is ignited at the ignition timing.
[0020]
In the exhaust passage 9 of the internal combustion engine 1, an air-fuel ratio sensor 10 that measures the air-fuel ratio of the air-fuel mixture from the upstream side, a three-way catalyst 11 that purifies exhaust gas by oxidizing hydrocarbons, and the temperature of the exhaust gas are measured. An exhaust gas temperature sensor 12 that performs this process and an N0x storage catalyst 13 that adsorbs N0x and performs a reduction process at a predetermined timing are provided. Further, the rotation angle and rotation speed of the crankshaft 14 of the internal combustion engine 1 are measured by a crank angle sensor 15, and the airflow sensor 3, throttle opening sensor 6, air-fuel ratio sensor 10, exhaust temperature sensor 12, crank angle sensor 15, and so on. These output signals are input to the control means 16 for controlling the internal combustion engine 1, and the control means 16 controls the internal combustion engine 1 based on the input signals from the sensors.
[0021]
The control means 16 involved in the present invention includes control of the fuel injection amount and injection timing by the injector (fuel injection means) 7 based on each signal input, and control of the ignition timing by the spark plug (ignition means) 8. For this purpose, the control means 16 incorporates arithmetic means, storage means, and the like. When the air-fuel mixture burns in the combustion chamber 5, as described above, N0x is generated particularly in the lean burn state. This NOx is occluded and reduced by the N0x occlusion catalyst 13, but SOx is simultaneously generated by combustion and adsorbed to the N0x occlusion catalyst 13 to lower the NOx occlusion function. In order to release the SOx, the control means 16 additionally injects fuel in the combustion stroke or exhaust stroke of the internal combustion engine to raise the temperature of the NOx storage catalyst 13, and in order to maintain this temperature, the ignition timing is retarded, etc. Is to do.
[0022]
As described above, the exhaust passage 9 is provided with the three-way catalyst 11 on the upstream side and the N0x storage catalyst 13 on the downstream side. When fuel is additionally injected to raise the temperature of the N0x storage catalyst 13, The three-way catalyst 11 and the exhaust gas are heated by the reaction between the fuel and the three-way catalyst 11, and this heat is transmitted to the downstream N0x storage catalyst 13 to raise the temperature of the N0x storage catalyst 13. Although the temperature difference between the three-way catalyst 11 and the N0x storage catalyst 13 differs depending on the operation state of the internal combustion engine 1, the temperature difference between the two operation states is obtained in advance, and the SOx release temperature of the N0x storage catalyst 13 is set as the target temperature. When the target temperature of the three-way catalyst 11 for bringing the N0x storage catalyst 13 to this temperature is Ttwc, if the temperature of the three-way catalyst 11 is controlled to Ttwc, the N0x storage catalyst 13 will rise in temperature. SOx will be released. The operation will be described below.
[0023]
FIG. 2 is a flowchart showing an operation related to the release of SOx in the control operation by the control means 16, and the processing of this flowchart is a set cycle of fuel injection for each cylinder of the internal combustion engine 1, for example, a predetermined crank angle. It is repeated every time. In FIG. 2, when the routine is started, first, at step 201, the control means 16 reads signals from each sensor and detects the operating state of the internal combustion engine 1. Here, the rotational speed from the output of the crank angle sensor 15 and the amount of load are detected from the output of the airflow sensor 3 and the like, and the exhaust gas temperature of the internal combustion engine 1 is estimated from the output of the air-fuel ratio sensor 10, and these parameters And the temperature of the three-way catalyst 11 and the temperature of the NOx storage catalyst 13 are estimated from the output of the exhaust temperature sensor 12.
[0024]
Next, in step 202, the SOx adsorption amount is estimated. The estimation of the SOx adsorption amount is performed, for example, by integrating the integrated value of the fuel injection pulse during the lean burn operation of the internal combustion engine, that is, the fuel injection amount. Subsequently, the routine proceeds to step 203, where the temperature rise permission determination of the N0x storage catalyst 13 is performed based on the detection of the above operating state and the estimation of the SOx adsorption amount. This temperature increase permission determination is based on whether the N0x storage catalyst 13 is in a region where the temperature can be increased from the operating state, whether the operating state is in a steady state, or whether the SOx adsorption amount exceeds a predetermined value. Is to be done.
[0025]
If the temperature increase permission determination is made in step 203, it is determined in step 204 whether or not the additional injection mode flag has been established. If not, the routine proceeds to step 205 and the ignition timing retard mode flag is established. Determine whether or not. If both steps 204 and 205 are not established, the SOx release is started from this routine. Therefore, the process proceeds to step 206 to establish the additional injection mode flag, and then the additional injection is performed in step 207. The period α, that is, the number of additional injection cycles is determined.
[0026]
This additional injection execution period α is a period until the temperature of the NOx storage catalyst 13 reaches the SOx dischargeable temperature Tlnt, in other words, a period until the three-way catalyst 11 reaches the target temperature Ttwc. The implementation period α is determined to be implemented. This determination is made by storing a characteristic map as shown in FIG. 3 in the control means 16 and searching for the value of α according to the operating conditions. The map in FIG. 3 is obtained by experimentally obtaining the additional injection execution period α according to the respective values using the rotational speed and load of the internal combustion engine 1 as parameters, and this map shows the temperature of each catalyst according to the operating state. Since the temperature difference between the two catalysts is different, a plurality of maps are prepared for each operation mode (stoichiometric, lean state, etc.). The control means 16 selects a map according to the operation state immediately before the start of control, searches the selected map for the execution period α of the additional injection using the rotation speed and load of the internal combustion engine 1 as parameters, and executes them. As shown in FIG. 3, the value of α increases as the rotational speed is low and the load is low.
[0027]
When the additional injection execution period α is determined in step 207, the process proceeds to step 208 where the additional injection execution period α is set in the additional injection counter, and in step 209 the additional injection is executed. The additional injection is performed in the combustion stroke or the exhaust stroke of the internal combustion engine 1, but the map is previously controlled by the map so that the amount of additional injection (fuel amount) does not deteriorate exhaust gas or combustion depending on the operating state. 16 and is searched using the rotational speed and load of the internal combustion engine 1 at the time of performing the additional injection as parameters.
[0028]
After performing the additional injection, the process proceeds to step 210, and the additional injection counter set in step 208 is decremented. Then, the process proceeds to step 211, where it is determined whether or not the additional injection counter has become zero, and if it is not zero, the routine of this time is terminated assuming that additional injection is being performed, and the routine is repeated. If the additional injection counter is zero, it is determined that the additional injection is completed, and the process proceeds to step 212. The additional injection mode flag is set to the OFF state, and the process proceeds to step 213. In step 213, the ignition timing retard mode flag is set to ON and the process returns to the start.
[0029]
In the above routine, if additional injection is being performed, the additional injection mode flag is ON in step 204, so the routine jumps from step 204 to step 209, and steps 209 to 213 are executed. become. If the ignition timing retard mode flag is ON in step 205, the routine proceeds to step 214, where the ignition timing retard amount and fuel injection amount at which the temperature of the NOx storage catalyst 13 is maintained are set. End this routine and return to the start. The control constants such as the retard amount of the ignition timing and the fuel injection amount are stored in advance in the control means 16 so that the exhaust gas and combustion do not deteriorate depending on the operating state, and the internal combustion engine when the retard control is performed. The search is performed using the rotation speed and load of 1 as parameters.
[0030]
In addition, when the SOx adsorbed by the NOx storage catalyst 13 is released during the routine and becomes equal to or less than a predetermined value, or when the operating state changes during the execution of the additional injection, the behavior becomes transient. In step 203, the determination in step 203 changes to not allowing temperature increase. If a non-permission determination is made, the process proceeds from step 203 to step 215. In step 215, both the additional injection mode flag and the ignition timing retard mode flag are turned OFF, and in step 216, additional injection is performed. The counter is initialized, and further, in step 217, the fuel injection mode suitable for the current operating state is switched.
[0031]
  As explained above,Reference form 1In the exhaust gas purification apparatus for an internal combustion engine according to the above, the temperature increase control of the NOx storage catalyst 13 is performed by additional fuel injection, and this temperature increase control is not performed only by the additional fuel injection, but at a temperature at which SOx can be released. The additional fuel injection is performed until the temperature rises, and after the temperature is raised, the ignition timing is retarded to maintain the SOx dischargeable temperature, so the fuel additional injection period can be shortened. It is possible to suppress the deterioration of exhaust gas and the deterioration of the combustion state due to the additional injection of fuel, and to prevent excessive temperature rise of the three-way catalyst 11.
[0032]
Reference form 2
  4 and 5Is shown as a reference form 2 for understanding another basic concept of the present invention.It is explanatory drawing of the correction coefficient which correct | amends the implementation period of the additional injection used for the exhaust gas purification apparatus of an internal combustion engine,Reference form 2The exhaust gas purification device for an internal combustion engine byReference form 1The method for determining the execution period α of the additional injection in step 207 of FIG. That is, the execution period α of the additional injection necessary for raising the temperature of the N0x storage catalyst 13 to the target temperature Tlnt is calculated and determined from the calorific value of the fuel to be additionally injected.
[0033]
The calorific value Qinj (cal / str) per one cycle stroke of the fuel to be additionally injected (hereinafter simply referred to as “stroke” and expressed as str) is:
Qinj = ((Gair / Af) −Gfuel) × Hgas (1)
Is calculated as
Here, Gair is the amount of intake air (g / str),
Gfuel is the fuel injection amount (g / str),
Hgas is the lower heating value (cal / g) of the fuel,
Af is the total air-fuel ratio of main injection and additional injection,
It is.
[0034]
Raising the temperature of the NOx storage catalyst 13 to the target temperature Tlnt is raising the temperature of the three-way catalyst 11 to the target temperature Ttwc as described in Embodiment 1, and the amount of heat required at this time is increased. By dividing by a calorific value Qinj per one stroke, that is, per additional injection, a necessary additional injection execution cycle can be calculated. However, the heat transfer rate at which the amount of heat generated by the additional injection is transferred to the three-way catalyst 11 varies depending on the operating state, and the heat transfer efficiency decreases as the exhaust flow rate increases, so this must be corrected. FIG. 4 shows the heat transfer correction coefficient Kht for this correction using the rotational speed and load of the internal combustion engine 1 as parameters, and this heat transfer correction coefficient Kht is stored in the control means 16 as a map. .
[0035]
In addition, the temperature of the three-way catalyst 11 and the NOx storage catalyst 13 does not depend only on the amount of heat generated by the fuel due to the additional injection, but also varies depending on the heat transfer coefficient between the exhaust gas of the internal combustion engine 1 and each catalyst. An exhaust temperature correction coefficient Ket for correcting the above is required. FIG. 5 shows the exhaust temperature correction coefficient Ket, which is determined for the difference between the exhaust temperature and the temperature of the three-way catalyst 11 and stored in the control means 16.
[0036]
Taking these correction factors into consideration, the number of additional injection cycles Cyinj can be calculated by the following equation (2). The unit of the number of execution cycles Cyinj is a stroke (str).
Cyinj = (Ttwc-Tr) x Gcal x Ccal / Qinj x Ket x Kht (2)
Where Ttwc is the target temperature of the three-way catalyst (° C)
Tr is the temperature of the three-way catalyst (℃)
Gcal is the weight of the three way catalyst (g)
Ccal is the specific heat of the three-way catalyst (cal / g · ° C)
Ket is the exhaust temperature correction factor
Kht is heat transfer correction coefficient
It is.
[0037]
  in this way,Reference form shown in FIG. 4 and FIG.In the exhaust gas purification apparatus for an internal combustion engine according to the above, the injection period for performing additional injection in order to raise the temperature of the N0x storage catalyst 13 to the target temperature Tlnt is calculated by the supply amount of the additionally injected fuel, that is, the heat generation amount. Therefore, the execution period of the additional injection can be determined with higher accuracy, the exhaust gas deterioration and the combustion state deterioration can be easily suppressed, and the excessive temperature rise of the three-way catalyst 11 and the like can be prevented. It is something that can be done.
[0038]
ImplementationForm 1.
  FIG. 6 shows the implementation of the present invention.Form 16 is a flowchart for explaining the operation of the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment. The exhaust gas purification apparatus for an internal combustion engine according to this embodiment increases the temperature of the N0x storage catalyst 13 to a predetermined temperature by additional injection, and then maintains the temperature. Further, the ignition timing retardation and the additional injection are alternately performed, and the execution period of the additional injection for maintaining the temperature and the execution period of the ignition timing retardation are stored in the control means 16 as a map. The map is searched according to the operating state of the internal combustion engine 1, the execution periods of the additional injection and the ignition delay are determined, and these are alternately performed. The configuration of the apparatus is the same as that shown in FIG.
[0039]
  Implementation of this inventionForm 1The operation in is as shown in the flowchart of FIG. 6, and the processing of this flowchart is repeatedly performed for each set period of fuel injection for each cylinder of the internal combustion engine 1, for example, every predetermined crank angle. In the figure, when the routine is started, first, at step 601, the control means 16 reads signals from the respective sensors to detect the operating state of the internal combustion engine 1. The detection of this operating state isReference form 1In the same manner as described above, the amount of load is detected from the rotational speed of the internal combustion engine 1 and the output of the air flow sensor 3 and the like, and the exhaust gas temperature of the internal combustion engine 1 is estimated from the output of the air-fuel ratio sensor 10 and these parameters. The temperature of the three-way catalyst 11 and the temperature of the NOx storage catalyst 13 are estimated from the output of the exhaust gas temperature sensor 12.
[0040]
  Then in step 602Reference form 1Similarly, the SOx adsorption amount adsorbed on the NOx occlusion catalyst 13 is estimated, and in step 603, the temperature rise permission determination of the N0x occlusion catalyst 13 is performed based on the detection of the operating state and the estimation of the SOx adsorption amount. This determination isReference form 1It is the same as the case of. If the permission determination is made in step 603, it is determined in step 604 whether or not the temperature increase mode flag is established. If not established, the process proceeds to step 605 to determine whether or not the temperature increase maintenance mode flag is established. To do.
[0041]
Here, the temperature increase mode refers to the target temperature Ttwc of the three-way catalyst 11 disposed upstream of the N0x storage catalyst 13 in order to raise the temperature of the N0x storage catalyst 13 to the target temperature Tlnnt by additional injection. In the temperature increase maintenance mode, additional injection and ignition timing retardation are alternately repeated, and the temperature of the NOx storage catalyst 13 that has been increased in temperature increase mode is made the SOx dischargeable temperature. To maintain. When both the flags are not established and are in the OFF state, it is determined that the temperature raising mode is started from this routine. In step 606, the temperature raising mode flag is turned ON, and in step 607, the additional injection execution period α is determined. That is, the number of additional injection cycles is determined.
[0042]
  The number of cycles of this additional injection is determinedReference form 1In other words, the temperature of the NOx storage catalyst 13 is necessary to raise the temperature to the target temperature Tlnt. In other words, the three-way catalyst 11 arranged upstream is raised to the target temperature Ttwc. The additional injection execution period for each operation state necessary for this is experimentally obtained in advance and stored in a map, and the rotational speed and load of the internal combustion engine are retrieved as parameters and obtained.
[0043]
  When the additional injection execution period α is determined in step 607, the process proceeds to step 608, where the additional injection execution period α is set in the additional injection counter, and in step 609 the additional injection is executed. This additional jet isReference form 1In the same manner as in the above, the combustion stroke or the exhaust stroke of the internal combustion engine 1 is performed, but the amount of additional injection (the amount of fuel) is determined in advance so that the exhaust gas and the combustion are not deteriorated depending on the operating state. It is stored in the control means 16 and is searched using the rotational speed and load of the internal combustion engine 1 at the time of performing the additional injection as parameters. In step 610, the additional injection counter set in step 608 is decremented.
[0044]
Subsequently, the routine proceeds to step 611, where it is determined whether or not the additional injection counter has become zero, and if it is not zero, the routine of this time is terminated assuming that additional injection is being performed, and the routine returns to the start. If the additional injection counter is zero, it is determined that the additional injection in the temperature raising mode is completed, and the process proceeds to step 612. In step 613, the temperature raising mode flag is turned off and the temperature raising maintenance mode is started. Turn on the temperature increase maintenance mode flag. In the temperature increase maintenance mode, first, in order to retard the ignition timing and maintain the temperature, the ignition timing retardation mode flag is set to ON in step 614, and in step 615, the ignition timing retardation execution period θ is set. decide.
[0045]
The execution period θ of the ignition timing retard is determined by experimentally obtaining in advance the period during which the temperature of the NOx storage catalyst 13 can be maintained up to the lower limit value of the SOx release temperature by the retard of the ignition timing, and as a map to the control means 16. It is stored and obtained by searching the rotational speed and load of the internal combustion engine as parameters when the ignition timing is retarded. At this time, the control constants such as the retard amount of the ignition timing and the fuel injection amount are stored in the map by selecting values that have a high temperature rising effect for each operating state and do not deteriorate the behavior. When the ignition timing retard execution period θ is determined in step 615, the routine proceeds to step 616, where the ignition timing retard counter is set to the execution period θ and the process returns to the start.
[0046]
In step 605, the temperature increase maintenance mode flag is established. If the flag is ON, the process proceeds to step 617 to check whether the additional injection mode flag is established. This confirmation is to distinguish between the additional injection mode and the ignition timing retarding mode in the temperature increase maintenance mode. If the additional injection mode flag is established, the process proceeds to step 625, and if not, the ignition timing retarding mode is established. And the process proceeds to step 618. In step 618, the ignition timing retard amount and the fuel injection amount are set by the above map search to execute the ignition timing retard, and the process proceeds to step 619 to decrement the ignition timing retard counter.
[0047]
Next, the routine proceeds to step 620, where it is determined whether or not the ignition timing retard counter is zero, that is, whether or not there is an ignition timing retard execution period, and if there is an implementation period, the process returns to the start. When the routine is repeated and it is determined that the counter is zero and the execution period has ended, the ignition timing retarding mode flag is turned OFF in step 621. Subsequently, in step 622, the additional injection mode flag is turned on to raise the catalyst temperature, and the process proceeds to step 623 to determine the additional injection execution period γ in the temperature rise maintenance mode, and in step 624, the additional injection is performed. The value of γ is set in the counter.
[0048]
The determination of the additional injection execution period γ in the temperature increase maintenance mode is the same as the determination of the additional injection execution period α in the temperature increase mode described above, but the additional injection execution period for each operating state is experimentally obtained in advance. The map is stored in a different map from the additional injection execution period map in the temperature raising mode, and the rotational speed and load of the internal combustion engine 1 are searched and set as parameters. If the value of γ is set in step 624, the current routine is terminated, and the next routine proceeds from step 617 to step 625 until the value of the counter becomes zero.
[0049]
If the additional injection mode flag is ON in step 617, the process proceeds to step 625 as described above. In step 625, the additional injection is performed by setting the injection amount of the additional injection in the temperature increase maintenance mode, Proceeding to 626, the counter for additional injection (set in step 624) is decremented. In step 627, it is determined whether or not the implementation period of the additional injection in the temperature rising maintenance mode has ended. If the counter is not zero, the implementation period has not ended, so the routine returns to the start and the routine is repeated. If the execution period has ended, the routine proceeds to step 628, where the additional injection mode flag is turned OFF.
[0050]
After the additional injection mode flag is turned off in step 628, the routine further proceeds to step 629, where the ignition timing retard mode flag is set to ON, and in step 630, the execution period θ is set in the ignition timing retard counter. Return to the start. In this way, while the temperature increase permission determination is made in step 603, the ignition timing retard execution period θ and the additional injection execution period γ are alternately repeated. When the SOx adsorbed on the N0x storage catalyst 13 is released and becomes a predetermined value or less during the execution of this process, and when the operating state changes and becomes a transient behavior, the determination in step 603 increases. In step 631, the flags of the additional injection mode and the ignition timing retarding mode are turned OFF, the counters are initialized in step 632, and the process proceeds to step 633, where the combustion corresponding to the operating state is performed. Return to mode to complete the process.
[0051]
As described above, in the exhaust gas purification apparatus for an internal combustion engine according to this embodiment, when the temperature increase permission is determined and the temperature increase mode is established, the additional injection is performed, and the temperature of the N0x storage catalyst 13 reaches the predetermined value by the additional injection. When the temperature rises, the retard of the ignition timing for maintaining the temperature rise and the additional injection for maintaining the temperature rise are alternately repeated, and in an operating state where the temperature rise cannot be maintained only by the retard of the ignition timing. In addition, the temperature of the NOx storage catalyst 13 can be maintained at a temperature at which SOx can be released, and the additional injection period for the first temperature increase is shortened, so that the exhaust gas deteriorates or the three-way catalyst 11 overheats. It becomes possible to prevent more effectively.
[0052]
ImplementationForm 2.
  FIG. 7 shows the implementation of the present invention.Form 2FIG. 3 is a flowchart for explaining the operation of the exhaust gas purification apparatus for an internal combustion engine according to FIG.Form 1The same step numbers are assigned to the same operation portions as those in FIG. An exhaust gas purification apparatus for an internal combustion engine according to this embodiment isForm 1Changed the method for setting the additional injection execution period in the temperature rising mode and the temperature rising maintenance mode and the method for setting the ignition timing retarding execution period in the temperature rising maintenance mode for the exhaust gas purification device for the internal combustion engine by Is.
[0053]
  In the flowchart of FIG. 7, steps 601 to 606 are performed as described above.Form 1Is the same process. That is, step 601 detects the operating state of the internal combustion engine 1 based on signals from each sensor, step 602 estimates the SOx adsorption amount adsorbed on the NOx storage catalyst 13, and step 603 indicates the operating state. The temperature increase permission determination of the N0x storage catalyst 13 is performed based on the detection of the NOx and the estimation of the SOx adsorption amount. In step 604, it is determined whether the temperature increase mode flag has been established. If not, the process proceeds to step 605 to determine whether the temperature increase maintenance mode flag has been established. If not, the temperature raising mode flag is established in step 606.Form 1Is the same.
[0054]
  When the temperature increase mode flag is established, the execution period α of the additional injection is determined in step 607a. The determination of the execution period α in this embodiment is as follows.Form 1Unlike the map search that was obtained experimentally in advance,Reference form 2As described above, the injection period α required to raise the temperature of the N0x storage catalyst 13 to the target temperature Tlnt is calculated from the calorific value of the additionally injected fuel. That is, the injection period α is set by the above-described equation (2). When the execution period α of the additional injection is set in step 607a, steps 608 to 614 are executed.Form 1The same processing as in the case ofForm 1As explained in.
[0055]
  In this embodiment, as will be described later, the method for setting the ignition timing retard period in the temperature increase maintenance mode is implemented.Form 1Therefore, if the ignition timing retardation mode flag at the time of maintaining the temperature rise is set to ON in step 614, the current routine is terminated without returning to the ignition timing retardation execution period, and the process returns to the start. If the temperature rising maintenance mode is established in step 605,Form 1In the same way as in step 617, the process proceeds to step 617. If the additional injection mode is not established, the process proceeds to step 618, where the ignition timing retard amount and the fuel injection amount are set and the ignition timing retard is performed. Subsequently, the routine proceeds to step 701, where it is determined whether or not to retard the ignition timing.
[0056]
The determination in step 701 is performed by the control means 16 storing the permitted temperature of ignition timing retardation control with respect to the temperature of the N0x storage catalyst 13 and comparing the temperature of the N0x storage catalyst 13 with the permitted temperature. That is, if the temperature of the N0x storage catalyst 13 is higher than the permitted temperature, the routine is ended in step 701 and the routine returns to the start, and the temperature increase maintenance mode based on the retard of the ignition timing is continued. If the temperature of the NOx storage catalyst 13 falls below the permitted temperature, the routine proceeds to step 621, where the ignition timing retard mode flag is turned off, and at step 622, the additional injection mode flag is turned on. Here, it is determined from the temperature of the NOx storage catalyst 13 that the temperature cannot be maintained in the ignition timing retard mode, and the mode is switched to the additional injection mode.
[0057]
  When the additional injection mode flag is turned ON in step 622, the additional injection execution period γ in the temperature raising mode is determined in step 623a. The determination method here is the same as in step 607a described above. It calculates from the calorific value of the fuel injected. In step 624, the value of γ is set in the additional injection counter and the process returns to the start. In the next routine, since the additional injection mode flag is ON, the process proceeds from step 617 to step 625.Form 1The additional injection is performed in the same manner as in. However, the implementationForm 1In comparison with the temperature increase mode, the ignition timing retardation execution period is determined by the temperature of the NOx storage catalyst 13 as described above, and therefore the ignition timing retardation counter setting (step 630 in FIG. 3) is not performed. Also, the counter decrement process (step 619 in FIG. 3) is not performed.
[0058]
  As described above, in the exhaust gas purification apparatus for an internal combustion engine according to this embodiment, the injection period of the additional injection is calculated based on the heat generation amount of the additionally injected fuel.And thenThe execution period of the additional injection can be determined with higher accuracy, the deterioration of the exhaust gas and the combustion state can be suppressed, the excessive temperature rise of the three-way catalyst 11 can be prevented, and the ignition timing retarded in the temperature increase maintenance mode. Is switched in a feedback manner using the temperature of the NOx storage catalyst 13 as an index, so that the temperature control accuracy of the NOx storage catalyst 13 can be improved, the processing can be simplified, and even if the internal combustion engine varies, This makes it possible to reliably release SOx.
[0059]
Reference form 3
  Reference form 3The exhaust gas purification device for an internal combustion engine byReference formThe temperature control value of the N0x occlusion catalyst 13 is changed according to the estimated amount of adsorption of SOx adsorbed by the N0x occlusion catalyst 13 to the exhaust gas purification devices of the internal combustion engine 1 and 2.Reference form2, when the SOx adsorption amount is estimated in step 202, the N0x storage catalyst 13 according to the adsorption amount is estimated.Standard temperatureSet the degree. This target temperature is set to a higher value as the estimated value of the SOx adsorption amount is larger.
[0060]
  In step 207 of FIG. 2, the additional injection execution period α is determined with respect to the target temperature set according to the SOx adsorption amount. That is, the larger the SOx adsorption amount, the larger the value of α is determined, and the heating time of the N0x storage catalyst 13 is extended. The control unit 16 determines the additional injection execution period α at this time.Reference formThe map of the additional injection execution period described in 1 is stored for each target temperature, and is made by switching this map.
[0061]
  By determining the additional injection execution period α in this manner, even when the amount of SOx adsorbed on the N0x storage catalyst 13 is large, the release speed can be increased and the release can be performed in a short time. In addition,Reference formIn the case of 2, the same effect can be obtained by changing the value of the target temperature Ttwc of the three-way catalyst shown in the above equation (2) according to the SOx adsorption amount.
[0062]
Embodiment 3 FIG.
  FIG. 8 shows the implementation of the present invention.Form 3FIG. 2 is a characteristic diagram for explaining the operation of the exhaust gas purification apparatus for an internal combustion engine according to the embodiment.1 and 2For exhaust purification system of internal combustion engineReference form 3As in the case of the above, the temperature control value of the NOx storage catalyst 13 is changed in accordance with the estimated SOx adsorption amount.
[0063]
  Embodiment1 and 2In the flowcharts of FIGS. 6 and 7 described in step 602, when estimating the adsorption amount of SOx in step 602,Reference form 3The target of the NOx storage catalyst 13 according to the amount of adsorption as in the case oftemperatureSet. In the flowchart of FIG. 6, when determining the execution period θ of the ignition timing delay when maintaining the temperature rise in step 615, a plurality of maps corresponding to the estimated SOx adsorption amount are prepared, and the SOx A map is selected and used according to the estimated adsorption amount. Further, in the flowchart of FIG. 7, in step 701, the control means 16 stores a plurality of permitted temperatures for ignition timing retardation control with respect to the temperature of the N0x storage catalyst 13, and selects these permitted temperatures according to the estimated SOx adsorption amount. To use.
[0064]
FIG. 8 shows such temperature control. When the estimated SOx adsorption amount is small, the setting of the additional injection execution period α in step 607 is selected as the time when the temperature of the NOx storage catalyst 13 becomes t1, When the temperature reaches t1, it shifts to a temperature increase maintenance mode by ignition timing retardation. Then, when the temperature of the N0x storage catalyst 13 decreases to t2, transition to additional injection in the temperature increase maintenance mode, and setting of γ in step 623 so as to continue the additional injection until the temperature of the N0x storage catalyst 13 reaches t1, In step 615, θ is set, and in step 701, the permitted temperature is set.
[0065]
When the estimated SOx adsorption amount is large, the additional injection execution period α in step 607 is set to a time when the temperature of the NOx storage catalyst 13 becomes t3 higher than t1, that is, the time is increased and the temperature is increased. When it reaches t3, it shifts to the temperature increase maintenance mode by the ignition timing retardation. When the temperature of the N0x storage catalyst 13 decreases to t4 higher than t2, the process proceeds to additional injection in the temperature rising maintenance mode, and the additional injection is continued until the temperature of the N0x storage catalyst 13 reaches t3. In this way, γ is set in step 623, θ is set in step 615, and allowed temperature is set in step 701.
[0066]
  As described above, by controlling the target temperature during temperature rise and the lower limit temperature during temperature rise maintenance,NEven when the amount of SOx adsorbed on the 0x storage catalyst 13 is large, the release rate can be increased to enable release in a short period of time, suppressing exhaust gas deterioration, excessive catalyst temperature rise, combustion deterioration, etc. It is possible to do that.
[0067]
Embodiment 4 FIG.
  ImplementationForm 4The exhaust gas purification apparatus for an internal combustion engine according to the present invention is the exhaust gas purification apparatus for an internal combustion engine according to each of the embodiments described above. Is to change.Reference forms 1 and 2about,Reference form 3In the same manner as in, the additional injection execution period α is set, the larger the SOx adsorption amount estimation value, the higher the target temperature, thereby extending the temperature maintenance time, and the time until the non-permission determination in step 203 is set. Lengthen. ImplementationForm 1 and 2In this case, the temperature increase maintenance mode time determined in step 603 is controlled in accordance with the SOx adsorption amount estimated value, and the temperature of the catalyst is excessively increased by controlling in this way. Thus, SOx can be effectively released.
[0068]
In each of the embodiments described above, the temperature of the three-way catalyst 11 and the temperature of the NOx storage catalyst 13 are estimated from the output of the air-fuel ratio sensor 10 and the value of the exhaust temperature sensor 12. However, it is also possible to provide a temperature sensor for each catalyst, and it is possible to estimate the operating state such as the rotational speed and load amount of the internal combustion engine as a parameter.
[0069]
【The invention's effect】
  As described above, in the exhaust gas purification apparatus for an internal combustion engine according to the present invention, according to the first aspect of the present invention, the fuel injection means for injecting fuel into the combustion chamber of the internal combustion engine and the ignition for igniting this fuel Means, a NOx storage catalyst provided in the exhaust passage, and a control means for controlling the fuel injection amount, the injection timing, and the ignition timing, and the control means estimates the adsorption amount of SOx adsorbed on the NOx storage catalyst. When it is determined that the SOx adsorption amount exceeds a predetermined value, the fuel is additionally injected for a predetermined period in the combustion stroke or the exhaust stroke of the internal combustion engine to raise the temperature of the NOx storage catalyst to a predetermined temperature.For a predetermined period after completion, the retard of the ignition timing and the additional injection are alternately performed.Since the temperature of the NOx storage catalyst is maintained, it is possible to sufficiently increase the temperature and maintain the temperature of the NOx storage catalyst while shortening the additional injection time of the fuel. It is possible to obtain excellent effects such as suppressing deterioration of the combustion state and preventing an excessive temperature rise of the three-way catalyst.
Further, the temperature of the NOx storage catalyst can be maintained at a temperature at which SOx can be released even in an operating state where the temperature rise cannot be maintained only by retarding the ignition timing.
[0070]
According to the second aspect of the invention, in the first aspect of the invention, the predetermined period for performing the additional injection is determined in accordance with the operating state of the internal combustion engine. There is no excess or deficiency in the temperature rise of the NOx storage catalyst, and the exhaust gas and the combustion state are prevented from deteriorating while reliably releasing SOx, thereby preventing the temperature rise of the three-way catalyst.
Further, according to the third aspect of the invention, since the predetermined period for performing the additional injection is calculated from the injection amount per one time of the additionally injected fuel, the temperature of the NOx storage catalyst can be accurately adjusted. It is possible to control well and to suppress the deterioration of exhaust gas and combustion state by the improvement in accuracy.
[0071]
Furthermore, according to the invention described in claim 4, the amount of heat necessary for raising the temperature of the NOx storage catalyst to a predetermined temperature and the amount of heat generated by the additionally injected fuel during the predetermined period for performing the additional injection Therefore, the temperature of the NOx storage catalyst can be controlled with higher accuracy, and SOx can be reliably released while suppressing the deterioration of the exhaust gas and the combustion state.
According to the fifth aspect of the invention, in the third and fourth aspects of the invention, the predetermined period for performing the additional injection is corrected in accordance with the operating state of the internal combustion engine. It is possible to control the temperature of the exhaust gas more accurately, and to suppress the deterioration of exhaust gas and combustion state.
[0072]
Further, according to the sixth aspect of the invention, in the third and fourth aspects of the invention, the predetermined period for performing the additional injection is corrected according to the exhaust gas temperature of the internal combustion engine. The temperature of the catalyst can be controlled with higher accuracy, the deterioration of the exhaust gas and the combustion state can be suppressed, and the excessive temperature rise of the three-way catalyst can be prevented.
[0073]
Furthermore, according to the invention of claim 7,Since the predetermined temperature when the NOx storage catalyst is heated to a predetermined temperature by additional injection is determined in accordance with the adsorption amount of SOx adsorbed on the NOx storage catalyst, it corresponds to the adsorption amount of SOx. Thus, the temperature of the NOx storage catalyst is controlled, and even when the amount of SOx adsorbed is large, the NOx storage catalyst can be released in a short time.
[0074]
According to the invention as set forth in claim 8,The temperature of the NOx storage catalyst is increased to a predetermined temperature by additional injection, and after completion of the additional injection, the temperature of the NOx storage catalyst is maintained by alternately repeating the ignition timing retardation and additional injection every predetermined period. As a result, the temperature of the NOx storage catalyst can be continuously maintained at a temperature at which SOx can be released even in an operating state in which the temperature rise cannot be maintained only by retarding the ignition timing, and the duration of the additional injection Is shortened, so that deterioration of exhaust gas and combustion state can be suppressed.
Also,According to the invention of claim 9, in the invention of claim 8,Predetermined period for retarding ignition timingAnd a predetermined period for performing additional injection,Since it is determined according to the operating state of the internal combustion engine, even if the time constant of the temperature decrease of the NOx storage catalyst varies depending on the operating state, it can be accurately shifted to additional injection, and SOx release is incomplete or a three-way catalyst It is possible to prevent an excessive temperature rise.
  further,According to the invention described in claim 10,In the invention, a predetermined period during which the ignition timing is retardedAnd a predetermined period for performing additional injection,Since the determination is made according to the amount of SOx adsorbed on the NOx storage catalyst, SOx can be effectively released without excessively raising the temperature of the three-way catalyst. is there.
[0075]
Furthermore,According to the eleventh aspect of the present invention,In the present invention, the ignition timing is retarded for a period until the temperature of the NOx storage catalyst decreases to a predetermined value, and additional injection for maintaining the temperature of the NOx storage catalyst when the temperature of the NOx storage catalyst decreases to a predetermined value. Therefore, the NOx storage catalyst maintenance temperature accuracy is improved, the SOx release time is shortened, and control that absorbs variations in the internal combustion engine is possible, and additional injection is required to maintain the temperature. Only at times can the deterioration of exhaust gas and combustion conditions be suppressed.
[0076]
Also,According to the invention of claim 12, the invention of claim 11 is provided., The predetermined value of the NOx occlusion catalyst temperature is determined in accordance with the adsorption amount of SOx adsorbed on the NOx occlusion catalyst, so that the temperature of the NOx occlusion catalyst can be controlled in correspondence with the adsorption amount of SOx, Even when the amount of SOx adsorbed is large, SOx can be released in a short time.The
[0078]
In the exhaust gas purification method for an internal combustion engine according to the present invention,Claim 13According to the invention, the fuel injection means is provided in the combustion chamber of the internal combustion engine to inject the fuel, and this is ignited by the ignition means, and the NOx storage catalyst is provided in the exhaust gas passage to store and reduce NOx. When it is estimated that the amount of SOx adsorbed on the NOx storage catalyst exceeds a predetermined value in the internal combustion engine that performs NO, the fuel is additionally injected in the combustion stroke or the exhaust stroke of the internal combustion engine to bring the NOx storage catalyst to the predetermined temperature. After raising the temperature and raising the temperature of the NOx storage catalystThe ignition timing retarded by the ignition means and the additional injection are alternately performed.Since the SOx is released from the NOx storage catalyst by maintaining the temperature of the NOx storage catalyst, it is possible to increase the temperature and maintain the temperature of the NOx storage catalyst while shortening the additional fuel injection time. It is possible to suppress the deterioration of the exhaust gas and the combustion state caused by the additional injection and prevent the excessive temperature rise of the three-way catalyst.Further, the temperature of the NOx storage catalyst can be maintained at a temperature at which SOx can be released regardless of the operating state of the internal combustion engine.
[0079]
further,Claim 14According to the exhaust gas purification method described in the above, the period for performing the additional injection is calculated from the amount of heat required to raise the NOx storage catalyst temperature to a predetermined value and the calorific value of the additionally injected fuel. Therefore, the temperature of the NOx storage catalyst can be accurately controlled, and SOx can be reliably released while suppressing deterioration of exhaust gas and combustion state.
[0081]
Also,Claim 15According to the exhaust gas purification method described in the above, the delay of the ignition timing for maintaining the temperature is continued until the NOx storage catalyst temperature decreases to a predetermined value, and when this temperature decreases to the predetermined value, it is again performed by additional injection. Since the temperature is raised, the maintenance temperature accuracy of the NOx storage catalyst is improved, the release of SOx is shortened, and control that absorbs variations in the internal combustion engine can be performed.
[0083]
further,Claim 16According to the exhaust gas purification method described in the above, the period of execution of the additional injection when the NOx storage catalyst is heated to a predetermined temperature by additional injection, and / or the ignition timing retardation and the additional injection when maintaining the temperature, Is determined in accordance with the adsorption amount of SOx adsorbed on the NOx storage catalyst, so that the temperature of the NOx storage catalyst can be controlled in correspondence with the adsorption amount of SOx as in the case of claim 18. Even when the amount of adsorption of SOx is large, SOx can be released in a short time, and SOx can be released while suppressing the temperature of the three-way catalyst or NOx storage catalyst.
[Brief description of the drawings]
FIG. 1 of the present inventionA reference for understanding basic concepts1 is a configuration diagram of an exhaust purification device for an internal combustion engine according to a first embodiment. FIG.
[Figure 2]Reference form 13 is a flowchart for explaining the operation of the exhaust gas purification apparatus for an internal combustion engine according to FIG.
[Fig. 3]Reference form 1It is explanatory drawing of the operating characteristic of the exhaust gas purification apparatus of the internal combustion engine by this.
FIG. 4 shows the present invention.A reference for understanding basic concepts6 is an explanatory diagram of a correction coefficient of an exhaust gas purification apparatus for an internal combustion engine according to a second embodiment. FIG.
[Figure 5]Reference form 2It is explanatory drawing of the correction coefficient of the exhaust gas purification device of the internal combustion engine by.
FIG. 6 shows the implementation of the present invention.Form 13 is a flowchart for explaining the operation of the exhaust gas purification apparatus for an internal combustion engine according to FIG.
FIG. 7 shows the implementation of the present invention.Form 23 is a flowchart for explaining the operation of the exhaust gas purification apparatus for an internal combustion engine according to FIG.
FIG. 8 shows the implementation of the present invention.Form 3It is a characteristic view explaining operation | movement of the exhaust gas purification apparatus of the internal combustion engine by FIG.

Claims (16)

Fuel injection means for injecting fuel into the combustion chamber of the internal combustion engine, ignition means for igniting fuel in the combustion chamber, NOx storage catalyst provided in the exhaust passage of the internal combustion engine, fuel injection amount and fuel injection of the fuel injection means And a control means for controlling the ignition timing of the ignition means, the control means estimates the amount of adsorption of SOx adsorbed on the NOx storage catalyst, and determines that the amount of adsorption of SOx exceeds a predetermined value In the combustion stroke or the exhaust stroke of the internal combustion engine, the fuel is additionally injected for a predetermined period to be in a temperature raising mode in which the NOx storage catalyst is heated to a predetermined temperature, and the ignition is performed for a predetermined period after completion of the additional injection. An exhaust gas purifying apparatus for an internal combustion engine, characterized in that a temperature increase maintaining mode for maintaining the temperature of the NOx storage catalyst by alternately performing a timing delay and the additional injection is provided . 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a predetermined period for performing the additional injection in the temperature raising mode is determined in accordance with an operating state of the internal combustion engine. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the predetermined period for performing the additional injection in the temperature raising mode is calculated from an injection amount per one additional injected fuel. The predetermined period for performing the additional injection in the temperature increasing mode is calculated from the amount of heat required to raise the temperature of the NOx storage catalyst to a predetermined temperature and the calorific value of the additionally injected fuel. The exhaust emission control device for an internal combustion engine according to claim 1. 5. The exhaust gas purification apparatus for an internal combustion engine according to claim 3, wherein a predetermined period for performing the additional injection in the temperature raising mode is corrected in accordance with an operating state of the internal combustion engine. The exhaust gas purification apparatus for an internal combustion engine according to claim 3 or 4, wherein a predetermined period during which the additional injection in the temperature raising mode is performed is corrected according to an exhaust gas temperature of the internal combustion engine. The predetermined temperature when the NOx storage catalyst is heated to a predetermined temperature by additional injection in the temperature increase mode is determined in accordance with the adsorption amount of SOx adsorbed on the NOx storage catalyst. The exhaust emission control device for an internal combustion engine according to claim 1 . 2. The temperature of the NOx storage catalyst is maintained by repeating the ignition timing retardation and the additional injection alternately in the temperature increase maintenance mode at predetermined intervals, respectively. The exhaust emission control device for an internal combustion engine according to claim 7 . 9. The internal combustion engine according to claim 8, wherein a predetermined period during which the ignition timing is retarded and a predetermined period during which additional injection is performed in the temperature increase maintenance mode are determined in accordance with an operating state of the internal combustion engine. Engine exhaust purification system. 9. The ignition timing retardation for maintaining the temperature of the NOx storage catalyst and the execution period of additional injection are determined according to the amount of SOx adsorbed on the NOx storage catalyst. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1. The ignition timing is retarded for a period of time until the temperature of the NOx storage catalyst decreases to a predetermined value. When the temperature of the NOx storage catalyst decreases to a predetermined value, the temperature of the NOx storage catalyst is maintained. 9. The exhaust emission control device for an internal combustion engine according to claim 8, wherein the shift to the additional injection is performed . The exhaust gas purification apparatus for an internal combustion engine according to claim 11, wherein the predetermined value of the NOx storage catalyst temperature is determined according to an adsorption amount of SOx adsorbed on the NOx storage catalyst . In the internal combustion engine in which the fuel injection means is provided in the combustion chamber of the internal combustion engine to inject the fuel, and this is ignited by the ignition means, and the NOx storage catalyst is provided in the exhaust gas passage to store and reduce NOx. When it is estimated that the amount of SOx adsorbed on the NOx storage catalyst exceeds a predetermined value, fuel is added during the combustion stroke or exhaust stroke of the internal combustion engine. The NOx storage catalyst is heated to a predetermined temperature to be heated to a predetermined temperature, and after the NOx storage catalyst is heated, the ignition timing retarded by the ignition means and the additional injection are alternately performed to perform the NOx storage. An exhaust purification method for an internal combustion engine, characterized in that SOx is released from the NOx storage catalyst by adopting a temperature increase maintenance mode for maintaining the temperature of the storage catalyst. The execution period of the additional injection in the temperature raising mode is calculated from the amount of heat required to raise the NOx storage catalyst temperature to a predetermined value and the heat generation amount of the additionally injected fuel. Item 14. An exhaust purification method for an internal combustion engine according to Item 13. The retardation of the ignition timing for maintaining the temperature is continued until the NOx storage catalyst temperature decreases to a predetermined value, and when the NOx storage catalyst temperature decreases to the predetermined value, the temperature is increased again by the additional injection. 15. The exhaust gas purification method for an internal combustion engine according to claim 13 , wherein the exhaust gas purification method is used. An execution period of additional injection when the NOx storage catalyst is heated to a predetermined temperature by additional injection in the temperature increase mode, and / or an ignition timing retard and additional injection for maintaining the temperature in the temperature increase maintenance mode; The exhaust gas purification method for an internal combustion engine according to claim 13, wherein an execution period is determined in accordance with an adsorption amount of SOx adsorbed on the NOx storage catalyst .

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