JP5904191B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

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

  When the air-fuel ratio of the inflowing exhaust gas is lean, the NOx in the exhaust gas is occluded, and when the air-fuel ratio of the inflowing exhaust gas becomes rich, the NOx occlusion catalyst that releases and reduces the stored NOx is reduced to the engine exhaust passage. In order to release NOx or SOx from the NOx storage catalyst, the air-fuel ratio of the exhaust gas flowing into the NOx storage catalyst is temporarily increased by injecting additional fuel into the combustion chamber during the combustion stroke or the exhaust stroke. 2. Description of the Related Art An exhaust gas purification device for an internal combustion engine that performs rich control for switching to rich is known.

  However, if rich control is performed, for example, when the torque is considerably low, the torque TRQ varies greatly due to the rich control, and drivability may be deteriorated. If rich control is performed when the engine speed is considerably high, a large amount of additional fuel may be required to switch the air-fuel ratio of the exhaust gas flowing into the NOx storage catalyst to rich, or the NOx storage catalyst. It becomes difficult to reliably release NOx or SOx from the gas.

  Therefore, when the rich control is to be executed, it is determined whether the rich control execution condition is satisfied based on the engine operating state. When it is determined that the rich control execution condition is satisfied, the rich control is permitted. An exhaust gas purification apparatus for an internal combustion engine that prohibits rich control when it is determined that the rich control execution condition is not satisfied is known (see Patent Document 1).

JP 2007-154771 A

  However, in the above-described exhaust purification device, whether or not the rich control execution condition is satisfied depends on the engine operating state, and the engine operating state depends on the operation of the vehicle operator. Therefore, the rich control execution condition is not satisfied for a long time, that is, the chance of executing the rich control may be reduced. As a result, NOx or SOx is not released from the NOx storage catalyst over a long period of time, and NOx may not be purified well.

  According to the present invention, NOx in the exhaust gas is occluded when the air-fuel ratio of the inflowing exhaust gas is lean, and NOx occluded is released and reduced when the air-fuel ratio of the inflowing exhaust gas becomes rich. In order to release the NOx or SOx from the NOx storage catalyst by disposing the storage catalyst in the engine exhaust passage, the exhaust gas flowing into the NOx storage catalyst is injected by injecting additional fuel into the combustion chamber during the combustion stroke or the exhaust stroke. Rich control means that performs rich control that temporarily switches the air-fuel ratio to rich is provided, and when rich control is to be executed, it is determined whether the rich control execution condition is satisfied based on the engine operating state, and rich control is executed The rich control is executed when it is determined that the condition is satisfied, and the rich control is prohibited when the rich control execution condition is determined not to be satisfied. The air purification apparatus includes a transmission whose gear position is changed by a vehicle operator, and an indicator which displays an instruction for changing the gear position of the transmission to the vehicle operator, and when rich control is to be executed. If it is determined that the rich control execution condition is not satisfied, the gear position at which the rich control execution condition is satisfied when the gear position is changed under the constant engine output is obtained, and the indicator is controlled to control the gear position. Is displayed to the vehicle operator, and the vehicle operator changes the gear position to the determined gear position, thereby determining that the rich control execution condition is satisfied. An exhaust purification device for an internal combustion engine is provided that executes rich control when it is performed.

  Preferably, the rich control execution condition is determined to be satisfied when the engine operation state is within the rich control allowable region, and the rich control execution condition is not satisfied when the engine operation state is outside the rich control allowable region. It is judged.

  Preferably, the engine operating state is represented by the engine load and the engine speed.

  Preferably, it is determined that the rich control execution condition is satisfied when the engine operation state is in the rich control allowable range and the gear position of the transmission is in a predetermined gear position range, and the engine operation state Is outside the rich control allowable range or the gear position of the transmission is outside the set gear position range, it is determined that the rich control execution condition is not satisfied.

  Preferably, it is determined that the rich control execution condition is satisfied when the engine operating state is within the rich control allowable range and the temperature of the NOx storage catalyst is within a predetermined set temperature range, and the engine operating state is It is determined that the rich control execution condition is not satisfied when it is outside the rich control allowable range or when the temperature of the NOx storage catalyst is outside the set temperature range.

  Preferably, it is determined that the rich control execution condition is satisfied when the engine operating state is in the rich control allowable range and the vehicle speed is in a predetermined vehicle speed range, and the engine operating state is in the rich control allowable range. When the vehicle is outside or the vehicle speed is outside the set vehicle speed range, it is determined that the rich control execution condition is not satisfied.

  Preferably, when rich control is being performed, it is determined whether or not the rich control execution condition is satisfied when it is assumed that the gear position is changed under a constant engine output, and the rich control execution condition is not satisfied. When it is determined that there is an instruction, the indicator is controlled to display an instruction to the vehicle operator that the gear position should not be changed.

  An opportunity to execute the rich control can be secured, and therefore NOx can be purified well.

FIG. 1 is an overall view of an internal combustion engine. FIG. 2 is an overall view of the indicator. 3A and 3B are diagrams showing display patterns of the indicator. FIG. 4 is a cross-sectional view of the surface portion of the NOx storage catalyst. FIG. 5 is a diagram for explaining injection of additional fuel. FIG. 6 is a time chart for explaining rich control for NOx release. FIG. 7 is a view showing a map of the NOx emission amount NOXA. FIG. 8 is a time chart for explaining the rich control for SOx release. FIG. 9 is a diagram showing a map of the SOx emission amount SOXA. FIG. 10 is a diagram showing the rich control allowable area AA. FIG. 11 is a diagram for explaining changes in the engine operating state when the gear position is changed. FIG. 12 is a diagram for explaining a change in the engine operation state when the gear position is changed. FIG. 13 is a flowchart showing a control routine for the flag XN. FIG. 14 is a flowchart showing a control routine for the flag XS. FIG. 15 is a flowchart showing an exhaust purification control routine. FIG. 16 is a flowchart showing the indicator control routine. 17 (A), 17 (B), and 17 (C) are diagrams showing display patterns of an indicator in another embodiment according to the present invention. FIG. 18 is a diagram for explaining changes in the engine operating state when the gear position is changed. FIG. 19 is a flowchart showing an indicator control routine in another embodiment according to the present invention.

  Referring to FIG. 1, 1 is a main body of a compression ignition internal combustion engine, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, and 4 is an intake manifold. Reference numeral 5 denotes an exhaust manifold. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 through the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 9 through the intake introduction pipe 8. An electrically controlled throttle valve 10 is arranged in the intake duct 6, and a cooling device 11 for cooling intake air flowing in the intake duct 6 is arranged around the intake duct 6. An intake air amount detector 12 is disposed in the intake air introduction pipe 8.

  On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the NOx storage catalyst 14 through the exhaust pipe 13. The outlet of the NOx storage catalyst 14 is connected to a particulate filter 15 for collecting particulate matter in the exhaust gas. A differential pressure sensor 16 that detects a differential pressure across the particulate filter 15 is attached to the particulate filter 15.

  The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 17, and an electronically controlled EGR control valve 18 is disposed in the EGR passage 17. A cooling device 19 for cooling the EGR gas flowing in the EGR passage 17 is disposed around the EGR passage 17. On the other hand, each fuel injection valve 3 is connected to a common rail 21 via a fuel supply pipe 20, and this common rail 21 is connected to a fuel tank 23 via an electronically controlled variable discharge pump 22. The fuel stored in the fuel tank 23 is supplied into the common rail 21 by the fuel pump 22, and the fuel supplied into the common rail 21 is supplied to the fuel injection valve 3 through each fuel supply pipe 20. In another embodiment, the internal combustion engine 1 is a spark ignition type internal combustion engine. In this case, the fuel in the fuel tank 23 is gasoline, CNG, hydrogen or the like.

  An output shaft (not shown) of the internal combustion engine 1 is connected to the transmission 25. In the example shown in FIG. 1, the transmission 25 is constituted by a manual transmission, and the gear position of the transmission 25 is changed by the vehicle operator operating the shift lever 26. In another example, the transmission 25 is composed of an automatic transmission with a manual mode. In this manual mode, the gear position is changed by the vehicle operator operating the shift lever. Further, an indicator 27 for displaying an instruction regarding the gear position of the transmission 25 to the vehicle operator is provided.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36. It comprises. As shown in FIG. 1, the output signals of the intake air amount detector 12 and the differential pressure sensor 16 are input to the input port 35 via the corresponding AD converters 37 respectively. A load sensor 41 that generates an output voltage proportional to the depression amount L of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. . Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °. The CPU 34 calculates the engine speed N based on the output pulse from the crank angle sensor 42. A signal indicating the position of the shift lever 26, that is, the gear position of the transmission 25 is input to the input port 35. On the other hand, the output port 36 is connected to the fuel injection valve 3, the actuator for driving the throttle valve 10, the EGR control valve 18, the fuel pump 22, and the indicator 27 via a corresponding drive circuit 38.

  FIG. 2 shows an example of the indicator 27. The indicator 27 includes a lamp 27a having an upward arrow shape and a lamp 27b having a downward arrow shape. In the embodiment according to the present invention, an instruction to change the gear position is displayed to the vehicle operator by the indicator 27. When an instruction to shift up, that is, to change the gear position to a high gear is displayed, the upward lamp 27a is lit or blinked in green, for example, and the downward lamp 27b is turned off as shown in FIG. As a result, the vehicle operator is prompted to shift up. On the other hand, when downshifting, that is, when an instruction to change the gear position to the low speed stage is displayed, as shown in FIG. 3B, the downward lamp 27b is lit or blinked in green, for example, and the upward lamp 27a is turned off. . As a result, the vehicle operator is prompted to shift down. FIG. 2 shows a case where the lamps 27a and 27b are turned off. At this time, an instruction regarding the gear position is not displayed. Thus, in the embodiment according to the present invention, the indicator 27 displays an instruction regarding the gear position to the vehicle operator by light. In another embodiment, the indicator 27 displays an instruction by sound, vibration or the like. In yet another embodiment, the indicator 27 displays the current gear position in addition to an indication regarding the gear position.

  On the other hand, a catalyst carrier made of alumina, for example, is supported on the base of the NOx storage catalyst 14 shown in FIG. 1, and FIG. 4 schematically shows a cross section of the surface portion of the catalyst carrier 45. As shown in FIG. 4, a noble metal catalyst 46 is dispersed and supported on the surface of the catalyst carrier 45, and a layer of NOx absorbent 47 is formed on the surface of the catalyst carrier 45.

  In the example shown in FIG. 4, platinum Pt is used as the noble metal catalyst 46, and the constituents of the NOx absorbent 47 include, for example, alkali metals such as potassium K, sodium Na, cesium Cs, barium Ba, and calcium Ca. At least one selected from alkaline earths such as these, lanthanum La, and rare earths such as yttrium Y is used.

  When the ratio of air and fuel (hydrocarbon) supplied into the engine intake passage, the combustion chamber 2 and the exhaust passage upstream of the NOx storage catalyst 14 is referred to as the air-fuel ratio of the exhaust gas, the NOx absorbent 47 is the air-fuel ratio of the exhaust gas. When NO is lean, it absorbs NOx, and when the oxygen concentration in the exhaust gas decreases, the absorbed NOx is released.

That is, the case where barium Ba is used as a component constituting the NOx absorbent 47 will be described as an example. When the air-fuel ratio of the exhaust gas is lean, that is, when the oxygen concentration in the exhaust gas is high, the NO contained in the exhaust gas 4 is oxidized on platinum Pt 46 to become NO ₂ as shown in FIG. 4 and then absorbed into the NOx absorbent 47 and combined with barium carbonate BaCO _{3 in} the form of nitrate ions NO ₃ ⁻ in the NOx absorbent 47. To spread. In this way, NOx is absorbed in the NOx absorbent 47. Exhaust oxygen concentration in the _gas, NO ₂ is produced on a high as long as the surface of the platinum Pt 46, as long as NO ₂ to NOx absorbing capability of the NOx absorbent 47 is not saturated is absorbed in the NOx absorbent 47 nitrate ions NO ₃ ^- is Generated.

On the other hand, when the air-fuel ratio of the exhaust gas is switched from lean to rich or the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas decreases, so the reaction proceeds in the reverse direction (NO ₃ ⁻ → NO ₂ ). Nitrate ions NO ₃ ⁻ in the NOx absorbent 47 are released from the NOx absorbent 47 in the form of NO ₂ . Next, the released NOx is reduced by HC and CO contained in the exhaust gas.

  Note that NOx may be temporarily adsorbed by the NOx absorbent 47. Therefore, when the term occlusion is used as a term including both absorption and adsorption, the NOx occlusion catalyst 14 occludes NOx in the exhaust gas when the air-fuel ratio of the inflowing exhaust gas is lean, and the exhaust gas in the inflowing exhaust gas is empty. When the fuel ratio becomes rich, the stored NOx is released and reduced.

  Now, combustion is performed in the engine body 1 under excess oxygen. Therefore, since the air-fuel ratio of the exhaust gas flowing into the NOx storage catalyst 14 is lean, NOx in the exhaust gas is stored in the NOx storage catalyst 14 at this time. However, if the engine operating time is lengthened, the amount of NOx stored in the NOx storage catalyst 14 increases, and eventually the NOx storage catalyst 14 cannot store NOx.

  Therefore, in the embodiment according to the present invention, in order to release NOx from the NOx storage catalyst 14, the air-fuel ratio of the exhaust gas flowing into the NOx storage catalyst 14 is temporarily switched to rich. In this case, as shown in FIG. 5, in addition to the main fuel Qm injected around the compression top dead center (TDC), additional fuel Qa is transferred from the fuel injection valve 3 to the combustion chamber 2 in the combustion stroke or the exhaust stroke. Is injected into.

  When this control is referred to as rich control for NOx release, as shown in FIG. 6, when the NOx amount NOX stored in the NOx storage catalyst 14 exceeds the allowable amount MAXN, rich control for NOx release is performed. It is. As a result, the air-fuel ratio (A / F) in of the exhaust gas flowing into the NOx storage catalyst 14 is temporarily switched to rich, and the NOx storage amount NOX is reduced. In the embodiment according to the present invention, the NOx occlusion amount NOX is calculated from, for example, the NOx amount discharged from the engine. That is, the NOx emission amount NOXA discharged from the engine per unit time is stored in advance in the ROM 32 as a function of the depression amount L of the accelerator pedal 40 and the engine speed N in the form of a map as shown in FIG. The NOx occlusion amount NOX is calculated by repeatedly integrating the NOx emission amount NOXA.

Meanwhile, the exhaust gas contains SOx That SO _2, when this SO ₂ flows into the NOx storing catalyst 14 the SO ₂ is the is oxidized SO ₃ in the platinum Pt 46. Next, this SO ₃ is absorbed in the NOx absorbent 47 and bonded to the barium carbonate BaCO ₃ while diffusing into the NOx absorbent 47 in the form of sulfate ions SO ₄ ²⁻ to produce stable sulfate BaSO ₄ . . However, since the NOx absorbent 47 has a strong basicity, the sulfate BaSO ₄ is stable and difficult to decompose. If the air-fuel ratio of the exhaust gas is simply made rich, the sulfate BaSO ₄ remains as it is without being decomposed. . Therefore, the sulfate BaSO ₄ increases in the NOx absorbent 47 as time elapses, and thus the amount of NOx that can be absorbed by the NOx absorbent 47 decreases as time elapses.

  On the other hand, when the air-fuel ratio of the exhaust gas flowing into the NOx storage catalyst 14 is made rich with the temperature of the NOx storage catalyst 14 raised to an SOx release temperature of 600 ° C. or higher, SOx is released from the NOx absorbent 47.

  Therefore, in the embodiment according to the present invention, in order to release SOx from the NOx storage catalyst 14, the temperature of the NOx storage catalyst 14 is set to the SOx release temperature by injecting additional fuel QA into the combustion chamber 2 during the combustion stroke or the exhaust stroke. While maintaining the above, the air-fuel ratio of the exhaust gas flowing into the NOx storage catalyst 14 is temporarily switched to rich.

  When this control is referred to as rich control for SOx release, as shown in FIG. 8, when the SOx amount SOX stored in the NOx storage catalyst 14 exceeds the allowable amount MAXS, rich control for SOx release is performed. It is. As a result, the temperature of the NOx storage catalyst 14 is raised to the SOx release temperature TS or higher, and the air-fuel ratio (A / F) in of the exhaust gas flowing into the NOx storage catalyst 14 is temporarily switched to rich, so that the SOx storage amount SOX. Is reduced. In the embodiment according to the present invention, the SOx occlusion amount SOX is calculated from, for example, the SOx amount discharged from the engine. That is, the SOx emission amount SOXA discharged from the engine per unit time is stored in the ROM 32 in advance in the form of a map as shown in FIG. 9 as a function of the depression amount L of the accelerator pedal 40 and the engine speed N. The SOx occlusion amount SOX is calculated by repeatedly integrating the SOx emission amount SOXA.

  In the embodiment according to the present invention, when rich control for NOx release or SOx release is to be executed, it is determined whether the rich control execution condition is satisfied based on the engine operating state, and the rich control execution condition is Rich control is executed when it is determined that the rich control is satisfied, and rich control is prohibited when it is determined that the rich control execution condition is not satisfied.

  Specifically, the rich control execution condition includes a first execution condition and a second execution condition. First, it is determined whether or not the first execution condition is satisfied. When it is determined that the first execution condition is satisfied, it is determined whether or not the second execution condition is satisfied. When it is determined that the second execution condition is satisfied, rich control for NOx release or SOx release is executed. When the first execution condition or the second execution condition is not satisfied, the rich control for NOx release or SOx release is not executed.

  In the embodiment according to the present invention, the first execution condition is satisfied when the temperature TC of the NOx storage catalyst 14 is within a predetermined set temperature range and the vehicle speed is within a predetermined set vehicle speed range. When the temperature TC of the NOx storage catalyst 14 is outside the set temperature range or the vehicle speed is outside the set vehicle speed range, it is determined that the first execution condition is not satisfied. Further, it is determined that the second execution condition is satisfied when the engine operating state is within a predetermined rich control allowable range and the gear position of the transmission 25 is within a predetermined set gear position range. Then, it is determined that the second execution condition is not satisfied when the engine operation state is outside the rich control allowable range and the gear position of the transmission 25 is outside the set gear position range. In the embodiment according to the present invention, the engine operating state is represented by a combination of torque TRQ representing the engine load and engine speed N. FIG. 10 shows an example of the rich control allowable area AA.

  In this way, NOx and SOx can be reliably released from the NOx storage catalyst 14. In addition, the drivability is prevented from decreasing at this time, the consumption of the additional fuel Qa is reduced, and the NOx storage catalyst 14 is suppressed from being damaged by heat.

  However, whether or not the rich control execution condition, in particular, the second execution condition is satisfied depends on the engine operating state, so that the rich control execution condition may not be satisfied for a long time. As a result, the chance of executing rich control may be reduced.

  Therefore, in the embodiment according to the present invention, when it is determined that the second execution condition is not satisfied when the rich control is to be executed, the second execution is performed when it is assumed that the gear position is changed under a constant engine output. The gear position where the condition is satisfied is obtained as the target gear position. This will be described with reference to FIG.

  In FIG. 11, point P represents the engine operating state when the gear position is at the Nth gear. In this case, the point P is outside the rich control allowable area AA, and therefore the second execution condition is not satisfied. In this state, when the upshift is performed under a constant engine output, that is, when the gear position is changed to the (N + 1) speed stage, the engine operating state is changed to the point PU. This point PU is outside the rich control allowable area AA, and therefore the second execution condition remains unsatisfied. On the other hand, when the downshift is performed under a constant engine output, that is, when the gear position is changed to the (N-1) speed stage, the engine operating state is changed to the point PD. The point PD is in the rich control allowable area AA. Therefore, the second execution condition is established on the condition that the (N-1) speed stage is in the set gear position range. As a result, the rich control execution condition is satisfied. Therefore, in the example shown in FIG. 11, the (N-1) speed stage is obtained as the target gear position.

  When the target gear position is obtained, an instruction that the gear position should be changed to the target gear position is displayed to the vehicle operator by the indicator 27. Next, when the vehicle operator changes the gear position to the target gear position, the second execution condition is satisfied, and thus the rich control execution condition is satisfied. For this reason, rich control is executed. As a result, an opportunity to execute rich control is ensured, and NOx can be purified well.

  Therefore, conceptually speaking, when it is determined that the rich control execution condition is not satisfied when the rich control is to be executed, the rich control execution condition is set when the gear position is changed under a constant engine output. Find the gear position that is established, control the indicator to display to the vehicle operator that the gear position should be changed to the requested gear position, and set the gear position to the gear position obtained by the vehicle operator. When it is determined that the rich control execution condition has been satisfied, the rich control is executed.

  The engine operating state after the gear position is changed, that is, the combination of the torque TRQ and the engine speed N is, for example, the engine operating state before the change, the gear ratio at the gear position before the change, and the gear ratio at the gear position after the change. Is calculated from That is, the gear ratio, torque, and engine speed before the gear position change are represented by R1, TRQ1, and N1, respectively, and the gear ratio, torque, and engine speed after the gear position change are represented by R2, TRQ2, and N2, respectively. The torque TRQ2 and the engine speed N2 after the position change are represented by (R1 / R2) · TRQ1 and (R2 / R1) · N1, respectively.

  In the example shown in FIG. 12, both the point PD and the point PU are outside the rich control allowable area AA. Therefore, the second execution condition remains unsatisfied regardless of whether the downshift is performed or the upshift is performed. In this way, the target gear position may not be obtained. In this case, the indication by the indicator 27 is not displayed.

  FIG. 13 shows a routine for controlling the flag XN. This routine is executed by interruption every predetermined time.

  Referring to FIG. 13, in step 100, the NOx emission amount NOXA per unit time is calculated from the map shown in FIG. 7, and the NOx occlusion amount NOX is calculated by integrating the NOx emission amount NOXA (NOX = NOX + NOXA). Next, at step 101, it is judged if the NOx occlusion amount NOX has exceeded the allowable value MAXN. When NOX ≦ MAXN, the processing cycle is terminated. When NOX> MAXN, the routine proceeds from step 101 to step 102, where the flag XN is set (XN = 1). This flag XN is set when rich control for NOx release is to be executed (XN = 1), and is reset otherwise (XN = 0).

FIG. 14 shows a routine for controlling the flag XS. This routine is executed by interruption every predetermined time.
Referring to FIG. 14, in step 200, the SOx emission amount SOXA per unit time is calculated from the map shown in FIG. 9, and the SOx storage amount SOX is calculated by integrating the SOx emission amount SOXA (SOX = SOX + SOXA). Next, at step 201, it is judged if the SOx occlusion amount SOX has exceeded the allowable value MAXS. When SOX ≦ MAXS, the processing cycle ends. When SOX> MAXS, the routine proceeds from step 201 to step 202, where the flag XS is set (XS = 1). This flag XS is set when rich control for SOx release is to be executed (XS = 1), and is reset otherwise (XS = 0).

FIG. 15 shows a routine for executing the exhaust purification control. This routine is executed by interruption every predetermined time.
Referring to FIG. 15, in step 300, it is determined whether or not the flag XS is set. When the flag XS is reset (XS = 0), that is, when rich control for releasing SOx should not be performed, the routine proceeds to step 301, where it is determined whether or not the flag XN is set. When the flag XN is reset (XN = 0), that is, when rich control for NOx release should not be performed, the processing cycle is terminated. When the flag XN is set (XN = 1), that is, when rich control for releasing NOx is to be performed, the routine proceeds to step 302 where it is determined whether or not the first execution condition is satisfied. When it is determined that the first execution condition is not satisfied, the processing cycle is ended. When it is determined that the first execution condition is satisfied, the routine proceeds to step 303, where it is determined whether or not the second execution condition is satisfied. When it is determined that the second execution condition is satisfied, the routine proceeds to step 304 where rich control for NOx release is performed. In the following step 305, it is determined whether or not the rich control for releasing NOx should be terminated. When it is determined that the rich control for NOx release should not be terminated, the processing cycle is terminated. When it is determined that the rich control should be terminated, the routine proceeds to step 306, where the flag XN is reset (XN = 0), and the NOx occlusion amount NOX is cleared (NOX = 0).

  On the other hand, when the flag XS is set at step 300 (XS = 1), that is, when rich control for SOx release is to be performed, the routine proceeds to step 307, where it is determined whether or not the first execution condition is satisfied. Determined. When it is determined that the first execution condition is not satisfied, the processing cycle is ended. When it is determined that the first execution condition is satisfied, the routine proceeds to step 308, where it is determined whether or not the second execution condition is satisfied. When it is determined that the second execution condition is satisfied, the routine proceeds to step 309, where rich control for SOx release is performed. In the subsequent step 310, it is determined whether or not the rich control for releasing SOx should be terminated. When it is determined that the rich control for releasing SOx should not be terminated, the processing cycle is terminated. When it is determined that the rich control should be terminated, the routine proceeds to step 311 where the flag XS is reset (XS = 0) and the SOx occlusion amount NOX is cleared (SOX = 0). Next, the routine proceeds to step 306, where the flag XN is reset (XN = 0), and the NOx occlusion amount NOX is cleared (NOX = 0). This is because NOx is released from the NOx storage catalyst 14 when rich control for releasing SOx is performed.

  On the other hand, when it is determined in step 303 or step 308 that the second execution condition is not satisfied, the routine proceeds to step 312 where the target gear position GPT is calculated. In the following step 313, it is determined whether or not the target gear position GPT has been calculated. When the target gear position GPT cannot be calculated, the processing cycle ends. When the target gear position GPT has been calculated, the process proceeds to step 314, where an instruction to change the gear position of the transmission 25 to the target gear position GPT is displayed by the indicator 27. When the vehicle operator changes the gear position to the target gear position GPT in accordance with the instruction displayed on the indicator 27, the first execution condition and the second execution condition are satisfied. As a result, rich control for NOx release or SOx release is started.

FIG. 16 shows a routine for executing the control of the indicator 27. This routine is executed by interruption every predetermined time.
Referring to FIG. 16, in step 400, it is determined whether or not the indicator 27 displays an instruction to change the gear position of the transmission 25. When the indicator 27 does not display an instruction, the processing cycle is terminated. When the indicator 27 displays an instruction, the process proceeds to step 401, where it is determined whether or not the current gear position GP matches the target gear position GPT. When the current gear position GP does not coincide with the target gear position GPT, the processing cycle is ended. When the current gear position GP coincides with the target gear position GPT, the process proceeds to step 402, and the display of the instruction by the indicator 27 is stopped.

Next, another embodiment according to the present invention will be described.
In another embodiment according to the present invention, the indicator 27 displays an instruction that the gear position should not be changed in addition to an instruction that the gear position of the transmission 25 should be changed. That is, when an instruction not to shift up is displayed, as shown in FIG. 17A, the upward lamp 27a is turned on or blinks in red, for example, and the downward lamp 27b is turned off. On the other hand, when an instruction not to shift down is displayed, as shown in FIG. 17B, the downward lamp 27b is turned on or blinks in red, for example, and the upward lamp 27a is turned off. When an instruction that both upshift and downshift should not be displayed is displayed, as shown in FIG. 17C, the upward lamp 27a and the downward lamp 27b are lit or blinked in red, for example.

  Now, when the gear position of the transmission 25 is changed while the rich control is being performed, the engine operating state is changed. In this case, the changed engine operating state may be outside the rich control allowable area AA. That is, in the example shown in FIG. 18, if the downshift is performed when the point Q representing the engine operating state is within the rich control allowable area AA, the engine operating state is changed to the point QD. This point QD is outside the rich control allowable area AA, and therefore the second execution condition is not satisfied. The second execution condition is also not satisfied when the gear position is changed outside the set gear position range during the rich control. As described above, when the rich control execution condition is not satisfied during the rich control, the rich control is interrupted.

  Therefore, in another embodiment according to the present invention, the rich control execution condition is satisfied when it is assumed that the gear position is changed under a constant engine output when rich control for NOx release or SOx release is performed. When it is determined that the rich control execution condition is not satisfied, the indicator 27 indicates to the vehicle operator that the gear position should not be changed. As a result, if the vehicle operator does not change the gear position, the state in which the rich control execution condition is satisfied is maintained, and therefore rich control is continued.

FIG. 19 shows a routine for executing the control of the indicator 27 in another embodiment according to the present invention. This routine is executed by interruption every predetermined time.
Referring to FIG. 19, in step 500, it is determined whether or not rich control is currently being performed. When rich control is not being performed, the processing cycle is terminated. Next, when the rich control is being performed, the routine proceeds to step 501, where the engine operating state EOCU is estimated when it is assumed that the upshift has been performed under a constant engine output. In the next step 502, whether or not the second execution condition is not satisfied when it is assumed that the shift-up is performed under a constant engine output, the engine operating state EOCU when the shift-up is performed and It is determined based on the gear position. If it is determined that the second execution condition continues to be satisfied even if the shift is up, then the routine jumps to step 504. When it is determined that the second execution condition is not satisfied when the upshift is performed, the process proceeds to step 503 where an instruction that the upshift should not be performed is displayed by the indicator 27. Next, the routine proceeds to step 504.

  In step 504, the engine operating state EOCD is estimated when it is assumed that a downshift is performed under a constant engine output. In the following step 505, whether or not the second execution condition is not satisfied when it is assumed that the downshift is performed under a constant engine output, the engine operating state EOCD when the downshift is assumed and It is determined based on the gear position. If it is determined that the second execution condition continues to be satisfied even if the downshift is performed, the processing cycle is terminated. When it is determined that the second execution condition is not satisfied when the downshift is performed, the process proceeds to step 506, and an instruction that the downshift should not be performed is displayed by the indicator 27.

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Combustion chamber 3 Fuel injection valve 13 Exhaust pipe 14 NOx occlusion catalyst 25 Transmission 26 Shift lever 27 Indicator

Claims (7)

When the air-fuel ratio of the inflowing exhaust gas is lean, the NOx in the exhaust gas is occluded, and when the air-fuel ratio of the inflowing exhaust gas becomes rich, the NOx occlusion catalyst that releases and reduces the stored NOx is reduced to the engine exhaust passage. In order to release NOx from the NOx storage catalyst, the air-fuel ratio of the exhaust gas flowing into the NOx storage catalyst is temporarily rich by injecting additional fuel into the combustion chamber during the combustion stroke or exhaust stroke. Rich control means for performing the rich control to switch to, and when the rich control is to be executed, it is determined whether the rich control execution condition is satisfied based on the engine operating state, and the rich control execution condition is satisfied In an exhaust gas purification apparatus for an internal combustion engine, rich control is executed when determined, and rich control is prohibited when rich control execution conditions are determined to be not satisfied. The transmission includes a transmission whose gear position is changed by an operator, and an indicator which displays an instruction for changing the gear position of the transmission to the vehicle operator. When it is determined that the engine position is not satisfied, the gear position satisfying the rich control execution condition is determined when the gear position is changed under a constant engine output, and the gear position is determined by controlling the indicator. When an instruction to change the position is displayed to the vehicle operator and the vehicle operator changes the gear position to the determined gear position and thereby determines that the rich control execution condition is satisfied, An exhaust emission control device for an internal combustion engine that executes control.   It is determined that the rich control execution condition is satisfied when the engine operating state is within the rich control allowable region, and the rich control execution condition is determined not to be satisfied when the engine operating state is outside the rich control allowable region. The exhaust emission control device for an internal combustion engine according to claim 1.   The exhaust emission control device for an internal combustion engine according to claim 1 or 2, wherein the engine operating state is represented by an engine load and an engine speed.   It is determined that the rich control execution condition is satisfied when the engine operation state is within the rich control allowable range and the gear position of the transmission is within a predetermined gear position range, and the engine operation state is rich control. The exhaust emission control device for an internal combustion engine according to claim 2 or 3, wherein it is determined that the rich control execution condition is not satisfied when it is outside the allowable range or when the gear position of the transmission is outside the set gear position range.   When the engine operating state is within the rich control allowable range and the temperature of the NOx storage catalyst is within the predetermined set temperature range, it is determined that the rich control execution condition is satisfied, and the engine operating state is rich control allowable. The internal combustion engine according to any one of claims 2 to 4, wherein the rich control execution condition is determined not to be satisfied when the engine is outside the region or the temperature of the NOx storage catalyst is outside the set temperature range. Exhaust purification device.   It is determined that the rich control execution condition is satisfied when the engine operating state is within the rich control allowable range and the vehicle speed is within the predetermined vehicle speed range, and the engine operating state is outside the rich control allowable range. 6. The exhaust gas purification apparatus for an internal combustion engine according to claim 2, wherein it is determined that the rich control execution condition is not satisfied when the vehicle speed is outside the set vehicle speed range.   When rich control is being performed, it is determined whether or not the rich control execution condition is satisfied when it is assumed that the gear position is changed under a constant engine output, and it is determined that the rich control execution condition is not satisfied. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 6, wherein when it is done, the indicator is controlled to display to the vehicle operator an instruction that the gear position should not be changed.

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