JP2017044147A - Poisoning determination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a poisoning determination device capable of appropriately determining whether or not an exhaust purification catalyst is in a poisoned state.SOLUTION: A poisoning determination device comprises: a first exhaust temperature detection section 74 which detects a temperature of exhaust flowing into an exhaust purification catalyst; a second exhaust temperature detection section 75 which detects the temperature of the exhaust flowing out of the exhaust purification catalyst; a determination value calculation section which carries out an operation to obtain a poisoning determination value on the basis of a temperature difference between the temperature detected by the first exhaust temperature detection section 74 and the temperature detected by the second exhaust temperature detection section 75; and a catalyst determination section 78 which determines that the exhaust purification catalyst is in a poisoned state when the poisoning determination value is less than a determination threshold.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a poisoning determination apparatus that determines whether or not an exhaust purification catalyst provided in an exhaust passage of an engine mounted on a vehicle is poisoned by sulfur oxides.

  Exhaust gas discharged from engines mounted on vehicles such as automobiles includes carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), particulate matter (PM), etc. Contains exhaust gas components. For this reason, the engine exhaust passage is provided with a three-way catalyst for decomposing (reducing or the like) the above substances, a particulate filter for capturing PM, and the like.

  For example, in the case of an engine that burns in an oxidizing atmosphere by controlling the air / fuel ratio from the stoichiometric air / fuel ratio (stoichiometric) to a lean air / fuel ratio, such as a diesel engine, a three-way catalyst uses nitrogen oxides in the exhaust gas. (NOx) cannot be sufficiently purified. For this reason, some exhaust passages of this type of engine are provided with a NOx storage catalyst as an exhaust purification catalyst. The NOx storage catalyst stores NOx in the exhaust if the air-fuel ratio of the exhaust gas is lean, and releases and reduces the stored NOx if the air-fuel ratio of the exhaust gas is rich. In a diesel engine or the like, normally, since the air-fuel ratio of exhaust gas is lean, nitrogen oxides are stored in the NOx storage catalyst. For this reason, it is necessary to perform a regeneration process (NOx purge) for decomposing (reducing) NOx stored in the NOx storage catalyst by enriching the air-fuel ratio of the exhaust gas at a predetermined timing.

  Further, the sulfur component contained in the fuel reacts with oxygen to become sulfur oxide (SOx) and is stored in the NOx storage catalyst instead of NOx (S poisoning). For this reason, it is necessary to perform a regeneration process (S purge) for removing the sulfur oxide at a predetermined timing, that is, at a timing when a certain amount of sulfur oxide is stored in the NOx storage catalyst. The S purge is performed, for example, by enriching the air-fuel ratio of the exhaust gas and raising the NOx storage catalyst to a high temperature that is equal to or higher than a predetermined temperature, as in the case of NOx purge.

  For example, in the case of a diesel engine, the S purge is generally performed together with a regeneration process of a diesel particulate filter (DPF: DPF). . Since the regeneration of the DPF is performed by raising the DPF to a high temperature, the S purge is also performed at that time (for example, refer to Patent Document 1).

Japanese Patent Laying-Open No. 2014-173465 (see paragraph [0037] etc.)

  However, the timing at which the S purge should be executed does not necessarily coincide with the timing at which the DPF regeneration process should be executed. By executing the S purge together with the DPF regeneration process, for example, when a fuel having a predetermined concentration of sulfur is used, the S purge may be executed at an appropriate timing. However, when using fuels having different sulfur concentrations, there is a possibility that the S purge cannot be executed at an appropriate timing. For example, when a fuel having a sulfur concentration lower than the predetermined concentration is used, the S purge is performed in a state in which the exhaust purification catalyst does not store much nitrogen oxides, and the fuel is wasted. There is a risk of consuming the fuel consumption.

  In order to suppress such deterioration of fuel consumption due to S purge, it is determined whether or not the exhaust purification catalyst is poisoned by sulfur oxide, that is, whether or not a predetermined amount of sulfur oxide is occluded in the exhaust purification catalyst. It is preferable to perform S purge when it is determined that the exhaust purification catalyst is in a poisoned state. However, at present, it is not possible to appropriately determine whether or not the exhaust purification catalyst is poisoned.

  This invention is made in view of such a situation, and provides the poison determination apparatus which can determine appropriately whether an exhaust purification catalyst is a poisoning state by sulfur oxide etc. With the goal.

  A first aspect of the present invention that solves the above problem is a poisoning determination device that determines whether or not an exhaust purification catalyst provided in an exhaust passage of an engine mounted on a vehicle is in a poisoned state, A first exhaust temperature detection unit for detecting the temperature of exhaust gas flowing into the exhaust purification catalyst; a second exhaust temperature detection unit for detecting the temperature of exhaust gas flowing out of the exhaust purification catalyst; and the first exhaust temperature. A determination value calculation unit for calculating a poisoning determination value based on a temperature difference between a temperature detected by the detection unit and a temperature detected by the second exhaust temperature detection unit; and when the poisoning determination value is smaller than a determination threshold value And a catalyst determination unit that determines that the exhaust purification catalyst is in the poisoning state.

  According to a second aspect of the present invention, in the poisoning determination apparatus according to the first aspect, a determination value for correcting the poisoning determination value in accordance with a speed region of the vehicle when the poisoning determination value is calculated. It exists in the poisoning determination apparatus characterized by having a correction | amendment part.

  According to a third aspect of the present invention, in the poisoning determination apparatus according to the second aspect, the determination value correction unit includes a first speed region in which the speed of the vehicle is the slowest, and the speed of the vehicle is the first speed. The poisoning determination value is corrected in a second speed region that is faster than the speed region and a third speed region in which the speed of the vehicle is faster than the second speed region, respectively. It is in the judgment device.

  According to a fourth aspect of the present invention, in the poisoning determination apparatus according to the second or third aspect, the determination value calculation unit is configured to perform the determination after a predetermined waiting period has elapsed since the vehicle speed entered a predetermined speed region. The poisoning determination apparatus is characterized in that a temperature difference is calculated as the poisoning determination value.

  According to a fifth aspect of the present invention, in the poisoning determination apparatus according to any one of the first to third aspects, the determination value calculation unit integrates the temperature difference over a predetermined measurement period. Is obtained as the poisoning judgment value.

  According to a sixth aspect of the present invention, in the poisoning determination apparatus according to any one of the first to fifth aspects, the deterioration determination unit that determines the degree of deterioration of the exhaust purification catalyst and the determination result of the deterioration determination unit And a threshold value correction unit that corrects the determination threshold value to a smaller value as the degree of deterioration of the exhaust purification catalyst is higher.

  According to the poisoning determination apparatus of the present invention, it is possible to appropriately determine whether or not the exhaust purification catalyst is in a poisoned state by sulfur oxide or the like, and it is possible to suppress erroneous determination. Therefore, the S purge can be executed at an appropriate timing by executing the regeneration process (S purge) of the exhaust purification catalyst based on the determination result of the poisoning determination device. Therefore, fuel consumption due to S purge can be suppressed, and fuel consumption can be improved.

1 is a schematic diagram illustrating an overall configuration of an engine according to an embodiment of the present invention. It is a block diagram explaining the poisoning determination apparatus which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the speed area | region of a vehicle, and a measurement period. It is a figure which shows the relationship between the measurement time in each speed area | region of a vehicle, and a temperature difference integrated value. It is a figure which shows the relationship between the temperature difference integrated value and determination threshold value in each speed area | region of a vehicle. It is a flowchart which shows the poisoning determination method which concerns on one Embodiment of this invention. It is a figure which shows the relationship between the travel distance of a vehicle, and the deterioration degree of a catalyst. It is a block diagram explaining the modification of the poisoning determination apparatus which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
First, the overall configuration of the engine 10 according to an embodiment of the present invention will be described. In FIG. 1, the engine 10 is a diesel engine. The engine body 11 includes a cylinder head 12 and a cylinder block 13, and a piston 15 is accommodated in each cylinder bore 14 of the cylinder block 13. The piston 15 is connected to the crankshaft 17 via a connecting rod 16. A combustion chamber 18 is formed by the piston 15, the cylinder bore 14, and the cylinder head 12.

  An intake port 19 is formed in the cylinder head 12, and an intake pipe (intake passage) 21 including an intake manifold 20 is connected to the intake port 19. An intake valve 22 is provided in the intake port 19, and the intake port 19 is opened and closed by the intake valve 22. An exhaust port 23 is formed in the cylinder head 12, and an exhaust pipe (exhaust passage) 25 including an exhaust manifold 24 is connected in the exhaust port 23. The exhaust port 23 is provided with an exhaust valve 26. Like the intake port 19, the exhaust port 23 is opened and closed by the exhaust valve 26.

  A turbocharger 27 is provided in the middle of the intake pipe 21 and the exhaust pipe 25. An intercooler 28 is disposed in the intake pipe 21 on the downstream side of the turbocharger 27. The intake pipe 21 on the downstream side of the intercooler 28 is provided with a throttle valve 29 for opening and closing the intake pipe (intake passage) 21. An EGR pipe (EGR passage) 30 communicating with the exhaust pipe 25 upstream of the turbocharger 27 is connected to the intake pipe 21 downstream of the throttle valve 29. An EGR cooler 31 is provided in the EGR pipe 30, and an EGR valve 32 is provided in a connection portion between the EGR pipe 30 and the intake pipe 21.

  The cylinder head 12 is provided with a fuel injection valve 33 that directly injects fuel into the combustion chamber 18 of each cylinder. Fuel is supplied to the fuel injection valve 33 from the common rail 34. Fuel in a fuel tank (not shown) is supplied to the common rail 34 by a supply pump 35, and fuel is supplied from the supply pump 35 to the common rail 34 at a predetermined pressure according to the rotational speed of the engine body 11. In the common rail 34, the fuel is adjusted to a predetermined fuel pressure, and high pressure fuel controlled to the predetermined fuel pressure is supplied from the common rail 34 to the fuel injection valve 33.

  The exhaust pipe 25 on the downstream side of the turbocharger 27 includes a diesel oxidation catalyst (hereinafter simply referred to as an oxidation catalyst) 51, a diesel particulate filter (DPF) 52, and a NOx storage catalyst that is an exhaust purification catalyst according to the present embodiment. 53 are provided in order from the upstream side.

  The exhaust pipe 25 near the entrance of the NOx storage catalyst 53 is provided with a first exhaust temperature sensor 54 that detects the temperature of the exhaust gas flowing into the NOx storage catalyst 53, and the exhaust pipe near the exit of the NOx storage catalyst 53. 25, a second exhaust temperature sensor 55 for detecting the temperature of the exhaust gas flowing out from the NOx storage catalyst 53 is provided. In the present embodiment, the second exhaust temperature sensor 55 detects the temperature of the exhaust gas near the outlet of the NOx storage catalyst 53. Of course, the second exhaust temperature sensor 55 detects the temperature of the exhaust gas in the NOx storage catalyst 53. It may be. Further, an air-fuel ratio sensor 56 such as LAFS for detecting the air-fuel ratio of the exhaust gas is provided in the vicinity of the outlet of the NOx storage catalyst 53. The air-fuel ratio sensor 56 may detect oxygen concentration in the exhaust gas.

The oxidation catalyst 51 is formed, for example, by supporting a noble metal such as platinum (Pt) or palladium (Pd) on a honeycomb structure carrier made of a ceramic material. In the oxidation catalyst 51, when exhaust gas flows in, nitrogen monoxide (NO) in the exhaust gas is oxidized to generate nitrogen dioxide (NO ₂ ).

  The DPF 52 is, for example, a honeycomb structure filter formed of a ceramic material. A plurality of exhaust gas passages are formed inside the DPF 52, and the plurality of exhaust gas passages are partitioned by a wall member having a number of fine holes. The exhaust gas flowing into the inside from the upstream side of the DPF 52 advances through the exhaust gas passage while passing through the fine holes of the wall member, and flows out to the downstream side of the DPF 52. At that time, the particulate matter (PM) in the exhaust gas is trapped on the surface of the wall member or inside the fine holes.

The NOx storage catalyst 53 includes, for example, a noble metal such as platinum (Pt) and palladium (Pd) supported on a honeycomb structure carrier formed of a ceramic material, and an alkali metal such as barium (Ba) as a storage agent. Alternatively, an alkaline earth metal is supported. The NOx occlusion catalyst 53 temporarily occludes NOx as an exhaust gas component in an oxidizing atmosphere, and releases NOx in a reducing atmosphere containing, for example, carbon monoxide (CO), hydrocarbon (HC), and the like (N ₂ ) Decomposes (reduces) into etc. Normally, the NOx storage catalyst 53 only adsorbs NOx and does not decompose the adsorbed NOx. For this reason, when a predetermined amount of NOx is adsorbed to the NOx storage catalyst 53, it is necessary to execute a regeneration process (NOx purge) at a predetermined timing. The NOx purge method is not particularly limited, but in this embodiment, fuel (light oil) as a reducing agent is additionally injected from the fuel injection valve 33. As a result, the exhaust gas mixed and enriched with the fuel is supplied to the NOx storage catalyst 53, the inside of the NOx storage catalyst 53 becomes a reducing atmosphere, and the stored NOx is decomposed (reduced).

  The NOx occlusion catalyst 53 occludes sulfur oxide (SOx), which is an exhaust gas component, similarly to nitrogen oxide (NOx). For this reason, when a predetermined amount or more of sulfur oxide is occluded in the NOx occlusion catalyst 53, that is, when the NOx occlusion catalyst 53 is poisoned by the sulfur oxide, the sulfur oxide is removed from the NOx occlusion catalyst 53. Therefore, it is necessary to execute a regeneration process (S purge). In the S purge, fuel (light oil) as a reducing agent is additionally injected from the fuel injection valve 33, the rich exhaust gas is supplied to the NOx storage catalyst 53, and the NOx storage catalyst 53 is kept at a predetermined temperature (for example, 650 ° C.). The occluded sulfur oxide (SOx) is decomposed (reduced) by raising the temperature to a degree or higher.

  Note that, also for the DPF 52 described above, it is necessary to execute a regeneration process (DPF regeneration) in which PM is forcibly burned when a predetermined amount or more of PM is captured. In this DPF regeneration, for example, fuel is additionally injected from the fuel injection valve 33, and the DPF 52 is heated to a predetermined temperature (for example, about 600 ° C.) or more to forcibly burn PM.

  The engine 10 includes an electronic control unit (ECU) 70. The ECU 70 includes an input / output device, a storage device that stores a control program, a control map, and the like, a central processing unit, timers and counters, and performs comprehensive control of the engine 10 based on information from various sensors. I do.

  The ECU 70 also controls, for example, regeneration processing (NOx purge, S purge) of the NOx storage catalyst 53 as an exhaust purification catalyst provided in the engine 10 and regeneration processing (DPF regeneration) of the DPF 52. Specifically, the ECU 70 includes a regeneration processing unit (regeneration processing device) 71. The regeneration processing unit 71 includes, for example, a first exhaust temperature sensor 54, a second exhaust temperature sensor 55, an air-fuel ratio sensor 56, and the like. Based on the information from the various sensors, regeneration processing of the NOx storage catalyst 53, the DPF 52, and the like is appropriately executed.

  The ECU 70 further includes a poisoning determination unit (poisoning determination device) 72 that determines whether or not the NOx storage catalyst 53 is poisoned by sulfur oxide (SOx). The regeneration processing unit 71 performs regeneration processing (S purge) of the NOx storage catalyst 53 based on the determination result of the poisoning determination unit 72. That is, when the poisoning determination unit 72 determines that the NOx storage catalyst 53 is poisoned by the sulfur oxide, the regeneration processing unit 71 performs the sulfur storage stored in the NOx storage catalyst 53 as a regeneration process of the NOx storage catalyst 53. S purge for decomposing (reducing) the oxide (SOx) is performed at a predetermined timing.

  The present invention is characterized by the poisoning determination unit 72 that determines whether or not the NOx storage catalyst 53 is poisoned by, for example, sulfur oxide (SOx). Below, this poisoning determination part 72 is demonstrated in detail.

  As shown in FIG. 2, the poisoning determination unit 72 includes a vehicle speed detection unit 73, a first exhaust temperature detection unit 74, a second exhaust temperature detection unit 75, a determination value calculation unit 76, and a period change unit. 77, a catalyst determination unit 78, and a determination value correction unit 79.

  The vehicle speed detection unit 73 detects the speed of the vehicle 1 based on information detected by the vehicle speed sensor 58. The first exhaust temperature detection unit 74 detects the temperature of the exhaust gas flowing into the NOx storage catalyst 53 based on the detection information from the first exhaust temperature sensor 54. The second exhaust temperature detection unit 75 detects the temperature of the exhaust gas flowing out from the NOx storage catalyst 53 to the downstream side based on detection information from the second exhaust temperature sensor 55.

  The determination value calculation unit 76 calculates a poisoning determination value based on the temperature difference ΔTe between the detection temperature Te1 detected by the first exhaust temperature detection unit 74 and the detection temperature Te2 detected by the second exhaust temperature detection unit 75. In the present embodiment, the temperature difference ΔTe between the detection temperature Te1 detected by the first exhaust temperature detection unit 74 and the detection temperature Te2 detected by the second exhaust temperature detection unit 75 is set in a predetermined measurement period (measurement time T in the present embodiment). The accumulated temperature difference value ΣΔTe is obtained as a poisoning determination value. The determination value calculation unit 76 integrates the temperature difference ΔTe over the measurement time T in a state where the speed (vehicle speed) V of the vehicle 1 detected by the vehicle speed detection unit 73 is within a predetermined speed range. The difference integrated value ΣΔTe is obtained.

  Therefore, for example, when the vehicle speed V has shifted from a predetermined speed region to another speed region after the measurement time T has elapsed since the integration of the temperature difference ΔTe was started at a predetermined timing, the determination value calculation unit 76 starts. Stops the accumulation of the temperature difference ΔTe at the time of transition, and starts again the accumulation of the temperature difference ΔTe in the transitioned speed region. That is, the determination value calculation unit 76 can calculate the temperature difference integrated value ΣΔTe only when the vehicle speed V is maintained within the predetermined speed range for the measurement time T or longer.

  In the present embodiment, as shown in FIG. 3, as a vehicle speed region, the first speed region A1 in which the vehicle speed V is the slowest region (V1 or less), and the vehicle speed V is higher than the first speed region A1. A second speed area A2 which is a fast area (V1-V2) and a third speed area A3 where the vehicle speed V is faster than the second speed area A2 (V2 or higher), that is, the area where the vehicle speed V is the fastest. And is divided into. When the vehicle speed V is maintained for at least the standby measurement T in any one of the first to third speed regions A1 to A3, the temperature difference integrated value ΣΔT is obtained by the determination value calculation unit 76.

  Here, the measurement time T for accumulating the temperature difference ΔTe may be a constant time regardless of which of the first to third speed regions A1 to A3 the vehicle speed V is. The changing unit 77 appropriately changes the measurement time T according to which of the first to third speed regions A1 to A3 the vehicle speed V is. Since the rate of change of the temperature difference integrated value ΣΔTe increases as the vehicle speed V increases, the period changing unit 77 appropriately changes the measurement time T according to the rate of change.

  Specifically, the period changing unit 77 changes the measurement time T to a shorter time as the speed region of the vehicle 1 is a higher speed region. When the first to third speed regions A1 to A3 are set as described above, the period changing unit 77 measures the time when the vehicle speed V is the first speed region A1, as shown in FIG. T is set (changed) to the longest measurement time T3, and when the vehicle speed V is in the second speed region A2, the measurement time T is set to a measurement time T2 that is shorter than the measurement time T3. The measurement time T is set to the shortest measurement time T1 in the speed region A3.

  Then, in the state where the vehicle speed V is in the first speed region A1, the judgment value calculation unit 76 integrates the temperature difference ΔTe over the measurement time T3 as shown in FIG. The value ΣΔTe1 is obtained. In a state where the vehicle speed V is in the second speed region A2, as shown in FIG. 4B, the temperature difference integrated value ΣΔTe2 is obtained by integrating the temperature difference ΔTe over the measurement time T2. Further, in a state where the vehicle speed V is in the third speed region A3, as shown in FIG. 4C, the temperature difference integrated value ΣΔTe3 is obtained by integrating the temperature difference ΔTe over the measurement time T1.

  Based on the temperature difference integrated value ΣΔTe (ΣΔTe1, ΣΔTe2, ΣΔTe3) obtained by the determination value calculating unit 76 and the preset determination threshold value ΣΔTeb, the catalyst determination unit 78 determines whether the NOx storage catalyst 53 is present. It is determined whether or not the poisoning state is caused by SOx. Here, in this embodiment, the determination threshold ΣΔTeb is set corresponding to the first speed region A1 where the vehicle speed V is the slowest. Therefore, when the vehicle speed V is in the first speed region A1, if the temperature difference integrated value ΣΔTe1 is equal to or less than the determination threshold value ΣΔTeb, it is determined that the NOx storage catalyst 53 is poisoned by SOx. For example, as shown by a solid line in FIG. 5A, when the temperature difference integrated value ΣΔTe is equal to or less than the determination threshold value ΣΔTeb when the measurement time T3 has elapsed, the NOx storage catalyst 53 is in a poisoned state due to SOx. Judge that there is. On the other hand, as shown by a dotted line in FIG. 5A, when the temperature difference integrated value ΣΔTe is higher than the determination threshold value ΣΔTeb when the measurement time T3 has elapsed, the NOx storage catalyst 53 is in a poisoned state by SOx. Judge that there is no.

  On the other hand, when the vehicle speed V is in the second speed region A2 or the third speed region A3, before the determination by the catalyst determination unit 78, the determination value correction unit 79 is a temperature difference that is a poisoning determination value. The integrated values ΣΔTe2, ΣΔTe3 are corrected as appropriate. For example, the temperature difference integrated value ΣΔTe2, ΣΔTe3 is adjusted to a value corresponding to the determination threshold ΣΔTeb by multiplying the temperature difference integrated value by a predetermined correction coefficient.

  For example, when the vehicle speed V is in the second speed region A2, the catalyst determination unit 78 has a value (ΣΔTe2 × K2) obtained by multiplying the temperature difference integrated value ΣΔTe2 by a predetermined correction coefficient K2 is equal to or less than the determination threshold ΣΔTeb. Sometimes, it is determined that the NOx storage catalyst 53 is poisoned by SOx. That is, as indicated by a solid line in FIG. 5B, when the corrected temperature difference integrated value (ΣΔTe × K2) is equal to or less than the determination threshold value ΣΔTeb when the measurement time T2 has elapsed, the NOx storage catalyst 53 is SOx. Determined to be poisoned by On the other hand, as shown by a dotted line in FIG. 5B, when the corrected temperature difference integrated value (ΣΔTe × K2) is higher than the determination threshold value ΣΔTeb when the measurement time T2 has elapsed, the NOx storage catalyst 53 is obtained. Is determined not to be poisoned by SOx.

  When the vehicle speed V is in the third speed region A3, the catalyst determination unit 78 determines that the NOx storage catalyst 53 is SOx when the corrected temperature difference integrated value (ΣΔTe3 × K3) is equal to or less than the determination threshold ΣΔTeb. Determined to be poisoned by For example, as shown by the solid line in FIG. 5C, when the corrected temperature difference integrated value (ΣΔTe × K3) is equal to or less than the determination threshold value ΣΔTeb when the measurement time T3 has elapsed, the NOx storage catalyst 53 Is determined to be poisoned by SOx. On the other hand, as shown by a dotted line in FIG. 5C, when the temperature difference integrated value after correction (ΣΔTe × K3) is higher than the determination threshold value ΣΔTeb when the measurement time T3 has elapsed, the NOx storage catalyst 53 is stored. Is determined not to be poisoned by SOx.

The correction coefficient may be appropriately determined in consideration of the difference in change rate of the temperature difference integrated value ΣΔTe in the first to third speed regions A1 to A3. Incidentally, in the present embodiment, the determination threshold value ΣΔTeb is set corresponding to the first speed region A1 in which the vehicle speed V is the slowest, so that the correction coefficients K2 and K3 are values smaller than 1.
Hereinafter, the poisoning determination control of the exhaust purification catalyst according to the present invention will be further described with reference to the flowchart of FIG.

  As shown in FIG. 6, when the engine 10 is started, it is first determined in step S1 whether or not the engine 10 is in a stable state. Specifically, it is determined whether or not the temperature (water temperature) WT of the cooling water of the engine 10 is higher than a predetermined temperature (for example, about 80 ° C.). If the water temperature WT is higher than the predetermined temperature, it is determined that the engine 10 is in a stable state (step S1: Yes), the process proceeds to step S2, and poisoning determination control is started.

  First, it is determined in which speed region the speed V of the vehicle 1 is. In the present embodiment, it is determined in step S2 whether or not the speed V of the vehicle 1 is in the first speed region A1. If the speed V of the vehicle 1 is within the first speed range A1 (step S2: Yes), the process proceeds to step S3.

  In step S3, the temperature difference ΔTe is integrated over the measurement time T3 corresponding to the first speed region A1 to obtain the temperature difference integrated value ΣΔTe1. As described above, when the speed V of the vehicle 1 is maintained in the first speed region A1 for the measurement time T3 or more, the temperature difference integrated value ΣΔTe1 is obtained. When the temperature difference integrated value ΣΔTe1 is obtained, it is then determined in step S4 whether or not the temperature difference integrated value ΣΔTe1 is equal to or less than a determination threshold value ΣΔTeb. If the temperature difference integrated value ΣΔTe1 is equal to or smaller than the determination threshold ΣΔTeb (step S4: Yes), it is determined that the NOx storage catalyst 53 is in a poisoned state, and thereafter, an S purge is executed at a predetermined timing ( Step S5). In the present embodiment, after it is determined that the temperature difference integrated value ΣΔTe1 is equal to or less than the determination threshold value ΣΔTeb, the next time the DPF regeneration is executed, the S purge is also executed. Of course, the timing for executing the S purge is not particularly limited. For example, the S purge may be executed separately from the DPF regeneration immediately after it is determined that the poisoning state is present.

  On the other hand, if the temperature difference integrated value ΣΔTe1 is larger than the determination threshold value ΣΔTeb in step S4 (step S4: No), it is determined that the NOx storage catalyst 53 is not in a poisoned state, and the S purge is not performed. A series of processing ends.

  If the speed V of the vehicle 1 is not in the first speed range A1 in step S2 (step S2: No), it is further determined in step S6 whether the speed of the vehicle 1 is in the second speed range A2. judge. If the speed V of the vehicle 1 is in the second speed range A2 (step S6: Yes), the process proceeds to step S7. In step S7, the temperature difference ΔTe is integrated over the measurement time T2 corresponding to the second speed region A2 to obtain the temperature difference integrated value ΣΔTe2. Also at this time, when the speed V of the vehicle 1 is maintained within the second speed region A2 for the measurement time T2 or more, the temperature difference integrated value ΣΔTe2 is obtained.

  When the temperature difference integrated value ΣΔTe2 is obtained, the temperature difference integrated value ΣΔTe2 is corrected according to the determination threshold value ΣΔTeb. In the present embodiment, the temperature difference integrated value ΣΔTe2 is multiplied by the correction coefficient K2 (step S8). Then, it is determined whether or not the corrected temperature difference integrated value (ΣΔTe2 × K2) is equal to or less than the determination threshold value ΣΔTeb (step S9). If the corrected temperature difference integrated value (ΣΔTe2 × K2) is equal to or smaller than the determination threshold value ΣΔTeb (step S9: Yes), it is determined that the NOx storage catalyst 53 is poisoned, and the process proceeds to step S5. On the other hand, when the corrected temperature difference integrated value (ΣΔTe2 × K2) is larger than the determination threshold value ΣΔTeb in step S9 (step S9: No), it is determined that the NOx storage catalyst 53 is not in a poisoned state. A series of processes is terminated without executing the purge.

  Furthermore, when the speed V of the vehicle 1 is not in the second speed area A2 in step S6, that is, when the speed V of the vehicle 1 is in the third speed area A3 (step S6: No), the process proceeds to step S10. In step S10, the temperature difference ΔTe is integrated over the measurement time T1 corresponding to the third speed region A3 to obtain the temperature difference integrated value ΣΔTe3. Also at this time, when the speed V of the vehicle 1 is maintained in the third speed region A3 for the measurement time T1 or more, the temperature difference integrated value ΣΔTe3 is obtained.

  When the temperature difference integrated value ΣΔTe3 is obtained, the temperature difference integrated value ΣΔTe3 is corrected according to the determination threshold value ΣΔTeb. In this embodiment, the temperature difference integrated value ΣΔTe3 is multiplied by the correction coefficient K3 (step S11). Then, it is determined whether or not the corrected temperature difference integrated value (ΣΔTe3 × K3) is equal to or less than the determination threshold value ΣΔTeb (step S12). When the corrected temperature difference integrated value (ΣΔTe3 × K3) is larger than the determination threshold value ΣΔTeb (step S12: No), it is determined that the NOx storage catalyst 53 is not in a poisoned state, and the series of processes is ended. On the other hand, if the corrected temperature difference integrated value (ΣΔTe3 × K3) in step S12 is equal to or smaller than the determination threshold ΣΔTeb (step S12: Yes), it is determined that the NOx storage catalyst 53 is in a poisoned state, and step S13. Proceed to

  In step S13, it is determined whether or not the temperature difference integrated value ΣΔTe3 is further lower than a failure determination threshold (for example, zero). If the temperature difference integrated value ΣΔTe3 is equal to or greater than the failure determination threshold value (step S13: No), the process proceeds to step S5 and S purge is executed. When the temperature difference integrated value ΣΔTe3 is lower than the failure determination threshold value, that is, when the temperature difference integrated value ΣTe3 is an extremely small value (step S13: Yes), the process proceeds to step S14 and the NOx storage catalyst 53 is set. It is determined that there is an abnormality (abnormal heat deterioration), and the abnormality is notified to the driver, for example, by turning on a warning lamp, and the series of processes is terminated.

  As described above, in the present embodiment, whether or not the NOx storage catalyst 53 is poisoned by SOx based on the temperature difference integrated value ΣΔTe that is the poisoning judgment value and the preset judgment threshold value ΣΔTeb. Judgment was made. That is, when the temperature difference integrated value ΣΔTe is lower than the determination threshold value ΣΔTeb, it is determined that the NOx storage catalyst 53 is poisoned by SOx. Thereby, it is possible to appropriately determine whether or not the NOx storage catalyst 53 is poisoned while suppressing erroneous determination. Therefore, by appropriately executing the S purge based on this determination result, unnecessary S purge can be suppressed, and the use of fuel can be suppressed to improve fuel efficiency.

  In the present embodiment, only one determination threshold value ΣΔTeb is set, and the temperature integrated value ΣΔTe is appropriately corrected depending on which of the first to third speed regions A1 to A3 the vehicle speed V is, and after the correction Whether or not the NOx occlusion catalyst 53 is in a poisoned state is determined based on the temperature integrated value and the determination threshold value ΣΔTeb. Thereby, compared with setting a determination threshold value according to each speed area | region, poisoning determination control can be performed easily.

  Furthermore, since the measurement time T is changed depending on which of the first to third vehicle speed regions A1 to A3, the vehicle speed V is in any of the speed regions A1 to A3. Therefore, it is possible to suppress erroneous determination in poisoning determination. Specifically, as the speed V of the vehicle 1 is slower, the instantaneous temperature difference ΔTe at the NOx storage catalyst 53 becomes smaller. However, in the present embodiment, the predetermined measurement time T is changed to a longer time as the vehicle speed V is slower. doing. For this reason, regardless of which speed region the vehicle speed V is in, the temperature difference integrated value ΣΔTe is a relatively large value. Therefore, erroneous determination can be more reliably suppressed regardless of which speed region the vehicle speed V is in. In addition, by making the measurement time T shorter as the vehicle speed V increases, the number of determinations can be increased compared to the case where the measurement time T is constant regardless of the vehicle speed V. Therefore, it can be more appropriately determined whether or not the NOx storage catalyst 53 is poisoned.

  In the present embodiment, it is determined whether or not the NOx storage catalyst 53 is poisoned based on the temperature integrated value ΣΔTe, but may be determined based on the temperature difference ΔTe, for example. Specifically, the determination value calculation unit 76 calculates the temperature difference ΔTe after the elapse of a predetermined standby period after the speed V of the vehicle 1 enters a predetermined speed region as a poisoning determination value. Then, the catalyst determination unit 78 may determine that the NOx storage catalyst 53 is poisoned when the temperature difference ΔTe is preset and smaller than the determination threshold value ΔTeb. Also in this case, it is possible to appropriately determine whether or not the NOx storage catalyst 53 is poisoned while suppressing erroneous determination.

  By the way, the rising temperature of the exhaust gas in the NOx storage catalyst 53 decreases as the deterioration degree of the NOx storage catalyst 53 progresses. As shown in FIG. 7, the deterioration degree of the NOx storage catalyst 53 increases as the travel distance of the vehicle 1 increases. Therefore, the determination threshold ΣΔTeb may be corrected according to the travel distance of the vehicle 1 (according to the degree of deterioration of the NOx storage catalyst 53). Specifically, as illustrated in FIG. 8, the poisoning determination unit 72 may further include a deterioration determination unit 80 and a threshold correction unit 81.

  The deterioration determination unit 80 determines the degree of deterioration of the NOx storage catalyst 53. For example, in the present embodiment, the deterioration determination unit 80 determines the deterioration state of the NOx storage catalyst 53 based on the travel distance of the vehicle 1 (see FIG. 7). The threshold correction unit 81 corrects the determination threshold ΣΔTeb to be a smaller value as the deterioration degree of the NOx storage catalyst 53 is higher in accordance with the determination result of the deterioration determination unit 80.

Thereby, it can be determined more accurately whether or not the NOx storage catalyst 53 is poisoned. Therefore, by appropriately executing the S purge based on the determination result, unnecessary S purge can be further suppressed, the use of fuel can be suppressed, and fuel consumption can be improved.
Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment.

  In the above-described embodiment, the temperature difference ΔTe is integrated by the predetermined measurement time T to obtain the temperature difference integrated value ΣΔTe. However, the temperature integrated value ΣΔTe may be obtained based on the travel distance of the vehicle. That is, while the vehicle 1 travels for a predetermined measurement distance (measurement period), the temperature difference integrated value ΣΔTe may be obtained by integrating the temperature difference ΔTe. Further, when determining the poisoning state based on the temperature difference ΔTe, the standby period until the temperature difference ΔTe is calculated is not limited to the time, and may be the travel distance of the vehicle 1 or the like.

  In the above-described embodiment, the determination threshold ΣΔTeb corresponding to the first speed region A1 is set. Of course, the determination threshold ΣΔTeb is set corresponding to the second speed region A2 or the third speed region A3. It may be. In the above-described embodiment, an example in which three speed regions of the vehicle 1 are set has been described. However, four or more speed regions may be set, or two speed regions may be set.

In the above-described embodiment, the air-fuel ratio of the exhaust gas is adjusted by performing additional injection from the fuel injection valve. However, a separate injector is provided at a predetermined position of the exhaust pipe, for example, near the inlet of the oxidation catalyst 51. The fuel may be injected from the injector into the exhaust pipe. In this case, a reducing agent (hydrocarbon) other than fuel may be injected from the injector.
Moreover, although the diesel engine was illustrated in embodiment mentioned above, of course, this invention is applicable also to another engine.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Engine 11 Engine main body 12 Cylinder head 13 Cylinder block 14 Cylinder bore 15 Piston 16 Connecting rod 17 Crankshaft 18 Combustion chamber 19 Intake port 20 Intake manifold 21 Intake pipe 22 Intake valve 23 Exhaust port 24 Exhaust manifold 25 Exhaust pipe 26 Exhaust valve 27 Turbocharger 28 Intercooler 29 Throttle valve 30 EGR pipe 31 EGR cooler 32 EGR valve 33 Fuel injection valve 34 Common rail 35 Supply pump 51 Oxidation catalyst 52 DPF
53 NOx storage catalyst 54 First exhaust temperature sensor 55 Second exhaust temperature sensor 56 Air-fuel ratio sensor 58 Vehicle speed sensor 70 ECU

Claims (6)

A poison determination device that determines whether or not an exhaust purification catalyst provided in an exhaust passage of an engine mounted on a vehicle is poisoned,
A first exhaust temperature detector that detects the temperature of exhaust flowing into the exhaust purification catalyst;
A second exhaust temperature detector for detecting the temperature of the exhaust gas flowing out from the exhaust purification catalyst;
A determination value calculation unit for calculating a poisoning determination value based on a temperature difference between a temperature detected by the first exhaust temperature detection unit and a temperature detected by the second exhaust temperature detection unit;
And a catalyst determination unit that determines that the exhaust purification catalyst is in the poisoning state when the poisoning determination value is smaller than a determination threshold. The poison determination apparatus according to claim 1,
A poisoning determination apparatus, comprising: a determination value correcting unit that corrects the poisoning determination value according to a speed region of the vehicle when the poisoning determination value is calculated. The poison determination apparatus according to claim 2,
The determination value correction unit includes a first speed region where the vehicle speed is the slowest, a second speed region where the vehicle speed is faster than the first speed region, and the vehicle speed is the second speed region. A poisoning determination apparatus that corrects the poisoning determination value in a third speed region that is faster than the speed region. The poison determination apparatus according to claim 2 or 3,
The determination value calculation unit calculates the temperature difference after a predetermined standby period has elapsed after the vehicle speed has entered a predetermined speed range as the poison determination value. The poison determination apparatus according to any one of claims 1 to 3,
The determination value calculation unit obtains a temperature difference integrated value obtained by integrating the temperature difference over a predetermined measurement period as the poisoning determination value. The poison determination apparatus according to any one of claims 1 to 5,
A deterioration determination unit that determines the degree of deterioration of the exhaust purification catalyst;
A poison determination device comprising: a threshold correction unit that corrects the determination threshold to a smaller value as the degree of deterioration of the exhaust purification catalyst is higher in accordance with a determination result of the deterioration determination unit.

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