JP2009203809A - Catalyst activation judgment device and filter regeneration device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a filter regeneration device and a catalyst activation determination device capable of quickly and accurately determining the activation of a catalyst. <P>SOLUTION: History that temperature of exhaust gas flowing out of an oxidation catalyst 5 exceeds a flow-out exhaust gas determination temperature corresponding to an activation temperature is stored. When a temperature of exhaust gas flowing in the oxidation catalyst 5 exceeds a flow-in exhaust gas determination temperature corresponding to the activation temperature and higher than the flow-out exhaust gas determination temperature in a state that a history is stored, it is determined that the oxidation catalyst 5 is activated and the regeneration process of the filter 6 is executed by supplying fuel to the oxidation catalyst 5 by a fuel addition device 7. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention performs a regeneration process on a catalyst activity determination device that determines the activity of a catalyst provided in an exhaust passage of an internal combustion engine and a filter that collects particulate matter on the condition that the activity of the catalyst is determined. The present invention relates to a filter regeneration device.

  Ideally, the temperature of the catalyst itself provided in the exhaust passage is directly measured, and the activity of the catalyst is determined based on whether or not the temperature has reached the activation temperature. However, actually measuring the temperature of the catalyst itself involves technical or cost difficulties. Therefore, it is widely performed to determine the activity of the catalyst based on the exhaust temperature flowing into or out of the catalyst.

  When the operation of the internal combustion engine is in a steady state, the exhaust temperature and the catalyst temperature are almost the same, but the exhaust temperature rises during the period from the start of the internal combustion engine to the completion of warm-up, or conversely In the process of decreasing, the catalyst temperature tends to change behind the change of the exhaust temperature. Therefore, considering the delay in the change in the catalyst temperature with respect to the change in the exhaust temperature, it is determined that the catalyst has been activated after a predetermined time has elapsed since the temperature of the inflowing exhaust gas flowing into the catalyst reaches the activation temperature, and the reducing agent for the catalyst Has been proposed (Patent Document 1). In addition, there has been proposed a method for judging the activity of a catalyst by using the temperature of the exhaust gas flowing out from the catalyst (Patent Document 2). In addition, Patent Documents 3 and 4 exist as prior art documents related to the present invention.

JP 11-247648 A JP 2005-171809 A Japanese Patent No. 3003213 JP 2006-291828 A

  The apparatus of Patent Document 1 determines that the catalyst has reached the activation temperature after a predetermined time since the temperature of the inflowing exhaust gas has reached the activation temperature. However, since the heat capacity of the catalyst is generally large, It does not resemble the waveform of catalyst temperature change. For this reason, the temperature of the catalyst does not necessarily reach the activation temperature after a predetermined time has elapsed since the temperature of the inflowing exhaust gas has reached the activation temperature. Further, even when the activity of the catalyst is judged based on the temperature of the outflow exhaust as in the apparatus of Patent Document 2, the exhaust gas temperature is set in consideration of the relationship between the outflow exhaust and the catalyst temperature when the exhaust temperature rises and falls. When the temperature of the exhaust gas reaches the set temperature, the temperature of the catalyst may already be lower than the activation temperature. Therefore, in order to avoid such a situation as much as possible, the set temperature must be increased. As a result, the time until the activity of the catalyst can be determined may be prolonged.

  Conventionally, a filter that collects particulate matter in exhaust gas is disposed downstream of the oxidation catalyst, and fuel is supplied to the oxidation catalyst, so that the particulate matter collected by the filter is burned and regenerated. It has been broken. Since this regeneration process uses heat generated by the oxidation catalyst, it is necessary to supply fuel after the activation of the oxidation catalyst. In order to execute this regeneration process promptly, an operation for increasing the exhaust temperature such as EGR cut is often performed for the purpose of promoting the temperature increase of the oxidation catalyst at the stage before the start of the regeneration process. When such an operation is performed, the combustion temperature of the internal combustion engine rises, so that the amount of nitrogen oxide generated is larger than usual. Therefore, if the time until the activation of the oxidation catalyst is determined before the start of the regeneration process as described above is prolonged, a state in which a large amount of nitrogen oxide is generated continues, leading to deterioration in exhaust performance.

  Accordingly, a first object of the present invention is to provide a catalyst activity determination device capable of determining the activity of a catalyst early and accurately. A second object of the present invention is to provide a filter regeneration device that can determine the activity of an oxidation catalyst early and accurately and suppress deterioration of exhaust performance associated with the regeneration processing of the filter.

  A catalyst activity determining device according to the present invention is a catalyst activity determining device for determining the activity of a catalyst provided in an exhaust passage of an internal combustion engine, and an inflow exhaust gas temperature detecting means for detecting the temperature of inflow exhaust gas flowing into the catalyst. , Outflow exhaust gas temperature detection means for detecting the temperature of the outflow exhaust gas flowing out from the catalyst, temperature history storage means for storing a history that the temperature of the outflow exhaust gas has exceeded the outflow exhaust gas determination temperature corresponding to the activation temperature of the catalyst, The catalyst is activated when the temperature of the inflowing exhaust gas exceeds the inflowing exhaust gas determination temperature corresponding to the activation temperature and higher than the outflowing exhaust gas determination temperature while the temperature history storage unit stores the history. The problem mentioned above is solved by providing the activity determination means which determines that it is (Claim 1).

  According to this determination apparatus, since the activity of the catalyst is determined by using the temperature of the inflowing exhaust gas flowing into the catalyst and the temperature of the outflowing exhaust gas flowing out of the catalyst, respectively, only one of the temperatures of the catalyst is used. An accurate determination with higher reliability than the case of determining the activity is possible. If the temperature of the outflow exhaust gas only exceeds the outflow exhaust gas determination temperature corresponding to the activation temperature, the catalyst temperature may be lower than the activation temperature at that time. In consideration of the possibility of such a temperature drop, this determination device does not immediately determine the activity of the catalyst when it exceeds the outflow exhaust determination temperature, but stores a history of exceeding the outflow exhaust determination temperature. In addition, the activity of the catalyst is determined when the temperature of the inflowing exhaust gas exceeds the inflowing exhaust gas determination temperature. Therefore, the activity of the catalyst can be accurately determined without setting the outflow exhaust gas determination temperature to be high in order to reduce the erroneous determination associated with the catalyst temperature drop as described above. In other words, since the outflow exhaust gas determination temperature can be set as low as possible, it is possible to prevent the time until the catalyst activity can be determined from being prolonged. Thereby, accurate determination of the activity of the catalyst can be realized at an early stage.

  In one aspect of the determination apparatus according to the present invention, there is further provided time measuring means for measuring an elapsed time from when the temperature of the outflow exhaust gas becomes equal to or lower than the outflow exhaust gas determination temperature after the temperature history storage means stores the history. The temperature history storage means may clear the history when the elapsed time measured by the time measuring means reaches a predetermined time. Depending on the operating state of the internal combustion engine, there may be a case where the interval between the temperature of the outflow exhaust gas rising exceeding the outflow exhaust gas determination temperature, and then starting to decrease and further rising is larger than usual. Meanwhile, the catalyst temperature gradually decreases. Therefore, if the history of the outflow exhaust gas temperature exceeding the outflow exhaust gas determination temperature is stored, the catalyst temperature does not reach the activation temperature even when the inflow exhaust gas temperature subsequently exceeds the inflow exhaust gas determination temperature. It can happen. According to this aspect, by appropriately setting the predetermined time for clearing the history, it is possible to accurately determine the activity of the catalyst even when the above-described interval is longer than usual.

  In one aspect of the determination apparatus according to the present invention, the lower limit peak value for storing the lower limit peak value of the outflow exhaust gas temperature based on the detection result of the outflow exhaust gas temperature detection unit before the temperature history storage unit stores the history. The temperature history storage unit may further clear the history when the temperature of the outflow exhaust gas becomes equal to or lower than the lower limit peak value in a state where the history is stored. . Depending on the operating state of the internal combustion engine, there may be a case where the interval between the temperature of the outflow exhaust gas rising exceeding the outflow exhaust gas determination temperature, and then starting to decrease and further rising is larger than usual. Meanwhile, the catalyst temperature gradually decreases. For this reason, if the history of the outflow exhaust gas temperature exceeding the outflow exhaust determination temperature remains stored, the catalyst temperature may not reach the activation temperature even if the inflow exhaust gas temperature subsequently reaches the inflow exhaust gas determination temperature. obtain. The rate of decrease in the catalyst temperature is not always constant due to the influence of the ambient temperature or the like. According to this aspect, the history is cleared based on the lower limit peak value of the temperature of the exhaust gas. The history is cleared when the rate of decrease in the catalyst temperature after reaching the outflow exhaust gas determination temperature is fast, and the history is maintained when the rate of decrease is slow. Therefore, the determination accuracy is improved because the activity of the catalyst can be determined in consideration of the rate of decrease in the catalyst temperature.

  The determination result of the activity of the catalyst by the determination apparatus described above can be used in various apparatuses. For example, the fuel is supplied to the oxidation catalyst provided in the exhaust passage, and the regeneration process is performed to burn the particulate matter collected by the filter arranged downstream of the oxidation catalyst using the heat generated by the oxidation catalyst. In this case, the fuel supply to the oxidation catalyst can be determined based on the determination result of the determination device described above. Therefore, the technical idea related to the determination device described above can be specified as a filter regeneration device that executes filter regeneration processing as follows.

  The filter regeneration device of the present invention supplies fuel to the oxidation catalyst with respect to a filter that is disposed downstream of the oxidation catalyst provided in the exhaust passage of the internal combustion engine and collects particulate matter in the exhaust gas. In the filter regeneration device for performing the regeneration process for burning the particulate matter collected by the filter, the inflow exhaust gas temperature detecting means for detecting the temperature of the inflow exhaust gas flowing into the oxidation catalyst, and the outflow from the oxidation catalyst Outflow exhaust temperature detection means for detecting the temperature of the outflow exhaust, temperature history storage means for storing a history that the temperature of the outflow exhaust exceeds the outflow exhaust determination temperature corresponding to the activation temperature of the oxidation catalyst, and the temperature history storage means In the state where the history is stored, the temperature of the inflowing exhaust gas exceeds the inflowing exhaust gas determination temperature corresponding to the activation temperature and higher than the outflowing exhaust gas determination temperature. Activation determining means for determining that the catalyst is active, and regeneration permitting means for permitting the supply of fuel to the oxidation catalyst, provided that the activity determining means determines the activity of the oxidation catalyst. By providing, the above-described problem is solved (claim 4). According to this filter regeneration device, it becomes possible to determine the activity of the oxidation catalyst early and accurately, so that it is possible to suppress the deterioration of the exhaust performance associated with the regeneration process.

  Further, as one aspect of the filter regeneration device, there is further provided a time measuring means for measuring an elapsed time from when the temperature of the outflow exhaust gas becomes equal to or lower than the outflow exhaust gas determination temperature after the temperature history storage means stores the history. The temperature history storage means may clear the history when the elapsed time measured by the time measuring means reaches a predetermined time (Claim 5), or the temperature history storage means may store the history. Prior to storage, the apparatus further comprises lower limit peak value storage means for storing the lower limit peak value of the temperature of the outflow exhaust gas based on the detection result of the outflow exhaust gas temperature detection means, and the temperature history storage means stores the history. In this state, the history may be cleared when the temperature of the exhaust gas becomes equal to or lower than the lower limit peak value (Claim 6). Also in these aspects, the same effect as each aspect of the determination apparatus mentioned above can be acquired.

  As described above, according to the catalyst activity determination device of the present invention, the catalyst activity is not immediately determined when the temperature exceeds the outflow exhaust gas determination temperature, and the inflow exhaust gas is stored after the reached history is stored. Since the catalyst activity is determined when the temperature exceeds the inflow exhaust gas determination temperature, the outflow exhaust gas determination temperature can be set as low as possible. Therefore, it is possible to prevent the time until the activity of the catalyst can be determined from being prolonged, and an accurate determination of the activity of the catalyst can be realized early. In addition, according to the filter regeneration device of the present invention, it is possible to determine the activity of the oxidation catalyst early and accurately, so that it is possible to suppress the deterioration of the exhaust performance associated with the regeneration process.

(First form)
FIG. 1 is a view showing a main part of an exhaust system of an internal combustion engine to which a catalyst activity determination device and a filter regeneration device according to an embodiment of the present invention are applied. The internal combustion engine 1 is configured as a diesel engine, and the exhaust passage 2 is provided with a PM reduction device 3 for reducing the emission of particulate matter (PM) in the exhaust gas. The PM reduction device 3 includes a casing 4 that forms a part of the exhaust passage 2, an oxidation catalyst 5 that is disposed upstream of the exhaust passage 2, a filter 6 that is disposed downstream of the oxidation catalyst 5, and a filter 6. And a fuel addition device 7 for supplying fuel to the oxidation catalyst 5 in order to burn the collected PM. The casing 4 has a cylindrical shape in which each of the inlet 4a and the outlet 4b is narrowed. The oxidation catalyst 5 and the filter 6 are fixed to the casing 4 with a predetermined gap S formed therebetween.

  An upstream temperature sensor 8 is provided in the vicinity of the inlet 4 a of the casing 4 as an inflow exhaust gas temperature detecting means for detecting the temperature of the inflow exhaust gas flowing into the oxidation catalyst 5. Further, a downstream temperature sensor 9 as an outflow exhaust gas temperature detecting means for detecting the temperature of the outflow exhaust gas flowing out from the oxidation catalyst 5 is provided in the gap S provided in the casing 4, that is, downstream of the oxidation catalyst 5.

  Light oil as fuel pumped from a fuel tank (not shown) is supplied to the fuel addition device 7 at a predetermined pressure. Although description of the detailed structure inside the fuel addition apparatus 7 is abbreviate | omitted, it is comprised as an electromagnetic needle valve which drives the needle which opens and closes the nozzle hole formed in the nozzle with electromagnetic force. The fuel addition device 7 can inject fuel into the exhaust passage 2 at a predetermined timing and period by controlling the electromagnetic force. The fuel injected into the exhaust passage 2 is supplied to the oxidation catalyst 5 located downstream thereof. When fuel is supplied to the oxidation catalyst 5, the oxidation catalyst 5 generates heat (more precisely, the fuel burns), and the PM collected by the filter 6 can be burned using this as a heat source. Since the amount of PM collected by the filter 6 can be reduced by the combustion, the PM collecting ability of the filter 6 can be recovered. This operation is a well-known process called a filter regeneration process. This filter regeneration process is executed when a predetermined condition such as the amount of PM collected by the filter 6 reaches an allowable limit is satisfied.

  The filter regeneration process is executed by an engine control unit (ECU) 10 configured as a computer that controls the operating state of the internal combustion engine 1. The ECU 10 executes various controls on the internal combustion engine 1 in addition to the filter regeneration process. Here, only the control related to the present invention will be described among the control performed by the ECU 10, and description of the other control will be omitted.

  The filter regeneration process is performed on the condition that the collection function of the filter 6 needs to be restored and the activity of the oxidation catalyst 5 is a condition. The necessity of function recovery is determined based on the amount of PM collected by the filter 6. The ECU 10 determines that the function recovery of the filter 6 is necessary when the amount of PM collected by the filter 6 reaches an allowable limit. The amount of PM collected by the filter 6 can be estimated from, for example, the differential pressure upstream and downstream of the filter 6. In addition, the amount of PM can be estimated by a known method such as estimation based on the operation history of the internal combustion engine 1. When the necessity of function recovery is affirmed, the ECU 10 performs an operation of increasing the exhaust temperature such as EGR cut in order to quickly raise the temperature of the oxidation catalyst 5 prior to the fuel supply by the fuel addition device 7. When the ECU 10 determines that the oxidation catalyst 5 is activated, the ECU 10 executes fuel supply by the fuel addition device 7. The activity of the oxidation catalyst 5 is determined by the ECU 10 based on the output signals of the upstream temperature sensor 8 and the downstream temperature sensor 9.

  FIG. 2 is a timing chart illustrating an example of a process in which the ECU 10 determines the activity of the oxidation catalyst 5. FIG. 2 is used to determine the vehicle speed in which the internal combustion engine 1 is mounted, the temperature of the exhaust gas flowing into the oxidation catalyst 5, the temperature of the exhaust gas flowing out from the oxidation catalyst 5, the catalyst temperature of the oxidation catalyst 5, and the activity. Each transition of the determination flag is shown on the same time axis.

  As shown in the figure, an inflow exhaust gas determination temperature T1 for determining the temperature of the inflow exhaust gas and an outflow exhaust gas determination temperature T2 for determining the temperature of the outflow exhaust gas are set according to the specific activation temperature of the oxidation catalyst 5. ing. The magnitude relationship between these determination temperatures T1 and T2 is T1> T2. In the illustrated case, since the load of the internal combustion engine 1 changes in response to changes in the vehicle speed, the temperature of the inflowing exhaust gas changes with the same tendency as the change in the vehicle speed. As the temperature of the inflowing exhaust gas changes, the catalyst temperature also tends to rise gently as a whole while repeatedly rising and falling. The temperature of the outflow exhaust gas changes with a similar tendency while being delayed with respect to the change in the catalyst temperature.

  At time t1, the upstream determination flag F1 is set to ON in response to the temperature of the inflowing exhaust gas exceeding the determination temperature T1. Thereafter, the temperature of the inflowing exhaust gas reaches the upper limit peak value and starts to decrease, and becomes lower than the determination temperature T1 at time t2. When the temperature becomes lower than the determination temperature T1, the upstream determination flag F1 is set to OFF. These flags F1 and F2 are variables assigned to a predetermined area of a storage device such as a RAM of the ECU 10, and the variables are defined so as to change between at least two values corresponding to ON and OFF. Yes.

  At time t3, the downstream determination flag F2 is set to ON in response to the temperature of the outflow exhaust gas exceeding the determination temperature T2. Unlike the upstream determination flag F1, the downstream determination flag F2 is not set to OFF and is maintained in the ON state even when the temperature falls below the determination temperature T2. Thereafter, at the timing when the temperature of the inflowing exhaust gas exceeds the determination temperature T1 at time t4, the upstream determination flag F1 is set to ON. At time t4, the flags F1 and F2 are set to ON. In this embodiment, the activation of the oxidation catalyst 5 is determined at time t4 when the flags F1 and F2 are set to ON, and fuel supply to the oxidation catalyst 5 is permitted.

  FIG. 3 is a timing chart for explaining another example of a process in which the ECU 10 determines the activity of the oxidation catalyst 5. In this case, the stop time TP of the vehicle equipped with the internal combustion engine 1 is longer than that in the case of FIG. Since the catalyst temperature significantly decreases with the stop time TP, the downstream determination flag F2 is turned OFF at time t3 ′ when the elapsed time after the temperature of the outflow exhaust gas becomes equal to or lower than the determination temperature T2 reaches the predetermined time Tth. Is set. Therefore, after that, even when the temperature of the inflowing exhaust gas exceeds the upstream determination temperature T1 at time t4, both the flags F1 and F2 are not turned on. For this reason, the activity of the oxidation catalyst is not determined, and fuel supply to the oxidation catalyst 5 is not permitted.

  FIG. 4 is a flowchart showing an example of a control routine for realizing the activity determination shown in FIGS. 2 and 3. The program for this routine is held in the ROM of the ECU 10, read out in a timely manner, and repeatedly executed at predetermined intervals.

  In step S1, it is determined whether or not the temperature Tin of the inflowing exhaust gas exceeds the inflowing exhaust gas determination temperature T1. If the inflow / exhaust determination temperature T1 is exceeded, the process proceeds to step S2, and the upstream determination flag F1 is set to ON. If the inflow / exhaust determination temperature T1 is not exceeded, the process proceeds to step S3, and the upstream determination flag F1 is set to OFF.

  In step S4, it is determined whether or not the temperature Tout of the outflow exhaust gas exceeds the outflow exhaust determination temperature T2. If it exceeds the outflow exhaust determination temperature T2, the process proceeds to step S5, and if it does not exceed the outflow exhaust determination temperature T2, the process proceeds to step S7.

  In step S5, the counter for managing the elapsed time from when the outflow exhaust gas temperature Tout becomes equal to or lower than the outflow exhaust gas determination temperature T2 is reset, and in the subsequent step S6, the downstream determination flag F2 is set to ON.

  In step S7, it is determined whether or not the downstream determination flag F2 is set to ON. If it is set to ON, the process proceeds to step S8, and if it is set to OFF, the process proceeds to step S12.

  In step S8, a predetermined addition value is added to the counter to update the counter. The added value for the counter is set to an appropriate value considering the calculation cycle of this routine.

  In step S9, it is determined whether the value of the counter is less than a predetermined value N. The predetermined value N is set in consideration of the relationship between the elapsed time from when the temperature Tout of the outflow exhaust gas becomes equal to or lower than the outflow exhaust gas determination temperature T2 and the decrease in the catalyst temperature. The predetermined value N is set as a limit value at which the decrease in the catalyst temperature cannot be ignored when determining the activity of the oxidation catalyst 5. If the counter value is less than the predetermined value N, the process proceeds to step S10, the downstream determination flag F2 is set to ON (the ON setting is maintained), and if the counter value is equal to or greater than the predetermined value N, the process proceeds to step S11. The upstream determination flag F2 is set to OFF.

  In step S12, the counter is reset, and in subsequent step S13, the downstream determination flag F2 is set to OFF (the setting of OFF is maintained).

  In step S14, it is determined whether both the upstream determination flag F1 and the downstream determination flag F2 are set to ON. When both the flags F1 and F2 are set to ON, the process proceeds to step S15 to determine the activity of the oxidation catalyst 5 and permit the fuel supply to the oxidation catalyst 5. On the other hand, when both the flags F1 and F2 are not set to ON, the process proceeds to step S16, and the fuel supply to the oxidation catalyst 5 is prohibited.

  By repeatedly executing the routine of FIG. 4, the activity determination described in FIGS. 2 and 3 can be performed. The ECU 10 functions as a temperature history storage unit, an activity determination unit, a timing unit, and a regeneration permission unit according to the present invention by executing the routine of FIG.

  That is, when the ECU 10 sets the downstream determination flag F2 to ON, the history of the outflow exhaust gas temperature exceeding the outflow exhaust determination temperature is stored, and when the downstream determination flag F2 is set OFF, the history is cleared. It corresponds to each. Therefore, the ECU 10 functions as a temperature history storage unit according to the present invention. Further, when both the flags F1 and F2 are set to ON, the ECU 10 determines the activity of the oxidation catalyst 5 when the temperature of the inflowing exhaust gas exceeds the inflow determination temperature in a state where the history is stored. This corresponds to the determination of the activity. Therefore, the ECU 10 functions as an activity determination unit according to the present invention. Further, since the ECU 10 adds a counter to measure the elapsed time from when the temperature of the outflow exhaust gas becomes equal to or lower than the outflow exhaust gas determination temperature, the ECU 10 functions as the time measuring means according to the present invention. Further, when both the flags F1 and F2 are set to ON, the ECU 10 determines the activity of the oxidation catalyst 5 and permits the fuel supply to the oxidation catalyst 5 in step S15. Therefore, the ECU 10 performs the regeneration according to the present invention. Functions as a permission means.

  According to the first embodiment, considering the possibility of temperature reduction of the oxidation catalyst 5 after the outflow exhaust gas exceeds the outflow exhaust gas determination temperature T2, the activity of the oxidation catalyst 5 is increased when the outflow exhaust gas determination temperature T2 is exceeded. Without determining immediately, the downstream determination flag F2 is maintained in the ON state, and when the temperature of the inflowing exhaust gas exceeds the inflowing exhaust gas determination temperature T1, the activity of the oxidation catalyst 5 is determined. Thereby, since the outflow exhaust gas determination temperature T2 can be set as low as possible, it can be prevented that the time until the activity of the oxidation catalyst 5 can be determined is prolonged. As a result, accurate determination of the activity of the oxidation catalyst 5 can be realized early. Moreover, the downstream determination flag F2 is set based on the elapsed time from when the temperature of the outflow exhaust gas becomes equal to or lower than the outflow exhaust gas determination temperature T2 without maintaining the state of the downstream determination flag F2 set to ON indefinitely. Since it is turned off, the activity of the oxidation catalyst 5 can be accurately determined even in a situation where the stop time is longer and the catalyst temperature is lower than expected.

(Second form)
Next, a second embodiment of the present invention will be described. The present embodiment is different from the first embodiment in the condition for setting the downstream determination flag F2 once set to ON to OFF, that is, clearing the history. Since the other points are the same as in the first embodiment, FIG. 1 is appropriately referred to regarding the physical configuration of the internal combustion engine.

  First, the basic concept of this embodiment will be described with reference to FIG. FIG. 5 shows the time variation of the temperature of the outflow exhaust gas. As shown in the drawing, the temperature of the outflow exhaust repeatedly rises and falls according to the operating state, as in the first embodiment. In this embodiment, the temperature of the outflow exhaust gas is monitored, and when the lower limit peak is reached at time t1, the lower limit peak value PL is stored. Then, after the temperature of the outflow exhaust gas exceeds the outflow exhaust gas determination temperature T2 at time t2 and the downstream determination flag F2 is set to ON, the downstream determination flag is set when the temperature of the outflow exhaust gas becomes equal to or lower than the lower limit peak value PL at time t3. F2 is set to OFF. On the other hand, as shown by the imaginary line in the figure, when the downstream exhaustion temperature drop after the downstream determination flag F2 is set to ON is moderate and does not fall below the lower limit peak value PL, the downstream determination flag F2 is ON. Maintained in a state. Thereafter, when the temperature of the inflowing exhaust gas exceeds the inflowing exhaust gas determination temperature T1 (see FIGS. 2 and 3), the activity of the oxidation catalyst 5 is determined and the fuel is supplied to the oxidation catalyst 5 as in the first embodiment. Is allowed.

  FIG. 6 is a flowchart showing an example of a control routine according to this embodiment. The program for this routine is held in the ROM of the ECU 10, read out in a timely manner, and repeatedly executed at predetermined intervals. Further, the control routine of FIG. 7 is executed in parallel with the control routine of FIG. 6 in order to monitor the temperature of the exhaust gas and store the above-described lower limit peak value PL.

  As shown in FIG. 6, in step S21, it is determined whether the temperature Tin of the inflowing exhaust gas exceeds the inflowing exhaust gas determination temperature T1. If the inflow / exhaust determination temperature T1 is exceeded, the process proceeds to step S22, and the upstream determination flag F1 is set to ON. If the inflow / exhaust determination temperature T1 is not exceeded, the process proceeds to step S23, and the upstream determination flag F1 is set to OFF.

  In step S24, it is determined whether or not the temperature Tout of the outflow exhaust gas exceeds the outflow exhaust determination temperature T2. When it exceeds the outflow exhaust gas determination temperature T2, the process proceeds to step S25, and the downstream determination flag F2 is set to ON. On the other hand, when it does not exceed the outflow exhaust gas determination temperature T2, the process proceeds to step S26.

  In step S26, it is determined whether or not the downstream determination flag F2 is set to ON. If it is set to ON, the process proceeds to step S27, and if it is set to OFF, the process proceeds to step S29.

  In step S27, it is determined whether or not the temperature Tout of the exhaust gas is higher than the lower limit peak value PL stored in the control routine of FIG. If it is higher than the lower limit peak value PL, the process proceeds to step S28, and the downstream determination flag F2 is set to ON (the ON setting is maintained). On the other hand, if it is less than or equal to the lower limit peak value PL, the process proceeds to step S29, and the downstream determination flag F2 is set to OFF. Instead of using the lower limit peak value PL itself as a determination value, a value (PL + α) slightly lower than the lower limit peak value PL as shown in FIG. 5 may be used as the determination value.

  In step S30, it is determined whether both the upstream determination flag F1 and the downstream determination flag F2 are set to ON. When both the flags F1 and F2 are set to ON, the process proceeds to step S31, where the activity of the oxidation catalyst 5 is determined and fuel supply to the oxidation catalyst 5 is permitted. On the other hand, if both the flags F1 and F2 are not set to ON, the process proceeds to step S32, and the fuel supply to the oxidation catalyst 5 is prohibited.

  The activity determination described with reference to FIG. 5 can be performed by repeatedly executing the routine of FIG. As in the case of the first embodiment, the ECU 10 functions as a temperature history storage unit, an activity determination unit, and a regeneration permission unit according to the present invention by executing the routine of FIG.

  The storage of the lower limit peak value PL is performed according to the control routine shown in FIG. First, in step S41, it is determined whether or not the downstream determination flag F2 is set to ON. If the downstream determination flag F2 is set to ON, the process proceeds to step S42. If not, the subsequent processing is skipped. Then, this routine is finished. In step S42, it is determined whether or not the temperature Tout of the outflow exhaust gas is higher than the lower limit peak value PL stored in the previous calculation. When it is higher than the lower limit peak value PL, the process proceeds to step S43, and the previous lower limit peak value PL is stored as the calculation result of the current lower limit peak value PL. On the other hand, when the temperature Tout of the outflow exhaust gas is equal to or lower than the lower limit peak value PL stored in the previous calculation, the process proceeds to step S44, and the outflow exhaust gas temperature Tout is stored as the calculation result of the current lower limit peak value PL. By repeatedly executing the routine shown in FIG. 7, the lower limit peak value PL of the temperature Tout of the outflow exhaust gas can be stored. By executing the routine of FIG. 7, the ECU 10 functions as a lower limit peak value storage unit according to the present invention.

  According to the second mode, early and accurate activity determination can be realized as in the first mode, and it is also possible to cope with a change in the rate of decrease in the catalyst temperature after reaching the outflow exhaust gas determination temperature T2. The determination accuracy regarding the activity of the catalyst 5 is improved.

  The present invention is not limited to the above embodiments, and can be implemented in various forms within the scope of the gist of the present invention. In the above embodiment, the catalyst activity determination is used for the filter regeneration process, but the determination result can also be used for other purposes. For example, when a NOx occlusion reduction type catalyst is provided, the activity determination according to the present invention can be used for determining whether or not the reducing agent can be supplied to the catalyst.

The figure which showed the principal part of the exhaust system of the internal combustion engine to which the catalyst activity determination apparatus and filter regeneration apparatus which concern on one form of this invention were applied. The timing chart explaining an example of the process in which ECU determines the activity of an oxidation catalyst. The timing chart explaining the other example of the process in which ECU determines the activity of an oxidation catalyst. The flowchart which showed an example of the control routine for implement | achieving the active determination shown in FIG.2 and FIG.3. The figure which showed the time change of the temperature of outflow exhaust. The flowchart which showed an example of the control routine which concerns on a 2nd form. The flowchart which showed an example of the control routine for memorize | storing a lower limit peak value.

Explanation of symbols

1 Internal combustion engine 2 Exhaust passage 5 Oxidation catalyst (catalyst)
8 Upstream temperature sensor (inflow exhaust temperature detection means)
9 Downstream temperature sensor (outflow exhaust gas temperature detection means)
10 ECU (temperature history storage means, activity determination means, timing means, regeneration permission means, lower limit peak value storage means)

Claims (6)

A catalyst activity determination device for determining the activity of a catalyst provided in an exhaust passage of an internal combustion engine,
Inflow exhaust temperature detection means for detecting the temperature of the inflow exhaust gas flowing into the catalyst, outflow exhaust temperature detection means for detecting the temperature of the outflow exhaust gas flowing out from the catalyst, and the temperature of the outflow exhaust gas corresponds to the activation temperature of the catalyst Temperature history storage means for storing a history exceeding the outflow exhaust determination temperature, and the temperature history storage means storing the history, and the temperature of the inflow exhaust corresponds to the activation temperature and the outflow exhaust determination An activity determination unit that determines that the catalyst is active when an inflow exhaust gas determination temperature that is higher than a temperature is exceeded. Further comprising time measuring means for measuring an elapsed time from when the temperature of the outflow exhaust gas becomes equal to or lower than the outflow exhaust gas determination temperature after the temperature history storage means stores the history;
2. The catalyst activity determination device according to claim 1, wherein the temperature history storage unit clears the history when the elapsed time measured by the timing unit reaches a predetermined time. The temperature history storage means further comprises lower limit peak value storage means for storing a lower limit peak value of the temperature of the outflow exhaust gas based on a detection result of the outflow exhaust gas temperature detection means before storing the history,
2. The catalyst activity determination device according to claim 1, wherein the temperature history storage means clears the history when the temperature of the outflow exhaust gas is equal to or lower than the lower limit peak value in a state where the history is stored. The filter is collected by supplying fuel to the oxidation catalyst with respect to a filter that is arranged downstream of the oxidation catalyst provided in the exhaust passage of the internal combustion engine and collects particulate matter in the exhaust gas. In a filter regeneration device that executes a regeneration process for burning particulate matter,
Inflow exhaust temperature detection means for detecting the temperature of the inflow exhaust gas flowing into the oxidation catalyst, outflow exhaust temperature detection means for detecting the temperature of the outflow exhaust gas flowing out from the oxidation catalyst, and the temperature of the outflow exhaust gas is the activity of the oxidation catalyst Temperature history storage means for storing a history exceeding the outflow exhaust gas determination temperature corresponding to the temperature, and in a state where the temperature history storage means stores the history, the temperature of the inflow exhaust corresponds to the activation temperature and On condition that the activity determination means determines that the oxidation catalyst is active when the inflow exhaust determination temperature higher than the outflow exhaust determination temperature is exceeded, and the activity determination means determines the activity of the oxidation catalyst, And a regeneration permission means for permitting the supply of fuel to the oxidation catalyst. Further comprising time measuring means for measuring an elapsed time from when the temperature of the outflow exhaust gas becomes equal to or lower than the outflow exhaust gas determination temperature after the temperature history storage means stores the history;
5. The filter regeneration device according to claim 4, wherein the temperature history storage means clears the history when the elapsed time measured by the timing means reaches a predetermined time. The temperature history storage means further comprises lower limit peak value storage means for storing a lower limit peak value of the temperature of the outflow exhaust gas based on a detection result of the outflow exhaust gas temperature detection means before storing the history,
5. The filter regeneration device according to claim 4, wherein the temperature history storage means clears the history when the temperature of the outflow exhaust gas becomes equal to or lower than the lower limit peak value in a state where the history is stored.

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