JP4957216B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to a device that restricts the start of forced regeneration of an exhaust gas purification device of an internal combustion engine according to an operating situation.

  In addition to HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide), exhaust gas exhausted from diesel engines includes particulate matter (hereinafter referred to as PM) such as soot that is fine particles. include. Therefore, an exhaust gas purification device for suppressing the emission of PM to the outside is provided in an exhaust system of an automobile equipped with a diesel engine. This type of exhaust gas purification device includes a diesel particulate filter (hereinafter referred to as DPF) that collects PM, an upstream side of the DPF, unburned fuel (HC, CO, etc.), and oxygen in the exhaust gas. And an oxidation catalyst that undergoes an oxidation reaction are known.

  In such an exhaust gas purification device, a forced regeneration process for periodically removing the soot in the PM collected by the DPF is necessary. As the forced regeneration process of the DPF, the soot is burned by raising the temperature of the DPF. It has been done to remove. The forced regeneration process is generally performed when it is determined that the soot accumulation amount on the DPF has exceeded a predetermined level based on the estimation of the soot accumulation amount on the DPF, the accumulated travel distance from the previous regeneration, or the like. As a method of raising the temperature, the DPF temperature is raised to approximately 600 ° C. or more by raising the temperature of the exhaust gas of the engine or generating heat by supplying HC to the oxidation catalyst, and soot is burned and removed. For example, during the regeneration process of the DPF, in order to maintain the oxidation catalyst at a high temperature, fuel is injected (after injection) in the expansion stroke after the main injection, and the exhaust temperature is increased. Fuel injection (post-injection) is performed at a timing that does not cause combustion at a low timing, unburned fuel is supplied to the catalyst, and the temperature required for forced regeneration of the DPF by the combustion heat (reaction heat) of the catalyst from the unburned fuel Have gained.

JP-A-2005-214203

By the way, for example, when the vehicle is in a driving state such as low-speed driving or downhill driving with a low engine load, frequent fuel cuts or low-load conditions of the engine may continue or the frequency may increase. For this reason, the DPF temperature may not be sufficiently raised or it may be difficult to continue the temperature rise. In such a case, in the conventional exhaust gas purification apparatus, forced regeneration is repeatedly started and interrupted, and thus the time until completion of regeneration of the DPF may become abnormally long. Longer regeneration time not only completes DPF regeneration, but also greatly reduces fuel consumption during that time, and also causes problems with engine oil dilution due to long-term post-injection fuel. There is a risk of reducing the performance.

  In order to cope with such a problem, in the exhaust gas purification apparatus of Patent Document 1, information data relating to a travel section supplied from a satellite navigation system (GPS), a traffic telemeter system, a travel section calculator, a navigation system, or the like. Based on the above, it is shown that the regeneration cycle is controlled. The exhaust gas purifying apparatus disclosed in Patent Document 1 controls the regeneration of the DPF based on the information data of the travel section, but does not detect the actual driving state of the vehicle, and forcibly regenerates the DPF. It was not enough to properly limit the start of More specifically, the travel section information used in the control of Patent Document 1 is data supplied from a navigation system or the like, and whether the road surface on which the vehicle actually travels is a completely paved road or an unpaved road. It is not data that directly incorporates the driving situation (engine load) that changes according to the running resistance, such as the number of passengers in the vehicle and the amount of luggage. Therefore, in Patent Document 1, it is difficult to say that the actual engine load information is accurately reflected in controlling the start or interruption of forced regeneration, and the above-described problems such as a prolonged DPF regeneration completion time are not possible. There is a possibility of inviting.

  The present invention has been made in view of the above problems, and it is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine that grasps an operation state and restricts the start of forced regeneration in a situation where it is difficult to perform stable DPF temperature rise. And

An exhaust gas purification apparatus for an internal combustion engine according to a first invention for solving the above-described problems is
A filter that collects particulates in the exhaust gas from the internal combustion engine of the vehicle;
Forced regeneration means for forcibly regenerating the filter by burning and removing the particulate when the amount of particulate deposited on the filter exceeds a predetermined amount;
When all the conditions that the speed of the vehicle is equal to or higher than the predetermined speed , the accelerator opening in the internal combustion engine is equal to or smaller than the predetermined opening, and the fuel injection amount in the internal combustion engine is equal to or smaller than the predetermined amount are satisfied. And a load state determination means for determining a low load state,
Limiting means for limiting the start of forced regeneration of the filter by the forced regeneration means when the load state determination means determines a predetermined low load state at a predetermined frequency;
It is characterized by providing.

An exhaust gas purifying apparatus for an internal combustion engine according to a second invention for solving the above-mentioned problems is
In the exhaust gas purification apparatus for an internal combustion engine according to the first aspect,
A time ratio calculating means for calculating a ratio of the time when the load state determining means determines the predetermined low load state during a predetermined time period;
When the time ratio calculated by the time ratio calculation means is a predetermined ratio or more, the restriction means restricts the start of the forced regeneration.

An exhaust gas purification apparatus for an internal combustion engine according to a third invention for solving the above-described problems is
In the exhaust gas purification apparatus for an internal combustion engine according to the second invention,
A first period calculating means for obtaining a period in which the ratio of the time is equal to or greater than the predetermined ratio;
When the period calculated by the first period calculating unit continues for a predetermined number of times, the limiting unit limits the start of the forced regeneration.

An exhaust gas purifying apparatus for an internal combustion engine according to a fourth invention for solving the above-mentioned problems is as follows.
In the exhaust gas purification apparatus for an internal combustion engine according to the second or third invention,
When the time ratio is equal to or less than another predetermined ratio different from the predetermined ratio, release means for canceling the restriction on the start of the forced regeneration is provided.

An exhaust gas purification apparatus for an internal combustion engine according to a fifth invention for solving the above-described problems,
In the exhaust gas purification apparatus for an internal combustion engine according to the fourth invention,
A second period calculating means for obtaining a period in which the ratio of the time is equal to or less than the other predetermined ratio;
When the period calculated by the second period calculation unit continues for another predetermined number of times different from the predetermined number of times, the release unit releases the restriction on the start of forced regeneration.

An exhaust gas purification apparatus for an internal combustion engine according to a sixth aspect of the invention for solving the above-described problem is provided.
In the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to fifth inventions,
Compulsory regeneration determining means for determining whether or not the filter is being forcedly regenerated by the forced regeneration means, and when the forced regeneration determining means determines that the forced regeneration is being performed, Regardless of the determination result, the forced regeneration of the filter is continued.

According to the first aspect of the present invention, as the operating status of the vehicle and / or the internal combustion engine, for example, when the frequency of a predetermined low load state is high, such as when driving at a low load speed or when driving downhill, that is, in a low load state If the operation status is continuity, the start of forced regeneration of the filter is restricted, so that forced regeneration of the filter is prohibited in situations where it is difficult to perform stable filter temperature rise. Increase in fuel consumption by control and dilution of engine oil by post-injected fuel can be prevented.
Also, when all the conditions that the vehicle speed is equal to or higher than the predetermined speed , the accelerator opening in the internal combustion engine is equal to or smaller than the predetermined opening, and the fuel injection amount in the internal combustion engine is equal to or smaller than the predetermined amount are satisfied. Since the low load state is determined, it is possible to more accurately determine the low load state as the operating state of the vehicle and / or the internal combustion engine.

  According to the second aspect of the invention, the frequency of the low load state is determined using the ratio of the time for determining the low load state during the predetermined time period. The situation where the implementation and release are repeated can be avoided.

  According to the third aspect of the invention, the frequency of the low load state is determined by checking whether or not the period in which the ratio of the time for determining the low load state is equal to or greater than the predetermined rate continues for a predetermined number of times or more. And / or the continuity of the operating condition of the internal combustion engine can be determined more accurately.

  According to the fourth aspect of the invention, the condition for canceling the restriction on the start of forced filter regeneration is set separately from the implementation condition, so that there is an advantage that loss of opportunity for forced regeneration of the filter can be easily suppressed.

  According to the fifth aspect of the present invention, the vehicle and / or the internal combustion engine is checked by checking whether or not the period in which the ratio of the time for determining the low load state is equal to or less than another predetermined ratio continues for another predetermined number of times. There are advantages such as more accurately determining the continuity of the driving situation and facilitating the loss of the opportunity for forced regeneration of the filter.

  According to the sixth invention, the forced regeneration of the filter can be appropriately continued based on the determination by the forced regeneration determination means.

  Hereinafter, an exhaust gas purification apparatus for an internal combustion engine and a forced regeneration method thereof according to the present invention will be described in detail with reference to FIGS.

  FIG. 1 is a schematic configuration diagram showing an example of an embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention. 2 and 3 are flowcharts showing the start restriction control for forced regeneration of the DPF in the exhaust gas purifying apparatus.

  In this embodiment, as the internal combustion engine, a diesel engine 1 is employed in which fuel such as light oil is directly injected into air that has been heated to a high temperature due to high compression, and is spontaneously ignited for combustion.

  As shown in FIG. 1, the cylinder head 2 of the diesel engine 1 is provided with an electromagnetic fuel injection nozzle 3 facing the combustion chamber 4 for each cylinder. The fuel injection nozzle 3 is connected to a common rail 6 by a high-pressure pipe 5. Connected. The common rail 6 is connected to a fuel tank 8 by a high-pressure pipe 7, and a high-pressure pump 9 is disposed in the middle of the high-pressure pipe 7.

  An intake port 10 and an exhaust port 12 are formed in the cylinder head 2 for each cylinder. An intake pipe (intake passage) 11 is connected via an intake manifold (not shown) so as to communicate with each intake port 10. An exhaust pipe (exhaust passage) 13 is connected to each exhaust port 12 through an exhaust manifold (not shown). Each intake port 10 and each exhaust port 12 are provided with leading ends of an intake valve 14 and an exhaust valve 15 respectively facing the combustion chamber 4, and the combustion chamber 4 and the ports 10 and 12 are opened and closed.

  The intake pipe 11 is provided with an electromagnetic intake throttle valve 16 that adjusts the intake air amount. Further, an air flow sensor 17 for measuring the intake air amount is attached. Further, an EGR pipe 18 is connected to the exhaust pipe 13, and a terminal end of the EGR pipe 18 is connected to the intake pipe 11. An electromagnetic EGR valve 19 is disposed in the middle of the EGR pipe 18.

An exhaust gas purification device main body 20 is interposed in the exhaust pipe 13. The exhaust gas purification device main body 20 includes a first oxidation catalyst 21 and a second oxidation catalyst 22 arranged in series, and a diesel particulate filter (DPF) 23 arranged on the downstream side of the second oxidation catalyst 22. . In the exhaust gas purification apparatus main body 20, the oxidizing agent (NO ₂ ) is generated in the first oxidation catalyst 21 and the second oxidation catalyst 22, and the particulate or PM (PM) deposited on the downstream DPF 23 by the generated oxidizing agent. It is configured so that the soot that is the fine particles in the inside is continuously oxidized and removed.

  A first temperature sensor 24, a second temperature sensor 25, and a third temperature sensor 26 are provided on the upstream side of the first oxidation catalyst 21, between the first oxidation catalyst 21 and the second oxidation catalyst 22, and on the downstream side of the DPF 23, respectively. It has been. From each temperature sensor 24, 25, 26, the temperature of the exhaust gas introduced into the first oxidation catalyst 21 (the temperature of the exhaust gas exhausted from the engine 1), the temperature of the exhaust gas introduced into the second oxidation catalyst 22, and the DPF 23 The temperature of the exhaust gas exhausted (the temperature of the DPF 23) is detected. The exhaust pipe 13 detects a differential pressure between the pressure of the exhaust gas upstream of the DPF 23 (exhaust gas introduced into the DPF 23) and the pressure of the exhaust gas downstream of the DPF 23 (exhaust gas exhausted from the DPF 23). A differential pressure sensor 27 is provided.

  The vehicle is provided with an ECU 31 that is an electronic control unit of the engine. In the ECU 31, on the input side, an airflow sensor 17, a first temperature sensor 24, a second temperature sensor 25, a third temperature sensor 26, a DPF differential pressure detection sensor 27, a crank angle sensor 28 for detecting a crank angle, an accelerator position. A sensor 29, a vehicle speed sensor 30 for measuring the speed of the vehicle, and the like are connected, and detection information from these sensors is input. The crank angle sensor 28 can detect the rotational speed of the internal combustion engine. On the other hand, the fuel injection nozzle 3 and the intake throttle valve 16 are connected to the output side. The fuel injection nozzle 3 and the intake throttle valve 16 are calculated based on detection information from various sensors. Optimum values such as the fuel injection amount and the throttle opening are output. Thereby, an appropriate amount of fuel is injected from the fuel injection nozzle 3 at an appropriate timing.

  The ECU 31 includes an input / output device, a storage device (ROM, RAM, etc.) for storing a control program and a control map, a central processing unit (CPU), a timer, and counters. The ECU 31 calculates a target torque of the engine based on various input information, appropriately controls various devices, and comprehensively controls the operation of the engine 1.

  Further, the ECU 31 performs the main injection for the main combustion by the fuel injection nozzle 3, and then performs additional supply of fuel, that is, post injection (sub-injection) in the expansion stroke or the exhaust stroke by the fuel injection nozzle 3, thereby the DPF 23 The soot collected in is forcedly burned and removed, and the DPF 23 is forcibly regenerated (forced regeneration means).

  During forced regeneration of the DPF 23, the ECU 31 determines the post-injection timing from the map based on the engine speed information and the load information, and further maps based on the detection result of the first temperature sensor 24 (temperature of exhaust gas from the engine 1). From this, the correction value for the post injection timing is determined. As described above, the ECU 31 performs correction control according to the temperature of the exhaust gas so that a predetermined amount of unburned fuel (HC, CO, etc.) can be supplied to the first oxidation catalyst 21 and the second oxidation catalyst 22 more reliably. Thus, the temperature rise of the DPF 23 is promoted by the reaction heat when the unburned fuel is burned (oxidation reaction) by the first oxidation catalyst 21 and the second oxidation catalyst 22, and the unburned residue of soot accumulated on the DPF 23 is suppressed. be able to.

  Here, the start restriction control of the forced regeneration of the DPF in the exhaust gas purifying apparatus of the present embodiment will be described with reference to the flowcharts shown in FIGS.

  First, an outline of the start restriction control for forced regeneration of the DPF in the exhaust gas purification apparatus of the present embodiment will be described.

  In the present embodiment, in order to perform the start restriction control of the forced regeneration of the DPF in the exhaust gas purification apparatus, first, it is determined whether or not the driving condition is in a low load condition by acquiring the driving condition of the vehicle and / or the engine. (Load state determination means: steps S1 to S3, S22). The ratio at which the low load condition is satisfied is obtained in a predetermined monitoring period (time ratio calculating means: steps S4 to S6), and the ratio at which the low load condition is satisfied continuously in a plurality of monitoring periods is a certain value or more. Is confirmed (first period calculation means: steps S7 to S11), the continuity of the low load condition is determined, and as a result, the forced regeneration of the DPF is newly started or the suspended state is The resumption of forced regeneration of the DPF is restricted (restriction means, forced regeneration determination means: steps S18, S19, S20).

  In addition, in order to release the forced regeneration start restriction, a determination condition set separately from the judgment condition for forced regeneration start restriction is provided, and the rate at which the low load condition is satisfied continues in a plurality of monitoring periods. (2nd period calculation means, release means: steps S12 to S17, S21), the loss of opportunity for forced regeneration of the DPF due to excessive determination is prevented.

  Next, the above-described control will be described in more detail.

(Step S1)
In the ECU 31, the accelerator opening APS in the accelerator position sensor 29 and the vehicle speed Vs in the vehicle speed sensor 30 are read, and the fuel injection amount Qfin calculated based on the detection information of various sensors is read to obtain the operation status of the vehicle and the engine. To do.

(Step S2)
It is determined whether or not the prescribed accelerator opening APS, vehicle speed Vs, and fuel injection amount Qfin are satisfied. Specifically, (1) the accelerator opening APS is equal to or lower than a first predetermined value (for example, 0.0%), or (2) the vehicle speed Vs is equal to or higher than a second predetermined value (for example, 30 km / h). (3) It is determined whether or not the fuel injection amount Qfin is equal to or smaller than a third predetermined value (for example, 10 mm ³ / st). The reason why the vehicle speed Vs is set to be equal to or higher than the second predetermined value (for example, 30 km / h) is to eliminate low-speed traveling due to traffic congestion or the like.

  Then, only when these three determination conditions (1), (2), and (3) are all satisfied, it is determined that the low load condition with a low load on the engine is satisfied, and the process proceeds to step S3. ), (2), if any one of (3) does not satisfy the condition, it is determined that the low load condition is not established, and the process proceeds to step S4.

In this embodiment, (1) accelerator opening APS, (2) vehicle speed Vs, and (3) fuel injection amount Qfin are used as the determination conditions for establishing the low load condition. ) In addition to the fact that the engine target torque is less than or equal to the fourth predetermined value and (5) the engine speed is greater than or equal to the fifth predetermined value, one or more of these determination conditions are used When any one or more or all of the conditions are satisfied, it may be determined that the low load condition is satisfied. The situation where the low load condition defined here is satisfied includes, for example, low load speed traveling , downhill traveling , and the like .

(Step S3)
When the above three determination conditions (1), (2), and (3) are all satisfied, it is determined that the low load condition is satisfied, and the low load condition satisfaction counter m = (m−1) +1 is calculated. Then, one low load condition satisfaction counter is added. In the initial state, m = 0.

(Step S4)
When all of the conditions (1), (2), and (3) are satisfied, one low load condition satisfaction counter is added, and then the calculation of the integration counter n = (n−1) +1 is performed. Add one. If any one of (1), (2), and (3) does not satisfy the condition, the integration counter n = (n−1) +1 is calculated without adding the low load condition establishment counter. , One addition counter is added. In the initial state, n = 0.

(Step S5)
Using the calculated low load condition establishment counter m and integration counter n, the low load condition establishment ratio r = low load condition establishment counter m / integration counter n × 100 is obtained.

(Step S6)
It is checked whether the integration counter n is a sixth predetermined value (for example, 60 seconds). If the integration counter n is the sixth predetermined value, the process proceeds to step S7, and if the integration counter n is not the sixth predetermined value, If it is less than the sixth predetermined value, the above procedure is repeated until the integration counter n reaches the sixth predetermined value. That is, the frequency of establishment of the low load condition is monitored by repeating steps S1 to S6 during the monitoring period of a fixed period set as the sixth predetermined value, and the time average low load condition establishment ratio of the monitoring period is monitored. Will be asked. In this way, by providing a predetermined monitoring period, it is possible to avoid that the start restriction of DPF forced regeneration, which will be described later, is repeatedly performed and canceled due to a change in the driving situation.

  In this embodiment, the determination condition is further added to the start restriction of the DPF forced regeneration. However, as a simple control, the low load condition establishment ratio r in the monitoring period is equal to or higher than a seventh predetermined value described later. In such a case, the start restriction of the DPF forced regeneration may be performed. In addition, although a determination condition is added to the cancellation of the start restriction of the DPF forced regeneration, as a simple control, the low load condition establishment ratio r in the monitoring period is below a ninth predetermined value described later. In addition, the start restriction of the forced DPF regeneration may be canceled.

(Steps S7, S8, S9)
It is confirmed whether the low load condition establishment ratio r obtained in step S5 is greater than or equal to a seventh predetermined value (for example, 15%). If the low load condition establishment ratio r is greater than or equal to the seventh predetermined value, the set counter Cs is set. When the low load condition establishment ratio r is less than the seventh predetermined value, the set counter Cs is reset and the process proceeds to step S10.

(Steps S10 and S11)
It is confirmed whether the set counter Cs is equal to or greater than an eighth predetermined value (for example, 5 times). If the set counter Cs is equal to or greater than the eighth predetermined value, the process proceeds to step S11, the set flag Fs is set to 1, and step S12 is performed. If the set counter Cs is less than the eighth predetermined value, step S11 is skipped and the process proceeds to step S12. That is, here, when the monitoring period in which the low load condition establishment ratio r is equal to or greater than the seventh predetermined value continues for the eighth predetermined value (five times) or more, the set flag Fs for limiting the start of forced DPF regeneration Is set to 1. As described above, in the continuous monitoring period, it is possible to more accurately determine the continuity of the low load traveling state by determining whether or not the start restriction of the DPF forced regeneration described later is necessary.

  In steps S7 to S9, as a counting method of the set counter Cs, the set counter Cs is reset when the low load condition establishment ratio r is less than the seventh predetermined value. However, the present invention is not limited to this. Cs may be subtracted. In this case, in steps S10 to S11, the monitoring period in which the low load condition establishment ratio r is equal to or greater than the seventh predetermined value is set when the total is equal to or greater than the eighth predetermined value (five times), even if not continuously. 1 is set to the flag Fs.

(Steps S12, S13, S14)
It is confirmed whether the low load condition establishment ratio r obtained in step S5 is equal to or less than a ninth predetermined value (for example, 40%) greater than the seventh predetermined value, and the low load condition establishment ratio r is equal to or less than the ninth predetermined value. In this case, the process proceeds to step S13, the clear counter Cc is added, and the process proceeds to step S15. If the low load condition establishment ratio r is larger than the ninth predetermined value, the process proceeds to step S14 and the clear counter Cc is reset. Then, the process proceeds to step S15.

(Steps S15 and S16)
It is confirmed whether the clear counter Cc is equal to or greater than a tenth predetermined value (for example, three times). If the clear counter Cc is equal to or greater than the tenth predetermined value, the process proceeds to step S16, the clear flag Fc is set to 1, and step S17 is performed. If the clear counter Cc is less than the tenth predetermined value, step S16 is skipped and the process proceeds to step S17. That is, here, when the monitoring period in which the low load condition establishment ratio r is equal to or greater than the ninth predetermined value continues for the tenth predetermined value (three times) or more, the clear flag Fc for canceling the start restriction of DPF forced regeneration Is set to 1.

  In steps S12 to S14, as a counting method of the clear counter Cc, the clear counter Cc is reset when the low load condition establishment ratio r is larger than the ninth predetermined value. May be subtracted. In this case, in steps S15 to S16, the clear flag is set when the total becomes equal to or greater than the tenth predetermined value (three times) even if the low load condition establishment ratio r is greater than the ninth predetermined value. 1 is set in Fc.

(Steps S17 and S21)
It is confirmed whether or not the clear flag Fc is 1, and if the clear flag Fc is not 1 (0), the process proceeds to step S18. When the clear flag Fc is 1, the process proceeds to step S21, the start restriction of DPF forced regeneration is canceled, and the process proceeds to step S22.

(Step S18)
If the clear flag Fc is not 1, it is further checked whether the set flag Fs is 1. If the set flag Fs is not 1, the process proceeds to step S22. If the set flag Fs is 1, the step Proceed to S19.

  That is, in steps S17 to S18, if the clear flag Fc is not 1 and the set flag Fs is 1, it means that the DPF forced regeneration start restriction is allowed, and the clear flag Fc is 1 This means that the start restriction of forced DPF regeneration is released regardless of the set flag Fs (permitted start of DPF forced regeneration).

  As described above, the set flag Fs as the implementation condition and the clear flag Fc as the release condition are set separately for the start restriction of the DPF forced regeneration, and the number of monitor periods for establishing the set flag Fs is increased (for example, 5 times), the number of monitoring periods for establishing the clear flag Fc is reduced (for example, 3 times). Thus, for example, even if the set flag Fs changes from “established (1) to not established (0)”, if the clear flag Fc is not established (0), the DPF forced regeneration start restriction is continued. Become. Therefore, even in a situation where the set flag Fs is relatively easy to change, by using the clear flag Fc together, the most recent driving situation is carefully judged, the restriction control for starting the DPF regeneration is stabilized, and the hunting of the operation is prevented. In addition, it is possible to prevent the loss of the opportunity for forced regeneration of the filter by setting the release condition so that the execution condition is hardly established and the release condition is relatively easily established.

(Steps S19 and S20)
After confirming the set flag Fs and the clear flag Fc, it is confirmed in step S19 whether the DPF regeneration is in progress. If the DPF regeneration is not in progress, the process proceeds to step S20, the DPF forced regeneration start restriction is performed, and the process proceeds to step S22. move on. If DPF regeneration is in progress, step S20 is skipped and the process proceeds to step S22. That is, when the set flag Fs is 1 and the DPF regeneration is not in progress, a new DPF forced regeneration start restriction is performed. This restriction also limits the resumption of suspended DPF regeneration. When the DPF regeneration is in progress, the DPF regeneration is continued even if the set flag Fs is 1. When DPF regeneration is in progress, the regeneration control may be interrupted when the set flag Fs becomes 1.

(Step S22)
When the DPF regeneration is in progress, or when the set flag Fs is not 1 (0), when the clear flag Fc is 1 and the DPF start restriction is released, the low load condition satisfaction counter m and the integration counter n are set to 0. Return to step S1.

  Incidentally, in the flowchart of FIG. 3, an example is given in the case where the start restriction is executed (step S20) and canceled (step S21) by giving priority to the state of the clear flag Fc. For example, as shown in FIG. Control can also be performed with priority given to the state of the flag Fs. Hereinafter, an example in which the state of the set flag Fs is prioritized will be described with reference to FIG. Note that steps S6 to S16 and step S22 in FIG. 4 are the same as those in FIG.

  In FIG. 4, when the process proceeds to step S31 through step S16, it is confirmed in this step S31 whether the set flag Fs is 1, and if the set flag Fs is 1, the process proceeds to step S32. In step S32, it is confirmed whether the DPF regeneration is in progress. If the DPF regeneration is not in progress, the process proceeds to step S33, the DPF forced regeneration start restriction is performed, and the process proceeds to step S22. On the other hand, if the DPF is being regenerated, step S33 is skipped and the process proceeds to step S22.

  If it is determined in step S31 that the set flag Fs is not 1 (0), the process proceeds to step S34, and it is confirmed in step S34 whether the clear flag Fc is 1. If the clear flag Fc is 1, the process proceeds to step S35, the start restriction of DPF forced regeneration is canceled, and the process proceeds to step S22. If the clear flag Fc is not 1, step S35 is skipped and the process proceeds to step S22.

  That is, in steps S31 and S34, if the set flag Fs is 1, it means that the start restriction of DPF forced regeneration is allowed, and the set flag Fs is not 1 and the clear flag Fc is 1 Means to release the restriction on the start of DPF forced regeneration (allowing start of DPF forced regeneration). Therefore, when the set flag Fs is 1, regardless of the clear flag Fc, the start restriction of the DPF forced regeneration is performed, and the set flag Fs is set to 1 to release the start restriction of the DPF forced regeneration. (They are 0) and the clear flag Fc needs to be 1.

  Even when the control is performed based on the flowchart of FIG. 4, the combination of the set flag Fs and the clear flag Fc is used to carefully determine the most recent driving situation, stabilize the DPF regeneration start restriction control, In addition to preventing hunting, it is possible to prevent the loss of opportunity for forced regeneration of the filter by setting the execution condition to be difficult to be satisfied and the release condition to be relatively easily satisfied.

  As described above, by performing the above-described control, it becomes possible to limit the start of DPF forced regeneration in a situation where a low load situation continues and stable DPF temperature rise is difficult, which is useless. It is possible to prevent increase in fuel consumption due to temperature rise control and dilution of engine oil with post-injected fuel.

  The present invention is particularly suitable for a diesel engine. By applying the present invention to a diesel engine, it is possible to appropriately control the DPF forced regeneration in the exhaust gas purifying apparatus according to the operating situation. However, the present invention can be applied to other than diesel engines.

It is a schematic block diagram which shows an example of embodiment of the exhaust gas purification apparatus of the internal combustion engine which concerns on this invention. 2 is a flowchart showing a restriction control for starting regeneration of a DPF in the exhaust gas purification apparatus shown in FIG. 2 is a flowchart showing a restriction control for starting regeneration of a DPF in the exhaust gas purification apparatus shown in FIG. 6 is a flowchart showing another example of the restriction control for starting the regeneration of the DPF in the exhaust gas purification apparatus shown in FIG.

Explanation of symbols

20 Exhaust gas purification device 21 First oxidation catalyst 22 Second oxidation catalyst 23 DPF (diesel particulate filter)
29 Accelerator position sensor 30 Vehicle speed sensor 31 ECU (control device)

Claims (6)

A filter that collects particulates in the exhaust gas from the internal combustion engine of the vehicle;
Forced regeneration means for forcibly regenerating the filter by burning and removing the particulate when the amount of particulate deposited on the filter exceeds a predetermined amount;
When all the conditions that the speed of the vehicle is equal to or higher than the predetermined speed , the accelerator opening in the internal combustion engine is equal to or smaller than the predetermined opening, and the fuel injection amount in the internal combustion engine is equal to or smaller than the predetermined amount are satisfied. And a load state determination means for determining a low load state,
Limiting means for limiting the start of forced regeneration of the filter by the forced regeneration means when the load state determination means determines a predetermined low load state at a predetermined frequency;
An exhaust gas purifying device for an internal combustion engine, comprising: The exhaust gas purification apparatus for an internal combustion engine according to claim 1,
A time ratio calculating means for calculating a ratio of the time when the load state determining means determines the predetermined low load state during a predetermined time period;
The exhaust gas purifying apparatus for an internal combustion engine, wherein the restriction means restricts the start of the forced regeneration when the time ratio calculated by the time ratio calculation means is a predetermined ratio or more. The exhaust gas purification apparatus for an internal combustion engine according to claim 2,
A first period calculating means for obtaining a period in which the ratio of the time is equal to or greater than the predetermined ratio;
The exhaust gas purifying apparatus for an internal combustion engine, wherein the restriction means restricts the start of the forced regeneration when the period calculated by the first period calculation means continues for a predetermined number of times or more. In the exhaust gas purification apparatus for an internal combustion engine according to claim 2 or 3,
An exhaust gas purifying apparatus for an internal combustion engine, comprising: release means for releasing a restriction on the start of forced regeneration when the time ratio is equal to or less than another predetermined ratio different from the predetermined ratio. The exhaust gas purification apparatus for an internal combustion engine according to claim 4,
A second period calculating means for obtaining a period in which the ratio of the time is equal to or less than the other predetermined ratio;
The exhaust gas purifying apparatus for an internal combustion engine, wherein when the period calculated by the second period calculating unit continues for another predetermined number of times different from the predetermined number of times, the canceling unit cancels the restriction on the start of the forced regeneration. . The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 5,
Compulsory regeneration determining means for determining whether or not the filter is being forcedly regenerated by the forced regeneration means, and when the forced regeneration determining means determines that the forced regeneration is being performed, An exhaust gas purification apparatus for an internal combustion engine, wherein forced regeneration of the filter is continued regardless of a determination result.

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