WO2015033519A1

WO2015033519A1 - Control of regeneration of a particulate filter of exhaust gas

Info

Publication number: WO2015033519A1
Application number: PCT/JP2014/004137
Authority: WO
Inventors: Noriyasu Kobashi; Takashi Tsunooka; Takayuki Otsuka
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2013-09-06
Filing date: 2014-08-08
Publication date: 2015-03-12
Also published as: JP2015052291A

Abstract

An exhaust gas purification apparatus of an internal combustion engine is provided with a filter that collects PM in exhaust gas, a first accumulation amount obtaining unit that obtains an accumulation amount of PM (Mpm at S201), a second accumulation amount obtaining unit that obtains an accumulation amount of ash (Mash at S201) and a control unit that executes a regeneration process to oxidize the accumulated PM, wherein, in a case (at S202) where the accumulation amount of ash (Mash) is equal to or larger than a threshold amount (Ma), the control unit executes the regeneration process provided (at S401) the accumulation amount of PM (Mpm) is in a state where it has reached a first predetermined amount (Mpmt of S206) which is an amount to raise a filter temperature (current temperature Tc) to a temperature (target temperature Tt) by oxidation heat generated by the regeneration process, the temperature (Tt) being a temperature at which the accumulated ash contracts, i.e. the incombustible matter increases density and decreases volume at >750-1050°C in order to reduce back pressure of the filter.

Description

[Title established by the ISA under Rule 37.2] CONTROL OF REGENERATION OF A PARTICULATE FILTER OF EXHAUST GAS

The present invention relates to an exhaust gas purification apparatus of an internal combustion engine.

Conventionally, in order to prevent particulate matter (hereinafter, referred to as PM), such as soot, contained in exhaust gas of an internal combustion engine from being discharged to the atmosphere, a filter for collecting PM is provided in an exhaust passage. When the collected PM is excessively accumulated, a decline in function of the filter, such as an increase in pressure loss, may occur. Thus, a regeneration process, in which the accumulated PM is removed by oxidation, is performed.

Meanwhile, exhaust gas may contain incombustible matter (hereinafter, referred to as ash) originating from chemical components contained in lubricating oil of the internal combustion engine, or the like. Since ash is also collected by the filter, an excessive accumulation of ash may cause a decline in function of the filter. As ash itself is incombustible, it cannot be easily removed by oxidation as is the case with PM. Thus, there is a known problem in which an accumulation of ash causes a decline in an oxidation rate of PM during a regeneration process. In order to solve this problem, a technique is proposed in which a target temperature of a filter during a regeneration process is adjusted in accordance with an amount and a state of ash that is accumulated in the filter (for example, refer to Patent Document 1). With this technique, the target temperature is adjusted to a higher temperature as the accumulation amount of ash increases, and a fuel injection amount and an injection timing are controlled so that the actual temperature of the filter reaches the target temperature. Accordingly, as the temperature of the filter is raised to the higher target temperature, an oxidation reaction of PM is further promoted. As a result, the oxidation rate of PM that has declined due to the accumulation of ash is restored.

JP2011-69374A

Another decline in function of a filter that is induced by accumulated ash is an increase in pressure loss caused by a decrease in filtration area of the filter due to the accumulation of the ash itself. Since the prior art described above is a technique for further raising the temperature of a filter in order to promote the oxidation reaction of PM, the technique does not actively solve pressure loss of the filter due to the accumulation of ash. In addition, in the prior art described above, an amount of unburned fuel contained in the exhaust gas is adjusted by controlling the fuel injection amount or the injection timing so that the filter temperature is raised to the adjusted higher target temperature. Thus, fuel consumption may eventually increase in this technique.

The present invention has been made in consideration of such circumstances and an object thereof is to effectively reduce pressure loss of a PM collecting filter that is attributable to accumulation of ash while preventing an increase in fuel consumption in an exhaust gas purification apparatus of an internal combustion engine having the filter disposed in an exhaust passage.

In order to solve the problem described above, an exhaust gas purification apparatus of an internal combustion engine according to the present invention comprises:
a filter being provided in an exhaust passage of the internal combustion engine that collects particulate matter in exhaust gas;
a first accumulation amount obtaining unit that obtains an accumulation amount of the particulate matter being accumulated in the filter;
a second accumulation amount obtaining unit that obtains an accumulation amount of incombustible matter being accumulated in the filter; and
a control unit that executes a regeneration process to oxidize the particulate matter being accumulated in the filter, wherein, in a case where the accumulation amount of the incombustible matter obtained by the second accumulation amount obtaining unit is equal to or larger than a threshold amount, the control unit executes the regeneration process provided the accumulation amount of the particulate matter obtained by the first accumulation amount obtaining unit is in a state where it has reached a first predetermined amount, the first predetermined amount being an amount to raise a temperature of the filter to a first predetermined temperature by oxidation heat generated by the regeneration process, the first predetermined temperature being a temperature at which the accumulated incombustible matter contracts.

The particulate matter (hereinafter, also referred to as PM) described above is a combustible solid substance such as soot that is generated when fuel is burned in an internal combustion engine. When the PM collected by the filter accumulates, pressure loss of the filter increases due to a decrease in filtration area of the filter. In consideration thereof, the first accumulation amount obtaining unit described above obtains the accumulation amount of PM that is accumulated in the filter on the basis of, for example, a differential pressure across the filter or an operation history of the internal combustion engine. The PM accumulated in the filter is oxidized when the temperature of the filter is sufficiently high (for example, approximately 400 degrees Celsius or higher) and a sufficient amount of oxygen exists in the filter. Therefore, in order to remove the accumulated PM in the filter, the control unit of the exhaust gas purification apparatus according to the present invention executes a regeneration process to oxidize the accumulated PM. The control unit executes the regeneration process while, for example, the accumulation amount of PM is relatively small in order to sufficiently prevent PM accumulation. In the regeneration process, processes such as heating of the filter and supplying oxygen to the filter are performed.

On the other hand, the incombustible matter (hereinafter, also referred to as ash) described above is an incombustible solid substance originating from chemical components such as additives contained in lubricating oil of the internal combustion engine or sulfur content contained in fuel. Since ash is collected by and accumulates in the filter in a similar manner to PM, pressure loss of the filter increases as the accumulation amount of ash increases. In consideration thereof, the second accumulation amount obtaining unit described above obtains the accumulation amount of ash that is accumulated in the filter on the basis of a differential pressure across the filter (in particular, a differential pressure across the filter immediately following the end of a regeneration process when it is conceivable that substantially only ash is accumulated), an operation history of the internal combustion engine, and the like. Since ash is incombustible, it cannot be easily removed by oxidation as is the case with PM. However, ash is known to contract (volume decreases while density increases) when heated to a predetermined temperature (for example, approximately 750 degrees Celsius). In particular, it is known that, when heated to approximately 1050 degrees Celsius or higher, ash contracts to a level where density increases by approximately 50%. Therefore, by raising the filter temperature to a predetermined temperature at which uncontracted ash that is accumulated in the filter contracts, the pressure loss of the filter can be reduced by increasing the filtration area of the filter. However, the predetermined temperature is higher than a temperature which the filter normally reaches during an operation of the internal combustion engine or during a regeneration process. Thus, it is necessary to additionally heat the filter in order to raise its temperature to the predetermined temperature and cause ash to contract. To this end, the temperature of the exhaust gas that flows into the filter may be raised in order to additionally heat the filter. However, this method increases fuel consumption and is therefore unfavorable.

In consideration thereof, in a case where the accumulation amount of ash obtained by the second accumulation amount obtaining unit is equal to or larger than a threshold amount, the control unit of the exhaust gas purification apparatus according to the present invention executes the regeneration process provided the accumulation amount of PM obtained by the first accumulation amount obtaining unit is in a state where it has reached a first predetermined amount, the first predetermined amount being an amount to raise a temperature of the filter to a first predetermined temperature by oxidation heat generated by the regeneration process, the first predetermined temperature being a temperature at which the accumulated ash contracts. The first predetermined amount can be obtained on the basis of, for example, the accumulation amount of ash obtained by the second accumulation amount obtaining unit and a difference between the first predetermined temperature and an actual temperature of the filter. In addition, the first predetermined temperature can be a temperature at which the accumulated ash sufficiently contracts while the filter is not overheated, and it may be set based on contraction characteristics of ash (for example, a rate of change of density of ash with respect to an ash temperature), heat resistance characteristics of the filter, and the like. Moreover, the threshold amount with respect to the accumulation amount of ash is an accumulation amount of ash that is set in order to determine whether or not a contraction of ash is required. The threshold amount can be, for example, an accumulation amount of ash when it can be expected that contraction of ash would reduce the pressure loss of the filter. The threshold amount may be set in advance by experiment or the like.

As described above, according to the present invention, the control unit executes a regeneration process for removing PM by oxidation, but when the accumulation amount of ash is equal to or larger than the threshold amount, the control unit does not execute the regeneration process before the accumulation amount of PM reaches the first predetermined amount. As an operation of the internal combustion engine continues in a state where the regeneration process is not executed, the accumulation amount of PM eventually reaches the predetermined amount. In other words, when the accumulation amount of ash is equal to or larger than the threshold amount, the control unit restricts the execution of the regeneration process until the accumulation amount of PM reaches the first predetermined amount and executes the regeneration process after the accumulation amount of PM reaches the first predetermined amount. As a result, according to the present invention, it becomes possible to execute the regeneration process in a state where a predetermined amount of PM that is necessary to generate oxidation heat to raise the filter temperature to the first predetermined temperature is being accumulated, and thus ash can be contracted without having to additionally consume fuel. Consequently, pressure loss of the filter can be effectively reduced while preventing an increase in fuel consumption.

In addition, according to the present invention, the second accumulation amount obtaining unit may be configured to obtain the accumulation amount of the incombustible matter accumulated in the filter on the basis of a differential pressure across the filter immediately after an execution of the regeneration process by the control unit. The differential pressure across the filter immediately after the execution of the regeneration process is a differential pressure across the filter immediately after the accumulated PM has been removed from the filter. Thus, this differential pressure is a differential pressure across the filter with an influence of the accumulated PM eliminated. Therefore, by using this differential pressure across the filter, the accumulation amount of ash can be obtained at high accuracy.

Furthermore, the exhaust gas purification apparatus of the internal combustion engine according to the present invention may further include a first predetermined amount obtaining unit that obtains the first predetermined amount on the basis of the accumulation amount of the incombustible matter obtained by the second accumulation amount obtaining unit and a difference between the first predetermined temperature and an actual temperature of the incombustible matter. The larger the accumulation amount of ash and the larger the difference between the first predetermined temperature and an actual temperature of ash, the larger an amount of oxidation heat that is required to heat the ash. Thus, a larger amount of PM is required. In consideration thereof, the first predetermined amount obtaining unit obtains the first predetermined amount on the basis of these relationships. Accordingly, an amount of PM that is required to raise the temperature of the filter to a temperature at which the accumulated ash contracts can be obtained with accuracy.

Moreover, according to the present invention, the internal combustion engine is a spark-ignition internal combustion engine capable of combustion at a stoichiometric air-fuel ratio, and the control unit executes the regeneration process by executing a fuel shutoff for the internal combustion engine during a decelerating operation of the internal combustion engine. In this type of internal combustion engine, as high concentration of oxygen is supplied to the filter when a fuel shutoff is performed, the PM accumulated in the filter can be oxidized preferably. Normally, fuel supply is not requested during a decelerating operation of the internal combustion engine. Therefore, the control unit executes a regeneration process by performing a fuel shutoff during a decelerating operation of the internal combustion engine. Moreover, as described above, when the accumulation amount of ash is equal to or larger than the threshold amount, the control unit does not execute the regeneration process until the accumulation amount of PM reaches the first predetermined amount. Thus, in this case, the control unit does not execute a fuel shutoff even during a decelerating operation of the internal combustion engine. The fuel shutoff is executed after the accumulation amount of PM reaches the first predetermined amount. Consequently, according to the present invention, when the accumulation amount of ash is equal to or larger than the threshold amount, the regeneration process can be executed in a state where the first predetermined amount of PM is accumulated. As a result, pressure loss of the filter can be effectively reduced while preventing an increase in fuel consumption.

In addition, according to the present invention, in a case where the accumulation amount of the incombustible matter is equal to or larger than the threshold amount, the control unit executes the fuel shutoff for the internal combustion engine during the decelerating operation of the internal combustion engine if the temperature of the filter is lower than a second predetermined temperature even if the accumulation amount of the particulate matter is smaller than the first predetermined amount, the second predetermined temperature being a temperature at which an oxidation reaction due to the regeneration process does not occur. In this case, when the filter temperature is lower than the second predetermined temperature, the fuel shutoff need not be restricted because the accumulated PM cannot be oxidized even when a fuel shutoff is executed and oxygen is supplied to the filter. Therefore, when the accumulation amount of ash is equal to or larger than the threshold amount, the control unit executes a fuel shutoff when the filter temperature is lower than the second predetermined temperature even before the accumulation amount of PM reaches the first predetermined amount. Accordingly, since an execution frequency of fuel shutoff increases, the fuel consumption of the internal combustion engine can be further reduced.

Furthermore, according to the present invention, the internal combustion engine is a compression-ignition internal combustion engine including an oxidation catalyst being provided on an upstream side of the filter in the exhaust passage, and a fuel adding unit that adds fuel to exhaust gas flowing into the oxidation catalyst, the control unit executes the regeneration process by adding the fuel from the fuel adding unit when the accumulation amount of the particulate matter accumulated in the filter is equal to or larger than a second predetermined amount that is smaller than the first predetermined amount, wherein in a case where the accumulation amount of the incombustible matter is equal to or larger than the threshold amount, the control unit executes the regeneration process by adding the fuel from the fuel adding unit if the accumulation amount of the particulate matter is equal to or larger than the first predetermined amount instead of the second predetermined amount. In this case, when fuel is added from the fuel adding unit, the fuel is oxidized by the oxidation catalyst and temperature of the exhaust gas rises and therefore the temperature of the filter that is disposed on a downstream side of the oxidation catalyst can be raised. In this type of internal combustion engine, as oxygen concentration of the exhaust gas is relatively high, by adding fuel from the fuel adding unit to raise the filter temperature to a temperature at which PM is oxidized, the accumulated PM in the filter can be oxidized. In addition, the second predetermined amount is, for example, an accumulation amount of PM set in order to determine whether or not a regeneration process to sufficiently prevent accumulation of PM and overheating of the filter is necessary. The second predetermined amount is an amount that is set smaller than the first predetermined amount so as to ensure that the filter temperature during the regeneration process does not exceed the first predetermined temperature at which ash contracts.

As described above, according to the present invention, the control unit adds fuel from the fuel adding unit when the accumulation amount of PM is equal to or larger than the second predetermined amount, but in a case where the accumulation amount of ash is equal to or larger than the threshold amount, the control unit adds fuel from the fuel adding unit when the accumulation amount of PM is equal to or larger than the first predetermined amount. In other words, when the accumulation amount of ash is equal to or larger than the threshold amount, the control unit does not execute a fuel addition until the accumulation amount of PM reaches the first predetermined amount even if the accumulation amount of PM has exceeded the second predetermined amount. Consequently, according to the present invention, when the accumulation amount of ash is equal to or larger than the threshold amount, the regeneration process can be executed in a state where the first predetermined amount of PM is accumulated. As a result, pressure loss of the filter can be effectively reduced while preventing an increase in fuel consumption.

According to the present invention, pressure loss of a PM collection filter that is attributable to accumulation of ash can be effectively reduced while preventing an increase in fuel consumption in an exhaust gas purification apparatus of an internal combustion engine in which the filter is provided in an exhaust passage.

FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and an exhaust gas purification apparatus according to a first example. FIG. 2 is a graph showing contraction characteristics of ash accumulated in a filter. FIG. 3 is a flow chart showing an execution procedure of fuel cut according to the first example. FIG. 4 is a flow chart showing a procedure of a process of setting a fuel cut prohibition flag according to the first example. FIG. 5 is a graph showing a relationship between accumulation amount of ash and pressure loss of a filter with respect to travel distance of a vehicle. FIG. 6 is a graph showing a relationship between target pressure loss and contraction rate of ash. FIG. 7 is a graph showing a relationship between contraction rate of ash and a target temperature. FIG. 8 is a graph showing a relationship between temperature increase and target PM accumulation amount, the temperature increase being a difference between a target temperature and a current temperature of a filter. FIG. 9 is a graph showing a relationship between PM accumulation amount and estimated overheating temperature. FIG. 10 is a diagram showing a schematic configuration of an internal combustion engine and an exhaust gas purification apparatus according to a second example. FIG. 11 is a flow chart showing a normal regeneration process according to the second example. FIG. 12 is a flow chart showing an ash contraction process according to the second example.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. It is to be understood that dimensions, materials, shapes, relative arrangements, and the like of components described in the embodiments are not intended to limit the technical scope of the invention to the embodiments unless otherwise noted.

(First example)
FIG. 1 is a diagram showing a schematic configuration of an exhaust gas purification apparatus of an internal combustion engine according to the present example. An internal combustion engine 10 is a spark-ignition internal combustion engine mounted on a vehicle. The internal combustion engine 10 is a gasoline engine for a vehicle having a plurality of cylinders 11 and is a so-called direct injection gasoline engine in which fuel is directly injected into the cylinder 11. The cylinder 11 is provided with a fuel injection valve 12 that injects fuel into a combustion chamber provided in an upper part of the cylinder 11, and a spark plug 13 that ignites an air-fuel mixture inside the cylinder 11. The spark plug 13 ignites the air-fuel mixture by generating a spark between electrodes provided at a tip of the spark plug 13.

An intake passage 20 connected to the combustion chamber of the cylinder 11 via an intake port is provided with a throttle valve 21 that adjusts a flow rate of intake air aspirated into the cylinder 11 and an air flow meter 22 that detects the flow rate. In addition, an exhaust passage 30 that is connected to the combustion chamber of the cylinder 11 via an exhaust port is provided with a catalyst 31 having an oxidation function and a filter 32 that collects particulate matter (PM) in exhaust gas. The catalyst 31 is a catalyst that removes unburned fuel and carbon monoxide in the exhaust gas by oxidation. For example, the catalyst 31 may be a three-way catalyst, an oxidation catalyst, an occlusion reduction type NOx catalyst, or a selective reduction type NOx catalyst. In addition, the filter 32 is a wall flow type filter formed from, for example, a porous substrate made from cordierite.

An air-fuel ratio sensor 33 that detects an air-fuel ratio of the exhaust gas is provided in the exhaust passage 30 on an upstream side of the catalyst 31. The air-fuel ratio sensor 33 may be an oxygen concentration sensor that detects an oxygen concentration of the exhaust gas. In addition, a first temperature sensor 34 that detects a temperature of the exhaust gas is provided in the exhaust passage 30 on a downstream side of the catalyst 31 i.e. an upstream side of the filter 32. A temperature of the catalyst 31 can be detected based on a detected value of the first temperature sensor 34. Furthermore, a second temperature sensor 35 that detects a temperature of the exhaust gas is provided in the exhaust passage 30 on a downstream side of the filter 32. A temperature of the filter 32 can be detected based on a detected value of the second temperature sensor 35. In addition, a differential pressure sensor 36 that detects a differential pressure across the filter 32 (a difference between the pressure of the exhaust gas on the upstream side of the filter 32 and the pressure of the exhaust gas on the downstream side of the filter 32) is provided in the exhaust passage 30.

Furthermore, the internal combustion engine 10 is provided with an ECU 40 that is an electronic control unit for controlling the internal combustion engine 10. The fuel injection valve 12, the spark plug 13, and the throttle valve 21 are electrically connected to and controlled by the ECU 40. In addition, the air flow meter 22, the air-fuel ratio sensor 33, the first temperature sensor 34, the second temperature sensor 35, and the differential pressure sensor 36 described above are electrically connected to the ECU 40 and output signals from these sensors are inputted to the ECU 40. Furthermore, an accelerator opening degree sensor 41 that detects an opening degree of an accelerator pedal (not shown) provided in the vehicle and a crank sensor 42 that detects a rotational position of a crankshaft 14 of the internal combustion engine 10 are connected to the ECU 40 via an electric wiring, and output signals from these sensors are inputted to the ECU 40.

During a normal operation of the internal combustion engine 10, the ECU 40 controls a fuel injection amount and the like from the fuel injection valve 12 based on detected values from the air flow meter 22, the air-fuel ratio sensor 33, and the like so that an air-fuel ratio of the air-fuel mixture inside the cylinder 11 equals or approximates a stoichiometric air-fuel ratio.

Moreover, by executing a fuel cut in which fuel supply to the internal combustion engine 10 is shut off, the ECU 40 executes a regeneration process for oxidizing PM that is accumulated in the filter 32. More specifically, when a fuel cut is executed, air aspirated into the cylinder 11 is discharged as it is, hence highly concentrated oxygen is supplied to the filter 32. Therefore, when the temperature of the filter 32 is within a predetermined temperature range in which PM is oxidized, PM accumulated in the filter 32 is oxidized and removed by the supplied oxygen. In the present example, the ECU 40 that executes a regeneration process in this manner corresponds to the control unit according to the present invention. The regeneration process according to the present example is normally executed so that the filter temperature remains within a predetermined temperature range (for example, approximately 500 degrees Celsius to approximately 650 degrees Celsius) that is sufficiently lower than a maximum temperature that the filter 32 can tolerate (for example, approximately 1400 degrees Celsius) in order to prevent the filter 32 from overheating. Hereinafter, such a regeneration process will be referred to as a normal regeneration process.

Meanwhile, exhaust gas that is discharged from the internal combustion engine 10 may contain ash that is an incombustible solid substance originating from components of additives contained in lubricating oil, or the like. The ash in the exhaust gas is also collected by and accumulated in the filter 32 in a similar manner to PM. When accumulation of the ash proceeds, there is a risk that a decrease in filtration area of the filter 32 causes an increase in pressure loss. However, it is difficult to remove the accumulated ash by oxidation as is the case with PM. Therefore, conventionally, it has been difficult to reduce pressure loss that had increased due to the ash.

A recent research has revealed that ash has characteristics of decreasing in volume while increasing in density (contracting) when heated to a temperature that is higher than the temperature range during a normal regeneration process. Hereinafter, the contraction characteristics of ash accumulated in a filter will be described in detail with reference to FIG. 2.

FIG. 2 is a diagram showing a relationship between temperature and a rate of change in density of ash accumulated in the filter 32 when the ash is heated. In FIG. 2, a horizontal axis represents a temperature of the ash and a vertical axis represents a rate of change in density of ash. As shown in FIG. 2, when the temperature of ash is within a range corresponding to the predetermined temperature range described earlier, the rate of change in density of ash is approximately 0%. In other words, the ash accumulated in the filter 32 hardly contracts during execution of a normal regeneration process. However, the rate of change in density of ash starts to rise once the temperature of ash exceeds a temperature T1 (approximately 750 degrees Celsius) then reaches approximately 50% at a temperature T2 (approximately 1050 degrees Celsius). In other words, contraction of ash can be realized by raising the filter temperature to at least the temperature T1, and ash can be contracted to a volume of approximately 2/3 by raising the filter temperature to the temperature T2. However, there is a risk that a failure such as melting may occur when the temperature of filter rises excessively.

In consideration of the above, the present example has been configured to realize contraction of ash accumulated in the filter 32 by further raising the filter temperature by a regeneration process that is different from a normal regeneration process. Specifically, when making the accumulated ash to contract, a regeneration process in which the filter temperature is raised to a predetermined contraction temperature is executed. The predetermined contraction temperature is a temperature at which a sufficient contraction of ash will occur (for example, the temperature T2 described above) but is within a range in which overheating of the filter 32 does not occur. Hereinafter, such a regeneration process will be referred to as an ash contraction process.

As described earlier, since a normal regeneration process is executed so that the temperature of the filter 32 remains in a temperature range that is lower than the temperature T1, it is difficult to cause the ash to contract during a normal regeneration process. To this end, the temperature of the exhaust gas that is discharged from the internal combustion engine 10 can conceivably be raised in order to raise the filter temperature to at least the temperature T1 or higher and favorably to the vicinity of a low temperature side of the temperature T2. However, since the catalyst 31 is arranged on the upstream side of the filter 32 in the exhaust gas purification apparatus of the internal combustion engine 10 in the present example, and an upper limit temperature of the exhaust gas that the catalyst 31 can tolerate is lower than the temperature T2, the filter 32 cannot be heated by the exhaust gas to the vicinity of the low temperature side of the temperature T2. In addition, since raising the exhaust gas temperature requires additionally consuming fuel, decrease in fuel efficiency due to an increase in fuel consumption becomes a concern.

In consideration thereof, the exhaust gas purification apparatus according to the present example is configured such that, when contraction of ash is required, the filter temperature is raised to a predetermined temperature at which contraction of ash occurs by using oxidation heat that is generated by PM accumulated in the filter 32. Specifically, execution of a regeneration process is restricted until a predetermined amount of PM that is required to raise the filter temperature to the predetermined temperature is accumulated. Then, a regeneration process (in other words, the ash contraction process) is executed in a state where the predetermined amount of PM has accumulated.

Next, the regeneration process according to the present example will be described in detail with reference to the drawings. First, a procedure of executing a fuel cut will be described with reference to FIG. 3. The flow shown in FIG. 3 is executed as a control program stored in the ECU 40, and is executed at predetermined intervals.

In step S101, the ECU 40 determines whether or not the internal combustion engine 10 is performing a decelerating operation. For example, the ECU 40 makes this determination based on a detected value of the accelerator opening degree sensor 41 or an operation state of the internal combustion engine 10. When a negative determination is made in this step, the present flow is terminated. On the other hand, when an affirmative determination is made in this step, the ECU 40 advances to step S102.

In step S102, the ECU 40 determines whether or not a fuel cut prohibition flag has been turned on. In this case, the fuel cut prohibition flag is a flag that is set by the flow shown in FIG. 4 to be described later. In the present example, a fuel cut prohibition flag that is set in advance by the flow shown in FIG. 4 is referred to in step S102. When an affirmative determination is made in the present step, the ECU 40 advances to step S103 to prohibit execution of a fuel cut and subsequently terminates the present flow. On the other hand, when a negative determination is made in the present step, the ECU 40 advances to step S104 and executes a fuel cut by stopping fuel injection by the fuel injection valve 12, then subsequently terminates the present flow.

Next, a process of setting a fuel cut prohibition flag will be described with reference to FIG. 4. FIG. 4 is a flow chart showing a procedure of a process of setting a fuel cut prohibition flag. The present flow is executed as a control program stored in the ECU 40, and is executed at predetermined intervals.

In step S201, the ECU 40 obtains Mpm denoting a PM accumulation amount and Mash denoting an ash accumulation amount upon execution of the present flow. The ECU 40 obtains the PM accumulation amount Mpm based on a detected value of the differential pressure sensor 36, an operation history of the internal combustion engine 10, or the like. In addition, the ECU 40 obtains the ash accumulation amount Mash based on a detected value of the differential pressure sensor 36, an operation history of the internal combustion engine 10, or the like, together with a detected value that has been detected by the differential pressure sensor 36 immediately after a previously executed normal regeneration process. Since this detected value is a value detected immediately after PM is removed, the detected value is a value with an influence of accumulated PM eliminated. Therefore, by using this detected value (for example, by using this detected value as well as another detected value or operation history after the detection of this detected value), the ash accumulation amount Mash can be obtained with accuracy.

In step S202, in order to determine whether contraction of ash is necessary, the ECU 40 determines whether or not the ash accumulation amount Mash obtained in the previous step is equal to or larger than a predetermined threshold amount Ma. Referring now to FIG. 5 which shows a relationship between the ash accumulation amount Mash and pressure loss DP of the filter 32 with respect to travel distance of a vehicle, a graph L1 shows that the ash accumulation amount Mash increases as the travel distance of the vehicle increases. Consequently, as depicted by graph L2, the pressure loss DP of the filter 32 also increases as the travel distance of the vehicle increases. In consideration thereof, the ECU 40 executes an ash contraction process and lowers the pressure loss DP to a target pressure loss Pt when the ash accumulation amount Mash exceeds the threshold amount Ma. The threshold Ma can be an accumulation amount of ash when it can be expected that contraction of ash would reduce the pressure loss of the filter. The threshold amount Ma may be set in advance by experiment or the like. When an affirmative determination is made in the present step, the ECU 40 advances to step S203. On the other hand, a negative determination made in the present step signifies that ash has not been accumulated to a level that requires an ash contraction process. In this case, since execution of a regeneration process need not be restricted, a fuel cut can be executed during deceleration of the internal combustion engine 10. Therefore, in order to allow a fuel cut, the ECU 40 advances to step S213 to turn off the fuel cut prohibition flag and subsequently terminates the present flow. Accordingly, when the flow shown in FIG. 3 described above is executed after the present flow is terminated, a fuel cut is executed in step S104 if the internal combustion engine 10 is decelerating. In addition, when PM is accumulated in the filter 32 and the filter temperature is sufficiently high, a normal regeneration process is executed in which the accumulated PM is oxidized and removed.

In step S203, the ECU 40 calculates a target pressure loss Pt that is a target value of the pressure loss. The ECU 40 calculates the target pressure loss Pt based on the ash accumulation amount Mash, an operation history of the internal combustion engine 10, a travel distance of the vehicle (or a travel distance from the last ash contraction process), a target fuel efficiency, or the like. For example, when the ash accumulation amount Mash is large or a deviation of actual fuel efficiency from the target fuel efficiency is large, the target pressure loss Pt is set smaller than otherwise.

In step S204, the ECU 40 calculates a contraction rate a of ash which makes it possible to lower the pressure loss DP to the target pressure loss Pt calculated in the previous step. A contraction rate is a numerical value expressed as (volume before contraction – volume after contraction)/volume before contraction, where the larger the contraction rate, the smaller the volume after contraction. When the ash accumulation amount Mash is constant, the target pressure loss Pt of the filter 32 and the contraction rate a of ash satisfy a relationship such as that shown in FIG. 6. Specifically, the smaller the calculated target pressure loss Pt, the higher the contraction rate a need to be set (in other words, ash is contracted more). In addition, although not illustrated, when the target pressure loss Pt is constant, the larger the ash accumulation amount Mash, the higher the contraction rate a need to be set. The ECU 40 calculates the contraction rate a to be set as a target in the present flow based on these relationships.

In step S205, the ECU 40 calculates a target temperature Tt of the filter 32 at which ash contracts to the contraction rate a calculated in the previous step. The target temperature Tt and the contraction rate a satisfy a relationship such as that shown in FIG. 7. Specifically, the higher the target contraction rate a (in other words, the more the ash need to be contracted), the higher the target temperature Tt need to be set. Based on this relationship, the ECU 40 calculates the target temperature Tt in the present flow. The target temperature Tt is set within a range in which the temperature T2 described earlier is the upper limit. The ECU 40 may obtain the target temperature Tt from the contraction characteristics of ash shown in FIG. 2. In the present example, the target temperature Tt corresponds to the first predetermined temperature according to the present invention.

In step S206, the ECU 40 calculates a target PM accumulation amount Mpmt that is an amount of the accumulated PM necessary for raising the temperature of the filter 32 to the target temperature Tt using oxidation heat from the accumulated PM. A temperature rise Tt – Tc, which is a difference between the target temperature Tt and a current temperature Tc (the filter temperature upon execution of the present flow), and the target PM accumulation amount Mpmt satisfy a relationship such as that shown in FIG. 8. It is assumed that the current temperature Tc corresponds to the temperature of ash upon execution of the present flow. In other words, the larger the temperature rise Tt – Tc, the larger the amount of oxidation heat required to heat the ash, and hence the target PM accumulation amount Mpmt needs to be larger. In addition, the larger the ash accumulation amount Mash, the larger the amount of oxidation heat required to heat the ash, and hence the target PM accumulation amount Mpmt needs to be larger. The ECU 40 calculates the target PM accumulation amount Mpmt in the present flow on the basis of these relationships, a thermal capacity of the filter 32, and the like. Meanwhile, a detected value from the second temperature sensor 35 can be used as the current temperature Tc. In the present example, the target PM accumulation amount Mpmt corresponds to the first predetermined amount according to the present invention.

In step S207, the ECU 40 calculates an estimated overheating temperature Tot that is a lower limit temperature of a predetermined filter temperature range. The predetermined filter temperature range is a filter temperature range when it is assumed that the filter 32 becomes overheated if the accumulated PM in the filter 32 is oxidized during the execution of the present flow. The PM accumulation amount Mpm and the estimated overheating temperature Tot satisfy a relationship such as that shown in FIG. 9. In other words, the larger the PM accumulation amount Mpm, the larger the amount of generated oxidation heat, and hence the lower the estimated overheating temperature Tot. Based on this relationship, the ECU 40 calculates the estimated overheating temperature Tot in the present flow.

In step S208, the ECU 40 determines whether or not the current temperature Tc of the filter 32 is lower than the estimated overheating temperature Tot calculated in the previous step. A negative determination signifies that there is a risk that the filter 32 may become overheated if the accumulated PM in the filter 32 is to be oxidized. Therefore, in order to prohibit a fuel cut, the ECU 40 advances to step S209 to turn on the fuel cut prohibition flag and subsequently terminates the present flow.

On the other hand, when an affirmative determination is made in step S208, the ECU 40 advances to step S210 to determine whether or not the PM accumulation amount Mpm is equal to or larger than the target PM accumulation amount Mpmt. A negative determination made in the present step signifies that an amount of PM necessary to raise the temperature of the filter 32 to the target temperature Tt is not accumulated in the filter 32 at the time of the execution of the present flow. Therefore, the ECU 40 advances to step S211 to determine whether or not the current temperature Tc of the filter 32 is lower than a regeneration-enabled temperature Tlo which is a minimum filter temperature for an oxidation reaction of PM to occur. A negative determination signifies that the accumulated PM is to be oxidized if a fuel cut is executed and oxygen is supplied to the filter 32. In this case, the temperature of the filter 32 would not rise to the target temperature Tt even if oxidation of PM is started because the PM accumulation amount Mpm is lower than the target PM accumulation amount Mpmt. Therefore, the ECU 40 advances to step S209 to turn on the fuel cut prohibition flag and subsequently terminates the present flow. Accordingly, when the flow shown in FIG. 3 described above is executed after the present flow is terminated, fuel cut is prohibited in step S103 even when the internal combustion engine 10 is decelerating. In other words, when an amount of PM necessary to raise the temperature of the filter 32 to the target temperature Tt is not accumulated in the filter 32, execution of a regeneration process is restricted. As a result, oxidizing PM under a situation where the temperature of the filter 32 cannot be raised to the target temperature Tt can be avoided. Meanwhile, the regeneration-enabled temperature Tlo described above corresponds to the second predetermined temperature according to the present invention.

On the other hand, an affirmative determination made in step S211 signifies that, even if a fuel cut is executed and oxygen is supplied to the filter 32, the accumulated PM is not oxidized because the filter temperature is lower than the regeneration-enabled temperature Tlo. Therefore, in this case, as the accumulated PM would not be consumed by oxidation even if a fuel cut is executed, a fuel cut can be executed for the purpose of improving fuel efficiency or the like. Thus, the ECU 40 advances to step S213 to turn off the fuel cut prohibition flag and subsequently terminates the present flow.

Meanwhile, when an affirmative determination is made in step S210, the ECU 40 advances to step S212 to determine whether or not the current temperature Tc is equal to or higher than the regeneration-enabled temperature Tlo. When an affirmative determination is made in the present step, the ECU 40 advances to step S213 to turn off the fuel cut prohibition flag and subsequently terminates the present flow. Accordingly, when the flow shown in FIG. 3 described above is executed after the present flow is terminated, a fuel cut will be executed in step S104 when the internal combustion engine 10 is decelerating, and PM accumulated in the filter 32 will be oxidized. Then, the filter temperature rises to the target temperature Tt due to oxidation heat that is generated by the oxidized PM, and thus the ash accumulated in the filter can be contracted to the contraction rate a. In other words, an ash contraction process is executed in this manner. Consequently, the pressure loss of the filter 32 can be lowered to the target pressure loss Pt.

Meanwhile, a negative determination made in step S212 signifies that the accumulated PM is not oxidized even if a fuel cut is executed. Therefore, the ECU 40 advances to step S209 to turn on the fuel cut prohibition flag and subsequently terminates the present flow. Accordingly, when the flow shown in FIG. 3 is executed after the present flow is terminated, a fuel cut will not be executed even when the internal combustion engine 10 is decelerating, and thus exhaust temperature will rise and the filter 32 will be heated. As a result, the temperature of the filter 32 can be more quickly raised to the regeneration-enabled temperature Tlo. On the other hand, when a negative determination is made in step S212, a fuel cut may be executed for the purpose of improving fuel efficiency or the like because the accumulated PM will not be consumed by oxidation even if a fuel cut is executed. In other words, in this case, the ECU 40 may advance to step S213 instead of step S209 to turn off the fuel cut prohibition flag.

As described above, according to the present example, even when it is necessary to cause contraction of ash accumulated in the filter 32, the fuel cut prohibition flag is turned on if the target PM accumulation amount Mpmt of PM is not accumulated. Accordingly, because fuel cut is prohibited until the PM accumulation amount reaches the target PM accumulation amount Mpmt, fuel cut is not executed even when the internal combustion engine 10 decelerates. Subsequently, after PM is further accumulated to the target PM accumulation amount Mpmt, fuel cut is allowed by turning off the fuel cut prohibition flag. Accordingly, a fuel cut will be executed and the accumulated PM will be oxidized during deceleration of the internal combustion engine 10, and thus ash accumulated in the filter 32 is contracted due to oxidation heat of PM. In other words, according to the present example, when ash needs to be contracted, a fuel cut is restricted until the target PM accumulation amount Mpmt of PM is accumulated. Then a fuel cut is performed and a regeneration process is executed in a state where the target PM accumulation amount Mpmt of PM is accumulated. As a result, pressure loss of the filter 32 can be effectively reduced while preventing an increase in fuel consumption.

In addition, according to the present example, in a case where ash needs to be contracted, a fuel cut is executed when the filter temperature is lower than the regeneration-enabled temperature Tlo even before the target PM accumulation amount Mpmt of PM is accumulated. Accordingly, an execution frequency of a fuel cut increases, and thus the fuel consumption of the internal combustion engine 10 can be further reduced.

Meanwhile, as described above, in the present example, the flow shown in FIG. 3 and the flow shown in FIG. 4 are executed independently of each other. The fuel cut prohibition flag set in advance by the flow shown in FIG. 4 is referred to in step S102 of the flow shown in FIG. 3. However, execution modes of the two flows are not limited thereto and, for example, the flow shown in FIG. 4 may be executed in step S102 of the flow shown in FIG. 3. In other words, during deceleration of the internal combustion engine 10 (step S101: Yes), the ECU 40 may determine execution and prohibition of a fuel cut by executing the flow shown in FIG. 4 in step S102.

(Second Example)
While the first example described above represents an example where the exhaust gas purification apparatus of an internal combustion engine according to the present invention is applied to an internal combustion engine 10 that is a spark-ignition internal combustion engine, the exhaust gas purification apparatus of an internal combustion engine according to the present invention can also be applied to an internal combustion engine having a fuel adding unit which adds fuel to exhaust gas flowing into a filter (including internal combustion engines other than a spark-ignition internal combustion engine). Hereinafter, a second example that represents an example where the exhaust gas purification apparatus of an internal combustion engine according to the present invention is applied to a compression-ignition internal combustion engine having a fuel adding unit will be described. Those components that are similar to those of the first example described above will be denoted by the same or similar reference numerals and descriptions thereof will be omitted.

FIG. 10 is a diagram showing a schematic configuration of an exhaust gas purification apparatus of an internal combustion engine according to the present example. An internal combustion engine 110 is a compression-ignition internal combustion engine mounted on a vehicle. The internal combustion engine 110 is a diesel engine for a vehicle having a plurality of cylinders 111. The cylinder 111 is provided with a fuel injection valve 112 that injects fuel into a combustion chamber provided in an upper part of the cylinder 111. In addition, sensors and devices with similar functions as those provided in the internal combustion engine 10 according to the first example are arranged in an intake passage 120 and an exhaust passage 130 which are connected to the combustion chamber of the cylinder 111. Furthermore, a filter 132 that collects PM in exhaust gas is provided in the exhaust passage 130. And a catalyst 131 with an oxidizing function is provided on an upstream side of the filter 132 in the exhaust passage 130. The catalyst 131 is a catalyst that removes unburned fuel and carbon monoxide in the exhaust gas by oxidation. In addition, the filter 132 is a wall flow type filter formed from, for example, a porous substrate made from silicon carbide (SiC).

Furthermore, a fuel adding valve 37 which adds fuel to exhaust gas flowing into the catalyst 131 is provided in the exhaust passage 130 on an upstream side of the catalyst 131. Moreover, the internal combustion engine 110 is provided with an ECU 140 for controlling the internal combustion engine 110. The ECU 140 controls various devices that are electrically connected to the ECU 140. In addition, the various sensors and the like described earlier are electrically connected to the ECU 140 and output signals from the various sensors and the like are inputted to the ECU 140.

Also in the present example, PM contained in exhaust gas that is discharged from the internal combustion engine 110 accumulates in the filter 132. Generally, a temperature of exhaust gas that is discharged from a diesel engine is lower than a temperature of exhaust gas that is discharged from a gasoline engine. Therefore, in the present example, when making the accumulated PM in the filter 132 to oxidize, a regeneration process that forcibly raises a temperature of the filter 132 to a temperature at which PM is oxidized (a forced regeneration process) is executed. In the forced regeneration process, the ECU 140 uses the fuel adding valve 37 to add fuel to the exhaust gas flowing into the catalyst 131. The added fuel is oxidized in the catalyst 131 and generates heat; hence the temperature of the exhaust gas that is discharged from the catalyst 131 rises. Accordingly, the heated exhaust gas flows into the filter 132,and thus the temperature of the filter 132 can be raised to a predetermined temperature range in which PM is oxidized (for example, approximately 400 degrees Celsius to 500 degrees Celsius). In the present example, the ECU 140 that executes a regeneration process corresponds to the control unit according to the present invention. In addition, hereinafter, a regeneration process that raises the filter temperature to the predetermined temperature range will be referred to as a normal regeneration process.

The exhaust gas that is discharged from the internal combustion engine 110 may contain ash originating from components of additives contained in lubricating oil, sulfur contained in fuel, or the like. Thus, ash accumulates in the filter 132. Meanwhile, contraction characteristics of the ash discharged from the internal combustion engine 110 are similar to the contraction characteristics shown in FIG. 2 described earlier. In consideration thereof, in the present example, an ash contraction process which is a regeneration process that is different from a normal regeneration process is similarly executed when contraction of ash is required. Specifically, until a predetermined amount of PM that is needed to raise the filter temperature to a predetermined temperature at which the accumulated ash contracts, addition of fuel to the exhaust gas is not executed. And the addition of fuel is executed in a state where the predetermined amount of PM is accumulated.

Next, the regeneration process according to the present example will be described in detail with reference to the drawings. First, a flow of a normal regeneration process will be described with reference to FIG. 11. The flow shown in FIG. 11 is executed as a control program stored in the ECU 140, and is executed at predetermined intervals.

In step S301, the ECU 140 determines whether or not Mpm that denotes a PM accumulation amount upon execution of the present flow is equal to or larger than a threshold accumulation amount Mth that represents an accumulation amount of PM set in order to determine whether or not execution of a normal regeneration process is necessary. The threshold accumulation amount Mth is a predetermined amount which is set sufficiently low in order to prevent PM from being excessively accumulated and to prevent overheating during a regeneration process. The threshold accumulation amount Mth is an amount smaller than a target PM accumulation amount Mpmt that is a PM accumulation amount necessary to raise the temperature of the filter 132 to a target temperature Tt at which the ash contracts. In the present example, the threshold accumulation amount Mth corresponds to the second predetermined amount according to the present invention. When a negative determination is made in the present step, it signifies that PM is not accumulated in the filter 132 to such an extent that it needs to be removed by a regeneration process, and thus the present flow is terminated. On the other hand, when an affirmative determination is made in the present step, the ECU 140 advances to step S302 to execute addition of fuel from the fuel adding valve 37. Accordingly, temperature of the filter 132 rises to the predetermined temperature range described earlier, and thus the PM accumulated in the filter 132 is removed by oxidation. Moreover, the ECU 140 controls an adding amount from the fuel adding valve 37 so that the filter temperature remains within the predetermined temperature range. Alternatively, fuel may be supplied to the catalyst 131 by post-injections from the fuel injection valves 112 instead of the fuel adding valve 37.

Next, a flow of the ash contraction process will be described with reference to FIG. 12. The flow shown in FIG. 12 is executed as a control program stored in the ECU 140, and is executed at predetermined intervals. Meanwhile, in the present flow, processes similar to the processes performed in steps S201 to S206 in the flow shown in FIG. 4 described earlier are performed. Therefore, the steps will be denoted by the same step numbers and descriptions thereof will be omitted where appropriate.

When an affirmative determination is made in step S202, the ECU 140 determines that an ash contraction process is necessary and calculates the target PM accumulation amount Mpmt by executing steps S203 to S206. As described in the description of the first example, the target PM accumulation amount Mpmt is the amount of PM that is necessary to raise the temperature of the filter to a temperature at which the accumulated ash contracts. Thus, the target PM accumulation amount Mpmt is larger than the threshold accumulation amount Mth. When step S206 is performed, the ECU 140 advances to step S401 to determine whether or not the PM accumulation amount Mpm upon execution of the present flow is equal to or larger than the calculated target PM accumulation amount Mpmt. In the present example, the target PM accumulation amount Mpmt corresponds to the first predetermined amount according to the present invention. When a negative determination is made in the present step, it signifies that an amount of PM that is necessary to raise the filter temperature to a predetermined temperature at which ash contracts is not accumulated in the filter 132, and thus the present flow is terminated. On the other hand, when an affirmative determination is made in the present step, the ECU 140 advances to step S402 to execute addition of fuel from the fuel adding valve 37. In other words, in the present example, addition of fuel from the fuel adding valve 37 is executed when the PM accumulation amount Mpm is equal to or larger than the target PM accumulation amount Mpmt instead of the threshold accumulation amount Mth. Accordingly, the filter temperature rises to the target temperature Tt due to oxidation heat that is generated by the oxidized PM, and thus the ash accumulated in the filter can be contracted to a contraction rate a. As a result, the pressure loss of the filter 132 can be lowered to the target pressure loss Pt. Meanwhile, when a negative determination is made in step S202, it signifies that the ash contraction process need not be executed, and thus the ECU 140 advances to step S403 to execute the normal regeneration process described earlier.

As described above, according to the present example, when ash accumulated in the filter 132 needs to be contracted, addition of fuel to the catalyst 131 is restricted until the PM accumulation amount Mpm reaches the target PM accumulation amount Mpmt even if the PM accumulation amount Mpm is exceeding the threshold accumulation amount Mth. As a result, pressure loss of the filter 132 can be effectively reduced by causing the accumulated ash to contract while preventing an increase in fuel consumption.

10, 110 internal combustion engine
31, 131 catalyst
32, 132 filter
40, 140 ECU

Claims

An exhaust gas purification apparatus of an internal combustion engine, comprising:
a filter being provided in an exhaust passage of the internal combustion engine that collects particulate matter in exhaust gas;
a first accumulation amount obtaining unit that obtains an accumulation amount of the particulate matter being accumulated in the filter;
a second accumulation amount obtaining unit that obtains an accumulation amount of incombustible matter being accumulated in the filter; and
a control unit that executes a regeneration process to oxidize the particulate matter being accumulated in the filter, wherein, in a case where the accumulation amount of the incombustible matter obtained by the second accumulation amount obtaining unit is equal to or larger than a threshold amount, the control unit executes the regeneration process provided the accumulation amount of the particulate matter obtained by the first accumulation amount obtaining unit is in a state where it has reached a first predetermined amount, the first predetermined amount being an amount to raise a temperature of the filter to a first predetermined temperature by oxidation heat generated by the regeneration process, the first predetermined temperature being a temperature at which the accumulated incombustible matter contracts.
The exhaust gas purification apparatus of an internal combustion engine according to claim 1, wherein the second accumulation amount obtaining unit obtains the accumulation amount of the incombustible matter accumulated in the filter on the basis of a differential pressure across the filter immediately after an execution of the regeneration process by the control unit.
The exhaust gas purification apparatus of an internal combustion engine according to claim 1 or 2, further comprising a first predetermined amount obtaining unit that obtains the first predetermined amount on the basis of the accumulation amount of the incombustible matter obtained by the second accumulation amount obtaining unit and a difference between the first predetermined temperature and an actual temperature of the incombustible matter.
The exhaust gas purification apparatus of an internal combustion engine according to any one of claims 1 to 3, wherein
the internal combustion engine is a spark-ignition internal combustion engine capable of combustion at a stoichiometric air-fuel ratio, and
the control unit executes the regeneration process by executing a fuel shutoff for the internal combustion engine during a decelerating operation of the internal combustion engine.
The exhaust gas purification apparatus of an internal combustion engine according to claim 4, wherein
in a case where the accumulation amount of the incombustible matter is equal to or larger than the threshold amount, the control unit executes the fuel shutoff for the internal combustion engine during the decelerating operation of the internal combustion engine if the temperature of the filter is lower than a second predetermined temperature even if the accumulation amount of the particulate matter is smaller than the first predetermined amount, the second predetermined temperature being a temperature at which an oxidation reaction due to the regeneration process does not occur.
The exhaust gas purification apparatus of an internal combustion engine according to any one of claims 1 to 3, wherein
the internal combustion engine is a compression-ignition internal combustion engine including an oxidation catalyst being provided on an upstream side of the filter in the exhaust passage, and a fuel adding unit that adds fuel to exhaust gas flowing into the oxidation catalyst,
the control unit executes the regeneration process by adding the fuel from the fuel adding unit when the accumulation amount of the particulate matter accumulated in the filter is equal to or larger than a second predetermined amount that is smaller than the first predetermined amount, wherein
in a case where the accumulation amount of the incombustible matter is equal to or larger than the threshold amount, the control unit executes the regeneration process by adding the fuel from the fuel adding unit if the accumulation amount of the particulate matter is equal to or larger than the first predetermined amount instead of the second predetermined amount.