JP5287940B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

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

  As described in Patent Document 1, as an exhaust purification device provided in an exhaust passage of an internal combustion engine, an apparatus including a filter that collects PM (Particulate Matter) in exhaust gas is known. In this exhaust purification device, as the amount of PM collected by the filter increases, the pressure loss of the filter increases, which adversely affects engine output and the like. Therefore, a so-called regeneration process is performed in which the collected PM is burned by raising the temperature of the filter.

  In this regeneration process, when the amount of PM deposited on the filter reaches a preset amount, an additive such as fuel is supplied to the exhaust passage. Then, when the temperature of the filter is raised by combustion of the additive, the oxidation of PM in the filter is promoted, and the PM deposited on the filter is reduced to a specified amount.

  In an apparatus that performs such regeneration processing, the amount of PM deposited on the filter is estimated by calculating the PM discharge amount and the PM oxidation amount per unit time.

JP 2007-23792 A

  Meanwhile, as described in Patent Document 1, ash that is a component derived from lubricating oil and difficult to burn by the regeneration process accumulates on the filter. When this ash is deposited on the filter, the oxidation rate of PM changes. Therefore, if the oxidation rate of PM is calculated without considering the influence of ash, the accuracy of the oxidation rate becomes low, and as a result, the amount of PM deposition on the filter is estimated. Accuracy will be reduced. If the estimation accuracy of the PM accumulation amount decreases in this manner, for example, PM may remain unburned when the regeneration process is completed.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an exhaust gas purification apparatus for an internal combustion engine that can calculate the PM oxidation rate in the filter more accurately.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is an exhaust gas purification apparatus for an internal combustion engine that includes a filter that collects particulate matter in exhaust gas and performs regeneration processing of the filter, and the oxidation rate of the particulate matter in the filter Is set based on the thickness of the ash deposited on the filter.

  The present inventor has found that the oxidation rate of particulate matter in the filter, that is, the PM oxidation rate, has a greater influence on the thickness of the ash deposited on the filter than on the amount of ash deposited on the filter. For example, when the density of ash (mass per unit volume) is small and the thickness of the deposited ash is large, the PM oxidation rate decreases even if the amount of ash deposited itself is small.

  Therefore, in this configuration, the oxidation rate of the particulate matter is set based on the thickness of the ash deposited on the filter, and the PM oxidation rate in the filter can be calculated with higher accuracy.

  The present inventor has confirmed that the actual PM oxidation rate decreases as the thickness of the ash deposited on the filter increases. Therefore, according to the invention described in claim 2, by adopting a configuration in which the oxidation rate is variably set so as to decrease as the thickness of the ash deposited on the filter increases, The PM oxidation rate based on the thickness can be suitably set.

  According to a third aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first or second aspect, the ash accumulation amount in the filter is calculated, and the ash accumulation density is calculated based on the maximum exhaust gas flow rate. The gist is to calculate the thickness of the ash deposited on the filter by calculating and dividing the accumulation amount by a value obtained by multiplying the collection area of the filter and the accumulation density.

  Ash deposited on the filter is compressed by the flow of exhaust. Therefore, the density of ash accumulated on the filter, that is, the ash accumulation density can be calculated based on the maximum flow rate of the exhaust gas. Therefore, in this configuration, the ash accumulation density is calculated based on the maximum exhaust gas flow rate. Then, the ash accumulation amount is divided by a value obtained by multiplying the accumulation density by the filter collection area, whereby the thickness of the ash accumulated on the filter can be calculated.

  The amount of accumulated ash is the operating time of the internal combustion engine that correlates with the difference between the upstream exhaust pressure and the downstream exhaust pressure of the filter after completion of the regeneration process, the consumption amount of the engine lubricating oil, or the consumption amount of the engine lubricating oil. Or the travel distance of the vehicle.

  According to a fourth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the third aspect, as the amount of accumulation, a wall surface accumulation amount that is an amount of ash accumulated on a radial wall surface of the filter is calculated. The gist is that a collection area in the radial direction of the filter is set as the collection area.

  In the filter, ash accumulates on the radial wall surface of the filter and the bottom surface of the filter on the exhaust downstream side. Here, since more PM is collected on the radial wall surface of the filter than the bottom surface of the filter on the exhaust downstream side, it is desirable to accurately calculate the PM oxidation rate on the radial wall surface of the filter. .

  In this regard, in the same configuration, the amount of ash deposited on the wall surface in the radial direction of the filter is calculated, and the collection area in the radial direction of the filter is set as the collection area. Therefore, it is possible to calculate the thickness of the ash deposited on the radial wall surface of the filter. Since the PM oxidation rate is set based on the thickness of the ash deposited on the radial wall surface of the filter, the PM oxidation rate on the radial wall surface of the filter can be accurately calculated.

  According to a fifth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fourth aspect, the wall surface accumulation amount is calculated so as to decrease as the fluctuation amount of the exhaust flow rate increases. To do.

  Ash deposited on the radial wall surface of the filter is separated from the wall surface due to fluctuations in the exhaust flow rate and collected again on the bottom surface of the filter on the exhaust downstream side. Therefore, the larger the fluctuation amount of the exhaust flow rate, the larger the amount of ash deposited on the radial wall surface of the filter, and the smaller the amount of ash deposited on the wall surface. Therefore, in this configuration, the amount of ash wall deposition is reduced as the fluctuation amount of the exhaust flow rate increases. Therefore, it becomes possible to appropriately estimate the ash wall surface deposition amount.

  According to a sixth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the fourth aspect, the number of times that the fluctuation amount of the exhaust flow rate exceeds a predetermined value is measured. The gist is that the amount of deposition is calculated to be small.

  As described above, the ash deposited on the radial wall surface of the filter is separated from the wall surface due to fluctuations in the exhaust flow rate, and is collected again on the bottom surface of the filter on the exhaust downstream side. Accordingly, as the number of fluctuations in the exhaust flow rate increases, the amount of ash deposited on the radial wall surface of the filter increases and the amount of ash remaining on the wall surface decreases. Therefore, in this configuration, the number of times the fluctuation amount of the exhaust flow rate exceeds a predetermined value is measured, and the amount of ash wall deposition is reduced as the measured number increases. Therefore, even with this configuration, the amount of ash wall deposition can be estimated appropriately.

  In order to calculate the amount of deposited ash on the wall surface, the ratio of the deposited amount on the wall surface to the total amount of deposited ash on the filter is calculated as in the invention according to claim 7, and the calculated ratio is calculated. It is possible to adopt a configuration in which the wall surface deposition amount is calculated based on the above. In this configuration, the total amount of ash accumulated is correlated to the difference between the upstream exhaust pressure and the downstream exhaust pressure of the filter after completion of the regeneration process, the consumption amount of engine lubricating oil, or the consumption amount of engine lubricating oil. It can be estimated from the operating time of the internal combustion engine, the travel distance of the vehicle, and the like. Further, the ratio of the accumulation amount on the wall surface can be set based on the above-described fluctuation amount of the exhaust flow rate and the number of fluctuations of the exhaust flow rate.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the internal combustion engine to which this is applied, and its periphery structure about one Embodiment of the exhaust gas purification device of the internal combustion engine concerning this invention. The graph which shows the relationship between engine rotational speed, fuel injection amount, and PM discharge amount. The flowchart which shows the procedure about the calculation process of PM oxidation rate. The graph which shows the relationship between the maximum flow volume of exhaust, and the accumulation density of ash. The graph which shows the relationship between the fluctuation | variation amount and the frequency | count of fluctuation | variation of exhaust flow volume, and a wall surface deposition rate. The graph which shows the relationship between the bed temperature of a filter, the thickness of an ash, and PM oxidation rate.

Hereinafter, an embodiment of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to FIGS.
FIG. 1 is a schematic configuration diagram showing a diesel engine (hereinafter simply referred to as “engine”) to which the exhaust emission control device according to the present embodiment is applied, and a peripheral configuration thereof.

  The engine 1 is provided with a plurality of cylinders # 1 to # 4. A plurality of fuel injection valves 4 a to 4 d are attached to the cylinder head 2. These fuel injection valves 4a to 4d inject fuel into the combustion chambers of the cylinders # 1 to # 4. Also, the cylinder head 2 is provided with intake ports for introducing fresh air into the cylinders and exhaust ports 6a to 6d for discharging combustion gas to the outside of the cylinders corresponding to the respective cylinders # 1 to # 4. It has been.

  The fuel injection valves 4a to 4d are connected to a common rail 9 that accumulates high-pressure fuel. The common rail 9 is connected to the supply pump 10. The supply pump 10 sucks fuel in the fuel tank and supplies high-pressure fuel to the common rail 9. The high-pressure fuel supplied to the common rail 9 is injected into the cylinder from the fuel injection valves 4a to 4d when the fuel injection valves 4a to 4d are opened.

  An intake manifold 7 is connected to the intake port. The intake manifold 7 is connected to the intake passage 3. An intake throttle valve 16 for adjusting the intake air amount is provided in the intake passage 3.

An exhaust manifold 8 is connected to the exhaust ports 6a to 6d. The exhaust manifold 8 is connected to the exhaust passage 26.
In the middle of the exhaust passage 26, there is provided a turbocharger 11 that supercharges intake air introduced into the cylinder using exhaust pressure. An intercooler 18 is provided in the intake passage 3 between the intake side compressor of the turbocharger 11 and the intake throttle valve 16. The intercooler 18 cools the intake air whose temperature has risen due to supercharging of the turbocharger 11.

  A converter 30 for purifying exhaust components is provided in the middle of the exhaust passage 26 and downstream of the exhaust side turbine of the turbocharger 11. Inside the converter 30, an oxidation catalyst 31 and a filter 32 are arranged in series with respect to the flow direction of the exhaust gas.

  The oxidation catalyst 31 carries a catalyst for oxidizing HC in the exhaust. The filter 32 is a member that collects PM (particulate matter) in the exhaust gas, and is made of porous ceramic. The filter 32 carries a catalyst for promoting the oxidation of PM, and the PM in the exhaust gas is collected when passing through the porous wall of the filter 32.

  The cylinder head 2 is provided with a fuel addition valve 5 for supplying fuel as an additive to the oxidation catalyst 31 and the filter 32. The fuel addition valve 5 is connected to the supply pump 10 via a fuel supply pipe 27, and fuel is injected from the fuel addition valve 5 into the exhaust port 6d of the fourth cylinder # 4. The injected fuel reaches the oxidation catalyst 31 and the filter 32 together with the exhaust gas. The arrangement position of the fuel addition valve 5 can be appropriately changed as long as it is in the exhaust system and upstream of the converter 30.

  In addition, the engine 1 is provided with an exhaust gas recirculation device (hereinafter referred to as an EGR device). This EGR device is a device that reduces the combustion temperature in the cylinder by introducing a part of the exhaust gas into the intake air, thereby reducing the amount of NOx generated. The exhaust gas recirculation device includes an EGR passage 13 serving as an exhaust gas recirculation passage communicating the intake passage 3 and the exhaust passage (exhaust manifold 8), an EGR valve 15 provided in the EGR passage 13 and functioning as a flow control valve, And an EGR cooler 14 or the like. By adjusting the opening degree of the EGR valve 15, the exhaust gas recirculation amount introduced into the intake passage 3 from the exhaust passage 26, that is, the EGR amount is adjusted. Further, the temperature of the exhaust gas flowing through the EGR passage 13 is lowered by the EGR cooler 14.

  Various sensors for detecting the engine operation state are attached to the engine 1. For example, the air flow meter 19 detects the intake air amount GA in the intake passage 3. The throttle valve opening sensor 20 detects the opening of the intake throttle valve 16. An exhaust gas temperature sensor 33 provided on the exhaust gas downstream side of the oxidation catalyst 31 measures an exhaust gas temperature TE that is the temperature of the exhaust gas immediately after passing through the oxidation catalyst 31. The differential pressure sensor 34 detects the pressure difference ΔP between the exhaust pressure upstream and downstream of the filter 32. The engine rotation speed sensor 23 detects the rotation speed of the crankshaft, that is, the engine rotation speed NE. The accelerator sensor 24 detects an accelerator pedal depression amount, that is, an accelerator operation amount ACCP.

  The outputs of these various sensors are input to the control device 25. The control device 25 includes a central processing control device (CPU), a read only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, a timer counter, an input The microcomputer is mainly configured with an interface, an output interface, and the like.

  The control device 25 controls, for example, the fuel injection amount control / fuel injection timing control of the fuel injection valves 4a to 4d and the fuel addition valve 5, the discharge pressure control of the supply pump 10, the discharge pressure control of the supply pump 10, and the intake throttle valve. Various controls of the engine 1 such as drive amount control of the actuator 17 that opens and closes 16 and opening control of the EGR valve 15 are performed. Various exhaust purification controls such as a regeneration process for a filter that burns the PM collected by the filter 32 are also performed by the controller 25.

The regeneration process of the filter 32 is basically performed as follows.
First, a PM emission amount PMe, which is the amount of PM discharged from all combustion chambers of the engine 1, is set through a prior experiment or the like, for example, as shown in FIG. 2, fuel injection of the fuel injection valves 4a to 4d It is calculated based on a PM emission amount calculation map using the amount Q and the engine speed NE as parameters. As shown in FIG. 2, the PM emission amount PMe is calculated such that the PM emission amount PMe increases as the engine speed NE increases or the fuel injection amount Q increases. Then, the calculation of the PM discharge amount PMe is repeatedly performed every predetermined period and the integrated value is calculated, whereby the PM accumulation amount PMsm that is the PM amount accumulated on the filter 32 is estimated.

  Then, when the calculated PM accumulation amount PMsm reaches the regeneration start value PMstart, the regeneration process of the filter 32 is started. In this regeneration process, fuel addition by the fuel addition valve 5 is executed. The fuel injected from the fuel addition valve 5 is combusted when it reaches the oxidation catalyst 31, thereby increasing the exhaust temperature. The exhaust gas whose temperature has been raised by the oxidation catalyst 31 flows into the filter 32, whereby the temperature of the filter 32 is raised, whereby the PM deposited on the filter 32 is oxidized and the filter 32 is regenerated.

The amount of PM that decreases by raising the temperature of the filter 32, that is, the PM accumulation amount PMsm during regeneration of the filter 32 is estimated based on the following equation (1).

PMsm during the regeneration process = PMsm + PMe−PMc at the start of the regeneration process (1)
PMsm: PM deposition amount
PMe: PM emissions
PMc: PM oxidation amount

The PM oxidation amount PMc is an amount by which the PM collected by the filter 32 is burned. The PM oxidation amount PMc is calculated based on a map set through a prior experiment or the like, for example, an oxidation rate map indicating the oxidation amount of PM per unit time. Then, the calculation of the PM oxidation amount PMc and the PM discharge amount PMe is repeatedly performed at predetermined intervals, and the PM deposition amount PMsm is calculated according to the above equation (1) in synchronization with the calculation, thereby performing the regeneration process. PM deposition amount PMsm is estimated.

  When the PM accumulation amount PMsm estimated during the regeneration process as described above becomes sufficiently small and falls below a predetermined regeneration end value PMf, the regeneration process of the filter 32 is terminated. As a result, the PM accumulation amount PMsm of the filter 32 is reduced to a specified amount corresponding to the regeneration end value PMf.

  By the way, ash that is a component derived from the lubricating oil and difficult to burn by the above-described regeneration process is deposited on the filter 32. In addition, as this ash, the component (metal components, such as Zn, Ca, Mg, Na, etc.) contained in the additive etc. of lubricating oil, etc. are mentioned, for example. When the ash is deposited on the filter 32, the PM oxidation rate PMcs changes. Therefore, if the PM oxidation rate PMcs is calculated without considering the influence of the ash, the accuracy of the oxidation rate is lowered. That is, the difference between the actual oxidation rate of PM and the PM oxidation rate PMcs obtained from the oxidation rate map increases. Thus, when the accuracy of the PM oxidation rate PMcs decreases, the estimation accuracy of the PM deposition amount PMsm at the filter 32 decreases. If the estimation accuracy of the PM accumulation amount PMsm is thus reduced, the regeneration process is completed before the regeneration end value PMf is reached, and there is a possibility that PM remains unburned when the regeneration process is completed.

  Here, the present inventor has found that the oxidation rate of particulate matter in the filter 32, that is, the PM oxidation rate PMcs, is more greatly affected by the thickness of the ash deposited on the filter 32 than the amount of ash deposited on the filter 32. I found it. More specifically, it was confirmed that the actual PM oxidation rate decreases as the thickness of the ash deposited on the filter 32 increases. The reason why this phenomenon occurs is currently estimated as follows. That is, as the ash becomes thicker, the contact area between the catalyst supported on the filter 32 and the PM decreases and the catalytic action decreases, so the oxidation rate of PM is considered to decrease.

  Therefore, in this embodiment, the PM oxidation rate PMcs is calculated more accurately by variably setting the PM oxidation rate PMcs based on the thickness At of the ash deposited on the filter 32.

FIG. 3 shows the procedure for calculating the PM oxidation rate PMcs in the present embodiment. This process is repeatedly executed by the control device 25 at predetermined intervals.
When this process is started, first, the current ash deposition amount Asm is calculated (S100). The calculation of the ash deposition amount Asm here is performed as follows. That is, as the amount of accumulated ash in the filter 32 increases, the pressure difference ΔP detected by the differential pressure sensor 34 increases. Therefore, the ash accumulation amount Asm is estimated based on the pressure difference ΔP.

  Next, the ash deposited on the filter 32 is compressed by the flow of exhaust. Therefore, the density of ash accumulated on the filter 32, that is, the accumulation density Ad can be calculated based on the maximum flow rate of the exhaust gas. Therefore, in step S200 following step S100, a deposition density Ad, which is a density of ash deposited on the filter 32, is calculated based on the maximum flow rate EXmax of the exhaust during engine operation (S200). In step S200, as shown in FIG. 4, the deposition density Ad is calculated such that the larger the maximum exhaust gas flow rate EXmax is, the larger the deposition density Ad is. The maximum exhaust flow rate EXmax is the maximum value of the exhaust flow rate during engine operation, and is updated as needed during engine operation. Further, the exhaust flow rate is estimated based on the intake air amount, the engine load, the engine speed, and the like.

  Next, the ash wall surface deposition ratio R is calculated based on the exhaust flow fluctuation amount EXh and the fluctuation frequency N (S300). The fluctuation amount EXh is an absolute value of the difference between the maximum value and the minimum value of the exhaust flow rate. The number of fluctuations N is the number of fluctuations in the exhaust flow rate. More specifically, the number of fluctuations N is the number of times the fluctuation amount EXh exceeds a predetermined value. The fluctuation amount EXh and the fluctuation frequency N are measured during the regeneration process of the filter 32 and stored in the storage device of the control device 25, and are read from the storage device of the control device 25 when this process is executed. The ash wall deposition ratio R is the amount of ash deposited on the radial wall surface of the filter 32 with respect to the total ash deposition amount (the ash deposition amount Asm) in the filter 32. It is a ratio. The wall surface deposition ratio R is set to a value between “0” and “1”. Incidentally, when all of the ash is deposited on the bottom surface of the filter 32, the wall surface deposition ratio R is set to “0”. When all of the ash is deposited on the radial wall surface of the filter 32, the wall surface deposition ratio R is set to “1”.

The process of step S300 is performed for the following reason.
First, ash accumulates on the filter 32 on the radial wall surface of the filter 32 and the bottom surface of the filter 32 on the exhaust downstream side. Here, since more PM is collected by the radial wall surface of the filter 32 than the bottom surface of the filter 32 on the exhaust downstream side, the PM oxidation rate PMcs on the radial wall surface of the filter 32 is accurately calculated. It is desirable.

In step S300, first, the ratio of the ash wall surface deposition amount to the ash deposition amount Asm is obtained.
Here, the ash deposited on the radial wall surface of the filter 32 is separated from the wall surface due to fluctuations in the exhaust flow rate and collected again on the bottom surface of the filter 32 on the exhaust downstream side. Therefore, as the exhaust gas flow rate fluctuation amount EXh increases, the amount of ash deposited on the radial wall surface of the filter 32 increases, and the amount of ash deposited on the wall surface decreases. Therefore, as shown in FIG. 5, the wall surface deposition ratio R is set to a smaller value as the fluctuation amount EXh of the exhaust flow rate is larger.

  Further, as described above, the ash deposited on the radial wall surface of the filter 32 is separated from the wall surface due to fluctuations in the exhaust flow rate and collected again on the bottom surface of the filter 32 on the exhaust downstream side. Therefore, as the number of fluctuations N of the exhaust flow rate increases, the amount of ash deposited on the radial wall surface of the filter 32 increases, and the amount of ash deposited on the wall surface decreases. Therefore, as shown in FIG. 5, the wall surface deposition ratio R is set to a smaller value as the exhaust gas flow rate variation number N increases.

As described above, the wall surface deposition ratio R is variably set based on the exhaust gas flow rate fluctuation amount EXh and the fluctuation frequency N.
Next, the ash is the thickness of the ash deposited on the radial wall surface of the filter 32 based on the ash deposition amount Asm, the wall surface deposition ratio R, the deposition density Ad, and the PM collection area S in the radial direction of the filter 32. The thickness At is calculated (S400). Here, since the relational expression [Ash density = Amount of ash accumulated / (Ash collection area × Ash thickness)] is established, the ash thickness is based on the following expression (2) obtained by modifying this relational expression. At is calculated.

At = (Asm × R) / (Ad × S) (2)
At: Ash thickness (mm)
Asm: Ash accumulation amount (g)
R: Wall deposition rate (Asm × R): Total amount of ash deposited on the radial wall surface of the filter 32 (g)
Ad: Ash accumulation density (g / mm ^ 3)
S: PM collection area in the radial direction of the filter 32 (mm ^ 2)

Next, the PM oxidation rate PMcs is calculated based on the ash thickness At and the bed temperature T of the filter 32 (S500). The bed temperature T is estimated from the exhaust temperature TE indicating the exhaust temperature flowing into the filter 32. In step S500, the oxidation rate map shown in FIG. 6 is referred to. The PM oxidation rate PMcs based on the oxidation rate map is calculated so that the PM oxidation rate PMcs increases as the bed temperature T increases. Further, the PM oxidation rate PMcs is variably set so as to decrease as the ash thickness At increases until the value of the ash thickness At reaches a predetermined value. When the value of the ash thickness At exceeds the predetermined value, the PM oxidation rate PMcs is fixed to a constant value regardless of the value of the ash thickness At.

  When the PM oxidation rate PMcs is calculated in this way, the present process is temporarily terminated. Then, the PM deposition amount PMsm is estimated by the above equation (1) using the PM oxidation rate PMcs calculated in this process.

Next, the operation of this embodiment will be described.
As described above, in the present embodiment, the PM oxidation rate PMcs is set based on the ash deposition thickness (ash thickness At) that affects the PM oxidation rate based on the inventor's knowledge. . Therefore, the PM oxidation rate PMcs can be calculated with high accuracy. When the accuracy of the PM oxidation rate PMcs is thus improved, the estimation accuracy of the PM deposition amount PMsm according to the above equation (1) is also improved. Since the estimation accuracy of the PM deposition amount PMsm is improved, the end timing of the regeneration process is optimized, and therefore it is possible to suppress the occurrence of unburned PM when the regeneration process is completed.

  Further, the ash deposited on the filter 32 is compressed by the exhaust flow. Therefore, the density of ash deposited on the filter 32, that is, the ash deposition density can be calculated based on the maximum flow rate of the exhaust gas. Therefore, the ash deposition density Ad is calculated based on the maximum exhaust gas flow rate EXmax. Then, the ash accumulation amount is divided by a value obtained by multiplying the accumulation density Ad by the collection area of the filter 32, so that the thickness of the ash accumulated on the filter 32 can be calculated. Become. At this time, in particular, a wall surface accumulation amount that is an amount of ash accumulated on the radial wall surface of the filter 32 is calculated, and a collection area S in the radial direction of the filter 32 is set as the collection area. Yes. Therefore, it is possible to calculate the thickness of the ash deposited on the radial wall surface of the filter 32. Since the PM oxidation rate PMcs is set based on the thickness of the ash deposited on the radial wall surface of the filter 32, the PM oxidation rate PMcs on the radial wall surface of the filter 32 can be accurately calculated. It becomes like this.

  Further, the ash deposited on the radial wall surface of the filter 32 is separated from the wall surface due to fluctuations in the exhaust flow rate, and is collected again on the bottom surface of the filter 32 on the exhaust downstream side. Therefore, the larger the fluctuation amount of the exhaust flow rate, the larger the amount of ash deposited on the radial wall surface of the filter 32, and the smaller the amount of ash deposited on the wall surface. Therefore, the wall surface deposition ratio R is calculated to be smaller as the fluctuation amount of the exhaust flow rate is larger. Therefore, it is possible to appropriately estimate the ash wall surface deposition amount.

  Further, as the number of fluctuations of the exhaust flow rate increases, the amount of ash deposited on the radial wall surface of the filter 32 increases, and the amount of ash deposited on the wall surface decreases. Therefore, the number of times the fluctuation amount EXh of the exhaust flow rate exceeds a predetermined value is measured, and the wall surface deposition ratio R is calculated to decrease as the measured number increases. Therefore, this also makes it possible to appropriately estimate the amount of ash wall deposition.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The PM oxidation rate PMcs in the filter 32 is set based on the thickness of the ash deposited on the filter 32. More specifically, the PM oxidation rate PMcs is variably set so as to decrease as the ash deposited on the filter 32 increases in thickness. Therefore, the PM oxidation rate PMcs in the filter 32 can be calculated with higher accuracy.

  (2) Since the PM oxidation rate PMcs is accurately calculated, the estimation accuracy of the PM deposition amount PMsm is improved. Therefore, it is possible to suppress the occurrence of unburned PM when the regeneration process is completed.

  (3) The ash accumulation amount Asm in the filter 32 is calculated, the ash accumulation density Ad is calculated based on the maximum exhaust gas flow rate EXmax, and the ash is multiplied by the collection area of the filter 32 and the accumulation density Ad. The accumulation amount Asm is divided. Therefore, it is possible to calculate the thickness of the ash deposited on the filter 32 (ash thickness At). In particular, the ash accumulation amount Asm is multiplied by the wall surface deposition ratio R to calculate the wall surface accumulation amount that is the amount of ash accumulated on the radial wall surface of the filter 32, and the filter 32 collecting area is the radial direction of the filter 32. The collection area S at is set. Therefore, it is possible to calculate the ash thickness At on the wall surface of the filter 32 where more PM is collected, so that the PM oxidation rate PMcs on the radial wall surface of the filter 32 can be accurately calculated. become.

  (4) The ash wall surface deposition ratio R is set to a smaller value as the exhaust gas flow rate fluctuation amount EXh is larger. Thus, the ash wall surface accumulation amount is calculated so as to decrease as the exhaust gas flow rate fluctuation amount EXh increases. Therefore, it becomes possible to appropriately estimate the ash wall surface deposition amount.

  (5) The fluctuation number N, which is the number of times the fluctuation amount EXh of the exhaust flow rate exceeds a predetermined value, is measured, and the ash wall deposition ratio R is set to a smaller value as the measured fluctuation number N increases. Like to do. As a result, the ash wall surface deposition amount is calculated so as to decrease as the exhaust flow rate variation number N increases. Therefore, this also makes it possible to appropriately estimate the amount of ash wall deposition.

In addition, the said embodiment can also be changed and implemented as follows.
The ash is derived from the lubricating oil of the engine 1, and the ash accumulation amount Asm tends to increase as the consumption amount of the lubricating oil increases. Therefore, the ash accumulation amount Asm may be calculated based on the consumption amount of the lubricating oil. The consumption amount of the lubricating oil can be grasped by detecting the lubricating oil amount in the oil pan of the engine 1. Further, as the total travel distance of the vehicle increases, the amount of lubricating oil consumed so far increases, so it is possible to estimate the consumption amount of lubricant based on the total travel distance of the vehicle. Also, the longer the total operating time of the internal combustion engine, the greater the amount of lubricating oil consumed so far, so the total operating time of the internal combustion engine or the integrated value of the fuel injection amount that is correlated with the total operating time It is also possible to estimate the consumption of the lubricating oil based on the above. When the ash accumulation amount Asm is calculated based on the consumption amount of the lubricating oil as in this modification, the ash accumulation amount Asm is calculated so that the ash accumulation amount Asm increases as the consumption amount increases. Thus, the ash deposition amount Asm can be calculated appropriately.

  Although the wall surface deposition ratio R is set based on the fluctuation amount EXh and the number of fluctuations N of the exhaust flow rate, the wall surface deposition ratio R is set based only on the fluctuation amount EXh of the exhaust flow rate or only the fluctuation number N. You may do it.

  Although the ash thickness At on the radial wall surface of the filter 32 is obtained, the ash thickness At on the bottom surface of the filter 32 on the exhaust downstream side is obtained, and the PM oxidation rate PMcs on the bottom surface is calculated first. It may be determined based on the map shown in FIG. In this modified example, the area of the bottom surface on the exhaust downstream side of the filter 32 is set as the collection area S in the above formula (2), and a part of the formula (2) is modified based on the following formula (3). The ash thickness At at the bottom can be calculated.

At = (Asm × (1-R)) / (Ad × S) (3)
At: Ash thickness at the bottom (mm)
Asm: Ash accumulation amount (g)
R: Wall deposition rate (Asm × (1-R): Total amount of ash deposited on the bottom surface of the filter 32 (g)
Ad: Ash accumulation density (g / mm ^ 3)
S: PM collection area on the bottom surface of the filter 32 (mm ^ 2)

According to this modification, the estimation accuracy of the PM oxidation rate PMcs on the bottom surface of the filter 32 can be increased.

  In the above-described embodiment, the ash thickness At in the radial wall surface of the filter 32 is obtained. However, the average value of the ash thickness At in the filter 32 is obtained, and this average value is shown in FIG. The average PM oxidation rate PMcs in the filter 32 may be obtained based on a map or the like. In this modification, the total collection area in the filter 32 is set as the collection area S in the above formula (2), and the filter 32 is based on the following formula (4) obtained by modifying a part of the formula (2). The average value of the ash thickness At can be calculated.

At = Asm / (Ad × S) (4)
At: Average value of ash thickness (mm)
Asm: Ash accumulation amount (g)
Ad: Ash accumulation density (g / mm ^ 3)
S: Total collection area of PM in the filter 32 (mm ^ 2)

The fuel for raising the temperature of the filter 32 is supplied from the fuel addition valve 5. In addition, the temperature of the filter 32 may be increased by executing post-injection (fuel injection performed again at a timing delayed from the execution timing of the main injection) by the fuel injection valves 4a to 4d. Further, the fuel supply by the fuel addition valve 5 and the fuel supply by post injection may be used in combination.

-Although the said additive was the fuel of the engine 1, what kind of thing may be sufficient as long as the effect | action similar to this is acquired.
The number of catalysts and filters disposed in the converter 30 can be arbitrarily set. For example, the present invention can be similarly applied to an exhaust purification apparatus that includes only the filter 32 and raises the temperature of the filter 32 by oxidizing fuel on the filter 32.

  Although the engine 1 is an in-line four-cylinder internal combustion engine, the present invention can be similarly applied to an exhaust gas purification apparatus for an internal combustion engine having other numbers of cylinders or cylinder arrangements.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Intake passage, 4a-4d ... Fuel injection valve, 5 ... Fuel addition valve, 6a-6d ... Exhaust port, 7 ... Intake manifold, 8 ... Exhaust manifold, 9 ... Common rail, DESCRIPTION OF SYMBOLS 10 ... Supply pump, 11 ... Turbocharger, 13 ... EGR passage, 14 ... EGR cooler, 15 ... EGR valve, 16 ... Intake throttle valve, 17 ... Actuator, 18 ... Intercooler, 19 ... Air flow meter, 20 ... Throttle valve opening Degree sensor, 23 ... Engine speed sensor, 24 ... Accelerator sensor, 25 ... Control device, 26 ... Exhaust passage, 27 ... Fuel supply pipe, 30 ... Converter, 31 ... Oxidation catalyst, 32 ... Filter, 33 ... Exhaust temperature sensor, 34: Differential pressure sensor.

Claims (7)

An exhaust purification device for an internal combustion engine that includes a filter that collects particulate matter in exhaust gas and that performs regeneration processing of the filter,
An exhaust gas purification apparatus for an internal combustion engine, wherein an oxidation rate of the particulate matter in the filter is set based on a thickness of ash deposited on the filter. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the oxidation rate is variably set so that the ash deposited on the filter is thicker. The ash accumulation amount in the filter is calculated, the ash accumulation density is calculated based on the maximum flow rate of the exhaust gas, and the accumulation amount is divided by a value obtained by multiplying the collection area of the filter and the accumulation density. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the thickness of the ash deposited on the filter is calculated. 4. The wall surface accumulation amount that is the amount of ash accumulated on the radial wall surface of the filter is calculated as the accumulation amount, and the collection area in the radial direction of the filter is set as the collection area. An exhaust gas purification apparatus for an internal combustion engine as described. The exhaust purification device for an internal combustion engine according to claim 4, wherein the wall surface accumulation amount is calculated so as to decrease as the fluctuation amount of the exhaust flow rate increases. The exhaust gas purification apparatus for an internal combustion engine according to claim 4, wherein the number of times the fluctuation amount of the exhaust flow rate exceeds a predetermined value is measured, and the wall surface accumulation amount is calculated to decrease as the measured number increases. The ratio of the accumulation amount on the wall surface to the total accumulation amount of ash in the filter is calculated, and the wall surface deposition amount is calculated based on the calculated ratio. An exhaust gas purification apparatus for an internal combustion engine as described.

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