JP2004301006A - Engine exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an engine exhaust emission control device capable of highly accurately estimating the amount of exhaust particulate captured in a particulate filter. <P>SOLUTION: In an engine equipped with an oxidation catalyst function and the particulate filter for capturing exhaust particulate, a control unit is structured so as to judge if a state of the particulate filter is in a stage where the exhaust particulates are burned and removed or in a storage where exhaust particulates are captured and stored, and so that the amount of captured particulates may be estimated in a different estimation method corresponding to a judged stage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to estimating the amount of particulate matter trapped by a particulate filter that traps particulate matter contained in exhaust gas of an engine, and belongs to the technical field of an exhaust gas purification device for an engine.
[0002]
[Prior art]
Generally, particulates called particulates are contained in the exhaust gas of a diesel engine, and a particulate filter for collecting and removing the particulates may be provided in the exhaust passage of the engine.
[0003]
In such a filter, the amount of exhaust particulates collected and accumulated in the filter increases with an increase in the operating time of the engine, thereby causing the filter to gradually become clogged. When it is established, the removal of the exhaust particulates in the filter, that is, the regeneration of the filter is performed. The determination as to whether or not the predetermined condition is satisfied is made by estimating the amount of exhaust particulates trapped in the filter based on, for example, the differential pressure between the pressure on the upstream side and the pressure on the downstream side of the filter. This is performed by determining whether the amount has become equal to or greater than a predetermined value.
[0004]
By the way, actually, even if the same differential pressure is detected, the amount of exhaust particulate actually collected may be different. In other words, simply detecting only the pressure difference between the upstream pressure and the downstream pressure of the filter cannot accurately estimate the amount of the trapped exhaust particulates. As a technique to cope with this, Patent Document 1 discloses that the difference in the differential pressure across the filter is caused by the operation history (for example, the ratio of the acceleration / deceleration operation state, the ratio of the operation state where the load is equal to or more than a predetermined value, etc.). The invention that finds out and changes the regeneration time of the filter according to the operation history is disclosed.
[0005]
[Patent Document 1]
JP-A-6-50130
[0006]
[Problems to be solved by the invention]
By the way, the present inventors examined the problem that the trapping amount and the differential pressure were not in a one-to-one relationship, and that the trapping amount could not be accurately detected from the differential pressure alone. The reason why does not match is considered as follows.
[0007]
That is, first, as exemplified in FIG. 7, the particulate filter 27 has a plurality of partitions 27a... 27a on which an oxidation catalyst is supported. 27a, the exhaust fine particles are collected by the partition walls 27a, 27a when they are discharged from the outlet 27c.
[0008]
Next, a portion indicated by reference numeral a in FIG. 7 is enlarged and shown in FIG. The partition walls 27a ... 27a are formed by innumerable fine pores 27d ... 27d penetrating between the front and back surfaces, and the pores 27d ... 27d have fine irregularities on the inner surface. Therefore, as shown in FIG. 8B, at the stage where the exhaust particulates X are collected by the partition walls 27a to 27a, initially, at the initial stage, the exhaust particulates X are mainly collected in the pores 27d to 27d, As a result, the pores 27d... 27d are clogged, and the flow resistance of the exhaust gas increases. After the exhaust particulate X collecting capability of the pores 27d ... 27d reaches a certain limit, the exhaust particulate X is mainly collected on the surface 27e of the partition walls 27a ... 27a as shown in FIG. 8 (c). Become like
[0009]
On the other hand, in the stage where the exhaust particulate X is burned and removed, first, as shown in FIG. 8D, the exhaust particulate X is collected in pores 27d... 27d having a large contact area between the exhaust particulate X and the oxidation catalyst. The exhaust particles X thus obtained are quickly burned and removed, and the exhaust particles X trapped on the partition surface 27e having a small contact area between the exhaust particles X and the oxidation catalyst are gradually removed by burning. The exhaust fine particles X collected so as to be stacked on 27e are expanded to the upper layer side. It is considered that such a phenomenon occurs because the exhaust fine particles X trapped in the pores 27d... 27d having a large contact area with the oxidation catalyst can more easily utilize the oxidation reaction.
[0010]
FIG. 9 shows the relationship between the differential pressure and the amount collected during this time. In the collection and accumulation stage, in the initial stage (R1) where the collection amount is small, a large pressure loss occurs due to clogging of the pores 27d... 27d, and the differential pressure increases sharply with an increase in the collection amount. In the middle and late period (R2), since the pressure is collected mainly on the partition wall surface 27e, the increase in the pressure loss becomes gentle, and the differential pressure gradually rises with the increase in the amount of collected air.
[0011]
On the other hand, in the combustion stage, in the initial stage (R3) in which relatively more exhaust particulates X remain than in the initial stage of collection, the flow resistance of the exhaust gas in the pores 27d. The pressure difference is greatly reduced, and the differential pressure is sharply reduced with the decrease in the trapping amount. However, in the middle and late period (R4), the fuel is burned mainly around the partition wall surface 27e. Decreases slowly with decreasing collection volume.
[0012]
That is, even if the same pressure difference is detected in the collection and accumulation stage of the exhaust particulate X and the combustion removal stage, the amount of the collected exhaust particulate is different. Therefore, in the technique described in Patent Literature 1 which does not take this into consideration, the amount of trapped exhaust fine particles cannot be accurately estimated.
[0013]
Therefore, an object of the present invention is to provide an exhaust gas purifying apparatus for an engine that can accurately estimate the amount of exhaust particulates collected by a particulate filter.
[0014]
[Means for Solving the Problems]
That is, according to the first aspect of the present invention, there is provided a collecting means which has an oxidation catalyst function and is provided in an exhaust passage of an engine for collecting exhaust particulates, and an amount of the exhaust particulates collected by the collecting means. An exhaust gas purifying apparatus for an engine, comprising: a trapping amount estimating means for estimating, wherein a state of the trapping means is either a stage of burning and removing the collected exhaust particulates or a stage of collecting and accumulating. There is provided a determining means for determining whether or not the collected amount is present, and the collected amount estimating means estimates the collected amount by a different estimating method according to the stage determined by the determining means.
[0015]
According to the present invention, depending on whether the state of the collecting means is at the stage of burning and removing the collected exhaust particulates or at the stage of collecting and accumulating, the collecting means is differently estimated. Since the amount of the collected exhaust particulates (collected amount) is estimated, the collected amount can be accurately estimated.
[0016]
According to a second aspect of the present invention, in the first aspect of the present invention, a parameter value detecting unit for detecting a parameter value related to the temperature of the collecting unit is provided, and the determining unit is configured to detect the parameter value. When the parameter value detected by the means is equal to or more than a predetermined value, it is determined that the state of the trapping means is in the stage of burning and removing the exhaust particulates.
[0017]
According to the present invention, whether the state of the collecting means is in the stage of burning and removing the exhaust particulates or in the state of collecting and collecting is determined based on the temperature of the collecting means scientifically, experimentally, and relatively simply. By such means, it is possible to determine with high accuracy.
[0018]
According to a third aspect of the present invention, in the second aspect of the present invention, an exhaust pressure detecting means for detecting an exhaust pressure is provided on at least an upstream side of the upstream side and the downstream side of the collecting means. The trapping amount estimating means has a burning amount calculating means for calculating a burning amount of the exhaust particulate based on the parameter value detected by the parameter value detecting means, and the state of the collecting means is detected by the judging means. When it is determined that it is in the collecting and accumulating stage, the trapping amount is estimated based on the differential pressure between the upstream exhaust pressure and the downstream exhaust pressure detected by the exhaust pressure detecting means or the upstream exhaust pressure, When it is determined that the state of the collecting means is in the combustion removal stage, the combustion amount calculated by the combustion amount calculation means from the collection amount estimated in the collection and accumulation stage before the combustion removal stage. Collection by subtracting And estimating a.
[0019]
According to the present invention, when the state of the collecting means is in the stage of collecting and accumulating exhaust particulates, the amount of collection is estimated based on the differential pressure or the upstream side exhaust pressure. On the other hand, when the state of the trapping means is in the exhaust particulate combustion removal stage, the amount of exhaust particulate combustion is calculated based on the parameter value related to the temperature of the trapping means, and in the trapping accumulation stage. The collection amount is estimated by subtracting the combustion amount from the collection amount estimated in (1). That is, when the state of the collecting means is in the combustion removal stage and in the collecting and accumulating stage, the collected amount is estimated in accordance with the hysteresis of the relationship between the exhaust pressure (differential pressure) and the collected amount. Since the method is switched, the accuracy of the estimation is improved.
[0020]
Further, according to a fourth aspect of the present invention, in the third aspect, a trapping amount with respect to a differential pressure between the upstream exhaust pressure and the downstream exhaust pressure detected by the exhaust pressure detecting means or the upstream exhaust pressure. The trapping amount estimating means, when the judgment by the judging means shifts from the combustion removal stage to the trapping and accumulating stage, stores the differential pressure detected at the shift. Alternatively, the trapping amount difference between the trapping amount defined in the above-described basic characteristics at the upstream exhaust pressure and the trapping amount calculated at the transition in the combustion removal stage is stored as an offset amount, and the trapping and accumulation stage after the transition is performed. Is calculated from the trapping amount and the offset amount determined based on the basic characteristics.
[0021]
According to the present invention, in the collection and accumulation stage, the collection amount is estimated according to the basic characteristics of the collection amount determined with respect to the differential pressure or the upstream exhaust pressure. Then, at the time of the transition from the combustion removal stage to the collection and accumulation stage, the amount of trapping remaining on the filter at the time of the transition varies depending on the situation at the time of the transition. The estimation is continued in accordance with the basic characteristics, taking into account the residual trapping amount, while taking into account the deviation (offset amount) from the basic characteristics.
[0022]
That is, when it is determined by the determination means that the process has shifted from the combustion removal stage to the collection and accumulation stage, the trapping amount determined in the above-described basic characteristics at the differential pressure or upstream exhaust pressure detected at the time of the shift and the combustion removal stage The difference between the trapping amount and the trapping amount calculated at the time of the determination is stored as an offset amount, and the trapping amount after the shift, that is, the trapping amount at the time of being determined to be in the trapping and accumulation stage by the determination means. The collection amount is calculated based on the collection amount and the offset amount obtained from the basic characteristics. This makes it possible to more accurately and accurately estimate the trapping amount according to the state of the trapping means.
[0023]
According to a fifth aspect of the present invention, in the fourth aspect of the present invention, there is provided a regenerating means for regenerating the collecting means by burning and removing the exhaust fine particles collected by the collecting means, The regenerating means starts regenerating the collecting means when the trapping amount estimated by the trapping amount estimating means is equal to or more than a predetermined amount.
[0024]
According to this invention, when the trapping amount estimated by the trapping amount estimating unit becomes equal to or more than the predetermined amount, the regeneration of the trapping unit is started. In this case, according to the first to fourth aspects of the present invention, the regeneration is started based on the accurately and accurately estimated trapping amount, so that the regeneration can be efficiently performed. It is possible to suppress problems such as damage caused by clogging of the trapping means, which may occur in the case where the fuel is collected, and deterioration in fuel efficiency caused by post-injection, which may occur when the regeneration is performed more than necessary. The deterioration problem occurs, for example, when the regeneration of the filter is realized by post-injecting the fuel in addition to the main injection.)
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0026]
In this embodiment, the present invention is applied to a diesel engine 1 shown in FIG. The engine 1 is, for example, a four-cylinder engine, and is provided with four pistons 3 that move up and down in a cylinder bore of an engine body 2 (only one piston is shown in FIG. 1). The cylinder head of the engine body 2 is provided with an injector 4 for each cylinder, and the injector 4 directly injects fuel into the in-cylinder combustion chamber.
[0027]
A high-pressure fuel pump 5 and a common rail 6 are arranged on a fuel supply path between the injector 4 and a fuel tank (not shown). The pump 5 pumps the fuel from the fuel tank to the common rail 6, and the common rail 6 stores the pumped fuel. When the injector 4 opens, the fuel accumulated in the common rail 6 is injected at a high pressure from the injection port of the injector 4. At this time, the fuel injection amount can be controlled by controlling the valve opening time of the injector 4 and the fuel pressure in the common rail 6. Further, the fuel injection timing can be controlled by controlling the valve opening timing of the injector 4. Note that, in the figure, arrows on the fuel supply path indicate the flow of fuel.
[0028]
In the intake passage 10, in order from the upstream side, an air cleaner 11, an air flow meter 12, a supercharger compressor 13, an intercooler 14, a throttle valve 15 for adjusting the intake air amount, an intake temperature sensor 16, an intake pressure sensor 17, and an intake air A valve 18 is provided.
[0029]
In the exhaust passage 20, an exhaust valve 21, a turbocharger turbine 22, a first exhaust gas temperature sensor 23, an oxidation catalyst device 24, a second exhaust gas temperature sensor 25, an upstream pressure sensor 26, an exhaust gas And a third exhaust gas temperature sensor 29 for collecting the particulates of the exhaust gas. Further, an EGR passage 30 is provided between a relatively upstream portion of the exhaust passage 20 and a relatively downstream portion of the intake passage 10, and an EGR valve 31 for adjusting the exhaust gas recirculation amount is provided on the passage 30. .
[0030]
Here, the particulate filter 27 constitutes the collecting means in the claims, and the filter 27 is coated with an oxidation catalyst material containing a noble metal such as platinum.
[0031]
An engine speed sensor 41 is provided in the crankcase of the engine body 2 and a water temperature sensor 42 is provided in the cylinder block. The common rail 6 is provided with a common rail pressure sensor 43 for detecting the accumulated pressure of the fuel. An accelerator opening sensor 45 for detecting an amount of depression of an accelerator pedal 44 is provided in the vehicle compartment.
[0032]
The control unit 50 of the engine 1 detects the amount of intake air, the intake air temperature, the intake air pressure, the exhaust gas temperature flowing into the oxidation catalyst device 24, the exhaust gas temperature flowing into the particulate filter 27, and the air temperature detected by the sensors. A control signal is output to the injector 4 and the high-pressure fuel pump 5 based on the following exhaust temperature, upstream and downstream pressures across the filter 27, engine speed, cooling water temperature, fuel pressure in the common rail 6, engine load, and the like. I do.
[0033]
The control unit 50 calculates the fuel injection amount by correcting the basic fuel injection amount obtained from the engine speed by the engine speed sensor 41 and the engine load by the accelerator opening sensor 45 with the cooling water temperature, the intake air temperature, and the like.
[0034]
The control unit 50 functions as a trapping amount estimating means, for example, estimating the amount of the exhaust particulate collected by the particulate filter 27 based on the pressure difference between the upstream side and the downstream side of the filter 27. I do.
[0035]
The control unit 50 also functions as a regeneration unit, and when the estimated trapping amount becomes equal to or more than a predetermined amount, adds fuel during the expansion stroke after the main injection near the compression top dead center of the piston 3. Injection (post-injection) starts regeneration of the filter 27 (combustion and removal of exhaust particulates collected by the filter 27). In this post-injection, the unburned components generated by the post-injection are oxidized by the oxidation catalyst device 24 and the particulate filter 27 carrying the oxidation catalyst, thereby raising the temperature of the particulate filter 27 and causing the filter 27 to pass through. The purpose is to burn the collected exhaust fine particles and quickly regenerate the filter 27.
[0036]
By the way, the exhaust fine particles collected by the filter 27 tend to be burned and removed when the temperature of the filter 27 becomes approximately 400 ° C. or more, and tend to be collected and accumulated when the temperature is less than 400 ° C. In other words, the state of the particulate filter 27 is switched between a stage in which the exhaust particulates are burned and removed and a stage in which the particulates are collected and stored in accordance with the change in the operating state of the engine 1. As described above, the pressure difference is different between the combustion removal stage and the trapping accumulation stage even if the trapping amount is the same, and there is no one-to-one relationship between the trapping amount and the trapping pressure. There is a problem that the collection amount cannot be detected with high accuracy.
[0037]
Therefore, in the present embodiment, the control unit 50 determines whether the state of the filter 27 is in the stage of burning and removing the exhaust particulates or in the stage of collecting and collecting the particulates (determining means). The collection amount W is estimated by different estimation methods according to the determined stage.
[0038]
Hereinafter, the details of the trapping amount estimation control will be described with reference to the flowchart of FIG.
[0039]
First, at step S1, the control unit 50 determines the temperature T of the particulate filter 27 (detected by the second exhaust gas temperature sensor 25), the exhaust pressure on the upstream side of the filter 27 (the value detected by the upstream pressure sensor 26). ), The downstream exhaust pressure (detected by the downstream pressure sensor 28), and various state quantities detected by the above sensors such as the engine speed, etc., and in step S2, the upstream exhaust pressure is converted to the downstream exhaust pressure. Is subtracted to calculate the differential pressure between the upstream exhaust pressure and the downstream exhaust pressure.
[0040]
Next, in step S3, it is determined whether or not this is the first operation of the control flow. If YES, that is, if it is the first time, in step S4, after setting an offset amount D to be described later to 0, in step S5, A basic trapping amount I corresponding to the current differential pressure is calculated based on a basic characteristic map (see FIG. 3) that defines a trapping amount corresponding to the detected (calculated) differential pressure. Here, this basic characteristic corresponds to the stage of R1 and R2 in FIG. 9 described above, that is, the stage in which exhaust particulates are collected and accumulated in the particulate filter 27. When the differential pressure is equal to or lower than P1, The increase in the trapping amount with respect to the increase in the differential pressure is gradual (in other words, the increase in the differential pressure with the increase in the trapping amount is abrupt). The amount of trapping increases rapidly with increasing pressure (in other words, the increase in differential pressure with increasing amount of trapping is gradual).
[0041]
Next, in step S6, the current trapping amount W is calculated based on the basic trapping amount I and the offset amount D, and the process returns to step S1. Here, the current collection amount W is a value obtained by adding the basic collection amount I and the offset amount D.
[0042]
On the other hand, if the determination in step S3 is NO, the processing after step S7 is executed. That is, in step S7, it is determined whether or not the temperature T is equal to or higher than a predetermined value α (determination means). If YES, the process proceeds to step S8. It is determined whether or not the temperature T before the cycle is equal to or higher than the predetermined value α. Here, the predetermined value α is a stage where the state of the particulate filter 27 collects and accumulates exhaust particulates (a stage of the phases Q1, Q2, Q4 and Q5 illustrated in FIG. 4) and a state where the particulate filter 27 is burnt and removed. The control unit 50 determines that the temperature T is equal to or higher than the predetermined value α, and the state of the particulate filter 27 burns the exhaust particulates. It is determined that it is in the stage of removal, and if the temperature T is not equal to or higher than the predetermined value α, it is determined that it is in the stage of collecting and accumulating exhaust particulates. In steps S7 to S9, it is determined whether or not a change has occurred in the current state (stage) of the particulate filter 27 and the state (stage) of the particulate filter 27 one control cycle before. Here, the value of the temperature T may be, for example, about 400 ° C.
[0043]
When both the determinations in step S7 and step S9 are NO, that is, when the collection and accumulation stage is continuing, the above-described steps S5 and S6 are executed to calculate the current collection amount W, It returns to step S1. Here, this is the stage of the phases Q1 and Q2 shown in FIG.
[0044]
On the other hand, when the determination in step S7 is YES and the determination in step S8 is NO, that is, when shifting from the collection and accumulation stage to the combustion removal stage, in step S10, the collection and accumulation stage one control cycle before is performed. The calculated trapping amount W is stored as the trapping amount A at the time of transition, and in step S11, an integrated combustion amount F and an integrated combustion amount described later are reset to zero. Here, the transition time is a time point when the phase Q2 shown in FIG. 4 is shifted to the phase Q3, and the trapping amount at that time is A.
[0045]
Next, in step S12, the integrated combustion amount F (the integrated value of the amount of exhaust particulate removed and burned from the point in time when the combustion removal stage is shifted) is calculated based on the temperature T and the like, and stored. Here, the integrated combustion amount F is obtained by reading the combustion amount (burning speed) Fn of the exhaust particulates per unit time from the map shown in FIG. 5 based on the current temperature T, and calculating the value Fn one control cycle before. This is a value added to the integrated combustion amount F. In this map, the burning amount (burning speed) Fn of the exhaust particulate per unit time is set to a larger value as the current temperature T becomes higher. The unit time corresponds to one control cycle.
[0046]
Next, in step S13, based on the engine speed and the engine load (basically represented by the accelerator opening, but preferably substituted by the fuel injection amount), the integrated emission amount G (in the combustion removal stage). Calculate and store the amount of exhaust particulates discharged from the point of transition (discharged from the in-cylinder combustion chamber and flow into the particulate filter 27). Here, the integrated emission amount G is calculated by a map shown in FIG. 6 (in this map, the engine speed and the engine load are separately shown, but they are integrated into one in consideration of both of them. As in the case of the integrated combustion amount F, the exhaust particulate emission amount Gn per unit time is read out based on the current engine speed and load, and the value Gn is calculated one control cycle before. This is a value added to the integrated discharge amount G. Here, in this map, the discharge amount Gn of the exhaust particulate per unit time is set to a larger value as the engine load (fuel injection amount) is larger, and is set to a larger value when the engine speed is small and large. I have. Here, the unit time corresponds to one control cycle.
[0047]
Next, in step S14, the current trapped amount W is calculated by subtracting the accumulated combustion amount F from the transitional trapped amount A and adding the accumulated discharge amount G, and then returning to step S1.
[0048]
When the determinations in steps S7 and S8 are both YES, that is, when the combustion removal step is continued, the above-described steps S12 to S14 are executed to calculate the current trapping amount W, and the step S1 is performed. Return to Here, this is the stage of phase Q3 shown in FIG.
[0049]
On the other hand, when the determination in step S7 is NO and the determination in step S8 is YES, that is, when shifting from the combustion removal stage to the collection and accumulation stage, the calculation is performed in step S15 in the combustion removal stage one control cycle before. After storing the collected trapping amount W as the trapping amount H at the time of transition, in step S16, a basic trapping amount C corresponding to the differential pressure P at the transition is determined from the basic characteristic map shown in FIG. In S17, the basic collection amount C is subtracted from the above-mentioned transition collection amount H, and the difference between them, that is, the offset amount D is calculated. Next, the current collection amount W is calculated by executing the above-described steps S5 and S6, and the process returns to step S1. Here, the transition time is a time point when the phase Q3 shown in FIG. 4 is shifted to the phase Q4, and the trapping amount at that time is set to H. That is, in the phases Q4 and Q5, the phases Q1 and Q2 are translated in the X-axis direction (the direction of the collection amount axis in FIG. 4) by the offset amount. Although only the phase Q5 is shown in FIG. 4, the combustion removal step and the trapping / accumulating step are thereafter repeated as indicated by a chain line.
[0050]
Although not described in the flowchart of FIG. 2, the control unit 50 controls the fuel injection timing and the like as described above when the estimated trapping amount W becomes equal to or larger than a predetermined amount. The regeneration of the filter 27 is started and executed by additionally executing (after-injection) the fuel injection in addition to the main injection.
[0051]
As described above, the exhaust gas purification device of the engine 1 according to the present embodiment has a function of an oxidation catalyst and is provided in the exhaust passage 20 of the engine 1 to collect the particulates of the exhaust gas. ) And a trapping amount estimating means (control unit 50) for estimating the amount of exhaust particulates trapped by the filter 27, wherein the state of the filter 27 is trapped. A determination unit (control unit 50) for determining whether the exhaust gas is in a stage of burning and removing the collected exhaust particulates or in a stage of collecting and collecting the exhaust particulates. The collection amount W is estimated by a different estimation method according to the stage determined by the means (control unit 50).
[0052]
According to this, the particulate filter 27 is collected by the filter 27 by a different estimation method depending on whether it is in the stage of burning and removing the exhaust particulate or the stage of collecting and storing the particulate. Since the amount (collection amount) W of the exhaust fine particles is estimated, the collection amount W can be accurately estimated.
[0053]
The exhaust gas purification device of the engine 1 further includes a second exhaust gas temperature sensor 25 (parameter value detecting means) for detecting the temperature T (parameter value related to the temperature) of the particulate filter 27, and a determining means (control unit 50). ) Determines that the state of the filter 27 is in the stage of burning and removing the exhaust particulates when the temperature T detected by the second exhaust gas temperature sensor 25 is equal to or higher than the predetermined value α.
[0054]
According to this, whether the state of the particulate filter 27 is in the stage of burning and removing the exhaust particulates or in the stage of collecting and accumulating is determined based on the temperature T of the particulate filter 27 based on a scientific The determination can be made experimentally and accurately with relatively simple means.
[0055]
The exhaust gas purification device of the engine 1 includes an upstream pressure sensor 26 for detecting exhaust pressure on the upstream side and a downstream side of the particulate filter 27, and a downstream pressure sensor 28 (exhaust pressure detecting means). The amount estimating means (control unit 50) includes a combustion amount calculating means (control unit 50) for calculating the amount of combustion F of exhaust particulates based on the temperature T detected by the second exhaust gas temperature sensor 25, and determines If the means (control unit 50) determines that the state of the filter 27 is in the trapping / accumulating stage, the upstream exhaust pressure and the downstream exhaust pressure detected by the upstream pressure sensor 26 and the downstream pressure sensor 28 are determined. The trapping amount W is estimated on the basis of the pressure difference or the upstream exhaust pressure, and the state of the filter 27 is set to the combustion removal stage by the determination means (control unit 50). Is determined, the combustion amount F calculated by the combustion amount calculation means (control unit 50) is subtracted from the collection amount A estimated at the collection and accumulation stage before the combustion removal stage. , The trapping amount W is estimated.
[0056]
According to this, when the state of the particulate filter 27 is in the stage of collecting and accumulating exhaust particulates, the trapping amount is estimated based on the differential pressure or the upstream side exhaust pressure. On the other hand, when the state of the filter 27 is in the exhaust particulate combustion removal stage, the combustion amount F of the exhaust particulate is calculated based on the temperature T of the filter 27, and the trapping estimated in the collection and accumulation stage is performed. The trapped amount W is estimated by subtracting the combustion amount F from the amount A. That is, the hysteresis of the relationship between the exhaust pressure (differential pressure) and the trapping amount differs between when the state of the filter 27 is in the combustion removal stage and in the trapping / accumulating stage (the path between R1 and R2 in FIG. Since the method of estimating the trapping amount is switched according to the difference between the routes of R3 and R4), the accuracy of the estimation is improved.
[0057]
Further, in the exhaust gas purifying apparatus of the present engine 1, the amount of trapping for the differential pressure between the upstream exhaust pressure and the downstream exhaust pressure detected by the upstream pressure sensor 26 and the downstream pressure sensor 28 or the upstream exhaust pressure is determined. Storage means (control unit 50) for storing the obtained basic characteristics, and the collection amount estimating means (control unit 50) determines whether the determination by the determination means (control unit 50) is from the combustion removal stage to the collection and accumulation stage. When the shift is made, the trapping amount C defined in the above-described basic characteristics at the differential pressure P or the upstream side exhaust pressure detected at the shift and the trapping amount calculated when the determination unit determines that the combustion removal step is performed. The difference between the amount (collection amount in the combustion removal stage calculated at the time of the shift) H and the collection amount is stored as an offset amount D, and is stored in the determination means (control unit 50). The trapping amount W (the trapping amount in the trapping and accumulating stage after the shift) W determined to be in the trapping and accumulating stage is calculated from the trapping amount C and the offset amount D determined based on the basic characteristics. calculate.
[0058]
According to this, in the collection and accumulation stages Q1, Q2, Q4, and Q5, the collection amount W is estimated only according to the basic characteristics of the collection amount determined with respect to the differential pressure or the upstream exhaust pressure. At the time of transition from the combustion removal stage to the collection and accumulation stage, the amount of trapped H remaining on the filter 27 at the time of the transition varies depending on the situation at the time of the transition. In consideration of the deviation (offset amount) D between the amount H and the trapping amount C determined from the basic characteristics, the estimation is continued according to the basic characteristics, starting from the remaining trapping amount H (Q4, Q5). . Thus, the trapping amount W can be more accurately and accurately estimated according to the state of the particulate filter 27.
[0059]
The exhaust gas purifying apparatus of the engine 1 further includes a regeneration unit (control unit 50) that burns and removes the exhaust particulates collected by the particulate filter 27 to regenerate the collection unit. ) Starts the regeneration of the filter 27 when the trapping amount estimated by the trapping amount estimating means (control unit 50) becomes equal to or more than a predetermined amount.
[0060]
According to this, when the trapping amount estimated by the trapping amount estimating means (control unit 50) becomes equal to or more than the predetermined amount, the regeneration of the particulate filter 27 is started. In this case, since the regeneration is started based on the trapping amount accurately and accurately estimated as described above, the regeneration can be performed efficiently, for example, which may occur when the reproduction start is delayed. In addition, it is possible to suppress problems such as breakage due to clogging of the particulate filter 27 and deterioration of fuel efficiency due to post-injection, which may occur when regeneration is continued more than necessary.
[0061]
In the present embodiment, the basic characteristic of the trapping amount with respect to the differential pressure is such that the gradient changes when the differential pressure is bent at a predetermined value P1, but this is merely an example. What is necessary is just to change according to the structure of the particulate filter actually used, etc. For example, what changes a curve smoothly as a differential pressure rises can be considered.
[0062]
Further, the trapping amount W trapped in the particulate filter 27 is calculated based on the differential pressure detected by the upstream pressure sensor 26 and the downstream pressure sensor 28. The calculation may be performed based on a basic characteristic map corresponding only to the detected pressure.
[0063]
【The invention's effect】
As described above, according to the present invention, the trapping amount is estimated by different estimation methods depending on whether the particulate filter is in the stage of burning and removing the exhaust particulates or in the stage of collecting and accumulating the particulates. By doing so, it is possible to accurately estimate the amount of exhaust particulates collected by the particulate filter.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram of an engine according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating an example of a preferable specific operation of trapping amount estimation control.
FIG. 3 is a map showing basic characteristics of a collected amount with respect to a differential pressure in a collecting and accumulating stage.
FIG. 4 is an example of a locus of a relationship between a differential pressure and a trapping amount when a trapping amount is estimated by the present control.
FIG. 5 is a map showing temperature characteristics of a combustion amount per unit time used when calculating an integrated combustion amount.
FIG. 6 is a map showing a fuel injection amount and an engine speed characteristic of an exhaust particulate emission per unit time used when calculating an integrated amount of exhaust particulates discharged from an engine.
FIG. 7 is a longitudinal sectional view of the particulate filter.
8 is an enlarged view of a portion indicated by reference numeral a in FIG. 7, and is an explanatory view of a process of collecting and accumulating exhaust particulates and removing them by combustion.
FIG. 9 is an explanatory diagram of a trajectory of a trapping amount with respect to a differential pressure in a process of collecting and accumulating and burning and removing exhaust particulates.
[Explanation of symbols]
1 engine
20 Exhaust passage
25 Second exhaust gas temperature sensor (parameter value detecting means)
26, 28 pressure sensor (exhaust pressure detecting means)
27 Particulate filter (collection means)
50 control unit (collection amount estimation means, determination means, combustion amount calculation means, storage means, regeneration means)

Claims (5)

A collecting means is provided in the exhaust passage of the engine and has an oxidation catalyst function for collecting exhaust particulates, and a trapping amount estimating means for estimating the amount of exhaust particulates collected by the collecting means. An exhaust gas purifying apparatus for an engine, comprising: a determination unit configured to determine whether a state of the collection unit is in a stage of burning and removing the collected exhaust particulates or in a stage of collecting and collecting the collected exhaust particulates. An exhaust gas purifying apparatus for an engine, wherein the trapping amount estimating means estimates the trapping amount by a different estimating method according to the stage determined by the determining means. Parameter value detection means for detecting a parameter value related to the temperature of the collection means; and a determination means for detecting a state of the collection means when the parameter value detected by the parameter value detection means is equal to or greater than a predetermined value. The exhaust gas purifying apparatus for an engine according to claim 1, wherein it is determined that the engine is in a stage of burning and removing the exhaust particulates. Exhaust pressure detecting means for detecting exhaust pressure is provided at least on the upstream side of the upstream side and the downstream side of the collecting means, and the trapping amount estimating means is provided with a parameter value detected by the parameter value detecting means. A combustion amount calculation unit that calculates a combustion amount of the exhaust particulate based on the exhaust gas pressure, and when the state of the collection unit is determined to be in the collection and accumulation stage by the determination unit, the state is detected by the exhaust pressure detection unit. The trapping amount is estimated based on the differential pressure between the upstream side exhaust pressure and the downstream side exhaust pressure or the upstream side exhaust pressure, and when the state of the collecting unit is determined to be in the combustion removal stage, 3. The trapping amount is estimated by subtracting the burning amount calculated by the burning amount calculating means from the trapping amount estimated in the trapping and accumulating stage before the combustion removing stage. Purification of engine exhaust as described in Location. There is provided storage means for storing a difference between the upstream exhaust pressure and the downstream exhaust pressure detected by the exhaust pressure detecting means or a basic characteristic in which a trapping amount for the upstream exhaust pressure is determined. The estimating means, when the judgment by the judging means shifts from the combustion removal stage to the trapping and accumulation stage, the trapping amount determined in the above-described basic characteristics at the differential pressure or the upstream exhaust pressure detected at the shift, and at the time of the shift. The difference between the calculated trapping amount in the combustion removal stage and the trapping amount is stored as an offset amount, and the trapping amount in the trapping and accumulation stage after the transition is determined as the trapping amount and the offset amount determined based on the basic characteristics. The exhaust gas purifying apparatus for an engine according to claim 3, wherein the value is calculated from: A regenerating means is provided for regenerating the collecting means by burning and removing the exhaust fine particles collected by the collecting means, and the regenerating means has a trapping amount estimated by the trapping amount estimating means of a predetermined amount or more. The exhaust gas purifying apparatus for an engine according to claim 4, wherein the regeneration of the trapping means is started when the following condition is satisfied.

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