JP4375988B2 - Engine exhaust purification system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the estimation of the amount of exhaust particulates collected by a particulate filter that collects exhaust particulates contained in engine exhaust gas, and belongs to the technical field of engine exhaust purification devices.
[0002]
[Prior art]
In general, exhaust gas of a diesel engine contains particulates called particulates, and a particulate filter that collects and removes the particulates may be provided in the exhaust passage of the engine.
[0003]
In such a filter, as the engine operating time increases, the amount of exhaust particulates collected and accumulated in the filter increases. As a result, the filter gradually becomes clogged. When established, the exhaust particulates in the filter are removed, that is, the filter is regenerated. The determination as to whether or not the predetermined condition is satisfied is performed by, for example, estimating the amount of exhaust particulate collected in the filter based on the differential pressure between the pressure on the upstream side and the pressure on the downstream side of the filter. This is done by determining whether or not the amount is equal to or greater than a predetermined value.
[0004]
Actually, the amount of exhaust particulates actually collected may be different even if the same differential pressure is detected. In other words, the amount of collected exhaust particulates cannot be accurately estimated only by detecting only the differential pressure between the upstream pressure and the downstream pressure of the filter. As a technique for coping with this, Patent Document 1 states that the difference in the differential pressure across the filter is caused by the operation history (for example, the proportion of the acceleration / deceleration operation state, the proportion of the operation state where the load is a predetermined value or more). An invention that finds 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 have examined the problem that the collected amount and the differential pressure are not in a one-to-one relationship and the collected amount cannot be detected accurately only from the differential pressure. The reason why does not match is considered as follows.
[0007]
That is, first, as illustrated in FIG. 7, the particulate filter 27 has a plurality of partition walls 27a... 27a on which an oxidation catalyst is supported, and the exhaust gas sucked from the suction port 27b is separated from the partition wall as indicated by an arrow. When exhausting 27a ... 27a and discharging from the outlet 27c, exhaust particulates are collected in the partition walls 27a ... 27a.
[0008]
Next, the part indicated by the symbol a in FIG. 7 is enlarged and shown in FIG. The partition walls 27a... 27a have innumerable fine pores 27d... 27d passing between the front and back surfaces, and the pores 27d. Therefore, as shown in FIG. 8 (b), at the stage where the exhaust particulate X is collected in the partition walls 27a ... 27a, first, the exhaust particulate X is mainly collected in the pores 27d ... 27d, As a result, the pores 27d to 27d are clogged, and the exhaust gas flow resistance increases. Then, after the exhaust particulate X collecting ability 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. It becomes like this.
[0009]
On the other hand, at the stage where the exhaust particulate X is burned and removed, first, as shown in FIG. 8D, the exhaust particulate X is collected in the pores 27d to 27d having a large contact area between the exhaust particulate X and the oxidation catalyst. The exhaust particulate X is quickly burned and removed, and the exhaust particulate X collected on the partition wall surface 27e having a small contact area between the exhaust particulate X and the oxidation catalyst is gradually burned and removed. It expands to the upper layer side of the exhaust particulate X collected so as to be stacked on 27e. Such a phenomenon is considered to occur because the exhaust particulate X collected in the pores 27d to 27d having a large contact area with the oxidation catalyst is more likely to use the oxidation reaction.
[0010]
The relationship between the differential pressure and the amount collected is shown in FIG. In the collection and accumulation stage, a large pressure loss occurs due to clogging of the pores 27d... 27d in the initial stage (R1) where the collection amount is small, and the differential pressure rapidly rises as the collection amount increases. In the middle and late period (R2), the pressure loss increases moderately as the trapped surface 27e is collected, and the differential pressure increases gradually as the collected amount increases.
[0011]
On the other hand, in the combustion stage, in the initial stage (R3) in which a relatively large amount of exhaust particulate X remains compared with the initial stage of collection (R3), the flow resistance of the exhaust gas in the pores 27d to 27d is reduced and the pressure loss is reduced. Although the pressure is greatly reduced and the pressure difference decreases sharply with the decrease in the collected amount, it is burned around the partition wall surface 27e in the middle and late stages (R4), so the pressure loss decreases gradually, and the pressure difference is Decreases gradually with a decrease in the amount collected.
[0012]
That is, even if the same differential pressure is detected in the collection and accumulation stage of exhaust particulate X and the combustion removal stage, the amount of collected exhaust particulates is different. Therefore, in the technique described in Patent Document 1 that does not take this into consideration, the amount of collected exhaust particulates cannot be accurately estimated.
[0013]
Therefore, an object of the present invention is to provide an engine exhaust purification device capable of accurately estimating the amount of exhaust particulates collected by a particulate filter.
[0014]
[Means for Solving the Problems]
That is, the invention according to claim 1 has an oxidation catalyst function and is provided in an exhaust passage of the engine to collect exhaust particulates; The An exhaust purification device for an engine provided with a collection amount estimation means for estimating the amount of exhaust particulates collected by the collection means, An exhaust pressure detecting means for detecting an exhaust pressure at least upstream of the upstream side and the downstream side of the collecting means; a parameter value detecting means for detecting a parameter value related to the temperature of the collecting means; When the parameter value detected by the parameter value detection means is greater than or equal to a predetermined value, it is determined that the state of the collection means is in the stage of burning and removing the collected exhaust particulates. Determination means for determining that the stage is collecting and accumulating, and The collection amount estimation means is It has combustion amount calculation means for calculating the combustion amount of exhaust particulates based on the parameter value detected by the parameter value detection means, and the determination means determines that the state of the collection means is in the collection and accumulation stage When this is done, the amount of collection is estimated based on the differential pressure between the upstream exhaust pressure and the downstream exhaust pressure detected by the exhaust pressure detection means or the upstream exhaust pressure. When it is determined that the state is in the combustion removal stage, the combustion amount calculated by the combustion amount calculation means is subtracted from the collection amount estimated in the collection and accumulation stage before the combustion removal stage. By The amount collected is estimated.
[0015]
According to the present invention, depending on whether the state of the collection means is the stage where the collected exhaust particulates are burned and removed or the stage where the collection and accumulation is performed, the collection means is provided with a different estimation method. Since the amount of collected exhaust particulates (collected amount) is estimated, the collected amount can be estimated with high accuracy.
[0017]
In that case, According to the present invention, whether the state of the collection means is in the combustion removal stage or the collection accumulation stage of the exhaust particulates is scientifically and experimentally and relatively simple based on the temperature of the collection means. Can be determined with high accuracy.
[0019]
And especially According to this invention, when the state of the collection means is in the collection and accumulation stage of exhaust particulates, the collection amount is estimated based on the differential pressure or the upstream exhaust pressure. On the other hand, when the collection means is in the exhaust particulate combustion removal stage, the exhaust particulate combustion amount is calculated based on the parameter value related to the temperature of the collection means and the collection particulate accumulation stage The amount of collection is estimated by subtracting the amount of combustion from the amount of collection estimated. In other words, the amount of collection is estimated corresponding to the hysteresis of the relationship between the exhaust pressure (differential pressure) and the amount of collection, which differs between when the collection means is in the combustion removal stage and when it is in the collection and accumulation stage. Since the method is switched, the accuracy of the estimation is improved.
[0020]
Claim 2 The invention described in Claim 1 In the invention described in (1), storage means for storing a basic characteristic in which a differential pressure between the upstream exhaust pressure and the downstream exhaust pressure detected by the exhaust pressure detection means or a collection amount with respect to the upstream exhaust pressure is determined is provided. When the determination by the determination means shifts from the combustion removal stage to the collection / accumulation stage, the collected amount estimation means is configured to capture the differential pressure detected at the time of transition or the basic characteristics defined in the upstream exhaust pressure. The difference in the collected amount between the collected amount and the collected amount at the combustion removal stage calculated at the time of transition is stored as an offset amount, and the collected amount in the collected and accumulated stage after the transition is determined based on the above basic characteristics. It is calculated from the collection amount and the offset amount.
[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. At the time of transition from the combustion removal stage to the collection and accumulation stage, depending on the situation at the time of transition, the amount of collection remaining in the filter at the time of transition varies. While taking into account the deviation (offset amount) from the basic characteristic, the estimation is continued according to the basic characteristic from the remaining collection amount as a starting point.
[0022]
That is, when it is determined by the determination means that the combustion removal stage has shifted to the collection / accumulation stage, the trapped amount determined in the basic characteristics in the differential pressure or upstream exhaust pressure detected during the transition, and the combustion removal stage Is stored as an offset amount, and the collected amount after the transition, that is, when the determination means determines that it is in the collection and accumulation stage. The collection amount is calculated from the collection amount and the offset amount obtained from the basic characteristics. Thereby, according to the state of the collection means, it becomes possible to estimate the collection amount more accurately and accurately.
[0023]
Also, Claim 3 The invention described in Claim 2 In the invention described in (1), a regeneration means for regenerating the collection means by combusting and removing exhaust particulates collected by the collection means is provided, and the regeneration means is configured to capture the amount estimated by the collection amount estimation means. When the collected amount becomes equal to or greater than a predetermined amount, regeneration of the collecting means is started.
[0024]
According to this invention, when the collection amount estimated by the collection amount estimation means becomes a predetermined amount or more, regeneration of the collection means is started. In that case, claim 1 Or claim 2 According to the invention, since the regeneration is started based on the collection amount accurately and accurately estimated, the regeneration can be performed efficiently. For example, the eye of the collecting means that can occur when the regeneration start is delayed. Damage caused by clogging, or the occurrence of deterioration in fuel consumption caused by post-injection, which may occur when regeneration is continued more than necessary, can be suppressed. Occurs when realized by post-injecting fuel in addition to main injection).
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0026]
In this embodiment, the present invention is applied to a diesel engine 1 shown in FIG. The engine 1 is a four-cylinder engine, for example, and includes four pistons 3 that move up and down in the cylinder bore of the engine body 2 (only one 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 disposed on a fuel supply path between the injector 4 and a fuel tank (not shown). The pump 5 pumps fuel from the fuel tank to the common rail 6, and the common rail 6 accumulates the pumped fuel. When the injector 4 is opened, 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. 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 turbocharger compressor 13, an intercooler 14, a throttle valve 15 for adjusting the intake air amount, an intake air temperature sensor 16, an intake pressure sensor 17, and an intake air A valve 18 is provided.
[0029]
In the exhaust passage 20, in order from the upstream side, an exhaust valve 21, a turbocharger turbine 22, a first exhaust temperature sensor 23, an oxidation catalyst device 24, a second exhaust temperature sensor 25, an upstream pressure sensor 26, and in exhaust gas The particulate filter 27 for collecting the exhaust particulates, the downstream pressure sensor 28, and the third exhaust temperature sensor 29 are provided. Further, an EGR passage 30 is disposed 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 a collecting means in claims, and the filter 27 is coated with an oxidation catalyst substance 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 that detects fuel pressure accumulation. An accelerator opening sensor 45 that detects the amount of depression of the accelerator pedal 44 is provided in the passenger compartment.
[0032]
The control unit 50 of the engine 1 exits from the filter 27, the intake air amount detected by the sensors, the intake air temperature, the intake pressure, the exhaust gas temperature flowing into the oxidation catalyst device 24, the exhaust gas temperature flowing into the particulate filter 27, and the filter 27. A control signal is output to the injector 4 and the high-pressure fuel pump 5 based on the exhaust temperature afterwards, the upstream and downstream pressures across the filter 27, the engine speed, the coolant temperature, the fuel pressure in the common rail 6, the engine load, etc. To do.
[0033]
The control unit 50 calculates the fuel injection amount by correcting the basic fuel injection amount obtained from the engine rotational speed by the engine rotational speed sensor 41 and the engine load by the accelerator opening sensor 45 with the cooling water temperature or the intake air temperature.
[0034]
The control unit 50 functions as a collection amount estimation unit, and for example, estimates the amount of exhaust particulates collected by the particulate filter 27 based on the differential pressure between the upstream and downstream pressures across the filter 27. To do.
[0035]
The control unit 50 also functions as a regeneration means, and when the estimated amount of collection exceeds a predetermined amount, fuel is added during the expansion stroke after the main injection near the compression top dead center of the piston 3 Injecting (post-injection) starts regeneration of the filter 27 (combustion removal of exhaust particulates collected by the filter 27). In this post-injection, the unburnt components generated in the post-injection are oxidized by the oxidation catalyst device 24 and the particulate filter 27 carrying the oxidation catalyst, whereby the temperature of the particulate filter 27 is raised, The purpose is to burn the collected exhaust particulates and quickly regenerate the filter 27.
[0036]
By the way, the exhaust particulates collected by the filter 27 start to be burned and removed when the temperature of the filter 27 is approximately 400 ° C. or higher, and tend to be collected and accumulated below 400 ° C. That is, as the operating state of the engine 1 fluctuates, the state of the particulate filter 27 is switched between a stage in which exhaust particulates are burned and removed and a stage in which they are collected and accumulated. As described above, the combustion removal stage and the collection and accumulation stage show different values of the differential pressure even if the collected quantity is the same, and the collected quantity and the differential pressure are not in a one-to-one relationship. There is a problem that the collected amount cannot be detected accurately.
[0037]
Therefore, in the present embodiment, the control unit 50 determines whether the state of the filter 27 is in a stage where the exhaust particulates are burned and removed or a stage where the particulates are collected and accumulated (determination means). The collection amount W is estimated by a different estimation method according to the determined stage.
[0038]
Hereinafter, the detail of this collection amount estimation control is demonstrated using the flowchart of FIG.
[0039]
First, in step S1, the control unit 50 detects the temperature T of the particulate filter 27 (detected by the second exhaust temperature sensor 25), the exhaust pressure upstream of the filter 27 (detected by the upstream pressure sensor 26). ) And downstream exhaust pressure (detected by the downstream pressure sensor 28), and various state quantities detected by the sensors such as the engine speed, and in step S2, from the upstream exhaust pressure to the downstream exhaust pressure. Is calculated 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 control flow is the first operation. If YES, that is, if it is the first time, an offset amount D described later is set to 0 in step S4, and then in step S5. A basic collection amount I corresponding to the current differential pressure is calculated based on a basic characteristic map (see FIG. 3) that defines the collection amount corresponding to the detected (calculated) differential pressure. Here, this basic characteristic corresponds to the stage of R1 and R2 in FIG. 9, that is, the stage in which exhaust particulates are collected and accumulated in the particulate filter 27. When the differential pressure is P1 or less, The increase in the collected amount with respect to the increase in the differential pressure is moderate (in other words, the increase in the differential pressure with respect to the increase in the collected amount is abrupt). The increase in the collected amount with respect to the increase in the pressure is rapid (in other words, the increase in the differential pressure with respect to the increase in the collected amount is moderate).
[0041]
Next, in step S6, the current collection amount W is calculated based on the basic collection 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, when the determination in step S3 is NO, the processes after step S7 are executed. That is, in step S7, it is determined whether or not the temperature T is equal to or higher than the predetermined value α (determination means). If YES, the process proceeds to step S8. If NO, the process proceeds to step S9, and one control is performed. It is determined whether or not the temperature T before the cycle is equal to or higher than a predetermined value α. Here, the predetermined value α is burned and removed when the particulate filter 27 collects and accumulates exhaust particulates (phases Q1, Q2, Q4, and Q5 illustrated in FIG. 4). It is a value for determining whether it is in the stage (stage of the same phase Q3). If the temperature T is equal to or higher than the predetermined value α, the control unit 50 burns the exhaust particulates if the temperature of the particulate filter 27 If the temperature T is not equal to or higher than the predetermined value α, it is determined that the exhaust particulates are being collected and accumulated. 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 about 400 ° C., for example.
[0043]
And when both the determinations of step S7 and step S9 are NO, that is, when the collection and accumulation stage continues, the above-described step S5 and step S6 are executed to calculate the current collection amount W, Return to step S1. Here, this is the stage of 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, at the transition from the collection and accumulation stage to the combustion removal stage, in step S10, during the collection and accumulation stage one control cycle before The calculated collection amount W is stored as the collection amount A at the time of transition, and an integrated combustion amount F and an integrated combustion amount, which will be described later, are reset to 0 in step S11. Here, the time of the transition is the time when the transition from the phase Q2 to the phase Q3 shown in FIG.
[0045]
Next, in step S12, an integrated combustion amount F (an integrated value of the amount of exhaust particulates that has been combusted and removed from the time of transition to the combustion removal stage) is calculated and stored based on the temperature T and the like. Here, the integrated combustion amount F is read from the map shown in FIG. 5 based on the current temperature T, and the combustion amount (combustion speed) Fn of the exhaust particulates per unit time is read, and the value Fn is calculated one control period before. It is a value added to the accumulated combustion amount F. In this map, the combustion amount (burning rate) Fn of exhaust particulate per unit time is set to a larger value as the current temperature T increases. The unit time corresponds to one control cycle.
[0046]
Next, in step S13, based on the engine speed and the engine load (represented basically by the accelerator opening, it is preferable to substitute the fuel injection amount here), the accumulated emission amount G (in the combustion removal stage). The accumulated value of the amount of exhaust particulate discharged from the time of transition (exhaust from the in-cylinder combustion chamber and flowing into the particulate filter 27) is calculated and stored. Here, the cumulative emission amount G is a map shown in FIG. 6 (in this map, the engine speed and the engine load are shown separately, but the trend is integrated into one that takes both of these into consideration. As in the case of the integrated combustion amount F, the exhaust particulate emission amount Gn per unit time is read 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 exhaust gas emission amount Gn per unit time becomes larger as the engine load (fuel injection amount) becomes larger, and becomes larger when the engine speed is small and large. Yes. Here, the unit time corresponds to one control cycle.
[0047]
Next, in step S14, the cumulative amount of combustion F is subtracted from the trapped amount A of transition and the cumulative amount of exhaust G is added to calculate the current amount of trapped W. Then, the process returns to step S1.
[0048]
Further, when both the determinations at step S7 and step S8 are YES, that is, when the combustion removal stage is continued, the above-described steps S12 to S14 are executed to calculate the current collection amount W, and step S1. 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, calculation is performed in step S15 during the combustion removal stage one control cycle before. After storing the collected amount W as the collected amount H at the time of transition, in step S16, the basic collected amount C corresponding to the differential pressure P at the time of transition is determined from the basic characteristic map shown in FIG. In S17, the basic collection amount C is subtracted from the collected amount H at the time of transition, and the difference, that is, the offset amount D is calculated. Next, the above-described steps S5 and S6 are executed to calculate the current collection amount W, and the process returns to step S1. Here, this transition time is a time point when the phase Q3 shown in FIG. 4 shifts to the phase Q4, and the amount of collection at that time is H. That is, the phases Q4 and Q5 are obtained by translating the phases Q1 and Q2 by the offset amount in the X-axis direction (the collection amount axis direction in FIG. 4). FIG. 4 shows only up to phase Q5, but thereafter, the combustion removal stage and the collection and accumulation stage are repeated as indicated by the 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 collection amount W estimated in this way becomes a predetermined amount or more. Thus, the regeneration of the filter 27 is started and executed by performing additional fuel injection (post-injection) in addition to the main injection.
[0051]
As described above, the exhaust emission control device for the engine 1 according to the present embodiment has an oxidation catalyst function and is provided in the exhaust passage 20 of the engine 1 to collect the particulate particulates (collecting means). ) And a collection amount estimating means (control unit 50) for estimating the amount of exhaust particulates collected by the filter 27, wherein the state of the filter 27 is collected. Determination means (control unit 50) is provided for determining whether the exhausted exhaust particulates are burned and removed or at a stage where they are collected and accumulated, and the collected amount estimation means (control unit 50) 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 different estimation methods depending on whether the state of the particulate particulates is in the stage of burning and removing exhaust particulates or the stage of collecting and accumulating. Since the amount (collected amount) W of the exhaust particulates is estimated, the collected amount W can be estimated with high accuracy.
[0053]
The exhaust emission control device of the engine 1 includes a second exhaust temperature sensor 25 (parameter value detection means) that detects the temperature T (parameter value related to temperature) of the particulate filter 27, and a determination means (control unit 50). ) Determines that the state of the filter 27 is in the exhaust particulate removal stage when the temperature T detected by the second exhaust temperature sensor 25 is equal to or higher than the predetermined value α.
[0054]
According to this, based on the temperature T of the particulate filter 27, whether or not the state of the particulate filter 27 is in the stage where the exhaust particulates are being burned and removed or is being collected and accumulated is determined scientifically. It can be determined experimentally and with a relatively simple means with high accuracy.
[0055]
The exhaust purification device of the engine 1 includes an upstream pressure sensor 26 for detecting the exhaust pressure on the upstream side and the downstream side of the particulate filter 27, and a downstream pressure sensor 28 (exhaust pressure detection means) for collecting the exhaust pressure. The amount estimation means (control unit 50) includes combustion amount calculation means (control unit 50) for calculating the combustion amount F of the exhaust particulates based on the temperature T detected by the second exhaust temperature sensor 25, and the determination. When it is determined that the state of the filter 27 is in the collection and accumulation stage in the means (control unit 50), the upstream exhaust pressure and the downstream exhaust pressure detected by the upstream pressure sensor 26 and the downstream pressure sensor 28 The trapped amount W is estimated based on the differential pressure or upstream exhaust pressure, and the state of the filter 27 is in the combustion removal stage by the determination means (control unit 50). Is determined by subtracting the combustion amount F calculated by the combustion amount calculation means (control unit 50) from the collection amount A estimated at the collection and accumulation stage before the combustion removal stage. The amount of collected W is estimated.
[0056]
According to this, when the state of the particulate filter 27 is in the collection and accumulation stage of exhaust particulates, the collection amount is estimated based on the differential pressure or the upstream exhaust pressure. On the other hand, when the filter 27 is in the exhaust particulate combustion removal stage, the exhaust particulate combustion amount F is calculated on the basis of the temperature T of the filter 27, and the estimated collection is in the collection accumulation stage. By subtracting the combustion amount F from the amount A, the trapped amount W is estimated. That is, the hysteresis of the relationship between the exhaust pressure (differential pressure) and the collected amount, which is different between when the filter 27 is in the combustion removal stage and when it is in the collection and accumulation stage (the paths of R1 and R2 in FIG. 9) Since the collection amount estimation method is switched in response to the difference between the R3 and R4 paths, the estimation accuracy is improved.
[0057]
Further, the exhaust purification device of the engine 1 determines the differential between the upstream side exhaust pressure and the downstream side exhaust pressure detected by the upstream side pressure sensor 26 and the downstream side pressure sensor 28 or the amount of trapped with respect to the upstream side exhaust pressure. Storage means (control unit 50) for storing the obtained basic characteristics is provided, and the collection amount estimation means (control unit 50) is determined by the determination means (control unit 50) from the combustion removal stage to the collection and accumulation stage. When the shift is made, the trapped amount C determined in the basic characteristic at the differential pressure P detected at the shift or the upstream exhaust pressure and the trapping calculated when the determination means determines the combustion removal stage. The difference between the amount (the amount collected at the combustion removal stage calculated at the time of transition) H and the amount collected is stored as an offset amount D, and the determination means (control unit 50) From the collection amount C and the offset amount D determined based on the basic characteristics, the amount of collection (collection amount in the collection and accumulation stage after the transition) W is determined as being in the collection and accumulation stage. calculate.
[0058]
According to this, in the collection and accumulation stages Q1, Q2, Q4 and Q5, the collection amount W 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 transition from the combustion removal stage to the collection and accumulation stage, the collection amount H remaining in the filter 27 at the time of transition varies depending on the situation at the time of transition. Considering the deviation (offset amount) D between the amount H and the collected amount C determined from the basic characteristics, the estimation is continued according to the basic characteristics, starting from the remaining collected amount H (Q4, Q5). . As a result, the collection amount W can be estimated more accurately and accurately according to the state of the particulate filter 27.
[0059]
In addition, the exhaust emission control device of the engine 1 includes regeneration means (control unit 50) that regenerates the collection means by burning and removing the exhaust particulates collected by the particulate filter 27, and the regeneration means (control unit 50). ) Starts the regeneration of the filter 27 when the collected amount estimated by the collected amount estimating means (control unit 50) becomes a predetermined amount or more.
[0060]
According to this, the regeneration of the particulate filter 27 is started when the collected amount estimated by the collected amount estimating means (control unit 50) becomes a predetermined amount or more. In that case, since the regeneration is started based on the collection amount accurately and accurately estimated as described above, the regeneration can be performed efficiently, and can occur, for example, when the regeneration start is delayed. In addition, it is possible to suppress problems such as damage caused by clogging of the particulate filter 27 and deterioration of fuel consumption caused by post-injection that may occur when regeneration is continued more than necessary.
[0061]
In the present embodiment, the basic characteristic of the collected amount with respect to the differential pressure is such that the differential pressure is bent at a predetermined value P1 and the inclination thereof changes, but this is an example. However, it may be changed according to the structure of the particulate filter actually used, and for example, it is conceivable that the curve changes smoothly as the differential pressure increases.
[0062]
In addition, the amount W collected 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, but the upstream pressure sensor 26 You may make it calculate based on the basic characteristic map corresponding only to the detected pressure.
[0063]
【The invention's effect】
As described above, according to the present invention, the amount of collection is estimated by a different estimation method depending on whether the particulate filter is in the stage of burning and removing exhaust particulate or in the stage of collecting and accumulating. 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 showing an example of a preferable specific operation of collection amount estimation control.
FIG. 3 is a map showing the basic characteristics of the collection amount with respect to the differential pressure in the collection and accumulation stage.
FIG. 4 is an example of a trajectory of the relationship between the differential pressure and the collected amount when the collected amount is estimated by this control.
FIG. 5 is a map showing temperature characteristics of the combustion amount per unit time used when calculating the integrated combustion amount.
FIG. 6 is a map showing a fuel injection amount of exhaust particulate emission per unit time and an engine speed characteristic used when calculating an integrated amount of exhaust particulate discharged from the engine.
FIG. 7 is a longitudinal sectional view of a particulate filter.
FIG. 8 is an enlarged view of a portion indicated by reference numeral a in FIG. 7, and is an explanatory diagram of a process of collecting and accumulating exhaust particulates and removing combustion.
FIG. 9 is an explanatory diagram of the trajectory of the collected amount with respect to the differential pressure in the process of collecting and storing exhaust particulates and removing combustion.
[Explanation of symbols]
1 engine
20 Exhaust passage
25 Second exhaust temperature sensor (parameter value detection means)
26, 28 Pressure sensor (exhaust pressure detection means)
27 Particulate filter (collecting means)
50 Control unit (collected amount estimation means, determination means, combustion amount calculation means, storage means, regeneration means)

Claims (3)

Comprising a collecting means for collecting the exhaust particulate is provided in an exhaust passage of the engine and having an oxidation catalytic function, a collection amount estimation means for estimating the amount of exhaust particulates trapped in the trapping means An exhaust purification device for an engine, wherein an exhaust pressure detecting means for detecting an exhaust pressure at least upstream of the upstream side and the downstream side of the collecting means, and a parameter related to the temperature of the collecting means A parameter value detecting means for detecting a value, and when the parameter value detected by the parameter value detecting means is equal to or greater than a predetermined value, the state of the collecting means is determined to be a stage in which the collected exhaust particulates are burned and removed. has the steps of the exhaust particulates are collected accumulated determining means is provided when less than the predetermined value, the collection amount estimation means, based on the detected parameter values in the above parameter value detection means A combustion amount calculating means for calculating the combustion amount of the exhaust particulates, and when the determination means determines that the state of the collection means is in the collection and accumulation stage, it is detected by the exhaust pressure detection means; When the collection amount is estimated based on the differential pressure between the upstream exhaust pressure and the downstream exhaust pressure or the upstream exhaust pressure, and when the determination means determines that the state of the collection means is in the combustion removal stage, An engine characterized by estimating a collection amount by subtracting a combustion amount calculated by the combustion amount calculation means from a collection amount estimated at the collection and accumulation stage before the combustion removal stage. Exhaust purification equipment. A storage means is provided for storing a basic characteristic in which a differential between the upstream exhaust pressure and the downstream exhaust pressure detected by the exhaust pressure detection means or a collection amount with respect to the upstream exhaust pressure is determined. When the judgment by the judgment means shifts from the combustion removal stage to the collection and accumulation stage, the estimation means determines the amount of collection determined in the basic characteristics in the differential pressure or upstream exhaust pressure detected at the time of transition, and at the time of transition. The difference between the calculated amount of collection and the amount collected in the combustion removal stage is stored as an offset amount, and the amount collected in the collection and accumulation stage after the transition is determined based on the basic characteristics described above. exhaust purification device for an engine according to claim 1, characterized in that calculated from. A regeneration means for regenerating the collection means by burning and removing the exhaust particulates collected by the collection means is provided, and the regeneration means has a collection amount estimated by the collection amount estimation means of a predetermined amount or more. 3. The engine exhaust gas purification apparatus according to claim 2, wherein regeneration of the collecting means is started when it becomes .

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