JP2006316733A - Exhaust emission control device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an internal combustion engine capable of properly prohibiting regeneration of a filter on the basis of an estimated particulate deposit quantity, by confirmably accurately estimating the deposit quantity of particulates deposited on a filter. <P>SOLUTION: As indicated in Fig. 1, this exhaust emission control device has the filter 11 for collecting the particulates in exhaust gas, filter regenerating means 6 and 2 for regenerating the filter 11 when the particulate deposit quantity DPFPM estimated by first deposit quantity estimating means 20 and 2 reaches a predetermined first threshold value PMSLMT1, and filter regeneration prohibiting means 6 and 2 for prohibiting regeneration of the filter 11 when a particulate deposit quantity DPFMSS estimated by second deposit quantity estimating means 22 and 2 is a predetermined second threshold value PMSLMT2 or more larger than the first threshold value in response to differential pressure DP between the upstream and downstream sides of the filter 11 detected by a differential pressure sensor 22 when an engine speed of the internal combustion engine 3 is increased to a predetermined engine speed NECHK. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, particularly an internal combustion engine that collects particulates in exhaust gas of a diesel engine.

  In an exhaust gas purification apparatus for a diesel engine, a filter is generally provided in an exhaust system of an internal combustion engine, and particulates in the exhaust gas discharged from the internal combustion engine are collected by the filter. When the accumulated amount of particulates in the filter increases, the exhaust pressure increases, leading to a decrease in output and fuel consumption of the internal combustion engine. For this reason, in order to prevent this, an exhaust gas purification device for an internal combustion engine that regenerates the filter by heating the filter to burn the accumulated particulates has been known. It is disclosed.

  In this exhaust gas purification device, during operation of the internal combustion engine, the pressure in the exhaust pipe on the upstream side and downstream side of the filter is detected, respectively, and according to the pressure difference between the former and the latter (hereinafter referred to as “differential pressure”), The collection amount of the particulates collected by the filter is calculated, and when the calculated collection amount is between the lower limit collection amount and the upper limit collection amount, the regeneration of the filter is executed. Further, in this exhaust gas purifying apparatus, when the collected amount is equal to or greater than the upper limit collected amount, the regeneration of the filter is prohibited because the particulates are excessively accumulated on the filter. This prevents the filter from becoming overheated due to thermal runaway due to sudden combustion of the excessively accumulated particulates, and prevents cracking or melting of the filter. Further, when the regeneration of the filter is prohibited, a warning lamp is turned on to inform the driver that particulates are excessively accumulated on the filter.

  However, the differential pressure between the upstream side and the downstream side of the filter varies depending not only on the amount of accumulated particulates but also on the operating state of the internal combustion engine. In particular, in a low rotation state such as idling, the amount of exhaust gas is small, so the exhaust pressure is small and the differential pressure is also small. On the other hand, in the conventional exhaust gas purifying apparatus, since the collection amount is calculated only in accordance with the differential pressure between the upstream side and the downstream side of the filter, there is a possibility that the accumulation amount cannot be accurately estimated. For example, in the low rotation state of the internal combustion engine as described above, since the differential pressure becomes small, the estimated collection amount is below the upper limit collection amount even though the particulates are excessively accumulated on the filter. There is a case. In this case, the regeneration of the filter is not prohibited, and the regeneration of the filter is executed, so that the filter is overheated, and there is a possibility that the filter is cracked or melted.

  The present invention has been made to solve such a problem, and can accurately and accurately estimate the amount of particulates deposited on the filter, and regenerate the filter based on the estimated amount of accumulated particulates. It is an object of the present invention to provide an exhaust gas purification apparatus for an internal combustion engine that can appropriately prohibit the above.

JP-A-8-284463

  In order to achieve this object, the invention according to claim 1 collects particulates in the exhaust gas discharged from the internal combustion engine 3 into the exhaust system (the exhaust pipe 5 in the embodiment (hereinafter the same applies in this section)). An exhaust gas purification apparatus 1 for an internal combustion engine 3 that purifies exhaust gas, and is provided between the filter 11 that is provided in the exhaust system and collects particulates in the exhaust gas, and between the upstream side and the downstream side of the filter 11. Differential pressure sensor 22 for detecting the differential pressure DP of the exhaust system, and first accumulation amount estimation means for estimating the accumulation amount of particulates collected by the filter 11 (crank angle sensor 20, ECU2, step 1 in FIG. 2) ) And the estimated particulate deposition amount (PM deposition amount DPFPMS) reaches a predetermined first threshold value PMSLMT1. Filter regeneration means (injector 6, ECU 2, step 5 in FIG. 2) that regenerates the filter 11 by burning, and the rotational speed (engine rotational speed NE) of the internal combustion engine 3 to a predetermined rotational speed (rotation for overdeposition determination According to the differential pressure DP detected by the differential pressure sensor 22 when the rotational speed of the internal combustion engine 3 is increased, and the rotational speed increasing means (ECU 2, step 12 in FIG. 3). The second accumulation amount estimating means (the differential pressure sensor 22, the ECU 2, step 15 in FIG. 3) for estimating the accumulation amount of the particulates collected in the particulate accumulation amount (the particulate accumulation amount estimated by the second accumulation amount estimating means ( Filter regeneration for prohibiting regeneration of the filter 11 when the PM accumulation amount DPFPMSS) is equal to or larger than a predetermined second threshold value PMSLMT2 larger than the first threshold value. Stop means, characterized in that it comprises a and (ECU 2, step 16 to 18 in FIG. 3).

  According to the exhaust gas purification apparatus for an internal combustion engine, the particulates in the exhaust gas discharged from the internal combustion engine are collected by the filter provided in the exhaust system. The first accumulation amount estimation means estimates the accumulation amount of the particulate deposited on the filter, and when the estimated particulate accumulation amount reaches a predetermined first threshold value, the filter regeneration means performs the regeneration of the filter. Is called. In addition, the rotational speed of the internal combustion engine is increased to a predetermined rotational speed by the rotational speed increasing means, and the second accumulation amount is estimated according to the differential pressure of the exhaust system between the upstream and downstream of the filter detected by the differential pressure sensor at that time. By means, the amount of particulates deposited on the filter is estimated. When the estimated particulate accumulation amount is equal to or larger than the predetermined second threshold value, it is assumed that the particulate is excessively accumulated on the filter, and the regeneration prohibiting means prohibits regeneration of the filter. Is done.

  As described above, the filter is regenerated when the particulate deposition amount estimated by the first deposition amount estimation unit reaches the first threshold value. Further, the rotational speed of the internal combustion engine is increased, and the particulate accumulation amount estimated by the second accumulation amount estimation means according to the differential pressure between the upstream and downstream of the filter detected at that time is the first threshold value. When the second threshold value is larger than the second threshold value, the regeneration of the filter is prohibited. By increasing the rotational speed of the internal combustion engine, the amount of exhaust gas increases, and the exhaust pressure increases accordingly. For this reason, the differential pressure between the upstream and downstream of the filter becomes larger and appears clearly. Further, since the internal combustion engine is held at a predetermined rotational speed, it is possible to eliminate the influence on the differential pressure due to the fluctuation of the exhaust pressure accompanying the change in the operating state. Therefore, the particulate deposition amount can be accurately estimated according to the differential pressure detected at this time, and when the estimated particulate deposition amount is equal to or greater than the second threshold value, the filter enters the particulate overdeposition state. As a result, the regeneration of the filter can be appropriately prohibited. As a result, it is possible to reliably prevent cracks or melting damage of the filter due to overheating.

  The invention according to claim 2 is the exhaust gas purification apparatus 1 for the internal combustion engine 3 according to claim 1, wherein the internal combustion engine 3 is mounted as a drive source in the vehicle V, and the particulate accumulation amount by the first accumulation amount estimation means. And the regeneration of the filter 11 by the filter regeneration means are executed while the vehicle V is traveling, the estimation of the particulate deposition amount by the second deposition amount estimation means, and the regeneration of the filter 11 based on the estimated particulate deposition amount Is prohibited at the time of service inspection of the vehicle V.

  According to this configuration, the internal combustion engine is mounted on the vehicle, and the regeneration of the filter based on the particulate accumulation amount estimated by the first accumulation amount estimation unit is executed while the vehicle is traveling. In addition, when a vehicle is brought into a service factory because a warning lamp that indicates the excessive accumulation of particulates is turned on while the vehicle is running, the internal combustion engine is operated by the speed increasing means during the service inspection. The engine speed is increased, the particulate accumulation amount at that time is estimated, and the regeneration of the filter is prohibited based on the estimated particulate accumulation amount.

  In this way, even when the vehicle is brought into the service factory due to the lighting of a warning lamp that displays the excessive accumulation state of the particulates, the filter is not immediately regenerated, but the second accumulation amount estimation means described above is used. Based on the estimated particulate deposition amount, it is determined in a deterministic manner whether or not it is in an excessive deposition state. Therefore, regardless of the reliability of the determination of the over-deposition state during traveling, it can be accurately and accurately determined whether or not the filter is actually in the over-deposition state. Then, according to the determination result, when the filter is determined to be in an overdeposited state, the regeneration of the filter is prohibited.For example, the filter is replaced, and when it is determined that the filter is not in an overdeposited state, Appropriate responses can be taken. Furthermore, since the amount of accumulated particulate matter can be estimated only by increasing the rotational speed of the internal combustion engine without running the vehicle, the above determination can be easily performed even in a service factory.

  According to a third aspect of the present invention, in the exhaust gas purification apparatus 1 for the internal combustion engine 3 according to the second aspect, when the estimated amount of accumulated particulates is equal to or greater than a predetermined third threshold value PMSLMT3 while the vehicle V is traveling. 2 further includes a running filter regeneration prohibiting means (ECU 2, steps 3 and 8 in FIG. 2) for prohibiting regeneration of the filter 11, and the second threshold value PMSLMT2 is set to a value larger than the third threshold value PMSLMT3. It is characterized by being.

  According to this configuration, during the traveling of the vehicle, when the estimated particulate is equal to or greater than the third threshold value which is smaller than the second threshold value, the filter regeneration prohibiting unit during travel prohibits the regeneration of the filter. The As described above, at the time of vehicle service inspection, the internal combustion engine is maintained at a predetermined high rotational speed, and the particulate accumulation amount is estimated according to the differential pressure at that time, so the estimated particulate accumulation amount is Reliability is high. Therefore, at the time of vehicle service inspection, a larger second threshold value close to the accumulation amount corresponding to the over-deposition state of the filter is used, and this second threshold value is compared with the estimated particulate accumulation amount. Thus, it is possible to accurately determine whether or not the filter is actually over-deposited.

  On the other hand, during driving of the vehicle, the estimated amount of accumulated particulates is likely to deviate from the actual amount of accumulated particulates due to changes in driving conditions, and the reliability is low. Therefore, when the vehicle is traveling, a third threshold value smaller than the second threshold value is used, and the third threshold value is compared with the estimated amount of accumulated particulates, so Accumulation judgment is performed on the safe side, and filter regeneration is prohibited early. Accordingly, it is possible to reliably avoid the regeneration in the over-deposited state, and to reliably prevent the filter from being cracked or melted due to overheating while the vehicle is running.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of an exhaust gas purification apparatus 1 according to an embodiment of the present invention and an internal combustion engine (hereinafter referred to as “engine”) 3 to which the exhaust gas purification apparatus 1 is applied. The engine 3 is, for example, a four-cylinder (only one shown) diesel engine mounted on the vehicle V.

  The engine 3 includes a piston 3a and a cylinder head 3b for each cylinder, and a combustion chamber 3c is formed by the piston 3a and the cylinder head 3b. An intake pipe 4 and an exhaust pipe 5 (exhaust system) are connected to the cylinder head 3b, and a fuel injection valve (hereinafter referred to as "injector") 6 is attached so as to face the combustion chamber 3c.

  The injector 6 (filter regeneration means) is disposed in the center of the top wall of the combustion chamber 3c, and is connected in turn to a high-pressure pump and a fuel tank (both not shown) via a common rail. The valve opening time and valve opening timing of the injector 6 are controlled by a drive signal from the ECU 2, thereby controlling the fuel injection amount QINJ and the injection timing.

  A magnet rotor 20a is attached to the crankshaft 3d of the engine 3, and a crank angle sensor 20 (first accumulation amount estimating means) is constituted by the magnet rotor 20a and the MRE pickup 20b. The crank angle sensor 20 outputs a CRK signal and a TDC signal, which are pulse signals, to the ECU 2 as the crankshaft 3d rotates.

  The CRK signal is output every predetermined crank angle (for example, 30 °). The ECU 2 obtains the rotational speed NE (hereinafter referred to as “engine rotational speed”) NE of the engine 3 based on the CRK signal. The TDC signal is a signal indicating that the piston 3a of each cylinder is at a predetermined crank angle position near the TDC (top dead center) at the start of the intake stroke, and in this example of the 4-cylinder type, every crank angle of 180 °. Is output.

  The intake pipe 4 is provided with an intake throttle valve 7 for adjusting the amount of intake air. The intake throttle valve 7 is connected to an actuator 7a made of, for example, a DC motor. The opening degree of the intake throttle valve 7 is controlled by the ECU 2 controlling the duty ratio of the current supplied to the actuator 7a. The intake pipe 4 is provided with an air flow sensor 21 upstream of the intake throttle valve 7. The air flow sensor 21 detects the intake air amount QA, and the detection signal is output to the ECU 2.

  An EGR passage 8 is connected between the intake pipe 4 and the exhaust pipe 5. The EGR passage 8 is connected so as to connect the exhaust pipe 5 and a downstream side of the intake throttle valve 7 of the intake pipe 4. A part of the exhaust gas of the engine 3 is recirculated to the intake pipe 4 as EGR gas through the EGR passage 8, thereby reducing the combustion temperature in the combustion chamber 3 c, thereby reducing NOx in the exhaust gas. .

  The EGR passage 8 is provided with an EGR valve 9. The EGR valve 9 is composed of a linear electromagnetic valve, and the valve lift amount is controlled by a duty-controlled drive signal from the ECU 2, whereby the EGR gas circulation flow rate is controlled.

  Further, an oxidation catalyst 10 and a filter 11 are provided on the downstream side of the exhaust pipe 5 from the EGR passage 8 in order from the upstream side. The oxidation catalyst 10 oxidizes HC and CO in the exhaust gas and purifies the exhaust gas.

  The filter 11 has a honeycomb core (not shown) made of porous ceramic or the like, and collects particulates such as soot in the exhaust gas (hereinafter referred to as “PM”) into the atmosphere. Reduce the amount of PM discharged. Further, an oxidation catalyst (not shown) similar to the oxidation catalyst 10 is supported on the honeycomb core of the filter 11. As described above, since the filter 11 carries the oxidation catalyst, the temperature of the filter 11 is increased by the oxidation reaction of the oxidation catalyst, whereby PM is combusted.

  Further, a pressure introduction passage 5a is connected to the exhaust pipe 5 between the oxidation catalyst 10 and the filter 11 and on the downstream side of the filter 11, and a differential pressure sensor 22 (second deposition) is connected to the pressure introduction passage 5a. A quantity estimation means) is provided. The differential pressure sensor 22 detects a differential pressure (hereinafter referred to as “differential pressure”) DP between the upstream side and the downstream side of the filter 11 in the exhaust pipe 5 and outputs a detection signal to the ECU 2. When the accumulated amount of PM deposited on the filter 11 (hereinafter referred to as “PM accumulated amount”) is small, the ventilation resistance of the filter 11 decreases, so that the differential pressure DP is reduced. When the PM accumulated amount is large, the filter 11 Since the differential pressure DP increases as the ventilation resistance increases, the PM deposition amount can be estimated according to the differential pressure DP.

  Further, a first exhaust gas temperature sensor 23 and a second exhaust gas temperature sensor 24 are respectively provided immediately upstream and downstream of the filter 11 of the exhaust pipe 5. The first exhaust gas temperature sensor 23 detects the temperature of the exhaust gas immediately upstream of the filter 11 (hereinafter referred to as “pre-filter gas temperature”) TDPFF, and the second exhaust gas temperature sensor 24 detects the exhaust gas temperature immediately downstream of the filter 11. Temperature (hereinafter referred to as “gas temperature after filter”) TDPFB is detected, and those detection signals are output to ECU 2.

  Further, the ECU 2 outputs a detection signal representing an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) from the accelerator opening sensor 25. Further, the ECU 2 is connected with a warning lamp 26 for informing the driver of a state where PM is excessively accumulated on the filter 11 (hereinafter referred to as “an excessive accumulation state of the filter 11”).

  The ECU 2 (first accumulation amount estimation means, filter regeneration means, rotation speed increase means, second accumulation amount estimation means, filter regeneration inhibition means and running filter regeneration inhibition means) includes an I / O interface, CPU, RAM, ROM, etc. It is comprised with the microcomputer which consists of. The detection signals from the various sensors 20 to 25 described above are each input to the CPU after A / D conversion and shaping by the I / O interface.

  In response to these input signals, the CPU executes a regeneration control process for regenerating the filter 11 while the vehicle V is traveling or during service inspection according to a control program stored in the ROM. In this process, the regeneration operation of the filter 11 is performed by post injection that additionally injects fuel into the combustion chamber 3 c during the expansion stroke or exhaust stroke of the engine 3. The post-injection fuel amount (hereinafter referred to as “post-injection amount”) POSTQ is controlled based on the pre-filter gas temperature TDPFF so that the temperature in the filter 11 becomes a target temperature (for example, 600 ° C.). Thereby, the filter 11 is regenerated by controlling the filter 11 to a high temperature state and burning the PM deposited on the filter 11.

  FIG. 2 is a flowchart showing a regeneration control process of the filter 11 that is executed while the vehicle V is traveling. This process is executed in synchronization with the generation of the TDC signal. In this process, first, in step 1 (illustrated as “S1”, the same applies hereinafter), the PM deposition amount DPFPMS is calculated. Specifically, the PM deposition amount DPFPMS is calculated as follows. First, a PM emission map (not shown) is searched according to the engine speed NE and the fuel injection amount QINJ to calculate the PM emission amount per TDC emitted from the engine 3, that is, for each combustion. To do. Further, by searching a PM regeneration amount map (not shown) according to the filter oxygen amount and the filter temperature, the regeneration amount of PM that is combusted and regenerated by the filter 11 is calculated. The filter oxygen amount is determined according to the fuel injection amount QINJ and the intake air amount QA, and the filter temperature is determined according to the intake air amount QA, the pre-filter gas temperature TDPFF, and the differential pressure DP. Next, the PM deposition amount per TDC is calculated by subtracting the PM regeneration amount from the calculated PM discharge amount. Then, the current PM accumulation amount DPFPMS is calculated by adding the calculated PM accumulation amount to the previous PM accumulation amount integrated value. The PM accumulation amount DPFPMS is reset at the end of the regeneration operation of the filter 11.

  Next, it is determined whether or not the calculated PM deposition amount DPFPMS is greater than or equal to a predetermined first threshold value PMSLMT1 (step 2). When the determination result is NO and DPFPMS <PMSLMT1, the PM accumulation amount DPFPMS is relatively small, so that the regeneration operation of the filter 11 is not performed, and the process proceeds to step 8 where the filter regeneration flag F_REOK is set to “0”. This process is terminated.

  On the other hand, when the determination result of step 2 is YES and DPFPMS ≧ PMSLMT1, it is determined whether or not the PM deposition amount DPFPMS is equal to or larger than a predetermined third threshold value PMSLMT3 that is larger than the first threshold value PMSLMT1. (Step 3). When the determination result is NO, that is, when PMSLMT1 ≦ DPFPMS <PMSLMT3, the PM accumulation amount DPFPMS is relatively large and the filter 11 is not in the overdeposition state, and the overdeposition flag F_PMSOV is set to “0” ( Step 4) Further, assuming that the regeneration operation of the filter 11 is to be executed, the filter regeneration flag F_REOK is set to “1” (step 5), and this processing is terminated.

  On the other hand, if the determination result of step 3 is YES and DPFPMS ≧ PMSLMT3, the filter 11 is over-deposited, and the warning lamp 26 is turned on to notify the driver of this (step 6). The deposition flag F_PMSOV is set to “1” (step 7). Further, in order to avoid cracks or melting damage of the filter 11 due to regeneration in an over-deposited state, step 8 is executed assuming that the regeneration operation of the filter 11 is not performed, and this processing is terminated.

  FIG. 3 is a flowchart showing an over-deposition determination process of the filter 11 that is executed at the time of service inspection of the vehicle V. This service inspection is performed at the service factory when the vehicle V is brought into the service factory in response to the lighting of the warning lamp 26. The overdeposition determination process is executed at predetermined time intervals by outputting a start signal from an external diagnostic machine (not shown) to the ECU 2. In this process, first, in step 11, it is determined whether or not a determination flag F_CHECK is “1”.

  When the determination result is NO, the target engine speed NEOBJ of the engine speed NE is set to a predetermined engine speed NECHK (for example, 2800 rpm) for overdeposition determination (step 12). By this setting, the engine speed NE is increased and controlled so as to become the engine speed NECHK for overdeposition determination. Next, after the determination flag F_CHECK is set to “1” (step 13), the process proceeds to step. By executing this step 13, in the second and subsequent loops of this process, the determination result in step 11 is YES, and in this case, the process proceeds directly to step 14.

  In step 14, it is determined whether or not the engine speed NE is substantially equal to the engine speed NECHK for overdeposition determination. If the determination result is NO, the present process is terminated. On the other hand, when the determination result in step 14 is YES and the engine speed NE is substantially equal to the engine speed NECHK for over-deposition determination, the PM accumulation amount DPFPMSS is calculated according to the differential pressure DP detected by the differential pressure sensor 22. (Step 15). Next, it is determined whether or not the calculated PM deposition amount DPFPMSS is greater than or equal to a predetermined second threshold value PMSLMT2 that is greater than the third threshold value PMSLMT3 (step 16). When the determination result is YES and DPFPMSS ≧ PMSLMT2, it is assumed that the differential pressure DP between the upstream and downstream of the filter 11 is large and the filter 11 is in an overdeposited state, so that the overdeposition flag F_PMSOVS is set to “1”. (Step 17). Further, in order to avoid cracks and breakage of the filter 11 due to regeneration in an over-deposited state, the regeneration operation of the filter 11 is prohibited, and the filter regeneration flag F_REOKS is set to “0” (step 18). Then, in order to indicate that the determination has been completed, the determination-in-progress flag F_CHECK is set to “0” (step 19), and the present process ends.

  On the other hand, if the determination result in step 16 is NO and DPFPMSS <PMSLMT2, the over accumulation flag F_PMSOVS is set to “0”, assuming that the filter 11 is not in the over accumulation state (step 20). Then, after the filter regeneration flag F_REOKS is set to “1” (step 21), the step 19 is executed, and this process is terminated.

  FIG. 4 is a flowchart showing the regeneration control process of the filter 11 that is executed at the time of service inspection according to the determination result by the above-described overdeposition determination process. This process is executed in synchronization with the generation of the TDC signal. In this process, first, in step 31, it is determined whether or not the filter regeneration flag F_REOKS set in step 18 or 21 in FIG. 3 is “1”. When the determination result is NO, the present process is terminated without performing the regeneration operation of the filter 11.

  On the other hand, if the determination result in the step 31 is YES and F_REOKS = 1, it is determined whether or not the reproducing flag F_DPFRE is “1” (step 32). When the determination result is NO, the target rotational speed NEOBJ of the engine rotational speed NE is set to a predetermined regeneration speed NERE (for example, 1500 rpm) (step 33). With this setting, the engine speed NE is controlled to be the regeneration control speed NERE. Next, by setting the post injection amount POSTQ according to the engine speed NE and the accelerator pedal opening AP (step 34), the regeneration operation of the filter 11 is started and the regeneration flag F_DPFRE is set to “1”. (Step 35), go to Step 36. If the determination result in step 32 is YES and the filter 11 is already being regenerated, the process proceeds directly to step 36.

In this step 36, the exhaust gas flow rate (hereinafter referred to as “exhaust gas flow rate”) EXQ discharged from the engine 3 is calculated. The exhaust gas flow rate EXQ is obtained from the gas equation of state according to the engine speed NE and the intake air amount QA. Next, the current corrected differential pressure DPC (n) is calculated by dividing the differential pressure DP by the square of the calculated exhaust gas flow rate EXQ ² (step 37). The reason why the differential pressure DP is corrected based on the exhaust gas flow rate EXQ is because the differential pressure DP changes according to the exhaust gas flow rate EXQ even when the PM accumulation amount DPFPMSS is the same.

Further, the reason why the differential pressure DP is divided by the square of the exhaust gas flow rate EXQ ² is as follows. The following equation (1) represents the relationship between the volume flow rate Q passing through the orifice, the sectional area A of the orifice, and the pressures P1 and P2 upstream and downstream of the orifice (orifice equation). Expressions (2) and (3) are modifications of the above expression (1).

ここで、Ｃｄはオリフィスの流体係数、ρは流体密度である。オリフィスの断面積Ａが一定であれば、式（２）から、オリフィスの上下流間の差圧（Ｐ１−Ｐ２）は、体積流量の自乗Ｑ²に比例し、また、式（３）から、差圧（Ｐ１−Ｐ２）／堆積流量の自乗Ｑ²が一定になることが分かる。したがって、フィルタ１１の有効断面積をこれらの式中の断面積Ａとみなし、排ガス流量ＥＸＱを体積流量Ｑとみなすと、式（３）から、ＤＰ／ＥＸＱ²がほぼ一定であれば、フィルタ１１の有効断面積がほぼ一定になっており、すなわち、フィルタ１１の再生が終了していると判定できる。なお、上記補正後差圧ＤＰＣには、フィルタ処理が施され、それにより、排ガスの脈動に伴う差圧ＤＰの脈動やノイズ成分などが除去される。

Here, Cd is the fluid coefficient of the orifice, and ρ is the fluid density. If the cross-sectional area A of the orifice is constant, from equation (2), the differential pressure (P1-P2) between the upstream and downstream of the orifice is proportional to the square Q ^{2 of the} volume flow rate, and from equation (3), It can be seen that the differential pressure (P1-P2) / the square of the deposition flow rate Q ² is constant. Therefore, when the effective sectional area of the filter 11 is regarded as the sectional area A in these equations and the exhaust gas flow rate EXQ is regarded as the volumetric flow rate Q, from the equation (3), if DP / EXQ ² is substantially constant, the filter 11 It can be determined that the effective cross-sectional area is substantially constant, that is, the regeneration of the filter 11 has been completed. Note that the post-correction differential pressure DPC is subjected to filter processing, thereby removing the pulsation of the differential pressure DP and the noise component associated with the pulsation of the exhaust gas.

  In step 38 following step 37, the corrected differential pressure DPC (nx) calculated when a TDC signal is generated a predetermined x times before (for example, equivalent to 30 seconds before) and the current corrected differential pressure DPC ( n) (= DPC (nx) -DPC (n)) is calculated as a differential pressure change amount ΔDPC. The corrected differential pressure DPC is stored using a ring buffer or the like.

  Next, it is determined whether or not the differential pressure change amount ΔDPC is equal to or less than a predetermined threshold value DPCLMT (step 39). When the determination result is NO, it is assumed that the effective area of the filter 11 has increased, the filter 11 is being regenerated, and the regenerating operation of the filter 11 is to be continued. finish.

  On the other hand, when the determination result in step 39 is YES and ΔDPC ≦ DPCLMT is satisfied, the counter value TDPC of the counter (not shown) is incremented (step 40), and the counter value TDPC is equal to the predetermined value TLMT (for example, 150 sec). It is determined whether or not the above is true (step 41).

  If the determination result is NO and TDPC <TLMT, this processing is terminated. On the other hand, when the determination result in step 41 is YES, that is, when the state where the differential pressure change amount ΔDPC is equal to or less than the threshold value DPCLMT continues for a predetermined time corresponding to the predetermined value TLMT, the effective cross-sectional area of the filter 11 is increased. Is substantially constant and the regeneration of the filter 11 is completed, the filter regeneration flag F_REOKS is set to “0” to indicate that (step 42).

  Then, in order to end the regeneration operation of the filter 11, the target rotational speed NEOBJ is set to a predetermined rotational speed NEENDEND (for example, 850 rpm) (step 43), and the post injection amount POSTQ is set to 0 (step) 44). In addition, the reproducing flag F_DPFRE is set to “0” (step 45), and the counter value TDPC is reset (step 46), and then this process is terminated.

  FIG. 5 is a timing chart showing an operation example when it is determined that the filter 11 is not in an excessive accumulation state and the regeneration operation of the filter 11 is performed in the processing of FIGS. 3 and 4. First, the engine speed NE is increased to the engine speed NECHK for overdeposition determination (timing t1). As the engine speed NE increases, the amount of exhaust gas increases and the exhaust pressure increases, whereby the differential pressure DP increases. When the differential pressure DP at this time is smaller than the second threshold value PMSLMT2, the engine speed NE is set to the regeneration speed NERE when it is determined that the filter 11 is not in an excessive accumulation state. At the same time, post injection is performed, and the regeneration operation of the filter 11 is started (t2).

  As the exhaust gas temperature rises along with the regeneration operation of the filter 11, the pre-filter gas temperature TDPFF gradually rises, and accordingly, the temperature in the filter 11 also rises gradually. Then, when the temperature in the filter 11 rises to near the target temperature (for example, 600 ° C.), PM begins to burn in the filter 11, and thus the post-filter gas temperature TDPFB also starts to rise (t 3). As PM is burned, the effective cross-sectional area of the filter 11 increases and the ventilation resistance decreases, whereby the differential pressure DP begins to decrease (t4). As combustion progresses, the differential pressure DP further decreases, and the gradient gradually decreases, whereby the differential pressure change amount ΔDPC gradually decreases and becomes lower than the threshold value DPCLMT (t5). Then, when the state continues for a predetermined time (t6), the regeneration operation of the filter 11 is terminated, assuming that the regeneration of the filter 11 is completed.

  As described above, according to the present embodiment, while the vehicle V is traveling, the PM accumulation amount DPFPMS is calculated according to the operating state of the engine 3, and the first threshold value PMSLMT1 ≦ PM accumulation amount DPFPMS <first. When the value is 3 threshold values PMSLMT3 (step 2: YES, step 3: NO in FIG. 2), the regeneration operation of the filter 11 is executed. When PM deposition amount DPFPMS ≧ third threshold value PMLMT3 (step 3: YES in FIG. 2), it is determined that the filter 11 is in an excessive deposition state, and the warning lamp 26 is turned on. When the vehicle V is brought into the service factory in response to the lighting of the warning lamp 26, the differential pressure DP detected in the state where the engine speed NE is increased to the engine speed NECHK for over-deposition determination in the service inspection. In accordance with the PM deposition amount DPFPMSS, when the calculated PM deposition amount DPFPMSS is equal to or larger than the second threshold value PMLMT2, it is determined that the filter 11 is actually over-deposited. Disable playback.

  As described above, the PM accumulation amount DFPPMSS is estimated by estimating the PM accumulation amount DPFPMSS according to the differential pressure DP detected when the engine rotation speed NE is greatly increased to the rotation number NECHK for overdeposition determination. Therefore, when the estimated PM accumulation amount DPFPMSS ≧ second threshold value PMLMT2, it is determined that the filter 11 is in an excessive accumulation state, and the regeneration operation of the filter 11 can be appropriately prohibited. Thereby, the crack of the filter 11 resulting from overheating, a melting loss, etc. can be prevented reliably.

  In addition, even when the vehicle V is brought into the service factory due to the lighting of the warning lamp 26 or the like, the regeneration operation of the filter 11 is not performed immediately, but based on the PM accumulation amount DFPPMSS estimated according to the differential pressure DP, Whether or not it is in an over-deposited state is determined for confirmation. Therefore, regardless of the reliability of the determination of the overdeposited state during traveling, it can be determined with accuracy with certainty whether or not the filter 11 is actually in the overdeposited state. When the filter 11 is determined to be in an overdeposited state according to the determination result, the regeneration operation of the filter 11 is prohibited. For example, the filter 11 is replaced, and when it is determined that the filter 11 is not in an overdeposited state, Appropriate measures can be taken such as performing a playback operation. Furthermore, since the PM accumulation amount DPFPMSS can be estimated only by increasing the engine speed NE without running the vehicle V, the above determination can be easily performed even in a service factory.

  Further, at the time of service inspection of the vehicle V, when the PM accumulation amount DPFPMSS is equal to or larger than the second threshold value PMSLMT2, it is determined that the filter 11 is in an overdeposition state, so the filter 11 is actually in an overdeposition state. Whether or not can be accurately determined. On the other hand, when the vehicle V is traveling, the regeneration operation of the filter 11 is prohibited when the PM accumulation amount DPFPMS is equal to or larger than the third threshold value PMSLMT3, so that the regeneration operation in the overdeposition state is surely performed. It is possible to avoid this, and it is possible to reliably prevent cracks or melting of the filter 11 caused by overheating while the vehicle V is traveling.

  In addition, this invention can be implemented in various aspects, without being limited to the described embodiment. For example, in the embodiment, the differential pressure DP is directly detected using the differential pressure sensor 22, but instead of this, pressure sensors are provided on the upstream side and the downstream side of the filter 11 to detect the detected values. It may be obtained from the difference. Further, in the embodiment, the PM accumulation amount DPFPMS during traveling of the vehicle V is estimated according to the operating state of the engine 3, but may be estimated according to the differential pressure DP detected by the differential pressure sensor 22. . Further, in the embodiment, the overdeposition determination process in FIG. 3 and the regeneration control process in FIG. 4 are described as being performed at the time of service inspection when the warning lamp 26 is turned on. You may carry out at the time of periodic inspection of V. In the embodiment, the regeneration operation of the filter 11 is performed by post injection. However, it may be performed by another appropriate method, for example, throttling of the intake throttle valve 7 in addition to or instead of it.

  Furthermore, although embodiment is an example which applied this invention to the diesel engine, this invention is not limited to this, Various engines other than a diesel engine, for example, the ship which arrange | positioned the gasoline engine and the crankshaft in the perpendicular direction It can be applied to an engine for a marine propulsion device such as an external unit. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.

1 is a diagram showing a schematic configuration of an exhaust gas purification apparatus of the present invention and an internal combustion engine to which the exhaust gas purification apparatus is applied. It is a flowchart which shows the regeneration control process of the filter performed while driving | running | working of a vehicle. It is a flowchart which shows the filter excessive accumulation determination process performed at the time of the service check of a vehicle. It is a flowchart which shows the regeneration control process of the filter performed at the time of vehicle service inspection. It is a timing chart which shows the operation example of the regeneration control of the filter performed at the time of the vehicle service inspection.

Explanation of symbols

1 Exhaust gas purification device
2 ECU (first accumulation amount estimation means, filter regeneration means, rotation speed increase
Means, second accumulation amount estimating means, filter regeneration prohibiting means, and traveling
Medium filter regeneration prohibition means)
3 Engine
5 Exhaust pipe (exhaust system)
6 Injector (filter regeneration means)
11 Filter
20 Crank angle sensor (first accumulation amount estimating means)
22 Differential pressure sensor (second accumulation amount estimation means)
V vehicle
DP differential pressure
PM particulates DPFPMS PM deposition amount DPFPMSS PM deposition amount PMSLMT1 first threshold value PMSLMT2 second threshold value PMSLMT3 third threshold value
NE engine speed NECHK Speed for over-deposition determination (predetermined speed)

Claims (3)

An exhaust gas purification apparatus for an internal combustion engine that purifies exhaust gas by collecting particulates in the exhaust gas discharged from the internal combustion engine into an exhaust system,
A filter provided in the exhaust system for collecting particulates in the exhaust gas;
A differential pressure sensor for detecting a differential pressure of the exhaust system between the upstream side and the downstream side of the filter;
First accumulation amount estimation means for estimating the accumulation amount of particulates collected by the filter;
Filter regeneration means for regenerating the filter by burning the particulate deposited on the filter when the estimated particulate accumulation amount reaches a predetermined first threshold;
A rotational speed increasing means for increasing the rotational speed of the internal combustion engine to a predetermined rotational speed;
Second accumulation amount estimation means for estimating the accumulation amount of the particulates collected by the filter according to the differential pressure detected by the differential pressure sensor when the rotational speed of the internal combustion engine is increased;
Filter regeneration prohibiting means for prohibiting regeneration of the filter when the particulate deposition amount estimated by the second deposition amount estimating means is equal to or greater than a predetermined second threshold value greater than the first threshold value; ,
An exhaust gas purifying device for an internal combustion engine, comprising: The internal combustion engine is mounted on a vehicle as a drive source,
Performing the estimation of the particulate accumulation amount by the first accumulation amount estimation means and the regeneration of the filter by the filter regeneration means during the traveling of the vehicle,
The particulate deposition amount estimation by the second deposition amount estimation means and the prohibition of regeneration of the filter based on the estimated particulate deposition amount are executed at the time of service inspection of the vehicle. 2. An exhaust gas purification apparatus for an internal combustion engine according to 1. A traveling filter regeneration prohibiting means for prohibiting regeneration of the filter when the estimated amount of accumulated particulates is equal to or greater than a predetermined third threshold during traveling of the vehicle;
The exhaust gas purifying apparatus for an internal combustion engine according to claim 2, wherein the second threshold value is set to a value larger than the third threshold value.

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