JP2006316746A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, capable of appropriately regenerating a filter while avoiding an excessively accumulated condition of particulates (PM) even when an abnormality occurs in devices affecting a calculation result of the accumulated amount of PM. <P>SOLUTION: This exhaust emission control device for the internal combustion engine 3 is provided with a discharge amount calculating means 2 calculating discharge amount QEX of PM discharged from the internal combustion engine 3; a natural regeneration amount parameter calculating means 2 calculating a natural regeneration amount parameter QRN; an accumulated amount estimating means 2 estimating the accumulated amount SQPMDPF of PM accumulated on the filter 18; filter regenerating means 6, 2 forcibly regenerating the filter 18 when the estimated PM accumulated amount reaches a threshold value SQREF; and a correction prohibiting means 2 prohibiting correction of PM discharge amount when it is determined that an abnormality occurs in the devices 33, 34 affecting accuracy of estimation of the accumulated amount of PM accumulated on the filter 18. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine that purifies exhaust gas by collecting particulates in the exhaust gas with a filter in a diesel engine or the like.

  As a conventional exhaust gas purifying device for an internal combustion engine, for example, one disclosed in Patent Document 1 is known. In the exhaust passage of the internal combustion engine, an exhaust temperature sensor, a catalytic converter, and an exhaust throttle valve are provided in order from the upstream side. In this exhaust gas purification device, during low-speed and low-load operation such as during warm-up operation of an internal combustion engine, in addition to performing main injection of fuel into the combustion chamber, the temperature is raised by restricting the exhaust throttle valve. Control is performed. By this temperature increase control, the temperature of the exhaust is increased by combustion of the sub-injected fuel, and the exhaust is maintained at a high temperature by the throttle of the exhaust throttle valve, thereby promoting oxidation of unburned HC in the exhaust passage. The unburned HC is reduced. The temperature rise state of the exhaust at this time is monitored based on the detection result of the exhaust temperature sensor.

  Moreover, in this exhaust gas purification apparatus, the presence or absence of abnormality of the exhaust gas temperature sensor is determined. When it is determined that the exhaust temperature sensor is abnormal, both the sub-injection of fuel and the throttle of the exhaust throttle valve are stopped, thereby causing erroneous temperature rise control due to the abnormality of the exhaust temperature sensor. Problems such as thermal deterioration of the catalytic converter due to abnormal temperature rise of the exhaust gas are prevented.

  However, in this conventional exhaust gas purification apparatus, immediately after it is determined that the exhaust temperature sensor is abnormal, the temperature rise control by the fuel sub-injection and the exhaust throttle valve is stopped. For this reason, although the above problems can be avoided, if the exhaust gas is not heated, the discharge amount of unburned HC may increase and the exhaust gas characteristics may be deteriorated.

  Further, as an exhaust gas purifying device such as a diesel engine, a device that has a filter in an exhaust system and collects particulates (hereinafter referred to as “PM”) in the exhaust gas with a filter has been conventionally known. In addition, in order to prevent a decrease in engine output and a deterioration in fuel consumption due to an increase in exhaust pressure when PM accumulates excessively on the filter, it is possible to regenerate the filter by burning the PM accumulated on the filter. Conventionally known, for example, disclosed in Patent Document 2.

  In this exhaust gas purification apparatus, temperature sensors are provided at the inlet and outlet of the filter, respectively, and the amount of PM accumulated on the filter is estimated according to the engine speed and load and the temperature of the filter detected by the temperature sensor. When the estimated amount of accumulated PM becomes larger than a predetermined threshold value, the filter regeneration operation is performed.

  As described above, in this conventional exhaust gas purification apparatus, the amount of PM deposited on the filter is estimated according to the temperature of the filter detected by the temperature sensor. For this reason, when an abnormality occurs in the temperature sensor, the PM accumulation amount on the filter cannot be properly estimated, and the regeneration operation based on the PM accumulation amount cannot be performed properly, thereby preventing the PM from being over-deposited on the filter. It may not be possible. In this case, for example, as disclosed in Patent Document 1, even if the presence or absence of the temperature sensor is determined and the control based on the detection result of the temperature sensor is stopped when it is determined to be abnormal, the PM deposition amount is still reduced. Since it cannot be estimated properly, it is impossible to prevent the PM from being over-deposited.

  The present invention has been made to solve such a problem, and even when an abnormality occurs in a device that affects the accuracy of estimation of the amount of accumulated particulates deposited on a filter, particulates are excessively deposited. An object of the present invention is to provide an exhaust gas purification apparatus for an internal combustion engine that can properly regenerate a filter while reliably avoiding the state.

JP 2001-123870 A JP 2001-280118 A

  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 to the exhaust system (the exhaust pipe 5 in the embodiment (hereinafter, the same applies in this section)). Thus, the exhaust gas purifying apparatus 1 of the internal combustion engine 3 purifies the exhaust gas, which is provided in the exhaust system and collects the particulates in the exhaust gas, and the discharge amount of the particulates discharged from the internal combustion engine 3 A discharge amount calculation means (ECU 2, step 1 in FIG. 3) for calculating (PM discharge amount QEX) and a natural regeneration amount parameter (natural regeneration amount QRN) representing the natural regeneration amount of the particulates naturally regenerated by the filter 18 The natural regeneration amount parameter calculation means (ECU 2, step 2 in FIG. 3) to be calculated, and the particulates calculated by the calculated natural regeneration amount parameters. The accumulated amount estimating means (ECU2, step of FIG. 3) for estimating the accumulated amount of particulates accumulated on the filter 18 (PM accumulated amount QPMDPF, PM accumulated amount integrated value SQPMDPF) by correcting the discharge amount to the decrease side. 5, 6) and filter regeneration means for forcibly regenerating the filter 18 by burning the particulate deposited on the filter 18 when the estimated particulate accumulation amount reaches a predetermined threshold value SQREF. Injector 6, ECU 2, steps 7 and 9) in FIG. 3, and abnormalities in the devices (first and second exhaust gas temperature sensors 33 and 34) that affect the accuracy of estimation of the amount of particulates deposited on filter 18 are detected. An abnormality determining means for determining (ECU 2, step 31 in FIG. 5) and when the device is determined to be abnormal Deposit amount estimating means correcting prohibiting means for prohibiting the correction of the particulate emissions, characterized in that it comprises a and (ECU 2, step 4 in FIG. 3).

  According to the exhaust gas purification apparatus for an internal combustion engine, the particulates in the exhaust gas are collected by the filter. Further, the discharge amount of the particulate discharged from the internal combustion engine is calculated by the discharge amount calculation means. Further, the natural regeneration amount parameter representing the natural regeneration amount of the particulates naturally regenerated by the filter is calculated by the natural regeneration amount parameter calculating means, and is calculated by using the natural regeneration amount parameter calculated by the accumulation amount estimating means. By correcting the particulate discharge amount to the decreasing side, the accumulation amount of the particulate deposited on the filter is estimated. When the particulate accumulation amount estimated in this way reaches a predetermined threshold value, the filter regeneration is performed by burning the particulate accumulated on the filter by the filter regeneration means.

  As described above, the natural regeneration amount parameter representing the natural regeneration amount of the particulate that is naturally regenerated by the filter is calculated, and the particulate discharge amount is corrected to the decreasing side by using this natural regeneration amount parameter. Since the accumulation amount is estimated, the actual particulate accumulation amount in the filter can be accurately estimated, and the filter can be appropriately regenerated based on the estimated particulate accumulation amount.

  Further, in this exhaust gas purifying apparatus, it is determined by the abnormality determining means whether or not the device that affects the accuracy of estimation of the accumulated amount of particulates accumulated on the filter is abnormal, and when determined to be abnormal, The reduction correction of the particulate discharge amount by the accumulation amount estimation means is prohibited. Thus, when it is determined that the device as described above is abnormal, the particulate discharge reduction correction is prohibited for the following reason.

  For example, (1) when a device that affects the calculation accuracy of the particulate discharge amount, for example, a sensor that detects a parameter used for calculating the particulate discharge amount is not normal, the particulate discharge calculated according to the detection parameter The reliability of the amount becomes low, and there is a possibility that the particulate discharge amount is calculated to be small. Similarly, (2) when a device that affects the accuracy of calculation of the natural reproduction amount parameter, for example, a sensor that detects a parameter used for calculating the natural reproduction amount parameter is not normal, the natural reproduction calculated according to the detected parameter. The reliability of the quantity parameter is low, and there is a risk that a large amount of the natural regeneration quantity parameter is calculated. Further, (3) when the device that influences the emission amount of the particulates discharged from the internal combustion engine, for example, the fuel injection valve or the EGR device directly related to the combustion state of the internal combustion engine is not normal, the above sensor is normal. Even so, the particulate discharge amount actually discharged from the internal combustion engine is different from the particulate discharge amount calculated by the discharge amount calculation means, and there is a risk of exceeding this.

  For this reason, when at least one of the above (1) to (3) occurs due to the occurrence of an abnormality in the device as described above, the calculated particulate discharge amount is corrected to decrease by the natural regeneration amount parameter. As a result, the accuracy of the estimated particulate deposition amount decreases, and the deviation from the actual particulate deposition amount becomes large, which may be underestimated. In that case, as a result of the amount of the particulate accumulation not reaching the threshold value, the regeneration of the filter is not performed in a timely manner, so that the particulate is excessively deposited on the filter. According to the present invention, when such a device that affects the accuracy of estimation of the particulate deposition amount is determined to be abnormal, correction by the deposition amount estimating means is prohibited, so that there is an abnormality in such a device. Even if it occurs, the possibility of underestimating the amount of particulate deposition is reduced, and therefore the particulate overdeposition state can be reliably avoided.

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

  A combustion chamber 3c is formed between the piston 3a of the engine 3 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 (filter regeneration means) is attached so as to face the combustion chamber 3c. It has been.

  The injector 6 is disposed at the central portion of the top wall of the combustion chamber 3c, and is sequentially connected to a high-pressure pump 6a and a fuel tank (not shown) via a common rail (not shown). The fuel in the fuel tank is pressurized by the high-pressure pump 6a and injected from the injector 6 into the combustion chamber 3c. The fuel pressure PRAIL is detected by a fuel pressure sensor 37 provided on the common rail, and the detection signal is output to the ECU 2 (see FIG. 3). 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 and the injection timing, respectively.

  An engine water temperature sensor 29 is attached to the main body of the engine 3. The engine water temperature sensor 29 detects the temperature (hereinafter referred to as “engine water temperature”) TW of the cooling water circulating in the cylinder block of the engine 3 and outputs a detection signal to the ECU 2.

  A magnet rotor 30a is attached to the crankshaft 3d of the engine 3, and a crank angle sensor 30 is configured by the magnet rotor 30a and the MRE pickup 30b. The crank angle sensor 30 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.

  A supercharging device 7 is provided in the intake pipe 4. The supercharging device 7 includes a supercharger 8 constituted by a turbocharger, an actuator 9 connected thereto, and a vane opening degree control valve 10.

  The supercharger 8 includes a rotatable compressor blade 8a provided in the intake pipe 4, a rotatable turbine blade 8b provided in the exhaust pipe 5, and a plurality of rotatable variable vanes 8c (only two are shown). And a shaft 8d for integrally connecting these blades 8a and 8b. The turbocharger 8 pressurizes the intake air in the intake pipe 4 by rotationally driving the compressor blade 8a integrated therewith as the turbine blade 8b is rotationally driven by the exhaust gas in the exhaust pipe 5. Perform supercharging operation.

  The actuator 9 is of a diaphragm type that is operated by negative pressure, and is mechanically connected to each variable vane 8c. A negative pressure is supplied to the actuator 9 from a negative pressure pump through a negative pressure supply passage (both not shown), and a vane opening degree control valve 10 is provided in the middle of the negative pressure supply passage. The vane opening control valve 10 is composed of an electromagnetic valve, and the negative pressure supplied to the actuator 9 changes when the opening is controlled by a drive signal from the ECU 2, and accordingly, the variable vane 8c The supercharging pressure is controlled by changing the opening degree.

  A water-cooled intercooler 11 and a throttle valve 12 are provided downstream from the supercharger 8 of the intake pipe 4 in order from the upstream side. The intercooler 11 cools the intake air when the temperature of the intake air rises due to the supercharging operation of the supercharging device 7 or the like. The throttle valve 12 is connected to an actuator 12a made of, for example, a DC motor. The opening degree TH of the throttle valve 12 (hereinafter referred to as “throttle valve opening degree”) TH is controlled by controlling the duty ratio of the current supplied to the actuator 12 a by the ECU 2. Further, the throttle valve opening TH is detected by a throttle valve opening sensor 38, and the detection signal is output to the ECU 2.

  The intake pipe 4 is provided with an air flow sensor 31 on the upstream side of the supercharger 8 and a supercharging pressure sensor 39 on the downstream side of the intercooler 11. The air flow sensor 31 detects the intake air amount QA, the supercharging pressure sensor 39 detects the supercharging pressure PACT in the intake pipe 4, and outputs these detection signals to the ECU 2. An intake air temperature sensor 32 is provided on the intake manifold 4 a of the intake pipe 4. The intake air temperature sensor 32 detects the temperature of intake air (hereinafter referred to as “intake air temperature”) TA and outputs a detection signal to the ECU 2.

  The intake manifold 4a is partitioned into a swirl passage 4b and a bypass passage 4c from the collecting portion to the branch portion, and these passages 4b and 4c communicate with the respective combustion chambers 3c via intake ports. A swirl device 13 is provided in the bypass passage 4c. The swirl device 13 includes a swirl valve 13a, an actuator 13b for opening and closing the swirl valve 13a, and a swirl control valve 13c. The opening degree of the swirl control valve 13c is controlled by the ECU 2, and the strength of the swirl generated in the combustion chamber 3c is controlled by changing the opening degree of the swirl valve 13a.

  The engine 3 is provided with an EGR device 14 having an EGR pipe 14a and an EGR control valve 14b. The EGR pipe 14 a is connected between the intake pipe 4 and the exhaust pipe 5, specifically, so as to connect the swirl passage 4 b of the collecting portion of the intake manifold 4 a and the upstream side of the supercharger 8 of the exhaust pipe 5. Has been. Through this EGR pipe 14a, a part of the exhaust gas of the engine 3 is recirculated to the intake pipe 4 as EGR gas, thereby reducing the combustion temperature in the combustion chamber 3c, thereby reducing NOx in the exhaust gas. .

  The EGR control valve 14b is configured by a linear electromagnetic valve attached to the EGR pipe 14a, and the EGR gas amount is controlled by controlling the valve lift amount linearly by a drive signal from the ECU 2.

  The EGR device 14 is provided with an EGR cooling device 15 for cooling the EGR gas. The EGR cooling device 15 includes an EGR passage switching valve 15b and an EGR cooler 15c provided on the downstream side of the EGR control valve 14b of the EGR pipe 14a. The EGR pipe 14a is provided with a bypass passage 15a so as to bypass the EGR cooler 15c, and the EGR passage switching valve 15b is attached to a branch portion of the bypass passage 15a. The EGR passage switching valve 15b selectively switches the passage on the downstream side of the EGR passage switching valve 15b of the EGR pipe 14a between the EGR cooler 15c side and the bypass passage 15a side under the control of the ECU 2.

  With the above configuration, when the EGR passage switching valve 15b is switched to the EGR cooler 15c side, the EGR gas is cooled by the EGR cooler 15c and then returned to the intake pipe 4. On the other hand, when switched to the bypass passage 15a side, the EGR gas returns to the intake pipe 4 as it is without being cooled by the EGR cooler 15c.

  Further, an oxidation catalyst 17 and a filter 18 are provided on the exhaust pipe 5 downstream of the supercharger 8 in order from the upstream side. The oxidation catalyst 17 oxidizes HC and CO in the exhaust gas and purifies the exhaust gas. The filter 18 collects particulates such as soot in the exhaust gas (hereinafter referred to as “PM”), thereby reducing PM discharged into the atmosphere. A catalyst (not shown) similar to the oxidation catalyst 17 is supported on the surface of the filter 18.

  A first exhaust gas temperature sensor 33 (device) and a second exhaust gas temperature sensor 34 (device) are provided on the upstream side of the oxidation catalyst 17 and the upstream side of the filter 18 in the exhaust pipe 5, respectively. The first exhaust gas temperature sensor 33 detects the temperature of the exhaust gas immediately upstream of the oxidation catalyst 17 (hereinafter referred to as “pre-catalyst gas temperature”) TCATG and outputs a detection signal to the ECU 2. The second exhaust gas temperature sensor 34 (exhaust temperature sensor) detects the temperature of the exhaust gas immediately upstream of the filter 18 (hereinafter referred to as “pre-filter gas temperature”) TDPFG, and outputs a detection signal to the ECU 2. The exhaust pipe 5 is connected to a pressure introduction passage 5a so as to straddle the filter 18, and a differential pressure sensor 40 is provided in the pressure introduction passage 5a. The differential pressure sensor 40 detects a pressure difference (hereinafter referred to as “filter differential pressure”) DP between the upstream and downstream of the filter 18 in the exhaust pipe 5 and outputs a detection signal to the ECU 2.

  The ECU 2 further receives a detection signal indicating an operation amount (hereinafter referred to as “accelerator opening”) AP of an accelerator pedal (not shown) from the accelerator opening sensor 35 and a detection signal indicating the atmospheric pressure PA from the atmospheric pressure sensor 36. The vehicle speed sensor 41 outputs a detection signal indicating the speed (vehicle speed) VP of the vehicle V, and the atmospheric temperature sensor 42 outputs a detection signal indicating the atmospheric temperature (atmospheric temperature) TAA. A dashboard (not shown) of the vehicle V is provided with a warning lamp 43 for displaying the state of the filter 18, and this warning lamp 43 is connected to the ECU 2.

  The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, EEPROM, and the like. In the present embodiment, the ECU 2 constitutes an emission amount calculation means, a natural regeneration amount parameter calculation means, a deposition amount estimation means, a filter regeneration means, an abnormality determination means, and a correction prohibition means.

  The detection signals from the various sensors 29 to 42 described above are A / D converted and shaped by the I / O interface and then input to the CPU. In accordance with these input signals, the CPU determines the operating state of the engine 3 according to a control program stored in the ROM and the like, and includes control of the fuel injection amount QINJ, the EGR amount, and the like according to the determined operating state. Various controls of the engine 3 are executed, and a regeneration control process for forcibly regenerating the filter 18 is performed by burning PM accumulated on the filter 18.

  FIG. 3 is a flowchart showing the reproduction control process. This process is executed in synchronization with the input of the TDC signal. First, in step 1 (illustrated as “S1”, the same applies hereinafter), the PM emission amount QEX discharged from the engine 3 per 1 TDC, that is, per combustion is calculated. The PM emission amount QEX is calculated by searching a map value of PM emission amount from a PM emission amount map (not shown) according to the engine speed NE and the fuel injection amount QINJ, and using this map value as the engine water temperature TW. The correction is performed by correcting the atmospheric pressure PA, the intake air temperature TA, the atmospheric temperature TAA, and the like. The PM emission amount map is obtained by experimentally determining the amount of PM discharged from the engine 3 and mapping the result according to the engine speed NE and the fuel injection amount QINJ. The fuel injection amount QINJ is determined by searching a fuel injection amount map (not shown) according to the engine speed NE and the accelerator pedal opening AP.

  Next, the PM natural regeneration amount QRN in the filter 18 is calculated (step 2). Here, the natural regeneration of the filter 18 is contrasted with the forced regeneration executed in this process, and a part of the PM accumulated on the filter 18 during the operation of the engine 3 that is not performing the forced regeneration. It means burning and disappearing.

  FIG. 4 shows a subroutine for calculating the natural reproduction amount QRN. First, in step 21, the filter temperature TDPF is calculated. This filter temperature TDPF represents the internal temperature of the filter 18, and the intake air amount QA, pre-filter gas temperature TDPFG, filter differential pressure DP, vehicle speed VP, etc. Depending on the requirements.

  Next, a basic value QRNBASE of the natural regeneration amount QRN is calculated by searching a corresponding map (not shown) according to the calculated filter temperature TDPF (step 22). As the temperature of the filter 18 is higher, natural regeneration is more likely to be performed and the amount of natural regeneration tends to increase. Therefore, in this map, the basic value QRNBASE is set to a larger value as the filter temperature TDPF is higher. Yes.

  Next, an oxygen amount correction coefficient KO2 is calculated (step 23). The oxygen amount correction coefficient KO2 is calculated by searching a corresponding map (not shown) according to the oxygen amount QO2DPF supplied to the filter 18. Since the amount of natural regeneration tends to increase as the amount of oxygen in the filter 18 increases, in this map, the oxygen amount correction coefficient KO2 is set to a larger value as the oxygen amount QO2DPF increases. The oxygen amount QO2DPF is determined according to the fuel injection amount QINJ and the intake air amount QA.

  Next, a deposition amount correction coefficient KDEPO is calculated (step 24). The accumulation amount correction coefficient KDEPO is calculated by searching a corresponding map (not shown) according to the PM accumulation amount integrated value SQPMDPF. This PM accumulation amount integrated value SQPMDPF is calculated as described later, and represents the accumulation amount of PM accumulated on the filter 18 at that time. As the amount of PM accumulated in the filter 18 increases, the natural regeneration amount tends to increase. Therefore, in this map, the accumulation amount correction coefficient KDEPO has a larger value as the PM accumulation amount integrated value SQPMDPF increases. Is set.

  Next, a CRT correction term QRNCRT is calculated (step 25). When the oxidation catalyst 17 is arranged on the upstream side of the filter 18 as in this embodiment, NO2 generated by oxidation in the oxidation catalyst 17 flows into the filter 18 and acts as an oxidant. Compared with the case where only O2 is present as an oxidizing agent, an effect that PM is burned at a lower temperature and natural regeneration is promoted (hereinafter referred to as “CRT effect”) is recognized. The CRT correction term QRNCRT corresponds to the natural regeneration amount due to the CRT effect. The engine speed NE, the fuel injection amount QINJ, the pre-catalyst gas temperature TCATG, the filter temperature TDPF calculated in the above step 21, and the PM accumulation amount It is calculated according to the integrated value SQPMDPF.

  Next, the natural regeneration amount QRN is calculated by multiplying the basic value QRNBASE by the oxygen amount correction coefficient KO2 and the deposition amount correction coefficient KDEPO and adding the CRT correction term QRNCRT using the parameters calculated in steps 22 to 25. (Step 26), and this subroutine is completed.

  Returning to FIG. 3, in step 3 following step 2 described above, it is determined whether or not the exhaust gas temperature sensor abnormality flag F_SETNG is “1”. This exhaust gas temperature sensor abnormality flag F_SETNG is set in the abnormality determination process of the exhaust gas temperature sensor shown in FIG. First, in step 31, it is determined whether or not the first exhaust gas temperature sensor 33 or the second exhaust gas temperature sensor 34 is abnormal.

  This determination is performed as follows, for example. That is, the detection signal of the first exhaust gas temperature sensor 33 is constantly monitored, and when the state in which the voltage value of the detection signal is substantially equal to the upper limit value or the lower limit value of the output range continues for a predetermined time or longer, the ECU 2 It is determined that an abnormality has occurred in the first exhaust gas temperature sensor 33 due to a short circuit or disconnection. The determination by the same method is also performed for the second exhaust gas temperature sensor 34, and the presence or absence of the abnormality is determined.

  Alternatively, the difference between the pre-catalyst gas temperature TCATG and the pre-filter gas temperature TDPFG detected by the first and second exhaust gas temperature sensors 33 and 34 during the fuel cut operation of the engine 3 is obtained, and this difference is larger than a predetermined value. Sometimes, both the temperature sensors 33 and 34 may determine that both are abnormal.

  As a result of the above determination, when the answer to step 31 is YES and at least one of the temperature sensors 33 and 34 is abnormal, the exhaust gas temperature sensor abnormality flag F_SETNG is set to “1” (step 32). On the other hand, if the answer to step 31 is NO and both the temperature sensors 33 and 34 are normal, the exhaust gas temperature sensor abnormality flag F_SETNG is set to “0” (step 33), and this process ends.

  Returning to FIG. 3, when the answer to step 3 is YES, the natural regeneration amount QRN calculated in step 2 is reset to 0 (step 4), and the process proceeds to step 5. On the other hand, when the answer to step 3 is NO, step 4 is skipped and the process proceeds to step 5.

  In this step 5, the PM accumulation amount QPMDPF per 1 TDC deposited on the filter 18 is calculated by subtracting the natural regeneration amount QRN calculated in step 2 or 4 from the PM emission amount QEX calculated in step 1. As is apparent from the above, the PM accumulation amount QPMDPF is obtained by subtracting the natural regeneration amount QRN from the PM emission amount QEX when the first and second exhaust gas temperature sensors 33 and 34 are both normal, that is, the natural regeneration amount. It is obtained as a value corrected by QRN. On the other hand, when it is determined that at least one of the temperature sensors 33 and 34 is abnormal, the natural regeneration amount QRN is reset to a value of 0 in step 4, whereby the PM accumulation amount QPMDPF is set to the PM discharge amount QEX, Correction by the reproduction amount QRN is substantially prohibited.

  Next, by adding the PM accumulation amount QPMDPF calculated in step 5 to the PM accumulation amount integrated value SQPMDPF obtained so far, the current PM accumulation amount SQPMDPF is calculated and stored in the EEPROM of the ECU 2. Store (step 6). This PM accumulated amount integrated value SQPMDPF is reset to the value 0 when the regeneration of the filter 18 is completed, and therefore represents the accumulated amount of PM deposited on the filter 18 at that time.

  Next, it is determined whether or not the calculated PM accumulation amount integrated value SQPMDPF is equal to or greater than a predetermined threshold value SQREF (step 7). If the answer is NO and SQPMDPF <SQREF, the accumulation amount of PM in the filter 18 is still small, so that the regeneration operation flag F_REON is set to “0”, assuming that the regeneration operation is not performed (step 8). Exit.

  On the other hand, if the answer to step 7 is YES and the PM accumulation amount integrated value SQPMDPF reaches the threshold value SQREF, the regeneration execution flag F_REON is set to “1” to start the regeneration operation (step 9), This process ends.

  When the regeneration execution flag F_REON is set to “1” in this way, post injection for injecting fuel into the combustion chamber 3c during the expansion stroke or exhaust stroke of the engine 3 is executed. In addition to the post-injection, the pre-filter gas temperature TDPFG is set to the target temperature (for example, 600 ° C.) by performing control for decreasing the throttle valve opening and EGR gas amount, and control for increasing the supercharging pressure. To control. Accordingly, the filter 18 is forcibly regenerated by controlling the filter 18 to a high temperature state and burning the accumulated PM.

  This regeneration operation is terminated when the PM accumulation amount integrated value SQPMDPF becomes smaller than a predetermined determination value, and the PM accumulated on the filter 18 is sufficiently burned and the regeneration is appropriately performed. The

  As described above, according to the present embodiment, the natural regeneration amount QRN of PM that is naturally regenerated by the filter 18 is determined based on the pre-catalyst gas temperatures TCATTG and DPF before detected by the first and second exhaust gas temperature sensors 33 and 34. It is calculated according to the temperature TDPFG or the like, and this natural regeneration amount QRN is subtracted from the PM emission amount QEX to be corrected. Accordingly, the PM accumulation amount integrated value SQPMDPF representing the PM accumulation amount in the filter 18 at that time can be appropriately calculated, and therefore the filter 18 is appropriately regenerated based on the calculated PM accumulation amount integrated value SQPMDPF. be able to.

  When it is determined that at least one of the first and second exhaust gas temperature sensors 33, 34 is abnormal, the natural regeneration amount QRN is set to a value of 0, and the subtraction of the natural regeneration amount QRN from the PM emission amount QEX is substantially reduced. Since the correction of the PM accumulation amount QPMDPF is prohibited, the PM accumulation amount integrated value SQPMDPF is not calculated too small and is calculated on the safe side. Therefore, the filter 18 can be properly regenerated while reliably avoiding the excessive accumulation of PM on the filter 18.

  In the above-described embodiment, the abnormality of the first and second exhaust gas temperature sensors 33 and 34 is determined as a device that affects the accuracy of estimation of the PM accumulation amount in the filter 18, but instead of this, At the same time, abnormality may be determined for devices other than the sensors 33 and 34, and subtraction correction of the PM emission amount QEX by the natural regeneration amount QRN may be prohibited according to the determination result. For example, as described above, the natural regeneration amount QRN is calculated using not only the pre-catalyst gas temperature TCATG and the pre-DFF gas temperature TDPFG, but also the parameters such as the filter differential pressure DP, the intake air amount QA, the accelerator opening AP, the vehicle speed VP, and the like. Therefore, the abnormality of the differential pressure sensor 40, the airflow sensor 31, the accelerator opening sensor 35, and the vehicle speed sensor 41 that detect these parameters may be determined, thereby obtaining the same effect as the embodiment. be able to.

  Further, as described above, the calculation of the PM emission amount QEX is performed by correcting the map value of the PM emission amount with parameters such as the engine water temperature TW, the atmospheric pressure PA, the intake air temperature TA, and the atmospheric temperature TAA. That is, the engine water temperature sensor 29, the atmospheric pressure sensor 36, the intake air temperature sensor 32, the atmospheric temperature sensor 42, and the like that detect these parameters have an influence on the calculation result of the PM emission amount QEX, and thus the accuracy of the PM accumulation amount integrated value SQPMDPF. It is an effect device. Therefore, abnormality may be determined for at least one of these devices, and subtraction correction using the natural reproduction amount QRN may be prohibited according to the determination result. Thereby, even when an abnormality occurs in these devices, the possibility of excessively calculating the particulate deposition amount is reduced, and therefore the same effect as that of the embodiment can be obtained.

  Further, the amount of PM actually discharged from the engine 3 is directly related to the combustion state of the engine 3. The fuel injection amount QINJ, the intake air amount QA, the EGR amount, the presence or absence of cooling of the EGR gas, the supercharging pressure It varies depending on the strength of PACT and swirl. That is, the injector 6, the high pressure pump 6 a, the fuel pressure sensor 37, the throttle valve 12, the EGR device 14, the EGR cooling device 15, the supercharging device 7, the swirl device 13, etc. that control these are actually discharged from the engine 3. It is a device that affects the accuracy of the PM emission amount, and consequently the PM accumulation amount integrated value SQPMDPF. Therefore, abnormality may be determined for at least one of these devices, and subtraction correction using the natural reproduction amount QRN may be prohibited according to the determination result. Thereby, even when an abnormality occurs in these devices, the possibility of excessively calculating the particulate deposition amount is reduced, and therefore the same effect as that of the embodiment can be obtained.

  Further, when the EEPROM of the ECU 2 is abnormal, it affects the accuracy of the accumulated PM accumulation amount SQPMDPF stored therein, or when the input interface of the ECU 2 is abnormal, the detection signal from the sensor is not properly input. Since it affects the accuracy of the PM emission amount QEX and the natural regeneration amount QRN, and consequently the accuracy of the PM accumulation amount integrated value SQPMDPF, an abnormality in the ECU 2 may be determined. Further, when abnormality such as perforation occurs in the filter 18, a part of the PM discharged from the engine 3 is not accumulated on the filter 18, and this also affects the accuracy of the PM accumulation amount integrated value SQPMDPF. The abnormality may be determined.

  If the configuration of the engine 3 and the parameters for calculating the PM emission amount QEX and the natural regeneration amount QRN are different from those in the embodiment, other devices that affect the accuracy of the PM accumulation amount integrated value SQPMDPF are Of course, abnormality determination may be performed as a target.

  Further, when the first or second exhaust gas temperature sensor 33, 34 is determined to be abnormal, correction by the natural regeneration amount QRN is prohibited, and a filter is used when the PM accumulated amount integrated value SQPMDPF becomes equal to or greater than the threshold value SQREF. However, the regeneration operation of the filter 18 may be prohibited together with the prohibition of correction by the natural regeneration amount QRN. In that case, for example, the calculation of the PM accumulation amount integrated value SQPMDPF is continued, and when the value becomes equal to or greater than the threshold value SQREF, the warning lamp 43 is blinked or lit to cause the driver to perform high-load driving or the like. By promoting the natural regeneration of the filter 18, it is possible to avoid the excessive accumulation state of PM.

  In the embodiment, the natural regeneration amount QRN is used as the natural regeneration amount parameter representing the natural regeneration amount of PM and is subtracted from the PM emission amount QEX. However, a correction coefficient less than 1.0 is set and PM The discharge amount QEX may be multiplied. Furthermore, in the embodiment, fuel post injection is performed as the regeneration operation of the filter 18, but the method is arbitrary, and it is needless to say that the regeneration operation may be performed without using the post injection.

  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 view schematically showing an exhaust gas purification apparatus to which the present invention is applied together with an internal combustion engine. It is a figure which shows a part of exhaust gas purification apparatus. It is a flowchart which shows the reproduction | regeneration control processing of a filter. It is a flowchart which shows the calculation subroutine of natural reproduction | regeneration amount. It is a flowchart which shows the abnormality determination process of an exhaust gas temperature sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2 ECU (Emission amount calculation means, Natural regeneration amount parameter calculation means, Deposit amount estimation means,
Filter regeneration means, abnormality determination means, correction prohibition means)
3 Internal combustion engine
5 Exhaust pipe (exhaust system)
6 Injector (filter regeneration means)
18 Filter 33 First exhaust gas temperature sensor (device)
34 Second exhaust gas temperature sensor (device)
QEX PM emissions (particulate emissions)
QRN Natural regeneration amount (natural regeneration amount parameter)
QPMDPF PM deposition amount (particulate deposition amount)
SQPMDPF PM accumulation amount integrated value (particulate accumulation amount)
SQREF threshold

Claims (1)

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;
An emission amount calculating means for calculating an emission amount of particulates discharged from the internal combustion engine;
A natural regeneration amount parameter calculating means for calculating a natural regeneration amount parameter representing the natural regeneration amount of the particulate naturally reproduced by the filter;
A deposit amount estimating means for estimating a deposit amount of the particulate deposited on the filter by correcting the calculated particulate discharge amount to a decreasing side by the calculated natural regeneration amount parameter;
Filter regeneration means for forcibly regenerating the filter by burning the particulate deposited on the filter when the estimated particulate accumulation amount reaches a predetermined threshold;
An abnormality determining means for determining an abnormality of the device affecting the accuracy of estimation of the amount of accumulated particulates deposited on the filter;
When the device is determined to be abnormal, a correction prohibiting unit that prohibits correction of the particulate discharge amount by the accumulation amount estimating unit;
An exhaust gas purifying device for an internal combustion engine, comprising:

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