JP2012036764A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of regenerating a filter at an appropriate timing.SOLUTION: An ECU calculates a PM generation amount based on the number of engine revolutions and a fuel injection amount from a fuel injection valve, and calculates an amount of PM accumulated so far from previous catalyst regeneration control as an estimated accumulation amount (Step S11). When it is determined that the estimated accumulation amount exceeds a predetermined value (YES in Step S12), the ECU performs catalyst regeneration control. Then, the ECU calculates a temperature difference ΔT between an upstream end and a downstream end of a PM filter 44 based on an exhaust gas amount Ga and exhaust temperature T6, and calculates an unburnt PM amount based on the temperature difference ΔT and a floor temperature at the downstream end of the PM filter 44 (Step S14). And then the ECU 100 subtracts the unburnt PM amount from the predetermined value (Step S15).

Description

  The present invention relates to an exhaust purification device, and more particularly to an exhaust purification device that performs regeneration of a catalytic function by adding fuel to exhaust gas.

  Conventionally, in a vehicle equipped with an internal combustion engine, a NOx occlusion reduction type catalyst for storing nitrogen oxide (NOx) contained in exhaust gas exhausted from the internal combustion engine, or hydrocarbon (HC) or carbon monoxide ( The exhaust pipe is provided with a catalytic converter including an oxidation catalyst that oxidizes (CO) and a particulate filter (hereinafter referred to as PM filter) for capturing PM (Particulate Matter).

  When NOx is occluded as the NOx occlusion reduction catalyst is used, the function as a catalyst is lowered. Therefore, it is necessary to execute regeneration control for decomposing the stored NOx and regenerating the function of the catalyst. As the regeneration control, for example, a reducing agent such as fuel is injected into the exhaust passage by an injector as a fuel addition valve provided in the exhaust pipe, and the exhaust gas mixed with the fuel is supplied to the NOx occlusion reduction type catalyst. (For example, refer to Patent Document 1).

  Further, since the NOx storage reduction catalyst also stores sulfur oxide (SOx) together with NOx, fuel is supplied to the NOx storage reduction catalyst, and the NOx storage reduction catalyst is heated to a high temperature to decompose SOx. ing.

  On the other hand, the PM filter needs to be appropriately subjected to regeneration control because PM accumulates inside and increases the passage resistance with use. As regeneration control, for example, a method is proposed in which a hydrocarbon-based liquid such as fuel is introduced into a PM filter to cause an exothermic reaction, and PM is burned off by the generated heat.

  An exhaust emission control device having an injector for performing regeneration control for the PM filter estimates the amount of PM accumulated in the PM filter, and when this estimated amount of accumulation reaches a predetermined value, the PM Playback control for the filter is started. As a predetermined value of the estimated accumulation amount for starting the regeneration control for the PM filter, the PM filter is overheated during regeneration due to excessive accumulation of PM on the PM filter, and the durability of the PM filter is increased. It is set to a value that prevents the drop.

  However, the bed temperature of the PM filter is not always constant inside. For example, since the exhaust gas heated by the combustion of PM flows to the downstream end, the bed temperature at the downstream end becomes higher than that at the upstream end. Moreover, the degree of PM combustion decreases as the bed temperature of the PM filter decreases. For this reason, there is a possibility that PM remains unburned in the low temperature part of the PM filter even though the regeneration control for the PM filter is executed.

  Therefore, an exhaust emission control device that corrects the estimated accumulation amount of PM in the PM filter and executes regeneration control based on the corrected estimated accumulation amount is known (for example, see Patent Document 2).

  The conventional exhaust purification device described in Patent Document 2 estimates a temperature difference between a low temperature part and a high temperature part of the PM filter based on the exhaust flow rate, and burns in the low temperature part of the PM filter based on this temperature difference. The amount of unburned PM is calculated, and the timing for starting the next regeneration control is corrected according to the amount of unburned fuel.

  As a result, an error between the actual PM accumulation amount and the estimated accumulation amount in the PM filter is reduced, and a decrease in durability due to an excessive temperature rise state of the PM filter is prevented.

JP 2007-64182 A JP 2008-169770 A

  However, in the conventional exhaust emission control device described in Patent Document 2 as described above, the temperature difference between the high temperature portion and the low temperature portion of the PM filter is calculated from the exhaust flow rate, but the high temperature of the PM filter is high. The factor that changes the temperature difference between the hot and cold parts is not considered enough.

  Therefore, for example, when an error occurs in the estimated value of the temperature in the low temperature part of the PM filter, there is a possibility that an error occurs in the estimated remaining amount of combustion, and the actual accumulation amount of PM deposited in the low temperature part of the PM filter There was a possibility that the estimated deposition amount did not agree well. Therefore, there is a possibility that regeneration control for the PM filter is not performed at an appropriate timing.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide an exhaust purification device capable of regenerating a filter at an appropriate timing.

  In order to achieve the above object, an exhaust emission control device according to the present invention includes (1) a filter that is installed in an exhaust passage of an internal combustion engine and collects particulate matter of exhaust gas discharged from the internal combustion engine; A fuel addition valve capable of adding fuel; and when the amount of particulate matter deposited on the filter exceeds a predetermined value, the fuel addition valve is controlled to control the fuel addition valve. In the exhaust gas purification apparatus for regenerating the filter by adding the fuel to exhaust gas, the temperature difference calculating means for calculating the temperature difference between the upstream end portion and the downstream end portion of the filter, and the temperature difference calculating means A non-burning amount calculating means for calculating the unburned amount of particulate matter in the filter based on the temperature difference and the bed temperature of the filter, and a non-burning amount calculated by the unburned amount calculating means. Flip characterized in that it comprises a correction means for correcting the timing of reproducing the filter.

  With this configuration, since the temperature difference between the upstream end portion and the downstream end portion of the filter can be accurately estimated, the amount of unburned particulate matter in the filter can be accurately estimated. Therefore, the timing of regeneration control for the filter is optimized, and this is caused by excessive temperature rise of the filter that occurs when the regeneration control is executed in a state where the particulate matter is excessively accumulated or unnecessary regeneration control. Reduction in fuel consumption can be suppressed.

  According to the present invention, it is possible to provide an exhaust emission control device that can regenerate a filter at an appropriate timing.

1 is a schematic configuration diagram showing a vehicle equipped with an exhaust emission control device according to an embodiment of the present invention. It is a schematic block diagram which shows the structure of the exhaust gas purification device which concerns on embodiment of this invention, and its periphery. It is a schematic block diagram which shows the structure of the addition injector which concerns on embodiment of this invention. It is a temperature difference calculation map which concerns on this Embodiment. It is a burnout amount calculation map which concerns on embodiment of this invention. It is a flowchart for demonstrating the reproduction | regeneration control correction | amendment process which concerns on embodiment of this invention. It is a figure which shows the bed temperature rise behavior of PM filter which concerns on embodiment of this invention. 5 is a correction amount calculation map according to the embodiment of the present invention.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the present embodiment, the case where the exhaust emission control device according to the present invention is applied to a vehicle 1 equipped with a four-cylinder diesel engine will be described.

  As shown in FIG. 1, the engine 10 includes a cylinder head 12 and a cylinder block (not shown), and the cylinder head 12 and the cylinder block form four cylinders 11. In each cylinder 11, a combustion chamber 11a is defined by a piston.

  The cylinder head 12 is provided with four fuel injection valves 13 for injecting fuel into the four combustion chambers 11a.

  The fuel injection valve 13 is connected to a common rail 14 that stores high-pressure fuel, and the common rail 14 is connected to a high-pressure fuel pump 16 that discharges fuel supplied from the fuel tank 15 as high-pressure fuel.

  The high-pressure fuel pump 16 is provided with a check valve on the discharge side to prevent the backflow of fuel from the common rail 14 to the high-pressure fuel pump 16. The high-pressure fuel supplied from the high-pressure fuel pump 16 to the common rail 14 is injected from the fuel injection valve 13 into the corresponding combustion chamber 11a by opening the fuel injection valve 13 based on the rotation angle of a crankshaft (not shown).

  The vehicle 1 further includes a low-pressure fuel pump 27 that sucks fuel stored in the fuel tank 15 via the fuel filter 28 and pumps the fuel to the fuel pressure regulator 26. The fuel tank 15 is configured by a known fuel tank that stores hydrocarbon fuel such as light oil.

  The fuel pressure regulator 26 returns a part of the fuel discharged from the low-pressure fuel pump 27 to the fuel tank 15 when the pressure of the fuel discharged from the low-pressure fuel pump 27, that is, the fuel pressure becomes higher than a predetermined set value. It is like that.

  Further, a fuel branching portion 29 is installed between the fuel pressure regulator 26 and the high pressure fuel pump 16, and a part of the fuel discharged from the low pressure fuel pump 27 is supplied to an addition injector 41 described later. It is like that.

  The cylinder head 12 is provided with an intake manifold 17 for introducing intake air into each combustion chamber 11a. The intake manifold 17 has an intake valve (not shown) for introducing intake air into each combustion chamber 11a. is doing. An intake pipe 20 is connected to the intake manifold 17. The air cleaner 21, the compressor wheel 22 a of the turbo unit 22, and an intercooler 23 for cooling the intake air are sequentially connected to the intake pipe 20 from the upstream side of the intake air. And an electric intake throttle valve 24 for adjusting the intake air amount. The air sucked into the intake manifold 17 through the intake pipe 20 is introduced into the combustion chamber 11a when the intake valve is opened according to the rotation angle of a crankshaft (not shown).

  Further, the cylinder head 12 is provided with an exhaust manifold 18 for exhausting the exhaust gas generated in each combustion chamber 11a. The exhaust manifold 18 is shown for exhausting the exhaust gas from each combustion chamber 11a. An exhaust valve is not provided. The exhaust gas generated in each combustion chamber 11a is exhausted to the exhaust manifold 18 when the exhaust valve is opened according to the rotation angle of a crankshaft (not shown).

  An exhaust gas recirculation (EGR) device 30 for recirculating exhaust gas is connected to the exhaust manifold 18. The EGR device 30 includes a communication pipe 31 that communicates the intake manifold 17 and the exhaust manifold 18, an EGR cooler 32 that is disposed in the middle of the communication pipe 31, and an electric EGR valve 33. The EGR device 30 cools a part of the exhaust gas discharged to the exhaust manifold 18 by the EGR cooler 32 and recirculates it to the intake manifold 17. An ECU (Electronic Control Unit) 100, which will be described later, controls the amount of exhaust gas recirculated by controlling the opening degree of the EGR valve 33.

  An exhaust pipe 45 is connected to the exhaust manifold 18, and a turbine wheel 22 b of the turbo unit 22 and a catalyst device 42 are disposed in the exhaust pipe 45 in order from the exhaust manifold 18 side.

  The turbo unit 22 includes a turbine wheel 22b that rotates by exhaust flowing through the exhaust passage 46, a compressor wheel 22a that is disposed in the intake passage 19, and a rotor shaft 22c that connects the turbine wheel 22b and the compressor wheel 22a. . When the turbine wheel 22b is rotated by the exhaust gas discharged from the combustion chamber 11a, this rotation is transmitted to the compressor wheel 22a via the rotor shaft 22c. Thereby, the engine 10 sends not only the negative pressure generated according to the movement of the piston but also the intake air to the combustion chamber 11a by the rotation of the compressor wheel 22a.

  Further, the turbo unit 22 surrounds the outer periphery of the turbine wheel 22b and has an exhaust path along the rotation direction of the turbine wheel 22b. The exhaust gas passes through this exhaust path and is blown onto the turbine wheel 22b. In the exhaust path, a plurality of nozzle vanes 22d are rotatably provided with respect to the ring-shaped nozzle back plate 22e.

  Further, the vehicle 1 includes an actuator 58 for opening and closing the plurality of nozzle vanes 22d at the same time. The ECU 100 drives the actuator 58 so that the flow area of the exhaust path is changed to control the opening degree of the nozzle vane 22d, that is, the VN opening degree, thereby making the flow rate of the exhaust gas sprayed to the turbine wheel 22b variable. . Thereby, the rotational speed of the turbine wheel 22b is adjusted, and the intake air to the combustion chamber 11a is supplied at a predetermined supercharging pressure.

  In the exhaust pipe 45, an addition injector 41 connected to the low pressure fuel pump 27 is disposed upstream of the catalytic converter 43. The addition injector 41 injects fuel as a reducing agent and adds it to the exhaust gas. Here, the addition injector 41 according to the present embodiment constitutes a fuel addition valve according to the present invention.

  The catalyst device 42 includes a catalytic converter 43 and a catalyst-carrying PM filter 44. The catalytic converter 43 includes an oxidation catalyst that oxidizes hydrocarbons (HC) and carbon monoxide (CO), and a NOx occlusion-type NOx catalyst. For example, when the exhaust gas in the lean state of the air-fuel ratio flows through the inside, NOx contained in the exhaust gas is occluded. On the other hand, when the exhaust gas in the rich air-fuel ratio flows inside, the stored NOx reacts with hydrocarbons and carbon monoxide contained in the exhaust gas, and the exhaust gas is purified by decomposing it into nitrogen, carbon dioxide, and water. It is supposed to be.

  The PM filter 44 is configured by a monolith type or pellet type filter, and collects particulates (hereinafter referred to as PM) contained in the exhaust gas. The PM filter 44 is also provided with the above-described storage-type NOx catalyst, and the PM trapped by the PM filter 44 is oxidized and removed by the oxidizing action of the catalyst.

  As shown in FIG. 2, the vehicle 1 includes an ECU 100 as an electronic control device. The ECU 100 includes a CPU (Central Processing Unit) 100a, a RAM (Random Access Memory) 100b, a ROM (Read Only Memory) 100c, an EEPROM (Electrically Erasable and Programmable Read Only Memory), which are connected to each other via a bidirectional bus. Trademark) 100d, an input port 100e, an output port 100f, and the like.

  The CPU 100a uses the temporary storage function of the RAM 100b to perform signal processing in accordance with programs stored in the ROM 100c and data stored in the EEPROM 100d in advance, thereby performing various controls such as output control of the engine 10 and catalyst regeneration control described later. Is supposed to run. Therefore, ECU 100 according to the present embodiment constitutes an exhaust purification device according to the present invention.

  The vehicle 1 also includes an engine speed sensor 52 that measures the speed of the engine 10, an intake air quantity sensor 53 that measures the intake air quantity of the engine 10, and an intake air that measures the temperature of the air taken into the engine 10. An air temperature sensor 54, an atmospheric pressure sensor 55, a throttle valve sensor 39 for measuring the opening of the intake throttle valve 24, and an accelerator opening sensor 37 for detecting the accelerator opening are provided. The sensor is connected to the input port 100e of the ECU 100.

  The engine rotational speed sensor 52 measures the rotational speed per unit time of the crankshaft and outputs the measured rotational speed to the ECU 100 as the engine rotational speed. The intake air amount sensor 53 is provided between the air cleaner 21 and the compressor wheel 22a in the intake pipe 20, and outputs a signal corresponding to the intake air amount in the intake pipe 20 to the ECU 100. The intake air temperature sensor 54 is provided between the air cleaner 21 and the compressor wheel 22a in the intake pipe 20, and outputs a signal corresponding to the intake air temperature that is the temperature of intake air in the intake pipe 20 to the ECU 100. .

  The atmospheric pressure sensor 55 is provided between the air cleaner 21 and the compressor wheel 22a in the intake pipe 20, and outputs a signal corresponding to the atmospheric pressure to the ECU 100. The throttle valve sensor 39 is configured by a Hall element that can obtain an output voltage corresponding to the opening degree of the intake throttle valve 24, and outputs a signal representing the opening degree of the intake throttle valve 24 to the ECU 100.

  The accelerator opening sensor 37 is composed of an electronic position sensor using a hall element. When the accelerator pedal mounted on the vehicle 1 is operated by the driver, the accelerator opening sensor 37 indicates the accelerator opening indicating the position of the accelerator pedal. A signal to be expressed is output to the ECU 100.

  The vehicle 1 further includes an exhaust temperature sensor 61 that detects an exhaust temperature T6 upstream of the catalytic converter 43, an exhaust gas amount sensor 62 that detects an exhaust gas amount Ga, and a PM filter 44 at the downstream end of the PM filter 44. A catalyst bed temperature sensor 63 for detecting the bed temperature and an air-fuel ratio sensor 64 installed on the downstream side of the PM filter 44 are provided, and these sensors are connected to an input port 100 e of the ECU 100. The exhaust temperature T6 may be estimated from the operating conditions of the engine 10. The air-fuel ratio sensor 64 may be installed on the upstream side of the PM filter 44.

  The output port 100f of the ECU 100 is connected to a solenoid or actuator for adjusting the opening degree of the fuel injection valve 13, the high pressure fuel pump 16, the intake throttle valve 24, the low pressure fuel pump 27, the EGR valve 33, the addition injector 41, and the like. ing. The ECU 100 calculates a command value for each solenoid or actuator, for example, a fuel injection amount for the fuel injection valve 13 or a fuel addition amount for the addition injector 41, based on the signal input from each sensor described above, and sets the command value. A corresponding command signal is output from the output port 100f to each solenoid or actuator.

  Then, the ECU 100 performs fuel injection timing control and injection amount control using the fuel injection valve 13, and performs intake air amount control and EGR amount control using the intake throttle valve 24 and the EGR valve 33. It has become.

  In the PM filter 44, the pressure loss in the PM filter 44 increases as the amount of accumulated PM increases. Therefore, as part of the catalyst regeneration control, the ECU 100 executes PM removal control for purifying the accumulated PM by combustion when the PM accumulation amount increases.

  Specifically, when the ECU 100 determines that the amount of PM accumulated on the PM filter 44 exceeds a predetermined value, the ECU 100 executes fuel addition by the addition injector 41 and performs an oxidation reaction of the fuel on the catalyst of the PM filter 44. To advance. As a result, the catalyst bed temperature of the PM filter 44 rises to 600 ° C. to 700 ° C. by the reaction heat of the oxidation reaction, and the PM deposited on the PM filter 44 is combusted.

  In addition, as a part of the catalyst regeneration control, the ECU 100 further determines the S poisoning for reducing the SOx stored in the catalytic converter 43 when it is determined that the stored amount of SOx in the catalytic converter 43 exceeds a predetermined value. Recovery control is executed, or NOx reduction control is executed when it is determined that the amount of NOx stored in the catalytic converter 43 exceeds a predetermined value.

  The addition injector 41 is attached to the exhaust pipe 45 so that the tip portion projects into the exhaust passage 46. As shown in FIG. 3, the addition injector 41 includes a metal housing 66 formed in a substantially cylindrical shape, and a needle valve 67 slidably provided in the housing 66.

  The housing 66 includes a cylindrical sleeve 69 that accommodates the needle valve 67 and a sack portion 70 that forms a hollow hemisphere. Further, a valve seat 68 on which the tip of the needle valve 67 is seated is formed on the inner peripheral portion of the tip of the housing 66.

  Part of the fuel discharged from the low-pressure fuel pump 27 is introduced into the internal space of the sack portion 70. An injection hole 71 that connects the internal space of the sack portion 70 and the exhaust passage 46 is formed at the tip portion of the sack portion 70.

  The needle valve 67 is connected to a solenoid, and while the ECU 100 is energized, the needle valve 67 is separated from the valve seat 68 so that fuel is added to the exhaust passage 46.

  The ECU 100 controls the addition injector 41 to add fuel to the exhaust passage 46, thereby reducing and releasing NOx occluded in the catalytic converter 43 and burning out the PM collected by the PM filter 44. Control is executed, and the catalyst functions of the catalytic converter 43 and the PM filter 44 are restored by this catalyst regeneration control.

  When the ECU 100 determines that the estimated integrated amount of PM calculated in this way exceeds a predetermined value, the ECU 100 supplies fuel to the exhaust passage 46 from the addition injector 41 and executes catalyst regeneration control.

  By the way, when fuel is added from the addition injector 41 in the catalyst regeneration control, the PM filter 44 generates heat from the upstream end portion on the added fuel and exhaust gas and the hydrocarbon component remaining in the exhaust gas. The bed temperature becomes higher as it goes from the upstream end to the downstream end, and a temperature difference occurs between the upstream end and the downstream end. Therefore, when the ECU 100 executes the catalyst regeneration control based on the signal input from the catalyst bed temperature sensor 63 installed at the downstream end of the PM filter 44, the actual bed temperature at the upstream end of the PM filter 44 is detected. If there is an error in the estimated temperature, there is a possibility that PM will remain at the upstream end of the PM filter 44.

  Therefore, in the present embodiment, the ECU 100 improves the estimation accuracy of the bed temperature at the upstream end of the PM filter 44 as described below, and reduces the error between the estimated accumulation amount of PM and the actual accumulation amount as compared with the prior art. Then, regeneration control correction processing for making the timing of catalyst regeneration control appropriate is executed.

  In the regeneration control correction process, the ECU 100 determines whether or not the estimated accumulation amount of PM accumulated after the previous fuel addition by the addition injector 41 exceeds a predetermined value.

  The estimated accumulation amount of PM is calculated based on a signal representing the engine speed input from the engine speed sensor 52 and the fuel injection amount from the fuel injection valve 13. Further, the predetermined value is a value that does not cause the PM filter 44 to be overheated due to combustion of excessively accumulated PM when fuel is added by the addition injector 41, and unnecessary fuel. A value that can suppress a decrease in fuel consumption due to the addition is set.

  When it is determined that the estimated amount of PM exceeds a predetermined value, the ECU 100 controls the addition injector 41 to add fuel to the exhaust passage 46 for a predetermined time.

  Further, when fuel is added by the addition injector 41 and PM burns, the ECU 100 calculates the unburned amount of PM remaining unburned at the upstream end of the PM filter 44 or in the vicinity thereof.

  In calculating the PM unburned amount, the ECU 100 acquires the exhaust temperature T6 and the exhaust gas amount Ga from the exhaust temperature sensor 61 and the exhaust gas amount sensor 62, respectively.

  Then, the ECU 100 calculates the temperature difference ΔT between the upstream end portion and the downstream end portion of the PM filter 44 with reference to the temperature difference calculation map stored in advance in the ROM 100c. As shown in FIG. 4, the temperature difference calculation map is a map in which an index obtained by dividing the exhaust gas amount Ga by the exhaust temperature T6 is associated with the temperature difference ΔT between the upstream end portion and the downstream end portion of the PM filter 44. There is a tendency that the larger the index, the larger the temperature difference ΔT. The relationship between this index and the temperature difference ΔT is obtained in advance by experimental measurement. Therefore, the ECU 100 constitutes a temperature difference calculation means according to the present invention.

  Further, the ECU 100 applies the PM filter 44 to the PM filter 44 in this fuel addition based on the temperature difference ΔT calculated as described above and the bed temperature at the downstream end of the PM filter 44 input from the catalyst bed temperature sensor 63. The remaining amount of remaining PM is calculated.

  The unburned amount of PM is acquired by referring to a unburned amount calculation map stored in advance in the ROM 100c. As shown in FIG. 5, this unburned amount calculation map is composed of a three-dimensional map in which the temperature difference ΔT and the bed temperature at the downstream end during regeneration of the PM filter 44 are associated with the unburned amount. As the temperature difference ΔT and the bed temperature at the downstream end of the PM filter 44 are lower, the amount of unburned PM tends to increase. This unburned amount calculation map is obtained in advance by experimental measurement. Therefore, the ECU 100 constitutes a remaining fuel amount calculating means according to the present invention.

  Further, the ECU 100 corrects the execution timing of the catalyst regeneration control by subtracting the unburned amount of PM from a predetermined value as a reference for starting execution of the catalyst regeneration control described above. Therefore, the ECU 100 constitutes correction means according to the present invention. As a result, regardless of the amount of unburned PM, the catalyst regeneration control can be started if the amount of accumulated PM exceeds a predetermined value.

  FIG. 6 is a flowchart for explaining the reproduction control correction process according to the embodiment of the present invention. The following processing is executed at predetermined time intervals by the CPU 100a constituting the ECU 100 and implements a program that can be processed by the CPU 100a.

  First, the ECU 100 calculates an estimated accumulation amount of PM accumulated on the PM filter 44 (step S11). Specifically, the ECU 100 calculates the PM generation amount based on the engine speed and the fuel injection amount from the fuel injection valve 13, and calculates this time to the estimated accumulation amount calculated by the previous regeneration control correction process. The estimated accumulated amount of PM is calculated by adding the generated amount of PM.

  Note that the estimated integrated amount of PM is stored in the RAM 100b. When the engine 10 is stopped, the value stored in the RAM 100b is transferred to the EEPROM 100d.

  Next, the ECU 100 determines whether or not the estimated integrated amount has exceeded a predetermined value (step S12). As described above, the predetermined value is set to a value at which the PM filter 44 does not overheat and the reduction in fuel consumption can be suppressed.

  When ECU 100 determines that the estimated integrated amount exceeds a predetermined value (YES in step S12), the ECU 100 proceeds to step S13. On the other hand, when it is determined that the estimated integrated amount does not exceed the predetermined value (NO in step S12), the process proceeds to RETURN.

  When the ECU 100 proceeds to step S13, the fuel is added to the exhaust passage 46 by the addition injector 41 for a predetermined time to execute the catalyst regeneration control.

  Next, the ECU 100 calculates the unburned amount of PM (step S14). As described above, when the exhaust gas amount Ga and the exhaust temperature T6 are acquired, the calculation of the PM unburned amount is performed by referring to the temperature difference calculation map stored in the ROM 100c and the upstream end portion of the PM filter 44. A temperature difference ΔT with the downstream end is calculated.

  When ECU 100 acquires the bed temperature at the downstream end of PM filter 44, ECU 100 associates the temperature difference ΔT and the bed temperature at the downstream end of PM filter 44 with the remaining amount of unburned PM. By referring to, the amount of unburned PM is calculated.

  Then, the ECU 100 subtracts the unburned amount of PM from the predetermined value (step S15). Thereby, in the next catalyst regeneration control, it is possible to prevent an excessive temperature rise of the PM filter 44 due to the actual accumulated amount of PM exceeding the estimated accumulated amount.

  As described above, the exhaust gas purification apparatus according to the embodiment of the present invention can accurately estimate the temperature difference ΔT between the upstream end portion and the downstream end portion of the PM filter 44. It can be estimated accurately. Therefore, the timing of regeneration control for the PM filter 44 is optimized, and excessive temperature rise of the PM filter 44 that occurs when the catalyst regeneration control is performed in a state where PM is excessively accumulated, or the catalyst regeneration control is performed unnecessarily. The reduction in fuel consumption due to the above can be suppressed.

  In the above description, the case where the ECU 100 subtracts the PM unburned amount from the predetermined value has been described. However, the present invention is not limited to this, and the ECU 100 uses the calculated PM unburned amount for the next catalyst regeneration control. It is good also as an initial value of the estimated integration amount in.

  In the above description, the case where the ECU 100 subtracts the unburned amount of PM from the predetermined value has been described. However, the present invention is not limited to this, and the ECU 100 calculates the unburned amount of PM and the unburned amount of PM. Depending on the amount, the EGR valve 33 may be controlled to change the EGR rate to reduce the PM generation amount. Thereby, even when the amount of unburned PM increases, it is possible to suppress an increase in the frequency of the catalyst regeneration control.

  In the above description, the case where the fuel is added to the exhaust gas by the addition injector 41 has been described. However, the present invention is not limited to this, and the fuel injection valve 13 injects the fuel into the combustion chamber 11a in the expansion stroke. Fuel may be added to the exhaust gas.

  In the above description, the ECU 100 calculates the temperature difference ΔT between the upstream end portion and the downstream end portion of the PM filter 44 based on the exhaust temperature T6 and the exhaust gas amount Ga. However, the present invention is not limited to this. First, the ECU 100 calculates the temperature difference ΔT between the upstream end portion and the downstream end portion of the PM filter 44 based on signals input from exhaust temperature sensors respectively installed on the upstream side and the downstream side of the PM filter 44. It may be.

  In the above description, the case where the ECU 100 calculates the bed temperature at the downstream end of the PM filter 44 based on the signal input from the catalyst bed temperature sensor 63 has been described, but the present invention is not limited to this. The catalyst bed temperature may be estimated based on the amount of heat generated by the PM filter 44 obtained from the amount of hydrocarbons flowing into the PM filter 44 and the exhaust gas amount Ga.

  Further, as will be described below, the ECU 100 may correct the calculation of the remaining amount of burn when noble metals such as platinum coated on the PM filter 44 are distributed so as to have a gradation.

  FIG. 7 shows the temperature distribution inside the PM filter 44, and FIG. 7A shows the temperature distribution when the precious metal coated on the PM filter 44 is uniformly distributed. b) represents the temperature distribution when the noble metal coated on the PM filter 44 has gradation.

  In FIG. 7B, the descriptions of large, medium, and small represent the magnitude of the noble metal loading density. As an example, the noble metal loading density at the upstream end of the PM filter 44 is 4 g / L, and in the central portion. The noble metal loading density is 2 g / L, and the noble metal loading density at the downstream end is 0.5 g / L.

  As shown by the solid line 82 in FIG. 7B, the temperature distribution of the PM filter 44 when the noble metal has gradation is uniformly distributed as the noble metal shown by the solid line 81 in FIG. 7A. Compared with the temperature distribution of the PM filter 44 in this case, the temperature difference ΔT between the upstream end portion and the downstream end portion of the PM filter 44 is substantially equal, but the temperature difference in the vicinity of the upstream end portion becomes large, The bed temperature at the downstream end tends to be higher than when it is uniform.

  Therefore, in the PM filter 44 in which the noble metal has gradation, the amount of unburned PM is reduced as compared with the PM filter 44 in which the noble metal is uniformly distributed.

  Therefore, the ECU 100 calculates the correction amount A according to the carrying density difference of the noble metal carrying density at the upstream end portion and the downstream end portion of the PM filter 44, and the PM burnup calculated from the unburned burnup amount calculation map as described above. By adding the correction amount A to the remaining amount, the PM unburned amount is corrected.

  The correspondence between the carrying density difference and the correction amount A is defined such that the larger the carrying density difference is, the smaller the correction amount A is, and is stored in advance in the ROM 100c as a correction amount calculation map shown in FIG. As shown in FIG. 8, the correction amount calculation map is defined such that the correction amount A takes a substantially constant value when the carrying density difference increases to some extent. In the above description, the case where the noble metal support density of the PM filter 44 is divided into three stages has been described. However, the case where the noble metal support density is divided into two stages or four or more stages, Even when the density continuously decreases from the upstream end toward the downstream end, the correction amount calculation map has a tendency similar to the correction amount A described above.

  As described above, the exhaust emission control device according to the present invention has an effect that the filter can be regenerated at an appropriate timing, and the exhaust that performs regeneration of the catalytic function by adding fuel to the exhaust gas. Useful for purification equipment.

DESCRIPTION OF SYMBOLS 1 Vehicle 10 Engine 11 Cylinder 13 Fuel injection valve 15 Fuel tank 19 Intake passage 20 Intake pipe 22 Turbo unit 24 Intake throttle valve 29 Fuel branch part 30 EGR device 33 EGR valve 39 Throttle valve sensor 41 Addition injector 42 Catalyst device 43 Catalytic converter 44 PM filter 45 Exhaust pipe 46 Exhaust passage 52 Engine speed sensor 53 Intake air amount sensor 54 Intake air temperature sensor 58 Actuator 61 Exhaust temperature sensor 62 Exhaust gas amount sensor 63 Catalyst bed temperature sensor 64 Air fuel ratio sensor 67 Needle valve 100 ECU

Claims (1)

To a vehicle provided with a filter installed in an exhaust passage of an internal combustion engine for collecting particulate matter of exhaust gas discharged from the internal combustion engine, and a fuel addition valve capable of adding fuel to the exhaust gas An exhaust purification device that is installed and regenerates the filter by controlling the fuel addition valve and adding the fuel to the exhaust gas when the amount of particulate matter deposited on the filter exceeds a predetermined value In
Temperature difference calculating means for calculating a temperature difference between the upstream end portion and the downstream end portion of the filter;
Unburned amount calculating means for calculating the unburned amount of particulate matter in the filter based on the temperature difference calculated by the temperature difference calculating means and the bed temperature of the filter;
An exhaust emission control device comprising: a correction unit that corrects a timing for regenerating the filter in accordance with the unburned amount calculation unit.

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