JP3911408B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technology for purifying exhaust gas from an internal combustion engine, and particularly to an exhaust gas purification technology provided with a mechanism for collecting particulates contained in the exhaust gas.
[0002]
[Prior art]
In recent years, internal combustion engines mounted on automobiles and the like have been required to improve exhaust emission. In particular, in compression ignition type diesel engines using light oil as fuel, carbon monoxide (CO), hydrocarbon (HC), nitrogen In addition to oxides (NOx) and the like, it is required to purify or remove particulates (PM) such as soot and SOF (Soluble Organic Fraction) contained in exhaust gas.
[0003]
For this reason, in a diesel engine, by disposing a particulate filter made of a porous base material having a large number of pores having a very small cross-sectional area in the exhaust passage, and flowing exhaust gas through the pores of the particulate filter, A method for collecting PM in exhaust gas is known.
[0004]
  On the other hand, when the amount of PM collected by the particulate filter increases excessively,To filterThe exhaust resistance in the exhaust gas increases, and the back pressure acting on the internal combustion engine may increase excessively.RutaIt is necessary to regenerate the PM collection ability of the particulate filter by purifying the collected PM at an appropriate time.
[0005]
In response to such a demand, for example, an exhaust emission control device for a diesel engine as described in JP-A-5-312021 has been proposed.
[0006]
The exhaust purification device for a diesel engine described in the above publication is a particulate filter disposed in the exhaust system of the diesel engine, and when the pressure loss value of the particulate filter exceeds the pressure loss value for regeneration timing determination. In a diesel engine exhaust gas purification apparatus equipped with a regeneration means for regenerating a particulate filter, a pressure loss value of the particulate filter is detected when the particulate filter is new, and a regeneration timing judgment pressure is detected according to the pressure loss value It is configured to set the loss value.
[0007]
[Problems to be solved by the invention]
  By the way, in the process of using the particulate filter, substances that cannot be removed by normal regeneration processing such as ash accumulate on the particulate filter., PM nonThe pressure loss of the particulate filter during collection may change, and the output characteristics of the sensor that detects the pressure loss value of the particulate filter are likely to change due to deterioration over time, so the actual pressure loss of the particulate filter There may be an error between the value and the pressure loss value detected by the sensor.
[0008]
  However, in the conventional technique described above, the regeneration timing of the particulate filter is determined according to the pressure loss value detected when the particulate filter is new., PM nonWhen the pressure loss value of the particulate filter at the time of collection changes, or when an error occurs between the actual pressure loss value of the particulate filter and the pressure loss value detected by the sensor, PMIt becomes impossible to accurately detect the pressure loss due to the collection, and it becomes difficult to accurately determine the regeneration timing of the particulate filter.
[0009]
The present invention has been made in view of the various problems as described above, and in an exhaust gas purification apparatus for an internal combustion engine having a collection mechanism for collecting particulates such as soot contained in exhaust gas. An object of the present invention is to provide a technique capable of accurately determining the regeneration timing of the mechanism.
[0010]
[Means for Solving the Problems]
The present invention employs the following means in order to solve the above-described problems.
That is, the exhaust gas purification apparatus for an internal combustion engine according to the present invention is
A collection mechanism provided in an exhaust passage of the internal combustion engine, capable of collecting fine particles contained in the exhaust;
Pressure loss detecting means for detecting pressure loss by the collection mechanism;
Regenerating means for removing the fine particles collected by the collecting mechanism when the pressure loss detected by the pressure loss detecting means is equal to or higher than a predetermined determination reference value;
Correction means for correcting the determination reference value based on the detection value of the pressure loss detection means immediately after the regeneration mechanism is regenerated by the regeneration means;
It has.
[0011]
The present invention relates to a collection mechanism provided in an exhaust passage of an internal combustion engine, a pressure loss detection means for detecting a pressure loss of the collection mechanism, and a detection value of the pressure loss detection means at a time when a detected value is equal to or greater than a predetermined determination reference value. In an exhaust gas purification apparatus for an internal combustion engine including a regeneration unit that performs regeneration processing of the collection mechanism, the determination reference value is corrected based on the detection value of the pressure loss detection unit immediately after the regeneration processing of the collection mechanism is performed. This is the biggest feature.
[0012]
In such an exhaust gas purification apparatus for an internal combustion engine, when the pressure loss detected by the pressure loss detection means is equal to or higher than the determination reference value, the regeneration means executes a regeneration process to remove the particulates collected by the collection mechanism.
[0013]
As soon as the regeneration process of the collection mechanism by the regeneration means is completed, the pressure loss detection means detects the pressure loss of the collection mechanism. The collection mechanism corrects the determination reference value according to the pressure loss detected by the pressure loss detection means immediately after the regeneration process is completed.
[0014]
In this case, the determination reference value is corrected according to the pressure loss of the collection mechanism in a state where the fine particles are not collected, and the corrected determination reference value has the fine particles collected by the collection mechanism. This is a value reflecting the detected value of the pressure loss detecting means in a situation where the pressure is not detected.
[0015]
As a result, even when the pressure loss of the collecting mechanism in a state where the fine particles are not collected due to the accumulation of substances other than the fine particles, or when the detection characteristics of the pressure loss detecting means change over time, the fine particles are captured. The pressure loss due to the collection is accurately detected.
[0016]
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, as a method for detecting the pressure loss of the collection mechanism, the exhaust pressure in the exhaust passage upstream of the collection mechanism and the exhaust pressure in the exhaust passage downstream of the collection mechanism are calculated. Examples thereof include a method for detecting a differential pressure and a method for estimating based on the intake air amount when the internal combustion engine is in a specific operating condition.
[0017]
  The exhaust gas purification apparatus for an internal combustion engine according to the present invention is based on the detected value of the pressure loss detection means immediately after the regeneration mechanism is regenerated by the regeneration means, and the pressure of the collection mechanism in the state where the particulates are not collected. lossLoss (hereinafter referred to as "pressure loss during non-collection")You may make it further provide the learning means to learn. In this case, the correction means is learned by the learning means.Non-collecting pressureThe determination reference value may be corrected according to the power loss.
[0018]
In addition, when the exhaust gas purification apparatus for an internal combustion engine according to the present invention further includes poisoning elimination means for removing sulfur oxides occluded in the collection mechanism, the learning means uses the regeneration means for the collection mechanism. Immediately after regeneration is performed, or immediately after the poisoning of the collection mechanism is eliminated by the poisoning elimination means, the detection value of the pressure loss detection means is the pressure loss of the collection mechanism in a state in which no particulates are collected. You may make it learn as.
[0019]
This is because when the sulfur oxide stored in the collection mechanism is removed, the fine particles collected in the collection mechanism are also removed.
[0020]
  In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the correction means is learned by the learning means.Non-collecting pressureThe criterion value may be increased as the power loss increases.. At this time, it is preferable that the increase amount of the determination reference value with respect to the increase amount of the non-collecting pressure loss is increased as the non-collecting pressure loss increases. This is because the increase rate of the pressure loss with respect to the increase in the amount of fine particles collected by the collection mechanism increases as the non-collection pressure loss increases.
[0021]
When the criterion value is corrected by such a method,Despite the small amount of fine particles collected by the collection mechanism, the pressure loss of the collection mechanism becomes the criterion value.Never reach. as a result,The number of regeneration processes executed by the collection mechanism is unnecessarily increased.It will not be.
[0022]
The exhaust gas purification apparatus for an internal combustion engine according to the present invention may further include an abnormality determination unit that determines that the collection mechanism is abnormal when the pressure loss learned by the learning unit exceeds a predetermined value. Good.
[0023]
This is because if the pressure loss of the collecting mechanism in a state where fine particles are not collected due to the accumulation of substances other than fine particles becomes excessively high, the back pressure acting on the internal combustion engine becomes excessively high, and fuel consumption is unnecessary. This is because it increases, drivability of the internal combustion engine decreases, and exhaust emission deteriorates.
[0024]
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, examples of the collection mechanism include a particulate filter, a particulate filter carrying a NOx catalyst, and the like.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, specific embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described with reference to the drawings.
[0026]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust gas purification apparatus according to the present invention is applied and its intake and exhaust system.
[0027]
An internal combustion engine 1 shown in FIG. 1 is a compression ignition type diesel engine having four cylinders 2. In the internal combustion engine 1, every time a fuel injection valve 3 that directly injects fuel into the combustion chamber of each cylinder 2 and a crankshaft that is an engine output shaft of the internal combustion engine 1 rotate by a predetermined angle (for example, 15 °). A crank position sensor 4 that outputs a pulse signal and a water temperature sensor 5 that outputs an electrical signal corresponding to the temperature of cooling water flowing through a water jacket (not shown) of the internal combustion engine 1 are attached.
[0028]
The fuel injection valve 3 described above is connected to a pressure accumulating chamber (common rail) 7 through a fuel pipe 6. The common rail 7 is connected to a fuel pump 9 attached to the fuel tank 8 via a fuel pipe 10 and to the fuel tank 8 via a return pipe 11.
[0029]
When the fuel pressure in the common rail 7 is lower than a preset maximum pressure, the common rail 7 is closed at the connecting portion of the return pipe 11 to cut off the conduction between the common rail 7 and the return pipe 11. When the internal fuel pressure becomes equal to or higher than the maximum pressure, there is provided a pressure regulating valve 12 that opens and allows the common rail 7 and the return pipe 11 to conduct.
[0030]
A fuel pressure sensor 13 for outputting an electric signal corresponding to the fuel pressure in the common rail 7 is attached to the common rail 7.
[0031]
In the fuel system configured as described above, the fuel pump 9 pumps up the fuel stored in the fuel tank 8 and pumps the pumped up fuel to the common rail 7 through the fuel pipe 10. At that time, the fuel discharge amount of the fuel pump 9 is feedback-controlled based on the output signal value of the fuel pressure sensor 13 described above.
[0032]
The fuel supplied from the fuel pump 9 to the common rail 7 is accumulated until the pressure of the fuel reaches a desired target pressure. The fuel accumulated up to the target pressure in the common rail 7 is distributed to the fuel injection valves 3 of the respective cylinders 2 through the fuel pipe 6. Each fuel injection valve 3 opens when a drive current is applied, and injects fuel at a target pressure supplied from the common rail 7 into the combustion chamber of each cylinder 2.
[0033]
In the fuel system described above, when the fuel pressure in the common rail 7 becomes higher than the maximum pressure, the pressure adjustment valve 12 is opened. In this case, a part of the fuel stored in the common rail 7 is returned to the fuel tank 8 through the return pipe 11, and the fuel pressure in the common rail 7 is reduced.
[0034]
Next, an intake branch pipe 14 formed so that a plurality of branch pipes merge into one collecting pipe is connected to the internal combustion engine 1. Each branch pipe of the intake branch pipe 14 communicates with the combustion chamber of each cylinder 2 via an intake port (not shown). A collecting pipe of the intake branch pipe 14 is connected to an intake pipe 15, and the intake pipe 15 is connected to an air cleaner box 16.
[0035]
An air flow meter 17 that outputs an electric signal corresponding to the mass of the intake air flowing in the intake pipe 15 and a temperature of the intake air flowing in the intake pipe 15 are disposed in the intake pipe 15 immediately downstream of the air cleaner box 16. And an intake air temperature sensor 18 for outputting an electrical signal corresponding to the above.
[0036]
A compressor housing 19a of a centrifugal supercharger (turbocharger) 19 that operates using the thermal energy of exhaust gas discharged from the internal combustion engine 1 as a drive source is provided in a portion of the intake pipe 15 downstream of the air flow meter 17. Yes.
[0037]
An intercooler 20 for cooling fresh air that has been compressed in the compressor housing 19a and has reached a high temperature is provided in a portion of the intake pipe 15 downstream of the compressor housing 19a.
[0038]
An intake throttle valve 21 for adjusting the flow rate of the intake air flowing through the intake pipe 15 is provided in a portion of the intake pipe 15 downstream of the intercooler 20. An intake throttle actuator 21a that opens and closes the intake throttle valve 21 and an intake throttle valve opening sensor 21b that outputs an electrical signal corresponding to the opening of the intake throttle valve 21 are attached to the intake throttle valve 21. It has been.
[0039]
In the intake system configured as described above, fresh air that has flowed into the air cleaner box 16 is removed through the intake pipe 15 after dust or dust in the fresh air is removed by an air cleaner (not shown) in the air cleaner box 16. It flows into the compressor housing 19a of the centrifugal supercharger 19.
[0040]
The fresh air flowing into the compressor housing 19a is compressed by the rotation of the compressor wheel built in the compressor housing 19a. The fresh air that has been compressed in the compressor housing 19 a and has reached a high temperature is cooled by the intercooler 20.
[0041]
The fresh air cooled by the intercooler 20 is guided to the intake branch pipe 14 with the flow rate adjusted by the intake throttle valve 21 as necessary. The fresh air guided to the intake branch pipe 14 is distributed from the collecting pipe of the intake branch pipe 14 to each branch pipe and is guided to the combustion chamber of each cylinder 2.
[0042]
The fresh air distributed to the combustion chamber of each cylinder 2 is compressed by a piston (not shown), and burns using the fuel injected from the fuel injection valve 3 as an ignition source.
[0043]
Next, an exhaust branch pipe 24 formed so that a plurality of branch pipes merge into one collecting pipe is connected to the internal combustion engine 1. Each branch pipe of the exhaust branch pipe 24 communicates with the combustion chamber of each cylinder 2 via an exhaust port (not shown). The collecting pipe of the exhaust branch pipe 24 is connected to the exhaust pipe 25 a via the turbine housing 19 b of the centrifugal supercharger 19.
[0044]
A portion of the exhaust branch pipe 24 located immediately upstream of the turbine housing 19b and a portion of the exhaust pipe 25a located immediately downstream of the turbine housing 19b are connected by a turbine bypass passage 26 that bypasses the turbine housing 19b. Has been.
[0045]
A waste gate valve 27 including a valve body 27a for opening and closing the turbine bypass path 26 and an actuator 27b for opening and closing the valve body 27a is attached to the turbine bypass path 26.
[0046]
The actuator 27b is connected to the intake pipe 15 located immediately downstream of the compressor housing 19a via the working pressure passage 28, and the pressure of fresh air flowing in the intake pipe 15 immediately downstream of the compressor housing 19a, in other words, The valve body 27a is driven to open and close using the pressure (supercharging pressure) of fresh air compressed in the compressor housing 19a.
[0047]
Specifically, the actuator 27b holds the valve body 27a in the closed position when a pressure less than a predetermined pressure is applied from the intake pipe 15 via the operating pressure passage 28, and the operating pressure passage from the intake pipe 15 When a pressure higher than a predetermined pressure is applied via 28, the valve element 27a is driven to open.
[0048]
That is, when the supercharging pressure of the intake air by the centrifugal supercharger 19 reaches a predetermined pressure or higher, the actuator 27b opens the valve body 27a to bring the turbine bypass passage 26 into a conductive state, and the exhaust gas flowing into the turbine housing 19b The flow rate is decreased so that the supercharging pressure does not exceed the predetermined pressure.
[0049]
The exhaust pipe 25a is connected to an exhaust purification mechanism 29 that purifies harmful gas components in the exhaust, particularly particulates such as soot (PM). The exhaust purification mechanism 29 is connected to an exhaust pipe 25b, and the exhaust pipe 25b is connected downstream to a muffler (not shown). Hereinafter, the exhaust pipe 25a upstream from the exhaust purification mechanism 29 is referred to as an upstream exhaust pipe 25a, and the exhaust pipe 25b downstream from the exhaust purification mechanism 29 is referred to as a downstream exhaust pipe 25b.
[0050]
The exhaust purification mechanism 29 is an embodiment of the collection mechanism according to the present invention, and is a DPF (Diesel Particulate Filter) that collects PM contained in the exhaust or a wall flow type made of a porous substrate. An example is a DPNR (Diesel Particulate NOx Reduction) catalyst in which an oxidation catalyst typified by platinum (Pt) and a NOx occluding agent typified by potassium (K) or cesium (Cs) are supported on the particulate filter. it can. Hereinafter, the exhaust purification mechanism 29 is referred to as a particulate filter 29.
[0051]
An exhaust temperature sensor 38 that outputs an electric signal corresponding to the temperature of the exhaust gas flowing through the upstream exhaust pipe 25a is attached to the upstream exhaust pipe 25a. Differential pressure that outputs an electrical signal corresponding to the differential pressure between the exhaust pressure in the upstream exhaust pipe 25a and the exhaust pressure in the downstream exhaust pipe 25b to the upstream exhaust pipe 25a and the downstream exhaust pipe 25b. A sensor 39 is attached.
[0052]
An exhaust throttle valve 33 that adjusts the flow rate of the exhaust gas flowing through the downstream exhaust pipe 25b is attached to the downstream exhaust pipe 25b. An exhaust throttle actuator 34 that opens and closes the exhaust throttle valve 33 is attached to the exhaust throttle valve 33.
[0053]
In the exhaust system configured as described above, the burned gas burned in the combustion chamber of each cylinder 2 of the internal combustion engine 1 is discharged to the exhaust branch pipe 24 through the exhaust port of each cylinder 2 and then the exhaust branch pipe. It flows into the turbine housing 19b of the centrifugal supercharger 19 from each branch pipe of 24 through the collecting pipe.
[0054]
When the exhaust gas flows into the turbine housing 19b of the centrifugal supercharger 19, the heat energy of the exhaust gas is converted into the rotational energy of the turbine wheel that is rotatably supported in the turbine housing 19b. The rotational energy of the turbine wheel is transmitted to the compressor wheel of the aforementioned compressor housing 19a, and the compressor wheel compresses fresh air by the rotational energy transmitted from the turbine wheel.
[0055]
At that time, when the pressure (supercharging pressure) of fresh air compressed in the compressor housing 19 a rises to a predetermined pressure or higher, the supercharging pressure is applied to the actuator 27 b of the wastegate valve 27 through the operating pressure passage 28. The actuator 27b drives the valve body 27a to open.
[0056]
When the valve element 27a of the wastegate valve 27 is opened, a part of the exhaust gas flowing through the exhaust branch pipe 24 flows to the upstream exhaust pipe 25a via the turbine bypass passage 26, so that the exhaust gas flowing into the turbine housing 19b is discharged. The flow rate decreases, and the thermal energy of the exhaust gas flowing into the turbine housing 19b, in other words, the thermal energy converted into the rotational energy of the turbine wheel in the turbine housing 19b decreases. As a result, rotational energy transmitted from the turbine wheel to the compressor wheel is reduced, and an excessive increase in supercharging pressure is suppressed.
[0057]
Exhaust gas discharged from the turbine housing 19b to the upstream side exhaust pipe 25a and exhaust gas guided from the turbine bypass passage 26 to the upstream side exhaust pipe 25a flow into the particulate filter 29 from the upstream side exhaust pipe 25a. The exhaust gas flowing into the particulate filter 29 is purified or removed from particulates such as soot contained in the exhaust gas, then discharged to the downstream exhaust pipe 25b, and then released into the atmosphere through the downstream exhaust pipe 25b.
[0058]
Further, an exhaust gas recirculation passage (EGR passage) 100 is connected to the exhaust branch pipe 24, and the EGR passage 100 is connected to the intake branch pipe 14. An EGR valve 101 that opens and closes an opening end of the EGR passage 100 in the intake branch pipe 14 is provided at a connection portion between the EGR passage 100 and the intake branch pipe 14. The EGR valve 101 is composed of an electromagnetic valve or the like, and the opening degree can be changed according to the magnitude of applied power.
[0059]
In the middle of the EGR passage 100, an EGR cooler 103 for cooling the exhaust gas flowing in the EGR passage 100 (hereinafter referred to as EGR gas) is provided.
[0060]
Two pipes 104 and 105 are connected to the EGR cooler 103, and these two pipes 104 and 105 are connected to a radiator 106 for radiating the heat of the cooling water of the internal combustion engine 1 into the atmosphere. ing.
[0061]
One of the two pipes 104 and 105 described above is a pipe for guiding a part of the cooling water cooled in the radiator 106 to the EGR cooler 103, and the other pipe 105 is This is a pipe for guiding the cooling water after circulating through the EGR cooler 103 to the radiator 106. Hereinafter, the pipe 104 will be referred to as a cooling water introduction pipe 104 and the pipe 105 will be referred to as a cooling water outlet pipe 105.
[0062]
In the middle of the cooling water outlet pipe 105, an on-off valve 107 for opening and closing a flow path in the cooling water outlet pipe 105 is provided. The on-off valve 107 is composed of an electromagnetically driven valve that opens when drive power is applied.
[0063]
In the exhaust gas recirculation mechanism (EGR mechanism) configured as described above, when the EGR valve 101 is opened, the EGR passage 100 becomes conductive, and a part of the exhaust gas flowing in the exhaust branch pipe 24 passes through the EGR passage 100. It is led to the intake branch pipe 14.
[0064]
At this time, if the on-off valve 107 is in the open state, the circulation path connecting the radiator 106, the cooling water introduction pipe 104, the EGR cooler 103, and the cooling water outlet pipe 105 becomes conductive, and the cooling water cooled by the radiator 106 Circulates through the EGR cooler 103. As a result, in the EGR cooler 103, heat exchange is performed between the EGR gas flowing in the EGR passage 100 and the cooling water circulating in the EGR cooler 103, thereby cooling the EGR gas.
[0065]
The EGR gas recirculated from the exhaust branch pipe 24 to the intake branch pipe 14 via the EGR passage 100 is guided to the combustion chamber of each cylinder 2 while being mixed with fresh air flowing from the upstream side of the intake branch pipe 14. The fuel injected from the fuel injection valve 3 is burned using an ignition source.
[0066]
Here, the EGR gas contains water (H₂O) and carbon dioxide (CO₂) And the like, and an inert gas component having endothermic properties is contained. For this reason, when EGR gas is contained in the air-fuel mixture, the combustion temperature of the air-fuel mixture is lowered, and thus nitrogen oxides (NO_x) Is suppressed.
[0067]
Further, when the EGR gas is cooled in the EGR cooler 103, the temperature of the EGR gas itself is lowered and the volume of the EGR gas is reduced. Therefore, when the EGR gas is supplied into the combustion chamber, the atmosphere in the combustion chamber is reduced. The temperature will not increase unnecessarily, and the amount of fresh air (volume of fresh air) supplied into the combustion chamber will not unnecessarily decrease.
[0068]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 35 for controlling the internal combustion engine 1. The ECU 35 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.
[0069]
In addition to the crank position sensor 4, the water temperature sensor 5, the fuel pressure sensor 13, the air flow meter 17, the intake air temperature sensor 18, the intake throttle valve opening sensor 21 b, the exhaust gas temperature sensor 38, and the differential pressure sensor 39, the ECU 35 An accelerator position sensor 37 that outputs an electrical signal corresponding to the amount of operation (accelerator opening) of an accelerator pedal 36 provided in the room is electrically connected, and the output signal of each sensor described above is input to the ECU 35. It has become.
[0070]
On the other hand, the ECU 35 is electrically connected to the fuel injection valve 3, the fuel pump 9, the intake throttle actuator 21a, the exhaust throttle actuator 34, the EGR valve 101, the on-off valve 107, and the like, and the ECU 35 controls the above-described parts. It is possible.
[0071]
Here, as shown in FIG. 2, the ECU 35 includes a CPU 41, a ROM 42, a RAM 43, a backup RAM 44, an input port 45, and an output port 46 connected to each other by a bidirectional bus 40. And an A / D converter (A / D) 47 connected to the input port 45.
[0072]
The input port 45 receives an output signal of a sensor that outputs a signal in the form of a digital signal like the crank position sensor 4 and transmits the output signal to the CPU 41 and the RAM 43 via the bidirectional bus 40.
[0073]
The input port 45 includes a water temperature sensor 5, a fuel pressure sensor 13, an air flow meter 17, an intake air temperature sensor 18, an intake throttle valve opening sensor 21b, an accelerator position sensor 37, an exhaust temperature sensor 38, a differential pressure sensor 39, and the like. An output signal of a sensor that outputs an analog signal format signal is input via the A / D 47, and these output signals are transmitted to the CPU 41 and the RAM 43 via the bidirectional bus 40.
[0074]
The output port 46 is electrically connected to the fuel injection valve 3, the fuel pump 9, the intake throttle actuator 21a, the exhaust throttle actuator 34, the EGR valve 101, the on-off valve 107, etc. via a drive circuit (not shown), and the CPU 41 The control signal output from is transmitted to each unit described above.
[0075]
The ROM 42 stores various application programs such as a fuel injection control routine, an intake throttle control routine, an exhaust throttle control routine, an EGR control routine, and various control maps.
[0076]
The RAM 43 stores output signals from the sensors, calculation results of the CPU 41, and the like. The calculation result is, for example, an engine speed calculated based on a time interval at which the crank position sensor 4 outputs a pulse signal. These data are rewritten to the latest data every time the crank position sensor 4 outputs a pulse signal.
[0077]
The backup RAM 44 is a non-volatile memory capable of storing data even after the operation of the internal combustion engine 1 is stopped.
[0078]
The CPU 41 operates in accordance with an application program stored in the ROM 42, and in addition to well-known controls such as fuel injection control, fuel pump control, intake throttle control, exhaust throttle control, EGR control, PM which is the gist of the present invention Perform playback control.
[0079]
In the PM regeneration control, the CPU 41 determines that the amount of PM trapped in the particulate filter 29 (hereinafter referred to as PM trapped amount) is equal to or greater than a predetermined upper limit value (hereinafter referred to as PM trapped amount upper limit value). At this point, the PM regeneration process is executed to burn and remove the PM collected by the particulate filter 29.
[0080]
The above-described upper limit of the amount of collected PM is a value determined within a range in which the combustion heat generated when PM burns does not adversely affect the particulate filter 29 (for example, melting damage due to overheating of the particulate filter 29). It is.
[0081]
As a method for determining whether or not the PM trapping amount of the particulate filter 29 is equal to or higher than the PM trapping amount upper limit value, when the pressure loss of the particulate filter 29 is equal to or higher than a predetermined determination reference value, PM trapping is performed. A method for determining that the amount of PM trapped is less than the upper limit when the amount is equal to or greater than the upper limit and the pressure loss of the particulate filter 29 is less than the determination reference value can be exemplified.
[0082]
This is because when PM is collected in the particulate filter 29, the cross-sectional area of the exhaust passage in the particulate filter 29 is narrowed, so that the exhaust resistance in the particulate filter 29 increases, and thus the particulate filter 29. This is because the pressure loss increases.
[0083]
Since the pressure loss of the particulate filter 29 corresponds to the difference between the exhaust pressure upstream of the particulate filter 29 and the exhaust pressure downstream of the particulate filter 29, the output signal value (differential pressure) of the differential pressure sensor 39 is changed to the particulate pressure. The pressure loss value of the curate filter 29 can be used.
[0084]
Therefore, when the output signal value of the differential pressure sensor 39 is less than the predetermined determination reference value, the CPU 41 indicates that the PM collection amount of the particulate filter 29 is less than the PM collection amount upper limit value, and the differential pressure sensor 39 When the output signal value is equal to or greater than the determination reference value, it can be determined that the PM trapping amount of the particulate filter 29 is equal to or greater than the PM trapping amount upper limit value.
[0085]
Next, in the PM regeneration process, the CPU 41 executes exhaust gas temperature raising control to raise the exhaust gas temperature to a temperature range where PM can burn. As a method of executing the exhaust gas temperature raising control, a method of increasing the fuel injection amount and simultaneously closing the exhaust throttle valve 33 by a predetermined amount, adding in the expansion stroke of each cylinder 2 in addition to normal fuel injection (main fuel injection). In addition to the main fuel injection, the exhaust of each cylinder 2 is performed in addition to the method of performing the fuel injection (expansion stroke injection), the method of increasing the fuel amount of the main fuel injection and the expansion stroke injection and simultaneously closing the exhaust throttle valve 33 by a predetermined amount. A method of supplying unburned fuel to the particulate filter 29 and burning it by performing additional fuel injection (exhaust stroke injection) during the stroke can be exemplified.
[0086]
When the PM regeneration process is executed in this way, the PM collected by the particulate filter 29 is burned and removed from the particulate filter 29.
[0087]
By the way, the particulate filter 29 may occlude and deposit substances other than PM. As a substance other than PM, a compound called ash can be exemplified.
[0088]
Ash is considered to be generated by the following mechanism.
[0089]
That is, various additives and impurities are contained in the fuel and lubricating oil (so-called engine oil) of the internal combustion engine, and these components are combined on the combustion chamber or the particulate filter of the internal combustion engine to produce various kinds. It is considered that ash is generated by agglomeration of these compounds on the particulate filter.
[0090]
For example, fuel and lubricating oil for internal combustion engines contain components such as sulfur (S) component, phosphorus (P) component, calcium (Ca), magnesium (Mg), etc., and blow-by gas (lubricating oil) in the combustion chamber ) And the components contained in the air-fuel mixture (fuel) combine to produce calcium sulfate (CaSO_Four), Calcium phosphate (Ca_Three(SO_Four)₂) Or magnesium sulfate (MgSO_Four) And the like, and these compounds are collected together with PM on the particulate filter and aggregated as ash.
[0091]
Further, since sulfur (S) has a characteristic that it is easily occluded by soot, sulfur (S) occluded with soot on the particulate filter is combined with calcium (Ca) and magnesium (Mg) in the exhaust. , Calcium sulfate (Ca) and magnesium sulfate (MgSO_Four) And the like, and these compounds are aggregated as ash.
[0092]
As described above, the ash is not removed from the particulate filter 29 even if the PM regeneration process is executed. Therefore, the ash accumulates in the particulate filter 29 as the usage time elapses, and increases the pressure loss of the particulate filter 29. Become.
[0093]
Therefore, the more ash is accumulated on the particulate filter 29, the more the output signal value of the differential pressure sensor 39 immediately after the execution of the PM regeneration process, in other words, the difference of the differential pressure sensor 39 when PM is not collected in the particulate filter 29. The output signal value (hereinafter referred to as non-collecting differential pressure) increases.
[0094]
On the other hand, in the process of using the differential pressure sensor 39, soot contained in the exhaust gas may adhere to the differential pressure sensor 39, and the output characteristics of the differential pressure sensor 39 may change.
[0095]
In this way, when the non-collecting differential pressure or the output characteristics of the differential pressure sensor 39 change, the execution timing of the PM regeneration process is determined using the determination reference value set when the particulate filter 29 is new. The execution timing of the PM regeneration process cannot be accurately determined, and there is a possibility that problems such as excessively shortening the execution period of the PM regeneration process may occur.
[0096]
On the other hand, in the exhaust gas purification apparatus for an internal combustion engine according to the present embodiment, every time the PM regeneration process is executed, the non-collecting differential pressure is calculated based on the output signal value of the differential pressure sensor 39 immediately after the PM regeneration process is executed. In addition to learning, the determination reference value is corrected according to the learned non-collecting differential pressure.
[0097]
Specifically, the CPU 41 reads the output signal value: ΔP of the differential pressure sensor 39 immediately after execution of the PM regeneration process, and learns the output signal value: ΔP as the latest non-collecting differential pressure: ΔP0. The CPU 41 corrects the determination reference value: ΔPbase using the latest non-collecting differential pressure: ΔP0 as a parameter.
[0098]
Here, as shown in FIG. 3, as the ash deposition amount in the particulate filter 29 increases, the non-collecting differential pressure: ΔP0 (ΔP01 to ΔP04 in FIG. 3; ΔP01 <ΔP02 < ΔP03 <ΔP04) increases, and the amount of PM trapped: Differential pressure with respect to increase in PM: Increase rate of ΔP: a (a1 to a4 in FIG. 3; a1 <a2 <a3 <a4) increases .
[0099]
This is because as the ash deposition amount in the particulate filter 29 increases, the cross-sectional area of the exhaust passage in the particulate filter 29 becomes narrower, and the exhaust resistance in the particulate filter 29 is increased by collecting a small amount of PM. It is thought that.
[0100]
As described above, when the ash accumulation in the particulate filter 29 increases the non-collecting differential pressure: ΔP0 and the PM trapping amount: the differential pressure with respect to the increase in PM: the increase rate of ΔP: a increases, the particulate filter 29 PM trapping amount: Δ When PM reaches PM trapping amount upper limit value: PMmax, the differential pressure: ΔP (hereinafter referred to as differential pressure upper limit value: ΔPmax) also increases (Δ in FIG. 3). Pmax1 to ΔPmax4; ΔPmax1 <ΔPmax2 <ΔPmax3 <ΔPmax4).
[0101]
Therefore, in the present embodiment, the relationship between the PM collection amount upper limit value: PMmax and the non-collection differential pressure: ΔP0 as shown in FIG. 3 is experimentally obtained in advance, and the relationship is mapped to the ROM 42. I remembered it. Then, the CPU 41 outputs an output signal value of the differential pressure sensor 39 immediately after execution of the PM regeneration process (non-collecting differential pressure): ΔP0 and the map from the non-collecting differential pressure: ΔP0 upper limit corresponding to ΔP0: ΔPmax is calculated, and the differential pressure upper limit value: ΔPmax is set as the determination reference value: ΔPbase. Hereinafter, a map indicating the relationship between the PM collection amount upper limit value: PMmax and the non-collection differential pressure: ΔP0 is referred to as a determination reference value control map.
[0102]
When the determination reference value is updated by such a method, even when ash or the like is accumulated on the particulate filter 29 or when the output characteristic of the differential pressure sensor 39 changes, the execution timing of the PM regeneration process is accurately set. Can be determined.
[0103]
The above-described determination reference value: ΔPbase is stored in the backup RAM 44 that can hold data even when the internal combustion engine 1 is in a stopped state, in other words, even when an ignition switch (not shown) is in an OFF state. To do.
[0104]
Hereinafter, PM regeneration control according to the present embodiment will be described with reference to FIG.
[0105]
FIG. 4 is a flowchart showing a PM regeneration control routine. This PM regeneration control routine is a routine stored in the ROM 42 in advance, and is a routine that is repeatedly executed by the CPU 41 every predetermined time (for example, every time the crank position sensor 4 outputs a pulse signal).
[0106]
In the PM regeneration control routine, the CPU 41 first inputs an output signal value (differential pressure): ΔP of the differential pressure sensor 39 in S401.
[0107]
In S <b> 402, the CPU 41 reads the determination reference value: ΔPbase from the backup RAM 44.
[0108]
In S403, the CPU 41 determines whether or not the differential pressure: ΔP input in S401 is equal to or larger than the determination reference value: ΔPbase read in S402.
[0109]
When it is determined in S403 that the differential pressure: ΔP is less than the determination reference value: ΔPbase, the CPU 41 determines that the PM collection amount of the particulate filter 29 is less than the PM collection amount upper limit value: PMmax. Assuming that there is, this routine is temporarily terminated.
[0110]
On the other hand, when it is determined in S403 that the differential pressure: ΔP is equal to or greater than the determination reference value: ΔPbase, the CPU 41 determines that the PM collection amount of the particulate filter 29 is the PM collection amount upper limit value: PMmax. Assuming that the above is true, the P reproduction process is executed in S404.
[0111]
In S405, the CPU 41 determines whether or not the PM regeneration process of the particulate filter 29 has been completed.
[0112]
If it is determined in S405 that the PM regeneration process of the particulate filter 29 has not been completed, the CPU 41 executes the processes after S404 described above again.
[0113]
On the other hand, if it is determined in S405 that the PM regeneration process of the particulate filter 29 has been completed, the CPU 41 proceeds to S406 and inputs again the output signal value (differential pressure): ΔP of the differential pressure sensor 39.
[0114]
In S407, the CPU 41 learns the differential pressure: ΔP input in S406 as the non-collecting differential pressure: ΔP0.
Since the differential pressure: ΔP is a value that varies depending on the exhaust gas temperature and the exhaust gas flow rate, the process of S406 is preferably executed when the exhaust gas temperature and the exhaust gas flow rate satisfy a certain condition, or detected in S406. The differential pressure: ΔP may be converted into the differential pressure: ΔP under a certain condition by correcting the differential pressure: ΔP according to the exhaust temperature and the exhaust flow rate at the time of detection.
[0115]
In S408, the CPU 41 determines whether or not the non-collecting differential pressure: ΔP0 is less than an allowable limit value. The allowable limit value described above is a value set based on the allowable limit value of the back pressure caused by the pressure loss of the particulate filter 29.
[0116]
When it is determined in S408 that the non-collecting differential pressure: ΔP0 is equal to or greater than the allowable limit value, the CPU 41 proceeds to S411 and determines that the particulate filter 29 is abnormal. At that time, it is preferable that a warning light or a warning buzzer is provided in the vehicle interior, and the warning light is turned on or the warning buzzer is operated by the CPU 41 to notify the vehicle occupant of the abnormality of the particulate filter 29. .
[0117]
On the other hand, if it is determined in S408 that the non-collecting differential pressure: ΔP0 is less than the allowable limit value, the CPU 41 proceeds to S409. In S409, the CPU 41 accesses the determination reference value control map of the ROM 42 using the non-collecting differential pressure: ΔP0 as a parameter, and calculates the differential pressure upper limit value: ΔPmax corresponding to the non-collecting differential pressure: ΔP0. To do.
[0118]
In S410, the CPU 41 updates the determination reference value: ΔPbase stored in the backup RAM 44 with the differential pressure upper limit value: ΔPmax calculated in S409, and temporarily ends the execution of this routine.
[0119]
As described above, when the CPU 41 executes the PM regeneration control routine, the determination reference value is corrected according to the output signal value of the differential pressure sensor 39 immediately after execution of the PM regeneration process.
[0120]
As a result, in the process of using the particulate filter 29, the output signal of the differential pressure sensor 39 when PM is not collected in the particulate filter 29 due to accumulation of ash or the like or change in the output characteristics of the differential pressure sensor 39, etc. Even when the value changes, the regeneration timing of the particulate filter 29 can be accurately determined.
[0121]
Further, since the non-collecting time differential pressure is detected every time the PM regeneration process is executed, it is possible to detect clogging of the particulate filter 29 due to substances other than PM based on the non-collecting time differential pressure. At the same time, the abnormality of the particulate filter 29 can be determined.
[0122]
In the present embodiment, the time immediately after the PM regeneration processing of the particulate filter 29 is illustrated as the time for learning the non-collecting differential pressure, but is not limited thereto. For example, when the NOx storage agent is carried on the particulate filter 29, it may be immediately after execution of the SOx poisoning elimination processing of the NOx storage agent.
[0123]
This is because, in the SOx poisoning elimination process of the particulate filter 29, the exhaust gas temperature is raised to a temperature at which PM can be burned or not as in the PM regeneration process. This is because the PM collected by the curative filter 29 is combusted and removed from the particulate filter 29.
[0124]
【The invention's effect】
According to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, when the pressure loss of the collection mechanism in a state where fine particles are not collected due to the accumulation of substances other than fine particles, or the detection characteristic of the pressure loss detection means is Even in the case of a change over time, the pressure loss due to the collection of the fine particles is accurately detected, so that the regeneration timing of the collection mechanism can be accurately determined.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which an exhaust emission control device according to an embodiment is applied.
FIG. 2 is a block diagram showing the internal configuration of the ECU
FIG. 3 is a diagram showing the relationship between differential pressure: ΔP and PM trapping amount: PM.
FIG. 4 is a flowchart showing a PM regeneration control routine.
[Explanation of symbols]
1 ... Internal combustion engine
2. Cylinder
17 ... Air flow meter
21 ... Inlet throttle valve
24 ... Exhaust branch pipe
25 ... Exhaust pipe
29 ... Exhaust gas purification mechanism
33 ... Exhaust throttle valve
39 ... Differential pressure sensor

Claims (5)

A collection mechanism provided in an exhaust passage of the internal combustion engine, capable of collecting fine particles contained in the exhaust;
Pressure loss detecting means for detecting pressure loss due to the collection mechanism;
Regenerating means for removing particulates collected by the collecting mechanism when the pressure loss detected by the pressure loss detecting means is equal to or higher than a predetermined determination reference value;
Learning means for learning the detection value of the pressure loss detection means immediately after the regeneration of the collection mechanism by the regeneration means as pressure loss during non-collection;
The higher the non-collecting time of pressure drop which is learned by the learning means is increased, Bei example and compensation means for correcting to increase the pre-Symbol determination reference value, and
The exhaust gas purification apparatus for an internal combustion engine , wherein an increase correction amount of the determination reference value with respect to an increase amount of the non-collecting pressure loss is increased as the non-collecting pressure loss is increased . The correction means multiplies the upper limit value of the amount of fine particles collected by the collection mechanism by the rate of increase in pressure loss with respect to an increase in the amount of fine particles collected by the collection mechanism, and the multiplied value is multiplied by the multiplication value. A correction is made with the value obtained by adding the pressure loss at the time of non-collection as the criterion value,
An exhaust purification system of an internal combustion engine according to claim 1 wherein the rate of increase which is characterized that you are great as the non-collecting time of the pressure loss increases. A poison elimination means for removing sulfur oxides occluded in the collection mechanism;
The learning means is a detection value of the pressure loss detection means immediately after regeneration of the collection mechanism by the regeneration means and / or immediately after poisoning of the collection mechanism is eliminated by the poisoning elimination means. It is learned as a non-collected when the pressure loss of the exhaust purification system of an internal combustion engine according to claim 2, wherein. The exhaust emission control device for an internal combustion engine according to claim 2 or 3, further comprising an abnormality determination unit that determines that the collection mechanism is abnormal when the pressure loss learned by the learning unit exceeds a predetermined value. . The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the collection mechanism is a particulate filter carrying an oxidation catalyst and a NOx storage agent.

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