JP3991710B2 - 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, if the amount of PM trapped by the particulate filter increases excessively, the exhaust resistance at the particulate increases, and the back pressure acting on the internal combustion engine may increase accordingly. It 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, conventionally, an “exhaust gas purification device for an internal combustion engine” as described in Japanese Patent Laid-Open No. 2001-158230 has been proposed. The exhaust gas purification apparatus for an internal combustion engine described in this publication obtains experimentally in advance an intake air amount when the internal combustion engine is in a predetermined operating state and the particulate filter is not clogged. In addition, the intake air amount is stored as a judgment reference value, and the particulate filter is compared by comparing the intake air amount when the internal combustion engine is in a predetermined operation state with the judgment reference value in the process of using the particulate filter. It is intended to determine the PM collection state.
[0006]
In this exhaust gas purification apparatus for an internal combustion engine, when PM is collected in the particulate filter, the pressure loss of the exhaust gas due to the particulate filter increases, so the back pressure acting on the internal combustion engine rises, and thus the internal combustion engine This is based on the knowledge that the amount of intake air decreases.
[Problems to be solved by the invention]
By the way, in an internal combustion engine equipped with a variable nozzle centrifugal supercharger, the intake supercharging pressure and the exhaust back pressure change according to the nozzle opening of the variable nozzle centrifugal supercharger. The intake air amount of the internal combustion engine also changes according to the nozzle opening of the feeder.
[0007]
Therefore, when the above-described conventional technology is applied to an internal combustion engine equipped with a variable nozzle centrifugal supercharger, not only the amount of PM collected by the particulate filter but also the nozzle opening of the variable nozzle centrifugal supercharger. As a result, the intake air amount of the internal combustion engine also changes, making it difficult to establish a correlation between the PM trapped amount of the particulate filter and the intake air amount of the internal combustion engine, thereby reducing the accuracy of determining the PM trap amount. There is a risk of doing.
[0008]
The present invention has been made in view of the above situation, and in an internal combustion engine including a collection mechanism for collecting fine particles in exhaust gas and a variable nozzle centrifugal supercharger, the fine particles of the collection mechanism. It aims at providing the technique which can determine the amount of collections accurately.
[0009]
[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 variable nozzle centrifugal supercharger provided in an intake passage and an exhaust passage of an internal combustion engine;
A collection mechanism provided in an exhaust passage of the internal combustion engine for collecting particulates contained in the exhaust;
Control means for fully opening the nozzle opening of the variable nozzle centrifugal supercharger when the internal combustion engine is in a deceleration operation state;
Detecting means for detecting an intake air amount of the internal combustion engine when the internal combustion engine is in a decelerating operation state and a nozzle opening of the variable nozzle centrifugal supercharger is fully open;
Estimating means for estimating the amount of particulate collection of the collection mechanism using the amount of intake air detected by the detection means as a parameter;
It is characterized by having.
The present invention relates to an exhaust gas purification apparatus for an internal combustion engine having a collection mechanism for collecting particulates in exhaust gas and a variable nozzle centrifugal supercharger, wherein the nozzle opening degree of the variable nozzle centrifugal supercharger is that of the internal combustion engine. The maximum amount of particulate trapping is determined using the intake air amount of the internal combustion engine as a parameter after fully opening the nozzle opening of the variable nozzle centrifugal supercharger during deceleration operation that does not affect the operating state. It is a feature.
[0010]
In such an exhaust purification device for an internal combustion engine, when the internal combustion engine is in a decelerating operation state, the nozzle opening degree of the variable nozzle centrifugal supercharger is controlled to be fully open, and the intake mechanism of the internal combustion engine at that time is used as a parameter for the collection mechanism The amount of collected fine particles will be determined.
[0011]
Inadvertent suction due to the nozzle opening of the variable nozzle centrifugal supercharger when the nozzle opening of the variable nozzle centrifugal supercharger is fixed fully open when determining the amount of particulates collected by the collection mechanism Changes in the air volume are prevented. As a result, the amount of intake air detected when determining the amount of collected particulates by the collection mechanism is an amount correlated with the amount of particulates collected by the collection mechanism.
[0012]
Therefore, when the particulate collection amount is determined using the intake air amount as a parameter when the internal combustion engine is in a decelerating operation state and the nozzle opening of the variable nozzle centrifugal turbocharger is fully open, the determination accuracy decreases. Will be prevented.
[0013]
Further, when the intake throttle valve is provided in the intake passage of the internal combustion engine to which the present invention is applied, when the internal combustion engine is in a deceleration operation state, the nozzle opening of the variable nozzle type centrifugal supercharger and the intake throttle valve By making the opening degree fully open, the correlation between the intake air amount and the particulate collection amount may be established.
[0014]
Further, when the EGR passage and the EGR valve are provided in the intake passage and the exhaust passage of the internal combustion engine to which the present invention is applied, the nozzle opening of the variable nozzle centrifugal supercharger is performed when the internal combustion engine is in a deceleration operation state. The correlation between the intake air amount and the particulate collection amount may be established by fully opening the degree and the opening degree of the EGR valve.
[0015]
When the internal combustion engine to which the present invention is applied includes an intake throttle valve, an EGR passage, and an EGR valve, when the internal combustion engine is in a deceleration operation state, By fully opening the opening of the intake throttle valve and the opening of the EGR valve, the correlation between the intake air amount and the particulate collection amount may be established.
[0016]
In addition, the exhaust gas purification apparatus for an internal combustion engine according to the present invention further includes a determination unit that determines that the clogging mechanism is clogged when the intake air amount detected by the detection unit falls below a predetermined amount. It may be.
[0017]
In addition, when determining the particulate collection amount of a collection mechanism, the method of controlling the nozzle opening degree of a variable nozzle type centrifugal supercharger to full closure is also considered.
[0018]
However, in a normal internal combustion engine, the variable nozzle centrifugal supercharger is disposed in the exhaust passage upstream of the collection mechanism. Therefore, if the nozzle opening is fully closed under such circumstances, the variable nozzle centrifugal While the exhaust pressure upstream from the supercharger increases, the exhaust pressure downstream from the variable nozzle centrifugal supercharger decreases. That is, if the nozzle opening degree of the variable nozzle centrifugal supercharger is fully closed, the pressure of the exhaust gas flowing into the collection mechanism is reduced.
[0019]
Here, when fine particles are collected in the collection mechanism, the resistance when the exhaust passes through the collection mechanism becomes high, so the pressure loss and back pressure of the exhaust caused by the collection mechanism increase, and accordingly As a result, the amount of intake air of the internal combustion engine decreases, but the increase in pressure loss and back pressure at that time increases as the pressure of the exhaust gas flowing into the collection mechanism increases.
[0020]
Therefore, when the pressure of the exhaust gas flowing into the collection mechanism is reduced by fully closing the nozzle opening degree of the variable nozzle centrifugal supercharger, the pressure loss of the exhaust gas and the increase of the back pressure are less likely to occur and the intake air The amount of decrease tends to be small.
[0021]
Furthermore, the influence of the nozzle opening of the variable nozzle centrifugal supercharger on the intake air volume is greater on the closing side than on the opening side, so the actual nozzle opening when fully closed is controlled. When a situation that slightly differs each time occurs due to, for example, it is difficult to establish a correlation between the amount of collected particulate matter and the amount of intake air.
[0022]
Considering these circumstances, it can be said that a method for determining the amount of collected particulates using the intake air amount when the nozzle opening degree of the variable nozzle centrifugal supercharger is fully closed as a parameter is not appropriate.
[0023]
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.
[0024]
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.
[0025]
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.
[0026]
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.
[0027]
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.
[0028]
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.
[0029]
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.
[0030]
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.
[0031]
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.
[0032]
Next, an intake branch pipe 14 formed so that four 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.
[0033]
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.
[0034]
A compressor of a variable nozzle type centrifugal supercharger (variable nozzle type turbocharger) 19 that operates by using the thermal energy of the exhaust gas discharged from the internal combustion engine 1 as a drive source is provided in a portion downstream of the air flow meter 17 in the intake pipe 15. A housing 19a is provided.
[0035]
An intercooler 20 for cooling the intake air that has been compressed in the compressor housing 19a and heated to a high temperature is provided in a portion of the intake pipe 15 downstream of the compressor housing 19a.
[0036]
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.
[0037]
In the intake system configured as described above, the intake air flowing into the air cleaner box 16 is variable via the intake pipe 15 after dust or dust in the intake air is removed by an air filter (not shown) in the air cleaner box 16. It flows into the compressor housing 19a of the nozzle type centrifugal supercharger 19.
[0038]
The intake air flowing into the compressor housing 19a is compressed by the rotation of the compressor wheel built in the compressor housing 19a. The intake air that has been compressed in the compressor housing 19 a and has reached a high temperature is cooled by the intercooler 20.
[0039]
The intake air cooled by the intercooler 20 is guided to the intake branch pipe 14 with the flow rate adjusted by an intake throttle valve 21 as necessary. The intake 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 guided to the combustion chamber of each cylinder 2.
[0040]
The intake air distributed to the combustion chamber of each cylinder 2 is compressed by a piston (not shown) and burned using the fuel injected from the fuel injection valve 3 as an ignition source.
[0041]
Next, an exhaust branch pipe 24 formed so that four 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 variable nozzle centrifugal supercharger 19.
[0042]
In the turbine housing 19b, a turbine wheel connected to the above-described compressor wheel is rotatably mounted, and the turbine wheel is rotated by receiving the pressure of exhaust gas.
[0043]
Further, the turbine housing 19b includes a nozzle vane that changes the cross-sectional area of the exhaust passage (nozzle passage) in the turbine housing 19b. This nozzle vane is driven to open and close by a VNT actuator 19c.
[0044]
When the nozzle vane opening (hereinafter referred to as nozzle opening) is reduced by the VNT actuator 19c, the cross-sectional area of the nozzle passage is reduced, so that the flow velocity and pressure of the exhaust gas flowing through the nozzle passage are increased. Thus, the rotational speed and rotational torque of the turbine wheel are increased.
[0045]
On the other hand, when the nozzle opening is increased by the VNT actuator 19c, the cross-sectional area of the nozzle passage is enlarged, so that the flow velocity and pressure of the exhaust gas flowing through the nozzle passage are reduced, and the rotational speed of the turbine wheel and An excessive increase in rotational torque is suppressed.
[0046]
Therefore, when the internal combustion engine 1 is in a low rotation operation state, in other words, when the flow velocity and pressure of the exhaust gas discharged from the internal combustion engine 1 are low, the rotational speed and rotational torque of the turbine wheel are reduced by reducing the nozzle opening. Thus, it becomes possible to increase the supercharging pressure of the intake air.
[0047]
Further, when the internal combustion engine 1 is in a high rotation operation state, in other words, when the flow velocity and pressure of the exhaust discharged from the internal combustion engine 1 increase, the rotational speed and rotational torque of the turbine wheel are increased by increasing the nozzle opening. It is possible to suppress an excessive increase in the intake pressure, and thus to suppress an excessive increase in the supercharging pressure of the intake air.
[0048]
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.
[0049]
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.
[0050]
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 intake air flowing in the intake pipe 15 immediately downstream of the compressor housing 19a, in other words, the compressor The valve body 27a is driven to open and close using the pressure of the intake air (supercharging pressure) compressed in the housing 19a.
[0051]
Specifically, the actuator 27b closes the valve body 27a when the intake supercharging pressure is less than a predetermined pressure set in advance, and the intake supercharging pressure becomes equal to or higher than the predetermined pressure. The valve element 27a is opened.
[0052]
When the valve body 27a is opened, a part of the exhaust gas flowing through the exhaust branch pipe 24 flows to the exhaust pipe 25a via the turbine bypass passage 26, so that the flow rate of the exhaust gas flowing into the turbine housing 19b decreases. The exhaust pressure applied to the turbine wheel in the turbine housing 19b decreases. As a result, the rotational energy transmitted from the turbine wheel to the compressor wheel is reduced, so that the supercharging pressure of the intake air is suppressed to the predetermined pressure or less.
[0053]
Next, the exhaust pipe 25a is connected to an exhaust gas purification mechanism 29 that purifies harmful gas components in the exhaust gas, 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.
[0054]
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.
[0055]
An exhaust temperature sensor 30 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.
[0056]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) combusted in 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. The fluid flows from the branch pipes of the pipe 24 into the turbine housing 19b of the variable nozzle centrifugal supercharger 19 through the collecting pipe.
[0057]
The exhaust gas flowing into the turbine housing 19b rotates the turbine wheel. The rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 19a described above, and the compressor housing 19a acts as a drive source for compressing the intake air.
[0058]
At that time, when the pressure (supercharging pressure) of the intake air compressed in the compressor housing 19a rises to a predetermined pressure or higher, the actuator 27b of the wastegate valve 27 opens the valve body 27a, and thus flows through the exhaust branch pipe 24. A part of the exhaust flows to the upstream side exhaust pipe 25a via the turbine bypass passage 26, and an excessive increase in the supercharging pressure is suppressed.
[0059]
Exhaust gas discharged from the turbine housing 19b (and exhaust gas that has passed through the turbine bypass passage 26) flows into the particulate filter 29 via 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.
[0060]
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.
[0061]
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.
[0062]
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.
[0063]
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.
[0064]
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.
[0065]
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.
[0066]
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.
[0067]
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 the intake air flowing from the upstream side of the intake branch pipe 14. The fuel injected from the injection valve 3 is burned using an ignition source.
[0068]
At that time, EGR gas contains water (H ₂ O) and carbon dioxide (CO ₂ ) And the like, if such an 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.
[0069]
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 intake air (intake volume) supplied into the combustion chamber will not unnecessarily decrease.
[0070]
The internal combustion engine 1 configured as described above is provided with an electronic control unit (ECU) 31 for controlling the internal combustion engine 1. The ECU 31 is an arithmetic logic circuit that controls the operating state of the internal combustion engine 1 in accordance with the operating conditions of the internal combustion engine 1 and the driver's request.
[0071]
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, and the exhaust gas temperature sensor 30, the ECU 31 is provided in the vehicle interior. An accelerator position sensor 33 that outputs an electrical signal corresponding to the amount of operation of the accelerator pedal 32 (accelerator opening) is electrically connected, and the output signals of the sensors described above are input to the ECU 31. .
[0072]
On the other hand, the fuel injection valve 3, the fuel pump 9, the VNT actuator 19c, the intake throttle actuator 21a, the EGR valve 101, the on-off valve 107 and the like are electrically connected to the ECU 31, and the above-described parts are controlled by the ECU 31. It is like that.
[0073]
Here, as shown in FIG. 2, the ECU 31 includes a CPU 41, a ROM 42, a RAM 43, a backup RAM 44, an input port 45, and an output port 46 that are connected to each other by a bidirectional bus 40. And an A / D converter (A / D) 47 connected to the input port 45.
[0074]
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.
[0075]
The input port 45 has an analog signal format such as 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 exhaust gas temperature sensor 30, an accelerator position sensor 33, and the like. Output signals of sensors that output signals are input via the A / D 47, and those output signals are transmitted to the CPU 41 and the RAM 43 via the bidirectional bus 40.
[0076]
The output port 46 is electrically connected to the fuel injection valve 3, the fuel pump 9, the VNT actuator 19c, the intake throttle actuator 21a, the EGR valve 101, the on-off valve 107, etc. via a drive circuit (not shown), and from the CPU 41. The output control signal is transmitted to each unit described above.
[0077]
The ROM 42 stores various application programs such as a fuel injection control routine, an intake throttle control routine, an EGR control routine, a VNT control routine, and various control maps.
[0078]
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.
[0079]
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.
[0080]
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, intake throttle control, VNT control, EGR control, etc., PM of the particulate filter 29 that is the gist of the present invention. The collection amount determination control is executed.
[0081]
Hereinafter, PM collection amount determination control in the present embodiment will be described.
[0082]
When PM is collected by the particulate filter 29, the exhaust passage in the particulate filter 29 is narrowed. Therefore, as shown in FIG. 3, the particulate filter 29 increases as the amount of PM collected by the particulate filter 29 increases. The exhaust resistance inside becomes high.
[0083]
Thus, when the exhaust resistance in the particulate filter 29 increases due to an increase in the amount of PM trapped, the back pressure acting on the internal combustion engine 1 increases, and accordingly, the intake air amount of the internal combustion engine 1 decreases accordingly. Become.
[0084]
Therefore, under the situation where the internal combustion engine 1 is in the same operating state, the intake air amount of the internal combustion engine 1 decreases as the PM collection amount of the particulate filter 29 increases as shown in FIG. .
[0085]
As a result, it is possible to estimate the amount of PM trapped by the particulate filter 29 using the intake air amount of the internal combustion engine 1 (the output signal of the air flow meter 17) as a parameter.
[0086]
By the way, the intake air amount of the internal combustion engine 1 changes not only according to the amount of PM trapped by the particulate filter 29 but also according to the opening degree of the intake throttle valve 21 and the opening degree of the EGR valve 101. When the amount of collected PM is estimated, it is preferable to fix the opening of the intake throttle valve 21 and the opening of the EGR valve 101 to fully open.
[0087]
Further, the intake air amount of the internal combustion engine 1 also varies depending on the nozzle opening degree of the variable nozzle centrifugal supercharger 19. This is because the supercharging pressure of intake air changes according to the nozzle opening of the variable nozzle centrifugal supercharger 19 and the back pressure acting on the internal combustion engine 1 also changes.
[0088]
On the other hand, a method of estimating the PM collection amount of the particulate filter 29 after fixing the nozzle opening of the variable nozzle centrifugal supercharger 19 to be fully closed or fully open is conceivable.
[0089]
By the way, in this embodiment, since the variable nozzle centrifugal supercharger 19 is disposed upstream of the particulate filter 29, the nozzle opening degree of the variable nozzle centrifugal supercharger 19 is fully closed under such circumstances. In this case, the exhaust pressure upstream from the variable nozzle centrifugal supercharger 19 increases, while the exhaust pressure downstream from the variable nozzle centrifugal supercharger 19 decreases. That is, when the nozzle opening of the variable nozzle centrifugal supercharger 19 is fully closed, the pressure of the exhaust gas flowing into the particulate filter 29 is reduced.
[0090]
Here, the increase in the back pressure caused by the amount of PM collected by the particulate filter 29 becomes more prominent as the pressure of the exhaust gas flowing into the particulate filter 29 becomes higher.
[0091]
Therefore, when the pressure of the exhaust gas flowing into the particulate filter 29 is lowered by fully closing the nozzle opening degree of the variable nozzle centrifugal supercharger 19, the back pressure is hardly increased and the amount of reduction in the intake air amount is also reduced. It tends to decrease.
[0092]
Furthermore, since the influence of the nozzle opening of the variable nozzle centrifugal supercharger 19 on the intake air amount is larger on the closing side than on the opening side, the actual nozzle opening when fully closed is controlled. When a different situation occurs every time due to accumulation or the like, it is difficult to establish a correlation between the amount of PM trapped and the amount of intake air.
[0093]
Considering these circumstances, a method for estimating the amount of PM trapped by the particulate filter 29 using the intake air amount when the nozzle opening of the variable nozzle centrifugal supercharger 19 is fully closed as a parameter is not appropriate. It can be said.
[0094]
Therefore, in the PM collection amount determination control according to the present embodiment, the CPU 41 fully opens the opening of the intake throttle valve 21, the opening of the EGR valve 101, and the nozzle opening of the variable nozzle centrifugal supercharger 19. After the control, the PM collection amount was estimated using the output signal of the air flow meter 17 as a parameter.
[0095]
However, when the internal combustion engine 1 is in a normal operating state, when the opening of the intake throttle valve 21, the opening of the EGR valve 101, and the nozzle opening of the variable nozzle centrifugal supercharger 19 are fully opened, Since the operating state and torque of the internal combustion engine 1 change carelessly and lead to a decrease in drivability, in the present embodiment, the intake throttle valve 21 is provided on condition that the internal combustion engine 1 is in a decelerating operation state. It is assumed that the PM collection amount is estimated by controlling the opening, the opening of the EGR valve 101, and the nozzle opening of the variable nozzle centrifugal supercharger 19 to be fully opened.
[0096]
Hereinafter, PM collection amount determination control according to the present embodiment will be specifically described with reference to FIG.
[0097]
FIG. 5 is a flowchart showing a PM collection amount determination control routine. This PM collection amount determination control routine 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).
[0098]
In the PM collection amount determination control routine, first, in step S <b> 501, the CPU 41 reads from the RAM 43 the engine speed: Ne, the output signal value of the air flow meter 17 (intake air amount): Gn, the fuel injection amount: Q, and the accelerator position sensor 33. Output signal value (accelerator opening): Read Accp.
[0099]
In S502, the CPU 41 determines whether or not the internal combustion engine 1 is in a decelerating operation state using the engine speed Ne read in S501, the fuel injection amount Q, and the accelerator opening degree Accp as parameters. For example, the CPU 41 decelerates the internal combustion engine 1 on the condition that the engine speed Ne is equal to or greater than a predetermined speed, the fuel injection amount Q is “0”, and the accelerator opening degree Accp is fully closed. It is determined that the vehicle is in an operating state.
[0100]
When it is determined in S502 that the internal combustion engine 1 is not in the deceleration operation state, the CPU 41 once ends the execution of this routine.
[0101]
On the other hand, if it is determined in S502 that the internal combustion engine 1 is in the deceleration operation state, the CPU 41 proceeds to S503. In S503, the CPU 41 controls the intake throttle valve 21, the EGR valve 101, and the intake nozzle actuator 21a, the EGR valve 101, and the VNT actuator 19c to fully open the nozzle vanes of the variable nozzle centrifugal supercharger 19.
[0102]
In S <b> 504, the CPU 41 reads the latest engine speed Ne at the present time and the output signal value (actual intake air amount): actual Gn of the air flow meter 17 from the RAM 43.
[0103]
In S505, a reference intake air amount control map stored in advance in the ROM 42 is accessed, and a reference intake air amount: Gnbase corresponding to the engine speed: Ne read in S504 is calculated.
[0104]
In the reference intake air amount control map described above, PM is not collected in the particulate filter 29, the internal combustion engine 1 is in a decelerating operation state, the intake throttle valve 21 is fully open, and the EGR valve 101 is fully open. 7 is a map showing the relationship between the engine speed and the intake air amount (reference intake air amount) under the condition that the nozzle vanes of the variable nozzle centrifugal supercharger 19 are fully open.
[0105]
In S506, the CPU 41 calculates a difference: ΔGn by subtracting the actual intake air amount: actual Gn read in S504 from the reference intake air amount: Gnbase calculated in S505.
[0106]
In S <b> 507, the CPU 41 converts the difference: ΔGn into the PM collection amount: PM of the particulate filter 29. At that time, the relationship between the difference: ΔGn and the amount of collected PM: PM may be experimentally obtained in advance, and the relationship may be mapped and stored in the ROM 42.
[0107]
In S508, the CPU 41 determines whether or not the PM collection amount: PM calculated in S507 is equal to or higher than a preset PM collection amount upper limit value (PM collection amount upper limit value): PMmax. .
[0108]
When it is determined in S508 that the PM collection amount: PM is less than the PM collection amount upper limit value: PMmax, the CPU 41 considers that there is no need to regenerate the PM collection capability of the particulate filter 29, and this Routine execution is temporarily terminated.
[0109]
On the other hand, when it is determined in S508 that the PM collection amount: PM is equal to or greater than the PM collection amount upper limit value: PMmax, the CPU 41 needs to regenerate the PM collection capability of the particulate filter 29. Therefore, the PM regeneration process is executed in S509.
[0110]
In the PM regeneration process, for example, 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, in addition to normal fuel injection (main fuel injection), a method of performing additional fuel injection (expansion stroke injection) during the expansion stroke of each cylinder 2, each cylinder in addition to main fuel injection For example, a method of supplying unburned fuel to the particulate filter 29 and burning it by performing additional fuel injection (exhaust stroke injection) in the second exhaust stroke can be exemplified.
[0111]
When the PM regeneration process is executed in this manner, the PM collected by the particulate filter 29 is burned and removed from the particulate filter 29, and the particulate collection ability of the particulate filter 29 is thus regenerated. The
[0112]
When the CPU 41 executes the PM trapping amount determination control in this way, the particulate filter with the intake air amount when the intake vane of the intake throttle valve 21, the EGR valve 101, and the variable nozzle centrifugal supercharger 19 is fully opened as a parameter is used. Since the amount of collected PM of 29 is determined, an inadvertent change in the intake air amount due to the nozzle opening degree of the variable nozzle centrifugal supercharger 19 is prevented. As a result, the amount of intake air detected when determining the amount of PM trapped by the particulate filter 29 becomes an amount correlated with the amount of PM trapped by the particulate filter 29. The collected amount can be accurately determined.
[0113]
【The invention's effect】
According to the exhaust gas purification apparatus for an internal combustion engine according to the present invention, in an internal combustion engine including a collection mechanism for collecting particulates in exhaust gas and a variable nozzle centrifugal supercharger, the intake air amount of the internal combustion engine is used as a parameter. It is possible to accurately estimate the amount of collected particulates of the collection mechanism.
[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 the exhaust resistance in the particulate filter and the amount of trapped PM.
FIG. 4 is a graph showing the relationship between the amount of PM trapped by the particulate filter and the amount of intake air of the internal combustion engine
FIG. 5 is a flowchart showing a PM collection amount determination control routine.
[Explanation of symbols]
1 ... Internal combustion engine
17 ... Air flow meter
19 ... Variable nozzle centrifugal supercharger
19a ・ Compressor housing
19b · Turbine housing
19c ・ ・ VNT actuator
21 ... Inlet throttle valve
29 ... Particulate filter (collection mechanism)
31 ... ECU
41 ... CPU
101 ・ ・ EGR valve

Claims (5)

A variable nozzle centrifugal supercharger provided in an intake passage and an exhaust passage of an internal combustion engine;
A collection mechanism provided in an exhaust passage of the internal combustion engine for collecting particulates contained in the exhaust;
Control means for fully opening the nozzle opening of the variable nozzle centrifugal supercharger when the internal combustion engine is in a deceleration operation state;
Detecting means for detecting an intake air amount of the internal combustion engine when the internal combustion engine is in a decelerating operation state and a nozzle opening of the variable nozzle centrifugal supercharger is fully open;
Estimating means for estimating the amount of particulate collection of the collection mechanism using the amount of intake air detected by the detection means as a parameter;
An exhaust emission control device for an internal combustion engine, comprising: An intake throttle valve provided in the intake passage of the internal combustion engine for reducing the flow rate of air flowing through the intake passage;
The control means controls the opening of the variable nozzle centrifugal supercharger and the opening of the intake throttle valve to be fully open when the internal combustion engine is in a decelerating operation state,
The detecting means detects an intake air amount of the internal combustion engine when the internal combustion engine is in a decelerating operation state and a nozzle opening of the variable nozzle centrifugal supercharger and an opening of the intake throttle valve are fully open. And
2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the estimation means estimates the amount of particulate collection of the collection mechanism using the intake air amount detected by the detection means as a parameter. An EGR passage that recirculates part of the exhaust gas flowing through the exhaust passage of the internal combustion engine to the intake passage;
An EGR valve that adjusts the flow rate of the exhaust gas flowing through the EGR passage,
The control means controls the opening of the variable nozzle centrifugal supercharger and the opening of the EGR valve to fully open when the internal combustion engine is in a decelerating operation state,
The detecting means detects an intake air amount of the internal combustion engine when the internal combustion engine is in a decelerating operation state and the opening degree of the variable nozzle centrifugal supercharger and the opening degree of the EGR valve are fully open. ,
2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the estimation means estimates the amount of particulate collection of the collection mechanism using the intake air amount detected by the detection means as a parameter. An intake throttle valve provided in the intake passage of the internal combustion engine for restricting the flow rate of air flowing through the intake passage;
An EGR passage that recirculates part of the exhaust gas flowing through the exhaust passage of the internal combustion engine to the intake passage;
An EGR valve that adjusts the flow rate of the exhaust gas flowing through the EGR passage,
The control means controls the opening of the variable nozzle centrifugal supercharger, the opening of the intake throttle valve, and the opening of the EGR valve to be fully opened when the internal combustion engine is in a decelerating operation state,
The detection means is when the internal combustion engine is in a decelerating operation state and the nozzle opening of the variable nozzle centrifugal supercharger, the opening of the intake throttle valve, and the opening of the EGR valve are fully open. Detecting the intake air amount of the internal combustion engine of
2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the estimation means estimates the amount of particulate collection of the collection mechanism using the intake air amount detected by the detection means as a parameter. 5. The apparatus according to claim 1, further comprising a determination unit that determines that the collecting mechanism is clogged when an intake air amount detected by the detection unit is less than a predetermined amount. An exhaust purification device for an internal combustion engine according to any one of the above.

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