JP3593962B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly, to an exhaust gas purification device for an internal combustion engine in which a filter is disposed in an engine exhaust passage for removing particulates such as soot contained in exhaust gas.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a diesel engine, a particulate filter capable of capturing fine particles in exhaust gas is disposed in an engine exhaust passage in order to remove fine particles such as soot contained in the exhaust gas. The particulate filter is once collected, and the particulate filter collected by the particulate filter is ignited, burned, and removed to regenerate the particulate filter.
[0003]
However, the collected fine particles do not ignite unless they reach a high temperature of about 600 ° C. or higher. On the other hand, the exhaust gas temperature of a diesel engine is usually considerably lower than 600 ° C. The exhaust gas temperature is only about 350 ° C to 400 ° C. Therefore, it is difficult to ignite the fine particles only by the heat of the exhaust gas.
[0004]
Therefore, there is a technology in which the catalyst is supported on the particulate filter to lower the ignition temperature of the fine particles so that the fine particles are ignited only by the exhaust gas heat. Hereinafter, "a particulate filter with a catalyst or simply referred to as a filter." For example, in the technique described in Japanese Patent Publication No. 7-106290, a catalyst composed of a mixture of a platinum group metal and an alkaline earth metal oxide is used as a particulate filter. The above problem is addressed by carrying.
[0005]
[Problems to be solved by the invention]
However, even with the particulate filter with a catalyst as described above, only a part of the fine particles may be ignited and the fine particles may remain unburned.
In detail, there is no problem when the amount of fine particles contained in the exhaust gas is small, but a large amount of fine particles may be generated depending on the operation state of the internal combustion engine. In this case, the fine particles adhering to the particulate filter are completely removed. Before burning, other fine particles are deposited on the fine particles to form a layered state. Then, for example, even if the upper layer of fine particles in a portion that is easily contacted with oxygen burns, for example, the lower layer of fine particles in a portion that is difficult to contact with oxygen do not burn, thus causing a phenomenon that the fine particles remain unburned. There is a possibility that the filter cannot be used because the exhaust gas is difficult to pass due to clogging due to the accumulation of the gas.
[0006]
In the case of an internal combustion engine equipped with a turbocharger, since the turbine is rotated by the energy of the exhaust gas, the exhaust gas and the filter are cooled by the turbine, so that the particulates cannot be ignited and burned, and clogging occurs. Easy to do. Then, when the filter is clogged, the turbocharger cannot easily rotate the turbine and cannot be sufficiently supercharged by the compressor. As a result, the turbocharger cannot produce a high output of the engine.
[0007]
The present invention has been made in view of the above points, and a problem to be solved is to provide a particulate filter with a catalyst in an exhaust gas purification device for an internal combustion engine in which a turbocharger and a particulate filter with a catalyst are installed in an exhaust pipe. It is an object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine, which can eliminate the clogged state and guarantee the normal rotation of the turbine.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention employs the following means.
That is, the exhaust gas purifying apparatus for an internal combustion engine of the present invention is provided in an exhaust passage, and a turbocharger that pressurizes intake air using exhaust pressure, and an inlet-side exhaust pressure that detects exhaust pressure upstream of the exhaust passage of the turbocharger. Detecting means, an outlet air flow rate detecting means for detecting an air flow rate pressurized and suctioned by the turbocharger, and a filter installed in the exhaust passage, carrying an oxidation catalyst and capable of capturing fine particles in exhaust gas, A bypass passage branching into the exhaust passage so that the exhaust gas bypasses the filter and the turbocharger, a bypass valve for opening and closing the bypass passage, and an exhaust gas detected by the inlet-side exhaust pressure detection means. Control means for controlling the opening and closing of the bypass valve based on the value of atmospheric pressure and the air flow rate detected by the outlet side air flow rate detection means, That (corresponding to claim 1).
[0009]
According to this configuration, the clogging state of the filter is determined by the control means based on a pressure loss difference between the value of the exhaust pressure flowing into the turbocharger and rotating the turbine and the air flow generated by the compressor directly connected to the turbine. If the condition is remarkable, the control means opens a bypass valve to allow a part of the exhaust gas to bypass the turbocharger and the filter and escape downstream of the exhaust passage, thereby reducing the amount of the exhaust gas flowing into the filter, and By raising the temperature, the fine particles are burned to eliminate the clogging. When the control means determines that the clogging state has been eliminated by the pressure loss difference, the control unit closes the bypass valve and causes the turbocharger to perform a normal supercharging operation.
[0010]
Here, an ECU (control means) for controlling the entire internal combustion engine will be briefly described, and components of the present invention will be described.
The ECU is composed of a digital computer as is well known, and includes a central processing unit CPU, a read-only memory ROM, a random access memory RAM, a backup RAM, an input interface circuit, an output interface circuit, etc., which are interconnected by a bidirectional bus. Be composed.
[0011]
The input interface circuit is electrically connected to various sensors mounted on the internal combustion engine or the vehicle. When output signals of these various sensors enter the ECU from the input interface circuit, these parameters are temporarily stored in the random access memory RAM. It is memorized. Then, based on these parameters, the CPU performs the necessary arithmetic processing. In executing the arithmetic processing, the CPU stores the parameters stored in the random access memory RAM through the bidirectional bus as necessary. call. Further, the output interface circuit is electrically connected to various output devices such as a bypass valve attached to the internal combustion engine or the vehicle, and a command of the ECU is output from the output interface circuit.
[0012]
As the “inlet side exhaust pressure detecting means”, a pressure sensor can be exemplified.
An example of the “outlet-side air flow rate detecting means” is an air flow meter.
When the internal combustion engine is a diesel engine, examples of the “fine particles” include carbon suits, unburned fuel, and oil.
When the internal combustion engine is a diesel engine, the "filter" can be exemplified by a so-called Diesel Particulate Filter: DPF for collecting fine particles discharged from the diesel engine.
[0013]
The "bypass valve" can be exemplified by a waste gate valve (Waste Gate Valve: WGV) (corresponding to claim 4).
The waste gate valve WGV is an exhaust bypass valve of a turbocharger, which normally prevents a supercharging pressure from exceeding a set pressure and bypasses a part of exhaust gas flowing into a turbine to a turbine outlet to reduce a turbine output. It controls the supercharging pressure. In the present invention, the waste gate valve WGV reduces the amount of exhaust gas flowing into the filter by escaping part of the exhaust gas to the exhaust passage downstream by bypassing the turbine outlet and the filter when the filter is clogged, By raising the temperature inside the filter, the fine particles are burned and clogging is eliminated.
[0014]
In the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the control unit may determine whether the filter is clogged abnormally based on a value of an exhaust pressure of the inlet-side exhaust pressure detecting unit and an air flow rate of the outlet-side air flow detecting unit. It may be configured to make a judgment and control the opening and closing of the bypass valve (corresponding to claim 2). According to this configuration, the clogging abnormality of the filter can be determined based on the value of the exhaust pressure and the air flow rate, so that the clogging abnormality determination process of the control unit can be facilitated.
[0015]
Further, in the exhaust gas purifying apparatus for an internal combustion engine of the present invention, when the control means determines that the filter is abnormally clogged based on the detected exhaust pressure value and the air flow rate, the control unit opens the bypass valve to remove the exhaust gas. A configuration may be adopted in which a detour and an alarm are generated (corresponding to claim 3). According to this configuration, when the clogging is abnormal, the driver can be notified of the abnormality by an alarm. Therefore, even if the clogging cannot be eliminated even by the bypass process using the bypass valve, an artificial regeneration operation or the like is performed. Preliminary measures can be taken.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an exhaust gas purification device for an internal combustion engine of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a case where the exhaust gas purifying apparatus for an internal combustion engine of the present invention is applied to a diesel engine which is a compression ignition type internal combustion engine.
Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 Denotes an exhaust valve, and 10 denotes an exhaust port.
[0017]
The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to a compressor 15 of an exhaust turbocharger 14 via an intake duct 13. An air flow meter (outlet air flow rate detection means) 81 is attached to the intake duct 13 near the compressor 15, and the air flow rate at the outlet side of the compressor 15 is detected based on an output signal of the air flow meter 81. On the other hand, an air cleaner 80 is provided in the intake pipe 71 to which the compressor 15 is attached.
[0018]
A throttle valve 17 driven by a step motor 16 is arranged in the intake duct 13, and a cooling device 18 for cooling intake air flowing through the intake duct 13 is arranged around the intake duct 13. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 18, and the engine cooling water cools the intake air.
[0019]
On the other hand, the exhaust port 10 is connected to a turbine 21 of the turbocharger 14 via an exhaust manifold 19 and an exhaust pipe 20. An exhaust pressure sensor (inlet side exhaust pressure detecting means) 82 is attached to the exhaust pipe 20 near the turbine 21, and the exhaust pressure on the inlet side of the turbine 21 is detected based on an output signal of the exhaust pressure sensor 82. . On the other hand, the outlet of the turbine 21 is connected to an exhaust gas purification device A provided in an exhaust pipe 70 serving as an exhaust passage. Further, a fuel addition nozzle (not shown) as a fuel supply means is attached to the exhaust port 10. Therefore, the fuel addition nozzle is located upstream of the exhaust gas purification device A in the exhaust pipe 70.
[0020]
The exhaust gas purifying apparatus A has a DPF carrying an oxidation catalyst and a particulate filter with a catalyst (hereinafter, referred to as a filter) 22 which is a filter capable of capturing fine particles in exhaust gas. is there. In order to remove fine particles such as soot in the exhaust gas using the exhaust gas purification device A, the fine particles are once collected by the filter 22, and the collected fine particles are ignited and burned. To ignite and burn the fine particles, in addition to utilizing the heat of the exhaust gas, fuel is supplied into the exhaust gas from the fuel addition nozzle, and the reaction heat generated by the oxidation reaction of the fuel is utilized. By burning and removing the fine particles in this manner, the fine particles are removed from the filter 22 and the filter 22 is regenerated.
[0021]
A bypass branched from the exhaust pipes 20 and 70 between the exhaust pipe 20 and the exhaust pipe (exhaust passage) 70 such that the exhaust gas bypasses the turbine 21 of the turbocharger 14 and the exhaust purification device A (or the filter 22). A passage 90 is provided. The bypass passage 90 is provided with a waste gate valve (WGV) 91 serving as a bypass valve.
[0022]
The WGV 91 is an exhaust bypass valve of the turbocharger 14, which normally prevents a supercharging pressure from exceeding a set pressure and controls a turbine output by diverting a part of exhaust gas flowing into the turbine to an outlet of the turbine 21. And controls the supercharging pressure. In the present invention, in addition to the control of the supercharging pressure, the WGV 91 opens a valve on the basis of a filter clogging abnormality determination described later, so that a part of the exhaust gas flows downstream of the exhaust pipe 70 through the bypass passage 90. Then, the bypass passage 90 is closed by closing the valve.
[0023]
Further, the exhaust manifold 19 and the surge tank 12 are connected to each other via an EGR passage 24 that is a component of an exhaust gas recirculation device (hereinafter, referred to as EGR). Further, the EGR passage 24 has an electrically controlled EGR control valve 25. In addition, a cooling device 26 for cooling the EGR gas flowing through the EGR passage 24 is arranged. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 26, and the EGR gas is cooled by the engine cooling water.
[0024]
On the other hand, the fuel injection valve 6 is connected to a common rail 27 which is a fuel reservoir via a fuel supply pipe 6a.
Fuel is supplied into the common rail 27 by an electrically controlled fuel pump 28 of variable discharge amount. Then, the fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 via the fuel supply pipe 6a. A fuel pressure sensor 29 for detecting the fuel pressure in the common rail 27 is attached to the common rail 27, and a fuel pump is provided so that the fuel pressure in the common rail 27 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 29. 28 is controlled.
[0025]
The amount of fuel injected from the fuel injection valve 6 is stored in a ROM 32 of an electronic control unit (ECU) 30 described below in the form of a map as a function of the depression amount of the accelerator pedal 40 and the engine speed. A required torque corresponding to the depression amount of the accelerator pedal 40 and the engine speed is obtained from the required torque calculation map (not shown), and the calculation is performed based on the required torque.
[0026]
The ECU 30 is composed of a digital computer and includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Microprocessor) 34, an input port 35, and an output port 36 connected to each other by a bidirectional bus 31.
[0027]
Output signals of the fuel pressure sensor 29, the air flow meter 81, and the exhaust pressure sensor 82 are input to the input port 35 via the corresponding AD converter 37.
[0028]
An exhaust gas temperature sensor 79 for detecting the temperature (exit gas temperature) To of the exhaust gas discharged from the exhaust gas purification device A is provided near the downstream side of the exhaust gas purification device A in the exhaust pipe 70. Further, an oxygen sensor (or an air-fuel ratio sensor) 83 for detecting the oxygen concentration in the exhaust gas discharged from the exhaust gas purification device A (filter) is attached downstream of the exhaust gas temperature sensor 79.
The output signals of the temperature sensor 79 and the oxygen sensor 83 also enter the input port 35 via the corresponding AD converter 37.
[0029]
Further, a downstream side of the oxygen sensor 81 in the exhaust pipe 70 is provided with, for example, a catalytic converter and an exhaust throttle valve (both not shown) for enclosing a storage-reduction NOx catalyst in the case body.
[0030]
A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 enters the input port 35 via the corresponding AD converter 37. Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse each time the crankshaft (not shown) rotates, for example, 30 °.
[0031]
On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 25, the fuel pump 28, and the WGV 91 via the corresponding drive circuit 38.
[0032]
Next, using the flowchart of FIG. 2, it is determined whether or not the filter included in the exhaust gas purification apparatus A according to the present embodiment has a clogging abnormality, and a filter clogging abnormality determination for avoiding the clogging state is performed. A program for realizing the avoidance control process will be described.
This program includes steps 101 to 108 described below. A program including these steps is stored in the ROM 32 of the ECU 30, and is called up as needed. The processing in each of the above steps is entirely performed by the CPU 34 of the ECU 30.
[0033]
In addition, in this filter clogging abnormality determination, an abnormality determination map M shown in FIG. 3 is used. The abnormality determination map M is a map in which the relationship between the pressure loss difference and the air flow rate is used as a parameter and the filter is abnormally clogged based on experimental values based on the parameters, and is stored in the ROM 32 of the ECU 30 in advance. The pressure loss difference refers to a pressure loss difference between the value of the exhaust pressure flowing into the turbocharger 14 and rotating the turbine 21 and the air flow generated by the compressor 15 directly connected to the turbine 21. A difference value between the corresponding exhaust pressure target value and the air flow rate may be calculated and used as the pressure loss difference.
[0034]
From the data of the air flow rate by the air flow meter 81 and the data of the exhaust pressure by the exhaust pressure sensor 82, the ECU 30 calculates the value of the exhaust pressure flowing into the turbocharger 14 to rotate the turbine 21 and the air generated by the compressor 15 directly connected to the turbine 21. A pressure loss difference from the flow rate is calculated, and a filter clogging abnormality is determined with reference to the abnormality determination map M.
[0035]
That is, the abnormality determination map M includes a coordinate plane in which the vertical axis represents the pressure loss difference and the horizontal axis represents the air flow generated by the compressor 15. This coordinate plane is divided into _three areas (mode 1E ₁ , mode 2E ₂ , mode 3E ₃ ) by two boundary lines. Mode 1E ₁ pressure loss difference is small area, clogging represents less normal mode, the mode 3E ₃ pressure loss difference is large area is a mode indicating clogging abnormality. The mode 2E ₂ located in the middle of the mode 1E ₁ and mode 3E _3, by although slightly clogging implementing normal filter regeneration process, is the DPF regeneration mode particles is capable of burning and removing .
[0036]
When the process is started, the ECU 30 reads out the abnormality determination map M from the ROM 30 (step 101), and constantly monitors the air flow rate by the air flow meter 81 and the exhaust pressure by the exhaust pressure sensor 82 to obtain the air flow rate data and the exhaust pressure data. Then, the pressure loss difference is calculated (step 102).
[0037]
Next, referring to the read abnormality determination map M, the ECU 30 performs filter clogging abnormality determination based on the calculated pressure loss value and the detected air flow rate (step 103).
[0038]
In the determination of step 103, if the pressure loss value and an air flow rate is in the mode 1E ₁ area, ECU 30 determines that the clogging is less normal mode (step 104), the process returns to the start position.
[0039]
In the determination of step 103, if the pressure loss value and the air flow rate is mode 2E ₂ area, ECU 30 is removed by burning the particulates by conventional filter regeneration is determined that the DPF regeneration mode (step 105), the start position To return.
[0040]
In the determination of step 103, if the pressure loss value and the air flow rate mode 3E ₃ areas, ECU 30 determines that the abnormal mode (step 106). In the abnormal mode, the filter 22 is so clogged that it is difficult to regenerate in the normal filter regeneration process. Therefore, the ECU 30 opens the WGV valve 91 (step 107) and shows a diagram (alarm) indicating the clogging abnormality of the filter 22. Is turned on (step 108), and the process returns to the start position.
[0041]
In step 107, when the WGV valve 91 is opened, a part of the exhaust gas flows to the bypass passage 90 bypassing the turbocharger 14 and the filter 22. Then, the amount of the exhaust gas flowing into the filter 22 is reduced, which acts to increase the temperature inside the filter 22, thereby burning the fine particles and eliminating the clogging.
[0042]
Further, in step 108, the lighting of the diagram allows the driver to know in real time that a clogging abnormality has occurred in the filter 22. Therefore, if the lighting of the diagram is repeated, it means that the clogging could not be resolved even by the detour processing by the WGV 91, and an artificial regeneration operation such as replacing the filter 22 is required. As described above, the countermeasures against the filter clogging abnormality are taken at an early stage, so that it is possible to prevent a danger such as stopping of the engine during operation caused by leaving the filter clogging abnormality and damage to the exhaust gas purification device itself. .
[0043]
【The invention's effect】
In the exhaust gas purifying apparatus for an internal combustion engine of the present invention, the clogging state of the filter is determined based on a pressure loss difference between an exhaust pressure value that flows into a turbocharger and rotates a turbine and an air flow rate generated by a compressor directly connected to the turbine, When the clogging state is remarkable, the control means opens the bypass valve to escape a part of the exhaust gas to the exhaust passage downstream by bypassing the turbocharger and the filter, thereby reducing the amount of the exhaust gas flowing into the filter. The temperature inside the filter can be increased, and the clogging can be eliminated by burning the fine particles.
Therefore, the present invention can provide an exhaust gas purifying apparatus for an internal combustion engine that can eliminate a clogged state of a particulate filter with a catalyst and ensure normal rotation of a turbine.
[Brief description of the drawings]
FIG. 1 is an overall view of an internal combustion engine to which an exhaust gas purification device for an internal combustion engine of the present invention is applied.
FIG. 2 is a flowchart showing a process for determining whether or not there is a clogging abnormality of a filter included in the exhaust gas purification device A according to the present embodiment and a process for avoiding a clogged state.
FIG. 3 is an explanatory diagram of an abnormality determination map.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine main body 2 Cylinder block 3 Cylinder head 4 Piston 5 Combustion chamber 6 Electric control type fuel injection valve 6a Fuel supply pipe 7 Intake valve 8 Intake port 9 Exhaust valve 10 Exhaust port 11 Intake branch pipe 12 Surge tank 13 Intake duct 14 Exhaust turbo Charger 15 Compressor 16 Step motor 17 Throttle valve 18 Cooling device 19 Exhaust manifold 20 Exhaust pipe 21 Turbine 22 Catalytic particulate filter (filter)
23 case body 24 EGR passage 25 electric control type EGR control valve 26 cooling device 27 common rail 28 fuel pump 29 fuel pressure sensor 30 ECU (control means)
31 bidirectional bus 32 ROM
33 RAM
34 CPU
35 input port 36 output port 37 AD converter 38 drive circuit 40 accelerator pedal 41 load sensor 42 crank angle sensor 70 exhaust pipe (exhaust passage)
79 exhaust temperature sensor 80 air cleaner 81 air flow meter (outlet air flow detecting means)
82 exhaust pressure sensor (inlet side exhaust pressure detection means)
83 oxygen sensor 90 bypass passage 91 WGV (bypass valve)
A Exhaust gas purification device

Claims (4)

A turbocharger installed in an exhaust passage and pressurizing intake air using exhaust pressure,
Inlet-side exhaust pressure detecting means for detecting exhaust pressure upstream of the exhaust passage of the turbocharger;
Outlet-side air flow rate detecting means for detecting an air flow rate pressurized and suctioned by the turbocharger,
A filter that is installed in the exhaust passage and carries an oxidation catalyst and can capture fine particles in exhaust gas;
A bypass passage branching into the exhaust passage so that the exhaust gas bypasses the filter and the turbocharger,
A bypass valve for opening and closing the bypass passage;
Control means for controlling opening and closing of the bypass valve based on an exhaust pressure value detected by the inlet-side exhaust pressure detecting means and an air flow rate detected by the outlet-side air flow rate detecting means. An exhaust gas purification device for an internal combustion engine. 2. The control unit determines a clogging abnormality of the filter based on a pressure value of the inlet-side exhaust pressure detecting unit and an air flow rate of the outlet-side air flow detecting unit, and controls opening and closing of the bypass valve. 3. Exhaust purification device for internal combustion engine. 3. The internal combustion engine according to claim 2, wherein the control unit opens the bypass valve to bypass the exhaust gas and generates an alarm when it is determined from the detected exhaust pressure value and the air flow rate that the filter is abnormally clogged. Engine exhaust purification device. The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein the bypass valve is a waste gate valve.

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