JP2001280118A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent the deterioration of the fuel consumption of an engine caused by the clogging of a filter, and the cracking and damage of a filter caused by the abnormal combustion with respect to a continuous regeneration-type particulate filter. SOLUTION: A DPF 10 is mounted on an exhaust pipe 15 of the engine 1. Signals from a rotating speed sensor 7, an opening of accelerator sensor 8 or the like are taken in a controller 9, an exhaust amount of the particulate and a combustion amount are respectively calculated on the basis of a particulate exhausting amount map and a combustion amount map, and an accumulation amount of particulate captured by the DPF 10 is calculated by integrating the difference therebetween. When the accumulation amount is over a predetermined amount, a temperature of the exhaust is raised by the after-injection of the fuel or the like to burn the accumulated particulate and to regenerate the DPF 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diesel particulate filter for reducing or removing soot-like particles contained in exhaust gas discharged from an internal combustion engine, particularly a diesel engine.

[0002]

2. Description of the Related Art Conventionally, a diesel particulate filter (hereinafter referred to as DP) has been used as a device for preventing the discharge of soot-like particles, that is, particulates, from a diesel engine.
F). This DP
F generally heats the filter periodically from the outside,
The collected particulates (hereinafter abbreviated as PM) are oxidized and regenerated. For example, a DPF or the like that regenerates by burning PM collected in a filter by an electric heater.

On the other hand, as disclosed in Japanese Patent Application Laid-Open No. H10-159552, NO in exhaust gas is oxidized by an oxidation catalyst disposed in front of a filter to generate NO2, and heat of the exhaust gas and NO2 Recently, a DPF called a CRT (continuous regeneration type) for continuously oxidizing and regenerating PM collected in a filter has been actively studied.

[0004] In the former general DPF, there is known a filter in which two filters are arranged in parallel to sequentially regenerate and collect. However, in order to regenerate the DPF by burning the collected PM. At present, it is not widely used because of high cost and difficulty in mounting. Compared with this, the latter CRT only requires an oxidation catalyst for oxidizing NO in the exhaust gas to generate NO2 at the previous stage of the filter, and thus requires a special device for regenerating the DPF. Instead, the regeneration is performed continuously, so that it can be practically realized by the configuration of one system of the catalyst and the filter. Therefore, the former general DPF is low in cost and excellent in mountability.

A mechanism in which PM collected in a DPF called CRT burns will be described. As described above, in this DPF, an oxidation catalyst is disposed in front of a filter that traps PM. In this oxidation catalyst, an oxidation reaction of 2NO + O2 → 2NO2... Occurs, and the PM collected in the filter is burned by the oxidation reaction of C + 2NO2 → CO2 + 2NO. In addition,
When the ambient temperature of the filter reaches about 600 ° C. or higher, PM directly reacts with oxygen and burns. Further, NO generated by the above reaction is purified using a NOx catalyst placed downstream of the DPF.

[Problems to be solved by the invention]

However, the above-mentioned oxidation reaction becomes difficult to occur below a certain temperature, and the temperature varies depending on the sulfur content of the fuel, and is about 250 ° C. when a fuel having a sulfur content of 50 ppm is used. . Therefore, when the temperature is lower than this temperature, further reaction becomes difficult to occur, and the PM trapped in the filter continues to accumulate without burning much. Therefore, when a vehicle equipped with a CRT runs under conditions where the exhaust gas temperature is always low, such as when traveling only in an urban area, PM accumulates on the filter without burning, and the exhaust pressure increases, resulting in a decrease in output and deterioration in fuel efficiency. Occurs. In addition, when the exhaust temperature rises and the regeneration is started by performing high-speed running or the like after a considerable amount of PM has been deposited, the deposited PM rapidly burns and the temperature in the filter rises rapidly, causing abnormal heat generation. There is a problem that cracks and breakage of the filter occur due to the above, and the durability of the filter is significantly reduced. This problem arises when the amount of deposition is detected using a pressure sensor.
Depending on the properties of M, even if the amount of deposition is large, the pressure loss may be small, so that it tends to be more remarkable.

[0007] The present invention has been made in view of the above problems, and when the amount of PM trapped in the filter exceeds a predetermined amount, the temperature is forcibly increased to regenerate the PM. In this case, the PM is prevented from accumulating unnecessarily on the filter to prevent an increase in exhaust pressure, so that the output does not decrease and fuel consumption does not deteriorate.
The purpose is to provide a PF.

[0008]

A DPF according to the present invention that achieves the above object oxidizes NO in exhaust gas of an internal combustion engine to NO2 by an oxidation catalyst, and burns PM trapped in a filter by the NO2. Regenerating DPF,
Temperature detecting means for detecting the temperature of the filter, operating state detecting means for detecting the rotation speed and load of the internal combustion engine, and the amount of PM discharged from the internal combustion engine based on information from the operating state detecting means. An emission amount calculating means for calculating, a combustion amount calculating means for calculating a combustion amount of PM burned by NO2 from information from the temperature detecting means, and a temperature of exhaust gas passing through the oxidation catalyst and the filter is forcibly set. A temperature increasing means for increasing the temperature, wherein when the integrated value of the difference between the value calculated by the emission amount calculating means and the value calculated by the combustion amount calculating means is equal to or more than a predetermined amount, the temperature increasing means It is characterized in that the temperature of the exhaust gas is raised.

According to a second aspect of the present invention, the emission amount calculating means has a PM emission map in which the emission amount of PM is determined by the rotation speed and load of the internal combustion engine, and calculates the emission amount of PM from the map. Wherein the combustion amount calculating means has a PM combustion amount map in which the amount of PM burned is determined from the value detected by the temperature detecting means.
The combustion amount of M is calculated.

According to a third aspect of the present invention, the temperature detecting means calculates an average value of values detected by temperature sensors provided at an inlet and an outlet of a DPF comprising the oxidation catalyst and the filter. It is characterized by the following.

The invention according to a fourth aspect is characterized in that the temperature increasing means is in-cylinder post-injection by a fuel injection device of the internal combustion engine.

[0012] The temperature increasing means may be an injection timing delay device for delaying the injection timing of the internal combustion engine.

[0013] As described in claim 6, the temperature increasing means may be an electric heater. In this case, the electric heater may be installed at the entrance of the DPF or wound around the DPF itself.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an overall configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to an embodiment of the present invention including a DPF 10 attached to an exhaust pipe 15. The diesel engine 1 shown in this embodiment includes a high-pressure pump 2, a common rail 4, and an injection nozzle 3. Fuel whose pressure is increased by the high-pressure pump 2 is accumulated in the common rail 4 and injected from the injection nozzle 3. The injection amount and the injection timing are controlled by the controller 9. At this time, the injection timing is based on a crank angle detected by a crank angle sensor 6 mounted near the flywheel 5.

The DPF 10 is attached to the exhaust pipe 15. The DPF 10 includes an oxidation catalyst 11 such as a platinum-based catalyst disposed at the front stage and a filter 12 disposed at the rear stage for trapping PM. The mechanism of DPF regeneration is as described above.

However, the regeneration of the DPF is not carried out at a certain temperature or lower (for example, 250 ° C. or lower) for the above-mentioned reason. Therefore, in the present invention, the accumulated amount of PM accumulated in the filter is calculated by the controller 9, and when the accumulated amount becomes equal to or more than a predetermined amount, post-injection is performed at a timing of, for example, 200 ° ATDC in addition to the normal fuel injection. The exhaust gas temperature is forcibly raised to burn the PM and the DPF is regenerated.

More specifically, the information of the load sensor 8 such as the rotation speed sensor 7 and the accelerator opening sensor is fetched at every sampling time (for example, several tens μs) in the controller 9 and stored in the controller 9 in advance. The amount We of PM emitted from the diesel engine 1 at that time is calculated from the PM emission map shown in FIG. Further, the temperature detected by the temperature sensor 13 provided at the entrance of the DPF 10 and the temperature detected by the temperature sensor 14 provided at the exit are simultaneously taken into the controller 9, and the average value is calculated as the representative temperature of the DPF 10. The combustion amount Wc of the PM burned by the DPF 10 is calculated from the PM combustion amount map shown in FIG. 3 stored in advance. Then, by subtracting the combustion amount Wc from the emission amount We, a calculated accumulation amount Wa of the PM accumulated in the DPF 10 is calculated, and this is integrated.

When the accumulated amount Wa exceeds a predetermined amount, the controller 9 controls a solenoid valve (not shown) provided in the injection nozzle 3 to forcibly perform the above-described post-injection. Then, the exhaust gas temperature is raised, and the PM deposited on the filter is burned and the DPF is regenerated.

Next, the flowchart shown in FIG. 4 will be described. First, in step S1, the PM accumulation amount Wa1 stored in the controller 9 when the exhaust gas purification device leaves the factory is initialized. The initialization is also performed after the accumulation amount Wa1 exceeds the predetermined amount and the DPF 10 is regenerated. Next, in step S2, the rotation speed sensor 7, the load sensor 8, and the temperature sensor 1
The outputs of Nos. 3 and 14 are read, and then in step S3, the emission amount We is calculated from the above-described PM emission amount map. Next, in step S4, the combustion amount Wc is calculated from the aforementioned PM combustion amount map. Further, in step S5, a calculated PM accumulation amount Wa is obtained by subtracting the combustion amount Wc from the emission amount We. This is added to the previously calculated accumulation amount Wa1 in step S6 to newly set the accumulation amount Wa1, and the accumulation amount Wa calculated next time is integrated.

The accumulated amount Wa1 integrated as described above.
In step S7, it is determined whether or not exceeds a predetermined amount predetermined in an experiment or the like. If it exceeds, a proper amount of fuel is injected at, for example, 200 ° ATDC in addition to the normal fuel injection in step S8, and the exhaust gas temperature is forced. DPF1
The PM trapped in 0 is burned.

In this embodiment, the case of performing post-injection as a means for forcibly burning the PM trapped in the DPF 10 has been described. Good. In this case, the fourth
In step S8 in the figure, control for delaying the injection timing is performed.

As a means for forcibly burning PM trapped in the DPF 10, a method in which an electric heater is provided to heat the PM is also conceivable. At this time, the electric heater may be installed at the entrance of the DPF 10 as described above, or may be wound around the DFP 10 itself. In this case, control for operating the electric heater is performed in step S8 in FIG.

Further, in the present embodiment, the common rail fuel injection device is shown as the fuel injection device, but it goes without saying that the fuel injection device of the present invention is not limited to the common rail fuel injection device.

Further, in this embodiment, the DPF of the type in which the oxidation catalyst is disposed upstream of the filter is shown.
A filter / catalyst integrated DPF in which an oxidation catalyst is supported on a filter may be used.

【The invention's effect】

As described above, according to the present invention, when the accumulated amount of PM trapped in the filter exceeds a predetermined amount, the PM is forcibly burned to regenerate the DPF.
For example, even if the exhaust temperature is low for a long time, such as when traveling only in an urban area, the filter will not be clogged due to the temperature below the regeneration temperature and the output will not decrease and the fuel consumption will not deteriorate. , And PM collected in large quantities
There is no problem of cracking or breakage of the filter due to the regenerated blast. In addition, PM
Since the amount of deposited PM is calculated, a pressure sensor for detecting the inlet pressure of the DPF is not required, which reduces the cost. In addition, the difference between the pressure rise that occurs when the amount of deposited PM is detected by the pressure sensor and the actual amount of deposited PM is reduced. The risk of abnormal combustion resulting from the above is also eliminated.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration diagram of an exhaust gas purification apparatus according to the present invention.

FIG. 2 is a diagram showing a particulate emission map.

FIG. 3 is a diagram showing a particulate combustion amount map.

FIG. 4 is a flowchart showing a control flow of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diesel engine 2 High pressure supply pump 3 Injection nozzle 4 Common rail 5 Flywheel 6 Crank angle sensor 9 Controller 10 Exhaust gas purification device (DPF) 11 Oxidation catalyst 12 Filter 13, 14 Temperature sensor Exhaust pipe

Continued on the front page F term (reference) 3G084 AA01 BA15 DA02 DA10 DA25 EA04 EA11 EB02 EB08 EB25 EC02 FA10 FA18 FA27 FA33 FA38 3G090 AA01 AA06 BA01 CA01 CB11 DA12 DA13 DA18 DA20 EA02 3G301 HA02 JA02 JA24 JA25 MA19 NA03 NA04 NA25 NE22 PA17Z PD11Z PE01Z PE03Z PF03Z

Claims (6)

[Claims] An internal combustion engine that oxidizes NO contained in exhaust gas of an internal combustion engine to NO2 by an oxidation catalyst (11) and burns and regenerates particulates collected by a filter (12) with the NO2. In the exhaust gas purifying apparatus, temperature detecting means (13, 14) for detecting a temperature of the filter (12), operating state detecting means (7, 8) for detecting a rotation speed and a load of the internal combustion engine, Emission calculation means for calculating the amount of particulates discharged from the internal combustion engine based on information from the state detection means (7, 8), and the temperature detection means (13, 14) Forcibly increasing the temperature of the exhaust gas passing through the combustion amount calculating means that calculates from the information from the above, and the oxidation catalyst (11) and the filter (12). Temperature increasing means, and when the integrated value of the difference between the value calculated by the emission amount calculating means and the value calculated by the combustion amount calculating means becomes equal to or more than a predetermined amount, the temperature is increased by the temperature increasing means. Exhaust gas purifying apparatus for an internal combustion engine characterized by raising the temperature of gas 2. The apparatus according to claim 1, wherein said emission amount calculating means has a particulate emission amount map in which the amount of particulate emission is determined by a rotation speed and a load of said internal combustion engine, and calculates the amount of particulate emission from said map. And
The combustion amount calculation means is the temperature detection means (13, 14).
2. The internal combustion engine according to claim 1, further comprising a particulate combustion amount map in which a particulate combustion amount is determined from a value detected by the method, and calculating the particulate combustion amount from the map. Engine exhaust gas purification equipment 3. Values detected by temperature sensors provided at an inlet and an outlet of a diesel particulate filter composed of the oxidation catalyst (11) and the filter (12). 2. The method of claim 1, further comprising calculating an average value of
Or an exhaust gas purifying apparatus for an internal combustion engine according to claim 2. 4. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said temperature increasing means is in-cylinder post-injection by a fuel injection device of said internal combustion engine. 5. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said temperature increasing means is an injection timing delay device for delaying an injection timing of said internal combustion engine. 6. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said temperature increasing means is an electric heater.