JPH0319888B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas treatment device for a diesel engine, and more particularly to a method for removing carbon particles and similar particulate matter (hereinafter referred to as exhaust particulates) contained in exhaust gas by a physical method. The present invention relates to an exhaust particulate purification device suitable for collecting the collected exhaust particulates on a suitable collecting material, periodically incinerating the collected exhaust particulates, and regenerating the collecting material.

Most of these types of exhaust particulates are flammable, such as carbon particles, and conventional methods have been used to collect these flammable particulates, incinerate the collected particulates, and regenerate the collection material. The following methods have been known since then, and each has the following drawbacks.

(1) A method of throttling the intake system of a diesel engine to reduce the amount of intake air and raise the temperature of exhaust gas to burn exhaust particulates. With this method, the exhaust temperature rises sufficiently in the high load range of the engine, making it possible to incinerate the exhaust particulates, but in the low load and low rotation ranges, the exhaust temperature does not rise sufficiently, and the exhaust particulates are incinerated and the collection material playback becomes impossible. Furthermore, in diesel engines equipped with turbocharging mechanisms, the amount of intake air is large, so even if the intake system is throttled, the exhaust gas temperature cannot be raised sufficiently, making it difficult to regenerate the collection material. .

(2) A method in which an oil burner is installed in the exhaust system of a diesel engine to raise the temperature of exhaust gas to a temperature at which exhaust particulates are combusted. This method has problems such as the durability and safety of the oil burner, as well as the generation of a large amount of HC when the oil burner is ignited, and the equipment is complicated.
The cost is also high, and the equipment becomes more complex, especially when dual exhaust gas flows are used and one flow is stopped for incineration and regeneration.

(3) A method in which an electric heater is attached to the entire surface of the collection material to burn the exhaust particulates adhering to the surface of the collection material, and use this as a heat source to cause the downstream particulates to self-combust. In this method, an electric heater is attached to the entire surface of the collection material, so power consumption is extremely large, making it difficult to use as an automobile part. In order to reduce power consumption, it is necessary to have a dual flow of exhaust gas, and to stop one flow and burn the stopped one with an electric heater, which makes the equipment complicated.
The cost will also be higher.

The purpose of the present invention is to eliminate the above-mentioned drawbacks,
The purpose of the present invention is to provide a diesel engine exhaust particulate purification device that is durable, safe, simple in structure, and low in cost.

In order to achieve such an object, the present invention provides an exhaust particulate purification device for a diesel engine having an exhaust particulate collecting material in the exhaust pipe, in which a throttle valve is provided in the exhaust pipe upstream of the collecting material. In addition, a means for increasing the fuel injection amount of the engine is provided, and an electric high-pressure spark generating means is provided in the recessed portion of the upstream end of the collecting material, and the throttle valve, the fuel injection amount increasing means, and A control means is provided to periodically operate the spark generating means in conjunction with the engine operation, and periodically burns exhaust particulates accumulated in the collection material to regenerate the collection material. It is characterized by

Such a throttle valve may be provided upstream or downstream of the collection material. Furthermore, it is also possible to provide this throttle valve in the exhaust manifold. By throttling the throttle valve, the back pressure of the exhaust gas increases and the temperature of the exhaust gas increases to the temperature required for combustion of exhaust particulates. Further, in the present invention, since the amount of fuel injected to the engine is increased when the exhaust throttle valve is throttled, the output and drivability of the diesel engine are not adversely affected. The means for increasing the fuel injection amount and the exhaust throttle valve are
It is controlled by a computer or the like so that it operates periodically while the engine is running.

Furthermore, in the present invention, an electric spark generating means is provided as an auxiliary means for combustion and ashing of exhaust particulates, so the generation of electric sparks imparts ignition energy to the combustible particulates accumulated in the collection material. This makes it easier to ignite and burn these exhaust particulates. As for generating the electric spark, the electric spark currently used in gasoline engines can be used with some modification, and the structure is extremely simple and suitable for mass production.
The timing and number of sparks can be controlled by a computer or the like.

The means for generating an electric spark is arranged such that its terminals are arranged on the upstream side and the electrodes are arranged opposite to each other on the downstream side, and the electrodes have a net-like or lattice-like structure and are buried in a recessed part at the end of the collecting material. is desirable.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In Fig. 1, 1 is the diesel engine body, 2 is the transmission, 3 is the intake manifold, 4 is the exhaust manifold, 5 is the fuel injection pump,
6 is a fuel pipe, 7 is a fuel injection valve (injector),
8 is a vacuum pump, 9 is a cooling fan, and these are the components of a normal diesel engine.

A trapping material (trapper) container 10 is attached to a portion of the exhaust pipe on the downstream side of the exhaust manifold 4. Inside the trapper container 10, as shown in FIG. 2, there is a trapping material 11.
The trap material 11 does not excessively restrict the flow of exhaust gas, allows the exhaust gas to flow therethrough, and is capable of collecting a considerable amount of exhaust particulates contained in the exhaust gas. ing.
In addition, the trap material 11 is made of an appropriate material that can sufficiently withstand the elevated temperature that is to be reached during combustion and ashing of exhaust particulates collected thereon periodically during engine operation. Made of materials into a suitable shape. Examples of materials suitable for such purposes include three-dimensional network foam ceramics, monolithic ceramics, bulk screen elements such as metal wire mesh or stainless steel.

In order to burn and ash the exhaust particulates collected by the trap material 11, it is usually necessary to raise the exhaust temperature to a level of approximately 560°C. Therefore, the material of which the trap is made must be able to withstand this temperature.

However, experience has shown that during normal engine operation (in the absence of special measures to increase the exhaust temperature) the temperature in the exhaust system varies considerably under different conditions of engine load and speed. Also, depending on the particulate trapper's location in the exhaust system, the temperature within the trapper may never reach the level necessary to burn off the particulates collected therein. This may be the case if the engine is not operated under full throttle, as is typical in many automotive applications, if it is equipped with a turbocharger, or if the arrangement shown in Figure 1 is used. This is particularly the case when the particular trapper is mounted in the exhaust line downstream of the engine's exhaust manifold, as in the example in FIG. Therefore, in order to periodically incinerate the collected particulates, it is necessary to provide some other means to raise the exhaust temperature to the required level of approximately 560°C.

A number of possible methods can be used singly or in combination to obtain the desired temperature level. One such method, which may be used under all engine operating conditions except full fuel or full load conditions, is to throttle the engine's exhaust system to increase the amount of fuel delivered to the engine. It has been found that appropriate throttling of the exhaust gas can substantially increase the exhaust temperature of the engine, and in some cases may be sufficient to raise the temperature within the particle trapper to ashing levels.

That is, in the present invention, the exhaust throttle valve 20 is provided in the exhaust pipe line which is not normally throttled. This exhaust throttle valve 20
is connected to a diaphragm valve 21 via a link, and this diaphragm valve 21 is driven by a vacuum switching valve (VSV) 22. VSV22 is
Vacuum pump 8 via vacuum piping 23
On the other hand, it is connected to a microcomputer (CPU) 30 via wiring 24.
Normally, the atmosphere port of the VSV 22 is open, and the atmosphere acts on the diaphragm valve 21.
The exhaust throttle valve 20 is open. When a signal is transmitted from the microcomputer (CPU) 30 through the wiring 24, the atmospheric port of the VSV 22 is closed, and the negative pressure from the vacuum pump 8 acts on the diaphragm valve 21 through the vacuum piping 23 and the VSV 22. Throttle valve 20 is closed, restricting the exhaust line to about 90% of its passage. Note that the exhaust throttle valve 20 may be provided on the downstream side of the trapper container 10.

Further, in the present invention, means is provided for increasing the amount of fuel injection supplied to the engine. That is, a negative pressure switching valve (VSV) 31 is provided to control the fuel increase device 33 of the fuel injection pump 5.
The VSV 31 is connected to a microcomputer (CPU) 30 via wiring 32 and to a vacuum pump 8 via piping 34. Therefore, microcomputer (CPU) 3
When a signal is transmitted from 0 through wiring 32,
The VSV 31 is connected to the fuel increaser 33 through the pipe 34.
This fuel increasing device 33 operates to increase the fuel injection amount.

Furthermore, in the present invention, an electric spark generator (spark plug) 12 is provided at the upstream end of the trapper 11 as an auxiliary means for igniting and burning exhaust particulates.

The spark plug 12, as shown in FIG.
Anode terminal 1 located on the upstream side and generating an electric spark
3, and a downstream electrode 14 (cathode) facing this at a constant interval. This electrode 14
is preferably in the shape of a wire mesh or a lattice, and the third
As shown in the figure, a recess (concave) 15 formed on the upstream end face of the trapper 11 is arranged perpendicular to the flow direction of the exhaust gas, that is, the direction of the electric spark, so that exhaust particulates can easily accumulate. . This electrode 14 is grounded, while the anode terminal 13
is connected to voltage converter 16 (FIG. 1).
Voltage converter 16 is connected to microcomputer (CPU) 30 via wiring 17.

The exhaust throttle valve 20, the fuel injection amount increasing means, and the electric spark generator 12 described above are periodically operated in conjunction with each other during operation of the diesel engine to burn, ash, and burn the exhaust particulates and the trapper container 10. Reproduction is performed, and the start timing of such reproduction operation and the operation of the means are controlled by a microcomputer (CPU) 30. For this purpose, the operating conditions of the recessed portion, the state of exhaust gas, etc. are detected and input to the CPU 30. That is,
In Fig. 1, 50 is the engine load, 51 is the engine speed, 52 is the engine water temperature, 53 is the exhaust pressure before the trapper, 54 is the exhaust gas temperature before the trapper, 55 is the temperature inside the trapper, and 56 is the temperature at the trapper outlet. is the exhaust gas temperature, and each of these detection signals is
It is input to the CPU 30. Note that 57 is a back pressure sensor that detects the exhaust pressure before the trapper.

The following points should be kept in mind in such a control system.

1. The trapper must be cleaned often enough so that the collected particulates do not create undue restrictions on the exhaust gas flow.

2 Throttling and fuel addition of the engine exhaust system must be controlled so as not to significantly alter the driveability or performance of the vehicle.

3. The control process should not result in a significant or noticeable increase in smoke emanating from the vehicle exhaust pipe.

4. The combustion cycle should be controlled so that only particulates are burned and ashed and the trapper bed is not damaged.

In order to achieve these objectives, in the present invention, a microcomputer (CPU 30) is programmed to operate as shown in FIG.

In FIG. 4, first, engine speed 51, engine load 50, trapper bed temperature 55, back pressure 53,
It is determined whether it is time for regeneration based on signals such as the trapper outlet exhaust gas temperature 56 and the engine water temperature 56. The determination of the regeneration timing is programmed so that the next regeneration will be performed after the vehicle has traveled approximately 70km after the previous regeneration was completed. This is because the Toratsupa becomes overloaded when traveling about 400 km.
A cleaning interval of approximately every 70km is considered appropriate. After determining that it is time for regeneration, control is performed by means as shown in the flowchart of FIG. That is, the exhaust throttle valve is throttled, the amount of fuel injection is increased, and the exhaust temperature is raised to a temperature necessary for incinerating exhaust particulates. When the exhaust temperature exceeds 560℃,
The spark plug on the front of the trap generates a spark for 20 seconds. Incidentally, troubles during trapper regeneration (for example, abnormal rise in exhaust gas temperature, etc.) are handled as shown in the flowchart. Toratsupa (inside)
The floor temperature is below 660℃ (However, the exhaust temperature at the Toratsupa inlet is 560℃ or less.
When the exhaust temperature after trapping remains below 580°C for 2 minutes, regeneration is completed and the microcomputer (CPU) is reset. In addition,
In the embodiment shown in FIG. 4, the combustion time is set to 2 minutes, but it can be set to an appropriate time depending on the accumulation of exhaust particulates and other conditions.

In FIG. 3, the ignition process is as follows. The exhaust particulates are collected by the trapper material 11, and since the recess 15 is provided on the upstream end face of the trapper material 11, the exhaust particulates accumulated in the recess 15 serve as an ignition source as described above. . When an electric spark is generated between the anode terminal 13 and the electrode 14 of the spark plug 12, the particulates accumulated in the recess 15 are combusted, and the combustion flame moves into the trapper material 11 along the flow of exhaust gas. do. Therefore, most of the exhaust particles accumulated in the trapper material 11 are burned, and the trapper material 11 is regenerated.

Note that the minimum number of spark plugs 12 is used so that regeneration proceeds smoothly.

The spark energy uses 4 jeels to ignite 10 mg of exhaust particles, but the spark time is:
About 5 seconds is sufficient. Therefore, since the energy is the same as that of spark plugs for gasoline engines currently in use, the effect on the engine charge/discharge system can be ignored. In this way, the spark plug 12 requires only some modification of the currently used spark plug for gasoline engines, so the structure is simple and the exhaust particulates can be reliably combusted.

Note that the present invention can also be applied to a diesel engine equipped with a turbocharging mechanism. This type of engine has a lower exhaust temperature than a normal engine, but by restricting the exhaust system and increasing the amount of fuel, it is possible to reduce the combustion of exhaust particulates and reduce the temperature necessary for ash fire.
A temperature of 560°C can be obtained, and the exhaust particulates are easily ignited by the spark plug.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a diesel engine using the present invention, Fig. 2 is a partial sectional view of the trapper container, Fig. 3 is a detailed view of the front end of the trapper material, and Fig. 4 is a microcomputer (CPU) 2 is a flowchart of a regeneration control process. DESCRIPTION OF SYMBOLS 1... Diesel engine main body, 5... Fuel injection pump, 10... Tratupa container, 11... Collection material (Tratsupa material), 12... Spark plug, 1
5... Recessed portion, 20... Exhaust throttle valve, 30... Microcomputer (CPU), 31... Actuator.

Claims (1)

[Claims] 1. In a diesel engine having a collection material for exhaust particulates in the exhaust gas path, an exhaust throttle valve is provided in the exhaust gas path, a means for increasing the amount of fuel injection supplied to the engine is provided, and the particulate matter collection material is provided in the diesel engine. An electric high-pressure spark generating means is provided adjacent to the recessed portion of the upstream end, and the throttle valve, the fuel injection amount increasing means, and the spark generating means are periodically operated in conjunction with each other during engine operation. An exhaust particulate purification device for a diesel engine, comprising a control means to periodically burn exhaust particulates accumulated in the collection material to regenerate the collection material.