JPH0527221U - Exhaust gas cleaning device for a diesel engine - Google Patents

Abstract

(57) [Summary] [Purpose] To regenerate a filter with catalyst at low power and in a short time. [Structure] The exhaust gas purification device 1 is provided with a filter 2 with a catalyst for collecting particulates. The catalyst-equipped filter 2 is configured by filling a casing 3 made of punching metal with a pellet catalyst. A filter 5 is mounted on the front surface of the catalyst-equipped filter 2 on the gas inflow side. The filter 5 is a filter material 6 such as ceramic fiber having a low thermal conductivity.
A heater wire 7 that is thicker than the filter material 6 is sandwiched between them, and the ventilation resistance in the vicinity of the heater wire 7 is smaller than that of other portions. A filter 5 is also mounted on the exhaust downstream side of the filter 2 with catalyst.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an exhaust emission control device for a diesel engine.

[0002]

[Prior Art]

 In the conventional exhaust gas purification device for a diesel engine, most of the diesel exhaust gas post-treatment filters are plugged honeycomb traps (see, for example, JP-A-56-124417).

A conventional reproducing device uses a burner (see, for example, Japanese Patent Laid-Open No. 60-13562). A heater disposed in front of the filter (see, for example, JP-A-59-907163, JP-A-58-162711, JP-A-62-279221, and JP-A-62-298615). Those that heat the filter by the heat of oxidation of the fuel (see, for example, JP-A-56-130545, JP-A-61-112716, and JP-A-59-162316). There has been a fuel system or an exhaust system in which an additive for lowering the regeneration temperature is supplied (see, for example, JP-A-60-153413).

Further, in order to increase the area that can be heated by the heater, a wire mesh heater is used, or a material having high thermal conductivity is provided in the vicinity of the heater to heat the front surface of the filter as uniformly as possible. For example, JP-A-62-279221 and JP-A-62-298615) have been devised.

[0005]

[Problems to be solved by the device]

 However, in such a conventional exhaust gas purification apparatus for a diesel engine, the plugging trap used in the diesel exhaust after-treatment filter has a high collection efficiency because it collects fine particles by filtration collection. Although it can be obtained, it is necessary to reliably remove the collected fine particles by burning. That is, it is necessary to have a means for detecting the regeneration time by detecting the amount of fine particles deposited in the trap and a regeneration means for increasing the temperature of the burner, and if the regeneration time detection or regeneration fails, the trap may be burnt out. Problem occurred.

Further, the ash (ash) in which the fine particles collected by the regeneration are burned cannot be removed by the usual method, and for example, the method of reversing the flowing direction of the exhaust gas has to be resorted to.

Further, the one using a burner has a problem that the structure becomes complicated such that it is necessary to provide a fuel supply device and an ignition source in the exhaust system. Further, in terms of safety, it was necessary to improve the corrosion resistance and structural strength of the exhaust system in order to supply the fuel to the exhaust system and form a flame.

Further, in the case of using a heater, when a power of a power supply system formed of a battery and an alternator in an automobile is used to reburn the particulates captured by the filter, the power is supplied. Since there is a limit to the amount of electric power, it is necessary to bypass the filter to reduce the amount of gas flowing into the filter, and the uncleaned gas that was bypassed is discharged during regeneration.

This is remarkable when the temperature of the exhaust gas is raised by the heater to regenerate the particulates deposited on the filter, but even when the particulates deposited by the heater are directly ignited, heat is taken from the heater. A bypass is required to prevent the particulates from being burned out, and in this case, it is necessary to perform flame electroplating of particulates. Therefore, it is necessary that the particulate accumulation amount is large to some extent when regenerating. However, there is a possibility that problems such as the above may occur.

Further, the heat of oxidation of the fuel requires a catalyst for oxidizing the fuel, a supply device for the fuel to be oxidized, and the like, which causes a problem that the structure is complicated like the burner. ..

In addition, the additive material system has a problem that the supplied additive material is discharged together with the exhaust gas, which may cause a new exhaust gas pollution depending on the material of the additive material. Furthermore, in order to expand the area that can be heated by the heater, a wire mesh heater is used or a material with high thermal conductivity is provided near the heater to heat the front surface of the filter as uniformly as possible. When the temperature of the filter is raised uniformly by regeneration with the heater, the heat capacity of the heater system is large, so the temperature rise characteristics from the start of heating are poor, and the power consumption up to the combustion start temperature of the particulates is reduced. If the material with high thermal conductivity is provided in the vicinity of the heater, the heat exchange rate to the exhaust gas with respect to the supplied power will be good, but the efficiency of heat conduction in the heater system will be high. , The surface temperature of the heater itself for the same supply power becomes lower, and the supply power must be increased in order to ignite the particulates themselves collected by the filter by the heater. There is a problem that no longer must be.

The present invention has been made in view of the above-mentioned conventional problems, and provides an exhaust gas cleaning device for a diesel engine that can regenerate a filter with a catalyst in a short time with a small amount of electric power. The purpose is to do.

[0013]

[Means for Solving the Problems]

 For this reason, the present invention is applied to an exhaust system of a diesel engine to purify the exhaust gas. In an exhaust gas purification device of a diesel engine, a fiber system having a low thermal conductivity is provided at least on the front side of the gas inlet side of the filter with catalyst. A filter having a heater surrounded by a filter material was arranged, and the ventilation resistance near the heater of the filter was set to be smaller than the ventilation resistance of other portions.

[0014]

[Action]

 At the time of collecting particulates, a part of the particulates is collected near the heater of the filter having the heater in front of the filter with catalyst.

When the heater is energized during regeneration, since the heater is surrounded by the filter material having a low thermal conductivity, the particulates near the heater are ignited with a small amount of power and in a short time. As a result, the particulate matter deposited on the filter with catalyst is also efficiently reburned by the effect of spread and heating.

[0016]

【Example】

 Hereinafter, the present invention will be described with reference to the drawings. 1 to 5 are views showing an embodiment of the present invention.

First, the configuration will be described. The exhaust gas purification device 1 is provided with a filter 2 with a catalyst that collects particulates contained in exhaust gas. The catalyst-equipped filter 2 is formed by filling a casing 3 made of punching metal with a pellet catalyst 4. A filter 5 is attached to at least the front surface of the gas inflow side 2a of the filter 2 with catalyst.

As shown in FIG. 2 in which the portion A of FIG. 1 is enlarged, the filter 5 is surrounded by a filter material 6 having a low thermal conductivity, such as a ceramic fiber or a ceramic woven fabric. The heater wire 7 is sandwiched between them, and the filter material 6 above and below the heater wire 7 is joined by being fastened or sewn together with a stop pin 8. That is, the filter 5 has a structure in which the heater wire 7 thicker than the filter material 6 is woven, and the gap 5 a exists near the heater wire 7. Therefore, the ventilation resistance near the heater wire 7 is low.

Further, in the present embodiment, the filter 5 is also mounted on the downstream side of the filter 2 with catalyst. Reference numeral 9 is a power source for the heater. 3 and 4 show examples of heater wire configurations. In FIG. 3, the heater wire 7 is arranged long in the longitudinal direction of the filter 7 with catalyst, and the upper and lower filter materials 6 are sewn together. The number of stitches is 10. In FIG. 4, the heater wire 7 is divided into short sections and the power source 9 is arranged for each divided heater wire 7.

In order to reduce the power consumption of the heater, the heater may be bypassed and the exhaust gas may flow during regeneration. Further, in the case shown in FIG. 3, the heater wires 7 may be used alternately. In the case of FIG. 4, the heater wires 7 may be energized all at once or sequentially.

Next, the operation will be described with reference to FIG. Part of the particulates in the exhaust gas discharged from the engine is collected in the filter 5 in which the heater wire 7 on the front surface of the filter 2 with catalyst is woven. At this time, as shown in FIG. 5, the filter 5 has the heater wire 7 woven into the material such as ceramic fiber or ceramic woven fabric, and the ventilation resistance in the vicinity of the heater wire 7 is set to be smaller than that of the other parts. As indicated by the arrow, the particulates are deposited in the vicinity of the heater wire 7 in contact with the heater wire 7.

On the other hand, the particulates not collected by the filter 5 on the front surface of the filter with catalyst 2 are collected by the pellet catalyst 4.

The pellet catalyst 4 has a low trapping efficiency because the trapping mechanism is adhering trap, but since the catalyst is supported, it also reduces the oxidation of the organic dissolved components together with the soot in the particulates.

Further, in this embodiment, since the filter 5 having the heater wire 7 woven therein is also arranged in the downstream portion of the filter 2 with catalyst, the particulates adhering to the pellets 4 or the like suddenly blow off. Can be prevented.

At the time of reproduction, the heater wire 7 is energized. At this time, the heater wire 7 is woven into the filter material 6 having a low thermal conductivity, and since the particulates are accumulated in the vicinity of the heater wire 7, a small amount of electric power is consumed in a short time. Can ignite particulates.

As a result, the particulates deposited on the filter 5 in which the heater wire 7 is woven are effectively burned, and the particulates collected by the pellet catalyst 4 inside the catalyst-equipped filter 2 are also spread and heated. Is efficiently reburned by.

As described above, according to this embodiment, at the time of collection, the particulates are efficiently collected and accumulated in the vicinity of the heater wire 7 of the filter 5, and the uncollected particulates are collected by the pellet catalyst 4. Since they are collected, the particulates are surely collected, and it is possible to reduce the oxidation of the organic dissolved components together with the soot in the particulates.

At the time of regeneration, the heater wire 7 has a shape like being woven into the filter material 6 having a low thermal conductivity, and since the particulates are accumulated in the vicinity of the filter wire 7, a small electric power is required. Moreover, the particulates can be ignited in a short time. Further, the particulate matter collected by the catalyst-equipped filter 2 can also be efficiently reburned by the effect of fire spread and heating.

FIG. 6 shows another embodiment of the present invention. In this embodiment, a foam filter 11 with a catalyst is used in place of the pellet catalyst of the above embodiment, and a filter 5 having a heater wire 7 arranged directly between filter materials 6 is arranged on the outer periphery of the foam filter 11. Is.

According to this embodiment, the same effect as the above embodiment can be obtained.

[0031]

[Effect of the device]

 Since it is configured as described above, according to the present invention, it is possible to efficiently reburn the trapped particulates.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view showing a portion A of FIG.

FIG. 3 is a sectional view showing a constituent side of a heater according to an embodiment of the present invention.

FIG. 4 is a plan view showing the constituent side of the heater of the embodiment.

FIG. 5 is a view for explaining the exhaust flow in the filter according to the embodiment. Sectional view.

FIG. 6 is a cross-sectional view showing another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Exhaust purification device, 2 ... Filter with catalyst, 4 ... Pellet catalyst, 5 ... Filter, 6 ... Filter material, 7 ... Heater wire,
8 ... Stopping pin, 10 ... Seam, 11 ... Foam filter with catalyst

Claims (1)

[Scope of utility model registration request] 1. An exhaust gas purification device for a diesel engine, which is mounted on an exhaust system of a diesel engine and purifies exhaust gas, wherein a fiber-based filter having a low thermal conductivity is provided on at least the entire gas inflow side of a filter with a catalyst. An exhaust gas purification device for a diesel engine, comprising: providing a filter having a heater surrounded by a material, and setting a ventilation resistance near the heater of the filter to be smaller than a ventilation resistance of other portions.