JPH0253605B2 - - 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.

(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 generation of a large amount of HC when the oil burner is ignited, the durability and safety of the oil burner, and the equipment is complicated and the cost is high.
In particular, the equipment becomes more complicated when dual flows of exhaust gas 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 collecting material made of ceramic in the exhaust gas path of a diesel engine, and an electric heating element is individually made of ceramic on the upstream end surface of the collecting material. The present invention is characterized in that a plurality of coated ceramic heater elements with a catalyst supported on their surfaces are distributed and arranged, and the catalyst is supported only on the surface of the upstream region of the collection material.

It is desirable that these plurality of ceramic heater elements be heated in sequence rather than all at once, thereby reducing power consumption. Further, when a catalyst is supported on a ceramic heater element, ignition becomes smoother and less energy is required for ignition. Since the ceramic heater elements are disposed in a distributed manner, they do not impede the flow of exhaust gas. The heating of the ceramic heater element is controlled by a computer device or the like.

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

In Fig. 1, reference numeral 1 is a diesel engine cooling fan, 2 is a fuel injection pump, 3 is an intake manifold, 4 is a fuel system pipe, 5 is a diesel engine body, 6 is a transmission, and 7 is an engine rotation speed detection. part, 7' is an engine load detection part,
8 is the engine water temperature detection part, 9 is the exhaust manifold,
10 is an exhaust gas pressure detection section, 11 is an exhaust gas temperature detection section, 12 is a collection material (trapper) container, 13 is a trapper internal temperature detection section, 14 is an exhaust gas temperature detection section downstream of the trapper, and 15 is a microcomputer ( CPU). Each detection section 7, 7', 8, 10,
11, 13, and 14 are each provided with a well-known sensor, and each detected value is input to a microcomputer (CPU) 15.

The trap vessel 12 is mounted immediately downstream of the exhaust manifold 9. However, the trap container 12 may be formed integrally with the exhaust manifold 9 by casting so as to be located downstream of the gathering portion of the exhaust manifold 9. Inside the trap container 12 there is a collection material (trap material) 20. As the trap material 20, known foamed ceramic or similar materials can be used.
That is, the trap material 20 has a three-dimensional mesh structure, through which exhaust gas can flow, and exhaust particulates contained in the exhaust gas can be collected between the meshes. In FIGS. 1 and 2, the upstream end surface of the trap material 20 is equipped with a ceramic heater element 16 as described below.
are distributed in a distributed manner. 16' is a power supply terminal provided for each ceramic heater element 16, 17 is a ceramic heater relay, and 18 is a ceramic heater power source.

The structure of the ceramic heater is shown in FIGS. 3 to 7. FIG. 3 is a front view showing one embodiment of the ceramic heater, and FIG. 4 is a partial sectional view thereof. In FIG. 3, eight ceramic heater elements 16 are installed in a distributed manner on the upstream end surface of the trap 20. As shown in FIG. Each ceramic heater element 16 is fixed by being embedded in a recess provided in the upstream end face of the trap material 20. Alternatively, the ceramic heater element 16 can be embedded in the trap material 20 when it is molded, and the trap material 20 can be integrally molded. Each ceramic heater element 16 is a suitable electrical heating element, such as tungsten, wrapped in aluminum foil and coated with ceramic. Such a ceramic heater element 16
The size and arrangement of the
Therefore, it is selected so that the increase in exhaust gas back pressure is minimized. Further, a catalyst is supported on the ceramic heater element 16, which makes ignition smoother and requires less ignition energy.

FIG. 5 is a front view showing another embodiment of the ceramic heater, FIG. 6 is a partial sectional view thereof, and FIG. 7 is an enlarged perspective view of one ceramic heater element. The difference from the embodiment shown in FIGS. 3 and 4 is that each ceramic heater element 26 is configured in a cross shape as shown. The cross-shaped ceramic heater element 26 is similarly constructed by wrapping a suitable electrical heating element, such as tungsten, in aluminum foil and coating it with ceramic. Each cross-shaped ceramic heater element 26 is arranged so that the cross shape can be seen from the exhaust gas flow direction (arrow P in FIG. 2) (FIG. 5). Such a cross-shaped ceramic heater element 26 can also be attached to the trap material 20 or integrally molded, as in the case described above. Thereby, the area through which the exhaust gas flows can be made as large as possible, and the back pressure of the exhaust gas can be prevented from increasing. In addition, in these figures, reference numeral 19 (Fig. 3, Fig. 4,
Figures 5 and 6) are terminal connectors, numbered 2.
7 (Fig. 7) shows each cross-shaped ceramic heater element 2.
6 power supply terminal.

The eight ceramic heater elements 16, 26 are energized and heated in the order of numbers 1, 2, 3, . . . 8, respectively.

FIG. 8 shows the operation of regeneration of the Tratspa container;
It is a flow diagram. First, the conditions are engine speed 7, engine load 7', engine water temperature 8, exhaust pressure before the trapper 10, trap material internal temperature 13, ceramic heater heating order, etc. as information on the CPU 15.
(Figure 1). The regeneration time is determined mainly based on the back pressure of the exhaust gas. That is,
The exhaust gas discharged from the diesel engine flows as shown by arrow P (Fig. 2), and the particulates contained therein are collected by the trapper material 20, and as the particulates accumulate, the exhaust gas flows upstream of the trapper container 12. Since the back pressure (detected by the detection unit 10) increases, this back pressure becomes an indicator of particulate accumulation. When it is determined that it is the regeneration time, the engine water temperature 8 is checked. This is to prevent regeneration from starting immediately after the engine is started. A count-up is performed when the engine water temperature is 110°>T>80°C. This is a ceramic heater element (number 1~
This is to determine the order in which to energize among 8). When 40 seconds have elapsed since the start of energization, the energization is stopped, the number of the ceramic heater element that was energized is memorized, and it is reset. If it is determined that regeneration is still necessary after being reset, energization of the next ceramic heater element that was previously energized is started. After that, the same process is repeated until energization is no longer required for reproduction.

The engine rotational speed 7 at which regeneration is started is not particularly limited, but it is desirable to include a condition such that regeneration is started at idling rotation.

FIG. 9 shows the state of combustion of exhaust particulates by the ceramic heater elements 16 and 26. Ceramic heater elements 16 and 26 are made of trap material 20
Since it is placed on the upstream end face of the exhaust gas, when it is heated by electricity, it burns the exhaust particulates attached in the vicinity, and the combustion flame propagates downstream along the flow of exhaust gas shown by arrow P. be done. In FIG. 9, region A is a region where exhaust particulates are burned and the trapping material is regenerated, and region B is a region where the trapping material is not regenerated, but in reality, a plurality of ceramic heater elements 16 and 26 are installed, so the trapping material is regenerated. 20 areas are playable. Therefore, the number of ceramic heater elements 16, 26 and their arrangement may be determined to be the minimum necessary number so that exhaust particulates can be completely burned over the entire area of trapper material 20.

As described above, the device of the present invention can be configured as a so-called single-type trapper (one exhaust gas path), and has a structure that does not require bypass valves or switching valves, compared to conventional dual-type trappers. It is simple and has advantages in terms of durability, safety, and cost. The device of the present invention does not need to particularly limit the operating conditions of the engine during regeneration, and can perform regeneration in any operating range.

Note that heating by the ceramic heater element 16,
In order to shorten the regeneration time, it is effective to use it in conjunction with throttling, which throttles the intake system. for example,
If the intake system is throttled to 400mmHg during idle rotation, the exhaust temperature will rise to approximately 200℃, and the exhaust flow rate will also decrease.
Cooling of the ceramic heater elements 16, 26 is reduced. Ceramic heater elements 16, 2
6 can be shortened. Further, if electrically permissible, it is also possible to energize all or any plurality of the ceramic heater elements 16, 26 to simultaneously heat them and incinerate the exhaust particulates more quickly.

Since the present invention uses a ceramic heater element in which the electric heating element (for example, tungsten) is coated with ceramic, there is no risk that the heating element will be oxidized and deteriorated in the exhaust gas. By supporting a catalyst on the surface of the ceramic heater element, the ignition of exhaust particulates is improved and power consumption can be reduced. Further, the ceramic heater element has the advantage that it can be constructed integrally with the ceramic foam constituting the trap material. Further, on the upstream surface of the trap material 20, a part of the catalyst 28 (FIG. 9) is supported to facilitate combustion of exhaust particulates.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a diesel engine using the present invention, Fig. 2 is a sectional view of a trapper container, Fig. 3 is a plan view showing an embodiment of a ceramic heater, Fig. 4 is a sectional view thereof, and Fig. 5 The figure is a cross-sectional view showing another embodiment of the ceramic heater, and FIG. 6 is a cross-sectional view thereof.
FIG. 7 is a perspective view of a cross-shaped ceramic heater element;
FIG. 8 is a flow diagram showing the operation of regenerating the trapper container, and FIG. 9 is a diagram showing the state of combustion of exhaust particulates by the electric heater element. 5... Diesel engine main body, 9... Exhaust manifold, 12... Collection material (trap material) container, 15... Microcomputer (CPU), 16, 26... Ceramic heater element, 20... Collection material (trap material).

Claims (1)

[Claims] 1. An exhaust particulate collection material made of ceramic is provided in the exhaust gas path of a diesel engine, and an electric heating element is coated with ceramic on the upstream end surface of the collection material, and a ceramic heater element is provided with a catalyst supported on the surface. 1. An exhaust particulate purification device for a diesel engine, characterized in that a plurality of the collecting materials are arranged in a dispersed manner, and a catalyst is supported only on the surface of the upstream region of the collecting material.