JPH0214524B2 - - 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 (trapper) suitable for collecting the collected exhaust particulates on an appropriate collection material, periodically incinerating the collected exhaust particulates, and regenerating the collection 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 becomes impossible to play.

(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 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.

In order to solve this problem, multiple electric heater elements are arranged in a distributed manner on the upstream end of the trapping material, and these electric heater elements are heated in turn when the trapping material is regenerated. A device according to the present invention has already been proposed by the present applicant (Japanese Patent Application No. 56-095215). This device effectively incinerates and disposes of exhaust particulates despite its low power consumption; however, the method of attaching the electric heater to the surface of the trap material is difficult and the installation structure is complicated; If the adhesion between the trap material and the electric heater is poor, there is a risk of ignition errors, and on the surface of the trap material where the electric heater element is not attached, the exhaust particulates will not be incinerated, which is disadvantageous for the pressure drop of the exhaust gas. There are other problems.

SUMMARY OF THE INVENTION An object of the present invention is to provide an exhaust treatment trapper that makes it easy and reliable to attach an electric heater to a trap material, and prevents ignition errors of exhaust particles and unburned portions.

Therefore, in the present invention, in an exhaust treatment trapper incorporating a collection material to be provided in the exhaust path of a diesel engine, a quartz wool layer is provided on the upstream end surface of the collection material, and an electric heater wire is installed inside the quartz wool layer. The quartz wool layer is fixed to the collection material.

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,
Reference numeral 8 indicates an engine water temperature detection section, 9 indicates an exhaust gas temperature detection section, 10 indicates an exhaust gas pressure detection section, 11 indicates an exhaust gas temperature detection section, 12 indicates a trapping material container, 13
14 is an exhaust gas temperature detection section downstream of the trapper, and 15 is a microcomputer (CPU). Each detection section 7, 7', 8, 1
Well-known sensors are provided at 0, 11, 13, and 14, respectively, 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 collecting 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 the exhaust gas can flow, and exhaust particulates contained in the exhaust gas can be collected between the meshes. 1 and 2, a quartz wool layer 30 is provided on the upstream end surface of the trap material 20, and an electric heater wire 16 is inserted into the quartz wool layer 30. In FIG. 2, reference numeral 17 is a heater power supply connector, 18 is a heater power supply terminal, and in FIG. 1, reference numeral 19 is wiring for the heater, 21 is a heater relay, and 22 is a heater power supply. 21 is connected to a microcomputer (CPU) 15 via a wiring 23.

In FIGS. 2 and 3, the quartz wool layer 30
As described above, the trap material 20 is disposed over the entire upstream end face, and its thickness is sufficient to hold the electric heater wire 16 inside and insulate it. The electric heater wire 16 is arranged inside the quartz wool layer 30 on a plane parallel to the upstream end surface of the trapping member 20, and is made up of a plurality of electric heating wires (for example, tungsten wire). One end of each electric heater wire 16 is connected to the heater power supply connector 17, and the other end is connected to body ground (24). These electric heater wires 16 are formed in a planar zigzag shape, as shown in FIG. 3, so as to uniformly apply heat to the entire area of the upstream end surface of the trap material 20. In addition, the reference numeral 2 in Figure 3
5 is a ground terminal.

The quartz wool layer 30 is an aggregate of quartz fiber bundles, and exhaust gas can easily flow through the quartz wool layer 30 . That is, it is made of a material that causes little pressure loss with respect to the flow of exhaust gas, and pressure loss at the front surface of the trap material 20 does not pose a problem. However, the collection rate of exhaust particulates contained in the exhaust gas is high, and the collected exhaust particulates become an ignition source when the electric heater wire 16 is heated. The quartz wool layer 30 itself is pushed to some extent toward the front of the trap material 20 by the exhaust gas flow P (FIG. 2), but in order to prevent it from protruding, it is pressed against the metal wires 31 arranged in a lattice pattern. Therefore, it is fixed to the front surface of the trap member 20. Note that the lattice-shaped metal wire 31 may be weak enough to prevent the quartz wool layer 30 from coming out.

When a certain amount of exhaust particulates contained in the exhaust gas is collected by the trap material 20, the trapper is periodically regenerated in order to maintain back pressure and the function of purifying the exhaust particulates. The regeneration process is roughly as follows.

First, the engine speed (7), engine load (7'), engine water temperature (8), exhaust pressure in front of the trapper (10), and trap material temperature (13) are input as information to the CPU 15 (Figure 1) as conditions. . 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 (Figure 2),
The fine particles contained in it are the trap material 20 (second
As the fine particles accumulate, the back pressure of the exhaust gas upstream of the trapper container 12 (a part of the particles are collected in the quartz wool layer 30).
This back pressure is an indicator of particulate accumulation. When it is determined that it is the regeneration time in this way, the engine water temperature (8) is checked. This is to prevent regeneration from starting immediately after the engine is started. Engine water temperature is 110°＞
When T>80° C., energization to the electric heater wire 16 is started. When a predetermined period of time has elapsed after the start of energization, the energization is stopped and one cycle of the regeneration process is completed. Note that in order to reduce power consumption, it is desirable to heat the plurality of electric heater wires 16 in sequence.

When the electric heater wire 16 is heated by electricity,
First, the exhaust particulates collected in the quartz wool layer 30 are combusted, which becomes an ignition source, and the combustion energy is propagated to the trapper material 20 on the downstream side along the flow of exhaust gas shown by arrow P. The exhaust particulates collected by the trapper material 20 are combusted and incinerated.

In the present invention, the quartz wool layer 30 with a high exhaust particulate collection rate is arranged on the front surface of the trapper material 20, and the electric heater wire 16 is provided inside it, so when the electric heater wire 16 is energized, the surrounding area is The amount of exhaust particulates is large and ignition is extremely easy. Also,
Since the combustion energy is transmitted to the entire area of the trapping material 20, combustion and regeneration are efficient.

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.

In addition, in order to shorten the heating and regeneration time using the electric heater wire 16, the exhaust gas temperature can be raised by throttling the intake system (that is, by throttling the throttle valve S shown in FIG. 1), or by throttling the exhaust gas. It is effective to use it in conjunction with a device that increases the amount of fuel and raises the exhaust temperature.

[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, and Fig. 3 is a view seen from the direction of the arrow in Fig. 2, showing the electric heater wire inside the quartz wool. It is a partially cutaway diagram showing the arrangement. 5... Diesel engine main body, 9... Exhaust manifold, 12... Collection material (trapper) container, 1
5... Microcomputer (CPU), 16...
Electric heater wire, 20... Collection material (trap material),
30...Quartz wool layer, 31...Metal wire.

Claims (1)

[Claims] 1. In an exhaust treatment trapper incorporating a collection material to be provided in the exhaust path of a diesel engine, a quartz wool layer is provided on the upstream end surface of the collection material, an electric heater wire is inserted inside the quartz wool layer, and the A diesel exhaust treatment trap characterized by a quartz wool layer fixed to a collection material.