JPH0447109A - Exhaust particulate purification device for diesel engine - Google Patents

Abstract

PURPOSE:To enable even heating of a filter by arranging a plurality of bar-like heaters for regeneration of a particulate filter spirally in respect to an exhaust passage, and elongating the heating parts of base ends located on an outer periphery of the heaters compared to the ends located on an outer peripheral part. CONSTITUTION:A space inside a cylindrical housing main body 2 are divided into four chambers 12, each housing a ceramic filter element 13a with the same sectional shape. A plurality of heater installing ports 14 are formed on a circular spacer 3 provided on an upstream side end of the main body 2 so as to spirally penetrate it. Strait bar-like sheathed heaters 15 to 17 are fitted into the installing ports 14. In each group classified corresponding to the filter element 13a, the centrally located first heater 15 is the longest in its heating part 15a. The end thereof is extended to the center of the spacer 3. The two second heaters 16 have the shortest heating parts 16a. Both side third heaters 17 have heating parts 17a shorter than those of those of the first heaters 15 and longer than those of second heaters 16.

Description

Detailed Description of the Invention (Field of Industrial Application) The second invention is an exhaust particulate purification system that collects and removes combustible particulates (particulates) mainly composed of carbon, etc. contained in the exhaust gas of a diesel engine. The present invention relates to an apparatus, and particularly to the structure of a regeneration means that burns particulates collected in a filter by heating.

(Conventional technology) Conventionally, in order to remove combustible particulates such as carbon contained in large amounts in the exhaust gas of a diesel engine and purify the exhaust gas, a method has been used to collect exhaust particulates and discharge them to the outside. It is known to install a particulate filter in the exhaust system to prevent this. In that case, after a certain period of time, the particulate filter will become clogged due to the accumulation of the collected particulates, leading to a decrease in the exhaust purification function and a decrease in engine output due to exhaust resistance. , it is necessary to remove the trapped particles and regenerate the filter.

When regenerating such a particulate filter, the filter is generally regenerated by burning and removing the particulates by heating, and various heating means have been proposed for heating the particulates. For example, in the method disclosed in Japanese Patent Application Laid-Open No. 61-11414, microwaves are applied to exhaust particulates, which are dielectric substances, and the particulates themselves are heated and burned by microwave heating. However, this method requires a magnetron or the like to generate microwaves, making the device expensive and large-scale.

In addition, a heater wire for heating is installed in the exhaust passage,
There is a device in which fine particles are burned and removed by heating the toner wire. This device has a simple device configuration, but the heater wire is exposed in the exhaust passage, so
There is a risk that fine particles (carbon), which is a dielectric substance, may adhere to this heater wire, causing a short circuit or electric leakage.

(Problem to be solved by the invention) For this reason, there is a method of using a sheathed heater in which the heater wire is inserted and filled into a heat-resistant tube, but this heater cannot adopt a sharp bending structure due to its structure, and it is shaped like a rod. Becomes the property of Therefore, if this rod-shaped heater is disposed in the exhaust passage along a plane perpendicular to its central axis, only the peripheral area of the heater is heated, making it difficult to uniformly heat the particles.

Therefore, it is conceivable to further arrange a plurality of rod-shaped heaters radially along a plane perpendicular to the central axis of the exhaust passage. However, in this case, the rod-shaped heaters are arranged so that their tip heating parts face the central axis of the exhaust gas, so the distribution of heat generation temperature becomes uneven between the center and the outer periphery of the exhaust passage. In the center of the passage, the spacing between the heaters is small and the density of heat generation is high, resulting in high temperature heating, whereas in the outer periphery of the exhaust passage, the spacing between the heaters is large and the heat generation is high. low density,
Heating temperature becomes lower. As a result, the effect of uniformly heating the filter cannot be sufficiently achieved.

In addition, thermal stress is applied to the filter due to the uneven heating temperature between the center portion and the outer peripheral portion, and there is a possibility that cracks may occur in the filter due to the fatigue limit being exceeded.

The present invention has been made in view of the above points, and its purpose is to change the heat generation structure of each heater in the configuration in which a plurality of rod-shaped heaters are arranged radially as described above.
The particulate filter is heated evenly by equalizing the density of the calorific value at the center and outer periphery of the exhaust passage of each heater, and the particulate filter is regenerated evenly by uniform combustion of exhaust particles. The purpose is to reduce fatigue.

(Means for Solving the Problem) In order to achieve this object, in the solving means of the invention of claim (1), the heat generation amount of the heat generating part of each heater is made different between the tip part and the base end part, and the The base end located on the outer periphery of the passage generated a larger amount of heat than the distal end located in the same center.

That is, in the present invention, the exhaust system includes a particulate filter that collects combustible particulates in the exhaust gas, and a heating unit that burns off the particulates collected by the particulate filter and regenerates the particulate filter. The heating means is a plurality of rod-shaped heaters arranged radially in a plane perpendicular to the central axis of the exhaust passage so that the heating end faces the exhaust passage. The heat generating portion of each heater has a larger amount of heat generated on the outer peripheral side of the exhaust passage than on the central side.

(Function) With the above configuration, in the invention of claim (1), even if a plurality of rod-shaped heaters are arranged radially in a plane perpendicular to the central axis of the exhaust passage, the heat generating portion of each heater is Since the amount of heat generated on the outer periphery of the exhaust passage is larger than that on the center side, the amount of heat generated on the outer periphery of the exhaust passage increases despite the large spacing between the heat generating parts of each heater. The amount of heat generated is small on the center side of the small exhaust passage, and by compensating for this amount of heat generated, the distribution of the amount of heat generated between the center and the outer circumference of the exhaust passage becomes equal. Therefore, during regeneration, the particulate filter can be heated evenly from the center to the outer periphery, and the collected particulates can be uniformly burned and removed, and the regeneration can be performed satisfactorily.

Moreover, as a result of the filter being heated evenly in the outer peripheral portion and the central portion, thermal stress is less likely to occur, and the occurrence of cracks can be suppressed.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 4 shows the overall configuration of an exhaust particulate purification device according to an embodiment of the present invention, in which 1 is a housing disposed in the middle of an exhaust passage of a diesel engine, and this housing 1 includes a cylindrical housing body 2, Fastening bolts 4, 4. 7. The upstream cover 5 is airtightly joined to the downstream end (right end) of the housing body 2. 7. ..., and an exhaust gas inlet 9 is provided at the end of the upstream cover 5, and an exhaust gas outlet 10 is provided at the end of the downstream cover 8. Although not shown, the exhaust gas inlet port 9 is connected to the exhaust port of the engine via an exhaust pipe, and the space inside the housing 1 is connected to the exhaust passage 1.
It forms part of 1.

As shown in FIG. 3, the space within the housing body 2 includes four chambers 12.12.・
..., and each chamber 12 accommodates a ceramic filter element 13a having a similar cross-sectional shape.
These four filter elements 13a, 13a,...
A particulate filter 13 is configured, and the filter 13 collects combustible particulates (particulates) mainly composed of carbon from the exhaust gas introduced into the housing 1 from the exhaust gas inlet 9, and collects other combustible particles (particulates). Only the gas components are allowed to pass through and are discharged from the exhaust gas outlet 10.

As shown in FIG. 2, the spacer 3 has 20 heater mounting holes 14, 14.
... is formed. These mounting holes 14, 14.
... are divided into four groups of five each corresponding to the filter elements 13a in the housing body 2, and each group has five mounting holes 14, 14, . ... are arranged at equal angular intervals. In each of the mounting holes 14, straight rod-shaped lens heaters 15 to 17 are installed at their tip heat generating portions 15a.
17a are inserted through the spacer 3 so as to face the exhaust passage 11 immediately upstream of the filter 13, and are fixed in an airtight manner. That is, the heaters 15 to 17 are connected to the tip heating section 15.
The heaters 15 to 17a are arranged radially in a plane orthogonal to the central axis of the exhaust passage 11 so as to face the exhaust passage 11, and the particulates collected by the particulate filter 13 are removed by the heaters 15 to 17. A heating means is configured to regenerate the particulate filter 13 by burning and removing the particulates by heating.

The heaters 15 to 17 are divided into three types depending on the length of the heat generating parts 15a to 17a, and the first heater 15 located in the center of each group has the longest length of the heat generating part 15a, and its tip is connected to the spacer 3. (center of exhaust passage 11)
It extends to Further, the heat generating parts 16a, 1 of the two second heaters 16, 16 located near both sides of the first heater 15
6a is the shortest, and the lengths of the heat generating parts 17a, 17a of the two third heaters 17, 17 located at both ends are shorter than the first heater 15 and longer than the second heater 16. ing.

Each of the heaters 15 to 17 has the same structure. For example, in the case of the first heater 15, as shown in enlarged detail in FIG. A spiral heater wire 15c is provided inside the tube 15b.
(heating coil) is inserted and insulating powder is filled around this heater wire 15c. As a feature of this invention, the wire diameter of the heater wire 15c is
The diameter D1 of the heater wire 15c on the proximal end, which is on the outer circumferential side of the exhaust passage 11 when the heater is installed, is larger than the wire diameter D2 on the distal end, which is on the same central side. ing. In other words, the resistance value of the heater wire 15C with a large wire diameter at the base end or the resistance value of the heater wire 1 with a small wire diameter at the center portion
The resistance value is smaller than the resistance value at 5c, and when heat is generated due to energization, the amount of heat generated is generated on the base end side of the heat generating part 15a, therefore, when installed, the amount of heat generated on the outer peripheral side of the exhaust passage 11 is on the center side. I try to make it bigger than the quantity.

In FIG. 4, reference numeral 18 indicates an inlet temperature sensor mounting hole formed through the upstream cover 5, and a filter 13 is inserted into this mounting hole.
An inlet temperature sensor (not shown) is hermetically mounted to detect the exhaust gas temperature before passing through the exhaust gas. In addition, in Figs. 3 and 4, 19°19, . . . indicate the housing body 2.
An outlet temperature sensor mounting hole is formed through the downstream end of the exhaust gas, and an outlet temperature sensor (not shown) for detecting the temperature of the exhaust gas after passing through the filter 13 is airtightly mounted in this mounting hole.

Next, to explain the operation of the above embodiment, exhaust gas discharged as the engine operates is introduced into the housing 1 from the exhaust gas inlet 9 of the upstream cover 5 of the housing 1. Particulate filter 1
3, the exhaust gas outlet 10 of the downstream cover 8
is discharged from. When the exhaust gas passes through the filter 13, combustible particulates are collected from the exhaust gas by the filter 13, so that only other gas components are discharged by collecting the particulates.

When it is determined that the filter 13 is clogged due to the accumulation of particulates based on the increase in the exhaust gas pressure on the upstream side of the filter 13, the heaters 15 to 17 are energized and the heat generating parts 15a to 17a become red-hot. And this heat generating part 15a~
17a heats the exhaust gas to a high temperature. This heated exhaust gas flows into the filter 13 while remaining at a high temperature, so the combustible particulates are heated and burned by this exhaust gas, and the particulates are thereby removed and filtered into the filter 13.
is played.

At that time, a plurality of heaters 15 to 17 are arranged radially with respect to the exhaust passage 11 in the housing 1, and for each filter element 13a, five heaters 15 to 17 are evenly distributed immediately upstream of the filter element 13a. Since it is covered, the exhaust gas flowing into each filter element 13a can be heated evenly over the entire filter element 13a. Moreover, since the amount of heat generated on the outer peripheral side of the exhaust passage 11 in the heat generating parts 15a to 17H of each heater 15 to 17 is larger than that on the center side, the plurality of rod-shaped heaters 15 to 1
Due to the radial arrangement of the heaters 7, the amount of heat generated increases on the outer peripheral side of the exhaust passage 11 even though the intervals between the heat generating parts 15a to 17a of the respective heaters 15 to 17 are increased. On the other hand, on the center side of the exhaust passage 11 where the intervals between the heat generating parts 158 to 17a of each heater 15 to 17 are small, the amount of heat generated is small, and the exhaust passage 1
The distribution of the amount of heat generated at the center and the outer periphery of 1 is the same.

Therefore, during regeneration, each filter element 13a can be heated uniformly from the center to the outer periphery, and the collected particulates can be uniformly burned and removed, allowing for good regeneration.

Furthermore, since each filter element 13a is heated equally in the outer peripheral portion and the center portion, thermal stress is less likely to occur, and the occurrence of cracks can be suppressed.

In addition, in the above embodiment, the heat generating portion 15 of each heater 15 to 17
The amount of heat generated between the distal end and the proximal end in a to 17a was changed by changing the wire diameter of the heater wire 15C. This may be achieved by changing the distal end and the proximal end.

Further, in the above embodiment, the cross section of the exhaust passage 11 is circular, but it may also be rectangular, and similar effects can be obtained.

(Effects of the Invention) As explained above, according to the present invention, a plurality of rod-shaped heaters are installed in the exhaust passage in order to regenerate the particulate filter for collecting combustible particulates arranged in the exhaust system of a diesel engine. On the other hand, by arranging them radially and making the heat generation amount of the base end located on the outer periphery of the exhaust passage larger in the heat generating part of each heater than the distal end located on the same outer periphery,
Due to the radial arrangement, even if the distance between the center and the outer periphery of the exhaust passage is different, the density of the calorific value is the same and the particulate filter can be heated evenly. Not only can regeneration be performed satisfactorily, but also the thermal stress of the filter can be reduced, cracks can be suppressed, and the life of the filter can be extended.

[Brief explanation of drawings]

1 to 4 show embodiments of the present invention, FIG. 1 is an enlarged front view of the heater with a part of the heat generating part cut away, and FIG. 2 is a sectional view taken along the line ■-■ in FIG. 4. , Figure 3 is a cross-sectional view along the line ■-■,
FIG. 4 is a front view of the exhaust particulate purification device with the upper half cut away. 1...Housing 11...Exhaust passage 13...Particulate filter 13a...Filter elements 15-17...Heater (heating means) 15a-17a...Heating part 15c...Heater wire Dl ...Wire diameter D2 of the proximal heater wire...Wire diameter of the distal heater wire

Claims (1)

[Claims] (1) The exhaust system is equipped with a particulate filter that collects combustible particulates in the exhaust gas, and a heating means that burns off the particulates collected by the particulate filter by heating and regenerates the particulate filter. In the diesel engine equipped with the above heating means, the heating means is composed of a plurality of rod-shaped heaters arranged radially in a plane orthogonal to the central axis of the exhaust passage so that the tip heat generating part faces the exhaust passage, and the heat generation of each heater is 1. An exhaust particulate purification device for a diesel engine, characterized in that the amount of heat generated on the outer circumferential side of the exhaust passage is larger than that on the central side.