JP3064322B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas purification device for an internal combustion engine,
In particular, the present invention relates to an apparatus for removing particulate components contained in exhaust gas of a diesel engine.

(Prior Art) Generally, the exhaust gas of a diesel engine contains a large amount of particulate components (particulates) composed of carbon particles and the like. As an exhaust gas purifying device that purifies exhaust gas by preventing the fine particle component from being released into the atmosphere as it is, a filter member having a partition wall having permeability such as ceramics is conventionally provided in an exhaust passage of an internal combustion engine. There is a known arrangement in which the particulates in the exhaust gas are collected by the partition wall while the exhaust gas passes through the filter member.

When the internal combustion engine is operated for a long period of time, the filter member is clogged due to the accumulation of particulate components, and the back pressure of the internal combustion engine increases, resulting in a decrease in output. There is a problem.

Therefore, conventionally, for example, JP-A-56-72212,
In the device disclosed in Japanese Patent Application Laid-Open No. 56-72213, a heater for heating is mounted in the case body, and the heater is energized periodically or when the filter member is clogged. The particulate component deposited on the filter member is heated and burned to regenerate the filter portion.

(Problems to be Solved by the Invention) However, in a conventional exhaust gas purifying apparatus for an internal combustion engine, a particulate component is ignited by a heat source such as an electric heater or a combustion burner attached to an end face of a filter, and a flow of a regeneration gas flowing in the filter is reduced. Since the combustion is propagated from the ignition portion to the downstream side of the regeneration gas by using the filter, according to this regeneration method, the filter is regenerated by the self-combustion of the particulate component. Due to such factors, combustion propagation may not be performed properly, and regeneration errors may occur.Starting from this, particulate components accumulate and burn at a stretch at a time, raising the temperature inside the filter and causing cracks and erosion in the filter. Etc. are liable to occur.

In the case where a heater is attached to the outer peripheral surface of the filter,
There is a problem that it is difficult to regenerate the entire filter without a burn-out of fine particle components in a generally used filter having a diameter of 100 mm or more.

The present invention has been made in order to solve such problems. An electric heater is provided on the outer peripheral surface of the filter and an end surface of the filter, and the flow rate of the regeneration gas is controlled, so that the combustion of the particulate component and the self-combustion by the heat of the heater are performed. It is still another object of the present invention to provide an exhaust gas purifying apparatus for an internal combustion engine capable of repeating stable and reliable regeneration by controlling the flow rate of a regeneration gas.

(Means for Solving the Problems) For this purpose, in the exhaust gas purifying apparatus for an internal combustion engine of the present invention, a large number of small holes extending in the axial direction are formed by a partition having air permeability, and one end of the small hole is formed. A filter in which the other end of the small hole adjacent to the small hole is alternately closed with a sealing member,
An electric heater is provided only on the outer peripheral wall surface of the filter and the upstream end surface of the filter, and the regeneration gas flows downstream at a flow rate exceeding 0 during regeneration of the filter, and the regeneration gas flows through the filter during regeneration of the filter. The flow rate of the regenerating gas flowing through is set to a predetermined value or less. The upstream side of the filter refers to the inflow side of the regeneration gas that is circulated during regeneration of the filter.

(Operation) When a regeneration gas is introduced into the filter during regeneration of the filter, the attached particulate components near the periphery of the filter burn due to the heating of the electric heater on the outer peripheral wall surface of the filter and the regeneration gas whose flow rate is controlled. When the electric heater on the end face of the filter is heated, the remaining particulate components are completely burned and removed. Then, the power supply to the electric heater is cut off. Then, the fine particles in the exhaust gas are collected again by the filter.

Since the electric heater is heated while the regeneration gas is passed through the filter, the supply of oxygen is sufficiently performed, and the regeneration of the filter can be promoted. Since the regeneration gas is supplied from the upstream side of the filter, it is not necessary to provide an electric heater downstream of the filter, and the power consumption of the electric heater is reduced.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the exhaust gas purification device 1 is provided between an unillustrated internal combustion engine and a muffler. Exhaust pipe 2
A ceramic honeycomb filter 4 is housed in a stainless steel case 3 having a diameter larger than the diameter. The connection between the case 3 and the upstream side exhaust pipe 2a and the downstream side exhaust pipe 2b is made by a tapered portion 6 and a tapered portion 7. As a result, the exhaust gas is smoothly introduced into the honeycomb filter 4.

The honeycomb filter 4 is made of cordierite, and has a large number of gas-permeable partition walls 8 extending in the axial direction inside the filter, and a large number of small holes 9 extending in the axial direction corresponding thereto. Some of the small holes 9 have their upstream opening ends closed by plugs 11 which are sealing members made of the same material as the filter or a heat-resistant ceramic material, and the remaining small holes 9 adjacent to the small holes 9 are downstream. Open end is plug 12
The adjacent small holes 9 are alternately closed by the plugs 11 and 12 at the upstream open end and the downstream open end. Therefore, when the exhaust gas introduced into the honeycomb filter 4 is introduced into the small hole 9 from the upstream opening end as shown by the arrow A in the drawing, it passes through the partition 8 between the small holes 9 and the downstream opening end. The particulate components contained in the exhaust gas flowing out of the filter cannot pass through the partition walls 18 and are collected in the honeycomb filter 4. As a material forming the honeycomb filter 4, a porous inorganic sintered body such as alumina may be used in addition to cordierite.

As shown in FIG. 2, an end face heater 14 made of a heating wire such as nichrome or a kanthal material is provided at the center of the upstream end face of the honeycomb filter 4. End heater 13
The heating wire is disposed so as to reciprocate repeatedly between the end face opening and a relatively shallow portion therefrom. The heating wire of the end face heater of the present invention may be non-contact or embedded in the honeycomb filter. The arrangement pattern of the heating wires may be a meandering shape, a spiral shape, or the like. The cross-sectional shape of the end face heater 14 may be circular, square, or any other polygon.

On the outer peripheral wall surface of the honeycomb filter 4, an outer peripheral heater 15 made of a heating wire such as nichrome or kanthal is wound. The outer peripheral heater 15 is wound so as to reciprocate in the axial direction on the outer peripheral surface of the filter. The cross-sectional shape of the heating wire of the outer peripheral heater 15 is preferably a quadrangle rather than a circle as shown in FIG. This is because the contact area with the outer peripheral wall of the filter is larger in the surface contact than in the line contact, so that the thermal conductivity is increased and the filter is suitable for rapid heating.

The end heater 14 and the outer peripheral heater 15 are taken out of the case 3 via an insulator as separate circuits, and are connected to a vehicle-mounted battery. The honeycomb filter 4 is housed in the case 3 in a state where a cushioning material 20 in which ceramic fibers are solidified in a sheet shape is wound.

Next, the operation of the filter used in the embodiment of the present invention will be described.

Exhaust gas discharged from the internal combustion engine passes through the upstream exhaust pipe 2a and passes through the small holes 9 of the honeycomb filter 4 in the direction indicated by arrow B in FIG.
And flows through the partition 8 to the outside of the honeycomb filter 4 through the small holes 9 adjacent to each other, flows out of the honeycomb filter 4 and flows to the muffler from the first arrow C direction in the drawing.

At this time, the fine particle components contained in the exhaust
Are deposited in the small holes 9 without being able to pass through. The exhaust gas from which the particulate components have been removed is discharged to the atmosphere via a muffler through a downstream exhaust pipe 2b. As the traveling distance of the vehicle increases, the accumulation amount of the particulate component increases, and the pressure loss at the front and rear portions of the honeycomb filter 4 increases. Then, for example, after traveling for a certain period of time, when particulate components accumulate in the honeycomb filter 4, the honeycomb filter 4 is regenerated as follows.

First, the regeneration gas flows into the honeycomb filter 4.
Exhaust gas or secondary air is used as the regeneration gas. The flow velocity of the gas flowing through the inside of the honeycomb filter 4 is controlled to be equal to or less than a predetermined value. After the introduction of the regeneration gas, power is supplied to the outer peripheral heater 15 provided on the outer peripheral wall surface of the filter. And the outer peripheral heater 15
When the power supply to the honeycomb filter 4 is maintained for a predetermined time, the particulate components attached near the outer periphery of the honeycomb filter 4 burn when the ignition temperature is reached. When the burning of the fine particle component is continued, as shown in FIGS. 4 and 5, the burning of the fine particle component proceeds in the direction of arrow D, and for example, about 80% of the filter volume burns.

Thereafter, the power supply to the end face heater 14 provided on the upstream end face of the honeycomb filter 4 is started. As a result, the particulate matter in the unburned portion E on the upstream central portion shown in FIG. 4 that could not be regenerated by the outer peripheral heater 15 alone is burned. After burning the particulate components of the honeycomb filter 4, the energization of the outer peripheral heater 15 and the end face heater 14 is cut off.

In this way, the particulate components adhering to the inside of the honeycomb filter 4 are removed, and the filter is regenerated. Then, the particulate component in the exhaust gas can be collected by the honeycomb filter 4 again.

In the case of the present embodiment, the flow rate of the regeneration gas is controlled to 0.1 m / s or less. This is because when only the outer peripheral heater 15 is operated, as shown in FIG. 7, if the flow rate of the regenerating gas is, for example, 0.02 m / s, almost no unburned particulate components remain,
If the flow rate of the regeneration gas is set to a value exceeding 0.1 m / s, unburned particulate components are generated.If the amount of trapped unburned gas increases, the combustion temperature may increase rapidly during regeneration. It was set at 0.1 m / s or less to prevent the combustion temperature from rising excessively and to control the regeneration slowly. If the flow rate of the regeneration gas is 0 m / s in a windless state, oxygen is insufficient and combustion is difficult, so the flow rate of the regeneration gas is set to a value exceeding at least zero.

According to the present embodiment, since the outer peripheral heater 15 and the end face heater 14 are provided, stable and reliable regeneration can be achieved without causing unburned particulate components to remain during filter regeneration. Therefore, it is possible to reliably prevent cracks and erosion that are likely to occur when the collected fine particle components burn at once. In addition, since an expensive metal catalyst for promoting the regeneration of the filter is not used, the regeneration of the honeycomb filter can be achieved at low cost, and the decrease in the output of the internal combustion engine can be minimized.

8 and 9 show the second embodiment of the present invention and the third embodiment.
FIG. In FIG. 8, three heating wires 30, 31, and 32 are wound around the outer peripheral surface of the honeycomb filter 4 in an upstream part, a middle part, and a downstream part, respectively, and are wound around once. In FIG. 9, the heating wire 40 is spirally wound around the outer peripheral surface of the honeycomb filter 4.
The cross-sectional shapes of these heating wires are round, polygonal, and the like, and their cross-sectional shapes are not specified.

(Effect of the Invention) As described above, according to the exhaust gas purifying apparatus for an internal combustion engine of the present invention, the particulate component adhering to the filter is surely burned and removed at the time of filter regeneration. Since the filter is removed, the regeneration rate of the filter is increased, cracks and erosion of the filter at the time of regeneration are prevented, and a decrease in output of the internal combustion engine and deterioration of fuel efficiency can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view of an exhaust gas purifying apparatus showing a first embodiment of the present invention, FIG. 2 is a perspective view showing a filter thereof, FIG. 3 is an explanatory view showing an operation of a heater, and FIG. 1 is a schematic explanatory view for explaining the operation of the embodiment of FIG. 1, FIG. 5 is a schematic explanatory view in the direction of the arrow V shown in FIG. 4, and FIG. 6 is a schematic view for illustrating the operation of the first embodiment. FIG. 7 is a characteristic diagram showing the relationship between the regeneration gas flow rate and the filter regeneration rate, comparing the embodiment of the present invention with the conventional example, and FIG. 8 is a perspective view of a filter showing a second embodiment of the present invention. FIG. 9 is a perspective view showing a filter according to a third embodiment of the present invention. 3 ... case (container), 4 ... filter, 8 ... partition, 9 ... small hole, 11, 12 ... plug (sealing member), 14 ... end face heater (electric heater), 15 ... outer periphery Heater (electric heater).

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Nobuhiko Murata 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-3-17225 (JP, A) JP-A-56- 72212 (JP, A) JP-A-56-72213 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F01N 3/02 341 F01N 3/02 301

Claims (1)

(57) [Claims] A large number of small holes extending in the axial direction are formed by a partition having air permeability, and one end of the small hole and the other end of a small hole adjacent to the small hole are alternately sealed with a sealing member. An electric heater is provided only on the outer peripheral wall surface of the filter and the upstream end surface of the filter, and at the time of regeneration of the filter, the regeneration gas is caused to flow to the downstream side at a flow rate exceeding 0 during the regeneration of the filter. An exhaust gas purifying apparatus for an internal combustion engine, wherein a flow rate of a regeneration gas flowing through the filter during regeneration of the filter is set to a predetermined value or less.