JPH0612171Y2 - Exhaust gas purification device for diesel engine - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an exhaust gas purifying apparatus for a diesel engine, and more specifically, to carbon fine particles contained in exhaust gas and similar particulate matter (hereinafter referred to as particulates). ) Is collected by a physical method on a filter member of an exhaust gas purifying apparatus, and the collected particulates are incinerated periodically to regenerate the filter member.

[Conventional technology and problems]

As particulate collection filter members for diesel engines, various filter members such as ceramic foam filters and honeycomb filters, and further ceramic fibers, metal fibers, and metal mesh have been proposed, but have excellent heat resistance, Honeycomb filters are regarded as promising because of their high thermal shock resistance and high collection performance.

By the way, when these filter members are used for a long period of time, clogging occurs due to the collected particulates, and therefore it is necessary to regenerate the filter members by periodically burning and removing the particulates.

For example, when regenerating a honeycomb filter, an external ignition means such as an electric heater is provided at the upstream end of the filter member,
It is general that the heater burns the particulates adhering to the front end surface of the filter and uses the exhaust gas flow as a heat source to self-burn the particulates downstream.

However, as will be described later, in the honeycomb filter, either the inlet side end face or the outlet side end face is alternately closed, and the exhaust gas flowing into the cells having the inlet side opened is a cell wall that partitions each cell and functions as a filter. Since it has a structure in which it enters into the adjacent cell where the outlet side is open through the exhaust and is discharged to the outside, most of the combustion heat generated in the upstream part of the filter by the external ignition means (heater) is in the downstream part of the cell. Before reaching the side, the particulates burned and passed through the cell wall with small passage resistance on the upstream side where filter regeneration was completed, and then flowed out to other adjacent cells steadily, and the particulates collected on the downstream side. The curate includes the problem of combustion propagation that it is difficult or not to self-combust, and as a result the filter is not properly regenerated, the filter function deteriorates and the regeneration state becomes unstable, Leading to the result that the damage to the filter in the case of evil.

In order to improve the combustion propagation property, the applicant of the present invention has
In 61-165659, a through hole is provided in the plug member on the outlet side end face of the honeycomb filter to the extent that the collection rate is not affected, and in consideration of clogging caused by particulates adhering to the through hole, the through hole We proposed a honeycomb filter in which the outlet-side plug member having a heat generating means was provided.

As a result, the combustion propagating property was improved as compared with a honeycomb filter having only through holes, and good regeneration was possible. However, in the purification device of the type in which the through holes are provided as described above, not only the structure becomes relatively complicated, but the through holes have the maximum size within a range that does not extremely deteriorate the collection rate of particulates. Since it is a hole, it is very difficult to completely prevent clogging even during long-term use.

Further, in the exhaust gas purifying apparatus described in Japanese Utility Model Laid-Open No. 60-1909, a plurality of heaters and filters are alternately arranged, and each heater is sequentially heated from the most upstream exhaust gas filter so that each filter is heated. It is intended to ensure combustion of the collected particulates to regenerate the entire filter. In such an apparatus, when the filters located downstream of the exhaust gas are heated, the combustion heat of the particulates in the upstream filter acts on the exhaust gas flow and acts on these filters. There was a risk of loss.

Therefore, an object of the present invention is to provide an exhaust gas purifying device that can solve such problems at the same time.

[Means for solving problems]

In order to achieve the above-mentioned object, an exhaust gas purifying apparatus for a diesel engine according to the present invention is provided in an exhaust gas passage of a diesel engine, and has a filter member for collecting exhaust particulates and a downstream end portion of the filter member. Is provided,
A first heater that is heated when the filter member is regenerated; and a second heater that is provided at an upstream end of the filter member and that is heated after the first heater has been heated when the filter member is regenerated. It is characterized by including.

[Action]

In the exhaust gas purifying apparatus for a diesel engine described above, during regeneration of the filter member, first, the first heater provided at the downstream end of the filter member is heated to remove the exhaust particulate matter collected in the downstream portion of the filter member. After burning off
The second heater provided at the upstream end of the filter member is heated.

〔Example〕

 Specific examples will be described below with reference to the drawings.

In FIG. 1, 1 is an engine, 2 is an intake manifold, 3 is an exhaust manifold, and 4 is an exhaust pipe. The filter container 5 has a filter member 6 for collecting particulates therein, an electric heater (hereinafter referred to as a front heater) 7 attached to an upstream end of the filter member 6 for heating and burning the particulates, Similarly, an electric heater (hereinafter referred to as a rear heater) attached to the downstream end 8
And is installed in the exhaust gas passage downstream of the exhaust manifold 3 and between the exhaust pipe 4. A bypass passage 11 is provided between the upstream side and the downstream side of the filter container 5 so as to bypass most of the exhaust gas and allow most of the exhaust gas to flow, and a bypass valve for controlling the exhaust gas flow rate is provided in the bypass passage 11. 9 are provided. The bypass valve 9 is for opening and closing the bypass passage 11 as necessary to control the flow rate of the exhaust gas flowing through the bypass passage 11, and thus the flow rate of the exhaust gas flowing through the filter 6, and is connected to the actuator 10. There is. The actuator 10 may be, for example, a negative pressure type diaphragm device (not shown), and is selectively connected to the atmosphere or a negative pressure source (eg, negative pressure pump) via a negative pressure switching valve (not shown). The bypass valve 9 is opened and closed.

As is well known, the timing of energizing the heater (timing of filter regeneration) is determined by the computer (CPU) 20 based on various parameter signals S such as engine speed, engine load, engine water temperature, filter internal temperature, and back pressure. Controlled.

In order to clarify the features of the configuration of the present invention, the above-mentioned conventional (prior application) technique is shown in FIGS. 3 and 4 for reference. Conventionally, there is no rear heater 8 as shown in FIG. 3, and the particulates collected in the filter member are appropriately heated and burned only by the front heater 7, and the downstream particulates are self-combusted by the flow of exhaust gas. Is played.

However, as understood from the figure, in the cell (inflow cell) 15 which is a flow path of the exhaust gas, the particulates collected by the cell wall (filter wall) 18 by the front heater 7 burn, When the cell wall 18 on the upstream side is regenerated, the pressure loss in that portion is sufficiently small, so most of the exhaust gas sent to the inflow cell 15 flows into the adjacent cell (adjacent cell) 16 from there, and Exhaust gas did not flow sufficiently downstream, and the particulates collected downstream remained unburned.

Therefore, in order to smoothly flow the exhaust gas from the upstream side to the downstream side in the inflow cell 15, the through hole 25 is provided in the plug member 22 on the end face on the outlet side of the inflow cell 15 as described above, and the plug member 22 generates heat. It was proposed to equip them with means (Fig. 4). As a result, the exhaust gas smoothly flows in the inflow cell 15, and the combustion propagating property is greatly improved as compared with the honeycomb filter of FIG. 3, but the structure becomes complicated and the price tends to be expensive. . In addition, the outlet plug member 22
Since there are holes 25 in the hole, there is a problem in the design that the collection rate of particulates is slightly lowered, and that if the hole diameter is made small to increase the collection rate, clogging easily occurs.

Therefore, according to the present invention, a heater is provided separately from the filter not only on the upstream side of the filter member but also on the downstream side, and the particulates on the outlet side of the inflow cell 15 are positively heated by effectively heating the particulates. By burning the exhaust gas and regenerating the outlet side filter portion, the pressure loss of the portion is reduced and the exhaust gas smoothly flows in the inflow cell 15. Without changing the function of the filter itself, that is, without providing through holes, etc., it does not reduce the collection rate,
In addition, good reproduction is possible.

FIG. 2 shows the flow of the exhaust gas when the honeycomb filter according to the present invention is energized (when the filter is regenerated). From the figure, the regeneration of the filter is ideally performed not only upstream of the filter but also downstream thereof. It will be understood. Although the above description is based on the honeycomb filter, the present invention achieves the improvement of the gas flow in the filter by providing a heater on the downstream side of the filter, and is not limited to the honeycomb filter, and other filters can be used. It is also applicable to.

An example of the regeneration operation of the filter of the device according to the present invention will be described below with reference to the flowchart of FIG.

When the filter regeneration is started, first, the bypass valve 9 is opened (step 501) to allow the exhaust gas from the engine 1 to flow into the bypass passage 11. Next, the rear heater 8 provided on the outlet side of the filter 6 is energized for a predetermined time (step 503) to incinerate the particulates adhering to the rear portion.

Then, the bypass valve 9 is once closed (step 50 to confirm whether or not the particulates in the rear portion are burned).
5) Then, the back pressure is measured, and when it is determined that it is time to perform the regeneration (at the time of determining the regeneration time), that is, the back pressure at the start is compared (step 507). If the measured back pressure has not decreased by a predetermined amount or more, it is determined that the particulate combustion by the rear heater is insufficient, and the process returns to step 501 and the operation at the start of filter regeneration is repeated until it decreases by a predetermined amount or more. If the back pressure is reduced by a predetermined amount or more, it is determined that the particulates in the rear part have sufficiently burned, and step 509
Then, the bypass valve 9 is opened again, and the front heater 7 is energized for a predetermined time (step 511) to ignite the front particulates and propagate the combustion. Next, when the energization of the front heater 7 is finished, the routine proceeds to step 515, and after a predetermined time (in this case, preferably 2 minutes) has passed, the routine proceeds to step 516, where the bypass valve 9 is closed and the regeneration is finished. In this way, the filter regeneration process is completed.

The above control can be easily performed by storing a program based on the flowchart of FIG. 5 in the memory (not shown) of the CPU 20, for example.

As can be seen from the above operation example, the exhaust gas purifying apparatus according to the present embodiment, by prioritizing the energization timing between the upstream side heater and the downstream side heater, that is, prior to upstream side particulate ignition, By heating the rear heater provided on the exhaust gas outlet side and incinerating the particulates adhering to the rear part, the effect of gas flow from the rear cell wall is made sufficient and the front heater is heated before regeneration. Good combustion propagation throughout the filter.

〔effect〕

As described above, according to the exhaust gas purifying apparatus for a diesel engine of the present invention, when the filter is regenerated, first, the first heater provided at the downstream end of the filter member is heated, and the downstream portion of the filter member is heated. After burning off the exhaust particulates collected in, the second heater provided at the upstream end of the filter member is heated to burn off the exhaust particulates collected at the upstream side of the filter member, The combustion is propagated in the downstream direction, the remaining exhaust particulates are burned and removed, and the entire filter can be reliably regenerated.

Further, when the second heater is heated, since the heating of the first heater is completed, both the heat of combustion on the upstream side and the heat of the first heater do not particularly act on the downstream side portion of the filter. The possibility that the part will be overheated and melted will be considerably reduced.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an entire exhaust gas purifying apparatus according to the present invention, FIG. 2 is a diagram showing a gas flow of a filter main portion according to the present invention, and FIG. 3 is a conventional filter without through holes. FIG. 4 is a diagram showing a gas flow in a portion, FIG. 4 is a diagram showing a gas flow in a conventional filter main portion having a through hole, and FIG. 5 is a diagram showing an example of a flow chart of a filter regeneration operation in the device according to the present invention. 1 ... Engine, 2 ... Intake manifold, 3 ... Exhaust manifold, 4 ... Exhaust pipe, 5 ... Filter container, 6 ... Filter member, 7 ... Front heater, 8 ... Rear heater, 9 ... ... bypass valve, 10 ... actuator, 11 ... bypass passage, 15 ... inflow cell, 16 ... adjacent cell, 18 ... cell wall, 20 ... computer, 22 ... plug member.

Claims (1)

[Scope of utility model registration request] 1. A filter member which is provided in an exhaust gas passage of a diesel engine and collects exhaust particulates, and a first heater which is provided at an end portion on a downstream side of the filter member and is heated when the filter member is regenerated. Exhaust gas of a diesel engine, comprising: and a second heater that is provided at an upstream end of the filter member and that is heated after the heating of the first heater is completed when the filter member is regenerated. Purification device.