JPS5977022A - Exhaust gas purifier for diesel engine - Google Patents

Abstract

PURPOSE:In a device where Diesel Particulate Filter (DPF) is provided in exhaust system, to perform DPF regeneration stably by utilizing suction negative pressure at the downstream of suction throttle valve to such fresh air from downstream of DPF to recombustion device. CONSTITUTION:Under normal operation, exhaust gas from engine 3 will enter into DPF6 placed in exhaust path 5 where paticulate is removed then discharged through muffler 7 to the outside. When choking of DPF6 is detected by a pressure sensor 10, suction throttle valve A is reduced first to exchange bypath exchange valves B, C to solid line position. Then a valve D is opened to feed secondary air through a filter 15a to recombustion device 11 through suction negative pressure and mixed with mixture from a fuel nozzle 14 to be burnt. Flame produced through combustion will cause combustion regeneration of DPF6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas purification device for an engine such as an automobile, particularly a diesel engine, which removes particulates consisting of fine particles whose main component is carbon from exhaust gas.

Conventional purifiers of this type have been installed in particulates and burned using the heat of exhaust gas.

However, when using a filter, clogging occurs, and when using a cyclone, no J? Because the ticulate is light and small, collection is not complete. For those equipped with a means to burn the air and ticulates collected by the filter using the heat of the exhaust gas, the exhaust temperature may exceed 500℃.
During high-speed, high-load operations at temperatures above ℃, particulates burn and clogging is less likely to occur, but particulates are difficult to burn during low-load operations. In normal city driving, if the exhaust gas is at a temperature of 500° C. or higher, a small amount of collected particulates will not be burned and the filter will become clogged.

Therefore, in the current situation, it is considered most appropriate to use a particulate filter to incinerate and regenerate the particulates when they become clogged. However, the biggest problem with incineration is The goal is to incinerate it evenly. For this reason, an air pump is required to supply secondary air to the particulate re-combustion device, but this pump requires a flow rate of about 200 t/min, and the diesel particulate filter (hereinafter referred to as DPF) is Since the resistance is large and the internal pressure is slightly high, the above flow rate cannot be ensured by using an air pump such as a sirocco fan or a turbo fan, and a large vane pump is required, which poses problems such as mountability, cost, and control equipment.

An object of the present invention is to provide an exhaust gas purification device for a diesel engine that solves the above-mentioned problems and can stably collect and purify particulates without clogging the diesel particulate filter even during light load running. is to provide.

In the present invention, an intake throttle is provided in the intake system of the engine to regenerate the DPF, and during regeneration, the engine's intake throttle generates negative pressure in the intake system, and the negative pressure causes fresh air to be sucked in from downstream of the DPF. Using this fresh air, fuel is injected through the fuel nozzle, ignited by a burner, and heated from downstream of the DPF.
It is configured to achieve the above objective by incinerating the i4 ticulate on F.

An embodiment of the present invention will be described below based on the accompanying drawings.

In Figure 1, 1 is the air cleaner, 2 is the intake passage, 3 is the engine, 5 is the exhaust passage, 6 is the diesel fuel filter or ticulate filter (DPF), and 7 is the muffler.The above are the parts used in normal operation. However, in order to regenerate the DPF, an intake throttle valve A provided in the intake passage 2 is connected between the intake passage 2 downstream of this throttle valve A and the upstream side of the DPF 6, and an on-off valve is provided in the middle. A second communication passage 8, a first communication passage 9 which connects the upstream and downstream of the DPF 6 with a pinhole and has /J path switching valves B and C at its inlet and outlet confluence, and the DPF
The pressure sensor 1o provided upstream of the DPF and the reburning device 11 provided upstream of the DPF are similar.

3 to S are detailed views of the reburning device 11, in which the negative pressure generated in the intake system due to the intake throttle of the engine is transmitted through the second communication passage 8, and is transferred to the secondary air valve E through the secondary air valve E. Next swirler-15
The secondary air swirl S generated by flowing into the vortex chamber through the nozzle 16 and the spray ejected from the fuel nozzle 14 to which the fuel pump 12 and the primary air pump 13 for improving fuel atomization are attached are completely mixed, This mixture λ flows out from the central outlet of the lower diaphragm plate 17 and is ignited by an arc 20 between the two electrodes 19 caused by the ignition Bragg 18.

The arc 20 and the nozzle of the fuel nozzle 14 are offset in length to prevent soot from forming. Further, a pressure sensor 10 is provided upstream of the DPF 6, and when the pressure at the core exceeds a predetermined pressure, this is detected and a DPF regeneration signal is output. DP in Figures 1 and 2
F6 has a ceramic honeycomb shape, 21 is an upstream Bragg, 22 is a downstream plug, and 23 is a thin wall that collects particulates when exhaust gas passes through.

The operation of the above embodiment will be explained.

In Fig. 1, during normal operation, air passes through the air cleaner l, intake pipe 2, and is taken into the engine 3, and after explosive combustion in the engine, the exhaust gas is filtered through the DPF 6 installed in the exhaust passage 5, and the muffler 7 It is released to the outside through the process. Therefore, the mother ticulate in the exhaust gas is removed and the exhaust gas is purified. However, the DPF 6 gradually becomes clogged. During high-speed, high-load operation, this i4 ticulate is spontaneously combusted and incinerated.

However, during light load operation, the DPF becomes clogged and particulates accumulate. In the above embodiment, in such a case, a reburning device 11 is provided to incinerate the particulates.

When regenerating the DPF, intake throttle valve A and switching valve B are used.

At the same time as the C1 on-off valve switches, the reburning device 11
When the secondary air valve opens, the fuel pump 12 and the primary air pump 13 attached to the fuel nozzle 14 operate, igniting with the discharge igniter and starting re-combustion.

That is, the DPF 6 is clogged by the pressure sensor 10,
When it is sensed that particulates have accumulated, the intake throttle A is throttled and the negative pressure in the intake pipe 2 downstream thereof increases. In addition, the Pynox switching valves B and C operate, and the first communication passage 9 is opened, and at the same time, the portion 5a of the exhaust passage communicating with the DPF is opened.
+5 b is closed. Therefore, a high degree of negative pressure due to the action of the intake throttle Dh is transmitted to the upstream and downstream parts of the DPF 6 via the second communication passage 8, and the secondary air to the afterburner 11 is sent to the filter 15a1, the secondary air valve E1, and the secondary air swirler. -15
, into the swirl chamber through the nozzle/l/16. The reburning device 11 includes a fuel pump 12 and a primary air pump 13 for improving fuel atomization.
Water-temperature gas is ejected from the nozzle outlet, completely mixed with the secondary air accompanied by the vortex, and flows out through the center hole of the throttle plate 17. This air-fuel mixture is ignited by the arc 20 thrown between the electrodes 19 by the spark plug 18, and this flame is drawn from the downstream side to the upstream side of the DPF 6 by the negative pressure of the engine, and the flames and ticulates on the DPF 6 are drawn from the inside. It is designed to be heated evenly and incinerated for recycling. The reburn time is controlled by a timer, e.g. fuel pump 12.1
Next, the air pump 13 is operated for 2 minutes, and then combustion continues for 2 minutes due to self-combustion of the DPF, and valves A, B, and C are activated.

Control such as returning D and E to their original values can be considered.

Normally, in order to regenerate the DPF 6, particulates 24 are heated and incinerated using a burner from upstream of the DPF 6 to which the particulates 24 are attached, as shown in FIG.

Therefore, the particulates 24 are ignited from the top and burn more violently as they move toward the bottom due to the heat of reaction at the top.

All of this combustion heat is applied to the cells 6a of the DPF 6, and if there are many particulates 24, cracking or melting damage may occur due to the heat in the DPF 7 cells 6a.

However, in the case of the present invention, as shown in FIG. 2(b), a large amount of 74
4 can be incinerated, and since air is passed from downstream, some of the guticulates come off, enter the intake system, and are incinerated by the engine, which has the advantage of extending the life of the DPF 6.

Note that, as the DPF 6, ceramic-coated wire mesh, glass fin fabric, etc. can also be used. Re-combustion can also be carried out by raising the temperature of the exhaust gas or by using an electric heater.

According to the present invention, an intake throttle A is provided in the intake system of the engine in order to regenerate the DPF, and the intake air is throttled based on a signal from a pressure sensor to generate negative pressure, and fresh air is sucked in from downstream of the DPF using the negative pressure. Using this fresh air, fuel is injected from the fuel nozzle, ignited by the discharge igniter, and heated from the downstream of the DPF.
Since the particulates on the F are incinerated, the DPF can be stably maintained without clogging even during light load driving. (b) is an explanatory diagram of how to incinerate particulates deposited on DPF (,)
The figure shows the conventional method, and the figure (b) shows the method according to this embodiment.

Figure 3 is a cross-sectional view of the reburning device, and Figure 4 is ■-I in Figure 2.
V sectional view, FIG. 5 is a sectional view taken along ■--■ in FIG. 2.

Claims (1)

[Claims] 1. In a diesel engine in which a diesel engine filter made of a breathable heat-resistant material is installed in the exhaust passage of a diesel engine, an intake throttle provided in the intake passage;
And the upstream and downstream of the filter are PiiJ? The first valve is equipped with pino master switching valves B and C at the upstream branch and the downstream confluence.
a second communication passage that connects the intake passage downstream of the intake throttle A and the upstream side of the filter and has an on-off valve in the middle;
A pressure sensor provided upstream of the filter and a re-combustion device provided downstream of the filter are used, and when the filter is regenerated, the throttle valve A is throttled. Open the on-off valve to open the second communication passage and bypass switching valve B. At C, the passage to the filter is closed, the first communication passage for the pie and base is opened, and the re-combustion device is activated, so that the particulates are combusted and incinerated by the backflow flame caused by the negative pressure of the engine. Exhaust gas purification device for diesel engines. 2. The reburning device includes a fuel nozzle that includes a fuel pump and a primary air pump and mixes fuel and primary air;
A secondary air swirler equipped with a secondary air valve E that mixes secondary air by applying a swirl to water-temperature air, a throttle plate provided below the nozzle and the swirler, and a central outlet of the throttle plate. 2. The exhaust gas purification device for a diesel engine according to claim 1, further comprising a discharge igniter disposed in the exhaust gas purifying device for a diesel engine.