JPH037011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust gas purification device that burns and processes particulate contained in the exhaust gas of a diesel engine.

Diesel engines contain harmful exhaust substances such as carbon in their exhaust gas, so various measures have been taken to remove these substances. As one of the exhaust gas countermeasures, an exhaust gas purification device is known that collects and processes particulate matter made of carbon or the like in the middle of the exhaust pipe (see Japanese Patent Laid-Open Publication No. 12029/1989, etc.).

Such a conventional exhaust gas purification device is shown in Fig. 1 and Fig. 2.
As shown in the figure, a trap device 3 for collecting particulate matter in the exhaust gas is provided in the middle of an exhaust pipe 2 of an engine 1, and a burner 4 for heating and incinerating the collected particulate matter is installed upstream of this trap device 3. .

In the trap device 3, a trap material 5 for collecting particulate matter is filled inside a casing 6, and the particulate matter in the exhaust gas is collected in this trap material 5 and gradually accumulates over time of operation. .

When the amount of particulate matter trapped in the trapping material 5 increases, the trapping ability of the trapping material 5 decreases and the exhaust pressure increases, making it impossible to ensure normal operation.
In order to avoid such a situation, a trap regeneration burner 4 is provided to heat and incinerate the collected particulate matter.

This burner 4 for trap regeneration is activated when a control circuit (not shown) detects a predetermined amount of particulate matter collected based on a detection signal such as an increase in exhaust pressure on the upstream side of the trap material 5 or the operating time of the engine 1. An ignition device 8 ejects fuel from a nozzle 7 and ignites a mixture of this fuel and exhaust gas (including air).
to ignite and produce combustion gas.

In this way, the high-temperature gas generated by the combustion action of the burner 4 is set at, for example, about 600° C., and heats and incinerates the particulate collected in the trap material 4 on the downstream side.

However, in such a conventional trap regeneration burner, since fuel is injected from the nozzle 7 in the exhaust gas for combustion, the nozzle 7 exposed to the exhaust gas may become clogged. Also,
When there is a lack of oxygen in the exhaust gas, such as in a high-load operating range, the burner 4 may misfire, and furthermore, in a low-load operating range, the exhaust temperature is low, resulting in problems in that the ignitability of the burner 4 deteriorates.

The present invention has been made in view of these problems, and involves igniting a mixture of fuel and air using an ignition device without exposing it to exhaust gas, growing a flame of this ignited gas, and then mixing it with exhaust gas. An object of the present invention is to provide an exhaust gas purification device that prevents clogging of a fuel supply nozzle and increases the combustion capacity of a burner by heating and incinerating collected particulate matter on the downstream side with this high-temperature gas.

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

As shown in FIG. 3, a burner 9 is installed in the middle of the exhaust pipe 2. Although not shown, a trap device is provided downstream of the burner 9 to collect particulate matter in the exhaust gas.

The exhaust pipe 2 in which the burner 9 is installed is formed into a large-diameter cylindrical shape, and a cylindrical combustion cylinder 10 is housed inside the exhaust pipe 2 along the exhaust pipe 2.

A wall surface 10a that prevents the inflow of exhaust gas is provided at the upstream end of the combustion tube 10, and a large number of small holes 10b are formed on the outer periphery of the combustion tube 10 to guide the exhaust gas into the internal combustion chamber 11.

A nozzle 12 for supplying an air-fuel mixture containing fuel into the combustion cylinder 10 is provided in the center of the wall surface 10a, and an evaporator inner cylinder 13 surrounds the tip 12a of this nozzle 12 and guides the air-fuel mixture to the downstream side. will be provided.

Then, an evaporator outer cylinder 14 that guides the air-fuel mixture (evaporated fuel) guided to the evaporator inner cylinder 13 to the upstream side conversely,
It is provided around the outside of the evaporator inner cylinder 13.

In this manner, the basic structure of the burner 9 is formed into a reverse flow evaporator cylinder type so that it is strong against exhaust pulsation and the fuel from the nozzle 12 does not need to be atomized.

On the other hand, fuel to the nozzle 12 is supplied from a fuel supply tank 15 through a conduit 17 via a fuel quantity control valve 16.

A three-way pipe 18 is provided in the middle of the conduit 17, where air from the air supply pump 19 and fuel from the fuel control valve 16 are mixed and supplied downstream.
The air supply pump 19 is driven by a pulley 21 which rotates synchronously with the engine 1 via an electromagnetic clutch 20.

The air-fuel mixture (fuel) injected from the nozzle 12 through the conduit 17 flows along the inner evaporator cylinder 13, is further guided to the outer evaporator cylinder 14, and is led into the combustion chamber 11 from the upstream side.

The air-fuel mixture guided into the combustion chamber 11 is then heated by an ignition device (heater) installed in the combustion chamber 11.
(such as a glow plug) 22, and the ignited high-temperature gas burns the collected particulate on the downstream side.

Next, to explain the operation, first, when the particulate in the exhaust gas of the engine 1 is collected by a trap device installed downstream of the burner 9 and deposited in a predetermined amount, the control circuit controls the burner 9 based on the exhaust pressure and other signals. Start the operation.

Specifically, when the glow plug 22 is energized, 10
After ~20 seconds, the glow plug 22 becomes red hot,
Thereafter, the fuel from the fuel supply tank 15 is metered by a fuel quantity control valve (electromagnetic valve) 16, and a predetermined amount of fuel is passed through a conduit 17 from the nozzle 12 to the evaporator inner cylinder 13.
It is squirted inside.

At this time, the air supply pump 19 connects the electromagnetic clutch 20 and is operated by the driving force of the pulley 21 to pump air to the three-way pipe 18 through the passage 22. As a result, air and fuel are mixed in the three-way pipe 188 to form an emulsion, and this emulsified air-fuel mixture is discharged from the nozzle 12 into the evaporator inner cylinder 13 through the conduit 17.

Therefore, the discharged mixture (fuel and air)
contacts the glow plug 22 through the evaporator inner cylinder 13 and the evaporator outer cylinder 14 in an oxygen-rich state without being affected by exhaust gas and ignites.

In this case, since the amount of air is relatively small near where the initial flame of the ignition gas is formed, the air-fuel ratio is in a rich state. However, since the exhaust gas containing oxygen flows into the combustion chamber 11 from the small hole 10b formed in the combustion tube 10 and promotes the combustion of the ignition gas, the exhaust gas temperature is sufficient to burn the particulate in the combustion chamber 11. The temperature rises to around 600℃.

The combustible air-fuel mixture ejected from the nozzle 12 in this way is ignited by the backflow evaporator type burner 9,
Since the combustion of this ignition gas is further promoted by the oxygen in the high-temperature exhaust gas, the exhaust gas can be reliably combusted even when the residual oxygen concentration in the exhaust gas is quite low.

The ignited and combusted gas incinerates particulate matter collected by a downstream trap device (not shown), thereby purifying the exhaust gas discharged from the end of the exhaust pipe 2.

When the particulate waste has been incinerated and the trap device has been regenerated, the fuel amount control valve 16 is
It turns OFF and stops igniting the glow plug 22. Note that instead of stopping the fuel amount control valve 16, a fuel supply device (not shown) may be stopped.

Even after ignition combustion is finished, the air supply pump 19 continues to operate for a while, and all of the fuel remaining in the conduit 17 is discharged from the nozzle 12. This prevents clogging due to fuel accumulation within the conduit 17.

When the air supply pump 19 is deactivated, the electromagnetic clutch 20 is disengaged, thereby terminating all trap regeneration strokes.

In this manner, according to the present invention, the mixture of fuel and air is ignited without being exposed to exhaust gas, and after the flame of this ignited gas has grown sufficiently, the exhaust gas is combusted, and this combustion gas is used to trap the trap device. By incinerating the collected particulate matter,
The nozzles that eject fuel and air do not become clogged, and the high-temperature ignition gas that reliably ignites the air-fuel mixture combusts the exhaust gas accurately even when the oxygen concentration in the exhaust gas is quite low. It is possible to perform burner combustion in a high load range where it is difficult to perform burner combustion, and to appropriately generate combustion gas for incinerating particulate matter. The inner evaporator cylinder and outer evaporator cylinder that ignite the air-fuel mixture become extremely hot, and if they are made of metal, there is a risk of melting, so as shown in Figure 4, the inner evaporator cylinder 13
The evaporator outer cylinder 14 and the evaporator outer cylinder 14 may be made of ceramic, or the metal evaporator inner cylinder 13 and evaporator outer cylinder 14 may be coated with ceramic to improve heat resistance.

As explained above, the present invention installs a combustion tube inside an exhaust passage, forms a wall surface that blocks the inflow of exhaust gas at the upstream end of this combustion tube, and allows exhaust to flow into the outer periphery of the combustion tube for combustion. A small hole leading to the chamber is formed, while a nozzle is provided on the wall surface to inject fuel and air into the combustion cylinder, and an evaporation inner cylinder is provided on the inner periphery of the nozzle to guide the ejected fuel downstream. An evaporator outer cylinder is provided around the evaporator inner cylinder, which causes the evaporated fuel to once flow back upstream along the outer periphery of the evaporator inner cylinder, and then guides it into the combustion chamber, making it possible to greatly expand the combustion load range of the burner. In addition, combustion gas for particulate incineration can be reliably generated even with a relatively simple configuration of the ignition device such as a glow plug, and therefore all collected particulate can be burnt and burnt in all engine operating ranges. It is.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a conventional example, Fig. 2 is a sectional view of its main part, Fig. 3 is a sectional view showing a burner according to an embodiment of the present invention, and Fig. 4 is a diagram showing a case where the evaporator cylinder is made of ceramic. FIG. 2...Exhaust pipe, 9...Burner, 10...Combustion cylinder, 10a...Wall surface, 10b...Small hole, 11...
Combustion chamber, 12... Nozzle, 13... Evaporation inner cylinder, 1
4... Evaporation outer cylinder, 15... Fuel supply tank, 17
... Conduit, 19 ... Air supply pump, 22 ... Glow plug (ignition device).

Claims (1)

[Claims] 1. In a particulate collection and regeneration burner equipped with a trap device installed in the exhaust pipe to collect particulate matter in the exhaust of a diesel engine, and a burner that generates combustion gas in which the collected particulate matter is incinerated upstream of the trap device, A combustion tube is installed inside the tube, a wall is formed at the upstream end of the combustion tube to block the inflow of exhaust gas, and a small hole is formed on the outer periphery of the combustion tube to allow exhaust gas to flow into the combustion chamber. A nozzle is provided to inject fuel and air into the combustion cylinder, and an evaporator inner cylinder is installed on the outer periphery of the nozzle to guide the ejected fuel and air downstream. 1. A burner for collecting and regenerating particulate matter for a diesel engine, characterized in that an outer evaporator cylinder is provided around an inner evaporator cylinder to cause the flow to flow backward into the combustion chamber.