JPS61182412A - Diesel particulate collecting apparatus - Google Patents

Abstract

PURPOSE:To suppress the formation of odor component and sulfate by installing a DPO consisting of a filter and a base-metal catalyst into the exhaust passage of a Diesel engine and installing a converter equipped with the base-metal catalyst for increasing the exhaust temperature on the upstream side of the DPO. CONSTITUTION:In ordinary case, the exhaust gas supplied from a Diesel engine 1 is supplied into a DPO5 to catch Diesel particulates. When a controller 8 receives the pressure-loss increase signal from a regeneration timing detecting means 11 and judges the regeneration timing for DPO5, a control signal is sent into a regeneration assisting mechanism 10 from the controller 8, and the temperature of exhaust is increased. The high-temperature exhaust is sup plied into the precious-metal catalyst part 5a of the DPO5, and the purification rate in the conversion of CO and HC into CO2 is improved, and the generated calorific heat at this time is supplied into the base-metal catalyst part 5b on the downstream side. Therefore, the temperature of the base-metal catalyst part 5b is speedily increased to accelerate the conversion of CO and HC into CO2.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a diesel particulate collection device inserted in the exhaust passage of a diesel engine, and particularly to a diesel particulate oxidizer (hereinafter referred to as rDP). This invention relates to a diesel particulate collection device equipped with a

[Conventional technology]

Diesel engine exhaust contains particulates, which are flammable, fine carbonized compounds, and are the main cause of black smoke in the exhaust gas. These particulates spontaneously ignite and burn when the vehicle is at high speed and under high load (hereinafter referred to as "self-combustion") when the temperature reaches 500°C or higher, for example, but when the temperature does not reach 500°C and the particulates are running normally. When the vehicle is idling (accounting for more than 90% of the time when the vehicle is in operation), it is directly released into the atmosphere.

However, since particulates may be harmful to the human body, in recent years there has been much research into installing diesel particulate oxidizers in the exhaust passages of vehicle diesel engines.

As shown in FIG. 4, in the conventional diesel particulate collection device, in the exhaust passage 2 of the diesel engine 1, the particulate matter discharged from the combustion chamber of the diesel engine 1 is collected upstream of the 77r 4. , one in which a catalyst-equipped DP○5' is inserted may be considered.

Note that the reference numeral 3 in FIG. 4 indicates an exhaust port.

By the way, as this DP○5' is used, it tends to collect and deposit particulates and block the exhaust passage 2.
In order to regenerate this DP05', research is being actively conducted on a mechanism that promotes the re-combustion of particulates.

Such regeneration assisting mechanisms include, for example, retarding the fuel injection timing, throttling the intake air, and increasing the amount of exhaust gas recirculation.

[Problem that the invention seeks to solve]

When regenerating such a conventional diesel particulate oxidizer 5', certain operating conditions 17I
: (For example, when left idle for several days, etc.), D
When trying to regenerate P05', the exhaust temperature from engine 1 does not rise enough and the amount of heat in DPO5' is large.
When the temperature of the DPO 5' is low in the early stage of the regeneration, there is a problem in that gas with a strong odor is discharged from the exhaust port 3.

That is, the catalyzed DPO 5' is a sulfate salt (sulfa salt).
The light-off temperature (light
t ofTtemperature) is high (e.g.
Since the engine is set so that it does not burn at 350°C and starts combustion at 400°C, the regeneration assist mechanism worsens engine combustion and produces a large amount of unburned HC and aldehyde (-C).
Even if malodorous components such as H○) are discharged, the malodorous components are discharged as they are.

On the other hand, when using a catalyst-equipped DPO5' with a low light-off temperature, the sulfur content in the fuel becomes S02 in the combustion chamber, which is more likely to turn into sulfuric acid, etc., and sulfuric acid easily absorbs moisture. Therefore, as the weight increases,
There is a problem α in that sulfuric acid is collected together with particulates in DP○5'.

The present invention aims to solve these problems, and has a low light-off temperature when regenerating a diesel particulate oxidizer using a regeneration auxiliary mechanism, etc., and can reduce the generation of odor components. An object of the present invention is to provide a diesel particulate collection device that can suppress the generation of diesel particulates.

[Means for solving problems]

For this reason, the diesel particulate collection device of the present invention includes a filter disposed in the exhaust passage of a diesel engine to collect particulates discharged from the combustion chamber of the diesel engine. A converter with a precious metal catalyst is provided in the exhaust passage upstream of the diesel particulate oxidizer in order to increase the temperature of the exhaust gas supplied to the diesel particulate oxidizer. is inserted, and the diesel particulate oxidizer and the converter with noble metal catalyst are integrally constructed.

[For production]

In the above-described diesel particulate collection device of the present invention, when the diesel particulate oxidizer is regenerated, exhaust gas whose temperature is not raised by the noble metal catalytic converter is supplied to the diesel particulate oxidizer, so that the light-off temperature can be lowered. The exhaust gas temperature at the beginning of regeneration is instantly raised by the low noble metal catalytic converter, and the temperature at the start of regeneration in the diesel particulate oxidizer is raised in a short time.

[Embodiments] Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
Figures 1 to 3 show a diesel particulate collection device as an embodiment of the present invention. Figure 1 is a schematic diagram showing its overall configuration, and Figures 2 and 3 are graphs showing its operation. It is.

As shown in FIG. 1, in this embodiment as well, in the exhaust passage 2 of the automobile diesel engine 1, a catalyst is installed upstream of the 77r 4 to collect particulates discharged from the combustion chamber of the diesel engine 1. A DPO 5 is inserted into the casing 5c.

Note that particulates here refer to combustible fine particles mainly composed of carbon and hydrocarbons, with an average diameter of about 0.3 μm, and which self-destruct at temperatures of approximately 500°C or higher (400°C or higher in the presence of an oxidation catalyst). set a fire.

In addition, as a trap carrier for this DPO5, a deep trap type heat-resistant ceramic 7 ohm (this is a 2 A flat plate with an oval, oblong, or rectangular cross-sectional shape is used, or a metal salt [Cu(NO= )] is used.
Silica alumina ceramic (SAL) whose main component is a base metal catalyst consisting of 2゜CuC (12, NH, Bo, ] or halide [L i F ] is used, and this diesel particulate collection member will be described below. It is called a base metal catalyst section 5b.

In this casing 5c, a noble metal catalyst section 5a containing a noble metal (platinum, rhodium, palladium) catalyst as a main component is in close contact with the upstream side of the base metal catalyst section 5b. It consists of two layers: a noble metal catalyst and a base metal catalyst.

This noble metal catalyst section 5a is a warm up catalytic converter (Warm Up Catalytic Convector).
rter), the conventionally known light-off temperature (l
light off temperature) low (
(200-300°C) used in catalytic converters for gasoline engines.

The volume ratio of the noble metal catalyst section 5a and the base metal catalyst section 5b is set such that 70 to 80% (or 50 to 90%) of the total volume is mainly composed of base metal.

A control signal is sent from the controller 8 to a regeneration assisting mechanism 10 attached to the diesel engine 1, and the regeneration assisting mechanism 10 consists of a fuel injection timing retard control mechanism and an intake throttle amount control mechanism. ing.

Further, a regeneration timing detection means 11 is provided which measures the difference in pressure drop between the upstream side and the downstream side of the DPO 5, which is composed of the noble metal catalyst section 5a and the base metal catalyst section 5b. It is designed to be supplied to

Since the diesel particulate collection device as an embodiment of the present invention is configured as described above, during non-regeneration, no control signal is sent from the CPU 8 to the regeneration auxiliary mechanism 10, and the fuel injection timing and intake throttle amount are controlled. Exhaust gas containing diesel particulates (Pat) discharged from the combustion chamber of the diesel engine 1 while being maintained in a normal operating state is supplied to the DPO 5, where the diesel particulates are collected.

When the controller 8 receives a pressure drop increase signal from the regeneration timing detection means 11 and determines that it is the regeneration time, the controller 8 supplies a control signal to the regeneration assisting mechanism 10 to determine the fuel injection timing and intake throttle amount. The temperature of the exhaust gas discharged from the combustion chamber of the diesel engine 1 is increased.

As a result, high-temperature exhaust gas discharged from the combustion chamber of the diesel engine 1 is supplied to the noble metal catalyst section 5a of the DPO 5 through the exhaust passage 2.

In the precious metal catalyst section 5a, as shown by the symbol A in FIG. 2, the purification rate (conversion efficiency) η at which CO and HC are converted to CO2 increases, and at this time, a large amount of heat is generated. , an amount of heat sufficient to instantaneously raise the temperature of the base metal catalyst carrier of the DPO 5 is supplied to the downstream base metal catalyst section 5b.

As a result, the temperature of the base metal catalyst portion 5b rises to a temperature at which diesel particulates can be combusted in a short period of time (t2-to), as shown by the symbol C in FIG.
At PO5, as shown by the symbol B' in Figure 2, the light-off temperature appears to have decreased, and CO and HC
is converted to Co2.

This time width (t2 to) is the time width (t+
This reduces the temperature range in which odor components are likely to occur from the regeneration start time L0 to the time t2 when the temperature rises to the predetermined temperature.

Note that the symbol B in FIG. 2 indicates the purification rate of the base metal catalyst alone.

In this way, according to the experimental example, the retard was reduced to 18°A.
(After) and when the intake air is throttled, if the inlet gas temperature of DPO5 is raised to 450℃ or higher, the odor will be significantly reduced and the odor will disappear within the dilution ratio range of 103 to 104. As a result, odor is almost no longer a problem.

The combination of the noble metal catalyst and the base metal catalyst in the DPO 5 solves the odor problem under various conditions of uphill road, downhill road, and city driving.

``In this way, when this device is installed in a direct injection engine that generates a large amount of HC during normal operation, it is effective in reducing exhaust HC.

In the particulate matter, 5OF (Solu
A substance soluble in an organic solvent called organic fraction (SOF is present in (1/2) to (1/10) in particulates. 1 and
Unnecessary substances (clry 5oot) are present,
This SOF reacts in the noble metal catalyst section 5a.

As a result, the amount of particulates entering the base metal catalyst portion 5b of the DPO 5 is reduced, so that the regeneration interval in the DPO 5 is extended.

As a modification of this embodiment, in the exhaust passage 2, a DPO 5 carrying only a base metal catalyst part 5111 and a Humbertata with a noble metal catalyst carrying a noble metal catalyst part 5a on the upstream side of this first carrier are arranged adjacent to each other in series. (You can also set it up.)

In this modification, substantially the same effect as the embodiment can be obtained in terms of the deodorizing effect.

In addition, in the base metal catalyst section 5b, a silica alumina ceramic containing each of the above-mentioned base metals as a main component, a catalyst containing platinum, palladium, or rhodium, or a catalyst consisting of platinum chloride H2PtC1s may also be used. As a mechanism, a mechanism for increasing the amount of exhaust gas recirculation may be used.

〔Effect of the invention〕

As described in detail above, the diesel particulate collection device of the present invention includes a filter disposed in the exhaust passage of the diesel engine to collect particulates discharged from the combustion chamber of the diesel engine. The diesel particulate oxidizer is equipped with a diesel particulate oxidizer consisting of a base metal catalyst supported on the filter, and in order to increase the temperature of the exhaust gas supplied to the diesel particulate oxidizer, With a simple structure in which a converter with a noble metal catalyst is inserted in the exhaust passage and the diesel particulate oxidizer and the converter with a noble metal catalyst are integrated, the following effects and advantages can be obtained.

(1) Light off temp
Since a noble metal catalyst with low erature is used, a reaction occurs at a low temperature during regeneration, oxidizing odorous components and producing odorless components of carbon dioxide and water.

(2) When a reaction occurs with a precious metal catalyst, a large amount of heat is generated, and the exhaust gas heated by this heat is supplied to the base metal catalyst of the diesel particulate oxidizer. DPO playback becomes easier and DPO playback is completed in a short time.

(3) According to item 2 above, regeneration by catalytic reaction (self-combustion)
Therefore, there is no need for frequent regeneration by the regeneration assist mechanism.

(4) According to the above item 2, it is possible to reduce the deterioration of the feeling and the deterioration of the fuel efficiency when increasing the exhaust temperature by intake throttling or timing retard.

[Brief explanation of the drawing]

Figures 1 to 3 show a diesel particulate collection device as an embodiment of the present invention. Figure 1 is a schematic diagram showing its overall configuration, and Figures 2 and 3 are graphs showing its operation. FIG. 4 is a schematic diagram showing the overall configuration of a conventional diesel particulate collection device. 1...Diesel engine, 2...Exhaust passage, 2a...
Regeneration exhaust passage, 2b... Bypass passage, 2C... Upstream confluence section, 3... Exhaust port, 4... Muffler, 5... Diesel particulate oxidizer (DPO), 5a
...Precious metal catalyst section, 5b.. Base metal catalyst section, 5C.. Casing, 8.. Controller (CP) as a control means.
U), 10: Regeneration assisting mechanism, 11: Regeneration time detection means.

Claims (1)

[Claims] A diesel particulate oxidizer is provided in the exhaust passage of the diesel engine, and includes a filter disposed to collect particulates discharged from the combustion chamber of the diesel engine, and a base metal catalyst supported on the filter. In order to increase the temperature of the exhaust gas supplied to the diesel particulate oxidizer, a converter with a noble metal catalyst is inserted in the exhaust passage upstream of the diesel particulate oxidizer, and a converter with a noble metal catalyst is inserted between the diesel particulate oxidizer and the noble metal. A diesel particulate collection device characterized by being integrated with a converter with a catalyst.