JPS6193219A - Diesel particulate oxidizer system - Google Patents

Abstract

PURPOSE:To make an excess air ratio larger without fail with a simple structure, by making a part of supercharging air out of a turbocharger so as to be fed to the upstream of an oxidizer in time of at least high load running of an engine. CONSTITUTION:A Diesel particulate oxidizer (DPO) 12 is set up in an exhaust passage 11 of a Diesel engine E and collects Diesel particulates out of a combustion chamber. A bypass 13 is installed in position between an intake manifold 7 and an exhaust manifold 10, and at the pint midway in this bypass, there is provided with an EGR valve 14 to be driven by a DPO regenerative auxiliary mechanism controlling device ECU. In time of at least high load running of the engine E, there is provided with a bypass device 18 capable of feeding the upstream of the DPO 12 with a part of supercharging air out of a turbocharger 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a diesel particulate oxidizer system for reducing particulates contained in diesel engine exhaust gas.

Diesel engine exhaust gas contains flammable particulates. These particulates are composed of soot and unburned carbonized compounds, and are not only the main cause of black smoke in exhaust gas, but also may be harmful to the human body. For this reason, research is actively being carried out on techniques for disposing a filter in the exhaust system of a diesel engine and using the filter to collect diesel particulates and purify the exhaust gas.

If the particulates collected in the filter are not properly removed, the filter will become clogged and the exhaust system will be blocked, resulting in a reduction in engine output. Since particulates are flammable, particulates are removed from the filter by supplying heat and oxygen to the filter to cause tM burning. When the engine is operating under high load,
Because the exhaust gas temperature is high and oxygen is included in the exhaust gas,
Particulates spontaneously ignite and burn. However, during part-load operation, which accounts for the majority of city driving, the exhaust gas temperature is low, so particulates do not burn unless ignited by another forced means.

Conventionally, a method using a burner has been commonly used as a forced ignition means. Systems equipped with a burner use diesel fuel for engine operation, but air for burner combustion is supplied from a dedicated air pump. Although there is a large amount of surplus oxygen left in the exhaust gas of a diesel engine, this is not used for burner combustion.The reason why this is not used for burner combustion is because the oxygen concentration in the exhaust gas fluctuates greatly depending on the engine operating mode, ensuring stable combustion in the burner. This is because it cannot be done. Therefore, burner combustion is performed using air from a dedicated air pump, and this air is introduced into the filter to regenerate the filter. During this time, all of the exhaust gas from the engine is released into the atmosphere via the bypass system so as not to interfere with stable combustion in the burner.

As described above, burner systems have the drawbacks of being extremely complex in structure, having a large number of parts, and being extremely expensive.

In contrast, in a filter with a catalyst called a diesel particulate oxidizer (hereinafter abbreviated as DPO), unburned carbonized compounds in the particulates react with the catalyst even at a relatively low temperature, and the heat of this reaction is transferred to the catalyst bed and particulate. Since the curates are heated, the particulates begin to burn even when the DPO inlet gas temperature is around 350°C, and the DP
Playback of O begins. Considering that, in general, without a catalyst, particulates do not burn unless the exhaust gas temperature reaches 550°C or higher, systems equipped with DPO are less likely to be clogged with particulates because the regeneration temperature of DPO is low. It can be said that this system is superior to a burner system in that it is low in cost because a relatively simple regeneration device can be used.

Regarding the DPO system, many proposals have been made by the applicant, but the recent results are as follows.
This is shown in Japanese Patent Application No. 59-64144. In summary, this consists of a DPO installed in the exhaust passage of a diesel engine to collect diesel particulates from the combustion chamber, and a DPO regenerated by burning the diesel particulates collected in the DPO. In order to achieve this, the system is equipped with a regeneration auxiliary mechanism for supplying high-temperature gas containing oxygen toward the DPO, and a regeneration auxiliary mechanism control means for controlling the operation of the regeneration auxiliary mechanism based on predetermined DPO regeneration conditions. There is. Specifically, the regeneration assist mechanism includes a mechanism that delays fuel injection timing and a mechanism that throttles intake air, and by operating these mechanisms, the temperature of the exhaust gas increases and particulates are combusted.

In the above-described DPO system, the oxygen contained in the exhaust gas is used to burn particulates. However, when the engine is operated under high load, the excess air ratio λ decreases, so the oxygen concentration in the exhaust gas also decreases, and even though the exhaust gas temperature rises to the extent that the particulates can self-ignite, the particulates are not combusted. It becomes impossible or difficult to do so.

An object of the present invention is to provide a PO system as described above, in which the excess air ratio is increased at least during high load operation of the engine to facilitate combustion of particulates collected in the DPO.

The DPO system according to the present invention includes a bypass means that can supply at least a portion of the supercharging air from the turbocharger to the upstream side of the DPO during high-load operation of the engine.

When the exhaust gas temperature upstream of the DPO has reached a temperature necessary and sufficient for combustion of particulates, if part of the supercharged air from the turbocharger is supplied to the upstream of the DPO, sufficient oxygen contained in the supercharged air will be This facilitates the combustion of particulates.

An embodiment of the present invention will be described below with reference to the accompanying drawings. The overall configuration of the DPO system on which this invention is based is explained in detail in the above-mentioned Japanese Patent Application No. 59-64144, so only the characteristic parts of this invention will be explained here. .

In the figure, an intake passage 2 from an air cleaner 1 is connected to an inlet of a compressor 4 of a turbocharger 3, and an outlet of the compressor 4 is connected to an intake manifold 7 that communicates with a combustion chamber 5 of an engine E via an intake valve 6. has been done. The inlet of the turbine 8 of the turbocharger 3 is connected to an exhaust manifold 10 that communicates with the combustion chamber 5 of the engine E via an exhaust valve 9, and the outlet of the turbine 8 is connected to the upstream side of the DPO 12 via an exhaust passage 11. The downstream side of the DPO 12 is connected to a main muffler (not shown).

A bypass 13 is provided between the intake manifold 7 and the exhaust manifold 10, and a D
An EGR valve 14 is provided which is driven by an ECU which is a PO regeneration assisting mechanism control means.

Further, a waste gate valve 16 is disposed in a bypass 15 provided between the exhaust manifold 10 and the exhaust passage 11, and this waste gate valve 16 is connected to the intake manifold 7.
The opening/closing is controlled by the supercharging pressure passing through the introduction pipe 17 connected to. A bypass 18 communicating upstream of the DPO 12 is connected to the intake manifold 7, and the opening and closing of the bypass 18 is controlled by a relief valve 19 disposed at the connection portion. The relief valve 19 is of a diaphragm type and is equipped with a position sensor 21 for detecting the amount of movement of the valve body 20, and its pressure chamber 22 is connected to a vacuum pump 25 via an introduction pipe 24 equipped with a solenoid valve 23. It is connected. Further, a pressure sensor 26 detects the difference between the exhaust gas pressure on the upstream side and the exhaust gas pressure on the downstream side of the DPO 12, and a temperature sensor 27 detects the exhaust gas temperature on the upstream side of the DPO 12.

The pressure sensor 26 detects that the pressure difference between the upstream side and the downstream side of the DPO 12 exceeds a certain level and that a certain level of particulates are collected in the DPO 12, and the temperature of the exhaust gas or the bed temperature of the DPO 12 is determined. When the temperature sensor 27 detects that the temperature is high enough to burn the curate, the solenoid valve 23 opens in response to a signal from the ECU, and negative pressure is introduced from the vacuum pump 25 into the pressure chamber 22 of the relief valve 19. The valve body 20 opens the bypass 18. As a result, part of the supercharged air in the intake manifold 7 is supplied upstream of the DPO 12 through the bypass 18, and particulates collected in the DPO 12 are removed by sufficient oxygen contained in this supercharged air. Combustion takes place.

The condition in which the exhaust gas temperature or the bed temperature of the DPO 12 reaches a sufficiently high temperature necessary for combustion of particulates is when the engine is operating at high load, or when the DPO regeneration auxiliary engine is operating during partial load operation. During partial load operation, the excess air ratio λ does not become smaller than during high load operation, so the oxygen concentration in the exhaust gas is also relatively high, which makes it possible to burn particulates. However, even though the oxygen concentration is high, it is lower than the oxygen concentration in the supercharged air, so it is difficult to supply part of the supercharged air upstream of the DPO when the DPO regeneration assist mechanism is working. Preferable for speeding up combustion.

During high-load operation of the engine, normally the supercharging pressure from the compressor 4 of the turbocharger 3 passes through the inlet pipe 17 to open the wastegate valve 16, and part of the exhaust gas in the exhaust manifold 10 passes through the bypass 15 and is exhausted. It flows into the passage 11 and prevents the turbine 8 from over-rotating.

When the supercharging pressure by the compressor 4 decreases, the wastegate valve 16 closes the bypass 15, the rotation of the turbine 8 increases, the supercharging pressure becomes high again, and a decrease in engine output is prevented. Therefore, if the relief valve 19 is opened at this time to release part of the supercharging air, the supercharging pressure will drop and the wastegate valve 16 will close, causing the rotation of the turbine 8 to increase and reducing the supercharging pressure from the compressor 4. to prevent a drop in engine output. At the same time, part of the supercharging air is converted into DPO
12 and contributes to the combustion of particulates.

The opening degree of the relief valve 19 is determined by the position sensor 21.
is detected and input to the ECU for feedback control. That is, if the engine output is significantly reduced, the relief valve 19 is closed or throttled so that no or very little supercharging air is released. If the relief valve 19 is opened while the DPO regeneration assist mechanism is operating during the above-mentioned partial load operation, the engine output may suddenly drop because the supercharging pressure is not originally that high during the partial load operation. Even in such a case, it is preferable to close the relief valve 19 to prevent the supercharged air from escaping. In this way, the relief valve 19 is controlled to open and close in various ways depending on the operating conditions of the engine.

As described above, the DPO system according to the present invention has a simple configuration because it is equipped with a bypass means that can supply at least a portion of supercharging air from the turbocharger to the upstream side of the DPO during high-load operation of the engine. The excess air ratio λ can be reliably increased, the particulates collected in the DPO can be self-ignited and easily combusted during high load operation of the engine, and the DPO can be regenerated during partial load. It can be done quickly.

[Brief explanation of drawings]

The figure is a schematic configuration diagram showing main parts in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Air cleaner, 2... Intake passage, 3... Turbocharger, 4... Compressor, 5... Combustion chamber, 6... Intake valve, 7... Intake manifold, 8...・Turbine, 9...Exhaust valve, 10・
...Exhaust manifold, 11...Exhaust passage,
12...DPO114...EGR valve, 16...
・Wastegate valve, 19... relief valve,
21...Position sensor, 27...Temperature sensor.

Claims (1)

[Claims] A diesel particulate oxidizer is disposed in an exhaust passage of a diesel engine to collect diesel particulates from a combustion chamber, and the diesel particulates collected in the oxidizer are combusted to regenerate the oxidizer. a regeneration auxiliary mechanism for supplying high-temperature gas containing oxygen toward the oxidizer, and a regeneration auxiliary mechanism control means for controlling the operation of the oxidizer based on predetermined oxidizer regeneration conditions. A diesel particulate oxidizer system comprising a bypass means capable of supplying a portion of supercharged air from a turbocharger to an upstream side of the oxidizer at least during high load operation of the engine.