JPH08319819A - Egr control device for diesel engine - Google Patents

Abstract

PURPOSE: To prevent breakage of a filter by carrying out self-ignition combustion by particulate collected on the filter of a particulate collection trap device in a diesel engine. CONSTITUTION: A device is provided with a means for detecting a range in which particulate collected in a trap device is carried out self ignition combustion, a means for judging a range in which the particulate is burnt abnormally from the operating condition of an engine by receiving the signal of the self ignition range detecting means, and a means for increasing the EGR rate of the engine by receiving the abnormal combustion generating range judging means. The EGR rate is controlled according to the result of a means for judging a range in which the particulate is burnt abnormally by receiving the signal of a means for judging a range in which the particulate is carried out self ignition combustion by respective signals of a pressure sensor for detecting the regenerating timing of the filter 9 of a particulate collecting trap device, an engine rotation sensor 13, and an engine load sensor 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an exhaust gas energy recovery system for an engine equipped with a turbocharger and an exhaust gas recirculation device.

[0002]

2. Description of the Related Art It is well known that when carbonized fine particles, that is, particulates, contained in the exhaust gas of a diesel engine are released into the atmosphere, they cause air pollution. It is also a widely known technique to arrange a trap device for trapping particulates in the exhaust pipe of a diesel engine in order to prevent the particulates from being released into the atmosphere. By the way, the trap device for collecting particulates is provided with a filter for collecting the particulates, and the carbonized compound is collected by the filter. When a large amount of particulates are collected by the filter, the filter becomes clogged, the exhaust pressure rises, and the drivability of the engine deteriorates significantly. To prevent this, the trap device for collecting particulates is equipped with a device for heating and burning the collected particulates in addition to the filter. As this device, an electric heater and a burner combustion type are known. These are called filter regenerators.

In order to operate this filter regenerator and burn particulates, the temperature of the filter must be 600 ° C. or higher. However, if exhaust gas with a high oxygen concentration flows in during regeneration, the particulates will undergo self-ignition combustion. There was a problem that the filter would melt. Therefore, at the time of regeneration, the exhaust gas is bypassed so that it does not flow into the particulate trap device. However, bypassing as described above releases particulates to the atmosphere during regeneration, which is not preferable from the viewpoint of preventing air pollution.

In order to solve the above problem, Japanese Patent Laid-Open No. 62-1
No. 62762 discloses that the exhaust gas recirculation device (EGR) is controlled by controlling the exhaust gas recirculation device (EGR) when the temperature of the filter and the amount of collected particulates are equal to or higher than a predetermined value and the engine load is equal to or lower than a predetermined value. A device is disclosed which increases the recirculation amount, lowers the exhaust gas temperature, and lowers the filter temperature.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The control device described in Japanese Patent No. 2762 is effective in preventing the filter from being melted due to self-ignition of particulates during regeneration as described above, but there is a problem that the effect is not exhibited during non-regeneration. there were. That is, as shown in FIG. 2A, when the engine speed is high and the engine load is high and the exhaust temperature is high and the exhaust gas oxygen concentration such as idling is high, the filter temperature changes rapidly. Therefore, it is impossible to prevent the particulate matter trapped in the filter from self-igniting and burning to raise the temperature of the filter above its allowable temperature and to cause the filter to melt. there were.

[0006]

In order to solve the above problems, the present invention relates to an EGR control device for a diesel engine equipped with a particulate trap device, wherein the particulate trapped in the trap device is self-contained. Self-ignition area detection means for detecting an area where ignition combustion occurs, and abnormal combustion occurrence area determination means for receiving a signal from the self-ignition area detection means and determining an area where particulates cause abnormal combustion from an engine operating state. , The EGR of the engine in response to the signal from the abnormal combustion occurrence region determination means
An EGR control device for a diesel engine, comprising: a means for increasing the amount; more specifically, an EGR control device for a diesel engine including a particulate collection trap device, wherein the particulate collection trap device is provided. A signal of a pressure sensor that detects the regeneration time of the filter, an engine rotation sensor, and an engine load sensor, and a determination unit that determines a region where particulates cause self-ignition combustion by the signal of each sensor, Provided is an EGR control device for a diesel engine, which is characterized by receiving a signal from the determination means and determining a region where abnormal combustion of particulates is caused, and controlling an EGR amount according to a result of the determination means. To be done.

[0007]

The present invention detects the operating state of the engine in which the particulates trapped in the filter of the particulate trapping trap device cause self-ignition combustion, thereby increasing the EGR amount of the engine. It is possible to prevent the collected particulates from being self-ignited, burned, and damaged.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of the present invention. In the figure, 1 is an internal combustion engine, and 2 is an intake pipe of the internal combustion engine. 3 is an exhaust pipe, 4 is E for normal EGR
The GR pipe connects the exhaust pipe 3 and the intake pipe 2 to the EGR valve 5
Are connected via. Reference numeral 5 is an EGR valve that controls the EGR during normal operation. That is, when EGR is required in the operating state of the engine, the EGR valve 5 is opened so that a part of the exhaust gas is circulated from the exhaust pipe 3 to the intake pipe 2 to reduce the combustion temperature of the engine 1. EG above
An EGR pipe 6 and an EGR valve 7 for emergency are installed in parallel with the R pipe 4 and the EGR valve 5, and when the temperature of the DPF described later is high, the EGR amount is increased more than in the normal state. 8 is an exhaust brake, 9 is a trap device (DPF) for collecting particulates,
Inside thereof, a filter for collecting fine particles and an electric heater for regeneration are installed. Reference numeral 10 is a temperature sensor installed in the exhaust pipe 3 for detecting the inlet temperature of the DPF 9.
Reference numeral 1 is a temperature sensor for detecting the temperature of the filter of the DPF 9. Reference numeral 12 is a throttle opening sensor, and 13 is an engine rotation sensor. The sensors 10, 11, 12 and 13 are input to the control device 14, and the control device 14 controls the EGR valves 5 and 7 based on the signals of these sensors. The controller 14 is a microcomputer, ROM, R
It is a well-known device composed of AM and I / O.

The concept of the present invention will now be described with reference to FIG. FIG. 2 (a) shows a temperature change of the DPF filter in the conventional case as described above. The engine rotation speed is high and the engine load is high, and the exhaust temperature is high. When the oxygen concentration changes to a high state, the filter temperature rises rapidly, causing the particulates trapped in the filter to self-ignite and burn, raising the temperature of the filter above its allowable temperature and causing the filter to melt. The occurrence of is as described above. On the other hand, in the present invention, the abnormal combustion of the DPF filter is predicted from the operating state of the engine, and when the abnormal combustion is predicted, the EGR valve for emergency is opened to increase the EGR amount as shown in FIG. 2B. The temperature of the filter is suppressed to a temperature at which abnormal combustion does not occur.

The control flow will be described with reference to FIG.
The exhaust gas temperature at the DPF inlet is detected by the temperature sensor 10,
It is determined whether the temperature is 0 ° C or higher. If the temperature is 600 ° C or lower, D
No abnormal control is performed because abnormal combustion of the PF filter does not occur. When the exhaust gas temperature at the DPF inlet is 600 ° C. or higher, the operating state of the engine is detected from the signals from the throttle opening sensor 12 and the engine rotation sensor 13, and it is determined whether or not it is in the DPF filter self-ignition region. This determination is to determine whether or not it is the self-ignition region as shown in the hatched portion of the graph of engine speed and fuel flow rate (= throttle opening) in FIG. Incidentally, this self-ignition region is determined by the engine and is determined in advance for each engine by experiments or the like. Also in this case, if it is not in the self-ignition region, abnormal control of the DPF filter does not occur, so no particular control is performed. When the engine is operating in the self-ignition region, the EGR emergency mode is activated.

In this embodiment, the dangerous area is determined in two stages from the operating state of the engine, that is, the first dangerous area and the second dangerous area, and the EGR amount is changed in each case. This is due to the fact that it was found as a result of an experiment that the region where the abnormal combustion certainly occurs depending on the operating condition of the engine (first dangerous region) and the region where the abnormal combustion occurrence probability is high (second dangerous region) exist. . Emergency E in the first risk area
The GR amount is maximized, that is, the EGR valve 7 is fully opened, and the emergency EGR amount is controlled in the second dangerous area. After the abnormal combustion avoidance operation as described above, whether or not the abnormal combustion can be avoided is determined by the DPF temperature sensor 11, the throttle opening sensor 12, the engine rotation sensor 13 and the like, and if not avoided, the EGR emergency mode. To continue. Normal EGR if abnormal combustion is avoided
Switch to mode.

Although the present invention has been described with reference to the above-described embodiments, various modifications are possible within the scope of the gist of the present invention, and these modifications are not excluded from the scope of the present invention.

[0013]

According to the present invention, the particulate matter trapped in the filter of the particulate trapping device detects the operating state of the engine in which self-ignition combustion occurs, thereby increasing the EGR amount of the engine. It is possible to prevent the particulate matter collected in the above from being self-ignited, burned and damaged. Further, since the dangerous state of a plurality of stages is detected by the operating state of the engine and the EGR amount is set according to the state, the operating state of the engine is rarely adversely affected.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing the concept of control of the present invention.

FIG. 3 is a diagram showing a control flow of an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between an engine self-ignition area and a dangerous area.

[Explanation of symbols]

 1 ... Engine, 2 ... Intake pipe, 3 ... Exhaust pipe 6 ... Emergency EGR pipe, 7 ... Emergency EGR valve, 9 ... DPF, 10 ... DPF inlet temperature sensor, 14 ... Control device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location F02M 25/07 570 F02M 25/07 570J 570G

Claims (2)

[Claims] 1. An EGR control device for a diesel engine equipped with a particulate trap device, comprising: self-ignition region detection means for detecting a region where particulate matter trapped in the trap device causes self-ignition combustion. Abnormal combustion occurrence region determining means for receiving a signal from the self-ignition region detecting means to determine a region where particulates cause abnormal combustion from the operating state of the engine, and EGR of the engine receiving a signal from the abnormal combustion occurrence region determining means An EGR control device for a diesel engine, comprising: a means for increasing the amount. 2. An EGR control device for a diesel engine equipped with a particulate trap device, a signal of a pressure sensor for detecting a regeneration time of a filter of the particulate trap device, an engine rotation sensor, and an engine load. A determination unit that includes a sensor, and determines the region where the particulates cause self-ignition combustion by the signal of each sensor; and the determination that determines the region where the particulates cause abnormal combustion by receiving the signal of the determination unit. Means for controlling the EGR amount according to the result of the determining means.