JPS5918221A - Exhaust gas purification device for diesel engine - Google Patents

Abstract

PURPOSE:To prevent securely a filter from being damaged due to melting by a method wherein when the filter in the exhaust system of the engine is heated to an abnormally high temperatue during the operation of a clogging removing means for the filter, a large quantity of low temperature exhaust gases is introduced into the filter. CONSTITUTION:Carbon particles and the like in the exhaust gases from the engine 1 are collected and removed when they pass through the filter 4. In case where the filter 4 is clogged and a clogging detector 6 generates a detecting signal, a control circuit 19 drives a fuel pump 13 and an air pump 14 and a burner 7 is operated by turning an ignition switch 9 ON to thereby make the filter 4 free from clogging. At the same time, an adjust valve 17 is opened to discharge the exhaust gases from a bypass passage 16. In this case, the temperature of the exhaust gases is detected by a thermosensor 15 and if the detected temperature is higher than a reference value, the adjust valve 17 is closed to cause the exhaust gases to flow into the filter to thereby cool the filter.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exhaust purification device for a diesel engine.

In general, exhaust purification devices for diesel engines are installed in the exhaust passage to avoid problems such as air pollution if fine particles such as carbon particles that are decomposed and liberated from fuel in a high-temperature smoldering chamber are released into the atmosphere. The exhaust gas is purified by collecting carbon particles and the like in the exhaust gas using a filter member. By the way, when this exhaust gas purification device is used for a long time and the amount of carbon particles collected increases, the carbon particles clog the filter member, and the exhaust gas on the upstream side of the filter member becomes clogged. The pressure increases and this becomes a resistance to the operation of the engine, resulting in a problem that the engine output decreases.

With conventional exhaust purification devices, in order to prevent a drop in engine output, when the mileage reaches a predetermined distance,
Or when a filter member becomes clogged,
A burner device heats the clogging carbon particles and burns the carbon particles, thereby eliminating the clogging of the filter member (Japanese Patent Laid-Open No. 49-71
(See Publication No. 315).

The inventor of the present invention conducted an experiment on the combustion state by changing the amount of carbon particles deposited in the filter member, and found that when the amount of carbon particles deposited in the filter member was large, the combustion of carbon particles, etc. It has been observed that when the filter member becomes high temperature and the exhaust gas temperature on the downstream side of the filter member exceeds 1100° C., the filter member may be melted and damaged.

One possible method for preventing such melting damage of the filter member is to stop the operation of the burner device when there is a risk that the filter member will reach an abnormally high temperature. However, the reason why the filter member reaches an abnormally high temperature is not due to heating by the burner device, but due to the rapid combustion of a large amount of carbon particles. Therefore, the method of simply stopping the burner device as described above cannot In this case, even if the burner device is stopped, the carbon particles will continue to burn due to the ambient temperature, etc., and it is a problem to reliably prevent partial erosion of the filter.

This invention was made in view of the above-mentioned problem that when there are many carbon particles, there is a risk that the filter member will become hot and melt. A bypass passage is formed to bypass the filter member, and a control valve for regulating the amount of exhaust gas is provided in this bypass passage, and when the clogging eliminating means is activated, a predetermined amount of exhaust gas is caused to flow through the bypass passage, and the clogging eliminating means is activated. Diesel engine exhaust purification designed to reliably prevent melting of filter parts by allowing a large amount of low-temperature exhaust gas to flow into the filter parts when they become abnormally hot during operation. The purpose is to provide equipment.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an exhaust purification device for a diesel engine according to an embodiment of the present invention. In the figure, 1 is a diesel engine, 2 is an intake passage, and 3 is an exhaust passage. A filter member 4 is disposed in the middle of the exhaust passage 3 to collect fine particles such as carbon particles in the exhaust gas. . This filter member 4 has honeycomb-shaped passages 4a and 4b formed therein, and the terminal opening of one of the adjacent passages 4a and 4b is closed by a blind plug 4C, and the opening of the other opening is closed by a blind plug 4C. . Further, a pair of electrodes 5a, 5b are attached to the filter member 4, and the electrodes 5a, 5b are connected to a clogging detector 6. The clogging detector 6 supplies electricity to the electrodes 5a, 5b to both Clogging of the filter member 4 is detected from the resistance value between the electrodes 5a and 5b.

Further, a burner device (clogging eliminating means) 7 is disposed on the upstream side of the filter member 4 of the exhaust passage 3.
The burner device 7 has a spark plug 8, and an ignition switch 9 is connected between the spark plug 8 and a power source (not shown). This burner device 7 has a fuel supply passage 10
and the air supply passage 11 are connected to the fuel supply passage 1.
A fuel pump 13 for pumping the fuel in the fuel tank 12 to the burner device 7 is disposed in the middle of the air supply passage 11, and an air pump 14 for feeding air to the burner device 7 is disposed in the middle of the air supply passage 11. There are also exhaust passages.

Further, a bypass passage 16 is branched into the exhaust passage 3 and communicates between the upstream side of the filter member 4 and the burner device 7 and the downstream side of the filter member 4. A control valve 17 is provided to adjust the amount of exhaust gas flowing through the exhaust gas, and the control valve 17 is opened and closed by an actuator 181. In the figure, 19 generates a drive signal while receiving the detection signal from the clogging detector 6, operates the burner device 7, and drives the actuator 18 to control the control valve 17.
This is a control circuit that opens the burner device 7 and stops generating the drive signal when the temperature detected by the temperature detector 15 reaches a predetermined value, for example, 1100° C. or higher during operation of the burner device 7.

FIG. 2 shows the circuit configuration of the exhaust gas purification device, and in the figure, 6, 9, 13, 14, 15, 17, and 18 are the above-mentioned clogging detector 1 ignition switch, fuel pump, air pump, temperature detector, These are control valves and actuators. Further, in the control circuit 19, 20 is a comparator that compares the output of the temperature detector 15 with the reference value E, 21 is normally open and allows the output of the clogging detector 6 to pass, and the inverted signal of the signal 1 of the comparator 21 is Gate circuit that closes while receiving, 22-2
In response to the detection signals from the clogging detector 6 that have passed through the gate circuit 21, ignition switches 9. fuel pump 13
．． This is a drive circuit that applies drive signals to the air pump 14 and actuator 18.

Next, the operation will be explained.

During operation of the engine 1, the control valve 17 of the bypass passage 16 is closed, and when exhaust gas containing fine particles such as carbon particles is discharged from the combustion chamber, most of this exhaust gas flows through the exhaust passage 3 and is filtered. It reaches one filter member 4 and enters a passage 4a in which the starting end side is open. Then, since the openings on the terminal side of these passages 4a are closed, the exhaust gas enters the adjacent passage 4b through the side wall of the passage 4a, and passes through the opening on the terminal side of the passage 4b to the filter member 4. is discharged from. At this time, fine particles such as carbon particles in the exhaust gas are collected and removed by the side walls of the passage, thereby purifying the exhaust gas and releasing it into the atmosphere.

Furthermore, if the filter member 4 is clogged due to carbon particles collected while purifying the exhaust gas in this manner, the clogging detector 6 detects the electrode 5a,
Since the resistance value between 5b and 5b decreases, it is detected from this resistance value that the filter member 4 is clogged, and the detection signal of the detector 6 is transmitted via the gate circuit 21 to the drive circuit 22 to
Added to 25. Then, the fuel pump 13 and air pump 14 are driven, the ignition switch 9 is turned on and the burner device 7 is activated, and at the same time, the actuator 18 opens the control valve 17 and a predetermined amount of exhaust gas flows through the bypass passage 16. As a result, the amount of exhaust gas flowing into the filter member 4 decreases, so that the carbon particles within the filter member 4 are rapidly heated and begin to burn. Then, when the clogging is cleared to some extent, the exhaust gas that had flowed into the bypass passage 16 will again flow into the filter member 4, and the temperature of the filter member 4 will increase by a considerable amount due to the cooling effect of this exhaust gas. The carbon particles burn without burning. In this way, the clogging of the filter member 4 is eliminated, and the temperature rise of the filter member 4 is suppressed, so that the durability is improved.

By the way, when carbon particles are burned to eliminate clogging, if there is a large amount of carbon particles deposited in the filter member 4, the filter member 4 becomes hot as described above. However, in such a case, this device prevents the filter member 4 from melting by stopping the operation of the burner device 7 and controlling the flow rate of exhaust gas flowing into the filter member 4. I'm trying to protect it. That is, the temperature detector 15 detects the exhaust gas temperature downstream of the filter member 4, and the comparator 20 compares the output of the temperature detector 15 with the reference value E. If the filter member 4 becomes hot and there is a risk of melting, the exhaust gas temperature on the downstream side of the filter member 4 will exceed the set value, for example 1100°C, so the output of the temperature detector 15 will increase to the reference value. E, the output of the comparator 20 becomes 1, the gate circuit 21 closes, the drive circuits 22 to 25 stop generating drive signals, the burner device 7 immediately stops operating, and the actuator 18 starts adjusting. Close valve 17. Then, the amount of exhaust gas flowing into the bypass passage 16 decreases, and the agitation of the exhaust gas flowing into the filter member 4 increases, and since the temperature of this exhaust gas is approximately 500° C., the filter member 4 is cooled. Therefore, melting damage of the filter member 4 can be reliably prevented.

FIG. 3 shows another embodiment of the present invention, in which a control valve 26 is provided at the connection between the upstream end of the bypass passage 16 and the exhaust passage 3, and this control valve 26 is normally The bypass passage 16 is closed as shown by the solid line in the figure, and the exhaust passage la is closed as shown by the dashed line in the figure while a drive signal is being applied to the actuator 18.

In this embodiment, as in the above-mentioned embodiments, it is possible to reliably prevent melting and damage of the filter member by a simple method of controlling the flow of exhaust gas flowing into the filter member, and furthermore, the burner device Since the inflow of exhaust gas into the filter member is cut during operation, the heating efficiency of the burner device that heats carbon particles within the filter member can be improved and fuel can be saved.

In the above embodiment, the clogging of the filter member was detected by electrical resistance, but the clogging may also be detected from the pressure of exhaust gas, the amount of deposited particulates such as carbon particles, etc. Further, the clogging may be cleared not after the clogging is detected, but when the travel distance reaches a predetermined distance. Further, the clogging eliminating means may be a heater device instead of a burner device.

As described above, according to the exhaust purification device for a diesel engine according to the present invention, a bypass passage is formed in the exhaust passage to bypass the clogging removal means such as a burner device and a filter member, and an exhaust gas position is provided in the bypass passage. A control valve is provided to flow a predetermined amount of exhaust gas into the bypass passage when the clogging eliminating means is activated, and when the filter member becomes abnormally high temperature while the clogging eliminating means is in operation, the filter member is turned off. Since a large amount of low-temperature exhaust gas is allowed to flow into the filter, it is possible to reliably prevent melting and damage of the filter member by a simple method, which has the effect of improving reliability.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an exhaust purification device for a diesel engine according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the device, and FIG. 3 is a block diagram of another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Engine, 3... Exhaust passage, 4... Filter member, 7... Burner device (clog eliminating means)
, 15... temperature detector (abnormality detection means), 16...
Bypass passage, 17... control valve, 19... control circuit (control means). Patent Applicant Toyo Kogyo Co., Ltd. Agent Patent Attorney Ken Hayase - No. 1
diagram

Claims (1)

[Claims] fi+ A filter member disposed in the exhaust passage of the engine to collect fine particles such as carbon particles in the exhaust gas, and a clogging eliminating means that heats the filter member to eliminate the clogging when the filter member becomes clogged. an abnormality detection means for detecting an abnormally high temperature state of the filter member; and a υF air passage upstream of the filter member and the clogging eliminating means; and an exhaust passage downstream of the filter member. a bypass passage that communicates with the bypass passage; a control valve that adjusts the amount of exhaust gas flowing through the bypass passage; and when the clogging eliminating means is activated, a predetermined amount of exhaust gas flows through the bypass passage and the clogging eliminating means is activated. and control means for driving and controlling the control valve so that the amount of exhaust gas in the bypass passage is reduced when an abnormally high temperature state of the filter member is detected.