JPS58107809A - Exhaust-gas purifier of diesel engine - Google Patents

Abstract

PURPOSE:To suppress progressing of clogging of a filter member by forming the captioned apparatus so that exhaust gas is arranged to automatically bypass the filter member and directly discharged into the atomosphere when the concentration of exhaust smoke in the exhaust gas discharged from a diesel engine is very low. CONSTITUTION:When clogging of a filter member 4 installed in an exhaust passage 3 progresses to a prescribed level, and an output is transmitted from a clogging detecting circuit 11, a fuel pump 14 and a blower 15 are operated by a control circuit 1, while a burner 7 is operated for combustion, and the minute particle component in the filter member 4 is burnt to eliminate clogging. A bypath passage 8 which detours around the filter member 4 and the burner 7 is connected to the exhaust passage 3 to form a branch, and a selector valve 9 is installed in the upstream side branched part. The opening of the valve 9 is controlled in accordance with the output of an exhaust smoke concentration detector 10, and also controlled so as to be set at the position for intercepting the exhaust passage 3, when the burner 7 is in operation.

Description

Detailed Description of the Invention The present invention is to provide a filter member in the exhaust passage for collecting particulate components such as carbon particles in the exhaust gas of a diesel engine, and to combust the particulate components collected by this filter member. The present invention relates to a diesel engine exhaust sludge purifying device that is equipped with a burner device that eliminates clogging of a filter member, and more specifically, the present invention relates to a diesel engine exhaust scum purifying device that is equipped with a burner device that eliminates clogging of a filter member. This invention relates to an exhaust gas purification device designed to prevent the above.

Exhaust gas from a diesel engine contains many particulate components such as iron particles, and it has been considered essential to remove these particulate components in purifying the exhaust gas of a diesel engine. As an exhaust gas purification device for removing such particulate components, for example, as shown in Japanese Patent Application Laid-Open No. 49-71315,
It is known that a filter member for collecting the particulate components listed above is disposed in the exhaust passage.

However, in conventional diesel engine exhaust gas purification devices that use such a filter component, the exhaust gas emitted from the engine always passes through the filter component, so even if the particulate components are Even if the concentration level of the exhaust smoke is so low that it does not require purification, the exhaust gas passes through the filter member, and the problem is that the progress of clogging of the filter member is significantly accelerated.

When the filter member becomes clogged, the exhaust pressure increases, resulting in an unfavorable situation for the engine, such as a decrease in combustion performance. Further, an exhaust gas purification device using the above-mentioned filter member is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 49-7131F1.
As shown in the above publication, in general, if clogging progresses, the captured components are burned by a burner device to eliminate the clogging, but the faster the clogging progresses, the more the burner The device operates more frequently, increasing the chances that the filter member will be exposed to high temperatures and shortening the lifespan of the filter member. Furthermore, the more frequently the burner device is operated, the more the burner fuel is consumed.

On the other hand, when operating the burner device for eliminating clogging as described above, if exhaust gas is sent at high speed, the burner device may go out or fail to ignite (hereinafter collectively referred to as quenching).
may occur. Even if such flame extinction occurs, burner fuel continues to be supplied unless a special detection means is provided, so that unburned gas is released into the exhaust gas and secondary pollution occurs.

The invention was made in view of the above circumstances, and an object thereof is to provide an exhaust gas purification device for a diesel engine in which the progress of clogging of a filter member is alleviated, and the flame extinguishing device does not occur. It is something to do.

An exhaust gas purification device for a diesel engine according to the present invention is an exhaust gas purification device that is provided with a filter member as described above and is configured to eliminate clogging of the filter member with a barring device. A bypass passage for bypassing the device is provided in the exhaust passage, and a valve is provided to change the ratio of the amount of exhaust gas sent to this bypass passage M and the amount of exhaust gas sent to the filter member, and furthermore, a valve is provided to change the ratio of the amount of exhaust gas sent to the bypass passage M and the amount of exhaust gas sent to the filter member. An exhaust smoke concentration detector for detecting the concentration of particulates and a valve control means for controlling the valve are provided, and the exhaust smoke is flowed into the bypass passage depending on whether the exhaust smoke concentration detected by the exhaust smoke concentration detector is high or low. The present invention is characterized in that the valve is controlled in the direction of decreasing or increasing the amount of exhaust gas.

- By providing a valve controlled as in F.
When the exhaust smoke concentration of the exhaust gas emitted from a diesel engine is sufficiently low that it is not necessary to purify the exhaust gas with the filter member, the exhaust gas automatically bypasses the filter member and directly enters the atmosphere. Since the particles are released, the progress of clogging of the filter member is alleviated.

The above-mentioned valve control means further sets the valve to an exhaust passage blocking position that blocks exhaust gas from flowing into the exhaust passage in which the filter member is provided when the burner device for eliminating clogging is in operation. 1 drive. Therefore, when the burner device is in operation, a large amount of exhaust gas is not sent into the exhaust passage in which the filter member and the burner device are installed, and the burner device is prevented from extinguishing the flame.

The exhaust passage blocking position of the above-mentioned valve is preferably a position where the exhaust gas supply to the exhaust passage in which the filter member and burner device are installed is completely cut off, and the entire amount of exhaust gas can flow to the bypass passage. one part and the burner device (even if the location is chosen such that the exhaust passage is not completely closed and a small amount of exhaust gas is sent into said exhaust passage, such that it is absolutely impossible to extinguish the burner unit) good.

If the entire amount (or almost the entire amount) of the exhaust gas is passed through the bypass passage without passing it through a filter member to prevent the flame from extinguishing in the burner device, highly concentrated exhaust smoke may be released depending on the engine operating condition at that time. However, the operating time of the burner device required to clear the blockage is usually 2
Approximately 0 to 30 seconds is sufficient, and the amount of particulate components released is not very large. On the other hand, if the filter components are left clogged, the exhaust pressure will increase, which will worsen the combustion condition of the engine and encourage the generation of harmful components other than the particulate components. It is preferable to promptly eliminate clogging of the members.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 schematically shows an exhaust gas purification device for a diesel engine according to an embodiment of the present invention. Diesel engine exhaust.

A honeycomb-shaped filter member 4 is disposed in an exhaust passage 3 connected to the manifold 2. This filter part 4 has a large number of coarse pores 4b formed by a porous partition wall 4a. The ends of every other pore 4b are changed and one end of each is closed with a blind plug 4C, and the exhaust gas flowing into the pore 4b whose upstream end is open passes through the porous partition wall 4ai. A pore 4 through which the downstream end is open
It flows out to b. When the exhaust gas passes through the partition wall 4ai, fine particles such as carbon particles contained in the exhaust gas are collected by the partition wall 4a. A pair of electrodes 5 and 6 are inserted into the filter member 4 in a direction perpendicular to its axis. These electrodes 5 and 6 are fixed to the peripheral wall of the filter member 40, and are arranged closely to each partition wall 4a, that is, to the partition wall 4a.
It is inserted so that there is no gap between the two. A burner 7 is provided in the exhaust passage 3 on the upstream side of the filter member 4.
is installed. This burner 7 consists of an air nozzle 7a, a fuel nozzle 7b, and a spark plug operating switch 7C.

A bypass passage 8 branches off from the exhaust passage 3 on the upstream side of the burner 7, and this bypass passage 8 bypasses the filter member 4 described above and returns to the exhaust passage 3.

The upstream branch of this bypass passage 8 is located at a bypass fully closed position (indicated by a solid line in FIG. position), and a bypass fully open position (position indicated by the dashed-dotted line in Fig. 1) where the inflow of exhaust gas into the filter member 4 is blocked and the entire amount of exhaust gas is sent into the bypass passage 8.
A switching valve 9 is provided which takes two positions. The switching valve 9 is composed of, for example, an air-operated diaphragm valve or an electric valve to which a diaphragm operating pressure is selectively applied or cut off by a solenoid valve, etc., and is operated by a signal from a control circuit, which will be described in detail later.

8- An exhaust smoke concentration sensor 10 as shown in detail in FIG. 2 is provided in the exhaust passage 3 on the downstream side of the part to which the downstream end of the bypass passage 8 is connected. This exhaust smoke concentration sensor 10 includes a light emitting diode 10a as a light source section and a phototransistor 10b as a light amount sensing section.
1 and the phototransistor], and an amplifier 10c for amplifying the output of the light-emitting diode 10a and the phototransistor 1], Ob are attached to the peripheral wall of the exhaust passage 3 so as to face each other. Light emitting diode]O
The light emitted from the phototransistor 10b crosses the exhaust passage 3 and reaches the first transistor 10b.
The amount of light received by b is inversely proportional to the concentration of exhaust smoke passing through the exhaust passage 3. Since the phototransistor 10b generates a voltage according to the amount of light received, this is detected, amplified by the amplifier IOC, and output.

Therefore, by measuring the voltage of this output signal Sl, the exhaust smoke concentration can be determined.

This exhaust smoke concentration signal Sl is generated by the pair of electrodes 5 and 6 mentioned above.
A clogging detection signal S2 is generated from a clogging detection circuit 11 which detects that the filter member 4 is clogged to a predetermined level in response to the output of It is input to the control circuit 12 together with a valve position signal S3 indicating the position of the valve.

The valve position signal S3 can be taken out, for example, by a limit switch connected to a valve movable part such as a valve stem, but the clogging detection signal S2 will be briefly explained below with reference to FIG.

The electric resistance between the pair of electrodes 5 and 6 described above has a characteristic that when fine particles such as carbon particles adhere to the partition wall 4a of the filter member 4, the electric resistance decreases as the amount of the adhered fine particles increases.

Therefore, when the electrodes 5 and 6 are connected via the battery E and the resistor R, the voltage difference across the resistor H increases in accordance with the increase in the amount of particles attached to the partition wall 4a.

Therefore, here, one end of the resistor is grounded and the other end is connected to the comparator COM+, while the burner 7 is burnt to remove the clogging of the filter member 40. One end of the reference voltage generator eO, which generates the same reference voltage as the voltage difference when If the electric signal S2f is generated when the difference exceeds the reference voltage, this electric signal Szf can be used as a clogging detection signal to automatically start burner operation when necessary. In addition to this type of clogging detection means, for example, one that detects clogging by detecting an increase in exhaust pressure may be used.

The operation of the diesel engine exhaust gas purification device of this embodiment having the above structure will be explained below. When the clogging of the filter member 4 progresses to a predetermined level and the clogging detection signal S2 is input to the control circuit 12 as described above, the control circuit 12 outputs a burner operation signal S4=2.

11--The fuel pump 14 sends burner fuel from the fuel tank 13 to the fuel nozzle 7b of the burner 7 in response to the burner activation signal S4. The blower I5 that sends burner combustion air to the air nozzle 7a is operated, while the ignition plug operating switch 7c is energized and the burner 7 is operated for combustion.

By operating this burner 7, the filter member 4
The particulate components that have been collected are burned, and the filter member 4 is unclogged.

In the device of this embodiment, the progress of clogging of the filter member 4 as described above is alleviated by using the bypass passage unique to the present invention. The mechanism will be explained in detail below. FIG. 4 shows the configuration of the control circuit 12, and the above-mentioned exhaust smoke concentration signal S1 is sent to the comparator C.
0M2, and the valve position signal s3 is input to the reference signal generator 1.
2a. Note that the circuit that generates the burner activation signal S4f in response to the input of the clogging detection signal S2 as described above is omitted in FIG.
The burner operating signal S4 is input to the AND gate 12b together with the output of the comparator C0M2.

The reference signal generator 12a has a first reference value, such as a legal regulation value, which corresponds to a limit exhaust smoke concentration beyond which it is undesirable to release it into the atmosphere at a higher concentration, and a first reference value lower than this first reference value. It is possible to generate two types of reference values, a second reference value corresponding to the exhaust smoke concentration, and when the switching valve 9 is in the bypass fully open position in response to the valve position signal 83, the first reference value is set to the switching valve. 9 is in the bypass fully closed position, the second reference value is output. The comparator C0M2 compares the first or second reference value with the actually measured exhaust smoke concentration signal S1, and if the actually measured exhaust smoke concentration exceeds the reference value, sets the switching valve 9 to the bypass fully closed position. It is configured to output a driving valve control signal 5a=i, and to output a full valve control signal S5 to drive the switching valve 9 to the bypass fully open position if the actually measured exhaust smoke concentration is less than a reference value. However, as mentioned above, the burner operation signal S4 is input to the fi, ND gate 12b as shown in the figure, and the comparator C0M2
The cell 11fl control signal S5 output from the AND gate 12b is also input as one input of the AND gate 12b, and the valve control signal S5 output from the comparator C0M2 is applied only when the burner operation signal S4 is not output. The control circuit 12 outputs the output from C0M2 as a signal that always drives the switching valve 9 to the bypass fully open position when the burner operation signal S4 is output.
It is designed to be output from 2.

Here, the second reference value corresponds to an exhaust smoke concentration that is slightly lower than the exhaust smoke concentration after the exhaust gas having the exhaust smoke concentration corresponding to the first reference value passes through the filter member 4. is set to .

Here, using FIG. 5, we will explain how the above control system operates with respect to the actually measured exhaust smoke concentration that changes. First, if the burner operation signal S4 is not output,
Consider the case where the output from the comparator C0M2 is output from the kneading control circuit 12. In FIG. 5, the curve a shows the actual exhaust smoke concentration measured by the exhaust smoke concentration sensor IO, the dashed line indicates that the switching valve 9 is in the bypass full open position, and the solid line indicates the actual exhaust smoke concentration measured by the exhaust smoke concentration sensor IO. This indicates that the switching valve 9 is in the bypass fully closed position. When the switching valve 9 is in the bypass fully open position, that is, when all the exhaust gas is passed through the bypass passage 8 and is not purified by the filter member 4, the exhaust smoke concentration is compared with the first reference value as described above. Is receiving. Therefore, if this exhaust smoke concentration exceeds the first standard value (point in the figure)
, the switching valve 9 is driven to the bypass fully closed position. Therefore, the entire amount of exhaust gas passes through the filter member 4, and the exhaust gas concentration of the exhaust gas that passes through the exhaust smoke concentration sensor 10 and is released into the atmosphere decreases rapidly (point C in the figure). 15- Even if the exhaust gas is sent to the filter member 4, if the trend of increasing the exhaust smoke concentration of the exhaust gas continues, the exhaust smoke concentration will of course gradually become higher than the above point C. 4 is selected and used to suppress the total exhaust smoke concentration to a range lower than the first reference value, so that the exhaust smoke concentration will not exceed the first reference value under the state where the bypass passage is completely closed. After the 0 point in the diagram, the actually measured exhaust smoke concentration is compared with the second reference value, so the exhaust smoke concentration tends to decrease and eventually falls below the second reference value. When this occurs (point d in the figure), the switching valve 9 is driven to the bypass fully open position, and the exhaust smoke concentration rapidly increases (point e in the figure). However, as mentioned above, the second reference value is set to correspond to an exhaust smoke concentration that is slightly lower than the exhaust smoke concentration at point C in the figure (that is, when m is set during control in Figure 5). Therefore, the exhaust smoke concentration at point e does not exceed the first reference value. With this bypass passage fully open, if the exhaust smoke concentration exceeds the first reference value again (point f in the figure), the switching valve 9 closes the bypass completely as described above. 6r position, and the exhaust smoke concentration is lowered (g in the figure, (Company)).

If the above-mentioned control rlEm is set too small, it will cause the changeover valve 9 to . Therefore, it is necessary to set the amount appropriately.

As explained above, in the device of this embodiment, when the burner 7 is not operating, the exhaust smoke concentration of the exhaust gas is
Although the first reference value, which must never be exceeded, will not be exceeded, since the filter member 4 is used only when necessary, the clogging of the filter member 4 may progress. can be alleviated.

Here, when the clogging of the filter member 4 progresses to a predetermined level and the burner activation signal S4 is output from the control circuit 12 and the burner 7 is activated, the control circuit 12 is always switched as described above. A valve control signal S5 that sets the valve 9 to the bypass fully open position is now output.

Therefore, the entire amount of exhaust gas is sent to the bypass passage 8 and does not flow into the exhaust passage 3 where the burner 7 is installed, so that the burner 7 is not extinguished by the flow of exhaust gas. .

In the above embodiment, the switching valve 9 is formed to selectively allow the entire amount of exhaust gas to flow into either the bypass passage 8 or the filter member 4; It is not limited to a switching device, but any device that can completely change the ratio between the amount of exhaust gas sent to the bypass passage and the amount of exhaust gas flowing to the filter member may be used; for example, 80% for the exhaust smoke concentration signal path 11, An arrangement may be used in which the flow path state is switched such that the exhaust gas full speed is 20% for one filter member, 20% for the exhaust smoke concentration signal path, and 80% full speed for the filter member. However, in such a case, the switching valve is formed so that, in addition to the two flow path switching positions as described above, it can take a position that completely blocks the flow of exhaust gas into the exhaust passage where the burner device is installed. When the burner device is in operation, it is necessary to form it so that it is forcibly driven to this exhaust passage blocking position regardless of the lid gas concentration. Further, an exhaust smoke concentration sensor that detects the entire exhaust smoke concentration for controlling the switching valve may be provided upstream of the switching valve, and in such a case, simply setting one predetermined exhaust smoke concentration value, If the exhaust smoke concentration exceeds this predetermined value, the switching valve is set to a position that completely reduces the bypass passage flow rate, and when the exhaust smoke concentration is below the predetermined value, the switching valve is set to a position that increases the bypass passage flow rate. 3 Furthermore, instead of the switching valve that takes two positions as described above, a control valve that can continuously change the amount of exhaust gas flowing into the bypass passage is provided, and this control valve is set to It is also possible to carry out feedback control based on the exhaust smoke concentration detected in the exhaust passage on the downstream side to maintain the exhaust smoke concentration of the exhaust gas released into the atmosphere at a desired value. Of course, in this case as well, the control valve must be formed so that it can be set at a position that blocks the exhaust passage and allows all of the exhaust gas to flow into the bypass passage.

As explained in detail above, the diesel engine exhaust gas purification device of the present invention is capable of suppressing the exhaust smoke concentration of the exhaust gas normally released into the atmosphere to a predetermined value or less, while alleviating the progress of clogging of the filter member. As a result, the combustion performance of the diesel engine is maintained at a high level, and since the burner device for removing clogging of the filter part does not operate frequently, the life of the filter part is extended, and burner fuel consumption is reduced. Become. Since the burner device for eliminating clogging is not extinguished by the flow of exhaust gas, the clogging of the filter member is reliably eliminated in a short time, and no harmful unburned gas is generated due to extinguishing of the burner device. do not have.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing one embodiment of the present invention, Figure 2 is a schematic diagram showing a part of the embodiment of Figure 1, and Figure 3 is a part of the electric circuit of the embodiment of Figure 1. FIG. 4 is an explanatory diagram illustrating the control circuit of the embodiment shown in FIG. 1, and FIG. 5 is an explanatory diagram illustrating how exhaust smoke concentration is controlled in the embodiment shown in FIG. 1. . 1...Diesel engine 3...
......Exhaust passage 7...Bass 8...Bypass passage 9...Switching valve 10 ...
...Exhaust W concentration sensor]2...Control circuit 12b.
...AND gate S1...Exhaust smoke concentration signal
S4... Burner operating signal S5... Valve control signal Fig. 3\11 Fig. 4 12' 41- Fig. 5 Time □

Claims (1)

[Claims] A diesel engine in which a filter member for collecting fine particles such as carbon particles in exhaust gas is disposed in an exhaust passage, and a burner device is provided in the exhaust passage upstream of the filter member to unclog the filter member. In the exhaust gas purification device, the exhaust passage includes a bypass passage that bypasses the filter member and the burner device, and a ratio of the amount of exhaust gas sent to the bypass passage and the amount of exhaust gas sent to the filter member is changed. an exhaust smoke concentration detector for detecting the concentration of the particulates; and an exhaust gas that receives the output of the exhaust smoke concentration detector and flows into the bypass passage depending on whether the exhaust smoke concentration is high or low. controlling the valve in the direction of decreasing or increasing the amount of the burner, and when the burner device is operating, shutting off the exhaust gas from flowing into the exhaust passage in which the filter member is provided; It is characterized by being provided with a valve control means for setting the position.