JPS58104315A - Exhaust gas purifier for diesel engine - Google Patents

Abstract

PURPOSE:To reduce the loading of a filter member by ejecting exhaust gas directly to the atmosphere bypassing the filter member when the exhaust smoke density of exhaust gas is sufficiently low so that the exhaust gas does not need to be purified by the filter member. CONSTITUTION:In operation of a Diesel engine 1, the exhaust smoke density signal S1 of an exhaust smoke density sensor 10 is sent to the input of a comparator COM2 in a control circuit 12 to send the valve position signal S3 of a change-over valve 9 to the input of a reference signal generator 12a which can generate a first reference value corresponding to the exhaust smoke density at a limit corresponding to the legal regulation value or the like and a second reference value lower than the first one so as to generate the outputs of the first reference value when the valve 9 is in the position of opening fully a bypass 8 and the second reference value when the valve 9 is in the position of closing fully the bypass 8. And these reference values are compared with said signal S1 by the comparator COM2 to generate the output of valve controlling signal S5 for driving the valve 9 to the position of opening fully the bypass 8 when the exhaust smoke density is less than the reference value.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to an exhaust gas purification device for a Tasel engine, in which a filter member for collecting particulate components such as carbon particles is provided in the exhaust passage, and more specifically, the present invention relates to an exhaust gas purification device for a Tasel engine, in which a filter member for collecting particulate components such as carbon particles is provided in the exhaust passage. This invention relates to an exhaust gas purification device designed to reduce the amount of exhaust gas.

The exhaust path of a diesel engine contains many particulate components such as carbon 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 above-mentioned particulate components 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. In addition, exhaust gas purification devices using the above-mentioned filter member are generally constructed in such a way that if clogging progresses, the trapped components are burned by a burner device to eliminate the clogging. The faster the burner equipment operates, the more frequently the burner equipment will operate, increasing the chances that the filter member will be exposed to high temperatures and shortening the life of the filter member. Furthermore, the more frequently the burner device is operated, the more the burner fuel is consumed.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an exhaust gas purification device for a diesel engine that can alleviate the progress of clogging of a filter member.

In the exhaust gas purification device for a diesel engine of the present invention, in the exhaust gas purification device using the filter member as described above, a bypass passage that bypasses the filter member is provided in the exhaust passage, and the exhaust gas is sent to the binox passage. A valve capable of changing the ratio between the amount of exhaust gas and the amount of exhaust gas flowing into the filter member is provided, and further includes an exhaust smoke concentration detector for detecting the concentration of particulates as described above, and a valve control means for controlling the valve. is provided, and the valve is controlled in the direction of reducing or increasing the amount of exhaust gas flowing into the path passageway, depending on whether the exhaust smoke concentration is high or low detected by the exhaust smoke concentration detector. It is characterized by this.

In the diesel engine exhaust gas purification device of the present invention which has the above structure, when the exhaust gas concentration of the exhaust gas discharged from the engine is sufficiently low and the exhaust gas purification by the filter member is not necessary, Since the exhaust gas automatically bypasses the filter member and is directly released into the atmosphere, the progress of clogging of the filter member is alleviated.

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. A honeycomb-shaped filter member 4 is disposed in an exhaust passage 3 connected to an exhaust manifold 2 of a diesel engine 1. This filter member 4 has a large number of pores 4b formed by porous partition walls 4a. The ends of the pores 4b are changed every other and one end of each is closed with a blind plug 4C, and the exhaust gas flowing into the pores 4b whose upstream end is open is passed through the porous partition wall 4a. It flows out into the pore 4b, which has an open downstream end. Exhaust gas is at bulkhead 4A
When the exhaust gas passes through the exhaust gas, fine particles such as carbon particles contained in the exhaust gas are collected by the partition wall 4a. A pair of electrodes 5 are provided on the filter member 4 in a direction perpendicular to its axis.
, 6 are inserted. These electrodes 5 and 6 are fixed to the peripheral wall of the filter member 4, and are inserted into each partition wall 4a closely, that is, without forming a gap between them and the partition wall 4a. A burner 7 is disposed in the exhaust passage 3 upstream of the filter member 4. This burner 7 consists of an air nozzle 7a, a fuel nozzle 7b, and a spark plug operating switch 7C.

An bypass passage 8 is branched from the exhaust passage 3 further upstream of the burner 7, and this bypass passage 8 is returned to the exhaust passage 3 by bypassing the filter member 4 described above. And at the upstream branch of this path path 8,
a bypass fully closed position (position indicated by a solid line in FIG. 1) in which the inflow of exhaust gas into the bypass passage 8 is cut off and the entire amount of exhaust gas is sent into the filter member 4; and the inflow of exhaust gas into the filter member 4. A switching valve 9 is provided which takes two positions: a bypass fully open position (position indicated by a dashed line in FIG. 1), which shuts off the exhaust gas and sends the entire amount of exhaust gas into the bypass passage 8;

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.

An exhaust smoke concentration sensor 10 as shown in detail in FIG. 2 is provided in the exhaust passage 3 downstream of the portion to which the downstream end of the bypass passage 8 is connected. This exhaust smoke concentration sensor 10 includes a light emitting diode IOa as a light source section and a phototransistor IOb as a light amount sensing section.
, and an amplifier 10C for amplifying the output of the phototransistor 10b.The light emitting diode 10a and the phototransistor 10b are mounted opposite to each other on the peripheral wall of the exhaust passage 30. The light emitted from the light emitting diode 10a crosses the exhaust passage 3 and reaches the phototransistor Job, but the amount of light received by the phototransistor 10b 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 and the amplifier 10c
Amplify and output.

Therefore, by measuring the voltage of this output signal S+, 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 electrical resistance between the pair of electrodes 5 and 6 described above has the property of 7 (when fine particles such as carbon particles adhere to the partition wall 4a of the router member 4, it decreases as the amount of the adhered fine particles increases). have

Therefore, when the electrodes 5 and 6 are connected through the batch IJE and the resistor R, the voltage difference across the resistor R 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. A reference voltage generator e generates the same reference voltage as the voltage difference . If one end is grounded and the other end is connected to the comparator COM+, this reference voltage and the voltage difference are compared, and when the voltage difference exceeds the reference voltage, the electric signal S2 is generated. ,
゛-Using this electrical signal S2 as a clogging detection signal, the scrubbing operation can be automatically started when necessary.

The operation of the exhaust gas purification device for a diesel engine according to this embodiment having the above-described structure will be described 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 the burner activation signal S4. This burner operation signal S4 causes the fuel nozzle 7 of the burner 7 to
Fuel pump 1 that sends burner fuel from fuel tank 13 to b
4 and the blower 15 that sends burner combustion air to the air nozzle 7a are operated, while the spark plug operating switch 7c is energized and the burner 7 is operated for combustion. By operating this burner 7, particulate components collected in the filter member 4 are burned, and the filter member 40 is unclogged.

In the apparatus 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, in which the aforementioned exhaust smoke concentration signal S1 is input to the comparator C0M2, and the valve position signal S3 is input to the reference signal generator 12a. Note that the circuit for generating the burner operation signal S4 in response to the input of the clogging detection signal S2 as described above is omitted in FIG. 4. The reference signal generator 12a generates a first reference value, such as a legal regulation value, which corresponds to a limit exhaust smoke concentration beyond which it is not allowed to be released into the atmosphere at a higher concentration, and this first reference value.
It is possible to generate two types of reference values, a second reference value corresponding to an exhaust smoke concentration lower than the reference value of The reference value is configured to output the second reference value when the switching valve 9 is in the bypass fully closed position. The comparator C0M2 is connected to the first or second reference value,
It compares the actually measured exhaust smoke concentration signal S1 and if the actually measured exhaust smoke concentration exceeds the reference value, it outputs a valve control signal S5 that drives the switching valve 9 to the bypass full open position, and conversely, the actually measured exhaust smoke concentration It is configured to output a valve control signal S5 that drives the switching valve 9 to the bypass fully open position if the concentration is below the reference value. 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. It is set.

Here, using FIG. 5, it will be explained how the above control system operates with respect to the actually measured exhaust smoke concentration that changes. In this FIG. 5, curve a shows the actual exhaust smoke concentration measured by the exhaust smoke concentration sensor 10, the part indicated by a broken line indicates that the switching valve 9 is at the bypass full open position, and the part indicated by a solid line indicates that the switching valve 9 is in the bypass full open position. 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 the exhaust gas is in the full amount pi, <
When the exhaust gas flows through the gas 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. Therefore, this exhaust smoke concentration is the first
exceeds the reference value (center 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). . Even if the exhaust gas is sent to the filter member 4, if the trend toward higher exhaust smoke concentration in the exhaust gas continues, the exhaust smoke concentration will of course gradually become higher than the above point C, but of course the filter member 4 will Since the one that suppresses the exhaust smoke concentration to a range lower than the first reference value is selected and used, the exhaust smoke concentration will not exceed the first reference value when the bypass passage is fully 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 happens (point d in the figure), the switching valve 9 is driven to the fully open position, and the exhaust smoke concentration rises rapidly (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 this zero point will not exceed the first reference value. When the bypass passage is fully open, if the exhaust smoke concentration exceeds the standard value in box 1 again (point 1 in the figure), the switching valve 9 is moved to the bypass fully closed position as described above. and the exhaust smoke concentration is lowered (point g in the figure).

If m is set too small, it will cause hunting of the switching valve 9, and if it is set too thick, it will encourage the use of filter parts in areas where exhaust gas purification is not required, and the effect of installing the bypass passage 8 will be reduced. Therefore, it is necessary to set φ to an appropriate amount.

As explained above, in the device of this embodiment, the exhaust smoke concentration of the exhaust gas never exceeds the first reference value, but the filter member 4 is used only when necessary. Therefore, the progress of clogging of the filter member 4 can be alleviated.

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 change the ratio of 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, when the concentration of exhaust smoke is low, 80% of the exhaust gas is sent to the bypass passage. , even if a device is used in which 20% of the exhaust gas is sent to one filter member, and when the exhaust smoke concentration is high, the flow path state is switched such that 20% of the exhaust gas is sent to the bypass passage and 80% of the exhaust gas is sent to the filter member. good. Further, an exhaust smoke concentration sensor that detects the 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 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. 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 feedback-controlled by the exhaust smoke concentration detected in the exhaust passage downstream of the bypass passage, and released into the atmosphere. It is also possible to maintain the exhaust smoke concentration of the exhaust gas at a desired value.

As explained in detail above, the diesel engine exhaust gas purification device of the present invention is intended to reduce the progress of clogging of the filter member while always keeping the exhaust smoke concentration of the exhaust gas released into the atmosphere below a predetermined value. As a result, the combustion performance of the diesel engine is maintained at a high level, and the burner device for removing clogging of the filter member does not operate frequently, so the life of the filter member is extended.
Burner fuel consumption also decreases.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, and Fig. 2 is a system diagram showing one embodiment of the present invention.
3 is a circuit diagram showing in detail a part of the electric circuit of the embodiment shown in FIG. 1; FIG. 4 is a schematic diagram illustrating a control circuit of the embodiment shown in FIG. 1. Explanatory Diagram FIG. 5 is an explanatory diagram illustrating the state of exhaust smoke concentration control in the embodiment of FIG. 1. 1...Diesel engine 3...Exhaust passage 8...
・Bypass passage 9...Switching valve 10...Exhaust smoke concentration upper sensor 12...Control j circuit □ S+...Exhaust smoke concentration signal S5...Valve control signal Fig. 1 Fig. 2 Fig. 3 12'

Claims (1)

[Scope of Claims] 1) In an exhaust gas purification device for a diesel engine, comprising a filter member disposed in an exhaust passage for collecting fine particles such as carbon particles in exhaust gas, the filter member is disposed in the exhaust passage. and a valve capable of changing the ratio of the amount of exhaust gas sent to the bypass passage and the amount of exhaust gas flowing to the filter member, and exhaust smoke concentration detection for detecting the concentration of the particulates. and a valve control means that receives the output of the exhaust smoke concentration detector and controls the valve in a direction to reduce or increase the amount of exhaust gas flowing into the bypass passage depending on whether the exhaust smoke concentration is high or low. An exhaust gas purification device for a diesel engine, characterized in that it is provided with. 2) The valve is a switching valve that takes first and second positions to increase or decrease the amount of exhaust gas flowing into the bypass passage, and the exhaust smoke concentration detector is located in the exhaust passage downstream of the bypass passage. and the valve control means controls the switching valve to the second position when the switching valve is in the first position and the exhaust smoke concentration detected by the exhaust smoke concentration detector exceeds a first reference value. and the switching valve is driven to the first position when the switching valve is in the second position and the exhaust smoke concentration is equal to or less than a second reference value that is lower than the first reference value. An exhaust gas purification device for a diesel engine according to claim 1, characterized in that the exhaust gas purification device is formed as described in claim 1. 3) The valve includes a switching valve that takes first and second positions to increase or decrease the amount of exhaust gas flowing into the bypass passage, and the exhaust smoke concentration detector is located in the exhaust passage upstream of the switching valve. The valve control means drives the switching valve to the second position when the exhaust smoke concentration detected by the exhaust smoke concentration detector exceeds a predetermined value, and drives the switching valve to the second position when the exhaust smoke concentration detected by the exhaust smoke concentration detector exceeds a predetermined value. 4) The exhaust gas purifying device for a diesel engine according to claim 1, wherein the switching valve is configured to drive the switching valve to the first position. The exhaust gas purification device for a diesel engine according to claim 2 or 3, characterized in that the exhaust passage communicating with the filter member is completely closed, and the bypass passage is completely closed in the second position. . 5) the valve is a control valve that continuously adjusts the amount of exhaust gas flowing into the bypass passage, and the exhaust smoke concentration detector is disposed in the exhaust passage downstream of the bypass passage;
Claim 1, wherein the valve control means is configured to control the control valve so that the exhaust smoke concentration detected by the exhaust smoke concentration detector is equal to or less than a predetermined value. Exhaust gas purification device for diesel engines.