JP2004285881A - Exhaust emission control device for diesel engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for a diesel engine capable of preventing breakdown and dissolution of a particle filter due to abnormal combustion by preventing abnormal heap of the particles in the particle filter. <P>SOLUTION: When the predetermined quantity or more of particles is heaped on the particulate filter carrying the catalyst and temperature of the exhaust gas is the predetermined temperature or less, the compressed air is led into the particle filter from a downstream side of the exhaust in the particulate filter to eliminate the particles heaped on the particulate filter, and the eliminated particles are burned up. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust purification device for removing particulates contained in exhaust gas of a diesel engine.
[0002]
[Prior art]
Regulations on the exhaust gas of recent internal combustion engines, particularly diesel engines, have been strengthened year by year, and there is an urgent need to reduce particulate matter (PM) containing carbon as a main component. A diesel particulate filter (DPF) is known as a device for removing the particulates from the exhaust gas, and a movement to require a vehicle equipped with a diesel engine to be equipped with the diesel particulate filter is in full swing.
[0003]
By the way, in a diesel particulate filter installed in a vehicle equipped with a diesel engine, collected particulates accumulate due to repeated operation of the engine, and the collected particulates are burned to burn the diesel particulate filter. Need to be played. As a means for this regeneration, a method of burning particulates by heating with an electric heater, a burner or the like is known. However, in this method, if the amount of collected particulates increases, the combustion temperature becomes high, and there is a problem that a filter formed of cordierite, silicon carbide, or the like is damaged or melted.
[0004]
In order to solve the above-mentioned problem, compressed air is introduced into the particulate filter from the exhaust gas downstream side of the particulate filter to remove the particulates accumulated on the particulate filter, and the removed particulates are subjected to particulate incineration. A so-called backwashing system has been proposed in which the wastewater is collected in a chamber and incinerated by a heater or the like. In this so-called backwashing method, the exhaust gas pressure on the exhaust gas upstream side and the exhaust gas downstream side of the particulate filter is measured, and when this pressure difference exceeds a predetermined value, a predetermined amount of particulates is deposited on the particulate filter. By making a judgment, the compressed air is introduced and the heater is operated. (For example, refer to Patent Document 1.)
[0005]
[Patent Document 1]
Japanese Patent Publication No. Hei 7-84846 [0006]
The exhaust gas purifying apparatus disclosed in the above publication is configured such that the particulate filter collects the particulate filter in the exhaust gas, so that the exhaust gas pressure difference between the upstream side and the downstream side of the exhaust gas reaches a predetermined amount each time. Since the heater is operated while the compressed air is introduced, the operation must be performed frequently.
[0007]
On the other hand, in recent years, as an exhaust gas purifying device for a diesel engine, a proposal has been made to carry a catalyst on a diesel particulate filter and continuously burn the particulates collected by the particulate filter depending on the temperature of the exhaust gas.
[0008]
[Problems to be solved by the invention]
Therefore, it is difficult to continuously burn the particulates on the catalyst depending on the exhaust gas temperature even if a particulate filter supporting the catalyst is used. That is, the catalyst carried on the particulate filter cannot burn the particulate below a predetermined temperature (for example, 350 ° C.), so that the particulate accumulates on the particulate filter in an operating region where the exhaust gas temperature is low. Will be. When particulates accumulate on the particulate filter, the airflow resistance increases and the fuel consumption rate deteriorates.
[0009]
The present invention has been made in view of the above points, and its main technical problem is that particulates do not abnormally accumulate on the particulate filter under any operating conditions, and the particulate filter is damaged by abnormal combustion. Another object of the present invention is to provide a diesel engine exhaust purification device capable of preventing erosion.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned technical problem, the present invention has a structure in which particulates are deposited on a particulate filter supporting a catalyst in a predetermined amount or more, and when the exhaust gas temperature is equal to or lower than a predetermined temperature, the particulate filter is disposed from the exhaust gas downstream side. Provided is an exhaust gas purifying apparatus for a diesel engine that introduces compressed air into a particulate filter to remove the particulates accumulated on the particulate filter, and incinerates the removed particulates.
[0011]
That is, according to the present invention, a particulate filter arranged in an exhaust passage of an engine and carrying a catalyst, an exhaust inflow chamber provided on an exhaust upstream side of the particulate filter, and an exhaust downstream side of the particulate filter , An air supply means for supplying high-pressure air to the air introduction chamber, a particulate incineration chamber formed at the bottom of the exhaust inflow chamber, and a particulate incineration chamber. Heating combustion means, and an exhaust purification device for a diesel engine comprising:
Exhaust gas temperature detecting means for detecting the temperature of the exhaust gas flowing into the exhaust inflow chamber;
Particulate deposition amount detection means for detecting the deposition amount of particulates deposited on the particulate filter;
Control means for controlling the air supply means and the heating combustion means based on a detection signal from the exhaust gas temperature detection means and the particulate matter deposition amount detection means,
The control unit is configured to control the air flow when the amount of particulate matter detected by the particulate matter amount detection unit is equal to or greater than a predetermined value and the exhaust gas temperature detected by the exhaust gas temperature detection unit is equal to or less than a predetermined temperature. Activating the supply means and the heating and combustion means,
An exhaust gas purification device for a diesel engine is provided.
[0012]
It is desirable that a suction means is connected to the particulate incineration chamber.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of an exhaust gas purification apparatus for a diesel engine configured according to the present invention will be described in more detail with reference to the accompanying drawings.
FIG. 1 shows an embodiment of a diesel engine exhaust gas purification apparatus constituted according to the present invention. The exhaust purification device in the illustrated embodiment includes a particulate filter 3 disposed between exhaust passages 2a and 2b connected to an exhaust manifold (not shown) of a diesel engine. The particulate filter 3 is formed by a so-called wall-through type or full-through type honeycomb filter formed of, for example, porous cordierite or silicon carbide, and its surface is coated with activated alumina or the like. A wash coat layer is formed, and a catalyst is supported on the wash coat layer. As the catalyst, an alkali metal compound or an alkaline earth metal compound, platinum, nickel, cobalt, ruthenium, rhodium, palladium or the like can be used.
[0014]
An exhaust inflow chamber 4 is provided on the exhaust upstream side of the particulate filter 3, that is, on one exhaust passage 2 a side connected to an exhaust manifold (not shown). At the bottom of the exhaust gas inflow chamber 4a, a particulate incineration means 5 is provided. The particulate incineration means 5 includes a particulate incineration chamber 51 formed at the bottom of the exhaust inflow chamber 4a, a filter 52 made of a heat-resistant material provided in the particulate incineration chamber 51, and an upper part of the filter 52. And a sheath heater 53 (HT) as a heating and burning means provided. The operation of the sheath heater 53 (HT) is controlled by control means described later.
[0015]
A suction means 6 is connected to the particulate incineration means 5. The suction means 6 includes a suction pipe 61 having one end connected downstream of the filter 52 of the particulate incineration means 5 and a vacuum pump 62 (VP) connected to the other end of the suction pipe 61. And a switching valve 63 (V1) provided in the suction pipe 61. The switching valve 63 (V1) includes a valve that opens and closes the passage of the suction pipe 61 and an actuator that operates the valve. The operations of the switching valve 63 (V1) and the vacuum pump 62 (VP) are controlled by control means described later.
[0016]
An air introduction chamber 4b is provided on the exhaust gas downstream side of the particulate filter 3, that is, on the other exhaust passage 2b side. An air supply means 7 is connected to the air introduction chamber 4b. The air supply means 7 includes an air ejection nozzle 71 provided in the air introduction chamber 4b so as to be open, an air supply pipe 72 having one end connected to the air ejection nozzle 71, and an air supply pipe 72 connected to the other end of the air supply pipe 72. It comprises a high-pressure air pump 73 (PP) connected and arranged, and a switching valve 74 (V2) arranged in the air supply pipe 72. The switching valve 74 (V2), like the switching valve 63 (V1), includes a valve that opens and closes the passage of the air supply pipe 72 and an actuator that operates the valve. The operation of the switching valve 74 (V2) and the high-pressure air pump 73 (PP) is controlled by control means described later.
[0017]
The exhaust gas purifying apparatus in the illustrated embodiment includes a thermocouple 8 (HS) as an exhaust gas temperature detecting means for detecting a temperature of exhaust gas flowing into the exhaust gas inflow chamber 4, an exhaust gas inflow chamber 4a, and an air introduction chamber. It has pressure detection sensors 9a (PS1) and 9b (PS2) for detecting the pressure of 4b. The pressure detection sensors 9a (PS1) and 9b (PS2) function as particulate accumulation amount detecting means for detecting the accumulation amount of the particulates accumulated on the particulate filter 3. The exhaust gas purifying apparatus in the illustrated embodiment operates the sheath heater 53 (HT), the vacuum pump 62 (VP) and the switching valve 63 (V1), the high-pressure air pump 73 (PP), and the switching valve 74 (V2). It has a control means 10 for controlling. The control means 10 is constituted by a microcomputer, and includes a central processing unit (CPU) for performing arithmetic processing according to a control program, a read-only memory (ROM) for storing a control program and the like, and a readable and writable random for storing an arithmetic result. An access memory (RAM), a timer, and the like are provided. The control means 10 receives detection signals from the thermocouple 8 (HS) and the pressure detection sensors 9a (PS1), 9b (PS2), etc., and outputs the sheath heater 53 (HT), the vacuum pump 62 (VP), and the switching valve. 63 (V1), and outputs control signals to the high-pressure air pump 73 (PP), the switching valve 74 (V2), and the like.
[0018]
The exhaust gas purifying apparatus in the illustrated embodiment is configured as described above, and its operation will be described below.
Exhaust gas discharged to an exhaust manifold (not shown) of the diesel engine flows into the exhaust inflow chamber 4a through one exhaust passage 2a. The exhaust gas flowing into the exhaust inflow chamber 4a passes through the particulate filter 3 and is discharged from the air introduction chamber 4b to the exhaust passage 2b. In this way, when the exhaust gas passes through the particulate filter 3, the particulates mainly composed of carbon contained in the exhaust gas are collected by the particulate filter 3. Since the particulate filter 3 carries the catalyst as described above, the collected particulates are burned. However, the combustion of particulates by the catalyst depends on the temperature of the exhaust gas. That is, the catalyst can continuously burn the particulates when the exhaust gas temperature is higher than 350 ° C., for example, but cannot burn the particulates when the exhaust gas temperature becomes 350 ° C. or lower. Therefore, if the operation is continued in a state where the exhaust gas temperature is 350 ° C. or less, the particulates will be deposited on the particulate filter 3.
[0019]
Next, the operation of the particulate incineration means 5, the suction means 6, and the air supply means 7 for incinerating the particulates accumulated on the particulate filter 3 will be described with reference to the flowchart shown in FIG.
Based on the pressure signals detected by the pressure detection sensors 9a (PS1) and 9b (PS2) in step S1, the control unit 10 determines the exhaust gas pressure (Pa) on the exhaust gas upstream side of the particulate filter 3 and the particulate filter 3 It is determined whether the pressure difference (Pa−Pb) from the exhaust gas pressure (Pb) on the exhaust downstream side is equal to or more than a predetermined pressure difference (P1) ((Pa−Pb) ≧ P1). The predetermined pressure difference (P1) is, for example, the exhaust gas pressure on the upstream side of the exhaust gas (Pa) and the exhaust gas pressure on the downstream side of the exhaust gas (Pb) when the amount of the particulates deposited on the particulate filter 3 is 5 g / liter. And the pressure difference. If the pressure difference (Pa-Pb) is lower than the predetermined pressure difference (P1) in step S1, the control means 10 determines that the particulates deposited on the particulate filter 3 are smaller than the predetermined amount, Proceeding to S2, the high-pressure air pump 73 (PP) and the switching valve 74 (V2), the vacuum pump 62 (VP) and the switching valve 63 (V1), and the sheath heater 53 (HT) are turned off, and the process ends. Therefore, the air supply means 7, the suction means 6, and the particulate incineration means 5 do not operate.
[0020]
If the pressure difference (Pa-Pb) is equal to or greater than the predetermined pressure difference (P1) in step S1, the control unit 10 determines that the amount of particulate accumulated on the particulate filter 3 has reached the predetermined amount or more. In step S3, it is checked whether the exhaust gas temperature (T0) detected by the thermocouple 8 (HS) is equal to or lower than a predetermined temperature (T1) (for example, 350 ° C.). If the exhaust gas temperature (T0) is higher than the predetermined temperature (T1), the control means 10 determines that the particulates accumulated on the particulate filter 3 can be burned, and proceeds to step S2. Then, the high-pressure air pump 73 (PP) and the switching valve 74 (V2), the vacuum pump 62 (VP), the switching valve 63 (V1), and the sheath heater 53 (HT) are turned off, and the process ends. Therefore, the air supply means 7, the suction means 6, and the particulate incineration means 5 do not operate.
[0021]
If the exhaust gas temperature (T0) is equal to or lower than the predetermined temperature (T1) in step S3, the control means 10 cannot burn the particulates accumulated on the particulate filter 3 and further particulates accumulate. It is determined that it is in a state of being turned on, and the process proceeds to step S4 to turn on the high-pressure air pump 73 (PP) to operate, and also to urge (ON) the switching valve 74 (V2) to open the circuit to operate the air supply means 7. . The vacuum pump 62 (VP) is energized (ON) to operate, and the switching valve 63 (V1) is energized (ON) to open the circuit to operate the suction means 6. Then, the sheath heater 53 (HT) constituting the particulate incineration means 5 is energized (ON) to heat. When the high pressure air pump 73 (PP) of the air supply means 7 is operated and the switching valve 74 (V2) is opened, high pressure air (so-called backwash air) generated by the high pressure air pump 73 (PP) passes through the air supply pipe 72. The air is jetted from the air jet nozzle 71 to the air introduction chamber 4b. The high-pressure air jetted into the air introduction chamber 4b flows through the particulate filter 3 in the direction opposite to the exhaust gas to the exhaust inflow chamber 4a. At this time, since the vacuum pump 62 (VP) of the suction means 6 operates and the switching valve 63 (V1) is open, the high-pressure air flowing into the exhaust inflow chamber 4a is sucked by the vacuum pump 62 (VP). In this way, the high-pressure air jetted into the air introduction chamber 4b passes through the particulate filter 3, whereby the particulates deposited on the particulate filter 3 are removed, and the particulates pass through the exhaust inflow chamber 4a by their own weight. It falls into the curated incineration chamber 51 and deposits on the filter 52. The particulates deposited on the filter 52 are incinerated because the sheath heater 53 (HT) is energized (ON) and heated. The high-pressure air ejected from the air ejection nozzle 71 to the air introduction chamber 4b is ejected in a pulsed manner, which is effective for removing the particulates accumulated on the particulate filter 3.
[0022]
As described above, according to the exhaust gas purifying apparatus in the illustrated embodiment, when the exhaust gas temperature (T0) is higher than the predetermined temperature (T1), the particulate matter deposited on the particulate filter 3 carrying the catalyst is removed. Is burned by the exhaust gas temperature. When the exhaust gas temperature (T0) is equal to or lower than the predetermined temperature (T1) and the amount of particulates accumulated in the particulate filter 3 is equal to or higher than a predetermined amount, so-called backwash air is blown out. The particulates accumulated on the particulate filter 3 are removed, and the removed particulates are incinerated in the particulate incineration chamber 51 by the sheath heater 53 (HT). Therefore, the particulates do not abnormally accumulate on the particulate filter 3 under any operating conditions, and damage and melting damage of the particulate filter 3 due to abnormal combustion can be prevented. In addition, since so-called backwash air also removes inorganic substances accumulated in the particulate filter 3 due to the direction components in the engine oil, clogging of the particulate filter 3 by the inorganic substances is prevented, and back pressure due to the clogging is prevented. It is possible to prevent the fuel efficiency from being deteriorated due to the rise, and to drastically extend the period for periodically replacing the particulate filter 3 due to clogging.
[0023]
As described above, the present invention has been described based on the illustrated embodiments. However, the present invention is not limited to only the embodiments, and various modifications are possible within the scope of the present invention. For example, in the illustrated embodiment, an example is shown in which pressure detection sensors 9a (PS1) and 9b (PS2) for detecting the pressure on the upstream side and the downstream side of the exhaust of the particulate filter 3 are used as the particulate deposition amount detecting means. However, the thermocouple 8 (HS) as the exhaust gas temperature detecting means can function as the particulate deposit amount detecting means. That is, the difference between the operating time when the exhaust gas temperature detected by the thermocouple 8 (HS) is equal to or lower than the predetermined temperature (T1) and the operating time when the exhaust gas temperature is higher than the predetermined temperature (T1) is the predetermined time. When the above is reached, it can be determined that the particulate accumulation amount has reached the predetermined amount. Further, the particulate accumulation amount can also be detected based on an exhaust gas temperature map obtained from the engine load and the rotation speed. That is, the exhaust gas temperature is obtained from the exhaust gas temperature map based on the detection signals from the engine load detection sensor and the rotation speed detection sensor. When the difference between the operation times in a state higher than the predetermined temperature (T1) exceeds the predetermined time, it can be determined that the particulate accumulation amount has reached the predetermined amount.
[0024]
【The invention's effect】
Since the exhaust gas purifying apparatus for a diesel engine according to the present invention is configured as described above, when the exhaust gas temperature is higher than a predetermined temperature, the particulates deposited on the particulate filter carrying the catalyst have the exhaust gas temperature. When the exhaust gas temperature is lower than a predetermined temperature and the particulate matter accumulated on the particulate filter is equal to or greater than a predetermined amount, so-called backwash air is blown out and the particulate matter accumulated on the particulate filter is burned. The removed particulates are incinerated by a heating and burning means in a particulate incineration chamber. Therefore, the particulates do not abnormally accumulate on the particulate filter under any operating conditions, and damage and melting damage of the particulate filter due to abnormal combustion can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an exhaust gas purification device for a diesel engine configured according to the present invention.
FIG. 2 is a flowchart showing an operation procedure of control means provided in the exhaust gas purification device shown in FIG.
[Explanation of symbols]
2a, 2b: Exhaust passage 3: Particulate filter 4a: Exhaust inflow chamber 4b: Air introduction chamber 5: Particulate incineration means 51: Particulate incineration chamber 52: Filter 53: Sheath heater (HT)
6: suction means 61: suction pipe 62: vacuum pump (VP)
63: On-off valve (V1)
7: Air supply means 71: Air ejection nozzle 72: Air supply pipe 73: High pressure air pump (PP)
74: On-off valve (V2)
8: Thermocouple (HS)
9a, 9b: pressure detection sensor 10: control means

Claims (2)

A particulate filter disposed in an exhaust passage of the engine and carrying a catalyst, an exhaust inflow chamber provided on the exhaust upstream side of the particulate filter, and an air introduction chamber provided on the exhaust downstream side of the particulate filter; An air supply means for supplying high-pressure air to the air introduction chamber, a particulate incineration chamber formed at the bottom of the exhaust inflow chamber, and a heating and combustion means disposed in the particulate incineration chamber. In diesel engine exhaust purification equipment,
Exhaust gas temperature detecting means for detecting the temperature of the exhaust gas flowing into the exhaust inflow chamber;
Particulate deposition amount detection means for detecting the deposition amount of particulates deposited on the particulate filter;
Control means for controlling the air supply means and the heating combustion means based on a detection signal from the exhaust gas temperature detection means and the particulate matter deposition amount detection means,
The control means is configured to control the air flow when the amount of particulates detected by the particulate deposition amount detection means is equal to or more than a predetermined amount and the exhaust gas temperature detected by the exhaust gas temperature detection means is equal to or less than a predetermined temperature. Activating the supply means and the heating and combustion means,
An exhaust gas purification device for a diesel engine, characterized in that: The exhaust purification device for a diesel engine according to claim 1, wherein a suction means is connected to the particulate incineration chamber.

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