JPH0715249B2 - Exhaust gas purification device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust gas purification device provided in an exhaust system of a diesel engine to collect particulates in exhaust gas.

[Conventional technology]

This exhaust gas purification device has, for example, a honeycomb filter,
When the trapped amount of particulates exceeds a predetermined value, the particulates are burned to regenerate the filter. Japanese Unexamined Patent Publication No. 61-223215 shows a conventional exhaust gas purification device, in which an electric heater is provided in a portion close to one end of a filter, and two exhaust pipes bypassing the filter are arranged. In addition, five valves are provided to control the flow of exhaust gas in these exhaust pipes and filters. When collecting particulates, the exhaust gas does not pass through the two exhaust pipes, flows through the filter, and then passes through the electric heater to be discharged into the atmosphere.
When the filter is regenerated, exhaust gas flows from one side of the exhaust pipe into the filter from the electric heater side, is discharged into the atmosphere through the other exhaust pipe, and the electric heater is energized to ignite the particulates. To burn.

[Problems to be Solved by the Invention]

However, since the above-mentioned conventional device has two exhaust pipes that bypass the filter, it has a problem in that it becomes large in size and is unsuitable for mounting on a vehicle. Further, when the filter is regenerated, the exhaust gas flows backward in the filter as compared with the normal time, and the conventional device has a problem that the pressure loss of the exhaust gas is large due to the resistance of the pipeline in the exhaust system.

It is an object of the present invention to obtain an exhaust gas purification device that is small in size, easy to mount on a vehicle, and has a small pressure loss. In the present invention, the inventors have exhausted gas in a muffler provided in an exhaust system. We paid attention to the fact that the gas was flowing back.

[Means for Solving the Problems]

An exhaust gas purification device according to the present invention is provided in a passage that connects first and second expansion chambers of a muffler, and a filter that collects particulates in exhaust gas and guides the exhaust gas into the first expansion chamber. An inlet means, an outlet means for discharging exhaust gas in the second expansion chamber to the outside, and a second filter of the filter.
It is provided on the side of the expansion chamber, and is provided with an ignition means for burning the particulates collected on the filter when the filter is regenerated, and a flow path control means for changing the flow path of the exhaust gas. The flow path control means guides at least a part of the exhaust gas guided by the inlet means to the second expansion chamber and discharges the exhaust gas in the first expansion chamber to the outside when the filter is regenerated.

〔Example〕

 The present invention will be described below based on the illustrated embodiments.

1 to 3 show a first embodiment of the present invention.

The first casing 11 is divided into a first expansion chamber 13 and a third expansion chamber 14 by a partition wall 12, and these first and third expansion chambers 13 and 14 are provided.
Communicate with each other by a short pipe 15 provided on the partition wall 12. Similarly, the second casing 21 is also divided into the second and fourth expansion chambers 23 and 24 by the partition wall 22, and these second and fourth expansion chambers 23 and 24 are
24 communicate with each other by a short pipe 25 attached to the partition wall 22. In the first casing 11, the second expansion chamber 13 is located on the side far from the second casing 21, and in the second casing 21, the second expansion chamber 23 is located on the side far from the first casing 11.

The inlet pipe 31 branches into first and second inlet pipes 32 and 33 on the way. The first inlet pipe 32 extends through the second casing 21 and the partition wall 12 of the first casing 11, communicates with the first expansion chamber 13, and the second inlet pipe 33 penetrates the partition wall 22 of the second casing 21. And extends to communicate with the fourth expansion chamber 24. The outlet pipe is the first outlet pipe 36
And the second outlet pipe 37. The first outlet pipe 36 extends through the partition wall 22 of the first casing 11 and the second casing 21,
It communicates with the second expansion chamber 23, and the second outlet pipe 37 is the first casing.
The partition wall 12 extends through 11 and communicates with the third expansion chamber 14.

The first control valve 41 is provided in the second inlet pipe 33, and the rod 42
Is connected to the actuator 43 via. First control valve 41
Normally closes the second inlet pipe 33, but opens the second inlet pipe 33 when the filter is regenerated, as will be described later. The second control valve 46 is provided in the second outlet pipe 37 and is connected to the actuator 51 via the rod 47. The second control valve 46, like the first control valve 41, normally closes the second outlet pipe 37 and opens the second outlet pipe 37 during filter regeneration.

The actuators 43 and 51 have the same structure and are both diaphragm type. As for the actuator 51, the inside of the shell 52 is divided into a constant pressure chamber 54 and a negative pressure chamber 55 by a diaphragm 53, and the diaphragm 53 is divided into a second chamber by a rod 47.
The control valve 46 is connected. The constant pressure chamber 54 is always in communication with the atmosphere, and the negative pressure chamber 55 is connected to the negative pressure supply mechanism 61 via the negative pressure control mechanism 56. The negative pressure chamber 55 is provided with a spring 59. The negative pressure control mechanism 56 has an orifice 57 and a check valve 58, and is configured to gradually guide the negative pressure to the negative pressure chamber 55 and rapidly guide the atmospheric pressure.

When the atmospheric pressure is introduced into the negative pressure chamber 55, the diaphragm 53 is displaced by the spring 59 toward the constant pressure chamber 54, and the second control valve 46 is closed. On the other hand, when the negative pressure is introduced into the negative pressure chamber 55, the diaphragm 53 compresses the spring 59 and displaces to the negative pressure chamber 55 side, whereby the second control valve 46 opens. On the other hand, an actuator 43 that opens and closes the first control valve 41
Is directly connected to the negative pressure supply mechanism 62 without passing through the negative pressure control mechanism, and opens the first control valve 41 when negative pressure is introduced and closes the first control valve 41 when atmospheric pressure is introduced. Let

The housing 71 of the filter is provided between the first casing 11 and the second casing 21. The openings 72, 73 at both ends of the housing 71 are cylindrical projections 16 formed in the first casing 11.
And the cylindrical projections 26 formed on the second casing 21, respectively, and these contacting portions are clamps 81 shown in FIG.
Is detachably connected. The clamp 81 has two semi-circular fasteners 82 and 83, which are connected by bolts 84 and nuts 85 at flange portions 82a and 83a formed at both ends. The first inlet pipe 32 and the first outlet pipe 36 have joints 34 and 38 in the portion between the first and second casings 11 and 21, and these joints 3
4, 38 are also detachably connected by a clamp 81.

Thus, the housing 71 has the first and second casings 11,2.
The first and second inlet pipes 32, 3 that form a passage connecting 1
3, the first and second casings 11 and 21, the housing 71, and the first and second outlet pipes 36 and 37 constitute a muffler. A filter 74 that collects particulates in the exhaust gas is provided in the housing 71. The electric heater 75 for igniting and burning the particulates on the filter 74 is provided on the second expansion chamber 23 side of the filter 74, that is, the second casing 21 side. The electric heater 75 is connected to the battery 77 via the relay 76, and is energized to generate heat when the amount of collected particulates reaches a certain value, and ignites the particulates. The particulate collection amount is determined to have reached a certain amount when the pressure detected by the pressure sensor 78 provided in the third expansion chamber 14 of the first casing 11 becomes higher than a certain value.

First and second control valves during normal particulate collection
As shown in FIG. 1, 41 and 46 are second inlet pipes 33, respectively.
The second outlet pipe 37 is closed. Therefore, the exhaust gas flows from the first inlet pipe 32 to the first expansion chamber 13 as shown by the arrow in FIG.
Flow into. While passing through the filter 74, the particulates in the exhaust gas are collected by the filter 74. After passing through the filter 74, the exhaust gas is exhausted from the fourth and second expansion chambers 24, 2
It passes through 3 and is discharged to the atmosphere from the first outlet pipe 36. Also, the exhaust noise is silenced while the exhaust gas passes through the expansion chambers 13, 14, 23, 24.

When the filter 74 is regenerated, the first and second control valves 41 and 46 are
As shown in FIG. 3, the second inlet pipe 33 and the second inlet pipe 33, respectively.
The outlet pipe 36 is opened. Therefore, the exhaust gas flows through the first and second inlet pipes 32 and 33 as shown by the arrow in FIG. 3, and the exhaust gas passing through the first inlet pipe 32 is transferred from the first expansion chamber 13 to the third expansion chamber 14. It flows in and is discharged into the atmosphere from the second outlet pipe 37. The exhaust gas passing through the second inlet pipe 33 flows into the fourth expansion chamber 24, a part of which flows into the filter 74, and the rest is discharged into the atmosphere through the second expansion chamber 23 and the first outlet pipe 36. .
Then, the direction of the exhaust gas flowing in the filter 74 is
This is the opposite of when collecting particulates. At this time, the electric heater is energized and generates heat, which causes the particulates on the filter 74 to ignite and burn.

During this regeneration, the flow rate of the exhaust gas passing through the filter 74 is adjusted to be about 1/10 of the total exhaust gas flow rate. That is, the first control valve 41 is opened at a predetermined opening degree, and exhaust gas flows through the first and second inlet pipes 32 and 33 at 1/2 of the total exhaust gas flow rate. And the first and second outlet pipes 3
Exhaust gas flows to 6 and 37 at 4/10 and 6/10 of the total exhaust gas flow rate, respectively. Therefore, about half of the exhaust gas passes through only two of the four expansion chambers, but there is no great difference in the noise reduction effect as compared with the case of collecting particulates. Note that the exhaust gas flow rate flowing through the filter 74 during regeneration is set to about 1/10 of the total exhaust gas flow rate in order to prevent cooling of the electric heater 75, stabilize the combustion of particulates, and prevent the filter 74 from flowing. This is to prevent the particulates from being blown off.

Further, at the start of regeneration, the second control valve 46 is gradually opened because the negative pressure is gradually transmitted by the action of the negative pressure control mechanism 56. Therefore, the exhaust sound does not change rapidly and the passenger does not feel uncomfortable.

Opening and closing of the first and second control valves 41, 46 and electric heater 75
Is energized by an electronic control unit (ECU) 91 equipped with a microcomputer. The ECU 91 includes an input port 92, an output port 93, a memory 94, and a central processing unit (CP
U) 95, which are interconnected by a bus 96. Input port 92 to pressure sensor 78 and output port 93
Are connected to the negative pressure supply mechanisms 61 and 62 and the relay 76, respectively.

FIG. 4 shows a filter regeneration routine by the ECU 91.
This routine is interrupted every predetermined time.

In step 101, it is judged whether or not the flag f is set to 1. The flag f indicates that the filter 74 is being reproduced
Is set to 0 and cleared to 0 at the time of normal particulate collection. Therefore, when collecting particulates, the routine proceeds to step 102, where it is judged whether or not the pressure ΔP detected by the pressure sensor 78 is larger than a predetermined target value. When the amount of collected particulates on the filter 74 is relatively small, the pressure ΔP is smaller than the target value, so the following steps 103 to 108 are skipped and this routine ends. On the other hand, when the amount of collected particulates increases and the pressure ΔP reaches the target value, step 103 and the following steps are executed to start the regeneration process of the filter 74.

In step 103, the flag f is set to 1. Next, at step 104, the first and second control valves 41, 46 are opened and the electric heater 75 is energized. The first control valve 41 opens immediately, but the second control valve 46 gradually opens due to the action of the negative pressure control mechanism 56. The electric heater 75 also generates heat, ignites the particulates on the filter 74, and burns them. In step 105, it is determined whether or not 3 minutes have passed since the electric heater 75 was turned on. Immediately after the reproduction of the filter 74 is started, since 3 minutes have not elapsed, steps 106 to 108
Is skipped and the routine ends.

When the reproduction process starts, in step 103 the flag f
Is set to 1, so this routine
Now you can go directly from step 101 to step 105, step 10
If it is determined that 5 minutes have elapsed in step 5, steps 106 to 108 are executed to end the reproduction process. Step 106
Then, the power supply to the electric heater 75 is cut off, and step 107
Then, the first and second control valves 41 and 46 are closed. Then, in step 108, the flag f is cleared to 0, and this routine ends.

As described above, in the first embodiment, the filter 74 is provided between the first and second casings 11 and 12 forming the muffler, and utilizes the fact that the exhaust gas flows backward between these casings 11 and 12. We are collecting particulates. Therefore, no special piping for backflowing the exhaust gas is required in the filter 74, and the structure of the exhaust purification device is simplified. As a result, the exhaust emission control device according to this embodiment is small in size and can be easily mounted on a vehicle.
Further, since the pipeline structure in the exhaust system is simplified, the pipeline resistance is small and the pressure loss of the exhaust gas is small.

In addition, in the first embodiment, the first and second casings 1
1, 21 are connected by a first inlet pipe 32 and a first outlet pipe 36, and the first inlet pipe 32 and the first outlet pipe 36 are welded to the partition walls 12, 22, respectively. Therefore filter 7
It is not necessary to particularly increase the coupling strength of the four housings 71 to the first and second casings 11 and 21. For this reason,
The housing 71 is connected to the casings 11 and 21 by a simple clamp 81 as shown in FIG. 2, and the filter 74 can be easily replaced. On the other hand, the first inlet pipe 33 is clamped at the seam 34, and the first outlet pipe 36 is clamped at the seam 38.
Connected by 81. Therefore, casings 11, 21,
Exchange of the inlet pipe 31 and the outlet pipe is easy.

Since the filter 74 is attached to the muffler, it is located at the rear end of the exhaust system. The exhaust temperature at this position is relatively low, and the particulate collection efficiency is high. Further, when the particulate matter accumulated in the muffler is blown off by the exhaust gas, the particulate matter can be collected, and the exhaust gas purification efficiency is enhanced.

FIG. 5 shows a second embodiment. In this embodiment, in addition to a filter 74 for collecting particulates, a monolithic adsorbent 201 for collecting malodorous components is provided in the housing 71. The adsorbent 201 is arranged on the second casing 21 side with respect to the filter 74, and the electric heater 75 is located between the filter 74 and the adsorbent 201. The adsorbent 201 is preferably sepiolite or zeolite, and the adsorbent 20
1 may be loaded with a catalyst for oxidizing a malodorous component. On the other hand, a throttle 202 is formed in a passage communicating with the negative pressure chamber 55 of the actuator 51 that drives the second control valve 46 to open and close, and a negative pressure is provided between this passage and the negative pressure supply mechanism 61 as in the first embodiment. No control mechanism is provided. Other configurations are similar to those of the first embodiment.

The operation is the same as that of the first embodiment except for the regeneration treatment of the adsorbent 201. That is, normally, the first and second control valves 41, 4
6 is closed, and the exhaust gas has the first inlet pipe 32, the first casing 11, the filter 74, the adsorbent 201, and the second casing 21.
And the first outlet pipe 36 flow in that order and are discharged into the atmosphere,
During this period, the sound is muted and the particulates and the malodorous components are collected. Since the adsorbent 202 is disposed on the downstream side of the filter 74, particulates in the exhaust gas, metals mixed in the engine oil, and other poisonous substances of the adsorbent are captured by the filter 74, and the adsorbent is absorbed. It will not reach 202. Therefore, the durability of the adsorbent 202 is improved.

The regeneration process of the filter 74 is performed by closing the first and second control valves 41 and 46 and energizing the electric heater 75 as in the first embodiment. Therefore, the exhaust gas during regeneration is adsorbed by the adsorbent 201. Flows toward the filter 74.

On the other hand, the regeneration process of the adsorbent 201 is performed independently of the regeneration process of the filter 74. During this regeneration process, the first control valve
41 remains closed, but the second control valve 46 is opened,
The electric heater 75 is energized to generate heat. As a result, the temperature of the exhaust gas rises, and the substance adsorbed on the adsorbent 201 separates from the adsorbent 201 or burns. When the regeneration process ends, the second control valve 46 closes. During the opening / closing operation of the second control valve 46, the transmission of negative pressure is delayed by the throttle 202.
The second control valve 46 gradually opens and closes. The regeneration process of the filter 74 is performed prior to the regeneration process of the adsorbent 201, and the frequency of the regeneration process is less in the filter 74.

FIG. 6 shows a regeneration routine of the adsorbent by the ECU (see FIG. 1). This routine is interrupted every predetermined time as in the filter 74 regeneration routine.

In step 11, it is determined whether the flag f is set to 1. At the time of collecting the malodorous component, the flag f is cleared to 0 as in the filter regeneration routine shown in FIG. 4, and therefore step 112 is executed. Step 112
Then, it is determined whether the integrated value N ₁ of the engine speed is larger than the target value. When the amount of the malodorous component collected on the adsorbent 202 is small, the integrated value N ₁ is smaller than the target value, so this routine ends as it is, but when the integrated value N ₁ becomes larger than the target value, the collected amount is large. It is determined that the adsorbent 201 needs to be regenerated. It should be noted that the target value is an engine speed integrated value that corresponds to a case where the vehicle travels steadily for 1 hour at 40 km / h.

In step 113, the flag f indicating that the regeneration process is being performed is set to 1, and in step 114, the second control valve 46 is opened and the electric heater 75 is energized. Second control valve 46
Is gradually opened by the action of the throttle 202, and the electric heater 7
5 generates heat to desorb or burn the malodorous component from the adsorbent 201. In step 115, it is judged whether or not 2 minutes have passed since the electric heater 75 was turned on, and if 2 minutes have not passed, this routine ends.

Since the flag f is set to 1 after the regeneration process is started, the process proceeds from step 111 to step 115, and the electric heater 75
If two minutes have passed since the power was turned on, steps 116 to 119
Is executed. That is, in step 116, the electric heater 7
The power supply to 5 is stopped, and in step 117, the second control valve 46 is closed. After the flag f is cleared to 0 in step 118, the integrated value N ₁ is reset in step 119, and this routine ends.

Therefore, according to the second embodiment, the same effect as that of the first embodiment can be obtained, and the malodorous component can be removed.

FIG. 7 shows a third embodiment. Explaining the portion of the configuration different from that of the first embodiment, the inside of the first casing 11 is divided into a first expansion chamber 13 and a resonance chamber 18 by a partition wall 12, and a second casing 21.
No partition wall is provided therein, and only the second expansion chamber 23 is formed therein. The inlet pipe 211 communicates with the first expansion chamber 13 and is provided outside the second casing 21 as in the first embodiment.
Instead of branching to the inlet pipe, it is basically one pipe, and the branch pipe 212 is connected in the second casing 21. The first control valve 41 is provided at the base of the branch pipe 212,
The inlet pipe 211 and the branch pipe 212 are selectively opened and closed. Outlet pipe
213 is also a single pipe, and the first expansion chamber 1 of the first casing 11
A branch pipe 214 is connected in the area 3. The second control valve 46 is provided in the branch pipe 214 and opens and closes the branch pipe 214. Further, in the third embodiment, the target value used to determine the start of the regeneration process of the filter 74 is set by the engine speed and the engine load, and therefore the input port 92 of the ECU 91 The rotation speed sensor 221 and the load sensor 222 are connected. Other configurations are similar to those of the first embodiment.

When collecting particulates, the first and second control valves 41, 46
Blocks the branch pipes 212 and 214, and the exhaust gas passes through the inlet pipe 211 and the first casing 11 as shown by solid arrows.
Into the atmosphere through the outlet pipe 213 after passing through the filter 74. When the filter 74 is regenerated, the electric heater 75 is energized to generate heat, the first control valve 41 closes the inlet pipe 211 and opens the branch pipe 212, and the second control valve 46 opens the branch pipe 214. Therefore, the exhaust gas flows from the branch pipe 212 into the second expansion chamber 23, as indicated by the dashed arrow. Part of the exhaust gas passes through the filter 74 and the first expansion chamber
13 to the atmosphere from the branch pipe 214 through the outlet pipe 213,
Further, the rest flows from the second expansion chamber 23 directly into the outlet pipe 213 and is discharged into the atmosphere. Then, the particulates on the filter 74 are ignited and burned. The ventilation resistance of the outlet pipe 213 and the opening degree of the second control valve 46 are adjusted so that the flow rate of exhaust gas flowing through the filter 74 is about 1/10 of the total flow rate of exhaust gas.

However, in the third embodiment, since the inlet pipe 211 and the outlet pipe 213 are a single pipe, the configuration is further simplified as compared with the first and second embodiments.

FIG. 8 shows a fourth embodiment. Explaining the portion of the configuration different from that of the third embodiment, the first control valve 41 is provided in the branch pipe 212 connected to the inlet pipe 211, and the third control valve 215 is provided in the middle of the outlet pipe 213. When collecting particulates,
The first and second control valves 41 and 46 are closed, and the third control valve 215 is fully open. Therefore, the exhaust gas is supplied to the inlet pipe 211, the first casing 11, the filter 74 as shown by the solid arrow.
Then, the gas flows in the order of the outlet pipe 213 and is discharged into the atmosphere. When the filter 74 is regenerated, the electric heater 75 is energized to generate heat,
Further, the first and second control valves 41 and 46 are opened, and the third control valve 2
15 will close. Therefore, a part of the exhaust gas flows from the branch pipe 212 into the second expansion chamber 23, passes through the filter 74 and flows into the first expansion chamber 13, and then passes through the branch pipe 214, as shown by a dashed arrow. It is discharged into the atmosphere from the outlet pipe 213. The rest of the exhaust gas that does not flow through the filter 74 flows into the first expansion chamber 13 through the inlet pipe 211, and is discharged into the atmosphere through the branch pipe 214 and the outlet pipe 213. During this time, the particulates on the filter 74 are ignited and burned to regenerate the filter. The ventilation resistance of the inlet pipe 211 and the opening degree of the first control valve 41 are adjusted in advance so that the exhaust gas flowing through the filter 74 becomes about 1/10 of the total exhaust gas flow rate during filter regeneration.

Therefore, the effect of the fourth embodiment is similar to that of the third embodiment.

〔The invention's effect〕

As described above, according to the present invention, the configuration for backflowing the exhaust gas in the filter is simplified, and as a result, special piping is not required as in the conventional case, and the exhaust emission control device is miniaturized to the vehicle. Easy to mount. Also, because the exhaust gas backflow in the muffler is used for the filter,
The pressure loss due to the exhaust gas line is reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a time of collecting particulates in the first embodiment, FIG. 2 is a front view showing a clamp, FIG. 3 is a cross-sectional view showing a filter regeneration in the first embodiment, and FIG. FIG. 5 is a sectional view showing a filter regeneration routine, FIG. 5 is a sectional view showing a second embodiment, FIG. 6 is a flowchart showing an adsorbent regeneration routine, FIG. 7 is a sectional view showing a third embodiment, and FIG. It is sectional drawing which shows 4 Example. 13 ... First expansion chamber, 23 ... Second expansion chamber, 31, 211 ... Inlet pipe, 32
... first inlet pipe, 33 ... second inlet pipe, 36 ... first outlet pipe, 37 ...
2nd outlet pipe, 41 ... 1st control valve, 46 ... 2nd control valve, 71 ... Housing, 74 ... Filter, 75 ... Electric heater, 91 ... Electronic control part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kotaro Hayashi 1 Toyota-cho, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd. (72) Shinichi Takeshima 1-cho, Toyota City, Aichi Prefecture Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A filter provided in a passage connecting the first and second expansion chambers of the muffler for collecting particulates in exhaust gas, and an inlet means for introducing the exhaust gas into the first expansion chamber. An outlet means for discharging the exhaust gas in the second expansion chamber to the outside and a second expansion chamber side of the filter for burning the particulates trapped on the filter when the filter is regenerated. Ignition means and flow path control means for changing the path of the exhaust gas are provided, and the flow path control means, when the filter is regenerated, at least part of the exhaust gas guided by the inlet means is in the second expansion chamber. An exhaust emission control device for a diesel engine, characterized in that the exhaust gas in the first expansion chamber is discharged to the outside.