JPH0627501B2 - Exhaust particulate removal device for diesel engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an exhaust particulate removal device for a diesel engine.

[Conventional technology and problems]

Exhaust gas of a diesel engine contains combustible fine particles made of a carbonized compound, that is, particulates, and when the particulates are released to the atmosphere, air pollution is caused. Therefore, conventionally, a diesel engine is provided with a particulate collection filter in the exhaust passage in order to prevent particulates from being released to the atmosphere. However, when the amount of particulates collected by the filter increases, the pressure loss in the exhaust passage increases,
For this reason, the particulates on the filter must be burned out regularly.

As a device for burning and removing particulates,
Japanese Patent Application Laid-Open Publication No. Sho-A-Kokai discloses a system in which air is introduced from the downstream side of the filter by the engine negative pressure generated in the intake system to burn particulates by a burner, and the regenerated gas is circulated in the intake system.
No. 59-77022. However, this conventional device has a problem that the structure is complicated because the filter is regenerated by the burner requiring the secondary air. Further, valves are required on the upstream side and the downstream side of the filter in order to generate a backflow of air near the filter during regeneration, but if the valve is not sufficiently closed, air backflow is less likely to occur. This causes a problem that reproduction becomes difficult. Further, when the regenerated gas is circulated in the intake system, fine particles in the regenerated gas are introduced into the combustion chamber, so that the fine particles may cause wear on the inner wall of the cylinder. Debris can get caught between the intake valve and the valve seat and damage them.

The present invention has been made for the purpose of obtaining an exhaust particulate removal device that has a simple structure, can reliably regenerate the filter, and does not impair the durability of the engine.

A configuration in which a heater is arranged on the downstream side of the filter as in the present invention is disclosed in JP-A-55-131518, but this is a configuration in which gas is made to flow from the heater side to the filter during filter regeneration. I don't have it.

[Means for solving problems]

An exhaust particle removing device according to the present invention is provided in an exhaust passage of a diesel engine, and directs an inlet part to an upstream side in an exhaust gas flow direction at the time of collecting particles and an outlet part to a downstream side in an exhaust gas flow direction. A filter, a heater provided near the outlet of the filter, a first valve that opens and closes a passage that connects the upstream side and the downstream side of the filter, and exhaust gas near the inlet end of the filter. And a second valve that opens and closes a passage communicating with the pipe. The first and second valves are closed when particulates are collected to allow the exhaust gas to flow from the inlet part to the outlet part of the filter, and when the filter is regenerated, the valve is opened to remove the exhaust gas in the filter. Flow from the outlet to the inlet.

〔Example〕

 The present invention will be described below with reference to illustrated embodiments.

FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 shows the particulate collection, and FIG. 2 shows the filter regeneration. An upstream partition wall 12 and a downstream partition wall 13 are provided in the housing 11. The upstream partition wall 12 extends from the housing upper wall 11a located on the inlet port 18 side toward the outlet port 22, and a first passage 14 is formed between the upstream partition wall 12 and the housing right wall 11b. Further, the downstream partition wall 13 extends from the outlet port 22 along the left wall 11c of the housing,
A second passage 15 is formed between the housing and the left wall 11c. The filter 16 includes an upstream partition wall 12 and a downstream partition wall 1.
3a, and the inlet portion 16a is provided on the upstream side (downward in the figure) in the exhaust gas flow direction during particulate collection.
To the downstream side of the exhaust gas flow direction (upper side in the figure)
The outlet portion 16b is arranged to face. The electric heater 17 is provided near the outlet 16b of the filter 16.

An inlet port 18 through which exhaust gas flows is formed on the upstream side of the first passage 14, and a hole 19 is formed in a portion of the upstream partition wall 12 near the housing upper wall 11a. The hole 19 is opened and closed by the first valve 21. This first
The valve 21 is closed as shown in FIG. 1 at the time of collecting particulates, but is opened as shown in FIG. 2 at the time of filter regeneration. The outlet port 22 formed on the downstream side of the first passage 14 and the second passage 15 is an exhaust pipe (not shown).
The downstream side portion of the first passage 14 of the outlet port 22 is opened and closed by the second valve 23. Second valve 2
No. 3 is closed as shown in FIG. 1 at the time of collecting particulates, but is opened as shown in FIG. 2 at the time of filter regeneration. When the second valve 23 is opened, the vicinity of the inlet 16a of the filter 16 is directly communicated with the exhaust pipe.

The first and second valves 21, 23 are opened and closed by diaphragm devices 31, 32, respectively. In the diaphragm device 31, the inside of the shell 33 is partitioned by the diaphragm 334 to form the variable pressure chamber 35, and
5 is provided with a spring 36. The diaphragm 34 is connected to one end of an arm 38 rotatably attached to the pin 37, and the other end of the arm 38 is connected to the first valve 21. The negative pressure or the atmospheric pressure is selectively introduced into the variable pressure chamber via the negative pressure switching valve 39. Then, when the atmospheric pressure is introduced into the variable pressure chamber 35, the diaphragm 34 is displaced by the spring 36 so as to increase the volume of the variable pressure chamber 35, as shown in FIG. Closes the hole 19. On the other hand, when a negative pressure is introduced into the variable pressure chamber 35, the diaphragm 34 compresses and displaces the spring 36, as shown in FIG. 2, whereby the first valve 21 opens the hole 19.

The diaphragm device 32 that drives the second valve 23 also has the same structure as the diaphragm device 31, and the diaphragm 41 is connected to the second valve 23 via the rod 42.
Negative pressure or atmospheric pressure is selectively introduced into the variable pressure chamber 43 via the negative pressure switching valve 44.

Pressure sensors 45 and 46 are provided in the first passage 14 and the second passage 15, respectively, in order to detect that it is necessary to regenerate the filter 16 due to an increase in the amount of particulates accumulated in the filter 16, and A temperature sensor 47 is provided in the first passage 14 and downstream of the pressure sensor 45. When the pressure loss due to the filter 16 detected by the pressure sensors 45 and 46 exceeds a predetermined value, the regeneration control of the filter 16 is started. This predetermined value changes with the engine speed and the engine load.

At the start of the regeneration control, first, the negative pressure switching valves 39, 44 are switched so that the variable pressure chambers 35, 4 of the diaphragm devices 31, 32 are switched.
Negative pressure is led to 3, which results in the first and second valves 2
1, 23 open the hole 19 and the outlet port 22, respectively. At this time, most of the exhaust gas is discharged from the first passage 14 directly to the exhaust pipe through the second valve 23, or passes through the hole 19 and flows into the second passage 15 to be discharged to the exhaust pipe. Then, a part of the exhaust gas flows from the hole 19 to the electric heater 17 side, passes through the filter 16, and passes through the second valve 23.
Exhausted to the exhaust pipe. Then, the electric heater 17 generates heat, the particulates accumulated on the filter 16 in the vicinity of the heater 17 are ignited first, and the flame gradually spreads downstream. Then, all the particulates deposited on the filter 16 are burned, and the regeneration of the filter 16 is completed. After this, the negative pressure switching valve 3
9, 44 are switched to introduce atmospheric pressure into the variable pressure chambers 35, 43 of the diaphragm devices 31, 32, and the first and second valves 21, 23 are closed.

3 and 4 show the combustion state of the particulate P on the filter 16 during regeneration. FIG. 3 shows the start of reproduction, at which time the particulate P
Exists up to every other plug 16d provided at the outlet 16b of each filter substrate 16c provided in parallel.
Exhaust gas flows into the filter 16 from the outlet portion 16b along the arrow, passes from the back surface of the filter substrate 16c to the surface on which the particulates P are accumulated, and enters the inlet portion 16a (see FIGS. 1 and 2). ) To. Particulate P is 4th
As shown in the figure, the material adjacent to the heater 17 is ignited and gradually burned to be removed. Then, during this regeneration, the exhaust gas is discharged from the filter substrate 16c to the particulate P.
Since it flows toward, the temperature of the exhaust gas passing through the filter base material 16c can be kept as low as possible,
Even if the amount of particulate P deposited is large, there is no risk of burning.

On the other hand, at the time of collecting the particulates, the first and second valves 21 and 23 are closed, and all the exhaust gas is discharged to the first
As shown in the figure, from the inlet portion 16a of the filter 16 to the outlet portion 16a
b to the exhaust passage through the heater 17 and the second passage 15.

The first and second valves 21, 23 and the electric heater 17 are controlled based on the output signal of the electronic control unit 50. As shown in FIG. 1, the electronic control unit 50 comprises a microcomputer, and a central processing unit (CPU) 5
1, a read only memory (ROM) 52, a random access memory (RAM) 53, an A / D converter 54, and an input / output (I / O) port 55, which are interconnected by a bus line 56. . Pressure sensors 45 and 46, a temperature sensor 47, and a load sensor 48 are connected to the A / D converter 54. The rotation speed sensor 49 is connected to the I / O port 55, and the negative pressure switching valves 39 and 44 and the electric heater 17 are connected via a drive circuit 57. The load sensor 48 is attached to a lever of a fuel injection pump (not shown) and detects the opening degree of this lever which is interlocked with the accelerator pedal, and the magnitude of this opening degree is detected as the magnitude of the load. On the other hand, the rotation speed sensor 49 detects the engine rotation speed.

5 and 6 show the regeneration control of the filter 16 performed by the electronic control unit 50.

FIG. 5 shows a main routine that is performed for each predetermined crank angle. First, at step 101, it is judged if the reproduction condition is satisfied. This regeneration condition is obtained by reading a map of the pressure loss of the filter 16 with respect to the engine speed and the engine load, which is stored in advance in the ROM 52, and is corrected according to the exhaust gas temperature, as is conventionally done. Desired. If the reproduction condition is satisfied, the flag f is set to 1 in step 102.

FIG. 6 shows a reproduction routine executed at regular intervals (every 200 msec in this embodiment). First, it is determined in step 201 whether or not the flag f is set to 1. If the flag f is not set, this routine ends as it is, but if the flag f is set, step 202
Then, it is determined whether the value of Casunta C is 600 or more.
The counter C is incremented by 1 each time step 206 described later is executed, and therefore, at step 202, it is judged if 120 seconds have elapsed since the counter addition started.
The counter C is initially set to 0 when the program is started.
It is set to 0 and is 0 when step 202 is executed for the first time. Therefore, first, the routine proceeds to step 203, where the first and second valves 21 and 23 are opened. Next, at step 204, it is judged if the counter C is 150 or more, that is, if 30 seconds have elapsed since the addition of the counter started. When the step 204 is executed for the first time, the counter C is 0, so that the flow first proceeds to the step 205,
The electric heater 17 is energized. Next, at step 206, the value of the counter C is incremented by 1, and this routine ends.

After 200 msec, this reproducing routine is executed again, but if the flag f is set, steps 201, 202, 20
3, 204, 205 and 206 are sequentially executed, and the counter C is incremented by 1. Then, 30 seconds after the regeneration process of the filter 16 is started, the counter C becomes 150, so that an affirmative decision is made in step 204, and the routine proceeds to step 207, where the energization of the electric heater 17 is stopped. Next, at step 206, the counter C is added so that the value of the counter C exceeds 150. After that, when this reproduction routine is interrupted, steps 201, 202, 203, 204, 20
It is executed in the order of 7,206. Then, 120 seconds after the regeneration process of the filter 16 is started, the counter C becomes 600, so that an affirmative decision is made in step 202, and step 2
At 08, the first and second valves 21 and 23 are closed, and at step 209, the flag f and the counter C are reset to 0, respectively.

When a plurality of electric heaters 17 are provided and each one is energized, steps 204, 205 and 207 may be executed for each electric heater. Further, it goes without saying that the opening time of the valves 21 and 23 and the energization time of the heater 17 are not limited to those in the above embodiment.

〔The invention's effect〕

As described above, according to the present invention, when the filter is regenerated, the exhaust gas flows from the filter base material side toward the particulates, so that the heat of combustion of the particulates is not conducted to the filter base material, and the filter base material is Since it is cooled by the exhaust gas at a relatively low temperature, it is not damaged by heat even if the amount of particulates deposited is large. Further, the present invention is
Since a special mechanism such as a burner is not required to regenerate the filter, the structure is simple and the filter can be regenerated reliably. Further, since the present invention does not circulate the regenerated gas to the intake system, it is advantageous in terms of engine durability.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention and is a cross-sectional view showing the particulate collection, FIG. 2 is a cross-sectional view showing the filter regeneration of the apparatus of FIG. 1, and FIG. 3 is a filter at the start of regeneration. 4 is a sectional view of the filter in the middle of regeneration, FIG. 5 is a flowchart showing a main routine, and FIG. 6 is a flowchart showing a regeneration routine. 14 ... 1st passage, 15 ... 2nd passage, 16 ... Filter, 16a ... Inlet part, 16b ... Outlet part, 17 ... Heater, 19 ... Hole, 21 ... 1st valve, 23 ... 2nd valve.

Claims (1)

[Claims] 1. A filter provided in an exhaust passage of a diesel engine, the inlet of which is directed to the upstream side in the exhaust gas flow direction when collecting particulates, and the outlet of which is directed downstream in the exhaust gas flow direction. A heater provided near the outlet of the filter, a first valve that opens and closes a passage that connects the upstream side and the downstream side of the filter, and a passage that connects the vicinity of the inlet of the filter to the exhaust pipe. And a second valve for opening and closing the filter, the first and second valves being closed when collecting fine particles to allow exhaust gas to flow from the inlet to the outlet of the filter and opened when the filter is regenerated. Then, the exhaust gas removing apparatus for a diesel engine, wherein the exhaust gas in the filter is caused to flow from the outlet portion to the inlet portion.