JPH0627497B2 - Exhaust gas purification device for diesel engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust emission control device for a diesel engine, and more particularly to a device for treating particulates and odor components discharged from the diesel engine.

[Conventional technology]

Due to incomplete combustion in diesel engines, the exhaust gas contains particulates (unburned hydrocarbon components, etc.) that are sources of black smoke, and odor components (aldehydes, etc.) that are sources of malodor. ing. In order to remove the particulates in the exhaust gas, many ideas have been made to provide a ceramic filter. In addition, JP-A-57-159
Japanese Patent No. 908 describes an exhaust emission control device in which an exhaust smoke adsorption carrier is arranged in an exhaust system of an engine. This is a device capable of desorbing odorous components.

[Problems to be solved by the invention]

In order to remove particulates and odorous components, it is advantageous to install a separate removal device suitable for each, so that a filter for collecting particulates in exhaust gas and an adsorbent for absorbing odorous components are installed. Arranging in series would be generally considered.

However, the filter becomes clogged over time and the odorous adsorbent can no longer adsorb when its equilibrium adsorption capacity is reached. Therefore, both the filter and the adsorbent must be regenerated at the proper time. The regeneration of the filter is to burn the accumulated particulates, and the regeneration of the adsorbent is to use it at a low temperature where the equilibrium adsorption amount increases after raising the temperature to a high temperature where the equilibrium adsorption amount decreases. . However, when the adsorbent is arranged downstream of the filter, there is a problem that the adsorbent is deteriorated by the particulate combustion heat when the filter is regenerated.

[Means for solving problems]

The exhaust purification device for a diesel engine according to the present invention has a bypass passage connected to an exhaust passage, and a filter for collecting particulates of exhaust gas from an upstream side of the bypass passage and an adsorbent for adsorbing odorous components are arranged, The forward flow of the exhaust gas is generated in the bypass pipe according to a certain operating state to perform purification by the filter and the adsorbent, and the reverse flow of the regenerated gas is passed through the bypass pipe according to another operating state. It is characterized in that the adsorbent and the filter are regenerated by generation.

〔Example〕

As shown in FIG. 1, the diesel engine body 10 includes an intake manifold 12 and an exhaust manifold 1 as is well known.
4 are connected. The intake manifold 16 has an intake pipe 16
And a throttle valve 17 is arranged in the intake pipe 16.
Further, a fuel injection device 18 is attached to the engine body 10. As is well known, the fuel injection device 18 has an accelerator lever for controlling the fuel injection amount, and in this embodiment, an accelerator lever opening degree sensor 20 for detecting the opening degree of the accelerator lever is provided.

An exhaust pipe 22 is connected to the exhaust manifold 14, and a muffler 24 is attached to the rearmost portion of the exhaust pipe 22. A bypass pipe 26 is connected to the exhaust pipe 22, and a filter 28 and an odor adsorbent 30 are arranged in this bypass pipe 26 in order from the upstream side. The filter 28 is composed of a ceramic honeycomb filter and collects particulates in the exhaust gas. Immediately downstream of the filter 28, an electric heater 32 for igniting the particulates deposited on the filter 28 is arranged. Activated carbon is generally known as an odor adsorbent. Further, an adsorbent obtained by coating a monolithic ceramic cordierite base material with gamma alumina can be used, and other adsorbents can also be used. Further, a connecting pipe 34 is provided that connects the upstream and downstream sides of the bypass pipe 26 with respect to the filter 28 and the intake side of the engine, that is, the intake pipe 16. A first valve 36 for controlling the flow of exhaust gas to the bypass pipe 26 is provided at an upstream connecting portion between the exhaust pipe 22 and the bypass pipe 26, and a connecting pipe is provided at a connecting portion between the bypass pipe 26 and the connecting pipe 34. A second valve 38 is provided to control the flow of regeneration gas to 34.

The regeneration gas is air or exhaust gas flowing in the reverse direction in the bypass pipe 26. In this embodiment, air is introduced from the second intake pipe 40 to the bypass pipe 26 at a position downstream of the adsorbent 30. This second intake pipe 40
Extends along the exhaust pipe 22 and thus the second intake pipe 40
The air passing through is heated by the exhaust heat. The second intake pipe 40 is connected to the bypass pipe 26, and a suitable air cleaner (not shown) is arranged at the upstream end thereof.
The second intake pipe 40 is connected to the connecting pipe 34 via the bypass pipe 26.
Throttle valve 1 arranged in the first intake pipe 16
Since the negative pressure is generated on the downstream side of the throttle valve 17, the air can be introduced from the second intake pipe 40 by the negative pressure. Then, in order to control the introduction of air from the second intake pipe 40, the bypass pipe 2
An introduction valve 42 is arranged at a connecting portion between the sixth intake pipe 40 and the second intake pipe 40.

The first valve 36, the second valve 38, and the introduction valve 42 described above.
Both are valves whose one end is rotatably instructed, and the respective pipelines can be selectively switched. Each valve 3
6, 38 and 42 are respectively driven by a negative pressure actuated actuator 44 having a diaphragm (not shown),
The negative working pressure is supplied from a vacuum tank (not shown) via a solenoid valve 46. Further, the throttle valve 17 arranged in the intake pipe 16 also has the same negative pressure actuated actuator 4
Driven by 4. However, in this case, the operating negative pressure is supplied from a vacuum tank (not shown) via the solenoid valve 46, and the operating negative pressure is bleed to the atmosphere by the second solenoid valve 48. The throttle valve 17 is controlled by controlling the bleed amount.
The opening can be adjusted.

The first valve 36, the second valve 38, and the introduction valve 42 are controlled so as to have the three positional relationships shown by (A), (B), and (C) in FIG. 3, respectively. The positional relationship of (A) is referred to as odor trap non-operation, and the first valve 36 is the bypass pipe 26.
Is closed to open the exhaust pipe 22, and the second valve 38 is connected to the communication pipe 34.
And the inlet valve 42 closes the second intake pipe 40. The positional relationship of (B) is called odor trap operation, and
Valve 36 opens the bypass pipe 26 and closes the exhaust pipe 22,
The second valve 38 closes the connecting pipe 34, and the introduction valve 42 closes the second intake pipe 34. At this time, the exhaust gas flowing from the exhaust manifold 14 enters the bypass pipe 26, passes through the filter 28 and the intake agent 30, and then returns to the exhaust pipe 22 and is discharged from the muffler 24. The positional relationship of (C) is referred to as an odor trap regeneration operation, the first valve 36 closes the bypass pipe 26, the second valve 38 opens the connecting pipe 34, and the introduction valve 42 opens the second intake pipe 40. Open and close bypass pipe 26 downstream of the opening. Therefore, at this time, the exhaust gas passes only through the exhaust pipe 22, and the air introduced from the second intake pipe 36 flows backward through the bypass pipe 26 and is further sucked into the engine through the connecting pipe 34. The (warmed) air desorbs the odorous components adsorbed on the adsorbent 30. Further, a part of the particulates deposited on the filter 28 is also purified by backwashing.

Further, a first temperature sensor 50 is attached to the exhaust pipe 22 at a position upstream of the filter 28, and the bypass pipe 2
A second temperature sensor 52 is attached to 6 at a position downstream of the adsorbent 30. These temperature sensors 50, 52
Signals from the accelerator lever opening sensor 20, the engine speed sensor, and the cooling water temperature sensor are input to the control device 54. The control device 54 is a microcomputer including a central processing unit (CPU) 56 having arithmetic and control functions, a read only memory (ROM) 58 for storing programs, and a random access memory (RAM) 60 for storing data and the like. Each of these elements are connected to each other by a bus together with an input / output (I / O) port 62. The controller 54 controls the first and second valves 36 and 38 and the introduction valve 4 based on the input signals from the respective sensors.
2. A control signal is sent to each solenoid valve 46, 48 for controlling the throttle valve 17, and a control signal is sent to the electric heater 32.

FIG. 2 shows the first and second valves 36 and 38 and the introduction valve 4.
2. A flow chart for controlling the throttle valve 17 is shown. First, at step 60, the accelerator opening and the engine speed are read. The accelerator opening and the engine speed are stored in the RAM 60 as the latest data, and the read accelerator opening is used in step 61 to determine whether the engine is in the idle state. If the engine is in the idle state, the routine proceeds to step 62, where it is judged if the temperature of the exhaust gas detected by the first temperature sensor 50 is higher than a predetermined value. The predetermined value T ₁ is set as a temperature at which the adsorbent 30 is not adversely affected. For example, when flammable activated carbon is used as the adsorbent, the predetermined value T ₁ is set at a value equal to or lower than the ignition temperature or deteriorates. The temperature is set so as not to promote deterioration in the case of an easily adsorbent. The second temperature sensor 52 is the adsorbent 30.
Monitor for unusual high temperatures. If YES in step 63, the process proceeds to step 64 to activate the odor trap, and FIG. 3 (B)
The first valve 36 opens the bypass pipe 26 as shown in FIG. As a result, the exhaust gas passes through the bypass pipe 26 in the forward direction, particulates are collected by the filter 28, and then the odorous component is adsorbed by the adsorbent 30. Especially, since the particulates are first purified, the adsorbent 3
No particulates adhere to the surface of 0, and the original adsorption performance of the adsorbent 30 is maintained.

If NO in step 61, the process proceeds to step 65. In step 65, it is determined whether the operating state is in the regeneration area of the adsorbent 30. The regeneration area of the adsorbent 30 is set as a two-dimensional map of the engine load and the engine speed, and is removed at the time of high rotation and high load. Step 6
If NO in step 5, the process proceeds to step 66, and if NO in step 63, the process proceeds to step 66 to make the odor trap inoperative (FIG. 3 (A)). In this case, since the bypass pipe 26 and the connecting pipe 34 are closed, the exhaust gas does not pass through the bypass pipe 26 and the connecting pipe 34, and the odor component previously adsorbed is maintained in the adsorbent 30.

If YES in step 65, the flow proceeds to step 67, in which the opening degree of the throttle valve 17 is set according to the engine load and the rotational speed, and in step 68, the odor trap regeneration operation (FIG. 3 (C)) is performed. In the state shown in FIG. 3C, the second air extends along the exhaust pipe 22.
Is introduced from the intake pipe 40 into the bypass pipe 26, flows in the reverse direction through the adsorbent 30 and the filter 28 in the bypass pipe 26, and is sucked into the intake side of the engine via the connecting pipe 34. Air is naturally also sucked from the first intake pipe 16. The air introduced from the second intake pipe 40 is heated,
When passing through the adsorbent 30, the adsorbent 3 is desorbed by removing odorous components.
0 is regenerated and the deodorized odor component is carried to the intake side of the engine. This air further passes through the filter 28, and the particulates adhering to the upstream partition wall surface of the filter 28 are backwashed from the downstream side. As a result, some of the particulates are also desorbed. Since the particulates and odorous components thus desorbed are combustible components in large quantities, they burn in the engine combustion chamber, and when discharged again, the particulates and odors disappear. Since the regeneration of the adsorbent 30 is performed by fresh intake air instead of exhaust gas,
The adsorbent 30 can be sufficiently regenerated. The regenerated adsorbent 30 can be prepared for odor component purification at the time of the next idle. The electric heater 32 can be periodically energized by the engine speed integrated value or the like. This energization is performed when the regeneration gas is flowing back to the bypass pipe, and the combustible and odorous component desorbed from the adsorbent 30 burns to promote regeneration of the filter 28.

〔The invention's effect〕

As described above, according to the present invention, the filter and the adsorbent are arranged in order to improve the exhaust gas purification performance, and the regeneration gas is flowed in the opposite direction so that the filter and the adsorbent are better regenerated. You can In particular, even when an electric heater is used for filter regeneration, the adsorbent is not overheated and the performance of the adsorbent is maintained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a control flowchart of FIG. 1, and FIG. 3 is a diagram for explaining the operation of each valve. 22 ... Exhaust pipe, 26 ... Bypass pipe, 28 ... Filter, 30 ... Adsorbent, 34 ... Connection pipe, 36, 38 ... Valve, 40 ... Second intake pipe.

Claims (1)

[Claims] 1. A bypass passage is connected to an exhaust passage of a diesel engine, and a filter for collecting particulates of exhaust gas and an adsorbent for adsorbing odorous components are arranged in this bypass passage in order from the upstream side. Generates a forward flow of exhaust gas in the bypass pipe according to the operating condition to perform purification by the filter and the adsorbent, and generates a reverse flow of regenerated gas in the bypass pipe according to other operating conditions An exhaust emission control device for a diesel engine, characterized in that the adsorbent and the filter are regenerated by performing the above.