JPH0625537B2 - Exhaust gas purification device for diesel engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an exhaust emission control device for a diesel engine, and more particularly to a device for treating odorous components discharged from a diesel engine.

[Prior Art] Japanese Patent Application Laid-Open No. 57-159908 describes an exhaust gas purification device in which an exhaust smoke adsorption carrier is arranged in an exhaust system of an engine.

Due to incomplete combustion in a diesel engine, the exhaust gas contains unburned hydrocarbon components that are sources of black smoke and odor components (aldehydes and the like) that are sources of malodor. This odorous component is emitted in large quantities, especially when the engine is idle, and emits a bad odor around the stopped vehicle. Therefore, it is preferable to adsorb the odorous component to the adsorbent as described in the above publication.

[Problems to be solved by the invention]

The adsorbent generally has an equilibrium adsorption amount according to its capacity, and when the adsorbed odorous component reaches the equilibrium adsorption amount, further adsorption cannot be performed. The equilibrium adsorption amount generally becomes smaller as the temperature rises, and the odorous component adsorbed at low temperature is desorbed at high temperature. Therefore, as described in the above publication, the odorous component can be adsorbed when the engine is started, and the odorous component can be desorbed by the heat after warming up. Thereby, the adsorbent is regenerated and can be adsorbed again at a low temperature.

However, odor adsorbents generally have low durability to high temperatures and have a problem that they deteriorate when exposed to high temperatures for a long time.

[Means for solving problems]

An exhaust emission control device for a diesel engine according to the present invention has a bypass passage connected to an exhaust passage, and an adsorbent for adsorbing an odor component of exhaust gas is arranged in the bypass passage, and the flow of the exhaust gas to the bypass passage is controlled. A valve device for
An idle detecting means for detecting an idle state of the engine, and a means for opening the valve device after a predetermined time delay after the idle is detected by the idle detecting means are provided.

〔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
Are connected. 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. or,
A throttle valve 21 is arranged in the intake pipe 16.

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 an odor adsorbent 28 is arranged in the bypass pipe 26. 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, the adsorbent 2 of the bypass pipe 26
A connecting pipe 30 that connects the downstream side of 8 and the intake side of the engine, that is, the intake pipe 16 is provided. A bypass valve 32 for controlling the flow of exhaust gas to the bypass pipe 26 is provided at an upstream side connecting portion between the exhaust pipe 22 and the bypass pipe 26, and a bypass valve 32 is provided at a connecting portion between the bypass pipe 26 and the connecting pipe 30. A regeneration valve 34 is provided to control the flow of the exhaust gas.

A second intake pipe 36 is provided to introduce air into the bypass pipe 26 upstream of the adsorbent. The second intake pipe 36 extends along the exhaust pipe 22, so that the air passing through the second intake pipe 36 is heated by the exhaust heat. The second intake pipe 36 is connected to the bypass pipe 26, and an appropriate air cleaner (not shown) is arranged on the upstream side thereof. When the second intake pipe 36 is electrically connected to the connecting pipe 30 via the bypass pipe 26, the throttle valve 21 arranged in the first intake pipe 16 is throttled, whereby negative pressure is generated on the downstream side of the throttle valve 21. Therefore, this negative pressure causes the second intake pipe 3 to
Air can be introduced from 6. Then, in order to control the introduction of air from the second intake pipe 36, an introduction valve 38 is arranged at the connecting portion between the bypass pipe 26 and the second intake pipe 36.

The bypass valve 32, the regeneration valve 34, and the introduction valve 38 described above.
Is a valve whose one end is rotatably supported, and each of the pipe lines can be selectively switched. Each valve 3
2, 34 and 38 are each driven by a negative pressure operation type actuator 40 having a diaphragm (not shown), and the operation negative pressure is supplied from a vacuum tank (not shown) through each solenoid valve 42. Further, the throttle valve 21 arranged in the intake pipe 16 also has a similar negative pressure actuated actuator 40.
Driven by. However, in this case, the operating negative pressure is supplied from a vacuum tank (not shown) via the solenoid valve 42, and the operating negative pressure is bleed to the atmosphere by the second solenoid valve 44.
The opening degree of the throttle valve 21 can be adjusted by controlling the bleed amount.

The bypass valve 32, the regeneration valve 34, and the introduction valve 38 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 called odor trap non-operation, the bypass valve 32 closes the bypass pipe 26 to open the exhaust pipe, the regeneration valve 34 and the connecting pipe 30 are closed, and the introduction valve 38 is set to the second intake pipe 36. Close. The positional relationship of (B) is called an odor trap operation, the bypass valve 32 opens the bypass pipe 26 and closes the exhaust pipe 22, the regeneration valve 34 closes the connecting pipe 30, and the introduction valve 38 sets the second intake pipe 38.
Close. At this time, the exhaust gas flowing from the exhaust manifold 14 enters the bypass pipe 26, passes through the adsorbent 28, and then returns to the exhaust pipe 22 again and is discharged from the muffler 24. The positional relationship of (C) is called an odor trap regeneration operation, the bypass valve 32 closes the bypass pipe 26, and the regeneration valve 3
4 opens the connecting pipe 30 and closes the bypass pipe 26 downstream of its opening, and the inlet valve 38 opens the second intake pipe 36. Therefore, at this time, the exhaust gas is exhaust gas 2
The air that has passed only 2 and is introduced from the second intake pipe 36 is sucked into the engine through the bypass pipe 26 and the connecting pipe 30, and the odor component that has been adsorbed by the adsorbent 28 by this (warmed) air. Desorbs.

Further, a first temperature sensor 46 is attached to the exhaust pipe 22 at a position upstream of the adsorbent 28, and the bypass pipe 26
A second temperature sensor 48 is attached at a position downstream of the adsorbent 28. Signals from the temperature sensors 46, 48, the accelerator lever opening sensor 20, the engine speed sensor, and the cooling water temperature sensor are input to the control device 50. The control device 50 is a microcomputer including a central processing unit (CPU) 52 having arithmetic and control functions, a read only memory (ROM) 54 for storing programs, and a random access memory (RAM) 56 for storing data and the like. Each of these elements is connected to each other by a bus together with an input / output (I / O) port 58. Control device 5
0 is a bypass valve 32 based on the input signal from each sensor,
A control signal is sent to each solenoid valve 42, 44 for controlling the regeneration valve 34, the introduction valve 38, and the throttle valve 21.

FIG. 2 shows the bypass valve 32, the regeneration valve 34 and the introduction valve 3.
8. A flow chart for controlling the throttle valve 21 is shown. First, at step 60, the accelerator opening and engine speed are read. The accelerator opening and engine speed are stored in the RAM 56 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, proceed to step 62 and measure the time immediately after the engine becomes idle.
At, it is determined whether the measurement time has passed a predetermined time. This predetermined time is set such that the exhaust gas temperature does not adversely affect the adsorbent 28 after the high load operation is shifted to the idle at once. If YES in step 63, the flow proceeds to step 64 to activate the odor trap, and the bypass valve 32 is opened as shown in FIG. 3 (B). As a result, the exhaust gas passes through the bypass pipe 26 and the odorous component is adsorbed by the adsorbent 28. That is, in the present invention, the odor trap operation is always performed when the engine is idle. However, the temperature of the exhaust gas is delayed so as to be lowered to an appropriate temperature in consideration of the case where the engine becomes idle from a high load.

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 28. The regeneration area of the adsorbent 28 is set as a two-dimensional map of the engine load and the engine speed, and is excluded at the time of high rotation and high load. At this time, the detection values of the temperature sensors 46 and 48 can be used supplementarily. If no in step 65, step 66
Further, if the result is NO in step 63, the process proceeds to step 66, and the odor trap operation (FIG. 3 (A)) is performed. In this case, since the bypass pipe 26 and the connection pipe 30 are closed, the exhaust gas does not pass through the bypass pipe 26 and the adsorbent 28 maintains the adsorbed odor component.

If YES in step 65, the flow proceeds to step 67, in which the opening degree of the throttle valve 21 is set according to the engine load and the rotation speed, and in step 68, the odor trap regeneration operation (FIG. 3 (C)) is performed. In the state shown in FIG. 3C, the air is sucked into the intake side of the engine through the adsorbent 28 from the second intake pipe 36 extending along the exhaust pipe 22, and through the connecting pipe 30. Air is naturally also sucked from the first intake pipe 16. The air introduced from the second intake pipe 36 is heated, and when passing through the adsorbent 28, the odor component is desorbed to regenerate the adsorbent 28, and the desorbed odor component is carried to the intake side of the engine. Since many odorous components are flammable components, the odor disappears when they are burned in the engine combustion chamber and discharged again. Since the regeneration of the adsorbent 28 is performed not by the exhaust gas but by the fresh intake air, the particulates of the exhaust gas do not adhere to the adsorbent 28 during and after the regeneration, and the regenerated adsorbent 28 is It is possible to prepare for the odor component when idle.

In the above embodiment, the second operation is performed during the odor trap regeneration operation.
Air is introduced into the bypass pipe 26 from the intake pipe 36, the adsorbent 28 is regenerated by passing the air through the adsorbent 28, and the regenerated gas is conveyed to the intake side through the connecting pipe 30. is there. However, as another embodiment of the present invention, the connection pipe 30, the second intake pipe 36, the regeneration valve 34, and the introduction valve 38 of FIG. 1 may be omitted. In this case, the odor trap is activated at the time of idling by opening the bypass valve 32 after a predetermined time delay after the idling is detected, and when the idling is finished, the bypass valve is closed to deactivate the odor trap, and further, step 65 of FIG. As described above, the bypass valve 32 is opened again in accordance with the predetermined operation state, and the adsorbent 28 can be regenerated by the exhaust gas having a temperature suitable for regenerating the adsorbent 28 and not degrading the adsorbent 28. it can. this is,
This is possible because the adsorbent 28 is arranged in the bypass pipe 26 and the bypass valve 32 is provided.

In order to delay the opening of the bypass valve 32 after the idle state is detected, instead of performing the time measurement and determination as in steps 62 and 63 in FIG. 2, the bypass valve 32 as in FIG.
Alternatively, the delay valve 41 may be arranged between the actuator 40 and the corresponding negative pressure switching solenoid valve 42. The delay valve 41 includes a throttle passage 41a and a check valve 4
1b is provided in parallel, and when the solenoid valve 42 is switched to introduce a negative pressure, only the throttle passage 42a is used, so that the operation of the actuator 40 is delayed, and conversely, when it is opened to the atmosphere, a check valve. 41b opens.

〔The invention's effect〕

As described above, according to the present invention, when the exhaust gas temperature is not high, the bypass valve can be opened to adsorb the odorous component of the exhaust gas to the adsorbent, and the adsorbent is arranged in the bypass passage. Therefore, the adsorbent can be regenerated under the condition that the exhaust gas is not deteriorated by the high temperature.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention, FIG. 2 is a control flowchart of FIG. 1, FIG. 3 is a diagram for explaining the operation of each valve, and FIG. 4 is a diagram showing a second embodiment. is there. 22 ... Exhaust pipe, 26 ... Bypass pipe, 28 ... Adsorbent, 32 ... Bypass valve.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-62-162714 (JP, A) Actually opened 62-93112 (JP, U) Actually opened 59-157518 (JP, U) Actually opened 62- 41813 (JP, U) Actually opened 62-10223 (JP, U) Special public 62-48048 (JP, B2) Actual public 41-20322 (JP, Y1) Actual public 50-41369 (JP, Y2)

Claims (1)

[Claims] 1. A valve device for connecting a bypass passage to an exhaust passage of a diesel engine, arranging an adsorbent for adsorbing an odor component of exhaust gas in the bypass passage, and controlling a flow of the exhaust gas to the bypass passage. A diesel detecting means for detecting an idle state of the engine; and a means for opening the valve device with a predetermined delay after the idle state is detected by the idle detecting means. Engine exhaust purification device.