JPS62162715A - Exhaust gas cleaning device for diesel engine - Google Patents

Abstract

PURPOSE:To promote refreshing of an absorbing agent and to reduce discharging of odor component, by disposing a catalyst oxide upstream of the odor component adsorbing agent provided with an exhaust passage of a Diesel engine. CONSTITUTION:An engine 10 has an exhaust pipe 22 including a bypass pipe 26 provided with an absorbing agent 28 for absorbing odor component of exhaust gas. In addition, a catalyst oxide 29 is disposed upstream of the absorbing agent 28 of the exhaust pipe 22. Although the catalyst oxide is not activated in idling, odor component of exhaust gas is absorbed to the absorbing agent. When a temperature of exhaust gas increases, the odor component adsorbed to the adsorbing agent is separated. However, since the adsorbing agent is refreshed by the exhaust gas cleaned by the activated catalyst oxide at this time, refreshing is promoted and discharging of odor component is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust purification device for a diesel engine, and more particularly to a device for treating odor components discharged from a diesel engine.

[Conventional technology]

Japanese Unexamined Patent Publication No. 57-159908 describes an exhaust purification device in which a carrier for adsorbing exhaust smoke is arranged in the exhaust system of an engine.

In diesel engines, due to incomplete combustion, the exhaust gas contains unburned hydrocarbon components that are a source of black smoke, as well as odor components (such as aldehydes) that are a source of bad odors. This odor component is emitted in large quantities especially when the engine is idling, emitting a foul odor around the parked car. Therefore, it is preferable to adsorb odor components as described in the above publication. In addition, odor components (
Aldehydes, etc.) become odorless components through oxidation, so placing an oxidation catalyst in the exhaust passage is also an effective odor prevention measure.

[Problem that the invention seeks to solve]

In order to treat odor components in exhaust gas using an oxidation catalyst, it is necessary that the temperature of the exhaust gas is 250° C. to 300° C. or higher. However, many odor components are generated during idling, and the temperature of exhaust gas during idling is as low as 100°C. Therefore, it is not possible to use an oxidation catalyst to treat odor components in exhaust gas during idling.

Therefore, in order to remove the odor components of the FJF gas during idling, it is necessary to use the above-mentioned adsorbent. However, adsorbents generally have an equilibrium adsorption amount that corresponds to their capacity, and once the adsorbed odor components reach the equilibrium adsorption amount, they cannot adsorb any more.The equilibrium adsorption amount generally decreases as the temperature increases. Therefore, the odor components that were adsorbed at low temperatures will be desorbed at high temperatures.Therefore, as stated in the above publication, the odor components are adsorbed when the engine is started, and the heat after warming up causes the odor components to be released. components can be eliminated.

Thereby, the adsorbent is regenerated and can adsorb again at low temperatures. However, when regenerating the adsorbent using high-temperature exhaust gas, the degree of regeneration of the adsorbent cannot be achieved satisfactorily because the exhaust gas used for regeneration itself contains odor components and other particulates. The problem was that it couldn't be done.

[Means for solving problems]

The exhaust purification device for a diesel engine according to the present invention is characterized in that an adsorbent for adsorbing odor components of exhaust gas is disposed in the exhaust passage, and an oxidation catalyst is disposed upstream of the adsorbent.

[For production]

At idle, the oxidation catalyst is not activated, but the odor components of the exhaust gas are adsorbed by the adsorbent. When the temperature of the exhaust gas rises depending on the operating state, the odor components adsorbed by the adsorbent will be desorbed. This adsorbent is supplied with exhaust gas that has passed through an oxidation catalyst placed upstream of the adsorbent, and the adsorbent is regenerated by the exhaust gas purified by the oxidation catalyst that becomes activated due to the rise in temperature. become.

〔Example〕

In FIG. 1, a diesel engine main body 10 includes an intake manifold 12 and an exhaust manifold 1, as is known in the art.
4 are connected. The intake manifold 12 has an intake pipe 16
are concatenated. Furthermore, 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 sensor 20 is provided for detecting the opening degree of the accelerator lever. .

An exhaust pipe 22 is connected to the exhaust manifold 14, and a muffler 24 is attached to the rearmost part of the exhaust pipe 22.

A bypass pipe 26 is connected to the exhaust pipe 22, and an odor absorbent 28 is disposed in the bypass pipe 26.

Activated carbon is generally known as an odor absorbent.

Further, it is also possible to use an adsorbent in which a monolith type ceramisocordite base material is coated with gamma alumina, and further, other adsorbents can also be used. Further, an oxidation catalyst 29 is arranged upstream of the odor absorbent 28. In FIG. 1, the oxidation catalyst 29 is connected to the exhaust pipe 22.
The bypass pipe 26 is disposed on the upstream side of the upstream connecting portion between the bypass pipe 26 and the bypass pipe 26 .

On the other hand, in FIG. 4, the oxidation catalyst 29 is connected to the bypass pipe 2.
6 , the odor absorbent 28 is disposed upstream of the odor absorbent 28 . Incidentally, since FIG. 4 is almost the same as FIG. 1 except for the arrangement of the oxidation catalyst, only the example of FIG. 1 will be described hereinafter.

Furthermore, a connecting pipe 30 is provided that connects the downstream side of the bypass pipe 26 from the adsorbent 28 to the intake side of the engine, that is, the intake pipe 16. A first valve 32 for controlling the flow of exhaust gas to the bypass pipe 26 is provided at the upstream connection between the exhaust pipe 22 and the bypass pipe 26, and a connection pipe is provided at the connection between the bypass pipe 26 and the connection pipe 30. A second valve 34 is provided to control the flow of exhaust gas to 30. The first valve 32 is driven by a known negative pressure operated actuator 36 having a diaphragm. The operating negative pressure is supplied from a vacuum tank (not shown) via a solenoid valve 38.

The solenoid valve 38 has a negative pressure introduction port and an atmosphere introduction boat, and the atmosphere introduction boat further communicates with the atmosphere through a second solenoid valve 40 and bleeds the atmosphere to transfer the operating negative pressure to the first valve. Adjust so that 32 occupies at least three positions. The first valve 32 is in a position where the bypass pipe 26 is closed and the exhaust pipe 22 is opened as shown in FIG. 3(A);
A position where the bypass pipe 26 is opened and the exhaust pipe 22 is closed as shown in FIG. 3(B), and a position where both the bypass pipe 26 and the exhaust pipe 22 are opened as shown in FIG. 3(C). be able to. On the other hand, the second valve 34 is also driven by a negative pressure operated actuator 42, and operating negative pressure is introduced via the electromagnetic valve 44. The second valve 34 is in a position where it closes the connecting pipe 30 and opens the bypass pipe 26 as shown in FIGS.
As shown in C), the connecting pipe 30 can be opened and the bypass pipe 26 can be closed.

Furthermore, a first temperature sensor 46 is attached to the exhaust pipe 22 at a position upstream of the adsorbent 28, and a first temperature sensor 46 is attached to the exhaust pipe 22 at a position upstream of the adsorbent 28.
A second temperature sensor 48 is attached at a position downstream of the adsorbent 28. These temperature sensors 46, 48
Signals from the accelerator lever opening sensor 20, engine speed sensor, and cooling water temperature sensor are input to the control device 50.

The control device 50 is a central processing bag with calculation and control functions!
(CPU) 52, a linear memory (ROM) 54 for storing programs, and a random access memory (RAM) 56 for storing data, etc., and each of these elements has input/output (I/O). ) along with the boat 58 are interconnected by a bus. Control bag 250 sends control signals to solenoid valves 38, 40, 44 to control first and second valves 32, 34 based on input signals from each sensor.

FIG. 2 shows a flowchart for controlling the second valves 32 and 34 shown in FIG. 1. First, in step 60, the accelerator opening degree is read. The accelerator opening degree is stored in the RAM 56 as the latest data, and the read accelerator opening degree is used in step 61 to determine whether the engine is in an idle state. If the engine is idle, proceed to step 62 and activate the odor trap. Figure 3 (B) shows how the odor trap works.
The first valve 32 opens the bypass pipe 26 and closes the exhaust pipe 22, and the second valve 34 opens the connecting pipe 3 as shown in FIG.
It means closing 0. As a result, the exhaust gas passes through the bypass pipe 26, and odor components are adsorbed by the adsorbent 28.

If the answer is NO in Step 1, proceed to Step 63 and disable the odor trap. Odor trap non-operation means that the first valve 32 closes the bypass pipe 26 and opens the exhaust pipe 22, and the second valve 34 closes the connecting pipe 30, as shown in FIG. 3(A). To tell. This prevents the exhaust gas from passing through the adsorbent 28. When the engine is not in an idling state, it means that the vehicle is running, and the adsorbent 28 is not activated when the engine is running, since the amount of odor components produced is generally small. And adsorbent 2
8 is isolated from the exhaust pipe 22, so it receives less heat, and the odor components adsorbed during idling are less likely to be desorbed from the adsorbent 28, and the odor components are retained in the adsorbent 28 and are not released into the atmosphere as they are. .

After Step 63, Step 64) and Stellaf.

Proceed to step 65 and check for changes in operating status, first step 6
In step 4, the exhaust gas temperature is read, and in step 65, it is determined whether the exhaust gas temperature is in the regeneration temperature range.

In the regeneration temperature range, the temperature of the exhaust gas detected by the first temperature sensor 46 is higher than a predetermined temperature suitable for desorbing odor components from the adsorbent 28 and lower than a predetermined temperature at which the adsorbent 28 deteriorates. This range varies depending on the type of adsorbent 28 used. When combustible activated carbon is used as the adsorbent, it is monitored by the second temperature sensor 48 on the outlet side, and when the temperature begins to rise abnormally, it is determined that it is outside the regeneration temperature range. If the answer in step 65 is NO, the process ends with the odor trap inoperative.

If YES in step 65, the process passes through steps 66 and 67 and proceeds to step 68, where the odor trap regeneration operation is performed.The odor trap regeneration operation is shown in FIG. 3(C).
The first valve 32 partially opens the bypass pipe 26 and the second valve 34 opens the connecting pipe 30 as shown in FIG.

In order to partially open the first valve (bypass valve) 32, the accelerator opening degree and engine rotational speed are read in the stainless steel 166, and in step 67, the accelerator opening degree and engine rotational speed are stored in the ROM 54 as a two-dimensional map. The opening degree of the first valve (bypass valve) 32 is determined from the obtained value. In the state shown in FIG. 3(C), most of the exhaust gas passes through the exhaust pipe 22, but the remaining part passes through the bypass pipe 26, flows into the connecting pipe 30, and circulates to the intake pipe 16. By passing the exhaust gas at an appropriate temperature through the bypass pipe 16, the odor components retained in the adsorbent 28 are desorbed from the adsorbent 28, thereby regenerating the adsorbent 28. The desorbed odor components enter the adsorption side of the engine together with the exhaust gas,
It is forced to burn again.

Many of the odor components are flammable, such as aldehydes and hydrocarbons, and are eliminated by combustion. Therefore, the adsorbent 28 is not directly released into the atmosphere. Further, it is preferable that the opening degree of the first valve 32 is determined to correspond to the conventional EGR amount,
A conventional EGR control region can also be added to step 65. Further, in order to control the opening degree of the first valve 32, two
Although two solenoid valves 38 and 40 are used, this could be a single solenoid valve with duty control. Furthermore, a flow control valve such as an EGR valve can also be provided in the middle of the connecting pipe 30.

In the above configuration and operation, when the odor trap is activated as shown in FIG. 3(B), the exhaust gas exhausted from the engine 10 passes through the oxidation catalyst 29 and the odor adsorbent 28, but since the oxidation catalyst 29 is at idle, the oxidation catalyst 29 is not activated. The adsorbent 28 removes odor components that have not been oxidized. Next, as shown in FIG. 3(A), the adsorbent 28 is separated from the exhaust gas and intake sides and holds the adsorbed odor components without emitting them until an appropriate regeneration time comes. Next, at the regeneration time when the oxidation catalyst 29 is activated and the temperature becomes suitable for regeneration of the adsorbent 28, a part of the exhaust gas purified by the oxidation catalyst 29 is adsorbed, as shown in FIG. 3(C). Through the agent 28, the odor components adsorbed on the adsorbent are desorbed and transported to the engine combustion chamber where they are burned. Since the regeneration of the adsorbent 28 is performed using purified exhaust gas, the odor components are more completely desorbed and the adsorbent 28 is regenerated.
There is no new adhesion of particulates, etc. to the adsorbent 28, and the adsorbent 28 is more completely regenerated.

〔Effect of the invention〕

As explained above, according to the present invention, the degree of regeneration of the odor adsorbent is improved, so the next time the adsorbent is operated, more odor components can be adsorbed, thereby reducing the release of odor. This makes it possible to reduce

[Brief explanation of drawings]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a flowchart of the control shown in Fig. 1, Fig. 3 is a diagram explaining the answering operation, and Fig. 4 is a diagram showing the second embodiment. . 22...Exhaust pipe, 26...Bypass pipe, 2
8... Adsorbent, 29... Oxidation catalyst, 30...
・Connecting pipe, 32, 34... valve. 22 Exhaust pipe 26 Pi/es pipe 1 Figure 28 Adsorbent 29 Oxidation catalyst 30 Connecting pipe 32.34 valve 20 (A) (C) Fathom 3@

Claims (1)

[Claims] An exhaust purification device for a diesel engine, characterized in that an adsorbent for adsorbing odor components of exhaust gas is disposed in an exhaust passage of the diesel engine, and an oxidation catalyst is disposed upstream of the adsorbent.