JPH08189342A - Exhaust gas purifying device - Google Patents

Abstract

PURPOSE: To prevent discharge of an unpurified HC, and to prevent thermal deterioration of a HC absorbing material due to high temperature by delaying temperature rising speed of HC absorbing material so as to improve absorbing efficiency. CONSTITUTION: Absorbing material layers 4a-4d for absorbing an unburned component, which is included in exist gas, are fixed to a wall surface, which are arranged opposite to exhaust ports 1a-1d, inside of an exhaust manifold 2 communicated with an exhaust ports 1a-1d of an engine 1, and a three way catalyst 5 is arranged in an exhaust passage 3 in the downstream of the exhaust manifold 2. The front surface of the absorbing material layer 4a is formed with a heat radiating layer 6 formed of a honeycomb structure layer so as to improve the heat radiating property, and temperature of the exhaust of be led into the absorbing material layer 4a is lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas purifying device for detoxifying a relatively large amount of hydrocarbons (HC) discharged during cold start of an internal combustion engine such as a gasoline engine.

[0002]

2. Description of the Related Art Conventionally, unburned components, such as hydrocarbons (HC), contained in the exhaust gas of an engine have been purified by a catalyst arranged in the exhaust passage. However, there is a problem that the above catalyst does not function sufficiently at the time of starting the engine until it reaches a certain purification temperature, during which HC is discharged without being purified. For this reason,
A zeolite-based HC adsorbent is provided along the wall surface of the exhaust manifold facing the exhaust port of the engine. Immediately after starting the engine, HC is captured by the adsorbent, and HC that starts desorption due to a rise in adsorbent temperature is There is an exhaust gas purification device that purifies by a catalyst arranged in a downstream exhaust passage (Japanese Patent Laid-Open No. 6-212951).

Since the temperature of the combustion chamber is low immediately after the engine is started, the discharged HC has a relatively large particle size and a large specific gravity. Therefore, when the exhaust gas containing a large amount of HC is discharged from the exhaust port, most of the gas components ride on the flow of the exhaust gas and flow out to the exhaust passage downstream, but the HC particles having a large specific gravity are small in amount due to the inertial force. It is introduced into the opposing HC adsorbent together with the exhaust gas and captured.

[0004]

In the above-mentioned structure, since the exhaust gas is not entirely introduced into the adsorbent, the temperature rise of the adsorbent is relatively slow, and the temperature of the downstream catalyst can be raised during that time. However, since the amount of exhaust gas introduced is different in each part of the adsorbent, the temperature locally rises in the central part of the adsorbent, etc. where the amount of adsorbent is large, or the saturated adsorption amount of HC is reached, and desorption of HC occurs early. Could start. For this reason, the temperature rise rate of the adsorbent is minimized and the adsorbent is
It is desired to maintain the temperature below the desorption temperature (generally about 100 ° C.) to improve the adsorption efficiency and enhance the HC retention capacity. Further, the zeolite-based HC adsorbent has a slightly low heat resistance, and there is a risk of excessive temperature rise and thermal deterioration during high rotation and high load operation in which the exhaust gas has a high temperature.

Further, in the above construction, since the rear end face of the adsorbent is closed by the exhaust manifold wall and the pressure wave generated by the exhaust gas is reflected at the rear end of the adsorbent, the exhaust gas does not flow into the rear part of the adsorbent. However, it has been a factor of lowering the utilization efficiency of the adsorbent.

Therefore, according to the present invention, in the exhaust gas purifying apparatus provided with the HC adsorbent facing the exhaust port,
By lowering the temperature rise rate of the adsorbent and improving the adsorption efficiency,
It is intended to prevent C from being discharged unpurified and to prevent the HC adsorbent from being thermally deteriorated due to high temperature.

[0007]

The present invention has been made in view of the above circumstances, and as shown in FIGS. 1A and 1B, inside an exhaust manifold 2 communicating with exhaust ports 1a to 1d of an internal combustion engine 1. The adsorbent layers 4a to 4d for adsorbing unburned components contained in the exhaust gas are fixed to the wall surfaces facing the exhaust ports 1a to 1d, and the exhaust gas is introduced into the exhaust passage 3 downstream of the exhaust manifold 2. An exhaust gas purifying device having a purifying catalyst 5 is provided with a heat dissipation layer 6 made of a honeycomb structure layer in front of the adsorbent layers 4a to 4d (claim 1).

Specifically (FIG. 1B), the heat dissipation layer 6 is
The catalyst layers 61 and 62 are formed by carrying a catalyst component for purifying unburned components in the exhaust gas on at least a part of the honeycomb structure forming the catalyst layers (claim 2). Further, the heat dissipation layer 6 is provided with cut-and-raised parts 64 for guiding the exhaust gas introduced from the exhaust port 1a to the outer cells on the wall of the honeycomb structure constituting the heat dissipation layer 6 (claim 3). . Alternatively, a cut-and-raised part 65 may be formed to guide the unburned component which is desorbed from the adsorbent layer 4a and flows into the heat dissipation layer 6 to the inner cell (claim 4). Also,
The heat dissipation layer 6 and the adsorbent layer 4a are arranged with a gap, and another heat dissipation layer 7 made of an air layer is provided in this gap (claim 5).

When a plurality of the adsorbent layers 4a to 4d are provided corresponding to each cylinder of the internal combustion engine, the adsorbent layers 4a to 4d are arranged so as to oppose the exhaust ports 1a to 1d communicating with the cylinders. Channels 8a that connect the rear ends of the layers 4a to 4d
8d is provided (Claim 6). Further, one end of the flow passage 8d is connected to the intake manifold 11 of the internal combustion engine, and a control valve 9 for controlling the amount of exhaust gas introduced into the intake manifold 11 from the flow passages 8a to 8d in the middle of the flow passage 8d. Can be provided (Claim 7).

[0010]

Since the HC particles discharged from the exhaust port 1a at the time of engine start-up have a larger specific gravity than the gas components, they travel straight due to inertial force, and head toward the adsorbent layer 4a facing with the small amount of exhaust gas. According to the configuration of claim 1, since the heat dissipation layer 6 is provided on the front surface of the adsorbent layer 4a, the exhaust gas releases its heat while flowing through the heat dissipation layer 6, and the exhaust gas having a lowered temperature absorbs the heat. It is introduced into the material layer 4a. Therefore, the temperature rise of the adsorbent layer 4a is suppressed, the amount of adsorbed HC increases, and the start of desorption of HC can be delayed. Further, even when the amount of heat supplied from the exhaust gas is large, such as during high rotation and high load, the amount of heat transferred to the adsorbent layer 4a can be significantly reduced, and therefore thermal deterioration of the adsorbent layer 4a is prevented. When the other heat dissipation layer 7 is provided between the heat dissipation layer 6 and the adsorbent layer 4a to form a two-layer structure, the heat dissipation is further improved.

According to the second aspect of the present invention, in the structure in which the catalyst layers 61 and 62 are provided in a part of the heat dissipation layer 6 of the honeycomb structure, the catalyst function is provided in addition to the heat dissipation function, and the adsorbent layer 4a is provided. The more desorbed HC can be purified in the exhaust manifold 2 whose temperature rises quickly. When the honeycomb structure walls forming the heat dissipation layer 6 are provided with the cut-and-raised parts 64, the exhaust gas flows toward the outer cells, so that the exhaust gas velocity flowing into the adsorbent layer 4a becomes uniform. To be done. Therefore, since the exhaust gas is uniformly introduced from the entire surface of the adsorbent layer 4a, the utilization efficiency of the adsorbent layer 4a is improved and the adsorption amount is increased. Further, in the present invention, when the cut-and-raised parts 64 are provided in the opposite direction to the cut-and-raised parts 64, the flow flowing into the heat-dissipating layer 6 from the adsorbent layer 4a side is directed to the center of the heat-dissipating layer 6. That is, since the HC particles desorbed from the adsorbent layer 4a head toward the central portion where the temperature of the catalyst layer 61 is likely to rise, the HC purification efficiency is further improved.

In the structure of claim 6, each adsorbent layer 4 is
The a to 4d are in communication with the flow paths 8a to 8d, and the exhaust gas flowing through the adsorbent layer 4a can flow out to the other adsorbent layers via the flow paths 8a to 8d. Due to this flow of the exhaust gas, the exhaust gas can be introduced to the rear end portion of the adsorbent layer 4a, and the utilization efficiency of the adsorbent is improved. Further, when the flow path 8 is connected to the intake manifold 11 as in claim 7, when the control valve 9 is opened, a flow of exhaust gas from the adsorbent layers 4a to 4d to the intake manifold 11 is generated, and the adsorbent is generated. The layers 4a to 4d are heated to promote desorption of HC. The desorbed HC is sent from the intake manifold 11 to the combustion chamber where it is burned and removed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1A, a 4-cylinder gasoline engine 1 has four exhaust ports 1a to 1d, and these exhaust ports 1a to 1d are connected to a side surface portion of an exhaust manifold 2. The exhaust gas discharged from the exhaust ports 1a to 1d is collected in the exhaust manifold 2 and discharged from the exhaust pipe 3 connected to the lower surface thereof. The exhaust pipe 3 is provided with a large-diameter part in the middle thereof, and the three-way catalyst 5 is arranged therein.

HC adsorbent layers 4a to 4d are arranged in the exhaust manifold 2 at positions facing the four exhaust ports 1a to 1d, respectively. FIG. 1B shows the details of the adsorbent layer 4a. The other adsorbent layers 4b to 4d
Since the structure is the same, the description is omitted here. In the figure, the adsorbent layer 4a is housed in the right half portion of a container body 41 having a substantially U-shaped cross section and forming a part of the wall of the exhaust manifold 2, and is made of, for example, metal foil or ceramics such as alumina. A honeycomb structure carrier is coated with an adsorbent such as zeolite.

A first heat dissipation layer 6 is arranged in the left half of the container body 41 (on the side of the exhaust port 1a). The first heat dissipation layer 6 is made of a carrier having a honeycomb structure, and is formed by spirally laminating a flat plate 6a and a corrugated plate 6b, for example, as shown in FIG. Then, heat is radiated from the wall of the container body 41 with which the outer periphery is in contact, so that the adsorbent layer 4a is formed.
It has the effect of reducing the temperature of the exhaust gas introduced into the. Further, the first heat dissipation layer 6 has catalyst components such as palladium and platinum supported on the carrier at the upstream end face and the downstream end face, and functions as the catalyst layers 61 and 62 ( FIG. 1B). Thus, the HC desorbed from the adsorbent layer 4a can be purified by the catalyst layers 61 and 62 that reach the purification temperature earlier than the downstream catalyst 5.

The middle portion of the first heat dissipation layer 6 functions as a diffusion layer 63 that guides the flow of exhaust gas to the outside. That is, as shown in FIGS. 2A and 2B, the upstream catalyst layer 6
A large number of cut-and-raised parts 64 are formed on the surface of the flat plate 6a subsequent to 1 with the projecting portion facing the center, and a part of the exhaust gas introduced from the exhaust port 1a is cut. The exhaust velocity is made uniform by changing the flow outward by being guided by the raising 64. Further, in the diffusion layer 63, a large number of cut-and-raised parts 65 are formed, which are open toward the downstream side and the protrusions are directed outward, as compared with the catalyst layer 62 on the downstream side (FIG. 1 (B)). The flow of the HC desorbed from the adsorbent layer 4a side is concentrated in the high temperature central portion of the catalyst layer 61.

A second heat dissipation layer 7 made of an air layer is provided between the adsorbent layer 4a and the first heat dissipation layer 6.
The temperature of the exhaust gas introduced into the adsorbent layer 4a is further lowered by heat dissipation. Here, the container body 41 has a step 411 for positioning the first heat dissipation layer 6 formed in an intermediate portion thereof, and the rear end surface of the first heat dissipation layer 6 abuts on the step 411, The width of the second heat dissipation layer 7 is made constant. The second heat dissipation layer 7 may be composed of a honeycomb structure that does not carry a catalyst component or an adsorbent.

The adsorbent layer 4a is provided with slits 42 at the rear end thereof for communicating the cells (FIG. 1).
(B)). A void 43 is formed on the outer circumference of the adsorbent layer 4a at the position where the slit 42 is formed, and a communication pipe 8a communicating with the void 43 is connected to the rear side wall of the container body 41 to form an adsorbent layer 4b adjacent to the adsorbent layer 4b. It is in communication (Fig. 1
(A)). Adsorbent layer 4b, adsorbent layer 4c, adsorbent layer 4c
The adsorbent layer 4d and the adsorbent layer 4d are also communicated with each other through the communicating pipe 8b and the communicating pipe 8c, respectively, and the other end of the communicating pipe 8d extending from the adsorbent layer 4d is connected to the intake manifold 11 wall via the EGR control valve 9. It has been opened. In this way, a flow path that connects the adsorbent layers 4a to 4d and reaches the intake manifold 11 is formed. The EGR control valve 9 is a control circuit 91.
It is driven by the drive valve 92, and the known EGR (exhaust gas recirculation) control can be performed. The space 43 is formed to reduce the flow resistance of the exhaust gas flowing into the communication pipe 8a.

In the above structure, the exhaust gas containing a large amount of HC exhausted when the engine is started is the exhaust port 1a.
When introduced into the first heat dissipation layer 6 facing (see FIG.
(B)) A part of the exhaust gas flows into the cell outside the cut-and-raised portion 64 provided on the upstream side of the diffusion layer 63, and further turns outward by the cut-and-raised portion 65 on the downstream side and flows. . As a result, as shown in FIG. 3, the flow velocity distribution in the diffusion layer 63 is made uniform, and exhaust gas having a uniform HC concentration is introduced from the entire surface of the adsorbent layer 4a. Use efficiency is improved. Further, since the exhaust gas is cooled while passing through the first heat dissipation layer 6 and the second heat dissipation layer 7, the HC particles flow into the adsorbent layer 4a while maintaining a state in which the HC particles are easily adsorbed and having a large particle size. And greatly improves the adsorption efficiency.

Here, the adsorbent layer 4a is the communication pipe 8
Therefore, when the pressure in the adsorbent layer 4a becomes higher than that in the other adsorbent layer during the exhaust stroke, the exhaust gas inside the adsorbent layer is It flows out to the adsorbent layer 4b adjacent to it via the communication pipe 8a. Then, the same volume of gas as the gas that has flowed out flows in. By such a flow of exhaust gas, more exhaust gas than before can be introduced, and since the pressure wave caused by exhaust pulsation is not repelled, the exhaust gas flows into the rear end portion of the adsorbent layer 4a, The utilization efficiency of the adsorbent is improved.

After the engine is started, the temperature of the adsorbent layer 4a also rises as the exhaust gas temperature rises, but the exhaust gas is cooled by the first heat radiation layer 6 and the second heat radiation layer 7. As shown in FIG. 4, the temperature rising rate of the adsorbent layer 4a can be slowed down. Therefore, the start of desorption of HC is delayed, and the temperature of the three-way catalyst 5 can be increased during that time. In addition, since the temperature rise of the adsorbent layer 4a is suppressed in the same manner even at the time of high engine rotation and high load,
It is possible to prevent excessive temperature rise and prevent deterioration of the adsorbent.

When the adsorbent layer 4a reaches a certain temperature, HC
Starts desorption and flows toward the downstream three-way catalyst 5 through the first heat dissipation layer 6. At this time, the temperature of the catalyst layers 61 and 62 provided in the first heat dissipation layer 6 rises faster than that of the three-way catalyst 5, so that even if HC is desorbed early, it can be surely purified. Also, the cut-and-raised part 65 on the wake side of the diffusion layer 63
As a result, the flow of HC is directed to the center of the catalyst layer 61 having a high temperature, so that the desorbed HC can be efficiently purified.

When the engine warms up and the operating condition of the engine satisfies the normal EGR condition, the drive valve 92 is operated by the control circuit 91 to open the EGR control valve 9. As a result, the intake manifold 11 and the adsorbent layers 4a to 4d are electrically connected, and a part of the exhaust gas flows through the adsorbent layers 4a to 4d. By the inflow of the exhaust gas, the entire adsorbent layers 4a to 4d are heated to promote the desorption of HC, and the adsorbed HC can be completely desorbed. The desorbed HC is introduced into the intake manifold 11 together with the EGR gas flow, and is burned in the combustion chamber. Thus, HC can be removed efficiently.

Although the exhaust gas temperature rises at high load, EGR is not normally performed at high load, so E
The GR control valve 9 is closed and exhaust gas does not flow, and the temperature of the adsorbent layers 4a to 4d does not rise excessively. Further, since EGR is not performed even when the engine is started, there is no EGR gas flow toward the intake manifold 11, and the HC adsorbed by the adsorbent layers 4a to 4d is temporarily retained by the adsorbent.

FIG. 5 shows another embodiment of the present invention. In this embodiment, the cylindrical mounting portion 44 is provided at the center of the rear surface of the container body 41.
The attachment pipe 44 is provided with a communication pipe 8a for connecting the adsorbent layer 4a and the adsorbent layer 4b adjacent thereto. The other structure is the same as that of the above embodiment. With such a structure, the exhaust gas can be introduced to the rear side of the adsorbent layer 4a. Further, the attachment property of the communication pipe 8a is improved, and the air gap 43 (see FIG. 1B) on the outer periphery of the adsorbent layer 4a for reducing the air flow resistance is not required.
There is an advantage that the process is unnecessary and the manufacturing is easy.

[0026]

As described above, according to the present invention, the rate of temperature rise of the HC adsorbent is slowed down, and the adsorption efficiency is significantly improved, so that H
Premature detachment of C can be prevented. Further, it is possible to prevent the adsorbent from being thermally deteriorated when the engine load is high.

[Brief description of drawings]

1 (A) is a partial cross-sectional plan view of an exhaust gas purifying apparatus showing an embodiment of the present invention, and FIG. 1 (B) is a partially enlarged cross-sectional view of FIG. 1 (A).

2A is an exploded perspective view of an adsorbent layer, FIG.
(B) is a partially enlarged perspective view of the adsorbent layer.

FIG. 3 is a partially enlarged cross-sectional view of an exhaust gas purification device for explaining the operation of the present invention.

FIG. 4 is a diagram showing the temperature rise characteristics of the HC adsorbent layer of the device of the present invention and the conventional device.

FIG. 5 is a partially enlarged cross-sectional view of an exhaust gas purification device showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine (internal combustion engine) 2 exhaust manifold 1a-1d exhaust port 3 exhaust pipe (exhaust passage) 4a-4d adsorbent layer 41 container 42 slit 43 void 5 three-way catalyst 6 first heat dissipation layer (heat dissipation layer) 61, 62 catalyst layer 63 diffusion layers 64, 65 cut and raised 7 second heat dissipation layer (other heat dissipation layer) 8a to 8d communication pipe (flow path) 9 EGR control valve 91 control circuit 92 drive valve

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Yoshinaga 14 Iwatani, Shimohakaku-cho, Nishio-shi, Aichi Japan Auto Parts Research Institute, Inc.

Claims (7)

[Claims] 1. An adsorbent layer for adsorbing unburned components contained in exhaust gas is provided on a wall surface facing an exhaust port in an exhaust manifold communicating with an exhaust port of an internal combustion engine, and an adsorbent layer downstream of the exhaust manifold is provided. In an exhaust gas purification device having a catalyst for purifying exhaust gas in the exhaust passage,
An exhaust gas purification device comprising a heat dissipation layer made of a honeycomb structure layer provided on the front surface of the adsorbent layer. 2. The exhaust gas purification apparatus according to claim 1, wherein a catalyst component for purifying unburned components in exhaust gas is carried on at least a part of the honeycomb structure forming the heat dissipation layer to form a catalyst layer. 3. The exhaust gas purifying apparatus according to claim 1, wherein a cut-and-raised portion for guiding the exhaust gas introduced from the exhaust port to outer cells is formed on a honeycomb structure wall forming the heat dissipation layer. . 4. The honeycomb structure wall forming the heat dissipation layer is provided with cut-and-raised parts that guide unburned components that are desorbed from the adsorbent and flow into the heat dissipation layer to inner cells. The exhaust gas purification device according to any one of claims 1 to 3. 5. The exhaust gas purifying apparatus according to claim 1, wherein the heat dissipation layer and the adsorbent layer are disposed with a gap, and another heat dissipation layer composed of an air layer is provided between the heat dissipation layer and the adsorbent layer. 6. A plurality of the adsorbent layers are provided, arranged so as to oppose each exhaust port communicating with each cylinder of an internal combustion engine, and a flow path communicating between the rear end portions of these adsorbent layers is provided. The exhaust gas purification device according to claim 1, which is formed. 7. A control valve for connecting one end of the flow passage to an intake manifold of an internal combustion engine, and for providing a control valve for controlling the amount of exhaust gas introduced from the flow passage to the intake manifold, in the middle of the flow passage. 6. The exhaust gas purification device according to 6.