JPH11182236A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device of simple structure purifying exhaust gas from a low temperature area to a high temperature area using a plurality of catalyst different in activation temperature. SOLUTION: An exhaust emission control device is provided with a catalyst unit 11 having a low temperature catalyst 12 and a high temperature catalyst 13, and a case member 17 having space for accommodating the catalyst unit 11 inside, an exhaust lead-in port 17c and an exhaust lead-out port 17d on one end face 17a side, an intermediate outlet 17k and an intermediate inlet 17m on the other end face 17b side, and a U-pipe 17e communicating the intermediate outlet 17k and intermediate inlet 17m with each other so that exhaust flowing in from the exhaust lead-in port 17c flows through catalysts in the catalyst unit 11 successively in series. The exhaust emission control device is further provided with a motor M1 changing the relative position of the catalyst unit 11 to the case member 17 so as to switch the layout position of each catalyst to an exhaust passage Ex, a catalyst temperature detecting sensor Se for discriminating the temperature state of the catalysts, and a control unit C1 for controlling the operation of the motor M1 according to the temperature state of the catalysts discriminated by the catalyst temperature detecting sensor Se.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust gas purification device for an internal combustion engine.

[0002]

In the exhaust purifying apparatus of an internal combustion engine is less exhaust gas is SO ₂ may be hot generated hot active catalyst is used. However, it is difficult for a high-temperature activated catalyst to effectively reduce HC and CO when the catalyst is at or below an optimum activation temperature, such as when the engine is started or when the exhaust gas temperature is lowered. However, there is a disadvantage that untreated exhaust gas is released. In order to avoid such inconvenience, Japanese Utility Model Application Laid-Open No. 3-8
As disclosed in Japanese Patent No. 3316, there is known an exhaust gas purification apparatus having a configuration in which a low-temperature active pre-catalyst is provided before a high-temperature active main catalyst. According to the exhaust gas purifying apparatus, even if the main catalyst is not activated, the low-temperature activation type pre-catalyst is H
C and CO can be reduced.

[0003]

By the way, in the exhaust gas purifying apparatus provided with the above-mentioned low-temperature activation type pre-catalyst, when the engine is warmed up, the exhaust gas is located upstream of the main catalyst in the exhaust passage, that is, the exhaust gas is exhausted. The temperature of the pre-catalyst disposed at the position where the temperature is high becomes too high, and there is a problem that SO ₂ is generated in the pre-catalyst.

In order to eliminate the above-mentioned problem, for example, as disclosed in Japanese Patent Application Laid-Open No. Hei 4-330317, a high temperature catalyst tank and a low temperature catalyst tank are provided, and the exhaust gas temperature is high and the high temperature catalyst falls to the activation temperature. When the exhaust gas temperature reaches the high-temperature catalyst tank side, the exhaust gas temperature is in the middle and low temperature range, and when only the low-temperature catalyst is in the active state, a switching valve for flowing the exhaust gas to the low-temperature catalyst tank side is provided. An exhaust gas purifying device having such a configuration has been proposed. However, in this embodiment, the exhaust passages and the switching valves are required by the number of the plurality of catalysts, so that there is a problem that the apparatus becomes large and complicated.

The present invention solves the above-mentioned problems in the exhaust gas purifying apparatus, and provides an exhaust gas purifying apparatus having a simple structure capable of purifying exhaust gas from a low temperature range to a high temperature range using a plurality of catalysts having different activation temperatures. The purpose is to provide.

[0006]

In order to achieve the above object, an exhaust gas purification apparatus according to the present invention comprises a plurality of catalysts having different activation temperatures arranged in a catalyst unit, and the catalyst unit is exhausted in a case member. It is arranged to rotate about an axis along the flow direction. Then, by selecting the catalyst in the optimum active state by determining the temperature state of the catalyst, the relative position of the catalyst unit with respect to the case member is changed so that the catalyst is located on the inlet side, and thereby the catalyst is changed. Is switched. Thus, the optimum catalyst can be selected only by the rotation of the catalyst unit. Moreover, in the exhaust gas purification apparatus of the present invention, an inlet and an outlet are provided at one end of the case member,
The intermediate outlet and the intermediate inlet at the other end are communicated with each other by a communication portion, and the exhaust gas is introduced from the inlet portion, passes through the catalyst at the inlet side, and is then introduced into the catalyst at the outlet side through the communication portion, It is derived from the exit. For this reason, since the exhaust gas flows through the two catalysts in the case member in series, the low-temperature active catalyst is located at the inlet and the high-temperature active catalyst is located at the outlet. The exhaust gas that has passed through the catalyst can warm up the high-temperature activation type catalyst.
On the other hand, when a high-temperature activation type catalyst is located on the inlet side and a low-temperature activation type catalyst is located on the exit side, the exhaust gas passing through the high-temperature activation catalyst can be further purified by the low-temperature activation catalyst. .

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. Exhaust gas purification device 1 according to the present invention, an exhaust passage of an internal combustion engine (diesel engine), i.e. disposed in the middle of the downstream exhaust pipe E _X of the exhaust manifold, low-temperature active catalyst (hereinafter, referred to as low-temperature catalyst) 12 and High temperature activated catalyst (hereinafter referred to as high temperature catalyst) 1
3 is rotatably accommodated in the case member 17.

As shown in FIGS. 2 and 3, the catalyst unit 11 includes a low-temperature catalyst 12 and a high-temperature catalyst 13 inside a cylindrical outer shell member 14 via a holding plate 15 in a flow direction of each exhaust gas. Are held and fixed so as to be parallel to each other and the flow is reversed, and have a short cylindrical shape as a whole. The low temperature catalyst 12 has a columnar shape with a circular cross section, and has a honeycomb structure in which a large number of narrow paths (cells) 12c are provided straight from one end face 12a to the other end face 12b. The low-temperature catalyst 12 is not particularly limited as long as a metal carrier or a ceramic carrier carries a catalyst layer having a low activation temperature that activates at a relatively low temperature. Can be used. Here, the use temperature range (activation temperature range) of the low-temperature catalyst is, for example, 150 ° C. to 250 ° C. In the case of a low-temperature catalyst, since its size is made smaller and the overall heat capacity is made smaller, the catalyst temperature easily rises and reaches the activation temperature in a short time.

On the other hand, the high-temperature catalyst 13 has a columnar shape with a substantially elliptical cross section, and similarly to the low-temperature catalyst 12, a large number of narrow paths (cells) extend straight from one end face 13a to the other end face 13b.
13c is provided with a honeycomb structure. The high-temperature catalyst 13 is not particularly limited as long as a catalyst layer having a high activation temperature that activates at a higher temperature than the low-temperature catalyst is supported on a metal carrier or a ceramic carrier. You can use what has been done. Here, the operating temperature range of the high-temperature catalyst is
For example, it is 250 ° C. to 325 ° C.

The holding plate 15 is a pair of plate members having a circular shape in a plan view. The outer peripheral portion of the holding plate 15 is adapted to the inner peripheral surface of the outer shell member 14. Holes 15a and 15b are provided that match the outer shape of the catalyst. The holding plate 15 is provided on one end faces 12a, 13a side of the low-temperature catalyst 12 and the high-temperature catalyst 13 and on the other end face 12a.
b and 13b are fitted one by one so that the end face of each catalyst and the plate face of the holding plate are flush with each other, and further fitted to the inner peripheral portion 14a of the outer shell member 14. As a result, the catalyst unit 11 having the low-temperature catalyst 12 and the high-temperature catalyst 13 juxtaposed.
Is obtained. As described above, the holding plate 15 forms the upper end surface and the lower end surface of the catalyst unit 11 and also functions to hold and fix the low-temperature catalyst 12 and the high-temperature catalyst 13.

The catalyst unit 11 is provided with a ring gear 14b at a substantially intermediate height of an outer peripheral wall thereof, and a rotating shaft 16 is fixedly provided at the center of the shaft. The case member 17 is, as shown in FIG.
It has a cylindrical shape with a space for accommodating the catalyst unit 11 therein. The inner diameter of the case member 17 is substantially the same as the outer diameter of the catalyst unit 11, and the height is set to be larger than the height of the catalyst unit 11. Thereby, when the catalyst unit 11 is housed, the peripheral edge of the catalyst unit 11 is adapted to the inner peripheral surface of the case member, and a space having a predetermined volume is formed above and below the catalyst unit 11.

The case member 17 has one end face 1 thereof.
Partition plates 18, 18 are arranged inside the inside 7 a and inside the other end face 17 b so that both ends reach the inner peripheral surface of the case member 17 through the axis of the case member 17. This partition plate 1
8, 18 are the upper ends 11 of the catalyst units, respectively.
a, it is disposed so as to be in contact with the lower end surface 11b. Thereby, the space above and below the catalyst unit 11 is
It is divided into left and right sides by 8, 18. That is, the upper space of the catalyst unit 11 is defined by the partition plate 18 into the inlet space 17 g and the outlet space 17 h, and the lower space of the catalyst unit 11 is partitioned by the partition plate 18 into the left space 1.
7i (corresponding to the entrance side space 17g) and a right side space 17j (corresponding to the exit side space 17h).

Here, on one end face 17a of the case member 17, an exhaust inlet 17c to which an upstream exhaust pipe E1 from the exhaust manifold is attached is provided in the inlet space 17g, and a downstream exhaust pipe E2 leading to the muffler is attached. An exhaust outlet 17d is provided in the outlet space 17h. At this time, in the case member 17, the left side in FIG. 1 where the exhaust inlet 17c is provided is referred to as an upstream region, and the right side in FIG. 1 where the exhaust outlet 17d is provided is referred to as a downstream region. Also, the other end surface 17 of the case member 17
b, the intermediate outlet 1 provided in the left space 17i
A U-shaped pipe 17e is provided as a communicating part that communicates 7k with the intermediate entrance 17m provided in the right space 17j. Outside the U-shaped tube 17e, a cooling fan F1 for cooling the U-shaped tube 17e is provided. This cooling fan F1
Serves to cool the exhaust gas flowing in the U-shaped tube 17e by cooling the U-shaped tube 17e.

Further, in the case member 17, bearings 18a, 18a supporting the rotating shaft 16 of the catalyst unit 11 are formed integrally with the partition plates 18, 18 at the shaft center thereof.
Are arranged. The catalyst unit 11 is rotatable in the case member 17 by the rotation shaft 16 being pivotally supported by the bearings 18a. At this time, the ring gear 1 of the catalyst unit 11 on the side surface of the case member 17
A bulging portion 17f is provided at a position opposed to 4b, and a driving gear portion 19 that meshes with the ring gear 14b is provided inside the bulging portion 17f. In the drive gear portion 19, a drive shaft 19a extends to the outside in a state where airtightness is maintained, and a motor M1 as a switching means is attached to the end of the drive shaft 19a. The drive of the motor M1 is controlled by a control unit C1 as control means. The control unit C1 includes a catalyst temperature signal from a catalyst temperature sensor Se disposed at a predetermined position on the side surface of the case member 17 as a determination unit for determining the temperature state of the catalyst, and an exhaust temperature sensor and an engine as required. The information signal of the cooling water temperature sensor is taken in, the motor M1 is driven in accordance with the temperature state of the catalyst determined thereby, and the catalyst unit 11 is rotated. Here, as a mode for determining the temperature state of the catalyst, in addition to using the above-described catalyst temperature sensor, the temperature state of the catalyst is determined by detecting the exhaust gas temperature near the catalyst related to the catalyst temperature, or A mode may be adopted in which the operating conditions such as immediately after the start of the engine, during traffic congestion, and during high-speed running are grasped, and the temperature state of the catalyst is thereby determined. The control unit C1 also controls the driving of the cooling fan F1.

In the exhaust gas purifying apparatus 1 having the above-described structure, the exhaust gas discharged from the engine passes through the exhaust manifold and is introduced into the upstream region of the case member 17 from the exhaust inlet 17c. Then, it passes through a catalyst located in the upstream region, and in the process, first purification is performed.
Thereafter, the exhaust gas that has passed through the catalyst in the upstream region passes through the U-shaped tube 17e and reaches the downstream region. Then, after the second purification in the process of passing through the catalyst in the downstream region, the exhaust gas is discharged from the exhaust outlet 17d to the downstream exhaust pipe E2 leading to the muffler. That is, the exhaust gas flows along a path shown by arrow A. As described above, in the exhaust gas purification apparatus 1, the exhaust gas sequentially passes through the two catalysts in the case member 17 in series. In this exhaust gas purification device 1,
During the operation, the catalyst located in the upstream region can be switched according to the temperature state of the catalyst. Here, the switching operation of the catalyst will be described below.

As shown in FIG. 4A, first, as an initial state when the engine is started, the low temperature catalyst 12 is located on the exhaust inlet 17c side, and the high temperature catalyst 13 is located on the exhaust outlet 17d side. In this case, by driving the motor M1,
Power is transmitted from the gear 19b of the drive gear unit 19 to the ring gear 14b of the catalyst unit, and the catalyst unit 11
Rotate in the direction. It should be noted that in FIG.
Reference numerals 7c and 17d denote the positions of the exhaust inlet and the exhaust outlet, respectively.

Next, as shown in FIG. 4 (b), when the partition plate 18 hits the low-temperature catalyst 12 and the high-temperature catalyst 13 during the switching, the exhaust gas is supplied to the low-temperature catalyst 12 located in the upstream region. Part 12d and part 13 of the high temperature catalyst 13
d, after passing through both the other part 12e of the low-temperature catalyst 12 and the other part 13e of the high-temperature catalyst 13 located in the downstream region via the U-shaped tube, the air is led out from the exhaust outlet 17d. To go. At this time, since the time required for the rotation of the catalyst unit is short, the above-mentioned transitional state during the switching is about several seconds, and no substantial trouble occurs.
Then, the rotation continues further, and as shown in FIG. 4C, the high-temperature catalyst 13 comes to be located in the upstream area, and the switching of the catalyst is completed.

As described above, in the exhaust gas purification device 1,
At the time of exhaust gas purification processing, the temperature state of the catalyst is determined,
The optimum catalyst can be switched to the upstream side according to the temperature state, and the purification efficiency of the exhaust gas can be increased. Next, a control method when the catalyst unit is rotated and the arrangement positions of the low-temperature catalyst and the high-temperature catalyst are switched will be described below.

First, the performance of purifying the exhaust gas of the low temperature catalyst and the high temperature catalyst is shown in FIG. As is clear from FIG. 5, in a relatively low temperature region, that is, in a range where only the low temperature catalyst is activated, the purification rate of CO and HC by the low temperature catalyst is high, but the high temperature catalyst is not activated. The purification rate of CO and HC by the high-temperature catalyst is low. On the other hand, in a relatively high temperature region, that is, in a range where the high temperature catalyst is activated, both the low temperature catalyst and the high temperature catalyst are activated and CO, H
Although the purification rate of C is both high, SO
_The inconvenience of ₂ begins to occur. For this reason, the temperature T _L of SO ₂ from the low-temperature catalyst starts to occur as the upper limit of the low-temperature catalyst operating temperature range, high temperature catalyst using the temperature T _L to a temperature T _H which SO ₂ starts to occur at higher temperatures the catalyst Temperature range. Then, it is determined whether or not the catalyst temperature T is higher or lower than the temperature _TL so that the low-temperature catalyst and the high-temperature catalyst can be effectively used in the respective operating temperature ranges. I do.

The above control will be described in detail with reference to the flowchart of FIG. First, at step S1, the temperature signal from the catalyst temperature sensor Se is taken in, and the catalyst temperature T is detected. Next, in step S2, it is determined whether or not the catalyst temperature T is equal to or higher than the upper limit temperature _TL of the low temperature catalyst use temperature range. If the determination in step S2 is negative,
Since the catalyst temperature T is lower than the temperature _TL and is within the operating temperature range of the low-temperature catalyst, it is determined that the low-temperature catalyst 12 should be provided on the upstream side (step S3). If the low temperature catalyst 12 is not located on the upstream side when the determination is made in this manner, a drive signal is transmitted to the motor M1 so that the low temperature catalyst 12 is located in the upstream region. Then, in step S4, a cooling fan stop signal is transmitted to stop the cooling fan F1. As described above, when the exhaust gas temperature is low and the catalyst temperature is low, for example, when the engine is started, a low-temperature catalyst that is activated even at a low temperature is disposed in the upstream region, thereby effectively purifying CO and HC in the exhaust gas. can do. At this time, since the cooling fan is stopped, the exhaust gas that has passed through the low-temperature catalyst 12 in the upstream region is
Since the gas flows into the high temperature catalyst 13 in the downstream region without being cooled in the U-shaped tube 17e, the high temperature catalyst 13 can be activated in a short time by the exhaust gas. Therefore, the next time the high temperature catalyst is switched to the upstream region, the exhaust gas can be purified immediately. Further, although the high-temperature catalyst 13 in the downstream region is not activated, the exhaust gas can be purified to some extent, so that the exhaust gas passing through the low-temperature catalyst 12 is also purified by the high-temperature catalyst 13. The purification rate can be improved.

On the other hand, if the determination in step S2 is affirmative, the catalyst temperature T is equal to or higher than the temperature _TL and is within the operating temperature range of the high-temperature catalyst 13, so that the high-temperature catalyst 13 is disposed on the upstream side. (Step S)
Five). When the high temperature catalyst 13 is not located on the upstream side even when the determination is made in this way, a drive signal is transmitted to the motor M1 so that the high temperature catalyst 13 is located in the upstream region. Then, in step S6, a cooling fan drive signal is transmitted to drive the cooling fan F1. As described above, when the exhaust gas temperature increases and the catalyst temperature also increases, the catalyst located in the upstream region is switched from the low-temperature catalyst 12 to the high-temperature catalyst 13, thereby suppressing the generation of CO ₂ while suppressing the generation of SO _2. , HC can be sufficiently purified. At this time, by driving the cooling fan F1, the exhaust gas that has passed through the high-temperature catalyst 13 can be cooled in the portion of the U-shaped tube 17e, and the exhaust gas whose temperature has decreased can be cooled by the low-temperature catalyst 12 located in the downstream region. Will be introduced. Thus, the low-temperature catalyst 12, can be purified in a temperature range of SO ₂ is not generated. As described above, the exhaust gas that has passed through the high-temperature catalyst 13 is purified again by the low-temperature catalyst 12, so that the purification rate is further increased.

[0022] Incidentally, in the exhaust purification system of the present invention, catalyst volume that does not exceed the upper limit T _H also becomes severe driving conditions the temperature of the catalyst is a high temperature catalyst operating temperature range, by designing the catalyst position, Generation of SO ₂ from the high-temperature catalyst can be suppressed as much as possible. A second embodiment of the present invention will be described with reference to FIG. The exhaust gas purifying apparatus 2 according to the present invention is the same as the exhaust gas purifying apparatus 1 according to the first embodiment except that the motor M2 as a switching means is connected to the rotating shaft 26 of the catalyst unit 21. Corresponding parts are denoted by corresponding reference numerals, and detailed description is omitted.

In the exhaust gas purification apparatus 2, the rotating shaft 26 of the catalyst unit 21 is connected to the U-shaped tube 27e of the catalyst unit 21.
A motor M2 as a switching means is connected to the extended portion from the side end surface 27b. Therefore, by driving the motor M2, the catalyst unit 21 can be directly rotated. In the exhaust gas purification device 2 having such a configuration, the exhaust gas purification device 1
As in the case of (1), control is performed to switch the position of the low-temperature catalyst 22 and the high-temperature catalyst 23 by rotating the catalyst unit 21 according to the temperature state of the catalyst. The rotating shaft 26 of the catalyst unit 21 may be extended from the end face of the catalyst unit 21 on the side where the exhaust inlet 27c and the outlet 27d are provided, and a motor may be connected to the extended portion.

Here, in the exhaust gas purifying apparatus according to the present invention, as shown in FIG. 8, conical guides 30a and 30g and ring-shaped guides 30b having tapered portions are provided in the upper space and the lower space of the catalyst unit 31. When 30h is provided, the exhaust gas introduced from the exhaust introduction port 37c is guided by these guides, and is easily introduced into the catalyst. On the exhaust outlet 37d side, the exhaust gas that has passed through the catalyst is discharged by these guides 30c. And the air is easily led out from the exhaust outlet 37d to the downstream exhaust pipe E2. On the other hand, also on the side of the U-shaped tube 37e, these guides facilitate the smooth introduction and discharge of exhaust gas to and from the catalyst.

In the above description, the number of catalysts held in the catalyst unit is two, but the present invention is not limited to this, and two or more catalysts may be provided. . Here, for example, a catalyst unit 40 including a low-temperature catalyst, a high-temperature catalyst, and a medium-temperature active catalyst (hereinafter, referred to as a medium-temperature catalyst) activated in a temperature range between the low-temperature catalyst and the high-temperature catalyst will be described with reference to FIGS. It will be explained based on.

The catalyst unit 40 provided with three catalysts has the same basic structure as the catalyst unit used in the exhaust gas purifying apparatus 1 and the like, and as shown in FIG. The low-temperature catalyst 41, the medium-temperature catalyst 42, and the high-temperature catalyst 43 are located in the respective areas. The catalyst unit 40 is rotatably accommodated in the holding case. Here, 47c and 4 shown by dotted lines in FIG.
7d indicates the positions of the exhaust inlet (47c) and the exhaust outlet (47d) provided at one end of the holding case. At the other end of the holding case, an intermediate outlet and an exhaust outlet 47d are provided at locations corresponding to the exhaust inlet 47c.
An intermediate inlet is formed at a location corresponding to the above, and these intermediate outlets and the intermediate inlet are connected by a U-shaped tube as a communication part. Further, in the case member, the partition plates 4 provided in the upper space and the lower space of the catalyst unit 40 are provided.
8, 48 are arranged so as to extend in three directions from the center of the case member, as shown in FIGS. That is, the partition plate 48 is fixed inside the case member so as to equally divide each of the upper and lower spaces of the catalyst unit 40 into 120 degrees each. Thereby, the area in the case member is divided into three. At this time, in the case member, of the three divided regions, the region where the exhaust inlet 47c is located is the upstream region 47n, the region where the exhaust outlet 47d is located is the downstream region 47p, and the remaining one is the region Let it be a sub area 47q.

The catalyst unit 40 having the above structure is
The catalyst is rotated according to the temperature state of the catalyst, and the position at which the catalyst is disposed is switched. That is, when the catalyst temperature is in the low-temperature catalyst use temperature range, the low-temperature catalyst 41
Is located, and when the catalyst temperature is in the middle-temperature catalyst use temperature range, the middle-temperature catalyst 42 is located in the upstream region 47n. When the catalyst temperature is in the high-temperature catalyst use temperature range, the upstream-side region 47n is used. The high temperature catalyst 43 is located at the position (see FIG. 11). Exhaust gas discharged from the engine is supplied to an exhaust inlet 47c as shown by an arrow E in FIG.
After passing through the catalyst in the upstream region 47n, and passing through the U-shaped tube as shown by the arrow F,
It is introduced into the catalyst in the downstream region 47p. Then, the exhaust gas that has passed through the catalyst in the downstream region 47p is discharged from the exhaust outlet 47d to the downstream exhaust pipe as indicated by the arrow G. At this time, when the catalyst located in the downstream region 47p has a higher operating temperature range than the catalyst located in the upstream region 47n, the exhaust gas passing through the catalyst located in the upstream region 47n causes the downstream region The catalyst located at 47p is warmed up. Conversely, when the catalyst located in the downstream area 47p has a lower operating temperature range than the catalyst located in the upstream area 47n, the cooling fan 46 disposed in the U-tube portion is driven. As a result, the exhaust gas passing through the U-shaped tube is cooled, and the exhaust gas whose temperature has decreased is introduced into the catalyst located in the downstream region 47p. This allows
Catalyst located downstream region 47p can perform purification in a temperature range of SO ₂ is not generated. In the above embodiment, the exhaust gas is not introduced into the catalyst located in the sub region 47q. However, in order to further increase the purification rate of the exhaust gas, the exhaust gas is introduced into the catalyst located in the sub region 47q. You may. That is, by branching the U-shaped pipe into two branches and connecting the branched pipe to an intermediate inlet provided at the lower end of the sub-region 47q, exhaust gas is introduced into the sub-region 47q as shown by a dotted arrow H in FIG. This allows the exhaust gas to pass through the catalyst located in the area. The exhaust outlet provided at the upper end of the sub area 47q and the downstream area 4
A communication pipe is connected between the exhaust pipe 47d and the downstream exhaust pipe connected to the exhaust outlet 47d of 7p, and the exhaust gas passing through the catalyst located in the sub-region 47q is transferred to the downstream exhaust pipe as indicated by a dotted arrow I. Discharge. Here, when the catalyst located in the sub-region 47q is a catalyst whose operating temperature range is lower than the catalyst located in the upstream region 47n, the cooling fan 49 provided in the branch pipe portion of the U-shaped pipe is activated. By driving, the exhaust gas passing through the branch pipe is cooled, and the exhaust gas whose temperature has decreased is introduced into the catalyst located in the sub-region 47q.

As described above, when a catalyst unit having three catalysts is employed, it is possible to precisely respond to changes in the temperature state of the catalyst, which contributes to an improvement in exhaust gas purification efficiency.

[0029]

According to the exhaust gas purifying apparatus of the present invention, the optimum catalyst can be switched and selected according to the temperature state of the catalyst only by rotating the catalyst unit having a plurality of catalysts having different activation temperatures. Therefore, the device can be reduced in size and simplified. Further, in the exhaust gas purification apparatus of the present invention, an inlet portion and an outlet portion are provided at one end side of the case member, and an intermediate outlet and an intermediate inlet at the other end side are communicated with each other by a communication portion. After passing through the catalyst on the inlet side and passing through the catalyst on the inlet side, it is introduced into the catalyst on the outlet side through the communicating part and is led out from the outlet part, so that the exhaust gas is sequentially connected to the plurality of catalysts in the case member in series. Pass through. For this reason,
When there is a low-temperature active catalyst on the upstream side, the high-temperature active catalyst on the downstream side can be warmed up, and then when the high-temperature active catalyst moves to the upstream side, the high-temperature active catalyst is already In the warm-up state (activated state), it is possible to prevent a decrease in the purification rate of exhaust gas. Conversely, when there is a high temperature active type catalyst on the upstream side, the low temperature active type catalyst further purifies the exhaust gas, so that the purification rate can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a configuration of an exhaust gas purification device according to a first embodiment of the present invention.

FIG. 2 is a front view of a catalyst unit.

FIG. 3 is a sectional view taken along the line III-III in FIG. 2;

FIG. 4 is an explanatory diagram showing a procedure for switching a catalyst.

FIG. 5 is a graph showing catalytic exhaust gas purification performance.

FIG. 6 is a flowchart showing a procedure for switching a catalyst.

FIG. 7 is a schematic configuration diagram illustrating a configuration of an exhaust gas purification device according to a second embodiment.

FIG. 8 is a schematic configuration diagram showing a configuration of a main part of an exhaust gas purification device provided with a guide.

FIG. 9 is a front view showing a configuration of a catalyst unit including three catalysts.

FIG. 10 is a perspective view illustrating a configuration of a main part of a catalyst unit including three catalysts.

FIG. 11 is a graph showing catalytic exhaust gas purification performance.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Exhaust purification device 11 Catalyst unit 12 Low temperature catalyst 13 High temperature catalyst 17 Case member 17a One end face 17b Other end face 17c Exhaust inlet 17d Exhaust outlet 17e U-shaped pipe 17k Middle outlet 17m Middle inlet C1 Control unit Ex exhaust passage M1 motor Se catalyst Temperature detection sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 45/00 ZAB F02D 45/00 ZAB 360 360C

Claims (1)

[Claims] 1. A catalyst unit having a plurality of catalysts having different activation temperatures and arranged in an exhaust passage of an internal combustion engine along an exhaust flow direction, and a space for accommodating the catalyst unit therein, and one end face thereof. Side has an inlet portion and an outlet portion, an intermediate outlet corresponding to the inlet portion and an intermediate inlet corresponding to the outlet portion are provided on the other end surface side, and a communication portion for communicating these intermediate outlets and the intermediate inlet is provided. And a case member in which exhaust gas flowing from an inlet portion flows through the catalyst in the catalyst unit in series, and an arrangement position of each catalyst with respect to an exhaust passage by changing a relative position of the catalyst unit with respect to the case member. Switching means for switching the temperature of the catalyst, determining means for determining the temperature state of the catalyst, and control means for controlling the operation of the switching means based on the temperature state of the catalyst determined by the determining means. An exhaust gas purification device characterized by the following.