JP2009180096A - Exhaust emission control device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device of an engine capable of sufficiently purifying exhaust gas by an inexpensive configuration while effectively suppressing the rise of the back pressure of the engine. <P>SOLUTION: In this exhaust emission control device of an engine, an adsorbing section 20 for adsorbing specific components in the exhaust gas and a purification section 30 for removing the specific components separated from the adsorbing section 20 are disposed in this order from the upstream side along the exhaust passage 2 of the engine. The purification section 30 is disposed in an exhaust gas collecting section 10 in which the exhaust gas discharged from the plurality of cylinders of an engine body 1 is collected. A space 12 of a predetermined volume into which the exhaust gas from the engine body 1 is made to flow is formed between the purification section 30 and the peripheral wall of the exhaust gas collecting section 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an engine exhaust gas in which an adsorbing portion that adsorbs a specific component in exhaust gas and a purification unit that purifies the specific component desorbed from the adsorbing portion are arranged in order from the upstream side along the exhaust passage of the engine. The present invention relates to a purification device.

  The exhaust gas of the engine contains unburned components such as HC, CO, and NOx, and in order to sufficiently purify these components, in many vehicles, a manifold direct connection catalyst arranged immediately downstream of the engine manifold is used. While exhaust gas purification at a low temperature is performed, exhaust gas purification at a high temperature is performed using this manifold direct-coupled catalyst and a U / F catalyst (underfloor catalyst) disposed in the lower floor of the downstream side.

  However, at the time of cold start of the engine, for example, it takes about several tens of seconds to reach the temperature at which the manifold directly connected catalyst is activated, and thus the exhaust gas cannot be sufficiently purified until that time. . In particular, since a large amount of HC is discharged during a short time immediately after the engine is started, it is necessary to suppress this HC component from being discharged to the outside as much as possible. Therefore, in order to suppress the discharge of such HC components, for example, an HC adsorbent typified by zeolite is disposed between the manifold direct-coupled catalyst and the U / F catalyst, or between these catalysts. Has been done.

  However, since the HC desorption start temperature in the HC adsorbent as described above is about 150 ° C. to 200 ° C., a general catalyst (for example, a three-way catalyst) activated at a temperature higher than this is used. When employed in a manifold direct connection catalyst or a U / F catalyst, the desorbed HC component cannot be sufficiently purified until the activation temperature is reached.

  Therefore, for example, in Patent Document 1 below, an upstream catalyst, an HC adsorbent, and a downstream catalyst are sequentially arranged from the upstream side of the exhaust passage of the engine, and the upstream catalyst and the downstream catalyst are combined into one. By accommodating the catalyst converter in the catalytic converter, the discharge of the HC component at the low temperature as described above is suppressed.

That is, according to the configuration of Patent Document 1, the exhaust gas discharged from the engine body first passes through the upstream catalyst in the catalytic converter and then flows into the downstream HC adsorbent, where HC components are adsorbed. Is done. When the exhaust gas temperature rises after a certain amount of time has elapsed since the start of the engine and the HC adsorbent reaches a predetermined temperature, desorption of the HC component adsorbed on the HC adsorbent begins, and the desorbed HC Components flow into the downstream catalyst in the catalytic converter. At this time, since the downstream catalyst is housed in the catalytic converter integrally with the upstream catalyst on the upstream side of the HC adsorbent, the temperature rises faster than the HC adsorbent and has already been activated. Therefore, the HC component desorbed from the HC adsorbent is sufficiently purified by the downstream catalyst already in an active state.
Japanese Unexamined Patent Publication No. 7-42539

  However, in the configuration of Patent Document 1, since two catalysts including an upstream catalyst and a downstream catalyst are arranged in the catalytic converter, the ventilation resistance of the exhaust gas when passing through the catalyst is increased, and the back of the engine is increased. The pressure is likely to rise. And when back pressure rises in this way, it will result in the fall of an engine output and a fuel consumption.

  In addition, the arrangement of two catalysts in the catalytic converter requires a larger amount of catalyst, increases the heat capacity of the entire catalyst, and increases the time required for the temperature to reach the activation temperature. End up. For this reason, it is necessary to adsorb HC components for as long as possible, and it is necessary to install a large amount of HC adsorbent on the exhaust passage. As a result, there arises a problem that the back pressure of the engine is more likely to increase and costs such as material costs are increased.

  The present invention has been made in view of the circumstances as described above, and is capable of sufficiently purifying exhaust gas with a lower cost configuration while effectively suppressing an increase in engine back pressure. An object is to provide a purification device.

  In order to solve the above problems, the present invention provides an adsorbing unit that adsorbs a specific component in exhaust gas and a purification unit that purifies the specific component desorbed from the adsorbing unit along the exhaust passage of the engine. An exhaust gas purification device for an engine disposed in order from the upstream side, wherein the purification unit is disposed in an exhaust gas collecting unit for collecting exhaust gas discharged from a plurality of cylinders of the engine body, and the purification unit, A space portion having a predetermined volume in which the exhaust gas from the engine main body can flow is formed between the peripheral wall of the exhaust gas collecting portion (claim 1).

  According to the present invention, since the space portion having a predetermined volume is formed between the peripheral wall of the exhaust gas collecting portion and the purifying portion therein, the exhaust gas introduced from the engine body into the exhaust gas collecting portion is transferred to the space portion. Can be smoothly discharged downstream. For this reason, it is possible to effectively suppress an increase in the back pressure of the engine, and there is an advantage that the output and fuel consumption can be favorably maintained.

  Moreover, according to the said structure which installed the said purification | cleaning part located in the downstream of an adsorption | suction part in a part of exhaust gas collection part, and used the other part as the space part, it is equivalent to the upstream catalyst in the said patent document 1 Of course, the purification unit is heated and activated relatively quickly, so even if the adsorbing unit does not adsorb the specific component in the exhaust gas for such a long time, The specific component that begins to desorb when it reaches a predetermined temperature can be reliably purified by the purification unit already in an active state. As a result, even if the amount of the adsorbent in the adsorbing portion is suppressed to a relatively small amount, the outflow of the specific component at a low temperature can be effectively suppressed, and the cleanliness of the exhaust gas discharged to the outside can be reduced at a lower cost. There is an advantage that it can be maintained well with a simple configuration.

  In the present invention, a bulging portion bulging in a predetermined direction is provided in the exhaust gas collecting portion, and is offset to the bulging portion side from a line connecting the exhaust pipes upstream and downstream of the exhaust gas collecting portion. It is preferable that the purification unit is disposed in a state (claim 2).

  According to this configuration, it is possible to effectively prevent the flow of the exhaust gas flowing through the space in the exhaust gas collecting portion from being largely bent due to the presence of the purification unit, so that the back pressure increase of the engine is further suppressed. There is an advantage that the output and fuel consumption can be further improved.

  It is preferable that the casing of the purification unit is provided with a heat receiving unit for receiving the heat of the exhaust gas passing through the space (Claim 3).

  According to this configuration, since the time required to activate the purification unit can be shortened, the period during which the specific component in the exhaust gas should be adsorbed by the adsorption unit is shorter, and the adsorbent in the adsorption unit There is an advantage that an increase in the back pressure of the engine due to the presence of the adsorption portion can be more effectively suppressed while further reducing the amount of the gas and reducing the cost.

  It is preferable that the purification section includes a catalyst body formed by coating a metal carrier with a catalyst layer containing a predetermined catalyst metal.

  According to this configuration, since the heat capacity of the purification unit can be made relatively small, there is an advantage that the temperature required for the purification unit can be promoted and the time required for its activation can be further shortened.

  It is preferable that at least a part of the exhaust pipe provided between the adsorption part and the purification part has a double pipe structure.

  According to this structure, it can suppress effectively that the temperature of exhaust gas falls and the temperature rise of the said purification part slows from an adsorption part to a purification | cleaning part, and the said purification | cleaning part can be activated more rapidly. There is an advantage.

  In the exhaust gas purifying apparatus of the present invention, when the adsorbing part rises to a predetermined temperature, the exhaust gas introduced from the engine body into the exhaust gas collecting part flows directly to the purifying part without passing through the adsorbing part. Thus, it is preferable to include a switching means for switching the flow of the exhaust gas.

  According to this configuration, while ensuring the cleanliness of the exhaust gas discharged to the outside appropriately, it is possible to prevent an increase in ventilation resistance due to the exhaust gas passing through a useless path, and the output caused by the increase in the back pressure of the engine There is an advantage that a reduction in fuel consumption can be more effectively suppressed.

  As described above, according to the present invention, it is possible to provide an engine exhaust gas purification device capable of sufficiently purifying exhaust gas with a lower cost configuration while effectively suppressing an increase in engine back pressure. Can do.

<Embodiment 1>
FIG. 1 is a diagram showing an overall configuration of an engine to which an exhaust gas purifying apparatus according to a first embodiment of the present invention is applied. An exhaust passage 2 for discharging the generated exhaust gas to the outside is connected to a main body portion (engine body) 1 of the engine shown in the figure, and this exhaust passage 2 is upstream (engine body 1 side). The first exhaust pipe 5, the second exhaust pipe 6, the third exhaust pipe 7, and the fourth exhaust pipe 8 are disposed in order. In FIG. 1, an arrow G indicates the flow of exhaust gas flowing through the exhaust passage 2.

  The first exhaust pipe 5 guides exhaust gas discharged from a plurality of cylinders (not shown) of the engine body 1 to the downstream side. For example, when the engine body 1 is an in-line four-cylinder engine, Consists of four pipes. In FIG. 1, a plurality of pipes constituting the first exhaust pipe 5 are arranged in a direction perpendicular to the paper surface.

  Further, an exhaust gas collecting portion 10 is connected to the downstream side of the first exhaust pipe 5, and the exhaust gas discharged from each cylinder of the engine body 1 is collected in the exhaust gas collecting portion 10. Then, the exhaust gas collected at one place by the exhaust gas collecting portion 10 passes through a U-shaped return passage composed of the second exhaust pipe 6 and the third exhaust pipe 7 and the like. Specifically, it is returned to a purifying section 30), which will be described later, provided in the interior thereof, and is discharged to the outside through the fourth exhaust pipe 8 extending downstream therefrom, the silencer (not shown), etc. It has become.

  Between the second and third exhaust pipes 6, 7, that is, in the middle part of the return passage for returning the exhaust gas led out from the exhaust gas collecting part 10 to the installation part of the exhaust gas collecting part 10, An adsorbing portion 20 for adsorbing specific components (HC, CO, NOx in this embodiment) at a low temperature is provided. Further, a purification unit 30 for purifying a specific component in the exhaust gas is disposed inside the exhaust gas collecting unit 10, and the specific component desorbed from the adsorption unit 20 at a high temperature is the first component. 3 is introduced into the purification section 30 through the exhaust pipe 7, and after being purified here, it is discharged to the outside through the fourth exhaust pipe 8 and the like.

  As shown in FIGS. 1 and 2, the purification unit 30 is disposed in a state where a clearance is formed from the peripheral wall of the exhaust gas collecting unit 10. As a result, a space 12 having a predetermined volume in which the exhaust gas discharged from the engine main body 1 can flow is formed between the purification unit 30 and the peripheral wall of the exhaust gas collecting unit 10. The exhaust gas collected in the exhaust gas collecting part 10 through the pipe 5 is led out to the second exhaust pipe 6 on the downstream side through the space part 12.

  Further, the exhaust gas collecting part 10 bulges in a predetermined direction with respect to the main body part 11 located between the first exhaust pipe 5 on the upstream side and the second exhaust pipe 6 on the downstream side, and the main body part 11. And a bulging portion 15 for accommodating the purifying portion 30. And the purification | cleaning part 30 accommodated in the bulging part 15 in this way is the said bulging part 15 side rather than the line L (refer FIG. 2) which connects the said 1st and 2nd exhaust pipes 5 and 6. FIG. It is arranged in the exhaust gas collecting part 10 in an offset state.

  As shown in FIGS. 1-3, the said 3rd exhaust pipe 7 which connects the said adsorption | suction part 20 and the purification | cleaning part 30 is comprised by the double piping which consists of two circular pipes arrange | positioned concentrically. .

  Next, the detailed structures of the adsorption unit 20 and the purification unit 30 will be described. First, as shown in FIG. 1, the adsorbing unit 20 includes a NOx adsorbent 21 that adsorbs NOx components in exhaust gas, a CO adsorbent 22 that adsorbs CO components, and an HC adsorbent 23 that adsorbs HC components. These three kinds of adsorbents are housed in a casing 24 and configured.

As the HC adsorbent 23, zeolite is preferable, and in particular, a large number of pores having a major diameter of about 7.0 mm and a minor diameter of about 5.0 mm suitable for adsorbing and holding HC components in exhaust gas are formed. Preferred is β-type zeolite. Examples of the CO adsorbent 22 include a material in which Pd is supported on a perovskite oxide such as SrTiO ₃ , a material in which Cu is supported on alumina, ceria, or the like, or Fe, Co, Ni, alumina. Those carrying at least one of W and Mo are preferred. Furthermore, as the NOx adsorbent 21, ceria-based, zeolite-based, alkali metal-based, alkaline earth metal-based, or manganese-based complex oxides (particularly Mn—Ce complex oxides), and Mn on silica. Mn / SiO ₂ was supported, Mn / ZrO ₂ was supported Mn zirconia or BaCuO ₂ Pd / BaCuO ₂ obtained by supporting Pd on, it is preferable.

  And by the effect | action of the said adsorption | suction part 20 containing various adsorbents 21,22,23 of such a structure, each component of HC, CO, NOx contained in exhaust gas is adsorbed and hold | maintained at the time of engine cold. At the same time, the adsorbents 21, 22, and 23 rise to a predetermined temperature after a certain period of time has elapsed since the engine is started, so that the components (HC, CO, NOx adsorbed on the adsorbing portion 20). ) Are sequentially desorbed and released to the downstream side (purifying unit 30 side).

  On the other hand, as shown in FIG. 2, the purification unit 30 includes a casing 31 and a conventionally known three-way catalyst (that is, a catalyst capable of purifying three components of HC, CO, and NOx) disposed therein. And a catalyst main body 33.

  Specifically, the catalyst body 33 includes a metal carrier (for example, made of a ferritic stainless steel made of 20Cr-5Al-La-remaining Fe) formed in a honeycomb shape or the like so as to have a relatively large surface area; And a catalyst layer coated on the metal carrier and containing a predetermined catalyst metal. As the catalyst layer, for example, Rd / aluminum in which Pd / alumina in which Pd is supported on alumina particles, and a composite material in which a composite oxide containing Zr and La is supported on the surface is supported on Rh / Contains ZrLaO-alumina and Rh / OSC in which Rh is supported on an oxygen storage material (for example, a complex oxide of Ce and Zr) capable of storing or releasing oxygen according to the oxygen concentration in the exhaust gas. Those are preferred.

  The catalyst body 33 having such a configuration is heated to a predetermined temperature by the heat of the exhaust gas and activated, and an oxidation / reduction function (that is, a function of oxidizing HC and CO in the exhaust gas and reducing NOx) by the catalyst layer. ) Is sufficiently increased, the HC, CO, and NOx components desorbed from the adsorption unit 20 flow into the purification unit 30, so that these components are appropriately purified by the catalyst body 33. As a detoxified substance, it is discharged to the outside.

  As shown in FIGS. 2 and 3, the casing 31 of the purification unit 30 is provided with a heat receiving unit 32 including a plurality of fins protruding in the circumferential direction. The heat receiving part 32 is for receiving heat of exhaust gas passing through the periphery thereof (that is, exhaust gas passing through the space part 12 in the exhaust gas collecting part 10) in a wider area. Due to the presence, the heat of the exhaust gas passing through the space 12 is efficiently transmitted to the casing 31 and the catalyst main body 33 therein.

  Next, the operation and effect of the exhaust gas purifying apparatus according to the first embodiment of the present invention configured as described above will be described in comparison with two comparative examples described below.

(Comparative Example 1)
Comparative Example 1 employs a structure as shown in FIG. That is, in Comparative Example 1, the adsorbing portion 120 that adsorbs a specific component such as HC contained in the exhaust gas in order from the upstream side along the exhaust passage 102 of the engine, and the above-mentioned specific desorbed from the adsorbing portion 120 A purification unit 130 that purifies the components is disposed.

(Comparative Example 2)
Comparative Example 2 employs a structure similar to that of Patent Document 1. That is, in this comparative example 2, as shown in FIG. 9, the upstream side catalyst 231 for purifying specific components such as HC contained in the exhaust gas in order from the upstream side along the exhaust passage 202 of the engine, and the above specified An adsorbing part 220 for adsorbing components and a downstream catalyst 232 having the same purification function as the upstream catalyst 231 are disposed. Of these, the upstream catalyst 231 and the downstream catalyst 232 are integrally accommodated in one catalytic converter 240.

  The performance of the exhaust gas purification apparatuses of Comparative Examples 1 and 2 as described above and the performance of the exhaust gas purification apparatus of the present embodiment will be compared and examined using the graph shown in FIG. FIG. 4 is a graph showing the relationship between the elapsed time t from the time when the engine is started in the cold state and the temperature Tm of the adsorption part, the purification part, etc. in the exhaust gas purification apparatus. In FIG. 4, the solid line denoted by reference numeral 71 indicates the temperature change of the suction part 20 in the present embodiment, and the broken line denoted by reference numeral 81 indicates the temperature change of the suction part 120 in the first comparative example. A one-dot chain line denoted by reference numeral 91 indicates a temperature change of the suction portion 220 in the second comparative example. On the other hand, the solid line denoted by reference numeral 72 in the same figure indicates the temperature change of the purification unit 30 in the present embodiment, the broken line denoted by reference numeral 82 indicates the temperature change of the purification unit 130 in the comparative example 1, A one-dot chain line denoted by reference numeral 92 indicates a temperature change of the upstream and downstream catalysts 231 and 232 in the second comparative example.

  Also, the temperature Tm1 in FIG. 4 is the temperature at which HC desorption begins in the adsorption unit (20, 120, 220) (HC desorption start temperature), and the temperature Tm2 is the purification unit (30, 130) or upstream. This is the temperature at which the side / downstream catalyst (231, 232) is activated (catalyst activation temperature). For example, when the same material as that of the present embodiment is used as the adsorption unit and the purification unit, the HC desorption start temperature Tm1 is about 200 ° C., and the catalyst activation temperature Tm2 is about 250 ° C. Then, by referring to such a graph, it is possible to determine the performance related to adsorption and purification of HC components by the exhaust gas purification device. In addition, although illustration is abbreviate | omitted, the graph of the tendency similar to the said FIG. 4 is obtained also about adsorption | suction and purification | cleaning of CO and NOx component which are contained in exhaust gas.

  First, Comparative Example 1 will be examined. In Comparative Example 1, first, the temperature curve 81 of the adsorption unit 120 reaches the HC desorption start temperature Tm1 (time point t1), and after a predetermined time has elapsed, the temperature curve 82 of the purification unit 130 reaches the catalyst activation temperature Tm2. It can be seen that this has been reached (time t5). That is, in Comparative Example 1, as shown in FIG. 8, since the adsorption unit 120 is disposed closer to the engine body 1 (upstream side) than the purification unit 130, the temperature curve 81 of the adsorption unit 120. The temperature rises faster than the temperature curve 82 of the purification unit 130, reaches the desorption start temperature Tm1 first, and starts desorbing HC. However, at the HC desorption start time t1, the temperature curve 82 of the purification unit 130 has not yet reached the catalyst activation temperature Tm2, and reaches the temperature Tm2 for the first time at the time t5 when the time difference Δt1 has passed. For this reason, during the time difference Δt1, the HC component desorbed from the adsorption unit 120 cannot be sufficiently purified by the purification unit 130, and a relatively large amount of HC component flows out to the outside. .

  Next, Comparative Example 2 will be examined. In Comparative Example 2, first, the temperature curve 92 of the upstream / downstream catalysts 231, 232 reaches the catalyst activation temperature Tm 2 (time point t 3), and after a predetermined time has elapsed, the temperature curve 91 of the adsorbing unit 220 becomes HC. It can be seen that the desorption start temperature Tm1 has been reached (time t6). That is, in the second comparative example, as shown in FIG. 9, the upstream and downstream catalysts 231 and 232 are integrally accommodated in the catalytic converter 240 positioned upstream (the engine body 1 side) from the adsorption unit 220. Therefore, the temperature curve 92 of each of the catalysts 231 and 232 rises faster than the temperature curve 91 of the adsorption unit 220 and reaches the catalyst activation temperature Tm2 first (that is, the respective catalysts 231 and 232). Activation is completed first). On the other hand, at the activation completion time t3, the temperature curve 91 of the adsorption unit 220 has not yet reached the desorption start temperature Tm1, and the time difference Δt2 still remains until the time t6 when HC begins to desorb from the adsorption unit 220. There is. For this reason, after the time point t6, the HC component desorbed from the adsorbing portion 220 is sufficiently purified by the downstream catalyst 232 that has already reached the catalyst activation temperature Tm2, and the situation as in the comparative example 1 ( In other words, a situation in which a relatively large amount of HC component temporarily flows out) is effectively avoided.

  On the other hand, such an advantage can be obtained similarly in the configuration of the present embodiment. That is, in this embodiment, since the purification unit 30 is accommodated in the exhaust gas collecting unit 10 located on the upstream side (engine body 1 side) of the adsorption unit 20, the temperature curve 72 of the purification unit 30 However, the temperature rises faster than the temperature curve 71 of the adsorption unit 20, and reaches the catalyst activation temperature Tm2 first (that is, the activation of the purification unit 30 is completed first). On the other hand, at the activation completion time t2, the temperature curve 71 of the adsorption unit 20 has not yet reached the desorption start temperature Tm1, and the time difference Δt3 still remains until the time t4 when HC begins to desorb from the adsorption unit 20. There is. For this reason, after the time point t4, the HC component desorbed from the adsorption unit 20 is sufficiently purified by the purification unit 30 that has already reached the catalyst activation temperature Tm2, and the outflow of the HC component to the outside is ensured. Will be prevented. In the above description, the adsorption and purification of the HC component contained in the exhaust gas has been described, but the same applies to other CO and NOx components.

  According to the above examination results, the present embodiment and Comparative Example 2 can prevent the specific components (HC, CO, NOx) in the exhaust gas from flowing out to the outside at a low temperature. It can be seen that this is a more advantageous configuration. However, when this embodiment and Comparative Example 2 are compared in detail, it can be said that this embodiment is superior in the following points.

  First, it is possible to suppress an increase in engine back pressure. That is, in Comparative Example 2, two catalysts including the upstream catalyst 231 and the downstream catalyst 232 are disposed in the catalytic converter 240, and the cross section in the catalytic converter 240 is filled with almost no gap by these catalysts. Therefore, the ventilation resistance of exhaust gas when passing therethrough increases, and the back pressure of the engine tends to increase. On the other hand, in this embodiment, since the space part 12 having a predetermined volume is formed between the peripheral wall of the exhaust gas collecting part 10 and the purification part 30 inside thereof, the exhaust gas collecting part 10 is introduced from the engine body 1. The exhausted gas can be smoothly discharged to the downstream side through the space 12. For this reason, it is possible to effectively suppress an increase in the back pressure of the engine, and there is an advantage that the output and fuel consumption can be favorably maintained.

  Secondly, an increase in costs such as material costs can be suppressed. That is, in Comparative Example 2, the two catalysts 231 and 232 are arranged in the catalytic converter 240, so that a larger amount of catalyst is required and the heat capacity of the catalyst as a whole increases, and the temperature is the activation temperature Tm2. It takes a long time to reach. For this reason, it is necessary to adsorb a specific component such as HC as long as possible in the adsorbing unit 220, and it is necessary to arrange a large amount of adsorbent in the adsorbing unit 220 correspondingly. On the other hand, in the present embodiment, the purification unit 30 is installed only in a part of the exhaust gas collecting unit 10, and the space part 12 having a predetermined volume other than the installation unit of the purification unit 30 is a material cost. Thus, there is an advantage that the purification performance of exhaust gas can be maintained well while effectively reducing the cost.

  That is, according to the configuration of the present embodiment in which the purification unit 30 located on the downstream side of the adsorption unit 20 is installed in a part of the exhaust gas collecting unit 10 and the other part is the space unit 12, It is considered that the heat capacity of the purification unit 30 is relatively small with respect to the flow rate of the exhaust gas introduced from the engine body 1 into the exhaust gas collecting unit 10 as well as that corresponding to the upstream catalyst 231 becomes unnecessary. Therefore, it is considered that the temperature of the purification unit 30 rises relatively quickly due to the heat of the exhaust gas flowing around the purification unit 30 (space portion 12) and reaches the activity temperature Tm2. This is why the temperature curve 72 of the purification unit 30 in the graph of FIG. 4 is steeper than the catalyst temperature curve 92 of Comparative Example 2.

  As the activation of the purification unit 30 is accelerated as described above, even if the specific component in the exhaust gas is not adsorbed by the adsorption unit 20 for such a long time, the adsorption unit 20 reaches the desorption start temperature Tm1. The specific component that begins to desorb when it reaches (time t4) can be reliably purified by the purification unit 30 already in the active state. As a result, even if the amount of the various adsorbents 21, 22, and 23 in the adsorbing portion 20 is suppressed to a relatively small amount, the outflow of the specific component at a low temperature can be effectively suppressed and discharged to the outside. There is an advantage that the cleanliness of the exhaust gas can be favorably maintained with a lower cost configuration.

  This is also advantageous in that it suppresses an increase in the back pressure of the engine. That is, since the amount of the adsorbents 21, 22, and 23 in the adsorbing unit 20 is small, an increase in the back pressure due to the presence of the adsorbing unit 20 is suppressed, so that engine output and fuel consumption are further improved. There is an advantage of doing.

  Furthermore, as a specific configuration of the exhaust gas purifying apparatus, according to the first embodiment employing the structure as shown in FIGS. 1 to 3, the following operational effects can be obtained.

  First, in the first embodiment, a bulging portion 15 that bulges in a predetermined direction is provided in the exhaust gas collecting portion 10, and the exhaust pipes (that is, the first and second exhaust pipes) upstream and downstream of the exhaust gas collecting portion 10 are provided. Since the purifying part 30 is disposed in a state offset from the line L connecting the exhaust pipes 5 and 6) to the bulging part 15 side, it flows through the space part 12 in the exhaust gas collecting part 10. It is possible to effectively prevent the flow of exhaust gas from being bent greatly due to the presence of the purifying unit 30 and to further reduce the ventilation resistance of the exhaust gas. As a result, there is an advantage that the output and fuel consumption can be further improved by further suppressing the back pressure increase of the engine.

  Moreover, in the said 1st Embodiment, since the heat receiving part 32 for receiving the heat | fever of the waste gas which passes the said space part 12 is provided in the casing 31 of the purification | cleaning part 30, the temperature rise of the said purification | cleaning part 30 is accelerated | stimulated. Thus, its activation can be accelerated. As a result, the period during which the specific component in the exhaust gas should be adsorbed by the adsorbing unit 20 is shorter, so the amount of the various adsorbents 21, 22, and 23 in the adsorbing unit 20 can be further reduced and the cost can be reduced. There is an advantage that an increase in the back pressure of the engine due to the presence of the adsorbing portion 20 can be more effectively suppressed while reducing the above.

  In the first embodiment, since the exhaust pipe (that is, the third exhaust pipe 7) provided between the adsorption unit 20 and the purification unit 30 has a double pipe structure, the exhaust pipe 7 passes through the exhaust pipe 7. In the meantime, it is possible to effectively suppress the temperature of the exhaust gas from decreasing and the increase in the temperature of the purification unit 30 to be delayed, and there is an advantage that the purification unit 30 can be activated more quickly.

  In the first embodiment, HC and the like are purified by the purification unit 30 having the catalyst body 33 formed by coating a metal carrier with a catalyst layer containing a predetermined catalyst metal. The catalyst body 33 may be constituted by a non-metallic carrier such as a ceramic carrier made of light or the like coated with a predetermined catalyst layer. However, as in the first embodiment, the use of the catalyst main body 33 including the metal carrier can relatively reduce the heat capacity of the purification unit 30 and promote the temperature rise thereof. This is advantageous in that the time required to reach the activation temperature Tm2 can be further shortened.

  In the first embodiment, the adsorption unit 20 and the purification unit 30 are configured to adsorb or purify all the components of HC, CO, and NOx in the exhaust gas. May be any one that can adsorb or purify any one or more of the above components of HC, CO, and NOx.

  Further, in the first embodiment, the specific component such as HC contained in the exhaust gas is purified only by the purification unit 30 disposed in the exhaust gas collecting unit 10. Another purifier having a three-way catalyst or the like may be further provided in the middle of the four exhaust pipes 8 or the like.

  Moreover, in the said 1st Embodiment, although all the said 3rd exhaust pipes 7 provided between the adsorption | suction part 20 and the purification | cleaning part 30 were made into the double pipe structure, only a part of the said piping 7 is doubled. A tube structure may be used.

<Embodiment 2>
5-7 has shown 2nd Embodiment of the exhaust gas purification apparatus of this invention. As shown in these drawings, in the second embodiment, a switching valve 50 for switching the flow of exhaust gas in the exhaust passage 2 is provided inside the exhaust gas collecting portion 10. 5 to 7, the same elements as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIG. 7, the switching valve 50 is installed so as to open and close an opening 53 (details will be described later) provided in the purification unit 30 and the like, and to extend from the valve body 50 a. And a supporting member 50b. And one end part (end part on the opposite side to the valve body 50a) of the support member 50b is pivotally supported by the side wall etc. of the said exhaust gas collection part 10 via the support shaft 51, and this support shaft 51 is centered. The switching valve 50 is provided in a rotatable state.

  As shown in FIGS. 6 and 7, an opening 53 having a predetermined area is formed in the casing 31 of the purification unit 30 in the vicinity of the connection portion with the third exhaust pipe 7. The opening 53 is closed by the valve body 50a of the switching valve 50 when the engine is cold, and the switching is performed when the temperature of the adsorption unit 20 rises to a predetermined temperature after a certain period of time has elapsed since the start of the engine. The valve 50 is operated to open the opening 53. Specifically, a temperature sensor (not shown) is provided in the adsorption unit 20, and when the temperature sensor detects that the temperature of the adsorption unit 20 has risen to a predetermined temperature, the adsorption unit 20 operates according to the detection signal. The switching valve 50 is driven by a driving means (not shown) so that the opening 53 of the purifying unit 30 is opened.

  Then, when the switching valve 50 is driven in a direction to open the opening 53, the valve body 50a of the switching valve 50 connects the exhaust gas collecting part 10 and the adsorbing part 20 as shown in FIG. The upstream end of the second exhaust pipe 6 is closed. Then, the exhaust gas flow from the exhaust gas collecting part 10 to the purification part 30 via the second exhaust pipe 6 and the adsorption part 20 (see FIG. 5) is blocked by the valve body 50a. The exhaust gas introduced into the part 10 flows into the inside through the opening 53 of the purification part 30. That is, in this embodiment, when the adsorption unit 20 rises to a predetermined temperature, the exhaust gas introduced from the engine body 1 to the exhaust gas collecting unit 10 directly goes to the purification unit 30 without passing through the adsorption unit 20. Switching means for switching the flow of the exhaust gas so as to flow is configured by the switching valve 30.

  Here, in the above-described configuration in which the switching valve 50 is activated when the adsorption unit 20 rises to a predetermined temperature, the predetermined temperature serving as an operation trigger for the switching valve 50 is the removal of the various adsorbents 21, 22, 23 in the adsorption unit 20. It is preferable to set the separation completion temperature (that is, the temperature at which each component of HC, CO, and NOx almost completely desorbs from each adsorbent) to the highest temperature. For example, when β-type zeolite is used as the HC adsorbent 23 and the desorption completion temperature in the HC adsorbent 23 is higher than the desorption completion temperatures of the other adsorbents (CO adsorbent 22 and NOx adsorbent 21). In this case, since the temperature at which the desorption of the HC component is completed in the β-type zeolite is about 250 ° C., this 250 ° C. is set as the predetermined temperature.

  When the temperature of the adsorption unit 20 rises to such a temperature, none of the HC, CO, NOx components contained in the exhaust gas is adsorbed by the adsorption unit 20, and the exhaust gas is adsorbed by the adsorption unit 20. The meaning of passing through is lost. In addition, at this time, as described in the first embodiment, since the purification unit 30 is sufficiently heated and activated, the exhaust gas introduced into the exhaust gas collecting unit 10 passes through the adsorption unit 20. Even if it flows directly into the purifying unit 30 without the above, the specific component such as HC is sufficiently purified. Therefore, when the switching valve 50 is operated in such a state and the flow of the exhaust gas is switched to a flow that does not pass through the second exhaust pipe 6 or the adsorbing portion 20, the exhaust gas discharged to the outside. While ensuring the cleanliness of the engine properly, it is possible to prevent an increase in ventilation resistance due to this exhaust gas passing through a useless route, and to more effectively suppress a decrease in output and fuel consumption due to an increase in engine back pressure. It becomes possible.

  Further, by switching the flow of the exhaust gas as described above, the high-temperature exhaust gas introduced into the exhaust gas collecting unit 10 can be directly flowed into the purification unit 30, so that the temperature of the purification unit 30 is lowered and its active state There is an advantage that it is possible to surely prevent damage. Furthermore, the HC adsorbent 23 typified by zeolite suitable for adsorbing HC components in the adsorbing portion 20 may change its crystal structure when exposed to high-temperature exhaust gas for a long time. However, according to the above configuration, since the exhaust gas having a high temperature does not pass through the adsorption unit 20, there is an advantage that the degradation of the adsorption unit 20 can be effectively suppressed and the performance can be maintained well over a long period of time. .

1 is a diagram illustrating an overall configuration of an engine to which an exhaust gas purifying apparatus according to a first embodiment of the present invention is applied. It is a partially expanded sectional view of FIG. It is front sectional drawing which shows the specific structure of the purification | cleaning part in the said exhaust gas purification apparatus. It is a graph which shows the relationship between the elapsed time after an engine start, and the temperature of the adsorption | suction part and purification | cleaning part of an exhaust gas purification apparatus. It is a figure which shows the whole engine structure to which the exhaust gas purification apparatus concerning 2nd Embodiment of this invention was applied. It is a partially expanded sectional view of FIG. It is front sectional drawing which shows the specific structure of the purification | cleaning part in the said exhaust gas purification apparatus. 2 is a diagram illustrating a schematic configuration of Comparative Example 1. FIG. 6 is a diagram illustrating a schematic configuration of Comparative Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine body 2 Exhaust passage 5 Exhaust pipe (upstream of exhaust gas collecting part) 6 Exhaust pipe (downstream of exhaust gas collecting part) 7 Exhaust pipe (between adsorption part and purification part) 10 Exhaust gas collecting part 12 Space Part 15 Swelling part 20 Adsorption part 30 Purification part 31 Casing (of purification part) 32 Heat receiving part 33 Catalyst body 50 Switching valve (switching means)
L line

Claims (6)

An engine exhaust gas purification apparatus in which an adsorption part that adsorbs a specific component in exhaust gas and a purification part that purifies the specific component desorbed from the adsorption part are arranged in order from the upstream side along the exhaust path of the engine. And
The purification unit is disposed in an exhaust gas collecting portion where exhaust gases discharged from a plurality of cylinders of the engine body are collected, and the exhaust gas from the engine main body is disposed between the purification unit and a peripheral wall of the exhaust gas collecting unit. An exhaust gas purification device for an engine, characterized in that a space portion having a predetermined volume through which the gas can flow is formed. The exhaust gas purification apparatus for an engine according to claim 1,
A bulging part bulging in a predetermined direction is provided in the exhaust gas collecting part, and the purification part is offset from the line connecting the exhaust pipes upstream and downstream of the exhaust gas collecting part to the bulging part side. An exhaust gas purification device for an engine characterized by comprising: The exhaust gas purification apparatus for an engine according to claim 1 or 2,
An exhaust gas purification apparatus for an engine, wherein a heat receiving portion for receiving heat of exhaust gas passing through the space portion is provided in a casing of the purification portion. The exhaust gas purification apparatus for an engine according to any one of claims 1 to 3,
An exhaust gas purifying apparatus for an engine, characterized in that the purification section includes a catalyst main body formed by coating a metal carrier with a catalyst layer containing a predetermined catalyst metal. The exhaust gas purification apparatus for an engine according to any one of claims 1 to 4,
An exhaust gas purifying apparatus for an engine, wherein at least a part of an exhaust pipe provided between the adsorption part and the purification part has a double pipe structure. The exhaust gas purification apparatus for an engine according to any one of claims 1 to 5,
Switching means for switching the flow of the exhaust gas so that the exhaust gas introduced from the engine body to the exhaust gas collecting portion flows directly to the purification portion without passing through the adsorption portion when the adsorption portion rises to a predetermined temperature. An exhaust gas purification device for an engine characterized by comprising:

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