JP5569667B2 - Exhaust purification device - Google Patents

Description

  The present invention relates to an exhaust gas purification device that purifies exhaust gas from an engine, and more particularly to an exhaust gas purification device in which a plurality of exhaust gas purification means are accommodated in two casings.

Exhaust gas discharged from engines such as diesel engines contains various air pollutants, and it is necessary to reduce them to an appropriate level. Therefore, multiple exhaust gas purification means for purifying exhaust gas are provided. An exhaust purification device is used.
For example, diesel engine exhaust contains particulates, NOx (nitrogen oxides), and the like as air pollutants. Therefore, with regard to particulates, a technology has been conventionally known in which a particulate filter is provided in the exhaust passage of the engine, and the particulates contained in the exhaust gas are collected by the particulate filter so that the particulates are not released into the atmosphere. ing.

  For NOx, an ammonia selective reduction type NOx catalyst is disposed in the exhaust passage of the engine, and ammonia is supplied to the ammonia selective reduction type NOx catalyst as a reducing agent so that NOx is selectively reduced to purify the exhaust gas. An exhaust emission control device is known. In this ammonia selective reduction type NOx catalyst, urea water is supplied into the exhaust on the upstream side, and ammonia generated by hydrolysis of the urea water by the heat of the exhaust is supplied. The NOx reduction is performed by promoting the denitration reaction between the ammonia supplied to the ammonia selective reduction type NOx catalyst and the NOx in the exhaust gas by the ammonia selective reduction type NOx catalyst.

In order to efficiently collect particulates and reduce NOx, a particulate filter and an ammonia selective reduction type NOx catalyst are combined and used as an exhaust purification device, for example, proposed in Patent Document 1 Has been.
The exhaust emission control device of Patent Document 1 includes an upstream casing and a downstream casing that is disposed on the downstream side of the upstream casing and communicated with the communication passage. A upstream oxidation catalyst is accommodated in the upstream casing, and a particulate filter is accommodated downstream of the upstream oxidation catalyst. The pre-stage oxidation catalyst oxidizes NO in the exhaust gas to generate NO ₂ , and this NO ₂ is used to perform continuous regeneration of the particulate filter.

On the other hand, the ammonia selective reduction type NOx catalyst is accommodated in the downstream casing, and the ammonia flowing out from the ammonia selective reduction type NOx catalyst is oxidized to N ₂ on the downstream side of the ammonia selective reduction type NOx catalyst. The latter stage oxidation catalyst is accommodated.
The communication passage that connects the upstream casing and the downstream casing is provided with a urea water injector that injects and supplies urea water into the exhaust gas in the communication passage. The urea water injected from the urea water injector is hydrolyzed by the heat of the exhaust to become ammonia, and is supplied as a reducing agent to the ammonia selective reduction type NOx catalyst.

  If the amount of ammonia supplied to the ammonia selective reduction type NOx catalyst is inappropriate, the exhaust gas purification efficiency of the ammonia selective reduction type NOx catalyst decreases due to the shortage of ammonia supply amount, or the ammonia selective reduction type due to the supply of excess ammonia. There is a problem in that ammonia outflow from the NOx catalyst, that is, so-called ammonia slip occurs. Therefore, in the exhaust gas purification device of Patent Document 1, whether or not urea water can be supplied is determined based on the exhaust temperature, and urea water is supplied based on the internal temperature of the ammonia selective reduction type NOx catalyst estimated from the exhaust temperature. I have control.

  Further, Patent Document 2 also proposes an exhaust purification device that controls the supply amount of urea water based on the exhaust temperature and the internal temperature of the ammonia selective reduction type NOx catalyst. Although the exhaust gas purification device of Patent Document 2 does not include a plurality of exhaust gas purification means, the exhaust gas purification performance of the ammonia selective reduction type NOx catalyst is improved by appropriately controlling the internal temperature of the ammonia selective reduction type NOx catalyst. I try to keep it.

As shown in these Patent Documents 1 and 2, accurately detecting the temperature of the exhaust gas flowing into the exhaust gas purification means is an extremely important factor in maintaining good purification performance of the exhaust gas purification device.
JP 2007-162487 A JP 2003-293736 A

  In the case of having a plurality of exhaust gas purification means as in the exhaust gas purification apparatus of Patent Document 1, each exhaust gas purification means is arranged in series in the exhaust passage. Therefore, when the exhaust gas purification means are arranged in a straight line, It can be long. In particular, when such an exhaust purification device is to be mounted on a vehicle, it may be difficult to mount the exhaust purification device due to interference with other on-vehicle equipment, so it is necessary to consider the layout of these exhaust purification means. is there.

  Therefore, after dividing the casing for containing the exhaust purification means into the upstream side and the downstream side casing, the exhaust outlet for discharging the exhaust from the upstream side casing is provided on the side peripheral wall of the cylindrical upstream side casing. It is conceivable that the exhaust gas purification device is configured so as to exhaust the exhaust gas from the side of the upstream casing toward the downstream casing. In this case, the upstream casing and the downstream casing need not be arranged in a straight line, and for example, the downstream casing can be disposed on the side of the upstream casing. Therefore, it is advantageous in terms of layout particularly when the exhaust purification device is mounted on a vehicle.

  However, when exhaust is caused to flow out from the exhaust outlet provided on the side peripheral wall of the upstream casing in this way, the exhaust does not flow along the central axis of the upstream casing, and the exhaust outlet from the central axis After changing the flow in the direction, it flows out from the exhaust outlet. For this reason, the flow of exhaust in the upstream casing is biased toward the exhaust outlet, and depending on the arrangement of the exhaust temperature sensor, the exhaust temperature sensor may not be in sufficient contact with the exhaust, and the exhaust temperature may not be detected accurately. is there.

  If the detection accuracy of the exhaust gas temperature by the exhaust gas temperature sensor decreases, for example, if the exhaust gas temperature sensor is used to control the exhaust gas purifying means to make the exhaust gas purifying performance appropriate, the exhaust gas purifying performance of the exhaust gas purifying means becomes appropriate. There is a problem that it cannot be maintained. That is, for example, if the detected value of the exhaust temperature sensor with reduced accuracy is used for urea water supply control as in the above-described exhaust gas purification devices of Patent Documents 1 and 2, an erroneous determination of whether or not urea water can be supplied, and the urea water supply amount Inappropriate control causes problems such as a reduction in exhaust gas purification efficiency of the ammonia selective reduction type NOx catalyst and generation of ammonia slip from the ammonia selective reduction type NOx catalyst.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an exhaust purification device capable of accurately detecting the exhaust temperature.

In order to achieve the above object, an exhaust emission control device according to the present invention comprises an upstream casing that has a cylindrical shape and contains first exhaust purification means for purifying engine exhaust inside, and the upstream casing. An exhaust outlet that is provided on a side peripheral wall at a position downstream of the first exhaust purification means, exhausts exhaust that has passed through the first exhaust purification means, and communicates with the exhaust outlet, and from the exhaust outlet A downstream casing containing second exhaust purification means for purifying exhaust gas that has flowed out, and disposed between the first exhaust purification means and the exhaust outlet in the flow direction of the exhaust in the upstream casing. attached to the side wall of the upstream casing, and an exhaust temperature sensor for detecting the temperature of the exhaust gas flowing out of the first exhaust gas purification device, the exhaust temperature sensor, the central axis and above the exhaust outlet In a second imaginary plane perpendicular to the first virtual plane containing the central axis of the flow casing containing the central axis of the upstream casing, the side peripheral wall of the upstream-side casing in the circumferential direction, the exhaust flow an outlet-side region located on the side of the outlet, to the side of the exhaust outlet when divided into two regions with the anti outlet side region located opposite, provided in the flow outlet side region The second exhaust purification means includes an ammonia selective reduction type NOx catalyst that selectively reduces NOx in the exhaust gas using ammonia as a reducing agent, and the upstream casing flows out of the first exhaust purification means. And a urea water injector for injecting urea water into the exhaust gas flowing toward the ammonia selective reduction type NOx catalyst via the exhaust gas outlet, the urea water injector being connected to the exhaust gas outlet. Provided on the side peripheral wall at a position where the urea water is injected toward the exhaust outlet, and the exhaust temperature sensor is disposed upstream of the urea water injector in the flow direction of the exhaust gas in the upstream casing. (Claim 1).

  According to the exhaust gas purification apparatus configured as described above, the exhaust gas that has passed through the first exhaust gas purification means accommodated in the upstream casing flows from the exhaust outlet toward the downstream casing, and enters the upstream casing. It passes through the accommodated second exhaust purification means. At this time, since the exhaust outlet is provided on the side peripheral wall of the upstream casing, the exhaust flow when flowing in the upstream casing from the first exhaust purification means to the exhaust outlet is the upstream casing. There is a tendency to deviate from the central axis of the exhaust gas toward the exhaust outlet.

Thus, the temperature of the exhaust flowing in the upstream casing is arranged between the first exhaust purification means and the exhaust outlet in the flow direction of the exhaust in the upstream casing and attached to the side peripheral wall of the upstream casing. It is detected by the exhaust temperature sensor. The exhaust temperature sensor is a second virtual plane that is orthogonal to a first virtual plane that includes the central axis of the exhaust outlet and the central axis of the upstream casing, and that includes the central axis of the upstream casing. When the side peripheral wall of the casing is divided into two regions in the circumferential direction, an outlet side region located on the exhaust outlet side and a counterflow outlet side region located on the opposite side of the exhaust outlet side Since the exhaust gas is provided in the outlet side region as described above, the temperature is located on the side where the exhaust gas is deflected with respect to the exhaust gas that tends to flow from the central axis of the upstream casing toward the exhaust outlet side. Is detected.
The second exhaust purification unit is configured to include an ammonia selective reduction type NOx catalyst, and the urea water injected from the urea water injector flows to the ammonia selective reduction type NOx catalyst via the exhaust outlet. Inside, it is hydrolyzed by the heat of the exhaust to produce ammonia. The produced ammonia is supplied to an ammonia selective reduction type NOx catalyst and used as a reducing agent for selective reduction of NOx. As a result, NOx in the exhaust gas is reduced and the exhaust gas is purified. At this time, the urea water injector is provided on the side peripheral wall at a position facing the exhaust outlet and injects urea water toward the exhaust outlet, and the exhaust temperature sensor detects the exhaust gas in the upstream casing. Since it is disposed upstream of the urea water injector in the flow direction, the temperature of the exhaust gas before the urea water is injected and supplied from the urea water injector is detected.

Further, in the exhaust purification apparatus, a cylindrical rectifier that extends from the exhaust outlet to the urea water injector so as to traverse the inside of the upstream casing and surrounds the urea water injector. And a plurality of communication holes for communicating the outside and the inside of the rectifying body are formed on the peripheral surface of the rectifying body (claim 2).

According to the exhaust gas purification apparatus configured as described above, the exhaust gas that has passed through the first exhaust gas purification unit flows into the rectifying body through the communication hole formed in the rectifying body, and then upstream through the exhaust outlet. It flows out of the casing and flows into the downstream casing. At this time, when urea water is injected from the urea water injector, the injected urea water is hydrolyzed by the heat of the exhaust gas flowing into the rectifier, and ammonia is generated.

  According to the exhaust gas purification apparatus of the present invention, the flow of exhaust gas when flowing in the upstream casing from the first exhaust gas purification means toward the exhaust gas outlet tends to be biased toward the exhaust gas outlet side from the central axis of the upstream casing. However, the exhaust temperature sensor is located on the side where the exhaust is deflected and detects the temperature with respect to the flow of the exhaust, so it can contact a relatively large amount of exhaust, and the exhaust temperature can be accurately measured. It is possible to detect well.

Therefore, for example, when the detection value of the exhaust temperature sensor is used for maintaining the exhaust purification performance of the first or second exhaust purification means, the first or second exhaust purification is performed according to the accurate exhaust temperature detected by the exhaust temperature sensor. The exhaust gas purification performance of the means can be maintained well.
Further, the second exhaust purification means is configured to include an ammonia selective reduction type NOx catalyst, and the urea water injector is provided on a side peripheral wall at a position facing the exhaust outlet, and urea water is directed toward the exhaust outlet. The injection and exhaust temperature sensor is disposed upstream of the urea water injector in the flow direction of the exhaust gas in the upstream casing, and therefore detects the temperature of the exhaust gas before the urea water is injected and supplied from the urea water injector. As a result, the exhaust gas temperature can be detected accurately without being affected by the urea water injected and supplied into the exhaust gas.

Therefore, for example, when the exhaust gas temperature detected by the exhaust gas temperature sensor is used for controlling the urea water injector, the amount of urea water supplied from the urea water injector can be controlled with high accuracy, and the occurrence of ammonia slip is prevented. In addition, the exhaust gas purification performance of the ammonia selective reduction type NOx catalyst can be maintained satisfactorily.
Furthermore, it is possible to satisfactorily prevent deterioration of the exhaust temperature sensor and deterioration of the detection function due to adhesion of urea water injected and supplied from the urea water injector.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an overall configuration diagram of a four-cylinder diesel engine (hereinafter referred to as an engine) to which an exhaust emission control device according to an embodiment of the present invention is applied, and the exhaust emission control device according to the present invention is based on FIG. Will be described.
The engine 1 includes a high-pressure accumulator chamber (hereinafter referred to as a common rail) 2 common to each cylinder, and a fuel injection valve 4 in which high-pressure fuel supplied from a fuel injection pump (not shown) and stored in the common rail 2 is provided in each cylinder. The fuel is injected into each cylinder from each fuel injection valve 4.

  The intake passage 6 is equipped with a turbocharger 8. The intake air drawn from an air cleaner (not shown) flows into the compressor 8a of the turbocharger 8, and the intake air supercharged by the compressor 8a is supplied to the intercooler 10 and the intake air control. It is introduced into the intake manifold 14 via the valve 12. An intake air amount sensor 16 that detects an intake air flow rate to the engine 1 is provided in the intake passage 6 upstream of the compressor 8a.

  On the other hand, an exhaust port (not shown) through which exhaust is discharged from each cylinder of the engine 1 is connected to an exhaust pipe 20 via an exhaust manifold 18. An EGR passage between the exhaust manifold 18 and the intake manifold 14 is connected to the exhaust manifold 18 and the intake manifold 14 via an EGR valve 22 to recirculate a part of the exhaust gas of the engine 1 to the intake side. 24 is provided.

The exhaust pipe 20 passes through the turbine 8 b of the turbocharger 8 and is connected to an exhaust aftertreatment device 28 via an exhaust throttle valve 26. In the turbocharger 8, the rotating shaft of the turbine 8b is connected to the rotating shaft of the compressor 8a, and the turbine 8b receives the exhaust gas flowing in the exhaust pipe 20 and drives the compressor 8a to perform supercharging.
The exhaust aftertreatment device 28 includes a cylindrical upstream casing 30 connected to the exhaust pipe 20 and a cylindrical downstream casing 34 communicated with the downstream side of the upstream casing 30 through a communication path 32. . The exhaust gas flowing into the upstream casing 30 from the exhaust pipe 20 flows into the downstream casing 34 through the communication path 32 after passing through the upstream casing 30, and the exhaust gas that has passed through the downstream casing 34 is It is discharged from the tail pipe 36 into the atmosphere.

A pre-stage oxidation catalyst 38 is accommodated in the upstream casing 30, and a particulate filter (hereinafter referred to as a filter) 40 is accommodated on the downstream side of the pre-stage oxidation catalyst 38. Therefore, in the present embodiment, the pre-stage oxidation catalyst 38 and the filter 40 correspond to the first exhaust purification unit of the present invention.
The filter 40 is provided for collecting particulates in the exhaust gas and purifying the exhaust gas of the engine 1. The filter 40 is made of a honeycomb-type ceramic body, and traps particulates in the exhaust as the exhaust of the engine 1 circulates inside. Since the pre-stage oxidation catalyst 38 oxidizes NO (nitrogen monoxide) in the exhaust gas to generate NO ₂ (nitrogen dioxide), the pre-stage oxidation catalyst 38 and the filter 40 are arranged in this manner, so that the filter 40 captures them. The collected particulates react with NO ₂ supplied from the pre-stage oxidation catalyst 38 to be oxidized, and the filter 40 is continuously regenerated.

On the other hand, in the downstream casing 34, an ammonia selective reduction type NOx catalyst (hereinafter referred to as an SCR catalyst) 42 that contains NOx in the exhaust and selectively purifies the exhaust by using ammonia in the exhaust as a reducing agent is housed. A downstream oxidation catalyst 44 for removing ammonia flowing out from the SCR catalyst 42 is accommodated on the downstream side of the SCR catalyst 42. Therefore, in the present embodiment, the SCR catalyst 42 and the post-stage oxidation catalyst 44 correspond to the second exhaust purification unit of the present invention. The post-stage oxidation catalyst 44 also has a function of oxidizing CO (carbon monoxide) generated when the particulates are incinerated by forced regeneration of the filter 40, which will be described later, and discharging it to the atmosphere as CO ₂ (carbon dioxide). ing.

A part of the NO ₂ generated by the front-stage oxidation catalyst 38 is used for continuous regeneration of the filter 40 as described above, but the remaining NO ₂ is supplied to the SCR catalyst 42 and the NO ₂ with respect to the NO in the exhaust gas is supplied. The exhaust purification efficiency of the SCR catalyst 42 is increased by increasing the ratio.
A urea water injector (ammonia supply means) 46 for injecting and supplying urea water into the exhaust gas flowing out from the filter 40 and flowing into the communication path 32 is provided on the downstream side of the filter 40 of the upstream casing 30. The urea water is supplied to the urea water injector 46 from a urea water tank (not shown).

The urea water injected from the urea water injector 46 is hydrolyzed by the heat of the exhaust to become ammonia, and is supplied to the SCR catalyst 42 as a reducing agent. The SCR catalyst 42 reduces NOx to harmless N ₂ by promoting a denitration reaction between the supplied ammonia and NOx in the exhaust. At this time, when ammonia flows out of the SCR catalyst 42 without reacting with NOx, the ammonia is converted into harmless N ₂ by the post-stage oxidation catalyst 44 and released from the tail pipe 36 into the atmosphere.

  In the upstream casing 30, an exhaust temperature sensor 52 that detects the temperature of the exhaust gas flowing out from the filter 40 is on the downstream side of the filter 40 in the flow direction of the exhaust gas in the upstream casing 30 and on the upstream side of the urea water injector 46. It is provided at the position. The exhaust temperature sensor 48 is used for forced regeneration control for forced regeneration of the filter 40 and urea water supply control for appropriately controlling the amount of urea water supplied from the urea water injector 46. The forced regeneration control and the urea water supply control are already known, and thus the details thereof are omitted.

Next, the configuration of the portion of the upstream casing 30 on the downstream side of the filter 40 will be described in more detail.
2 is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. 3 is a cross-sectional view taken along the virtual plane P1 in FIG. As shown in FIG. 2 and FIG. 3, an exhaust outlet 30 a that protrudes outward of the upstream casing 30 at a position on the downstream side of the filter 40 is formed on the peripheral surface of the side wall of the cylindrical upstream casing 30. Is connected to the exhaust outlet 30a through a flange.

  The upstream casing 30 is provided with a urea water injector 46 on the side wall circumferential surface at a position facing the exhaust outlet 30a, and injects urea water toward the exhaust outlet 30a. The exhaust outlet 30a is integrally formed with a rectifier 30b extending from the welded portion to the upstream casing 30 so as to cross the upstream casing 30, and is opposite to the exhaust outlet 30a of the rectifier 30b. The end portion on the side is welded and fixed to the peripheral surface of the side wall facing the exhaust outlet 30a so as to surround the urea water injector 46. And many communication holes 30c which connect the outer side and inner side of the rectification body 30b are formed in the surrounding surface of the rectification body 30b.

  By configuring the exhaust outlet 30a and the rectifier 30b in this way, the exhaust gas that has passed through the filter 40 flows into the rectifier 30b through the communication hole 30c formed in the rectifier 30b, and then the exhaust outlet It flows into the communication path 32 from 30a and further flows into the downstream casing 34. Since the exhaust outlet 30a is provided on the side peripheral wall of the upstream casing 30, the exhaust gas flowing out from the filter 40 is exhausted from the central axis of the upstream casing 30 as shown by the arrow in FIG. It flows to the side.

  At this time, when urea water is injected from the urea water injector 46, the injected urea water is hydrolyzed by the heat of the exhaust gas flowing out of the filter 40 and flowing into the rectifier 30b, thereby generating ammonia. The produced ammonia is supplied to the SCR catalyst 42 in the downstream casing 34 and used as a reducing agent for the selective reduction of NOx by the SCR catalyst 40 as described above.

  As shown in FIG. 2, the exhaust temperature sensor 48 that detects the temperature of the exhaust gas flowing out from the filter 40 and flowing into the rectifier 30 b is connected to the central axis of the exhaust outlet 30 a at the connection portion to the upstream casing 30. Of the two intersecting lines of the virtual plane P1 including the central axis of the upstream casing 30 and the side peripheral wall of the upstream casing 30, it is disposed on the intersecting line on the exhaust outlet 30a side. Then, on this intersection line, as shown in FIG. 3, the exhaust temperature sensor 48 becomes downstream of the filter 40 in the flow direction of the exhaust gas in the upstream casing 30, and the exhaust gas outlet 30 a and the urea water injector 46. It is arranged at a position on the upstream side.

  As described above, the exhaust gas that has flowed out of the filter 40 flows while being biased toward the exhaust outlet 30a side from the central axis of the upstream casing 30 as indicated by an arrow in FIG. Since the exhaust gas is arranged in a direction in which the flow of the exhaust gas is biased, a relatively large amount of exhaust gas can be contacted. Accordingly, it is possible to accurately detect the temperature of the exhaust gas flowing out from the filter 40 and flowing into the rectifying body 30b.

In this embodiment, the detection value of the exhaust temperature sensor 48 is used for forced regeneration control of the filter 40 and urea water supply control of the urea water injector 46 as described above. In the forced regeneration control of the filter 40, by using such a highly accurate detection value of the exhaust temperature sensor 48, the filter 40 is properly regenerated and the particulate collection function by the filter 40 is maintained well. It becomes possible to do. Further, in the urea water supply control of the urea water injector 46, by using such a highly accurate detection value of the exhaust temperature sensor 48,
The supply amount of urea water can be accurately controlled, and the exhaust purification efficiency of the SCR catalyst 42 can be maintained well while preventing the occurrence of ammonia slip.

  Further, since the exhaust temperature sensor 48 is disposed at a position upstream of the urea water injector 46 in the flow direction of the exhaust gas in the upstream casing 30, before the urea water is injected and supplied from the urea water injector 46. By detecting the temperature of the exhaust gas, it is possible to detect the exhaust gas temperature accurately without being affected by the urea water injected and supplied into the exhaust gas. Therefore, the supply amount of urea water can be controlled with higher accuracy, and the exhaust purification efficiency of the SCR catalyst 42 can be maintained well while preventing the occurrence of ammonia slip. Furthermore, it is possible to satisfactorily prevent the exhaust temperature sensor 48 from being deteriorated and the detection function from being deteriorated due to adhesion of urea water injected and supplied from the urea water injector 46.

In the present embodiment, as shown in FIG. 2, a virtual plane P <b> 1 including the central axis of the exhaust outlet 30 a and the central axis of the upstream casing 30 in the connection portion to the upstream casing 30, and the upstream casing 30. The exhaust temperature sensor 48 is disposed on the intersection line on the exhaust outlet 30a side of the two intersecting lines with the side peripheral wall of the exhaust gas, but the circumferential exhaust temperature sensor 48 is disposed on the side peripheral wall of the upstream casing 30. Is not limited to this. That is, in the circumferential direction of the side peripheral wall of the upstream casing 30, the outlet side area A located on the exhaust outlet 30a side and the counterflow outlet side area B located on the opposite side of the exhaust outlet 30a. If the exhaust gas temperature sensor 48 is provided in the outlet side region A, the exhaust temperature sensor 48 can come into contact with a relatively large amount of exhaust gas.

Specifically, in FIG. 2, when the side peripheral wall of the upstream casing 30 is divided into two in the circumferential direction by a virtual plane P2 that includes the central axis of the upstream casing 30 and is orthogonal to the virtual plane P1, the exhaust outlet port The region occupied by the side peripheral wall portion located on the side of 30a is the outlet side region A, and the region occupied by the side peripheral wall portion located on the side opposite to the exhaust outlet 30a side is the counterflow side region B. It becomes. As shown in FIG. 3, the exhaust gas flowing out of the filter 40 flows biased toward the exhaust outlet 30a side, that is, the outlet side area A, and therefore, the exhaust temperature sensor 48 is disposed in the outlet side area A. By doing so, the exhaust temperature sensor 48 comes into contact with a relatively large amount of exhaust gas. As a result, the exhaust temperature sensor 48 can accurately detect the exhaust temperature.

  Even when the exhaust temperature sensor 48 is provided at any position in the outlet side region A, the exhaust temperature sensor 48 is located downstream of the filter 40 in the flow direction of the exhaust gas in the upstream casing 30, and the exhaust outlet 30 a and urea. By disposing the exhaust temperature sensor 48 at a position upstream of the water injector 46, it is possible to accurately detect the exhaust temperature without being affected by the urea water injected and supplied from the urea water injector 46 into the exhaust gas. It becomes possible.

Although the description of the exhaust emission control device according to one embodiment of the present invention is finished above, the present invention is not limited to the above embodiment.
For example, in the above embodiment, the detection value of the exhaust temperature sensor 48 is used for the forced regeneration control of the filter 40 and the urea water supply control of the urea water injector 46. It is not limited to these. That is, the detection value of the exhaust temperature sensor 48 can be used for various controls that require information on the exhaust temperature. As described above, the exhaust temperature is accurately detected by the exhaust temperature sensor 48, so that the exhaust temperature is detected. The accuracy of control using the detection value of the sensor 48 can be maintained satisfactorily.

  In the above embodiment, the upstream oxidation catalyst 38 and the filter 40 are housed in the upstream casing 30 as the first exhaust purification means of the present invention, and the SCR catalyst is disposed in the downstream casing 34 as the second exhaust purification means of the present invention. 42 and the post-stage oxidation catalyst 44 are accommodated, but the first and second exhaust purification means are not limited to these, and various exhaust purification means can be used as necessary.

  Moreover, in the said embodiment, although the rectifier 30b extended from the exhaust outlet 30a was provided, the form of the rectifier 30b is not limited to this. For example, the rectifier 30b may be extended from the exhaust outlet 30a to the middle of the upstream casing 30 without reaching the side peripheral wall of the upstream casing 30, or the rectifier 30b may be omitted entirely. It may be. Further, the shape, arrangement, number, etc. of the communication holes 30c formed in the rectifying body 30b can be changed as necessary.

In the above embodiment, the exhaust outlet 30a is provided so as to protrude outward from the peripheral wall of the upstream casing 30, and the communication passage 32 is connected to the exhaust outlet 30a. It is also possible to form an exhaust outlet opening in the side peripheral wall itself and connect the communication passage 32 directly to the upstream casing 30.
In the above embodiment, the exhaust aftertreatment device 28 is configured so that the upstream casing 30 and the downstream casing 34 are communicated with each other by the communication path 32. However, the upstream casing 30 and the downstream casing 34 are adjacent to each other, and You may make it connect the edge part of the exhaust outlet 30a of the side casing 30 to the downstream casing 34 directly. Further, the exhaust outlet 30a protruding outward from the side peripheral wall of the upstream casing 30 is omitted, and the upstream casing 30 and the downstream casing are connected via an exhaust outlet opening in the side peripheral wall of the upstream casing 30 itself. 34 may be communicated directly.

  Further, in the above embodiment, the engine 1 is a four-cylinder diesel engine, but the number of cylinders and the type of the engine 1 are not limited thereto.

1 is an overall configuration diagram of an engine to which an exhaust emission control device according to an embodiment of the present invention is applied. It is sectional drawing which follows the II-II line | wire in FIG. It is sectional drawing which follows the virtual plane P1 in FIG.

Explanation of symbols

1 Engine 30 Upstream casing 30a Exhaust outlet 34 Downstream casing 38 Pre-stage oxidation catalyst (first exhaust purification means)
40 particulate filter (first exhaust purification means)
42 Ammonia selective reduction type NOx catalyst (second exhaust purification means)
44 Second-stage oxidation catalyst (second exhaust purification means)
46 Urea water injector 48 Exhaust temperature sensor

Claims (2)

An upstream casing that has a cylindrical shape and contains first exhaust purification means for purifying engine exhaust inside;
An exhaust outlet that is provided on a side peripheral wall of the upstream casing at a position downstream of the first exhaust purification means and exhausts exhaust gas that has passed through the first exhaust purification means;
A downstream casing that communicates with the exhaust outlet and contains second exhaust purification means for purifying exhaust that has flowed out of the exhaust outlet;
It is arranged between the first exhaust purification means and the exhaust outlet in the flow direction of the exhaust gas in the upstream casing, is attached to the side peripheral wall of the upstream casing, and flows out from the first exhaust purification means. An exhaust temperature sensor for detecting the temperature of the exhaust,
The exhaust temperature sensor is a second imaginary plane that includes a central axis of the upstream casing orthogonal to a first imaginary plane that includes a central axis of the exhaust outlet and a central axis of the upstream casing. the side wall of the upstream casing circumferentially, two areas of the outlet-side region located on the side of the exhaust outlet, to the side of the exhaust outlet and the anti-outlet side region located opposite Is provided in the outlet side area when divided into
The second exhaust gas purification means includes an ammonia selective reduction type NOx catalyst that selectively reduces NOx in the exhaust gas using ammonia as a reducing agent,
The upstream casing includes a urea water injector that injects urea water into the exhaust gas flowing toward the ammonia selective reduction type NOx catalyst through the exhaust outlet after flowing out from the first exhaust purification unit,
The urea water injector is provided on the side peripheral wall at a position facing the exhaust outlet and injects urea water toward the exhaust outlet,
The exhaust gas purification device, wherein the exhaust gas temperature sensor is arranged upstream of the urea water injector in the flow direction of the exhaust gas in the upstream casing. The exhaust outlet is provided with a cylindrical rectifier that extends from the exhaust outlet to the urea water injector so as to cross the inside of the upstream casing and surrounds the urea water injector,
The exhaust purification device according to claim 1, wherein a plurality of communication holes communicating the outside and the inside of the rectifying body are formed on a peripheral surface of the rectifying body .

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